Supporting Information

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1 Thomas Özgün, Guo-Qiang Chen, Constantin G. Daniliuc, Alison C. McQuilken, Timothy H. Warren, Robert Knitsch, Hellmut Eckert, Gerald Kehr, Gerhard Erker* Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, Münster, Germany Department of Chemistry, Georgetown University, Box , Washington, D.C , United States Institut für Physikalische Chemie, Westfälische Wilhelms-Universität, Corrensstrasse 30, Münster, Germany Supporting Information S1

2 Table of contents 1 General Procedures Experimental Part Synthesis of compounds... 5 Synthesis of compound Synthesis of compound 10a... 7 Synthesis of compound 10b Synthesis of compound Synthesis of compound Synthesis of compound Synthesis of compound Generation of compound 14-D Synthesis of compound Synthesis of compound Synthesis of compound Synthesis of compound Synthesis of compound Synthesis of compound Solid State NMR Data EPR Data S2

3 1 General Procedures All syntheses involving air- and moisture sensitive compounds were carried out using standard Schlenk-type glassware (or in a glove box) under an atmosphere of argon. Solvents were dried and stored under an argon atmosphere. NMR spectra were recorded on an Agilent DD2-500 MHz ( 1 H: 500 MHz, 13 C: 126 MHz, 19 F: 470 MHz, 11 B: 160 MHz, 31 P: 202 MHz) and on an Agilent DD2-600 MHz ( 1 H: 600 MHz, 13 C: 151 MHz, 19 F: 564 MHz, 11 B: 192 MHz, 31 P: 243 MHz). 1 H NMR and 13 C NMR: chemical shifts are given relative to TMS and referenced to the solvent signal. 19 F NMR: chemical shifts are given relative to CFCl 3 (δ = 0, external reference), 11 B NMR: chemical shifts are given relative to BF 3 Et 2O (δ = 0, external reference), 31 P NMR: chemical shifts are given relative to H 3PO 4 (85% in D 2O) (δ = 0, external reference). NMR assignments were supported by additional 2D NMR experiments. Elemental analyses were performed on an Elementar Vario El III. IR spectra were recorded on a Varian 3100 FT-IR (Excalibur Series). Melting points and decomposition points were obtained with a DSC 2010 (TA Instruments). HRMS was recorded on GTC Waters Micromass (Manchester, UK). X-Ray diffraction: For compounds 10a, 10b, 12, 14, 19, 21 and 22 data sets were collected with a Nonius Kappa CCD diffractometer. Programs used: data collection, COLLECT (R. W. W. Hooft, Bruker AXS, 2008, Delft, The Netherlands); data reduction Denzo-SMN (Z. Otwinowski, W. Minor, Methods Enzymol. 1997, 276, ); absorption correction, Denzo (Z. Otwinowski, D. Borek, W. Majewski, W. Minor, Acta Crystallogr. 2003, A59, ); structure solution SHELXS-97 (G. M. Sheldrick, Acta Crystallogr. 1990, A46, ); structure refinement SHELXL-97 (G. M. Sheldrick, Acta Crystallogr. 2008, A64, ) and graphics, XP (BrukerAXS, 2000). For compound 18 and 20 data sets were collected with a Kappa CCD APEXII Bruker diffractometer. For compounds 11, 17, 20 data sets were collected with a D8 Venture Dual Source 100 CMOS diffractometer. Programs used: data collection: APEX2 V (Bruker AXS Inc., 2014); cell refinement: SAINT V8.34A (Bruker AXS Inc., 2013); data reduction: SAINT V8.34A (Bruker AXS Inc., 2013); absorption correction, SADABS V2014/2 (Bruker AXS Inc., 2014); structure solution SHELXT-2014 (Sheldrick, 2014); structure refinement SHELXL-2014 (Sheldrick, 2014) and graphics, XP (Bruker AXS Inc., 2014). R- values are given for observed reflections, and wr 2 values are given for all reflections. Exceptions and special features: For compound 11 one pentane molecule, for compound 14 one dichloromethane molecule, for compounds 19 and 20 two dichloromethane molecules and for compound 21 one phenyl group and one part of the six membered ring C5 to C10 are disordered over two positions. Several restraints (SADI, SAME, ISOR and SIMU) were used in order to improve refinement stability. For compounds 10a and 12 one badly pentane molecule and for compounds 17 and 18 one badly half pentane molecule were found in the asymmetric unit and could not be satisfactorily refined. The program SQUEEZE (A. L. Spek J. S3

4 Appl. Cryst., 2003, 36, 7-13) was therefore used to remove mathematically the effect of the solvent. The quoted formula and derived parameters are not included the squeezed solvent molecules. Compound 10b presents one tbu group and one six membered ring at C1 atom disordered over two positions. Several restraints (SADI, SAME, ISOR and SIMU) were used in order to improve refinement stability. Moreover, one badly disordered pentane molecule was found in the asymmetrical unit and could not be satisfactorily refined. The program SQUEEZE was therefore used to remove mathematically the effect of the solvent. The quoted formula and derived parameters are not included the squeezed solvent molecule. Materials: Vinylboranes 6a, 6b [Ekkert, O.; Tuschewitzki, O.; Daniliuc, C. G.; Kehr, G.; Erker, G. Chem. Commun., 2013, 49, ; Parks, D. J.; Piers, W. E.; Yap, G. P. A. Organometallics, 1998, 17, ] were prepared according to the literature. S4

5 2 Experimental Part 2.1 Synthesis of compounds Synthesis of compound 9 For analogous synthesis of the diphenylphospane derivative see: Chen, G.-Q.; Kehr, G.; Daniliuc, C. G.; Erker, G. Org. Biomol. Chem. 2015, 13, Scheme S1 n-butyllithium (10.0 ml, 16.0 mmol, 1.0 eq) was added dropwise to a solution of 1- ethynylcyclohexene (1.9 ml, 1.7 g, 16.0 mmol, 1.0 eq) in tetrahydrofuran (80 ml) at -78 C. The reaction mixture was warmed to r. t. and stirred for 10 min. Then a solution of chlorodimesitylphosphane (4.9 g, 16.0 mmol, 1.0 eq) in tetrahydrofuran (30 ml) was added dropwise to the obtained dark brown suspension at -78 C. The reaction mixture was stirred for 10 min at -78 C and subsequently stirred for 2 hours at ambient temperature. Then all volatiles were removed in vacuo and the sticky residue was suspended in pentane (100 ml). The resulting suspension was filtered via cannula (WHATMAN glass fiber filter) and all volatiles were removed from the filtrate in vacuo to give a brown oil. After Purification via column chromatography (silica: CH 2Cl 2:CyH = 15:85; R f: 0.70) compound 9 was obtained as a colorless, crystalline solid (5.1 g, 13.6 mmol, 85%). IR (KBr): ṽ [cm -1 ] = 3063 (w), 2958 (w), 2855 (w), 2727 (w), 2661 (w), 2466 (w), 2300 (w), 2133 (m), 1908 (w), 1881 (w), 1720 (w), 1601 (m), 1553 (w), 1465 (m), 1433 (s), 1407 (m), 1372 (m), 1346 (w), 1074 (w), 1028 (m), 996 (w), 917 (m), 845 (s), 787 (m), 712 (w), 689 (m), 616 (m), 600 (m), 558 (s), 460 (w), 431 (w). M.p. 80 C. Anal. Calc. for C 26H 31P: C: 83.39; H: Found: C: 83.20; H: H NMR (500 MHz, dichloromethane-d 2, 299 K): δ 6.81 (dm, 4 J PH = 3.2 Hz, 4H, m-mes), 6.08 (m, 1H, 2-CH), 2.37 (s, 12H, o-mes), 2.24 (s, 6H, p-mes), 2.11 (m, 2H, 6-CH 2), 2.09 (m, 2H, 3- CH 2), 1.62 (m, 2H, 5-CH 2), 1.57 (m, 2H, 4-CH 2). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 299 K): δ (d, 2 J PC = 15.6 Hz, o-mes), (p-mes), (d, 4 J PC = 2.6 Hz, 2-CH), (d, 1 J PC = 12.6 Hz, i-mes), (d, 3 J PC = 3.6 Hz, m-mes), (d, 3 J PC = 1.5 Hz, 1-C=), (d, 2 J PC = 8.8 Hz, C), 84.3 (d, 1 J PC = 3.4 Hz, PC ), 28.8 (d, 4 J PC = 1.6 Hz, 6-CH 2), 26.1 (3-CH 2), 23.0 (d, 3 Mes J PC = 14.4 Hz, o-ch 3 ), 22.6 (5-CH 2), 21.8 (4-CH 2), Mes 21.0 (p-ch 3 ). S5

6 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 299 K): δ ( 1/2 ~ 3 Hz). Figure S1: 1 H NMR (500 MHz, dichloromethane-d2, 299 K) spectrum of compound 9 Figure S2: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 299 K) spectrum of compound 9 S6

7 Figure S3: 31 P{ 1 H} NMR (202 MHz, dichloromethane-d2, 299 K) spectrum of compound 9 Synthesis of compound 10a Scheme S2 A solution of phosphane 9 (417.6 mg, 1.1 mmol, 1.0 eq) in toluene (6 ml) was added to a solution of borane 6a (500.0 mg, 1.1 mmol, 1.0 eq) in toluene (4 ml). The reaction mixture was stirred at 60 C for 3 d and then all volatiles were removed in vacuo. The resulting sticky residue was dissolved in pentane (3 ml), which was subsequently removed in vacuo. The obtained solid was washed with pentane (5 x 3 ml) to give compound 10a as a white powdery solid (822.0 mg, 1.0 mmol, 90%). IR (KBr): ṽ [cm -1 ] = 3696 (w), 3023 (m), 2929 (s), 2856 (m), 2347 (w), 1947 (w), 1723 (w), 1642 (s), 1604 (s), 1553 (w), 1515 (s), 1455 (m), 1380 (m), 1341 (w), 1287 (s), 1269 (m), 1248 (m), 1152 (w), 1091 (s), 1034 (m), 1024 (w), 996 (s), 852 (s), 805 (m), 773 (m), 741 (s), 696 (s), 643 (m), 629 (m), 607 (m), 575 (m), 553 (m), 499 (m), 453 (w), 418 (m). Decomp. 200 C. Anal. Calc. for C 46H 38BF 10P: C: 67.17; H: Found: C: 66.78; H: H NMR (600 MHz, dichloromethane-d 2, 213 K): δ 7.28 (m, 2H, o-ph), 7.23 (m, 2H, m-ph), 7.18 (m, 1H, p-ph), 7.14 (br d, 3 J HH = 16.3 Hz, 1H, =CH), 6.97 (d, 4 J PH = 3.5 Hz, 1H, m- Mes a ), 6.81 (s, 1H, m -Mes a ), 6.79 (m, 1H, m-mes b ), 6.40 (d, 3 J HH = 16.3 Hz, 1H, =CH Ph ), 6.38 (d, 4 J PH = 2.5 Hz, 1H, m -Mes b Mes,b ), 5.87 (s, 1H, 2-CH), 2.57 (s, 3H, o-ch 3 ), 2.45 (m, 3H, o- Mes,a CH 3 ), 2.30, 2.20 (each m, each 1H, 3-CH 2) t Mes,a, 2.23 (s, 3H, p-ch 3 ), 2.20 (s, 3H, o - S7

8 Mes,a Mes,b CH 3 ), 2.10 (s, 3H, p-ch 3 ), 1.77, 1.70 (each m, each 1H, 5-CH 2) t, 1.65, 1.52 (each m, each 1H, 4-CH 2) t Mes,b, 1.61 (s, 3H, o -CH 3 ), 1.58, 1.43 (each m, each 1H, 6-CH 2) t. [ t tentatively assigned] 13 C{ 1 H} NMR (151 MHz, dichloromethane-d 2, 213 K): δ (d, 2 J PC = 29.6 Hz, BC=), (d, 2 J PC = 17.8 Hz, o-mes a ), (o -Mes a ), (d, 2 J PC = 3.4 Hz, o-mes b ), (d, 4 J PC = 2.4 Hz, p-mes a ), (p-mes b ), (d, 2 J PC = 10.2 Hz, o -Mes b ), (d, 1 J PC = 50.6 Hz, PC=), (=CH Ph ), (i-ph), (d, 2 J PC = 3.3 Hz, 1-C=), (d, 3 J PC = 8.3 Hz, m- Mes b ), (d, 3 J PC = 8.3 Hz, 2-CH), (d, 3 J PC = 5.9 Hz, m -Mes a ), (d, 3 J PC = 9.2 Hz, m-mes a ), (d, 3 J PC = 9.2 Hz, m -Mes b ), (m-ph), (p-ph), (o-ph), (d, 1 J PC = 25.3 Hz, i-mes a ), (d, 1 J PC = 39.9 Hz, i-mes b ), (d, 3 J PC = 46.8 Hz, =CH), 27.4 (5-CH 2) t, 25.3 (3-CH 2) t, 25.0 (br d, 3 Mes,b J PC = 13.5 Hz, o-ch 3 ), 23.7 (dm, J = 8.7 Hz, o- Mes,a CH 3 ), 22.4 (6-CH 2) t, 22.3 (d, 3 Mes,a J PC = 2.2 Hz, o -CH 3 ), 22.0 (dd, J = 9.5 Hz, J = 3.9 Hz, Mes,b o -CH 3 ), 21.5 (4-CH 2) t Mes,a Mes,b, 20.7 (p-ch 3 ), 20.1 (p-ch 3 ). [C 6F 5 not listed; t tentatively assigned] 31 P{ 1 H} NMR (243 MHz, dichloromethane-d 2, 213 K): δ 8.8 (partial relaxed 1:1:1:1 q, J PB ~ 25 Hz). 11 B{ 1 H} NMR (192 MHz, dichloromethane-d 2, 213 K): δ 2.0 ( 1/2 ~ 1900 Hz) 19 F NMR (564 MHz, dichloromethane-d 2, 213 K): δ (m, o), (m, o ), (t, 3 J FF = 21.3 Hz, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F mp = 5.8, 6.6], (o), (o ), (m, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F mp = 6.2, 6.5]. Figure S4: 1 H NMR (600 MHz, dichloromethane-d2, 213 K) spectrum of compound 10a S8

9 Figure S5: 13 C{ 1 H} NMR (151 MHz, dichloromethane-d2, 213 K) spectrum of compound 10a Figure S6: 11 B{ 1 H} NMR (192 MHz, dichloromethane-d2, 213 K) and 31 P{ 1 H} NMR (243 MHz, dichloromethaned2, 213 K) spectra of compound 10a S9

10 Figure S7: 19 F NMR (564 MHz, dichloromethane-d2, 213 K) spectrum of compound 10a Figure S8: Dynamic 1 H NMR (600 MHz, dichloromethane-d2) spectra of compound 10a S10

11 Figure S9: Dynamic 19 F NMR (564 MHz, dichloromethane-d2) spectra of compound 10a G [T c, (T)] = RT c( ln(tc/ )) [J/mol] T c = coalescence temperature [K]: 286 K ( 19 F, p-bc 6F 5) = chemical shift difference [Hz] ( 19 F, p-bc 6F 5, 233 K): 883 Hz R = J/(mol K); 1 J = cal G [286 K, (233 K) = 883 Hz] = J/mol = 12.4 ± 0.3 kcal/mol Crystals suitable for the X-ray crystal structure analysis were obtained from a dichloromethane solution of compound 10a at -35 C: X-ray crystal structure analysis of compound 10a: formula C 46H 38BF 10P, M = , colourless crystal, 0.15 x 0.10 x 0.06 mm, a = (2), b = (2), c = (3) Å, α = (1), β = (1), γ = (1), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.981 T 0.992), Z = 2, triclinic, space group P1 (No. 2), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), 7974 independent (R int = 0.047) and 6146 observed reflections [I>2σ(I)], 529 refined parameters, R = 0.070, wr 2 = 0.191, max. (min.) residual electron density 0.31 (-0.31) e.å -3, hydrogen atoms were calculated and refined as riding atoms. S11

12 Figure S10: X-ray crystal structure of compound 10a (thermal ellipsoids are shown at the 30% probability level) Synthesis of compound 10b Scheme S3 A solution of borane 6b (1.54 g, 3.60 mmol, 1.0 eq) in toluene (5 ml) was added dropwise to a solution of phosphane 9 (1.35 g, 3.60 mmol, 1.0 eq) in toluene (5 ml). The reaction mixture was stirred at 60 C for 3 days and then all volatiles were removed in vacuo. The resulting sticky red residue was dissolved in pentane (5 ml), which was subsequently removed in vacuo. The obtained solid was washed with pentane (5 x 3 ml) and dried to finally give compound 10b as an off-white solid (1.26 g, 1.6 mmol, 43%). IR (KBr): ṽ [cm -1 ] = 5340 (w), 4382 (w), 4310 (w), 3901 (w), 3819 (w), 3747 (w), 3673 (w), 3628 (w), 3156 (w), 3026 (s), 2954 (s), 2863 (s), 2739 (w), 2632 (w), 2568 (w), 2400 (w), S12

13 2360 (w), 2220 (w), 2093 (w), 1828 (w), 1772 (w), 1735 (w), 1699 (w), 1645 (s), 1605 (m), 1515 (m), 1445 (m), 1381 (m), 1177 (w), 1114 (s), 1032 (m), 966 (m), 925 (m), 854 (s), 805 (m), 772 (m), 743 (s), 695 (s), 668 (s), 630 (s), 609 (s), 574 (m), 554 (m), 533 (m), 498 (m), 456 (m), 417 (m). Decomp. 212 C. Anal. Calc. for C 44H 42BF 10P: C: 65.85; H: Found: C: 65.79; H: H NMR (500 MHz, dichloromethane-d 2, 213 K): δ 6.95 (d, 4 J PH = 3.0 Hz, 1H, m-mes a ), 6.78 (s, 1H, m -Mes a ), 6.76 (s, 1H, m -Mes b ), 6.34 (s, 1H, m-mes b ), 6.15 (d, 3 J HH = 16.0 Hz, 1H, =CH), 5.72 (s, 1H, 2-CH), 5.62 (d, 3 J HH = 16.0 Hz, 1H, =CH tbu Mes,b ), 2.53 (s, 3H, o -CH 3 ), 2.44 (br, 3H, Mes,a Mes,a o-ch 3 ), 2.21 (s, 3H, p-ch 3 ), 2.18, 2.13 (each m, each 1H, 3-CH 2) t, 2.16 (s, 3H, o - Mes,a Mes,b CH 3 ), 2.09 (s, 3H, p-ch 3 ), 1.71, 1.67 (each br m, each 1H, 5-CH 2) t, 1.59, 1.45 (each m, each 1H, 4-CH 2), Mes,b 1.56 (s, 3H, o-ch 3 ), 1.53, 1.40 (each m, each 1H, 6-CH 2), 0.75 (s, tbu 9H, CH 3 ). [ t tentatively assigned] 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 213 K): δ (br d, 2 J PC = 30 Hz, BC=), (=CH tbu ), (d, 2 J PC = 17.2 Hz, o-mes a ), (o -Mes a ), (d, 2 J PC = 3.4 Hz, o -Mes b ), (d, 4 J PC = 1.7 Hz, p-mes a ), (d, 2 J PC = 13.2 Hz, o-mes b ), (d, 4 J PC = 2.1 Hz, p- Mes b ), (d, 1 J PC = 51.1 Hz, PC=), (d, 2 J PC = 3.5 Hz, 1-C=), (d, 3 J PC = 8.2 Hz, m -Mes b ), (d, 3 J PC = 6.9 Hz, 2-CH), (d, 3 J PC = 6.9 Hz, m -Mes a ), (d, 3 J PC = 9.1 Hz, m-mes a ), (d, 3 J PC = 9.1 Hz, m-mes b ), (d, 1 J PC = 25.0 Hz, i-mes a ), (d, 1 J PC = 39.6 Hz, i-mes b ), (d, 3 J PC = 45.5 Hz, =CH), 33.3 (C tbu tbu ), 28.0 (CH 3 ), 27.4 (5-CH 2) t, 25.2 (3-CH 2) t Mes,b Mes,a, 24.9 (m, o -CH 3 ), 23.6 (m, o-ch 3 ), 22.4 (6-CH 2) t, 22.3 (d, 3 J PC = 2.3 Hz, Mes,a Mes,b o -CH 3 ), 22.0 (dd, J = 9.3 Hz, J = 3.4 Hz, o-ch 3 ), 21.5 (4-CH 2) t Mes,a, 20.7 (p-ch 3 ), 20.0 Mes,b (p-ch 3 ). [C 6F 5 not listed; t tentatively assigned] 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 213 K): δ 10.9 (partial relaxed 1:1:1:1 q J PB ~ 26 Hz). 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 299 K): δ 12.8 ( 1/2 ~ 37 Hz). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 213 K): δ -3.0 (ν 1/2 ~ 2400 Hz). 19 F NMR (470 MHz, dichloromethane-d 2, 213 K): δ (m, o), (m, o ), (br t, 3 J FF = 21.3 Hz, p), (m, m), (m, m )(each 1F, C 6F 5)[ 19 F m,p = 6.0, 6.2]; (m, o), (m, o ), (br t, 3 J FF = 17.0 Hz, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F m,p = 6.1, 6.3] S13

14 Figure S11: 1 H NMR (500 MHz, dichloromethane-d2, 213 K) spectrum of compound 10b Figure S12: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 213 K) spectrum of compound 10b S14

15 Figure S13: 19 F NMR (470 MHz, dichloromethane-d2, 213 K) spectrum of compound 10b Figure S14: 31 P{ 1 H} NMR (202 MHz, dichloromethane-d2) spectra of compound 10b at 299 K (1) and 213 K (2) Figure S15: 11 B{ 1 H} NMR (160 MHz, dichloromethane-d2) spectra of compound 10b at 299 K (1) and 213 K (2) S15

16 Figure S16: Dynamic 1 H NMR (500 MHz, dichloromethane-d2) spectra of compound 10b Figure S17: Dynamic 19 F NMR (470 MHz, dichloromethane-d2) spectra of compound 10b S16

17 G [T c, (T)] = RT c( ln(tc/ )) [J/mol] T c= coalescence temperature [K]: 286 K ( 19 F, p-bc 6F 5) = chemical shift difference [Hz] ( 19 F, p-bc 6F 5, 233 K): 567 Hz R = J/(mol K); 1 J = cal G [286 K, (233 K) = 567 Hz] = J/mol = 12.7 ± 0.3 kcal/mol Crystals suitable for the X-ray crystal structure analysis were obtained from a solution of 10b in pentane at -35 C: X-ray crystal structure analysis of compound 10b: formula C 44H 42BF 10P, M = , colourless crystal, 0.22 x 0.06 x 0.01 mm, a = (3), b = (3), c = (6) Å, α = (1), β = (1), γ = (2), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.973 T 0.998), Z = 2, triclinic, space group P1 (No. 2), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), 8122 independent (R int = 0.067) and 5633 observed reflections [I>2σ(I)], 603 refined parameters, R = 0.087, wr 2 = 0.233, max. (min.) residual electron density 0.29 (-0.29) e.å -3, hydrogen atoms were calculated and refined as riding atoms. Figure S18: X-ray crystal structure of compound 10b (thermal ellipsoids are shown at the 30% probability level) S17

18 Synthesis of compound 11 Scheme S4 A solution of compound 10a (515.2 mg, mol, 1.0 eq) in toluene (5 ml) was stirred at 80 C for 3 days. Then all volatiles were removed in vacuo and the resulting sticky residue was dissolved in pentane (3 ml), which was subsequently removed in vacuo. After suspending the obtained sticky solid in pentane (3 ml) the precipitate was collected, washed with pentane (3 x 2 ml) and dried in vacuo to give compound 11 as a white solid (454.2 mg, mol, 88%). IR (KBr): ṽ [cm -1 ] = 3696 (w), 3027 (m), 2959 (m), 2934 (s), 2856 (m), 2797 (w), 2295 (w), 1642 (m), 1602 (s), 1556 (w), 1515 (s), 1460 (s), 1384 (m), 1283 (m), 1246 (m), 1204 (w), 1094 (s), 1040 (w), 1011 (w), 968 (s), 907 (w), 853 (s), 834 (w), 769 (m), 739 (s), 702 (s), 675 (m), 640 (m), 597 (w), 555 (s), 534 (w), 510 (w), 482 (w), 427 (m). M.p. 130 C. Anal. Calc. for C 46H 38BF 10P: C: 67.17; H: Found: C: 66.79; H: A solution of the white solid in dichloromethane-d 2 showed at 213 K a mixture of two isomers 11 and 11 [ratio ca. 77 : 23 ( 31 P)]. Major component (11): 1 H NMR (500 MHz, dichloromethane-d 2, 213 K): δ 7.29 (m, 2H, m-ph), 7.22 (m, 2H, o-ph), 7.19 (m, 1H, p-ph), 7.00 (d, 4 J PH = 3.2 Hz, 1H, m-mes a ), 6.79 (m, 1H, m-mes b ), 6.78 (m, 1H, m -Mes a ), 6.51 (m, 1H, m -Mes b ), 5.88 (br, 1H, 3-CH), 4.14 (br d, J = 10.3 Hz, 1H, 4-CH), 2.62 Mes,b Mes,a Mes,a (s, 3H, o-ch 3 ), 2.45 (s, 3H, o-ch 3 ), 2.34 (m, 1H, 5-CH), 2.26 (s, 3H, p-ch 3 ), 2.15 Mes,b (s, 3H, p-ch 3 ), 2.09 (2H), 1.47 (1H), 1.07 (1H), 1.29 (1H), 0.63 (1H), 1.17 (1H), 0.81 (1H)(each m, CH 2), Mes,b Mes,a 1.96 (s, 3H, o -CH 3 ), 1.83 (s, 3H, o -CH 3 ). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 213 K): δ (br dm, J = 3.8 Hz, 10-C) t, (br, 2-C) t, (d, 2 J PC = 19.1 Hz, o-mes a ), (i-ph) t, (d, 2 J PC = 6.5 Hz, o-mes b ), (d, 2 J PC = 6.5 Hz, o -Mes a ), (d, 2 J PC = 14.9 Hz, o -Mes b ), (d, 4 J PC = 3.1 Hz, p- Mes a ), (d, 4 J PC = 2.1 Hz, p-mes b ), (d, 3 J PC = 7.2 Hz, m -Mes a ), (d, 3 J PC = 11.2 Hz, m-mes a ), (d, 3 J PC = 7.8 Hz, m-mes b ), (o-ph), (d, 3 J PC = 9.9 Hz, m - Mes b ), (m-ph), (d, 1 J PC = 53.5 Hz, 1-C), (p-ph), (br d, J = 42.7 Hz 3- CH), (d, 1 J PC = 41.9 Hz, i-mes b ), (d, 1 J PC = 25.6 Hz, i-mes a ), 47.9 (d, 3 J PC = 10.9 Hz, S18

19 5-CH), 45.6 (4-CH), 33.5 (dm, J = 6.8 Hz), 27.8, 27.6, 25.8 (CH 2), 25.4 (d, 3 J PC = 10.5 Hz, o- Mes,a CH 3 ), 24.3 (d, 3 Mes,a Mes,b Mes,b J PC = 3.3 Hz, o -CH 3 ), 22.9 (m, o-ch 3 ), 20.7 (m, o -CH 3 ), 20.6 Mes,a Mes,b (d, J = 1.4 Hz, p-ch 3 ), 20.3 (d, J = 1.1 Hz, p-ch 3 ). [C 6F 5 not listed, t tentatively assigned]. 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 213 K): δ 10.4 ( 1/2 ~ 40 Hz) 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 213 K): δ 3.6 (broad). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 299 K): δ 6.4 ( 1/2 ~ 550 Hz) 19 F NMR (470 MHz, dichloromethane-d 2, 213 K): δ , , , (each br, each 1F, o-c 6F 5), (br t, 3 J FF = 19.7 Hz), (br t, 3 J FF = 20.8 Hz)(each 1F, p-c 6F 5), , (each m, each 2F, m-c 6F 5). Minor component (11 ): 1 H NMR (500 MHz, dichloromethane-d 2, 213 K): δ 7.20 (m, 2H, m-ph), 7.16 (m, 2H, o-ph), 7.14 (m, 1H, p-ph), 7.01 (br, 1H, m-mes a ), 6.94 (br, 1H, m-mes b ), 6.80 (br, 1H, m -Mes a ), 6.47 (br, 1H, m -Mes b ), 5.92 (br, 1H, 3-CH), 3.47 (br m, 1H, 4-CH), 2.78 (m, 1H, 5-CH), 2.76 (s, 3H, Mes,b Mes,a Mes,a Mes,b o-ch 3 ), 2.27 (s, 3H, p-ch 3 ), 2.21 (s, 3H, o-ch 3 ), 2.18 (s, 3H, p-ch 3 ), 2.14 (1H), 1.61 (1H), 1.48 (1H), 1.46 (1H), 1.27 (1H), 1.14 (1H), 1.05 (1H), 0.94 (1H)(each m, CH 2), 1.98 Mes,b Mes,a (s, 3H, o -CH 3 ), 1.76 (s, 3H, o -CH 3 ). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 213 K): δ (br d, J =.4.2 Hz, 10-C), (d, 2 J PC = 20.0 Hz, o-mes a ), (m, o-mes b ), (i-ph) t, (m, o -Mes b ), (m, p- Mes a ), (d, 2 J PC = 6.5 Hz, o -Mes a ), (m, p-mes b ), (d, 3 J PC = 8.2 Hz, m -Mes a ), (d, 3 J PC = 10.1 Hz, m-mes a ), (d, 3 J PC = 8.2 Hz, m-mes b ), (o-ph), (d, 1 J PC = 53.2 Hz, 1-C), (m, m -Mes b ), (m-ph), (br, 3-CH), (p-ph), (d, 1 J PC = 41.6 Hz, i-mes b ), (d, 1 J PC = 26.6 Hz, i-mes a ), 45.4 (br, 4-CH), 39.8 (d, 3 J PC = 9.6 Hz, 5-CH), 31.7 (d, 3 J PC = 8.2 Hz), 28.5, 25.2, 23.3 (CH 2), 24.2 (d, 3 J PC = 3.3 Hz, o - Mes,a CH 3 ), 24.2 (d, 3 Mes,a Mes,b Mes,b J PC = 9.0 Hz, o-ch 3 ), 21.4 (m, o-ch 3 ), 20.7 (m, o -CH 3 ), 20.6 Mes,a Mes,b (m, p-ch 3 ), 20.4 (p-ch 3 ), n.o. 2-C. [C 6F 5 not listed, t tentatively assigned]. 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 213 K): δ 12.7 (partial relaxed br 1:1:1:1 q, 1 J PB ~ 15 Hz) 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 213 K): δ 3.6 (broad). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 299 K): δ 6.4 ( 1/2 ~ 550 Hz) 19 F NMR (470 MHz, dichloromethane-d 2, 213 K): δ , , , (each m, each 1F, o-c 6F 5), (br t, 3 J FF = 19.8 Hz), (t, 3 J FF = 20.2 Hz)(each 1F, p-c 6F 5), (2F), (1F), (1F)(each m, m-c 6F 5). S19

20 Figure S19: 1 H NMR (500 MHz, dichloromethane-d2, 213 K) spectrum of compound 11 [admixed with pentane] Figure S20: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 213 K) spectrum of compound 11 [admixed with pentane] S20

21 Figure S21: 19 F NMR (470 MHz, dichloromethane-d2, 213 K) spectrum of compound 11 Figure S22: 31 P{ 1 H} NMR (202 MHz, dichloromethane-d2) spectra of compound 11 at 299 K (1) and 213 K (2). Figure S23: 11 B{ 1 H} NMR (160 MHz, dichloromethane-d2) spectra of compound 11 at 299 K (1) and 213 K (2) S21

22 Figure S24: Dynamic 1 H NMR (500 MHz, dichloromethane-d2) spectra of compound 11 [admixed with pentane] Figure S25: Dynamic 19 F NMR (470 MHz, dichloromethane-d2) spectra of compound 11 S22

23 G [T c, (T)] = RT c( ln(tc/ )) [J/mol] T c= coalescence temperature [K]: 286 K ( 19 F, p-bc 6F 5) = chemical shift difference [Hz]: ( 19 F, p-bc 6F 5, 233 K): 476 Hz R = J/(mol K); 1 J = cal G [286 K, (233 K) = 476 Hz] = J/mol = 12.8 ± 0.3 kcal/mol Crystals suitable for the X-ray crystal structure analysis were obtained by slow diffusion of pentane into a solution of compound 11 in dichloromethane at -35 C: X-ray crystal structure analysis of compound 11: A colorless prism-like specimen of C 46H 38BF 10P C 5H 12, approximate dimensions mm x mm x mm, was used for the X-ray crystallographic analysis. The X-ray intensity data were measured. A total of 346 frames were collected. The total exposure time was 4.33 hours. The frames were integrated with the Bruker SAINT software package using a narrow-frame algorithm. The integration of the data using a monoclinic unit cell yielded a total of reflections to a maximum θ angle of (0.83 Å resolution), of which 7874 were independent (average redundancy 6.145, completeness = 99.9%, R int = 10.95%, R sig = 6.65%) and 5407 (68.67%) were greater than 2σ(F 2 ). The final cell constants of a = (7) Å, b = (9) Å, c = (5) Å, β = (10), volume = (3) Å 3, are based upon the refinement of the XYZ-centroids of 9539 reflections above 20 σ(i) with < 2θ < Data were corrected for absorption effects using the multi-scan method (SADABS). The ratio of minimum to maximum apparent transmission was The calculated minimum and maximum transmission coefficients (based on crystal size) are and The structure was solved and refined using the Bruker SHELXTL Software Package, using the space group P 1 21/n 1, with Z = 4 for the formula unit, C 46H 38BF 10P C 5H 12. The final anisotropic full-matrix least-squares refinement on F 2 with 620 variables converged at R1 = 5.00%, for the observed data and wr2 = 10.32% for all data. The goodness-of-fit was The largest peak in the final difference electron density synthesis was e - /Å 3 and the largest hole was e - /Å 3 with an RMS deviation of e - /Å 3. On the basis of the final model, the calculated density was g/cm 3 and F(000), 1864 e -. S23

24 Figure S26: X-ray crystal structure of compound 11 (thermal ellipsoids are shown at the 50% probability level) Synthesis of compound 12 Scheme S5 A solution of TEMPO (152.0 mg, mol, 2.0 eq) in benzene (2 ml) was added to a solution of compound 11 (400.0 mg, mol, 1.00 eq) in benzene (3 ml). The reaction mixture was stirred at 60 C for 2 days. Then all volatiles were removed in vacuo and the resulting sticky red residue was dissolved in pentane (3 ml), which was subsequently removed in vacuo. After addition of pentane (3 ml) to the obtained residue the resulting suspension was stored at -35 C for 1 day. Subsequently the off-white solid material was collected and washed with cold pentane (5 x 2 ml) to yield compound 12 as a white fluffy solid (319.2 mg, 0.4 mmol, 80%). S24

25 IR (KBr): ṽ [cm -1 ] = 3688 (m), 3016 (w), 3028 (w), 2935 (m), 2860 (m), 2773 (w), 2739 (w), 2473 (w), 2399 (w), 2348 (w), 2314 (w), 1962 (w), 1886 (w), 1812 (w), 1735 (w), 1642 (s), 1603 (s), 1559 (m), 1515 (s), 1464 (m), 1381 (m), 1324 (w), 1305 (m), 1270 (m), 1260 (m), 1201 (w), 1178 (m), 1160 (m), 1092 (s), 1030 (m), 962 (s), 894 (m), 851 (s), 771 (s), 704 (s), 678 (m), 637 (m), 574 (w), 554 (m), 509 (w), 473 (w), 440 (m), 408 (w). M.p. 136 C. Anal. Calc. for C 46H 36BF 10P: C: 67.33; H: Found: C: 67.65; H: H NMR (500 MHz, dichloromethane-d 2, 299 K): δ 7.42 (3H), 7.34 (3H)(each m, Ph, 3-CH), 6.81 (d, 4 J PH = 3.2 Hz, 4H, m-mes), 2.55 (2H), 2.37 (2H), 1.60 (4H) (each br m, CH 2), 2.25 (s, Mes Mes 6H, p-ch 3 ), 2.09 (s, 12H, o-ch 3 ). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 299 K): δ (br d, 2 J PC = 30.2 Hz, 2-C), 148.2, (d, J = 2.8 Hz) (d, J = 0.9 Hz), (d, J = 8.5 Hz)(4,5,10-C) t, (dm, 1 J FC~ 240 Hz, C 6F 5), (br d, 2 J PC = 8.9 Hz, o-mes), (d, J = 1.9 Hz, i-ph), (br d, 4 J PC = 2.9 Hz p-mes), (dm, 1 J FC~ 250 Hz, C 6F 5), (dm, 1 J FC~ 250 Hz, C 6F 5), (d, 1 J PC = 53.5 Hz, 1-C) t, (dm, J = 46.2 Hz, 3-CH), (br d, 3 J PC = 8.9 Hz, m-mes), 129.5, 128.4, (p) (Ph), (br, i-c 6F 5), (br dm, 1 J PC = 35.1 Hz, i-mes), 28.7 (d, J = 1.0 Hz), 27.9 (d, J = 4.1 Hz), 23.5, 22.4 (CH 2), 22.8 (br dm, 3 Mes J PC = 5.4 Hz, o-ch 3 ), 20.8 (d, J = 1.4 Hz, Mes p-ch 3 ). [ t tentatively assigned]. 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 299 K): δ 5.8 ( 1/2 ~ 36 Hz). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 299 K): δ 5.7 ( 1/2 ~ 500 Hz). 19 F NMR (470 MHz, dichloromethane-d 2, 299 K): δ (br, 2F, o-c 6F 5), (t, 1F, 3 J FF = 20.2 Hz, p-c 6F 5), (m, 2F, m-c 6F 5)[ 19 F mp = 6.4]. 1 H NMR (500 MHz, dichloromethane-d 2, 193 K): δ 7.39 (2H), 7.31 (4H)(each m, Ph, 3-CH), 6.94 (d, 4 J PH = 2.3 Hz, 1H, m-mes a ), 6.85 (s, 1H, m -Mes a ), 6.66 (s, 1H, m-mes b ), 6.52 (d, 4 J PH = 2.0 Hz, 1H, m -Mes b ), 2.55 (2H), 2.43 (1H), 1.97 (1H), 1.61 (1H), 1.52 (2H), 1.38 (1H) (each br m, CH 2), Mes,a Mes,b Mes,b 2.25 (s, 3H, p-ch 3 ), 2.09 (s, 3H, p-ch 3 ), 2.06 (s, 3H, o -CH 3 ), Mes,b Mes,a Mes,a 2.03 (s, 3H, o-ch 3 ), 1.96 (s, 3H, o-ch 3 ), 1.83 (s, 3H, o -CH 3 ). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 193 K): δ (br d, 2 J PC = 30.6 Hz, 2-C), 146.8, 137.7, (d, J = 8.4 Hz)(4,5,10-C) t, (d, 2 J PC = 18.3 Hz, o-mes a ), (o -Mes a ), (m, i-ph), (p-mes a ), (d, 2 J PC = 16.0 Hz, o -Mes b ), (o-mes b ), (m, p-mes b ), (d, 1 J PC = 54.2 Hz, 1-C) t, (br d, 3 J PC = 7.0 Hz, m -Mes a ), (dd, J = 45.0 Hz, J = 12.0 Hz, 3-CH), (br d, 3 J PC = 10.7 Hz, m-mes a ), (d, 3 J PC = 7.4 Hz, m- Mes b ), 128.8, 128.4, 127.8, 127.5, (p) (each br, Ph), (d, 3 J PC = 9.4 Hz, m -Mes b ), (d, 1 J PC = 40.3 Hz, i-mes b ), (d, 1 J PC = 28.5 Hz, i-mes a ), 28.2, 27.2 (d, J = 3.7 Hz), 22.6, 21.5 (CH 2), 24.7 (d, 3 Mes,a J PC = 3.6 Hz, o -CH 3 ), 22.9 (dd, J = 10.1 Hz, J = 4.0 Hz, o- S25

26 Mes,a Mes,b Mes,b Mes,a Mes,b CH 3 ), 21.0 (m, o-ch 3 ), 20.7 (m, o -CH 3 ), 20.5 (p-ch 3 ), 20.0 (p-ch 3 ). [C 6F 5 not listed; t tentatively assigned]. 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 193 K): δ 4.1 ( 1/2 ~ 40 Hz). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 193 K): δ 2.0 (broad). 19 F NMR (470 MHz, dichloromethane-d 2, 193 K): δ (m, o), (m, o ), (br t, 3 J FF = 21.4 Hz, p), (m, m), (m, m )(each 1F, C 6F 5)[ 19 F mp = 5.6, 5.8], (m, 1F, o), (m, 1F, o ), (br t, 1F, 3 J FF = 21.6 Hz, p), (m, 2F, m,m )(C 6F 5)[ 19 F mp = 7.7]. Figure S27: 1 H NMR (500 MHz, dichloromethane-d2, 193 K) spectrum of compound 12 [admixed with pentane] S26

27 Figure S28: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 193 K) spectrum of compound 12 [admixed with pentane] Figure S29: 19 F NMR (470 MHz, dichloromethane-d2, 193 K) spectrum of compound 12 S27

28 Figure S30: 31 P{ 1 H} NMR (202 MHz, dichloromethane-d2, 193 K) spectrum of compound 12 Figure S31: 11 B{ 1 H} NMR (160 MHz, dichloromethane-d2) spectra of compound 12 at 299 K (1) and 193 K (2) S28

29 Figure S32: Dynamic 1 H NMR (500 MHz, dichloromethane-d2) spectra of compound 12 [admixed with pentane] Figure S33: Dynamic 19 F NMR (470 MHz, dichloromethane-d2) spectra of compound 12 S29

30 G [T c, (T)] = RT c( ln(tc/ )) [J/mol] T c= coalescence temperature [K]: 243 K ( 19 F, p-bc 6F 5) = chemical shift difference [Hz] ( 19 F, p-bc 6F 5, 193 K): 426 Hz R = J/(mol K); 1 J = cal G [243 K, (193 K) = 426 Hz] = J/mol = 10.8 ± 0.3 kcal/mol Crystals suitable for the X-ray crystal structure analysis were obtained by slow diffusion of pentane into a solution of compound 12 in dichloromethane at -35 C: X-ray crystal structure analysis of compound 12: formula C 46H 36BF 10P, M = , colourless crystal, 0.08 x 0.06 x 0.02 mm, a = (3), b = (5), c = (3) Å, β = (1), V = (2) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.989 T 0.997), Z = 4, monoclinic, space group P2 1/n (No. 14), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), 7819 independent (R int = 0.103) and 5035 observed reflections [I>2σ(I)], 529 refined parameters, R = 0.106, wr 2 = 0.234, max. (min.) residual electron density 0.90 (-0.47) e.å -3, hydrogen atoms were calculated and refined as riding atoms. Figure S34: X-ray crystal structure of compound 12 (thermal ellipsoids are shown at the 30% probability level) S30

31 Synthesis of compound 13 Scheme S6 Phenylacetylene (12.4 mg, 122 µmol, 1.0 eq) was added dropwise to a solution of compound 11 (100 mg, 122 µmol, 1.0 eq) in toluene (4 ml) at ambient temperature and then the reaction mixture was stirred for 16 hours at 80 C. Subsequently all volatiles were removed in vacuo and the resulting yellow oil suspended in pentane (2 ml). Then the reaction suspension was dried in vacuo and the resulting solid was washed with pentane (3 x 2 ml). After drying in vacuo, compound 13 was obtained as a white solid (43.8 mg, 47.4 μmol; 39%). IR (KBr): ṽ [cm -1 ] = 3060 (w), 3027 (w), 2931 (w), 2361 (w) 1945 (w), 1747 (w), 1639 (w), 1603 (w), 1547 (w), 1511 (m), 1452 (s), 1382 (w), 1296 (w), 1269 (m), 1248 (m), 1154 (w), 1083 (s), 1033 (w), 966 (s), 910 (w), 854 (w), 784 (w), 757 (m), 738 (w), 696 (m), 645 (m), 605 (w), 558 (w), 490 (w), 421 (w). M.p. 182 C. Anal. Calc. for C 54H 44BF 10P: C: 70.14; H: Found: C: 68.60; H: H NMR (500 MHz, dichloromethane-d 2, 253 K): δ 9.70 (d, 1 J PH = Hz, PH), 7.31 (m, 2H, o-ph ), 7.30 (m, 2H, m-ph), 7.24 (m, 2H, m-ph ), 7.21 (m, 1H, p-ph ), 7.20 (m, 1H, p-ph), 7.15 (m, 2H, o-ph), 6.91 (br d, 3 J PH = 4.1 Hz, 1H, m-mes a ), 6.84 (br d, 3 J PH = 4.4 Hz, 1H, m- Mes b ), 6.82 (br d, 3 J PH = 3.8 Hz, 1H, m -Mes a ), 6.77 (br d, 3 J PH = 4.6 Hz, 1H, m -Mes b ), 5.90 (br, 1H, 3-CH), 3.82 (dm, 3 Mes,b J HH = 8.8 Hz, 1H, 4-CH), 2.66 (s, 3H, o-ch 3 ), 2.65 (s, 3H, o- Mes,a CH 3 ), 2.52/2.04, 1.72/1.24, 1.63/1.17, 1.47/0.95 (each m, each 1H, CH 2), 2.34 (m, 1H, 5- Mes,b Mes,a Mes,b CH), 2.26 (s, 3H, p-ch 3 ), 2.23 (s, 3H, p-ch 3 ), 1.89 (s, 3H, o -CH 3 ), 1.77 (s, 3H, Mes,a o -CH 3 ). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 253 K): δ (d, 2 J PC = 7.7 Hz, 10-C) t, (d, 2 J PC = 9.2 Hz, o-mes b ), (d, 4 J PC =2.8 Hz, p-mes a ), (d, 4 J PC = 2.8 Hz, p-mes b ), (d, 2 J PC = 11.0 Hz, o-mes a ), (d, 2 J PC = 9.4 Hz, o -Mes a ), (i-ph), (d, 2 J PC = 10.9 Hz, o -Mes b ), (br dm, J = 14.2 Hz, 3-CH), (d, 3 J PC = 11.3 Hz, m - Mes a ), (d, 3 J PC = 11.5 Hz, m-mes b ), (o-ph ), (d, 3 J PC = 10.8 Hz, m -Mes b ), (d, 3 J PC = 10.7 Hz, m-mes a ), (o-ph), (m-ph), (m-ph ), (i-ph ), (p-ph ), (p-ph), (d, 1 J PC = 77.8 Hz, i-mes a ), (d, 1 J PC = 83.4 Hz, i- S31

32 Mes b ), (d, 1 J PC = 73.1 Hz, 1-C) t, (br 1:1:1:1 q, 1 J CB ~ 80 Hz, BC ), 98.7 (br, PhC ), 51.3 (d, 3 J PC = 12.4 Hz, 5-CH), 43.0 (4-CH), 35.0 (d, 3 J PC = 9.8 Hz), 31.7, 29.2, 26.3 (CH 2), 23.8 (d, 3 Mes,a J PC = 10.7 Hz, o-ch 3 ), 22.3 (d, 3 Mes,a J PC = 5.8 Hz, o -CH 3 ), 21.5 (d, 3 J PC = Mes,b Mes,a Mes,b 4.4 Hz, o-ch 3 ), 21.1 (p-ch 3 ), 20.9 (p-ch 3 ), 20.4 (d, 3 Mes,b J PC = 10.4 Hz, o -CH 3 ), n.o. (2-C). [C 6F 5 not listed; t tentatively assigned]. 31 P NMR (202 MHz, dichloromethane-d 2, 253 K): δ (d, 1 J PH = Hz). 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 253 K): δ ( 1/2 ~ 15 Hz ). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 253 K): δ 17.7 ( 1/2 ~ 50 Hz) 19 F NMR (470 MHz, dichloromethane-d 2, 253 K): δ (br, 2F, o), (t, 3 J FF = 20.8 Hz, 1F, p), (m, 2F, m)(c 6F 5)[ 19 F mp = 3.2], (m, 2F, o), (t, 3 J FF = 20.7 Hz, 1F, p), (m, 2F, m)(c 6F 5)[ 19 F mp = 4.9]. Figure S35: 1 H NMR (500 MHz, dichloromethane-d2, 253 K) spectrum of compound 13 S32

33 Figure S36: 13 C NMR (126 MHz, dichloromethane-d2, 253 K) spectrum of compound 13 Figure S37: 19 F NMR (470 MHz, dichloromethane-d2, 253 K) spectrum of compound 13 S33

34 Figure S38: 31 P{ 1 H} NMR (1) and 31 P NMR (2) (202 MHz, dichloromethane-d2, 253 K) spectra of compound 13 Figure S39: 11 B{ 1 H} NMR (160 MHz, dichloromethane-d2, 253 K) spectrum of compound 13 Crystals suitable for the X-ray crystal structure analysis were obtained from a dichloromethane solution of compound 13 at -35 C: X-ray crystal structure analysis of compound 13: A colorless prism-like specimen of C 61H 52BF 10P, approximate dimensions mm x mm x mm, was used for the X-ray crystallographic analysis. The X-ray intensity data were measured. A total of 460 frames were collected. The total exposure time was 4.47 hours. The frames were integrated with the Bruker SAINT software package using a narrow-frame algorithm. The integration of the data using a monoclinic unit cell yielded a total of reflections to a maximum θ angle of S34

35 (0.80 Å resolution), of which were independent (average redundancy 3.970, completeness = 99.9%, R int = 5.56%, R sig = 4.69%) and 8954 (87.49%) were greater than 2σ(F 2 ). The final cell constants of a = (7) Å, b = (5) Å, c = (7) Å, β = (2), volume = (2) Å 3, are based upon the refinement of the XYZ-centroids of 9863 reflections above 20 σ(i) with < 2θ < Data were corrected for absorption effects using the multi-scan method (SADABS). The ratio of minimum to maximum apparent transmission was The calculated minimum and maximum transmission coefficients (based on crystal size) are and The structure was solved and refined using the Bruker SHELXTL Software Package, using the space group P 1 n 1, with Z = 2 for the formula unit, C 61H 52BF 10P. The final anisotropic full-matrix least-squares refinement on F 2 with 669 variables converged at R1 = 3.89%, for the observed data and wr2 = 8.45% for all data. The goodness-of-fit was The largest peak in the final difference electron density synthesis was e - /Å 3 and the largest hole was e - /Å 3 with an RMS deviation of e - /Å 3. On the basis of the final model, the calculated density was g/cm 3 and F(000), 1056 e -. Figure S40: X-ray crystal structure of compound 13 (thermal ellipsoids are shown at the 50% probability level) S35

36 Synthesis of compound 14 Scheme S7 A yellow solution of compound 12 (200.0 mg, mol, 1.0 eq) in CH 2Cl 2 (2 ml) was degassed at -78 C and then exposed to a dihydrogen atmosphere (1.5 bar) at room temperature. The solution was stirred for 24 h at ambient temperature, before all volatiles were removed in vacuo. The obtained off-white residue was washed with pentane (3 x 2 ml) and dried in vacuo to give compound 14 as a white solid (175.7 mg, mol, 88%). IR (KBr): ṽ [cm -1 ] = 3418 (w), 3316 (w), 3055 (w), 3028 (w), 2941 (w), 2854 (w), 2443 (w), 2360 (w), 1939 (w), 1775 (w), 1639 (m), 1604 (m), 1559 (w), 1509 (s), 1461 (s), 1380 (m), 1332 (w), 1293 (w), 1271 (m), 1206 (w), 1176 (w), 1134 (w), 1083 (s), 1030 (m), 967 (s), 905 (m), 857 (m), 768 (m), 741 (w), 698 (m), 678 (w), 647 (m), 617 (w), 575 (w), 555 (m), 512 (w), 488 (w), 429 (m). Decomp. 167 C. Anal. Calc. for C 46H 38BF 10P: C: 67.17; H: Found: C: 67.36; H: H NMR (600 MHz, dichloromethane-d 2, 299 K): δ 9.48 (d, 1 J PH = Hz, 1H, PH), 7.38 (m, 2H, m-ph), 7.31 (m, 1H, p-ph), 7.24 (m, 2H, o-ph), 7.22 (d, 4 J PH = 5.5 Hz, 1H, 3-CH), 7.07 (d, 4 J PH = 4.4 Hz, 1H, m-mes a ), 7.00 (d, 4 J PH = 4.6 Hz, 1H, m-mes b ), 6.96 (d, 1H, 4 J PH = 3.5 Hz, m -Mes a ), 6.81 (d, 4 J PH = 4.4 Hz, 1H, m -Mes b ), 3.90 (partial relaxed 1:1:1:1 q, 1 J BH ~ 85 Hz, 1H, BH), 2.67/ 2.20 (each m, each 1H, 9-CH 2) t, 2.54 (m, 2H, 6-CH 2) t Mes,a, 2.34 (s, 3H, p-ch 3 ), Mes,b Mes,a Mes,b 2.32 (s, 3H, p-ch 3 ), 2.31 (s, 3H, o-ch 3 ), 2.23 (s, 3H, o-ch 3 ), 2.14 (s, 3H, o - Mes,b Mes,a CH 3 ), 1.91 (s, 3H, o -CH 3 ), 1.69 (1H), 1.50 (2H), 1.39 (1H)(each m, 7,8-CH 2) t. [ t tentatively assigned] 13 C{ 1 H} NMR (151 MHz, dichloromethane-d 2, 299 K): δ (d, 4 J PC = 3.9 Hz, 4-C), (d, 4 J PC = 2.8 Hz, p-mes b ), (d, 4 J PC = 3.0 Hz, p-mes a ), (d, 2 J PC = 10.1 Hz, o -Mes b ), (d, 2 J PC = 11.8 Hz, o-mes a ), (d, 2 J PC = 8.4 Hz, o -Mes a ), (d, 2 J PC = 9.9 Hz, o- Mes b ), (d, J = 0.9 Hz, i-ph), (d, 2 J PC = 14.2 Hz, 10-C) t, (br d, 3 J PC = 16.8 Hz, 3-CH), (d, 3 J PC = 12.4 Hz, 5-C) t, (d, 3 J PC = 11.0 Hz, m -Mes a ), (d, 3 J PC = 11.5 Hz, m -Mes b ), (d, 3 J PC = 10.6 Hz, m-mes a ), (d, 3 J PC = 10.5 Hz, m-mes b ), (o-ph), (m-ph), (p-ph), (d, 1 J PC = 83.1 Hz, 1-C), (d, 1 J PC = 76.3 Hz, i- Mes a ), (d, 1 J PC = 80.9 Hz, i-mes b ), 32.1 (d, 3 J PC = 7.7 Hz, 9-CH 2) t, 28.1 (d, 4 J PC = 1.6 Hz, S36

37 6-CH 2) t, 22.5 (7,8-CH 2) t, 22.4 (d, 3 Mes,a Mes,a J PC = 5.2 Hz, o -CH 3 ), 21.4 (d, J = 1.4 Hz, p-ch 3 ), 21.3 (d, 3 Mes,a Mes,b J PC = 11.5 Hz, o-ch 3 ), 21.2 (p-ch 3 ), 21.1 (br d, 3 Mes,b J PC = 6.1 Hz, o -CH 3 ), 21.0 (d, 3 Mes,b J PC = 11.9 Hz, o-ch 3 ), n.o. (2-C).[C 6F 5 not listed; t tentatively assigned] 31 P NMR (243 MHz, dichloromethane-d 2, 299 K): δ (br d, 1 J PH ~ 508 Hz). 31 P{ 1 H} NMR (243 MHz, dichloromethane-d 2, 299 K): δ (m). 11 B NMR (192 MHz, dichloromethane-d 2, 299 K): δ 20.8 (d, 1 J BH ~ 83 Hz) 11 B{ 1 H} NMR (192 MHz, dichloromethane-d 2, 299 K): δ 20.8 ( 1/2 ~ 55 Hz) 19 F NMR (564 MHz, dichloromethane-d 2, 299 K): δ (m, 2F, o), (t, 3 J FF = 20.1 Hz, 1F, p), (m, 2F, m)(c 6F 5)[ 19 F mp = 3.7], (m, 2F, o), (t, 3 J FF = 20.1 Hz, 1F, p), (m, 2F, m)(c 6F 5)[ 19 F mp = 3.6]. Figure S41: 1 H NMR (600 MHz, dichloromethane-d2, 299 K) spectrum of compound 14 S37

38 Figure S42: 13 C{ 1 H} NMR (151 MHz, dichloromethane-d2, 299 K) spectrum of compound 14 Figure S43: 19 F NMR (564 MHz, dichloromethane-d2, 299 K) spectrum of compound 14 Figure S44: 31 P{ 1 H} NMR (1) and 31 P NMR (2) (243 MHz, dichloromethane-d2, 299 K) spectra of compound 14 S38

39 Figure S45: 11 B{ 1 H} NMR (1) and 11 B NMR (2) (192 MHz, dichloromethane-d2, 299 K) spectra of compound 14 Crystals suitable for the X-ray crystal structure analysis were obtained from a solution of compound 14 in dichloromethane at -35 C: X-ray crystal structure analysis of compound 14: formula C 46H 38BF 10P CH 2Cl 2, M = , colourless crystal, 0.07 x 0.06 x 0.04 mm, a = (3), b = (3), c = (5) Å, α = (1), β = (1), γ = (2), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.981 T 0.989), Z = 2, triclinic, space group P1 (No. 2), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), 7274 independent (R int = 0.038) and 4952 observed reflections [I>2σ(I)], 592 refined parameters, R = 0.085, wr 2 = 0.177, max. (min.) residual electron density 0.40 (- 0.29) e.å -3. The hydrogen atoms at P1 and B1 were refined freely; others were calculated and refined as riding atoms. S39

40 Figure S46: X-ray crystal structure of compound 14 (thermal ellipsoids are shown at the 30% probability level) Generation of compound 14-D2 Scheme S8 A yellow solution of compound 12 (20.0 mg, 24.4 mol, 1.0 eq) in CD 2Cl 2 (0.5 ml) was degassed at -78 C using a J-Young NMR tube. Then the solution was exposed to a deuterium gas atmosphere (1.5 bar). After shaking the tube for 16 h at room temperature, the reaction mixture was characterized by NMR experiments. A mixture of compounds 12 and 14-D 2 (12 : 14-D 2 ~ 54 : 46 ( 31 P{ 1 H}) was observed. S40

41 The NMR data of compounds 14-D 2 and 12 are consistent with those listed for isolated compounds 14 and 12 (see above). Compound 14-D 2 2 H NMR (92 MHz, dichloromethane, 299 K): δ 9.46 (d, 1 J PD = 77.1 Hz, 1D, PD), 3.88 (br, 1D, BD). 31 P NMR (243 MHz, dichloromethane-d 2, 299 K): δ (br 1:1:1 t, 1 J PD ~ 79 Hz). 31 P{ 1 H} NMR (243 MHz, dichloromethane-d 2, 299 K): δ (br 1:1:1 t, 1 J PD ~ 79 Hz). 11 B NMR (192 MHz, dichloromethane-d 2, 299 K): δ 21.0 ( 1/2 ~ 70 Hz) 11 B{ 1 H} NMR (192 MHz, dichloromethane-d 2, 299 K): δ 21.0 ( 1/2 ~ 70 Hz) 19 F NMR (564 MHz, dichloromethane-d 2, 299 K): δ , (each m, each 2F, o), , (each t, 3 J FF = 20.1 Hz, each 1F, p), , (each m, each 2F, m)(c 6F 5). Figure S47: 1 H NMR (600 MHz, dichloromethane-d2, 299 K) spectra of (1) the isolated compound 14 and (2) the reaction of compound 12 with D2; (3) 1 H NMR (500 MHz, dichloromethane-d2, 299 K) spectrum of the isolated compound 12. S41

42 Figure S48: 19 F NMR (564 MHz, dichloromethane-d2, 299 K) spectra of (1) the isolated compound 14 and (2) the reaction of compound 12 with D2; (3) 19 F NMR (470 MHz, dichloromethane-d2, 299 K) spectrum the isolated compound 12. Figure S49: 2 H NMR (92 MHz, dichloromethane, 299 K) spectrum of the reaction compound 12 with D2 S42

43 Figure S50: (1) 11 B{ 1 H} and (2) 11 B NMR (192 MHz, dichloromethane-d2, 299 K) spectra of the isolated compound 14; (3) 11 B NMR (192 MHz, dichloromethane-d2, 299 K) spectrum of the reaction of compound 12 with D2; (4) 11 B NMR (160 MHz, dichloromethane-d2, 299 K) spectrum of the isolated compound 12 Figure S51: (1) 31 P{ 1 H} and (2) 31 P NMR (243 MHz, dichloromethane-d2, 299 K) spectra of the isolated compound 14; (3) 31 P NMR (243 MHz, dichloromethane-d2, 299 K) spectrum of the reaction of compound 12 with D2; (5) 31 P NMR (202 MHz, dichloromethane-d2, 299 K) spectrum of the isolated compound 12 S43

44 Synthesis of compound 17 Scheme S9 A solution of dimethylacetylenedicarboxylate (17.9 L, 20.7 mg, mol, 1.0 eq) in toluene (1 ml) was added to a solution of compound 11 (120.0 mg, mol, 1.0 eq) in toluene (2 ml). The orange reaction mixture was stirred at 75 C for 6 days. Then all volatiles were removed in vacuo and the resulting sticky residue was dissolved in pentane (5 ml), which was subsequently removed in vacuo. After adding pentane (3 ml) to the obtained sticky solid the resulting suspension was filtered via cannula (Whatman glass fiber filter). The remaining solid was washed with pentane (5 x 3 ml) and dried in vacuo to give compound 17 as a pale yellow solid (70.8 mg, 73.4 mol, 50%). IR (KBr): ṽ [cm -1 ] = 3448 (w), 3193 (w), 3121 (w), 3604 (w), 3029 (m), 2991 (m), 2942 (m), 2862 (m), 2788 (w), 2735 (w), 2688 (w), 2390 (w), 2087 (w), 1946 (w), 1872 (w), 1792 (w), 1736 (s), 1683 (w), 1643 (m), 1605 (m), 1558 (w), 1515 (m),1451 (s), 1041 (w), 1377 (m), 1341 (m), 1276 (m), 1248 (m), 1206 (m), 1180 (w), 1148 (w), 1088 (s), 1030 (m), 972 (s), 926 (w), 859 (m), 801 (w), 783 (m), 741 (m), 691 (s), 658 (m), 642 (s), 616 (w), 654 (m), 525 (w), 460 (w), 435 (w). M.p. 259 C. Anal. Calc. for C 52H 44BF 10O 4P: C: 64.74; H: Found: C: 64.99; H: A solution of the yellow solid in dichloromethane-d 2 showed at 299 K a mixture of two compounds, the major component was assigned as compound 17, the minor one was not identified yet [ratio ca. 64 : 36 ( 31 P)]. [Ar = 4,6-dimethylphenylene] Major component 17: 1 H NMR (600 MHz, dichloromethane-d 2, 299 K): δ 7.23 (m, 2H, m-ph), 7.17 (m, 1H, p-ph), 7.11 (m, 1H, 3-CH Ar ), 7.00 (m, 2H, o-ph), 6.97 (br d, 4 J PH = 5.5 Hz, 1H, 5-CH Ar ), 6.75 (br d, 4 J PH = 2.7 Hz, 1H, m-mes), 6.57 (br d, 4 J PH = 3.9 Hz, 1H, m -Mes), 5.86 (m, 1H, 3-CH), 3.95 (dm, 3 J HH = 10.8 Hz, 1H, 4-CH), 3.68 (s, 3H, OMe C=O ), 3.49 (s, 3H, OMe), 2.72 (s, 3H, o - Mes CH 3 ), 2.55/2.06 (each m, each 1H, 9-CH 2), Ar 2.35 (s, 3H, 4-CH 3 ), 2.35 (m, 1H, 5-CH), 2.25 S44

45 Mes Mes Ar (s, 3H, o-ch 3 ), 2.20 (s, 3H, p-ch 3 ), 2.07 (s, 3H, 6-CH 3 ), 1.91 (s, 3H, CH 3), 1.53, 1.16 (each m, each 1H, 7-CH 2), 1.33/1.02 (each m, each 1H, 6-CH 2), 1.30/0.94 (each m, each 1H, 8-CH 2). 13 C{ 1 H} NMR (151 MHz, dichloromethane-d 2, 299 K): δ (d, 3 J PC = 6.9 Hz, O=C), (d, 2 J PC = 18.3 Hz, O 2C=), (d, 2 J PC = 21.8 Hz, 2-C Ar ), (d, 2 J PC = 6.7 Hz, 10-C), (d, 2 J PC = 10.0 Hz, o-mes), (d, 4 J PC = 2.7 Hz, 4-C Ar ), (d, 2 J PC = 12.7 Hz, o -Mes), (d, 4 J PC = 2.9 Hz, p-mes), (i-ph), (d, 2 J PC = 10.3 Hz, 6-C Ar ), (br, 2-C), (br, 3-CH), (d, 3 J PC = 10.3 Hz, 5-CH Ar ), (d, 3 J PC = 12.3 Hz, m -Mes), (d, 3 J PC = 11.0 Hz, m-mes), (o-ph), (m-ph), (p-ph), (d, 1 J PC = 81.6 Hz, 1-C), (d, 1 J PC = 86.5 Hz, 1-C Ar ), (d, 3 J PC = 10.2 Hz, 3-CH Ar ), (d, 1 J PC = 82.0 Hz, i-mes), 71.8 (d, 1 J PC = Hz, PC=), 56.7 (d, 2 J PC = 15.3 Hz, CMe), 53.7 (OMe), 52.4 (OMe C=O ), 48.4 (d, 3 J PC = 13.0 Hz, 5-CH), 43.8 (d, 4 J PC = 2.1 Hz, 4-CH), 33.5 (d, 3 J PC = 9.4 Hz, 9-CH 2), 29.7 (CH 3), 29.5 (m, 6-CH 2), 28.6 (d, J = 1.5 Hz, 8-CH 2), 26.6 (7-CH 2), 24.9 Mes (m, o -CH 3 ), 23.8 (d, 3 Mes Ar J PC = 6.8 Hz, o-ch 3 ), 21.7 (d, J = 1.3 Hz, 4-CH 3 ), 20.9 (d, 3 J PC = Ar Mes 3.7 Hz, 6-CH 3 ), 20.7 (p-ch 3 ). [C 6F 5 not listed] 31 P{ 1 H} NMR (243 MHz, dichloromethane-d 2, 299 K): δ 15.9 ( 1/2 ~ 4 Hz). 11 B{ 1 H} NMR (192 MHz, dichloromethane-d 2, 299 K): δ 0.8 ( 1/2 ~ 330 Hz). 19 F NMR (564 MHz, dichloromethane-d 2, 299 K): δ (m, o), (m, o ), (t, 3 J FF = 20.2 Hz, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F mp = 4.5, 5.1], (m, o), (m, o ), (t, 3 J FF = 20.4 Hz, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F mp = 3.7, 5.5]. Minor component: 31 P{ 1 H} NMR (243 MHz, dichloromethane-d 2, 299 K): δ 16.5 ( 1/2 ~ 30 Hz). 11 B{ 1 H} NMR (192 MHz, dichloromethane-d 2, 299 K): δ 0.8 ( 1/2 ~ 330 Hz). 19 F NMR (564 MHz, dichloromethane-d 2, 299 K): δ , , , (each br, each 1F, o), , (each br, each 1F, p), not resolved (4F, m)(c 6F 5). S45

46 Figure S52: 1 H NMR (600 MHz, dichloromethane-d2, 299 K) spectrum of compound 17 Figure S53: 13 C{ 1 H} NMR (151 MHz, dichloromethane-d2, 299 K) spectrum of compound 17 S46

47 Figure S54: 19 F NMR (564 MHz, dichloromethane-d2, 299 K) spectrum of compound 17 Figure S55: 31 P{ 1 H} NMR (243 MHz, dichloromethane-d2, 299 K) spectrum of compound 17 Figure S56: 11 B{ 1 H} NMR (192 MHz, dichloromethane-d2, 299 K) spectrum of compound 17 Crystals suitable for the X-ray crystal structure analysis were obtained from a dichloromethane solution of compound 17 at room temperature: X-ray crystal structure analysis of compound 17: A colorless prism-like specimen of C 52H 44BF 10O 4P, approximate dimensions mm x mm x mm, was used for the X-ray crystallographic analysis. The X-ray intensity data were measured. A total of 748 frames S47

48 were collected. The total exposure time was 8.31 hours. The frames were integrated with the Bruker SAINT software package using a narrow-frame algorithm. The integration of the data using a monoclinic unit cell yielded a total of 8271 reflections to a maximum θ angle of (0.84 Å resolution), of which 8271 were independent (average redundancy 1.000, completeness = 99.8%, R int = 8.35%, R sig = 3.22%) and 6534 (79.00%) were greater than 2σ(F 2 ). The final cell constants of a = (7) Å, b = (7) Å, c = (8) Å, β = (10), volume = (4) Å 3, are based upon the refinement of the XYZ-centroids of 9841 reflections above 20 σ(i) with < 2θ < Data were corrected for absorption effects using the multi-scan method (SADABS). The ratio of minimum to maximum apparent transmission was The calculated minimum and maximum transmission coefficients (based on crystal size) are and The structure was solved and refined using the Bruker SHELXTL Software Package, using the space group P 1 21/n 1, with Z = 4 for the formula unit, C 52H 44BF 10O 4P. The final anisotropic full-matrix least-squares refinement on F 2 with 621 variables converged at R1 = 4.87%, for the observed data and wr2 = 11.16% for all data. The goodness-of-fit was The largest peak in the final difference electron density synthesis was e - /Å 3 and the largest hole was e - /Å 3 with an RMS deviation of e - /Å 3. On the basis of the final model, the calculated density was g/cm 3 and F(000), 1992 e -. Figure S57: X-ray crystal structure of compound 17 (thermal ellipsoids are shown at the 50% probability level) S48

49 Synthesis of compound 18 Scheme S10 A solution of dimethyl acetylenedicarboxylate (18.0 L, 20.8 mg, mol, 1.0 eq) in toluene (1 ml) was added to a solution of compound 12 (120.0 mg, mol, 1.0 eq) in toluene (3 ml) and the reaction mixture was stirred at 100 C for 6 days. Then all volatiles were removed in vacuo and the formed sticky residue was dissolved in pentane (5 ml), which was subsequently removed in vacuo. After adding pentane (3 ml) to the obtained sticky solid the resulting suspension was filtered via cannula (Whatman glass fiber filter). Then the remaining solid was washed with pentane (5 x 3 ml) and dried in vacuo to give compound 18 as a pale orange solid (87.7 mg, 91.1 mol, 62%). IR (KBr): ṽ [cm -1 ] = 3473 (w), 3027 (w), 2938 (m), 2864 (w), 2668 (w), 2540 (w), 2293 (w), 2092 (w), 1744 (s), 1613 (s), 1561 (w), 1515 (s), 1450 (s), 1377 (w), 1338 (m), 1244 (m), 1024 (w), 1150 (w), 1088 (s), 1030 (w), 974 (s), 926 (w), 875 (w), 854 (m), 814 (w), 778 (m), 764 (w), 747 (m), 710 (w), 690 (m), 662 (w), 641 (w), 604 (w), 563 (w), 521 (w), 459 (w), 444 (w), 419 (w). M.p. 268 C. Anal. Calc. for C 52H 42BF 10O 4P: C: 64.88; H: Found: C: 64.91; H: [Ar = 4,6-dimethylphenylene] 1 H NMR (500 MHz, dichloromethane-d 2, 299 K): δ 7.34 (m, 2H, m-ph), 7.27 (m, 1H, p-ph), 7.16 (m, 2H, o-ph), 7.13 (dd, J = 8.1 Hz, J = 5.3 Hz, 1H, 3-CH), 7.04 (m, 1H, 3-CH Ar ), 7.03 (m, 1H, 5-CH Ar ), 6.84 (dm, 4 J PH = 3.6 Hz, 1H, m-mes), 6.42 (dm, 4 J PH = 4.6 Hz, 1H, m -Mes), 3.66 (s, 3H. OMe C=O ), 3.38 (s, 3H, OMe), 2.74/2.28 (each m, each 1H, 9-CH 2) t, 2.55/2.50 (each m, each 1H, 6-CH 2) t Ar Mes, 2.39 (d, J = 0.8 Hz, 3H, 4-CH 3 ), 2.34 (s, 3H, o-ch 3 ) t, 2.20 (s, Mes Ar Mes 3H, p-ch 3 ), 2.09 (s, 3H, 6-CH 3 ), 1.90 (s, 3H, o -CH 3 ) t, 1.59/1.43 (each m, each 1H, 7- CH 2) t, 1.58 (s, 3H, CH 3), 1.51 (m, 2H, 8-CH 2) t. [ t tentatively assigned] 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 299 K): δ (d, 3 J PC = 8.6 Hz, O=C), (d, 2 J PC = 16.3 Hz, O 2C=), (d, 2 J PC = 22.4 Hz, 2-C Ar ), (d, 2 J PC = 9.8 Hz, o-mes) t, (d, 4 J PC = 2.6 Hz, 4-C Ar ), (d, 2 J PC = 12.9 Hz, o -Mes) t, (d, 4 J PC = 3.0 Hz, p- S49

50 Mes), (dd, J = 3.4 Hz, J = 1.1 Hz, 4-C) t, (d, J = 1.2 Hz, i-ph), (d, 2 J PC = 9.9 Hz, 6-C Ar ), (dd, J = 18.5 Hz, J = 9.8 Hz, 3-CH), (d, 1 J PC = 80.8 Hz, 1-C), (d, 2 J PC = 11.3 Hz, 10-C) t, (d, 3 J PC = 11.5 Hz, 5-C) t, (d, 3 J PC = 10.2 Hz, 5- CH Ar ), (d, 3 J PC = 6.2 Hz, m -Mes), (d, 3 J PC = 5.1 Hz, m-mes), (o-ph), (m-ph), (p-ph), (d, 1 J PC = 84.2 Hz, 1-C Ar ), (d, 3 J PC = 10.0 Hz, 3-CH Ar ), (d, 1 J PC = 82.8 Hz, i-mes), 77.8 (d, 1 J PC = Hz, PC=), 55.7 (d, 2 J PC = 15.2 Hz, CMe), 53.7 (d, 4 J PC = 1.2 Hz, OMe), 52.4 (OMe C=O ), 29.4 (d, 3 J PC = 7.1 Hz, 9-CH 2) t, 28.7 (d, 4 J PC = 1.6 Hz, 6-CH 2) t, 28.2 (CH 3), 24.2 (dd, J = 5.8 Hz, J = 3.3 Hz o -Mes) t, 23.9 (dd, J = 7.0 Hz, J = 1.5 Hz, o-mes) t, 23.0 (8-CH 2) t, 22.3 (7-CH 2) t Ar, 21.7 (d, J = 1.3 Hz, 4-CH 3 ), 20.9 (d, 3 Ar J PC = 3.4 Hz, 6-CH 3 ), 20.7 (p-mes), n.o. (2-C). [C 6F 5 not listed; t tentatively assigned] 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 213 K): δ 15.1 ( 1/2 ~ 5 Hz). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 299 K): δ 1.1 ( 1/2 ~ 350 Hz). 19 F NMR (470 MHz, dichloromethane-d 2, 299 K): δ (m, o), (m, o ), (t, 3 J FF = 20.3 Hz, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F mp = 4.9, 5.5], (m, o), (m, o ), (t, 3 J FF = 20.4 Hz, p), (m, m ), (m, m)(each 1F, C 6F 5)[ 19 F mp = 3.4, 5.8]. Figure S58: 1 H NMR (500 MHz, dichloromethane-d2, 299 K) spectrum of compound 18 S50

51 Figure S59: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 299 K) spectrum of compound 18 Figure S60: 19 F NMR (470 MHz, dichloromethane-d2, 299 K) spectrum of compound 18 Figure S61: 31 P{ 1 H} NMR (202 MHz, dichloromethane-d2, 299 K) spectrum of compound 18 S51

52 Figure S62: 11 B{ 1 H} NMR (160 MHz, dichloromethane-d2, 299 K) spectrum of compound 18 Crystals suitable for the X-ray crystal structure analysis were obtained from a dichloromethane solution of compound 18 at -35 C: X-ray crystal structure analysis of compound 18: A colorless plate-like specimen of C 52H 42BF 10O 4P, approximate dimensions mm x mm x mm, was used for the X-ray crystallographic analysis. The X-ray intensity data were measured. A total of 1592 frames were collected. The total exposure time was hours. The frames were integrated with the Bruker SAINT software package using a wide-frame algorithm. The integration of the data using a monoclinic unit cell yielded a total of 8235 reflections to a maximum θ angle of (0.84 Å resolution), of which 8235 were independent (average redundancy 1.000, completeness = 99.8%, R int = 9.30%, R sig = 5.39%) and 6008 (72.96%) were greater than 2σ(F 2 ). The final cell constants of a = (15) Å, b = (17) Å, c = (18) Å, β = (5), volume = (8) Å 3, are based upon the refinement of the XYZ-centroids of 9144 reflections above 20 σ(i) with < 2θ < Data were corrected for absorption effects using the multi-scan method (SADABS). The ratio of minimum to maximum apparent transmission was The calculated minimum and maximum transmission coefficients (based on crystal size) are and The final anisotropic full-matrix least-squares refinement on F 2 with 621 variables converged at R1 = 4.81%, for the observed data and wr2 = 12.26% for all data. The goodness-of-fit was The largest peak in the final difference electron density synthesis was e - /Å 3 and the largest hole was e - /Å 3 with an RMS deviation of e - /Å 3. On the basis of the final model, the calculated density was g/cm 3 and F(000), 1984 e -. S52

53 Figure S63: X-ray crystal structure of compound 18 (thermal ellipsoids are shown at the 50% probability level) Synthesis of compound 19 Scheme S11 A solution of compound 11 (200.0 mg, mol, 1.0 eq) in CH 2Cl 2 (1 ml) was degassed at -78 C and exposed to a nitric oxide atmosphere (1.5 bar). The solution turned dark turquoise upon stirring for 15 min. Then all volatiles were removed in vacuo and pentane (3 ml) was added to the obtained residue. The suspension was filtrated via cannula (Whatman glass fiber filter) and the remaining solid was washed with pentane (3 x 2 ml). After drying in vacuo compound 19 was obtained as a pale turquoise solid (166.4 mg, mol, 80%). IR (KBr): ṽ [cm -1 ] = 3515 (w), 3063 (w), 3032 (w), 2937 (m), 2862 (w), 2811 (w), 2349 (w), 2297 (w), 1739 (w), 1644 (s), 1604 (m), 1577 (w), 1553 (w), 1515 (s), 1453 (s), 1382 (m), 1318 (w), S53

54 1280 (m), 1249 (w), 1183 (w), 1149 (w), 1098 (s), 1033 (w), 974 (s), 926 (w), 853 (m), 817 (w), 794 (w), 772 (w), 743 (w), 703 (s), 646 (s), 599 (w), 567 (m), 510 (w), 468 (w). Decomp. 168 C. Anal. Calc. for C 46H 38BF 10PNO: C: 64.80; H: 4.49; N: Found: C: 64.63; H: 4.49; N: Crystals suitable for the X-ray crystal structure analysis were obtained by slow diffusion of pentane into a solution of compound 19 in dichloromethane at -35 C: X-ray crystal structure analysis of compound 19: formula C 46H 38BF 10NOP 2 x CH 2Cl 2, M = , colourless crystal, 0.18 x 0.05 x 0.05 mm, a = (2), b = (2), c = (3) Å, α = (1), β = (1), γ = (2), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.937 T 0.982), Z = 2, triclinic, space group P1 (No. 2), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), 8004 independent (R int = 0.045) and 6444 observed reflections [I>2σ(I)], 657 refined parameters, R = 0.070, wr 2 = 0.161, max. (min.) residual electron density 0.53 (- 0.60) e.å -3, hydrogen atoms were calculated and refined as riding atoms. Figure S64: X-ray crystal structure of compound 19 (thermal ellipsoids are shown at the 30% probability level) S54

55 Synthesis of compound 20 Scheme S12 1,8-Cyclohexadiene (131.6 mg, 1.64 mmol, 10.0 eq) was added to a turquoise solution of compound 19 (140.0 mg, mol, 1.0 eq) in benzene (2 ml) at room temperature. The solution became colorless upon stirring for 1 hour. Then all volatiles were removed in vacuo and the off-white residue crystallized by the layering method with CH 2Cl 2 (1 ml) and pentane (7 ml). The crystalline solid was ground and washed with pentane (3 x 1 ml). After drying in vacuo, compound 20 was obtained as a white solid (88.4 mg, mol, 63%). IR (KBr): ṽ [cm -1 ] = 3515 (m), 3061 (w), 3033 (w), 2936 (m), 2859 (w), 2816 (w), 2733 (w), 2340 (w), 1946 (w), 1640 (m), 1603 (m), 1590 (w), 1554 (w), 1512 (s), 1456 (s), 1406 (w), 1385 (w), 1340 (w), 1276 (m), 1246 (w), 1207 (w), 1162 (w), 1139 (w), 1084 (s), 1040 (m), 967 (s), 927 (w), 892 (w), 852 (m), 803 (w), 779 (w), 754 (w), 741 (w), 703 (m), 689 (m), 645 (s), 599 (w), 572 (m), 510 (w), 473 (w), 452 (w). Decomp. 214 C. Anal. Calc. for C 46H 39BF 10PNO: C: 64.73; H: 4.61; N: Found: C: 64.71; H: 4.50; N: H NMR (500 MHz, dichloromethane-d 2, 299 K): δ 7.33 (m, 2H, m-ph), 7.29 (m, 2H, o-ph), 7.23 (m, 1H, p-ph), 7.00 (d, 4 J PH = 4.3 Hz, 2H, m-mes a ), 6.92 (d, 4 J PH = 4.6 Hz, 2H, m-mes b ), 6.33 (br, 1H, 3-CH), 4.63 (t, J = 9.1 Hz, 1H, OH), 3.89 (br dd, 3 J HH = 9.5 Hz, J = 2.0 Hz, 1H, 4-CH), 2.60/2.13 (each m, each 1H, 9-CH 2), Mes,a Mes,a 2.37 (s, 6H, o-ch 3 ), 2.36 (s, 3H, p-ch 3 ), Mes,b Mes,b 2.33 (m, 1H, 5-CH), 2.29 (s, 3H, p-ch 3 ), 2.20 (s, 6H, o-ch 3 ), 1.56/1.13 (each m, each 1H, 6-CH 2), 1.53/1.14 (each m, each 1H, 7-CH 2), 1.27/0.46 (each m, each 1H, 8-CH 2). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 299 K): δ (d, 2 J PC = 12.8 Hz, 10-C), (d, 4 J PC = 3.0 Hz, p-mes b ), (d, 2 J PC = 11.4 Hz, o-mes b ), (d, 4 J PC = 2.9 Hz, p-mes a ), (i-ph), (br, 2-C), (d, 2 J PC = 10.4 Hz, o-mes a ), (d, 3 J PC = 11.7 Hz, m- Mes b ), (d, 3 J PC = 11.7 Hz, m-mes a ), (o-ph), (br m, 3-CH), (m-ph), (p-ph), (d, 1 J PC = 86.3 Hz, i-mes a ), (d, 1 J PC = 90.0 Hz, i-mes b ), (d, 1 J PC = 99.3 Hz, 1-C), 50.5 (d, 3 J PC = 13.3 Hz, 5-CH), 44.1 (4-CH), 35.6 (d, 3 J PC = 7.3 Hz, 9-CH 2), 30.2 (br d, 4 J PC = 1.9 Hz, 8-CH 2), 30.0 (br, 6-CH 2), 26.9 (7-CH 2), 24.2 (d, 3 J PC = 4.2 Hz, o- S55

56 Mes,a CH 3 ), 23.8 (d, 3 Mes,b Mes,b J PC = 5.4 Hz, o-ch 3 ), 21.2 (d, J = 1.9 Hz, p-ch 3 ), 21.2 (d, J = 1.3 Hz, Mes,a p-ch 3 ). [C 6F 5 not listed] 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 299 K): δ 28.7 ( 1/2 ~ 25 Hz). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 299 K): δ 6.6 ( 1/2 ~ 130 Hz) 19 F NMR (470 MHz, dichloromethane-d 2, 299 K): δ (m, 2F, o), (t, 3 J FF = 20.3 Hz, 1F, p), (m, 2F, m)(c 6F 5)[ 19 F mp = 4.4], (m, 2F, o), (t, 3 J FF = 20.3 Hz, 1F, p), (m, 2F, m)(c 6F 5)[ 19 F mp = 2.7]. Figure S65: 1 H NMR (500 MHz, dichloromethane-d2, 299 K) spectrum of compound 20 S56

57 Figure S66: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 299 K) spectrum of compound 20 Figure S67: 19 F NMR (470 MHz, dichloromethane-d2, 299 K) spectrum of compound 20 Figure S68 31 P{ 1 H} NMR (202 MHz, dichloromethane-d2, 299 K) spectrum of compound 20 S57

58 Figure S69: 11 B{ 1 H} NMR (160 MHz, dichloromethane-d2, 299 K) spectrum of compound 20 Crystals suitable for the X-ray crystal structure analysis were obtained by slow evaporation from a dichloromethane solution of compound 20: X-ray crystal structure analysis of compound 20: A colorless prism-like specimen of C 46H 39BF 10NOP, approximate dimensions mm x mm x mm, was used for the X-ray crystallographic analysis. The X-ray intensity data were measured. A total of 1605 frames were collected. The total exposure time was hours. The frames were integrated with the Bruker SAINT software package using a wide-frame algorithm. The integration of the data using a monoclinic unit cell yielded a total of reflections to a maximum θ angle of (0.84 Å resolution), of which 7063 were independent (average redundancy 8.098, completeness = 99.2%, R int = 7.46%, R sig = 3.97%) and 5503 (77.91%) were greater than 2σ(F 2 ). The final cell constants of a = (5) Å, b = (6) Å, c = (9) Å, β = (2), volume = (3) Å 3, are based upon the refinement of the XYZ-centroids of 9971 reflections above 20 σ(i) with < 2θ < Data were corrected for absorption effects using the multi-scan method (SADABS). The ratio of minimum to maximum apparent transmission was The calculated minimum and maximum transmission coefficients (based on crystal size) are and The structure was solved and refined using the Bruker SHELXTL Software Package, using the space group P 1 21/n 1, with Z = 4 for the formula unit, C 46H 39BF 10NOP. The final anisotropic full-matrix least-squares refinement on F 2 with 551 variables converged at R1 = 4.75%, for the observed data and wr2 = 12.71% for all data. The goodness-of-fit was The largest peak in the final difference electron density synthesis was e - /Å 3 and the largest hole was e - /Å 3 with an RMS deviation of e - /Å 3. On the basis of the final model, the calculated density was g/cm 3 and F(000), 1760 e -. S58

59 Figure S70: X-ray crystal structure of compound 20 (thermal ellipsoids are shown at the 50% probability level) Synthesis of compound 21 Scheme S13 A solution of compound 12 (100.0 mg, mol, 1.0 eq) in CH 2Cl 2 (1 ml) was degassed at -78 C and exposed to a nitric oxide atmosphere (1.5 bar). The solution turned dark green upon stirring for 15 min. Then all volatiles were removed in vacuo and pentane (3 ml) was added to the obtained dark green residue. The suspension was filtrated via cannula (Whatman glass fiber filter) and the remaining solid was washed with pentane (3 x 2 ml). After drying in vacuo compound 21 was obtained as a pale green solid (87.4 mg, 91.9 mol, 84%). IR (KBr): ṽ [cm -1 ] = 3518 (w), 3455 (w), 3031 (w), 2940 (m), 2864 (w), 2741 (w), 2624 (w), 2386 (w), 2348 (w), 2302 (w), 1732 (w), 1642 (m), 1604 (m), 1554 (w), 1515 (s), 1459 (s), 1382 (m), 1322 (w), 1283 (m), 1253 (m), 1205 (w), 1178 (w), 1157 (w), 1103 (s), 1029 (w), 974 (s), 926 S59

60 (w), 881 (w), 850 (m), 836 (m), 809 (w), 772 (m), 748 (w), 702 (m), 659 (m), 643 (m), 609 (w), 571 (w), 515 (w), 478 (w), 455 (w), 429 (w). Decomp. 193 C. Anal. Calc. for C 46H 36BF 10PNO: C: 64.96; H: 4.27; N: Found: C: 65.34; H: 4.28; N: Crystals suitable for the X-ray crystal structure analysis were obtained by slow diffusion of pentane into a solution of compound 21 in dichloromethane at -35 C: X-ray crystal structure analysis of compound 21: formula C 46H 36BF 10NOP, M = , pale green crystal, 0.15 x 0.12 x 0.10 mm, a = (3), b = (3), c = (4) Å, β = (1), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.976 T 0.984), Z = 4, monoclinic, space group P2 1/n (No. 14), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), 6794 independent (R int = 0.053) and 5010 observed reflections [I>2σ(I)], 639 refined parameters, R = 0.066, wr 2 = 0.139, max. (min.) residual electron density 0.31 (-0.29) e.å -3, hydrogen atoms were calculated and refined as riding atoms. Figure S71: X-ray crystal structure of compound 21 (thermal ellipsoids are shown at the 30% probability level) S60

61 Synthesis of compound 22 Scheme S14 1,8-Cyclohexadiene (75.4 mg, mol, 10.0 eq) was added to a green solution of compound 21 (80.0 mg, 94.1 mol, 1.0 eq) in benzene (2 ml) at room temperature. The solution became colorless upon stirring for 1 hour. Then all volatiles were removed in vacuo and the remaining off-white residue was washed with pentane (3 x 1 ml). After drying in vacuo, compound 22 was obtained as a white solid (70.8 mg, 83.1 mol, 88%). IR (KBr): ṽ [cm -1 ] = 3494 (w), 2934 (w), 2864 (w), 1642 (m), 1604 (m), 1556 (w), 1515 (s), 1456 (s), 1381 (w), 1342 (w), 1227 (m), 1252 (m), 1212(w), 1159 (w), 1090 (s), 1041 (w), 971 (s), 933 (w), 853 (m), 822 (w), 775 (m), 741 (w), 703 (m), 659 (m), 642 (m), 576 (w), 507 (w), 482 (w), 440 (w). Decomp. 220 C. Anal. Calc. for C 46H 37BF 10PNO: C: 64.88; H: 4.38; N: Found: C: 65.00; H: 4.44; N: H NMR (500 MHz, dichloromethane-d 2, 299 K): δ 7.82 (br, 1H, 3-CH), 7.42 (m, 2H, m-ph), 7.35 (m, 1H, p-ph), 7.33 (m, 2H, o-ph), 6.97 (d, 4 J PH = 4.4 Hz, 4H, m-mes), 4.76 (quint, J = 5.0 Hz, 1H, OH), 2.68 (m, 2H, 9-CH 2), 2.56 (m, 2H, 6-CH 2), Mes 2.33 (s, 6H, p-ch 3 ), 2.13 (s, Mes 12H, o-ch 3 ), 1.67 (m, 2H, 8-CH 2), 1.57 (m, 2H, 7-CH 2). 13 C{ 1 H} NMR (126 MHz, dichloromethane-d 2, 299 K): δ (br, 2-C), (dm, 1 J FC~ 240 Hz, C 6F 5), (dm, (d, 4 J PC = 3.1 Hz, 4-CH), (d, 4 J PC = 2.9 Hz, p-mes), (br d, 2 J PC = 10.8 Hz, o-mes), (d, J = 0.9 Hz, i-ph), (d, 2 J PC = 16.6 Hz, 10-C), (dm, 1 J FC~ 240 Hz, C 6F 5), (dm, 1 J FC~ 250 Hz, C 6F 5), (d, 3 J PC = 12.2 Hz, 5-C), (m, 3-CH), (d, 3 J PC = 11.6 Hz, m-mes), (o-ph), (m-ph), (d, 1 J PC = Hz, 1-C), (br, i-c 6F 5), (p-ph), (d, 1 J PC = 87.4 Hz, i-mes), 30.3 (d, 3 J PC = 5.6 Hz, 9-CH 2), 29.0 (d, 4 J PC = 1.8 Hz, 6-CH 2), 23.5 (br d, 3 Mes J PC = 3.6 Hz, o-ch 3 ), 23.0 (8- CH 2), 22.9 (7-CH 2), Mes 21.2 (d, J = 1.5 Hz, p-ch 3 ). 31 P{ 1 H} NMR (202 MHz, dichloromethane-d 2, 299 K): δ 33.7 ( 1/2 ~ 40 Hz). 11 B{ 1 H} NMR (160 MHz, dichloromethane-d 2, 299 K): δ 5.4 ( 1/2 ~ 150 Hz) 19 F NMR (470 MHz, dichloromethane-d 2, 299 K): δ (br, 2F, o-c 6F 5), (t, 3 J FF = 20.3 Hz, 1F, p-c 6F 5), (m, 2F, m-c 6F 5)[ 19 F mp = 4.2]. S61

62 Figure S72: 1 H NMR (500 MHz, dichloromethane-d2, 299 K) spectrum of compound 22 Figure S73: 13 C{ 1 H} NMR (126 MHz, dichloromethane-d2, 299 K) spectrum of compound 22 S62