Supporting Information Borata-alkene Derivatives Conveniently Made by Frustrated Lewis Pair Chemistry

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1 Supporting Information Borata-alkene Derivatives Conveniently Made by Frustrated Lewis Pair Chemistry Juri Möbus 1, Gerald Kehr, Constantin G. Daniliuc $, Roland Fröhlich $, Gerhard Erker* 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 or were distilled from appropriate drying agents and stored under an argon atmosphere. NMR spectra were recorded on a Bruker AC 200 P ( 1 H: MHz, 13 C: 50.3 MHz, 11 B: 64.2 MHz, 31 P: 81.0 MHz), on a Agilent DD2 500 ( 1 H: MHz, 13 C: MHz, 19 F: MHz, 11 B: MHz, 31 P: MHz, 29 Si: 99.3 MHz) and on a Agilent DD2 600 ( 1 H: MHz, 13 C: MHz, 19 F: MHz, 11 B: MHz, 31 P: MHz, 29 Si: MHz). 1 H NMR and 13 C NMR: chemical shifts δ are given relative to TMS ( = 0) and referenced to the solvent signal. 19 F NMR: chemical shifts δ are given relative to CFCl 3 ( = 0, external reference), 11 B NMR: chemical shifts δ are given relative to BF 3 Et 2 O ( = 0, external reference), 31 P NMR: chemical shifts δ are given relative to H 3 PO 4 (85% in H 2 O) ( = 0, external reference). NMR assignments were supported by additional 2D NMR experiments. Elemental analyses were performed on a ElementarVario El III. IR spectra were recorded on a Varian 3100 FT-IR (Excalibur Series). Melting points were obtained with a DSC Q20 (TA Instruments). X-Ray diffraction: Data sets were collected with a Nonius KappaCCD 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). Thermals ellipsoids are shown with 30% probability, R-values are given for observed reflections, and wr 2 values are given for all reflections. Exceptions and special features: For the compound 14b the group at C12 atom was found disordered over two positions. Several restraints (SADI, SAME, ISOR and SIMU) were used in order to improve refinement stability. Preparation of the Bis(alkynyl)phosphanes Preparation of dimesitylmagnesium Mes 2 Mg(thf) 2 was prepared according to a modified literature procedure. [W. Seidel, I. Bürger, Z. Anorg. Allg. Chem. 1978, 447, ; M. Waggoner, P. P. Power, Organometallics 1992, 11, ] Mg turnings (1.3 g, 55 mmol, 1.1 eq) were suspended in THF (60 ml) and activated with iodine. Subsequently mesityl bromide (10.0 g, 50 mmol, 1 eq) was added in portions and the reaction mixture was stirred at rt overnight. Then 1,4-dioxane (4.4 g, 50 mmol, 1 eq, freshly dried over molecular sieves) was added to the reaction mixture with vigorous stirring. After stirring for 5 h at rt the insolubles 1 Juri Möbus is a member of the Graduate School of Chemistry, Universität Münster. $ X-ray crystal structure analyses. S1 of 24

2 were sedimented overnight and removed by cannula filtration. Removal of the volatiles in vacuo from the filtrate yields dimesitylmagnesium as colourless powder (10.5 g, 19.2 mmol, 77%). 1 H NMR (200 MHz, 300 K, benzene-d 6 ): δ 1 H: 6.55 (br m, 2H, m-mes), 3.51 (m, 4H, thf), 2.29 (br s, 6H, o-ch 3 mes ), 2.09 (s, 3H, p-ch 3 mes ), 1.57 (m, 4H, thf), [3.40 (s, 1H, 1,4-dioxane (ca. 25 mol%)]. 1 H NMR (200 MHz, 300 K, benzene-d 6) spectrum of dimesitylmagnesium. Preparation of mesityl phosphorus dihalide (mespxy) Mes 2 Mg(thf) 2 (5.0 g, 12 mmol, 1 eq) was suspended in Et 2 O (40 ml) at -70 C and PCl 3 (6.7 g, 48 mmol, 4 eq) was added. The reaction mixture was allowed to warm to room temperature overnight. Insolubles were removed by filtration over Celite and all volatiles were evaporated from the filtrate at 50 C to give mespxy (mespcl 2 ca. 82%, mespclbr ca.17%, mespbr 2 ca. 1%, from the 31 P{ 1 H} NMR spectrum) as a pale yellow oil (4.0 g, 18 mmol, 75%) 1 H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 6.47 (m, 2H, m-mes), 2.51 (m, 6H, o-ch mes 3 ), 1.90 (m, 3H, p-ch mes 3 ). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 26.8 Hz, o-mes), (s, p-mes), (d, 1 J PC = 66.2 Hz, i-mes), (d, 3 J PC = 3.9 Hz, m-mes), 21.4 (d, 3 J PC = 25.7 Hz, o-ch mes 3 ), 21.0 (s, p-ch mes 3 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: (s, 1/2 13 Hz, mespcl 2 ), (s, 1/2 16 Hz, mespbrcl), (s, 1/2 20 Hz, mespbr 2 ). S2 of 24

3 1 H NMR (600 MHz, 299 K, benzene-d 6), 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound mespxy. Preparation of 2,4,6-triisopropylphenyl phosphorus dihalide (tipppxy) TippPXY was synthesized according to a modified literature procedure. [D. G. Yakhvarov, E. Hey- Hawkins, R. M. Kagirov, Yu. H. Budnikova, Yu. S. Ganushevich, O. G. Sinyashin, Russ. Chem. Bull. 2007, 56, ; J. Möbus, Q. Bonnin, K. Ueda, K. Itami, R. Fröhlich, G. Kehr, G. Erker, Angew. Chem. Int. Ed. 2012, 51, ] Mg turnings (1.2 g, 48 mmol, 1.5 eq) were suspended in THF (60 ml) and activated with I 2 at reflux for 1 h. 2,4,6-Triisopropylphenyl bromide (9.0 g, 32 mmol, 1 eq) was added dropwise at 50 C and the reaction mixture was refluxed for 3 h. The filtered solution was added slowly to a solution of PCl 3 (11 g, 80 mmol, 2.5 eq) in THF (40 ml) at 0 C. The reaction mixture was allowed to warm to room temperature and stirred for 4 h at room temperature. Volatiles were removed in vacuo and the residue was taken up in Et 2 O (50 ml). The precipitated magnesium salts were filtered off over Celite at 30 C and washed with Et 2 O (25 ml) at 30 C twice. The filtrate was concentrated to ca. 50 ml and pentane (50 ml) was added. The solution was cooled to -78 C for 1 h for precipitation. The supernatant solution was removed by cannula filtration and the precipitate was washed twice with pentane (50 ml) at -78 C. Drying in vacuo yields the product tipppxy as a mixture of compounds [tipppcl 2 62%, S3 of 24

4 tipppclbr 33%, tipppbr 2 5% (from the 31 P{ 1 H} NMR spectrum)] as an off-white solid (8.9 g, 27.7 mmol, 87%). 1 H NMR (200 MHz, 300 K, benzene-d 6 ): δ 1 H: 7.05 (m, 2H, m-tipp), 4.20 (m, 2H, o-ch tipp ), 2.61 (sept, 3 J HH = 6.9 Hz, 1H, p-ch tipp ), 1.21 (d, 3 J HH = 6.8 Hz, 12H, o-ch tipp 3 ), 1.09 (d, 3 J HH = 6.9 Hz, 6H, p- CH tipp 3 ). 31 P{ 1 H} NMR (81 MHz, 300 K, benzene-d 6 ): δ 31 P: (tipppcl 2 ), (tipppclbr), (tipppbr 2 ). 1 H NMR (200 MHz, 300 K, benzene-d 6) and 31 P{ 1 H} NMR (81 MHz, 300 K, benzene-d 6) spectra of compound tipppxy. 2 nd experiment: Tipp 2 Mg(thf) 2 (4.0 g, 7 mmol, 1 eq) was suspended in Et 2 O (60 ml) at -78 C and PCl 3 (4.8 g, 35 mmol, 5 eq) was added with vigorous stirring. The reaction mixture was stirred for 4 h at -78 C and then allowed to warm to rt. The suspension was concentrated to ca. 20 ml and pentane (50 ml) was added. Insolubles were removed by filtration over Celite and the filtrate was saturated by evaporation at 35 C and cooled to -78 C for precipitation. The precipitate was washed with pentane (20 ml) at -78 C and dried in vacuo to give tipppcl 2 as a mixture of compounds (tipppcl 2 91%, tipppclbr 9% by integration of the 31 P{ 1 H} NMR spectrum) as colourless solid (3.1 g, 11 mmol, 79%). Crystals of tipppcl 2 suitable for the X-ray crystal structure analysis were obtained by cooling of a concentrate pentane solution of tipppcl 2. X-ray crystal structure analysis of tipppcl 2 : formula C 15 H 23 Cl 2 P, M = , colourless crystal, 0.30 x 0.20 x 0.17 mm, a = (2), b = (3), c = (2) Å, β = (1), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.869 T 0.922), Z = 4, monoclinic, space group P2 1 /c (No. 14), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), [(sin )/λ] = 0.67 Å -1, 3946 independent (R int = 0.027) and 3520 observed reflections [I>2σ(I)], 169 refined parameters, R = 0.034, wr 2 = 0.093, max. (min.) residual electron density 0.29 (-0.28) e.å -3, hydrogen atoms were calculated and refined as riding atoms. S4 of 24

5 Preparation of compound 9a 2-Methylbutenyne (680 mg, 10 mmol, 2.7 eq) in pentane (80 ml) was cooled to -50 C and n-buli (5.9 ml, 1.6 M in hexane, 9.4 mmol, 2.5 eq) was added dropwise. The resulting colourless suspension was stirred for 30 min at -50 C and allowed to warm to rt. Then mespcl 2 (850 mg, 3.7 mmol, 1 eq) was added in a glovebox and the reaction mixture was stirred for 2 h at rt [Completion of the reaction was confirmed by 31 P NMR spectroscopy]. Then insolubles were filtered off over Celite at 40 C and washed with pentane (20 ml) twice at 40 C. The clear colourless solution was concentrated to ca. 10 ml and the product precipitated at -95 C. Removal of the supernatant solution by cannula filtration and drying of the residue in vacuo yielded compound 9a as colourless, microcrystalline solid (830 mg, 3.0 mmol, 78%). Anal. Calc. for C 19 H 21 P: C, 81.40; H, Found C, 81.22; H, IR (KBr) [cm -1 ] = 3744 (w), 3446 (m), 3094 (w), 2968 (m), 2918 (m), 2852 (w), 2407 (w), 2284 (w), 2153 (m, C C), 2122 (w), 1602 (s), 1558 (m), 1456 (m), 1436 (m), 1372 (m), 1275 (s), 1031 (s), 983 (m), 900 (s), 853 (s), 716 (w), 616 (m), 574 (m), 534 (m), 436 (w), 407 (s). Melting point (DSC): 120 C. Decomposition (DSC): 209 C. S5 of 24

6 1 H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 6.71 (dm, 4 J PH = 3.3 Hz, 2H, m-mes), 5.22 (m, 2H, =CH Z 2 ), 4.92 (m, 2H, =CH E 2 ), 2.84 (m, 6H, o-ch mes 3 ), 2.00 (s, 3H, p-ch mes 3 ), 1.59 (dd, 4 J PH = 1.6 Hz, 4 J PH = 1.1 Hz, 6H, CH 3 ). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 19.8 Hz, o-mes), (d, 4 J PC = 1.6 Hz, p-mes), (d, 3 J PC = 5.9 Hz, m-mes), (d, 3 J PC = 1.8 Hz, C=), (d, 1 J PC = 1.1 Hz, i-mes), (d, 4 J PC = 2.7 Hz, =CH 2 ), (d, 2 J PC = 10.0 Hz, C ), 83.2 (d, 1 J PC = 2.5 Hz, PC ), 23.2 (d, 3 J PC = 19.1 Hz, o-ch mes 3 ), 22.7 (d, 5 J PC = 1.5 Hz, p-ch mes 3 ), 21.0 (CH 3 ). 1 H, 1 H GCOSY (600 MHz/600 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 6.71 / 2.84, 2.00 (m-mes / o-ch mes 3, p-ch mes 3 ), 1.59 / 5.22, 4.92 (CH 3 / =CH Z 2, =CH E 2 ). 1 H, 13 C GHSQC (600 MHz/151 MHz, 299 K, benzene-d 6 ): δ 1 H / δ 13 C: 6.71 / (m-mes), 5.22, 4.92 / (CH 2 ), 2.84 / 23.2 (o-ch mes 3 ), 2.00 / 21.0 (p-ch mes 3 ), 1.59 / 22.7 (CH 3 ). 1 H, 13 C GHMBC (500 MHz/126 MHz, 298 K, benzene-d 6 )[selected traces]: δ 1 H / δ 13 C: 5.22 / 127.0, 107.2, 22.7 (=CH Z 2 / C=, C, CH 3 ), 2.84 / 144.8, 130.0, (o-ch mes 3 / o-mes, m-mes, i-mes), 2.00 / 140.8, (p-ch mes 3 / p-mes, m-mes). 1 H{ 1 H} NOESY (600 MHz, 299 K, benzene-d 6 )[selected experiments]: δ 1 H irr / δ 1 Z H res : 5.22 / 4.92 (=CH 2 / =CH E 2 ), 4.92 / 5.22, 1.59 (=CH E 2 / =CH Z 2, CH 3 ), 2.84 / 6.71, 5.22, 2.00, 1.59 (o-ch mes 3 / m-mes, =CH Z 2, p-ch mes 3, CH 3 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: ( 1/2 1 Hz). 1 H NMR (600 MHz, 299 K, benzene-d 6), 13 C{ 1 H}NMR (151 MHz, 299 K, benzene-d 6) and 31 P{ 1 H}NMR (243 MHz, 299 K, benzene-d 6) spectra of compound 9a. S6 of 24

7 Preparation of compound 9b Cyclohexenylacetylene (460 mg, 4.3 mmol, 2.2 eq) in pentane (80 ml) was cooled to -60 C and n- BuLi (2.6 ml, 1.6 M in hexane, 4.1 mmol, 2.1 eq) was added. The resulting colourless suspension was stirred for 30 min at -60 C, then allowed to warm to rt and stirred another 15 min. Then mespcl 2 (480 mg, 2 mmol, 1 eq) was added and the reaction mixture was stirred for 2 h at rt [Completion of the reaction was confirmed by 31 P NMR spectroscopy]. Subsequently the insolubles were filtered off over Celite/Silica gel (10:1) and the obtained residue was washed with pentane (20 ml) twice. The combined clear colourless filtrates were concentrated to ca. 15 ml and the colourless product precipitated at -70 C. Removal of the supernatant solution by cannula filtration and drying in vacuo yielded compound 9b as colourless wax (680 mg, 1.9 mmol, 90%). Anal. Calc. for C 25 H 29 P: C, 83.30; H, Found C, 83.15; H,8.18. IR (KBr) [cm -1 ] = 2927, 2857, 2146 ( C C ), 1602, 1559, 1457, 1448, 1435, 1376, 1347, 1266, 1238, 1168, 1135, 1043, 918, 843, 799, 693, 613, H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 6.75 (dm, 4 J PH = 3.3 Hz, 2H, m-mes), 6.03 (m, 2H, =CH), 2.92 (m, 6H, o-ch mes 3 ), 2.03 (s, 3H, p-ch mes 3 ), 1.98 (m, 4H, β-ch 2 ), 1.69 (m, 4H, γ'-ch 2 ), 1.24 (m, 4H, γ-ch 2 ), 1.19 (m, 4H, δ-ch 2 ). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 19.6 Hz, o-mes), (d, 4 J PC = 1.6 Hz, p-mes), (d, 4 J PC = 2.8 Hz, =CH), (d, 3 J PC = 5.7 Hz, m-mes), (d, 1 J PC = 1.5 Hz, i-mes), (d, 3 J PC = 1.7 Hz, C=), (d, 2 J PC = 10.2 Hz, C ), 81.4 (d, 1 J PC = 0.8 Hz, PC ), 28.9 (d, 4 J PC = 1.7 Hz, β-ch 2 ), 25.8 (γ'-ch 2 ), 23.3 (d, 3 J PC = 19.3 Hz, o-ch mes 3 ), 22.3 (γ-ch 2 ), 21.5 (δ-ch 2 ), 21.0 (p-ch mes 3 ). 1 H, 1 H GCOSY (600 MHz/600 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 6.75 / 2.92, 2.03 (m-mes / o-ch mes 3, p-ch mes 3 ), 6.03 / 1.98, 1.69 (=CH / β-ch 2, γ'-ch 2 ), 1.98 / 6.03, 1.69, 1.24 (β-ch 2 / =CH, γ'-ch 2, γ-ch 2 ), 1.69 / 6.03, 1.98, 1.19 (γ'-ch 2 / =CH, β-ch 2, δ-ch 2 ). 1 H, 13 C GHSQC (600 MHz/151 MHz, 299 K, benzene-d 6 ): δ 1 H / δ 13 C: 6.75 / (m-mes), 6.03 / (=CH), 2.92 / 23.3 (o-ch mes 3 ), 2.03 / 21.0 (p-ch mes 3 ), 1.98 / 28.9 (β-ch 2 ), 1.69 / 25.8 (γ'-ch 2 ), 1.24 / 22.3 (γ-ch 2 ), 1.19 / 21.5 (δ-ch 2 ). 1 H, 13 C GHMBC (600 MHz/151 MHz, 299 K, benzene-d 6 ) [selected traces]: δ 1 H / δ 13 C: 6.03 / 107.8, 28.9, 25.8, 21.5 (=CH / C, β-ch 2, γ'-ch 2, δ-ch 2 ), 2.92 / 144.7, 130.0, (o-ch mes 3 / o-mes, m- mes, i-mes), 2.03 / 140.4, (p-ch mes 3 / p-mes, m-mes), 1.98 / 136.5, 121.4, 107.8, 22.3, 21.5 (β- CH 2 / =CH, C=, C, γ-ch 2, δ-ch 2 ). S7 of 24

8 1 H{ 1 H} NOESY (600 MHz, 299 K, benzene-d 6 )[selected experiments]: δ 1 H irr / δ 1 H res : 6.75 / 2.92, 2.03 (m-mes / o-ch mes 3, p-ch mes 3 ), 6.03 / 2.92, 1.69 (=CH / o-ch mes 3, γ'-ch 2 ), 1.69 / 6.03, 1.24 (w), 1.19 (γ'-ch 2 / =CH, γ-ch 2 (w), δ-ch 2 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: ( 1/2 1 Hz). 1 H NMR (600 MHz, 299 K, benzene-d 6), 13 C{ 1 H}NMR (151 MHz, 299 K, benzene-d 6) and 31 P{ 1 H}NMR (243 MHz, 299 K, benzene-d 6) spectra of compound 9b. Preparation of compound 10a 2-Methylbutenyne (1.13 g, 17 mmol, 2.5 eq) in pentane (80 ml) was cooled to 0 C and n-buli (10 ml, 1.6 M in hexane, 16 mmol, 2.4 eq) was added. Subsequently the resulting colourless suspension was stirred for 15 min at 0 C and another 15 min at rt. Then tipppxy (2.3 g, 6.8 mmol, 1 eq) was added in portions in a glovebox. The stirred reaction mixture was then cooled to 0 C and allowed to warm to rt overnight. Insolubles were filtered off over Celite and washed with pentane (15 ml) twice. Removal of the volatiles in vacuo yielded compound 10a as colourless solid (2.21 g, 90%). Anal. Calc. for C 25 H 33 P: C, 82.38; H, Found C, 82.36; H, IR (KBr) [cm -1 ] = 2963, 2952, 2867, 2150 ( C C ), 2117, 1816, 1598, 1544, 1462, 1435, 1380, 1315, 1273, 1166, 1135, 1101, 1061, 1039, 1010, 981, 940, 907, 881, 854, 649, 633, 550, 440, 417. S8 of 24

9 Melting point (DSC): 119 C. Decomposition (DSC): 209 C. 1 H NMR (500 MHz, 298 K, benzene-d 6 ): δ 1 H: 7.16 (d, 4 J PH = 3.1 Hz, 2H, m-tipp), 5.22 (m, 2H, =CH E 2 ), 4.92 (m, 2H, =CH Z 2 ), 4.57 (m, 2H, o-ch tipp ), 2.73 (sept, 3 J HH = 6.9 Hz, 1H, p-ch tipp ), 1.59 (m, 6H, CH 3 ), 1.38 (d, 3 J HH = 6.7 Hz, 12H, o-ch tipp 3 ), 1.17 (d, 3 J HH = 6.9 Hz, 6H, p-ch tipp 3 ). 13 C{ 1 H} NMR (126 MHz, 298 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 17.4 Hz, o-tipp), (d, 4 J PC = 1.6 Hz, p-tipp), (d, 3 J PC = 2.0 Hz, C=), (i-tipp), (d, 4 J PC = 2.8 Hz, =CH 2 ), (d, 3 J PC = 5.8 Hz, m-tipp), (d, 2 J PC = 10.0 Hz, C ), 84.2 (d, 1 J PC = 3.0 Hz, PC ), 34.8 (p-ch tipp ), 33.2 (d, 3 J PC = 19.8 Hz, o-ch tipp ), 24.9 (o-ch tipp 3 ), 24.0 (p-ch tipp 3 ), 22.8 (d, 4 J PC = 1.5 Hz, CH 3 ). 1 H, 1 H GCOSY (500 MHz/500 MHz, 298 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 4.57 / 1.38 (o- CH tipp / o-ch tipp 3 ), 2.73 / 1.17 (p-ch tipp / p-ch tipp 3 ), 1.59 / 5.22, 4.92 (CH 3 / =CH Z 2, =CH E 2 ). 1 H, 13 C GHSQC (500 MHz/126 MHz, 298 K, benzene-d 6 ): δ 1 H / δ 13 C: 7.16 / (m-tipp), 5.22, 4.92 / (CH 2 ), 4.57 / 33.2 (o-ch tipp ), 2.73 / 34.8 (p-ch tipp ), 1.59 / 22.8 (CH 3 ), 1.38 / 24.9 (o-ch tipp 3 ), 1.17 / 24.0 (p-ch tipp 3 ). 1 H, 13 C GHMBC (500 MHz/126 MHz, 298 K, benzene-d 6 ) [selected traces]: δ 1 H / δ 13 C: 5.22, 4.92 / 127.0, 107.4, 22.8 (CH 2 / C=, C, CH 3 ), 4.57 / 155.4, 126.4, 122.8, 24.9 (o-ch tipp / o-tipp, i-tipp, m-tipp, o-ch tipp 3 ), 2.73 / 152.3, 122.8, 24.0 (p-ch tipp / p-tipp, m-tipp, p-ch tipp 3 ). 1 H{ 1 H} NOESY (500 MHz, 298 K, benzene-d 6 )[selected experiments]: δ 1 H irr / δ 1 Z H res : 5.22 / 4.92 (=CH 2 / =CH E 2 ), 4.92 / 5.22, 1.59 (=CH E 2 / =CH Z 2, CH 3 ). 31 P{ 1 H} NMR (202 MHz, 298 K, benzene-d 6 ): δ 31 P: ( 1/2 2 Hz). 1 H NMR (500 MHz, 298 K, benzene-d 6), 13 C{ 1 H} NMR (126 MHz, 298 K, benzene-d 6) and 31 P{ 1 H} NMR (202 MHz, 298 K, benzene-d 6) spectra of compound compound 10a. S9 of 24

10 Crystals suitable for the X-ray crystal structure analysis were obtained by slow evaporation of a pentane solution of the reaction of compound 10a with MeB(C 6 F 5 ) 2. X-ray crystal structure analysis of compound 10a: formula C 25 H 33 P, M = , pale yellow crystal, 0.12 x 0.05 x 0.02 mm, a = (1), b = (1), c = (1) Å, β = (1), V = (3) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.886 T 0.979), Z = 4, monoclinic, space group Cc (No. 9), λ = Å, T = 223(2) K, ω and φ scans, 6371 reflections collected (±h, ±k, ±l), [(sin )/λ] = 0.60 Å -1, 3532 independent (R int = 0.047) and 2848 observed reflections [I>2σ(I)], 244 refined parameters, R = 0.057, wr 2 = 0.141, max. (min.) residual electron density 0.18 (-0.17) e.å -3, hydrogen atoms calculated and refined as riding atoms. Flack parameter: 0.48(4). Preparation of compound 10b Cyclohexenylacetylene (640 mg, 6 mmol, 2.4 eq) in pentane (80 ml) was cooled to -78 C and n- BuLi (3.4 ml, 1.6 M in hexane, 5.5 mmol, 2.2 eq) was added. Subsequently, the resulting colourless suspension was stirred for 1 h at -78 C and warmed to rt. Then tipppxy (800 mg, 2.5 mmol, 1 eq) was added in and the reaction mixture was stirred for 3 h at rt [Completion of the reaction was confirmed by 31 P NMR spectroscopy]. CH 2 Cl 2 (5 ml) was added at rt, the insolubles were filtered off over Celite and washed with boiling pentane (20 ml) twice. Removal of the volatiles in vacuo yielded compound 10b as colourless crystalline solid (985 mg, 89%). S10 of 24

11 Anal. Calc. for C 31 H 41 P: C, 83.74; H, Found C, 83.78; H, IR (KBr) [cm -1 ] = 3027(m), 2968(s), 2146 (s, C C), 1624(m), 1599(s), 1559(m), 1458(s), 1434(s), 1380(m), 1361(m), 1311(w), 1266(m), 1237(s), 1167(s), 1134(s), 1102(s), 1072(s), 1042(s), 936(m), 918(s), 879(s), 863(m), 841(m), 787(s), 692(s), 636(m), 575(w), 545(s), 470(w). Melting point (DSC): 145 C. Decomposition (DSC): >250 C. 1 H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 7.18 (d, 4 J PH = 3.2 Hz, 2H, m-tipp), 6.05 (m, 2H, =CH), 4.65 (oct, 3 J HH 4 J PH = 6.8 Hz, 2H, o-ch tipp ), 2.76 (sept, 3 J HH = 6.9 Hz, 1H, p-ch tipp ), 1.98 (m, 4H, β- CH 2 ), 1.71 (m, 4H, γ'-ch 2 ), 1.42 (d, 3 J HH = 6.8 Hz, 12H, o-ch tipp 3 ), 1.26 (m, 4H, γ-ch 2 ), 1.21 (m, 4H, δ- CH 2 ), 1.20 (d, 3 J HH = 6.9 Hz, 6H, p-ch tipp 3 ). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 17.2 Hz, o-tipp), (d, 4 J PC = 1.5 Hz, p-tipp), (dm, 4 J PC = 2.7 Hz, =CH), (d, 1 J PC = 1.5 Hz, i-tipp), (d, 3 J PC = 5.7 Hz, m-tipp), (d, 3 J PC = 1.8 Hz, C=), (d, 2 J PC = 10.2 Hz, C ), 82.5 (d, 1 J PC = 1.3 Hz, PC ), 34.8 (p-ch tipp ), 33.0 (d, 3 J PC = 20.0 Hz, o-ch tipp ), 29.0 (d, 4 J PC = 1.6 Hz, β-ch 2 ), 25.8 (γ'-ch 2 ), 25.1 (o-ch tipp 3 ), 24.1 (p-ch tipp 3 ), 22.4 (γ-ch 2 ), 21.6 (δ-ch 2 ). 1 H, 1 H GCOSY (600 MHz/600 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 6.05 / 1.98, 1.71 (=CH / β-ch 2, γ'-ch 2 ), 4.65 / 1.42 (o-ch tipp / o-ch tipp 3 ), 2.76 / 1.20 (p-ch tipp / p-ch tipp 3 ), 1.26 / 1.98, 1.21 (γ-ch 2 / β-ch 2, δ-ch 2 ). 1 H, 13 C GHSQC (600 MHz/151 MHz, 299 K, benzene-d 6 ): δ 1 H / δ 13 C: 7.18 / (m-tipp), 6.05 / (=CH), 4.65 / 33.0 (o-ch tipp ), 2.76 / 34.8 (p-ch tipp ), 1.98 / 29.0 (β-ch 2 ), 1.71 / 25.8 (γ'-ch 2 ), 1.42 / 25.1 (o-ch tipp 3 ), 1.26 / 22.4 (γ-ch 2 ), 1.21 / 21.6 (δ-ch 2 ), 1.20 / 24.1 (p-ch tipp 3 ). 1 H, 13 C GHMBC (600 MHz/151 MHz, 299 K, benzene-d 6 ) [selected traces]: δ 1 H / δ 13 C: 6.05 / 121.4, 108.0, 29.0, 25.8, 21.6 (=CH / C=, C, β-ch 2, γ'-ch 2, δ-ch 2 ), 4.65 / 155.3, 127.4, 122.7, 25.1 (o-ch tipp / o-tipp, i-tipp, m-tipp, o-ch tipp 3 ), 2.76 / 151.9, 122.7, 24.1 (p-ch tipp / p-tipp, m-tipp, p-ch tipp 3 ), 1.21 / 136.6, 29.0, 25.8, 22.4 (δ-ch 2 / =CH, β-ch 2, γ'-ch 2, γ-ch 2 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: ( 1/2 1 Hz). 1 H NMR (600 MHz, 299 K, benzene-d 6) spectrum of compound 10b. S11 of 24

12 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound 10b. Preparation of the Borata-alkene derivatives Preparation of compound 12a Compound 9a (90 mg, 0.32 mmol, 1 eq) and HB(C 6 F 5 ) 2 (110 mg, 0.32 mmol, 1 eq) were suspended in pentane (5 ml) at rt and stirred overnight. Then insolubles were filtered off at rt and washed with pentane (1 ml) three times. The combined organic phases (brown solution) were cooled to -95 C and the resulting precipitate was allowed to sediment for 1 h at -95 C. Subsequently the supernatant solution was removed by cannula filtration. Drying of the residue in vacuo yielded compound 12a as a yellow-brown powder (140 mg, 70%). Anal. Calc. for C 31 H 22 BF 10 P: C, 59.45; H, Found C, 58.77; H, IR (KBr) [cm -1 ] = 3022, 2966, 2925, 2854, 2168 ( C C ), 1644, 1606, 1513, 1464, 1378, 1292, 1098, 1018, 975, 919, 894, 868, 852, 823, 782, 755, 733, 719, 678, 654, 630, 600, 566, 550, 530, 493, 416. Melting point (DSC): 50 C. Decomposition (DSC): >80 C. 1 H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 6.50 (dm, 4 J PH = 4.6 Hz, 2H, m-mes), 6.36 (dm, 3 J PH + 4 J PH = 44.3 Hz, 1H, H3), 5.34 (sext, 4 J HH 2 J HH 5 J PH = 1.1 Hz, 1H, =CH E 2 ), 4.99 (m, 1H, =CH Z 2 ), 2.59 (dm, 2 J PH = 9.4 Hz, 2H, H5), 2.36 (s, 6H, o-ch mes 3 ), 1.94 (s, 3H, p-ch mes 3 ), 1.62 (m, 3H, 4-CH 3 ), 1.56 (tm, 4 J HH 4 J HH = 1.2 Hz, 3H, CH 3 ). S12 of 24

13 1 H{ 31 P} NMR (600 MHz, 299 K, benzene-d 6 )[selected resonances]: δ 1 H: 6.50 (s, 2H, m-mes), 6.36 (m, 1H, H3), 5.34 (quint, 4 J HH = 2 J HH = 1.1 Hz, 1H, =CH Z 2 ), 4.99 (quint, 4 J HH = 2 J HH = 1.1 Hz, 1H, =CH E 2 ), 2.59 (m, 2H, H5), 1.56 (t, 4 J HH = 4 J HH = 1.2 Hz, 3H, CH 3 ). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 11.4 Hz, o-mes), (d, 4 J PC = 3.2 Hz, p-mes), (d, 2 J PC + 3 J PC = 24.6 Hz, C3), (d, 3 J PC = 12.0 Hz, m-mes), (=CH 2 ) a, (d, 3 J PC = 4.4 Hz, C=), (d, 2 J PC + 3 J PC = 13.5 Hz, C4), (d, 1 J PC = 92.8 Hz, i- mes), (d, 2 J PC = 24.7 Hz, C ), 94.7 (br, C2), 79.3 (d, 1 J PC = Hz, PC ), 40.6 (d, 1 J PC = 64.6 Hz, C5), 22.6 (d, 3 J PC = 4.6 Hz, o-ch mes 3 ), 21.1 (CH 3 ), 20.6 (d, 5 J PC = 1.6 Hz, p-ch mes 3 ), 18.2 (d, 3 J PC + 4 J PC = 11.2 Hz, 4-CH 3 ), [not listed C 6 F 5 ; a from ghsqc]. 1 H, 1 H GCOSY (600 MHz/600 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 6.50 / 2.36, 1.94 (m-mes / o-ch mes 3, p-ch mes 3 ), 1.62 / 6.36, 2.59 (4-CH 3 / H3, H5), 1.56 / 5.34, 4.99 (CH 3 / =CH Z 2, =CH E 2 ). 1 H, 13 C GHSQC (600 MHz/151 MHz, 299 K, benzene-d 6 ): δ 1 H / δ 13 C: 6.50 / (m-mes), 6.36 / (3-CH), 5.34, 4.99 / (=CH 2 ), 2.59 / 40.6 (5-CH 2 ), 2.36 / 22.6 (o-ch mes 3 ), 1.94 / 20.6 (p- CH mes 3 ), 1.62 / 18.2 (4-CH 3 ), 1.56 / 21.1 (CH 3 ). 1 H, 13 C GHMBC (600 MHz/151 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 13 C: 6.36 / 118.5, 94.7, 40.6, 18.2 (H3 / C4, C2, C5, 4-CH 3 ), 2.59 / 135.9, 118.5, 79.3 (H5/ C3, C4, PC ), 2.36 / 143.8, 131.7, (o-ch mes 3 / o-mes, m-mes, i-mes), 1.94 / 143.5, (p-ch mes 3 / p-mes, m-mes), 1.56 / 127.8, 125.0, (CH 3 / =CH 2, C=, C ). 1 H{ 1 H} NOESY (600 MHz, 299 K, benzene-d 6 )[selected experiments]: δ 1 H irr / δ 1 H res : 6.36 / 2.36, 1.62 (H3 / o-ch mes 3, 4-CH 3 ), 5.34 / 4.99 (=CH Z 2 / =CH E 2 ), 4.99 / 5.34, 1.56 (=CH E 2 / =CH Z 2, CH 3 ), 2.59 / 2.36, 1.62 (H5 / o-ch mes 3, 4-CH 3 ). 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6 ): δ 11 B: 33.5 ( 1/2 600 Hz). 19 F NMR (564 MHz, 299 K, benzene-d 6 ): δ 19 F: (m, 2F, o-c 6 F A 5 ), (m, 2F, o-c 6 F B 5 ), (t, 3 J FF = 20.6 Hz, 1F, p-c 6 F B 5 ), (t, 3 J FF = 20.3 Hz, 1F, p-c 6 F A 5 ), (m, 2F, m-c 6 F B 5 ), (m, 2F, m-c 6 F A 5 ), [ 19 F mp = 5.8 Hz A, 6.8 Hz B ]. 19 F, 19 F GCOSY (564 MHz/564 MHz, 299 K, benzene-d 6 )[selected traces]: δ 19 F / δ 19 F: / , (m-c 6 F B 5 / o-c 6 F B 5, p-c 6 F B 5 ), / , (m-c 6 F A 5 / o-c 6 F A 5, p-c 6 F A 5 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: 11.4 ( 1/2 ~ 6 Hz). 31 P NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: 11.4 (dm, 3 J PH + 4 J PH = 44.3 Hz). 1 H NMR (600 MHz, 299 K, benzene-d 6) spectrum of compound 12a. S13 of 24

14 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6) spectrum of compound 12a. 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6), 19 F NMR (564 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound 12a. Crystals suitable for the X-ray crystal structure analysis were obtained from a concentrate pentane solution of compound 12a at -35 C. X-ray crystal structure analysis of compound 12a: formula C 31 H 22 BF 10 P, M = , yellow crystal, 0.27 x 0.12 x 0.04 mm, a = (5), b = (3), c = (7) Å, β = (2), V = (2) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.666 T 0.937), Z = 4, monoclinic, space group P2 1 /c (No. 14), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), [(sin )/λ] = 0.60 Å -1, 5019 independent (R int = 0.044) and 4304 observed reflections [I>2σ(I)], 401 refined parameters, R = 0.042, wr 2 = 0.118, max. (min.) residual electron density 0.25 (-0.25) e.å -3, the hydrogens at C14 atom were refined freely; others were calculated and refined as riding atoms. S14 of 24

15 In situ reaction to generate compound 12a (NMR scale) without workup Compound 9a (40 mg, 0.14 mmol, 1 eq) and HB(C 6 F 5 ) 2 (49 mg, 0.14 mmol, 1 eq) in C 6 D 6 (1 ml) were stirred for 5 min at rt. 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6), 19 F NMR (564 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of the in situ generated compound 12a. S15 of 24

16 Preparation of compound 14a HB(C 6 F 5 ) 2 (95 mg, 0.28 mmol, 1 eq) was added to a solution of compound 9b (105 mg, 0.28 mmol, 1 eq) in pentane (3 ml) at rt and the reaction mixture was stirred overnight. Then insolubles were removed by filtration and the obtained solid was washed with pentane (1 ml) twice at rt. The filtrates were combined and all volatiles were removed in vacuo to give compound 14a as a green solid (140 mg, 70%). The compound was further purified by precipitation from pentane at -95 C. Anal. Calc. for C 37 H 30 BF 10 P: C, 62.91; H, Found C, 62.38; H, IR (KBr) [cm -1 ] = 3025 (w), 2934(s), 2860(m), 2162 (s, C C), 1643(m), 1605(m), 1514(m), 1473(m), 1383(w), 1319(w), 1127(m), 1095(m), 1043(w), 972(s), 881(m), 859(m), 803(m), 738(w), 677(w), 650(m), 614(w), 574(w). Decomposition (DSC): >80 C (decomp.). 1 H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 6.70 (m, 1H, m-mes), 6.52 (m, 1H, m'-mes), 6.35 (dm, 3 J PH + 4 J PH = 41.4 Hz, 1H, H3), 6.22 (m, 1H, =CH), 3.14 (m, 1H, H5), 2.84 (s, 3H, o-ch mes 3 ), 2.39/1.88 (each m, each 1H, 9-CH 2 ) t, 2.38 (s, 3H, o'-ch mes 3 ), 2.00/1.94 (each m, each 1H, β-ch 2 ) t, 1.94 (s, 3H, p-ch mes 3 ), 1.72 (m, 2H, γ'-ch 2 ) t, 1.48/0.96 (each m, each 1H, 8-CH 2 ) t, 1.36/0.95 (each m, each 1H, 7- CH 2 ) t, 1.35/0.95 (each m, each 1H, 6-CH 2 ) t, 1.29 (m, 2H, γ-ch 2 ) t, 1.20 (m, 2H, δ-ch 2 ) t, [ t position in the cyclic subunit tentatively assigned]. 1 H{ 31 P} NMR (600 MHz, 299 K, benzene-d 6 )[selected resonance]: δ 1 H: 6.35 (m, 1H, H3). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 15.5 Hz, o-mes), (d, 4 J PC = 3.2 Hz, p-mes), (d, 4 J PC = 3.0 Hz, =CH), (d, 2 J PC = 6.2 Hz, o'-mes), (d, 2 J PC + 3 J PC = 26.0 Hz, C3), (d, 3 J PC = 13.0 Hz, m-mes), (d, 3 J PC = 10.3 Hz, m'-mes), (d, 2 J PC + 3 J PC = 14.9 Hz, C4), (d, 3 J PC = 4.7 Hz, C=), (d, 1 J PC = 84.8 Hz, i-mes), (d, 2 J PC = 25.7 Hz, C ), 92.4 (br m, C2), 76.8 (d, 1 J PC = Hz, PC ), 48.7 (d, 1 J PC = 61.4 Hz, C5), 30.7 (d, 3 J PC = 7.2 Hz, C9) t, 27.5 (m, C6) t, 27.5 (m, β-ch 2 ) t, 26.6 (C8) t, 26.2 (d, 3 J PC = 13.9 Hz, C7) t, 26.0 (γ'-ch 2 ) t, 25.3 (d, 3 J PC = 5.8 Hz, o'-ch mes 3 ), 23.2 (br, o-ch mes 3 ), 21.8 (γ-ch 2 ) t, 21.0 (δ-ch 2 ) t, 20.7 (d, 5 J PC = 1.5 Hz, p-ch mes 3 ), [C 6 F 5 not listed; t position in the cyclic subunit tentatively assigned]. 1 H, 1 H GCOSY (600 MHz/600 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 6.70 / 6.52, 2.84, 2.38, 1.94 (m-mes / m'-mes, o-ch mes 3, o'-ch mes 3, p-ch mes 3 ), 6.22 / 2.00, 1.94, 1.72 (=CH / β-ch 2, γ'- CH 2 ), 3.14 / 6.35, 2.39, 1.88, 1.48, 0.96, 1.36, 1.35 (H5 / H3, 9-CH 2, 8-CH 2, 7-CH 2, 6-CH 2 ), 1.20 / 1.72, 1.29 (δ-ch 2 / γ'-ch 2, γ-ch 2 ). 1 H, 13 C GHSQC (600 MHz/151 MHz, 299 K, benzene-d 6 ): δ 1 H / δ 13 C: 6.70 / (m-mes), 6.52 / (m'-mes), 6.35 / (3-CH), 6.22 / (=CH), 3.14 / 48.7 (5-CH), 2.84 / 23.2 (o-ch mes 3 ), S16 of 24

17 2.39, 1.88 / 30.7 (9-CH 2 ), 2.38 / 25.3 (o'-ch mes 3 ), 2.00, 1.94 / 27.5 (β-ch 2 ), 1.94 / 20.7 (p-ch mes 3 ), 1.72 / 26.0 (γ'-ch 2 ), 1.48, 0.96 / 26.6 (8-CH 2 ), 1.36, 0.95 / 26.2 (7-CH 2 ), 1.35, 0.95 / 27.5 (6-CH 2 ), 1.29 / 21.8 (γ-ch 2 ), 1.20 / 21.0 (δ-ch 2 ). 1 H, 13 C GHMBC (600 MHz/151 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 13 C: 6.70 / 131.3, 117.2, 23.2, 20.7 (m-mes / m'-mes, i-mes, o-ch mes 3, p-ch mes 3 ), 6.52 / 132.1, 117.2, 25.3, 20.7 (m'-mes / m-mes, i-mes, o'-ch mes 3, p-ch mes 3 ), 6.35 / 127.7, 92.4, 48.7, 30.7 (H3 / C4, C2, C5, 9-CH 2 ), 6.22 / 113.4, 27.5, 21.0 (=CH / C, β-ch 2, δ-ch 2 ), 2.39, 1.88 / 127.7, 48.7, 26.6, 26.2 (9-CH 2 / C4, C5, 8- CH 2, 7-CH 2 ), 1.48, 0.96 / 127.7, 27.5 (8-CH 2 / C4, 6-CH 2 ), 1.29 / 119.3, 27.5, 26.0, 21.0 (γ-ch 2 / C=, β-ch 2, γ'-ch 2, δ-ch 2 ). 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6 ): δ 11 B: 34.0 ( 1/2 850 Hz). 19 F NMR (564 MHz, 299 K, benzene-d 6 ): δ 19 F: (m, 2F, o-c 6 F A 5 ), (m, 2F, o-c 6 F B 5 ), (t, 3 J FF = 20.6 Hz, 1F, p-c 6 F B 5 ), (t, 3 J FF = 20.5 Hz, 1F, p-c 6 F A 5 ), (m, 2F, m-c 6 F B 5 ), (m, 2F, m-c 6 F A 5 ), [ 19 F mp = 5.9 Hz A, 6.3 Hz B ]. 19 F, 19 F GCOSY (564 MHz/564 MHz, 299 K, benzene-d 6 ): δ 19 F / δ 19 F: / , (m-c 6 F B 5 / o-c 6 F B 5, p-c 6 F B 5 ), / , (m-c 6 F A 5 / o-c 6 F A 5, p-c 6 F A 5 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: 15.4 (ca. 94%, 1/2 ~ 5 Hz), 18.4 (impurity, ca. 6%, 1/2 2 Hz). 31 P NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: 15.4 (ca. 94%, d, 3 J PH + 4 J PH = 41.4 Hz), 18.0 (impurity, ca. 6%, 1/2 65 Hz). 1 H NMR (600 MHz, 299 K, benzene-d 6) and 1 H{ 1 H} tocsy (600 MHz, 299 K, benzene-d 6, *Irradiation point) spectra of compound 14a. S17 of 24

18 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6) spectrum of compound 14a. 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6), 19 F NMR (564 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound 14a. 1 H, 13 C ghsqc (600 MHz/151 MHz, 299 K, benzene-d 6) spectrum of compound 14a. S18 of 24

19 Crystals suitable for the X-ray crystal structure analysis were obtained from a pentane solution of compound 14a at -35 C. X-ray crystal structure analysis of compound 14a: formula C 37 H 30 BF 10 P, M = , yellow crystal, 0.30 x 0.25 x 0.10 mm, a = (2), b = (2), c = (3) Å, β = (1), V = (2) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.952 T 0.983), Z = 4, monoclinic, space group P2 1 /c (No. 14), λ = Å, T = 223(2) K, ω and φ scans, reflections collected (±h, ±k, ±l), [(sin )/λ] = 0.59 Å -1, 5809 independent (R int = 0.032) and 4852 observed reflections [I>2σ(I)], 445 refined parameters, R = 0.054, wr 2 = 0.142, max. (min.) residual electron density 0.33 (-0.24) e.å -3, hydrogen atoms were calculated and refined as riding atoms. In situ reaction to generate compound 14a (NMR scale) without workup HB(C 6 F 5 ) 2 (43 mg, 0.12 mmol, 1 eq) was added at rt to a solution of compound 9b (45 mg, 0.12 mmol, 1 eq) in C 6 D 6 (1 ml). The reaction mixture was shaken for 15 min before it was charcterized by NMR experiments. S19 of 24

20 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6), 19 F NMR (564 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound the in situ generated compound 14a. Preparation of compound 14b Compound 10b (115 mg, 0.25 mmol, 1 eq) and HB(C 6 F 5 ) 2 (87 mg, 0.25 mmol, 1 eq) were suspended in pentane (3 ml) at rt and then stirred overnight. Subsequently the reaction mixture was cooled to -35 C for precipitation. The green supernatant solution was removed by decantation and the residue was washed with pentane (1 ml) at -35 C twice. Drying of the residue in vacuo yielded compound 14b as a yellow-green solid. Concentration of the filtrate and a second crystallization at -35 C yields another 20 mg of compound 14b (overall: 140 mg, 70%). Anal. Calc. for C 43 H 42 BF 10 P: C, 65.33; H, Found C, 65.16; H, IR (KBr) [cm -1 ] = 3015(w), 2963(s), 2935(s), 2867(s), 2824(m), 2163 (s, C C), 1644(m), 1600(m), 1514(m), 1473(m), 1415(w), 1383(w), 1364(w), 1346(w), 1319(w), 1291(m), 1184(w), 1130(m), 1040(w), 972(s), 881(s), 865(s), 845(w), 804(m), 739(m), 718(m), 675(m), 649(s), 626(m), 571(m), 555(m), 504(w), 485(w), 462(w). Melting point (DSC): 160 C. 1 H NMR (600 MHz, 299 K, benzene-d 6 ): δ 1 H: 7.24 (dd, 4 J PH = 4.7 Hz, 4 J HH = 1.8 Hz, 1H, m-tipp), 7.07 (dd, 4 J PH = 3.9 Hz, 4 J HH = 1.8 Hz, 1H, m'-tipp), 6.45 (dm, 3 J PH + 4 J PH = 40.7 Hz, 1H, H3), 6.21 (m, 1H, =CH), 3.88 (m, 1H, o-ch tipp ), 3.77 (m, 1H, o'-ch tipp ), 3.35 (m, 1H, H5), 2.71 (sept, 3 J HH = 6.9 Hz, 1H, p- CH tipp ), 2.43/1.92 (each m, each 1H, 9-CH 2 ) t, 1.98/1.88 (each m, each 1H, β-ch 2 ) t, 1.74 (m, 2H, γ'- CH 2 ) t, 1.65 (d, 3 J HH = 6.4 Hz, 3H, o-ch tipp 3 ), 1.63/1.22 (each m, each 1H, 6-CH 2 ) t, 1.50/0.99 (each m, S20 of 24

21 each 1H, 8-CH 2 ) t, 1.46/1.00 (each m, each 1H, 7-CH 2 ) t, 1.30 (m, 2H, γ-ch 2 ) t, 1.23 (d, 3 J HH = 6.4 Hz, 3H, o'-ch tipp 3 ), 1.21 (m, 2H, δ-ch 2 ) t, 1.20, 1.19 (each d, each 3 J HH = 6.9 Hz, each 3H, p-ch tipp 3 ), 1.09 (d, 3 J HH = 6.7 Hz, 3H, o-ch 3 tipp ), 1.01 (d, 3 J HH = 6.7 Hz, 3H, o'-ch 3 tipp ), [ t position in the cyclic subunit tentatively assigned]. 1 H{ 31 P} NMR (600 MHz, 299 K, benzene-d 6 )[selected resonances]: δ 1 H: 7.24 (d, 4 J HH = 1.8 Hz, 1H, m- tipp), 7.07 (d, 4 J HH = 1.8 Hz, 1H, m'-tipp), 6.45 (m, 1H, H3), 6.21 (m, 1H, =CH), 3.88 (m, 1H, o-ch tipp ), 3.77 (m, 1H, o'-ch tipp ), 3.35 (m, 1H, H5), 2.71 (sept, 3 J HH = 6.9 Hz, 1H, p-ch tipp ), 2.43 (d, 2 J HH = 14.2 Hz, 1H, H9 eq ). 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6 ): δ 13 C: (d, 2 J PC = 16.4 Hz, o-tipp), (d, 4 J PC = 3.1 Hz, p-tipp), (d, 2 J PC = 6.9 Hz, o'-tipp), (d, 4 J PC = 3.1 Hz, =CH), (d, 2 J PC + 3 J PC = 25.5 Hz, C3), (d, 2 J PC + 3 J PC = 14.9 Hz, C4), (d, 3 J PC = 13.0 Hz, m-tipp), (d, 3 J PC = 10.2 Hz, m'-tipp), (d, 3 J PC = 4.6 Hz, C=), (d, 1 J PC = 84.4 Hz, i-tipp), (d, 2 J PC = 25.3 Hz, C ), 95.2 (br dm, J 64 Hz, C2), 77.3 (d, 1 J PC = Hz, PC ), 48.6 (d, 1 J PC = 60.3 Hz, C5), 34.5 (p-ch tipp ), 33.0 (d, 3 J PC = 6.3 Hz, o'-ch tipp ), 31.3 (d, 3 J PC = 6.0 Hz, o-ch tipp ), 30.5 (d, 3 J PC = 7.2 Hz, C9) t, 27.8 (d, 4 J PC = 1.5 Hz, β-ch 2 ) t, 27.5 (d, 2 J PC = 3.3 Hz, C6) t, 27.1 (o- CH 3 tipp ), 26.5 (C8) t, 26.2 (o'-ch 3 tipp ), 26.1 (d, 3 J PC = 14.0 Hz, C7) t, 26.0 (γ'-ch 2 ) t, 25.1 (o'-ch tipp 3 ), 23.6 (p-ch tipp 3 ) t, 23.5 (o-ch tipp 3 ) t, 23.4 (p-ch 3 tipp ) t, 21.8 (γ-ch 2 ) t, 21.0 (δ-ch 2 ) t, [C 6 F 5 not listed; t position in the cyclic subunit tentatively assigned]. 1 H, 1 H GCOSY (600 MHz/600 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 1 H: 7.24 / 7.07 (m-tipp / m'-tipp), 6.21 / 1.98, 1.88, 1.74 (=CH / β-ch 2, γ'-ch 2 ), 3.88 / 1.65, 1.09 (o-ch tipp / o-ch tipp 3 ), 3.77 / 1.23, 1.01 (o'-ch tipp / o'-ch tipp 3 ), 3.35 / 6.45, 2.43, 1.92, 1.63, 1.22, 1.00 (H5 / H3, 9-CH 2, 6-CH 2, 7- CH 2 ), 2.71 / 1.19 (p-ch tipp / p-ch tipp 3 ), 2.43/1.92 / 6.45, 1.50, 1.46, 0.99 (9-CH 2 / H3, 8-CH 2, 7-CH 2 ), 1.30 / 1.98, 1.88, 1.21 (γ-ch 2 / β-ch 2, δ-ch 2 ). 1 H, 13 C GHSQC (600 MHz/151 MHz, 299 K, benzene-d 6 ): δ 1 H / δ 13 C: 7.24 / (m-tipp), 7.07 / (m'-tipp), 6.45 / (3-CH), 6.21 / (=CH), 3.88 / 31.3 (o-ch tipp ), 3.77 / 33.0 (o'-ch tipp ), 3.35 / 48.6 (5-CH), 2.71 / 34.5 (p-ch tipp ), 2.43, 1.92 / 30.5 (9-CH 2 ), 1.98, 1.88 / 27.8 (β-ch 2 ), 1.74 / 26.0 (γ'- CH 2 ), 1.65 / 23.5 (o-ch tipp 3 ), 1.63, 1.22 / 27.5 (6-CH 2 ), 1.50, 0.99 / 26.5 (8-CH 2 ), 1.46, 1.00 / 26.1 (7- CH 2 ), 1.30 / 21.8 (γ-ch 2 ), 1.23 / 25.0 (o'-ch tipp 3 ), 1.21 / 21.0 (δ-ch 2 ), 1.19 / 23.6, 23.4 (p-ch tipp 3 ), 1.09 / 27.1 (o-ch 3 tipp ), 1.01 / 26.2 (o'-ch 3 tipp ). 1 H, 13 C GHMBC (600 MHz/151 MHz, 299 K, benzene-d 6 )[selected traces]: δ 1 H / δ 13 C: 6.45 / 125.7, 95.2, 48.6, 30.5 (H3 / C4, C2, C5, C9), 6.21 / 111.6, 27.8, 26.0, 21.0 (=CH / C, β-ch 2, γ'-ch 2, δ- CH 2 ), 3.88 / 158.1, 124.7, 117.2, 27.1, 23.5 (o-ch tipp / o-tipp, m-tipp, i-tipp, o-ch tipp 3 ), 3.77 / 154.0, 123.4, 117.2, 26.2, 25.0 (o'-ch tipp / o'-tipp, m'-tipp, i-tipp, o'-ch tipp 3 ), 3.35 / 133.4, 125.7, 117.2, 77.3, 27.5 (H5 / C3, C4, i-tipp, PC, C6), 2.71 / 154.3, 124.7, 123.4, 23.6, 23.4 (p-ch tipp / p-tipp, m-tipp, m'- tipp, p-ch tipp 3 ), 2.43, 1.92 / 133.4, 125.7, 48.6, 26.5 (9-CH 2 / C3, C4, C5, C8), 1.46, 1.00 / 48.6, 30.5 (7-CH 2 / C5, C9), 1.21 / 142.6, 27.8, 26.0, 21.8 (δ-ch 2 / =CH, β-ch 2, γ'-ch 2, γ-ch 2 ). 1 H{ 1 H} TOCSY (600 MHz, 299 K, benzene-d 6 )[selected experiments]: δ 1 H irr / δ 1 H res : 3.35 / 6.45, 2.43, 1.92, 1.63, 1.50, 1.46, 1.22, 1.00, 0.99 (H5 / H3, 9-CH 2, 6-CH 2, 8-CH 2, 7-CH 2 ), 1.74 / 6.21, 1.98, 1.88, 1.30, 1.21 (γ'-ch 2 / =CH, β-ch 2, γ-ch 2, δ-ch 2 ). 1 H{ 1 H} NOESY (600 MHz, 299 K, benzene-d 6 )[selected experiments]: δ 1 H irr / δ 1 H res : 3.35 / 6.45, 3.77, 1.92, 1.63, 1.46 (w), 0.99 (H5 / H3, o'-ch tipp, 9-CH 2, 6-CH 2, 7-CH 2, 8-CH 2 ). S21 of 24

22 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6 ): δ 11 B: 33.8 ( 1/2 900 Hz). 19 F NMR (564 MHz, 299 K, benzene-d 6 ): δ 19 F: (m, 2F, o-c 6 F A 5 ), (m, 2F, o-c 6 F B 5 ), (t, 3 J FF = 20.5 Hz, 1F, p-c 6 F B 5 ), (t, 3 J FF = 20.5 Hz, 1F, p-c 6 F A 5 ), (m, 2F, m-c 6 F B 5 ), (m, 2F, m-c 6 F A 5 ), [ 19 F mp = 5.8 Hz A, 6.3 Hz B ]. 19 F, 19 F GCOSY (564 MHz/564 MHz, 299 K, benzene-d 6 )[selected traces]: δ 19 F / δ 19 F: / , (m-c 6 F B 5 / o-c 6 F B 5, p-c 6 F B 5 ), / , (m-c 6 F A 5 / o-c 6 F A 5, p-c 6 F A 5 ). 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: 16.4 ( 1/2 4 Hz). 31 P NMR (243 MHz, 299 K, benzene-d 6 ): δ 31 P: 16.4 (dm, 3 J PH + 4 J PH 41 Hz). 1 H NMR (600 MHz, 299 K, benzene-d 6) and 1 H{ 1 H} tocsy (600 MHz, 299 K, benzene-d 6, *Irradiation point) spectra of compound 14b. 13 C{ 1 H} NMR (151 MHz, 299 K, benzene-d 6) spectrum of compound 14b. S22 of 24

23 1 H, 13 C ghsqc (600 MHz/151 MHz, 299 K, benzene-d 6) spectrum of compound 14b. 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6), 19 F NMR (564 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound 14b. Crystals suitable for the X-ray crystal structure analysis were obtained from a pentane solution of compound 14b at -35 C. X-ray crystal structure analysis of compound 14b: formula C 43 H 42 BF 10 P, M = , greenyellow crystal, 0.20 x 0.10 x 0.03 mm, a = (2), b = (3), c = (3) Å, β = (1), V = (1) Å 3, ρ calc = gcm -3, μ = mm -1, empirical absorption correction (0.971 T 0.995), 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), [(sin )/λ] = 0.59 Å -1, 6883 independent (R int = 0.061) and 4860 observed reflections [I>2σ(I)], 557 refined parameters, R = 0.066, wr 2 = 0.131, max. S23 of 24

24 (min.) residual electron density 0.28 (-0.27) e.å -3, hydrogen atoms were calculated and refined as riding atoms. In situ reaction to generate compound 14b (NMR scale) without workup 10b (45 mg, 0.10 mmol, 1 eq) was dissolved in C 6 D 6 (1 ml) and HB(C 6 F 5 ) 2 (35 mg, 0.10 mmol, 1 eq) was added at rt and the reaction mixture left to stand overnight at rt. 11 B{ 1 H} NMR (192 MHz, 299 K, benzene-d 6), 19 F NMR (564 MHz, 299 K, benzene-d 6) and 31 P{ 1 H} NMR (243 MHz, 299 K, benzene-d 6) spectra of compound the in situ generated compound 14b. S24 of 24