SUPPORTING INFORMATION

Transcription

1 SUPPORTING INFORMATION Preparing (Multi)Fluoroarenes as Building Blocks for Synthesis: Nickel-Catalyzed Borylation of Polyfluoroarenes via C-F Bond Cleavage Jing Zhou, a,b Maximilian W. Kuntze-Fechner, b Rüdiger Bertermann, b Ursula S. D. Paul, b Johannes H. J. Berthel, b Alexandra Friedrich, b Zhenting Du, a Todd B. Marder,* b Udo Radius* b u.radius@uni-wuerzburg.de, todd.marder@uni-wuerzburg.de a College of Science, Northwest A&F University, Yangling, Shaanxi , P. R. China; b Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg, Germany Table of Contents I. General Information S2 II. Optimization Details S3-S4 III. Experimental Procedures and Characterization of Products S5-S16 IV. NMR Spectra, GC-MS and HRMS data of Products S17-S44 V. Investigations Concerning the Reaction Mechanism S45-S63 VI. X-ray Crystal Structures S64-S68 VI. References S69 S1

2 I. General Information All manipulations, unless otherwise stated, were carried out under an atmosphere of argon using conventional Schlenk, vacuum-line and glove-box techniques. All reactions were carried out in oven-dried glassware. Toluene, hexane, MTBE and THF were purified by distillation from an appropriate drying agent (sodium with benzophenones as indicator). C 6 D 6 and CDCl 3 were purchased from Sigma-Aldrich. Commercially available methylcyclopentane and methylcyclohexane were used directly without drying. All other reagents were purchased from Aldrich or ABCR. AllyChem Co. Ltd. provided B 2 pin 2. [Ni(IMes) 2 ] and [Ni(IPr) 2 ] used were prepared according to the literature procedures. 1 Anhydrous NMe 4 F is commercially available; for this work, however, it was synthesized according to a literature procedure. 2 Analytical methods All NMR spectra were recorded at 298 K using a Bruker Avance I 500 ( 1 H NMR, MHz; 13 C{ 1 H} NMR, MHz; 19 F NMR, MHz; 11 B{ 1 H} NMR, MHz), a Bruker DPX 400 ( 19 F{ 1 H} NMR, MHz), and a Bruker Avance I 200 ( 19 F{ 1 H} NMR, MHz). 1 H NMR chemical shifts are reported relative to TMS and were referenced via residual proton resonances of the corresponding deuterated solvent (CHCl 3 : 7.26 ppm; C 6 D 5 H, 7.16 ppm) whereas 13 C{ 1 H} NMR spectra are reported relative to TMS using the naturalabundance carbon resonances (CDCl 3 : 77.0 ppm; C 6 D 6, ppm). 19 F and 19 F{ 1 H} NMR spectra are reported relative to external CFCl 3. GC-MS analyses were performed using an Agilent 7890A gas chromatograph (column: HP-5 MS 5% phenyl methyl siloxane, 30 m, 0.25 mm, film 0.25 μm; injector: 250 C; oven: 40 C (2 min), 40 C to 280 C (20 C min 1 ); carrier gas: He (1.2 ml min 1 ) equipped with an Agilent 5975C inert MSD with triple-axis detector operating in EI mode and an Agilent 7693A series auto sampler/injector. Elemental analysis was performed in the microanalytical laboratory of Institute of Inorganic Chemistry, University Würzburg, with an Elementar vario micro cube. Infrared spectra were recorded on a Bruker Alpha FT-IR spectrometer as solids by using an ATR unit and are reported in cm -1. HRMS were measured on a Thermo Scientific Exactive Plus equipped with an Orbitrap. ESI measurements were conducted using a HESI Source with an Aux-gas temperature of 50 C. Measurements were conducted using an APCI Source with a Corona Needle; aux-gas temperature was 400 C. S2

3 II. Optimization Details General Procedure for Catalyst Screening A mixture of [Ni(IMes) 2 ] (0.02 mmol, 13 mg), NMe 4 F (0.1 mmol, 9 mg) )/CsF (0.2 mmol, 31mg) (unless specified otherwise) and B 2 pin 2 (0.2 mmol, 51 mg; unless specified otherwise) was dissolved in the solvent (1 ml) in a Schlenk tube equipped with a magnetic stirring bar. The fluoroarene (0.22 mmol) was then added to the solution. The reaction mixture was heated at 80 C for 15 h and the products and yields were determined afterwards using in situ 19 F{ 1 H} NMR. The yields are based on B 2 pin 2, if 1 eq. was used, otherwise on the fluoroarene. Table S1: Screening of solvent for the borylation of 1,2,3-trifluorobenzene (1a). Entry 1a/B 2 pin 2 B 2 pin 2, base Solvent Yield (%) a,b eq. B 2 pin 2 (1 eq.), CsF (1 eq.) THF eq. B 2 pin 2 (1 eq.), CsF (1 eq.) hexane eq. B 2 pin 2 (1 eq.), CsF (1 eq.) mesitylene 50 (55) c eq B 2 pin 2 (1 eq.), CsF (1 eq.) methylcyclopentane 50 (29) d eq. B 2 pin 2 (1 eq.), CsF (1 eq.) MTBE eq. B 2 pin 2 (1 eq.), CsF (1 eq.) CH 3 CN 0 a Reaction conditions: [Ni(IMes)2] (10 % mmol), solvent (1 ml), 80 C, 15 h. The yields were determined by in situ 19 F NMR spectroscopy. b Trace amounts of isomeric C-F and C-H borylation products were detected by GC-MS. c Stirring for 2 days. d Microwave, 100 C, 2 h. Table S2: Screening of different equivalents of substrates for the borylation of 1,2,3-trifluorobenzene (1a). Entry 1a/B 2 pin 2 Base Solvent Yield (%) a,b 1 1.1:1 CsF (1 eq.) mesitylene :1 CsF (1 eq.) mesitylene :1 CsF (1 eq.) mesitylene :1 CsF (1 eq.) mesitylene :2 CsF (2 eq.) mesitylene 27 a Reaction conditions: [Ni(IMes)2] (10 % mmol), solvent (1 ml), 80 C, 15 h. The yields were determined by in situ 19 F NMR spectroscopy. b Trace amounts of isomeric C-F and C-H borylation products were detected by GC-MS. S3

4 Table S3: Screening of different bases for the borylation of 1,2,3-trifluorobenzene (1a). Entry 1a/B 2 pin 2 Base Solvent Yield (%) a,b 1 1.1:1 CsF (1 eq.) mesitylene 50 (55) c 2 1.1:1 / mesitylene trace 3 1.1:1 KF (1 eq.) mesitylene :1 Cs 2 CO 3 (1 eq.) mesitylene :1 KO t Bu (1 eq.) mesitylene < :1 KOAc (1 eq.) mesitylene :1 NaOAc (1 eq.) mesitylene :1 NMe 4 F (1 eq.) mesitylene :1 TBAF (1eq.) methylcyclopentane 0 a Reaction conditions: [Ni(IMes)2] (10 % mmol), solvent (1 ml), 80 C, 15 h. The yields were determined by in situ 19 F NMR spectroscopy. b Trace amounts of isomeric C-F and C-H borylation products were detected by GC-MS. c Small amounts of C- H borylation product of mesitylene was observed by GC-MS. Table S4: Screening of different equivalents of NMe 4 F for the borylation of 1,2,3-trifluorobenzene (1a). Entry 1a/B 2 pin 2 Base Solvent Yield (%) a,b 1 1.1:1 NMe 4 F (1 eq.) mesitylene :1 NMe 4 F (0.5 eq.) mesitylene :1 NMe 4 F (0.5 eq.) methylcyclopentane :1 NMe 4 F (1 eq.) methylcyclopentane :1 NMe 4 F (0.1 eq.) methylcyclopentane 49 a Reaction conditions: [Ni(IMes)2] (10 % mmol), solvent (1 ml), 80 C, 15 h. The yields were determined by in situ 19 F NMR spectroscopy. b Trace amounts of isomeric C-F and C-H borylation products were detected by GC-MS. S4

5 III. Experimental Procedures and Characterization of Products General procedures for the synthesis of boronate esters Method A This method requires anhydrous NMe 4 F. A mixture of [Ni(IMes) 2 ] (0.02 mmol, 13.0 mg), NMe 4 F (0.10 mmol, 9 mg) and B 2 pin 2 (0.20 mmol, 51.0 mg) was dissolved in methylcyclopentane (1 ml) in a Schlenk tube equipped with a magnetic stirring bar. The fluoroarene (0.22 mmol) was added to the solution. The reaction mixture was heated at 80 C for 15 h and the yield determined using in situ 19 F{ 1 H} NMR. The yields are based on B 2 pin 2 if 1 eq. of B 2 pin 2 was used, otherwise on the fluoroarene. Method B This method uses CsF and was performed on a preparative scale. A mixture of [Ni(IMes) 2 ] (0.20 mmol, 133 mg), CsF (2.00 mmol, 304 mg) and B 2 pin 2 (2.00 mmol, 508 mg) was dissolved in methylcyclopentane (10 ml) in a Schlenk tube equipped with a magnetic stirring bar. The fluoroarene (2.20 mmol) was added to the solution. The reaction mixture was heated at 80 C for 15 h and was then filtered and the remaining solid was washed with diethyl ether (5 ml Et 2 O). The filtrate was concentrated in vacuo and purified by silica-gel column chromatography with hexane and afterwards a hexane and ethyl acetate mixture (hexane/etoac =100/1) as eluent. The solvent of the product containing fraction of the eluent was evaporated in vacuo. Yields are based on B 2 pin 2. 2-(2,3-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2a): Method A was employed for the preparation of 2a, using 1,2,3-trifluorobenzene (23.0 μl, 29.4 mg, 0.22 mmol), which afforded the 19 F{ 1 H} NMR spectrum given in Figure S1 (79% yield of 2a). The reaction was also performed using method A on a larger/preparative scale: [Ni(IMes) 2 ] (0.20 mmol, 133 mg), NMe 4 F (1.00 mmol, 90.0 mg) and B 2 pin 2 (2.00 mmol, 508 mg) in methylcyclopentane (10 ml), which afforded 336 mg (1.40 mmol, 70 %) of 2a as a pale yellow liquid after workup (for workup see method B). Method B was employed for the preparation of 2a, using 1,2,3-trifluorobenzene (227 μl, 291 mg, 2.20 mmol), which resulted in the isolation of 183 mg (0.76 mmol, 38 % based on B 2 pin 2 ) of 2a as a pale yellow liquid. S5

6 Figure S1: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,2,3-trifluorobenzene. Characterization of 2a (see also Figures S11-S15 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 1 H), (m, 1 H), (m, 1 H), 1.36 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (dd, 1 J F-C = Hz, 2 J F-C = 11.7 Hz), (dd, 1 J F-C = Hz, 2 J F-C = 14.4 Hz), (dd, J F- C = 4.1 Hz, J F-C = 6.7 Hz), (dd, J F-C = 4.3 Hz, J F-C = 5.8 Hz), (dd, 2 J F-C = 17.1, J F-C = 1.2 Hz), (br, CB), 84.2, F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (d, 3 J F-F = 21.5 Hz, 1 F), (d, 3 J F-F = 21.5 Hz, 1 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 1 F), (m, 1 F); 11 B{ 1 H} NMR (160.5 MHz, CDCl 3 ) δ = 30.0 ppm. HRMS [C 12 H 15 BF 2 O 2 H] + (M+H) + calcd , found The spectroscopic data for 2a match with those previously reported in the literature. 3 2-(3,5-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2b): Method A was employed for the preparation of 2b, using 1,3,5-trifluorobenzene (23.0 μl, 29.4 mg, 0.22 mmol), which led to the 19 F{ 1 H} NMR spectrum shown in Figure S2 (93 % yield of 2b). Diborylation compound 2,2'-(5-fluoro-1,3-phenylene)bis(4,4,5,5-tetramethyl- 1,3,2-dioxaborolane) 2b was also observed in low yield (4 %). Method B was employed for the preparation of 2b, using 1,3,5-trifluorobenzene (227 μl, 290 mg, 2.20 mmol) to give 360 mg (1.50 mmol, 75 %) 2b as a colorless solid. Multigram scale synthesis of 2b: A mixture of 10 % [Ni(IMes) 2 ] (2.07 mmol, 1.38 g), NMe 4 F (10.3 mmol, 0.96 g), and B 2 pin 2 (20.7 mmol, 5.24 g) was dissolved in methylcyclopentane (50 ml) in a Schlenk tube equipped with a magnetic stirring bar. 1,3,5-Trifluorobenzene (22.71 mmol, 3.00 g) was added and the reaction mixture was heated at 80 C for 17 h, filtered through a pad of celite and the remaining solid was washed with diethylether (60 ml). The filtrate was concentrated in vacuo and then purified by silica-gel column chromatography with hexane and afterwards with hexane/etoac = 100/1 as eluent. The fractions containing the product were combined and evaporated to dryness in vacuo to give 4.16 g (17.3 mmol, 84 % based on B 2 pin 2 ) of 2b as a colorless solid. S6

7 Mercury test for the synthesis of 2b: A mixture of [Ni(IMes) 2 ] (0.02 mmol, 13 mg), NMe 4 F (0.1 mmol, 9 mg) and B 2 pin 2 (0.2 mmol, 51 mg) was dissolved in methylcyclopentane (1 ml) in a Schlenk tube equipped with a magnetic stirring bar. 1,3,5-C 6 F 3 H 3 (0.22 mmol, 21μL) and Hg (190 mg, 0.95 mmol) were added and the reaction mixture was heated at 80 C for 15 h. Products and yields were determined using in situ 19 F{ 1 H} NMR spectroscopy: 85 % based on B 2 pin. Figure S2: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,3,5-trifluorobenzene. Characterization of 2b (see also Figures S16-S20 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 2 H), 6.87 (tt, 3 J F-H = 9.0 Hz, 4 J H-H = 2.4 Hz, 1 H), 1.34 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (dd, 1 J F-C = 249.7, 3 J F-C = 11.0 Hz), (m), (t, 2 J F- C = 25.1 Hz), CB not detected, 84.4, 24.8; 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (s, 2 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 2 F); 11 B{ 1 H} NMR (160.5 MHz, CDCl 3 ) δ = 30.3 ppm. HRMS [C 12 H 15 BF 2 O 2 H] + (M+H) + calcd , found Spectroscopic data for 2b match with those previously reported in the literature. 4 2-(2,5-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2c): Method A was employed for the preparation of 2c, using 1,2,5-trifluorobenzene (23.0 μl, 29.1 mg, 0.22 mmol), which led to the 19 F{ 1 H} NMR spectrum shown in Figure S3 (77 % yield 2c + 2c + 2c ). Method B was employed for the preparation of 2c and side products 2c and 2c using 1,2,4-trifluorobenzene (227 μl, 289 mg, 2.20 mmol) in methylcyclohexane as a solvent at 100 C. 287 mg (1.20 mmol, 60 % based on B 2 pin 2 ) of a mixture of 2c, 2c and 2c (ratio approximately 10:1:1) was isolated as a pale yellow liquid. S7

8 Figure S3: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,3,5-trifluorobenzene. Characterization of 2c (see also Figures S21-S25 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 1 H), (m, 1H), (m, 1 H), 1.36 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (dd, 1 J C-F = Hz, 4 J C-F = 2.0 Hz), (dd, 1 J C-F = Hz, 4 J C-F = 2.5 Hz), (dd, 2 J C-F = 22.4 Hz, 3 J C-F = 8.8 Hz), (dd, 2 J C-F = 24.3 Hz, 3 J C-F = 9.4 Hz), (dd, 2 J C-F = 27.3 Hz, 3 J C-F = 7.8 Hz), CB not detected, 84.2, F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (d, 5 J F-F = 19.4 Hz, 1 F), (d, 5 J F-F = 19.4 Hz, 1 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 1 F), (m, 1 F); 11 B{ 1 H} NMR (160.5 MHz, CDCl 3 ) δ = 29.9 ppm. HRMS [C 12 H 15 BF 2 O 2 H] + (M+H) + calcd , found Spectroscopic data for 2c match with those previously reported in the literature. 3 Characterization of 2-(3,4-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane 2c : 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (d, 3 J F-F = 20.3 Hz, 1 F), (d, 3 J F-F = 20.3 Hz; 1 F) ppm. Spectroscopic data for 2c match with those previously reported in the literature. 5 Characterization of 2-(2,4-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane 2c : 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (d, 4 J F-F = 11.0 Hz; 1 F); (d, 4 J F-F = 11.0 Hz, 1 F) ppm. Spectroscopic data for 2c match with those previously reported in the literature. 5 4,4,5,5-tetramethyl-2-(2,3,5-trifluorophenyl)-1,3,2-dioxaborolane (2d): Method A was employed for the preparation of 2d, using 1,2,3,5-tetrafluorobenzene (24.0 μl, 33.4 mg, 0.22 mmol), which led to the 19 F{ 1 H} NMR spectrum shown in Figure S4 (99 % yield 2d + 2d ). Method B was employed for the preparation of 2d, using 1,2,3,5-tetrafluorobenzene (237 μl, 330 mg, 2.20 mmol), which afforded 367 mg (1.42 mmol, 71 % based on B 2 pin 2 ) 2d as a pale yellow liquid. S8

9 Figure S4: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,2,3,5-tetrafluorobenzene. Characterization of 2d (see also Figures S26-S30 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 1 H), (m, 1 H), 1.36 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (ddd, J F-C = 2.6 Hz, J F-C = 8.8 Hz, 1 J F-C = Hz), (ddd, J F-C = 3.2 Hz, J F-C = 10.6 Hz, 1 J F-C = Hz), (ddd, J F-C = 9.9 Hz, J F-C = 12.4 Hz, 1 J F-C = Hz), (ddd, J F-C = 4.0 Hz, J F-C = 6.8 Hz, 2 J F-C = 22.0 Hz), (ddd, J F-C = 1.2 Hz, J F-C = 20.6 Hz, J F-C = 27.5 Hz), CB not detected, 84.5, 24.8; 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (dd, 4 J F-F = 3.8 Hz, 5 J F-F = 17.1 Hz, 1 F), (dd, 3 J F-F = 21.4 Hz, 4 J F-F = 3.8 Hz, 1 F), (dd, 3 J F-F = 21.4 Hz, 5 J F-F = 17.1 Hz, 1 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 1 F), (m, 1 F), (m, 1 F); 11 B NMR (160.5 MHz, CDCl 3 ) δ = 29.6 ppm. HRMS [C 12 H 14 BF 3 O 2 H] + (M+H) + calcd , found Characterization of 4,4,5,5-tetramethyl-2-(3,4,5-trifluorophenyl)-1,3,2-dioxaborolane 2d : 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (d, 3 J F-F = 19.4 Hz, 1 F), (d, 3 J F-F = 19.4 Hz, 1 F) ppm. 4,4,5,5-tetramethyl-2-(2,4,5-trifluorophenyl)-1,3,2-dioxaborolane (2e): Method A was employed for the preparation of 2e, using 1,2,4,5-tetrafluorobenzene (89.0 μl, mg, 0.80 mmol) in methylcyclohexane as solvent at 100 C. The reaction led to the 19 F{ 1 H} NMR spectrum shown in Figure S5 (70 % yield). Method B was employed for the preparation of 2e, using 1,2,4,5-tetrafluorobenzene (893 μl, 1200 mg, 8.00 mmol) in methylcyclohexane at 100 C, which led to isolation of 336 mg (1.30 mmol, 65 % based on B 2 pin 2 ) 2e in the form of a pale yellow liquid. S9

10 Figure S5: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,2,4,5-tetrafluorobenzene. Characterization of 2e (see also Figures S31-S35 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = 7.51 (td, 4 J F-H = 5.2 Hz, 3 J F-H = 9.9 Hz, 1 H), 6.88 (ddd, 4 J F-H = 6.0 Hz, 4 J F-H = 8.3 Hz, 3 J F-H = 10.4 Hz, 1 H), 1.35 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (ddd, 4 J F-C = 2.2 Hz, 3 J F-C = 9.7 Hz, 1 J F-C = Hz), (ddd, J F-C = 13.1 Hz, J F-C = 14.7 Hz, 1 J F-C = Hz), (ddd, 4 J F-C = 3.9 Hz, 2 J F-C = 12.1 Hz, 1 J F- C = Hz), (ddd, J F-C = 1.9 Hz, J F-C = 10.3 Hz, J F-C = 17.7 Hz), (br, CB), (dd, J F-C = 20.0 Hz, J F-C = 30.4 Hz), 84.3, 24.8; 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (dd, 4 J F-F = 7.2, 5 J F-F = 16.7 Hz, 1 F), (dd, 4 J F-F = 7.2, 3 J F-F = 21.2 Hz, 1 F), (dd, 5 J F-F = 16.7 Hz, 3 J F-F = 21.2 Hz, 1 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 1 F), (m, 1 F), (m, 1 F); 11 B NMR (160.5 MHz, CDCl 3 ) δ = 29.6 ppm. HRMS [C 12 H 14 BF 3 O 2 H] + (M+H) + calcd , found ,2'-(2,5-difluoro-1,4-phenylene)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (2e ): Method A was employed for the preparation of 2e, using 1,2,4,5-tetrafluorobenzene (22.0 μl, 29.6 mg, 0.20 mmol), B 2 pin 2 (101 mg; 0.40 mmol, 2.0 equiv.) and CsF (0.40 mmol, 61.0 mg) in methylcyclohexane at 100 C. The reaction led to the 19 F{ 1 H} NMR spectrum shown in Figure S7 (85 % yield). Method B was employed for the preparation of 2e using 608 mg (4.00 mmol) CsF, 1011 mg (4.00 mmol) B 2 pin 2 and 1,2,4,5-tetrafluorobenzene (223 μl, 300 mg, 2.00 mmol) in methylcyclohexane at 100 C. The product was purified by silica-gel column chromatography with a hexane and ethyl acetate mixture (hexane/etoac = 100/1) and afterwards a hexane and diethyl ether mixture (hexane/et 2 O = 20/1) as eluent. The procedure afforded 534 mg (1.46 mmol, 73 % based on B 2 pin 2 ) of compound 2e in the form of a white solid. S10

11 Figure S6: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,2,4,5-tetrafluorobenzene. Characterization of 2e (see also Figures S36-S40 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = 7.35 (AA XX system, 3 J F-H + 4 J F-H = 12.7 Hz, 2 H), 1.35 (s, 24 H); 13 C{ 1 H}NMR (125.8 MHz, CDCl 3 ) δ = (dd, 1 J F-C = Hz, 4 J F-C = 4.0 Hz), (AXX system, 2 J F-C + 3 J F-C = 34.0 Hz), (br, CB), 84.3, 24.8; 19 F{ 1 H} NMR (376.8 MHz, CDCl 3 ) δ = (m, 2 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (AA XX system, 3 J F-H + 4 J F-H = 12.7 Hz, 2 F); 11 B NMR (160.5 MHz, CDCl 3 ) δ = 29.9 ppm; HRMS [C 12 H 26 B 2 F 2 O 4 H] + (M+H) + calcd , found Spectroscopic data for 2e match with those previously reported in the literature. 6 4,4,5,5-tetramethyl-2-(2,3,4,5-tetrafluorophenyl)-1,3,2-dioxaborolane (2f): Method A was employed for the preparation of 2f using pentafluorobenzene (24.0 μl, 36.3 mg, 0.22 mmol) and [Ni(IPr) 2 ] (0.02 mmol, 17 mg) as the catalyst in methylcyclohexane at 100 C. The reaction led to a 19 F{ 1 H} NMR spectrum as shown in Figure S7 (85 % yield). Method B was employed for the preparation of 2f, using pentafluorobenzene (243 μl, 368 mg, 2.20 mmol) and [Ni(IPr) 2 ] (0.20 mmol, 167 mg) as the catalyst, which led to the isolation of 441 mg (1.60 mmol, 80 % based on B 2 pin 2 ) 2f in the form of a pale yellow liquid. In addition, traces of other C-F borylation isomers as well as diborylation compounds 2f, 2e and 2e were observed in the GC-MS of the reaction mixture (see also Figure S10). S11

12 Figure S7: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using pentafluorobenzene. Characterization of 2f (see also Figures S41-S45 in Section IV): 1 H NMR (500.1 MHz, C 6 D 6 ) δ = 7.19 (m, 1 H), 1.04 (s, 12 H); 13 C{H}NMR (125.8 MHz, CDCl 3 ) δ = (dddd, J F-C = 1.7 Hz, J F-C = 3.1 Hz, J F-C = 9.4 Hz, 1 J F-C = Hz), (ddd, J F-C = 3.2 Hz, J F-C = 9.8 Hz, 1 J F-C = Hz), (dddd, J F-C = 3.9 Hz, J F-C = 12.4 Hz, J F-C = 16.9 Hz, 1 J F-C = Hz ), (dddd, J F-C = 3.0 Hz, J F-C = 11.9 Hz, J F-C = 18.7 Hz, 1 J F-C = Hz), (ddd, J F-C = 4.1 Hz, J F-C = 8.3 Hz, 2 J F-C = 17.6 Hz), (br, CB), 84.6, 24.7; 19 F{H}NMR (188.1 MHz, CDCl 3 ) δ = (ddd, 4 J F-F = 6.9 Hz, 5 J F-F = 14.9 Hz, 3 J F-F = 21.3 Hz, 1 F), (ddd, 4 J F-F = 2.9 Hz, 5 J F-F = 14.9 Hz, 3 J F-F = 20.6 Hz, 1 F), (ddd, 4 J F-F = 6.9 Hz, 3 J F-F = 19.4 Hz, 3 J F-F = 20.6 Hz, 1 F), (ddd, 4 J F-F = 2.9 Hz, 3 J F-F = 19.4 Hz, 3 J F-F = 21.3 Hz, 1 F); 19 F NMR (470.6 MHz, C 6 D 6 ) δ = (m, 1 F), (m, 1 F), (m, 1 F), (m, 1 F); 11 B{ 1 H} NMR (160.5 MHz, C 6 D 6 ) δ = 29.5 ppm. HRMS [C 12 H 13 BF 4 O 2 H] + (M+H) + calcd , found (2-fluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2g): Method A was employed for the preparation of 2g, using 1,2-difluorobenzene (39.0 μl, 45.6 mg, 0.40 mmol), which led to the 19 F{ 1 H} NMR spectrum shown in Figure S8 (48 % yield). Method B was employed for the preparation of 2g using 1,2-difluorobenzene (394 μl, 456 mg, 4.00 mmol), which led to the isolation of 133 mg (0.60 mmol, 30 % based on B 2 pin 2 ) 2g in the form of a pale yellow liquid. S12

13 Figure S8: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,2-difluorobenzene. Characterization of 2g (see also Figures S46-S50 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 1 H), (m, 1 H), (m, 1 H), (m, 1 H), 1.36 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (d, 1 J F-C = Hz), (d, 3 J F-C = 8.0 Hz), (d, 3 J F-C = 8.7 Hz), (d, 4 J F-C = 3.3 Hz), (br, CB), (d, 2 J F-C = 23.9 Hz), 83.9, 24.8; 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (s, 1 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 1 F); 11 B{ 1 H} NMR (160.5 MHz, CDCl 3 ) δ = 30.2 ppm. HRMS [C 12 H 16 BFO 2 H] + (M+H) + calcd , found Spectroscopic data for 2g match with those previously reported in the literature. 4 2-(3-fluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2h): Method A was employed for the preparation of 2h, using 1,3-difluorobenzene (39.0 μl, 45.3 mg, 0.40 mmol), which led to the 19 F{ 1 H} NMR spectrum shown in Figure S9 (50 % yield). Method B was employed for preparation of 2h, using 1,3-difluorobenzene (394 μl, 458 mg, 4.00 mmol), which led to the isolation of 155 mg (0.70 mmol, 35 % based on B 2 pin 2 ) 2h in the form of a pale yellow liquid. S13

14 Figure S9: 19 F{ 1 H} NMR (188.1 MHz) spectrum of the reaction mixture using 1,2,3-trifluorobenzene. Characterization of 2h (see also Figures S51-S55 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 1 H), (m, 1 H), (m, 1 H), (m, 1 H), 1.35 (s, 12 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (d, 1 J F-C = Hz), (br, CB), (d, 4 J F-C = 3.0 Hz), (d, 3 J F- C = 7.1 Hz), (d, 2 J F-C = 19.2 Hz), (d, 2 J F-C = 21.1 Hz), 84.1, 24.8; 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (s, 1 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 1 F); 11 B NMR (160.5 MHz, CDCl 3 ) δ = 30.6 ppm. HRMS [C 12 H 16 BFO 2 H] + (M+H) + calcd , found Spectroscopic data for 2h match with those previously reported in the literature. 4 4,4,5,5-tetramethyl-2-phenyl-1,3,2-dioxaborolane (2i): Method A was employed for the preparation of 2i, using monofluorobenzene (37.0 μl, 37.9 mg, 0.40 mmol). The reaction mixture was examined by GC-MS using C 12 H 26 as an internal standard, as shown in Figure S10 (20 % yield). Method B was employed for the preparation of 2i, using monofluorobenzene (375 μl, 384 mg, 4.00 mmol) to afford 41.0 mg (0.20 mmol, 10 % based on B 2 pin 2 ) 2i in the form of a a pale yellow liquid. S14

15 Figure S10: GC/MS trace of the reaction mixture using monofluorobenzene against standard C12H26 (top) and mass spectrum of 2i obtained by GC/MS. Characterization of 2i (see also Figures S56-S58 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 2 H), (m, 1 H), (m, 2 H), 1.35 (s, 12H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = 134.7, 131.2, 127.7, CB not detected, 83.8, 24.9; 11 B NMR (160.5 MHz, CDCl 3 ) δ = 31.1 ppm. HRMS [C 12 H 16 BO 2 H] + (M+H) + calcd , found Spectroscopic data for 2i match with those previously reported in the literature. 7 For some fluorobenzenes (1,2,3-C 6 F 3 H 3, 1,2-C 6 F 2 H 4, 1,3-C 6 F 2 H 4, C 6 FH 5 ) products from C-H bond borylation have been observed in very low amounts. For the reaction of 1a using method B we could, for example, isolate compound 3a as a white solid in very small amounts. Characterization of 3a (see also Figures S59-S63 in Section IV): 1 H NMR (500.1 MHz, CDCl 3 ) δ = (m, 2 H), 1.36 (s, 24 H); 13 C{ 1 H} NMR (125.8 MHz, CDCl 3 ) δ = (dd, 2 J F-C = 15.6 Hz, 1 J F-C = Hz), (AXX system, 3 J F-C + 4 J F-C = 10.3 Hz), (br, CB), 84.2, 24.8; 19 F{ 1 H} NMR (188.1 MHz, CDCl 3 ) δ = (s, 2 F); 19 F NMR (470.6 MHz, CDCl 3 ) δ = (m, 2 F); 11 B NMR (160.5 S15

16 MHz, CDCl 3 ) δ = 30.2 ppm. HRMS [C 18 H 26 B 2 F 2 O 4 H] + (M+H) + calcd , found Synthesis of trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] (5): 1,2,3,5-Tetrafluorobenzene (39 μl, 0.36 mmol) was added to a solution of [Ni(IMes) 2 ] (239 mg, 0.35 mmol) in toluene (20 ml) and the reaction was stirred overnight. All volatiles were removed in vacuo and the remaining solid was suspended in 5 ml hexane. The product was collected by filtration and dried in vacuo to give a yellow product (200 mg, 70%). Crystals of 5 for X-ray diffraction have been obtained from a C 6 D 6 solution of 5. Characterization of 5 (see also Figures S64-S67 in Section IV): 1 H NMR (500.1 MHz, C 6 D 6 ) δ = 6.94 (s, 4 H), 6.87 (s, 4 H), (m, 1 H), 5.90 (s, 4 H), (m, 1 H), 2.42 (s, 12 H), 2.13 (br s, 12 H), 1.89 (br s, 12 H); 13 C{H}NMR (125.8 MHz, C 6 D 6 ) δ = (d, 2 J C-F = 7.9 Hz), (dd, J F-C = 7.5 Hz, 1 J F-C = Hz), (ddd, J F-C = 2.6 Hz, J F-C = 8.1 Hz, 1 J F-C = Hz), (ddd, J F-C = 12.1 Hz, J F-C = 22.1 Hz, 1 J F-C = Hz ), (br dd, J F-C = 30 Hz, J F-C = 45 Hz), 137.7, (br), 137.0, 129.0, 128.9, 122.1, (ddd, J F-C = 3.6 Hz, J F-C = 17.6 Hz, J F-C = 18.3 Hz), 96.2 (dd, J F-C = 21.3 Hz, J F-C = 28.0 Hz), 21.4, 18.3 (br), 18.1 (br); 19 F{ 1 H} NMR (188.1 MHz, C 6 D 6 ) δ = (ddd, 4 J F-F = 7.7 Hz, 5 J F-F = 16.9 Hz, 3 J F-F = 32.0 Hz, 1 F), (d, 5 J F-F = 16.9 Hz, 1 F), (d, 3 J F-F = 32.0 Hz, 1 F), (d, 4 J F-F = 7.7 Hz, NiF, 1 F); 19 F NMR (470.6 MHz, C 6 D 6 ) δ = (m, 1 F), (dt, 3 J F-H = 8.3 Hz, 5 J F-F = 16.9 Hz, 1 F), (dd, 3 J F-H = 10.6 Hz, 3 J F-F = 32.0 Hz, 1 F), (s, NiF, 1 F) ppm. C 48 H 50 F 4 N 4 Ni [ g/mol] Calcd. (found): C, (70.09) H, 6.16 (5.83) N, 6.85 (6.93); HRMS [C 48 H 50 F 4 N 4 NiH] + (M+H) + calcd. (found): ( ), [C 48 H 50 F 3 N 4 Ni] + (M-F) + calcd. (found): ( ); IR (ATR[cm -1 ]): 423 (w), 452 (w), 460 (m), 517 (m), 575 (w), 593 (w), 605 (w), 703 (vs), 732 (w), 758 (m), 800 (m), 819 (w), 847 (s), 886 (w), 927 (w), 974 (w), 1035 (w), 1094 (w), 1160 (w), 1190 (w), 1221 (w), 1264 (m), 1319 (m), 1381 (m), 1398 (m), 1434 (m), 1486 (m), 1575 (w), 1603 (w), 2856 (w), 2914 (m). S16

17 IV. NMR Spectra of Products 2-(2,3-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2a): Figure S11: 1 H NMR spectrum of 2a (500.1 MHz, CDCl3). Figure S12: 13 C{ 1 H} NMR spectrum of 2a (125.8 MHz, CDCl3). S17

18 Figure S13: 19 F{ 1 H} NMR spectrum of 2a (188.1 MHz, CDCl3). Figure S14: 19 F NMR spectrum of 2a (470.6 MHz, CDCl3). S18

19 Figure S15: 11 B{ 1 H} NMR spectrum of 2a (160.5 MHz, CDCl3). 2-(3,5-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2b): Figure S16: 1 H NMR spectrum of 2b (500.1 MHz, CDCl3). S19

20 Figure S17: 13 C{ 1 H} NMR spectrum of 2b (125.8 MHz, CDCl3). Figure S18: 19 F{ 1 H} NMR spectrum of 2b (188.1 MHz, CDCl3). S20

21 Figure S19: 19 F NMR spectrum of 2b (470.6 MHz, CDCl3). Figure S20: 11 B{ 1 H} NMR spectrum of 2b (160.5 MHz, CDCl3). S21

22 2-(2,5-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2c): Figure S21: 1 H NMR spectrum of 2c (500.1 MHz, CDCl3). Figure S22: 13 C{ 1 H} NMR spectrum of 2c (125.8 MHz, CDCl3). S22

23 Figure S23: 19 F{ 1 H} NMR spectrum of 2c (188.1 MHz, CDCl3). Figure S24: 19 F NMR spectrum of 2c (470.6 MHz, CDCl3). S23

24 Figure S25: 11 B{ 1 H} NMR spectrum of 2c (160.5 MHz, CDCl3). 4,4,5,5-tetramethyl-2-(2,3,5-trifluorophenyl)-1,3,2-dioxaborolane (2d): Figure S26: 1 H NMR spectrum of 2d (500.1 MHz, CDCl3). S24

25 Figure S27: 13 C{ 1 H} NMR spectrum of 2d (125.8 MHz, CDCl3). Figure S28: 19 F{ 1 H} NMR spectrum of 2d (188.1 MHz, CDCl3). S25

26 Figure S29: 19 F NMR spectrum of 2d (470.6 MHz, CDCl3). Figure S30: 11 B NMR spectrum of 2d (160.5 MHz, CDCl3). S26

27 4,4,5,5-tetramethyl-2-(2,4,5-trifluorophenyl)-1,3,2-dioxaborolane (2e): Figure S31: 1 H NMR spectrum of 2e (500.1 MHz, CDCl3). Figure S32: 13 C{ 1 H} NMR spectrum of 2e (125.8 MHz, CDCl3). S27

28 Figure S33: 19 F{ 1 H} NMR spectrum of 2e (188.1 MHz, CDCl3). Figure S34: 19 F NMR spectrum of 2e (470.6 MHz, CDCl3). S28

29 Figure S35: 11 B NMR spectrum of 2e (160.5 MHz, CDCl3). 2,2'-(2,5-difluoro-1,4-phenylene)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (2e ) Figure S36: 1 H NMR spectrum of 2e (500.1 MHz, CDCl3). S29

30 Figure S37: 13 C{ 1 H} NMR spectrum of 2e (125.8 MHz, CDCl3). Figure S38: 19 F{ 1 H} NMR spectrum of 2e (376.8 MHz, CDCl3). S30

31 Figure S39: 19 F NMR spectrum of 2e (470.6 MHz, CDCl3). Figure S40: 11 B NMR spectrum of 2e (160.5 MHz, CDCl3). S31

32 4,4,5,5-tetramethyl-2-(2,3,4,5-tetrafluorophenyl)-1,3,2-dioxaborolane (2f): Figure S41: 1 H NMR spectrum of 2f (500.1 MHz, C6D6). Figure S42: 13 C{ 1 H} NMR spectrum of 2f (125.8 MHz, CDCl3). S32

33 Figure S43: 19 F{ 1 H} NMR spectrum of 2f (188.1 MHz, CDCl3). Figure S44: 19 F NMR spectrum of 2f (470.6 MHz, C6D6). S33

34 Figure S45: 11 B{ 1 H} NMR spectrum of 2f (160.5 MHz, C6D6). 2-(2-fluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2g): Figure S46: 1 H NMR spectrum of 2g (500.1 MHz, CDCl3). S34

35 Figure S47: 13 C{ 1 H} NMR spectrum of 2g (125.8 MHz, CDCl3). Figure S48: 19 F{ 1 H} NMR spectrum of 2g (188.1 MHz, CDCl3). S35

36 Figure S49: 19 F NMR spectrum of 2g (470.6 MHz, CDCl3). Figure S50: 11 B{ 1 H} NMR spectrum of 2g (160.5 MHz, CDCl3). S36

37 2-(3-fluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2h): Figure S51: 1 H NMR spectrum of 2h (500.1 MHz, CDCl3). Figure S52: 13 C{ 1 H} NMR spectrum of 2h (125.8 MHz, CDCl3). S37

38 Figure S53: 19 F{ 1 H} NMR spectrum of 2h (188.1 MHz, CDCl3). Figure S54: 19 F NMR spectrum of 2h (470.6 MHz, CDCl3). S38

39 Figure S55: 11 B NMR spectrum of 2h (160.5 MHz, CDCl3). 4,4,5,5-tetramethyl-2-phenyl-1,3,2-dioxaborolane (2i): Figure S56: 1 H NMR spectrum of 2i (500.1 MHz, CDCl3). S39

40 Figure S57: 13 C{ 1 H} NMR spectrum of 2i (125.8 MHz, CDCl3). Figure S58: 11 B NMR spectrum of 2i (160.5 MHz, CDCl3). S40

41 2,2'-(2,3-difluoro-1,4-phenylene)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (3a): Figure S59: 1 H NMR spectrum of 3a (500.1 MHz, CDCl3). Figure S60: 13 C{ 1 H} NMR spectrum of 3a (125.8 MHz, CDCl3). S41

42 Figure S61: 19 F{ 1 H} NMR spectrum of 3a (188.1 MHz, CDCl3). Figure S62: 19 F NMR spectrum of 3a (470.6 MHz, CDCl3). S42

43 Figure S63: 11 B NMR spectrum of 3a (160.5 MHz, CDCl3). [Ni(IMes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5: Figure S64: 1 H NMR spectrum of 5 (500.1 MHz, C6D6). S43

44 Figure S65: 13 C NMR spectrum of 5 (125.8 MHz, C6D6). Figure S66: 19 F{ 1 H} NMR spectrum of 5 (188.1 MHz, C6D6). S44

45 Figure S67: 19 F NMR spectrum of 5 (470.6 MHz, C6D6). S45

46 V. Investigations Concerning the Reaction Mechanism a) The reaction of [Ni(IMes) 2 ] with 1,2,3,5-tetrafluorobenzene in C 7 D 8 In a Young s tap NMR tube, a mixture of [Ni(IMes) 2 ] (37.5 µmol, 25.0 mg), was dissolved in C 7 D 8 (700 µl), cooled down to -78 C, and 1,2,3,5-tetrafluorobenzene (37.5 µmol, 4.1 µl, 5.6 mg) was added. The NMR tube was transferred in the NMR machine with a precooled probehead (-50 C). The temperature of the probehead was raised slowely in 5 C steps. 1 H- and 19 F{ 1 H}-NMR spectra were taken at each temperature. At -50 C starting materials and the beginning of the insertion reaction were detected, without any evidence for an insertion into one of the C-H bonds (no nickel hydride detected; see Figure S68). The final product is trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5. Figure S68: 1 H NMR spectra (C7D8) (8 ppm -20 ppm) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at variable temperatures. Figure S69: 1 H NMR spectrum (C7D8) (8 ppm 0 ppm) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at variable temperatures. S46

47 Figure S70: 19 F{ 1 H} NMR spectrum (C7D8) (-80 ppm -360 ppm) of the reaction of [Ni(IMes)2] and 1,2,3,5- tetrafluorobenzene at variable temperatures. b) The reaction of [Ni(IMes) 2 ], NMe 4 F, B 2 pin 2 with 1,2,3,5-tetrafluorobenzene in C 6 D 6 In a Young s tap NMR tube, a mixture of [Ni(IMes) 2 ] (16.5 µmol, 11.0 mg, 0.15 eq.), NMe 4 F (110 µmol, 10.0 mg, 1.00 eq.) and B 2 pin 2 (110 µmol, 27.9 mg., 1.00 eq.) was dissolved in C 6 D 6 (700 µl) and 1,2,3,5- tetrafluorobenzene (110 µmol, 12.0 µl, 16.7 mg, 1.00 eq.) was added at room temperature. The mixture was shaken for 30 min at room temperature. During this time the color changed from black to orange and the mixture was analyzed using 1 H, 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy. No precatalyst [Ni(IMes) 2 ] was observed anymore, but the quantitative formation of the C-F bond activation product trans- [Ni(IMes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5 was detected (Figures S71-S73). Furthermore, unreacted 1,2,3,5- tetrafluorobenzene and B 2 pin 2 and no borylation product 1-Bpin-(2,3,5-C 6 F 3 H 2 ) 2d was observed (see Scheme 1). IMes Ni IMes 15 mol% B 2 pin 2 NMe 4 F F 1eq. 1eq. 1eq. F F F C 6 D 6 RT, 30 min F F F IMes Ni F IMes B 2 pin 2 NMe 4 F Scheme 1: Reaction of [Ni(IMes)2] with B2pin2 and 1,2,3,5-tetrafluorobenzene at catalytic conditions in C6D6 at room temperature. 5 F F F F S47

48 Figure S71: 1 H NMR spectrum (C6D6) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions at room temperature, which leads to the formation of trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Figure S72: 19 F{ 1 H} NMR spectrum (C6D6) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions at room temperature, which leads to the formation of trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. S48

49 Figure S73: 11 B{1H} NMR spectrum (C6D6) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions at room temperature, which shows a resonance at ppm for unreacted B2pin2. After the above spectra were recorded, the mixture was heated to 80 C for 16 h. During that time the color of the solution deepens to dark orange and a colorless precipitate was formed. The reaction mixture was analyzed by 1 H, 19 F{ 1 H}, and 11 B{ 1 H} NMR spectroscopy (see Figures S74-S78). In these spectra, the formation of 1-Bpin-(2,3,5-C 6 F 3 H 2 ) 2d and traces of 1-Bpin-(3,4,5-C 6 F 3 H 2 ) 2d was detected (see 19 F{ 1 H} and 11 B{ 1 H} NMR spectra below; peaks of 2d in the 1 H NMR spectrum overlap with the signals of 2d), as well as intact trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5. Scheme 2: Reaction of [Ni(IMes)2] with B2pin2 and 1,2,3,5-tetrafluorobenzene at catalytic conditions in C6D6 after 16 h at 80 C. Figure S74: 1 H NMR spectrum (C6D6) of the reaction mixture of the reaction of [Ni(IMes)2], 1,2,3,5-tetrafluorobenzene, B2pin2 and NMe4F at catalytic conditions after heating the reaction to 80 C for 16 h. The formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d was detected (in 1 H NMR spectrum; peaks overlap with the signals of 2d), as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 5 and 1,2,3,5-tetrafluorobenzene. S49

50 Figure S75: 1 H NMR spectrum (C6D6) of the reaction mixture of the reaction of [Ni(IMes)2], 1,2,3,5-tetrafluorobenzene, B2pin2 and NMe4F at catalytic conditions after heating the reaction to 80 C for 16 h. The formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d was detected (in 1 H NMR spectrum; peaks overlap with the signals of 2d), as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 2d and B2pin2. Figure S76: 19 F{ 1 H} NMR spectrum (C6D6) of the soluble components of the reaction of [Ni(IMes)2] and 1,2,3,5- tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 16 h. The formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d were detected, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 5 and 1,2,3,5-tetrafluorobenzene. S50

51 Figure S77: 19 F{ 1 H} NMR spectrum (C6D6) of the soluble components of the reaction of [Ni(IMes)2] and 1,2,3,5- tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 16 h. The formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d were detected, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 2d and 2d. Figure S78: 11 B{ 1 H} NMR spectrum (C6D6) of the soluble components of the reaction of [Ni(IMes)2] and 1,2,3,5- tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 16 h. The formation of 1-Bpin-(2,3,5-C6F3H2) 2d and an unidentified decomposition product was detected. After heating the reaction mixture for another three days at 80 C, the solution was filtered through a cannula and the remaining solid was dried in vacuo. The solution and the isolated solid, which was dissolved in CD 3 CN, were analyzed separately using 1 H, 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy (benzene soluble components: see Figures S79-S83; benzene residue in CD 3 CN: see Figures S86-S88). The benzene solution was additionally analyzed by GC/MS. The C 6 D 6 -soluble components consist of the products of the catalysis, 1-Bpin-(2,3,5-C 6 F 3 H 2 ) 2d and traces of 1-Bpin-(3,4,5-C 6 F 3 H 2 ) 2d, as well as intact resting state of the catalyst, trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5. The separated solid analyzed in CD 3 CN consists of the salts [F 2 Bpin] [NMe 4 ]+ and traces of [BF 4 ] [NMe 4 ]+. S51

52 Figure S79: 1 H NMR spectrum (C6D6) of the soluble components of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 3 d. Detected was the formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 2d and B2pin2. Figure S80: 1 H NMR spectrum (C6D6) of the soluble components of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 3 d. Detected was the formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 5 and remaining 1,2,3,5-tetrafluorobenzene. S52

53 Figure S81: 19 F{ 1 H} NMR spectrum (C6D6) of the reaction mixture of the reaction of [Ni(IMes)2] and 1,2,3,5- tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 3 d. Detected was the formation of 1-Bpin- (2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d (peaks overlap with the signals of 2d) as well as intact trans- [Ni(IMes)2(F)(2,3,5-C6F3H2)] 5. Highlighted in this Figure are the resonances of 5 and 1,2,3,5-tetrafluorobenzene. Figure S82: 19 F{ 1 H} NMR spectrum (C6D6) of the reaction mixture of the reaction of [Ni(IMes)2] and 1,2,3,5- tetrafluorobenzene at catalytic conditions after heating the reaction to 80 C for 3 d. Detected was the formation of 1-Bpin- (2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 2d and 2d. Figure S83: 11 B{ 1 H} NMR spectrum (C6D6) of the decomposition product after heating to 80 C for 3 d. S53

54 Starting material B 2 pin 2 itself is stable under these conditions (20 h at 80 C in C 6 D 6, see Figure S84). A 1:1 mixture of B 2 pin 2 and 1,2,3,5-tetrafluorobenzene also does not react without a catalyst (20 h at 80 C in C 6 D 6, see Figure S85, S86). Figure S84: 11 B{ 1 H} NMR spectrum (C6D6) after heating the starting material B2pin2 to 80 C for 20 h without forming any decomposition product. Figure S85: 19 F{ 1 H} NMR spectrum (C6D6): after heating B2pin2 and 1,2,3,5-tetrafluorobenzene to 80 C for 20 h without reacting. S54

55 Figure S86: 11 B{ 1 H} NMR spectrum (C6D6): after heating B2pin2 and 1,2,3,5-tetrafluorobenzene to 80 C for 20 h without reacting. The deutero-benzene residue was dissolved in CD 3 CN and analyzed using 1 H, 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy. The insoluble components consist of the salts [F 2 Bpin] [NMe 4 ]+ and traces of [BF 4 ] [NMe 4 ]+ (Figures S87-S89). Figure S87: 1 H NMR spectrum (CD3CN) of the C6D6 residue, which contains the salts [F2Bpin] [NMe4]+ and traces of [BF4] [NMe4]+. S55

56 Figure S88: 19 F{ 1 H} NMR spectrum (CD3CN) of the C6D6 residue, which contains the salts [F2Bpin] [NMe4]+ and traces of [BF4] [NMe4]+. Figure S89: 11 B{ 1 H} NMR spectrum (CD3CN) of the C6D6 residue, which contains the salts [F2Bpin] [NMe4]+ and traces of [BF4] [NMe4]+. c) The reaction of [Ni(IMes) 2 ], NMe 4 F, B 2 pin 2 with 1,2,3,5-tetrafluorobenzene in methylcyclopentane The same experiment was carried out in the solvent methylcyclopentane instead of C 6 D 6. Therefore, a mixture of [Ni(IMes) 2 ] (16.5 µmol, 11.0 mg), NMe 4 F (110 µmol, 10.0 mg) and B 2 pin 2 (110 µmol, 27.9 mg) was dissolved in methylcyclopentane (700 µl) in a Young s tap NMR tube. 1,2,3,5-Tetrafluorobenzene (110 µmol, 12.0 µl, 16.7 mg) was added at room temperature. After 30 min at room temperature the color changed from black to orange and the formation of trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5 and unreacted 1,2,3,5-tetrafluorobenzene was detected by 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy (Figures S90, S91) without any formation of the product 1-Bpin-(2,3,5-C 6 F 3 H 2 ) 2d (see Scheme 3). S56

57 Scheme 3: Reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions at room temperature in methylcyclopentane, which leads to the formation of trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5 after 30 min. Figure S90: 19 F{ 1 H}-NMR spectrum (methylcyclopentane) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions at room temperature after 30 min, which leads to the formation of trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Figure S91: 11 B{ 1 H} NMR spectrum (methylcyclopentane) of the reaction of [Ni(IMes)2] and 1,2,3,5-tetrafluorobenzene at catalytic conditions at room temperature after 30 min, which shows a resonance at ppm for unreacted B2pin2. S57

58 After the spectra were recorded, the reaction mixture was heated to 80 C for 16 h. During that time the color of the solution deepened to dark orange and a colorless precipitation was formed. The reaction mixture was analyzed by 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy. The formation of 1-Bpin-(2,3,5-C 6 F 3 H 2 ) 2d and traces of 1-Bpin-(3,4,5-C 6 F 3 H 2 ) 2d as well as intact trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5 were detected by 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy (Scheme 4, Figures S92-S94). IMes Ni IMes 15 mol% B 2 pin 2 F F NMe 4 F F 1eq. 1eq. 1eq. F C 6 H C, 16 h F F 5 F IMes Ni F IMes B 2 pin 2 NMe 4 F F F F F F F F 2d Bpin F F Bpin 2d' F Scheme 4: Reaction of [Ni(IMes)2] with B2pin2 and 1,2,3,5-tetrafluorobenzene at catalytic conditions in C6H12 after 16 h at 80 C. Figure S92: 19 F{ 1 H} NMR spectrum (methylcyclopentane) of the reaction of [Ni(IMes)2], 1,2,3,5-tetrafluorobenzene and B2pin2 at catalytic conditions after heating to 80 C for 16 h. Detected was the formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 5 and 1,2,3,5-tetrafluorobenzene. S58

59 Figure S93: 19 F{ 1 H} NMR spectrum (methylcyclopentane) of the reaction of [Ni(IMes)2], 1,2,3,5-tetrafluorobenzene and B2pin2 at catalytic conditions after heating to 80 C for 16 h. Detected was the formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted in this Figure are the resonances of 2d and 2d. Figure S94: 11 B{ 1 H} NMR spectrum (methylcyclopentane) of the reaction of [Ni(IMes)2], 1,2,3,5-tetrafluorobenzene and B2pin2 at catalytic conditions after heating to 80 C for 16 h. Detected was the formation of 1-Bpin-(2,3,5-C6F3H2) 2d and traces of 1-Bpin-(3,4,5-C6F3H2) 2d as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. After heating for another 3 d at 80 C, the solution was filtered through a cannula, the methylcyclopentane was evaporated and the remaining solid was dried in vacuo. The solution and the isolated solid, dissolved in CD 3 CN, were analyzed by 1 H, 19 F{ 1 H}, 11 B{ 1 H} NMR spectroscopy and the solution by GC/MS analysis. In the C 6 D 6 -soluble components, the products of the catalysis, 1-Bpin-(2,3,5-C 6 F 3 H 2 ) 2d and traces of 1-Bpin- S59

60 (3,4,5-C 6 F 3 H 2 ) 2d, as well as intact resting state of the catalyst, trans-[ni(imes) 2 (F)(2,3,5-C 6 F 3 H 2 )] 5, were detected (Figures S95-S98). The CD 3 CN soluble residue consists of the salts [F 2 Bpin] [NMe 4 ]+ and traces of [BF 4 ] [NMe 4 ]+ (Figures S99-S101). Figure S95: 1 H NMR spectrum of the methylcyclopentane soluble fraction in C6D6, which shows the formation of 1-Bpin- (2,3,5-C6F3H2) 2d and in traces trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Figure S96: 19 F NMR spectrum of the methylcyclopentane soluble fraction in C6D6, which shows the formation of 1-Bpin- (2,3,5-C6F3H2) 2d, traces of 1-Bpin-(3,4,5-C6F3H2) 2d, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted are the resonances of 2d and 2d. S60

61 Figure S97: 19 F-NMR of the methylcyclopentane soluble fraction in C6D6, which shows the formation of 1-Bpin-(2,3,5- C6F3H2) 2d, traces of 1-Bpin-(3,4,5-C6F3H2) 2d, as well as intact trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5. Highlighted are the resonances of 5. Figure S98: 11 B-NMR spectrum of the methylcyclopentane soluble fraction in C6D6, which shows the formation of 1-Bpin- (2,3,5-C6F3H2) 2d and an unidentified decomposition product. The methylcyclopentane insoluble components were filtered off and the colorless residue was dried in vacuo and dissolved in CD 3 CN. 1 H, 19 F{ 1 H} and 11 B{ 1 H} NMR spectroscopy reveals the formation of the salts [F 2 Bpin] [NMe 4 ]+ and minor amounts of [BF 4 ] [NMe 4 ]+ (Figures S99-S101). S61

62 Figure S99: 1 H NMR spectrum (CD3CN) of the methylcyclopentane insoluble components, which reveals the formation of [F2Bpin] [NMe4F]+ and minor amounts of [BF4] [NMe4]+. Figure S100: 19 F{ 1 H} NMR spectrum (CD3CN) of the methylcyclopentane insoluble components, which reveals the formation of [F2Bpin] [NMe4F]+ and minor amounts of [BF4] [NMe4]+. S62

63 Figure S101: 11 B{ 1 H} NMR spectrum (CD3CN) of the methylcyclopentane insoluble components, which reveals the formation of [F2Bpin] [NMe4F]+ and minor amounts of [BF4] [NMe4]+. S63

64 IV. X-ray Crystal Structures Figure S102: Molecular structure of trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5 with thermal ellipsoids drawn at the 50% probability level; some hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles ( ): Ni1 C1_ (3), Ni1 C2_ (3), Ni1 C (5), Ni1 F (16), C13 F (6), C15 F (5), C16 F (6); C1_1-Ni1-C2_ (11), F1-Ni1-C (2), F1-Ni1-C1_ (9), F1-Ni1-C2_ (9), C1_1-Ni1-C (3), angle between planes spanned by (C1_1/Ni1/C2_2/C11/F1) and carbene (N1_1/C1_1/N2_1) 65.95(9), angle between planes spanned by (C1_1/Ni1/C2_2/C11/F1) and carbene (N1_2/C2_2/N2_2) 85.27(10), angle between planes spanned by (C1_1/Ni1/C2_2/C11/F1) and aromatic ring (C11/C12/C13/C14/C15/C16) 74.46(15). The aromatic ring of the fluorobenzene is positionally disordered combined with a rotation of the ring by about 180 around the F1-Ni1-C11 axis. The major structural conformation with a refined occupancy of 0.717(3) is shown here. Figure S103: Molecular structure of trans-[ni(imes)2(f)(2,3,5-c6f3h2)] 5 C6D6 with thermal ellipsoids drawn at the 50% probability level; some hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles ( ): Ni1_1 C1_ (16), Ni1_1 C1_ (16), Ni1_1 C1_ (3), Ni1_1 F2_ (10), C2_8 F7_ (2), C3_8 F8_ (3), C5_8 F9_ (2); C1_2-Ni1_1-C1_ (6), F2_1-Ni1_1-C1_ (9), F2_1-Ni1_1-C1_ (5), F2_1-Ni1_1-C1_ (5), C1_3-Ni1_1-C1_ (12), angle between planes spanned by (C1_2/Ni1_1/C1_3/C1_8/F2_1) and carbene (N2_3/C1_3/N5_3) 57.78(4), angle between planes spanned by (C1_2/Ni1_1/C1_3/C1_8/F2_1) and carbene (N2_2/C1_2/N5_2) 82.19(5), angle between planes spanned by (C1_2/Ni1_1/C1_3/C1_8/F2_1) and aromatic ring (C1_8/C2_8/C3_8/C4_8/C5_8/C6_8) 75.96(6). The aromatic ring of the fluorobenzene is positionally disordered combined with a rotation of the ring by about 180 around the F2_1-Ni1_1-C1_8 axis. The major structural conformation with a refined occupancy of 0.870(2) is shown here. S64