Supporting Information for: Dehydrocoupling of Dimethylamine Borane. Catalysed by Rh(PCy3)2H2Cl

Transcription

1 Supporting Information for: Dehydrocoupling of Dimethylamine Borane Catalysed by Rh(PCy3)2H2Cl Laura J. Sewell, 1 Miguel A. Huertos, 1 Molly E. Dickinson, 1 Guy C. Lloyd-Jones 2 and Andrew S. Weller 1,* 1 Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK. 2 School of Chemistry, University of Bristol, Cantock s Close, Bristol, BS8 1TS, UK Experimental S-2 Dehydrocoupling Procedure S-2 Synthesis of New Complexes S-3 Catalytic Dehydrocoupling S-6 Initial Rates S-13 Crystallographic Data S-15 References S-18 S-1

2 Experimental All manipulations, unless otherwise stated, were performed under an atmosphere of argon, using standard Schlenk and glove-box techniques. Glassware was oven dried at 130⁰C overnight and flamed under vacuum prior to use. Pentane and MeCN were dried using a Grubbs type solvent purification system (MBraun SPS-800) and degassed by successive freezepump-thaw cycles. 1 CD2Cl2 and 1,2-F2C6H4 were dried over CaH2, vacuum distilled and stored over 3 Ǻ molecular sieves. H3B. NMe3 was sublimed once and H3B. NMe2H twice prior to use ( Torr, 298 K). Na[BAr F 4], 2 [H2BNMe2]2, 3 Rh(PCy3)2H2Cl, 4 D3B. NMe2H, 5 H3B. NMe2D 5 and D3B. NMe2D 5 were prepared by literature methods. All other chemicals are commercial products and were used as received. NMR spectra were recorded on a Varian Unity Plus 500 MHz or a Bruker AVD 500 MHz spectrometer at room temperature unless otherwise stated. In 1,2- F2C6H4, 1 H NMR spectra were referenced to the centre of the downfield solvent multiplet (δ = 7.07). 31 P and 11 B NMR spectra were referenced against 85% H3PO4 (external) and BF3.OEt2 (external) respectively. Chemical shifts are quoted in ppm and coupling constants in Hz. ESI-MS were recorded on a Bruker MicrOTOF instrument interfaced with a glovebox. 6 Microanalyses were performed by Stephen Boyer at London Metropolitan University. Dehydrocoupling Procedure Open System To a 3-necked Schlenk flask, connected to an external oil bubbler and charged with a magnetic stirrer bar and the catalytic precursor was added a solution of H3B. NMe2H in 1,2-F2C6H4. Regular aliquots (0.1 ml) of the reaction solution were taken, diluted with 0.25 ml 1,2-F2C6H4 under argon and rapidly frozen in liquid N2. The samples were warmed to room temperature and immediately analysed by 11 B NMR spectroscopy. Closed System To a high pressure NMR tube was added a solution of the catalyst in 1,2-F2C6H4 (100 μl). To this was added a solution of H3B. NMe2H in 1,2-F2C6H4 (300 μl). The NMR tube was immediately sealed and frozen in liquid N2. The NMR tube was later warmed to room temperature and the reaction was immediately followed, in situ, by 11 B NMR spectroscopy. S-2

3 Synthesis of New Complexes [(PCy3)2H2Rh(μ-Cl)RhH2(PCy3)2][BAr F 4] (3) C6H5F (1 ml) was added to a Young s flask containing Rh(H)2(PCy3)2Cl (0.030 g, mmol) and Na[BAr F 4] (0.038 g, mmol). The mixture was filtered in to a crystallisation tube containing Rh(PCy3)2H2Cl (0.030 g, mmol) yielding a dark yellow solution. The solution was layered with pentane and held at 2 C for several days yielding the product as yellow crystals. Yield: g (66%). Crystals suitable for single crystal X-Ray diffraction were grown from a concentrated C6H5F solution at room temperature. 1 H NMR (CD2Cl2, 500 MHz): δ 7.73 (s, 8H, BAr F 4), 7.57 (s, 4H, BAr F 4), (m, 132H, Cy), (br, 4H, RhH). 1 H NMR (CD2Cl2, 500 MHz, 200 K): δ 7.73 (s, 8H, BAr F 4), 7.57 (s, 4H, BAr F 4), (m, 132H, Cy), (br, 0.31H, RhH, rotamer 1), (br, 0.47H, RhH, rotamer 2), (br, 3.22H, RhH, rotamer 3). 31 P { 1 H} NMR (CD2Cl2, 202 MHz): δ 49.6 (br). 31 P { 1 H} NMR (CD2Cl2, 202 MHz, 200 K): δ 49.7 (d, 1 JRhP = 115, rotamer 2), 47.5 (d, 1 JRhP = 114, rotamer 1), 46.1 (d, 1 JRhP = 113, rotamer 3). Peaks assigned by relative integrals. Approximate percentage of the 3 rotamers by relative 31 P integrals: 1, 8%; 2, 12%; 3, 80%. Anal. Calcd for C104H148BClF24P4Rh2 ( g mol -1 ): C, 56.01; H, Found: C, 56.12; H, ESI-MS (1,2-F2C6H4, 60 C) positive ion: m/z [M +, minor] (calc ), [M + - Rh(PCy3)2H2Cl, major] (calc ). The observed isotopomer patterns (7 lines and 3 lines) are fully consistent with the molecular formulae. S-3

4 Figure S-1: 31 P{ 1 H} and hydridic region of 1 H NMR spectra of [(PCy 3) 2(H) 2Rh(μ- Cl)Rh(H) 2(PCy 3) 2][BAr F 4] at a range of temperatures (200 K 298 K) in CD 2Cl 2. Ir(PCy3)2H2(η 2 -BH4) (5) Fluorobenzene (15 ml) was added to Ir(PCy3)2H2Cl (100 mg, 0.13 mmol) with stirring until the solid had completely dissolved. The solution was cannula transferred to a Young s flask containing H3B. NMe2H (37.3 mg, 0.63 mmol) and left to stir for 12 h. A colour change from orange to colourless was observed. Half the solvent was then removed in vacuo and pentane was added until solid began to crash out. After filtration into a Schlenk and concentration, the solution was held at 2 C overnight resulting in the formation of colourless crystals. Yield: g (52%). 1 H NMR (500 MHz, CD2Cl2): δ 6.33 (br, 2H, terminal BH2), (m, 66H, Cy), (br, 2H, σ-bound BH2), (m, 2H, IrH2). 31 P{ 1 H} NMR (202 MHz, CD2Cl2): δ 33.4 (s). 11 B NMR (160 MHz, CD2Cl2): δ 11.4 (br). S-4

5 Rh(PCy3)2H2(η 2 -BH4) (6) Although a known compound, 7 Rh(PCy3)2H2(η 2 -BH4) was synthesised via an alternative method to that reported in the literature. Degassed ethanol (5 ml) was added to a Schlenk containing Rh(PCy3)2H2Cl (0.050 g, mmol) and Na[BH4] (0.013g, mmol). The mixture was sonicated for 3 hours before filtration. The cream solid was washed with ethanol (2 x 5 ml) and dried in vacuo. Yield 64%. NMR data was as reported in the literature. Additional characterisation by VT-NMR was performed. 1 H NMR (500 MHz, CD2Cl2, 295 K): δ (m, 66H, Cy), (br, 4H, BH4), (m, 2H, IrH2). 31 P{ 1 H} NMR (202 MHz, CD2Cl2, 295 K): δ 55.5 (d, 1 JPRh = 111, 2P). 11 B NMR (160 MHz, CD2CL2, 295 K): δ -4.2 (br). 1 H NMR (500 MHz, CD2Cl2, 250 K): δ 3.02 (br, 2H, terminal BH2), (m, 66H, Cy), (br, 2H, σ-bound BH2), (m, 2H, IrH2). 31 P{ 1 H} NMR (202 MHz, CD2Cl2, -250 K): δ 55.0 (d, 1 JPRh = 110, 2P). S-5

6 Catalytic Dehydrocoupling Open System 2 mol% Rh(PCy3)2H2Cl To a 3-necked Schlenk flask, connected to an external oil bubbler and charged with a magnetic stirrer bar and the catalytic precursor Rh(PCy3)2H2Cl (0.005 g, mmol) was added a solution of H3B. NMe2H (0.072 M, 5.0 ml, 0.36 mmol, 20 equiv) in 1,2-F2C6H4. Catalysis was monitored by analyzing regular aliquots of the reaction solution (0.1 ml; diluted with 0.25 ml 1,2-F2C6H4 under argon) by 11 B NMR spectroscopy. Figure S-2: Plot of 11 B concentration over time for the dehydrocoupling of H 3B. NMe 2H (initial concentration = M) using Rh(PCy 3) 2H 2Cl. 0.1 ml samples diluted with 0.25 ml 1,2-F 2C 6H 4 under argon., H 3B. NMe 2H;,H 2B=NMe 2;, H 3B. NMe 2BH 2. NMe 2H;, [H 2BNMe 2] 2;, HB(NMe 2) 2. S-6

7 0.5 mol% Rh(PCy3)2H2Cl To a 3-necked Schlenk flask, connected to an external oil bubbler and charged with a magnetic stirrer bar and the catalytic precursor Rh(PCy3)2H2Cl ( g, mmol) was added a solution of H3B. NMe2H (0.072 M, 5.0 ml, 0.36 mmol, 20 equiv) in 1,2-F2C6H4. Catalysis was monitored by analyzing regular aliquots of the reaction solution (0.1 ml; diluted with 0.25 ml 1,2-F2C6H4 under argon) by 11 B NMR spectroscopy. This graph has previously been reported (L.J. Sewell, G.C. Lloyd-Jones and A.S. Weller, J. Am. Chem. Soc. 2012, 134, ) but is shown again here for contextual information. Figure S-3: Plot of 11 B concentration over time for the dehydrocoupling of H 3B. NMe 2H (initial concentration = M) using Rh(PCy 3) 2H 2Cl. 0.1 ml samples diluted with 0.25 ml 1,2-F 2C 6H 4 under argon., H 3B. NMe 2H;,H 2B=NMe 2;, H 3B. NMe 2BH 2. NMe 2H;, [H 2BNMe 2] 2;, HB(NMe 2) 2. S-7

8 0.5 mol% [(PCy3)2(H)2Rh(μ-Cl)Rh(H)2(PCy3)2][BAr F 4] To a 3-necked Schlenk flask, connected to an external oil bubbler and charged with a magnetic stirrer bar and the catalytic precursor [(PCy3)2(H)2Rh(μ-Cl)Rh(H)2(PCy3)2][BAr F 4] ( g, mmol) was added a solution of H3B. NMe2H (0.072 M, 5.0 ml, 0.36 mmol, 20 equiv) in 1,2-F2C6H4. Catalysis was monitored by analyzing regular aliquots of the reaction solution (0.1 ml; diluted with 0.25 ml 1,2-F2C6H4 under argon) by 11 B NMR spectroscopy. Figure S-4: Plot of 11 B concentration over time for the dehydrocoupling of H 3B. NMe 2H (initial concentration = M) using [(PCy 3) 2(H) 2Rh(μ-Cl)Rh(H) 2(PCy 3) 2][BAr F 4]. 0.1 ml samples diluted with 0.25 ml 1,2-F 2C 6H 4 under argon., H 3B. NMe 2H;,H 2B=NMe 2;, H 3B. NMe 2BH 2. NMe 2H;, [H 2BNMe 2] 2;, HB(NMe 2) 2. S-8

9 Closed System 2 mol% Rh(PCy3)2H2Cl To a high pressure NMR tube was added a solution of Rh(PCy3)2H2Cl in 1,2-F2C6H4 (100 μl, M, x 10-3 mmol). To this was added a solution of H3B. NMe2H in 1,2-F2C6H4 (300 μl, M, 28.8 x 10-3 mmol). The reaction was followed in situ by 11 B NMR spectroscopy. Figure S-5: Plot of 11 B concentration over time for the dehydrocoupling of H 3B. NMe 2H (initial concentration = M) using Rh(PCy 3) 2H 2Cl. Followed in situ by 11 B NMR spectroscopy., H 3B. NMe 2H;,H 2B=NMe 2;, H 3B. NMe 2BH 2. NMe 2H;, [H 2BNMe 2] 2;, HB(NMe 2) 2. S-9

10 Addition of a second amount of H3B. NMe2H Method as for closed systems. After seconds, the catalytic mixture was transferred to a second high pressure NMR tube containing H3B. NMe2H ( g, 28.8 x 10-3 mmol), and catalysis was monitored by in situ 11 B NMR spectroscopy. Figure S-6: Plot of 11 B concentration over time for the dehydrocoupling of H 3B. NMe 2H (initial concentration = M) using Rh(PCy 3) 2H 2Cl. Followed in situ by 11 B NMR spectroscopy. After seconds, further H 3B. NMe 2H was added., H 3B. NMe 2H;,H 2B=NMe 2;, H 3B. NMe 2BH 2. NMe 2H;, [H 2BNMe 2] 2;, HB(NMe 2) 2. S-10

11 20 mol% Ir(PCy3)2H2Cl 0.2 ml 1,2-F2C6H5 was added to a high pressure NMR tube containing Ir(PCy3)2H2Cl ( g, 2.53 x 10-3 mmol). To this was added a solution of H3B. NMe2H in 1,2- F2C6H4 (200 μl, M, x 10-3 mmol). The reaction was followed in situ by 11 B NMR spectroscopy. Figure S-7: Plot of 11 B concentration over time for the dehydrocoupling of H 3B. NMe 2H (initial concentration = M) using Ir(PCy 3) 2H 2Cl (20 mol%). Followed in situ by 11 B NMR spectroscopy., H 3B. NMe 2H;,H 2B=NMe 2;, [H 2B(NMe 2H) 2]Cl;, [H 2BNMe 2] 2;, unknown S-11

12 Reversibility of BH/NH Activation Rh(PCy3)2H2Cl ( g, x 10-3 mmol) and D3B. NMe2D ( g, 28.8 x 10-3 mmol) were added to a high pressure NMR tube. 0.4 ml 1,2-F2C6H4 was added the solution was immediately sealed and frozen in liquid nitrogen. The Ar headspace was removed (8 x 10-2 mbar) and replaced with H2 (~4 atm). The solution was warmed to warm temperature and followed periodically by 1 H and 11 B NMR spectroscopy. Representative 11 B NMR spectra are shown below. No H incorporation into N-D was observed by 1 H NMR spectroscopy. Figure S-8: 11 B NMR spectra from the dehydrocoupling of D 3B. NMe 2D catalysed by Rh(PCy 3) 2H 2Cl under an atmosphere of H 2. S-12

13 Initial Rates Samples were made up as per the methodology for the closed system and frozen in liquid nitrogen until needed. Samples were monitored by in situ 11 B NMR spectroscopy over the first 180 seconds. A sample plot is shown in Figure S-6. Figure S-9: Initial rate over 180 seconds (2 mol% Rh(PCy 3) 2H 2Cl, M H 3B. NMe 2H). Table S-1: Initial rates for the dehydrocoupling of H 3B. NMe 2H using Rh(PCy 3) 2H 2Cl in a sealed system (high pressure NMR tube). Errors given are the intrinsic error. *0.036 M exogenous [H 2BNMe 2] 2 at the start. Entry [Rh] / M [H3B. NMe2H] / M [D3B. NMe2H] / M [H3B. NMe2D] / M [D3B. NMe2D] / M Initial Rate x 10-5 / M s ± ± ± ± ± ± ± ± * ± 0.4 S-13

14 Order in DMAB Entries 1, 2 and 3 in Table S-1. Figure S-10: Plot of observed initial rate vs. [DMAB]. Order in Rh Entries 1, 4 and 5 in Table S-1. Figure S-11: Plot of observed initial rate vs. [Rh] 0.5. S-14

15 Kinetic Isotope Effect Entries 1, 6, 7, 8 and 9 in Table S-1. Table S-2: Kinetic isotope effects for the dehydrocoupling of H 3B. NMe 2H using Rh(PCy 3) 2H 2Cl with various deuterations. kh/kd D3B. NMe2H 1.2 ± 0.1 H3B. NMe2D 5.3 ± 1.2 D3B. NMe2D 5.1 ± 1.2 Crystallographic Data Relevant details about structures refinement are given in Table S-3. Data were collected on a Enraf Nonious Kappa CCD diffractometer using graphite monochromated Mo Kα radiation (λ = Å) and a low temperature device; 8 data were collected using COLLECT, reduction and cell refinement was performed using DENZO/SCALEPACK. 9 The structures were solved by direct methods using SIR92 10 and refined full-matrix least squares on F 2 using SHELX Structure 3: All non-hydrogen atoms were refined anisotropically. H1 and H2 were located on the Fourier difference map. All other hydrogen atoms were placed in calculated positions using the riding model. Rotational disorder of the CF3 groups of the anion was treated by modelling the fluorine atoms over three sites and restraining their geometry in respect to both the ipso and methyl carbons on which they were present. Structure 5: All non-hydrogen atoms were refined anisotropically. H101, H102, H103, H104, H111, H112, H201, H202, H203, H204, H221 and H223 were located on the Fourier difference map. The B-H and R-H bonds were restrained. All other hydrogen atoms were placed in calculated positions using the riding model. Disorder of the Ir, BH4 ligand and hydrides was treated by modelling over two sites and restraining their geometry. A picture of this disorder is showed in the Figure S-12. Structure 6: All non-hydrogen atoms were refined anisotropically. H01, H02, H100, H200, H300 and H400 were located on the Fourier difference map. The Rh1-H01 and Rh1-H02 bonds were restrained to equal length. All other hydrogen atoms were placed in calculated positions using the riding model. S-15

16 Crystals of 5 and 6 are not of a good enough quality for an exhaustive discussion about the structure (lengths and angles). But they are of sufficient quality to confirm both the structure and the connectivity between the metal and ligands. Table S-3: Crystallographic data for 3, 5 and CCDC number Formula C58H73B0.50Cl0.50F13P2Rh C36H72BIrP2 C36H72BRhP2 M Crystal System Monoclinic Triclinic Triclinic Space group P 2/c P-1 P-1 T [K] 150(2) 150(2) 150(2) a [Å] (2) (3) (5) b [Å] (2) (3) (7) c [Å] (3) (4) (6) α [deg] (10) (3) β [deg] (10) (10) (3) γ [deg] (2) (2) V [Å 3 ] (13) (8) (15) Z Density [gcm -3 ] μ [mm -1 ] θ range [deg] 5.10 θ θ θ Reflns collected Rint Completeness Data/restr/param / 198 / /34/ /3/385 R1 [I > 2σ(I)] wr2 [all data] GoF Largest diff. pk and , , and hole [eå -3 ] S-16

17 Figure S-12: a) Solid-state structure of 5. Displacement ellipsoids drawn at 50% probability level. Most H atoms are omitted for clarity. b) Picture of 5 showing the disorder at the Ir atom. Figure S-13: Solid-state structure of 6. Displacement ellipsoids drawn at 50% probability level. Most H atoms are omitted for clarity. S-17

18 References 1. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen and F. J. Timmers, Organometallics, 1996, 15, W. E. Buschmann and J. S. Miller, Inorganic Syntheses, Vol 33, 2002, 33, C. A. Jaska, K. Temple, A. J. Lough and I. Manners, Journal of the American Chemical Society, 2003, 125, L. J. Sewell, G. C. Lloyd-Jones and A. S. Weller, Journal of the American Chemical Society, 2012, 134, M. E. Sloan, A. Staubitz, T. J. Clark, C. A. Russell, G. C. Lloyd-Jones and I. Manners, Journal of the American Chemical Society, 2010, 132, A. T. Lubben, J. S. McIndoe and A. S. Weller, Organometallics, 2008, 27, H. L. M. Vangaal, J. M. J. Verlaak and T. Posno, Inorganica Chimica Acta, 1977, 23, J. Cosier and A. M. Glazer, Journal of Applied Crystallography, 1986, 19, Z. Otwinowski and W. Minor, Method Enzymol, 1997, 276, A. Altomare, G. Cascarano, C. Giacovazzo and A. Guagliardi, Journal of Applied Crystallography, 1994, 27, G. M. Sheldrick, Acta Crystallogr A, 2008, 64, S-18