Deprotonation of chiral triazolium salts 1 and reaction of the structure analysis. The application of the rhodium(COD) complexes as catalysts in an asymmetric hydrosilylation resulting nucleophilic carbenes with [(COD)RhCl] 2 or [(NBD)RhCl] 2 afforded square-planar complexes 2-6 in reaction has been examined, resulting in enantiomeric excesses of up to 44%. Similar results were achieved for yields of 65-95%. The complexes contain an axis of chirality and a diastereomeric excess of up to 97% was achieved. The aromatic and aliphatic ketones and a nonlinear temperature effect (principle of isoinversion) was observed. relative and absolute configurations of these complexes were determined by NMR spectroscopic investigations and X-ray
FULL PAPER
Conclusion
ϩ63 (c ϭ 0.1, CHCl 3 ). Ϫ IR (KBr): ν ˜ϭ 3029 cm Ϫ1 (m), 2978 (s), 2933 (s), 2875 (s), 2829 (s), 1531 (s), 1495 (s), 1474 (s), 1404 (s), Axially chiral (triazolinylidene)rhodium(COD) and -1383 (s), 1335 (s), 794 (s), 732 (s), 701 (s). Ϫ 1 H NMR (300 MHz): (NBD) complexes have been prepared with diastereomeric δ ϭ 1.74 (m, 1 H, CH 2 CH 2 ), 1.92 (d, J ϭ 7.14 Hz, 3 H, CHCH 3 ), excesses of up to 97%. The NMR spectroscopic and theo-2.00 (m, 3 H, CH 2 CH 2 ), 2.40 (m, 4 H, CH 2 CH 2 ), 2.93 (m, 1 H, retical investigations show the steric requirements needed CHCH), 3.36 (m, 2 H, CHCH), 4.27 (s, 3 H, NCH 3 ), 5.12 (m, 2 for hindered rotation about the carbene carbonϪrhodium H, CHCH), 6.73 (q, J ϭ 7. bond. This new type of chiral complex was examined in ). Ϫ 13 C NMR asymmetric hydrosilylation reactions with enantiomeric ex-(75 MHz): δ ϭ 22.93 (CH 3 ), 28.35, 29.18, 32.20, 33.36 (CH 2 CH 2 ), cesses of up to 44% for aromatic and aliphatic ketones. This 39.98 (NCH 3 ), 58.48 (CHCH 3 ), 68.40 (d, J ϭ 14.3 Hz, CHCH), represents a good result for a nonchelating ligand, probably 69.61 (d, J ϭ 15.0 Hz, CHCH), 99.46 (d, J ϭ 7.4 Hz, CHCH), caused in part by the axis of chirality. 99.85 (d, J ϭ 6.9 Hz, CHCH), 126.36, 128.36, 129.20 (C 5 H 5 CR), This work was supported by the Fonds der Chemischen Industrie, 138.80 (C 5 H 5 CR), 140.24 (N 2 CH), 186.02 (d, J ϭ 50.3 Hz, NCRh). the Deutsche Forschungsgemeinschaft (Leibniz award) and the For-Ϫ MS (70 eV); m/z (%): 433.0 (11.0) [M ϩ ], 324.9 (100) [M ϩ Ϫ schungsverbund Katalyse Nordrhein-Westfalen. We are grateful to COD], 288.8 (17.5) [M ϩ Ϫ COD Ϫ Cl], 260.9 (45.5), 105.0 (42.8). BASF AG, Degussa AG, Boehringer Mannheim GmbH, Bayer AG Ϫ HR-MS; m/z: C 19 H 25 ClN 3 Rh [M ϩ ]: calcd. 433.0785; found and Hoechst AG for the donation of chemicals. 433.0784. (R)-Chloro(η 4 -1,5-cyclooctadiene)(1-phenyl-4-(1-phenylethyl)-Experimental Section 4,5-dihydro-1H-1,2,4-triazol-5-ylidene)rhodium(I) (3b): Yield 94 mg (95%), de 40%, m.p. 207°C. Ϫ [α] D 25 ϭ ϩ142 (c ϭ 0.1, CHCl 3 ). General: All solvents were dried and distilled before use. The Ϫ IR (KBr): ν ˜ϭ 3031 cm Ϫ1 (m), 2995 (m), 2969 (m), 2935 (s), triazolium perchlorates [16] , [(COD)RhCl] 2 and [(NBD)RhCl] 2 [17] 2914 (s), 2874 (s), 2829 (s), 1597 (s), 1531 (s), 1500 (s), 1476 (m), were prepared according to literature procedures. Ϫ Column chro-1452 (m), 1409 (s), 1387 (m), 1345 (s), 762 (s), 718 (s), 691 (s), 663 matography: Merck silica gel 60, 0.040Ϫ0.063 mm (230Ϫ400 mesh) (s). Ϫ 1 H NMR (300 MHz): δ ϭ 1.65 (m, 1 H, CH 2 CH 2 ), 1.76 (m, (flash). Ϫ Optical rotation values: Perkin-Elmer P 241, solvent 2 H, CH 2 CH 2 ), 1.90 (m, 2 H, CH 2 CH 2 ), 2.00 (d, J ϭ 7.15 Hz, 3 UVASOL-quality. Ϫ Melting points (uncorrected): Büchi 510. Ϫ H, CHCH 3 ), 2.15 (m, 1 H, CH 2 CH 2 ), 2.35 (m, 2 H, CH 2 CH 2 ), 2.68 IR: Perkin-Elmer FT 1750. Ϫ NMR: Varian VXR 300 and Gemini (m, 1 H, CHCH), 2.81 (m, 2 H, CHCH), 5.15 (m, 2 H, CHCH), 300 (300 and 75 MHz for 1 H and 13 C, respectively), Varian Unity 7.02 (q, J ϭ 7.14 Hz, 1 H, CHCH 3 ), 7.39 (m, 2 H, C 6 H 5 ), 7.46 (m, 500 (500 and 125 MHz for 1 H and 13 C, respectively), CDCl 3 as 4 H, C 6 H 5 ), 7.56 (m, 2 H, C 6 H 5 ), 7.72 (s, 1 H minor diastereomer, solvent, TMS as internal standard, room temperature if not other-N 2 CH), 8.18 (s, 1 H, N 2 CH), 8.55 (m, 2 H, C 6 H 5 ). Ϫ 13 C NMR wise noticed. Ϫ MS: Finnigan MAT (70 eV) and Finnigan SSQ (75 MHz): δ ϭ 22.79 (CH 3 ), 28.20, 29.17, 32.18, 32.76 (CH 2 CH 2 ), 7000 (70 eV). 59.49 (CHCH 3 ), 68.76 (d, J ϭ 14.3 Hz, CHCH), 71.02 (d, J ϭ 13.8 1. General Procedure for the Preparation of (Chloro)rhodium-Hz, CHCH), 98.50 (d, J ϭ 7.5 Hz, CHCH), 99.42 (d, J ϭ 7.4 Hz, (COD) Complexes 2؊4: (COD)RhCl] 2 (50 mg, 0.10 mmol), NEt 3 CHCH), 123.95, 125.55, 128.41, 128.47, 128.84, 129.25 (C 5 H 5 CR), (0.2 ml, 1.4 mmol) and 1.1 equiv. of the corresponding triazolium 138.28, 139.89 (C 5 H 5 CR), 140.67 (N 2 CH), 186.85 (d, J ϭ 51.0 Hz, perchlorate 1 (0.22 mmol) were dissolved in 40 ml of THF and the NCRh). Ϫ MS (70 eV); m/z (%): 495.0 (36.3) [M ϩ ], 386.9 (66.5) solution was stirred at room temperature for 14 h. The solution [M ϩ ϪCOD], 350.9 (64.3) [M ϩ Ϫ COD Ϫ HCl], 246.9 (44.9), 105.0 was evaporated to dryness in vacuo and the products were purified (77.7). Ϫ HR-MS, m/z: C 24 H 27 ClN 3 Rh [M ϩ ]: calcd. 495.0942; by column chromatography (silica gel, Et 2 O/pentane, 2:1).
found 495.0942. Chloro(η 4 -1,5-cyclooctadiene) (1-phenyl-4-benzyl-4,5-dihydro-(R)-(1-tButyl-4-(1-phenylethyl)-4,5-dihydro-1H-1,2,4-triazol-5-1H-1,2,4-triazol-5-ylidene)rhodium(I) (2): Yield 86 mg (90%), m.p. ylidene)(chloro)(η 4 -1,5-cyclooctadiene)rhodium(I) (3c): Yield 74 184°C. Ϫ IR (KBr): ν ˜ϭ 3110 cm Ϫ1 (m), 3047 (m), 3005 (m), 2931 mg (78%), de 36%, m.p. 81°C. Ϫ [α] D 25 ϭ ϩ38 (c ϭ 0.1, CHCl 3 ). (s),