Cationic and Neutral Diphenyldiazomethanerhodium(I) Complexes as Catalytically Active Species in the CC Coupling Reaction of Olefins and Diphenyldiazomethane
✍ Scribed by Helmut Werner; Michael E. Schneider; Marco Bosch; Justin Wolf; Jan H. Teuben; Auke Meetsma; Sergei I. Troyanov
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 256 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Cationic rhodium(i) complexes cis-[Rh(acetone) 2 (L)(L')] (2: L L' C 8 H 14 ; 3: L C 8 H 14 ; L' PiPr 3 ; 4: L L' PiPr 3 ), prepared from [{RhCl-(C 8 H 14 ) 2 } 2 ] and isolated as PF 6 salts, catalyze the CÀC coupling reaction of diphenyldiazomethane with ethene, propene, and styrene. In most cases, a mixture of isomeric olefins and cyclopropanes were obtained which are formally built up by one equivalent of RCHCH 2 (R H, Me, Ph) and one equivalent of CPh 2 . The efficiency and selectivity of the catalyst depends significantly on the coordination sphere around the rhodium(i) center. Treatment of 4 with Ph 2 CN 2 in the molar ratio of 1:1 and 1:2 gave the complexes trans-[Rh-(PiPr 3 ) 2 (acetone)(h 1 -N 2 CPh 2 )]PF 6 (8) and trans-[Rh(PiPr 3 ) 2 (h 1 -N 2 CPh 2 ) 2 ]PF 6 (9), of which 8 was characterized by X-ray crystallography. Since 8 and 9 not only react with ethene but also catalyze the reaction of C 2 H 4 and free Ph 2 CN 2 , they can be regarded as intermediates (possibly resting states) in the CÀC coupling process. The lability of 8 and 9 is illustrated by the reactions with pyridine and NaX (X Cl, Br, I, N 3 ) which afford the mono(diphenyldiazomethane)rhodium(i) compounds trans-[Rh(PiPr 3 ) 2 (py)(h 1 -N 2 CPh 2 )]PF 6 (10) and trans-[RhX(h 1 -N 2 CPh 2 )(PiPr 3 ) 2 ] (11 ± 14), respectively. The catalytic activity of the neutral complexes 11 ± 14 is somewhat less than that of the cationic species 8, 9 and decreases in the order Cl > Br > I > N 3 .