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  • 1
    ISSN: 0947-6539
    Keywords: carbene complexes ; C—C coupling ; diazo compounds ; ligand effects ; rhodium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic methodology to obtain square-planar carbenerhodium(I) complexes of the general composition trans-[RhCl(=CRR′)(L)2] where L is a tertiary phosphane, arsane, or stibane has been developed. The starting material trans-[RhCl(C2H4)(SbiPr3)2] (3) reacts with diazoalkanes RR′CN2 [RR′ = Ph2, Ph(C6H4X), (C6H4X)2, Ph(CF3), C12H8] under mild conditions to give the compounds trans-[RhCl(=CRR′)(SbiPr3)2] (4-11) almost quantitatively. On treatment of 3 with EtO2CCHN2 and PhC(N2)C(O)R, the olefinrhodium and diazoalkanerhodium compounds trans-[RhCl{(E)-C2H2(CO2Et)2}(SbiPr3)2] (12) and trans-[RhCl{N2C(R)C(O)Ph}(SbiPr3)2] (13, 14) are obtained instead of carbene complexes. Displacement of the SbiPr3 ligands in 4 (R = R′ = Ph) by PiPr3, PiPr2Ph, PiPrPh2, PPh3, PPh2Me, AsiPr3, and SbEt3 leads to the corresponding carbene complexes trans-[RhCl-(=CPh2)(L)2] (15-21) in high yields. The results of the X-ray crystal structure analyses of 4 and 15 (L = PiPr3) illustrate that the different donor - acceptor properties of SbiPr3 and PiPr3 have little influence on the Rh—C bond length. The reactions of 4 and 15 with CO and CNtBu afford, by metal-assisted C—C coupling, diphenylketene Ph2C=C=O (23) and the corresponding imine Ph2C=C=NtBu (26). On treatment of 4 and 15 with ethene, however, two different olefinic products, 3,3-diphenyl-1-propene (31) and 1,1-diphenyl-1-propene (32), are formed. Compound 15 reacts with KBr, NaOPh, and NaC5H5 by substitution of the chloride to give trans-[RhBr(=CPh2)-(PiPr3)2] (33), trans-[Rh(OPh)(=CPh2)-(PiPr3)2] (34) and [C5H5Rh(=CPh2)-(PiPr3)] (35), and with HCl by oxidative addition to yield [RhCl2(CHPh2)-(PiPr3)2](36).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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