The complexes Ir(acac)(cyclooctene)(PR3) (PR3 = PiPr3 (2), PCy3 (3)), which are prepared by reaction of Ir(acac)(cyclooctene)2 (1) with the corresponding phosphine, react with carbon monoxide and acetylenedicarboxylic methyl ester to give Ir(acac)(CO)(PR3) (PR3 = PiPr3 (4), PCy3 (5)) and Ir(acac)(η2-CH3O2C-C≡C-CO 2CH3)(PR3) (PR3 = PiPr3 (6), PCy3 (7)). The reactions of 6 and 7 with H2SiPh2 afford Ir(acac){C[CH(OCH3)OSiPh2]=CHCO2CH 3}(PR3) (PR3 = PiPr3 (8), PCy3 (9)). The X-ray crystal structure analysis of 9 (monoclinic, space group P21/c with a = 21.408(1) Å, b = 10.246(1) Å, c = 18.983(1) Å, and β = 106.89(1)°) reveals that the bonding situation in the Ir-Si-O sequence could be described as an intermediate state between metal-silylene stabilized by an oxygen base and a tetrahedral silicon. © 1995 American Chemical Society.

We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project, Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the DGA (Diputación General de Aragón) for a grant. L. R. thanks the Spanish Government for a grant (Programa de Formación Científica para Iberoamérica).

Peer Reviewed