Reactions of the square-planar compounds Ir(C(2)Ph)L(2)(PCy(3)) (L(2)=2 CO, TFB) with HSiR(3) (R=Et, Ph) and H(x+1)SiPh(3-x) (x=1, 2): Stoichiometric and catalytic formation of Si-C bonds

The square-planar cis-dicarbonyl complex Ir(C(2)Ph)(CO)(2)(PCy(3)) (1) reacts with ca. 1 equiv of HSiR(3) to give, in quantitative yield, the corresponding alkynyl-hydrido-silyl derivatives Ir(C(2)Ph)(H)(SiR(3))(Co)(2)(PCy(3)) (SiR(3) = SiEt(3) (2), SiPh(3) (3), SiHPh(2) (4), and SiH(2)Ph(5)). The reactivity of the related tetrafluorobenzobarrelene compound Ir(C(2)Ph)(TFB)(PCy(3)) (6) toward HSiR(3) has been also studied by NMR spectroscopy. The addition of ca. 2 equiv of HSiEt(3) to a benzene-d(6) solution of 6 affords IrH2(SiEt(3))(TFB)(PCy(3)) (7) and PhC=CSiEt(3) in a 1:1 molar ratio, while the reaction of 6 with ca. 1 equiv of HSiPh(3) yields, after 1 h and 30 min, IrH2(SiPh(3))(TFB)(PCy,)(10, 8%), Ir{C(SiPh(3))=CHPh}(TFB)(PCy(3)) (11, 52%), and PhC=CSiPh(3) (8%). The addition of ca. 1 equiv of H(2)SiPh(2) to a benzene-d(6) solution of 6 leads, after 1 h, to IrH2{Si(C(2)Ph)Ph(2)}(TFB)(PCy(3)) (12) in 90% yield. The alkynyl compounds 1 and 6 have been found to be active catalysts for the addition of triethylsilane to phenylacetylene. In all experiments, PhCH=CH2, PhC=CSiEt(3), cis-PhCH=CH(SiEt(3)), trans-PhCH=CH(SiEt(3)), and Ph(SiEt(3))C=CH2 were obtained. On the basis of the results from the stoichiometric reactions together those from the catalytic experiments, reaction pathways for the formation of these silylate products are discussed.