On the reactivity of [IrCl(N2)(PPh3)2] with alkynylsilanes – A new route to vinylidene iridium(I) complexes

The iridium dinitrogen complex [IrCl(N2)(PPh3)2] (1) was found to react with alkynylsilanes RCCSiR3′ to form the vinylidene iridium(I) complexes trans  -[IrCl{CCR(SiR3′)}(PPh3)2] (R/R′ = Ph/Me, 2; Me/Me, 3; Bn/Me, 4; SiMe3/Me, 5; SiEt3/Et, 6; iPr/Me, 7) and with Me3SiCCC(O)R to yield the iridium η2-alkyne complexes trans-[IrCl{η2-Me3SiCCC(O)R}(PPh3)2] (R = OEt, 9; Me, 11). Complex 9 was found to isomerize upon heating or upon UV irradiation yielding the vinylidene complex trans-[IrCl{CC(SiMe3)CO2Et}(PPh3)2] (10). The reaction of 1 with Me3SiCCCCSiMe3 yielded the complex trans-[IrCl{CC(SiMe3)CCSiMe3}(PPh3)2] (8), whereas with MeO2CCCCO2Me the iridacyclopentadiene complex [Ir{C4(CO2Me)4}Cl(PPh3)2] (13) was formed. The complexes were characterized by means of 1H, 13C and 31P NMR spectroscopy as well as by IR spectroscopy and microanalysis.

The dinitrogen iridium complex [IrCl(N2)(PPh3)2] (1) was found to react with alkynylsilanes RCCSiR3′ (R = Me, iPr, Bn, Ph, SiMe3, SiEt3, C(O)Me, CO2Et; R′ = Me, Et) to form vinylidene iridium(I) complexes trans  -[IrCl{CCR(SiR3′)}(PPh3)2] (3), being the first examples of Werner’s type complexes with other than PiPr3 co-ligands. With R = C(O)Me and CO2Et the intermediate η2-alkyne iridium complexes trans-[IrCl{η2-RCCSiMe3}(PPh3)2] (2) were isolated.Figure optionsDownload as PowerPoint slide