Cationic complexes of iridium. Part I. The preparation and properties of some phosphine and arsine complexes

Abstract

A series of cationic five-co-ordinate complexes of formula [Ir(CO)₃L₂]BPh₄(I)(L = tertiary phosphine or arsine) have been prepared by passage of carbon monoxide through solutions of trans-[IrCl(CO)L₂] in the presence of sodium tetraphenylborate. From these, the corresponding cationic dihydride complexes [IrH₂(CO)₂L₂]BPh₄(II) have been obtained by reaction with hydrogen under mild conditions. Some of the complexes (I) lose carbon monoxide reversibly to give stable four-co-ordinate complexes of formula [Ir(CO)₂L₂]BPh₄(III). Addition of MeO₂C·C⋮C·CO₂Me (A) to (I) acetylene complexes of formula [Ir(A)(CO)₂L₂]BPh₄. The hydride complex (II)(where L = PMePh₂) reacts with π-bonding ligands L′(L′= CO, tertiary phosphines, phosphites, etc.) to give complexes of formula [Ir(CO)₂(PMePh₂)₂L′]BPh₄ which, for L′= PMePh₂, reacts further with hydrogen to give [IrH₂(CO)(PMePh₂)₃]BPh₄. Reaction of trans-[IrCl(CO)(PMePh₂)₂] with tertiary phosphites, L′, in the presence of NaBPh₄ gives complexes of formula [Ir(CO)(PMePh₂)₂L′₂]BPh₄. The i.r. and ¹H n.m.r. spectra of the new complexes prepared are reported, and are used in making stereochemical assignments.