Iridium complexes of tertiary t-butyl- and di-t-butylphosphines including some five-co-ordinate iridium(III) complexes with hydride resonances at τca. 60

Abstract

Treatment of chloroiridous acid with di-t-butyl-n-alkylphosphines (4 mol. equivalents) in boiling isopropyl alcohol gives purple, five-co-ordinate, square pyramidal hydrides [IrHCl₂(PBu^t₂R)₂](R = Me, Et, or Prⁿ). These complexes have a hydride resonance at τca. 60, the highest yet observed. With 2 or 3 mol. equivalents of PBu^t₂Prⁿ in isopropyl alcohol, chloroiridous acid gives [PBu^t₂PrⁿH][Ir₂Cl₇(PBu^t₂Prⁿ)₂] but with 2 equivalents of PBu^t₂Me a hydride is formed, possibly [PBu^t₂MeH][Ir₂HCl₆(PBu^t₂Me)₂]. With primary alcohols as solvents, hydride formation is generally accompanied by abstraction of carbon monoxide from the alcohol; thus chloroiridous acid and t-butyldi-n-propylphosphine in 2-methoxyethanol eventually give a mixture of trans-[IrCl(CO)(PBu^tPrⁿ₂)₂] and [IrHCl₂(CO)(PBu^tPrⁿ₂)₂] in very high yield. [IrHCl₂(PBu^t₂Prⁿ)₂] reacts with boiling 2-methoxymethanol to give trans-[IrCl(CO)(PBu^t₂Pr ⁿ₂)₂] in 90% yield. ¹H- and ³¹P-N.m.r. and i.r. data are given.