Oxidative Addition of Functionalized Alkyl-Halides to Iridium(I) Complexes IrCl(Co)L₂ (L = PMe₂Ph₂>, IrCl(Co)PMe₃)

Abstract

Iridium(I) complexes IrCl (CO)L₂ (L = PMePh₂, PMe₂Ph, PMe₃) oxidatively add alkyl bromides RBr bearing electron-withdrawing substituents on the α-carbon atom (R = CH₂CO₂Et,CH₃CHCO₂Et,CH₃CHCOCH₃,C₂H₅CHNO₂) to give octahedrally coordinated alkyliridium (III) complexes IrBrClR (CO)L₂, for which ¹H and ³¹P n.m.r . data are reported. In the secondary alkyls, the mutually trans tertiary phosphine ligands are inequivalent, consequently the P-Me resonance is not the usual 1 : 2 : 1 'virtual' triplet. In some cases the pattern is a doublet or a doublet of doublets, similar to that expected for mutually cis tertiary phosphine ligands . In contrast to simple s- alkyliridium (III) complexes, the functionalized s-alkyls do not isomerize under any conditions to the corresponding n-alkyls, and the reverse process does not occur for n-alkyls such as IrBrCl (CH₂CH₂CO₂Et)(CO)(PMe₃)₂ and IrClI (CH₂CH₂CN)(CO)(PMe₃)₂. Diiodomethane and chloroiodomethane readily add to IrCl (CO)L₂ to give haloalkyliridium (III) complexes IrClI (CH₂Y)(CO)L₂(Y = Cl , I). These contain mutually trans tertiary phosphine ligands , although in the case of L = PMe₂Ph unstable cis - isomers can be detected. Attempts to form complexes containing Ir - CHBrCH₃ or Ir -CH(OC₂H₅)CH₃ by addition of CH₃CHBr₂ or CH₃CHClOC₂H₅ to IrCl (CO)(PMe₃)₂ gave only IrBr₂Cl(CO)(PMe₃)₂ and IrHCl₂(CO)(PMe₃)₂, respectively.