Oxidative addition of allylic halides to complexes of the type trans-[IrCl(CO)L2](L = dimethylphenyl- and methyldiphenyl-phosphine and dimethylphenylarsine

Abstract

Allyl chloride, 2-methylallyl chloride, or 2-chloroallyl chloride add cis to complexes of the type trans-[IrCl(CO)L₂] where L = PMe₂Ph or AsMe₂Ph in benzene. In the adducts [IrCl₂(σ-all)(CO)L₂] the ligands L are mutually cis. These adducts isomerise in chloroform or ethanol and the isomers have the ligands L mutually trans. The isomerisation probably goes via a π-allylic cation [IrCl(π-all)(CO)L₂]⁺ and such ions were isolated as their BPh₄^– or PF₆^– salts. These adducts [IrCl₂(σ-all)(CO)L₂] with trans-phosphines or -arsines can be prepared directly by treating trans-[IrCl(CO)L₂] with the allylic chloride in methanol. Allyl bromide adds to trans-[IrCl(CO)(PMe₂Ph)₂] in benzene to give [IrBrCl(σ-allyl)(CO)(PMe₂Ph)₂] with mutually cis phosphines and bromide trans to phosphine. In ethanol bromide ion is solvolysed off to give [IrCl(π-allyl)(CO)(PMe₂Ph)₂]⁺Br^– which then rearranges to [IrClBr(σ-allyl)(CO)(PMe₂Ph)₂] with trans-phosphines and bromide trans to the σ-allyl ligand. Other similar reactions are described. [IrCl(π-C₃H₅)(CO)(PMe₂Ph)₂]PF₆ reacts with PMe₂Ph to give [IrCl(σ-C₃H₅)(CO)(PMe₂Ph)₃]PF₆. N.m.r. and i.r. data {ν(CO), ν(Ir–Cl) and ν(CC)} are given and discussed.