Synthesis of O-Co-ordinated platinum(II) complexes of carbonyl-stabilized arsonium ylides and the mechanism of conversion to their C-Co-ordinated isomers

Abstract

The reaction of [{PtCl(dppe)}₂][BF₄]₂[dppe = 1,2-bis(diphenylphosphino)ethane] with ylides Ph₃AsCHCOR (R = Me, Ph or OMe) led to novel platinum(II) complexes [PtCl(dppe){OC(R)CH(AsPh₃)}]BF₄(R = Me 1, Ph 2 or OMe 3) in which the carbonyl stabilized arsonium ylides are co-ordinated to the metal centre via the oxygen carbonyl atom. These derivatives are not stable in chlorinated solvents and slowly undergo isomerization to their C-co-ordinated analogues 4–6 following a first-order rate law. The mechanism proposed for this rearrangement implies both intramolecular and free-ylide promoted intermolecular paths with k_obs values of the whole process depending on the basicity of the ylide.