Reaction of chlorine with cis-[PtCl 2 {C(NHR)(NHR′) }PEt 3] and trans-[PtCl{C(NHR)(NHR′)}(PEt 3) 2]ClO 4 gives analogous platinum(IV) carbene complexes when R = R′ = Me; but when R = Me or Et and R′ = Ph, 2-metallation and 4-chlorine substitution of the phenyl group occurs, shown by the X-ray structure of [PtCl 2 {C(Cl·C 6H 3NH)(NHMe)}(PEt 3) 2]ClO 4.