Kinetics of oxidation of dichlorobis(substituted pyridine)platinum(II) and of reduction of tetrachlorobis(substituted pyridine)platinum(IV) complexes

Abstract

The kinetics of oxidation of cis-[PtCl₂L₂] by [AuCl₄]^– in the presence of [NEt₄]Cl and of the reduction of cis-[PtCl₄L₂] by [NEt₄] I have been investigated in acetonitrile [L = pyridine (py), 3Me-, 2Me-, 2,4Me₂^–, 3Cl-, 4Cl-, 3CN-, or 4CN-py]. The rate law for the oxidation of cis-[PtCl₂L₂] has the form: Rate =k₃[PtCl₂L₂][AuCl_4^–][Cl^–]. The k₃ rate term is not affected by changes in the co-ordinated pyridine and has a value ca. 100 times higher than that previously found for related phenanthrolineplatinum(II) complexes. The rate law for the reduction of cis-[ PtCl₄L₂] has the form: Rate =k₂[PtCl₄L₂][I^–]. The k₂ rate term is strongly influenced by the basicity of L. according to an identical relation to that previously found for the reduction of related phenanthrolineplatinum(IV) derivatives. The kinetic results are discussed in terms of σ and π interactions between the central metal atom and the heterocyclic ligands.