Cyclic voltammetric behaviour of some cationic η3-allyl complexes of Pd(II) and Pt(II) in comparison with hydride reduction

η3-Allyl complexes of the type [M(η3-allyl)(L2)]+ (M Pd; allyl = 1-MeC3H4; L2 = 1,5-C8H12, 2MeCN; allyl = C3H5: L2 = 1,5-C8H12, 2PPh3, 2P(C6H11)3, 2MeCN; allyl = 2-MeC3H4; L2 = 1,5-C8H12, 2MeCN, 2PPh3; M Pt; allyl = C3H5; L2 = 2PPh3, 2P- (C6H11)3) are reduced by H- and by cathodic electron transfer. In both cases the nature of the reduction products is determined by the coordination properties of L2, elemental metal appearing when L2 = 1,5-C8H12 or 2MeCN, and ML2 species being formed in other cases. The reduction potentials are related to the stabilities of the starting complexes, and a parallel is dxawn with nucleophilic attack on η3-allyl complexes of d8 transition metal ions. The one-electron demand for electrochemical reduction and loss of the allyl group to form 1,5-hexadienes agree with the proposed reaction mechanism in which elimination of the allyl radical is proposed. © 1986