Electrochemistry of platinum(II) coordination compounds I. Electroreduction of dihalogenobis(isocyanides)-platinum(II) complexes

Electroreduction of cis and trans dihalogeobis(isocyanide)platinum(II) complexes PtL₂X₂ (X = Cl, Br, I; L = cyclohexyl isocyanide or tert-butyl isocyanide) on gold and platinum electrodes has been studied in propylene carbonate and acetonitrile containing tetraethylammonium perchlorate as supporting electrolyte. The first, monoelectronic, reduction step is irreversible, the half-wave potential being critically dependent on the chemical nature of X in PtL₂X₂. Potentiostatic reductive coulometry of PtX2L2 in the cavity of an ESR spectrometer produces a signal attributed to a monomeric paramagnetic Pt^I complex. It is also shown that one halide anion is liberated per PtX₂L₂ in this first reduction step. A second monoelectronic reduction step is observed, which results in the decomposition of the complex to form a solid deposit containing platinum on the electrode. A reduction scheme is proposed for PtX₂L₂, on the basis of these results.