Cyclic voltammetric studies on some manganese(II) tertiary arylphosphine complexes

Abstract

A series of manganese(II) arylphosphine complexes, [{Mn[P(aryl)₃]X₂}_n][aryl = Ph, 4-ClC₆H₄, 4-MeC₆H₄, 4-MeOC₆H₄ or 2,4,6-(MeO)₃C₆H₂; X = Cl, Br, I or NCS], have been synthesised and characterised. At ambient temperature all the complexes are inactive towards dioxygen binding, but at 228 K a toluene solution of [Mn{P(C₆H₄OMe-4)₃}I₂] absorbs 1 mol of O₂ per mol of complex; this represents the first triarylphosphine manganese(II) complex to bind dioxygen. Cyclic voltammetric studies on these compounds suggest a one-electron transfer process which becomes more reversible as the temperature is lowered, thus indicating an electrochemical–chemical mechanism, with E°′ values influenced by both the anion and phosphine ligands.