Redox-activated ligand-exchange reactions of tetrabutylammonium trans-bis(tert-butyl isocyanide)tetrahalogenoruthenate(III) complexes, [NBu4][RuX4(CNBut)2] (X = Cl or Br)

Abstract

In situ IR and UV-VIS spectroelectrochemical studies have shown that reduction of the ions trans-[RuX₄(CNBu^t)₂]⁻ (X = Cl or Br) in the presence of acetonitrile or pyridine results in the formation of mer,trans-[RuX₃(CNBu^t)₂L]⁻ (L = MeCN or py), which can be oxidised reversibly to mer,trans-[RuX₃(CNBu^t)₂L]. The same reaction carried out in the presence of triphenylphosphine or tert-butyl isocyanide yields the disubstituted product, trans,trans,trans-[RuX₂(CNBu^t)₂L₂] (L = PPh₃ or CNBu^t), which can be oxidised reversibly in each case to the isostructural monocation. Oxidation of trans-[RuX₄(CNBu^t)₂]⁻ can also be achieved, but the products are dependent upon the identity of the halide. For X = Cl the oxidation is chemically reversible at low temperature forming trans-[RuCl₄(CNBu^t)₂], whilst for X = Br the oxidation is irreversible and, in the presence of acetonitrile, pyridine or tert-butyl isocyanide, results in the formation of mer,trans-[RuBr₃(CNBu^t)₂L] (L = MeCN or py) or mer-[RuBr₃(CNBu^t)₃] (L = CNBu^t). All of the redox products have been characterised in situ by IR and UV-VIS spectroscopy in as many oxidation states as possible.