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

In situ IR and UV-VIS spectroelectrochemical studies have shown that reduct ion of the ions trans-[RuX4(CNBut)(2)](-) (X = Cl or Br) in the presence of acetonitrile or pyridine results in the formation of mer, trans-[RuX3(CNBu t)(2)L](-) (L = MeCN or py), which can be oxidised reversibly to mer, trans -[RuX3(CNBut)(2)L]. The same reaction carried out in the presence of triphe nylphosphine or tert-butyl isocyanide yields the disubstituted product, tra ns, trans, trans[ RuX2(CNBut)(2)L-2] (L = PPh3 or CNBut), which can be oxid ised reversibly in each case to the isostructural monocation. Oxidation of trans-[RuX4(CNBut)(2)](-) can also be achieved, but the products are depend ent upon the identity of the halide. For X = Cl the oxidation is chemically reversible at low temperature forming trans[ RuCl4(CNBut)(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(CNBut)(2)L] (L = MeCN or py) or mer-[RuBr3(CNBut)(3)] (L = CNBut). Al l of the redox products have been characterised in situ by IR and UV-VIS sp ectroscopy in as many oxidation states as possible.