In situ IR and UV-VIS spectroelectrochemical studies have shown that reduction 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(CNBut)2L]− (L = MeCN or py), which can be oxidised reversibly to mer,trans-[RuX3(CNBut)2L]. The same reaction carried out in the presence of triphenylphosphine or tert-butyl isocyanide yields the disubstituted product, trans,trans,trans-[RuX2(CNBut)2L2] (L = PPh3 or CNBut), which can be oxidised reversibly in each case to the isostructural monocation. Oxidation of trans-[RuX4(CNBut)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(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)2L] (L = MeCN or py) or mer-[RuBr3(CNBut)3] (L = CNBut). All of the redox products have been characterised in situ by IR and UV-VIS spectroscopy in as many oxidation states as possible.