The electrochemistry of two new classes of halogen-sulphoxide-Ru(III) complexes of general formula Na[trans – RuCl₄(R₂SO)L] and mer,cis - RuCl₃(R₂SO)(R₂SO)L (R₂SO = dimethylsulphoxide, tetramethylenesulphoxide; L = dimethylsulphoxide, tetramethylenesulphoxide, N-donor base) is reported. The parent compounds, namely Na[trans – RuCl₄(DMSO)₂] (1) and mer,trans- RuCl₃(DMSO)₂(DMSO) (2), display the richest behaviour in dimethylsulphoxide and water solution: on the time scale of cyclic voltammetry both give rise to square schemes trigered by the change in the coordination mode (from S-bonded to O-bonded and viceversa) of one dimethylsulphoxide ligand. The mechanism of these reacions as well as the long term behaviour on the bulk electrolysis time scale are fully investigated. The N-donor base substituted  derivatives give rise to reversible Ru(III)/Ru(II) electron transfers in water. Their redox potentials are discussed in connection with a recently proposed predictive additive model.