Reversible binding of water, methanol, and ethanol to a five-coordinate ruthenium(ii) complex

Abstract

The known green, five-coordinate, square-pyramidal trans-RuCl₂(P–N)(PPh₃) complex reversibly binds water, MeOH and EtOH in the vacant coordination site in the solid state and in CH₂Cl₂ solution to give pink adducts (P–N = o-diphenylphosphino-N,N′-dimethylaniline). The adducts are well characterized, including X-ray analysis of the aqua complex, trans-RuCl₂(P–N)(PPh₃)(H₂O), which crystallizes in two different benzene-solvated forms. Comparison of the structural data with those determined previously for the binding of H₂S, thiols, and H₂, which form cis-RuX₂(P–N)(PPh₃)L products (X = Cl, Br; L = a S-ligand or H₂) reveals the trans-influence trend P > H₂S ∼ thiols > H₂ > Cl ∼ Br > H₂O. Thermodynamic data for the binding of water were estimated in solution by UV-Vis spectroscopy, and ΔH^o data for the aqua and alcohol adducts in the solid state were obtained by differential scanning calorimetry. Inclusion of published data for the S-ligand adducts reveals the thermal stability trend of the solid complexes as MeSH > MeOH > H₂S > H₂O > EtSH > EtOH.