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 ΔHo 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.