Evidence for the formation of the triaquatricarbonylmanganese(I) cation and related derivatives from pentacarbonylchloromanganese

Abstract

Ready ligand-exchange reactions between water and [Mn(CO)₅Cl] in non-aqueous solution are described. Evidence of various kinds, stoicheiometric, spectroscopic, and electrochemical, is presented which is consistent with the formation under these conditions of aqueous solutions of [Mn(CO)₃(OH₂)₃]Cl (1) which appears to be the first example of this type of complex. The derivative could not be isolated by evaporation of water from the aqueous solution at room temperature since this resulted in decomposition. The ionic equilibria in aqueous solutions of (1) are described, particularly in relation to conductivity and electrolytic data. Photolysis of (1) is believed to lead to protonation and subsequent decomposition with generation of formyl radicals. When benzene solutions of [Mn(CO)₅Cl] are treated with low concentrations (up to 2.5 × 10^–2 mol dm^–3) of water, non-ionic species of intermediate type appear to be formed, notably [Mn(CO)₄(OH₂)Cl], [{Mn(CO)₃(OH₂)Cl}₂], and [Mn(CO)₃(OH₂)₂Cl].