Stability of phosphite coordinated to ruthenium(II) in aqueous media

Changes in the reactivity of phosphorus(III) esters, which are promoted by coordination to the ruthenium(II) metal centre, were the focus of this study. Nuclear magnetic resonance data, which were acquired as a function of time, suggest that the phosphite coordination to the ruthenium(II) centre stabilises these molecules in terms of hydrolysis. This stabilisation is greater when the coordination occurs to the trans-[Ru(H2O)(NH3)4]2+ rather than to the trans-[Ru(NO)(NH3)4]3+ fragment, and these results are interpreted considering the 4dπ(RuII) → 3dπ(P(III)) back-bonding interactions. The correlation between the data on alkyl phosphite hydrolysis constants in trans-[Ru(NO)(NH3)4P(III)]n+ (P(III) = P(OEt)3, P(O)(OEt)2, P(OiPr)3 and P(OBu)3) complexes and the δ13C data show that the hydrolysis of phosphites that are coordinated to Ru(II) preferably occurs via the Michaelis–Arbuzov mechanism. Only the nitrosyl complex, where P(III) = P(OMe)3, did not exhibit this correlation, which suggests that the hydrolysis likely occurs via the Aksnes mechanism in this case.

Hydrolysis rate constants for phosphites coordinated to [Ru(NO)(NH3)4]3+ and [Ru(H2O)(NH3)4]2+ fragments are described. The data indicate that Michaelis–Arbuzov mechanism for hydrolysis reaction is the favourable in coordinated phosphites. The knowledge of how achieve phosphites hydrolysis stability is useful in tailoring new complexes for catalytic and medical applications.Figure optionsDownload as PowerPoint slide