The effect of ligand basicity on the unconventional hydrogen-bond in H(μ-H)Os 3(CO) 10L (L=amine) derivatives

Abstract

The reaction of amine ligands with the unsaturated 46 e − cluster Os 3(μ-H 2)(CO) 10 yields a series of complexes of formula Os 3H(μ-H)(CO) 10(amine). In these derivatives the presence of an unconventional hydrogen-bond MH⋯HN is detected by the evaluation of proton spin-lattice relaxation times. In order to elucidate the relationship between p K b and H⋯H length, the MH⋯HN distances were quantified for amines of known p K b. In practice, this was achieved by comparing the T 1 values of the terminal hydride resonances of the protonated isotopomer with the T 1 values of the corresponding derivative containing selectively deuterated amine. A nice correlation between the MH⋯HN distances and the p K b of the amine ligands was found. DFT calculations were carried out for the cluster on Os 3H(μ-H)(CO) 10(Benzylamine) to gain a fuller understanding of the possible coordination geometries of an amine ligand on the surface of a tri-osmium cluster.