Synthesis and structure of two tetranuclear osmium carbonyl isotopomers: a crystallographic isotope effect

摘要

A synthetic route to [Os-4(mu-H)(mu-OH)(mu-CO)(CO)(12)] (1) has been devised through the activation of [Os-4(CO)(14)] with Me3NO. The pyrolysis and photolysis of the reactant in the presence of a trace amount of water produces 1 in low yield. The solid-state structure of [Os-4(mu-H)(mu-OH)(mu-CO)(CO)(12)center dot H2O] (1 center dot H2O) reveals a butterfly Os-4 skeleton with bridging H, OH and CO ligands as well as hydrogen-bonded molecules of water in the crystal lattice. A low-temperature C-13{H-1} NMR spectroscopic study revealed a merry-go-round exchange of CO ligands around the Os-3 plane containing the asymmetric bridging CO. The exposure of 1 center dot H2O to D2O yielded [Os-4(mu-H)(mu-OD)(mu-CO)(CO)(12)] (2). Although the solid-state, intramolecular structure of 2 closely matched that of 1 center dot H2O, the intermolecular structure did not: its crystal lattice contained no water of crystallization, a previously unreported crystallographic isotope effect.