Ruthenium carbonyl cluster complexes with nitrogen ligands

The reaction between piperidine and Ru3(CO)12 in refluxing tetrahydrofuran gave the title compounds Ru3(mu-H)(mu-eta2-NC5H8)(CO)10 (1) and Ru3(mu-H)(mu3-eta2-NC5H8)(CO)9 (2), both of which have been characterized by means of X-ray diffraction studies, with location and refinement of the core hydrogen atoms. Analysis of the cluster core distances for 1, 2 and related structures suggests that there is substantially more N-C weakening for mu3-eta2-compared to mu-eta2-coordination. Interconvertibility of 1 and 2 has been demonstrated. Mild thermolysis cleanly converted 1 into 2; the reverse reaction could be quantitatively effected by carbonylation at room temperature. Hydrogenation of 2 effected the elimination of the mu3-eta2-piperidyl ligand.