RUTHENIUM CARBONYL CLUSTER COMPLEXES WITH NITROGEN LIGANDS .3. REACTION OF RU-3(MU-AUPPH(3))(MU-CL)(CO)(10) WITH PYRIDINE - CRYSTAL-STRUCTURES OF RU-3(MU-H)(MU-NC5H4)(CO)(9)(PPH(3)), RU-3(MU-CL))(2)(CO)(8)(NC5H5)(PPH(3)) AND RU-3(MU-CL)(2)(CO)(8)(NC5H5)(2)

The reaction between Ru-3(mu-AuPPh(3))(mu-Cl)(CO)(10)(1) and pyridine afforded a mixture of products from which the title complexes Ru-3(mu-H)(mu-NC5H4)(CO)(9)(PPh(3)) (4), Ru-3(mu-Cl)(2)(CO)(8)(NC5H5)(PPh(3)) (6) and Ru-3(mu-Cl)(2)(CO)(8)(NC5H5)(2) (7) have been obtained together with the previously reported pyridyl cluster Ru-3(mu-H)(mu-NC5H4)(CO)(10)(2) and the phosphine-substituted clusters Ru-3(CO)(10)(PPh(3))(2) (3) and Ru-3(mu-Cl)(2)(CO)(8)(PPh(3))(2) (5). Complex 4 has also been obtained with a high yield by phosphine substitution of 2 under mild conditions. The structural study of 4 reveals site-specific substitution at the N-ligated ruthenium. Products 5-7 are dichloro-bridged complexes related by successive replacement of PPh(3) by NC5H5. Single-crystal X-ray diffraction studies of 6 and 7 indicate that these complexes contain triruthenium cores incorporating one and two sigma-bound equatorially disposed pyridine ligands respectively, a new coordination mode for unsupported pyridine ligands on triruthenium clusters. Extremely long Ru-N distances in 6 and 7 are consistent with the ''lightly stabilizing'' nature of the pyridine ligand in trinuclear cluster chemistry. A comparison of the core geometries of 5-7 has revealed a contraction in the Ru-Ru distances on sequential replacement of the P-donor ligand by the N-donor ligand.