Ruthenium carbonyl cluster complexes with nitrogen ligands

Abstract

The reaction between Ru3(μ-AuPPh3)(μ-Cl)(CO)10 (1) and pyridine afforded a mixture of products from which the title complexes Ru3(μ-H)(μ-NC5H4)(CO)9(PPh3) (4), Ru3 (μ-Cl)2(CO)8(NC5H5)(PPh3) (6) and Ru3(μ-Cl)2(CO)8(NC5H5)2 (7) have been obtained together with the previously reported pyridyl cluster Ru3(μ-H)(μ-NC5H 4)(CO)10 (2) and the phosphine-substituted clusters Ru3(CO)10(PPh3)2 (3) and Ru3(μ-Cl)2(CO)8(PPh3)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 PPh3 by NC5H5. Single-crystal X-ray diffraction studies of 6 and 7 indicate that these complexes contain triruthenium cores incorporating one and two σ-bound equatorially disposed pyridine ligands respectively, a new coordination mode for unsupported pyridine ligands on triruthenium clusters. Extremely long RuN 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 RuRu distances on sequential replacement of the P-donor ligand by the N-donor ligand.