Nonanuclear cluster complexes [Ru-9(mu(3)-H)(2)(mu-H)(mu(5)-O)(mu(4)-ampy)(mu(3)-Hampy)(CO)(21)] (4) (H(2)ampy = 2-amino-6-methylpyridine), [Ru-9(mu 5-O)(2)(mu(4)-ampy)(mu(3)-Hampy)(2)(mu-CO)(CO)(20)] (5), [Ru-9(mu(5)-O)(2)(mu 4-ampy)(mu(3)-Hampy)(2)(mu-CO)(2)(CO)(19)] (6), and [Ru-9(mu(4)-O)(mu(5)-O)(mu(4)-ampy)(mu(3)-Hampy)(mu-Hampy)(mu-CO)(CO)(19 )] (7), together with the known hexanuclear [Ru-6(A(3)-H)(2)(mu(5)-ampy)(mu-CO)(2)(CO)(14)] (2) and the novel pentanuclear [Ru-5(mu(4)-ampy)(2)(mu-CO)(CO)(12)] (3) complexes, are products of the thermolysis of [Ru-3(mu-H)(mu 3-Hampy)(CO)(9)] (1) in decane at 150 degrees C. Two different and very unusual quadruply bridging coordination modes have been observed for the ampy ligand. Compounds 4 - 7 also feature one (4) or two ( 5 - 7) bridging oxo ligands. With the exception of one of the oxo ligands of 7, which is in a distorted tetrahedral environment, the remaining oxo ligands of 4 - 7 are surrounded by five metal atoms. In carbonyl metal clusters, quadruply bridging oxo ligands are very unusual, whereas quintuply bridging oxo ligands are unprecedented. By using O-18-labeled water, we have unambiguously established that these oxo ligands arise from water.