Di- and trinuelear ruthenium and osmium bis(2-pyridyl) ketone oximate derivatives

Treatment of [Ru-3(CO)(12)] with bis(2-pyridyl) ketone oxime (Hdpko) in refluxing THF leads to a separable mixture of [Ru-3(mu,eta(3)-dpko-N,N,O)(2)(CO)(8)] (1) and [Ru-2(mu,eta(3)-dpko-N,N,O)(2)(CO)(4)] (2). In both complexes, two Ru atoms are doubly bridged by two dpko ligands, which are attached to a Ru atom through the oximate O atom while chelating the other Ru atom through the N atoms of a pyridyl group and the oximate fragment. While the Ru-Ru distance of the bridged edge of complex 1 is very long [3.5388(9) Angstrom], that of complex 2 is very short [2.620(1) Angstrom]. The acetonitrile complexes [M-3(CO)(10)(MeCN)(2)] (M = Ru, Os) react with Hdpko in THF at room temperature to give [M-3(mu-H)mu,eta(3))-dpko-N,N,O)(CO)(9)]. [M = Ru (3) Os (4)], in which the dpko ligand behaves in the same way as in 1 and 2. The thermal reaction of 3 with Hdpko leads to a mixture of 1 and 2, while an analogous treatment of complex 4 gives [Os-3(mu,eta(3)-dpko-N,N,O)(2)(CO)(8)] (5), which is isostructural with complex 1. Compounds 1 and 3 are the first examples of ruthenium clusters containing oximate ligands. These oximate complexes display low activity as DNA cleavage agents, requiring high complex concentrations, long incubation times, and the use of UV light as a trigger. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).