Dinuclear and trinuclear osmium complexes incorporating 1,2-bis(2-pyridyl)ethene as doubly and triply bridging ligands: crystal structures of [Os2(μ:η4-C12H10N2)(CO)6], [Os3(μ-H)2(μ3:η3-C12H10N2)(CO)8] and [Os3(μ-H)(μ3:η4-C12H9N2)(CO)8]

Treatment of trans-1,2-bis(2-pyridyl)ethene (C12H10N2) with the labile cluster [Os3(CO)10(CH3CN)2] in refluxing THF generated the products: [Os2(μ:η4-C12H10N2)(CO)6] (1) and [Os3(μ:η4-C12H10N2)(CO)10] (2). When the reaction is carried out in refluxing acetonitrile the products [Os3(μ-H)2(μ3:η3-C12H10N2)(CO)8] (3), [Os3(μ-H)(μ3:η4-C12H9N2)(CO)8] (4) and [Os3(μ-CO)(μ3:η3-C12H10N2)(CO)8] (5) are obtained in addition to compounds 1 and 2. The X-ray structures for 1, 3 and 4 are reported. We have established that both pyridine nitrogen atoms are co-ordinated in all five complexes. 1 and 2 contain the ligand incorporated in a doubly-bridging manner, and for clusters 3, 4 and 5 hydrogen atom transfer at the central ethene group has lead to bridging alkylidene and vinyl systems within triply-bridging ligands.