The photochemical reactivity of triosmium cluster complexes containing 2-mercaptopyridine ligands: The crystal and molecular structures of the linked clusters [{Os3H(CO)(10)}(2)(mu-SC5H3NCO2)] and [{Os3H(CO)(9)}(mu-SC5H3NCO2){Os3H(CO)10}]

The 2-mercaptopyridine triosmium cluster complexes, [{Os3H(CO)(10)}(2)(mu-SC5H3NCO2)], [Os3H(CO)(10){SC5H3N(OH)}] and [Os3H(CO)(10)(SC5H4N)] upon exposure to irradiation at 366 nm undergo photochemical decarbonylation reactions in which the nitrogen of the mercaptopyridine ligand displaces a carbonyl on the third osmium of the thiolate-bridged triangle to yield [{Os3H(CO)(9)}(mu-SC5H3NCO2){Os3H(CO)(10)}], [Os3H(CO)(9){SC5H3N(OH)}] and [Os3H(CO)(9)(SC5H4N)]. The reactions proceed cleanly and quantum yields have been determined. The clusters have been characterised by spectroscopic means and the structures of [{Os3H(CO)(10)}(2)(mu-SC5H3NCO2)] and [{Os3H(CO)(9)}(mu-SC5H3NCO2){Os3H(CO)(10)}] established by single-crystal X-ray analyses. In both structures the osmiums form two triangles, with the carboxylate bridging one edge of one triangle and the sulphur that of a second. For [{Os3H(CO)(9)}(mu-SC5H3NCO2){Os3H(CO)(10)}] the nitrogen has displaced a carbonyl from the third osmium of the thiolate-bridged osmium triangle.