THE PHOTOCHEMICAL REACTIVITY OF TRIOSMIUM CLUSTER COMPLEXES CONTAINING 2-MERCAPTOPYRIDINE LIGANDS - THE CRYSTAL AND MOLECULAR-STRUCTURES OFTHE 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 decarbon ylation reactions in which the nitrogen of the mercaptopyridine ligand displaces a carbonyl on the third osmium of the thiolate-bridged tria ngle to yield [{Os3H(CO)(9)}(mu-SC5H3NCO2){Os3H(CO)(10)}], [Os3H(CO)(9 ){SC5H3N(OH)}] and [Os3H(CO)(9)(SC5H4N)]. The reactions proceed cleanl y and quantum yields have been determined. The clusters have been char acterised by spectroscopic means and the structures of [{Os3H(CO)(10)} (2)(mu-SC5H3NCO2)] and [{Os3H(CO)(9)}(mu-SC5H3NCO2){Os3H(CO)(10)}] est ablished by single-crystal X-ray analyses. In both structures the osmi ums form two triangles, with the carboxylate bridging one edge of one triangle and the sulphur that of a second. For [{Os3H(CO)(9)}(mu-SC5H3 NCO2){Os3H(CO)(10)}] the nitrogen has displaced a carbonyl from the th ird osmium of the thiolate-bridged osmium triangle.