Synthesis and structural characterization of some tetraosmium carbonyl clusters incorporating pyridyl type ligands;: mass spectrometric studies of the water soluble cationic tetraosmium carbonyl cluster [Os4(μ-H)4(CO)10(dppH)]+ [dpp = 2,3-bis-(2-pyridyl)pyrazine] by electrospray techniques

The reactions of the activated tetraosmium carbonyl cluster [Os-4(mu-H)(4)(CO)(10)(NCMe)(2)] 1 with some pyridyl-containing ligands, namely, 2,2'-bipyrimidine (bpm), 2,3-bis(2-pyridyl)pyrazine (dpp) and 2,3'-bis(2'-pyridyl)-5,6-dimethylquinoxaline (dpq), gave the new clusters: [Os-4(mu-H)(4)(CO)(10)(bpm)] 2, [Os-4(mu-H)(4)(CO)(10)(dpp)] 3 and [Os-4(mu-H)(4)(CO)(10)(dpq)] 4, respectively. The molecular structures of clusters 2, 3 and 4 were established by X-ray diffraction analysis. Compound 3 underwent protonation to give the corresponding water soluble cationic cluster [Os-4(mu-H)(4)(CO)(10)(dppH)](+) 5 which has been characterized by positive-mode electrospray mass spectrometric analysis of the aqueous phase. Incorporation of compound 3 as a building block in the heterometallic supramolecular system has also been established.