Reactions of the alkylidyne cluster [Os₃(μ-H)₂(CO)₉(μ₃-CNC₅H₄CHCH₂)]. Crystal structures of [Os₃(μ-H)₂(CO)₉(μ₃-CNC₅H₄CHCH₂)], [Os₃(μ-H)₂(CO)₉(μ₃-CNC₅H₄-...

Full title: Reactions of the alkylidyne cluster [Os3(μ-H)2(CO)9(μ3-CNC5H4CHCH2)]. Crystal structures of [Os3(μ-H)2(CO)9(μ3-CNC5H4CHCH2)], [Os3(μ-H)2(CO)9(μ3-CNC5H4-μ-η2-CHCH)Os3(μ-H)(CO)10] and [Os3(μ-H)2(CO)9(μ-3-CN C5H4-C(O)CH3)]. The neutral triosmium alkylidyne cluster [Os3(μ-H)2(CO)9(μ3-CNC5H4CHCH2)] (1) has been made in good yield by the reaction of [Os3(μ-H)3(CO)9(μ3-CCl )] with one equivalent of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in the presence of an excess of 4-vinylpyridine. The reaction of 1 with [Os3(CO)10(NCMe)2] in refluxing n-hexane affords the linked cluster [Os3(μ-H)2(CO)9(μ3-CNC5H4-μ-η2-CHCHOs3(μ -H)(CO)10] (2) in in moderate yield, while the Wacker-type reaction of 1 with a trace amount of water in the presence of Wilkinson's catalyst RhCl(PPh3)3in refluxing dichloromethane yields the 4-acetylpyridine derivative of the corresponding alkylidyne cluster [Os3(μ-H)2(CO)9(μ3-CNC5H4C(O)CH3)] (3). The structures of compounds 1-3 have been determined by single crystal X-ray diffraction studies. The structure of 1 involves a triosmium alkylidyne metal core with the 4-vinylpyridine moiety bonded to the μ3-bridging alkylidyne carbon atom. In the case of 2 the triosmium alkylidyne metal core is linked to another triosmium cluster unit via a 4-vinylpyridine moiety, while 3 contains an alkylidyne metal core with the 4-acetylpyridine ligand attached to the apical carbon atom. The M.L.C.T. transitions of all three complexes show strong solvent dependency, displaying unusually large negative solvatochromism in a wide range of organic solvents. This suggests that a less polar excited state is produced by photoexcitation.