REACTIONS OF THE ALKYLIDYNE CLUSTER [OS-3(MU-H)(2)(CO)(9)(MU(3)-CNC5H4-CH=CH2)] - CRYSTAL-STRUCTURES OF [OS-3(MU-H)(2)(CO)(9)(MU(3)-CNC5H4-CH=CH2)], [OS-3(MU-H)(2)(CO)(9)(MU(3)-CNC5H4-MU-ETA(2)-CH=CH)OS-3(MU-H)(CO)(10)] AND [OS-3(MU-H)(2)(CO)(9)(MU(3)-CNC5H4-C(O)CH3)]

The neutral triosmium alkylidyne cluster [Os-3(mu-H)(2)(CO)(9)(mu(3)-CNC5H4-CH=CH2)] (1) has been made in good yield by the reaction of [Os-3(mu-H)(3)(CO)(9)(mu(3)-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 [Os-3(CO)(10)(NCMe)(2)] in refluxing n-hexane affords the linked cluster [Os-3(mu-H)(2)(CO)(9)(mu(3)-CNC5H4-mu-eta(2)-CH=CH)Os-3(mu-H)(CO)(10)] (2) in moderate yield, while the Wacker-type reaction of 1 with a trace amount of water in the presence of Wilkinson's catalyst RhCl(PPh(3))(3) in refluxing dichloromethane yields the 4-acetylpyridine derivative of the corresponding alkylidyne cluster [Os-3(mu-H)(2)(CO)(9)(mu(3)-CNC5H4-C(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 mu(3)-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.