Linking and fragmentation of alkynes at a triruthenium centre

The triruthenium mu(3)-alkyne complex [Ru-3(CO)(3)(mu-CO)(mu(3)-CO){mu(3)-C-2(CF3)(2)}(eta-C5H5)(2)] 1 reacted with Me(3)NO in MeCN to give [Ru-3(MeCN)(CO)(2)(mu-CO)(mu(3)-CO){mu(3)-C-2(CF3)(2)}(eta-C5H5)(2)] 2. This with hexafluorobut-2-yne at or below room temperature gave [Ru-3(CO)(2)(mu-CO){mu(3)-eta(3)-C-3(CF3)(3)}(mu(3)-CCF3)(eta-C5H5)(2)] 3, shown by X-ray diffraction to contain a ruthenium triangle with mu(3)-perfluoroethylidyne and mu(3)-eta(3)-C-3(CF3)(3) ligands arising from cleavage of one of the hexafluorobut-2-yne molecules. In contrast, 2 reacted at room temperature with alkynes diphenylethyne, methyl but-2-ynoate and but-2-yne to yield the species [Ru-3(CO)(2)(mu-CO)(2){mu(3)-C-4(CF3)(2)R(R')}(eta-C5H5)(2)] (R = R' = Ph; R = Me, R' = CO(2)Me; or R = R' = Me) respectively. X-ray diffraction studies on the first two of these showed that the alkynes have linked to form a mu(3)-C-4(CF3)(2)R(R') ligand bound to a closed Ru-3 triangle via a doubly bridging interaction with one pair of metal atoms and an eta(3)-allyl mode with the other. Dimethyl acetylenedicarboxylate (dmad) reacted with 2 at room temperature differently again to give a structurally unidentified species [Ru-3(CO)(5){C-2(CF3)(2)}{C-2(CO(2)Me)(2)}(eta-C5H5)(2)], which on heating afforded [Ru-3(CO)(3){mu(3)-C-4(CF3)2(CO(2)Me)(2)}(eta-C5H5)(2)] 12, revealed by X-ray diffraction to contain a closo-pentagonal-bipyramidal Ru3C4 cluster in which a mu(3)-C-4(CF3)(2)(CO(2)Me)(2) ligand bridges an open ruthenium triangle. This complex was formed directly when 1 was heated with dmad in refluxing toluene. Analogous complexes [Ru-3(CO)(3){mu(3)-C-4(CF3)(2)R(R')}(eta-C5H5)(2)] (R = Me, R' = CO(2)Me; R = R' = Ph; or R = R' = Me) were produced on heating 1 with methyl but-2-ynoate, diphenylethyne and but-2-yne respectively. The last two reactions also gave isomers [Ru-3(CO)(3){mu(3)-C-4(CF3)R(2)(CF3)}(eta-C5H5)(2)] (R = Ph or Me) in which formal insertion of the incoming alkyne into the co-ordinated CF3C=CCF3 bond has occurred. In addition, the reaction of 1 with but-2-yne produced [Ru-3(CO)(2)(mu-CO){mu(3)-eta(3)-C-3(CF3)Me(2)}(mu(3)-CCF3)(eta-C5H5)(2)] analogous to 3. Diruthenium species [Ru-2(CO){mu-C-4(CF3)(2)R(R')}(eta-C5H5)(2)] are formed in both toluene reflux reactions of 1 and room-temperature reactions of 2 as a result of triruthenium cluster degradation. Heating the room-temperature products [Ru-3(CO)(2)(mu-CO)(2){mu(3)-C-4(CF3)(2)R(2)}(eta-C5H5)(2)] confirms that these are intermediates in the formation of the complexes [Ru-3(CO)(2)(mu-CO){mu(3)-eta(3)-C-3(CF3)R(2)}(mu(3)-CCF3)(eta-C5H5)(2)] and the isomeric closo clusters [Ru-3(CO)(3){mu(3)-C-4(CF3)(2)R(2)}(eta-C5H5)(2)] and [Ru-3(CO)(3){mu(3)-C-4(CF3)R(2)(CF3)}(eta-C5H5)(2)]. Pathways for the processes leading to the various products are discussed.