Reactions of nido-1,2-(Cp*RuH) 2B 3H 7 with RCCR′ (R, R′=H, Ph; Me, Me) to yield novel metallacarboranes

Abstract

Addition of the internal alkyne, 2-butyne, to nido-1,2-(Cp*RuH) 2B 3H 7 ( 1) at ambient temperature produces nido-1,2-(Cp*Ru) 2(μ-H)(μ-BH 2)-4,5-Me 2-4,5-C 2B 2H 4 ( 2), nido-1,2-(Cp*RuH) 2-4,5-Me 2-4,5-C 2B 2H 4 ( 3), and nido-1,2-(Cp*RuH) 2-4-Et-4,5-C 2B 2H 5 ( 4), in parallel paths. On heating, 2, which contains a novel exo-polyhedral borane ligand, is converted into closo-1,2-(Cp*RuH) 2-4,5-Me 2-4,5-C 2B 3H 3 ( 5) and nido-1,6-(Cp*Ru) 2-4,5-Me 2-4,5-C 2B 2H 6 ( 6) the latter being a framework isomer of 3. Heating 2 with 2-butyne generates nido-1,2-(Cp*RuH) 2-3-{CMeCMeB(CMeCHMe) 2}-4,5-Me 2-4,5-C 2B 2H 3 ( 7) in which the exo-polyhedral borane is triply hydroborated to generate a boron bound CMeCMeB(CMeCHMe) 2 cluster substituent. Along with 3, 4, 5, 6, and 7, the reaction of 1 with 2-butyne at 85 °C gives closo-1,7-(Cp*Ru) 2-2,3,4,5-Me 4-6-(CHMeCH 2Me)-2,3,4,5-C 4B ( 8). Reaction of 1 with the terminal alkyne, phenylacetylene, at ambient temperature permits the isolation of nido-1,2-(Cp*Ru) 2(μ-H)(μ-CHCH 2Ph)B 3H 6 ( 9) and nido-1,2-(Cp*Ru) 2(μ-H)(μ-BH 2)-3-(CH 2) 2Ph-4-Ph-4,5-C 2B 2H 4 ( 11). The former contains a RuB edge-bridging alkylidene fragment generated by hydrometallation on the cluster framework whereas the latter contains an exo-polyhedral borane like that of 2. Thermolysis of 11 results in loss of hydrogen and the formation of closo-1,2-(Cp*RuH) 2-3-(CH 2) 2Ph-4-Ph-4,5-C 2B 3H 3 ( 12).