Ni-Catalyzed Double Gemylation of Alkynes and Alkenes

The reaction of 1,2-bis(dimethylgermyl)carborane with Ni(PEt3)4 yielded the cyclic bis(germyl)nickel complex 2. 2 was found to be a good catalyst for the double germylation reaction. Thus, the reaction of 1 with RC⋮CR‘ in the presence of a catalytic amount of 2 yielded the six-membered digermyl ring compounds B10H10C2(GeMe2)2(RCCR‘) (R = R‘= Ph (3); R = Ph, R‘ = H (4); R = R‘ = Et (5); R = Ph, R‘ = Me (6); R = R‘ = Me (7); R = Ph, R‘ = SiMe3 (8); R = R‘ = SiMe3 (9); R = R‘ = CO2Me (10)). In contrast, the reaction of 1 with 1-hexyne under the same reaction conditions yielded the five-membered digermyl ring compound B10H10C2(GeMe2)2(CC(C4H9)H) (11). The intermediate was also found to be a good reactant for the double germylation of some alkenes. Thus, the stoichiometric reaction of 2 with 4-vinylanisole and 1,1-diphenylethylene gave the five-membered digermylene compounds (14 and 15). However, the stoichiometric reaction of 2 with 2,3-dimethylbutadiene afforded a different type of five-membered digerma compound 17 via the 1,4-migration of the hydride. The crystal structures of 2, 6, 12, 14, and 17 are described.