SILICON-CARBON UNSATURATED-COMPOUNDS .51. NICKEL-CATALYZED REACTIONS OF 3,4-BENZO-1,1,2,2-TETRAETHYL-1,2-DISILACYCLOBUT-3-ENE WITH ALKENES AND DIENES

The reactions of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene (1) with alkenes in the presence of a catalytic amount of tetrakis(triethylphosphine)nickel(0) at 150 degrees C have been investigated. With 1,1-diphenylethylene, 1 afforded 1,2-bis(diethylsilyl)benzene (2), 4,5-benzo-1,1,3,3-tetraethyl-2-diphenylmethylene-1,3-disilacyclopent-4-ene, and 1-[diethyl(2, 2-diphenylethenyl)silyl]-2-diethylsilylbenzene in 4%, 55%, and 7% yields. The reaction of 1 with styrene gave 4,5-benzo-1,1,3,3-tetraethyl-2-phenylmethylene-1,3-disilacyclopent-4-ene and (E)-1-tetraethyl(2-phenyl)disilanyl-2-phenylethene in 12% and 47% yields, while with 1- and 2-hexene, 1 produced 4,5-benzo-1,1,3,3-tetraethyl-2-(n-pentylidene)-1,3-disilacyclopent-4-ene, together with a product arising from hydrosilation of 2 and 1-hexene. Similar treatment of 1 with ethylene in an autoclave afforded 4,5-benzo-1,1,3,3-tetraethyl-2-methylene-1 ,3-disilacyclopent-4-ene, tetraethyl-1-phenyl-2-vinyldisilane, and 2,3-benzo-1,1,4,4-tetraethyl-1,4-disilacyclohex-2-ene in 7%, 34%, and 10% yields. Similarly, the nickel-catalyzed reaction of 1 with 2,3-dimethylbutadiene yielded 4,5-benzo-1,1,3,3-tetraethyl-2-(1,2,2-trimethylethenyl)-1,3-disilacyclopent-4-ene and 2,3-benzo-1,1,4,4-tetraethyl-6,7-dimethyl-1 ,4-disilacycloocta-2,6-diene in 33% and 30% yields, while with 1,3- and 1,4-cyclohexadiene, 1 afforded 5,5,10,10-tetraethyl-8,9,13,14-tetrahydrosilanthrene, as the sole product. The results of MO calculations for 1-nickela-2,5-disilacydopent-3-ene are also reported.