Silicon−Carbon Unsaturated Compounds. 56. Nickel-Catalyzed Reaction of 3,4-Benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene with Bis(trimethylsilyl)acetylene

The reaction of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene ( 1 ) with bis(trimethylsilyl)acetylene in the presence of a catalytic amount of tetrakis(triethylphosphine)nickel(0) in a sealed glass tube at 150 °C for 24 h gave 5,6-benzo-1,1,4,4-tetraethyl-2,3-bis(trimethylsilyl)-1,4-disilacyclohexa-2,5-diene ( 2 ), 4,5-benzo-1,1,3,3-tetraethyl-2-[bis(trimethylsilyl)methylene]-1,3-disilacyclopent-4-ene ( 3 ), 5,5,6,6,11,11,12,12-octaethyl-5,6,11,12-tetrasilanaphthacene ( 4 ), and 1,1‘-bis(3,4-benzo-2,2,5,5-tetraethyl-2,5-disilacyclopent-3-enylidene) ( 5 ), in 10%, 21%, 41%, and 9% yields, in addition to a 34% yield of hexamethyldisilane. Similar reaction of 1 with bis(trimethylsilyl)acetylene in the presence of dimethylphenylsilane produced 5,6-benzo-1,1,4,4-tetraethyl-2-(dimethylphenylsilyl)-1,4-disilacyclohexa-2,5-diene ( 12 ) in 7% yield, along with 2 and 3 . Treatment of 2 with dimethylphenylsilane in the presence of the nickel catalyst afforded 12 in 29% yield, together with a 28% yield of hexamethyldisilane and a trace amount of 4,5-benzo-1,1,3,3-tetraethyl-2-[(dimethylphenylsilyl)methylene]-1,3-disilacyclopent-4-ene ( 13 ). Similar treatment of 3 with dimethylphenylsilane again gave 12 and 13 in 30% and 1% yields, respectively, in addition to a 32% yield of hexamethyldisilane.