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 degrees 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.