Synthesis and Reactions of Silicon Unsaturated Compounds

We have demonstrated that the reaction of l-mesityl-3-phenyl-1，2-bis(tri-methylsilyl)-1-silacyclopropene with1equiv of tetrakis(Triethylphosphine)-nickel(0)affords nickelasilacyclobutene(1)in almost quantitative yield。Compound1 involves a nickel atom and a silicon atom in the four-membered cyclic system and seems to be useful for synthetic chemistry，as well as structural chemistry.Thermolysis of 1led to the formation of a silapropadiene-nickel complex which underwent further isomerization to give two isomers of a benzodisilacyclo-hexene，3and4，via intramolecular C-H bond activation of a mesityl group.The photolysis of 1 also gave3 and 4.We have investigated the reaction of2-phenylethynyl-2-(o-tolyl)hexamethyl-trisilane(2)with a nickel catalyst.Heating2 with a catalytic amount of tetrakis(Triethylphosphine)nickel(0)at 220°C gave benzodisilacyclohexenes analogous to3and4.Whereas at 260°C，2 produced a silylene-nickel complex which could be trapped by methyldiphenylsilane.Similar treatment of 2 with a catalytic amount of an iron-complex in the presence of methyldiphenylsilane as a trapping agent afforded a product arising from insertion of the silylene-iron complex into an Si-H bond of the hydrosilane.

We have demonstrated that the reaction of l-mesityl-3-phenyl-1,2-bis(tri-methylsilyl)-1-silacyclopropene with 1 equiv of tetrakis(triethylphosphine)-nickel(0) affords nickelasilacyclobutene (1) in almost quantitative yield. Compound 1 involves a nickel atom and a silicon atom in the four-membered cyclic system and seems to be useful for synthetic chemistry, as well as structural chemistry.Thermolysis of 1 led to the formation of a silapropadiene-nickel complex which underwent further isomerization to give two isomers of a benzodisilacyclo-hexene, 3 and 4, via intramolecular C-H bond activation of a mesityl group. The photolysis of 1 also gave 3 and 4.We have investigated the reaction of 2-phenylethynyl-2-(o-tolyl)hexamethyl-trisilane (2) with a nickel catalyst. Heating 2 with a catalytic amount of tetrakis(triethylphosphine)nickel(0) at 220゜C gave benzodisilacyclohexenes analogous to 3 and 4. Whereas at 260゜C, 2 produced a silylene-nickel complex which could be trapped by methyldiphenylsilane. Similar treatment of 2 with a catalytic amount of an iron-complex in the presence of methyldiphenylsilane as a trapping agent afforded a product arising from insertion of the silylene-iron complex into an Si-H bond of the hydrosilane.