Novel Decomposition Modes of Transition Metal Metallocycles Containing the Silicon–Silicon Bond: 1‐Nickela‐ and 1‐Platina‐3,4‐Disilacyclopentane Ring Systems

Reaction of 1,2‐bis(bromomethyl)tetramethyldisilane with magnesium in ether gave 1,1,3,3‐tetramethyl‐1,3‐disilacyclobutane ( 3 ) (∼ 20%) together with ca. 60% yield of the di‐Grignard reagent ( 5 ). Treatment of 5 with [Ni(PPh 3 ) 2 Cl 2 ] ( 7 ) in refluxing ether formed 3 in ca. 20% yield. Decomposition of 1‐nickela‐3,4‐disilacyclopentane intermediate, prepared from 7 with 5 at low temperatures, in the presence of 1‐naphthyl bromide, triphenylphosphine or 2,3‐dimethyl‐1,3‐butadiene also formed 3 in 12–20% yields. Reaction of 5 with Pt(COD)Cl 2 (COD = 1,5‐cyclooctadiene) gave a 1‐platina‐3,4‐disilacyclopentane derivative as stable crystals, which gave 3 in quantitative yield when heated with PPh 3 in benzene. Mechanisms for the formation of 3 have been discussed.