Vinylmetalloids : I. Coupling reactions of group IV metalloidal halides with magnesium in tetrahydrofuran

Abstract

The reaction of vinyl bromide with a mixture of magnesium and either dichlorodimethylsilane or dichlorodiethylgermane in tetrahydrofuran was found to give the corresponding coupled products: 1,1,2,2-tetramethyl-1,2-divinyldisilane (II) and 1,1,2,2-tetraethyl-l,2-divinyldigermane (XI), respectively, in ca. 30% yield. Other vinyl bromides also were investigated. The reaction of dichlorodimethylsilane with vinyl bromide/magnesium appears to proceed via chloro(dimethyl)vinylsilane (III) which was found to react directly with magnesium in THF to give II in 53% yield. It is shown that the reaction of a vinylsilyl halide with magnesium, if carried out in the presence of chlorotrimethylsilane or chlorotriethylgermane, leads to pentamethylvinyldisilane (VI) or triethyl(vinyldimethylsilyl)germane (V) in yields of 67 and 43%, respectively. However, the reaction of III and chlorotrimethylgermane with magnesium in THF gives a 40/60 mixture of trimethyl(vinyldimethylsilyl)germane (VII) and hexamethyldigermane (VIII). Under similar conditions, chlorotrimethylgermane was found to give VIII directly with magnesium in THF in 48% yield while chlorotriethylgermane is inert to Mg. These results are discussed in terms of the formation of metalloidalmagnesium bonds.