Electroreductive synthesis of oligosilanes and polysilanes with ordered sequences

The stepwise elongation of SiSi or SiGe chain was achieved by the electroreductive cross-coupling reaction of chlorohydrosilanes with dichlorooligosilanes using magnesium electrodes. The electroreductive cross-coupling reaction of chlorodimethylsilane (1) with dichlorodiphenylsilane (2) or dichlorodiphenylgermane (4), for instance, gave 1,3-dihydro-1,1,3,3-tetramethyl-2,2-diphenyltrisilane (3) or bis(hydrodimethylsilyl)germane (5) in good yield. Compounds 3 and 5 were readily transformed to the corresponding 1,3-dichlorotrisilane (6) and bis(chlorosilyl)germane (7), respectively. The electroreductive polymerization of the resulting dichlorooligosilanes using magnesium electrodes in tetrahydrofuran was successfully applied to the synthesis of sequence-ordered polysilanes.