Reductive Coupling of 2,2-Dibromo-1,1,1,3,3,3-hexaalkyltrisilanes. A Novel Route to Persilylcyclotetrasilanes of the Type [(R1R2R3Si)2Si]4

Persilylcyclotetrasilanes of the type [(R1R2R3Si)2Si]4 (R1 = R2 = R3 = Me; R1 = Et, R2 = R3 = Me) were readily obtained by the reductive coupling of the corresponding 2,2-dibromo-1,1,1,3,3,3-hexaalkyltrisilanes using sodium; the Si4 frameworks of these persilyl compounds act as much more intense chromophore than those of peralkyl analogues.