The reduction of 2- and 1-disilagermirenes 1 and 2 with (BuLi)-Bu-t proceeded regio- and stereospecifically to produce germyllithium derivative 4-the product of the formal addition of LiH across the M=M' bond (M, M' = Si, Ge) through single electron transfer steps. Reduction of 1,2-disila-3-germacyclopenta-2,4-diene derivative 3 with (BuLi)-Bu-t also proceeded specifically, but with an opposite regioselectivity to form silyllithium derivative 7.