New stable germenes

Abstract Two new stable fluorenylidene germenes 5 and 6 substituted on germanium with two bulky bisyls [(Me 3 Si) 2 CH] or with a bisyl and a mesityl group have been synthesized by dehydrofluorination of the corresponding fluorogermanes by tert-butyllithium. The ditert-butylfluorenylidene germene 7 could not be obtained by this route, but its lithio precursor 8 can be used as its synthetic equivalent.