Varied Reactivity of the Germene Mes<sub>2</sub>GeCR<sub>2</sub> toward Nitriles

The germene Mes<sub>2</sub>GeCR<sub>2</sub> (<b>1</b>, CR<sub>2</sub> = fluorenylidene) shows varied behavior toward nitriles. It reacts as a 1,2-dipole with <i>t</i>-BuCN giving a four-membered ring heterocycle, 2-aza-3-germacyclobut-1-ene, as a 1,4-dipole with PhCN, leading to a six-membered ring heterocycle, 3,4-dihydro-3-germaisoquinoline, and as a base, abstracting the α-H of R‘CH<sub>2</sub>CN to give α-cyanogermanes (R‘ = H, 2-thienyl, 2-FC<sub>6</sub>H<sub>4</sub>, 4-FC<sub>6</sub>H<sub>4</sub>).