Cooperative Ge–N Bond Activation in Hydrogallation Products of Alkynyl(diethylamino)germanes (Et2N)nGe(CCtBu)4–n

Treatment of the alkynyl­(diethylamino)­germanes Et2NGe­(CCtBu)3 (1) and (Et2N)2Ge­(CCtBu)2 (2) with dialkylelement hydrides tBu2MH (M = Al, Ga) afforded in high yields the hydrometalation products (tBuCC)2(Et2N)­Ge­[C­(MtBu2)C­(H)tBu] (3), (tBuCC)­(Et2N)­Ge­[C­(MtBu2)C­(H)tBu]2 (4) and (tBuCC)­(Et2N)2Ge­[C­(GatBu2)C­(H)tBu] (6). The Lewis acidic aluminum and gallium atoms showed a close contact to the nitrogen atoms of the amino groups attached to germanium, which resulted in relatively long Ge–N bonds and short Al–N or Ga–N distances. The structures of these molecules and the strengths of the interactions were investigated by dispersion-corrected density functional theory. This activation of the Ge–N bonds caused an unprecedented reactivity of compounds 4b and 6. 4b reacted with PhCCH under mild conditions and elimination of HNEt2 to give the mixed dialkynyl compound (tBuCC)­(PhCC)­Ge­[C­(GatBu2)C­(H)tBu]2 (5), while facile insertion of RNCX into a Ge–N bond of 6 led to the formation of the six-membered Ge–C–Ga–X–C–N heterocycles 7 (R = Ph, Et; X = O, S).