Multiple ethylene activation by heteroleptic L(Cl)Ga-substituted germylenes

Ethylene insertion into the Ga-Ge bond of the L(Cl)Ga-substituted germylene LGa(mu-Cl)GeDMP 1 (L = HC(C(Me)NAr)2, Ar = 2,6-iPr2C6H3; DMP = 2,6-Mes2C6H3, Mes = 2,4,6-Me3C6H2) at ambient temperature is followed by dimerization of the as-formed germylene to give the digermene 3, which further reacted with ethylene in a [2 + 2] cycloaddition to give the 1,2-digermacyclobutane 4. In marked contrast, the amino-substituted germylene L(Cl)GaGeN(SiMe3)Ar 2 reacted directly to the 1,2-digermacyclobutane 5. Quantum chemical calculations confirmed the assumed reaction mechanism, hence demonstrating the crucial role of the substituent on the reaction mechanism. L(Cl)Ga-substituted germylenes react with ethylene with insertion into the Ga-Ge bonds to digermenes, which undergo [2 + 2] cycloaddition with ethylene to give 1,2-digermacyclobutanes.