Isomerization of an N-Heterocyclic Germylene to an Azagermabenzen-1-ylidene and Its Coupling to a Unique Bis(germylene)

N-Heterocyclic germylene LGe [L = CH{(CCH2)(CMe)(N(aryl))2}, aryl = 2,6-iPr2C6H3] 1 reacts with HN(C6F5)2 solely to give the 1,4-addition product L′GeN(C6F5)2 2 (L′ = CH(CMe)2[N(aryl)]2), which contains a Ge(II)-N(C6F5)2 moiety. In contrast, HN(SiMe3)2 does not add to 1 but induces isomerization of 1 to generate the first N(aryl)H-substituted, heteroaromatic azagermabenzen-1-ylidene intermediate. The latter readily undergoes 1,4-addition to a second equivalent of 1 to form the unprecedented bis(germylene) 3, which contains two- and three-coordinate Ge(II) centers. The isomerization process and the nature of the six π-electron aromatic character of the C4NGe heterocycle in 2 are explored and supported by DFT calculations.