Reaction of the diarylgermylene Ge(Ar-Me6)(2) [Ar-Me6 = C6H3-2,6-(C6H2-2,4,6-(CH3)(3))(2)] with tert-butyl isocyanide gave the Lewis adduct species (Ar-Me6)(2)GeCNBut, in which the isocyanide ligand displays a decreased C-N stretching frequency consistent with an n --> pi* back-bonding interaction. Density functional theory confirmed that the HOMO is a Ge-C bonding combination between the lone pair of electrons on the germanium atom and the C-N pi* orbital of the isocyanide ligand. The complex undergoes facile C-H bond activation to produce a new diarylgermanium hydride/cyanide species and isobutene via heterolytic cleavage of the N-Bu-t bond.