Computational Experiments Probing the Adaptability of the [NCCH(2)](-) Electronic Structure to Various Bonding Environments

Using combined geometry optimization and electronic analyses, it is examined how metal nature (alkali and Cu(I)), solvation (THF), ligands, and aggregation modulate the N- versus C-bonding balance in metalated acetonitrile. C-binding is energetically favored in covalent Cu(I) complexes, while lithiated species prefer N-binding. Surprisingly, N-metalated species do not all exhibit the expected ketenimine-like character (CCN, lone pair on N), but a nitrile-like one (C(b)C≡N, lone pair on C(b)) also emerges from the natural bond orbital analyses. Ketenimines are stabilized by polarizing or covalent MN bonds, while nitriles are obtained with weakly coordinating cations or in anionic species. Notably, an external electric field can induce a similar electronic reorganization, thus revealing the electronic flexibility of metalated nitriles.