Metal-Template-Controlled Stabilization of β‑Functionalized Isocyanides

Reaction of 2-azidoethyl isocyanide 1, 2-azidophenyl isocyanide 2, or 2-nitrophenyl isocyanide 3 with complexes [Mo­(CO)3(dppe)­(py)] [4] or [W­(CO)3(dppe)­(NCCH3)] [5] yields the isocyanide complexes [Mo­(CO)3(dppe)­(CNR)] ([6]: CNR = 1; [12]: CNR = 2; [13]: CNR = 3) and [W­(CO)3(dppe)­(CNR)] ([7]: CNR = 1; [14]: CNR = 2; [15]: CNR = 3). Reduction of the nitro or azido groups attached to the isocyanide ligands by Zn/NH4Cl (azidoethyl or azidophenyl isocyanides) or Raney-nickel/hydrazine hydrate (nitrophenyl isocyanide) yields exclusively the complexes bearing the 2-amino-functionalized isocyanides. The normally unstable 2-amino-functionalized isocyanides are stabilized by M→CNR back-bonding, which deactivates the isocyanide carbon atom for an intramolecular nucleophilic attack by the primary amine.