Template Synthesis of Ruthenium Complexes with Saturated and Benzannulated NH,NH-Stabilized N-Heterocyclic Carbene Ligands

Reaction of [RuCl2(p-cymene)]2 with 2-azidoethyl isocyanide (1a) or 2-azidophenyl isocyanide (1b) leads to the isocyanide complexes [RuCl2(p-cymene)(1a)] [2a] and [RuCl2(p-cymene)(1b)] [2b], respectively. Complex [2a] reacts with triphenylphosphine to yield the complex with a phosphinimine-substituted isocyanide ligand [3]. The attempted hydrolysis of the phosphinimine group in [3] with HCl·Et2O produced the complex with a protonated phosphinimine ligand [4]Cl instead of the expected complex with a 2-aminoethyl isocyanide ligand. An alternative method for the reduction of the azido group in [2a] and [2b] using FeCl3/NaI has been applied leading to complexes with the 2-amino-substituted isocyanide ligands, which undergo intramolecular ring closure to yield the complexes of type [RuI2(p-cymene)(NHC)], [5a] and [5b].