Preparation of Dinuclear Vinylidene Complexes and Their New Deprotonation Reactions

The dinuclear dicationic vinylidene complex {[Ru]CC(Ph)CH₂C(CH₂CN)C[Ru]}²⁺ (7a, [Ru] = Cp(PEt₃)₂Ru) is prepared from the reaction of ICH₂CN with {[Ru]CC(Ph)CH₂C⋮C[Ru]}⁺ (6a). Deprotonation of 7a by n-Bu₄NOH is followed by a cyclization process yielding the stable complex 9a, containing a five-membered carbocyclic ring ligand, which is fully characterized by 2D-NMR analysis and a single-crystal X-ray diffraction analysis. Similarly deprotonation of {[Ru]CC(Ph)CH₂C(CH₂COOEt)C[Ru]}²⁺ (8a) gave the stable product 11a containing a bridging ligand also with a similar five-membered carbocyclic ring. The cyclization process is affected by an ancillary ligand on the Ru metal center. Thus the analogous dinuclear complex 9b, with a bistriphenylphosphine ligand on one metal, which is prepared in a similar manner from {[Ru]CC(Ph)CH₂C(CH₂CN)C[Ru‘]}²⁺ (7b, [Ru‘] = Cp(PPh₃)₂Ru), is unstable, undergoing isomerization to give the dinuclear complex 10b, containing a cyclopropenyl ligand.