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.