A novel zerovalent ruthenium complex with a π-acidic ligand, Ru(η (6)-cyclooctatriene)(η (2)-dimethyl fumarate)2 (1), was prepared from Ru(η (4)-cyclooctadiene)(η (6)-cyclooctatriene) [Ru(cod)(cot)]. Complex 1 or Ru(cod)(cot) catalyzes various new carbon-carbon bond-forming reactions that include the [2 + 2] cycloaddition of alkenes and alkynes via ruthenacycles, the creation of a new hydrocarbon, pentacyclo[6.6.0.0(2,6).0(3,13).0(10,14)]tetradeca-4,11-diene [PCTD], by dimerization of 2,5-norbornadiene via C-C bond cleavage, and the codimerization of alkynes and/or alkenes. Complex 1 was shown to be an excellent mother complex for various zerovalent ruthenium complexes. Complex 1 reacts with amines, phosphines or water to give new zerovalent ruthenium complexes with the ligands. The resulting aqua complexes have a water ligand with an oxygen atom that is a chiral center, i.e., ruthenium complexes with a 'chiral water' ligand were prepared and fully characterized.
Keywords: [2 + 2] cycloaddition; aqua complex; chiral water; codimerization; ruthenacycle; zerovalent ruthenium complex.