Mechanistic study of half-titanocene-based reductive pinacol coupling reaction

The reductive pinacol coupling reaction of aldehydes or ketones creating a new C-C bond has been a major tool to produce 1,2-diol compounds. The reaction mechanism is known to be composed of sequential three steps (activation, coupling, and dissociation). In this work, we studied the dissociation step of half-titanocene-based catalytic systems. Cp and Cp* derivatives of the pinacolato-bridged dinuclear complex were synthesized and evaluated as possible models for intermediates from the coupling step. We monitored 1H-NMR spectra of the reaction between the metalla-pinacol intermediates and D2O. New reaction routes of the dissociation step including oxo- and pinacolato-dibridged dinuclear complexes and oxo-bridged multinuclear complexes have been suggested.