Co-Complexes Derived from Alkene Insertion to Alkyne-Dicobaltpentacarbonyl Complexes: Insight into the Regioselectivity of Pauson−Khand Reactions of Cyclopropenes

Described are the X-ray crystallographic and spectral properties of Co-complexes that were isolated from two Pauson−Khand reactions of chiral cyclopropenes. These are the first examples of isolated Co-complexes derived from the putative alkene-insertion intermediates of Pauson−Khand reactions. The binuclear Co-complexes are coordinated to μ-bonded, five-carbon “flyover” carbene ligands. It is proposed that the complexes result from cyclopropane fragmentation subsequent to alkene insertion. The observation of these metal complexes provides a rationale for the origin of regioselectivity in Pauson−Khand reactions of cyclopropenes.