Bis(allyl)zinc Revisited: Sigma versus Pi Bonding of Allyl Coordination

The reinvestigation of two allyl zinc compounds, parent bis­(allyl)­zinc [Zn­(C3H5)2] (1) and 2-methallyl chloro zinc [Zn­(C4H7)­Cl] (2), revealed two new coordination modes in the solid state for the allyl ligand, viz cis- and trans-μ2-η1:η1. These results call for modification of the conventional interpretation of zinc–allyl interactions. Computational results indicate that the classical η3-bonding mode of the allyl ligand is not favored in zinc compounds. A rare case of a zinc–olefin interaction in the dimer of [Zn­(η1-C3H5)­(OC­(C3H5)­Ph2)] was found in the monoinsertion product of 1 with benzophenone.