Molybdenum(II) Complexes Containing Cyclopentadienyl-Functionalized N-Heterocyclic Carbenes: Synthesis, Structure, and Application in Olefin Epoxidation

A set of four different (Cpx-NHC)Mo(CO)2I (Cpx = Cp, Cp*, and CpBz, NHC = N-heterocyclic carbenes) complexes has been prepared from the one-pot reaction of [MoCl(η3-C3H5)(CO)2(NCMe)2] and the corresponding lithium NHC-cyclopentadienides. The modification of the Cpx-NHC affords a smooth way to tune the stereoelectronic properties of these new molybdenum complexes. These compounds are air stable both in solution and in the solid state. Preliminary studies on the catalytic epoxidation with cis-cyclooctene and TBHP as oxidant show that the activity of the catalysts clearly depends on the nature of the Cpx-NHC ligand. The reaction proceeds smoothly toward epoxide; no diols or any other byproduct was detected along the reaction course.