Faster initiating olefin metathesis catalysts from introducing double bonds into cyclopropyl, cyclobutyl and cyclopentyl derivatives of Hoveyda-Grubbs precatalysts

We have used the M06-D3 flavor of density functional theory (DFT) to investigate the structures and free energies of initiation for a series of Hoveyda-Grubbs-like complexes in which the isopropoxy part replaced by selected saturated or unsaturated derivatives of cyclopropane, cyclobutane and cyclopentane. We show that the introduction of the double bond into this part of the complex weakens the ruthenium-oxygen bond, creating a series of potential catalysts capable of fast initiation metathesis. The addition to the nitro group in the para position of the benzylidene part of the complex also creates a potentially highly efficient ruthenium catalyst. We demonstrate that the Gibbs free energy of activation correlates with various structural and computational parameters of the precatalyst, including the Ru-O bond strength and partial charges on selected atoms.