Theoretical Investigations of Heterogeneous Olefin Metathesis Catalysts

Abstract

Olefin metathesis catalysed by solid systems has found a number of industrial applications. During the last decade, heterogeneous catalysts for olefin metathesis were comprehensively studied by experimental and theoretical methods. A great progress has been achieved in the field of both conventional and well-defined catalytic systems. The computational approach, taking advantage of growing computer power, enabled for the development of advanced models representing surface species relevant to olefin metathesis. In the case of the conventional ill-defined heterogeneous catalysts, the main achievements concern detailed description of the mechanism of the propagation steps and understanding the role of the support. The initiation stage of the olefin metathesis process was also explored, however, further investigations of the active sites generation, and, especially, catalyst deactivation are still required. Quantum chemistry methods, being complementary to experimental techniques, have become a standard tool for the characterization of the well-defined heterogeneous systems. The propagation and deactivation routes for olefin metathesis catalysed by various silicasupported Re, Mo and W alkylidene complexes were recognized in detail and the structure-activity relationships are now well established. Computational studies of alkane metathesis confirmed that olefin metathesis steps play a key role in the mechanism of this process. Keywords: Alkylidene complexes, Cluster model, DFT, Heterogeneous catalyst, Mechanism, Olefin metathesis, Periodic model.