THE UNION-CARBIDE CATALYST (CP(2)CR-STATE NMR(SIO2) STUDIED BY SOLID)

The Union Carbide catalyst, that can be synthesized by reaction of chr omocene (Cp(2)Cr) with silica (SiO2), allows the polymerization of ole fins at low pressure and low temperature without any cocatalyst. Despi te the interest in this heterogeneous catalyst, the nature of the acti ve species is still unknown. In this contribution it is demonstrated t hat H-1 solid-state NMR serves as a powerful method for the investigat ion of the surface species. The spectra are evidence for the presence of one mononuclear and two dinuclear surface-attached complexes. The n ature of these species is discussed on the basis of molecular model co mpounds and their NMR characteristics.