Cp[TmMe]ZrCl2, a Tris(2-mercapto-1-methylimidazolyl)hydroborato Complex of Zirconium and a New Type of Precatalyst for Olefin Polymerization

Abstract

Cp[TmMe]ZrCl2, the first tris(2-mercapto-1-methylimidazolyl)hydroborato complex of zirconium, is obtained by reaction of CpZrCl3 with [TmMe]K. The molecular structure of Cp[TmMe]ZrCl2 has been determined by X-ray diffraction, and the geometry closely resembles the bent-metallocene motif of Cp2ZrCl2. An important distinction, however, is that Cp[TmMe]ZrCl2 is chiral, with C1 symmetry. The chirality of Cp[TmMe]ZrCl2 is a consequence of the fact that the [TmMe] ligand exhibits a propeller-like twist such that it has local C3 symmetry and is therefore devoid of a mirror plane. Variable-temperature 1H NMR studies demonstrate that enantiomer interconversion does not occur on the NMR time scale. In combination with methylalumoxane, Cp[TmMe]ZrCl2 produces an active catalyst for ethylene polymerization.