Brian C. Peoples

Development of Imine Derivative Ligands for the Exocyclic Activation of Late Transition Metal Polymerization Catalysts

Transition metal complexes bearing imine and imine derivative ligands represent a growing number of polymerization catalysts in development. The ease of synthesis and large number of structural variations which are readily accessible make these systems of great interest both academically and industrially. One subset of imine-based complexes are those which bear exocyclic functionality which can interact with Lewis acids. These systems are particularly interesting as the activation of the complex occurs remotely, away from the active center, and that the activation can proceed using stoichiometric concentrations of activators. In addition, the presence of the exocyclic functionality may present an effective method to heterogenize polymerization catalysts. In this chapter, the development of such systems and in particular ?-iminocarboxamide nickel catalysts and derivative species are discussed.

Chromium(III) complexes bearing bis(benzotriazolyl)pyridine ligands: synthesis, characterization and ethylene polymerization behavior

Abstract Reaction of benzotriazole with 2,6-bis(bromomethyl)pyridine and 2,6-pyridinedicarbonyl dichloride yields the tridentate ligands 2,6-bis(benzotriazol-1-ylmethyl)pyridine (1) and 2,6-bis(benzotriazol-1-ylcarbonyl) pyridine (2). The molecular structures of the ligands were determined by single-crystal X-ray diffraction. These ligands react with CrCl3(THF)3 in THF to form neutral complexes, [CrCl3{2,6-bis(benzotriazolyl)pyridine-N,N,N}] (3, 4), which are isolated in high yields as air stable green solids and characterized by mass spectra (ESI), FTIR spectroscopy, UV–Visible, thermogravimetric analysis (TGA), and magnetic measurements. After reaction with methylaluminoxane (MAO), the chromium(III) complexes are active in the polymerization of ethylene showing a bimodal molecular weight distribution. A DFT computational investigation of the polymerization reaction mechanism shows that the most likely reaction pathway originates from the mer configuration when the spacer is CH2 (complex 3) and from the fac configuration when the spacer is CO (complex 4).