Formation of Cyclodimeric (sp2-C1)-Bridged Cp/-Oxido (“CpC1O”MIVX2) Group 4 Metal Ziegler−Natta Catalyst SystemsHow Important Is the “Constrained Geometry” Effect?

Publisher Website
Google Scholar
Abstract
Deprotonation of sodium acetylcyclopentadienide (11) was achieved by treatment with LDA in THF to generate the dianion equivalent [Cp−C(CH2)−O]2- (12). Transmetalation with Cl2Ti(NMe2)2 gave {[Cp−C(CH2)−O]Ti(NMe2)2}2 (17); treatment of 12 with Cl2Zr(NEt2)2(THF)2 furnished {[Cp−C(CH2)−O]Zr(NEt2)2}2 (18). Cryoscopy in benzene revealed a dimeric structure of 18 in solution. Complex 18 was characterized further by an X-ray crystal structure analysis and by DFT calculations. The two zirconium centers of 18 are connected by means of two symmetry-equivalent η5:κO[Cp−C(CH2)−O] ligands. The ligand backbone shows no specific steric constraints, different from the formally related “constrained geometry” systems such as [Cp*−SiMe2−NCMe3]Zr(NMe2)2 (1b). Nevertheless, upon treatment with MAO the CpCO group 4 metal complex system (18) generates an active homogeneous Ziegler−Natta catalyst for effective ethene/1-octene copolymerization, with up to 20% 1-octene having become incorporated in the resulting copolymer at 90 °C.

This publication has 21 references indexed in Scilit: