Issue 37, 2014

Highly active half-sandwich chromium(iii) catalysts bearing bis(imino)pyrrole ligands for ethylene (co)polymerization

Abstract

A series of half-sandwich Cr(III) complexes bearing bis(imino)pyrrole ligands, Cp′[2,5-C4H2N(CH[double bond, length as m-dash]NAr)2]CrCl [Cp′ = C5H5, Ar = C6H5 (2a), 2,6-Me2C6H3 (2b), 2,6-iPr2C6H3 (2c), C6F5 (2d); Cp′ = C5Me5, Ar = C6H5 (3a), 2,6-iPr2C6H3 (3c)] were synthesized with good yields. The complexes were characterized by FTIR and mass spectrometry in addition to elemental analyses. X-ray structural analyses for 2a–c showed that the Cr complexes have a pseudo-octahedral coordination environment with a three-legged “piano stool” geometry. One of the imino nitrogen atoms is coordinated with the Cr metal. On activation with methylaluminoxane, the Cp-based complexes showed high catalytic activities for ethylene polymerization. High molecular weight polymers with unimodal molecular weight distributions were obtained, indicating that the nature of the polymerization was single site. The copolymerization of ethylene with norbornene by the pre-catalysts 2a–d was also explored in the presence of methylaluminoxane. The catalytic activity, co-monomer incorporation and the properties of the resultant polymers can be controlled over a wide range by tuning the catalyst structures and reaction parameters.

Graphical abstract: Highly active half-sandwich chromium(iii) catalysts bearing bis(imino)pyrrole ligands for ethylene (co)polymerization

Supplementary files

Article information

Article type
Paper
Submitted
09 Mar 2014
Accepted
02 Apr 2014
First published
09 Apr 2014

RSC Adv., 2014,4, 19433-19439

Author version available

Highly active half-sandwich chromium(III) catalysts bearing bis(imino)pyrrole ligands for ethylene (co)polymerization

J. Liu, P. Tao, Y. Wang and Y. Li, RSC Adv., 2014, 4, 19433 DOI: 10.1039/C4RA02039A

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