Computational studies of the Brookhart's type catalysts for ethylene polymerization. 1. Effect of the active site conformations on the catalyst activities

DFT calculations have been carried out on the cationic species for the two different Brookhart's catalyst systems: [{ArN=CH-HC=NAr}NiR "](+) (3a) and [{ArN=CMe-MeC=NAr}NiR "] + (3b) (where Ar = {2,6-C6H3(Me)(2)} and R " = Me) . These calculations reveal that the conformation of aryl groups attached t o nitrogen atoms could provide a suitable explanation for the large experim ental differences found in the ethylene polymerization activity. (C) 2001 E lsevier Science Ltd. All rights reserved.