Computational studies of the Brookhartʹs 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 Brookhartʹs 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 to nitrogen atoms could provide a suitable explanation for the large experimental differences found in the ethylene polymerization activity.