Tridentate diarylamido-based pincer complexes of nickel and palladium: sidearm effects in the polymerization of norbornene.

Nickel and palladium complexes bearing new diarylamido-based unsymmetrical [NNNox] and [SNNox] pincer ligands were synthesized and tested for the polymerization of norbornene. Upon the activation of MAO, all the palladium complexes showed high catalytic activities for the vinyl-addition polymerization of norbornene up to 5.32 × 107 g of PNB (mol of Pd)-1 h-1, while the corresponding nickel complexes exhibited unsatisfactory catalytic activities. Besides the usual steric and electronic effects, the sidearm effects of quinolino ([NNNox] ligands) and phenylthio ([SNNox] ligands) moieties have also exhibited obvious influence on the catalytic performance for the polymerization of norbornene and were further studied by density functional theory (DFT) calculations.