Phosphine (oxide)-(thio) phenolate palladium complexes: Synthesis, characterization and (co)polymerization of norbornene

A series of palladium complexes (2a-2g) (2a: [6-Bu-t-2-PPh2-C6H3O]PdMe(Py); 2b: [6-C6F5-2-PPh2-C6H3O]PdMe(Py); 2c: [6-Bu-t-2-(PPhBu)-Bu-t-C6H3O]PdMe(Py); 2d: [2-(PPhBu)-Bu-t-C6H4O] PdMe(Py); 2e: [6-SiMe3-2-PPh2-C6H3O]PdMe(Py); 2f: [2-Bu-t-6-(Ph2P=O)-C6H3O]PdMe(Py); 2g: [6-SiMe3-2-(Ph2P=O)-C6H3S]PdMe(Py)) bearing phosphine (oxide)-(thio) phenolate ligand have been efficiently synthesized and characterized. The solid-state structures of complexes 2d, 2f and 2g have been further confirmed by single-crystal X-ray diffraction, which revealed a square-planar geometry of palladium center. In the presence of B(C6F5)(3), these complexes can be used as catalysts to polymerize norbornene (NB) with relatively high yields, producing vinyl-addition polymers. Interestingly, 2a/B(C6F5)(3) system catalyzed the polymerization of NB in living polymerization manner at high temperature (polydispersity index 1.07, M-n up to 1.5x10(4)). The co-polymerization of NB and polar monomers was also studied using catalysts 2a and 2f. All the obtained co-polymers could dissolve in common solvent.