Long-Lived Palladium Catalysts for CO/Vinyl Arene Polyketones Synthesis: A Solution to Deactivation Problems

A series of cationic palladium complexes of general formula [Pd(Me)(MeCN)(N-N)][PF(6)] (N-N = (phen) la, 4,7-dichloro-1,10-phenanthroline (4,7-Cl(2)-phen) 2a, 4,7-diphenyl-1,10-phenanthroline (4,7-Ph(2)-phen) 3a, 4-methyl-1,10-phenanthroline (4-Me-phen) 4a, 4,7-dimethyl-1,10-phenanthroline (4,7-Me(2)-phen) 5a, 5,5,6,6tetrafluoro-5,6-dihydro-1,10-phenan- throline (F(4)-phen) 6a, containing different substituted phenanthroline ligands.. have been prepared from the corresponding neutral chloro derivatives [Pd(Me)(Cl)(N-N)], (1b-6b). The X-ray crystal structure of [Pd(Cl)(2)(4,7-Cl(2)-phen)] (2b) was determined. DFT calculations show that the electron density on the metal is tuned by the substituents on the ligands. The catalytic behavior of complexes 1a-6a in the CO/styrene and CO/p-Me-styrene copolymerizations was studied in detail, showing that the generated catalysts are active for at least 90 h, yielding copolymers of high molecular weight.