Cationic methyl-palladium(II) complexes containing bidentate N-O and P-O ligands and a tridentate P-O-N ligand: Synthesis, carbonylation and catalytic applications in the copolymerisation of carbon monoxide and ethene

Cationic methyl-palladium complexes, containing chelating N-O, P-O and P-O-N ligands, of the type {[PdMe(Y-O)L]BF4} and {[PdMe(P-O-N)]BF4} [Y-O = methylpicolinate, L = PPh3, Ph2PCH2COOEt; Y-O = Ph2PCH2COOEt, L = PPh3, 2,6-lutidine; P-O-N = diphenylphosphine-acetic acid-methyl-2-pyridylester (Ph2PCH2CO2CH2(NC5H4-2))] have been synthesized. The crystal structure of the complex {[PdMe(N-O)PPh3]BF4} indicates distorted square-planar coordination around the palladium centre. The bite angle of the methylpicolinate ligand is small [74.8(4)°] and the Pd-N [2.141(9)Å] and Pd-O [2.180(7) Å] bonds to the ligand are somewhat elongated. The complexes react readily with CO to give the corresponding acyl complexes, and with the exception of {[PdMe(N-O)Ph2PCH2COOEt]BF4} catalyse the reaction between CO and ethene at room temperature to give polyketone.