180850-61-7Relevant academic research and scientific papers
Cationic methylpalladium(II) complexes containing bidentate N-O ligands as catalysts for the copolymerisation of CO and ethylene. Identification and isolation of intermediates from the stepwise insertion reactions, and subsequent detailed mechanistic interpretation
Green, Melinda J.,Britovsek, George J. P.,Cavell, Kingsley J.,Gerhards, Frank,Yates, Brian F.,Frankcombe, Katrina,Skelton, Brian W.,White, Allan H.
, p. 1137 - 1144 (2007/10/03)
A series of cationic methylpalladium(II) complexes containing bidentate N-O ligands, of the general formula [PdMe(N-O)L]BF4 (N-O = methyl picolinate, methyl 6-methylpicolinate, N,N-diisopropylpicolinamide, 6-methyl-N,N-diisopropylpicolinamide; L = PPh3 or PCy3) have been prepared and characterised. The solid-state structure of [PdMe(N-O)(PPh3)]BF4 (N-O = N,N-diisopropylpicolinamide), in comparison with that for the complex with N-O = methyl picolinate, indicates a significant lengthening of the Pd-P bond [Δ(Pd-P) = 0.018(3) A] possibly due to the presence of the more strongly co-ordinating N-O ligand. Complexes with L = PPh3 were found to be active for the copolymerisation of CO and ethylene to give polyketone. The complexes [PdMe(N-O)(PPh3)]BF4 (N-O = methyl 6-methylpicolinate or diisopropylpicolinamide) have the highest catalytic activities (80 g polymer per g Pd per hour and 58 g polymer per g Pd per hour respectively, at 20°C). Examples of the complexes form simple acyl complexes when treated with CO at room temperature and pressure and the spectroscopic data of the resulting acetyl complexes are reported. The stepwise migratory insertion of CO and ethylene into the complex [PdMe(N-O)(PPh3)]BF4 (N-O = methyl picolinate) has been carefully monitored and the individual insertion products have been characterised. Insertion of ethylene into the Pd-acyl bond of [Pd(COMe)(N-O)(PPh3)]BF4 (N-O = methyl picolinate) affords one of the first examples of an isolable product from insertion of an unstrained alkene into a Pd-acyl bond. A detailed mechanism for the co-reaction of CO and ethylene catalysed by complexes containing chelate ligands with distinct donor groups is discussed and an explanation of the observed reaction behaviour provided. The proposed mechanism represents one of the most comprehensive interpretations of this important reaction.
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
Britovsek, George J.P.,Cavell, Kingsley J.,Green, Melinda J.,Gerhards, Frank,Skelton, Brian W.,White, Allan H.
, p. 201 - 212 (2007/10/03)
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)A] and Pd-O [2.180(7) A] 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.
