1136070-51-3Relevant academic research and scientific papers
Palladium(II) complexes with phosphanylferrocenecarboxylate ligands and their use as catalyst precursors for semialternating CO-ethylene copolymerization
Bianchini, Claudio,Meli, Andrea,Oberhauser, Werner,Segarra, Anna Maria,Passaglia, Elisa,Lamac, Martin,Stepnicka, Petr
, p. 441 - 452 (2008)
Neutral [Pd(κP,κO-P～O)(κ3C,C,C- carbocycloenyl)] complexes, where P～O is a chiral or achiral chelating phosphanylferrocenecarboxylate ligand, were synthesized and characterized by multinuclear NMR spectroscopy. The crystal structure of a representative complex was determined by single-crystal X-ray diffraction analysis. In all complexes, the palladium(II) ion is located at the centre of a square plane formed by the P and O donor atoms from an anionic P～O- ligand, a σ-carbon atom and a C-C double bond from a carbocycloenyl ligand. Neutral methyl complexes with the formulas [PdCl(Me)(κP,κH-P～OH)] and [Pd(Me)(OTs)(κP,κH-P～OH)] were also synthesized and characterized. On the basis of IR, NMR and MS-FAB data, the methyl complexes are proposed to be formulated with the fourth coordination position occupied by an agostic O-H...Pd interaction from a free carboxylic acid moiety [P～OH = 1′-(diphenylphosphanyl)ferrocenecarboxylic acid] or a solvent molecule. Selected complexes were employed as catalyst precursors for CO-ethylene copolymerization in MeOH in the presence of an excess of p-toluenesulfonic acid. In all cases, low molecular weight semialternating polyketones were produced. The catalytic activities were rather low and the extra-ethylene insertion reached a maximum value of 4.3%. An operando high-pressure NMR experiment with [Pd(Me)(S)2(κP-P～OH)]OTs (S = solvent, adventitious water) precursor showed that this monocationic PdII alkyl complex is readily converted into a catalytically inactive binuclear carbonyl-bridged Pd I compound, which, however, regenerates catalytically active Pd II-H species by reaction with TsOH and that β-chelates of the formula [Pd(CH2CH2C(O)P)(S)(κP-P～OH)]OTs (P = propagating polyketone chain) are catalyst resting states. For the first time, β-chelate propagating species have been intercepted in a CO-olefin copolymerization assisted by catalysts devoid of a chelating ligand. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
