929209-76-7Relevant academic research and scientific papers
Ethylene oligomerization catalyzed by a unique phosphine - Oxazoline palladium(II) complex. Propagation and chain transfer mechanisms
Doherty, Mark D.,Trudeau, Stephane,White, Peter S.,Morken, James P.,Brookhart, Maurice
, p. 1261 - 1269 (2008/10/09)
Palladium(II)-catalyzed ethylene oligomerization reactions using a new [(P∧N)Pd(CH3)(NCArF)][SbF6] complex, 2b (P∧N = phosphine-oxazoline, ArF = 3,5-(CF3)2C 6H3), are described. Analysis of the X-ray crystal structure of the (P∧N)Pd(CH3)Cl precatalyst, 2a, reveals a unique axial Pd...H interaction (2.33 A) with a ligand Csp3-H bond. Exposure of this complex to ethylene in methylene chloride produces a Schulz-Flory distribution of α-olefins ranging from C4 to C24. Effects of varying ethylene pressure and reaction temperature on oligomerizations are reported. The turnover frequency exhibits saturation behavior as ethylene pressure is increased; carrying out a Lineweaver - Burk analysis provides a barrier of 17.5 kcal/mol for migratory insertion of the palladium alkyl ethylene species. The invariance of the SchulzFlory constant with added quantities of nitrile suggests that chain transfer occurs through a process best described as chain transfer to monomer. The catalyst resting state is shown to vary as a function of ethylene pressure and nitrile concentration. Oligomerization experiments performed with a related phosphine-oxazoline complex lacking Pd...H-Csp3 axial interaction lead only to ethylene dimerization.
