280584-93-2Relevant academic research and scientific papers
In situ preparation of palladium diphosphane catalysts
Marson, Angelica,Van Oort, A. Bart,Mul, Wilhelmus P.
, p. 3028 - 3031 (2007/10/03)
The efficiency of a superficially simple preparation procedure for palladium-diphosphane catalysts has been examined. Preparation of Pd(dppe)X2 in situ by mixing equimolar amounts of Pd(OAc)2 and 1,2-bis(diphenylphosphanyl)-ethane (dppe) in methanol in the first step unexpectedly affords the bischelate [Pd(dppe)2](OAc)2 as the (main) kinetic product. Subsequently, the slow reaction of [Pd(dppe)2]-(OAc)2 and unreacted Pd(OAc)2 forms the thermodynamically favored monochelate [Pd(dppe)(OAc)2] (following first-order kinetics). Conversion of the bischelate into the monochelate stops after addition of strong acid (HX) in the second step, thus affording a mixture of active - Pd(dppe)X2 - virtually inactive - [Pd(dppe)2]X2 - and unstable - PdX2 - species. This procedure was also evaluated for some other diphosphane ligands and methods are given to overcome the encountered problem.
