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In Situ Preparation of Palladium Diphosphane Catalysts
Author(s) -
Marson Angelica,
van Oort A. Bart,
Mul Wilhelmus P.
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200211)2002:11<3028::aid-ejic3028>3.0.co;2-8
Subject(s) - chemistry , palladium , catalysis , methanol , medicinal chemistry , kinetics , combinatorial chemistry , in situ , organic chemistry , physics , quantum mechanics
The efficiency of a superficially simple preparation procedure for palladium‐diphosphane catalysts has been examined. Preparation of Pd(dppe)X 2 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)X 2 — virtually inactive — [Pd(dppe) 2 ]X 2 — and unstable — PdX 2 — species. This procedure was also evaluated for some other diphosphane ligands and methods are given to overcome the encountered problem.