Palladium-catalyzed amination of aryl bromides and aryl triflates using diphosphane ligands: a kinetic study.
[Pd(P-O-P)(Ar)]+ complexes with ligands that have wide bite angles are active catalysts for the coupling of aniline derivatives with aryl triflates. Kinetic studies show that for these systems a fast equilibrium that involves coordination of the amine precedes the deprotonation, which is the rate-limiting step of the reaction. This reaction is faster for compounds with a smaller P-Pd-P angle. When halide salts are present, the base sodium tert-butoxide is activated and adds to the palladium complex. This rate-limiting step is preceded by a fast equilibrium that involves decoordination of the halide. The initial reaction rate is faster for compounds with a larger P-Pd-P angle. This is due to the closer proximity of the oxygen to the Pd center, and this assists in the dissociation of the halide.
Guari
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Institute of Molecular Chemistry, Department of Inorganic Chemistry, Universiteit van Amsterdam, The Netherlands.
van Strijdonck
G P
GP
Boele
M D
MD
Reek
J N
JN
Kamer
P C
PC
van Leeuwen
P W
PW