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.
Institute of Molecular Chemistry, Department of Inorganic Chemistry, Universiteit van Amsterdam, The Netherlands.
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Y
Guari
G P
GP
van Strijdonck
M D
MD
Boele
J N
JN
Reek
P C
PC
Kamer
P W
PW
van Leeuwen