Autocatalytic oxidative addition of PhBr to Pd(PtBu3)2 via Pd(PtBu3)2(H)(Br)

被引:83
作者
Barrios-Landeros, Fabiola
Carrow, Brad P.
Hartwig, John F.
机构
[1] Univ Illinois, Dept Chem, Urbana, IL 61801 USA
[2] Yale Univ, Dept Chem, New Haven, CT 06520 USA
关键词
D O I
10.1021/ja711159y
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We report that Oxidative addition of bromobenzene to Pd ((PBu3)-Bu-t)(2) Occurs by an unusual autocatalytic mechanism. Studies on the effect of various additives showed that the degree of rate acceleration followed the trend: ((PBu3)-Bu-t)Pd (Ph)(Br) approximate to (Hp(t)Bu(3))Br < [((PBu3)-Bu-t)Pd(P-Br)](2) < ((PBu3)-Bu-t)(2)Pd (H)(Br). Studies on the reactions of Pd((PBu3)-Bu-t)(2) in the Presence of ((PBu3)-Bu-t)(2)Pd(H)(Br) showed that the concentration of ((PBu3)-Bu-t)(2)Pd(H)(Br) decreased only after the Pd(O) complex had been consumed. These data indicated that the catalyst in this Process is ((PBu3)-Bu-t)(2)Pd(H)(Br). Thermal decomposition of the three-coordinate Oxidative addition product ((PBu3)-Bu-t)(2)Pd(Ar)(Br) during the reaction of Pd((PBu3)-Bu-t)(2) and bromoarenes ultimately leads to formation Of ((PBu3)-Bu-t)(2)Pd(H)(Br). Parallel reactions of bromobenzene with ((PBu3)-Bu-t)(2)Pd(H)(Br) and Pd((PBu3)-Bu-t)(2) showed that the bromoarenes reacted considerably faster with the Pd(II) species than with the Pd(O) species. We therefore propose a catalytic cycle for oxidative addition in which PBu3t center dot HBr reacts with the Pd(O) species to form ((PBu3)-Bu-t)(2)Pd(H)(Br), and ((PBu3)-Bu-t)(2)Pd (H)(Br) reacts with the bromoarene, possibly though the anionic species [(HPBu3+)-Bu-t][((PBu3)-Bu-t)Pd(Br)(-)], to form [Pd((PBu3)-Bu-t)(Ar)(Br)].
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页码:5842 / +
页数:3
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