制备了一系列的三(三乙基膦)-连接的有机铑(I)配合物,并研究了它们与电子贫芳基腈和二芳基酮的反应。[(PEt 3)3 Rh(Ar)](Ar =苯基(1a)或邻-茴香基(1e))与过量的电子贫芳基Ar'C≡N(Ar'= p -CF 3 C 6 H 4或3,5-bis(CF 3)C 6 H 3)形成Rh(I)亚氨基络合物{(PEt 3)3 Rh [N═C(Ar)(Ar')]}(2h - j) 。相反,3,5-bis(CF 3)C 6 H 3 CN没有插入芳基铑(I)配合物[(PEt 3)3 Rh(Ar)](Ar = p -CF 3 C 6 H 4(1f)或3, 5-双(CF 3)C 6 H 3(1g)),含有更多的贫电子芳基。腈插入的动力学数据与涉及初始配体解离,随后经典的迁移插入的途径最一致。亚胺基络合物2i - j在较高温度下通过β-芳基消除而分解,同时电子侧差的芳基3,5-双(CF 3)C
Directly Observed Transmetalation from Boron to Rhodium. β-Aryl Elimination from Rh(I) Arylboronates and Diarylborinates
作者:Pinjing Zhao、Christopher D. Incarvito、John F. Hartwig
DOI:10.1021/ja068587q
日期:2007.2.1
Transmetalation from boron to rhodium in the absence of basic activators is reported to proceed by beta-aryl elimination from a series of triethylphospine-ligated rhodium(I) arylboronates and diarylborinates. [Rh(PEt3)(3)OB(OH)Ar] were prepared by treating Rh(PEt3)(2)[N(SiMe3)(2)} with the corresponding arylboronic acid, ArB(OH)(2), in the presence of added PEt3. One example of these complexes was characterized by X-ray diffraction. [Rh(PEt3)(3)OB(mesityl)(2)] and [Rh(PEt3)(2)OB(mesityl)(2)] were prepared by analogous methods from dimesitylborinic acid in the presence and absence of added PEt3. Heating of the trisphosphine boronate complexes in cyclohexane generated the rhodium aryl complexes, [(PEt3)(3)RhAr] and boroxin in good to high yields. [Rh(PEt3)(3)OB(mesityl)(2)] also underwent aryl migration to form [(PEt3)(3)Rh(mesityl)] and a cyclic boroxine. Kinetic studies showed that migration of more electron-poor aryl groups from the boronate complexes was slightly faster than migration of more electron-poor aryl groups and that migration of the o-anisyl group was particularly fast. Kinetic results are most consistent with a ligand dissociation pathway with a rate-limiting beta-aryl elimination from a 14-electron, bis(phosphine) intermediate.