Three-coordinate nickel(I) complexes stabilised by six-, seven- and eight-membered ring n-heterocyclic carbenes: synthesis, EPR/DFT studies and catalytic activity.-猫眼课题宝

DOI：

10.1002/chem.201202950

发表时间：

2013-02

期刊：

Chemistry

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

M. Page;W. Lu;Rebecca C. Poulten;Emma Carter;Andrés G. Algarra;B. Kariuki;S. Macgregor;M. Mahon;K. Cavell;D. Murphy;M. Whittlesey

[Ni(CoD)(2)](CoD=环辛二烯)和[Ni(PPh(3))(2)X(2)](X=Br，Cl)在六、七和八元环N-芳基取代杂环卡宾(NHCS)存在下的缩合反应提供了一系列等结构的三配位镍(I)配合物[Ni(NHC)(PPh(3))X](X=Br，Cl；NHC=6-MES 1，6-ANIS 2，6-ANISMES 3，7-O-TOL 4，8-MES 5，8-O-TOL 6，O-8-O-TOL 7)。1，4，5，6和7的连续波(CW)和脉冲EPR测量表明，自旋哈密顿参数对NHC环尺寸、N取代基和卤化物的变化特别敏感。结合密度泛函理论计算，观察到了|3dz2>和|3dx2-y2>特征的混合自组织元，它依赖于复杂的几何结构，并与EPR谱的实验g值进行了比较。还发现了与PPh(3)基团显著的(31)P超精细耦合，这与磷上的大自旋密度以及部分分解的溴耦合是一致的。1、4、5和6作为预催化剂用于芳基氯化物和氟化物与ArMgY(Ar=Ph，Mes)的Kumada偶联反应，对较小的环系和/或较小的取代基(即1&gt；4≈6≫5)表现出最高的活性。

Comproportionation of [Ni(cod)(2)] (cod = cyclooctadiene) and [Ni(PPh(3))(2)X(2)] (X = Br, Cl) in the presence of six-, seven- and eight-membered ring N-aryl-substituted heterocyclic carbenes (NHCs) provides a route to a series of isostructural three-coordinate Ni(I) complexes [Ni(NHC)(PPh(3))X] (X = Br, Cl; NHC = 6-Mes 1, 6-Anis 2, 6-AnisMes 3, 7-o-Tol 4, 8-Mes 5, 8-o-Tol 6, O-8-o-Tol 7). Continuous wave (CW) and pulsed EPR measurements on 1, 4, 5, 6 and 7 reveal that the spin Hamiltonian parameters are particularly sensitive to changes in NHC ring size, N substituents and halide. In combination with DFT calculations, a mixed SOMO of ∣3d z 2〉 and ∣3d x 2-y 2〉 character, which was found to be dependent on the complex geometry, was observed and this was compared to the experimental g values obtained from the EPR spectra. A pronounced (31)P superhyperfine coupling to the PPh(3) group was also identified, consistent with the large spin density on the phosphorus, along with partially resolved bromine couplings. The use of 1, 4, 5 and 6 as pre-catalysts for the Kumada coupling of aryl chlorides and fluorides with ArMgY (Ar = Ph, Mes) showed the highest activity for the smaller ring systems and/or smaller substituents (i.e., 1>4≈6≫5).

Three-coordinate nickel(I) complexes stabilised by six-, seven- and eight-membered ring n-heterocyclic carbenes: synthesis, EPR/DFT studies and catalytic activity.

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