Abstract：
We report the first examples of metal-promoted double geminal activation of C(sp3 )-H bonds of the N-CH2 -N moiety in an imidazole-type heterocycle, leading to nickel and palladium N-heterocyclic carbene complexes under mild conditions. Reaction of the new electron-rich diphosphine 1,3-bis((di-tert-butylphosphaneyl)methyl)-2,3-dihydro-1H-benzo[d]imidazole (1) with [PdCl2 (cod)] occurred in a stepwise fashion, first by single C-H bond activation yielding the alkyl pincer complex [PdCl(PC sp 3 H P)] (3) with two trans phosphane donors and a covalent Pd-C sp 3 bond. Activation of the C-H bond of the resulting α-methine C sp 3 H-M group occurred subsequently when 3 was treated with HCl to yield the NHC pincer complex [PdCl(PCNHC P)]Cl (2). Treatment of 1 with [NiBr2 (dme)] also afforded a NHC pincer complex, [NiBr(PCNHC P)]Br (6), but the reactions leading to the double geminal C-H bond activation of the N-CH2 -N group were too fast to allow identification or isolation of an intermediate analogous to 3. The determination of six crystal structures, the isolation of reaction intermediates and DFT calculations provided the basis for suggesting the mechanism of the stepwise transformation of a N-CH2 -N moiety in the N-CNHC -N unit of NHC pincer complexes and explain the key differences observed between the Pd and Ni chemistries.
摘要：
我们报道了咪唑型杂环中N-CH2-N部分的C（sp3）-H键的金属促进的双叉激活的第一个例子，在温和条件下产生镍和钯N-杂环卡宾配合物。新的富电子二膦1,3-双（（二叔丁基膦酰基）甲基）-2,3-二氢-1H-苯并[d]咪唑（1）与[PdCl2（cod）]的反应逐步发生，首先通过单个C-H键活化产生具有两个反式磷烷供体和共价Pd-Csp3键的烷基钳配合物[PdCl（PCsp3HP）]（3）。当用HCl处理3时，随后发生产生的α-次甲基Csp3H-M基团的C-H键的活化，产生NHC钳形络合物[PdCl（PCNHCP）]Cl（2）。用[NiBr2（dme）]处理1也提供了NHC钳复合物，[NiBr(PCNHCP)]Br(6),但是导致N-CH2-N基团的双叉C-H键激活的反应太快，无法鉴定或分离类似于3的中间体。六种晶体结构的测定，反应中间体的分离和DFT计算为建议NHC钳形配合物的N-CNHC-N单元中N-CH2-N部分逐步转化的机理提供了基础，并解释了观察到的关键差异Pd和Ni化学。
