Abstract：
The pincer complexes [NiIIBr(CNC)]Br (4), [CrIIIBr3(CNC)] (5 a) and [CrIIIBr2.3Cl0.7(CNC)] (5 b), where CNC=3,3\'-(pyridine-2,6-diyl)bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene), were obtained from the novel ligand CNC, generated in situ from the precursor (CHNCH)Br2 and [NiIIBr2(PPh3)2] or from [CrII{N(SiMe3)2}2(THF)2] and (CHNCH)Br2 by aminolysis, respectively. The tetrahedrally distorted square planar (τ4≅0.30) geometry and the singlet ground state of Ni in 4 were attributed to steric constraints of the CNC backbone. Computational methods highlighted the dependence of the coordination geometry and the singlet-triplet energy difference on the size of the N-substituent of the tetrahydropyrimidine wingtips and contrasted it to the situation in 5-membered imidazolin-2-ylidene pincer analogues. The octahedral CrIII metal center in 5 a and 5 b is presumably formed after one electron oxidation from CH2Cl2. 4/MAO and 5 a/MAO were catalysts of moderate activity for the oligomerization and polymerization of ethylene, respectively. The analogous (CH^N^CH)Br2 precursor, where (CH^N^CH)=3,3\'-(pyridine-2,6-diylbis(methylene))bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-1-ium), was also prepared, however its coordination chemistry was not studied due to the inherent instability of the resulting free C^N^C ligand.
摘要：
夹式配合物[NiIIBr(CNC)]Br(4)，[CrIIIBr3(CNC)](5a)和[CrIIIBr2.3Cl0.7(CNC)](5b),其中CNC=3,3'-(吡啶-2,6-二基)双(1-均三基-3,4,5,6-四氢嘧啶-2-亚基),是从新型配体CNC获得的，通过氨解从前体（CHNCH）Br2和[NiIIBr2（PPh3）2]或从[CrII{N（SiMe3）2}2（THF）2]和（CHNCH）Br2原位生成，分别。四面体扭曲的正方形平面（τ4^0.30）几何形状和4中Ni的单重态基态归因于CNC骨架的空间约束。计算方法强调了配位几何形状和单线态-三重态能量差对四氢嘧啶翼尖的N-取代基的大小的依赖性，并将其与5元咪唑啉-2-亚基钳类似物的情况进行了对比。5a和5b中的八面体CrIII金属中心大概是在CH2Cl2的一个电子氧化之后形成的。4/MAO和5a/MAO是乙烯低聚和聚合的中等活性催化剂，分别。类似的(CH^N^CH)Br2前体，其中(CH^N^CH)=3,3'-(吡啶-2,6-二基双(亚甲基))双(1-均三甲基-3,4,5,6-四氢嘧啶-1-铵),也准备好了,然而，由于所得游离C^N^C配体的固有不稳定性，其配位化学没有研究。
