We report the first example of a cobalt PC_carbeneP pincer complex (1) featuring a central alkylidene carbon donor accessed through the dehydration of an alcoholic POP proligand. Complex 1 shares bonding similarities with cobalt PBP and PNP pincer complexes where the donor atom engages in π-bonding with the cobalt centre, and thus completes the PXP (X = B, C, N) pincer ligand series for cobalt (for X donors that partake in M–L π-bonding). As compared to PBP and PNP pincer complexes, which are known to be good hydride and proton acceptors (respectively), complex 1 is found to be an effective hydrogen atom acceptor. Complex 1 partakes in cooperative ligand reactivity, engaging in several small molecule activations with styrene, bromine, carbon disulphide, phenyl acetylene, acetonitrile, hydrogen, benzaldehyde and water (through microreversibility). The mechanism for the formation of complex 1 is studied through the isolation and computational analysis of key intermediates. The formation of 1 is found to avoid C–H activation of the proligand, and instead proceeds through a combination of O–H activation, hydrogen atom transfer, β-hydride elimination and hydrogen activation processes.

中文翻译：

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PCcarbeneP 钴 (i) 配合物的合成和反应性：钴 PXP 钳系列中的缺失环节（X = B、C、N）†

我们报告了钴 PC_卡宾P 钳形配合物 ( 1 ) 的第一个例子，该复合物具有中央亚烷基碳供体，可通过酒精 POP proligand 的脱水获得。配合物1与钴 PBP 和 PNP 钳形配合物具有键合相似性，其中供体原子与钴中心进行 π 键合，从而完成钴的 PXP (X = B, C, N) 钳形配体系列（对于 X 供体，参与 M-L π-键合）。与已知为良好的氢化物和质子受体（分别）的 PBP 和 PNP 钳形配合物相比，发现配合物1是有效的氢原子受体。复合体1参与协同配体反应，与苯乙烯、溴、二硫化碳、苯乙炔、乙腈、氢气、苯甲醛和水（通过微可逆性）进行多种小分子活化。通过关键中间体的分离和计算分析研究了络合物1的形成机制。发现1的形成避免了前配体的 C-H 活化，而是通过 O-H 活化、氢原子转移、β-氢化物消除和氢活化过程的组合进行。