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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Phenylvinylcobalamin: An alkenylcobalamin featuring a ligand with a large trans influence
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Phenylvinylcobalamin: An alkenylcobalamin featuring a ligand with a large trans influence

机译：苯基乙烯基钴胺素：特征在于配体具有较大反式影响的链烯基钴胺素

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Cob(i)alamin reacts with phenylacetylene to produce two diastereomers in which the organic ligand is coordinated to the upper (β) and lower (α) face of the corrin ring, respectively. The isomers were separated chromatographically and characterised by ESI-MS and, in the case of the β isomer, by ~~1H and ~(13)C NMR. Only the β isomer crystallised and its molecular structure, determined by X-ray diffraction, shows that the organic ligand coordinates Co(iii) through the β carbon of the phenylvinyl ligand. The Co-C bond length is 2.004(8) ? while the Co-N bond length to the trans 5,6-dimethylbenzimidazole (dmbzm) base is 2.217(8) ?, one of the longest Co-N_(dmbzm) bond lengths known in an organocobalamin. Unlike benzylcobalamin (BzCbl), phenylvinylcobalamin (PhVnCbl) is stable towards homolysis. DFT calculations (BP86/TZVP) on model compounds of BzCbl and PhVnCbl show that the Co-C bond dissociation energy for homolysis to Co(ii) and an organic radical in the former is 8 kcal mol~(-1) lower than in the latter. An analysis of the electron density at the Co-C bond critical point using Bader's QTAIM approach shows that the Co-C bond in PhVnCbl is shorter, stronger and somewhat more covalent than that in BzCbl, and has some multiple bond character. Together with calculations that show that the benzyl radical is more stable than the phenylvinyl radical,
机译：钴（i）丙氨酸与苯乙炔反应生成两种非对映异构体，其中有机配体分别与柯林环的上（β）和下（α）配位。色谱分离该异构体，并通过ESI-MS进行表征;对于β异构体，则通过~~ 1H和〜（13）C NMR进行表征。通过X射线衍射仅结晶的β异构体及其分子结构表明，有机配体通过苯基乙烯基配体的β碳配位Co（iii）。 Co-C键长度为2.004（8）？反式5，6-二甲基苯并咪唑（dmbzm）碱的Co-N键长度为2.217（8）Ω，这是有机钴胺素中已知的最长的Co-N_（dmbzm）键长度之一。与苄基钴胺素（BzCbl）不同，苯基乙烯基钴胺素（PhVnCbl）对均质稳定。对BzCbl和PhVnCbl的模型化合物进行的DFT计算（BP86 / TZVP）表明，与Co（ii）和有机基团同质的Co-C键离解能比前者低8 kcal mol〜（-1）。后者。使用Bader的QTAIM方法分析Co-C键临界点的电子密度，结果表明，PhVnCbl中的Co-C键比BzCbl中的Co-C键更短，更牢固且共价更高，并且具有某些多重键特征。连同计算结果表明，苄基比苯基乙烯基更稳定，

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