Elucidation of the Formation Mechanisms of the Octahydrotriborate Anion (B3H8−) Through the Nucleophilicity of the B−H Bond,Journal of the American Chemical Society

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Elucidation of the Formation Mechanisms of the Octahydrotriborate Anion (B3H8−) Through the Nucleophilicity of the B−H Bond
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-05-07 , DOI: 10.1021/jacs.8b03785
Xi-Meng Chen ₁ , Nana Ma ₁ , Qian-Fan Zhang ₂ , Jin Wang ₁ , Xiaoge Feng ₁ , Changgeng Wei ₁ , Lai-Sheng Wang ₂ , Jie Zhang ₁ , Xuenian Chen ₁

Affiliation

Boron compounds are well-known electrophiles. Much less known are their nucleophilic properties. By recognition of the nucleophilicity of the B-H bond, the formation mechanism of octahydrotriborate (B3H8-) was elucidated on the bases of both experimental and computational investigations. Two possible routes from the reaction of BH4- and THF·BH3 to B3H8- were proposed, both involving the B2H6 and BH4- intermediates. The two pathways consist of a set of complicated intermediates, which can convert to each other reversibly at room temperature and can be represented by a reaction circle. Only under reflux can the B2H6 and BH4- intermediates be converted to B2H5- and BH3(H2) via a high energy barrier, from which H2 elimination occurs to yield the B3H8- final product. The formation of B2H6 from THF·BH3 by nucleophilic substitution of the B-H bond was captured and identified, and the reaction of B2H6 with BH4- to produce B3H8- was confirmed experimentally. On the bases of the formation mechanisms of B3H8-, we have developed a facile synthetic method for MB3H8 (M = Li and Na) in high yields by directly reacting the corresponding MBH4 salts with THF·BH3. In the new synthetic method for MB3H8, no electron carriers are needed, allowing convenient preparation of MB3H8 in large scales and paving the way for their wide applications.

中文翻译：

通过 B-H 键的亲核性阐明八氢三硼酸阴离子 (B3H8-) 的形成机制

硼化合物是众所周知的亲电试剂。鲜为人知的是它们的亲核特性。通过对 BH 键亲核性的认识，在实验和计算研究的基础上阐明了八氢三硼酸盐 (B3H8-) 的形成机制。提出了 BH4- 和 THF·BH3 反应生成 B3H8- 的两种可能途径，均涉及 B2H6 和 BH4- 中间体。这两条途径由一组复杂的中间体组成，它们可以在室温下可逆地相互转化，可以用一个反应环来表示。只有在回流下，B2H6 和 BH4- 中间体才能通过高能垒转化为 B2H5- 和 BH3(H2)，从中发生 H2 消除以产生 B3H8- 最终产物。通过 BH 键的亲核取代，THF·BH3 形成 B2H6 被捕获和鉴定，并且 B2H6 与 BH4- 反应生成 B3H8- 被实验证实。基于B3H8-的形成机制，我们开发了一种简便的MB3H8（M = Li和Na）合成方法，通过将相应的MBH4盐与THF·BH3直接反应，以高产率合成MB3H8（M = Li和Na）。MB3H8的新合成方法不需要电子载体，可以方便地大规模制备MB3H8，为其广泛应用铺平道路。通过将相应的 MBH4 盐与 THF·BH3 直接反应，我们开发了一种简便的 MB3H8（M = Li 和 Na）合成方法。MB3H8的新合成方法不需要电子载体，可以方便地大规模制备MB3H8，为其广泛应用铺平道路。通过将相应的 MBH4 盐与 THF·BH3 直接反应，我们开发了一种简便的 MB3H8（M = Li 和 Na）合成方法。MB3H8的新合成方法不需要电子载体，可以方便地大规模制备MB3H8，为其广泛应用铺平道路。

更新日期：2018-05-07

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