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Frustrated Lewis Acid-Base-Pair-Catalyzed Amine-Borane Dehydrogenation.
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-01-07 , DOI: 10.1021/acs.inorgchem.9b02561
Ishita Bhattacharjee 1 , Sourav Bhunya 1 , Ankan Paul 1
Affiliation  

Metal-free catalysis by sterically encumbered Lewis Acid-Base pairs, popularly known as frustrated Lewis pairs (FLPs), is gaining importance by the day due to its promise of providing a greener alternative to transition-metal-based catalysis. One of the stumbling blocks in achieving catalytic dehydrogenation of amine-boranes is catalyst deactivation by the reaction product. Herein, we have theoretically investigated the routes of a dimethylxanthene-derived B,P-FLP-catalyzed dehydrogenation of dimethylamine-borane (DMAB), a rare instance which avoids catalyst inhibition by the reaction product. Our computational findings reveal that the dehydrogenation proceeds via formation of the ion pair [FLP-H]- and [HMe2N-BH2-H-BH2-NMe2H]+. This step is followed by indirect B-H activation assisted by a second DMAB molecule and further H2 release via deprotonation by the PPh2 center. It is revealed that the binding of NMe2BH2 to the FLP is unfavorable which ensures smooth propagation of the catalytic cycle. Catalytic dehydrogenation by the same mechanistic pathway is somewhat inhibited in the case of ammonia-borane by the same FLP due to the latent stabilization provided by strong hydrogen bonding interaction to FLP-NH2BH2 adduct which renders partial deactivation of the catalyst.

中文翻译:

沮丧的路易斯酸碱-对-催化的胺-硼烷脱氢。

通过空间受限的路易斯酸碱对(通常被称为沮丧的路易斯对(FLP))进行的无金属催化由于其有望提供一种绿色的替代金属过渡催化方法而日益受到重视。实现胺-硼烷的催化脱氢的绊脚石之一是反应产物使催化剂失活。在本文中,我们从理论上研究了二甲基the吨衍生的B,P-FLP催化的二甲胺硼烷(DMAB)脱氢的路线,这种情况很少会避免催化剂被反应产物抑制。我们的计算发现表明,脱氢是通过形成离子对[FLP-H]-和[HMe2N-BH2-H-BH2-NMe2H] +进行的。此步骤之后是间接的BH活化,辅以第二个DMAB分子,然后通过PPh2中心的去质子作用进一步释放H2。揭示了NMe2BH2与FLP的结合是不利的,这确保了催化循环的顺利传播。在氨硼烷的情况下,由于FFP-NH2BH2加合物与氢的牢固氢键相互作用提供了潜在的稳定作用,从而使催化剂部分失活,因此通过相同的FLP在某种程度上抑制了通过相同机理途径进行的催化脱氢。
更新日期:2020-01-08
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