Rousseau Roger, Schenter Gregory K, Fulton John L, Linehan John C, Engelhard Mark H, Autrey Thomas
Fundamental & Computer Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
J Am Chem Soc. 2009 Aug 5;131(30):10516-24. doi: 10.1021/ja901480u.
We present the results of a detailed operando XAFS and density functional theory (DFT)-based ab initio molecular dynamics (AIMD) investigation of a proposed mechanism of the dehydrogenation of dimethylaminoborane (DMAB) by a homogeneous Rh(4) cluster catalyst. Our AIMD simulations reveal that previously proposed Rh structures, based on XAFS measurements, are highly fluxional, exhibiting both metal cluster and ligand isomerizations and dissociation that can only be accounted for by examining a finite temperature ensemble. It is found that a fluxional species Rh(4)(H(2)BNMe(2))(8)(2+) is fully compatible with operando XAFS measurements, suggesting that this species may be the observed catalyst resting state. On the basis of this assignment, we propose a mechanism for catalytic DMAB dehydrogenation that exhibits an energy barrier of approximately 28 kcal/mol.
我们展示了一项详细的基于操作条件下X射线吸收精细结构（XAFS）和密度泛函理论（DFT）的从头算分子动力学（AIMD）研究结果，该研究针对一种由均相Rh(4)簇催化剂催化二甲基氨基硼烷（DMAB）脱氢的 proposed 机制。我们的AIMD模拟表明，基于XAFS测量先前提出的Rh结构具有高度的流动性，表现出金属簇和配体的异构化和解离，这只能通过研究有限温度系综来解释。发现一种流动性物种Rh(4)(H(2)BNMe(2))(8)(2+)与操作条件下的XAFS测量完全兼容，这表明该物种可能是观察到的催化剂静止状态。基于这一归属，我们提出了一种催化DMAB脱氢的机制，其能量垒约为28 kcal/mol。 （注：原文中“proposed”疑为“proposed”拼写错误，翻译时按“提出的”处理）
