Half-Sandwich Iminophosphonamide Rhodium Complexes as Highly Efficient Catalysts for Dehydrogenation of Dimethylamine-Borane

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research Pub Date : 2024-08-15 DOI:10.1134/S1070328424600098

R. I. Nekrasov, T. A. Peganova, A. M. Kal’sin, N. V. Belkova

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Abstract

The dehydrogenation of dimethylamine-borane (DMAB) catalyzed by the iminophosphonamide rhodium(III) complexes [Cp*RhCl{Ph₂P(N–p-Tol)(NR)}] (Iа, R = p-Tol; Ib, R = Me) as well as their in situ formed fulvene [(η⁴-C₅Me₄CH₂)Rh(NPN)] (IIa, IIb) and diene [(η⁴-C₅Me₅H)Rh(NPN)] (IIIa, IIIb) rhodium(I) derivatives is studied. Catalysts IIIa and IIIb turn out to be the most active and demonstrate a TOF activity of 110 (IIIа) and 540 h^–1 (IIIb) at 40°С in toluene. The activity decreases significantly in more polar and coordinating THF. At the same time, the rate of DMAB dehydrogenation by complexes Iа and Ib is lower by 10–30 times, and fulvene complexes Iа and Ib are rapidly deactivated after the active initial period (<20% conversion). The kinetic studies show that the reaction has the first order with respect to the substrate and the catalyst. The model ¹¹В NMR experiments confirm that the reaction proceeds via the intermediate formation of a monomer Me₂N=BH₂, which rapidly dimerizes to (Me₂N–BH₂)₂. The mechanism of DMAB dehydrogenation with the formation of unstable hydride intermediate [Cp*RhH{Ph₂P(N–p-Tol)(NR)}] (IVa, IVb) is proposed on the basis of the preliminarily ³¹Р NMR results and published data.

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半三明治氨基膦酰胺铑络合物作为二甲胺-硼烷脱氢反应的高效催化剂

摘要亚氨基膦酰胺铑(III)配合物[Cp*RhCl{Ph2P(N-p-Tol)(NR)}]（Iа，R = p-Tol；Ib，R = Me）及其原位形成的富烯[(η4-C5Me4CH2)Rh(NPN)]（IIa，IIb）和二烯[(η4-C5Me5H)Rh(NPN)]（IIIa，IIIb）铑（I）衍生物进行了研究。催化剂 IIIa 和 IIIb 的活性最高，在甲苯中 40°С 时的 TOF 活性分别为 110（IIIа）和 540 h-1（IIIb）。在极性和配位性更强的四氢呋喃中，活性明显降低。同时，Ⅰа和Ⅰb 复合物的 DMAB 脱氢速率降低了 10-30 倍，Ⅰа和Ⅰb 复合物在活性初期（20% 转化率）后迅速失活。动力学研究表明，该反应在底物和催化剂方面均为一阶反应。模型 11В NMR 实验证实，反应是通过中间体单体 Me2N=BH2 的形成进行的，该单体迅速二聚为 (Me2N-BH2)2。根据初步的 31Р NMR 结果和已发表的数据，提出了 DMAB 脱氢并形成不稳定氢化物中间体 [Cp*RhH{Ph2P(N-p-Tol)(NR)}] (IVa, IVb) 的机理。

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来源期刊

Accounts of Chemical Research 化学-化学综合

CiteScore

31.40

自引率

1.10%

发文量

312

审稿时长

2 months

期刊介绍： Accounts of Chemical Research presents short, concise and critical articles offering easy-to-read overviews of basic research and applications in all areas of chemistry and biochemistry. These short reviews focus on research from the author’s own laboratory and are designed to teach the reader about a research project. In addition, Accounts of Chemical Research publishes commentaries that give an informed opinion on a current research problem. Special Issues online are devoted to a single topic of unusual activity and significance. Accounts of Chemical Research replaces the traditional article abstract with an article "Conspectus." These entries synopsize the research affording the reader a closer look at the content and significance of an article. Through this provision of a more detailed description of the article contents, the Conspectus enhances the article's discoverability by search engines and the exposure for the research.