The high efficiency of widely applied Noyori-type hydrogenation catalysts arises from the N–H moiety coordinated to a metal centre, which stabilizes rate-determining transition states through hydrogen-bonding interactions. It was proposed that a higher efficiency could be achieved by substituting an N–M′ group (M′ = alkali metals) for the N–H moiety using a large excess of metal alkoxides (M′OR); however, such a metal-hydride amidate intermediate has not yet been isolated. Here we present the synthesis, isolation and reactivity of a metal-hydride amidate complex (HMn–NLi). Kinetic studies show that the rate of hydride transfer from HMn–NLi to a ketone is 24-fold higher than that of the corresponding amino metal-hydride complex (HMn–NH). Moreover, the hydrogenation of N-alkyl-substituted aldimines was realized using HMn–NLi as the active catalyst, whereas HMn–NH is much less effective. These results highlight the superiority of M/NM′ bifunctional catalysis over the classic M/NH bifunctional catalysis for hydrogenation reactions.
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The crystallographic data for the structures of [Mn]-2*, [Mn]-5, [Mn]-7 and [Mn]-9 reported in this work have been deposited at the Cambridge Crystallographic Data Centre (CCDC) under deposition numbers CCDC 2089177, 2128243, 2128247 and 2128248, respectively. The data supporting the findings of this study are available within the paper and its Supplementary Information.
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Financial support from the National Key R&D Program of China 2021YFF0701600 (Q.L.), the National Natural Science Foundation of China 22171159 (Q.L.), 21822106 (Q.L.), the Foundation of the Department of Education of Guangdong Province 2021KTSCX140 (Q.L.) and the China Postdoctoral Science Foundation 2020M680021 (Y.W.), 2021T140366 (Y.W.) is greatly appreciated. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. We thank the National Supercomputing Center, Zhengzhou. We are very grateful to the referees for their valuable comments and suggestions that improved the quality of this paper. We thank Y. Xia and R. Jian from Tsinghua University for high-resolution mass spectroscopy analysis of [Mn]-5. We also acknowledge G. Sun from Chongqing University for helpful discussions about theoretical calculations. This paper is dedicated to Prof. Matthias Beller on occasion of his 60th birthday.
The authors declare no competing interests.
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Supplementary Figs. 1–30, Tables 1–4, experimental procedures and characterization data, DFT calculation results, discussion and references.
x,y,z coordinates for DFT calculations.
Crystallographic data for compound [Mn]-2*; CCDC reference 2089177.
Crystallographic data for compound [Mn]-5; CCDC reference 2128243.
Crystallographic data for compound [Mn]-7; CCDC reference 2128247.
Crystallographic data for compound [Mn]-9; CCDC reference 2128248.
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Wang, Y., Liu, S., Yang, H. et al. Structure, reactivity and catalytic properties of manganese-hydride amidate complexes. Nat. Chem. 14, 1233–1241 (2022). https://doi.org/10.1038/s41557-022-01036-6
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