1. Mechanistic Insight of High-Valent First-Row Transition Metal Complexes for Dehydrogenation of Ammonia Borane
- Author
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Gogoi, Amrita, Dixit, Mudit, and Pal, Sourav
- Abstract
Designing an efficient and cost-effective catalyst for ammonia borane (AB) dehydrogenation remains a persistent challenge in advancing a hydrogen-based economy. Transition metal complexes, known for their C–H bond activation capabilities, have emerged as promising candidates for ABdehydrogenation. In this study, we investigated two recently synthesized C–H activation catalysts, 1(CoIV–dinitrate complex) and 2(NiIV–nitrate complex), and demonstrated their efficacy for ABdehydrogenation. Using density functional theory calculations and a detailed analysis, we elucidated the ABdehydrogenation mechanism of these complexes. Our results revealed that both complexes 1and 2can efficiently dehydrogenate ABat room temperature, although the abstraction of molecular H2from these complexes requires slightly elevated temperatures. We utilized H2binding free energy calculations to identify potentially active sites and observed that complex 2can release two equivalents of H2at a temperature slightly higher than room temperature. Furthermore, we investigated ABdehydrogenation kinetics and thermodynamics in iron (Fe)-substituted systems, complexes 3and 4. Our results showed that the strategic alteration of the central metal atom, replacing Ni in complex 2with Fe in complex 4, resulted in enhanced kinetics and thermodynamics for ABdehydrogenation in the initial cycle. These results underscore the potential of high-valent first-row transition metal complexes for facilitating ABdehydrogenation at room temperature. Additionally, our study highlights the beneficial impact of incorporating iron into such mononuclear systems, enhancing their catalytic activity.
- Published
- 2024
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