SE2 reaction in noncarbon system: Metal-halide catalysis for dehydrogenation of ammonia borane

Title
SE2 reaction in noncarbon system: Metal-halide catalysis for dehydrogenation of ammonia borane
Authors
한상수배성진
Keywords
Ammonia borane; Dehyrogenation; Metal-halide catalysis; SE2 reaction; First-prinicples calculation
Issue Date
2017-12
Publisher
Proceedings of the National Academy of Sciences of the United States of America
Citation
VOL 114, NO 52-13630
Abstract
An electrophilic substitution (SE) reaction of BN isosteres has been investigated for the dehydrogenation of ammonia borane (AB) by metal chlorides (MCl2) using various ab initio calculations. In contrast to the typical SE reaction occurring at the carbon atom, the nitrogen atom in AB serves as the reaction center for the SE reaction with the boron moiety as the leaving group when the MCl2 approaches the AB. The SE2 backside reaction is favored as a trigger step for the dehydrogenation of AB by the MCl2. The SE2 reaction is found for 3d-transition-metal chlorides (e.g., FeCl2, CoCl2, NiCl2, CuCl2, and ZnCl2), while PdCl2 leads to the dehydrogenation of AB by a direct B– H σ-bond activation, similar to most organometallic catalysts. Interestingly, the polymerization of AB promoted by MCl2 can be explained with the similar SE2 mechanism, and the dehydrogenation of the BN derivative 3-methyl-1,2-BN-cyclopentane (CBN) bearing a carbon backbone ring also follows the SE2 reaction. In particular, the experimental observation that the use of metalchloride catalysis decreases the by-products obtained during the hydrogenation of AB can be explained by our mechanism involving the SE2 reaction. This work is helpful for the development of novel metal-halide catalysts for practical hydrogen storage materials, including the BN moiety.
URI
http://pubs.kist.re.kr/handle/201004/67169
ISSN
0027-8424
Appears in Collections:
KIST Publication > Article
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