Two Co(I) hydrides containing the tripodal polyphosphine ligand EP, (κ-EP)Co(H) [E(CHCHPPh); E = N (1), P (2)], have been exploited as ammonia borane (NHBH, AB) dehydrogenation catalysts in THF solution at T = 55 °C. The reaction has been analyzed experimentally through multinuclear (B, P{H}, H) NMR and IR spectroscopy, kinetic rate measurements, and kinetic isotope effect (KIE) determination with deuterated AB isotopologues. Both complexes are active in AB dehydrogenation, albeit with different rates and efficiency. While 1 releases 2 equiv of H per equivalent of AB in ca. 48 h, with concomitant borazine formation as the final "spent fuel", 2 produces 1 equiv of H only per equivalent of AB in the same reaction time, along with long-chain poly(aminoboranes) as insoluble byproducts. A DFT modeling of the first AB dehydrogenation step has been performed, at the M06//6-311++G** level of theory. The combination of the kinetic and computational data reveals that a simultaneous B-H/N-H activation occurs in the presence of 1, after a preliminary AB coordination to the metal center. In 2, no substrate coordination takes place, and the process is better defined as a sequential BH/NH insertion process on the initially formed [Co]-NHBH amidoborane complex. Finally, the reaction of 1 and 2 with NH-acids [AB and MeNHBH (DMAB)] has been followed via VT-FTIR spectroscopy (in the -80 to +50 °C temperature range), with the aim of gaining a deeper experimental understanding of the dihydrogen bonding interactions that are at the origin of the observed H evolution.
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http://dx.doi.org/10.1021/acs.inorgchem.6b02673 | DOI Listing |
Polymers (Basel)
December 2024
Center for Sustainable Future Technologies-CSFT@POLITO, Via Livorno 60, 10144 Torino, Italy.
The utilization of hydrogen in safety conditions is crucial for the development of a hydrogen-based economy. Among all methodologies, solid-state hydrogen release from ammonia borane through thermal stimuli is very promising due to the high theoretical hydrogen release. Generally, carbonaceous or inorganic matrices have been used to tune the reactivity of ammonia borane.
View Article and Find Full Text PDFJ Colloid Interface Sci
December 2024
School of Materials Science and Engineering, Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, Hebei University of Technology, Tianjin 300130, China. Electronic address:
Ammonia borane (NHBH, AB) is considered a promising chemical hydrogen storage material. The development of efficient, stable, and economical catalysts for AB hydrolysis is essential for realizing the hydrogen energy economy. In this study, a series of p-p heterojunction catalysts, labeled M (P/S/Cl)-CuCoO, were fabricated using the high-temperature vapor phase method to achieve anionic interface gradient doping.
View Article and Find Full Text PDFLangmuir
December 2024
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
The development of effective catalysts for hydrogen (H) generation from chemical hydrides is essential for advancing hydrogen-based energy technologies. Herein, we synthesized a Pd-dispersed CPO-27 catalyst exhibiting exceptional performance for hydrolysis of two boron-based chemical hydrides, i.e.
View Article and Find Full Text PDFChemistry
December 2024
Leibniz Institute for Catalysis Rostock (LIKAT), Albert-Einstein-Str. 29a, 18059, Rostock, Germany.
Ammonia borane and amine boranes are main group analogues of alkanes, which are characterised by their large gravimetric hydrogen content. This hydrogen can be released in dehydrocoupling and dehydropolymerisation reactions to obtain B-N oligomers and polymers that are of importance as precursors for functional B-N materials. Furthermore, amine boranes are potent reagents for application in transfer hydrogenation reactions, representing a versatile, easy-to-handle alternative to the use of gaseous hydrogen for the reduction of organic compounds.
View Article and Find Full Text PDFChem Asian J
December 2024
Department of Chemistry, Indian Institute of Technology Bhilai, Durg, Chhattisgarh, 491002, India.
A simple and sustainable protocol has been developed to reduce isocyanates to the N-methyl anilines under metal-free conditions. The reaction proceeds with BF ⋅ OEt as a catalyst and ammonia borane as a hydrogen source in THF at room temperature, leading to the formation of a wide range of substituted aniline derivatives. Control experiments and deuterium labeling studies were performed to understand the mechanism of the present procedure.
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