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Metal‐Free Activation of Enthalpically Strong Bonds: Unraveling the Potential of Hitherto Unexplored Singlet Carbenes
Author(s) -
Bharadwaz Priyam,
Dewhurst Rian D.,
Phukan Ashwini K.
Publication year - 2018
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201800873
Subject(s) - chemistry , electrophile , carbene , nucleophile , alkyl , singlet state , computational chemistry , reactivity (psychology) , phosphine , gibbs free energy , photochemistry , medicinal chemistry , stereochemistry , organic chemistry , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics , nuclear physics , excited state
Density functional theory calculations have been carried out on a number of ambiphilic and electrophilic carbenes (both experimentally known and computationally designed) to understand their reactivity profile towards the activation of thermally robust bonds. Based on the calculated values of activation energy barriers, it was found that for ammonia (NH 3 ), most of the molecules favor an electrophilic mode of activation. On the other hand, even though the electrophilic pathway is found to be more favorable than the nucleophilic one for activation of phosphine (PH 2 Ph) by majority of the carbenes, the barrier heights for both pathways are calculated to be comparable for diamidocarbene (DAC), cyclic amino aryl carbenes (CAArCs) and bicyclic alkyl amino carbene (BICAAC). In agreement with their better electron donation and acceptance abilities, the hitherto unexplored BICAAC, CAArCs and cyclic alkyl amido carbenes (CAAmC) are predicted to be more effective than cyclic alkyl amino carbenes (CAACs) towards the activation of both ammonia and phosphine. For the activation of silane (SiH 3 Ph), a hydride transfer pathway is found to be more favorable than the proton transfer pathway. Further, the calculated values of total Gibbs free energies and activation energy barriers for the splitting of N−H, P−H and Si−H bonds by a majority of the molecules are found to be comparable to those of the experimentally evaluated ones, implying that these known ‐yet unexplored‐ carbenes may be considered as suitable candidates for the activation of such enthalpically strong bonds.