Revisiting mechanistic studies on dinitrogen reduction to ammonia by an iron dinitrogen complex as nitrogenase mimic. Issue 24 (13th July 2019)

• Record Type: Journal Article
• Authors: Vyas, Nidhi; Pandey, Bhawana; Ojha, Animesh; Grover, Abhinav
• Is Part Of: International journal of quantum chemistry. Volume 119:Issue 24(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-07-13
• Subjects: DFT -- NBO -- nitrogenase enzyme; Quantum chemistry -- Periodicals; 541.28
• DOI: 10.1002/qua.26025
• Languages: English
• ISSNs: 0020-7608

Abstract

Abstract: Conversion of free nitrogen to ammonia is a required chemical reaction for both biologically and industrially but their mechanism, specifically the attachment of electron and proton transfer during the cycle, is still doubtful. In this view, a thorough knowledge of the mechanism is crucial. In this article, we employ a density functional method on [(TPB)FeN2 ] −, the iron‐dinitrogen complex carrying the tris(phosphine)borone (TPB) ligand, for the ammonia production with the inclusion of electrons and protons. The electronic structures, reactivity, and mechanistic possibilities have been extensively explored using the B3LYP functional. Both asymmetric and symmetric pathways in addition to the possible intermediates species and transition states are considered here. Our results conclude tremendously small energy barrier of 3.5 kJ/mol for the first protonation ( S = 1/2) for the N─H bond activation by the [(TPB)FeN2 ] − species. However, high activation barrier for the third protonation was estimated to be 78.5 kJ/mol, which is explained by the high energy of the unoccupied δx 2 ‐y 2 orbital in 1 ts4 species. The computed spectroscopic parameters such as absorption, electron paramagnetic resonance, and Mössbauer also established the electronic structure details of the species. The calculated parameters are compatible with the experimental results. Abstract : In biology, the nitrogenase enzymes are able to efficiently catalyze the production of NH3 from N2 at ambient temperature and pressure. Therefore, it is of great importance to clarify the mechanistic details of the enzymatic N2 fixation, specifically the order of proton and electron attachment. Therefore, its reactivity and the intricate mechanistic details of ammonia production have been explored by explaining molecular orbital analysis and spectroscopic calculations.