Carbon dioxide (CO2) capture has attracted considerable attention from both experimental and theoretical chemists. In comparison, Carbon disulfide (CS2) activation is less developed. Here, we carry out a thorough comparative density functional theory study to examine the reaction mechanisms of CS2 activation by five-membered heterocycles-bridged P/N frustrated Lewis pairs (FLPs).
Activation of the strongest triplet bond in molecular nitrogen (N2) under mild conditions is particularly challenging. Recently, its fixation and reduction were achieved by highly reactive dicoordinated borylene species at ambient conditions, ripping the limits of harsh reaction conditions by metallic species. Less reactive species with a facile preparation could be desirable for next-generation N2 activation. Now density functional theory calculations reveal that tricoordinated boranes could be a potential candidate of N2 activation/functionalization.
Aromaticity and frustrated Lewis pairs (FLP), two important concepts in chemistry, have attracted considerable attention from theoretical and experimental chemists. However, combining these two concepts together for H2 activation is less developed. Herein, we report a density functional theory study on antiaromaticity-promoted H2 splitting. The antiaromatic borole (as Lewis acid) and aromatic pyridine (as Lewis base) were introduced into the cyclooctetraene skeleton. Due to the geometric constraints, such systems can be classified as FLPs.
Molecular nitrogen (N2) is abundant in the atmosphere and nitrogen, found in many biomolecules, is an essential element of life. The Haber–Bosch process, developed over 100 years ago, requires relatively harsh conditions to activate N2 on the iron surface and generate ammonia for use as fertilizer or to produce other chemicals, leading to consumption of more than 2% of the world’s annual energy supply. Thus, developing approaches for N2 activation under mild conditions is particularly important and urgent.
Recent progress in frustrated Lewis pairs (FLPs) has attracted increasing attention. However, most of the FLPs are composed of Lewis basic phosphines and Lewis acidic boranes. In 2015, Kinjo and co-workers reported the first intramolecular boron–boron FLP, namely, 1,3,2,5-diazadiborinine (1), which showed high regioselectivity in the reactions with methyl trifluoromethansulfonate, phenylacetylene, and CO2. More interestingly, the activation of CO2 was found to be reversible when the temperature was elevated to 90 °C.
The sequestration of carbon disulfide (CS2), a common pollutant in environmental systems, is of great importance due to its physical harm to human beings. Compared with CO2 capture, that of CS2 is much less developed. The use of P/N-based frustrated Lewis pairs (FLPs) has been proven, both experimentally and theoretically, to be an alternative strategy to efficiently sequestrate CO2. Therefore, we pose the question of whether the analogue CS2 could also be sequestrated by the same FLPs, given that the C═S bond in CS2 is weaker than the C═O bond in CO2.