Sequestration of Carbon Dioxide with Frustrated Lewis Pairs Based on N-Heterocycles with Silane/Germane Groups

Abstract

Frustrated Lewis pairs (FLPs) based on nitrogen heterocycles (pyridine, pyrazole, and imidazole) with a silane or germane group in the α-position of a nitrogen atom have been considered as potential molecules to sequestrate carbon dioxide. Three stationary points have been characterized in the reaction profile: a pre-reactive complex, an adduct minimum, and the transition state connecting them. The effect of external (solvent) or internal (hydroxyl group) electric fields in the reaction profile has been considered. In both cases, it is possible to improve the kinetics and thermodynamics of the complexation of CO 2 by the FLP and favor the formation of adducts.

Use of 5,10‐Disubstituted Dibenzoazaborines and Dibenzophosphaborines as Cyclic Supports of Frustrated Lewis Pairs for the Capture of CO2

“…In the calculated coordinate of the reaction between the selected DHA derivatives and CO 2 three stationary points were found, a minimum corresponding to a complex, another minimum corresponding to an adduct and a TS connecting them (Figure 5). Similar profiles have been described for other reactions with CO 2 [22,78–81,84] …”

“…Similar profiles have been described for other reactions with CO 2 . [22,[78][79][80][81]84] From the Monomers to the Complexes As shown in Figure 5, all complexes are more stable than the entrance channel, and very close in energy (around À 15 kJ • mol À 1 ). The complexes formed with phenyl derivatives (i. e. N-Ph-B-Cl and P-Ph-B-Cl) are more stable than those unsubstituted in the pnicogen atoms (N-H-B-Cl and P-H-B-Cl) by 3 kJ • mol À 1 and 1 kJ • mol À 1 , respectively.…”

“…In addition, FLPs are being used to activate CO 2 and reduce it to useful chemicals, [5,31–33] like for example methanol, [24,25,34] methane, [35] formates, [17,31] methoxysilane, [36] in a catalytic fashion or not. Theoretical studies were added to those experimental results, to better understand the reaction mechanism behind the capture and reduction of CO 2 , as well as proposing a systematic way to improve the existing FLP playing with the intrinsic properties of the atoms involved [18,22,37–51] …”

“…Theoretical studies were added to those experimental results, to better understand the reaction mechanism behind the capture and reduction of CO 2 , as well as proposing a systematic way to improve the existing FLP playing with the intrinsic properties of the atoms involved. [18,22,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] Considering phosphorus as a LB, boron as a LA, and that the distance between both atoms, may be imposed by a ring structure and/or large substituents, it is possible to design FLP systems to ). [52][53][54][55][56][57][58] The p roperties as se (CSD), twe ed to a varie sis set [61] ms at the The Natural Bond Orbital method [63] was applied on some compounds to explain the orbital interactions utilizing the NBO-7.0 program.…”

Boron based intramolecular heterocyclic frustrated Lewis pairs as organocatalysts for CO2 adsorption and activation

“…Since then, a vast variety of Boron/Phosphorus, Boron/Aluminium and Boron/Nitrogen based intermolecular and intramolecular FLPs have been explored for the capture or catalytic conversion of CO 2. 63–73 Among these FLPs the IFLP projects an interesting class of organic compounds for CO 2 sequestration because the intramolecular disposition of Lewis base and acid diminishes the entropic effects by adding rigidity to the system. Thus, in the present work we have investigated the intramolecular FLP based on N‐heterocycles with boron group at α‐position to the nitrogen atom (Figure 2) for capture and activation of CO 2 by forming adducts.…”