Computational Study of Triphosphine-Ligated Cu(I) Catalysts for Hydrogenation of CO₂ to Formate

Abstract

The catalyzed hydrogenation of CO2 to formate via a triphosphine-ligated Cu­(I) was studied computationally at the density functional theory level in the presence of a self-consistent reaction field. Of the four functionals benchmarked, M06 was generally in the best agreement with the available experimentally estimated values. Two bases, DBU and TBD, were studied in the context of two proposed mechanisms in the MeCN solvent. Activation of H2 was explored by using LCu­(DBU)+ to form LCuH. Dissociation of a ligand arm results in higher barriers to form the key hydride complex, LCuH. The preferred mechanism passes through a transition state, where the H2 has one H atom interacting with the copper center and the other H atom interacting with the N atom of the base, similar to H2 insertion into a frustrated Lewis pair. There is no significant difference between the choice of a base, DBU or TBD, with respect to the proposed mechanisms. We propose that the experimentally observed differences between DBU and TBD reactivities for this mechanism are due to off-pathway changes.

Alkoxide-Decorated Copper Nanoparticles on Amidine-Modified Polymers as Hydrogenation Catalysts for Enabling H2 Heterolysis

“…A vicinally-oriented free DBU group or BTMG in the liquid phase can deprotonate the alcoholic solvent near the Cu species to promote alkoxide generation (c-i) and (c-ii). Similar to homogeneous formate synthesis, 59 vicinal DBUassisted H 2 activation by formato-Cu species (reaction d) may be assumed as an alternative pathway to complete the cycle. However, the observed catalytic function suggests that the FLP-like activation pathway was not favored.…”

“…In subsequent studies, a tridentate phosphine−Cu(I) complex served as a decent catalyst for CO 2 hydrogenation using the DBU base, 57,58 and a density functional theory (DFT) study proposed the frustrated Lewis pair (FLP)-like activation of H 2 by insertion into the Cu−DBU bond. 59 Heterolytic H 2 activation by the molecular Cu species ensures that incorporating a Lewis basic counterpart into Cu nanostructures allows unhindered access to Cu hydrides on the heterogeneous hydrogenation catalyst. Recently, we used an amidine-modified polymer, polystyrene-bound DBU (PS-DBU), as a potent Lewis basic support to immobilize Cu species.…”

“…Meanwhile, in our ongoing study on the homogeneous hydrogenation of CO 2 to formate salts via heterolytic H 2 cleavage in the presence of highly basic amidines or guanidines, the use of 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU) effectively induced the catalytic function of Cu by acting as a supporting ligand and base. In subsequent studies, a tridentate phosphine–Cu­(I) complex served as a decent catalyst for CO 2 hydrogenation using the DBU base, , and a density functional theory (DFT) study proposed the frustrated Lewis pair (FLP)-like activation of H 2 by insertion into the Cu–DBU bond …”

Silicon and Carbon nanocages as catalysts of CO 2 reduction reaction

“…The structures of complexes of important intermediates of processes of CO 2 reduction reactions with acceptable mechanisms are optimized and their frequencies of these optimized complexes are calculated by PW91PW91/6-311 + G (2d, 2p) model and M06-2X/cc-pVQZ model [25][26][27]. The calculated adsorption energies (∆E adsorption ) of CO 2 and other possible intermediates of processes of CO 2 reduction reactions on surfaces of Ni-C 50 and Ni-Si 50 nanocages are calculated [28][29][30] as following: (1) where the E nanocage are total energies of Ni-C 50 and Ni-Si 50 nanocages and E specie are total energies of possible intermediates of processes of CO 2 reduction reactions and the E specie−nanocage are total energies of complexes of Ni-C 50 and Ni-Si 50 nanocages with intermediates of processes of CO 2 reduction reactions [31][32][33]. The changing of Gibbs free energy (∆G reaction ) of reaction steps of possible mechanisms for CO 2 reduction reactions on surfaces of Ni-C 50 and Ni-Si 50 nanocages are calculated [34][35][36][37] as following:…”

Challenges and recent advancements in the transformation of CO2into carboxylic acids: straightforward assembly with homogeneous 3d metals

“…Recently, in 2021 Dixon et al performed computational studies of Cu( i ) catalysts for the reduction of CO 2 to formate. 229 In this model, the solvent is displaced by the base to form the catalyst resting state. This resting state reacts with H 2 to form LCuH, which in turn inserts CO 2 (Scheme 34).…”