Computational study of the CO$$_2$$ hydrogenation to formic acid catalyzed by a P,P-bidentate copper(I) complex

Abstract

Abstract Context Carbon dioxide (CO $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> ) hydrogenation is a promising route for converting CO $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> into value-added products. This work presents a computational investigation of CO $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> hydrogenation to formic acid catalyzed by the copper(I) complex [CuI(dtbpf)], previously reported as the P,P-bidentate 1,1’-bis(di-tert-butylphosphino)ferrocene (dtbpf)-ligated copper(I) complex. We employ electronic structure methods to characterize the catalytic cycle, highlighting the role of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), a Lewis base, in H $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> heterolysis. Computational analyses revealed the interactions that govern Cu–H bond cleavage and Cu–O bond formation during the nucleophilic attack of the copper hydride on CO $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> , as well as the role of DBU in the catalyst regeneration. Good correspondence was obtained between experimental and computed turnover frequency (TOF) values. Additionally, correlations involving the P-Cu-P bite angle and other geometric parameters were used to rationalize the stability of Cu-containing reaction intermediates, thereby providing insights into the electronic and steric effects of the complexes on the overall catalytic efficiency. Methods Density functional theory (DFT) calculations at the B3LYP-D3/def2-TZVP//B3LYP-D3/def2-SVP (LanL2DZ for Cu) level were employed to examine the energy profile of the catalytic cycle. The energy span model (ESM) was used to quantify the turnover frequency (TOF) of the catalytic system. In addition, natural bond orbital (NBO), fuzzy bond order (FBO), and interaction region indicator (IRI) analyses were conducted to investigate the interactions within the complexes that govern the catalytic activity.