Trans Influence of Boryl Ligands in CO2 Hydrogenation on Ruthenium Complexes: Theoretical Prediction of Highly Active Catalysts for CO2 Reduction

Abstract

In this work, we study the trans influence of boryl ligands and other commonly used non-boryl ligands in order to search for a more active catalyst than the ruthenium dihydride complex Ru(PNP)(CO)H2 for the hydrogenation of CO2. The theoretical calculation results show that only the B ligands exhibit a stronger trans influence than the hydride ligand and are along increasing order of trans influence as follows: –H < –BBr2 < –BCl2 ≈ –B(OCH)2 < –Bcat < –B(OCH2)2 ≈ –B(OH)2 < –Bpin < –B(NHCH2)2 < –B(OCH3)2 < –B(CH3)2 < –BH2. The computed activation free energy for the direct hydride addition to CO2 and the NBO analysis of the property of the Ru–H bond indicate that the activity of the hydride can be enhanced by the strong trans influence of the B ligands through the change in the Ru–H bond property. The function of the strong trans influence of B ligands is to decrease the d orbital component of Ru in the Ru–H bond. The design of a more active catalyst than the Ru(PNP)(CO)H2 complex is possible.

Hidden Role of Borane in Directed C–H Borylation: Rate Enhancement through Autocatalysis

“…From complex 11 , a subsequent transition state is required to break this boron–hydrogen interaction to form complex 12 , which has a nitrogen-bound product and a terminal hydride trans to the nitrogen of the pyridyl ligand (a hydride trans to the pyridyl nitrogen is lower in energy than other isomers here and throughout the computations). This spatial arrangement is consistent with the work of Fujita and likely governed by the relative order of trans influence for the ligands involved: Bpin ≥ hydride ≥ pyridine ≥ tertiary amine . Complex 19 has a nitrogen-bound product and a σ-bound H–Bpin.…”

“…This spatial arrangement is consistent with the work of Fujita 102 and likely governed by the relative order of trans influence for the ligands involved: Bpin ≥ hydride ≥ pyridine ≥ tertiary amine. 103 Complex 19 has a nitrogen-bound product and a σbound H−Bpin.…”

Understanding the Influence of Lewis Acids on CO2 Hydrogenation: The Critical Effect Is on Formate Rotation

“…For insertion of CO 2 into metal–R bonds (R = hydride or alkyl/aryl), generally two mechanisms can be considered (Scheme A): i ) An inner sphere path , involving an interaction between CO 2 and the metal at the transition state for H–CO 2 bond formation (TS inn ). ,− Note that a precoordination of CO 2 is not required ,,,− Subsequently, the resulting η 1 -σ-intermediate rearranges (TS2) , to allow for formation of a κ 1 -O-(or κ 2 -O,O-)­carboxylate species. It is important to note that although TS inn and TS2 both are cyclic, they are entirely different transition states, whose optimized geometries will show distinct features.…”

Substituent’s Effects of PNP Ligands in Ru(II)-Catalyzed CO2 Hydrogenation to Formate: Theoretical Analysis Considering Steric Hindrance and Promotion of Hydrogen Bonding

“…For instance, Pidko and coworkers [23] developed a PNP-type Ru(II) dihydride complex ([Ru(PNP)(CO)H 2 ], i.e., PNP = 2,6-(ditert-butylphosphinomethyl)-pyridine) that increased the TOF to 1,892,000 h −1 at lower temperature and pressure (132 • C and 4.0 MPa). To elucidate the reaction mechanism of CO 2 hydrogenation to formate catalyzed by these PNP-type Ir or Ru complexes, a number of theoretical studies have been conducted, focused on understanding the rate-limiting step [24,25], the relation between the mechanism of CO 2 insertion and the property of the metal−hydride bond [26,27], the impact of metal−ligand cooperation [28,29], the trans influence of boryl ligands [30], the role of base, solvent, and noninnocent ligands [31], and so on [32][33][34][35]. Corminboeuf and coworkers [36], lately, analyzed in theory the pincer ligand effects by constructing various PNP, PNN, or NNN pincer ligands.…”