Ab Initio Molecular Dynamics Study of Hydrogen Cleavage by a Lewis Base [tBu₃P] and a Lewis Acid [B(C₆F₅)₃] at the Mesoscopic Level—Dynamics in the Solute–Solvent Molecular Clusters

Abstract

With the help of state-of-the-art ab initio molecular dynamics methods, we investigated the reaction pathway of the {tBu3 P + H2 + B(C6 F5 )3 } system at the mesoscopic level. It is shown that: i) the onset of H2 activation is at much larger boron⋅⋅⋅phosphorus distances than previously thought; ii) the system evolves to the product in a roaming-like fashion because of quasi-periodic nuclear motion along the asymmetric normal mode of P⋅⋅⋅HH⋅⋅⋅B fragment; iii) transient configurations of a certain type are present despite structural interference from the solvent; iv) transient-state configurations with sub-picosecond lifetime have potentially interesting infrared activity in the organic solvent (toluene) as well as in the gas phase. The presented results should be helpful for future experimental and theoretical studies of frustrated Lewis pair (FLP) activity.

Reaction mechanism of hydrogen activation by frustrated Lewis pairs

“…The results showed that H2 activation by tBu3P/B(C6F5)3 pair mainly consists of two elementary steps: hydride (H − ) transfer to B and proton (H + ) transfer to P, which is quite consistent with the previous AIMD studies. [53][54][55] The important insight made by the authors is the explanation of the roles of LA and LB. 56 On the one hand, the results showed that the H − transfer to B has a much higher energy barrier than that of H + transfer to P (11.1 versus 0.8 kcal mol −1 ).…”

Chemistry of Intermolecular Frustrated Lewis Pairs in Motion: Emerging Perspectives and Prospects

“…In a typical reaction scenario of [ 2 ], a trajectory is trapped in the TS region for a sub‐picosecond period of time 47–49. Such a scenario takes place irrespective of the choice of the origin of trajectories (i.e., NACs or the TS structure).…”

Ab Initio Molecular Dynamics with Explicit Solvent Reveals a Two‐Step Pathway in the Frustrated Lewis Pair Reaction

“…Solvent effects-that is, the group of effects that as olvent has on chemical reactivity-have long been of generali nterest in chemistry. [21][22][23][24][25][26] In theoretical studies, the complexity of the problem calls for an approximate treatment of the solventa nd the solute-solvent interactions. The so-calledi mplicitm odels describe the solventa sacontinuous medium surrounding the solutei na ccordance to its van der Waals surface-that is, af amilyo fp olarizable continuumm odels( PCMs) using the self-consistentr eaction field (SCRF) approach with the solute cavity composed of overlapping spheres.…”

“…Ac oncern is that the FLP reaction" LB + LA + X" might be such ac ase. [25] It is wellu nderstood that the non-covalent interactions between ab ulky Lewis base and ab ulky Lewis acid-for example, CH···X interactions involving the electronegative atom Xs uch as F(or Cl)-are highlyr elevant forthe reaction mechanism. [10,38] But, let us not forget that these non-co-valentL B···LA interactions are essentially of the same kind as the solute-solvent interactions-for example, CH···Cl(DCM) and CH(DCM)···F for tBu 3 Pa nd B(C 6 F 5 ) 3 in dichloromethane (DCM), respectively.…”

“…The initial solute-solvent molecular clusters for BOMDs imulation of CO 2 interactions with tBu 3 Pa nd B(C 6 F 5 ) 3 were obtained similarly to our earlier work. [25] In short, the procedure is as follows. From long-durationB OMD simulations of the {tBu 3 P + B(C 6 F 5 ) 3 }s ystem plus about 100 solvent molecules (toluene or dichloromethane) at 300 K, we have randomly selected snapshotso ft he solute-solvent molecularc luster for further all-atom geometry optimizations.…”