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

The role solvent plays in reactions involving frustrated Lewis pairs (FLPs)-for example, the stoichiometric mixture of a bulky Lewis acid and a bulky Lewis base-still remains largely unexplored at the molecular level. For a reaction of the phosphorus/boron FLP and dissolved CO2 gas, first principles (Born-Oppenheimer) molecular dynamics with explicit solvent reveals a hitherto unknown two-step reaction pathway-one that complements the concerted (one-step) mechanism known from the minimum-energy-path calculations. The rationalization of the discovered reaction pathway-that is, the stepwise formation of P-C and O-B bonds-is that the environment (typical organic solvents) stabilizes an intermediate which results from nucleophilic attack of the phosphorus Lewis base on CO2. This finding is significant because presently the concerted reaction-path paradigm predominates in the rationalization of FLP reactivity. Herein we point out how to attain experimental proof of our results.