A molecular electron density theory study of the insertion of CO into frustrated Lewis pair boron-amidines: a [4 + 1] cycloaddition reaction
The insertion of CO into hydrogenated boron-amidine 1 yielding five-membered diazaborolone (5DAB) 3 has been studied within the molecular electron density theory (MEDT) at the DFT ωB97X-D/6-311G(d,p) level. This is a domino process comprised of two consecutive reactions: (i) the dehydrogenation of 1 yielding the frustrated Lewis pair (FLP) boron-amidine 4, which quickly equilibrates with four-membered diazaborolone (4DAB) 2; and (ii) the addition of CO into FLP 4, yielding the final 5DAB 3. Analysis of the Gibbs free energies indicates that the extrusion of H2 demands a high ΔG≠ of 28.6 kcal·mol-1, being endergonic by 6.7 kcal·mol-1. The subsequent addition of CO into FLP 4 presents a low Δ…
A computational and conceptual DFT study on the mechanism of hydrogen activation by novel frustrated Lewis pairs.
A computational and conceptual density functional theory (DFT) study on the mechanism of molecular hydrogen activation by a set of three frustrated Lewis pairs (FLPs) was performed at the ωB97X-D/6-311G(d,p) level of theory. A reduced model and other two prototypes derived from experimental data, based on the donor nitrogen and acceptor boron atoms, were used. Analysis based on the energy results, geometries and the global electron density transfer at the TSs made it possible to obtain some interesting conclusions: (i) despite the well-known very low reactivity of molecular hydrogen, the catalytic effectiveness of the three FLPs produces reactions with almost unappreciable activation energi…