Chemical reactivity of the frustrated Lewis pairs in borophosphines: a theoretical analysis of their Lewis acidity, Lewis basicity and Fukui function

摘要

The chemical reactivity of a set of borophosphines of the general formula R2B-G-PY2, where G is the connector group between the Lewis acidic site, a borane group, and the Lewis basic site, a phosphine fragment, is theoretically investigated through their Lewis acidity and Lewis basicity, as well as the location of the Fukui function and the shape of the molecular electrostatic potential. The role of some global reactivity descriptors, like the vertical ionization potential, I, and the vertical electron affinity, A, is also analyzed in order to gain a deeper insight on the intrinsic chemical reactivity of these borophosphines. We also use the energies involved in the formation of the adducts between the borophosphine and the ions H- and H+ to estimate the Lewis acidity and Lewis basicity, respectively; by their nature, these energies represent local reactivity descriptors. Some of these borophosphines are able to activate the covalent bond in the hydrogen molecule. Possible paths for the hydrogen release reaction from the zwitterion RHB-G-PH are studied using the mentioned quantities, suggesting that an intramolecular hydride shift mechanism seems to be more favorable than a proton migration process. The acceptor Fukui function f (+)(r) proved to be useful to identify the acidic molecular sites for the interaction with the hydride ion and the relative stability of the corresponding adducts is related to the relative values of this function.