Reactivities and Bohmian perspectives on pnictogen N-heterocyclic carbene analogues reactions with methane and ethene

Abstract

The chemical reactions of monocationic pnictogen N-heterocyclic carbene (NHC) analogues [(tBu2DAB)M+, M = N, P, As, Sb, and Bi, and tBu2DAB =1,4-tert-butyl-1,4-diaza-1,3-butadiene] with methane and ethene are studied by the density functional theory. The activation energies and reaction enthalpies are analyzed by the natural energy decomposition analysis (NEDA) to understand the reactivities of the reactions. The activation energies and reaction enthalpies of the ethene reactions, and the activation energies of the methane reactions decrease with the atomic numbers of the pnictogen elements M. However, the reaction enthalpies of the methane reactions do not follow a monotonic trend because the size and geometry of the methane structure are better accommodated by the product states of (tBu2DAB)P+ than (tBu2DAB)N+. The NEDA also suggests that the carbene and hydrocarbon fragments are subject to singlet–singlet interactions for all reactions of this work. The electronic and energetic structures of the reactions involving the N-centered NHC reactant, (tBu2DAB)N+ characteristically differ from all other carbenic reactants, which is in agreement with the well-known fact that the 2s and 2p orbitals of the N atom are more amenable to hybridization than the higher s and p orbitals of other pnictogen elements. The Bohmian perspectives on the stationary states of the pnictogen NHC reactions are also explored. It is found that the Bohmian potentials may reveal some bonding informations of the complexes, but further investigations are still required for deeper understanding.