Computational Study of van der Waals Complexes between Borylenes and Hydrocarbons

Abstract

The addition of borylenes (RB) to prototypical carbon-carbon multiple bonds (ethyne, ethene) and the insertion into a C-H bond of methane involves weakly bound van der Waals complexes of the reaction partners according to computational chemistry methods. Geometries of all complexes were optimized using spin-component scaled second-order Møller-Plesset perturbation theory (SCS-MP2) in combination with a quadruple-ζ (def2-QZVP) basis set. Energies were further refined using the coupled-cluster (CCSD(T)) method in combination with basis sets up to quadruple-ζ quality (def2-QZVP and aug-cc-pVTZ). All of the complexes of borylenes studied correspond to shallow minima on their potential-energy surfaces. Borylene complexes with ethyne are the most stable and those with methane are the least stable ones. Aminoborylene complexes BNHR with ethyne and ethene are stabilized mainly by NH⋅⋅⋅π interactions. Symmetry-adapted perturbation theory (SAPT) was performed to analyze the nature of the interaction between borylene molecules and hydrocarbons. Most of the ethyne complexes are dominated by electrostatic interactions, whereas for most of the ethene and all of the methane complexes the interaction is mainly dispersive.

Coordination and Insertion: Competitive Channels for Borylene Reactions

“…The transition state structures that were found to link the coordinated CF 3 H and BR systems (Figure a) to the insertion product (Figure c) are shown in Figure . They are quite similar to structures identified in refs and for borylene insertion into the CH bonds of methane.…”

“…The chemistry of borylenes, including base-stabilized borylenes, has expanded in the past decade to include careful assessments of their potential viability as ligands. ,,, We consider in the next sections the tendencies of borylene species to engage in σ-hole interactions and to form complexes with Lewis acids, specifically monofluoromethane and its Si and Ge analogues.…”

“…So, although B–R species are usually generated at high temperatures and tend to be unstable, the literature on monovalent boron continues to grow. , Efforts have been made in recent years to locate free borylenes (B–R), terminal borylenes coordinated to other atomic centers (Q←B–R), and metal–borylene complexes (MB–R)examples of which are already known. , A borylene dicarbonyl complex was reported recently, reaffirming the ability of borylenes to serve as Lewis acids (Q → B–R) and as “metallomimics”, forming coordination complexes with ligands that donate into one or both of the empty p-orbitals of boron in B–R. Borylenes stabilized by donors, including heterocyclic carbenes, have also been identified experimentally in the past few years. , Additionally, borylene insertion into C–H and C–C single bonds and cycloaddition to higher order bonds have been identified experimentally ,,,, and investigated computationally. , In those insertion and addition reactions, the boron center in the BR molecule plays dual roles: as acceptor (electrophile), by its empty p-orbitals, and as σ-donor (nucleophile) by its lone pair.…”

“…15,19 Additionally, borylene insertion into C−H and C−C single bonds and cycloaddition to higher order bonds have been identified experimentally 4,10,12,20,21 and investigated computationally. 22,23 In those insertion and addition reactions, the boron center in the BR molecule plays dual roles: as acceptor (electrophile), by its empty p-orbitals, and as σ-donor (nucleophile) by its lone pair.…”

Photoreactions of Phenylborylene with Dinitrogen and Carbon Monoxide

“…The available experimental evidence from trapping studies suggests that borylenes RB are highly reactive transient species. Computational analysis of the reactions with prototypical carbon multiple bonds has revealed that borylenes behave as electrophilic species because of their vacant p orbitals. , The transition states for cycloaddition resemble those of carbenes, and changes in barrier heights, distances, and angles can similarly be associated with varying borylene philicities. , …”