Cycloaddition Reactions between H₂C = CHR (R = H, CN, CH₃) and a Cyclic P/B Frustrated Lewis Pair: A DFT Study

Abstract

The cycloaddition of ethylene, cyanoethylene, and propylene to a five-membered P/B frustrated Lewis pair (FLP) is shown to be highly favorable under normal conditions, as confirmed by the computed thermodynamic and kinetic data. All of these cycloaddition reactions are concerted as highlighted by the intrinsic reaction coordinate (IRC) and Wiberg bond index calculations. Almost 70% of the reaction force is required for structural orientation to initiate electronic activity. The reactions are interpreted by the frontier molecular orbital (FMO) analysis and conceptual density functional theory (DFT)-based reactivity descriptors. It appears that ethylene and propylene will act as nucleophiles, while the FLP will act as an electrophile throughout the cycloaddition reaction, however, cyanoethylene will act as an electrophile and the FLP as a nucleophile. Regioselectivities of the cycloadditon of cyanoethylene and propylene to the FLP are further verified through philicity and dual descriptors. It is demonstrated that an FLP can be forced to act as an electrophile or a nucleophile by intelligently selecting its partner in a cycloaddition reaction. Even the P and B centers would behave differently within the same FLP. This strategy may be properly exploited by the experimentalists in designing a suitable reaction for the synthesis of any useful molecule possessing the desired property.

Activation of Small Molecules and Hydrogenation of CO2 Catalyzed by Frustrated Lewis Pairs

“…(Adapted from ref. [93] with permission from American Chemical Society. Copyright © 2022, American Chemical Society).…”

“…The bond distances are provided in Å unit. (Adapted from ref [93]. with permission from American Chemical Society.…”

Insights into the Factors Controlling the H–H Bond Cleavage Reactions by Five-Membered G13/P (G13 = Group 13 Element) and B/G15 (G15 = Group 15 Element) Frustrated Lewis Pairs

“…The abovementioned experimental findings inspired the present theoretical work. To our knowledge, substantially limited attention has been paid to the study of the influence of the nature of either Lewis acids or bases on the reactivity of such cyclic five-membered FLPs. − To further understand the relationship between the nature of active sites of heterocyclic FLPs and their related reactivity, we investigated herein the heterolytic cleavage of dihydrogen by five-membered FLPs, which is the simplest and most essential chemical reaction in FLP-related chemistry. In the present study, the investigation of crucial dihydrogen activation reactions by cyclic five-membered G13/P-Rea (G13 = group 13 element) and B/G15-Rea (G15 = group 15 element) FTPs, which are represented in eqs and , respectively, was undertaken …”

Significant Insight into the Origin of Reaction Barriers Determining Dihydrogen Activation by G13-P-P (G13 = Group 13 Element) and G15-P-Ga (G15 = Group 15 Element) Frustrated Lewis Pairs

“…The purpose of the present work is thus to enlarge the experimental findings by using theoretical methods to explore the origin of activation barriers and rationalize the reactivity of these heteroatomic double bonds between group 13/15 elements of FLP-related molecules. In fact, designing and developing the FLP-associated compounds involving a G13-acceptor (G13 = B, Al, Ga, In, and Tl) or a G15-donor (G15 = N, P, As, Sb, and Bi) that can act as a good dihydrogen catcher are still rather poorly understood (see below). ,,,,,,− A study of the dihydrogen activation reactions involving the multiply bonded P-bridged G13-P-P FLP (eq ) and Ga-P-Ga15 FLP (eq ) molecules was thus undertaken. − We hope that the theoretical conclusions arising from this work can provide a better understanding of which factor is responsible for the feasible reactivity of dihydrogen activation of these FLP-type molecules with a G13/G15 multiply bonded skeleton for the design and synthesis of new FLP-related dihydrogen catchers. …”