Halide‐Triel Bonds between R₃SiX (X=F, Cl and Br) and TrY₃ (Tr=Al, B and Ga)

Abstract

Halide‐triel bonds between halosilane donors and alane/borane/gallane acceptors are investigated considering 24 model complexes using quantum chemical calculations. Nature and strength of Si−X….Tr interactions (X=F, Cl, Br and Tr=Al, B, Ga) binding these complexes has been studied using Electrostatic Potential (ESP), Quantum Theory of Atoms in Molecules (QTAIM), Natural Bond Orbital (NBO), and Energy Decomposition Analysis (EDA) techniques. Basis Set Superposition Error (BSSE) corrected binding energy of the complexes ranges from −3.19 to −29.40 kcal mol−1. QTAIM parameters Laplacian and the total electron density at the Bond Critical Points (BCPs) indicate that the halide‐triel bonds studied here are largely electrostatic in nature (closed‐shell interactions); this has also been revealed through ESP analysis and EDA scheme. In addition, role of charge transfer in these halide‐triel bonds has also been established through NBO analysis. Two charge transfer orbital interactions are responsible for the primary interaction Si−X….Tr: n(F/Cl/Br)→n*(Al/Ga/B)4pt ${n(F/Cl/Br)\to {n}^{^{\ast}}(Al/Ga/B){\rm \ }}$ and σ(Si−X) →4ptn*(Al/Ga) ${\to {\rm \ }{n}^{^{\ast}}(Al/Ga)}$ . EDA analysis identifies electrostatic term as the biggest contributor towards the binding of the complexes followed by the polarisation and dispersion terms in most of the complexes. Results of this study have relevance in the Si−F bond activation methodology in organic synthesis.