Unique Interactions Between Diborane and π Orbitals: Blue- or Red-Shifted Hydrogen Bonding?

Abstract

A new type of hydrogen-bonding interaction in the diborane (B 2H 6)...pi (benzene C 6H 6, 1,3-cyclopentadiene C 5H 6, and cyclobutadiene C 4H 4) system is identified with the natural bond orbital and atoms-in-molecules analyses based on ab initio calculations. In comparison with the symmetric and asymmetric stretching vibrational modes of the bridging hydrogen atoms in free B 2H 6, the frequencies of the symmetric mode are red-shifted for B 2H 6...C 6H 6 and B 2H 6...C 5H 6 but blue-shifted for B 2H 6...C 4H 4. The frequency blue shifts of the asymmetric mode are found for all three complexes; the most significant blue shift is 14.73 cm (-1) for the asymmetric mode in B 2H 6...C 4H 4. In these complexes, the electron-deficient three-center two-electron bond B-H 1-B facing the pi orbital is shortened, while the opposite B-H 2-B bond is elongated.

DFT Study on the Formation of Homo and Hetero dimers of BN‐doped Tetracyclic fused Aromatics via π⋯π Stacking

“…This validates the involvement of electrostatic interaction between the monomers to some extent. Recent literatures have also reported Δq values of about 0.002 e − and suggested the secondary role of electrostatic interaction in stabilizing the complexes formed via B‐H b ⋅⋅⋅π interaction ,…”

“…Besides, qualitative idea about the role of electrostatic component can also be predicted from the charge transfer (Δq) upon complexation . Therefore, Hirshfeld charges of the system before and after complexation are calculated and from their difference the extent of charge transfer is measured [charge transfer, Δq = charge of the site before complexation (q o ) − charge of the same site after complexation (q), in calculating Δq for un‐doped system charge C‐atom at the edge is considered whereas for doped system the charge at the dopant i.e; B and N is considered], presented in Table .…”

Enhancing the hydrogen bond between the bridged hydrogen atom of diborane and ammonia

“…Diborane has long been of interest to chemists because of its unusual structure and bonding [3][4][5][6], it is very useful in many synthetic applications [7], electrics industry [8], crystal engineering [9], and so on. It is worth mentioning that boranes have even been the subject of the Nobel Prize work by Brown [10].…”

The B–H–B bridging interaction in B-substituted oxazaborolidine–borane complexes: a theoretical study

“…A well-known example demonstrating strong unsaturation in boron compounds is borane, BH 3 , which easily dimerizes into diborane, B 2 H 6 , forming electron-deficient three-center two-electron B-H-B bonds [2,3]. Although very useful in many synthetic applications, gaseous diborane is, however, not convenient to handle and is thus commonly replaced in organic reactions by appropriate BH 3 complexes with tetrahydrofuran and dimethyl sulfide [4].…”