Theoretical prediction of donor–acceptor type novel complexes with strong noble gas–boron covalent bond

Abstract

The experimental identification of NgBeO molecules, followed by the recent theoretical exploration of super-strong NgBO⁺ (Ng = He–Rn) ions motivated us to investigate the stability of iso-electronic NgBNH⁺ (Ng = He–Rn) ions using various ab initio-based quantum chemical methods. The hydrogen-like chemical behavior of gold in small clusters and molecules also inspired us to study the nature of the bonding interactions in NgBNAu⁺ ions compared to that in NgBNH⁺ ions. The calculated Ng–B bond lengths in the predicted ions have been found to be much lower than the corresponding covalent limits, indicating a covalent Ng–B interaction in both the NgBNH⁺ and NgBNAu⁺ ions. In addition, the Ng–B bond dissociation energies are found to be in the range of 136.7–422.8 kJ mol⁻¹ for NgBNH⁺ and 77.4–319.1 kJ mol⁻¹ for NgBNAu⁺, implying the stable nature of the predicted ions. Interestingly, the Ng–B bond length (except for Ne) is the lowest reported to date together with the highest He–B and Ne–B binding energies considering all the neutral and cationic complexes containing Ng–B bonding motifs. Moreover, the natural bonding orbital (NBO) and electron density-based atoms-in-molecule (AIM) analysis reveal the covalent nature of the Ng–B bond in the predicted ions. Furthermore, the energy decomposition analysis together with the natural bond orbital in the chemical valence (EDA-NOCV) studies indicate that the orbital interaction energy is the main contributor to the total attraction energy in the Ng–B bonds. All the calculated results indicate the hydrogen-like chemical behavior of gold in the predicted NgBNM⁺ ions, showing further evidence of the concept of “gold-hydrogen analogy”. Also, for comparison, the corresponding Cu and Ag analogs are investigated. All the computed results together with the experimental identification of the NgMX (Ng = Ar–Xe; M = Cu, Ag, Au; X = F, Cl), ArOH⁺, and NgBeO (Ng = Ar–Xe) systems clearly indicate that it may be possible to prepare and characterize the predicted NgBNM⁺ ions experimentally using suitable technique(s).