Bonding and stability of elusive silaboryne (SiB) and germaboryne (GeB) with donor base ligands

Abstract

Stabilizing the exotic chemical species possessing multiple bonds is often extremely challenging due to insufficient orbital overlap, especially involving one heavier element. Bulky aryl groups and/or carbene as ligand have previously stabilized the SiSi, GeGe, and BB triple bonds. Herein, theoretical calculations have been carried out to shed light on the stability and bonding of elusive silaboryne/germaboryne (Si/GeB triple bond) stabilized by donor base ligands ((cAAC)BE(Me)(L); E = Si, L = cAACMe, NHCMe, PMe3; E = Ge, L = cAACMe). The heavier analogues (Sn, Pb) have been further studied for comparison. Additionally, the effects of bulky substituents at the Si and N atoms on the structural parameters and stability of those species have been investigated. Energy decomposition analysis coupled with natural orbital for chemical valence (EDA‐NOCV; for Si) showed that cAAC/NHC ligands could stabilize the exotic BSi‐Me species more efficiently than PMe3 ligands. The BSi partial triple bond of the corresponding species possesses a mixture of one covalent electron sharing BSi σ‐bond and two dative π‐bonds (B ← Si, B → Si).