Alkali‐Metal‐Supported Be—X (X = C, N, and B) Quadruple Orbital Overlapping Interactions

The formation of quadruple bonds in main‐group chemistry has long been constrained by fundamental electronic limitations, notably the electron deficiency and inactive d orbitals of early second‐row elements. Herein, we propose a series of alkali‐metal‐supported Be‐XLi n z (X = B, C, and N; n = 2 and 3; z = +1, 0, and −1) complexes. In particular, the quadruple orbital interaction patterns in octet valence electron structures such as BeBLi 3 , BeCLi 2 , BeCLi 3 + , and BeNLi 2 + have rarely been reported. Lithium atoms effectively mitigate the electron deficiency of the core Be‐X unit, enabling eight‐ or ten‐valence electron systems that feature distinct Be‐X quadruple orbital interactions with coexisting polar and delocalized characters. Comprehensive bonding analyses, including orbital composition, EDA‐NOCV, adaptive natural density partitioning (AdNDP), atoms in molecules (AIM), and Electron Localization Function (ELF), confirm that this multiple bond consists of a highly polar Be → XLi n z σ component and three reverse‐dative Be ← XLi n z interactions, which are formed by one σ and two π bonding modes. This study not only further extends the system of quadruple bonding interactions between Be and second‐row elements (B, C, and N) but also presents a series of eight‐valence electron environments in BeBLi 3 , BeCLi 2 , BeCLi 3 + , and BeNLi 2 + clusters with fewer electrons, deepening the understanding of the nature of multiple bonds in main‐group elements.