Structural stability of a bent tetra(amino)tetraborane ring across four charge states

Abstract

Boron rings with electron-precise (i.e., non-cluster) bonds represent a largely untapped area in boron chemistry, and investigating their properties could potentially open up exciting new research avenues. In this work, we present an efficient method for synthesizing the cyclic tetraborane B₄(NCy₂)₄ by reduction of the amino(dihalo)borane (Cy₂N)BCl₂ (Cy, cyclohexyl). This puckered, covalently bonded compound features unprecedented stability across four charge states, highlighting the capacity of the B₄ ring to adapt to varying σ- and π-electron counts. Density functional theory (DFT) calculations elucidate the electronic structure of all species, revealing how electron delocalization is modulated.