What Is the Limit of Atom Encapsulation for Icosahedral Carboranes?

Area of Science:

• Computational Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Carboranes are cage-like boron-carbon clusters with unique electronic properties.
• Endohedral and exohedral complexes involving metal cations and carborane cages are of interest for potential applications.

Purpose of the Study:

• To investigate the stability of endohedral and exohedral complexes of lithium and beryllium cations with carborane cages.
• To determine preferred binding sites and energy minima for these complexes using theoretical methods.

Main Methods:

• Electronic structure calculations were performed using the B3LYP/6-311+G(d,p) model.
• The study focused on carboranes of the type X@{1,n-C2B10H12} and X@{CB11H12(-)}, where X = Li(+) or Be(2+).

Main Results:

• All investigated endohedral carborane compounds were found to be local energy minima.
• For exohedral complexes, the global energy minimum consistently occurred when the cation was positioned above a triangular face of the icosahedral cage.
• Unlike beryllium complexes, exohedral lithium complexes did not exhibit global energy minima when a carbon atom was located beneath the cation on the triangular face.

Conclusions:

• Both endohedral and exohedral carborane complexes with Li(+) and Be(2+) are computationally stable.
• The preferred binding site for exohedral cations is above a triangular face, maximizing distance from cage carbon atoms.
• The behavior of Li(+) and Be(2+) differs in exohedral complexes, particularly concerning interactions with cage carbon atoms.