Nature of Metal‐Metal Bond in Group‐V Dinuclear Metallaborane Compounds: Open‐Shell – Open‐Shell Vs Closed‐Shell – Closed‐Shell Interaction

Abstract

The investigation of metal‐metal bonding is interesting due to the captivating structural features, unique chemical reactivity and physical properties of this class of complexes. The bonding situation in the metallaboranes [(Cp*)2M2(B2H6)2] of group‐V elements (M) in the +3 oxidation state [M = V (1), Ta (2)] was investigated by the DFT, NBO, QTAIM calculations and further with Energy Decomposition Analyses coupled with Natural Orbital for Chemical Valence (EDA‐NOCV). Even though the metallaboranes are isostructural, the nature of metal‐metal bonding interaction was found to be different, showing open‐shell ‐ open‐shell interaction for vanadium while closed‐shell – closed‐shell interaction between two tantalum atoms. The EDA‐NOCV analyses suggest that TaIII‐TaIII bonding interactions are stronger than those of divanadaborane analogue, having an intrinsic interaction energy of ‐247.6 kcal/mol (2), and the V‐V bond has an interaction energy of ‐192.5 kcal/mol (1). The analyses indicate that the strength of the metal‐metal bond becomes stronger as the metal becomes heavier. This is due to the higher contribution from electrostatic stabilization energy. The pairwise orbital analysis of the metal‐metal bond denotes significant dative‐interaction between two tantalum metals, contributing 52.6% (2) to total orbital interaction energy. The electron‐sharing interaction energy has been computed to be 44.3% for 1.