The additive nature of energy penalties in 10-vertex nido-(Car)boranes

A structural increment system, i.e. quantitative rules that govern the relative stabilities of 10-vertex nido-boranes and-carboranes, has been determined. Density functional theory computations at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level with ZPE corrections were carried out for 81 different boron hydride and carborane structures from [B10H12](2-) to C3B7H11 to determine their relative stabilities. A set of eleven disfavored geometrical features that destabilize a cluster structure relative to a hypothetical ideal situation were identified and weighted by so-called energy penalties. The latter show good additive behavior and allow us to reproduce the DFT computed relative energies mostly with an accuracy of 6.0 kcal mol(-1). Some unknown 10-vertex nido-carboranes that are thermodynamically more stable than their known isomers are also identified.