Nature of weak inter- and intramolecular interactions in crystals. Communication 5. Interactions Na...H-B in a crystal of sodium salt of charge compensated nido-carborane [9-SMe2-7,8-C2B9H10]-

The character of electron density distribution in the C2B3 open face, the influence of the SMe2 group on the character of electron density distribution, and the nature of the sodium-anion interaction were studied based on the data of high-resolution X-ray diffraction study of crystals of the sodium salt of charge-compensated nido-carborane [9-SMe2-7,8- C2B9H10]- and quantum-chemical calculations for the Na...H-B-bonded dimer, the isolated [9-SMe2-7,8-C2B9H10]- anion, and the [7,8-C2B9H10]2- dianion. The character of electron density distribution in the C2B3 open face is analogous to the electron distribution in the cyclopentadienyl ligand. In nido-carborane, a substantial charge redistribution takes place compared to that observed in the closo analogs. The topological analysis of the electron density distribution function demonstrated that the cation-anion interactions are determined predominantly by Na...H-B contacts. The total energy of these contacts in the {[9-SMe2-7,8-C2B9H10]Na(thf)2}2 dimer estimated from X-ray diffraction data is 11.74 kcal mol-1