STABILITY AND NMR CORRELATIONS, EXPERIMENTAL VS CALCULATIONAL, AMONG ISOELECTRONIC CLOSO-HEXABORANE CARBORANE COMPOUNDS/

The results of IGLO/NMR and GIAO/NMR calculations on the known closo-h exaborate ions [R-XB5H5](2-) and their protonated counterparts [R-XB5H 6](-) (R = H, CH3, CN, CI; X = B. R = H, CH3; X = C) are correlated wi th experimental data. A consideration of plausible transition states f or [Me-B6H6](-) bridging hydrogen tautomerism leads to the conclusion that such tautomerism is expected to be more facile for the compound [ R-XB5H6](-) where X = B than for the compounds where X = C. MCS calcul ations are performed on all compounds and compared to those reported e arlier for 'aromatic' vs. 'non-aromatic' systems. (C) 1998 Elsevier Sc ience S.A.