Sg. Kozlova et al., STRUCTURAL FEATURES OF POTASSIUM AND CESIUM DODECAHYDRO-CLOSO-DODECABORATES(2-) ACCORDING TO H-1 AND B-11 NMR DATA, Journal of structural chemistry, 34(2), 1993, pp. 244-247
The structural and dynamic characteristics of the salts K2B12H12 (I) a
nd Cs2B12H12 (II), containing an icosahedral closo-anion B12H122-, wer
e investigated by the NMR method. Disagreement was found between the o
btained NMR data and the published results from an x-ray crystallograp
hic analysis with respect to the position of the H and B atoms in the
crystal lattices of the compounds. The H-1 and B-11 NMR data give reas
on to suppose that compounds (I) and (II) can be assigned to the quasi
periodic crystal class with respect to the positions of the H and B at
oms. From analysis of the line shapes in the H-1 NMR spectra the inter
atomic separations r(B-H) in the B12H122- anion in the salts (I) and (
II) were determined (1.21 +/- 0.01 Angstrom). Activation dynamics char
acterized by activation barriers of 54.4 and 38.9 kJ/mole respectively
were obtained for the B12H122- anions.