Collect. Czech. Chem. Commun. 1988, 53, 2742-2752

Revision of nido-2,6-C2B7H11 to the arachno-4,5-C2B7H13 structure. Determination of the structure from NMR spectra and chemical origin

Stanislav Heřmánek, Tomáš Jelínek, Jaromír Plešek, Bohumil Štíbr and Jiří Fusek

Institute of Inorganic Chemistry, Czechoslovak Academy of Sciences, 250 68 Řež near Prague


The assymetric C2B7 carborane held until the present for 2,6-C2B7H11, is in reality the arachno-4,5-C2B7H13 carborane (I) with two adjacent B-H-B bridges, one BH2, one CH2 and one CH group in the hexagonal open-face. The arrangement of the boron network was determined on the basis of the 11B, 11B-11B COSY, 1H and 13C NMR spectra and on the T1(B) study. The connection of B- with C-skeletal atoms was deduced from the positions of deuterium in the deutero analogs prepared by the CH2O/D3O+ degradation of three selectively deuterated nido-[7,8-C2B9H12]- anions. A selective transmission of D from CD2O to the B(9) vertex in the course of the CD2O/D3O+ degradation was observed. The structure of arachno-4,5-C2B7H13 is consistent with the different pathways of its preparation.