Collect. Czech. Chem. Commun. 1999, 64, 993-1000

4,6-Dicarba-8-thia-arachno-nonaborane(10) Revisited. Theoretical Refinement of Its Structure

Drahomír Hnyka,*, Matthias Hofmannb and Paul von Ragué Schleyerb

a Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, CZ - 250 68 Řež near Prague, Czech Republic
b Computer Chemistry Center, Institute of Organic Chemistry, University Erlangen-Nürnberg, Nägelsbachstrasse 25, D-91052 Erlangen, Germany


The structure of the nine-vertex arachno-thiadicarbaborane C2SB6H10 has been established employing the ab initio/IGLO/NMR method. Theoretical IGLO 11B chemical shifts support C and S atom placements at the 4, 6 and 8 positions, respectively, and unambiguously rule out the 4,6,5-C2SB6H10 structural alternative, suggested earlier on the basis of IR and Raman spectroscopy. Important structural features of the 4,6,8-C2SB6H10 geometry include a small B(7)-S(8)-B(9) angle (MP2(fc)/6-31G*: 97.9°) and long S-B bonds (MP2(fc)/6-31G*: 1.905 and 1.924 Å) compared to B-B bonds spanning the 1.71-1.85 Å range.

Keywords: Boranes; Heteroboranes; Thiaboranes; Ab initio calculations; NMR spectroscopy; Structure elucidation.