The Structure of B8H82- in Solution. Is B8H9- also Involved? An Ab Initio/IGLO/NMR Study

cited authors

  • Bühl, M; Mebel, AM; Charkin, OP; von Ragué Schleyer, P

fiu authors

abstract

  • Ab initio calculations at the MP2/6-31G*//MP2/6-31G* + ZPE(6-31G*) level give relative energies of 0.0, 5.0, and 17.2 kcal/mol for the D2d, C2v, and D4d forms of B8H82-, respectively. Solvation (modeled by self consistent reaction field [SCRF] calculations) and ion pairing (computed for the Li2B8H8 isomers) do not significantly affect the energetic relationships. The Ca, form is a transient species involved in the fluxional rearrangement of the D2d form. The chemical shift calculations (IGLO) indicate that the fluxional D2d structure corresponds to the species which shows a single δ(11B) NMR signal in solution. While no B8H82- form was found to correspond with the 2:4:2 NMR chemical shift pattern, we raise the possibility that the second species observed under certain conditions might be the protonated form, B8H9- (4), rather than a second B8H82- isomer. The observed nB NMR chemical shifts, the 2:4:2 intensity pattern, and the topomerization barrier (ca. 12 kcal/mol) all are consistent with the computed values for 4. © 1992, American Chemical Society. All rights reserved.

publication date

  • January 1, 1992

Digital Object Identifier (DOI)

start page

  • 3769

end page

  • 3775

volume

  • 31

issue

  • 18