Boroxol rings

The boroxol ring, and its protonated form, HjBjO, have also... 

Tossell, J. A., and P. Lazzeretti (1990). Calculation of the structure, vibrational spectra, and polarizability of boroxine, H3B3O3, a model for boroxol rings in vitreous BjO,. J. Phys. Chem. 94, 1723-24. 

Table III. Infrared Vibrations of Boroxole Ring Structure Goubeau h- ...

Figure 7.13. One-dimensional B NMR spectra of B2O3 glass acquired using several different techniques for narrowing the spectra and improving resolution. Asterisks denote spinning sidebands. Peaks marked A and B arise from the boroxol ring site and the non-ring BO3 site respectively. Adapted from Youngman et al. (1996).

B03]3- in boroxol rings [BO3F] - and [B02F2p distorted tetrahedrons -O- bridges... 

The structure of the alkoxyboron difluorides has recently aroused some interest, and the historical consideration of the structure of these compounds has been outlined. Although the chemical shifts of these compounds are comparatively high (+01 to -f0 8) this does not imply quadricovalency (see above discussion) > however, the formation of the pyridine co-ordination complexes of the alkoxyboron difluorides (11) did not give appreciably higher B chemical shifts, and it was concluded that the boron atom in alkoxyboron difluorides was already tetracovalent. Molecular-weight determination confirmed the trimeric structure similar to the boroxole ring system. 

Figure 5.4 Boroxol ring structures in vitreous boric oxide and alkali borate glasses...

NQCC values for the BgOisHe cluster, which serves as a model for the boroxol and non-ring B s. The boroxol ring B s are systematically deshielded, while the O shieldings are unexpectedly lowest for the central atoms. 

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