NMR assignments of [6-R-nido-5,6-C2B8H10](-) anions (where R = H, Me, and n-C6H13). An irreversible 5 -> 6 alkyl migration via a B9 vertex-swing mechanism
Z. Janousek et al., NMR assignments of [6-R-nido-5,6-C2B8H10](-) anions (where R = H, Me, and n-C6H13). An irreversible 5 -> 6 alkyl migration via a B9 vertex-swing mechanism, COLL CZECH, 64(6), 1999, pp. 986-992
Citations number
28
Categorie Soggetti
Chemistry
Journal title
COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS
Deprotonation by "proton sponge" (PS = 1,8-dimethylaminonaphthalene) of the
parent dicarbaborane nido-5,6-C2B8H12 (1) and its 6-R-substituted derivati
ves (where R = Me and n-C6H13) leads to the anions [nido-5,6-C2B8H11](-) [1
](-) and [6-R-nido-5,6-C2B8H10](-) [6-R-1](-) respectively. In contrast, th
e deprotonation of the 5-substituted isomers, 5-R-nido-5,6-C2B8H11 (5-R-1),
results in irreversible conversion into the 6-substituted anions [6-R-1]-,
from which the neutral compounds 6-R-1 can be obtained via reprotonation.
This 5 --> 6 alkyl migration can be explained by the B9 vertex-swing mechan
ism previously proposed for the interenantiomeric fluxionality of [1]-, but
now with the product dictated by the higher thermodynamic stabilities of t
he 6-substituted derivatives. The work has also resulted in complete assign
ments of B-11 and H-1 NMR spectra of the [nido-5,6-C2B8H11](-) anion and of
11B NMR spectra of the [6-R-nido-5,6-C2B8H10]- anions.