Unusual cage rearrangements in 10-vertex nido-5,6-dicarbaborane derivatives: An interplay between theory and experiment

0470382 - ÚACH 2017 RIV US eng J - Journal Article
Štíbr, Bohumil - Holub, Josef - Bakardjiev, Mario - Lane, P. D. - McKee, M. - Wann, D. A. - Hnyk, Drahomír
Unusual cage rearrangements in 10-vertex nido-5,6-dicarbaborane derivatives: An interplay between theory and experiment.
Inorganic Chemistry. Roč. 56, č. 2 (2017), s. 852-860. ISSN 0020-1669. E-ISSN 1520-510X
R&D Projects: GA ČR(CZ) GA16-01618S
Institutional support: RVO:61388980
Keywords : dicarbaborane derivatives * nuclear-magnetic-resonance * regular 2-component hamiltonians
OECD category: Inorganic and nuclear chemistry
Impact factor: 4.700, year: 2017

The reaction between selected X-nido-5,6-C2B8H11 compounds (where X = Cl, Br, I) and "Proton Sponge" [PS; 1,8-bis(dimethylamino)naphthalene], followed by acidification, results in extensive rearrangement of all cage vertices. Specifically, deprotonation of 7-X-5,6-C2B8H11 compounds with one equivalent of PS in hexane or CH2Cl2 at ambient temperature led to a 7 → 10 halogen rearrangement, forming a series of PSH+[10-X-5,6-C2B8H10]- salts. Reprotonation using concentrated H2SO4 in CH2Cl2 generates a series of neutral carbaboranes 10-X-5,6-C2B8H11, with the overall 7 → 10 conversion being 75%, 95%, and 100% for X = Cl, Br, and I, respectively. Under similar conditions, 4-Cl-5,6-C2B8H11 gave ∼66% conversion to 3- Cl-5,6-C2B8H11. Since these rearrangements could not be rationalized using the Bvertex swing mechanism, new cage rearrangement mechanisms, which are substantiated using DFT calculations, have been proposed. Experimental 11B NMR chemical shifts are well reproduced by the computations; as expected δ(11B) for B(10) atoms in derivatives with X = Br and I are heavily affected by spin-orbit coupling.
Permanent Link: http://hdl.handle.net/11104/0270287


Research data: ACS publications