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

TY - JOUR

T1 - Unusual cage rearrangements in 10-vertex nido-5,6-dicarbaborane derivatives

T2 - An interplay between theory and experiment

AU - Štíbr, Bohumil

AU - Holub, Josef

AU - Bakardjiev, Mario

AU - Lane, Paul D.

AU - McKee, Michael L.

AU - Wann, Derek A.

AU - Hnyk, Drahomír

N1 - © 2016 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

PY - 2017/1/17

Y1 - 2017/1/17

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85009724676&partnerID=8YFLogxK

U2 - 10.1021/acs.inorgchem.6b02320

DO - 10.1021/acs.inorgchem.6b02320

M3 - Article

AN - SCOPUS:85009724676

SN - 0020-1669

VL - 56

SP - 852

EP - 860

JO - Inorganic Chemistry

JF - Inorganic Chemistry

IS - 2

ER -