Darstellung, 11B-NMR- und Schwingungsspektren isomerenreiner Halogenohydrododecaborate XnB12H12–n 2–; X = Cl, n = 1–3; X = Br, n = 1,2; X = I, n = 1 / Preparation, nB NMR and Vibrational Spectra of Pure Isomeric Halohydrododecaborates XnB12H12-n 2-; X = Cl, n = 1-3; X = Br, n = 1,2; X = I, n = 1

Abstract

Pure isomers of XnB12H12-n 2-; X = Cl, Br, I are isolated by ion exchange chromatography on diethylaminoethyl cellulose. The structures are determined by 11B and 11B {1H}NMR spectroscopy. With X = Cl, Br the signal of ipso-B atomes is shifted to lower, with X = I to higher field compared with B12H12 2-. The resonances of B-atoms influenced by the antipodal effect are observed at high field, increasing within the series I<Br<Cl. The chemical shifts are explained by the anisotropy effect and by the paramagnetic term due to different -I and +M effects of the halogens. In agreement with theoretical predictions the substitution of B12H12 2- with chlorine proceeds successively at vicinal positions B(1) -B(2) -B(3). The IR and Raman spectra of 1-XB12H11 2- show in the region 175 - 380 cm -1 two characteristic bands shifting to lower frequencies in the series Cl, Br, I and are therefore assigned to (B12) -X stretching and (B12) -X bending modes, respectively