Kristallstrukturen von (n-Bu4N)[B6Cl6], (n-Bu4N)[B6Br6] und (Ph3P=N=PPh3)[B6I6] sowie Schwingungsspektren und Normalkoordinatenanalyse der Hexahalogeno-c/osö-Hexaboratradikalanionen [B6X6]-, X = Cl, Br, I / Crystal Structures of (n-Bu4N)[B6Cl6], (n-Bu4N)[B6Br6], and (Ph3P=N=PPh3)[B6I6], and Vibrational Spectra and Normal Coordinate Analysis of the Hexahalogeno-closo-hexaborate Radical Anions [B6X6]- , X = Cl, Br, I

Abstract

Abstract Oxidation of hexahalogeno-closo-hexaborates [B6X6]2-, X = Cl, Br, I, with (NH4)2[Ce(NO3)6] in ethanol yields coloured radical ions [B6X6]-. X-ray structure determina­ tions have been performed on single crystals of (n-Bu4N)[B6Cl6] (1) (monoclinic, space group P21/c,a = 13.144(2),6 = 12.594(2),c = 17.688(5) Å, β = 107.29(2)°,Z=4),(n-Bu4N)[B6Br6] (2) (monoclinic, space group P21/c, a = 13.529(5), b = 13.096(5), c = 17.863(5) Å, β = 107.20(5)°, Z = 4) and (Ph3P=N=PPh3)[B6I6] (3) (triclinic, space group P1̄, a = 9.3137(8), b = 10.6988(10), c = 11.8760 Å , a = 102.220(7), β = 99.34J(8), 7 = 96.030(7)°, Z = 1). The average B-B distances are nearly equal (1.733 Å (1), 1.728 Å (2), 1.728 Å (3)) while the B-X distances increase (1.762 Å (1), 1.912 Å (2), 2.120 Å (3)). Using the molecular parameters, normal coordinate analyses have been performed and a good agreement of observed and calculated frequencies of 10B and 11B labelled derivatives has been achieved. The valence force constants fd(BB) and fd(BX) of [B6X6]- are 1.17 and 4.17 (X = Cl), 1.18 and 3.34 (Br) and 1.18 and 2.60 mdyn/Å (I), respectively.