title: Weakly coordinating nature of a carborane cage bearing different halogen atoms. Synthesis and structural characterization of icosahedral mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I).
abstract: Mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I), have been prepared by treatment of [Me3NH][1-H-CB11H5X6] (X = Cl, Br, I) with proper halogenating reagents at 180-220 degrees C in a sealed tube in high yield. These new anions are fully characterized by 1H, 13C, and 11B NMR, IR, and negative-ion MALDI MS spectroscopy. Some are further confirmed by single-crystal X-ray analyses. The weakly coordinating nature of these anions is probed by 29Si chemical shifts of the resulting Pri3Si(1-H-CB11Y5X6) compounds. The results suggest that the coordinating ability of these anions is mainly dependent on the substituents at 7-12 positions (namely, X atoms), and the contribution from the upper belt substituents Y is relatively small. These suggestions are consistent with the results obtained from the structural study of silver salts of mixed halo- and perhalocarborane anions.
authors.affiliation: Department of Chemistry, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: C W
authors.initials: CW
authors.lastname: Tsang
authors.forename: Q
authors.initials: Q
authors.lastname: Yang
authors.forename: E T
authors.initials: ET
authors.lastname: Sze
authors.forename: T C
authors.initials: TC
authors.lastname: Mak
authors.forename: D T
authors.initials: DT
authors.lastname: Chan
authors.forename: Z
authors.initials: Z
authors.lastname: Xie