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).
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.
Tsang
C W
CW
Department of Chemistry, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
Yang
Q
Q
Sze
E T
ET
Mak
T C
TC
Chan
D T
DT
Xie
Z
Z