Collect. Czech. Chem. Commun. 2010, 75, 931-947
Published online 2010-09-09 07:39:22

Incremental iodination of the eight-vertex closo monocarborane anion [closo-1-CB7H8]: Preparation and characterization of [closo-1-CB7H5-6,7,8-I3] and [closo-1-CB7H2-2,3,4,6,7,8-I6], and the synthesis of the first eight-vertex C-methylated carborane anion [1-CH3-closo-1-CB7H4-6,7,8-I3]

Radim Dostála,b,*, Michael G. S. Londesborougha,*, Magdalena Kvíčalováa, Jan Macháčeka, Ivana Císařovác and Zbyněk Janoušeka

a Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., 250 68 Řež, Czech Republic
b University of Pardubice, Faculty of Chemical Technology, Department of General and Inorganic Chemistry, Studentská 573, 532 10 Pardubice, Czech Republic
c Charles University, Faculty of Science, Department of Inorganic Chemistry, Hlavova 2030, 128 40 Prague, Czech Republic


Iodination of [closo-1-CB7H8] (anion 1) with elemental iodine under various controlled conditions yields a continuum from mono- to hexaiodinated derivatives including the previously unknown [closo-1-CB7H5-6,7,8-I3] (anion 5) and [closo-1-CB7H2-2,3,4,6,7,8-I6] (anion 8). These species, characterized by mass spectrometry and NMR spectroscopy, and, in the case of 8, by single-crystal X-ray diffraction, provide insight into the fluxional molecular behavior of anion 1 in solution. Investigation of direct electrophilic substitution on the carbon-vertex of anion 1 using standard conditions and reagents (deprotonation by BuLi followed by addition of electrophile) proved futile, but the same conditions when using the new triiodo-deravitive anion 5 resulted in the formation of the first eight-vertex C-methylated carborane anion [1-CH3-closo-1-CB7H4-6,7,8-I3] (anion 9), in 60% yield.

Keywords: Carboranes; Monocarborane anions; Eight-vertex; Low nucleophilic and weakly coordinating anions; Halogen derivatives; Electrophilic substitution; Iodination.

References: 35 live references.