SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF [(CH3)(3)NH][NIDO-9,11-I-2-7,8-C2B9H10] AND [(CH3)(3)NH][NIDO-9-I-7,8-C2B9H11]

Electrophilic halogenation of the boron atom vertices of closocarboranes is a well-known reaction(1) which leads to a variety of isomeric products containing fluoro,(2) bromo,(3) chloro,(4) and iodo(5) substituents. Few halogenated nido-carborane compounds are known. Among the halogenated nido-carboranes,(6-8) the products of the relatively rapid electrophilic attack by formal I+ upon the open face of the nido-[7,8-C2B9H12](-) ion and its derivatives have been most widely studied. The use of these easily formed iodinated nido-carborane derivatives as both radioiodine carriers and as potential boron neutron capture therapy (BNCT) reagents' remains under investigation. Earlier structural characterization(6) of halogenated nido-carborane anions was performed by B-11 NMR, and only one single-crystal X-ray diffraction study of an iodinated nido-carborane anion has been reported.(7) This fact coupled with the recent interest in the presence of {BH2} vertices in certain nido-carborane anions(9-12) prompted us to investigate the structures of [(CH3)(3)NH][nido-9,11-I-2-7,8-C2B9H10] (1) and [(CH3)(3)NH]-[nido-9-I-7,8-C2B9H11] (2) using X-ray diffraction methods. We here report the first synthesis and structural characterization of a diiodinated nido-carborane anion (1) which contains an endo B-H bond in the open five-membered face, as well as the structure of the previously reported(6) monoiodinated nido-carborane anion (2).