Polyhedral borane dianions

An essential feature of the Wade-Mingos rules [13-16] is the partitioning of the valence electrons of the cluster atoms into skeletal electrons and external electrons. For polyhedral boranes, the external electrons are used to form bonds to external groups, such as hydrogen atoms in the prototypical borane dianions However, for bare post-transition element clusters, these external electrons formally correspond to nonbonding electron pairs. Subsequent experimental and theoretical... 

Zahradnlk, Balaji, and Michl also reported an SCF study of 10-vertex and 12-vertex polyhedral boranes and heteroboranes. Thus, they obtained complete optimized geometries for BioHio , Bi2Hi2 , and their isoelectronic analogues with a single heteroatom (C, N, O, Al, Si, P, S) using the 3-2IG and 6-3IG basis sets. For the anionic and dianionic species, the geometry optimization was also carried out using the 6-31+G basis set. The harmonic vibrational frequencies were obtained at the Hartree—Fock 3-2IG level. The calculated results compared well with experiment. 

Sulfhydryl derivatives of polyhedral borane anions have been of interest to BNCT researchers for many years because of the mercaptoundecahydro-c/o5t -dodecaborate dianion ([B,2H SH] , abbreviated borocaptate sodium (BSH) that has been used in a variety of preclinical and clinical BNCT trials (Hawthorne, 1993 Soloway et al., 1998 Hawthorne and Lee, 2003). Although only the free sodium salt of the [B,2H SHp has been used in the trials researchers have investigated the biodistribution of BSH encapsulated in liposomes (Shelly et al., 1992 Maruyama et al., 2004 Doi et al.. 

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