Smaller Heteropolyboranes

These compounds were found to isomerize in the presence of mild Lewis bases to produce isomers in which the R3 M is terminally bound to either the apical boron (I-R3MB5H8) or to one of the basal boron atoms (2-R3MB5H8). In most cases the 2-isomer is formed preferentially, while the 1-isomer is only accessible at elevated temperatures or in the presence of strong bases [33]. However, the stabilities can be reversed through bulky organometal groups. For example, the 1-isomer 

In comparison with the enormous number of carboranes the family of the heavier group 14 heteroborane clusters is yet very small. Most of the heteropoly-borane skeletons with Si, Ge, Sn or Pb atoms belong to the group of larger sized closo- and nido-clusters and the chemistry of these heteroboranes is essentially concentrated on the heteroatoms. 

Hosmane, J. A. Maguire, in Electron-Deficient Boron and Carbon Clusters, G. A. Oiah, K. Wade, R. E. Williams, eds., Wiley, New York, 

Maguire, J. Cluster Sci., 1993, 4, 297-349. (f) A. K. Saxena, J. A. Maguire, J. J. Banewicz, N. S. Hosmane, Main Group Chem. News, 1993, 1(2), 14. (g) N. S. Hosmane, in Main Group Elements and Their Compounds, V. G. Kumar Das, Narosa Publishing House/Springer-Verlag, New Delhi, India, 1996, 299. (h) N. S. Hosmane, Curr. Sci., 2000, 78, 452-463. (i) N. S. Hosmane, in Contemporary Boron Chemistry, M. Davidson, 

Hughes, T. B. Marder, K. Wade, eds., Royal Society of Chemistry, Cambridge, 2000, pp. 299-307. 

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