Boron-rich compound

Other boron modifications have been described and also compounds such as B50C2 or B50N2, previously believed to be pure boron forms. For a detailed discussion on the bonding in boron modifications and boron-rich compounds see King (1993). 

In boron-rich compounds, the structure can often be described in terms of a three-dimensional network of boron clusters (octahedra, icosahedra, and cubo-octahedra), which are linked to one another directly or via non-cluster atoms. 

In boron-rich compounds the structure can often be described as being built up of a three-dimensional network of boron clusters, for instance, octahedra, icosahedra, and cubo-octahedra (see Figure 4), which are linked to each other directly or via noncluster atoms. The metal atoms are accommodated in cages between the octahedra or icosahedra, thereby providing external bonding electrons to the electron deficient boron network. The structures of the boron modifications are also built up of icosahedral boron units. 

Table 3 Structure types of some binary boron-rich compounds...

H. Werheit, Boron and Boron-Rich Compounds, in Electric Refractory Materials , ed. Y. Kumashiro, Marcel Dekker, New York, 2000, p. 589. 

Liposomes have been suggested as promising candidates for the transport of boron-rich compounds in BNCT1 7, and encouraging results have been reported for the liposomal delivery of both hydrophilic and lipophilic compounds to tumours.17... 

Concentration of Boron Atoms in Structures of Boron and Boron-Rich Compounds... 

Sivaev, I. B., S. Sjoberg, and V. I. Bregadze. 2003. [CjBiqHBu] double cage boron compounds -/A new approach to the synthesis of water-soluble boron-rich compounds for BNCT. J. Organomet. Chem. 680 106-110. 

The third modification is a-tetragonal boron, which is based on four icosahedra per unit cell, which are bound to each other either directly or through two single boron atoms. This allotrope has the structure of many binary boron-rich compounds of nonmetals. 

The boron-rich compounds N Bj2 of nonmetals (N = C, Si, P, As, O n = 1-3, but usually 2) are structurally related to both a-rhombohedral and a-tetragonal boron, which are built up of boron icosahedra and intericosahedral boron atoms (Figure 4.13). In the boron carbides B12Q (n = 1-3) the boron atoms in and between the icosahedra are replaced by carbon atoms. In the other compounds in this category the atoms (called N above) are between the polyhedra and not in them. 

Cosset, D., Query, M., and Kryger, B., Thermal Properties of Some Boron-rich Compounds, in Boron-Rich Solids, AIP Conf. Proc. 140 (D. Aselage, et al., eds), Am Inst, of Physics, New York (1986)... 

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