Application of ‘molecular’ theories to the structure of the crystalline state
Recent years have seen the development of simple molecular orbital based ideas to view the structures of molecular ring, cage and cluster compounds. The principles of these methods are used here to demonstrate in a new way how the structures of solids depend on electronic configuration.
A study of the arsenic, black phosphorus, and other structures derived from rock salt by bond‐breaking processes. I. Structural enumeration
The structures of arsenic and black phosphorus can be regarded as distortions of the simple cubic or NaCl structure. The presence of more than four electrons per site results in the breaking of three of the six linkages around each atom in the NaCl structure. A generalization of Polya’s enumeration theorem is proven which allows counting of the 36 possible ways of breaking bonds to produce structures containing trigonal pyramidal coordination at each site and having the same size unit cell as NaCl. Larger cells are considered briefly.
Carboranes and Organo-Substituted Boron Hydrides
Publisher Summary The term “carborane” designates a carbon-boron-hydrogen system, where both the carbon and boron atoms are incorporated into a skeletal network. In comparison, the carbon atoms of compounds designated as organoboron hydrides are of a ligand nature. Additional characteristic features of the carboranes include the polyhedral arrangement of atoms and the absence of bridge hydrogens so commonly present in the boron hydrides. The dihydrocarboranes, with two extra hydrogens present in bridge positions, may be a hydrid of the carborane and boron hydride structural patterns. All of the known carboranes have been derived either directly or indirectly from the reactions of alkynes with various boron hydrides. In these reactions, only the carbons participating in the triple bond of the alkyne become skeletal atoms in the carborane. The dehydrogenation of the cyclic diborane derivatives prepared from butadiene should lead to C 4 BH 5 and C 4 B 2 H 6 . However, such a conversion may require electric discharge conditions, where extremely low yields can be expected. The chapter also describes the organosubstituted boron hydrides, such as diborane and borane derivatives, tetraborane derivatives, pentaborane derivatives, decaborane derivatives, and B 10 H 10 2- and B 12 H 12 2- derivatives.