Electron counting carbaboranes, 370

At first glance, electron count in these clusters gives a remarkable analogy to the carbaboranes. Each aluminum atom contributes two electrons to the cluster, three electrons are from each carbon atom, and one electron is added by the bridging hydrogen atom. A total count of 32 electrons or 16 electron pairs results, which in accordance with the Wade rules [6] gives an arachno-type 13-vertex cluster. Indeed,... 

Wade electron counting rules borane-like cluster nomenclature. On initially studying compounds such as boranes (boron hydrides) and carboranes (or carbaboranes boron—carbon hydrides), Wade (1976) proposed a number of rules which have then been extended to several compounds and which relate the number of skeletal electrons with the structure of deltahedral clusters. A polyhedron which has only A-shaped, that is triangular, faces is also called a deltahedron. 

The electron-counting schemes can be extended to isoelectronic species such as the carboranes (also known as carbaboranes). The CH" unit is isoelectronic with BH many compounds are known in which one or more BH groups have been replaced by CH (or by C, which also has the same number of electrons as BH). For example, replacement of two BH groups by CH" " in yields closo-C- Bayif, a neutral compound. 

A few review articles on carbaboranes have appeared during the year, including those on cobalt carbaboranes, structure and property modification of m-carbaborane siloxanes, and further electron counting correlations between boron clusters and metal carbonyl clusters. ... 

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