Borane clusters Heteroboranes

Nido Clusters 2n + 4 Systems). Many closo boranes and heteroboranes add two electrons and undergo a concomitant stmctural transformation from a deltahedron to a deltahedral fragment. For instance, closo-2 ()-(Z, [17764-89-OJ, (2n + 2 = 24e ), is readily reduced to... 

Arachno Clusters 2n + 6 Systems). In comparison to the number of known closo and nido boranes and heteroboranes, there are relatively fewer arachno species. Partly because of the lack of a large number of stmctures on which to base empirical rules, arachno stmctures appear to be less predictable than their closo and nido counterparts. For example, there are two isomeric forms of one with the arachno [19465-30-6] framework shown... 

Coordination chemistry of boranes and heteroboranes is a major field of research in cluster science. By far the most extensively studied clusters are the eleven vertex carboranes dicarba-nicfo-undecaborane, carba-mt/o-undecaborane and the six vertex carborane dicarba-m fifo-hexaborane. The synthesis of the elven vertex silaborate [MeSiBioHu] prompted us to study the coordination abilities of this cluster towards transition metals. In... 

Rudolph RW (1976) Boranes and heteroboranes aparadigmfOTthe electron requiremtaits of clusters Acc Chem Res 9 446-452... 

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. 

In the following section, we give a survey of the known types of heteroboranes in question and discuss the structures in terms of the Wade-Williams rules. Readers, who are interested in the synthesis of heteroatom clusters, in their skeletal transformations, or in reactions at the ligand sphere, are referred to the cited literature. conjuncto- Boranes with heteroatoms in the skeleton are not considered in this brief discussion. 

The boron hydrides, including the polyhedral boranes, heteroboranes, and their metaUa derivatives, encompass an amazingly diverse area of chemistry. This class contains the most extensive array of structurally characterized cluster compounds known. Included here are many novel clusters possessing idealized molecular geometries ranging over every point group symmetry from identity (C[) to icosahedral (I[). Because boron hydride clusters may be considered in some respects to be progenitorial models of metal clusters, their development has provided a framework for the development of cluster chemistry in... 

In Chapter 15 we observed that I he l electron rule was adequate For predicting stabilities of small organometallic clusters. In this chapter we have seen that Wade s rules allow us Lo make predictions about borune structures based on the number of framework electrons. These rules ulso are adequate for most curboranes. metallacar-boranes, and other heteroboranes. i1" Furthermore, organometallic clusters that are not derived from boranes can be dealt with in a similar fashion. More sophisticated extensions are required for complex larger clusters.139... 

Recently, an extension of Wade s rules has been described for electron counting in boranes, heteroboranes, metallaboranes, other clusters, and even metallocenes. This approach called the mno rule, states that for a closed cluster structure to be stable, there must be m + n + o skeletal electron pairs, where... 

This chapter provides an overview of the structural and electronic properhes of polyhedral heteroborane clusters and their potenhal use as building blocks in nanotechnology. These clusters comprise polyhedral boranes (boron hydrides),... 

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