Hypervalent antimony

The metalloid elements include boron, silicon, germanium, arsenic, antimony, tellurium, and astatine. Ligand exchange reactions complete much faster for silicon complexes when compared with carbon complexes because the silicon atom can form a hypervalent transition state that carbon cannot. 

Hypervalent heterocyclic structures are typical of arsenic, antimony, and bismuth. The chemistry of these compounds has been overviewed by K.-Y. Akiba (2011HC207) and several specific examples are illustrated by structures 36—44 (Figure 9). 

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