Organogallium peroxides

Organogallium peroxides form a fascinating class of compounds because they have the oxidizing function of the peroxo group in close proximity to the reducing properties of the Ga-C bonds. However, their synthesis and isolation have proven to be extraordinarily challenging.
These compounds are highly reactive, and fast decomposition by the formation of alkoxides was usually observed.They were postulated as transient species in some cases, but generally not isolated in a pure form and thoroughly characterized.
Recently, Werner Uhl and Mohammad Reza Halvagar, published a series of articles describing synthesis and characterization of many new organo-gallium peroxides. Among them a unique peroxide was isolated, in which three peroxo (O<sub>2</sub> ) ligands bridge three alkyl gallium groups to form a nine-membered heterocycle.
Reveled by single crystal X-ray diffraction analysis, this peroxide consists of two identical dianions. The anionic part of the product contains an unprecedented and extraordinarily remarkable structural motif, in which three μ-1,2-peroxo groups bridge three alkyl gallium moieties to form a nine-membered, strongly corrugated heterocycle. The structure of the anionic part is reminiscent of the structure of triacetone triperoxide, peroxyacetone, (TATP).
The gallium atoms are further coordinated by a single central oxygen atom. The central oxygen atom further coordinates the gallium atoms. Hence, a chalice-like, tricyclic dianion is formed. Two anions are linked by four lithium cations to give a Capsule-like structure.
A few month after the publication of the article the results has been highlighted by Nachrichten aus der Chemie (the most important information medium in German for chemists). The research has been described as “Feuer samt Wasser” (Fire on Water), pointing to the presence of conflicting properties in a single molecule or the presence of a Strongly Oxidizing and Reducing Functions in a Single molecule.

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