Suboxide

Suboxides (from Latin sub = under ) are chemical compounds of oxygen to more electropositive elements, where less oxygen atoms are bonded, as would be expected according to the valence of oxygen. The formal oxidation state of the other element is located so that in these compounds, at less than 1. To compensate for this, are in this class of compounds against element - element bonds. Suboxides are primarily of the alkali metals rubidium and cesium, as well as boron and carbon known.

Suboxides are usually unstable and decompose to form the more stable oxides.

Alkalimetallsuboxide

The only alkali metals rubidium and cesium form the heavy suboxides. There are very reactive, colored solids that show due to the metal contained electrical conductivity. They are manufactured suboxides from the elemental alkali metals and small, well-defined amounts of oxygen. This can be done for example by decomposition of suitable oxides such as silver or mercury.

All Alkalimetallsuboxide very easily react with water, oxygen or carbon dioxide, forming the more stable oxides or Hyperoxide.

Rubidiumsuboxide

The most important Rubidiumsuboxid has the empirical formula Rb9O2. It is a copper-colored solid having a melting point of 40.2 ° C. The structure consists of individual Rb9O2 clusters. In these, the nine Rb atoms are arranged in two face-sharing octahedra. The oxygen atoms are located at the centers of the octahedra.

It can also be mounted further rubidium to each cluster, the bronze Rb6O there are for example three rubidium atoms per cluster. However, these are unstable, then Rb6O decomposes even at -7.7 ° C

Caesiumsuboxide

Cesium also forms a number of sub-oxides. The most important cesium suboxide has the formula Cs11O3. It is a violet solid having a melting point of 52.5 ° C. The structure is as in rubidium from face-sharing octahedra, in the middle are the oxygen atoms. There are, however, the cesium three octahedra instead of two as in rubidium.

As the rubidium additional metal atoms can be incorporated in the cesium. There are connections with up to 10 other known cesium atoms, which corresponds to a ratio formula of Cs7O.

Caesiumsuboxide arise in certain photo-cathode, the so-called S1 photocathodes which consist of thin silver - cesium and cesium oxide layers. The resulting from the reaction of cesium with cesium oxide suboxides are responsible for ensuring that the cathode can adsorb light in the infrared region and emit in accordance with electrons.

Kohlenstoffsuboxide

Carbon suboxide C3O2 differs significantly from the alkali metal suboxides. It is a molecularly constructed, gaseous compound, which readily polymerizes to a brown-red solid. Pentakohlenstoffdioxid C5O2 is also known.

Borsuboxide

There are known several Borsuboxide. The trigonal suboxide B6O is one of the hardest known materials with a cubic boron nitride comparable hardness. A further boron suboxide (I ) oxide ( B2O ) x which is isoelectronic to graphite and has a corresponding structure.