Phosphides

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Phosphides are anionic compounds of phosphorus . They are structurally derived from the phosphines . Here, hydrogen atoms by metal ion such as lithium - or sodium ions replaced. Phosphides of the alkali and alkaline earth metals belong to the Zintl phases .

Alkali metal phosphides are unstable and sensitive to moisture. In contrast, transition metal phosphides are often very stable, thermally conductive and electrically conductive.

Phosphides with a high phosphorus content are usually relatively unstable and semiconductors .

There are isolated phosphorus ions P 3− in metal phosphides as well as more complicated polyphosphide structures, for example in chains, rings or cages made of phosphorus atoms. The reason for the large number of polyphosphides (in contrast to oxides or sulfides, for example ) is the tendency of phosphorus to form P – P bonds.

The ratio of metal to phosphorus ranges from M 3 P (monophosphide) to MP 15 in the case of alkali metal phosphides, for example .

Monophosphides

Monophosphide have the general structure (M x + ) 3 (P 3 ) x (x = 1, 2) are in their isolated P 3 - anions before. An example of a monophosphide is calcium phosphide Ca 3 P 2 (polytanol), which reacts to phosphane on contact with water and was used to combat voles .

Dihydrogen phosphides and monohydrogen phosphides

In the dihydrogen phosphides and monohydrogen phosphides, the hydrogen atoms are only partially replaced by metal ions. The general formulas (M x + ) (PH 2 - ) x for the dihydrogen phosphides and (M x + ) y (PH 2− ) x for the monohydrogen phosphides result.

Polyphosphides

Polyphosphides have complex structures. There are, for example, helical (e.g. Li n P n ) and planar P 6 4− six-membered rings. Cage and tube structures are also known.

Azanidopolyphosphides

If one or more phosphorus atoms in the phosphides are replaced by nitrogen , azanidopolyphosphides are obtained. The largest azanidopolyphoshid known to date is Na 5 P 30 N, which can be isolated as a dimer from tetrahydrofuran (THF) with the exclusion of air and moisture.

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