In chemistry, a phosphide is a compound containing the P3− ion or its equivalent. Many different phosphides are known, with widely differing structures. Most commonly encountered on the binary phosphides, i.e. those materials consisting only of phosphorus and a less electronegative element. Numerous are polyphosphides, which are solids consisting of anionic chains or clusters of phosphorus. Phosphides are known with the majority of less electronegative elements with the exception of Hg, Pb, Sb, Bi, Te, and Po. Finally, some phosphides are molecular.
Binary monophosphides
Examples of group 1 include. Notable examples include aluminium phosphide, zinc phosphide, calcium phosphide exploiting their tendency to release toxic phosphine upon hydrolysis. Magnesium phosphide also is moisture sensitive. Indium phosphide and GaP are used as a semi-conductors, often in combination of related arsenides. Copper phosphide illustrates a rare stoichiometry for a phosphide. These species are insoluble in all solvents - they are 3-dimensional solid state polymers. For those with electropositive metals, the materials hydrolyze:
Polyphosphides
Polyphosphides contain P-P bonds. The simplest polyphosphides contain ions;. Others contain the cluster ions and polymeric chain anions and complex sheet or 3-D anions. The range of structures is extensive. Potassium has nine phosphides: K3P, K4P3, K5P4, KP, K4P6, K3P7, K3P11, KP10.3, KP15. Eight mono- and polyphosphides of nickel also exist:. Two polyphosphide ions, found in and found in K5P4, are radical anions with an odd number of valence electrons making both compounds paramagnetic.
Preparation of phosphide and polyphosphide materials
There are many ways to prepare phosphide compounds. One common way involves heating a metal and red phosphorus under inert atmospheric conditions or vacuum. In principle, all metal phosphides and polyphosphides can be synthesized from elemental phosphorus and the respective metal element in stoichiometric forms. However, the synthesis is complicated due to several problems. The exothermic reactions are often explosive due to localoverheating. Oxidized metals, or even just an oxidized layer on the exterior of the metal, causes extreme and unacceptably high temperatures for beginning phosphorination. Hydrothermal reactions to generate nickel phosphides have produced pure and well crystallized nickel phosphide compounds, Ni2P and Ni12P5. These compounds were synthesized through a solid-liquid reaction between NiCl2∙12H2O and red phosphorus at 200 °C for 24 and 48 hours, respectively. Metal phosphides are also produced by reaction of trisphosphine with metal halides. In this method, the halide is liberated as the volatile trimethylsilyl chloride. A method for the preparation of K2P16 from red phosphorus and potassium ethoxide has been reported.
Molecular phosphides
Compounds with triple bonds between a metal and phosphorus are rare. The main examples have the formula Mo3, where R is a bulky organic substituent.
Many organophosphides are known. Common examples have the formular R2PM where R is an organic substituent and M is a metal. One example is lithium diphenylphosphide. The Zintl cluster is obtained with diverse alkali metal derivatives.
Natural examples
The mineral Schreibersite3P is common in some meteorites.
