Metal Phosphides Introduction

Early studies of metal phosphides were carried out by Pelletier [1] in 1789, and the first metallq)hospho-rus coordination complex (M-P-E type with E=H), was reported by Rose [2] in 1832. The first M-P-E type with E=C was a tertiary phosphine complex made by Hoffmann [3] in 1857. Although this was followed by the synthesis of a few other complexes of this type by Cahors and Gal in 1870, it was not until after the pioneering work of Mann, Chatt [4] and Jensen [5] in the field of organometallic chemistry during the 1930-1960, that the exponential rise of metallophosphorus chemistry was to begin. 

Although the vast majority of known metallophosphorus complexes remain of academic interest only, a few have well-established uses of great importance. These are mainly in the fields of catalysts and medicinals where interest and development continues unabated. Among the smaller but nevertheless growing applications are in chemical vapour deposition, chemical synthesis and various electrical devices. 

It is only since about 1960 that most of the metal phosphides have been properly characterised and obtained in a sufficiently high state of purity to enable reliable measurements of their properties to be 

P forming bonds to M E atoms (E = non-metal p block element) 

The majority of metal phosphides have a metal arsenide analogue which they usually resanble in properties and structure (Table 8.2). Metal phosphides, arsenides and nitrides not infrequently exhibit properties similar to those of metal carbides, silicides and germanides. Some metal phosphides are very useful semiconductors, while others shew superconduction or a variety of magnetic properties. Light-emitting diodes (LEDs) and nanostructured materials are other modem applications (Chapter 12.19). 

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Hydrochloric acid or HCl gas is noncombustible. Contact of acid with alkali metals such as sodium or potassium can result in explosion. It reacts violently with alkaline-earth metals. Hydrogen is produced from the reaction of metals with HCl. Phosphine (flammable) is generated when a metal phosphide reacts with the acid. Its reaction with caustic alkalies is exothermic and can be vigorous to violent. Crowley and Block (1989) reported rupture of vessels resulting from the accidental introduction of HCl solution into hydrogen peroxide. 

The formation of secondary phosphide anions by metallation of secondary phosphines with butyllithium is an extremely efficient practical route for the introduction of the -PPh2 group, and numerous examples are cited in the following sections.50... 

It may be possible to increase wear resistance by the introduction of boron phosphide, BP (Chapter 4.7), at aUoy and metal surfaces by laser or other treatments. 

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