Phosphides—

Phosphides.—An arc melting technique, which offers advantages in purity of product and higher attainable temperatures over the conventional approach to phosphide preparation, has been used to re-examine the V-P system (the V-As and Cr-As systems were also investigated). The phases in the V-P system were confirmed, but in the corresponding arsenic system two new orthorhombic phases have been identified. 

A manganese phosphide, MnP4, has been prepared from the elements in a tetrahedral high-pressure device at 30-55 kbar and shown to contain condensed 

Several phosphides of technetium were prepared by reaction of technetium metal powder with red phosphorus at 1220 K using the tin-flux technique or iodine as a mineralizer. The preparation was carried out in evacuated, sealed silica tubes. 

TC3P crystallizes in the tetragonal FcjP-type structure. The lattice constants of Tc. P are a = 9.568 and c = 4.736 A. Tc-,P proved to be isoslructural with Mn P. CrsP, and NisP and shows a high coordination number for all atoms, which is typical for intermc-tallic compounds and other electron-deficient compounds with high metal content. With Z = 8 formula units in the cell, the calculated density is 10.04 g cm [16]. 

TCP3 w as shown to crystallize in a new structure type with four formula units per cell in the orthorhombic space group Pnma. The lattice constants are a = 15.359, h = 3.092, and c = 5.142 A. TeP , is isostructural with ReP. The metal atoms arc octahed-rally surrounded by phosphorus atoms. Each metal atom forms two metal-metal bonds across the common edges of adjacent octahedra (Fig. lO.l.A). Thus all spins are compensated in agreement with the diamagnetism observed for ReP. The TCP5 octahedra arc linked via corners and edges to form two-dimcnsionally infinite, puckered sheets perpendicular to the a axis [17]. 

Most elements combine with phosphorus to give binary phosphides exceptions include Hg, Pb, Sb, Bi and Te. Types of solid state phosphides are very varied, and simple classification is not possible. Phosphides of the d-block metals tend to be inert, metallic-looking compounds with high melting points and electrical conductivities. Their formulae are often deceptive in terms of the oxidation state of the metal and their structures may contain isolated P centres, P2 groups, or rings, chains or layers of P atoms. 

The group 1 and 2 metals form compounds M3P and M3P2 respectively which are hydrolysed by water and can 

The P-P bond distances of 215 pm are shorter than a typical single bond (220 pm) but longer than a double bond (see Section 23.6). Cyclic [P4] is a 67r-aromatic system, and the bonding is explored in the exercise below. 

Three of the occupied MOs of [P4] are shown below. The eg orbitals are the highest lying occupied MOs. Assume that the P4-ring is oriented in the xy-plane. 

The most complex P ligand so far characterized is the astonishing fu.5 hexadentate Pio unit in [ Cr( j -C5H5)(CO)2 5Pio] (see ref. 62 for details). 

The most general preparative route to phosphides (Faraday s method) is to heat the metal with the appropriate amount of red P at high temperature in an inert atmosphere or an evacuated sealed tube  

An alternative route (Andrieux s method) is the electrolysis of fused salts such as molten 

Variation in current, voltage and electrolyte composition frequently results in the formation of phosphides of different stoichiometries. Less-general routes (which are nevertheless extremely valuable in specific instances) include  

Phosphides resemble in many ways the metal borides (p. 145), carbides (p. 297), and nitrides (p. 417), and there are the same difficulties in classification and description of bonding. Perhaps the least-contentious procedure is to classify according to stoichiometry, i.e. (a) metal-rich phosphides (M/P 1), (b) monophosphides (M/P =1), and (c) phosphorus-rich phosphides (M/P 1)  

The gaseous equilibria shown in equations (1)—(3) have been studied by Knudsen-cell mass spectrometry,191 and values have been obtained for the dissociation energies (D%) and heats of formation of AsP and BiP (Do 429.7 and 278 kJ mol-1 AH°298 187.0 and 262 kJ mol-1, respectively). 

Ion-molecule reactions in phosphine at source temperatures greater than 25 °C give the PHI ion, which reacts further with PH3 giving P2HI, P,HI, and P4HI.199 With source temperatures below 25 °C, however, similar ions are obtained, but they are solvated with further PH3 molecules. 

Values of the magnetic rotation, p(P—H), which vary markedly with the s -character of the P—H bond have been obtained from a magneto-optical study of compounds in the series PH X3 n, OPH X3 n, and SPHnX3 (X= R or OR R = Me, Et, Pr, Pr , or Bu ).200 The barriers to internal rotation and the dipole moments of a number of methyl derivatives, including MePH2 and MeSiH3, have been investigated by semi-empirical M.O. calculations.201 

Mass spectrometric studies in the C-P system give the following data  

The readily hydrolysed calcium iodophosphide CagPI and its arsenic analogue can be obtained from the elements at 700—750 °C. Compounds 

Marinkovic, C. Suznjevic, A. Tukovic, I. Dezarov, and D. Cerovic, Carbon, 1973, 

Anugul, C. Pontchour, and S. Rundqvist, Acta Ghent. Scand., 1973, 27, 26. 

Bromine analogues M2PBr (M = Ca, Sr, or Ba) of the chlorides reported last year have been prepared and characterized. The cubic phases for Ca2PBr and Sr2PBr are stabilized by an excess of the metal dibromide, while the corresponding rhombohedral phases are stabilized by an excess of the phosphide M3P2. 

Two new silyl phosphanes, (Me3Si)3P7 and (Me3Si)4Pi4, can be isolated from the products of the reaction between white phosphorus and trimethylchlorosilane in the presence of Na-K alloy at ca. 80 The P7 species forms colourless crystals that are readily decomposed by oxygen but stable to ca. 300 °C in the absence of air the P14 compound is isolated as a yellow powder which decomposes at ca. 210 °C. 

AIN in terms of ionic formulations. Hydrolysis of saline nitrides liberates NH3. Sodium nitride is very hygroscopic, and samples are often contaminated with NaOH (reaction 15.52). 

Among the nitrides of the p-block elements, Sn3N4 and the 7-phase of Si3N4 represent the first examples of spinel nitrides (see Section 14.12). 

Nitrides of the d-block metals are hard, inert solids which resemble metals in appearance, and have high melting points and electrical conductivities (see Box 15.4). They can be prepared from the metal or metal hydride with N2 or NH3 at high temperatures. Most possess structures in which the nitrogen atoms occupy octahedral holes in a close-packed metal lattice. Full occupancy of these holes leads to the stoichiometry MN (e.g. TiN, ZrN, HfN, VN, NbN). Cubic close-packing of the metal atoms and an NaCl-type structure for the nitride MN is favoured for metals in the earliest groups of the d-block. 

Classifying nitrides is not simple, but nearly all nitrides fall into one of the following groups, although, as we have seen for the borides and carbides, some care is needed in attempting to generalize  

The classification of saline nitride implies the presence of the N ion, and as we discussed in Section 15.1, this is unlikely. However, it is usual to consider Li3N, Na3N (see Section 11.4), Be3N2, Mg3N2, Ca3N2, Ba3N2 and 

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Rinnen K D, Kolenbramder K D, DeSantolo A M and Mandioh M L 1992 Direst infrared and visible absorption speotrosoopy of stoiohiometrio and nonstoiohiometrio olusters of indium phosphide J. Chem. Phys. 96 4088... 

Xu C, de Beer E, Arnold D W, Arnold C C and Neumark D M 1994 Anion photoeleotron speotrosoopy of small indium phosphide olusters x, y = 1-4) J. Chem. Phys. 101 5406... 

Trentler T J ef a/1997 Solution-liquid-solid growth of indium phosphide fibers from organometallic precursors elucidation of molecular and non-molecular components of the pathway J. Am. Chem. Soc. 119 2172... 

Douglas T and Theopold K H 1991 Molecular precursors for indium phosphide and synthesis of small lll-V semiconductor clusters in solution inorg. Chem. 30 594... 

TAL SURFACE TREATlffiNTS - CHEMICAL AND ELECTROCHEMICALCONVERSIONTREATlffiNTS] (Vol 16) Titanium phosphide [12037-65-9]... 

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