Cadmium phosphides

Cadmium phosphides are inorganic chemical compounds of cadmium from the group of phosphides . Several cadmium phosphides are known with tricadmium diphosphide Cd ₃ P ₂ , cadmium diphosphide CdP ₂ , cadmium tetraphosphide CdP ₄ and Cd ₇ P ₁₀ and Cd ₆ P ₇ .

Extraction and presentation

Cadmium phosphides can be obtained by reacting cadmium with phosphorus . Depending on the temperature, the ratio of the starting materials and the process, the various known phosphides are formed, with tricadmium diphosphide being the easiest to represent. It arises at temperatures around 600 ° C. If there is an excess of phosphorus, cadmium diphosphide is formed and at temperatures of 575 ° C cadmium tetraphosphide is formed.

${\displaystyle \mathrm {3\ Cd+2\ P+Cd_{3}P_{2}} }$

${\displaystyle \mathrm {Cd+2\ P\longrightarrow CdP_{2}} }$

${\displaystyle \mathrm {Cd+4\ P\longrightarrow CdP_{4}} }$

The high temperature form of cadmium diphosphide can be obtained by thermolysis of ammonium phosphate or mercury phosphate with cadmium carbonate and carbon . Tricadmium diphosphide can also be obtained from cadmium phosphate .

properties

Cadmium phosphides

Surname	Tricadmium diphosphide	Cadmium diphosphide	Cadmium tetraphosphide
CAS number	12014-28-7	12133-44-7	12050-26-9	12689-75-7	12400-38-3
PubChem	159393
Molecular formula	Cd 3 P 2	CdP 2	CDP 4	Cd 7 P 10	Cd 6 P 7
Molar mass	399.18 g mol −1	174.3 g mol −1	236.3 g mol −1	1096.6 g mol −1	891.2 g mol −1
Physical state	firmly	firmly	firmly	firmly	firmly
Brief description	gray solid	orange-red solid	black solid		gray solid
Melting point	700 ° C	782 ° C	755 ° C (decomposition)
density	5.60 g cm −3	4.19 g cm −3	3.90 g cm −3	4.97 g cm −3
GHS labeling	no classification available
H and P phrases	see above
	see above

Tricadmium phosphide is a solid in the form of gray, shiny needles or flakes that is soluble in hydrochloric acid with the formation of monophosphane . An explosive reaction occurs with concentrated nitric acid . The compound has a tetragonal crystal structure of the zinc phosphide type (a = 87.6 pm, c = 123.0 pm). Cadmium diphosphide is an orange to red needle-like solid that is available in two different modifications. The high-temperature form β-CdP ₂ has a tetragonal crystal structure with the space group P 4 ₁ 2 ₁ 2 (space group no. 92) and the lattice parameters a = 529 pm and c = 1974 pm. The low-temperature form α-CdP ₂ has an orthorhombic crystal structure and changes to the high-temperature form at 420 ° C. Cadmium tetraphosphide is a black, highly reflective, crystalline, very inert solid that is soluble in hot aqua regia . When heated in a vacuum , it disintegrates into the elements. It has a monoclinic crystal structure with the space group P 2 ₁ / c (No. 14) and the lattice parameters a = 527 pm, b = 519 pm, c = 766 pm and β = 80.53 °. Cd ₆ P ₇ is a steel-gray solid with a cubic crystal structure with the space group P 4 3 m (No. 215) and a semiconductor. It can be obtained from the elements. It is only stable at temperatures between 670 ° C and 734 ° C and below that it breaks down to cadmium diphosphide and tricadmium diphosphide. Cd ₇ P ₁₀ is a crystalline solid with an orthorhombic crystal structure and a semiconductor.

Individual evidence

1. ↑ ^{a b c d e f g} Jane E. Macintyre: Dictionary of Inorganic Compounds . CRC Press, 1992, ISBN 0-412-30120-2 , pp. 2808 ( limited preview in Google Book Search).
2. ↑ ^{a b c d e f g h i j k} Georg Brauer , with the collaboration of Marianne Baudler u. a. (Ed.): Handbook of Preparative Inorganic Chemistry . 3rd, revised edition. tape I . Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , pp. 1046 .
3. ↑ V. Bagula Sankrithyan, DR Rao, RA Tewari: On the energy storage properties of cadmium phosphate (α-Cd3 (PO4) 2). In: Nuclear Tracks and Radiation Measurements (1982). 10, 1985, p. 249, doi : 10.1016 / 0735-245X (85) 90030-4 .
4. ↑ ^{a b} E. I. Zavalishin, KB Aleinikova, NS Rabotkina, AV Arsenov: The crystal structure of Cd7P10. In: Journal of Structural Chemistry. 20, 1979, pp. 120-122, doi : 10.1007 / BF00746304 .
5. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
6. ↑ W. Frey country A. Goltzene, P. Grosse, G. Harbeke, H. Lehmann, O. Madelung, W. Richter, C. Schwab, G. Weiser, H. Werheit, W. Zdanowicz: Physics of Non-tetrahedrally Bonded elements and Binary compounds I / physics of non-tetrahedrally bonded elements and binary compounds I . Springer, 1983, ISBN 3-540-11780-6 , pp. 238 ( limited preview in Google Book search).