Magnesium phosphide

Crystal structure
__ Mg 2+      __ P 3−
Crystal system	cubic
Space group	Ia 3 (No. 206)
Lattice parameters	a = 12.01 Å
General
Surname	Magnesium phosphide
other names	Trimagnesium diphosphide
Ratio formula	Mg 3 P 2
Brief description	gray-green pellets with a garlic-like odor
External identifiers / databases
CAS number 12057-74-8 EC number 235-023-7 ECHA InfoCard 100,031,827 PubChem 61546 Wikidata Q412216
properties
Molar mass	134.86 g · mol -1
Physical state	firmly
density	2.16 g cm −3
Melting point	> 750 ° C
solubility	decomposes in water
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 260-300-311-330-400 EUH: 029-032 P: 501-405-402 + 404-370 + 378-335-321-301 + 310-280-273-234-232-223
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Magnesium phosphide is a compound from the group of phosphides . It is a gray-green solid with the smell of monophosphine , which is caused by the reaction with the humidity .

Manufacturing

Magnesium phosphide can be produced by adding liquid phosphorus to heated magnesium under an inert gas atmosphere.

${\displaystyle {\ce {6Mg + P4 -> 2Mg3P2}}}$

properties

Magnesium phosphide can be mixed with various substances such as B. halogens , oxidizing agents , acids or water react violently. Magnesium phosphide releases toxic monophosphine even when it comes into contact with humidity :

${\displaystyle {\ce {Mg3P2 + 6H2O -> 2PH3 + 3Mg(OH)2}}}$

Magnesium phosphide crystallizes in a cubic crystal structure with the space group Ia 3 (space group number 206) and the lattice parameter a = 12.01 Å . Similar to the Na ₂ O structure, the structure consists of a distorted, cubic close-packed spherical packing of phosphide ions, in which three quarters of all tetrahedral gaps are occupied by magnesium ions.

use

The property that magnesium phosphide releases monophosphine even when it is damp is used to combat voles or protect plants. The gas penetrates the caves and passages of the animals and kills them there.

Magnesium phosphide can also be used for the laboratory preparation of monophosphine, but the gas thus obtained mostly ignites by itself due to traces of diphosphine in the air.

safety instructions

Magnesium phosphide is very toxic if swallowed, as gastric acid also creates toxic monophosphine. Furthermore, the resulting gases can ignite by themselves, which is why you should not add water to accelerate the gas development.

Individual evidence

1. ↑ ^{a b} M. von Stackelberg, R. Paulus: Investigations on the crystal structure of the nitrides and phosphides of divalent metals. In: Journal for Physical Chemistry, Department B: Chemistry of Elementary Processes , Structure of Matter , 22, 1933, pp. 305–322, doi: 10.1515 / zpch-1933-2226 .
2. ↑ ^{a b c d e f} Entry on magnesium phosphide in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
3. ↑ Entry on Trimagnesium diphosphide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
4. ↑ agrosanita: EG-SDB - Degesch Plate ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 661 kB). 
5. ↑ Patent DE2945647A1 : Process for the production of aluminum phosphide and / or magnesium phosphide. Registered on November 12, 1979 , published on May 21, 1981 , Applicant: Degesch , Inventor: Franziskus Horn, Ekkehard Fluck. ‌