Arsenic pentachloride

Arsenic pentachloride
Names
	IUPAC name arsenic pentachloride
	Other names arsenic(v) chloride
Identifiers
CAS Number	22441-45-8 ;
3D model (JSmol)	Interactive image;
PubChem CID	13643880;
CompTox Dashboard (EPA)	DTXSID60545765 ;
	InChI InChI=1S/AsCl5/c2-1(3,4,5)6 Key: ZSRZHCIWJJKHAU-UHFFFAOYSA-N;
	SMILES Cl[As](Cl)(Cl)(Cl)Cl;
Properties
Chemical formula	AsCl5
Molar mass	252.1866 g/mol
Melting point	−50 °C (−58 °F; 223 K)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H280, H350, H361, H370, H372
Precautionary statements	P201, P202, P260, P264, P270, P281, P307+P311, P308+P313, P314, P321, P405, P410+P403, P501
	NIOSH (US health exposure limits):
PEL (Permissible)	[1910.1018] TWA 0.010 mg/m3
REL (Recommended)	Ca C 0.002 mg/m3 [15-minute]
IDLH (Immediate danger)	Ca [5 mg/m3 (as As)]
Structure
Molecular shape	Trigonal Bipyramidal (D3h)
Related compounds
Related group 5 chlorides	Phosphorus pentachloride; Antimony pentachloride
Related compounds	Arsenic pentafluoride; Arsenic trichloride; Arsenic pentoxide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Arsenic pentachloride is a chemical compound of arsenic and chlorine.^[2] This compound was first prepared in 1976 through the UV irradiation of arsenic trichloride, AsCl₃, in liquid chlorine at −105 °C.^[3] AsCl₅ decomposes at around −50 °C. The structure of the solid was finally determined in 2001.^[4] AsCl₅ is similar to phosphorus pentachloride, PCl₅ in having a trigonal bipyramidal structure where the equatorial bonds are shorter than the axial bonds (As-Cl_eq = 210.6 pm, 211.9 pm; As-Cl_ax= 220.7 pm).

The pentachlorides of the elements above and below arsenic in group 15, phosphorus pentachloride and antimony pentachloride are much more stable and the instability of AsCl₅ appears anomalous. The cause is believed to be due to incomplete shielding of the nucleus in the 4p elements following the first transition series (i.e. gallium, germanium, arsenic, selenium, bromine, and krypton) which leads to stabilisation of their 4s electrons making them less available for bonding. This effect has been termed the d-block contraction and is similar to the f-block contraction normally termed the lanthanide contraction.

References

^ ^a ^b ^c NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH).
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ K. Seppelt (1976). "Arsenic Pentachloride, AsCl₅". Angew. Chem. Int. Ed. Engl. 15 (6): 377–378. doi:10.1002/anie.197603771.
^ Haupt S, Seppelt K (2002). "Solid State Structures of AsCl₅ and SbCl₅". Zeitschrift für anorganische und allgemeine Chemie. 628 (4): 729–734. doi:10.1002/1521-3749(200205)628:4<729::AID-ZAAC729>3.0.CO;2-E.

[PGCH-1] NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH).

[2] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[3] K. Seppelt (1976). "Arsenic Pentachloride, AsCl₅". Angew. Chem. Int. Ed. Engl. 15 (6): 377–378. doi:10.1002/anie.197603771.

[4] Haupt S, Seppelt K (2002). "Solid State Structures of AsCl₅ and SbCl₅". Zeitschrift für anorganische und allgemeine Chemie. 628 (4): 729–734. doi:10.1002/1521-3749(200205)628:4<729::AID-ZAAC729>3.0.CO;2-E.

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