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| Names | |
|---|---|
| IUPAC name arsenic pentachloride | |
| Other names arsenic(v) chloride | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
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| Properties | |
| AsCl5 | |
| Molar mass | 252.1866 g/mol |
| Melting point | −50 °C (−58 °F; 223 K) |
| Hazards | |
| GHS labelling: | |
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| Danger | |
| H280,H350,H361,H370,H372 | |
| 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[1] |
REL (Recommended) | Ca C 0.002 mg/m3 [15-minute][1] |
IDLH (Immediate danger) | Ca [5 mg/m3 (as As)][1] |
| Structure | |
| Trigonal Bipyramidal (D3h) | |
| Related compounds | |
Related group 5chlorides | Phosphorus pentachloride Antimony pentachloride |
Related compounds | Arsenic pentafluoride Arsenic trichloride Arsenic pentoxide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Arsenic pentachloride is achemical compound ofarsenic andchlorine[2] with the formulaAsCl5. This compound was first prepared in 1976 through the UV irradiation ofarsenic 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 tophosphorus pentachloride, PCl5 in having atrigonal bipyramidal structure where the equatorial bonds are shorter than the axial bonds (As-Cleq = 210.6 pm, 211.9 pm; As-Clax= 220.7 pm).
The pentachlorides of the elements above and below arsenic in group 15, phosphorus pentachloride andantimony 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, andkrypton) which leads to stabilisation of their 4s electrons making them less available for bonding. This effect has been termed thed-block contraction and is similar to the f-block contraction normally termed thelanthanide contraction.
Although AsCl5 is quite unstable, adducts withphosphorus pentachloride andtrimethylphosphine oxide are stable understandard conditions.[5]
