Arsenic pentachloride
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| Identifiers | |
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| Properties | |
| AsCl5 | |
| Molar mass | 252.1866 g/mol |
| Hazards | |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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[1910.1018] TWA 0.010 mg/m3 |
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REL (Recommended)
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Ca C 0.002 mg/m3 [15-minute] |
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IDLH (Immediate danger)
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Ca [5 mg/m3 (as As)] |
| Structure | |
| Trigonal Bipyramidal (D3h) | |
| Related compounds | |
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Related group 5 chlorides
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Phosphorus pentachloride Antimony pentachloride |
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Related compounds
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Arsenic pentafluoride Arsenic trichloride Arsenic pentoxide |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
Arsenic pentachloride is a chemical compound of arsenic and chlorine. This compound was first prepared in 1976 through the UV irradiation of arsenic trichloride, AsCl3, in liquid chlorine at −105 °C. AsCl5 decomposes at around −50 °C. The structure of the solid was finally determined in 2001. AsCl5 is similar to phosphorus pentachloride, PCl5 in having a trigonal 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 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 elements following the first transition series (i.e. gallium, germanium, arsenic, selenium and bromine) which leads to stabilisation of their 4s electrons making them less available for bonding. This effect has been termed d-block contraction and is similar to the f-block contraction normally termed the lanthanide contraction.
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