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| Names | |
|---|---|
| IUPAC name Bis(η8-cyclooctatetraene)neptunium[1] | |
| Other names Neptunium cyclooctatetraenide Np(COT)2 | |
| Identifiers | |
3D model (JSmol) | |
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| Properties | |
| C16H16Np | |
| Molar mass | 445 g·mol−1 |
| Appearance | dark brown crystals as a solid, yellow in dilute solution |
| insoluble, does not react with water | |
| Solubility in chlorocarbons | sparingly soluble (ca. 0.5 g/L) |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | radiation hazard, pyrophoric |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Neptunocene, Np(C8H8)2, is an organoneptunium compound composed of aneptunium atomsandwiched between twocyclooctatetraenide (COT2-) rings. As a solid it has a dark brown/red colour but it appears yellow when dissolved inchlorocarbons, in which it is sparingly soluble.[2][3][4][5][6] The compound is quiteair-sensitive.[2][3][6]
It was one of the first organoneptunium compounds to be synthesised, and is a member of theactinocene family ofactinide-basedmetallocenes.[3]
The sandwich structure of neptunocene has been determined bysingle crystal XRD.[5] The COT2- rings are found to be planar with 8 equivalent C–C bonds of 1.385 Å length, and sit parallel in an eclipsed conformation. The Np–COT distance (to the ring centroid) is 1.909 Å and the individual Np–C distances are 2.630 Å.[5]
Neptunocene assumes amonoclinic crystal structure (P21/nspace group) which isisomorphous touranocene andthorocene but not toplutonocene.[5]
Neptunocene was first synthesised in 1970 by reactingneptunium(IV) chloride (NpCl4) withdipotassium cyclooctatetraenide (K2(C8H8)) indiethyl ether orTHF:[2]
The same reaction conditions have been routinely reproduced since then for the synthesis of the compound.[4][5]
The three actinocenesuranocene, neptunocene, andplutonocene share virtually identical chemistry: they do not react in the presence of water or dilute base, but are very air-sensitive, quickly forming oxides.[2][3][4] All three are only slightly soluble (up to about 10−3 M concentrations) in aromatic or chlorinated solvents such asbenzene,toluene,carbon tetrachloride orchloroform.[2][3][5][6]
