Neptunocene
Chemical compound
From Wikipedia, the free encyclopedia
Neptunocene, Np(C8H8)2, is an organoneptunium compound composed of a neptunium atom sandwiched between two cyclooctatetraenide (COT2-) rings. As a solid it has a dark brown/red colour but it appears yellow when dissolved in chlorocarbons, in which it is sparingly soluble.[2][3][4][5][6] The compound is quite air-sensitive.[2][3][6]
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| Names | |
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| 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 their standard state (at 25 °C [77 °F], 100 kPa).
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It was one of the first organoneptunium compounds to be synthesised, and is a member of the actinocene family of actinide-based metallocenes.[3]
Structure
The sandwich structure of neptunocene has been determined by single 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 a monoclinic crystal structure (P21/n space group) which is isomorphous to uranocene and thorocene but not to plutonocene.[5]
Synthesis and properties
Neptunocene was first synthesised in 1970 by reacting neptunium(IV) chloride (NpCl4) with dipotassium cyclooctatetraenide (K2(C8H8)) in diethyl ether or THF:[2]
- NpCl4 + 2 K2(C8H8) → Np(C8H8)2 + 4 KCl
The same reaction conditions have been routinely reproduced since then for the synthesis of the compound.[4][5]
The three actinocenes uranocene, neptunocene, and plutonocene 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 as benzene, toluene, carbon tetrachloride or chloroform.[2][3][5][6]