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73138-26-8 YesY
ECHA InfoCard 100.149.777
PubChem 24199707
Molar mass 185.13 g·mol−1
Appearance amber solid < 159 °C, pink > 159 °C
Melting point 175 °C (347 °F; 448 K)
Boiling point 245 °C (473 °F; 518 K)
Harmful Xn Highly Flammable F
R-phrases R11, R14, R20/21/22, R36/37/38
S-phrases S16, S26, S36/37/39
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuel Health (blue): no hazard code Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 52 °C (126 °F; 325 K)
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

Manganocene or bis(cyclopentadienyl)manganese(II) is an organomanganese compound with the formula [Mn(C5H5)2]n. It is a thermochromic solid that degrades rapidly in air. Although the compound is of little utility, it is often discussed as an example of a metallocene with ionic character.[1]

Synthesis and structure[edit]

It may be prepared in the manner common for other metallocenes, i.e., by reaction of manganese(II) chloride with sodium cyclopentadienide:

MnCl2 + 2 CpNa → Cp2Mn + 2 NaCl

In the solid state below -159 °C, manganocene adopts a polymeric structure with every manganese atom coordinated by three cyclopentadienyl ligands, two of which are bridging ligands. Above -159 °C, the solid changes color from amber to pink and the polymer converts to the structure of a normal sandwich complex, i.e., the molecule Mn(η5-C5H5)2.[1]


  1. ^ a b Richard A. Layfield "Manganese(II): the black sheep of the organometallic family" Chem. Soc. Rev., 2008, vol. 37, pp. 1098-1107.doi:10.1039/B708850G