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Manganocene or bis(cyclopentadienyl)manganese(II) is an organomanganese compound with the formula Mn(C5H5)2n. It is a thermochromic solid that air sensitivity. Although the compound is of little utility, it is often discussed as an example of a metallocene with ionic character.
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.
Manganocene polymerizes ethylene to high molecular weight linear polyethylene in the presence of methylaluminoxane or diethylaluminium chloride as cocatalysts. It does not polymerize propylene.
Reactions
The ionic character of manganocene gives it an unusual pattern of reactivities compared to metallocenes of other transition metals in the same row. It is kinetically labile, being readily Hydrolysis by water or hydrochloric acid, and readily forms with two- or four-electron Lewis bases.
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