Structural characterization of potassium salts of the decamethylmanganocene anion Cp*2Mn.

For the first time the crystal structure of a permethylated metallocene anion has been obtained. The 17 valence electron complex decamethylmanganocene Cp*2Mn is reduced by molten potassium in THF to its extremely air-sensitive anion [Cp*2Mn]-. The potassium salt [K(THF)2]+[Cp*2Mn]- crystallizes upon cooling from hot THF and forms infinite polymeric chains exhibiting strong KC contacts. In the presence of 18-crown-6 the polymeric structure is broken up. Crystals of [K(18-crown-6)(THF)2]+[Cp*2Mn]- were obtained upon slow cooling from THF to -80 °C displaying well separated cations and anions.