Calcium cyclopentadienide

From the divalent chalcogenides the trend continues as expected, through the cyclopentadienide, which has been shown to be ionic in the case of other rare earths, alkaline earths and even manganese (II), through the chloride, the hydroxide (which is a strong base comparable to calcium hydroxide), and finally to the highly ionic sulfate. 

Schumann, G. A. Molander, and co-workers in 79% yield each from the respective potassium cyclopentadienide and calcium iodide in THF. The inability to bind THF is quite remarkable when the tenacity of coordinated THF in other calcocenes is considered. ... 

Calcium, strontium, and barium cyclopentadienides, e.g. (C5Hs)2Ca, are known and may have ionic constitutions. The bright red bistriphenyl-methyl of calcium, Ca(THF)..,6(Ph3C)2, appears to be a salt. 

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