Ether and crown ether adduct complexes of sodium and potassium cyclopentadienide and methylcyclopentadienide molecular structures of [Na(dme)Cp](infinity), [K(dme)(0.5)Cp](infinity), [Na(15-crown-5)Cp], [Na(18-crown-6)Cp-Me] and the naked Cp- complex [K(15-crown-5)(2)][Cp]

The molecular structure, spectroscopy and mass spectrometry of the following compounds are described: [Na(dme)Cp](infinity) (polymeric zigzag chain), [K(dme)(0.5)Cp](infinity) (2-dimensional polymeric zigzag), [Na(15-crown-5)Cp] (monomeric), [Na(18-crown-6)Cp-Me] (monomeric) and [K(15-crown-5)(2)][Cp] {K(15-crown-5)(2) cation/naked cyclopentadienide anion}. The syntheses of the related species [Na(dme)Cp-Me], [K(dme)(0.5)Cp-Me], [Na(15-crown-5)Cp-Me], [Na(18-crown-6)Cp] and [K(15-crown-5)(2)][Cp-Me] are reported. The choice of coordination modes displayed by those species structurally characterised is discussed, particularly in terms of steric and electrostatic considerations.