Structural characterization of the columnar alkali metal cyclopentadienide [K{C5H2(SiMe3)(3)-1,2,4}](infinity)

Unsolvated 1,2,4-tris(trimethylsilyl)cyclopentadienyl potassium (K[Cp-3Si]) crystallizes as a base-free super-sandwich of alternating potassium ions and Cp' rings. The polymeric chains in the structure are not connected as in other unsolvated KCp' structures, but uniquely consist of independent columns. This type of structure has previously been observed in base-free lithium cyclopentadienyl complexes; however, K[Cp-3Si] is the first base-free potassium cyclopentadienyl complex that crystallizes without interactions between neighboring chains.