Abstract:

The single crystal structure analyses of the acicular and lamellar potassium dioxalato copper(II) crystals indicated that not only Cu²⁺ but also K⁺ ions coordinate with C₂O₄²⁻ ligands and locate in the inner boundary of the complexes. In addition, H₂O molecules also participate in coordination with Cu²⁺ or K⁺ ions as bridging ligands. So, according to the rules of writing of the chemical formula of the complexes, the chemical formulas of the acicular and lamellar crystal products should be written as [K₂Cu(C₂O₄)₂(H₂O)₄]_n and [K₂Cu(C₂O₄)₂(H₂O)₂]_n and not as K₂[Cu(C₂O₄)₂]∙4H₂O and K₂[Cu(C₂O₄)₂]∙2H₂O. This paper provides a clarification to this long-standing misconception.

Key words: Potassium dioxalato copper(II), Crystal structure, Chemical formula