A New Layered Compound Containing [PMo12O40]3- and Both 5- and 6-Coordinated Homoleptic (1-(2-Chloroethyl)tetrazole)Copper(II) Cations

The synthesis, crystal structure and physical properties of the complex obtained from the reaction between the polyoxometalate anion [PMo₁₂O₄₀]_3- copper(II) and the ligand 1-(2-chloroethyl)tetrazole (teec) are described. This compound has been synthesized as a model for designing materials containing both magnetic polyoxometalate anions and iron(II) spin-crossover cations. Keywords. Coordination chemistry; Heterocycles; Polyoxometalates; Structure elucidation; Tetrazole.The compound, with formula [Cu(teec₅]₂[Cu(teec₆][PMo₁₂O₄₀]₂ · 2H₂O, consists of alternating layers of polyoxometalates and cationic complexes. Both, five and six coordinated Cu(II) ions are present,each positioned in different layers. Despite these layers having a similar width, the layer of pentacoordinated Cu(II) ions contains twice as many cationic complexes as the layer of hexacoordinated Cu(II) ions. This unusual coexistence of complexes with different coordination number is most likely caused by the steric hindrance induced by the bulky polyoxometalates in the layer of pentacoordinated Cu(II) which prevents the presence of a sixth teec ligand.