Synthesis, characterization and magnetic behaviour of tetra-μ3-fluorododecakis(5-methylpyrazole-N2)tetrametal(II) tetrakis(tetrafluoroborates)

Abstract 3(5)-Methylpyrazole (3(5)-MPZ) was found to induce tetrafluoroborate decomposition upon the reaction with M(BF 4 ) 2 ·aq salts, yielding fluoride containing compounds, analysing as MF(5-MPZ) 3 (BF 4 ). For M = Cd and Mn this reaction proceeds at room temperature, while for M = Co and Ni higher reaction temperatures (up to 80 °C) have to be used. According to IR, UV and EPR spectroscopy and X-ray powder diagrams a tetrameric structure is proposed in correspondence to the known structure of [Co 4 F 4 (N-ethylimidazole) 12 ](BF 4 ) 4 . The ligand 3(5)-MPZ is believed to bind to the metals with the methyl substituent in the 5-position. Magnetic susceptibility studies down to 2 K indicate weak antiferromagnetic interaction between the metal ions in the cluster. The magnitude of the exchange parameter for the Co-compound (J/k≈ − 7 K) is comparable to the one found previously for Co 4 F 4 (N-ethylimidazole) 12 (BF 4 ) 4 .