Oxidation of the iron(II) complex with 3,5-dimethylpyrazole by air in acetonitrile and dibenzyl ether

The reaction of the polymeric complex FeCl₂(NCMe)₂ (1) with 3,5-dimethylpyrazole (Hdmpz) yields the tetrahedral complex Fe(Hdmpz)₃Cl]Cl (2), which is oxidized by air in acetonitrile to give Fe(Hdmpz)₃Cl₂]₂(μ-O) (3). The reaction of FeCl₃ · 6H₂O with Hdmpz also leads to complex 3. The oxidation of complex 2 in a dichloromethane solution of dibenzyl ether gives the complex (Hdmpz)FeCl₂η²-N,O-(dmpz)C(O)H(Ph)] (4), which contains a coordinated tetrahedral intermediate product of condensation of Hdmpz and benzaldehyde. The structures of complexes 1–4 are discussed on the basis of X-ray crystallographic data.