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)FeCl2[η2-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.