Complexes of 2,6-diacetylpyridine dihydrazone with middle and late first row transition metals

• A series of 2,6-diacetylpyridine dihydrazone (DAPH) complexes with middle and late first row transition metal ions are presented.
• Control of reagent stoichiometry can produce either 1:1 or 2:1 ligand to metal complexes.
• The 2:1 complexes are homoleptic, and the 1:1 complexes can either be mononuclear or dinuclear.
• All compounds have been structurally elucidated via X-ray crystallography.

A study of the transition metal chemistry with the planar tridentate ligand 2,6-diacetylpyridine dihydrazone (1, DAPH) is presented, expanding the chemistry of this ligand across the first row of the transition metals. Ligand 1 forms both 1:1 and homoleptic 2:1 complexes with transition metal ions, depending on the metal salt used and reaction conditions, and seven new complexes with Mn, Fe, Co, Cu and Zn are presented. All compounds, including the ligand, have been characterized by X-ray crystallography. DAPH (1) binds to metal ions in an asymmetric fashion, with a M–Npyr bond that is shorter than the flanking M–Nimine bonds. Additionally, the Nimine–M–Nimine bonds form acute angles ranging from ~ 140 to 160°, depending on the identity of the metal ion and ligand environment. All compounds are compared with previously elucidated DAPH structures from the literature.

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