2.6- diacetylpyridine hydrazones

Transition Metal Complexes with Bis(Hydrazone) Ligands of 2, 6-Diacetylpyridine. Hepta-Coordination of 3d Metals... 

TRANSITION METAL COMPLEXES WITH BIS(HYDRAZONE) LIGANDS OF 2,6-DIACETYLPYRIDINE. HEPTA-COORDINATION OF 3d METALS... 

Yet another hydrazine-based ligand, 2,6-diacetylpyridine bis(benzoic acid hydrazone) (dpbh 10) forms an interesting complex with La(N03)3 in which the coplanar penannular pentaden-tate dpbh coordinates together with three bidentate nitrate ions to give an 11-coordinated complex. One nitrate ion is disposed near the gap in the dpbh chain with the other two above and below the dpbh plane. Interatomic distances are La—N(ligand) = 2.769-2.790, La— O(ligand) = 2.507 and 2.560, and La—O(nitrate) = 2.563-2.648 A. 

Condensation of a monocarbonyl compound with a dihydrazone initially yields a macrocycle with a tetraaza six-membered chelate ring, e.g. (21 Scheme 8) or (23 Scheme 9), but this can isomerize to give a triaza five-membered chelate ring, as for (27 Scheme 10), where cyclization is by a reaction subsequent to the hydrazone/carbonyl condensation,21 or for the isomeric pair of compounds (25) and (26) of Scheme 9. Compounds with triaza (28) and tetraaza (22) seven-membered chelate rings have also been prepared.22 Tetradentate and pentadentate aza macrocycles are formed by condensations of 2,6-diacetylpyridine with hydrazine (29) or with dihydrazines (30).21... 

---