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Transition metal complexes with Girard reagent-based ligands. Part V. Synthesis, characterization and crystal structure of pentagonal-bipyramidal manganese(II) complex with 2,6-diacetylpyridine bis(Girard-T hydrazone)

“…A number of manganese(II) complexes have been synthesized in which bis (hydrazone) chelating agents may possess various sets of donor atoms, including the N 3 O 2 set [33][34][35][36][37], involved also in the title ligand. In [38], the ligands, 2,6-diacetylpyridine bis(Girard-T/P hydrazone) dichloride were obtained in the form of anhydrous salts, although they were recrystallized from water-ethanol systems.…”

<strong>Study of the conformational rearrangement of a tetradentate hydrazone ligand</strong>

“…A significant rearrangement of the molecule structure must occur for the mononuclear complexation, as found in the case of the analogous pyridine ligand H 4 daps for manganese, cobalt and cadmium compounds. 8,9,18 In these metal complexes, both molecular threads are almost planar and the ligand shows a syn-close conformation (Scheme 1) due to a similar twisting around the C-C bonds adjacent to the benzene ring. Consequently the metal ions will be coordinated to the [ONNO] donor set of [L] 2-.…”

“…[1][2][3][4][5][6] In the past few years the coordination properties of hydrazone ligands have been extensively investigated. [7][8][9][10][11][12] The development of this coordination chemistry is, in part, the result of the interesting donor systems which could be obtained. The structural characterization of the resulting mononuclear or polynuclear complexes has led to some emerging patterns and improved the design of molecular threads that may be twisted, yielding helical molecular systems.…”

Bis[2-hydroxy-N′-(3-phenylprop-2-enylidene)benzohydrazidato-κ2N′,O]bis(methanol-κO)nickel(II) and bis[2-hydroxy-N′-(3-phenylprop-2-enylidene)benzohydrazidato-κ2N′,O]bis(pyridine-κN)nickel(II)

“…Firstly, the salicyloylhydrazone product of the condensation between salicylhydrazide and an aldehyde coordinates to a metal atom through its carboxyl O and hydrazine N atoms, not via its phenol O atom. Therefore, the salicyloylhydrazone complexes formed between a metal and this type of hydrazone are usually mononuclear (Bonardi et al, 1991;Bermejo et al, 2000;Dang et al, 2006) (see top of second scheme). Secondly, when a salicyloylhydrazone is synthesized by condensation between salicylhydrazide and a ketone, the salicyloylhydrazone is coordinated through its carboxyl O, hydrazine N and phenol O atom.…”