The reaction between vanadium(III) acetylacetonate and N-hexanoylsalicylhydrazide (H3hshz) yields a linear trinuclear mixed valence vanadium(V/IV/V) complex, V3O3(hshz)2(OEt)2, 1 (where hshz3- is a triply deprotonated trianionic N-hexanoyl salicylichydrazidate), with a pseudo C2 symmetry. A V(IV)O2+ group is at the center of complex 1 and is spanned by two terminal vanadium(V) ions with a square pyramidal geometry bridged via hydrazido ligands. In the crystalline form, the oxo group of the central vanadium(IV) ion is weakly coordinated to one of the terminal square pyramidal vanadium(V) ions of the neighboring trinuclear complex to form a dimeric structure. These dimers are linked via bis mu-alkoxo bridges to form a one-dimensional zigzag chain structure. In chloroform or methylene dichloride, the weak linkages between the trinuclear complexes present in the crystalline form are broken, and only the mixed valence trinuclear complex can be identified. In dimethyl sulfoxide or dimethylformamide, the trinuclear complex partially dissociates, and the unligated ligands remain in equilibrium with the trinuclear complex.
Polymorphic mono-oxo mono-alkoxo square-pyramidal [V V O(Hacshz)(OEt)] (where Hacshz 2-is a doubly deprotonated dianionic acetylacetosalicylhydrazone; thick plateshaped dark-greenish-brown crystals for 1a and blockshaped dark-reddish-brown crystals for 1b) and mononuclear trigonal-prismatic [V IV (Hacshz) 2 ] (block-shaped dark-bluishbrown crystals for 2a and triangular-shaped dark-violet crystals for 2b) were synthesized and characterized. The crystals were prepared by simple addition of vanadium(III) acetylacetonate to an ethanol solution of salicylhydrazide (H 3 shz). Depending on the ratio of the ligand to the metal ion, the extent of exposure to molecular oxygen, and the filtration of the intermediate, various polymorphs could be obtained as both mixtures and pure forms. A common π-π stacked dimeric
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