Synthesis, Characterization, and Crystal Structure of [Co₄(CH₃CO₂)₂L₄]₂[BPh₄]₄·0.5H₂O, Where HL = 4-(Salicylaldiminato)antipyrine

Abstract

The title complex was isolated as a red solid from the reaction of 4-(salicylaldiminato)antipyrine, HL, and cobalt (II) acetate in ethanol. The complex has been characterized by elemental analysis, FTIR, UV-Vis, and X-ray single crystal diffraction. Two crystallographically different cationic units, A and B, of the title complex are found. Both units are essentially isostructural; nevertheless, small differences exist between them. Both units contain four cobalt atoms arranged at the corners of distorted cubane-like core alternatively with phenoxy oxygen of the Schiff base. In both cases, one cobalt binds to three coordinated sites from the corresponding tridentate Schiff base ligand, and the fourth one was bonded by the acetate oxygen, and the fifth and the sixth donor sites come from the phenolate oxygen of another Schiff base ligand.

Synthesis, Crystal Structure, and Magnetic Properties of a New Mixed Metal (Co(II), Ni(II)) Cubane

“…The IR spectrum of the complex has the same pattern of the well-known structure of [${\mathrm{Co}}_4{\mathrm{L}}_4{false({\mathrm{CH}}_3\mathrm{COO}false)}_2{]}_2{false[{\mathrm{BPh}}_{4}false]}_4·0.5{\mathrm{H}}_2\mathrm{normalO}$ [12] and exhibits strong absorptions at 1625 and 1562 cm −1 assignable to the carbonyl group of the pyrazolone ring, $\nu$(C–O), and azomethine group $\nu$(HC=N) of “L”, respectively. The first absorption band of the complex was shifted by about 29 ${\mathrm{cm}}^{-1}$ to a lower frequency relative to the corresponding signal of the free ligand (1654 ${\mathrm{cm}}^{-1}$), indicating that the ligand coordinates through the carbonyl oxygen of the pyrazolone ring.…”

“…The title complex ( 1 ) was prepared using previously described method [12]. A solution of HL (2.0 mmol, 0.60 g) in 15 ml ethanol, cobalt(II) acetate (1.0 mmol) and Ni(II) acetate (1.0 mmol) in 15 mL ethanol were mixed and refluxed for about 2 h. After that time, an orange solid material precipitated from the solution.…”

“…Red solid of ( 2 ) was prepared using the previously described method [12]. A solution of HL (2.0 mmol, 0.60 g) in 15 mL ethanol and cobalt(II) acetate (2.0 mmol) in 15 mL ethanol were refluxed together; after 2 h, a red solid material was precipitated.…”

“…The final product was dissolved in acetone and filtered; on slow evaporation, red crystals of ( 2 ) were formed (yield 62%). The final product was characterized by elemental analysis, FTIR, UV-Vis, and single-crystal X-ray diffraction analysis [12]. …”

“…Ferromagnetic interaction correlates to the Ni–O–Ni angle within the cubane, being active only when the Ni-O-Ni angle is lower than 98°. Such angular values were found for ${\mathrm{Co}}_4$-tetranuclear cubane cores complex with the general formula [${\mathrm{Co}}_4{\mathrm{L}}_4{false({\mathrm{CH}}_3\mathrm{COO}false)}_2{]}_2{false[{\mathrm{BPh}}_{4}false]}_4·0.5{\mathrm{H}}_2\mathrm{normalO}$ where HL is 4-(salicylaldimine)antipyrine (Scheme 1) [12]. This type of Schiff base which can act as bi and tri-dentate ligand often forms polynuclear complexes with cubane core structure where the phenoxy oxygen acts as a good bridging group.…”