A niobium(V) complex with the composition [NbCl(OC₆H₄CH(CH₃)₂-2)₄] was synthesized by reacting niobium pentachloride with four equivalents of 2-isopropylphenol in carbon tetrachloride as a solvent, yielding the product in good quantity. The complex was characterized using elemental analysis, molar conductance measurements, IR spectroscopy, ¹H and ¹³C NMR spectroscopy, and mass spectrometry. Spectroscopic results indicate that the complex exists in a dimeric form, with bridging occurring through isopropylphenoxo ligands. X-ray diffraction analysis suggests that the complexes are amorphous in nature.

The methanolic solution of the synthesized complex, monochlorotetrakis(2-isopropylphenoxo)niobium(V), [NbCl(OC₆H₄CH(CH₃)₂-2)₄], reacts with equimolar amounts of potassium benzohydroxamate and p-chlorobenzohydroxamate in benzene to form mixed-ligand phenoxo-hydroxamato niobium(V) complexes. These products were confirmed through physicochemical studies along with IR and ¹H NMR spectral analyses. The spectral evidence indicates that potassium benzohydroxamate and p-chlorobenzohydroxamate effectively cleave the isopropylphenoxo bridging bonds, resulting in the formation of monomeric (unimolecular) complexes.

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