Crystal structure of alaninato-κ²N,O-bis(hydroxylamido-κ²N,O)-oxido-vanadium(V), C₃H₁₀N₃O₅V

Source of material

All reagents were obtained from commercial sources and used without further purification. The compound was synthesized by aqueous reactions: NH₄VO₃ (1.72 mmol), alanine (5.00 mmol) and NaOH (6.61 mmol) was dissolved in 12 mL of aqueous solution at room temperature. The resulting yellow solution was cooled to 275 K in an ice bath. NH₂OH…HCl (4.31 mmol) was added slowly with constant stirring. The pH of the solution was about 6.5. The obtained yellow solution was filtered. Colorless crystals were obtained by slow evaporation of the filtrate from ethanol at 277 K for a few days. Anal. Calcd. for C₃H₁₀N₃O₅V (%): C, 16.45; H, 4.60; N, 19.18; V, 23.25. Found: C, 16.51; H, 4.56; N, 19.20; V, 23.22. The vanadium content was determined by spectrophotometry.

Experimental details

The structure was solved by direct methods with the SHELXS-2018 program [2]. The H atoms bonded to N3 atoms were located in difference maps and refined freely. Other H atoms were placed in calculated positions. The Carbon atoms C2 and C3 are disordered over two positions.

Comment

Vanadium is a trace element in biochemical systems to play an important role in metalloenzymes and impact insulin regulation [5]. In recent years, a number of vanadium hydroxylamido complexes have shown that the hydroxylamido ligand coordinates in a side-on manner as does the peroxo functionality [6]. To the best of our knowledge, the coordination chemistry of vanadium hydroxylamine complexes has been less studied so far [7], [8], [9]. Therefore, we have synthesized the title compound, and report crystal structure.

In the crystal structure of the title compound the vanadium(V) centers are seven-coordinated in pentagonal bipyramidal geometry containing two bidentate hydroxylamido ligands, one oxido, and one alaninato ligand. The two hydroxylamine molecules and the amine nitrogen atom of alanine molecule define a pentagonal equatorial plane approximately perpendicular to V=O bond, while the two oxygen atoms [O3, O4] occupy the axial position, and the distance of vanadium from the equatorial plane is 0.238 Å. The hydroxylamido ligands are coordinated with the nitrogen atoms cis to the alaninato ligand. The carboxylate oxygen atom of alanine is coordinated trans to the oxido group in the complex, the V–N bond lengths are 2.018(2) and 2.004(2) Å, respectively, and the V–O bond lengths are 1.906(2) and 1.912(2) Å, respectively. The molecular structure of the compound is very similar to the other vanadium(V) hydroxylamido complexes with amino acid ligands [10, 11].