Oxido{N-[(2-oxido-1-naphthyl-κO)methylidene]asparaginato-κ2 O 1,N 2}(1,10-phenanthroline-κ2 N,N′)vanadium(IV) N,N-dimethylformamide monosolvate

The tridentate Schiff base ligand of the title complex, [V(C15H12N2O4)O(C12H8N2)]·C3H7NO, was derived from the condensation of 2-hydroxy-1-naphthaldehyde and l-asparagine. The central VIV atom is six-coordinated by one oxide O atom, two N atoms from 1,10-phenanthroline and one N atom and two O atoms from the Schiff base ligand in a distorted octahedral geometry. In the crystal structure, intermolecular N—H⋯O hydrogen bonds connect molecules into centrosymmetric dimers. The C atoms of the dimethylformamide solvent molecule are disordered over two sites with site-occupancy factors of 0.732 (13) and 0.268 (13).

In the molecular structure of the title compound ( Fig. 1), the tridentate Schiff base ligand is derived from the condensation of 2-hydroxy-1-naphthaldehyde and L-asparagine. The central V IV atom is six-coordinated by one oxide O atom, two N atoms from 1,10-phenanthroline and one N atom and two O atoms from the schiff base ligand in a distorted octahedral geometry. The V═O bond distance is 1.587 (3)Å which is typical for oxovandium complexes (Hoshina et al., 1998;Otieno et al., 1996). The Schiff base with the vanadium atom has formed a five-member ring (O1/C1-2/N2/V1) and a six-member ring (N2/C5-7/O4/V1], and the two rings have the dihedral angle 20.89 (17)°, which increases the stability of the complex.
In the crystal structure, the intermolecular N-H···O hydrogen bonds (Table 1) connect molecules into centrosymmetric dimers (Fig. 2). The solvate molecules are also hydrogen bonded to the Schiff base ligand. The structure is stablilized by inter-and intra-molecular hydrogen bonds of the type C-H···O.

Experimental
L-Asparagine (1 mmol, 150.1 mg) and potassium hydroxide (1 mmol, 56.1 mg) were dissolved in hot methanol (5 ml) with stirring and added successively to a methanol solution (5 ml) of 2-hydroxy-1-naphthaldehyde (1 mmol, 172.2 mg). The mixture was stirred at 323 K for 2 h. Subsequently, an aqueous solution (2 ml) of vanadyl sulfate hydrate (1 mmol, 225.4 mg) was added dropwise and stirred for 2 h continuously. 1,10-Phenanthroline (1 mmol, 198.2 mg) was then added to the stirring mixture and further refluxed for 4 h and then filtered. The precipitate was dissolved in N,N-dimethylformamide (10 ml) and held at room temperature for several days, whereupon brown blocky crystals suitable for X-ray diffraction were obtained.

Refinement
All H atoms were placed in geometrically calculated positions, with C-H = 0.93-0.98 Å, and allowed to ride on their respective parent atoms, with U iso (H) = 1.2U eq (C) or 1.5U eq (C methyl ). The C-atoms of the N,N-dimethylformamide solvate were disordered over two sites with site occupancy factors 0.732 (13) and 0.268 (13).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme. The smaller fraction of the disordered C-atoms of the solvate have been joined by hollow bonds.