Synthesis and crystal structure of [Co(L)(NO2)3]H2O (L = piridoxylene Girar-T hydrazone)

Dark red monocrystals of title complex were prepared by the reaction of water solutions of Na3[Co(NO2)6] and L×2H2O in mole ratio 1:1. The Co(III) is sited in an octahedral environment. The equatorial plane is formed by a tridentate coordination of the ligand (L) and one NO2 molecule, while the other two NO2 molecules are in axial positions. The ligand is coordinated to the Co(III) atom through O3, N1 and O4 atoms, forming two fused chelate rings, one being five-membered and one a six-membered one. All atoms in the chelate and phenyl rings are approximately coplanar. The angle between the mean plan of the equatorial NO2 and the mean plane defined by the two chelate rings is 28.1(3)°. The Co-N bond lengths for the two axial NO2 are about 0.03 Å longer than that with the equatorial NO2. The two axial NO2 are coplanar. The complex molecule possesses eight oxygen atoms capable of acting as proton acceptors in the hydrogen bonds, but there are only two groups (one N-H and one O-H) able to participate as proton donors. As a consequence, six oxygen atoms from NO2 ligands form weak C-H...O hydrogen bonds with only one exception for O4 atom which participates in two strong O-H...O hydrogen bonds. Because of that the N-O4 bond is significantly longer than the rest of N-O bonds in the NO2 ligands. Data were collected on an Enraf-Nonius CAD-4 diffractometer using Mo K radiation ( = 0.71069 Å) and /2 scans in 1.41 to 25.47° range and were corrected for Lorentz and polarization effects. The structure was solved by direct methods and difference-Fourier methods, and refined by full matrix least-squares using SHELXL97 program to a final R = 0.0431 for 2938 reflections with I > 2 I. Crystallographic data: CoC13H22N7O10, Mr = 495.3, monoclinic, space group P 21/c, a = 14.936(3) Å, b = 7.773(3) Å, c = 17.463(3)Å, = 104.26(3) °, V = 1964.9(9) Å, Z = 4, Dc = 1.674 Mg/m , (MoK ) = 0.944 mm, Mo K radiation, = 0.71073 A, GooF = 1.055.