SYNTHESIS, GEOMETRICAL AND ELECTRONIC-STRUCTURE OF IRON MONONITROSYL COMPLEXES WITH BIS(S-ALKYLISOTHIOSEMICARBAZONES) OF BETA-DICARBONYL COMPOUNDS

Complex [Fe(HL)NO]NO3 (1), where H-3L=2,4-pentanedione bis(S-methylisothiosemicarbazone), has been synthesized by template reaction of S-methylisothiosemicarbazidehydrogen-nitrate, sodium acetylacetonate monohydrate and Fe(NO3)3.9H2O in ethanol, while [Fe(R2Q)NO] (2), where R=C 3 (2a), C2H5 (2b), n-C3H7 (2c), n-C4H9 (2d), has been obtained by the interaction of Fe(NO3)3-9H2O with nitromalondialdehyde bis(S-methylisothiosemicarbazone) (R3H3Q) in the presence of nitric oxide in ethanol. The crystal structures of 1 and 2c have been determined by X-ray diffraction methods. Crystal 1 belongs to the monoclinic system, space group P2(1)/n; a = 7.660(l), b=21.092(2), c=10.385(2) angstrom, gamma=96.15(2)-degrees, rho(calc)=1.367 g CM-3, Z=4, molecular formula C9H16FeN8O3S2. Crystal 2c is triclinic, space group P1BAR; a=8.108(2), b=9.489(2), c=12.872(3) angstrom, alpha=103.51(2), beta=106.02(2), gamma=75.09(2)-degrees, rho(calc), = 1.578 g cm-3, Z=2, molecular formula C11H18FeN8O3S2. The structures 1 (2c) were solved by direct methods. Least-squares refinement using 1829 (1794) unique reflections with I greater-than-or-equal-to 3 sigma(I) has led to the final R of 0.026 (0.034) for 1 (2c). The cation [Fe(HL)NO]+ and complex 2c have a square-pyramidal structure with the corresponding quadridentate ligand (HL2- and C3H7Q3-) around the central ion in the basal plane (deviation from the pyramid base plane 0.477 (1) and 0.473 (2c) angstrom) and the NO in the apical position. The FeNO group is approximately linear (the FeNO angle is equal to 172.7 (175.5-degrees)). The data of the H-1 NMR, IR, Mossbauer and electronic absorption spectra indicate that 2a-2d have a similarly structured coordination polyhedron. On the basis of X-ray analysis, IR, Mossbauer spectra and calculations of the electronic structures, it was concluded that the FeNO group is a highly covalent entity.