Synthesis, geometrical and electronic structure of iron mononitrosyl complexes with bis( S-alkylisothiosemicarbazones) of β-dicarbonyl compounds

Abstract

Complex [Fe(HL)NO]NO 3 ( 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(NO 3) 3·9H 2O in ethanol, while [Fe(R 2Q)NO] ( 2), where RCH 3 ( 2a), C 2H 5 ( 2b), n-C 3H 7 ( 2c), n-C 4H 9 ( 2d), has been obtained by the interaction of Fe(NO 3) 3·9H 2O with nitromalondialdehyde bis( S-methylisothiosemicarbazone) (R 3H 3Q) 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(1), b=21.092(2), c=10.385(2) Å, γ=96.15(2)°, ϱ calc=1.367 g cm −3, Z=4, molecular formula C 9H 16FeN 8O 3S 2. Crystal 2c is triclinic, space group P 1 ; a=8.108(2), b=9.489(2), c=12.872(3) Å, α=103.51(2), β=106.02(2), γ=75.09(2)°, ϱ calc=1.578 g cm −3, Z=2, molecular formula C 11H 18FeN 8O 3S 2. The structures 1 ( 2c) were solved by direct methods. Least-squares refinement using 1829 (1794) unique reflections with I⩾3σ( 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 (HL 2− and C 3H 7Q 3−) around the central ion in the basal plane (deviation from the pyramid base plane 0.477 ( 1) and 0.473 ( 2c) Å) and the NO in the apical position. The FeNO group is approximately linear (the FeNO angle is equal to 172.7 (175.5°)). The data of the 1H NMR, IR, Mössbauer and electronic absorption spectra indicate that 2a– 2d have a similarly structured coordination polyhedron. On the basis of X-ray analysis, IR, Mössbauer spectra and calculations of the electronic structures, it was concluded that the FeNO group is a highly covalent entity.