New iron(II) coordination compounds with 1-aryl-5-(benzothiazol-2-yl) formazans were prepared. Their compositions and structures were determined by electronic spectroscopy, mass spectrometry, single crystal X-ray diffraction analysis, and magnetochemical measurements. © 2008 Pleiades Publishing, Ltd.Russian Foundation for Basic Researc

Gorbatenko, Y. A.

Lipunov, I. N.

Lipunova, G. N.

Maslakova, T. I.

Pervova, I. G.

Rezinskikh, Z. G.

Slepukhin, P. A.

Russian Journal of Applied Chemistry

English

Electronic archive of the Ural State Forest Engineering University

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 12, pp. 2127–2131. © Pleiades Publishing, Ltd., 2008. Original Russian Text © Yu.A. Gorbatenko, Z.G. Rezinskikh, G.N. Lipunova, I.G. Pervova, T.I. Maslakova, P.A. Slepukhin, I N. Lipunov, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 12, pp. 2016–2020. 2127 Synthesis and Spectroscopic Features of Iron(II) 1-Aryl-5-benzothiazol-2-ylformazanates  Yu. A. Gorbatenko, Z. G. Rezinskikh, G. N. Lipunova, I. G. Pervova, T. I. Maslakova, P. A. Slepukhin, and I. N. Lipunov  Ural State University of Forestry Engineering, Yekaterinburg, Russia  Ural State Technical University–Ural Polytechnic Institute, Yekaterinburg, Russia  Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia  Received June 18, 2008  Abstract—New iron(II) coordination compounds with 1-aryl-5-(benzothiazol-2-yl)formazans were prepared. Their compositions and structures were determined by electronic spectroscopy, mass spectrometry, single crystal X-ray diffraction analysis, and magnetochemical measurements. Iron coordination compounds with polydentate nitrogen-containing heterocyclic ligands are unique chemical systems. The specific features of their prop-erties and structure are determined by the nature of the coordination core and by the steric arrangement of side functional groups. Iron chelates has demonstrated good performance as effective catalysts of not only industrial (synthesis of ammonia, dehydrogenation of hydrocarbons, etc.) [1–3] but also biochemical processes [4]. Many of these compounds are characterized by exchange interactions of both ferro- (ferri-) and antiferromagnetic type, which lead under the action of certain external factors (tem-perature, pressure, irradiation at a definite wavelength) to transitions into a magnetically ordered state or to spin transitions S = 5/2 ? S = 1/2 [5–7] and  make the iron complexes attractive objects for molecular electronics. In this context, synthesis and study of structural features of new coordination compounds of iron with ambidentate ligands are of both scientific and practical interest. Among such ligands are, in particular, hetarylfor-mazans, for which both bridging and chelate coordina-tion is typical. The polydenticity and high flexibility of the formazan molecule, as well as the ability of such compounds to act as both bi-, tri-, and tetradentate ligands and also the possibility of controlling their properties through the substituent effect make them attractive for design of organometallic complexes with required stereochemistry [8, 9]. This study is concerned with synthesis of iron co-ordination compounds with formazans I–V and with the substituent effect on the composition, structure, and spin state of the metal complexes. DOI: 10.1134/S1070427208120161 ORGANIC SYNTHESIS AND INDUSTRIAL ORGANIC CHEMISTRY I–V EXPERIMENTAL The compounds were prepared from FeCl3 · 6H2O of analytically pure grade. 1-Aryl-5-benzothiazol-2-yl-formazans were synthesized by the procedures de-scribed in [10–13]. The purity of the metal complexes was verified by TLC on Silufol UV-254 plates. Iron 1-(4-sulfophenyl)-3-methyl-5-(benzothiazol-2-yl)formazanate (IFe). A solution of 0.3 mmol of iron(III) chloride in 15 ml of water was added dropwise with continuous stirring at 40 ± 5°C to a solution of 0.9 mmol of formazan in 100 ml of aqueous ethanol (1 : 1). The resulting mixture was stirred for 30 min and evaporated to a volume of 10 ml. The precipitate RUSSIAN  JOURNAL  OF  APPLIED  CHEMISTRY   Vol.  81   No.  12   2008 was filtered off, washed with a small amount of dis-tilled water, and dried in air. Iron 1-phenyl-3-(propen-1-yl)-5-(benzothiazol-2-yl)-formazanate (IIFe). A solution of 0.3 mmol of iron(III) chloride in 15 ml of acetone was added dropwise with continuous stirring at 40 ± 5°C to a solution of 0.9 mmol of formazan in 100 ml of acetone. The resulting mix-ture was stirred for 30 min and evaporated to a volume of 10 ml. The precipitate was filtered off, washed with warm distilled water and ethanol, and dried in air. Iron formazanates IIIFe, IVFe, and VFe were prepared similarly. The compositions of the ligands and com-plexes obtained are listed in Table 1. The electronic absorption spectra of the ligands and their metal complexes in aqueous ethanol (1 : 1) for I or acetone for II–V were recorded on a Beckman UV-5260 double-beam spectrophotometer in the wave-length range 350–800 nm. The compositions of the complexes and equilibrium concentrations were deter-mined from the plots of the optical densities of solutions vs. the volume of the salt solution added. The equi-valence point corresponded to the salt solution volume required to attain the saturation. From these data, the stoi-chiometric composition of the complexes formed was calculated. An elemental analysis was performed on a CHN PE2400SII automatic analyzer (Perkin–Elmer Instru-ments, the United States). The metal content was deter-mined by express gravimetric analysis with a device produced by Khimlaborpribor Joint-Stock Company (Klin, Moscow oblast, Russia). The IR spectra of the ligands and complexes ob-tained were recorded with a Specord 75-IR spectropho-tometer in KBr pellets in the range 400–4000 cm–1. Mass spectra of iron formazanates were measured in the electron impact ionization mode on an MAT-ZPA device (Varian) with the reverse configuration in the design of magnetic and electrostatic analyzers, which allowed the spectra of metastable ions to be ob-tained directly. The spectra were measured under stan-dard conditions: accelerating voltage 3 kV, cathode emission current 300 μA, and ionizing electron energy 70 eV. The samples were introduced into the ion source using the direct inlet system. The magnetic characteristics of the compounds were measured with a Quantum Design 5-XL SQUID magnetometer in the temperature range 0–300 K in magnetic fields of strength 30 and 50 kOe.  Single-crystal X-ray diffraction analysis of com-plex IVFe was performed at 295(2) K with an Xcalibur 3 autodiffractometric system equipped with a CCD detector. Crystals of IVFe (C36H36N10O2S2Fe, red prisms) belong to the monoclinic system. Unit cell parameters: a = 10.3951(18), b = 21.968(2), с = 15.9281(16) Å; α = 90.00°, β = 99.347(11)°, γ = 90.00°; V = 3589.0(8) Å3; ρcalc = 1.408 g cm–3; M = 760.72; Z = 4; space group P2(1)/n. The experiment completeness at θ ≤ 26.38° was 99.5% (ω-scanning at 1° step and 10-s exposure per frame, crystal–detector distance 50 mm). A total of 7299 unique re-flections were measured, including 2515 reflections with I > 2σ(I ). The absorption correction was ne-GORBATENKO et al. 2128 Table 1. Elemental analyses and melting points of iron(II) formazanate complexes I CH3 4-SO3H IFe C30H24N10S4O6Fe · 3Н2О >250 41.93 41.96 3.61 3.53 – II CH=CH–CH3 H IIFe C34H28N10S2Fe 180 59.79 58.61 4.28 4.06 19.68 20.11 III CH(CH3)2 H IIIFe C34H32N10S2Fe 245 58.30 58.27 4.63 4.61 19.75 19.99 IV CH(CH3)2 4-OCH3 IVFe C36H36N10S2O2Fe 190 56.45 56.83 4.97 4.78 18.06 18.41 V C6H5 H VFe C40H28N10S2Fe 215 62.61 62.52 3.64 3.71 18.21 18.18 –––––––––—— Ligand R1 R2 Complex Empirical formula Tm, °C Found, % Calculation, % C H N RUSSIAN  JOURNAL  OF  APPLIED  CHEMISTRY   Vol.  81   No.  12   2008 tures and properties are determined not only by the set of donor atoms in the ligand structure, but also by the electronic configuration of the central metal ion. For example, in complexation of tridentate forma-zan IV with nickel(II) nitrate in an acetone solution, the intensity of the absorption band of the starting forma-zan at λmax = 430 nm gradually decreases, and an absorp-tion band of the metal complex appears at λmax = 630 nm. The spectral pattern is characterized by the presence of one isobestic point, which suggests that only two for-mazan species are involved in the process: the starting formazan and the forming nickel(II) formazanate. With iron(III), a metal ion with a variable oxida-tion state, the spectral pattern (Fig. 1) observed in the course of titration is more complicated. A decrease in the intensity of the absorption band of formazan is mainly associated with its tranformation into a product with λmax < 350 nm. Apparently, formazan is oxidized into a tetrazolium salt (a well-known reaction of for-mazans [8]), with Fe(III) acting as oxidant. A weak absorption band appearing at 625 nm can be assigned to Fe(II) formazanate. This behavior has been already noted for complexation of some benzazolylformazans with Fe(III) and Mn(III) ions [16, 17]. The reactions of ethanol solutions of iron(III) chloride with benzothiazolylformazans I–V yielded glected because of its insignificance (μ = 0.585 mm–1). To collect and edit the experimental data and refine the unit cell parameters, we used the CrysAlis CD pro-gram [14]. The structure was solved by the direct method using the SHELX-97 program package [15]. The hydrogen atoms were placed in calculated posi-tions and included in refinement in the rider model with dependent thermal parameters. The structure was solved by the least-squares method in the anisotropic approximation for nonhydrogen atoms and isotropic approximation for H atoms. The final divergence fac-tors were R1 = 0.0670, wR2 = 0.0803 [I > 2σ(I )] at goodness-of-fit S = 0.994. Depending on the structure of the initial formazan group, the ligands can coordinate М2+ and М3+ ions either in the tridentate fashion via N1 and N4 atoms of the formazan chain and nitrogen atom of the heteroring to give complexes ML2 with a nitrogen-containing co-ordination core, or, if the aryl fragment contains an additional  o-OH or o-COOH group, in the tridentate or tetradentate fashion to give complexes ML2 or ML with NxM or NxOyM coordination cores, depending on the synthesis conditions [8]. The variations in the mode of coordination of hetarylformazans in their complexes with metal ions, to give coordination compounds with diverse struc-   SYNTHESIS AND SPECTROSCOPIC FEATURES OF IRON(II) 1-ARYL-5-BENZOTHIAZOL-2-FORMAZANATES 2129 Fig. 1. Electronic spectra of formazan IV in acetone, recorded in the course of titration with a solution of (a) nickel(II) nitrate ([IV] = 2.85 × 10–5, [Ni(NO3)2] = 10–3 M) and (b) iron(III) chloride ([IV] = 2.85 × 10–5, [FeCl3] =1 × 10–2 M) in acetone. (A) Absorption and (λ) wavelength. crystalline iron complexes IFe–VFe, which have, ac-cording to the analytical data (Table 1), electronic spec-tra, and mass spectra (Table 2), the composition L2Fe. For formazanate IFe, we failed to detect the mo-lecular ion and recorded only weak peaks of fragmen-tation ions. In the electronic spectra of the iron-containing com-plexes, we observed, along with the major absorption bands at 670–680 nm, weak bands at 490–520 nm. In the IR spectra of the iron formazanates, absorp-tion bands assignable to ν(Fe–N) vibrations [18, 19] appear at about 745 and 500 cm–1. In the IR spectra of the initial ligand, these bands are lacking. The measured effective magnetic moments μeff of the metal complexes IIIFe, IVFe, and VFe, containing bulky substituents in the 3-position of the formazan mole-cule, are as low as 0.22, 0.45, and 1.18 μB, respectively, which suggests formation of Fe(II) complex compounds predominantly in the low-spin (LS) state [20, 21]. For the metal complexes IFe and IIFe containing alkyl substituents in the 3-position of the formazan molecule, μeff was 2.09 and 1.97 μB, respectively, which, according to [21], can be attributed to the pres-ence of low- and high-spin (HS) iron(II) complexes and an admixture of Fe(III) complexes. Formazans with the alkyl substituent at the С3 atom are oxidized to the tetrazolium salt somewhat more difficultly. Therefore, the probability of formation of impurity iron(III) complexes is higher. The structure of the metal chelate core formed in complexation of formazans I–V with iron(III) chloride solutions was finally confirmed by single-crystal X-ray diffraction analysis for IVFe as an example. The general view of the molecule of IVFe is shown in Fig. 2. The structure of IVFe is, on the whole, similar to that of 1,3-diphenyl-5-(benzothiazol-2-yl)formazanate VFe prepared previously [16].  The molecule of the iron complex occupies a spe-cial position on a twofold axis. Two formazan ligands are coordinated in the tridentate fashion via N1 and N4 atoms of the formazan chain and nitrogen atom of the heteroring to form the metal complex L2Fe with the N6Fe coordination core. The angle between the planes of the formazan ligands in the complex is 81.93°. The N(8)FeN(7) (157.77°) and N(5)FeN(1) (157.66°) angles correspond to the meridional (mer) isomer; in the facial (fac) isomer this angle would be 90°. The iron coordination polyhedron is a distorted octahedron. De-spite that all the vertices of the coordination polyhe-dron are occupied by nitrogen atoms, the Fe–N bonds noticeably differ in the length and can be subdivided into three groups, each with two bonds. The shortest Fe–N bonds, 1.850 and 1.856 Å, are formed by the N(10) and N(3) atoms occupying the vertex po-sitions, i.e., the octahedron is compressed along the N(10)···N(3) axis. The intermediate-length Fe–N bonds, 1.933 and 1.942 Å, are formed with the N(1) and N(7) atoms, and the N(5) and N(8) atoms are the most remote from the Fe atoms: 1.997 and 2.003 Å, respectively. RUSSIAN  JOURNAL  OF  APPLIED  CHEMISTRY   Vol.  81   No.  12   2008 GORBATENKO et al. 2130 Table 2. Data furnished by electronic spectroscopy, mass spectrometry, and magnetochemical measurements for iron(II) complexes Fig. 2. Structure of iron 1-(4-methoxyphenyl)-3-isopropyl-5-(benzothiazol-2-yl)formazanate IVFe. Selected bond lengths, Å: Fe(1)–N(1) 1.933(4), Fe(1)–N(5) 1.997(4), Fe(1)–N(10) 1.850(4), N(5)–C(7) 1.313(5), N(6)–N(1) 1.321(4), N(6)–C(10) 1.364(6), N(9)–C(7) 1.346(5), N(10)–N(9) 1.366(5), N(10)–C(10) 1.332(6), N(5)–C(16) 1.373(5), C(7)–S(1) 1.745(5), C(10)–C(15) 1.500(6), N(1)–C(20) 1.411(5). Selected bond angles, deg: N(3)–Fe(1)–N(7) 79.27(18), N(3)–Fe(1)–N(8) 78.48(19), N(10)–Fe(1)–N(1) 78.80(18), N(10)–Fe(1)–N(5) 78.81(19). Com-plex M m/z (I, %) λmax, nm μeff, μB (μ2eff) IFe 858.64 – 670, 490 2.09 (4.4) IIFe 696.72 696 (32.26) 675, 510 1.97 (3.9) IIIFe 700.76 700 (100) 670, 520 0.22 (0.05) IVFe 760.82 760 (100) 675, 490 0.45 (0.2) VFe 768.78 768 (100) 680, 495 1.18 (1.4) The hetaryl nitrogen atom involved in the coordi-nation behaves like an additional complexing group. The complexation leads to changes in the electronic structure of the initial ligand, which is in the amino form with the EEZ configuration of the formazan ring. The molecular configuration also changes significantly: in the formazanate, the ligand is in the imino form, with the open EZE configuration. The above spectral data suggest that compounds IIIFe–VFe are metal complexes containing Fe(II) pre-dominantly in the LS state with the coordination con-figuration similar to that in IVFe:   2. Arutyunov, V.S., Katal. Prom–sti., 2003, no. 3, pp. 31–38.   3. Borutskii, P.N. and Podkletnova, N.M., Katal. Prom–sti., 2003, no. 2, pp. 57–61.   4. Ulakhovich, N.A., Soros. Obraz. Zh., 1997, no. 8, pp. 27–32.   5. Lavernova, L.G., Ikorskii, V.N., Larionov, S.V., et al., Zh. Neorg. Khim., 1993, vol. 28, no. 9, pp. 1517–1525.   6. Stassen, A.F., Kooijman, H., Spec, A.L., et al., Inorg.  Chеm., 2002, vol. 41, no. 24, pp. 6468–6471.   7. Shvedenkov, Yu.G., Virovets, A.V., and Lavrenova, L.G., Izv. Ross. Akad. Nauk, Ser. Khim., 2003, no. 6,   pp. 1281–1288.   8. Buzykin, B.I., Lipunova, G.N., Sysoeva, L.P., and Rusinova, L.I., Khimiya formazanov (Chemistry of Formazans), Moscow: Nauka, 1992.   9. Lipunova, G.N., Rusinova, L.I., and Maslakova, T.I., Ross. Khim. Zh., 1996, vol. 40, nos. 4–5, pp. 148–154. 10. Bednyagina, N.P. and Lipunova, G.N.,  Khim. Geterotsikl. Soedin., 1968, no. 5, pp. 902–910. 11. Petrova, G.M., Bednyagina, N.P., Malkina, T.G., and Podchainova, V.N., Khim. Geterotsikl. Soedin., 1968, no. 4, pp. 709–715. 12. Lipunova, G.N., Lekomtseva, E.G., Sharova, L.I., et al., Zh. Obshch. Khim., 1985, vol. 55, no. 4, pp. 895–899. 13. Validuda, G.I., Lipunova, G.N., Garnovskii, A.D., et al., Zh. Obshch. Khim., 1986, vol. 56, no. 4, pp. 827–833. 14. CrysAlis CCD, Oxford Diffraction Ltd., Version 1.171.29.9 (release 23-03-2006 CrysAlis 171. NET). 15. Sheldrick, G.M., SHELX-97: A Software Package for the Solutions and Refinement of X-ray Data, Univ. of Göttingen (Germany), 1997. 16. Brown, D., Bogge, H., Lipunova, G.N., et al., Inorg. Chеm., 1998, vol. 280, pp. 30–38. 17. Muller, A., Bogge, H., Diemann, E., et al., Naturwiss., 1994, vol. 81, pp. 136–137. 18. Nakanishi, K., Infrared Absorption Spectroscopy, San Francisco: Holden-Day, 1962.  19. Nakamoto, K., Infrared Spectra of Inorganic and Coordination Compounds, New York: Wiley, 1963. 20. El-Sawaf, A.K., West, D.X., El-Saied, F.A., et al., Synth. Inorg. Met.-Org. Chem., 1997, vol. 27, no. 8, pp. 1127–1134. 21. Bushuev, M.B., Lavrenova, L.G., Ikorskii, V.N., et al., Koord. Khim., 2004, vol. 30, no. 4, pp. 305–311. CONCLUSION ACKNOWLEDGMENTS REFERENCES RUSSIAN  JOURNAL  OF  APPLIED  CHEMISTRY   Vol.  81   No.  12   2008 2131    SYNTHESIS AND SPECTROSCOPIC FEATURES OF IRON(II) 1-ARYL-5-BENZOTHIAZOL-2-FORMAZANATES In the course of synthesis of coordination com-pounds from tridentate benzothiazolylformazans and solutions of iron(III) chloride, formazan is oxidized to tetrazolium salts, iron(III) is reduced, and, as a result, iron(II) formazanates are formed with various spin states of Fe(II). The study was financially supported by the Rus-sian Foundation for Basic Research (project nos. 06-03-08040ofi and 07-03-12 050ofi).   1. Malina, N.K., Raznitie issledovanii v oblasti sinteza ammiaka (Progress of Studies in the Field of Ammonia Synthesis), Moscow: Nauka, 1983. 

Synthesis and spectroscopic features of iron(II) 1-aryl-5-benzothiazol-2- ylformazanates

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Synthesis and spectroscopic features of iron(II) 1-aryl-5-benzothiazol-2- ylformazanates

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