Acta Chini. Slov. 2001, 48, 439-443. 439 TRANSITION METAL COMPLEXES WITH A NEW THIOAMIDE OF THE DIBENZOFURAN SERIES V. Muresana, L. S. Sbirna8, S. Sbirnab, C. I. Lepadatuc and N. Muresana "Faculty of Chemistry, University of Craiova, Calea Bucuresti 165, Craiova, Romania b Department of Research and Development, Aircraft Craiova S.A., Aeroportului 1, Craiova, Romania c Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202B, Bucharest, Romania Received 15-03-2001 Abstract The paper reports the conclusions about the structure of some new complexes of Fe(II), Co(II), Ni(II) and Cu(II), with a new thioamide, 3-(2'-thiothenoylamino)dibenzofuran (TTADBF). These were obtained by elemental analysis, UV-VIS, IR and EPR spectral analysis, conductivity and magnetic susceptibility measurements. Introduction The coordination chemistry of sulphur donor ligands is an active area of research. A great deal of attention in this area has been focused on the complexes formed by transition metals with thioamides, that act as bidentate ligands using both sulphur and nitrogen as donor atoms. " We here report the preparation and characterization of the complex compounds of Fe(II), Co(II), Ni(II) and Cu(II) with a new thioamide, 3-(2'-thiothenoyl-amino)dibenzofuran (TTADBF). o TTADBF Experimental All the chemicals we used were of analytical grade: FeCi2.2H20 (Fluka A.G. p.a.), C0CI2.6H2O (Merck p.a.), NiCl2.6H20 (Merck p.a.), CuCl2.2H20 (Merck, p.a.), TTADBF (double recrystallized). The IR spectra were recorded on a Perkin Elmer F.T.-1600 Hewlett Packard instrument in anhydrous KBr pellets. The electronic spectra were obtained in 10" M acetone solutions, with an Unicam UV 2-300 spectrophotometer, while the EPR specra were registered in powder form at room temperature by means of an Art-5-Ifm Bucharest V. Muresan, L. S. Sbirna, S. Sbirna, C. I. Lepadatu, N. Muresan: Transition metal complexes with... 440 Acta Chini. Slov. 2001, 48, 439-443. spectrometer, that operates in X band, the modulation of magnetic field being 100 kHz, using Mn + as an internal standard. The molar conductivities were determined by using an OK-102(Hungary) conductivity meter at 22 °C. The magnetic susceptibility measurements were performed on a Gouy balance at room temperature. All the complexes were prepared using the reported method.1 General procedure: A 0.02 M thioamide (TTADBF) in ethanol solution was added (dropwise with continuous stirring) to an ethanolic or aqueous solution of the metal dichloride (0.02 M), in a 1:1 molar ratio. It was gently stirred for one hour, and then left at room temperature for three hours. The resulting metal complexes were washed with ethanol and diethyl ether and then dried under reduced pressure. Results and discussion The complexes obtained were microcrystalline colored powders, whose melting points are higher than of the pure thioamide. They are stable at room temperature and their solubilities in common inorganic and organic solvents are medium. The elemental analysis of these complexes leaded to the formula: [FeLCi2(H20)2], [C0LCI2], [NiLCl2], [CuLCl2], where L=TTADBF. Molar electric conductivities showed that all the complexes are non-electrolytes with X = 0.98 - 1.45 Q"1 cm2 mol"1 in DMF (IO"3 M) solutions at room temperature. We have recorded IR spectra both for pure thioamide and for the corresponding complexes in the 600-1650 cm" and 3000-3500 cm" ranges, where characteristic bands of ligand appear and the changes due to the complex formation can be seen. In literature it is stated that thioamide forms a complex vibrational group. A comparative interpretation of the infrared spectral data suggests that 3-(2'-thiothenoylamino)dibenzofuran (TTADBF) act as a bidentate ligand in the investigated complex compounds, using both sulphur and nitrogen as donor atoms. The bands in the 3030-3150 cm" interval, characteristic for vNH , appear in complexes at lower frequencies than in the respective thioamide. The changes suggest that the NH2 group participates to the coordination. The characteristic band of the thioamide at 1450 cm'^Vc-N, Vc.s coupling) is displaced towards higher frequencies with V. Muresan, L. S. Sbirna, S. Sbirna, C. I. Lepadatu, N. Muresan: Transition metal complexes with... Acta Chini. Slov. 2001, 48, 439-443. 441 a lower intensity. These changes may be explained by electronic migrations corresponding to the thioamidic group. Very important for the discussion of the bond character is the band at 1220 cm" , in which the frequency of the C=S bond has an important contribution. In complexes, this band almost disappears. This is a proof that the sulphur atom participates as a donor atom in the complex formation. The band in the 630-680 cm" interval is also significant. Generally assigned to the C=S vibration, it appears with a much lower intensity in the complexes, thus confirming that the sulphur atom participates as a donor atom to the coordination of the thioamide to the transition metal ion. A band due to coordinated water appears in the spectrum of the Fe(II) complex around 890 cm"1 and 3500 cm"1 . The magnetic moment value of [Fe(TTADBF)Cl2(H20)2] is 4.88 B.M., which indicates that the complex is spin-free and it has octahedral geometry. The electronic spectrum shows a broad absorption band at 16700 cm" , which may be assigned to the T2g —> Eg transition. For [Co(TTADBF)Cl2], the magnetic moment value is 2.18 B.M. and its electronic spectrum displays two bands, at 16850 cm"1 and 21600 cm"1, which may be assigned to 7 7 7 7 the Aig —> B2g transition and to the Aig —> Eg transition, respectively, in a square- o planar configuration around the transition metal ion. As far as [Ni(TTADBF)Cl2] is concerned, it appears to be diamagnetic. Its electronic spectrum exhibits four bands, at 21200 cm" , 30300 cm" , 33500 cm" and 38300 cm"1. The first band and the second one are of low intensity, being purely d-d transitions, assigned to the Aig —> A2g transition and to the Aig —> B2g transition, respectively. The third band is developed by a strong charge transfer transition, while the fourth one is due to interligand interactions (71—> n*). These results also suggest a square-planar configuration around the transition metal ion. The room temperature magnetic moment value is 1.90 B.M. for [Cu(TTADBF)Cl2], indicating the presence of one free electron. The electronic spectrum displays three spectral bands, at 14500 cm" , 20600 cm" and 26500 cm" . The first band corresponds 7 7 7 7 to the Big —> Aig transition and the second one to the Big —> Eg transition, the third band being assigned to a charge transfer transition. All these observations lead to V. Muresan, L. S. Sbirna, S. Sbirna, C. I. Lepadatu, N. Muresan: Transition metal complexes with... 442 Acta Chini. Slov. 2001, 48, 439-443. the conclusion that the geometry is also square planar. The compound [Cu(TTADBF)Ci2] present a very intense EPR spectrum,with anizotropic parameters g|| = 2.2404 and gj_ = 2.0704, in agreement with the d electronic configuration for Cu(II) in this square-planar complex compound (Figure 1). --A/] 300 310 320 330 ------------------------> H,mT Figure 1. EPR spectrum of [CuLCl2] Conclusions On the basis of all these results, obtained by elemental analysis, UV-VIS, IR, EPR spectral analysis, conductivity and magnetic susceptibility measurements, the following structure are proposed for the complex compounds: a) b) a) [MLC12(H20)2], where M=Fe(II) and L=TTADBF b) [MLCl2],where M=Co(II) Ni(II) Cu(II) and L=TTADBF ¦NH2" OH, M OH, CI CI V. Muresan, L. S. Sbirna, S. Sbirna, C. I. Lepadatu, N. Muresan: Transition metal complexes with... Acta Chini. Slov. 2001, 48, 439-443. 443 References 1. K. A. Jensen, P. H. Nielsen, Acta Chem. Scand. 1996, 20, 597-602. 2. V. Muresan, N. Muresan, A. Reiss, Polish J. Chem. 1993, 67, 2113-2119. 3. V. Muresan, S. Florea, A. Reiss, Polish J. Chem. 1995, 69, 385-388. 4. V. Muresan, A. Reiss, L. S. Sbirna, N. Muresan, Polish J. Chem. 1998, 72, 2034-2036. 5. A. Kriza, A. Reiss, V. Muresan, S. Florea, J. Indian Chem. Soc. 1999, 76, 406-407. 6. S. Florea, Rev. Roum. Chim. 1994, 39, 1138-1142. 7. H. O. Desseyn, M. A. Herman, Spectrochim. Acta 1967, 23 A, 2457-2463. 8. A. B. P. Lever, Inorganic Electronic Spectra, Elsevier, N. Y., 1984, pp. 503-520. 9. H. B. Gray, C. J. Ballhausen, J. Amer. Chem. Soc. 1963, 85, 260-268 Povzetek Določili smo strukture kompleksov Fe(II), Co(II), Ni(II) in Cu(II) z novim tioamidom 3-(2'-tiotenoilamino)dibenzofuranom (TTADBF). Strukture smo potrdili z elementno analizo, UV/Vis, IR in EPR spektroskopijo ter z merjenjem prevodnosti in magnetne susceptibilnosti. V. Muresan, L. S. Sbirna, S. Sbirna, C. I. Lepadatu, N. Muresan: Transition metal complexes with...