Acta Chini. Slov. 2001, 48, 445-452. 445 COMPLEXES OF TIN (IV) WITH SOME BIDENTATE SCHIFF BASES DERIVED FROM l-#-LNDOL-2,3-DIONE A. Kriza, C. Parnau* Faculty of Chemistry, Department of Inorganic Chemistry, University of Bucharest, Str. Dumbrava Rosie 23; Tel: +40(1) 210.34.97., +40(1) 315.71.87; Fax: +40(1) 313.17.60; E-mail: tvio@hades.ro, Romania Received 07-03-2001 Abstract A series of new metal complexes of tin (IV) with Schiff bases of isatin (1-H - indol -2,3-dione) with aniline, p-toluidine and w-nitro aniline have been synthesized and characterized by elemental analysis, IR, NMR and electronic spectroscopy and conductance measurements. Two types of such complexes were been synthesized: SnCL(HL) and SnCl2(L)2. Electronic, IR and NMR spectral data agree with the coordination of the metallic center through nitrogen and oxygen donor atoms. Conductance data reveal a non-electrolytic nature of the complexes. Introduction Containing different donor atoms, the Schiff bases are an important class of ligands in the coordination chemistry, widely reported. " Nevertheless, a survey of the literature reveals that no work treating complexes of tin(IV) with Schiff bases derived from 1-H -indol -2,3-dione (isatin) were since reported. Our interest in this category of ligands is justified by their already proved medical and biological implications. " On the other hand, a great deal of our precedent work is 7 I 7 focused on the complex compounds generated by Group 14 metal halides, " also important in some biological processes. Our purpose was to synthesize and characterize some metal complexes of tin (IV) with Schiff bases derived from isatin and aniline //?-toluidine / m-nitro aniline, hereafter abbreviated: HIAN (isatin - aniline Schiff base), HIPT (isatin - /?-toluidine), HIMNA (isatin - m-nitro aniline). In different conditions, two kinds of complexes of the same Schiff base were obtained, SnCi4(HL) and SnCi2(L)2, where HL are the Schiff bases mentioned above. A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione 446 Acta Chini. Slov. 2001, 48, 445-452. Results and discussion The Schiff bases under present consideration react with tin(IV) chloride in anhydrous ethanol medium, to give colored amorphous compounds, stable in air and insoluble in most common organic solvents. Elemental analysis data suggest 1:1 or 1:2 metal : ligand stoichiometrics, the general formula, in each being SnCl4(HL) and SnCl2(L)2, respectively, (see Table 1). Table 1: Analytical and physical data of the synthesized compounds Compound Empirical formula* Melting point (°C) Color Am** (Q'Wmol"1) SnCl4(HIAN) SnCl4(C14H10N2O) 207 Pale brown 6.5 SnCl2(IAN)2 SnCl2(Ci4H9N20)2 250 Beige - SnCl4(HIPT) SnCl4(C15H12N20) 170 Reddish brown 8.8 SnCl2(IPT)2 SnCl2(Ci5HiiN20)2 250 Beige - SnCl4(HIMNA) SnCl4(C14H9N303) 90 Dark brown 10.4 SnCl2(IMNA)2 SnCl2(Ci4H8N303)2 211rf Pale brown - *: The elemental analysis data were in good agreement with the calculated percentages of Sn, C, H, N and CI for all the synthesized compounds. **: The conductance was recorded in DMF solutions. d: The compound decompose at 211 °C. Spectral data In order to clarify the manner of the ligand coordination at the metallic center IR spectra on the 400 - 4000 cm"1 range were recorded. The most important IR bands, presented and assigned in table 2 show the following characteristics: The three bands appearing at 3190, 1740 and 1654 cm" in the ligands spectra, were assigned to stretching vibration modes Vnh, vc=o and Vc=n, respectively. In the cases of the SnCl4(HL)compounds, the spectra reveal that the band having a maximum at 1740 cm" in the free ligands is shifted to lower wave numbers with a Av between 26-37 cm" . This shift indicates the implication of carbonyl oxygen in the coordination at the metallic center. A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione Acta Chini. Slov. 2001, 48, 445-452. 447 Table 2. IR data (cm" ) Compound vnh vc=o ^skeleton Vc=N VC=N* Vc-0 HIAN 3191 1743 1614 1654 - - SnCl4(HIAN) 3180 1706 1617 - - - SnCl2(IAN)2 - - 1606 - 1572 1224 HIPT 3180 1744 1614 1654 - - SnCl4(HIPT) 3173 1711 1615 - - - SnCl2(IPT)2 - - 1606 - 1568 1232 HIMNA** 3196 1737 1617 1653 - - SnCl4(HIMNA)** 3180 1717 1620 - - - SnCl2(IMNA)2** - - 1606 - 1582 1227 *: New azomethine band **: Supplementary intense bands assigned to v(N02 asym) and v(N02sym) at 1526, respectively 1348 cm"1 were recorded. In the cases of the SnCi4(HL)compounds, the spectra reveal that the band having a maximum at 1740 cm" in the free ligands is shifted to lower wave numbers with a Av between 26-37 cm" . This shift indicates the implication of carbonyl oxygen in the coordination at the metallic center. The band appearing at 1650 cm" in the free ligands, assignable to the Vc=n vibration mode, disappears in the complexes spectra, this indicating the participation of azomethinic nitrogen atom in coordination. The band due to the Vnh vibration mode in isatin, having the maximum at 3190 cm" in the free ligands, remains largely unaffected in the chelates. All the bands assigned to stretching vibration modes Vnh, Vc=o and Vc=n respectively in the free ligands disappear in the spectra of the SnCl2(L)2 compounds, but new bands are recorded at 1580 and 1220 - 1230 cm"1. These new bands, assigned to the Vc=n* (new azomethine bond) and Vc-o vibration modes respectively, suggest the enolysation of NH hydrogen and the coordination at tin through the oxygen of the C-0 group. A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione 448 Acta Chini. Slov. 2001, 48, 445-452. Identification of the bands assignable to the Sn - O, respectively Sn - N vibration modes was rather difficult, because in the corresponding region the ligands display quite intense bands. NMR data Supplementary data have been obtained by H- and C-NMR spectroscopy, recorded for the ligands and for their SnCUCHL) chelate compounds. The H spectra of the ligands can be resolved into three distinct regions. The spectra exhibit two multiplets at 7,0 - 7,3 and 6,3 - 6,8 ppm (corresponding to the isatin and amine aromatic rings) and one singlet at 10,3 ppm (corresponding to the isatin NH residue). The only H-NMR signal displaying a down field shift in complex compounds (from 10,3 to 10,9 ppm) is those associated with the hydrogen of the isatin NH residue. This behavior is related with a decrease of the electron density and a deshielding of the NH proton, as a result of the participation oh the adjacent carbonyl group in coordination ' . This behavior is in good agreement with IR spectra of complexes where the maximum of the Vc=o vibration mode appears at lower frequencies as in the corresponding free ligands. UV-VISspectra were recorded in the region 200 - 1000 nm. The electronic spectra of the ligands in ethanol exhibit mainly three bands at 230 nm(7i—»7i ), 290 nm(n—>n ) and 396 nm. The reflectance spectra are similar and shifted toward lower frequencies. In the visible region, the bands of the ligands, appearing at 415-420 nm, are less intense. In the SnCU (HL) complexes spectra the bands are shifted with about 20 nm to lower frequencies, proving the ligands coordination at metallic centers.In the cases of the SnCi2(L)2 compounds the shift is even greater(of 35-40 nm), indicating a more accentuate conjugation between the azomethine group and the aromatic ring (see table 3). A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione Acta Chini. Slov. 2001, 48, 445-452. 449 Table 3. UV-VIS data Compound Absorption maxima (nm/cm" ) HIAN 250(40000) 300(33333) 415(24096) SnCl4(HIAN) 245(40816) 340(29411) 430(23255) SnCl2(IAN)2 260(38461) 352(28409) 445(22471) HIPT 248(40322) 290(34482) 420(23809) SnCl4(HIPT) 243(41152) 343(29154) 460(21739) SnCl2(IPT)2 250(40000) 350(28571) 480(20833) HIMNA 242(41322) 290(34482) 420(23809) SnCl4(HIMNA) 240(41666) 332(30120) 440(22727) SnCl2(IMNA)2 245(40816) 341(29325) 460(21739) Conductance data for the SnCL^HL) compounds (in DMF, 10" mol, 25 C), 17 1 ranging in the 6,5 - 10,4 Q" cm mol" region, indicate the non-electrolytic nature of the compounds. Conclusions We report here the synthesis and the characterization of six new complexes of tin(rV) with Schiff bases derived from isatin and aniline / /?-toluidine / m-nitro aniline. The syntheses were conducted in conditions allowing the bi-dentate (neutral or monobasic) function of the ligands and the stability of tin(IV). Varying the conditions under these requirements, two kinds of complexes of the same Schiff base were obtained, SnCL^HL) and SnCl2(L)2, where HL are the Schiff bases mentioned above. The synthesized compounds were characterized by elemental analysis, IR, NMR and electronic spectroscopy, as well as by conductance measurements. The correlation of the experimental data allows assigning a octahedral stereochemistry to all the reported complex compounds. The proposed structural representations are presented in figure 1 : A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione 450 Acta Chini. Slov. 2001, 48, 445-452. CI ou: .M / CI N^O^ I \l oxx.. H CI R:H,p-CH3, w-N02 IVI 1> N^o^,V pò Figure 1. Propose structures of complex compounds; a: SnCL^HL); b: SnCl2(L)2 Experimental Reagents and methods. All the reagents were AR grade. Tin tetrachloride (Riedel), aniline, /?-toluydine and m-nitro-aniline (Aldrich) were used without further purification.Anhydrous ethanol was obtained using the method presented in literature. Tin and chlorine content was determined by a conventional method and C, H, and N were determined by micro-analytical methods. The IR spectra were recorded in KBr pellets, using a BIO-RAD FTS 135 spectrometer. The reflectance UV-VIS spectra were recorded with a VSU 2P spectrometer, at room temperature. H- and C-NMR data were recorded on VARIAN T 60 and BRUKER WH 2790 spectrometers. Digital conductivity meter K 612 was used to measure the molar conductivities in DMF solutions. Schiff bases preparation. The preparation of the Schiff Bases was conducted as follows: an ethanol solution of isatin (0,001 mol, 25 ml) was added to an ethanol solution of aromatic amine (0,001 mol, 25 ml) and refiuxed for four hours on a water bath. After solution concentration, the precipitate was separated by suction filtration, washed with ethanol and dried over CaCl2 in vacuum. HIAN: Anal. C14H10N2O: Cale: C, 75.67; H, 4.50; N, 12.61. Found: C, 75.5; H, 4.7; N, 12.4. lR NMR: ôi =10.0(s); ô2 = 7.3(m); ô3 = 6.8(m). 13C NMR: ôi = 165.8 (C=0); ô2= 154.5 (C=N). HIPT: Ci5H12N20; Cale: C, 76.27; H, 5.08; N, 11.86. Found: C, 76.2; H, 5.0; N, 12.0. 'hNMR: ò>10.4(s); ô2 = 7.3(m); ô3 = 6.9(m); S4 = 2.41(s,CH3); 13C NMR: ôi = 165.6; ô2 = 154.4; ô3 = A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione Acta Chini. Slov. 2001, 48, 445-452. 451 21(CH3). HIMNA: C14H9N3O3: Cale: C, 62.92; H, 3.37; N, 15.73. Found: C, 62.8;H, 3.5;N, 15.72/H NMR: Si = 10.7(s); S2 = 7.3(m); S3 = 6.7(m). 13C NMR: Si = 165.7; 82 = 154.5. SnCU(HL) complexes: 0,002mol SnCU in 50 ml anhydrous ethanol was treated with 0,002 mol ligand dissolved in 50 ml anhydrous ethanol. The mixture was stirred during one hour under nitrogen atmosphere and than was refluxed on a water bath for eight hours. The solvent excess was distilled. The compound was filtered, washed with anhydrous ethanol and dried over P2O5 in vacuum. Anal. SnCl^HIAN): Cale: Sn, 24.59; C, 34.80; H, 2.07; N, 5.80; CI, 29.42. Found : Sn, 24.60; C, 34.70; H, 2.10; N, 5.90;C1, 29.5. lR NMR (DMSO+CDCI3): 8i=11.0; S2= 7.0-7.3; S3 = 6.3-6.8. 13C NMR (DMSO+CDCI3): Si=178.3(C=0); Ô2=163.4(C=N). SnCl4(HIPT): Cale: Sn, 23.90; C36.24; H,2.41; N,5.64; CI, 28.59. Found: Sn, 23.89; C, 36.20; H, 2.40; N,5.60; CI, 28.49. SnCl4(HIMNA): Cale: Sn, 22.49; C, 31.84; H,1.70; N, 7.96;C1, 26.91. Found: Sn, 22.40;C, 31.90;H, 1.90;N, 8.01;C1, 26.40. SnCh(L)2 complexes: appropriate Schiff base (0,002mol in 50 ml anhydrous ethanol) wad added drop wise, under nitrogen atmosphere, to tin (IV) chloride (0,00lmol SnCU in 25 ml anhydrous ethanol); then, under nitrogen atmosphere and continuous stirring, sodium methoxide was added until pH reaches 7,4. The reaction mixture was refluxed on water bath, for eight hours. The compound was filtered, washed with anhydrous ethanol and dried over P2O5 in vacuum. The compounds are insoluble in most common organic solvents, so that their NMR and conductance measurement were not available. Anal. SnCl2(IAN)2: Cale: Sn, 18.79; C, 53.19; H, 2.84; N, 8.86; CI, 11.24. Found: Sn, 18.81; C, 53.17; H, 2.90; N, 8.82; CI, 11.24. SnCl2(IPT)2: Cale: Sn, 17.99; C, 54.57; H, 3.33; N, 8.49; CI, 10.76. Found: Sn, 18.01; C, 54.60; H, 3.35; N, 8.49; CI, 10.80. SnCl2(IMNA)2: Cale: Sn, 16.44; C, 46.56; H, 2.22; N, 11.64; CI, 9.84. Found: Sn, 16.50; C, 46.58; H, 2.23; N, 11.50; CI, 9.80. A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione 452 Acta Chini. Slov. 2001, 48, 445-452. References and Notes 1. Fachinetti G., C. Floriani C, Zanazzi V.Jnorg. Chem. 1979,18, 3469. 2. Hobday M. D., Smith T. D., J. Chem. Soc. Dalton Trans. 1972, 20, 2287. 3. Shin X., Yang Q. L. C, Xie Y., Synth. React. Inorg. Met. Org. Chem. 1996, 26, 1135. 4. Varma R. S, Khan I. A., Indian J. Med. Res. 1978, 67, 315. 5. Popp F. D., Pajouhesh H., J. Pharm. Sci. 1982,17, 1052. 6. Kukushkin V. Y., Nishiota T., Nakamura T., Kinoshita L, Isobe K., Chem. Lett. 1977, 189. 7. Kriza A., Nasta M., Calinescu M., Meghea A.,Gioaba A., Rev. Roum. Chim. 1992, 37(3), 371. 8. Kriza A., Ioanovici M., Marinescu D., Kriza A. F., Bul. IPB 1990, 52(3-4), 57. 9. Kriza A., Negoiu M., Bui IPB 1986, 48, 75. 10. Kriza A, Nasta M, Rev. Roum. Chim. 1981, 26(5), 693. 11. Kriza A., Nasta M., Rev. Roum. Chim. 1979, 24(4), 479. 12. Kriza A, Nasta M, Rev. Roum. Chim. 1978, 23(8), 1267. 13. Negoiu D.., Kriza A, Nasta M.,Rev. Roum. Chim. 1974,19(12), 1921. 14. Negoiu D., Kriza A., Anal. Univ. Bue. 1971, 20(1), 39. 15. Negoiu D., Kriza A., Rev. Roum. Chim. 1971,16(12), 1855. 16. Negoiu D., Kriza A., Merches M.,Anal. Univ. Bue. 1971, 20(2), 25. 17. Kriza A., Spinu C, J. Indian Chem. Soc. 2000, 76, 84. 18. Hassan A. M., Khalifa M. A., Shehata A. K., Bull. Soc. Chim. Belg. 1995,104(3), 121. 19. Daw J. M, Henderson W., Nicholson B.K.,J Chem. Soc. Dalton Trans. 1997, 4587. 20. Vogel A. L, A Text book of Organic Chemistry, 3rd ed., ELBS, London, 1968. 21. Vogel A. I., A Text book of Quantitative Inorganic Analysis, 3rd ed., ELBS, Longmann, London, 1971. Povzetek Pripravili smo serijo kompleksov kositra(IV) s Schiffovimi bazami, pripravljenimi iz izatina in anilina, p-toluidina oziroma p-nitroanilina. Strukture spojin smo potrdili z elementno analizo, IR, NMR, UV/Vis spektroskopijami in z merjenjem prevodnosti. Izolirali smo dve vrsti kompleksov in sicer: SnCL(HL) ter SnCl2(L)2. Spektroskopski podatki potrjujejo koordinacijo ligandov preko dušikovih in kisikovih atomov, merjenje prevodnosti pa ne-elektrolitske lastnosti. A. Kriza, C. Parnau: Complexes of tin (IV) with some bidentate Schiff Bases derived from l-H-2,3-dione