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Synthesis and Structural Characterization of Metal Complexes of 2-Formylpyrrole 4jV-Methylthiosemicarbazone (4MLx) and 2-Acetyl- pyrrole 47V-Methylthiosemicarbazone (4ML2). The X-Ray Crystal Structures of [Ni(4ML!-H)2], [Pd(4ML!-H)2] and [Cd(4ML2)2I2]Ruben A lonso3, Elena Berm ejoa, Rosa Carballob, Alfonso Castiñeirasa, and Teresa Péreza

a Departamento de Qufmica Inorgänica, Universidad de Santiago de Compostela,E-15706 Santiago de Compostela, Spain

b Departamento de Qufmica Inorgänica, Facultad de Ciencias, Universidad de Vigo,E-36200 Vigo, Spain

Reprint requests to Prof. Dr. A. Castineiras. Fax: +34 981547163. E-mail: qiac01@usc.es

Z. Naturforsch. 56 b, 219-228 (2001); received January 15, 2001Thiosemicarbazones, Nickel, Palladium

Reaction of 4/V-methyl-2-[l-(pyrrol-2-yl)methylidene]hydrazinecarbothioamide (4ML0 and 4/V-methyl-2-[l-(pyrrol-2-yl)-ethylidene]hydrazine carbothioamide (4MLi) with zinc(II), cad- mium(II) and mercury(II) halides afforded complexes with formulas [M(L)X2] [(L; M; X) = (4MLi; Cd; Cl) (4), (4MLi; Hg; Cl, Br, I) (7 - 9), (4ML>; Cd; Cl) (17), (4ML2; Hg; Cl, Br,I) (20 - 22)] or [M(L)2X2] [(L; M; X) = (4MLi; Zn; Cl, Br, I) (1 - 3), (4MLi; Cd; Br, I)(5, 6), (4ML2; Zn; Cl, Br, I) (14 - 16), (4ML2; Cd; Br, I) (18, 19)]. Reaction of 4MLi with salts of copper(II), nickel(II), palladium(II) and platinum(II) afforded complexes of formula [M(4MLi-H)2] (10 -13). Crystals of 11, 12 and 19 were studied by X-ray diffractometry, and all new compounds were characterized by elemental analysis, mass spectrometry, and IR, elec­tronic and *H and 13C NMR spectroscopy and, when pertinent and allowed by the solubility of the compound, 113Cd or 199Hg NMR spectroscopy. In the complexes of Group 12 metals, both ligands are neutral and S-monodentate. In the complexes of copper or Group 10 metals, 4MLi is monodeprotonated and S,N-bidentate.

Introduction

Research on heterocyclic thiosem icarbazones and their complexes with metals is primarily m o­tivated by their broad spectrum o f biological activ­ity [1]. M ost studies o f their coordination chemistry have concerned transition metals, copper(II) espe­cially [2, 3], but the pharm acological activity o f cer­tain zinc(II) complexes [4] has also prompted stud­ies of complexes o f non-transition metals [5 -9 ] .Group 12 metal cations are of particular interest be­cause both their chemical nature and their biological significance differ from those o f transition metals (zinc(II) lies at the active centre o f biomolecules such as carbonic anhydrase, and the extreme toxi­city o f cadmium(II) and mercury(II) is due to their ability to block functional groups o f biomolecules).Here we describe the synthesis and characteriza­tion, in the solid state and in solution, o f complexes of Group 12 metal halides with tw o thiosem icar­bazones containing a pyrrole ring, 2-formylpyrrole

4/V-methylthiosemicarbazone (4M L 0 and 2-acetyl- pyrrole 4V-methylthiosem icarbazone (4MLo), and of complexes of 4ML] with copper(II) and Group 10 metals.

Experimental

All reagents were supplied by Aldrich, Ventron or Merck and were used without further purification. Ele­mental analyses (H, C, N, S) were performed on a Carlo Erba 1108 elemental analysers. Melting points were de­termined in a Büchi apparatus. IR spectra were recorded between KBr discs (4000 - 400 cm-1) or polyethylene- sandwiched Nujol mulls (500 - 100 cm-1). Electronic spectra (900 - 350 nm) were recorded on a Shimadzu UV-3101PC spectrophotometer. 'H and 13C NMR spec­tra in DMSO-d6 were recorded on Bruker AMX-300 and WM-300 spectrometers, respectively, with TMS as in­ternal reference. 113Cd NMR spectra in DMF referred to D20 , and 199Hg NMR spectra in DMSO-d6, were recorded on a Bruker AMX-500 apparatus and referred to 0.1 M Cd(C104)2 and HgMe2, respectively. Mass spectra (FAB, 3-nitrobenzyl alcohol, Xe, 8 KV) were obtained on

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2 2 0 R. A lonso et al. • Synthesis and Structural Characterization o f M etal Complexes

a Kratos MS-50 apparatus equipped with a DS-90 data acquisition unit.

47V-Methyl-2-[ 1 -(pyrrol-2-yl)methylidene]hydrazine carbothioamide (4ML0 and 4/V-methyl-2-[l-(pyrrol-2- yl)ethylidene]hydrazine carbothioamide (4ML2) were prepared as previously described [10] using a general procedure for condensation of amines with aldehydes or ketones.

Synthesis o f the complexes. Group 12 metal complexes of formulas [M(L)X2] [(L; M; X) = (4MLi; Cd; Cl) (4), (4MLi; Hg; Cl, Br, I) (7 - 9), (4ML2; Cd; Cl) (17), (4ML2; Hg; Cl, Br, I) (20 - 22)] or [M(L)2X2] [(L; M; X) = (4MLi; Zn; Cl, Br, I) (1 - 3), (4MLi; Cd; Br, I) (5, 6), (4ML2; Zn; Cl, Br, I) (14-16), (4ML2; Cd; Br, I) (18,19)] were synthesized by reaction in ethanolic media between 4MLi or 4ML2 (3 mmol) and the corresponding metal halide (3 mmol). Prolonged stirring at room temperature afforded solids that were filtered off, washed with ethanol; and dried in vacuo or over calcium chloride.

Complexes of formula [M(4MLi-H)2] (M = Cu11, Ni11, Pd11, Pt11; 10 -13) were synthesized by mixing a solu­tion of 4ML] (4 mmol) in ethanol with aqueous solu­tions of copper(II) acetate, nickel(II) acetate, potassium tetrachloropalladate(II) and potassium tetrachloroplatina- te(II), (2 mmol). The mixtures were refluxed for 1 h, and then stirred for 40 h at room temperature. The solids fil­tered out were washed repeatedly with ethanol and dried over calcium chloride.

[Zn(4MLi)2Cl2] 1. Violet (0.09 g, 12%); M.p. (°C) 217; Ci4H20Cl2N8S2Zn (500.81): calcd. C 33.6, H 4.03, N 22.3, S 12.8; found C 33.6, H 4.02, N 22.0, S 12.9. v tc m '1 (KBr): 3349, 3283, 3207 (N-H), 1615, 1588 [(C=N) + (C=C)], 1307 [(C=S) + (C=N)], 1033 (N-N), 732 (C=S), 278 (Zn-Cl), 295 (Zn-S). ‘HNMR (6, DMSO- dfi): 11.37 (s, 1H,N1H), 11.31 (s, 1H, N3H), 8.44 (d, 1H, N4H), 7.81 (s, 1H, C5H), 6.92 (s, 1H, C1H), 6.38 (s, 1H, C3H), 6.09 (s, 1H, C2H), 3.41 - 3.01 (d, 3H, C7H). 13C NMR (6, DMSO-d6): 177.58 (C6), 133.63 (C5), 128.04 (Cl), 121.98 (C2), 112.98 (C4), 109.60 (C3), 31.07 -30.72 (C7).

[Zn(4MLi)2Br2] 2. Beige (0.67 g, 75%); M.p. (°C) 220; Ci4H20Br2N8S2Zn (589.73): calcd. C 28.5, H 3.30, N 19.0, S 10.9; found C 28.5, H 3.34, H 18.8, S 10.75. ///cm-1 (KBr): 3347, 3287, 3208 (N-H), 1618, 1588 [(C=N) + (C=C)], 1307, 1242 [(C=S) + (C=N)], 1036 (N-N), 737 (C=S), 199 (Zn-Br), 292 (Zn-S). ‘H NMR (6, DMSO-dö): 11.32 (s, 1H, N1H), 11.29 (s, 1H,N3H),8.44 (d, 1H, N4H), 7.81 (s, 1H, C5H), 6.99 (s, 1H, C1H), 6.38 (s, 1H, C3H), 6.08 (s, 1H, C2H), 3.01 (d, 3H, C7H). 13C NMR (6, DMSO-d6): 177.56 (C6), 133.64 (C5), 128.03 (Cl), 121.98 (C2), 112.90 (C4), 109.61 (C3), 30.73 (C7).

[Zn(4MLi)2I2] 3. White (0.37 g, 36%); M. p. (°C) 223;C,4H2oI2N8S2Zn (683.71): calcd. C 24.5, H 2.90, N 16.0,

S 9.4; found C 24.5, H 2.78, N 16.0, S 9.4. Wem-1 (KBr): 3347, 3287, 3208 (N-H), 1617, 1588 [(C=N) + (C=C)],1307, 1239 [(C=S) + (C=N)], 1036 (N-N), 733 (C=S), 192, 165 (Zn-I), 283 (Zn-S). *H NMR (6, DMSO-d6):11.32 (s, 1H, N1H), 11.30 (s, 1H, N3H), 8.42 (d, 1H, N4H), 7.80 (s, 1H, C5H), 6.98 (s, 1H, C1H), 6.37 (s, 1H, C3H), 6.08 (s, 1H, C2H), 3.00 (d, 3H, C7H). 13C NMR (6, DMSO-dö): 177.48 (C6), 133.66 (C5), 127.98 (Cl), 121.99 (C2), 112.97 (C4), 109.62 (C3), 30.76 (C7).

[Cd(4ML,)Cl2] 4. Beige; (0.63 g, 57%); M.p. (°C) 215; C7Hi0CdCl2N4S (365.57): calcd. C 23.1, H 2.76, N15.3, S 8.8; found C 23.1, H 2.72, N 15.4, S 9.0. ulcm-1 (KBr): 3336, 3302, 3286 (N-H), 1617, 1588 [(C=N) + (C=C)], 1307 [(C=S) + (C=N)], 733 (C=S), 212 (Cd- Cl), 274 (Cd-S). lH NMR (6, DMSO-d6): 11.31 (s, 1H, N1H), 11.28 (s, 1H, N3H), 8.49 (d, 1H, N4H), 7.81 (s,IH, C5H), 6.98 (s, 1H, C1H), 6.38 (s, 1H, C3H), 6.09 (s, 1H, C2H), 3.02 (d, 3H, C7H). 13C NMR (6, DMSO- d6): 177.49 (C6), 133.68 (C5), 128.03 (Cl), 121.99 (C2), 112.90 (C4), 109.60 (C3), 30.73 (C7).

[Cd(4MLj)2Br2] 5. Grey; (0.20 g, 62%); M.p. (°C) 225; Ci4H20Br2CdN8S2 (636.76): calcd. C 26.4, H 3.14, N 17.6, S 10.0; found C 26.2, H 3.12, N 17.2, S 9.6. Wem-1 (KBr): 3336, 3302, 3212 (N-H), 1617, 1584 [(C=N) + (C=C)], 1305, 1240 [(C=S) + (C=N)], 1035 (N- N), 734 (C=S), 189, 172 (Cd-Br), 269 (Cd-S). *H NMR (6, DMSO-d6): 11.31 (s, 1H,N1H), 11.28 (s, 1H, N3H),8.43 (d, 1H, N4H), 7.80 (s, 1H, C5H), 6.99 (s, 1H, C1H),6.38 (s, 1H, C3H), 6.10 (s, 1H, C2H), 3.37 - 3.02 (d, 3H, C7H). 13C NMR (6, DMSO-d6): 177.54 (C6), 133.66 (C5), 128.04 (Cl), 121.99 (C2), 112.90 (C4), 109.60 (C3), 31.07- 30.73 (C7).

[Cd(4ML,)2I2] 6. White; (0.76 g, 70%); M. p. (°C) 215; Ci4H20CdI2N8S2 (730.74): calcd. C 23.0, H 2.76, N 15.3, S 8.8; found C 23.0, H 2.58, N 15.3, S 8.7. i//cm-1 (KBr): 3337, 3301, 3232 (N-H), 1616, 1584 [(C=N) + (C=C)],1308, 1279 [(C=S) + (C=N)], 1034 (N-N), 733 (C=S), 188, 160 (Cd-I), 269 (Cd-S). *H NMR (6, DMSO-de):II.31 (s, 1H, N1H), 11.28 (s, 1H, N3H), 8.43 (d, 1H, N4H), 7.80 (s, 1H, C5H), 6.99 (s, 1H, C1H), 6.38 (s, 1H, C3H), 6.09 (s, 1H, C2H), 3.34 - 3.00 (d, 3H, C7H). 13C NMR (6, DMSO-dö): 177.49 (C6), 133.66 (C5), 128.03 (Cl), 121.99 (C2), 112.90 (C4), 109.60 (C3), 31.08 -30.74 (C7).

[Hg(4MLi)Cl2] 7. White; (1.03 g, 76%); M.p. (°C) 205; C7H10Cl2HgN4S (453.76): calcd. C 18.5, H 2.18, N12.3, S 7.0; found C 8.2, H 2.11, N 12.0, S 7.0. i//cm-1 (KBr): 3320, 3202 (N-H), 1602 [(C=N) + (C=C)], 1323 [(C=S) + (C=N)], 1033 (N-N), 754 (C=S), 210 (Hg-Cl), 269 (Hg-S).'HNMR (6, DMSO-d6): 12.15 (s, 1H,N1H),11.30 (s, 1H, N3H), 9.09 (d, lH,N4H),7.96(s, 1H,C5H), 6.92 (s, 1H, C1H), 6.39 (s, 1H, C3H), 6.22 (s, 1H, C2H),3.76 -3.13 (d, 3H, C7H). 13C NMR (6, DMSO-ck): 169.02

R. A lonso et al. • Synthesis and Structural Characterization o f Metal Complexes 221

(C6), 139.29 (C5), 127.06 (Cl), 123.68 (C2), 115.20 (C4),110.32 (C3), 31.83-31.13 (C l).

[Hg(4MLi)Br2] 8. Beige; (1.51 g, 93%); M.p. (°C) 217; C7HioBr2HgN4S (542.68): calcd. C 15.5, H 1.86, N10.3, S 5.9; found C 15.8, H 1.88, N 10.2, S 6.1. Wem“ 1 (KBr): 3348, 3325, 3214 (N-H), 1598 [(C=N) + (C=C)], 1321 [(C=S) + (C=N)], 1032 (N-N), 754 (C=S), 192,171 (Hg-Br), 273 (Hg-S). *H NMR (6, DMSO-dö): 12.15 (s,1H, N1H), 11.37 (s, 1H, N3H), 9.10 (d, 1H, N4H), 7.96 (s, 1H, C5H), 7.12 (s, 1H, C1H), 6.59 (s, 1H, C3H), 6.16 (s, 1H, C2H), 3.14 (d, 3H, C7H). 13C NMR (6, DMSO- d6): 169.17 (C6), 139.20 (C5), 127.08 (Cl), 123.66 (C2), 115.14 (C4), 110.30 (C3), 31.80 (C7).

[Hg(4ML0I2] 9. Yellow; (1.24 g, 65%); M. p. (°C) 195; C7HioHgI2N4S (636.66): calcd. C 13.2, H 1.56, N 8.7, S 5.0; found C 13.3, H 1.57, N 8.6, S 5.2. v lcm "1 (KBr): 3368, 3320, 3235 (N-H), 1621, 1594 [(C=N) + (C=C)], 1285 [(C=S) + (C=N)], 1030 (N-N), 749 (C=S), 155,142 (Hg-I), 271 (Hg-S). lH NMR (6, DMSO-d6): 12.04 (s,1H, N1H), 11.37 (s, 1H, N3H), 9.06 (d, 1H, N4H), 7.96 (s, 1H, C5H), 7.10 (s, 1H, C1H), 6.57 (s, 1H, C3H), 6.16 (s, 1H, C2H), 3.14 (d, 3H, C7H). 13C NMR (6, DMSO- d6): 170.42 (C6), 138.64 (C5), 127.21 (Cl), 123.46 (C2), 114.89 (C4), 110.23 (C3), 31.84 (C7).

[Cu(4MLi-H)2] H20 10. Brown; (0.56 g, 63%); M.p. (°C) 230: Ci4H20CuN8OS2 (444.08): calcd. C 37.9, H 4.31, N 25.2, S 14.4; found C 38.2, H 3.86, N 24.8, S14.7. iz/cm“ 1 (KBr): 3340 (N-H), 1602, 1514 [(C=N) + (C=C)], 1277, 1239 [(C=S) + (C=N)], 1038 (N-N), 800 (C=S), 447 (Cu-N), 322 (Cu-S).

[Ni(4ML,-H)2] 11. Green; (0.71 g, 84%); M.p. (°C) 270; Ci4Hi8N8NiS2 (421.23): calcd. C 39.9, H 4.27, N26.6, S 15.2; found C 39.0, H 4.13, N 26.7, S 15.1. WcnT1 (KBr): 3357, 3285 (N-H), 1591, 1547 [(C=N) + (C=C)], 1288,1242 [(C=S) + (C=N)], 1041 (N-N), 818 (C=S), 332 (Ni-S).1H NMR (6, DMSO-d6): 11.38 (s, 1H, N1H), 7.34 (d, 1H, N4H), 7.16 (s, 1H, C5H), 7.08 (s, 1H, C1H), 6.78 (s, 1H, C3H), 6.18 (s, 1H, C2H), 2.82 (d, 3H, C7H). 13C NMR (6, DMSO-de): 127.25 (Cl), 124.22 (C2), 118.44 (C4), 110.37 (C3), 31.91 - 31.05 (C7).

Single crystals suitable for an X-ray crystal structure analysis were obtained from a solution of 11 in ethanol by slow evaporation of the solvent at room temperature.

[Pd(4MLi-H)2] 12. Orange; (0.76 g, 81%); M.p. (°C)> 300; Ci4Hi8N8PdS2 (467.92): calcd. C 35.8, H 3.80, N23.9, S 13.6; found C 35.0, H 3.70, 23.8, S 13.3. Wem"1 (KBr): 3366, 3310 (N-H), 1598, 1535 [(C=N) + (C=C)], 1286, 1242 [(C=S) + (C=N)], 1040 (N-N), 810 (C=S), 479 (Pd-N), 328 (Pd-S). *H NMR (6, DMSO-d6): 11.47 (s, 1H, N1H), 7.82 (d, 1H, N4H),7.16(s, 1H, C5H),7.13 (s, 1H, C1H), 6.80 (s, 1H, C3H), 6.21 (s, 1H, C2H), 2.84 (d, 3H, C7H). 13C NMR (6, DMSO-d6): 126.63 (Cl),124.72 (C2), 119.03 (C4), 110.56 (C3), 32.32 (C7).

Single crystals suitable for an X-ray crystal structure analysis were obtained from a solution of 12 in ethanol by slow evaporation of the solvent at room temperature.

[Pt(4MLi-H)2]-5H20 13. Black; (0.43 g, 33%); M.p. (°C) > 300; Ci4H28N80 5PtS2 (647.91): calcd. C 26.0, H4.36, N 17.3, S 9.9; found C 25.8, H 4.62, N 6.7, S 9.9. iz/cm '1 (KBr): 3343,3242 (N-H), 1581 [(C=N) + (C=C)], 1305,1270 [(C=S) + (C=N)], 1036 (N-N), 823 (C=S), 425 (Pt-N), 317 (Pt-S). 'HNM R (6, DMSO-d6): 11.65 (s, 1H, N1H), 8.23 (d, 1H, N4H), 7.81 (s, 1H, C5H), 7.23 (s,IH, C1H), 6.98 (s, 1H, C3H), 6.29 (s, 1H, C2H), 2.87 (d, 3H, C7H).

[Zn(4ML2)2Cl2l 14. Grey greenish; (0.68 g, 86%); M. p. (°C) 248; Ci6H24Cl2N8S2Zn (528.87): calcd. C 36.3, H 4.54, N 21.1; S 12.1; found C 36.2, H 4.73, N 21.1, SII.8. iz/cm“ 1 (KBr): 3397,3370,3302 (N-H), 1600,1572 [(C=N) + (C=C)], 1319, 1274 [(C=S) + (C=N)], 1045 (N-N), 736 (C=S), 288 (Zn-S). 'H NMR (6, DMSO-d6):11.31 (s, 1H, N1H), 10.06 (s, 1H, N3H), 8.68 (d, 1H, N4H), 6.95 (d, 1H, C1H), 6.47 (d, 1H, C3H), 6.08 (c, 1H, C2H), 3.03 (t, 3H, C7H), 2.14 (s, 3H, C8H). 13C NMR (6, DMSO-d6): 178.33 (C6), 141.34 (C5), 130.63 (Cl), 121.61 (C2), 111.37 (C4), 109.10 (C3), 30.98 (C7),13.72 C(8).

[Zn(4ML2)2Br2] 15. Grey greenish; (0.45 g, 49%); M. p. (°C) 247; Ci6H24Br2N8S2Zn (617.79): calcd. C 31.0, H 3.88, N 18.1, S 10.3; found C 31.0, H 3.79, N 17.5, S10.0. Wem - 1 (KBr): 3396,3372,3300 (N-H), 1598,1573 [(C=N) + (C=C)], 1319, 1274 [(C=S) + (C=N)], 1045 (N- N), 736 (C=S), 215,184 (Zn-Br), 283 (Zn-S).1H NMR (6, DMSO-de): 11.30 (s, 1H,N1H), 10.04 (s, 1H,N3H),8.67 (d, 1H, N4H), 6.95 (d, 1H, C1H), 6.46 (d, 1H, C3H), 6.05 (c, 1H, C2H), 3.13 (t, 3H, C7H), 2.14 (s, 3H, C8H). 13C NMR (6, DMSO-dö): 178.35 (C6), 141.32 (C5), 130.63 (Cl), 121.61 (C2), 111.36 (C4), 109.10 (C3), 30.99 (C7),13.73 C(8).

[Zn(4ML2)2I2] 16. Grey greenish; (0.63 g, 59%); M. p. (°C) 243; Ci6H24I2N8S2Zn (711.77): calcd. C 27.0, H3.37, N 15.7, S 9.0; found C 27.0, H 3.38, N 15.5, S8.9. iz/cm“ 1 (KBr): 3391, 3360 (N-H), 1573 [(C=N) + (C=C)1, 1320, 1274 [(C=S) + (C=N)], 1040 (N-N), 733 (C=S), 196,177 (Zn-I), 286 (Zn-S). *H NMR (6, DMSO- dö): 11.31 (s, 1H, N1H), 10.07 (s, 1H, N3H), 8.70 (d, 1H, N4H), 6.96 (d, 1H, C1H), 6.47 (d, 1H, C3H), 6.07 (c, 1H, C2H), 3.04 (t, 3H, C7H), 2.15 (s, 3H, C8H). 13C NMR (6, DMSO-dö): 178.37 (C6), 141.29 (C5), 130.61 (Cl), 121.61 (C2), 111.37 (C4), 109.07 (C3), 30.99 (C7),13.74 C(8).

[Cd(4ML2)Cl2] 17. Yellow; (0.97 g, 85%); M.p. (°C) 233; C8Hi2CdCl2N4S (379.60): calcd. C 25.3, H 3.18, N14.8, S 8.4; found C 25.8, H 3.1, N 15.0, S 8.3. Wem-' (KBr): 3407, 3370 (N-H), 1598, 1571 [(C=N) + (C=C)], 1320, 1269 [(C=S) + (C=N)], 1046 (N-N), 736 (C=S),

222 R. Alonso et al. • Synthesis and Structural C haracterization o f M etal Complexes

Table 1. Summary of crystal data and data collection and structure refinement parameters for [Ni(4MLi-H)2] (11), [Pd(4ML,-H)2] (12) and [Cd(4ML2)2l2l (19).

C om pound 11 12 19

Empirical formula Ci4Hi8N8S2Ni Ci4H18N8S2Pd Ci6H24CdI2N8S2Colour, habit brown, prism caramel, prism yellow, prismCrystal size (ram3) 0.15x0.15x0.15 0.25x0.15x0.10 0.35x0.10x0.10Radiation (A, A) Mo-Ka , (0.71073) M o-A'q , (0.71073) Cu-Ka , (1.54180)Crystal system monoclinic monoclinic triclinicSpace group P2\/n (No. 14) P2xln (No. 14) PI (No. 2)a (A) 5.4659(5) 5.556(1) 7.574(2)b (A) 16.6267(8) 16.760(4) 11.724(2)c (A) 9.6190(6) 9.599(1) 15.586(2)a ( ° ) 90 90 82.00(1)ß C ) 100.968(6) 100.92(2) 78.19(2)7(°) 90 90 74.05(2)Volume (A ) 858.2(1) 877.7(3) 1297.4(4)Z 2 2 2Formula weight 421.19 468.88 758.75Density (calc.) g/cm3 1.630 1.774 1.942Absorption coeff. mm-1 1.390 1.311 27.081F(000) 436 472 7240 Range (°) 2.45 - 26.28 2.43 - 26.29 2.91 -74.31Absorption corr. ^-scans empirical empiricalMax./min. transm. 0.988 / 0.925 0.880/0.735 0.972 / 0.392Reflex, collected 3832 1871 5717Data / parameters 1736/ 151 1772/ 151 5298 / 267Final R [I > 2a(/)] R l = 0.025, wR2 = 0.062 R\ =0.036, wR2 = 0.071 Rl =0.071, wR2 =R Indices (all data) R l =0.039, wR2 = 0.068 R\ = 0.105, wR2 = 0.086 Rl = 0.103, wR2 =Goodness-of-Fit 1.100 0.981 1.108Largest diff. peak/hole (eA-3) 0.260/-0.212 0.576/-0.679 1.418 /-1 .417

256, 203 (Cd-Cl). 'H NMR (6, DMSO-d6): 11.32 (s, 1H, N1H), 10.08 (s, 1H, N3H), 8.76 (d, 1H, N4H), 6.95 (d, 1H, C1H), 6.49 (d, 1H, C3H), 6.07 (c, 1H, C2H), 3.04 (t, 3H, C7H), 2.16 (s, 3H, C8H). 13C NMR (6, DMSO- d6): 177.68 (C6), 141.78 (C5), 130.52 (Cl), 121.75 (C2),111.56 (C4), 109.15 (C3), 31.03 (C7), 13.84 C(8).

[Cd(4ML2)2Br2] 18. Yellow; (0.89 g, 89%); M. p. (°C) 233; Ci6H24Br2CdN8S2 (664.82); C 29.0, H 3.61, N 16.8,S 9.6; found C 29.0, H 3.67, N 16.8, S 9.5. iz/cm“ 1 (KBr): 3407, 3370 (N-H), 1597, 1570 [(C=N) + (C=C)], 1318,1267 [(C=S) + (C=N)], 1046 (N-N), 737 (C=S), 189 (Cd- Br), 275 (Cd-S). 'H NMR (6, DMSO-d6): 11.32 (s, 1H, N1H), 10.07 (s, 1H, N3H), 8.68 (d, 1H, N4H), 6.96 (d, 1H, C1H), 6.47 (d, 1H, C3H), 6.07 (c, 1H, C2H), 3.03 (t, 3H, C7H), 2.15 (s, 3H, C8H). 13C NMR (6, DMSO- d6): 178.14 (C6), 141.47 (C5), 130.61 (Cl), 121.65 (C2),111.41 (C4), 109.10 (C3), 31.00 (C7), 13.77 C(8).

[Cd(4ML2)2I2] 19. Yellow; (0.84 g, 74%); M. p. (°C) 231; Ci6H24Cdl2N8S2 (758.80); calcd. C 25.3, H 3.16, N 14.7, S 8.4; found C 25.4, H 3.17, N 14.7, S 8.1. tz/cra'1 (KBr): 3367, 3295 (N-H), 1598, 1573 [(C=N) + (C=C)], 1321, 1264 [(C=S) + (C=N)], 1044 (N-N), 757 (C=S), 297 (Cd-I).1H NMR (6, DMSO-d*,): 11.32 (s, 1H,

N1H), 10.06 (s, 1H, N3H), 8.71 (d, 1H, N4H), 6.96 (d, 1H, C1H), 6.47 (d, 1H, C3H), 6.07 (c, 1H, C2H), 3.04 (t, 3H, C7H), 2.15 (s, 3H, C8H). 13C NMR (6, DMSO- dö): 178.05 (C6), 141.54 (C5), 130.60 (Cl), 121.67 (C2),111.45 (C4), 109.12 (C3), 31.04 (C7), 13.80 C(8).

Single crystals suitable for an X-ray crystal structure analysis were obtained from a solution of 19 in ethanol by slow evaporation of the solvent at room temperature.

[Hg(4ML2)Cl2] 20. Yellow; (1.08 g, 77%); M.p. (°C)> 300; C8Hi2Cl2HgN4S (467.79): calcd. C 20.6, H 2.56, N 11.9, S 6.8; found C 20.6, H 2.51, N 11.9, S 6.7. u/cm~1 (KBr): 3316, 3259 (N-H), 1580, 1558 [(C=N) + (C=C)], 1277 [(C=S) + (C=N)], 1044 (N-N), 757 (C=S), 229 (Hg- C l).1H NMR (<5,DMSO-d6): 11.41 (s, 1H,N1H), 10.81 (s, 1H, N3H),9.37 (d, 1H, N4H),7.14(d, 1H,C1H),6.65 (d, 1H, C3H), 6.13 (c, 1H, C2H), 3.15 (t, 3H, C7H), 2.30 (s, 3H, C8H). 13C NMR (<5, DMSO-d6): 169.99 (C6), 147.43 (C5), 129.55 (Cl), 123.13 (C2), 113.63 (C4), 109.69 (C3),31.75 (C7), 14.68 C(8).

[Hg(4ML2)Br2] 21. Yellow; (1.17 g, 70%); M.p. (°C) 232; C8H12Br2HgN4S (556.71): calcd. C 17.3, H 2.15, N10.1, S 5.7; found C 17.5, H 2.25, N 10.5, S 5.9. vlcm ~x (KBr): 3354, 3284, 3250 (N-H), 1576 [(C=N) + (C=C)],

R. Alonso et al. • Synthesis and Structural C haracterization o f M etal Complexes 223

1316, 1270 [(C=S) + (C=N)], 1043 (N-N), 753 (C=S), 203, 150 (Hg-Br). *H NMR (6, DMSO-d6): 11.42 (s, 1H, N1H), 10.79 (s, 1H, N3H), 9.37 (d, 1H, N4H), 7.08 (d, 1H, C1H), 6.65 (d, 1H, C3H), 6.13 (c, 1H, C2H), 3.16 (t, 3H, C7H), 2.29 (s, 3H, C8H). 13C NMR (6, DMSO- de): 170.67 (C6), 146.98 (C5), 129.65 (Cl), 123.03 (C2),113.46 (C4), 109.65 (C3), 31.78 (C7), 14.64 C(8).

[Hg(4ML2)I2] 22. Yellow, (1.27 g, 65%); M.p. (°C) 200; C8Hi2Hgl2N4S (650.69): calcd. C 14.8, H 1.84, N8.6, S 4.9; found C 15.2, H 1.77, N 8.6, S 4.8. v tc m '1 (KBr): 3442, 3332 (N-H), 1573 [(C=N) + (C=C)], 1319,1268 [(C=S) + (C=N)], 1042 (N-N), 742 (C=S), 146 (Hg-I), 286 (Hg-S). 'H NMR (6, DMSO-d6): 11.41 (s, 1H, N1H), 10.69 (s, 1H, N3H), 9.31 (d, 1H, N4H), 7.07 (d, 1H, C1H), 6.63 (d, 1H, C3H), 6.14 (c, 1H, C2H), 3.16 (t, 3H, C7H), 2.28 (s, 3H, C8H). 13C NMR (6, DMSO- d6): 171.63 (C6), 141.41 (C5), 129.75 (Cl), 122.92 (C2),113.31 (C4), 109.62 (C3), 31.77 (C7), 3.72 C(8).

Crystallography. Crystals of [Ni(4MLj-H)2] (11), [Pd(4MLi-H)2] (12) and [Cd(4MLi)2I2] (19) suitable for X-ray diffraction were mounted on glass fibers and trans­ferred to an Enraf-Nonius CAD4 diffractometer for data collection, using Mo-Ka radiation (A = 0.71073 Ä) for 11 and 12 and Cu-KQ radiation (A = 1.54180 A) for 19. Crys­tal data and details of the data collection and refinement are given in Table 1. The data were corrected for LP effects and for the observed linear decay of reference reflections. An empirical absorption correction (DIFABS) [11] was applied for 12 and 19, and a semi-empirical correction

Fig. 1. The molecule of [Ni- (4MLi-H)2] 11, with the num­bering scheme of the non-hydro­gen atoms. Displacement ellip­soids are plotted at the 80% probability level and H atoms are presented as spheres of ar­bitrary radii.

for 11 [12]. The structures were solved by direct methods and subsequent difference Fourier techniques (SHELXS- 86) [13], and were refined by full-matrix least-squares procedures on F 2 (SHELXL-97) [14]. The hydrogen atoms were located in difference Fourier syntheses and refined isotropically. Geometrical calculations were per­formed and illustrations produced with the SHELXL97[14], and PLATON [16] packages. Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as Supplementary Publica­tions Nos. CCDC-144953 (11), CCDC-144954 (12) and CCDC-144955 (19). Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: int. code +44-1223/336- 033; E-mail: deposit@ccdc.cam.ac.uk].

Results and Discussion

Reactions between Group 12 metal halides and the pyrrolethiosemicarbazones 4M Li and 4ML2 in ethanolic m edia afforded complexes 1 - 9 and14 - 22. All have analytical data indicative of metal:ligand ratios of 1:2 except for the mercury complexes and the cadm ium chloride complexes, which have 1:1 stoicheiometry. Reactions between 4M Lj and salts o f copper(II) or Group 10 metals, with metal and ligand in 1:2 mole ratio, afforded

224 R. A lonso et al. • Synthesis and Structural C haracterization o f M etal Complexes

Fig. 2. The molecule of [Pd- (4MLi-H)2] 12, with the num­bering scheme of the non-hydro- gen atoms. Displacement ellip­soids are plotted at the 80% prob­ability level and H atoms are presented as spheres of arbitrary radii.

complexes 10 -13, the analytical data of which in­dicate the same stoicheiometry as used in their preparation. All the new compounds were stable in air, moderately soluble in polar solvents other than water, and insoluble in apolar solvents. The FAB mass spectra of the Group 12 metal com­plexes show the molecular ion only for 4ML2; following loss of a halogen atom by these 4 ML2

complexes, the fragmentation sequence is gener­ally [M(L)X]+ -> [M(L)]+ [L]+ for 1:1 com­plexes, and [M(L)2X]+ -» [M(L)2]+ -+ [M(L)]+ -> [L]+ for 1:2 complexes. Similar fragmentation se­quences have been reported for other compounds of this type [16-20]. The mass spectra of com­pounds 10 -1 3 show the molecular ion [M(4MLi- H)2]+ and the fragment resulting from loss of one ligand, [M(4MLi-H)]+; this sequence parallels the behaviour of other metal complexes of monodepro- tonated thiosemicarbazones [2 1 , 2 2 ].

M olecu lar structures

Figs. 1 and 2 show the molecular structures of compounds 11 and 12, and Table 2 lists their main bond lengths and angles. They are isotypic, both be­ing planar centrosymmetric complexes in which the metal atom is tetracoordinated to the sulphur and azomethine nitrogen atoms of each of two monode- protonated 4MLi ligands. The M-S bonds are longer

Table 2. Selected bond lengths (A) and angles (°) in [Ni(4MLi-H)2] (11), [Pd(4MLi-H)2] (12) and [Cd(4ML2)2l2] (19).

11 12 19a

M -S(l) 2.1803(6) 2.293(1) 2.568(4) -

M-S(2) - - 2.564(4) -M -I(l) - - 2.739(2) -M-I(2) - - 2.729(2) -M-N(2) 1.919(2) 2.029(4) - -N(2)-N(3) 1.397(2) 1.386(5) 1.40(2) 1.39(2)N(3)-C(6) 1.302(3) 1.311(6) 1.35(2) 1.35(2)C(6)-S1) 1.726(2) 1.721(5) 1.71(1) 1.70(1)C(6)-N(4) 1.349(3) 1.341(7) 1.32(2) 1.32(2)

S(l)-M -N(2) 85.69(5) 83.0(1) - -S(l)-M -N(2b) 94.31(5) 97.0(1) - -S(l)-M -S(2) - - 103.3(2) -S(l)-M -I(l) - - 112.7(1) -S(l)-M -I(2) - - 104.7(1) -S(2)-M -I(l) - - 100 .2 ( 1) -S(2)-M-I(2) - - 115.3(1) -I(l)-M-I(2) - - 119.9(1) -C(5)-N(2)-N(3) 114.0(2) 115.3(4) 117.6(1) 117(1)N(2)-N(3)-C(6) 113.0(2) 114.1(4) 119(1) 117(1)N(3)-C(6)-S(l) 123.1(2) 125.1(4) 120 ( 1) 118(1)N(3)-C(6)-N(4) 117.7(2) 116.9(5) 117(1) 120( 1)S(l)-C(6)-N(4) 119.3(2) 117.9(4) 122(1) 123(1)

a The second numbers are for the analogous bond distances and angles in the second molecule; b symmetry transforma­tions used to generate equivalent atoms: — x + 2, —y, —z (11); —x, —y, —z + 1 (12).

R. A lonso et al. • Synthesis and Structural Characterization o f M etal Complexes 225

Fig. 3. Molecular structure of the [Cd(4ML2)2l2] 19. The non-hydrogen atoms are drawn at 50% probability contours of the thermal motion, while the hydrogen atoms have an arbitrary size.

Table 3. Inter- and intramolecular hydrogen bonding (A, °) in [Cd(4ML2)2l2].

D -H -A d(D-H) d (H -A ) d (D -A ) Z(DHA)

N(11)-H(1 l)-I(l') 0 .8 6 2.91 3.72(1) 156.7N(13)-H(13)-S(2) 0 .8 6 3.02 3.79(1) 150.2N(14)-H(14)-I(l') 0 .8 6 3.03 3.77(1) 144.9N(21)-H(21)-I(2") 0 .8 6 2.93 3.72(1) 153.3N(23)-H(23)-S(l) 0 .86 2.87 3.71(1) 165.7N(24)-H(24)-I(2") 0 .86 3.05 3.76(1) 142.0

Symmetry transformations used to generate equivalent atoms: 1 ~ y + 15 — 2; 11 —x, —y, —z + 1.

than the M-N bonds, making the coordination fig­ure a rhombus rather than a square. In 11 the Ni-S distance, 2.181(1) A, is similar to those found in other tetracoordinate complexes of nickel(II) with monodeprotonated thiosemicarbazones [22], and slightly longer than in nickel(II) bis(thiosemicarb- azonates) [23], but the Ni-N distance, 1.919(2) A, is in the ranges found in both thiosemicarbazonates[22] and bis(thiosemicarbazonates) [23] of Ni11. In12, the Pd-S distance, 2.293(1) A, is in the usual range for tetracoordinate Pd11 complexes [16, 22], and the Pd-N distance, 2.029(4) A, is likewise simi­lar to those of other complexes of palladium(II) with thiosemicarbazones [22, 24] although it is slightly shorter than those in which the Pd atom binds a chlorine atom trans to an azomethine nitrogen [25]. As in other metal complexes of monodeprotonated

thiosemicarbazones [22, 23], the C-S distances in­dicate considerable single bond character and the thioamide C-N distances considerable double bond character, and are thus consistent with delocaliza­tion of the negative charge throughout the thiosemi- carbazonato moiety.

Fig. 3 shows the structure of compound 19, and Tables 2 and 3 lists its main bond lengths and angles. The cadmium atom coordinates to two iodine atoms and to the sulphur atom of each of two dissimilar thiosemicarbazone ligands, in a distorted tetrahedral environment in which the main angular deviations from ideal tetrahedral geometry appear in S(2)-Cd- I( 1) (100.19(9)°) and I( 1 )-Cd-I(2) (119.85(6)°). The neutral, S-monodentate nature of the ligands is re­flected in the C-S distances (both about 1.69 A) and in C(6)-N(3) distances longer than 1.30 A [26]. The Z' conformation adopted by the free ligand[10] persists upon formation of [Cd(4ML2)2l2L as it does in complexes of Group 12 metals with sim­ilar thiosemicarbazones [27]. The Cd-I and Cd-S distances are within the ranges found in complexes of Cd(II) iodide with N,N,S-tridentate thiosemicar­bazones [25, 28 - 30], but the Cd-S distances are rather longer than in the complex of Cd(II) io­dide with 2-acetylpyrrole thiosemicarbazone [27], in which, as in 19, a distorted tetrahedral coordina­tion polyhedron is created by coordination to two S-monodentate ligands.

226 R. A lonso et al. • Synthesis and Structural Characterization of M etal Com plexes

The parameters of the numerous intra- and in- termolecular hydrogen bonds in crystals of 19 are listed in Table 4. Four are N-H- - I bonds, and two N- H---S bonds. The crystal-stabilizing hydrogen bond network created this way is similar to those found in other complexes of Group 12 metal halides withS-monodentate pyrrole thiosemicarbazones [27].

Infrared spectra

The main IR bands of 4ML] and 4ML2 together with those of the new complexes are described in [10]. In the spectra of most of the Group 12 metal complexes, three z/(N-H) bands lie at virtually the same positions as in the free ligand, in keeping with the non-deprotonation shown by X-ray diffractome- try for 19. By contrast, the spectra of the complexes of 4MLj with Cu11 and Group 10 metals lack at least one z/(N-H) band, in keeping with the deprotonation shown by X-ray diffractometry for 11 and 12. None of the compounds have any bands between 2500 and 2 0 0 0 cm-1 , suggesting that the ligands are not in thiol form either before or after coordination, at least in the solid state. In most of the complexes, including all those of the Group 12 metals, coor­dination shifts the u(C=S) band to lower energies, corroborating the involvement of the S atom in coor­dination. Coordination through the azomethine ni­trogen atoms of the Cu11 and Group 10 metal com­plexes is confirmed by shifts of z/(N-N) to higher wavenumbers that are much more marked than for the Group 12 complexes. To sum up, the data for the 4000-400 cm - 1 region of the spectra indicate that both ligands are neutral and S-monodentate in their complexes with Group 12 metals, whereas in the complexes of copper or Group 10 metals, 4MLi is monodeprotonated and S,N-didentate.

In most of the spectra the 269 - 332 cm - 1 re­gion shows a fairly strong band attributed to metal- sulphur stretching. The metal-halogen stretching bands have been identified in accordance with the literature [31, 32] and with the ratios i/(M-Br)/i/(M- Cl) = 0.74 - 0.77 and z/(M-I)MM-Cl) = 0.65 found in previous work [25, 27, 33].

In conclusion, the IR spectra suggest that, in keeping with the X-ray results for 19, the 1:2 com­plexes of Zn11, Cd11 and Hg11 have coordination number four, the metal atom being coordinated to two halogen atoms and to the sulphur atom of each thiosemicarbazone ligand. In view of X-ray re­sults for analogous pyrrolethiosemicarbazone com­

plexes [27], it seems likely that in the 1:1 com­plexes the metal atom is also tetracoordinated, bind­ing the thiosemicarbazone sulphur and three halo­gen atoms, two of which bridge neighbouring metal centres.

Electronic spectra

The electronic spectra of compounds 10 - 13 were recorded by diffuse reflection spectroscopy. The spectra of the Group 10 compounds, 1 1 -1 3 , each show three absorption peaks that can be at­tributed to the spin-allowed d-d transitions of square planar complexes with electronic configuration d8: in decreasing order of wavenumber, lA \g —» lE g, !A ig — ^ i g and ^ ig —> 1 A jg. These peaks lie at 22171, 18868 and 15456 cm - 1 in 11, 25126, 23585 and 21413 cm“ 1 in 12 and 27322, 17953 and 16103 cm - 1 in 13, wavenumbers similar to those found in similar complexes of Ni, Pd and Pt with hetercyclic thiosemicarbazones [22, 27].

In the copper(II) compound, 10, the effective magnetic moment at 300 K, 2.20 indicates sig­nificant magnetic dilution. The electronic spectrum has peaks at 17452 and 13755 cm - 1 corresponding to d —> d transitions, and at 23866 cm - 1 shows the characteristic Cu(II)-thiosemicarbazone peak due to charge transfer from sulphur to copper [33].

NMR spectra

Scheme 1 shows the numbering used for assign­ment of !H and l3C NMR signals [10]. The presence of all the ligand proton signals in the ’HNMR spec­tra of complexes 1 - 9 and 14 - 22 confirms non-de­protonation. The absence of the N(3)H signal from

Scheme 1. 7 CH3

R. Alonso e t al. • Synthesis and Structural Characterization o f Metal Complexes 227

Table 4. 113Cd and 199Hg NMR chemical shifts (<5, ppm).

Compound X = C1 X = Br X = I

[Cd(4ML0nX2] 260 272 164[Hg(4ML0X2] -980 - -[Cd(4ML2)nX2] 329 295 -

[Hg(4ML2)X2] -962 -1497 -

the spectra of compounds 11-13 shows the per­sistence of deprotonation in these complexes, and for 11 and 12 the upfield shift of the C(5)H signal suggests that coordination through the azomethine nitrogen atom is likewise maintained in solution. In the mercury complexes, coordination through the sulphur atom is reflected by a slight deshield­ing of N(4)H and N(3)H; the apparent absence of this deshielding in the zinc and cadmium complexes may be due to ligand-exchange equilibria involving the solvent, while in 11-13 the protons on N(4) and its substituent C(7) are shielded. The shielding of the C(7) protons in all the 4 ML2 complexes, and the

splitting of the C(7)H signal in the spectra of some of the 4MLi complexes with Group 12 metals, may be due to the ligand-exchange equilibria mentioned above.

In the 13C NMR spectra (Table 9), all the C(5) signals are shifted downfield (those of the mer­cury compounds and [Zn(4 MLi)2l2] much more markedly than the others), while the C(6 ) signals of the mercury compounds are shifted upfield. The 4MLi compounds with split !H NMR signals for C(7)H also have split 13C signals for C(7), as does compound 1 1 .

Table 4 lists the 113Cd and 199Hg NMR signals of the Cd and Hg complexes that were soluble enough to allow these spectra to be recorded. The 113Cd chemical shifts are all within the expected range for tetrahedral environments [34 - 37] except for the [Cd(4 MLi)Cl2] signal, the low value of which may be due to partial displacement of the ligand by the solvent. The 199Hg NMR signals are within the usual range for tetracoordinated mercury [38].

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