Spectral and Structural Studies of Transition Metal Complexes of2-Pyridineformamide N(4)-ethylthiosemicarbazone

Elena Bermejoa, Alfonso Castineirasa,* Isabel Garcıa-Santosa, Larissa M. Fostiakb, John K. Swearingenb, andDouglas X. Westc

a Santiago de Compostela/Spain, Departamento de Quımica Inorganica, Universidad de Santiago de Compostelab Normal/USA, Department of Chemistry, Illinois State Universityc Seattle/USA, Department of Chemistry, University of Washington

Received August 4th 2004; revised November 1st 2004.

Abstract. The reduction of 2-cyanopyridine in the presence of N(4)-ethylthiosemicarbazide produces 2-pyridineformamide N(4)-ethyl-thiosemicarbazone, HAm4E. Complexes with cobalt(III), nickel-(II), copper(II), palladium(II) and platinum(II) have been preparedand characterized by molar conductivity, magnetic susceptibilityand spectroscopic techniques. In addition, the crystal structuresof HAm4E, [Co(Am4E)2](ClO4), [Ni(HAm4E)2](ClO4)2, and[Ni(HAm4E)2]Cl(OAc)·AcOH·H2O have been obtained. Coordina-

1 Introduction

Thiosemicarbazones possess a range of biological appli-cations and antitumor, antiviral, antibacterial, antimalarialand antifungal activities have been studied [1]. HeterocyclicN(4)-substituted thiosemicarbazones and their copper(II)complexes show activity against animal and human tumorstrains [2]. Although 2-formyl-, 2-acetyl- and 2-benzoylpyri-dine N(4)-substituted thiosemicarbazones [3�5] haveshown substantial in vitro activity against various humantumor lines [6], their lack of solubility in aqueous solutionsmakes them and their copper(II) complexes less promisingin terms of in vivo tests. In an effort to enhance the watersolubility of these systems, we have prepared a new seriesof thiosemicarbazones and related complexes [7�20] inwhich the thiosemicarbazone moiety is attached to an am-ide carbon atom rather than an aldehyde or ketone carbonatom. We report here the physical, spectral and structuralproperties of 2-pyridineformamide N(4)-ethylthiosemicar-bazone, HAm4E, and a selection of its metal complexes.These new compounds are compared to related complexesof 2-pyridineformamide N(4)-methylthiosemicarbazone,HAm4M [8, 9], as well as other NNS coordinating thiosem-icarbazone complexes.

* Prof. Alfonso CastineirasUniversidad de Santiago de CompostelaDepartamento de Quımica InorganicaFacultad de FarmaciaE-15782 Santiago de CompostelaFax: �34 981 547 163E-mail: qiac01@usc.es

728 © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim DOI: 10.1002/zaac.200400345 Z. Anorg. Allg. Chem. 2005, 631, 728�738

tion occurs through the pyridyl nitrogen, imine nitrogen and eitherthe thione or thiolato sulphur atom when coordinating as the neu-tral or anionic ligand, respectively. Extensive hydrogen bonding oc-curs in both HAm4E and its metal complexes, with the amide hy-drogen atoms being significant contributors.

Keywords: Thiosemicarbazone; 2-Pyridineformamide; Crystalstructure; Cobalt; Copper; Nickel; Palladium, Platinum

HAm4DE

2 Experimental

2.1 Synthetic methods

Synthesis of HAm4E (1): 2-Cyanopyridine and N(4)-ethylthiosemi-carbazide were both purchased from Aldrich and used as received.Following the literature procedure for the reduction of 2-cyanopyri-dine [21], sodium (0.092 g, 4.0 mmol) was added to MeOH(25 mL), which had been dried over Mg and I2 [22], and the solu-tion stirred until complete dissolution was achieved. 2-Cyanopyrid-ine (2.60 g, 24.9 mmol) was then added, the mixture stirred for30 min and N(4)-ethylthiosemicarbazide (2.96 g, 24.9 mmol) wasadded in small portions over a period of 1 h. A further quantity ofMeOH (20 mL) was added and the mixture was heated under refluxfor a minimum of 4 h. Slow evaporation of the MeOH producedthe yellowish crystals of HAm4E.

Yield: 3.5 g (62.5 %). Elemental analysis, Found: C, 48.3; H, 5.9;N, 31.3; S, 14.6 %. Calcd. for C9H13N5S (223.30): C, 48.4; H, 5.9;N, 31.4; S, 14.4 %.

IR (νmax/cm�1): 3343�3186 (NH), 1609�1541 (C�N, C�C), 997(NN); 825 (CS). 1H-NMR (dmso-d6, ppm): 8.24 (1H, s, H1); 8.14(2H, s, br, H3�H4); 7.73 (1H, s, H2); 7.37 (2H, s, NH2); 6.80 (1H,s, N4H); 3.16 (2H, q, CH2); 1.04 (3H, t, CH3). 13C-NMR (dmso-d6, ppm): 175.9 (C7); 150.1 (C5); 149.9 (C1); 141.9 (C6); 136.6 (C3);

Spectral and Structural Studies of Transition Metal Complexes of 2-Pyridineformamide N(4)-ethylthiosemicarbazone

124.4 (C2); 121.0 (C4); 38.1 (C8); 14.80 (C9). EI MS m/z (assign-ment): 223 (HAm4E), 206 (HAm4E � NH3), 178 (C7H6N4S), 145(C7H5N4), 122 (C6H8N3), 105 (C6H5N2), 60 (CH2NS).

Synthesis of [Co(Am4E)2](ClO4) (2): A solution of Co(ClO4)2·6H2O(0.73 g, 2 mmol) (caution, perchlorate compounds are potentially ex-plosive) in EtOH (30 mL) was mixed with a solution of HAm4E(0.89 g, 4 mmol) in EtOH (20 mL). The solution was heated underreflux for 2 h and the resulting solids were filtered off from thewarm solutions, washed with anhydrous ether to apparent drynessand dried on a hot plate at 35 °C.

Yield: 0.44 g (73.2 %). Elemental analysis, Found: C, 35.8; H, 4.2;N, 23.5; S, 10.3 %. Calcd. for C18H24ClCoN10O4S2 (602.97): C,35.9; H, 4.0; N, 23.2; S, 10.6 %.

IR (νmax/cm�1): 3383�3231 (NH), 1580�1538 (C�N, C�C), 1089(ClO4), 1016 (NN); 862 (CS); 627 (ClO4); 453 (Co�N); 375(Co�S). FAB� MS m/z (assignment): 503 ([Co(HAm4E)-(Am4E)]�), 280 ([Co(Am4E)]�).

Synthesis of [Ni(Am4E)(OAc)] (3): A solution of Ni(AcO)2·4H2O(0.28 g, 1.12 mmol) in EtOH (20 mL) was mixed with a solution ofHAm4E (0.25 g, 1.12 mmol) in EtOH (20 mL) and the mixture washeated under reflux for 2 h. A brown solution was obtained andslow evaporation of the solvent gave a brown solid, which wasrecrystallized from acetonitrile. The brown crystalline productwas isolated.

Yield: 0.27 g (72.5 %). Elemental analysis, Found: C, 39.1; H, 4.5;N, 21.0; S, 9.6 %. Calcd. for C11H15N5NiO2S (340.03): C, 38.9; H,4.5; N, 20.6; S, 9.4 %.

IR (νmax/cm�1): 3274�3143 (NH), 1643 (COO); 1585�1536 (C�

N, C�C), 1417 (COO); 1022 (NN); 871 (CS); 465 (Ni�N); 375(Ni�O); 349 (Ni�S). 1H-NMR (dmso-d6, ppm): 8.24 (1H, s, H1);8.14 (2H, s, br, H3�H4); 7.73 (1H, s, H2); 7.37 (2H, s, NH2); 6.80(1H, s, N4H); 3.16 (2H, q, CH2); 1.04 (3H, t, CH3). FAB� MSm/z (assignment): 280 ([Ni(Am4E)]�).

Synthesis of [Ni(HAm4E)2](ClO4)2 (4): A solution ofNi(ClO4)2·6H2O (0.20 g, 0.56 mmol) in EtOH (20 mL) (caution,perchlorate compounds are potentially explosive) was mixed with asolution of HAm4E (0.25 g, 1.12 mmol) in EtOH (20 mL). Thesolution was heated under reflux for 2 h. The resulting green solidwas filtered off. Slow evaporation of the mother liquors gavegreen crystals.

Yield: 0.33 g (84.0 %). Elemental analysis, Found: C, 30.5; H, 3.7;N, 19.9; S, 9.1 %. Calcd. for C18H26Cl2N10NiO8S2 (704.19): C, 30.7;H, 3.7; N, 19.9; S, 9.1 %.

IR (νmax/cm�1): 3366�3277 (NH), 1629�1566 (C�N, C�C), 1108(ClO4), 1044 (NN); 856 (CS); 628 (ClO4); 465 (Ni�N); 373 (Ni�S).FAB� MS m/z (assignment): 782 ([Ni2(Am4E)3]�), 503([Ni(HAm4E)(Am4E)]�), 280 ([Ni(Am4E)]�).

Synthesis of [Ni(HAm4E)2](NO3)2 (5): A solution ofNi(NO3)2·6H2O (0.16 g, 0.56 mmol) in EtOH (20 mL) was mixedwith a solution of HAm4E (0.25 g, 1.12 mmol) in EtOH (20 mL).The solution was heated under reflux and the resulting green prod-uct was filtered off.Yield: 0.25 g (69.6 %). Elemental analysis, Found: C, 34.1; H, 4.7;N, 26.4; S, 10.1 %. Calcd. for C18H26N12NiO6S2 (629.30): C, 34.4;H, 4.2; N, 26.7; S, 10.2 %.

IR (νmax/cm�1): 3311�3182 (NH), 1635, 1568 (C�N, C�C), 1384(NO3), 1017 (NN); 860 (CS); 834 (NO3); 467 (Ni�N); 354 (Ni�S).FAB� MS m/z (assignment): 782.1 ([Ni2(Am4E)3]�), 560

Z. Anorg. Allg. Chem. 2005, 631, 728�738 zaac.wiley-vch.de © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 729

([Ni2(Am4E)2]�), 503 ([Ni(HAm4E)(Am4E)]�), 280([Ni(Am4E)]�).

Synthesis of [Ni(HAm4E)Cl2] (6): A solution of NiCl2·6H2O(0.20 g, 0.89 mmol) in EtOH (20 mL) was mixed with a solution ofHAm4E (0.21 g, 0.89 mmol) in EtOH (20 mL). The mixture washeated under reflux for 2 h and the resulting green solid was fil-tered off.

Yield: 0.26 g (80.7 %). Elemental analysis, Found: C, 30.9; H, 3.5;N, 19.9; S, 8.6 %. Calcd. for C9H13Cl2N5NiS (352.90): C, 30.6; H,3.7; N, 19.9; S, 9.1 %.

IR (νmax/cm�1): 3350�3199 (NH), 1598�1557 (C�N, C�C), 1017(NN); 864 (CS); 466 (Ni�N); 343 (Ni�S); 294 (Ni�Cl). FAB� MSm/z (assignment): 316 ([Ni(HAm4E)Cl]�), 280 ([Ni(Am4E)]�).

Brown crystals suitable for X-ray diffraction were obtained from amixture of MeOH/AcOH and were found to be[Ni(HAm4E)2]Cl(OAc)·HOAc·H2O (6a).

Synthesis of [Cu(Am4E)(AcO)] (7): A solution of Cu(AcO)2·H2O(0.40 g, 2 mmol) in EtOH (30 mL) was mixed with a solution ofHAm4E (0.45 g, 2 mmol) in EtOH (20 mL). The solution washeated under reflux and the resulting green product was filtered off.Yield: 0.27 g (78.3 %). Elemental analysis, Found: C, 38.5; H, 4.6;N, 20.2; S, 9.0 %. Calcd. for C11H15CuN5O2S (344.88): C, 38.3; H,4.4; N, 20.3; S, 9.3 %.

IR (νmax/cm�1): 3360�3320 (NH), 1635 (COO), 1570�1516 (C�

N, C�C), 1404 (COO), 1011 (NN); 862 (CS); 458 (Cu�N); 408(Cu�O); 351 (Cu�S). FAB� MS m/z (assignment): 285([Cu(Am4E)]�).

Synthesis of [{Cu(Am4E)}2(succ)] (8): A solution of copper(II) suc-cinate (0.36 g, 2 mmol), prepared by adding a stoichiometricamount of succinic acid to basic copper(II) carbonate, in EtOH(30 mL) was mixed with a solution of HAm4E (0.45 g, 2 mmol) inEtOH (20 mL). The solution was heated under reflux and the re-sulting green product was filtered off from the warm solution,washed with anhydrous ether to apparent dryness and dried furtheron a hot plate at 35 °C.

Yield: 0.46 g (67.2 %). Elemental analysis, Found: C, 37.5; H, 3.8;N, 20.5; S, 8.9 %. Calcd. for C22H30Cu2N10O5S2 (687.74): C, 38.4;H, 4.1; N, 20.4; S, 9.3 %.

IR (νmax/cm�1): 3427�3134 (NH), 1586 (COO), 1562�1539 (C�

N, C�C), 1427 (COO), 1011 (NN); 859 (CS); 444 (Cu�N); 407(Cu�O); 371 (Cu�S). FAB� MS m/z (assignment): 571([Cu2(Am4E)2]�).

Synthesis of [{Cu(Am4E)}2(tart)]·H2O (9): A solution ofCu2(C4H4O6)·xH2O (0.42 g, 2 mmol) in EtOH (30 mL) was mixedwith a solution of HAm4E (0.45 g, 2 mmol) in EtOH (20 mL). Thesolution was heated under reflux and the resulting green productwas filtered off from the warm solution, washed with anhydrousether to apparent dryness and dried further on a hot plate at 35 °C.Yield: 0.49 g (66.1 %). Elemental analysis, Found: C, 36.7; H, 3.8;N, 19.5; S, 9.1 %. Calcd. for C22H28Cu2N10O6S2 (737.76): C, 35.8;H, 4.1; N, 19.0; S, 8.7 %.

IR (νmax/cm�1): 3298�3134 (NH), 1592 (COO), 1563�1538 (C�

N, C�C), 1430 (COO), 1015 (NN); 856 (CS); 442 (Cu�N); 409(Cu�O); 351 (Cu�S). FAB� MS m/z (assignment): 570([Cu2(Am4E)2]�).

Synthesis of [Pd(Am4E)Cl]·2H2O (10): A solution of K2[PdCl4](0.16 g, 1.12 mmol) in H2O (5 mL) was mixed with a solution ofHAm4E (0.25 g, 1.12 mmol) in EtOH (30 mL). The solution was

E. Bermejo, A. Castineiras, I. Garcıa-Santos, L. M. Fostiak, J. K. Swearingen, D. X. West

heated under reflux for 2 h and the resulting brown precipitate wasfiltered off.

Yield: 0.31 g (69.6 %). Elemental analysis, Found: C, 26.6; H, 3.8;N, 17.4; S, 8.1 %. Calcd. for C9H16ClN5O2PdS (400.19): C, 27.0;H, 4.0; N, 17.5; S, 8.0 %.

IR (νmax/cm�1): 3288 (OH, NH), 1609�1535 (C�N, C�C), 1015(NN); 864 (CS); 471 (Pd�N); 384 (Pd�S); 363 (Pd�Cl). 1H-NMR(dmso-d6, ppm): 8.58 (1H, dd, H1); 8.21 (1H, td, H3); 8.08 (1H, d,H4); 7.68 (1H, m, H2); 7.36 (2H, s, NH2); 7.06 (1H, s, N4H); 3.25(2H, q, CH2); 1.06 (3H, t, CH3). 13C-NMR (dmso-d6, ppm): 170.6(C7); 152.9 (C5); 150.9 (C6); 147.8 (C1); 140.6 (C3); 126.8 (C2);40.9 (C8); 14.5 (C9). FAB� MS m/z (assignment): 693([Pd2(Am4E)2Cl]�).

Synthesis of [Pt(Am4E)Cl]·H2O (11): A solution of K2[PtCl4](0.16 g, 1.12 mmol) in H2O (5 mL) was mixed with a solution ofHAm4E (0.25 g, 1.12 mmol) in EtOH (20 mL). The solution washeated under reflux for 2 h and the resulting red precipitate wasfiltered off.

Yield: 0.30 g (56.7 %). Elemental analysis, Found: C, 22.5; H, 2.8;N, 14.2; S, 6.5 %. Calcd. for C9H14ClN5OPtS (470.84): C, 23.0; H,3.0; N, 14.9; S, 6.8 %.

IR (νmax/cm�1): 3419�3309 (OH, NH), 1567�1539 (C�N, C�C),1024 (NN); 868 (CS); 466 (Pt�N); 367 (Pt�S); 324 (Pt�Cl). 1H-NMR (dmso-d6, ppm): 8.83 (1H, dd, H1); 8.22 (1H, td, H3); 8.04(1H, d, H4); 7.23 (2H, s, NH2); 6.75 (1H, s, N4H); 6.69 (1H, m,H2); 3.69 (2H, s, br, CH2); 1.07 (3H, t, CH3). 13C-NMR (dmso-d6,ppm): 178.7 (C7); 152.9 (C5); 150.7 (C6); 146.5 (C1); 140.5 (C3);126.0 (C2); 41.1 (C8); 15.0 (C9). 195Pt-NMR (dmso-d6, ppm):2957.8. FAB� MS m/z (assignment): 869 ([Pt2(Am4E)2Cl]�), 223(HAm4E), 192 (C9H14N5).

2.2 Instrumental methods

Elemental analyses of the complexes were performed by NationalChemical Consulting, Inc. of Tenafly, N.J. using Carlos Erba 1108and Perkin-Elmer 240B microanalysers. The magnetic susceptibilit-ies were measured with a Johnson-Matthey magnetic susceptibilitybalance and an Alpha MSB-MK1 balance. NMR spectra were ob-tained with a Varian 300 MHz Gemini spectrometer or a BrukerAMX300 spectrometer using [d6]-DMSO or CDCl3 as the solvent;the chemical shifts are reported in parts per million downfield fromtetramethylsilane. Infrared spectra were recorded with Nicolet5SXC and Magna 850 FT-IR spectrometers and a Bruker IFS-66vmachine using Nujol mulls between CsI plates; electronic spectrawere acquired as nujol mulls impregnated on filter paper and asDMF solutions in 1 cm cells with a Cary 5E spectrophotometerand a Shimadzu UV-3101PC spectrophotometer. EPR spectra wereobtained in 3 mm pyrex tubes with a Brucker EMX spectrometerusing a conventional Dewar insert at liquid nitrogen temperature.Mass spectra were obtained with a Hewlett Packard HP5988Aspectrometer.

2.3 Crystal structure determination, refinement andsolution

A colourless prismatic crystal of HAm4E, green prismatic crystalof [Ni(HAm4E)2](ClO4)2 and brown prisms of [Ni(HAm4E)2]-(OAc)Cl.H2O.HAcO and [Co(Am4E)2](ClO4) were mounted onglass fibres and used for data collection. Crystal data were collectedat 293(2) K using a Bruker SMART CCD 1000 or Enraf Nonius

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2005, 631, 728�738730

CAD4 and MACH3 diffractometers. The structures were solved bydirect methods using the program SHELXS-97 [23] and refined byfull-matrix least-squares techniques against F2 using SHELXL-97[24]. Positional and anisotropic atomic displacement parameterswere refined for all non-hydrogen atoms. In [Co(Am4E)2](ClO4),the ethyl carbon atoms have a considerable degree of disorder, asshown by their high anisotropic and thermal displacement param-eters. It was not possible to localize these atoms better and theywere refined isotropically. Final refinement included the constraintAFIX for ethyl carbon atoms. The hydrogen atoms of HAm4Ewere located from difference Fourier maps, apart from those of themethyl groups C29 and C49, which were located in their calculatedpositions. The hydrogen atoms of the metal complexes were placedgeometrically. In the final refinement, the positional parameters ofall hydrogen atoms were included as fixed contributions riding onattached atoms with isotropic thermal parameters 1.2 or 1.5 timesthose of their carrier atoms. In [Ni(HAm4E)2](OAc)Cl.H2O.HAcO,the contribution of the density of two disordered water moleculeswas subtracted from the measured structure factors by using theSQUEEZE option [25]. Subsequent refinement then convergedwith R factors and parameter errors significantly better than forall attempts to model the solvent disorder. The criteria for a satis-factory complete analysis for all structures were (i) the ratio of rmsshift to a standard deviation of less than 0.001 and (ii) no signifi-cant features in the final difference maps. Atomic scattering factorswere obtained from “International Tables for Crystallography” [26]and molecular graphics are from PLATON [25]. A summary of thecrystal data, experimental details and refinement results is given inTable 1.

3 Results and Discussion

The reduction of 2-cyanopyridine in the presence of N(4)-ethylthiosemicarbazide produces 2-pyridineformamideN(4)-ethylthiosemicarbazone, HAm4E (1). Reaction of thethiosemicarbazone with salts of cobalt(III), nickel(II), cop-per(II), palladium(II) and platinum(II) in EtOH affordedcomplexes of formulae [Co(Am4E)2](ClO4) (2), [Ni(Am4E)-(OAc)] (3), [Ni(HAm4E)2](ClO4)2 (4), [Ni(HAm4E)2]-(NO3)2 (5), Ni(HAm4E)Cl2] (6), [Cu(Am4E)(AcO)] (7),[{Cu(Am4E)}2(succ)] (8), [{Cu(Am4E)}2(tart)]·H2O (9),[Pd(Am4E)Cl]·2H2O (10) and [Pt(Am4E)Cl]·H2O (11) ingood yields. The compounds were characterized by theiranalytical data and by molar conductivity, magnetic suscep-tibility and spectroscopic techniques. Compounds 1, 2, 4and [Ni(HAm4E)2]Cl(AcO)·HAcO·H2O (6a) were alsocharacterized by single crystal X-ray crystallography. Thebond distances for HAm4E, [Co(Am4E)2]ClO4, [Ni(H-Am4E)2](ClO4)2 and [Ni(HAm4E)2]Cl(OAc)·H2O·OAcHare shown in Table 2 and the corresponding bond angles inTable 3. The hydrogen bonding interactions are given inTable 4 and the mean plane data and angles between planesare given in Table 5.

3.1 Structure of HAm4E (1)

Like HAm4M [8], HAm4E crystallizes in the space groupP21/c with four similar, but crystallographically indepen-dent molecules in the E conformation in terms of the car-

Spectral and Structural Studies of Transition Metal Complexes of 2-Pyridineformamide N(4)-ethylthiosemicarbazone

Table 1 Crystal data and structure refinement for HAm4E (1), [Co(Am4E)2](ClO4) (2), [Ni(HAm4E)2](ClO4)2 (4) and[Ni(HAm4E)2]Cl(OAc)·H2O·OAcH (6a).

Compound 1 2 4 6a

Emp. Formula C9H13N5S C18H24ClCoN10O4S2 C18H26Cl2N10NiO8S2 C22H35ClN10NiO5S2

Formula weight 223.30 602.97 704.22 677.88Temperature/ K 293(2) 293(2) 293(2) 293(2)

Cryst. size/mm 0.40 � 0.25 � 0.25 0.61 � 0.14 � 0.10 0.35 � 0.10 � 0.05 0.35 � 0.19 � 0.16

Crystal System monoclinic monoclinic monoclinic triclinicSpace Group P21/c (No. 14) P21/n (No. 14) P21/c (No. 14) P1 (No. 2)Unit Cell Dim.a / A 10.6754(3) 13.1459(11) 21.151(12) 8.6491(19)b / A 34.9230(19) 12.8044(10) 15.5969(19) 8.9653(19)c / A 12.5725(5) 15.4002(12) 8.7156(4) 21.834(5)α / ° 90 90 90 81.487(4)β / ° 93.776(3) 103.629(2) 90.614(11) 85.777(4)γ / ° 90 90 90 84.546(4)Volume / A3 4677.2(3) 2519.3(3) 2875.0(5) 1663.8(6)Z 16 4 4 2Density / (Mg/m3) 1.268 1.590 1.627 1.353Abs. coeff. / mm�1 2.276 1.000 4.588 0.835Radiation, (λ / A) CuKα, (1.54184) MoKα, (0.71073) CuKα, (1.54184) MoKα, (0.71073)θ range / ° 2.43 to 74.23 1.84 to 26.44 3.52 to 75.92 0.94 to 26.41Index Ranges 0 � h � 13 �26 � h � 26 �26 � h � 26 �10 � h � 10

�43 � k � 0 �19 � k � 0 �19 � k � 0 �11 � k � 11�15 � l � 15 �10 � l � 0 �10 � l � 0 0 � l � 27

Absorption Corr. ψ-scan SADABS ψ-scan SADABSRefl. collected 10042 18380 6409 18942Independent refl. 9525 Rint � 0.0178 5167 Rint � 0.0352 5996 Rint � 0.0311 6791 Rint � 0.0223Max./min. transm. 0.986 / 0.915 0.907 / 0.581 0.973 / 0.745 0.878 / 0.759Data / parameters 9525 / 728 5167 / 289 5996 / 373 6791 / 370

Final R Indices R1 � 0.0444 R1 � 0.0780 R1 � 0.0687 R1 � 0.0577wR2 � 0.1217 wR2 � 0.2330 wR2 � 0.1929 wR2 � 0.1477

R Ind. (all data) R1 � 0.0784 R1 � 0.1561 R1 �0.1485 R1 � 0.0814wR2 � 0.1402 wR2 � 0.2894 wR2 � 0.2351 wR2 � 0.1541

Goodness-of-Fit 1.024 1.052 1.055 1.072

peak/hole / eA�3 0.625 / �0.264 1.082 / �0.956 1.262 / �0.548 0.483 / �0.368

Table 2 Selected bond distances /A for HAm4E, (1); [Co(Am4E)2](ClO4), (2); [Ni(HAm4E)2](ClO4)2, (4); and[Ni(HAm4E)2]Cl(OAc)·H2O·OAcH, (6a).

Bond 1a) 2b) 4b) 6ab

S1�C17 1.705(2) 1.693(3) 1.699(2) 1.689(3) 1.738(6) 1.736(9) 1.677(6) 1.687(6) 1.701(4) 1.687(5)C16�N12 1.292(3) 1.295(3) 1.292(3) 1.287(3) 1.319(9) 1.317(13) 1.289(7) 1.299(8) 1.300(5) 1.294(6)N12�N13 1.387(2) 1.384(3) 1.390(3) 1.387(3) 1.365(8) 1.376(12) 1.382(6) 1.380(7) 1.376(5) 1.390(5)

N13�C17 1.350(3) 1.352(3) 1.353(3) 1.362(6) 1.284(8) 1.276(15) 1.361(7) 1.348(8) 1.361(7) 1.348(8)C17�N14 1.319(3) 1.325(3) 1.316(3) 1.308(4) 1.383(8) 1.584(18) 1.331(7) 1.337(8) 1.329(5) 1.332(6)

N14�C18 1.453(3) 1.459(4) 1.468(4) 1.466(5) 1.526(9) 1.227(12) 1.454(8) 1.452(10) 1.469(5) 1.454(7)C16�N15 1.337(3) 1.340(3) 1.340(3) 1.348(3) 1.339(9) 1.352(10) 1.334(7) 1.324(8) 1.328(5) 1.346(6)M�S1 � � � � 2.225(2) 2.221(3) 2.422(2) 2.449(2) 2.413(1) 2.439(1)M�N11 � � � � 1.972(6) 1.968(6) 2.144(5) 2.110(5) 2.113(4) 2.104(4)M�N12 � � � � 1.865(6) 1.854(7) 2.022(4) 2.011(4) 2.012(3) 1.997(3)

a) Listed in the order S1, S3 , S2, S4 molecules; b) listed in the order S1, S2 ligands

bon-imine nitrogen bond. The thiosemicarbazone moiety isdirected away from the pyridine ring and the structure isrepresented in Figure 1. 2-Acetylpyridine N(4)-ethylthiose-micarbazone, HAc4E [27], crystallized in the P21/n space

Z. Anorg. Allg. Chem. 2005, 631, 728�738 zaac.wiley-vch.de © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 731

group with one unique molecule in the unit cell. This mol-ecule is also the E isomer with the thiosemicarbazone moi-ety directed away from the pyridine ring. The averageS1�C17 bond distance for the four unique molecules of

E. Bermejo, A. Castineiras, I. Garcıa-Santos, L. M. Fostiak, J. K. Swearingen, D. X. West

Table 3 Selected bond angles / ° for HAm4E, (1); [Co(Am4E)2](ClO4), (2); [Ni(HAm4E)2](ClO4)2, (4); and [Ni(HAm4E)2]Cl(OAc)H2O·OAcH, (6a).

Bond 1a) 2b) 4 b) 6ab

N15�C16�N12 127.8(2) 127.5(2) 127.5(2) 127.8(2) 123.4(8) 123.7(12) 125.2(5) 125.5(6) 125.7(4) 126.1(5)C15�C16�N12 115.1 (2) 115.6(2) 115.5(2) 115.8(2) 113.8(7) 113.5(8) 113.8(5) 113.4(5) 114.2(4) 114.0(4)

C16�N12�N13 117.3 (2) 117.3(2) 117.9(2) 118.1(2) 116.9(7) 115.9(9) 118.3(4) 118.1(5) 119.7(3) 118.4(4)

N12�N13�C17 117.5(2) 117.3(2) 117.1(2) 118.0(2) 108.6(6) 108.7(10) 117.6(4) 118.4(5) 118.7(3) 117.8(4)

N13�C17�N14 116.9(2) 115.9(2) 116.4(2) 115.8(3) 117.8(6) 128.0(10) 113.8(5) 114.8(6) 115.3(4) 114.3(4)

N13�C17�S1 119.1(2) 119.9(2) 120.1(2) 120.2(2) 128.0(5) 125.9(9) 123.2(4) 121.9(5) 122.2(3) 122.7(3)N14�C17�S1 123.9(2) 124.1(2) 123.5(2) 124.0(2) 114.1(5) 106.1(8) 122.9(4) 123.3(5) 122.6(3) 123.0(4)C17�N14�C18 126.2(2) 125.3(3) 125.9(3) 126.8(4) 121.9(7) 115.7(2) 125.3(5) 124.6(6) 125.0(4) 123.8(5)S1�M�N11 167.6(2) 167.0(2) 157.5(1) 157.3(1) 159.6(1) 158.2(1)S1�M�N12 85.60(19) 83.9(3) 82.1(1) 80.9(2) 82.1(1) 81.5(1)S1�M�N21 88.36(17) 90.8(2) 93.3(1) 91.8(1) 92.8(1) 87.2(1)S1�M�N22 96.5(2) 96.5(2) 101.6(2) 96.9(2) 99.9(1) 103.8(1)S1�M�S2 92.15(9) 96.18(6) 97.2(1)N11�M�N12 82.1(3) 83.1(3) 76.1(2) 77.1(2) 77.5(1) 77.7(1)N11�M�N21 91.5(2) 87.2(2) 90.1(1)N11�M�N22 95.8(3) 96.6(3) 100.5(2) 104.8(2) 100.4(1) 96.7(1)N21�M�N22 177.9(3) 175.9(2) 174.1(2)M�S1�C17 92.1(2) 94.1(4) 96.1(2) 96.1(2) 96.1(2) 96.2(2)M�N12�C16 117.4(5) 116.9(7) 119.9(4) 119.3(4) 119.4(3) 119.5(3)M�N12�N13 125.5(5) 127.0(8) 120.0(3) 121.5(4) 120.5(3) 121.8(3)

a) Listed in the order S1, S3 , S2, S4 molecules; b) listed in the order S1, S2 ligands

HAm4E is longer than that in HAc4E; cf. 1.697(3) A and1.676(2) A. In terms of the other bonds of the thiosemicar-bazone moiety, only N12�N13 is significantly different,with an average length of 1.387(3) A for HAm4E and1.370(2) A for HAc4E. The differences in the bond anglesof the two thiosemicarbazones are less marked and mostangles are within a one degree range. The average bond dis-tances and angles of HAm4E and HAm4M [8] are essen-tially the same.

In contrast to HAc4E [27], in which the intermolecularH···D distances are no less than 3.00 A and intramolecularhydrogen bonding was not reported, HAm4E (in a similarway to HAm4M [6]) has intramolecular and intermolecularhydrogen bonding (Figure 2). HAm4E has theN14�H14···N12 interaction with an average H···N distanceand N�H···N angle of 2.15(3) A and 109(2)°, respectively.The same interactions are also found for the other crystallo-graphically different molecules and such interactions arecommonly found in N(4)-alkylthiosemicarbazones [28]. Incomparison, the average values for the four different mol-ecules of HAm4M are 2.58(5) A and 113(4)° [8]. The secondintramolecular hydrogen bond in HAm4E involves one ofthe NH2 hydrogen atoms � H15B (and H25B, H35B,H45B) � interacting with the pyridine nitrogen � N11 (andN21, N31, N41). The average H···N bond distance andN�H···N angle is 2.31(3) A and 108(2)°, respectively, andthese compare to averages of 2.69(1) A and 114(5)° forHAm4M.

Intermolecular hydrogen bonding between the secondNH2 hydrogen atom, H15A, and a thione sulphur on an-other molecule, S2, as well as between the thioamide hydro-

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2005, 631, 728�738732

gen atom, H130, and the same sulphur also occurs. TheNH2 hydrogen atom and thioamide hydrogen atom of thesecond molecule interact in the same manner with sulphurS1 in the original molecule and this gives rise to a dimer. Asimilar situation was found for HAm4M [8]. The S3 and S4molecules also form a dimer and the average values for thefour non-bonding distances and angles are 3.378(5) A and170(5)° (e.g., N15�H15A···S2) and 3.450(2) A and 173(5)°(e.g., N13�H13···S2). These averages are similar to thosefound for HAm4M [8]; N15�H15A···S2 has values of3.357(5) A and 171(5)° and N12�H12···S4 has 3.429(4) Aand 167(5)°. The difference between the two dimers ofHAm4E is that the S1-S2 pair has a weak N14�H14···S2interaction, but the analogous interaction is not present inthe S3-S4 pair.

The average mean plane deviation of the thiosemicarba-zone moieties (e.g., C16�N12�N13�C17�N14�S1) ofthe four crystallographically different molecules of HAm4Eis 0.0327 A and the pyridine rings average 0.0070 A, whichis similar to the average planes of HAm4M. The averageangle between the mean planes of the pyridine ring andthiosemicarbazone moiety is 7.2(1)°, indicating thatHAm4E is more planar than HAm4M, which has an angleof 14.1(4)°. The apparently stronger intramolecular interac-tions found for HAm4E compared to HAm4M probablyresult from the greater planarity of HAm4E.

3.2 Structure of [Co(Am4E)2](ClO4) (2)

As in other heterocyclic N(4)-substituted thiosemicarba-zones [8, 28a, 29] (but not semicarbazones [28a]), HAm4E

Spectral and Structural Studies of Transition Metal Complexes of 2-Pyridineformamide N(4)-ethylthiosemicarbazone

Table 4 Hydrogen bonding interactions for HAm4E, (1); [Co(A-m4E)2](ClO4), (2); [Ni(HAm4E)2](ClO4)2, (4); and [Ni(HAm4E)2]-Cl(OAc) H2O·OAcH, (6a).

Compound D�H···A d(D�H) d(H···A) d(D···A) �(DHA)

1a) N14�H140···N12 0.89(3) 2.15(3) 2.595(3) 111(2)N15�H15B···N11 0.81(3) 2.38(3) 2.706(3) 105(2)N24�H240···N22 0.89(3) 2.09(3) 2.574(3) 113(2)N25�H25B···N21 0.83(3) 2.28(3) 2.691(3) 111(3)N34�H340···N32 0.97(3) 2.07(3) 2.567(3) 110(2)N35�H35B···N31 0.85(3) 2.30(3) 2.678(3) 107(2)N44�H440···N42 0.80(4) 2.29(4) 2.574(3) 102(3)N45�H45B···N41 0.92(3) 2.26(3) 2.673(2) 107(2)N13�H130···S21 0.89(3) 2.63(3) 3.474(2) 166(2)N14�H140···S2 0.85(3) 2.90(3) 3.587(2) 136(2)N15�H15A···S21 0.87(3) 2.52(2) 3.371(2) 166(3)N15�H15B···N212 0.81(3) 2.36(3) 3.108(3) 154(3)N23�H230···S13 0.90(3) 2.55(3) 3.445(2) 179(3)N25�H25A···S123 0.80(3) 2.64(3) 3.430(3) 168(2)N25�H25B···N114 0.83(3) 2.37(3) 3.093(3) 146(3)N33�H330···S45 0.91(3) 2.54(3) 3.450(2) 174(2)N35�H35A···S45 0.85(3) 2.53(3) 3.376(3) 176(3)N35�H35B···N416 0.90(3) 2.33(3) 3.087(3) 149(2)N43�H430···S35 0.90(3) 2.53(3) 3.430(3) 174(2)

N45�H45A···S35 0.85(4) 2.50(4) 3.335(3) 170(3)N45�H25B···N316 0.92(3) 2.43(3) 3.246(2) 148(2)

2b) N14�H14···O131 0.86 2.29 3.14(2) 174.8N15�H15B···S22 0.86 2.89 3.669(7) 151.1N25�H25A···O11 0.86 2.47 3.323(14) 172.5N25�H25B···O123 0.86 2.63 3.32(2) 137.8N25�H25B···N144 0.86 2.64 3.302(13) 135.2

4c) N13�H13···O131 0.86 2.47 3.228(11) 147.1N13�H13···O121 0.86 2.49 3.251(10) 147.3N14�H14···O131 0.86 2.23 3.066(8) 163.7N15�H15A···O121 0.86 2.29 3.062(10) 149.9N15�H15B···O122 0.86 2.19 3.002(9) 158.1N23�H23···O243 0.86 2.30 3.134(15) 163.3N24�H24···O233 0.86 2.21 3.049(12) 164.9N25�H25A···O243 0.86 2.09 2.938(13) 171.0

6ad) N13�H13A···Cl11 0.91 2.18 3.079(4) 174.2N14�H14A···Cl12 0.91 2.68 3.317(4) 128.1N14�H14A···Cl11 0.91 2.87 3.658(4) 146.4N15�H15A···O4212 0.96 2.14 3.058(6) 157.9N15�H15B···Cl11 0.88 2.38 3.209(4) 156.9

N23�H23A···O313 0.95 2.47 3.291(8) 145.0N25�H25A···O313 1.11 1.94 2.960(9) 150.7O41�H41···O14 1.14 1.47 2.583(7) 165.5O1�H1A···O42 0.95 2.01 2.892(7) 153.1O1�H1B···Cl15 0.94 2.29 3.195(5) 161.1

Symmetry transformations used to generate equivalent atoms: a) 1: x,�y�1/2, z�1/2; 2: x�1, �y�1/2, z�1/2; 3: x, �y�1/2, z �1/2; 4: x�1,�y�1/2, z�1/2; 5: �x�1, �y, �z�2; 6: �x, �y, �z�2. b) 1: x�1/2,�y�3/2, z�1/2; 2: �x�1, �y�1, �z; 3: �x�2, �y�2, �z; 4: �x�3/2,y�1/2, �z�1/2. c) 1: �x�1, �y�1, �z�1; 2: �x��1, y�1/2, �z�1/2; 3:�x, �y�1, �z�1. d) 1: �x�1, �y, �z�1; 2: x, y�1, z; 3: �x�1, �y�1,�z; 4: �x, �y�1, �z�1, 5: �x�1, �y�1, �z�1

forms a cobalt(III) complex, [Co(Am4E)2](ClO4) (Figure3), when reacted with cobalt(II) perchlorate in the presenceof triethylamine. In a similar way to [Ni(HAm4E)2](ClO4)2,the nearly octahedral symmetry has the two tridentate li-gands in a meridonal arrangement. The trans N11�Co�S1and N21�Co�S2 angles of ca. 167° {compared to ca. 157°for the analogous angles in [Ni(HAm4E)2](ClO4)2} and theN12�Co�N22 angle of close to 180° indicate less distor-tion from octahedral symmetry. The smaller cobalt(III) cen-tre, as well as the conjugated nature of the anionic thiosem-

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Table 5 Rms mean planes for HAm4E, (1); [Co(Am4E)2](ClO4),(2); [Ni(HAm4E)2](ClO4)2, (4); and [Ni(HAm4E)2]Cl(OAc)H2O·OAcH, (6a).

Com- Plane rms dev. largest dev. Angle withpound previous plane

1 C16�N12�N13�C17�N14�S1 0.0561 N12, 0.114(2) �N11�C11�C12�C13�C14�C15 0.0088 C12, 0.012(2) 10.90(16)C26�N22�N23�C27�N24�S2 0.0307 N22, 0.062(2) 60.41(8)N21�C21�C22�C23�C24�C25 0.0070 C21, 0.011(2) 8.91(10)C36�N32�N33�C37�N34�S3 0.0177 N32, 0.034(2) 11.92(10)N31�C31�C32�C33�C34�C35 0.0069 C32, 0.009(3) 3.94(13)C46�N42�N43�C47�N44�S4 0.0262 N42, 0.051(2) 63.77(8)N41�C21�C22�C23�C24�C25 0.0052 C43, 0.007(2) 5.09(19)

2 N11�C11�C12�C13�C14�C15 0.0048 C14, 0.008(5) �C16�N12�N13�C17�N14�S1 0.0416 N12, 0.077(4) 9.83(25)C26�N22�N23�C27�N24�S2 0.0710 N22, 0.142(8) 85.87(10)N21�C21�C22�C23�C24�C25 0.0048 N21, 0.008(4) 13.87(27)

4 N11�C11�C12�C13�C14�C15 0.0025 C12, 0.004(4) �C16�N12�N13�C17�N14�S1 0.0076 N12, 0.015(3) 8.50(13)C26�N22�N23�C27�N24�S2 0.0433 N22, 0.076(3) 85.66(9)N21�C21�C22�C23�C24�C25 0.0074 C23, 0.013(4) 1.32(18)

6a N11�C11�C12�C13�C14�C15 0.0094 C15, 0.015(5) �C16�N12�N13�C17�N14�S1 0.0305 N12, 0.055(5) 6.74(34)

C26�N22�N23�C27�N24�S2 0.0209 N23, 0.040(8) 88.87(19)N21�C21�C22�C23�C24�C25 0.0087 C23, 0.015(7) 6.28(19)

Figure 1 Molecular structure of HAm4E, showing its numberingscheme for the non-hydrogen atoms and the intramolecular hydro-gen bonding.

icarbazonato ligand, causes the thiosemicarbazone ligandto form N11�Co�S1 and N21�Co�S2 bond angles thatare close to linear. Confirmation that the cobalt(III) centreis dictating the stereochemistry comes from the fact that[Co(Fo4M)2]BF4 [Fo4M is the anion of 2-formylpyridineN(4)-methylthiosemicarbazone] has an average angle of169.2(3)° [29b], [Co(Ac4M)2]BF4 [Ac4M is the anion of 2-acetylpyridine N(4)-methylthiosemicarbazone] an averageangle of 167.0(1)° [29b] and [Co(Am4M)2]ClO4 [Am4M isthe anion of 2-pyridineformamide N(4)-methylthiosemicar-bazone] has an average value of 167.5(2)° for this angle [8].

Comparison of the bond angles of 2 with the analogousangles in HAm4E and [Ni(HAm4E)2](ClO4)2, Table 3,shows that coordination of the anion in 2 causes a greaterchange in the angles of the thiosemicarbazone moiety thancoordination of the neutral ligand in [Ni(HAm4E)2](ClO4)2.For example, the averages for the angle represented by

E. Bermejo, A. Castineiras, I. Garcıa-Santos, L. M. Fostiak, J. K. Swearingen, D. X. West

Figure 2 The arrangement of the 4 unique molecules of HAm4E.

Figure 3 Molecular structure of [Co(Am4E)2](ClO4) showingthe hydrogen bond within the asymmetric unit in the perchlorateanion.

N15�C16�N12 are 127.7(2)° in HAm4E, 125.4(6)° in [Ni-(HAm4E)2](ClO4)2, 126.0(4)° in [Ni(HAm4E)2]Cl(OAc)·H2O·OAcH, 123.6(12)° in 2 and the average angles forN13�C17�S1 are 119.8(2)° in HAm4E, 122.5(5)° in [Ni(H-Am4E)2](ClO4)2, 124.2(3)° in [Ni(HAm4E)2]Cl(OAc)

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2005, 631, 728�738734

H2O·OAcH and 126.9(9)° in 2. Note that the angles in thethioamide part of the thiosemicarbazone moiety of 2 aresignificantly different in the two ligands. Compared toHAm4E and the neutral ligands in [Ni(HAm4E)2](ClO4)2,coordination of the anionic Am4E causes large changes inthe following distances; the bonds represented by N13�C17are considerably shorter due to formation of a formal singlebond, S�C bonds are longer due to the formation of for-mal single bonds, and the bonds representative ofC16�N12 are longer after coordination.

Hydrogen bonding in 2 is less extensive than in [Ni(H-Am4E)2](ClO4)2 due to the loss of H13 on formation of theanionic ligand. In contrast to [Ni(HAm4E)2](ClO4)2 thereare interactions with ligands in adjacent cobalt(III) centresin 2, although the two ligands interact differently, Table 4.In addition, in contrast to [Ni(HAm4E)2](ClO4)2, in whichonly two of the perchlorate oxygen atoms are hydrogenbond acceptors, three of the four perchlorate oxygens inter-act with hydrogen atoms from the two ligands.

3.3 Structure of [Ni(HAm4E)2](ClO4)2 (4)

HAm4E forms [Ni(HAm4E)2](ClO4)2 (Figure 4) when it re-acts with nickel(II) perchlorate and this is the expectedcomposition based on HAm4M forming [Ni(H-Am4M)2](ClO4)2 [14]. The approximately octahedral stereo-chemistry has the two tridentate ligands in a meridonal ar-rangement due to the strong tendency toward planarity thatis characteristic of heterocyclic thiosemicarbazones. Thetrans N11�Ni�S1 and N21�Ni�S2 angles of ca. 157°, aswell as the N12�Ni�N22 angle of 175.9(2)°, indicate dis-tortion from octahedral symmetry, Table 3. The magnitudeof the former angle is due to the thiosemicarbazone ligandbeing unable to accommodate a large change in its bondangles. Comparison of the bond angles of HAm4E with theanalogous angles in 4 (Table 3) shows only small differ-ences. Similarly, the bond distances of HAm4E and the li-gands in 4 are not markedly different; S1�C17 is mar-ginally shorter in 4.

All of the hydrogen bonding by the coordinated HAm4Eis to oxygen atoms of the perchlorate ions rather than toligands on neighbouring nickel(II) centres. Only two oxygenatoms from each perchlorate ion are involved, which sug-gests that the ion approaches C2v symmetry in the solidstate. Virtually all of the N�H bonds present in theHAm4E ligands interact with perchlorate oxygen atomsand hydrogen atoms attached to N13 and N15. Further-more, N23 and N25 interact with the same oxygen atom ina similar way to those in [Ni(HAm4M)2](ClO4)2·2H2O [14].The N13H13···O and N14H14···O interactions for the lattercomplex involve a hydrate water molecule rather than a per-chlorate ion, as found for 4.

The angle between the average planes of the thiosemicar-bazone moieties is ca. 86°, indicating that distortion fromoctahedral symmetry for this complex is primarily causedby the inability of the ligands to coordinate the pyridinenitrogen and thione sulphur atom to give N11�Ni1�S1

Spectral and Structural Studies of Transition Metal Complexes of 2-Pyridineformamide N(4)-ethylthiosemicarbazone

Figure 4 Molecular structure of [Ni(HAm4E)2](ClO4)2.

(and N21�Ni1�S2) angles closer to 180°. The average an-gle formed by the mean planes of the pyridine ring andthiosemicarbazone moiety, 11.9(3)°, is larger than thatfound in HAm4E, 7.2(1)°, indicating some loss of planarityon coordination.

3.4 Structure of[Ni(HAm4E)2](OAc)Cl·HOAc·H2O (6a)

The reaction of HAm4E with NiCl2·6H2O gave the com-plex [Ni(HAm4E)Cl2] with five coordinate Ni atom andrecrystallization of this compound from a MeOH/OAcHmixture gave rise to the complex [Ni(HAm4E)2]-Cl(OAc)·H2O·OAcH with six coordinate Ni atom (Figure5). The NiII ion is surrounded by one sulfur and two nitro-gen atoms from each ligand. The azomethinic nitrogenatoms are situated in a trans disposition. Both ligands arein a mer configuration and the acetate group and chloroion act as counterions. Moreover, the complex also has twoneutral HOAc and H2O molecules.

The cationic complex [Ni(HAm4E)2]2� is similar to [Ni-(HAm4E)2](ClO4)2, which was discussed previously, and thedistances and angles are also very similar. The transN11�Ni�S1 and N21�Ni�S2 angles of ca. 167° andN12�Ni�N22 angle of 179.9(3)°, are both larger than in[Ni(HAm4E)2](ClO4)2 (4), indicating distortion from theoctahedral symmetry. One of the C�S distances is slightlylonger, 1.701(4) A, than in 4.

There are numerous hydrogen bonds due to the coun-terions and neutral molecules outside the coordinationsphere. The N(3)H, N(14)H and N(15)H atoms present inthe HAm4E ligand and O(1)H in the hydrate water mol-ecule interact with an oxygen atom of acetic acid; N(23)H

Z. Anorg. Allg. Chem. 2005, 631, 728�738 zaac.wiley-vch.de © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 735

and N(25)H interact with the oxygen atom of the acetategroup and the OH of acetic acid is involved in hydrogenbonding with the oxygen atom of the water molecule.

The angle formed by the mean planes of the pyridine ringand thiosemicarbazone are slightly different; in one ligandthe angle is 8.50(13)s and in the other it is 1.3(2)°, which isnearer to planarity. However, both of these angles aresmaller than in 4 [11.9(3)°]. The angle between the twothiosemicarbazone ligands is 85.66(1)°, which is similar tothat found in 4 and indicates distortion from octahedralsymmetry.

3.5 Physical and spectral properties of[Co(Am4E)2]ClO4 (2)

2 is diamagnetic, which is consistent with the cobalt atombeing oxidized to cobalt(III) during the preparation of thecomplex. In DMSO the 1H-NMR spectrum shows a verybroad NH2 resonance but the following signals can be as-signed � N4H, 7.80, s; C6H � 8.19, d; CH2 � 3.35, t; andCH3 � 1.06, q. The IR bands are assigned as follows:ν(CN), 1578 cm�1; ν(CS), 742 cm�1 and ν(CoN), 445 cm�1.The band assigned to ν(CN) is broad, indicating that it alsoincludes the stretching mode of the N13�C17 bond. Theν(CS) band is shifted to substantially lower energy than thatfor [Ni(HAm4E)2](ClO4)2 (4) and this is consistent with itformally becoming a single bond in (2). The bands at 29490,21330, 16100 and 6730 cm�1 are assigned as having contri-butions from 1A1g � 1T2g, 1A1g � 1T1g, 1A1g � 3T2g and1A1g � 3T1g, respectively, and allow the calculation [30] ofthe following ligand field parameters: Dq � 2400 cm�1,B � 840 cm�1 and β � 0.76. The value of β is lower thanthat for [Ni(HAm4E)2](ClO4)2 (4) and this is consistent witha greater degree of covalent bonding to a �3 metal centrein (2).

3.6 Physical and spectral properties of the nickel(II)complexes

The molar conductivity of [Ni(HAm4E)2](ClO4)2 (4) inDMF is 152 ohm�1cm2mol�1, which is consistent with a1:2 electrolyte [31] and the structural results showing ionicperchlorate ions. The mass spectrum shows fragmentationproducts at m/z � 782, 503 and 280, which probably rep-resent the cations of Ni2(Am4E)3, Ni(Am4E)2 and Ni-(Am4E), and other major ion fragments are at m/z � 307,154, which is consistent with decomposition of the HAm4Eligands. The infrared bands for coordinated HAm4E (withthe values for the free ligand given in brackets) are as fol-lows: ν(CN) � 1566 (1592) cm�1, ν(N�N) � 1044(997) cm�1 and ν(CS) � 856 (871) cm�1. The bands at 465and 373 cm�1 are assigned to ν(NiN, imine) and ν(NiS),respectively. The spectrum of 4 presents a strong band at1108 cm�1, corresponding to ν3(ClO4), and a medium bandat 628 cm�1, which is due to ν4(ClO4). A medium intensityband is observed at 924 cm�1 and is assigned to ν1(ClO4).These data are consistent with distortion toward C2v sym-

E. Bermejo, A. Castineiras, I. Garcıa-Santos, L. M. Fostiak, J. K. Swearingen, D. X. West

Figure 5 Molecular packing for the cation [{Ni(HAm4E)2}Cl·H2O]� of 6a, showing the hydrogen bonds to neighbouring units and theformation of a supramolecular self-assembly.

metry due to the hydrogen bonding interactions discussedabove. Although intraligand and charge transfer bandsoften obscured by the weaker d � d bands, we have as-signed 3A2g � 3T1g(P) to 11260 cm�1 and 3A2g � 3T1g to17950 cm�1, which allows the calculation [32] of 3A1g �3T1g(P), B, β and Dq as 29050 cm�1, 880 cm�1, 0.85 and1126 cm�1, respectively.

[Ni(HAm4E)Cl2] (6) (green), [Ni(Am4E)(OAc)] (3)(brown) and [Ni(HAm4E)2](NO3)2 (5) (green) were also iso-lated but, unfortunately, crystals suitable for structure deter-mination could not be obtained. 6 has a magnetic suscepti-bility of 2.65 B.M. and a molar conductivity in DMF(10�3M) of 40 ohm�1cm2mol�1. These values indicate thatboth chlorine atoms are coordinated and that the complexcontains 5-coordinate nickel atom, although the latter valuecould be considered to be a bit high, maybe due to thedifferent equilibria proposed for this kind of complex[33�35]. Ion fragment peaks in the mass spectrum are ob-served at 316 and 280 due to Ni(HAm4E)Cl� andNi(Am4E)�, respectively. Assignments of the solid-state d� d bands at 7520, 10550, 11820 and 15290 cm�1 to 3B �3E, � 3B2, � 3A2 and � 3E transitions, respectively, isindicative of an approximate square pyramidal geometry.Strong or medium intensity IR bands for ν(CN)(1572 cm�1), ν (NN) (1017 cm�1), ν (CS) (864 cm�1), ν(NiN) (466 cm�1), ν (NiS) (343 cm�1) and ν (NiCl)(294 cm�1) are consistent with NNS coordination ofHAm4E and the two chloro ligands.

[Ni(Am4E)(OAc)] (3) is diamagnetic and a non-electro-lyte, suggesting that it is a complex containing planar coor-dination of the Ni atom with d � d bands at 16860 and20280 cm�1, which can be assigned to 1A1g � 1E1g and �1A2g, respectively. An ion fragment peak in the mass spec-

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2005, 631, 728�738736

trum appears at 280 due to Ni(HAm4E)� and in the IRspectrum bands due to νa(CO2) � 1643 cm�1 andνs(CO2) � 1417 cm�1 indicate monodentate coordinationof the acetate ligand. Other important IR bands are as fol-lows: ν (CN) (1568 cm�1), ν (NN) (1022 cm�1), ν (CS)(871 cm�1), ν (NiN) (465 cm�1), ν (NiS) (349 cm�1) and ν(NiO) (375 cm�1). The 1H-NMR spectrum does not con-tain a signal for N3H, which is clearly due to deprotonationof the ligand. The presence of a new signal at 1.86 ppm isconsistent with coordination of the acetate ligand. The 1H-NMR spectrum was registered immediately after the prep-aration of the complex but it was not possible obtain the13C spectrum, probably due to the evolution to the octa-hedral compound in DMSO. These physical and spectro-scopic properties are similar to those found for the planarcomplex [Ni(Am4M)(OAc)] [8] and we suggest that 3 has avery similar structure.

[Ni(HAm4E)2](NO3)2 (5) is paramagnetic and shows IRbands at 3182 and 3311 cm�1, which can be assigned to NHvibrations. The bands at 1635 and 1568 cm�1 correspondto ν(CN) � ν(CC) and bands due to the ν(NN) and ν(CS)vibrations appear at 1017 and 860 cm�1, respectively. Coor-dination of the ligand is shown by the Ni�N and Ni�Sbands at 467 and 354 cm�1. The spectrum of 5 also has astrong band at 1384 cm�1, which is assigned to ν3(NO3),and a weak band at 834 cm�1, assigned to ν2(NO3). In theelectronic spectra we have assigned 3A2g � 3T1g (P) to11429 cm�1, 3A2g � 3T1g (F) to 17007 cm�1 and this is inagreement with the octahedral geometry. The mass spec-trum shows fragmentation products at m/z � 782, 560, 503and 280, which probably represent the cations of Ni2-(Am4E)3, Ni2(Am4E)2, Ni(HAm4E)(Am4E) and Ni-(Am4E), respectively. These fragments are very similar to

Spectral and Structural Studies of Transition Metal Complexes of 2-Pyridineformamide N(4)-ethylthiosemicarbazone

those found in the octahedral compound [Ni(HAm4E)2]-(ClO4)2 (4). The molar conductivity in DMF is 121.0ohm�1cm2mol�1, which is consistent with a 1:2 electrolyte[31].

3.7 Physical and spectral properties of the copper(II)complexes

Copper(II) complexes prepared from copper(II) acetate,succinate (succ) and tartrate (tart) failed to produce crystalssuitable for structural studies. The resulting complexes arevarious shades of green, have similar IR bands to [Ni-(Am4E)(OAc)] (3) and have a composite d � d band at16460, 17000 and 17390 cm�1 for [Cu(Am4E)(OAc)] (7),[{Cu(Am4E)}2(succ)] (8) and [{Cu(Am4E)}2(tart)]·H2O (9),respectively. The room temperature ESR spectrum of solid7 is rhombic with g3 � 2.196, g2 � 2.064 and g1 � 2.032(average 2.097), 8 has g3 � 2.192, g2 � 2.056 and g1 �2.036 (average 2.094) and [{Cu(Am4E)}2(tart)] ·H2O (9) hasg3 � 2.155, g2 � 2.063 and g1 � 2.035 (average 2.084). Weexpect that 7 will have a “4 � 1” coordination like [Cu-(Am4DM)(OAc)], where Am4DM is the anion of 2-pyri-dineformamide N(4)-dimethylthiosemicarbazone; the se-cond oxygen atom is ca. 2.92 A from the CuII centre andcan be considered to be “semi-coordinated“. The structuresof 8 and 9 are likely to be similar to that of[{Cu(Amhexim)}2(succ)] [19]. In the latter complex the twocopper(II) centres are NNS coordinated with Amhexim,bridged by the succinate ligand coordinating to each cop-per(II) centre in a monodentate manner, and the “4�1”copper(II) centres discussed earlier are also present.

3.8 Physical and spectral properties of [Pd(Am4E)-Cl]·2H2O (10) and [Pt(Am4E)Cl]·H2O (11)

10 (brown) and 11 (red) show ion fragments for dimericspecies in their mass spectra. Both are expected to be com-plexes with planar coordinate metal atoms like [Pd(Amhex-im)Cl] [19]. Important IR bands are as follows: ν(CN)(1572, 1567 cm�1), ν(NN) (1015, 1024 cm�1), ν(CS) (864,868 cm�1), ν(MN) (471, 466 cm�1), ν(MS) (384, 367 cm�1)and ν(MCl) (363, 324 cm�1) for 10 and 11, respectively. The1A1g � 1Eg transition is at 19700 cm�1 for 10 but 1A1g �1A2g is obscured by intraligand and charge transfer tran-sitions; the bands at 18530 and 21530 cm�1 are assigned to1A1g � 1Eg and 1A1g � 1A2g, respectively, in the spectrumof 11. The 1H-NMR signal due to the N3H proton is notobserved due to deprotonation of the ligand. Moreover, thepeak corresponding to the thioamide group (N4H) isshifted upfield with respect to the NH2 amide signal and,in the 13C-NMR spectrum, the signal for C7 of the thiocar-bonyl group is the most deshielded: 170.6 ppm for [Pd(A-m4E)Cl] and 178.74 ppm for [Pt(Am4E)Cl]. The 195Pt-NMR spectrum of [Pt(Am4E)Cl]·H2O contains a singlet ataround �2958 ppm, which is in the expected range for acoordination number of four.

Z. Anorg. Allg. Chem. 2005, 631, 728�738 zaac.wiley-vch.de © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 737

Supplementary material

Crystallographic data for the structures reported in thispaper (excluding structure factors) have been depositedwith the Cambridge Crystallographic Data Centre as Sup-plementary Publication No. CCDC-244026 HAm4E;CCDC-244027, [Co(Am4E)2](ClO4); CCDC-244028, [Ni-(HAm4E)2](ClO4)2; and [Ni(HAm4E)2]Cl(OAc)·H2O·OAcH, CCDC-244029. Copies of the data can be obtainedfree of charge on application to CCDC, 12 Union Road,Cambridge CB2 1EZ, UK (Fax: � 44-1223/336-033. E-mail: deposit@ccdc.cam.ac.uk).

Acknowledgement. Acknowledgement is made to the Donors of thePetroleum Research Fund, administered by the American ChemicalSociety, for partial support of this research.

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