1290 Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... DOI: 10.17344/acsi.2020.6252 Scientific paper Four Different Crystalline Products from One Reaction: Unexpected Diversity of Products of the CuCl2 Reaction with N-(2-Pyridyl)thiourea Sara Tomšič, Janez Košmrlj and Andrej Pevec* Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia * Corresponding author: E-mail: andrej.pevec@fkkt.uni-lj.si Received: 07-10-2020 Abstract The reaction of N-(2-pyridyl)thiourea with CuCl2 in methanol yields four different crystalline products: yellow dimeric complex, [Cu2Cl2(µ-Cl)2(L)2] (1), red polymeric complex, [Cu3Cl8L2]n (2), orange crystalline product with ionic struc- ture, L2[CuCl4] (3), and colourless ionic compound LCl (4), where L = 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation as a result of oxidative cyclization of N-(2-pyridyl)thiourea. The crystal structures of all these crystalline products have been determined by single-crystal X-ray diffraction analysis. Compound 1 involves a copper(I) ion while in 2 and 3 the copper centre is in the divalent state. 1H NMR spectra for compounds 1–3 are identical and confirm deprotonated thioamide groups of N-(2-pyridyl)thiourea and the formation of a thiadiazolopyridinium cation in solution. The hydro- gen bonding and π–π stacking interactions were investigated in the solid state. In addition, all crystalline products 1–4 exhibit also S···Cl bonding interactions which consolidate the complexes into networks. The X-ray diffraction analyses indicate the absence of other crystalline phases in the crude reaction mixture. Keywords: Cu(II) complex; Cu(I) complex; oxidative cyclization; crystal structure, thiourea 1. Introduction Thiourea and its derivatives are readily oxidized in both aqueous and non-aqueous solutions by several oxi- dizing agents including bromine, iodine and copper(II) ions.1 The reaction of thiourea and its derivatives with copper(II) salts in solution results in a reduction of Cu(II) ions into Cu(I) and the formation of many different stabile polynuclear products.2–12 The chemistry of thioureas in copper-ion containing solutions is complex due to a vari- able and frequently uncertain nature of the redox process- es involved. A number of copper(I) and even copper(II) complexes have been obtained with different molecular structures.13 The oxidation and redox kinetics in cop- per(II) – thioureas systems have been investigated.14,15 Nitrogen-heterocyclic thiourea ligands can act as bridging units in some systems through thiourea sulfur and ring nitrogen atoms. Such coordination modes have been encountered especially in platinum group metal complex- es.16–19 The nitrogen-heterocyclic thiourea ligands are also efficient ligands for coordination to a Cu(I) cation produc- ing a variety of monomeric and polymeric structures.20,21 In addition, thioureas are widely recognized for their ability of hydrogen-bond formation and consequently supramolecu- lar network arrangement.22 Pyridine-thiourea derivatives also reveal great potential as ionophores for the detection of copper(II) ions in aqueous phase.23 Interestingly, treating N’-aryl and N’-benzoyl func- tionalized N-(2-pyridyl)thiourea derivatives with cop- per(II) chloride resulted in a variety of coordination com- pounds where a [1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation was coordinated to the copper centre.24–26 It has been established that the N-(2-pyridyl)thiourea could eas- ily be oxidized by copper(II) into the corresponding [1,2,4] thiadiazolo[2,3-a]pyridin-4-ium cation. These types of co- ordination compounds have been examined in vitro for their cytotoxic activity against human cancer cell lines showing promise in anticancer treatment.26 Although reported to undergo oxidative cyclisation into 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cat- ion on treatment with sulphuryl chloride,27,28 or bro- mine,27,29–31 to our knowledge the cyclisation of the parent unsubstituted N-(2-pyridyl)thiourea with CuCl2 has not been studied yet. Herein we report that the reaction of N-(2-pyridyl) thiourea with CuCl2 in methanol solution affords four dif- 1291Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... ferent crystalline products: small yellow crystals, [Cu- 2Cl2(µ-Cl)2(L)2] (1), a red polymeric complex, [Cu3Cl8L2]n (2), a larger orange crystalline product with ionic struc- ture, L2[CuCl4] (3) and a colourless ionic compound LCl (4) (L = 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation). The 2-amino-[1,2,4]thiadiazolo[2,3-a]pyri- din-4-ium cation is the result of oxidative cyclization of N-(2-pyridyl)thiourea with copper(II). The structures of compounds 1–4 were determined by single-crystal X-ray diffraction analysis. The powder X-ray diffraction analysis was performed to analyse multicomponent products in the reaction mixture. 2. Experimental General Procedure. N-(2-Pyridyl)thiourea and oth- er reagents were purchased from commercial sources and were used as received. Proton NMR spectra were recorded at 500 MHz with a Bruker Avance III 500 spectrometer and referenced to Si(CH3)4 as an internal standard. Synthesis. N-(2-pyridyl)thiourea (100 mg; 0.653 mmol) was dissolved in MeOH (10 mL). A few drops of Et3N were added, followed by the addition of solid CuCl2 (88 mg; 0.653 mmol). The resulting suspension was stirred for 40 min at room temperature. The undissolved residue was filtered off and the clear green filtrate was kept at room temperature. After 4–5 days, slow evaporation of methanol from the filtrate afforded crystals of 1–4. The relative yields were 1 > 3 > 2 > 4. Small quantities of each of these com- pounds were separated from the mixture of products man- ually under microscope. X-ray Crystallography. Crystal data and refinement parameters of compounds 1–4 are listed in Table 1. The X-ray intensity data were collected on a Nonius Kappa CCD diffractometer equipped with graphite‒monochro- mated Mo Kα radiation (λ = 0.71073 Å) at room tempera- ture. The data were processed using DENZO.32 The struc- tures were solved by direct methods using SHELXS-2013/133 or SIR-201434 and refined against F2 on all data by a full‒ matrix least‒squares procedure with SHELXL‒2016/4.33 All non‒hydrogen atoms were refined anisotropically. All hydrogen atoms bonded to carbon were included in the model at geometrically calculated positions and refined us- ing a riding model. The nitrogen bonded hydrogen atoms were located in the difference map and refined with the dis- tance restraints (DFIX) with d(N‒H) = 0.86 Å and with Uiso(H) = 1.2Ueq(N). Finally, the three residual peaks in the structure of compound 2 higher than 1 eÅ–3 were observed near to the Cu or Cl atoms, with no chemical meaning. X-Ray powder diffraction data were collected using a PANalytical X’Pert PRO MPD diffractometer with θ–2θ Table 1. Crystal data and structure refinement details for 1–4. 1 2 3 4 formula C12H12Cl4Cu2N6S2 C12H12Cl8Cu3N6S2 C12H12Cl4CuN6S2 C6H6ClN3S Fw (g mol–1) 573.28 778.62 509.74 187.65 crystal size (mm) 0.10 × 0.08 × 0.05 0.10 × 0.05 × 0.03 0.25 × 0.20 × 0.05 0.40 × 0.08 × 0.05 crystal color yellow red orange colorless crystal system monoclinic monoclinic triclinic triclinic space group C 2/c C 2/c P –1 P –1 a (Å) 17.1791(9) 14.8897(4) 8.5710(2) 5.2892(2) b (Å) 7.1000(5) 13.1658(3) 10.4873(4) 7.4109(5) c (Å) 15.5496(8) 12.0204(3) 11.9667(5) 10.2184(6) α (º) 90 90 110.638(2) 81.224(3) β (º) 95.548(4) 94.174(2) 106.838(2) 80.666(3) γ (º) 90 90 93.453(2) 82.732(3) V (Å3) 1887.72(19) 2350.17(10) 947.51(6) 388.48(4) Z 4 4 2 2 calcd density (g cm-3) 2.017 2.201 1.787 1.604 F(000) 1136 1524 510 192 no. of collected reflns 4034 5130 6643 2807 no. of independent reflns 2127 2655 4219 1753 Rint 0.0320 0.0208 0.0222 0.0191 no. of reflns observed 1535 2156 3257 1403 no. of parameters 124 149 238 106 R[I > 2σ (I)]a 0.0440 0.0446 0.0354 0.0314 wR2 (all data)b 0.1025 0.1252 0.0812 0.0832 Goof , Sc 1.095 1.045 1.067 1.053 Largest diff. peak/hole (e Å–3) +0.42/–0.52 +2.36/–0.691 +0.34/–0.35 +0.22/–0.26 a R = ∑||Fo| – |Fc||/∑|Fo|. b wR2 = {∑[w(Fo2 – Fc2)2]/∑[w(Fo2)2]}1/2. c S = {∑[w(Fo2 – Fc2)2]/(n–p)}1/2 where n is the number of reflections and p is the total number of parameters refined. 1292 Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... reflection geometry, primary side Johansson type mono- chromator and Cu Kα1 radiation (λ = 1.54059 Å). The am- bient temperature XRD spectrum of a sample was acquired from 2θ angles of 5° to 80° in steps of 0.034° with integra- tion time of 100 seconds using a 128 rtms channel detec- tor. Simulated powder diffraction pattern were calculated from single crystal structural data by Mercury35 program. 3. Results and Discussion Synthetic Aspects. The reaction between equimolar amounts of N-(2-pyridyl)thiourea and CuCl2 was per- formed in methanol solution in the presence of a small quantity of Et3N. Four different crystalline products were obtained after evaporation of solvent from the clear green solution. Figure 1 shows a photography of the crystalline products: yellow (1), red (2), orange (3) and colourless crystals (4). Samples of each type could be manually col- lected and characterized by 1H NMR spectroscopy and X-ray diffraction analyses. Small quantities of an amor- phous green deposit were also found at the bottom of the vial but we are unable to characterize it. From the crystal structure analyses it was evident that in all cases the N-(2-pyridyl)thiourea starting com- pound underwent oxidative cyclization into a 2-ami- no-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation (L) as shown in Scheme 1. A part of CuCl2, added to the reaction Figure 1. Photography of the bottom of vial containing the prod- ucts of reaction between N-(2-pyridyl)thiourea and CuCl2: yellow (1), red (2), orange (3) and colourless crystals (4). Scheme 1. Oxidative cyclization of N-(2-pyridyl)thiourea with CuCl2 forming 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation (L). Figure 2. Molecular structure of 1 showing the atom-labeling scheme. The ellipsoids are shown at a probability level of 50%. Sym- metry code: (i) –x+1/2, –y+3/2, –z+1. Table 2. Selected bond lengths (Å) and angles (°) of compounds 1–4.a 1 Cu1–Cl1 2.2837(12) Cl1–Cu1–Cl2 116.92(4) Cu1–Cl1i 2.5352(13) Cl1–Cu1–Cl1i 104.50(4) Cu1–Cl2 2.3072(12) Cl1–Cu1–N2 116.26(10) Cu1–N2 2.069(3) Cl2–Cu1–N2 115.66(10) N1–S1 1.731(3) Cu1–Cl1–Cu1i 75.50(4) S1–C6 1.762(4) N1–S1–C6 86.92(18) 2 Cu1–Cl1 2.2799(9) Cl1–Cu1–Cl2 91.16(4) Cu1–Cl2 2.2985(9) Cl1–Cu1–Cl3 173.28(3) Cu1–Cl3 2.2931(9) Cl1–Cu1–Cl4 91.22(4) Cu1–Cl4 2.3076(9) Cl1–Cu1–Cl5 85.11(3) Cu1–Cl5 2.946(1) Cl1–Cu1–N2 95.52(8) Cu1–N2 2.546(3) Cl1–Cu2–Cl1ii 180.00(4) Cu2–Cl1 3.005(1) Cl1–Cu2–Cl4ii 105.35(3) Cu2–Cl4 2.3290(9) Cu1–Cl1–Cu2 74.47(3) Cu2–Cl5 2.2672(9) Cu1–Cl4–Cu2 88.97(3) N1–S1 1.710(3) Cu1–Cl5–Cu2 75.87(3) S1–C6 1.756(4) N1–S1–C6 88.21(17) 3 Cu1–Cl1 2.2932(8) Cl1–Cu1–Cl2 99.32(3) Cu1–Cl2 2.2184(8) Cl1–Cu1–Cl3 122.87(3) Cu1–Cl3 2.2567(7) Cl1–Cu1–Cl4 99.55(3) Cu1–Cl4 2.2300(8) Cl2–Cu1–Cl3 98.65(3) N1–S1 1.720(2) Cl2–Cu1–Cl4 139.35(3) S1–C6 1.761(3) N1–S1–C6 86.95(12) 4 N1–S1 1.7293(15) N1–S1–C6 86.38(8) S1–C6 1.7632(17) N3–C6–S1 121.23(14) a Symmetry transformations used to generate equivalent atoms: (i) –x+1/2, –y+3/2, –z+1; (ii) –x+1/2, –y+1/2, –z. 1293Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... mixture was reduced into copper(I) during oxidative cy- clization and got involved into the coordination. Triethyl- Table 3. Hydrogen bonding geometry for 1, 2, 3 and 4. D – H ··· A d(D – H)/ Å d(H ··· A)/ Å d(D ··· A)/ Å <(DHA)/ º Symmetry transformation for acceptors 1 N3–H2N∙∙∙Cl1 0.86(2) 2.78(5) 3.258(4) 116(4) x, –y+1, z+1/2 N3–H1N∙∙∙Cl2 0.86(2) 2.57(3) 3.391(4) 159(5) N3–H2N∙∙∙Cl2 0.86(2) 2.40(3) 3.160(4) 148(5) –x+1/2, y–1/2, –z+3/2 2 N3–H1N∙∙∙Cl1 0.848(19) 2.64(3) 3.398(4) 150(5) N3–H2N∙∙∙Cl1 0.85(2) 2.63(4) 3.273(4) 134(5) x, –y, z+1/2 N3–H2N∙∙∙Cl5 0.85(2) 2.82(4) 3.533(4) 142(5) x, –y, z+1/2 3 N3–H1N∙∙∙N5 0.855(18) 2.265(18) 3.119(3) 176(3) N3–H2N∙∙∙Cl4 0.861(18) 2.48(2) 3.250(2) 149(3) N6–H3N∙∙∙Cl3 0.849(18) 2.416(19) 3.254(3) 169(3) N6–H4N∙∙∙Cl1 0.853(18) 2.47(2) 3.234(3) 149(3) –x+1, –y+1, –z+2 4 N3–H1N∙∙∙Cl1 0.865(16) 2.27(2) 3.0319(18) 147(2) N3–H2N∙∙∙N2 0.860(16) 2.286(18) 3.123(2) 164(2) –x+2, –y+1, –z+2 Figure 3. Layer formation in 1 through N–H···Cl hydrogen bonds and S···Cl contacts. The hydrogen atoms on aromatic rings have been removed for clarity. The ellipsoids are shown at a probability level of 50%. Symmetry codes: (i) x, –y+1, z+1/2; (ii) –x+1/2, y–1/2, –z+3/2. amine assisted deprotonation of the thiamine group and neutralized the reaction mixture. 1294 Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... 5). One type of copper atoms is coordinated by six chlorine atoms whereas the other is surrounded by five chlorine at- oms and one L ligand. The Cu–N distance to the ligand L is 2.546 Å and is significantly longer than in the case of com- plex 1. The Cu–Cl distances are in the range from normal 2.267 Å to very long Cu···Cl interaction of 3.005 Å. The structures with such elongated octahedra and very long Cu···Cl interaction can be found in the literature.36 The elongated Cu···Cl and Cu···N interactions likely result from Jahn-Teller distortion. Two different Cu···Cu separations of 3.25 Å and 3.36 Å are longer than in compound 1 where copper is in +1 oxidation state. All the chlorido bridged copper atoms form a zig-zag chain, with the angles between the neighboring Cu atoms of 139° and 180°. The whole structure is stabilized by the N–H···Cl hydrogen bonding interactions, π–π stacking (3.878 Å) and by S···Cl interac- tions of 3.112 Å constructing a 3D network (Fig. 6, Table 3). X-ray analysis of compound 3. The asymmetric unit of 3 consists of one [CuCl4]2– anion and two L cations (Fig. S3). The packing of the structural units is depicted in Fig. 7. The coordination environment of the copper atom is tetrahedral with Cu–Cl distances ranging from 2.218 Å to 2.293 Å (Table 2), which is typical for tetrahedral [CuCl4]2– ions. The cationic ligand L does not coordinate to the Cu atom in the structure of compound 3. Four cat- ions and two anions are connected by N–H···Cl and N–H···N hydrogen bonds (Table 3) and also by S···Cl inter- Figure 4. Fragment of the crystal packing of 1 with π–π stacking between pyridine rings. The ellipsoids are shown at a probability level of 50%. X-ray analysis of complex 1. The molecular struc- ture of 1 shows the dinuclear complex to be a bis-chlori- do-bridged copper(I) compound (Fig. 2 and Fig. S1). Se- lected bond lengths and angles are summarized in Table 2. The coordination polyhedron of each copper atom in the structure of complex 1 is a distorted tetrahedron. Each copper atom is coordinated by ligand L, one terminal and two bridging chlorine atoms. One bridging Cu–Cl bond- ing distance (2.284 Å) is shorter whereas the other (2.535 Å) is longer as compared to the terminal Cu–Cl bonding distance (2.307 Å). The Cu–N bond distance of 2.069 Å is slightly longer than the corresponding Cu(II)–N bond dis- tance in similar compounds (from 1.988 to 1.996 Å).26 The Cu···Cu separation of 2.957 Å suggest a narrow Cu–Cl–Cu angle in 1. Discrete dinuclear units are connected into a 2D network parallel to the bc plane by N–H···Cl hydrogen bonds (Fig. 3, Table 3) and by S···Cl interactions of 2.945 Å. The 2D layers are then π–π stacked with a centroid-to-cen- troid separation distance between two pyridine rings of 3.731 Å into 3D array (Fig. 4). X-ray analysis of complex 2. The structure of 2 fea- tures a linear homonuclear Cu(II) chloride polymer in which the Cu3Cl8L2 is the repeating unit (Fig. 5 and Fig. S2). Selected bond lengths and angles are given in Table 2. All chlorine atoms in these infinite chains are in the bridg- ing positions. The coordination geometry around all cop- per atoms can be described as a distorted octahedron (Fig. 1295Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... actions into a discrete unit in the crystal structure. The S···Cl interaction distances are of two types, 3.029 and 3.113 Å, respectively. These units are then connected by π–π stacking interactions between the fused thiadiazole rings into chains along the c-axis with an interring dis- tance of 3.673 Å (Fig. 8). X-ray analysis of compound 4. The colorless crys- tals are an ionic phase without copper incorporated into the structure (Table 2 and Fig. S4). The reaction of forma- tion of this ionic compound 4 is depicted in Scheme 1. Two cationic ligands L are connected by N–H···N hydro- gen bonds into dimeric species (Fig. 9). The chloride anion is acceptor of a N–H···Cl hydrogen bond from the amino group of the ligand L (Table 3). These dimeric species are also stabilized by S···Cl interaction of 2.868 Å. In addition, the chloride anion is involved in other weak C–H···Cl hy- drogen bonding interactions to form the 2D network in the crystal structure. NMR spectra. The 1H NMR spectra of compounds 1, 2 and 3 recorded in DMSO-d6 solutions (Figures S5–S7) are nearly identical indicating ligand L dissociation from the copper center in the solution. In comparison to the Figure 5. Molecular structure of 2 showing the atom-labeling scheme (above) and distorted octahedra representation (below). The ellipsoids are shown at a probability level of 50%. 1296 Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... Figure 6. Fragment of the crystal packing in 2 with N–H···Cl hydrogen bonds, π–π stacking and S···Cl contacts. The hydrogen atoms on aromatic rings have been removed for clarity. The ellipsoids are shown at a probability level of 50%. Symmetry code: (i) x, –y, z+1/2. Figure 7. Fragment of crystal packing and the atom-labeling scheme of 3 with N–H···Cl and N–H···N hydrogen bonds and S···Cl interactions. The ellipsoids are shown at a probability level of 50%. Symmetry code: (i) –x+1, –y+1, –z+2. 1297Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... Figure 8. Fragment of crystal packing of 3 with π–π stacking between thiadiazole rings. The ellipsoids are shown at a probability level of 50%. Figure 9. Fragment of crystal packing and the atom-labeling scheme of 3 with N–H···Cl and N–H···N hydrogen bonds and S···Cl interactions. The ellipsoids are shown at a probability level of 50%. Symmetry code: (i) –x+2, –y+1, –z+2. starting N-(2-pyridyl)thiourea (Figure S8), the spectra of compounds 1–3 lack broad N–H resonance at δ 8.90 ppm (Fig. 10). The presence of 2-amino-[1,2,4]thiadi- azolo[2,3-a]pyridin-4-ium cation is confirmed by a signif- icant downfield shift of the electron-deficient fused pyri- dine protons resonating at δ 9.05 (d), 8.06 (dd), 7.70 (d) 7.33 (dd) ppm as compared to the N-(2-pyridyl)thiourea (δ 8.24 (d), 7.77 (dd), 7.16 (d), 7.05 (dd) ppm) and upfield shift for amino NH2 hydrogen atoms (from 10.59 (s), 10.53 (s) ppm to 9.70 (s), 9.48 (s) ppm). The 1H NMR chemical shifs of ligand L are in agreement with those for the substi- tuted [1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cations re- ported in the literature.25,26 Powder diffraction X-ray analysis. The product of the reaction was characterized by X-ray powder diffrac- tion. There is clear evidence that the sample is a mixture of compounds 1–4 (Fig. 11). No other crystalline phases were additionally present since all diffraction peaks in the powder pattern of the sample can be contributed to com- pounds 1–4. 4. Conclusion In summary, four different crystalline complexes have been found as products of the reaction between Figure 10. Selected parts of 1H NMR spectra of compound 2 (above) and N-(2-pyridyl)thiourea (below). 1298 Acta Chim. Slov. 2020, 67, 1290–1300 Tomšič et al.: Four Different Crystalline Products ... N-(2-pyridyl)thiourea and CuCl2. Oxidative cyclization of N-(2-pyridyl)thiourea occurred with copper(II) chloride as an oxidant affording thiadiazolopyridinium cation as planar ligand. The complexes consist of a dimeric dinucle- ar unit (1), polymeric chains (2) and ionic (3) compounds. Copper(I) ions, which are a product of reduction of Cu(II) to Cu(I) and concomitant oxidation of N-(2-pyridyl) thiourea, are incorporated in complex 1. Complexes 2 and 3 contain copper(II) while the ionic compound 4 contains a cationic ligand L with chlorine counter ion. The crystal structure determinations have established the existence of N–H···Cl hydrogen bonding interactions in all crystal structures. The remarkable feature of the 1–4 compounds is that there are S···Cl interactions involved in the crystal packing. Intermolecular or interionic S···Cl contacts with distances from 2.87 to 3.11 Å are significantly shorter than the corresponding van der Waals radii sum of 3.65 Å.37 The short S···Cl contacts are now widely interpreted as chalcogen bonds.38–41 The X-ray diffraction analysis com- pared the experimental powder diffraction pattern of the product of the reaction with the simulated diffraction pat- terns for all compounds 1–4 obtained from the single-crys- tal structure analysis. Supplementary Material The Supporting Information is available: ORTEP view of compounds 1–4, 1H NMR spectra of compunds 1–3 and N-(2-pyridyl)thiourea. CCDC 1812471–1812474 contain the supplementa- ry crystallographic data for this paper. This data can be obtained free of charge via www.ccdc.cam.ac.uk/data_re- quest/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Cen- tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. Acknowledgements This work was supported by the Slovenian Research Agency (Grants: P1-0175 and P1-0230). Authors also thank to Dr. Marta Počkaj for her extremely helpful com- ments on powder diffraction analysis. 5. References 1. E. W. Ainscough, A. M. Brodie, Coord. Chem. Rev. 1978, 27, 59–86. DOI:10.1016/S0010-8545(00)80353-7 2. R. G. Vranka, E. L. Amma, J. Am. Chem. Soc. 1966, 88, 4270– 4271. DOI:10.1021/ja00970a036 3. A. G. Gash, E. H. Griffith, W. A. Spofford, III, E. L. Amma, J. Chem. Soc., Chem. Commun. 1973, 256–257. DOI:10.1039/c39730000256 4. I. F. Taylor, Jr., M. S. Weininger, E. L. Amma, Inorg. Chem. 1974, 13, 2835–2842. DOI:10.1021/ic50142a014 5. E. H. Griffith, G. W. Hunt, E. L. Amma, J. Chem. Soc., Chem. 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Povzetek Pri reakciji med N-(2-piridil)tiosečnino in CuCl2 v metanolu smo dobili štiri različne kristalinične produkte: rumene di- merne kristale, [Cu2Cl2(µ-Cl)2(L)2] (1), rdeč polimerni kompleks, [Cu3Cl8L2]n (2), oranžni kristalinični product z ionsko zgradbo, L2[CuCl4] (3), in brezbarvno ionsko spojino, LCl (4). Pri tem je L = 2-amino-[1,2,4]tiadiazolo[2,3-a]piridin- 4-ijev kation, ki je nastal v raztopini kot produkt oksidativne ciklizacije N-(2-piridil)tiosečnine. Kristalne strukture vseh kristaliničnih produktov so bile določene s pomočjo rentgenske strukturne analize. V spojini 1 je baker(I) ion, medtem ko je v spojinah 2 in 3 baker kolt centralni ion v oksidacijskem stanju +2. 1H NMR spektri spojin 1–3 so identični in po- trjujejo deprotonacijo tioamidne skupine N-(2-piridil)tiosečnine ter tvorbo tiadiazolopiridinijevega kationa v raztopini. V kristalnih strukturah so bile proučene tudi vodikove vezi in π–π interakcije. Poleg teh interakcij pa spojine 1–4 vse- bujejo tudi S···Cl interakcije, ki povezujejo komplekse v trodimenzionalne tvorbe. Primerjava izračunanih rentgenskih praškovnih difraktogramov s difraktogramom produkta po reakciji nakazuje na odsotnost drugih kristaliničnih primesi. Except when otherwise noted, articles in this journal are published under the terms and conditions of the  Creative Commons Attribution 4.0 International License