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The reduction of 2-cyanopyridine in the presence of N(4)-ethylthiosemicarbazide produces 2-pyridineformamide N(4)-ethylthiosemicarbazone, HAm4E. Complexes with cobalt(III), nickel(II), copper(II), palladium(II) and platinum(II) have been prepared and characterized by molar conductivity, magnetic susceptibility and spectroscopic techniques. In addition, the crystal structures of HAm4E, [Co(Am4E)2](ClO4), [Ni(HAm4E)2](ClO4)2, and [Ni(HAm4E)2]Cl(OAc)·AcOH·H2O have been obtained. Coordination occurs through the pyridyl nitrogen, imine nitrogen and either the thione or thiolato sulphur atom when coordinating as the neutral or anionic ligand, respectively. Extensive hydrogen bonding occurs in both HAm4E and its metal complexes, with the amide hydrogen atoms being significant contributors.

Reduction of 2-cyanopyridine in the presence of N(4)-ethylthiosemicarbazide produces 2-pyridineformamide N(4)-ethylthiosemicarbazone, HAm4E. Complexes with various zinc(II) and cadmium(II) salts have been prepared and characterized using physical and spectral methods. In addition, the crystal and molecular structure of [Zn(Am4E)(OAc)]2 (1), [Zn(HAm4E)I2] (4a), [Cd(Am4E)2] (5a), [Cd(HAm4E)Br2] · DMSO (7a) and [Cd(HAm4E)I2] · DMSO (8a) have been obtained. Coordination is via the pyridyl nitrogen, imine nitrogen and thione or thiolato sulfur when coordinating as the neutral and anionic ligand, respectively. [Zn(Am4E)(OAc)]2 is the first example of a binuclear complex with a 2-pyridineformamide thiosemicarbazonato ligand in which the two acetate bridging groups are equivalent resulting in a center of symmetry.

Sodium in dry methanol reduces 2-cyanopyridine in the presence of N(4)-dimethylthiosemicarbazide to produce 2-pyridineformamide N(4)-dimethylthiosemicarbazone, HAm4DM. Complexes with iron(III), cobalt(III), nickel(II), copper(II), palladium(II) and platinum(II) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of [Ni(Am4DM)(OAc)], [Ni(Am4DM)(CH3CN)]ClO4, [Cu(Am4DM)(OAc)] and [Pt(Am4DM)(DMSO)]Cl·2H2O are included. Coordination of the anionic thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thiolato sulfur atoms. The acetato groups in [Ni(Am4DM)(OAc)] and [Cu(Am4DM)(OAc)] are coordinated as monodentate ligands by one oxygen and the other oxygen interacts intermolecularly with the amide NH2 function of Am4DM. Coordination of the DMSO molecule in [Pt(Am4DM)(DMSO)]Cl·2H2O is through sulfur to give an essentially planar cation.

Reaction of 4-formylantipyrine with N(4)-dimethylthiosemicarbazide and 3-piperidylthiosemicarbazide produces the N(4)-dimethylthiosemicarbazone (1), and the 3-piperidyl-thiosemicarbazone (2), respectively. Compound 1 is triclinic, space group P-1 with a = 6.329(1) A, b = 11.699(1) A, c = 11.943(1) A, α = 65.83(1)°, β = 80.83(1)°, γ = 84.90(1)°, and V = 796.1(1) A3 with Z = 2, for Dcalc = 1.324 g/cm3. Compound 2 is triclinic, space group P-1 with a = 6.784(1) A, b = 10.485(2) A, c = 13.462(3) A, α = 102.05(2)°, β = 98.61(2)°, γ = 101.32(2)°, and V = 899.8(5) A3 with Z = 2, for Dcalc = 1.319 g/cm3. Reaction of 4-aminoantipyrine with phenyl isothiocyanate produced N-antipyrine-N′-phenylthiourea (3). Compound 3 is monoclinic, space group P21/n with a = 6.863(7) A, b = 15.361(3) A, c = 16.332(5) A, β = 90.35(6)°, and V = 1720.7(18) A3 with Z = 4, for Dcalc = 1.306 g/cm3. Compounds 1 and 2 have intermolecular hydrogen bonding between the carbonyl oxygen of the antipyrine moiety and the NH hydrogen of the thiosemicarbazone moiety. In 3 the two unique molecules are held together as a dimer by interactions of the two thiourea NH's and the antipyrine moiety's\break oxygen.

Mono- and di-functional aromatic amines bearing p -alkoxy substituents have been shown to react with the hexamolybdate ion, [Mo6O19] 2 , in dry pyridine or acetonitrile (N2, heat), to form arylimido adducts. The products of these reactions have been characterized by 1 H NMR, IR, and mass spectral studies and, in the case of the p -anisidine adduct, X-ray crystallography. The p

Reduction of cyanopyrazine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces pyrazineformamide N(4)-methylthiosemicarbazone, HPzAm4M. Electrochemical synthesis in acetonitrile produced [Zn(PzAm4M)2]/2CH3CN and/[Cd(PzAm4M)2]/0.5CH3CN. The crystal structures of HPzAm4M and the two complexes have been obtained. Coordination of anionic PzAm4M in the two complexes is via the pyridyl nitrogen, imine nitrogen and thiolato sulfur and the ligands are in a meridional arrangement with the imine nitrogens trans. Hydrogen-bonding interactions are an important property of HPzAm4M and its complexes. Both pyrazine nitrogens are involved in hydrogen-bonding in HPzAm4M, and the non-coordinated pyrazine nitrogen is involved in both complexes. HPzAm4M and the coordinated PzAm4M ligands are quite planar. # 2002 Elsevier Science Ltd. All rights reserved.

N -2-(4-picolyl)- N ′-2-chlorophenylthiourea, 4PicTu2Cl, monoclinic, P 2 1 / c , a =10.068(5), b =11.715(2), c=11.185(6) A , β =96.88(4)°, V=1309.8(2) A 3 and Z =4; N -2-(6-picolyl)- N ′-2-chlorophenylthiourea, 6PicTu2Cl, triclinic, P -1, a =7.4250(8), b =7.5690(16), c=12.664(3) A , α =105.706(17), β =103.181(13), γ =90.063(13)°, V=665.6(2) A 3 and Z =2 and N -2-(6-picolyl)- N ′-2-bromophenylthiourea, 6PicTu2Br, triclinic, P -1, a =7.512(4), b =7.535(6), c=12.575(4) A , a =103.14(3), β =105.67(3), γ =90.28(4)°, V=665.7(2) A 3 and Z =2. The intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen, as well as the planarity of the molecules, are affected by the position of the methyl substituent on the pyridine ring. The enthalpies of fusion and melting points of these thioureas are also affected. 1 H NMR studies in CDCl 3 show the NH′ hydrogen resonance considerably downfield from other resonances in their spectra.

A synthetic strategy for constructing ionic hydrogen-bonded materials by combining perhalometallate anions with cations able to serve as hydrogen bond donors is presented. The approach is based on identification of well defined hydrogen bond acceptor sites on the anions by a combination of experimental and theoretical approaches. Selective population of these sites by hydrogen bond donors has the potential to afford organized crystalline arrays in one, two, or three dimensions. The approach is applicable to a wide range of metal centers.

Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of 3-piperidylthiosemicarbazide produces 2pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with nickel(II) have been prepared and characterized by magnetic susceptibility and spectroscopic techniques. The crystal structures of [Ni(Ampip)2], [Ni(Ampip)OAc], and [Ni(HAmpip)Cl]Cl have been solved. Coordination of the anionic and neutral ligand is via the pyridyl nitrogen, imine nitrogen, and thiolato � / thione sulfur. [Ni(Ampip)2] is an approximately octahedral NiN4S2 center with the tridentate ligands in a meridonal arrangement. [Ni(Ampip)OAc] is essentially planar except for the acetato ligand, which is � /808 out of the coordination plane, and the ionic [Ni(HAmpip)Cl]Cl involves the neutral thiosemicarbazone ligand. # 2002 Published by Elsevier Science Ltd.

The following molecules were found to have intramolecular hydrogen bonding between the N′H and the pyridine nitrogen and intermolecular hydrogen bonding between the NH and a thione sulfur of a second molecule to form dimers: N-(2-pyridyl)-N′-(4-methoxyphenyl)thiourea, PyTu4OMe, triclinic, P-1, a=7.158(4), b=8.742(3), c=10.833(4) A , α=70.53(3), β=74.38(3), γ=73.97(4)°, V=635.5(5) A 3 and Z=2; N-(2-pyridyl)-N′-(4-nitrophenyl)thiourea, PyTu4NO2, monoclinic, P21/c, a=11.670(1), b=5.9225(9), c=18.792(4) A , β=107.99(1)°, V=1244.8(7) A 3 and Z=4; N-(2-pyridyl)-N′-(4-chlorophenyl)thiourea, PyTu4Cl, triclinic, P-1, a=9.939(3), b=11.399(4), c=12.264(5) A , α=65.50(4), β=87.46(3), γ=76.63(3)°, V=1228.1(7) A 3 and Z=4 and N-(2-pyridyl)-N′-(4-bromophenyl)thiourea, PyTu4Br, triclinic, P-1, a=10.020(2), b=11.444(2), c=12.353(5) A , α=64.76(2), β=87.61(3), γ=77.88(2)°, V=1250.8(7) A 3 and Z=4. The methoxy and nitro moieties of PyTu4OMe and PyTu4NO2 also interact with N′H, and there is a weak intermolecular interaction between one of the pyridine hydrogen atoms and the thione sulfur in PyTu4Br. Solution 1H NMR spectral studies (DMSO-d6) show the N′H resonance considerably downfield for each thiourea and its chemical shift, as well as that of NH, is affected by substituents on the phenyl ring.

N-2-(4,6-lutidyl)-N′-2-chlorophenylthiourea, 4,6LutTu2ClPh, triclinic, P-1, a=7.512(1), b=7.695(2), c=12.870(3) A, α=82.50(2), β=77.07(2), γ=83.50(2)°, V=716.2(3) A3 and Z=2; N-2-(4,6-lutidyl)-N′-3-chlorophenylthiourea, 4,6LutTu3ClPh, monoclinic, C2/c, a=25.162(3), b=7.220(4), c=16.272(2) A, β=94.71(1)°, V=2946.0(2) A3 and Z=8 and N-2-(4,6-lutidyl)-N′-4-chlorophenylthiourea, 4,6LutTu4ClPh, monoclinic, C2/c, a=33.1254(15), b=4.3025(1), c=20.3298(9) A, β=107.070(10)°, V=2769.80(19) A3 and Z=8. The strength and nature of the intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen are affected by the position of the chloro substituent on the phenyl ring. N′H is bifurcated in 4,6LutTu2Cl interacting with the chlorine (and the pyridine nitrogen), and the aromatic hydrogens interact weakly with sulfur and chlorine in neighboring molecules in these thioureas. The enthalpies of fusion and melting points are in the order 4,6-LutTu4Cl≫4,6LutTu2Cl>4,6LutTu3Cl. 1H NMR studies in CDCl3 show the N′H hydrogen resonance considerably downfield from other resonances in the spectrum for each thiourea.

Reactions of 2-aminopicolines with 2- and 4-tolyl isothiocyanates yielded N-2-(4-picolyl)-N′-4-tolylthiourea, 1, N-2-(3-picolyl)-N′-4-tolylthiourea, 2, and N-2-(4-picolyl)-N′-2-tolylthiourea, 3. Compound 1 is monoclinic, of space group P21/c with a = 7.456(1) A, b = 13.135(3) A, c = 13.959(3) A, β = 104.99(3)°, and V = 1320.5(5) A3 with Z = 4, for d calc = 1.294 g/cm3. Compound 2 is triclinic, of space group $$P\bar 1$$ with a = 6.877(3) A, b = 7.590(5) A, c = 13.213(9) A, α = 78.38(2)°, β = 77.96(4)°, γ = 86.36(4)°, and V = 660.5(7) A3 with Z = 2, for d calc = 1.294 g/cm3. Compound 3 is monoclinic, of space group P21/c with a = 12.604(2) A, b = 15.592(3) A, c = 6.875(2) A, β = 91.05(2)°, and V = 1350.9(2) A3 with Z = 4, for d calc = 1.265 g/cm3. The three thioureas are found in both solid state and solution in a conformation resulting from intramolecular $${\text{N}}{\kern 1pt} ---{\kern 1pt} {\text{H}} \cdot \cdot \cdot {\text{N}}$$ hydrogen bonding. Compounds 1 and 3 present an intermolecular hydrogen bond involving the thione sulfur and the NH hydrogen, which is not present in 2 owing to the steric hindrance of the methyl group in the phenyl ring. The geometry of the molecule is affected by the position of the methyl groups on the pyridine and aryl rings.

Reaction of 2-amino-6-picoline with 2-, 3-, and 4-tolyl isothiocyanates produces the three N-2-(6-picolyl)-N′-tolylthioureas, 6PicTu2T, 6PicTu3T, and 6PicTu4T. 6PicTu2T is mono-clinic, space group P21/n with a = 8.1700(3) A, b = 25.5840(6) A, c = 12.6840(5) A, β = 98.8750(16)°, and V = 2619.5(2) A3 with Z = 8, for d calc = 1.305 g/cm3. 6PicTu3T is monoclinic, space group C2/c with a = 23.879(3) A, b = 6.744(3) A, c = 17.116(10) A, β = 99.26(4)°, and V = 2720(3) A3 with Z = 8, for d calc = 1.257 g/cm3. 6PicTu4T is triclinic, space group P-1 with a = 8.829(6) A, b = 8.8950(15) A, c = 10.495(3) A, α = 68.63(3)°, β = 72.19(4)°, γ = 63.06(4)°, and V = 681.2(5) A3 with Z = 2, for d calc = 1.255 g/cm3. Intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen and the planarity of the thiourea are affected by the position of substitution on the aryl ring. 1H NMR studies in CDCl3 show the NH′ hydrogen resonance considerably downfield from other signals in the spectrum of each thiourea. The enthalpies of fusion of the present thioureas reflect the extent of intermolecular hydrogen bonding and are compared to other heterocyclic thioureas.

Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)2]ClO4, [Cu(HAmpip)Cl2]·CH3OH and [Zn(HAmpip)Br2]·C2H6SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.

Sodium in dry methanol reduces 2-cyanopyridine in the presence of N(4)-dimethylthiosemicarbazide to produce 2-pyridyl-formamide N(4)-dimethylthiosemicarbazone, HAm4DM. Com­plexes with zinc(II) and cadmium(II) of formulae [M(Am4DM)(OAc)]2 and [M(HAm4DM)X2] (M = Zn or Cd, X = Cl, Br or I) have been prepared and characterized by spectro­scopic techniques. In addition, the crystal structures of HAm4DM, [Zn(HAm4DM)Br2], and [Cd(HAm4DM)l2] DMSO have been solved. HAm4DM is in the zwitterionic form with a hydrogen bonding interaction between the iminium hydrogen and the thiolato sulfur atom. Co­ ordination of the neutral thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thione sulfur atoms, while the anionic ligand in [M(Am4DM)(OAc)]2 coordinates with the same two nitrogen atoms and a thiolato sulfur atom. The [M(HAm4DM)X2] complexes are 5-coordinate with the tridentate thiosemicarbazone and two halogen ligands approaching a square pyramidal stereochemistry.

The crystal structures of two 5-coordinate copper(II) complexes containing neutral, tridentate 2-formylpyridine N(4)-substituted thiosemicarbazones have been determined. 2-Formylpyridine N(4)-cyclohexylthiosemicarbazone, HFo4CHex coordinates via the pyridine nitrogen, imine nitrogen and thione sulfur with two chloro ligands to produce [Cu(HFo4CHex)Cl 2 ]. Similarly, 2-formylpyridine 3-(4-methylpiperazine)thiosemicarbazone, HFoppz4M, produces [Cu(HFoppz4M)Cl 2 ] with one major difference; rather than the expected thione form of the thiosemicarbazone moiety, it coordinates as the thiol isomer. Both complexes are close to a square pyramid structure with axial and equatorial chloro ligands and the thiosemicarbazone moieties of both ligands nearly planar. Also included is the crystal structure of N-cyclohexylthiosemicarbazide, CHextsc.

Cobalt(II), nickel(II) and copper(II) complexes of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone have been prepared and characterized by physical and spectral methods. Use of different ligand-to-metal chloride molar ratios in the preparation of the complexes has produced both mononuclear and polynuclear species for the three metal ions. Crystal structures of the uncomplexed di-2-pyridyl ketone N(4)-methylthiosemicarbazone and a nickel(II) complex, di-2-pyridyl ketone N(4)-dimethylthiosemicarbazone, have been determined and aid the assignments of the i.r., n.m.r., u.v.–vis.–n.i.r. and e.s.r. spectra.

N -(2-pyridylethyl)- N ′-phenylthiourea, triclinic, P-1, a=8.616(1) A , b=9.663(1) A , c=9.761(1) A , α =102.05(1)°, β =102.36(1)°, and γ =116.17(1)°, V=668.5(1) A 3 , Z =2, μ=2.022 mm −1 , N -(2-pyridylethyl)- N ′- p -tolylthiourea, triclinic, P-1, a=8.804(3) A , b=9.951(2) A , c=10.255(2) A , α =115.03(2)°, β =105.93(2)°, γ =104.04(2)°, V=713.43(1) A 3 , Z =2, μ=2.173 mm −1 , N -(2-pyridyl-ethyl)- N ′- p -bromophenylthiourea, triclinic, P-1, a=9.536(1) A , b=9.809(1) A , c=10.042(2) A , α =115.88(1)°, β =96.80(1)°, and γ =110.44(1)°, V=750.0(6) A 3 , Z =2, μ=28.73 mm −1 , N -(2-pyridyl-ethyl)- N ′- p -nitrophenylthiourea, triclinic, P-1, a=8.046(2) A , b=8.602(3) A , c=10.938(3) A , α =80.74(3)°, β =89.77(2)°, γ =77.00(3)°, V=727.6(6) A 3 , Z =2, μ=2.325 mm −1 and N -(2-pyridylethyl)- N ′- p -methoxyphenylthiourea, monoclinic, P2 1 /n, a=11.526(2) A , b=9.723(2) A , c=13.460(2) A , β =100.49(2)°, V=1483.3(2) A 3 , Z =4, μ=1.929 mm −1 . All five molecules possess an intramolecular hydrogen bond between NH and the pyridyl nitrogen, as well as intermolecular hydrogen bonding between N′H and a thione sulfur of a second molecule to form centrosymmetric dimers. Solution 1 H NMR studies (CDCl 3 ) show the N′H resonance downfield for each thiourea and its shift, as well as that of NH, is affected by substituents on the phenyl ring.

The multidentate ligand, 2,6-diacetylpyridine bis(3-hexamethyleneiminylthiosemicarbazone) monohydrate, H22,6Achexim·H2O, crystallizes with one thiosemicarbazone moiety in an intramolecular hydrogen bonded, bifurcated E′ form. The other thiosemicarbazone moiety is E and is not involved in intramolecular hydrogen bonding, but is involved in hydrogen bonding with the hydrate water molecule. The dianion (loss of N3a and N3b hydrogens) of H22,6Achexim acts as a pentadentate ligand, 2,6Achexim, in a planar conformation to a central tin(IV) ion, and as a bridging tetradentate ligand with the two thiosemicarbazone moieties of 2,6Achexim coordinating to different zinc atoms. The tin(IV) is heptacoordinate in a distorted pentagonal dipyramidal configuration, with the five SNNNS donor atoms of 2,6Achexim in the pentagonal plane and the two n-butyl groups in the axial positions. The binuclear zinc complex has two equivalent tetrahedral zinc centers, with the pyridyl nitrogens of the two ligands not coordinated.

N -2-(4,6-lutidyl)- N ′- o -tolylthiourea, 4,6LuTuoT, triclinic, P-1 , a =7.470(2), b =9.799(5), c=10.269(3) A , α =90.514(4), β =98.89(3), γ =90.14(3)°, V=742.5(9) A 3 , Z =2, μ=2.09 mm −1 ; N -2-(4,6-lutidyl)- N ′- m -tolylthiourea, 4,6LuTumT, monoclinic, P2 1 /a , a =7.2393(2), b =16.636(3), c=12.557(1) A , β =101.968(9)°, V=1479.4(6) A 3 , Z =4, μ=2.10 mm −1 and N -2-(4,6-lutidyl)- N ′- p -tolylthiourea, 4,6LuTupT, triclinic, P-1 , a =7.883(2), b =7.9024(8), c=23.273(4) A , α =86.49(1), β =86.48(2), γ =88.45(2)°, V=1443.9(7) A 3 , Z =4, μ=2.15 mm −1 . These molecules have an intramolecular hydrogen bond between N′H and the pyridyl nitrogen, as well as intermolecular hydrogen bonding between NH and a thione sulfur of a second molecule to form centrosymmetric dimers. Solution 1 H NMR studies (CDCl 3 ) show the N′H resonance considerably downfield for each thiourea and its position, as well as that of NH, are affected by substituents on the phenyl ring.

The synthesis and spectral characterization of a new triangular, trinuclear palladium(II) complex with the dianion of 2-hydroxy-4-methoxyacetophenone N4-dimethylthiosemicarbazone, 4MeOAp4Me is reported. The X-ray crystal structure determination of [Pd(4MeOAp4Me2)]3·DMSO shows it to contain a chair-type hexagon of alternating Pd and S atoms which form a molecular bowl. The crystal structure of H24MeOAp4Me2 shows that it is the E isomer with respect to the imine bond of the thiosemicarbazone moiety.

Cobalt(II), nickel(II) and copper(II) complexes of two new bis(di-2-pyridyl ketone) dithiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. The bis(di-2-pyridyl ketone) dithiosemicarbazones were prepared from dithiosemicarbazides derived from piperazine and N,N′-dimethylethylenediamine. N.m.r., i.r., and electronic spectra of the dithiosemicarbazones and their complexes along with e.s.r. spectra of the copper(II) complexes have been recorded. The complexes are bi-, tri- and tetranuclear and involve the dithiosemicarbazones coordinating as dianionic, anionic and neutral ligands.

Reduction of 2-cyanopyridine by sodium in dry MeOH in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. Copper(II) complexes have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. Coordination is via the pyridyl nitrogen, imine nitrogen and thione or thiolato sulfur, when coordinating as the neutral or anionic ligand, respectively.

Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. Complexes with iron(III), cobalt(II,III) and nickel(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAm4M, [Ni(Am4M)(OAc)], [Fe(Am4M)2]ClO4 and [Co(Am4M)2]ClO4 have been solved. Coordination is via the pyridyl nitrogen, imine nitrogen and thione or thiolato sulfur when coordinating as the neutral and anionic ligand, respectively.

Pyruvaldehyde mixed bis(thiosemicarbazones) have been prepared in which the two thiosemicarbazone moieties have different N(4)-substituents. The mixed bis(thiosemicarbazones) and their copper(II) and nickel(II) complexes have been characterized with IR, electronic, mass, 1H NMR (Ni) and EPR (Cu) spectra. Representative crystal structures have been solved of nickel(II) complexes with either a pyruvaldehyde mixed bis(thiosemicarbazone) or a bis(thiosemicarbazone) with identical N(4)-substituents acting as a tetradentate ligand. [Ni(Pu4M4DE)] has an N(4)-methylthiosemicarbazone substituent on the keto “arm” and N(4)-diethylthiosemicarbazone substituent on the aldehyde arm. [Ni(Pu4M)] contains two N(4)-methylthiosemicarbazone moieties. Both bis(thiosemicarbazones) form square-planar N2S2 complexes with nickel(II) and copper(II).

N-(2-pyridyl)-N′- o -tolylthiourea, monoclinic, P2 1 /c, a =5.127(1), b =19.854(2), c=12.077(2) A , β =94.96(1)°, V=1224.7(2) A 3 , Z =4, μ=2.177 mm −1 , N-(2-pyridyl)-N′-m-tolylthiourea, triclinic, P−1, a =9.811(2), b =9.887(4), c=13.595(3) A , α =74.91(3), β =83.58(2), γ =76.27(2)°, V=1235.(7) A , Z =4, m=2.469 mm −1 and N-(2-pyridyl)-N′-p-tolylthiourea, triclinic,P−1, a =9.935(2), b =11.488(2), c=12.569(2) A , α =63.91(2), β =88.60(2), γ =75.04(2)°, V=1238.1(2) A 3 , Z =4, μ=2.154 mm −1 all have an intramolecular hydrogen bond between N′H and the pyridyl nitrogen, as well as intermolecular hydrogen bonding between NH and a thione sulfur of a second molecule to form centrosymmetric dimers. Solution 1 H NMR studies (CDCI 3 ) show the N′H resonance considerably downfield for each thiourea and its position, as well as that of NH, are affected by substituents on the phenyl ring.

Nickel (II) , copper (II) and palladium (II) complexes of 1-phenylglyoxal bis {N (3) -diethylthiosemicarbazone} , H2Pg4DE, have been prepared, studied spectroscopically and their crystal structures solved. H2Pg4DE and the three complexes have been characterized by IR, electronic, 1H NMR (Ni, Pd) and ESR (Cu) spectra. Upon formation of these complexes, loss of the N (2) H hydrogens from both thiosemicarbazone moieties occurs, and the ligands coordinate to the metal centers as dianionic, tetradentate N2S2 ligands. The nickel (II) and copper (II) complexes, [M (Pg4DE) ] , coordinate in the expected 5-5-5-chelate ring system, but [Pd (Pg4DE) ] coordinates with 5-6-4-membered chelate rings. The thiosemicarbazone moiety attached to the phenyl keto carbon in [Pd (Pg4DE) ] forms the 4-membered chelate ring coordinating via N (2) rather than the azomethine nitrogen, N (1) .

The crystal and molecular structure of N-2-pyridylethyl- N’-3- tolylthiourea, 1, was determined. 1 crystallizes as triclinic, P-1, a = 9.024(2) Å, b = 9.718(3) Å, c = 9.765(4) Å, #945; = 102.26(3)°, #946; = 114.18(3)°, #947; = 103.12(2)°, V = 714.4(4) Å3, Z = 2. Both thiourea NH groups form intermolecular hydrogen bonds, N’H with the thione sulfur atom and the NH with the pyridine nitrogen. When compared with other N-2-pyridylethyl-N’-arylthioureas it is observed that the centro-symmetric N’H #8901; #8901; #8901;S hydrogen bond is always present and the NH #8901; #8901; #8901;N always H-bonds to the pyridine N atom but in some cases as an intra-molecular H-bond and in the other as an intermolecular Hbond. This difference may be due to variables introduced by the flexibility of the molecules, whose effects on the crystal packing can not be predicted.

The hydrogen acceptor capability of the sulfur atom in the biologically relevant N-2-pyridylmethyl-N′-arilthioureas was explored. N-2-Pyridylmethyl thioreas were selected to avoid the formation of intramolecular six-membered hydrogen-bonded ring. The compounds studied were N-2-pyridylmethyl-N′-phenylthiourea (1), N-2-pyridylmethyl-N′-2-methoxythiourea (2), N-2-pyridylmethyl-N′-4-methoxyphenylthiourea (3), and N-2-pyridylmethyl-N′-4-bromophenylthiourea (4). 1 crystallizes in the monoclinic space group P21/c, with a = 7.419(1) A, b = 18.437(2) A, c = 9.656(1) A, β = 106.277(6)°, V = 1267.8(3) A3, Z = 4. 2 crystallizes in the monoclinic space group P21/c, with a = 8.064(2) A, b = 18.382(7) A, c = 9.865(5) A, β = 97.81(3)°, V = 1448.8(11) A3, Z = 4. 3 crystallizes in the monoclinic space group P21/c, with a = 11.472(1) A, b = 13.520(1) A, c = 10.088(1) A, β = 112.60(1)°, V = 1444.5(2) A3, Z = 4. 4 crystallizes in the triclinic space group P-1, with a = 4.583(3) A, b = 10.263(3) A, c = 14.396(3) A, α = 77.92(2)°, β = 88.55(4)°, γ = 80.02(4)°, V = 652.1(5) A3, Z = 2. Both thiourea N–H groups form intermolecular hydrogen bonds, one with the thione sulfur atom and the other with the pyridine nitrogen atom but the H-bonding schemes are not the same maybe due to the flexibility of the molecules.