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The reactions of PbPh(2)Cl(2) in methanol with acetophenone, salicylaldehyde, pyridine-2-carbaldehyde, 2-acetylpyridine, and 2-benzoylpyridine thiosemicarbazones (HATSC, HSTSC, HPyTSC, HAcPyTSC, and HBPyTSC, respectively) were explored. Despite the similarities among these ligands, the reactions afforded solids with very diverse compositions and structural characteristics, which were in most cases analyzed by X-ray diffractometry (as was the structure of the free ligand HBPyTSC). In the complexes [PbPh(2)Cl(2)(HATSC)](2), [PbPh(2)Cl(2)(HSTSC)(2)], [(PbPh(2)Cl(HPyTSC)(2))][PbPh(2)Cl(3)(MeOH)](2), and [PbPh(2)Cl(PyTSC)] the metal atoms are surrounded by more or less distorted octahedral coordination polyhedra; if both strong and weak interactions are considered, the lead atom in [PbPh(2)Cl(AcPyTSC)] has coordination number 7 and distorted pentagonal bipyramidal coordination geometry, while [(PbPh(2)(BPyTSC))(2)(PbPh(2)Cl(4))].2MeOH contains two different types of lead atom, one with octahedral and the other with pentagonal bipyramidal coordination. The complexes (H(2)AcPyTSC)[PbPh(2)Cl(3)] and [PbPh(2)Cl(HAcPyTSC)][PbPh(2)Cl(3)], which were also isolated, could not be crystallized. All these complexes are soluble in DMSO, and the compositions of these solutions were investigated using conductivity measurements and (1)H and (207)Pb NMR spectroscopy.

The molecular structure of [Cu(sulfadimet)(2)].SO(CH(3))(2) (sulfadimet=sulfadimethoxine=4-p-aminobenzenesulfonamido-2,6-dimethoxypyrimidine) was determined by single crystal X-ray diffractometry. It crystallizes in the monoclinic space group P2(1)/c with Z=4. The Cu(II) cation is in a distorted CuN(5) square pyramidal coordination, involving four sulfadimethoxine molecules, one of them acting as a bidentate ligand. The infrared spectrum is briefly discussed on the basis of the structural peculiarities of the complex.

The interaction of lower rim calix(4)arene derivatives containing ester (1) and ketone (2) functional groups and bivalent (alkaline-earth, transition- and heavy-metal) cations has been investigated in various solvents (methanol, N,N-dimethylformamide, acetonitrile, and benzonitrile). Thus, 1H NMR studies in CD3OD, C3D7NO, and CD3CN show that the interaction of these ligands with bivalent cations (Mg2+, Ca2+, Sr2+, Ba2+, Hg2+, Pb2+, Cd2+) is only observed in CD3CN. These findings are corroborated by conductance measurements in these solvents including benzonitrile, where changes upon the addition of the appropriate ligand (1 or 2) to the metal-ion salt only occur in acetonitrile. Thus, in this solvent, plots of molar conductance against the ligand/metal cation ratio reveal the formation of 1:1 complexes between these ligands and bivalent cations. Four metal-ion complex salts resulting from the interaction of 1 and 2 with cadmium and lead, respectively, were isolated and characterized by X-ray crystallography. All four structures show an acetonitrile molecule sitting in the hydrophobic cavity of the ligand. The mode of interaction of the neutral guest in the cadmium(II) complexes differs from each other and from that found in the lead(II) complexes and provides evidence of the versatile behavior of acetonitrile in binding processes involving calix(4)arene derivatives. The thermodynamics of complexation of these ligands and bivalent cations in acetonitrile is reported. Thus, the selective behavior of 1 and 2 for bivalent cations is for the first time demonstrated. The role of acetonitrile in the complexation process in solution is discussed on the basis of 1H NMR and X-ray crystallographic studies. It is suggested that the complexation of 1 and 2 with bivalent cations is likely to involve the ligand-solvent adducts rather than the free ligand. Plots of complexation Gibbs energies against the corresponding data for cation hydration show a selectivity peak which is explained in terms of the predominant role played by cation desolvation and ligand binding energy in complex formation involving metal cations and macrocycles in solution. A similar peak is found in terms of enthalpy suggesting that for most cations (except Mg2+) the selectivity is enthalpically controlled. The ligand effect on the complexation process is quantitatively assessed. Final conclusions are given highlighting the role of the solvent in complexation processes involving calix(4)arene derivatives and metal cations.

The molecular structure of diosgenone, a natural steroidal sapogenin, closely related to diosgenin and isolated from Solanum nudum, was solved by single crystal X-ray diffractometry at 120 K and refined by full-matrix least-squares to an agreement factor, R1 = 0.054. It crystallizes in the monoclinic space group P2(1), with a = 15.1870(4) A, b = 7.2710(2) A, c = 21.2840(6) A, beta = 99.251(1) degrees, and four molecules in the unit cell (Z = 4). The results constitute the first structural report on a steroidal sapogenin from the diosgenin group.

The title compound, tetrakis(mu-3,4,5-triethoxybenzoato-kappa(2)O:O')bis[(pyrazine-kappa N)rhodium(II)](Rh[bond]Rh), [Rh(2)(C(13)H(17)O(5))(4)(C(4)H(4)N(2))(2)], crystallizes on an inversion centre in the triclinic space group P1. The equatorial carboxylate ligands bridge the two Rh(II) atoms, giving a binuclear lantern-like structure. The pyrazine molecules occupy the two axial coordination sites. The phenyl rings are tilted by ca 10 degrees with respect to the attached carboxylate groups. The pyrazine planes have a torsion angle of ca 19 degrees around the Rh-N bond with respect to the plane of the nearer carboxylate group and are not coplanar with the Rh[bond]Rh bond.

The crystal structures of two salts of bis(thiourea)gold(I) complexes, namely bis(thiourea-kappaS)gold(I) chloride, [Au(CH(4)N(2)S)(2)]Cl, (I), and bis[bis(thiourea-kappaS)gold(I)] sulfate, [Au(CH(4)N(2)S)(2)](2)SO(4), (II), have been determined. The chloride salt, (I), is isomorphous with the corresponding bromide salt, although there are differences in the bonding. The Au(I) ion is located on an inversion centre and coordinated by two symmetry-related thiourea ligands through the lone pairs on their S atoms [Au-S 2.278 (2) A and Au-S-C 105.3 (2) degrees ]. The sulfate salt, (II), crystallizes with four independent [Au(CH(4)N(2)S)(2)]+ cations per asymmetric unit, all with nearly linear S-Au-S bonding. The cations in (II) have similar conformations to that found for (I). The Au-S distances range from 2.276 (3) to 2.287 (3) A and the Au-S-C angles from 173.5 (1) to 177.7 (1) degrees. These data are relevant in interpreting different electrochemical processes where gold-thiourea species are formed.

The octahedral title compound, [Ru(C(2)H(5)O)(NO)(NO(2))(2)(C(6)H(16)N(2))], crystallizes in the rhombohedral space group P3(1) with an ethoxy ligand axially coordinated trans to the nitrosyl ligand. The RuII ion is equatorially coordinated by a tetramethylethylenediamine group acting as a bidentate ligand, and to two nitro moieties whose planes are tilted with respect to the mean equatorial plane. Each nitrogen ligand bonded to the metallic centre has a different hybridization state.

The reactions of Zn(OAc)(2) with acetoacetanilide, methyl acetoacetate, o-acetoacetanisidide, and ethyl 2-methylacetoacetate thiosemicarbazones (HTSC(1), HTSC(2), HTSC(3), and HTSC(4), respectively) were explored in methanol. With HTSC(1), HTSC(2), and HTSC(3), following isolation of the corresponding zinc(II) thiosemicarbazonates [Zn(TSC(x))(2)] (x = 1, 2, 3), the mother liquors afforded pyrazolonate complexes [ZnL(1)(2)(H(2)O)] (HL(1) = 2,5-dihydro-3-methyl-5-oxo-1H-pyrazole-1-carbothioamide) that had been formed by cyclization of the corresponding TSC(-). The reaction of HTSC(4) with zinc(II) acetate gave only the pyrazolonate complex [ZnL(2)(2)(H(2)O)] (HL(2) = 2,5-dihydro-3,4-dimethyl-5-oxo-1H-pyrazole-1-carbothioamide). All compounds were studied by IR and NMR spectroscopy, and HTSC(3), [Zn(TSC(3))(2)] x DMSO, [ZnL(1)(2)(H(2)O)] x 2DMSO, and [ZnL(2)(2)(H(2)O)] x 2DMSO were also studied by X-ray diffractometry, giving a thorough picture of the cyclization process. In preliminary tests of the effects of HL(1) and [ZnL(1)(2)(H(2)O)] on rat paw inflammatory edema induced by carrageenan, HL(1) showed antiinflammatory activity.

The title compound, catena-poly[[tetrakis(mu-decanoato-kappa(2)O:O')diruthenium(II,III)(Ru-Ru)]-mu-octanesulfonato-kappa(2)O:O'], [Ru(2)(C(10)H(19)O(2))(4)(C(8)H(17)O(3)S)], is an octanesulfonate derivative of the mixed-valence complex diruthenium tetradecanoate. The equatorial carboxylate ligands are bidentate, bridging two Ru atoms to form a dinuclear structure. Each of the two independent dinuclear metal complexes in the asymmetric unit is located at an inversion centre. The octanesulfonate anion bridges the two dinuclear units through axial coordination. The alkyl chains of the carboxylate and sulfonate ligands are arranged in a parallel manner. The global structure can be seen as infinite chains of polar moieties separated by a double layer of non-polar alkyl groups, without interdigitation of the alkyl chains.

We report the synthesis and the structural and magnetic characterization of two new compounds: dibromobis(pdmp)copper(II), CuBr(2)C(22)H(24)N(4) (1), and dichlorobis(pdmp)copper(II), CuCl(2)C(22)H(24)N(4) (2), where pdmp = 1-phenyl-3,5-dimethylpyrazole. The structures were refined by full-matrix least-squares techniques to R1 = 0.0620 and 0.0777, respectively. Compound 1 belongs to the space group P2(1)/n with a = 8.165(5) Å, b = 10.432(3) Å, c = 13.385(4) Å, beta = 100.12(4) degrees, and Z = 2. Compound 2 belongs to the space group P2(1)/c with a = 8.379(2) Å, b = 22.630(2) Å, c = 12.256(2) Å, beta = 98.43(3) degrees, and Z = 4. It has the same molecular formula as a compound reported previously but a different crystal structure. Detailed single-crystal EPR measurements were performed for single-crystal samples of 1 and 2 at 9 and 35 GHz and at room temperature. The positions and line widths of the EPR lines were measured as a function of the magnetic field orientation in three orthogonal planes. The data were used to study the electronic properties of the copper ions and to evaluate the exchange interactions between them. Our results are discussed in terms of the electronic pathways for superexchange between copper ions, which are provided by the stacking of pyrazole and phenyl rings of neighboring molecules and by hydrogen-halogen bonds.

A new route was developed for preparing a series of trans nitrosyl complexes of general formula trans-[Ru(NH(3))(4)L(NO)](BF(4))(3), where L = imidazole, L-histidine, pyridine, or nicotinamide. The complexes have been characterized by elemental analysis, molar conductance measurements, UV-visible, infrared, proton nuclear magnetic, and electron paramagnetic resonance spectroscopies, and electrochemical techniques. The compounds possess relatively high nu(NO) stretching frequencies indicating that a high degree of positive charge resides on the coordinated nitrosyl group. The nitrosyl complexes react with OH(-) according to the equation trans-[Ru(NH(3))(4)L(NO)](3+) + 2OH(-) right arrow over left arrow trans-[Ru(NH(3))(4)L(NO(2))](+) + H(2)O, with a K(eq) (at 25.0 degrees C in 1.0 mol/L NaCl) of 2.2 x 10(5), 5.9 x 10(7), 9.7 x 10(10), and 4.6 x 10(13) L(2) mol(-)(2) for the py, nic, imN, and L-hist complexes, respectively. Only one redox process attributed to the reaction [Ru(II)(NH(3))(4)L(NO(+))](3+) + e(-) right arrow over left arrow trans-[Ru(II)(NH(3))(4)L(NO(0))](2+) was observed in the range -0.45 to 1.20 V for all the nitrosyl complexes. Linear correlations are observed in plots of nu(NO) versus E(1/2) and of E(1/2) versus summation operatorE(L) showing that the oxidizing strength of the coordinated NO increases with increase in L pi-acidity. The crystal structure analysis of trans-[Ru(NH(3))(4)nicNO](2)(SiF(6))(3) shows that the mean Ru-N-O angle is very close to 180 degrees (177 +/- 1 degrees ) and the mean N-O distance is 1.17 +/- 0.02 Å, thus confirming the presence of the Ru(II)-NO(+) moiety in the nitrosyl complexes studied.