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In this paper, we report the synthesis and the characterization of a novel series of lanthanide (III) complexes with two potentially hexadentate ligands. The ligands contain a rigid phenanthroline moiety and two flexible hydrazonic arms with different donor atom sets (NNN 0 N 0 OO and NNN 0 N 0 N 00 N 00 , respectively for H2L 1 (2,9-diformylphenanthroline)bis(benzoyl)hydrazone and H2L 2 (2,9-diformylphenanthroline)bis(2-pyridyl)hydrazone). Both nitrate and acetate complexes of H2L 1 with La, Eu, Gd, and Tb were prepared and fully characterized, and the X-ray crystal structure of the complex [Eu(HL 1 )(CH3 COO)2] AE 5H2O is presented. The stability constants of the equilibria Ln 3+ +H 2L 1 = [Ln(H2L 1 )] 3+ and Ln 3+ +( L 1 ) 2� = [Ln(L1)] + (Ln = La(III), Eu(III), Gd(III), and Tb(III)) are determined by UV spectrophotometric titrations in DMSO at t =2 5� C. The nitrate complexes of H2L 2 with La, Eu, Gd and Tb were also synthesized, and the X-ray crystal structures of [La(H2L 2 )(NO3)2(H2O)](NO3), [Eu(H2L 2 )(NO3)2](NO3) and [Tb(H2 L 2 )(NO3)2](NO3) are discussed.

The new potentially hexadentate ligand (2,9-diformylphenanthroline) bis(benzoyl)hydrazone (H 2 L) is synthesised and spectroscopically characterised. It reacts with dibutyltin diacetate and diphenyllead dichloride giving the complexes [(C 4 H 9 ) 2 SnL] and [(C 6 H 5 ) 2 PbL], respectively; their X-ray structure and spectroscopic characterization are reported.

Palladium(II) and nickel(II) complexes with tetradentate ligands derived from pyrrole 2-carboxaldehyde and various diamines have been synthesized and characterized. The complexes are neutral and the coordination around the metal is square-planar; they are able to activate the molecular hydrogen and to catalyse the homogenous hydrogenation of phenylacetylene. The X-ray structures of N,N′-cycloexylenebis(pyrrol-2-ylmethyleneamine) (H2L4), PdL4 and PdL3 (H2L3, N,N′-propylenebis(pyrrol-2-ylmethyleneamine)) are discussed.

The synthesis of complexes of the type trans -[RhL 4 X 2 ] + {L = N -alkylimidazoles ( N -RIm) [R = methyl (Me), ethyl (Et), n-propyl (Pr 0 , n-butyl (Bu n )], 4(6)-hydroxypyrimidine (4(6)-hydPm); X = Cl − or Br − ) is achieved by the general catalytic method involving the use of ethanol. The formation of complexes with L = N -Melm was reexamined and a new procedure has been established. The distribution of the trans -[RhL 4 X 2 ] + and [RhL 5 X] 2+ ions as reaction products strongly depends on the nature of the solvent and the structure of the ligand. We proposed that the initial product trans -[RhL 4 X(sol)] 2+ produced by catalytic action of ethanol, undergoes nucleophilic substitution reactions either by halogenide anions X or by ligand molecules L, thus giving rise to the formation of trans -[RhL 4 X 2 ] + or [RhL 3 X] 2+ complexes. The direction of the nucleophilic substitution is determined by the concentration of ethanol, the L ligand and the X halogen. IR, Raman, electronic absorption and 1 H NMR spectra were used to characterize the complexes. The prepared complexes show significant antifungal activity. The crystallographic structure of rans -[Rh( N -Melm) 4 Cl 2 ]Cl·2H 2 O has been determined. The octahedron is slightly distorted since it has, in a square plane, four nitrogen ligands and two Cl atoms at the two apical sites. The octahedral bond angles are very close to the ideal values and are in the range of 88.1(1)–89.6(1)°. The Rh atom is located on the two-fold rotation axis which relates two pairs of N -methylimidazole molecules and Cl atoms.

A new hydrazonic ligand, 2,6-diacetylpyridine bis(octanoylhydrazone) (H 2 dapo), has been prepared and examined as chelating agent towards iron(II), cobalt(H), nickel(II) and palladium(II) ions. All the compounds have been characterized by IR and 1 H and 13 C NMR spectroscopies. The X-ray diffraction analysis carried out on [Ni(H 2 dapo)(OH 2 ) 2 ]Cl 2 showed a pentagonal bipyramidal stereochemistry which can be also assumed for the Fe and Co chloro complexes, while for Ni(dapo) and Pd(dapo) the spectroscopic investigation suggests a square planar coordination and a different configuration ( E and Z ) for the two hydrazonic chains.

Two paramagnetic octahedral nickel(II) complexes containing the tetradentate 1,3-propanediamine-N,N′-diacetate (1,3-pdda) or ethylenediamine-N,N′-propionate (eddp) anions and water in the remaining two coordination positions were prepared and characterized. In both cases, only one (uns-cis) of the three geometrical isomers, was found to dominate. The 1,3-pdda and eddp ligands prefer the uns_cis configuration, indicating that six-membered chelate rings have a profound effect on the distribution of geometrical isomers. The infrared and electronic absorption spectra of these complexes are discussed in comparison with those of an edda-Ni(II) complex (eedda=ethylenediamine-N,N′-diacetate ion) of known s-cis configuration. The electronic absorption spectra have been treated in terms of Oh symmetry but the splitting of the 3T2g(Oh) bands of the complexes indicates that the tetragonal field is enhanced. The splitting patterns are assigned with the D4h model: 3B1g→3B2gand 3B1g→3Eg. The magnetic measurements are also reported for the complexes studied. The uns-cis-[Ni(1,3-pdda)(H2O)2] complex crystallizes in the space group P212121 of the orthorhombic crystal system with a=15.982(4), b=8.502(2), c=8.032(2) (A) and Z=4. The six-membered diamine ring assumes the stable ‘chair’ conformation. The five-membered glycinate rings show a relatively small puckering resembling an ‘envelope’ conformation.

2,6-Diacetylpyridine bis{[dl-hydroxy(phenyl)acetic]hydrazone} (H4dapm) has been synthesized and spectroscopically characterized (IR and NMR) along with six metal (Cu, Ni, Fe) complexes. The crystal structure of [Ni(H4dapm)(H2dapm)]·13H2O has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group C2c with a=20.977(6), b=20.040(6), c=14.328(3) A, β=100.67(2)° and Z=4. The complex has twofold crystallographically imposed symmetry with the nickel atom in a distorted octahedral environment consisting of six nitrogen atoms from two ligand molecules.

The new potentially tetradentate aroylhydrazone ligands, Hbitp and Hsitp, produced by condensation of 5-acetyl-2,2′- pyridylthiophene with benzoyl- and salicyloylhydrazine, respectively, have been reacted with several metal(II) acetates. Deprotonation at the amide nitrogen occurs and neutral complexes of the type [M(bitp)2L2] and [M(sitp)2L2] are obtained, where L is a solvent molecule. An X-ray crystal structure determination carried out on [Co(bitp)2(dmso)2] (I) revealed that these ligands behave as bidentate through the (O)CNN hydrazide moiety, assuming the Z configuration around the CN hydrazone bond. The coordination environment is distorted octahedral, the solvent molecules occupying the axial positions. The crystal structure of the Ligand Hbitp (II) has also been determined for comparison.

2-(2′-Thienyl)pyridine (pyth) and its acetylated derivative (apyth) ( III ) react with copper chloride to give compounds of formulae [Cu(pyth) 2 Cl 2 ] ( I ) and [Cu(apyth) 2 Cl 2 ] ( II ). The crystal structures of I , II and III have been determined by X-ray methods. In both copper complexes the metal atom is surrounded by two N atoms (CuN, 2.025(5) A in I and 2.021(2) A in II ) from two ligands molecules and two Cl atoms (2.265(2) A in I and 2.264(1) A in II ) in a typical square planar environment. Two thiophene S atoms (CuS, 2.968(2) A in I and 2.904(1) A in II ) complete the coordination sphere, making the complex elongated octahedral. By contrast, in all complexes of general formula [Cu(bipy) 2 X]X, (bipy= 2,2′-bipyridyl) the coordination environment around copper is quasi- trigonal bipyramidal, the pyridine rings in each bidentate ligand being almost coplanar, and one anion does not participate to coordinative bonding.

The title compound has been synthesized and its IR spectroscopic properties and X-ray structure have been studied. Crystals are triclinic, space group P 1 , with unit-cell dimensions: a = 8.987(3), b = 16.649(6) c = 11.002(5) A; α = 97.4(2), π = 113.1(1), γ =100.0(1)° and Z = 2. The structure has been solved from X-ray diffractometric data by the heavy-atom method and refined by least-squares techniques to R 0.038 for 3823 independent reflections. Coordination around tin is pentagonal bipyramidal with the bidentate nitrate groups and the triphenylarsine oxide molecule occupying the equatorial positions and the two phenyl rings at the apices.

Single crystal spectra of Me 4 N) 2 OU 2 Cl 4 have been recorded at 4.2 °K, using polarized radiation. The analysis of the electronic absorption bands shows several progressions in the region 20,000–28,000 cm −1 , some of them strongly polarized. The most intense bands clearly show progressions (R + nv 1 ), where v 1 assumes the mean value of 700 cm −1 and therefore it has been taken as the symmetric stretching wavenumber of the uranyl group in the excited states.

Crystals of K2Pb(NO2)3(NO3)·H2O are orthorhombic (Pbca) with unit-cell dimensions: a = 6.766(5), b = 11.999(7), c = 26.61(2) A, Z = 8. The structure has been determined from diffractometer data by the heavy-atom technique and refined by full-matrix least-squares to an R value of 7.13% for 1285 independent reflections. The lead atom is surrounded by nine ligating atoms belonging to nitrate and nitrite groups. The NO−3 ion and two NO−2 ions are chelating to metal in a bidentate fashion through their oxygen atoms, while the third NO−2 ion acts as a bridge through two metal centers involving in coordination all its three atoms. The two K+ ions are in different structural environments which differ by the number and the arrangement of the ligating atoms.

From the reaction of nitratotriphenyltin with bis(diphenylphosphinyl)ethane, a dinuclear adduct of formula [{SnPh3(NO3)}2{OPPh2(CH2)2Ph2PO}] has been obtained, in which the organic ligand is present in oxidised form. Crystals are triclinic (P 1 ), with unit-cell dimensions: a = 12.519(15), b = 11.798(12), c = 10.399(10) A, α = 98.2(1), β = 89.2(1), γ = 111.2(1)°, Z = 1. The structure has been determined from diffractometer data by conventional Patterson and Fourier techniques and refined by full-matrix least-squares to an R value of 3.68% for 4291 independent relfections. The adduct has a trigonal bipyramidal coordination geometry with the three phenyl rings occupying equatorial coordination sites, while the unidentate nitrate group and the bis(diphenylphosphinyl)ethane molecule are trans to each other and occuppy the apical positions.

The reactions of R4-nSn(NO3)n Ph, Bun; n = 1,2) compounds with benzimidazole and 2-aminobenzthiazole have been mad and investigated in relation to the reaction conditions. The IR, NMR and MS techniques have been used to characterize the final reaction products.

NaAgS2O3H2O monoclinic, Pc: a = 7.78(1), b = 9.07(1), c = 7.71(1) A, β = 96.3†(.2†), Z = 4. The crystal structure has been determined at a room temperature from three-dimensional X-ray photographic data and defined by differential methods using anisotropic thermal parameters; final R = 10.8%. In the asymmetric unit there are two independent silver atoms both tetrahedrally surrounded by three sulphur atoms from three thiosulphate groups and by one oxygen atom from the water molecule. Each thiosulphate group behaves as a monodentate ligand through the external sulphur which coordinates to three adjacent silver atoms (Ag(1)S = 2.48, 2.54, 2.60 A; Ag(2) S = 2.52, 2.52, 2.65, A) so that the coordination polyhedra result linked in layers running parallel to (010). These layers are joined together by sodium atoms which interact, in a distorted octahedral environment, with the oxygen atoms