Paolo Zannini

Electronic Properties and Crystal Structure of Aqua(1,10‐phenanthroline)(oxalato‐ O1O2)copper(II) monohydrate

Abstract The compound aqua(1,10-phenanthroline)(oxalato-O1O2) copper(II)monohydrate was synthesized and characterized by spectroscopy, thermal analysis, EPR and structural measurements. The crystal and molecular structure, refined to the final R = 4.28% (Rw = 4.52%) value, shows a monomeric nature. Copper coordination is 4 + 1 in a slight distorted square pyramidal geometry, with a water oxygen atom in the apical position, at 2.237(4) A from the metal atom. At 4.44 A from copper lies a lattice water molecule, linked to the former by a hydrogen bond.

Coordinating ability of methylpiperidine dithiocarbamates towards platinum group metals

Abstract New rhodium(III), iridium(III), palladium(II) and platinum(II) dithiocarbamate complexes of the types M(Rdtc)3 and M(Rdtc)2 (Rdtc = 2-, 3- and 4-methylpiperidine dithiocarbamate) have been prepared and characterized by chemical analyses, conductance measurements, electronic and IR spectral studies, magnetic measurements and thermal analyses (TG and DTG techniques). From the electronic absorption spectra the values of the ligand field parameters were determined; the nephelauxetic parameters are indicative of a strong covalency in the metal-ligand bond. All the complexes here reported are diamagnetic and nonconducting both in the solid state and in DMF solution.

Preparation and study of some antimony and bismuth trisdithiocarbamate and five-coordinate monohalobisdithiocarbamate derivatives

Abstract The complexes of antimony(III) and bismuth(III) with piperidinedithiocarbamate (Pipdtc), morpholinedithiocarbamate (Morphdtc) and thiomorpholinedithiocarbamate (Timdtc) of general formula M(Rdtc) 3 have been prepared, and characterized by spectroscopic methods. The data show that the complexes have a distorted octahedral stereochemistry, this distortion being due to the stereochemically active lone-pair of electrons on the antimony and bismuth atoms. A new series of pentacoordinate complexes of general formula M(Rdtc) 2 X, M being antimony or bismuth, X a halogen and Rdtc the above dithiocarbamates, has been prepared by reacting the corresponding trisdithiocarbamates with chlorine, bromine and iodine. The compounds have been characterized by IR and electronic spectroscopy and molecular weight determinations. The infrared spectra suggest that each dithiocarbamate group coordinates as a bidentate ligand; the metal—halide and metal—sulphur stretching modes have also been assigned. The spectral data are discussed and compared with those of the corresponding trisdithiocarbamate derivatives. The molecular weight determinations indicate that the trisdithiocarbamate complexes are monomeric; for the monohalobisdithiocarbamates, the antimony derivatives are shown to be monomeric, while the bismuth derivatives tend to dimerize.

Investigations of chromium(III), manganese(III), tin(II) and lead(II) dithiocarbamate complexes

Abstract Piperidine-, morpholine-4-, N-methylpiperazine-4- and thiornorpholine-4-carbodithioate complexes of chromium(III), manganese(III), tin(II) and lead(II) are prepared and characterized by chemical analyses, spectroscopic methods (I.R. and electronic spectra), magnetic susceptibilities, conductivity measurements and mass spectra. The complexes are of the type M(R2dtc)n, where n is the oxidation number of the metal ion. Where possible a tentative stereochemistry of the complexes is discussed on the basis of the results obtained. In all the complexes the dithiocarbamate ligands show bidentate behaviour.

Synthesis and spectroscopic characterization of arsenic(III), antimony(III), bismuth(III), tin(II) and lead(II) dithiocarbamate adducts

Abstract The complexes of arsenic(III), antimony(III), bismuth(III), tin(II) and lead(II) with monomethylsubstituted piperidinodithiocarbamates of general formula M(Rdtc)3 and M(Rdtc)2 have been prepared and characterized by spectroscopic methods. The results of the spectroscopic studies indicate that the dithiocarbamate ligands are always bidentate, in both the 1:3 and the 1:2 complexes. All the complexes are nonconducting in DMF solution. The thermal behaviour of the complexes has been investigated by TG and DTG techniques. The molecular weight determinations indicate that the trisdithiocarbamates of arsenic and antimony are monomeric, while the bismuth trisderivatives tend to dimerize: polymeric structures can be suggested for the tin(II) and lead(II) compounds.

Synthesis and characterization of ruthenium dithiocarbamate complexes

Abstract Piperidine carbodithioate (Pipdtc), morpholine-4-(Morphdtc), thiomorpholine-4-(Timdtc), piperazine-4-(Pzdtc) and N-methylpiperazine-4-carbodithioate (CH3-Pzdtc) complexes of ruthenium have been prepared and characterized by spectroscopic methods (IR and electronic spectra), magnetic susceptibilities and conductivity measurements. Where possible a tentative stereochemistry of the complexes is discussed based upon the obtained results. The dithiocarbamate ligands show in all the complexes a bidentate behaviour. A distorted octahedral geometry is proposed for the water containing 1:2 derivatives: in fact from a detailed analysis of the infrared spectra the water resulted always coordinated to the metal. The Pzdtc 1:2 derivative resulted polymeric octahedral with the NH group of the heterocyclic ring involved in the coordination.

Transition metal complexes with 2-methyl-, 3-methyl-, and 4-methyl-piperidine dithiocarbamate as ligands

SummaryA new series of manganese(III), cobalt(II), nickel(II), zinc(II), cadmium(II) and mercury(II) complexes with monomethylsubstituted dithiocarbamates as ligands has been synthesized and studied. Their structures are discussed in relation to their spectroscopic, magnetic and thermal properties. The dithio-ligands exhibit bidentate behaviour acting as S,S′donors in all the complexes. In the far i.r. region particular attention is paid to a comparison of the spectra of the octahedral complexes with those of the other metal derivatives (1∶2 metal to ligand molar ratio). The e.s.r. spectra are indicative of aD2h symmetry in the cobalt(II) complexes.

Viscosimetric properties and internal structure of N,N-dimethylformamide + 1,2-dimethoxyethane binary mixtures

Abstract The kinematic viscosities (ν) of liquid binary mixtures of N,N-dimethylformamide and 1,2-dimethoxyethane were measured at 19 temperatures in the range −10⩽ t / °C ⩽ 80, employing the pure species and 9 their solutions covering the whole miscibility range expressed by the condition 0 ⩽ χi ⩽ 1. The measured values have been used to test some empirical equations of the type ν=ν(T), ν=ν(χi, and ν=ν(T,χi), in order to obtain useful correlation models with predictive ability in correspondence of the experimental data gaps. Starting from the experimental data, the excess kinematic viscosities (νE) have been calculated. Sign and magnitude of these quantities have been discussed in terms of type and nature of specific intermolecular interactions. Some derived quantities such as thermodynamic parameters of the viscous flow (ΔG∗, ΔH∗ and ΔS∗), have been calculated on the basis of Eyrings model. Furthermore, the fluidity of this binary solvent system was analysed and interpreted following Hildebrand and modified-Hildebrand correlation models.

Refractive Properties of Binary Mixtures Containing N,N- Dimethylformamide + 2-Methoxyethanol or 1,2-Dimethoxyethane

Abstract Refractive index (n) and related properties such as molar refraction (R) have been investigated for DMF + ME and DMF+DME binary mixtures over the entire composition range, at 15 different temperatures in the range 0 ≤ t/°C ≤ 70. Some relationships have been applied to study the dependence of the measured and derived quantities by temperature and composition. Furthermore, the excess functions n E, R E and the excess Kirkwood correlation parameters Δg have been examined, in order to identify the presence of solvent-cosolvent adducts in these binary mixtures. The results obtained have been interpreted on the basis of specific intermolecular interactions between different species.

X-ray powder diffraction quantitative analysis performed in situ at high temperature: application to the determination of NiO in ceramic pigments

Although nickel(II) oxide (NiO) is a potential carcinogenic agent, it is still used in the synthesis of ceramic pigments because during their preparation at high temperature, NiO is thought to combine with other compounds, crystallizing as new phases with spinel-like structures. Unfortunately, there are no widely accepted methods for the determination of free NiO in ceramics, the main reason being experimental difficulties. In fact, quantitative phase analysis (QPA) by X-ray powder diffraction (XRPD) may fail because diffraction peaks of NiO with space group Fm3¯m and a ≃ 4.18 A overlap with those of the spinel with space group Fd3¯m and a ≃ 8.4 A. To overcome this problem, in this work QPA has been performed in situ at high temperature to resolve the peak overlap of NiO and spinel by taking advantage of the different thermal expansion of each phase. It is believed that this is the first report of the application of this technique.