Solid Metal Complexes Research Articles

Experimental determination of specific reaction rates for solid state decomposition processes exhibiting a ‘contracting volume’ behaviour

Combined evaluation of quantitative thermoanalytical, structural and morphological investigations revealed a ‘contracting volume’ behaviour for the thermal decomposition of various solid metal complexes and - under high vacuum conditions - of calcite single crystals. It is shown that the determination of specific and reproducible kinetic data is not feasible unless reaction rates are defined with respect to the crystal structure and/or morphology of the initial phase. Moreover, the actual reaction mechanism is strongly dependent on the experimental conditions.

Further studies on the effects of temperature and γ-radiation doses on the electrical conductivity of solid metal complexes

The prepared dry solid metal complexes were compressed at a saturated and suitable pressure of 400 kg cm −2 at room temperature into pellets 1.22 cm in diameter and 0.2 cm thick. The DC electrical conductivity was measured at room and elevated temperatures up to 388 K. The test samples were then subjected to various γ-radiation doses ranging from 10 7 to 10 10 rads, using a 60Co gamma cell. The temperature dependence of electrical conductivity was also undertaken before and after each radiation dose. The results obtained indicate that the materials under investigation exhibit semiconducting properties in the temperatures range studied. The dependence of electrical conductivity and activation energy on temperature and γ-radiation doses is discussed and correlated with the type of substitution and the polymeric nature of the complex. The relative stability of the investigated materials towards irradiation damage is established and discussed on the bases of the ligand field strength and γ-irradiation induced polymerization.

The coordination chemistry of 2,2?-oxydibenzoic acid, 2,2?-thiobenzoic acid, 3,3?-oxydipropionic acid and 3,3?-thiodipropionic acid with selected first row transition metal ions

Solid metal complexes of the title ligands are described. The largest range is prepared with 2,2′-oxydibenzoic acid, namely ZnIIL · 1.5 H2O, CuIIL · H2O, CoIIL · H2O, FeIIIL · (OH) and FeIIIL · (OH) · H2O where L denotes the ligand dianion. Zinc(II) and copper(II) complexes of the other ligands are prepared for comparison and these have, generally, the stoichiometry ML · xH2O (0.5⩽ x ⩽ 1.5; M = Cu or Zn).

Studies of adduct formation between diisopropyl methylphosphonate and various metal salts and complexes

The formation of adducts of diisopropyl methylphosphonate (L) with a variety of metal salts and complexes was studied by means of conductimetric titrations and gas-solid interactions. Conductimetric titration data indicate that L forms 1:1 and 2:1 adducts with SnCl 4, TiCl 4, FeCl 3 and MnCl 2; in addition, the possibility of existence of 1.5:1, 3:1 and 6:1 adducts with FeCl 3 and a 4:1 adduct with MnCl 2 was suggested by the titration curves. Studies of the interaction of L vapor with solid metal salts and complexes, under a vacuum of 5 × 10 −5 mm Hg, suggest that adducts involving the following L to metal molar ratios are the most stable and, therefore, easiest to isolate species: 2:1 with MCl 2 (MCo, Ni, Cu, Zn) and NiX 2 (XBr, I, NO 3); 4:1 with Ni(ClO 4) 2; and 1:1 with Ni(II) acetylacetonate and nickelocene. Most of these adducts involve normal donor-acceptor interactions between L and metal ion, as shown by sizeable v P = O shifts to lower wavenumbers; however, the nickelocene adduct seems to involve a weak interaction of L and Ni 2+( Δv P = O of only 3 cm −1). NiF 2 and Ni(CH 3COO) 2 did not uptake any L during gas-solid interaction, while IrCl 3 uptook only 0.15 mol L/mol, forming an authentic adduct on its surface. Finally, a number of new solid 2:1 adducts of L with metal salts were synthesized and characterized as follows: [MnX 2L 2] (XCl, I), tetrahedral; [VCl 3L 2] and [VOCl 2L 2], both trigonal bipyramidal; [M(O 2NO) 2L 2] (MMn, Cd) and [Sn(O 2SO 2) 2L 2], low-symmetry hexacoordinated; [FeCl 2L 4][FeCl 4], ionic with a hexacoordinated complex cation combined with the tetrahedral [FeCl 4] −.

A Simple “Plastic Bag” Technique for Visible Spectra of Solid Metal Complexes

The techniques commonly used to study the visible spectra of transition metal complexes in the solid state involve diffuse reflectance from the powdered sample or transmission through a mull of the compound in mineral oil on filter paper. Pressed KBr (for anhydrous compounds) and AgCl (for compounds containing water or other highly polar ligands) disk techniques have been used even for low temperature spectra. All of the transmission techniques mentioned are based on mixing the sample with another compound which may induce changes in the compound under study via chemical reactions. Air- and water-sensitive complexes also need special care. These interferences may be reduced by the use of the following simple and rapid technique.

Interpretation of high spin⇌low spin transition in iron (II) complexes. I. A phenomenological thermodynamic model

A phenomenological thermodynamic model suited for the interpretation of the high spin⇌low spin transition in solid transition metal complexes is described. The model is based on the idea of the spin transition taking place through a significant phonon-assisted coupling between the electronic state of the primary spin change center and n−1 neighboring complex molecules undergoing secondary spin transitions and thus forming a cooperative domain as suggested by Sorai and Seki. The model has been applied to interpret the spin transition in polycrystalline solid solutions of [FexZn1−x(2-pic)3]Cl2⋅C2H5OH(2-pic=2-picolylamine) with 1.0⩾x⩾0.0009. The spin transition temperature Tc may be calculated using the effective changes of enthalpy and entropy, respectively, obtained from 1nK vs 1/T plots. Phenomenological expressions for the transition temperature Tc (x) as well as for the effective enthalpy and entropy changes ΔHeff(x) and ΔSeff(x) have been adjusted to the measured data. The average domain size for the pure iron compound has been calculated to be n≈3.5 which indicates comparatively weak intermolecular coupling strength for the present system. The domain size n depends markedly on the iron concentration x and tends to one at very low iron concentration. The volume expansion of the domain size n approximated by n (x) =1+noxγ, decreases rather strongly with falling iron concentration (γ≈1.7). In the pure iron compond, the sum of the intramolecular enthalpy contributions changes by some 550 cal mol−1 and that of the intermolecular enthalpy contributions, responsible for the cooperative effect, by some 200 cal mol−1 on going from low spin to high spin.

Crystallographic Evidence for Ade-AdeH Hydrogen-bonded Pairs in a Cobalt-Adenine Complex

INTEREST in the role of metal ions in the biochemical reactions of nucleotides and nucleic acids1 has led us to study the isolation of solid metal complexes with nucleotides and their bases, and to perform X-ray structural studies on suitably crystalline materials. In this way unequivocal information can be obtained concerning the preferred coordination sites of a given metal ion and also concerning the important question of hydrogen-bonding interactions in these systems. We report here the isolation of a crystalline complex of cobalt (II) sulphate with adenine (Ade) and details of its crystal structure.

Correlation of the 1.R. data with the stability of transition metal complexes of 8-amino-7-hydroxy-4-methylcoumarin

The i.r. spectra of a number of solid transition metal complexes of AHMC have been investigated and it has been possible to determine three vibrations of the ligated molecules in these complexes. The decrease in stretching NH 2 vibrations have been observed in the region 3320-3200 cm −1; the NH 2 rocking deformation in the region 790-650 cm −1 and the metal-nitrogen stretching frequencies in the region 510−480 cm −1. On the basis of these frequencies a correlation has been sought in with the stability of transition metal complexes which is supported by their 10 D q values.

Hydroxamic Acids and Their Metal Complexes: Preparation, Properties, and Infrared Spectra

Abstract The preparation and properties of ten metal complexes of N-phenyl-benzohydroxamic acid (PBHA) with Mg+2, Zr+4, Cd+2, Sb+3, La+3, Ce+3, Pr+3, Nd+3, Sm+3, and Th+4 have been described. These solid-metal complexes were prepared by reacting an aqueous solution of the metal ion with an alcohol solution of PBHA at 60° and adjusting the pH. The pH range for precipitation of these complexes is between 2 to 10. The infrared spectra of these complexes have been discussed.

Preparation and characterization of some binary and ternary metal complexes of thenoyltrifluoroacetone and phosphorus esters

Two new ternary cadmium (II) complexes containing thenoyltrifluoroacetone anion (TTA) and tri- n-octyl phosphine oxide (TOPO) or triphenyl phosphine oxide (TPPO) have been prepared in the crystalline state and characterized by molecular weight, proton magnetic resonance and infra-red spectral studies. The phosphorus magnetic resonance method has been used to determine the equilibrium constant of the reaction Cd(TTA) 2 + TOPO = Cd(TTA) 2·TOPO: K = 10·1 1/mole in anhydrous carbon tetrachloride medium. Cd(II), Pb(II), Al(III) and Co(III) complexes of TTA have also been prepared in the crystalline state and investigated. It was not possible to prepare solid ternary metal complexes containing TTA and a phosphorus compound when the metal is Al(III) or Co(III). The visible spectra of Ni(TTA) 2 in acetone show that the complex is octahedral.