Showing papers in "Journal of Inorganic and Nuclear Chemistry in 1977"

Abstract: The formation of Li 2 S n in certain aprotic media can be accomplished either by electrochemical reduction of S 8 or by direct in situ reaction of S 8 with Li or Li 2 S. Polysulfide solubilities and spectra vary widely in different solvents as a result of solvent-solute interactions. A requirement for high polysulfide concentration is high solvent basicity. In some cases, such as dimethyl sulfoxide and tetrahydrofuran, S solubility (as Li 2 S n ) can exceed 10M. The favored order of dissolved polysulfides depends on the dielectric constant of the solvent, lower values favoring the formation of longer chains.

Abstract: Tris- and bis-ligand complexes of nickel(II) with S-benzyldithiocarbazate (SBDTC) having the general formulae Ni(SBDTC) 3 X 2 ·H 2 O (X = Cl, Br and NO 3 ) and Ni(SBDTC) 2 X 2 (X = Cl and NCS), respectively, were synthesized and characterized by electronic and IR spectroscopy and magnetic measurements. The ligand acts as a bidentate sulphur-nitrogen chelating agent. Both the tris- and bis-ligand cationic nickel(II) complexes are high-spin with magnetic moments of ca. 3.10 B.M. On the basis of magnetic and spectral evidence octahedral structures are assigned to these complexes. Under alkaline conditions complexes of the deprotonated ligand having the formulae M(SBDTCA) 2 [M = Ni(II) and Zn(II); SBDTCA = anion of SBDTC] were isolated. The nickel(II) complex is square-planar. The Schiff base CH=N-NHCSS 2 C 6 H 5 (NNSH)forms intensely coloured crystalline complexes with nickel(II) and copper(II) having the general formula M(NNS)X [M = Ni(II) and Cu(II); X = Cl, Br or NO 3 and NNS is the anion of NNSH]. The nickel(II) complexes are diamagnetic. The magnetic behaviour of the Cu(NNS)X (X = Cl and Br) complexes over the temperature range 320-93°K obeys the Curie-Weiss law. The variable-temperature magnetic data coupled with IR and electronic spectral evidence support square-planar stereochemistries for the copper(II) complexes.

Abstract: The reactions of [RuCl3(AsPh3)3] with ligands containing nitrogen (ammonia, hydrazines, amine and thiocyanate) and oxygen (carboxylates) and the reactions of β-diketones (acetylacetone, dibenzoylmethane and benzoylacetone) with [RuCl2(PPh3)2]n and [RuCl2(AsPh3)2]2 have been studied. Apart from this, a new Ru(III) complex, [RuBr3(AsPh3)3] has also been synthesized. The compounds obtained have been characterised by analyses, conductivity and magnetic measurements, molecular weight and spectral studies (IR and visible). An equilibrium between hexacoordinated and pentacoordinated species is suggested on the basis of electronic spectral studies.

Abstract: Four undecatungstosilicic and germanic isomers have been prepared. Their UV spectra and their polarograms are given and their acido basic properties are studied. The conditions of formation and the preparations of these isomers are deduced from the reactions of isomerization. A new method for the preparation of β-dodecatungstosilicate is given which do not require fractional crystallisations. This method is valuable for the germanate.

Abstract: New complexes with Schiff base ligands derived from S-benzyldithiocarbazate have been prepared and characterized by IR and electronic spectroscopy and magnetic measurements. The 2-methoxybenzaldehyde Schiff base (MeONSH) forms mono-ligand complexes of the general formula, [M(MeONS)X], where MeONS is the uninegatively charged tridentate ligand, M = Ni(II) or Cu(II) and X = Cl − , Br − or NO 3 − ion. The ligand does not produce bis-ligand complexes with Ni(II) and Cu(II) ions. The nickel(II) complexes are diamagnetic and squareplanar. The ligand oxidizes cobalt(II) chloride to produce a cobalt(III) complex, [Co(NeONS) 2 ]Cl, which is spin-paired and octahedral. The 2-hydroxybenzaldehyde Schiff base (HONSH) forms diamagnetic complexes with nickel(II) having formula [Ni(ONS)X], where X = H 2 O or pyridine. The neutral copper(II) complex [Cu(ONS)], has an anomalously low magnetic moment of 1.02 B.M. An oxygen-bridged binuclear structure is proposed for the complex. The ligand oxidizes cobalt(II) salts to form a cobalt(III) complex of composition [Co(HONS)(ONS)]. Magnetic susceptibility data and electronic spectrum suggest a spin-paired octahedral structure for the complex.

Abstract: At about 200°C, synthetic magnetites are oxidised to maghemites without any significant changes in morphology and surface area. This oxidation is accompanied by a contraction of the cubic unit cell. During oxidation the excess Fe probably moves towards the surface and combines with oxygen to form a film of maghemite, the thickness of which increases with time. The data on changes in Fe(II) content during the oxidation can be fitted to an equation describing the diffusion in a sphere. At 190°C the diffusion coefficients of Fe are in the range 0.8 to 2.1 × 10−15 cm2/sec and decrease with the increasing isomorphous substitution of Co, Ni and Zn for Fe(II) in the magnetite.

Abstract: The stability constants for the formation of complexes between the trivalent lanthanide series of cations and a series of aminocarboxylic acid ligands are reported. The measurements were conducted at 25°C at an ionic strength of 0.50 M (NaClO4).

Abstract: The hydrous lanthanide oxides and hydroxides comprise a complex series of both amorphous and crystalline compounds. One important member of this system is the hexagonal form of M(OH)3 where M studied here are La, Nd, Sm, Gd, Tb, Dy, Ho, Y and Er. The lattice constants and structure for these nine isotypic compounds has been determined by three-dimensional X-ray diffraction. The space group is P63/m or P63 with two formula units per cell. The metal is 9-coordinate (tri-capped trigonal prism) with two independent metal-oxygen bond distances and three independent oxygenz.sbnd;oxygen bond distances. The metaloxygenoxygen bond distances both exhibit monotonic decreases proceeding from La to Er. The metal to oxygen distances range from 2.588(3) A to 2.403(3) A for MO2 and from 2.551(3) A to 2.439(3) A for MO1. At the low atomic number end of the series the MO1, bond distance is shorter than the MO2 bond distance. The two bond distances become the same at the spherically symmetric gadolinium and switch in relative magnitude as you proceed to erbium. The oxygenoxygen bond distances range from 3.033(5) A to 2.856(5) A for O1O2, 2.992(6) A to 2.826(7) A for O2O2 and 2.900(6) A to 2.710(6) A for the second O1O2 bond distance. Approximate positions for the hydrogen atoms have been found for the M(OH)3 compounds Gd, Dy, Ho, Y and Er. A set of crystal radii for the lanthanides La, Nd, Sm, Gd, Tb, Dy, Ho and Er has been derived.

Abstract: The kinetics of magnesium hydride decomposition in an atmosphere of hydrogen has been followed gravimetrically. At hydrogen pressures appreciably different from the equilibrium dissociation pressure the experimental data fit the rate expression 1−(1−α)12 = k1t (1) where α is the fraction of hydride dissociated after t minutes. At 384 kPa, ln k1 = 19.47−14441/T where T is the temperature (608K < T < 641K). At 667K, k1 = 0.1105−0.0000435P where P is the pressure in kPa (450 < P < 1850). The form of the rate expression indicates that movement of the phase boundary is the rate-determining step at these pressures. At pressures near the equilibrium dissociation pressure the experimental data fit the expression (−ln(1−α))12 = k2t (2)/ At 384 kPa, ln k2 = 21.25−15198/T (608K < T < 641K). Although the rate expression (2)_indicates that nucleaction could be random instead of fast at these pressures, the experimental data support the conclusion that nucelation is kinetically unimportant and that the rate-determining mechanism is phase boundary movement.

Abstract: The preparation of a new inorganic ion-exchanger with the formula Ti(HPO4)2·2H2O and its ion-exchange properties towards sodium and strontium ions, are reported and discussed. This exchanger is shown to be very stable to hydrolysis and to have high exchange capacity in strongly acid medium. Comparison with the corresponding zirconium phosphate dihydrated phase (γ-ZP), suggests that Ti(HPO4)2·2H2O possesses a different lattice structure from that reported for the monohydrated exchanger.

Abstract: Several methods for the synthesis of ammonia-borane and its deuterated derivatives have been investigated. Results including yields and product quality are reported. A modification of a previously reported synthesis involving the reaction of ammonium carbonate with sodium tetrahydroborate in tetrahydrofuran was found to be the most effective synthesis giving 80% yields of H3N·BH3. New syntheses of D3N·BH3 and D3N·BD3 are also described.

Abstract: The values of the free energy, enthalpy and entropy of complexation are reported for a series of aminocarboxylate ligands. For all the systems, a region of “compensation” between ΔH 1 , and ΔS 1 exists between Nd(III) and Ho(III) which is related to dehydration effects. The entropies are a function of the number of ligand carboxylate groups coordinated. Correction of the enthalpy for the coordination of the carboxylate groups gives a residual enthalpy which is a linear function of the basicity of the nitrogen groups. In the HEDTA complexes, the data are consistent with outer sphere coordination of the alcohol group in the light lanthanides and with inner sphere coordination in the heavy members.

Abstract: Complexes of Co(II) and Zn(II) halides and perchlorates have been prepared. Chemical analysis suggests their respective formulae to be: MX 2 L 2 (X = Cl − Br − and I − ) and [M(L) 4 ](ClO 4 ) 2 . On the basis of electrolytic conductivities in nitromethane, room-temperature magnetic moments, solid state IR and visible spectra as well as visible spectra in anhydrous solution the complexes have been shown to be tetrahedral in character. The ligand is monodentate and S-bonded in all cases. X-ray powder diffraction photographs have been used to assess the extent of isomorphism among the solid complexes.

Abstract: Tetrakis-(4-N-methyl)pyridylporphineiron(III) (FeTMpyP) was synthesized and its aqueous solution properties studied. The visible spectrum of FeTMpyP was found to be dependent on pH and ionic strength. The following equilibria were sufficient to account for the titration data: H 2 O + FeP ( H 2 O ) 5+ ⥂ FeP ( OH )( H 2 O ) 4+ + H + ;p K a1 =4.7±0.2 FeP ( OH )( H 2 O ) 4+ ⥂ FeP (OH) 2 3+ + H + ; p K a2 =6.5±0.3 2 FeP ( OH ) 2 3+ ⥂O−( FePOH ) 2 6+ + H 2 O ; K D ≃9×10 5 M −1 . Magnetic susceptibility measurements and Mossbauer spectroscopy were used to characterize the FeTMpyP species at low and high pH. In the range pH 1–3, monomeric, high-spin, pentacoordinated iron(III) is the primary species. A μ-oxo dimer involving low-spin hexacoordinated iron(III) exists at pH 10–12. The rate of dissociation of the dimer at μ = 0.05 M and t = 25°C was found a two-term rate law: − d [ dimer ] d t =(k 1 +k′ 1 [ H + ])[ dimer ] where k1 = 0.42 sec−1 and K1 = 31 M−1 sec−1. These results are compared with those obtained for the dissociation of dimer of tetraphenylporphinesulfonatoferrate(III), FeTPPS.

Abstract: Through a study of the kinetics and equilibria of the interfacial mass transfer of this system and correlating it with studies of interfacial tension vs concentration data, it has been possible to determine a consistant and revealing mechanism of extraction. This mechanism is as follows: The subscripts A, I and O indicate the environment of the species—the aqueous phase, the interface, or the organic phase. HDEHP is di(2-ethylhexyl)phosphoric acid and DEHP is the corresponding base. Mass transfer studies were performed under conditions of a quiescent constant interface with moderate stirring in one or both phases. The effects of changes in interfacial area, temperature and the stirring rate in each phase on the rate parameters, k1, k2 and k −2 k −1 , and the distribution ratio were determined and are discussed. The salient features of the proposed mechanism are threefold: (1) HDEHP and generally all extractants have important interfacial activity; (2) the actual complexation of calcium ion does not occur in the aqueous phase but at the interface; and (3) there is a structured layer of water at the interface that impedes the progress of calcium ion from the bulk aqueous phase to the interface.

Abstract: Detailed thermal expansion data have been obtained by high temperature X-ray diffractometry of U3O8 and U3O8−z in air between 22 and 1100°C. Stoichiometric U3O8 changes continuously, reversibly and anisotropically above room temperature with expansion along the a-axis and contraction along the b-axis from orthorhombic to hexagonal symmetry at 350 ± 10°C. A small but continuous contraction along the c-axis occurs up to 1100°C. Both parameters of the hexagonal phase expand smoothly and reversibly to approximately 875°C and exhibit no discontinuity as a result of loss of oxygen which begins near 600°C. At 875–925°C the structure changes to lower symmetry by contraction along the a-axis and expansion along the b-axis. This structural change is accompanied by a more extensive loss of oxygen and is usually irreversible unless the crystallite size is sufficiently small, ∼0.05 μm for which both the compositional and structural changes are reversible with temperature. Calculated unit cell volumes undergo slight expansion and contraction up to 350°C, with a broad maximum at approx. 200°C and a smooth expansion at a decreasing rate from 350–875°C. The irreversible transition beginning at 875°C is ostensibly associated with an expansion-contraction anomaly in the temperature range 875–925°C, followed by smooth expansion at a decreasing rate to 1100°C. The thermal expansion characteristics have been interpreted in terms of rotation of octahedral linkages in the orthorhombic and hexagonal structures and the irreversible transition has been tentatively explained in terms of two U3O8−z phases, one orthorhombic and one monoclinic. The apparently contradictory structural analyses for the U3O8 and U3O8−z phases in the literature can be reconciled on the basis of the thermal expansion results which involve both changes in temperature and composition.

Abstract: Several new complexes of copper(II) halides, isothiocyanate, perchlorate, sulphate and nitrate with a series of 1-substituted, 2-substituted and 1,2-disubstituted imidazoles were synthesised and characterised. The microanalytical data, conductivity, magnetic susceptibility, IR and electronic spectral measurements were employed to deduce the possible stereochemistry. 1-vinyl 2-methyl imidazole formed a bis compound with CuX 2 (X = Cl, 0.5 SO 4 ), a tris compound with X = NCS, but tetrakis compounds with all other anions studied. 1-Vinyl imidazole formed a tris compound with X = 0.5 SO 4 and tetrakis compounds in all other cases. 2-Ethyl imidazole formed a tris compound with X = Br and tetrakis compounds with other anions. 2-Isopropyl imidazole formed tris compounds with X = Cl, Br and tetrakis compounds with X = NO 3 , ClO 4 . All bis compounds are shown to be 4-coordinate and square planar the tris compounds to be 5-coordinate with perhaps a trigonal-bipyramidal geometry and the tetrakis compounds to be 6-coordinate with a tetragonally distorted octahedral structure. On the basis of IR evidence, it is shown that the NO 3 groups are unidentate, the SO 4 groups bidentate and the ClO 4 groups involved in unidentate “semi-coordination”. The TGA, DTG and DTA studies have been made and the complexes were found to dissociate endothermically through loss of imidazole ligands. The stoichiometry of the thermal dissociation reactions was determined.

Abstract: The present work reports successful results on the synthesis of the hydrated ferrous phosphates of the homologous series Fe32+(PO4)2(H2O)n. By hydrothermal synthesis with vivianite Fe32+(PO4)2·8H2O as starting material we have syntherized two known hydrated species ludlamite (n = 4) and phosphoferrite (n = 3) and two anhydrous forms that occur as minerals, sarcopside and graphtonite, three new species with n = 4, n = 2 and n = 1. One acidic ferrous trihydrate and two basic ferrous species with 2 and 1 water molecules respectively were also synthetized. Of the synthetized species for the trihydrate and the monohydrates the three dimensional structure has been determined by P. B. Moore. The three sites for Fe2+ in the monohydrate are non-equivalent, Fe(1) and Fe(3) are distorted octahedra but Fe(2) is only 5-coordinated, a distorted square pyramid. Octahedra edge sharing is one of the main features of this unusual structure. Mossbauer spectra has been determined for all minerals and synthetic compounds at room and liquid nitrogen temperatures. Oxidation under controlled condition has been investigated and the results correlated with X-ray structure and Mossbauer determinations.

Abstract: The limetime of uranyl luminescence was measured in aqueous solution. The quenching of uranyl luminescence by water molecules was satisfactorily interpreted by an electron transfer mechanism in terms of oxidation-reduction potentials of uranyl ion and water molecule. The proposed mechanism could also explain the variation in the luminescence lifetime (and the quenching rate constant) with change in pH of the uranyl solution and in the degree of formation of uranyl complex with fluoride, sulfate and phosphate anion.

Abstract: A study of the mode of coordination in the complexes of a number of nitrogen and sulfur containing ligands with Co(II) and Ni(II) ions has been made, based on the i.r. data of the shifts in the thioamide bands I, II, III and IV in the ligands on complexation. The ligands are 1-substituted tetrazoline-5-thiones (1ST5TH), 3-(4-pyridyl)triazoline-5-thione (3, 4PT5TH) thiazolidine-2-thione (tt) and thiocarbohydrazide (Htcaz). A number of complexes Co(1-ST5T) 2 , Ni(1ST5T) 2 , Co(tt) 2 Cl 2 , Ni(tt) 2 I 2 , Co(3, 4PT5T) 2 -Py 2 , M(Htcaz) 2 X 2 (where X = CNS, Cl, Br, I, NO 3 and M = Co(II), Ni(II), and Co(Htcaz) 2 SO 4 . 3H 2 O, have been prepared.

Abstract: Nonexponential uranyl luminescence decay curves corresponding to the liminescence of different complex species was found in solutions containing very small amounts of fluoride or phosphate. The luminescence lifetimes of uranyl aquo ion, 1:1 and 1:2 uranyl fluoro complexes are determined to be 2.4, 75 and 150 μs, respectively (25°C, 0.1 M HClO 4 , μ = 1), The rate of formation of 1:1 uranyl fluoro complex in an excited state (UO 2 2+∗ + F − → UO 2 F +∗ ) is smaller than the rate of deactivation of uranyl aquo ion, but the equilibrium UO 2 F +∗ + F − ⇄ UO 2 F 2 ∗ is attained within the luminescence lifetimes of UO 2 F +∗ and UO 2 F 2 ∗ . Kinetic characteristics of complexes formed between UO 2 2+ and sulfate or phosphate was also discussed.

Abstract: The growth kinetics of gypsum was studied in supersaturated solutions both in pure water and in the presence of NaCl, using a seeded growth technique. Radioactive tracer techniques were employed to follow the growth process. The mean linear growth rate R was plotted against the relative supersaturation σ. For low σ values the relation between R and σ is given by a linear law, for higher σ values by a parabolic law and for the highest σ values by a growth “order” higher than two. It was shown that the addition of sodium chloride increased the crystallization rate remarkably. The higher the NaCl concentration the higher the growth rate.

Abstract: Structural models of the four undecatungstosilicate isomers are proposed. Relations between isomerisation reactions, properties of transition metal complexes of undecatungstosilicates, and structures, are studied.

Abstract: The 1:1 complexes of the complete series of lanthanide nitrates with a diazatetraoxa 18-membered macrocycle have been synthesized under anhydrous conditions. The complexes were characterized by elemental analysis, conductometric and spectral data. It is established that the macrocycle adopts a non-planar conformation and that the nitrate ions are bonded differently in the heavier (La—Sm) and lighter (Gd—Yb) lanthanide complexes. The coordinating abilities relative to the rare earths of the macrocycle and of dibenzo-18-crown-6 are discussed.

Abstract: The equilibrium in solution between the tricarbonate and dicarbonate complexes of the uranyl ion has been investigated It has been shown that these species are the only species of the uranyl ion existing in solutions of sodium bicarbonate in the concentration range 003 M–015 M It has also been concluded that it is not feasible to isolate the dicarbonate complex as the only form of UO22+ in carbonate media A spectrophotometric determination of the third formation constant of UO2(CO3)34− gave a value for k3 = 301 × 105 solvent extraction method previously applied to the determination of the overall stability constant of UO2(CO3)22− gave a value of β2(C) = 167 × 1016 (t = 20°, μ = 01) The absorption spectrum of UO2(CO3)22− has been calculated from equilibrium and optical density measurement

Abstract: The quenching reaction of uranyl luminescence by metal ions in a lower valence state such as Fe 2+ , Tl + and Ce 3+ is diffusion-controlled and the dominant process of the reaction is concluded to be an electron transfer from the quenchers to uranyl ion. In case of many transition metal and lanthanide ions including Ce(IV), MnO 4 − and Cr 2 O 7 2− , the electron transfer is impossible energetically and the energy transfer is predominant.

Abstract: Complexes of general formula M 2+ ( L − ) 2 have been prepared, where M stands for Co, Ni, Zn, Cd or Hg and L − represents deprotonated bismuthiol I. The complexes have been characterized by chemical analysis, IR and electronic spectral studies and by magnetic measurements. The cobalt and nickel complexes have been found to be square planar and the zinc, cadmium and mercury complexes have a tetrahedral structure. It appears that the complexes are polymeric in nature. The nickel complex is of particular interest as it has the nickel ions in both the square planar as well as in octahedral environment.