Joseph I. Bullock

Schiff base complexes of the lanthanoids and actinoids. Part 2. Lanthanoid(III) and cerium (IV) nitrato complexes with the zwitter-ionic form of NN′-ethylenebis(salicylideneimine) and related bases.

Abstract The Schiff bases form complexes of the types Ln(H2L)2(NO3)3·nH2O (Ln = La, Pr, Nd, Gd, and Yb, H2L = the charge-separated (zwitter-ionic) form of the Schiff base, n = 0,1, or 2), Nd2(H2L)3(NO3)6, and Ce(H2L)2(NO3)4·H2O. Because of marked spectral similarities with Ca(H2L)(NO3)2, the Schiff bases co-ordinate through the negatively-charged oxygen and not the nitrogen atoms which carry the protons transferred from the phenolic groups on co-ordinate. The nitrato groups are bidentate. The NdIII and LaIII complexes have co-ordination numbers in the range 10–12 as deduced from a hypresensitive transition for Nd compounds and an isomorphous relationship.

Schiff-base complexes of the lanthanoids and actinoids. Part 1. Lanthanoid(III) halide complexes with the un-ionised form of NN′-ethyl-enebis(salicylideneimine) and related bases

The Schiff base NN′-ethylenebis(salicylideneimine) and related bases, H2L, react with hydrated lanthanoid(III) halides to give the complexes Ln(H2L)Cl3·nH2O (Ln = La or Ce; n= O—2), Ln2(H2L)3Cl6·nH2O (Ln = La, Ce, Pr, Nd, Sm, Gd, Ho, or Yb; n= O–2). Ln(H2L)2X3·nH2O (Ln = La, Ce, Pr, Nd, Sm, Gd, Ho, or Yb; X = Cl or Br; n= O–2). and Ln(H2L)3X3·nH2O (Ln = La, Ce, Pr, Nd, Sm. or Gd; X = Cl or Br; n= 0 or 1). Spectroscopic and other evidence has indicated that: (i) halide is co-ordinated to the metal ion except in the case of Ln(H2L)3X3·nH2O where the results were ambiguous; and (ii) the potentially quadridentate ligands are bidentate in these complexes with the un-ionised phenolic groups being unco-ordinated.

Schiff base complexes of the lanthanoids and actinoids. Part 3. Lanthanoid(III), cerium(IV), thorium(IV), and Uranium(IV) complexes with NN′-ethylenebis(5-t-butylsalicylideneimine); 1H N.M.R. and other spectroscopic properties

Abstract The Schiff base, H 2 busalen, forms polymeric M 2 (busalen) 3 (M = Pr, Nd, Sm, Eu, Gd, and Ho) and monomeric M(busalen) 2 (M = Ce, Th, and U) complexes which are readily soluble in CDCl 3 , a properly conferred by the presence of the t-butyl groups. The 1 H n.m.r. spectra are reported. Very large shifts to low and high field were observed for the paramagnetic complexes and the U IV spectrum was well-resolved with very little broadening. The lanthanoid(III) complexes (M = Pr, Nd, and Sm) are probably eight-coordinate both in solution and the solid state.

The Chemistry of the trivalent actinoids. Part 7 [1]. Crystal structure analysis of [NH4]U[SO4]2·4H2O and comments on the structure of U2[SO4]3·9H2O

Abstract The crystal structure of an hydrated uranium(III) compound has been determined for the first time. Crystals of [NH4]U[So4]2·4H2O are monoclinic with a = 6.7065(2), b = 19.0328(6), c = 8.8305(3) A, β = 97.337(10°, z = 4 and space group P21/c. The structure was solved by the heavy-atom method from Cu-Kα diffractometer data, and refined by full-matrix least aquares to R = 0.096 for 1647 observed reflections. The compounds is isostructural with [NH4]M[SO4]2·4H2O (M = LaTb, except Pm). Each uranium atom is coordinated to nine oxygen atoms; six of them are contributed by four sulphate groups and the remaining three are from water molecules. The uranium-oxygen bond lengths were 2.37-2.60 A (to sulphate ion) and 2.47-2.56 A (to water). Each asymmetric unit contains a non-coordinated water molecule. The X-ray powder diffraction photograph of a substance previously reported as U2[So4]3·8H2O and that of La2[SO4]3·8H2O showed that compounds are isomorphous, with space group P63/m. Thus, the stoichiometry U2[So4]3·9H2O is more likely with nine/twelve-coordination found for the lanthanoid(III) sulphate octahydrates and Am2[SO4]3·8H2O. By comparing the diffuse reflectance electronic spectra of the title compounds with those of various uranium(II) solutions, it is confirmed that both water and sulphate ion have similar nephelazuxetic factors.

Copper(II) and iron(III) complexes of N-nitroso-N- alkylhydroxylamines, and the X-ray crystal structures of bis(N-nitroso-N-isopropylhydroxylaminato)copper(II) and tris(N-nitroso-N-propylhydroxylaminato)iron(III)

Abstract N-nitroso-N-alkylhydroxylamines have been prepared by hydrolysis of the mixture obtained by reaction of nitric oxide with Grignard reagents, and stabilized as their copper(II) or iron(III) complexes, Cu(RN2O2)2 and Fe(RN2O2)3, where R is, for example, Me, Et, Pri, Buiso, Ph, n-C8H17 or n-C12H25. The complexes have been characterized by analytical, magnetic and spectroscopic measurements. By single-crystal X-ray methods Cu(PriN2O2)2 has been found to be trans-planar and Fe(PrnN2O2)3 has a facial octahedral structure; in each complex the NO bond lengths are equal with no significant variation between the copper and iron complexes.

Effect of temperature on the protonation constants of some aromatic, heterocyclic nitrogen bases and the anion of 8-hydroxyquinoline

Concentration-based association constants for the heterocyclic nitrogen atoms of 4,4′-bipyridyl (4,4′-bipy), 8-hydroxyquinoline (oxine), 8-aminoquinoline (amquin), pyridine (py) and the 2-(aminomethyl)pyridinium cation (2-ampy) with hydrogen ion have been determined in aqueous solution at various temperatures between 278 K and at least 373 K from spectrophotometric data. All the reactions are isoelectric and the constants decrease with increasing temperature. In two cases (oxine and 2-ampy) non-linear plots of pKa against T–1 were obtained. The reaction of base with oxine to yield the oxinate anion is also isoelectric but a non-linear plot of pKb against T–1 was obtained. The published, high-temperature pKa values and associated thermodynamic quantities for 1,10-phenanthroline, some of its derivatives and 2,2′-bipyridyl have been re-evaluated using more realistic experimental errors.

Effect of temperature on the ionisation constants of 2-, 3- and 4-nitrobenzoic, phthalic and nicotinic acids in aqueous solution

The association constants (equivalent to pKa) on the molar scale for the equilibria between hydrogen ion and the 2-, 3- and 4-nitrobenzoate, phthalate, hydrogen phthalate and nicotinate anions and the nicotinic acid zwitterion have been determined in aqueous solution at constant ionic strength from spectrophotometric data at various temperatures between 288 and, in some cases, 473 K. 3- and 4-nitrobenzoic acids were stable to 473 K, 2-nitrobenzoic acid decomposed at 423 K and nicotinic acid at 408 K, and the absorption spectrum for the phthalic acid system was unsuitable for use above 448 K. Only one reaction, namely the protonation of the nicotinate anion [C6H4NO2]–, was isoelectric and the association constant describing the formation of the zwitterion decreased with increasing temperature. The plot of pKa against reciprocal temperature was linear within experimental error leading to temperature-invariant values of ΔH(exothermic) and ΔS with ΔCp= 0 for the association reaction. To 408 K, the association constant for the protonation of the zwitterion changed little in terms of the experimental errors. For 2-nitrobenzoic acid the plot of pKa against reciprocal temperature was also approximately linear. In this case the abnormally high acid strength at room temperature is caused largely by the highly endothermic nature of the association reaction and the acid becomes appreciably weaker at high temperature. For the rest the association constants (pKa) were greater at the highest temperatures employed than at 298 K which was largely caused by the high, positive entropy change for the association reaction resulting from a decrease in the dielectric constant of the bulk solvent as the temperature increased. Plots of pKa against reciprocal temperature were markedly non-linear with minima observed in some cases. These plots were analysed in terms of continually varying values of ΔH, ΔS and ΔCp over the temperature range although in some cases the changes in ΔCp were hardly significant in terms of the likely experimental errors.

Substituted phenols as ligands. Part V. Six co-ordinate cobalt(II) and nickel(II) adducts with nitrogen bases and water

Abstract The preparation and properties of nickel(II) and cobalt(II) complexes of phenolates with 2-methoxy, 2-ethoxy, and 2,6-dichloro-substituents as adducts with pyridine, N,N,N 1 ,N 1 -tetramethylethylenediamine, and water are reported. The electronic spectra and magnetic moments for the nickel(II) complexes are consistent with octahedral, weak field stereochemistry but those for the high spin cobalt(II) compounds are less readily explained. Isomorphism is found for one pair of complexes suggesting that the stereochemical arrangements of both metal ions are similar. Large distortions from regular octahedral (O h ) symmetry would account for the properties observed for the cobalt(II) compounds.

Nine-coordinate adducts of tetrakis(thenoyltrifluoroacetonato)uranium(IV): equilibrium constants from 1H NMR and electronic spectroscopy

Time-averaged chemical shifts in the 1H NMR spectra of aniline, pyridine and some derivatives, induced by coordination in 1:1 complexes to the paramagnetic 5f2 uranium(IV) as its complex with the thenoyltrifluoroacetonato anion [U(TTA)4], have been used to find equilibrium constants in benzene and acetone solution. The bound chemical shifts are shown to be solvent independent. In acetone the equilibrium constant for the formation ofU(TTA)4·H2O was found to be 4.0±0.2 dm3 mol−1 from 1H NMR spectroscopy. Equilibrium constants have also been determined by electronic spectroscopy in benzene solution, in which U(TTA)4 itself is eight-coordinate. The results were correlated with the basicity of the substrate and the effects of steric hindrance were evaluated. U(TTA)4 is nine-coordinate in acetone through solvent coordination and the addition of substrate caused no or small changes to the electronic spectrum.

Some metal halide–phosphorus halide–alkyl halide complexes. Part II. Reactions with niobium and tantalum pentachlorides and tungsten hexachloride

The reaction systems RCl + R′PCl2+ MClx(R = t-butyl, R′= chloride or methyl) have been investigated with the metal halides NbCl5, TaCl5, and WCl6. In each case, complexes of the type (RR′PCl2)(MVCl6) have been characterised by vibrational spectroscopy. Magnetic susceptibility measurements are reported for the tungsten complexes.