A. Cassol

Synthesis and x-ray crystal structure of a tin(IV) tetrahalide adduct with a crown ether

The polymeric structure of the complex, [SnCl 4 (H 2 O) 2 ]18-crown-6·2H 2 O, prepared by the addition of a solution of SnCl 4 to 18-crown-6, has been determined by X-ray analysis. The structure has been solved by three-dimensional Patterson-Fourier synthesis to a conventional R-factor of 0.13, by using 1394 reflections with I>3σ(I). The crystals are monoclinic, with a = 15.753(3), b = 15.072(3), c = 12.209(4), β = 97.77°(1.0), z = 4, and space group P2 1/ a . The tin atom is octahedrally coordinated to four chlorine atoms and two water molecules in cis positions. A very complex network of hydrogen bonding links together the tin coordination octahedron, the two water hydration molecules, and the two crystallographically-different half crown-ethers.

Crown ether complexes of lanthanoid and actinoid elements. Crystal and molecular structure of Nd(NO3)3 (18-crown-6)

Abstract Nd(NO3)3. 18-Crown-6 crystallizes in the orthorhombic system, space group Pbca with eight molecules in a cell of dimensions a = 15.512(9), b = 21.662(1), c = 12.141(6) A. The structure has been determined by Patterson heavy -atom methods and refined by full-matrix least squares to R = 0.038. The neodymium atom is coordinated by 6 oxygen atoms of the 18-crown-6 unit and by three bidentate nitrate groups; one of the more hindered side of the ring and two on the opposite side.

Relative stabilities of complexes of MO22+ (M = U, Np, and Pu) with monocarboxylate anions

Abstract Stability data for complexes of yl(VI) ions MO 2 2+ (M = U, Np, and Pu) with monocarboxylic ligands L are reported and discussed (L = CH 3 CO 2 − , C 2 H 5 CO 2 − , and CH 2 ClCH 2 CO 2 − ). Stability constants refer to the formation equilibria of complexes in aqueous NaClO 4 solution at 20° and 1 M ionic strenght. In the range of ligand concentrations examined, complexes are formed in which the highest average ligand number, n is three. The stability order of complexes of the various ligands examined is UO 2 2+ >NpO 2 2+ >PuO 2 2+ . The stabilities of complexes of a given MO 2 2+ ion increase with increasing ligand basicity, which suggests a strong hard character for these oxycations.

Preparation, crystal and molecular structure of GdCl3(18-crown-6)·EtOH

Abstract The structure of the title compound has been determined from single-crystal X-ray analysis. The triclinic cell has dimensions a = 13.225(3), b = 10.246(2), c = 8.283(2) A, α = 112.1(1), β = 101.9(1) and γ = 85.0(1)°, space group P 1 , Z = 2. The structure was refined by least square methods to the conventional R value 0.032 for 2791 observed reflections. The molecule is formed by [GdCl 2 EtOH(18-crown-6)] + cations and Cl − anions. In the cation the crown ether ligand, which includes the Gd ion, is folded away from the side where a chlorine and the ethanolic oxygen are coordinated to the metal ion; a second chloride ion is coordinated on the opposite side.

Thermodynamic properties of actinide complexes—IV Thorium(IV)- and uranyl(VI)-malonate systems

Abstract The stability constants and the enthalpies of formation of thorium(IV)- and uranyl(VI)-malonate complexes have been determined by potentiometric and calorimetric titrations in 1.00 M solutions of Na(ClO 4 ) at 25°C. All complexes formed are found to be stabilized by a large entropy gain. The values for the stability constants agree with an ionic bonding model. The malonate behaves as a bidentate ligand forming only chelate complexes.

Thermodynamics of complex formation in dimethyl sulphoxide. Silver(I) with quadridentate polyamines

The changes in free energy, enthalpy, and entropy for the complex-formation reactions in dimethyl sulphoxide (DMSO) between silver(I) and tetraamines 1,4,7,10-tetraazadecane (TRIEN), tris(2-aminoethyl)amine (TREN), and 1,5,8,12-tetraazadodecane (TNENTN) have been determined by potentiometric and calorimetric measurements at 25 °C and an ionic strength of 0.1 mol dm–3. All three amines form the very stable 1 : 1 complexes, acting as tetradentate ligands. Only TREN and TNENTN form other mono- and poly-nuclear coordinated species. Compositions and stabilities of the complexes are discussed in relation to the different structures of the ligands. From a comparison of the available experimental results on silver (I)–amino complexes in the two solvents, water and DMSO, some conclusions are made regarding the main factors determining the coordination properties in these systems.

Uranyl complexes with cyclic polyethers

Abstract Uranyl(VI) nitrate, chloride, and perchlorate complexes with the cyclic polyethers dibenzo-18-crown-6 and benzo-15-crown-5 have been synthesized. The compounds have been characterized by elemental analyses, molar conductances, infrared and electronic spectra, and thermal analyses. The infrared and conductivity data, together with a consideration on the general coordination behaviour of the uranyl ion, suggest that the uraniun is not located at the center of the cyclic ligand.

Complex of plutonyl ion with acetate

Abstract The complex formation between plutonyl and acetate ion has been investigated by means of potentiometric [H + ] measurements. The value of the complexity constants of the three mononuclear complexes have been determined in perchlorate medium of ionic strength I = 1 M at 20°C.

Silver(I)–polyamine systems in dimethyl sulphoxide. A thermodynamic and spectroscopic investigation

The thermodynamic parameters ΔG°, ΔH° and ΔS° of complexes of silver(I) with 3,3′-diaminopropylamine(DPT) as well as the heats of formation of silver(I) with 1,2-diaminoethane (EN), 1,3-diaminopropane (TN), and diethylenetriamine (DIEN) have been measured in dimethyl sulphoxide (DMSO) at 25 °C and in a medium of ionic strength 0.1 mol dm–3. N.m.r. spectra of solutions of silver(I) and ligands investigated have also been performed. From a combination of thermodynamic and spectroscopic data conclusions are drawn about the nature and structure of the complexes formed in solution. The silver(I) complexes are all stronger in DMSO than in water, reflecting the higher solvation of the ligands in water, through stronger hydrogen bonds, than in DMSO.

Coordination chemistry of lanthanides with cryptands. An X-ray and spectroscopic study of the complex Nd2(NO3)6 [C18H36O6N2]•H2O

By reacting neodymium nitrate hexahydrate with the cryptand 〈222〉 in methanol, the complex Nd 2 -(NO 3 ) 6 [C 18 H 36 O 6 N 2 ]·H 2 O was obtained and analyzed by single-crystal X-ray diffraction. The cell is triclinic P with a = 14.870(2) A, b = 13.261(2) A, c = 8.832(1) A, α = 91.2(1)°, β = 93.4(1)°, γ = 87.6(1)°, Z = 2 and U = 1736.6 A 3 . The structure was refined by least-squares methods to the conventional R = 0.039 for 6177 observed reflections. The compound contains the cations [Nd〈222〉(NO 3 )] 2+ and the anions [Nd(NO 3 ) 5 ·H 2 O] 2− , and is isostructural with the samarium analogue. Solid state fluorescence spectra of the title complex were measured at room and liquid nitrogen temperature, and the transitions 4 F 3/2 → 4 I 9/2 and 4 F 3/2 → 4 I 11/2 analyzed.