Showing papers on "Isostructural published in 1973"

HoPtSn and other intermetallic compounds with the Fe2P-type structure

Abstract: Crystallographic and Mossbauer studies have been made on new ternary equiatomic compounds R.E.XSn (X = Rh, Pd, Ir, Pt) which have a hexagonal crystal structure, isostructural with Fe2P ( D 3 3 h — P 6 2m ). A typical example is HoPtSn with a 0 = 7.418 ± 0.001 A , c a = 0.535 , and V M = 63.00 A . The X-ray analysis leads to the following site assignments: Ho located in 3(g) sites at x, 0, 1 2 ; Pt atoms in 1(b) at 0, 0, 1 2 and 2(c) at 1 3 , 2 3 ,0; and Sn atoms in 3(f) at x, 0, 0. The volume per formula weight of YbRhSn is intermediate between those of TmRhSn and LuRhSn which indicates that Yb is trivalent in these compounds. The 119Sn Mossbauer spectra at 295 K are symmetrical or slightly asymmetrical doublets which have been fitted to the model of site occupation given by the Crystallographic results for HoPtSn. An asymmetry in the spectrum at 295 K vanishes at 77.3 K for TbRhSn; this behavior is indicative of an anisotropic Debye-Waller factor. The isomer shift at 295 K is similar for all alloys; a typical value is + 1.8 mm/s (compared to + 2.6 mm/s for β-Sn). However, the quadrupolar coupling varies by a factor of two (0.34–0.70 mm/s). At 4.2 K TbRhSn and HoPtSn show asymmetric broadening which is interpreted as magnetic in origin.⧹At 77.3 K GdRhSn is broadened by 40% which may indicate magnetic order above this temperature.

Conformations of the Li-Antamanide Complex and Na-[Phe4, Val6]Antamanide Complex in the Crystalline State

Abstract: Antamanide, a cyclic decapeptide isolated from the poisonous mushroom Amanita phalloides, preferably complexes with Na+, but in less polar solvents, e.g., acetonitrile, also with Li+ or K+. The selectivity of complexation makes it an important model for the study of conformational requirements of ion binding. The conformations of the lithium antamanide complex and the Na-[Phe4, Val6]antamanide complex have been established by x-ray diffraction analyses of single crystals. The two compounds are isostructural, but not isomorphous. The complexes are folded into a globular shape with an approximate 2-fold axis. Two of the peptide linkages are in the cis conformation, Pro2-Pro3 and Pro7-Pro8. There are only two intramolecular hydrogen bonds. Four C==O groups have their O atoms directed inward to form four Li-O or Na-O ligands. The fifth ligand to the metal ion is provided by a solvent molecule. The conformation found in the crystalline state is different from any of the conformations proposed for the sodium antamanide complex in solution on the basis of nuclear magnetic resonance data.

The Crystal Data of Ternary Rare Earth Borides, RCo2B2

Abstract: Compounds with the composition of RCo2B2 (R=La, Nd, Sm, Gd, Tb, Dy, and Y) were prepared by arcmelting methods. Their crystal structure was investigated by means of X-ray diffraction. These ternary rare earth borides crystallize in the tetragonal lattice. The lattice parameters are a=3.616±0.003 A and c=10.215±0.005 A for LaCo2B2 and a=3.561±0.002 A and c=9.358±0.005 A for YCo2B2. The good agreement between the X-ray diffraction intensities observed and those calculated shows that the ternary borides, LaCo2B2 and YCo2-B2, crystallize in the ThCr2Si2-type structure. The crystallographic data obtained for LaCo2B2 and YCo2B2 are as follows: space group 14/mmm(D4h17); 2R in 2(a), 4Co in 4(d), and 4B in 4(e) with z∼3⁄8. The boron atoms in this structure are situated at the center of a trigonal prism formed by four rare earth atoms and two cobalt atoms. We also found the RCo2B2 compounds to be isostructural with LaCo2B2 and YCo2B2, where R=Nd, Sm, Gd, Tb, and Dy. However, efforts to prepare CeCo2B2 and ErCo2B2 ...

Crystal and molecular structures of two polymeric organotin carboxylates, C5H12O2Sn and C5H9F3O2Sn

Abstract: The crystal and molecular structures of trimethyltin(IV) acetate and trimethyltin(IV) trifluoroacetate have been determined from three-dimensional X-ray data collected by counter methods using MoKα radiation. Both compounds crystallize in the orthorhombic space groupPnma withZ = 4. The acetate hasa = 10·516,b = 8·013,c = 9·706 A and the trifluoroacetate hasa = 10·567,b = 9·237,c = 9·985 A. ConventionalR-factors for the two compounds following least squares refinement are, for the acetate, 0·018 (for 731 reflexions) and, for the trifluoroacetate, 0·055 (for 460 reflexions) respectively. The compounds are isostructural and are polymeric with tin atoms linked by carboxylate bridges which are exactly planar. The tin atoms are in five-fold trigonal bipyramidal coordination with the methyl groups in the basal plane and oxygen atoms at the apices. Sn-O interatomic distances are, for the acetate, 2·205(3) and 2·391(4) A, and for the trifluoroacetate, 2·18(1) and 2·46(2) A.

Les hypovanadates MV3O7 (M = Ca, Sr, Cd). Structure cristalline de CaV3O7

Abstract: The phases MV3O7 with M = Ca, Sr, Cd are isostructural. The structure type has been determined by the X-ray single-crystal method...

Synthesis and Structural Studies of the Metal(II) Mercury Tetrathiocyanate Complexes with Lewis Bases

Abstract: Complexes of the type MHg(SCN)4•2L, where M = Mn2+ to Zn2+ and Cd2+ and L = THF or Py, have been synthesized and characterized by spectroscopic methods. The thiocyanato groups are bridging between M2+ and Hg2+ whereas the donor atom of the ligand is coordinated to M2+ which now attains octahedral configuration. Definite shifts in certain absorption bands of the ligands upon coordination to M2+ are correlated to the formation constant of the metal atom involved in coordination. Electronic spectral data as well as magnetic measurements show that the M2+ is a high spin species in an octahedral environment. The X-ray powder photographs indicate that Co2+ and Zn2+ complexes are isostructural and also most probably are Mn2+ and Fe2+. Tentative assignments for metal–NCS, M–ligand, Hg—S, and L—M—L absorption bands are discussed.

Crystal structures of tris(NN-diethyldithiocarbamato)oxo-niobium(V) and -vanadium(V)

Abstract: The crystal and molecular structures of the isomorphous and isostructural title compounds [MO(CS2·NEt2)3][(I), M = Nb; (II), M = V] have been determined by single crystal X-ray diffraction, the structures being solved by heavy-atom methods and refined by least-squares methods to R 0·096 [(I) 1680 visually estimated reflections] and 0·103 [(II) 671 diffractometer reflections]. Both are monoclinic, space group P21/a, Z= 4; (I): a= 17·28(1), b= 13·305(5), c= 10·774(5)A; β= 90·09(6)°; (II): a= 17·27(1), b= 13·22(1), c= 10·72(1)A, β= 90·5(1)°.In each structure the seven-co-ordinate metal atom is surrounded by an oxygen atom [NbO, 1·74(1), VO, 1·65(2)A] and three bidentate dithiochelates, two lying in the equatorial plane of a distorted pentagonal bipyramid. The five equatorial distances are almost equal (Nb–S 2·547–2·596, V–S 2·46–2·50 A) while that opposite to the oxygen is longer (Nb–S 2·753, V–S 2·63 A). All 0M–S angles are greater than 90°.

Preparation and Crystal Structures of Some Compounds of the A3 BX5 Type (A = Cs, Tl, NH4, B = Mn, Fe, Co, X = Cl, Br)

Abstract: The compounds Cs3 FeBr5, Cs3MnBr5,Tl3FeCl5, Tl3CoCl5, (NH4)3FeCl5 and (NH4)3CoCl5 were prepared and their crystal structures determined. Cs3FeBr5, Cs3MnBr5, Tl3FeCl5 and Tl3CoCl5 belong to the tetragonal system, space group 14/mcm, isostructural with Cs3CoCl5 [1]. (NH4)3FeCl5 and (NH4)3CoCl5 belong to the orthorhombic system, space group Pnma, isostructural with (NH4)3ZnCl5 [2].

Alkali-metal complexes. Part VII. Crystal and molecular structures of the o-nitrophenolatobis(1,10-phenanthroline) complexes of sodium and rubidium

Abstract: The structures of the title complexes have been determined by X-ray analysis from diffractometer data. The sodium complex has triclinic crystals, a= 10·436(6), b= 10·062(6), c= 14·867(7)A, α= 96·98(2), β= 104·02(1), γ= 119·12(4)°, and its structure was determined by direct methods. The rubidium complex, isostructural with the corresponding potassium and caesium complexes, is also triclinic, a= 11·413(6), b= 13·214(6), c= 10·068(15)A, α= 99·06(5)β= 114·80(5), γ= 101·78(3)°; this structure was determined from Patterson and electron-density maps. The structures were refined by least-squares methods to R 0·074 (Na complex, 1371 observed reflections) and 0·051 (Rb complex, 2107 observed reflections).In the sodium complex, the cation is six-co-ordinate, interacting with the three chelating ligands in pseudo 32 symmetry, and the crystal structure of this complex is of monomeric units. The rubidium complex has a similar pseudo-three-fold symmetry of the chelating ligands but, with a larger co-ordination sphere, the cation also accepts co-ordination with a second o-nitrophenolate ion, which thus bridges cations about a centre of symmetry. Dimeric units, bound by van der Waals' forces, form the crystal structure. The packing arrangements in both complexes appear to depend on the interactions of overlapping phenanthroline molecules about centres of symmetry.The phenanthroline molecules in both complexes have similar dimensions: all are non-planar, but there is no characteristic pattern of bending or twisting. The cations are displaced from the mean planes of the phenanthroline molecules by up to 0·63 A. In the o-nitrophenolate ions, the variations in bond lengths and angles in the ions are significant and are explained in terms of resonance structure and second-order hybridisation effects. The nitro-groups are rotated about the C–N bonds by 18·6 (Na) and 14·5°(Rb).

The crystal structure of cesium aquopentachlororhodate(iii)

Abstract: The crystal structure of cesium aquopentachlororhodate(III) has been determined by X-ray diffraction using counter techniques. The complex crystallizes in the orthorhombic space group D 2h 17-Amam with a=8.023(3) A, b=17.271(10) A, and c=7.353(4) A. The crystal sank in methylene iodide (density 3.32 g-cm−3) in agreement with a density of 3.69 g-cm−3 calculated for four formula units in the unit cell. A total of 679 independent reflections was used in solving the structure, which was refined to a conventional R factor of 0.065 and a weighted R factor of 0.069. The complex is approximately octahedral, with Rh-Cl distances of 2.300 A and 2.337 A, and a Rh-O distance of 2.096 A. The rhodium compound is isostructural with its ruthenium analogue.

Structures and some reactions of π-diene derivatives of octacarbonyldicobalt

Abstract: Norbornadiene and conjugate dienes react with Co2(CO)8 to give {(π-diene)Co2(CO)6}(I) and then {(π-diene)-Co(CO)2}2(II)(diene = norbornadiene, isoprene, and 2,3-dimethylbuta-1,3-diene). The hexacarbonyl derivatives (I) are not tautomeric, and have structures based on that of the bridged isomer of octacarbonyldicobalt. Both (I) and (II) react with iodine to give {(π-diene)Co(CO)2I} derivatives which could be detected but not isolated, with SnX4 to give mixtures of {(π-diene)Co(CO)2SnX3} and {Co(CO)4SnX3}(X = Cl, Br, or I), and with Ph3PAuCl, HgX2, and Ph3SnCl to give only Ph3PAuCo(CO)4, Hg{Co(CO)4}2, and Ph3SnCo(CO)4 respectively. Monodentate tertiary phosphines convert (I) to a mixture of (II) and {(R3P)Co(CO)3}2via the unstable intermediate ionic species [(π-diene)Co(CO)2PR3][Co(CO)4]. Similar salts are stable and have been isolated with Ph2PCH2CH2PPh2i.e.[{(π-diene)Co(CO)2}2{Ph2PCH2CH2PPh2}][Co(CO)4]2. They are reduced by NaBH4 to {(π-allyl)Co(CO)2}2{Ph2PCH2CH2PPh2}. The i.r. spectra of the products are reported and their structures discussed. The reactions are compared, and contrasted, with those of the related isoelectronic and isostructural π-cyclopentadienyl complexes of iron.

Photoconductive copolymer of N-vinylcarbazole and N-vinylphthalimide

Abstract: Polymeric compositions comprising the product of the addition polymerization of N-vinylcarbazole and at least one member selected from the group consisting of N-vinylphthalimide and the isostructural modifications thereof. Many of the above polymeric products are photoconductive and, thus, are suitable for use in electrophotography.

Some properties of cesium and rubidium perchloratoberyllates

Abstract: 1. An x-ray study was made of the isostructural Cs2Be(ClO4)4 and Rb2Be(ClO4)4. The parameters of the cubic unit cells were determined. 2. The method fo differential-thermal and thermogravimetric analyses was used to study the heat stability of the cesium and rubidium perchloratoberyllates.

Cation Disorder and Magnetic Properties of Certain Garnet Type Crystals

Abstract: The garnet of composition Bi3−2xCa2xFe5−xVxO12 (BiCaVIG) is derived from the well known yttrium iron garnet (YIG) wherein Y3+ ions are completely replaced by a combination of Ca2+ and Bi3+ ions and Fe3+ ions are partly substituted with V5+ ions (1, 2).Though BiCaVIG is isostructural to YIG one can expect a certain amount of difference between the crystal fields in the crystallographic sites in these two compounds. One way to study the crystal fields would be to study and compare the magnetic behaviour of a paramagnetic ion when present in these two crystals, as it is well known that the energy levels of an ion are perturbed by the crystal field and its symmetry. Further one can also expect that the presence of cations of different chemical nature as in the BiCaVIG lattice to modify the energy levels as it will be shown later. In this work we will describe the magnetic properties of some paramagnetic ions such as Co2+ (3d7), Ru3+ (4d5) and Tb3+ (4f8), when they are doped in BiCaVIG crystals and compare the results with those obtained when they are present in YIG crystal. Such differences in behaviour could tell us about the sites wherein are present the paramagnetic ions.