Colin H. L. Kennard

Preparation and crystal structures of the silver(I) carboxylates [Ag2{C6H4(CO2)2}(NH3)2], [NH4][Ag5{C6H3(CO2)3}2(NH3)2(H2O)2]·H2O and [NH4][Ag{C4H2N2(CO2)2}]

Two silver ammine complexes with the polyprotic aromatic acids benzene-1,2-diacarboxylic acid (phthalic acid) and benzene-1,3,5-tricarboxylic acid (trimesic acid) have been prepared and their structures determined using single-crystal X-ray diffraction and infrared spectroscopy. Complex 1, [Ag2{C6H4(CO2)2}(NH3)2], is a hydrogen-bonded polymer based on a simple diamminephthalatodisilver(I) species, with an ammonia molecule and a single phthalate carboxylate oxygen bonded to separate silver atoms, giving essentially linear co-ordination [Ag–N 2.116(3), Ag–O 2.134(2)A, O–Ag–N 175.3(1)°]. All three ammine hydrogens are involved in intermolecular hydrogen-bonding interactions, giving a chain polymer. Complex 2, [NH4][Ag5{C6H3(CO2)3}2(NH3)2(H2O)2]·H2O, is a two-dimensional sheet polymer based on a pseudo-centrosymmetric S-type trimer unit, linked by the carboxylate groups of two independent trimesate residues [Ag ⋯ Ag 2.928(1), 2.946(1)A]. The two ammonia molecules are also bonded linearly to two independent silvers [Ag–N 2.141 (6), 2.159(7)A; N–Ag–O 166.1(2), 170.2(2)°]. The terminal silvers provide bonding links to adjacent trimesate carboxyl oxygens between the layers while the third trimesate carboxyl group forms conventional centrosymmetric bis[(carboxylato-O,O′)silver(I)] dimers [Ag ⋯ Ag 2.847(1), 2.856(4)A], with water molecules in the axial sites for the dimer. A third compound 3, ammonium silver(I) pyrazine-2,3-dicarboxylate [NH4][Ag{C4H2N2(CO2)2}], has also been prepared using a procedure similar to that for 1 and 2. However, unlike them, it has no bonded ammines but has a distorted trigonal-planar co-ordination involving two carboxylate oxygens [Ag–O 2.333(6), 2.376(5)A] and one heteronitrogen [Ag–N 2.249(6)A], from three separate ligand molecules, giving a polymer structure.

STRUCTURE OF CALCIUM ALUMINATE SULFATE CA4AL6O16S

The commensurately modulated structure of polycrystalline calcium aluminate sulfate was determined using spectroscopic and electron microscopic information and calculations with the bond-valence method. The neutron powder diffraction data were refined by the Rietveld profile technique. Calcium aluminate sulfate, Ca4Al6O16S, MW = 2440 Da, orthorhombic, Pcc2, a = 13.028(3) Angstrom, b = 13.037(3) Angstrom, c = 9.161(2) Angstrom, U = 1556(1) Angstrom(3), Z = 4, Dc = 2.60 g cm(3), lambda (neutron) = 1.893 Angstrom (Ge monochromated), mu R(neutron) = 0.42, R(Bragg) = 0.046, R(p) = 0.06, R(wp) = 0.08 is a twofold superstructure of sodalite which is generated by z modulation of the framework along [1 1 0] of the cubic subcell

Synthesis, spectral characterisation, redox studies of isomeric dichloro-bis-[1-alkyl-2-(naphthyl-(α/β)-azo)imidazole]ruthenium(II). Single crystal X-ray structure of blue-green dichloro-bis-[1-ethyl-2-(naphthyl-α-azo)imidazole] ruthenium(II)

Abstract Ruthenium(II) complexes with 1-alkyl-2-(naphthyl-(α/β)-azo)imidazoles (α/β-NaiR), where R=Me, Et and Bz have been synthesised. Two isomers, blue-green, trans–cis–cis and blue, cis–trans–cis of the composition Ru(NaiR)2Cl2, are chromatographically separated. With reference to the pairs Cl, N(imidazole) and N(azo), the blue-green isomer is assigned to a trans–cis–cis configuration and the blue, isomer is assigned to a cis–trans–cis configuration. They are characterized by IR and 1H NMR data. The structure of the blue-green complex, Ru(α-NaiEt)2Cl2 has been determined by X-ray crystallography and the trans–cis–cis configuration has been confirmed. The complexes exhibit t2(Ru)→π* (ligand) MLCT transitions in the visible region. Cyclic voltammetry shows a Ru(III)/Ru(II) couple for the blue-green isomer at 0.4–0.5 V and the blue complexes at 0.5–0.6 V versus SCE, as well as multiple azo reductions.

The Crystal Structure of Silver(i) (2-Carbamoylphenoxy)acetate

The crystal structure of anhydrous silver(i) (2-carbamoylphenoxy)acetate has been determined by X-ray diffraction and refined to a residual of 0.041 for 1532 observed reflections. The complex forms crystals with space group C 2/c and Z 4 in a unit cell of dimensions a 20.789(6), b 5.202(1) c 17.318(6) A, s 105.89(2)°. The structure is based on a centrosymmetric bis-carboxylate bridged dimer [Ag-O 2.228(3), 2-266(3) A, O-Ag-O 155.8(1)° Ag…Ag 3-001(1) A] which is extended into an infinite zigzag polymer through the axial positions via the carbamoyl oxygens of adjacent ligands [Ag-O 2.494(3) A]. Symmetrical long-range interactions of phenyl-carbon to silver are also found in the structure [Ag-C 3.094, 3.078(4) A].

Characterization of stress-whitening of tensile yielded isotactic polypropylene

The microstructure of tensile tested isotactic polypropylene (iPP) specimens was studied by grey level measurement, scanning electron microscopy (SEM), differential scanning calorimetry (d.s.c.) and X-ray diffraction (XRD). SEM revealed that the necked regions of specimens in which stress-whitening had occurred as determined by the grey level measurement had craze-like structures which were parallel to the drawing direction. D.s.c. analysis showed that the necked regions of tensile specimens which remained transparent after yielding had an additional low-melting temperature peak. However, no additional melting peaks were found in the stress-whitened specimens. Inspection of the XRD patterns indicated that, apart from its original α-crystallites (a monoclinic structure) which were broken and reoriented after drawing, there was no new types of crystals formed in the transparent specimens. It was found by quantitative XRD analysis that the crystallites were broken into finer pieces in the whitened specimens than in the transparent ones.

Silver(I) carboxylates—part 11. The preparation and crystal structures of silver(I) nicotinate, ammonium silver(I) nicotinate monohydrate, ammonium silver(I) dipicolinate dihydrate, and silver(I) N-acetylanthranilate dihydrate

Abstract Two silver(I) complexes with pyridine-3-carboxylic acid (nicotinic acid) one with pyridine-2,6-dicarboxylic acid (dipicolinic acid) and one with N-acetylanthranilic acid have been prepared and their crystal structures determined by X-ray diffraction. Complex 1, catena-{[pyridine-3-carboxylato-(O,O′)]silver(I)} is based on a three-coordinate silver repeating unit [AgO, 2.258, 2.280(8) A; AgN, 2.362(10 A], with the carboxylate groups bridging alternating silvers in the convoluted sheet structure [AgAg, 3.035(1) A]. Complex 2, ammonium bis[pyridine-3-carboxylato-(itO,N,N′)]silver(I) monohydrate is also polymeric but with the three-coordinate distorted trigonal planar silver centres involving two nitrogens from the two nicotinate ligands [AgN, 2.248, 2.269(3) A]. The bridging link in the chain polymer is provided by a carboxylate oxygen [AgO, 2.342(3) A]. Partial refinement of the structure of ammonium dipicolinate dihydrate (3) indicates that it is a polymer based on a five-coordinate pentagonal planar silver centre with bonds to a nitrogen and two oxygens of a dipicolinate ligand and two carboxylate oxygens of an adjacent ligand. Complex (4), bis[(N-acetylanthranilato)-aquasilver(I)] dihydrate forms discrete centrosymmetric bis-carboxylato-(O,O′) dimers [AgO, 2.185(2), 2.207(3) A; AgAg, 2.831(2) A]. An unusual feature of the structure is the presence of waters in the axial sites of the dimer [AgO, 2.518(4) A.

Lead macrocyclic complexes : the synthesis, complex formation and X-ray crystal structures of [Pb(L1)(NO3)2] and [Pb(L2)(NO3)2] (L1 = 1,4,7,10-tetraoxa-13-azacyclopentadecane, L2 = 1,4,7,10,13-pentaoxa-16-azacyclooctadecane)

Lead(II) complexes of the 15- and 18-membered ring macrocycles 1,4,7,10- tetraoxa-13-azacyclopentadecane (L1) and 1,4,7,10,13-pentaoxa-16-azacyclooctadecane (L2) have been prepared. The stability constants for the 1 : 1 lead complexes [L1, log β 6.0(1); L2, log β 8.4(1)] have been determined potentiometrically (0. 1 M NEt4ClO4, 95% methanol). The complexes [Pb(L1)(NO3)2] and [Pb(L2)(NO3)2] have been examined by 13C NMR spectroscopy and single-crystal X-ray structural analysis. In the molecule [Pb(L1)(NO3)2] the lead(II) cation is situated 1.52 A above the plane of the macrocyclic ring. The Pb-N(1) distance of 2.465(5) A is the shortest bond to lead(II) in the structure which also exhibits two short [2.627(4) and 2.643(4) A] and two long [2.909(4) and 2.992(5) A] PbOmacrocycle distances. The presence of a stereoactive lone pair of electrons on the cation is inferred from this stereochemistry. In [Pb(L2)(NO3)2] the lead(II) cation lies in the macrocyclic cavity. As for [Pb(L1)(NO3)2], the PbN(1) distance of 2.539(9) A is the shortest bond to lead in this structure, which has in addition two short [2.694(7) and 2.697(8) A] and three long [2.877(10), 2.951(6) and 2.999(9) A] PbOmacrocycle interactions. There is no evidence for a stereoactive lone pair of electrons in this structure.

The crystal structure of (hydrogen ethylenediaminetetraacetato) aquoferrate(III) and gallate(III)

The crystal structure of (hydrogen ethylenediaminetetraacetato)-aquoferrate(III) has been determined using three dimensional x-ray diffraction data. There are four molecules in the monoclinic unit cell, spacegroup P21/c with dimensions, a = 8.36, b = 8.94, c = 17.83 A, β = 99.5°. In the structure, the ethylenediaminetetraaceticacid group wraps itself around the iron atom as a pentadentate ligand, leaving one uncomplexed carboxylic acid. A water molecule completes the octahedral co-ordination sphere currounding the metal, (FeN, 2.22; FeO, 1.98; FeH2O, 2.07 A). The crystal structure of isomorphous (hydrogen ethylenediaminetetraacetato)-aquogallate(III) has also been refined (a = 8.35, b = 8.84, c = 17.56 A, β = 99.9°, P21/c Z = 4, GaN, 2.14; GaO, 1.95; GaH2O, 1.95 A).

The utility of 4-aminobenzoic acid in promotion of hydrogen bonding in crystallization processes: the structures of the cocrystals with halo and nitro subsituted aromatic compounds, and the crystal structures of the adducts with 4-nitroaniline (1:1), 4-(4-nitrobenzyl)pyridine (1:2), and (4-nitrophenyl)acetic acid (1:1)

A number of molecular adducts of 4-aminobenzoic acid (4-ABA) have been prepared and characterized using infrared spectroscopy and in three cases by X-ray diffration methods. These three compounds are with 4-nitroaniline [(4-ABA) (C6H6N2O2)], 4-(4-nitrobenzyl) pyridine, [(4-ABA)2(C12H10N2O2)4], and (4-nitrophenyl)acetic acid, [(4-ABA) (C8H7NO4)]. Other compounds described are with 4-chlorobenzoic acid, [(4-ABA) (C7H5ClO2)], 4-bromobenzoic acid, [(4-ABA) (C7H5BrO2)], 4-cyanobenzoic acid, [(4-ABA) (C7H6N2)], 2-nitrobenzoic acid, [(4-ABA) (C7H5NO4)], and 3-nitrobenzoic acid, [(4-ABA) (C7H5NO4)]. All compounds have 1:1 stoichiometry except that with 4-(4-nitrobenzyl)pyridine (1:2) which is unique in being retro-stoichiometric. A review of the systematics of the 4-aminobenzoic acid adducts is also made, particularly with respect to the infrared characterization of the cocrystalline materials and prediction of their NLO potential.

The stereochemistry of organomercury compounds. II. A redetermination of the structure of mercury(II) cyanide by neutron diffraction

The crystal structure of mercury(II) cyanide, Hg(CN)2, has been determined using three dimensional neutron diffraction data. The compound crystallizes out in a tetragonal unit cell, space group I42d; cell dimensions, a = 9.643, c = 8.88 ». There are eight molecules per unit cell. Interatomic distances and angles are: Hg-C, 2.015(3); C-N, 1.137(3); non bonding Hg-N, 2.742(3) »; C-Hg-C, 175.0(2)°; Hg-C-N, 177.0(3)°.