Philip G. Harrison

Structural studies in main group chemistry : XXIII. Estertin derivatives, structural and spectroscopic studies

Abstract The crystal and molecular structures of three ‘estertin’ derivatives, Cl3SnCH2CH2CO2Me, Cl2Sn[CH2CH2CO2Me]2 and Cl2Sn[CH2CH2CONH2]2, are reported. Cystals of Cl3SnCH2CH2CO2Me are orthorhombic, space group P212121, with a 9.2981, b 10.5389, and c 10.0885 A; those of Cl2Sn[CH2CH2CO2Me]2 are monoclinic, space group P21/c, with a 8.0107, b 15.9104, c 13.4109 A, and β 131.0044°; and those of Cl2Sn[CH2CH2CONH2]2 are also monoclinic, space group Cc, with a 9.1314, b 12.8672, c 13.0317 A, and β 126.6032°. Crystals of Cl3Sn(CH2CH2CO2Me) and Cl2Sn[CH2CH2CO2Me]2 both consist of discrete molecules, but extensive intermolecular hydrogen-bonding occurs in crystals of Cl2Sn[CH2CH2CONH2]2. Intramolecular carbonyl oxygen-to-tin coordination occurs in all three compounds. Vibrational and mass spectra are also reported, and are assigned in accordance with the determined structures. Tin-119 Mossbauer studies demonstrate that it is possible to investigate the nature of organotin additives to PVC by this method. Preliminary investigations show that Bu2Sn(IOTG)2 added to PVC undergoes only partial IOTG for chlorine exchange at the milling stage, but is completely converted to Bu2SnCl2 after thermal degradation. Both BuAcSn(IOTG)3 and BuAcSn(βMeOct)3 undergo complete sulphur ligand for Cl exchange during the milling process giving BuAcSnCl3 as the species detected. Degradation to some unidentified organotin species occurs on heating.

The Mössbauer recoil-free fraction and structure : II. Di-μ3-oxo-bis-(μ-dichloro)-bis[μ-dimethyltin(IV)]-bis-[chlorodimethyltin(IV)], and its ethyl homologue

Abstract The crystal structure of the title compound, [ClMe 2 SnOSnMe 2 Cl] 2 , the partial structure of its ethyl homologue, [ClEt 2 SnOSnEt 2 Cl] 2 , and tin-119 Mossbauer data for the two compounds in the temperature range 77–175.5 K are reported. Crystals of [ClMe 2 SnOSnMe 2 Cl] 2 are monoclinic, space group P 2 1/ c , with a 7.258(1), b 18.581(6), c 8.733(8) A, β 109.76(4)°, Z = 4. The structure consists of centrosymmetric dimeric units held in a two-dimensional polymeric lattice by anionic chloride bridges. The central part of the dimeric unit consists of an essentially planar four-membered Me 2 ovbar|SnOSnMe 2 O ring, to the oxygen atoms of which are appended [ClMe 2 Sn] units. The geometries at both endo- and exo-cyclic tin atoms are similar, forming contacts to six neighbouring atoms in a distorted arrangement midway between trigonal bipyramidal and octahedral. Crystals of [ClEt 2 SnOSnEt 2 Cl] 2 are also monoclinic, space group P 2 1/ n , with a 10.3712(4), b 9.4699(6), c 15.9432(1) A, β 106.43(3)°, Z = 4, but the structure has only been partly solved due to disorder. The major component of the disorder (∼75%) has a structure similar to that of [ClMe 2 SnOSnMe 2 Cl] 2 . The second component is best described as a series of alternating [R 4 Sn 2 O 2 ] and [R 2 SnX 2 ] units, in which two of the latter units chelate [Sn 2 O 2 ] four-membered rings. Tin-119 Mossbauer isomer shift, quadrupole splitting, and recoil-free fraction temperature dependence have also been studied and correlated with the crystallographic data. The variation of the recoil-free fraction of [Me 4 Sn 2 Cl 2 O] 2 varies linearly with temperature in the range 77–175.5 K with a temperature coefficient of −1.26 × 10 −2 K −1 . In contrast, the ethyl compound exhibits a discontinuity at ca. 110 K, attributed to a phase change involving a relaxation of the coordination about one of the two crystallographically independent tin atoms.

Lead(II) carboxylate structures

Abstract The structures of four lead(II) carboxylate complexes, lead(II) formate, lead(II) acetate trihydrate, lead(II) pentafluorobenzoate bis(methanol) solvate, and the lead(II)-EDTA hydrate, Pb2(EDTA)2 3H2O, are described. Lead(II) formate has a three-dimensional polymeric structure, lead(II) acetate trihydrate a chain structure linked by hydrogen-bonding to form parallel sheets, lead(II) pentafluorobenzoate bis(methanol) solvate a linear chain structure, and the lead(II)-EDTA hydrate, a structure comprising both isolated monomeric and dimeric units. In each case, the lead atom is eight-coordinated although with vastly differing stereochemistries, except for the monomeric units in the lead(II)-EDTA complex, which contain seven-coordinated lead.

Tin oxide surfaces. Part 17.—An infrared and thermogravimetric analysis of the thermal dehydration of tin(IV) oxide gel

The thermal dehydration of high-surface-area (ca. 180 m2 g–1) tin(IV) oxide gel has been studied by thermogravimetric analysis and infrared spectroscopy in the temperature range 293–673 K. The thermogravimetricanalysis data show that two types of physisorbed water are present, one which is largely removed by evacuation at ambient temperature and a more strongly held type which is removed by evacuation at 373–423 K. Further mass loss occurring at higher temperatures is due to the condensation of hydroxyl groups on the surface of the oxide particles. The amount of physisorbed molecular water present on the freshly prepared gel corresponds to a ca. three-monolayer coverage, reducing to ca. 0.74 of a monolayer after evacuation at 295 K, and is totally removed after evacuation at 423 K. The surface concentration of hydroxyl groups is determined to be 19.8 nm–2 at 423–473 K, falling to 16.2 nm–2 at 573 K and 13.0 nm–2 at 673 K. Infrared spectra confirm that physisorbed molecular water [v(OH) 3800–2000 cm–1, δ(OH) 1640 cm–1] is removed by 423 K. Isolated and hydrogen-bonded surface hydroxyl groups give rise to stretching modes at 3640 cm–1(sharp) and 3500 cm–1(very broad), respectively. Surface hydroxyl deformation bands are found at 870, 940, 1175 and 1245 cm–1. The bands at 870 and 950 cm–1 are removed on evacuation by 473 and 523 K, respectively. The deformation bands at 1175 and 1245 cm–1 which remain at 523 K are assigned to isolated surface hydroxyl groups. The band at 770 cm–1, which increases in intensity during dehydration, is assigned to surface Sn—O—Sn linkages formed by the dehydroxylation process. The results are interpreted in terms of hydroxylated exposed [100], [101](both of which contain clusters of three hydroxyl groups attached to each surface tin atom) and [110](which contains both isolated and geminal pairs of hydroxyl groups attached to surface tin atoms) crystal planes of the rutile structure, the former predominating.

X-ray photoelectron spectroscopic study of the oxidation and reduction of a cerium(III) oxide/cerium foil substrate

X-ray photoelectron spectroscopy has been used to examine the nature of the oxide overlayers on a passivated cerium metal foil as a function of a variety of oxidation and reduction treatments. Oxidation of a clean uncontaminated cerium(III) oxide surface is facile at room temperature and produces non-stoichiometric ceria (CeO2−x) at oxygen doses as low as 10 L. At higher doses the overlayer thickens, and after a dose of 160 L the layer depth exceeds the Ce 3d photoelectron attenuation distance of about 20 Å. High pressure treatment of the foil in oxygen (0.5 bar at RT and 473 K) produces CeO2 in a high degree of crystallographic order such that O 1s photoelectron intensities are increased above that expected from a randomly oriented powder. An attempt to reduce the CeO2 layer formed by controlled oxidation with CO (633 K, 14 h, 0.6 bar) results in the formation of a carbonated surface layer. Results following attempts to reoxidise this layer are discussed.

Normalization of Shear Test Data for Rate-independent Compressible Fabrics

This article describes a method of using both picture frame (PF) and bias extension (BE) tests together to characterize accurately the trellis shearing resistance of engineering fabrics under low in-plane tension conditions. Automated image analysis software has been developed to reduce the amount of laborious manual analysis required to interpret BE data accurately. Normalization methods for both PF and BE tests on rate-independent compressible fabrics are presented. Normalization of PF test results is relatively straightforward while normalization of BE test results for direct comparison with PF data is more complicated. The normalization method uses a number of simple assumptions to account for the nonuniform shear strain field induced across BE samples during testing. Normalized results from BE tests on samples of different aspect ratios are compared and provide validation of the theory.

Structural studies in main group chemistry: XXI. Complex formation between diphenyltin dichloride and benzthiazole and 2-aminobenzthiazole

Abstract Diphenyltin dichloride forms 1 1 adducts with both benzthiazole and 2-aminobenzthiazole, for which tin-119m Mossbauer quadrupole splitting data suggest trigonal bipyramidal and distorted octahedral geometries, respectively. X-ray diffraction studies of the adduct with benzthiazole confirm the five-coordinated structure, and crystals are orthorhombic, space group P 2 1 2 1 2 1 with a 11.521(4), b 12.349(8) and c 13.500(5) A. The structure was determined from diffractometer data using Patterson and Fourier techniques, and crystals consist of discrete non-interacting Ph 2 SnCl 2 · (benzthiazole) molecules. the two phenyl groups occupy two equatorial positions of the trigonal bipyramidal arrangement about the tin (mean SnC 2.112(8) A), the third equatorial site being occupied by a chlorine atom at a SnCl distance of 2.336(1) A. The second chlorine atom and the nitrogen atom of the benzthiazole ligand occupy the two axial positions (SnCl 2.446(1) A; SnN 2.548(2) A].

Structural studies in main group chemistry : XXIV. Trimethyltin 2-pyridylcarboxylate monohydrate

Abstract The crystal and molecular structure of the title compound has been determined by Patterson and Fourier techniques from diffractometer data using 4266 independent non-zero reflections. Cyrstals are orthohombic, space group Pca 2, with a 27.015(6), b 13.471(3), c 14.028(4) A, Z  4. The geometry at all four crystallographically independent tin atoms resembles that in Me 3 SnO 3 SPh.H 2 O and Me 3 SnNo 3 .H 2 0, with trigonal bipyramidal coordination and planar (Me 3 Sn) units. Axial coordination sites are occupied by an unidentate 2-pyridylcarboxylate group (mean SnO 2.18(2) A) and a water molecule (mean SnO 2.43(3) A). The crystal structure differs from that of the analogous phenylsulphonate and nitrate in possessing a three-, rather than a one-dimensional, network of hydrogen-bonds involving the pyridyl nitrogen atom, the carbonyl oxygen atom, and the water molecule.

Proton and phosphorus-31 nuclear magnetic resonance study of zinc(II)O,O′-dialkyl dithiophosphates in solution

Proton and 31P n.m.r. have been employed to investigate the constitution and behaviour of zinc(II)O,O′-dialkyl dithiophosphates in solution. The complexes Zn[S2P(OR)2]2(R = Et or Pri) are principally dimeric in chloroform and toluene with dissociation constants, KD(R, solvent), to monomers of 1.81 × 10–2(Et, CDCl3), 3.08 × 10–2(Et, toluene), 4.45 × 10–2(Pri, CHCl3), and 7.17 × 10–2 mol I–1(Pri, toluene) at 29 °C. Higher 31P chemical shift values and conductance data for solutions of these compounds in ethanol and tetrahydrofuran indicate that co-ordination of solvent and ligand ionization occur in these solvents. The 31P chemical shifts for complexes Zn[S2P(OR)2]2·L increase in the order L = pyridine < 2,2′-bipyridine < 2,2′: 6′,2″-terpyridine, and comparison with known structural data has shown that this change is due primarily to an opening of the SPS bond angle of the S2P(OR)2 ligands. The ‘basic’ zinc(II)O,O′-dialkyl dithiophosphates, Zn4[S2P(OR)2]6O, are unstable in solution, spontaneously, though reversibly, decomposing to ‘normal’ Zn[S2P(OR)2]2 and zinc(II)oxide as the temperature is increased. Pyridine (py) causes an irreversible decomposition of Zn4[S2P(OR)2]6O to Zn[S2P(OR)2]2·py and zinc(II).

Structural studies in main group chemistry : XXII. Structural and tin-119 mössbauer studies of some five-coordinate triorganotin anions

The structures of two complexes, [Ph3PCH2Ph]+[Bu3SnCl2−]− and [Ph3AsCH2COPh]+[Ph3SnCl2]−, have been determined by X-ray diffraction. Both materials are monoclinic, space group P21/c. Unit cell data for [Ph3PCH2Ph]+−[Bu3SnCl2]− are a 9.8521(6), b 16.9142(4), c 22.3517(7) A, β 91.4235(9)°; and for [Ph3AsCH2COPh]+[Ph3SnCl2]−a 34.9760(3), b 11.1290(5), c 24.2410(2) A, β 108.56(2)°, and both consist of the component ionic species. The organotin anions each have trigonal bipyramidal geometry with equatorial organic groups and axial halogens. In the [Ph3SnCl2]− anion the two SnCl bond distances are the same (2.58(1) and 2.60(1) A), but in [Bu3SnCl2]−, as in [Me3SnCl2]−, they are substantially different (2.573(7) and 2.689(6) A). The SnC bond distances also vary: [Ph3SnCl2]− 2.15(4), 2.16(3) and 2.25(5); [Bu3SnCl2]− 2.21(1), 2.20(2) and 2.29(2) A. Tin-119 Mossbauer data for these and several other similar complexes are also reported.