Ian W. Nowell

Organotin biocides: I. The structure of triphenyltin acetate

Abstract The crystal structure of triphenyltin acetate has been determined using heavy atom methods in conjunction with least squares refinement of data measured on a two-circle diffractometer. Crystals are monoclinic, space group P 2 1 / c , cell dimensions a 8.969(4), b 10.146(5), c 19.540(7) A, β 93.70(4)°, U = 1774.5 A and Z = 4. The structure was refined using 1841 observed reflections to give conventional discrepancy factors of R = 0.022 and R ′ = 0.023. The environment at tin is described in terms of a distorted, six-coordinate, mer -Ph 3 SnO 3 geometry, the first six-coordinate triorganotin structure authenticated crystallographically. Carboxylate bridges link subunits together to form a flattened helical polymer. Variable temperature Mossbauer spectroscopy ( a = dln A ( T )/d T =−1.91 × 10 −2 K −1 ) suggests that polymers of this type afford tin atoms the same vibrational freedom normally associated with non-interacting lattices.

Crystal and molecular structure of dimethylchlorotin 2-pyridinecarboxylate

Abstract The crystal and molecular structure of the title compound has been determined using Patterson and Fourier techniques from diffractometer data. Crystals are monoclinic, space group P2 1 / c with a 10.805(7), b 20.292(15), c 10.804(8) A, β 113.20(5)°, U 2177.37 A 3 . D m 1.85, D c 1.87 mg m −3 for Z = 8, with two independent molecules in the asymmetric unit. The structure has been refined using 1153 observed reflections to a final R = 0.075 and R ′ = 0.080. The 2-pyridinecarboxylate ligand bridges adjacent tin atoms to give a polymeric structure consisting of chains which run parallel to the a axis. The pyridine ring is orientated to facilitate a close approach of the nitrogen atom to tin and the Snue5f8N distances of 2.468(20), 2.505(25) A indicate the presence of a significant interaction. The resulting coordination about each tin atom is that of a distorted octahedron.

Mercury(II)halide complexes of tertiary phosphines. Part VI. The crystal structure of HgCl2(PPh32 and a comparison with related compounds

Abstract Dichlorobis(triphenylphosphine)mercury(II) has been confirmed as having a discrete monomeric structure by a full single-crystal X-ray diffraction study. However, the structure is distorted, with angles about mercury ranging from 134.1(1)° (Pue5f8ue5f8Hgue5f8P) to 98.6(1)° (Clz.sbnd;Hgue5f8P).The extent of the angular distortion, and the bond length data, have been compare with values for HgI2(PPh3)2 and HgCl2 (PEt3)2, and with initial data obtained in the present work for HgBr2(PPh3)2.It is thus confirmed that: (a) the greater the donor strength of the phosphine (e.g. PEt3), the more the Pue5f8Hg bonding dominates over Xue5f8Hg, with larger Pue5f8Hgue5f8P angles and longer Hgue5f8X bond lengths, and (b) the greater the mercury-halogen interaction (i.e. in iodides), the less significant is the Hgue5f8P bonding, with smaller Pue5f8Hgue5f8P angles and longer Hgue5f8P bonds.

Mercuric halide complexes of tertiary phosphines. Part I. The crystal structures of 1:1 complexes of triphenylphosphine, tributylphosphine and 1,2,5-triphenylphosphole

Abstract Complete crystal structure analyses have been carried out for 1:1 adducts of mercuric chloride with triphenylphosphine and 1,2,5-triphenylphosphole. In each case the structure consists of discrete centro-symmetric chlorine-bridged dimers, with mercury atoms in distorted tetrahedral environments, but with different Hgue5f8Cl bridge distances. Preliminary single-crystal X-ray photographs indicate that HgX2(PPH3) [X = Br or I] and HgBr2)1,2,5-triphenylphosphole) are isostructural with their chloro analogues. A full X-ray study has shown that the α-form of HgCl2(PBu3) comprises a discrete tetrameric unit, in which two unsymmetric dimers, related by a centre of symmetry, are loosely linked by further Hgue5f8Cl bridges.

Organotin biocides. Part 8. The crystal structure of triphenyltin formate and a comparative variable-temperature tin-119 Mössbauer spectroscopic study of organotin formates and acetates

The structure of triphenyltin formate has been determined by an X-ray study. Crystal data: monoclinic, space group B21/a, a= 20.176(8), b= 15.539(6), c= 21.952(10)A, β= 90.30(6)°, Z= 16. The geometry about tin is trigonal bipyramidal with a trans-O2SnR3 stereochemistry (R = Ph), leading to a chain polymeric structure for the lattice. The geometric distortions which accompany polymer formation are assessed, and used to interpret variable-temperature Mossbauer spectroscopic data for triphenyl-, tricyclohexyl-, and trimethyl-tin formates and acetates.

Mercuric halide complexes of tertiary phosphine. Part II. Crystal structures of 1:1 complexes of trimethylphosphine and triethylphosphine, and a rationalisation of structureal differences in the HgX2(PR3 series

Abstract The crystal structures of the complexes HgCl 2 (PMe 3 ) and HgCl 2 (PEt 3 ) have been completely characterised by single crystal X-ray analysis. In each case the structures are polymeric, with mercury atoms in distorted trigonal bipyramidal environments, but the actual arrangements are different. Whereas HgCl 2 (PEt 3 ) may be regarded as an extended chlorinebridged chain with essentially covalent bonding throughout, a very larg Pue5f8Hgue5f8Cl angle, and other structural features, characterise the trimethylphosphine complex as being of ionic formation, HgCl(PMe 3 ) + CL − . Preliminary single crystal photographs show that HgBr 2 (PMe 3 ) is isostructural with chloride, but HgI 2 (PMe 3 ) is apparently structurally different. The structures found are thus in marked contrast to those previously reported for 1:1 adducts of mercuric chloride with bulker phosphine, and the origins of the differences are discussed.

Complexes of zinc dialkyldithiocarbamates. Part I. Complexes with bidentate nitrogen ligands; crystal structure of 1, 10-phenanthroline zinc dibutyldithiocarbamate

Abstract Reactions of Zn(S 2 CNR 2 ) 2 (R=Me, Et, Bu, PhCH 2 ) with an excess of 2,2′-bipyridyl, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline or 3,4,7,8-tetramethyl-1,10-phenanthroline produce crystalline 1:1 complexes which are non-electrolytes. Thermogravimetric studies show that the 2,2′-bipyridyl complexes decompose by loss of ligand whereas the phenanthroline and substituted phenanthroline complexes undergo more complex decomposition. The crystal structure of [(1,10-phenanthroline)Zn(S 2 CNBu 2 ) 2 ] shows the monomeric nature of the complex, octahedral coordination of the metal, approximate planarity of the chelated ZnS 2 C unit and confirms infrared evidence for a degree of π-bonding in the Cue5f8N bond of the dithiocarbamate moiety.

Preparation, characterisation and crystal structure of dichloro tetrakis-(1-methylimidazoline-2(3H)-thione)palladium(II) dihydrate

Abstract The preparation of a complex of 1-methylimidazoline-2(3H)-thione (MImt) with palladium dichloride in acid solution is described. The stoichiometry, Pd(MImt)4Cl2·2H2O has been established by chemical and thermal analysis. The compound has been characterised by means of infrared spectroscopy and a single crystal X-ray study. The latter has confirmed the presence of uncoordinated water molecules, ionic chloride ions and square-planar [PdS4]2+ units bridged by H-bonds.

Mercury(II) halide complexes of tertiary phosphines. Part III. The crystal structure and vibrational spectra of the discrete dimer β-HgCl2(PBu3), and a comparison with the ‘tetrameric’ α-form ☆

Abstract A discrete dimeric form of the 1:1 adduct of mercury(II) chloride with tributylphosphine, β-HgCl2(PBu3), has been characterised by full single-crystal X-ray diffraction analysis. In contrast to the previously reported α-form, which has been described as ‘tetrameric’, β-HgCl2(PBu3) consist of centrosymmetric halogen-bridged dimers with no indication of any further association; the far-i.r. and Raman spectra may readily be assigned on this basis. The spectra of the α-form are markedly different to those of the β-isomer, yet these too are best interpreted in terms of a dimeric structure, albeit one significantly distorted by weak inter-dimer interactions rather than the ‘tetrameric’ structure previously advocated.

Mercury(II) halide complexes of tertiary phosphines. Part IV. The crystal structure of HgCl2(PCy3) and a re-interpretation of its vibrational spectra

Abstract The previously proposed dimeric structure of HgCl2(PCy3) has been confirmed by full single-crystal X-ray diffraction analysis. However, rather than consisting of asymmetrically halogen-bridged dimeric molecules, the unit cell contains two independent centrosymmetric dimers. Differences between the molecular parameters of the two types of dimer are discussed and their origins considered. The structure determination has shown that the previous assignments of the far-infrared and Raman spectra are erroneous, and correct re-interpretation is given.