John C. Dewan

The zirconocene induced coupling of benzyne with nitriles: Synthesis, structure and reactions of novel azametallacyclopentenes

Abstract A series of novel azazirconacyclopentenes have been prepared by the thermolysis of diphenylzirconocene in the presence of one equivalent of a wide variety of nitriles. An X-ray crystal structure shows these metallacycles to be dimeric in the solid state.

Crystal structures of HM(SiPh3)(CO)3(PPh3)(M=Fe, Ru) formed from photolysis of M(CO)4PPh3 in the presence of HSiPh3

Abstract Near-UV irradiation of M(CO)4PPh3 (M=Fe, Ru) at 298 K in deoxygenated hydrocarbon solutions containing molecules having a Si-H bond gives clean formation of products of the formula HM(CO)3(PPh3)(Si ). Several isomers of such species are possible and X-ray crystallography has been used to unambiguously establish the isomer formed in the photochemical reaction. The crystal structure of the isomer of HM(SiPh3)CO)3(PPh3) formed by the photochemical reaction of M(CO)4PPh3 with HSiPh3 is reported for M=Fe (1) and Ru (2). Both complexes have the same geometry, a distorted octahedron with the COs meridional and the H cis to both the SiPh3 and the PPh3. The crystals are triclinic, space group P 1 . Crystal parameters for 2, (followed in square brackets by those for 1), are: a=12.535(3) [12.32(2)], b=14.244(3) [14.50(4)], c=10.174(3) [10.06(2)] A, α=104.98(2) [106.3(2)], β=98.52(2) [98.2(2)], γ=71.92(2)° [72.0(2)°], V=1663.63 [1637.38] A3.

Fluoride crystal structures. Part 28. Bis(tetraethylammonium)µ-oxo-bis[pentafluorotantalate(V)]

The structure of the title compound has been determined by the heavy-atom method from 1 267 reflections, measured with a diffractometer, and refined by full-matrix least-squares methods to R 0.069. Crystals are monoclinic, space group P21/n, a= 8.57(1), b= 13.68(2), c= 11.79(2)A, β= 96.1 (1)°, Z= 2. In the structure two tetraethylammonium ions counterbalance each [Ta2OF10]2– complex anion in which the two tantalum atoms are bridged by an oxygen atom (Ta–O 1.875 A; Ta–O–Ta 180° by symmetry); the five remaining octahedral sites around each tantalum atom are occupied by fluorine atoms (mean Ta–F 1.90 A).

Studies on tellurium–carbon bonded compounds. Part 1. The crystal structure of 3,3-dimethylpentane-2,4-dionato(2–)-C1,C5-tellurium(II)

The structure of the title compound has been determined by the heavy-atom method from 765 reflections, measured with a diffractometer, and refined by full-matrix least-squares methods to R 0.033.Crystals are orthorhombic, space group Pmnb, a= 9.37(1), b= 7.96(1), c= 10.93(1)A, Z= 4. In the discrete molecules of the complex a tellurium atom is bonded to one bivalent pentane-2,4-dione ligand via the two α-carbon atoms [Te-C 2.168(5)A, C–Te–C 86.4(2)°]. This structure is the first to be reported wherein a pentane-2,4-dione ligand binds in this manner. All hydrogen atoms have been located and refined. There is no evidence for any hydrogen-bonding between the molecules.

Crystal structure of bis-[(1,8-naphthyridine)mercury(I)] diperchlorate

The crystal structure of the title compound has been determined from X-ray diffractometer data by the heavy-atom method and refined by full-matrix least-squares to R 0·08 for 1033 observed reflections. Crystals are monoclinic, space group P21/n, a= 18·639(3), b= 5·164(1), c= 11·224(1)A, β= 105·95(1)°, with two of the dimeric species in the cell. Hg–Hg is 2·511(1)A; the naphthyridine ligand is essentially unidentate and coplanar with the mercury and has a very short Hg–N distance of 2·03(2)A.

Structural studies of the 1 : 1 addition complexes of niobium and tantalum pentachlorides with o-phenylenebis(dimethylarsine)

The addition of o-phenylenebis(dimethylarsine), ‘diars.’ in equimolar ratio to the pentachlorides of tantalum and niobium has yielded addition complexes shown by X-ray crystallographic structure determination to have the probable stoicheiometries [TaCl4(diars)2]+[TaCl5(OEt)]–(I), [NbCl4(diars)2]+2[NbCl3O2]2–(II), and [NbCl4-(diars)2]+[NbOCl4]–(III). Crystals of (I) are triclinic, space group P. a= 12.983(4), b= 14.484(6), c= 12.359(6)A, α= 108.04(3), β= 102.17(5), γ= 110.35(5)°, Z= 2, 2 448 observed reflections being refined to R 0.09. Crystals of (II) are monoclinic, space group C2/c or Cc, a= 20.877(4), b= 16.086(3), c= 19.458(2)A, β= 106.25(1)°, Z= 4, 1 183 observed reflections refined to R 0.08. Crystals of (III) are triclinic, space group Pa= 14.815(3), b= 12.273(2), c= 10.397(2)A, α= 92.03(1), β= 103.56(2), γ= 110.80(2)°, Z= 2, 2 473 observed reflections refined to R 0.06. In all three, an eight-co-ordinate dodecahedral cation is found; mean distances: Ta–As 2.761, Ta–Cl 2.40, Nb–As 2.743, and Nb–Cl 2.426A. The structures were determined from diffractometer data [(I) and (III) by the heavy-atom method, (II) by direct methods].

Solid-state properties of materials of the type Cs4MX6(where M = Sn or Pb and X = Cl or Br)

Two new compounds Cs4SnBr6 and Cs4SnCl6 have been prepared and the CsBr–SnBr2 phase diagram is described. Phases of the type Cs4Sn1 –nPbnBr6 –xClx(where n= 0–1, x= 0–6) have been examined by X-ray diffraction, electrical conductivity, Mossbauer spectral, and optical reflectance techniques. The electrical conductivity and optical properties of the phases are explained in terms of the population of solid-state bands by the non-bonding electron pairs of the Group 4 atoms. The structures of all the phases are related to that of Cs4PbCl6 which has been redetermined.

Fluoride crystal structures. Part 27. Seleninyl difluoride at –35 °C

The structure of the title compound (m.p. 15 °C) has been determined by the heavy-atom method from 184 diffractometer reflections, measured at –35 °C by use of a nitrogen-gas cooling device, and refined by full-matrix least-squares methods to R 0.082. Crystals are orthorhombic, space group Pca21, a= 5.65(1), b= 7.46(1), c= 6.24(1)A,Z= 4. In the structure each selenium atom has one close oxygen (Se–O 1.62A) and two close fluorine neighbours (mean Se–F 1.70 A) giving a pyramidal co-ordination. These units are then linked through two oxygen bridges (mean Se ⋯ O 2.76 A) and one fluorine bridge (Se ⋯ F 3.03 A) to form a layer arrangement perpendicular to [010]. with a much distorted octahedral co-ordination around the selenium atom.

Structural studies of potassium tetrafluorochromate(III), K[CrF4], and the novel mixed chloride fluoride, dipotassium dichlorohexafluorotrichromate(II), K2[Cr3Cl2F6]

The crystal structures of potassium tetrafluorochromate(III), K[CrF4](1), and dipotassium dichlorohexafluorotrichromate(II), K2[Cr3Cl2F6](2), are reported. The structure of (1) consists of infinite triangular anionic columns comprising approximately planar Cr3F9 units linked above and below by fluoride bridges, the columns being separated by K+ ions. Each CrIII atom is octahedrally co-ordinated by six F atoms. The structure of (2) contains two crystallographically independent CrII atoms which have distorted octahedral co-ordination by four equatorial F atoms and two axial Cl atoms. The Cr atoms are linked together by single Cr–F–Cr bridges and also by a novel chloride fluoride double bridge. The structure can also be thought of as comprising two-dimensional CrF2 sheets, held together by Cl atom bridges. Charge balance is maintained by K+ ions. Crystal data for (1) are: a= 15.76(1), b= 7.43(1), c= 18.38(1)A, Z= 24, orthorhombic, space group Pnma, final R= 0.041 for 1 975 diffractometer data with Io > 3σ(Io). Crystal data for (2) are: a= 6.726(1), b= 11.157(5), c= 7.391(3)A, β= 125.31(4)°, Z= 2, monoclinic, space group P21/c, final R= 0.041 for 1 044 diffractometer data with Io > 2σ(Io).

Crystal structures of octacaesium and octarubidium docosaniobates

Crystals of Cs8Nb22O59 and Rb8Nb22O59are isomorphous. The structures of the two compounds have been determined by direct methods from 967 (Cs) and 791 (Rb) independent reflections, measured with a diffractometer, and refined by full-matrix least-squares methods to R 0.043 (Cs) and 0.102 (Rb). Crystals are rhombohedral (indexed on the hexagonal triple cell), space group Rm, a= 7.53(1) and c= 43.02(6)A(Cs), a= 7.53(1) and c= 43.39(6)A(Rb). The structure consists of NbO6 octahedra linked together through corners and edges, with the alkali-metal cations occupying positions which give an approximately close-packed array with the oxygen atoms.