Timothy J. R. Weakley

X-Ray crystallographic and tungsten-183 nuclear magnetic resonance structural studies of the [M4(H2O)2(XW9O34)2]10– heteropolyanions (M = COII or Zn, X = P or As)

The crystal structures of K10[Co4(H2O)2(PW9O34)2]·22H2O (1) and isomorphous K10[Zn4(H2O)2(AsW9O34)2]·23H2O (2) have been determined {Mo-Kα radiation, space group P21/n, Z= 2; (1)a= 15.794(2), b= 21.360(2), c= 12.312(1)A, β= 91.96°, R= 0.084 for 3 242 observed reflections [I 3σ(I)]; (2)a= 15.842(4), b= 21.327(5), c= 12.308(4)A, β= 92.42(4)°, R= 0.066 for 4 675 observed reflections [F 3σ(F)]}. The anions have crystallographic symmetry and non-crystallographic symmetry very close to 2/m(C2h). Each consists of two [XW9O34]9– moieties [α-B isomers; X = P (1) or As (2)] linked via four CoIIO6 or ZnO6 groups. Two Co or Zn atoms each carry a water ligand. The 183W n.m.r. spectra of the anions [Zn4(H2O)2(XW9O34)2]10–(X = P or As) confirm that the anions retain 2/m symmetry in aqueous solution. Homonuclear coupling constants between 183W atoms are 5.8–9.0 Hz for adjacent WO6 octahedra sharing edges, and 19.6–25.0 Hz for octahedra sharing corners.

Heteropolytungstate complexes of the lanthanoid elements. Part III. Crystal structure of sodium decatungstocerate(IV)–water (1/30)

Crystals of the title compound are monoclinic, space group C2/c, a= 18·14(1), b= 18·62(1), c= 18·51 (1)A, β= 95·9(5)°, Z= 4. The heavy atoms were located by direct methods and the oxygen and sodium atoms by difference Fourier analyses, with block-diagonal least-squares refinement to R 0·083 for 2781 independent reflections measured on a diffractometer. The analysis confirms that the heteropolyanion is a heterodecatungstate, and not an octatungstate as originally reported. The cerium atom, on a two-fold crystal axis, takes two pentatungstate ligands, W5O18H5–, each of which is derived from a W6O192– anion by the loss of one tungsten atom and its apical oxygen and consists of five WO6 octahedra sharing edges. The eight oxygen atoms about the cerium define a square antiprism. The sodium cations have distorted octahedral co-ordination.

A versatile synthetic route to dehydrobenzoannulenes via in situ generation of reactive alkynes

This paper outlines the development of a protocol that allows in situ generation of unstable alkynes under Pd-catalyzed cross-coupling conditions. Cu-mediated intramolecular cyclization of the resultant α,ω-polyynes provides dehydrobenzoannulenes as singular species, in very good overall yields, and in a variety of topologies that are inaccessible by traditional routes or previously available in low yield only. In addition, we will discuss the solid-state structure and reactivity of these macrocycles, as well as the ability of the planar dehydrobenzoannulenes to support weak induced ring currents.

Crystal structures of [NEt3H]5[XCoIIW11O39]·3H2O (X = P or As)

The orthorhombic crystal structures of [NEt3H]5[XCoIIW11O39]·3H2O for X = P and As have been determined with data collected at room temperature, and for X = P at –100 °C, using Mo-Kα radiation. For the latter the space group is Pna21, a= 21.670(11), b= 14.805(4), c= 20.393(5)A and Z= 4. The structure consists of chains of α-Keggin-type molecules joined by W–O–links aligned in the a-axis direction. The Co/W occupancy at the link is disordered, with 61% Co on one side and 39% on the other. Further probable disorder, by lamellar merohedral twinning on (001) and by misorientation of the triethylammonium ions, has obscured the ethyl groups and the water molecules. In polarized light the crystals are deep wine-red normal to the chains (in the b direction), but nearly colourless in the a and c directions. The structure of the arsenate is similar to that of the phosphate.

Crystal structure of the pyridine salt of gambogic acid

Pyridinium gambogate, (C5H6N)+(C38H43O8)−, crystallizes in space group P212121 with cell parameters a = 9.536(3) Å, b = 18.502(4) Å, c = 22.223(4) Å, Z = 4. The X-ray structural analysis [R(F) = 0.098 for 1714 data with I ≥ σ(I); wR(F2) = 0.157 for all 3874 independent data] confirms the structure assigned to gambogic acid on the basis of NMR analysis and of the X-ray structure of isomorellin p-bromobenzenesulfonate. A hydrogen bond links the pyridinium nitrogen atom to a carboxylate oxygen atom. The gambogate ion has two distinct faces that differ in polarity. The hydrophobic face is dominated by the alkenyl chains attached to C(2) and C(17) and a segment of the polycyclic ring system. The hydrophilic face includes the carboxylate ion and several oxygen atoms.

Synthesis, Characterization, and Isomerization of an Iridabenzvalene

Metal- halogen exchange of vinylcyclopropene 4 followed by addition of [(Me3P)2Ir(CO)Cl] produced iridabenzvalene 5. The metallabenzene valence isomer was characterized by NMR and IR spectroscopy and by X-ray crystallography. Isomerization of complex 5 to iridabenzene derivatives 6 and 13 was accomplished by thermolysis and by Ag+ ions, respectively. The former transformation was a clean and quantitative process that displayed first-order kinetics.

Structure of sodium bis(pentadecatungstodiphosphato)diaquatetrazincate hydrate (16∶1∶50)

AbstractCrystals of Na16[Zn4(H2O)2(α-P2W15O56)2]·∼50H2O are triclinic,

Triaquahenicosatungstodiphosphate(6–) heteropolyanion, [P2W21O71(OH2)3]6– : X-ray crystallographic and 183W nuclear magnetic resonance structural studies

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