A. Navaza

Crystal structure of the clathrate compound [dibromotetra(pyridine)copper(II)]·pyridine. Characterization by EXAFS of the pyridine desorption product

Powder samples of the new compound [Cu(C5H5N)4·Br2](C5H5N) and of its desorption product have been studied by EXAFS. The crystal structure of [Cu(C5H5N)4Br2]·(C5H5N) has been determined from three-dimensional X-ray diffraction data and refined to theR value 0.038 for 379 observed reflections. (orthorhombic,Ccca,a=12.033(8),b=14.764(3),c=16.768 Å,V=1897(3) Å3,Z=4). The copper atom lies on a 222 symmetry site and is hexacoordinated with four nitrogen and two bromine atoms, forming an elongated octahedron with the bromine atoms in apical positions (Cu−Br distance: 3.201(2) Å, Cu−N1/N2 distances: 2.02(1)/2,07(1) Å). The host molecules (Cu(C5H5N)4Br2) form layers parallel to the (001) plane. Cavities in the space between these layers, bound by pyridine ligands protruding into this space, are occupied by the guest molecules (C5H5N). The guest desorption at room temperature is accompanied by a chemical and structural destruction of the host, leading to the known compound Cu(C5H5N)2Br2.

Bis(μ-benzoato-κO:κO')-bis[(benzoato-κ2O,O')(N,N-dimethylformamide-κO)dioxouranium(VI)]

The action of dimethylformamide on diaqua(benzoato)chlorodioxouranium(VI), in the presence of β-cyclodextrin, yields the title compound. The crystal structure of this new complex reveals that the linear uranyl is equatorially surrounded by five O atoms, one form a dmf molecule, two form a bidentate, benzoate anion and one each from two separate bridging benzoate ligands, shared by the U atoms forming a neutral dimeric entity. The average U-O distance involving the bridging benzoates [2.31 (1) A] is significantly shorter than that involving the other benzoates [2.44 (2) A]

The Heptakis-(2,6-di-O-methyl)-β-cyclodextrin Inclusion Complex with Acetic Acid

A novel monomer-type structure of heptakis-(2,6-di-O-methyl)-β-cyclodextrin in a typical monoclinic herringbone scheme has been determined by single crystal X-ray diffraction. Crystal data: space group P21, Z = 2, a = 15.165(6), b = 10.613(3), c = 23.188(8) Å, β = 102.02(4)°, V = 3650(3) Å3 and R = 0.094 for 2933 observed MoKα reflections with I > 3σ(I). A unique water molecule located in the intermolecular spaces, reinforces the cohesion between the herringbone chains. The analysis of the electron density distribution suggests that an acetic acid molecule is trapped within the macrocycle cavity, alternately with a water molecule.

Nesting inclusion compounds : the X-ray structure of the 15-crown-5 sodium diphenylethyl diphenylmethyl cyanoacetonate complex

The action of sodium cyanide ongem -diphenyl-chloropropanone under phase transfer conditions in the presence of 15-crown-5 yields the title compound as a minor product. The crystal structure of this complex reveals that, in the solid state, the [15-crown-5-Na+] guest species is found within a loose cage of diphenylethyl diphenyl cyanoacetonate molecules with one open side of the cage blocked by an adjacent 15-crown-5 molecule. Colourless crystals of the compound belong to the monoclinic space groupP21/n witha = 12,255(2) Å,b = 13,005(1) Å,c = 23,433(2) Å, β = 95,92(1) ° andDc = 1.23 g cm−3 forZ = 4.