Crystal structure analysis of the carbon tetrabromide clathrate of hexakis(phenylseleno)benzene

The 12 inclusion compound of hexakis(phenylseleno)benzene (1) with CBr₄ is trigonal, space groupR , witha=14.474(3),c=21.487(4) Å, and three host and six guest molecules in a unit cell referred to hexagonal axes. A true clathrate structure is found and in each closed cage there are two carbon tetrabromide guest molecules, orientated such that a C–Br bond of each is colinear with thec-axis of the crystal. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82002. To obtain copies, see page ii of this issue.     

Structural studies of 2,2-Diphenyl-1-picrylhydrazine: A clathrate forming compound

2,2-Diphenyl-1-picrylhydrazine was crystallized from both tetrahydrofuran and chloroform. The crystal structures of samples from both preparations were determined by X-ray diffraction at low temperatures. Both crystals are clathrates with solvent molecules included as guest species in a host framework formed by the diphenylpicrylhydrazine molecules. The structures are rhombohedral, space groupR3. For the crystal from tetrahydrofuran, at 228 K,a = 25.820(4),c = 15.096(2) Å,Z = 18,R = 0.084 andwR = 0.133. For the crystal from chloroform, at 115 K,a = 25.453(12),c = 15.083(3) Å,Z = 18,R = 0.117 andwR = 0.153. Each unit cell contains three cavities which have approximate cylindrical shape with diameter 7.8 Å and height 6.0 Å, and 3 point symmetry. The integrity of the host framework is maintained only through van der Waals forces rather than through intermolecular hydrogen bonding as is found in many other known organic cathrates. The conformation of the trinitroanilino group of the hydrazine molecule is similar to that in the related trinitroanilinocarbazole molecule. The N-N bond approximates a single bond, and both hydrazine N atoms aresp ² hybridized.     

A Fourier-transform infrared and laser-Raman spectroscopic investigation of 4,4′-bipyridyl-transition metal(II) tetracyanonickelate clathrates

The FT-IR and Raman spectra are reported of M(4,4-bipyridyl)Ni(CN)₄·nG (where M = Mn, Fe, Co, Cu or Zn and G = benzene or aniline;n = 0–2) clathrates. The host structure consists of a three-dimensional rigid lattice formed by infinite polymeric layers of {M-Ni(CN)₄} and 4,4-bipyridyl bridges between the metal (M) atoms of the adjacent polymeric layers. Bidentate 4,4-bipyridyl molecules are found to be centrosymmetric in the structure.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Superconductivity and crystal structure of the solid solutions of Ba8−δSi46−xGex (0?x?23) with Type I clathrate structure

The solid solutions of barium containing Type I clathrate, Ba_8−δSi_46−xGe_x (0?x?23) were prepared under high-pressure and high-temperature conditions of 3 GPa at 800°C. All the solid solutions showed superconductivity, and the transition temperature (T_c) decreased from 8.0 to 2.0 K as the germanium content increased from x=0 to 23 in Ba_8−δSi_46−xGe_x. The single crystals with five different compositions were obtained and the structures, compositions, and site occupancies were determined from X-ray single-crystal analysis. A slight barium deficiency was observed at Ba1 (2a) sites for all the clathrates. The Ge atoms replaced the Si atoms at the Si3 (24k) site in the composition range of x<8, and then at the Si2 (16i) site. The crystals had a slight deficiency in the covalent (Si, Ge) network and the deficiency increased with the increase of the Ge content.     

FT-IR Spectroscopic Study of M(1,2-Ethanedithiol)Ni(CN)4·Benzene (M=Co,Cd) Clathrates

New Hofmann-ethanedithiol-type clathrates, M(1,2-Ethanedithiol)Ni(CN)₄·Benzene (M=Cd,Co), have been obtained in the powdered form. By vibrational spectroscopy of these two new compounds, it is exhibited that their structures are similar to those of the other Hofmann-type clathrates.     

A new host compound for the selective inclusion of ethanol

A new host compound of the onium salt type,N-(3-biphenylmethyl)quininium bromide (1), is described. This host compound shows an unusually high selectivity for the inclusion of ethanol. Using this clathrand, ethanol can be extracted from a variety of solvent mixtures. In most cases, a remarkable enrichment of the ethanol is observed. The following solvents in a mixture with ethanol remain in the mother liquid: methanol,n-propanol,n-hexane, pyridine.     

Inclusion complexes of the natural product gossypol. The formation of different gossypol polymorphs on decomposition of channel type inclusion complexes

The existence of seven gossypol polymorphs has been established. Two of them are obtained by direct crystallization from solution. The remaining five polymorphs are the products of desolvation of channel type complexes (tubulates). Each isostructural group of the complexes on decomposition gives one polymorph. Gossypol thus possesses specific peculiarities in terms of the decomposition of its tubulates, and also the absence of thermotropic polymorphic transitions.     

Vibrational Spectroscopic Study of [1,2-bis(4-pyridyl)ethane]metal(II) Tetracyanonickelate(II). 2 m-Xylene Clathrates

Four new Hofmann-type clathrates of the form M(bpa)₂Ni(CN)_4· 2m-xylene (M = Mn , Fe , Co and Ni; bpa = 1,2-bis(4-pyridyl)ethane) have been synthesized and characterized by vibrational spectroscopy. The M(bpa)₂Ni(CN)₄ (M = Fe and Co) host structure is similar to the classical Hofmann-type host framework composed of layers of a two dimensional catena-metal tetra--cyanonickelate(II) network, but in M(bpa)₂Ni(CN)₄ (M = Mn and Ni), the Ni(CN)₄ moiety behaves as a bidentate –[NC-Ni(CN)₂-CN–]– unit in the host framework.     

Two clathrates of bis(isothiocyanato)tetrakis(4-methylpyridine)magnesium(II) as a host with 4-methylpyridine as a guest

Two clathrate modifications of the title host with 4-methylpyridine (4-CH₃C₅H₄N) as a guest have been determined at –50°C. [Mg(4-CH₃C₅H₄N)₄(NCS)₂] · 2/3(4-CH₃C₅H₄N) · 1/3H₂O is trigonal, space group , witha=27.630(7),c=11.219(3) ÅV=7417(4) ų,Z=9,D _calc=1.171 g cm^–3,(CuK )=18.506 cm^–1, finalR=0.064. [Mg(4-CH₃C₅H₄N)₄(NCS)₂] · (4-CH₃C₅H₄N) is tetragonal, space group I4_l/a, witha=16.944(7),c=23.552(9)Å,V=6762(5) Å,Z=8,D _calc=1.191 g cm^–3, (CuK )=18.200 cm^–1, finalR=0.071.The structures consist of molecular packings of the same host complex units and the guest species. The Mg(II) cation is octahedrally coordinated to theN-atoms of four 4-methylpyridine and twotrans-coordinated isothiocyanato ligands in the host molecule. The conformations of the molecule are considerably different both in symmetry and in geometry in these two structures. The guest 4-methylpyridine molecules are disordered into channels which have different topology in these two clathrates resulting in different thermal stability.     

Inclusion compounds formed between α,ω-(long-carbon-chain)-diaminecademium(II) tetracyanonickelate(II) host and aromatic guest molecules

Inclusion compounds with the general formula Cd(NH₂(CH₂) _n NH₂)Ni(CN)₄·xG were prepared forn=4 to 8, and for G of such an aromatic guest molecule as pyrrole, benzene, aniline, toluene, toluidine, xylene, xylidine, dichlorobenzene, trimethylbenzene, tetramethylbenzene, ethylbenzene, styrene, or isopropylbenzene, with varyingx. Generally, longer chain lengths of ,-diamine in the host permit the inclusion of bulkier guest molecules. However, the presence of an amino group on the phenyl ring of the guest appears to impart a special affinity with the hosts.