August 1998 issue
cif-access (inorganic compounds)
The crystal structure of the sanidine feldspar analogue potassium iron germanate, quenched from 873 K, has been determined in the C2/m space group using a flux-grown single crystal. A partial ordering of Fe is observed on the two tetrahedral sites, with a preferential occupancy for the T1 site (32%) over the T2 site (18%). This ordering is also reflected by the difference in the size of the tetrahedral sites [mean <T1-O> 1.765 (2) Å versus <T2-O> 1.749 (2) Å].
cif-access (metal-organic compounds)
The structure of bis(1,2-ethanediammonium) dichloride tetrachloromercurate, originally determined at 153 K [Wen et al. (1992). Inorg. Chim. Acta, 193, 77-85], has been redetermined with room-temperature data carefully corrected for absorption effects.
This compound was isolated as a deactivation product from olefin metathesis polymerization and its crystal structure was determined. The W atom has a square-pyramidal coordination geometry with the phenylimido ligand occupying the apical position. A relatively short W-N(imido) bond, 1.736 (3) Å, is interpreted as arising from the interaction of the lone pair of N(imido) and the W metal center.
This complex is isostructural with the analogous nickel complex but has slightly longer metal-oxygen bonds. The crystal is built up from infinite one-dimensional chains of hydrogen-bonded molecules.
The structure of [Co(C18H20N4O4)]ClO4.H2O is isomorphous with that of the corresponding tetrafluoroborate monohydrate [Mandel & Douglas (1989). Inorg. Chim. Acta, 155, 55-69]. The cobalt(III) atom has distorted octahedral coordination with trans carboxylato groups.
The structure of bis(di-n-propyldithiocarbamato-S,S')nickel(II) has been reported previously in the rhombohedral space group R-3. The new triclinic polymorph shows similar structural features with a square-planar environment for the Ni atoms.
cif-access (organic compounds)
The pyrrolidine ring has an envelope conformation. The crystal packing is stabilized by an intermolecular hydrogen bond.
The pyrrolidine ring has a conformation intermediate between a twist and an envelope. The crystal packing is stabilized by an intermolecular hydrogen bond.
3C4H14N22+.P6O186−.3H2O contains tetragonal channels parallel to the a direction of the unit cell built up by four rows of P6O18 rings and completed by organic groups. The condensed phosphoric groups are centrosymmetric, while the three independent organic cations have no internal symmetry.
C4H12N22+.H2P2O72− has a typical layer structure composed of organic and inorganic groups centred on planes parallel to (100). The formula unit consists of one acidic anion and two crystallographically independent organic half cations. The H2P2O72− anions have no internal symmetry whereas the piperazinium cations are centrosymmetric.
Neutron powder diffraction studies confirm the results of a previous X-ray single-crystal study of the protonated compound. The water molecules form hydrogen bonds of different strengths. Deviation from a random distribution of the H atoms (H/D enrichment effect) has been established.