James S. McKechnie

X-Ray studies on constrained ferrocene derivatives. Part I. Crystal structure of 1,12-dimethyl[1,1]ferrocenophane (1,1″:1′,1‴-diethylidendiferrocene)

The crystal and molecular structure of the title compound has been detrmined by X-ray diffraction methods. Crystals are monoclinic with a= 18·14(3), b= 6·10(2), c= 18·67(3)A, β= 119° 40′(10′), space group P2/c, and Z= 4; each molecule has C2 crystallographic symmtry. The structure was refined to R 0·083 on 1765 nonzero structure amplitudes collected photographically. The molecules exist in the eclipsed-form with an exo-methyl configuration. The cyclopentadienyl rings bonded to one iron atom are twisted with respect to each other by 21·5 and 23·9° in the two independent molecules, while the angle of tilt between such rings in slight (2–3°). There are dihedral angles of 30° 10′ and 31° 28′ between cyclopentadienyl rings in the same ligand in the two molecules. There is considerable geometric evidence that the molecular conformation is dictated by intramolecular H ⋯ H contacts, both within ligands and between ligands. The Fe ⋯ Fe distances are 4·620(2) and 4·595(2)A.

Crystal and molecular structure of a 1 : 1 bullvalene–silver tetrafluoroborate complex

The crystal structure of a 1 : 1 bullvalene–silver tetrafluoroborate monohydrate has been determined by X-ray methods on photographic data. The crystals are monoclinic with a= 8·49, b= 14·84, c= 18·74 A, and β= 107°40′. The space group is P21/c with Z= 8. The structure has been refined to a conventional R-factor of 0·12 on 2165 observed reflexions, incorporating individual anisotropic temperature factors for the silver ions and the atoms of the fluoroborate anions. The structure consists of irregular spirals of alternating bullvalence molecules and silver ions, which are also covalently bonded to water molecules. The water molecules form weak hydrogen bonds to the fluoroborate anions. There is no evidence for valence tautomerism occurring in the crystal. Some correlations between the position of the silver ion with respect to the double bond and the Ag+⋯ CC distances are presented.

Crystal and molecular structure of 6α-bromo-17β-hydroxy-17α-methyl-4-oxa-5α-androstan-3-one

The crystal and molecular structure of 6α-bromo-17β-hydroxy-17α-methyl-4-oxa-5α-androstan-3-one (I) has been determined by three-dimensional X-ray analysis. The crystals of (I) are orthorhombic with a= 12·23, b= 7·30, and c= 20·14 A, and the space group is P212121 with Z= 4. The structure has been refined to an R of 0·12 on 1500 reflexions collected photographically. The A : B, B : C, and C : D ring junctions are all trans. The lactone group in ring A is significantly non-planar with a C(2)–C(3)–O(4)–C(5) torsion angle of –23°. Some comparisons are made with other molecules containing lactone groups. The molecules in the crystal are linked in the c-directon by O–H⋯O hydrogen bonding.

Molecular structure in the crystalline state of a dicarbonium ion containing two triphenylmethylium ion groups

The X-ray analysis of the crystalline material C38H28Cl12Sb2 shows it to consist of a dicarbonium ion ([C38H28]2+), having two triphenylmethylium ions joined by a C–C bond through the para-positions of two of the phenyl rings, and two hexachloroantimonate anions. The crystals are monoclinic with a= 16·67(3), b= 12·81(3), c= 21·52(5)A, and β= 105° 0′(20′), and there are four [C38H28]2+[SbCl6–]2 entities in the unit cell; the space group is P21/c. The structure has been refined to R 0·10 for 3118 non-zero independent structure amplitudes collected photographically. The dicarbonium ion can be thought of as two triphenylmethylium ions separated by a biphenyl-like bond and each having a ‘propeller-like’ conformation around the plane defined by the central carbon atom and its three bonded neighbours; the phenyl rings make angles from 26·7 to 38·0° with the planes defined by the central carbon atoms and their bonded neighbours. The central biphenyl group has a dihedral angle of 39·5°. The shortest C⋯Cl– contact is 3·42 A.

Molecular structure of nordihydroguaiaretic acid

The structure and stereochemistry of nordihydroguaiaretic acid has been confirmed by the single-crystal X-ray analysis of a heavy-atom derivative. The crystals of 2,3-di-(2-bromo-4,5-dimethoxybenzyl)butane are monoclinic, space group P2/c, with a= 16·92, b= 4·81, c= 13·91 A, and β= 93° 55′, and Z= 2. The structure was determined from photographic data and has been refined to an R-factor of 0·11 on 1586 independent reflexions. The molecule has a centre of inversion and exists as the meso-form. Some effects due to intramolecular steric influences are described.

The molecular structure of the oxidised condensation product of o-benzoylbenzaldehyde and ethylenediamine

The structure of the oxidised condensation product of o-benzoylbenzaldehyde and ethylenediamine has been shown to be 2-(1-imidazolin-2-yl)benzophenone in the crystalline state by the results of an X-ray single-crystal structure analysis on the hydrobromide. The salt crystallises in the space group P212121 with four molecules of C16H14N2O,HBr in the unit cell with a= 7·54 ± 0·02, b= 8·66 ± 0·02, and c= 23·30 ± 0·04 A. The structure was refined to an R-factor of 0·11 on 1443 independent reflexions. The conformation of the molecule is discussed and compared to that of other benzophenone derivatives.