Following the discovery of a first-order phase transition in annealed KOH-doped ice at 72 K, which was identified as the order–disorder transition associated with the proton positions, a structural study has now been made. Powder neutron diffraction measurements on KOD-doped D2O above and below the phase transition, together with x-ray diffraction measurements, reveal a partial ordering of the hydrogen atoms at low temperatures. The equilibrium structure of ice at low tempertures has orthorhombic symmetry, space group Cmc21, with the same lattice as the high-temperature Ih (P63/mmc) modification. The structure is polar and there is evidence that the ordered domains are less than about 40 Å in dimension.

Potent and selective inhibitors of matrix metalloproteinases (MMPs), a family of zinc proteases that can degrade all the components of the extracellular matrix, could be useful for treatment of diseases such as cancer and arthritis. The most potent MMP inhibitors are based on hydroxamate as zinc-binding group (ZBG). alpha-Arylsulfonylamino phosphonates incorporate a particularly favorable combination of phosphonate as ZBG and arylsulfonylamino backbone so that their affinity exceptionally attains the nanomolar strength frequently observed for hydroxamate analogues. The detailed mode of binding of [1-(4'-methoxybiphenyl-4-sulfonylamino)-2-methylpropyl]phosphonate has been clarified by the crystal structures of the complexes that the R- and S-enantiomers respectively form with MMP-8. The reasons for the preferential MMP-8 inhibition by the R-phosphonate are underlined and the differences in the mode of binding of analogous alpha-arylsulfonylamino hydroxamates and carboxylates are discussed.

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N-(Diphenylmethylene)aniline, C19HlsN, is orthorhombic with a = 8"436 (3), b = 18.771 (5), c = 17"361 (5) at -160°C, space group Pbca, Z= 8. The atomic positions have been determined by direct methods and refined by least-squares analysis of counter data measured at -160°C. Refinement converges with an R of 0.088 for 5832 reflexions. Mean bond lengths are C-C (in phenyl rings) 1.393, C(sp2)-C(phenyl) 1.492, C(sp2)=N 1.287 and C(phenyl)-N 1.420 A. The molecular geometry is compared with that of triphenylnitrone. The orientation of the phenyl groups and the relation between experimental bond lengths and calculated bond orders is discussed.

Die aus DMF und P‐oxychlorid gebildete Dimethyliminium‐Verbindung addiert sich an das Methylen‐C‐Atom des in dem p‐Co(III)‐Komplex (I) zweizähnig gebundenen Glycinats unter Bildung des als Tetrachlorozinkat‐cl?orid‐Monohydrat isolierten Komplexes (II).

XeF2.WOF4, M=445.2, monoclinic, space group P2Jc, a=5.44 (1), b=9.97 (1), c=12.17 (2) A, fl=92.0 (2) °, U= 659.4 A 3, z=4, D~=4.50 g cm -3. The atomic positions have been determined by blockdiagonal least-squares refinement of counter intensities, the final R being 0.081 for 817 reflexions. Mean bond lengths are W-F(terminal) 1.79, W-F(bridging) 2.18, W-O 1.65, Xe-F(terminal) 1.89 and Xe-F(bridging) 2.04 A. The geometry of the fluorine bridge is related to the degree of covalency of the adduct.

Crystals of the title compound (or-modification. m.p. 190 " C ) are triclinic, a = 14-07, b = 11.67, c = 9.00 A, o! = 99.7. p = 88-5, y = 102.1 O , space group P i . Z = 2. The structure was solved by direct methods; atomic positions were determined by least-squares refinement from X-ray diffractometer intensity data, the final R being 0.056 for 451 9 reflections. The eight-membered phosphazene ring has an irregular crown conformation with P-N-P angles ranging from 133.1 to 142.0'. Mean bond lengths are : P-N 1 -570, P-CI 2.041, P-C 1.783, and C-C 1.39 A. The bond lengths are discussed in terms of the electronegativity of the exocyclic groups and the ring conformation is discussed in terms of steric factors.

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