The crystal structure of L-alanylglycine has been determined by X-ray diffraction. L-Alanylglycine crystallizes in the space group P21 with cell dimensions a= 5.283, b= 11.810, c= 5.510/~ andfl= 101-58 ° with Z=2. This non-centrosymnaetric structure was solved by the 'quadrant permutation' method. The structure is simple but interesting in that one proceeded from the collection of data to the correct solution with scarcely any human intervention. It was refined by three-dimensional anisotropic matrix least-squares analysis (block-diagonal approximation). A final R index of 0.047 for 586 observed reflexions was obtained. The molecules are held together by hydrogen bonds forming a three-dimensional network. The planes of the carboxyl and the amide groups are nearly perpendicular. The bond lengths and angles are in close agreement with the mean values proposed by Marsh & Donohue.

No abstract

The reaction of tetrachlorocyclopropene with SeCl4 or TeCl4 in CH2Cl2 under solvothermal conditions at 120 °C and 90 °C, respectively, is a suitable route to 1,2‐dichalcogenolylium ions. Yellow crystals of (C3Cl3Se2)+Cl− or red crystals of {(C3Cl3Te2)+}2[Te2Cl10]2− are formed in such reactions. The reaction of hexachloropropene with elemental sulfur — the well‐known route to 3,4,5‐trichloro‐1,2‐dithiolylium chloride (C3Cl3S2)Cl — turned out not to be transferable to selenium and tellurium chemistry. NMR investigations of the reaction solutions allowed to set up reaction equilibria also involving hexachloropropene and dichalcogen dichlorides E2Cl2. The crystal structures of all three compounds were determined by X‐ray diffraction. All contain planar, five‐membered ring shaped cations (C3Cl3E2)+ (E = S, Se, Te). Short E−E bonds (S−S 201, Se−Se 231, Te−Te 266 pm) indicate substantial π‐bonding and charge delocalisation. The anion in (C3Cl3Te2)2[Te2Cl10] consists of two tetragonal pyramidal [TeCl5]− units linked by long Te−Cl bridges to centrosymmetric dimers in the form of edge‐sharing double octahedra. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Abstract. C24Ha2N202, M.W. 380"5; triclininc, PT; a= 15.965 (6), b=9.395 (4), c= 15.137 (5) ]k, ~=90.40 (2), fl=91.32 (1), 7=93-18 (2)°; 25°C; Z=4.