Die Heptabromodigermanate(II) A3Ge2Br7 (A = Rb,NH4) Synthesen,Charakterisierung und Kristallstrukturen

Heptabromodigermanates(II) A₃Ge₂Br₇ (A ? Rb, NH₄) — Syntheses, Characterization, and Crystal Structures Heptabromodigermanates(II) A₃Ge₂Br₇ (A ? Rb, NH₄) have been obtained by crystallization from aqueous ABr? GeBr₂? HBr solutions. The compounds can be characterized as double salts ABr · 2 AGeBr₃, because the crystal structures (monoclinic, space group P2₁/c, Z = 4) consist of pyramidal GeBr₃ groups.     

Structural study on the carbohydrate moiety of calf intestinal alkaline phosphatase

Surprisingly alkaline phosphatase (AP) (EC 3.1.3.1) of calf intestine is found in large amounts, e.g. 80%, within chyme. Most of the enzyme is present as a mixture of four differently hydrophobic anchor-bearing forms and only the minor part is present as an anchorless enzyme. To investigate whether changes in the N-glycosylation pattern are signals responsible for large-scale liberation from mucosa into chyme, the glycans of the two potential glycosylation sites predicted from cDNA were investigated by matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry in combination with exoglycosidase treatment after tryptic digestion and reversed-phase chromatography. The glycans linked to Asn249 are at least eight different, mainly non-fucosylated, biantennary or triantennary structures with a bisecting N-acetylglucosamine. For the most abundant glycopeptide (40%) the following glycan structure is proposed: [carbostructure: see text]. The glycans linked to Asn410 are a mixture of at least nine, mainly tetraantennary, fucosylated structures with a bisecting N-acetylglucosamine. For the most abundant glycopeptide (35%) the following glycan structure is proposed: [carbostructure: see text]. For the structures the linkage data were deduced from the reported specificities of the exoglycosidases used and the specificities of the transglycosidases active in biosynthesis. The majority of glycans are capped by alpha-galactose residues at their non-reducing termini. In contrast to the glycans linked to other AP isoenzymes, no sialylation was observed. Glycopeptide 'mass fingerprints' of both glycosylation sites and glycan contents do not differ between AP from mucosa and chyme. These results suggest that the observed large-scale liberation of vesicle-bound glycosylphosphatidylinositol (GPI)-anchored AP from mucosa into chyme is unlikely to be mediated by alteration of glycan structures of the AP investigated. Rather, the exocytotic vesicle formation seems to be mediated by the controlled organization of the raft structures embedding GPI-AP. (c) 2001 John Wiley & Sons, Ltd.     

PdCl2Se6 und PdBr2Se6, neue chalkogenreiche Komplexe von Palladium(II)-Halogeniden mit Se6-Gruppen als Liganden

PdCl₂Se₆ and PdBr₂Se₆, New Chalcogenrich Complexes of Palladium(II) Halides with Se₆ Groups as Ligands PdCl₂Se₆ und PdBr₂Se₆, chalcogenrich complexes of palladium halides with Se₆ groups as ligands have been prepared by reactions of Pd metal with melts of selenium and SeX₄ (X = Cl, Br) at 180°C in closed silica ampoules. The new compounds have been characterized by vibrational spectra and thermal analysis. The X-ray analysis of PdCl₂Se₆ showed a polymeric structure, built up by chains of linear PdX₂ groups connected by Se₆ groups in a chair conformation.     

Synthesis and studies of catalysts prepared by supporting Hf(CH2Ph)4 on SiO2 and Al2O3

Catalysts prepared by supporting Hf(CH₂Ph)₄ on silica and alumina were studied. Their catalytic activity in ethylene polymerization was shown to increase considerably upon heating in hydrogen. IR spectroscopic studies of catalysts heated in hydrogen show the formation of surface Hf hydrides.

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, Hf (CH₂Ph)₄ . , . .

     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 52. Darstellung,Charakterisierung und Reaktionen von (C5H5)3Ce · THF und Na[Ce(C5H5)4] · THF

Contributions to the Chemistry of Organo Transition Metal Compounds. 52. Preparation, Characterization, and Reactions of (C₅H₅)₃Ce · THF and Na[Ce(C₅H₅)₄] · THF (C₅H₅)₃ · THF ( I ) was synthesized in a simple manner by reaction of (NH₄)₂[Ce(NO₃)₆] with C₅H₅Na. With excess C₅H₅Na the complex Na[Ce(C₅H₅)₄] · THF ( II ) could be obtained. In addition of cyclovoltammetric and polarographic measurements it was tried without success to transfer I and II into organocerium( IV ) compounds by means of different oxidizing agents. II reacts with I₂ and (C₆H₅)₃CCl forming Na[(C₅H₅)₃CeI] · THF or Na[(C₅H₅)₂CeI₂] · 4 THF and I besides of (C₆H₅)₃CCl respectively. At interaction of I with Co(acac)₃ the cobalticinium salt [(C₅H₅)₂Co][C₅H₅Ce(acac)₃] is formed. The compounds obtained were characterized by elementary analysis, hydrolysis products, magnetic moments, i.r., ¹H-n.m.r. und u.v.-vis spectra, and measurements of electric conductivity.     

Subgroup 4 (Ti,Zr, Hf) derivatives of Cobalt Carbonyls

Bimetallic and trimetallic compounds containing unsupported bonds of subgroup 4 metals (M = Ti, Zr, Hf) and Co were prepared by hydride elimination (A) from RM derivatives (R¹ = PhCH₂; RN; R² = Me, Et)) and by salt elimination (B) from RMX (X = Cl, Br; R.¹ = PhCH₂, RN and R³O; R³= i-Pr, n-Bu)) by reaction with HCo(CO)₄ and Na[Co(CO)₄], respectively. Compounds RMCo(CO)₄ with R¹ = PhCH₂, RM[Co(CO)₄]₂ R.¹ = PhCH₂, were prepared both by methods A and B, while (R³O)₄-n Ti[Co(Co)₄]n (n = 1, 2) compounds were obtained by reaction B. Several tertiary phosphine and phosphite derivatives of the former two types were obtained by substitution of a carbonyl group by PR ligand or by A type reaction of HCo(CO)³(PR with RM compounds.     

Untersuchungen zur Struktur von Thallium(I)-halogenomercuraten(II)

Investigations on the Structure of Thallium(I) Halide Mercurates(II) Tl₄HgBr₆ crystallizes tetragonal with a = 8.978, c = 8.812 Å and Z = 2 in the space group P4/mnc. Singlecrystal methods revealed isolated HgBr₆-octahedra, compressed alonged the [001] axis, with thallium atoms between them. The results have been extended to clarify the structures of the isomorphous compounds (NH₄)₄HgBr₆ (a = 9.011, c = 8.660 Å), Tl₄HgJ₆ (a = 9.529, c = 9.387 Å) and Tl₄HgCl₂Br₄ (a = 8.896, c = 8.735 Å). It was impossible to obtain Tl₄HgCl₆; all attempts resulted in the formation of Tl₁₀Hg₃Cl₁₆, which crystallizes tetragonal (a = 8.477, c = 23.699 Å).     

Darstellung und Kristallstruktur von Ptl3, einem valenzgemischten Platin (II,IV)-iodid

Preparation and Crystal Structure of PtI₃, a Mixed-valence Platinum (II, IV) Iodide PtI₃ was obtained by thermal decomposition of PtI₄ in a closed system at 300°C and 8 atm iodine pressure. Single crystals were formed by the reaction of PtI₄ with aqueous solutions of KI and I₂ at 270°C. The crystal structure of the monoclinic compound (a = 673.5(2) pm; b = 1206.1(4) pm; c = 1331.3(5) pm; β = 101.25(6)°; Z = 8; space group C2/c-C_2h⁶) contains square planar PtI₄ and octahedral PtI₆ groups which are connected by common edges to chains.