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'Tungsten' in keywords Facet   Publication Year 1995  [X]
Facet   section ZfN Section B:Volume 050  [X]
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Publication Year
1995[X]
1Author    T. Gressling, Hk Müller-BuschbaumRequires cookie*
 Title    Zur Kristallstruktur von Ce2(W 0 4)3 On the Crystal Structure of Ce2(W 0 4)3  
 Abstract    Single crystals of Ce2(W 0 4)3 have been prepared by crystallisation from molten mixtures of W 0 3 and C e 0 2. The compound shows m onoclinic symmetry, a = 7.813(4), b = 11.720(2), c = 11.586(3), ß = 109.36(3)°, Z = 4, and is isotypic to Eu2(W 0 4)3, but shows large differences of the atomic coordinates especially of oxygen. The crystal structure of Ce2(W 0 4)3 is charac­ terized by W (1)0 4 tetrahedra, square W (2)0 5 pyramids and a distorted capped trigonal prism of oxygen around cerium. The decrease o f the oxidation states of C e4+ or W6+ was proved by thermogravimetric and magnetic measurements as well as by calculations of the Coulomb terms of lattice energy. 
  Reference    Z. Naturforsch. 50b, 1513—1516 (1995); eingegangen am 25. Mai 1995 
  Published    1995 
  Keywords    Cerium, Tungsten, Oxygen, Crystal Structure 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-1513.pdf 
 Identifier    ZNB-1995-50b-1513 
 Volume    50 
2Author    Thomas Schmidt, Stephan Neis, Richard GoddardRequires cookie*
 Title    Synthesis, Structure, and Properties of Homoleptic l-Oxa-l,3-diene Molybdenum and Tungsten Complexes  
 Abstract    Homoleptic tris(l-oxa-l,3-diene)m olybdenum and tungsten complexes are formed as yel­ low, crystalline compounds in 54-80% isolated yield on treatm ent of the corresponding /3-unsubstituted a,/3-unsaturated ketones with W (CO)3(CH 3CH 2CN)3 or (y6-C6H 6)M o(CO)3 in refluxing hexane. Reaction of these oxadienes with (^6-C6H 5CH3)2Mo in tetrahydrofuran or /7-hexane provides a new high yield route to homoleptic molybdenum complexes that are otherwise difficult to prepare. X-ray crystal structure analyses of two air-stable, isomeric tungsten complexes reveal a significant contribution of a cr2,?/2-bonding mode in the coordi­ nated oxadiene moieties. U nder reaction conditions that allow the platinum catalyzed hydro­ genation of phenyl substituents in these ligands, the coordinated oxadiene fragments are inert, thus demonstrating an unprecedented chemoselectivity in the hydrogenation of aryl-substituted enones. On the other hand, the complexes are labile enough to catalyze the cyclotrimerization of alkynes such as methyl propiolate. 
  Reference    Z. Naturforsch. 50b, 315—325 (1995); received September 7 1994 
  Published    1995 
  Keywords    Oxadiene Complex, Molybdenum, Tungsten, X-Ray, Selective Hydrogenation 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-0315.pdf 
 Identifier    ZNB-1995-50b-0315 
 Volume    50 
3Author    KatrinA. Köhler, H. Lexander Steiner, W. Erbert, RoeskyRequires cookie*
 Title    Die Kristallstrukturen von (j75-C5Me5)MoMe4 und (j75-C5Me5)WMe4 The Crystal Structures of (?75-C5Me5)M oMe4 and (^5-C5Me5)W M e4  
 Abstract    The crystal structures of (/75-C5Me5)MoMe4 1 and (j/5-C5Me5)WMe4 2 are reported. 1 and 2 crystallize in the orthorhom bic space group Pbcm with the lattice param eters a = 681.4(2) pm, b = 1538.6(6) pm, c = 1402.4(6) pm with 4 units per cell (1), and a = 684.99(6) pm, b = 1547.3(2) pm, c = 1405.5(2) pm with 4 units per cell (2). Both compounds are monomeric and have a square-pyramidal geometry. 
  Reference    Z. Naturforsch. 50b, 1207—1209 (1995); eingegangen am 20. Januar 1995 
  Published    1995 
  Keywords    Molybdenum, Tungsten, Alkyl Complexes, Crystal Structures 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-1207.pdf 
 Identifier    ZNB-1995-50b-1207 
 Volume    50 
4Author    C. Ogric, W. Schütt, T. Lehotkay, E. Herdtweck, F. R. KreißlRequires cookie*
 Title    Umwandlung von ?72-Thiocarbenkomplexen des Molybdäns und Wolframs in Metalla-thia-cyclopropan-Systeme Conversion of ?/2-Thiocarbene Complexes of M olybdenum and Tungsten to Metalla-thio-cyclopropane Systems  
 Abstract    Cationic ^2-thiocarbene complexes of molybdenum and tungsten [Cp(CO)2M =C(R)S-Me][BF4] (M = Mo, W; R = Ph, Tol; L = CO, PM e3) react with the germylene G e{N('Bu)CH 2CH2N('Bu)}, the plumbylene Pb{N(SiM e3)2}2, or with sodium azide and sodium thiosulfate to give neutral metalla-thia-cyclopropane com plexes C p(CO)2-M -C(R)(SM e)SM e. Instead of the expected cycloaddition or substitution reactions the formal addition of thiomethanolat at the carbene carbon atom is observed. On treating the corre­ sponding trimethylphosphine substituted /;2-thiocarbene com plex of molybdenum [Cp(CO)(PM e3)M o=C(Tol)SM e][BF4] with diethylamine or N,N,N',N'-tetramethylguanidine a cationic molybda-thia-cyclopropane system is formed. The products have been characteri­ zed by 'H, 13C, 31P NMR, IR and mass spectra. The crystal structure of 5a has been determin­ ed; space group with a = 1340,4(2), b -1097,7(1), c = 1101,8(5) pm and Z = 4. 
  Reference    Z. Naturforsch. 50b, 1839—1844 (1995); eingegangen am 11. Mai 1995 
  Published    1995 
  Keywords    ?72-Thiocarbene Complexes, Molybdenum, Tungsten, Carbon Sulfur Coupling 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-1839.pdf 
 Identifier    ZNB-1995-50b-1839 
 Volume    50