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1980 (1)
1979 (1)
1Author    Hans-Ludwig Krauss, Erich HumsRequires cookie*
 Title    Oberflächenverbindungen yon Übergangsmetallen, XXIII [1] Die Umsetzung cyclischer Olefine mit Oberflächen-Chrom(II) auf Silicagel bei höherer Temperatur Surface Compounds of Transition Metals, XXIII [1] The Reaction of Cycloolefines with Surface Chromium (II) on Silicagel at Higher Temperature  
 Abstract    By reaction with surface chromium(II) on silicagel at T > 150 °C, cycloolefins can undergo ring contraction, methylation/demethylation, hydrogenation/dehydrogenation, and iso-meri7ation. Furthermore, n-alkanes (Ci... C4) are formed incorporating support hydrogen. -As in the case of the corresponding acyclic olefins, a common intermediate MC3 (metalla-cyclobutane^HM-allyl complex) for all these reactions is postulated; the transfer of Ci units is claimed to proceed via a carbene M = CH2 derived from the MC3 precursor. 
  Reference    Z. Naturforsch. 35b, 848—854 (1980); eingegangen am 21. Februar 1980 
  Published    1980 
  Keywords    Surface Compounds, Ring Contraction, Methylation/Demethylation, Hydrogenation/Dehydrogenation, Carbene Intermediates 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-0848.pdf 
 Identifier    ZNB-1980-35b-0848 
 Volume    35 
2Author    Hans-Ludwig Krauss, Erich HumsRequires cookie*
 Title    Oberflächenverbindungen von Übergangsmetallen, XXII [1] Die Umsetzung von Oberflächen-Chrom(II) auf Silicagel mit Olefinen bei höherer Temperatur. - Zum Mechanismus von Aufbau-, Abbau-, Metathese- und Isomerisierungs-Reaktionen an koordinativ ungesättigten Oberflächen-Metallionen Surface Compounds of Transition Metal, XXII [1] The Reaction of Surface Chromium(II) on Silica with Olefins at Higher Temperature. - A Contribution to the Mechanism of Growth, Degradation, Metathesis and Isomerization on Coordinatively Unsaturated Surface Metal Ions  
 Abstract    With chromium(II) supported on silica, at T > 150 °C olefins undergo growth/degra-dation/metathesis reactions by addition/elimination of even and uneven chain fragments including Ci. Simultaneously, catalytic double bond isomerization and C-rearrangements to methyl branched olefins occur. One mechanism is proposed for all these reactions via a pseudo-tetrahedral MC3 intermediate. Polyethylene synthesis at lower temperatures may follow the same way. For growth/degradation/metathesis the formation of a metal carbene unit is postulated as a characteristic step; in case of ethylene, >Cr=CH2 will be formed as a precursor of the final CH4 (resulting from a secondary reaction with support hydrogen). 
  Reference    Z. Naturforsch. 34b, 1628—1636 (1979); eingegangen am 23. Juli 1979 
  Published    1979 
  Keywords    Surface Compounds, Olefin Polymerization/Degradation, Olefin Metathesis, Olefin Isomerization, Carbene Intermediates 
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 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-1628.pdf 
 Identifier    ZNB-1979-34b-1628 
 Volume    34