Browsing by Author "Mehari, Tetemke"

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    Investigations on the Reaction of Molybdenum Pentaobiloride and Chloroxtomolylbdenum Cohplexes with Sodium Azide
    (Addis Ababa Universty, 1984-06) Mehari, Tetemke; Seyferth, M.(PhD)
    The reaction of MoC15 with NaN 3 in acetonitrile followed by addition of OPPh3 resulted in the formation of impure MOOC1 3 (OPFh)2 rather than the expected nitrido analogue. NaN 3 acts here as a;reducing agent generating a molybdenum(IV) chloride derivative which was trapped as impure MoC14(Py)2~ The reaction of MoOC14 with acetonitrile or NaN3 produced a green solution containing an MOOC13(MeCN)2 COl'1plex which could not be isolated but trapped with OPPh 3 and identified as MOOC13(OPPh3)2'. Addition of NaN 3 to the green molybdenum oxotrichloride intermediate, MOOC1 3 (MeCN)2 produced a deep violet solution, The viole product could not be isolated but was inferred to consist of [NaHMoOC13(N3)(MeCN)J, a loose adduct of MoOC13(MeCN)2 and NaN 3 , Thus, addition of OPPh 3 to the violet solution resulted in the formation of impure MOOC1 3 (OPPh 3 )2' The violet intermediate obtained from MOOC13(MeCN)2 and NaN3 is stable in acetonitrile but decomposes in CH2C12 under evolution of N2 and reduction yielding MOOC12(MeCN)3 as a brown crystalline product which is sensitive to; 'hytirolyoiB. ~13(OPPh3)2 itselfr.eacts slower Vii th NaN" in acetonitrile Hi th :J exchange yielding MOOC12(N 3 )(OPPh 3 )2'
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    Phytochemical investigation of Vernonia amygdalina
    (Addis Ababa Universty, 2006-07) Hamza, Salah; Mehari, Tetemke
    Methanol extract of V.amygdalina, after repeated chromatography led to the isolation of different compounds, one of these compounds is partially characterized based on the spectral data.