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Catalytic and stoichiometric reactivity of new organometallic derivatives of group 5 metal compounds supported by bulky achiral and chiral aryloxide ligation

By Scott William Schweiger


Treatment of [MCl5] (M = Nb, Ta) with two equivalents of [ArOH] (ArO = substituted phenol rings) leads to the formation of metal trichlorides [(ArO)2MCl3]. The trichlorides will undergo one electron reduction (Na/Hg) in the presence of a donor ligand to afford d1-six coordinate adducts. Alternatively, [(ArO)2MCl3] can be alkylated to give [(ArO)2MCl3−xRx] (R = CH2SiMe3, CH2Ph, C5H 9, C6H11). These alkyl compounds have been shown possess interesting structural differences and to be precursors/catalysts in the hydrogenation of unsaturated substrates. The bis and tris-alkyls [Nb(OAr) 2Cl3−xRx] (x \u3e 1 R = CH2SiMe 3) have also been shown to undergo α-hydrogen abstraction to generate two new niobium alkylidenes. Also, [(ArO)2MCl3] or [(ArO) 2MCl3−xRx] may be treated with HSn nBu3 or H2 in the presence of phosphine donors to generate new hydride reagents. Treatment of [TaCl3(NMe2)2(HNMe 2)] with two equivalents of [ArOH] or one equivalent of [3,3 ′-{R}2-BINOL] (R = SiMe3, SiMe2Ph, SiMePh2, SiPh3; BINOL = 2,2′-dihydroxy-1,1 ′-binaphthyl) leads to the formation of the six coordinate dichlorides [TaCl2(ArO)2(NMe2)(HNMe2)] and [TaCl2(3,3′-{R}2-BINOL)(NMe 2)(HNMe2)] respectively. Investigation into the probable intermediates of the reaction explains the observation that not both amido groups are displaced upon treatment with either mono- or bis-(phenol) reagents

Topics: Chemistry
Publisher: 'Purdue University (bepress)'
Year: 2002
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Provided by: Purdue E-Pubs
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