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Synthesis, characterisation and reactivities of transition metal complexes of hard base ligands

Authors Chow, Ernest K.F.
Issue Date 1994
Summary A series of chiral transition metal complexes of (R,R)-(-)-N,N'-bis-(3,5- di-tert-butylsalicylidene)-1,2-cyclohexanediamine[L1] including Al(L1)Et, Zr(Ll)Cl2, Ru(Ll)(CO)2, Co(Ll), Ti(Ll)CI2, V(Ll)O, V(Ll)Cl2, MoO2(Ll), Fe(Ll)CI and Fe(Ll)(OMe) have been synthesized. The structures of Al(L1)Et and Co(L1) have been determined by X-ray crystallography. Al(L1)Et was characterized by 1H COSY, 13C DEPT and 27Al NMR analysis. The compounds Al(Ll)Et, Zr(Ll)Cl2 and Ti(Ll)Cl2 were found to catalyze ring opening for cyclohexene oxide with trimethylsilyl azide to give azido alcohols. Furthermore, the compound Co(L1) is found to be active catalyst for cyclopropanation of olefins with diazoester with modest e.e.(>42%). High valent osmiurm complexes of bistoluenesulfonamide, [pph4]2[Os2O4(L2)2(μ-OH)2 and Os2N2(L2)2(μ-OH)2, were synthesized with full characterization and detailed structural analysis. The Os=O and Os-N(nitrido) bond lengths of 1.740 ÅA and 1.55 ÅA respectively are typical values for this class of compounds. The latter compound was found to be photoluminescent. Copper and chromium complexes of quadridentate pyridine-amine ligands were synthesized. The chromium complexes catalyze the epoxidation of olefins with PhIO while the copper complexes are unreactive. An oxo-transfer mechanism from high valent chromium-oxo intermediate to olefins is proposed. Reactions of Cr(NBut)Cl3(dme), Cr(NBut)2Cl2, Mo(NBut)2Cl2 and W(NBut)2(NHBut)2 with styrene oxide, cyclohexene oxide and 1,2- epoxyhexane in the presence of trimethylsilyl azide were investigated. The isolated yields for the reaction of styrene oxide are high and the ratio of corresponding regioisomers was determined by GC analysis. A catalytic cycle is proposed for the epoxide ring-opening reactions by chromium and molybdenum imido complexes.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 1994
Language English
Format Thesis
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