Synthesis, structure and properties of some chiral-at-metal transition metal organometallics

Yu, Yongfei (1998) Synthesis, structure and properties of some chiral-at-metal transition metal organometallics. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Although chirality can arise in various guises in organometallic systems, metal centered chirality has become an ever growing concern due to its potential high efficiency in asymmetric synthesis. This thesis focuses on the synthesis, structure and properties of some chiral-at-metal transition metal organometallics. -- Reactions of CpCo(X)(Y)(I) (X=(S)-Ph₂PNHCH(Me)Ph, Y=I, CF₃; XY=PhCH(Me)-N=CH-C₄H₃N) with Et₂NP(OMe)₂ toward diastereoselective synthesis of novel Co- and P-chiral amidophosphonate Co(III) complexes were studied by a combination of ¹H, ¹³C, ¹⁹F, ³¹P NMR, proton NOED, CD spectroscopy and single crystal X-ray diffraction in order to rationalize the Co*-P chiral induction and to establish the solid-state structure, configuration and solid-state/solution conformations. The results show that chemical outcome varies from one system to another. -- Study on reaction of a series of resolved chiral aminophosphine Co(III) complexes (CpCo(I)(P(0)(R)(OMe))(Ph₂NHCH(Me)Ph)) with gaseous HCl shows that the reaction affords regioselective P-N bond cleavage products with retention of configuration at Co* and establishes a convenient method to obtain homochiral transition metal complexes. The regioselectivity was discussed based on EHMO calculations. ¹H NMR evidence for the formation of isobutene, resulting from P-C bond activation via β-elimination in a diastereoselctive, Arbuzov dealkylation reaction involving dimethyl t-butylphosphite, was found. -- A series of new chiral-at-metal and non-chiral titanocene derivatives with general formula Cp(C₅R₅)Ti(X)(Ar) (R=Me, X=Cl, Ar=C₆F₅, o-FC₆H₄; R=H, X=Cl, Ar=C₆F₅, o-FC₆H₄; R=H, X=Ar=C₆F₅, o-FC₆H₄) was synthesized and characterized. The barrier of aryl rotation around Ti-Cipso and the possibility of coordination of ortho-F to Ti were examined by variable temperature NMR, MMX and EHMO methods, as well as solid state single crystal X-ray diffraction.

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