Synthesis and reactivity of some Co-, P-Chiral Co(III) complexes

Sun, Lihui (1998) Synthesis and reactivity of some Co-, P-Chiral Co(III) complexes. Masters thesis, Memorial University of Newfoundland.

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Abstract

Chiral phosphorus compounds have attracted research interest due to their biological activity and potential applications. Asymmetric synthesis of chiral phosphorus compounds via transition-metal-mediated (TMM) chemistry, with its possibility to modify reaction conditions and to control stereochemistry of phosphorus through coordination, holds promise as a synthetic avenue for synthesis of new phosphorus materials. This thesis focuses on a novel method to synthesize chiral pentavalent phosphorus compounds via optical induction from transition metal complexes and examines the chemistry of the resulting inorganometallic phosphorus moieties for further transformations. -- Three series of Co-, P-chiral Co(III) complexes are synthesized via transition- metal-mediated (TMM) Arbuzov reactions. The structures and spectroscopic properties are described and the reactivity of the synthesized chiral phosphonate moieties are examined. Unlike their organic analogs, the inorganometallic phosphonates are inert to nucleophiles. Reaction with PCl₅or SOCl₂ under prolonged heating cleaves the Co-P bond. In the presence of BCI₃, the perfluoro-substituted P- phosphito Co(III) complex reacts with the nucleophile to give a novel product, which involves C-F bond cleavage. -- The LUMOs of the inorganometallic phosphonates and their organic analogs are analysed at the Hückel level. The LUMOs of the inorganometallic phosphonates are metal-based while those of their organic analogs are dominated by the orbitals of phosphorus centre. The shift of the LUMO from phosphorus to metal explains the behavioural difference between organic and inorganometallic pentavalent phosphorus compounds.

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