I. Magnesium Promoted Coupling of Carbodiimides and Terminal Acetylenes, II. Bismuth Compounds Supported by Di(amido) Chelating Ligands

摘要

The work presented in this thesis is divided into two parts, both of which investigate the chemistry of main group elements supported by N,N'-donor ligands.Part 1 investigates the use of Mg(mesC{NCy}₂)(N{SiMe₃}₂)(THF) (mes = 2,4,6- Me₃C₆H₃, Cy = C₆H₁₁) as a pre-catalyst for the coupling of terminal acetylenes to carbodiimides. A catalytic cycle for the reaction is proposed, based on a series of stoichiometric reactions. Ligand redistribution via Schlenk equilibria is a prominent feature of the proposed catalytic cycle. The scope of catalysis was also investigated, indicating a strong dependence on the sterics and electronics of both the carbodiimide and the terminal acetylene. Investigation of other magnesium species identified other pathways into the catalytic cycle.Part 2 explores the derivitisation of Bi(Me₂Si{NAr})Cl (Ar = 2,6-i-Pr₂C₆H₃) to form a number of novel bismuth(III) species of the general formula Bi(Me₂Si{NAr})X (X = alkyl, aryl, amide, aryloxide, phosphide). In addition, a number of cationic bismuth species have been isolated from the reaction of Bi(Me₂Si{NAr})Cl with ECl₃ (E = Al, Ga). Preliminary investigations reveal that the amide and aryloxide derivatives are active as initiators for the ring-opening polymerisation of lactide and ε-caprolactone. A number of bismuth(III) compounds bearing the related di(amido)ether ligands [O(Me₂Si{NAr})₂]²⁻ have also been synthesised.