Oxazoline and imidazoline complexes : synthesis, reactivity and asymmetric catalysis

• Main Author: Davenport, Adam James
• Published: University of Leicester 2001
• Subjects: 547
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.696957

Chapter One introduces chiral half-sandwich complexes, with emphasis on the stability of the configuration at the metal, the stereochemistry of substitution reactions at the metal and methods for studying these. This is followed by an overview of the chemistry of arene-ruthenium and Cp*-rhodium complexes in particular their complexes with chiral bidentate ligands. Chapter Two describes the synthesis and characterisation of chiral-at-metal complexes [MCl(R-phenmox)(ring)] (M = Rh, ring = Cp*; M = Ru, ring = arene) and various derivatives [RuL(R-phenmox)(arene)]n+ (L = py, 2-Me-py, 4-Me-py, PPh3, n = 1; L = Br, I, n = 0). The stereochemistry of substitution reactions of [Ru(OH2(iPr-pymox)(mes)[(SbF6)2, with X- and the kinetics of epimerisation of the products are reported. In the latter part of the chapter, the syntheses of new chiral imidazoline ligands, and half-sandwich complexes of these and of some Schiff-base ligands are described. Throughout the chapter X-ray diffraction (14 structures), variable temperature and 2-D NMR experiments have been used to examine the factors affecting the diaseteroselectivity and epimerisation of the complexes. Chapter Three describes attempts to make cyclometallated C, N-bonded phenyl-oxazoline half-sandwich complexes. Two cyclometallated tin complexes and a number of palladium derivatives are reported. Finally, the synthesis and X-ray structure of the first example of an arene ruthenium phenyl-oxazoline complex is described. Chapter Four provides a brief introduction to asymmetric catalysis particularly using half-sandwich complexes as Lewis acid catalysts. The complexes [Ru(OH2)(L)(arene)](SbF6)n (L = phenmox, pymim, ketimine) were found to be moderately efficient and enantioselective catalysts for the Diels-Alder reaction of acrylic dienophiles with simple dienes. Preliminary investigations of other Lewis-acid catalysed reactions including Hetero-Diels Alder, Mukaiyama Aldol and inverse electron-demand Hetero Diels-Alder are reported.