Structural studies on silver(I) complexes containing phenylcyanamido ligands and uranyl(VI) complexes with beta-ketophenolates : a dissertation presented in partial fulfilment for the degree of Master of Science in Chemistry at Massey University

Abstract

This thesis is divided into two parts. In Section One studies on the interaction of phenylcyanamides with silver(I) are reported. Section Two describes the results of studies on the complexes formed from β-ketophenol ligands and the uranyl ion. Section One Chapter 1 is a brief overview of the use of phenylcyanamides in forming coordination complexes with transition metals. In Chapter 2 the preparation of a series of silver complexes of the general formula [Ag(Ph₃P)₃(pcyd)], where pcyd is a phenylcyanamido anion, is described. The crystal structures of [Ag(Ph₃P)₃(4-Brpcyd)] and [Ag(Ph₃P)₃(4-MeOpcyd)] have been determined, in which the silver atom occupies a distorted tetrahedral environment, and the latter complex has a very short terminal C-N bond within the 4-methoxyphenylcyanamido ligand. Chapter 3 provides a comparison of all those transition metal complexes of phenylcyanamides that have been structurally characterised. Section Two Chapter 4 is a brief overview of the use of β-diketonate ligands in forming dinuclear complexes, especially those in which the uranyl ion (UO₂²+) is present. In Chapter 5 the preparation of the mononuclear complexes [UO₂(HL¹)₂(MeOH)], (UO₂(HL²)₂(EtOH)], the heterobinuclear complexes [U0₂Mn(L¹)₂(EtOH)]·1.5H₂O, and [UO₂Mn(L²)₂(EtOH)]·2H₂₂O and the oxo-ligand adducts [UO₂(HL¹)₂(Ph₃AsO)]·2H₂O, [U0₂(HL²)₂(Ph₃PO)] and [UO₂(HL²)₂(Ph₃AsO)] (H₂L¹ = 1-(2-hydroxyphenyl)-3- butanedione and H₂L² = 1-(2-hydroxyphenyl)-3-phenyl-l,3-propanedione) is described. The complexes have been characterized by a variety of physicochemical techniques and the crystal structures of [UO₂(HL¹)₂(EtOH)] and [UO₂(HL²)₂(EtOH)]·EtOH determined. Both complexes contain seven coordinate uranium(VI) in a pentagonal bipyramidal geometry in which the two bidentate β-diketonato ligands and the ethanol ligand make up the equatorial pentagonal plane. For the complex [UO₂(HL¹)₂(EtOH)] the HL¹ ligands are in a trans arrangement with respect to one another, whereas for the [UO₂(HL²)₂(EtOH)]·EtOH complex the HL² ligands adopt a cis arrangement. However, in solution variable temperature ¹H NMR spectra indicate that the cis and trans isomers are in equilibrium for both complexes.