The Effects of Electron-Withdrawing Ring Substituents on the Reactivity of Cyclopentadienyl Ruthenium Complexes
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This thesis describes the synthesis of ruthenium complexes which contain cyclopentadienyl ligands with electron-withdrawing ring substituents and the effects of these substituents on the reactivity of the metal centre. Two metal complexes containing the dibenzoylcyclopentadienyl ligand have been reported in the literature. However, the effects of these substituents on the reactivities of the complexes have not been investigated. Several dibenzoylcyclopentadiene analogues react readily with triruthenium dodecacarbonyl in toluene when heated under reflux to form bridging carbonyl dimeric complexes. The metal¿metal bond in the dimers is cleaved upon reaction with halogen sources. These halide complexes undergo CO substitution with tertiary phosphines. The rate constants for the CO substitution reactions of the (n5-1,2-(COPh)2C5H3)Ru(CO)2X complexes with tertiary phosphines have been measured. Reaction rates for the parent cyclopentadienyl complexes, [RuCp(CO)2X], have been repeated and the rates of the related indenyl complexes, [Ru(indenyl)(CO)2X], have been measured for comparison.The electron withdrawing ring substituents activate the complexes for CO substitution. The reaction mechanism is dissociative in all cases except the [RuCp(CO)2I] which has an Id mechanism. DFT calculations for second row transition metals are limited to 3-21G* basis sets. However, they are able to reproduce new vMC-O stretching frequencies and atom charges for the metal atoms which reflect the electron withdrawing effects of the ring substituents.