Abstract
M.Sc. (Chemistry)
A series of pyrazolyl and ferrocenyl-pyrazolyl ligands were synthesized. These ligands were reacted with ruthenium dimeric metal complex [RuCl2(Cy)]2 (where Cy = p – cymene) and a ruthenium carbonyl dimer [(ղ4-Ph4C4C=O)(CO)2Ru]2 to produce a series of monometallic and heterobimetallic Ru(II) arene complexes, as well as monometallic and heterobimetallic Ru(0) carbonyl complexes respectively. All the complexes were characterized by various spectroscopic and analytical techniques including 1H NMR and 13C NMR spectroscopy, FT-IR spectroscopy, mass spectrometry, elemental analysis (CHN) and single-crystal X-ray diffraction (complex C1). These techniques revealed that the proposed structures were indeed what had been formed. The techniques were also able to show that the various complexes were chemically different and displayed different chemical traits (such as functional groups). All the complexes, including the ferrocenyl-pyrazolyl ligands were tested as catalyst precursors in the hydroformylation of 1-octene.
The Ru(II) and Ru(0) complexes were all active hydroformylation catalyst precursors and converted 1-octene to mainly aldehydes and alcohols, with minimal amounts of internal alkenes and octane produced. Branched and linear aldehydes as well as alcohol products were produced as a result of hydroformylation, followed by hydrogenation, while internal octenes and octane were produced via isomerization and hydrogenation reactions respectively. Of the various catalysts, Ru(II) complexes C1 and C2 displayed better hydroformylation/hydrogenation activity than their Ru(0) analogues, with C2 being the better of the two. On the contrary, catalyst precursors C4 – C6 possessed a higher degree of isomerization. The Ru(0) complexes showed no hydrogenation activity throughout the reactions conduted. Collectively, Ru(II) catalysts C1 – C3 favoured a regioselectivity for branched aldehydes compared to the Ru(0) catalysts C4 – C6.
The substituents (tBu and Ph) on the pyrazolyl ring of the monometallic complexes have an influence on the regioselectivity of the catalyst. The tBu substituent favoured the formation of branched aldehydes in a minority of instances whereas the phenyl group resulted in an exclusive preference of linear aldehydes produced. Branched aldehydes were more favoured with the Ru(II) heterobimetallic catalyst precursor whilst the Ru(0) analogue yielded linear aldehydes...