Pyridone-substituted Pyridyl imines as Functionalised ligands in Coordination Chemistry and Catalysis

In this thesis, the synthesis and coordination chemistry of a series of novel NNN and NN proton responsive ligands are described. All the ligands and complexes have been characterized by a combination of multinuclear NMR spectroscopic techniques, mass spectrometry, IR spectroscopy and by single crystal X-ray diffraction studies. Chapter 1 presents an introduction to functional ligands/complexes and their applications in catalysis. In Chapter 2, the synthesis and characterisation of a series of OH-functionalised NNN pincer ligands are discussed. The coordination chemistry of these pyridone-substituted pyridyl-imines towards platinum group metals is thoroughly investigated. It is envisaged that these ligands can remain protonated or undergo deprotonation reactions on coordination to give complexes of the type L1PdX (X = Cl, OAc), [HL1PdCl][X] (X = Cl, PF6, OTf), HL1RuCl2(PPh3) and [HL1PtCl][PtCl3(DMSO)]. Additionally, the reactivity of the palladium chloride complexes towards stoichiometric amounts of AgPF6 is explored with a view to introducing two electron donor ligands (L) to the coordination sphere of the metal centre, including acetonitrile and 3,5-lutidine. In Chapter 3, the synthesis and reactions of two classes of OH-functionalised NN-bidentate ligands towards group 10 metal salts of Pd(II), Pt(II) and Ni(II) including Pd(OAc)2, (MeCN)2PdCl2 (DMSO)2PtCl2 and (DME)NiBr2 are described. A thorough investigation is performed to ascertain the preferred coordination mode and charge on the heterocyclic unit of the NN-ligand. In addition, the reactivity of a selection of the palladium complexes towards some two electron donor ligands (L), including acetonitrile and triphenylphosphine is also studied. Furthermore, the reactions of a selection of the resulting compounds towards acids and bases is investigated to explore their proton responsiveness. In Chapter 4, the NNN-Ru and -Pd complexes developed in Chapter 2 have been used as catalysts in transfer hydrogenation. Additionally, the NN-nickel complexes described in Chapter 3 have been investigated as pre-catalysts in ethylene oligo-/polymerisation. In both these types of catalysis the effect of the pendant OH group on the particular transformation is probed. Chapter 5 details the experimental work carried out in Chapters 2-4.