The results reported in this thesis are an investigation into the coordination abilities of some multidentate ligands, the majority of which possess more than one type of donor atom. In Section One studies on the reactivity of triosmium cluster compounds with phenylthioureas and substituted triphenylphosphines are reported. Section Two details the results of studies on selected multidentate ligands containing phosphorus and nitrogen donor atoms.
Chapter 1 is a brief overview of osmium cluster compounds reported to date in the literature and in particular the reactions of triosmium clusters with organic substrates, organosulphur compounds and phosphines.
In Chapter 2 the reactions of the 'lightly stabilised' triosmium cluster [Os3(CO)i 0(CH3CN)2] with phenylthiourea and diphenylthiourea are reported. Single crystal X-ray structural determinations were performed for the compounds [HOs3(CO) x(dptu)] (where x = 9, 10 dptu = diphenylthiourea). The photochemically
induced decarbonylation of the clusters [HOs3(CO)io(L)] ( where L = phenylthiourea, diphenylthiourea) has also been investigated, with quantum yields and apparent activation energies reported.
Detailed in Chapter 3 are the results of studies on the reactivity of triphenylphosphine ligands which possess aldehyde (2-PCHO, 4-PCHO) or amine (2-PNH2, 3-PNH2) substituents, with the triosmium clusters [Os3(C0)12-x(CH3CN)xJ (where x = 1, 2). A single crystal X-ray structural determination was performed on the complex [HOs3(C0)9(2-PNH)].
Chapter 4 is a brief overview of the use of multidentate ligands in forming coordination complexes with transition metals.
The results of an investigation on the coordination complexes of Cu(l) and Ag(I) with the potentially tridentate ligands pyridine-2-carbaldehyde 2'-pyridylhydrazone and 2,2':6',2"-terpyridine are reported in Chapter 5. Many of these compounds have been shown by single crystal X-ray structural determinations to possess an unusual five coordinate stereochemistry at the metal centre.
In Chapter 6 the results of studies on the coordination complexes of Cu(I) and Ni(II) with mixed phosphorus and nitrogen donor ligands are reported. These have been shown to form stable complexes where both the phosphorus and nitrogen donor atoms are coordinated.