The optimisation of I-alkene polymerisation processes by highly active metallocene systems such as racSBIZrMe2 activated by [Ph3C][CN{B(C6Fs)3h] (I) or by [Ph3C][B(C~s)4] (II) was perfonned. Subsequently. a systematic quantitative study of ligand effects on polymerisation activity, molecular weight and polymer microstructure was carried out. Non-bridged and bridged C2y-symmetry zirconocene dimethyls and dichlorides alkylated (or alkyl exchanged) by AlBu'3 (TIBA) and activated by 1 are much less active than Crsymmetric zirconocenes. Propene polymerisations catalysed by those systems afford low molecular weight atactic polypropene. TIBA rapidly alkylates dichloride zirconocenes affording pre-catalysts which, once activated, give a catalytic profile comparable with that obtained with dimethyl zirconocenes. Activities of Crsymmetry raczirconocenes / AlBui3 / I or [Ph3C][H2N{B(C6Fs)3h] (III) in propene polymerisation decrease according to the order SBMbiZrCh (17) > SBIZrCh (16) > EBIZrCh (13) > MBBIZrCh (18) > EBIDMZrCh (19) > EBTHIZrCb (20) > SBSCZrCh (14) > SBBCZrCh (15). These values are not distorted by side effects such as mass transport limitation, so represent real activities, which are the highest reported to date for most of these catalysts under the experimental conditions fixed. The molecular weight of polypropene obtained in propene polymerisation reactions at 1 bar monomer pressure and 20°C ranges from high to low molecular weight (336000 to 4600 g/mol), decreasing according to the precatalyst, in the following order: SBMbiZrCh (17) > SBIZrCh (16) > MBBIZrCh (18) > EBIZrCh (13) > EBTHIZrCh (20) > SBsczrCh (14) > EBIDMZrCh (19) > SBBCZrCh (15). Experiments carried out at 1 bar of monomer pressure and 60°C afford polymers of medium to low molecular weight and the same trend. The order of isotacticity and regiospecificity of the polypropene obtained is: SBMbiZrCh (17) > SBSCZrCh (14) > SBBCZrCh (15) > MBBIZrCh (18) >EBIZrCh (13) > EBDMIZrCh (19) The trityl salt 1 generates more active catalysts than III for the polymerisations perfonned at 20°C, but the situation is reversed at 60 0c. The molecular weight of the polymers obtained by systems activated by III is slightly higher than those obtained using I under both experimental regimes (20 and 60°C / 1 bar). Reactions of L2ZrMe2 (where 4, L= CsMes; 6, L= CSMe4H) with III in presence of AIMe3, fonn [(~)Zr(JlMe) 2AIMe2][H2N{B(C6Fs)3h] (23, L= CsMes; 24, L= CSMe4H) whereas with I, ~ZrMe(Il-Me)B-(C6F5h and L2ZrMe(Il-NC)B-(C6FS)3 were obtained. The protolysis reaction ofY[N(SiMe3)2h with (2-C~sN=CH)(6-Bu)C6H30H (HL3 ) led to a variety of products. Y[N(SiMe3)2h(L3) (29), alongside Y[N(SiMe3)2](L3)2 (30) and Y(L3h (31) were synthesised. M(CH2SiMe3)2(THF)(Ll) (25, M = Sc; 26, M = Y; and L 1 = 2,3,6-Me3C6H3N=CH(6-Bu')C~30H) are highly effective catalysts for the ring-opening polymerisation of E-caprolactone. 26 and 30 also initiate polymerisation of cyc10hexene oxide (CHO).

xx, 204 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Efforts toward developing improved methods of synthesizing acrylamides are ongoing. Several homogeneous organometallic and coordination complexes have proven useful in catalytic acrylonitrile hydration; however, none of these complexes have been tested in the hydration of cyanohydrins used to synthesize substituted acrylamides. This dissertation describes the reactivity of molybdocene and Pt phosphinito nitrile hydration catalysts toward cyanohydrin substrates and the effect of Cp ring substituents on aqueous molybdocene chemistry. Chapter I identifies the motivation for developing a transition metal-catalyzed process for cyanohydrin hydration and the strategy used to improve on the reactivity of molybdocene catalysts. Chapter II reports the effect of cyclopentadienyl ring substituents on the electronic and geometric structure, solution behavior, and hydrolytic activity of molybdocenes. To examine the effect of Cp ring substituents, ansa -molybdocenes containing the fragment {C 2 Me 4 (C 5 H 4 ) 2 }Mo 2+ were compared to non-bridged molybdocenes containing (C 5 H 5 ) 2 Mo 2+ and (C 5 H 4 Me) 2 Mo 2+ . Addition of a tetramethylethylene-bridge decreases the electron density on the Mo center and exerts a small effect on the structure of the metallocene. However, the catalytic activity of the molybdocene catalysts is unchanged or slowed because of counteractive effects on the bound nucleophile and electrophile. Although adding substituents to the Cp rings did not change the catalytic activity of the molybdocene, the substituents led to significant changes in the equilibrium behavior. The equilibria have practical consequences that warrant investigation. Chapters III and IV chronicle the effect of Cp ring substituents on the monomer-dimer equilibria and the acidity of the molybdocene complexes, respectively. Interestingly, the monomer-dimer equilibrium established by ansa -{C 2 Me 4 (C 5 H 4 ) 2 }Mo(OH)(OH 2 ) + exhibits a strong solvent dependence. New equilibrium schemes are reported for the ansa and non- ansa complexes. Chapter V describes the reactivity of the molybdocene and Pt phosphinito catalysts toward cyanohydrins. Both catalysts gave unsatisfactory results; however, the à à à à à ±-hydroxy substituent of cyanohydrins facilitates nitrile hydration. The low reactivity exhibited by these systems was due to liberation of hydrogen cyanide from the cyanohydrin leading to acute poisoning of either catalyst. As discussed in Chapter VI, this study will expedite the innovation of new catalysts that are better suited to overcome the challenges associated with cyanohydrin hydration. This dissertation includes previously published and unpublished co-authored material. / Adviser: David R. Tyler

Rh(III) and Ir(III) dimeric complexes with tunable cyclopentadienyl (Cp) rings have proven versatile for both catalysis and as synthetic precursors. An efficient microwave method to synthesize Rh(III) and Ir(III) dimeric complexes [(η5-ring)MCl]2(μ2-Cl)2, (where (η5-ring)MCl = (η5-Me4C5R)Rh(III)Cl or (η5-Me4C5R)Ir(III)Cl) was developed. A modular design for the substituted cyclopentadienes HC5Me4R was based on Grignard reactions of 2,3,4,5-tetramethylcyclopent-2-en-1-one (R = alkyl, 12 examples; R = aryl, 3 examples) or by SNAr reactions of potassium tetramethylcyclopentadienide with perfluoroarenes (R = perfluoroaryl, 3 examples). Reaction of the Me4CpHR ligands with [M(COD)](μ2-Cl)2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) produced the dimeric complexes [Cp*RMCl]2(μ2-Cl)2 in moderate to excellent yield. The resulting dimers were characterized by nuclear magnetic resonance (NMR) spectroscopy, single-crystal X-ray diffraction (XRD), high-resolution mass spectrometry (HRMS), elemental analysis, and examined as catalysts for oxidative lactonization of 1,4- and 1,5-diols. Oxidative lactonization of 1,4-butanediol to afford γ-butyrolactone proceeded selectively and efficiently using [(η5-Me4C5R)IrCl]2(μ2-Cl)2 as the catalyst. Several R substituents were tested to assess electronic substituent effects. The most active complex contained an electron donating group, R = CHMe2 and successfully catalyzed the formation of diols to lactones across a range of 1,4- and 1,5-diols, generally in high yield. Computational analysis of the rate-determining b-hydrogen elimination reactions provided an atomistic account of observed trends in reaction yield and selectivity as a function of substrate structure, while accounting neatly for the observed selective formation of lactones (vs. succinaldehyde) in the transfer dehydrogenation of 1,4-butyrolactone. / Doctor of Philosophy / Rhodium(III) and iridium(III) complexes are useful synthetic precursors, catalysts, and biologically active compounds. This dissertation explores a rapid synthesis of these metal complexes and their subsequent catalytic applications with 1,4- and 1,5-diols. The oxidative lactonization of diols with rhodium and iridium complexes is an attractive one-pot synthesis, opening a variety of lactones to be produced. Structural studies involving novel fluorinated rhodium and iridium chloro-bridged dimers are discussed in detail.