Important reactions are catalyzed by enzymes employing polynuclear cofactors, often characterized by weak-field ligands and transition metal ions within the sum of the van der Waals radii. While the overall stoichiometries and, in many cases, the structures, of the cofactors are known, the roles of the individual metal ions remain uncertain. Our approach is to investigate model clusters stabilized by a hexadentate, trinucleating ligand. The hexaamine ligand \((MeC (CH_2NHC_6H_4-o-NHPh)_3) (^{Ph}LH_6)\) allows facile synthesis of the clusters \((^{Ph}L)Fe_3(thf)_3\), \((^{Ph}L)Fe_3 (py)_3\), and \((^{Ph}L)Fe_3(PMe_2Ph)_3\) (thf = tetrahydrofuran, py = pyridine). The phenyl substituents on the ligand sterically prevent strong M–M bonding, but permit weaker M–M orbital interactions, with Fe–Fe distances near those found in Fe metal. The complex \((^{Ph}L)Fe_3(thf)_3\) exhibits a well-isolated S = 5 or S = 6 ground state over 5 - 300 K, as evidenced by magnetic susceptibility and reduced magnetization data. However, in the stronger-field pyridine and phosphine complexes, temperature dependent susceptibility is observed which is best modeled as a spin state transition from S = 2 to S = 4. Variable-temperature crystallography and Mössbauer spectroscopy reveal a whole-molecule, rather than site-isolated, spin transition. The all-ferrous cluster \((^{Ph}L)Fe_3(thf)_3\) can be oxidized with triphenylmethyl halides or iodine to give singly-oxidized clusters of the form \((^{Ph}L)Fe_3X(L)\) and \([(^{Ph}L)Fe_3(\mu-X)]_2 (X = Cl, Br, I; L = thf, py)\), in which one Fe–Fe distance contracts to 2.30 Å and the others lengthen to 2.6-2.7 Å. The halide and solvent ligands coordinate a unique Fe, but Mössbauer spectroscopy shows that the diiron pair bears the oxidation. Magnetic data can be modeled by considering a high-spin ferrous ion ferromagnetically coupled to an \(S = 3/2 [Fe_2]^{5+}\) unit. When \([(^{Ph}L)Fe_3(\mu-Cl)]_2\) is reacted with two or five equivalents of \(CoCl_2\) in tetrahydrofuran, the fully-substituted complexes \((^{Ph}L)Fe_2CoCl(acn)\) and \((^{Ph}L)FeCo_2Cl(acn)\) (acn = acetonitrile) can be isolated. \(^1H\) nuclear magnetic resonance shows that they are distinct species, not a mixture, and the elemental ratios are confirmed by X-ray fluorescence spectroscopy. Mössbauer spectroscopy shows that the Co preferentially substitutes into the \([M_2]^{5+}\) unit, as the ferrous site doublet is completely absent in \((^{Ph}L)FeCo_2Cl(acn)\). / Chemistry and Chemical Biology

Palladium is one of the most common and versatile transition metals used in modern organometallic chemistry. The chemistry of palladium in its 0, +II, and +IV oxidation states is well-known; by comparison, the chemistry of palladium in its +III oxidation state is in its infancy. The work in this thesis involves the study of previously unknown Pd(III) complexes, including applications in materials chemistry and catalysis. / Chemistry and Chemical Biology

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [165]-173).

This dissertation details the use of click chemistry to prepare linear and nonlinear polymers containing metal-metal bonds. The incorporation of metal-metal bonds into the polymer simplfies the degradation mechanism, allowing fundamental mechanistic studies of polymer degradation. Click chemistry offered a brand new route to explore the preparation of these useful but intricate metal-metal bond-containing polymers. Chapter I discusses the utility of these types of polymers for mechanistic studies, the preparation of metal dimers with reactive functionalities, and the previous polymerization methods which have been explored. The need for a new polymerization strategy, such as click chemistry, is described. Chapter II explains the preparation of a new metal dimer click synthon, [(η5-C5H4(CH2)3OC(O)(CH2)2C≡CH)Mo(CO)3]2, and the necessary conditions needed to polymerize the synthon using click chemistry. A high molecular weight linear polymer was prepared, suggesting click chemistry is a viable route to nonlinear polymers. Chapter III presents a second novel metal dimer click synthon, [(η5-C5H4(CH2)3N3Mo(CO)3]2, and attempts to use click chemistry to prepare a star polymer containing metal-metal bonds. A small amount of nonlinear polymer was prepared but several reactivity problems were also discovered and addressed. Due to these problems with click chemistry, Chapter IV details a brand new method for preparing asymmetric metal dimers. CpMo(CO)3-Mo(CO)3Cp(CH2)3CH=CH2 is the first reported example of an asymmetric dimer, and (CH3)3CSi(CH3)2O(CH2)3CpMo(CO)3-Mo(CO)3Cp(CH2)3OC(CH3)2OCH3 is the first example of a bifunctional asymmetric dimer. Chapter V describes the synthesis of a different type of metal dimer, (CH3)2Si[(C5H5)Mo(CO)3]2, which is polymerized by thermal ring opening polymerization. The dimer did not polymerize as expected and yielded an interesting polymer which has both Mo-Mo single bonds and Mo≡Mo triple bonds. Finally, Chapter VI provides a summary of the work as well as an honest perspective of using click chemistry to prepare metal-metal bond-containing polymers. This dissertation includes previously published and unpublished co-authored material. / 10000-01-01

Orientador: Oswaldo Luiz Alves / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-03T05:27:03Z (GMT). No. of bitstreams: 1 Gimenez_IaradeFatima_D.pdf: 7431924 bytes, checksum: 111d7a36f4eca023aa58750b7969eb99 (MD5) Previous issue date: 2002 / Doutorado

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1982 / Includes bibliographical references. / by Lynda Gail Sturgeoff. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Chemistry

No description available.

No description available.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

This Thesis describes the synthesis and characterisation of new alkaline earth metal and aluminium gallyl complexes. Experimental studies were performed to investigate their structure. The reactivity of these species was also studied. <b>Chapter 1</b> introduces metal-metal bonded complexes containing alkaline earth metals and aluminium and the use of gallium(I) analogues of N-heterocyclic carbenes in the synthesis of heterobimetallic complexes of gallium. <b>Chapter 2</b> describes the synthesis and reactivity of alkaline earth gallyl complexes supported by beta-diketiminate ligands. <b>Chapter 3</b> presents the synthesis and reactivity of alkaline earth gallyl complexes supported by the carbazolide ligand CzOx. <b>Chapter 4</b> describes synthesis of aluminium-gallium bonded complexes supported by amidinate and b-diketiminate ligands and the attempted study of their reactivity. <b>Chapter 5</b> presents full experimental procedures and characterising data for the new complexes reported.