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Thesis (Ph.D.)--University of Tulsa, 1992. / Bibliography: leaves 109-113.

Inaug.-diss.--München. / Includes bibliographical references.

Thesis (Ph. D.)--Columbia University, 1935. / Vita.

The work described in this thesis is a study of iron-sulphur-nitrosyls and related compounds. Chapter One is an introduction to the work presented. Chapter one is introduction to the work presented. Chapter Two is concerned with the analogous Fe2(SR)2(CO)6 and its conversion to Fe2(SR)2(NO)4. Chapter Three is concerned with an n.m.r. study of Fe2(SR)2(NO)4, Fe2X4(NO)4 and [Fe4X3(NO)7] (X=S, Se). Chapter four is concerned with an e.p.r. examination with an n.m.r. study of Fe2(SR)2(NO)4, Fe2X4(NO)4 [Fe4X3(NO)7] (X=S,Se). Chapter four is concerned with an e.p.r. examination of Fe2(SR)2(NO)4 and bridging ligand exchange reactions. Chapter Five is concerned with a similar examination of Fe2I2(NO)4.Chapter six is concerned with an examination of ligand exchange processes in Fe4S4(NO)4 and [Fe4S4(NO)4]. Chapter Seven is concerned with an investigation of iron-sulphur protein models and their conversion to iron-nitrosyls.

Salts of the bls(μ-thiosulphato-S)-bis(dinitrosylferrate)(2-) anion, [Fe2(S2o3)2(NO)4]2- can be prepared by the reaction of iron(ll)/thiosulphate mixtures with nitrite ion. The crystal structure of {(Ph3P)2N}2[ Fe2(S203)2(NO)4] reveals it to adopt a trans structure. 15N n.m.r. studies of this salt also show it to adopt the trans structure in solution. The anion reacts with thiolate ion, RS-, to provide good yields of Fe2(SR)2(NO)4; e.p.r. studies show the mononitrosyl [Fe(N0)(SR)3]3− to be a major intermediate in this reaction. Salts of the Black Roussin ion, [Fe4S3(NO)7]- react with aryldiazonium salts, ArN2+ , to produce Fe2(SAr)2(NO)4. 13C n.m.r. studies of Fe2(SC6H4F)2(NO)4 reveal it to exist in a 1:1 ratio of cis and trans isomers. Reaction of the Black anion with trialkylsulphonium or sulphoxonium salts leads to the metathesis product. The crystal structure of Me3S[Fe4S3(NO)7] shows no evidence for the closure of the iron-sulphur cage by the sulphur of the Me3S cation. Reaction of the Black anion with trialkyloxonium salts provides good yields of Fe2(SR)2(NO)4. Electrochemical studies on Fe2(SR)2(NO)4 by conventional cyclic voltammetry shows two chemically and electrochemically reversible one electron reductions to produce [Fe2(SR)2(NO)4]− and [Fe2(SR)2(NO)4]2−. The monoanion is a paramagnetic complex with g= 1.995; coupling to four equivalent nitrogens shows the presence of a delocalised electron. The electrochemical behaviour of the dianion is dependent on the electrode material; reversible on a glassy carbon electrode but quasi-reversible on platinum. Fe2(SR)2(NO)4 also exhibits a three electron oxidation; the anodic current of which increases in the presence of primary amines. Electrochemical studies on the Black Roussin ion and its selenium analogue [Fe4Se3(NO)7]− show similar electrochemical responses: three reversible one electron reductions and an irreversible multielectron oxidation. Extended Huckel molecular orbital calculations on [Fe2S2(NO)4]2− , Fe2(SMe)2(NO)4 and [Fe2(S203)2(N0)4]2− reveal little direct Fe-Fe interaction in these complexes. Reduction or oxidation would result in the addition or removal of electron density from orbitals of mainly Fe-S character. An electrochemical study of Fe(NO)(S2C N R2)2 by cyclic voltammetry shows a reversible one electron reduction and an Irreversible oxidation in tetrahydrofuran and dichloromethane. In acetonitrile the reduction of the complex is coupled to a chemical step making the reduction chemically irreversible at low scan rates. The observed variation of E with R is due to the inductive effect of R.

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Iron-catalysed carbonyl reduction, nitro reduction, formal hydroamination, and the radical alkenylation of alkyl halides have been developed. A Simple, easy-to-make, air- and moisture-stable iron(III) amine-bis(phenolate) complex catalysed the hydrosilylation of carbonyl compounds efficiently using triethoxysilane as the reducing agent. The reaction tolerated a wide range of substrates to give the corresponding alcohol products in good to excellent yields after hydrolysis of the hydrosilylated products (Scheme A1). Scheme A1. Iron-Catalysed Hydrosilylation of Carbonyl Compounds. The same catalyst was also an active catalyst for the chemoselective reduction of nitro arenes into corresponding amines using triethoxysilane as reducing agent. The method exhibited excellent chemoselectivity as other reducible functional groups such as halogen, ester, nitrile all kept unchanged during the reaction. This catalytic system was then successfully applied to the formal hydroamination of alkene to give substituted amine in synthetic useful yields under mild condition. The reaction is hypothesised to proceed through a radical intermediate (Scheme A2). Scheme A2. Iron-Catalysed Nitro Reduction and Alkene Formal Hydroamination. Finally, FeCl2-catalysed formal Heck cross-coupling has been developed between alkyl halides and styrenes. The reaction tolerated both electron-rich and electron-neutral substrates to give the products in moderate to excellent yields. Initial studies revealed that the reaction also proceeds through a radical intermediate (Scheme A3). Scheme A3. Iron-Catalysed Formal Heck Cross-Coupling of Functionalised Alkyl Halides.

Graduate / 0485