The chemistry of transition metal clusters has been a fast developing area of organometallic research in recent years. Compared to mononuclear metal complexes, polynuclear clusters offer more opportunities to study cooperative effects and electron reservoir properties between contiguous metal centers, in addition to functioning as storehouses for the release of catalytically active small fragments capable of exhibiting heterosite subtrate activation. Theoretically, metal clusters are intermediates between mononuclear complexes and metal surfaces, i.e., they serve as a bridge between molecular and solid-state chemistry. Transition metal clusters are ideal candidates to study M-M interactions stretching from the single bond to the collective metallic behavior found in a three-dimensional network of metal atoms. The reaction between the redox-active diphoshpine ligand bpcd and RU(CO) has been examined under a variety of conditions. The disubstituted cluster Ru3(CO)10(bpcd)(2) has been synthesized and shown to contain a chealating bpcd ligand, on the basis of IR and 31P NMR data. The cluster 2 (chelating isomer) undergoes cluster fragmentation at ambient temperatures in the dark to give the binuclear compound 3 and Ru3(CO)12, with no evidence for the formation of 4. Both 3 and 4 have been isolated and fully characterized in solution by IR and NMR spectroscopy, and …

With the values of 6Li T1 measured and the literature values of J(13C-6Li) for these compounds, three new 13C NMR techniques are developed for the analysis of organolithium compounds. Modifications to the spectrometer are discussed, as well as calibrations of the 6Li decoupler channel needed to set up these new experiments. The theoretical development of each technique is presented, as well as data from their verification, using organolithium compounds of known structure. Once qualified, the new experimental techniques are used to analyze a series of alkyllithium / lithium alkoxide mixed aggregates in solution, where structures and values of J(13C-6Li) may not be known. The combination of Ti relaxation measurements and 13C{1H, 6Li} triple resonance techniques serves as a means of determining the structure of organolithium aggregates in solution.

Flash photolysis techniques were applied to studies of solvent displacement by Lewis bases (L) from solvated metal carbonyl complexes of Cr, Mo, and W. On the basis of extensive studies of the reaction rate laws, activation parameters , and linear-free-energy-relationships, it was concluded that the mechanisms of solvent displacement reactions depend on the electronic and steric properties of the solvents and L, as well as the identities of the metal atoms. The strengths of solvent-metal bonding interactions, varying from ca. 7 to 16 kcal/mol, and the bonding "modes" of solvents to metals are sensitive to the structures of the solvent molecules and the identities of the metal centers. The results indicate dissociative desolvation pathways for many arene solvents in (solvent)Cr(CO)_5 (solvent = benzene, fluorobenzene, toluene, etc.) complexes, and are consistent with competitive interchange and dissociative pathways for (n-heptane)M(CO)_5. Different types of (arene)-Cr(CO)_5 interactions were suggested for chlorobenzene (CB) vs. fluorobenzene and other non-halogenated arenes, i.e. via σ-halogen-Cr bond formation in the CB solvate vs. π-arene-Cr bond formation through "isolated" double bonds in solvates of the other arenes. The data also indicate the increasing importance of interchange pathways for solvent displacement from the solvates of Mo and W vs. that of …

The United States leads the world in per capita production of Municipal Solid Waste (MSW), generating approximately 200 million tons per year. By 2000 A.D. the US EPA predicts a 20% rise in these numbers. Currently the major strategies of MSW disposal are (i) landfill and (ii) incineration. The amount of landfill space in the US is on a rapid decline. There are -10,000 landfill sites in the country, of which only 65-70% are still in use. The Office of Technology Assessment (OTA) predicts an 80% landfill closure rate in the next 20 years. The development of a viable energy resource from MSW, in the form of densified Refuse Derived Fuel (dRDF), provides solutions to the problems of MSW generation and fossil fuel depletions. Every 2 tons of MSW yields approximately 1 ton of dRDF. Each ton of dRDF has an energy equivalent of more than two barrels of oil. At current production rates the US is "throwing away" over 200,000,000 barrels of oil a year. In order to be considered a truly viable product dRDF must be extensively studied; in terms of it's cost of production, it's combustion properties, and it's potential for environmental pollution. In 1987 a research …

The purpose of this dissertation is to investigate the thermodynamic properties of nonelectrolyte solutes dissolved in ternary solvent mixtures, and to develop mathematical expressions for predicting and describing that behavior in the solvent mixtures. Thirty-four ternary solvent systems were studied containing either alcohol (1-propanol, 2-propanol, 1-butanol, and 2-butanol), alkane (cyclohexane, heptane, and 2,2,4-trimethylpentane) or alkoxyalcohol (2-ethoxyethanol and 2-butoxyethanol) cosolvents. Approximately 2500 experimental measurements were performed. Expressions were derived from the Combined Nearly Ideal Multiple Solvent (NIMS)/Redlich-Kister, the Combined Nearly Ideal Multiple Solvent (NIMS)/Bertrand, Acree and Burchfield (BAB) and the Modified Wilson models for predicting solute solubility in ternary solvent (or even higher multicomponent) mixtures based upon the model constants calculated from solubility data in sub-binary solvents. Average percent deviation between predicted and observed values were less than 2%, documenting that these models provide a fairly accurate description of the thermodynamic properties of nonelectrolyte solutions. Moreover, the models can be used for solubility prediction in solvent mixtures in order to find the optimum solvent composition for solubilization or desolubilization of a solute. From a computational standpoint, the Combined Nearly Ideal Multiple Solvent/Redlich-Kister equation is preferred because the needed model constants can be calculated with a simple linear regressional analysis. Model constants …

This study is an investigation of the chemical vapor deposition (CVD) of aluminum and copper on fluoropolymer surfaces and the subsequent interfacial interactions.

Part I. Diels-Alder cycloadditions of 1,2,3,4,9,9-hexachloro-1α,4α,4aα,8aβ-tetrahydro-l,4-methanonaphthalene (32) and 1,2,3,4,9,9-hexachloro-lα,4α,6,7- tetrahydro-l,4-methanonaphthalene (33) to 4-methyl- and 4-phenyl-l,2,4-triazoline-3,5-dione [MTAD and PTAD, respectively] and to N-methylmaleimide (NMM) have been studied. The structures of several of the resulting cycloadducts were determined by X-ray crystallographic methods. The observed stereoselectivity of each of these Diels-Alder reactions was further investigated via application of theoretical methods. Thus, semiempirical (AMI) and ab initio molecular orbital calculations were used to calculate relative energies. Ab initio calculations were employed to perform frontier molecular orbital analyses of diene-dienophile interactions.

The focus of this research is to explore the molecular-level interactions between reactive metal surfaces and aqueous environments by combined ultra-high vacuum/electrochemistry (UHV-EC) methodology. The objectives of this work are to understand (1) the effects of sulfate ions on the passivity of metal oxide/hydroxide surface layer, (2) the effects of sulfur-modification on the evolution of metal oxide/hydroxide surface layer, and (3) the effects of sulfur adsorbate on cation adsorption at metal surfaces.

This study was intended to provide a fuller understanding of the surface chemical processes which result in the corrosion of ferrous materials.

The kinetics of ligand substitution for CO in Co4(CO)10(mu4-PPh2) , 1, have been investigated for the ligands P(OMe)3, P(OEt)3, PPh2H, P(0-i-Pr)3, P(n-Bu)3, PPh3, P(i-Pr)3, and PCy3 over a wide temperature range.

The purpose of this study was to determine the factors affecting the acid degradation of chrysotile asbestos (Mg_3Si_2O_5(OH_4)) . Millions of tons of asbestos have found use in this country as insulative or ablative material. More than 95 percent of the asbestos in use is of the chrysotile variety. The remaining 5 percent is composed of various types of fibrous amphiboles. The inhalation of asbestos can lead to several diseases in humans. Asbestosis, lung cancer and mesothelioma are the most common afflictions associated with asbestos inhalation, and they may occur up to 40 years after the initial exposure. It has previously been reported that if more than 50 percent of the magnesium is removed from a chrysotile sample its carcinogenicity is reduced to nil. Several inorganic acids were studied to determine their ability to leach magnesium from chrysotile. It was found that the ability to leach magnesium was dependent upon the acidic anion in addition to the concentration of the acid. The ordering of the efficiency of the acids in their ability to remove magnesium from chrysotile was found to be HCl > H_2SO_4 > H_3PO_4 > HNO_3. Predictive equations were developed to allow the calculation of the amount of …

The purpose of this dissertation is to investigate the behavior of polycyclic aromatic hydrocarbons (PAHs) in binary solvent systems and determine and/or develop predictive mathematical expressions for describing solutions in which hydrogen-bonding occurs.

New one- and two-dimensional NMR techniques were used to elucidate the solution structures of these complex mixtures. The system, lithium tert-butoxide/tert-butyllithium, was studied as a model system with O/Li ratios varying from 0/1 to 1/1. It was found that at low O/Li ratios, a single mixed tetrameric aggregate was formed. At higher O/Li ratios, mixed hexameric species were formed. Two other systems, lithium isopropoxide/iso-propyllithium and lithium n-propoxide/n-propyllithium were also studied at low O/Li ratios.

The tricobalt cluster PhCCo3(CO)9 (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in the presence of added Me3NO to give the diphosphine-substituted cluster PhCCo3(CO)7(bma) (2). Cluster 2 is unstable in solution, readily losing CO to afford Co3(CO)6[(μ2-η2/η1-C(Ph)C=C(PPh2)C(O)OC(O)](μ2-PPh2) (3) as the sole observed product. VT-31P NMR measurements on cluster 2 indicate that the bma ligand functions as both a chelating and a bridging ligand. At -97 °C, 31P NMR analysis of 2 reveals a Keq of 5.7 in favor of the bridging isomer. The bridged bma cluster 2 is the only observed species above -50°C. The solid-state structure of 2 does not correspond to the major bridging isomer observed in solution but rather the minor chelating isomer. The conversion of 2 to 3 followed first-order kinetics, with the reaction rates being independent of the nature of the reaction solvent and strongly suppressed by added CO, supporting a dissociative loss of CO as the rate-determining step. The activation parameters for CO loss were determined to be ΔH≠ = 29.9 ± 2.2 kcal/mol and ΔS≠ = 21.6 ± 6 eu.

A group of azabiphenyl complexes and supramolecules, and their reduced and oxidized forms when possible, were characterized by cyclic voltammetry and electronic absorption spectroscopy. The oxidized and reduced species, if sufficiently stable, were further generated electrochemically inside a specially designed quartz cell with optically transparent electrode, so that the spectra of the electrochemically generated species could be taken in situ. Assignments were proposed for both parent and product electronic spectra. Species investigated included a range of Ru(II) and Pt(II) complexes, as well as catenanes and their comparents. Using the localized electronic model, the electrochemical reduction can be in most cases assigned as azabiphenyl-based, and the oxidation as transition metal-based. This is consistent with the fact that the azabiphenyl compounds have a low lying π* orbital. The electronic absorption spectra of the compounds under study are mainly composed of π —> π* bands with, in some cases, charge transfer bands also.

Part I: In the first study of pyrethroids, twenty-one novel pyrethroid esters bearing strong electron-withdrawing groups (e.g., halomethylketo and nitro groups) in the double bond side chain of the cyclopropane acid moiety have been synthesized and evaluated for insect toxicity. Rather than the usually employed Wittig reaction for these syntheses, the novel pyrethroid acid moieties were prepared by amino acidcatalyzed Knoevenagel condensations under mild conditions. In the second study of pyrethroids, fourteen pyrethroid-like carbonates were synthesized by condensation of a variety of alcohols and the chloroformates of the corresponding known pyrethroid alcohols.

This research investigated the chemistries and mechanisms involved in lead-cement systems through the study of a larger number of lead compounds.

The fluorescence spectrum of many polycyclic aromatic compounds (PACs) depends upon solvent polarity. The emission spectrum of PAC monomers consists of several major vibronic bands labeled I, II, etc., in progressive order. Emission intensity enhancement of select bands is observed in polar solvents.

Pulsed laser flash photolysis with both visible and infrared detection has been applied to the study of the displacement of weakly coordinating ligands (Lw) by strongly "trapping" nucleophiles (Ls) containing either an olefinic functionality (Ls = 1-hexene, 1-decene, 1-tetradecene) or nitrogen (Ls = acetonitrile, hydrocinnamonitrile) from the photogenerated 16 electron pentacarbonylchromium (0) intermediate. 5-Chloropent-l-ene (Cl-ol), a potentially bidentate ligand, has been shown to form (ol-Cl) pentacarbonylchromium (0), in which Cl-ol is bonded to Cr via a lone pair on the chlorine, and isomerize to (Cl-ol) pentacarbonylchromium (0), in which Cl-ol is bonded to the olefinic functionality on the submillisecond time scale. This process has been studied in both the infrared and visible region employing both fluorobenzene or n-heptane as the "inert" diluent. Parallel studies employing 1-chlorobutane and 1-hexene were also evaluated and showed great similiarity with the Cl-ol system. The data supported a largely dissociative process with a possibility of a small interchange process involving the H's on the alkyl chain. Studies were also carried out for various Cr(CO)6/arene/Ls systems (arene = various alkyl or halogenated substituted benzenes). The data indicated that for both C6H5R (R=various alkyl chains) or multi-alkyl substituted arenes (i.e. o-xylene, 1,2,3-trimethylbenzene) containing an "unhindered" ring-edge, bonding …

Dissertation research involves development of Mobile Order Theory thermodynamic models to mathematically describe and predict the solubility, spectral properties, protonation equilibrium constants and two-phase partitioning behavior of solutes dissolved in binary solvent mixtures of analytical importance. Information gained provide a better understanding of solute-solvent and solvent-solvent interactions at the molecular level, which will facilitate the development of better chemical separation methods based upon both gas-liquid and high-performance liquid chromatography, and better analysis methods based upon complexiometric and spectroscopic methods. Dissertation research emphasizes chemical equilibria in systems containing alcohol cosolvents with the understanding that knowledge gained will be transferable to more environmentally friendly aqueous-organic solvent mixtures.

The Sn/Pb eutectic alloy system is the most widely used joining material in the electronics industry. In this application, the solder acts as both an electrical and mechanical connection within and among the different packaging levels in an electronic device. Recent advances in packaging technologies, however, driven by the desire for miniaturization and increased circuit speed, result in severe operating conditions for the solder connection. In an effort to improve its mechanical integrity, metallic or intermetallic particles have been added to eutectic Sn/Pb solder, and termed composite solders. It was the goal of this study to investigate the growth and morphology of the two intermetallic phases (Cu6Sn5 and Cu3Sn) that form between a Cu substrate and Sn/Pb solder under different aging and annealing conditions.

A novel crown ether precursor was developed in which a rigid 4-oxahexacyclo (5.4.1.26.3,10.05,9.08,11) dodecyl cage moiety ("cage functionality") was incorporated.

Sulfur adsorbed on metallic and oxide surfaces, whether originating from gaseous environments or segregating as an impurity to metallic interfaces, is linked to the deterioration of alloy performance. This research dealt with investigations on the interactions between sulfur and iron or iron alloy metallic and oxide surfaces under ultrahigh vacuum conditions. Sulfur was either intentionally dosed from a H2S source on an atomically clean metal surface, or segregated out as an impurity from the bulk to the metal surface by annealing at elevated temperatures.

Detection, identification and separation of polycyclic aromatic compounds in environmental samples are of extreme importance since many of these compounds are well known for their potential carcinogenic and/or mutagenic activities. Selective quenching of molecular fluorescence can be utilized effectively to analyze mixtures containing different polycyclic aromatic hydrocarbons. Molecularly organized assemblies are used widely in detection and separation of these compounds mainly because of less toxicity and enhanced solubilization capabilities associated with these media. Feasibility of using nitromethane and the alkylpyridinium cation as selective fluorescence quenching agents for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is critically examined in several molecularly organized micellar solvent media. Fluorescence quenching is used to probe the structural features in mixed micelles containing the various combinations of anionic, cationic, nonionic and zwitterionic surfactants. Experimental results provide valuable information regarding molecular interactions between the dissimilar surfactants.