The novel bimetallic hydrides [(n⁵-C₅H₅)W(N0)IH]₂ and [(n⁵-C₅H₅)W(N0)H₂]₂ can be prepared sequentially by the metathesis of [(n⁵-C₅H₅)W(N0)IH₂]₂ with Na[H₂Al(0CH₂CH₂0CH₃)₂]. Analyses of the ¹H NMR spectra of C[(n⁵-C₅H₅)W(N0)IH]₂ and [(n⁵-C₅H₅)W(N0)IH₂]₂ show the former contains hydride ligands bound to tungsten in a terminal fashion, while the latter possesses two terminal and two bridging hydrides. Addition of a Lewis base to [(n⁵-C₅H₅)W(N0)IH]₂ results in the formation of hydride species (n⁵-C₅H₅)W(N0)IHL (L = P(0Ph)₃, P(0Me)₃, PPh₃); in like manner, the dimer [(n⁵-C₅H₅)W(N0)IH₂]₂ is cleaved by triphenylphosphite to form the monomer cis or trans [(n⁵-C₅H₅)W(N0)IH₂[P(0Ph)₃]. A comparison is made of the reactivity of the tungsten-hydrogen link in the nitrosyl hydrides (n⁵-C₅H₅)- W(N0)IH[P(0Ph)₃], (n⁵-C₅H₅)W(N0)₂H, and (n⁵-C₅H₅)W(N0)IH₂[P(0Ph)₃]. The Mo(N0)₂²⁺ unit is obtained as the tetrakis-solvate via chloride abstraction from Mo(N0)₂Cl₂ by AgBF₄ or nitrosylation of Mo(C0)₆ by NOPF₆ in coordinating solvents such as nitromethane, acetonitrile, or tetrahydro-furan. The unsolvated complex [Mo(N0)₂(PF₆)₂][aub=n] is produced if the latter reaction is performed in dichloromethane; however, it readily converts to [Mo(N0)₂S₄](PF₆)₂ upon exposure to coordinating solvents (S). Hard Lewis bases (L = CH₃CN , 0PPh₃ or L₂ = 2 ,2-bipyridine replace the solvent molecules in [Mo(N0)₂S₄]X₂ (X = BF₄⁻, PF₆⁻) forming complexes [Mo(N0)₂L₄]²⁺ or [Mo(N0)₂L₂S₂]²⁺ depending upon the solvent employed. Reagents capable of being oxidized appear to reduce the dinitrosyl dication without permanent coordination to the molybdenum centre. Reduction of [Mo(NO)₂S₄](PF₆)₂ or [Mo(N0)₂(PF₆)₂][sub=b] is effected by sodium amalgam (one equivalent); addition of a ligand L₂ (L₂ = 2,2-bipyridyl, 3,4,7,8-tetramethyl-1,1O-phenanthroline) to the reaction mixture permits the isolation of [M(NO)₂L₂]₂(PF₆)₂. Addition of excess ligand results in the formation of non-nitrosyl containing species [Mp(L₂)₃]PF₆ (L = 0PPh₃ or L₂ = 3,4,7,8-tetramethyl-1 ,10-phenanthro- line). Decomposition of the nitrosyl species results from attempts to reduce [Mo(NO)₂S₄]²⁺ by two electrons. New complexes are identified by the aid of IR and ¹H, ¹⁹F, or ³¹P NMR spectroscopy and conductance measurements. Attempts to prepare thionitrosyl analogues of [Mo(N0)₂L₄]²⁺ have met with limited success; the only wel1-characterized thionitrosyls isolated in this study are the known (n⁵-C₅H₅)Cr(C0)₂NS and the new [(n⁵-C₅H₅)Mo-(N0)(NS)PPh₃]BF₄. Also discussed is the interaction of NOPF₆ with solvents. NOPF₆ has been found to react slowly with acetonitrile, a common solvent for nitro-sonium salts. / Science, Faculty of / Chemistry, Department of / Graduate

<p> 1-nitropyrene and 1,8-dinitropyrene are environmental pollutants and direct-acting mutagens in bacteria. Studies have shown that reduction of the nitro group is essential for the expression of the mutageneity of these compounds and the formation of covalent DNA adducts in Salmonella typhimurium. It has also been shown that the corresponding amino compounds are only slightly mutagenic. Since the reduction of nitro compounds to amino compounds must proceed via the nitroso and hydroxylamino intermediates, it has been proposed that the hydroxylamines derived from 1-nitropyrene and 1,8-dinitropyrene are the ultimate mutagens.</p> <p> 1-nitrosopyrene and 1-nitroso-8-nitropyrene were synthesized and reduced to their corresponding hydroxylamines with ascorbic acid. While 1-nitrosopyrene (50,226 rev/nmole) was 50X more potent than 1-nitropyrene (985 rev/nmole) in the Ames Test, 1-nitroso-8-nitropyrene (8,000 rev/nmole) was 10X less potent than 1,8-dinitropyrene (85,830 rev/nmole). The hydroxylamines derived from these compounds proved to be very labile species and could not be characterized.</p> / Thesis / Master of Science (MSc)

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Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Ph.D. (Chemistry) / Please refer to full text to view abstract

The redox behavior of a series of organometallic complexes containing Cp'M(NO) groups (Cp' = ƞ⁵-C₅H₅(Cp) or ƞ⁵-C₅Me₅(Cp*) ; M = Mo or W) has been investigated both by cyclic voltammetry and by chemical means. The neutral 16-electron Cp'Mo(N0)X₂ compounds (X = CL, Br or I) undergo a single, essentially reversible, one-electron reduction in CH₂CL₂/O.1M [n-Bu₄N]PF₆ at relatively low potentials (<-0.1 V vs SCE). The electrochemically observed reductions can be effected on a preparative scale by employing CP₂C0 as the chemical reductant. The isolable 17-electron [Cp'Mo (NO)X₂]•⁻ radical anions are cleanly reconverted to their 16-electron neutral precursors by treatment with [Cp₂Fe]BF₄. In contrast, the Cp'W(NO)I₂ compounds undergo rapid decomposition to their [Cp'W(NO)I]₂ monohalo dimers upon electrochemical reduction. Electrophiles NE⁺ (E = O or ϱ-O₂NC₆H₄N) undergo unprecedented insertions into the Cr-C ϭ-bonds of CpCr(NO)₂R complexes (R = Me, CH₂SiMe₃ or Ph) to afford [CpCr(N0)₂{N(E)R}]⁺ cationic complexes. Present evidence is consistent with these insertions occurring via charge-controlled, intermolecular attacks by NE⁺ at the Cr-R groups in classical SE2 processes. The newly-formed N(E)R ligands function as Lewis bases through nitrogen atoms toward the formally 16-electron [CpCr(NO)₂]⁺ cations and may be displaced from the chromium's coordination sphere by the more strongly coordinating CL⁻ anion. The resulting CpCr(NO)₂CL can be reconverted to CpCr(NO)₂R. thereby completing a cycle by regenerating the initial organometallic reactant. The entire sequence of stoichiometric reactions forming the cycle thus constitutes a selective method for the formation of new carbon-nitrogen bonds, the net organic conversions mediated by the CpCr(NO)₂ group being NE⁺ + R⁻ → N(E)R. The electrophilic [Cp'M(NO)₂]⁺ cations (Cp'=Cp or Cp* ; M = Cr, Mo or W) condense with methyl propiolate and 2,3-dimethyl-2-butene to afford cationic organometallic lactone complexes. These complexes undergo facile ⍜-dealkylation to yield the neutral Cp'M(NO)₂(ƞ¹-lactone) derivatives. Furthermore, the neutral Cp'W(NO)₂(ƞ¹-lactone) compounds decompose in air to their Cp'W(O)₂(ƞ¹-lactone) dioxo products. / Science, Faculty of / Chemistry, Department of / Graduate

Although hydrides of metal carbonyls are widely known, the number of hydrides in the related family of metal nitrosyls is extremely small. The preparation of a series of nitrosyl hydrides from the treatment of [CpW(NO)I₂]₂ (Cp=ƞ⁵-C₅H₅) with Na[H₂Al(OCH₂CH₂OCH₃)₂] is described. The addition of one or two equivalents of the aluminum reagent results in the formation of [CpW(NO)IH]₂ or [CpW(NO)H₂]₂ respectively. The reaction of [CpW(NO)IH]₂ with a Lewis base (L=P(OPh)₃, P(OMe)₃, PPh₃ or PMe₃) gives the monometallic CpW(NO)IHL, while [CpW(NO)H₂]₂ reacts with P(OPh)₃ or P(OMe)₃ to yield [CpW(NO)HL]₂ which undergoes further reaction to give CpW(NO)H₂L. Proton NMR spectroscopy shows that all bimetallic species contain bridging hydride ligands and are therefore best, formulated as [CpW(NO)1]₂(µ-H)₂, [CpW(NO)H]₂(µ-H)₂ and [CpW(NO)L]₂(µ-H)₂. The ¹H NMR spectrum of [CpW(NO)H]₂(µ-H)₂ shows that there is no hydride ligand exchange on the NMR time scale and that ¹jH(terminal)W ≃ ¹jH(bridging)w > ²jHW. From this finding, it is possible to develop new criteria for assessing the static or fluxional nature of hydride ligands for several families of organotungsten hydrides (Cp₂W, CpW(CO)₃, W(CO)₃ and CpW(NO)x (x=l or 2)). Within each family, the magnitude of ¹JHW strongly reflects the type of metal hydride bonding, i.e. [Formula Omitted] and suggests that bridge bonding involves all the atoms in the bridge and therefore the "fused" notation is introduced. Treatment of CpW(NO)(CH₂SiMe₃)₂ with low pressures of H₂ (60-80 psig) in the presence of Lewis bases (L=P(0Ph)₃, PMePh₂) gives the unusually stable alkyl hydride compounds CpW(NO)(H)(CH₂SiMe₃)L. This chemistry is then extended to the Cp* (Cp*=ƞ⁵ -C₅Me₅) analogues, including the preparation of the appropriate starting materials. Upon thermolysis of Cp*W(NO)(H)(CH₂SiMe₃)(PMe₃) in C₆H₆, the intermolecular C-H activation product Cp*W(N0)(H)(C₆H₅)(PMe₃) is cleanly formed. However, intermolecular activation of CH₄, C₆H₁₂ or n-C₆H₁₄ does not occur under similar experimental conditions. Hydrogenolysis of Cp*W(NO)(CH₂SiMe₃)₂ at high pressures (≃920 psig) with no Lewis base present results in the formation of isolable [Cp*W(NO)H]₂(µ-H)₂ and [Cp*W(N0)H](µ-H)₂[Cp*W(N0)(CH₂SiMe₃)]. The latter is a new example of the rare class of dinuclear alkyl hydride complexes. Proton NMR spin tickling experiments on this compound allow the complete assignment of all couplings in the spectrum and show that ¹jH(terminal)W' ¹JH(bridging)W and ²jHW have the same sign. / Science, Faculty of / Chemistry, Department of / Graduate

The nitrosyl complex CpW(NO)R₂ (R = CH₂SiMe₃) forms 1:1 adducts via isonitrosyl linkages to Lewis acids such as AlMe₃ and Cp₃Er, i.e. CpWR₂(NO→A) (A = AlMe₃, ErCp₃). These adducts regenerate the starting dialkyl complex when treated with water. Protonation of CpW(NO)R₂ by HBF₄⋅0Me₂ can also be effected. Whether the site of protonation is the nitrogen or the oxygen atom of the nitrosyl ligand is not known with certainty, although O-protonation is postulated by analogy with the other Lewis-acid adducts of CpW(NO)R₂. In these adducts, the nitrosyl stretching frequency is shifted to lower wavenumbers relative to that of the parent dialkyl, to an extent which increases as harder Lewis acids are employed. The colour of the adducts also ranges from red to orange to yellow as progressively harder acids are used. Treatment of CpW(NO) (CH₂SiMe₃)₂ with [Ph₃C]⁺ PF₆⁻ in Ch₂CL₂ results in electrophilic cleavage of a carbon-silicon bond to yield the mixed dialkyl CpW(NO)(CH₂SiMe₃)(CH₂CPh₃), which has been fully characterized by spectroscopic methods and by a single-crystal X-ray crystallographic study. The formation of Me₃SiF and PF₅ (coordinated to Lewis bases in the reaction mixture) as by-products of this reaction has been confirmed by ³¹P and ¹⁹F NMR spectroscopy of the reaction mixture in CD₂CL₂. Preliminary attempts to extend this novel reaction of a silicon-containing ligand by using other carbocations were unsuccessful. This is attributed to the high reactivity of the required carbocations and the large number of possible reaction sites on the metal complex. Some reactions of the mixed dialkyl CpW(NO)RR¹ (R = CH₂SiMe₃ R¹ = CH₂CPh₃) were found to be analogous to those of the parent CpW(NO)R₂, while other reactions followed a different course because of the ability of the CH₂CPh₃ ligand to orthometallate. Thus, CpW(NO)RR¹ is much less thermally stable than CpW(NO)R₂. As a solid or a solution in non-coordinating solvents, it decomposes in a matter of days at room temperatures to a mixture of products which were not identified. In acetonitrile solution, an orthometallated complex derived from CpW(NO)RR¹ can be trapped by coordination of solvent. The product CpW(NO)(CH₂C(C₆H₄)Ph₂)(NCMe) has been isolated and crystallographically characterized. Cyclic voltammograms of CpW(NO)R₂ and CpW(NO)RR¹ show that both complexes undergo an apparently chemically reversible reduction and an irreversible oxidation. The mixed dialkyl CpW(NO)RR¹ is somewhat easier both to reduce and to oxidize than CpW(NO)R₂. Like CpW(NO)R₂, CpW(NO)RR¹ reversibly forms a 1:1 adduct with PMe₃. Also analogously to CpW(NO)R₂, it reacts with 0₂ to form a 5:1 mixture of dioxoalkyl complexes CpW(0)₂R and CpW(0)₂R¹, and with NO(g) to form 2 CpW(NO)R¹(ƞ² -0₂N₂R). In this product, insertion of NO has occurred exclusively in the W-CH₂SiMe₃ bond. Upon photolysis, both complexes CpW(NO)R¹¹(ƞ²-0₂N₂R) (R¹¹ = CH₂SiMe₃ or CH₂CPh₃) form dioxo alkyls CpW(O)₂R¹¹ in an unprecedented reaction. The ability of CpW(NO)RR¹ to orthometallate also results in the formation, when this complex is treated with sulphur, of CpW(O)(CH₂C(C₆H₄)Ph₂)-(SR). No analogue to this compound can be obtained from reaction of CpW(NO)R₂ with sulphur. The sequence of reactions leading to the formation of this product is not known. / Science, Faculty of / Chemistry, Department of / Graduate