The thermal and photochemical reactions of the dianion of rhodizonic acid (1,2-dihydroxycyclohexenetetrone) and the kinetics of the photochemical reactions of the dianion of croconic acid (1,2-dihydroxycyclopentenetrione) have been studied in aqueous solution in the presence and absence of electron acceptors. For rhodizonate dianion, both thermal and photochemical reactions are initiated by electron transfer to an acceptor which is a sufficiently strong oxidizing agent. With hydrogen peroxide and ferricyanide, a square root dependence of the rate of disappearance of rhodizonate dianion on the concentration of additive was observed, whereas with tetracyanoethylene the rate was first order with respect to the concentration of additive. This difference in behavior is explained on the basis of the rate of separation of ions from the initial charge transfer complex. For croconate dianion, the quantum yield for disappearance of croconate dianion was small (10$\sp{-3}$) in neutral solution, but was substantially increased in basic solution and in the presence of electron acceptors. At pH 12 in the presence of 4-nitrobenzylbromide or biacetyl, a quantum yield of 1 was observed. The kinetics of the rate of disappearance of croconate dianion as a function of pH and concentration of acceptor showed that the excited dianion is oxidized by acceptors and reacts with hydroxyl ion. A mechanism is proposed that is shown to be consistent with the results. The main reaction product for rhodizonate dianion is croconate dianion, while for croconate dianion, the main reaction product is squarate dianion. Photopolymerization of acrylamide was initiated by the photochemical reactions of rhodizonate dianion and croconate dianion in the presence of various acceptors. Photoinitiation was most efficient with croconate dianion where a maximum quantum yield for polymerization of acrylamide of $2\times10\sp3$ was observed in neutral solution. Kinetic studies using croconate dianion as initiator showed that the rate of polymerization was a linear function of the concentration of monomer and proportional to the square root of the light absorbed by the croconate dianion. The rate of initiation of radicals calculated from the rate of polymerization was compared with the rate of production of radicals calculated from the steady state photolysis study of croconate dianion. Laser-induced flash photolysis study of rhodizonate and croconate dianions has been performed both in the presence and absence of electron acceptors. The rate constant for the recovery of the ground state from the excited state (k$\sb{\rm D})$ is $2.4\times10\sp5\ {\rm s}\sp{-1}$ for rhodizonate dianion and $2.8\times10\sp5\ {\rm s}\sp{-1}$ for croconate dianion in neutral solution. Absorption spectra of croconate monoanion radical with a maximum at 500 nm were observed in the presence of the additives 4-nitrobenzylbromide, biacetyl and methyl viologen. Rate constants for the diffusion-controlled electron transfer reactions from the excited croconate dianion to the acceptors (k$\sb{\rm T})$ were measured. The values of k$\sb{\rm T}$ were $\rm 2.0\times10\sp8\ M\sp{-1}s\sp{-1}$ for biacetyl, $\rm 2.8\times10\sp9\ M\sp{-1}s\sp{-1}$ for 4-nitrobenzylbromide and $\rm 3.7\times10\sp \ M\sp{-1}s\sp{-1}$ for methyl viologen. The rate constant for quenching of the excited state of croconate dianion by oxygen was $\rm 4.5\times10\sp9\ M\sp{-1}s\sp{-1}.$

Aromatic and aliphatic vinyl sulfones and sulfoxides have been hydroformylated with CO/H$\sb2$ in the presence of the zwitterionic rhodium complex, 1,5-cyclooctadiene rhodium(I) tetraphenylborate, (1,5-(COD)Rh$\sp+(\eta\sp6$-$\rm C\sb6H\sb5)B(C\sb6H\sb5)\sb{3\sp-}),$ to give previously unknown aldehydic sulfones and sulfoxides in excellent yields and regioselectivities. The hydroformylation of phenyl vinyl sulfoxide in the presence of 1,5-(COD)Rh$\sp+(\eta\sp6$-$\rm C\sb6H\sb5)B(C\sb6H\sb5)\sb{3\sp-}$ and the chiral phosphine ligand, BINAP, demonstrated considerable stereodifferentiating ability (up to 50% de). The hydroesterification of vinyl esters with CO/MeOH/bis(triphenylphosphine)palladium(II) dichloride, $\rm ((PPh\sb3)\sb2PdCl\sb2),$ has been studied. The critical necessity of catalytic amounts of acid, such as $\rm H\sb3PO\sb4$ (1 mol% relative to substrate), was revealed. This reaction is also catalyzed by the cationic palladium(II) hydrido complex, $\rm \lbrack (Cy\sb3P)\sb2Pd(H)(H\sb2O)\rbrack\sp+BF\sb{4\sp-}.$ Lactic acid derivatives can be synthesized with modest ee's (up to 30%) using $\rm \lbrack (Cy\sb3P)\sb2Pd(H)(H\sb2O)\rbrack\sp+BF\sb{4\sp-}$ in the presence of BINAP. Design and synthesis of new chiral borate ligands and their rhodium complexes have been undertaken.

This thesis describes the palladium-catalyzed carbonylation of alkynes with formic acid. Terminal alkynes react with formic acid in the presence of catalytic amounts of Pd(OAc)$\sb2$ and suitable phosphine ligands (120 psi of CO gas pressure, 100-110$\sp\circ$C) to produce the unsaturated carboxylic acids CR(COOH)=CH$\sb2,$ 1, and (E)-CHR=CH(COOH), 2. The combined yields of 1 and 2 for various R's range from 60 to 90%. The regioselectivity is approximately 90:10 in favour of 1 when R is a phenyl or a straight chain alkyl group; 2 is the favoured product when R is t-Bu and the exclusive one when R is SiMe$\sb3.$ Under similar conditions, internal alkynes react with formic acid to produce the unsaturated carboxylic acids (E)-CR(COOH)=CHR$\sp\prime$, 3, and (E)-CHR=CR$\sp\prime$(COOH), 4, also in 60-90% combined yields. The regioselectivity of this reaction, however, is not as high as for terminal alkynes. Oxalic acid can be used instead of formic acid in both of these reactions. The most suitable phosphine ligands for alkyne hydrocarboxylation in the present system are PPh$\sb3$ and dppb (1,4-bis(diphenylphosphino)butane). In some cases, using a mixture of these two ligands remarkably improves the reaction yields; the implications of such ligand synergism are discussed. On the basis of deuterium labelling studies and other experimental results, a reaction mechanism has been proposed which involves the addition of the O-H bond of formic acid to form a cationic hydrido(alkyne) intermediate. This intermediate is thought to undergo a sequence of reactions, including hydride and CO insertions, to give the acid product and regenerate the active catalyst. Terminal alkynes undergo dicarbonylation upon reacting with formic acid and/or water in a catalytic system consisting of $\rm PdCl\sb2/CuCl\sb2/O\sb2/CO$ (room temperature, atmospheric pressure); the products are monosubstituted maleic anhydrides and the corresponding maleic and fumaric acids in 30-75% combined yields. The product distribution is influenced by both the steric bulk of the alkyne substituent and the amount of water present in the reaction medium. Internal alkynes are unreactive in this system. Among the solvents tested, THF is the most suitable one. Phosphines and phosphites completely inhibit the reaction. In contrast to most systems in which CuCl$\sb2$ acts as the principal oxidant for converting Pd(0) to Pd(II), the role of CuCl$\sb2$ in the present system seems to be secondary to that of oxygen. For instance, modest catalytic turnovers are observed in the absence of CuCl$\sb2$, whereas no catalysis occurs if oxygen is excluded from the system, even in the presence of excess CuCl$\sb2$. These and other observation are rationalized by invoking various oxidation schemes involving oxygen as the main oxidant. The role of CuCl$\sb2$ is thought to be one of facilitating the catalysis by forming a heterometallic Cu/Pd complex.

In order to obtain more information required for the catalytic conversion of methane, the interaction of methane and ethylene with various supported metal catalysts was investigated. The metals used were Ni, Fe, Co, Mo, Ru, Rh, Pd, Re, Ir, and Pt, all supported on $\rm Al\sb2O\sb3.$ Silica supported nickel was also used. The technique of temperature programmed reaction was mainly used. This method gives temperatures at which the adsorption and/or the reaction of a gas starts to occur. The present results showed wide differences in the interaction of methane or ethylene with each catalyst. The isothermal reaction of methane was also carried out in order to further investigate the behaviour of the CH$\sb{\rm n}$ species which were formed upon the chemisorption of methane. As a process for converting methane to higher hydrocarbons, the catalytic coupling of methane with ethylene (CH$\sb4$ + $\rm C\sb2H\sb4\to C\sb3H\sb8$) was examined by using the catalysts listed above. At 250 and 350$\sp\circ$C, no propane was produced on any of the catalysts, except for alumina supported platinum. A trace of propane was found in this case for the reaction at 250$\sp\circ$C. The results were discussed based on the interaction of the reactants with these metals as revealed by the temperature programmed reactions.

Part A. Chapter 1. The Sharpless epoxidation product from E-4-phenyl-2-butene-1-ol and diethyl D-tartrate was converted into L-($-$)-phenylalanine in three steps. After completion of the above synthesis Sharpless published an extensive study of the synthesis of $\alpha$-amino acids via essentially the same route. Therefore the project was abandoned. Optically active 2-arylpropionic acids such as 2-phenylpropionic acid, 2-napthylpropionic acid, and 2-(4-isobutylphenyl)-propionic acid (Ibuprofen) were synthesized in two steps from Sharpless epoxidation products. Part B. Chapter 2. The synthesis of 4-carboethoxy-4,6-dihydro-thieno (3,4-b) thiophene 5,5-dioxide and 4-phenyl analogue, precursors to thiophene xylylenes, are reported. Attempts to trap the carboethoxy substituted xylylene with electron rich or electron poor dienophiles failed and only dimers were produced. In contrast, the phenyl substituted xylylene gave moderate yields of Diels-Alder adducts in trapping experiments with dienophiles such as dimethylacetylene dicarboxylate, dimethyl fumarate, and benzoquinone. Chapter 3. Several additional examples of a conceptually new route to 1,3-dihydrobenzothiophene-2,2-dioxides from $\alpha$-diazo-$\beta$-sulfonyl esters via a formal rhodium carbenoid insertion into an aromatic C-H bond is reported. Our attempts to extend the scope of this reaction to include insertion into furan derivatives failed. We obtained very unusual furan ring opened products. When the same rhodium carbenoid reactions were carried out with $\alpha$-diazo-$\beta$-ketoamides, 2-hydroxy-3-acetylindole derivatives were formed. Chapter 4. In order to gain insight into the rhodium carbenoid reaction mechanism, the diazo precursors to 1,3-dihydrobenzothiophene-2,2-dioxide, 2-indanone, and 2-tetralone which were mono substituted at the ortho position of the aromatic ring were synthesized and the hydrogen/deuterium isotope effects were measured. The observed isotope effects ranged from 3.3-4.9. Furthermore, deuterium NMR indicated that scrambling had occurred during the cyclization step. These data have been interpreted to show that these rhodium carbenoid reactions should be considered as electrophilic aromatic substitution reactions.

The intercalation of polyethylene glycol (PEG) into the interlamellar region of magadiite was performed using leading two different methods, leading to interesting new nanocomposites materials. In the first approach, magadiite was acidified and pre-intercalated with DMSO before PEG was inserted in between the layers. In this approach, instead of dissolving the PEG in a solvent, a large excess of polymer was used. This was the first reported example of the intercalation of a polymer in the acidified derivative of magadiite. In the second approach, sodium ions of magadiite were first exchange with octadecylammonium ions (the three different derivatives obtainable were discussed extensively) before PEG was intercalated in the interlayer region. As in the first approach, the PEG intercalation was solvent-free. A pellet consisting of a 50:50 (w/w) mixture of the polymer and the silicate derivative was prepared and heated. In this case two different nanocomposites were formed depending on the temperature at which the pellets were heated. Both methods described lead to the formation of new intercalated nanocomposites. Finally, the synthesis of a polyrotaxane composed of PEG and alpha-cyclodextrin was achieved. The methylation of the polyrotaxane was also performed. The intercalation of both the polyrotaxane and the methylated polyrotaxane was not successful using the first approach described earlier.

Organic thiols adsorb on metallic surfaces and form so-called self-assembled monolayers (SAMs). These interfacial systems have attracted a lot of attention because of their possible use in various technologies such as electrochemical sensors, organic conductors or corrosion inhibitors. These applications make use of the ability of thiols to prevent charge transfer between the metal surface and the electrolyte solution. However, organic materials can undergo phase transitions in the range of temperature where modified electrodes are used. Few studies have been done on the thermal stability of molecular films. This thesis is a study of the electrochemical properties of alkanethiols chemisorbed on Au(111) between 5°C and 60°C. We found that soluble alkanethiols are reduced in a single step. We found that insoluble alkanethiols are reduced in two steps. The reduced products (thiolates) are insoluble and thus remain physisorbed at the electrode surface. They can be oxidatively redeposited when the potential is scanned in the positive direction. The development of a fine structure in the voltammogram of insoluble thiols is shown to be caused by the low solubility of the thiols. We propose a model in which the reductive desorption and the oxidative redeposition processes proceed through the same two-step mechanism. We have studied the effect of temperature on insoluble thiols that can be induced, by the application of an electric field, to reversibly go from a chemisorbed state to a physisorbed state. We found that the physisorbed thiolates remain at the electrode surface at temperatures as high as 70°C. Our results reveal a change in the reductive desorption/oxidative redeposition at 23°C. We assign this change to an order-disorder transition. The ion blocking properties of insoluble thiols were studied with differential capacitance and with cyclic voltammetry using ferricyanide as a redox probe. We found that monolayers with low numbers of defects are formed after a single incubation in a solution of thiols. Multiple incubations in a solution of thiols give a monolayer with such an extremely low number of defects that electron transfer occurs via tunneling. Finally, we determined the oxidation mechanism of adsorbed butanethiol in neutral and alkaline aqueous solutions. Under neutral conditions, the butanethiols are oxidized via a nine electrons process, whereas in alkaline solutions, the oxidation is greater and requires thirteen electrons. These results are found to be related to the greater electrocatalytic activity of gold in alkaline solutions. (Abstract shortened by UMI.)

The reaction of LiN(SiMe3)2 with RNCNR [R = iPr, Cy] resulted in formation of the new tetra substituted guanidinate ligands Li(RN)2CN(SiMe3)2. Chapter 2 describes the reactions of these ligands with MCl4 [M = Zr, Hf] to give Cl2M[(RN)2CN(SiMe3)2] 2 or [Cl4M(CyN)2CN(SiMe3)2] - depending on the metal ligand ratio employed. Reaction of [Cl4Zr(CyN)2CN(SiMe3)2] - with 3 equivalents of BzMgCl gave the first example of an organo-zirconium complex supported by a guanidinate ligand. Chapter 3 reports on the reaction between triisopropyl guanidine ( iPrN)C(NHiPr)2 and group 5 metal alkyl precursors such as Me3TaCl2 and Me2NbCl3. These species react by protonation/elimination of metal bonded chloride groups and incorporation of a monoanionic guanidinate ligand. Reactions of triisopropyl guanidine with ZrBz4 and ZrCl 4 are reported in chapter 4. The products isolated from these reactions are Bz2Zr[(iPrN)2C(NHiPr)] 2 or the mixture Cl3Zr[(iPrN)2C(NH iPr)] + (iPrNH)3CCl. Also reported in chapter 4 are the results obtained when the dilithium salt of triisopropyl guanidine was reacted with ZrCl4: a unique dimer [Cl2Zr(iPrN)3C]2 which possessed a bridging dianionic guanidinate ligand. Preliminary reactions of this dimer with ethylene and propylene in the presence of MAO showed encouraging catalytic properties. (Abstract shortened by UMI.)

SmI2(THF)5 acted as a reducing agent in the reaction with phenylenebis(3,5-But4salicylidene)iminato sodium, (3,5-But4salophen)Na2(THF) 2, to yield a dimeric compound [Sm2(SB-SB)(THF)3] ·2toluene (2.2) [SB-SB = C-C bonded (3,5-Bu t4salophen dimer] arising from the reductive C-C coupling of two imine functional groups of two (3,5-But4salophen)Sm units. Complex 2.2 reacts with MeLi resulting in a novel oxo-bridged dimer, {[(Me2-SB)Sm(mu-CH3)Li(THF)][(Me2-SB)Sm(mu-CH 3)Li(THF)2Li(TBT)2]}(mu-O)(mu-Li)3 (2.3) [Me2SB = phenylenebis (3,5-But 4salicyl)dimethyldiamidato], featuring alkylation of both Sm atoms and arising from cleavage of the C-C bond connecting the two units, as well as complete reduction of the imine groups of the two salophen ligands and TBF deoxygenation. Similar cleavage of the connecting C-C bond of complex 2.2 was also observed during the reaction with dry O2 to form a distorted cuboid cluster in which four Sm atoms are bridged by four hydroxyl groups [(3,5-But4salophen)Sm (OH)] 4·4toluene (2.4). The nature of the substituents present on the calix-tetrapyrrole tetra-anion ligand {[R2C(C4H2N)]4} 4- [R = 1/2-(CH2)5- (a), Et (b)] determines the type of reactivity of the corresponding Sm(II) compounds with acetylene. Where R = 1/2-(CH2)5- dehydrogenation occurred to yield the nearly colorless dinuclear diacetylide complex. Conversely, where R = Et, acetylene coupling in addition to dehydrogenation resulted in the formation of a dimeric butatrienediyl enolate derivative. Reaction of the trivalent hydride or of the terminally bonded methyl derivative with acetylene resulted in a mixture of the carbide and the dimerization product 5.2b. The same reaction also yielded a third product, a trivalent complex in which the macrocycle was isomerized by shifting the ring attachment of one of the four pyrrole rings. Reaction of the mononuclear and trivalent (6.1a), ( 6.1b) with lithium under Ar in THF afforded the mononuclear divalent 6.3a where the enolate was formed by a THF cleavage process. In the case of direct reaction of SmI2(THF)5 with the tetralithiated form of the Rn-calix-pyrrole ligand, the two isomorphous enolates (6.3a and 6.3b) were the only isolated products. Complexes 6.3 react reversibly with ethylene to afford the corresponding light-green dinuclear ethylene adducts. The nature of the substituents; present on a dipyrrolide dianion ligand determines the assembly of Sm(II) clusters which participate to various extents in dinitrogen fixation and THF cleavage. Reaction of SMI2(THF) 2 with the methylphenyl dipyrromethanyl dianion resulted in the pentameric cluster 10.1 which exhibited no reactivity with dinitrogen. Conversely, reaction of SmI2(THF)2 with the cyclohexyl dipyrromethanyl dianion resulted in TBF cleavage to yield the tetranuclear oxo-bridged complex 10.2. (Abstract shortened by UMI.)

This thesis has been divided into three major sections. The first section deals with the preparation and characterization of silica-supported vanadium(V) complexes. The reactions of O=VX3, X = Cl or OiPr, with the surface of partially dehydroxylated silica gives a single well-defined surface complex, ≡SiOVOX2. These complexes have been characterized by 51V magic angle spinning and 13C cross-polarization magic angle spinning NMR spectroscopy and infrared spectroscopy. The incorporation of 18O labels into specific positions of the silica-supported vanadium complexes has been achieved. When the hydroxyl groups are first exchanged with H218O, the subsequent reaction with O=VX 3 gives exclusively ≡SI18OV16OX 2. Reaction of 18O=VCl3 with unlabelled silica gives only ≡Si16OV18OCl2. The surface complexes undergo clean ligand replacement without displacing or diluting the isotope labels. Other reactions are investigated which are analogous to molecular vanadium reactions and relevant to the understanding of mechanisms in heterogeneous catalysis. The second section deals with a special type of reactivity of silica-supported vanadium(V) complexes. A nonhydrolytic low-temperature route to ternary V-Ti-Si catalysts has been developed. Ti(OiPr)4 migrates underneath the silica-supported vanadium overlayer to give a heterobinuclear complex containing one Ti per V, bound to the silica surface via Si-O-Ti linkages. When Ti(OiPr)4 reacts with the surface of partially dehydroxylated silica, a dinuclear species is formed. Because of this reaction it was not possible to form the mixed Ti-V species by depositing the Ti first. However once a method was developed for the formation of mononuclear silica-supported titanium complexes, we demonstrate that indeed the heterobinuclear species can also be formed by the reaction of O=V(OiPr)3 with ≡SiOTi(OiPr)3. Although there is precedence in the literature for nonhydrolytic condensation of metal chloride alkoxides, this is the first example of such a stoichiometric reaction on a surface. The last part of this thesis deals with the study of silica-supported organovanadium species. The reaction of V(CH2SiMe3) 4 with the surface of partially dehydroxylated silica gives exclusively (≡SiO)2V(CH2SiMe3)2. This surface complex undergoes a surprisingly clean thermal transformation to generate a supported alkylidene complex, (≡SiO)2V=CHSiMe3, with concurrent liberation of SiMe4. The reaction is quantitative and kinetically first order. The mechanism is believed to be a surface assisted alpha-H elimination. The unusual supported vanadium alkylidene reacts with olefins in the absence of alkylaluminum cocatalysts.