The reactions of nitro complexes of nickel and palladium with CO have been examined to determine the mechanism(s) by which CO₂ is produced. The solution and solid state structures of square planar Ni(NO₂)₂(L)₂ reactants and pseudotetrahedral Ni(NO₂)(NO)(L)₂ products have been determined and related to their reactivity. Infrared, ³¹P{¹H}, and crystallographic data indicate rapid isomerization between nitro and nitrito bonding modes of the NO⁻₂ ligands. The crystal structures of Ni(NO₂)₂(PPh₂(Ch₂)₂PPh₂) (I), Ni(NO₂) (NO) (PMe₃)₂ (II), and [Ni(ONO) (NO) (PPh₂(CH₂)₂PPh₂]₂ (III), show the NO⁻₂ groups to be N-bonded in I and II and O-bonded in III. The nitrosyl ligands in II and III are non-linear (Ni-N-O = 165.5(8) ° and 153.4(8) °, respectively). Furthermore, III crystallizes as a dimer bridged by two phosphine ligands even though molecular weights show this complex to be monomeric in solution. Each Ni(NO₂) (NO) (L)₂ complex reacts with CO to produce stoichiometric amounts of Ni(NO₂) (NO) (L)₂ and CO₂. Rate date indicate the reaction proceeds associatively through formation of a carbonyl intermediate which has been directly observed in the reaction of Ni(NO₂)₂(P(C₆H₁₁)₃)₂ with CO. The reaction of C¹⁸O with Ni(NO₂)₂(PMe₃)₂ results in no incorporation of ¹⁸O into the nickel product while ¹⁸O is incorporated into CO₂ to form ¹⁸OC¹⁶O. The mechanism consistent with all of the data involves a rapid equilibrium between both forms of NO⁻₂ coordination followed by the reaction of CO with either isomer in the rate determining step to form a monocarbonyl complex. Irreversible oxygen atom transfer to CO and loss of CO₂ terminate the reaction. The corresponding square planar palladium complexes, Pd(NO₂)₂L₂, react with CO to form N₂O, CO₂ and novel tetranuclear palladium clusters (Pd₄(CO)₅L₄). A crystal structure of Pd₄(CO)₅ - (PMePh₂)₄ shows the cluster to be a distorted tetrahedron of metal atoms with one open edge and the five remaining edges each bridged by a carbonyl group.

The synthesis of ligands has been identified as the limitation for wider application of catalytic asymmetric synthesis. Indeed, synthesis of phosphorus-based ligands, has been often shown to be challenging and not always efficient. It has also been observed that subtle changes in the ligand structure can lead to big differences in the catalytic activity of the ligand when coordinated to a metal. Therefore, it was considered useful to develop a methodology in order to obtain a library of phosphines. The first chapter of the thesis is a review of recent development in catalytic phosphine synthesis. In the second chapter of this thesis, the microwave mediated Suzuki cross coupling reaction has been investigated. In particular, attention has been focussed on the coupling of different arylboronic acids to chloroarylphosphine oxides, which are, in general, considered challenging coupling partners for this type of reaction. The reaction conditions have been optimised starting from the coupling of phenylboronic acid to tris(4-chlorophenyl)phosphine oxide. Different solvents, bases, and catalysts have been then tested and the better conditions have been developed for this substrate. Indeed, it was shown that the coupling occurs in only 30 minutes at 140°C, leading to reasonably high yields. These conditions were then applied to two other different chloroarylphosphine oxides with a range of boronic acids, with the aim to verify if the optimised reaction conditions could be applied to other substrates and it was noticed that good yields could be attained. This methodology led us to obtain a library of phosphine oxides. It was then decided to investigate the reduction of phosphine oxides under microwave irradiation. This reaction occurs under conventional heating but it can take several hours. It was observed that reaction times could be importantly reduced when reducing some phosphine oxides under microwave heating. It was found that some phosphine oxides are reduced rapidly under conventional conditions but for more difficult substrates to reduce there are significant advantage to microwave method. We decided to investigate the microwave mediated P-C bond forming reaction, with the aim to rapidly synthesise a library of phosphines cleanly. The conditions were optimised at first using o- trifluoromethylbromobenzene as the substrate. Once the appropriate reaction conditions and catalyst were identified, the reaction was run on other substrates to verify that this could be a general methodology for the synthesis of phosphines. It was found that it is indeed a general method for the synthesis of monophosphines. However, the synthesis of diphosphines with the microwave assisted P-C bond forming reaction on dibromo- and diiodo- aryl compounds proved to be very challenging. The fourth chapter presents different attempts for the synthesis of the new ligand Ph-DuPHOS. The synthesis of this ligand was considered interesting because of the previous results of other phospholane-based ligands, such as Ph-BPE and Me-DuPHOS. However, the synthesis of this ligand has proven to be elusive. A monodentate P-N phospholane-based ligand was prepared and its catalytic activity was tested in the rhodium catalysed hydrogenation of alkenes. Moreover, a bidentate (1,2-bisphospholano)xylene ligand was also prepared and its catalytic activity was also tested in the rhodium catalysed hydrogenation of alkenes. This latter ligand was also used in the hydroxycarbonylation of styrene, since for this reaction bulky diphosphines are required to give branched selectivity. In hydroxycarbonylation it is very rare to give good branched selectivity and there were no examples of substantial enantioselectivity prior to this work. The high regioselectivity and moderate e.e.’s observed suggest promise for future studies. Finally, mechanistic studies on the hydroxycarbonylation of styrene have been carried out in order to investigate the intermediates involved in the reaction as well as the role of the promoters. The possibility of (1-chloroethyl)benzene was proposed as the active intermediate of the reaction. Our results have disproved this possibility, suggesting that the reaction is likely to proceed through the hydride mechanism.

Ph.D. (Chemistry) / Compounds 3-ferrocenylpyrazole (L1) 3-ferrocenyl-5-methylpyrazole (L2) and 4- ferrocenyl-1-methyl diketone (L7) were synthesized according to literature procedure, while compounds 3-ferrocenylpyrazolyl-methylenepyridine (L3), 3-ferrocenyl-5- methylpyrazolyl-methylenepyridine (L4), 3-ferrocenylpyrazolyl-ethyl amine (L5) and 3- ferrocenyl-5-methylpyrazolyl-ethylamine (L6) were prepared by phase transfer alkylation of the 2,6-bis(bromomethyl)pyridine or 2-bromoethylamine with the appropriate ferrocenylpyrazole L1 or L2 in a 1:1 ratio. These compounds L3-L6 show structural isomers labelled a and b. The isomers were in a ratio of 4:1 for L3 and L4 while for L5 and L6 the isomers were 2:1 ratio...

M.Sc. (Chemistry) / Please refer to full text to view abstract

by Fuk Yee Kwong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 183-196).

No description available.

The hydrogenation of aromatic sulfonyl chloride to produce aromatic thiol is an important industrial reaction. The aromatic thiol is a critical intermediate in the production of many pharmaceuticals as well as several agrochemicals. Density Functional Theory (DFT), a quantum mechanical method, was used to investigate the new aromatic thiol production technology at the molecular level in aspects including reaction species adsorption and transition state determination. Plant design methods and economic analysis were performed to determine the economic feasibility of the new technology in the current specialty chemicals market. The quantum mechanical calculations showed that the molecules adsorbed to three simulated (100) Pd catalyst surfaces will preferentially move to configurations that are favorable for reaction progression. The calculations also show that the proposed reaction sequence by DuPont is the most feasible option despite the investigation into an alternative sequence that arose from molecular observations during calculations. Predicted activation energies (Ea) were in the range of 6.88 ? 38.1 kcal/mol which is comparable to the 14.58 kcal/mol determined experimentally by DuPont, and the differences between experimental and simulated values are easily explained. Plant design calculations show that a semi-batch reactor plant can easily produce 2MM lb of thiol/year, giving the owner of the plant an immediate 18% market share in the worldwide market of benzenethiol. Economic analysis shows that a grassroots plant construction is not currently an economically feasible option for corporate investment unless a source of cheap, skilled labor can be found in addition to a means of a 25% discount on certain raw material feed stocks. However, if both of these requirements can be fulfilled then new plant construction will have a payback time of 3.71 years based on the price of benzenethiol in the summer of 2007, $2.27/lb thiol.

No description available.

Thesis (Ph. D.)--Worcester Polytechnic Institute. / Keywords: hydrodechlorination; reaction kinetics; reaction steps; chlorinated compounds; Palladium catalysts. Includes bibliographical references.