Phosphine complexes of nickel and palladium provide the best catalysts for the homogeneous catalysed carbon-carbon bond forming reaction between an organometallic nucleophile and an organic electrophile. Use of a homochiral ligand on the catalyst can lead to stereoselectivity in the cross-coupling reaction, with high ee's of coupled product being obtained. The processes of selectivity in the transmetalation step of the catalytic cycle have not been elucidated and the initial aim of the project was to study these processes. Initial experiments using organotin derivatives as the organometallic nucleophile highlighted the problems of selectivity and the forcing conditions needed in the attempted transfer of a benzyl group from the tin to the palladium catalyst. The compounds [8- (dimethylamino)-1-naphthyl]methyldiphenyltin (60) and [2-((dimethylamino)methyl) phenyl]methyldiphenyltin (70) were prepared and their reactivity in the palladium catalysed cross-coupling with 2-furoyl chloride, to give 2-benzoylfuran, was investigated. These molecules were found to undergo facilitated transfer of a phenyl group compared to transfer from control molecules. The effect was tested and attributed to the internal nucleophilic attack at the tin atom by the lone pair on the nitrogen atom. The compound [2- ((dimethylamino)methyl)-3-trimethylsilylphenyl]methyldiphenyltin (79) was prepared to test the effects of steric buttressing within the molecule, but was found to be of the same order of magnitude of reactivity as (60) and (70). All three molecules showed a reactivity of at least an order of magnitude greater than control compounds. The effect did not prove applicable to the transfer of a benzyl group or in other coupling reactions. The effect of palladium ligation was tested and the ligand triphenyl arsine found to increase the rate of the coupling reaction. The two facilitating processes were found to work in a co-operative fashion, giving a rate enhancement of ca. one hundredfold over control reactions. The nickel catalysed cross-coupling of α-substituted sp³ hybridised Grignard reagents with allylic esters was attempted, but proved unsuccessful. Stoichiometric reactions with nickel complexes were also found to be unsatisfactory in yielding coupled products. The synthesis of α-substituted diorganozinc reagents was attempted, but furnished only homocoupled products. The reaction of dibenzylzinc with aldehydes was found to proceed in the absence of catalyst, highlighting the reactivity of a benzylzinc moiety.

The field of metal-catalyzed C–H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The introduction chapter will cover the mechanistic aspects of the C–H bond functionalization with metal-carboxylate complexes. The mechanistic facets of this reaction will be the main conducting line between the different sections and chapters of the first part of this thesis. In the second chapter, will be described additives that can readily promoted C–H bond arylation of poorly reactive substrates. More specifically, we will revisit the intramolecular direct arylation reaction we will demonstrate the effect of pivalic acid as a co-catalyst by developing milder reaction conditions. In the third chapter we be described experimental and computational studies which suggested that the a single pathway might be involved in the palladium-catalyzed C–H bond functionalization of a wide range of (hetero)arene. Following this we will describe a general set of conditions for the direct arylation of wide range of heteroarenes. Also, we will present two different strategies to selectively and predictably arylate substrates containing multiple functionalizable C–H bonds. In the fourth chapter will be presented our efforts toward the development of new C–H bond functionalization methods in which we could apply our knowledge on the C–H bond cleavage and apply it to the formation of new scaffolds. The development of two new palladium-catalyzed methods were also described. In the fifth chapter, our effort toward the development of ligands to specifically promoted C–H bond cleavage will be presented. In the sixth chapter will be presented the latest results on the study of the mechanism of the C–H bond cleavage combining experimental and computational studies. In part B of this thesis will be presented our strategy toward the total synthesis of ginkgolide C that included two gold(I)-catalyzed reactions as key steps in the preparation of the spiro[4.4]nonane core of this natural product. The first studies on the feasibility of the key steps of the synthesis will be described.

No description available.

Catalytically relevant metal clusters were deposited on metal oxide supports. Palladium and gold were deposited on mixed morphology ZnO, and palladium was deposited on MgO(100). The materials were characterized with electron microscopy, photoluminescent spectroscopy, and X-ray photoelectron spectroscopy. The behavior of hydrogen on these materials, as well as bare ZnO, was studied using volumetric isotherms. The isotherms were used to determine the monolayer gas coverage, surface area, and heats of adsorption of hydrogen on these materials over the temperature range of approximately 8-13 K. At the temperatures and pressures studied, hydrogen physically adsorbed onto the materials. Additional investigations with inelastic neutron scattering were conducted on palladium decorated ZnO and bare ZnO. These revealed that hydrogen molecules on bare ZnO act as three dimensional free rotors, but hydrogen on palladium decorated ZnO acts as a two-dimensional planar molecule and undergoes a 6.2% bond length extension.

This thesis describes the synthesis and characterisation of new examples of meso-n1-organometallic porphyrins. These porphyrins were originally encountered as catalytic intermediates in the C-C bond forming reaction on the porphyrin periphery using palladium catalysts. They have now become a research topic in their own right and no other examples of this type of organometallic porphyrins had been reported at the outset of this work. In Chapter 2, several examples of meso-palladioporphyrins were prepared in high yield using oxidative addition of the porphyrin-bromine bond to a suitable Pd(0)phosphine precursor. These phosphine precursors were prepared from Pd(PPh3)4 or Pd2dba3 plus either PPh3 or a chelating diphosphine. Several new examples of mono- and di palladium complexes of chelating diphosphines were prepared. Chapter 3 looks at the preparation of meso-platinioporpyrins and the insertion of various central metal ions into the porphyrin ligand. Pairs of cis- and transisomers of the Pt(II) complexes were isolated from the oxidative addition of Pt(PPh3)3 to the free base and Ni(II) bromoporphyrins. The cis-isomer converted to the trans upon heating. At room temperature the two isomers are geometrically stable and survive unchanged through column chromatography and slow recrystallisation. The central metal ion can be introduced either before or after the oxidative addition to Pt(0). However, it is preferable to insert the metal ion last as the complexes of Br(MDPP) are rather insoluble (especially that of MnCl) and are more difficult to handle than the common intermediate trans- [PtBr(H2DPP)(PPh3)2]. The oxidative addition of Pt(dba)2 to meso-bromo-DPP in the presence of PPh3 has also been shown to be an effective method of synthesising n1-organo platinum porphyrins in high yield. However, this method was unsuccessful when using chelating diphosphines. In Chapter 4, the physical properties of meso- metalloporphyrins are reported including electrochemistry, fluorescence spectroscopy and crystal structure determinations. The fluorescence intensities of the meso-substituted porphyrins (freebase and zinc complexes) are dramatically reduced in comparison with the unsubstituted porphyrins. This fluorescence quenching is a dramatic example of the "heavy atom effect". Electrochemical measurements of freebase and Ni(II)porphyrins indicate that the organometallic fragment is a strong electron donor. The visible absorption spectra for all Pd(II) and Pt(II) complexes are typical for diarylporphyrins. All groups other than H in the 5- or 5- and 15-positions cause a red shift of the major absorption bands for both the free bases and central-metal complexes. The crystal structure studies of the Pt(II) complexes include the complexes, cis- [PtBr(MDPP)(PPh3)2] (M = H2, Ni), trans-[PtBr(MDPP)(PPh3)2] (M = H2, Ni, Zn and Co), trans-[PtCl(H2DPP)(PPh3)2] and trans-[PtBr(NiDPPBr)(PPh3)2]. In all these structures, the free bases are virtually planar while the metallo derivatives adopt a hybrid of the ruffled and saddled conformations. Chapter 5 contains the initial studies of chiral palladioporphyrins, using three different types of chiral chelating diphosphine ligands. These chiral palladioporphyrins are readily prepared by oxidative addition of the Pd(0) precursor with bromoporphyrin. The asymmetry of the chiral ligand is detectable at the remote B-pyrrole protons in all the chiral complexes as eight doublets are observed in 1H NMR spectra. The chirality of these ligands in the porphyrin complexes induces circular dichroism in the region of the porphyrin electronic absorption. High optical activity is observed for the BINAP complexes.

Doctor of Philosophy(PhD) / The present study deals with the synthesis and characterization of six tri-palladium complexes code named MH3, MH4, MH5, MH6, MH7 and MH8 that contained two planaramine ligands bound to the central or each of the terminal metal ions. The activity of the compounds against human cancer cell lines: A2780, A2780cisR and A2780ZD0473R, cell uptake, levels of DNA-binding and nature of interaction with salmon sperm and pBR322 plasmid DNA have also been determined. Whereas cisplatin binds with DNA forming mainly intrastrand GG adduct that causes local bending of a DNA strand, the tri-palladium complexes are expected to bind with DNA forming a number of long-range interstrand GG adducts that would cause a global change in DNA conformation. Among the designed complexes, MH6 that has two 2-hydroxypyridine ligands bound to each of the two terminal palladium ions is found to be most active. The compound also has the highest cell uptake and Pd-DNA binding levels. In contrast, MH8 which has two 4-hydroxypyridine ligands bound to each of the two terminal palladium ions is found to be least active. The results indicate that, as applied to the terminal metal centres, 2-hydroxypyridine would be more activating than 4-hydroxypyridine perhaps because of greater protection provided to the terminal centres from coming in contact with the solvent molecules. In contrast, when bound to the central metal centre, 4-hydroxypyridine appears to play a slightly greater activating role than 2-hydroxypyridine or 3-hydroxypyridine, suggesting that non-covalent interactions such as hydrogen bonding associated with the ligand rather than its steric effect may be a more important determinant of antitumour property. The results illustrate structure-activity relationships and suggest that the tri-palladium complex containing two 2-hydroxypyridine ligands bound to each of the three metal centres or the compound that contains two 2-hydroxypyridine ligands bound to each of the two terminal metal centres and two 4-hydroxypyridine ligands bound to the central metal centre, may be much more active than any of the designed complexes.

Proefschr. Rijksuniversiteit Groningen. / Met lit. opg.-Met samenvatting in het Nederlands en Italiaans.

Proefschrift Universiteit van Amsterdam. / Met samenvattingen in het Frans, Nederlands en Spaans.

Techn. Universiẗat, Diss., 2006--Darmstadt.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 4 uppsatser.