Berlin, Techn. Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Berlin, Techn. Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Berlin, Humboldt-Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Berlin, Humboldt-Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Berlin, Freie Universiẗat, Diss., 1999. / Dateiformat: zip, Dateien im PDF-Format.

Berlin, Humboldt-University, Diss., 2003.

Berlin, Freie Universiẗat, Diss., 2002. / Dateiformat: zip, Dateien im PDF-Format.

Kinetic studies of a number of interesting and significant reactions involving reaction of molecular hydrogen, olefins and carbon monoxide with solutions of ruthenium chloride complexes are described. Ruthenium trichloride trihydrate, "RuCl₃.3H₀0", which is a mixture of ruthenium(III) and ruthenium(IV), was found to react with molecular hydrogen in dimethylacetamide (DMA) solution under mild conditions, to produce ruthenium(II) and ruthenium(I) in successive steps involving activation of the hydrogen by ruthenium(III) and ruthenium(II): [forumulae omitted] In aqueous acid solution, the reverse of reaction (1) prevents reduction of ruthenium(III); in DMA, a more basic solvent, the released proton is stabilized and reduction is observed all the way to the univalent state. Convincing evidence was found for the existence of ruthenium(I) in DMA, although no well-characterized ruthenium(I) solid complexes were isolated. The present studies are the first reported on the solution chemistry of ruthenium(I) chlorides. Ruthenium(I) chloride complexes in DMA (80°) were found to activate molecular hydrogen through dihydride formation for the catalyzed reduction of olefins. The following mechanism is indicated: [formulae omitted] Accompanying olefin isomerization and some deuterium isotope studies suggest that reaction (5) goes through an ϭ-alkyl hydride intermediate, the hydrogen transfer process involving two consecutive single hydrogen atom transfers to a coordinated olefin. Addition of triphenylphosphine (PPh₃) to the ruthenium(I) catalyst solution decreases the hydrogenation rate. However, reaction of hydrogen with a ruthenium(I) solution containing PPh₃ and no substrate gave evidence for the formation of a hydride species. In the presence of PPh₃, reaction of H₂ with ruthenium(II) chloride in DMA does not produce ruthenium(I). The ruthenium(II) hydride intermediate is stabilized by the phosphine ligand yielding the well-known complex RuHCl(PPh₃)₃ which has been found to be extremely active in catalyzing the hydrogenation of olefins. An extremely simple method for the preparation of the catalyst "in situ" is demonstrated, again utilising the basic properties of DMA. A mechanism involving a predissociation of the catalyst, and formation of an ϭ-alkyl intermediate is thought to be operative in the catalyzed hydrogenation of olefins: [formulae omitted] Both ruthenium(I) and ruthenium(II) chlorides in DMA were found to absorb carbon monoxide readily at ambient temperatures, producing Ru[superscript I](CO) and Ru[superscript I](CO)₂, and Ru[superscript II](CO) and Ru[superscript II](CO)₂respectively. The introduction of carbonyl groups into these ruthenium complexes was found to inhibit catalytic activity for the hydrogenation of olefins. The anion [RuCI₄(bipyridine)]²⁻ , in 3 M HC1, was found to be a hydrogenation catalyst for olefin reduction, though not a very efficient one. A mechanism similar to the RuHCl(PPh₃)₃ catalyzed system seems to be involved, and is quite different to that reported for a corresponding system involving the tetrachlororuthenate(II) complex, [RuCI₄]²⁻. / Science, Faculty of / Chemistry, Department of / Graduate

The previously known complexes, RU₂H₄Cl₂(PR₃)₄, have now been correctly reformulated as the η²-H₂ species (η²-H₂)(PR₃)₂Ru(μ-Cl)₂(μ-H)RuH(PR₃)₂ (R = Ph, p-tol), 1a and 1b, and it is confirmed that in solution they are dimeric and undergo no ligand dissociation. Also, a new analogue of complexes of type 1 is reported: the complex (η²-H₂)(isoPFA)Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂,4, is formed from the reaction of RuCl₂(PPh₃)(isoPFA), 3b, with H₂ in methanol/benzene, and a crystal structure of 4 shows the η²-H₂ ligand; isoPFA and PPFA (see below) are ferrocene based, chelating P-N ligands, with the structures: [Chemical compound diagram omitted] R = Pri and Ph for isoPFA and PPFA, respectively. Complexes 1a, 1b and 4 all react with 1-hexene to give hexane; the main ruthenium phosphine product in the case of 1 is the corresponding RuHCl(PR₃)₃ complex, while 4 reacts to give a complex mixture of ruthenium phosphine complexes, including 3b. The amount of hexane formed from the reaction of 4 with hexene is quantified as 2 mol/mol 4. The hydrogenation of 1-hexene catalyzed by 1a is re-interpreted as occurring via the mechanism: (η²-H₂)(PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ + hexene K₁→(PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ + hexane (1) (PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ + H₂ K₂⇆(η²-H₂)(PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ (2) Reactions of RuCl₂(PPh₃)(PPFA), 3a, and RuCl₂(PPh₃)(isoPFA), 3b, with H₂ have been further studied, in connection with earlier mechanistic studies on hydrogenation of organic substrates catalyzed by complex 3a. The complex 3a reacts with 2-8 atm H₂ in n-butanol to give ruthenium phosphine products including 1a. The complex 3b reacts with H₂ in methanol/benzene to give 4, as mentioned above, as well as a number of unidentified hydrides; in DMA, the reaction of 3b with H₂ gives 1a, 4, RuHCl(PPh₃)(isoPFA) (7), RuHCl(PPh₃)₃ and other unidentified ruthenium phosphine complexes. The product H₂NMe₂+Cl⁻ was also isolated from the methanol/benzene reaction mixture, and this product provides evidence that the amine functionality of the P-N ligands is involved in the promotion of the heterolytic cleavage of dihydrogen to give a proton and a hydride (H₂→ H⁺ + H⁻). Kinetic studies on the hydrogenation of 1-hexene catalyzed by 3a, and by 3b in the present work, are now interpreted according to the mechanism [Chemical compound diagram omitted] Reactions involving 3b and methanol have also been studied, and 3b is also active for the transfer hydrogenation (from methanol) of ketones and activated olefins. The reaction of 3b with methanol in the absence of base is proposed to occur with the stoichiometry: RuCl₂(PPh₃)(isoPFA) + 2MeOH→ H₂NMe₂⁺Cl⁻ + H₂ + 3b RuHCl(CO)(PPh₃)(isoPOF), 5 (5) where the ligand isoPOF is formed from isoPFA by replacement of the NMe₂ group on isoPFA by a methoxo group; reaction 6 could occur via the following steps: RuCl₂(PPh₃)(isoPFA) + MeOH→ RuHCl(CO)(PPh₃)(isoPFA), 6 3b + H₂ + HCl (6) RuHCl(CO)(PPh₃)(isoPFA) + MeOH→ RuHCl(CO)(PPh₃)(isoPOF), 5 + HNMe₂ (7) HCl + HNMe₂ H₂NMe₂⁺Cl⁻ (8) A mechanism for reaction 7 is presented and invokes reversible attack by MeOH with replacement of Cl⁻, followed by reversible deprotonation of coordinated MeOH to give successively methoxo, formaldehyde and formyl intermediates, and finally the hydrido-carbonyl, 6. The reaction of 3b with methanol in the presence of KOH is proposed to occur according to the stoichiometry: RuCl₂(PPh₃)(isoPFA) + KOH + CH₃OH→ RuHCl(CO)(PPh₃)(isoPFA) + KCI + H₂ + H₂O (9) and two pathways have been identified, one base-independent, identical to that proposed for reaction 7, and one showing a second-order dependence on KOH. The latter pathway invokes initial reversible attack on RuCl₂(PPh₃)(isoPFA), 3b, by MeO⁻, replacing Cl⁻ to give RuCl(OMe)(PPh₃)(isoPFA), and subsequent reversible replacement of PPh₃ by OH⁻, followed by concerted loss of OH⁻ and hydride transfer from coordinated OMe⁻ to give a hydrido-formaldehyde complex RuHCl(η²-CH₂O)(isoPFA). A subsequently formed formyl intermediate reacts via intramolecular hydride transfer from the formyl to the metal, H₂ loss, and phosphine coordination to give the hydrido-carbonyl 6. / Science, Faculty of / Chemistry, Department of / Graduate

Syntheses of a number of chiral and non-chiral sulphoxides and corresponding Ru(II) sulphoxide compounds are described, as well as significant reactions of some of these complexes with molecular hydrogen, olefins, and carbon monoxide. The new sulphoxides presented are: (S,R;S,S)-(+)-2-methylbutyl methyl sulphoxide, (MBMSO), (2R,3R)-(-)-2,3-0-isopropylidene-2,3-dihydroxy-1,4-bis(methyl sulphinyl)butane‧H₂0, (Dios), and (2R,3R)-(-)-2,3-0-isopropylidene-2,3-dihydroxy-l,4-bis(benzyl sulphinyl)butane‧H₂0, (BDios). These sulphoxides are prepared as mixtures of diastereomers. Other sulphoxides discussed are: dimethyl (DMSO), methyl n-propyl, (MeⁿprS0), methyl phenyl, (MPSO), and R-(+)-methyl p-tolyl sulphoxide, (MPTSO) and (2R,3R)-2,3-dihydroxy-l,4-bis(methyl sulphinyl)butane, (DDios). The previously unknown complexes, [NH₂Me₂][RuCl₃(DMSO)₃], [NH₂Me₂][RuCl₃(MeⁿprS0)₃], [RuCl₂(MBMSO)₂]₃, [RuCl₂(MPTSO)₂]₃, [RuCl₂(MPS0)₂]n, RuCl₂(DDios)₂‧2H₂0, RuCl₂(Dios)(DDios) and RuC1₂(DDios)(DMSO)(MeOH) have been prepared using newly developed synthetic routes. The previously prepared compounds, RuCl₂(DMS0)₄ and RuBr₂(DMSO)₄ are more fully described and in collaboration with A. Mercer and J. Trotter of this department the structures of the chloro-complex and the [NH₂Me₂][RuC1₃(DMSO)₃] compound were determined by x-ray crystallography. Both [NH₂Me₂][RuCl₃(DMSO ₃] and RuC1₂(DMSO)₄ react readily with molecular hydrogen in N,N'-dimethylacetamide (DMA) in the presence of a strong base, proton sponge R . The net heterolytic cleavage of H₂ results in hydride species which although not well characterized have anomalously high *H n.m.r. hydride chemical shifts at least for Ru(II). The anionic DMSO complex catalyses the hydrogen reduction of activated olefins in DMA at 60°C under 1 atm and kinetic and spectral studies indicate the following mechanism: [equation omitted] Activation of H₂ is thought to occur by net heterolytic cleavage of molecular hydrogen and this and an olefin insertion step are considered to be rate determining, (k₃ and k₄). Reduction proceeds by two pathways, one olefin-dependent and the other olefin-independent; the final step involves protonolysis of a σ-alkyl complex. Catalytic hydrogenation of acrylamide in DMA at 70°C using [RuCl₂(MBMSO)₂]₃ is described and the postulated mechanism is summarized below [equation omitted]. As with the anion system a two-path reduction occurs, one olefin-dependent and one olefin-independent, with the H₂-activation steps rate determining, (k₁ and k₄); however, H₂ activation is this time via oxidative addition. Asymmetric hydrogenation studies using the catalysts [RuCl₂(MBMSO)₂]₃, [RuCl₂ (MPTSO) ₂]₃, RuCl₂ (DDios) ₂•2H₂0, RuCl₂ (Dios)(DDios), and RuCl₂(DDios)(DMSO)(MeOH) are presented. The largest optical purities obtained are 25 and 15%, for the RuCl₂(Dios)(DDios)-itaconic acid and [RuCl₂(MBMSO)₂]₃-itaconic acid systems, respectively. The preparation of carbonyl derivatives of [RuCl₂(MBMSO)₂]₃ and [RuCl₂ (MPTS0) ₂]₃ are described; these derivatives have anomalously high v(C0) values. / Science, Faculty of / Chemistry, Department of / Graduate