[PDF] Investigations Of The Reactivity Of Palladium And Platinum Complexes With Molecular Oxygen And Characterization Of A Goldiii Alkene Complex eBook

Author : Margaret Louise Scheuermann
Publisher :
Page : 119 pages
File Size : 22,5 MB
Release : 2013
Category : Gold compounds
ISBN :

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Understanding the reactivity of metal complexes with molecular oxygen will facilitate the development of catalysts that can enable the widespread use of molecular oxygen as an oxidant for organic synthesis. This thesis presents two new classes of reactions between metal complexes and molecular oxygen. Neutral five-coordinate Pt complexes were tested for reactivity in the presence of molecular oxygen. In arene solution, the complexes (t̳B̳u̳̳M̳e̳2̳ nacnac)PtMe3 (1, t̳̳B̳u̳M̳e̳2̳ nacnac- = [((4-tBu-2,6-Me2C6H2)NC(CH3))2CH]-), (M̳e̳3̳ Me-nacnac)PtMe3 (2, M̳e̳3̳ Me-nacnac- = [((2,4,6-Me3C6H2)NC(CH3))2CCH3]-), and (t̳B̳u̳2̳ PyPyr)PtMe3 (3, t̳B̳u̳2̳ PyPyr- = 3,5-di-tert-butyl-2-(2-pyridyl)pyrrolide) reacted immediately with oxygen to form peroxo species in which two oxygen atoms bridge between the metal center and a carbon atom in the ligand backbone. In contrast, no reaction between ( i̳P̳r̳2̳ AnIm)PtMe3 (4a, i̳P̳r̳2̳ AnIm− = [o- C66H4-{N(C6H3 i Pr2)}(CH=NC6H3 i Pr2)]−) or (M̳e̳3̳ AnIm)PtMe3 (4b, M̳e̳̳3̳ AnIm− = [o-C6H4- {N(C6H2Me3)}(CH=NC6H2Me3)]−) and oxygen was observed. As activation of oxygen by five- coordinate PtIV species was found to involve cooperation between the metal center and the ligand, the ability of the ligand to participate in the oxygen binding appears to be a vital component. Oxygen atom transfer reactions of the novel peroxo species are also presented. In a separate study, an unusual reaction involving the activation of both molecular oxygen and a C-H bond at the same metal center was investigated. Pd(P(Ar)(tBu)2)2 (15, Ar = naphthyl) was found to react with molecular oxygen at room temperature in arene solvent to form a hydroxide dimer in which one equivalent of phosphine per Pd was lost and the remaining phosphine was cyclometalated through the naphthyl ring. At low temperature, two intermediates were observed. The nature of these intermediates suggests a mechanism involving initial reaction of Pd(P(Ar) (tBu)2)2 with O2 followed by the C-H activation step. In a final chapter unrelated to oxygen reactivity, the generation and characterization of a gold III̳-alkene complex by NMR and X-ray crystallography is presented. Such species have been proposed as intermediates in catalytic reactions but until recently none had been observed.

Author : Allan J. Canty
Publisher : Springer
Page : 195 pages
File Size : 28,85 MB
Release : 2011-02-25
Category : Science
ISBN : 3642174299

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Kyle A. Grice, Margaret L. Scheuermann and Karen I. Goldberg: Five-Coordinate Platinum(IV) Complexes.- Jay A. Labinger and John E. Bercaw: The Role of Higher Oxidation State Species in Platinum-Mediated C-H Bond Activation and Functionalization.- Joy M. Racowski and Melanie S. Sanford: Carbon-Heteroatom Bond-Forming Reductive Elimination from Palladium(IV) Complexes.- Helena C. Malinakova: Palladium(IV) Complexes as Intermediates in Catalytic and Stoichiometric Cascade Sequences Providing Complex Carbocycles and Heterocycles.- Allan J. Canty and Manab Sharma: h1-Alkynyl Chemistry for the Higher Oxidation States of Palladium and Platinum.- David C. Powers and Tobias Ritter: Palladium(III) in Synthesis and Catalysis.- Marc-Etienne Moret: Organometallic Platinum(II) and Palladium(II) Complexes as Donor Ligands for Lewis-Acidic d10 and s2 Centers.

Author : David Michael Pearson
Publisher :
Page : pages
File Size : 10,24 MB
Release : 2011
Category :
ISBN :

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Palladium is a versatile metal used prominently in synthesis. The rapid growth of palladium oxidation chemistry in the past decade has spurred a number of new processes that allow for the selective oxidation of substrates under mild conditions. This growth, specifically in the field of aerobic alcohol oxidation, attracted our attention, with the hope that it would provide new catalysts for use in direct methanol fuel cells. Toward that goal we developed a new cationic palladium complex, [(neocuproine)Pd(OAc)]2[OTf]2, which shows unprecedented initial turnover frequencies for aerobic alcohol oxidation at room temperature. However, catalyst lifetimes are limited due to the generation of reactive partially reduced oxygen species that promote oxidation of the ligand and deactivation of the catalyst. The use of milder oxidant like benzoquinone extended catalyst lifetimes prompting a further exploration of the substrate scope. Oxidation of glycerol proceeds exclusively at the secondary alcohol to yield dihydroxyacetone. Other 1,2-diols also favors oxidation of the secondary alcohol. Methanol oxidation proceeds at a much slower rate, but yields methyl formate with selectivities greater than 90 %. The mechanism for this process was probed through the use of model studies and isotopic labels suggesting the transient generation and oxidation of methyl hemiformal. In a parallel effort toward the extension of catalyst lifetimes, a number of new oxidatively resistant ligands were synthesized and used toward the formation of palladium catalysts that exhibit extended catalyst lifetimes. Additional efforts have focused on the use of similar catalyst for the oxidative carbonylation of 1,2- and 1,3-diols to yield 5-membered and 6-membered cyclic carbonates in the presence of N-chlorosuccinimide, iodosylbenzene, or dichloroisocyanuric acid. Finally, a new platinum dimer containing a trimethylplatinum unit and bridging amides was synthesized and characterized. Its reactivity toward the reductive elimination of ethane of methanol derivatives was explored. Additional work with known platinum dimers suggests these species, upon addition of silver triflate, facilitates the C-H activation of a number of unactivated arenes and promotes the C-H functionalization of propargyl aryl ethers.

Author : Bruce Wayne Flint
Publisher :
Page : 184 pages
File Size : 45,28 MB
Release : 2001
Category : Gold
ISBN :

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Platinum complexes have been synthesized and characterized. Relative Pt-X Bond Dissociation Energies (BDE's) for these complexes have been calculated from experimentally measured equilibrium and organic BDE's. Changes in relative BDE's are noted when ligands for the complexes are exchanged. Oxygen atom transfer reactions by a new platinum hydroxo catalyst have been studied. This catalyst is generated by the reaction of a platinum oxo complex with water and catalytically activates the reaction of the this complex with ethylene. The kinetics of this reaction have been studied and a reaction pathway has been proposed. The synthesis and characterization of a series of heteroatom substituted gold imido complexes have been reported. It has been demonstrated that the stability of gold imido complexes has a linear free energy relationship with the donor strength of the adjacent phosphine ligand. The decomposition of the complex involves the release of a free nitrene. Larger phosphine ligands retard the decomposition, and the decomposition is blocked by alkylation of the hydrazido ligand.

Author : Seher Kuyuldar Tastan
Publisher :
Page : 206 pages
File Size : 40,90 MB
Release : 2009
Category :
ISBN :

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Synthetic, structural, spectroscopic, and redox studies of platinum(II) and palladium(II) compounds with mer-coordinating ligands have been undertaken in an effort to better understand the role of the metal and the ligands in controlling d^6/d^8 electron-transfer reactions. A series of Pd(pip2NCN)X (pip2NCNH=1,3-bis(piperdylmethyl)benzene) and [Pd(pip2NNN)X]X (X=Cl, Br, I) (pip2NNN=2,6- bis(piperdyl-methyl)pyridine) complexes are reported. Electronic spectra are consistent with stabilization of ligand-to-metal-charge-transfer states as the ancillary ligand is varied along the ClBr

Author : P. Henry
Publisher : Springer Science & Business Media
Page : 458 pages
File Size : 25,69 MB
Release : 1979-12-31
Category : Science
ISBN : 9789027709868

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The field of organometallic chemistry has emerged over the last twenty-five years or so to become one of the most important areas of chemistry, and there are no signs of abatement in the intense current interest in the subject, particularly in terms of its proven and potential application in catalytic reactions involving hydrocarbons. The development of the organometallic/ catalysis area has resulted in no small way from many contributions from researchers investigating palladium systems. Even to the well-initiated, there seems a bewildering and diverse variety of organic reactions that are promoted by palladium(II) salts and complexes. Such homogeneous reactions include oxidative and nonoxidative coupling of substrates such as olefins, dienes, acetylenes, and aromatics; and various isomerization, disproportionation, hydrogenation, dehydrogenation, car bonylation and decarbonylation reactions, as well as reactions involving formation of bonds between carbon and halogen, nitrogen, sulfur, and silicon. The books by Peter M. Maitlis - The Organic Chemistry of Palladium, Volumes I, II, Academic Press, 1971 - serve to classify and identify the wide variety of reactions, and access to the vast literature is available through these volumes and more recent reviews, including those of J. Tsuji [Accounts Chem. Res. , 6, 8 (1973); Adv. in Organometal. , 17, 141 (1979)], R. F. Heck [Adv. in Catat. , 26, 323 (1977)], and ones by Henry [Accounts Chem. Res. , 6, 16 (1973); Adv. in Organometal. , 13, 363 (1975)]. F. R. Hartley's book - The Chemistry of Platinum and Palladium, App!. Sci. Pub!.