Download or read book Synthesis and Reactivity of Palladium Complexes that Contain Redox active Verdazyl Ligands written by Corey A. Sanz and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the synthesis, characterization and reactivity of a series of palladium complexes that contain redox-active verdazyl ligands. This work was motivated by the possibility of discovering new and interesting reactivity that may eventually lead to the development of new chemical reactions. A bidentate verdazyl radical ligand that contains an aryl phosphine was synthesized. Reaction of this ligand with (PhCN)2PdCl2 yielded a square planar (verdazyl)PdCl2 complex. Structural and spectroscopic data suggest that this compound consists of a ligand-centered radical coordinated to a Pd(II) center. The radical complex was chemically reduced by one-electron to generate a binuclear chloride-bridged [(verdazyl)PdCl]2 complex. In this reduced complex, both metals were still Pd(II) and the verdazyl ligand was determined to be in its singly reduced, monoanionic charge state. The original radical PdCl2 complex could be regenerated via one-electron oxidation of the reduced complex using PhICl2. The verdazyl ligands in the reduced complex could also be reversibly protonated to generate "leuco" verdazyl complex (verdazyl-H)PdCl2. Reaction of the radical (verdazyl)PdCl2 complex with water triggers a ligand-centered redox disproportionation reaction. A series of bis(verdazyl) palladium complexes were synthesized using a bidentate pyridine-substituted verdazyl ligand. Reaction of two equivalents of radical ligand with (CH3CN)4Pd2+ yielded a (verdazyl)2Pd(solvent)2+ complex (solvent = CH3CN or DMSO). In this complex, one verdazyl radical ligand chelates to palladium and the other binds as a monodentate ligand. Two-electron reduction of this complex generated a (verdazyl)2Pd complex in which two monoanionic verdazyl ligands are bound to a central Pd(II) ion. This reduced complex could also be made via reaction of 0.5 equivalents of Pd(0)2(dba)3 with two equivalents of radical ligand. In this reaction, the metal is oxidized by two electrons and each ligand is reduced by a single electron. Two-electron oxidation of the reduced complex in the presence of DMSO yielded the original bis(radical)complex, (verdazyl)2Pd(DMSO)2+. Chlorination of the reduced complex using one equivalent of PhICl2 (two-electron oxidation) resulted in dissociation of one verdazyl ligand to afford a 1:1 mixture of free verdazyl : (verdazyl)PdCl2, in which both of the verdazyls are neutral radicals. Reaction of the reduced complex with 0.5 equivalents of PhICl2 (one-electron oxidation) yielded a (verdazyl)2PdCl complex that contained a bidentate reduced verdazyl ligand and a monodentate radical ligand. All three of the oxidation reactions described above adhere to ligand-centered redox chemistry. Reaction of the reduced (verdazyl)2Pd complex with excess HCl resulted in protonation of both the anionic verdazyl ring and the pyridyl group to generate a leuco/pyridinium tetrachloropalladate salt, (verdazyl-H2)2(PdCl4). The protonated salt could be converted back to the original (verdazyl)2Pd complex by deprotonation with water. Palladium complexes of a tridentate NNN-chelating verdazyl ligand were prepared and their redox chemistry was explored. Reaction of the radical ligand with (CH3CN)4Pd2+ yielded radical complex (verdazyl)Pd(NCCH3)2+. The tridentate ligand was also prepared in its reduced, leuco form (verdazyl-H). Reaction of the leuco verdazyl with (CH3CN)2PdCl2 generated HCl and a (verdazyl)PdCl complex in which the ligand is in its monoanionic charge state. The reduced (verdazyl)PdCl complex was reacted with AgBF4 to afford (verdazyl)Pd(NCCH3)+ via chloride abstraction; the verdazyl remained in its reduced charge state following the reaction. Both reduced complexes (chloro and acetonitrile) were oxidized by a single electron to afford the corresponding radical complexes. These radical complexes could be reduced by a single electron to regenerate the original reduced complexes. Like the previous two projects, all of the redox chemistry was ligand-centered. The reactivity of these complexes with primary amines was also explored. Reaction of radical complex (verdazyl)Pd(NCCH3)2+ with n-butylamine resulted in one-electron reduction of the verdazyl ligand. We were unable to determine the mechanism of the reaction, but the reactivity that was observed demonstrates the potential for verdazyl-palladium complexes to be used in the design of new radical reactions.

Download or read book Synthesis Reactivity and Multi electron Redox Behavior of a Bis phenoxy amide Ligand Coordinated to a Tantalum Metal Center written by Ryan A. Zarkesh and published by . This book was released on 2012 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the synthesis and reactivity of tantalum metal complexes containing a tridentate redox-active ligand. Fundamental studies have focused on utilizing the redox-active ligand to store multiple electron equivalents for oxidative addition and reductive elimination reactions. Chapter 1 provides an introduction to the characteristics of redox-active ligands and provides an overview of group transfer reactions involving redox-active ligands. The previous published results of bidentate redox-active ligands coordinated to Group IV d0 metals are discussed in terms of their decomposition side reactions. Chapter 2 describes the coordination of a known tridentate redox-active bis(phenoxy)amide ligand, (ONO), to a d0 tantalum(V) metal center and the examination of the redox properties of the resulting chloro oxidation products by electrochemical and spectroscopic methods. Chapter 3 examines the reactivity of the (ONO)TaR2 complexes in the general context of organometallic chemistry with a focus on protonolysis and reactivity with aryl azides, a known source of nitrene fragments upon oxidation. Chapter 4 examines the reactivity of the (ONO)TaX2 (X = Me, Cl) compounds with bulky diazoalkanes, a known carbene transfer reagent. The (ONO)TaCl2 complex proved to be a competent catalyst to generate cyclopropanes from styrene and the corresponding diazoalkane. Chapter 5 explores the utilization of the (ONO) ligand to store electron equivalents for the catalytic nitrene-nitrene coupling reactions with organoazides to afford organodiazenes. Finally, Chapter 6 addresses the electronic considerations of a related redox-active triamido ligand in an effort to tune the ligand's redox potentials.

Download or read book Organic Synthesis with Palladium Compounds written by Jiro Tsuji and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: Around 30 years ago the transition metal chemistry received great impulses. In the focus have been reactions of nickel and cobalt and herein especially their carbonyls. Also industrial processes have been developed. When the technical oxidation of ethylene with palladium chloride had been discovered, and a great number oflaboratory reactions, many groups have turned towards this subject. Apart from two important industrial processes - acetaldehyde and vinylacetate from ethylene - a great number of conversions and catalytic reactions with palladium compounds have been researched. Their mechanisms have been cleared up and have con tributed to a better understanding of the complex chemistry of palladium. Last but not least these reactions have also served for more understanding of organic transition metal compounds and catalyses in general. Numerous conventional reactions appear today in a different light. The effects of co-

Download or read book Synthesis Characterization and Reactivity of Mononuclear Palladium Complexes Bearing Nitrogen and Carbon donor Ligands written by Nicholas Ruhs and published by . This book was released on 2017 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: The importance of Pd-catalyzed C--H functionalization reactions for chemical transformations has been widely studied over the last several decades. Much of the research to date has focused on conventional Pd0/II catalytic cycles. However, more recent studies have shown that many transformations can also follow a PdII/IV catalytic cycle. High-valent PdIII and PdIV species are often proposed to be important intermediates in such transformations. C--H coupling reactions involving high-valent intermediates often involve the oxidation of a PdII species to a PdIII or PdIV complex, which can then undergo subsequent C--heteroatom bond formation. However, the need for harsh oxidants and reaction conditions in many of these reactions hinders their practical applicability. The focus of this work is to study the properties and reactivity of PdII, PdIII, and PdIV complexes through modifications of the supporting macrocyclic ligands. Another goal of this work is to probe the ability of these complexes to facilitate C--H activation and C--heteroatom bond formation reactions using environmentally benign oxidants.Our lab reported the synthesis and characterization of the first organometallic mononuclear PdIII complexes stabilized by the tetradentate ligand N,N'-di-tert-butyl-2,11-diaza[3,3](2,6)pyridinophane (tBuN4). In order to further probe the Pd chemistry with this class of ligands, we prepared ligands with modifications to the steric bulk on the amine groups. In the first study detailed in chapter 2, the synthesis and characterization of PdII and PdIII complexes supported by N,N'-di-neo-pentyl-2,11-diaza[3,3](2,6)-pyridinophane(NpN4) and N,N'-di-benzyl-2,11-diaza[3,3](2,6)-pyridinophane(BzN4) is reported. Interestingly, the spectroscopic and crystallographic property of the newly synthesized complexes falls between the tBuN4 and MeN4 complexes. The C--C and C--heteroatom bond formation reactivity of the NpN4 and BzN4 supported complexes is also similar to our group's previously reported complexes.We also prepared and studied a series of Pd complexes bearing a modified tetradentate pyridinophane ligand, tBuN3CH. Essentially, we have replaced one of the nitrogen donor atoms from the N4 ligand with a carbon atom and have also introduced a new C--H bond. Due to its expected positioning near the metal center, this bond has the potential to undergo intramolecular C--H bond activation. In order to study the reactivity of this ligand, electronic modifications were made by substituting various electron-donating and withdrawing groups in the para position to this new C--H bond. In chapter 3, the synthesis and characterization of a series of PdII, PdIII, and PdIV complexes stabilized by the N3CH ligand is reported. Interestingly, a spectroscopic and crystallographic study of the pRN3CHPdII(OAc)2 complexes reveals that the Cipso--H bond remains unactivated at the PdII stage. However, upon oxidation to PdIII, the Cipso--H bond is activated.Interestingly, we discovered that the aerobic oxidation of the PdII complex [pRN3CHPdII(MeCN)](BF4) leads to the formation of the PdIII complex [pRN3CHPdIII(MeCN)](ClO4)2 at room temperature. Surprisingly, the C--H activation reaction proceeds in the presence of oxygen without the need for external base. Furthermore, the moderate rate of the reaction allowed us to investigate the mechanism of the reaction by utilizing kinetics and UV-Vis spectroscopy. Detailed mechanistic studies revealed that C--H activation of the Cipso--H bond is the rate determining step of the reaction.

Download or read book Higher Oxidation State Organopalladium and Platinum Chemistry written by Allan J. Canty and published by Springer. This book was released on 2011-02-25 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Synthesis Reactivity and Catalytic Applications of Ruthenium and Palladium Complexes Supported by New Pincer Ligands written by Morgan C. MacInnis and published by . This book was released on 2011 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT continued: These transfer hydrogenation studies are among the first catalytic studies of silyl-pincer complexes and establish [R-PSiP]M species as viable candidates for catalysis. The synthesis and reactivity of 4- and 5-coordinate RuII complexes featuring the [Cy-PSiP] ligand were explored. Reaction of [Cy-PSiP]H with [(p-cymene)RuCl2]2 in the presence of NEt3 and PCy3 resulted in the formation of ([Cy-PSiP]RuCl)2, which serves as a precursor to a series of unprecedented 4-coordinate, formally 14-electron [Cy-PSiP]RuX (X = NHAr, N(SiMe3)2, OtBu) complexes that feature an unusual trigonal pyramidal geometry at Ru. The reactivity of these novel diamagnetic complexes is described, including the reaction of [Cy-PSiP]RuOtBu with amine-boranes resulting in the formation of rare bis(?-BH) complexes. Computational studies confirmed the key role of the strongly ?-donating silyl group of the Cy-PSiP ligand in facilitating the synthesis of such low-coordinate Ru species and enforcing the unusual trigonal pyramidal geometry. The mechanism of ammonia-borane activation was also examined computationally. Lastly, the synthesis and structural characterization of PdII complexes supported by the pincer-like bis(amino)phosphido ligand [?3-(2-Me2NC6H4)2P]- ([NPN]) is described. Examples of ?1-, ?2-, and ?3-NPN coordination to Pd are described, as is the catalytic activity of ([NPN]PdX)2 (X = Cl, OAc, OTf) complexes in the Heck olefin arylation reaction. In an effort to discourage the formation of phosphido-bridged dinuclear complexes, pre-coordination of the Lewis acid BPh3 to [NPN] was pursued. Upon reaction of [N(P?BPh3)N]K with [PdCl(C3H5)]2, the ?1-allyl complex [?3-N(P?BPh3)N]Pd(?1-C3H5) was isolated, which establishes the coordination of a Lewis acid to the phosphido donor of the [NPN] ligand as a viable strategy for encouraging the formation of mononuclear ?3-NPN complexes.

Download or read book Handbook of Organopalladium Chemistry for Organic Synthesis written by Ei-ichi Negishi and published by John Wiley & Sons. This book was released on 2003-11-24 with total page 1697 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organized to provide maximum utility to the bench synthetic chemist. The editor is well-known for his work in exploring, developing, and applying organopalladium chemistry. Contributors include over 24 world authorities in the field.

Download or read book Synthesis Characterization and Redox Studies of Platinum and Palladium Complexes with Mer coordinating Ligands written by Seher Kuyuldar Tastan and published by . This book was released on 2009 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Metal Complexes written by Peter Maitlis and published by Elsevier. This book was released on 2012-12-02 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Organic Chemistry of Palladium, Volume 1: Metal Complexes deals with the number of organic reactions that can be catalyzed by palladium, particularly as regards the structures bonding, and reactions of the metal complexes. The book discusses monodentate ligands which are either neutral (carbonyls, isonitriles, carbenes) or anionic (methyl, phenyl, ethynyl, hydride). The text also examines the complexes formed by 1,3-. 1,4-, and 1,5-diolefins where four carbon atoms are bound to the metal. Palladium (II) can undergo a reaction with the 1,3-dienes and results in a ?-allylic complexes where only three carbon atoms are coordinated to the metal. (The bonding situation in complexes 1,4- and 1,5-dienes, where no great interaction between the olefins are similar to that in monoolefin complexes, is straightforward), Olefins can also react with palladium chloride in protic solvents to produce ketones (or aldehydes) or organic coupling products. Some experiments conducted by Huttel et al shows that some palladium was precipitated from the reactions giving lower yields, resulting in various aldehydes and ketones as by products. The book also discusses cyclopentadienyl and benzene complexes. The text can prove beneficial for researchers, investigators and scientists whose works involve organic chemistry, analytical chemistry, physical chemistry and inorganic chemistry.

Download or read book Synthesis and Reactivity of Nickel Palladium and Platinum Phosphine Complexes with Hydridoamido Hydridophenoxo and Dithiooxalato Ligands written by Robert L. Cowan and published by . This book was released on 1989 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Palladium in Organic Synthesis written by Jiro Tsuji and published by Springer. This book was released on 2010-11-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Palladium is a remarkable metal. In particular, organopalladium chemistry has made remarkable progress over the last 30 years. That progress is still continuing, without any end in sight. This book presents a number of accounts and reviews on the novel Pd-catalyzed reactions discovered mainly in the last five years. The book covers Pd-catalyzed reactions that are new – entirely different from the more standard ones. Topics such as new reactions involving ß-carbon elimination and formation of palladacycles as key reactions, cross-coupling of unactivated alkyl electrophiles with organometallic compounds, arylation via C-H bond cleavage, Pd/norbornene-catalyzed aromatic functionalizations, three-component cyclizations of allenes, use of N-heterocyclic carbenes as ligands, asymmetric reactions catalyzed by Pd(II) compounds such as Lewis acids, cycloadditions of arynes and alkynes, and nucleophilic attack by Pd species are surveyed in detail by researchers who have made important contributions to these fields. The book addresses graduate students majoring in organic synthesis and researchers in academic and industrial institutes.

Download or read book Platinum and Palladium Isocyanides as Platforms on which to Study Metal Lewis Acid Cooperativity and Ligand based Redox Noninnocence written by Brandon Richard Barnett and published by . This book was released on 2016 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes various investigations into the reactivity and electronic structure of platinum and palladium complexes supported by m-terphenyl isocyanides. Use of these encumbering ligands facilitated the formation of two-coordinate Pt(CNArDipp2)2, which serves an isolable mimic of the unstable carbonyl Pt(CO)2. Importantly, Pt(CNArDipp2)2, along with its palladium congener Pd(CNArDipp2)2, represent the only monomeric and zero-valent binary isocyanide complexes of these metals. These complexes can act as the Lewis basic component of Metal-only Lewis Pairs (MOLPs), binding thallium(I) and silver(I) via retrodative [sigma]-bonds. Reactivity studies of Pt(CNArDipp2)2 culminated in the discovery of a very rare singly-buttressed metal-borane adduct Pt([kappa]2-N,B-Cy2BIM)(CNArDipp2), which is synthesized via hydroboration of a coordinated isocyanide ligand to form an ambiphilic (boryl)iminomethane (BIM) ligand. This complex exhibits rich reactivity with small molecules via metal/borane cooperation. It is shown to effect various E-H and E-X bond activations, as well as oxidative insertions of organoazides, organocarbonyls and organonitriles, most of which represent unprecedented reactivity modes for metal-borane adducts. Unligated Cy2BIM can also be synthesized upon hydroboration of CNArDipp2 with dicyclohexylborane. It is shown to be monomeric in solution, allowing it to act as a highly competent Frustrated Lewis pair despite bearing a Lewis acid of only moderate acidity. Two vignettes of ligand-based redox-noninnocence can be found in Chapters 5 and 6. The trinuclear dianion K2[Pt3([mu]-CO)3(CNArDipp2)3] and radical anion K(THF)4[Pt3([mu]-CO)3(CNArDipp2)3] were synthesized, notable as the all-carbonyl variants [Pt3(CO)6]2–/1– are unstable and have never been crystallographically characterized. Most importantly, it is shown that the highest occupied molecular orbital in these complexes is primarily CO/CNR [pi]*, producing the first example of an ensemble of CO and isocyanide ligands exhibiting redox-noninnocence. Finally, solution dynamics of the palladium bis-nitroxide diradicals trans-Pd([kappa]1-N-ArNO)2(CNArDipp2)2 were examined to gain insights into their stability and mode of decomposition. Judicious electronic modulation of the redox-active nitrosoarene ligands revealed that installation of para-formyl or para-cyano substituents greatly increased the kinetic stability of the corresponding diradicals, signaling a potentially general strategy for the stabilization of inherently short-lived classical nitroxide spin adducts.

Download or read book Palladium catalyzed Carbonylative Synthesis of Acid Chorides and Use in Multicomponent Coupling Reactions written by Jeffrey Quesnel and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The palladium-catalyzed carbonylation of aryl halides has proven to be a powerful method for the synthesis of carbonyl-containing compounds. This thesis describes a unique way of performing palladium-catalyzed carbonylations: through the generation of acid chlorides as products and as reactive intermediates.Chapter 2 describes the application of palladium-catalyzed aryl iodide carbonylation to the five-component synthesis of imidazolinium carboxylates. This reaction involves the coupling of the palladium-catalyzed carbonylation of aryl halides with the cyclocarbonylation of [alpha]-chloroamides, and provides an efficient route to generate imidazolinium salts from aryl iodides, imines, and carbon monoxide. A variety of imidazolinium products can be synthesized, including those whose derivatives are relevant to pharmacologically active compounds. Subsequent deprotection and aromitization can then lead to triaryl-substituted imidazoles.In Chapter 3, we report a new approach to acid chloride synthesis via the palladium-catalyzed carbonylation of aryl iodides. The combination of sterically encumbered phosphines (PtBu3) and CO coordination has been found to facilitate the rapid carbonylation of aryl iodides into acid chlorides via reductive elimination from (tBu3P)(CO)Pd(COAr)Cl. The formation of acid chlorides can also be exploited to perform traditional aminocarbonylation reactions under exceptionally mild conditions (ambient temperature and pressure), and with a range of weakly nucleophilic substrates.Chapter 4 describes the adaptation of this acid chloride synthesis to include less reactive aryl bromide coupling partners. Interestingly, the same PtBu3 ligand found to be most efficient for acid chloride synthesis from aryl iodides also proved best for aryl bromide chlorocarbonylation, suggesting the unusual ability of this ligand to efficiently mediate both oxidative addition and reductive elimination reactions. Mechanistic studies show that the palladium coordination environment is an important aspect of the key C-Cl reductive elimination step. In contrast to smaller phosphine ligands, the bulky PtBu3 leads to the in situ formation of a three coordinate (tBu3P)(CO)Pd(COAr)Cl complexes, which can readily coordinate CO to facilitate reductive elimination. Trapping of in situ generated acid chlorides with simple hydrazine allows, for the first time, the efficient synthesis of unsubstituted aroyl hydrazides via a palladium-catalyzed carbonylation reaction.In Chapter 5, we describe density functional theory (DFT) study of the mechanism for the palladium/PtBu3 catalyzed chlorocarbonylation of aryl iodides into acid chlorides. The results demonstrate a synergistic effect of CO and phosphine ligands on oxidative addition and reductive elimination chemistry of aryl/aroyl halides, consistent with what has been noted in experiments. The reductive elimination of PhCOCl from the four-coordinate PhCOPd(PtBu3)Cl(CO) complex is found to proceed via a surprisingly low energy pathway, and is facilitated by the coordination of CO to the three-coordinate PhCOPd(PtBu3)Cl. Examination of a series of PhCOPd(PR3)Cl(CO) complexes (R = Me, Et, iPr, tBu) shows that while most phosphines generate relatively stable four-coordinate complexes, the tertiary steric bulk of PtBu3 destabilizes this complex by steric clashing with the cis-CO ligand. This significantly lowers the barrier to acid choride reductive elimination, and makes this step thermodynamically favourable.Chapter 6 presents an alternative to the catalytic acid chloride chemistry discussed in Chapters 3 and 4, where instead 4-dimethylaminopyridine (DMAP) is shown to couple with aryl halides and carbon monoxide to form isolable and highly electrophilic aroyl-DMAP salts. The reaction is easily scalable to prepare multigram quantities of product with low catalyst loadings, while the precipitation of these salts as they form leads to products with low impurities. " --

Download or read book Synthesis Reactivity and Catalytic Applications of Palladium and Platinum Complexes Containing Rigid Bidentate Nitrogen Ligands written by Robert van Asselt and published by . This book was released on 1993 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Electrochemistry Studies of Palladium and Platinum Complexes Containing Chiral C subscript 2 symmetric Bis oxazoline Ligands and Platinum Complexes of the Chiral C subscript 2 symmetric Bidentate Phosphine Ligand Diop written by Kara Leigh Cetto and published by . This book was released on 2003 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an effort to design complexes in which electrochemical reduction does not result in loss of the chiral ligand, five different bis(oxazoline) ligands were prepared (3, 5, 7, 8 and 9). 3 was found to have poor solubility and an exceedingly negative reduction potential of Ep[subscript]c= -2.38 V. Chemical reduction studies of 5 revealed that the bis(oxazoline) ligand is ejected during the reduction process. Compound 7 was found to have a reduction potential of Ep[subscript]c= -1.12 V. However, ejection of the chiral ligand occurs when other bis(oxazoline) platinum and palladium dichloride complexes are reduced. Therefore, a neutral PdClMe complex (8) with a reduction potential of Ep[subscript]c= -2.97 V and a cationic Pd(CH[subscript]3CN)Me complex (9) (Ep[subscript]c= -1.38 V) were also prepared. A platinum complex of the bidentate phosphine ligand was then investigated. Electrochemistry studies revealed that 11 undergoes a two-electron reduction process in which the ligand remains bound to the metal. The synthesis of Pt(DIOP)(trans-stilbene) through the chemical and electrochemical reduction of 11 further demonstrated that DIOP remains bound to platinum after reduction of 11.

Download or read book Synthesis and Reactivity of Unusual Palladium II Complexes Supported by a Diarylamido BIS Phosphine PNP Pincer Ligand written by Rafael Huacuja and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation discusses the synthesis and reactivity of divalent palladium complexes supported by diarylamido bis-phosphine pincer ligands (PNP). The PNP is a tridentate pincer type ligand which typically adopts meridional type coordination. The rigidity and tight coordination of the PNP ligand provides the unique opportunity to study the coordination of ligands such as O2 and C2H4 to a single coordination site on palladium, or the reactivity of a single empty coordination site trans to a weak trans-influencing ligand such as diarylamido. Irradiation of [(^(F)PNP^(iPr))Pd-]2 under an atmosphere of dioxygen irreversibly produces a mixture of a monohapto palladium(II) superoxide ((^(F)PNP^(iPr))PdO2) and a palladium micro-peroxide ([(^(F)PNP^(iPr))PdO-]2). Under photolytic conditions these two complexes are in equilibrium with each other. (^(F)PNP^(iPr))PdO2, an open-shell paramagnetic species, was characterized by a combination of single-crystal X-ray crystallography, EPR, and 19F NMR spectroscopies. In addition, irradiation of [(PNP)Pd-]2 under an atmosphere of C2H4 produces a mixture of [(PNP)Pd-]2 and a ethylene-bridged dinuclear palladium complex ([(PNP)Pd-CH2-]2). If the ethylene headspace is removed, and [(PNP)Pd-CH2-]2 is irradiated it is completely converted to [(PNP)Pd-]2. This suggests that in the presence of ethylene these two complexes are in photolytic equilibrium with each other. In addition, this dissertation will also discuss the synthesis and reactivity of [(PNPR)Pd]+ (R = ^(i)Pr, ^(t)Bu) cations. [(^(F)PNP^(iPr))Pd]+ cations are highly electrophilic complexes that are able to coordinate Lewis bases such as THF, H2O, and even extremely poor Lewis bases such as toluene and benzene. In addition, irradiation of [(^(F)PNP^(iPr))Pd]+ cations in bromobenzene induces the abstraction of a bromine atom from bromobenzene, consistent with a metalloradical species. Addition of dioxygen to [(^(F)PNP^(iPr))Pd]+ cations generates a paramagnetic, cationic [eta]1 superoxide. In non-halogenated arene solvents [(^(F)PNP^(iPr))Pd]+ cations undergo a highly unusual photo-induced isomerization of the isopropyl groups on the supporting phosphines to n-propyl. This unprecedented isomerization is believed to occur via C-P bond cleavage and is driven by the decrease in sterics around the metal, which allows for the facilitated coordination of the arene solvent. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152457

Download or read book Redox Active Ligands written by Marine Desage-El Murr and published by John Wiley & Sons. This book was released on 2024-01-31 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Redox-Active Ligands Authoritative resource showcasing a new family of ligands that can lead to better catalysts and promising applications in organic synthesis Redox-Active Ligands gives a comprehensive overview of the unique features of redox-active ligands, describing their structure and synthesis, the characterization of their coordination complexes, and important applications in homogeneous catalysis. The work reflects the diversity of the subject by including ongoing research spanning coordination chemistry, organometallic chemistry, bioinspired catalysis, proton and electron transfer, and the ability of such ligands to interact with early and late transition metals, lanthanides, and actinides. The book is divided into three parts, devoted to introduction and concepts, applications, and case studies. After the introduction on key concepts related to the field, and the different types of ligands and complexes in which ligand-centered redox activity is commonly observed, mechanistic and computational studies are described. The second part focuses on catalytic applications of redox-active complexes, including examples from radical transformations, coordination chemistry and organic synthesis. Finally, case studies of redox-active guanidine ligands, and of lanthanides and actinides are presented. Other specific sample topics covered include: An overview of the electronic features of redox-active ligands, covering their historical perspective and biological background The versatility and mode of action of redox-active ligands, which sets them apart from more classic and tunable ligands such as phosphines or N-heterocyclic carbenes Preparation and catalytic applications of complexes of stable N-aryl radicals Metal complexes with redox-active ligands in H+/e- transfer transformations By providing up-to-date information on important concepts and applications, Redox-Active Ligands is an essential reading for researchers working in organometallic and coordination chemistry, catalysis, organic synthesis, and (bio)inorganic chemistry, as well as newcomers to the field.