Zerovalent Palladium Complexes Research Articles

パラジウム錯体によるカルボン酸無水物の炭素‐酸素結合活性化とその応用

Acyclic and cyclic carboxylic anhydrides oxidatively add to zerovalent palladium complexes having tertiary phosphines with carbon-oxygen bond cleavage to give corresponding acyl (carboxylato) palladium complexes, which subsequently react with atmospheric dihydrogen at room temperature to form aldehydes and carboxylic acids. Application of these results led us to the discovery of novel aldehyde synthesis by hydrogenation of carboxylic anhydrides catalyzed by palladium complexes. Furthermore we have developed atom-efficient and environmentally benign, direct hydrogenation of carboxylic acids to corresponding aldehydes in the presence of trimethylacetic anhydride catalyzed by palladium complexes.

Palladium diphenyl-2-pyridylphosphine complexes

The stoichiometric reaction of diphenyl-2-pyridylphosphine (Ph2PC5H4N-2) and palladium(II) acetate afforded the palladium(I) dimer [Pd2(µ-Ph2PC5H4N)2(OAc)2] 1. Attempts to isolate the monomer, [Pd(µ-Ph2PC5H4N)2(OAc)2], from 2∶1 stoichiometry reactions (Ph2PC5H4N∶Pd), resulted only in the isolation of 1. When >3 mole equivalents of Ph2PC5H4N were used the zerovalent palladium complex [Pd(Ph2PC5H4N)3] was isolated. Other palladium(I) dimers with carboxylic or sulfonic anionic ligands have been prepared by a metathesis reaction of the co-ordinated acetates. The complexes 1 and [Pd2(µ-Ph2PC5H4N)2(O2CCF3)2] 2 have been structurally characterised as head-to-tail dimers. The mononuclear complex [Pd(Ph2PC5H4N)2(O2CCF3)2] has been obtained by reaction of Ph2C5H4N with [Pd(CH3CN)2(O2CCF3)2]. Complex 1 reacts with dimethyl acetylenedicarboxylate to give [Pd2(µ-Ph2PC5H4N)2(OAc)2(µ-MeO2CCCCO2Me)], while attempts to isolate an A-frame carbonyl complex were unsuccessful.

Bis-Chelated Palladium(II) Complexes with Nitrogen-Donor Chelating Ligands Are Efficient Catalyst Precursors for the CO/Styrene Copolymerization Reaction

A series of dicationic bis-chelated palladium(II) complexes [Pd(N-N)2][X]2 (N-N = 2,2‘-bipyridine (bipy), 1,10-phenanthroline (phen), and their substituted derivatives; X = PF6-, BF4-, OTf-, OTs-) has been synthesized and completely characterized both in the solid state and in solution. The synthetic procedure involves a simple one-pot reaction between Pd(MeCOO)2 and [(N-N)H][X]. These compounds are very active precatalysts for the CO/styrene copolymerization yielding perfectly alternating polyketones. The crystal structures of some complexes of the series provide evidence that a distorsion from the ideal square planar geometry toward a twist conformation occurs. In DMSO solution, one of the two nitrogen-donor ligands is involved in a dissociative equilibrium yielding a monochelated complex with two cis coordination sites available for the copolymerization catalytic process. The catalytically active species is very stable in 2,2,2-trifluoroethanol, where its activity was found unaltered for at least 48 h of reaction without apparent decomposition to palladium metal. The addition of 1,4-benzoquinone (BQ) to the catalytic system has a strong influence on the yield and, above all, on the molecular weight of polyketones. The zerovalent palladium complexes [Pd(N-N)(BQ)], which might be formed during the copolymerization process, have been synthesized and characterized. The crystal structure of [Pd(bipy)(BQ)] shows that benzoquinone acts as a mono-olefinic ligand to Pd. In the presence of protons, the Pd(0) complexes are readily oxidized to Pd(II) with the reduction of benzoquinone to hydroquinone. When [(N-N)H][X] is used as the source of protons, the resulting Pd(II) species is the precatalyst and can immediately re-enter the catalytic cycle.

Phosphaazaallene Dimerization and Phosphaallene Isomerization: Catalysis by Zerovalent Palladium and Platinum Complexes

Several Pd(0) complexes catalyze the dimerization of Mes*PCNPh [2, Mes* = 2,4,6-(t-Bu)3C6H2] to the unsymmetrical heterocycle Mes*P(μ-CNPh)NPh(μ-CPMes*) (5). The symmetrical dimer [Mes*P(μ-CNPh)]2 (7), which forms slowly by uncatalyzed dimerization of 2, does not interconvert with 5; both 5 and 7 were structurally characterized by X-ray crystallography. The Pt complexes PtL2[η2-(P,C)-Mes*PCNPh] [8, L = 1/2 dppe (Ph2PCH2CH2PPh2); 9, L = PPh3; 10, L = PCy3 (Cy = c-C6H11)], models for intermediates in the catalysis, were prepared. Isomerization of Mes*PCCPh2 (3) to the phosphaindan [2,4-(t-Bu)2C6H2(6-CMe2CH2PCHCPh2)] (6), which we previously observed with Rh(I) catalysts, is catalyzed by Pt(PCy3)2 or the known Pt(PPh3)2[η2-(P,C)-Mes*PCCPh2] (12). Comparison of the metal-mediated reactions of 2 and 3 suggests that the initial steps in the catalyses, coordination of the phosphacumulene to M(0), followed by loss of a ligand, are similar.

Di- and trinuclear complexes of palladium with a triphosphine ligand, bis(diphenylphosphinomethyl)phenylphosphine

Reaction of [Pd 2(RNC) 6](PF 6) 2 with dpmp (2 equiv.) generated dipalladium complexes, [Pd 2(dpmp) 2(RNC) 2](PF 6) 2 ( 1), in good yields, where R = 2,6-xylyl (Xyl) and 2,4,6-mesityl (Mes), Complex 1a (R = Xyl) was characterized by X-ray crystallography to have a metal-metal bonded dinuclear structure (Pd−Pd = 2.607(2) Å) without bridging ligand. The dpmp ligand chelates to the metal through only the terminal phosphorus atoms. Complex 1a in acetonitrile easily lost one isocyanide ligand and was transformed into a dpmp-bridged dipalladium complex, anti-[Pd 2(μ-dpmp) 2(XylNC)] (PF 6) 2 · CH 3CN (( 2a)CH 3CN). The dinuclear core of 2a consists of a three- and a four-coordinate Pd atom bridged by two dpmp ligands (Pd−Pd = 2.702(1) Å). Complex la was restored by treatment of 2a with an excess of XylNC. When compound 1 was treated with zero-valent palladium complex [Pd 3(RNC) 6], A-frame trinuclear complex, A-frame-[Pd 3(μ-dpmp) 2(RNC) 2](PF 6) 2 ( 4), was obtained. The trimer 4 was also prepared by the reaction of [Pd 3(RNC) 8](PF 6) 2 with dpmp (2 equiv.) via a linear dpmp-bridged trimer, linear-[Pd 3(μ-dpmp) 2(RNC) 2](PF 6) 2 ( 3). Complex 4a (R = Xyl) was analyzed by X-ray crystallography to be a trinuclear A-frame structure joined by two Pd−Pd σ-bonds (Pd−Pd = 2.592(2) Å, Pd−Pd−Pd = 79.19(8)°). The two dpmp ligands doubly bridge between the three metal atoms. Whereas, complex 4 was thermally and chemically stable, complex 3a (R = Xyl) reacted with I 2 to lead to a trinuclear Pd(II) complex, [{PdI 2(dpmp) 2)2PdI 2] ( 5), which was characterized by an X-ray analysis. The two cis-PdI 2(dpmp) units were joined by trans-PdI 2 fragment without metal-metal bonds.

Palladium(0)–tetracyanoethylene complexes of diphosphines and a dipyridine with large bite angles, and their crystal structures

M. Kranenburg, J. G. P. Delis, P. C. J. Kamer, P. W. N. M. van Leeuwen, K. Vrieze, N. Veldman, A. L. Spek, K. Goubitz and J. Fraanje, J. Chem. Soc., Dalton Trans., 1997, 1839 DOI: 10.1039/A607927J

Oxidative Addition of Aryl Halides to Transient Anionic à‐Aryl–Palladium(0) Intermediates—Application to Palladium‐Catalyzed Reductive Coupling of Aryl Halides

AbstractThe rates and mechanism of the reactions of a series of aryl‐ligated, anionic palladium(0) complexes Ar‐Pd0‐(PPh3)‐2 with para‐substituted iodobenzenes were investigated by means of transient electrochemistry. The reaction was found to be first order in each reactant and to proceed similarly to oxidative addition of aryl halides to the halide‐ligated species X‐Pd0(PPh3)‐2, although much faster and less sensitive to electronic factors. Owing to the short lifetime (t1/2 ≈︁ 1 – 5 ms) of the product of this reaction, it could not be characterized in detail. However, based on kinetic results, this transient species is thought to be an anionic pentacoordinated bisarylpalladium(II) complex, which undergoes rapid loss of halide ligand to yield, most probably, a bisarylpalladium(II) neutral species. Based on the study of this reaction and on previously reported results, we propose a mechanism for the palladium‐catalyzed homocoupling of aryl halides consisting of a catalytic cycle initiated by oxidative addition of an aryl halide to a zerovalent tris‐ligated palladium center. Two‐electron reduction of the pentacoordinated arylpalladium(II) anionic species thus formed gives a tris‐ligated anionic arylpalladium(0) center, which undergoes oxidative addition with a second aryl halide molecule to eventually lead to a bisaryl‐palladium(II) neutral species. Reductive elimination of a bisaryl molecule from this center closes the catalytic cycle by regenerating the initial zerovalent palladium complex. The application of this sequence to the catalytic heterocoupling of aryl halides is discussed, and it is concluded, on the basis of Hammett correlations, that statistical yields should be observed, in agreement with the results obtained for preparative reactions in DMF.

Equilibria and rates of olefin substitution in zerovalent palladium complexes containing a 2-pyridylmethanimine ligand

Equilibrium constants Ke have been determined for the olefin susbtitution in palladium(0)α-diimine olefin (ol) complexes [Pd(η2-ol)(L–L)] by ol′ in chloroform [L–L = 2-NC5H4CHNC6H4OMe-4; ol = dimethyl fumarate (dmf), ol′= acrylonitrile (an), l-chloro-l-cyanoethylene, 1,4-naphthoquinone (nq), tetramethyl ethyleneteracarboxylate (tmetc), fumaronitrile (fn) or maleic anhydride (ma); ol = nq, ol′= tmetc, fn or ma]. The substitution equilibria are rapidly established except when ol = dmf, nq, ol′= tmetc and were studied by UV/VIS and 1H NMR spectrometry. The Ke values increase with increasing electron affinity of the entering activated olefin. The kinetics of slow approach to equilibrium were monitored by UV/VIS techniques at various temperatures. When ol = dmf, ol′= tmetc, only the second-order rate constant k2 for the forward step could be measured with sufficient accuracy, whereas for ol = nq, ol′= tmetc the constants for both the forward (k2) and the reverse (k–2) steps were determined. Activation parameters indicate an essentially associative mechanism for these paths.

Electrochemical behaviour of PdII(PPh3)2Cl2 in the presence of carbon monoxide and its use in the palladium-catalyzed electrochemical formylation of iodoanisole

“Pd °(PPh3)2” generated by electroreduction of PdII(PPh3)2Cl2 in the presence of carbon monoxide exists mainly in the form of low-ligated zerovalent palladium complex Pd °(PPh3)2CO. On the basis of the experimental results, a mechanism is proposed for its formation. The oxidative addition of 4-iodoanisole to zerovalent palladium centre to afford a cyclic palladium(II) centre seems to be very efficient, but the 4-anisaldehyde formation undergoes severe competition with the two-electron reduction yielding anisole.

Rate and Mechanism of Oxidative Addition of Aryl Triflates to Zerovalent Palladium Complexes. Evidence for the Formation of Cationic (.sigma.-Aryl)palladium Complexes

Rate and Mechanism of Oxidative Addition of Aryl Triflates to Zerovalent Palladium Complexes. Evidence for the Formation of Cationic (.sigma.-Aryl)palladium Complexes

Rates and Mechanism of the Formation of Zerovalent Palladium Complexes from Mixtures of Pd(OAc)2 and Tertiary Phosphines and Their Reactivity in Oxidative Additions

Rates and Mechanism of the Formation of Zerovalent Palladium Complexes from Mixtures of Pd(OAc)2 and Tertiary Phosphines and Their Reactivity in Oxidative Additions

Palladium-catalysed electrochemical reduction of vinyl and aryl triflates

Abstract The reduction of vinyl and aryl triflates 1 , in the presence of stoichiometric amounts of benzoic acid and catalytic amounts of PdCl 2 (PPh 3 ) 2 results in the formation of the corresponding alkenes and arenes 2 . Most probably, the reaction proceeds via a catalytic cycle initiated by the one-step two-electron reduction of the palladium complex followed by oxidative addition of unsaturated triflates to the low-ligated zerovalent palladium complex Pd 0 (PPh 3 ) 2 Cl − . The resultant σ-vinyl and σ-arylpalladium(II) intermediate undergoes a one-step two-electron reduction to afford 2 in moderate to good yield, regenerating the low-ligated zerovalent palladium complex.

Oxidative addition of organic halides to zerovalent palladium complexes containing rigid bidentate nitrogen ligands

Zerovalent complexes of the type Pd(Ar-BIAN)(alkene), i. e. complexes containing the rigid bidentate nitrogen ligands bis(arylimino) acenaphthene (Ar = p-Tol, p-MeOC 6H 4, o-Tol, o, o′-Me 2C 6H 3, o, o′- iPr 2C 6H 3) and an electron-poor alkene have been shown to react with a variety of (organic) halides RX, including methyl, benzyl, aryl, acyl and allylic halides, to give the corresponding square planar divalent Pd(R)X(Ar-BIAN) or [Pd(η 3-allyl)(Ar-BIAN)]X complexes. The new complexes obtained have been fully characterized and their fluxional behaviour in solution studied by 1H NMR spectroscopy. The rate of oxidative addition of iodomethane to Pd( p-Tol-BIAN)(alkene) complexes was found to decrease with increasing Pd-alkene bond strength, i. e. dimethyl fumarate ⪢ fumaronitrile, but oxidative addition to the fumaronitrile complex was accelerated by irradiation with a mercury lamp. Oxidative addition of allylic ha

Rigid Bidentate Nitrogen Ligands in Organometallic Chemistry and Homogeneous Catalysis. 6. Zerovalent Palladium and Platinum Complexes Containing Rigid Bidentate Nitrogen Ligands and Alkenes: Synthesis, Characterization, Alkene Rotation and Substitution Reactions. X-ray Crystal Structure of [Bis((2,6-diisopropylphenyl)imino)acenaphthene](maleic anhydride)palladium(0)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRigid Bidentate Nitrogen Ligands in Organometallic Chemistry and Homogeneous Catalysis. 6. Zerovalent Palladium and Platinum Complexes Containing Rigid Bidentate Nitrogen Ligands and Alkenes: Synthesis, Characterization, Alkene Rotation and Substitution Reactions. X-ray Crystal Structure of [Bis((2,6-diisopropylphenyl)imino)acenaphthene](maleic anhydride)palladium(0)Rob van Asselt, Cornelis J. Elsevier, Wilberth J. J. Smeets, and Anthony L. SpekCite this: Inorg. Chem. 1994, 33, 7, 1521–1531Publication Date (Print):March 1, 1994Publication History Published online1 May 2002Published inissue 1 March 1994https://doi.org/10.1021/ic00085a050RIGHTS & PERMISSIONSArticle Views956Altmetric-Citations134LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Intimate mechanism of oxidative addition to zerovalent palladium complexes in the presence of halide ions and its relevance to the mechanism of palladium-catalyzed nucleophilic substitutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntimate mechanism of oxidative addition to zerovalent palladium complexes in the presence of halide ions and its relevance to the mechanism of palladium-catalyzed nucleophilic substitutionsChristian Amatore, Anny Jutand, and Alejandra SuarezCite this: J. Am. Chem. Soc. 1993, 115, 21, 9531–9541Publication Date (Print):October 1, 1993Publication History Published online1 May 2002Published inissue 1 October 1993https://doi.org/10.1021/ja00074a018RIGHTS & PERMISSIONSArticle Views2513Altmetric-Citations213LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Rates and mechanisms of oxidative addition to zerovalent palladium complexes generated in situ from mixtures of Pd0(dba)2 and triphenylphosphine

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRates and mechanisms of oxidative addition to zerovalent palladium complexes generated in situ from mixtures of Pd0(dba)2 and triphenylphosphineChristian Amatore, Anny Jutand, Fouad Khalil, Mohamed A. M'Barki, and Loic MottierCite this: Organometallics 1993, 12, 8, 3168–3178Publication Date (Print):August 1, 1993Publication History Published online1 May 2002Published inissue 1 August 1993https://doi.org/10.1021/om00032a045RIGHTS & PERMISSIONSArticle Views2032Altmetric-Citations186LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Infrared spectra of a zero-valent palladium complex with ethylenediamine

From the reaction system in which acetic acid solutions of palladium(II) acetate and ethylenediammonium acetate were present, a product was obtained in the infrared spectra of which there were no acetate bands. With some reservations, this unexpected result was interpreted as an indication that a palladium(0) complex was obtained.

Synthesis of asymmetric secondary phosphines by the cross coupling of arylhalides with silylphosphines

The cross coupling of aryl halides with alkyl(trimethylsilyl)phosphines catalyzed by zero-valent palladium complexes yields secondary alkylarylphosphoranes containing both electron-donor and electron-withdrawing substituents in the aromatic ring. The reversible disproportionation of alkylsilylphosphines to give AlkPH2 and AlkP(SiMe3)2 was observed for the first time during this reaction. This disproportionation does not affect the yield of AlkArPH, which are formed in virtually quantitative yield, due to the high rate of cross coupling with AlkP(SiMe3)H2 and the reversibility of the disproportionation process.

Role and effects of halide ions on the rates and mechanisms of oxidative addition of iodobenzene to low-ligated zerovalent palladium complexes Pd0(PPh3)2

Role and effects of halide ions on the rates and mechanisms of oxidative addition of iodobenzene to low-ligated zerovalent palladium complexes Pd0(PPh3)2

Comparative studies on reactions of .alpha.,.beta.- and .beta.,.gamma.-unsaturated amides and acids with nickel(0), palladium(0), and platinum(0) complexes. Preparation of new five- and six-membered nickel- and palladium-containing cyclic amide and ester complexes

The nickel complex has the highest propensity to form metallacyclic amides and esters. The isolated nickel-containing five-and six-membered cyclic amide and ester complexes readily undergo CO insertion and subsequent reductive elimination to generate five- and six-membered cyclic imides and anhydrides. The related zerovalent palladium complex Pd(PCy 3 ) 2 showed much less reactivity toward the unsaturated amides and acids. Only in one case was a palladium-containing six-membered cyclic ester complex obtained. The platinum analogue Pt(cod) 2 gave no metallacycle but afforded olefin-coordinated complexes as well as oxidative-addition products