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PubMed2004

The reactions of palladium(II), thallium(III) and lead(IV) trifluoroacetates with 3beta-acetoxyandrost-5-en-17-one: crystal structure of the first trifluoroacetate bridged 5,6,7-pi-allyl steroid palladium dimer.

A number of metal trifluoroacetates were reacted with the olefin 3beta-acetoxyandrost-5-en-17-one (6). Palladium(II) trifluoroacetate afforded bis[micro-trifluoroacetato(alpha-5,7-eta-3beta-acetoxyandrostenyl-17-one)palladium(II)] (20), a new ring B pi-allyl steroid-palladium complex, in quantitative yield. Thallium(III) trifluoroacetate gave 3beta-acetoxy-5alpha-hydroxy-6beta-trifluoroacetoxyandrostan-17-one (16), 3beta-acetoxy-6beta-trifluoroacetoxyandrost-4-en-17-one (9), 3beta-acetoxy-4beta-trifluoroacetoxyandrost-5-en-17-one (10), and 3beta-acetoxy-5alpha,6beta-dihydroxyandrostan-17-one (17). Lead(IV) trifluoroacetate yielded 9, 10 and 16. 3beta-Acetoxy-5alpha,6beta-bis(trifluoroacetoxy)androstan-17-one (15), a new compound, was also formed in this reaction. During the course of the lead(IV) studies the dichlorosteroid 21 and the rearranged allylic oxidation product 24 were formed. Their formation was attributed to the generation of lead(IV) chloride in the reaction. Silver(I) and copper(II) trifluoroacetates proved to be unreactive towards 6.

Crystallography↗
PubMed1997

Palladium(II) complexes of 2-acetylpyridine N(4)-methyl, N(4)-ethyl and N(4)-phenyl-thiosemicarbazones. Crystal structure of chloro(2-acetylpyridine N(4)-methylthiosemicarbazonato) palladium(II). Synthesis, spectral studies, in vitro and in vivo antitumour activity.

The reactions of 2-acetylpyridine N(4)-methyl, (HAc4Me) N(4)-ethyl (HAc4Et) and N(4)-Phenyl (HAc4Ph) thiosemicarbazone with palladium(II) were studied. The ligands and the palladium(II) complexes have been characterized by spectroscopic techniques. The structure of [Pd(Ac4Me)Cl] has been determined by single-crystal x-ray diffraction. The protonation constants of HAc4Me and HAc4Et, Ka1 and Ka2, were determined by spectrophotometry. The effect of palladium compounds on DNA synthesis of P388 and L1210 cell cultures is also reported. Some of these compounds increased the life span of mice bearing tumors.

Animals↗
PubMed2002

Allenes as carbon nucleophiles in palladium-catalyzed reactions: observation of anti attack of allenes on (pi-allyl)palladium complexes.

In the palladium-catalyzed cyclization of allenic allylic esters using Pd(dba)2 as catalyst, it was shown that the allene acts as a carbon nucleophile. Intermediates were isolated and stereochemical studies established that the double bond of the allene has attacked the (pi-allyl)palladium intermediate on the face opposite to that of palladium.

Journal Article↗
PubMed2003

Palladium-catalyzed deracemization of allylic carbonates in water with formation of allylic alcohols: hydrogen carbonate ion as nucleophile in the palladium-catalyzed allylic substitution and kinetic resolution.

The palladium-catalyzed deracemization of racemic cyclic and acyclic allylic methyl carbonates in water in the presence of N,N'-(1R,2R)-1,2-cyclohexanediylbis[2-(diphenylphophino)benzamide] proceeds with high enantioselectivities to give the corresponding allylic alcohols in high yields. This deracemization involves a palladium-catalyzed allylic substitution with the in-situ-formed hydrogen carbonate ion and an irreversible decomposition of the intermediate allylic hydrogen carbonates, with formation of the corresponding allylic alcohols. The palladium-catalyzed reaction of racemic cyclic allylic acetates with potassium hydrogen carbonate in water in the presence of the chiral bisphosphane proceeds with a highly selective kinetic resolution to give the corresponding allylic alcohols and allylic acetates.

Journal Article↗
PubMed2005

On the mechanism of the palladium(II)-catalyzed decarboxylative olefination of arene carboxylic acids. Crystallographic characterization of non-phosphine palladium(II) intermediates and observation of their stepwise transformation in Heck-like processes.

Mechanistic studies of a palladium-mediated decarboxylative olefination of arene carboxylic acids are presented, providing spectroscopic and, in two instances, crystallographic evidence for intermediates in a proposed stepwise process. Sequentially, the proposed pathway involves carboxyl exchange between palladium(II) bis(trifluoroacetate) and an arene carboxylic acid substrate, rate-determining decarboxylation to form an arylpalladium(II) trifluoroacetate intermediate (containing two trans-disposed S-bound dimethyl sulfoxide ligands in a crystallographically characterized form), then olefin insertion and beta-hydride elimination. Because of the unique mode of generation of the arylpalladium(II) trifluoroacetate intermediate, a species believed to be substantially electron-deficient relative to phosphine-containing arylpalladium(II) complexes previously studied, it has been possible to gain new insights into those steps that are common to the Heck reaction, namely, olefin insertion and beta-hydride elimination. The present results show that there are notable differences in reactivity between arylpalladium(II) intermediates generated by decarboxylative palladation and those produced in conventional Heck reactions. Specifically, we have found that more electron-rich alkenes react preferentially with an arylpalladium(II) trifluoroacetate intermediate formed by decarboxylative palladation, whereas an opposite trend is found in conventional Heck reactions. In addition, we have found that the aralkylpalladium(II) trifluoroacetate intermediates that are formed upon olefin insertion in the present study are stabilized with respect to beta-hydride elimination as compared to the corresponding phosphine-ligated aralkylpalladium(II) complexes. We have also crystallographically characterized an aralkylpalladium(II) trifluoroacetate intermediate derived from arylpalladium(II) insertion into norbornene, and this structure, too, contains an S-bound dimethyl sulfoxide ligand; the ipso-carbon of the transferred aryl group and trifluoroacetate function as the third and fourth ligands in the observed distorted square-planar palladium(II) complex.

Journal Article↗
PubMed1980

Observatons on gold-palladium-silver and gold-palladium alloys.

Properties, heat treatment response, structure, and composition of three high-fusing crown and fixed partial denture alloys were studied. Except for elongation, the properties of two gold-palladium-silver based materials were compared to those of a gold-palladium alloy. The greater elongation of the latter material was attributed to its intragranular homogeneity.

Chemical Phenomena↗
PubMed1990

Platinum and palladium complexes of 3-methyl orotic acid: a route toward palladium complexes with good antitumor activity.

In order to design and develop potential anticancer drugs involving the same structural pattern as platinum(II) antitumor complexes, complexes of palladium and platinum with 3-methyl-orotic acid as the leaving ligand have been synthesized. The study of the anticancer activity of these compounds toward L1210 leukemia and sarcoma 180 in mice is presented and discussed in terms of the nature of the ligand and the metal involved. The (3-methylorotato)(1,2-diamino-cyclohexane) palladium(II) has an activity (sarcoma 180) similar to that for cis-DDP itself. The crystal structure of (3-methylorotato)(dl-trans-1,2-diaminocyclohexane) platinum(II) is described.

Animals↗
PubMed2005

Synthesis and characterization of new palladium-clotrimazole and palladium-chloroquine complexes showing cytotoxicity for tumor cell lines in vitro.

New palladium complexes of chloroquine (CQ) and clotrimazole (CTZ) have been prepared, characterized, and evaluated against four tumor cell lines in vitro. [Pd (CQ)2Cl2] (1) was synthesized by the reaction of PdCl2(CH3CN)2 with CQ, and the [Pd (CTZ)2Cl2] (2) complex by a similar reaction. The new compounds were characterized by a combination of FAB-MS (fast atom bombardment-mass spectrum), elemental analysis, molar conductivity, IR, and NMR spectroscopy. The solid-state structure of 2 has been determined by X-ray crystallography. 2 crystallizes in the monoclinic space group P(2(1)/c), with a = 21.100(4) A, b = 13.408(3) A, c = 22.642(5) A. The structure refinement converged at R1 = 0.0728, wR2 = 0.1918. The cytotoxicity of these two complexes for the tumor cell lines, PANC-1, SKBR-3, MDA-MB231 and HT-29, was compared with that of the original ligands. Ligation of palladium to CTZ led to an increase in the IC50, although a three-fold reduction in the IC50 of CQ was observed on ligation to the metal when tested against the MDA-MB231 cell line.

Antineoplastic Agents↗
PubMed2002

Synthesis, crystal structure and initial biological evaluation of the new enantiomerically pure chiral palladium(II) complex trans-bis[endo-(1R)-1,7,7-trimethylbicyclo[2.2.1]-heptan-2-amino]palladium(II)dichloride.

The palladium(II) complex trans-bis[(R)-(+)-bornylamino]palladium(II) dichloride was synthesised and characterised. The solid state structure of the complex was determined by X-ray structure analysis. The compound crystallises in the monoclinic space group P2(1) with a=12.383(2), b=23.689(5), c=12.769(3) A, beta=93.25(3) degrees, and V=3739.6(13) A(3). The complex was tested for its cytotoxicity against L(929), K(562) and HeLa cell lines using the MTT assay technique. It is also tested for its anticomplementary activity using a test that detects complement proteins inhibition. These activities were compared with those of the reference standards, cisplatin, carboplatin and oxaliplatin. The significance of these results is given and discussed.

Antineoplastic Agents↗
PubMed1992

Contact dermatitis from metallic palladium in patients reacting to palladium chloride.

1307 consecutive patients were patch tested with PdCl2 1% pet. 32 patients were positive; 29 also showed a reaction to NiSO4. 470 patients were additionally tested with a metallic palladium disc. 3 had a positive reaction, and none of them reacted to PdCl2 or NiSO4 pet. A positive patch test to PdCl2 pet. is in most cases probably due to a cross-reaction with nickel in nickel-sensitive subjects. Patients positive to PdCl2 tolerate skin contact with metallic palladium.

Dermatitis, Contact↗
PubMed1995

Patch test results with serial dilutions of nickel sulfate (with and without detergent), palladium chloride, and nickel and palladium metal plates.

Clinical experience suggests the existence of different degrees of sensitivity in nickel-allergic patients. For quantification of this phenomenon, 462 consecutive patients with previously diagnosed or strongly suspected nickel allergy were tested with serial dilution patch tests with 5 ppm to 5% nickel sulfate in pet. (Ni), and 5 ppm to 1% nickel sulfate in pet. with 1% detergent (Ni/D). Additionally, nickel and palladium metal plates were tested in 103, and cobalt salts, dichromate and palladium chloride (PdCl2) in most patients. 332 patients reacted positively to Ni or Ni/D. The influence of a concomitantly administered detergent was not significant. A significant correlation was found between positive reactions to low concentrations of Ni (or Ni/D), i.e., 0.1% or less (N = 166), and concomitant reactions to nickel metal plates, cobalt salts and PdCl2 and a history of ear piercing with metal intolerance. The clinical relevance of reactions to PdCl2 is at present not clear. A subgroup of nickel-allergic patients with "high sensitivity" can be defined. In future studies further addressing the clinical relevance of high versus low sensitivity, patch testing with 0.01, 0.1, 1.0 and 5% nickel sulfate in pet. is recommended instead of routine tests with 5% only.

Adult↗
PubMed1980

A Palladium-palladium oxide miniature pH electrode.

A wire-form miniature palladium-palladium oxide electrode has been fabricated for pH measurement. The electrode exhibits a super-Nernstian behavior and gives a mean pH response of 71.4 millivolts per [pH] (standard deviation, 5.2 millivolts). Uncorrected zero current potential values can be used to determine the pH value of the medium to within 0.012 pH. The electrode should find applications in biological, medical, and clinical studies.

Buffers↗
PubMed2002

Modular bis(oxazoline) ligands for palladium catalyzed allylic alkylation: unprecedented conformational behaviour of a bis(oxazoline) palladium eta3-1,3-diphenylallyl complex.

New families of enantiopure bis(oxazolines) with 4,5-trans (5 a-g) or 4,5-cis (6 c) stereochemistry at the individual rings have been prepared in high yield. Their eta(3)-allyl palladium complexes (8 a-g, 9 c and 10) have been used as catalytic precursors in allylic alkylation reactions with excellent enantioselectivities (up to 96 %) for the trans oxazoline derivatives, while Pd/6 c system was inactive. NMR studies on palladium eta(3)-1,3-diphenylallyl intermediates (11 a, c and e) showed the presence of syn/syn- and syn/anti-allyl isomers in solution; this resembles the first example of eta(3)-eta(1)-eta(3) isomerism in Pd allylic complexes containing bis(oxazolines) derived from malonic acid.

Journal Article↗
PubMed1997

cis-Dichloro(alpha,omega-diamino carboxylate ethyl ester)palladium(II) as Palladium(II) versus Platinum(II) Model Anticancer Drugs: Synthesis, Solution Equilibria of Their Aqua, Hydroxo, and/or Chloro Species, and in Vitro/in Vivo DNA-Binding Properties.

cis-Dichloro(d,l-2,3-diaminopropionate ethyl ester)palladium(II), cis-[Pd(Etdap)Cl(2)] (I), and cis-dichloro(d,l-2,4-diaminobutyrate ethyl ester)palladium(II), cis-[Pd(Etdab)Cl(2)] (II), were synthesized and characterized by elemental analysis, IR spectroscopy, and TG-DTA thermal analysis. The equilibrium model and log beta(pqr) constants of hydrolytic species of I and II were also investigated by potentiometric methods (I = 0.15 M (NaClO(4)) and 37 degrees C). Aqueous solutions of cis-[Pd(Etdaa)(H(2)O)(2)](ClO(4))(2) (Etdaa = Etdap (III) or Etdab (IV)) were prepared by stoichiometric reaction of I or II with AgClO(4). Thus, log beta(pqr) of the corresponding cis-aquahydroxo (pqr = 1,0,-1) and di(&mgr;-hydroxo) (pqr = 2,0,-2) species were obtained from E(H(+)) data of alkalimetric titrations of solutions of III or IV. Such constants were then used as fixed values to obtain log beta(pqr)() of chloro-containing species (cis-dichloro (1,2,0), cis-chloroaqua (1,1,0), and cis-chlorohydroxo (1,1,-1)) from E(H(+)) and E(Cl(-)) data pairs simultaneously obtained by titration of solutions of III or IV with NaOH and NaCl. All log beta(pqr) were fitted by the SUPERQUAD program. Appropriate log beta(pqr)() sets give good simulations of experimental titration curves and several species distribution diagrams. In addition the interaction of I and/or II with DNA in vitro and in vivo was studied by various methods. UV spectral data and melting and renaturation curves indicate that both compounds destabilize the DNA helicoidal structure. Compound II disrupts in vivo the structure and transcription process of polytene chromosomes of Drosophila hydei.

Journal Article↗
PubMed2006

Mechanism of the palladium-catalyzed homocoupling of arylboronic acids: key involvement of a palladium peroxo complex.

The mechanism of the palladium-catalyzed homocoupling of arylboronic acids ArB(OH)(2) (Ar = 4-Z-C(6)H(4) with Z = MeO, H, CN) in the presence of dioxygen, leading to symmetrical biaryls, has been fully elucidated. The peroxo complex (eta(2)-O(2))PdL(2) (L = PPh(3)), generated in the reaction of dioxygen with the Pd(0) catalyst, was found to play a crucial role. Indeed, it reacts with the arylboronic acid to generate an adduct (coordination of one oxygen atom of the peroxo complex to the oxophilic boron atom of the arylboronic acid) characterized by (31)P NMR spectroscopy and ab initio calculations. This adduct reacts with a second molecule of arylboronic acid to generate trans-ArPd(OH)L(2) complexes. A transmetalation by the arylboronic acid gives trans-ArPdArL(2) complexes. The biaryl is then released in a reductive elimination. This reaction is at the origin of the formation of biaryls as byproducts in palladium-catalyzed Suzuki-Miyaura reactions when they are not conducted under oxygen-free atmosphere.

Journal Article↗
PubMed2006

Synthesis of small palladium nanoparticles stabilized by bisphosphine BINAP bearing an alkyl chain and their palladium nanoparticle-catalyzed carbon-carbon coupling reactions under room-temperature.

A new bisphosphine ligand, C8-BINAP, and C8-BINAP-stabilized palladium nanoparticles have been prepared; C8-BINAP was found to be an effective protecting ligand for preparing and stabilizing palladium nanoparticles with very small core size and narrow size distribution and the C8-BINAP-Pd nanoparticles behave as an efficient catalyst for carbon-carbon coupling reactions at room temperature.

Journal Article↗
PubMed2002

Tetrakis(dimethyl sulfide)palladium(II) bis(tetrafluoroborate) and tetrakis(1,4-oxathiane-kappaS)palladium(II) bis(tetrafluoroborate).

Tetrakis(dimethyl sulfide)palladium(II) bis(tetrafluoroborate), [Pd(C(2)H(6)S)(4)](BF(4))(2), (I), and tetrakis(1,4-oxathiane-kappaS)palladium(II) bis(tetrafluoroborate), [Pd(C(4)H(8)OS)(4)](BF(4))(2), (II), both crystallize as mononuclear square-planar complexes with tetrafluoroborate as the counter-ions. The Pd atom accepts four S-donor atoms and is positioned at an inversion centre in both compounds. The two unique S atoms in the dimethyl sulfide complex, (I), are disordered. The Pd-S distances are in the range 2.3338(12)-2.3375(12)A in (I), and the corresponding distances in the thioxane complex, (II), are 2.3293(17) and 2.3406(17)A. The anions in both compounds interact weakly with the Pd atom.

Journal Article↗