Kinetic Analysis of the Thermal Decomposition of Dialkyldithiocarbamates Chelates of Indium(III)

The kinetics of thermal decomposition of solid In(S₂CNR₂)₃ complexes, (R=CH₃, C₂H₅, n-C₃H₇,i-C₃H₇, n-C₄H₉ and i-C₄H₉), has been studied using isothermal and non-isothermal thermogravimetry. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions occur in the liquid phase, except for the In(S₂CNMe₂)₃ and In(S₂CNPrⁱ ₂)₃ compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermochemical parameters of dimethyl and di-iso-propyl dithiocarbamate complexes of palladium(II)

The standard molar enthalpy of formation of crystalline dialkyldithiocarbamate chelates, [Pd(S₂CNR₂)₂], with R=CH₃ and i-C₃H₇, was determined through reaction-solution calorimetry in 1,2-dichloroethane, at 298 K. Using the standard molar enthalpies of formation of the gaseous chelates, the homolytic (526±18 and 666±10) and heterolytic (2693±18 and 2957±10 kJ mol^-1) mean enthalpies of palladium-sulphur bond dissociation were calculated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Anionic Palladium(0) and Palladium(II) Ate Complexes

Palladium ate complexes are frequently invoked as important intermediates in Heck and cross‐coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray‐ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron‐poor catalyst [L₃Pd] (L=tris[3,5‐bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br⁻ ions to afford the anionic, zero‐valent ate complex [L₃PdBr]⁻. In contrast, more‐electron‐rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L₃Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the Pd^II ate complex [L₂Pd(Ar)I₂]⁻.     

Thermochemical properties of polycyclic hydrocarbons including fragments of norbornane and small cycles

Combustion enthalpies of three polycyclic hydrocarbons were measured by the precision bomb calorimetry method and their enthalpies of formation in the liquid state were calculated: for pentacyclo[6.3.1.1^3.6.0^2.7.0^9.11]tridecene, –7713.9±3.8 and 25.8±3.8 kJ mol^–1; for 10-met hylpentacyclo[6.3.1.1^3.6.O^2,.7.0^9.11 It ridecene, -8348.8±3.9 and -18.7+-3.9 k] mol^–1; and for 11-methylpentacyclo[6.4.1.1^3.6.0^2.7.0^9.12]tetradecene-10-spirocyclopropane,clopropane, –10157.9±3.4 and 38.1±3.8 kJ mol^–1. The thermochemical I parameters obtained agree with calculated values as well as with experimental and calculated enthalpies of formation of some hydrocarbons that contain the same fragments as the compounds studied.The authors thank Academician O. M. Nefedov and Yu. V. Tomilov for submitting the samples and for discussion of the results obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2676–2678, November, 1996.     

Spectral Studies of Palladium(II)-Allyl Thiourea System

Abstract

Palladium(II) forms 1:1 and 1:4 complexes with allyl thiourea. The molar composition of the complexes was determined by molar-ratio and continuous variation methods and confirmed by means of elemental analysis of the compounds isolated from solution.

Conformity to Beer's law was observed for up to 12 μg ml^?1 of 4 palladium in strongly acidic medium (molar absorptivity 2.28×10⁴ 1 mol^?1 cm^?1 at 292 nm);the Sandell's sensitivity of the reaction for palladium is 0.0047 μg cm^?2 per 0.001 absorbance unit.

The tolerance of the system to platinum metals and other common cations is satisfactory.

A statistical evaluation of the analytical procedure of palladium determination has been undertaken.

The infrared spectra of allyl thiourea and of its 1:1 and 1:4 palladium complexes have been measured in the 2.5–50μ region. The absorption bands have been assigned. The spectra reveal that allyl thiourea forms sulphur-to-metal bonds only, rather than nitrogen-to-metal bonds in the complexes studied.     

Chemistry of N,N-Dimethylaminoalkylchalcogenolate Complexes of Palladium(II) and Platinum(II)

Abstract

Four different series of N,N-dimethylaminoalkylchalcogenolates, viz. Me₂NCH₂ CH₂E^?, Me₂NCH(Me)CH₂E^?, Me₂NCH₂CH(Me)E^?, and Me₂NCH₂CH₂CH₂E^? (E = S, Se, Te), (referred as E^∩N) have been synthesized and characterized. Their reactions with palladium(II) and platinum(II) precursors have been explored. Complexes of the general formula, [MCl(E^∩N)]_n, [MCl(E^∩N)₂]_n, [MCl(E^∩N)(PR₃)], [M₂Cl₂(μ-E^∩N)₂(PR₃)₂], [M₂(μ-E^∩N)₂(P^∩P)₂]²⁺, etc. have been isolated. All the complexes have been characterized by elemental analysis, IR, NMR (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹²⁵Te, ¹⁹⁵Pt), UV-vis, and FAB mass spectral data. A weak absorption in the electronic spectra of [MCl(E^∩N)(PR₃)] has been attributed to metal mediated ligand-to-ligand charge transfer and showed pronounced chalcogen dependence being red shifted on moving from S → Se → Te. Structures of several complexes have been established by X-ray diffraction analyses. Thermal behavior of some of these complexes has been investigated by TGA.     

Synthesis of Well-Defined High-Valent Palladium Complexes by Oxidation of Their Palladium(II) Precursors

The last decade has witnessed the rapid development of high-valent Pd-involved organic transformations. This has also led to a steadily growing number of publications concerning the preparation of isolable and characterizable palladium(III) and palladium(IV) complexes. A variety of one-electron and two-electron oxidants have been employed to give access to high-oxidation-state Pd compounds. Undoubtedly, the study of these stoichiometric reactions has great implications for relevant Pd-mediated catalysis. In this minireview, the focus is on the synthetic approaches to structurally determined Pd^III/IV complexes starting from their Pd^II precursors, and the advances in this research area from early 2010 to late 2019 will be highlighted. Chemical oxidations exploiting various oxidizing agents including 1) hypervalent iodine reagents; 2) halogens; 3) electrophilic fluorination reagents; 4) alkyl/aryl halides; 5) ferrocenium salts; 6) peroxides/O₂; 7) sulfonyl chlorides; and 8) others are covered. A “greener” electrooxidation manner has also been reviewed.     

Palladium(II)-Catalyzed Enantioselective Azidation of Unactivated Alkenes

The first Pd-catalyzed enantioselective azidation of unactivated alkenes has been established by using readily accessible 1-azido-1,2-benziodoxol-3(1H)-one (ABX) as an azidating reagent, which affords a wide variety of structurally diverse 3-N₃-substituted piperidines in good yields with excellent enantioselectivity. The reaction features good functional-group compatibility and mild reaction conditions. Notably, both an electrophilic azidating reagent and the sterically bulky chiral pyridinyl-oxazoline (Pyox) ligand are crucial to the successful reaction.     

聚γ-巯丙基硅氧烷钯(0)配合物的合成及催化性能研究

γ－巯丙基三乙氧基硅烷依次与气相法二氧化硅，氯化钯作用，然后用水合肼还原，合成了新配合物聚γ－巯丙基硅氧烷钯。该配合物是丙烯酰胺及丙烯酸丁酯的Ｈｅｃｋ芳基化反应的有效催化剂，为立体选择性地２Ｅ－不饱酰胺及不饱和酯提供了简便且实用的方法。     

Asymmetric Cyclizative Dimerization of (ortho-Alkynyl Phenyl) (Methoxymethyl) Sulfides with Palladium(II) Bisoxazoline Catalyst

The first example of an asymmetric cyclization–dimerization of (ortho-alkynyl phenyl) (methoxymethyl) sulfides with a palladium(II) bisoxazoline (box) catalyst has been developed. The box ligand enhances the alkynophilicity of benzothienyl palladium(II) intermediate A and thus promotes coordination of the second alkyne substrate, leading to the dimerization. The characteristic properties of the box ligand were supported by density functional theory (DFT) calculations of the intermediate. Axially chiral bibenzothiophenes were obtained in good yields with good enantioselectivities.     

Preparation of Palladium(II) and Platinum(II) Phosphine Complexes Promoted by Phase-Transfer Catalysts

The synthesis of M(PR₃)₂Cl₂ (M = Pd and Pt, R = alkyl or aryl) front K₂MCl₄ (in H₂O) and PR₃ (in CH₂Cl₂) was promoted by the addition of phase-transfer catalysts (PTC). The greater the amount of PTC used, the more quickly the reaction completed. ³¹P NMR spectra of some M(PR₃)₂Cl₂ in the presence of free PR₃ were measured; these NMR resulls were used to explain problems encountered during the preparations.     

Intermolecular Methoxycarbonylation of Terminal Alkynes Catalyzed by Palladium(II) Bis(oxazoline) Complexes

Boxing clever : Direct conversion of a terminal alkyne group into a β‐methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid‐sensitive glycosidic bonds are not affected under the reaction conditions. The one‐pot synthesis of (±)‐dihydrokawain from the homopropargyl alcohol is also achieved. tfa=trifluoroacetate

     

聚-4-氧杂-6,7-二甲硒基庚基硅氧烷钯(0)配合物的合成及其催化性能研究

4 氧杂 6,7 二氯庚基三甲氧基硅烷依次与气相法二氧化硅、甲硒基钠、氯化钯作用 ,然后用水合肼还原 ,合成了二氧化硅负载的聚 4 氧杂 6,7 二甲硒基庚基硅氧烷钯 ( 0 )配合物 .该配合物是苯乙烯及丙烯酸的Heck芳基化反应的有效催化剂 ,为立体选择性地合成各种取代的反式 1,2 二苯乙烯及反式肉桂酸提供了简便且实用的新方法 .     

Palladium(II) 4,5-Diphenylimidazole Cyclometalated Complexes: DNA Interaction

In this paper, we show the synthesis of palladium(II) 4,5-phenylimidazole cyclometalated complexes. They have been characterized by IR, ¹H- and ¹³C-NMR spectroscopy. The cyclometalated dimer compound 2 [Pd(C₁₅H₁₁N₂)(μ-OAc)]₂ and the cyclometalated monomer compound 5 [PdBr(SEt₂)(C₁₅H₁₁N₂)], having OAc and Br as leaving groups, interact with DNA, modifying its secondary structure (as measured by T_m and CD), without modifying its tertiary structure (as determined by measurement of the electrophoretic mobility in agarose gels). The monomeric compound 5 seems to be the one that induces the highest alterations in DNA secondary structure since it strongly modifies the CD spectrum of the DNA. Melting data of drug–DNA complexes suggest that, at low drug concentration, the 4,5-Imd ligand intercalates between the base pairs in the DNA molecule, increasing the T_m, while at high drug concentrations the palladium(II) centers destabilize the double helix, producing a lowering in T_m values. These results indicate that complexes containing planar structures might selectively bind to DNA that is not supercoiled, and that therefore it only has a secondary structure. © 1997 John Wiley & Sons, Ltd.     

Palladium(II) chloride catalyzes the cross-coupling reaction of 2,5-bis-(butyltelluro)-furan and 1-alkynes

Palladium(II) chloride catalyzed the cross-coupling reaction of 2,5-bis-(butyltelluro) furan and terminal alkynes yielding both symmetrically and unsymmetrically substituted 2,5-bis-acetylenic furan derivatives. The methodology represents a general and efficient protocol for carrying out the synthesis of furan derivatives with potential biological activities.     

Syntheses and Crystal Structures of Three Palladium(II) Complexes with Isonitrosobenzoylacetoneimine Ligand

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