The role of water molecules in formation of heterometallic palladium acetate complexes with cerium and neodymium

The reactions of palladium(II) acetate with neodymium(III) and cerium(III) acetates in acetic acid containing a specified amount of water have been studied. The following homo- and heterometallic complexes have been synthesized and characterized by X-ray diffraction: Nd₂(μ-OOCMe)₂(μ,η²-OOCMe)₂(η²-OOCMe)₂(HOOCMe)₂(OH₂)₂ · 4HOOCMe, [Pd(μ-OOCMe)₄Ce(OH₂)₂(μ,η²-OOCMe)]₂ · 2HOOCMe · 6H₂O, [Pd(μ-OOCMe)₄Ce(OH₂)₂(μ,η²-OOCMe)]₂ · 14H₂O, [Pd(μ-OOCMe)₄M(HOOCMe)₂(OH₂)₂]⁺ [Pd(μ-OOCMe)₄M(μ-OOCMe)₄Pd]⁻ · 2MeCOOH · 1.5H₂O (M = Nd, Ce), and {[Pd(μ-OOCMe)₄Ce(OOCMe)₄]₂ [Pd₄(μ-OOCMe)₄]₂(μ₄-O)₈CePd₄}(OH)₃ · 27H₂O. From kinetic and structural data and optical spectra of reaction solutions, the conclusion was drawn that hydrolytic processes play a decisive role in complexation reactions.     

On the nature of the chemical bond in heterobimetallic palladium(II) complexes with divalent 3<Emphasis Type="Italic">d</Emphasis> metals

The complex Pd(μ-OOCMe)₄Cu(OH₂) · 2Pd₃(μ-OOCMe)₆ was synthesized and characterized by X-ray crystallography. In the heterometallic moiety of this complex, the Pd^II and Cu^II atoms are at an extraordinary short distance (2.521(3) Å). DFT quantum-chemical calculations of the geometric and electronic structure of a series of heterobinuclear paddlewheel complexes Pd^IIM^II(μ-OOCMe)₄L (M = Zn^II, Ni^II, Cu^II, Co^II, Fe^II; L = OH₂ and NCH) and their formate analogues Pd^IIM^II(μ-OOCH)₄L (M = Zn^II, Ni^II, Fe^II) showed that the extraordinary short Pd?M distance in all these complexes is caused only by the tightening effect of carboxylate bridges rather than by the metal-metal bond. The direct Pd-M interaction becomes possible only after removal of electrons from the antibonding orbitals and formation of oxidized complexes of the [Pd^III(μ-OOCMe)₄Ni^III]²⁺ type.     

Re(III) complexes in the synthesis of platinum acetate complexes and the structure of [PPh3Pt(OAc)2]2

Reaction of tetrachlorodiacetatodirhenium dihydrate with triphenylphosphineplatinum (II) triacetatoargentate(I) produces a new binuclear platinum complex with acetate bridges, bis[(²-acetato)acetatotriphenylphosphine]diplatinum(II). The new complex is characterized by x-ray structural analysis, IR, and PMR spectroscopies. The Re(III) complex in this reaction is not only the source of chloride ions, which are necessary for precipitation of silver, and the acetate acceptor, but also the silver(I) reductant which is oxidized during the reaction to Re(IV).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1894–1899, August, 1989.     

Unusual selective allylation of norbornadiene in the presence of palladium nanoclusters

The reaction of norbornadiene (NBD) with allyl acetate in the presence of the nanocluster Pd₁₄₇phen₃₂O₆₀(OCOBu^t)₃₀ (Pd-147; phen is 1,10-phenanthroline) and PPh₃ in acetonitrile is nonselective and is accompanied by the decomposition of the cluster, affording the same allylation products of NBD as the reaction with Pd₃(OAc)₆ or Pd(dba)₂ (dba is dibenzylideneacetone) combined with PPh₃. In contrast, in the ionic liquid [bmim][BF₄] (bmim is 1-butyl-3-methylimidazolinium), the Pd-147 is not decomposed and the reaction occurs selectively to give methylidene(vinyl)norbornene as the sole product. The data obtained suggest that in an ionic liquid, the reaction under study is catalyzed by the nanocluster Pd-147 rather than by the products of its decomposition.     

Thermolysis of binuclear heterometallic pivalate with Pd(II)-Ce(III) metal core in dibenzyl ether

A reaction between palladium(II) acetate and aqueous cerium(III) acetate in acetic acid with subsequent boiling in benzene with excess pivalic acid is found to yield the complex Pd(μ-OOCBu^t)₄Ce(OOCBu^t)(HOOCBu^t)₃ (1). The liquid-phase thermolysis of complex 1 in dibenzyl ether (190°C) leads to the formation of the tetranuclear complex [Pd(μ-OOCBu^t)₄Ce(HOOCBu^t)]₂(μ-OOCBu^t)(μ-OH₂) (2). The structure of the synthesized complexes is established by X-ray diffraction.     

Highly selective catalysts for liquid-phase hydrogenation of substituted alkynes based on Pd—Cu bimetallic nanoparticles

Catalytic properties of Pd—Cu bimetallic catalysts supported on SiO₂ and Al₂O₃ were studied in a model reaction of selective hydrogenation of diphenylacetylene. Application of PdCu₂(AcO)₆ heterobimetallic acetate complex as a precursor made it possible to obtain homogeneous Pd—Cu bimetallic nanoparticles. This result was supported by the data of IR spectroscopy of adsorbed CO. The Pd-Cu catalysts showed considerably higher selectivity than monometallic samples. Moreover, the introduction of copper decreases the hydrogenation rate of diphenylethylene (DPE) to diphenylethane. As a result, the maximum yield of the target product, DPE, increased from 78 to 93% in the presence of Pd—Cu catalysts.     

Dry reforming of methane on porous membrane catalytic systems

A method of high-performance dry reforming of methane into syngas at temperatures below 650 °C on membrane catalytic systems was proposed. The membrane catalytic systems consist of porous inorganic membrane-supports, prepared by self-propagating high-temperature synthesis and modified by nanosized metallocomplex components, which are uniformly distributed inside membrane pores. The influence of the composition of the supported active components, temperature, and flow rate on the activity and selectivity of CH₄ and CO₂ transformations into syngas, as well as the dynamics of CH₄ and CO₂ conversion on the membrane catalytic systems were studied.     

PdAg2 nanoparticles in aqueous solution: Preparation, characterization, and catalytic properties

The reduction of a heterobimetallic complex, Pd(OOCMe)₄Ag₂(HOOCMe)₄, with hydrogen or sodium borohydride in an aqueous solution produces PdAg₂ nanoparticles of an alloy or intermetallic type. It is shown that the catalytic activity of the particles in the reduction of methyl viologen with hydrogen is lower than that of palladium nanoparticles of the same size. Therewith, ??borohydride?? nanoparticles manifest a higher catalytic activity than do ??hydrogen?? ones. Unlike silver nanoparticles, PdAg₂ nanoparticles do not catalyze the decomposition of hydrazine.     

Determination of the local structure of a highly dispersed Pd-Nanosystem located on a titanium dioxide carrier

This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO₂ matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(μ-OOCMe)₄(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.