Reaction of coordinated phosphines—II: Arylation of substituted olefins by palladium(II) acetate and triarylphosphine

Phenylation of 1-octene, cyclohexene, styrene, acrylonitrile, vinyl acetate, ethyl acrylate, and ethyl but-3-enoate with Pd(PAr₃)₂(OAc)₂ was carried out in acetic acid at 50°. para-Substituted triphenylphosphine palladium acetate complex produced corresponding para substituted phenyl derivatives.     

Facile Hydrolysis and Alcoholysis of Palladium Acetate

Palladium(II) acetate is readily converted into [Pd₃(μ²‐OH)(OAc)₅] ( 1 ) in the presence of water in a range of organic solvents and is also slowly converted in the solid state. Complex 1 can also be formed in nominally anhydrous solvents. Similarly, the analogous alkoxide complexes [Pd₃(μ²‐OR)(OAc)₅] ( 3 ) are easily formed in solutions of palladium(II) acetate containing a range of alcohols. An examination of a representative Wacker‐type oxidation shows that the Pd‐OH complex 1 and a related Pd‐oxo complex 4 can be excluded as potential catalytic intermediates in the absence of exogenous water.     

Structural Chemistry of Magnesium Acetates

Magnesium acetate solvates, Mg(OAc)₂ · nL, and their hydrates were prepared by crystallization of Mg(OAc)₂ · 4H₂O or Mg(OAc)₂ from different solvents (L = MeOH, EtOH, HOAc). Anhydrous Mg(OAc)₂ was obtained by thermal dehydration of the tetrahydrate at 150 °C. X‐ray single crystal diffraction mostly with the use of synchrotron radiation allowed the structure determination of Mg(OAc)₂(H₂O)₃(EtOH) ( I ), Mg(OAc)₂(HOAc)₂(H₂O)₂ ( II ), Mg₃(OAc)₆(MeOH)₆ ( III ), Mg₃(OAc)₆(HOAc)₂(H₂O)₂ · 2HOAc ( IV ), Mg(OAc)₂(HOAc) · 1.8(HOAc) ( V ), Mg(OAc)₂ · H₂O ( VI ), [Mg₃(OAc)₆(EtOH)₂] · 2EtOH ( VII ), and Mg(OAc)₂ ( VIII ). Structural data were discussed in terms of the number of neutral O‐donor ligands per magnesium atom, coordination environment of magnesium atoms, structural functions of acetate groups, and hydrogen bonding systems.     

A series of (NHC)Pd(N˄O)(OAc) complexes: synthesis,characterization and catalytic activities towards desulfinative Sonogashira coupling of arylsulfonyl hydrazides with arylalkynes

A series of well-defined N-heterocyclic carbene palladium (II) complexes with general formula (NHC)Pd(N^˄O)(OAc) were prepared through reaction of Pd (NHC)(OAc)₂(H₂O) with 1-methyl-1H-pyrazole-3-carboxylic acid or 1-methyl-1H-indazole-3-carboxylic acid in the presence of K₂CO₃. These complexes were then used for desulfinative Sonogashira coupling of arylsulfonyl hydrazides with terminal alkynes. With low catalyst loading, all synthesized palladium compounds exhibited moderate to high catalytic activities for the reactions.     

Studies of the oxidation of palladium complexes by the advanced oxidation process Pretreatment of model catalysts for precious metal analysis

The advanced oxidation process (AOP) for the pretreatment of model palladium catalysts has been studied. Most standard metal analysis techniques are for metal ions free of organic ligands. Spent palladium catalysts contain organic ligands that need to be removed prior to analysis. AOP uses a combination of hydrogen peroxide and UV light to generate radicals that decompose such ligands, freeing up metals for further analysis. Palladium acetate Pd(OAc)₂, palladium acetylacetonate Pd(acac)₂, and tris(dibenzylideneacetone)dipalladium (Pd₂(dba)₃) were chosen as model precious metal catalysts for investigation. AOP was found to decompose ligands in Pd(OAc)₂, Pd(acac)₂ and give accurate Pd(II) quantification, while ligand decomposition and oxidation of Pd(0) to Pd(II) were demonstrated in treatments involving Pd₂(dba)₃. The effects of solubility of the palladium complexes, continuous addition of H₂O₂ during AOP treatments, sample pH, concentration of H₂O₂, and length of UV irradiation are reported.     

Palladium‐Catalyzed Direct C2 Arylation of N‐Substituted Indoles with 1‐Aryltriazenes

A novel and efficient palladium‐catalyzed C2 arylation of N‐substituted indoles with 1‐aryltriazenes for the synthesis of 2‐arylindoles was developed. In the presence of BF₃ ? OEt₂ and palladium(II) acetate (Pd(OAc)₂), N‐substituted indoles reacted with 1‐aryltriazenes in N,N‐dimethylacetamide (DMAC) to afford the corresponding aryl–indole‐type products in good to excellent yields.     

Structural and photophysical studies on a linear trinuclear zinc complex of 2-[(2-hydroxyethylimino)methyl]quinolin-8-ol

A linear trinuclear zinc complex was obtained when after refluxing 8-hydroxyquinoline-2-carboxaldehyde and 2-aminoethanol (in a 1:1 molar ratio) until the formation of the H₂L ligand, a methanol solution of zinc acetate dihydrate was added. Reaction between Zn(OAc)₂·2H₂O and H₂L, both in 3:2 or 4:2 ratios, yielded Zn₃(HL)₂(OAc)₄. This latter could be crystallographically characterised, and rather surprisingly, the potentially tetradentate HL⁻ is only acting as an O,N-donor, while two phenolate and four acetate bridges hold together the three zinc ions. A study of the luminescence properties in methanol solution showed that the quantum yield of Zn₃(HL)₂(OAc)₄ (Φ_F = 0.07) is slightly higher than that of 8-hydroxyquinoline-2-carboxaldehyde (Φ_F = 0.06).     

A facile, microwave-assisted, palladium-catalyzed arylation of acetone

We report an expedient method for the heteroarylation of acetone under tin-free conditions. The coupling is performed using the commercially available enol silane of acetone (2-trimethylsilyloxypropene) and a corresponding aryl bromide, chloride or triflate under microwave-assisted conditions, with tris(dibenzylideneacetone)dipalladium (Pd₂(dba)₃) or palladium acetate (Pd(OAc)₂) and 2-(2′,6′-dimethoxybiphenyl)dicyclohexylphosphine (S-Phos) as the catalyst system.     

Different Metal Aggregation in Copper Acetate Chain Coordination Polymers with Dipyridyl Tethers Bearing Hydrogen Bonding Capable Functional Groups

Hydrothermal synthesis has afforded a pair of divalent copper acetate coordination polymers containing either 4, 4′‐dipyridylamine (dpa) or 4‐pyridylisonicotinamide (4‐pina), both of which hydrogen‐bonding capable central functional groups. X‐ray crystallography revealed that both exhibit a 1D chain dimensionality. Use of the kinked tethering ligand dpa produced [Cu(OAc)₂(dpa)]_n ( 1 ), which possesses a simple chain based on dpa linkage of isolated copper ions. On the other hand, employing the straighter amide ligand 4‐pina generated {[Cu(OAc)₂(4‐pina)] · 0.5H₂O}_n ( 2 ), which exhibits {Cu₂O₂} rhomboid dimers formed through bridging acetate ligands. Weak antiferromagnetic coupling [g = 1.984(3), J = –3.2(3) cm^–1] was observed within the axial‐equatorial bridged {Cu₂O₂} dimers in 2 , with possible ferrimagnetism due to spin canting below 11 K.     

Ready Access to Anhydrous Anionic Lanthanide Acetates by Using Imidazolium Acetate Ionic Liquids as the Reaction Medium

Access to lanthanide acetate coordination compounds is challenged by the tendency of lanthanides to coordinate water and the plethora of acetate coordination modes. A straightforward, reproducible synthetic procedure by treating lanthanide chloride hydrates with defined ratios of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) has been developed. This reaction pathway leads to two isostructural crystalline anhydrous coordination complexes, the polymeric [C₂mim]_n[{Ln₂(OAc)₇}_n] and the dimeric [C₂mim]₂[Ln₂(OAc)₈], based on the ion size and the ratio of IL used. A reaction with an IL : Ln-salt ratio of 5 : 1, where Ln=Nd, Sm, and Gd, led exclusively to the polymer, whilst for the heaviest lanthanides (Dy−Lu) the dimer was observed. Reaction with Eu and Tb resulted in a mixture of both polymeric and dimeric forms. When the amount of IL and/or the size of the cation was increased, the reaction led to only the dimeric compound for all the lanthanide series. Crystallographic analyses of the resulting salts revealed three different types of metal-acetate coordination modes where η²μκ² is the most represented in both structure types.     

Polycondensation of haloarylketones catalyzed by palladium compounds bearing N-heterocyclic carbene (NHC) ligands

Palladium-catalyzed α-arylation of ketones, which can efficiently give coupling products by using appropriate ligands and bases, could be applied to a polycondensation reaction. Stable N-heterocyclic carbenes (NHC) were used as favorable ligands coordinating the Pd catalysts, which were generated in situ from commercially available palladium compounds such as Pd(OAc)₂ and Pd₂(dba)₃ as suitable catalyst precursors in this polymerization. Using small amounts of binary catalysts, poly(aryl alkyl ketone)s were afforded in high yields from haloarylketones in the presence of a base. A primarily prepared palladium catalyst having an NHC ligand, [Pd(OAc)₂(NHC)], also efficiently catalyzed the polycondensation, whereas a palladium compound bearing two carbene ligands, [PdX₂(NHC)₂], did not.     

Oxygenation of saturated and unsaturated hydrocarbons with sodium periodate catalyzed by manganese(III) tetra-arylporphyrins, to study the axial ligation of imidazole

Competitive oxygenation of cyclooctene and tetralin with sodium periodate catalyzed by Mn^(III)(TPP)OAc, TPP = meso-tetraphenylporphyrin; Mn^(III) (TNP)OAc, TNP =meso-tetrakis(1-naphthyl) porphyrin; Mn^(III) (TMP)OAc, TMP =meso-tetrakis(2,4,6-trimethyl-phenyl)porphyrin; Mn^(III) (TDCPP)OAc, TDCPP =meso-tetrakis(2,6-dichlorophenyl) porphyrin, and Mn^(III) (TPNMe₂-TFPP)OAc, TPNMe₂-TFPP =meso-tetrakis(para-NMe₂-tetrafluorophenyl)porphyrin, was carried out in the presence or absence of imidazole. This study showed that, in the absence of imidazole, selectivity for epoxide formation was high with electron-rich catalysts such as Mn(TPP)OAc, Mn(TNP)OAc and Mn(TMP)OAc, but low with electron-deficient catalysts such as Mn(TDCPP)OAc and Mn(TPNMe₂-TFPP)OAc. Presumably, not only the axial ligation of imidazole to the four-coordinate Mn(III)-center, but also the steric and electronic influences of aryl-substituents on the porphyrin periphery affect the selectivity of the catalytic oxidation reaction.     

Metal-proton interactions in palladium(II) and rhodium(I) complexes ofortho-alkylanilines

Summary Reaction of 1 equivalent ofo-alkylaniline with Pd(OAc)₂ gave the acetate bridged complexes [Pd(OAc)₂L]₂. The^*H n.m.r. spectra showed downfield shifts for theo-benzylic protons indicating an above-plane geometry involving a significant interaction with the metal orbitals. Similar interactions were found for Pd(OAc)₂L₂ and Pd(OAc)₂L(L) (L= differento-alkylaniline; t-butylpyridineetc.) prepared from the dimer and for Rh(CO)₂Cl(L) complexes. Theo-benzylic carbons of the palladium complexes did not show downfield shifts in the¹³C n.m.r. spectra.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

Ruthenium(II)-Catalyzed Transfer Hydrogenation of Aromatic and Heteroaromatic Aldehydes in Air

Aromatic and heteroaromatic aldehydes are efficiently reduced to their corresponding alcohols in the presence of [RuCl₂(p-cymene)]₂ and KOAc in 2-propanol under air at 80 °C. The presence of KOAc in the reaction is essential; in its absence no reduction takes place. A highly efficient, external-base-free reduction of aldehydes has also been reported with (η⁶-arene)ruthenium(II) complexes containing O^O chelate ligand such as [Ru(OAc)₂(p-cymene)] and [RuCl(KA)(p-cymene)], obtaining alcohol in excellent yield (OAc, acetate; KA, kojic acetate). The scope of the reaction has been extended to a broad range of aromatic and heteroaromatic aldehydes.     

Autocatalytic Intermolecular versus Intramolecular Deprotonation in C?H Bond Activation of Functionalized Arenes by Ruthenium(II) or Palladium(II) Complexes

The activation of the C? H bond of 1‐phenylpyrazole ( 2 ) and 2‐phenyl‐2‐oxazoline ( 3 ) by [Ru(OAc)₂(p‐cymene)] is an autocatalytic process catalyzed by the co‐product HOAc. The reactions are indeed faster in the presence of acetic acid and water but slower in the presence of a base K₂CO₃. A reactivity order is established in the absence of additives: 2‐phenylpyridine>2‐phenyl‐2‐oxazoline>1‐phenylpyrazole (at RT). The accelerating effect of added acetate ions reveals an intermolecular deprotonation after C? H bond activation by a cationic Ru^II center (S_E3 mechanism). The reactions of 1‐phenylpyrazole and 2‐phenyl‐2‐oxazoline first lead to the neutral cyclometalated complexes A₂ and A₃ ligated by one acetate. The latter dissociate to the cationic complexes B₂ ⁺ and B₃ ⁺ , respectively, and acetate. A slow incorporation of one or two D atoms into 2 , 3 , and 2‐phenylpyridine ( 1 ) was observed in the presence of deuterated acetic acid. The “reversibility” of the C? H bond activation/deprotonation takes place from the cationic complexes B _n ⁺ (n=1–3). They are also involved in oxidative additions to PhI, which are rate‐determining and lead to the mono‐ and bis‐phenylated products at high temperatures. A general mechanism is proposed for the arylation of arenes 1–3 catalyzed by [Ru(OAc)₂(p‐cymene)]. In contrast, the reaction of Pd(OAc)₂ with 2‐phenylpyridine ( 1 ), is much faster: Pd(OAc)₂>[Ru(OAc)₂(p‐cymene)]. Since the kinetics is not affected by added acetates, the reaction proceeds through a CMD mechanism assisted by a ligated acetate (intramolecular process) and is irreversible. A bis‐cyclometalated Pd^II^Pd^II dimer D′₁ is formed whose bielectronic electrochemical oxidation leads to a [Pd^III^Pd^III]²⁺ dimer, in agreement with the result of a reported chemical oxidation used in arene functionalizations catalyzed by Pd(OAc)₂.     

1H, 13C, 15N NMR and IR Spectroscopic Studies of a Rh(II) Complex of Thiourea

A rhodium(II) complex of thiourea (Tu), Rh₂(OAc)₄Tu₂, has been prepared from Rh₂(OAc)₄(H₂O)₂ and characterized. A shift of the ν(N?H) vibration towards higher frequencies in the IR spectrum is consistent with sulfur coordination to rhodium(II). ¹³C NMR spectra recorded in DMSO-d ₆ reveal that thiourea is replaced by DMSO-d ₆ solvent, followed by replacement of acetate ions by free thiourea. ¹⁵N NMR indicates some nitrogen involvement in coordination to form an S?N chelate.     

Oxidation of cis-Diamminediacetato PtII with Hydrogen Peroxide Can Give Rise to Two Isomeric PtIV Products

The oxidation of cis-[Pt(NH₃)₂(OAc)₂] with H₂O₂ yields a mixture of two isomers: ctc-[Pt(NH₃)₂(OH)₂(OAc)₂] and ctc-[Pt(NH₃)₂(OH)(OAc)(OH)(OAc)]. Following modification with 4-phenylbutyric (PhB) anhydride, two isomers were separated and characterized; the symmetric ctc-[Pt(NH₃)₂(PhB)₂(OAc)₂] ( 1 ) and the nonsymmetric ctc-[Pt(NH₃)₂(PhB)(OAc)(PhB)(OAc)] ( 2 ). They differ in their log P values and despite having similar cellular uptake and similar DNA platination levels, the symmetric ctc-[Pt(NH₃)₂(OH)₂(OAc)₂] is more than 4-fold more potent than the nonsymmetric isomer in a panel of 4 cancer cell lines.     

Synthesis and structural characterization of new trinuclear cobalt(II) and nickel(II) complexes possessing five- and six-coordinated geometry

Tri-nuclear cobalt and nickel complexes ([(CoL)₂(OAc)₂Co]?·?THF (I) and [(NiL)₂(OAc)₂(THF)₂Ni]?·?THF (II)) have been synthesized by reaction of a new Salen-type bisoxime chelating ligand of 2,2′-[ethylenedioxybis(nitrilomethylidyne)]dinaphthol(H₂L) with cobalt(II) acetate tetrahydrate or nickel(II) acetate tetrahydrate, respectively. Complexes I and II were characterized by elemental analyses, IR, TG-DTA and ¹H-NMR etc. The X-ray crystal structures of I and II reveal that two acetate ions coordinate to three cobalt or nickel ions through M–O–C–O–M (M?=?Co or Ni) bridges and four μ-naphthoxo oxygen atoms from two [ML] units also coordinate to cobalt(II) or nickel(II). Complex I has two distorted square-pyramidal coordination spheres and an octahedral geometry around Co1. In complex II all three nickel ions are six-coordinate.     

Reaction of coordinated phosphines: VI. Divalent palladium promoted cleavage of carbon—phosphorus bonds in tertiary phosphines

The important role of divalent palladium in the cleavage of carbon—phosphorus bond of tertiary phosphines is revealed by the study of the phenylation in the Pd(OAc)₂Ph₃P-styrene system under various conditions; reaction atmosphere, ratio of Ph₃P/Pd(OAc)₂, and addition of ethanol or Cu^II(OAc)₂ · H₂O.