Photoinitiation of polymerization of styrene by oxotris(dimethyl dithiocarbamato) vanadium(V)

Oxotris(dimethyl dithiocarbamato) vanadium(V) [VO(S₂CN(CH₃)₂)₃] sensitizes the polymerization of styrene when irradiated by light of λ = 365 nm at 25°C. Under the experimental conditions employed, no retardation occurs, and the rate of initiation is independent of monomer concentration. The mean values of the quantum yield of iniiation (?_i) and polymerization (?_o) are 2.85 × 10^?3 and 6.72 respectively. Spectroscopic analysis shows that initiation occurs predominatly through scission of the N,N-dimethyl dithiocarbamate ligand (—SC(S)N(CH₃)₂) with reduction of vanadium(V) to (IV), and VO (S₂CN(CH₃)₂)₂ is the final photolytic product. A reaction mechanism is proposed based on an intramolecular photoredox reaction which leads to the primary formation of SC(S)N(CH₃)₂ radicals and a vanadium(IV) chelate complex. The rellevant kinetic parameters are evaluated. The polystyrene produced shows a photoactivity when irradiated with UV-light.     

Metallkomplexe mit biologisch wichtigen Liganden. CXXIII. Darstellung von Isophthaloyl‐ und Terephthaloyl‐di‐[(β,γ,δ)‐amino‐α‐aminocarboxylat]‐verbrückten zweikernigen Ruthenium‐, Rhodium‐ und Iridium‐Halbsandwich‐Komplexen

The reaction of the Cu(II) bis N,O‐chelate‐complexes of L‐2,4‐diaminobutyric acid, L‐ornithine and L‐lysine {Cu[H₂N–CH(COO)(CH₂)_nNH₃]₂}²⁺(Cl^–)₂ (n = 2–4) with terephthaloyl dichloride or isophthaloyl dichloride gives the polymeric complexes {‐OC–C₆H₄–CO–NH–(CH₂)_n–CH(nh₂)(COO)Cu(OOC)(NH₂)CH–CH₂)_n–NH‐}_x 1 – 5 . From these the metal can be removed by precipitation of Cu(II) with H₂S. The liberated ω,ω′‐N,N′‐diterephthaloyl (or iso‐phthaloyl)‐diaminoacids 6 – 10 react with [Ru(cymene)Cl₂]₂, [Ru(C₆Me₆)Cl₂]₂, [Cp*RhCl₂]₂ or [Cp*IrCl₂]₂ to the ligand bridged bis‐amino acidate complexes [L_n(Cl)M–(OOC)(NH₂)CH–(CH₂)_nNH–CO]₂–C₆H₄ 11 – 14 .     

Thermal decomposition of aluminium hydroxycarboxylates—lactate,citrate and tartrate

The thermal transformation of anhydrous alumina obtained by the decomposition of the lactate, citrate and tartrate of aluminium has been examined by thermal analysis(TGA and DTA), infrared spectrophotometry and X-ray diffraction study. It is found that under an atmosphere of air the thermal decomposition of aluminium hydroxycarboxylates to anhydrous amorphous alumina, which transforms to α-alumina via γ-, δ- and θ-aluminas, proceeds as follows for Al[CH₃CH(OH)COO]₃, the decomposition of skeleton and the combustion of its decomposition products; for Al[CH₂C(OH)CH₂(COO)₃] and Al₂{[CH(OH)COO]₂}₃, dehydroxylation, decomposition of skeleton and the combustion of its decomposition products.     

Co-polymerization of propylene oxide and CO2 using early transition metal (groups IV and V) metallocalix[n]arenes (n = 4, 6, 8)

A number of metallocalix[n]arenes, where n = 4, 6, or 8, of titanium and vanadium have been screened for their ability to act as catalysts for the co-polymerization of propylene oxide and CO₂ to form cyclic/polycarbonates. The vanadium-containing catalysts, namely [VO(L¹Me)] (1), [(VO₂)L²H₆] (2), [Na(NCMe)₆]₂[(Na[VO]₄L²)(Na(NCMe))₃]₂ (3), [VO(μ-OH)L^3/H₂]₂∙6CH₂Cl₂ (4), {[VO]₂(μ-O)L⁴[Na(NCMe)₂]₂} (5), {[V(Np-tolyl)]₂L⁴} (6) and [V(Np-RC₆H₄)Cl₃] (R = Cl (7), OMe (8), CF₃ (9)), where L¹H₃ = methylether-p-tert-butylcalix[4]areneH₃, L²H₈ = p-tert-butylcalix[8]areneH₈, L³H₄ = p-tert-butylthiacalix[4]areneH₄, L⁴H₆ = p-tert-butyltetrahomodioxacalix[6]areneH₆, performed poorly, affording, in the majority of cases, TONs less than 1 at 90°C over 6 h and low molecular weight oligomeric products (M_n ≤ 1665). In the case of the titanocalix[8]arenes, {(TiX)₂[TiX(NCMe)]₂(μ₃-O)₂(L²)} (X = Cl (10), Br (11), I (12)), which all adopt a similar, ladder-type structure, the activity under the same conditions is somewhat higher (TONs >6) and follows the trend Cl > Br > I; by comparison the non-calixarene species [TiCl₄(THF)₂] was virtually inactive. In the case of 10, it was observed that the use of PPNCl (bis[triphenylphosphine]iminium chloride) as co-catalyst significantly improved both the polymer yield and molecular weight (M_n 3515). The molecular structures of the complexes [HNEt₃]₂[VO(μ-O)L³H₂]₂∙3CH₂Cl₂ (4∙3CH₂Cl₂), [VO(μ-OH)L^3/H₂]₂∙6CH₂Cl₂ (4^/) (where L^3/H₂ is a partially oxidized form of L³H₄) and {(TiCl)₂[TiCl(NCMe)]₂(μ₃-O)₂(L²)}·6.5MeCN (10·6.5MeCN) are reported.     

Synthesis,characterization and catalytic activity of a new sandwich-type tungstophosphate functionalized by carboxyethyltin

Reaction of the trivacant Keggin-type tungstophosphate (A-α-Na₉PW₉O₃₄⋅ 7H₂O, abbreviated as {PW₉}) with estertin (Cl₃Sn(CH₂)₂COOCH₃) in an acetate buffer solution leads to the formation of a new sandwich-type tungstophosphate functionalized by carboxyethyltin, Na₃K₈[K₃{Sn(CH₂)₂COO}₂(A-α-PW₉O₃₄)₂]·18H₂O (1). The title compound was characterized by single crystal X-ray diffraction, elemental analysis, IR, TG, PXRD, ¹³C, ³¹P and ¹¹⁹Sn NMR. Structural analysis reveals that the basic skeletal structure of 1 is made up of two [Sn(CH₂)₂COO]^2 + groups and three K⁺ ions sandwiched by two A-α-[PW₉O₃₄]^9 − building blocks, which shows the original estertin precursors hydrolyzed into carboxyethyltin. The catalytic activity of 1 has been investigated.     

Electrochemical characterization of self-assembly process of nano-scaled polyoxomolybdate (NH4)42[Mo72Mo60O372(CH3COO)30(H2O)72]·ca.300H2O

Cyclic voltammetry and electrochemical admittance were used to characterize the self-assembly process of nano-scaled spheres of polyoxomolybdate (NH₄)₄₂[Mo^VI₇₂Mo^V₆₀O₃₇₂(CH₃COO)₃₀(H₂O)₇₂]·ca.300H₂O·ca.10CH₃COONH₄) or {Mo₁₃₂}. Cyclic voltammetry indicated that the self-assembly process could be detected after 8 h and completed after one day. Electrochemical admittance showed that the molybdenum species in the CH₃COONH₄-CH₃COOH buffer (pH 4.46) were totally different from those in the pure (NH₄)₆Mo₇O₂₄ solution (pH 5.54) and the (NH₄)₆Mo₇O₂₄ solution (pH 4.21) acidified by hydrochloric acid. However, the molybdate species in the latter two solutions should be mixtures of non-protonated and/or protonated [Mo₇O₂₄]⁶⁻ and [Mo₈O₂₆]⁴⁻ anions. Detailed analysis of admittance results could support the existence of the molybdate species related to the {Mo^VI₆} fragment which was one of the components of {Mo₁₃₂} clusters. Admittance results on the self-assembly process were coincident with those from cyclic voltammetry.     

Novel Scorpionate and Pyrazole Dioxovanadium Complexes,Catalysts for Carboxylation and Peroxidative Oxidation of Alkanes

The dioxovanadium(V) complexes [VO₂(3,5‐Me₂Hpz)₃][BF₄] ( 1 ) (pz=pyrazolyl), [VO₂{SO₃C(pz)₃}] ( 2 ), [VO₂{HB(3,5‐Me₂pz)₃}] ( 3 ) and [VO₂{HC(pz)₃}][BF₄] ( 4 ), bearing pyrazole or scorpionate ligands, were obtained by reaction of triethyl vanadate [VO(OEt)₃] with hydrotris(3,5‐dimethyl‐1‐pyrazolyl)methane [HC(3,5‐Me₂pz)₃] or 3,5‐dimethylpyrazole (3,5‐Me₂Hpz; 1 ), lithium tris(1‐pyrazolyl)methanesulfonate {Li[SO₃C(pz)₃], 2 }, potassium hydrotris(3,5‐dimethyl‐1‐pyrazolyl)borate {K[HB(3,5‐Me₂pz)₃], 3 } and hydrotris(1‐pyrazolyl)methane [HC(pz)₃, 4 ], respectively. Treatment of [VO(OEt)₃] with potassium hydrotris(1‐pyrazolyl)borate {K[HB(pz)₃]} led to the mixed η³‐tris(pyrazolyl)borate and η²‐bis(pyrazolyl)borate oxovanadium(IV) complex [VO{HB(pz)₃}{H₂B(pz)₂}, 5 ]. The compounds were characterized by elemental analyses, IR, NMR and EPR spectroscopy, FAB and ESI mass spectrometry, cyclic voltammetry and, for 5 , also by single crystal X‐ray diffraction analysis. All complexes exhibit catalytic activity in the single‐pot carboxylation [in trifluoroacetic acid/potassium peroxodisulfate (CF₃COOH/K₂S₂O₈)] of gaseous alkanes (methane and ethane) to carboxylic acids (yields up to 40%, TONs up to 157) and in the peroxidative oxidation [in water/acetonitrile (H₂O/NCMe)] of liquid alkanes (cyclohexane and cyclopentane) to the corresponding alcohols and ketones (yields up to 24%, TONs up to 117), under mild conditions.     

Synthesis and structure of K2[HMo6VIVVO22(NH3CH2COO)3]·8H2O: a new example of a polyoxomolybdovanadate coordinated by a glycinato ligand

A new complex of formula K₂[HMo₆^VIV^VO₂₂(NH₃CH₂COO)₃]·8H₂O has been prepared from molybdenum(VI) oxide and vanadium(V) oxide in aqueous solution by adding glycine and potassium chloride, and its structure determined by X-ray structure analysis. The molybdovanadate anion is built up of six MoO₆ edge-sharing octahedra connected into a ring centered by a VO₄ tetrahedron. The MoO₆ octahedra are in pairs linked by the bridging glycine-carboxylato ligands.     

A tetranuclear oxofluorovanadium(IV) cluster encapsulating a Na(H2O)n+ subunit

Hydrothermal reactions of sodium vanadate, methylenediphosphonic acid, hydrogen fluoride and the appropriate organoamine yielded the vanadium(IV)-oxyfluoride compounds [NH₃(CH₂)₂(NH₂)(CH₂)₂NH₃]₃[{Na(H₂O)} ⊂ {V₄O₄F₂(O₃PCH₂PO₃)₄}]·8H₂O (1·8H₂O) and [NH₃(CH₂)₂(NH₂)(CH₂)₂(NH₂)(CH₂)NH₃]₂[{Na(H₂O)} ⊂ {V₄HO₄F₂(O₃PCH₂PO₃)₄}]·7H₂O (2·7H₂O). The vanadium-oxyfluoride cationic unit {V₄O₄F₂(O₃PCH₂PO₃)₄}^10 − of the compounds consists of pairs of fluoride bridged {VFO₅} octahedra linked through η⁴-diphosphonate ligands into a three polyhedra thick band. The {Na(H₂O)_n}⁺ groups occupy the interior of the band but are displaced from the centroid toward one face so as to project the aqua ligands into the extra-annular domain. The fluoride ligands bridge two vanadium sites as well as coordinating to the sodium cation.     

Polymer Complexes. XLIII. EPR, Spectra, and Stereochemical Versatility of Novel Copper(II)Polymer Complexes

Copper(II) polymer complexes of empirical formula [Cu(ligand)₂X₂] (where X = Cl, Br, I, NO₃, and SO₄) and [Cu(ligand)(CH₃COO)₂] have been prepared with poly(3-phenylacrylidine semicarbazone). All the polymer complexes prepared have been characterized by elemental analysis, magnetic moment, conductance, IR, electronic, ¹H-NMR, and electronic paramagnetic resonance spectral studies. The polymer complexes [Cu(ligand)₂X₂] and [Cu(ligand) (CH₃COO)₂] may have tetragonal symmetry while the [Cu(ligand)₂( SO₄)₂] may be five-coordinate trigonal bipyramidal in structure. All complexes exhibit normal magnetic moments corresponding to one unpaired electron except [Cu(ligand)(CH₃COO)₂] which shows a subnormal magnetic moment. EPR spectra of the polymer complexes have been studied with a view to assigning their stereochemistries. Various EPR parameters have been calculated. The g, A, G values for all the polymer complexes are consistent with a tetragonal 1–5 and trigonal bipyramidal 6 stereochemistry in the Cu(II) polymer complexes of homopolymer.     

Synthesis and characterization of soluble polyphosphazenes having pendent Cp* Fe(dppe) groups

Summary The reaction of HOC₆H₄CH₂CN , N₃P₃(O₂C₁₂H₈)₂(OC₆H₄CH₂CN)₂ and – [{NP(O₂C₁₂H₈)}_0.8 {NP (OC₆H₄CH₂CN)₂}_0.18 ]_n with Cp*Fe(dppe)I in dichloromethane solution and in the presence of TIPF₆ affords the new compounds [Cp*Fe(dppe)NCCH₂C₆H₄OH][PF₆]1 Cp* = C₅(CH₃)₅ [{N₃P₃ (O₂C₁₂H₈)₂(OC₆H₄CH₂CN•Cp*Fe(dppe))₂] [PF₆]₂ 2 and the copolymer [{NP{(O₂C₁₂H₈}_0.8 {NP(OC₆H₄CH₂CN•[Cp*Fe(dppe)][PF₆])₂}_O.8]_n 3 respectively. The σ coordination of the Cp*Fe(dppe) fragment toward the nitrile group is indicated by spectroscopic data. The copolymer 3 is soluble in several organic solvents with no significant cross-linking and has a Mw on the order of 1.260.000. Thermal effects of the incorporation of the organometallic fragment to the copolymer were investigated using differential scanning calorimetry (DSC) and therrnogravimetric analysis (TGA). Received: 7 May 2002/Revised version: 21 March 2003/ Accepted: 27 March 2003 Correspondence to C. Diaz     

3D supramolecular open-framework constructed by inorganic [B5O6(OH)4]− and organic [CH3COO]− anions

A borate compound [Ni(en)₃][B₅O₆(OH)₄][CH₃COO] (1) has been synthesized under mild hydrothermal conditions. The newly synthesized compound was characterized by single-crystal X-ray diffraction, elemental analysis and thermogravimetry. The three-dimensional (3D) supramolecular open-framework of compound 1 is constructed by inorganic [B₅O₆(OH)₄]⁻ building units and organic [CH₃COO]⁻ anions through hydrogen bonds, and the charge-balancing [Ni(en)₃]^2 + cations are located in 3D channels. It is very interesting that there exist two helical chains formed by [B₅O₆(OH)₄]⁻ building units and organic [CH₃COO]⁻ anions through hydrogen bonds in compound 1 along different axes. Magnetic measurement indicates that compound 1 exhibits paramagnetic behavior down to 4 K.     

Two novel isomeric complexes supported by vanadates {V4O12}: [{Cu(dpa)2}2V4O12] (dpa = 2,2′-dipyridylamine)

Two Cu(II) complexes supported by tetravanadates, [{Cu(dpa)₂}₂V₄O₁₂] (1 and 2), have been synthesized under hydrothermal reactions. Structural analysis indicates that complexes 1 and 2 are isomeric and consist of a cyclic [V₄O₁₂]^4- anion bridged to two [Cu(dpa)₂]²⁺ moieties. Close inspection of complexes 1 and 2 reveals that the [V₄O₁₂]^4- anions adopt chair-like and boat-like configurations respectively, and are coordinated to each Cu(II) ions through a single terminal oxygen atom of two cross vanadium sites. Moreover, Complexes 1 and 2 exhibit trans- and cis-configurations, respectively.     

A new polyoxoniobate with NbIVO8 center and Cu24 core

A new polyoxoniobate with Nb^IVO₈ center and Cu₂₄ core K₁₂Na[H₂₃Nb^IVO₈Cu₂₄(Nb₇O₂₂)₈]·81H₂O (1) has been synthesized by the reaction of K₇HNb₆O₁₉·13H₂O with Cu(CH₃COO)₂·H₂O in the presence of Nb^IVO₂, and characterized by elemental analyses, IR spectrum, TG analysis, magnetic property and single-crystal X-ray diffraction. The structure analysis reveals that the polyoxoanion is composed of one Nb^IVO₈ cube-like unit, 24 copper centers and eight [Nb₇O₂₂]^9? fragments. The magnetic investigation shows that compound 1 exhibits antiferromagnetic interactions.     

Metallopolymer Films Exhibiting Three-Color Electrochromism in the UV/Vis and Near-IR Region: Remarkable Utility of Trimetallic Clusters Bearing Thienyl Pendants and Their Mixed-Valent Charge Transfer Transitions

Novel oxo-centered, acetate-bridged trinuclear ruthenium clusters functionalized with two pyridine ligands with thienyl substituents, [Ru₃O(CH₃COO)₆(CO)(L1)₂] (1) and [Ru₃O(CH₃COO)₆(CO)(L2)₂] (2), where L1 = 4-(2-thienyl)pyridine and L2 = 4-(2,2′-bithienyl)pyridine, have been synthesized and characterized. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. One-electron oxidation of 2 with silver(I) cation has led to the isolation of a CO-dissociated product, [Ru₃O(CH₃COO)₆(H₂O)(L2)₂]PF₆ (3·PF ₆ ), and subsequent reaction with 4-dimethylaminopyridine (dmap) gave [Ru₃O(CH₃COO)₆(dmap)(L2)₂]PF₆ (4·PF ₆ ). Linear metallopolymers containing the {Ru₃O(CH₃COO)₆} groups have been deposited onto indium-tin oxide surface via oxidative electropolymerization of 2, 3·PF ₆ , and 4·PF ₆ . These metallopolymer thin films exhibit three-color electrochromism in the UV/Vis and near-IR region associated with the Ru₃ ^II,III,III, Ru₃ ^III,III,III, and Ru₃ ^III,III,IV oxidation states.     

A Decade of Oxothiomolybdenum Wheels: Synthesis,Behavior in Solution,and Electrocatalytic Properties

The last decade has see the development of sulfur-containing polyoxometalates (POTMs) as a subclass of the polyoxometalate family. The structural and physico-chemical properties of this emerging class of compounds is dominating by the striking coordination properties of the [Mo₂O₂S₂(OH₂)₆]²⁺ oxothio cation, used as a building block. The cyclic topology of this arrangement corresponds to the main feature of the {Mo₂O₂S₂}-based compounds, able to develop cycle-based chemistry. The control of the linear oligomerization of the {Mo₂O₂S₂} core is achieved by the presence of the anionic component, which acts as a template. Here, we report on recent examples which illustrate how the use of various template ions such as halide, sulfate, polyphosphate, and polycarboxylate anions allows to tune the nuclearity of the inorganic host from {Mo₈} to {Mo₁₈}. A special focus on behavior in solution is given, highlighting the dynamic and fluxional character of these host–guest systems. The Diffusion Ordered Spectroscopy (DOSY) ¹H NMR, carried out on a large series of cycle-based and capsule-like compounds, demonstrates that such a method can be applied for the speciation of POM anions in solution. Finally, electrocatalytic behavior of the {Mo₂O₂S₂}-based compounds is presented. Preliminary results show that the electrocatalytic reduction of protons into hydrogen (HER) could constitute one of the most relevant applications for this class of molecular compounds.     

Polymerizable inorganic–organic hybrid: Syntheses and structures of mono-lacunary Dawson polyoxometalate-based olefin-containing organosilyl derivatives

Three olefin-containing organosilyl derivatives supported on the mono-lacunary Dawson polyoxometalate (POM), [α₂-P₂W₁₇O₆₁{(RSi)₂O}]⁶⁻ (R = {CH₂C(CH₃)COO(CH₂)₃}, {CH₂CHCOO(CH₂)₃} and {CH₂CH}), as Me₂NH₂ salts, which can act as precursors for the immobilization of the POMs in polymer networks, were obtained by the 2:1 molar ratio reaction of the organosilyl precursor RSi(OCH₃)₃ with K₁₀[α₂-P₂W₁₇O₆₁] · 19H₂O in acidic MeOH/H₂O mixed solutions. X-ray crystallography revealed that the two organic chains connected through an –Si–O–Si– bond were grafted onto the mono-lacunary site of the POM. The four-coordination of each Si atom was attained with the bridging oxygen atom, the terminal organic group R in the organosilyl group, and 2 of the 4 oxygen atoms in the mono-lacunary site of the POM.     

Effect of subcritical CO2 on the structural and electrical properties of ORMOCERS-APE systems based on Zr and Al

Two series of hybrid inorganic-organic polymer electrolytes of the organically modified ceramics as polymer electrolytes (ORMOCERS-APE) type with formulas {Al[O(CH₂CH₂O)_8.7]_ρ/(LiClO₄)_z}_n (1.85 ≤ ρ ≤ 2.24, 0 ≤ z ≤ 1.06) and {Zr[O(CH₂CH₂O)_8.7]_ρ/(LiClO₄)_z}_n (1.80 ≤ ρ ≤ 1.99, 0 ≤ z ≤ 0.90) were treated with CO₂ in subcritical conditions (293 K and 5 MPa). The effect of CO₂ on the samples was investigated by using ESEM, thermal analysis (TG and DSC) and broad band dielectric spectroscopy (BDS).Both complexes {Al[O(CH₂CH₂O)_8.7]_ρ/(LiClO₄)_z}_n and {Zr[O(CH₂CH₂O)_8.7]_ρ/(LiClO₄)_z}_n after CO₂ treatment exhibited a change in the segmental relaxation with respect to the untreated samples. This phenomenon has been interpreted in terms of higher portion of free volume in the samples. The CO₂ treatment primarily lowered the conductivity of {Al[O(CH₂CH₂O)_8.7]_ρ/(LiClO₄)_z}_n complexes of about one order of magnitude, as opposed to {Zr[O(CH₂CH₂O)_8.7]_ρ/(LiClO₄)_z}_n complexes, where an increment of two orders of magnitude was observed. In both cases the conductivity of the treated and untreated materials versus the reciprocal absolute temperature presents the typical Vogel-Tamman-Fulcher (VTF) behavior. The different effects on the conductivities of the treated complexes are explained in terms of the modified anion-trapping ability of Al centers and in terms of the interactions of subcritical CO₂ with the host polymer and the salt. Insight about the conductivity mechanisms were provided by the study of the VTF parameters and the relaxation times determined from the Debye peaks of the imaginary resistivity, the imaginary permittivity and the correlated motion analysis.     

Single‐Pot Ethane Carboxylation Catalyzed by New Oxorhenium(V) Complexes with N,O Ligands

The oxorhenium(V) chelates [ReOCl(N,O‐L)(PPh₃)] [N,O‐L=(OCH₂CH₂)N(CH₂CH₂OH)(CH₂COO) ( 2 ), (OCH₂CH₂)N(CH₂COO)(CH₂COOCH₃) ( 3 )] and [ReOCl₂(N,O‐L)(PPh₃)] [N,O‐L=C₅H₄N(COO‐2) ( 4 ) C₅H₃N(COOCH₃‐2)(COO‐6) ( 5 )] have been prepared by reaction of [ReOCl₃(PPh₃)₂] ( 1 ), in refluxing methanol, with N,N‐bis(2‐hydroxyethyl)glycine [bicine; N(CH₂CH₂OH)₂(CH₂COOH)], N‐(2‐hydroxyethyl)iminodiacetic acid [N(CH₂CH₂OH)(CH₂COOH)₂], picolinic acid [NC₅H₄(COOH‐2)] or 2,6‐pyridinedicarboxylic acid [NC₅H₃(COOH‐2,6)₂], respectively, with ligand esterification in the cases of 3 and 5 . All these complexes have been characterized by IR and multinuclear NMR spectroscopy, FAB⁺‐MS, elemental and X‐ray diffraction structural analyses. They act as catalysts, in a single‐pot process, for the carboxylation of ethane by CO, in the presence of potassium peroxodisulfate K₂S₂O₈, in trifluoroacetic acid (TFA), to give propionic and acetic acids, in a remarkable yield (up to ca. 30%) and under relatively mild conditions, with some advantages over the industrial processes. The picolinate complex 4 provides the most active catalyst and the carboxylation also occurs, although much less efficiently, by the TFA solvent in the absence of CO. The selectivity can be controlled by the ethane and CO pressures, propionic acid being the dominant product for pressures about ca. 7 and 4 atm, respectively (catalyst 4 ), whereas lower pressures lead mainly to acetic acid in lower yields. These reactions constitute an unprecedented use of Re complexes as catalysts in alkane functionalization.     

Extraction of iridium(III) by ion-pair formation with 2-octylaminopyridine in weak organic acid media

To extract iridium(III), various physicochemical parameters were studied. 2-Octylaminopyridine was used for the extraction of iridium(III) from acetate medium at 8.5 pH. Quantitative extraction of iridium(III) was achieved via ion-pair formation of cation [2-OAPH⁺] and anion [Ir(CH₃COO)₄]^?. The stripping of iridium(III)-laden organic phase was carried out 2 M HCl (3 × 10 mL) . The stoichiometry of the extracted ion–pair complex was found to be 1:4:1 (metal: acetate: extractant). The extracted species [2-OAPH⁺. Ir(CH₃COO)₄^?] is assumed to be an ion association product of [Ir(CH₃COO)₄] ^? and [2-OAPH]⁺. The proposed method was successfully used in the separation of iridium(III) from binary and ternary mixtures. Analysis of various alloy samples was also carried out.