Rhodium amino complexes [Rh(COD)(Amine)2]PF6 immobilized on poly(4-vinylpyridine) as catalysts in the water gas shift reaction

Catalysts for the water gas shift reaction prepared from Rh(COD)(amine)₂ PF₆ (COD=1,5-cyclooctadiene, amine=4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) immobilized on poly(4-vinylpyridine) in contact with 80% aqueoux 2-ethoxyethanol for 1×10⁻⁴ mol Rh/0.5 g of polymer, P(CO)=0.9 atm at 100 °C, are described. The role of the coordinated amine effect on the catalytic activity was investigated.     

Homogeneous Catalysis of the Water Gas Shift Reaction by Bridged Dinuclear Pyrazolate Rhodium Complexes. FT-IR, 1H and 13C NMR In Situ Studies

Homogeneous catalysts for the water gas shift reaction prepared from Rh₂(-Pz)₂(COD)₂ (Pz = pyrazolate ion and COD = 1,5-cyclooctadiene) in aqueous organic solvent media (pyridine, 4-picoline or 2-ethoxyethanol) and Rh₂(-Pz)₂(CO)₂(TPPMS)₂ (TPPMS = meta-sulfonatophenyl-diphenyldiphosphine) in acidic aqueous media under mild conditions are described. In situ FT-IR, ¹H and ¹³C NMR spectroscopic studies of the Rh₂(-Pz)₂(COD)₂ catalytic system reveal the presence of hydrido-Rh complexes with linear and bridging carbonyls. These complexes also catalyze the reduction of nitrobenzene to aniline.     

Hydroxycarbonylation of 1-hexene catalyzed by [Rh(COD)(amine)2](PF6) complexes immobilized on poly(4-vinylpyridine)

Summary Rhodium(I) complexes, [Rh(COD)(amine)₂](PF₆) (COD = 1,5-cyclooctadiene, amine = 4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) immobilized on poly(4-vinylpyridine) in contact with water catalyzed both the hydroxycarbonylation of 1-hexene to propionic acid and the water-gas shift reaction (WGSR). The role of the coordinated amine on the catalytic activity was examined.     

Mechanism of the hydroxycarbonylation of 1-hexene catalyzed by immobilized rhodium complexes of pyridine ligands

Summary In this work, a mechanistic study of the hydroxycarbonylation of 1-hexene to heptanoic acid and the water gas shift reaction (WGSR) catalyzed by the rhodium(I) complexes, [Rh(COD)(amine)₂](PF₆) (COD = 1,5-cyclooctadiene, amine = 4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) immobilized on poly(4-vinylpyridine) in contact with water under CO is discussed. Catalytic cycles for these reactions bearing common Rh-H catalytic species are proposed.     

Hydroformylation of 1-Hexene Catalyzed by [Rh(COD)(2-Picoline)2]PF6 Immobilized on Poly(4-Vinylpyridine) Under Water Gas Shift Reaction Conditions

Reported here is the influence of the reaction conditions variation (1-hexene/rhodium content (S/C) = 16 - 105, temperature (T) = 70 - 110 °C and carbon monoxide pressure (P(CO)) = 0.6 - 1.8 atm) on the catalytic hydroformylation of 1-hexene to aldehydes (heptanal and 2-methyl-hexanal) by the rhodium(I) complex, [Rh(COD)(2-picoline)₂]PF₆ (COD = 1,5-cyclooctadiene)immobilized on poly(4-vinylpyridine) in contact with 10 mL of 80% aqueous 2-ethoxyethanol, under water gas shift reaction condition. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pentacoordinated iridium(I) complexes incorporating azopyridine chelation. Synthesis,structure and bonding

The reaction of [Ir(COD)Cl]₂ with 2-(arylazo)pyridine (L) in dichloromethane solution has afforded the nonelectrolytic pentacoordinated species of type Ir(L)(COD)(Cl) from which the corresponding bromides and iodides have been synthesised by metathesis (COD=1,5-cyclooctadiene). L ligands used are: 2-(phenylazo)pyridine (L¹); 2-(m-tolylazo)pyridine (L²) and 2-(p-chlorophenylazo)pyridine (L³). The X-ray structures of Ir(L²)(COD)(Cl)·0.5 CH₂Cl₂ and Ir(L³)(COD)(I) have been determined revealing square-pyramidal geometry. The relatively short IrN(azo) lengths (∼2.00 Å) and the relatively long NN bond distance (∼1.30 Å) are consistent with significant dππ* (azo) back-bonding. The HOMO (50% Ir and 15% azo character) and LUMO (50% azo and 30% Ir character) are primarily localised in the IrL fragment and the absorption bands near 600 nm is assigned tentatively to the HOMO→LUMO transition. The stability of the pentacoordinated structures and the inertness to oxidative addition of the present complexes in contrast to the behaviour of corresponding 2,2′-bipyridine species (tetracoordinated, reactive) is rationalised in terms of π-acidity order L≫bpy.     

Mixed-ligand complexes of tris(acetylacetonato)iridium(III) with <Emphasis Type="Italic">N</Emphasis>-heterocyclic ligands: synthesis and crystal structure

A series of mixed-ligand complexes of tris(acetylacetonato) iridium(III) with N-heterocyclic ligands, namely [bis(acac-O,O′)(acac-C³)Ir(L)], where acac = acetyacetonato; L = 2-picoline (1), 3-picoline (2), 4-picoline (3), have been synthesized via the reaction of [bis(acac-O,O′) (acac-C³)Ir(H₂O)] with the corresponding ligand, respectively. Molecular structures of all complexes were determined by using single-crystal X-ray diffraction. The results reveal that these complexes have slightly distorted octahedral coordination geometries.     

Addition Compounds of Organotin Halides. V. Adducts of phenyl tin Trichloride with amines

Complexes of phenyl tin trichloride with bases as pyridine, β-picoline, γ-picoline, isoquinoline, piperidine, morpholine, aniline and benzylamine have been prepared. Their infrared spectra have been studied in the region 4000–250 cm^?1 and molar conductance measurements carried out in nitrobenzene solutions.     

Gossypol clathrates: Structure and thermal behavior of gossypol solvates with two picoline isomers

Gossypol forms stable solvates with 4- and 2-picolines at room temperature. The solvates are investigated by single crystal X-ray diffraction and thermal analysis. Solvate crystals of gossypol with 4-picoline (1) have the 1:3 composition (gossypol:4-picoline) and crystallize in the P2₁/c space group. This substance is isostructural to a trisolvate of gossypol with pyridine. Solvate crystals of gossypol with 2-picoline (2) have the 1:4 composition (gossypol:2-picoline) and crystallize in the P-1 space group. The unit cell parameters for the investigated structures are as follows: 1 monoclinic crystals, C₃₀H₃₀O₈·3C₆H₇N, a = 10.7530(1) ?, b = 20.7834(3) ?, c = 19.1166(2) ?, β = 95.537(1)°, V = 4252.32(9) ?³, M = 797.92, Z = 4, d _x = 1.246 g/cm³, and R = 0.0489 for 4102 reflections; 2 triclinic crystals, C₃₀H₃₀O₈·4C₆H₇N, a = 11.467(1) ? b = 14.962(2) ?, c = 15.570(3) ?, α = 75.62(1)°, β = 69.83(1)°, γ = 79.58(1)°, V = 2414.6(7) ?³, M = 891.04, Z = 2, d _x = 1.226 g/cm³, and R = 0.0528 for 3779 reflections. The results of the single crystal XRD and thermal analysis confirm that gossypol with 4-picoline forms a trisolvat, and a tetrasolvate with 2-picoline. The transition from 4-picoline to 2-picoline proves to change the type of the host-guest association from one-dimensional to zero-dimensional, i.e., to lead to a new crystal structure. Desolvation of compound 2 begins at a lower temperature than that for compound 1, which is explained by their different crystal structures. Keywords: gossypol, 4-picoline, 2-picoline, clathrate formation, crystal structure.     

Catalysis of the water gas shift reaction by cis -[Rh(CO)2(AMINE)2](PF6) complexes in an aqueous tetrabutylammonium hydrogensulfate solution

Rhodium(I) complexes, cis-[Rh(CO)₂(amine)₂](PF₆) (amine = 4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) dissolved in an aqueous solution of tetrabutylammonium hydrogensulfate (N(C₄H₉)₄HSO₄), catalyze the water-gas shift reaction (WGSR). The role of the coordinated amine on the catalytic activity was examined.     

Thermodynamics of coordination of pyridine and its substituted derivatives to osmium tetroxide

Complexation of osmium tetroxide (OsO₄) with pyridine and its substituted derivatives (i.e. 4-picoline, 3 -picoline, 4-tertbutylpyridine, methyl nicotinate, 3,4-dimethylpyridine, 3-chloropyridine, and 3-phenylpyridine) has been studied at different temperatures in benzene. Spectrophotometric measurements have been carried out to obtain the equilibrium constants and thermodynamic parameters. The equilibrium constants of the resulting 1:1 complexes are found to vary in the order 3,4-Me₂Py > 4-^tBuPy > 4-MePy > 3-MePy > Py > 3- PhPy > 3-C(O)OMePy ≈ 3-ClPy. All complexes are enthalpy stabilized whereas the entropy changes counteract the complexation. The results are discussed in terms of different basicities of the substituted pyridines.     

NMR and theoretical study on the interaction between diperoxovanadate and 3-picoline derivatives

To understand the substituent effects of 3-picoline derivatives on reaction equilibrium, the interactions between a series of 3-picoline-like ligands and [OV(O₂)₂(D₂O)]^?/[OV(O₂)₂(HOD)]^? in solution were explored by multinuclear (¹H, ¹³C, and ⁵¹V) magnetic resonance, COSY, and HSQC in 0.15 mol L^?1 NaCl ionic medium for mimicking physiological conditions. The relative reactivity among the 3-picoline derivatives is 3-methyl pyridine > nicotinate >nicotinamide > ethyl nicotinate. Competitive coordination results in the formation of a series of new six-coordinated peroxovanadate species [OV(O₂)₂L] ^{n ?} (L = 3-picoline derivatives, n = 1 or 2). Density functional calculations provide a reasonable explanation on the relative reactivity of the 3-picoline derivatives. Solvation effects play an important role in these reactions.     

Reduction of nitrobenzene to aniline with carbon monoxide and water

Modified catalytic system composed of selenium and cocatalysts such as pyridine and aniline, applied in the reduction of nitrobenzene to aniline in the presence of carbon monoxide and water is described. The reaction proceeds at 150–200°C and 3–4 MPa gauge pressure. After 1–2 h the reaction is complete, reaching nitrobenzene conversions of up to 98% with selectivity to aniline near 100%.     

Hydrogen transfer hydrogenation of nitrobenzene to aniline with Ru(acac)3 as the catalyst

Tris(acetylacetonato)ruthenium(III)(Ru(acac)₃) was synthesized with RuCl₃·nH₂O and acetylacetone as raw materials. The structure of Ru(acac)₃ was identified by FI-IR, ¹H NMR, ¹³C NMR, and elemental analysis. It was used in the catalytic hydrogen transfer hydrogenation of nitrobenzene with sodium formate as hydrogen donor. The effects of reaction conditions on the process, such as temperature, time, dosage of catalyst, and kinds of hydrogen donor, were investigated. The optimal reaction parameters were determined as follows: 80 °C, 4.0 h, the substrate nitrobenzene 20 mL, sodium formate 27.20 g, Ru(acac)₃ 0.96 g, the conversion of nitrobenzene is 100.0 %, the yield of aniline and the selectivity to aniline are 96.65 %. The reaction mechanism is proposed and analyzed. It exhibited excellent catalytic properties in the hydrogen transfer hydrogenation of nitrobenzene to aniline.     

Synthesis of new mixed ligand complexes of copper(II) dithiocarbamates

New mixed ligand complexes of copper(II) dithiocarbamates of the general formula, [CuCl(R₂dtc)L] or [CuCi(R′ dtc)L] (RCH₃ or C₂H₅, R′ = (CH₂)₅, dtc =-NCSS^? and L = Pyridine, 3-picoline or 4-picoline), have been prepared by the reaction of bis(dithiocarbamato)di-μ-chloro-dicopper(II) complexes with pyridine or picolines. The complexes are found to be non-electrolytes in nitrobenzene. Magnetic susceptibilities, i.r. and electronic spectra of the complexes are reported. A psuedo-tetrahedral structure is suggested for these complexes.     

Synthesis and structural characterization of mixed ligand complexes of nickel(II) with 1-cyano-1-carboethoxyethylene-2,2-dithiolate and some nitrogen donors

Mixed ligand complexes of Ni^II ion with 1-cyano-1-carboethoxyethylene-2,2-dithiolate (CED²⁻[S₂C = C (CN)(COOC₂H₅)]²⁻) as a primary ligand and o-phenylenediamine (OPD), pyridine (py), α-picoline (α-pic), β-picoline (β-pic) or γ-picoline (γ-pic) as secondary ligands have been isolated and characterized on the basis of analytical data, molar conductance, magnetic susceptibility, electronic and infrared spectral studies. The molar conductance data reveal that the complexes have 1:1 electrolytic nature in DMF solution. Magnetic and electronic spectral studies suggest distorted octahedral stereochemistry around Ni^II ion in its complexes. Infrared spectral studies suggest bidentate chelating behaviour of CED²⁻ ion and OPD while other ligands show unidentate behaviour in their complexes.     

Complexes of divalent ions in mixed solvent media. III. Outer-sphere interactions in amine + diluent solutions

The standard enthalpies and (in part) free energies and entropies of transfer from amine (L) to amine + diluent (D) mixtures have been determined for MX₂L₂ complexes at 25°C using chloroform, 1,1,2,2,-tetrachloroethane (TCE), benzene, chlorobenzene, and ethyl acetate as diluents (M=Co and Zn; X=Cl and Br; L = pyridine, -picoline, and -picoline). Thermodynamic functions of transfer indicate specific outer-sphere interactions of the complexes with amine and protic diluents (chloroform and TCE) and reveal solvent-solvent interactions of amine + protic diluent mixtures. The effects of the nature of X, L, and M of the MX₂L₂ complexes on their interaction with the components of the mixed solvent are discussed.Deceased.     

Kinetic studies on the nucleophilic activation of carbon monoxide in [Ru(NH3)5CO](PF6)2

CO activation in the [Ru(NH₃)₅CO]²⁺ ion has been demonstrated under nucleophilic conditions in pyridine or 2-ethoxyethanol solution at 100 °C. In the presence of Me₃NO the observed pseudo-first order rate constants were found to be sensitive only to auxiliary ligand concentration (pyridine or methyl pyridines), but with a tendency towards rate saturation and the same limiting rate at large excess of each entering ligand. A mechanism is proposed in which the rate-limiting step is viewed as an auxiliary ligand-assisted CO₂ elimination, preceded by a fast reversible addition of Me₃NO. This reaction pathway is also supported by the values determined for ΔH ^‡ (81 ± 13 kJ mol⁻¹) and ΔS ^‡ (−114 ± 36 J mol⁻¹ K⁻¹). This revised version was published online in June 2006 with corrections to the Cover Date.     

Extraction of HCl,HBr, HNO3, HClO4, H2SO4 and CH3COOH by 4-(5-Nonyl)pyridine and 2-hexylpyridine in benzene and determination of their pKBH+ values

The extraction of HCl, HBr, HNO₃, HClO₄, H₂SO₄ and CH₃COOH into solutions of 4-(5-nonyl)pyridine (NPy) and 2-hexylpyridine (HPy) dissolved in benzene has been studied. The results show that the larger, less basic anions extract better (ClO ₄ ⁻ >CH₃COO⁻≥NO ₃ ⁻ >Br⁻>Cl⁻>HSO ₄ ⁻ ) due to their low aqueous hydration. The ionization constants of NPyH⁺ and HPyH⁺ as determined spectrophotometrically were found to be 5.97±0.06 and 5.94±0.05, respectively, at 25°C.