Acetylacetonato Complexes Research Articles

Structure, Electrochemistry and Hydroformylation Catalytic Activity of the Bis(pyrazolylborato)rhodium(I) Complexes [RhBp(CO)P] [P = P(NC4H4)3, PPh3, PCy3, P(C6H4OMe‐4)3

AbstractRhodium complexes of formula [RhBp(CO)P] [Bp = bis(pyrazolylborate), P = P(NC4H4)3 1, PPh3 2, PCy3 3, P(C6H4OMe‐4)3 4] have been prepared by exchange of the acetylacetonate (acac−) ligand in [Rh(acac)(CO)P] complexes. The spectroscopic and electrochemical properties as well as X‐ray data of [Rh(acac)(CO)P] and [RhBp(CO)P] complexes have been compared with the aim to estimate the relative donor properties of both anionic ligands (acac− and Bp−). The cyclic voltammetric results indicate that the Bp− ligand behaves as a much stronger electron donor than acac− and a value of the Lever EL ligand parameter identical to that of the pyrazolate ligand (−0.24 V vs. NHE for each coordinating arm) is proposed for the bis‐ and tris(pyrazolyl)borate ligands, whereas P(C6H4OMe‐4)3 is also shown to have an identical EL value (0.69 V) to that of P(NC4H4)3. An improved linear relationship between the oxidation potential and the sum of the ligand EL values for square‐planar RhI complexes is also obtained and adjusted values for the Lever SM and IM parameters for the RhI/RhII redox couple are given. The trans influence of phosphanes was not observed in crystals of complexes 2 and 3, in contrast to analogous acetylacetonato complexes in which the Rh−O bonds differ by ca. 0.04−0.06 Å. Complexes 1−4 are very attractive precursors for hydroformylation catalysts and yields of aldehydes of 80−87% have been obtained with all complexes without extra phosphane as co‐catalyst. During the hydroformylation reaction, however, small amounts of a catalytically inactive [RhBp(CO)2] complex were formed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The effect of the central ion of tris-β-diketonato complexes of transition metals on their retention on thin layers of silica gel

The effect of the central ion of tris-β-diketonato complexes of transition metals on their hR F values in thin layer chromatography (TLC) on silica gel has been investigated for 24 Co(III), Cr(III), and Ru(III) complexes of the types [M(acac) 3-n (phacphac) n ] and [M(acac) 3-n (phacphSac) n ], where n = 0-3, and with four complexes of the type [M(acac) 3 ], where M = Sc(III), Y(III), Nd(III), or La(III), acac is the 2,4-pentanedionato ion, phacphac is the 1,3-diphenyl-1,3-propanedionato ion, and phacphSac is the 3-mercapto-1,3-diphenylprop-2-en-1-one ion. One- and two-component nonaqueous mobile phases were used for the chromatographic separations. The dependence of retention data on the length of ionic radius and on En/r i value is discussed. The mobility (hR F values) of the tris(acetylacetonato) complexes on thin layers of silica gel is directly proportional to the ionic radius of the central ion. On the basis of the results obtained, adsorption was assumed to be the dominant mechanism of separation under the chromatographic conditions used.

Synthesis and spectroscopic characterization of organometallic chromophores for photoluminescent materials: cyclopalladated complexes

A homologous series of isostructural and isoelectronic palladium acetylacetonato complexes containing different cyclometalated ligands HL (HL =2-phenylpyridine H(PhPy), benzo[h]quinoline H(BhQ), 9-diethylamino-benzo[a]phenoxazin-5-one H(NR), azobenzene H(Azo), 5-[(4′-methyl)-phenylazo]-8-methoxyquinoline H(QAzo), 2-benzoylpyridine H(BKPy), phenyl-2-pyridylketone-2,4-dinitrophenylhydrazone, H(BHPy)) has been prepared. The photophysical characterization of the newly synthesized products shows that many of them are luminescent in solution at room temperature. The best performances are exhibited by the H(NR) derivative ( Φ em=0.23, λ em=660, in dichloromethane solution), which improves the emission features displayed by the unmetalated ligand ( Φ em=0.13, λ em=602, in dichloromethane solution). H(NR) is a well known laser dye commonly named nile red and to the best of our knowledge [(NR)Pd(acac)] is the first example reported up to now of its incorporation in a transition metal complex. Interestingly, the results of the present investigation prove that “[(NR)Pd]” can be an useful building block for the preparation of luminescent organometallic complexes.

Mono- and bis-(acetylacetonato) complexes of arene-ruthenium(II) and arene-osmium(II): variation of the binding mode of η<sup>1</sup>-acetylacetonate with the nature of the arene

Mono- and bis-(acetylacetonato) complexes of arene-ruthenium(II) and arene-osmium(II): variation of the binding mode of η<sup>1</sup>-acetylacetonate with the nature of the arene

Isomerization and anti-Markovnikov arylation of olefin catalyzed by an iridium complex

An iridium acetylacetonato complex, a catalyst for anti-Markovnikov arylation of olefins, was found to work as a catalyst for olefin isomerization. 2-butene was obtained with 0.55 cis/trans ratio in isomerization of 1-butene. Moreover, in 1-hexene/benzene solution, isomerization and arylation of 1-hexene were simultaneously catalyzed by the iridium complex.

Nanoscale Assembly of Metal Clusters in Block Copolymer Films with Vapor of a Metal–Acetylacetonato Complex Using a Dry Process

Nanoscale Assembly of Metal Clusters in Block Copolymer Films with Vapor of a Metal–Acetylacetonato Complex Using a Dry Process

Rate of Complex Formation and Solvent Extraction of Chromium(III) Produced by the Reduction of Chromium(VI) with Acetylacetone in Aqueous Solutions

Abstract The rate and degree of solvent extraction of chromium(III), which was produced by the reduction of chromium(VI) with ascorbic acid in 0.1 mol dm-3 sodium nitrate solutions containing acetic acid/acetate ion as the buffer, were examined by using acetylacetone as the extractant and chloroform as the solvent. The rate of formation of an extractable acetylacetonato complex was greater than that when metal ion was added as hydrated Cr3+ until a certain amount of chromium(III) was extracted. Although the rate was first order with respect to the acetylacetone concentration and inverse first order with respect to the hydrogen-ion concentration, the extraction of chromium(III) formed in this way was dependent on the concentration of acetate ions in the aqueous solution. From these results, it was assumed that the chromium(III) produced from chromium(VI) formed a complex with an acetate ion just after the reduction occurred, and that the complex functions as a precursor to the extraction. The acetylacetone reacted with the precursor much more rapidly than the hydrated chromium(III) ion. From the change in the UV-vis spectrum of the complex and in the easiness of stripping of chromium(III) from chloroform with a nitric acid solution, the thus-formed extractable complex was assumed to be an intermediate which changed to a final complex similar to that obtained by the dissolution of crystals of tris(acetylacetonato)chromium(III) in chloroform.

Spectroscopic characterization of an MoOx layer on the surface of silica. An evaluation of the molecular designed dispersion method

Silica-supported molybdenum oxide catalysts have been prepared by liquid and gas phase deposition, followed by calcination of the deposited molybdenyl acetylacetonato complex. Fourier-transform infrared spectroscopy indicated a hydrogen bonding anchorage mechanism for the liquid phase deposition and a two step reaction mechanism for the gas phase deposition. After calcination of the absorbed molybdenum complexes, the supported molybdenum oxides were characterized by combining Fourier-transform infrared and Raman spectroscopy. X-ray diffraction was used to probe the possible clustering towards crystallites. An evaluation of the molecular designed dispersion method has been made by comparing the deposited molybdena structures obtained by the designed dispersion of MoO2(acac)2 with catalysts prepared by the conventional impregnation method using ammonium heptamolybdate. It is concluded that the molecular designed dispersion method results in a better grafting (more Si–O–Mo bonds) and thus a stronger metal oxide–support interaction than the conventional impregnation methods.

Rhodium(I) acetylacetonato complexes with functionalized phosphines

Rhodium(I) complexes [Rh(acac)(CO)(PR3)] with 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane (tpa), tris(2-cyanoethyl)phosphine (cyep), tris(3-sodium sulfonatophenyl)phosphine (tppts), tris(o-methoxyphenyl)phosphine (ompp), tris(p-methoxyphenyl)phosphine (pmpp), tris(2,4,6-trimethoxyphenyl)phosphine (tmpp), PPh2(pyl), PPh(pyl)2 and P(pyl)3 (pyl=2-pyridyl) have been synthesized and characterized with 1H- and 31P-NMR and IR spectra. The measured 31P coordination chemical shifts, Δδ31P{1H}, correlate well with ν(CO). Differences in 1H chemical shifts of methyl groups of acac ligand, ΔδMe, depend both on steric and electronic properties of phosphine ligand. Thus ΔδMe increases with decrease of Δδ31P{1H} and increases with increase of the cone angle of phosphine. Catalytic activity of complexes with tpa, cyep and tppts has been investigated. They are efficient catalysts for hydrogenation of CC and CO bonds, isomerization of alkenes and hydroformylation of alkenes. The mechanism of isomerization of allyl alcohol to propanal has been elucidated.

FT-Raman spectroscopy and density functional theory studies on silica-supported rhodium complexes

FT-Raman spectra of catalytically active rhodium complexes with various olefinic and various anionic ligands were recorded in benzene solution. Immobilization of these complexes on a SiO 2-surface yielded heterogeneous catalysts, which were investigated. Activation with SiCl 4 or TiCl 4 improved the catalytic activity. Therefore the FT-Raman spectroscopic investigations were also extended to this case. On the basis of density functional theory calculations a complete band assignment has been performed for the acetylacetonato complex [Rh(acac)(C 2H 4) 2].

Bis-tropolonato derivatives of Cobalt(III) complexes of bidentate aliphatic nitrogen mustards as potential hypoxia-selective cytotoxins

A series of cobalt(III) complexes, [Co(trop) 2(L)] +, where trop is the tropolonate anion and L is a bidentate amine or nitrogen mustard, have been prepared as potential hypoxia-selective cytotoxins (L = BEE, N,N′-diethylethylenediamine; DEE, N,N-diethylethylenediamine; BCE, N,N′-bis(2-chloroethyl)ethylenediamine; DCE, N,N-bis(2-chloroethyl)ethylenediamine). The 1H NMR and 13C{ 1H} NMR spectra of the complexes were assigned on the basis of chemical shift considerations, 2D NMR studies (including 13C- 1H and 1H- 1H COSY correlation experiments), and comparison to the related, known acetylacetonato (acac) complexes [Co(acac) 2(L)] +. An x-ray crystal structure determination of the analogue [Co(trop) 2(BEE)]ClO 4 showed it to be the ΔSS/ΛRR enantiomeric pair of diastereomers. The tropolonato complexes have significantly higher reduction potentials than the corresponding acac complexes, suggesting more facile cellular reduction. In agreement with this, the mustard complexes have IC 50 values in cells little different to those of the free mustards even under aerobic conditions, and do not show hypoxic selectivity in a clonogenic assay under conditions where the corresponding 3-methylacac complex of DCE showed significant selectivity.

Composite membranes of group VIII metal supported on porous alumina

Asymmetric membranes consisting of palladium, ruthenium and platinum deposited on the surface or inside the pores (average size, 200 nm) of a tubular alumina membrane were prepared by the chemical vapor deposition (CVD) technique. Sublimation and decomposition temperatures of their acetylacetonato complexes used as metal sources for CVD were important factors in preparing the membranes selected for hydrogen separation. Among the membranes prepared by CVD, the palladium membrane gave the highest flux of hydrogen and was about 1.6 times higher than a dense palladium membrane with a thickness of 4.5 μm prepared by an electroless plating technique. The hydrogen permeation through the membranes prepared by CVD are related to the surface diffusion of spillover hydrogen.

Aerobic epoxidation of cyclic alkenes catalyzed by poly(vinylbenzyl)acetylacetonato cobalt(II complex

Poly(vinylbenzyl)acetylacetonato complex of cobalt is an effective and stable catalyst for the epoxidation of cycloalkenes with molecular oxygen under 25°C with i-butyraldehyde as the sacrificial reductant. The acetylacetone ligand/Co mole ratio, the reaction time, and the strain and electronic nature of cycloalkenes all affect the conversions of alkenes and selectivities to the corresponding epoxides. The catalyst can be recycled at least seven times without loss of its activity.

Effects of a vanadate-support on the reactivity of theBis(Methallyl)Rhodium Complex [{(η3-C4H7)2Rh}2(V4O12)]2−. A comparison with the acetylacetonato complex

The methallyl moieties of [{(η3-C4H7)2Rh}2(V4O12)]2− couple to yield 2,5-dimethyl-1,5-hexadiene in a selective manner by the action of P(OEt),3, while the reaction of [(η3-C4H7)2 Rh(acac)] with P(OEt)3 produces a mixture of organic compounds. The result shows that the vanadate support has a significant influence on the reactivity of organometallic complexes.

Reactions of Ir(acac)(cyclooctene)(PCy3) with H2, HC⋮CR, HSiR3, and HSnPh3: The Acetylacetonato Ligand as a Stabilizer for Iridium(I), Iridium(III), and Iridium(V) Derivatives

The acetylacetonato complex Ir(acac)(cyclooctene)(PCy3) (1) reacts with molecular hydrogen in the presence of 1 equiv of PCy3 to give Ir(acac)H2(PCy3)2 (2). The addition of 1 equiv of PhC⋮CH to a benzene-d6 solution of 1 causes the displacement of the coordinated olefin and the formation of Ir(acac)(η2-PhC⋮CH)(PCy3) (3). The addition of hexane to this solution reverses the reaction and precipitates 1. The treatment of 1 with 3 equiv of PhC⋮CH affords Ir{κ3-CHC(Ph)CH[C(O)CH3]2}(C2Ph)(CPhCH2)(PCy3) (4), which is a result of the oxidative addition of the HC⋮ bond of an alkyne, the insertion of a second alkyne into an Ir−C3(acac) bond, and the subsequent insertion of a third alkyne into the Ir−H bond, previously formed. The structure of 4 was determined by an X-ray investigation. The coordination geometry around the iridium atom can be rationalized as a distorted octahedron with the bicyclic ligand occupying three coordination sites of a octahedral face. In the presence of PCy3 the reaction of 1 and PhC⋮CH le...

Improved synthetic routes to tris(acetylacetonato)ruthenium(III) and a redetermination of the structure of the β-polymorph

The ruthenium-blue cluster-mediated synthesis of Ru(dike) 3 complexes (dike = β-diketone) has been investigated in view of the low yields this route usually produces. Only the acetylacetonato complex of the metal was isolated without modifications to the procedure, allowing a redetermination of the crystal structure to be carried out; previously published data relating to the structure of the racemic complex is incorrect and is now superseded by a more accurate determination. Two forms of this complex have now been isolated, and a comparative analysis of these is presented here.

Determination of Trace Amounts of Indium by Graphite-Furnace Atomic Absorption Spectrometry after Preconcentration as the Acetylacetonato Complex on Activated Carbon

A rapid and simple preconcentration method by selective adsorption using activated carbon as an adsorbent and acetylacetone as a complexing agent is described for the determination of trace amounts of indium by graphite-furnace atomic absorption spectrometry. The indium-acetylacetonato complex is easily adsorbed onto activated carbon at pH 6.0-8.0. After the activated carbon phase, the adsorbing indium-acetylacetonato complex is separated and dispersed in 5ml of a 2%(v/v) glycerine solution containing 700μg of palladium. The resulting suspension of activated carbon is introduced directly into the graphite-furnace atomizer. The detection limit was 0.025μg/l(s/n=3), and the relative standard deviation was 4.0-5.0% at 1.0μgIn/100ml (n=10). This method was applied to the determination of indium in water samples and proved to be a useful technique for the preconcentration of trace amounts of indium in water samples.

C. Isolation, X-Ray Crystal Structure and 59Co Nuclear Magnetic Resonance Spectral Investigation of the Partially Nitrated Cobalt(III) Acetylacetonato Complex [Co(acac)2(NO2acac)] (Vol 45, Pg 797, 1992)

c. Isolation, X-Ray Crystal Structure and 59Co Nuclear Magnetic Resonance Spectral Investigation of the Partially Nitrated Cobalt(III) Acetylacetonato Complex [Co(acac)2(NO2acac)] (Vol 45, Pg 797, 1992)

Formation of acetylacetonato iron complexes in acetonitrile and their resonance Raman spectra

Formation of acetylacetonato from complexes in acetonitrile, Fe(acac) 2+, Fe(acac) 2 + and Fe(acac) 3, (the expression represents the solvated species: acac - is the 2, 4-pentanedionate ion), were spectrophotometrically studied. On addition of Hacac to an acetonitrile solution of Fe(ClO 4) 3, Fe(acac) 2+ was quantitatively formed. When excess Hacac was added, only Fe(acac) 2 + was obtained without forming Fe(acac) 3. On the other hand, Fe(acac) 2 + was quantitatively obtained by adding HClO 4 to an acetonitrile solution of Fe(acac) 3, and Fe(acac) 2+ was also formed by adding an excess of HClO 4. All the species of acetylacetonato complexes: Fe(acac) 2+, Fe(acac) 2 + and Fe(acac) 3 were formed in the system of Fe(ClO 4) 3 with an addition of tetraethylammonium acetylacetonate. The resonance Raman spectra of the obtained solutions of Fe(acac) 2+ and Fe(acac) 2 + and of the solution of Fe(acac) 3 were measured. The peaks mainly associated with v(FeO) and v(CO) are observed near 450 and 1600 cm -1, respectively. The order of v(FeO) is Fe(acac) 2+ (474 cm -1) > Fe(acac) 2 + (462 cm -1) > Fe(acac) 3 (451 cm -1) and that of v(CO) is Fe(acac) 2+ (1554 cm -1) < Fe(acac) 2 + (1578 cm -1) < Fe(acac) 3 (1603 cm -1). These results indicate that the coordination strength of acac - to Fe becomes weaker, because the Lewis acidity of the metal decreases as the number of coordinated acac - increases.

Isolation, X-Ray Crystal Structure and 59Co Nuclear Magnetic Resonance Spectral Investigation of the Partially Nitrated Cobalt(III) Acetylacetonato Complex [Co(acac)2(NO2acac)

The complex [Co( acac )2(NO2acac)] has been isolated after fractional crystallization from a reaction mixture of [Co( acac )3] and nitrating agent. The complex crystallizes in the triclinic space group P1, with c 14.557(2) � , α 78.98(1), β 83.71(2), γ75.32(1)° and Z 2. The structure refined to a final R value of 0.074 for 2287 'observed' [I &gt; 3 σ(I)] reflections. The structure consists of discrete complex molecules with the cobalt atom surrounded by six oxygen atoms at the corners of a distorted octahedron. The NO2 group is twisted at 50.7� to the chelate ring on which it is situated and has little influence on the geometry, with intrachelate and interchelate oxygen-oxygen separations essentially the same as those found in [Co( acac )3]. The 59Co n.m.r. spectra of the [Co( acac )2(NO2acac)] complex, as well as [Co( acac )3], [Co(NO2acac)3] and [Co( acac )(NO2acac)2], have been recorded, this resonance being particularly sensitive to substitution on they γcarbon atom of the acetylacetonato chelate ring. The 59CO relaxation rates for the [Co( acac )2(NO2acac)] and [Co( acac )(NO2acac)2] complexes are faster than that displayed by the symmetric [Co(NO2acac)3] complex, (1948 � 20, 2765 � 30 and 1696 � 20 s-1, respectively). The results obtained for the relaxation rates for these complexes are compared with those obtained for similar halide-substituted complexes [Co( acac )3-n( Xacac )n] � (X = Cl , Br, I; n = 0-3).