Hexafluoroacetylacetonato Ligands Research Articles

Heterometallic [Ln(hfac)3Cu(acac)2] complexes with late 4f ions

Heterometallic [Ln(hfac)3Cu(acac)2] complexes (Ln = Eu 1, Dy 2, Er 3) can be prepared along the f-transition series. X-rays diffraction studies on well-shaped single crystals revealed for 1 – 3 a dinuclear structure. No ligand scrambling occurred, a Lewis acid-base interaction has been observed with the two metals bridged through two oxygen atoms of the acetylacetonato ligands and an oxygen atom of a hexafluoroacetylacetonato ligand. Compounds 2 and 3 can be obtained only in anhydrous conditions. (1) can be sublimed under reduced pressure, and crystals of the sublimed product, 1a, showed a polymorph structure with the same molecular identity. Magnetic studies have been carried out on 2, displaying an antiferromagnetic interaction and a field-induced slow relaxing magnetic moment with a significant phonon bottleneck effect. Compound 3, on the other hand, did not present any magnetization dynamics, with or without applied field. Quantum mechanical calculations rationalize the variation of the bond strengths from the reagents to the heterometallic complexes and quantify the Ln and Cu direct interaction, which is relevant, especially for 2.

Tribo-Excited Chemical Reaction Using an EuIII Complex with a Stacked Anthracene Framework.

A spin-selective tribo-chemical reaction using a dinuclear lanthanide complex is demonstrated for the first time. The dinuclear complex is composed of two EuIII ions, hexafluoroacetylacetonato ligands, and anthracene-based phosphine oxide bridges. Single-crystal analysis revealed a face-to-face-type anthracene dimer structure in the dinuclear EuIII complex. Mechanical stimulus on the dinuclear EuIII complex induced selective formation of oxidized anthracene. The tribo-chemical reaction is based on a characteristic energy-transfer pathway for the selective formation of an excited triplet state.

Luminescent Europium(III) Coordination Zippers Linked with Thiophene‐Based Bridges

AbstractNovel EuIII coordination polymers [Eu(hfa)3(dpt)]n (dpt: 2,5‐bis(diphenylphosphoryl)thiophene) and [Eu(hfa)3(dpedot)]n (dpedot: 2,5‐bis(diphenylphosphoryl)ethylenedioxythiophene) with hydrogen‐bonded zipper structures are reported. The coordination polymers are composed of EuIII ions, hexafluoroacetylacetonato ligands, and thiophene‐based phosphine oxide bridges. The zig‐zag orientation of single polymer chains induced the formation of densely packed coordination structures with multiple intermolecular interactions, resulting in thermal stability above 300 °C. They exhibit a high intrinsic emission quantum yield (ca. 80 %) due to their asymmetrical and low‐vibrational coordination structures around EuIII ions. Furthermore, the characteristic alternative orientation of substituents also contributes to the dramatically high ligand‐to‐metal energy transfer efficiencies of up to 80 % in the solid state.

Luminescent Europium(III) Coordination Zippers Linked with Thiophene-Based Bridges.

Novel Eu(III) coordination polymers [Eu(hfa)3 (dpt)]n (dpt: 2,5-bis(diphenylphosphoryl)thiophene) and [Eu(hfa)3 (dpedot)]n (dpedot: 2,5-bis(diphenylphosphoryl)ethylenedioxythiophene) with hydrogen-bonded zipper structures are reported. The coordination polymers are composed of Eu(III) ions, hexafluoroacetylacetonato ligands, and thiophene-based phosphine oxide bridges. The zig-zag orientation of single polymer chains induced the formation of densely packed coordination structures with multiple intermolecular interactions, resulting in thermal stability above 300 °C. They exhibit a high intrinsic emission quantum yield (ca. 80 %) due to their asymmetrical and low-vibrational coordination structures around Eu(III) ions. Furthermore, the characteristic alternative orientation of substituents also contributes to the dramatically high ligand-to-metal energy transfer efficiencies of up to 80 % in the solid state.

Supported monocationic copper(II) complexes obtained by coordination with dialkylphosphonate groups on styrene–divinylbenzene copolymer as catalysts for oxidation of organic compounds

New catalysts were synthesized by immobilization of neutral and monocationic copper complexes Cu(hfac)2 (hfac−=hexafluoroacetylacetonato ligand) and [Cu(acac)(tmen)]NO3 (acac−=acetylacetonato ligand, tmen=N,N,N′,N′-tetramethyl-ethylendiamine) on styrene–divinylbenzene copolymer functionalized with four different dialkyl phosphonate moieties typified by PPO(OR)2 (with R=CH3, C2H5, iC3H7, and nC4H9). The formation of P(O)(OR)2 phosphonates groups has been confirmed by the FT-IR spectra. Thermogravimetric analysis results reveal that the thermal stability of polymer support depend on the functional group attached. The complexes were anchored by coordination interaction between the copper(II) ion and the phosphonate oxygen atom on each of the four functionalized supports and the strength of the PO⋯Cun+ coordination interaction was influenced by the nature of the R group. The effect of functionalized supports on the structure and catalytic activity of Cu(hfac)2 and [Cu(acac)(tmen)]+ mononuclear species was determined in oxidation of several organic compounds (anisole, cyclohexene, toluene, styrene, phenol) with hydrogen peroxide. The catalytic activity results show that the activity and selectivity of Cu(II) complexes depends on the equilibrium between steric factor and inductive electron-releasing effect. The best selectivity was obtained in oxidation of anisole, phenol and styrene for all the catalysts. The main products were for 2-methoxyphenol, catechol and benzaldehyde, respectively.

ChemInform Abstract: Volatile Barium β-Diketonates for Use as MOCVD Precursors

Metal-organic chemical vapor deposition (MOCVD) techniques have been used to deposit thin superconducting films of YBa2Cu3O7-x. A limitation of the technique lies in the volatility of the barium(II) precursors. A review of attempts to enhance volatility through substitution of fluorinated chelating agents and studies to limit oligomerization of the barium chelates are reviewed. Within the past five years, substantial progress has been made in synthesizing more volatile barium complexes, and the most volatile barium compound yet reported is a monomeric chelate in which five hexafluoroacetylacetonato ligands are bonded to barium(II).

Organometallic red-emitting chromophores: a computational and experimental study on cyclometallated Nile Red complexes of palladium(ii) and platinum(ii) acetylacetonates and hexafluoroacetylacetonates

A comparative photophysical, electrochemical and computational study of a series of Nile Red cyclopalladated and newly synthesised cycloplatinated complexes is reported. All complexes are luminescent at room temperature and the emission properties are governed by the nature of the cyclometallated dye. However, the presence of platinum(II) as metal centre decreases severely the emission quantum yield, while the electronegativity of the ancillary hexafluoroacetylacetonato ligand enhanced the emission properties of the Nile Red complexes.

Synthesis, structures, and magnetic and optical properties of a series of europium(III) and gadolinium(III) complexes with chelating nitronyl and imino nitroxide free radicals.

This paper reports the synthesis, structures, and magnetic and optical properties of a series of gadolinium(III) (1a-4a) and europium(III) (1b-4b) complexes with nitronyl or imino nitroxide radicals. The crystal structures of compounds 1a and 1b consist of [Ln(III)(radical)(2)(NO(3))(3)] entities in which the gadolinium(III) (1a) or europium(III) ion (1b) is 10-coordinated to two nitronyl nitroxide radicals and three nitrato ligands. The crystal structures of compounds 2a-4a and 2b-4b consist of [Ln(III)(hfac)(3)(radical)] entities in which the gadolinium(III) (2a-4a) or europium(III) ion (2b-4b) is 8-coordinated to one nitronyl (2a and 2b) or one imino (3a, 4a and 3b, 4b) nitroxide radical and three hexafluoroacetylacetonato ligands. The gadolinium(III) complexes (1a-4a) are isostructural with their europium(III) analogues (1b-4b). The magnetic properties of the gadolinium complexes were studied. Along the series 1a-4a only compound 2a exhibits a ferromagnetic Gd(III)-radical coupling (J(Gd-rad) = +1.7 cm(-1)), while for the others this coupling is antiferromagnetic (1a: J(Gd-rad1) = -4.05 cm(-1) and J(Gd-rad2) = -0.80 cm(-1); 3a: J(Gd-rad) = -2.6 cm(-1); 4a: J(Gd-rad) = -1.9 cm(-1)). The first full luminescence spectra of lanthanide complexes with free radical ligands are reported between 650 and 1200 nm. The rich vibronic structure in luminescence and absorption spectra indicates that several excited states define the absorption spectra between 400 and 800 nm. Qualitative trends can be established between magnetic ground state properties and the energies and fine structure of the title compounds.

Trans-Diaquabis(hexafluoroacetylacetonato-O,O')manganese(II) Monohydrate

In the crystals of trans-diaquabis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-O,O')manganese(II) monohydrate, [Mn(C5HF6O2)2(H2O)2].H2O, the Mn atom and all three water molecules lie on a crystallographic mirror plane. Two of the water molecules are coordinated to the Mn atom in a trans geometry and the third links the structure into hydrogen-bonded sheets. The two planar hexafluoroacetylacetonato ligands related by the mirror plane form a dihedral angle of 41.6 (2)° with one another. One CF3 group displayed significant disorder.

Organometallic Chemical Vapor Deposition of Palladium under Very Mild Conditions of Temperature in the Presence of a Low Reactive Gas Partial Pressure

Palladium thin-film deposition was carried out from the known precursors Pd(η3-C3H5)(Cp), and Pd(η3-C3H5)(hfa), where Cp is (η5-C5H5), cyclopentadienyl ligand and hfa is (CF3COCHCOCF3), hexafluoroacetylacetonato ligand. The use of a reactive gas such as dihydrogen led to unexpected low temperatures of deposition (30−60 °C). XPS and electron microprobe analyses revealed that low levels of carbon are incorporated to the palladium films. X-ray analyses showed crystalline deposits and scanning electron microscopy revealed grains of 300−1000 nm. Gas-phase analyses by mass spectrometry and GC/MS of deposition residues were realized to clarify the reaction mechanisms. Such a deposition process leads to metallic palladium with a good purity level.

Enhancement of luminescence of Nd 3+ complexes with deuterated hexafluoroacetylacetonato ligands in organic solvent

Tris-(hexafluoroacetylacetonato)neodymium(III), [Nd(HFA-D) 3], was prepared by chelation of Nd 3+ ion with deuterated hexafluoroacetylacetone in CD 3OD. Luminescence of the Nd 3+ complex was observed for the first time in organic solvents and the quantum yield was estimated to be of the order of 10 −2 in deuterated acetone solution. The absorption spectrum of [Nd(HFA-D) 3] dissolved in acetone was comparable with that of Nd 3+ ion in Y 3Al 5O 15 matrix (Nd:YAG). Splitting of the 4 F 3 2 level was determined to be 82.3 cm −1 in this system. These spectral characteristics suggest that the physical nature of Nd 3+ coordination environments should be uniform and well defined by coordination of HFA in solution.

Volatile barium β-diketonates for use as MOCVD precursors

Metal-organic chemical vapor deposition (MOCVD) techniques have been used to deposit thin superconducting films of YBa 2Cu 3O 7-x. A limitation of the technique lies in the volatility of the barium(II) precursors. A review of attempts to enhance volatility through substitution of fluorinated chelating agents and studies to limit oligomerization of the barium chelates are reviewed. Within the past five years, substantial progress has been made in synthesizing more volatile barium complexes, and the most volatile barium compound yet reported is a monomeric chelate in which five hexafluoroacetylacetonato ligands are bonded to barium(II).

Preparation and pH dependent reversible color change of (hexafluoroacetylacetonato)bis(ethylenediamine)chromium(III) complex

The title complex ion was newly prepared as a hexafluorophosphate perchlorate salt. The aqueous solution of this complex shows a pH dependent, rapid and reversible color change. This phenomenon is analogous to that observed for its Co(III) analog and may be explained by a hydroxide ion addition equilibrium to the coordinating hexafluoroacetylacetonato ligand. The estimated equilibrium constant is significantly larger than that for its Co(III) analog.

Preparation and the pH dependent reversible color change of complexes of cobalt(III) and chromium(III) with a hexafluoroacetylacetonato ligand

Thirteen complexes of Co(III) and Cr(III) with a hexafluoroacetylacetonato (hfac) ligand were newly prepared as perchlorate salts. These are CoL(hfac) 2+ with L=(tn) 2, tren, β-2,3,2-tet, β-3,2,3-tet, (EtNH 2) 4, (n-PrNH 2) 4, (n-BuNH 2) 4, (bpy) 2, (phen) 2; and CrL(hfac) 2+ with L(NH 3) 4, (tn) 2, α-2,3,2 -tet, 3,2,3-tet. In these complexes the ligand L occupies four coordination sites and the hfac ligand acts as a bidentate. Aqueous or methanolic solutions of these complexes show a pH dependent rapid and reversible color change; orange in an acid and violet in a base. The origin of this chromism may be a covalent hydration equilibrium, where a lyate anion forms a σ bond with one of the carbonyl carbon atoms of the coordinating hfac ligand. The equilibrium constant in water is 2∼12×10 6 M −1 for Co(III) complexes and 1∼6×10 10 M −1 for Cr(III) complexes (M=mol dm −3).

ChemInform Abstract: Spectrophotometric Study of the Methoxide Addition to Hexafluoroacetylacetonato Complexes of Co(III) and the Crystal Structure of β‐(Co(trien)(hfacOCH3))(ClO4).

AbstractIn methanolic solution a rapid and reversible methoxide addition occurs to the hexafluoroacetylacetonato ligand in a tetraamine‐β‐diketonatocobalt(III) complex with formation of (I).

(Hexafluoroacetylacetonato-O,O')(1-hydroxy-2,2,6,6-tetramethylpiperidinato-O,N)palladium(II), [Pd(C5HF6O2)(C9H18NO)], a metal complex containing a reduced nitroxylradical

[ PtC12(C6 H 13N)(CsH 11P)] The shortest intermolecular contact [3.46 (2)A], observed between N and Cl(2)[~+x, ~--y, - z ] , is probably due to an N - H . . . C 1 hydrogen bond. The packing arrangement is shown in Fig. 3. Thanks are due to Dr G. Consiglio (ETH, Zfirich) who kindly prepared the compound. The drawings were made by Mr M. Viola. References AMBUEHL, J., PREGOSIN, P. S., VENANZI, L. M., CONSIGLIO, G., BACHECHI, F. ~ ZAMBONELLI, L. (1979). J. Organomet. Chem. Fig. 3. Packing arrangement of the molecules viewed down a. It can be observed that the conformation of the unsubstituted pyrrolidine ring in (II) may be considered intermediate between the conformation of the ring in (IV) and that in (III), perhaps closer to the confor- mation in (IV) which has an envelope-like form with C(4) at the flap. Therefore the five structures seem to represent five phases of the pseudorotation of the pyrrolidine ring in the sequence (IV)--,(II)--,(III)--, (V)-,(I) or, to stress the influence of the methyl sub- stituents, (IV),-- (II)-,(III)--,(V) ~(I). BACHECHI, F., MURA, P. & ZAMBONELLI, L. (1980). Acta Cryst. B36, 2604-2608. BACHECHI, F., ZAMBONELLI, L. & MARCOTRIGIANO, G. (1977). J. Cryst. MoL Struct. 7, 11-20. CERRINI, S. & SPAGNA, R. (1977). 4th Eur. Crystallogr. Meet., Oxford. Abstracts, p. 7. CHATT, J. & VENANZI, L. M. (1955). J. Chem. So¢. pp. 3858-3864. CO'rTIN, H. (1966). Bull. Soe. Ch#n. Fr. p. 2731. International Tables for X-ray Crystallography (1974). Vol. 1V, Tables 2.2B and 2.3.1 Birmingham: Kynoch Press. (Present distributor D. Reidel, Dordrecht.) MCCANDLISH, L. E., STOUT, G. H. & ANDREWS, L. C. (1975). Aeta Cryst. A31, 245-249. NORTH, A. C. T., PHILLIPS, D. C. & MATHEWS, F. S. (1968). Acta Cryst. A24, 351-359. SPAGNA, R. & ZAMBONELLI, L. (1971). J. Chem. Soc. A, pp. Acta Cryst. (1985). C41, 838-840 (Hexafluoroacetylacetonato-O,O')(l-hydroxy-2,2,6,6-tetramethylpiperidinato- O,N)palladium(II), [Pd(C5 HF602) (C9H lsN O)], a Metal Complex Containing a Reduced Nitroxyl Radical BY LEIGH C. PORTER AND ROBERT J. DOEDENS* Department of Chemistry, University o f California, Irvine, California 92717, USA (Received 28 September 1984; accepted 10 December 1984) M r=469.7, monoclinic, P21/n, a= b=20.511(8), c=11.655(3)A, t= V = 1812 (1) A 3, Z = 4, Dx= 1.722 Mg m -3, 2(Mo Kct) = 0,71073 A, /t = 1.08 mm -1, F(000) = 936, T = 297 K, final R = 0.042 for 2498 observed reflections. The Pd atom is bound to a chelating hexafluoroacetylacetonato ligand and to a reduced nitroxyl radical coordinated in an r/2 fashion through its N and O atoms. Principal bond distances include P d - O ( F 6 a c a c ) = 2.058 (4), 2.078 (4), P d - O(nitroxyl) = 2.009 (4), P d - N = 1.985 (4), N - O = 1.346 (5) A. Abstract. * To whom correspondence should be addressed. Introduction. The title compound was prepared in the course of exploratory studies of the reactions of stable nitroxyl radicals with transition-metal complexes con- taining a strongly Lewis-acidic metal center. Previous studies in this series have yielded examples of various types of interactions of the nitroxyl group, including metal coordination of the nitroxyl radical through O (Dickman & Doedens, 1981; Porter, Dickman & Doedens, 1983; Porter & Doedens, 1985), bidentate N,O binding of the reduced radical (Dickman & Doedens, 1982), hydrogen bonding to coordinated water (Dickman & Doedens, 1983), and formation of a co-crystallized solid with no specific interactions involv- ing the nitroxyl group (Porter & Doedens, 1984). We © 1985 International Union of Crystallography

Kinetics and mechanism of an unique hydrolysis reaction of (hexafluoroacetylacetonato)bis(ethylenediamine)cobalt(III) in aqueous solution

Addition of base to the title complex results in the rapid reversible formation of the hydrolysed species Co(en)2-(hfac · OH)+ in which the coordinated hexafluoroacetylacetonato ligand contains a hydroxyl group on the carbonyl carbon atom. The kinetics of both the forward hydrolysis and reverse acidolysis reactions were followed spectrophotometrically using stopped-flow and T-jump techniques. The corresponding rate constants areca. 3×106 and 1×108 M−1s−1, respectively, for various buffer systems at 25 °C and ionic strength 1.0 M. A combination of the kinetic and equilibrium data enables the estimation of the uncatalyzed (spontaneous) forward and reverse reaction components. The results are discussed with reference to similar data reported for the hydrolysis and reverse acidolysis reactions of the uncoordinated acetylacetonato ligand.