Trifluoroacetate Complexes Research Articles

Processes Involved in the Reduction of a Cyclometalated Palladium(II) Complex

Reaction of [Pd(TFA)2] (1; TFA = trifluoroacetate) with 2 equiv of benzyldiisopropylphosphine resulted in formation of the metalated complex [Pd{C6H4(CH2PiPr2)}{(C6H5CH2)PiPr2}(TFA)] (2). The dinuclear trifluoroacetate complex [Pd{C6H4(CH2PiPr2)}(TFA)]2 (3) was formed when the reaction was performed with an equimolar amount of the phosphine. Both complexes were structurally characterized. Reduction of the cyclometalated palladium complex 2 with sodium metal in THF gave a mixture of cis and trans isomers of the dimetalated bis(o-benzyldiisopropylphosphine)palladium(II) (6a,b) and bis(benzyldiisopropylphosphine)palladium(0) (7). A mechanism for the reduction process is presented. Treatment of the reaction mixture of 6a,b and 7 with an equimolar amount of hydrochloric acid led to a mixture of 7, [Pd{C6H4(CH2PiPr2)}{(C6H5CH2)PiPr2}(Cl)] (9), [Pd{(C6H5CH2)PiPr2}2(H)(Cl)] (8), [Pd{(C6H5CH2)PiPr2}2(Cl)2] (4), and both isomeric forms of [Pd{C6H4(CH2PiPr2)}2] (6a,b). All complexes were independently prepared and fully characterized. The addition of another 1 equiv of hydrochloric acid to this reaction mixture resulted in the exclusive formation of 4. Reduction of 4 with sodium metal in THF cleanly yielded the Pd0 complex 7 in high yields, offering a new, facile, and high-yield route toward the synthesis of dicoordinated bis(phosphine) Pd0 complexes. Reaction of 7 with an equimolar amount of HCl led to the clean formation of [Pd{(C6H5CH2)PiPr2}2(H)(Cl)] (8). The addition of another 1 equiv of HCl led to the quantitative formation of 2 and H2. Reactions of 9 and an equimolar amount of NaBHEt3 cleanly yielded complex 7, which was also exclusively formed by treatment of 4 with 2 equiv of NaBHEt3. Mixtures of the cis and trans isomers 6a,b were formed by the addition of 2 equiv of (o-lithiobenzyl)diisopropylphosphine to benzene solutions of bis(diethyl sulfide)palladium dichloride (5) at room temperature.

Ruthenium(II,III,III) μ3-oxotrifluoroacetate with dimethyl sulfoxide: Synthesis, structure, and DTF quantum-chemical calculations

The reaction of [Ru 3 III (μ3-O)(μ-O2CCF3)6(H2O)3](O2CCF3) in methanol gives two solvates, [Ru3O(O2CCF3)6(DMSO)3] · 1/2H2O (I) and [Ru3O(O2CCF3)6(DMSO)3] · H2O (II), of a novel trinuclear mixedvalence Ru(II,III,III) trifluoroacetate complex, where two DMSO molecules are coordinated to the Ru atoms through the O atom, while the third DMSO molecule is coordinated through the S atom. According to the X-ray diffraction data, the complex can crystallize in two crystal systems: triclinic (I) (space group P $$\overline 1 $$ ) and monoclinic (II) (space group P21/m). The unit cell parameters for I are: a = 9.354, b = 11.005, c = 20.846 A, α = 99.10, β = 96.38, γ = 92.17, Z = 2; R = 7.27%; for I are: a = 9.186, b = 17.044, c = 13.091 A, β = 101.10, Z = 2; R = 14.18%.

From Trifluoroacetate Complex Precursors to Monodisperse Rare‐Earth Fluoride and Oxyfluoride Nanocrystals with Diverse Shapes through Controlled Fluorination in Solution Phase

We report the first systematic synthesis of monodisperse rare-earth (RE=La to Lu, Y) fluoride and oxyfluoride nanocrystals with diverse shapes (trigonal REF3 triangular, truncated-triangular, hexagonal, and polygonal nanoplates; orthorhombic REF3 quadrilateral and zigzag-shaped nanoplates; cubic REOF nanopolyhedra and nanorods) from single-source precursors (SSP) of [RE(CF(3)COO)(3)] through controlled fluorination in oleic acid (OA)/oleylamine (OM)/1-octadecene (ODE). To selectively obtain REF3 or REOF nanocrystals, the fluorination of the RE-O bond to the RE-F bond at the nucleation stage was controlled by finely tuning the ratio of OA/ODE or OA/OM, and the reaction temperature. For phase-pure REF3 or REOF naocrystals, their shape-selective syntheses could be realized by further modifying the reaction conditions. The two-dimensional growth of the REF3 nanoplates and the one-dimensional growth of the REOF nanorods were likely due to the selective adsorption of the capping ligands on specific crystal planes of the nanocrystals. Those well-shaped nanocrystals with diverse geometric symmetries (such as D(3h), D(6h), C(2h), O(h), and D(nh)) displayed a remarkable capability to form self-assembled superlattices. By manipulating the solvent-substrate combination, the plate-shaped REF3 nanocrystals could form highly ordered nanoarrays by means of either the face-to-face formation or the edge-to-edge formation. By using this SSP strategy, we also obtained high-quality LaF3:Eu and LaF3:Eu/LaF3 triangular nanoplates that showed photoluminescent red emissions of Eu3+ ions sensitive to the surface effect.

The Interplay between Yttrium and Barium or Copper Trifluoroacetates and N‐Methyldiethanolamine: Synthesis of a Heterometallic Y3Cu Trifluoroacetate Complex and a Homometallic Ba‐TFA 1D Polymer

AbstractThe reactions between [Y(TFA)3(H2O)3] and either [Cu(TFA)2(MeOH)] or [Ba(TFA)2]∞ in the presence of excess N‐methyldiethanolamine (mdeaH2) have been investigated in relation with their use as precursors for high Tc superconductors. They afford the heterometallic Y3Cu complex [CuY3(μ3‐OH)(μ‐η3:η1‐mdeaH)3(μ3‐η3:η1:η1‐mdeaH)2(η2‐TFA)(μ,η2‐TFA)2](TFA)2(H2O) (1) and the homometallic Ba‐TFA 1D polymer [Ba3(η3‐mdeaH2)2(μ‐η3:η1‐mdeaH2)2(η1‐TFA)2(η2‐TFA)2(μ3‐η2:η2:η1‐TFA)2]1∞ (2), respectively, in high yield. These compounds were characterised by X‐ray diffraction and FT‐IR, ESR (for 1) and NMR (for 2) spectroscopy. Single‐crystal X‐ray diffraction studies show the versatile bonding modes of the trifluoroacetate and N‐methyldiethanolamine ligands, with the former acting not only as a terminal (η1 and η2) or bridging‐chelating (μ,η2 and μ3‐η2:η2:η1) ligand but also as a counterion, whereas the latter, either protonated or partially deprotonated, binds the metal centres in a chelating (η3) or bridging‐chelating (μ,η3:η1 and μ3‐η3:η1:η1) manner. The triangular Y3 unit [3.480(6)–3.550(6) Å] in the cation of 1 consists of one nine‐coordinate and two eight‐coordinate Y atoms, the former of which are quite scarce in alkoxide chemistry. The unique feature of the 1D polymeric structure of 2 is the secondary F···cation bond, which has not been observed so far for TFA ligands. In addition, it is the only example where the Ba atom is linked to monodentate, bidentate and bridging trifluoroacetate ligands simultaneously. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Acid Co(II) and Ni(II) trifluoroacetate complexes: Synthesis and crystal structure

Anhydrous and partially hydrated acid trinuclear trifluoroacetates of divalent transition metals of the composition [M3(CF3COO)6(CF3COOH)6)](CF3COOH) and [M3(CF3COO)6(CF3COOH)2(H2O)4)](CF3COOH)2, respectively, where M = Co (I, III) Ni (II, IV), were synthesized and studied by X-ray diffraction. Complexes I and II were obtained by crystallization from solutions of M(CF3COO)2 · 4H2O in trifluoroacetic anhydride; complexes III and IV were synthesized under the same conditions with the use of 99% trifluoroacetic acid as a solvent. Crystals I are triclinic: space group $$P\bar 1$$ , a = 13.199(6) A, b = 14.649(6) A, c = 15.818(6) A, α = 90.04(4)°, β = 114.32(4)°, γ = 108.55(4)°, V = 2611.3(19) A3, Z = 2, R = 0.0480. Crystals II are trigonal: space group $$R\bar 3$$ , a = 13.307(2) A, c = 53.13(1) A, V = 8148(2) A3, Z = 6, R = 0.1112. Crystals III are triclinic: space group $$P\bar 1$$ , a = 9.001(8) A, b = 10.379(9) A, c = 12.119(9) A, α = 83.67(5)°, β = 72.33(5)°, γ = 83.44(5)°, V = 1068.3(15) A3, Z = 1 A, R = 0.1031. Crystals IV are triclinic: space group $$P\bar 1$$ , a = 9.121(18) A, b = 10.379(2) A, c = 12.109(2) A, α = 84.59(3)°, β = 72.20(3)°, γ = 82.80(3)°, V = 1080.94(40) A3, Z = 1, R = 0.0334.

Heterolytic CH Activation with a Cyclometalated Platinum(II) 6-Phenyl-4,4‘-di-tert-butyl-2,2-Bipyridine Complex

The more electron-rich, thermally, air, and protic stable, cyclometalated Pt(II)(NNC) trifluoroacetate complex (3) (NNC = κ^3-6-phenyl-4,4‘-di-tert-butyl-2,2‘-bipyridine) was synthesized with the expectation that it would be less susceptible to H_2O inhibition than the Pt(bpym)(TFA)_2 system (bpym = κ^2-2,2‘-bipyrimidine) for the catalytic oxidation of hydrocarbons. Complex 3 was found to catalyze the H/D exchange between benzene and trifluoroacetic acid via CH activation but at a rate slower than the Pt(bpym) complex. Experimental and theoretical studies show that while the use of the more electron-rich NNC ligand motif lowered the ΔH for substrate coordination relative to the Pt(bpym) system, a larger increase in the barrier for CH cleavage led to an increase in the overall barrier for CH activation.

Synthesis, Crystal Structure and Magnetic Behaviour of Dimeric and Polymeric Gadolinium Trifluoroacetate Complexes

The gadolinium(III) trifluoroacetates ((CH3)2NH2)[Gd(CF3COO)4] (1), ((CH3)3NH)[Gd(CF3 COO)4(H2O)] (2), Gd(CF3COO)3(H2O)3 (3) as well as Gd2(CF3COO)6(H2O)2(phen)3 · C2H5OH (4) (phen = 1,10-phenanthroline) were synthesized and structurally characterized by X-ray crystallography. These compounds crystallize in the space group P1̅ (No. 2, Z = 2) (1, 2 and 4) and P 21/c (No. 14, Z = 4) (3), respectively, with the following lattice constants 1: a = 884.9(2), b = 1024.9(2), c = 1173.1(2) pm, α = 105.77(2), β = 99.51(2), γ = 107.93(2)°; 2: a = 965.1(1), b = 1028.6(1), c = 1271.3(2) pm, α = 111.83(2), β = 111.33(2), γ = 90.44(2)°; 3: a = 919.6(2), b = 1890.6(4), c = 978.7(2) pm, β = 113.94(2)°; 4: a = 1286.7(8), b = 1639.3(8), c = 1712.2(9) pm, α = 62.57(6), β = 84.13(5), γ = 68.28(5)°. The compounds consist of Gd3+ ions which are bridged by carboxylate groups either to chains (1 and 2) or to dimers (3 and 4). In addition to the Gd3+ dimers, compound (4) also contains monomeric Gd3+ units. The magnetic behaviour of 2 and 3 was investigated in a temperature range of 1.77 to 300 K. The magnetic data for these compounds indicate weak antiferromagnetic interactions

The Structural Systematics of Protonation of Some Important Nitrogen‐base Ligands. III. Some (Univalent) Anion Salts of some Hindered Unidentate Nitrogen Bases

AbstractRecent structural studies of salts of the 2,2,6,6‐tetramethylpiperidinium cation [tmpH]+ (chloride, bromide; thiocyanate) present as interesting dimeric or polymeric associations linked by pairs of directional hydrogen‐bonds from the cationic = ${\rm NH}^{+}_{2}$ moieties to ‘two‐coordinate’ anions. Present single crystal X‐ray studies have characterized the iodide, perchlorate, nitrate and trifluoroacetate complexes, all, like those of the preceding studies, of composition [tmpH]+X− (anhydrous). A variety of forms are found: the nitrate compound is dimeric [[tmpH](O·NO·O)2[Htmp]], the trifluoroacetate compound being similar in form while the iodide and perchlorate salts are mixtures of dimers (with the anions essentially single atom bridges) and single‐stranded helical polymers, the stoichiometric ratio of these being 1:1 and 2:1 in terms of [tmpH]X formula units, respectively. A study of 4‐keto‐2,2,6,6‐tetramethyl‐piperidinium thiocyanate shows it to be a dimer $\left [ [{\rm OtmpH}] \left (^{\rm SCN}_{\rm NSC} \right ) [{\rm HtmpO}] \right ]$ unlike its previously studied chloride analogue which is a cyclic tetramer. A new P21/n phase of di‐isopropylammonium chloride, derivative of the previously described P212121 and P21 forms, is reported, together with descriptions of protonated salts of the other hindered unidentate bases 2,6‐lutidine (as the chloride salt), quinoline (as the perchlorate, trifluoroacetate, hexachlorostannate and bisulfate salts) and 2‐quinaldine (as the chloride (anhydrous and monohydrate) and hexachlorostannate salts), all displaying arrays derivative of ion‐pair formation (extended by anion‐anion hydrogen‐bonds as well in the bisulfate salt) and, in the case of the aromatic bases, dominated by parallel stacking.

Synthesis, Characterization and Molecular Structures of Yttrium Trifluoroacetate Complexes with O‐ and N‐Donors: Complexation vs. Hydrolysis

AbstractDehydration and complexation reactions of [Y(TFA)3(H2O)3] (1; TFA = O2CCF3) were investigated with O‐ and N‐donor ligands in order to obtain suitable precursors for MOD (Metal Organic Deposition). Anhydrous adducts such as [Y2(μ,η2‐TFA)4(η1‐TFA)2(OHC2H4OiPr)4] (3), [Y2(μ,η2‐TFA)4(η1‐TFA)2(OHC2H4OC2H4OMe)2] (4), or [Y(TFA)3(triglyme)] (5) were isolated. The reactions with N‐donor ligands are more complex and afford mixed‐ligand derivatives such as [Y(TFA)3(H2O)2(LL)]m [LL = TMEDA (9), Me2NC2H4NMeC2H4NMe2 (10)] and, in the case of primary amines, yttrium oxohydroxo derivatives such as [H3O][Y3(μ3‐OH)(μ‐O)3(η1‐TFA)3(H2O)6(en)3] (6; en = NH2C2H4NH2). All complexes were characterized by elemental analysis, FT‐IR, and by single‐crystal X‐ray diffraction for 3, 4, and 6. All structurally characterized complexes contain on eight‐coordinate Y centers. Perfluorobutyrate and difluoroacetate derivatives were also prepared. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Effects of Trifluoroacetic Acid Modification on the Surface Microstructures and Photocatalytic Activity of Mesoporous TiO2 Thin Films

Enhancement of the photocatalytic activity of sol−gel-derived TiO2 thin films by a simple treatment with trifluoroacetic acid (TFA) was investigated. The thin films were characterized with N2 adsorption, Fourier transform infrared spectroscopy, UV−visible spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, X-ray diffraction, atomic force microscopy, and differential thermal analysis/thermogravimetry analysis. The photocatalytic activity of the thin films was evaluated by the photocatalytic decomposition of acetone in air. The results show that TFA is chemisorbed on the surface of the TiO2 films as a trifluoroacetate complex. The photocatalytic activity of modified TiO2 thin films is higher than that of unmodified TiO2 thin films, and the modified film treated at 250 °C shows the highest activity. This is ascribed to the fact that the TFA complex bound on the surface of TiO2 acts as an electron scavenger and, thus, reduces the recombination of photogenerated electrons and holes....

Synthesis, and crystal and molecular structures of the triflato and trifluoroacetato complexes of zinc, Zn(O 3SCF 3) 2(DME) 2 and [Zn(O 2CCF 3) 2(DME)] n

Anhydrous Zn(O 3SCF 3) 2 and Zn(O 2CCX 3) 2, X=F, Cl, Br were obtained in substantially quantitative yields from ZnO (or ZnEt 2 in the case of the bromide derivative) and a mixture of the corresponding acid and anhydride in heptane as medium. The reactions are rapid and moderately exothermic. Recrystallization of the triflate and trifluoroacetate complexes from dimethoxyethane (DME) produced single crystals of Zn(O 3SCF 3) 2(DME) 2 ( 1) and [Zn(O 2CCF 3) 2(DME)] n ( 2) suitable for X-ray diffraction studies. In both compounds zinc is hexacoordinated with a pseudo-octahedral geometry. Compound 1 is constituted by mononuclear molecules with terminal monodentate O 3SCF 3 ligands in trans position. A polynuclear chain structure was found for 2 with zinc atoms joined alternatively by triple and single carboxylato bridges, and with bidentate terminal DME.

Lanthanide Trifluoroacetate Complexes with 2-azacyclononanone. Thermal and kinetic studies

Ln(TFA)3⋅3AZA (Ln=La, Sm, Er; TFA=trifluoroacetate and AZA=2-azacyclononanone)compounds were synthesized and characterized by microanalytical procedures, IR spectroscopy, X-ray powder diffraction, and thermal analysis. A kinetic study using La, Sm and Er thermogravimetric curves was carried out aiming to proposing a mechanism for the thermal decomposition of such complexes.

Synthesis, properties of lanthanide trifluoroacetate complexes with 2-azacyclononanone and X-ray crystal structure of [Sm(CF 3COO) 3(AZA) 2·(H 2O)] 2·2AZA

Lanthanide trifluoroacetate complexes (Ln=La, Pr, Nd, Sm, Tb, Gd, Tb, Er) with 2-azacyclononanone (AZA) were synthesized and characterized. Complexometric analysis with EDTA and microanalytical procedures agree with the general formula Ln(TFA) 3 ·3AZA; thermogravimetric curves in N 2 dynamic atmosphere show their thermal stability until about 100 °C. The europium emission spectrum indicates more than one Eu 3+ symmetry centre. The X-ray structure of the samarium complex consists of dimeric species where the metal atoms are connected through four TFA bridges, a monodentate TFA, two O-bonded AZA ligands and a water molecule complete the coordination sphere about each samarium.

Synthesis and characterization of ruthenium, rhenium and titanium formate, acetate and trifluoroacetate complexes. Correlation of IR spectral properties and bonding types

New formate ( 1– 3; 4b, 6 and 7), acetate ( 8, 9) and trifluoroacetate ( 12, 13 and 15) complexes have been synthesized and characterized by elemental analysis and by IR and 1H and 13C NMR spectroscopies. New data or new synthetic procedures are provided for several known complexes ( 4a, 5, 19, 11 and 14). X-ray structural data for cis-Ru(bpy) 2(CO)(OCHO)(PO 2F 2) ( 4b) clearly identify the η 1-bound formate ligand bound to an octahedral ruthenium center and the data for fac-Re(CO) 3(PPh 3(OCOMe) ( 9) show an η 2-bound acetate ligand bound to an octahedral rhenium center. Infrared spectral data for four types of formate complexes, three bonding types of acetates and the two known types of trifluoroacetate ligands are discussed. Comparisons of the v OCO bands for the carboxylate ligands in all of the complexes show that these bands are useful in identifying the bonding type of each carboxylate ligand.

Kinetic and mechanistic investigation of the sequential hydrogenation of phenylacetylene catalyzed by rhodium (I) phosphine complexes of the type [Rh( η2-O 2Z)(PR 3) 2

Chelate complexes of the type [Rh( η 2-O 2Z)(PR 3) 2] (Z  CCH 3, CCF 3, C tBu, S(O)- p-C 6H 4-CH 3; PR 3  P iPr 3, PPh iPr 2, PPh 2 iPr) catalyze the hydrogenation of phenylacetylene in toluene solution at 60°C. Selectivities close to 100% are achieved for the hydrogenation of the alkyne to the alkene in the presence of the acetate and trifluoroacetate complexes [Rh( η 2-O 2CR) (P iPr 3) 2] (R  CH 3 1, CF 3 2). However, in other cases the reduction of the C-C double bond is also observed. In general, the selectivity of the hydrogenation reaction depends both on the phosphine and the anionic ligand. For the reduction of PhCCH catalyzed by 1, the addition of acetic acid leads to a dramatic decrease in the catalytic activity.

Acetonitrile complexes of diiridium Part 1. Isolation and characterization of the partially solvated cations [Ir 2(COD)(μ-form) 2(MeCN) 3] 2+ and [Ir 2(μ-form) 2(MeCN) 6] 2+ (COD = 1,5-cyclooctadiene, form = N, N′ -di- p-tolylformamidinate)

The partially solvated dinuclear complexes of the Ir 2 4+ core have been prepared from reactions of Ir 2(COD)(μ-form) 2 (O 2CCF 3) 2(H 2O) ( 1) with an alkylating reagent in acetonitrile. The compound [Ir 2(COD)(μ-form) 2(MeCN) 3][BF 4] 2 ( 2) is produced in essentially quantitative yields from reactions of 1 with an excess of Et 3OBF 4 in acetonitrile at room temperature whereas the thermal substitution product [Ir 2(μ-form) 2(MeCN) 6[BF 4] 2 ( 3) is isolated in ∼ 60% yield when the identical reaction is refluxed. Both compounds were fully characterized by IR and NMR spectroscopies, electrochemistry and X-ray crystallography. Single crystal X-ray data for 2·(CH 3) 2CO·(C 2H 5) 2O: monoclinic, P2 1/n, a = 19.534(6), b = 13.285(5), c = 22.113(4) A ̊ , β = 105.07(2)° , V = 5541(5) A ̊ 3, Z = 4, R = 0.074, R W = 0.107; 3: orthorhombic , Pbca, a = 21.670(6), b = 31.407(5), c = 14.543(6) A ̊ , V = 9898(9) A ̊ 3, Z = 8, R = 0.047, R W = 0.053 . The molecular structure of [Ir 2(COD)(μ-form) 2(MeCN) 3] 2+ is very similar to the parent trifluoroacetate complex and consists of an Ir-Ir unit bridged by two cis-tolylformamidinate groups, with one Ir atom ligated by a cyclooctadiene ligand in the equatorial plane and the other Ir center ligated by three MeCN molecules. The absence of an axial ligand on the Ir center bonded to the COD ligand and the short Ir-NCCH 3(axial) interaction of the other Ir atom (2.02(3) Å) support the formulation of the compound as a mixed-valence Ir(I)-Ir(III) species. The more symmetrical cation [Ir 2(μ-form) 2(MeCN) 6] 2+ is comprised of cis-tolyformamidinate ligands and six acetonitrile molecules that occupy four equatorial and two axial sites. In spite of the presence of two bridging ligands, the cations in 2 and 3 are considerably distorted from an eclipsed geometry with average torsional twist angles χ of 28 and 20°, respectively. The Ir-Ir distances of 2.717(2) Å for ( 2) and 2.601(1) Å for ( 3) are shorter than the corresponding metal-metal interaction in the parent complex Ir 2(COD)(μ-form) 2(O 2CCF 3) 2(H 2O) (2.774(1) Å) but are appreciably longer than the Ir-Ir bond length in the previously reported tetra-bridged molecule Ir 2(μ-form) 4 (2.524(3) Å). The 1H NMR spectral properties of the new compounds are in accord with retention of the solid state structures in solution ( C s symmetry for 2 and C 2 v symme in acetone at a glassy carbon electrode revealed quite different electronic properties for the two diiridium species, with 2 exhibiting behavior similar to the starting compound 1 which is in agreement with its description as a mixed-valence species. The syntheses and structures of the two new compounds in this study are discussed in light of their potential use as precursors to other metal-metal bonded Ir 2 4+ complexes including bridging carboxylase compounds and a fully solvated dinuclear cation.

Evidences of Electronic Effects in the Vibrational Spectra of Some Rhodium(II) Carboxylate Complexes

Abstract Abstract - A series of dirhodium tetracarboxylate complexes, containing triphenylphosphine as axial ligand was investigated by electronic and Raman spectroscopy, aiming to detect the influence of electronic effects of the carboxylate substituents on the v1[v(RhRh)] and v2[v(RhO)] Modes. When pairs of complexes with similar molecular weights are compared, as in the case of the cyclopentanecarboxylate and trifluoroacetate complexes, the striking difference in the inductive character of the two species results in substantial shifts of the v1 and v2 modes as a consequence of variations in the corresponding force constants rather than a simple mass effect as previously observed for non-substituted rhodium-carboxylates.

Electrochemical synthesis and structural characterization of bis(triphenylphosphine)copper(I) fluoroacetates

Bis(triphenylphosphine)copper(I) fluoroacetate complexes have been prepared by the electrochemical oxidation of copper metal in acetonitrile solutions of triphenylphosphine and mono-, di- and tri-fluoro-acetic acid respectively. Recrystallization from toluene yields unsolvated mononuclear complexes [Cu(PPh3)2(O2CCH3–nFn)], n= 1–3, which have been characterized by single-crystal X-ray crystallographic determinations. Crystals of the three complexes are isomorphous with the acetate complex (n= 0), crystallizing in the monoclinic space group P21/a with cell dimensions a≈ 18.0, b≈ 11.0 and c≈ 19.3 A and β≈ 120°. Residuals for the complexes with n= 1,2 and 3 were R= 0.077, 0.045 and 0.048 for 3677, 2789 and 3527 ‘observed’[I > 3σ(I)] reflections respectively. The bond distances Cu–P are 2.232(3), 2.222(3); 2.234(2), 2.219(2); and 2.235(2), 2.228(2)A with the corresponding P–Cu–P angles increasing from 135.0(1) to 135.8(1) to 136.7(1)°, this latter value being the largest recorded for [Cu(PPh3)2]+. The asymmetry of the co-ordination of the carboxylate group increases along the series with Cu–O distances of 2.144(6) and 2.363(7); 2.118(4), 2.465(6); and 2.113(4), 2.545(5)A for n= 1, 2 and 3 respectively. Crystallization of the difluoro- and trifluoro-acetate complexes from ethanol results in isomorphous orthorhombic Pb21a crystals (a≈ 22.2, b≈ 18.5, c≈ 9.0 A) with monodentate carboxylate and co-ordinated ethanol; the monofluoroacetate is unsolvated. For [Cu(PPh3)2(O2CCHF2)(EtOH)]R was 0.052 for 2090 ‘observed’ reflections with Cu–P 2.248(3), 2.236(3)A and P–Cu–P 120.5(1)°; Cu–O (carboxylate) is 2.074(8)A and Cu–O (ethanol) is 2.169(8)A. For [Cu(PPh3)2(O2CCF3)(EtOH)]R was 0.043 for 2350 ‘observed’ reflections, Cu–P being 2.248(2), 2.240(2)A and P–Cu–P 120.8(1)°; Cu–O (carboxylate) is 2.104(6)A and Cu–O(ethanol) is 2.160(6)A.

Preparation and characterisation of seven-co-ordinate trifluoroacetate and oxalate complexes of molybdenum(II) and tungsten(II)

The 1 : 1 reaction of sodium trifluoroacetate with either [MBr2(NCMe)(CO)2(PR3)2](M = Mo or W, PR3= PMe2Ph or PMePh2) or [MBr2(CO)2(PPh3)2](M = Mo or W) formed the mononuclear complexes [MBr(O2CCF3)(CO)2(PR3)2] containing a bidentate carboxylate ligand. Addition of a second equivalent of the carboxylate salt generated [M(O2CCF3)2(CO)2(PR3)2] in which the oxygen-donor ligands adopt one bidentate and one monodentate bonding mode. Single-crystal X-ray diffraction studies of [MoBr(O2CCF3)(CO)2(PPh3)2] confirm a 4 : 3 polytopal form. The treatment of [MBr2(NCMe)(CO)2(PR3)2](M = Mo, PR3= PMePh2; M = W, PR3= PMe2Ph or PMePh2) or [MBr2(CO)2(PPh3)2](M = Mo or W) with a suspension of sodium oxalate in acetone yielded the complexes [{MBr(CO)2(PR3)2}2(µ-C2O4)]. The tungsten species [{WBr(CO)2(PMe2Ph)2}2(µ-C2O4)] crystallises in two forms both of which contain a planar oxalate bridge linking two seven-co-ordinate metal centres, but have different 4 : 3 geometries. The triangular face of the polygon in each of the three structures is occupied by a bromine atom and two oxygens of a carboxylate group, and the quadrilateral face by pairs of carbonyl and phosphine ligands.

X-ray photoelectron spectra of Rh(III) trifluoroacetate

A study was made of the x-ray photoelectron spectra of Rh(I) and Rh(III) trifluoroacetate complexes. It was shown by using the Cls bond energies of the carboxylate carbon atom as a basis that bridging and monodentate coordination of the trifluoroacetate group could be distinguished with high resolution.