Difluoro Complex Research Articles

Bis(diiminate)-based boron difluoro complexes: effective synthon for bis(borenium) cations.

A series of boron difluoro bis(diiminate) complexes have been prepared and used to obtain triflate substituted fluoroborane complexes. The corresponding well-defined bis(borenium) cations were subsequently synthesized and structurally authenticated. We are also presenting the first experimental and theoretical study of bis(borenium) cations that are derivative of cationic borinic acid.

Thiazole Boron Difluoride Dyes with Large Stokes Shift, Solid State Emission and Room-Temperature Phosphorescence.

The small Stokes shift and weak emission in the solid state are two main shortcomings associated with the boron-dipyrromethene (BODIPY) family of dyes. This study presents the design, synthesis and luminescent properties of boron difluoro complexes of 2-aryl-5-alkylamino-4-alkylaminocarbonylthiazoles. These dyes display Stokes shifts (Δλ, 77-101 nm) with quantum yields (ϕFL ) up to 64.9 and 34.7 % in toluene solution and in solid state, respectively. Some of these compounds exhibit dual fluorescence and room-temperature phosphorescence (RTP) emission properties with modulable phosphorescence quantum yields (ϕPL ) and lifetime (τp up to 251 μs). The presence of intramolecular H-bonds and negligible π-π stacking revealed by X-ray crystal structure might account for the observed large Stokes shift and significant solid-state emission of these fluorophores, while the enhanced spin-orbit coupling (SOC) of iodine and the self-assembly driven by halogen bonding, π-π and C-H… π interactions could be responsible for the observed RTP of iodine containing phosphors.

Aryl C(sp2)-X Coupling (X = C, N, O, Cl) and Facile Control of N-Mono- and N,N-Diarylation of Primary Alkylamines at a Pt(IV) Center.

We present the first example of an unprecedented and fast aryl C(sp2)–X reductive elimination from a series of isolated Pt(IV) aryl complexes (Ar = p-FC6H4) LPtIVF(py)(Ar)X (X = CN, Cl, 4-OC6H4NO2) and LPtIVF2(Ar)(HX) (X = NHAlk; Alk = n-Bu, PhCH2, cyclo-C6H11, t-Bu, cyclopropylmethyl) bearing a bulky bidentate 2-[bis(adamant-1-yl)phosphino]phenoxide ligand (L). The C(sp2)–X reductive elimination reactions of all isolated Pt(IV) complexes follow first-order kinetics and were modeled using density functional theory (DFT) calculations. When a difluoro complex LPtIVF2(Ar)(py) is treated with TMS–X (TMS = trimethylsilyl; X= NMe2, SPh, OPh, CCPh) it also gives the corresponding products of the Ar–X coupling but without observable LPtIVF(py)(Ar)X intermediates. Remarkably, the LPtIVF2(Ar)(HX) complexes with alkylamine ligands (HX = NH2Alk) form selectively either mono- (ArNHAlk) or diarylated (Ar2NAlk) products in the presence or absence of an added Et3N, respectively. This method allows for a one-pot preparation of diarylalkylamine bearing different aryl groups. These findings were also applied in unprecedented mono- and di-N-arylation of amino acid derivatives (lysine and tryptophan) under very mild conditions.

Electrophilic Fluorination of Organoplatinum(II) Iodides: Iodine and Platinum Atoms as Competing Fluorination Sites

A series of diphosphine Pt(II) aryl iodo complexes were reacted with XeF(2) to cleanly produce the corresponding Pt(II) difluoro complexes and free iodoarenes. However, when aryl ligands bearing fluoro substituents in the ortho positions were used, the formation of the corresponding Pt(II) aryl fluoro complexes was observed in the reaction with XeF(2). In the case of the Pt-C(6)F(5) complex, the products of the fluoride-for-iodide exchange were the only products observed by means of (31)P and (19)F NMR spectroscopy. The experimental and theoretical studies suggest that the formation of iodine-fluorine bond may accompany this transformation. The plausible "I-F" species could be trapped by electron-richer organoplatinum complexes to give a Pt(IV) transient which subsequently eliminates the corresponding aryl iodide. Hence, in some cases a pathway involving an attack of XeF(2) at the iodo ligand of Pt(II) aryl iodo complexes to generate I-F species can be operative in addition to or instead of the XeF(2) attack at the metal center. Our DFT studies demonstrate that the electrophilic attacks of XeF(2) at both sites, platinum and iodide, can be competitive.

Complexation of Cm(III) with Fluoride in Aqueous Solution in the Temperature Range from 20 to 90 °C. A Joint TRLFS and Quantum Chemical Study

The formation of hydrated CmF2+ and CmF2+ species in aqueous solutions are studied in the temperature range of 20−90 °C at different fluoride concentrations and at constant ionic strength as well as at constant fluoride concentration and different ionic strengths by means of time-resolved laser fluorescence spectroscopy (TRLFS). The molar fractions of the Cm3+ aqua ion, CmF2+, and CmF2+ species are determined by peak deconvolution of the emission spectra. An increase of the mono- and difluoro complexes is observed with increasing fluoride concentration and/or increasing temperature. Using the specific ion interaction theory (SIT), the thermodynamic stability constants log K10 (CmF2+) and log K20 (CmF2+) as well as the values of Δε1 and Δε2 are determined as a function of temperature. The log K10 values increase from 3.56 ± 0.07 to 3.98 ± 0.06 and the log K20 values increase from 2.20 ± 0.84 to 3.34 ± 0.21 with increasing temperature from 20 to 90 °C. The value of Δε1 determined at 25 °C is in good agreement with literature data and shows a negligible temperature dependency in the studied temperature range. The value of Δε2 also shows only a moderate variation in the studied temperature range. The thermodynamic standard state data (ΔrHm0, ΔrSm0, ΔrGm0) are determined from the temperature dependence of the equilibrium constants at Im = 0 using the integrated Van’t Hoff equation. The fluorescence lifetime of the 6D′7/2(Cm3+) state is found to be constant at 63 ± 5 μs with increasing fluoride concentration. A model based on density functional theory (DFT) calculations is introduced to account for the additional quenching occurring through the near second sphere waters in the [Cm(H2O)8F]2+(H2O)18 complex.

ChemInform Abstract: The First Isolation and Crystal Structure of a Boron Difluoro Complex (Isoflavone Yellow). Biologically Active Intermediates Produced During Isoflavone Synthesis.

The yellow intermediate 4f produced during the reaction of the deoxybenzoin 3f with N,N′-dimethyl(chloromethylene)ammonium chloride in the presence of BF3·Et2O prior to the formation of the corresponding isoflavone was isolated for the first time and characterized by NMR, MS and single-crystal X-ray diffraction techniques. These yellow intermediates showed anticancer, nematicidal and mosquitocidal activities.

N-Heterocyclic carbene-containing ruthenium difluoro complexes and their reactivity towards BF3

Treatment of tetranuclear [RuF(-F)(CO)3]4 (1) with the free N-heterocyclic carbenes (NHCs), IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) and IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), followed by work-up in carbon tetrachloride leads to fluoride-bridge cleavage in 1 and the formation of the mononuclear octahedral complexes cis,cis,trans-[RuF2(CO)2(NHC)2] [NHC = IMes (2a), IPr (2b)], respectively. Complexes 2a and 2b can also be obtained by interaction of 1 with the corresponding imidazolium chloride, [-N(Ar)CHN(Ar)CHCH-]Cl (Ar = 2,4,6-Me3C6H2, 2,6-i-Pr2C6H3), in the presence of KOtBu. However, extension of this latter base-assisted approach to [-N(Ar)CHN(Ar)CHCH-]Cl (Ar = 2,6-Me2C6H3, 2,4,6-i-Pr3C6H2) results in halide exchange with the work-up solvent (CCl4) to generate cis,cis,trans-[RuCl2(CO)2(IMe)2] (3) and dinuclear [RuCl(mu-Cl)(CO)2(ITPr)]2 (4), respectively. Reaction of 2a with gaseous BF3 in dichloromethane and subsequent carbonylation affords in high yield monocationic [Ru(FBF3)(CO)3(IMes)2](BF4) (5), while with 2b, BF3 addition alone results in solvent exchange to yield dinuclear monocationic [Ru2(mu-Cl)3(CO)4(IPr)2](BF4)/(F) (6). Conversely, interaction of 2a and 2b with BF3.OEt2 in acetonitrile furnishes dicationic cis,cis,trans-[Ru(CO)2(NCMe)2(NHC)2](BF4)2 [NHC = IMes (7a), IPr (7b)]; in the case of 7a carbonylation gives [Ru(CO)4(IMes)2](B2F7)2 (8). Single crystal X-ray structures are presented for 3, 4, 5, 6 and 8.

Xenon Difluoride Induced Aryl Iodide Reductive Elimination: a Simple Access to Difluoropalladium(II) Complexes

Palladium(II) aryliodo complexes bearing chelating diphosphine ligands react with XeF2, giving iodoarene and rare palladium(II) difluoro complexes. The reaction is general with regard to the aryl group, with even C6F5-I undergoing facile reductive elimination from a Pd center.

Unexpected PtIIMigration between the Calixarene Oxygen Atoms

Reaction between the 1,3-bis(trimethylsilyl) ether of calix[4]arene and platinum(II) difluoro complexes unexpectedly results in the formation of the 1,2-bridging platinum(II) calixarene complex, which, upon treatment with 2 equiv of acyl chloride, reinstates the 1,3-disubstitution pattern in the calixarene moiety.

Difluoro Complexes of Platinum(II) and -(IV) with Monodentate Phosphine Ligands: An Exceptional Stability of d6 Octahedral Organometallic Fluorides

Complexes (R3P)2PtF2 were prepared by reaction of the corresponding diiodo precursors with AgF in dichloromethane. The intermediate formation of trans- and cis-(R3P)2Pt(I)F was also observed. All fluoro complexes demonstrate a strong preference for the cis-configuration (R = Ph or Et) unless a bulky phosphine ligand is used (R = i-Pr), in which case the trans complex was observed. The Pt(IV) difluoro compounds (R3P)2Ar2PtF2 were obtained by reacting the Pt(II) diaryl precursors with XeF2. The fluoro ligands are located in the trans-position relative to the aryl groups in the overall octahedral environment. The representative Pt(II) and Pt(IV) difluoro complexes were characterized by X-ray crystallography. All fluoro compounds react rapidly with chlorotrimethylsilane to give the corresponding chloro complexes. The Pt(IV) difluorides are remarkably stable in the C-C reductive elimination reaction, relative to their dichloro analogs which reductively eliminate diaryl within several hours at 45 degrees C in N-methylpyrrolidone. It was found that phosphine dissociation from the octahedral Pt(IV) complex is essential for the reductive elimination reaction to take place, the difluoro complex being kinetically stable even at 60 degrees C.

Toward Metal-Mediated C−F Bond Formation. Synthesis and Reactivity of the 16-Electron Fluoro Complex [RuF(dppp)2]PF6 (dppp = 1,3-Bis(diphenylphosphino)propane)

The five-coordinate fluoro complex [RuF(dppp)2]PF6 (1a) has been prepared by reacting [RuCl(dppp)2]PF6 (1b) with TlF (dppp = 1,3-bis(diphenylphosphino)propane). An X-ray investigation of 1a shows a distorted trigonal bipyramidal geometry (Y-shaped). The 16-electron complex 1a reacts with a number of donors, including CO, H2, and F-. The X-ray structure of trans-[RuF(CO)(dppp)2]PF6 (2aBPh4) suggests that the π-donor ability of the fluoro ligand is only slightly higher than that of chloride. The reaction of 1a with [Me4N]F gives cis-[RuF2(dppp)2] (3), a rare difluoro complex not stabilized by π-acidic co-ligands. The Ru−F bond of 1a is hydrogenolyzed upon reaction with H2 to give [RuH(η2-H2)(dppp)2]+. The coordinatively unsaturated complex 1a reacts with activated haloalkanes R−X (X = Cl or Br) in 1:1 molar ratio to give the fluorinated organic derivative and [RuX(dppp)2]+. The halide metathesis proceeds instantaneously and quantitatively with (E)-3-bromo-1,3-diphenylpropene and chlorotriphenylmethane. Substrate conversion decreases with decreasing substitution at the halogen-bearing carbon atom.

The first isolation and crystal structure of a boron difluoro complex (isoflavone yellow). Biologically active intermediates produced during isoflavone synthesis

The yellow intermediate 4f produced during the reaction of the deoxybenzoin 3f with N,N′-dimethyl(chloromethylene)ammonium chloride in the presence of BF3·Et2O prior to the formation of the corresponding isoflavone was isolated for the first time and characterized by NMR, MS and single-crystal X-ray diffraction techniques. These yellow intermediates showed anticancer, nematicidal and mosquitocidal activities.

Vibrational and Electronic Resonance Raman Effects in Tetraphenylporphyrinato Complexes of High-spin and Low-spin Iron(III)

A vibrational resonance Raman effect of the totally symmetric Fe - F stretching mode at 453 cm−1is observed for high-spin tetra-n-butylammonium di(fluoro)tetraphenylporphyrinatoferrate(III). Typical A-term scattering with a high intensity overtone progression is proposed to be due to coincidence of the excitation energy with a ‘trip-sextet’ transition at 21 000 cm−1. The complex salt crystallizes as a dichloromethane solvate in the monoclinic space group P12/n1 (No. 13): a = 12.287(3) Å, b = 12.381(4) Å, c = 20.761(5) Å,β = 105.05(2)°,Z = 4. The iron atom is in the centre of the slightly distorted porphyrinate core. The Fe - F distance is 1.907(2) Å, the averaged Fe - Npdistance 2.072(2) Å. There is no hydrogen bonding of the floride ligand to the cation or solvate. Contrary to the high-spin difluoro complex, a molecular electronic resonance Raman effect is detected for low-spin pyridine(cyano)- and -(thiocyanato( N )tetraphenylporphyrinatoiron(III) at 550 and 561/578 cm−1respectively. This Γ7 g→Γ8 gtransition is a consequence of the spin-orbit splitting of the2T2 gground state of low-spin FeIIIassuming octahedral symmetry. B-term scattering is active by excitation with 476.5 nm, effectively enhancing the intensity of non-totally symmetric electronic and vibrational transitions.

Potentiometrie Study of Magnesium Fluoro Complexes in Aqueous Solutions up to 473 K and 1 kbar

Abstract The formation of magnesium fluoro complexes in a hydrothermal fluorite-bearing model solution has been potentiometrically studied up to 473 K and 1 kbar at the ionic strength I = 1 m (NaCl), in order to estimate the competition with the formation of the lanthanide fluoro and fluorohydroxo complexes in such systems. No evidence of difluoro complex was found at p, T, [F- ] and pH conditions which are relevant to fluorite formation. The apparent formation constant Q, as well as the apparent thermodynamic data ΔG, ΔS and ΔH of MgF+ have been determined. The effect of pressure was found to be negligible. The competition with the lanthanide complexes becomes increasingly negligible with increasing T and in particular with increasing pH.

The prediction of the 19F NMR spectra of fluoro-substituted arenetricarbonylchromium complexes

The tricarbonylchromium complexes of the following derivatives of fluorobenzene have been prepared: 2,4- and 3,5-dimethyl-, 2,4,6-trimethyl-, 3,4- and 3,5-dimethoxy- and 4-methoxy-2-methylfluorobenzene, 4-fluorocumene,4- fluoro- N,N-dimethylaniline, 3-fluoro-2-methoxyaniline and 4-fluoro-2-methylacetophenone. Preparative, microanalytical, IR, UV-Vis and 1H and 19F NMR spectral data are presented for these new compounds. Both literature and new 19F NMR spectral data have been analysed for thirty-five monofluoro complexes and seven difluoro complexes. A statistical prediction method for both these types of complexes is presented with correlation coefficients of observed versus predicted line positions of 0.986 and 0.993, respectively.

ChemInform Abstract: Synthesis, Characterization, and Photobehavior of Macrocyclic Difluoro Complexes of Chromium(III).

AbstractThe complexes (I) and (II) are prepared with 85% and 62% yield by refluxing the corresponding macrocycles with trans‐(Cr(Py)4F2)ClO4 in methoxyethanol.

Synthesis, characterization, and photobehavior of macrocyclic difluoro complexes of chromium(III)

Synthese des complexes cis-[Cr(cyclane)F 2 ]ClO 4 et trans-[Cr(teta)F 2 ]ClO 4 . Le complexe cis est photoactif en solution aqueuse a temperature ordinaire. Proprietes de phosphorescence

Characterization of a unique electrochemical oxidation catalyst: the difluoro complex of iron(III) tetraphenylporphyrin

Characterization of a unique electrochemical oxidation catalyst: the difluoro complex of iron(III) tetraphenylporphyrin

Metal Complexes Coordinating Pyridine Derivatives. II. Circular Dichroism and Magnetic Circular Dichroism Spectra of Chromium(III) Complexes in the Region of Pyridine Ring Absorption Band

Abstract Dianionochromium(III) complexes coordinating (S)-N,N′-bis(2-pyridylmethyl)propylenediamine (abbrev. S-picpn) or (S)-1-(2-pyridyl)ethylamine (abbrev. S-pea) show CD spectra of a dispersion type in the region of pyridine ring absorption band. Utilizing the data of X-ray crystal structure analysis of Δ-cis-α-[CrCl2(S-picpn)]Cl, the difluoro complex shows the correct exciton CD sign pattern expected from a simple theory but the dichloro and dibromo complexes the inverse sign pattern. The latter fact is explained in terms of overlapping of the pyridine ring absorption band with the halogeno-to-chromium charge transfer band, referring to MCD spectra. The absorption and MCD bands appeared in the region 30–35×103 cm−1 for all the chromium(III) complexes are assigned to the spin-forbidden π→π* transition of the coordinated pyridine group.

Complex formation of trace elements in geochemical systems—I: Potentiometric study of fluord complexes of rare earth elements in fluorite bearing model systems

With regard to the assumption that thermodynamic processes such as complex formation and distribution equilibria of the rare earth elements (REE) are responsible for their fractionation during the mineralization of fluorites, the formation of the fluoro complexes of the REE has been studied. The investigation was carried out in 1 M NaCl-aqueous medium at 25°C and pH-rang ⩽ 5. From all the ligands to be considered at this pH-range only SO 4 2− participate to the complex formation. Within the REE-series the stability constant of the monofluoro complexes has a maximum at Tb and the decrease Tb to La is more than its decrease Tb to Lu. The stability constant of difluoro complexes, on the contrary, increases gradually from La to Lu.