Tetrahydrofuran Complex Research Articles

Concerning the structures of Lewis base adducts of titanium(IV) hexafluoroisopropoxide.

The reaction of titanium(IV) chloride with sodium hexafluoroisopropoxide, carried out in hexafluoroisopropanol, produces titanium(IV) hexafluoroisopropoxide, which is a liquid at room temperature. Recrystallization from coordinating solvents, such as acetonitrile or tetrahydrofuran, results in the formation of bis-solvate complexes. These compounds are of interest as possible Ziegler-Natta polymerization catalysts. The acetonitrile complex had been structurally characterized previously and adopts a distorted octahedral structure in which the nitrile ligands adopt a cis configuration, with nitrogen lone pairs coordinated to the metal. The low-melting tetrahydrofuran complex has not provided crystals suitable for single-crystal X-ray analysis. However, the structure of chloridotris(hexafluoroisopropoxido-κO)bis(tetrahydrofuran-κO)titanium(IV), [Ti(C3HF6O)3Cl(C4H8O)2], has been obtained and adopts a distorted octahedral coordination geometry, with a facial arrangement of the alkoxide ligands and adjacent tetrahydrofuran ligands, coordinated by way of metal-oxygen polar coordinate interactions.

Redox Behavior of Cobalt-Phosphine Complexes vs Their Catalytic Activity in Organozinc Compound Formation: Background for Mechanistic Investigations.

Catalytic activity in arylzinc compound formation was studied for eight Co complexes with phosphines along with their redox properties for implementing the idea of rational design. It was found that Co(XantPhos)Cl2 and Co(N-XantPhos)Cl2 demonstrated distinct reversible CoII/CoI redox processes and acted as efficient catalysts of arylzinc compound formation. Meanwhile, for Co(DPEphos)Cl2, Co(dppf)Cl2, Co(dppb)Cl2, Co(PPh3)2Cl2, and Co(XantPhos)(Piv)2 (the latter one without the addition of LiCl), reversible redox processes were not observed. These catalysts did not act efficiently for the model process of organozinc compound formation. Co4(dppe)5Cl8 was the only exception, explained by a completely different structure (CoP4Cl and CoPCl3) of donor sets instead of CoP2X2 (X = Cl or O). The stability of complexes in tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) solutions was studied by UV-vis spectroscopy. Previously unknown X-ray structures for Co(XantPhos)(Piv)2, Co(N-XantPhos)Cl2, and {Co(DMF)6}{(CoCl3)2(dppb)} were determined. The use of pivalate counterions instead of chloride for Co(XantPhos)2+ led to a significant (ca. 20 times) increase of the kinetic solubility in THF compared to Co(XantPhos)Cl2, preserving high catalytic productivity upon the addition of LiCl. This allowed the latter to be efficiently used in combination with LiCl as the catalyst for arylzinc compound formation on a 2 g scale. The data obtained in this work can be regarded as experimental confirmation of the first and last stages of the plausible reaction pathway of arylzinc compound formation, involving CoII → CoI and CoI → CoII transformations, which could be a significant framework for further mechanistic investigations.

Synthesis and Spectroscopic and Luminescent Properties of Er, Yb and Lu Complexes with Cyano-Substituted Phthalocyanine Ligands

Based on 4,4′-[1,3/4-phenilenebis(oxy)]phthalodinitriles, the mixture of phthalocyaninates of various structures with rare-earth metals were obtained by template fusion method minimizing the side polymerization processes. Target monophthalocyaninates were isolated from the reaction mixture and purified using column and then gel permeation chromatography. The compounds were characterized by NMR, IR spectroscopy, mass spectrometry, and elemental analysis. The spectral properties were studied and the aggregation behavior of the synthesized Er, Yb, and Lu phthalocyaninates in chloroform, acetone, and tetrahydrofuran was determined. It has been shown that lutetium complexes with 3,4-dicyanophenoxyphenoxy ligands are the least stable and least resistant to aggregation in solution, while erbium and ytterbium phthalocyaninates proved to be stable in all studied media. The quantum yields and fluorescence lifetimes of the complexes in chloroform and tetrahydrofuran were calculated.

Medium-Dependent Crossover from the Red to Blue Shift of the Donor's Stretching Fundamental in the Binary Hydrogen-Bonded Complexes of CDCl3 with Ethers and Ketones.

Mid-infrared spectra for C-D···O hydrogen (H)-bonded binary complexes of CDCl3 with acetone (AC), cyclohexanone (CHN), diethyl ether (DEE), and tetrahydrofuran (THF) have been measured in the vapor phase at room temperature and in an argon matrix at 8 K. Remarkable matrix effect has been observed in each case with respect to the spectral shift of the donor group's stretching fundamental (ΔνC-D). In the case of complexes with AC and CHN, the sign of ΔνC-D changes from a few wavenumbers positive (blue shift) in the vapor phase to a few tens of wavenumbers negative (red shift) in the argon matrix. For the two ether complexes, although no apparent reversal in the sign of ΔνC-D occurs, but the magnitudes of the red shifts in the matrix are manifold larger, and the bands appear with large enhancement in transition intensity. The medium effect has been explained consistently in terms of the local hyperconjugative charge transfer interaction at the H-bonding sites of the complexes and its interplay with the H-bond distance that varies with the physical conditions of the medium. Under the matrix isolation condition, νC-D bands of CHN and THF complexes depict a large number of substructures, which has been interpreted in terms of matrix site effect as well as Fermi resonance enhancement of the fingerprint combination tones and trapping of more than one isomer of the complexes in the matrix sites.

Effects of fluorine and phenyl substituents on oxygen sensitivity and photostability of cyclometalated platinum(II) complexes

Fluorinated cyclometalated Pt(II) complexes Pt(Fppy)(acac) and Pt(dFppy)(acac), phenyl-substituted LA1, and 2,4-difluorophenyl-substituted LA2 were synthesized and applied as phosphorescent probes for monitoring of molecular oxygen compared with a model complex Pt(ppy)(acac). The phosphorescence of all Pt(II) complexes in tetrahydrofuran (THF) or immobilized in ethyl cellulose (EC) films was gradually quenched with the increase of the oxygen concentration. The intensity ratio I0/I9.61 and I0/I100 were used to evaluate oxygen sensitivities of the Pt(II) complexes in THF and in EC film, respectively. LA1 demonstrates the highest oxygen sensitivity with I0/I9.61 of 19.5 in THF, and I0/I100 of 13.5 and a KSVapp of 16.9 bar–1 in EC film. The photostability tests of the Pt(II) complexes immobilized EC films show that, phenyl and fluorine substituents have a synergistic effect on improving the photostability of the complexes. The LA2-immobilized EC film demonstrates the highest photostability and excellent operational stability (3.8 s on going from 100% N2 to 100% O2 and 4.5 s on going from 100% O2 to 100% N2), which is a potential photostable probe for online monitoring of molecular oxygen.

FTIR studies, DFT calculations and time domain reflectometry studies on tetrahydrofuran - methanol binary solutions.

FTIR signature of neat tetrahydrofuran (THF), methanol (MeOH) and their binary solutions at various molefractions (0.8:0.2 (THF:MeOH), 0.6:0.4, 0.4:0.6 and 0.2:0.8) have been recorded. Density Functional Theory (DFT) calculations have also been carried out on THF, MeOH multimers and possible THF-MeOH complex molecules. The results of FTIR studies and DFT calculations confirm the formation of 1:3 (THF:MeOH) and 1:4 complex structures with (MeOH)O - H⋯O(THF), (MeOH methyl)C - H⋯O(THF) and (THF methylene)C - H⋯O(MeOH) H-bond interactions. (MeOH)O - H⋯O(MeOH) homointeractions among the MeOH trimers and tetramers are stronger than the THF-MeOH heterointeractions in complexes. But, the stability of 1:4 complexes is more than that of the trimers and tetramers as inferred from the interaction energy values obtained by DFT calculations. Time Domain Reflectometry (TDR) study has also been carried out on the THF-MeOH binary solutions in the frequency range 10 MHz-30 GHz at 298 K. The results of dielectric studies have been correlated with that of FTIR studies and DFT calculations.

Synthesis and Electronic Structure of Neutral Square-Planar High-Spin Iron(II) Complexes Supported by a Dianionic Pincer Ligand.

Two square-planar high-spin FeII complexes bearing a dianionic pyridine dipyrrolate pincer ligand and a diethyl ether or tetrahydrofuran ligand were synthesized and structurally characterized, and their electronic structures were elucidated by a combined spectroscopic and computational approach. In contrast to previous examples, the S = 2 ground states of these square-planar FeII complexes do not require an overall anionic charge of the compounds or incorporation of alkali metal cations. The tetrahydrofuran complex exhibits an equilibrium between four- and five-coordinate species in solution, which was supported by 1H NMR and 57Fe Mössbauer spectroscopy and comparison to a structurally characterized five-coordinate pyridine dipyrrolate iron bis-pyridine adduct. A detailed computational analysis of the electronic structures of the four- and five-coordinate species via density functional theory provides insight into the origins of the unusual ground state configurations for FeII in a square-planar ligand field and explains the associated characteristic spectroscopic parameters.

Correction to “Process Safety Considerations for the Use of 1 M Borane Tetrahydrofuran Complex under General Purpose Plant Conditions”

Correction to “Process Safety Considerations for the Use of 1 M Borane Tetrahydrofuran Complex under General Purpose Plant Conditions”

Intermolecular dissociation energies of hydrogen-bonded 1-naphthol complexes.

We have measured the intermolecular dissociation energies D 0 of supersonically cooled 1-naphthol (1NpOH) complexes with solvents S = furan, thiophene, 2,5-dimethylfuran, and tetrahydrofuran. The naphthol OH forms non-classical H-bonds with the aromatic π-electrons of furan, thiophene, and 2,5-dimethylfuran and a classical H-bond with the tetrahydrofuran O atom. Using the stimulated-emission pumping resonant two-photon ionization method, the ground-state D 0(S 0) values were bracketed as 21.8 ± 0.3 kJ/mol for furan, 26.6 ± 0.6 kJ/mol for thiophene, 36.5 ± 2.3 kJ/mol for 2,5-dimethylfuran, and 37.6 ± 1.3 kJ/mol for tetrahydrofuran. The dispersion-corrected density functional theory methods B97-D3, B3LYP-D3 (using the def2-TZVPP basis set), and ωB97X-D [using the 6-311++G(d,p) basis set] predict that the H-bonded (edge) isomers are more stable than the face isomers bound by dispersion; experimentally, we only observe edge isomers. We compare the calculated and experimental D 0 values and extend the comparison to the previously measured 1NpOH complexes with cyclopropane, benzene, water, alcohols, and cyclic ethers. The dissociation energies of the nonclassically H-bonded complexes increase roughly linearly with the average polarizability of the solvent, (S). By contrast, the D 0 values of the classically H-bonded complexes are larger, increase more rapidly at low (S), but saturate for large (S). The calculated D 0(S 0) values for the cyclopropane, benzene, furan, and tetrahydrofuran complexes agree with experiment to within 1 kJ/mol and those of thiophene and 2,5-dimethylfuran are ∼3 kJ/mol smaller than experiment. The B3LYP-D3 calculated D 0 values exhibit the lowest mean absolute deviation (MAD) relative to experiment (MAD = 1.7 kJ/mol), and the B97-D3 and ωB97X-D MADs are 2.2 and 2.6 kJ/mol, respectively.

Synthesis of <i>ansa</i>-Fluorenylamidotitanium(tetrahydrofuran) Complex and Its Catalytic Ability for Polymerization of Olefins

Synthesis of <i>ansa</i>-Fluorenylamidotitanium(tetrahydrofuran) Complex and Its Catalytic Ability for Polymerization of Olefins

Rapid Metal‐Free Formation of Free Phosphines from Phosphine Oxides

AbstractA rapid method for the reduction of secondary phosphine oxides under mild conditions has been developed, allowing simple isolation of the corresponding free phosphines. The methodology involves the use of pinacol borane (HBpin) to effect the reduction while circumventing the formation of a phosphine borane adduct, as is usually the case with various other commonly used borane reducing agents such as borane tetrahydrofuran complex (BH3⋅THF) and borane dimethyl sulfide complex (BH3⋅SMe2). In addition, this methodology requires only a small excess of reducing agent and therefore compares favourably not just with other borane reductants that do not require a metal co‐catalyst, but also with silane and aluminium based reagents.magnified image

CdS thin films deposition by AACVD: effect of precursor type, decomposition temperature and solvent

Hexagonal cadmium sulfide (CdS) thin films were deposited on glass substrates by aerosol assisted chemical vapour deposition (AACVD) using cadmium(II) dithiocarbamate and xanthate complexes in tetrahydrofuran (THF) and mixed solvents (THF + chloroform) at 400 and 450 °C. The surface morphology and size of the CdS films determined using scanning electron microscopy, showed the formation of films of various morphologies depending on the precursor, the deposition temperature and solvent used. An increase in temperature resulted in an increase in particle size and a change in morphology with the formation of CdS films with distorted structures. The CdS films showed an overall blue shift in their absorption band edge (2.35–2.49 eV) compared to bulk CdS. In dithiocarbamates, a slight blue shift was observed with a shift to higher wavelengths with the reduction of the carbon chain of the dithiocarbamate and an increase in temperature. Films from xanthate complexes showed a strong blue shift at both deposition temperatures. The use of mixed THF + chloroform solvent at 450 °C showed the formation of films with irregular structures compared to those deposited using THF solvent alone, indicating the role of the solvent in shape direction of the films formation. The elemental composition determined by energy dispersive X-ray spectroscopy measurements revealed a 1:1 (Cd:S) ratio in all the samples confirming the stoichiometry of the CdS films.

Effective poly(ethylene glycol) methyl ether grafting technique onto Nylon 6 surface to achieve resistance against pathogenic bacteria Staphylococcus aureus and Pseudomonas aeruginosa

Our study is focused on an efficient reduction of amide functional groups to secondary amine on Nylon 6 surface with borane–tetrahydrofuran (BH3–THF) complex, followed by N-alkylation with benzyl chloride (C6H5CH2Cl) which has been successfully used as a model system for further grafting of the reduced Nylon 6 surface by poly(ethylene glycol) methyl ether tosylate (Me-PEG-OTs). The amine-activated surface has been obtained by treatment of reduced Nylon 6 with n-butyllithium or tert-butyllithium in THF. Modified Nylon 6 has been found to be antibacterial particularly due to the presence of hydrophilic poly(ethylene glycol) methyl ether (H3C-PEG) chains. The surface modifications were successfully characterized by various techniques. Water contact angle and free surface energy analyses indicated a significant change in the surface morphology. It was further supported by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. Finally, antibacterial tests were performed against two pathogenic bacterial strains Pseudomonas aeruginosa (CCM 3955) and Staphylococcus aureus (CCM 3953).

Electrochemical Investigation of the Kinetics of Chloride Substitution upon Reduction of [Ru(porphyrin)(NO)Cl] Complexes in Tetrahydrofuran

AbstractThe front cover artwork is provided by the Shaw [Southern Illinois University Edwardsville (SIUE), USA] and Richter‐Addo groups [University of Oklahoma (OU), USA]. The image shows cartoons of species formed during cyclic voltammetry analysis of [Ru(porphyrin)(NO)Cl] in tetrahydrofuran. The initial redox‐induced reversible solvent‐for‐chloride metathesis is shown in the reaction at the top. Read the full text of the Article at 10.1002/celc.201701001.

Titanium(III, IV)-Containing Catalytic Systems for Production of Ultrahigh Molecular Weight Polyethylene Nascent Reactor Powders, Suitable for Solventless Processing-Impact of Oxidation States of Transition Metal.

Catalytic systems containing TiCl4 or TiCl3, THF, organomagnesium (n-Bu2Mg) and organoaluminum compounds capable of producing ultrahigh molecular weight polyethylene (UHMWPE) were developed. The resulting polymers were characterized by a molecular weight in the range of (1.8–7.8) × 106 Da and desirable morphology, suitable for modern methods of polymer processing—the solvent-free solid-state processing of superhigh-strength (tensile strength up to 2.1 GPa) and high-modulus (elastic modulus up to 125 GPa) oriented films and film tapes. The impacts of a THF additive, the oxidation state of the titanium atom, and the composition and nature of the nontransition organometallic compounds on the formation of catalytic systems for UHMWPE production were evaluated. The results indicate the suitability of individual titanium chloride tetrahydrofuran complex application for the formation of THF-containing catalytic systems. This approach also results in a significant increase in the system catalytic activity and mechanical properties of UHMWPE. The catalysts based on Ti(III) were inferior to systems containing Ti(IV) in productivity but were markedly superior in the mechanical properties of UHMWPE.

Electrochemical Investigation of the Kinetics of Chloride Substitution upon Reduction of [Ru(porphyrin)(NO)Cl] Complexes in Tetrahydrofuran

AbstractThe electrochemistry of several ruthenium porphyrin nitrosyl chloride complexes [Ru(por)(NO)Cl] have been examined in tetrahydrofuran (THF). The complexes undergo one‐electron irreversible reductions, which result in diffusion‐limited substitutions of the chloride ligands for THF. This chloride metathesis is reversible in the presence of added NBu4Cl, and equilibrium constants and rate constants for chloride loss have been estimated. These parameters correlate with the NO stretching frequencies of the parent complexes, with more electron‐donating porphyrin ligands favoring chloride loss from the reduced complexes. The [Ru(por)(NO)(THF)] products of the reductions can be detected by IR, EPR, and visible spectroscopies. These species undergo three further reductions, with good reversibility at scan rates >0.40 V s−1. The [Ru(por) (NO)(THF)]+/0 couples have also been determined, and the rate constants and equilibrium constants for recombination with chloride have been estimated. One‐electron reductions of the [Ru(por)(NO)Cl] complexes result in approximately 1018 enhancement of the rates of chloride loss.

Novel Dendritic PNP Chromium Complexes: Synthesis, Characterization, and Performance on Ethylene Oligomerization

Three dendritic PNP ligands with ethylenediamine, 1,4‐butanediamine, 1,6‐diaminohexane as bridged groups are synthesized in good yields, respectively. Three dendritic PNP chromium complexes (C1 – C3) are prepared with the ligands and chromium(III) chloride tetrahydrofuran complex (CrCl3(THF)3) as materials. The dendritic PNP ligands and the synthetic chromium complexes are fully characterized by spectroscopic and analytical methods. All chromium complexes activated with methylaluminoxane (MAO) exhibited moderate activities on ethylene oligomerization (7.90 × 104 – 2.15 × 105 g (mol Cr h)−1] and had better selectivity for C6 and C8 oligomer, reaching up to 81%. The chromium complex (C1) activated with diethylaluminium chloride (Et2AlCl) has higher catalytic activity than the chromium complex C1 activated with MAO, although the chromium complex (C1) activated with Et2AlCl had lower selectivity for C6 and C8 oligomer. The effects of solvent and reaction parameters on ethylene oligomerization are also studied using the chromium complex C1 as pre‐catalyst and MAO as co‐catalyst. Under optimized conditions ([complex] = 2 μmol, Al/Cr = 500, 25 °C, 0.9 MPa ethylene, 30 min), the catalytic activity of complex C1 in toluene is 2.15 × 105 g (mol Cr h)−1 and the selectivity for C6 and C8 oligomer is 36.76%. In addition, the structure of complexes significantly affects both the catalytic activity and the selectivity on ethylene oligomerization.

A photoactive layer in photochromic glazing

Different approaches have been studied to evaluate the efficiency of the photoactive layer in a photochromic (PC) device. The studied device combines materials typically used in dye-sensitized solar cell (DSSC) and an electrochromic (EC) layer of WO3. First, we examine if the dye could be attached directly to the EC layer forming an efficient photoactive layer to colour the PC device. Further, different TiO2 layers have been coated on the EC layer to enhance dye loading and two different sol-gel TiO2 layers and the post-treatment of the EC layer with a titanium(IV) chloride tetrahydrofuran complex have been studied. The dye loading of different photoactive layers and their efficiencies in DSSC have been evaluated and discussed with regard to the performance of the PC devices. The results confirmed that the dye could be attached to the WO3 layer, but that the voltage of the DSSC is too low to colour the device. To realize a functioning PC device, the addition of TiO2 is necessary. The best performance (deep and fast colouration) is obtained for a PC device with a TiO2 sol-gel layer; the solar transmittance of the PC device decreases from 57% to 7.5% in under three minutes. According to our knowledge, this is the first study of the impact of the photoactive layer on the photochromic glazing's response.

Process Safety Considerations for the Use of 1 M Borane Tetrahydrofuran Complex Under General Purpose Plant Conditions

The safe handling of 1 M borane tetrahydrofuran complex (BTHF) in the context of storage and shipping has been well-characterized in literature. However, its safe use within the context of general purpose plant conditions is not discussed in detail. This article evaluated the thermal stability of BTHF within the context of general purpose plant equipment at near reflux and explored the diborane evolution–BTHF temperature relationship utilizing reaction calorimetry and headspace mass spectroscopy. In addition, a review of the autoignition temperature (AIT) for diborane reported in literature was performed, and new data were generated using the current ASTM (E659) standard. The testing showed that the AIT of pure diborane in air is 136–139 °C. An enhanced basis of safe operation for using BTHF in general purpose plant was established.

Cationic polymerization of glycidol

Polymerization of glycidyl alcohol induced by boron trifluoride tetrahydrofuran complex (BF3 ∙ THF) in ethylene glycol dimethyl ether (DME) and in the presence of BF3–water or BF3–glycerol catalyst system was studied. Under any of the conditions employed, the reaction gave water-soluble oligoether with polydispersity of ~1.1. It was shown by mass spectrometry that during polymerization in DME, DME is incorporated into the polymer and glycidol polymerization gives the alkyl-ether. According to calculations for glycidol polymerization in the presence of hydroxy compounds, the calculated number-average degrees of polymerization were higher than the experimental values both in the presence of water and with glycerol; this may be attributable to initiation of new molecules on the hydroxy group of the unreacted monomer.