Lewis Acid BF3 Research Articles

1,3-Dipolar [3 + 2] Cycloaddition of N-α-Diphenyl Nitrone to the Benzene Ligand in Reductively Activated [Mn(CO)3(η4-C6H6)]-

We have established that the η4-benzene ligand in [Mn(CO)3(η4-C6H6)]- undergoes a stepwise cycloaddition reaction with N-α-diphenyl nitrone in a sequence in which the Lewis acid BF3 is first used to induce nucleophilic addition of [Mn(CO)3(η4-C6H6)]- to N-α-diphenyl nitrone. The BF3 can be removed by protonation to give the neutral intermediate [Mn(CO)3{η5-C6H6CHPhN(Ph)OH}], which can be cyclized by addition of excess KH and PPNCl to drive ring closure and form containing an isoxazolidine ligand that is the [3 + 2] cycloaddition product of the nitrone with benzene.

“Latent” Trialkylphosphine and Trialkylphosphine Oxide Organogelators Activated by Brønsted and Lewis Acids

The weak bases tri-n-alkylphosphines (R3P, where R = C14H29, C18H37) and phosphine oxides (R3PO) have been reacted with the strong Lewis acid BF3 to form zwitterions (R3P+−OBF3- or R3P+−BF3-) and w...

Characterization of residues formed by anhydrous hydrogen fluoride etching of doped oxides

The byproducts in residue layers produced after etching doped oxide films with anhydrous hydrogen fluoride (HF) in a commercial gas phase wafer processing tool operated at atmospheric pressure and 55 °C have been characterized using transmission Fourier transform infrared (FTIR) spectroscopy. Approximately 4000 Å was etched from the borophosphosilicate glass (BPSG), borosilicate glass (BSG), and phosphosilicate glass (PSG) films, creating a condensed layer on the oxide surfaces during etching. The primary etching products in the condensed layer on BPSG were found to be a mixture of boric acid B(OH)3, phosphoric acid H3PO4, and water. The etching products in the residue on PSG were H3PO4 and water. The reaction of boric oxide (B2O3) crystallites with water to produce B(OH)3 is thermodynamically favorable and should react further to boron trifluoride BF3 in the presence of HF. The formation of B(OH)3 rather than BF3 in the etching residue on BPSG indicates that a kinetic limitation exists due to either the relatively low HF exposure used or the chemistry within the mixed acid film. The etching product in the residue on BSG, which was exposed to a higher HF flux, was primarily boron trifluoride dihydrate BF3⋅2H2O. The condensed layer supports the etching of the Si–O matrix by concentrating the HF and water reactants close to the surface, which explains the enhancement in the etching rate when a condensed layer is formed. The etching products identified by FTIR could also play a direct role in the etching reaction since hydroxyl groups on the acids can activate Si–O bonds similar to water and the Lewis acid BF3 can attach to Si–O via the pair of electrons on the O atom.

A Lewis Acid-Base Computational Chemistry Exercise for Advanced Inorganic Chemistry

A computational chemistry exercise dealing with Lewis acids and bases has been developed for use in advanced inorganic chemistry courses. The exercise employs ab initio or semiempirical quantum mechanical calculations to investigate the adducts of the Lewis acids BH3, BF3, BCl3, AlH3, and AlCl3 with the Lewis bases NH3 and PH3. Adducts of BCl3 with pyridine, 3,5-dimethylpyridine, and 2,6-dimethylpyridine are also investigated. Binding energies, geometric changes upon adduct formation, structural reorganizational energies, and partial atomic charges are calculated. Factors influencing binding energies between Lewis acids and bases can be inferred from the results.

Chemistry of nickel tetrafluoropyridyl derivatives: their versatile behaviour with Brønsted acids and the Lewis acid BF3 †

Treatment of trans-[NiF(2-C5NF4)(PEt3)2] (C5NF4 = tetrafluoropyridyl) (1) with HCl effects the formation of the air stable chloride complex trans-[NiCl(2-C5NF4)(PEt3)2] (2). The reaction of 2 with excess HCl slowly yields 2,3,4,5-tetrafluoropyridine (4). On reaction of 4 with [Ni(COD)(PEt3)2], the C–F activation product trans-[NiF(2-C5NF3H)(PEt3)2] (5) is formed instantly. The bifluoride compound trans-[Ni(FHF)(2-C5NF4)(PEt3)2] (6) is obtained on treatment of 1 with Et3N·3HF. Reaction of 2 with HBF4 yields the binuclear complex [NiCl{μ-κ2(C,N)-(2-C5NF4)}(PEt3)]2 (7). The X-ray crystal structure of 7 reveals a “butterfly”-shaped dimeric complex with square-planar coordination at both nickel atoms, with Ni–N distances of 1.965(4) and 1.955(4) A and Ni–C distances of 1.884(5) and 1.875(5) A. Treatment of 1 with BF3·OEt2 in the presence of acetonitrile yields the cationic compound trans-[Ni(2-C5NF4)(NCMe)(PEt3)2]BF4 (8), while reaction of trans-[Ni(OTf)(2-C5NF4)(PEt3)2] (3) with NaBAr′4 and acetonitrile gives trans-[Ni(2-C5NF4)(NCMe)(PEt3)2]BAr′4 (9) [Ar′ = 3,5-C6H3(CF3)2]. The studies reported in this paper provide methods for the synthesis of tetrafluoropyridines substituted in the 2-position and demonstrate the behaviour of nickel derivatives with Bronsted acids and the Lewis acid BF3.

Ab Initio Study of Intramolecular Ring Cyclization of Protonated and BF(3)-Coordinated trans- and cis-4,5-Epoxyhexan-1-ol.

The potential energy surface for the rearrangement of cis- and trans-4,5-epoxyhexan-1-ol with acid and the Lewis acid BF(3) to five- and six-membered cyclic ethers has been investigated by ab initio methods. The transition structures involving both inversion and retention of configuration at the reaction center at the HF/6-31G and B3LYP/6-31G levels are characterized. The preference for furan formation over pyran is attributed to the more favorable O-C(ep)-O bond angles at the transition structures for furan formation. The torsional O-C(ep)-C(ep)-O angles associated with tetrahydrofuran and tetrahydropyran formation vary with structure and do not directly correlate with the preferred pathway.

Photoionization investigation of cluster formation in heterocyclic compounds and their reactions with acidic species

The formation of homogeneous molecular clusters by six different nitrogen-containing, heterocyclic (Het) compounds has been investigated using multiphoton ionization combined with time-of-flight mass spectrometry. The substances considered were pyridine, 3-picoline, 4-picoline, pyrazine, 2-methyl pyrazine, and pyridazine, and homogeneous clusters (Het) n with n ≤ 15 were observed. None of the clusters displayed sharp spectral features and consequently the information available was limited to mass spectra. In order to gain some information regarding the properties of these clusters, the effects of introducing the Lewis acids BF 3, BCl 3, and B(OH) 3 and also HF and HCl, into the free-jet expansion were investigated. The heterocyclic compounds listed above are all basic in character and consequently strongly bound complexes (donor–acceptor complexes) with these acids were expected to be formed. It was reasoned that a determination of the number of acidic molecules that attached themselves to a given cluster would give some insight into the structure of that cluster. The most extensive investigation was carried out with BF 3 and, surprisingly, not all the heterocyclics listed above formed mixed clusters with this Lewis acid under our experimental conditions. Our observations indicated the following: (1) the stability of the (Het) n homogeneous clusters and the (Het) n -(BF 3) m mixed clusters appears to be related to the pKa value associated with the heterocyclics involved; (2) under the conditions used in this work, the mixed clusters appear to be produced by the addition of BF 3 to homogeneous clusters that had already formed; and (3) the cations of mixed clusters in which n = m are unstable and hence not detected. The results obtained with the other acids generally confirmed these conclusions and showed that the stability of the cation of the mixed cluster is the main factor influencing its detection. Ab initio calculations were also carried out and the results obtained are in good agreement with the experimental observations. These calculations showed there appears to be several structures for the pyridine dimer with similar stability. Several of these structures have two nonequivalent heterocyclic nitrogen atoms, which may explain the experimental observation that mixed-clusters containing only one BF 3 molecule appeared to be preferentially formed.

Combined modifier/in situ derivatization effects on supercritical fluid extraction of polycyclic aromatic hydrocarbons from soil

Supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs) from a real environmental soil sample containing a high content of humic acids was enhanced by using modifier and in situ derivatization. The addition of 10 mol% methanol increased the ability of the supercritical CO 2 (recovery set to 100%) to displace PAHs from matrix active sites up to an average value of 145%. In situ derivatization was performed under dynamic SFE conditions using boron trifluoride (BF 3) in methanol as modifier. Comparing the results of the SFE extraction with methanol and with BF 3 in methanol showed that the addition of BF 3 increased the PAH recoveries further. Increasing BF 3 concentration gave higher extraction yields of PAHs. A second SFE of the same sample with CO 2–methanol improved the average extraction yield for only 2%, whereas a second SFE of a CO 2–methanol extracted sample with CO 2–methanol–BF 3 increased the average yield for 18%. Especially the recoveries of the penta- and hexacyclic PAHs were increased by the addition of BF 3. The results indicate that the strong Lewis acid BF 3 cleave humic substances of the matrix releasing aromatic acids in the extract which were detected by HPLC–diode array detection. As a result of this PAHs associated to the matrix were also released in the extract.

Lewis Acidic Borane Adducts of Pyridines and Stilbazoles for Nonlinear Optics

A series of neutral pyridyl adducts involving the strong Lewis acids BF3 and B(C6F5)3 has been prepared, and their second-order nonlinear optical coefficients (EFISH method) have been examined. The formation of the pyridyl−boron bond leads to enhancement of the dipole moments and second-order NLO coefficients (β and β(0)). Reactions of DMAP (4-Me2N−C5H4N) with BH3, BF3, and B(C6F5)3 give the corresponding neutral pyridine adducts DMAP·BH3 (orthorhombic, Pbca, a = 9.6914(7) A; b = 11.7173(9) A; c = 22.718(2) A; V = 1622.4(5) A3; Z = 8; p = 1.114 g cm-3), DMAP·BF3 (orthorhombic, Pbca, a = 10.430(3) A; b = 8.111(2) A; c = 20.295(7) A; V = 1717.0(9) A3; Z = 8; p = 1.470 g cm-3), and DMAP·B(C6F5)3 (orthorhombic, Pbca, a = 12.322(1) A; b = 20.556(2) A; c = 28.455(3) A; V = 7207.4(14) A3; Z = 8; p = 1.508 g cm-3). Reactions of Me2N−4-C6H4−CHCH−C5H4N, MeO−4-C6H4−CHCH−C5H4N, and Me2N−4-C6H4−C⋮C−C5H4N with BF3 and B(C6F5)3 result in materials that are highly luminescent and incorporate structural features that are ...

Convenient synthesis of 2,2-disubstituted-2,3-dihydro-1,4-benzodioxins from 2-substituted-2-hydroxy-2,3-dihydro-1,4-benzodioxins

Convenient syntheses of relatively rare 2,2-disubstituted-2,3-dihydro-1,4-benzodioxins from 2-substituted-2-hydroxy-2,3-dihydro-1,4-benzodioxins, as key synthetic intermediates, are reported. These new synthetic approaches require Lewis acid BF 3-Et 2O mediated nucleophilic substitution reaction or cyclization of suitable hydroxyphenols.

Molar mass distribution of polybutadiene synthesized with nickel‐based Ziegler‐Natta catalysts, II

AbstractCis‐1,4‐polybutadiene was produced by polymerization of 1,3‐butadiene using a catalyst system containing Ni(OOC8H15)2 and Al(C2H5)3 and the Lewis acids BF3 · O(C2H5)2 or TiCl4. The molar mass distributions (MMD) of the polybutadienes are investigated by means of size exclusion chromatography (SEC). The MMD's were fitted by a sum of Schulz‐Flory‐Functions (SFF). Taking into account that one kind of active species gives one SFF defined by molar mass averages, one comparable active species in both systems and one different were found. This way it was tried to find a relationship between the grown up of the active species depending on components and reactions conditions.

Reaction of three-coordinate phosphorus compounds with organophosphorus pseudohalogens 3. Phosphonium and phosphorane intermediates in the desulfurization and deoxygenation of bis(phosphinoyl) disulfides. Influence of Lewis acids on the reaction chemoselectivity

The reactions of bis(phosphinoyl) disulfides RR1P(O)S–S–P(O)RR11 with PIII compounds have been investigated and various mechanistic features have been elucidated by variable-temperature 31P NMR spectroscopy. These studies show that in most cases phosphonium intermediates [[graphic omitted]P(O)–S–[graphic omitted]–O–P(S)[graphic omitted]]5 and [[graphic omitted]P(S)–O–[graphic omitted] –O–P(S)[graphic omitted]]6 are involved. In cases where ligands on PIII increase the stability of the five-coordinate structures phosphorane intermediates are observed. In the isomerization 5→6, the mode of decomposition (desulfurization, deoxygenation or dealkylation) to give stable end products is influenced by electronic and steric factors. The presence of the Lewis acid BF3 influences considerably the stability of the transient species 5 and 6 and the chemoselectivity of the reaction.

Preparation, chemical reactions, and some physical properties of neptunium pentafluoride

The preparation of NpF 5 by reacting a solution containing NpF 6 − with the Lewis acid BF 3 in anhydrous HF is reported. The purity of NpF 5 was established by its Mössbauer spectrum, which showed only the presence of Np 5+. Thermal decomposition and some chemical reactions of NpF 5 are described. Debye-Scherrer powder data from NpF 5 appear similar to those obtained from α-UF 5, indexing as tetragonal with cell constants a = 6.5358(18) A ̊ and c = 4.4562(14) A ̊ . Photochemical irradiation of NpF 6 produced an amorphous material believed, but not confirmed, to be NpF 5.

Displacement of Lewis Acid Gases - PF5, BF3 and SiF4 from Their Ammonium, Alkali Metal and Pyridinium Fluorocomplexes by Sulphur Trioxide at Room Temperature

Abstract Lewis acid gases, PF5, BF3 and SiF4 are liberated from their ammonium, alkali metal and pyridinium fluorocomplexes, NH4PF6, NaPF6, KPF6, C5H5NHPF6, C5H5NHBF4 and (C5H5NH)2SiF6, when treated with sulphur trioxide at room temperature. The dissociated ammonium/alkali metal fluorides as well as the pyridinium fluoride react further with the excess sulphur trioxide to form the corresponding fluorosulphates. The products, Lewis acid gases and the fluorosulphates, have been 19 characterised by I. R., F NMR and wet chemical analysis. This is the first report of the synthesis of these gases from pyridinium fluorosulphate at room temperature in good yields.

Nonempirical SQM FF calculation of vibrational spectra for the acetonitrile molecule coordinated to Lewis acids BF3 and BCl3

In terms of SQM FF methods, nonempirical quantumchemical calculations of vibrational spectra for acetonitrile molecule coordinated to Lewis acids BF3 and BCl3 were carried out. Scaling factors were obtained from the conditions to reproduce vibrational spectra of CH3CN and CD3CN molecules. Contribution of the increase in the power force constant and the kinetic effect of the N→B bond to the shift of νCN and νCC under coordination has been determined.

The synthesis of fluorine‐containing porphyrins

AbstractThe synthesis of polyfluoroalkoxyl substituted tetrakisphenylporphyrin is reported. The reaction is carrying out using Lewis acid BF3·OEt2 as catalyst and p‐chloranil as oxidant. The yields of the porphyrins are about 30–40%.

ChemInform Abstract: Syntheses of Carba‐Analogues of Qinghaosu.

Abstract The syntheses of carba-analogues of qinghaosu 7, 8, 9 are first described. Arteannuic acid 11 was converted into key intermediate cyclic enol ether 14 in four steps. Reaction of 14 with paraformadehyde under the catalysis of Lewis acid BF 3 ·OEt 2 afforded 7 . Oxidation of 7 with RuO 4 gave 8 and 9 .

Syntheses of carba-analogues of qinghaosu

The syntheses of carba-analogues of qinghaosu 7, 8, 9 are first described. Arteannuic acid 11 was converted into key intermediate cyclic enol ether 14 in four steps. Reaction of 14 with paraformadehyde under the catalysis of Lewis acid BF 3·OEt 2 afforded 7. Oxidation of 7 with RuO 4 gave 8 and 9.

Derivates of 1,2-diborabenzene: II. (1,2-Dibora-3,5-cyclohexadiene)metal complexes. Crystal structure of (C 5Me 5)Rh(C 4H 4B 2Cl 2)

The 1,2-diboratabenzene derivative Li 2[C 4H 4B 2(NMe 2) 2] (I) reacts with various transition metal compounds to form sandwich and triple-decked complexes such as (C 6Me 6RuL (III), (C 5Me 5)RhL (IV), (μ-L)[Rh(COD)] 2 (V), NiL 2 (VI), Fe(CO)L 2 (VII), and Co 2(CO) 4L 2 (VIII), where L is the 1,2-bis(dimethylamino)-1,2-dibora3,5-cyclohexadiene ligand. Barriers to internal rotation around the BN bond are 48(1), 56(1), and 38(1) kJ/mol for III, IV, and V, respectively, while VII and VIII are rigid on the NMR time scale. Nucleophilic substitution reactions at boron were examined for the rhodium complex IV. The Lewis acids BF 3·OEt 2 and BCl 3 bring about substitution to give (C 5Me 5)Rh[C 4H 4B 2F(NMe 2 · BF 3)] (XI) and (C 5Me 5)Rh(C 4B 2Cl 2) (XII), respectively. Attempted substitution with Al 2Me 6 and with AlH 3 in THF effected a novel ring contraction to produce the borole complexes (C 5Me 5)Rh(C 4H 4BR) (XIII: R = Me; XIV: R = H); similarly, traces of air transform XII into (C 5Me 5)Rh(C 4H 4BCl) (XV). The structure of XII determined by X-ray diffraction confirms the η 6-bonding mode of the diboracyclohexadiene ligand.

Selective Conversion of 2-Mercaptoalkanols to Thiirans with Orthocarbonates

Abstract Tetraalkyl orthocarbonates 1 were demonstrated to serve as potent cyclodehydrating agents for 2-mercaptoalkanols 2 to give the corresponding thiirans in good yields in acid-catalyzed reactions in aprotic solvents. Effects of catalysts, solvents, and alkyl substituents of 1 were examined. Activity of the acid catalysts depended on their acidity (pKa), and the strong Lewis acid BF3·OEt2 also had high catalytic activity. Effects of solvents and alkyl substituents of 1 were little observed.