Bu 4N Research Articles

Preparation, crystal structure and spectroscopic characterization of nickel(II) complexes with dithiocarbimate derivated of sulfonamides

This work describes the syntheses of three compounds containing [Ni(RSO 2N CS 2) 2] 2− anions: (Bu 4N) 2[Ni(CH 3CH 2SO 2N CS 2) 2] ( 1), (Bu 4N) 2[Ni(4-IC 6H 4SO 2N CS 2) 2] ( 2) and (Bu 4N) 2[Ni(2,5-Cl 2C 6H 3SO 2N CS 2) 2] ( 3). They were obtained in the crystalline form by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate (RSO 2N CS 2K 2) with nickel(II) chloride hexahydrate in methanol/water. Elemental analyses were consistent with the proposed formulae. UV–Vis and IR data are consistent with the formation of nickel–sulfur diamagnetic planar complexes. The 1H NMR and 13C NMR spectra showed the expected signals for the tetrabutylammonium cation and the dithiocarbimate moieties. Single crystal structure analyses showed that 1 crystallizes in the monoclinic space group P2 1/ n, 2 crystallizes in the monoclinic space group P2 1/ c and 3 crystallizes in the triclinic space group P 1 ¯ . In these compounds the Ni atom is coordinated to four S atoms in a distorted square plane geometry due to the asymmetric bidentade chelation by each ligand.

Synthesis, spectroscopic studies and crystal structure of a polyoxoanion cluster incorporating para-bromophenylimido ligand, (Bu 4N) 2[Mo 6O 18(NC 6H 4Br- p)

An organic–inorganic hybrid compound, (Bu 4N) 2[Mo 6O 18(NAr)] (Ar = p-BrC 6H 4) has been synthesized via the DCC dehydrating protocol of the reaction of [α-Mo 8O 26] 4− with 4-bromoaniline hydrochloride in anhydrous acetonitrile, which has been characterized by UV–Vis spectra, 1H NMR and single crystal X-ray diffraction study. By comparing the UV–Vis spectra, which were used to monitor the reaction, the optimum preparative condition for this compound was also determined. This compound crystallizes in the monoclinic space group P2 1/ n, which is featured in a terminal para-bromophenylimido group linked to an Mo atom of a hexamolybdate cluster by a Mo–N triply bond. In addition, there are π–π dimerization of the neighboring cluster anions though the parallel aromatic rings in their crystals.

Reactions of Tp–Os nitrido complexes with the nucleophiles hydroxide and thiosulfate

The reaction between TpOs(N)Cl 2 ( 1) [Tp = hydrotris(1-pyrazolyl)borate] and aqueous ( n Bu 4N)(OH) in THF- d 8 forms the nitrosyl complex TpOs(NO)Cl 2 ( 5) among other products, suggesting an initial hydroxide attack at the nitrido ligand. In contrast, the reaction of the acetate complex TpOs(N)(OAc) 2 ( 2) with NaOH in Me 2CO/H 2O yields the osmium bis-hydroxide complex TpOs(N)(OH) 2 ( 3), which has been structurally characterized by single-crystal X-ray diffraction. Acetate for hydroxide exchange could occur by ligand substitution or by nucleophilic attack at the carbonyl carbon of the acetate ligands (saponification). Reacting 2 with Na 18OH in H 2 18O/CD 3CN yields predominantly doubly 18O-labeled TpOs(N)( 18OH) 2 ( 3- 18 O 2 ) and unlabeled acetate, by ESI/MS and 13C{ 1H} NMR. This indicates that hydroxide reacts by substitution rather than by attack at the ligand. The reaction of 2 with the softer nucleophile thiosulfate occurs at the nitrido ligand, giving the thionitrosyl complex TpOs(NS)(OAc) 2 ( 4). Reacting 4 with NaOH in (CD 3) 2CO/D 2O also generates the bis-hydroxide complex 3.

Voltammetric studies of polyoxometalate microparticles in contact with the reactive distillable ionic liquid DIMCARB

The voltammetry of the polyoxometalate salts [Bu 4N] 4[SiW 12O 40] (α, β, γ* isomers), [Bu 4N] 4[S 2W 18O 62] (α, γ* isomers) and [Bu 4N] 4[S 2Mo 18O 62] (α isomer) has been studied in the “distillable ionic liquid” DIMCARB (a mixture of adducts, both ionic and neutral, of dimethylamine and carbon dioxide). Dissolution of these salts tended to be slow and the anions, except [α-SiW 12O 40] 4−, reacted with DIMCARB. However, high quality voltammograms were obtained from microparticles of the salts adhered to a glassy carbon electrode in contact with DIMCARB. Rapid dissolution of the reduced forms of each of the polyoxometalate anions provided reversible potential data. The higher basicity of the more highly reduced anions promoted interactions with the acidic solvent component of this medium. Comparison of reversible potentials indicated that the polarity of DIMCARB is similar to CH 3CN, but smaller than that of conventional non-volatile ionic liquids and water.

Oxidative nucleophilic substitution of hydrogen in nitroarenes with phenylacetic acid derivatives

Oxidative nucleophilic substitution of hydrogen (ONSH) in nitroarenes with carbanion of isopropyl phenyl acetate gives various products depending on the conditions and oxidant. The reaction carried out in liquid ammonia and KMnO 4 oxidant gives iso-propyl α-hydroxy-α-nitroarylphenylacetates formed via hydroxylation of the initial ONSH products. In some cases additionally dimeric, trimeric and tetrameric products are formed. In THF and Bu 4N +MnO 4 − or DDQ oxidants simple ONSH products are formed whereas oxidation by dimethyl dioxirane (DMD) gave iso-propyl hydroxyaryl phenyl acetates. The dimeric and trimeric products are apparently formed via coupling of nitrobenzylic radicals generated in course of oxidation with nitrobenzylic carbanions of the ONSH products.

A trifluoromethyl substituted organoimido derivative of the hexametalate cluster: Synthesis, crystal structure and bioactivity of [Mo 6O 17(NAr) 2] 2− (Ar = o-CF 3C 6H 4)

The hexamolybdate cluster has been functionalized with fluorine-containing aromatic amine by the DCC ( N, N′-dicyclohexylcarbodiimide) dehydrating protocol and a novel bifunctionalized arylimido derivative of hexamolybdate bearing the electron-withdrawing trifluoromethyl group, (Bu 4N) 2[Mo 6O 17(NAr) 2] (Ar = o-CF 3C 6H 4), has been prepared. Complete assignments were achieved for the title compound by elemental analysis, IR, 1H NMR, UV/visible and single-crystal X-ray diffraction analyses. The preliminary agricultural biological activity test indicated that it has some herbicidal and insecticidal activities.

A new arylimido derivative of polyoxometalate (Bu 4N) 2[Mo 6O 17(NAr) 2] [Ar = 2,6-(CH 3) 2C 6H 3]: Synthesis, structure and physicochemical properties

A novel bifunctionalized arylimido derivative of hexamolybdate, (Bu 4N) 2[Mo 6O 17(NAr) 2] [Ar = 2,6-(CH 3) 2C 6H 3] ( 1), in which the two 2,6-dimethylaniline groups are bounded to hexamolybdate at the cis positions, was synthesized by a facile reaction of α-octamolybdate with 2,6-dimethylaniline using DCC as a dehydration agent. The existence of strong non-typical C–H⋯O hydrogen bonds plays an important role in crystal structure stabilization of compound 1. The results of fluorescence spectra show that the formation of a covalent bond between 2,6-dimethylaniline molecule and hexamolybdate could efficiently quench the fluorescence intensity of 2,6-dimethylaniline molecule, with a fluorescence quencher efficiency of 87.7%. Thermal analysis results indicate that two substituted 2,6-(CH 3) 2C 6H 3 molecules bonding to the same cluster dissociated at different temperature, in well agreement with the different Mo N bond length in compound 1. The electrochemical behavior of modified 1-CPE has been studied in detail. Compared with the conventional polyoxometalate (POM)-modified electrode, 1-CPE presents a merit of remarkable stability over 500 cycles due to the insolubility of the POM nanoparticles, which is especially important for practical applications.

Catalytic selective oxidation of benzyl alcohols to aldehydes with rhenium complexes

The system ( n Bu 4N)ReO 4 5/PhIO/CH 2Cl 2, T = 298 K catalyses effectively and with total selectivity the anaerobic oxidation of a range of primary substituted benzyl alcohols ( o-, m-, p-X-C 6H 4-CH 2OH, X = H, Me, MeO, Cl, NO 2, CF 3) to the corresponding aldehydes; in contrast, it is unreactive towards secondary benzyl and aliphatic (primary and secondary) alcohols. This may prove of interest in synthetic organic transformations, when several alcoholic functionalities are present in the same molecule.

A linear bifunctionalized organoimido derivative of hexamolybdate: Convenient synthesis and crystal structure

A new disubstituted imido derivative [Bu 4N] 2[Mo 6O 17(NAr) 2] ( 1) (Ar = 2,4-(CH 3) 2C 6H 3), has been synthesized under a mild and convenient reflux reaction of [Bu 4N] 2[Mo 6O 19], 2,4-dimethylaniline, and DCC, and characterized by IR spectroscopy, elemental analysis, UV–vis absorption spectroscopy, and single-crystal X-ray diffraction. The most interesting characteristic of 1 is that its anion segment is linear and centrosymmetric with two imido groups occupying two terminal positions of hexamolybdate in an unusual trans fashion. This is the first trans-bis(imido)hexamolybdate prepared via a convenient synthetic route.

Biomimetic oxidation of Hantzsch 1,4-dihydropyridines with tetra- n-butylammonium periodate catalyzed by tetraphenylporphyrinatomanganese(III) chloride [Mn(TPP)Cl

Efficient oxidation of Hantzsch 1,4-dihydropyridines to their corresponding pyridine derivatives with (Bu 4N)IO 4 catalyzed by tetraphenylporphyrinatomanganese(III) chloride [Mn(TPP)Cl] is reported. This catalytic system shows high efficiency in the oxidation of 1,4-dihydropyridines at room temperature in the presence of imidazole.

The synthesis of functional derivatives of the [1-CB 9H 10] − anion by Brellochs reaction

Reactions of decaborane with various aldehydes in alkaline media were studied. The reactions with HCOH and 2-MeOC 6H 4CHO give the corresponding arachno-carboranes [6-R- arachno-CB 9H 13] − (R = H, C 6H 4-2-OMe), whereas the reactions with C 6H 5CHO, 4-BrC 6H 4CHO, 4-MeCONHC 6H 4CHO, and 2-SC 4H 3CHO result in the nido-carboranes [6-R- nido-CB 9H 11] − (R = C 6H 5, C 6H 4-4-Br, C 6H 4-4-NHCOMe, 2-SC 4H 3). Both the arachno- and nido-carboranes can be easily oxidized with elemental iodine in an alkaline aqueous solution giving the corresponding closo-derivatives [2-R- closo-2-CB 9H 9] −. These closo-2-isomers, under heating in solution, undergo rearrangement to more thermodynamically favorable closo-1-isomers [1-R- closo-1-CB 9H 9] −. The structure of (Bu 4N)[1-(4-BrC 6H 4)-1-CB 9H 9] was determined using single crystal X-ray diffraction.

The role of protons in cyclohexene oxidation with H 2O 2 catalysed by Ti(IV)-monosubstituted Keggin polyoxometalate

The effect of the number of protons in the Ti(IV)-monosubstituted Keggin polyoxometalate Na 5 − n H n PTiW 11O 40 ( n = 1–5; Ti-POM) on its catalytic behaviour in cyclohexene (CyH) oxidation with aqueous H 2O 2 in MeCN is reported. It has been found that Ti-POMs with n = 2–5 catalyse efficiently CyH oxidation to yield trans-cyclohexane-1,2-diol as the main reaction product, while Ti-POM containing only one proton shows lower activity in CyH oxidation and produces allylic oxidation products, 2-cyclohexene-1-ol and 2-cyclohexene-1-one, along with comparable amounts of the corresponding epoxide and diol. The obtained results strongly support homolytic oxidation mechanism for CyH oxidation in the presence of the monoprotonated Ti-POM and heterolytic oxygen-transfer mechanism in the presence of Ti-POMs having two and more protons. The 31P and 183W NMR studies revealed that Ti-POMs are stable towards at least 100-fold excess of H 2O 2 and the high catalytic activity of Ti-POMs with n = 2–5 is not due to the formation of lower nuclearity species. The addition of one equivalent of H + to the monoprotonated peroxo complex [Bu 4N] 4[HPTi(O 2)W 11O 39] ( I, 31P NMR in MeCN: −12.40 ppm) results in the formation of the diprotonated titanium peroxo species [H 2PTi(O 2)W 11O 39] 3− ( II, 31P NMR in MeCN: −12.14 ppm). This peroxo species can also be obtained by adding an excess of H 2O 2 to Na 5 − n H n PTiW 11O 40 ( n = 2–5) in MeCN. The presence of the second proton in the peroxo species is a crucial factor determining the capability of II to oxidise alkenes via heterolytic oxygen transfer mechanism. Both 31P NMR and GC–MS studies corroborated that II reacts with CyH producing trans-cyclohexane-1,2-diol as the main reaction product, whereas I is not reactive towards CyH under stoichiometric conditions.

Synthesis, structural determination and magnetic properties of a heterobimetallic Cu IIRe IV complex containing a macrocyclic ligand

Reaction of the rhenium(IV) compound, [Bu 4N] 2ReCl 4ox, with the highly unsaturated tetraazabismacrocyclic copper(II) complex cation [CuCuL] 4+ (L = 6,13-Bis(dodecylaminomethylidene)-1,4,8,11-tetraazacyclotetradeca-4,7,11,14-tetraene) produced a new kind of heterobimetallic compound: [CuCuL][ReCl 4ox] 2 · 2DMF in which [ReCl 4ox] 2− anions and [CuCuL] 4+ cations are linked by electrostatic forces. The crystal structure of this compound was determined at 173(2) K. It crystallizes triclinic, space group P 1 ¯ , with a = 9.441(4), b = 11.032(5), c = 15.261(7) Å, α = 89.05(1)°, β = 88.93(1)°, γ = 77.09(1)°, Z = 1, R 1 = 0.0557, wR 2 = 0.1332. The magnetic behavior of this compound has been investigated over the temperature range 1.72–300 K. The compound behaves as a ferrimagnetic Cu IIRe IV bimetallic, chain with intrachain antiferromagnetic coupling.

Ion association and solvation of perchlorate salts in N, N-dimethylformamide and N, N-dimethylacetamide : A dielectric relaxation study

The results of dielectric relaxation experiments on solutions of LiClO 4, NaClO 4 and Bu 4NClO 4 in N, N-dimethylformamide (DMF), and N, N-dimethylacetamide (DMA), performed at 25°C in the frequency range 0.2≤ ν/GHz≤89 are presented. For all electrolytes, a solute relaxation process due to ion pairs is observed in addition to the solvent relaxation. The alkali salts form predominantly solvent-shared ion pairs in DMF and DMA, whereas contact ion pairs are observed for Bu 4NClO 4. In all cases, the rate of ion-pair formation is nearly diffusion-controlled. Effective solvation numbers were deduced from the solvent dispersion amplitude. Data suggest that the anion–solvent interactions are weak, whereas the alkali ions form a well-defined primary solvation shell. Interestingly, irrotational bonding of solvent molecules by Bu 4N + is observed, possibly due to steric interactions.

Electro- and magneto-electrochemistry of zeolite Y- and MCM-41-associated bipyrylium ion

The electrochemical response of bipyrylium bication [1,4-bis(3,5-diphenyl-4-pyrylium)phenylene] associated with Y and MCM-41 aluminosilicates (BTP@Y and BTP@MCM, respectively) is described using polymer-film electrodes immersed into Et 4N + + MeCN and Bu 4N + + MeCN electrolytes. BTP@MCM provides a solution-like response in all electrolytes consisting in two successive strongly comproportionation mediated one-electron reduction processes near to +0.05 and −0.12 V vs. Ag|AgCl. The response of BTP@Y in Bu 4N + + MeCN is restricted to a unique reduction process near to −0.40 V, while in Et 4N + + MeCN, it differs significantly: here, two reduction processes at −0.22 and −0.36 V appear. This response suggests the presence of different boundary-associated topological redox isomers for which no significant comproportionation reaction occurs. Under the application of a static magnetic field, the electrochemical response of BTP@MCM remains almost unchanged while that of BTP@Y in contact with Et 4N + + MeCN is sensitive to changes in the orientation and strength of the external magnetic field. Such magnetoelectrochemical effects are consistent with the idea that different boundary-associated orientation isomers of BTP@Y exist.

Pd-PVP colloid as catalyst for Heck and carbonylation reactions: TEM and XPS studies

Pd-PVP colloid (stabilized with polyvinylpyrrolidone) with a diameter of 19.8 nm in [Bu 4N]Br medium catalyzes Heck coupling of bromobenzene with butyl acrylate and methoxycarbonylation of iodobenzene reactions. Oxidative addition of PhI or PhBr to Pd-PVP as the first step of a catalytic reaction was confirmed by TEM and XPS measurements. TEM studies showed significant reduction of Pd nanoparticle size after their reaction with PhX (X = I, Br) and [Bu 4N]X (X = Cl, Br, I). The biggest shift of the center of nanoparticle size distribution, from 19.8 nm to 7.6 nm, was found when Pd-PVP reacted with PhI and [Bu 4N]Br. The formation of [Bu 4N] 2[Pd(Ph)Br 3]- and [Bu 4N] 2[PdBr 4]-type complexes in that system was evidenced by XPS and UV–vis spectra.

Highly efficient utilization of H 2O 2 for oxygenation of organic sulfides catalyzed by [γ-SiW 10O 34(H 2O) 2] 4−

Remarkable efficiency of hydrogen peroxide utilization is reported for oxygenation of four organic sulfides catalyzed by a divacant lacunary silicotungstate, (Bu 4N) 4[γ-SiW 10O 34(H 2O) 2] ( 1 ), under mild conditions. The addition of imidazole, phosphate, or carboxylates significantly enhances the rate of organic sulfide oxygenation. Most notably, use of 1 and imidazole, both at 1% molar concentration, resulted in the quantitative conversion of phenylsulfide to sulfoxide with 1 equiv of H 2O 2 in 3 h, and to sulfone with 2 equiv of H 2O 2 in 6 h.

Tetrabutylammonium phosphomolybdate on fluorapatite: an efficient solid catalyst for solvent-free selective oxidation of sulfides

A new synthetic method of sulfoxides and sulfones using solvent-free oxidations of sulfides with urea–hydrogen peroxide complex (urea–H 2O 2) and tetrabutylammonium phosphomolybdate catalyst on fluorapatite ((Bu 4N) 3[PMo 12O 40]/FAp). In the solid-phase system the oxidations of aromatic and alkyl sulfides proceeded at 4–25 °C and the corresponding sulfoxides or sulfones were selectively obtained in good yields by controlling the amount of urea–H 2O 2.

Ferrimagnetic, bimetallic chain systems: [Ni(tetren)]ReCl 6 and [Ni(tetren)]ReCl 6·CH 3OH where tetren=tetraethylenepentamine

Reaction of nikiel (II) chloride with tetraethylenepentamine (tetren) and tetrabutylammonium hexachlororhenate [Bu 4N] 2ReCl 6 produced a new kind of binuclear compounds: [Ni(tetren)]ReCl 6 ( 1) and [Ni(tetren)]ReCl 6·CH 3OH ( 2) in which [ReCl 6] 2− anions and [Ni(tetren)] 2+ cations are held united by electrostatic forces. The magnetic behaviour of 1 and 2 has been investigated over the temperature range 1.7–300 K. Compound 1 behaves as a ferrimagnetic Ni II Re IV bimetallic, one-dimensional (1D) chain with intrachain antiferromagnetic coupling. A hysteresis loop characteristic of a soft magnet has been obtained. Compound 2 shows weak antiferromagnetic interactions within Ni II–Re IV units.

Asymmetric synthesis of enantiomerically pure 4-aminoglutamic acids via methylenedimerization of chiral glycine equivalents with dichloromethane under operationally convenient conditions

We found that simple stirring of a biphasic mixture of the Ni(II) complex of glycine Schiff base 2 solution in dichloromethane with 30% aqueous NaOH in the presence of PT catalyst n Bu 4N +Br − at room temperature for 24 h results in the formation of diastereo- and enantiomerically pure Ni(II) complex 3 , containing (2 S,4 S) 4-aminoglutamic acid, in high chemical yield. The procedure described in this communication represents a synthetically efficient method for the asymmetric synthesis of 4-aminoglutamic acid on large scale.