Exploring Alkylated Ferrocene Sulfonates as Electrocatalysts for Sulfide Detection

Alkylated ferrocene sulfonate compounds, 1,1′‐dimethyl ferrocene sulfonate, t‐butyl ferrocene sulfonate, ethyl ferrocene sulfonate, and n‐butyl ferrocene sulfonate are explored for the electrocatalytic detection of sulfide at a boron‐doped diamond electrode. Voltammetric interrogation of the ferrocene sulfonate compounds is investigated to determine oxidizing potentials, diffusion coefficients and responses towards sulfide. In the latter case, measurement of the electrocatalytic rate constants by means of chronoamperometry indicates a high electrocatalytic activity (ca. 10³ M^?1 s^?1) towards sulfide.     

Synthesis, structural characterization and electrochemical study of 1,1′-ferrocenylene labeled amino acids

Unsymmetrical 1,1′-disubstituted ferrocenes bearing an amino acid moiety and a conjugated electron density controlling substituent were synthesized conveniently starting from 1,1′-ferrocenedicarbaldehyde. The novel ferrocene amino acid derivatives were completely characterized from their MS, ¹H NMR and ¹³C NMR spectra. Their electrochemical behavior was studied by cyclic voltammetry. Their formal redox potentials E_f were slightly influenced by the nature of the amino acid and mainly by the kind of the ethenyl substituent. Furthermore all the (Z)-isomers exhibited a slight anodic shift compared with the corresponding (E)-isomers.     

Synthesis, NMR, IR spectroscopic and X-ray study of novel [pyridazin-3(2H)-one-6-yl]ferrocenes and related ferrocenophane derivatives. Study on ferrocenes. Part 14

On treatment with glyoxylic acid and hydrazine hydrate, 1,1′-diacetylferrocene was converted into the separable mixture of 1,1′-bis [pyridazin-3(2H)-one-6-yl]ferrocene and the hydrazone as well as the azine of 1-acetyl-1′-[pyridazin-3(2H)-one-6-yl]ferrocene. Successful cyclizations of 1,1′-bis[pyridazin-3(2H)-one-6-yl]ferrocene resulting in a series of novel ferrocenophanes containing heterocyclic units were performed under phase transfer- and homogeneous catalytic (RCM) conditions by the application of versatile dialkylating agents and second generation Grubbs’ catalyst, respectively. The structures were determined by mass spectrometry, IR, ¹H and ¹³C NMR spectroscopy including 2D-COSY, HMQC and HMBC measurements. The solid phase structure of a dimer product with π-stacking interaction was revealed by X-ray analysis.     

Chemical investigation of the bitter substances of the fruit of Lonicera caerulea

Esters of malic and citric acids have been isolated from an ethyl acetate fraction of an ethanolic extraction ofLonicera caerulea L.: dibutyl malate (I), 4-butyl 1-methyl malate (II), 1-butyl 4-methyl malate (III), tributyl citrate (IV), 1,5-dibutyl citrate (V), 1,1-dibutyl citrate (VI), 1,5-dibutyl 1-methyl citrate (VII), 1,1-dibutyl 5-methyl citrate (VIII), 1-butyl citrate (IX), 1-butyl citrate (X), 1-butyl 1,5-dimethyl citrate (XI), and 1-butyl 1,5-dimethyl citrate (XII). Compounds (I-IV, VII, VIII, XI, and XII) had a bitter taste and were the main components of the bitter substances of the fruit ofLonicera caerulea. The structures of compounds (I-XII) were established on the basis of their¹H and¹³C NMR spectra, by FAB mass spectrometry and chromato-mass spectrometry.Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Sverdlovsk Institute of the National Economy. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 338–342, May–June; 1989.     

A specific change of the electronic and 1C NMR spectra and redox potentials in 1,n-dithia[n]ferrocenophanes. A novel interaction between the sulphur atom and the ferrocene nucleus

Of the 1,n-dithia[n]ferrocenophanes prepared from disodium 1,1′-ferrocenedithiolate and polymethylene dibromides, the ferrocenophane with n = 7 showed the largest shift in the electronic and ¹³C NMR spectra and the largest decrease of the redox potential. This can be interpreted by a new type of stereoelectronic interaction between the sulfur atom and the ferrocene nucleus.     

Formation of intramolecular hydrogen bonds in heterodisubstituted ferrocene diamides with a secondary and a tertiary amido group: X-ray structure of 1′-(N′-butyl-carbamoyl)-morpholino ferrocenecarboxamide

Various unsymmetrically substituted ferrocene 1,1′-diamides have been synthesized via homogeneous catalytic carbonylation starting from 1,1′-diiodoferrocene. The unique features observed in the ¹H NMR and IR spectra of the compounds bearing a secondary and a tertiary amido group are explained by the formation of an internal hydrogen bond between the substituents. Addition of chloride ions (as a tetrabutylammonium salt) into the solutions of these compounds results in spectroscopic changes due to the formation of intermolecular hydrogen bonds between the ferrocene diamide and the anion. The solid state structure of 1′-(N′-butyl-carbamoyl)-morpholino ferrocenecarboxamide (1a) has also been determined by X-ray crystallography. A strong intramolecular H-bond between the NH group of the N′-butyl-carbamoyl moiety and the CO of the tertiary amido group was observed.     

Stereochemical studies—XXV: Conformational equilibria of 2-substituted 1,1-dialkylcyclohexanes

The positions of the conformational equilibria in a series of 1,1,2-trisubstituted cyclohexanes have been determined by ¹H NMR. The gauche-interaction of substituents in the 1,1-dimethyl series are, in general, very close to those of monosubstituted cyclohexanes. However, in the spiro-compounds 5 and 6 the equatorial conformers are somewhat destabilized by gauche-interactions though still enthalpy preferred. In contrast, the enthalpy preferred conformer in the 1,1-diethyl series is the axial one.     

Synthesis of symmetrically and unsymmetrically 3,5-dimethylbenzyl-substituted 1,1′-ferrocene diamines

1,1′-Ferrocene diamides have shown remarkable efficacy as supporting ligands for electrophilic metal centers. While different substituents have been used, most ferrocene diamines are employed as dianionic precursors, thus limiting the possible scope and reactivity of these metal complexes. The use of a 3,5-dimethylbenzyl (xylyl) substituent allowed the successful synthesis of tri- and tetra-substituted ferrocene 1,1′-diamines, providing monoanionic and neutral pro-ligands. In addition, an unsymmetrically disubstituted 1,1′-ferrocene diamine was obtained containing both the 3,5-dimethylbenzyl and t-butyldimethylsilyl substituents.     

Radical alternating copolymerization of vinyl ethers

New alternating equimolar copolymers of electrophilic trisubstituted ethylenes, methyl 3-phenyl-2-cyanopropenoate and 2-phenyl-1,1-dicyanoethene, with ethyl, n-butyl, i-butyl, t-butyl, 2-chloroethyl, and phenyl vinyl ethers were prepared by free radical initiation. Chemical compositions of the copolymers are 1 : 1 in broad ranges of monomer ratios. The copolymerization rate of both electrophilic monomers with the vinyl ethers increase in the series 2-chloroethyl > ethyl > phenyl > n-butyl > i-butyl > t-butyl. These variations in the reactivity of the vinyl ethers are discussed in terms of their preferred conformations in donor-acceptor complexes with electrophilic trisubstituted ethylenes. © 1993 John Wiley & Sons, Inc.     

Ferrocenophanes with Interannular Nitrogen–Gallium Bridges. 1,3,2‐Diazagalla‐[3]Ferrocenophanes and an 1‐Aza‐3‐Azonia‐2‐Gallata‐[3]Ferrocenophane. Synthesis and Structure

1,1′‐Bis(trimethylsilylamino)ferrocene reacts with trimethyl‐ and triethylgallium to give the μ‐[ferrocene‐1,1′‐diyl‐bis(trimethylsilylamido)]tetraalkyldigallanes. These were converted into the 1,3‐bis(trimethylsilyl)‐2‐alkyl‐2‐pyridine‐1,3,2‐diazagalla‐[3]ferrocenophanes, of which the ethyl derivative was characterized by X‐ray structural analysis. Treatment of gallium trichloride with N,N′‐dilithio‐1,1′‐bis(trimethylsilylamino)ferrocene affords μ‐[ferrocene‐1,1′‐diyl‐bis(trimethylsilylamido)]tetrachlorodigallane along with bis(trimethylsilyl)‐2,2‐dichloro‐1‐aza‐3‐azonia‐2‐gallata‐[3]ferrocenophane as a side product, and both were structurally characterized by X‐ray analysis. The solution‐state structures of the new gallium compounds and aspects of their molecular dynamics in solution were studied by NMR spectroscopy (¹H, ¹³C, ²⁹Si NMR).     

De-aggregation of polyfluorene derivative by blending with a series of poly(alkyl methacrylate)s with varying sidegroup sizes

A polyfluorene derivative of the PPV, poly(9,9′-n-dihexyl-2,7-fluorenedilvinylene-alt-1,4-phenylenevinylene), with a strong tendency to aggregation was blended with several members of a series composed by poly(alkyl methacrylate)s with the following substituents in the ester position: methyl, ethyl, isopropyl, isobutyl, n-butyl, and cyclohexyl. The de-aggregation effect in blends was studied by steady-state photoluminescence spectroscopy using several blend compositions. The efficiency of each dispersing phase was discussed in terms of the polymer miscibility, controlled by interaction parameters between the polyfluorene and every poly(alkyl methacrylate)s, here described using Hildebrand solubility parameters.     

Synthesis, optical, and electrochemical properties of conjugated oligomers derived from 4-bromo-4-(n-butyl)-2,2-biphenyl

The synthesis, optical, and electrochemical properties of semi-conducting co-oligomers of biphenyl/oligothiophenes and homo-oligophenylenes derived from a precursor 4-bromo-4^′-(n-butyl)-2,2^′-biphenyl, which was synthesized by a direct alkylation from 4,4^′-dibromo-2,2^′-biphenyl using n-butyl lithium, are reported.     

Studies on ferrocene derivatives. Part 12. Substituent effects for the disproportionation, synproportionation and ligand exchange reactions of t-butylferrocenes

Summary The disproportionations and synproportionations of t-butylferrocenes and the ligand exchanges between the ferrocenes and benzene have been studied. The steric effects of the t-butyl groups were found to significantly affect the ratio of the products obtained. In these reactions, aluminium chloride attacks and abstracts the cyclopentadienyl ring. As a result, the ferrocene molecule decomposes into two fragments. The aluminium chloride selectively attacks the least sterically hindered cyclopentadienyl ring. The steric effect for a cyclopentadienyl ring bearing two t-butyl groups is substantial and inhibits attack by aluminium chloride. The product therefore contains the cyclopentadienyl ring which has the higher steric hindrance (i.e. the 1,3-di-substituted cyclopentadienyl ring). T. Hayashi, Y. Okada and T. Yamashita, Nippon Kagaku Kaishi, 900 (1995) (Part 11 of this series).     

The synthesis and properties of ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione and -2-one) derivatives

The t-butyl and bis(t-butyl) derivatives of hexathia[3.3]ferrocenophane were prepared from the corresponding trithia[3]ferrocenophanes. The former was a mixture of chair-chair and chair-boat isomers, and the latter existed only chair-boat isomer. The hexathia[3.3]ferrocenophanes were led to the tetrathiols with LiAlH₄, which allowed to react with 1,1′-thiocarbonyldiimidazol to give the corresponding ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione) derivatives. Mono t-butyl and unsubstituted analogs were prepared in a similar manner. The X-ray structural determination showed that these derivatives adopted the conformation in which the 1,3-dithiol-2-thione rings were heaped on top of each other. In the crystal of ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione), the molecules packed so as to put the axis of molecule in order and to overlap one another above and below. The desulfurizative coupling of the ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione) derivatives was unsuccessful.     

Alkylation of acylmetalates with alkyl halides to prepare Fischer carbene complexes: an improved protocol

Alkoxy Fischer carbene complexes have been synthesized by alkylation of lithium acylmetalates with alkyl halides in the presence of catalytic amount (5-10 mol %) of n-tetrabutylammonium bromide (n-Bu₄NBr) restricting the temperature below 55 °C to minimize decomposition of the product. The reaction occurs in a biphasic condition involving water and alkyl halide. The effect of cesium on this alkylation reaction has been studied. The presence of a radical quencher, di-tert-butyl phenol, neither affects the yield nor leads to the formation of dimer of di-tert-butyl phenol, which rules out the possibility of radical pathway mechanism. The kinetic study and the ¹H NMR spectra of products suggest an S_N2 pathway particularly involving alkyl halides.     

Synthesis and mass spectrum of 3-(3′-pyridinyloxymethyl)pyridine and polarography of its dialkyl diquaternary salts

3-(3′-Pyridinyloxymethyl)pyridine is prepared by reaction of 3-hydroxymethylpyridine with 3-bromopyridine and converted to the 1,1′-dimethyl and 1,1′-diethyl diquaternary salts with alkyl iodides. The salts are reduced polarographically at a potential (E_o) of about - 1.02 to - 1.10 V in the pH range of 5.5-8.5.     

The effect of substituents and operating conditions on the electrochemical fluorination of alkyl phenylacetates in Et3N·4HF medium

Selective electrochemical fluorination of alkyl phenylacetates (Ph-CH₂-COOR, where R is methyl, ethyl, n-propyl, n-butyl, i-propyl and sec-butyl) under galvanostatic conditions were reported in Et₃N·4HF medium. Preparative electrolysis experiments were carried out both in pre-electrolysed dry Et₃N·4HF and the same electrolyte medium without pre-electrolysis. Very little hydrolysed fluorinated products were obtained in pre-electrolysed medium where as significant quantities of hydrolysed products leading to fluorinated phenylacetic acid were obtained from Et₃N·4HF without pre-electrolysis. Under optimum experimental conditions up to 87% selectivity of monofluoro ester could be achieved. Difluoro alkyl phenylacetate, monofluoro and difluoro phenylacetic acids were the other predominant side products obtained. The hydrolysis appears to be initiated by tautomeric transformation of proton after the initial electro oxidative formation of the cation radical. ¹⁹F as well as ¹H NMR spectroscopy have been employed to identify the minor constituents formed during the electro oxidative process.     

A new P-chiral bisphosphine, 1,1′-bis[(t-butyl)methyl-phosphino]ferrocene,as an effective ligand in catalytic asymmetric hydrosilylation of simple ketones

The asymmetric hydrosilylation of simple ketones was catalyzed by a rhodium complex with a P-chiral bisphosphine, 1,1′-bis[(t-butyl)methylphosphino]ferrocene, to give optically active alcohols with enantiomeric excesses of up to 92%.     

N-substitution of polybenzimidazoles: Synthesis and evaluation of physical properties

Series of N-substituted polybenzimidazoles (PBI) were synthesized using selective alkyl groups with varying bulk and flexibility, viz., methyl, n-butyl, methylene trimethylsilane and 4-tert-butylbenzyl. PBI-I based on 3,3′-diaminobenzidine (DAB) and isophthalic acid and PBI-BuI based on DAB and 5-tert-butyl isophthalic acid were chosen for N-substitution. Structural characterizations of substituted polymers by FT-IR and ¹H NMR revealed elimination of hydrogen bonding. Evaluation of their physical properties revealed that N-substitution rendered better solvent solubility in common organic solvents, more open polymer matrix, but reduced thermal properties in comparison to their respective parent PBI. 4-tert-butylbenzyl, methylene trimethylsilane or n-butyl group substituted polymers were soluble even in chlorinated solvents (CHCl₃ and TCE). Substantial variations in gas permeability of inert gases, He and Ar and attractive P_He/P_Ar selectivity, especially after methyl group substitution depicted potential of these materials for gas separation.     

Synthesis and Spectroscopic Characterization of Some Ferrocenyl Schiff Bases Containing Pyridine Moiety and Their Complexation with Cobalt,Nickel, Copper and Zinc

Three novel ferrocenyl Schiff base ligands containing pyridine moiety have been formed by 1:2 molar condensation of 1,1′‐diacetylferrocene with 2‐aminopyridine, 2‐amino‐5‐picoline or 2‐amino‐5‐chloropyridine, respectively. The ligands are 1,1′‐bis[1‐(pyridyl‐2‐imino)‐ethyl]ferrocene (L1); 1,1′‐bis[1‐(5‐methyl‐pyridyl‐2‐imino)ethyl]ferrocene (L2) and 1,1′‐bis[1‐(5‐chloropyridyl‐2‐imino)ethyl]ferrocene (L3). These ligands form 1:1 complexes with Co(II), Cu(II), Ni(II) and Zn(II) ions. The prepared ligands and their complexes have been characterized by IR, ¹H NMR, ¹³C NMR, UV/Vis spectra as well as elemental analysis. The spectral data of the ligands and their complexes are discussed in connection with the structural changes due to complexation.