Reaction of ferrocenylmethyl derivatives of silicon and germanium with methanol: Solvolysis of the metal-carbon bond in the presence of ferric ions

Nine ferrocenylmethyl derivatives of silicon and germanium were prepared and found to undergo methanolysis of their C---M (M = Si or Ge) bonds in the presence of ferric ions to give ferrocenylmethyl methyl ether. For this reaction, relative rate studies and polarographic studies of the pertinent ferrocene derivatives were carried out to obtain some insight into the reaction mechanism. The substituted ferricenium ion intermediate which is formed by oxidation with ferric ions can readily undergo nucleophilic attack by methanol on the metal (Si or Ge) atom. The observed higher reactivity of the germanium derivative relative to the silicon congener in this reaction is not that expected for the usual base-catalyzed attack at the metal atom, and may be reasonably interpreted in terms of a possible change in the transition state depending on the nature of the leaving group, viz. on the acidity of the corresponding hydrocarbon acid, in the solvolysis of the C---M bond.     

Reaction of [α-(trimethylsilyl)benzyl]ferrocenes with α-ferrocenylbenzyl cations

Although methanolysis of [α-(trimethylsilyl)benzyl]ferrocene (I) and [p-methyl-α-(trimethylsilyl)benzyl]ferrocene (II) in the presence of anhydrous ferric chloride merely gave α-ferrocenylbenzyl methyl ether (III) and p-methyl-α-ferrocenylbenzyl methyl ether (IV), respectively, acid-catalyzed methanolysis of (I) and (II) in the presence of an equimolar amount of (III) or (IV) afforded 1,2-diferrocenyl-l,2-diarylethanes. It is suggested that one electron oxidation of [α-(trimethylsilyl)benzyl]ferrocene by α-ferrocenylbenzyl cation generated from α-ferrocenylbenzyl methyl ether, and subsequent methanolysis of the resulting substituted ferricenium ion may occur to give the two species of α-ferrocenylbenzyl radical, which in turn undergo an approximately statistical coupling.     

Photometric determination of selenium with ferrocene

A sensitive spectrophotometric method for the determination of selenium has been developed. The method depends on a redox reaction between selenious acid in 8M hydrochloric acid and a chloroform solution of ferrocene. One mole of selenious acid produces 4 moles of ferricenium ions, which are then oxidized by bromine water. The resulting iron(III) is reduced to iron(II) and determined with 1,10-phenanthroline. The relative standard deviation for 20 mug of selenium was 1.1%. The apparent molar absorptivity of the final solution, referred to selenious acid, is 4.23 x 10(4) 1. mole(-1). cm(-1) at 512 nm. This method has been used to determine selenium in copper metal.     

Visual detection and removal of mercury ions by a ferrocene derivative

New ferrocene naphthyridine derivatives were successfully synthesized. The di-substituted ferrocene derivative FecDN behaves as a selective visual chemosensor for mercury ions, exhibiting a rapid and clearly visible precipitation with good selectivity (precipitation) and sensitivity (0.01 μM). The interaction of the ferrocene derivatives and metal ions was investigated by ultraviolet–visible spectroscopy (UV–vis), electrochemical methods, ¹H NMR, as well as infrared (IR), and energy dispersive X-ray spectroscopy (EDX). The application of FecDN in the detection and removal of mercury ions is very simple, rapid, and intuitive.     

The mono- and bis-(trichloroacetic acid)-solvates of ferricenium trichloroacetate

Summary Inconsistent literature reports on the preparation of the mono- and bis-(trichloroacetic acid)-solvated ferricenium trichloroacetates, (1) and (2) have prompted a comprehensive investigation of the experimental conditions giving rise to the formation of the two ferricenium salts. In agreement with the majority of authors, (2) is reproducibly obtained from trichloroacetic acid and ferrocene in molar ratios of 3 and higher in benzene over a wide range of experimental variables in the presence of air or, preferably, under conditions of oxygen saturation. Treatment of aqueous ferricenium sulfate solutions with trichloroacetic acid in an acid/ferrocene ratio of 3 and above affords the di-solvate, whereas at lower reactant ratios, and under conditions of reduced acidity, formation of the mono-solvate prevails. More efficiently, and in a higher degree of purity, the latter salt is generated from the former by a controlled recrystallization from water. Representative spectroscopic features of the two salts are discussed.     

Ferrocene and Ferricenium Ion as Versatile Photometric Titrants of H2O2 and D-Glucose in the Presence of Peroxidase and Glucose Oxidase. A Ferrocene-Peroxidase Stairway #

Abstract

Hydrogen peroxide can routinely be determined in the presence of ferrocene (FcH) and horseradish peroxidase by monitoring at 617 nm the enzymatically produced ferricenium dye. In contrast, D-glucose can be assayed by following the fading of the ferricenium dye FcH⁺PF₆ ^? in the presence of glucose oxidase. The change in absorbance in both cases corresponds to the amount of analyte. viz. H₂O₂ or D-glucose, in solution. The routine is very simple, invariant to the concentrations of both ferrocenes/ferricenium salt and enzyme and allows numerous “one pot” measuremeats with the detection limit of 10^?4 M for both the analytes. It takes 2–4 and 5–10 min to accomplish one analysis of H₂O₂ and D-glucose in the presence of peroxidase and glucose oxidase, respectively.

     

A joint experimental and theoretical study of cation-pi interactions: multiple-decker sandwich complexes of ferrocene with alkali metal ions (Li+, Na+, K+, Rb+, Cs+)

A systematic study of cation-pi interactions between alkali metal ions and the cyclopentadienyl ring of ferrocene is presented. The alkali metal (Li+, Na+, K+, Rb+, Cs+) salts of the ditopic mono(pyrazol-1-yl)borate ligand [1,1'-fc(BMe2pz)2]2- crystallize from dimethoxyethane as multiple-decker sandwich complexes with the M+ ions bound to the pi faces of the ferrocene cyclopentadienyl rings in an eta5 manner (fc = (C5H4)2Fe; pz = pyrazolyl). X-ray crystallography of the lithium complex reveals discrete trimetallic entities with each lithium ion being coordinated by only one cyclopentadienyl ring. The sodium salt forms polyanionic zigzag chains where each Na+ ion bridges the cyclopentadienyl rings of two ferrocene moieties. Linear columns [-CpR-Fe-CpR-M+-CpR-Fe-CpR-M+-](infinity) (R = [-BMe2pz]-) are established by the K+, Rb+, and Cs+ derivatives in the solid state. According to DFT calculations, the binding enthalpies of M+-eta5(ferrocene) model complexes are about 20% higher as compared to the corresponding M+-eta6(benzene) aggregates when M+ = Li+ or Na+. For K+ and Rb+, the degree of cation-pi interaction with both aromatics is about the same. The binding sequence along the M+-eta5(ferrocene) series follows a classical electrostatic trend with the smaller ions being more tightly bound.     

Photochemical properties of ferrocene,cobaltocene and nickelocene and their complexes with 2,2,2-trichloroethanol in liquid phase

Summary Photochemical changes in the solutions of ferrocene, cobaltocene, nickelocene and their complexes with 2,2,2-trichloroethanol exposed to near u.v. and argon laser (=514.5 nm) radiation were investigated. The solutions of cobaltocene, nickelocene and their complexes were found to undergo photolysis, whereas ferrocene solutions are not sensitive to this kind of irradiation and the ferrocene bound in a complex undergoes photooxidation to give the ferricenium cation. The activating effect of laser irradiation of ferrocene was revealed as a tendency to complex formation. The quantum yield of the investigated photoreactions, equilibrium constant of complex formation,K, and their molar extinction coefficients, _c, were determined.     

The electrophilic substitution of ferrocene by protonated carbonyl compounds

The α-ferrocenylalkyl caebenium ions are formed from ferrocene and carbonyl compounds in strongly acidic media, in particular mixtures of fluorosulfuric acid and trichloroacetic acid. The α-ferrocenylalkyl carbenium ions are scavenged by nucleophiles or bases. The addition of nucleophiles produces the corresponding α-substituted ferrocenyl alkanes. Proton abstraction by base from the β-position leads to the ferrocenylethene derivatives.Such electrophilic substitutions of ferrocene by carbonyl compounds, followed by suitable scavengeing of the α-ferrocenylalkyl carbenium ion, form the basis of one-pot syntheses of various ferrocene derivatives.     

Electron impact mass spectral fragmentation of 3a,5-disubstituted 1, 3-diphenyl-3a,4,5,6-tetra-hydro-3H-1,2,4-triazolo[4,3-a][1, 5]benzo-diazepines

The mass spectrometric behaviour of six 3a,5-disubstituted 1, 3-diphenyl-3a,4,5,6-tetrahydro-3H-1,2,4-triazolo[4,3-a][1, 5]benzodiazepines has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under electron impact ionization. All compounds show a tendency to eliminate (substituted) styrene molecules, aryl radicals, arylmethyl radicals or phenylnitrene (PhN:). All of the resulting fragment ions, except [M - PhN:](+.), could further undergo a reverse [2 + 3] cycloaddition. The [M - PhN:](+.) ions could further lose styrene derivatives and undergo a ring enlargement rearrangement. The molecular ions also show a tendency to eliminate a phenyl radical, and the [M - Ph](+) ions could eliminate styrene derivatives. The [M - R(1)CH = CH(2)](+.) ions could further lose NH(2) to yield stable tetracyclic 1,3-diphenyl-1,2,4-triazolo[4,3-d]phenanthridine ions, which could further lose benzonitrile, or undergo a reverse [2 + 3] cycloaddition. The molecular ions could also undergo a reverse [2 + 3] cycloaddition to produce N-phenylbenzonitrile imine ions and 2, 4-disubstituted 2,3-dihydro-1H-1,5-benzodiazepine ions, whose further fragmentations were also investigated.     

Synthesis and Mossbauer spectroscopic studies of chemically oxidized ferrocenyl(phenyl)phosphines

The electrochemical potentials of Fc3-xPPhx, (1-3, x = 0-2) and (FcPPh)n (4) indicate that iodine should oxidize ferrocenyl(phenyl)phosphines. The molar conductivity of solutions of 1-3 increases sharply when the solutions are titrated with iodine, leveling off after the addition of > 2 equiv of oxidant, consistent with formation of 1:1 electrolytes. Diamagnetic salts 6-9 are observed upon addition of a benzene solution of iodine to a benzene solution of 1-4 at ambient temperature in ratios of I2/metallocene ranging from 1:1 to 2:1. Well-resolved 1H and 31P NMR spectra are obtained for 6-8. Absorptions assigned to the I3- anion dominate the UV-vis spectrum of 6-8, whereas characteristic absorptions for [Fc][I3] are absent. Mossbauer spectra of 7-9 reveal isomer shifts consistent with low-spin iron(II) in ferrocene derivatives rather than those in ferricenium ions. Small amounts of low-spin FeIII appear to be present in 6. Taken together, the results suggest that 6-9 are iodophosphonium salts and not ferricenium salts. Diferrocenyl(phenyl)phosphine oxide (5) reacts with iodine to produce a diamagnetic, dark solid 10. Low-spin FeII is observed at 77 and 293 K in the Mossbauer spectra of 10 with no evidence for oxidation of FeII to FeIII. Compound 10 is proposed to be a neutral complex between 5 and I2. Reactions between 5 and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yield [Fc2P(=O)][DDQ]2 (11). Mossbauer spectroscopy of 11 indicates the presence of a mixture of low-spin FeII and low-spin FeIII at 77 K, suggesting that some electron transfer occurs from 5 to DDQ. The fraction of low-spin FeIII increases at room temperature.     

Ferrocenylalkyl azoles: bioactivity,synthesis, structure

The toxicity of ferrocenylethyl benzotriazole ( 1 ) and other ferrocene compounds including ferrocenylmethyl benzimidazoles ( 4,5,6,11 ), ferricenium salts ( 3,9,10 ) and ferrocenylmethyl adenine ( 7 ), was studied. All ferrocene complexes under investigation showed low or medium toxicities. On the basis of an earlier model of chemical carcinogenesis, the antitumor activity of ferrocenylalkyl azoles 1, 8 and ferricenium salts 9, 10 was studied in vivo in the so‐called sub‐capsular test on human tumors. This effectiveness was compared with that of cisplatin. A series of ferrocenylalkyl azoles were synthesized by interacting azoles either with α‐hydroxyalkyl ferrocenes FcC(OH)R₁R₂ in organic solvent in the presence of aqueous HBF₄ in quantitative yields or with trimethyl(aminomethyl)ferrocene iodide in an aqueous‐basic medium in good yields. The X‐ray determinations of molecular and crystal structures of α‐(1‐benzotriazolyl)ethylferrocene ( 1 ) and α‐(1‐naphthatriazolyl)ethylferrocene ( 12 ) were performed. Copyright © 2008 John Wiley & Sons, Ltd.     

Antineoplastic activity of polyaspartamide–ferrocene conjugates

The ferrocene/ferricenium redox system plays a significant role in biological oxidation, reduction and free-radical reactions. Of particular interest are the findings of earlier investigations which showed certain water-soluble ferricenium salts to possess appreciable antiproliferative activity against various murine tumor lines and a xenografted human colorectal adenocarcinoma. Solubility in water, a prerequisite for efficacious transport and dissipation in central circulation, was then proposed as a principal requirement for the ferrocene complex system to exert antineoplastic activity irrespective of the oxidation state in which it is administered. In order to shed more light on this question, we decided to investigate the antiproliferative properties of polymer–ferrocene conjugates containing the metal complex in the non-oxidized (ferrocene) form while fulfilling the critical requirement of water solubility. To this end, five selected, water-soluble conjugates, synthesized by reversible coupling of 4-ferrocenylbutanoic acid to variously structured polyaspartamides featuring pendant primary amino groups as coupling sites, were tested in vitro against cultured HeLa cells at concentrations up to 50 µg Fe ml⁻¹. Optimal antiproliferative activities, with IC₅₀ in the range of 2–7 µg Fe ml⁻¹, were determined for three compounds possessing tertiary-amine functions susceptible to protonation at physiological pH. Lower activities (IC₅₀ = 45–60 µg Fe ml⁻¹) were demonstrated for two poly(ethylene oxide)-containing conjugates. However, no reasonable structure–performance relationships can be derived at this stage from the small number of compounds tested. Copyright © 1998 John Wiley & Sons, Ltd.     

Oxametallacycloalcanes : V. Synthese de sila-2, germa-2 et stanna-2 oxa-1 cyclopentanes par deshydrocondensation intramoleculaire d'hydrures silicies,germanies ou stanniques γ-hydroxyles

The γ-hydroxymetal hydrides

OH (M = Si, Ge, Sn) were synthesized by reduction of γ-acetoxychloro- or γ-hydroxychloro-silanes, -germanes and -stannanes. These derivatives with MH bonds lead, by cyclisation at room- or higher temperatures, with or without catalyst, depending on the nature of the metal, to various oxametallacyclopentanes. The cyclisation proceeds by intramolecular dehydrocondensation between MH and OH bonds. These dehydrocondensation reactions are analysed and discussed according to the polarity of the MH bonds. Intramolecular addition of the MH bond into the unsaturated carboncarbon bonds of the corresponding non-cyclic compounds is also an excellent way of preparing the same heterocycles.The IR and NMR analyses of all new compounds are given.     

Antitumor effects of binuclear ferrocene derivatives

On the basis of an earlier model of chemical carcinogenesis, the antitumor activity of the mono-, bi- and poly-nuclear ferrocene derivatives ferricenium tri-iodide (1), ferricenium tetrachloroferrate (2), 1, 1′-diethylferricenium triiodide: (3), N-(ferrocenylmethyl)hexamethylenetetramine tetrafluoroborate (4), bis(ferrocenylmethyl)benzotriazolium tetrafluoroborate (5), bis(ferrocenyl-α-ethyl)benzotriazolium tetrafluoroborate (6) and bis(ferrocenylmethyl)-2-methylbenzimidazolium tetrafluoroborate (7), and the oligomer (—Fc—CH₂—Fc^+˙—CH₂—)_7–8^? (PF₆)_7–8 (8) was studied in vivo (Fc?C₁₀H₈Fe). The tumor models studied included MCH-11 (mouse sarcoma induced by methylcholantrene), P-815 (mouse mastocytoma of DBA/2 origin) and virus-induced Raucher leukemia (RLV). The cytotoxic effects of these preparations were examined against in vitro cultured normal murine cells (line L-929). The binuclear ferrocene derivatives 5, 6 and 7 inhibited the development of experimental tumors in mice. Ferricenium tri-iodide (1) was effective in Rauscher leukemia. Kinetic dependencies for most complexes had a two-phase character: the region of inhibition of tumorogenesis was followed by a region in which the complexes accelerated the development of this process. The link between the structure of compounds 1–8 and their antitumor effects is discussed.     

Fe+ chemical ionization of peptides

Laser-desorbed peptide neutral molecules were allowed to react with Fe⁺ in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe⁺ ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne⁺. Prior to reaction with laser-desorbed peptide molecules, Fe⁺ ions undergo 20–100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe⁺ ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe⁺] and fragment ions that result from the loss of small, stable molecules, such as H₂O, CO, and CO₂, from the metal ion-peptide complex.     

A first one-pot synthesis, isomerization and synthetic utility of mono- and bis Morita-Baylis-Hillman adducts of 1,1′-ferrocenedialdehyde

A one-pot synthesis of mono- and bis-Morita-Baylis-Hillman adducts of 1,1′-ferrocenedialdehyde has been achieved. These adducts undergo a facile and efficient stereoselective isomerization with a number of saturated, unsaturated, aromatic alcohols, phenols and thiophenol with a montmorillonite K10 clay catalyst to afford highly functionalized trisubstituted alkene derivatives of ferrocene. The synthetic utility of isomerized derivatives has been demonstrated by a ferrocene appended novel macrocycle synthesis, a ferrocenyl bis-triazole synthesis and an evaluation of the liquid crystalline property of a cholesterol derivative of ferrocene.     

Mass spectrometry of systems containing a group IVB—transition metal bond : I. The phenyl- and pentafluorophenyl- silicon, -germanium and -tin derivatives of pentacarbonylmanganese

The 70 eV mass spectra of the series Ph_3?n(C₆F₅)_nMMn(CO)₅ (n = 0 to 3 and M = Si, Ge or Sn) and Ph₃PbMn(CO)₅ have been examined and the proposed fragmentation schemes are supported by the observance of the appropriate metastable ions. Most of the total ion current is carried by metal-containing ions, particularly those containing just a Group IV metal. In all cases the initial fragmentation is by the loss of one or more carbonyl groups from the molecular ion, followed, except in the case of the fully fluorinated silicon derivatives, by the cleavage of the metal—metal bond. The fragmentation of the remainder of the molecule is then controlled by the nature of M and the number of pentafluorophenyl groups, the silicon derivatives showing a greater abundance of ions formed by the cleavage of the CC, CH or CF bonds in the aromatic ring, in contrast to the tin and lead derivatives which fragment almost exclusively by the cleavage of the metal—carbon bond. The formation of metal fluoride species plays an important part in the fragmentation of the pentafluorophenyl derivatives and becomes more important as the Group IV metal becomes heavier, while except for Ph₃PbMn(CO)₅ the abundances of the ions resulting from the migration of a complete aromatic ring from one metal to the other remain essentially constant. However, some of the observed changes in the fragmentation modes are not readily predicted on the basis of the expected variation in the relative metal—carbon or metal—metal bond strengths since these appear to be more dependent on the stabilities of the radical species or on the ion species formed. The tin—metal molecular bond dissociation energies in Ph₃SnMn(CO)₅ and Ph₃SnFe(CO)₂Cp were found to be 61 ± 8 and 54 ± 9 kcal mol^?1, respectively.     

Solvent effects on the electron donor acceptor complex properties of ferrocene and tetranitromethane

Summary Spectral investigations in the 350–800 nm range of ferrocene (FcH) and tetranitromethane [C(NO₂)₄] solutions in cyclohexane and carbon tetrachloride at concentration-constant (FcH) and variable (tetranitromethane) were made. The electron donor acceptor (EDA) complex of ferrocene and tetranitromethane and its dissociation to the ferricenium cation (FcH⁺) were studied as a function of the solvent, the initial C(NO₂)₄ concentration and reaction time.     

Colorimetric detection of Cu[II] cation and acetate, benzoate, and cyanide anions by cooperative receptor binding in new alpha,alpha'-bis-substituted donor-acceptor ferrocene sensors

New ferrocene derivatives bearing two donor-acceptor systems are capable of selectively sensing cations and anions by cooperative binding of the two alpha,alpha'-groups bonded to the ferrocene nucleus, thus permitting the naked-eye selective colorimetric detection of copper[II] cation and acetate, benzoate, or cyanide anions, which are ions of toxicological and biological relevance.