Cyclopentadienyliron Cations Research Articles

From Phosphidic to Phosphonium? Umpolung of the P4 -Bonding Situation in [CpFe(CO)(L)(η1 -P4 )]+ Cations (L=CO or PPh3 ).

Upon coordinating P4 to electron poor cyclopentadienyl-iron cations, the average P-P bond distances shrink and the respective P4 breathing mode in the Raman spectra (600 cm-1 , P4, free ) is blueshifted by >40 cm-1 in [CpFe(CO)(L)(η1 -P4 )]+ cations (L=CO or PPh3 ). Analysis suggests that this corresponds to an umpolung of the bonding from more phosphidic in the known, electron-rich systems to more phosphonium-like in the reported electron-poor versions. This may open new functionalization pathways for white phosphorus P4 .

Antimicrobial and anticancer activities of organoiron melamine dendrimers capped with piperazine moieties

Three generations of a biologically active class of melamine dendrimers containing arene- cyclopentadienyliron cations were synthesized using the divergent method. These dendrimers were decorated with chloro-, hydroxyl-, or piperazine moieties. Cyclic voltammetric studies showed that dendrimers with chloro- or hydroxyl- terminal group exhibit reversible redox activity while dendrimers with piperazine moieties showed two distinct irreversible reductive waves. Organoiron dendrimers were thermally stable with the first degradation step at 200°C associated with the decomplexation of the iron moieties. All dendrimers were evaluated against Gram-positive bacteria [Methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus warneri and vancomycin-resistant Enterococcus faecium (VRE)], and showed significant activities against bacterial strains but were found to be less active in the case of chloro- terminal group. Second generation dendrimer 8 capped with piperazine exhibited inhibitory activity against Gram-positive bacteria generally comparable to that of reference vancomycin and rifampicin. Also, all dendrimers were screened against MCF-7 and HTB-26 breast cancer cell lines and dendrimer 8 exhibited significant inhibitory activity against MCF-7 compared with dendrimers in lower generations.

ChemInform Abstract: A Molecular Bowl Sumanene

AbstractReview: 93 refs.

A molecular bowl sumanene

Nonplanar polyaromatic carbon molecules including fullerenes and carbon nanotubes have been attracting great interest due to their potential as materials, catalysts, etc. In this context, bowl-shaped polyaromatic hydrocarbons (π bowls) are considered to be key materials in the science of nonplanar π-conjugated carbon systems. Among π bowls, we focused on a molecular bowl "sumanene (C(21)H(12))" featuring a C(3v) symmetric structural motif present in fullerenes or carbon nanotube molecules. In this article, we present the research on sumanenes to date, including their synthesis, structural characterization, derivatization, complexation, and their potential uses as electrical materials. The characteristic structural feature of a sumanene depends on three sp(3) hybridized carbon atoms at the benzylic positions. Facile functionalization via selective formation of benzylic anions gives stereoselective substituted compounds, the π-extended derivatives, and the deeper π bowls. Furthermore, the dynamically flexible aspect based on bowl-to-bowl inversion is also described. The crystal with a columnar bowl-in-bowl stacking exhibits a high electron transport ability with anisotropy. Complexation with a cyclopentadienyl iron cation results in the first selective formation of the concave-bound complex as a π-bowl complex.

Synthesis and Polymerization of Cationic bis(cyclopentadienyliron)arene Complexes Containing Arylazo Dyes

The synthesis of the title complexes was achieved via the reaction of $$\eta^{6}$$ -p-dichlorobenzene- $$\eta^{5}$$ -cyclopentadienyliron cations with 4,4′-bis(4-hydroxyphenyl)valeric acid to produce the diiron complexes which were then reacted with a number of arylazo dyes to give cationic bis(cyclopentadienyliron)arene complexes containing the arylazo dyes. These iron-containing monomers were subsequently polymerized via nucleophilic aromatic substitution using 1,8-octanedithiol, 4,4′-thiobisbenzenethiol, or bisphenol A to produce the desired coloured cationic organoiron polymers. The weight – average molecular weights were estimated to range from 11,800 to 31,600. UV–vis studies conducted in dimethylformamide (DMF) showed that the metallated polymers exhibited $$\lambda_{\max}$$ of 412–491 nm. Addition of HCl to the polymer solution caused a bathochromic shift into the range of 515–530 nm. Thermogravimetric analysis (TGA) revealed that the iron moieties were cleaved between 205 and 248 °C while the polyether/thioether backbone degraded between 380 and 613 °C. Differential scanning calorimetry (DSC) showed that the polymers exhibited glass transition temperatures (Tg) ranging from 106 to 184°C.

Neutral and Cationic Macromolecules based on Iron Sandwich Complexes

This article is one of a number of reviews in the special issue of the Journal of Inorganic and Organometallic Polymers and Materials, celebrating the 50th anniversary of the discovery of metallocene-based polymers. Since the first examples of polyferrocenes in 1955, research into the design of organometallic polymers has grown exponentially. Organoiron polymers have incorporated ferrocene and arene cyclopentadienyl complexes, and have been developed for materials, liquid crystals, and electrocatalysts. The focus of this review is on the synthesis, properties, and characterization of macromolecules based on ferrocene or arene cyclopentadienyliron cations. Ferrocene-based polymers in which the ferrocene moieties are in or pendent to the backbone are described, as well as, the use of arene cyclopentadienyliron complexes in the design of polymeric materials. The design of star-shaped macromolecules and dendrimer materials that contain ferrocene and/or arene cyclopentadienyliron units will be discussed as well.

Hydrogenation of Iron(II) Cationic Complexes of Naphthalene and Methyl-Substituted Naphthalenes

Complexation of one ring of naphthalene as an η6-ligand by cyclopentadienyliron(II) cation significantly disrupts aromaticity in the noncomplexed ring, rendering it more “diene-like”. This was demo...

Molecular design in organometallic chemistry: the first example in the synthesis of poly(cyclopentadienyliron) cations of polyaromatic ethers and thioethers

Polyaromatic ethers and thioethers with pendent cyclopentadienyliron moieties have been prepared in very high yield using a highly efficient and mild methodology.

ChemInform Abstract: Carbanion Addition to a Metalated Acetaldehyde. A New Regiospecific Alkene Synthesis.

Abstract The reaction of 2-[(dicarbonyl)(η 5 -cyclopentadienyl)iron]acetaldehyde with organolithium and Grignard reagents results in efficient addition to the aldehyde carbonyl. The intermediate alkoxides have been treated with tetrafluoroboric acid to give high yields of isolated η 2 -alkene complexes of the dicarbonyl(η 5 -cyclopentadienyl)iron cation. Using this procedure the following alkenes were produced as complexed ligands to iron in 50–90% yield: propene, 1-hexene, 3-methyl-1-pentene, 3,3-dimethyl-1-butene, 1,3-butadiene, and styrene.

Ligand exchange reactions with η 6-arene-η 5-cyclopentadienyliron cations under thermal or photochemical conditions

Reactions of various η 6-arene-η 5-cyclopentadienyliron or substituted cyclopentadienyliron cations with trimethyl, triethyl or triphenyl phosphite under either thermal or photochemical conditions all resulted in the replacement of the arene ligand with three phosphite ligands to give η 5-tris(trimethyl, triethyl or triphenyl phosphite)-η 5-cyclopentadienyliron or substituted cyclopentadienyliron cations. The yields of the phosphite complexes were higher from photolysis than from the analogous thermolysis. Photolysis of the η 6-chlorobenzene-η 5-cyclopentadienyliron cation (IX) carried out in the presence of a more basic or more electron-rich aromatic ligand resulted in the exchange of the chlorobenzene of IX with the more basic arene, thus providing synthetic routes to cyclopentadienyliron complexes that may be difficult to prepare by other means. New complexes synthesized in this way are the η 6-2-phenylethyl tosylate-η 5-cyclopentadienyliron cation and the CpFe + complexes of thiophene, 2-methylthiophene, 3-methylthiophene and 2,5-dimethylthiophene.

Yanovsky reaction of η6-arene-η5-cyclopentadienyliron cations with carbanions derived from ketones. Regiospecific attack ortho to electron withdrawing functions

η6-Arene-η5-cyclopentadienyliron salts containing electron withdrawing groups such as nitro, halogeno, benzoyl, cyano, and sulphonyl on the arene ring react with carbanions to give eletroneutral adducts of the Yanovsky type; these adducts give the corresponding substituted benzene on treatment with buffered cerium(IV) ammonium nitrate.

The use of ferrocene in organometallic synthesis: A two-step preparation of cyclopentadienyliron acetonitrile and phosphine cations via photolysis of cyclopentadienyliron tricarbonyl or arene cations

UV photolysis of [CpFe II(CO) 3] + PF6 6 − (I) or [CpFe II(η 6-toluene)] + PF 6 − − (II) in CH 3CN in the presence of 1 mole of a ligand L gives the new air sensitive, red complexes [CpFe II(NCCH 3) 2L] +PF 6 − (III, L = PPh 3; IV; L = CO; VIII, L = cyclohexene; IX, L = dimethylthiophene) and the known air stable complex [CpFe II(PMe 3) 2(NCMe)] + PF 6 − (V). The last product is also obtained by photolysis in the presence of 2 or 3 moles of PMe 3. In the presence of dppe, the known complex [CpFe II (dppe)(NCCH 3)] + (XI) is obtained. Complex III reacts with CO under mild conditions to give the known complex [CpFe(NCCH 3)(PPh 3)CO] + PF 6 − (X). UV photolysis of I in CH 3CN in the presence of 1-phenyl-3,4-dimethylphosphole (P) gives [CpFe IIP 3] + PF 6 − (XII); UV photolysis of II in CH 2Cl 2 in the presence of 3 moles of PMe 3 or I mole of tripod (CH 3C(CH 2Ph 2) 3) provides an easy synthesis of the known complexes [CpFe II(PMe 3) 3] + PF 6 − (VII) or [CpFe IIη 3-tripod] + PF 6 t- (XIII). Since I and II are easily accessible from ferrocene, these photolytic syntheses provide access to a wide range of piano-stool cyclopentadienyliron(II) cations in a 2-step process from ferrocene.

Transformation of organoiron complexes of synthetic and chemical interest

Abstract

Electrochemical evidence for the generation of new sandwich complexes of iron; cyclopentadienyl(arene)iron anion and cyclopentadienyl(cyclohexadienyl)iron cation

Cyclopentadienyl(arene)iron cations may be successively reduced electrochemically to their corresponding radicals and anions, which react with electrophilic reagents leading to the substituted cyclohexadienyl (cyclopentadienyl)iron derivatives; the latter are electrochemically oxidized to the corresponding cations, isoelectronic with the well known ferricinium cation.

ChemInform Abstract: DIENYL COMPLEXES OF TRANSITION METALS. VI. THE ADDITION OF HYDRIDE TO (METHYLBENZOATE)CYCLOPENTADIENYLIRON CATION

AbstractDie Reduktion des Eisen‐Komplexes (I) mit Natriumborhydrid in 1,2‐Dimethoxyäthan liefert vorwiegend den Cyclohexadienyl‐Komplex (II).

Dienyl complexess of transition metals : VI. The addition of hydride to (methyl benzoate)cyclopentadienyliron cation

The addition of hydride to (methyl benzoate)cyclopentadienyliron cation occurs exclusively at the arene ring with reaction at the positions ortho to the ester group strongly favoured. Factors affecting the product distribution in nucleophilic addition reactions of arenecyclopentadienyliron cations are discussed in relation to the results obtained in this and earlier studies.

Dienyl complexes of transition metals. Part II. The addition of hydride to halogen-substituted arenecyclopentadienyliron cations

The addition of hydride to a series of (halogenoarene)cyclopentadienyliron cations has been shown to occur exclusively at the arene ring, with reaction at positions ortho to the halogen substituent favoured. The bromoarene derivatives undergo partial debromination both under the conditions of their formation from ferrocene and by reaction with borohydride. The 1H n.m.r. spectra of these compounds are discussed.