Decamethylferrocene Research Articles

Iron versus Ruthenium: Dramatic Changes in Electronic Structure Result from Replacement of One Fe by Ru in [{Cp*(dppe)Fe}-CC-CC-{Fe(dppe)Cp*}]n+(n= 0, 1, 2)

The reactions of FeCl(dppe)Cp* and Ru(C⋮CC⋮CH)L2Cp‘ with Na[BPh4] and 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu; 2 equiv) in a mixed thf/NEt3 solvent afford {Cp*(dppe)Fe}(C⋮CC⋮C){Ru(PP)Cp‘} (PP = dppe, Cp‘ = Cp*, 7; PP = (PPh3)2, Cp‘ = Cp, 8). Cyclic voltammetry shows that these mixed Fe/Ru complexes undergo sequential loss of up to three electrons, with the mono- and dioxidized species being isolated following chemical oxidation. Computational (DFT) and spectroscopic (IR, NMR, ESR, Mössbauer) studies are consistent with a polarized ground-state structure with oxidation leading to the gradual evolution of cumulenic character in the FeC4Ru moiety and a greater degree of orbital mixing between the Fe, C, and Ru centers than found in the related heterometallic complex [{Cp*(dppe)Fe}(C⋮CC⋮C){Re(NO)(PPh3)Cp*}]n+ ([6]n+). In contrast to the two-electron oxidation products derived from the diiron complex {Cp*(dppe)Fe}(C⋮CC⋮C){Fe(dppe)Cp*} (1) and iron/rhenium complex 6, the dications [7]2+ and [8]2+ feature a dominant contribution from a singlet ground state. Thus, while 6 behaves in a manner closely related to 1, 7 and 8 are more closely related to {Cp(Ph3P)2Ru}(C⋮CC⋮C){Ru(PPh3)2Cp} (2) and {Cp*(dppe)Ru}(C⋮CC⋮C){Ru(dppe)Cp*} (3), clearly demonstrating the pronounced role that choice of metal as well as formal electron count can play in tuning the electronic and magnetic properties of this fascinating class of compound.

The unusual reactions of indium(I) trifluoromethanesulfonate with some first row metallocenes and the structure of “indium(II) cyclopentadienide”

The soluble reagent indium(I) trifluoromethanesulfonate, InOTf, does not appear to react or interact with ferrocene (Cp 2Fe, Cp = C 5H 5) whereas cobaltocene reacts with InOTf to produce [Cp 2Co] +[OTf] − and indium metal. Unexpectedly, the reaction of InOTf with manganocene results in the formation of the unprecedented salt [In(μ 2,η 5-Cp)In] +[Cp 3In(μ 2,η 1-Cp)InCp 3] −: a form of “Cp 2In” that is characterized by X-ray crystallography. Similarly, the reaction of InOTf with [Cp 2Fe] +[PF 6] − produces Cp 2Fe and “In 4OTf 6” in addition to other products. The unusual structural features and the formation of the new indium-containing products are rationalized.

Marcus theory of outer-sphere heterogeneous electron transfer reactions: High precision steady-state measurements of the standard electrochemical rate constant for ferrocene derivatives in alkyl cyanide solvents

The High Speed Channel Electrode is used to precisely measure the standard electrochemical rate constants under steady state conditions for the oxidation of substituted ferrocenes in alkyl cyanide solvents. First, the oxidation of ferrocene itself is kinetically analysed in the solvents: acetonitrile, propionitrile, butyronitrile and valeronitrile. Second, the oxidation kinetics of the ferrocene derivatives: ferrocene carboxylic acid, decamethyl ferrocene, bis(diphenylphosphino) ferrocene, ferrocene carboxaldehyde, α-hydroxyethyl ferrocene, t-butyl ferrocene, dimethyl aminomethyl ferrocene, dimethyl ferrocene and n-butyl ferrocene are measured in acetonitrile for comparison to ferrocene. The rate of electron transfer in the different alkyl cyanides is shown to depend on the longitudinal dielectric relaxation times of the solvents in accordance with solvent dynamic theory, whilst the electron transfer rates of the different ferrocene derivatives in acetonitrile are shown to depend on the hydrodynamic radii of the molecules. In both cases, a measured k 0 = 1.0 ± 0.2 cm s −1 for ferrocene oxidation in acetonitrile shows an excellent fit to the theoretical dependences.

Kinetics of Anion Transfer across the Liquid | Liquid Interface of a Thin Organic Film Modified Electrode, Studied by Means of Square-Wave Voltammetry

The electrochemical oxidation of lutetium bis(tetra-tert-butylphthalocyaninato) (LBPC) and decamethylferrocene (DMFC), as well as the reduction of LBPC, lutetium bis(phthalocyaninato) (LPC), and lutetium (tetra-tert-butylphthalocyaninato hexadecachlorphthalocyaninato) (LBPCl), has been studied in a thin nitrobenzene (NB) film deposited on the surface of a graphite electrode (GE) by means of square-wave voltammetry (SWV). The organic film-modified electrode was immersed in an aqueous (W) electrolyte solution and used in a conventional three-electrode configuration. When the aqueous phase contains ClO4-, NO3-, or Cl- (ClO4-, or NO3- only, in the case of DMFC), both LBPC and DMFC are oxidized to stable monovalent cations in the organic phase. The electron transfer at the GE | NB interface is accompanied by a simultaneous anion transfer across the W | NB interface to preserve the electroneutrality of the organic phase. LBPC, LPC, and LBPCl are reduced to stable monovalent anions accompanied by expulsion of the anion of the electrolyte from the organic into the aqueous phase. In all cases, the overall electrochemical process comprises simultaneous electron and ion transfer across two separate interfaces. Under conditions of SWV, the overall electrochemical process is quasireversible, exhibiting a well-formed "quasireversible maximum" that is an intrinsic property of electrode reactions occurring in a limiting diffusion space. For all the redox compounds that have been studied, the kinetics of the overall electrochemical process is controlled by the rate of the ion transfer across the liquid | liquid interface. Based on the quasireversible maximum, a novel and simple methodology for measuring the rate of ion transfer across the liquid | liquid interface is proposed. A theoretical background explaining the role of the ion-transfer kinetics on the overall electrochemical process at the thin organic film modified electrode under conditions of SWV is presented. Comparing the positions of the theoretical and experimental quasireversible maximums, the kinetics of ClO4-, NO3-, and Cl- across the W | NB interface was estimated. The kinetics of the overall process at the thin organic film modified electrode, represented by the second-order standard rate constant, is 91 +/- 8, 90 +/- 4, and 133 +/- 10 cm(4) s(-1) mol(-1), for the transfer of ClO4-, NO3-, and Cl- respectively.

Synthesis and reactivity of mixed-ring indenyl complexes of molybdenocene

The complex [IndCpMo(NCMe) 2][BF 4] 2 provides a suitable entry to the synthesis of IndCpMoBr 2 and IndCpMoMe 2. The latter, also available from IndCpMoX 2 (X = Cl, Br) and MeMgCl, reacts with HCl to give IndCpMoCl(Me) which, in turn reacts with NaSPh to yield IndCpMo(SPh)(Me). Cyclic voltammetry shows that these three alkyl complexes undergo a 1e reversible oxidation to 17 e Mo V cations. IndCpMoCl(Me) is oxidized by [Cp 2Fe]BF 4 to afford [IndCpMoCl(Me)]BF 4 in 95% yield. Reaction of [IndCpMo(NCMe) 2][BF 4] 2 with KBPz 4 in CH 2Cl 2/NMF leads to [IndCpMo(κ 2-BPz 4)]BF 4. Taken together with previous reports these results show that the indenyl ring slows down substitutional chemistry at the Cp 2 ′ Mo ( IV ) fragment (Cp′ = Cp, Ind) by steric reasons, overshadowing any acceleration due to a possible indenyl effect.

Electrodeposition of Metal Nanostructures by Galvanic Displacement Powered with Insoluble Crystals of a Ferrocene Derivative

The deposition of metal nanostructures (wires and particles) on a graphite surface from an aqueous electrolyte solution was induced by galvanic displacement, via the oxidation of insoluble crystals of a ferrocene derivative (either n-butyl ferrocene or decamethyl ferrocene) present on the same substrate. Micron-to-millimetre-scale crystallites of decamethyl ferrocene were deposited on the graphite surface by evaporation from a solution of a nonpolar solvent (1,2-dichloroethane). Immersion of this modified surface into a dilute solution of a metal ion (e.g., CuII, AgI, PdII, PtII and others) caused the deposition of metal nanoparticles at step edges present on the graphite surface. The reducing equivalents required for the metal deposition process are provided by oxidation of the ferrocene derivative on the surface, as directly evidenced by elemental analysis and chronoamperometric experimental data presented here.

Cover Picture: Electrodeposition of Metal Nanostructures by Galvanic Displacement Powered with Insoluble Crystals of a Ferrocene Derivative (ChemPhysChem 12/2004)

The cover picture shows the mechanism by which crystals of a ferrocene derivative power the deposition of metal nanowires on a graphite surface. In the background a colorized scanning electron microscope image is showing the graphite surface after crystallization of decamethyl ferrocene from a solution of 1,2‐dichloroethane. Such a surface served as the starting point for the deposition of nanowires, as described in the Article by Dryfe et al. on page 1879.

Iron(II) and iron(III) complexes containing ethynyl thiophene fragments

The synthesis of the new complexes Cp*(dppe)Fe C C 2,5-C 4H 2SR (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; dppe = 1,2-bis(diphenylphosphino)ethane; 2a, R = C CH; 2b, R = C C Si(CH 3) 3; 2c, R = C C Si(CH(CH 3) 2) 3; 3a, R = C C 2,5-C 4H 2S C CH; 3c, R = C C 2,5-C 4H 2S C C Si(CH(CH 3) 2) 3) is described. The 13C NMR and FTIR spectroscopic data indicate that the π-back donation from the metal to the carbon rich ligand increases with the size of the organic π-electron systems. The new complexes were also analyzed by CV and the chemical oxidation of 2a and 3c was carried out using 1 equiv of [Cp 2Fe][PF 6]. The corresponding complexes 2a[PF 6] and 3c[PF 6] are thermally stable, but 2a[PF 6] was too reactive to be isolated as a pure compound. The spectroscopic data revealed that the coordination of large organic π-electron systems to the iron nucleus produces only a weak increase of the carbon character of the SOMO for these new organoiron(III) derivatives.

Electroneutrality Coupling of Electron Transfer at an Electrode Surface and Ion Transfer across the Interface between Thin-layer of 1-Octyl-3-methylimidazolium Bis(perfluoroalkylsulfonyl)imide Covering the Electrode Surface and an Outer Electrolyte Solution

The electrode reaction of decamethylferrocene (DMFc) dissolved in a thin layer of a room-temperature molten salt (RTMS), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) or 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (C8mimC2C2N), on a self-assembled monolayer-modified gold electrode is coupled with the ion transfer across the interface between the RTMS and the outer aqueous solution (W) to give a voltammogram whose shape resembles a voltammogram of a simple one-electron transfer process. The electroneutrality of the RTMS layer during the oxidation of DMFc to decamethylferricenium ion is maintained by the concomitant dissolution of C8mim+ ion from the RTMS phase to the W phase, and the reduction of decamethylferricenium ion to DMFc is accompanied by the transfer of either C1C1N- or C2C2N- from RTMS to W. The midpoint potential of the voltammogram varies with the concentration of the salt in the aqueous phase, C8mimCl or LiCnCnN (n = 1 or 2), in a Nernstian manner, showing that the phase-boundary potential between the RTMS and the W is controlled by the partition of these ions. Although the phase-boundary potential across the RTMS / W interface is Nernstian with respect to the ions common to both phases at the equilibrium, the polarization at the RTMS / W interface under current flow distorts the shape of the voltammograms, resulting in a wider peak separation in the voltammogram.

Redox reactions via outer sphere charge transfer complexation: the interaction of ferrocenes with σ- and π-type acceptors

Decamethylferrocene Cp 2 ∗ Fe , ferrocene (Cp 2Fe), 1,1′-dimethylferrocene. ((MeCp) 2Fe), and 1,2-diferrocenylethane (Fc 2C 2H 4) were studied as donors for charge transfer complexation with iodine (I 2) as a typical σ-type CT acceptor and with 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ), and p-chloranil (CHL) as typical π-type CT acceptors. Oxidation of the ferrocenes to the corresponding ferricinium salts is proposed to occur via initial formation of outer sphere charge transfer complexes. UV–Vis spectra for the mixtures of any of the ferrocene donors with I 2 or DDQ in CH 2Cl 2 showed the characteristic bands of the triiodide ion, I 3 - and the DDQ - anion radical. With CHL, the same behavior occurred only for Cp 2 ∗ Fe to give Cp 2 ∗ Fe + and CHL - radicals. Elemental analyses of the isolated solid complexes indicated the formation of [ferrocene]I 3 for ferrocenes and I 2, except for (Fc 2C 2H 4) which gave [(Fc 2C 2H 4)]I 5. Ferrocene–DDQ complexes were 1:1 except for (MeCp) 2Fe and (Fc 2C 2H 4) which gave 1:2 complexes. By using n-hexane as a non-polar solvent instead of CH 2Cl 2, the CT band of the Cp 2 ∗ Fe adduct has been observed and the formation constant for this CT complexation was found to be 3900 (±500) dm 3 mol −1.

Bucky ferrocene and ruthenocene: serendipity and discoveries

An idea of making a ferrocene/fullerene hybrid, “bucky ferrocene”, has intrigued chemists for some time, but the compounds remained to be hypothetical. The synthesis of such hybrid molecules as Fe(C 60Me 5)Cp, Ru(C 60Me 5)Cp and Fe(C 70Me 3)Cp as well as their functionalized derivatives from [60] and [70]fullerenes has been achieved in recent years. With their esthetically pleasing structures and the dual character of metallocene and graphite, these molecules may stimulate the interest of both chemists and non-chemists.

Organometallic Mixed-Valence Systems. Electronic Coupling through an Alkyndiyl Bridge Incorporating Methylene Groups

The binuclear complexes [Cp*(dppe)FeC≡C-(CH 2 ) x -C≡CFe(dppe)Cp*] (x = 3 (8a), x = 4 (8b)) were prepared by deprotonation of the parent bis(vinylidene) derivatives [Cp*(dppe)-Fe=C=C(H)-(CH 2 ) x -(H)C=C=Fe(dppe)Cp*] [PF 6 ] 2 (x = 3 (7a), x = 4 (7b)). The X-ray crystal structure of 8a revealed that the metal-metal distance (8.706 A) is much shorter that the sum of the bond distances of the Fe-Fe assembly (12.24 A). An X-ray powder diffraction analysis of an amorphous sample shows that the Fe-Fe distance may fall into the wide range 8.50-10.75 A. The resolved separations between the redox processes in the cyclic voltammograms evidenced the through-bridge interaction between the iron centers and enabled computations of the comproportionation constants (K c ) and the molar fractions of the different species 8a n + and 8b n + (n = 0, 1, 2) present in solution. The dicationic complexes 8a[PF 6 ] 2 and 8b[PF 6 ] 2 were prepared in good yield by oxidation of 8a and 8b with 2 equiv of ferrocenium. The IR, Mossbauer, ESR, and UV-vis spectra provided evidence for a small through-bridge interaction between the Fe I I I sites. The NIR spectroscopy study of the MV complexes 8a[PF 6 ] and 8b[PF 6 ] clearly shows that through-bridge electron transfer occurs for both compounds, which well obey Hush's theory.

Synthesis and crystal structure of the double cluster [Cp 3Fe 4(CO) 4(C 5H 4)] 2( p-C 6H 4)

[Cp 4Fe 4(CO) 4] ( 1) reacts with p-BrC 6H 4Li and MeOH in sequence to afford the functionalized cluster [Cp 3Fe 4(CO) 4(C 5H 4- p-C 6H 4Br)] ( 2), while the reaction of 2 with n-BuLi and MeOH produces [Cp 2Fe 4(CO) 4(C 5H 4Bu)(C 5H 4- p-C 6H 4Br)] ( 3). The double cluster [Cp 3Fe 4(CO) 4(C 5H 4)] 2( p-C 6H 4) ( 4) has been prepared by treatment of [Cp 4Fe 4(CO) 4] with p-C 6H 4Li 2 and MeOH in sequence. The electrochemistry of 2 and 4, as well as the crystal structure of 4 have been investigated.

Synthesis of cationic (arene)IronCp complexes via arene exchange

Rates and regioselectivity of arene exchange reactions in cationic fused arene Fe(II)Cp complexes were investigated. Thermal exchange of pyrene, naphthalenes, and cyclooctatetraene occurs in the temperature range of 90–140 °C. The most labile complex in the series studied is [(η 6-(1-4,4a,8a)-1,4-dimethoxynaphthalene)FeCp][PF 6] having the FeCp coordinated to the substituted ring. Pyrene and other naphthalene complexes come next, followed by the cyclooctatetraene complex. Phenanthrene, veratrol, and dihydronaphthalene do not undergo exchange at temperatures up to 130 °C. With Me- and OMe-substituted naphthalenes, exchange is reversible and favors the product having the metal coordinated to the non-substituted ring. The X-ray crystal structures of the two regioisomeric 1,4-dimethoxynaphthalene complexes were determined. Arene exchange in fused arene complexes is shown to be a useful synthetic method and provides new arene complexes cleanly and efficiently. The method is particularly attractive for arenes that contain functionalities that are not compatible with the Lewis acid-mediated routes. The starting materials are readily accessible via the TiCl 4-assisted Cp exchange in ferrocene.

Synthesis and Crystal Structure of [Fe(Cp)2]3(Bi2Cl9)·thf

AbstractSingle crystals of [Fe(Cp)2]3(Bi2Cl9)·thf were obtained from a thf solution containing ferrocene and BiCl3. The structure shows disorder at room temperature which disappears upon cooling, coupled with a decrease in symmetry. The title compound crystallizes in the orthorhombic space group P212121 [a = 1698.64(2), b = 2318.69(3), c = 1085.66(2) pm] with three ferrocenium ions, one nonachlorodibismutate ion and one molecule of thf in the asymmetric unit.

Voltammetric study on the electron transport through a bilayer lipid membrane containing neutral or ionic redox molecules

Voltammograms for the electron transport through a bilayer lipid membrane, BLM, from one aqueous phase, W1, to another, W2, were recorded with the BLM containing 7,7,8,8-tetracyanoquinodimethane, TCNQ, or decamethyl ferrocene, DMFc, exposed to W1 containing [Fe(CN) 6] 4− and W2 containing [Fe(CN) 6] 3−. The formation of an anion radical of TCNQ or a cation of DMFc in the BLM followed by the interfacial redox reactions at both W1 ∣ BLM and BLM ∣ W2 interfaces were demonstrated experimentally, based on the comparison with voltammograms observed using a liquid membrane. The BLM containing TCNQ gave a large current for the electron transport controlled by the electron exchange in the BLM, although the BLM containing DMFc gave a small peak current for the electron transport controlled by mass transfer in the BLM. Such two mechanisms were also observed with BLMs containing other ionic redox species in the BLM. It was found that the electron transport through the BLM requires the proximity between the redox potential of redox species in the BLM and that in aqueous phases as well as the existence of both the oxidized and reduced form in the BLM.

Structural and Magnetic Characterisation of [Fe(Cp*)2][Ni(dmio)2]·THF

The crystal structure of [Fe(Cp*) 2 ][Ni(dmio) 2 ].THF consists of 2D layers composed of parallel chains, where side-by-side pairs of donors alternate with the acceptors, ..D + D + A - D + D + A - ... In these chains there is a net charge (+) per repeat unit (D + D + A - ) and these layers are separated by acceptor layers. The magnetic behaviour of [Fe(Cp*) 2 ][Ni(dmio) 2 ].THF is dominated by FM interactions, which are attributed to the DA intrachain interactions.

Bucky ferrocene. Hybrid of ferrocene and fullerene

Abstract The idea of “bucky ferrocene” intrigues chemists owing to its aesthetic beauty and to its polarized, extended conjugated system, but the idea has remained hypothetical. The synthesis of close analogs of Fe(C60Me5)Cp and Fe(C70Me3)Cp was achieved in two steps from [60] and [70]fullerenes, relying on an oxidative C–H bond activation starting with an iron(I) complex and the corresponding cyclopentadienyl precursors, respectively. The molecules can be regarded as members of a new organometallic conjugated system connected to a graphitic system. Numerous synthetic transformations and self-organization procedures that are known for the parent ferrocenes and fullerenes are expected to be employable toward productive use of the ferrocene/fullerene hybrid molecules in chemistry and materials sciences.

Cyanoacetylenes and cyanoacetylides: versatile ligands in organometallic chemistry

The nitrile like lone pair of the cyanoacetylene PhCCCN (1) has been found to coordinate readily to the Ru(PPh3)2Cp fragment, to give [Ru(NCCCPh)(PPh3)2Cp]PF6 (2) which may be considered as an “extended” derivative of the more common benzonitrile complex [Ru(NCPh)(PPh3)2Cp]PF6 (3). Reaction of 1 with [Co2(CO)6(dppm)] readily forms the μ,η2 complex [Co2(μ,η2-PhC2CN)(CO)4(dppm)] (4), which reacts with [RuCl(PPh3)2Cp] to give the mixed metal species [{Co2(μ,η2-PhC2CN){Ru(PPh3)2Cp}(CO)4(μ-dppm)}]PF6 (5). The η1(N) bonded PhCCCN ligand is labile, being displaced by NCMe at ambient temperature to afford [Ru(NCMe)(PPh3)2Cp]PF6, or by tcne to give trans-[{Ru(PPh3)2Cp}2(μ-tcne)}][PF6]2 (9). The metallocyanoacetylide [Ru(CCCN)(PPh3)2Cp] (6) was prepared by lithiation (BuLi) of [Ru(CCH)(PPh3)2Cp] followed by treatment with PhOCN. Coordination of the metal fragments Ru(PPh3)2Cp or Fe(dppe)Cp to the N terminus in 6 occurs readily to give the homo- or hetero-bimetallic cations [{Cp(PPh3)2Ru}(μ-CCCN){ML2Cp}]+, which were isolated as the PF6 salts [ML2Cp = Ru(PPh3)2Cp (7); Fe(dppe)Cp (8)]. The crystal structures of 2–5, 7 and 9 are reported. The electrochemical response of these complexes suggests there are considerable electronic interactions between the heterometallic end-caps in 8 through the polarised C3N bridge.

The hydrogen oxalate anion allows one-dimensional columnar aggregation of organometallic sandwich cations

Oxalic acid reacts with sandwich compounds such as decamethyl ferrocene, decamethyl cobaltocene, bis-benzene chromium and cobaltocene, in the presence of oxygen, via a multi-step process involving oxidation, deprotonation and precipitation, to form crystalline superstructures containing columns of organometallic sandwich cations and hydrogen oxalate anions. Five novel crystalline compounds are reported, namely [Fe(η5-C5Me5)2][HC2O4]·[H2C2O4]0.5, 1a, [Co(η5-C5Me5)2][HC2O4]·[H2C2O4]0.5, 1b, [Fe(η5-C5Me5)2][HC2O4]·[H2C2O4], 2, [Cr(η6-C6H6)2][HC2O4]·[H2O], 3, and [Co(η5-C5H5)2][HC2O4]·[H2C2O4]0.5[H2O] 4. The anionic network in [M(η5-C5Me5)2][HC2O4]·[H2C2O4]0.5 (M = Fe, Co) is based on an unusual deca-atomic ring formed by hydrogen oxalate anions linked side-to-side via(−)O–H⋯O(−) hydrogen bonding interactions. The magnetic behaviour of compounds 1a, 2, and 3 has been investigated by SQUID magnetometry. Both compounds 1a and 2 present weak antiferromagnetic interactions, which are significantly stronger in 1a. The structure of the chloride salt [(η5-C5H5)2Co][Cl]·[H2C2O4][H2O], 5, is also described.