Decamethylferrocene Research Articles

Boosting the cell voltage in biphasic flow batteries via Galvani potential difference.

Galvani potential differences between aqueous and organic phases of biphasic flow batteries can be utilized to boost the cell voltage by ca. 600 mV. This effect is demonstrated by comparing batteries utilizing three different solvents, trifluorotoluene, dichloroethane and propylene carbonate, with ferrocene and decamethyl ferrocene as model organic redox couples.

Voltammetry in Microemulsion Formed by Electron Donor Solution in Organic Solvent|Ionic Liquid Microdroplets in Aqueous Electrolyte

Oxygen reduction reaction (ORR)1 or hydrogen evolution reaction (HER)2 at liquid|liquid interface provide the possibility of separation of their products: hydrogen peroxide or hydrogen.3,4 Typically, these reactions are studied at single interface formed between immiscible electrolyte solutions in quiescent conditions. In such geometry the frequency of successful reaction events when highly hydrophobic electron donor (i.e. decamethylferrocene (DMFc) or excited form of decamethylruthenocene (DMRc)) dissolved in organic phase meet proton from aqueous phase is rather limited. Importantly, electrochemical recycling of electron donor at electrode positioned close to the liquid|liquid interface increases efficiency of this reaction.5,6 The use of microemulsion is promising higher efficiency alternative, because of extended interfacial area of numerous organic droplets. As efficient electron exchange between oxidized form of electron donor and the electrode is crucial for biphasic ORR and HER one has to focus on electrochemical studies of DMFc or DMRc in emulsions.are important. Voltammetric signal of various redox probes as ferrocene or ferrocene surfactants in quiescent emulsions is similar to that in single phase with some variation of peak density currents or redox potential.7-11 Other studies focused on chronoamperometric experiments to detect collisions of redox probe (e.g. ferrocene12) containing droplets with the electrode surface. It was found that the addition of an hydrophobic ionic liquid, typically trihexyltetradecyl-phosphonium bis(trifluoro-methylsulfonyl) amide to the organic phase as stabiliser and electrolyte, does not influence the magnitude of the electrochemical signal.13 Here we will report results of electrochemical studies of emulsion prepared from aqueous HClO4 and DMFc or DMRc and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide (IL-PI) solution in toluene. As aqueous phase acid solution was selected, because in biphasic ORR or HER it serves as a source of protons. During the measurements the microemulsion was stirred to achieve faster droplets transport towards the electrode surface. Results will be compared with these obtained in a single organic phase.Voltammograms obtained with glassy carbon disc electrode indicate reversible oxidation/reduction of the redox probe similar to the seen with an electrode immersed in single organic phase. During continuous scanning redox only small change of peak currents is seen. Importantly, when after experiment in emulsion working electrode was transferred to aqueous HClO4, the voltammetric signal is still seen, but the peak currents are significantly smaller. This may indicate the redox reaction in liquid film formed on the electrode surface. Formation of liquid organic film is confirmed by the results of chronoamperometric experiments. When the electrode is set at potential corresponding to the oxidation of the redox probe, of the current is seen after c.a. 100 s drop, what may indicate the gradient of redox probe concentration. As DMFc is insoluble in water this points out on gradient of organic phase close to the glassy carbon surface.14 In turn voltammetric current related to electroreduction of highly hydrophilic hexacyanoferrate(III) is significantly diminished in emulsion as compared to pure aqueous electrolyte indicating partial coverage of the GC surface by hydrophobic film.Other effects related with electrochemical behavior of studied emulsions will be also presented and discussed.

Synthesis and structural and spectroscopic properties of a cyanido-bridged mixed-valence compound [Fe–NC–Ru–CN–Fe

Five cyanide-bridged compoundstrans-[Cp(dppe)Fe(NC)RuII(py)4(CN)Fe(dppe)Cp][PF6]nandtrans-[Cp(dppe)Fe(NC)RuII(MeOpy)4(CN)Fe(dppe)Cp][PF6]nwere systematically synthesized and characterized.

Three half-sandwiched iron(II) monocarbonyl complexes with PNP ligands: Their chemistry upon reduction and catalysis on proton reduction

Three half-sandwiched iron(II) monocarbonyl cationic complexes (1+−3+) containing a azadiphoshine ligand (PNP, L1–3) and an iodide as the counter anion, [Fe(II)Cp(CO)(L1–3)]Ι (Cp = η5-cyclopentadienyl; L1 = Ph2PN(cyclohexyl)PPh2, 1+; L2 = Ph2PN(phenyl)PPh2, 2+; L3 = Ph2PN(benzyl)PPh2, 3+) were reported. All the complexes were fully characterized, of which complexes 2+ and 3+ were crystallographically analysed to confirm their “piano stool” geometry. Electrochemically, complexes 1+−3+ exhibited two major reduction events at about −1.9 V and −2.3 V, respectively, assigned to Fe(II) → Fe(I) and Fe(I) → Fe(0), respectively. The first reduction produces a 19e-species, [Fe(I)Cp(CO)(L1–3)] (1, 2, and 3) whereas the second event is not assigned to the further reduction of the 19e-species but a 17e-intermediate ([Fe(I)Cp(CO)(m-L1–3)]; 1′, 2′ and 3′) which is chemically generated from the 19e-species by cleaving one of the two Fe−P bonds. However, the 19e-species 3 is considerably more stable than the other two analogues (1 and 2) due to H−π interaction between the ortho-H atoms from one of the four phenyl rings on the phosphine atom and the phenyl ring of the benzyl group as revealed by theoretic calculations. Therefore, species 3 is stable enough for the reduction of 3 → 3− to be electrochemically detected right before the second major reduction. To further shed some light on the electrochemical mechanism, both bulk electrolysis and chemical reduction of complexes 1+−3+ with cobaltocene as the reducing agent were conducted. Under N2 atmosphere, the neutral 17e-species, [Fe(I)Cp(CO)(m-L1–3)] (1′-3′) was spectroscopically detected whereas under CO atmosphere, CO-adducts, [Fe(I)Cp(CO)2(m-L1–3)], were generated. The formation of CO-adduct explains the loss of reversibility of the first reduction (3+) under CO atmosphere in its electrochemistry. With acetic acid as the proton source, only the second major reduction of the complexes exhibited significant catalytic activity, of which complex 1+ possessed the best performance. Significant proton-coupled electron transfer (PCET) effect was observed for complex 1+ due to the strong electron-donating capability of the ligand (L1).

Enhanced hydrogen evolution via in situ generated 2D black phosphorous nanocomposites at the liquid/liquid interfaces

The mimicry of bio-membrane with a liquid/liquid interface between two immiscible electrolyte solutions is intrinsically defect-free to study catalysis of energy conversion reactions i.e., CO2 reduction, oxygen reduction, and hydrogen evolution. Herein, we report the in-situ generation of electrodeposited black phosphorous (BP) based nanocomposites at the liquid/liquid interface for the first time and their catalysis in hydrogen evolution reaction (HER). The catalytic HER activities of these catalysts have been investigated electrochemically and also chemically by two-phase reactions. The BP/MoSx, BP/Cu, and BP/Pt nanocomposites were formed by reducing the catalyst precursors such as (NH4)2MoS4, (NH4)2PtCl4, and CuCl2 salts, respectively on the BP nanosheets by decamethylferrocene (DMFc) electron donor during the catalytic HER. The electrodeposited nanocomposites were collected from the interface and characterized by using advanced analytical techniques. Among them, the BP/MoSx nanocomposites showed the highest HER activity with a reaction rate constant of 0.202 min−1 was about 230- and 7-times greater than the ones obtained by non-catalytic reaction and the free-MoSx catalyst. Moreover, the nucleation of the catalysts and the HER mechanisms were also explained in detail. The BP/MoSx also showed higher HER activity compared to that of carbon nanotubes CNTMoSx and reduced graphene oxide rGOMoSx nanocomposites.

In Situ Copper Nanoparticles on Reduced Graphene Oxide (rGO/Cu) for Biphasic Hydrogen Evolution

AbstractGraphene‐based nanocomposites have attracted a tremendous attention, showing excellent performance in energy conversion applications, such as reduction of carbon dioxide and hydrogen evolution reaction (HER). Herein, a study on in situ generation Cu nanoparticles on reduced graphene oxide (rGO/Cu) by reducing simultaneously both graphene oxide and Cu2+ ions during the biphasic HER by organic sacrificial agent decamethylferrocene (DMFc) was reported. The in situ‐generated rGO/Cu catalyst was morphologically and structurally characterized by microscopic and spectroscopic techniques, respectively. The hydrogen evolution catalytic activity of rGO/Cu was investigated by using 4‐electrode voltammetry and two‐phase reaction methods. rGO/Cu nanocomposite catalyst displayed a better catalytic activity than the non‐catalyzed reaction and free‐Cu catalyst by enhancing the HER rate approximately 208‐ and 3‐times, respectively. The HER activity of rGO/Cu gave results comparable to the noble metallic and the other nanocomposite catalysts such as Pt, Pd, MoSx and their nanocomposites with carbon‐based materials.

Hydrogen peroxide generation catalyzed by battery waste material

Lithium-ion battery (LiB) waste powder is a valuable source of various materials, including carbon and metals. Although this material exhibits electrical conductivity, nanostructured morphology, and may contain metal oxides, it has not been used as an electrocatalyst. Here, we demonstrated the application of LiB waste powder as a catalyst for electrochemical H2O2 generation. The powder was both immobilized on a glassy carbon (GC) electrode and assembled at a liquid–liquid interface formed by decamethylferrocene (DMFc) solution in trifluorotoluene and aqueous perchloric acid in the presence of oxygen. The electrochemistry was studied by cyclic voltammetry and also with a rotating disk electrode (RDE), and a 2-electron ORR pathway was confirmed. H2O2 generation at the liquid–liquid interface and oxidation of DMFc were detected by colorimetry, UV–vis spectroscopy and scanning electrochemical microscopy (SECM). The use of LiB waste powder reduces the ORR onset potential by ca. 0.3 V compared to an unmodified GC. When assembled at a liquid–liquid interface the waste powder increases the efficiency of H2O2 generation by ca. 20 times.

Synthesis, structural and metal-to-metal charge transfer properties of cyanide-bridged compound [FeII/III-NC-RuII-CN-FeII/III

Cyanide-bridged mixed-valence complexes trans-[Cp(dppe)Fe(NC)RuII(tbupy)4(CN)Fe(dppe)Cp][PF6]n (n = 2, 3 and 4, respectively, 1–3) were systematically synthesized and characterized in three distinct redox states.

The Solvent Effect on H2 O2 Generation at Room Temperature Ionic Liquid|Water Interface.

H2 O2 is a versatile chemical and can be generated by the oxygen reduction reaction (ORR) in proton donor solution in molecular solvents or room temperature ionic liquids (IL). We investigated this reaction at interfaces formed by eleven hydrophobic ILs and acidic aqueous solution as a proton source with decamethylferrocene (DMFc) as an electron donor. H2 O2 is generated in colorimetrically detectable amounts in biphasic systems formed by alkyl imidazolium hexafluorophosphate or tetraalkylammonium bis(trifluoromethylsulfonyl)imide ionic liquids. H2 O2 fluxes were estimated close to liquid|liquid interface by scanning electrochemical microscopy (SECM). Contrary to the interfaces formed by hydrophobic electrolyte solution in a molecular solvent, H2 O2 generation is followed by cation expulsion to the aqueous phase. Weak correlation between the H2 O2 flux and the difference between DMFc/DMFc+ redox potential and 2 electron ORR standard potential indicates kinetic control of the reaction.

Catalysis of hydrogen evolution reaction by in situ electrodeposited amorphous molybdenum sulfide at soft interfaces

Amorphous molybdenum sulfide (MoSx) is considered a suitable alternative to Pt for catalyzing the hydrogen evolution reaction (HER) in electrochemical water splitting because of its simple and inexpensive preparation process. Herein, the template-free in situ electrodeposition of amorphous MoSx at freestanding soft interfaces is reported for the first time. The biphasic catalysis of the HER by the electrodeposited MoSx at the water-1,2-dichloroethane interface with decamethylferrocene (DMFc) was also investigated. DMFc acts as an organic sacrificial reducing agent for both (NH4)2MoS4 and protons to afford MoSx and H2, respectively. The nucleation of MoSx and the HER was examined using both four-electrode voltammetry and the biphasic reactions at the liquid-liquid interfaces. MoSx particles were collected from the interface and subjected to structural and morphological characterization. The HER kinetics was investigated using the UV-Vis absorption method with varying DMFc+ concentrations. The amount of H2 evolved and the reaction rates obtained over the in situ electrodeposited MoSx catalyst were compared with those obtained over electrodeposited metallic nanoparticles and commercial MoS2 catalysts.

Rip It off: Nitro to Nitroso Reduction by Iron Half-Sandwich Complexes.

Activation of [FeCl(dppe)Cp] (1) by chloride abstraction with Na[BArX4] (X = F, [B(3,5-(CF3)2-C6H3)4]; X = Cl, [B(3,5-Cl2-C6H3)4]) permits reactions with a range of nitro aromatics, RC6H4NO2 (R = halogen, Me, OMe, NO2 or NMe2), to give the cationic iron nitroso complexes [Fe{N(O)-C6H4R}(dppe)Cp][BArX4]) ([3][BArX4]). Similar reactions of 1 and Na[BArX4] with [Fe(NCC6H4NO2)(dppe)Cp][BArX4] gave bimetallic [{Fe(dppe)Cp}2{μ-N≡CC6H4N(O)}][BArF4]2. However, reactions of 1 and Na[BArX4] with 4-nitrophenol gave the first example of the bench-stable iron half-sandwich phenolate complex [Fe(OC6H4NO2)(dppe)Cp]+ rather than NO2 activation. The formation of complexes [3]+ likely proceeds via the unusual blue bimetallic species [{Fe(dppe)Cp}2{μ,κ2O,O'-O2NAr}]2+. This compound undergoes N-O bond cleavage, resulting in [3]+ and a FeIV═O species, which reacts via an internal C-H activation of the dppe ligand to give [FeIII(κ3O,P,P'-P(2-O-C6H4)(Ph)-C2H4-PPh2)Cp]+. Complexes [3]+ are stable under ambient conditions, are readily purified by column chromatography and can be isolated in up to 50% yield, considering that 0.5 equiv of 1 is required as the oxygen acceptor.

Ultraviolet photodissociation of gas-phase transition metal complexes: dicarbonylcyclopentadienyliodoiron(II)

The ultraviolet photodissociation of the prototypical organometallic half-sandwich compound dicarbonylcyclopentadienyliodoiron(II) [η 5-CpFe(CO)2I] has been studied in the gas phase across the wavelength range 260 ≤ λ ≤ 310 nm using multi-mass velocity-map ion imaging with photoproducts detected using both resonance enhanced multiphoton and vacuum ultraviolet (λ = 118.2 nm) single photon ionisation methods. Ion images recorded for the atomic iodine and the cyclopentadienyl photoproducts reveal fast, anisotropic components to their recoil velocity distributions. The experimental work is supported by multi-reference (spin–orbit averaged) electronic structure calculations that suffice to illustrate the high electronic state density in such transition metal complexes and provide insights into the rival fragmentation dynamics. The ground state parent molecule has singlet spin multiplicity, but the product energy disposal measured following Fe–Cp bond fission shows the involvement of nominally spin-forbidden transitions. The Fe–I and Fe–Cp bond fissions should both be viewed as homolytic and occurring on excited state potentials that are dissociative in the relevant ligand elimination coordinate.

Catalytic Activity of Alkali Metal Cations for the Chemical Oxygen Reduction Reaction in a Biphasic Liquid System Probed by Scanning Electrochemical Microscopy.

Chemical reduction of dioxygen in organic solvents for the production of reactive oxygen species or the concomitant oxidation of organic substrates can be enhanced by the separation of products and educts in biphasic liquid systems. Here, the coupled electron and ion transfer processes is studied as well as reagent fluxes across the liquid|liquid interface for the chemical reduction of dioxygen by decamethylferrocene (DMFc) in a dichloroethane‐based organic electrolyte forming an interface with an aqueous electrolyte containing alkali metal ions. This interface is stabilized at the orifice of a pipette, across which a Galvani potential difference is externally applied and precisely adjusted to enforce the transfer of different alkali metal ions from the aqueous to the organic electrolyte. The oxygen reduction is followed by H2O2 detection in the aqueous phase close to the interface by a microelectrode of a scanning electrochemical microscope (SECM). The results prove a strong catalytic effect of hydrated alkali metal ions on the formation rate of H2O2, which varies systematically with the acidity of the transferred alkali metal ions in the organic phase.

Further Evidence for 'Extended' Cumulene Complexes: Derivatives from Reactions with Halide Anions and Water.

Reactions of [Ru{C=C(H)-1,4-C6 H4 C≡CH}(PPh3 )2 Cp]BF4 ([1 a]BF4 ) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C6 H4 -C(X)=CH2 }(PPh3 )2 Cp] [X=Cl (2 a-Cl), Br (2 a-Br)], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C6 H4 =C=CH2 )(PPh3 )2 Cp]+ . Similarly, [M{C=C(H)-1,4-C6 H4 -C≡CH}(LL)Cp ]BF4 [M(LL)Cp'=Ru(PPh3 )2 Cp ([1 a]BF4 ); Ru(dppe)Cp* ([1 b]BF4 ); Fe(dppe)Cp ([1 c]BF4 ); Fe(dppe)Cp* ([1 d]BF4 )] react with H+ /H2 O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C6 H4 -C(=O)CH3 }(LL)Cp'] (3 a-d) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [1 a-d]+ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C6 H4 =C=CH2 )(LL)Cp']+ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C6 H4 -C≡CH)(PPh3 )2 Cp] (4 a) and [Ru(C≡C-1,4-C6 H4 -C≡CH)(dppe)Cp*] (4 b) reacted with the relatively small electrophiles [CN]+ and [C7 H7 ]+ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh3 ]+ ) electrophile reacted with [M(C≡C-1,4-C6 H4 -C≡CH)(LL)Cp'] [M(LL)Cp'=Ru(PPh3 )2 Cp (4 a); Ru(dppe)Cp* (4 b); Fe(dppe)Cp (4 c); Fe(dppe)Cp* (4 d)] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C6 H4 =C=C(H)CPh3 }(LL)Cp']+ , which were isolated as the water adducts [M{C≡C-1,4-C6 H4 -C(=O)CH2 CPh3 }(LL)Cp'] (6 a-d). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-c C4 H2 S-C≡CH}(LL)Cp']BF4 ([7 a-d]BF4 add water readily to give [M{C≡C-2,5-c C4 H2 S-C(=O)CH3 }(LL)Cp'] (8 a-d)].

1D Amorphous Tungsten‐Based Ternary Refractory Metal Sulfides for Catalytic Hydrogen Evolution at Soft Interfaces

AbstractTransition metals incorporated into molybdenum sulfide and tungsten sulfide matrixes are promising candidates for hydrogen evolution due to the unique chemical and physical properties. Here, we first describe a general strategy for the synthesis of rod‐like ternary refractory metal sulfides (MWSx; M=Ni, Co, Fe and Mn) through a simple hot‐injection method. The newly developed materials are affirmed as valuable alternatives to noble metal Pt due to their simple fabrication, inexpensive and impressive catalytic performance. We present that highly efficient catalysts for the hydrogen evolution at a polarized water/1,2‐dichloroethane (DCE) interface by using the decamethylferrocene (DMFc). Kinetics of hydrogen evolution studies are monitored by two phase reactions using UV/Vis spectroscopy, and also further proved by gas chromatography. These ternary refractory metal sulfide catalysts show high catalytic activities on hydrogen evolution comparable to platinum. The rate of hydrogen evolution for the MWSx catalysts changed in the order Ni>Co>Fe>Mn according to the type of first row transition metals.

Syntheses, crystal structures and MMCT properties of cyanide-bridged binuclear Ru–Fe complexes

In this report, two new binuclear mixed-valence (MV) compounds and their one-electron oxidation products, [MeCpLRu(μ-CN)Fe(dppe)Cp][PF6]n (L = dppe, (PPh3)2) (n = 1, 2), were synthesized and thoroughly characterized by single-crystal X-ray diffraction analysis. Complexes 12+ and 22+ are one-electron oxidation products of 11+ and 2+, respectively. The electronic absorption results indicate that there exists metal to metal charge transfer (MMCT) in the one-electron oxidation products, which is strongly supported by the theoretical calculations. Complexes 12+ and 22+ can be defined as Class II MV compounds. It is found that the MMCT band is obviously red-shifted on going from 12+ to 22+, because the donating electron ability of (PPh3)2 is stronger than that of dppe.

1,4-Dimethoxybutadienediyl-Bridged Diiron Compounds in Three Oxidation States: Evaluation of Delocalization Effects

The binuclear iron complexes [Cp*(PMe3)(CO)Fe–C(OCH3)═CH–CH═C(OCH3)–Fe(PMe3)(CO)Cp*] (1meso and 1dl) were prepared by double deprotonation of their known parents [Cp*(PMe3)(CO)Fe═C(OCH3)CH2–CH2–C(OCH3)═Fe(PMe3)(CO)Cp*](PF6)2 (5meso and 5dl) and were isolated in good yield (90%). These complexes were characterized by ESI-mass spectrometry, IR and multinuclear NMR spectroscopy, and cyclic voltammetry. The singly and doubly oxidized forms 1meso(PF6)n and 1dl(PF6)n (n = 1, 2) were prepared by oxidation of the parent neutral complexes with 1 and 2 equiv of ferrocenium salt (93–100% yield). The related complex [Cp*(dppe)Fe–C(OCH3)═CH–CH═C(OCH3)–Fe(dppe)Cp*](PF6) (2(PF6)) was obtained by reduction of the known dicationic derivative [Cp*(dppe)Fe–C(OCH3)═CH–CH═C(OCH3)–Fe(dppe)Cp*](PF6) (2(PF6)2) with 1 equiv of cobaltocene (100% yield). Multinuclear NMR spectroscopy allowed us to establish the diiron(II) conjugated μ-bis(carbene) structure for 1meso(PF6)2 and 1dl(PF6)2. In the case of the meso derivative, 1H NMR r...

Mössbauer Spectroscopy and Theoretical Studies of Iron Bimetallic Complexes Showing Electrocatalytic Hydrogen Evolution.

Mössbauer spectroscopy and density functional theory (DFT) calculations are reported for the mononuclear Fe-nitrosyl complex [Fe( N, N'-bis(2-mercaptoethyl)-1,4-diazacycloheptane)NO] {[Fe(bme-dach)(NO)] (1)} and the series of dithiolate-bridged dinuclear complexes M-Fe(CO)Cp [M = Fe(bme-dach)(NO) (1-A), Ni(bme-dach) (2-A), and Co(bme-dach)(NO) (3-A)], in which M is a metallo-ligand to Fe(CO)Cp+ (Fe'Cp). The latter is an organometallic fragment in which Fe is coordinated by one CO and one cyclopentadienyl ligand. Complexes 1-A and 2-A were previously shown to have electrocatalytic hydrogen evolution activity. Mononuclear {Fe-NO}7 complex 1, with overall spin of 1/2, has an isomer shift of 0.23(2) mm/s [Δ EQ = 1.37(2) mm/s] and magnetic hyperfine couplings of {-38 T, -26.8 T, 8.6 T}. In complexes 2-A and 3-A, Fe'(CO)Cp+ has a diamagnetic ground state and δ = 0.33(2) mm/s (Δ EQ ≈ 1.78 mm/s), consistent with a low-spin FeII site. In contrast, in complex 1-A, M = Fe(bme-dach)(NO) (i.e., complex 1) the magnetic hyperfine interactions of both metallo-ligand, M, and low-spin Fe'Cp are perturbed and Fe'Cp exhibits small magnetic hyperfine interactions, although its isomer shift and quadrupole splittings are largely unaltered. The DFT calculations for 1-A are in agreement with the paramagnetism observed for the Fe'(CO)Cp+ iron site.

Redox Properties of Ferrocenyl Ene-diynyl-Bridged Cp*(dppe)M–C≡C–1,4-(C6H4) Complexes

The complexes FcCH═C{1,4-C≡C–C6H4–C≡CM(dppe)Cp*}2 (Fc = ferrocenyl (FeCp(η-C5H4−); M = Fe (1), Ru (2)) were prepared from FcCH═C{1,4-C≡C–C6H4–C≡CSiMe3}2 (3) via a desilylation/metalation protocol in good (2; 65%) to excellent (1; 97%) yield. The iron compound 1 could also be prepared in a stepwise fashion by desilylation of 3 to give FcCH═C{1,4-C≡C–C6H4–C≡CH}2 (4), reaction with FeCl(dppe)Cp* to give the vinylidene complex FcCH═C{1,4-C≡C–C6H4–CH═C═Fe(dppe)Cp*}2](PF6)2 (5(PF6)2; 65%), and deprotonation. The cyclic voltammograms of 1 and 2 are characterized by an initial oxidation wave resulting from the overlap of two closely spaced oxidation processes, the potentials of which are sensitive to the identity of M, and a subsequent, one-electron-oxidation wave. Thus, while the dications 12+ and 22+ could be prepared by oxidation with 2 equiv of ferrocenium hexafluorophosphate and isolated as the PF6– salts 1(PF6)2 and 2(PF6)2 at low temperature, the monocations 1+ and 2+ could only be detected and studied as ...

Influence of the Substitution of the Ligand on MM′CT Properties of Mixed Valence Heterometallic Cyanido-Bridged Ru–Fe Complexes

We investigated how substitution of the ligand around the lower valent metal ion influences the electron transfer properties from the lower valent metal ion to the higher valent metal ion in heterometallic complexes. A series of new binuclear cyanido-bridged Ru/Fe complexes [TpmRu(L)(μ-CN)Fe(dppe)Cp][PF6]n (n = 2, 3) (Tpm = Tris(1-pyrazolyl)methane, dppe = bis(diphenylphosphino)ethane, L = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (4,4′-(CH3)2-bpy)) were synthesized and characterized. In the one-electron oxidized [TpmRuII(L)(μ-CN)FeIII(dppe)Cp][PF6]3 binuclear system, the cyanide bridge promotes the electron transfer from the RuII ion to the FeIII ion. As the substitution of L changes from 1,10-phenanthroline to 4,4′-dimethyl-2,2′-bipyridine, their molecular structure, cyclic voltammetry, IR and UV present obvious changing trends. Moreover, the assignment of MM′CT transition and the differences of electronic properties in the different mixed complexes with different ...