- Studies on polyhalides. 31 on 1,1′-dimethylferriciniumpolyiodides [(MeH4C5)2Fe]Ix with x = 3, 5: Preparation and crystal structures of a triiodide (diMeFc)I3 and a pentaiodide (diMeFc)I5
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Dimethylferrocene (diMeFc) may be oxidized by iodine analogous to ferrocene (Fc) and decamethylferrocene (DMFc) to the dimethylferrocenium ion (diMeFc)+ and precipitated as crystalline solids dimethylferrocenium triiodide (diMeFc)I3, dimethylferrocenium pentaiodide (diMeFc)I5 and dimethylferrocenium heptaiodide (diMeFc)I7. The two compounds with higher iodine content are new. The first two compounds are characterized by X-ray diffraction methods on single crystals. The structures are built up from complex cations with ecliptic conformation and isolated triiodide ions or remarkably concatenated pentaiodide ions. Dimethylferrocenium triiodide C12H14FeI3 crystallizes triclinically in P1? with a = 743.3(2) pm, b = 796.8(2) pm, c = 1471.7(4) pm, α = 98.53(2)°, β = 97.30(2)°, γ = 109.50° and Z = 2. The already known simple crystal structure may now be described without disordered anions. Dimethylferrocenium pentaiodide C12H14FeI5 crystallizes orthorhombically in Pnna with a = 1807.7(6) pm, b = 1543.4(10) pm, c = 1413.0(11) pm and Z = 8. The crystal structure contains pentaiodide chains 1∞[I3- · ? I2] with alternating planar and helical regions.
- Tebbe, Karl-Friedrich,Buchem, Rita
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- Oxidation of iodide by a series of Fe(III) complexes in acetonitrile
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The oxidations of iodide by [FeIII(bpy)2(CN) 2]NO3, [FeIII(dmbpy)2(CN) 2]NO3, [FeIII(CH3Cp) 2]PF6, and [FeIII(5-Cl-phen) 2-(CN)2]NO3 at 25°C, ionic strength of 0.10 M in acetonitrile, are catalyzed by trace levels of copper ions. This copper catalysis can be effectively masked with the addition of 5.0 mM 2,2′-bipyridine (bpy), which permits the rate law of the direct reactions to be determined: -d[Fe(III)]/dt = 2(k1[1-] + k 2[l-]2)[Fe(III)]. According to 1H NMR and UV-vis spectra, the products of the reaction are I3 - and the corresponding Fe(II) complexes, with the stoichiometric ratio (Δ[I3-] /Δ[Fe(II)]) of 1:2. Linear free-energy relationships (LFERs) are obtained for both log k1 and log k2 vs E1/2 with slopes of 16.1 and 13.3 V -1, respectively. A mechanism is inferred in which k1 corresponds to simple electron transfer to form I. plus Fe(II), while k2 leads directly to I2-.. From the mild kinetic inhibition of the k1 path by [FeII(bpy) 2(CN)2] the standard potential (E°) of l ./l- is derived: E° = 0.60 ± 0.01 V (vs [Fe(Cp)2]+/0).
- Wang, Xiaoguang,Stanbury, David M.
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- Spin-Doctoring Cobalt Redox Shuttles for Dye-Sensitized Solar Cells
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A new low-spin (LS) cobalt(II) outer-sphere redox shuttle (OSRS) [Co(PY5Me2)(CN)]+, where PY5Me2 represents the pentadentate ligand 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine, has been synthesized and characterized for its potential application in dye-sensitized solar cells (DSSCs). Introduction of the strong field CN- ligand into the open axial coordination site forced the cobalt(II) complex, [Co(PY5Me2)(CN)]+, to become LS based upon the complex's magnetic susceptibility (1.91 ± 0.02 μB), determined by the Evans method. Interestingly, dimerization and subsequent cobalt hexacyanide cluster formation of the [Co(PY5Me2)(CN)]+ monomer was observed upon long-term solvent exposure or addition of a supporting electrolyte for electrochemical characterization. Although long-term stability of the [Co(PY5Me2)(CN)]+ complex made it difficult to fabricate liquid electrolytes for DSSC applications, short-term stability in neat solvent afforded the opportunity to isolate the self-exchange kinetics of [Co(PY5Me2)(CN)]2+/+ via stopped-flow spectroscopy. Use of Marcus theory provided a smaller than expected self-exchange rate constant of 20 ± 5.5 M-1 s-1 for [Co(PY5Me2)(CN)]2+/+, which we attribute to a Jahn-Teller effect observed from the collected monomer crystallographic data. When compared side-by-side to cobalt tris(2,2′-bipyridine), [Co(bpy)3]3+, DSSCs employing [Co(PY5Me2)(CN)]2+ are expected to achieve superior charge collection, which result from a smaller rate constant, ket, for recombination based upon simple dark J-E measurements of the two redox shuttles. Given the negative redox potential (0.254 V vs NHE) of [Co(PY5Me2)(CN)]2+/+ and the slow recombination kinetics, [Co(PY5Me2)(CN)]2+/+ becomes an attractive OSRS to regenerate near IR absorbing sensitizers in solid-state DSSC devices.
- Baillargeon, Josh,Xie, Yuling,Raithel, Austin L.,Ghaffari, Behnaz,Staples, Richard J.,Hamann, Thomas W.
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supporting information
p. 11633 - 11645
(2018/09/12)
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- Highly efficient reduction of ferrocenyl derivatives by borane
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Borane, as a DMS or a THF complex, can efficiently reduce a large range of ferrocenyl derivatives (aldehydes, ketones, ethers, acetals, carboxylic acids, esters,...) if they bear at least one oxygen at a carbon at the α position. On the contrary, similar molecules, which contain nitrogen instead of oxygen, do not react with borane.
- Routaboul, Lucie,Chiffre, Jér?me,Balavoine, Gilbert G.A.,Daran, Jean-Claude,Manoury, Eric
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p. 364 - 371
(2007/10/03)
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- Reductive deoxygenation of α-ferrocenyl carbonyls and alcohols to alkylferrocenes by borane-dimethyl sulfide
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The reductive deoxygenation of α-ferrocenyl aldehydes, ketones, alcohols, and carboxylic acid into the corresponding alkylferrocenes is accomplished solely by borane-dimethyl sulfide (BMS) in the absence of any Lewis acid catalyst. This is the first example of such reactivity of BMS. The present method allows the synthesis of alkylferrocenes including those bearing terminally functionalized pendant chains.
- Kim, Dong-Hoo,Ryu, Eun-Sook,Cho, Chan Sik,Shim, Sang Chul,Kim, Hong-Seok,Kim, Tae-Jeong
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p. 5784 - 5786
(2008/10/08)
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- Solid-state mechanochemical synthesis of ferrocene
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Solid-state mechanochemical reactions of iron(II) chloride with cyclopentadienides of alkaline metals or thallium, which lead to the formation of ferrocene, were studied. The dependence of the yield of the product on the parameters of mechanical loading f
- Makhaev,Borisov,Petrova
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p. 222 - 226
(2007/10/03)
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- Improvements in the preparation of cyclopentadienyl thallium and methylcyclopentadienylthallium and in their use in organometallic chemistry
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Improved preparation methods of cyclopentadienylthallium and methylcyclopentadienylthallium, giving quantitative yields and incorporating ultrasound techniques, are described. Their use as starting materials for a wide range of organometallic syntheses is discussed and demonstrated.
- Neto, Alberto Federman,Borges, Aurea Donizete Lanchote,Miller, Joseph,Darin, Vitor Andre
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p. 1299 - 1314
(2008/10/09)
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- An expedient, mild, reductive method for the preparation of alkylferrocenes
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Reductive deoxygenation of acylferrocenes to the corresponding alkylferrocenes proceeded in excellent yields on utilizing a combination of sodium cyanotrihydroborate and boron trifluoride-diethyl ether.This method allows the synthesis of alkylferrocenes with functionalized tethers and is adaptable to large-scale preparations.
- Bhattacharyya, Sukanta
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p. 4617 - 4620
(2007/10/03)
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- Simple reduction of ferrocenyl aldehydes and ketones by sodium boranuide in trifluoroacetic acid: New, efficient, general preparation of alkylferrocenes
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Alkylferrocenes are obtained in excellent yields by ionic hydrogenation of ferrocenyl aldehydes and ketones using sodium boranuide and trifluoroacetic acid.
- Bhattacharyya, Sukanta
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p. 1381 - 1383
(2007/10/03)
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- Ionic hydrogenation of acylferrocenes using zinc borohydride: An efficient, mild method for the preparation of alkylferrocenes
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An effective mild procedure for the reductive deoxygenation of α-ferrocenyl aldehydes, ketones, and alcohols into the corresponding alkylferrocenes is described using a combination of zinc borohydride and zinc chloride. This is the first example of such reactivity of zinc borohydride. The present method allows the synthesis of alkylferrocenes bearing terminally functionalized pendant chains.
- Bhattacharyya, Sukanta
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p. 1065 - 1066
(2008/10/08)
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- Reaction of ferrocene with acetylene to generate methylferrocene. An unusual labeling result
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Heating a gaseous mixture of ferrocene and acetylene (1:6.3 mol ratio) at 450°C results in the formation of methylferrocene. When 13C2H2 is the substrate, GC/MS analysis reveals that the methylferrocene fraction consists of predominately two compounds: methylferrocene-13C1 and methylferrocene-13C6 in a 1:2.5 ratio. A mechanism involving initial addition of the alkyne C-H bond across the Fe-Cp bond to generate an (ethynyl-η4-cyclopentadiene)iron hydride is proposed to explain both products.
- Chuang, I.-Wen,Shevlin, Philip B.
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p. 1556 - 1558
(2008/10/08)
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- Kinetics of the Dissociation Reaction of Ferricenium Tri-iodide in Benzene Solution
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The dissociation of ferricenium tri-iodide in benzene solution has been studied by a photochemical technique under conditions where the concentration of the ion pair is many times greater than the equilibrium value.Kinetically the reaction is found to be of ca. three-halves order, with variations towards first-order or towards second-order behaviour, depending on the concentrations of iodine and ferrocene.The Arrhenius activation energy lies in the range 95-125 kJ mol-1, showing lower values at low concentrations.More rapid dissociation is found for phenylferroceneand slower reaction for 1,1'-diphenyl-, methyl- and 1,1'-dimethyl-ferrocene and for ferrocenophane.A mechanism has been proposed which involves the intermediates Fn+I4-, Fn+I2-, and Fn+I-, and it is suggested that the variations in reaction order are a consequence of the variable importance of the reverse process of some of these reaction steps.
- Logan, S. R.,Welsh, Michael R.
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p. 1259 - 1266
(2007/10/02)
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- Mechanistic Study on the Photochemical Conversion of Disilanyliron(II) Complexes to Monosilyliron(II) Complexes
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Photolysis of a C6D6 solution of CpFe(CO)2SiMe2SiMe3 (Cp=η5-C5H5) or (MeCp)Fe(CO)2SiMe2SiMe3 (MeCp=η5-C5H4Me) resulted in the formation of monosilyl derivative, CpFe(CO)2SiMe3 or (MeCp)Fe(CO)2SiMe3 in 64 or 59percent yield, respectively, together with small quantities of ferrocene and Cp2Fe2(CO)4 or their methylated derivatives.The yield of CpFe(CO)2SiMe3 increased to 88percent when the photolysis was carried out under a carbon monoxide atmosphere, while decreased to 22percent when argon was vigorously bubbled through the reaction mixture.These results are consistent with a mechanism involving dissociation and recombination of a carbonyl ligand which are common processes in photoreactions of transition-metal carbonyl derivatives.Dimethylsilylene moiety released during the photolysis was tried to be trapped with a hydrosilane, diene, and cyclotrisiloxane, but none of the expected products from the trapping reactions was detected, even in a trace amount.Photolysis of CpFe(CO)2SiMe2SiMeEt2 afforded, accompanying alkyl migration between silicon atoms, CpFe(CO)2SiMeEt2, CpFe(CO)2SiMe2Et, and CpFe(CO)2SiMe3 in 26, 33, and 4percent yields, respectively.Photolysis of a 1 : 1 mixture of CpFe(CO)2SiMe2SiMeEt2 and (MeCp)Fe(CO)2SiMe2SiMe3 provided only products expected from intramolecular alkyl migration mechanism.A possible mechanism involving silyl(silylene)iron intermediates is proposed to explain these results.
- Tobita, Hiromi,Ueno, Keiji,Ogino, Hiroshi
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p. 2797 - 2804
(2007/10/02)
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- On the Electron-Proton-Electron Mechanism for 1-Benzyl-1,4-dihydronicotinamide Oxidations
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The reaction of 1-benzyl-1,4-dihydronicotinamide (BNAH) with serveral ferrocenium (Fc+) salts in aqueous propanol was studied.The mechanism was shown to involve electron-proton-electron transfer with rate-limiting electron transfer from BNAH to Fc+.From the rate constants and E0(BNAH/BNAH.+) was estimated to be 0.89 V (SCE).The electrochemistry of BNAH was investigated in order to evaluate a previously determined E0(BNAH/BNAH.+).A reconsideration of the literature data for (non-DDQ) quinone oxidations of reduced nicotinamide adenine dinucleotide (NADH) in water and BNAH in CH3CN shows that the data are consistent with a hydride-transfer mechanism and inconsistent with an electron-proton-electron mechanism involving free NADH.+.A mechanismin which the hydride is transferred by electron-proton-electron transfer within one complex cannot be excluded.
- Miller, Larry L.,Valentine, James R.
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p. 3982 - 3989
(2007/10/02)
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- Photochemistry of [(η-C5H5)Fe(η-p-xyl)]PF6 in acetonitrile solution. Characterization and reactivity of [(η-C5H5)Fe(CH3CN)3]+
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The photolysis of [(η-C5H5)Fe(η-p-xyl)]+ (xyl = xylene) in acetonitrile solution at -40°C produces a purple intermediate that we have characterized as [(η-C5H5)Fe(CH3CN)3]+ by 1H NMR, electronic spectroscopy, and chemical reaction studies. Room-temperature photolysis of [(η-C5H5)Fe(η-p-xyl)]+ in acetonitrile also generates this species, which rapidly yields ferrocene and Fe(II) as the final products. Mechanistic studies on this system suggest that ferrocene is generated when [(η-C5H5)Fe(CH3CN)3]+ releases C5H5-, which subsequently replaces three CH3CN molecules on an unreacted [(η-C5H5)Fe(CH3CN)3]+ ion. This tris(acetonitrile) complex is a convenient starting material for the synthesis of substituted complexes of the form [(η-C5H5)Fe(CH3CN)(L)2] +, [(η-C5H5)Fe(CH3CN)(L)2] +, [(η-C5H5)Fe(L)(L′)2]+, and [(η-C5H5)Fe(L)(L′)(L″)]+, where L, L′, and L″ = isocyanides, phosphites, or phosphines. Room-temperature photolysis of [(η-C5H5)Fe(η-p-xyl)]+ in CH3CN in the presence of excess L produces [(η-C5H5)Fe(CH3CN)(L)2] +. Photolysis at -40 °C in CH3CN, followed by the addition of 1 equiv of L and a warm-up step in the presence of excess L′, produces [(η-C5H5)Fe(CH3CN)(L)(L′)] +. The reaction of the disubstituted compounds with excess ligand produces complexes of the form [(η-C5H5)Fe(L′)(L)2]+ and [(η-C5H5)Fe(L)(L′)(L″)]+, respectively. Reactivity comparisons of [(η-C5H5)Fe-(CH3CN)n(L) 3-n]+ and [(η-C5H5)Ru(CH3CN)n(L) 3-n]+ (n ≠ 0) have also been made. In every case the Fe complex has been found to undergo substitution reactions more readily than the corresponding Ru analogue.
- Gill, Thomas P.,Mann, Kent R.
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p. 1986 - 1991
(2008/10/08)
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