Electrochemical Behaviour of the Fe(CO)3NO⊖ Ion (original) (raw)
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Journal of Organometallic Chemistry, 2001
A mechanism is proposed for the electrochemical reduction of [Fe(h 5-C 6 H 7)(CO) 3 ][PF 6 ] based on cyclic voltammetry and simulation techniques. In [NBu 4 ][X]/CH 3 CN (X=BF 4 or ClO 4) but not in [NBu 4 ][BF 4 ]/CH 2 Cl 2 , a rapid equilibrium prior to the electron transfer process is identified between [Fe(h 5-C 6 H 7)(CO) 3 ][PF 6 ] and a species formulated as [Fe(h 3-C 6 H 7)(CO) 3 (NCMe)] +. The formation of the species under equilibrium involves solvent coordination and h 5 to h 3 ring slippage of the cyclohexadienyl ligand as the response of the system to the high electron count. Electrochemical electron transfer to [Fe(h 3-C 6 H 7)(CO) 3 (NCMe)] + affords a highly reactive 19-electron intermediate exhibiting chemical reactivity (ECE mechanism) that leads to the formation of dimer-type species. A 'father-son' type mechanism is proposed for the formation of the products of the electrochemical reduction of [Fe(h 5-C 6 H 7)(CO) 3 ][PF 6 ]. All the species involved in the mechanism were analysed by theoretical means and are proposed on the basis of calculations made with the B3LYP HF/DFT hybrid functional.
Journal of Organometallic Chemistry, 2001
The structure of [Fe(h 5 -C 5 H 5 )(h 5 -C 5 H 4 CH NNHC 5 H 4 N)]·HCl (1·HCl) has been solved to R= 0.05 and is described. The parent compound has been shown to act as a ligand for a range of M 2 + cations in the form 1MCl 2 (where M =Cd 2 + , Cu 2 + , Zn 2 + , Sn 2 + , Pd 2 + and Fe 2 + ). 57 Fe Mö ssbauer spectroscopy has been used to probe the ferrocenyl iron electronic environments to give a ligand's eye view of the metal bonding. Two compounds of the formula [1M(H 2 O) 4 ][PF 6 ] 2 where M = Fe 2 + or Zn 2 + were also prepared. The ferrocenyl quadrupole splittings of these two compounds were much smaller than those of the corresponding chloride. The change is explained in terms of the electric field experienced by the ferrocenyl iron atoms. In the chloride complexes the field from the M 2 + is compensated by the chloride anions, whereas in the two [PF 6 ] − salts the charge on the M 2 + is not compensated in the first coordination sphere. The ferrocenyl iron is thus directly exposed to the M 2 + charge and it is the effect of this that gives rise to the small quadrupole splitting value. This is the first time such a field effect has been observed on a ferrocenyl iron by Mö ssbauer spectroscopy. The coordination geometry of the inorganic iron(II) environment is also elucidated as tetrahedral in 1MCl 2 and distorted octahedral in [LM(H 2 O) 4 ][PF 6 ] 2 .
On the [Fe(H2O)5XO]2+ (XC, N, O) complex ions via density functional theory
Journal of Molecular Structure: THEOCHEM, 2005
The coordination of XO (XaC, N, O) to metal iron is important in biochemistry. In this paper, the properties of spin ground states for [Fe(H 2 O) 5 XO] 2C are studied via UB3LYP method. The spin ground states for [Fe(H 2 O) 5 CO] 2C , [Fe(H 2 O) 5 NO)] 2C , and Fe(H 2 O) 5 O 2 ] 2 are determined to be SZ2, 3/2, and 1, respectively. Both the Fe-CO bond in [Fe(H 2 O) 5 CO] 2C and Fe-NO bond in [Fe(H 2 O) 5 NO] 2C are linear. The Fe-O-O bond in [Fe(H 2 O) 5 O 2 ] 2C is bent. The order of the Fe-X distances is Fe-N!Fe-C!Fe-O, and that of net charge on XO ligands is O 2 !CO!NO. To determine the characteristics of the central Fe, the Fe I (H 2 O) 6 C , Fe II (H 2 O) 6 2C , and Fe III (H 2 O) 6 3C ions are employed as references. Results indicate that the [Fe(H 2 O) 5 CO] 2C (SZ2), [Fe(H 2 O) 5 NO] 2C (SZ3/2), and Fe(H 2 O) 5 O 2 ] 2C (SZ1) are best described by Fe II (SZ2) coupled to CO (SZ0), NO (SZ1/2), and O 2 (SZ1), respectively. The determined atomic net charges of Fe are robust even when the XO ligands undergo internal rotation. These results can be used as references models in understanding the bindings between XO and metal iron.
Electrochimica Acta, 2014
An innovative study on the electrochemical behaviour of mixed d metal-iron containing Wells-Dawson sandwich-type complexes [(FeOH 2 ) 2 M 2 (X 2 W 15 O 56 ) 2 ] 14− and [(MOH 2 ) 2 Fe 2 (X 2 W 15 O 56 ) 2 ] 14− (with M = Cr III , Mn II , Mn III , Co II , Ni II , Cu II or Zn II and X = P V or As V ) was carried out. These complexes have a four-centre equatorial metal cluster constituted of two Fe atoms and two atoms of another metal. The Fe III centres are either in an external position, [(FeOH 2 ) 2 M 2 ], or in an internal position, [M 2 (OH 2 ) 2 Fe 2 ]. Experimental methods (cyclic voltammetry and controlled potential coulometry) and theoretical calculations (density functional theory) allowed us to determine and analyse the redox potential values associated with the reduction of the Fe III centres in these species. The influence of the position of the Fe III centres, the nature of the metal centre M and the electron density distribution in the tetranuclear cluster (either [(FeOH 2 ) 2 M 2 ] or [(MOH 2 ) 2 Fe 2 ]) have been studied and rationalised in order to account for the observed behaviours. The data suggest that the most stable isomers are those where Fe III centres are internally-located, [(MOH 2 ) 2 Fe 2 ]. Consequently, their reduction is more difficult than those having externally-located Fe III isomers, [(FeOH 2 ) 2 M 2 ]. Some experimental results revealed a few exceptions to this rule which have not been rationalised yet.
Voltammetry of Dissolved Iron(III)-Nitrilotriacetate-Hydroxide System in Water Solution
Electroanalysis, 2005
The investigation of the dissolved iron(III) -nitrilotriacetate -hydroxide system in the water solution (I = 0.1 mol L -1 in NaClO 4 ; pH = 8.0±0.1) using differential pulse cathodic votammetry, cyclic voltammetry, and sampled direct current (d.c.) polarography, was carried out on a static mercury drop electrode (SMDE). The dissolved iron(III) ion concentrations varied from 2.68×10 -6 to 6×10 -4 mol L -1 and nitrilotriacetate concentrations were 1×10 -4 and 5×10 -4 mol L -1 . By deconvoluting of the overlapped reduction voltammetric peaks using Fourier transformation, four relatively stable, dissolved iron(III) complex species were characterized, as follows: [Fe(NTA) 2 ] 3-, mixed ligand complexes [FeOHNTA]and [Fe(OH) 2 NTA] 2-, showing a one-electron quasireversible reduction, and binuclear diiron(III) complex [NTAFeOFeNTA] 2-, detected above 4×10 -4 mol L -1 of the added iron(III) ions, showing a one-electron irreversible reduction character. The calculations with the constants from the literature were done and compared with the potential shifts of the voltammetric peaks. Fitting was obtained by changing the following literature constants: log β 2 ([Fe(NTA) 2 ] 3-) from 24 to 27.2, log β 1 ([FeNTA] -) from 8.9 to 9.2, log β 2 ([Fe(NTA) 2 ] 4-) from 11.89 to 15.7 and log β 2 ([Fe(OH) 2 NTA] 3-) from 15.63 to 19. The determination of the electrochemical parameters of the mixed ligand complex [FeOHNTA] -, such as: transfer coefficient (α), rate constant (k s ) and formal potential (E o ') was done using a sampled d.c.
Dalton transactions (Cambridge, England : 2003), 2015
In this paper we study the influence of substituting one CO ligand in [Fe2(CO)6{μ-(SCH2)2(Ph)P[double bond, length as m-dash]O}] () by better σ-donor L ligands affording [Fe2(CO)5(L){μ-(SCH2)2(Ph)P[double bond, length as m-dash]O}] {L = PPh3 () and P(OEt)3 ()} in relation to the steric interactions and the voltammetric behavior. Cyclic voltammetric investigations under N2 and CO showed remarkable differences in the electrochemical behaviour of complexes and : (i) Complex tends to expel PPh3 upon reduction whereas complex exhibits chemical reversibility and (ii) Under CO, complex reacts with CO affording a new compound , which shows a reversible wave at E1/2 ∼ -0.9 V (vs. ferrocenium/ferrocene couple). The presence of CO assists the formation of after electrochemically induced loss of PPh3 during the voltammetric experiment of . Using DFT calculations we provide an explanation for the difference in stabilities between the Fe-PPh3 and Fe-P(OEt)3 bonds.
Journal of Molecular Spectroscopy, 2002
In this contribution, we report density functional theory calculations on the transition metal complex (η 5 -C 5 H 5 )Fe(CO) 2 Cl and its fragments in differently charged states (anionic, neutral, cationic). The results are compared to literature data. The work is motivated by the long-term objective of a charge reversal or "NeNePo" (negative-neutral-positive) experiment (Wolf, Sommerer, Rutz, Schreiber, Leisner, Wöste, and Berry, Phys. Rev. Lett. 74, 4177-4180 (1995)). The calculated data explain results from preliminary mass spectroscopical experiments on anions. The calculations show that the complex could be well suited for a successful "NeNePo" experiment. C 2002 Elsevier Science 58