Synthesis, characterization, and electrochemical study of diiron organometallic derivatives of 2,6-dibutyl-4,8-dimethyl-1,5-dihydro-S-indacene

Article abstract of DOI:10.1139/cjc-2013-0062

A new fused ring compound, 2,6-dibutyl-4,8-dimethyl-1,5-dihydro-s-indacene (VII) (H₂L), has been synthesized from 2,5-dimethyl-1,4- dibromomethylbenzene in almost quantitative yield. Two organomtallic binuclear complexes, [CpFe-L-FeCp] (1) and the mixed-valence compound [CpFe-L-FeCp] ⁺ BF^-₄ (2), have been characterized by spectroscopic and electrochemical techniques. The cyclic voltammogram of 1 exhibits a potential difference of 668 mV between two redox peaks and the UV-vis-NIR spectra of compound 2 shows an intervalance charge transfer band at 1794 nm. The information gathered by these techniques indicates that the studied binuclear complex has strong interaction between the two metal centres.

Full text of DOI:10.1139/cjc-2013-0062

727
ARTICLE
Synthesis, characterization, and electrochemical study of diiron
organometallic derivatives of 2,6-dibutyl-4,8-dimethyl-1,5-dihydro-s-
indacene
M.K. Amshumali, Veronica Arancibia, Juan M. Manriquez, and Ivonne Chavez
Abstract: A new fused ring compound, 2,6-dibutyl-4,8-dimethyl-1,5-dihydro-s-indacene (VII) (H2L), has been synthesized from
2,5-dimethyl-1,4-dibromomethylbenzene in almost quantitative yield. Two organomtallic binuclear complexes, [Cp*Fe-L-FeCp*]
(1) and the mixed-valence compound [Cp*Fe-L-FeCp*]+ BF– (2), have been characterized by spectroscopic and electrochemical
4
techniques. The cyclic voltammogram of 1 exhibits a potential difference of 668 mV between two redox peaks and the UV-vis-NIR
spectra of compound 2 shows an intervalance charge transfer band at 1794 nm. The information gathered by these techniques
indicates that the studied binuclear complex has strong interaction between the two metal centres.
Key words: cyclic voltammetry, mixed-valance complexes, substituted indacene.
Résumé : On a synthétisé un nouveau composé a` noyau fusionné, 2,6-dibutyl-4,8-diméthyl-1,5-dihydro-s-indacène (VII) (H2L), a`
partir du 2,5-diméthyl-1,4-dibromométhylbenzène avec un rendement presque quantitatif. On a caractérisé deux complexes
organométalliques binucléaires, [Cp*Fe-L-FeCp*] (1) et le composé a` valence mixte [Cp*Fe-L-FeCp*]+BF− (2), par des méthodes
4
spectroscopiques et électrochimiques. Le voltammogramme cyclique de 1 présente une différence de potentiel de 668 mV entre
deux pics rédox et le spectre UV-Vis-PIR du composé 2 révèle une bande de transfert de charge d’intervalance a` 1 794 nm.
L’information obtenue par ces deux méthodes indique qu’il existe une forte interaction entre les deux centres métalliques du
complexe binucléaire étudié. [Traduit par la Rédaction]
Mots-clés : voltammétrie cyclique, complexes a` valence mixte, indacène substitué.
to the steric and inductive effect of the substituent. Thus, here, we
described the synthesis and some chemistry of 2,6-dibutyl-4,8-
dimethyl-1,5-dihydro-s-indacene.
Introduction
Oligomers or polymers based on metallocenes bridged by
fused-ring ligands such as pentalene or s-indacene are anticipated
to show interesting delocalized electronic properties like
Experimental
conductivity.1,2 One way to realize such materials may be a poly-
Instrumental
mer in which metal atoms alternate with ligands such as pen-
talene and s-indacene; these ligands can be regarded as two
cyclopentadienyl units fused to one another, either directly or
through a benzene ring, respectively. Indeed, EPR, Mossbauer,
electrochemical, and magnetic data show very strong metal–
metal interactions in the bimetallic species {L1[M(C5Me5)]2}n+ (L1 =
pentalene, s-indacene; M = iron, cobalt, nickel; n = 0, 1, 2).3 How-
ever, the stepwise construction of higher oligomers has been
hampered by escalating insolubility with increasing oligomeriza-
tion. Trimetallic iron species based on pentalene have been re-
ported,4 but the molecule shown in Fig. 1, which could, in
principle, function as a building block for higher oligomers, has a
solubility in boiling toluene of only approximately 400 mg L–1.5–8
Clearly, further progress will require a readily available fused-
ring ligand with solubilizing substituent. To this end, we have
begun investigating the organometallic chemistry of substituted
s-indacene ligand systems. Our first strategy was to investigate the
effect of substituent on the s-indacene system, since many differ-
ences, including solubility, have been reported between C5H5 and
C5Me5 chemistry.9–16 We also hoped that this substitution would
afford kinetic and (or) thermodynamic stability to {M(h-C5Me5)}2L-
type complexes for metals other than iron, cobalt, and nickel due
1H and 13C{H} NMR spectra were recorded on a Bruker AC-200P
(200 MHz and 50 MHz for 1H and 13C, respectively), and chemical
shifts are reported in parts per million relative to tetramethylsi-
lane. FT-IR spectra were recorded on a Bruker Vector-22 spectro-
photometer using a nujol mull between KBr disks. NIR spectra
were performed on a UV-vis-NIR SHIMADZU UV-3101 PC scanning
spectrophotometer. Elemental analyses were carried out with a
Fisons instruments EA-1108 CHNS elemental analyzer.
Cyclic voltammetry measurements were carried out with a Bio-
analytical Systems voltammetric analyzer (model CV-50w, version
2.3). The working electrode was platinum or a glassy carbon disk.
The auxiliary electrode was a platinum coil electrode, which was
isolated from bulk solution by a glass tube with a small-porosity
glass frit at the end. Neutral aluminum oxide was placed on the
frit and the tube was filled with a 0.1 mol L−1 solution of support-
ing electrolyte, [N(Bu)4]BF4 (Bu = butyl). The reference electrode
was an Ag/AgCl wire placed in a tube with a cracked glass bead at
the end and containing aqueous tetramethyl ammonium chlo-
ride. The concentration of this solution was varied until the po-
tential value was 0.0 V versus the saturated calomel electrode
(SCE). This electrode was located inside a Luggin capillary in the
Received 13 February 2013. Accepted 4 April 2013.
M.K. Amshumali. Department of Chemistry, Vijayanagara Sri Krishnadevaraya University, Jnana Sagara Campus, Vinayakanagara, 583104 Bellary, India.
V. Arancibia, J.M. Manriquez, and I. Chavez. Departamento de Quimica Inorganica, Facultad de quimica, Pontificia Universidad Catolica de Chile, Vicuna Mackena 4860, Casilla 306,
Correo 22, Santiago de Chile, Chile.
Corresponding author: M.K. Amshumali (e-mail: amshumali.m@gmail.com).
Can. J. Chem. 91: 727–731 (2013) dx.doi.org/10.1139/cjc-2013-0062
Published at www.nrcresearchpress.com/cjc on 24 April 2013.

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Can. J. Chem. Vol. 91, 2013
Fig. 1. Schematic view of an organometallic polymer based on pentalene or s-indacene.
electrochemical cell. The solvent used was dichloromethane. All
of the experiments were carried out under argon atmosphere at
room temperature (20 °C).
CH2), 3.60 (m, 4H, CH2), 4.48 (broad, OH), 7.12 (s, 2H, aromatic
protons). Elemental analysis: calcd. for C24H34O8: C 64, H 7.55;
found: C 63.89, H 7.51.
General considerations
2-[4-(2,2-Dicarboxy-hexyl)-2,5-dimethyl-benzyl]-2-butyl propionic
acid (IV)
All reactions were carried out under nitrogen and in dry sol-
vents. The following materials were used as supplied commer-
cially without further purification: diethyl methyl malonate,
KOH, HCl, n-butyllithium (1.6 mol L−1), polyphosphoric acid, and
ethyl alcohol. Reported procedures were followed to synthesize
Cp*Fe(acac).17
Tetra acid III (27 g, 60 mmol) was placed in a round-bottom flask
with a nitrogen inlet. The solid was heated and the water evolu-
tion observed. Water was removed under vacuum and heating
continued to 190 °C; when the tetra acid started melting, heating
was continued up to 200 °C until the evolution of CO2 was
stopped. The product obtained was a white solid (19 g, 52.7 mmol)
Syntheses
1
Yield: 97%; mp: 208–210 °C. H NMR (DMSO-d6 ppm): 0.81 (t, 6H,
CH3), 1.22 (t, 4H, CH2), 1.48 (t, 4H, CH2), 2.15 (s, 6H, CH3), 2.28 (t, 4H,
CH2), 2.78 (m, 4H, CH2), 4.33 (broad, OH), 6.84 (s, 2H, aromatic
protons). Elemental analysis: calcd. for C22H34O4: C 72.89, H: 9.43;
found: C 72.61, H 9.41.
Diethyl-2-butylmalonate (I)
To 75 cm3 of ethanol in a 500 cm3 round-bottom flask were
added sodium pieces (3.91 g, 17.0 mmol) with stirring at room
temperature. When all sodium was consumed, diethyl malonate
(26.6 mL, 17.5 mmol) was slowly added. After 30 min of stirring
at room temperature, 1-bromobutane (18.9 mL, 17.5 mmol) was
added and the solution and heated under reflux for 3 h. The excess
ethanol was distilled and to the residue was added at 0 °C water
and diethyl ether. After stirring and decantation, the two phases
were separated. The solvent of the organic phase was removed on
a rotary evaporator and the liquid product was distilled under
reduced pressure at 67 °C resulting in a colourless liquid (31 g,
2,6-Dibutyl-4,8-dimethyl-2,3,6,7-tetrahydro-s-indacen-1,
5-dione (V)
A large excess of polyphosphoric acid (500 g) and IV (19 g,
52.7 mmol) were placed in a 1 L round-bottom flask fitted with a
mechanical stirrer and a nitrogen inlet. The mixture was stirred
vigorously under nitrogen at 80 °C for 2 h. Then it was poured in
to a mixture of 500 g of ice in 2 L of water and the resulting yellow
precipitate was filtered, washed with water, and dried. The solid
was dissolved in chloroform (300 mL), filtered, and the solvent
removed under vacuum to afford a yellow solid. This was further
purified by recrystallizing in hexane (12 g, 37.03 mmol). Yield: 73%.
FT-IR (KBr): 1710 cm−1 (C=O). 1H NMR: 0.91 (t, 6H, CH3), 1.39 (t, 8H,
CH2), 1.9 (q, 4H, CH2), 2.5 (s, 6H, benzylic CH3), 3.2 (q, 4H, CH2).
Elemental analysis: calcd. for C22H30O2: C 80.98, H 9.2; found: C
80.88, H 9.15.
1
14.34 mmol). Yield: 81%. H NMR (CDCl3, ppm): 0.71 (t, 3H, butyl
CH3), 1.08 (t, 6H, ethyl CH3), 1.11 (m, 4H, CH2), 1.71 (m, 4H, CH2),
3.1 (q, 4H, ethoxy CH2), 4.02 (q, H, CH2).
2-[4-(2,2-Bis-ethoxycarbonyl-hexyl)-2,5-dimethyl-benzyl]-
2-butylmalonic acid diethyl ester (II)
To 75 cm3 of ethanol in a 500 cm3 round-bottom flask were
added sodium pieces (3.174 g, 13.8 mmol) with stirring at
room temperature. When all sodium was consumed, diethyl-2-
butylmalonate (30 g, 13.8 mmol) was slowly added. After 30 min of
stirring at room temperature, 2,5-dibromo methyl-p-xylene
(21.22 g, 6.9 mmol) was added and the solution heated under
reflux for 3 h. The excess ethanol was distilled and to the residue
was added at 0 °C water and diethyl ether. After stirring and
decantation, the two phases were separated. The solvent of the
organic phase was removed on a rotary evaporator affording a
2,6-Dibutyl-4,8-dimethyl-1,2,3,5,6,7-hexahydro-s-indacene-1,
5-diol (VI)
To LiAlH4 (0.72 g, 18.9 mmol) in 25 cm3 of diethyl ether placed in
a round-bottom flask (250 cm3) was added V (3.72 g, 11.48 mmol)
slowly with stirring at room temperature. After 3 h of stirring and
reflux, the mixture was cooled to 0 °C and a solution of HCl (18%,
100 cm3) was added. The ether layer was separated and the water
layer was extracted twice with 100 cm3 of ether. The ether layer
and the extracts were combined and dried under vacuum to give
a white solid. (3.5 g, 10.73 mmol). Yield: 93.6%. 1H NMR (DMSO-d6,
ppm): 0.81 (t, 6H, CH3), 1.42 (m, 8H, CH2), 2.08 (s, 6H, CH3), 2.42 (q,
4H, CH2), 2.71 (q, 2H, CH), 3.05 (q, 4H, CH2), 4.00 (broad, OH).
Elemental analysis: calcd. for C22H34O2: C 79.25, H 10.37; found: C
79.05 H, 10.11.
1
thick yellow oily liquid (53.8 g 12.7 mmol). Yield: 92%. H NMR
(CDCl3 ppm): 0.91 (t, 6H, butyl CH3), 1.28 (t, 12H, methyl CH3), 2.2 (s,
6H, benzylic CH3), 3.2 (q-8H, CH2), 4.12 (m, 8H, OCH2), 4.4 (m, 8H,
CH2), 6.82 (s, 2H, aromatic). Elemental analysis: calcd. for
C32H50O8: C 68.32, H 8.39; found: C 68.18, H 8.31.
2-[4-(2,2-Dicarboxy-hexyl)-2,5-dimethyl-benzyl]-2-butyl malonic
acid (III)
To a solution of KOH (180 g, 3.2 mol) in 100 cm3 of water, placed
in a round-bottom flask with a nitrogen inlet, tetra ester II (53.8 g,
95.7 mmol) was added and refluxed until the ester was completely
dissolved. This solution was poured into a mixture of water and
ice. Then, HCl (37%) was added until a pH of 3–4 was reached. The
compound, insoluble in water, was filtered, washed with water,
and dried giving a white crystalline solid (27 g, 60 mmol): Yield:
68%; mp: 183–186 °C. 1H NMR (DMSO-d6 ppm): 0.91 (t, 6H, CH3), 1.28
(t, 4H, CH2), 1.81 (t, 4H, CH2), 2.30 (s, 6H, benzylic CH3), 3.35 (q, 4H,
2,6-Dibutyl-4,8-dimethyl-1,5-dihydro-s-indacene (VII)
The diol VI (3.5 g.10.73 mmol) was stirred for 2 h under nitrogen
with p-toluene sulphonic acid (250 mg) in 100 cm3 of benzene at
75 °C. Then the solution was cooled to 0 °C and filtered to remove
unreacted VI. The organic phase was washed with water and dried
over MgSO4 for 18 h and filtered. After evoparation of the solvent
under vacuum, crude material obtained as a yellow powder was
recrystallized from pentane (2.4 g, 8.16 mmol). Yield: 81%. Mass
spectrum: M+ = 294.234. 1H NMR (CDCl3, ppm): 0.90 (t, 6H, CH3),
Published by NRC Research Press

Amshumali et al.
729
Scheme 1. Preparation of the ligand. 1, Na/EtOH; 2, KOH/H2O; 3, heating; 4, PPA/80 °C; 5, LiAlH4/ether; 6, p-TsOH.
1.3 (m, 4H, CH2), 1.55 (m, 4H, CH2), 2.3 (s, 6H, benzylic CH3), 2.38 (t,
4H, CH2), 3.01 (s, 4H, CH2), 6.72 (s, 2H, enylic H). 13C{1H} NMR
(CDCl3, ppm): 13.90 (methyl), 16.44 (benzylic methyl), 24.00 (CH2,
butyl), 30.53 (CH2, butyl), 33.35 (CH2 butyl), 39.00 (CH2, pentenyl),
123.98 (C−C, secondary, aromatic), 127.13 (C−H, pentanyl), 129.35
(C−C, tertiary, butyl-pentadienyl), 135.10 (C-pentadienyl), 141.32
(tertiary-pentadienyl). Elemental analysis: calculated for C22H30: C
89.73, H 10.27; found: C 89.29, H 10.12.
with diethyl ether, and dried under vacuum. the yield of 2 was 0.16
(0.19 mmol). Yield: 48%. Elemental analysis: calcd. for
C42H58Fe2BF4: C 66.25, H 7.48; found: C 65.29, H 5.38.
g
Results and discussion
Ligand synthesis
We have synthesized the substituted indacene ligand expecting
its greater solubility and kinetic and (or) thermodynamic stability
of its organometallic compounds and hoping it would lead to an
expansion of attempts to obtain the organometallic oligomers
based on the s-indacene spacer. The adopted route for synthesis is
shown in Scheme 1. It was based on previously described prepara-
tions of partially alkylated dihydro-s-indacenes.18
The alkylation of butyl diethylmalonic ester II produced a tetra
acid III in almost quantitative yield. Saponification and decarbox-
ylation of III gave a good yield of diacid IV). Upon treatment with
polyphosphoric acid, diacid IV underwent regioselective symmet-
rical cyclization yielding diketones V. The high specificity of these
reactions is due to the presence of the methyl groups on the
starting material II, which prevents any other cyclization. The
diols VI then are easily formed by hydrolysis. Subsequent acidic
intramolecular dehydration of alcohol functions led to ligand VII.
The overall yields of these six steps was above 35%. This new
substituted ligand shows a high solubility in most common or-
ganic solvents like pentane, hexane, and aromatics.
[Cp*Fe(2,6-dibutyl-4,8-dimethyl indacenyl)FeCp*] (1)
Fe(acac)2 (0.86 g, 3.4 mmol) was dissolved in tetrahydrofuran
(30 cm3) and cooled to –78 °C. A suspension of Cp*Li (0.48 g,
3.4 mmol) was then added to the mixture and subsequently
warmed to room temperature. In another flask, a hexane solution
of n-butyllithium (1.6 mol L−1, 2.1 cm3, 3.4 mmol) was added drop-
wise to VII (0.5 g, 1.7 mmol) dissolved in tetrahydrofuran at –78 °C
to form the dilithium salt. This mixture was warmed to room tem-
perature before the Cp*Fe (acac) solution was added with stirring at
–78 °C. This mixtuture was warmed to room temperature and
stirred for 2 h. Solvent was removed under vacuum and the prod-
uct was extracted with the toluene until the extraction become
colourless. The combined extracts were put together and evapo-
rated to dryness. The residue was dissolved in pentane (10 cm3)
and the solution cooled to –78 °C. The precipitate was filtered and
dried, yielding 0.6 g (1.1 mmol of red microcrystalline product.
1
Yield: 65%. This was further recrystalized from pentane. H NMR
(C6D6, ppm): 4.52 (s, 4H, CH), 2.66 (s, 6H, CH3, benzylic), 2.31 (t,
CH2, butyl), 1.62 (d, CH2, butyl), 1.45 (s, 30H, Cp*), 1.30 (q, CH2,
butyl), 0.85 (t, 6H, CH3). Elemental analysis: calcd. for C42H58Fe2:
C 74.87, H 8.61; found: C 74.21, H 8.31.
Synthesis and characterization of [{(␩5-C5Me5)-Fe}2L] (1)
Our synthetic stratergy for biferrocene, [{(␩5-C5Me5)-Fe}2L]
(1) was salt elimination, utilizing the reaction of the dianion
of the ligand [(Li+)2(L2–)] prepared in situ, with 2 mol of
(␩5-C5Me5)Fe(acac), as shown in Scheme 2. The reaction af-
forded a red solution from which air-sensitive red crystals of 1
were obtained after recrystallization from pentane. NMR spec-
troscopy showed only a single isomer to be present.
[Cp*Fe(2,6-dibutyl-4,8-dimethyl indacenyl)FeCp*]+BF–4 (2)
Compound 1 (250 mg, 0.4 mmol) dissolved in tetrahydrofuran
(20 cm3) was added to [FeCp2]+[BF4]– (0.11 g 0.4 mmol) and the
mixture was stirred at room temperature for 4 h, resulting in the
formation of a blue precipitate. The mixture was filtered and
the solid was washed with diethyl ether and dried under vacuum.
The crude solid was recrystallized by slow diffusion of diethyl
ether into a concentrated dichloromethane solution of 2. Blue
crystals appeared within 24 h. The crystals were filtered, washed
Synthesis and characterization of [{(␩5-C5Me5)-Fe}2L]+
BF–4 (2)
Treatment of 1 equiv. of THF solution of 1 with 1 equiv. of ferro-
cenium tetrafluoroborate gave, after washing with diethyl ether
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Can. J. Chem. Vol. 91, 2013
Scheme 2. Preparation of organometallic compounds.
Fig. 2. Cyclic voltammetry of [Cp*Fe(2,6-dibutyl-4,8-dimethyl-1,
5-dihydro-s-indacene)FeCp*].
Fig. 3. UV-Vis-NIR of [Cp*Fe(2,6-dibutyl-4,8-dimethyl-1,5-dihydro-s-
indacene)FeCp*] (Neutro) and its mixed-valence compound (Valencia
mixta).
to remove all ferrocene, a dark blue precipitate of salt [{(␩5-C5Me5)-
Fe}2L]+ BF–4 (2); these dark blue paramagnetic air-sensitive micro-
crystals were obtained after recrystallization of the solid by slow
diffusion of diethyl ether into a concentrated dichloromethane
solution of the salt.
Day’s classification.20 On the other hand, both oxidized com-
plexes are stable in the dichloromethane solution without
oxygen. The first anodic process (Epa1) presents an intensity cur-
rent ratio equal to unity (Ipa1/Ipa2 = 1), thus indicative of the revers-
ibility of the process whereas in the second anodic process (Epa2),
the intensity current ratio presents a slight deviation from unity.
A UV-Vis-NIR spectrum was recorded for complex 2. (Fig. 3). The
mixed-valence complex obtained by electrolysis in dichlorometh-
ane presents an intervalence charge transfer band at 1794 nm.
This band is not present in the neutral complex and this band is
not observed when the complex is oxidized twice. The same band
was observed for the mixed-valence complex prepared by chemi-
cal procedures. The position of intervalence transfer of complex
2 when recorded in acetonotrile and acetone shifts to 1790 and
1794 nm, respectively, indicating that unlike class II compounds,
this band is solvent independent.
Electrochemical characterization of [{(␩5-C5Me5)-Fe}2L] (1)
Cyclic voltammetry studies of 1 were carried out in dichloro-
methane solvent with tetrabutylammonium tetrafluoroborate as
a supporting electrolyte. The cyclic voltammograms present a
first reversible redox couple and a second quasi-reversible couple
(Fig. 2); the values of the potential change slightly with the scan
rates. At 50 mV s−1, the oxidations (Epa) occur at Epa1 = –550 mV and
E
pa2 = 118 mV versus the saturated calomel electrode. Controlled
potential electrolysis at 118 mV allowed us to determine that
1 equiv. of charge per mole of complex has been transferred in this
first redox process.
The initial dark red solution changes to a violet colour solution.
Reverse electrolysis reestablished the initial neutral binuclear
complex. When the complex is electrolyzed at 300 mV, the com-
plex is completely oxidized and the solution becomes blue. The
difference of potential (⌬Epa) between the oxidation peaks was
668 mV. This value of ⌬E indicates more than a moderate interac-
tion between the iron atoms, indicative of the classification of
class II and III complexes according to the modern method of
classification,19 than that of class II complexes of Robin and
Conclusion
We have developed a high yield synthesis for the new fused ring
ligand 2,6-dibutyl-4,8-dimethyl-1,5-dihydro-s-indacene (H2L) (VII).
We have proven that by means of a salt elimination strategy, it is
possible to obtain binuclear organometallic complexes that can
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Amshumali et al.
731
Munoz, N.; Visconti, G.; Aizman, A.; Manríquez, J. M. J. Am. Chem. Soc. 1988,
110, 6596. doi:10.1021/ja00227a068.
(6) Reiff, W. M.; Manríquez, J. M.; Ward, M. D.; Miller, J. S. Mol. Cryst. Liq. Cryst.
1989, 176, 423. doi:10.1080/00268948908037499.
(7) Reiff, W. M.; Manríquez, J. M.; Miller, J. S. Hyperfine Interact. 1990, 53, 397.
doi:10.1007/BF02101073.
(8) Barlow, S.; O’Hare, D. Chem. Rev. 1997, 97, 637. doi:10.1021/cr960083v.
(9) Bordwell, F. G.; Bausch, M. J. J. Am. Chem. Soc. 1983, 105, 6188. doi:10.1021/
ja00357a057.
(10) King, R. B.; Bisnette, M. B. J. Organomet. Chem. 1967, 8, 287. doi:10.1016/S0022-
328X(00)91042-8.
(11) Maitlis, P. M. Acc. Chem. Res. 1978, 11, 301. doi:10.1021/ar50128a003, and refs.
therein.
(12) Nesmeyanov, A. S.; Materikova, R. B.; Lyatifov, I. R.; Kurbanov, T. K.;
Kochetkova, N. S. J. Organomet. Chem. 1978, 145, 241. doi:10.1016/S0022-
328X(00)91129-X.
(13) Robbins, J. L.; Edelstein, N.; Spencer, B.; Smart, J. C. J. Am. Chem. Soc. 1982,
104, 1882. doi:10.1021/ja00371a017.
(14) Pez, G. P.; Armor, J. N. Adv. Organomet. Chem. 1981, 19, 1. doi:10.1016/S0065-
3055(08)60362-7, and refs. therein.
(15) Jutzi, P. Pure Appl. Chem. 1989, 61, 1731. doi:10.1351/pac198961101731, and refs.
therein.
(16) King, R. B. Coord. Chem. Rev. 1976, 20, 155. doi:10.1016/S0010-8545(00)80323-9,
and refs. therein.
(17) Robbins, J. L.; Edelstein, N. M.; Cooper, S. R.; Smart, J. C. J. Am. Chem. Soc.
1979, 101, 3853. doi:10.1021/ja00508a023, and refs. therein.
(18) (a) Bunel, E. E.; Valle, L.; Manriquez, J. M. Organometallics 1985, 4, 1680.
doi:10.1021/om00128a034; (b) Dahrouch, M.; Jara, P.; Mandez, L.; Portialla, Y.;
Abril, D.; Alfonso, G.; Chavez, I.; Manriquez, J. M.; Baudet, M. R.; Riviere, P.;
Castel, A.; Rouzaud, J.; Gornitzka, H. Organometallics 2001, 20, 5591. doi:10.
1021/om010119w.
(19) Demadis, K. D.; Harrtshom, C. M.; Meyer, T. J. Chem. Rev. 2001, 101, 2655.
doi:10.1021/cr990413m.
(20) Robin, M. B.; Day, P. Adv. Inorg. Chem. Radiochem. 1967, 10, 247–422. doi:10.
1016/S0065-2792(08)60179-X.
be further oxidized chemically or electrochemically to afford the
corresponding mixed-valence complex. Compounds 1 and 2 are
more readily soluble in solvents like pentane and toluene com-
pared with unsubstituted and methylated indacenyl complexes.
From spectroscopic data and electrochemical studies, we can con-
clude that in the complex [{(␩5-C5Me5)-Fe}2L]+BF– (2), there is a
4
stronger interaction between the metal centres when compared
with the other class II complexes of the Robin and Day
classification.20
Acknowledgements
We acknowledge support from Fondecyt (grants 1020314 and
1020525) and a scholarship from Mecesup2003 for the award for
completion of a Ph.D.
References
(1) Katz, T. J.; Schulman, J. J. Am. Chem. Soc., 1964, 86, 3169. doi:10.1021/
ja01069a053.
(2) Katz, T. J.; Acton, N.; McGinnis, J. J. Am. Chem. Soc. 1972, 94, 6205. doi:10.1021/
ja00772a053.
(3) (a) Manriquez, J. M.; Ward, M. D.; Reiff, W. M.; Calabrese, J. C.; Jones, N. L.;
Carroll, P. J.; Bunel, E. E.; Miller, J. S. J. Am. Chem. Soc. 1995, 117, 6182.
doi:10.1021/ja00128a004; (b) Roussel, P.; Cary, D. R.; Barlow, S.; Green, J. C.;
Varret, F.O.; Hare, D. Organometallics 2000, 19, 1071. doi:10.1021/om990937c;
(c) Mac-Leod Carey, D.; Verdejo, C. M.; Castro, A. M.; Burgos, F.; Abril, D.;
Adams, C.; Molins, E.; Cador, O.; Chavez, I.; Manríquez, J. M.; Pérez, R. A.;
Saillard, J. Y. Polyhedron 2010, 29, 1137. doi:10.1016/j.poly.2009.12.002.
(4) Oelckers, B.; Chávez, I.; Manríquez, J. M.; Román, E. Organometallics 1993, 12,
3396. doi:10.1021/om00033a007.
(5) Bunel, E. E.; Valle, L.; Jones, N. L.; Carroll, P. J.; Barra, C.; Gonzalez, M.;
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