Preparation and ESR characterization of polyalkyl-s-indacenyl anion-radicals from polyalkyl-1,5-dilithio-s-indacenes

Article abstract of DOI:10.1016/j.ica.2010.10.002

Polyalkyl-(or chloropolyalkyl)-s-indacenyl anion radicals were obtained from the organodilithium derivatives of the corresponding substituted-1,5- dihydro-s-indacenes by three different methods: (i) UV photolysis, (ii) oxidation by a ferrocenium salt, (iii) single electron transfer reaction from an electron rich olefin. The last reaction (iii) involves transient formation of an unstable polyalkyl-lithio-s-indacenyl imidazolidinium salt. The same salt, obtained by another way by reacting 1,3-dimethylimidazolidinium chloride with the polyalkyl-1,5-dilithio-s-indacene, also leads to the corresponding lithium polyalkyl-s-indacenyl anion radical. All lithium polyalkyl-s-indacenyl anion radicals studied were characterized from their ESR spectra. They present a characteristic symmetrical spin distribution. On the contrary a Rhodium-COD polyalkyl-s-indacene radical presents a non symmetrical spin distribution.

Full text of DOI:10.1016/j.ica.2010.10.002

Inorganica Chimica Acta 366 (2011) 44–52
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Inorganica Chimica Acta
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Preparation and ESR characterization of polyalkyl-s-indacenyl anion-radicals
from polyalkyl-1,5-dilithio-s-indacenes
C. Adams a, J. Araneda a, C. Morales a, I. Chavez a, J.M. Manriquez a, D. Mac-Leod Carey b, N. Katir c, A. Castel c,
P. Rivière c, , M. Rivière-Baudet c, M. Dahrouch d, N. Gatica d
⇑
a Facultad de Química, Pontificia Universidad Católica de Chile, Casilla 306, Correo 22, Santiago de Chile, Chile
b Departamento de Química, Universidad Andres Bello, República 275, Santiago de Chile, Chile
c Laboratoire d’Hétérochimie Fondamentale et Appliquée, UMR 5069 du CNRS, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex 94, France
d Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile
a r t i c l e i n f o
a b s t r a c t
Article history:
Polyalkyl-(or chloropolyalkyl)-s-indacenyl anion radicals were obtained from the organodilithium deriv-
atives of the corresponding substituted-1,5-dihydro-s-indacenes by three different methods: (i) UV pho-
tolysis, (ii) oxidation by a ferrocenium salt, (iii) single electron transfer reaction from an electron rich
olefin. The last reaction (iii) involves transient formation of an unstable polyalkyl-lithio-s-indacenyl imi-
dazolidinium salt. The same salt, obtained by another way by reacting 1,3-dimethylimidazolidinium
chloride with the polyalkyl-1,5-dilithio-s-indacene, also leads to the corresponding lithium polyalkyl-s-
indacenyl anion radical. All lithium polyalkyl-s-indacenyl anion radicals studied were characterized from
their ESR spectra. They present a characteristic symmetrical spin distribution. On the contrary a Rho-
dium-COD polyalkyl-s-indacene radical presents a non symmetrical spin distribution.
Received 9 June 2010
Accepted 6 October 2010
Available online 13 October 2010
Keywords:
Polyalkyl-(or chloropolyalky)l-s-indacenyl
anion radicals
ESR
1,10,2,20-Tetramethyl-2,20-bisimidazolidine
Polyalkyl-lithio-s-indacenylimidazolidinium
salt
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
Ev), or a Rybermag R10-10 spectrometer operating in Ei mode, or
by chemical desorption (DCi/CH4 or NH3). Infrared spectra were
Because of their potential use as ligands or spacers in the syn-
thesis of binuclear complexes, conducting polymers and biological
compounds, polyalkyl-s-indacenes and polyalkyl-1,5-dihydro-s-
indacenes, as well as some of their radical anions, radical cations
or radicals have been prepared and studied [1–10].
recorded on a Perkin–Elmer 1600FT spectrometer. ESR spectra
were recorded on a Brüker spectrometer EPR ELFXSYS E 500. g Val-
ues were calculated by the Brüker Xepr software using the fre-
quencemeter integrated to the ER049X microwave bridge. The
magnetic field was controlled by the NMR teslameter Brüker and
verified against dpph. Elemental analyses were done by the ‘‘Cen-
tre de Microanalyses de l’Ecole Nationale Supérieure de Chimie de
Toulouse”. All Density Functional (DF) calculations reported here
were performed with the Amsterdam Density Functional package,
ADF 2006.01 [11]. All the structures were fully optimized (without
any geometry constrain) via analytical energy gradient techniques
employing the Local Density Approximation [12] (LDA), and the
Generalized Gradient Approximation (GGA) method using Vosko,
Wilk and Nusair’s local exchange correlations [13], with nonlocal
exchange corrections by Becke [14], and non local electronic corre-
lations by Perdew [15]. We used uncontracted type IV basis set
used Triple-n accuracy sets of Slater-Type Orbitals [16] (STO) with
a single polarization function added for the main group elements
(2p on H and 3d on C). Frozen Core approximation [17] was applied
to the inner orbitals of the constituent atoms: the C core up to 1s,
Cl up to 2p and Rh up to 3d. For recrystallized compounds, melting
points were measured on a Leitz microscope.
Here we report the lithium anion-radicals (Ar)ꢀÅ Li+ of various
polyalkyl-s-indacenes or halopolyalkyl-s-indacenes which have
been prepared by three different ways and then characterized by
ESR.
2. Experimental section
All reactions were performed under nitrogen using standard
Schlenk tube and dry solvents. NMR spectra were recorded on Bru-
ker AC 80 (1H, 80 MHz), ARX400 (1H, 400.13 MHZ); AC 200 (13C,
50.32 MHz), ARX 400 (13C, 100.62 MHz) spectrometers. Mass and
gas chromatography (GC/mass) and mass spectra were recorded
with a Hewlett Packard HP5989 in electron impact mode (Ei, 70
⇑
Corresponding author. Tel.: +33 5 61 55 83 48; fax: +33 5 61 55 82 04.
E-mail address: riviere@chimie.ups-tlse.fr (P. Rivière).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.10.002

C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
45
2.1. Preparation of Ic
(M+347 – HCOOEt) 273 (81); (M+Å ꢀ 2 BuC(COOEt)2) 132 (31). Anal.
Calc. for C32H50O8: C, 68.30; H, 8.96. Found: C, 68.10; H, 8.79%.
Ligand Ic was synthesized following the multi step process of
Dahrouch et al. [3], using reagents A–F prepared as follow.
2.1.3. Preparation of C: 2,20-(2,5-dimethyl-1,4-phenylene)
bis(methylene)bis(2-butylmalonic acid)
2.1.1. Diethyl 2-butyl-malonate A
CH3
(f)
(c)
(d)
(g)
(b)
7
2
COOH
COOH
H3C
COOCH2CH3
3
1
(e)
(d)
H3C
(e)
(b)
(a)
HOOC
HOOC
6
COOCH2CH3
4
CH3
5
(f)
(c)
(g)
(a)
CH3
To 100 mL of ethanol in a 300 mL round-bottomed flask was
added Na pieces (3.91 g, 0.17 mol) with stirring at room tempera-
ture. When all Na was consumed, diethylmalonate (28.03 g,
0.175 mol) was added slowly. After 30 min stirring at room tem-
perature, 1-bromobutane (23.96 g, 0.175 mol) was added and the
solution heated at reflux for 3 h. The excess of ethanol was dis-
tilled. To the refreshed residue (0 °C) was added water and dieth-
ylether. After stirring and decantation, the two phases were
separated. The solvent of the organic phase was removed on a ro-
tary evaporator affording a liquid which was purified by distilla-
tion in vacuum, yielding 31 g (82%) of A. Bp: 67 °C/0.8 mm Hg,
conforming to [18]. 1H NMR (CDCl3) d 0.71 (t, 3H, CH3 (a),
3Jab = 7.1 Hz); 1,00–1.30 (m, 10H, CH2 (b,c) and CH3 (g)); 1.81 (q,
To a solution of KOH (180 g, 3.21 mol) in 75 mL of 1/1 EtOH/H2O
placed in a round-bottomed flask with a nitrogen inlet, was added
B (53.8 g, 0.096 mol).The reaction was exothermic and was heated
further 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 was reached. The resulting compound, insoluble in
water, was filtered, washed with water and then dried at 60 °C un-
der low pressure giving 29.41 g of C. Yield 68%. m.p.: 189 °C; 1H
3
NMR: (DMSO): d 0.85 (t, 6H, CH3 (a); Jab = 6.8 Hz); 1.23 (m, 8H,
CH2(b,c)); 1.62 (bs, 4H, CH2(d)); 2.14 (s, 6H, CH3 (in 2,5)); 3.02 (s,
4H, CH2(7)); 6.84 (s, 2H, CHar (3,6)); 12.86 (s, 4H, COOH). 13C{1H}
NMR (DMSO): d 14.6 (CH3 (a)); 19.7 (CH3 in 2,5); 22.6, 23.0 (CH2
(b,c)); 32.1 (CH2(d)); 34.5 (CH2 (7)); 57.7 (C(e)); 132.1 (CH (3,6));
3
3
2H, CH2 (d), Jcd = 3Jde = 7.5 Hz); 3.23 (t, 1H, CH (e), Jde = 7.5 Hz);
3
4.12 (q, 4H, CH2 (f), Jfg = 7.1 Hz) conform to [19]; 13C{1H} NMR
132.9, 134.3 (C(1,2,4,5); 176.98 (CO). IR (KBr pellet, cmꢀ1
) m:
(CDCl3): 13.35 (CH3 (a)); 13.8, 13.9 (CH2 (b,c)); 28.23 (CH2 (d));
29.26 (CH3 (g)); 51.81 (CH (e)); 60.94 (CH2 (f)); 169.32 (CO). Anal.
Calc. for C11H20O4: C, 61.09; H, 9.32. Found: C, 61.28; H, 9.28%.
3339, 3239 (OH); 1738 (C@O). Anal. Calc. for C24H34O8 C, 63.98;
H, 7.61. Found: C, 63.89; H, 7.53%.
2.1.4. Preparation of D: 2,2’(2,5-dimethyl-1,4-phenylene)bis
(methylene)dihexanoic acid
2.1.2. Preparation of B: tetraethyl 2,20-(2,5-dimethyl-1,4-
phenylene)bis(methylene)bis(2-butylmalonate)
CH3
CH3
(f)
(g)
7
2
H3C
COOH
(b)
COOCH2CH3
7
2
H3C
3
(e)
(d)
1
(2)
3
COOCH2CH3
1
6
(e) (2)
(d)
(b)
6
4
(2`)
HOOC
CH3
(a)
5
CH3CH2OOC
CH3CH2OOC
(c)
(2`)
4
CH3
5
(c)
CH3
(a)
CH3
Compound C (27.08 g, 0.060 mol) was placed in a round-bot-
tomed flask (500 mL) fitted with a nitrogen inlet and melted
(190–200 °C) releasing CO2. The cooled residue (21.18 g) was a
white solid identified as D. Yield 97%; m.p.: 132 °C. 1H NMR:
Following the same procedure, but using ethanol (100 mL), Na
(3.17 g, 0.14 mol), butyldiethylmalonate (30.00 g, 0.14 mol), and
1.4-bis bromomethyl-2,5-dimethylbenzene (20.22 g, 0.069 mol)
35.83 g of B were obtained. Yield 92%. m.p: 69 °C. 1H NMR (CDCl3):
0.86 (t, 6H, CH3(a), 3Jab = 7.1 Hz); 1.10–1.25 (m, 8H, CH2(b,c)); 1.18
3
(DMSO): d 0.79 (t, 6H, CH3 (a), Jab = 7.0 Hz); 1.20 (m, 8H, CH2
(b,c)); 1.43 (m, 4H, CH2 (d)); 2.13 (s, 6H, CH3 in 2,5); 2.41 (m, 4H,
CH2(7)); 2.70 (m, 2H, CH (e)); 6.82 (s, 2H, CH(3,6)); 11.70 (s, 2H,
COOH). 13C{1H} NMR (DMSO): d 13.8 (CH3 (a)); 18.6 (CH3 in 2,5);
22.1, 29.1 (CH2 (b,c)); 31.6 (CH2 (d)); 34.8 (CH2 (7)); 45.7 (CH
(e)); 131.1 (CH (3,6)); 132.7, 135.5 (C(1,2,4,5)); 176.6 (COOH). IR
3
(t, 12H, CH3 (g)), Jfg = 7.0 Hz); 1.77 (m, 4H, CH2 (d)); 2.14 (s, 6H,
CH3(in 2,5)); 3.17 (s, 4H, CH2(7)); 4.11 (m, 8H, CH2 (f)), 6.78 (s,
2H, CH (3,6)). 13C{1H} NMR (CDCl3): 13.7 (CH3 (a)); 13.9 (CH3
(g)); 19.2 (CH3 in 2,5); 22.8, 26.4 (CH2 (b,c)); 32.3 (CH2 (d)); 34.0
(CH2 (7)); 58.6 C (e)); 60.9 (CH2 (f)); 132.1 (CH (3,6)); 133.1,
(KBr pellet, cmꢀ1
) m 1704 (C@O), 2975 (OH).
MS (Ei, m/z (%)): M+Å 362 (14); (M+Å – BuCHCOOH) 247 (100);
(M+Å – 2BuCHCOOH) 132 (16); Anal. Calc. for C22H34O4: C, 72.89;
H, 9.45. Found: C, 73.20; H, 9.51%.
134.0 (C(1,2,4,5)); 171.6 (CO). IR (KBr pellet, cmꢀ1
)
m
1730 (C@O).
MS (Ei, m/z (%): M+Å 562 (12); (M+Å – BuC(COOEt)2 347 (100) and

46
C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
3
2.1.5. Preparation of E: 2,6-dibutyl-4,8-dimethyl-2,3,6,7 tetrahydro-s-
(a), Jab = 7.2 Hz); 1.30–1.80 (m, 14H, CH2 (b,c,d) and CH (2,6));
2.28 (s, 60%); 2.29 (s, 40%), 6H, CH3 in 4,8); 2.25(m) and 2.58(m)
60% of 4H, in 3, 7); 2.90 (d,d) and 3.10 (d,d) (40% of 4H in 3,7,
2J = 16 Hz, 3J = 7.6 Hz); 4.89 (m, 40% of 2H in 1, 5); 5.06 (d, 60% of
indacene-1,5-dione
2H in 1,5,3J CHCH = 5.6 Hz). IR (KBr, cmꢀ1
) m 3355 (OH).
CH3
O
4
2.1.7. Preparation of Ic: 2,6-dibutyl-4,8-dimethyl-1,5-dihydro-s-
indacene
5
3
6b
6a
6c
3a
8a
4a
7a
2a
CH3
2
6
2d
2c
H3C
6d
1
CH3
2b
7
8
O
4
5
3
6b
6a
6c
CH3
3a
8a
4a
7a
2a
CH3
2
6
2d
2c
H3C
6d
Polyphosphoric acid (500 g, a large excess) and D (19.17 g,
0.053 mol) were placed in a round-bottomed flask (1L) fitted with
a mechanical stirrer and a nitrogen inlet. The mixture was stirred
vigorously under nitrogen at 80 °C for 5 h. It was then poured into
a solution of 500 g of ice in 2L of H2O. The resulting bright yellow
precipitate was filtered, washed with water and dried affording
14.37 g of crude E. Yield 83%, which was then recrystallized in
hexane.
1
2b
7
8
CH3
In a round-bottomed flask (250 mL) were mixed 3.53 g of crude
F (10.68 mmol) and 0.25 g of paratoluenesulfonic acid in 100 mL of
C6H6.The mixture was heated 2 h at 60 °C. The solution was then
cooled to 0 °C and filtered. The liquid phase was washed with
water. The organic phase was dried over MgSO4 for 24 h. After
evaporation of solvent in vacuo, the crude Ic was crystallized in
pentane yielding 2.46 g. Yield 78%; m.p. 142 °C; 1H NMR (CDCl3):
m.p. 113 °C; 1H NMR: (CDCl3):
d 0.92 (t, 6H, CH3 (a),
3Jab = 7.1 Hz); 1.38–1.50 (m, 12H, CH2 (b,c,d)); 2.59 (s, 6H, CH3 in
4,8); 1.94 (dd, 2H, 50% of 4H, CH2 (3,7)); 2.64 (m, 2H, CH (2,6);
3.19 (dd, 2H, 50% of 4H, CH2 (3,7); 2J = 17.6 Hz, 3J = 8.6 Hz).
13C{1H} NMR (CDCl3): d 12.8 (CH3 (a), 13.9 (CH3 in 4,8)); 22.7,
29.5 (CH2 (b,c)); 31.3 (CH2 (d)); 30.6 (CH2 (3,7)); 48.4 (CH (2,6));
3
d 0.97 (t, 6H, CH3 (2a, 6a), Jab = 7.5 Hz); 1.41 (sext, 4H, CH2 (2b,
132.7, 137.2, 152.5 (CIVAr); 210.5 (CO). IR (CDCl3, cmꢀ1
) m 1708
6b); Jab = 3Jbc = 7.5 Hz); 1.63 (quint, 4H, CH2 (2c, 6c); Jbc
=
3
3
3Jcd = 7.5 Hz); 2.37 (s, 6H, CH3 in 4,8); 2.52 (t, 4H, CH2 (2d, 6d),
(C@O). Anal. Calc. for C22H30O2: C, 80.94; H, 9.26. Found: C,
3Jcd = 7.5 Hz); 3.23 (bs, 4H, CH2 (1,5)); 6.63 (t, 2H, CH (3,7), J1,3
=
4
80.88; H, 9.15%.
4J5,7=1.3 Hz).
C NMR (CDCl3): d 14.00 (CH3(2a, 6a)); 15.04
13
(CH3 in 4,8); 22.59 (CH2 (2b, 6b)); 31.32 (CH2 (2c,(6c)); 31.50
(CH2 (2d, 6d)); 40.06 (CH2 (1,5)); 124.72 (CH (3, 7)); 140.58,
140.68 (CIV ar, 3a, 4a, 7a, 8a, 4, 8)). 148.69 (C (2,6)); IR (CDCl3,
2.1.6. Preparation of F: 2,6-dibutyl-4.8-dimethyl-1,2,3,5,6,7,-
hexahydro-s-indacene-1,5-diol
cmꢀ1 1601 (C@C). MS (Ei, m/z (%)): M+Å 294 (84); M+Å – Pr 251
) m
(100); M+Å – 2Pr 208 (6) ; M+Å – (2Pr + 2 Me) 178 (3). Anal. Calc.
for C22H30: C, 89.73; H, 10.27. Found: C, 89.59; H, 10.42%.
CH3
HO
4
5
3
6b
6a
6c
3a
8a
4a
7a
2.2. Preparation of If (1-chloro-2,6-diethyl-4,5,8-trimethyl-3,7-
dihydro-s-indacene)
2a
CH3
2
6
2d
2c
H3C
6d
1
2b
7
8
CH3
OH
H3C
CH3
4
3
5
3a
8a
4a
7a
CH3
11
6
2
10
12
To LiAlH4 (0.71 g, 18.7 mmol) in 25 mL of diethylether placed in
a round-bottomed flask (250 mL), E (3.72 g, 11.4 mmol) in 25 mL of
diethyl ether was added slowly with stirring at room temperature.
After 3 h stirring at reflux, the mixture was cooled to 0 °C and a
solution of HCl 18% was added slowly. After extraction with dieth-
ylether, drying with Na2SO4 and concentration of the solvent in va-
cuo, the residue of 3.52 g was identified as crude F: Yield 93%.
The F formed here is never pure because of partial dehydration
[3] leading to Ic. Therefore, the crude compound F was immedi-
ately transformed into Ic with no further spectroscopic
characterization.
In order to characterize the transient diol the same preparation
was repeated but performing the hydrolysis with water instead of
HCl. to limit dehydration. The compound obtained was identified
as crude F. (m.p. 143–150 °C) under two major isomeric forms in
relative proportions 60/40%. 1H NMR: (CDCl3): d 0.96 (t, 6H, CH3
9
H3C
1
7
8
Cl
CH3
To a solution of 2,6-diethyl-4,8-dimethyl-2,3,6,7 tetrahydro-s-
indacene-1,5-dione [3,20] (4.03 g, 14.05 mmol) in 100 ml of CH2Cl2
in a round-bottomed flask (500 mL) fitted with a nitrogen inlet and
a reflux condenser was added at room temperature and with stir-
ring PCl5 (4.16 g, 20 mmol) in suspension in 80 mL of CH2Cl2. The
mixture was stirred at reflux for 48 h and then cooled to 0 °C before
water (100 mL) was added. After 2 extractions with 30 mL of
CH2Cl2 and 30 mL of ether, the organic phase was treated with

C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
47
R"
R
R
I
R'
- nBuLi, THF
- 80°C
R"
Li*
Li*
R
R
R'
II
Toluene, THF (1/1)
-
Cp2Fe+ BF4
ii)
hν
ERO, -Li
iii)
i)
-BF4Li, Cp2Fe
-Li
R"
R"
Li*
Li+
Toluene, THF (1/1)
R
R
R
R
III
R'
lithium anion radical
R'
lithiated radical
I, II, III:
a) R = Me, R'=R"=H; b) R= Et, R'=R"=H;
c) R= nBu, R'= R"=H; d) R=Me, R'=R"=Me;
e) R=Et, R'=R"=Me;
f) R=Et, R'=Cl, R"=Me
* for clarity, complexation of Lithium with THF is not represented here
Scheme 1.
e-
N
N
N
N
N
N
N
N
N
N
hν
2 Mes3GeCl +
2 [Mes3GeCl]
+
2
(ERO)
2 Mes3GeCl
Cl
N
N
Cl
4 Mes3Ge
+
2
Scheme 2.
50 mL of an aqueous solution of Na2CO3 (10%) and then was sepa-
rated and dried over MgSO4 for one night prior to removal of sol-
vent on a rotary evaporator. The sticky residue (3.57 g) was
analyzed by IR and GC/mass(EI), and identified as a mixture of ini-
tial diketone (GC/Mass, Ei, m/z: M+Å 270 (85%); M+Å – C2H4 242
(100%); M+Å – C2H4 260 (83%). Since these compounds could not
be easily separated, the whole mixture was dissolved in 50 mL of
ether and treated with 10 mL of an aqueous solution of KOH (1%)
to convert X to Y. The organic phase was dried over MgSO4 for
48 h and then treated with an excess of methylmagnesium iodide
(52.5 mmol, i.e. 35 mL of 1.5 M CH3MgI in ether). The mixture was
stirred and heated for 6 h at reflux, then cooled and hydrolyzed
with HCl (37%) and extracted with 50 mL of ether. The organic
(100%); IR (KBr): 1697
m C@O), compound intermediate X (Scheme
4) (GC/mass, Ei, m/z%: M+Å 324 (100%); M+Å – Cl 289 (63%)) and
mainly compound Y (Scheme 4) (GC/mass, Ei, m/z%: M+Å 288

48
C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
Fig. 1. ESR spectra of IIIc: (A) experimental spectrum obtained by reaction (iii) Scheme 1 (or 3a,b,d,e Scheme 3); (B) simulated spectrum L/G = 0.5, IW: 0.15; (C) experimental
spectrum obtained by reaction (3f) Scheme 3.
phase was dried over MgSO4 for one night prior to the removal of
the solvent on a rotary evaporator. The residue was dissolved in
25 mL of hexane and stored in a deep freezer. After a few days, yel-
low brown large needles (0.73 g) were isolated by filtration. Yield
17%. A GC/mass analysis of a benzene solution of these needles
shows that they are formed from a cocrystalization of two com-
pounds: about 80% of the dissymmetric If (R = Et, R0 = Cl, R00 = Me),
GC/mass, Ei, m/z%: M+Å 286 (100%); M+Å – Cl 251 (77%) and 20% of
the symmetric hexaalkyl-s-indacene (R = Et, R0 = R00 = Me), GC/
mass, Ei, m/z%: M+Å 266 [3]. These two compounds were separated
(C (5)); 135.04 (C (8a)); 139.58 (C (3a)); 141.48 (C (4a)); 141.99
(C (7a)); 142.58 (C (2)); 144.10 (C (6)). IR (CDCl3, cmꢀ1
) m 1605,
1622 (C@C); MS (Ei, m/z (%)): M+.286 (100), M+Å – Cl 251 (77);
M+Å – Me 271 (83); M+Å – (Cl + Et) 22 (31). Anal. Calc. for
C19H23Cl: C, 79.56; H, 8.08; Cl, 12.36. Found: C, 79.37; H, 8.17, Cl,
12.24%.
2.3. Preparation of IIa–f
The dilithium derivatives of Ia, b, d, e [3], Ic, If, were prepared
according to the general procedure described in reference [3].To
the solution of I in THF was added at ꢀ80 °C and with stirring a
solution of 2 M equivalents of BuLi (1.6 M in hexane). The solution
was warmed to room temperature.
by preparative HPLC on a column of silicagel microspheres 12 lm
(20 g, Merck), pressure 10 bar, eluent: 90% petroleum ether and
10% of (CH2Cl2: 75%, ethylacetate: 25%). Each compound was crys-
tallized and identified. The predominant one was identified as
If.mp: 176–178 °C; 1H NMR (CDCl3): d 1.15 (t, 3H, CH3 (12),
Monolithium derivative IV was prepared using the same proce-
dure, from only 1 M equivalent of BuLi [3,6].
3
3J11,12 = 7.6 Hz); 1.18 (t, 3H, CH3 (10), J9,10 = 7.6 Hz); 2.26 (s, 3H,
3
CH3 on 5); 2.48 (q, 2H, CH2(11), J11,12 = 7.6 Hz); 2.51 (s, 3H, CH3
3
on 4); 2.57 (q, 2H, CH2(9), J9,10 = 7.6 Hz); 2.65 (s, 3H, CH3 on 8);
2.4. Preparation of III a–f and V; ESR experiments
13
3.19 (s, 2H, CH2 (7)); 3.22 (s, 2H, CH2(3)).
C NMR (CDCl3): d
13.22 (C(10)); 14.19 (CH3 on 5); 14.30 (C (12)); 14.47 (CH3 on 8);
14.95 (CH3 on 4); 21.63 (CH2 (9, 11)); 37.54 (CH2 (3)); 38.84
(CH2(7)); 122.95 (C (4, 8)); 123.0 (C (6)); 126.70 (C (1)); 133.24
Each THF/pentane solution of dilithium derivatives IIa–f or
monolithium derivative IV in approximately 0.04 M concentration
was divided into three ESR quartz tubes (i), (ii) and (iii).

C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
49
(b)
(a)
(c)
Li+
III
a
Fig. 2. ESR spectrum of IIIa and simulation.
(b)
(a)
(c)
Li+
IIIb
Simulation: L/G:0.5; l.W./0.2
Fig. 3. ESR spectrum of IIIb and simulation.
To (ii) frozen in liquid nitrogen was added a solution of Cp2Fe+
ꢀ
BF4 in dichloromethane and the ESR spectrum was recorded at
243 K.
To (iii) frozen in liquid nitrogen was added a solution of the ERO
in toluene and ESR spectra were recorded at 243 K (Figs. 1–5 and
Table 1).
To a similar sample of IIc was added a solution of 1,3-dimethy-
limidazolidinium chloride[10] solubilized in THF/DMSO and at
243 K the ESR spectrum observed is the same as the spectrum of
IIIc (Fig. 1). The remaining reaction mixture was then analyzed
by GC/mass allowing the characterization of 1,10,3,30-tetramethyl
bis-imidazolidine (M+Å = 198 amu).
Fig. 4. Spin density localization for IIIb.
3. Results and discussion
To (i) was added one volume of toluene and the sample was
irradiated at 254 nm at 243 K in the ESR cavity.
All radical anions presented here were prepared from the
corresponding dimetallated derivatives of various polyalkyl-1,5-

50
C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
g : 2.0028
aHa: 6.35 G (t)
Hb: 5.83 G (sept.)
D
E
F
a
aHc: 1.17 G (quint)
aHd: 0.56 G (quart.)
Simulation: L/G :0.5
l.W : 0.2
Subtraction D-E at the
same scale
Fig. 5. ESR spectra of IIIf, (D) Experimental spectrum and ESR characteristics, (E) simulation, (F) subtraction (D and E) showing only background noise.
Table 1
ESR characteristics of IIIa–e.
(b)
(b)
(d)
R" (a)
IIIa: R = Me, R'=R"=H; IIIb: R= Et, R'=R"=H;
IIIc: R= nBu, R'= R"=H; IIId: R=Me, R'=R"=Me;
(a)
(c)
R
(c)
R
IIIe:
R=Et, R'=R"=Me;
R'(d)
III
g
aHa
aHb
aHc
aHd
IIIa
III b
IIIc
IIId
IIIe
2.0029
2.0028
2.0027
2.0028
2.0028
5.75 (quint.)
5.76 (quint)
5.78 (quint.)
8.93 (t)
3.75 (sept.)
3.74 (sept.)
3.70 (sept.)
5.70 (sept.)
4.85 (sept.)
1.30 (sept.)
1.10 (quint.)
0.99 (quint.)
1.33 (sept.)
1.00 (quint.)
–
–
–
3.25 (sept.)
2.70 (sept.)
10.06 (t)
dihydro-s-indacenes[3] or from chloropolyalkyl-1,5-dihydro-s-
indacene using three different ways (Scheme 1).
lithiated analogs using the same method [10] and is supported by
the fact that when the salt (S0) (Scheme 2) is generated in another
way by addition of 1,3-dimethylimidazolidinium chloride on II
(reaction 3f), it also decomposes with formation of the anion rad-
ical III (Fig. 1) and the corresponding dihydroERO (M+Å = 198 amu).
The ESR characteristics of the paramagnetic species III a–f were
established and verified with the help of theoretical simulations of
the spectra (Figs. 2 and 3 and Table 1). In each case, the observed
spin distribution, verified by theoretical calculations, show that,
in a 1/1 toluene/THF solution, the ESR spectra of IIIa–e (Figs. 2
and 3 and Table 1) are consistent with the structure of an anion
radical [9,31], all of which present a very symmetrical distribution
of spin (e.g. Fig. 4 for IIIb), also showing that the localization of the
odd electron does not go farther than the methylene group of the R
side chain as observed experimentally (Fig. 3 and Table 1). The g
values are in the expected range for similar anion radicals [9,31].
In order to introduce a dissymmetry on the spin distribution,
the dissymmetric indacene If (R = R00 = Me, R0 = Cl) was prepared
(Scheme 4) by chlorination (PCl5) and subsequent methylation
(MeMgI) of the corresponding carbonyl groups of the 2,6-diethyl-
4,8-dimethyl-2,3,6,7-tetrahydro-s-indacene-1,5-dione [3,20].
Chlorination of the carbonyl appeared selective and limited to
one carbonyl group even in the presence of an excess of phospho-
rus pentachloride. One possible explanation is that the spontane-
ous elimination of HCl [32] (Scheme 4, ii) induces the
protonation of the second carbonyl preventing its chlorination.
The first method of preparation, (Scheme 1, i), has often been
reported in the literature [21–25]. The second way, (Scheme 1, ii)
occurs by a chemical oxidation of II using [Cp2Fe]+ [BF4]ꢀ. The
third, a very simple and useful method (Scheme 1, iii) proceeds
by a SET/retro – SET process (SET = Single Electron Transfer) initi-
ated from the reaction between the dilithium derivative II and an
electron rich olefin (ERO); it generates radical anions continuously
in the middle and is detailed in Scheme 3.
The ERO has been used before to produce metal-centred radi-
cals, by reduction of the metal in group 14 metal chlorides (MCl),
followed by chlorine abstraction [24,26,27] (Scheme 2) and also
to produce organic radicals [10] and anion radicals [28,29]. The ini-
tial SET processes were also established in the case of various com-
pounds electron acceptors [10,28–30].
Scheme 3 details the reaction of ERO with polyalkyl-1,5-dilith-
io-s-indacenyl compounds.
In this monoelectronic reaction process (Scheme 3), the initial
SET leads to the formation of the salt (S) which could directly
decompose (reaction 3d) leading to the polysubstituted-s-indacene
anion radical III. Although reaction 3d is expected, reaction 3e
(Scheme 3) is probable as already stated [10] because of the great
ability of the diazolidinium intermediate to pick an hydrogen from
the reaction middle (reaction 3c).The same mechanism explains
the formation of polyalkyl-hydro-s-indacenyl radicals from mono-

C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
51
Li
R'
N
N
N
2
+
R
R
N
ERO
R"
Li
(a) SET
II
Li
R'
N
N
2
ERO2+
+
2
R
R
R
R"
Li
-2Li
(b)
N
-
R'
N
N
N
2
R
Fig. 6. Spin distribution for IIIf.
(d) retro SET
R'
R"
Li
S
Li+
dilithiated according to Scheme 1 and converted to the anion rad-
ical IIIf (Fig. 5) following Scheme 1, iii. The anion radical IIIf ap-
pears homogeneously delocalized. The hyperfine coupling with
chlorine is not observed which is consistent with the calculated
spin distribution (Fig. 6).
R
R
2
(c)
H
R'
R"
N
H
III
2
R
R
(e) retro SET
N
R"
Li
N
On the contrary, the metallated polyalkyl-s-indacenyl radical V
(Scheme 5) [10] which cannot dissociate into the corresponding
metallated anion radical presents an unsymmetrical spin distribu-
tion (Fig. 7) in accordance with the calculated spin distribution, the
odd electron being mainly distributed on the cyclopentadienyl
ring opposite to the Rhodium metal and also on the aromatic
system.
S'
-
H
(f )
N
-2LiCl
x2
N
N
N
N
H
2 II
+
2
Cl
N
N
(R= Bu)
= 198 amu
M
II, III :
a) R = Me, R'=R"=H; b) R= Et, R'=R"=H;
4. Conclusion
c) R= nBu, R'= R"=H; d) R=Me, R'=R"=Me;
e) R=Et, R'=R"=Me;
f) R=Et, R'=Cl, R"=Me
It is now established within the indacenyl series that the SET/
RetroSET reaction between the organolithium compounds studied
and an electron rich olefin constitutes a general route to the corre-
sponding radicals [10] and radical anions. In polyalkyl- and chloro-
polyalkyl-s-indacenyl anion radicals the donor effects of the alkyl
substituents or of chlorine (mesomer donor) on the s-indacene
Scheme 3.
The methylation of the chloroketone Y (Scheme 4, iii)) then gives
the expected chloropolyalkyl-s-indacene If through dehydration
of the transient alcohol in acidic medium. This compound was
Cl
Cl
O
i)
ii)
Cl
PCl5, CH2Cl2
- HCl
- POCl3
O
O
O
X
Y
iii)
Cl
1) MeMgI excess
2) H3O+
CH3
If
Scheme 4.
(b)
(a')
(a)
ERO, - Li
THF / toluene
(c)
nBuLi
THF / toluene
RhCOD
RhCOD
RhCOD
Li
V
IV
Scheme 5.

52
C. Adams et al. / Inorganica Chimica Acta 366 (2011) 44–52
Fig. 7. ESR characteristics and spin distribution of V.
[8] H. Kawai, R. Katoono, K. Fujiwara, T. Tsuji, T. Suzuki, Chem. Eur. J. 11 (2005)
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conjugated system, leads to a symmetric homogeneous spin local-
ization which induces a coupling of the odd electron with the pro-
ton of the rings and the protons in alpha position on the side
chains. On the contrary, in the case of Rhodium-COD polyalkyl-s-
indacenyl radical V, the influence of the metal induces a non sym-
metric repartition of spin mainly located in the opposite Cp ring,
regardless of the small contribution from rhodium atom compared
to the Indacene ligand.
The easy formation of radicals and anion-radicals from metal-
lated polyalkyl-s-indacene derivatives evidenced here opens the
route to new anion-radicals from binuclear complexes of polyalkyl
s-indacene; the study of which, now in progress, could be a help in
the understanding of the catalytic activity of such complexes.
[13] S.H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 58 (1980) 1200.
[14] A.D. Becke, Phys. Rev. A 38 (1988) 3098.
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Acknowledgments
[23] C. Chatgilialoglu, Organosilanes, in: Radical Chemistry: Principles, Methods
and Applications, Wiley, Chichester, UK, 2004.
[24] P. Rivière, M. Rivière-Baudet, J. Satgé, in: E.W. Abel, F.G.A. Stone, G. Wilkinson
(Eds.), Comprehensive Organometallic Chemistry, Pergamon Press Oxford, UK,
1982, p. 399.
[25] P. Rivière, A. Castel, M. Rivière-Baudet, Alkaline and alkaline earth metal 14
compounds: preparation, spectroscopy, structure and reactivity, in: S. Patai, Z.
Rappoport, Y. Apeloig (Eds.), the Chemistry of Organogermanium, Tin and Lead
Compound, Wiley, Chichester, UK, 2002, p. 653.
The authors thank the ECOS CONICYT program C08E01, FOND-
ECYT 1040455, 1060588, 1060589, 1100283, proyecto Nùcleo
Milenio P07-006-F for partial financial support and Apoyo de Tesis
Doctoral CONICYT 23070215, 24080034.
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