Synthesis, Spectroscopy, Electrochemical Characterization, and Nonlinear Optical Properties of Ferrocenyloligosilanes: FcSinMe2n(C6H5) (n = 1-6) and FcSi2Me4(C6H4-X) (

Article abstract of DOI:10.1021/om990733w

New ferrocenyloligosilylene aryl complexes have been synthesized, FcSi_nMe_2nC₆H₅ (n = 1-6) and FcSi₂Me₄{C₆H₄-X} (X = m-CF_3· p-Cl, p-Br, p-OMe, p-NMe₂

Full text of DOI:10.1021/om990733w

770
Organometallics 2000, 19, 770-774
Syn th esis, Sp ectr oscop y, Electr och em ica l
Ch a r a cter iza tion , a n d Non lin ea r Op tica l P r op er ties of
F er r ocen yloligosila n es: F cSin Me2n (C6H5) (n ) 1-6) a n d
F cSi2Me4(C6H4-X) (X ) m -CF 3, p-Cl, p-Br , p-OMe, p-NMe2,
p-CHdC(CN)2)
Hemant K. Sharma,† Keith H. Pannell,*,† Isabelle Ledoux,‡ J oseph Zyss,*,‡
Antonio Ceccanti,§ and Piero Zanello*,§
Department of Chemistry, The University of Texas at El Paso, El Paso, Texas 79968,
Centre National d’Etudes des Telecommunications, 196 Avenue Henry Ravera,
92120 Bagneux, France, and Dipartimento di Chimica dell’Universita` di Siena,
Pian dei Mantellini, 4453100 Siena, Italy
Received September 20, 1999
New ferrocenyloligosilylene aryl complexes have been synthesized, FcSinMe2nC6H5 (n )
1-6) and FcSi2Me4{C6H4-X} (X ) m-CF3. p-Cl, p-Br, p-OMe, p-NMe2, p-CHdC(CN)2). The
complexes have been evaluated with respect to their electrochemical redox and NLO
hyperpolarizability properties. All complexes possess oxidation potentials that reflect,
systematically but weakly, the various substituents on the aryl group, thereby indicating
an aryl-ferrocenyl interaction via the silicon chains. However, hyperpolarizabilities of the
complexes are generally similar to those of the corresponding substituted benzenes, with
the exception of the most electron-withdrawing substituents, p-Cl and p-CHdC(CN)2.
In tr od u ction
On the basis of these data we have synthesized and
studied a series of complexes in which the Fc group is
separated from an acceptor group by an oligosilane
chain: FcSinMe2n(C6H5) (n ) 1-6 (1-6)) and FcSi2Me4-
(C6H4-X) (X ) m-CF3 (2a ), p-Cl (2b), p-Br (2c), p-OMe
(2d ), p-NMe2 (2e), p-CHdC(CN)2) (2g))
There is current interest in the synthesis of new
materials with large second-order optical nonlinearities,
and organometallic compounds have been shown to be
a useful general class of such materials.1-4 For example,
Marder et al. demonstrated that when the donor ferro-
cenyl group [(η5-C5H4)Fe(C5H5)] (Fc) was connected by
an ethylene linkage to the 1-methylpyridinium acceptor
group, large powder SHG efficiencies (up to 200 times
that of urea) were obtained.1b In a separate series of
articles we reported that nonlinear optical properties
were observed for oligosilanes and that the efficiency
of such systems depended upon the number of silicon
atoms in the chain.5 We have also reported that ferro-
cenyl groups bridged via oligosilyl chains exhibit sig-
nificant charge communication between the two Fc
groups when the chain possesses one to four Si atoms.6
Exp er im en ta l Section
Synthetic manipulations were performed under an argon
atmosphere using standard Schlenk techniques. The starting
silicon compounds Me2SiCl2 and PhSiMe2Cl were purchased
from Hu¨ls America Inc., chloromercurioferrocene was obtained
from Strem Chemicals, and malononitrile, 1,4-dichlorobenzene,
1,4-dibromobenzene, 4-bromoanisole, 3-bromobenzotrifluoride,
4-bromo-N,N-dimethylaniline, and piperidine were purchased
from Aldrich Chemicals and were used as received. N,N-
Dimethylformamide (Aldrich) was allowed to stand on 4 Å
molecular sieves. NMR spectra were recorded on a Bruker NR
200 MHz spectrometer, IR spectra were recorded on a Perkin-
Elmer 1600 FT IR spectrometer, and mass spectra were
obtained on a 70 eV Hewlett-Packard 5890/5971 GC/mass
spectrometer. Elemental analyses were performed by Gal-
braith Laboratories, Inc.
† The University of Texas at El Paso.
‡ Centre National d’Etudes des Telecommunications.
§ Universita` di Siena.
(1) (a) Green, M. L. H.; Marder, S. R.; Thompson, M. E.; Bandy, J .
A.; Bloor, D.; Kolinsky, P. V.; J ones, R. J . Nature 1987, 330, 360. (b)
Marder, S. R.; Perry, J . W.; Tiemann, B. G.; Schaefer, W. P. Organo-
metallics 1991, 10, 1896. (c) Coe, B. J .; J ones, C. J .; McCleverty, J . A.;
Bloor, D.; Kolinsky, P. V.; J ones, R. J . J . Chem. Soc., Chem. Commun.
1989, 1485. (d) Doisneau, G.; Balavoine, G.; Fillebeen-Khan, T.; Clinet,
J .-C.; Delaire, J .; Ledoux, I.; Loucif, R.; Puccetti, G. J . Organomet.
Chem. 1991, 421, 299.
Ferrocenyloligosilanes FcSinMe2n(C6H5) (n ) 1-6) and
FcSiMe2SiMe2(C6H4-X) (X ) p-Cl, p-Br, p-OMe, m-CF3) were
synthesized by two general procedures. As typical examples
the two syntheses of FpSiMe2SiMe2Ph are described below.
(2) For recent reviews in the area see: (a) Cheng, L.-T.; Tam, W.;
Meredith, G. R. Mol. Cryst. Liq. Cryst. 1990, 189, 137. (b) Nalwa, H.
S. Appl. Organomet. Chem. 1991, 5, 349. (c) Long, N. J . Angew. Chem.,
Int. Ed. Engl. 1995, 34, 21.
(3) For a theoretical (SCF-LCAO MECI formalism) treatment of
organometallic NLO materials, see: Kanis, D. R.; Ratner, M. A.; Marks,
T. J . J . Am. Chem. Soc. 1990, 112, 8203.
(4) (a) Wright, M. E.; Sigman, M. S. Macromolecules 1992, 25, 6055.
(b) Wright, M. E.; Toplikar, E. G. Macromolecules 1992, 25, 6050. (c)
Wright, M. E.; Toplikar, E. G. Macromolecules 1992, 25, 1838.
(5) (a) Mignani, G.; Kra¨mer, A.; Puccetti, G.; Ledoux, I.; Soula, G.;
Zyss, J .; Meyrueix, R. Organometallics 1990, 9, 2640. (b) Mignani, G.;
Kra¨mer, A.; Puccetti, G.; Ledoux, I.; Soula, G.; Zyss, J . J . Mol. Eng.
1991, 1, 11. (c) Mignani, G.; Kra¨mer, A.; Puccetti, G.; Ledoux, I.; Zyss,
J . Soula, G. Organometallics 1991, 10, 3656. (d) Mignani, G.; Barzou-
kas, M.; Zyss, J . Soula, G.; Balegroune, F.; Grandjean, D.; J osse, D.
Organometallics 1991, 10, 3660.
(6) Dement’ev, V. V.; Cervantes-Lee, F.; Parkanyi, L.; Sharma, H.;
Pannell, K. H.; Nguyen, M. T.; D´ıaz, A. Organometallics 1993, 12, 1983.
10.1021/om990733w CCC: $19.00 © 2000 American Chemical Society
Publication on Web 02/01/2000

Ferrocenyloligosilanes
Organometallics, Vol. 19, No. 5, 2000 771
The spectroscopic and analytical data for the ferrocenyl-
oligosilanes are recorded in Table 1.
crystal of iodine. To this was added slowly a solution of
1-ferrocenyl-2-(4-bromophenyl)-1,1,2,2-tetramethyldisilane (3.7
g, 8.1 mmol) in 20 mL of THF. The mixture was refluxed for
17 h. This Grignard reagent was slowly cannulated into a
solution of DMF (1.17 g, 16.0 mmol) in 10 mL of THF. The
mixture was stirred for 20 h at room temperature. The reaction
was quenched with 100 mL of 5% NaOH solution, and the
resulting mixture was extracted with 100 mL of ethyl acetate.
The organic layer was dried over MgSO4, and the solvent was
removed. Column chromatography on silica gel (hexane/
methylene chloride, 90/10) yielded FcSiMe2SiMe2(C6H4-p-CHO)
as a yellow powder, recrystallized from hexane (1.35 g, 3.32
mmol, 41%).
Syn t h esis of F cSiMe2SiMe2(C6H 4-p -CHdC(CN)). To a
solution of 0.86 g (2.1 mmol) of FcSiMe2SiMe2(C6H4-p-CHO)
dissolved in a mixture of THF (3 mL) and ethanol (15 mL)
was added 0.14 g (2.1 mmol) of solid malononitrile and a drop
of piperidine. An immediate color change from yellow to dark
red was observed. The mixture was stirred for 15 min, and
then solvents were removed in vacuo. The red sticky residue
was extracted with 5 mL of methylene chloride and passed
through a silica gel column (25 × 2 cm), and a red band was
eluted with methylene chloride. Evaporation of the solvent
yielded the title complex as a red solid (0.63 g, 1.39 mmol,
66%).
Syn t h esis of F cSiMe2SiMe2P h . Met h od A. F cLi
+
ClSiMe2SiMe2P h (2). To a stirred solution of l-chloro-2-
phenyl-l,1,2,2-tetramethyldisilane7 (6 g, 7.0 mmol) in 20 mL
of THF at -25 °C was added slowly a 50 mL solution of
ferrocenyllithium obtained from 2.95 g (7.0 mmol) of chlo-
romercurioferrocene and n-BuLi.8 The mixture was stirred for
30 min and then warmed to room temperature and stirred for
a further 12 h. The solvent was removed in vacuo, and the
orange residue was extracted into hexane (60 mL) and filtered.
The filtrate was concentrated to 10 mL, and the di-n-butyl-
mercury was removed by distillation (61-62 °C/0.5 mmHg).
The red liquid residue was purified by molecular distillation
with a Kugelrohr (108-110 °C/0.03 mmHg) to yield 1.75 g (4.63
mmol, 66%) of the title complex.
Meth od B. F cSiMe2SiMe2Cl + P h MgBr . (a ) Syn th esis
of F cSiMe2SiMe2Cl. A solution of ferrocenyllithium was
prepared from 6.3 g (15 mmol) of chloromercurioferrocene and
n-butyllithium (15.8 mmol) in 60 mL of THF. After the solvent
was removed in vacuo, 60 mL of degassed cyclohexane was
added to the solid [Fc]-Li+. A solution of 1,2-dichlorotetram-
ethyldisilane7 (2.80 g, 15.0 mmol) in 60 mL of cyclohexane was
added dropwise to the heterogeneous mixture at 0 °C. The
reaction mixture was stirred vigorously for 2 h, and then the
mixture was filtered through a sintered-glass frit and concen-
trated in vacuo to about 5 mL. Di-n-butylmercury was removed
by fractional distillation (52-54 °C/0.1 mmHg), and FcSiMe2-
SiMe2Cl was distilled at 108-110 °C/0.1 mmHg as a red liquid,
yield 1.5 g (4.45 mmol, 30%).
(b) Rea ction of F cSiMe2SiMe2Cl w ith P h MgBr . To an
ice-cooled solution of FcSiMe2SiMe2Cl (0.62 g, 1.8 mmol) in
10 mL of THF was added dropwise over 45 min a solution of
PhMgBr (prepared from 0.29 g (1.8 mmol) of bromobenzene
and 0.04 mol of Mg). The mixture was stirred for 12 h at room
temperature. At this time, THF was removed in vacuo, the
residue was extracted with 30 mL of hexane, and the resulting
mixture was filtered. The filtrate was concentrated to 5 mL
and chromatographed on a silica gel column (20 × 2 cm). The
orange band that developed with hexane was collected and
upon evaporation of the solvent yielded FcSiMe2SiMe2Ph as a
red oil, yield 0.31 g (0.82 mmol, 45%).
Electr och em ica l a n d NLO Mea su r em en ts. Materials
and apparatus for electrochemistry and coupled UV-visible
spectroscopy have been described elsewhere;20 the data are
recorded in Table 2. Hyperpolarizability (â) measurements
were performed using the electric field induced second har-
monic (EFISH) method.10-14 The absorption maxima, dipole
moments, and hyperpolarizabilities of the ferrocenyloligosilane
complexes are listed in Table 3.
Resu lts a n d Discu ssion
Syn th esis a n d Sp ectr oscop ic P r op er ties of F er -
r ocen yloligosila n es. The incorporation of the fer-
rocene unit into the oligosilane chains posed no signifi-
cant synthetic problems and standard Grignard and
salt-elimination chemistry was used (eq 1 and Scheme
1).
Syn th esis of F cSiMe2SiMe2(C6H4-p-N(CH3)2). To a sus-
pension of magnesium (0.64 mol) in 20 mL of THF was added
a crystal of iodine followed by 5.0 g (26.7 mmol) of 1,2-
dichlorotetramethyldisilane. To this mixture was added 5.3 g
(26.5 mmol) of 4-bromo-N,N-dimethylaniline in 20 mL of THF
slowly by syringe. The reaction mixture was stirred for 4 h at
room temperature. To this in situ generated ClSiMe2SiMe2-
C6H4-p-NMe2 was added slowly, over 1 h at -25 °C, 100 mL
of a THF solution of ferrocenyllithium (prepared from 10.0 g,
23.7 mmol, of chloromercurioferrocene). The mixture was
stirred at low temperature for 1 h and then slowly warmed to
room temperature and further stirred for 12 h. At this time,
the solvent was removed on a rotary evaporator, the residue
was extracted with 100 mL of hexane, and the extracts were
filtered. The filtrate was concentrated to 10 mL, di-n-butylm-
ercury was removed by fractional distillation (60-62 °C/0.5
mmHg), and the residue was chromatographed on a silica gel
column (2.5 × 15 cm) developed with hexane. The orange band
that developed with 90/10 hexane/methylene chloride mixture
was collected and, after removal of the solvent, yielded
FcSiMe2SiMe2(C6H4-p-N(CH3)2) as an orange solid, which was
recrystallized from hexane (2.5 g, 5.94 mmol, 25%).
The spectroscopic properties of the complexes are
unremarkable. The 29Si NMR data illustrate weak
electronic effects of different substituents on the â-sil-
icon in the series FcSiMe2SiMe2(C6H4X). For example,
compared to X ) H, substitution of the benzene ring
(9) Compound 1 was previously synthesized by the hydrolysis of
lithium (1′-(phenyldimethylsilyl)-1-ferrocenyl)dimethylsilanolate and
was characterized by elemental analysis and infrared spectroscopy:
Kan, P. T.; Lenk, C. T.; Schaaf, R. L. J . Org. Chem. 1961, 26, 4038.
(10) Ouder, J . L. J . Chem. Phys. 1977, 67, 446.
Syn th esis of F cSiMe2SiMe2(C6H4-p-CHO). To a suspen-
sion of magnesium (0.19 mol) in 15 mL of THF was added a
(11) Levine, B. F.; Bethea, C. G. Appl. Phys. Lett. 1974, 24, 445.
(12) Ledoux, I.; Zyss, J . Chem. Phys. 1982, 73, 203.
(13) Bazoukas, M.; Fremaux, P.; J osse, D.; Kajzar, F.; Zyss, J . Mater.
Res. Soc. Symp. Proc. 1988, 109, 171.
(7) Sakurai, H.; Tominaga, K.; Watanabe, T.; Kumada, M. Tetra-
hedron Lett. 1966, 5493.
(8) Seyferth, D.; Hofmann, H. P.; Burton, R.; Helling, J . F. Inorg.
Chem. 1962, 1, 227.
(14) Hedestrand, G. Z. Phys. Chem. 1929, B2, 428.

772 Organometallics, Vol. 19, No. 5, 2000
Ta ble 1. Sp ectr oscop ic a n d An a lytica l Da ta for F er r ocen yloligosila n esa
FcSiMe2Ph (1)b
Sharma et al.
mp, °C
81-82
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
0.47 (6H, s, SiMe2); 3.97 (5H, s), 4.05 (t, 2H, J ) 1.6 Hz), 4.20 (t, 2H, J ) 1.6 Hz, Fc); 7.19, 7.55 (m, 5H, Ph)
-1.45 (SiMe2); 68.5, 69.9, 71.3, 73.7 (Fc); 129.1, 133.3, 134.0, 139.9 (Ph)
-7.22
320 (100); 305 (55); 289 (1); 255 (8); 183 (5); 121 (11); 56 (6)
FcSiMe2SiMe2Ph (2)
C, 63.47 (63.55); H, 6.92 (6.90)
0.33 (6H, s), 0.34 (6H, s, SiMe2); 3.92 (2H, t), 4.00 (5H, s), 4.17 (2H, t, Fc); 7.18, 7.45 (5H, m, Ph)
-3.65, -2.91 (SiMe2); 68.3, 71.0, 73.2 (Fc); 128.7, 134.2, 139.5 (Ph)
-22.59, -21.75
anal. calcd (found)
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
378 (35); 363 (1); 243 (100); 135 (7); 121 (5); 93 (5), 56 (2)
FcSiMe2SiMe2(C6H4-m-CF3) (2a )
C, 56.49 (56.10); H, 5.64 (5.79)
0.23, 0.26 (12H, s, SiMe2); 3.83 (2H, t, J ) 1.8 Hz), 4.01, (5H, s), 4.17 (2H, t, J ) 1.8 Hz);
7.00, 7.36-7.39, 7.79 (4H, m, Ph)
-4.09, -3.87 (SiMe2); 68.2, 70.4, 71.2, 73.0 (Fc); 125.28, 125.34, 128.18, 130.46, 137.33, 141.39 (Ph and CF3)
-21.79, -21.65
446 (32); 427 (2); 243 (100); 313 (9); 203 (12); 148 (5); 121 (11); 93 (8)
anal. calcd (found)
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
FcSiMe2SiMe2(C6H4-p-Cl) (2b)
C, 58.18 (57.66); H, 6.10 (6.31)
0.24, 0.28 (12H, SiMe2); 3.85 (2H, t), 4.00 (5H, s), 4.16 (2H, 5, Fc); 7.16-7.17 (4B, m, Ph)
-3.83, -3.15 (SiMe2); 68.3, 70.7, 71.1, 73.1 (Fc); 128.2, 135.1, 135.5, 137.9 (Ph)
-22.27, -21.88
anal. calcd (found)
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
412 (20); 397 (1); 243 (100); 169 (7); 121 (6); 93 (5)
FcSiMe2SiMe2(C6H4-p-Br) (2c)
C, 52.52 (52.63); H, 5.51 (5.55)
54-55
0.36, 0.37 (12H, s, SiMe2); 3.98 (2H, t, J ) 1.6 Hz), 4.13 (5H, s), 4.29 (2H, t, J ) 1.6 Hz),
7.19-7.23 (2H, d, J ) 8 Hz), 7.45-7.49 (2H, d, J ) 8 Hz, Ph)
-3.89, -3.17 (SiMe2); 68.3, 70.7, 71.1, 73.1 (Fc); 123.6, 131.1, 135.7, 138.4 (Ph)
-21.74, -21.48
anal. calcd (found)
mp, °C
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
458 (16); 243 (100); 213 (9); 121 (10); 93 (8), 73 (2)
FcSiMe2SiMe2(C6H4-p-OMe) (2d )
C, 61.75 (61.70); H, 6.91 (6.33)
0.363, 0.367 (12H, s, SiMe2); 3.32 (3H, s, OMe); 3.95 (2H, t, J ) 1.4 Hz), 4.01 (5H, s) 4.18 (2H, t, J ) 1.4 Hz, Fc);
6.84-6.88 (2H, d, J ) 8.4 Hz), 7.36-7.41 (2H, d, J ) 8.4 Hz, Ph)
-3.31, -2.81 (SiMe2); 54.5 (OMe); 68.3, 71.0,71.2, 73.2 (Fc); 114.1, 128.5, 135.5, 160.7 (Ph)
-22.99, -21.89
anal. calcd (found)
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
408 (33); 393 (3); 243 (100); 213 (7); 165 (12); 121 (10); 93 (6); 73 (1)
FcSiMe2SiMe(C6H4-p-NMe2) (2e)
C, 62.69 (61.20); H, 7.41 (6.99); N, 3.33 (3.11)
80
0.41, 0.43 (12H, s, SiMe2); 2.52 (6H, s, -NMe2); 3.97-4.03 (7H, s, t), 4.19 (2H, t),
6.64-6.68 (2H, d, J ) 8.2 Hz), 7.44-7.48 (2H, d, J ) 8.2 Hz, Ph)
-3.1, -2.59 (SiMe2); 39.88 (-NMe2); 68.3, 70.9, 71.8, 73.3 (Fc); 112.6, 124.1, 135.2, 151.1 (Ph)
-23.54, -21.92
anal. calcd (found)
mp, °C
1H NMR
13C NMR
29Si NMR
MS, m/e (%)
504 (20); 485 (2); 243 (100); 203 (9); 121 (10); 73 (11)
FcSiMe2SiMe2(C6H4-p-CHO) (2f)
anal. calcd (found)
mp, °C
C, 62.05 (60.36); H, 6.44 (6.62)
94
0.40, 0.41 (12H, s, SiMe2); 3.98 (2H, t, J ) 1.8 Hz), 4.13 (5H, s), 4.30 (2H, t, J ) 1.8 Hz, Fc);
7.29, 7.71 (4H, dd, J ) 8 Hz, Ph); 9.85 (-CHO)
-4.12, -3.21 (SiMe2); 68.3, 70.5, 71.1, 73.1 (Fc); 134.5, 138.9, 148.1 (Ph); 191.5 (CdO)
-21.41, -21.11
1710 ν(CdO)
1H NMR
13C NMR
29Si NMR
IR (hexane), cm-1
FcSiMe2SiMe2(C6H4-p-CHdC(CN)2) (2g)
C, 63.42 (62.70); H, 5.76 (5.92)
84-85
0.33, 0.35 (12H, s, SiMe2); 3.92 (2H, t, J ) 1.6 Hz), 4.08 (5H, s), 4.26 (2H, t, J ) 1.6 Hz, Fc);
6.64 (1H, s, -CHdC); 7.25, 7.37-7.41 (4H, m, Ph)
-4.24, -3.22 (SiMe2); 68.4, 68.6, 71.2, 73.0 (Fc); 82.5 (-CHdC(CN)2); 113.1, 114.1 (-CHdC(CN)2);
129.3, 130.9, 134.6, 149.3 (Ph); 158.8 (-CHdC)
-21.0, -20.9
anal. calcd (found)
mp, °C
1H NMR
13C NMR
29Si NMR
IR (hexane), cm-1
2227 ν(CN), 1588 ν(CdC)
FcSiMe2SiMe2Cl (2h )
0.37 (12H, s, SiMe2); 3.95 (2H, t), 4.02 (5H, s), 4.17 (2H, t, Fc)
-3.63 (SiMe2); 2.27 (SiMe2Cl); 68.9, 72.5, 73.3 (Fc)
21.28 (SiMe2Cl), -21.39 (SiMe2Fc)
1H NMR
13C NMR
29Si NMR

Ferrocenyloligosilanes
Organometallics, Vol. 19, No. 5, 2000 773
Ta ble 1 (Con tin u ed )
FcSiMe2SiMe2SiMe2Ph (3)
anal. calcd (found)
mp, °C
C, 60.52 (60.52); H, 7.38 (7.51)
60
1H NMR
0.14 (6H, s, -SiMe2-), 0.32, 0.33 (12H, s, Fc-SiMe2 & Ph-SiMe2); 3.91 (2H, t, J ) 1.6 Hz),
4.04 (5H, s), 4.18 (2H, t, J ) 1.6 Hz, Fc); 7.16-7.20, 7.42-7.45 (5H, m, Ph)
-6.30, -2.97, -2.54 (SiMe2); 68.3. 71.0, 72.0. 73.1 (Fc); 128.5, 134.1, 139.9 (Ph)
-48.37 (SiMe2); -18.65 (Fc-SiMe2 & Ph-SiMe2)
13C NMR
29Si NMR
MS, m/e (%)
436 (25); 421 (0.5); 299 (1); 243 (100); 135 (12); 121 (5); 93 (6); 73 (7)
FcSiMeSiMe2SiMe2SiMe2Ph (4)
C, 58.26 (58.03); H, 7.74 (7.64)
44
anal. calcd (found)
mp, °C
1H NMR
0.11, 0.15 (12H, s, -SiMe2-SiMe2-), 0.37, 0.38 (12H, s, Fc-SiMe2 & Ph-SiMe2); 3.93 (2H, t, J ) 1.6 Hz),
4.01 (5H, s), 4.18 (2H, t, J ) 1.6 Hz, Fc); 7.16-7.19, 7.43 (5H, m, Ph)
-5.34, -2.75, -2.28 (SiMe2); 68.3, 71.0, 72.1, 73.1 (Fc); 128.5, 128.7, 134.1, 139.1 (Ph)
-44.72, -44.63, -18.15, -18.02
13C NMR
29Si NMR
MS, m/e (%)
494 (24); 479 (0.5); 299 (3); 243 (100), 135 (12); 73 (8)
FcSiMe2SiMe2SiMe2SiMe2SiMe2Ph (5)
C, 56.48 (55.95); H, 8.02 (8.19)
75-76
anal. calcd (found)
mp, °C
1H NMR
0.15. 0.18. 0.21, 0.40, 0.41 (s, SiMe2); 3.96 (2H, t), 4.06 (5H, s), 4.18 (2H, t, Fc); 7.16, 7.45-7.49 (5H, m, Ph)
-5.09, -4.39, -2.79, -2.26 (SiMe2); 68.3, 71.0, 72.2, 73.1 (Fc); 128.4, 134.0, 139.9 (Ph)
-43.12, -42.85, -40.03, -17.73, -17.54
13C NMR
29Si NMR
MS, m/e (%)
552 (1); 343 (3); 299 (5); 285 (6); 243 (100); 177 (5); 135 (23); 73 (25)
FcSiMe2SiMe2SiMe2SiMe2SiMe2SiMe2Ph (6)
C, 55.03 (54.51); H, 8.24 (8.55)
0.24, 0.26, 0.27, 0.29, 0.46, 0.48 (SiMe2); 4.02 (2H, t), 4.11 (SiH, s), 4.24 (2H, t, Fc); 7.21-7.25, 7.51 (5H, m, Ph)
-5.03, -4.08, -2.73. -2.20 (SiMe2); 68.3, 71.0, 72.2, 73.1 (Fc); 128.7, 134.1, 139.2 (Ph)
-43.02, -42.74, -38.83, -38.61, -17.69, -17.47
anal. calcd (found)
1H NMR
13C NMR
29Si NMR
a
Samples with no melting point data are oils. NMR data (ppm) were recorded in C6D6. In 13C NMR spectra, some resonances due to
b
the phenyl group were masked by the solvent resonances. See ref 9.
Sch em e 1
with electron-releasing groups such as p-NMe2 and
p-OMe causes an ∼1 ppm high field shift of the â-silicon,
whereas introduction of the electron-withdrawing groups
m-CF3, p-CHdC(CN)2, and p-CHO onto the ring causes
a 1 ppm low-field shift.
Electr och em ica l Stu d ies. The electrochemical be-
havior of silicon-substituted ferrocenes,6,15,16 poly-
ferrocenes,16a,c,d,17 and ferrocenyl and ferrocenylene
polymers18 is a routine characterization. Yellow-orange
dichloromethane solutions of the complexes FcSinMe2n
-
(C6H5) (n ) 1-3) undergo the expected oxidation of the
ferrocenyl unit through chemically reversible electron
transfers, resulting in blue ferrocenium ion solutions
(Table 2). Controlled-potential coulometry and appropri-
ate cyclic voltammograms on the complexes with n ) 1
and 3 signify transfer of one electron/molecule.19 How-
(15) (a) Osborne, A. G.; Hollands, R. E.; Nagy, A. G. J . Organomet.
Chem. 1989, 373, 229. (b) Cerveau, G.; Chuit, C.; Colomer, E.; Corriu,
R. J . P.; Rey, C. Organometallics 1990, 9, 2415. (c) Casado, C. M.;
Mora´n, M.; Losada, J .; Cuadrado, I. Inorg. Chem. 1995, 34, 1668. (d)
Pudelski, J . K.; Foucher, D. A.; Honeyman, C. H.; Lough, A. J .;
Manners, I.; Barlow, S.; O’Hare, D. Organometallics 1995, 14, 2470.
(16) (a) Atzkern, H.; Hiermeier, J .; Kohler, F. H.; Steck, A. J .
Organomet. Chem. 1991, 408, 281. (b) Kreisz, J .; Kirss, R. U.; Reiff,
W. M. Inorg. Chem. 1994, 33, 1562. (c) Pannell, K. H.; Dement’ev, V.
V.; Li, H.; Cervantes-Lee, F.; Nguyen, M. T.; Diaz, A. F. Organome-
tallics 1994, 13, 3644. (d) Rulkens, R.; Lough, A. J .; Manners, I. J .
Am. Chem. Soc. 1994, 116, 797. (e) Zechel, D. L. D.; Foucher, A.;
Pudelski, J . K.; Yap, G. P. A.; Rheingold, A.; Manners, I. J . Chem.
Soc., Dalton Trans. 1995, 1893. (f) Park, J .; Seo, Y.; Cho, S.; Whang,
D.; Kim, K.; Chang, T. J . Organomet. Chem. 1995, 489, 23.
(17) (a) Casado, C. M.; Cuadrado, I.; Mora´n, M.; Alonso, B.; Lobete,
F.; Losada, J . Organometallics 1995, 14, 2618. (b) Mora´n, M.; Casado,
C. M.; Cuadrado, I.; Losada, J . Organometallics 1993, 12, 4327.
(18) (a) Inagaki, T.; Lee, H. S.; Skotheim, T. A.; Okamoto, Y. J .
Chem. Soc., Chem. Commun. 1989, 1181. (b) Foucher, D. A.; Tang, B.
Z.; Manners, I. J . Am. Chem. Soc. 1992, 114, 6246. (c) Foucher, D. A.;
Honeyman, C. H.; Nelson, J . M.; Tang, B. Z.; Manners, I. Angew.
Chem., Int. Ed. Engl. 1993, 32, 1709. (d) Nguyen, M. T.; Diaz, A. F.;
Dementiev, V. V.; Sharma, H.; Pannell, K. H. SPIE Proc. 1993, 1910,
230. (e) Nguyen, M. T.; Diaz, A. F.; Dement’ev, V. V.; Pannell, K. H.
Chem. Mater. 1993, 5, 1389. (f) Nguyen, M. T.; Diaz, A. F.; Dement’ev,
V. V.; Pannell, K. H. Chem. Mater. 1994, 6, 952.
(19) Brown, E. R.; Sandifer, J . In Physical Methods of Chemistry:
Electrochemical Methods; Rossiter, B. W., Hamilton, J . F., Eds.;
Wiley: New York, 1986; Vol. 2, Chapter 4.

774 Organometallics, Vol. 19, No. 5, 2000
Sharma et al.
Ta ble 2. F or m a l Electr od e P oten tia ls (V, vs SCE),
P ea k -to-P ea k Sep a r a tion (m V), Op tica l P r op er ties
(n m ), a n d Releva n t Ha m m ett Su bstitu en t
Con sta n ts for th e Oxid a tion of Su bstitu ted
F er r ocen es
Ta ble 3. Absor p tion Wa velen gth s (λm a x),a Dip ole
Mom en ts (µ).b a n d F r equ en cy-In d ep en d en t
c
Secon d -Or d er P ola r iza bilities (âo ) for F er r ocen yl
Oligosila n es
a
compd
λmax
µ, D
âo, 10-30 esu
a
b
f
complex
E°′0/+ Ep
λmax
IX
FcSiMe3
1
2
3
4
5
6
2a
2b
2d
2e
2g
448
456
455
457
456
456
456
457
456
456
455
342
1.26
4.5
1.75
1.8
1.1
4.0
5.1
3.15
2.4
1.1
2.4
0.5
0.5
-0.6
0.4
6.4
1.76
1.0
2.2
1.6
FcSiMe3
+0.42c 82
+0.40d 90
+0.44c 84
+0.41d 81
+0.42c 78
+0.38d 95
+0.41c 80
+0.37d 86
+0.43c 90
+0.39d 94
+0.42c 72
+0.40d 90
+0.43c 80
+0.40d 82
626
631
e
FcSiMe2Ph (1)
FcSiMe2SiMe2Ph (2)
FcSiMe2SiMe2SiMe2Ph (3)
FcH
684
620
e
-0.26
3.5
7
4.7
FcSiMe2SiMe2(C6H4-m-CF3) (2a )
FcSiMe2SiMe2(C6H4-p-Cl) (2b)
+0.43
+0.24
-0.28
-0.83
+0.42
+0.54
a
b
Measured in chloroform. Measured in dioxane.
FcSiMe2SiMe2(C6H4-p-OMe) (2d ) +0.41c 88
+0.37d 74
dipole moment occur upon substituting electron-with-
drawing or electron-accepting groups onto the phenyl
ring of compound 2. The largest increase is obtained for
the vinyldicyano derivative 2g, resulting in a value >2
times higher than that of (2,2-dicyanoethenyl)benzene.22
The same behavior is observed for compound 2b, where
the â value is 5 times that of chlorobenzene.10 However,
both the dipole moment and the hyperpolarizability of
these materials are similar to those of the trimethylsilyl
analogues.5b
e
e
FcSiMe2SiMe2(C6H4-p-NMe2) (2e) +0.40c 75
+0.36d 78
FcSiMe2SiMe2(C6H4-p-CHO) (2f)
+0.42c 84
+0.37d 72
+0.43c 77
+0.40d 70
e
e
FcSiMe2SiMe2(C6H4-p-CHd
C(CN)2) (2g)
a
b
Measured at 0.2 V s-1
.
Referred to the ferrocenium cation.
c Supporting electrolyte [NBu4]ClO4 (0.2 M). Supporting electro-
lyte [NBu4]PF6 (0.2 M). e Coupled to chemical complications (see
text). f From ref 21.
d
ever, similar studies on the disilane complexes FcSiMe2-
SiMe2Ar indicate that a side reaction accompanies the
electrogeneration of [FcSiMe2SiMe2Ar]+ (E°′0/+ ) +0.42
V for Ar ) Ph) and generates a new oxidizable species
(Eox is ∼60 mV lower than that of FcSiMe2SiMe2Ph)
which we have been unable to identify. The various aryl
substituents have small, but predictable, effects on the
redox potentials of the Fe center. Thus, changing from
the most electron-donating substituent (NMe2) to the
most electron-withdrawing substituent (CHdC(CN)2)
causes a shift of 30 mV.
Ack n ow led gm en t. This research was supported by
the NSF and the R. A. Welch Foundation of Houston,
TX.
Su p p or t in g In for m a t ion Ava ila b le: Text giving NLO
experimental details. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM990733W
Non lin ea r Op tica l P r op er ties. In the oligosilane
series Fc(SiMe2)nPh (n ) 1-6) moderate dipole moments
and weak â0 values are observed. Hyperpolarizabilities
are 1 order of magnitude smaller than that of p-
nitroaniline and are similar to those of monosubstituted
benzenes. In the disilane series significant changes of
(20) Togni, A.; Hobi, M.; Rihs, G.; Rist, G.; Albinati, A.; Zanello, P.;
Zech, D.; Keller, H. Organometallics 1994, 13, 1224.
(21) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165.
(22) Cheng, L.-T.; Tam, W.; Stevenson, S. H.; Meredith, G. R.;
Rikken, G.; Marder, S. R. J . Phys. Chem. 1991, 95, 10631.