Structural characterization and electrochemical study of novel ferrocene derivatives prepared from [(β-ferrocenylvinyl)imino]phosphorane by aza Wittig reactions

Article abstract of DOI:10.1021/om9706166

A rapid and efficient synthetic procedure has been developed to prepare new ferrocene derivatives such as β-ferrocenylvinyl heterocumulenes and ferrocene-containing imidazole ring bearing one, two, or three ferrocene subunits. The method is based on the aza Wittig reaction of [(β-ferrocenylvinyl)immo]phosphorane 3, readily available from ferrocenecarboxaldehyde by sequential treatment with ethyl azidoacetate and triphenylphosphine, with isocyanates and further treatment with the appropriate primary amine. The crystal structures of compounds 6c (monoferrocene derivative), 11c, and 12b (biferrocene derivatives) have been determined by single-crystal X-ray methods. The electrochemical properties of these new compounds are also reported.

Full text of DOI:10.1021/om9706166

5836
Organometallics 1997, 16, 5836-5843
Str u ctu r a l Ch a r a cter iza tion a n d Electr och em ica l Stu d y
of Novel F er r ocen e Der iva tives P r ep a r ed fr om
[(â-F er r ocen ylvin yl)im in o]p h osp h or a n e by Aza Wittig
Rea ction s
Pedro Molina,* Aurelia Pastor, M. J esu´s Vilaplana, and
M. Desamparados Velasco
Departamento de Qu´ımica Orga´nica, Facultad de Qu´ımica, Universidad de Murcia,
Campus de Espinardo, E-30071 Murcia, Spain
M. Carmen Ramirez de Arellano
Departamento de Qu´ımica Inorga´nica, Facultad de Quı´mica, Universidad de Murcia,
Campus de Espinardo, E-30071 Murcia, Spain
Received J uly 21, 1997X
A rapid and efficient synthetic procedure has been developed to prepare new ferrocene
derivatives such as â-ferrocenylvinyl heterocumulenes and ferrocene-containing imidazole
ring bearing one, two, or three ferrocene subunits. The method is based on the aza Wittig
reaction of [(â-ferrocenylvinyl)imino]phosphorane 3, readily available from ferrocenecarbox-
aldehyde by sequential treatment with ethyl azidoacetate and triphenylphosphine, with
isocyanates and further treatment with the appropriate primary amine. The crystal
structures of compounds 6c (monoferrocene derivative), 11c, and 12b (biferrocene derivatives)
have been determined by single-crystal X-ray methods. The electrochemical properties of
these new compounds are also reported.
Considerable attention has been paid in the last few
P- or sp/sp2/sp3/N-donor groups which may be able to
act as ligand toward transition-metal ions. To our
knowledge, no ferrocenylimidazole derivatives have
been described, in spite of the fact that ferrocenyl-
substituted pyrazoles7 and many ferrocenyl-substituted
pyridines8 have been studied, especially in the context
of the design of redox spectators.
years to supramolecular systems containing a ferrocene
unit and a fragment able to act as ligand, with a well-
defined geometry because of its fixed intramolecular
spacing, toward transition-metal ions; these systems can
behave either as chemical sensors1 or as redox-active
and photoactive molecular devices.2 In addition, su-
pramolecular systems containing more than one met-
allocene unit have attracted a great deal of attention.3
In particular, bridging two or three ferrocene subunits
generates redox systems which have been the subject
of recent studies due to their great potential as partially
oxidized species exhibiting mixed-valence behavior or
electronic delocalization4 and as models for poly(ferro-
cenyl)silane materials.5 On the other hand, the fer-
rocene subunit has been incorporated into more complex
structures, which then displayed a high degree of
nonlinear optical (NLO) behavior, liquid crystalline,
ferromagnetic, or catalytic properties.6
Resu lts a n d Discu ssion
We chose to use the [(â-ferrocenylvinyl)imino]phos-
phorane 3 as a building block for the synthesis of the
new ferrocene derivatives. Ferrocenecarboxaldehyde (1)
underwent Knoevenagel condensation with ethyl azi-
doacetate in the presence of NaEtO at -15 °C to give
the â-ferrocenylvinyl azide 2 in 82% yield. Staudinger
reaction of azide 2 with triphenylphosphine in dry
dichloromethane at room temperature provided the key
intermediate, iminophosphorane 3, in 93% yield. The
1H NMR spectrum of 3 is characteristic: the ferrocenyl
substituent gives rise to a five-proton singlet at 4.04
ppm for the unsubstituted cyclopentadienyl ring and
two apparent triplets at 4.17 and 4.87 ppm, respectively,
corresponding to the AA′MM′ pattern for the monosub-
The present work was undertaken to synthesize and
characterize a range of ferrocene-containing species with
X Abstract published in Advance ACS Abstracts, December 1, 1997.
(1) Beer, P. D. Chem. Soc. Rev. 1989, 18, 409.
(2) Beniston, A. C.; Goulle, V.; Harriman, A.; Lehn, J . M.; Ma-
razinke, B. J . Phys. Chem. 1994, 98, 7798. Butler, I. R.; Roustau, J . L.
Can. J . Chem. 1990, 68, 2212. Beer, P. D.; Kocian, O.; Mortimer, R. J .
J . Chem. Soc., Dalton Trans. 1990, 3283.
(3) For a review, see: Mueller-Westerhoff, O. T. Angew. Chem., Int.
Ed. Engl. 1986, 25, 702.
(4) Hendr¨ıckson, D. N.; Oh, S. N.; Dong, T. Y.; Kambara, T.; Cohn,
M. F. Comments Inorg. Chem. 1985, 4, 329. Delville, M. H.; Robert,
F.; Gouzerrh, P.; Linares, J .; Boukheddaden, K.; Varret, F.; Astruc,
D. J . Organomet. Chem. 1993, 451, C10. Barlow, S.; Murphy, V.; Evans,
J . S. O.; O’Hare, D. Organometallics 1995, 14, 3461.
(5) Rulkens, R.; Lough, A. J .; Manners, I. J . Am Chem.. Soc. 1994,
116, 797. Pannell, K. H.; Dementiev, V. V.; Li, H.; Cervantes-Lee, F.;
Nguyen, M. T.; Diaz, A. F. Organometallics 1994, 13, 3644.
(6) For a recent overview, see: Ferrocenes, Homogeneus Catalysis,
Organic Synthesis, Material Science; Togni, A., Hayashi, T., Eds.;
VCH: Weinheim, 1995.
(7) Cain, C. E.; Mashburn, T. A., J r.; Hauser, C. R. J . Org. Chem.
1961, 26, 1030. Pagel, K.; Werner, A.; Friedrichsen, W. J . Organomet.
Chem. 1994, 481, 109. Chabert-Couchouron, N.; Reibel, C.; Tarrago´,
G. An. Quim. Int. Ed. 1996, 92, 70.
(8) Schlogl, K.; Fried, M. Monatsh. Chem. 1963, 94, 537. Booth, D.
J .; Rockett, B. W. J . Chem. Soc. (C) 1971, 3341. Butler, I. R.
Organometallics 1992, 11, 74. Carugo, O.; De Santis, G.; Fabrizzi, L.;
Lichelli, M. Monichino, A.; Pallavicini, P. Inorg. Chem. 1992, 31, 765.
Constable, E. C.; Edwards, A. J .; Martinez-Man˜ez, R.; Raithbly, P. R.;
Thompson, M. W. C. J . Chem. Soc., Dalton Trans. 1994, 645. Constable,
E. C.; Martinez-Man˜ez, R.; Thompson, M. W. C.; Walker, J . J . Chem.
Soc., Dalton Trans. 1994, 1585. Constable, E. C.; Edwards, A. J .;
Raithbly, P. R.; Soto, J .; Tendero, M. J . L.; Martinez-Man˜ez, R.
Polyhedron 1995, 14, 3061.
S0276-7333(97)00616-X CCC: $14.00 © 1997 American Chemical Society

Ferrocene Derivatives Prepared by Aza Wittig Reactions
Sch em e 1
Organometallics, Vol. 16, No. 26, 1997 5837
Sch em e 2
Ta ble 1. F er r ocen ylim id a zole Der iva tives 6, 11,
a n d 12
stituted ring. Similar behavior was observed in the 13
NMR spectrum.
It is important to note that the iminophosphorane
moiety possesses a high complex-forming capacity with
a wide variety of metal compounds9 and metal carbon-
yls,10 so 3 could be of valuable interest for the prepara-
tion of redox-functionalized metal complexes.
(Vinylimino)phosphorane 3 was converted in a one-
flask reaction into the corresponding highly function-
alized ferrocenylimidazole 6 in yields higher than 70%.
This conversion involves aza Wittig reaction with benzyl
or alkyl isocyanates at room temperature and further
treatment of the resulting carbodiimide 4 with aliphatic
or aromatic primary amines to give ferrocenylguanidines
5 as intermediates, which undergo cyclization at room
temperature to give 6. Compound 3 also reacted with
aromatic isocyanates to give the expected carbodiimide
7, which by reaction with aliphatic amines provided 6
but did not react with aromatic amines at room tem-
perature. At higher temperatures, complex mixtures
C
compd
R1
R2
R3
yield (%)
6a
6b
6c
CH3
C2H5
C3H7
C6H5-CH2
4-H3C-C6H5
H
H
H
CH3
CH3
CH3
86
98
72
65
94
86
83
62
26
40
C2H5
C6H5
C6H5
CH3
C2H5
C6H5
CH3
6d
11a
11b
11c
11d
12a
12b
H
H
H
H
H
CH3
CH3
CH3
were obtained, from which the corresponding imidazoles
8 could not be detected (Table 1, Scheme 1). The 1H
and 13C NMR spectra of compounds 6 showed the same
type of signals for the ferrocene unit as observed in the
(vinylimino)phosphorane 3. An X-ray structure deter-
mination confirmed unambiguously the structure 6c
(Figure 1, Table 2).
(Vinylimino)phosphorane 3 also reacted with solid
carbon dioxide at 110 °C in a sealed tube to afford the
â-ferrocenylvinyl isocyanate 9 as crystalline solid in 86%
yield; however, when the reaction was carried out at
(9) Abel, E. W.; Mucklejohn, S. A. Phosphorus Sulfur 1981, 9, 235.
(10) Dehnicke, K.; Strahle, J . Polyhedron 1981, 9, 235.

5838 Organometallics, Vol. 16, No. 26, 1997
Molina et al.
F igu r e 1. ORTEP plot of 6c with 50% probability el-
lipsoids.
F igu r e 2. ORTEP plot of 11c with 50% probability
ellipsoids.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 6c
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 11c
Lengths (Å)
O-C(3)
1.231(2)
1.402(2)
1.403(2)
1.346(2)
1.349(2)
1.482(2)
N(1)-C(4)
N(2)-C(3)
N(2)-C(5)
N(3)-C(6)
C(1)-C(11)
1.303(2)
1.372(2)
1.467(2)
1.462(2)
1.447(2)
Lengths (Å)
N(1)-C(2)
N(2)-C(4)
N(3)-C(4)
C(1)-C(2)
C(2)-C(3)
O(1)-C(3)
N(1)-C(4)
N(2)-C(4)
N(3)-C(4)
C(1)-C(2)
C(2)-C(3)
C(6)-C(8)
1.235(7)
1.402(13)
1.416(7)
1.249(11)
1.325(12)
1.493(9)
1.478(8)
N(1)-C(2)
N(2)-C(3)
N(2)-C(5)
N(3)-C(6)
C(1)-C(11)
C(6)-C(7)
1.395(10)
1.350(11)
1.458(10)
1.414(7)
1.457(10)
1.346(8)
Angles (deg)
C(4)-N(1)-C(2) 105.24(13) C(3)-N(2)-C(4)
107.04(13)
128.80(12)
C(3)-N(2)-C(5) 123.91(13) C(4)-N(2)-C(5)
Angles (deg)
C(4)-N(3)-C(6) 118.31(14) C(2)-C(1)-C(11) 127.1(2)
C(2)-N(1)-C(4)
C(3)-N(2)-C(5)
C(4)-N(3)-C(6)
C(1)-C(2)-N(1)
N(1)-C(2)-C(3)
O(1)-C(3)-C(2)
N(3)-C(4)-N(1)
N(1)-C(4)-N(2)
C(7)-C(6)-C(8)
C(6)-C(7)-C(31)
112.3(5)
124.4(5)
120.1(6)
133.7(5)
104.2(7)
127.0(8)
133.5(5)
104.3(8)
116.2(5)
128.2(5)
C(3)-N(2)-C(4)
C(4)-N(2)-C(5)
C(2)-C(1)-C(11)
C(1)-C(2)-C(3)
O(1)-C(3)-N(2)
N(2)-C(3)-C(2)
N(3)-C(4)-N(2)
C(7)-C(6)-N(3)
N(3)-C(6)-C(8)
112.4(6)
123.1(8)
131.4(6)
122.0(6)
126.3(6)
106.7(5)
122.2(7)
124.8(5)
118.7(4)
C(1)-C(2)-N(1) 127.8(2)
N(1)-C(2)-C(3) 108.99(13) O-C(3)-N(2)
O-C(3)-C(2) 130.9(2)
C(1)-C(2)-C(3)
123.17(14)
124.8(2)
104.26(13)
114.46(13)
N(2)-C(3)-C(2)
N(1)-C(4)-N(3) 125.36(14) N(1)-C(4)-N(2)
N(3)-C(4)-N(2) 120.16(14)
160 °C, a mixture of isocyanate 9 (70%) and the bis(â-
ferrocenylvinyl)carbodiimide 10 (20%) was obtained.
The latter compound can be obtained in 95% yield by
intermolecular aza Wittig reaction of the (vinylimino)-
phosphorane 3 and the vinyl isocyanate 9 in toluene at
under the same conditions afforded two compounds. The
major product (62%) was found to be 11d , whose
spectroscopic properties are nearly identical to those of
11a -c. The minor product 12a (26%) has the same
microanalytical data; however, the 1H and 13C NMR
spectra showed striking differences with respect to those
of 11d . The 13C NMR spectrum not only showed
separate sets of signals for the two ferrocene subunits,
as in 11, but also showed five separate resonances for
each substituted Cp ring, thus indicating the lack of any
symmetry element relating to them.12 When 10 was
treated with tert-butylamine at room temperature,
starting material was recovered unaltered; however,
when the reaction was carried out at 100 °C, 12b was
isolated as the only reaction product in 40% yield. The
spectroscopic properties of 12b are nearly identical to
those of 12a . The behavior of carbodiimide 10 toward
primary amines can be rationalized by initial formation
of a guanidine derivative which undergoes cyclization
across either the alkylamino group or the (â-ferroce-
reflux temperature (Scheme 2). The H and 13C NMR
1
spectra of 10 revealed that the two ferrocene subunits
are equivalent. Compound 10, whose structure has
been determined by X-ray analysis,11 represents a novel
example of biferrocene compounds in which the bridging
unit is an unsaturated carbodiimide.
The present approach to ferrocenylimidazoles enables
the design of novel complex ferrocene-containing het-
erocycles bearing two or three ferrocene subunits. Thus,
carbodiimide 10 reacted with R-unsubstituted primary
amines in dry dichloromethane at room temperature to
give bis(ferrocenyl)imidazole derivatives 11 in yields
1
ranging from 83% to 95% (Table 1, Scheme 3). The H
and 13C NMR spectra of compounds 11 showed two sets
of signals for the two ferrocene subunits, indicating that
they are nonequivalent. Namely, in the 13C NMR
spectra of 11, only three resonances are observed for
each substituted Cp ring (and one resonance for each
unsubstituted ring), implying that the Cp rings undergo
rapid rotation. The reaction of 10 with isopropylamine
(12) Herrick, R. S.; J arret, M. R.; Curran, T. P.; Dragoli, D. R.;
Flaherty, M. B.; Lindyberg, S. E.; Slate, R. A.; Thornton, L. C.
Tetrahedron Lett. 1996, 5289. Barbaro, P.; Togni, A. Organometallics
1995, 14, 3570.
(11) Molina, P.; Pastor, A.; Vilaplana, M. J .; Ramirez de Arellano,
M. C. Tetrahedron Lett. 1996, 7829.

Ferrocene Derivatives Prepared by Aza Wittig Reactions
Sch em e 3
Organometallics, Vol. 16, No. 26, 1997 5839
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 12b‚1/2Et2O
nylvinyl)amino group, depending on the degree of
substitution on the carbon atom adjacent to the amino
group.
Lengths (Å)
O(1)-C(3)
N(1)-C(2)
N(2)-C(3)
N(3)-C(4)
C(1)-C(2)
C(2)-C(3)
C(6)-C(8)
1.201(5)
1.401(5)
1.405(5)
1.333(5)
1.327(6)
1.489(5)
1.477(6)
N(1)-C(4)
N(2)-C(4)
N(2)-C(6)
N(3)-C(21)
C(1)-C(11)
C(6)-C(7)
C(7)-C(31)
1.322(5)
1.403(5)
1.424(5)
1.495(5)
1.452(5)
1.351(5)
1.435(6)
In order to identify unambiguously the proposed
structures, X-ray structure determination of 11 and 12
was performed. The structures 11c (Figure 2, Table 3)
and 12b (Figure 3, Table 4) reveal that the two ferrocene
subunits are orthogonal (Cp11-Cp31 ) 86.8° for 11c,
and Cp11-Cp31 ) 87.2° for 12b) with respect to each
other, and the intramolecular Fe-Fe separation is
almost the same (9.572 Å) for both compounds. A final
point is concerned with the conformation of the cyclo-
pentadienyl ring in each subunit. The conformation is,
in both subunits, almost eclipsed. It has been pointed
out that the energy difference between the two conform-
ers is rather small,13 and the stability order may be
altered through the introduction of substituents on the
cyclopentadienyl ring(s).
Angles (deg)
105.7(3)
C(4)-N(1)-C(2)
C(4)-N(2)-C(6)
C(4)-N(3)-C(21)
C(1)-C(2)-N(1)
N(1)-C(2)-C(3)
O(1)-C(3)-C(2)
N(1)-C(4)-N(3)
N(3)-C(4)-N(2)
C(7)-C(6)-C(8)
C(6)-C(7)-C(31)
C(4)-N(2)-C(3)
C(3)-N(2)-C(6)
C(2)-C(1)-C(11)
C(1)-C(2)-C(3)
O(1)-C(3)-N(2)
N(2)-C(3)-C(2)
N(1)-C(4)-N(2)
C(7)-C(6)-N(2)
N(2)-C(6)-C(8)
107.6(3)
122.3(3)
127.3(4)
122.5(4)
125.3(4)
103.0(3)
113.7(3)
123.1(4)
117.5(3)
126.6(3)
123.9(3)
127.6(4)
109.8(3)
131.6(4)
126.8(4)
119.5(3)
119.3(3)
130.4(4)
Sch em e 4
Carbodiimide 10 also reacted with ferrocenylmethy-
lamine14 in dichloromethane at room temperature to
give the tris(ferrocenyl) compound 13 in 60% yield. The
13C NMR spectrum showed three sets of signals for the
three ferrocene subunits (Scheme 4).
The cyclic voltammograms of 6a -c (Figure 4) show
that the ratio of the current intensity of the anodic peak
over the intensity of the cathodic peak (ipa/ipc) was
approximatly equal to 1 over the potential scan rate
range 0.01-0.2 V s-1, and the peak-to-peak separation
was 65-67 mV. Under the same experimental condi-
tions, the one-electron oxidation of ferrocene itself
displays an Ep of 64 mV, thus indicating that departure
from the constant value of 59 mV expected for an
(13) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th
ed., Wiley: New York, 1988; p 79.
(14) Grimshow, J .; Trocha-Grimshow, J . J . Chem. Soc., Perkin
Trans. 2 1991, 751.
F igu r e 3. ORTEP plot of 12c with 50% probability
ellipsoids.

5840 Organometallics, Vol. 16, No. 26, 1997
Molina et al.
Ta ble 5. Cyclic Volta m m etr y Da ta of F er r ocen yl
Der iva tives
compd E1/2(1), V E1/2(2), V ∆Epa, mV ∆E1/2(1), mV Kc
FcH
6a
6b
6c
10
0.404
0.355
0.351
0.372
0.463
0.425
64
66
67
65
106
141
0.539
0.517
76
92
19
36
11c
a
Peak-to-peak separation measured at 100 mV s-1
.
they show the electron-donating abilities of the substit-
uents, which makes the electron removal about 32-53
mV easier when compared with that of ferrocene.
Biferrocene derivatives 10 and 11c exhibit cyclic
voltammograms characteristic of superimposed one-
electron waves,16 with a peak-to-peak separation nota-
bly higher than the 57 mV expected for a two-electron
process involving non-interacting centers.17 The values
of E1/2(1) and E1/2(2) were estimated by using the method
outlined by Richarson and Taube.18 The difference (E1/2
)
between the first and second half-wave potentials gives
values of Kc significantly higher than the statitiscal
value for 4, which reveals a small but significant
electronic interaction between the two redox centers
through the organic chain attached to the ferrocenyl
subunits.
The cyclic voltammogram of derivative 13 (Figure 4)
shows one oxidation wave at Epa ) 0.603 V vs SCE,
which implies that only very weak interactions between
the ferrocenyl subunits are presented.
In conclusion, the aza Wittig reaction, which has not
been used before in ferrocene chemistry, appears to be
a simple but very effective new way to prepare a wide
variety of ferrocene derivatives, in which the ferrocene
group is conjugated either to a heterocumulene frag-
ment or to a highly functionalized imidazole ring. The
method also works for the preparation of bi- and
triferrocene derivatives. These relatively complex and
unreported structures are prepared under mild reaction
conditions, with high yields, and from the readily
available starting material [(â-ferrocenylvinyl)imino]-
phosphorane 3.
Exp er im en ta l Section
Gen er a l Meth od s. General experimental conditions and
spectroscopic instrumentation used have been described.19
The cyclic voltammetric measurements were performed with
a QUICELTRON potentiostat/galvanostat, controlled by a
personal computer and driven by dedicated software. Experi-
ments were carried out in a three-electrode cell. The counter
electrode was platinum foil, and the reference was a saturated
calomel electrode (SCE). The cyclic voltammetry was per-
formed at a platinum disk working electrode with a variable
scan rate.
First, 5 mL of CH2Cl2/CH3CN (1:1) solution containing 0.1
M [nBu4N][ClO4] was poured into the cell, followed by 5 mmol
of the derivative (10-3 M). The same electrodes were used for
cyclic voltammetry performed in DMF. Deoxygenation of the
F igu r e 4. Cyclic voltammograms of (A) 6c (1 mM) in
MeCN/CH2Cl2 (1:1) solution containing 0.10 M TBAP, scan
rate 0.1 V s-1; (B) 11c in MeCN/CH2Cl2 (1:1) solution
containing 0.10 M TBAP, scan rate 0.1 V s-1; (C) 13 (0.25
mM) in DMF solution containing 0.10 M TBAP, scan rate
(15) Nicholson, R. S.; Shain, I. Anal. Chem. 1964, 706.
(16) Ammar, F.; Saveant, J . M. J . Electroanal. Chem. Interfacial
Electrochem. 1973, 47, 215. Polcyn, D. S.; Shain, I. Anal. Chem. 1966,
38, 370.
(17) Flanagan, J . B.; Margell, S.; Bard, A. J .; Anson, F. C. J . Am.
Chem. Soc. 1978, 100, 4248.
(18) Richarson, D. E.; Taube, H. Inorg. Chem. 1981, 20, 1278.
(19) Molina, P.; Pastor, A.; Vilaplana, M. J . J . Org. Chem. 1996,
61, 8094.
0.5 V s-1
.
electrochemically reversible one-electron trasfer15 should
be due to uncompensated solution resistences. Table 5
shows the half-wave potentials of compounds 6, and

Ferrocene Derivatives Prepared by Aza Wittig Reactions
Organometallics, Vol. 16, No. 26, 1997 5841
Ta ble 6. Cr ysta l Da ta for 6c, 11c, a n d 12b‚1/2Et2O
6c
11c
12b‚1/2Et2O
molecular formula
molecular weight
habit
C28H25N3OFe
475.36
tablet
C36H33N3O3Fe2
667.35
prism
C35H40N3O3.5Fe2
670.40
prism
color
source
dark red
dark red
dark red
liquid diffusion
CH3COOEt/n-hexane
11.042(2)
12.570(2)
13.440(4)
110.18(2)
92.38(2)
93.43(1)
1744(1)
liquid diffusion
CH2Cl2/Et2O
8.007(1)
23.699(2)
11.700(1)
liquid diffusion
CH2Cl2/iPr2O
32.212(3)
13.216(2)
21.668(3)
a, Å
b, Å
c, Å
R, deg
â, deg
93.88(1)
91.33(1)
γ, deg
V, Å3
2215(1)
4
6079(1)
8
Z
2
λ, Å
temp, K
0.710 73
173(2)
0.710 73
173(2)
0.710 73
173(2)
radiation
monochromator
space group
crystal size, mm
absorpt correction
max/min trans, %
diffractometer
scan method
2θ range
hkl limits
reflns measured
independent reflns
Rint
Mo KR
graphite
P21/c
0.56 × 0.44 × 0.14
ψ-scans
0.99/0.74
Siemens P4
ω
6.2-50.0
(h -k (l
8636
3899
0.025
Mo KR
graphite
C2/c
0.32 × 0.30 × 0.28
ψ-scans
0.77/0.74
Siemens P4
ω
6.2-50.0
-h +k (l
5442
2789
0.036
Mo KR
graphite
P1h
0.40 × 0.38 × 0.32
ψ-scans
0.95/0.74
Siemens P4
ω
6.2-50.2
(h (k +l
5852
5636
0.015
R1a
0.0254
0.0668
0.0516
0.1380
0.0557
0.2096
wR2b
a
b
2
R1 ) σ||Fo| - |Fc||/σ|Fo| for reflections with I > 2σI. wR2 ) [σ[w(Fo - Fc2)2]/σ[w(Fo2)2]]0.5 for all reflections; w-1 ) σ2(F2) + (aP)2 +
bP, where P ) (2Fc + Fo2)/3, and a and b are constants set by the program.
2
solutions was achieved by bubbling nitrogen for at least 10
min. All of the potential values are referred to SCE.
yielded a crude material, which was chromatographed on a
silica gel column using ethyl acetate/n-hexane (1:3) as eluent
to give 2 in 82% yield, which was recrystallized form diethyl
ether/n-hexane (1:1): mp 84-86 °C, red prisms; 1H NMR
(CDCl3) δ 1.39 (t, 3H, J ) 7.1 Hz), 4.15 (s, 5H), 4.33 (q, 2H, J
) 7.2 Hz), 4.40 (t, 2H, J ) 1.7 Hz), 4.47 (t, 2H, J ) 1.7 Hz),
6.78 (s, 1H); 13C NMR (CDCl3) δ 14.3, 61.9, 69.6, 70.8, 70.7,
122.5, 127.6, 163.5; EI-MS m/z (relative intensity) 325 (M+,
8), 224 (100), 121 (54). Anal. Calcd for C15H15N3O2Fe: C,
55.41; H, 4.65; N, 12.99. Found: C, 55.54; H, 4.76; N, 13.34.
X-r a y Cr ysta llogr a p h y. Crystals obtained by liquid dif-
fusion from CH2Cl2/Et2O (6c), CH2Cl2/iPr2O (11c), and CH3-
COOEt/n-hexane (12b‚1/2Et2O) were respectively mounted in
inert oil on a glass fiber and transferred to the diffractomer
(Siemens P4 with LT2 low-temperature attachment), as sum-
marized in Table 6. The data were collected at 173 K using
graphite monochromated Mo KR radiation (0.710 73 Å) ac-
cording to the ω-scans method in the region 6.2 e 2θ e 50.0°.
Unit cell parameters were determined from a least-squares
fit of 72 (6c), 42 (11c), and 74 (12b‚1/2Et2O) accurately centered
reflections (9 < 2θ < 25°). An absorption correction based on
æ-scans was applied, with transmision factors 0.74-0.99 (6c),
0.74-0.76 (11c), and 0.74-0.95 (12b‚1/2Et2O). The structures
were solved by direct methods and refined on F2 by means of
the full-matrix least-squares method. The N-H hydrogen atom
was found in the final Fourier F map and refined as a free
variable for all three compounds. Other hydrogen atoms were
included using a riding model, except for those of the methyl
groups of 6c, which were refined as rigid. The programs use
the neutral atom scattering factors, ∆f ′ and ∆f ′′, and absorp-
tion coefficients.20
P r ep a r a tion of r-Azid o-â-fer r ocen ylp r op en oic Acid
Eth yl Ester (2). A mixture of ethyl azidoacetate (4.82 g, 37.2
mmol) and ferrocenecarboxaldehyde (1, 2.00 g, 9.3 mmol) was
added dropwise under nitrogen at -15 °C to a well-stirred
solution containing sodium (0.86 g, 37.2 mmol) in 25 mL of
anhydrous THF. The reaction mixture was stirred at that
temperature for 7 h and then allowed to warm to room
temperature. The resultant solution was poured into aqueous
30% ammonium chloride (50 mL) and then extracted with
diethyl ether (3 × 50 mL). The combined organic layers were
washed with water (3 × 50 mL), dried over anhydrous
magnesium sulfate, and filtered. Concentration to dryness
P r ep a r a tion of â-F er r ocen yl-r-[(Tr ip h en ylp h osp h o-
r a n ylid en e)a m in o]p r op en oic Acid Eth yl Ester (3). To a
solution of 2 (0.25 g, 0.8 mmol) cooled at 0 °C in anhydrous
dichloromethane (10 mL) was added a solution of Ph3P (0.22
g, 0.9 mmol) in the same solvent (5 mL) dropwise under
nitrogen. The resultant mixture was then allowed to warm
at room temperature and stirred for 24 h. The solvent was
removed under reduced pressure, and the crude solid was
chromatographed on a silica gel column using ethyl acetate/
n-hexane (1:3) as eluent to give 3 in 93% yield, which was
recrystallized from dichloromethane/diethyl ether/n-hexane
1
(1:2:1): mp 142-144 °C, red prisms; H NMR (CDCl3) δ 0.97
(t, 3H, J ) 7.1 Hz), 3.82 (q, 2H, J ) 7.2 Hz), 4.04 (s, 5H), 4.17
4
(t, 2H, J ) 1.8 Hz), 4.87 (t, 2H, J ) 1.7 Hz), 6.52 (d, 1H, J PH
3
3
) 6.3 Hz), 7.39-7.45 (m, 9H) 7.76 (ddd, 6H, J PH ) 12, J )
7.8, and J ) 1.6 Hz); 13C NMR (CDCl3) δ 14.1, 60.4, 68.3, 68.9,
4
69.7, 82.9, 117.0 (d, 3J PC ) 20.6 Hz), 128.1 (d, 3J PC ) 20.6 Hz),
4
2
130.8 (d, J PC ) 20.6 Hz), 132.4 (d, J PC ) 9.6 Hz), 133.5 (d,
1J PC ) 102.7 Hz), 134.1 (d, J PC ) 7.1 Hz), 167.7 (d, J PC
)
2
3
20.6 Hz); 31P NMR (CDCl3) δ 4.9; EI-MS m/z (relative intensity)
559 (M+, 100), 226 (16), 183 (59), 121 (57). Anal. Calcd for
C
33H30NO2PFe: C, 70.85; H, 5.41; N, 2.51. Found: C, 70.61;
H, 5.59; N, 2.29.
Gen er a l P r oced u r e for th e P r ep a r a tion of F er r oce-
n ylim id a zoles 6. To a solution of iminophosphorane 3 (0.25
g, 0.5 mmol) in anhydrous dichloromethane (15 mL) was added
the appropriate isocyanate (0.5 mmol) in the same solvent (5
mL). The resultant reaction mixture was stirred at room
(20) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic Publishers: Dordrecht, 1992; Vol. C, pp 193-199,
219-222, and 500-502.

5842 Organometallics, Vol. 16, No. 26, 1997
Molina et al.
temperature for 24 h. The corresponding amine (0.5 mmol)
was then added, and the reaction mixture was stirred at that
temperature for 24 h. The solution was concentrated to
dryness, and the residual material was chromatographed on
a silica gel column using ethyl acetate/n-hexane (1:3) as eluent
to give compounds 6, which were recrystallized from the
appropriate solvent.
6a : yield 86%; mp 197-198 °C; red prisms (dichloromethane/
diethyl ether 1:3); IR (Nujol) 3326, 1686, 1652 cm-1; 1H NMR
(CDCl3) δ 1.23 (t, 3H, J ) 7.2 Hz), 1.35 (t, 3H, J ) 7.2 Hz);
3.55-3.67 (m, 4H)), 4.13 (s, 5H), 4.37 (br s, 2H), 4.66 (m, 1H),
4.94 (br s), 6.59 (s, 1H); 13C NMR (CDCl3) δ 14.3, 15.0, 33.8,
36.9, 69.4, 70.2, 70.7, 79.2, 118.8, 137.6, 155.3, 169.2; EI-MS
m/z (relative intensity) 351 (M+, 100), 286 (74), 121 (60). Anal.
Calcd for C18H21N3OFe: C, 61.55; H, 6.03; N, 11.96. Found:
C, 61.93; H, 6.21; N, 11.67.
6b: yield 98%; mp 134-135 °C; red prisms (dichloromethane/
diethyl ether 1:3); IR (Nujol) 3318, 1686, 1644 cm-1; 1H NMR
(CDCl3) δ 0.96 (t, 3H, J ) 7.5 Hz), 1.04 (t, 3H, J ) 7.5 Hz),
1.63 (qn, 3H, J ) 7.4 Hz), 1.76 (qn, 3H, J ) 7.3 Hz), 3.47-
3.56 (m, 4H), 4.13 (s, 5H), 4.38 (t, 2H, J ) 1.8 Hz), 4.49 (m,
1H), 4.93 (br s, 2H), 6.59 (s, 1H); 13C NMR (CDCl3) δ 11.4,
11.5, 22.4, 22.9, 40.7, 43.7, 69.4, 70.2, 70.7, 79.3, 118.8, 137.5,
155.6, 169.4; EI-MS m/z (relative intensity) 379 (M+, 100), 314
(26), 121 (51). Anal. Calcd for C20H25N3OFe: C, 63.34; H, 6.64;
N, 11.08. Found: C, 63.59; H, 6.22; N, 11.43.
32), 121 (100). Anal. Calcd for C31H30N2O4Fe2: C, 61.41; H,
4.99; N, 4.62. Found: C, 61.75; H, 4.82; N, 4.44.
Rea ction of Ca r bod iim id e 10 w ith P r im a r y Am in es.
Gen er a l P r oced u r e. To a solution of carbodiimide 10 (0.25
g, 0.41 mmol) in dry dichloromethane (15 mL) was added the
corresponding amine (0.41 mmol). The resultant reaction
mixture was stirred at room temperature for 24 h. The
solution was concentrated to dryness, and the residual mate-
rial was chromatographed on a silica gel column using diethyl
ether/n-hexane (1:3) (for 11a and 11b) or ethyl acetate/n-
hexane (1:3) (for 11c, 11d , 12a , 12b, and 13) as eluents to
give 11 and/or 12, or 13, which were recrystallized from the
appropriate solvent.
11a : yield 94%; mp 68-70 °C; red prisms (dichloromethane/
diethyl ether 1:3); IR (Nujol) 3276, 1681, 1659 cm-1; 1H NMR
(CDCl3) δ 1.37 (t, 3H, J ) 7.2 Hz), 1.43 (t, 3H, J ) 7.2 Hz),
3.93 (q, 2H, J ) 6.9 Hz), 4.07 (s, 5H), 4.15 (s, 5H), 4.25 (t, 2H,
J ) 1.8 Hz), 4.29-4.33 (m, 6H), 4.58 (t, 2H, J ) 1.8 Hz), 6.33
(s, 1H), 7.00 (s, 1H), 7.13 (s, 1H); 13C NMR (CDCl3) δ 13.7,
14.4, 34.4, 61.5, 68.7, 69.6, 69.5, 70.2, 70.3, 70.4, 77.3, 78.0,
108.7, 125.9, 127.9, 130.7, 144.6, 163.5, 166.6; EI-MS m/z
(relative intensity) 605 (M+, 15), 121 (100). Anal. Calcd for
C
31H31N3O3Fe2: C, 61.51; H, 5.16; N, 6.94. Found: C, 61.28;
H, 5.40; N, 6.71.
11b: yield 86%; mp 79-80 °C; red prisms (dichloromethane/
diethyl ether/n-hexane 1:1:4); IR (Nujol) 3275, 1684, 1655 cm-1
;
1H NMR (CDCl3) δ 1.05 (t, 3H, J ) 7.4 Hz), 1.36 (t, 3H, J )
7.2 Hz), 1.89 (sext, 2H, J ) 7.5 Hz), 3.82 (m, 2H), 4.07 (s, 5H),
4.14 (s, 5H), 4.20 (t, 2H, J ) 1.9 Hz), 4.23-4.34 (m, 6H), 4.57
6c: yield 72%; mp 186-188 °C; red prisms (ethyl acetate/
n-hexane 1:3); IR (Nujol) 3333, 1682, 1647 cm-1 1H NMR
;
(CDCl3) δ 4.12 (s, 5H), 4.39 (t, 2H, J ) 1.8 Hz), 4.59 (s, 3H),
4.76 (s, 2H), 4.95 (br s, 2H), 6.72 (s, 1H), 7.20-7.31 (m, 10H);
13C NMR (CDCl3) δ 42.8, 45.7, 69.5, 70.5, 70.9, 78.9, 120.5,
127.0, 127.5, 127.6, 128.2, 128.7, 129.2, 135.4, 136.9, 138.1,
155.4, 169.2; EI-MS m/z (relative intensity) 475 (M+, 29), 91
(100). Anal. Calcd for C28H25N3OFe: C, 70.75; H, 5.30; N,
8.84. Found: C, 70.39; H, 5.47; N, 9.09.
(t, 2H, J ) 1.9 Hz), 6.33 (s, 1H), 7.08 (s, 1H), 7.26 (s, 1H); 13
C
NMR (CDCl3) δ 11.4, 14.4, 21.6, 61.4, 68.7, 69.5, 69.6, 70.2,
70.3, 70.4, 77.3, 78.0, 108.7, 125.7, 127.0, 130.6, 144.7, 163.8,
165.9; EI-MS m/z (relative intensity) 619 (M+, 14), 573 (11),
121 (100). Anal. Calcd for C32H33N3O3Fe2: C, 62.06; H, 5.37;
N, 6.79. Found: C, 62.29; H, 5.16; N, 6.92.
11c: yield 83%; mp 174-176 °C; red prisms (dichloromethane/
diethyl ether 1:3); IR (Nujol) 3309, 1682, 1657 cm-1; 1H NMR
(CDCl3) δ 1.36 (t, 3H, J ) 7.1 Hz), 4.06 (s, 5H), 4.08 (s, 5H),
4.16 (t, 2H, J ) 1.8 Hz), 4.25-4.33 (m, 8H), 5.05 (s, 2H), 6.38
(s, 1H), 7.01 (s, 1H), 7.09 (s, 1H), 7.32-7.41 (m, 3H), 7.53-
7.55 (m, 2H); 13C NMR (CDCl3) δ 14.4, 42.7, 61.4, 68.7, 69.4,
69.5, 70.3, 70.4, 70.5, 77.2, 77.8, 109.2, 125.7, 127.2, 127.5,
128.3, 128.6, 130.3, 136.7, 144.5, 163.7, 165.9; EI-MS m/z
(relative intensity) 667 (M+, 6), 191 (100), 121 (41). Anal.
Calcd for C36H33N3O3Fe2: C, 64.79; H, 4.98; N, 6.30. Found:
C, 64.56; H, 5.13; N, 6.48.
6d: yield 68%; mp 186-188 °C; red prisms (dichloromethane/
diethyl ether 1:3); IR (Nujol) 3361, 1705, 1658 cm-1; 1H NMR
(CDCl3) δ 3.27 (s, 3H), 4.15 (s, 5H), 4.40 (t, 2H, J ) 1.8 Hz),
4.70 (s, 3H), 4.99 (t, 2H, J ) 1.8 Hz), 6.73 (s, 1H), 7.39-7.61
(m, 9H); 13C NMR (CDCl3) δ 21.2, 45.8, 69.5, 70.4, 70.8, 79.0,
120.2, 127.2, 127.8, 128.0, 128.8, 129.3, 130.8, 136.8, 138.2,
139.2, 154.6, 168.6; EI-MS m/z (relative intensity) 475 (M+,
58), 121 (73), 91 (100). Anal. Calcd for C28H25N3OFe: C,
70.75; H, 5.30; N, 8.84. Found: C, 70.43; H, 5.49; N, 8.67.
r-(Eth oxyca r bon yl)-â-fer r ocen ylvin yl Isocya n a te (9).
A mixture of iminophosphorane 3 (0.25 g, 0.5 mmol), dry
toluene (30 mL), and solid CO2 (0.4 g) was heated in a sealed
tube at 110 °C for 12 h. After cooling, the solvent was removed
under reduced pressure, and the residue was chromatographed
on a silica gel column using dichloromethane/n-hexane (1:2)
as eluent to give 9 in 86% yield, which was recrystallyzed from
dichloromethane/diethyl ether/n-hexane (1:2:1): mp 104-105
11d (Rf ) 0.44): yield 62%; mp 61-63 °C; red prisms; IR
(Nujol) 3267, 1659, 1105 cm-1 1H NMR (CDCl3) δ 1.35 (t,
;
3H, J ) 7.1 Hz), 1.64 (d, 6H, J ) 7.0 Hz), 4.05 (s, 5H), 4.14 (s,
5H), 4.21-4.34 (m, 8H), 4.55 (t, 2H, J ) 1.8 Hz), 4.78 (sept,
1H, J ) 7.0 Hz), 6.26 (s, 1H), 6.82 (br s, 1H), 7.11 (s, 1H); 13
C
NMR (CDCl3) δ 14.4, 19.8, 44.4, 61.4, 68.6, 69.4, 69.5, 70.1,
70.2, 70.3, 77.5, 78.1, 107.9, 125.8, 126.3, 131.0, 144.7, 163.6,
165.8; EI-MS m/z (relative intensity) 619 (M+, 11), 121 (100).
Anal. Calcd for C32H33N3O3Fe2: C, 62.06; H, 5.37; N, 6.78.
Found: C, 62.35; H, 5.19; N, 6.54.
°C; red prisms; IR (Nujol) 2232, 1698, 1637 cm-1
;
1H NMR
(CDCl3) δ 1.32 (t, 3H, J ) 7.1 Hz), 4.09 (s, 5H), 4.27 (q, 2H, J
) 7.1 Hz), 4.36 (t, 2H, J ) 1.8 Hz), 4.70 (t, 2H, J ) 1.8 Hz),
6.73 (s, 1H); 13C NMR (CDCl3) δ 14.3, 62.6, 69.6, 70.6, 71.0,
76.1, 130.1, 131.2, 164.3; EI-MS m/z (relative intensity) 525
(M+, 68), 121 (100). Anal. Calcd for C16H15NO3Fe: C, 59.10;
H, 4.65; N, 4.31. Found: C, 59.46; H, 4.79; N, 4.16.
Bis[r-(Eth oxyca r bon yl)-â-fer r ocen ylvin yl]ca r bod iim -
id e (10). A mixture of iminophosphorane 3 (0.38 g, 0.7 mmol),
isocyanate 9 (0.22 g, 0.7 mmol), and dry toluene (30 mL) was
heated at reflux temperature for 2 h. After cooling, the
solution was concentrated to dryness, and the residue was
chromatographed on a silica gel column using dichloromethane
as eluent to give 10 in 99% yield, which was recrystallized
from dichloromethane/diethyl ether (1:1): mp 195-197 °C; red
prisms; IR (Nujol) 2132, 2069, 1700 cm-1; 1H NMR (CDCl3) δ
1.36 (t, 6H, J ) 7.1 Hz), 4.20 (s, 10H), 4.29 (q, 4H, J ) 7.1
Hz), 4.41 (t, 4H, J ) 1.9 Hz), 4.90 (t, 4H, J ) 1.8 Hz), 7.01 (s,
2H); 13C NMR (CDCl3) δ 14.3, 61.7, 69.6, 70.6, 70.9, 77.2, 122,
130.0, 133.9, 164.4; EI-MS m/z (relative intensity) 606 (M+,
12a (Rf ) 0.22): yield 26%; mp 213-214 °C; red prisms; IR
(Nujol) 3285, 1704, 1656 cm-1; 1H NMR (CDCl3) δ 1.16 (d, 3H,
J ) 6.6 Hz), 1.25 (d, 3H, J ) 6.6 Hz), 1.30 (t, 3H, J ) 6.9 Hz),
4.04 (d, 1H, J ) 7.8 Hz), 4.17 (s, 5H), 4.22 (s, 5H), 4.25-4.46
(m, 9H), 4.97 (br s, 1H), 5.09 (br s, 1H), 6.70 (s, 1H), 7.92 (s,
1H); 13C NMR (CDCl3) δ 14.2, 22.7, 22.8, 43.9, 61.6, 68.9, 69.6,
70.2, 70.3, 70.4, 70.7, 71.0, 71.9, 72.7, 72.9, 73.7, 79.2, 115.6,
118.9, 137.2, 145.2, 152.9, 163.9, 168.3; EI-MS m/z (relative
intensity) 619 (M+, 100), 121 (18). Anal. Calcd for C32H33
-
N3O3Fe2: C, 62.06; H, 5.37; N, 6.78. Found: C, 61.69; H, 5.54;
N, 7.08.
12b: yield 40%; mp 116-118 °C; red prisms (ethyl acetate/
n-hexane 1:2); IR (Nujol) 3344, 1710, 1652 cm-1 1H NMR
;
(CDCl3) δ 1.31 (t, 3H, J ) 7.1 Hz), 1.47 (s, 9H), 4.04 (s, 1H),
4.16 (s, 5H), 4.22 (s, 5H), 4.25-4.47 (m, 8H), 4.98 (br s, 1H),
5.09 (br s, 1H), 6.68 (s, 1H), 7.91 (s, 1H); 13C NMR (CDCl3) δ

Ferrocene Derivatives Prepared by Aza Wittig Reactions
Organometallics, Vol. 16, No. 26, 1997 5843
14.2, 28.9, 52.4, 61.5, 69.0, 69.5, 70.2, 70.3, 70.4, 70.7, 70.9,
71.9, 72.5, 72.8, 73.7, 79.1, 115.7, 118.8, 137.2, 145.2, 151.8,
163.9, 167.7; EI-MS m/z (relative intensity) 633 (M+, 100), 121
(77). Anal. Calcd for C33H35N3O3Fe2: C, 62.58; H, 5.57; N,
6.64. Found: C, 62.19; H, 5.39; N, 6.82.
(M+ + 1, 81). Anal. Calcd for C40H37N3O3Fe3: C, 61.97; H,
4.81; N, 5.42. Found: C, 61.80; H, 4.89; N, 5.63.
Ack n ow led gm en t. We gratefully acknowledge the
financial support of the Direccion General de Investi-
gacio´n Cient´ıfica y Te´cnica (Project No. PB95-1019). A.P.
also thanks the MEC for a studentship.
13: yield 60%; mp 216-217 °C; orange prisms (dichlo-
romethane/diethyl ether 1:1); IR (Nujol) 3349, 1678, 1659 cm-1
;
Su p p or tin g In for m a tion Ava ila ble: A listing of all
refined and calculated atomic coordinates, all the anisotropic
thermal parameters, and full bond lengths and angles for
compounds 6c and 11c and 12b‚1/2Et2O (20 pages). See any
current masthead page for ordering information and Internet
access instructions.
1H NMR (CDCl3) δ 1.37 (t, 3H, J ) 7.2 Hz), 4.04 (s, 5H), 4.14
(s, 5H), 4.15 (t, 2H, J ) 1.5 Hz), 4.21 (t, 2H, J ) 1.8 Hz), 4.22
(s, 5H), 4.27-4.33 (m, 6H), 4.51 (t, 2H, J ) 1.8 Hz), 4.56 (t,
2H, J ) 1.8 Hz), 4.78 (s, 2H), 6.29 (s, 1H), 6.91 (s, 1H), 7.11 (s,
1H); 13C NMR (CDCl3) δ 14.5, 38.6, 61.5, 68.2, 68.7, 68.8, 69.5,
69.6, 70.1, 70.2, 70.4, 70.6, 77.1, 78.8, 83.5, 108.7, 125.7, 126.8,
130.7, 144.4, 163.3, 166.0; EI-MS m/z (relative intensity) 776
OM9706166