Synthesis of 1′-substituted derivatives of 1,2,3,4,5-pentaphenylferrocene

Article abstract of DOI:10.1021/om0204989

Pentaphenylferrocene was synthesized in 57% overall yield from 1-bromopentaphenylcyclopentadiene. Functionalization of the unsubstituted cyclopentadienyl ring using the Friedel - Crafts reaction gave 1′-formyl-and 1′-(2-chlorobenzoyl)-substituted derivatives. Hydrolysis of the latter provided the corresponding 1′-carboxylic acid. This was readily transformed via a modified Curtius rearrangement into 1′-amino-1,2,3,4,5-pentaphenylferrocene. This methodology also provided (η⁵-aminocyclopentadienyl)(η⁴-tetraphenylcyclobuta diene)-cobalt and gave an improved synthesis of aminoferrocene.

Full text of DOI:10.1021/om0204989

Organometallics 2002, 21, 5433-5436
5433
Notes
Syn th esis of 1′-Su bstitu ted Der iva tives of
1,2,3,4,5-P en ta p h en ylfer r ocen e
David C. D. Butler and Christopher J . Richards*
Department of Chemistry, Queen Mary, University of London, Mile End Road,
London, E1 4NS, U.K.
Received J une 24, 2002
Sch em e 1
Summary: Pentaphenylferrocene was synthesized in 57%
overall yield from 1-bromopentaphenylcyclopentadiene.
Functionalization of the unsubstituted cyclopentadienyl
ring using the Friedel-Crafts reaction gave 1′-formyl-
and 1′-(2-chlorobenzoyl)-substituted derivatives. Hy-
drolysis of the latter provided the corresponding 1′-
carboxylic acid. This was readily transformed via a
modified Curtius rearrangement into 1′-amino-1,2,3,4,5-
pentaphenylferrocene. This methodology also provided
(η5-aminocyclopentadienyl)(η4-tetraphenylcyclobutadiene)-
cobalt and gave an improved synthesis of aminofer-
rocene.
In tr od u ction
Since its discovery, the chemistry of ferrocene has
been prevalent within the literature, and it continues
to be a subject of intense study.1 Substituted derivatives
such as pentamethylferrocene, which offer contrasting
steric and redox properties, have also been extensively
investigated.2 Recently, phosphine-substituted deriva-
tives of pentaphenylferrocene were reported as effective
ligands in palladium-catalyzed transformations,3 and
enantiopure planar chiral pentaphenylferrocene deriva-
tives have been utilized as nucleophilic catalysts in
asymmetric synthesis.4 These 1,2,3,4,5-pentaphenylfer-
rocenes containing 1′- and 1′,2′-substituents, respec-
tively, are prepared either by introduction of five phenyl
groups onto a ferrocene precursor3a,5 or by use of a
prefunctionalized cyclopentadiene to construct the
metallocene.4d,g Pentaphenylferrocene 1 itself has re-
ceived hardly any attention, although some aspects of
its physical chemistry have been explored.6 In addition,
there is a single report on the direct functionalization
of this metallocene, although no experimental methods
or spectroscopic results were presented.7 We report
herein an improved method for the preparation of pen-
taphenylferrocene 1 and describe the synthesis of 1′-
substituted derivatives.8 We additionally report on the
facile synthesis of aminometallocenes, including an im-
proved synthesis of aminoferrocene itself.
Resu lts a n d Discu ssion
Pentaphenylferrocene was prepared by a modification
of the original synthesis by Pauson and McVey9 employ-
ing a procedure with no requirement for the isolation
and purification of air-sensitive intermediates (Scheme
1). This method provides a rapid and reliable synthesis
of multigram quantities of 1 in an overall yield of 57%.
The commercially available starting material 1-bro-
mopentaphenylcyclopentadiene may also be prepared by
an efficient literature method from inexpensive starting
materials.10
* Corresponding author. E-mail: c.j.richards@qmul.ac.ul. Fax: +44
(0)207 882 7794.
(1) Ferrocenes. Homogeneous Catalysis, Organic Synthesis, Materials
Science; Togni, A., Hayashi, T., Eds.; VCH: Weinheim, Germany, 1995.
(b) 50th Aniversray Issue, Adams, R. D., Ed. J . Organomet. Chem.
2001, 637-639.
(2) Bildstein, B.; Hradsky, A.; Kopacka, H.; Malleier, R.; Ongania,
K.-H. J . Organomet. Chem. 1997, 540, 127.
(3) Shelby, Q.; Kataoka, N.; Mann, G.; Hartwig, J . F. J . Am. Chem.
Soc. 2000, 122, 10718. (b) Beare, N. A.; Hartwig, J . F. J . Org. Chem.
2002, 67, 541.
(4) Tao, B.; Lo M. M.-C.; Fu, G. C. J . Am. Chem. Soc. 2001, 123,
353. (b) Bellemin-Laponnaz, S.; Tweddell, J .; Ruble, J . C.; Breitling,
F. M.; Fu, G. C. Chem. Commun. 2000, 1009. (c) Ie, Y.; Fu, G. C. Chem.
Commun. 2000, 119 (d) Tao, B. T.; Ruble, J . C.; Hoic, D. A.; Fu, G. C.
J . Am. Chem. Soc. 1999, 121, 5091 (e) Garrett, C. E.; Lo, M. M.-C.;
Fu, G. C. J . Am. Chem. Soc. 1998, 120, 7479. (f) Ruble, J . C.; Tweddell
J .; Fu, G. C. J . Org. Chem. 1998, 63, 2794. (g) Ruble, J . C.; Latham,
H. A.; Fu, G. C. J . Am. Chem. Soc. 1997, 119, 1492.
(5) Miura, M.; Pivsa-Art, S.; Dyker, G.; Heiermann, J .; Satoh, T.;
Nomura, M. Chem. Commun. 1998, 1889.
(6) Aroney, M. J .; Buys, I. E.; Dennis, G. D.; Field, L. D.; Hambley,
T. W.; Lay, P. A.; Masters A. F. Polyhedron 1993, 12, 2051.
(7) Slocum, D. W.; Duraj, S.; Matusz, M.; Cmarik, J . L.; Simpson,
K. M.; Owen, D. A. In Metal-Containing Polymeric Systems; Plenum:
New York, 1985; p 59.
(8) Some preliminary results have been previously reported: J ones,
G.; Butler, D. C. D.; Richards, C. J . Tetrahedron Lett. 2000, 41, 9351.
(9) McVey, S.; Pauson, P. L. J . Chem. Soc. 1965, 4312.
(10) Field, L. D.; Ho, K. M.; Lindall, C. M.; Masters, A. F.; Webb, A.
G. Aust. J . Chem. 1990, 43, 281.
10.1021/om0204989 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 11/01/2002

5434 Organometallics, Vol. 21, No. 24, 2002
Notes
Sch em e 2
Sch em e 3
Sch em e 4
The initial step of the sequence involves refluxing a
mixture of 1-bromopentaphenylcyclopentadiene and
Fe(CO)5 in benzene (3 h) to obtain a solution of crude
(η5-C5Ph5)FeBr(CO)2, which is converted to insoluble
(η5-C5Ph5)(η1-C5H5)Fe(CO)2 by reaction with Na(η5-
C5H5) at ambient temperature. Subsequent pyrolysis of
the crude product at 160 °C in vacuo gives a mixture
containing 1 and 10-15% pentaphenylcyclopentadiene,
even when moisture is rigorously excluded. Pure 1 can
be obtained from this mixture by a single recrystalli-
zation from toluene. We have found that a larger
amount of pentaphenylcyclopentadiene is produced
when 1-bromopentaphenylcyclopentadiene is used in a
concentration greater than 1 g per 20 cm3 of solvent.
Functionalization of the unsubstituted cyclopentadi-
enyl ring was achieved by employing the Friedel-Crafts
reaction (Scheme 2). Addition of R,R-dichloromethyl-
methyl ether to a cooled solution of 1 and SnCl4 gave
1,2,3,4,5-pentaphenyl-1′-formylferrocene 2 in 70% yield.
No formylation of the phenyl groups was noted using
these conditions, with only 2 and starting material being
isolated from the product mixture. Other Lewis acids
(AlCl3, TiCl4) and formylating agents (e.g., phenyl-
methylformamide with POCl3) gave much poorer re-
sults. A further substitution reaction was performed
with 2-chlorobenzoyl chloride in the presence of AlCl3.
The resulting aryl ketone 3 was hydrolyzed as previ-
ously described for the synthesis of ferrocene carboxylic
acid,11 providing an excellent overall yield of pentaphen-
ylferrocene carboxylic acid 4.
It is noteworthy that all attempts to effect direct
lithiation of 1 were unsuccessful, including the use of
tBuLi at elevated temperatures or a superbasic mixture
of BuLi and KOtBu.12 In all cases only starting material
was recovered. In this context it has been reported that
attempts to lithiate the related 18-electron complex (η5-
cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt also
failed, although this metallocene was successfully mer-
curated.13 Repetition of this mercuration procedure with
1 resulted only in oxidation of pentaphenylferrocene by
Hg2+, as revealed by a change in the reaction mixture
from yellow to dark orange-red with an accompanying
deposition of elemental mercury. The process is revers-
ible, and pentaphenylferrocene was reclaimed by reduc-
tion with sodium thiosulfate solution.
verted into aminoferrocene through formation of an
intermediate acyl azide, followed by Curtius rearrange-
ment in the presence of acetic anhydride and subse-
quent hydrolysis of the resulting N-acetyl aminofer-
rocene (30-37% yield).14 Thus, the required acyl azide
5 was obtained cleanly in 81% yield from the acid
chloride (prepared from the carboxylic acid with oxalyl
chloride) by reaction with NaN3 under phase trans-
fer conditions (Scheme 3). The Curtius rearrangement
was best achieved by heating 5 in the presence of
2-trimethylsilylethanol.15 Carbamate 6 was formed
cleanly and was quantitatively deprotected on treatment
with excess TBAF to give amine 7 in 76% overall yield.
The success of this reaction sequence prompted its
repetition on acids 8 and 1016 to give the known and
new amines 9 and 11, again in excellent overall yield.
Aminoferrocene 10 has been the subject of many syn-
thetic investigations.14,17 In addition to the Curtius
protocol mentioned above it may be obtained in moder-
ate (∼40%)17a to low (12%)17d yield by direct lithiation
of ferrocene followed by addition of a nitrogen electro-
(11) Reeves, P. C. Org. Synth. 1977, 56, 28.
(12) Schlosser, M. Angew. Chem., Int. Ed. Engl. 1974, 13, 701. (b)
Schlosser, M.; Choi, J . H.; Takagishi, S. Tetrahedron 1990, 46, 5633.
(13) Rausch, M. D.; Genetti, R. A. J . Org. Chem. 1970, 35, 3888.
(14) Herbehold, M.; Ellinger, M.; Haumaier, L. In Organometallic
Syntheses; King, R. B., Eisch, J . J ., Eds.; Elsevier: Amsterdam, 1986;
Vol. 3, p 81.
(15) Capson, T. L.; Poulter, C. D. Tetrahedron Lett. 1984, 25, 3515.
(16) Stevens, A. M.; Richards, C. J . Organometallics 1999, 18, 1346.
(17) van Leusen, D.; Hessen, B. Organometallics 2001, 20, 224. (b)
Bildstein, B.; Malaun, M.; Kopacka, H.; Wurst, K.; Mitterbo¨ck, M.;
Onagania, K.-H.; Opromolla, G.; Zanello, P. Organometallics 1999, 18,
4325. (c) Montserrat, N.; Parkins, A. W.; Tomkins, A. R. J . Chem. Res.
(S) 1995, 336. (d) Knox, G. R.; Pauson, P. L.; Willison, D.; Sole`a´niova´,
E.; Toma, S. Organometallics 1990, 9, 301. (e) Herberhold, M.; Ellinger,
M.; Kremnitz, W. J . Organomet. Chem. 1983, 241, 227. (f) Knox, G.
R.; Pauson, P. L. J . Chem. Soc. 1961, 4615. (g) Nesmejanov, A. N.;
Ssazonowa, W. A.; Drosd, V. N. Chem. Ber. 1960, 93, 2717.
Without a metalation protocol, our attempts to gener-
ate further derivatives of 1 instead focused on acid 4.
Ferrocenecarboxylic acid 8 has previously been con-

Notes
Organometallics, Vol. 21, No. 24, 2002 5435
phile. Given both the ready availability of 811 and its
commercial availability, we believe the Curtius meth-
odology for the synthesis of aminoferrocene represents
a significant improvement over these existing methods.
We found that the acyl azides synthesized were stable
to normal manipulations in the solid state and in
solution, although no direct investigation of their stabil-
ity was performed.
All attempts to introduce a halogen onto the unsub-
stituted cyclopentadieyl ring of pentaphenylferrocene
have so far proved unsuccessful. Due to its instability
toward mild oxidizing agents, direct halogenation or
mercuration of 1 or diazotization of 7 followed by the
Sandmeyer reaction (even under nonaqueous conditions
employing alkyl nitrites in place of strong acids) are not
viable methods to obtain halopentaphenylferrocenes.
However, the improved synthesis of 1 reported in this
paper together with the generation of carbon- and
nitrogen-substituted derivatives offers many possibili-
ties for the incorporation of this bulky metallocene into
new structures.
dried (MgSO4) and filtered, and the solvent was removed in
vacuo. Column chromatography (CH2Cl2) gave starting mate-
rial as an initial orange band (0.25 g) and a second red band,
which yielded, after removal of the solvent, the title compound
as a cherry-red solid (0.73 g, 70%). An analytical sample was
obtained by recrystallization from CH2Cl2. Mp: 290 °C (dec).
Anal. Found: C, 82.15; H, 5.15. Calcd for C41H30FeO‚1/4H2O:
C, 82.21; H, 5.13. IR (νmax; CH2Cl2): 1682 (CdO) cm-1. 1H NMR
(δ; 400 MHz, CDCl3): 4.55 (2 H, s, Fc-â), 4.84 (2 H, s, Fc-R),
6.98 (10 H, d, J ) 7, Ar-ortho), 7.06 (10 H, t, J ) 7, Ar-meta),
7.14 (5 H, t, J ) 7, Ar-para), 9.87 (1 H, s, CHO). 13C{1H} NMR
(δ; 100 MHz, CDCl3): 74.8 (Cp), 79.7 (Cp), 81.7 (Cp-ipso), 88.6
(C5Ph5), 126.6 (Ar-para), 127.2 (Ar), 132.2 (Ar), 134.4 (Ar-ipso),
197.0 (CdO). MS (m/z; FAB): 594 (M+, 100%), 566 (7), 501
(7). High-resolution MS (m/z, FAB): found for M+ 594.1663;
calcd for C41H30FeO, 594.1646.
1,2,3,4,5-P en ta p h en yl-1′-(2-ch lor oben zoyl)fer r ocen e, 3.
1,2,3,4,5-Pentaphenylferrocene 1 (6.05 g, 10.7 mmol) was
dissolved in CH2Cl2 (200 mL) and the reaction vessel cooled
in an ice bath. Granular AlCl3 (1.50 g, 11.3 mmol) was added
to the orange solution and stirred for 0.5 h at 0 °C, whereupon
2-chlorobenzoyl chloride (2.07 g, 1.50 mL, 11.8 mmol) was
added dropwise via syringe over 1 min. The dark mixture was
stirred at room temperature for 18 h, then poured onto ice.
The organic layer was separated, and the aqueous layer was
extracted with CH2Cl2 (2 × 20 mL). The combined organic
fractions were dried (MgSO4) and filtered, and the solvent was
removed in vacuo to give a crimson solid. Column chromatog-
raphy (1:1 CH2Cl2/petroleum ether) gave starting material as
an orange band followed by a purple band, which yielded, after
removal of solvent, the title compound as a red solid (6.84 g,
91%). An analytical sample was obtained by recrystallization
from a mixture of CH2Cl2 and petroleum ether. Mp: 195-198
°C. Anal. Found: C, 76.75; H, 4.71. Calcd for C47H33ClFeO‚1/
2CH2Cl2: C, 76.32; H, 4.58. IR (νmax; CH2Cl2): 1643 (CdO)
Exp er im en ta l Section
All reactions were performed under an atmosphere of
dinitrogen employing standard Schlenk techniques18 in oven-
dried (150 °C) glassware. In the following section, petrol-
eum ether refers to the fraction boiling between 40 and 60 °C.
CH2Cl2 and DME were distilled under nitrogen from CaH2.
Toluene was distilled under nitrogen from molten sodium.
Benzene was distilled from sodium benzophenone ketyl.
Column chromatography was performed on Matrix silica 60
(35-70 µm). 1-Bromopentaphenylcyclopentadiene was pre-
pared as previously described.10 All other reagents were
obtained from commercial sources and used as received.
1,2,3,4,5-P en ta p h en ylfer r ocen e, 1. 1-Bromopentaphenyl-
cyclopentadiene (20.0 g, 38 mmol) was dissolved in benzene
(400 mL). Fe(CO)5 (8.9 g, 6.0 mL, 45 mmol) was added in a
single portion, and the resulting purple solution was heated
at reflux for a period of 3 h. On cooling, NaCp (40 mL of a 2.0
M solution in THF, 80 mmol) was added in a single portion
and the mixture was stirred at room temperature for 18 h.
The resulting orange precipitate was filtered and washed with
toluene, dried, and heated at 160 °C in vacuo for 2 h. The tan
solid thus obtained was dissolved in hot toluene (400 mL) and
passed through a plug of silica to give a dark orange solution.
Removal of the solvent by rotary evaporation and recrystal-
lization from boiling toluene gave the title compound (12.3 g,
57% yield). Mp > 300 °C (lit.9 356-358 °C). Anal. Found: C,
84.87; H, 5.46. Calcd for C40H30Fe: C, 84.80; H, 5.34. 1H NMR
(δ; 400 MHz, CDCl3): 4.05 (5 H, s, C5H5), 6.86-6.92 (20 H, m,
Ar), 6.92-6.99 (5 H, m, Ar). 13C{1H} NMR (δ; 100 MHz,
CDCl3): 75.1 (C5H5), 87.9 (C5Ph5), 126.0 (Ar-para), 127.0 (Ar),
132.2 (Ar), 136.0 (Ar-ipso). MS (m/z; APCI): 567 ([M + 1]+,
100%).
cm-1 1H NMR (δ; 400 MHz, CDCl3): 4.55 (2 H, t, J ) 3,
.
Cp-â), 4.86 (2 H, t, J ) 3, Cp-R), 6.14 (1 H, d, J ) 11, Ar), 6.92
(10 H, d, J ) 7, Ar-ortho), 7.00 (10 H, t, J ) 7, Ar-meta), 7.05-
7.08 (1 H, m, Ar), 7.11 (5 H, t, J ) 7, Ar-para), 7.36 (2 H, d, J
) 6, Ar). 13C{1H} NMR (δ; 100 MHz, CDCl3): 79.9 (Cp), 83.0
(Cp), 88.5 (C5Ph5), 126.6 (Ph5-para), 126.8 (Ar), 127.3 (Ph5),
130.0 (Ar), 130.1 (Ar), 131.0 (Ar), 131.1 (Ar) 132.4 (Ph5), 134.6
(Ph5-ipso), 140.1 (Ar), 196.3 (CdO). MS (m/z; FAB): 706 (M+,
37%), 704 (M+, 100%), 566 (28%). High-resolution MS (m/z,
FAB): found for M+ 704.1580; calcd for C47H33ClFeO, 704.1569.
1,2,3,4,5-P en ta p h en ylfer r ocen e-1′-ca r boxylic Acid , 4.
1,2,3,4,5-Pentaphenyl-1′-(2-chlorobenzoyl)ferrocene 3 (6.84 g,
9.7 mmol) was taken up in DME (100 mL). KOtBu (5.4 g 48
mmol) and H2O (0.26 mL, 14 mmol) were added, and the
resulting solution was heated at reflux for 1 h, cooled to room
temperature, and acidified with 1 M HCl (50 cm3). The tan
solid obtained was separated by filtration, washed with water,
and partially dried, and the solid was suspended in toluene
(100 mL). Residual water was removed by azeotropic distilla-
tion until a volume of ca. 50 mL of toluene remained. The
resulting suspension was cooled, and the orange solid was
isolated by filtration. Drying in air then in vacuo afforded the
title compound as a light orange powder (5.23 g, 88%). Mp:
267-270 °C (dec). Anal. Found: C, 80.71; H, 5.25. Calcd for
1,2,3,4,5-P en ta p h en yl-1′-for m ylfer r ocen e, 2. 1,2,3,4,5-
Pentaphenylferrocene 1 (1.00 g, 1.8 mmol) was dissolved in
dichloromethane (30 mL) and cooled in an ice bath. SnCl4 (5.3
mL of a 1.0 M solution in dichloromethane) was added
dropwise over 5 min, and the solution was stirred for a further
15 min. R,R-Dichloromethylmethyl ether (0.61 g, 0.48 cm3, 5.3
mmol) was added over 1 min, whereupon the ice bath was
removed and the dark mixture was stirred for 2 h followed by
the additon of water (30 mL). The red organic fraction was
separated from the aqueous fraction which was extracted with
dichloromethane (15 mL). The combined organic fractions were
C
41H30FeO2: C, 80.66; H, 4.95. IR (νmax; CH2Cl2): 1724 (CdO,
monomer) and 1678 (CdO, dimer) cm-1. 1H NMR (δ; 400 MHz,
CDCl3/DMSO-d6): 4.32 (2 H, t, J ) 2, Cp-â), 4.74 (2 H, t, J )
2, Cp-R), 6.90-7.25 (25 H, m, Ar). 13C{1H} NMR (δ; 100 MHz,
CDCl3): 75.7 (Cp), 77.2 (Cp-ipso), 78.1 (Cp), 88.0 (C5Ph5), 126.2
(Ar-para), 127.0 (Ar), 132.2 (Ar), 134.9 (Ar-ipso), 170.7
(CdO). MS (m/z; FAB): 610 (M+, 100%).
1,2,3,4,5-P en taph en yl-1′-acylazidofer r ocen e, 5. 1,2,3,4,5-
Pentaphenylferrocene-1′-carboxylic acid 4 (2.00 g, 3.3 mmol)
was suspended in CH2Cl2 (20 mL). Oxalyl chloride (0.84 g, 0.58
mL, 6.6 mmol) was added, followed by a drop of dimethylfor-
mamide. The mixture was stirred at room temperature for 3
(18) Shriver, D. F. The Manipulation of Air-Sensitive Compounds;
McGraw-Hill: New York, 1969.

5436 Organometallics, Vol. 21, No. 24, 2002
Notes
h, after which the solvent and residual oxalyl chloride were
removed in vacuo. The red solid thus obtained was taken up
in CH2Cl2 (20 mL). Tetrabutylammonium bromide (0.004 g,
0.01 mmol) was added, followed by a solution of NaN3 (0.32 g,
4.9 mmol) in H2O (4 mL), and the mixture was stirred rapidly
at room temperature for 18 h. Additional water (50 mL) was
added to the mixture, and the organic layer was separated.
The aqueous layer was extracted with CH2Cl2 (2 × 20 mL),
the combined organic layers were dried (MgSO4) and filtered,
and the solvent was removed in vacuo. Column chromatogra-
phy (1:1 CH2Cl2/petroleum ether) gave the title compound as
a red solid (1.69 g, 81%). Mp: 250 °C (dec). IR (νmax; CH2Cl2):
1,2,3,4,5-P en ta p h en yl-1′-a m in ofer r ocen e, 7. 1,2,3,4,5-
Pentaphenylferrocene-1′-(2-trimethylsilyl)ethyl carbamate 6
(1.55 g, 2.1 mmol) was dissolved in
a 1 M solution of
tetrabutylammonium fluoride in THF (8.6 mL, 8.6 mmol) and
the solution heated to 50 °C for 15 min. The solvent was
removed in vacuo, then water (50 mL) and CH2Cl2 (50 mL)
were added. The organic layer was separated, and the aqueous
layer extracted with CH2Cl2 (2 × 20 mL). The combined
organic layers were dried (MgSO4) and filtered through silica,
and the solvent was removed in vacuo to give the title
compound as an orange solid (1.23 g, 99%). An analytical
sample was obtained by recrystallization from a mixture of
2137 (N3) 1682 (CdO) cm-1 1H NMR (δ; 400 MHz, CDCl3):
.
CH2Cl2 and petroleum ether. Mp: 270-275 °C (dec). IR (νmax
;
CH2Cl2): 3690 (NH2), 1601, 1502 cm-1. 1H NMR (δ; 400 MHz,
CDCl3): 2.50 (2 H, brs, NH2), 3.80 (2 H, brs, Cp), 3.90 (2 H,
brs, Cp), 6.90-7.20 (25 H, m, Ar). 13C{1H} NMR (δ; 100 MHz,
CDCl3): 64.1 (Cp), 71.3 (Cp), 87.5 (C5Ph5), 107.2 (Cp-ipso),
125.9 (Ar-para), 127.1 (Ar), 132.2 (Ar), 136.1 (Ar-ipso). MS (m/
z; FAB): 581 (100%, M+), 242 (87). High-resolution MS (m/z,
FAB): found for M+ 581.1833; calcd for C40H31FeN, 581.1806.
Am in ofer r ocen e, 9. Using the same procedure, ferrocen-
ecarboxylic acid 8 (2.29 g, 10.0 mmol) was converted via the
corresponding acyl azide (IR (νmax; CH2Cl2) 2135 (N3), 1684
(CdO) cm-1) into 9 obtained as a brown solid (1.61 g, 80%).
Mp: 126-130 °C (dec) (lit.17c 148-150 °C). IR (νmax; CH2Cl2):
3757 and 3692 (NH2) cm-1. 1H NMR (δ; 400 MHz, CDCl3): 2.60
(2 H, brs, NH2); 3.85 (2 H, brs, Fc), 4.00 (2 H, brs, Cp), 4.09 (5
H, s, C5H5). 13C{1H} NMR (δ; 100 MHz, CDCl3): 58.8 (Fc) 63.5
(Fc), 68.9 (C5H5), 105.6 (Fc-ipso).
4.04 (2 H, t, J ) 2, Cp-â), 4.76 (2 H, t, J ) 2, Cp-R), 6.95-7.01
(20 H, m, Ar), 7.05-7.10 (5 H, m, Ar). 13C{1H} NMR (δ;
100 MHz, CDCl3): 76.3 (Cp), 78.0 (Cp-ipso), 80.1 (Cp), 89.0
(C5Ph5), 127.7 (Ar-para), 127.7 (Ar), 132.7 (Ar), 134.9 (Ar-ipso),
176.1 (CdO). MS (m/z; FAB): 607 ([M+ - N2]+, 100%). High-
resolution MS (m/z, FAB): found for [M - N2]+ 607.1608; calcd
for C41H29FeNO, 607.1598.
1,2,3,4,5-P en t a p h en ylfer r ocen e-1′-(2-t r im et h ylsilyl)-
eth yl Ca r ba m a te, 6. 1,2,3,4,5-Pentaphenyl-1′-acylazidefer-
rocene 5 (1.48 g, 2.3 mmol) was dissolved in toluene (15 mL),
the soluton was heated to 105 °C, and 2-(trimethylsilyl)ethanol
(0.67 mL, 4.7 mmol) was added in a single portion. The red
solution obtained was stirred at this temperature for 3 h, by
which time the color had changed to dark orange. The mixture
was cooled to room temperature, NaOH (1 M, 50 mL) added,
and the solution stirred for 5 min. The organic layer was
separated and the aqueous layer extracted with CH2Cl2 (2 ×
20 mL). The combined organic layers were dried (MgSO4) and
filtered, and the solvent was removed in vacuo to give an
orange solid. Chromatography (1:1 CH2Cl2/petroleum ether)
gave the title compund as an orange solid (1.61 g, 95%). An
analytical sample (fine orange needles) was obtained by
recrystallization from a mixture of CH2Cl2 and petroleum
ether. Mp: 132-134 °C. Anal. Found: C, 75.65; H, 5.94. N,
1.97. Calcd for C46H43FeNO2Si‚1/4H2O: C, 75.66; H, 6.00; N,
(η5-Am in ocyclop en ta d ien yl)(η4-tetr a p h en ylcyclobu ta -
d ien e)coba lt, 11. Using the same procedure acid 1016 (3.18,
6.1 mmol) was converted via the corresponding acyl azide (IR
(νmax; CH2Cl2) 2137 (N3), 1682 (CdO) cm-1) into 11 obtained
as a dark orange-brown crystalline solid (2.46 g, 82%). Mp:
212-215 °C. IR (νmax; CH2Cl2): 3688 (NH2), 1597, 1501 cm-1
.
1H NMR (δ; 400 MHz, CDCl3): 2.16 (2 H, brs, NH2), 4.13 (2
H, t, J ) 2, Cp), 4.39 (2 H, t, J ) 2, Cp), 7.15-7.30 (12 H, m,
Ar), 7.35-7.50 (8 H, m, Ar). 13C{1H} NMR (δ; 100 MHz,
CDCl3): 72.6, 74.6, 78.1 (2 × Cp and C4H4), 113.3 (Cp-ipso),
125.8 (Ar-para), 128.0 (Ar), 128.6 (Ar), 136.7 (Ar-ipso). MS (m/
z; FAB): 495 (M+, 84%), 415 (100). High-resolution MS (m/z,
FAB): found for M+ 495.1413; calcd for C33H26CoN, 495.1397.
1.92. IR (νmax; CH2Cl2): 1726 (CdO) cm-1 1H NMR (δ; 400
.
MHz, CDCl3): 0.0 (9 H, s, Si(CH3)3), 0.9 (2 H, m, CH2TMS),
4.04-4.15 (4 H, m, Cp + OCH2), 4.40 (2 H, brs, Cp), 5.70 (1
H, brs, NH), 7.00-7.20 (25 H, m, Ar). 13C{1H} NMR (δ; 100
MHz, CDCl3): -1.4 (Si(CH3)3), 17.6 (CH2TMS), 63.5 (Cp), 67.9
(Cp), 72.4 (OCH2), 87.8 (C5Ph5), 96.0 (Cp-ipso), 126.2 (Ar-para),
127.2 (Ar), 132.2 (Ar), 135.5 (Ar-ipso), 154.7 (CdO). MS (m/z;
FAB): 725 (M+, 100%), 698 (31), 625 (45), 581 (27), 501 (25).
High-resolution MS (m/z, FAB): found for M+ 725.2440; calcd
for C46H43FeNO2Si, 725.2412.
Ack n ow led gm en t. We wish to thank the EPSRC
for financial support (GR/M55893) and the EPSRC
National Mass Spectrometry Service Centre, University
of Wales, Swansea.
OM0204989