The isocyanate route to cyclopentadienyl-carboxamide-and cyclopentadienyl-amino ester-substituted metallocene complexes

Article abstract of DOI:10.1021/om960234k

Lithium cyclopentadienide adds to a variety of isocyanates [R-N=C=O, R = tert-butyl (a), n-butyl (b), cyclohexyl (c), phenyl (d), 3-pyridyl (e), 2-tetrahydropyranyl (f), adamantyl (g)] to yield the monocarbamoyl-substituted cyclopentadienides C₅H₄CONHR^- 3 admixed with varying amounts of the respective 1,2-dicarbamoyl-substituted C₅H₃(CONHR)₂^- systems 4 and a corresponding quantity of the C₅H₅^- starting material. Subsequent treatment of these reaction mixtures with anhydrous FeCl₂ gave the 1,1′-dicarbamoylferrocenes 6 and the corresponding monocarbamoylferrocenes 5, which were easily separated by chromatography. The carbamoylferrocenes 5b, 5c, and 6d were characterized by X-ray crystal structure analyses. The (N-phenyl- and (N-adamantylcarbamoyl)cyclopentadienides were treated with CpTiCl₃ to give the carboxamide-substituted titanocene dichloride complexes [Cp(C₅H₄-CONHR)TiCl₂] 8a (R = Ph) and 8b (R = adamantyl), respectively. Complex 8b was also characterized by X-ray diffraction. The valine ester-derived isocyanate reacts with lithium cyclopentadienide to give the N-valinyl-substituted carbamoylcyclopentadienide 3h. Subsequent treatment with FeCl₂ or FeCl₂/CpLi, respectively, produces the 1,1′-difunctionalized ferrocene 6h or the monofunctionalized ferrocene 5h. Both complexes were characterized by X-ray crystal structure analyses.

Full text of DOI:10.1021/om960234k

Organometallics 1996, 15, 4005-4011
4005
Th e Isocya n a te Rou te to Cyclop en ta d ien yl-Ca r boxa m id e-
a n d Cyclop en ta d ien yl-Am in o Ester -Su bstitu ted
Meta llocen e Com p lexes
Markus Oberhoff, Lothar Duda, J o¨rn Karl, Roland Mohr, Gerhard Erker,*
Roland Fro¨hlich, and Matthias Grehl
Organisch-Chemisches Institut der Universita¨t Mu¨nster,
Corrensstrasse 40, D-48149 Mu¨nster, Germany
Received March 27, 1996X
Lithium cyclopentadienide adds to a variety of isocyanates [R-NdCdO, R ) tert-butyl
(a ), n-butyl (b), cyclohexyl (c), phenyl (d ), 3-pyridyl (e), 2-tetrahydropyranyl (f), adamantyl
(g)] to yield the monocarbamoyl-substituted cyclopentadienides C5H4CONHR- 3 admixed
with varying amounts of the respective 1,2-dicarbamoyl-substituted C5H3(CONHR)2- systems
-
4 and a corresponding quantity of the C5H5 starting material. Subsequent treatment of
these reaction mixtures with anhydrous FeCl2 gave the 1,1′-dicarbamoylferrocenes 6 and
the corresponding monocarbamoylferrocenes 5, which were easily separated by chromatog-
raphy. The carbamoylferrocenes 5b, 5c, and 6d were characterized by X-ray crystal structure
analyses. The (N-phenyl- and (N-adamantylcarbamoyl)cyclopentadienides were treated with
CpTiCl3 to give the carboxamide-substituted titanocene dichloride complexes [Cp(C5H4-
CONHR)TiCl2] 8a (R ) Ph) and 8b (R ) adamantyl), respectively. Complex 8b was also
characterized by X-ray diffraction. The valine ester-derived isocyanate reacts with lithium
cyclopentadienide to give the N-valinyl-substituted carbamoylcyclopentadienide 3h . Sub-
sequent treatment with FeCl2 or FeCl2/CpLi, respectively, produces the 1,1′-difunctionalized
ferrocene 6h or the monofunctionalized ferrocene 5h . Both complexes were characterized
by X-ray crystal structure analyses.
In tr od u ction
late transition metals via electrophilic “aromatic” sub-
stitution routes or by using Cp-metalated metallocene
systems.5 Analogously substituted early transition
metal metallocene systems do not seem to be available
this way;6 here the COX type substituents must be
attached to the Cp-ligand systems before connecting
them with the respective metal centers. Rausch et al.
have developed such a way of introducing, for example,
carboxylate-substituted Cp ring systems. A few ex-
amples of (CpCO2R)CpMX2 and (CpCO2R)2MX2 systems
of the group 4 metals were prepared by this route, and
their structures have been described in the literature.2
Functional groups at their Cp rings can change the
electronic properties and the range of potential applica-
tions of metallocene complexes considerably. This is
especially true for the Cp-attached COX functionalities.
The presence of acyl- and carboxylic acid-derived func-
tional groups opens novel pathways for chemical modi-
fications of metallocene complexes and their use in
organic synthesis and catalysis.1 In this context, it is of
great interest to bind COX functions to the Cp ring
systems of electrophilic early transition metal com-
plexes2 and to attach amino acid-derived side chains to
metallocene complexes.3,4 Both of these synthetic tar-
gets cannot be achieved by direct substitution reactions
at the organometallic framework.
In 1968, Effenberger et al. described the reaction of
activated fulvenoid substrates with isocyanates
RsNdCdO that directly led to the respective carbox-
amide-substituted systems.7 Both of these reactions
The COX type functional groups can very easily be
introduced at ferrocene and related metallocenes of the
X Abstract published in Advance ACS Abstracts, August 1, 1996.
(1) Macomber, D. W.; Hart, W. P.; Rausch, M. D. Adv. Organomet.
Chem. 1982, 21, 1. Coville, N. J .; Pickl, W. Coord. Chem. Rev. 1992,
116, 1, and references cited in these articles.
(2) Hart, W. P.; Macomber, D. W.; Rausch, M. D. J . Am. Chem. Soc.
1980, 102, 1196. Hart, W. P.; Shihua, D.; Rausch, M. D. J . Organomet.
Chem. 1985, 282, 111. Rausch, M. D.; Lewison, J . F.; Hart, W. P. J .
Organomet. Chem. 1988, 358, 161. J ones, S. S.; Rausch, M. D.;
Bitterwolf, T. E. J . Organomet. Chem. 1990, 396, 279. Ogasa, M.;
Mallin, D. T.; Macomber, D. W.; Rausch, M. D.; Rogers, R. D.; Rollins,
A. N. J . Organomet. Chem. 1991, 405, 41. J ones, S. S.; Rausch, M. D.;
Bitterwolf, T. E. J . Organomet. Chem. 1993, 450, 27.
(3) Gorfti, A.; Salmain, M.; J aouen, G.; McGlinchey, M. J .; Ben-
nouna, A.; Mousser, A. Organometallics 1996, 15, 142. Klapo¨tke, T.
M.; Ko¨pf, H.; Tornieporth-Oetting, I. C.; White, P. S. Angew. Chem.
1994, 106, 1587; Angew. Chem., Int. Ed. Engl. 1994, 33, 1518.
Tornieporth-Oetting, I. C.; White, P. S. Organometallics 1995, 14, 1632.
Liang, Q.; Eason, P. D.; Long, E. C. J . Am. Chem. Soc. 1995, 117, 9625.
Severin, K.; Beck, W.; Trojandt, G.; Polborn, K.; Steglich, W. Angew.
Chem. 1995, 107, 1570; Angew. Chem., Int. Ed. Engl. 1995, 34, 1449.
(4) Carlstro¨m, A.-S.; Freid, T. J . Org. Chem. 1990, 55, 4175. Amiens,
C.; Balavoine, G.; Guibe´, F. J . Organomet. Chem. 1993, 443, 207.
(5) Woodward, R. B.; Rosenblum, M.; Whiting, M. C. J . Am. Chem.
Soc. 1952, 74, 3458. Review: Watts, W. E. in Comprehensive Orga-
nometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Pergamon: New York; 1982, Vol. 8, Chapter 59, p 1013. See also
Cunningham, A. F., J r. Organometallics 1994, 13, 2480.
(6) For a notable exception, see: Ruwwe, J .; Erker, G.; Fro¨hlich, R.
Angew. Chem. 1996, 108, 108; Angew. Chem., Int. Ed. Engl. 1996, 35,
80.
S0276-7333(96)00234-8 CCC: $12.00 © 1996 American Chemical Society

4006 Organometallics, Vol. 15, No. 19, 1996
Oberhoff et al.
involve as the essential carbon-carbon coupling step
the addition of a (substituted) cyclopentadienide anion
equivalent to the sp-carbon center of the heterocumu-
lene. Therefore, it was tempting to extend this interest-
ing reaction by adding Cp anions to suitably substituted
isocyanates RsNdCdO to produce the carboxamide-
substituted cyclopentadienides. We have carried out a
number of such reactions and have found it to be a
useful synthetic sequence for the preparation of car-
boxamide-substituted cyclopentadienide-ligand sys-
tems and their respective metallocene complexes. Even
the respective amino ester-substituted metallocenes can
be synthesized in this way. Several typical examples
are described in this article.
dienyl hydrogens at δ 6.06 and 5.73, and the broad NH
resonance at δ 5.80. The 1,2-(Me3CNHCO)2C5H3Li
byproduct (Li-4a ) shows the 1H NMR signals of the
cyclopentadienyl group at δ 6.72 (m, 2H) and 6.39 (m,
1H). The NH resonance is at δ 5.98 (br s, 2H), and the
Me3C signal is at δ 1.30 (s, 18H).
-
The 1,2-(Me3CNHCO)2C5H3 system is much less
reactive toward metal exchange than the corresponding
monocarboxamide-substituted system 3a . Thus, Na-4a
was reacted with anhydrous FeCl2 in tetrahydrofuran.
It required 2 days of stirring at room temperature to
bring this reaction to completion. The product of
composition [1,2-(Me3CNHCO)2C5H3]2Fe (7a ) was iso-
lated (65%). It was characterized spectroscopically (see
Experimental Section), but its detailed structural de-
scription must await the results of an X-ray crystal
structure analysis.
Resu lts a n d Discu ssion
Cyclopen tadien yl-Car boxam ide-Su bstitu ted Met-
a llocen es. tert-Butyl isocyanate was treated with
cyclopentadienyl anion (with lithium or sodium coun-
teranion) in a 1:1 molar ratio. The reaction was usually
started at low temperature (-78 °C) and the reaction
mixture allowed to warm to room temperature over a
period of several hours before the resulting product
mixture was analyzed spectroscopically or used in a
subsequent metathetical metal exchange reaction to
form the corresponding metallocene systems (see the
following). Under these conditions a rapid addition
reaction ensues, leading to CC coupling between cyclo-
pentadienide and the heterocumulene sp-carbon center.
In view of the pKa difference between a carboxamido
anion and cyclopentadiene, it is likely that a rapid
favorable proton transfer subsequently takes place.
Consequently, the carboxamido-substituted cyclopen-
tadienide system 3a is observed to be formed as the
major addition product. In the case of Cp- addition to
Me3CNCO, and in most other cases as well (see the
following), the mono-RNHCO-functionalized cyclopen-
tadienide is not the only product obtained. The product
3a was usually obtained admixed with a substantial
quantity of the doubly functionalized product 4a . The
latter is likely to be formed in a subsequent reaction
step employing the primarily formed product 3a as a
nucleophile that adds to another RNCO unit. Conse-
quently, some residual unreacted Cp anion makes up
the third component of the product mixture. The 3a :
4a product ratio is slightly dependent on the actual
reaction conditions; usually 3a :4a values were observed
ranging between 60:40 and 80:20. Employment of Cp
anion and tert-butyl isocyanate in a 1:2 ratio led to the
sole formation of the bis-adduct 4a . It may seem
surprising that the CpCONHR- anion that bears an
electron-withdrawing substituent exhibits such a high
nucleophilicity that it may successfully compete with
the unsubstituted cyclopentadienide for the RNCO
reagent, but this is probably due to the especially high
anion stabilization of the resulting product. The 1,2-
Out of the mixture of 3a , 4a , and Cp- anions, the
mono- and unsubstituted cyclopentadienides react much
faster with, for example, FeCl2 than their congener 4a .
Iron(II) chloride was added at -10 °C to the reagent
mixture produced by treatment of CpLi with Me3CNCO
in a 1:1 molar ratio. The reaction is essentially complete
after allowing the mixture to warm to room temperature
over several hours with stirring. As expected, a mixture
of two organometallic products is obtained. Most of the
(Me3CNHCO)C5H4Li reagent is used in the formation
of the symmetrically difunctionalized 1,1′-dicarbamoyl-
ferrocene derivative [(Me3CNHCO)C5H4]2Fe (6a ). How-
ever, most of the remaining unreacted CpLi component
of the reagent mixture is also used in ferrocene forma-
tion, giving rise to a proportional quantity of the “mixed”
ferrocene product [(Me3CNHCO)C5H4]CpFe (5a ). These
two products were separated by chromatography. Com-
plex 6a was isolated in ca. 20% yield, whereas only a
very small amount of the 5a byproduct was obtained,
which was just sufficient for characterization.
A variety of differently substituted carbamoylfer-
rocenes were prepared in this way. CpLi was treated
with n-butyl isocyanate in a 1:1 molar ratio and then
reacted with an excess of FeCl2. Chromatographic
workup furnished the mono(n-butylcarbamoyl)ferrocene
complex (5b) in 24% yield. A second larger fraction of
the corresponding 1,1′-dicarbamoylferrocene complex 6b
was subsequently eluted from the column. However,
this product was only isolated admixed with ca. 20% of
5b. Analogously, the (cyclohexylcarbamoyl)ferrocene
complex (5c) was obtained and isolated after chroma-
tography. Single crystals of both complexes 5b and 5c
were obtained, and these products were identified by
X-ray crystal structure analyses (for details see the
Experimental Section and the supporting information).
The ferrocene framework of 5b exhibits an eclipsed
metallocene conformation in the crystal.9 The N-(n-
butyl)carboxamide substitutent is oriented in plane with
its adjacent Cp ring system. The amide CdO and N-H
-
(RNHCO)2C5H3 system is to be regarded as a “ful-
(8) Linn, W. J .; Sharkey, W. H. J . Am. Chem. Soc. 1957, 79, 4970.
Peters, D. J . Chem. Soc. 1959, 1757. J ackman, L. M.; Trewella, J . C.;
Haddon, R. C. J . Am. Chem. Soc. 1980, 102, 2519. Hartke, K.; Kohl,
A.; Ka¨mpchen, T. Chem. Ber. 1983, 116, 2653. Bruce, M. I.; Walton, J .
K.; Williams, M. L.; Hall, S. R.; Skelton, B. W.; White, A. H. J . Chem.
Soc., Dalton Trans. 1982, 2209; 1983, 2183. Bruce, M. I.; Humphrey,
P. A.; Patrick, J . M.; Skelton, B. W.; White, A. H.; Williams, M. L.
Aust. J . Chem. 1985, 38, 1441. Bruce, M. I.; Humphrey, P. A.; Skelton,
B. W.; White, A. H. J . Organomet. Chem. 1989, 361, 369. Kool, L. B.;
Kotora, G. J . Macromolecules 1992, 25, 2582, and references cited in
these articles.
venologous” â-dicarbonyl system, exhibiting a highly
increased anion stabilization.8
The carboxamido-substituted cyclopentadienides were
1
identified by their typical H NMR spectra. The mono-
carboxamido-substituted (Me3CNHCO)C5H4Li product
(Li-3a ) in THF-d8/benzene-d6 (1:10) exhibits a tert-butyl
singlet at δ 1.31, an AA′BB′ pattern of the cyclopenta-
(7) Effenberger, F.; Gleiter, R.; Heider, L.; Niess, R. Chem. Ber. 1968,
101, 502.
(9) Elschenbroich, Ch.; Salzer, A. Organometallchemie; Teubner:
Stuttgart, 1990; pp 380 ff.

Carboxamide-Substituted Metallocene Complexes
Organometallics, Vol. 15, No. 19, 1996 4007
Sch em e 1a
F igu r e 1. View of the molecular structure and association
pattern of 6d in the solid state (with unsystematical atom
numbering scheme). Selected bond lengths (Å) and angles
(deg): Fe-C1, 2.046(6); Fe-C2, 2.047(6); Fe-C3, 2.036-
(6); Fe-C4, 2.029(5); Fe-C5, 2.025(6); Fe-C21, 2.040(6);
Fe-C22, 2.046(6); Fe-C23, 2.039(5); Fe-C24, 2.036(5);
Fe-C25, 2.024(6); C4-C6, 1.481(8); C6-O7, 1.236(6); C6-
N8, 1.339(7); N8-C9, 1.420(7); C24-C26, 1.477(7); C26-
O27, 1.223(6); C26-N28, 1.346(7); N28-C29, 1.422(7); O7-
C6-N8, 123.4(5); O7-C6-C4, 121.8(5); N8-C6-C4,
114.8(5); C6-N8-C9, 127.6(5); O27-C26-N28, 124.1(5);
O27-C26-C24, 120.3(5); N28-C26-C24, 115.7(5); C26-
N28-C29, 126.3(5).
a
R ) CMe3 (a ), n-C4H9 (b), cyclo-C6H11 (c), Ph (d ), 3-pyridyl
(e), 2-tetrahydropyranyl (f).
vectors are E-oriented at the connecting CsN bond. The
CsC connection between the functional group and the
Cp ring is in the typical range for a C(sp2)sC(sp2) single
bond10 at 1.476(7) Å. Complex 5c exhibits a very similar
molecular arrangement in the solid state.
Phenyl isocyanate was treated with lithium cyclopen-
tadienide (1:1) in THF and then, without isolation of
the intermediate (PhNHCO)C5H4Li reagent, reacted
with anhydrous FeCl2 at ambient temperature. Soxhlet
extraction of the product mixture with ether followed
by chromatographic separation (silica gel/ether) and
recrystallization gave the 1,1′-bis(phenylcarbamoyl)-
ferrocene complex (6d ) in 25% yield. Single crystals of
6d were obtained from ether and the complex was
characterized by X-ray diffraction (Figure 1).
The view of the structure shows that the ferrocene
6d has an N-phenylcarboxamido substituent bonded to
each of the cyclopentadienyl ring systems. The Cp rings
are oriented in an eclipsed metallocene conformation,
and the PhNHCO substituents are arranged in the
closest possible gauche-like orientation.11 In contrast
to the related monocarbamoylferrocenes (5b,c, see
above), the carboxamido planes in 6d are not located
coplanarly with the Cp ring planes, but markedly
rotated toward each other. The corresponding dihedral
angles amount to 144.3° (C25-C24-C26-O27) and
-27.2° (C5-C4-C6-O7), respectively. This deviation
from coplanarity of the carboxamide and cyclopentadi-
enyl π-systems is probably due to hydrogen bonding
between the carboxamide functions in complex 6d .12 In
the crystal, 6d forms two types of hydrogen bonds: an
intramolecular one between H28 and O7 (calculated
separation ) 2.181 Å) and an intermolecular hydrogen
bond (2.131 Å ) calculated distance between H8 and
O27*). The combination of these two weak interactions
leads to a characteristic association pattern of 6d
molecules in the solid state. A view of the resulting
suprastructure is given in Figure 1.
The isocyanate addition route may offer advantages
over the classical electrophilic ferrocene substitution
routes when carboxamides are attached that contain
acid-labile or basic functional groups in the side chain.
This was demonstrated by two selected examples. 3-
Pyridyl isocyanate was treated with CpLi and then with
FeCl2. Workup and chromatographic separation gave
the N-(m-pyridyl)carboxamide-substituted ferrocenes 5e
and 6e in 22% and 8% yields, respectively. The analo-
gous reaction sequence was also carried out starting
from 2-tetrahydropyranylisocyanate. The N-(2-tetrahy-
dropyranyl)carboxamide-substituted ferrocenes 5f and
6f were isolated in 54% and 21% yields, respectively.
(12) Weinbach, S. P.; J acquemain, D.; Leveiller, F.; Kjaer, K.; Als-
Nielsen, J .; Leiserowitz, L. J . Am. Chem. Soc. 1993, 115, 11110. Bisson,
A. P.; Carver, F. J .; Hunter, C. A.; Waltho, J . P. J . Am. Chem. Soc.
1994, 116, 10292. Dado, G. P.; Gellman, S. H. J . Am. Chem. Soc. 1994,
116, 1054. Houlton, A.; Mingos, D. M. P.; Williams, D. J . J . Chem.
Soc., Chem. Commun. 1994, 503. Gardner, R. R.; Gellman, S. H. J .
Am. Chem. Soc. 1995, 117, 10411. Kimizuka, N.; Kawasaki, T.; Hirata,
K.; Kunitake, T. J . Am. Chem. Soc. 1995, 117, 6360. Nadin, A.; Derrer,
S.; McGeary, R. P.; Goodman, J . M.; Raithby, P.; Holmes, A. B.;
O’Hanlon, P. J .; Pearson, N. D. J . Am. Chem. Soc. 1995, 117, 9768.
Bernstein, J .; Davis, R. E.; Shimoni, L.; Chang, N.-L. Angew. Chem.
1995, 107, 1689; Angew. Chem., Int. Ed. Engl. 1995, 34, 1545, and
references cited therein.
(10) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2, 1987, S1.
(11) Luke, W. D.; Streitwieser, A., J r. J . Am. Chem. Soc. 1981, 103,
3241, and references cited therein. Kaluski, Z. L.; Gusev, A. I.; Kalinin,
A. E.; Struchkov, Yu. T. Zh. Strukt. Khim. 1972, 13, 950; Chem. Abstr.
1972, 78, 34920a. Eiermann, M.; Hafner, K. J . Am. Chem. Soc. 1992,
114, 135.

4008 Organometallics, Vol. 15, No. 19, 1996
Oberhoff et al.
Our new method has turned out to also be suited to
prepare cyclopentadienyl-carboxamide-containing bent
metallocene complexes of the early transition metals.
This is illustrated by the synthesis of two representative
examples originating from the chemistry of titanocenes.
Sodium (N-phenylcarbamoyl)cyclopentadienide was gen-
erated by the addition of CpNa to phenyl isocyanate.
The resulting reagent was then allowed to react with
(cyclopentadienyl)titanium trichloride13 for several hours
at 50 °C in toluene solution. Sodium chloride was
removed by filtration and the resulting organometallic
product twice recrystallized from dichloromethane. The
product [(N-phenylcarbamoyl)cyclopentadienyl](cyclo-
pentadienyl)titanium dichloride (8a ) was isolated as a
red solid (mp 155 °C) in 38% yield. The product shows
very characteristic NMR spectra [1H NMR in THF-d8 δ
9.22 (br s, 1H, NH), 6.68 (s, 5H, Cp), 7.38 and 6.68
(AA′BB′, 2H each, C5H4); 13C NMR in THF-d8 δ 160.8
F igu r e 2. Projection of the molecular geometry of 8b (with
unsystematical atom numbering scheme). Selected bond
lengths (Å) and angles (deg): Ti-Cl1, 2.356(3); Ti-Cl2,
2.345(3); Ti-C1, 2.429(9); Ti-C2, 2.418(10); Ti-C3, 2.348-
(10); Ti-C4, 2.364(9); Ti-C5, 2.380(9); Ti-C18, 2.343(13);
Ti-C19, 2.382(12); Ti-C20, 2.350(11); Ti-C21, 2.351(11);
Ti-C22, 2.325(12); C5-C6, 1.481(14); C6-O6, 1.235(12);
C6-N7, 1.348(13); N7-C8, 1.472(13); O6-C6-N7, 124.7-
(10); O6-C6-C5, 119.6(10); N7-C6-C5, 115.7(9); C6-
N7-C8, 126.0(9); Cl2-Ti-Cl1, 95.69(11).
(CONH)]. The IR ν˜ (NH) band is observed at 3453 cm-1
.
In a related experiment, we have reacted adamantyl
isocyanate with CpNa in a 1:1 molar ratio. This leads
to a ca. 10:3 mixture of the products of 1- and 2-fold
addition. Again, the fulvenoid bis-addition product
seems to be the much higher stabilized anion system
that is much less reactive toward transition metal
electrophiles than the monocarbamoylcyclopentadien-
ide. Consequently, the reaction of the 10:3 mixture with
CpTiCl3 leads to a product mixture from which pure [(N-
adamantylcarbamoyl)cyclopentadienyl]CpTiCl2 (8b) was
isolated in close to 30% yield. Single crystals of 8b
suited for an X-ray crystal structure analysis were
obtained from toluene.
Sch em e 2
Complex 8b attains a typical bent metallocene con-
formation in the solid state. The carboxamido substitu-
ent is arranged coplanarly with the attached Cp ring.
The RNHCO- group is oriented toward the lateral sector
of the bent metallocene wedge. In this arrangement,
the amido oxygen atom points toward the narrow back
side of the bent metallocene, whereas the NH group is
oriented in the direction of the open front side of the
bent metallocene wedge. In this orientation the very
bulky adamantyl group probably experiences the least
steric interference with the other groups present in
complex 8b. Consequently, the bonding parameters
around the titanium center are as typically observed in
many other group 4 metallocene dihalide complexes.14
Am in o Ester -Der ived System s. On the basis of the
observation that Cp anion equivalents may be added to
some simple alkyl or aryl isocyanates to yield the (N-
hydrocarbylcarbamoyl)cyclopentadienides, a route to
Cp-ligand systems bearing amino ester-derived side
chains was developed. We have treated valine methyl
ester hydrochloride (9) with excess diphosgene to yield
the corresponding isocyanate (10).15 Subsequent reac-
tion of 10 with lithium cyclopentadienide proceeded
cleanly to give the N-CH(CHMe2)CO2Me-substituted
carbamoylcyclopentadienide system 3h . Again, it must
be assumed that 11 is formed as a primary product in
this addition reaction. Due to the pronounced pKa dif-
ferences between the CpH and carboxamide moieties,
proton transfer occurs rapidly to yield 3h . The re-
agent 3h ‚0.5THF was isolated and characterized spec-
troscopically .
Anhydrous FeCl2 was treated with the valine ester-
derived carbamoyl cyclopentadienide 3h in a 1:2 molar
ratio in THF at 60 °C for 1 week to give the correspond-
ing 1,1′-dicarbamoyl-substituted ferrocene 6h , which
was isolated in >80% yield. Complex 6h was character-
ized spectroscopically (see Experimental Section) and
by an X-ray crystal structure analysis (see Figure 3).
In the solid state, the substituted ferrocene derivative
exhibits an eclipsed metallocene conformation with the
valine ester-substituted carboxamide substituents ori-
ented in the closest gauche-like positions. The carboxa-
mide π-systems are both arranged in plane with their
(13) Chandra, K.; Sharma, R. K.; Kumar, N.; Garg, B. S. Chem. Ind.
(London) 1980, 288. Erker, G.; Korek, U.; Petrenz, R.; Rheingold, A.
L. J . Organomet. Chem. 1991, 421, 215.
(14) Bochmann, M. In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: New York,
1995; Vol. 4 (Lappert, M. F., Ed.), pp 311-430.
(15) Grassmann, W.; Wu¨nsch, E.; Riedel, A. Chem. Ber. 1958, 91,
455. Goldschmidt, S.; Wick, M. Liebigs Ann. Chem. 1952, 575, 217.

Carboxamide-Substituted Metallocene Complexes
Organometallics, Vol. 15, No. 19, 1996 4009
tion routes starting from the simple unsubstituted
parent bent metallocene complexes. We expect that
group 4 metallocenes exhibiting highly functionalized
perimeters will become available by variations of this
route, e.g., employing the isocyanates of oligopeptides
as reagents. Such systems would be interesting can-
didates for developing novel electrophilic metallocene
catalysts. Work directed at opening synthetic entries
to such systems is currently being carried out in our
laboratory.
Exp er im en ta l Section
Most reactions were carried out in an inert atmosphere
(argon) using Schlenk type glassware or in a glovebox. Alkyl
and aryl isocyanates employed in this study were commercially
available. Details of experimental conditions and instruments
used for spectroscopic and physical product characterization
are as previously described by us in the literature.16
F igu r e 3. View of the molecular geometry of 6h (with
unsystematical atom numbering scheme). Selected bond
lengths (Å) and angles (deg): Fe-C1 2.026(3); Fe-C2,
2.045(4); Fe-C11, 2.036(4); Fe-C3, 2.046(4); Fe-C12,
2.042(4); C1-C4, 1.488(5); C4-O4, 1.222(4); C4-N, 1.354-
(4); N-C5, 1.448(5); C11-C1-C2, 107.9(3); C11-C1-C4,
129.6(3); C2-C1-C4, 122.2(3); O4-C4-N, 122.4(3); O4-
C4-C1, 120.9(3); N-C4-C1, 116.7(3); C4-N-C5, 120.1-
(3); θ C4-N-C5-C9, -91.5(4).
Rea ction of Lith iu m Cyclop en ta d ien id e w ith ter t-
Bu tyl Isocya n a te. A solution of 2.00 g (20.2 mmol) of Me3-
CNCO in 50 mL of tetrahydrofuran was added dropwise at
-30 °C to a solution of 1.45 g (20.1 mmol) of CpLi in 50 mL of
THF. The dark red colored reaction mixture was allowed to
warm to room temperature overnight. Solvent was then
removed in vacuo, and the solid residue was washed twice with
pentane (30 mL). The resulting product mixture (3.0 g)
consists of 3a , 4a , and CpLi in a 62:22:16 ratio. Complex 3a
was characterized spectroscopically: 1H NMR (THF-d8) δ 5.93
and 5.53 (m, 2H each, C5H4), 5.82 (br s, 1H, NH), 1.37 (s, 9H,
CMe3). In a separate experiment, 6.34 g (64.0 mmol) of Me3-
CNCO was added to 1.68 g (23.4 mmol) of CpLi in 50 mL of
THF at room temperature. The mixture was stirred overnight,
the solvent removed in vacuo, and the residue washed twice
with pentane. Drying in vacuo at room temperature gave 8.4
g of 4a ‚0.8THF, mp 133 °C (DSC). The residual THF could
be removed at 130 °C in vacuo. IR (KBr): ν˜ ) 3446 cm-1, 3402
(NH), 1565, 1500 (CONH). 1H NMR (benzene-d6/THF-d8, 10:
1): δ 6.72 (d, 3J ) 3.6 Hz, 2H), 6.39 (t, 3J ) 3.6 Hz, 1H, C5H3),
5.98 (br s, 2H, NH), 1.30 (s, 18H, CMe3), THF signals at 3.55
(2H) and 1.43 (2H). 13C NMR (THF-d8): δ 171.9 (CONH),
116.1 (ipso-C, Cp), 115.8, 108.2 (CH of Cp), 50.6 and 29.7
(CMe3). Anal. Calcd for C15H24LiN2O2‚0.8C4H8O (329.0): C,
66.65; H, 9.04; N, 8.54. Found: C, 66.41; H, 8.94; N, 8.40.
(N-ter t-Bu tylca r ba m oyl)fer r ocen e (5a ) a n d 1,1′-Bis(N-
ter t-bu tylca r ba m oyl)fer r ocen e (6a ). CpLi (600 mg, 8.33
mmol) was reacted with 0.95 mL (822 mg, 8.29 mmol) of tert-
butyl isocyanate in 50 mL of THF as described earlier and then
treated with 634 mg (5.00 mmol) of anhydrous FeCl2. Solvent
was removed and the residue extracted with dichloromethane.
The CH2Cl2 solvent was removed and the product chromato-
graphed with ether on silica gel to give a trace amount of 5a
and 6a (170 mg, 12%) as an orange-colored solid. 5a : mp 202
°C (dec). 1H NMR (CDCl3): δ 5.4 (br s, 1H, NH), 4.58 and
4.28 (m, each 2H, C5H4), 4.17 (s, 5H, Cp), 1.42 (s, 9H, CMe3).
6a : mp 109 °C (DSC), 237 °C (dec). HRMS: calcd 384.1500,
found 384.1509. IR (KBr): ν˜ ) 3334 cm-1 (NH), 1631 and 1537
(CONH). 1H NMR (CDCl3): δ 6.36 (br s, 2H, NH), 4.42 and
4.32 (m, each 4H, C5H4), 1.46 (s, 18H, CMe3). 13C NMR
(CDCl3): δ 169.2 (CONH), 79.3 (ipso-C of Cp), 70.6 and 70.4
(CH of Cp), 51.3 and 28.9 (CMe3). Anal. Calcd for C20H28N2O2-
Fe (384.3): C, 62.51; H, 7.34. Found: C, 61.82; H, 7.45.
P r ep a r a tion of th e (N-n -Bu tylca r ba m oyl)fer r ocen e
Com p lexes 5b a n d 6b. CpLi (738 mg, 1.02 mmol) was
treated with 1.03 g (1.04 mmol) of n-butyl isocyanate in 100
mL of THF (12 h), 490 mg (3.87 mmol) of FeCl2 was added,
and the mixture stirred for 24 h at room temperature. Solvent
was removed in vacuo. Washing with pentane and then
toluene gave 1.57 g of the crude reaction product. Of this
adjacent cyclopentadienyl ring systems. The overall
molecular geometry is C2-symmetric. Thus, the car-
boxamide CdO vectors are pointing to opposite direc-
tions normal to the Cp-Fe-Cp axis.
Treatment of the isocyanate 10 with excess LiCp
followed by the reaction with FeCl2 gave, as usual, a
mixture of the monofunctionalized ferrocene 5h and the
difunctionalized product 6h . They were separated
chromatographically. Complex 5h was also character-
ized by an X-ray crystal structure analysis. Again, the
carboxamido substituent is oriented in plane with the
attached Cp ring. The structural data are very similar
to those of complex 6h (for details see the Experimental
Section and the supporting information).
Con clu sion s
We conclude that a variety of carboxamido-substitut-
ed cyclopentadienides, including the respective amino
ester-derived systems, can be generated by Cp anion
addition to the corresponding isocyanates. The amide
anion 2 formed in the first step is rapidly converted to
the corresponding (RNHCO)C5H4- reagent 3 by proton
transfer. A certain problem in this reaction scheme is
the rapid subsequent additional isocyanate addition to
give the fulvenoid bis-adducts 4. However, it seems that
the metallocene formation is not severely hampered by
the presence of the additional reagent 4 because of its
reduced nucleophilicity. This side reaction during the
formation of the (RNHCO)C5H4- reagent in many cases
makes it inevitable that a contamination with residual
unsubstituted Cp anion will occur. In the following
treatment with the transition metal halide, this results
in the formation of a proportional quantity of the
“mixed” [(RNHCO)C5H4]CpM product in addition to the
[(RNHCO)C5H4]2M main product. In the case of the
ferrocenes, these two final products can often be sepa-
rated quite easily by chromatography.
An advantage of this new route is the possibility to
introduce carboxamido substituents carrying acid-labile
and also basic groups bonded to the amido nitrogen. In
addition, our novel route can be used to synthesize
CpCONHR-substituted early transition metal metal-
locenes that cannnot be made by electrophilic substitu-
(16) Erker, G.; Wilker, S.; Kru¨ger, C.; Nolte, M. Organometallics
1993, 12, 2140.

4010 Organometallics, Vol. 15, No. 19, 1996
Oberhoff et al.
product, 510 mg was chromatographed with ether on silica gel
to give 71 mg (24%) of 5b and 70 mg of 6b that contained ca.
20% 5b. 5b: mp 146 °C. IR (KBr): ν˜ ) 3296 cm-1 (NH),
1622 and 1539 (CONH). 1H NMR (CDCl3): δ 5.76 (br s, 1H,
NH), 4.64 and 4.29 (m, each 2H, C5H4), 4.19 (s, 5H, Cp), 3.35
(m, 2H), 1.53 (m, 2H), 1.38 (m, 2H), 0.92 (br t, 3H, n-butyl).
13C NMR (CDCl3): δ 169.0 (CONH), 69.2 and 67.0 (CH of
C5H4), 68.7 (Cp), 38.3, 31.1, 19.1, 12.8 (n-butyl). Anal. Calcd
for C15H19NOFe (285.2): C, 63.18; H, 6.72. Found: C, 62.84;
H, 6.68. X-ray crystal structure analysis: single crystals from
CDCl3; formula, C15H19NOFe; M ) 285.16 g mol-1; orthorhom-
bic space group Pbca (No. 61); cell constants a ) 9.870(2) Å, b
) 10.154(2) Å, c ) 26.612(5) Å, V ) 2667.1(9) Å3; T ) -50 °C,
structure analysis: single crystals from CDCl3; formula
C24H20N2O2Fe‚CDCl3; M ) 543.64 g mol-1; monoclinic space
group P21/n (No. 14); cell constants a ) 9.281(2) Å, b ) 14.956-
(3) Å, c ) 17.540(4) Å, â ) 93.52(3)°, V ) 2430.1(9) Å3; T ) 20
°C; crystal size 0.5 × 0.3 × 0.1 mm; Z ) 4; Fcalcd ) 1.486 g
cm-3; λ ) 0.710 73 Å; [sin θ/λ]max ) 0.63 Å-1; µ ) 9.8 cm-1
;
4842 reflections collected (-h, +k, (l), 4561 independent and
3159 observed reflections; 305 refined parameters, R ) 0.076,
wR2 ) 0.159.
P r ep a r a tion of th e N-(3-P yr id yl)ca r ba m oylfer r ocen es
5e a n d 6e. 3-Pyridyl isocyanate (400 mg, 3.33 mmol) was
treated with 240 mg (330 mmol) of CpLi and then with 220
mg (1.74 mmol) of FeCl2 in THF analogously as described
earlier. After removal of the solvent, the crude product was
purified by filtration over a short silica gel column with
dichloromethane/methanol (10:1). The products were then
separated by preparative thick-layer chromatography with
dichloromethane/methanol (100:1, then 10:1) on silica gel to
yield 110 mg (22%) of 5e and 60 mg (8%) of 6e, the latter after
additional recrystallization from toluene. 5e: mp 185 °C. IR
(KBr): ν˜ ) 3302 cm-1 (NH), 1644 and 1534 (CONH). 1H NMR
(THF-d8): δ 8.75 (br s, 1H, NH), 8.71 (m, 1H), 8.26 (m, 1H),
8.22 (m, 1H), 7.21 (m, 1H, pyridyl; pyridyl coupling constants
crystal size 0.3 × 0.2 × 0.05 mm; Z ) 8; Fcalcd ) 1.420 g cm-3
;
λ ) 0.710 73 Å; [sin θ/λ]max ) 0.62 Å-1; µ ) 11.2 cm-1; 2714
reflections collected (+h, -k, -l), 2713 independent and 1589
observed reflections; 167 refined parameters, R ) 0.049, wR2)
0.119. Programs used: SHELX 86, SHELX 93, XP. 6b: 1H
NMR (CDCl3) δ 6.75 (br s, 2H, NH), 4.46 and 4.34 (m, each
4H, C5H4), 3.39 (m, 4H), 1.61 (m, 4H), 1.41 (m, 4H), 0.96 (br t,
6H, n-butyl).
(N-Cycloh exylca r ba m oyl)fer r ocen e (5c). CpLi (3.19 g,
44.3 mmol) was reacted with 5.43 mL (5.32 g, 42.5 mmol) of
cyclohexyl isocyanate in 50 mL of THF (-78 °C to ambient
temperature, 24 h) and then treated with 2.24 g (17.7 mmol)
of FeCl2 in 20 mL of THF. The resulting crude product was
Soxhlet extracted with ether for 4 days, and the resulting
extract was chromatographed with ethyl acetate/ether (2:1) on
silica gel to yield 265 mg (4.8%) of 5c. IR (KBr): ν ) 3296
cm-1 (NH), 1623 and 1538 (CONH). 1H NMR (CDCl3): δ 5.48
(br s, 1H, NH), 4.64 and 4.32 (m, each 2H, C5H4), 4.19 (s, 5H,
Cp), 3.92 (br m, 1H), 1.99 (m, 2H), 1.79-1.15 (m, 8H,
cyclohexyl). Anal. Calcd for C17H21NOFe (311.2): C, 65.61;
H, 6.80; N, 4.50. Found: C, 65.91; H, 7.22; N, 4.64. X-ray
crystal structure analysis: single crystals from CDCl3; formula,
3
3
4
4
(PANIC) J 4,5 ) 4.7 Hz, J 5,6 ) 8.3 Hz, J 4,6 ) 1.5 Hz, J 2,6
)
4
5
2.5 Hz, J 2,4 ) 0.5 Hz, J 2,5 ) 0.3 Hz), 4.91 (m, 2H), 4.39 (m,
2H, C5H4R), 4.20 (s, 5H, Cp). 13C NMR (CDCl3): δ 169.5
(CONH), 135.9 (ipso-C, pyridyl), 144.6, 141.0, 127.3, 124.3 (CH
of pyridyl), 77.2 (ipso-C of C5H4R), 71.2 and 68.5 (CH of C5H4R),
70.0 (Cp). 6e: IR (KBr): ν˜ ) 3335 cm-1 (NH), 1645 and 1535
(CONH). 1H NMR (THF-d8): δ 9.53 (br s, 2H, NH), 8.89 (m,
2H), 8.29 (m, 2H), 8.26 (m, 2H), 7.23 (m, 2H, pyridyl), 4.78
and 4.50 (m, each 4H, C5H4). 13C NMR (THF-d8): δ 169.6
(CONH), 137.2 (ipso-C of pyridyl), 145.3, 142.6, 127.1, 124.0
(CH of pyridyl), 80.0 (ipso-C of C5H4R), 72.2 and 72.0 (CH of
C5H4R). Anal. Calcd for C16H14N2OFe (306.2): C, 62.77; H,
4.61; N, 9.15. Found: C, 62.62; H, 4.46; N, 9.28.
C
17H21NOFe; M ) 311.20 g mol-1; orthorhombic space group
P212121 (No. 19); cell constants a ) 9.722(1) Å, b ) 10.159(1)
Å, c ) 29.952(2) Å, V ) 2958.2(5) Å3; T ) -50 °C; crystal size
0.6 × 0.3 × 0.05 mm; Z ) 8; Fcalcd ) 1.397 g cm-3; λ ) 0.710 73
Å; [sin θ/λ]max ) 0.62 Å-1; µ ) 10.1 cm-1; 3419 reflections
collected (-h, +k, -l), 3419 independent and 2582 observed
reflections; 369 refined parameters, R ) 0.051, wR2 ) 0.139.
P r ep a r a tion of th e N-(2-Tetr a h yd r op yr a n yl)ca r ba m -
oylfer r ocen e Com p lexes 5f a n d 6f. CpLi (770 mg, 10.7
mmol) was reacted with 1.26 mL (1.37 g, 10.8 mmol) of
2-tetrahydropyranyl isocyanate in THF and then treated with
800 mg (6.31 mmol) of anhydrous FeCl2 as described earlier.
The crude product was filtered over a short silica gel column
with dichloromethane/methanol (10:1) and then chromato-
graphed (thick-layer chromatography) with dichloromethane/
methanol (100:1; several times developed) on silica gel to yield
900 mg (54%) of 5f and 500 mg (21%) of 6f. 5f: mp 196 °C.
IR (KBr): ν˜ ) 3306 cm-1 (NH), 1644 and 1534 (CONH). 1H
NMR (CDCl3): δ 6.04 (br d, 1H, NH), 5.22 (m, 1H, THP 2-H),
4.71 (m, 1H), 4.63 (m, 1H), 4.33 (m, 2H, C5H4R), 4.22 (s, 5H,
Cp), 3.99 (br d, 1H), 3.65 (m, 1H, THP 6-H/6-H′), 1.88-1.51
(m, 6H, THP CH2). 13C NMR (CDCl3): δ 169.8 (CONH), 78.0
(THP C2), 75.3 (ipso-C of C5H4R), 70.6 (double intensity), 68.6
and 67.9 (CH of C5H4R), 69.9 (Cp), 67.5 (THP C6), 32.0 (THP
C3), 25.1 and 23.0 (THP CH2). Anal. Calcd for C16H19NO2Fe
(313.2): C, 61.36; H, 6.11; N, 4.47. Found: C, 61.11; H, 6.32;
N, 4.54. 6f: IR (KBr): ν˜ ) 3334 cm-1 (NH), 1647 and 1534
(CONH). 1H NMR (CDCl3): δ 6.98 (br d, 2H, NH), 5.41 (m,
2H, THP 2-H), 4.84 (m, 2H), 4.52 (m, 2H), 4.37 (m, 2H), 4.31
(m, 2H, C5H4R), 4.08 (br d, 2H), 3.73 (m, 2H, THP 6-H/6-H′),
1.96-1.57 (m, 12H, THP CH2). 13C NMR (CDCl3): δ 169.6
(CONH), 78.6 (THP C2), 75.6 (ipso-C of C5H4R), 72.3, 72.1,
71.6, 70.9 (CH of C5H4R), 67.9 (THP C6), 30.7 (THP C3), 25.2
and 23.2 (THP CH2).
(N-P h en ylca r ba m oyl)fer r ocen e (5d ). The reaction mix-
ture obtained by treatment of 83 mg (1.15 mmol) of CpLi and
87.7 mL (96.1 mg, 0.81 mmol) of phenyl isocyanate in 30 mL
of THF at 0 °C (24 h) was added to 72 mg (0.57 mmol) of
anhydrous FeCl2 and stirred for 3 days at 50 °C. The
suspension was concentrated in vacuo to a volume of 10 mL
and then filtered. The yellow crude product (166 mg) was
chromatographed on a short silica gel column with ether/ethyl
acetate (10:1, plus 1% of dimethylethylamine) to give, as the
first fraction, 72 mg (41%) of 5d as a yellow amorphous solid,
mp 208 °C (DSC). HRMS: calcd 305.0503, found 305.0495.
IR (KBr): ν˜ ) 3294 cm-1 (NH), 1643 and 1596 (CONH). 1H
NMR (CDCl3): δ 7.58 (m, 2H, Ph), 7.30 (m, 3H, Ph and NH),
7.10 (m, 1H, Ph), 4.76 (m, 2H), 4.40 (m, 2H, C5H4R), 4.24 (s,
5H, Cp). 13C NMR (CDCl3): δ 168.6 (CONH), 138.1 (ipso-C of
Ph), 129.1, 124.0, 119.8 (Ph), 70.9 and 68.3 (C5H4R), 69.9 (Cp),
ipso-C of C5H4R not observed. Anal. Calcd for C17H15NOFe
(305.2): C, 66.91; H, 4.95; N, 4.59. Found: C, 66.43; H, 5.05;
N, 4.71.
1,1′-Bis(N-p h en ylca r ba m oyl)fer r ocen e (6d ). CpLi (1.00
g, 13.9 mmol) was reacted with 1.55 mL (1.69 g, 14.2 mmol)
of phenyl isocyanate and then treated with 1.00 g (7.89 mmol)
of FeCl2 in THF as described earlier. The crude product was
Soxhlet extracted with ether, and the extracted product was
chromatographed with ether on silica gel to yield 750 mg (25%)
of 6d as an orange red solid, mp 152 °C. IR (KBr): ν˜ ) 3446
cm-1, 3207 (NH), 1645 and 1595 (CONH). 1H NMR (CDCl3):
δ 8.72 (br s, 2H, NH), 7.78 (m, 4H), 7.36 (m, 4H), 7.13 (2H,
Ph), 4.64 and 4.49 (m, each 4H, C5H4). 13C NMR (CDCl3): δ
169.0 (CONH), 138.4 (ipso-C of Ph), 128.4, 124.2, 120.0 (Ph),
79.3 (ipso-C of C5H4R), 71.4, 71.2 (CH of Cp). X-ray crystal
P r ep a r a tion of Bis[1,2-bis(ter t-bu tylca r ba m oyl)cyclo-
p en ta d ien yl]ir on (7). Sodium cyclopentadienide (4.28 g, 48.6
mmol) was dissolved in 100 mL of THF and cooled to -78 °C.
tert-Butyl isocyanate (11.1 mL, 97.28 mmol) was added drop-
wise with stirring. The mixture was allowed to warm to room
temperature overnight. Solvent was removed in vacuo and
the residue washed twice with 40 mL of pentane to give 4a as
a pale yellow powder [quantitative, 1H NMR (THF-d8): δ 8.13
3
3
(br s, 2H, NH), 6.28 (d, J ) 3.6 Hz, 2H), 5.59 (t, J ) 3.6 Hz,
1H, C5H3), 1.37 (s, 18H, CMe3)]. The sodium salt 4a thus

Carboxamide-Substituted Metallocene Complexes
Organometallics, Vol. 15, No. 19, 1996 4011
prepared was dissolved in 100 mL of THF. FeCl2 (3.08 g, 24.3
mmol) was added. The mixture was stirred for 2 days. Solvent
was removed in vacuo, and the residue was extracted with 100
mL of dichloromethane. The extract was washed with water
(100 mL). The aqueous phase was extracted twice with 50
mL of dichloromethane, and the combined organic layers were
dried over magnesium sulfate. Solvent was removed in vacuo.
The residue was washed twice with 100 mL of pentane and
then dried in vacuo to yield 9.26 g (65%) of 7: mp 272 °C. IR
(KBr): ν˜ ) 3267 cm-1, 3209 (NH), 1645, 1622, 1584 (CONH).
3.37 (s, 3H, OCH3), 2.11 (m, 1H), 0.94 (2d, 6H, isopropyl). 13C
NMR (benzene-d6/THF-d8, 10:1.5): δ 174.0, 169.2 (CONH, CO2-
Me), 111.6 (ipso-C of C5H4R), 110.8, 109.3 (CH of C5H4R), 58.4
(NHCH), 51.5 (OCH3), 32.4, 19.6, 18.6 (isopropyl). The reagent
3h thus prepared contains less than 5% of the bis(isocyanate)
addition product. This product was treated with 320 mg (2.5
mmol) of FeCl2 in 60 mL of THF at 60 °C for 1 week. Solvent
was removed in vacuo and washed with pentane. Chromato-
graphic separation with THF on silica gel gave 1.04 g (83%)
of 6h : mp 168 °C (DSC), [R]D ) +115° (c ) 0.59 in CH2Cl2).
20
3
1H NMR (CDCl3): δ 8.52 (br s, 4H, NH), 4.82 (d, J ) 1.9 Hz,
HRMS: calcd 500.1610, found 500.1597. IR (KBr): ν˜ ) 3395
cm-1 (NH), 1743, 1723 (CO2Me), 1655, 1529 (CONH). UV
(CH2Cl2): λ ) 256 nm (ꢀ ) 1730). 1H NMR (CDCl3): δ 7.48
4H), 4.22 (t, 3J ) 1.9 Hz, 2H, C5H3R2), 1.45 (s, 36H, CMe3).
13C NMR (CDCl3): δ 168.6 (CO), 78.0 (ipso-C of C5H3R2), 77.9
(double intensity) and 74.9 (CH of C5H3R2), 51.8 and 28.7
(CMe3). Anal. Calcd for C30H46N4O4Fe (582.6): C, 61.85; H,
7.96; N, 9.62. Found: C, 61.56; H, 7.72; N, 9.74.
3
(d, J ) 9.0 Hz, 2H, NH), 4.83, 4.74, 4.50, 4.35 (m, each 2H,
3
CH of C5H4R), 4.63 (dd, J ) 9.0, 7.2 Hz, 2H, NHCH), 3.78 (s,
3
6H, OCH3), 2.16 (m, 2H), 0.98 and 0.97 (each d, J ) 6.7 Hz,
[(N -P h e n y lc a r b a m o y l)c y c lo p e n t a d i e n y l](c y c lo -
p en ta d ien yl)d ich lor otita n iu m (8a ). Solid sodium (N-phen-
ylcarbamoyl)cyclopentadienide (Na-3d ) (1.00 g, 4.83 mmol) and
1.10 g (5.01 mmol) of solid CpTiCl3 were mixed in a Schlenk
flask, and toluene (50 mL) was slowly added at 0 °C. The
mixture was stirred at 50 °C for 20 min and then overnight at
room temperature. Solvent was removed in vacuo. The
residue was extracted with dichloromethane, and the extract
was filtered over silica gel. Solvent was removed in vacuo and
the residue recrystallized twice from dichloromethane to yield
704 mg (38%) of 8a : mp 155 °C (DSC). IR (KBr): ν˜ ) 3453
cm-1 (NH), 1581 and 1525 (CONH). 1H NMR (THF-d8): δ 9.22
(br s, 1H, NH), 7.69 (m, 2H), 7.24 (m, 2H), 7.04 (m, 1H, Ph),
7.38 and 6.60 (m, each 2H, C5H4R), 6.68 (s, 5H, Cp). 13C NMR
(THF-d8): δ 160.8 (CONH), 139.9 and 120.8 (ipso-C of Ph and
C5H4R), 129.4, 124.5, 123.6, 122.2, 121.2 (CH of Ph and C5H4R),
122.7 (Cp).
[(N -1-Ad a m a n t ylca r b a m oyl)cyclop e n t a d ie n yl](cy-
clop en ta d ien yl)d ich lor otita n iu m (8b). A suspension of
370 mg (1.30 mmol) of a 10:3 mixture of Na-3g and Na-4g in
20 mL of toluene was mixed with a suspension of CpTiCl3 (281
mg, 1.28 mmol) in 15 mL of toluene at 0 °C. The mixture was
allowed to warm to room temperature overnight with stirring.
Solvent was removed in vacuo, and the residue was washed
with pentane. The solid was extracted with 30 mL of hot
toluene and filtered while still hot. The product 8b crystallizes
from the toluene solution upon cooling. The product was
collected by filtration to yield 156 mg (28%) of 8b: mp 156 °C
(DSC). IR (KBr): ν˜ ) 3402 cm-1 (NH), 1660 and 1526 (CONH).
1H NMR (dichloromethane-d2): δ 6.02 (br s, 1H, NH), 7.01 and
6.63 (m, each 2H, C5H4R), 6.47 (s, 5H, Cp), 2.05 (m, 9H), 1.71
(m, 6H, adamantyl). 13C NMR (dichloromethane-d2): δ 161.4
(CONH), 128.5 and 124.8 (CH of C5H4R), 122.1 (Cp), 119.2
(ipso-C of C5H4R), 41.8, 36.7, 30.0 (adamantyl), one adamantyl
resonance not observed. Anal. Calcd for C21H25NOCl2Ti
(426.2): C, 59.18; H, 5.91; N, 3.29. Found: C, 59.47; H, 6.06;
N, 3.70. X-ray crystal structure analysis: single crystals from
toluene; formula, C21H25Cl2NOTi; M ) 426.22 g mol-1; mono-
clinic space group P21/c (No. 14); cell constants a ) 13.446(1)
Å, b ) 10.937(1) Å, c ) 13.308(1) Å, â ) 92.41(1)°, V ) 1955.3-
(3) Å3; T ) -50 °C; crystal size 0.2 × 0.15 × 0.01 mm; Z ) 4;
Fcalcd ) 1.448 g cm-3; λ ) 0.710 73 Å; [sin θ/λ]max ) 0.53 Å-1; µ
) 7.21 cm-1; 2518 reflections collected (+h, +k, (l), 2397
independent and 1501 observed reflections; 239 refined pa-
rameters, R ) 0.068, wR2 ) 0.183.
each 6H, isopropyl). 13C NMR (benzene-d6): δ 175.6, 170.3
(CONH and CO2Me), 77.5 (ipso-C of C5H4R), 71.9, 71.7, 70.9,
70.7 (CH of C5H4R), 58.5 (NHCH), 51.8 (OCH3) 30.4, 19.5, 19.2
(isopropyl). Anal. Calcd for C24H32N2O6Fe (500.4): C, 57.61;
H, 6.45; N, 5.60. Found: C, 57.35; H, 6.21; N, 5.73. X-ray
crystal structure analysis: single crystals from CH2Cl2; for-
mula, C24H32N2O6Fe; M ) 500.37 g mol-1, crystal size 0.5 ×
0.5 × 0.4 mm; space group P41212 (No. 92); cell parameters a
) b ) 11.374(5) Å, c ) 18.750(5) Å, V ) 2426(2) Å3; T ) -50
°C; Z ) 4; rcalcd ) 1.370 g cm-1; λ ) 0.710 73 Å; [(sin θ)/λ]max
)
0.62 Å-1; µ ) 6.6 cm-1; 2780 reflections collected, (+h, +k, +l),
2464 independent and 1795 observed reflections; 156 refined
2
parameters, R ) 0.039, Rw ) 0.099.
P r ep a r a tion of 5h . Lithium cyclopentadienide (136 mg,
1.89 mmol) and 207 mg (1.32 mmol) of 10 were mixed at 0 °C
in 40 mL of THF. The reaction mixture was allowed to warm
to room temperature and then stirred for 16 h. FeCl2 (115
mg, 0.91 mmol) was added and the mixture was stirred for 1
week at 50 °C. Solvent was removed in vacuo and the product
filtered through a short silica gel column with THF (with ca.
1% of triethylamine added). The eluted material (193 mg) was
then chromatographed on silica gel with ethyl acetate/ether
(1:5, plus 1% of triethylamine) to give 50 mg (16% of 5h )
followed by 108 mg (24%) of 6h . 5h : mp 120 °C (DSC); [R]D
20
) -27.2° (c ) 0.083 in CH2Cl2). IR (KBr): ν˜ ) 3321 cm-1 (NH),
1743 (CO2Me), 1626, 1531 (CONH). 1H NMR (CDCl3): δ 6.14
(br d, 3J ) 8.6 Hz, 1H, NH), 4.68 (m, 3H, CH of C5H4R and
NHCH), 4.35 (m, 2H, CH of C5H4R), 4.23 (s, 5H, Cp), 2.22 (m,
3
1H), 0.99 and 0.96 (d, J ) 6.9 Hz, 6H, isopropyl). 13C NMR
(CDCl3): δ 172.9 170.3 (CONH and CO2Me), 75.5 (ipso-C of
C5H4R), 70.5, 68.2 (CH of C5H4R), 69.7 (Cp), 56.8 (NHCH), 52.3
(OCH3) 31.3, 19.1, 17.9 (isopropyl). Anal. Calcd for C17H21
-
NO3Fe (343.2): C, 59.49; H, 6.17; N, 4.08. Found: C, 58.88;
H, 5.85; N, 4.10. X-ray crystal structure analysis: single
crystals from CH2Cl2; formula, C17H21NO3Fe; M ) 343.20 g
mol-1, crystal size 0.5 × 0.4 × 0.2 mm; space group P21 (No.
4); cell parameters a ) 10.084(2) Å, b ) 11.182(2) Å, c )
14.364(3) Å, â ) 92.20(2)°, V ) 1618.5(5) Å3; T ) -50 °C; Z )
4; rcalcd ) 1.408 g cm-3; λ ) 0.710 73 Å; [(sin θ)/λ]max ) 0.62
Å-1; µ ) 9.4 cm-1; 3644 reflections collected, (+h, +k, (l), 3451
independent and 1732 observed reflections; 403 refined pa-
2
rameters, R ) 0.059, Rw ) 0.113.
Ackn owledgm en t. Financial support from the Fonds
der Chemischen Industrie and the Wissenschaftsmin-
isterium des Landes Nordrhein-Westfalen is gratefully
acknowledged.
Rea ction of Va lin e Meth yl Ester Isocya n a te (10) w ith
Cp Li: P r ep a r a tion of 3h a n d Su bsequ en tly 6h . Lithium
cyclopentadienide (390 mg, 5.4 mmol) in 30 mL of THF was
combined with a solution of 860 mg (5.5 mmol) of methyl (S)-
2-isocyanato-2-isopropyl acetate (10) in 30 mL of THF at -78
°C. The mixture was allowed to warm to ambient temperature
overnight. Solvent was removed in vacuo, and the residue was
washed with pentane and dried in vacuo to give 1.32 g (91%)
of 4‚0.5THF. 1H NMR (benzene-d6/THF-d8, 10:1.5): δ 6.49-
6.45 (m, 3H, R-CH of C5H4R and NH, overlapping), 6.20 (m,
Su p p or tin g In for m a tion Ava ila ble: Details of the X-ray
crystal structure determinations of the complexes 5b, 5c, 5h ,
6d , 6h , and 8b including tables of bond lengths and angles
and positional parameters (47 pages). Ordering information
is given on any current masthead page.
3
2H, â-CH of C5H4R), 4.68 (dd, J ) 8.9, 6.2 Hz, 1H, NHCH),
OM960234K