Synthesis and reactivity of Cp*RuII η6-π-adducts of functionalized arenes with useful side chains: X-ray molecular structure of [Cp*Ru(η6-N-succinimidyl 3-(4-methoxyphenyl)propionate)][CF3SO3]

Article abstract of DOI:10.1021/om950987r

Several novel organoruthenium complexes [Cp*Ru(η⁶-arene)][CF₃SO₃] (3, 4, 6), were prepared in which the arene unit possesses an alkyl chain terminated with carboxylic acid, ester, and activated ester functions. These compo

Full text of DOI:10.1021/om950987r

Organometallics 1996, 15, 2303-2307
2303
Syn th esis a n d Rea ctivity of Cp *Ru II η6-π-Ad d u cts of
F u n ction a lized Ar en es w ith Usefu l Sid e Ch a in s: X-r a y
Molecu la r Str u ctu r e of [Cp *Ru (η6-N-su ccin im id yl
3-(4-m eth oxyp h en yl)p r op ion a te)][CF 3SO3]
H. El Amouri,*,† S. Canceil,† Y. Besace,† and L. Ricard‡
Ecole Nationale Supe´rieure de Chimie de Paris, URA CNRS 403, 11, rue Pierre et
Marie Curie, 75231 Paris Cedex 05, France, and Laboratoire “He´te´roe´le´ments et Coordination”,
URA CNRS 1499, DCPH Ecole Polytechnique, 91128 Palaiseau Cedex, France
Received December 27, 1995X
Several novel organoruthenium complexes [Cp*Ru(η6-arene)][CF3SO3] (3, 4, 6) were
prepared in which the arene unit possesses an alkyl chain terminated with carboxylic acid,
ester, and activated ester functions. These compounds were fully characterized by spectro-
scopic methods, and in particular, the activated ester complex [Cp*Ru(η6-MeOC6H4(CH2)2-
COONS)][CF3SO3] (6) (NS ) N-succinimidyl) was identified by X-ray analysis. The reactivity
of 6 with respect to benzylamine and â-alanine ethyl ester was examined and afforded
quantitatively the stable conjugates [Cp*Ru(η6-MeOC6H4CH2CH2CONHCH2Ph][CF3SO3] (7)
and [Cp*Ru(η6-MeOC6H4(CH2)2CONH(CH2)2COOEt][CF3SO3] (8). Furthermore, the stability
and reactivity of 6 relative to the analogous dicationic organoiridium complex [Cp*Ir(η6-
MeOC6H4(CH2)2COONS)][BF4]2 (10) and the neutral metallocarbonyl derivatives of the type
[LnMCpCOONS] (12-14) [LnM ) Fe(CO)2Me, Mo(CO)3Me, Co(CO)2] are presented and
discussed.
In tr od u ction
The use of (pentamethylcyclopentadienyl)metal frag-
ments to form stable complexes in coordination chem-
istry is a widely documented area.1 Recently these
species [Cp*M] (M ) Rh, Ir, Ru) have been employed
F igu r e 1.
as organometallic synthons to bind amino acids2 or
amino acid derivatives,2a prompted by the roles of
metals in biochemistry and amino acids in producing
chiral catalysts.3,4 Further it has been shown that
organometallic complexes of the type [Cp*(Cl)Rh-
{peptide-OR-H+}] exhibit chiral centers both at the
R-carbon in the ligand and at the metal and possess
considerable potential for the enantioselective synthesis
of peptides.5 On the other hand, the presence of the
F igu r e 2.
organometallic moiety [Cp*M] helped to bring about the
We reported previously the preparation of a series of
organometallic succinimidyl esters (see Figure 2) in
which a [Cp*Ir] unit is coordinated at the arene pos-
sessing an alkyl chain terminated by a succinimidyl
ester moiety.7 Such derivatives can be regarded as
Bolton-Hunter reagents, in which the aryl ring bears
a [Cp*Ir] moiety. The use of such derivatives for
selective labeling of amino acids in peptides has proved
to be a valuable method. Unfortunately these dicationic
iridium derivatives showed signs of decomposition even
in the solid state. Thus we focused our efforts to prepare
the analogous monocationic complex but using the
[Cp*Ru] unit.
crystallization of the modified amino acid or amino acid
derivatives; for instance, Grotjahn and co-workers have
isolated and determined the X-ray molecular structures
of the stable conjugates [Cp*Ir(N-tosylglycine)] and
[Cp*Ir(N-tosylphenylglycine)].2a,6
† URA CNRS 403.
‡ URA CNRS 1499.
X Abstract published in Advance ACS Abstracts, April 1, 1996.
(1) (a) Deeming, A. J . In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, U.K., 1982; Vol. 4, pp 475-504. (b) Tilley, T. D.; Grubbs, R.
H.; Bercaw, J . E. Organometallics 1984, 3, 274. (c) Oshima, N.; Suzuki,
H.; Moro-Oka, Y. Chem. Lett. 1984, 1161.
(2) (a) Grotjahn, D. B.; Groy, T. L. Organometallics 1995, 14, 3669-
3682. (b) Sheldrick, W. S.; Gleichmann, A. J . Organomet. Chem. 1994,
470, 183-187. (c) Gleichmann, A. J .; Wolff, J . M.; Sheldrick, W. S. J .
Chem. Soc., Dalton Trans. 1995, 1549.
(3) Metalloproteins: Structural Aspects. Adv. Prot. Chem. 1991, 42.
Ibers, J . A.; Holm, R. H. Science 1980, 209, 223-235.
(4) (a) Brunner, H. Top. Stereochem. 1988, 18, 129-247. (b) Chiral
Catalysis, Asymmetric Synthesis; Morrison, J ., Ed.; Academic: Orlando,
FL, 1985; Vol. 5. (c) Asymmetric Catalysis in Organic Synthesis; Noyori,
R., Ed; Wiley: New York, 1994. (d) Catalysis in Asymmetric Synthesis;
Ojima, I., Ed.; VCH: New York, 1993.
In this paper we describe the high-yield synthesis of
[Cp*Ru(η6-MeOC6H4(CH2)2COONS)][CF3SO3] (6) as well
as its X-ray molecular structure. Two general synthetic
routes were followed to attain our objective: (a) prepa-
ration of the organometallic carboxylic acid [Cp*Ru(η6-
(6) Grotjahn, D. B.; Groy, T. L. J . Am. Chem. Soc. 1994, 116, 6969.
(7) El Amouri, H.; Gruselle, M.; Vaissermann, J .; McGlinchey, M.
J .; J aouen, G. J . Organomet. Chem. 1995, 485, 79.
(5) Beck, W.; Kramer, R. Angew. Chem., Int. Ed. Engl. 1991, 30,
1467-1469.
S0276-7333(95)00987-3 CCC: $12.00 © 1996 American Chemical Society

2304 Organometallics, Vol. 15, No. 9, 1996
El Amouri et al.
Sch em e 1
Sch em e 2
MeOC6H4(CH2)2COOH][CF3SO3] (3) followed by at-
tempted esterification with N-hydroxysuccinimide in the
presence of dicyclohexyldiimide (DCC); (b) direct com-
plexation of of the succinimidyl ester MeOC6H4(CH2)2-
COONS (5) by Cp*Ru. Method b turned out to be more
convenient to attain our goal.
Sch em e 3
Finally the reactivity of [Cp*Ru(η6-MeOC6H4(CH2)2-
COONS)][CF3SO3] (6) with benzylamine and â-alanine
ethyl ester was investigated and afforded the corre-
sponding stable adducts [Cp*Ru(η6-MeOC6H4CH2CH2-
CONHCH2Ph][CF3SO3] (7) and [Cp*Ru(η6-MeOC6H4-
(CH2)2CONH(CH2)2COOEt][CF3SO3] (8). The stability
and reactivity of 6 was compared to those of the anal-
ogous dicationic iridium derivative [Cp*Ir(η6-MeOC6H4-
(CH2)2COONS)][BF4]2 (10) and the neutral metallocar-
bonyl succinimidyl derivatives [LnMCpCOONS] (12-14)
[LnM ) Fe(CO)2Me, Mo(CO)3Me, Co(CO)2].
Resu lts a n d Discu ssion
and in particular the presence of a singlet at 52.35 ppm
is attributed to the methyl group of the ester function.
Esterification of carboxylic acids by MeOH in the
presence of acidic medium (H+) as catalyst is a well-
known process.11 We feel that the formation of 4 results
from the esterification of the organometallic carboxylic
acid intermediate [Cp*Ru(η6-MeOC6H4(CH2)2COOH]-
[CF3SO3] (3) mediated by the couple [Cp*Ru(µ-OMe)]2/
The organometallic fragment “Cp*Ru” is a very strong
areneophile and often forms compounds which are
stable in the solid state. There are several methods to
introduce a Cp*Ru unit to an arene: (i) Reflux of isolobal
[Cp*Ru(CH3CN)3][CF3SO3] with an arene affords the
desired [Cp*Ru-π-arene][CF3SO3].8 (ii) Reduction of
[Cp*RuCl2]2 with zinc powder followed by addition of
the arene in the presence of KPF6 also gives the
corresponding π-arene complexes of ruthenium(II).9 (iii)
Preparation of [Cp*Ru(µ-OMe)]2 followed by addition of
CF3SO3H in CH2Cl2 in the presence of the arene affords
the Cp*Ru-complexed arenes as shown in (Scheme 1).10
We have found that method iii was the most conve-
nient to prepare our compounds, since this type of arene
possesses functional groups such as an ester, an acti-
vated ester, and carboxylic chains which hydrolyze
easily.
H
+ as a source of MeOH unit and catalyzed by the acidic
medium (CF3SO3H) (see Scheme 3). Another explana-
tion13 could be that several equivalents of MeOH
remained in the crude [Cp*Ru(µ-OMe)]2 (1) obtained
after solvent removal, and this explains the successful
esterification of the carboxylic acid intermediate [Cp*Ru-
(η6-MeOC6H4(CH2)2COOH][CF3SO3] (3).
In order to isolate the organometallic carboxylic acid
intermediate 3, we repeated the previous experiment,
but the reaction mixture was stirred for only 30 min.
Reaction workup afforded a dark brown precipitate
identified as [Cp*Ru(η6-MeOC6H4(CH2)2COOH][CF3-
SO3] (3), while the supernatant phase gave a mixture
of the carboxylic acid adduct 3 and the corresponding
methyl ester derivative [Cp*Ru(η6-MeOC6H4(CH2)2-
COOMe][CF3SO3] (4). The 1H-NMR spectrum of 3
recorded in (CD3)2CO exhibits the usual pair of doublets
for the arene in the area 5.4-6.1 ppm downfield relative
to the free ligand and we also note the presence of a
broad peak at 5.5 ppm attributed to the hydroxyl unit
of the carboxylic function.
(a ) Rea ction of [Cp *Ru (µ-OMe)]2 (1) w ith MeO-
C6H4(CH2)2COOH (2). Treatment of [Cp*Ru(µ-OMe)]2
(1) with 3-(4-methoxyphenyl)propanoic acid (2) in CH2-
Cl2 and in the presence of CF3SO3H for 14 h afforded
unexpectedly the methyl ester adduct [Cp*Ru(η6-
MeOC6H4(CH2)2COOMe][CF3SO3] (4) see Scheme 2.
Complex 4 was identified by spectroscopic methods:
1
The H-NMR spectrum recorded in CD3CN showed the
presence of a pair of doublets for the π-complexed arene
in the range of 5.5-6.0 ppm and a multiplet attributed
to the ethylene chain (-CH2CH2-) at 2.58 ppm. Fur-
ther we note the presence of two singlets at 3.72 and
3.60 ppm attributed to the MeO- groups of the phenyl
and that of the ester function. The 13C-NMR also
confirms the formation of 4 (see Experimental Section),
It has been reported previously that treatment of
[Cp*Ru(µ-OMe)]2 (1) with benzoic acid gave the benzoate
zwitterion species [Cp*Ru(PhCOO)]. When the previous
reaction was repeated in the presence of CF3SO3H, the
corresponding organometallic benzoic acid was obtained
(8) Fagan, P. J .; Ward, M. D.; Calabrese, J . C. J . Am. Chem. Soc.
1989, 111, 1698.
(9) Chaudret, B.; J alon, F. J . Chem. Soc., Chem. Commun. 1989,
711.
(10) Koelle, U.; Kossakowski, J . J . Chem. Soc., Chem. Commun.
1988, 549. Koelle, U.; Wang, M. H.; Raabe, G. Organometallics 1991,
10, 2537-2577.
(11) Vollhardt, K. P. C. Organic Chemistry; W. H. Freeman and
Co.: New York, 1987; pp 751-757.
(12) He, X. D.; Chaudret, B.; Dahan, B.; Huang, Y.-S. Organome-
tallics 1991, 10, 970-979.
(13) We appreciate the insight of a reviewer who pointed this out.

Ru(II) Adducts of Functionalized Arenes
Organometallics, Vol. 15, No. 9, 1996 2305
[Cp*Ru(PhCOOH)][CF3SO3]. These compounds were
identified by spectroscopic methods, and the X-ray
molecular structure of [Cp*Ru(PhCOO)] was reported
and found to be disordered. The disorder in the
structure of the latter was attributed to the presence of
the corresponding methyl ester derivative [Cp*Ru-
(PhCOOMe)][CF3SO3] with an occupancy factor of 30%.
The authors suggested the esterification of the benzoato-
adduct [Cp*Ru(PhCOO)] during the reaction course.12
In order to attain our target compound [Cp*Ru(η6-
MeOC6H4(CH2)2COONS)][CF3SO3] (6) we attempted to
treat the crude mixture of [Cp*Ru(η6-MeOC6H4(CH2)2-
COOH][CF3SO3] (3)/[Cp*Ru(η6-MeOC6H4(CH2)2COOMe]
(4) by N-hydroxysuccinimide (NHS) in the presence of
dicyclohexyldiimide (DCC) in THF for 12 h. Analysis
of the reaction mixture by 1H-NMR suggested the
formation of our desired product but in low yield (10%
by integration) while the major compounds were the
starting materials. Further, we found that separation
of these cationic species is a difficult task and time
consuming, so we decided to attain our target complex
by first preparing the organic N-hydroxysuccinimide
ester species MeOC6H4(CH2)2COONS (5) and then in a
second step to treat it with [Cp*Ru(µ-OMe)]2 (1) in the
presence of CF3SO3H.
F igu r e 3. Molecular structure and atom labeling for
[Cp*Ru(η6-MeOC6H4(CH2)2COONS)][CF3SO3] (6). Selected
bond distances (Å) and angles (deg): Ru-C1 ) 2.215(3),
Ru-C(2) ) 2.191(3), Ru-C3 ) 2.28(3), Ru-C4 ) 2.272(3),
Ru-C5 ) 2.204(3), Ru-C6 ) 2.192(3), Ru-C21 ) 2.190-
(3), Ru-C22 ) 2.179(3), Ru-C22 ) 2.179(3), Ru-C23 )
2.157(3), Ru-C24 ) 2.181(3), Ru-C25 ) 2.201(3), C4-O19
) 1.346(4), O19-C20 ) 1.438(5), C1-C7 ) 1.519(4), C9-
O10 ) 1.188(4); C8-C9-O10 ) 127.6(3), C8-C9-O11 )
111.1(2), O10-C9-O11 ) 121.3(3), C4-O19-C20 ) 116.4-
(3).
Ta ble 1. Exp er im en ta l Deta ils for 6a
(b) Reaction of [Cp*Ru (OMe)]2 (1) with MeOC6H4-
(CH2)2COONS (5). As described previously, MeOC6H4-
(CH2)2COONS (5) was added to a brown solution of
[Cp*Ru(µ-OMe)]2/H+ and the reaction mixture was
stirred for 1 h affording the desired compound [Cp*Ru-
(η6-MeOC6H4(CH2)2COONS)][CF3SO3] (6) in 70% yield.
cryst description
brownish yellow cube;
0.30 × 0.30 × 0.30
Enraf-Nonius CAD4
diffractometer
Lorentz polarization
54.0
instrument
corrs
max 2θ
hkl ranges
h ) -12 to 12
1
k ) 0 to 23
The H-NMR spectrum of 6 showed the expected pair
l ) -19 to 0
of doublets for the π-complexed arene in the range 6-6.2
ppm; we also note the presence of the -CH2CH2- chain
of complex 6 appearing as pair of triplets at 3.10 and
2.80 ppm and two signals at 3.90 and 2.90 ppm at-
tributed to the methoxy group and to the methylene
groups of the N-hydroxysuccinimidyl unit. The 13C-
NMR data also confirmed the formation of the target
compound (see Experimental Section). The infrared
showed three carbonyl absorptions at 1815, 1784, and
1739 cm-1. In order to confirm the structure of the
activated ester complex [Cp*Ru(η6-MeOC6H4CH2CH2-
COONS][CF3SO3] (6) without ambiguity, we carried out
an X-ray structural determination of 6 (see below).
(c) X-r a y Molecu la r Str u ctu r e of [Cp *Ru (η6-Me-
OC6H4CH 2CH 2COONS][CF 3SO3] (6). Crystals of 6
suitable for an X-ray analysis were grown from a CH2-
Cl2/hexane solution. The compound crystallizes in the
monoclinic unit cell P21/c. Figure 3 shows the ORTEP
view of [Cp*Ru(η6-MeOC6H4CH2CH2COONS]+, and crys-
tal data are shown in Table 1. The structure shows that
the organometallic fragment Cp*Ru is coordinated
no. of refls measd
no. of unobsd
refls included
solution
least-squares details
H atoms
6439 tot., 6017 unique
0
2
2
4656 with Fo > 3.0σ(Fo
)
direct methods
included as fixed contributions
to the structure factors
352
0.059
0.095
1.96
params refined
unweighted agreement factor
weighted agreement factor
GOF
convergence, largest shift/error 0.01
minimization function
least-squares weights
w(|Fo| - |Fc|)2, where w )
4F2/σ2(F2)
4Fo2/σ2(Fo2), with σ2(F2) )
σ2(I) + (pF2)2
instrument instability factor, p 0.08
high peak in final diff map
low peak in final diff map
0.31(8) e/Å3
0.00(8) e/Å3
a
X-ray data abstract: C26H30F3NO7RuS, fw ) 658.66; space
group P21/c (No. 14); a ) 9.949(1), b ) 18.442(2), c ) 15.657(2) Å;
â ) 106.19(1)°; V ) 2758.76(92) Å3; Z ) 4; Dcalc ) 1.586 g/cm3;
radiation ) Mo KR (λ ) 0.710 73 Å); µ ) 6.9 cm-1; F(000) ) 1344;
temperature ) -150 ( 0.5 °C; final R ) 0.059; number of observed
reflections ) 4656.
symmetrically to the arene unit with a d(Ru---C1-6
)
93°, while that between the arene C1-6 and the
succinimidyl unit is θ ) 20°. The structure also shows
that the N-succinimidyl unit (-NS) is situated away
from the organometallic fragment; this implies that
there is no steric influence created by the organometallic
entity; hence, we would expect to observe a high
reactivity of complex 6 with respect to amines and
amino esters in view of formation of stable conjugates
with peptide linkage. Finally we are not aware of any
other X-ray structure reported for cationic species
belonging to such a family of organometallic activated-
ester complexes.
average of 2.21 Å. The C9--O10 bond distance is 1.188
Å and is typical of a double bond.14a,15
This bond distance is similar to those carbonyls of the
succinimidyl unit;13a we also note that the C9-O11 bond
distance is 1.367 Å. Furthermore, the angle between
the plane of the succinimidyl unit C13-N12-C16 and
that of the ester defined by O11-C9-O10-C8 is θ )
(14) (a) El Mouatassim, B.; El Amouri, H.; Vaissermann, J .; J aouen,
G. Organometallics 1995, 14, 3296. (b) El Amouri, H.; Besace, Y.;
Vaissermann, J .; J aouen, G. J . Organomet. Chem., in press.
(15) Doney, J . J .; Bergman, R. G.; Heathcock, C. H. J . Am. Chem.
Soc. 1985, 107, 3724.

2306 Organometallics, Vol. 15, No. 9, 1996
El Amouri et al.
Sch em e 4
F igu r e 4.
mentioning that the reaction proceeds slowly and an
average of 12 h was required to attain the conjugate
species, and this should be compared to that of 6 which
needs only 1 h to give the corresponding amide coun-
terpart.
In conclusion we feel that the monocationic ruthenium
derivative exhibits a higher stability relative to the
analogous iridium species, yet this compound is more
reactive than the neutral metallocarbonyl succinimidyl
derivatives of the type [LnMCpCOONS] (12-14) [LnM
) Fe(CO)2Me, Mo(CO)3Me, Co(CO)2]. Efforts are cur-
rently directed toward the study of the reactivity and
selectivity of 6 with peptides possessing several reactive
sites. These investigations will be the subject of future
reports.
(d ) Rea ctivity of 6 w ith Ben zyla m in e a n d â-Ala -
n in e Eth yl Ester . Scheme 4 describes the reaction of
6 with amines and amino esters.
Treatment of 6 with benzylamine for 1 h gave the
stable conjugate adduct [Cp*Ru(η6-MeOC6H4CH2CH2-
CONHCH2Ph][CF3SO3] (7) in quantitative yield. The
1H-NMR spectrum of 7 recorded in CD2Cl2 showed the
expected pair of doublets in the range of 5.5-5.8 ppm;
we also note the presence of a broad peak at 7.32 ppm
attributed to the -NH unit, while the phenyl protons
appear as a multiplet at 7.24 ppm. It is worth mention-
ing that separation of the cationic conjugate adduct 7
from the starting material could be achieved by simple
addition of ether to the reaction mixture, thus affording
7 as a precipitate while the organic reagents remain
soluble in the supernatant phase.
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were carried out
under argon atmosphere using Schlenk techniques. Solvents
were purified and dried prior to use by conventional distillation
techniques. All reagents obtained from commercial sources
were used without further purification. 1H and 13C NMR were
recorded on Bruker AM 250MHz instrument. 1H-NMR chemi-
cal shifts are reported in parts per million referenced to
residual solvent proton resonance. Infrared spectra were
obtained on a FT Bruker IR45 spectrometer from samples
prepared either on KBr disks or in CH2Cl2 solutions. All
absorptions are expressed in wavenumbers (cm-1). Elemental
analyses were performed by the Microanalytical Laboratory
of the CNRS of the University of Paris VI.
In a similar manner when 6 was treated with â-ala-
nine ethyl ester in CH2Cl2 for 1 h the amide counterpart
[Cp*Ru(η6-MeOC6H4(CH2)2CONH(CH2)2COOEt][CF3-
SO3] (8) was obtained quantitatively. The 1H-NMR
spectrum of 8 recorded in CD2Cl2 shows the expected
pair of doublets for the coordinated arene in the range
of 5.5-6.0 ppm and a broad triplet attributed to the
-NH unit of the peptide linkage at 7.0 ppm; all other
signals were assigned without ambiguity (see Experi-
mental Section). At this stage it is worth comparing
the reactivity of the monocationic organoruthenium
complex 6 with that of the analogous bicationic iridium
complex [Cp*Ir(η6-MeOC6H4CH2CH2COONS]2+ (10).
Previously we reported the synthesis of a series of
dicationic iridium complexes of the type [Cp*Ir(η6-
MeOC6H4(CH2)nCOONS]2+ (n ) 1, 2, 3) (9-11) and
found that these complexes decompose during the
reaction course with primary amines and amino esters.7
The instability of these species was attributed to the
presence of the dicationic fragment [Cp*Ir]2+ on the
aromatic ring of the succinimidyl esters 9-11, which
weakens the “CH2-COO” bond of the ester unit and
facilitates its cleavage, affording several side products
in their reactions with amino substrates. On the other
hand, we have found that the neutral succinimidyl
derivatives of the type [LnMCpCOONS] (12-14) [LnM
) Fe(CO)2Me, Mo(CO)3Me, Co(CO)2] (Figure 4) react
with amino substrates to give the conjugate products
which possess the primary amide linkage.14 It is worth
Syn t h esis of [Cp *R u (η6-MeOC6H 4CH 2CH 2COOH ]-
[CF 3SO3] (3). This compound was prepared in a similar way
to that of 4 (see below), but the reaction mixture was stirred
for only 30 min and using the following reagents and quanti-
ties: [Cp*RuCl2]2 (0.2 g, 0.32 mmol), K2CO3 (0.6 g, 4.28 mmol),
triflouromethanesulfonic acid (80 µL, 0.70 mmol), and MeOC6H4-
CH2CH2COOH (2) (180 mg, 1.0 mmol). Compound 3 was
obtained as a dark brown precipitate by addition of Et2O (30
mL) to the solution mixture, while the supernatant phase gave
a mixture of 3 and 4 in a ratio of 1/1 (54 mg).
Total yield for 3: 134 mg, 50%. IR (ν/cm-1) (KBr): -OH,
3458, CdO, 1733. 1H NMR (CD3CN): δ 5.95 (d, 2H, aromatic),
5.85 (d, 2H, aromatic), 5.45 (b, 1H, -COOH), 3.75 (s, 3H,
-MeO), 2.55 (m, 4H, -CH2CH2-), 1.90 (s, 15H, -Cp*). 13C
NMR (CD3)2CO): δ, 173.13 (COO), 133.16 (Cipso), 122.10 (CF3,
1
q, J CF ) 320.6 Hz), 101.19 (Cipso), 96.30 (-Cp*, -CdC-),
87.73, 76.63 (aromatics, -CdC-), 57.33 (MeO-), 35.39 (-CH2-
), 28.03 (-CH2-), 10.39 (Cp*, Me-). An analysis could not
be obtained for this compound, since it hydrolyzes rapidly
when exposed to air and becomes gummy.
Syn t h esis of [Cp *R u (η6-MeOC6H 4CH 2CH 2COOMe]-
[CF 3SO3] (4). The general procedure for the preparation of
these Cp*Ru π-adducts is as follows: K2CO3 (0.6 g, 4.28 mmol)
was added to a solution of [Cp*RuCl2]2 (0.5 g, 0.817 mmol) in
MeOH (20 mL), and the mixture was refluxed for 1 h under
argon. The suspension becomes deep red, and then the solvent
was removed under vacuum, 30 mL of CH2Cl2 was added, and
the mixture was filtered with care. A total of 300 µL (3.4
mmol) of triflouromethanesulfonic acid was added to the deep
red sensitive solution of [Cp*Ru(µ-OMe)]2 (1), which changes
rapidly to brown yellow. The mixture was stirred for 15 min,

Ru(II) Adducts of Functionalized Arenes
Organometallics, Vol. 15, No. 9, 1996 2307
and then a CH2Cl2 solution of 3-(4-methoxyphenyl)propionic
acid (400 mg, 2.22 mmol) was added and the reaction mixture
stirred for 14 h. The solution was concentrated under vacuum,
and 30 mL of Et2O was added affording a brown precipitate.
The supernatant phase was removed, and the precipitate was
washed with Et2O several times, recrystallized from CH2Cl2/
Et2O, and dried under vacuum. Yield: 350 mg, 70%.
was added to a warm THF solution (20 mL) of â-alanine ethyl
ester‚HCl (85 mg, 0.45 mmol) to give a white precipitate
(NEt3‚HCl). The mother liquor was filtered and then added
dropwise to a CH2Cl2 solution (20 mL) of 6 (70 mg, 0.1 mmol).
The reaction mixture was stirred for 1 h. The solvent was
reduced under vacuum, and then Et2O (30 mL) was added to
give an oil-like precipitate. This compound was washed
several times with Et2O and then dried under vacuum.
Yield: 65 mg, 93%. IR (ν/cm-1) (KBr): -OH, 3500; -CdO
ester, 1733; -CdO amide, 1680; CF3SO3, 1030, 638. 1H NMR
(CD2Cl2): δ 7.00 (t, 1H, -NH), 5.73 (d, 2H, arene), 5.64 (d,
2H, arene), 4.09 (m, 2H, -COOCH2-), 3.40 (m, 2H, -CONCH2-
), 2.48 (t, 2H, -CONCCH2-), 1.91 (s, 15H, -Cp*), 1.24 (t, 3H,
-COOCCH3). 13C NMR (CD2Cl2): δ 171.55 (CON), 170.65
IR (ν/cm-1) (KBr): CdO, 1740; CF3SO3, 1025, 640. 1H NMR
(CD3CN): δ 5.73 (d, 2H, aromatic), 5.66 (d, 2H, aromatic), 3.72
(s, 3H, -MeO), 3.60 (s, 3H, COOMe), 2.58 (m, 4H, -CH2CH2-
), 1.89 (s, 15H, Me-Cp). 13C NMR (CD3CN): δ 173.24 (CdO),
133.11 (Cipso), 100.89 (Cipso), 96.59 (Cp*, -CdC-), 87.52
(aromatics, CdC), 76.53 (aromatics, CdC), 57.63 (MeO-),
52.34 (COOMe), 35.64 (-CH2-), 28.11 (-CH2-), 10.60 (Cp*,
Me-). An analysis could not be obtained for this compound,
since it hydrolyzes rapidly when exposed to air and becomes
gummy.
1
(COO), 131.51 (Cipso), 120.34 (CF3, q, J CF ) 320.2 Hz), 99.97
(Cipso), 95.17 (-Cp*, -CdC-), 86.337 (aromatics, -CdC-),
75.26 (aromatics, -CdC-), 60.15 (COOCH2-), 56.31 (MeO-
), 36.69 (-CH2CONH), 34.78 (-CH2COO), 31.20 (-CH2), 27.87
(-CH2), 13.57 (CH3-), 9.91 (Cp*, Me-).
Syn t h esis of [Cp *R u (η6-MeOC6H 4CH 2CH 2COONS]-
[CF 3SO3] (6). This compound was prepared in a similar way
to that of 4 but using the following reagents and quantities:
0.1 g, 0.16 mmol, of [Cp*RuCl2]2, 0.3 g, 0.490 mmol, of K2CO3,
40 mL, 0.35 mmol, of triflouromethanesulfonic acid, and 100
mg, 0.35 mmol, of MeOC6H4CH2CH2COONS (5). Yield: 150
mg, 70%. IR (ν/cm-1) (KBr): -OH, 3509; CdO, 1815, 1784,
1739; CF3SO3, 1031, 638. 1H NMR (CD3)2CO): δ 6.10 (d, 2H,
aromatic), 6.05 (d, 2H, aromatic), 3.90(s, 3H, -MeO), 3.05 (t,
2H, -CH2-), 2.90 (s, 4H, -CH2-, -NS), -CH2 signal obscured
by residual H2O in (CD3)2CO, 2.01 (s, 15H, -Cp*) 13C NMR
(CD2Cl2): δ 168.72 (CON), 167.09 (COO), 131.99 (Cipso), 97.75
(Cipso), 95.59 (-Cp*, -CdC-), 86.33 (aromatics, -CdC-),
56.57 (MeO-), 32.17 (-CH2-), 27.17 (-CH2-), 25.25 (-NS),
9.91 (Cp*, Me-). Anal. Calcd for C25H30O8NF3SRu‚CH2Cl2:
C, 41.76; H, 4.28; N, 1.87. Found: C, 38.81; H, 4.20; N, 1.76.
Syn th esis of [Cp*Ru (η6-MeOC6H4CH2CH2CONHCH2P h ]-
[CF 3SO3] (7). A 40 µL (0.192 mmol) amount of benzylamine
was added to a CH2Cl2 solution (20 mL) of 6, and the reaction
mixture turned rapidly to deep orange. The mixture was
stirred for 1 h and 45 min, and then the solution was
concentrated under vacuum to 1 mL. Addition of Et2O (30 mL)
afforded a brown precipitate, which was filtered off and washed
several times with ether and then dried under vacuum.
Yield: 45 mg, 90%. IR (ν/cm-1) (KBr): -OH, 3432; CdO, 1680;
CF3SO3, 1030, 638. 1H NMR (CD2Cl2): δ 7.32 (b, 1H, -NH),
7.23 (m, 5H, aromatics), 5.68 (d, 2H, aromatics), 5.54 (d, 2H,
aromatics), 4.30 (d, 2H, -CH2-), 3.73 (s, 3H, -MeO), 2.57 (s,
4H, -CH2CH2-). Anal. Calcd for C28H34O5NF3SRu‚3H2O: C,
47.45; H, 5.65. Found: C, 47.34; H, 5.34.
Str u ctu r a l Deter m in a tion of [Cp *Ru (η6-MeOC6H4CH2-
CH2COONS][CF 3SO3] (6). Single crystals were grown from
a CH2Cl2/hexane solution using the slow diffusion method.
Data were collected at -150 ( 0.5 °C on an Enraf Nonius
CAD4 diffractometer using Mo KR radiation (λ ) 0.710 73 Å)
and a graphite monochromator . The crystal structure was
solved and refined using the Enraf Nonius MOLEN package.
The compound crystallizes in space group P21/c (No. 14), with
a ) 9.949(1) Å, b ) 18.442(2) Å, c ) 15.657(2) Å, â ) 106.19-
(1)°, V ) 2758.76(92) Å3, Z ) 4, dcalc ) 1.586 g/cm3, µ ) 6.9
cm-1, and F(000) ) 1344. A total of 6439 unique reflections
were recorded in the range 2° e 2θ e 54.0° of which 1783 were
considered as unobserved (F2 < 3.0σ(F2)), leaving 4656 for
solution and refinement. Direct methods yielded a solution
for all atoms. The hydrogen atoms were included as fixed
contributions in the final stages of least-squares refinement
while using anisotropic temperature factors for all other atoms.
A non-Poisson weighting scheme was applied with a p factor
equal to 0.08. The final agreement factors were R ) 0.059,
Rw ) 0.095, and GOF ) 1.96.
Ack n ow led gm en t. We thank the CNRS for sup-
porting this work.
Su p p or tin g In for m a tion Ava ila ble: Tables S1-S4, list-
ing bond lengths and angles, atomic coordinates and B values,
and anisotropic displacement coefficients (4 pages). Ordering
information is given on any current masthead page.
Syn th esis of [Cp *Ru (η6-MeOC6H4(CH2)2CONH(CH2)2-
COOEt][CF 3SO3] (8). A 50 µL (0.45 mmol) amount of NEt3
OM950987R