Synthesis of enantiopure planar-chiral cyclopentadienyl-ruthenium binuclear complexes bridged by aromatic systems

Article abstract of DOI:10.1039/b107051g

Planar-chiral trisubstituted cyclopentadienyl-ruthenium binuclear complexes [(Cp³Ru)₂(μ-η⁶,η⁶- arene)][PF₆]₂ (Cp³ = (R_C1)- or (S_C1)-l-PrⁱNHCO-2,4

Full text of DOI:10.1039/b107051g

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Synthesis of enantiopure planar-chiral cyclopentadienyl-ruthenium
binuclear complexes bridged by aromatic systems†
Mari Yamamoto, Kiyotaka Onitsuka, Mitsunari Uno and Shigetoshi Takahashi*
The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047,
Japan
Received 3rd August 2001, Accepted 17th December 2001
First published as an Advance Article on the web 1st March 2002
Planar-chiral trisubstituted cyclopentadienyl-ruthenium binuclear complexes [(Cp3Ru)2(µ-η6,η6-arene)][PF6]2
(Cp3 = (RC1)- or (SC1)-1-PriNHCO-2,4-Me2C5H2) bridged by aromatic π-ligands such as biphenyl b, triphenylene c,
diphenylmethane d, and 9,10-dihydroanthracene e were synthesized and isolated in an enantiomerically pure form.
The molecular structures of (SC1)-[Cp3Ru(η6-biphenyl)][PF6] (S)-1b(Cp3), [{(SC1)-Cp3Ru}2(η6,η6-biphenyl)][PF6]2
(R,R)-3b(Cp3), and [Cp3Ru(η6-triphenylene)][PF6] 1c(Cp3) were established by X-ray crystallography. These
complexes were characterized by optical and electrochemical analyses.
Table 1 Abbreviations of cyclopentadienyl ligands
Introduction
Multinuclear transition metal complexes linked by π-electron
conjugation have attracted considerable interest due to their
potential applications in electronic, magnetic, and optical
Cpn
R1
R2
R3
materials. In particular, multinuclear polymetallocenes bridged
by π-aromatic systems have been extensively studied with
regard to molecular electronics due to communication among
the metals through π-electron conjugation.1,2 If these complexes
are optically active, unusual electronic, magnetic, and optical
properties might be expected, and helical-chiral metallocene
oligomers have already been studied in terms of such character-
istics.3 Although there have been several reports on multi-
nuclear π-polyarene complexes,1,2,4–6 there are relatively few
reports on optically active forms.7
Cp1
Cp2
Cp3
Cp4
CH3
CH3
CH3
H
CH3
CH3
CH3
H
CO2(l )-menthyl
CO2C2H5
CONHiPr
CO2CH3
Results and discussion
Synthesis of enantiopure planar-chiral [bis(ꢀ5-cyclopenta-
dienylruthenium)](ꢁ-ꢂ-polyarene) complexes
Recently, we reported a new method for the synthesis of
enantiopure planar-chiral cyclopentadienyl-ruthenium com-
plexes by using a trisubstituted cyclopentadiene (Cp1H, Table 1)
For the synthesis of planar-chiral bis(cyclopentadienylruthen-
ium)(polyarene) complexes, we initially chose biphenyl as a
bridging π-aromatic ligand. There may be two routes, direct
(A) and stepwise (B), to [bis(η5-cyclopentadienylruthenium)]-
µ-biphenyl complex 3b (Scheme 3). We first examined the direct
route, and a preliminary experiment using a racemic mixture of
[Cp2Ru(AN)3][PF6] 2 (Cp2, see Table 1) showed that stepwise
route B is preferable with respect to the yield of 3b, since 2 is
not very stable in refluxing dichloroethane and considerable
decomposition of 2 was observed during the reaction. There-
fore, we adopted the stepwise reaction for the synthesis of
optically active planar-chiral [bis(η5-cyclopentadienylruthen-
ium)-µ-biphenyl][PF6]2 complexes 3b. Thus, a racemic mixture
of [Cp2Ru(C6H6)][PF6] 1a(Cp2) was converted to 2(Cp2) by
photolysis in acetonitrile, followed by treatment with an
equiamount of biphenyl in dichloromethane at 40 ЊC for 3 h
to give planar-chiral mononuclear complex [Cp2Ru(η6-C6H5-
C6H5)] 1b(Cp2) in good yield. When complex 1b(Cp2) was again
reacted with tris(acetonitrile) complex 2(Cp2) in 1,2-dichloro-
ethane under reflux, biphenyl-bridging binuclear complex
3b(Cp2) was obtained as a pale yellow powder in 81% yield.
Using this method, we attempted to prepare an optically pure
planar-chiral analog of 3b (Scheme 4). Thus, [(SC1)-Cp1Ru-
(C6H6)][PF6] (S)-1a(Cp1) was converted to tris(acetonitrile)
complex 2, which was reacted with an equiamount of biphenyl
with a removable chiral auxiliary, an (l )-menthyl group.8,9
A
usual reaction of Cp1Na with a ruthenium source gives a mix-
ture of diastereomers 1a(Cp1), which can also be obtained from
an ester exchange reaction between [Cp2Ru(C6H6)][PF6] and
(l )-menthol9 (Scheme 1). The diastereomers (S)-1a and (R)-1a
are separated by fractional recrystallization. (η5-Cyclopenta-
dienyl)(η6-benzene)ruthenium complexes 1a are readily con-
verted to tris(acetonitrile) complexes, [Cp1Ru(CH3CN)3][PF6] 2,
by a photoreaction with acetonitrile, which is a useful precursor
for a CpRu moiety. Complexes 2 can easily be re-converted to
π-arene complexes 1 by treatment with arenes10,11 (Scheme 2).
Thus, the photoreaction of diastereopure (S)-1a(Cp1) in
acetonitrile, followed by ligand exchange with benzene again
gave (η5-Cp1)(η6-benzene)ruthenium without any detectable
change in optical purity, indicating that racemization of the
Cp1-Ru moiety is not involved in the photoreaction.9 We
applied this transformation to the synthesis of enantiopure
planar-chiral cyclopentadienyl bi-ruthenium complexes bridged
by polyaromatic π-ligands such as biphenyl and triphenylene.
† Electronic supplementary information (ESI) available: physical and
spectral data of enantiopure mononuclear and binuclear complexes.
See http://www.rsc.org/suppdata/dt/bl/b107051g/
DOI: 10.1039/b107051g
J. Chem. Soc., Dalton Trans., 2002, 1473–1478
This journal is © The Royal Society of Chemistry 2002
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Scheme 1 Synthesis of diastereomers. Reagents: i, [Ru(C6H6)Cl2]2; ii, (1) hydrolysis, (2) (COCl)2, (3) (l )-menthol; iii, fractional recrystallization.
Scheme 2 Arene ligand-exchange reaction.
Scheme 3 Syntheses of binuclear complex 3b. Reagents: i, 1/2 biphenyl;
ii, biphenyl; iii, 2(Cp2).
in dichloromethane under reflux for 3 h to give planar-chiral
mononuclear complex [(SC1)-Cp1Ru(η6-C6H5-C6H5)] (S)-1b-
(Cp1) in 87% yield. To synthesize a planar-chiral binuclear
complex bridged by a biphenyl ligand according to Route B-1 in
Scheme 4, mononuclear complex (S)-1b(Cp1) was treated with
tris(acetonitrile) complex (S)-2(Cp1) in refluxing 1,2-dichloro-
ethane. However, the formation of binuclear complex 3b(Cp1)
was not observed, probably due to the steric effect of a sterically
large menthyl group, since an X-ray structural analysis12 of a
Cp1Co complex showed that the menthyl group lies perpendic-
ular to the Cp ring. Therefore, we chose another synthetic route,
Route B-2 (Scheme 4), in which enantiopure complex 1a(Cp3)
with a smaller substituent is used as a starting material. Enantio-
pure [(SC1)-Cp3Ru(C6H6)][PF6] (S)-1a(Cp3), which has a trisub-
stituted cyclopentadienyl ligand bearing an isopropylamide
group and is easily prepared from (S)-1a(Cp1),9 was converted
to [Cp3Ru(CH3CN)3][PF6] (S)-2(Cp3) by a photoreaction in
CH3CN, followed by a reaction with excess biphenyl (b) in
dichloromethane under reflux for 3 h to afford mononuclear
complex [Cp3Ru(η6-C6H5-C6H5)][PF6] (S)-1b(Cp3) in 84%
yield. In the 1H and 13C NMR spectra, signals due to the
hydrogens and carbons of a phenyl group coordinating to a
Ru atom showed an upfield shift relative to those of the non-
coordinating ring,5 indicating hexahapto coordination of the
biphenyl ligand to the ruthenium atom (Experimental sec-
tion). Mononuclear complex (S)-1b(Cp3) further reacted with
(S)-2(Cp3) in 1,2-dichloroethane under reflux to afford a
C2-symmetric binuclear complex [{(SC1)-Cp3Ru}2(µ-η6,η6-
Scheme 4 Syntheses of enantiopure planar-chiral complexes.
biphenyl)][PF6]2 (S,S)-3b(Cp3) in 73% yield. Reflecting the C2
symmetry of the molecule, the Cp3Ru(η6-C6H5-) units were
equivalent with regard to both 1H and 13C{1H} NMR spectra.
Optically pure (R)-isomers [(RC1)-Cp3Ru(η6-biphenyl)][PF6]
(R)-1b(Cp3) and [{(RC1)-Cp3Ru}2(µ-η6,η6-biphenyl)][PF6]2
(R,R)-3b(Cp3) were similarly prepared from [(SC1)-Cp3Ru-
(η6-benzene)][PF6] (R)-1a(Cp3).9 Binuclear complex [{(SC1)-
Cp3Ru:(RC1)-Cp3Ru}(µ-η6,η6-biphenyl)][PF6]2 (R,S)-3b(Cp3)
was also prepared by reacting (R)-1b(Cp3) with (S)-2(Cp3).
These optically active complexes were identified by usual ana-
lyses including optical rotations and circular dichroism (CD)
spectra. Planar-chiral mono-ruthenium complexes (R)-1b(Cp3)
and (S)-1b(Cp3) showed the same melting point and absolute
value of [α]D (Table 2). The CD spectrum of (R)-1b(Cp3) is the
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Table 2 Physical data of enantiomers
Complex
Yield (%)a
mp/ЊC
[α]2D5/deg
(in CH3CN)b
(R)-1b(Cp3)
(S)-1b(Cp3)
(R,R)-3b(Cp3)
(S,S)-3b(Cp3)
(S,R)-3b(Cp3)
(S)-1c(Cp3)
90
84
94
73
95
83
79
73
99
69
94
141.5–142.0
141.5–142.0
218.5–219.0c
217.5–218.5c
255.0–255.5c
251.0–251.5c
218.8–219.8c
170.2–170.7
109.0–110.0
155.2–155.7
244.0–244.5c
Ϫ59.3
ϩ59.3
Ϫ40.8
ϩ39.9
0
ϩ117.4
ϩ94.5
ϩ40.5
ϩ39.5
ϩ38.7
ϩ43.7
(c 0.497)
(c 0.500)
(c 0.500)
(c 0.517)
(c 0.507)
(c 0.499)
(c 0.504)
(c 0.478)
(c 0.504)
(c 0.499)
(c 0.503)
(S,S)-3c(Cp3)
(S)-1d(Cp3)
(S,S)-3d(Cp3)
(S)-1e(Cp3)
(S,S)-3e(Cp3)
a Based on 2(Cp3) used. b c/g per 100 ml. c Decomposition.
Scheme 5 Synthesis of mono- and binuclear complexes linked by polyaromatics.
mirror-image of that of (S)-1b(Cp3) (Fig. 1a). A similar relation-
pentadienylruthenium moiety. Similarly, the reaction of tri-
ship was observed between the spectra of (R,R)-3b(Cp3) and
(S,S)-3b(Cp3) (Fig. 1b), indicating that (R)-1b(Cp3) and (S)-
1b(Cp3) as well as (R,R)-3b(Cp3) and (S,S)-3b(Cp3) are pairs of
enantiomers. Meso isomer (R,S)-3b(Cp3) had an [α]D of almost
zero and no Cotton effect in the CD spectrum, as expected
(Fig. 1b).
phenylene (c) with excess (S)-2(Cp3) gave binuclear complex
(S,S)-3c(Cp3). The binuclear complex bridged by triphenylene
should be obtained as a mixture of diastereomers (Fig. 2).
Fig. 2 A diastereomeric pair of (S,S)-3c(Cp3).
1
Actually, the H NMR spectrum suggested that the resulting
product was a 1 : 1 mixture of diastereomers, which could not
be separated. There is still one free benzene ring in 3c(Cp3),
and we tried to react the third moiety of CpRuϩ, but failed,
probably due to steric hindrance. These results suggest that two
moieties of Cp3Ru are unable to combine simultaneously with a
π-system on the same side of a triphenylene ligand.
The planar-chiral complexes synthesized in the present study
were characterized by usual analyses (Experimental section),
and some were examined by X-ray crystallography.
Fig. 1 (a) CD Spectra of (R)- and (S)-1b(Cp3). (b) CD Spectra of
(R,R)-, (S,S)- and (R,S)-3b(Cp3).
Several binuclear complexes 3c–e, in which planar-chiral
Cp–Ru moieties are linked by polyaromatic π-ligands, such
as triphenylene (c), diphenylmethane (d), and 9,10-dihydro-
anthracene (e), were also synthesized in a similar manner
(Scheme 5). Isolated yields are summarized in Table 2 along
with [α]D values and melting or decomposition points. The reac-
tion of dihydroanthracene (e) with (S)-2(Cp3) in a molar ratio
of 1 : 2 yielded binuclear complex (S,S)-3e(Cp3) as a sole pro-
duct, while its isomer (S,S)-3eЈ(Cp3) was not observed,
probably due to steric constraints imposed by the large cyclo-
Molecular structures of (S)-1b(Cp3), (R,R)-3b(Cp3), and 1c(Cp3)
Recrystallization of (S)-1b(Cp3) and (R,R)-3b(Cp3) from a
mixture of ethanol, acetonitrile and ether gave single crystals
suitable for X-ray analysis. Single crystals of 1c(Cp3) were
obtained by recrystallization from a racemic mixture, but not
J. Chem. Soc., Dalton Trans., 2002, 1473–1478
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Fig. 3 Molecular structure of (S)-1b(Cp3); all hydrogen atoms and the
PF6 anion have been omitted for clarity (as in all the present structures).
from the enantiomers. The molecular structure of (S)-1b(Cp3)
is illustrated in Fig. 3. The Cp3 and η6-phenyl rings, which are
bonded to a Ru atom, are nearly parallel to one another
(dihedral angle, 1.4Њ). The two phenyl rings of biphenyl are
twisted relative to each other by 18.1Њ. The amide group is
almost coplanar with the Cp3 ring (dihedral angle, 0.8Њ). The
bond distances and angles of Cp–Ru as well as C6H5-Ru are
within normal ranges.5,6
Fig. 5 Molecular structure of 1c(Cp3).
tials of the complexes by cyclic voltammetry (CV). Both the
mono- and binuclear complexes underwent reduction in
acetonitrile at a Pt electrode. The potentials of the complexes
with reference to an internal ferrocene standard are listed in
Table 4. To compare the effects of substituents on the cyclo-
pentadienyl ligand, we also prepared mononuclear complexes
[Cp4Ru(η6-biphenyl)][PF6] (Cp4 = C5H4CO2Me) 1b(Cp4) and
[(C5H5)Ru(η6-biphenyl)][PF6] 1b(C5H5), and binuclear com-
plexes [(Cp4Ru)2(µ-biphenyl)][PF6]2 3b(Cp4) and [{(C5H5)Ru}2-
(µ-biphenyl)][PF6]2 3b(C5H5), and then recorded their CVs. The
potentials of complexes 1b and 3b should reflect the electronic
effects of the cyclopentadienyl ligand on the central metal. In
fact, reversible or irreversible reduction was observed for these
complexes, and the reduction potentials of trisubstituted
cyclopentadienyl complexes 1b as well as 3b bearing an ester
or an amide group on the cyclopentadienyl ligand were more
positive than those of non-substituted cyclopentadienyl com-
plexes 1b(C5H5) and 3b(C5H5). As expected, the most positive
potential was observed for 1b(Cp4) as well as 3b(Cp4), which
only has an electron-withdrawing ester group on the cyclo-
pentadienyl ligand. The general pattern of voltammograms
consists of one irreversible reduction peak for mononuclear
complexes 1b containing an η6-biphenyl ligand, as reported for
a (C5Me5)Ru analog.13 In contrast to the case of mononuclear
complexes 1b, a characteristic feature of voltammograms of bi-
The molecular structure of (R,R)-3b(Cp3) is depicted in
Fig. 4. The bond distances and angles found in (R,R)-3b-
nuclear complexes 3b is the single reversible wave found at E1/2
=
Ϫ1.06 to Ϫ1.25 V vs. SCE. Compared with the corresponding
binuclear iron complexes,14 ruthenium complexes 3b showed a
different behavior and did not show a second wave up to a
potential of Ϫ2.5 V. Comparison of the peak height of 3b with
that of ferrocene used as an internal reference at the same con-
centration showed that the waves of 3b correspond to a one-
electron process. This is in contrast to a binuclear (C5Me5)Ru
analog which reportedly undergoes irreversible one-electron
reduction.13 Binuclear 3b shows more positive reduction poten-
tial than mononuclear 1b, suggesting that there is some
interaction between the two ruthenium centers bridged by a
biphenyl ligand in 3b. We also recorded the CV of mono-
and binuclear triphenylene complexes. Mononuclear complex
1c(Cp3) showed one reversible wave, whereas binuclear 3c(Cp3)
showed two reversible waves. A similar phenomenon has been
reported for (C5Me5)Ru analogs with condensed-ring com-
pounds such as triphenylene and anthracene.15
Fig. 4 Molecular structure of (R,R)-3b(Cp3).
(Cp3) are similar to those reported for [(CpRu)4(η6,η6,η6,η6-
quaterphenyl)][PF6]4.5 The Cp3 and η6-phenyl rings are nearly
parallel to one another (dihedral angles, 2.2Њ and 1.1Њ) and the
torsion angle between the two phenyl rings of biphenyl is 14.4Њ.
The molecular structure of 1c(Cp3) is shown in Fig. 5. The
dihedral angle between the Cp3 ring and C6 ring 1 bonded to a
Ru atom is 4.9Њ, which is slightly larger than that of (S)-1b(Cp3)
or (R,R)-3b(Cp3). C6 ring 2 bends to the opposite side of the
Cp3 ring to avoid steric repulsion by the isopropyl group
(dihedral angle between rings 1 and 2, 11.1Њ). On the other
hand, ring 3 bends in the direction of the Cp3 ring to maintain
the aromaticity of triphenylene (dihedral angle between rings 1
and 3, 6.9Њ). Crystal data are given in Table 3.
Electrochemistry
Experimental
To evaluate the electronic effect of trisubstituted cyclopenta-
dienyl ligands on the ruthenium center and to determine
whether there is communication between two ruthenium cen-
ters bridged by a π-aromatic ligand, we measured redox poten-
General
All reactions except hydrolysis were performed under an
atmosphere of argon. 1H and 13C NMR spectra were measured
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Table 3 Crystal and refinement data for (S)-1b(Cp3), (R,R)-3b(Cp3), and 1c(Cp3)
Complex
(S)-1b(Cp3)ؒEtOH
(R,R)-3b(Cp3)
1c(Cp3)
Chemical formula
M
Crystal system
Space group
a/Å
b/Å
c/Å
C25H32NO2RuPF6
624.57
C34H42N2O2Ru2P2F12
1002.79
Triclinic
P1 (no. 1)
10.576(2)
11.833(3)
8.557(3)
92.90(3)
112.03(2)
76.36(2)
963.8(5)
1
C29H28NORuPF6
652.58
Triclinic
P1 (no. 1)
8.331(3)
9.722(3)
8.317(2)
95.87(2)
99.12(2)
74.53(3)
639.7(4)
1
Triclinic
¯
P1 (no. 2)
12.050(2)
12.101(3)
10.445(2)
111.74(2)
103.61(2)
72.34(2)
1335.0(6)
2
α/deg
β/deg
γ/deg
V/Å3
Z value
µ/cmϪ1
7.43
9.59
7.14
Total data collected
Unique data
3155
2953
(Rint = 0.025)
2951
4677
4437
(Rint = 0.024)
3949
6419
6129
(Rint = 0.021)
5250
Observed data
(I > 3σ(I ))
0.016
0.021
(I > 3σ(I ))
0.030
0.035
(I > 3σ(I ))
0.057
0.088
R
Rw
GOF
1.05
1.08
1.25
Table 4 Electrochemical dataa
b
[compound]nϩ
Epc
Epa
E1/2
Cp4Ru(η6-biphenyl)
1b(Cp4)
Ϫ1.56
Ϫ1.65
Ϫ1.75
Ϫ1.80
Ϫ1.08
Ϫ1.16
Ϫ1.34
Ϫ1.30
Ϫ1.54
Ϫ1.31
Ϫ1.86
Cp2Ru(η6-biphenyl)
1b(Cp2)
1b(Cp3)
1b(C5H5)
3b(Cp4)
3b(Cp2)
3b(Cp3)
3b(C5H5)
1c(Cp3)
3c(Cp3)
Cp3Ru(η6-biphenyl)
(C5H5)Ru(η6-biphenyl)
(Cp4Ru)2(η6,η6-biphenyl)
(Cp2Ru)2(η6,η6-biphenyl)
(Cp3Ru)2(η6,η6-biphenyl)
(C5H5Ru)2(η6,η6-biphenyl)
Cp3Ru(η6-triphenylene)
(Cp3Ru)2(η6,η6-triphenylene)
Ϫ1.03
Ϫ1.12
Ϫ1.10
Ϫ1.20
Ϫ1.30
Ϫ1.22
Ϫ1.63
Ϫ1.06
Ϫ1.14
Ϫ1.22
Ϫ1.25
Ϫ1.42
Ϫ1.27
Ϫ1.75c
a Measured in acetonitrile solution of 0.1 M n-Bu4NClO4 at room temperature at a scan rate of 200 mV sϪ1 b E1/2 = (Epa ϩ Epc)/2, where Epa and Epc
.
are anodic and cathodic peak potentials in V, respectively, and are referred to SCE based on a simultaneous measurment of the ferrocene redox
potential (0.40 V). c Second wave.
in d6-acetone on a JEOL JNM LA-400 (400 MHz) or
BRUKER ARX-400 (400 MHz). IR spectra were recorded on
a Perkin–Elmer System 2000 FT-IR. Mass spectrometry was
performed with a Shimadzu GCMS-QP-2000 spectrometer.
Optical rotation was measured on a JASCO DIP-1000 digital
polarimeter and circular dichroism spectra were taken on a
JASCO circular dichroism J-725. Cyclic voltammograms were
recorded on a BAS 100B/W (CV-50). CV cells were fitted with
Pt working electrodes, Pt wire counter electrodes, and Ag/
Agϩ reference electrodes. Unless stated otherwise, commercial-
grade chemicals were used without further purification.
Trisubstituted cyclopentadienyl-ruthenium complexes (R)-1a-
(Cp1), (S)-1a(Cp1), and 1a(Cp2) were prepared as reported
elsewhere.9
were then added to the suspension. The mixture was vigorously
stirred for 6 h at room temperature to give the correspond-
ing acid chloride. After the removal of dichloromethane and
excess oxaryl chloride under reduced pressure, the resulting
solid was dissolved in 10 ml of acetonitrile. The solution was
added dropwise to a solution of isopropylamine (35.2 mmol)
and a small amount of 4-dimethylaminopyridine in aceto-
nitrile (60 ml). The mixture was stirred at room temperature
overnight and the solvent was removed under reduced pressure.
The crude product was suspended in water, and ammonium
hexafluorophosphate (1.15 g, 7.04 mmol) was added. The
mixture was extracted with dichloromethane and the extract
was dried over anhydrous sodium sulfate and passed through
an alumina column. Purification by recrystallization from
ethanol gave [(SC1)-{η5-1-isopropylaminocarbonyl-2,4-di-
methylcyclopentadienyl}(η6-benzene)ruthenium](hexafluoro-
phosphate) (S)-1a(Cp3) as pale yellow needles (1.25 g, 71%).
mp 207.0–207.5 ЊC. (Found: C, 40.81; H, 4.14; N, 2.86; F,
22.87; P, 6.03. C17H22F6NOPRu requires C, 40.64; H, 4.41; N,
2.79; F, 22.69; P, 6.17%); νmax/cmϪ1 (C᎐O), 1666 (KBr); δ
Preparation of enantiopure mononuclear complexes
(S)-1a(Cp3).
[(SC1)-(η5-1-(l )-Menthyloxycarbonyl-2,4-di-
methylcyclopentadienyl)(η6-benzene)ruthenium](hexafluoro-
phosphate) (S)-1a(Cp1) (2.11 g, 3.52 mmol) was heated under
reflux in a mixture of acetonitrile (50 ml) and water (50 ml)
saturated with Na2CO3. After continuous stirring for 8 h,
the reaction mixture was neutralized with 6M HCl and then
evaporated to dryness. The residue was extracted with aceto-
nitrile and the solution was dried over anhydrous sodium
sulfate. Evaporation of the solvent from the resulting solu-
tion gave a carboxylic acid derivative as pale yellow solids.
The carboxylic acid was suspended in 60 ml of dichloro-
methane, and a few drops of DMF and oxaryl chloride (1 ml)
᎐
H
(acetone-d6) 7.26(1 H, br, NH), 6.27(6 H, s, η6-C6H6), 5.88(1 H,
s, Cp–H), 5.63(1 H, s, Cp–H), 4.15–4.05(1 H, m, CH(CH3)2),
2.27(3 H, s, Cp–CH3), 2.04(3 H, s, Cp–CH3), 1.20(3 H, d,J =
6.6 Hz, CH(CH3)) and 1.16(3 H, d, J = 6.6 Hz, CH(CH3));
δ (acetone-d ) 163.4(s, C᎐O), 100.7(s, Cp–CH ), 99.3(s, Cp–
᎐
C
6
3
CH3), 91.4(s, Cp–CONHiPr), 88.8(s, η6-C6H6), 85.6(s, Cp–H),
81.0(s, Cp–H), 42.5(s, CH(CH3)), 22.5(s, CH(CH3)), 22.3(s,
CH(CH3)), 13.4(s, Cp–CH3) and 13.3(s, Cp–CH3); m/z 358
(Mϩ Ϫ PF6).
J. Chem. Soc., Dalton Trans., 2002, 1473–1478
1477

View Article Online
1
(S)-1b(Cp3). In a quartz glass vessel, (S)-1a(Cp3) (301 mg,
0.60 mmol) was dissolved in 100 ml of acetonitrile. The solution
was irradiated with ultraviolet light using a 500-W high-
pressure mercury lamp for 15 h. Evaporation of the acetonitrile
from the solution gave tris(acetonitrile) complex [Cp3Ru(CH3-
CN)3][PF6] 2(Cp3) as an orange solid. A mixture of solid 2(Cp3)
and biphenyl (925 mg, 6.0 mmol) was dissolved in 50 ml of
dichloromethane, and the solution was stirred under reflux
for 3 h. The solvent was evaporated under reduced pressure
and excess biphenyl was removed by extraction with ether.
Purification by recrystallization from ethanol gave [(SC1)-{η5-
1-isopropylaminocarbonyl-2,4-dimethylcyclopentadienyl}(η6-
biphenyl)ruthenium](hexafluorophosphate) (S)-1b(Cp3) as pale
yellow needles (291 mg, 84%). mp 141.5–142.0 ЊC (Found: C,
47.95; H, 4.27; N, 2.32; F, 19.65; P, 5.19. C23H26F6NOPRu
requires C, 47.75; H, 4.53; N, 2.42; F, 19.70; P, 5.35%; νmax/cmϪ1
complexes. The analytical data, including H and 13C NMR,
IR, and mass spectra, are provided in the ESI.†
X-Ray diffraction analyses
Crystals suitable for X-ray diffraction were mounted on a glass
fiber with epoxy resin. Measurements were performed on a
Rigaku AFC7R automated four circles diffractometer for (S)-
1b(Cp3), (R,R)-3b(Cp3), and 1c(Cp3) using graphite mono-
chromated Mo-Kα radiation (λ = 0.71069 Å) at Ϫ75 ЊC. An
empirical absorption collection was made for (S)-1b(Cp3) and
1c(Cp3) using the ψ-scan technique. The structures were solved
by Patterson methods (DIRDIF92 Patty or SAPI). Absolute
configurations were determined on the basis of those of the
starting materials. All non-hydrogen atoms were refined aniso-
tropically by full-matrix least-squares refinement while mini-
mizing Σω(|Fo| Ϫ |Fc|)2. The hydrogen atoms were included at
the calculated positions (dC–H = 0.95 Å) and their parameters
were not refined. The final cycles of full-matrix least-squares
refinement were converged. All calculations were performed
using the teXsan crystallographic software package.
(C᎐O) 1666; δ (acetone-d ) 7.85–7.83 (2 H, m, Phortho), 7.57–
᎐
H
6
7.54 (3 H, m, Phmeta, Phpara), 7.20 (1 H, br, NH), 6.79 (1 H, d, J =
6.3 Hz, η6-Phortho), 6.75 (1 H, d, J = 6.6 Hz, η6-Phortho), 6.45–6.36
(3 H, m, η6-Phmeta, η6-Phpara), 5.80 (1 H, s, Cp–H), 5.55 (1 H, s,
Cp–H), 4.04–3.95 (1 H, m, CH(CH3)2), 2.06 (3 H, s, Cp–CH3),
1.87 (3H, s, Cp–CH3) and 1.11 (6H, d, J = 6.6 Hz, CH(CH3)2);
CCDC reference numbers 168484–168486.
See http://www.rsc.org/suppdata/dt/b1/b107051g/ for crystal-
lographic data in CIF or other electronic format.
δ (acetone-d ) 163.1 (s, C᎐O), 134.2 (s, C H ), 131.2 (s, C H ),
᎐
C
6
6
5
6
5
130.2 (s, C6H5), 128.8 (s, C6H5), 104.9 (s, η6-C6H5), 100.7 (s,
Cp–CH3), 99.4 (s, Cp–CH3), 92.1 (s, Cp–CONHiPr), 88.9 (s,
η6-C6H5), 88.7 (s, η6-C6H5), 88.5 (s, η6-C6H5), 87.5 (s, η6-C6H5),
87.3 (s, η6-C6H5), 85.9 (s, Cp–H), 81.5 (s, Cp–H), 42.6
(s, CH(CH3)), 22.4 (s, CH(CH3)), 22.4 (s, CH(CH3)), 13.0
(s, Cp–CH3) and 12.7 (s, Cp–CH3); m/z 434 (Mϩ Ϫ PF6).
Enantiopure mononuclear complexes (R)-1b(Cp3), (S)-
1c(Cp3), (S)-1d(Cp3) and (S)-1e(Cp3) were similarly prepared
from (R)- or (S)-1a(Cp3) with arenes. Complexes 1b(Cp2) and
1b(Cp4) were prepared by a similar method using 1a(Cp2) and
1a(Cp4), respectively, with biphenyl. The analytical data, includ-
ing 1H and 13C NMR, IR, and mass spectra, are provided as ESI.†
Acknowledgements
This work was supported in part by a Grant-in-Aid for
Scientific Research from the Ministry of Education, Science,
Sports and Culture. We are grateful to the Material Analysis
Center, ISIR, Osaka University, for their support with the
spectral measurements and microanalyses.
References
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(S,S)-3b(Cp3). In a quartz glass vessel, (S)-1a(Cp3) (100 mg,
0.20 mmol) was dissolved in 100 ml of CH3CN. The solution
was irradiated with ultraviolet light using a 500-W high-
pressure mercury lamp for 15 h. The reaction solution was
evaporated to dryness and tris(acetonitrile) complex [Cp3-
Ru(CH3CN)3][PF6] 2 was obtained. A mixture of solid 2 and
(S)-1b(Cp3) (58 mg, 0.10 mmol) was dissolved in 50 ml of 1,2-
dichloroethane, and the solution was stirred at 83 ЊC for 3 h.
The solvent was evaporated under reduced pressure and purifi-
cation by recrystallization from ethanol–acetonitrile–ether gave
[{(SC1)-Cp3Ru}2(µ-η6,η6-biphenyl)][PF6]2 (S,S)-3b(Cp3) as pale
yellow needles (74 mg, 73%). mp 217.5–218.0 ЊC(dec.) (Found:
C, 40.84; H, 4.01; N, 2.95; F, 22.52; P, 6.39. C34H42F12N2O2-
P2Ru2 requires C, 40.72; H, 4.22; N, 2.79; F, 22.73; P, 6.18%);
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νmax/cmϪ1 (C᎐O) 1665 (KBr); δ (acetone-d ) 7.41 (2 H, br, NH),
᎐
H
6
6.94–6.92 (4 H, m, η6-Phortho), 6.59–6.53 (6 H, m, η6-Phmeta, η6-
Phpara), 5.90 (2 H, s, Cp–H), 5.64 (2 H, s, Cp–H), 3.96–3.92 (2 H,
m, CH(CH3)2), 2.09 (6 H, s, Cp–CH3), 1.96 (6 H, s, Cp–CH3),
1.13 (6 H, d, J = 6.6 Hz, CH(CH3)) and 1.10 (6 H, d,J = 6.6 Hz,
CH(CH )); δ (acetone-d ) 162.6 (s, C᎐O), 101.7 (s, η6-C H ),
᎐
3
C
6
6
5
100.5 (s, Cp–CH3), 97.3 (s, Cp–CH3), 93.5 (s, Cp–CONHiPr),
89.3 (s, η6-C6H5), 88.9 (s, η6-C6H5), 88.9 (s, η6-C6H5), 87.7 (s,
η6-C6H5), 87.4 (s, η6-C6H5), 86.2 (s, Cp–H), 82.0 (s,Cp–H), 42.6
(s, CH(CH3)), 22.4 (s, CH(CH3)), 22.3 (s, CH(CH3)), 13.1
(s, Cp–CH3), 12.6 (s, Cp–CH3); m/z 859 (Mϩ Ϫ PF6) and 713
(Mϩ Ϫ 2PF6).
Enantiopure binuclear complexes (R,R)-3b(Cp3), (S,R)-3b-
(Cp3), (S,S)-3c(Cp3), (S,S)-3d(Cp3), and (S,S)-3e(Cp3) were
similarly prepared from (R)- or (S)-1a(Cp3) with the corre-
sponding mononuclear complexes. Complexes 3b(Cp2) and
3b(Cp4) were prepared by a similar method using 1a(Cp2) and
1a(Cp4), respectively, with the corresponding mononuclear
1478
J. Chem. Soc., Dalton Trans., 2002, 1473–1478