Chelated ruthenium complexes of functionalized pentaarylcyclopentadienes

Article abstract of DOI:10.1021/om100727d

The Pd-catalyzed arylation of tetraphenylcyclopentadiene (7) and the classical "tetracyclone route" are tested as preparative entries to a variety of pentaarylcyclopentadienes 4 monofunctionalized in the ortho-position. The corresponding chelated rutheniu

Full text of DOI:10.1021/om100727d

Organometallics 2011, 30, 215–229 215
DOI: 10.1021/om100727d
Chelated Ruthenium Complexes of Functionalized
Pentaarylcyclopentadienes
Matthias Kanthak, Alexandra Aniol, Marco Nestola, Klaus Merz, Iris M. Oppel,† and
Gerald Dyker*
€
Faculty for Chemistry and Biochemistry, Ruhr-University Bochum, Universitatstrasse 150, D-44780
Bochum, Germany. † Institute of Inorganic Chemistry, RWTH Aachen, Landoltweg 1, D-52074 Aachen,
Germany
Received July 26, 2010
The Pd-catalyzed arylation of tetraphenylcyclopentadiene (7) and the classical “tetracyclone
route” are tested as preparative entries to a variety of pentaarylcyclopentadienes 4 monofunctiona-
lized in the ortho-position. The corresponding chelated ruthenium complexes 6 can be formed either
thermally induced or by photochemical irradiation. These complexes contain stereogenic ruthenium
centers. Enantiopure complexes 6f and 6g, with chiral oxazoline moieties, were tested for the
asymmetric transfer hydrogenation of phenyl ketones 9.
Introduction
from both chelate stabilization and steric shielding of the
phenyl groups. In addition, the aryl substituents are pre-
destined as anchor groups for donor ligands,5 which might
even carry chiral information. Of special interest are “stereo-
genic-at-metal complexes”,6,7 which recently gained impor-
tance in asymmetric synthesis.8 Therefore we decided to
Cyclopentadienyl ligands with a side chain bearing an
additional donor ligand have attracted considerable atten-
tion for the formation of stabilized half-sandwich com-
plexes,1 some of which exhibit extraordinary catalytic activ-
ity, especially in the area of olefin polymerization.2 To our
knowledge no sterically demanding pentaarylcyclopenta-
diene congeners have been studied so far,3 although their
notoriously labile transition metal complexes4 should profit
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Schaefer, W. P.; Labinger, J. A.; Bercaw, J. E J. Am. Chem. Soc. 1994,
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P.-F.; Stern, C. L.; Marks, T. J. Organometallics 1997, 16, 5958–5963. (d)
Knight, A. L.; Waymouth, R. M. Chem. Rev. 1998, 98, 2587–98. (e)
€
€
*Corresponding author. E-mail: gerald.dyker@ruhr-uni-bochum.de.
Tel: þ49 (0)234/32-24551.
Dohring, A.; Gohre, J.; Jolly, P. W.; Kryger, B.; Rust, J.; Verhovnik,
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W.; Weis, A. J. Organomet. Chem. 2001, 628, 161–182. (g) Enders, M.;
Ludwig, G.; Pritzkow, H. Organometallics 2001, 20, 827–33. (h) Enders, M.;
(1) For reviews on cyclopentadienyl complexes with pendant donors
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Siemeling, U. J. Organomet. Chem. 1995, 500, 175–185. (c) Jutzi, P.;
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2010 American Chemical Society
Published on Web 12/16/2010
pubs.acs.org/Organometallics

216 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
Scheme 1. Synthesis of Chelated Ru Complexes 6a
synthesize a couple of model compounds 4 as ligand pre-
cursors, preferring the classical tetracyclone route,9 which
can be easily scaled-up in contrast to our experiences with
our palladium-catalyzed arylation of cyclopentadienes,10
particularly of 1,2,3,4-tetraphenylcyclopenta-1,3-diene (7).
These ligand precursors should eventually function as bi-
dentate ligands in ruthenium complexes 6, which are poten-
tial catalysts, for instance for transfer hydrogenations at
phenyl ketones.
Results and Discussion
Tetracyclone (1) smoothly reacted at room temperature in
THF or Et2O with various functionalized lithioarenes 2,
generally to give the corresponding pentaarylcyclopentadie-
nols 3 in moderate to good yields (Scheme 1, Table 2).
The 1H NMR spectra of the cyclopentadienols 3a and 3c
exhibit outstanding downfield shifts for the hydroxy pro-
tons: whereas the OH signal of the quinolinyl-substituted
system 3c appears at 10.91 ppm, the corresponding signal of
the dimethylamino derivative 3a was found even further
downfield-shifted at 11.35 ppm. This effect is due to strong
intramolecular hydrogen bonds (O-H-N), confirmed by
X-ray structure analysis of suitable crystals (Figure 1). In
addition, the IR spectrum of 3a exhibits a broad absorption
at 2500 cm-1
.
(4) For examples of metal complexes stabilized by pendant donors,
see: (a) Fryzuk, M. D.; Jafarpour, L.; Rettig, S. J. Organometallics 1999,
18, 4050–58. (b) Enders, M.; Fink, J.; Pritzkow, H. Eur. J. Inorg. Chem.
2000, 1923–1925. (c) Buil, M. L.; Esteruelas, M. A.; Lopez, A. M.; Mateo,
A. C. Organometallics 2006, 25, 4079–4089.
(5) For examples of bidentate cyclopentadienyl complexes with func-
tionalized phenyl groups see refs 2g, 2h, 2j, and 2n-2p.
(6) For chiral cyclopentadienyl complexes with sidearm coordina-
tion;not cited in ref 1 or 2;see for example: (a) Zeijden, A. A. H. v. d.
J. Organomet. Chem. 1996, 518, 147–153. (b) Zeijden, A. A. H. v. d.; Jiminez,
J.; Mattheis, C.; Wagner, C.; Merzweiler, K. Eur. J. Inorg. Chem. 1999,
1919–1930. (c) Trost, B. M.; Vidal, B.; Thommen, M. Chem.;Eur. J. 1999,
5, 1055–1069. (d) Onitsuka, K.; Ajioka, Y.; Matsushima, Y.; Takahashi, S.
Organometallics 2001, 20, 3274–3282. (e) Becker, E.; Mereiter, K.;
Puchberger, M.; Schmid, R.; Kirchner, K.; Doppin, A. Organometallics
2003, 22, 3164–3170. (f) Doppiu, A.; Englert, U.; Salzer, A. Chem.
a Ar =aryl group, G, G0 =functional groups. (a) 1. functionalized
aryl-Li reagent 2 in THF or Et2O, 2. Hþ/H2O; (b) 1. strong base, 2.
LiAlH4; (c, c0) 1. Ru3(CO)12, toluene or xylene, decane, 160-175 °C,
sealed tube, 2. CHCl3 added, 160-175 °C, 3. silica gel; (d) hν.
€
Commun. 2004, 2166–2167. (g) Brunner, H.; Kollnberger, A.; Mehmood,
However, in some cases;with an acetal, cyano, or oxazo-
line functionality in the ortho-position;a subsequent equi-
librium favored the formation of spirocyclic isomers spiro-3,
the acetal spiro-3d, and the imidic acid esters spiro-3e and
spiro-3f.
A.; Tsuno, T.; Zabel, M. Organometallics 2004, 23, 4006–4008. (h)
Matsushima, A. Y.; Onitsuka, K.; Takahashi, S. Organometallics 2005, 24,
2747–2754. (i) Onitsuka, K.; Okuda, H.; Sasai, H. Angew. Chem., Int. Ed.
2008, 47, 1454–1457.
(7) For general reviews on metal-centered stereochemistry see: (a)
Brunner, H. Angew. Chem., Int. Ed. 1999, 38, 1194–1208. (b) Brunner, H.
Eur. J. Inorg. Chem. 2001, 905–912. (c) Ganter, C. Chem. Soc. Rev. 2003,
32, 130–138.
(8) (a) Muniz, K.; Bolm, C. Chem.;Eur. J. 2000, 13, 2309–2316. (b)
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Hamelin, O.; Rimbound, M.; Pecaut, J.; Fontecave, M. Inorg. Chem. 2007,
46, 5354–5360. (c) Gott, A. L.; Clarke, A. J.; Clarkson, G. J.; Scott, P. Chem.
Commun. 2008, 1422–1424. For an impressive example concerning the role
of a stereogenic metal center of a non-cyclopentadienyl complex in metath-
esis reactions see: (d) Sattely, E.; Meek, S. J.; Malcomson, S. J.; Schrock,
R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 943–953. (e) Lee, Y.-J.;
Schrock, R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 10652–
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(9) (a) Ziegler, K.; Schnell, B. Justus Liebigs Ann. Chem. 1925, 445,
266. (b) Chambers, J. W.; Baskar, A. J.; Bott, S. G.; Atwood, J. L.; Rausch,
M. D. Organometallics 1986, 5, 1635–1641. (c) Janiak, C.; Schuhmann, H.;
Stader, C.; Wrackmeyer, B.; Zuckerman, J. J. Chem. Ber. 1988, 121, 1745–
1751. (d) Field, L.; Ho, K. M.; Lindall, C. M.; Masters, A. F.; Webb, A. G.
Aust. J. Chem. 1990, 43, 281–91. For a variation with substituted tetra-
Most interestingly, the subsequent desoxygenation suc-
ceeded through treatment with LiAlH4 when starting both
from tertiary alcohols 3 and from the spirocyclic isomers
spiro-3d and spiro-3e, giving access to the functionalized
pentaarylcyclopentadienes 4 in acceptable yields. In con-
trast, the usual reduction protocol9c with HBr/Zn failed.
Commonly, a deprotonation of the alcohol with a strong
base before the LiAlH4 reduction was necessary. Therefore
we decided to try the in situ reduction of the intermediary
ꢁ
cyclone derivatives, see: (e) Thepot, J.-Y.; Lapinte, C. J. Organomet. Chem.
2001, 627, 179–188.
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J.-I.; Pivsa-Art, S.; Satoh, T.; Momura, M. Chem.;Eur. J. 2000, 6, 3426–
3433. (c) Dyker, G.; Heiermann, J.; Miura, M. Adv. Synth. Catal. 2003, 345,
1127–1132.

Article
Organometallics, Vol. 30, No. 2, 2011 217
Table 1. Crystallographic Data of 3a and 3c
3a
3c
empirical formula
fw
cryst syst
C
37H31NO
C38H27NO
513.61 g/mol
monoclinic
P21/n
6.3367(13)
20.450(4)
21.361(4)
90
505.63 g/mol
monoclinic
P2(1)
10.112(19)
10.020(15)
13.54(3)
90
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
99.33(9)
90
92.10(3)
90
3
˚
V [A ]
T [K]
1354(4)
293(2)
2
4290
309
2766.2(10)
293(2)
4
4887
366
0.0673
0.1768
Z
no. of unique data
no. of refined params
R1 (I > 2σ(I))
wR2 (all data)
0.0622
0.1559
Table 2. Synthesis of Compounds 3-6
Figure 1. ORTEP representations of cyclopentadienols 3a (top)
and 3c (bottom). Thermal ellipsoids are displayed at 50%
probability. Hydrogens are omitted for clarity except the ones
in the hydrogen bonds, shown with dashed lines.
alkoxides from the reaction of lithioarenes 2 with tetra-
cyclone (1), in analogy to earlier, alkyl-functionalized
examples.11 Thus, 4c-d and 4f-h were synthesized in a
one-pot procedure, circumventing the isolation of the alco-
hols 3c,d and spirocycles spiro-3f-h, respectively.
Remarkably, the oxazoline group as well as the nitrile
remained intact despite the strongly reducing conditions.
Nevertheless, the oxazoline-substituted cyclopentadienes
4f-h contained minor impurities after column chromatog-
raphy and were applied as crude products in the complexa-
tion step.
The ferrocenyl-substituted alcohol 3i as well as its reduced
derivative 4i exhibit an aging phenomenon in chloroform
solution, registered as an increasing broadening of the
1
signals in the H NMR spectrum, probably due to para-
magnetic impurities being formed. Presumably, an acid-
induced elimination of the hydroxyl group in 3i and proton-
ation of the double bond in 4i, respectively, lead to the
a Prepared by a one-pot procedure without isolation of 3 and 4,
respectively. b Yield based on converted 4e; n.i.: not isolated.
ꢀ
€
(11) Martin-Matute, B.; Edin, M.; Bogar, K.; Kaynak, F. B.; Backvall,
J.-E. J. Am. Chem. Soc. 2005, 127, 8817–8825.

218 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
formation of a cation, which is especially stabilized by the
ferrocene moiety12 and has paramagnetic character as proved
by qualitative EPR measurements.
Scheme 2. Synthesis of Nitrile 4e and Aldehyde 4d0 by Pd-
Catalyzed Arylation of Tetraphenylcyclopentadiene (7)a
Thus, addition of trifluoro acetic acid to a CDCl3 solution
of the alcohol 3i or cyclopentadiene 4i leads to highly colored
solutions and an extreme broadening of the 1H NMR
signals. In contrast, the NMR signals of the ferrocenyl
alcohol 3j are sharp. Presumably, the phosphinyl group
intercepts the protonation of the alcohol functionality as
the initial step of the carbocation formation.
a (a) 1. 5% Pd(OAc)2, 10% PPh3, Cs2CO3, DMF, 140 °C, 2 d; 2.
p-TsOH.
This is confirmed by a test with the phosphinyl-substituted
derivative 3j in CDCl3 solution in the NMR tube: upon
treatment with a drop of trifluoroacetic acid, a significant
change in color occurred and a change in chemical shifts, but
no broadening of the NMR signals was observed. However,
the addition of the stronger acid HBF4 led to a tremendous
darkening of the solution and a considerable broadening of
the 1H NMR signals.
approach10 by applying the direct arylation to 1,2,3,4-tetra-
phenylcyclopenta-1,3-diene (7) and 2-bromobenzonitrile
(8e) as coupling components (Scheme 2). 4e was obtained
in 78% yield, a superior result compared to the overall 34%
yield of the two-step tetracyclone route. Equally, aldehyde
4d0 could also be synthesized by this method in 81% yield,
starting from ortho-bromophenyl-1,3-dioxolane (8d) and
1,2,3,4-tetraphenylcyclopenta-1,3-diene (7), with the hydro-
lysis proceeding during workup. However, these are cer-
tainly special cases since nitrogen and phosphine ortho-
substituents generally interfere with the Pd-catalyzed pro-
cess. Thus, applying this method to the coupling reaction
with 2-bromophenyloxazolines remained unsuccessful ac-
cording to orientating results.
The aldehyde 4d0, the dioxolane 4d, and the nitrile 4e
provide opportunities for further derivatization. For exam-
ple, reductive amination of the aldehyde 4d0 would lead to a
variety of amines with the tether extended by one methylene
unit compared to cyclopentadiene 4a. Orientating tests
have already been successful and are currently the focus of
ongoing studies.
Because of the lability of the ferrocenyl-substituted cyclo-
pentadienols, they are especially easy to reduce by LiAlH4
without prior deprotonation, giving the cyclopentadienes 4i
and 4j in reasonable yields. Most interestingly, the reduction
of the ferrocenyl alcohols 3i and 3j resulted virtually in single
isomers of 4i and 4j; only small amounts of other double-
bond isomers could be detected by NMR, and finally only
one isomer was isolated. In both cases the isomer with the
diene and the ferrocene moiety linearly conjugated should be
thermodynamically favored. This was proved for the ferro-
3
cene 4j through the HMBC spectrum: a J-coupling of the
cyclopentadienyl proton and the tertiary ferrocenyl carbon
was clearly registered. In contrast, regularly a mixture of
three double-bond isomers of cyclopentadienes 4 is expected:
usually, the diagnostic signals of the double allylic protons at
about 5 ppm allow the determination of the isomeric ratio.
Thus, the cyclopentadiene 4b exhibits three distinct singlets
We envisioned a ruthenation protocol reported by
11
Backvall et al. to be suitable for the synthesis of chelated
€
ruthenium complexes with chiral metal centers. Indeed, the
synthesis of the corresponding ruthenium chloride carbonyl
complexes 5 generally succeeds by refluxing a toluene/decane
mixture of pentaarylcyclopentadienes 4 and Ru3(CO)12 in a
sealed tube, followed by treatment with chloroform. Usually
the reaction mixture is directly submitted to column chro-
matography to give the corresponding complexes in moder-
ate yields. Only in the case of the phosphinyl-substituted
ferrocene 4j did we fail to isolate a pure Ru complex. In
contrast, the synthesis of the unsubstituted ferrocenyl com-
plex 5i worked very smoothly, which might imply an in-
compatibility of phosphinyl groups in this complexation
reaction.
1
in the H NMR at 5.18, 5.55, and 5.60 ppm in a ratio of
1:3.2:2.6 as well as three diagnostic ddd signals of the
pyridine ring at 8.44, 8.47, and 8.54 ppm. In addition, with
increasing steric demand of the ortho-substituents rotamers
might become observable in the 1H NMR spectrum.10c For
example, the ortho-dimethylaminophenyl-substituted cyclo-
pentadiene 4a exhibits four different cyclopentadienyl pro-
tons and three singlets for the dimethylamino groups since
two of them are isochronal. In contrast, only two isomers
were observed after purification by washing with methanol
in the ultrasonic bath for the dioxolane 4d with one isomer
remarkably predominating.
Similarly, the synthesis and the isolation of the nitrile
complex 5e succeeded in low yield. After chromatography
In the case of the nitrile-substituted derivative 4e we could
prove the feasibility of our alternative palladium-catalyzed
1
the H NMR spectrum appears to be quite pure. But the
presence of the C-N absorption band at 2228 cm-1 (2223
cm-1 in the free ligand) suggests that the nitrile is not
coordinated to the metal (N-Ru distance of 356 pm).
Within the resulting ruthenium complexes the interaction
of the tethered ligand with the metal center strongly depends
(12) Similar observations were made in the ferrocene-tetracyclone
adduct and its protonated form: (a) Gupta, H. K.; Stradiotto, M.;
Hughes, D. W.; McGlinchey, M. J. J. Org. Chem. 2000, 65, 3652–3658.
(b) Harrington, L. E.; Vargas-Baca, I.; Reginato, N.; McGlinchey, M. J.
Organometallics 2003, 22, 663–669, and references therein for further examples
of cations stabilized by ferrocene.

Article
Organometallics, Vol. 30, No. 2, 2011 219
Figure 3. ORTEP representation of chelated ruthenium com-
plex 6a. Thermal ellipsoids are displayed with 50% probability.
˚
Hydrogens are omitted for clarity. Selected bond lengths (A) and
angles (deg): Ru-CO 1.884(2), Ru-Cl 2.4377(5), Ru-N 2.225(2),
range Ru-CCp 2.096(2)-2.270(2); Cl-Ru-CO 92.29(6), Cl-
Ru-N 88.81(4), N-Ru-CO 95.17(8).
presumably due to the unfavorable distance of the donor
nitrogen, which would afford a ring slippage before the pyridine
nitrogen could coordinate to the ruthenium.14 For similar
reasons a chelation of the nitrile 5e probably failed as well.
The reaction of 4c with Ru3(CO)12 and CHCl3 yielded a
poorly soluble ruthenium complex. Although two CO ab-
sorption bands in the IR spectrum suggest the formation of a
ruthenium dicarbonyl complex, the number of signals in the
HMBC spectrum (the solubility for a good-quality 13C
NMR was too poor) implies the inequivalence of the phenyl
groups and the cyclopentadienyl carbons, which is in accor-
dance with the chelated complex 6c with a stereogenic
ruthenium atom.
This is in accordance with the observation that an irradia-
tion did not lead to any conversion, although the position of
the nitrogen donor is comparable to the dimethylamino
derivative 5a, which was easily decarbonylated to 6a by
irradiation (vide supra). These results suggest the presence
of the chelated quinoline ruthenium complex 6c rather than
the dicarbonyl complex 5c.15
Figure 2. ORTEP representations of ruthenium complexes 5a
(top) and 5b (bottom). Thermal ellipsoids are displayed at 50%
(5a) and 30% (5b) probability. The carbonyl and chloride
ligands in 5b are systematically disordered and were not shown
as ellipsoids. Hydrogens are omitted for clarity.
on the position of the donor atom: the X-ray crystal structure
analyses of complexes 5a and 5b enable an informative
comparison (Figure 2): whereas the nitrogen of the pyridine
in 5b is directed toward the ruthenium, we might postulate a
weak electronic interaction between the nitrogen and the
metal. In contrast, the dimethylamino group in the ruthe-
nium dicarbonyl complex 5a is orientated away from the
metal, probably because of steric reasons.13
The oxazoline-substituted cyclopentadienes 4f-h directly
led to chelated complexes 6f-h, thermally induced at 175 °C
without need of a photoinduced decarbonylation.
Because of their inherent chiral information, these oxazo-
linyl complexes are of special interest, allowing the formation
of diastereomers with the second stereogenic center at the
metal.6,7 In all cases we were pleased to isolate only one
diastereoisomer after chromatography of the reaction mix-
ture with a diastereomeric ratio of at least 95:5 in the case of
the isopropyl system 6f. When the reaction was performed at
the somewhat lower temperature of 160 °C, we observed
impurities that could not be separated by chromatography.
We assigned them to the nonchelated ruthenium dicarbonyl
complex rather than to the other chelate diastereomer, as we
Nevertheless, an irradiation of a toluene solution of 5a led
to loss of a carbonyl group and to a subsequent intramole-
cular coordination of the nitrogen to the metal. This coordi-
nation is additionally indicated by a tremendous change in
color from yellow to deep purple. Most interestingly, the
coordination establishes the ruthenium as a stable stereo-
genic center, which makes the two methyl groups distin-
1
guishable in the H NMR as they become diastereotopic.
Remarkably, one methyl group experiences a chemical
downfield shift of about 1 ppm (Figure 4). In addition, the
structure has been proved by an X-ray analysis of suitable
crystals (Figure 3).
In contrast, a corresponding photoinduced chelate forma-
tion could not be observed for the pyridine derivative 5b,
(14) Coordination of pyridine tethered to cyclopentadienyl ligands
.
was observed when a methylene bridge was introduced: see refs 1w and 2q
(a) Paolucci, G.; Vignola, M.; Coletto, L.; Pitteri, B.; Benetollo, F.
J. Organomet. Chem. 2003, 687, 161–170. (b) Krutko, D. P.; Kirsanov, R. S.;
Belov, S. A.; Borzov, M. V.; Churakov, A. V. J. Organomet. Chem. 2007,
692, 1465–1471.
(13) Similar observations were made with less sterically hindered
cyclopentadienyl-aniline complexes: see refs 2g and 2i and for an indenyl
complex: Baker, R. W.; Luck, I. J.; Turner, P. Inorg. Chem. Commun.
2005, 8, 817–820.
(15) Bidentate cyclopentadienyl quinoline complexes have been pub-
lished mostly by Enders et al. See for example refs 1n, 1p, 1u, 2g, 2m,
.
and 4b

220 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
Figure 4. Comparison of the 1H NMR spectra of 5a (top) and its chelated derivative 6a (bottom) with diastereotopic methyl groups.
Table 3. Crystallographic Data of 5a, 5b, and 6a
5a
5b
6a
empirical formula
fw
cryst syst
C
39H30NO2ClRu
C24H16Cl0.67N0.67O1.33Ru0.67
C39.5H36NO2.5ClRu
701.21 g/mol
monoclinic
C2/c
34.1453(9)
10.6540(2)
19.7747(6)
90
681.16 g/mol
monoclinic
P2(1)/n
8.7240(2)
31.6975(8)
12.0248(3)
90
426.05 g/mol
orthorhombic
Pbca
20.623(4)
13.899(5)
20.763(5)
90
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
104.984(3)
90
90
90
115.737(3)
90
3
˚
V [A ]
T [K]
3212.14(14)
110(2)
4
7367
399
0.0288
0.0571
5951(3)
223(2)
12
5209
365
6480.1(3)
113(2)
8
6695
418
0.0239
0.0561
Z
no. of unique data
no. of refined params
R1 (I > 2σ(I))
wR2 (all data)
0.0833
0.2654
detected Ru(CO)2 fragments in the FAB mass spectra as well
as two additional CO absorption bands in the IR spectrum.
Since we were able to get X-ray quality crystals of the
chelated oxazolinyl complexes 6f-h (Figures 5-7), we could
determine the ruthenium center to have an S-configuration,
which avoids steric interaction between the oxazoline moiety
and the chloride. In addition, the substituents at the oxazo-
line;whether the isopropyl group of 6f, the isobutyl group
in 6g, or the benzyl group in 6h;are directed away from the
crowded metal center. The pure diastereomers show a re-
markable configurational stability.7 Even after weeks at room
temperature, solutions of the complexes in CDCl3 did not show
any evidence of an epimerization at the metal center.
Interestingly, the isobutyl-substituted oxazolinyl com-
plex 6g exhibits a double carbonyl absorption at 1952 and
1964 cm-1. In contrast, complexes 6f and 6h both show only
one distinct CO absorption in the IR spectrum.
We envisioned the enantiopure metal complexes 6f-6h as
potential catalysts for various enantioselective reactions.
Thus, we applied these complexes in preliminary tests in
the asymmetric transfer hydrogenation of prochiral phenyl
ketones 9 with 2-propanol as hydrogen donor to give the
(16) Selected recent examples of asymmetric Ru(II)-catalyzed trans-
fer hydrogenations of ketones with the 2-propanol/base system: (a)
Hannedouche, J.; Clarkson, G. J.; Wills, M. J. Am. Chem. Soc. 2004,
126, 986–987. (b) Gomez, M.; Jansat, S.; Muller, G.; Aullon, G.; Maestro,
M. A. Eur. J. Inorg. Chem. 2005, 4341–4351. (c) Reetz, M. T.; Li, X. J. Am.
Chem. Soc. 2006, 128, 1044–1045. (d) Fukuzawa, S.-I.; Suzuki, T. Eur. J.
Org. Chem. 2006, 1012–1016. (e) Enthaler, S.; Hagemann, B.; Bhor, S.;
Anilkumar, G.; Tse, M. K.; Bitterlich, B.; Junge, K.; Erre, G.; Beller, M. Adv.
Synth. Catal. 2007, 439, 853–860. (f) Baratta, W.; Chelucci, G.; Herdtweck,
E.; Magnolia, S.; Siega, K.; Rigo, P. Angew. Chem., Int. Ed. 2007, 46, 7651–
7654. (g) Ikariya, T.; Blacker, A. J. Acc. Chem. Res. 2007, 40, 1300–1308.
(h) Chakka, S. K.; Andersson, P. G.; Maguire, G. E. M.; Kruger, H. G.;
Govender, T. Eur. J. Org. Chem. 2010, 5, 972–980.

Article
Organometallics, Vol. 30, No. 2, 2011 221
Figure 5. ORTEP representation of chiral chelated ruthenium
complex 6f. Thermal ellipsoids are displayed at 50% probabil-
˚
ity. Hydrogens are omitted for clarity. Selected bond lengths (A)
and angles (deg): Ru-CO 1.875(2), Ru-Cl 2.4258(5), Ru-N
2.104(2), range Ru-CCp 2.117(2)-2.323(2); Cl-Ru-CO 89.43(7),
Cl-Ru-N 90.88(5), N-Ru-CO 94.86(8).
Figure 7. ORTEP representation of chiral chelated ruthenium
complex 6h. Thermal ellipsoids are displayed at 50% probabil-
˚
ity. Hydrogens are omitted for clarity. Selected bond lengths (A)
and angles (deg): Ru-CO 1.890(2), Ru-Cl 2.422(6), Ru-N
2.118(2), range Ru-CCp 2.120(2)-2.311(2); Cl-Ru-CO 88.23(6),
Cl-Ru-N 90.14(5), N-Ru-CO 95.26(8).
Table 4. Crystallographic Data of 6f-h
6f
6g
6h
empirical
formula
fw
C42H34NO2
ClRu
721.22 g/mol
orthorhombic monoclinic
P2(1)2(1)2(1) C2
12.4054(2)
16.6340(2)
16.6340(2)
90
90
90
C
44H38NO2
C
ClRu
46H34NO2
Cl3Ru
820.17 g/mol 769.26 g/mol
cryst syst
space group
orthorhombic
P2(1)2(1)2(1)
10.7789(2)
11.2912(2)
28.9700(5)
90
˚
a [A]
35.5952(13)
12.2693(6)
17.6505(9)
90
100.756(4)
90
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
90
90
3
˚
V [A ]
T [K]
3432.45(8)
110(2)
4
7573.0(6)
110(2)
8
16172
895
3525.84(11)
113(2)
4
6898
460
0.0201
0.0417
Z
no. of unique data
Figure 6. ORTEP representation of chiral chelated ruthenium
complex 6g. Thermal ellipsoids are displayed at 50% probability.
˚
Hydrogens are omitted for clarity. Selected bond lengths (A) and
7863
no. of refined params 426
R1 (I > 2σ(I))
wR2 (all data)
0.0245
0.0517
0.0586
0.1380
angles (deg): Ru-CO 1.896(7), Ru-Cl 2.413(2), Ru-N 2.110(5),
range Ru-CCp 2.132(7)-2.285(7); Cl-Ru-CO 89.6(2), Cl-
Ru-N 90.0(2), N-Ru-CO 95.3(3).
Although the use of KOtBu gave a quantitative yield of
phenylethanol (10a), the ee values for KOH were signifi-
cantly higher, still with excellent yield. Accordingly, we
applied the catalytic system with 1 mol % of the catalyst
precursor and 90 mol % of KOH for the asymmetric transfer
hydrogenations of prochiral phenyl ketones 9 to elucidate
the influence of both the substituent at the carbonyl carbon
and the substituent on the oxazoline moiety (Table 6).
There was no distinct correlation between the steric de-
mand of the phenyl ketone 9 and the obtained ee values for
10, suggesting that steric reasons are not crucial for the chiral
induction. On the other hand, the yield is unambiguously
affected by the steric demand of the substituents at the
carbonyl carbon. Nevertheless, yields above 90% were ob-
tained for the ketones 9a-c under individually optimized
benzylic alcohols 10.16 Acetophenone (9a) was chosen as the
first model substrate and the isopropyl-substituted oxazoline
complex 6f as catalyst precursor in combination with differ-
ent bases (Table 5), which are known for being crucial for
yield and enantiomeric excess in transfer hydrogenations.16
As a result strong bases generally furnished phenylethanol
(10a) in high yields after 3 h in refluxing 2-propanol with
just 1 mol % of catalyst precursor 6f (Table 5, entries 1-7).
In contrast, the weaker carbonates afforded only minor
amounts of 10a (Table 5, entries 9-11). Furthermore,
potassium-coordinated bases were more active than its
sodium and lithium analogues.

222 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
Table 5. Transfer Hydrogenation of Acetophenone (9a) with 6f As
Catalyst Precursor
Table 6. Catalytic Transfer Hydrogenations of Various
Phenylketones 9 with 6f-h As Catalyst Precursors
entry
S/Ca
base
base (mol %)
yieldb
eec
38
30
24
20
12
20
entry
R
cat
S/Ca
yieldb
eec
38
35
37
1
2
3
4
5
6
7
8
100
100
67
100
100
100
100
67
KOH
KOH
90
35
40
100
70
70
70
50
70
70
70
95
68
86
99
83
95
79
10
,1
<1
5
1
2
3
4
5
6
7
8
a
a
a
b
b
b
b
b
b
c
c
c
c
d
d
d
d
e
e
e
e
Me
Me
Me
6f
100
100
100
100
100
100
50
50
50
100
50
50
50
100
50
50
50
100
50
95
94
98
44
72
58
50
94
88
47
94
99
99
30e
76e
84e
67e
36
69
70
61
6g
6h
6f
6g
6h
6f
6g
6h
6f
KOtBu
KOtBu
NaOH
NaOtBu
LiOtBu
LiOH
Na2CO3
K2CO3
Cs2CO3
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
n-Bu
n-Bu
n-Bu
n-Bu
Cy
Cy
Cy
Cy
Bnz
Bnzd
Bnz
Bnzd
22
n.d.f
n.d.f
20
2
n.d.d
n.d.d
n.d.d
n.d.d
32
9
10
11
100
100
100
9
29
10
11
12
13
14
15
16
17
18
19
20
21
n.d.f
36
6f
a Substrate to catalyst ratio. Substrate concentration: 0.35-0.58 M.
b Yield determined by GC with decane as internal standard. c ee deter-
mined by derivatization with Mosher’s acid to its diastereomeric esters.
The configuration was R, determined by comparison of the NMR of the
ester with literature.17 d n.d.: not determined.
6g
6h
6f
43
29
n.d.f
25
6f
6g
6h
6f
6f
6g
6h
42
38
n.d.f
43
conditions. The transfer hydrogenation of 9d and 9e still
afforded the benzylic alcohols 10d and 10e in good yields
of 84% and 70%, respectively. The ee values were generally
moderate, with a maximum at 50% ee, achieved with deso-
xybenzoin (9e) as substrate.
π-Interactions of the benzyl group with the oxazoline
moiety of the catalyst seem to be beneficial for the achieving
highest ee values in our series. CH-π attractions were
supposed to be responsible for the high enantioselectivities
of Noyori’s catalyst in the transfer hydrogenation,18b placing
the threshold for these types of reactions clearly above
90% ee.16a,c-h,18a
50
50
50
45
a Substrate to catalyst ratio. Substrate concentration: 0.30-0.65 M.
b Yield determined by GC with internal standards: decane (a), tridecane
(b), tetradecane (c), pentadecane (e). c ee determined by derivatization
with Mosher’s acid to its diastereomeric esters. The configuration was R,
established by determination of the sign of rotation and comparison
with literature. d 0.12 M. e Yield determined by 1H NMR. f n.d.: not
determined.
Experimental Section
General Procedures. All reactions were carried out under
argon atmosphere in dried glassware. All workup procedures
were carried out in air. Solvents were dried according to standard
procedures. Chemicals were used as received from Acros, Al-
drich, Strem, and Fluorochem, respectively. 8-Bromoquinoline,19
1-bromo-10-diphenylphosphinoferrocene,20 and 2-(2-bromophenyl)-
1,3-dioxolane21 (8d) and the enantiopure 2-bromophenyloxazo-
lines22 and phenyloxazolines,22,23 respectively, were synthesized
by literature procedures or slight modifications of these proto-
cols. The data of all reproduced compounds were in accordance
Conclusions
In conclusion, we have tested stoichiometric and catalytic
preparative pathways for the synthesis of pentaphenylated
cyclopentadienes monofunctionalized in one ortho-position.
It was shown that the reaction with Ru3(CO)12 and chloro-
form yielded the corresponding cyclopentadienyl complexes.
Chelation to the tethered functional group occurred either
thermally induced or finally by photochemical irradiation.
Thus, a stereogenic center might be induced at the ruthe-
nium. When the tether is an enantiopure oxazoline, the
complexes were isolated as single diastereomers. These novel
enantiopure oxazoline ruthenium complexes showed high
catalytic activity for the enantioselective transfer hydroge-
nation of phenyl ketones with 2-propanol as hydrogen
donor. The corresponding benzylic alcohols were obtained
in up to 99% yield and with ee values up to 50%. We intend
to extend our tests to other Ru-catalyzed processes, focusing
on the influence of π-interactions between substrate and
catalyst.
1
with literature except the H NMR of 1-bromo-10-diphenyl-
phosphinoferrocene.20 Melting points (uncorrected): Buchi;
€
IR: Bruker Equinox 55; UV: Varian Cary 1; MS (EI, FAB,
EI(HRMS)): Varian MATCH5; MS (MALDI-TOF): Bruker
Autoflex, ABP matrix; MS (LIFDI): JMS-T100GCV; elemental
analysis: Vario EL. NMR spectra (1H and 13C) were recorded on
(19) Wada, K.; Mizutani, T.; Kitagawa, S. J. Org. Chem. 2003, 68,
5123–5131.
(20) Butler, I. R.; Davies, R. L. Synthesis 1996, 11, 1350–1354. The
literature contained a mistake in the reported 1H NMR since one signal is
missing. We found: 1H NMR (CDCl3, 200 MHz) δ 3.99 (t, 2H, J=1.8 Hz),
4.15 (m, 2H), 4.32 (t, 2H, J=1.8 Hz), 4.42 (t, 2H, J=1.6 Hz), 7.28-7.42 ppm
(m, 10H). The mp (97-101 °C) was in accordance with the one reported.
(21) Wytko, J. A.; Graf, E.; Weiss, J. J. Org. Chem. 1992, 57, 1015–
1018.
(17) Ward, D. E.; Rhee, C. K. Tetrahedron Lett. 1991, 32 (49), 7165–
7166.
(18) (a) Fujii, A.; Hashiguchi, S.; Uematsu, N.; Ikariya, T.; Noyori,
R. J. Am. Chem. Soc. 1996, 118, 2521–2522. (b) Yamakawa, M.; Yamada,
I.; Noyori, R. Angew. Chem., Int. Ed. 2001, 40, 2818–2821.
(22) Zhou, Q.-L.; Pfaltz, A. Tetrahedron 1994, 15, 4467–4478.
1
(23) The H NMR of (S)-4-isobutyl-2-phenyl-4,5-dihydrooxazole is
published in: Fukuhara, T.; Hasegawa, C.; Hara, S. Synthesis 2007, 10,
1528–1534.

Article
Organometallics, Vol. 30, No. 2, 2011 223
a Bruker DPX 200 and a Bruker DRX 400 and calibrated by the
residual solvent peak or by TMS as an internal standard. All GC
analyses were conducted on a Silicon OV-17 stationary phase
(43 m, 0.28 mm).
The mixture was stirred at room temperature for 16 h and hydro-
lyzed with aqueous NH4Cl (2 N, 5 mL), and the separated
organic layer was dried with MgSO4. After evaporation of the
solvents, EtOAc was added to the residue and the mixture was
treated in the ultrasonic bath. The precipitate was isolated
by filtration to yield tertiary alcohol 3c as a pale yellow solid
(370 mg, 52%) with mp 239-241 °C. IR (KBr): 3423 br w, 3052 w,
3027 w, 1594 w, 1496 m, 1494 m, 1438 w, 1369 w, 1245 w, 1125 w,
1051 w, 1027 w, 776 m, 763 m, 694 s cm-1. 1H NMR (CDCl3, 400
MHz): δ 6.87-6.94 (m, 6 H, PhH), 6.99-7.03 (m, 8 H, PhH),
7.06-7.11 (m, 6 H, PhH), 7.22 (dd, J=4.3, 8.4 Hz, 1 H, Qui-H3),
7.48 (t, J=7.7 Hz, 1 H, Qui-H6), 7.66 (dd, J=1.2, 8.1 Hz, 1 H,
Qui-H5), 7.99 (dd, J=1.3, 7.4 Hz, 1 H, Qui-H7), 8.07 (dd, J=1.7,
8.4 Hz, Qui-H4, 1 H), 8.43 (dd, J=1.8, 4.2 Hz, 1 H, Qui-H2),
10.91 ppm (s, 1 H, OH). 13C NMR (CDCl3, 100 MHz): δ 94.57
(COH), 120.21 (Qui-C3), 126.36, 126.60 (both d), 126.72 (Qui-
C7), 126.94 (d), 127.20 (Qui-C6), 127.26 (d), 127.64 (Qui-C5),
128.75 (Qui-C4a), 129.86, 129.95 (both d), 135.05 (s), 135.34
(Qui-C8), 135.43 (s), 137.20 (Qui-C4), 141.31 (s), 146.45 (Qui-
C2), 148.69 (Qui-C8a), 149.50 ppm (s). UV-vis (MeCN): λmax
(log ε) 215 sh (4.55), 231 (4.59), 244 sh (4.50), 340 nm (3.86). MS
(FAB): m/z (%) 536 (5) [M þ Na]þ, 514 (100) [M þ H]þ; 496 (22)
[M - OH]þ. HRMS (EI): calcd for C38H27NO 513.2093, found
513.2090.
1-(2-N,N-Dimethylaminophenyl)-2,3,4,5-tetraphenylcyclopen-
ta-2,4-dienol (3a). TMEDA (1.0 mL, 6.4 mmol) and N,N-
dimethylaniline (0.90 mL, 7.00 mmol) were added to a solution
of n-BuLi (1.6 M in hexane, 4.0 mL, 6.4 mmol), and the mixture
was heated at reflux temperature for 3 h. After cooling to room
temperature tetracyclone (1) (1.70 g, 4.42 mmol) was added as
a solid in small portions with additional THF (10 mL) within
30 min. The mixture was stirred for 16 h, hydrolyzed with brine
(20 mL), and extracted with EtOAc (3 ꢀ 30 mL). The combined
organic layers were dried (MgSO4) and concentrated. The crude
product was subjected to flash column chromatography (silica,
PE/EtOAc, 5:1, Rf =0.25, 0.28, 0.37, 0.48, 0.55 (tetracyclone
(1)), 0.61), and the fractions containing Rf=0.25 were recrys-
tallized from EtOAc to give the tertiary alcohol 3a as colorless
crystals (1.59 g, 71%) with mp 186 °C. For a sufficient purity for
the reduction step the crude product was suspended in EtOAc,
and this mixture was treated in the ultrasonic bath. The cyclo-
pentadienol 3a thus obtained by filtration only contained
minor tetracyclone impurity. IR (KBr): 3074 w, 3052 m, 3043 m,
3026 w, 2997 w, 2986 w, 2955 w, 2499 br m, 1595 m, 1573 m,
1483 s, 1439 m, 1328 w, 1280 w, 1176 m, 1163 m, 1137 w, 1096 m,
1072 w, 1046 w, 1027 m, 928 m, 865 w, 846 w, 811 w, 787 m,
771 m, 754 m, 743 m, 721 m, 700 s cm-1. 1H NMR (CDCl3, 400
MHz): δ 2.28 (s, 6 H, CH3), 6.94-6.97 (dd, J=1.8, 7.6 Hz, 4 H),
7.02-7.12 (m, 16 H), 7.13-7.20 (m, 3 H), 7.53 (d, J=7.6 Hz,
1 H), 11.35 ppm (s, 1 H, OH). 13C NMR (CDCl3, 100 MHz):
δ 46.46 (CH3), 94.91 (s, COH), 124.01, 126.87, 126.96, 127.05,
127.52, 127.80, 127.87, 128.42, 130.14, 130.30 (all d), 133.62,
135.55, 136.05, 141.19, 150.66, 153.89 ppm (all s). UV-vis
(MeCN): λmax (log ε) 209 (4.52), 246 (4.35), 343 nm (3.70). MS
(FAB): m/z (%) 528 (4) [M þ Na]þ, 506 (100) [M þ H]þ, 488 (8)
[M - OH]þ. HRMS (EI): calcd for C37H31NO 505.2406, found
505.2405.
1-(2,3,4,5-Tetraphenylcyclopenta-2,4-dienol-1-yl)ferrocene (3i).
To a solution of ferrocene (564 mg, 2.97 mmol) in dry THF
(5 mL) was added t-BuLi (1.48 M in pentane, 1.70 mL, 2.56
mmol) at 0 °C, and the mixture was stirred for 15 min. After
warming to room temperature tetracyclone (1) (412 mg, 1.07 mmol)
was added as a solid in small portions with additional THF
(15 mL). The mixture was stirred for 30 min, hydrolyzed with
water (5 mL), and extracted with MTBE (2 ꢀ 15 mL). The
combined organic extracts were dried with Na2SO4 and con-
centrated, and the crude product was subjected to flash column
chromatography (silica, PE/EtOAc, 10:1; Rf=0.19, 0.41, 0.56,
0.78; PE/EtOAc 25:1 f 5:1). The fraction with Rf = 0.78
afforded ferrocene (300 mg, 54% recovery), the fraction with
Rf=0.56 gave 1 (55 mg, 13% recovery), and the fraction with
Rf=0.49 yielded ferrocenyl alcohol 3i (375 mg, 0.66 mmol, 71%
based on converted tetracyclone (1)) as a yellow-orange powder,
which decomposes at 215 °C. IR (KBr): 3464 m, 3079 w, 3051 w,
3027 w, 1954 w, 1898 w, 1595 w, 1572 w, 1487 m, 1439 w, 1409 w,
1380 w, 1347 w, 1313 w, 1274 w, 1237 w, 1216 w, 1180 w, 1155 w,
1119 m, 1105 m, 1073 m, 1063 m, 1047 m, 1027 s, 999 m, 914 w,
811 m, 779 w, 771 w, 754 s, 747 m, 725 m, 697 vs, 616 w, 579 m,
1-(2-Pyridyl)-2,3,4,5-tetraphenylcyclopenta-2,4-dienol (3b).
To a solution of t-BuLi (1.48 M in pentane, 2.70 mL, 4.00
mmol) in Et2O (4 mL) was added 2-bromopyridine (315 mg,
0.19 mL, 1.99 mmol) at -78 °C, and the mixture was stirred for
30 min. Tetracyclone (1) (620 mg,1.60 mmol) was added as a
solid in small portions with additional Et2O (25 mL) within
15 min, and the mixture was stirred and slowly warmed to room
temperature over a period of 2 h. The mixture was hydrolyzed
with aqueous NH4Cl (1 N, 20 mL), and the precipitate was
filtered and recrystallized from EtOAc to afford tertiary alcohol
3b as colorless crystals (620 mg, 84%) with mp 207-210 °C. IR
(KBr): 3242 br m, 3057 w, 3025 w, 1589 m, 1569 m, 1487 m, 1472 m,
1437 m, 1401 w, 1329 w, 1191 w, 1139 m, 1098 w, 1080 w, 1058 w,
1069 w, 1028 w, 1000 w, 977 w, 922 m, 851 w, 825 w, 792 m,
1
547 m cm-1. H NMR (CDCl3, 400 MHz): δ 2.74 (br s, 1 H,
OH), 3.68 (br s, 5 H, FcH5), 3.90 (br s, 2 H, FcH2H2), 4.03 (br s, 2
H, FcH2H2), 6.92 (br d, 4 H, J=5.0 Hz, PhH), 6.03 (br d, J=5.31
Hz, 6 H, PhH), 7.22-7.30 (br m, 6 H, PhH), 7.40 ppm (br d, J=
7.01 Hz, 4 H, PhH). 13C NMR (CDCl3, 100 MHz): δ 66.68,
67.26 (both FcCpH4), 68.42 (FcCpH5), 86.86, 94.33 (both s),
126.52, 127.03, 127.26, 127.60, 129.91, 130.73 (all d), 135.04,
136.05, 142.06, 146.58 ppm (all s). UV-vis (MeCN): λmax (log ε)
211 (4.77), 245 (4.58), 358 nm (3.58). MS (FAB): m/z (%) 593 (6)
[M þ Na]þ, 570 (100) [M]þ, 553 (15) [M - OH]þ. Anal. Calcd for
C39H30FeO: C 82.11, H 5.30. Found: C 81.80, H 5.24.
1-(2,3,4,5-Tetraphenylcyclopenta-2,4-dienol-1-yl)-10-diphenyl-
phosphinoferrocene (3j). To a solution of 1-bromo-10-diphenyl-
phosphinoferrocene (1.10 g, 2.45 mmol) in dry THF (10 mL)
was added n-BuLi (1.6 M in hexane, 1.50 mL, 2.40 mmol) at
-78 °C, and the mixture was stirred for 15 min. During slow
warming to room temperature tetracyclone (1) (845 mg, 2.20
mmol) was added in several portions with additional THF
(35 mL). The mixture was stirred for 30 min at room tempera-
ture, hydrolyzed with water (15 mL), and extracted with MTBE
(2 ꢀ 15 mL). The combined organic extracts were dried with
Na2SO4 and concentrated, and the crude product was subjected
to flash column chromatography (PE/EtOAc, 15:1 f 2:1; silica,
PE/EtOAc, 15:1; Rf = 0, 0.17, 0.29, 0.47 (1), 0.54 (Fe(C5H5)
(C5H4PPh2)). The fraction with Rf =0.17 afforded ferrocenyl
1
777 w, 755 w, 737 s, 708 s, 696 s cm-1. H NMR (CDCl3, 400
MHz): δ 6.42 (s, 1 H, OH), 6.92-6.94 (d, J = 7.1 Hz, 4 H),
6.98-7.05 (m, 10 H, PhH), 7.10-7.17 (m, 7 H, PhH, Py-H5),
7.59 (d, J=7.8 Hz, 1 H, Py-H6), 7.64-7.68 (t, J=7.9 Hz, 1 H, Py-
H4), 8.41 ppm (d, J=4.8 Hz, 1 H, Py-H3). 13C NMR (CDCl3,
100 MHz): δ 89.82 (COH), 119.72 (Py-C6), 122.86, 127.13,
127.35, 127.94, 128.17, 129.68, 130.23 (all d), 134.51, 135.47
(both s), 137.73 (Py-C4), 143.70 (s), 147.73 (all s), 148.01 (Py-
C3), 157.91 ppm (Py-C1). UV-vis (CH2Cl2): λmax (log ε) 215
(3.31), 246 (3.36), 346 nm (2.88). MS (EI, 70 eV): m/z (%) 463
(100) [Mþ], 447 (5), 434 (70), 386 (15), 358 (75).. Anal. Calcd
for C34H25NO: C 88.09, H 5.44, N 3.02. Found: C 87.76, H 5.73,
N 2.77.
1-(8-Quinolinyl)-2,3,4,5-tetraphenylcyclopenta-2,4-dienol (3c).
To a solution of 8-bromoquinoline (435 mg, 2.10 mmol) in
dry THF (5 mL) was added n-BuLi (1.6 M in hexane, 1.50 mL,
2.40 mmol) at -100 °C within 20 min, and the mixture was
stirred for 30 min. Tetracyclone (1) (411 mg, 1.07 mmol) was
added in several portions with additional THF (25 mL).

224 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
alcohol 3j (620 mg, 51%) as a yellow-orange solid with mp
197-200 °C. IR (KBr): 3480 m, 3050 w, 3051 w, 3027 w, 1952 w,
1884 w, 1813 w, 1762 w, 1596, 1571 w, 1560 w, 1488 m, 1478 m,
1434 m, 1362 m, 1307 w, 1180 w, 1159 m, 1120 m, 1069 m, 1027
1442 m, 1334 m, 1229 s, 1255 m, 1217 w, 1163 w, 1145 m cm-1
.
1H NMR (CDCl3, 400 MHz): δ 6.79-6.81 (dd, J=1.5, 7.8 Hz, 4
H), 6.94-7.04 (m, 10 H), 7.09-7.18 (m, 6 H), 7.36-7.40 (t, J=
7.3 Hz, 1 H), 7.42 (d, J=7.8 Hz, 1 H), 7.51 (t, J=7.6 Hz, 1 H),
7.78 ppm (d, J=7.6 Hz, 1 H). The NH proton was not detected.
13C NMR (CDCl3, 100 MHz): δ 99.92 (C-O), 120.85, 124.55,
127.42, 127.51, 127.96, 128.09, 129.10, 129.15, 130.06 (all d),
130.97 (s), 132.67 (d), 133.39, 134.32, 142.72, 144.10, 145.73 (all s),
167.67 ppm (CdN). UV-vis (MeCN): λmax (log ε) 243 (4.54),
347 nm (3.80). MS (EI, 70 eV): m/z (%) 487 (100) [M]þ, 459 (5),
410 (5), 382 (15). Anal. Calcd for C36H25NO: C 88.68, H 5.17, N
2.87. Found: C 88.88, H 5.18, N 2.65.
m, 940 w, 865 m, 830 m, 779 w, 742 s, 697 s, 579 w, 547 w cm-1
.
1H NMR (CDCl3, 400 MHz): δ 2.58 (d, J=0.7 Hz, 1 H, OH),
3.58 (d, J=1.0 Hz, 4 H, (PPh2)FcH4), 3.75 (t, J=1.8 Hz, 2 H,
(C5Ph4OH)FcH), 3.85 (t, J=1.8 Hz, 2 H, (C5Ph4OH)FcH), 6.78
(dd, J = 2.0, 7.5 Hz, 4 H, PhH), 6.88-6.92 (m, 6 H, PhH),
7.12-7.26 ppm (m, 20 H, PhH). 13C NMR (CDCl3, 100 MHz): δ
67.61 ppm, 68.76 (both (C5Ph4OH)FcCH), 71.54 (d, JC-P
=
3.8 Hz, FcC-PPh2), 73.38 (d, JC-P = 14.5 Hz, HCFc(PPh2)),
76.08 (d, JC-P =5.6 Hz, HCFc(PPh2)), 87.09, 94.70 (both s),
126.65, 127.16, 127.39, 127.74 (all d), 128.30 (d, JC-P=6.9 Hz),
128.71, 130.03, 130.83 (all d), 135.58 (d, JC-P=19.4 Hz), 135.16,
136.05, 138.83 (d, JC-P=9.3 Hz, P(CC5H5)), 142.10, 146.67 ppm
(all s). UV-vis (MeCN): λmax (log ε) 224 (4.35), 243 (4.35),
359 nm (3.27). MS (FAB): m/z (%) 793 (10) [M þ O þ Na]þ,
770 (100) [M þ O]þ, 754 (53) [M]þ. Anal. Calcd for C51H39FeOP:
C 81.17, H 5.21. Found: C 81.02, H 5.09.
(S)-3-Methyl-2-(2,3,4,5-tetraphenyl-30H-spiro[cyclopenta-
[2,4]diene-1,10-isobenzofuran]-30-ylideneamino)butan-1-ol (spiro-3f).
To a solution of (S)-2-(2-bromophenyl)-4-isopropyl-4,5-dihy-
drooxazole (950 mg, 3.54 mmol) in dry THF (7 mL) was
added n-BuLi (1.6 M in hexane, 2.2 mL, 3.52 mmol) at -78 °C,
and the mixture was stirred for 1 h. Tetracyclone (1) (670 mg,
1.75 mmol) was added as a solid in several portions with
additional THF (25 mL) within 30 min, and the mixture was
stirred at room temperature for 12 h. The mixture was hydro-
lyzed with aqueous NH4Cl (1 N, 20 mL) and extracted with
EtOAc (3 ꢀ 30 mL). The combined organic extracts were dried
with MgSO4 and concentrated. The crude product was sub-
jected to flash column chromatography (silica, PE/EtOAc, 2:1;
Rf =0.17, 0.48, 0.60, 0.72, 0.83). The fraction with Rf =0.17
afforded spiro-3f (850 mg, 85%) as a slightly yellow foam.
Crystallization from DCM/PE yielded colorless crystals with
mp 126-128 °C. IR (KBr): 3079 w, 3052 w, 3028 w, 2956 w, 2869 w,
1700 s, 1598 w, 1490 w, 1467 w, 1441 w, 1288 w, 1246 w, 1132 w,
1100 w, 1073 m, 1058 m, 1029 w, 964 m, 935 w, 774 m, 741 m
cm-1. 1H NMR (CDCl3, 400 MHz): δ 0.62 (d, J=6.7 Hz, 3 H,
CH3), 0.83 (d, J=6.7 Hz, 3 H, CH3), 1.49 (br t, J=6.4 Hz, 1 H,
OH) 1.68-1.80 (sep, J=6.8 Hz, 1 H, CH(CH3)2), 3.54-3.66 (m,
2 H, CH2OH), 3.82 (td, J = 3.5, 7.5 Hz, 1 H, NCHCH2),
6.73-6.75 (m, 2 H, PhH), 6.83-6.85 (m, 2 H, PhH),
6.93-7.03 (m, 10 H, PhH), 7.09-7.17 (m, 6 H, PhH), 7.36 (td,
J=1.1, 7.6 Hz, 1 H, m-H Ph-CdN), 7.43 (d, J=7.7 Hz, 1 H, m-
H Ph-CdN), 7.48 (td, J=1.1, 7.4 Hz, 1 H, p-H Ph-CdN), 7.74
(d, J=7.6 Hz, 1 H, o-H Ph-CdN); δ 19.26, 19.61 (CH3), 30.39
(CH(CH3)2), 64.45 (NCHCH2OH), 65.23 (NCHCH2OH),
100.06 (C-O), 120.75 (m-CH Ph-CdN), 124.12 (o-CH
Ph-CdN), 127.32, 127.48, 127.51, 127.94, 127.98, 128.13,
128.96, 129.18, 129.30, 130.11, 130.17 (all d), 132.02 (p-CH
Ph-CdN), 132.26 (d), 133.62, 133.72, 134.33, 143.22, 143.35,
143.64, 143.75, 144.68 (all s), 159.77 ppm (CdN), 4 signals are
missing due to overlapping. UV-vis (MeCN): λmax (log ε) 240
(4.48), 344 nm (3.80). MS (FAB): m/z (%) 573 (100) [M]þ, 542
(65) [M - CH2OH]þ, 530 [M - C4H9]þ (10), 487 (15) [M -
CH2OH - C4H9 þ H]þ, 472 (10) [M - NC5H10OH]þ. Anal.
Calcd for C41H35NO2: C 85.83, H 6.15, N 2.44. Found: C 85.91,
H 6.43, N 2.26.
1-(2-N,N-Dimethylaminophenyl)-2,3,4,5-tetraphenylcyclopenta-
2,4-diene (and isomers) (4a). To a solution of alcohol 3a (1.09 g,
2.16 mmol) in dry THF (40 mL) was added n-BuLi (1.6 M in
hexane, 2.0 mL, 3.2 mmol) at room temperature, and the
mixture was stirred for 30 min. LiAlH4 (230 mg, 6.08 mmol)
was added in several portions, and the mixture was stirred for
2 h, hydrolyzed with aqueous NH4Cl (2 N, 40 mL), and filtrated.
The layers were separated, and the aqueous layer was extracted
with EtOAc (25 mL). The organic extracts were dried (Na2SO4)
and concentrated. The crude product was suspended in MeOH
(8 mL) and treated in the ultrasonic bath for 1 h. The precipitate
was isolated by filtration to afford cyclopentadiene 4a (mixture
of isomers) (1.86 g, 79%) as a pale yellow powder with mp
144-147 °C. IR (KBr): 3077 w, 3058 w, 3022 w, 2975 w, 2935 w,
2909 w, 2853 w, 2820 w, 2776 w, 1597 m, 1574 w, 1488 s, 1452 m,
1441 m, 1429 w, 1316 w br, 1193 w, 1157 w, 1098 w, 1071 w,
1051 w, 952 w, 930 w, 909 w, 836 w, 801 w, 787 w, 772 m, 757 m,
721 m, 693 s cm-1. 1H NMR (CDCl3, 400 MHz): δ 2.27, 2.44, 2.73
2-(2,3,4,5-Tetraphenyl-30H-spiro[cyclopenta[2,4]diene-1,10-
isobenzofuran]-30-yloxy)ethanol (spiro-3d). To a solution of 2-(2-
bromophenyl)-1,3-dioxolane (700 mg, 3.05 mmol) in THF
(15 mL) was added n-BuLi (1.6 M in hexane, 2.20 mL, 3.52 mmol)
at -65 °C, and the mixture was stirred for 30 min. Tetracyclone
(1) (1.76 g, 3.35 mmol) was added as a solid in several portions
with additional THF (30 mL) within 30 min, and the mixture
was stirred at room temperature for 12 h. The mixture was hydro-
lyzed with aqueous NH4Cl (1 N, 20 mL) and extracted with
EtOAc (3 ꢀ 30 mL). The combined organic layers were dried
with MgSO4 and concentrated, and the crude product was
subjected to flash column chromatography (silica, PE/EtOAc,
5:1; Rf = 0.10, 0.24, 0.38, 0.48). The fraction with Rf = 0.24
afforded spiro-3d (740 mg, 81%) as a slightly yellow foam, which
was suspended in MeOH and treated in the ultrasonic bath to
give an off-white solid with mp 156-158 °C. IR (KBr): 3450 w,
3078 w, 3050 w, 3027 w, 2926 w, 2870 w, 1597 m, 1573 w, 1489 m,
1460 w, 1441 m, 1383 w, 1344 w, 1266 w, 1226 w, 1190 w, 1117 br
m, 1094 m, 1071 m, 1049 m, 1030 m, 967 s, 937 w, 913 w, 812 w,
785 w, 752 m, 742 m, 697 vs cm-1. 1H NMR (CDCl3, 400 MHz):
δ 1.98 ppm (br s, 1 H, OH), 3.32-3.37 (m, 1 H, OCH2CH2OH),
3.40-3.45 (m, 1 H, OCH2CH2OH), 3.71 (t, J=8.8 Hz, 2 H,
OCH2CH2OH), 6.18 (s, 1 H, OCHO), 6.79 (d, J=6.8 Hz, 2 H),
6.91-6.93 (m, 6 H); 6.70-7.12 (m, 12 H), 7.27-7.33 (m, 3 H),
7.37-7.41 ppm (dt, J=2.1, 6.1 Hz, 1 H). 13C NMR (CDCl3,
100 MHz): δ 61.14 (OCH2CH2OH), 71.71 (OCH2CH2OH),
102.25 (CO), 108.62 (OCO), 120.72, 123.64, 126.91, 126.94,
127.04, 127.49, 127.61, 127.69, 128.38, 129.47, 129.71, 129.95,
129.98, 130.10 (all d, two d signals are missing due to over-
lapping), 134.38, 134.57, 134.61, 134.68, 139.18, 139.98, 142.22,
142.63, 145.66, 146.07 ppm (all s). UV-vis (MeCN): λmax (log ε)
248 (4.31), 361 nm (3.61). MS (FAB): m/z (%) 557 (10)
[M þ Na]þ, 534 (100) [M]þ, 517 (51) [M - OH]þ, 473 (61)
[M - HOC2H4O]þ. HRMS (EI): calcd for C38H30O3 534.2195,
found 534.2191.
2,3,4,5-Tetraphenyl-30H-spiro[cyclopenta[2,4]diene-1,10-iso-
benzofuran]-30-imine (spiro-3e). To a solution of 2-bromobenzo-
nitrile (780 mg, 4.30 mmol) in dry THF (5 mL) was added
n-BuLi (1.6 M in hexane, 2.70 mL, 4.32 mmol) at -78 °C, and
the mixture was stirred for 30 min. Tetracyclone (1) (990 g, 2.60
mmol) was added as a solid in several portions with additional
THF (50 mL) within 30 min, and the mixture was stirred at room
temperature for 12 h. The mixture was hydrolyzed with water
(30 mL) and extracted with MTBE (2 ꢀ 15 mL). The combined
organic extracts were dried (MgSO4) and concentrated. The
crude product was subjected to flash column chromatography
(silica, PE/EtOAc, 2:1; Rf=0.25, 0.44, 0.63, 0.81). The fraction
with Rf=0.25 yielded spiro-compound spiro-3e (930 mg, 73%)
as a colorless solid with mp 225 °C. IR (KBr): 3287 m, 3081 w,
3052 w, 3023 w, 1768 w, 1685 s, 1600 w, 1574 w, 1489 m, 1466 m,

Article
Organometallics, Vol. 30, No. 2, 2011 225
(s, 6 H, N(CH3)2), 5.05, 5.16, 5.65, 6.09 (s, 1 H, 6.2:4.6:1.7:1,
CpC-H), 6.48 (t, J=7.1 Hz, one isomer), 6.52-6.54 (dd, J=1.8,
7.6 Hz, one isomer), 6.63 (d, J=8.08 Hz, one isomer), 6.75 (d, J=
8.1 Hz, one isomer), 6.80-6.82 (dd, J=1.0, 7.3 Hz, one isomer),
6.83-6.93 (m, 3 H), 6.93-7.07 (m, 11 H), 7.07-7.14 (m, 3 H),
7.14-7.19 (m, 3 H), 7.19-7.26 (m, 2 H), 7.27-7.31 (m, 1 H),
7.32-7.36 ppm (dd, J=1.6, 7.5, one isomer). 13C NMR (CDCl3,
100 MHz): δ 42.34, 43.06, 43.40, 45.97 (all CH3), 57.09, 60.61,
62.01, 62.79 (all Cp-CH), 117.32, 118.14, 118.60, 120.78, 120.91,
121.83 (all d), 124.84 (assignment not possible), 126.09, 126.16,
126.17, 126.26, 126.30, 126.36, 126.40, 126.48, 126.53, 126.63,
126.85, 127.12, 127.22, 127.54, 127.70, 127.71, 127.82, 127.85,
127.87, 127.92, 127.98, 128.13, 128.36, 128.39, 128.41, 128.68,
128.72, 128.83, 128.98, 129.04, 129.12, 129.48, 129.59, 129.68,
129.97, 130.31, 130.33, 130.35, 132.10, 132.86, 132.98 (all d),
135.29, 135.77, 136.15, 136.36, 136.76, 136.79, 136.87, 137.03,
137.10, 139.00, 139.42, 141.85, 143.74, 144.19, 144.36, 144.56,
145.06, 145.44, 145.60, 145.77, 147.01, 148.29, 149.23, 151.76,
152.23, 152.36, 153.77 ppm (all s). UV-vis (MeCN): λmax (log ε)
210 (4.49), 242 (4.36), 361 nm (3.76). MS (EI, 70 eV): m/z (%)
489 (100) [M]þ, 398 (75). HRMS (EI): calcd for C37H31N
489.2456, found 489.2455.
1-(2-Pyridyl)-2,3,4,5-tetraphenylcyclopenta-2,4-diene (and
isomers) (4b). To a mixture of alcohol 3b (900 mg, 1.94 mmol) in
dry THF (20 mL) was added n-BuLi (1.6 M in hexane, 1.25 mL,
1.94 mmol) at -78 °C, and the mixture was stirred for 10 min.
LiAlH4 (230 mg, 5.97 mmol) was added in small portions,
and the mixture was stirred for 30 min and hydrolyzed with
water (2 mL), aqueous KOH (2 mL, 15%), and water (15 mL).
EtOAc (20 mL) was added, the mixture was transferred into a
separation funnel, and the aqueous layer was separated with its
solid contents. The solid in the organic layer was isolated by
filtration and washed with EtOAc (5 mL), acetone (5 mL), and
CH2Cl2 (5 mL) to give cyclopentadiene 4b (mixture of isomers)
(780 mg, 90%) as a poorly soluble off-white solid with mp
265 °C. Also after extended drying in vacuo THF keeps being
enclatherated. IR (KBr): 3076 w, 3053 w, 3025 w, 2996 w,
2924 w, 2967 w, 1597 w, 1683 m, 1560 w, 1487 m, 1458 m,
1442 m, 1430 m, 1384 w, 1334 w, 1312 w, 1279 w, 1172 w, 1150 w,
1124 w, 1091 w, 1072 w, 1028 w, 1012 w, 994 w, 936 w, 918 w, 908 w,
838 w, 790 m, 774 m, 761 m, 741 m, 719 m, 694 s, 618 w, 567 w,
557 m, 542 m cm-1. 1H NMR (CDCl3, 400 MHz): δ 1.79-1.90
(m, THF), 3.68-3.80 (m, THF), 5.18, 5.55, 5.60 (all s, 1 H,
1:3.2:2.6, CpC-H), 6.78 (dt, J=0.9, 7.8 Hz, “0.4 H”), 6.85-6.89
(ddd, J=1.1, 4.9, 7.4 Hz, “0.4 H”), 6.95-7.25 (m, 20 H), 7.29
(dd, J = 1.1, 8.1 Hz, “0.8 H”), 7.41-7.46 (m, “0.8 H”),
8.43-8.45, 8.47-8.49, 8.53-8.55 ppm (all ddd, J = 0.8, 1.7,
4.9 Hz, J=0.9, 1.7, 4.8 Hz, J=0.9, 1.7, 4.9 Hz, 1 H, all Py-H3).
13C NMR (CDCl3, 100 MHz): δ 61.70, 62.80, 64.79 (all CpCH),
121.01, 121.56, 121.87, 123.99, 126.41, 126.60, 126.66, 126.70,
126.86, 127.08, 127.25, 127.92, 127.97, 128.03, 128.11, 128.21,
128.41, 128.73, 128.79, 129.06, 129.16, 129.28, 130.08, 130.17,
130.22, 130.24 (all d), 135.23, 135.36, 135.94, 136.22 (all s),
136.46, 136.49 (no assignment possible), 136.76, 138.52, 144.43,
145.27, 145.53 (all s), 149.27, 149.32, 149.50 (all Py-C3), 149.50,
154.49, 159.32 ppm (all Py-C1), several signals are missing due
to overlapping and noise. UV-vis (MeCN): λmax (log ε) 212
(4.26), 247 (4.11), 341 nm (3.84). MS (EI, 70 eV): m/z (%) 447
(100) [M]þ, 369 (8) [M - C5H4N]þ. HRMS (EI): calcd for
C34H25N, 447.1987, found 447.1979.
filtered through a plug of silica. Evaporation afforded a
yellow foam, which was suspended in MeOH and treated in
the ultrasonic bath. The precipitate was isolated by filtration
to afford acetal 70 (mixture of two isomers) (750 mg, 65%) as
a colorless solid with mp 155-157 °C. IR (KBr): 3055 w, 3022 w,
2949 w, 2888 w, 2854 w, 1598 w, 1490 m, 1442 w, 1395 w, 1109 w,
1073 m, 1028 w, 992 w, 965 w, 948 w, 772 m, 757 m, 730 w,
698 s cm-1 1H NMR (CDCl3, 400 MHz): δ 3.70-3.78,
.
3.83-3.94, 3.94-4.01, 4.05-4.19 (all m, 4 H, CH2CH2),
5.12, 5.18 (5:1, both s, 1 H, CpCH), 5.60, 5.91 (1:5, both s,
1 H, OCHO), 6.90 (d, J=8.5 Hz, major isomer), 6.94-7.11 (m,
16 H, PhH), 7.11-7.20 (m, 3 H, PhH), 7.20-7.28 (m, 2 H,
PhH), 7.29-7.33 (dd, J = 1.1, 8.7 Hz, major isomer, PhH),
7.41-7.46 (m, minor isomer, PhH, o-PhCH-COO), 7.56-7.62
ppm (dd, J=7.8, 0.9 Hz, major isomer, o-PhCH-COO). 13C
NMR (CDCl3, 100 MHz): δ 61.88, 62.33 (both CpCH), 64.89,
65.02, 65.20, 65.26 (all CH2CH2), 101.63, 101.78 (both OCO),
125.86 (o-PhCH-COO), 126.32, 126.37, 126.40, 126.46, 126.51,
126.67, 126.73, 127.47, 127.67, 127.71, 127.75, 127.78, 127.84,
128.15, 128.35, 128.37, 128.55, 128.58, 128.74, 128.81, 129.01,
129.17, 129.72, 129.94, 130.03, 130.15, 131.26 (all d), 135.41,
135.69, 135.72, 135.74, 135.77, 135.90, 135.92, 136.15, 136.21, 136.47,
138.50, 138.61, 142.52, 142.62, 144.28, 144.53, 145.70, 146.22,
146.79 ppm (all s). UV-vis (MeCN): λmax (log ε) 361 (3.73),
244 (4.26), 217 nm (4.29). MS (EI, 70 eV): m/z (%): 518 (100)
[M]þ, 490 (82) [M - C2H4]þ, 474 (45) [M - C2H4 - O]þ. Anal.
Calcd for C38H30O2: C 88.00, H 5.83. Found: C 87.68, H 5.42.
General Procedure for the Palladium-Catalyzed Arylation of
Tetraphenylcyclopentadiene (7) with ortho-Functionalized Bro-
mobenzenes. A mixture of the ortho-functionalized bromoben-
zene (1.25 mmol), tetraphenylcyclopentadiene (7) (1 mmol),
Cs2CO3 (652 mg, 2.0 mmol), Pd(OAc)2 (14 mg, 5 mol %), and
PPh3 (34 mg, 10 mol %) in DMF (10 mL) in a screw-capped
flask was heated to 140 °C for 2 days. After cooling to rt CH2Cl2
(50 mL) and p-TsOH (1.5 g) were added, and the mixture was
stirred for 10 min. The mixture was filtrated over a short plug of
silica and eluted with CH2Cl2 (50 mL). After evaporation and
drying in vacuo (1mbar, 75 °C) the sticky crude product was
subjected to flash column chromatography (silica, PE/EtOAc).
1-(2-Formylphenyl)-2,3,4,5-tetraphenylcyclopenta-2,4-diene
(and isomers) (4d0). According to the general procedure, the
reaction of 2-(2-bromophenyl)-1,3-dioxolane (8d) (286 mg, 1.25
mmol) yielded after chromatography (PE/EtOAc, 20:1; Rf=0,
0.12, 0.18-0.27 (4d0), 0.42, 0.48, 0.54) cyclopentadiene 4d0
(mixture of isomers) (382 mg, 81%) as a yellow foam with mp
149-151 °C. IR (KBr): 3056 m, 3024 m, 1694 s, 1596 m, 1572 w,
1491 m, 1441 m, 1385 w, 1266 w, 1192 w, 1072 w, 1027 w cm-1
.
1H NMR (CDCl3, 400 MHz): δ 5.09, 5.16, 5.25, 5.25 (all s,
1:11:7.1:2, 1 H, all CpC-H), 6.77 (dd, J =1.6, 8.2 Hz, minor
isomer), 6.85-6.90 (m, 1 H), 6.90-6.95 (m, 2 H), 6.95-7.04
(m, 9 H), 7.04-7.13 (m, 5 H), 7.13-7.28 (m, 4 H), 7.31 (t, J=7.5
Hz, 1 H), 7.34-7.41 (m, 1 H), 7.45-7.52 (td, J=1.3, 7.5 Hz, one
isomer), 7.61 (t, J=8.2 Hz, minor isomer), 7.73, 7.79 (both dd,
J=0.8, 7.4 Hz; J=1.1, 7.7 Hz, major isomers), 9.72, 9.97, 10.20,
10.26 ppm (all s, 1 H, CHO). 13C NMR (CDCl3, 100 MHz):
62.35, 63.14, 64.89 (all CpC-H), 126.64, 126.75, 126.78, 126.83,
127.03, 127.07, 127.23, 127.42, 127.50, 127.75, 127.78, 127.80,
127.84, 127.87, 127.92, 128.00, 128.05, 128.08, 128.13, 128.25,
128.30, 128.57, 128.67, 128.69, 128.79, 128.83, 128.88, 128.94,
128.99, 129.94, 130.06, 130.11, 131.21, 131.39, 132.13 (all d),
132.98 (s), 133.54, 133.88, 133.99 (all d), 134.61, 134.72, 134.76,
135.14, 135.32, 135.34, 135.55, 136.74, 137.54, 137.73, 140.21,
140.38, 140.40, 140.52, 143.31, 143.95, 144.23, 146.52, 146.71,
146.86, 148.72, 149.08 (all s), 191.15, 191.23, 191.36 ppm (all
CHO). UV-vis (MeCN): λmax (log ε) 216 (4.43), 247 (4.40), 331
nm (3.97). MS (EI, 70 eV): m/z (%) 474 (100) [M]þ, 383 (15).
HRMS (EI): calcd for C36H26O 474.1984, found 474.1972.
1-(2-Cyanophenyl)-2,3,4,5-tetraphenylcyclopenta-2,4-diene
(and isomers) (4e). According to the general procedure, the
reaction of 2-bromobenzonitrile (460 mg, 1.24 mmol) yielded
1-(2-(1,3-Dioxolan-2-yl)phenyl)-2,3,4,5-tetraphenylcyclopenta-
2,4-diene (and isomer) (4d). To a solution of 2-(2-bromo-
phenyl)-1,3-dioxolane (706 mg, 3.08 mmol) in dry THF
(10 mL) was added n-BuLi (1.6 M in hexane, 2.20 mL,
3.52 mmol) at -78 °C, and the mixture was stirred for 30 min.
Tetracyclone (1) (855 mg, 2.23 mmol) was added in several
portions with additional THF (60 mL), and the mixture was
stirred at room temperature for 2 h. LiAlH4 (250 mg,
6.59 mmol) was added, and the mixture was stirred for 1 h.
After hydrolyzation with water (30 mL), the organic layer was

226 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
after chromatography (PE/EtOAc, 10:1; Rf =0.05, 0.22-0.28
(4e), 0.48, 0.53, 0.63) cyclopentadiene 4e (mixture of isomers)
(450 mg, 77%) as a yellow foam with mp 91 °C. IR (KBr): 3078 w,
3056 m, 3024 w, 2223 w, 1597 m, 1574 w, 1488 m, 1441 m,
1384 w, 1332 w, 1281 w, 1266 w, 1178 w, 1157 w, 1127 w, 1072 m,
1028 m, 912 w, 803 w, 757 m, 696 s, 563 w, 549 w, 517 w cm-1. 1H
NMR (CDCl3, 400 MHz): δ 5.12, 5.24, 5.27, 5.33, 5.69 (all s, 1 H,
6.8:1:4.4:3.4:3.5, CpC-H), 6.85 (d, J=7.7 Hz, minor isomer),
6.90-7.24 (m, 21 H), 7.23-7.54 ppm (3 H, several d). 13C NMR
(CDCl3, 100 MHz): δ 59.65, 62.65, 62.71, 63.32, 63.49 (all
CpCH), 109.70, 112.92, 113.39, 114.15, 114.23, 117.97, 118.55,
118.71, 119.02 (all s, CtN and CCtN), 126.57, 126.70, 126.73,
126.78, 126.81, 126.91, 126.97, 127.57, 127.62, 127.71, 127.88,
127.94, 128.03, 128.05, 128.10, 128.13, 128.17, 128.51, 128.61,
128.75, 128.78, 128.82, 128.85, 128.91, 129.05, 129.07, 129.13,
130.06, 130.09, 130.17, 130.20, 130.29 (all d), 130.85 (s), 131.68,
131.85, 132.11, 132.58 (no unambiguous assignment possible),
132.76, 132.97, 133.20, 134.73, 134.93, 135.00, 135.11, 135.39,
135.51, 135.53, 135.71, 135.76, 135.95, 136.78, 137.18, 137.72,
140.52, 140.87, 140.98, 141.02, 141.60, 142.98, 143.41, 143.92,
145.28, 146.68, 146.89, 146.94, 147.22, 147.42, 149.36, 150.18
ppm (all s). UV-vis (MeCN): λmax (log ε) 213 (4.44), 308 (3.86),
331 nm (3.90). HRMS (EI): calcd for C36H25N 471.1987, found
474.1984.
PE/toluene, 3:2; Rf=0, 0.18 (4j). IR (KBr): 3050 w, 3022 w, 2922 w,
2852 w, 1945 w, 1874 w, 1804 w, 1743 w, 1598 m, 1572 w, 1491 m,
1478 m, 1450 w, 1433 m, 1382 w, 1325 w, 1306 w, 1179 w, 1158 w,
1120 w, 1080 w, 1069 w, 1026 m, 999 w, 942 w, 910 w, 887 w,
867 w, 842 m, 767 m, 742 m, 727 w, 695 s, 631 w, 565 w cm-1. 1H
NMR (CDCl3, 400 MHz): δ 3.68 (td, J = 1.4, 2.9 Hz, 1 H,
(PPh2)FcCH), 3.81 (dt, J=1.3, 2.6 Hz, 1 H, (C5Ph4)FcCH), 3.84
(dt, J=1.3, 2.5 Hz, 1 H, (C5Ph4)FcCH), 3.88-3.90 (m, 2 H,
(C5Ph4)FcCH), 3.98 (td, J=1.2, 2.4, 1 H, (PPh2)FcCH), 4.04
(ddd, J=1.2, 2.4, 3.4 Hz, 1 H, (PPh2)FcCH), 4.15 (dd, J=2.3,
3.0 Hz, 1 H, (PPh2)FcCH), 5.07(s, 1H, CpCH), 6.95-7.02 (m, 7 H),
7.07-7.10 (m, 4 H), 7.15 (br s, 2 H), 7.21 (t, 3 H), 7.26-7.34 ppm
(m, 14 H). 13C NMR (CDCl3, 100 MHz): δ 61.98 (Ph4CpCH),
68.05, 69.09, 69.89, 70.0 (all (PPh2)FcCH), 72.56-72.66 (two
overlapping d signals, (PPh2)FcCH), 73.41 (d, JC,P =4.5 Hz),
74.89 (d, JC,P =18.5 Hz) (all (C5Ph4)FcCH), 76.44 (d, JC,P
=
6.6 Hz, FcC-PPh2), 81.63 (FcC-C5Ph4), 126.19, 126.65, 126.70,
127.08, 127.77, 127.93, 128.21, 128.25, 128.27, 128.43, 128.59,
128.63, 128.66, 129.17, 130.15, 130.14 (all d, no assignment
possible to C,P coupling), 133.30 (d, JC,P = 19.0 Hz), 133.76
(d, JC,P=19.4 Hz) (both d), 135.51, 136.03, 137.51 (all s), 138.83
(d, JC,P=10.2 Hz), 139.52 (d, JC,P=10.5 Hz) (both s), 139.59,
143.60, 143.73, 144.22, 146.31 ppm (all s). UV-vis (MeCN):
λ
max (log ε) 215 (4.70), 246 (4.57), 368 (3.54), 458 nm (3.27). MS
Alternatively, 4e was synthesized by reduction of spiro-3e
according to the general procedure for the reduction of the
ferrocenyl alcohols 3i-j (vide infra). spiro-3e (608 mg, 1.25
mmol) and LiAlH4 (75 mg, 1.98 mmol) gave after chromatog-
raphy (PE/EtOAc, 10:1; Rf =0, 0.1, 0.22-0.28 (4e)) nitrile 4e
(295 mg, 50%), whose spectroscopic data are in accordance with
the product from the palladium-catalyzed reaction.
(EI, 70 eV): m/z (%) 738 (100) [M]þ, 553 (7) [M - PPh2]þ, 489
(16) [M - C5H4PPh2]þ. Anal. Calcd for C51H39FeP: C 82.93, H
5.32. Found: C 82.76, H 5.39.
Chlorodicarbonyl-η5-[1-(2-N,N-dimethylaminophenyl)-2,3,4,5-
tetraphenylcyclopentadienyl]ruthenium(II) (5a). A mixture
of Ru3(CO)12 (115 mg, 0.18 mmol) and cyclopentadiene 4a
(285 mg, 0.54 mmol) in a mixture of toluene (2 mL) and
decane (4 mL) in a screw-capped flask was placed in a preheated oil
bath at 160 °C and was stirred for 2 days. After cooling to
room temperature, chloroform (0.5 mL) was added and the
mixture was stirred for 1.5 h at 160 °C. At room temperature the
reaction mixture was directly subjected to flash column chro-
matography (silica, toluene). The second yellow fraction yielded
ruthenium complex 5a (210 mg, 57%) as an orange-yellow foam.
Crystallization by slow diffusion of methanol into a solution of
5a in dichloromethane afforded orange crystals that decompose
at 187-190 °C. IR (KBr): 3061 w, 2669 w, 2934 w, 2858 w, 2826 w,
2775 w, 2036 vs, 1988 vs, 1596 w, 1578 w, 1566 w, 1499 m, 1477 w,
1446 m, 1429 w, 1406 w, 1329 w, 1262 w, 1198 w, 1180 w,
1158w, 1134 w, 1097 w, 1076 w, 1055 w, 1030 w, 953 w, 938w, 914
General Procedure for the Reduction of the Ferrocenyl Alcohols
3i-j to Cyclopentadienes 4i-j. The ferrocenyl alcohol was
dissolved in THF (5 mL), lithium aluminum hydride (in excess)
was added, and the mixture was stirred for 16 h. The mixture
was hydrolyzed with water (15 mL) and extracted with MTBE
(3 ꢀ 15 mL). The combined organic extracts were filtered through a
short plug of silica, and the filtrate was evaporated. The result-
ing foam was suspended in MeOH and treated in the ultrasonic
bath. The product was isolated by filtration. Column chroma-
tography of the mother liquor afforded additional product.
1-(2,3,4,5-Tetraphenylcyclopenta-1,3-dienyl)ferrocene (4i). Ac-
cording to the general procedure the reaction of ferrocenyl
alcohol 3i (475 mg, 083 mmol) and LiAlH4 (150 mg, 3.96 mmol)
yielded cyclopentadiene 4i (345 mg, 75%) as a red-orange powder
with mp 97-102 °C. TLC, silica: PE/EtOAc, 50:1; Rf=0.03, 0.07,
0.20 (4i). IR (KBr): 3078 w, 3054 m, 3022 m, 2923 w, 2853 w, 1944
w, 1871, 1598 m, 1574 w, 1491 m, 1441 m, 1410 w, 1384 w, 1331 w,
1259 w, 1177 w, 1156 w, 1105 m 1070 m, 1028 w, 1001 m, 942 w,
911 w, 867 w, 817 m, 766 m, 696 s, 565 m, 537 w, 504 cm-1 m. The
best quality 1H NMR spectrum was obtained directly after
isolation of the product at 200 MHz. Later signal broadening
became more obvious. 1H NMR (200 MHz, CDCl3): δ 3.83 (s, 1
H, FcCH, (C5Ph4)FcCH), 3.91 (s, 6 H, FcCH, (C5Ph4)FcCH),
3.99 (s, 2 H, FcH, (C5Ph4)FcCH), 4.97 (s, 1 H, CpCH,
(C5Ph4)FcCH), 6.88-6.94 (m, 6 H), 7.01-7.31 ppm (m, 14 H).
13C NMR (CDCl3, 100 MHz): δ 61.97 (CpCH), 66.60, 68.21,
68.27, 68.45 (all (C5Ph4)FcCH), 69.18 (FcCH), 80.64 (s, FcC-
C5Ph4), 126.00, 126.54, 126.90, 127.63, 127.78, 128.02, 128.49,
128.96, 129.90, 129.99 (all d), 135.41, 135.98, 137.61, 139.55,
142.81, 143.85, 144.70, 145.59 ppm (all s), two signal are missing
due to overlapping. UV-vis (MeCN): λmax (log ε) 207 (4.59), 240
(4.30), 368 (3.86), 456 nm (3.09). MS (EI, 70 eV): m/z (%) 554
(100) [M]þ, 489 (18) [M-C5H5]. HRMS (EI): calcd for C39H30Fe
554.1697, found 554.1695.
w, 845 w, 800 w, 763 m, 754 m, 736 m, 725 w, 697 m, 570 m cm-1
.
1H NMR (CDCl3, 400 MHz): δ 2.24 (s, 6 H, CH3), 6.74 (d, J=
8.1 Hz, 1 H), 6.88 (t, J=7.3 Hz, 1 H), 6.93 (d, J=7.3 Hz, 4 H),
7.00 (t, J=7.3 Hz, 4 H), 7.08-7.15 (m, 10 H), 7.20-7.25 (m, 3 H),
7.46 ppm (dd, J=7.6, 1.4 Hz, 1 H, (NMe2)PhH3). 13C NMR
(CDCl3, 100 MHz): δ 41.86 (CH3), 103.51, 105.31, 109.01 (all
CpC), 119.38, 121.93 (both d), 123.20 (s), 127.20, 128.00, 128.08,
129.29, 129.87 (all d), 130.18, 130.22 (both s), 130.88, 132.42
(all d), 135.75 ((NMe2)Ph-C3), 151.69 (s), 197.00 ppm (Ru-CO).
UV-vis (MeCN): λmax (log ε) 222 (4.50), 360 nm (3.17). MS
(FAB): m/z (%) 704 (7) [M þ Na]þ, 681 (18) [M]þ, 646 (45)
[M - Cl]þ, 625 (100) [M - 2CO]þ, 588 (45) [M - 2CO - Cl]þ.
Chlorodicarbonyl-η5-[1-(2-pyridyl)-2,3,4,5-tetraphenylcyclo-
pentadienyl]ruthenium(II) (5b). A mixture of Ru3(CO)12 (210 mg,
0.33 mmol) and cyclopentadiene 4b (447 mg, 0.97 mmol) in a
mixture of toluene (2 mL) and decane (4 mL) in a screw-capped
flask was placed in a preheated oil bath at 160 °C and was stirred
for 3 days. After cooling to room temperature, chloroform
(1 mL) was added and the mixture was stirred for 1.5 h at
160 °C. The solvents were evaporated, and the crude product was
purified by flash column chromatography (TLC silica: PE/
CH2Cl2, 1:1 f 1:4). The orange-yellow fraction yielded ruthe-
niumcomplex 5b (285 mg, 46%) as a yellow solid. Crystallization
by slow diffusion of methanol into a solution of 5b in dichloro-
methane afforded yellow-orange crystals that decompose at
182-185 °C. IR (KBr): 3086 w, 3057 w, 3025 w, 2048 vs, 1988 vs,
1-Diphenylphosphino-10-(2,3,4,5-tetraphenylcyclopenta-1,3-
dienyl)ferrocene (4j). According to the general procedure the
reaction of ferrocenyl alcohol 3j (280 mg, 0.37 mmol) and
LiAlH4 (38 mg, 1 mmol) yielded cyclopentadiene 4j (210 mg,
77%) as a red powder or foam with mp 106-109 °C. TLC, silica:

Article
Organometallics, Vol. 30, No. 2, 2011 227
1585 m, 1566 w, 1541 w, 1502 w, 1481 w, 1445 w, 1420 w, 1384 w,
1285 w, 1181 w, 1155 w, 1073 w, 1029 w, 993 w, 914 w, 843 w, 810
w, 788 w, 746 m, 697s, 572w cm-1. 1H NMR(CDCl3, 400MHz):
δ 6.99 (dd, J=3.3, 5.2 Hz, 4 H), 7.03-7.11 (m, 11 H), 7.11-7.23
(m, 6 H), 7.35 (dt, J=1.0, 7.8 Hz, 1 H, Py-H6), 7.50 (td, J=1.8,
7.7 Hz, 1 H, Py-H5), 8.42 ppm (ddd, 1 H, J=0.9, 1.7, 4.8 Hz,
Py-H3). 13C NMR (CDCl3, 100 MHz): δ 104.19, 106.15, 109.12
(all CpC), 123.02 (Py-C4), 127.61, 127.87, 128.08, 128.54, 128.55
(all d), 129.53, 129.82 (both s), 131.95, 132.37, 136.24 (Py-C5),
149.43 (Py-C3), 150.78 (Py-C1), 196.77 ppm (Ru-CO). UV-vis
(MeCN):λmax (logε) 219(4.45), 265(sh, 4.20), 361nm(3.04). MS
(FAB): m/z (%): 662 (2) [M þ Na]þ, 640 (10) [M þ H]þ, 604 (8)
[M - Cl]þ, 583 (30) [M - 2CO]þ, 548 (40) [M - 2CO - Cl]þ, 486
(10), 464 (100).
745 (36) [M - 1]þ, 711 (37) [M - Cl]þ, 690 (100) [M - 2CO]þ,
655 (100) [M - 2CO - Cl]þ.
Chlorocarbonyl-η5-[1-(2-N,N-dimethylaminophenyl)-2,3,4,5-
tetraphenylcyclopentadienyl]ruthenium(II) (6a). A solution of
complex 5a (98 mg, 0.14 mmol) in toluene (200 mL) was
irradiated for 12 h with a high-pressure mercury lamp (125 W).
The solvent was evaporated, and the residue was subjected to
column chromatography (silica, toluene). The obtained purple
fraction was recrystallized from CH2Cl2/MeOH to give the
decarbonylated ruthenium complex 6a as a deep purple solid
(57 mg, 64%) that decomposes at 251 °C. IR (KBr): 3109 w, 3082
w, 3055 w, 3026 w, 2971 w, 2924 w, 2905 w, 2863 w, 2833 w, 2785
w, 1942 vs, 1600 w, 1578 w, 1502 m, 1464 w, 1444 m, 1413 w, 1385
w, 1312 w, 1262 w 1178 w, 1155 w, 1132 w, 1094 w, 1073 w, 1028
w, 999 w, 912 w, 802 w, 755 m, 735 m, 697 s, 621 w, 600 w, 582 m,
556 m cm-1. 1H NMR (CDCl3, 400 MHz): δ 2.40 (s, 3 H, CH3),
3.19 (s, 3 H, CH3), 6.89-7.07 (m, 18 H), 7.11 (d, J=9.1 Hz, 2 H),
7.17-7.20 (m, 1 H), 7.26 (d, J=7.6 Hz, 1 H), 7.35 ppm (dd, J=
1.4, 7.8 Hz, 2 H). 13C NMR (CDCl3, 100 MHz): δ 55.69, 59.47
(both CH3), 91.25, 92.09, 92.27, 102.51, 108.97 (all CpC), 120.77,
127.20, 127.53, 127.62, 127.68, 127.76, 127.82, 127.85, 127.97 (no
unambiguous assignment possible), 129.67 (d), 130.81 (s),
131.16, 131.34, 131.43, 131.58, 131.65, 131.78, 132.18, 132.27
(no unambiguous assignment possible), 132.52 (d), 165.38 (s),
204.35 ppm (Ru-CO). UV-vis (MeCN): λmax (log ε) 245 (4.16),
383 (3.01), 503 nm (2.70). MS (FAB): m/z (%) 652 (5) [M - 1]þ,
625(100) [M - CO]þ, 618 (50) [M - Cl]þ, 590 (20) [M - CO -
Cl]þ, 588 (30), 572 (35), 560 (20).
Chlorodicarbonyl[η5-1-(2-cyanophenyl)-2,3,4,5-tetraphenylcyclo-
pentadienyl]ruthenium(II) (5e). A mixture of Ru3(CO)12 (129 mg,
0.20 mmol) and cyclopentadiene 4e (283 mg, 0.61 mmol) in a
mixture of toluene (1.5 mL) and decane (3 mL) in a screw-capped
flask was placed in a preheated oil bath at 160 °C and was stirred
for 2 days. After cooling to room temperature, chloroform
(0.5 mL) was added and the mixture was stirred for 1.5 h at
160 °C. The solvents were evaporated, and the residue was
subjected to chromatography (TLC: silica, PE/CH2Cl2 1:1;
Rf=0, 0.25, 0.34-0.42 (4e, 140 mg recovered), 0.50, 0.56, 0.72,
0.84). The yellow fraction with Rf=0.25 yielded slightly impure
ruthenium complex 5e as a yellow solid (50 mg, 26%, based on
converted 4e) that could be further purified by crystallization
from CH2Cl2/MeOH to give a yellow solid that decomposes at
190 °C, but still contained minor impurities and CH2Cl2. IR
(KBr): 3109 w, 3059 w, 3031 w, 2991 w, 2959 w, 2922 w, 2852 w,
2228 w, 2049 vs, 2004 vs, 1972 m (impurity), 1635w, 1597 w, 1578 w,
1500 w, 1442 m, 1420 w, 1387 w, 1314 w, 1277 w, 1187 w, 1158 w,
1097 w, 1075 w, 1028 w, 1003 w, 920 w, 908 w, 853 w, 847 w,
780 m, 761 m, 732 m, 705 s, 695 s, 625 w, 605 w, 580 m, 568 m,
552 cm-1 s. 1H NMR (CDCl3, 400 MHz): δ6.98 (dd, J=1.1, 8.3 Hz,
4 H), 7.03-7.18 (m, 14 H), 7.23 (ddd, J=1.5, 6.6, 2.9 Hz, 2 H),
7.39(td, J=1.1, 7.7Hz, 1 H), 7.51-7.56(m, 2 H), 7.93 ppm(d, J=
7.4 Hz, 1 H). 13C NMR (CDCl3, 100 MHz): δ 104.18, 113.55,
115.46, 115.69 (all s, 3 ꢀ CpC), 127.85, 128.33, 128.49, 128.78,
128.97, 129.15 (all d), 129.49 (s), 131.99, 132.42, 132.77 (all d),
133.54 (s), 136.57 (d), 196.49 ppm (CO), one carbon is missing
due to overlapping and noise. UV-vis (MeCN): λmax (log ε) 216
(4.52), 249 (sh, 4.33), 359 nm (3.40). MS (MALDI-TOF): m/z
(%) 1216 (26) [2M - 2CO]þ, 1181 (100) [2M - 2CO - Cl]þ, 572
(68) [M - 2CO - Cl]þ.
Chlorocarbonyl-η5-[1-(8-quinolinyl)-2,3,4,5-tetraphenylcyclo-
pentadienyl]ruthenium(II) (6c). To a solution of 8-bromoquino-
line (455 mg, 2.10 mmol) in THF (5 mL) was added n-BuLi
(1.6 M in hexane, 1.35 mL, 2.16 mmol) at -100 °C within 20 min,
and the mixture was stirred for 30 min. Tetracyclone (1) (576 mg,
1.50 mmol) was added in several portions with additional THF
(30 mL), and the mixture wasstirred for 2 h at roomtemperature.
LiAlH4 (150 mg, 4.00 mmol) was added in small portions, and
the mixture was stirred for 1 h, hydrolyzed with water (30 mL),
and extracted with EtOAc (2 ꢀ 30 mL). The combined organic
extracts were filtrated over a plug of silica (EtOAc), the filtrate
was evaporated, MeOH was added to the residue, and the
mixture was sonicated in the ultrasonic bath. The crude cyclo-
pentadiene 4c (188 mg, 25%) was isolated by filtration as a
yellowish, poorly soluble powder, dried in vacuo, and subjected
to the complexation step without further purification. HRMS
(EI): calcd for C38H27N 497.2143, found 497.2155. A mixture of
Ru3(CO)12 (48 mg, 0.07 mmol) and quinoline 4c (111 mg, 0.22
mmol) in a mixture of xylene (1 mL) and decane (2 mL) in a
screw-capped flask was placed in a preheated oil bath at 160 °C
and was stirred for 3 days. After cooling to room temperature,
chloroform (0.5 mL) was added and the mixture was stirred for
1.5 h at 160 °C. The resulting red precipitate was isolated by
filtration, dissolved in CH2Cl2, and filtrated over a short plug of
silica. Evaporating of dichloromethane yielded ruthenium com-
plex 6c (75 mg, 52%, based on the assumption of pure 4c) as a
red solid that decomposes at 263 °C. IR (KBr): 3105 w, 3085 w,
3052 w, 3036 w, 1955 vs, 1932 vs, 1599 w, 1585 w, 1501 s, 1444 m,
1413 w, 1376 w, 1308 w, 1260 w, 1231 w, 1212 w, 1198 w, 1183 w,
1155 m, 1137 w, 1072 m, 1028 m, 1001 w, 986 w, 965 w, 939 w, 922 w,
833 m, 800 m, 785 w, 770 s, 746 s, 727 s, 696 vs, 585 m, 570 m, 551 m,
538 m cm-1. 1H NMR (CDCl3, 400 MHz): δ 6.92-7.12 (m, 14 H),
7.14-7.18 (m, 2 H), 7.19-7.22 (m, 2 H), 7.30 (dd, J=5.1, 8.4 Hz,
1 H, Qui-H3), 7.38 (dd, J=1.8, 7.8 Hz, 2 H, o-PhH), 7.49 (dd,
J=7.2, 8.1 Hz, 1 H, Qui-H6), 7.62 (dd, J=1.1, 8.2 Hz, 1 H, Qui-
H5), 7.83 (dd, J=1.2, 7.1 Hz, 1 H, Qui-H7), 8.00 (dd, J=1.4, 8.4
Hz, 1 H, Qui-H4), 8.93 ppm (dd, J=1.5, 5.1 Hz, 1 H, Qui-H2).
13C NMR (CDCl3, 100 MHz): δ 90.3, 96.8, 99.2, 104.4 (all CpC),
110.3 (CpC-Qui), 123.7 (Qui-C3), 127.2 (Qui-C6), 127.4, 127.5,
127.6, 127.7, 127.8, 127.9, 128.0 (no unambiguous assign-
ment possible), 128.1 (Qui-C5), 129.2 (Qui-C4a), 131.7, 131.8,
132.4 (two overlapping signals) 133.1 (Qui-C7), 136.9 (Qui-C4),
Chlorodicarbonyl-η5-[1-ferrocenyl-2,3,4,5-tetraphenylcyclo-
pentadienyl]ruthenium(II) (5i). A mixture of Ru3(CO)12 (48 mg,
0.075 mmol) andferrocene 4i (120 mg, 0.21 mmol) in a mixture of
toluene (0.5 mL) and decane (1 mL) in a screw-capped flask was
placedin a preheatedoilbath at160 °C and wasstirred for 2 days.
After cooling to room temperature, chloroform (0.5 mL) was
added and the mixture was stirred for 1.5 h at 160 °C. After
cooling to room temperature the reaction mixture was directly
subjected to flash column chromatography (silica, toluene). The
deep red band yielded ruthenium complex 5i (110 mg, 70%) as a
red-purple solid. Crystallization by slow diffusion of methanol
into a solution of 5i in dichloromethane afforded red-purple
crystals that decompose at 250 °C. IR (KBr): 3083 w, 3056 w,
3020 w, 2030 vs, 1980 vs, 1638 br w, 1601 w, 1578 w, 1501 w, 1479 m,
1444 m, 1390 w, 1356 w, 1345 w, 1315 w, 1180 w, 1159 w, 1106 w,
1074 w, 1045 w, 1030 w, 1002 w, 909 w, 873 w, 860 w, 820 w,
781 w, 769 m, 724 w, 699 m, 583 m, 570 m, 541 w, 500 w cm-1. 1H
NMR (CDCl3, 400 MHz): δ 3.47 (s, 2 H, (C5Ph4)Fc-CH), 3.99 (s,
5 H, Fc-CH), 4.10 (s, 2 H, (C5Ph4)Fc-CH), 7.01 (t, J=7.3 Hz,
4 H), 7.08 (d, J=7.3 Hz, 6 H), 7.42 (s, 6 H), 7.64 ppm (s, 4 H). 13
C
NMR (CDCl3, 100 MHz): δ 69.84, 69.88, 69.91 (allFcCH), 74.97
(FcC-C5Ph4), 99.68, 110.30, 115.75 (all CpC), 127.66, 128.30,
128.54, 128.89 (all d), 129.76, 131.86 (both s), 132.10, 133.69
(both d), 196.74 ppm (Ru-CO). UV-vis (MeCN): λmax (log ε)
214 (4.60), 382 (3.24), 478 nm (3.17). MS (FAB): m/z (%)

228 Organometallics, Vol. 30, No. 2, 2011
Kanthak et al.
156.9 (Qui-C2), 160.7 ppm (Qui-C8a). Six signals are missing due
to overlapping and noise. Most quaternary carbons were detected
by their cross-peaks in the HMBC spectrum since the poor
solubility of the substance impedes a high-quality 13C NMR
spectrum. UV-vis (MeCN): λmax (log ε) 229 (4.50), 367 (3.52),
434 nm (3.34). MS (LIFDI): m/z (%) 661 (100) [M]þ.
(SRu)-Carbonylchloro-η5-[1-(2-((S)-4-isobutyloxazolinyl)-
phenyl)-2,3,4,5-tetraphenylcyclopentadienyl]ruthenium(II) (6g).
According to the general procedure (S)-2-phenyl-4-isopropyl-
4,5-dihydrooxazole (457 mg, 2.25 mmol), n-BuLi (1.6 M in
hexane, 1.50 mL, 2.40 mmol), tetracyclone (1) (600 mg, 1.56
mmol), and LiAlH4 (220 mg, 5.81 mmol) yielded “crude”
cyclopentadiene 4g (365 mg, 41%) after chromatography
(TLC, silica: PE/EtOAc, 10:1 Rf = 0, 0.24-0.38 (4g), 0.51,
0.69). MS (FAB): m/z 572 (100) [M þ 1]þ. The reaction of 4g
(210 mg, 0.37 mmol) with Ru3(CO)12 (80 mg, 0.13 mmol) yielded
the chelated ruthenium oxazolinyl complex 6g as a red solid
(160 mg, 58% based on the assumption of pure 4g), which
decomposes at 210 °C. IR (KBr): 3084 w, 3056 w, 3032 w, 2955
m, 2901 w, 2869 w, 1964 vs, 1952 vs, 1611 m, 1576 w, 1500 m,
1444 m, 1420 w, 1404 w, 1371 m, 1348 w, 1314 w, 1269 w, 1246 m,
1231 m, 1181 w, 1148 w, 1138 w, 1058 m, 1073 m, 1055 w, 1028
m, 973 w, 958 w, 922 w, 805 w, 785 w, 767 w, 747 m, 736 s, 698 s,
622 w, 581 s, 568 m, 537 w cm-1. 1H NMR (CDCl3, 400 MHz): δ
0.97 (d, J=6.6 Hz, 3 H, CH3), 1.01 (d, J=6.6 Hz, 3 H, CH3), 1.27
(ddd, J=4.1, 11.4, 13.0 Hz, 1 H, CH2CH(CH3)2), 1.58-1.66 (m,
1 H, CH(CH3)2), 2.04 (ddd, 1 H, J=2.6 Hz, 10.1, 12.8 Hz, 1 H,
CH2CH(CH3)2), 3.93 (t, J=8.8 Hz, 1 H, CH2(Oxaz)), 4.31 (dd,
J=4.3, 8.4 Hz, 1 H, CH2(Oxaz)), 4.82-4.89 (m, 1 H, CH(Oxaz)),
6.88 (d, J=8.6 Hz, 2 H, o-PhH), 6.93-7.16 (m, 19 H, PhH,
(Oxaz)Ph-H6), 7.31-7.37 (m, 2 H, (Oxaz)Ph-H5, (Oxaz)Ph-
H4), 7.76-7.78 ppm (m, 1 H, (Oxaz)Ph-H3). 13C NMR (CDCl3,
100 MHz): δ 21.69, 24.23 (both CH3), 25.75 (CH(CH3)2), 42.14
(CH2CH(CH3)2), 64.38 (CH(Oxaz)), 71.96 (CH2(Oxaz)), 86.33
(CpC-Ph(Oxaz)), 89.45, 94.93, 95.57, 118.23 (all CpC), 127.21,
127.44, 127.47, 127.64, 127.71, 127.96, 128.03, 128.07 (all d),
128.15 ((Oxaz)Ph-C4/5), 130.27 ((Oxaz)Ph-C2), 130.41
((Oxaz)Ph-C3), 130.91, 131.47 (both s), 131.64, 131.88, 132.04,
132.28, 132.31 (no unambiguous assignment possible), 132.77,
133.12, 133.44 (all d), 163.28 (CdN), 204.58 ppm (Ru-CO), one
signal is missing due to overlapping. UV-vis (MeCN): λmax (log ε)
240 (4.17), 368 (3.29), 484 nm (2.86). MS (FAB): m/z (%) 735 (2)
[M]þ, 707 (100) [M - CO]þ, 700 (23) [M - Cl]þ, 686 (5), 670
[M - CO - Cl - 2]þ.
General Procedure for the Synthesis of Ruthenium(II) Oxazo-
line Complexes 6f-h. To a solution of the phenyloxazoline or
2-bromophenyloxazoline in THF (10 mL) was added n-BuLi
(1 equiv) at -78 °C within 10 min, and the mixture was stirred
for 30 min. Tetracyclone (1) was added in several portions with
additional THF until tetracyclone (1) is detectable by TLC
(approximately 0.6 equiv). The solution was slowly warmed to
room temperature and was stirred for 1 h. LiAlH4 (XS) was
added in small portions, and the mixture was stirred for 1 h and
hydrolyzed with aqueous saturated NH4Cl. The mixture was
extracted with MTBE, and the organic extracts were filtrated
over a short plug of silica (MTBE). The filtrate was evaporated
to give a sticky residue or foam, which was subjected to flash
column chromatography. The fractions with the desired cyclo-
pentadiene contained the oxazolinylbenzene as an impurity,
which could be removed by Kugelrohr distillation (100 °C,
1 mbar). The residue was directly subjected to the complexation
reaction. The cyclopentadienes 4f-h and Ru3(CO)12 (0.33
equiv) were suspended in a mixture of toluene (1.5 mL) and
decane (3 mL) in a screw-capped flask and placed in a preheated
oil bath at 175 °C. The mixture was stirred for 3 days. After
cooling to room temperature, CHCl3 (0.5 mL) was added and
the mixture was stirred for 1.5 h at 175 °C. After cooling to room
temperature the reaction mixture was directly subjected to
column chromatography (silica, toluene). The red fraction
yielded the ruthenium oxazolinyl complexes, which could be
recrystallized from CH2Cl2/MeOH if necessary.
(SRu)-Carbonylchloro-η5-[1-(2-((S)-4-isopropyloxazolinyl-
phenyl)-2,3,4,5-tetraphenylcyclopentadienyl]ruthenium(II) (6f).
According to the general procedure (S)-2-(2-bromoph-
enyl)-4-isopropyl-4,5-dihydrooxazole (618 mg, 2.30 mmol),
n-BuLi (1.6 M in hexane, 1.44 mL, 2.30 mmol), tetracyclone (1)
(647 mg, 1.68 mmol), and LiAlH4 (230 mg, 6.08 mmol) yielded
“crude” cyclopentadiene 4f (590 mg, 62%) after chromatogra-
phy (TLC: silica, PE/EtOAc, 10:1; Rf=0, 0.18-0.33 (4f), 0.42,
0.53, 0.61, 0.70). EI (70 eV): m/z 557 (100) [M]þ. The reaction of
4f (380 mg, 0.68 mmol) with Ru3(CO)12 (149 mg, 0.18 mmol)
yielded chelated ruthenium oxazoline complex 6f as a red solid
(245 mg, 48% based on the assumption of pure 4f), which
decomposes at 258 °C. IR (KBr): 3111 w, 3058 w, 3033 w,
2963 m, 2932 m, 2901 w, 2873 w, 1954 vs, 1608 m, 1501 m, 1479 w,
1459 w, 1444 w, 1430 w, 1391 w, 1368 m, 1334 w, 1300 w, 1286 w,
1265 w, 1240 m, 1181 w, 1147 w, 1079 w, 1054 w, 1028 w, 1003 w,
963 w, 919 w, 847 w, 803 w, 783 w, 765 w, 748 m, 738 m, 700 s,
679 w, 621 w, 578 s cm-1. 1H NMR (CDCl3, 400 MHz): δ 0.73
(d, J = 6.9 Hz, 3 H, CH3), 0.88 (d, J = 7.0 Hz, 3 H, CH3),
2.47-2.63 (dhept, J=3.2, 6.7 Hz, 1 H, CH(CH3)2), 3.77 (dd, J=
8.9, 10.0 Hz, 1 H, CH2(Oxaz)), 4.34 (dd, J=4.4, 8.7 Hz, 1 H,
CH2(Oxaz)), 4.73-4.83 (m, 1 H, CH(Oxaz)), 6.87 (dd, J=1.3,
8.5 Hz, 2 H, o-PhH), 6.91-7.03 (m, 19 H, PhH, (Oxaz)Ph-H6),
7.29-7.39 (m, 2 H, (Oxaz)Ph-H4, (Oxaz)Ph-H5), 7.71-7.79
ppm (m, 1 H, (Oxaz)Ph-H3). 13C NMR (CDCl3, 100 MHz): δ
13.91, 18.66 (both CH3), 28.21 (C(CH3)2), 67.62 (CH2(Oxaz)),
69.15 (CH(Oxaz)), 85.38 (CpC-Ph(Oxaz)), 88.76, 94.36, 96.62,
120.30 (all CpC), 127.24, 127.42, 127.49, 127.56, 127.71, 127.78,
128.13 (all d), 128.16 ((Oxaz)Ph-C4), 130.17 (s), 130.41
((Oxaz)Ph-C3), 130.91 (s), 131.63, 131.65, 131.89, 132.02
(all d), 132.31 ((Oxaz)Ph-C5), 132.43, 132.83, 133.35, 133.53 (no
unambiguous assignments possible), 163.83 (CdN), 204.35 ppm
(Ru-CO), two carbons are missing due to overlapping. UV-vis
(MeCN): λmax (log ε) 217 (4.61), 368 (3.32), 468 nm (2.91). MS
(FAB): m/z (%) 721 (4) [M]þ, 693 (100) [M - CO]þ, 658 (36) [M
- CO - Cl]þ, 572 (11).
(SRu)-Carbonylchloro-η5-[1-(2-((S)-4-benzyloxazolinyl)phenyl)-
2,3,4,5-tetraphenylcyclopentadienyl]ruthenium(II) (6h). According
to the general procedure (S)-2-(2-bromophenyl)-4-benzyl-4,5-
dihydrooxazole (1.06 g, 3.35 mmol), n-BuLi (1.6 M in hexane,
2.10 mL, 3.36 mmol), tetracyclone (1) (1.01 g, 2.63 mmol), and
LiAlH4 (280 mg, 7.40 mmol) yielded “crude” cyclopentadiene 4h
(730 mg, 46%) after chromatography (TLC, silica: PE/EtOAc,
10:1; Rf=0, 0.16-0.32 (4h), 0.48, 0.53, 0.77). MS (FAB): m/z 606
(100) [M þ 1]þ. The reaction of 4h (400 mg, 0.66 mmol) with
Ru3(CO)12 (157 mg, 0.24 mmol) yielded the chelated ruthenium
oxazolinyl complex 6h as a red solid (210 mg, 42% based on the
assumption of pure 4h), which decomposes at 254-257 °C. IR
(KBr): 3105 w, 3083 w, 3057 w, 3029 w, 3001 w, 2971 w, 2961 w,
2951 w, 2925 w, 2909 w, 2852 w, 1960 vs, 1610 m, 1589 w, 1576 w,
1499 m, 1444 w, 1473 w, 1453 w, 1444 m, 1422 w, 1405 w, 1380 m,
1332 w, 1268 w, 1239 m, 1226 w, 1198 w, 1177 w, 1169 w, 1157 w,
1136 w, 1110 w, 1088 w, 1077 w, 1069 w, 1054 w, 1028 w, 1001 w,
975 w, 931 w, 915 w, 890 w, 857 w, 842 w, 803 w, 786 w, 765 w,
749 m, 739 m, 698 s cm-1. 1H NMR (CDCl3, 400 MHz): δ 2.41
(dd, J = 11.0, 12.8 Hz, 1 H, Ph-CH2), 3.67-3.72 (m, 2 H,
Ph-CH2, CH2(Oxaz)), 4.30 (dd, J = 8.7, 4.2 Hz, 1 H, CH2-
(Oxaz)), 5.09-5.16 (m, 1 H, CH(Oxaz)), 6.93-6.99 (m, 6 H),
7.02-7.23 (m, 16 H), 7.26-7.29 (m, 2 H), 7.36-7.41 (m, 4 H, Ph-
H4(Oxaz), o-PhH-CH2), 7.75-7.77 ppm (m, 1 H, Ph-H3-
(Oxaz)). 13C NMR (CDCl3, 100 MHz): δ 39.2 (Ph-CH2), 66.3
(CH(Oxaz)), 71.1 (CH2(Oxaz)), 85.4 (CpC-Ph(Oxaz)), 88.8,
94.1, 96.6, 120.0 (all CpC), 126.8, 127.2, 127.4, 127.4, 127.7,
127.7, 128.1, 128.1, 128.7 (all d), 129.8 (o-PhCH-CH2), 130.0
(s), 130.4 (d), 130.7 (Ph-C3(Oxaz)), 131.4 (both s), 131.5, 131.8,
131.9 (all d), 132.3 (s), 132.4 (Ph-C5(Oxaz)), 132.7 (s), 133.2,
133.4 (both d), 137.4 (s), 164.5 (CdN), 204.4 (Ru-CO) ppm,
seven carbons are missing due to overlapping. UV-vis (MeCN):

Article
Organometallics, Vol. 30, No. 2, 2011 229
λ
max (log ε) 235 (4.44), 368 (3.32), 468 nm (2.89). MS (FAB): m/z
dry CH2Cl2 (0.8 mL) was added the benzylic alcohol 10
(ca. 0.06 mmol). The mixture was sonicated in the ultrasonic
bath for 5 min and allowed to stand for 12 h. The urea was
filtered off. GC without further manipulation of the filtrate
directly gave the ratio of the diastereomeric esters, reflecting the
ratio of enantiomers in the benzylic alcohols 10. In the case of
the starting alcohols 10d and 10e the filtrate was washed with
1 N HCl (2 mL), saturated aqueous NaHCO3 (2 mL), and brine
(2 mL). The organic layer was filtrated over a short plug of silica
(CH2Cl2) and evaporated. The crude product was not purified;
NMR afforded the ratio of the diastereomeric esters by integra-
tion of the diagnostic benzylic hydrogens (around 6 ppm). In all
cases complete conversion was additionally controlled since the
diastereomeric esters exhibit different rates of formation.
(%) 793 (2) [M þ Na þ 1]þ, 769 (5) [M]þ, 741 (100) [M - CO]þ,
734 [M - Cl]þ (35), 706 [M - CO - Cl]þ (60).
Representative Procedure for Transferhydrogenation of Phenyl
Ketones 9. A mixture of the phenyl ketone 9 (0.29 mmol), KOH
(0.26 mmol), and the ruthenium complex (1-2 mol %) in dry
2-propanol (0.5 mL) in a screw-capped vessel was placed in a
preheated oil bath (82 °C) and stirred for 3 h. The internal
standard (see Table 2) was added, and the mixture was filtrated
over a short plug of silica (2-propanol). GC24 of the filtrate
revealed the formation of the benzylic alcohol 10. The residue
was distilled bulb-to bulb to give the benzylic alcohol, depending
on the conversion of the catalysis together with unreacted
starting material. This distillate was used without further ma-
nipulation for the preparation of Mosher’s ester in the next step
to determine the ee.
Acknowledgment. We thank R. W. Seidel for the X-ray
analysis of compound 6g and Dr. E. Breuckmann for
recording the MALDI-TOF spectrum of compound 5e.
Representative Procedure for the Formation of the Mosher
Ester from Benzylic Alcohols 10. To a solution of (R)-(þ)-R-
methoxy-R-trifluoromethylphenylacetic acid (20 mg, 0,085 mmol),
DCC (27 mg, 0.13 mmol), and 4-DMAP (5 mg, 0.04 mmol) in
Supporting Information Available: 1H and 13C NMR spectra
of new compounds and X-ray data in CIF format. This material
is available free of charge via the Internet at http://pubs.acs.org.
(24) In case of the transfer hydrogenation of cyclohexyl phenyl
ketone the yield was determined by 1H NMR of the distillate.