Preparation and photochemical behavior of organoruthenium derivatives of photochromic dithienylethene (DTE):

Article abstract of DOI:10.1021/om700537s

A series of organoruthenium complexes containing photochromic 1,2-di(2-methylthien-3-yl)-3,3,4,4,5,5-hexafluorocyclopentene fragments (DTE), DTE-(RRuL_m)_n (RRuL_m = (η⁶-C ₆H₅)Ru(η⁵

Full text of DOI:10.1021/om700537s

5030
Organometallics 2007, 26, 5030-5041
Preparation and Photochemical Behavior of Organoruthenium
Derivatives of Photochromic Dithienylethene (DTE):
DTE-(RRuLm)n (RRuLm ) (η6-C6H5)Ru(η5-C5Me5),
(η6-C6H5)RuCl2(PPh3), (η5-C5Me4)Ru(CO)2; n ) 1, 2)†
Kazunori Uchida, Akiko Inagaki, and Munetaka Akita*
Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku,
Yokohama 226-8503, Japan
ReceiVed May 31, 2007
A series of organoruthenium complexes containing photochromic 1,2-di(2-methylthien-3-yl)-3,3,4,4,5,5-
hexafluorocyclopentene fragments (DTE), DTE-(RRuLm)n (RRuLm ) (η6-C6H5)Ru(η5-C5Me5) (I): n )
1 (3), 2 (4); (η6-C6H5)RuCl2(PPh3) (II): n ) 1 (10), 2 (11); (η5-C5Me4)Ru(CO)2 (III): n ) 1 (25), 2
(24); substituted at the 5-position of the thiophene ring), are prepared and characterized by 1H NMR and
UV-vis spectroscopy, and molecular structures of the 1:2 adducts 4, 11, and 24 are determined by X-ray
crystallography, which reveals the antiparallel conformation of the two thiophene rings suitable for
photocyclization, causing the photochromism. It is revealed that the metalated DTE derivatives show
photochromic behavior through the photochemical, electrocyclic conrotatory ring-closing and -opening
processes in a manner analogous to the organic counterparts, but the efficiency of the photochromic
processes is dependent on the attached metal fragments. The cationic Cp*Ru(η6-arene)-type (I) and neutral
Cp*Ru(CO)2Cl-type complexes (III) show photochromic behavior (content of the closed isomers at the
UV photostationary states: 25-88%), and subsequent visible light irradiation of the equilibrated mixtures
reverts the process to afford the open forms quantitatively. The ring-closing and -opening processes are
reversible and can be repeated without notable deterioration. As for the series of Ph derivatives of I (1,
3, and 4), metalation improves the efficiency of the ring-closing process. In contrast to these derivatives,
no significant photochromic behavior is noted for the benzo-fused derivatives of I, and UV irradiation
of II (10 and 11) causes irreversible dissociation of the arene ligand (DTE).
Scheme 1
Introduction
Photochromic compounds have attracted increasing attention,
because various physicochemical properties of them, in par-
ticular, color, can be switched by the action of electromagnetic
radiation and/or heat in a reversible manner.1 Diarylethenes
constitute a class of efficient photochromic compounds and
exhibit such behavior through reversible, photochemical ring
opening-closing processes.2 A number of diarylethene deriva-
tives were prepared and their photochemical properties were
examined. Among them, 1,2-di(heteroaryl)ethenes, in particular,
1,2-di(2-methylthien-3-yl)-3,3,4,4,5,5-hexafluorocyclopentene
derivatives developed by Irie (Scheme 1), turned out to show
excellent photochromic properties superior to other derivatives
with respect to many aspects such as fatigue resistance, quick
response, high quantum yield, and reversibility.3
The dithienylethene (DTE) derivatives exhibit photochromic
behavior through the processes shown in Scheme 1. The
colorless open form O containing the cross-conjugated π-system
is converted, upon UV irradiation, to the closed form C, where
the π-conjugated system is extended over the molecule to show
an absorption in the visible region. The electrocyclic conrotatory
ring-closing process can be reverted by visible light irradiation.
The change of the conjugated system induces not only the color
change but also a significant change of the electronic structure
of the DTE part.
† This paper is dedicated to the late Professor Yoshihiko Itoh, not only
an outstanding chemist but also a great mentor of science and life.
* To whom correspondence should be addressed. Fax: +81-45-924-
5230. E-mail: makita@res.titech.ac.jp.
(1) Bamfield, P. Chromic Phenomena, Technological Applications of
Color Chemistry; RSC: Cambridge, 2001. Du¨rr, H.; Bouas-Laurent, H.
Photochromism: Molecules and Systems; Elsevier: Amsterdam, 2003. The
special thematic issue of Chem. ReV. for “Photochromism: Memories and
Switches-Introduction”, Chem. ReV. 2000, 100, 1683-1890. Organic
Photochromic and Thermochromic Compounds; Crano, J. C., Guglielmetti,
R. J., Eds.; Main Photochromic Families; Plenum Press: New York, 1999;
Vol. 1.
Combination of the chromic properties with other chemical
auxiliaries would lead to a new phase of the chemistry, and
various attempts have been made to add more sophisticated
functions.3 If a metallic fragment is attached to the chromic
(2) Kellogg, R. M.; Groen, M. B.; Wynberg, H. J. Org. Chem. 1967,
32, 3093.
(3) Irie, M. Chem. ReV. 2000, 100, 1683. Tian, H.; Yang, S. Chem. Soc.
ReV. 2004, 33, 85.
10.1021/om700537s CCC: $37.00 © 2007 American Chemical Society
Publication on Web 08/30/2007

Organoruthenium DeriVatiVes of Photochromic Dithienylethene
Scheme 2
Organometallics, Vol. 26, No. 20, 2007 5031
molecule, the different forms of the chromic compounds with
the different colors (i.e., different electronic structures) would
show distinctive coordination properties, which turn on and off
the functions unique to the attached metallic species (e.g.,
catalysis).3-5 From this viewpoint, we have been studying
introduction of organometallic fragments to chromic compounds
such as photochromic spiropyranes and halochromic pH indica-
tors.6 Herein we describe the synthesis and photochromic
behavior of three types of DTE-ruthenium complexes bearing
the η6-arene and η5-cyclopentadienyl functional groups I-III
(Scheme 1).
(i) Cationic (η6-DTE)RuCp*-Type Complexes (I).7 The
I-type, cationic η6-arene-coordinated complexes 3 and 4 were
readily prepared by ligand displacement reactions of the labile
acetonitrile adduct [Cp*Ru(NCMe)3]PF6, 2,7g with DTE-Ph2, 1
(Scheme 2). The 1:1 (3) and 1:2 adducts (4) were obtained in
a selective manner by adjusting the 1/2 ratio. The obtained
products were characterized by spectroscopic and crystal-
lographic methods. As a typical example, a 1H NMR spectrum
of 4 is shown in Figure 1a (UV 0 h). (For the abbreviations for
the assigned signals, see Scheme 1). The η6-Ph coordination
(5) Spirobenzopyrane complexes: ref 6a. Miyashita, A.; Iwamoto, A.;
Kuwayama, T.; Shitara, H.; Aoki, Y.; Hirano, M.; Nohira, H. Chem. Lett.
1997, 965. Atabekyan, L. S.; Chibisov, A. K. J. Photochem. 1986, 34, 323.
Kimura, K.; Yamashita, T.; Yokoyama, M. J. Chem. Soc., Perkin Trans. 2
1992, 613. Atabekyan, L.; Chibisov, A. Mol. Cryst. Liq. Cryst. Sci. Tech.,
Sect. A 1994, 246, 263. Atabekyan, L. S.; Lilikin, A. I.; Zakharova, G. V.;
Chibisov, A. K. High Energy Chem. 1996, 30, 409. Kimura, K.; Teranishi,
T.; Yokoyama, M. Supramol. Chem. 1996, 7, 11. Filley, J.; Ibrahim, M.
A.; Nimlos, M. R.; Watt, A. S.; Blake, D. M. J. Photochem. Photobiol., A:
Chem. 1998, 117, 193. Gorner, H.; Chibisov, A. K. J. Chem. Soc., Faraday
Trans. 1998, 94, 2557. Collins, G. E.; Choi, L.-S.; Ewing, K. J.; Michelet,
V.; Bowen, C. M.; Winkler, J. D. Chem. Commun. 1999, 321. Kimura, K.;
Sakamoto, H.; Kado, S.; Arakawa, R.; Yokoyama, M. Analyst 2000, 125,
1091. Nakamura, M.; Fujioka, T.; Sakamoto, H.; Kimura, K. New J. Chem.
2002, 26, 554. Bulanov, A. O.; Luk’yanov, B. S.; Kogan, V. A.; Stankevich,
N. V.; Lukov, V. V. Russ. J. Coord. Chem. 2002, 28, 46. Querol, M.; Bozic,
B.; Salluce, N.; Belser, P. Polyhedron 2003, 22, 655. Liu, S. Mol. Cryst.
Liq. Cryst. 2004, 419, 97. Kimura, K.; Sakamoto, H.; Uda, M. Macromol-
ecules 2004, 37, 1871. Azobenzene complex: Nishihara, H. Coord. Chem.
ReV. 2005, 249, 1468, and references therein. See also a recent example:
Tang, H.-S.; Zhu, N.; Yam, V. W.-W. Organometallics 2007, 26, 22.
Dihydropyrene complexes: Mitchell, R. H.; Brkic, Z.; Sauro, V. A.; Berg,
D. J. J. Am. Chem. Soc. 2003, 125, 7581. Zhang, R.; Fan, W.; Twamley,
B.; Berg, D. J.; Mitchell, R. H. Organometallics 2007, 26, 1888.
(6) (a) Moriuchi, A.; Uchida, K.; Inagaki, A.; Akita, M. Organometallics
2005, 24, 6382. (b) Takano, K.; Inagaki, A.; Akita, M. Chem. Lett. 2006,
35, 434. (c) Hirasa, M.; Inagaki, A.; Akita, M. J. Organomet. Chem. 2007,
692, 93.
Results and Discussion
Preparation and Characterization of Dithienylethene-
Ruthenium Complexes. The three types of ruthenium com-
plexes prepared in the present study were the η6-arene-
coordinated diphenyl-DTE compounds containing the cationic
Ru(η5-C5Me5) (I) and neutral RuCl2(L) fragments (II) and the
η5-cyclopentadienyl complexes (III) (Scheme 1).
(4) (a) Gilat, S. L.; Kawai, S. H.; Lehn, J.-M. J. Chem. Soc., Chem.
Commun. 1993, 1439. (b) Gilat, S. L.; Kawai, S. H.; Lehn, J.-M. Chem.-
Eur. J. 1995, 1, 275. (c) Ferna´ndez-Acebes, A.; Lehn, J.-M. AdV. Mater.
1998, 10, 1519. (d) Takeshita, M.; Irie, M. Chem. Lett. 1998, 1123. (e)
Chen, B. Z.; Wang, M. Z.; Wu, Y. Q.; Tian, H. Chem. Commun. 2002,
1060. (f) Tian, H.; Chen, B. Z.; Tu, H.; Mu¨llen, K. AdV. Mater. 2002, 14,
918. (g) Peter, A.; McDonald, R.; Branda, N. R. Chem. Commun. 2002,
2274. Ahmed, S. A. J. Phys. Org. Chem. 2002, 15, 392. (h) Liang, Y.;
Dvornikov, A. S.; Rentzepis, P. M. J. Mater. Chem. 2003, 13, 286. (i)-
Yam, V. W.-W.; Ko, C.-C.; Zhu, N. J. Am. Chem. Soc. 2004, 126, 12734.
(j) Jukes, R. T. F.; Adamo, V.; Hartl, F.; Belser, P.; De Cola, L. Inorg.
Chem. 2004, 43, 2779. (k) Odo, Y.; Matsuda, K.; Irie, M. Chem.-Eur. J.
2006, 12, 4283. (l) Ahmed, S. A. J. Phys. Org. Chem. 2006, 19, 402. (m)
Ko, C.-C.; Kwok, W. M.; Yam, V. W.-W.; Phillips, D. L. Chem.-Eur. J.
2006, 12, 5840. (n) Lee, P. H.-M.; Ko, C.-C.; Wong, K. M.-C.; Zhu, N.;
Yam, V. W.-W. Organometallics 2007, 26, 15. (o) Lee, P. H.-M.; Ko, C.-
C.; Zhu, N.; Yam, V. W.-W. J. Am. Chem. Soc. 2007, 129, 6058.

5032 Organometallics, Vol. 26, No. 20, 2007
Uchida et al.
1
Figure 1. Spectral changes upon UV and vis light irradiation of 1-4. (a) H NMR spectral changes of 4 upon UV light irradiation
(observed in acetone-d6). (b) UV-vis spectral changes of 4 upon UV light irradiation (observed in CH2Cl2: [4] ) 2.49 × 10-5 M). (c)
Visible absorption changes of 1-4 upon UV and vis light irradiation. The absorptions were monitored at the maxima of the visible absorptions
(1O: 589 nm; 3O: 600 nm; 4O: 594 nm).
was confirmed by the upfield shift of the η6-Ph signals (1H
Scheme 3
NMR; 7.3-7.6 f 6.1-6.6).8 The 1H NMR data for 4 indicate
1
a symmetrical structure, whereas a H NMR spectrum of the
1:1 adduct 3 contained two sets of the shifted and nonshifted
signals (Figure S2; UV 0 h). The open (O) and closed forms
(C) of the DTE part can be readily discriminated by a couple
of spectroscopic features such as (i) the appearance of a visible
1
absorption for C3 and (ii) the H NMR signal for the methyl
groups attached to the thiophene rings (δH(Me-Th) (Scheme
1)); that is, the Me-ThC signal appears in the lower field
compared to that of the Me-ThO signal.4a For 4, no absorption
was observed in the visible region (Figure 1b; 0 min), and the
Me-Th signal (1H NMR; Figure 1a, 0 h) appeared in the higher
that (1) two isomers are feasible for the open form of DTE,
i.e., antiparallel (O) and parallel conformers (O′), (2) the two
conformers interconvert with each other, and (3) only the
antiparallel isomer O undergoes the conrotatory photocyclization
field compared to that of the closed form, as will be discussed
later. Similar features were noted for 3, indicating that the
thermal metal complexation (Scheme 2) of the open DTE
molecule 1 gave the adducts 3 and 4 with retention of the open
leading to the closed isomer (C) (Scheme 4).3 The two species
structure. The open structure of the 1:2 adduct 4 was also
of 12 and 13 were then assigned to the two conformers of the
verified by X-ray crystallography (Figure 2a), and details will
be discussed later.
The benzo-fused derivatives 13 and 14 were also prepared
open form O and O′. Preliminary X-ray crystallography for the
1:2 adduct 149 revealed that the two benzothiophene rings in
14 were arranged in a parallel fashion O′ in contrast to the
as references in a manner similar to the synthesis of 3 and 4
antiparallel arrangement O observed for the other derivatives
(Scheme 3). While they showed spectroscopic features similar
described in this paper (see below).
to those of the Ph derivatives, formation of two conformational
(ii) Neutral (η6-DTE)RuCl2(PPh3)-Type Complexes (II).
isomers was noted for 13 (ca. 6:4) as also observed for 12. The
dinuclear adduct 14 contained only one isomer. It is established
mentioned complexes 3 and 4 was known to be rather sluggish
Because the (η6-arene)RuCp* fragment included in the above-
with respect to its chemical reactivity, we attempted introduction
(7) See, for example: (a) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J.
Am. Chem. Soc. 1989, 111, 1698. (b) Schrenk, J. L.; McNair, A. M.;
of a more functionalizable ruthenium unit such as (η6-arene)-
McCormick, F. B.; Mann, K. R. Inorg. Chem. 1986, 25, 3501. (c) He, X.
D.; Chaudret, B.; Dahan, F.; Huang, Y.-S. Organometallics 1991, 10, 970.
(d) Vichard, D.; Gruselle, M.; Amouri, H. E.; Jaouen, G.; Vaissermann, J.
Organometallics 1992, 11, 976. (e) Seiders, T. J.; Baldridge, K. K.;
O’Connor, J. M.; Siegel, J. S. J. Am. Chem. Soc. 1997, 119, 4781. (f) Pasch,
R.; Koelle, U.; Ganter, B.; Englert, U. Organometallics 1997, 16, 3950.
(g) Steinmetz, B.; Schenk, W. A. Organometallics 1999, 18, 943.
(8) Ku¨ndig, E. P. Transition Metal Arene π-Complexes in Organic
Synthesis and Catalysis; Springer: Berlin, 2004.
RuCl2(L).
Of a few methods established for synthesis of (η6-arene)-
RuCl2(L)-type complexes,10 we chose chlorination of the Ru(0)-
(9) Crystallographic data for 14: formula: C43H44F18P2S2Ru2, mono-
clinic, space group P21/c, a ) 15.96(4) Å, b ) 21.95(5) Å, c ) 16.19(3)
Å, â ) 72.68(9)°, V ) 5414(19) Å3, d ) 1.510 g‚cm-3. Current R value )
0.20. An ORTEP view is shown in Figure S6.

Organoruthenium DeriVatiVes of Photochromic Dithienylethene
Organometallics, Vol. 26, No. 20, 2007 5033
was inseparable and unstable to the air and, then, was subjected
to chlorination with aqueous HCl. The obtained chlorinated
brown products 8 and 9 were separated by taking advantage of
their different solubilities. The dimeric 1:1 adduct 8 was soluble
in acetone, whereas the 1:2 adduct 9 was slightly soluble in
acetone presumably because of its polymeric structure. Subse-
quent treatment of 8 and 9 with PPh3 readily gave the desired
red, monomeric (η6-arene)RuCl2(PPh3)-type products II (10 and
11), respectively. The η6-arene complexes 8-11 were readily
characterized on the basis of the spectroscopic features as
described for the Cp* derivatives 3 and 4.8,10 The η6-arene
coordination was confirmed by the upfield shift of the coordi-
nated η6-Ph signals (1H NMR; for 10, see the spectrum for 0 h
in Figure 3a; the data for 11 are shown in Figure S3).
Incorporation of PPh3 in 10 and 11 was confirmed by the 31P
NMR signals, which were comparable to the signal reported
for (η6-arene)RuCl2(PPh3).10 The η6-arene complexes 8-11
contained the open DTE ligand as revealed by their UV-vis
1
and H NMR features, as discussed for 3 and 4, and the open
structure of the 1:2 adduct 11 was confirmed crystallographically
(Figure 2b; see below).
(iii) (DTE-η5-C5Me4)Ru(CO)2Cl-Type Complexes (III).12
As described below, the η6-arene coordination in II (10 and
11) turned out to be so labile under UV irradiation as to undergo
dissociation of the arene moiety, and then, we examined the
synthesis of the η5-cyclopentadienyl derivative 24, which should
be more resistant to photodissociation (Scheme 5). Because the
functionalized cyclopentadiene 20 was not reported, we designed
its synthetic route as summarized in Scheme 5.13 The 1:1 adduct
25 was also prepared as a reference via 21. Selective lithiation
of 3,5-dibromo-2-methylthiophene 15 with n-BuLi followed by
treatment with tetramethylcyclopentenone 16 and acidic workup
gave the 5-C5Me4H-substituted 3-bromo-2-methylthiophene
17.14 Perfluorocyclopentene derivatives are known to be sus-
ceptible to nucleophilic substitution at the dC-F moieties.15
(12) The related η5-C5R5-type Rh complex 26 was also prepared
following the procedures reported for the η5-C5Me5 derivative (Kang, J.
W.; Moseley, K.; Maitlis, P. M. J. Am. Chem. Soc. 1969, 91, 5970).
Successive treatment of 20 with RhCl3‚3H2O (in refluxing methanol) and
PPh3 (in diethyl ether at r.t.) gave 26 as red powder, which was characterized
spectroscopically. In a manner similar to 12 and 13, UV light irradiation of
26 caused appearance of a weak UV-vis shoulder band around 600 nm,
which disappeared upon subsequent visible light irradiation (Figure S8),
Figure 2. ORTEP views of the DTE-ruthenium complexes 4 (the
cationic part), 11, and 24 drawn with thermal ellipsoids at the 30%
probability level.
1
while no apparent change was detected by H NMR. 26: δH(CDCl3) 7.60
(14H, br, Ph), 7.35 (8H, br, Ph), 7.23 (8H, br, Ph), 7.11 (2H, s, Th), 2.08
Scheme 4
(6H, s, Me-Th), 1.54 (12H, d, J ) 4.6, C5Me4), 1.37 (12H, d, J ) 2.7,
C5Me4). 31P NMR (CDCl3): 24.9 (d, JRh-P ) 143). UV-vis (CH2Cl2) λmax
nm (ꢀ/M-1 cm-1): 419, 280 nm.
/
(η6-arene)(cod) precursor (Scheme 2). Treatment of the labile
Ru(η6-naphthalene)(η4-cod) complex 511 with 1 in a THF-
MeCN mixed solvent gave a mixture of the 1:1 (6) and 1:2
adducts (7) of the (η6-arene)Ru(0)(cod) intermediates, which
(10) Werner, H.; Werner, R. Chem. Ber. 1982, 115, 3766. Bennett, M.
A.; Smith, A. J. Chem. Soc., Dalton Trans. 1974, 3011. Bennett, M. A.;
Huang, T.-N.; Matheson, T. W.; Smith, A. K. Inorg. Synth. 1982, 21, 74.
Bennett, M. A.; Neumann, H.; Thomas, M.; Wang, X. Q.; Pertici, P.;
Salvadori, P.; Vitulli, G. Organometallics 1991, 10, 3237.
(11) Albers, M. O.; Ashworth, T. V.; Oosthuizen, H. E.; Singleton, E.
Inorg. Synth. 1989, 26, 68. Powell, P. J. Organomet. Chem. 1974, 65, 89.
See also ref 10.

5034 Organometallics, Vol. 26, No. 20, 2007
Uchida et al.
1
Figure 3. Spectral changes of 10 upon UV and visible light irradiation. (a) H NMR spectral changes (observed in CDCl3). (b) UV-vis
NMR spectral changes (observed in CH2Cl2: [10] ) 2.18 × 10-5 M).
1
Scheme 5
appeared. A H NMR spectrum of 24 is shown in Figure 4a
(UV 0 h). The open DTE structures in 22-25 were confirmed
by their spectroscopic features (no visible absorption and δH-
(Me-ThO)), as discussed for 3 and 4, and, for the 1:2 adduct
24, by X-ray crystallography (Figure 2c).
(iv) X-ray Crystallography of the DTE-Ruthenium Com-
plexes 4, 11, and 24 (1:2 Adducts). Molecular structures of
the three 1:2 adducts 4, 11, and 24 were verified by X-ray
crystallography. ORTEP views and selected structural param-
eters are shown in Figure 2 and Table 1, respectively. The three
molecules are imposed on the crystallographic C2 axis, leading
to disorder of the central C5F6 ring. The structural parameters
including the C1‚‚‚C1* separations as well as the dihedral angles
between the perfluorocyclopentene’s olefin part and the thiophene
ring ( C1-C2-C11-C11*: 45-51°) are similar and compa-
rable to those of the nonmetalated derivative 1,18 indicating that
linking the bulky organometallic fragments does not cause
significant conformational changes of the central DTE parts.
On the other hand, the dihedral angles between the thiophene
(13) Preparation of a less sterically hindered indenyl derivative was
attempted as shown below but unsuccessful. Via route 1, the desired product
was formed but could not be separated from a mixture containing the mono-
indenyl compound and the starting compound. For route 2, although the
intermediate corresponding to 17 could be obtained, subsequent lithiation
with n-BuLi was followed by proton-transfer to give the debrominated
product, as confirmed by D2O quenching. The less acidic C5Me4-H proton
in 17 was resistant to the proton transfer, and therefore, 20 was obtained
successfully.
Lithiation of 17 with s-BuLi and subsequent treatment with the
appropriate perfluorocyclopentene derivatives 18/19 gave the
bis- (20) and mono-tetramethylcyclopentadiene derivatives (21),
respectively, which were converted to the (η5-C5R5)Ru(CO)2-
Cl-type complexes 24/25 according to the conventional methods,
i.e., metalation with Ru3(CO)12 followed by aerobic oxidative
chlorination with HCl(aq).16,17
(14) Fendrick, C. M.; Schertz, L. D.; Mintz, E. A.; Marks, T. J.;
Bitterwolf, T. E.; Horine, P. A.; Hubler, T. L.; Sheldon, J. A.; Belin, D. D.
Inorg. Synth. 1992, 29, 193.
(15) Hanazawa, M.; Sumiya, R.; Horikawa, Y.; Irie, M. J. Chem. Soc.,
Chem. Commun. 1992, 206.
(16) Humphries, A. P.; Knox, S. A. R. J. Chem. Soc., Dalton Trans. 1975,
1710. Knox, S. A. R.; Morris, M. J. Inorg. Synth. 1990, 28, 189. Nagashima,
H.; Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.; Fukahori, T.; Suzuki,
H.; Akita, M.; Moro-oka, Y.; Itoh, K. Organometallics 1990, 9, 799.
The (η5-C5Me4)Ru(CO)2 parts in 22/23 and 24/25 showed
spectroscopic features similar to those of the corresponding Cp*
derivatives, Cp*Ru2(CO)4 and Cp*Ru(CO)2Cl, respectively.16
For example, the ν(µ-CO) absorptions observed for 22/23
disappeared upon chlorination, and instead two ν(η1-CO) bands

Organoruthenium DeriVatiVes of Photochromic Dithienylethene
Organometallics, Vol. 26, No. 20, 2007 5035
Figure 4. Spectral changes of 24 and 25 upon UV and visible light irradiation. (a) 1H NMR spectral changes of 24 (observed in CD2Cl2).
(b) UV-vis spectral changes of 24 (observed in CH2Cl2: [24] ) 2.50 × 10-5 M). (c) Reversible photochromism of 24 monitored by
UV-vis spectroscopy ([24] ) 2.60 × 10-5 M; alternating UV (16 min) and visible light (2 min) irradiations). (d) Reversible photochromism
of 25 monitored by UV-vis spectroscopy ([25] ) 2.50 × 10-5 M; alternating UV (16 min) and visible light (6 min) irradiations). For c
and d, only the final absorbances are shown from the second cycle.
ring and the attached aromatic rings (Ph and η5-C5R5) are
dependent on the attached metal fragments. As for the phenyl
derivatives 4 and 11 ( C3-C4-C21-C22 < 18°), the ar-
rangements of the phenyl rings with respect to the thiophene
rings are closer to a coplanar one, to lead to extension of the
π-conjugated system to some extent. On the other hand, the
2,5-dimethyl substituents on the η5-C5Me4 rings in 24 hinder
such an orientation, and as a result, the C5Me4 rings are twisted
with respect to the thiophene rings, as indicated by the
substantially large dihedral angle ( C3-C4-C20-C21: 57.4-
(6)°).
As for the conformation of the two thiophene rings (Scheme
4), the three DTE complexes 4, 11, and 24 adopt the antiparallel
conformation O, as is evident from the ORTEP views (Figure
2), whereas the two benzothiophene rings in 14 are arranged in
a parallel fashion O′, as revealed by the preliminary X-ray
crystallography (Figure S6).9 The two different conformations
affect the efficiency of the photochemical processes as described
below and as pointed out by the previous studies.19
The structural features of the organoruthenium moieties are
essentially the same as those of the corresponding counter-
parts, e.g., [Cp*Ru(η6-C6H6)]-,20 (η6-C6H6)RuCl2(PPh3),21 and
Cp*Ru(CO)2Cl.22 The C-C distances of the η6-coordinated Ph
parts in 4 and 11 are elongated compared to the free arene 1
owing to the back-donation from the Ru centers.8
(17) Because the thiophene part may participate in the reaction with
Ru3(CO)12, a preliminary experiment using a simpler thiophene-containing
substrate was carried out and the expected product was obtained successfully
and characterized spectroscopically (δH (CDCl3) 6.99, 6.72 (2H × 2, m ×
2, Th), 2.49 (6H, s, Me-Th), 1.95, 1.77 (12H × 2, s × 2, C5Me4); IR
(CH2Cl2) 1932, 1763 cm-1). But attempted preparation of the Cp*RuCl-
(PPh3)2-type complex by successive treatment of the simpler thiophene with
RuCl3‚nH2O (in refluxing EtOH) and PPh3 resulted in the formation of a
small amount of unidentified products.
(19) Uchida, K.; Nakayama, Y.; Irie, M. Bull. Chem. Soc. Jpn. 1990,
63, 1311. Irie, M.; Miyatake, O.; Uchida, K.; Eriguchi, T. J. Am. Chem.
Soc. 1994, 116, 9894. Takeshita, M.; Yamada, M.; Kato, N.; Irie, M. J.
Chem. Soc., Perkin Trans. 2 2000, 619. Yamaguchi, T.; Fujita, Y.;
Nakazumi, H.; Kobatake, S.; Irie, M. Tetrahedron 2004, 60, 9863.
(20) See, for example, the [Cp*RuBr3]- salt: Gemel, G.; Mereiter, K.;
Schmid, R.; Kirchner, K. Organometallics 1996, 15, 532. See also ref 7.
(21) Elsegood, M. R. J.; Tocher, D. A. Polyhedron 1995, 14, 3147.
(22) Fan, L.; Turner, M. L.; Adams, H.; Bailey, N. A.; Maitlis, P. M.
Organometallics 1995, 14, 676. Knowles, D. R. T.; Adams, H.; Maitlis, P.
M. Organometallics 1998, 17, 1741. Martin-Matute, B.; Edin, M.; Bogar,
K.; Kaynak, F. B.; Backvall, J.-E. J. Am. Chem. Soc. 2005, 127, 8817.
(18) Irie, M.; Lifka, T.; Kobatake, S.; Kato, N. J. Am. Chem. Soc. 2000,
122, 4871. See also: Yamada, T.; Muto, K.; Kobatake, S.; Irie, M. J. Org.
Chem. 2001, 66, 6164.

5036 Organometallics, Vol. 26, No. 20, 2007
Table 1. Selected Structural Parameters for the Diruthenium Complexes 4, 11, and 24a
Uchida et al.
4
11b
24c
1d
1.715(5)
Interatomic Distances
1.71(2)
S1-C1
1.719(3)
1.721(4)
S1-C4
1.731(3)
1.370(4)
1.497(6)
1.432(5)
1.470(4)
1.361(4)
1.472(5)
1.351(6)
1.504(4)
1.515(4)
3.593(5)
1.396-1.422(5)
2.209-2.234(4)
1.415-1.428(6)
1.497-1.507(7)
2.166-2.186(3)
1.75(2)
1.42(3)
1.52(3)
1.41(3)
1.41(2)
1.43(3)
1.42(3)
1.44(3)
1.52(4)
1.47(4)
3.63(5)
1.35-1.41(3)
2.13-2.27(2)
1.727(4)
1.383(5)
1.486(5)
1.454(5)
1.451(5)
1.350(6)
1.479(5)e
1.353(8)
1.510(5)
1.46(2)
1.727(5)
1.374(7)
1.498(7)
1.422(6)
1.449(6)
1.346(6)
1.471(7)
1.343(6)
1.493(7)
1.500(7)
3.507(3)
1.348-1.380(7)
C1-C2
C1-C5
C2-C3
C2-C11
C3-C4
C4-C21
C11-C11*
C11-C12
C12-C13
C1···C1*
3.906(8)
C-C in Ph
Ru-C(Ph)
C-C in η5-C5R5
C-Me in η5-C5R5
Ru-C(η5-C5R5)
1.407-1.448(8)
1.473-1.526(8)
2.192-2.258(5)
Bond Angles
96(1)
C1-S1-C4
92.9(2)
93.0(2)
93.1(2)
S1-C1-C2
110.6(3)
119.4(2)
130.0(3)
112.9(2)
123.7(3)
123.2(2)
113.2(3)
110.4(3)
120.6(2)
129.0(3)
129.3(2)
119.8(2)
119.9(2)
121.4(3)
109(2)
119(2)
132(2)
113(2)
121(2)
126(2)
114(2)
107(2)
128(1)
125(2)
130(1)
125(2)
123(2)
114(2)
110.6(3)
120.3(3)
129.1(4)
112.1(3)
125.1(3)
122.8(3)
113.0(3)
111.3(3)
121.8(3) f
126.9(3) g
128.9(2)
120.3(4)
126.3(4)
124.8(3)
110.4(4)
120.0(4)
129.5(5)
112.1(4)
124.7(4)
123.3(4)
114.6(4)
109.7(4)
121.5(4)
128.8(5)
129.2(4)
120.8(4)
121.3(5)
123.1(5)
S1-C1-C5
C2-C1-C5
C1-C2-C3
C1-C2-C11
C3-C2-C11
C2-C3-C4
S1-C4-C3
S1-C4-C21
C3-C4-C21
C2-C11-C11*
C2-C11-C12
C4-C21-C22
C4-C21-C26
Dihedral Angles
51(4)
C1-C2-C11-C11*
C3-C4-C21-C22
45.6(5)
5.4(4)
45.7(6)
48.5(5)
15.7(5)
18(3)
57.4(6)h
b
c
a Interatomic distances in Å and bond and dihedral angles in deg. Ru1-Cl1: 2.374(5), Ru1-Cl2: 2.385(5), Ru1-P1: 2.344(4). Ru1-Cl1: 2.400(1),
d
e
f
g
h
Ru1-C31: 1.888(6), Ru1-C32: 1.899(5), O1-C31: 1.129(8), O2-C32: 1.120(6). Ref 18. C4-C20. C4-C20-C21. C4-C20-C24. C3-C4-C20-
C21.
Photochromic Behavior of the DTE Complexes. The
photochromic behavior of the obtained DTE-Ru complexes was
species was assigned to the closed isomer 4C on the basis of
(1) the above-mentioned electronic absorption appearing in the
visible region and (2) the Me-Th signal (δH(Me-ThC) 2.34;
cf. δH(Me-ThO) 2.21).4a After 10 h irradiation the system
reached the photostationary state with the composition being
as large as 4C/4O ) 88:12, and subsequent visible light
irradiation completely replaced the signals for 4C with those
of 4O. Thus the cationic (η6-arene)RuCp*-type complex 4
showed photochromic behavior originating from the ring-
opening and -closing processes in a manner similar to the free
DTE molecule 1.24 The photochemical electrocyclic processes
were reversible, and no apparent deterioration of 4 was observed
after repeating the processes several times. As can be seen from
Figure 1a (1H NMR), no decomposition product was detected
for the sample after the visible light irradiation.
1
examined by means of UV-vis and H NMR spectroscopy as
compared with the free DTE molecule 1. UV and visible light
irradiation was performed with a high-pressure mercury lamp
(λ < 360 nm) and a Xe lamp (λ > 420 nm), respectively, with
appropriate cutoff filters.
1
(i) Cationic (η6-Arene)RuCp* Complexes I (3 and 4). H
NMR and UV-vis spectral changes of 4 brought about upon
UV and visible light irradiation are shown in Figure 1, and the
data for 1 and 3 are included in the Supporting Information
(Figures S1 and S2).23
UV irradiation of a CH2Cl2 solution of 4 caused a color
change to purple. The change was followed by UV-vis
spectroscopy (Figure 1b), and the intensities of the absorption
maximum (594 nm) are plotted as a function of the irradiation
time as shown in Figure 1c. After irradiation for 16 min the
system reached a photostationary state, which, upon subsequent
visible light irradiation, was reverted to the original state within
The purple closed isomer 4C could be isolated from a 4C-
rich photoequilibrated mixture by column chromatography
1
(eluted with CH2Cl2-MeOH, 100:1) and characterized by H
NMR (δH(acetone-d6) 7.18 (2H, s, Th), 6.66, 6.44 (2H × 2, m
× 2, m- and m′-η6-Ph), 6.29 (6H, m, o- and p-η6-Ph), 2.34 (6H,
s, Me-Th), 2.05 (30H, s, Cp*)). Because the chiral, central
part was fixed by the ring closure, the m- and m′-η6-Ph protons
became inequivalent. The isolated closed isomer 4C was stable
in the dark.
1
10 min. The change was also followed by H NMR (Figure
1a). UV light irradiation caused the appearance of a set of new
signals with the disappearance of the signals for 4C. The new
1
(23) The different rates of the photochromic processes observed by H
NMR and UV-vis measurements should result from the different concen-
trations of the samples. In the case of the 1H NMR sample of a higher
concentration, light does not transmit the sample completely to make the
photochemical process less efficient.
(24) Irie, M.; Lifka, T.; Kobatake, S.; Kato, N. J. Am. Chem. Soc. 2000,
122, 4871.

Organoruthenium DeriVatiVes of Photochromic Dithienylethene
Organometallics, Vol. 26, No. 20, 2007 5037
Figure 5. UV-vis spectral changes of 12 (a; [12] ) 4.00 × 10-5 M), 13 (b; [13] ) 1.07 × 10-5 M), and 14 (c; [14] ) 2.13 × 10-5 M)
upon UV light irradiation for 1 h (observed in CH2Cl2).
Scheme 6
Similar behavior was noted for the 1:1 adduct 3 and the free
DTE molecule 1 (Figures S1,2), and their UV-vis spectral
changes are compared with that of 4 as shown in Figure 1c and
Scheme 6.25 As can be seen from Figure 1c, the ring-closing
rates for the three species were comparable, but the metal
complexes reached the photostationary states slightly faster than
the free DTE molecule (ca. 16 min for 3 and 4 and ca. 30 min
for 1). No significant difference, however, was observed for
the reverse ring-opening processes (within 10 min), which were
faster than the ring-closing process. The metalation did not cause
a notable shift of the absorption maxima of the closed isomers
(λmax(C): 589-600 nm) but affected the efficiency of the ring-
closing process (Scheme 6). The metalation promoted the
photochemical cyclization process, as can be seen from the O/C
ratio at the UV photostationary state (from 43:57 (1) up to 12:
88 (4)).
In order to see the effect of the thiophene unit, the benzo-
fused derivative 1226 was also subjected to metalation and the
desired 1:1 (13) and 1:2 adducts (14) were obtained successfully
as described above. Although no 1H NMR spectral change was
observed at all upon UV irradiation (Scheme 6), UV-vis
spectral monitoring revealed formation of very small amounts
of the closed isomers for 12 and 13, but the 1:2 adduct 14 turned
out to be totally inert with respect to the photochemical
conversion (Figure 5).23 Preliminary X-ray crystallography of
14 (Figure S6) revealed the parallel conformation of the two
benzothiophene rings, which hindered the photocyclization
(Scheme 4).19 The benzo-fused derivative 12, therefore, was
not further subjected to the following metal complexation
reactions.
(ii) Neutral (η6-Arene)RuCl2(PPh3) Complexes 10 and 11
(II). UV irradiation of 10 and 11 caused a color change to blue,
suggesting photochromic behavior, and spectral changes induced
by the UV irradiation are shown in Figures 3 and S3,
respectively. However, it was concluded that complex 10 did
not undergo reversible photochemical processes but irreversible
decomposition, as is evidenced by (1) the disappearance of the
isomers of the free ligand 1O/C, and (3) the UV-vis spectrum
1
upfield-shifted H NMR signals for the η6-Ph part indicating
obtained after visible light irradiation, being dissimilar to the
dissociation of the Ph part from the Ru center, (2) the appearance
original spectrum, in particular, in the UV region. The spectral
changes observed for 10 are interpreted in terms of Scheme 7;
of the 1H NMR signals assignable to the open and closed
UV irradiation caused the phenyl ligand dissociation rather than
(25) No significant solvent effect was noted, and the difference was within
the ring closure to give the closed form of the free ligand 1O,
5%; for example, 25O/25C ) 39:61 in CDCl3 and 24O/24C ) 78:22 in
which was subsequently converted to the closed isomer 1C by
the action of the UV light. The 1:2 adduct 11 followed the
analogous decomposition pathway; that is, photolysis of 11
caused the phenyl ligand dissociation27 to give the 1:1 adduct
CD2Cl2. The results shown in Scheme 6 are for the solvent, in which the
largest C/O ratios were observed. In the case of 4, because the dicationic
species was not soluble in CD2Cl2 enough for a 1H NMR measurement,
acetone-d6 was used as the solvent.
(26) Kobatake, S.; Yamada, M.; Yamada, T.; Irie, M. J. Am. Chem. Soc.
1999, 121, 8450.
1
10 (as detected by H NMR; Figure S3), which underwent

5038 Organometallics, Vol. 26, No. 20, 2007
Uchida et al.
2039 and 1988 cm-1 to 2041 and 1991 cm-1 (photostationary
state) (Figure S7). The higher energy shifts indicate that the
DTE moiety in the closed isomer 25C is a better π-acceptor
than that in the open form 25O because of the extended
π-conjugated system included in 25C, but the extent of the shifts
is not significant. This is because, as discussed above, the 2,5-
methyl substituents of the η5-C5Me4 rings prevent a coplanar
conformation. Such a twisted conformation should hinder
effective electronic interaction between the central DTE part
and the attached organometallic moieties.
Scheme 7
Conclusions
Three types of organoruthenium complexes containing the
photochromic DTE functional groups are prepared and char-
acterized spectroscopically and crystallographically.
It is revealed that the metalated DTE derivatives show
photochromic behavior through the photochemical, electrocyclic
conrotatory ring-closing and -opening processes in a manner
similar to the organic counterparts, but the efficiency of the
photochromic processes is dependent on the attached metal
fragments. The cationic Cp*Ru(η6-arene)-type (I) and neutral
Cp*Ru(CO)2Cl-type complexes (III) show photochromic be-
havior. UV light irradiation causes formation of equilibrated
mixtures of the closed and open forms with C/O ratio of 25:75
to 88:12. Visible light irradiation of the equilibrated mixtures
reverts the process to afford the open form O quantitatively,
and the ring-closing and -opening processes can be repeated
without notable deterioration even for the possibly photolabile
carbonyl complexes such as 24 and 25 (up to ca. 10 times). As
for the series of the Ph derivatives of I (1, 3, and 4), metalation
improves the efficiency of the ring-closing process. The closed
isomers of I and III turn out to be stable (at least for 24 h),
when they are kept in the dark. In contrast to these derivatives,
no significant photochromic behavior is noted for the benzo-
fused derivatives of I (12 and 13), and UV irradiation of the
neutral (η6-arene)RuCl2(PPh3)-type complexes II (10 and 11)
causes irreversible dissociation of the arene ligand (DTE). The
reason for the different photochemical properties of the DTE
complexes is not clear at the moment: The steric repulsion in
the closed form caused by the bulky metal fragments may be
more severe than that in the open form. Many metal auxiliaries
having absorptions in the visible region are also regarded as
chromophores, and irradiation may excite not only the DTE part
but also the metal auxiliaries to affect the photochromic
properties. Further studies are needed to clarify these factors.
The change of the electronic properties at the metal centers
induced by the photochromic process is estimated for the III-
type complex 25 on the basis of the ν(CO) vibrations, and it is
found that the change is not significant, presumably because
the π-conjugated system of the central DTE moiety is not
effectively extended to the η5-C5Me4 rings owing to the twisted
arrangements of the η5-C5Me4 rings with respect to the thiophene
rings. Studies targeting systems where the metallic auxiliaries
can respond sensitively to the change of the DTE part (e.g.,
σ-bonded complexes: DTE-MLn) are now underway, and the
results will be reported in due course.
further ligand dissociation to give the free, open (1O) and then
closed ligand (1C). Thus it was concluded that the blue
coloration of the solutions of II is due to formation of 1C, not
due to formation of the closed isomers of 10 and 11.
(iii) (η5-C5R5)Ru(CO)2Cl Complexes III (24 and 25) and
(η5-C5R5)RhCl2(PPh3) Complex IV (27). The photolabile
nature of the (η6-arene)Ru complexes 10 and 12 described
above prompted us to examine the derivative with the nega-
tively charged η5-C5R5-type ligand. Photolysis of the 1:2 adduct
24 was followed by 1H NMR and UV-vis spectroscopy23
(Figure 4a,b; spectral changes for 25 are shown in Figure S4),
which revealed photochromism of the Cp*Ru(CO)2Cl-type
complexes 24 and 25 similar to that observed for the cationic
(η6-arene)RuCp* adducts 3 and 4 (I). The absorption maxima
of the closed isomers 24C and 25C are higher in energy
compared to the Ph derivatives 3 and 4 (Scheme 6), presumably
because the π-conjugated system of the central DTE part is not
extended to the η5-C5R5 rings owing to their considerably
twisted arrangements with respect to the thiophene rings (see
above).
It took ca. 16 min to reach the photostationary states, whereas
the cycloreversion was completed within 2 (24) and 6 min (25).
Thus the rates of cyclization of 24 and 25 were comparable to
those of 3 and 4, but the cycloreversion processes of 24 and 25
were slightly faster than those of 3 and 4. The ring-opening
efficiency of 24 and 25, however, was inferior to that of 3 and
4 (Scheme 6), and only a quarter of the open 1:2 adduct 25O
was converted to the closed isomer 25C.
Carbonylmetal complexes such as 24 and 25 may be prone
to photochemical decarbonylation,28 which may result in
decomposition. The stability of 10 and 11 with respect to the
photochemical decarbonylation process was examined by re-
peating the UV and visible light irradiation cycles, and the
change of the intensity of the absorption maximum of the visible
absorption was monitored by UV-vis spectroscopy. Because
any notable deterioration was not observed, as can be seen from
Figures 4c,d, the carbonylruthenium complexes 24 and 25 turned
out to be fatigue-resistant up to at least ca. 10 times.
The difference between the electronic states of the open and
closed forms was estimated by IR. Because 25O was converted
to the closed isomer more efficiently than 24O (Scheme 6), the
changes of the ν(CO) absorptions of 25 were monitored by IR.
UV irradiation brought about shifts of the ν(CO) stretches from
Experimental Section
General Methods. All manipulations were carried out under an
inert atmosphere by using standard Schlenk tube techniques. THF,
(27) See ref 8. See also: Dougan, S. J.; Melchart, M.; Habtemariam,
A.; Parsons, S.; Sadler, P. J. Inorg. Chem. 2006, 45, 10882. Tudose, A.;
Demonceau, A.; Delaude, L. J. Organomet. Chem. 2006, 691, 5356.
Delaude, L.; Demonceau, A.; Noels, A. F. Chem. Commun. 2001, 986.
Cambie, R. C.; Clark, G. R.; Coombe, S. L.; Coulson, S. A.; Rutledge, P.
S.; Woddgate, P. D. J. Organomet. Chem. 1996, 507, 1. Pearson, A. J.;
Lee, K. J. Org. Chem. 1994, 59, 2304.
(28) Yamamoto, A. Organotransition Metal Chemistry; Wiley-Inter-
science: New York, 1986. Collman, J. P.; Hegedus, L. S.; Norton, J. R.;
Finke, R. G. Principles and Applications of Organotransition Metal
Chemistry, 2nd ed.; University Science Books: Mill Valley, CA, 1987;
Crabtree, R. H. The Organometallic Chemistry of the Transition Metals,
4th ed.; Wiley-Interscience: New York, 2005.

Organoruthenium DeriVatiVes of Photochromic Dithienylethene
Organometallics, Vol. 26, No. 20, 2007 5039
diethyl ether (Na-K alloy), CH2Cl2(P2O5), acetone (KMnO4), and
(s × 2, 3H × 2, Me-Th). ESI-MS: 1349.0 (M+(dimer) - Cl). 9:
1H NMR (DMSO-d6): δ 7.76 (2H, s, Th), 6.34 (4H, d, J ) 5.9,
o-η6-Ph), 6.11 (4H, d, J ) 5.5, m-η6-Ph), 5.96 (2H, t, J ) 5.5,
p-η6-Ph), 2.04 (s, 6H, Me-Th). ESI-MS: 831.1 (M+(monomer)
- 2Cl).
Preparation of 10. A CH2Cl2 solution (10 mL) of 8 (93 mg,
0.13 mmol) and PPh3 (43 mg, 0.162 mmol) was stirred for 3.5 h.
After removal of the volatiles the residue was subjected to
chromatographic separation (alumina; eluted with THF). Precipita-
tion from THF-pentane gave 10 as red powders (95 mg, 0.099
mmol, 74% based on crude 8; 36% based on 1). 1H NMR
(CDCl3): δ 7.75-7.26 (22H, m, aromatic), 5.73 (2H, d, J ) 5.9,
o-η6-Ph), 5.19 (2H, t, J ) 5.1, m-η6-Ph), 4.87 (1H, br, p-η6-Ph),
2.08, 1.99 (3H × 2, s × 2, Me-Th). 31P NMR (CDCl3): δ 21.6
(s). UV-vis (CH2Cl2) λmax/nm (ꢀ/M-1 cm-1): 273 (2.46 × 104).
ESI-MS: 956 (M+). Anal. Calcd for C46H35F6PS2Cl4Ru (10‚CH2-
Cl2; a sample obtained from CH2Cl2-diethyl ether): C, 53.14; H,
3.39. Found: C, 53.46; H, 3.53.
MeOH (Mg(OMe)2) were treated with appropriate drying agents,
1
distilled, and stored under argon. H and 13C NMR spectra were
recorded on Bruker AC-200 (1H, 200 MHz) and JEOL EX-400
spectrometers (1H, 400 MHz; 13C, 100 MHz). Solvents for NMR
measurements containing 0.5% TMS were dried over molecular
sieves, degassed, distilled under reduced pressure, and stored under
Ar. Coupling constants are reported in Hz. UV-vis and IR spectra
(KBr pellets) were obtained on a JASCO V570 and FT/IR 5300
spectrometer, respectively. ESI-mass spectra were recorded on a
ThermoQuest Finnigan LCQ Duo mass spectrometer. UV and
visible light irradiations were performed with an Ushio high-
pressure mercury lamp (UM-452; λ < 360 nm with a U-360 cutoff
filter) and a Soma Kogaku Xe lamp (150 W; λ > 420 nm with an
L42 cutoff filter), respectively. Elemental analyses were performed
at the Center for Advanced Materials Analysis, Technical Depart-
ment, Tokyo Institute of Technology. The organic compounds (1,24
12,15 15,29 and 1930) and the metal reagents (2,7g 5,11 and
Ru3(CO)1231) were prepared following the published procedures.
Other chemicals were purchased and used as received.
Preparation of 11. The 1:2 adduct 9 (109 mg, 0.122 mmol)
was treated with PPh3 (83 mg, 0.32 mmol) as described for the
synthesis of 10. Similar workup and precipitation from THF-
pentane gave 11 as red powders (119 mg, 0.0857 mmol, 79% based
Preparation of 3. To a CH2Cl2 solution (10 mL) of 1 (232 mg,
0.446 mmol) cooled at -78 °C was added slowly 2 (205 mg, 0.406
mmol) dissolved in CH2Cl2 (10 mL), and the resultant mixture was
stirred for 2 h. Removal of the volatiles followed by chromato-
graphic separation (alumina; eluted with CH2Cl2) gave 3 as a
1
on crude 9; 28% based on 1). H NMR (CDCl3): δ 7.75-7.67
(12H, m, aromatic), 7.39-7.28 (20H, m, Ph), 5.73 (4H, d, J )
5.9, o-η6-Ph), 5.20-5.17 (4H, m, m-η6-Ph), 4.70 (1H, td, J ) 5.2
and 2.2, p-η6-Ph), 2.24 (6H, s, Me-Th). 31P NMR (CDCl3): 22.0
(s). UV-vis (CH2Cl2) λmax/nm (ꢀ/M-1 cm-1): 308 (2.68 × 104,
sh), 252 (4.65 × 104, sh). ESI-MS: 1353.0 (M+ - Cl), 1090.0
(M+ - Cl- PPh3). Anal. Calcd for C63H48F6P2S2Cl4Ru2: C, 54.47;
H, 3.48. Found: C, 54.25; H, 3.58.
1
colorless powder (81 mg, 0.089 mmol, 22%). H NMR (CDCl3):
δ 7.57 (2H, d, J ) 7.1, o-Ph), 7.39 (2H, t, J ) 7.3, m-Ph), 7.38
(1H, s, Th), 7.31 (1H, t, J ) 7.3, p-Ph), 7.24 (1H, s, Th), 6.07 (2H,
d, J ) 5.9, o-η6-Ph), 6.00 (2H, t, J ) 5.7, m-η6-Ph), 5.94 (1H, t, J
) 5.6, p-η6-Ph), 2.04, 2.07 (3H × 2, s × 2, Me-Th), 1.82 (15H,
s, Cp*). UV-vis (CH2Cl2) λmax/nm (ꢀ/M-1 cm-1): 279 (3.03 ×
104). ESI-MS: 757.6 (M+ - PF6). Anal. Calcd for C37H33F12S2-
PRu: C, 49.28; H, 3.69. Found: C, 48.96; H, 3.73.
Preparation of 4. A mixture of 1 (103 mg, 0.197 mmol) and 2
(302 mg, 0.599 mmol) dissolved in CH2Cl2 (20 mL) was stirred
for 6 h. Removal of the volatiles followed by chromatographic
separation (alumina; eluted with acetone) and crystallization from
acetone-diethyl ether gave 4 as yellow crystals (185 mg, 0.144
mmol, 73%). 1H NMR (acetone-d6): δ 7.80 (2H, s, Th), 6.52 (4H,
d, J ) 5.9, o-η6-Ph), 6.19-6.12 (6H, m, m- and p-η6-Ph), 2.02
(6H, s, Me-Th), 1.89 (30H, s, Cp*). UV-vis (CH2Cl2) λmax/nm
(ꢀ/M-1 cm-1): 308 (2.46 × 104), 261 (2.54 × 104). ESI-MS:
1139.2 (M+ - PF6). Anal. Calcd for C47H48F18P2S2Ru2: C, 44.00;
H, 3.77. Found: C, 43.91; H, 4.03.
Preparation of 8 and 9. 5 (1.27 g, 3.77 mmol) and 1 (0.92 g,
1.77 mmol) dissolved in THF (130 mL)-MeCN (1.3 mL) were
stirred for 64 h, and then, the volatiles were removed under reduced
pressure. The resultant mixture of 6 and 7 was subjected to
chlorination without separation. The residue was dissolved in
acetone (35 mL) and cooled at -78 °C. To the mixture was added
36% HCl(aq) (2 mL) diluted with acetone (35 mL). The resultant
mixture was stirred for 1 h at -78 °C and for 1 h at room
temperature. Addition of diethyl ether caused precipitation of 9 as
a brown solid, which was washed with acetone (0.56 g, 0.63 mmol,
35%). The supernatant solution was evaporated, and dissolution of
the residue in acetone followed by precipitation with diethyl ether
gave 8 as a brown solid (0.59 g, 0.86 mmol, 48%). The crude
samples of 8 and 9 were characterized spectroscopically and used
without further purification. 8: 1H NMR (DMSO-d6): δ 7.83 (1H,
s, Th), 7.63 (2H, d, J ) 7.6, o-η6-Ph), 7.46 (1H, s, Th), 7.42 (2H,
t, J ) 7.3, m-Ph), 7.33 (1H, t, J ) 7.2, p-Ph), 6.36 (2H, d, J ) 5.4,
o-η6-Ph), 6.11 (2H, br, m-η6-Ph), 5.93 (1H, br, p-η6-Ph), 2.02, 1.99
Preparation of 13. To a CH2Cl2 solution (15 mL) of 12 (279
mg, 0.596 mmol) cooled at -78 °C was added a CH2Cl2 solution
(15 mL) of 2 (273 mg, 0.541 mmol) dissolved in CH2Cl2 (15 mL),
and the resultant mixture was stirred for 1 h at the same temperature.
After removal of the volatiles at room temperature under reduced
pressure the residue was subjected to chromatography (alumina;
eluted with THF). Precipitation of the obtained product from CH2-
Cl2-diethyl ether gave 13 as a colorless solid (126 mmol, 0.148
mmol, 27%). 1H NMR (acetone-d6): δ Ar: 7.82 (1H, d, J ) 8.1),
7.76-7.79 (1H, m), 7.69 (1H, br), 7.55 (1H, d, J ) 7.8), 6.87 (1H,
d, J ) 5.9), 6.80 (1H, d, J ) 5.9), 6.60 (1H, d, J ) 6.1), 6.15 (1H,
t, J ) 5.7), 6.07 (1H, t, J ) 5.7), 6.63 (1H, d, J ) 6.1), 6.60 (1H,
d, J ) 6.1), 6.15 (1H, t, J ) 5.7), 6.07 (1H, t, J ) 5.7), 5.91 (1H,
t, J ) 5.7), 5.82 (1H, t, J ) 5.7), 2.74, 2.58 (3H × 2, s × 2, Me-
Th), 1.83 (15H, s, Cp*). UV-vis (CH2Cl2) λmax/nm (ꢀ/M-1 cm-1):
330 (4.0 × 103, sh). ESI-MS: 705.4 (M+ - PF6). Anal. Calcd for
C33H29F12PS2Ru: C, 46.64; H, 3.44. Found: C, 46.28; H, 3.31.
Preparation of 14. A mixture of 12 (102 mg, 0.219 mmol) and
2 (320 mg, 0.634 mmol) dissolved in CH2Cl2(15 mL) was stirred
for 10 h. After removal of the volatiles under reduced pressure the
residue was subjected to chromatography (alumina; eluted with
MeCN). Extraction with THF followed by crystallization from CH2-
Cl2-diethyl ether gave 14 as colorless powders (72 mg, 0.058
mmol, 27%). 1H NMR (acetone-d6): δ Ar: 6.83 (2H, d, J ) 5.9),
6.62 (2H, d, J ) 5.9), 5.97 (H, t, J ) 5.9), 5.90 (2H, t, J ) 5.9),
2.67 (6H, s, Me-Th), 1.80 (30H, s, Cp*). UV-vis (CH2Cl2) λmax
/
-
nm (ꢀ/M-1 cm-1): 340 (4.1 × 103, sh). ESI-MS: 1086.2 (M+
PF6). Anal. Calcd for C43H44F18P2S2Ru2: C, 41.95; H, 3.60.
Found: C, 41.50; H, 3.71.
Preparation of 17. To a THF solution (160 mL) of 15 (26.0 g,
102 mmol) cooled at -78 °C was added n-BuLi (1.57 M, 70 mL,
110 mmol), and the resultant mixture was stirred for 20 min at the
same temperature. After addition of a THF solution (120 mL) of
16 (18.0 mL, 120 mmol) the mixture was stirred for 28 h at room
temperature. To the mixture was added water (200 mL) and
concentrated HCl(aq) (200 mL) and stirred for 1 h. The acidic
mixture was neutralized by Na2CO3(aq), and the organic phase was
(29) Lantz, R.; Ho¨rnfeldt, A. B. Chem. Scr. 1972, 2, 9.
(30) Peters, A.; Vitols, C.; McDonald, R.; Neil R. Branda, N. R. Org.
Lett. 2003, 5, 1183.
(31) Bruce, M. I.; Jensen, C. M.; Jones, N. L. Inorg. Synth. 1990, 28,
216.

5040 Organometallics, Vol. 26, No. 20, 2007
Uchida et al.
Table 2. Crystallographic Data
4
11
24
solvate
formula
fw
cryst syst
space group
a/Å
(acetone)2
C53H60O2F18P2S2Ru2
1399.23
monoclinic
C2/c
22.918(2)
16.0017(8)
17.421(2)
116.007(3)
5741.9(8)
4
(CH2Cl2)2
C65H52F6P2S2Cl8Ru2
1558.95
monoclinic
P21/n
9.908(8)
14.60(2)
22.54(3)
89.52(6)
3260(7)
C37H32O4F6S2Cl2Ru2
991.81
monoclinic
C2/c
26.694(5)
13.400(2)
13.509(3)
112.257(1)
4472(1)
b/Å
c/Å
â/deg
V/Å3
Z
d
2
4
calcd/g‚cm-3
1.618
0.753
23 577
376
1.588
0.961
18 077
283
1.473
0.947
16 063
271
µ/mm-1
no. of diffractions collected
no. of variables
R1 for data
0.0444
0.0949
0.0626
with I > 2σ(I)
wR2
(for 5716 data)
0.1309
(for 1447 data)
0.2853
(for 4549 data)
0.2237
(for all 6537 data)
(for all 6873 data)
(for all 5003 data)
washed with water and dried over Na2SO4. Removal of the volatiles
by a rotary evaporator followed by chromatographic separation
(silica gel eluted with hexane) gave a mixture of 17 and a small
amount of 3-bromo-2-methylthiophene, and the latter was removed
under reduced pressure. The crude 17 (23.6 g, 79.4 mmol, 78%)
and Th), 7.05 (1H, s, Th), 2.01, 1.92 (3H × 2, s × 2, Me-Th),
1.92, 1.77 (6H × 2, s × 2, C5Me4). IR (KBr): 1938, 1763 cm-1
.
Preparation of 24. Crude 22 (200 mg, 0.217 mmol) was
dissolved in a mixture of CHCl3 (3 mL), ethanol (1 mL), and 2 N
HCl(aq) (1 mL). After addition of concentrated HCl(aq) (0.1 mL)
air was passed through the mixture for 4 h. CHCl3 was occasionally
added to maintain the amount of the solution. The product was
extracted with CHCl3 several times, and the combined organic
solution was dried over Na2SO4. After filtration the filtrate was
concentrated and passed through an alumina plug (eluted with CH2-
Cl2). The yellow band was collected and purified by precipitation
from CH2Cl2-pentane, and 24 was obtained as a pale yellow solid
(126 mg, 0.127 mmol, 59% based on crude 22; 21% based on Ru3-
1
was used without further purification. H NMR (CDCl3): δ 6.65
(1H, s, Th), 2.99 (1H, m, C5Me4H), 2.40 (3H, s, Th-Me), 2.08
(3H, d, J ) 1.6, C5Me4), 1.91, 1.84 (3H × 2, s × 2, C5Me4), 1.11
(3H, d, J ) 7.4, CHMe). FD-MS: 296 (M+).
Preparation of 20. To an ethereal solution (100 mL) of 17 (5.17
g, 17.4 mmol) cooled at -78 °C was added n-BuLi (0.98 M, 20
mL, 19.6 mmol), and the mixture was stirred for 30 min. Upon
addition of the resultant mixture to an ethereal solution (100 mL)
of 18 (1.20 mL, 8.94 mmol) cooled at 0 °C, the yellow solution
turned to red. After the mixture was stirred for 3 h at 0 °C the
reaction mixture was quenched with 1.2 N HCl(aq). The separated
organic phase was washed with water and dried over Na2SO4.
Chromatographic separation (silica gel) gave 20 (2.12 g, 3.48 mmol,
40% based on crude 17; 32% based on 15) as a green oil. 1H NMR
(CDCl3): δ 6.76 (2H, s, Th), 3.02 (1H, d, J ) 7.3, C5Me4H), 2.06,
1.96, 1.91, 1.84 (3H × 4, s × 4, C5Me4 and Me-Th), 1.08 (3H, d,
J ) 7.6, CHMe). FD-MS: 608 (M+).
Preparation of 21. To an ethereal solution (10 mL) of 17 (370
mg, 1.24 mmol) cooled at -78 °C was added n-BuLi (1.00 M, 1.4
mL, 1.4 mmol), and the mixture was stirred for 30 min. Upon
addition of the resultant mixture to an ethereal solution (10 mL) of
19 (395 mg, 1.08 mmol) cooled at 0 °C, the yellow solution turned
to red. The workup as described for 20 gave 21 (314 mg, 0.556
mmol, 44% based on crude 17; 34% based on 15) as a green oil.
1H NMR (CDCl3): δ 7.56-7.28 (6H, m, Ar), 6.76 (1H, s, Th),
3.04 (1H, m, C5Me4H), 2.06 (3H, s, C5Me4), 1.97 (3H, s, Me-
Th), 1.08 (3H, d, J ) 7.6, CHMe). FD-MS: 564 (M+). Anal. Calcd
for C30H26F6S2: C, 63.81; H, 4.64. Found: C, 63.43; H, 4.91.
1
(CO)12). H NMR (C6D6): δ 7.04 (2H, s, Th), 1.70 (6H, s, Me-
Th), 1.62, 1.43 (6H × 2, s × 2, C5Me4). IR (KBr): 2035, 1981
cm-1. UV-vis (CH2Cl2): no characteristic absorption. FD-MS: 991
(M+), 936 (M+ - 2CO), 908 (M+ - 3CO), 879 (M+ - 4CO).
Anal. Calcd for C37H32O4F6S2Cl2Ru2: C, 44.81; H, 3.25. Found:
C, 44.93; H, 3.49.
Preparation of 25. Crude 23 was chlorinated as described for
the synthesis of 24 and obtained as a pale yellow solid (93% based
on crude 23; 74% based on Ru3(CO)12). 1H NMR (C6D6): δ 7.38-
7.27 (3H, m), 7.12-7.01 (3H, m), 6.92 (1H, s, Th), 1.73, 1.65 (3H
× 2, s × 2, Me-Th), 1.55, 1.38 (6H × 2, s × 2, C5Me4). IR
(KBr): 2036, 1982 cm-1. UV-vis (CH2Cl2) λmax/nm (ꢀ/M-1 cm-1):
280 (2.65 × 104), 258 (2.62 × 104). FD-MS: 756 (M+). Anal.
Calcd for C32H25FS2ClRu: C, 50.83; H, 3.33. Found: C, 50.69;
H, 3.46.
Photochromic Behavior of DTE-Ru Complexes. Photochro-
1
mic behavior of the DTE-Ru complexes was monitored by H
NMR and UV-vis spectroscopy. As a typical example, the
procedures for UV-vis monitoring of 24 (Figure 4b,c) are
described, and other experiments were carried out in essentially
the same manner. A CH2Cl2 solution of 24 (conc ) 2.50 × 10-5
M) was prepared, and its UV-vis spectrum was recorded. Then
the solution was placed at a distance of 10 cm from the UV lamp,
and the intensity of the absorption at 556 nm was monitored by
UV-vis spectroscopy at appropriate time intervals (Figure 4c).
After 16 min the mixture reached the photostationary state, as can
be seen from Figure 4b. Then the sample was placed at a distance
of 6 cm from the Xe lamp, and the change was monitored by UV-
vis spectroscopy; after 2 min the visible absorption completely
disappeared. From the second cycle the absorption maxima observed
after UV irradiation (16 min) and visible light irradiation (2 min)
were monitored and plotted as shown in Figure 4c.
Preparation of 22. A mixture of 20 (1.12 g, 1.84 mmol) and
Ru3(CO)12 (0.78 g, 1.22 mmol) suspended in decane (degassed by
evacuation for a short period) was heated at 165 °C. The mixture
turned into a red solution. After the mixture was left at room
temperature for 1 day an orange precipitate appeared, which was
collected and washed with pentane. Dissolution in THF followed
by chromatographic separation (alumina) gave crude 22 (596 mg,
0.649 mmol, 35% based on Ru3(CO)12) as an orange solid. 1H NMR
(CDCl3): δ 7.11 (2H, s, Th), 1.98 (6H, s, Me-Th), 1.95, 1.79 (6H
× 2, s × 2, C5Me4). IR (KBr): 1938, 1763 cm-1
.
Preparation of 23. Treatment of 21 (296 mg, 0.53 mmol) with
Ru3(CO)12 (123 mg, 0.293 mmol) as described for the synthesis of
22 gave crude 23 (332 mg, 0.230 mmol, 80% based on Ru3(CO)12)
X-ray Crystallography. Single crystals were obtained by
recrystallization from acetone-diethyl ether (4) and CH2Cl2-diethyl
1
as an orange solid. H NMR (CDCl3): δ 7.55-7.28 (6H, m, Ph

Organoruthenium DeriVatiVes of Photochromic Dithienylethene
Organometallics, Vol. 26, No. 20, 2007 5041
ether (11 and 24) and mounted on glass fibers. Diffraction
measurements were made on a Rigaku RAXIS IV imaging plate
area detector with Mo KR radiation (λ ) 0.71069 Å) at -60 °C.
Indexing was performed from three oscillation images, which were
exposed for 3 min. The crystal-to-detector distance was 110 mm
(2θmax ) 55°). In the reduction of data, Lorentz and polarization
corrections and empirical absorption corrections were made.32
Crystallographic data and results of structure refinements are listed
in Table 2.
The structural analysis was performed on an IRIS O2 computer
using the teXsan structure solving program system obtained from
the Rigaku Corp., Tokyo, Japan.33 Neutral scattering factors were
obtained from the standard source.34
hydrogen atoms were refined anisotropically, and hydrogen atoms
were fixed at the calculated positions. All three DTE derivatives
were imposed on a crystallographic C2 axis, and the F atoms of
the hexafluorocyclopentene moieties were disordered and refined
taking into account two components (F1,2:F1A,2A ) 0.5:0.5;
occupancy of F3,4 ) 0.5). 4: The disordered acetone solvate
molecule was refined taking into account two components (O1-
C42-C43:O1A-C42A-C43A ) 0.766:0.234). 11: The disordered
F1,2 atoms were refined isotropically. The carbon atoms of the
PPh3 ligand were refined isotropically because of the small number
of diffraction data with I > 2σ(I). The disordered Cl atoms of the
CH2Cl2 solvate molecule were also refined isotropically taking into
account two components (Cl1,2:Cl1A,2A ) 0.5:0.5).
The structures were solved by a combination of the direct
methods (SHELXS-86)35 and Fourier synthesis (DIRDIF94).36
Least-squares refinements were carried out using SHELXL-9735
(refined on F2) linked to teXsan. Unless otherwise stated, all non-
Acknowledgment. This research was financially supported
by the Ministry of Education, Culture, Sports, Science and
Technology of the Japanese Government (Grant-in-Aid for
Scientific Research on Priority Areas, No. 18065009, “Chem-
istry of Concerto Catalysis”), which is gratefully acknowledged.
We are grateful to ZEON Corporation for a generous gift of
perfluorocyclopentene 18.
(32) Higashi, T. Program for Absorption Correction; Rigaku Corp.:
Tokyo, Japan, 1995.
(33) teXsan; Crystal Structure Analysis Package, Ver. 1. 11; Rigaku
Corp.: Tokyo, Japan, 2000.
(34) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, 1975; Vol. 4.
(35) (a) Sheldrick, G. M. SHELXS-86: Program for crystal structure
determination; University of Go¨ttingen: Go¨ttingen, Germany, 1986. (b)
Sheldrick, G. M. SHELXL-97: Program for crystal structure refinement;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(36) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF
program system, Technical Report of the Crystallography Laboratory;
University of Nijmegen: Nijmegen, The Netherlands, 1992.
Supporting Information Available: Spectral changes of the
DTE complexes upon UV and visible light irradiation and crystal-
lographic results. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM700537S