Unique preferential conformation and movement of Ru(acac)2 fragment(s) coordinated in an η4-s-trans fashion to all diene unit(s) of α,ω-diphenylpolyenes

Article abstract of DOI:10.1021/om050089n

α,ω-Diphenylpolyene complexes bearing bis(acetylacetonato) ruthenium(II) of the general formula Ru_n(acac)_2n(polyene) [1: n = 1, polyene = 1,4-diphenylbuta-1,3-diene; 2: n = 1, polyene = 1,6-diphenylhexa-1,3,5-triene; 3: n = 2, polyen

Full text of DOI:10.1021/om050089n

3932
Organometallics 2005, 24, 3932-3938
Unique Preferential Conformation and Movement of
Ru(acac)2 Fragment(s) Coordinated in an η4-s-trans
Fashion to All Diene Unit(s) of r,ω-Diphenylpolyenes
Hiroki Fukumoto and Kazushi Mashima*
Department of Chemistry, Graduate School of Engineering Science, Osaka University,
Toyonaka, Osaka 560-8531, Japan
Received February 8, 2005
R,ω-Diphenylpolyene complexes bearing bis(acetylacetonato)ruthenium(II) of the general
formula Run(acac)2n(polyene) [1: n ) 1, polyene ) 1,4-diphenylbuta-1,3-diene; 2: n ) 1,
polyene ) 1,6-diphenylhexa-1,3,5-triene; 3: n ) 2, polyene ) 1,8-diphenylocta-1,3,5,7-
tetraene; 4 and 6: n ) 2, polyene ) 1,10-diphenyldeca-1,3,5,7,9-pentaene; 5: n ) 3, polyene
) 1,12-diphenyldodeca-1,3,5,7,9,11-hexaene] were prepared by reaction of Ru(acac)3 with
the corresponding polyene in the presence of excess amounts of zinc dust. The Ru(acac)2
fragments in 1-6 coordinated in an η4-s-trans fashion to each diene unit of the polyene
ligands. The ∆-Ru(acac)2 unit and its enantiomer Λ-Ru(acac)2 were assigned to coordinate
to the re-face and the si-face of the diene unit, respectively, on the basis of the crystal
structure of complexes 1 and 2 together with the previously reported 3. Hexaene complex 5
was assumed to have the structure anti,anti-∆,Λ,∆-5a, and its enantiomer, anti,anti-Λ,∆,Λ-
5b. Pentaene complex 4, in which two Ru(acac)2 fragments were bound to C(1)-C(4) and
C(7)-C(10) of the pentaene ligand, was isolated. The Ru(acac)2 fragment of 4 moved over
the pentaene in CHCl3 to settle in the thermodynamically stable 6, in which two ruthenium
fragments are located at adjacent positions. The metal migration process, as monitored by
the decrease of 4, was found to be of first-order for 4, giving the activation parameter
∆Gq(25 °C) ) 15.8 ( 0.2 kcal/mol.
Introduction
led to pπ-dπ conjugated organometallic systems that
have several features: hapticity (η2, η4, etc.), various
coordination modes (s-cis5 or s-trans6 modes for diene
complexation), stereochemistry (syn or anti for poly-
nuclear complexes), nuclearity (mononuclear,5,6 dinu-
clear,7 polynuclear,8 etc.), and fluxionality.9,10 However,
polyacetylene is sensitive to air and insoluble in any
organic solvent, resulting in the difficulty of handling
its metal complexes. As a partial model system, we
focused on the use of R,ω-diphenylpolyenes, Ph-
One-dimensional π-conjugated polymers1 and their
metal complexes2 are attractive materials for showing
unique chemical, electrical, and optical properties orig-
inating from the delocalization of π-electrons along their
polymer main chains. Polyacetylene is the most funda-
mental one-dimensional π-conjugated polymer, and ac-
tive investigations have been carried out since the
discovery of its conducting doped films.3 Polyacetylene
might act as olefin or conjugated diene units that can
coordinate to various transition metal compounds.4
Thus, incorporation of transition metal chromorphores
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* To whom correspondence should be addressed. E-mail: mashima@
chem.es.osaka-u.ac.jp. Fax: 81-6-6850-6296.
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10.1021/om050089n CCC: $30.25 © 2005 American Chemical Society
Publication on Web 06/30/2005

Ru(acac)2 Fragment(s) of R,ω-Diphenylpolyenes
Organometallics, Vol. 24, No. 16, 2005 3933
Figure 2. ORTEP drawing of complex 1 with the atom-
numbering scheme. The enantiomer, ∆-1a, is shown.
ylpolyenes. The treatment of R,ω-diphenylpolyenes
with Ru(acac)3 in the presence of excess amounts of zinc
dust in ethanol afforded the corresponding bis(acetyl-
acetonato)ruthenium(II) complexes of the general for-
mula Run(acac)2n(polyene) [1: n ) 1, polyene ) 1,4-
diphenylbuta-1,3-diene; 2: n ) 1, polyene ) 1,6-
diphenylhexa-1,3,5-triene; 3: n ) 2, polyene ) 1,8-
diphenylocta-1,3,5,7-tetraene; 4 and 6: n ) 2, polyene
) 1,10-diphenyldeca-1,3,5,7,9-pentaene; 5: n ) 3, poly-
ene ) 1,12-diphenyldodeca-1,3,5,7,9,11-hexaene] (eq 1),
where odd-numbered polyene complexes 2 and 4 (and
its isomer 6) have a free olefinic part. Each Ru(acac)2
fragment coordinated in an η4-s-trans fashion to each
diene unit of the polyene. All complexes show IR bands
in the region 1600-1500 cm-1 due to the CdO group of
the acac ligand bound to the ruthenium atom.6f,g The
twisted η4-s-trans-diene ruthenium configuration was
confirmed by 1H NMR spectroscopy: the coupling
constants of the outer protons and the inner protons of
the diene unit bound to the ruthenium center lie in the
range 3J ) 10-11 Hz, while the coupling constant
between the inner protons of the diene moiety was found
to be 7-8 Hz, which is comparable to the coupling
constants (3J ) 7-8 Hz) between the inner protons
observed for the typical s-trans-diene bound to mono-
nuclear transition metals.6h,i,14
Figure 1. Four isomers of alkene complexes of Ru(acac)2-
(alkene with a donor ligand).
(CHdCH)nPh,11 which are stable in air and act as
unique, versatile ancillary ligands for transition metals.
We have already prepared two dinuclear tetraene
complexes bearing RuClCp* (Cp* ) C5Me5) or Ru(acac)2
and have found that the tetraene ligand was flexible,
which enabled its coordination to RuClCp* in an s-cis-
η4 fashion and to Ru(acac)2 in an s-trans-η4 fashion.12a
Kurosawa et al. recently reported several linear pal-
ladium cluster complexes supported by two polyene
ligands.7e,f,8,12b
In this paper, we report that the Ru(acac)2 fragment
coordinated in an s-trans fashion to R,ω-diphenylpolyene
(polyene ) diene, triene, tetraene, pentaene, and
hexaene) to give mononuclear, dinuclear, and trinuclear
ruthenium-polyene complexes. We found that all diene
units are fully metalated, and one double bond remained
intact in triene and pentaene complexes. Since Bennett
et al. demonstrated that alkenes with a donor moiety
coordinated to Ru(acac)2 to form four diastereomers (R∆,
SΛ; RΛ, S∆) (Figure 1),13 the diastereochemistry of the
polyene complexes of Ru(acac)2 has been described.
Structural characterization of these complexes, as well
as the unique movement of the ruthenium fragment in
the pentaene complex, is the subject of this paper.
Results
Preparation and Characterization of Bis(acetyl-
acetonato)ruthenium(II) Complexes of r,ω-Diphen-
The single-crystal X-ray analysis of 1 (Figure 2 and
Table 1), together with its 1H NMR spectrum, revealed
that ∆-1a and its Λ-enantiomer, Λ-1b,15 were predomi-
nantly formed. This indicates that ∆-Ru(acac)2 and
Λ-Ru(acac)2 fragments thermodynamically favored the
re- and si-faces of 1,4-diphenylbuta-1,3-diene, respec-
tively. The NMR spectral data and results of X-ray
analysis of 3 indicated that the structure of dinuclear
tetraene complex 3 is anti-∆,Λ-3a,12a which is consistent
with the preferential geometry of 1. The steric hindrance
(7) (a) Sasse, H. E.; Ziegler, M. L. Z. Anorg. Allg. Chem. 1972, 392,
167. (b) Lewandos, G. S.; Knox, S. A. R.; Orpen, A. G. J. Chem. Soc.,
Dalton Trans. 1987, 2703. (c) Tachikawa, M.; Shapley, J.; Haltiwanger,
R. C.; Pierpont, C. G. J. Am. Chem. Soc. 1976, 98, 4651. (d) Pierpont,
C. G. Inorg, Chem. 1978, 17, 1976. (e) Murahashi, T.; Kanehisa, N.;
Kai, Y.; Otani, T.; Kurosawa, H. J. Chem. Soc., Chem. Commun. 1996,
825. (f) Murahashi, T.; Otani, T.; Mochizuki, E.; Kai, Y.; Kurosawa,
H. J. Am. Chem. Soc. 1998, 120, 4536.
(8) Murahashi, T.; Mochizuki, E.; Kai, Y.; Kurosawa, H. J. Am.
Chem. Soc. 1999, 121, 10660.
(9) (a) Nakamura, A.; Hagihara, N. Bull. Chem. Soc. Jpn. 1959, 32,
880. (b) Cotton, F. A.; Hunter, D. L. J. Am. Chem. Soc. 1976, 98, 1413.
(c) Albright, T. A.; Hofmann, P.; Hofmann, R.; Lillya, C. P.; Dobosh,
P. A. J. Am. Chem. Soc. 1983, 105, 3396. (d) Bennett, M. A.; Bown,
M.; Hockless, D. C. R.; McGrady, J. E.; Schranz, H. W.; Stranger, R.;
Willis, A. C. Organometallics 1998, 17, 3784.
(10) (a) Whitlock, H. W.; Chuah, Y. N. J. Am. Chem. Soc. 1965, 87,
3605. (b) Whitlock, H. W.; Reich, C.; Woessner, W. D. J. Am. Chem.
Soc. 1971, 93, 2483. (c) Whitlock, H. W.; Markezich. J. Am. Chem. Soc.
1971, 93, 5290 and 5291.
(11) Beriln, L. In Offenkettige und cyclische Polyene, En-ine in
Methoden der organischen Chemie (Houben-Weyl); Bu¨chel, K. H.,
Ed.: G. Thieme: Stuttgart, 1972.
between two Ru(acac)2 fragments ruled out syn-isomers.
12a
Trinuclear hexaene complex 5 was isolated in 10%
yield. The 1H NMR spectrum of 5 in CDCl3 showed only
one set of six olefinic protons together with three
(14) (a) Benyunes, S. A.; Day, J. P.; Green, M.; Al-Saadoon, A. W.;
Waring, T. L. Angew. Chem., Int. Ed. Engl. 1990, 29, 1416. (b)
Benyunes, S. A.; Green, M.; Grimshire, M. J. Organometallics 1989,
8, 2268.
(15) For distinguishing isomers, we named all isomers by using the
number with “a” and “b”, which stand for a ruthenium fragment bound
to a C1-C4 diene unit from the re-face and si-face, respectively.
(12) (a) Mashima, K.; Fukumoto, H.; Tani, K.; Haga, M.; Nakamura,
A. Organometallics 1998, 17, 410. (b) Murahashi, T.; Higuchi, Y.;
Katoh, T.; Kurosawa, H. J. Am. Chem. Soc. 2002, 124, 14288.
(13) Bennett, M. A.; Heath, G. A.; Hockless, D. C. R.; Kovacik, I.;
Willis, A. C. J. Am. Chem. Soc. 1998, 120, 932.

3934 Organometallics, Vol. 24, No. 16, 2005
Fukumoto and Mashima
Scheme 1
Table 1. Selected Bond Distances and Angles of 1
Distances (Å)
Ru-O(1)
Ru-O(3)
Ru-C(1)
Ru-C(3)
C(1)-C(2)
C(3)-C(4)
2.048(2)
2.045(2)
2.259(3)
2.110(3)
1.380(4)
1.391(4)
Ru-O(2)
Ru-O(4)
Ru-C(2)
Ru-C(4)
C(2)-C(3)
2.052(2)
2.059(2)
2.114(3)
2.285(3)
1.447(4)
Angles (deg)
O(1)-Ru-O(2)
O(1)-Ru-O(4)
O(2)-Ru-O(4)
C(1)-Ru-C(2)
C(1)-Ru-C(4)
C(2)-Ru-C(4)
Ru-C(1)-C(2)
Ru-C(3)-C(4)
Ru-C(3)-C(2)
C(1)-C(2)-C(3)
92.44(8)
83.55(8)
173.89(8)
36.6(1)
O(1)-Ru-O(3)
O(2)-Ru-O(3)
O(3)-Ru-O(4)
C(1)-Ru-C(3)
C(2)-Ru-C(3)
C(3)-Ru-C(4)
Ru-C(2)-C(3)
Ru-C(2)-C(1)
Ru-C(4)-C(3)
C(2)-C(3)-C(4)
84.87(8)
82.26(8)
92.77(8)
67.8(1)
40.1(1)
36.6(1)
69.8(2)
77.4(2)
64.9(2)
116.7(3)
101.3(1)
66.5(1)
66.0(2)
78.5(2)
4 (and its isomer 6), with odd numbers of olefinic units,
have an uncoordinated CdC moiety on their polyene
70.1(2)
119.4(3)
1
backbone, as evident from their H NMR spectra. The
Torsion Angles (deg)
C(1)-C(2)-C(3)-C(4)
conformational preference for these complexes was not
controlled since we obtained these complexes as a
mixture of isomers. The 1H NMR spectrum of 2 in CDCl3
indicated that there are two sets of signals due to two
magnetically nonequivalent isomers, ∆-2a and ∆-2b
(and their enantiomers, Λ-2a and Λ-2b) in a 2:1 integral
ratio (Scheme 1). There was no equilibrium between the
two isomers, as judged from the results of variable-
temperature 1H NMR spectroscopy. Each isomer shows
signals between 5 and 7 ppm, which are assignable to
the protons of a free CdC part. The major isomer is
determined to be ∆-2a and Λ-2b from the crystal
structure of complex 2, which is consistent with the
preferred coordination mode of the Ru(acac)2 unit, as
found for 1 and 3.
Figure 3 shows the molecular structure of Λ-2b. ∆-2a
is also included in the crystal because of the centrosym-
metric space group P21/a. Complex 2 has a structural
feature similar to that found for diene complex 1; the
∆-Ru(acac)2 fragment favors the re-face of the triene
ligand. As shown in Table 2, the bond distances of C(1)-
C(2), C(2)-C(3), and C(3)-C(4) are 1.370(5), 1.436(6),
and 1.360(6) Å, respectively. The observed short-long-
short pattern of the carbon-carbon bonds is typical for
an s-trans-1,3-diene ligand bound to a ruthenium
atom.6f,g,i The bond distance (1.309(6) Å) of C(5)-C(6)
is normal for a free CdC bond. Not only the diene unit
coordinating to the ruthenium atom but also the re-
maining olefin part of the triene ligand adopts the
s-trans geometry, although the torsion angle (128.1(5)°)
of C(1)-C(2)-C(3)-C(4) indicates that the diene unit
is greatly deformed compared with that of C(4)-C(5)-
C(6)-C(13) (178.7(4)°). The bond distances of Ru-O lie
in the range 2.050(3)-2.063(3) Å, which is in good
accordance with those reported for Ru(acac)2(diene)
complexes.6f,g,i
126.9(3)
methine signals due to the acetylacetonato groups being
in a 1:1:1 integration ratio. These data indicated that 5
has a C2-axis passing through the central ruthenium
atom and the center of the polyene ligand. On the basis
of the preferential geometries of 1 and 3, where the
∆-Ru(acac)2 and the Λ-Ru(acac)2 units preferentially
coordinate to re- and si-faces of the polyene ligand,
respectively (vide supra), it is assumed that complex 5
has the structure anti,anti-∆,Λ,∆-5a, and its enanti-
omer, anti,anti-Λ,∆,Λ-5b No partially metalated com-
plex with one or two Ru(acac)2 fragments was obtained,
indicating that sequential complexation with ruthenium
spontaneously proceeded to give only the fully metalated
complex 5. The coordination of a ruthenium fragment
to a diene unit lowered the HOMO level of the adjacent
diene unit of the polyene so that the following ruthe-
nium fragment can readily coordinate to it. Additionally,
the coupling constant (10.3 Hz) of the terminal protons
(H4, H5, and H8, H9) between two s-trans-diene units
suggested an all-trans geometry of the whole hexaene
moiety.
In contrast to polyene complexes 1, 3, and 5, which
contain even numbers of olefinic units, complexes 2 and
Figure 3. ORTEP drawing of triene complex 2 with the
atom-numbering scheme. The enantiomer, Λ-2b, is shown.

Ru(acac)2 Fragment(s) of R,ω-Diphenylpolyenes
Organometallics, Vol. 24, No. 16, 2005 3935
Table 2. Selected Bond Distances and Angles of 2
Scheme 2
Distances (Å)
Ru-O(1)
Ru-O(3)
Ru-C(1)
Ru-C(3)
C(1)-C(2)
C(3)-C(4)
C(5)-C(6)
2.050(3)
2.056(3)
2.281(4)
2.099(4)
1.370(5)
1.360(6)
1.309(6)
Ru-O(2)
Ru-O(4)
Ru-C(2)
Ru-C(4)
C(2)-C(3)
C(4)-C(5)
2.054(3)
2.063(3)
2.100(4)
2.275(4)
1.436(6)
1.448(6)
Angles (deg)
O(1)-Ru-O(2)
O(1)-Ru-O(4)
O(2)-Ru-O(4)
C(1)-Ru-C(2)
C(1)-Ru-C(4)
C(2)-Ru-C(4)
Ru-C(1)-C(2)
Ru-C(3)-C(4)
Ru-C(3)-C(2)
C(1)-C(2)-C(3)
C(3)-C(4)-C(5)
92.8(1)
85.1(1)
174.4(1)
36.1(1)
100.7(2)
67.2(2)
64.7(3)
79.1(3)
70.1(2)
118.9(5)
126.9(5)
O(1)-Ru-O(3)
O(2)-Ru-O(3)
O(3)-Ru-O(4)
C(1)-Ru-C(3)
C(2)-Ru-C(3)
C(3)-Ru-C(4)
Ru-C(2)-C(3)
Ru-C(2)-C(1)
Ru-C(4)-C(3)
C(2)-C(3)-C(4)
C(4)-C(5)-C(6)
86.0(1)
83.3(1)
91.4(1)
66.8(2)
40.0(2)
36.0(1)
70.0(2)
79.1(3)
65.0(3)
120.2(4)
124.7(5)
Torsion Angles (deg)
C(1)-C(2)-C(3)-C(4) 128.1(5) C(4)-C(5)-C(6)-C(13) 178.7(4)
The pentaene complex was isolated in 81% yield.
NMR and mass spectral data, together with results of
combustion analysis, confirmed that the pentaene com-
plex has two Ru(acac)2 fragments, and accordingly, one
CdC bond remained intact. There are two possible
isomers, 4 and 6, if the chirality of the Ru(acac)2
fragments is neglected (eq 2). The isolated compound
was assigned as 4, which was found to be stable in
1
benzene solution. The H NMR spectrum of 4 in C6D6
displayed one set of five proton signals due to the
pentaene ligand, indicating that the two ruthenium
fragments were coordinated in an η4-s-trans fashion at
C1-C4 and C7-C10, the central double bond (C5-C6)
remained intact, and the pentaene ligand has the all-
transoid conformation.
°C. The decrease in the intensity of H5 and H6 protons
of 4 was found to be of first-order relative to complex 4,
and the activation parameter ∆Gq(25 °C) ) 15.8 ( 0.2
kcal/mol was estimated. Such a movement of the
ruthenium fragment may explain how ruthenium frag-
ments coordinate to the polyene and cause the observed
full metalation of polyenes.
Discussion
First, we discuss the stereochemistry of complexes 1,
3, and 5, which have even numbers of olefinic parts. We
have determined the crystal structures of 1 and 3, which
revealed that ∆-Ru(acac)2 and Λ-Ru(acac)2 fragments
thermodynamically favored re- and si-faces, respectively,
of the 1,4-diphenylbuta-1,3-diene and 1,8-diphenylocta-
1,3,5,7-tetraene. There are 24 possible structures for
tetraene complex 3, eight anti and eight syn isomers,16
of which syn isomers were ruled out due to the steric
congestion of the syn isomers. Taking account of the
symmetry of 3 (Scheme 2), anti-∆,∆-3a, anti-Λ,Λ-3a,
anti-∆,Λ-3a, and anti-Λ,∆-3a equal the corresponding
anti-∆,∆-3b, anti-Λ,Λ-3b, anti-Λ,∆-3b, and anti-∆,Λ-
3b respectively. Moreover, anti-∆,∆-3a is the enanti-
omer of anti-Λ,Λ-3b, and anti-Λ,Λ-3a is that of anti-
∆,∆-3b. Thus, the number of possible isomers for 3 is
reduced to three magnetically nonequivalent isomers.
Among them, according to the observed structure where
∆-Ru(acac)2 and Λ-Ru(acac)2 fragments preferred to
coordinate to re- and si-faces of the diene, respectively,
When complex 4 was dissolved in CDCl3, the 1H NMR
spectrum gradually changed and displayed 10 new
magnetically nonequivalent protons of the pentaene
ligand due to another isomer, 6. NMR spectroscopy
revealed the final ratio of 4 and 6 to be 1:4. The two
signals observed at δ 6.26 and 6.58 were assignable to
H9 and H10, suggesting that the C(9)-C(10) double bond
of 6 is uncoordinated. The other eight signals of the
pentaene ligand of 6 lie in the region δ 3.67-4.47 and
are assignable to the protons of the two neighboring
diene units bound in an η4-s-trans fashion to two
ruthenium atoms. The 1H NMR spectrum also exhibited
a total of eight nonequivalent signals (δ 1.55-2.32) due
to the methyl protons of four acac ligands for two
nonequivalent Ru(acac)2 fragments.
As shown by eq 2, one of the two Ru(acac)2 fragments
of 4 moved along the pentaene ligand to give 6 in
chloroform solution. This is the second example of
organometallic fragment movement over a linear poly-
ene system: Fe(CO)3(1-phenyl-6-(p-tolyl)-1,3,5-hexatriene)
was previously reported by Whitlock et al.10 Thermo-
dynamic parameters of this process were monitored by
1H NMR spectroscopy in the temperature range 15-27
(16) The total number, N, of the theoretically possible isomers for
the polyene complexes can be expressed by equation, N ) 2m, where
m is the number of CdC bonds of the polyene.

3936 Organometallics, Vol. 24, No. 16, 2005
Fukumoto and Mashima
Scheme 5
Scheme 3
Scheme 4
not proceed due to steric interaction between the two
Ru(acac)2. The observed ratio of the amounts of 4 and
6 suggests that 80% of the pentaene complex was anti-
∆,Λ-4a () anti-Λ,∆-4b), which was readily converted
to anti-∆,Λ-6a and anti-∆,Λ-6b in chloroform, while the
ruthenium fragment of syn-∆,∆-4a and syn-Λ,Λ-4b did
not move, and thus these syn-isomers were observed as
the minor product.
the structure of 3 was expected to be anti-∆,Λ-3a, which
is in accordance with the result of the X-ray analysis of
3.
Conclusion
We demonstrated that the Ru(acac)2 fragment coor-
dinates in an η4-s-trans fashion to the diene unit of R,ω-
diphenylpolyenes to afford the corresponding polyene
complexes 1-6. A noteworthy finding was that all diene
units of the ligands were fully metalated. We also found
that ∆-Ru(acac)2 and Λ-Ru(acac)2 could distinguish the
re-face and si-face of the diene unit, respectively, as
revealed by X-ray structural studies of 1 and 2 together
with 3. On the basis of such preferential geometry and
bulkiness of Ru(acac)2, we discussed the structures of
pentaene and hexaene complexes: hexaene complex 5
was assumed to be an anti,anti-isomer, ∆,Λ,∆-5a, and
its enantiomer, Λ,∆,Λ-5b. The structure of the pentaene
complex with one free CdC bond was more complicated
because there are two isomers, 4 and 6, and further-
more, we found irreversible movement of one of two Ru-
(acac)2 fragments of 4, which yields 6. We assigned 4 to
be a mixture of anti-∆,Λ-4a and syn-isomers, syn-∆,∆-
4a and syn-Λ,Λ-4b. The Ru(acac)2 fragment of anti-∆,Λ-
4a migrated to afford thermodynamic stable isomers,
anti-∆,Λ-6a and anti-∆,Λ-6b, while syn-∆,∆-4a and syn-
Λ,Λ-4b were not converted. We are currently interested
in the full metalation of soluble polymers containing
polyene units.
The structure of complex 5 is very complicated.16 All
syn,syn-, syn,anti-, and anti,syn-isomers are ruled out
because of the severe congestion among the ruthenium
fragments. According to the preferential geometries of
1 and 3 (vide supra), complex 5 was assumed to be
anti,anti-∆,Λ,∆-5a and anti,anti-Λ,∆,Λ-5b instead of
the other diastereomer pair, anti,anti-Λ,∆,Λ-5a and
anti,anti-∆,Λ,∆-5b (Scheme 3).
After the completion of the irreversible isomerization
from 4 to 6 at ambient temperature, we found that 20%
of 4 always remained at any measured temperature.
Possible structures for 4 are anti-∆,Λ-4a and syn-∆,∆-
4a and their enantiomers (anti-Λ,∆-4b and syn-Λ,Λ-4b,
respectively) because of the conformational preference
(Scheme 4). All ruthenium fragments shown in Scheme
4 are magnetically equivalent since anti-∆,Λ-4a () anti-
Λ,∆-4b) has the inversion at the center of C(5)-C(6) in
the pentaene backbone, and syn-∆,∆-4a and syn-Λ,Λ-
4b have the C2-axis passing through the center of the
pentaene ligand.
After migration of the Ru(acac)2 fragment, it is
reasonably assumed that the stereochemistry of complex
6 may adopt the anti-geometry. Scheme 5 shows the
suprafacial movement of one of the two ruthenium
fragments of anti-∆,Λ-4a, whereby two magnetically
equivalent anti-∆,Λ-6a isomers resulted via η2-inter-
mediates, depending on which ruthenium fragment
moved. On the other hand, suprafacial migration of the
ruthenium fragment on syn-∆,∆-4a and syn-Λ,Λ-4b did
Experimental Section
General Procedures. All manipulations involving air- and
moisture-sensitive organometallic compounds were carried out
by standard Schlenk techniques under an argon atmosphere.

Ru(acac)2 Fragment(s) of R,ω-Diphenylpolyenes
Organometallics, Vol. 24, No. 16, 2005 3937
Table 3. Crystal and Refinement Data for 1 and 2
Toluene was dried over sodium benzophenone ketyl. Ethanol
was distilled from magnesium ethoxide. 1,6-Diphenylhexa-
1,3,5-triene was purchased from Aldrich Chemical Co., Inc.
Ru(acac)3,17 1,10-diphenyldeca-1,3,5,7,9-pentaene,18 and 1,12-
diphenyldodeca-1,3,5,7,9,11-hexaene18 were prepared accord-
ing to the reported procedures. Zinc dust was activated by
aqueous HCl, washed twice with acetone, and then dried under
reduced pressure before use.
Nuclear magnetic resonance [1H (400 MHz)] spectra were
measured on a JEOL JNM-GSK400 spectrometer. Other
spectra were recorded using the following instruments: IR,
Jasco FT/IR-120 and Hitachi 295; low- and high-resolution
mass spectra, JEOL SX-102; UV/vis spectra, Jasco Ubest-30
and Shimadzu UV-265FS. X-ray crystallographic studies were
performed on a Rigaku AFC-7 diffractometer interfaced with
a TEXSAN computer system. Elemental analyses were per-
formed using a Perkin-Elmer 2400 microanalyzer. All melting
points were measured in sealed tubes and were not corrected.
1
2
formula
fw
cryst syst
space group
a, Å
b, Å
c, Å
C
26H28O4Ru
C28H30O4Ru
531.61
505.57
monoclinic
P21/a (#14)
11.203(4)
11.469(3)
18.592(3)
92.52
monoclinic
P21/a (#14)
11.864(3)
11.809(2)
18.611(4)
103.49(1)
4
â, deg
Z
4
V, Å3
2386(1)
1.407
2535.6(9)
1.392
dcalcd, g cm-3
radiation
Mo KR (λ )
0.71069 Å)
+h, +k, (l
0.2 × 0.2 × 0.3
6.85
Mo KR (λ )
0.71069 Å)
+h, +k, (l
0.2 × 0.2 × 0.2
6.49
reflns measd
cryst size, mm
abs coeff, cm-1
scan mode
ω-2θ
ω-2θ
temp, °C
2θmax, deg
no. of data collected
no. of unique data
no. of observations
20
20
Preparation of 2. 1,6-Diphenylhexa-1,3,5-triene (0.140 g,
0.600 mmol) and zinc dust (0.13 g) were added to a suspension
of Ru(acac)3 (0.242 g, 0.60 mmol) in ethanol (30 mL). The
reaction mixture was refluxed for 12 h until the color became
orange. The solvent was removed in vacuo, and then the
residue was extracted with toluene (40 mL). Zinc dust and the
Zn(acac)2 formed were removed by centrifugation. The super-
natant was concentrated and then cooled to -20 °C to give 2
(0.16 g, 51% yield) as a yellow-orange solid (mp 165-170 °C
(dec)). Major isomer: 1H NMR (CDCl3, 30 °C): δ 1.56 (s, 3H),
55.0
55.0
6046
6401
5760
6116 (Rint ) 0.021)
3748
4361
(I > 1.5σ(I))
392
(I > 3.0σ(I))
298
no. of variables
Ra
0.034
0.035
b
Rw
0.025
0.038
1.54
0.73 (max.)
-0.49 (min.)
GOF
2.59
∆, e Å-3
0.34
-0.62
1.91 (s, 3H), 1.97 (s, 3H), 1.98 (s, 3H), 3.86 (dd, 1H, H3, J3,4
)
10.3 and J2,3 ) 6.9 Hz), 4.42 (d, 1H, H1, J1,2 ) 11.0 Hz), 4.46
(dd, 1H, H2, J1,2 ) 11.0 and J2,3 ) 6.9 Hz), 4.57 (dd, 1H, H4,
J4,5 ) 10.7 and J3,4 ) 10.3 Hz), 5.37 (s, 1H), 5.44 (s, 1H), 6.31
(dd, 1H, H5, J5,6 ) 15.6 and J4,5 ) 10.7 Hz), 6.62 (d, 1H, H6,
J5,6 ) 15.6 Hz), 7.13-7.23 (m, 10H, C6H5). Minor isomer: 1H
NMR (CDCl3, 30 °C): δ 1.68 (s, 3H), 1.76 (s, 3H), 1.78 (s, 3H),
1.90 (s, 3H), 3.60 (dd, 1H, H3, J3,4 ) 10.3 and J2,3 ) 7.8 Hz),
4.30 (dd, 1H, H2, J1,2 ) 11.5 and J2,3 ) 7.8 Hz), 4.70 (s, 1H),
5.20 (s, 1H), 5.35 (dd, 1H, H4, J3,4 ) 10.3 and J4,5 ) 10.7 Hz),
5.37 (d, 1H, H1, J1,2 ) 11.5 Hz), 5.97 (dd, 1H, H5, J5,6 ) 15.6
and J4,5 ) 10.7 Hz), 6.76 (d, 1H, H6, J5,6 ) 15.6 Hz), 7.13-
7.23 (m, 10H, C6H5). FAB-MS (N.B.A. matrix): m/z 532 (M+).
IR (Nujol): ν (CO)/cm-1 1570 (m), 1550 (w), 1515 (s). UV/vis
(CH2Cl2): λmax 340 nm (ꢀ ) 2.1 × 104 M-1 cm-1). Anal. Calcd
for C28H30O4Ru: C, 63.25; H, 5.69. Found: C, 62.45; H, 5.73.
a R ) ∑||Fo | - |Fc||/|Fo|. bRw ) [∑w(| Fo | - | Fc |)2/∑wFo
]
1/2, w
2
) 1/σ2(Fo); function minimized: ∑w(| Fo | - | Fc |)2.
The reaction mixture was refluxed for 12 h until the color
became orange. The solvent was removed in vacuo, and then
the residue was extracted with toluene (60 mL). The remaining
zinc dust and Zn(acac)2 were removed by centrifugation. The
supernatant was concentrated and then cooled at -20 °C to
yield 5 (0.10 g, 16% yield) as a yellow-orange solid (mp 125-
130 °C (dec)). 1H NMR (CDCl3, 30 °C): δ 1.56 (s, 6H), 1.84 (s,
6H), 1.85 (s, 6H), 1.95 (s, 6H), 2.23 (s, 6H), 2.34 (s, 6H), 3.70
(m, 2H, H3 and H10), 3.87 (m, 2H, H6 and H7), 3.93 (m, 2H, H5
and H8), 4.00 (dd, 2H, H4 and H9, J3,4 ) J9,10 ) 10.3 Hz, J4,5
J8,9 ) 10.3 Hz), 4.38 (d, 2H, H1 and H12, J1,2 ) J11,12 ) 11.2
Hz), 4.41 (dd, 2H, H2 and H11, J1,2 ) J11,12 ) 11.2 and J2,3
)
)
J10,11 ) 7.3 Hz), 5.38 (s, 2H), 5.43 (s, 2H), 5.54 (s, 2H), 7.12-
7.18 (m, 10H, C6H5). FAB-MS (N.B.A. matrix): m/z 1209 (M+).
IR (Nujol): ν (CO)/cm-1 1571 (s), 1517 (s). UV/vis (CH2Cl2):
λmax 340 nm (ꢀ ) 4.3 × 104 M-1 cm-1). Elemental analysis did
not give satisfactory data due to the presence of free ligands,
which could not be removed by repeated recrystallization.
Kinetic Study of the Isomerization of 4 to 6. A sample
of recrystallized pentaene complex 4 (6.6 mg, 7.4 mmol) in
CDCl3 (0.6 mL) was sealed in NMR tubes under argon
atmosphere at room temperature. After the sample was
prepared, isomerization of the pentaene complex was moni-
tored by 1H NMR at various temperatures (15, 18, 20, 21, 23,
25, and 27 °C). The value [C]t, the concentration of 4 at reaction
time t, was determined from the intensity of signals assignable
to uncoordinated protons () H5 and H6) to ruthenium in 4.
The new signals were observed and assigned to 6 together with
the result of its COSY spectrum. The concentration of 6 was
estimated from the intensity of the doublet () H10) observed
at 6.57 ppm. 6: 1H NMR (CDCl3, 25 °C): δ 1.55 (s, 3H), 1.85
(s, 3H), 1.86 (s, 3H), 1.92 (s, 3H), 1.94 (s, 3H), 1.95 (s, 3H),
2.31 (s, 3H), 2.32 (s, 3H), 3.67 (dd, 1H, H3, J2,3 ) 7.8 and J3,4
) 10.3 Hz), 3.78 (dd, 1H, H6, J5,6 ) 10.7 and J6,7 ) 7.8 Hz),
3.96 (dd, 1H, H5, J4,5 ) 10.3 and J5,6 ) 10.7 Hz), 3.97 (dd, 1H,
H7, J7,8 ) 10.8 and J6,7 ) 7.8 Hz), 4.07 (dd, 1H, H4, J4,5 ) 10.3
and J3,4 ) 10.3 Hz), 4.32-4.43 (dd, 1H, H8, J8,9 ) 10.7 and J7,8
) 10.3 Hz), 4.32-4.43 (d, 1H, H1, J1,2 ) 10.3 Hz), 4.47 (dd,
1H, H2, J2,3 ) 7.8 and J1,2 ) 10.3 Hz), 5.38 (s, 1H), 5.47 (s,
Preparation of 4. A reaction mixture of Ru(acac)3 (0.224
g, 0.56 mmol), 1,10-diphenyldeca-1,3,5,7,9-pentaene (0.03 g,
0.10 mmol), and zinc dust (0.13 g) in ethanol (40 mL) was
refluxed for 12 h. The color of the resulting solution became
orange. After all volatiles were removed under reduced pres-
sure, the residue was extracted with toluene (40 mL) to remove
zinc dust and Zn(acac)2. The extract was concentrated and
cooled at -20 °C to give 4 (0.2 g, 81% yield) as a yellow-orange
solid (mp 195-200 °C (dec)). 4: 1H NMR (C6D6, 30 °C): δ 1.57
(s, 6H), 1.71 (s, 6H), 1.76 (s, 6H), 2.25 (s, 6H), 3.96 (dd, 2H, H3
and H8, J3,4 ) J7,8 ) 11.0 and J2,3 ) J8,9 ) 7.3 Hz), 4.46 (dd,
2H, H2 and H9, J1,2 ) J9,10 ) 10.7 and J2,3 ) J8,9 ) 7.3 Hz),
4.50 (dd, 2H, H4 and H7, J3,4 ) J7,8 ) 11.0 and J4,5 ) J6,7 ) 6.9
Hz), 4.58 (d, 2H, H1 and H10, J1,2 ) J9,10 ) 10.7 Hz), 5.31 (s,
2H), 5.34 (s, 2H), 6.19 (dd, 2H, H5 and H6, J5,6 ) 10.7 and J4,5
) J6,7 ) 6.9 Hz), 7.08-7.37 (m, 10H, C6H5). FAB-MS (N.B.A.
matrix): m/z 833 (M+). IR (Nujol): ν (CO)/cm-1 1577 (m), 1514
(s). UV/vis (CH2Cl2): λmax 343 nm (ꢀ ) 3.5 × 104 M-1 cm-1).
Anal. Calcd for C42H48O8Ru2: C, 57.12; H, 5.48. Found: C,
57.31; H, 5.69.
Preparation of 5. 1,12-Diphenyldodeca-1,3,5,7,9,11-hexaene
(0.16 g, 0.51 mmol) and zinc dust (0.36 g) were added to a
mixture of Ru(acac)3 (0.60 g, 1.50 mmol) in ethanol (30 mL).
(17) Johnson, A.; Everett, G. W. J. Am. Chem. Soc. 1972, 94, 1419.
(18) Spangler, C. W.; McCoy, R. K.; Dembek, A. A.; Sapochak, L.
S.; Gates, B. D. J. Chem. Soc., Perkin Trans. 1989, 151.

3938 Organometallics, Vol. 24, No. 16, 2005
Fukumoto and Mashima
1H), 5.50 (s, 1H), 5.52 (s, 1H), 6.26 (dd, 1H, H9, J9,10 ) 15.6
and J8,9 ) 10.7 Hz), 6.57 (d, 1H, H10, J9,10 ) 15.6 Hz), 7.08-
7.37 (m, 10H, C6H5). Signals of H1and H8 overlapped each other
and were assigned on the basis of the HH-COSY spectrum and
the coupling constants between other protons.
Crystallographic Data Collection and Structural De-
termination of Complexes 1 and 2. The crystals of 1 and 2
suitable for X-ray diffraction study were sealed in glass
capillaries under argon atmosphere, and then a crystal of each
complex was mounted on a Rigaku AFC-7R four-circle data
collector using Mo KR radiation. The unit cell parameters at
23 °C were determined by a least-squares fit to 2θ values of
25 strong higher reflections for all complexes and are shown
in Table 3. Three standard reflections were chosen and
monitored every 150 reflections. Empirical absorption correc-
tion was carried out based on an azimuthal scan. Complexes
1 and 2 showed no significant intensity decay during data
collection.
calculated structure factor amplitudes, respectively. The agree-
ment indices are defined as R ) ∑||Fo| - |Fc||/∑|Fo| and Rw
)
[∑w(|Fo| - |Fc|)2/∑w(|Fo|)2]1/2 where w-1 ) σ2(Fo) ) σ2(Fo )/(4Fo ).
The positions of all non-hydrogen atoms of 1 and 2 were
determined from a difference Fourier electron density map and
refined anisotropically. All hydrogen atoms for each complex
were placed at the calculated positions (C-H ) 0.95 Å) and
kept fixed. All calculations were performed using the TEXSAN
crystallographic software package, and illustrations were
drawn with ORTEP.
2
2
Acknowledgment. The present research was sup-
ported in part by a grant-in-aid for Scientific Research
from the Ministry of Education, Culture, Sports, Science
and Technology, Japan. We appreciate Professor Emeri-
tus K. Tani for fruitful suggestions.
OM050089N
The structures of 1 and 2 were determined by a direct
method (SHELXS 86)19 and refined by the full-matrix least-
squares method. In the refinement, the function ∑w(|Fo| -
|Fc|)2 was minimized, where |Fo| and |Fc| are the observed and
(19) Shedrick, G. M. In Crystallographic Computing 3; Shedrick, G.
M., Kru¨ger, C., Goddard, R., Eds.; Oxford University Press: Oxford,
U.K., 1985; p 179.