Synthesis of conjugated diene complexes of ruthenium(0) derived from Ru(η6-naphthalene)(η4-1,5-COD): Z to e isomerisation of coordinated 1,3-pentadiene

Article abstract of DOI:10.1016/j.jorganchem.2012.02.018

The naphthalene complex of zerovalent ruthenium, [Ru(η⁶- C₁₀H₈)(η⁴-1,5-COD)] (1), readily reacts with 1,3-dienes in the presence of a ligand (L) to produce complexes [Ru(η⁴-cisoid-1,3-diene)(η⁴-1,5-COD)(L)] [1,3-diene = butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-cyclohexadiene; L = MeCN, ^tBuCN, PhCN, NCC₆H₄CN, CO, ^tBuNC, pyridine, P(OMe) ₃, P(OPh)₃, PMe₃, PEt₃, PPh ₃, PCy₃]. The single-crystal X-ray structures of [Ru(η⁴-cisoid-1,3-butadiene)(η⁴-1,5-COD)(MeCN)] (2a) and [Ru{η⁴-(E)-cisoid-1.3-pentadiene}(η⁴-1,5- COD)(PPh₃)}] (E-5l) show the expected, approximately square pyramidal geometry about the metal atom, with the auxiliary ligand occupying the axial site. [Ru{η⁴-(Z)-cisoid-1,3-pentadiene}(η⁴-1,5- COD)(PPh₃)] (Z-5l) irreversibly isomerises to E-5l in benzene-d ₆ at 30 °C, the reaction obeying a first-order rate law [k = (2.89 ± 0.06) × 10^-4 s^-1]. This reaction is significantly retarded by addition of PPh₃ suggesting that a vacant site is required for the E/Z isomerisation.

Full text of DOI:10.1016/j.jorganchem.2012.02.018

Journal of Organometallic Chemistry 708-709 (2012) 46e57
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of conjugated diene complexes of ruthenium(0) derived from Ru(h6
-
naphthalene)(h
4-1,5-COD): Z to E isomerisation of coordinated 1,3-pentadiene
*
Masafumi Hirano , Yumiko Sakate, Haruka Inoue, Yasutomo Arai, Nobuyuki Komine, Sanshiro Komiya,
**
,
Xian-qi Wang 1, Martin A. Bennett 1
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of A & T, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan, and Research School of Chemistry,
Australian National University, Canberra, ACT0200, Australia
a r t i c l e i n f o
a b s t r a c t
The naphthalene complex of zerovalent ruthenium, [Ru(h h
6-C10H8)(
4-1,5-COD)] (1), readily reacts with
Article history:
1,3-dienes in the presence of a ligand (L) to produce complexes [Ru(
h
4-cisoid-1,3-diene)( 4-1,5-COD)(L)]
h
Received 26 December 2011
Received in revised form
14 February 2012
[1,3-diene ¼ butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-
cyclohexadiene; L ¼ MeCN, tBuCN, PhCN, NCC6H4CN, CO, tBuNC, pyridine, P(OMe)3, P(OPh)3, PMe3,
Accepted 16 February 2012
PEt3, PPh3, PCy3]. The single-crystal X-ray structures of [Ru(h h
4-cisoid-1,3-butadiene)( 4-1,5-COD)(MeCN)]
(2a) and [Ru{
square pyramidal geometry about the metal atom, with the auxiliary ligand occupying the axial site. [Ru
h h
4-(E)-cisoid-1.3-pentadiene}( 4-1,5-COD)(PPh3)}] (E-5l) show the expected, approximately
Keywords:
Ruthenium(0)
Conjugated diene
1,3-Pentadiene
E/Z isomerisation
{h h
4-(Z)-cisoid-1,3-pentadiene}( 4-1,5-COD)(PPh3)] (Z-5l) irreversibly isomerises to E-5l in benzene-d6 at
30 ꢀC, the reaction obeying a first-order rate law [k ¼ (2.89 ꢁ 0.06) ꢂ 10ꢃ4
s
ꢃ1]. This reaction is signifi-
cantly retarded by addition of PPh3 suggesting that a vacant site is required for the E/Z isomerisation.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
low temperature [12]. Similar mechanisms probably apply also to
the other cross dimerisations mentioned above.
The lability of the coordinated naphthalene in [Ru(
h
6-C10H8)(h4
-
Addition of a compact Lewis base (L) to complex 1 causes facile
1,5-COD)] (1) [1e3] is responsible for the ability of this complex,
especially in the presence of acetonitrile, to catalyse some impor-
tant organic reactions, including alkene hydrogenation [3] and
isomerisation [4,5], the selective tail-to-tail dimerisation of unsat-
urated compounds such as methyl acrylate [6,7], methyl methac-
rylate [8] and acrylonitrile [9], and cross dimerisations between
butadiene and methyl methacrylate [10], and between 2,5-
dihydrofuran and methyl methacrylate [11]. An excess of buta-
diene in the absence of acetonitrile completely displaces naph-
ring slippage of the naphthalene to give isolable complexes [Ru(h4
-
C10H8)(
h
4-1,5-COD)(L)] [ L ¼ PMe3, PEt3, P(OMe)3] and this decrease
in hapticity encourages displacement of the naphthalene by
incoming substrates [13]. As already reported briefly [14], acyclic
1,3-dienes such as 2,3-dimethylbutadiene in the presence of
acetonitrile undergo this reaction to give labile complexes of the
type [Ru(h h
4-cisoid-1,3-diene)( 4-1,5-COD)(NCMe)], from which
acetonitrile is readily displaced by the ligands L.
We now present a full report on this work, including observations
on the Z to E isomerisation of the 1,3-pentadiene complexes [15].
thalene from complex 1 to give supine, prone-[Ru(h3
octadiene-1,8-diyl)(
4-1,5-COD)] as a result of oxidative coupling
of the butadiene units in an intermediate [Ru(
4-cisoid-butadie-
ne)(
2-transoid-butadiene)( 4-1,5-COD)] that can be detected at
:h
3-2,6-
h
h
2. Results
h
h
2.1. Synthesis of conjugated diene complexes
The complexes prepared in this work are listed in Table 1
together with the 1H NMR data of the coordinated 1,3-diene
units.
Abbreviation: COD, cyclooctadiene (C8H12).
* Corresponding author. Tel./fax: þ81 42 388 7044.
** Corresponding author. Tel.: þ81 61 2 6125 3639; fax: þ81 61 2 6125 3216.
E-mail addresses: hrc@cc.tuat.ac.jp (M. Hirano), bennett@rsc.anu.edu
(M.A. Bennett).
Research School of Chemistry, Australian National University, Canberra,
ACT0200, Australia.
Treatment of a slurry of [Ru(
acetonitrile with a saturated solution of 1,3-butadiene in benzene
gave [Ru(
4-cisoid-1,3-butadiene)( 4-1,5-COD)(NCMe)] (2a), which
h h
6-C10H8)( 4-1,5-COD)] (1) in
1
h
h
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.02.018

M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
47
was isolated as air-sensitive, thermally unstable brown crystals in
34% yield (Eq. (1)).
In an attempt to distinguish between these extremes, Müller
et al. [19] have employed the parameter d, which is the difference
D
The crystalline solid could be stored under nitrogen at dry-ice
temperature for a few weeks. Although the 1H and 13C NMR
spectra were in agreement with the formulation, elemental anal-
yses were not completely satisfactory owing to the instability and
sensitivity of the solid. After many attempts, a single-crystal of 2a
suitable for X-ray analysis was finally obtained. The molecular
structure of 2a is depicted in Fig. 1 and selected bond distances and
angles are listed in Table 2.
between the average of the outer RuꢃC (RuꢃC(1) and RuꢃC(4)) and
inner RuꢃC (RuꢃC(2) and RuꢃC(3)) distances, and the C(1)ꢃ
RuꢃC(4) angle (
a
a
). For the diene form,
D
d lies between ꢃ0.1
d and values
and þ0.1 Å, and
between 75ꢀ and 90ꢀ. For 2a, the
D
a
are estimated to be þ0.009 Å and 79.33ꢀ, respectively. Therefore,
according to this analysis, the diene extreme is the main contrib-
utor to the bonding in 2a.
Similar complexes containing either acetonitrile or other nitriles
were obtained from 2,3-dimethylbutadiene (3aed), isoprene (4a,
4c), (E)- and (Z)-1,3-pentadiene (5a), (E)-2-methyl-1,3-pentadiene
[(E)-6a, 6c, 6f] and 1,3-cyclohexadiene (7c). The benzonitrile
complexes are slightly more stable than those of acetonitrile or t-
butyl cyanide.
Spectroscopic evidence shows that the coordinated nitriles are
very labile. The EI-mass spectra do not show molecular ion peaks but,
for example, a peak at m/z 291 in the spectra of the 2,3-
dimethylbutadiene complexes 3aed can be assigned to the frag-
ment [Ru(C6H10)(C8H12)]þ and there are also intense peaks arising
The crystallographic analysis clearly shows a cisoid-h
4-coordi-
nation of the 1,3-butadiene fragment at the Ru centre. If the mid-
points of the olefinic double bonds are regarded as coordination
sites, the molecular structure of 2a can be described as being a five-
coordinate, approximately square pyramid, with the nitrile ligand in
the axial position. It is similar to that observed in [Ru(
C8H10)(
4-1,5-COD){P(OPh)3}] [16], [Ru( 4-C10H8)( 4-1,5-COD)(L)]
4-1,3-diene)(CO)3
h
4-1,3,5-
h
h
h
[L ¼ PMe3, PEt3, P(OMe)3] [13], and numerous Fe(
h
complexes [17,18]. The RueC distances to the 1,3-diene unit fall in
the range 2.176e2.191 Å and are similar to those observed in the
compounds cited above and in [Ru(
h
6-C6H6)(
h
4-1,3-butadiene)]
from the nitrile. The IR spectra show a n(CN) band at ca.
[19]. The distance C(2)eC(3) between the central atoms of the 1,3-
diene [1.421(5) Å] is the same as the terminal CeC distances
[1.419(7),1.416(5) Å] within the standard deviation, a pattern that is
2220e2240 cmꢃ1
,
close to the value for the free nitrile
[20]. The red 1,4-phthalonitrile 2,3-
(2222e2260 cmꢃ1
)
dimethylbutadiene complex 3d shows only one
n(CN) band at
generally similar to that observed in the Fe(
complexes and different from the short-long-short pattern
observed in [Ru(
6-C6H6)( 4-1,3-butadiene)] [19]. The observed
h
4-1,3-diene)(CO)3
2220 cmꢃ1 (2234 cmꢃ1 for free phthalonitrile), even though only one
of the CN groups is presumed to be coordinated. Although a dinuclear
structure bridged by 1,4-phthalonitrile is a possible alternative, the
elementalanalysisof 3dclearlysupportsa mononuclear formulation.
Coordination of a nitrile through nitrogen usually causes an observ-
ablehigh frequencyshift; a shift to lowerfrequencyoccurs only when
the metal centre has a strong back-bonding ability [21]. We assume
that the bands due to free and coordinated CN in 3d probably overlap.
The 1H NMR spectra of the acyclic 1,3-diene complexes show
h
h
pattern is consistent with the usual assumption of a minor contri-
bution to the metal-diene bond of an ene-diyl extreme (Chart 1).
4
4
2
3
1
3
1
resonances characteristic of h d ca. 0.5 and 1.7 due
4-coordination at
2
to the inner and outer protons of the terminal methylene groups.
They are shielded considerably relative to the corresponding
resonances of the free dienes and resemble those of other cisoid-
M
M
1,3-diene complexes of ruthenium(0), e.g., [Ru(h h
6-arene)( 4-1,3-
diene
ene-diyl
diene)] [19,22] and [Ru(L)(
[23e25]. The 1,5-COD olefinic protons usually appear as two well-
h
4-1,3-diene)2] [L ¼ CO, PPh3, P(OMe)3]
Chart1.

48
M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
Table 1
1H NMR data for 1,3-diene fragments in Ru( 4-cisoid-1,3-diene)( 4-1,5-COD)L.a
h h
3
4
R
R
2
6
R
R
1
5
R R
Comp.
Diene
L
R1
R2
R3
R4
R5
R6
0.70 (d, 2H)
J ¼ 7.2
1.89 (d. 2H)
J ¼ 6.5
2a
3a
MeCN
MeCN
5.26 (m, 2H)
2.02 (s, 6H)
e
e
e
e
e
e
0.52 (s, 2H)
1.71 (s, 2H)
3b
3c
3d
3e
tBuCN
PhCN
NCC6H4CN
CO
0.53 (s, 2H)
0.66 (s, 2H)
0.56(s, 2H)
0.14 (d, 2H)
J ¼ 2.4
1.70 (s, 2H)
1.76 (s, 2H)
1.72 (s, 2H)
0.84 (d, 2H)
J ¼ 2.4
2.01 (s, 6H)
2.03 (s, 6H)
2.12(s, 6H)
1.82 (s, 6H)
e
e
e
e
e
e
e
e
e
e
e
e
3e*
13CO
0.14 (dd, 2H)
J ¼ 3.0, 2.4
0.21 (s, 2H)
0.84 (d, 2H)
J ¼ 2.4
1.82 (s, 6H)
2.11 (s, 6H)
e
e
e
e
e
e
3f
tBuNC
1.07 (d, 2H)
J ¼ 1.8
3g
3h
NC5H5
P(OMe)3
0.40 (s, 2H)
1.74 (s, 2H)
1.99 (s, 6H)
2.22 (d, 6H)
J ¼ 16.5d
e
e
e
e
e
e
ꢃ0.11 (dd, 2H)
J ¼ 15.8,d 1.3
ꢃ0.87 (dd, 2H)
J ¼ 13.2,d 1.8
ꢃ1.10 (dd, 2H)
J ¼ 14.5,d 1.8
1.05 (br s, 2H)
3kb
3l
PEt3
0.88 (d, 2H)
J ¼ 2.0
2.09 (d, 6H)
J ¼ 2.2
e
e
e
e
e
e
PPh3
1.37 (d, 2H)
J ¼ 1.8
2.17 (d, 6H)
J ¼ 2.4
4.73 (t, 1H)
J ¼ 7.7
ꢃ0.02 (d, 1H)
J ¼ 8.2
1.24 (d, 1H)
J ¼ 7.0
4a
4c
MeCN
PhCN
0.15 (s, 1H)
0.25 (s, 1H)
1.28 (s, 1H)
1.35 (s, 1H)
1.98 (s, 3H)
2.03 (s, 3H)
4.80 (dd, 1H)
0.08 (d, 1H)
1.32 (d, 1H)
J ¼ 8.2, 6.8
J ¼ 8.2
J ¼ 6.6
0.30 (d, 1H)
J ¼ 8.3
1.61 (d, 1H)
J ¼ 6.9
5.05 (q, 1H)
J ¼ 6.9
5.12 (t, 1H)
J ¼ 6.2
1.24e1.27
(distorted m, 1H)
1.30 (distorted
d, 3H)
E-5a
MeCN
E-5e
E-5h
E-5i
CO
ꢃ0.01 (dd, 1H)
J ¼ 6.7, 2.5
0.89 (m, 1H)
4.76e4.80
(overlapped)
5.0e5.06
(m, 1H)
5.00 (m, 1H)
4.76e4.80
(overlapped)
5.09e5.11 (m, 1H)
0.78 (m, 1H)
0.82 (s, 3H)
P(OMe)3
P(OPh)3
PMe3
PPh3
ꢃ0.26 (dd, 1H)
J ¼ 13.8,d 7.4
0.08 (dd, 1H)
J ¼ 14.5,d 7.1
ꢃ0.83 (dd, 1H)
J ¼ 13.1,d 7.1
ꢃ0.53 (dd, 1H)
J ¼ 12,d 6.2
1.08
(overlapped)
1.08
(overlapped)
0.90
(overlapped)
1.60
0.78 (qui, 1H)
J ¼ 6.2
1.07 (d, 3H)
J ¼ 2.8
5.11 (m, 1H)
1.03 (overlapped)
1.07 (d, 3H)
J ¼ 3.2
E-5j
4.99e5.03
(m, 1H)
5.1 (m,
overlapped)
4.91 (m, 1H)
5.05e5.08 (m, 1H)
ꢃ0.02 (qui, 1H)
J ¼ 6.2 Hz
0.90 (br.d, 3H)
J ¼ 6
Ee5l
E-5m
5.1 (m,
ꢃ0.67 (qui, 1H)
J ¼ 6.2
0.92 (dd, 3H)
J ¼ 6.0, 1.4
1.2 (overlapped)
(d) J ¼ 6.0
overlapped)
5.10 (t, 1H)
J ¼ 6.0
PCy3
ꢃ0.43 (t, 1H)
J ¼ 8.7
1.36
0.39 (qui, 1H)
J ¼ 6.2
(overlapped)
1.02 (d, 1H)
J ¼ 8.7
1.29 (d, 1H)
J ¼ 7.3
4.95 (q, 1H)
J ¼ 8
4.68 (t, 1H)
J ¼ 6
0.74 (d, 3H)
J ¼ 8.7
Z-5a
MeCN
1.7 (overlapped)
Z-5h
Z-5j
P(OMe)3
PMe3
1.07 (dd, 1H)
J ¼ 6.0, 2.8
1.42 (dt, 1H)
J ¼ 7.3, 1.9
1.38 (br d, 1H)
J ¼ 7.4
5.12 (m, 1H)
5.1 (m, 1H)
5.05 (t, 1H)
J ¼ 6.4
1.03 (dd, 3H)
J ¼ 6.9, 2.8
1.60 (qui, 1H)
J ¼ 6.9
0.61 (br dd, 1H)
J ¼ 12.1,d 7.1
ꢃ0.06 (t, 1H)
J ¼ 8.2
5.1 (m, 1H)
0.83 (dd, 3H)
J ¼ 7.1, 2.5
1.1 (overlapped)
Ze5l
PPh3
1.18 (dd, 1H)
J ¼ 7.8, 2.3
5.19 (q, 1H)
J ¼ 7.5
5.04 (t, 1H)
J ¼ 7
0.51 (dd, 3H)
J ¼ 6.9, 3.2
2.30 (qui, 1H)
J ¼ 7.2
4.76 (d, 1H)
J ¼ 7.6
0.98 (d, 1H)
J ¼ 5.0
Ee6ac
MeCN
ꢃ0.18 (s, 1H)
1.05 (s. 1H)
1.97 (s, 3H)
0.86 (m, 3H)

M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
49
Table 1 (continued )
Comp.
Diene
L
R1
R2
R3
R4
R5
R6
Ee6cb
Ee6fb
Ee6kb
PhCN
tBuCN
PEt3
0.43 (s, 1H)
1.59 (s, 1H)
2.31 (s, 3H)
2.15 (s, 3H)
4.90 (d, 1H)
J ¼ 7.6
1.29 (d, 1H)
J ¼ 6.0
1.20 (m, 3H)
ꢃ0.47 (s, 1H)
0.50 (br s, 1H)
4.75 (d, 1H)
J ¼ 7.4
0.34 (dq, 1H)
J ¼ 7.4, 7.1
ꢃ0.03 (m, 1H)
0.87 (d, 3H)
J ¼ 7.1
ꢃ0.62 (d, 1H)
J ¼ 12.1d
0.95
(overlapped)
2.36 (d, 3H)
J ¼ 2.3
5.00 (d, 1H)
J ¼ 7.3
1.21 (d, 3H)
J ¼ 6.1
7c
PhCN
2.22 (br.s, 4H)
2.78 (br.s, 2H)
5.22 (br.s, 2H)
e
e
e
7h
7j
P(OMe)3
PMe3
2.17 (m, 4H)
2.04 (m, 4H)
2.92 (m, 2H)
2.19 (m, 2H)
5.14 (m, 2H)
5.17 (m, 2H)
e
e
e
e
e
e
7.03 (t, 2H)
J ¼ 7.4
7.20 (t partly
overlapped,
4H) J ¼ 7.4
7.24 (d,4H)
J ¼ 7.4
2.51(d, 2H)
J ¼ 6.9
5.86 (d, 2H)
J ¼ 6.9
8a
MeCN
e
e
e
1.50 (dsep, 1H)
J ¼ 8.2, 6.4
1.04 (d, 3H)
J ¼ 6.4
4.88 (d, 1H)
J ¼ 8.2
0.77 (t, 1H)
J ¼ 8.2
9a
MeCN
0.27 (s, 1H)
1.48 (s, 1H)
2.09 (s, 3H)
1.23 (d, 3H)
J ¼ 6.4
a
Measured in C6D6 at room temperature. Coupling constants are reported as observed splittings (in Hz).
b
c
In CD2Cl2 at r.t..
In CD2Cl2 at 20 ꢀC.
d
JPeH
.
separated pairs of multiplets in the region
therefore, pairwise inequivalent; there are also four 2H multiplets,
often overlapping, in the region 2.1e2.8 due to the methylene
protons of COD. Correspondingly, the 13C NMR spectra show a pair
of signals at ca. 100 and 42 due to the inner and outer 1,3-diene
d
3.3e3.7 and are,
signals in the regions
resonance of coordinated acetonitrile at
probably owing to rapid intermolecular exchange, and the MeCN
resonances could not be detected.
d
70e75 and 32e35, respectively. The methyl
ca. 0.7e0.9 was broad,
d
d
d
The labile acetonitrile is displaced irreversibly from complexes
2ae6a by ligands such as CO, tBuNC, tertiary phosphines, P(OMe)3
and P(OPh)3 at room temperature. The resulting derivatives, which
are listed in Table 1, are colourless or pale yellow solids that are
usually moderately air-stable, though air-sensitive in solution. In
contrast to their precursors, they often show parent-ion peaks in
their EI-mass spectra. Their 1H and 13C NMR spectra resemble in
their general features those of the acetonitrile complexes, with the
addition of 31P coupling where appropriate. The spectroscopic data
for all these complexes are consistent with a square pyramidal
ligand arrangement about ruthenium, with the nitrile or other
auxiliary ligand in the axial position.
carbon atoms, respectively, while the olefinic and methylene
carbon atoms of COD are inequivalent in pairs, each giving a pair of
C(3)
C(4)
C(2)
The 1,3-cyclohexadiene complexes [Ru(h h
4-1,3-C6H8)( 4-1,5-
C(1)
C(6)
N(1)
Ru(1)
C(5)
COD)(NCR)] (R ¼ Me, Ph) decomposed on attempted isolation but
the benzonitrile complex (R ¼ Ph, 7c) was identified by its 1H NMR
spectrum. The nitriles were readily displaced to give the yellow,
C(7)
C(14)
stable P-donor complexes [Ru(h h
4-1,3-C6H8)( 4-1,5-COD)(L)]
C(8)
Table 2
Selected bond distances (Å), bond angles and torsion angles (deg) for 2a.
Ru(1)eC(1)
Ru(1)eC(3)
Ru(1)eN(1)
C(2)eC(3)
C(1)eC(2)eC(3)
Ru(1)eN(1)eC(5)
Ru(1)eC(4)eC(3)
C(1)eC(2)eC(3)eC(4)
2.191(4)
2.176(4)
2.103(4)
1.421(5)
119.0(4)
178.7(3)
70.81(19)
ꢃ0.1(5)
Ru(1)eC(2)
Ru(1)eC(4)
C(1)eC(2)
C(3)eC(4)
C(2)eC(3)eC(4)
Ru(1)eC(1)eC(2)
C(1)eRu(1)eC(4)
2.179(4)
2.182(4)
1.419(7)
1.416(5)
118.8(4)
70.6(2)
C(12)
C(9)
C(13)
C(11)
C(10)
Fig. 1. ORTEP drawing with numbering schemes for 2a. All hydrogen atoms except
those in the 1,3-butadiene moiety are omitted for clarity. Ellipsoids represent 50%
probability.
79.33(13)

50
M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
C(7)
Table 3
C(8)
Selected bond distances (Å), bond angles and torsion angles (deg) for 8a.a
C(6)
C(9)
Ru(1)eC(1)
Ru(1)eC(3)
Ru(1)eN(1)
C(2)eC(3)
2.247(3)
2.191(3)
2.112(3)
1.417(4)
1.478(4)
119.9(3)
174.2(3)
69.77(16)
ꢃ0.6(4)
Ru(1)eC(2)
Ru(1)eC(4)
C(1)eC(2)
C(3)eC(4)
2.189(3)
2.234(3)
1.425(4)
1.410(4)
1.491(4)
119.8(3)
69.08(16)
78.20(10)
C(2)
C(3)
C(10)
C(5)
C(1)
C(1)eC(5)
C(4)eC(11)
C(4)
C(11)
C(16)
C(1)eC(2)eC(3)
Ru(1)eN(1)eC(17)
Ru(1)eC(4)eC(3)
C(1)eC(2)eC(3)eC(4)
C(2)eC(3)eC(4)
Ru(1)eC(1)eC(2)
C(1)eRu(1)eC(4)
C(15)
Ru(1)
C(26)
N(1)
C(12)
C(24)
C(17)
a
C(18)
Only one of the two crystallographically independent molecules is shown in this
C(13)
C(19)
C(14)
table.
C(20)
C(25)
C(23)
C(21)
presence of acetonitrile. The product, isolated in 31% yield as
analytically pure brown crystals, was [Ru(
4-cisoid-2,5-dimethyl-
4-1,5-COD)(NCMe)] (9a),, instead of the expected
4-cisoid-2,5-dimethyl-2,4-hexadiene)( 4-1,5-COD)
(NCMe)] (Eq. (2)). No trace of either the 2,5-dimethyl-2,4-
hexadiene complex or free 2,5-dimethyl-1,3-hexadiene was
observed by NMR spectroscopy. A white solid that deposited during
the preparation of 9a is assumed to be a polymer, since it was
insoluble in most common organic solvents.
h
C(22)
1,3-hexadiene)(
product [Ru(
h
h
h
Fig. 2. ORTEP drawing with numbering schemes for 8a. All hydrogen atoms except
those in the 1,4-diphenyl-1,3-butadiene moiety are omitted for clarity. Ellipsoids
represent 50% probability.
[L ¼ P(OMe)3 (7h), PMe3(7j)], which were isolated in 30e50% yield
and characterized by NMR spectroscopy, EI-mass spectra and
elemental analysis. When solutions of the nitrile 1,3-
cyclohexadiene complexes were left in contact with 1,3-
cyclohexadiene for several hours, the 1,5-COD was displaced;
acyclic 1,3-dienes did not behave similarly. The benzonitrile
The molecular structure of 9a is depicted in Fig. 3 and selected
bond distances and angles are summarized in Table 4.
The molecular structure confirms the structural assignment
based on 1H NMR spectroscopy. A characteristic feature of the 1H
complex [Ru(NCPh)(h
4-1,3-C6H8)2] was isolated in 10e15% yield as
NMR spectrum of 9a is the presence of a pair of doublets, at
d 1.04
air-sensitive brown crystals that gave satisfactory elemental anal-
yses but, like its acetonitrile analogue, it was very unstable in
solution. Its EI-mass spectrum showed the highest mass peak at m/z
261 corresponding to the fragment [Ru(C6H8)2]þ.
and 1.23, due to the inequivalent methyl protons of the isopropyl
group. The diastereotopicity arises from coordination of the
conjugated diene to the Ru centre. The observed isomerisation can
be explained as follows: (i) without exception, all the conjugated
diene ligands studied here have the cisoid conformation on the Ru
centre, (ii) a cisoid conformation of the original 2,5-dimethyl-2,4-
hexadiene would force the methyl groups at both endo-positions
into close proximity, and (iii) finally, isomerisation to the thermally
more stable cisoid-2,5-dimethyl-1,3-hexadiene complex can occur
via a formal 1,5-hydrogen shift. Although we do not have mecha-
nistic information, a similar 1,5-hydrogen shift occurs in the (Z)-1,3-
pentadiene complex, as described in the next section. It is also
worth noting that a similar isomerisation to that described here
occurs, under much more forcing conditions, when 2,5-dimethyl-
2,4-hexadiene is heated with [Fe(CO)5] to give the Fe(CO)3 complex
of cisoid-(E)-2,5-dimethyl-1,3-hexadiene [27].
The 1,4-diphenyl-1,3-butadiene complex [Ru(
h
4-cisoid- PhCH ¼
CHCH ¼ CHPh)(
h
4-1,5-COD)(NCMe)] (8a) was formed as analyti-
cally pure orange-yellow crystals by treatment of
1 with
1,4-diphenylbuta-1,3-diene in acetonitrile at room temperature.
An X-ray quality single-crystal of 8a was obtained; the
molecular structure is shown in Fig. 2 and selected metrical data are
in Table 3.
Compound 8a also has the h
4-cisoid-diene structure, both phenyl
rings being coplanar with the diene fragment, suggesting conjuga-
tion between these fragments. This hypothesis is supported by the
observed distances of 1.478(4) and 1.491(4) Å, respectively, for C(1)e
C(5) and C(4)eC(11). However, since the 1H NMR spectrum of 8a at
room temperature showed only one A2B2X pattern for the ortho-,
meta- and para-phenyl protons, the phenyl groups must be rotating
2.2. Complexes of 1,3-pentadiene
in solution. Erker et al. have reported formation of the h
4-transoid-
1,4-diphenylbuta-1,3-diene complex of Zr(II) [26]. In both 2a and 8a
the coordinated acetonitrile ligands are almost linear.
An interesting reaction occurred when the naphthalene
complex 1 was treated with 2,5-dimethylhexa-2,4-diene in the
These are of interest because there are several examples of the
interconversion of the E and Z-isomers coordinated both to ruthenium
[12,28,29] and to other transition elements [26,27,30e32], although
the mechanism of interconversion remains a matter for discussion.

M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
51
C(8)
C(2)
C(3)
C(1)
C(7)
C(4)
C(5)
Ru(1)
N(1)
C(11)
C(17)
C(12)
C(18)
C(6)
C(16)
C(9)
C(10)
C(15)
C(13)
Fig. 4. ORTEP drawing with numbering schemes for E-5l. All hydrogen atoms except
those in the 1,3-pentadiene moiety are omitted for clarity. Ellipsoids represent 50%
probability.
C(14)
Fig. 3. ORTEP drawing with numbering schemes for 9a. All hydrogen atoms except
those in the conjugated diene moiety are omitted for clarity. Ellipsoids represent 50%
probability.
coordination geometry about ruthenium is similar to that in
complexes 2a, 8a and 9a.
The 1H NMR and COSY spectra of the product obtained by
treatment of 1 with (E)-1,3- pentadiene in the presence of aceto-
2.3. Irreversible Z to E isomerisation of coordinated 1,3-pentadiene
nitrile contained two spin-coupled 1H-doublets at
assigned to the endo- and exo-1-CH2 protons, respectively, together
with a 1H-multiplet at 1.24e1.27 and a 3H-doublet at 1.30 due to
the 4-CHMe and 5-Me protons, respectively. Double quantum-
filtered NOESY showed a clear cross-peak between 0.30 and
ca.1.3. Since the methine and methyl signals appeared very close
together at 1.3, this NOESY experiment did not establish unam-
biguously the stereochemistry of the coordinated 1,3-pentadiene,
i.e., whether the complex is E-5a or Z-5a, but the 1H NMR spectrum
of the complex formed by displacement of acetonitrile by PPh3 at
room temperature showed the former alternative to be correct. The
d 0.30 and 1.61
In an in situ NMR experiment, addition of (Z)-1,3-pentadiene to
a solution of 1 in acetonitrile-d3 at room temperature caused
immediate liberation of free naphthalene and characteristic new
d
d
signals were observed at
d
0.8e1.2 (br, 5H), 1.7e2.2 (overlapped),
4.67 (t, JHeH ¼ 6 Hz, 1H), and 4.8e5.2 (br, 1H). Unexpectedly, the
resonance at 4.67 appeared as a sharp triplet, whereas all the
3
d
d
d
other peaks were broad at room temperature. On cooling the
MeCN-d3 solution to ꢃ40 ꢀC, all the resonances sharpened. The
1H-1H COSY analysis at ꢃ40 ꢀC showed clear spin correlations,
indicating that the resonances at d 0.75 (d, 3H), 1.02 (d, 1H), 1.29 (d,
1H), 1.7 (overlapped), 4.68 (t, 1H), and 4.95 (q, 1H) should be
assigned to 5-Meendo, 1-CHendo, 1-CHexo, 4-CHexo, 3-CH and 2-CH,
spectrum of E-5l contains a pair of 1H-signals at
0.55(dd) due to the inner diene protons H1 and H5, respectively,
together with a methyl resonance at 0.92. The double quantum
NOESY showed clear cross-peaks between the signals at
ꢃ0.67
d 0.67(quin) and
respectively. The 5-Me group in this compound (d 0.75) is more
d
shielded than that in E-5a ( 1.30), suggesting that it occupies the
d
d
endo site, i.e., that the product is Z-5a. The broad signals due to Z-5a
decreased in intensity over time at room temperature in acetoni-
trile-d3 and were replaced by the sharp signals assigned to E-5a,
conversion being complete within 4 h. Free (Z)- and (E)-1,3-
pentadiene do not interconvert under these conditions, hence the
isomerisation must occur at the metal centre. In addition, because
E-5a does not show such fluxionality, the dynamic behaviour in Z-
5a must be independent of the E/Z isomerisation of the 1,3-
pentadiene ligand on ruthenium(0). As noted above, the triplet at
and ꢃ0.53, and between the latter and the methyl resonance,
indicative of throughespace interactions and consistent only with
the presence of (E)-1,3-pentadiene.
This conclusion has been confirmed by a single-crystal X-ray
structural analysis of complex E-5l; the molecular structure is
shown in Fig. 4 and selected metrical data are listed in Table 5.
In agreement with the conclusion drawn from the 1H NMR
spectrum, the methyl group of 1,3-diene is in the exo-position. The
d
4.68 due to 3-CH in Z-5a remains sharp, even at room tempera-
ture, while the other signals broaden. This feature can be explained
Table 4
Selected bond distances (Å), bond angles and torsion angles (deg) for 9a.
Table 5
Ru(1)eC(1)
Ru(1)eC(3)
Ru(1)eN(1)
C(2)eC(3)
C(3)eC(4)
C(5)eC(6)
C(1)eC(2)eC(3)
Ru(1)eN(1)eC(9)
Ru(1)eC(4)eC(3)
C(1)eC(2)eC(3)eC(4)
2.183(3)
2.1966(19)
2.1217(18)
1.420(3)
1.418(3)
1.526(4)
116.78(18)
175.59(16)
69.87(11)
ꢃ0.4(3)
Ru(1)eC(2)
Ru(1)eC(4)
C(1)eC(2)
C(2)eC(8)
C(4)eC(5)
C(5)eC(7)
C(2)eC(3)eC(4)
Ru(1)eC(1)eC(2)
C(1)eRu(1)eC(4)
2.192(2)
2.235(3)
1.429(3)
1.510(4)
1.514(3)
1.536(4)
120.78(17)
71.27(12)
78.30(8)
Selected bond distances (Å), bond angles and torsion angles (deg) for E-5l.
Ru(1)eC(1)
Ru(1)eC(3)
C(1)eC(2)
C(3)eC(4)
C(1)eC(2)eC(3)
C(3)eC(4)eC(5)
Ru(1)eC(4)eC(3)
C(1)eC(2)eC(3)eC(4)
2.190(2)
2.202(2)
1.421(3)
1.414(3)
119.3(2)
121.0(2)
70.28(13)
2.0(3)
Ru(1)eC(2)
Ru(1)eC(4)
C(2)eC(3)
C(4)eC(5)
C(2)eC(3)eC(4)
Ru(1)eC(1)eC(2)
C(1)eRu(1)eC(4)
C(2)eC(3)eC(4)eC(5)
2.165(2)
2.231(2)
1.401(3)
1.499(3)
119.6(2)
69.85(13)
78.44(8)
174.2(3)

52
M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
Table 6
Exchanging protons in Z-5a in acetonitrile-d3 as observed by EXSY at ꢃ40 ꢀC.
Fig. 5. First-order rate plot for the conversion of Z-5l into E-5l in benzene-d6 at 30 ꢀC.
Closed circles: complex Z-5l (3.7 mg, 0.0069 mmol) and C6D6 (500 l). Open circles:
complex Z-5l (7.7 mg, 0.014 mmol) with 1 equiv of PPh3 (4.0 mg, 0.015 mmol) and C6D6
(600 l).
m
m
3. Discussion
by assuming that the 3-CH proton lies on a centre of symmetry of
the dynamic operation, which is most likely a 1,5-hydrogen shift
between the methyl and methylene groups [33]. A similar mecha-
nism has been proposed for the corresponding process in [RuCp
{(Z)-1,3-pentadiene}(CO)]þ by Green et al. [27]. Moreover, an EXSY
[34] measurement of Z-5a in acetonitrile-d3 at ꢃ40 ꢀC clearly
indicated proton exchange between the methyl and methylene
fragments (Table 6), consistent with the occurrence of an intra-
molecular 1,5-hydrogen shift in Z-5a in acetonitrile.
The nitrile-assisted reaction of [Ru(h h
6-C10H8)( 4-1,5-COD)] (1)
with 1,3-dienes provides
complexes under mild conditions. The nitrile assists the removal of
the naphthalene by promoting a decrease in its hapticity, h6 to h4
and the resulting ligand is then easily replaced by the entering diene.
Many 1,3-diene complexes of both Ru(0) and Ru(II) are known,
in addition to the ruthenium analogue of [Fe(
butadiene)(CO)3] [35]. They contain auxiliary ligands such as
tertiary phosphines [23],
6-arenes [19,22], 5-cyclopentadienyl
and substituted cyclopentadienyl [36e39],
4-tetraphenylcyclobu-
a range of 1,3-diene ruthenium(0)
,
h
4-cisoid-1,3-
When complex 1 was treated with (Z)-1,3-pentadiene in aceto-
nitrile at room temperature for an hour, and then PPh3 was added
h
h
h
immediately afterwards,
a pale yellow powder immediately
tadiene [29], and acetylacetonate [40]. The complexes described
here differ from these in the presence of an auxiliary ligand (the
nitrile) that can be readily replaced even at room temperature, thus
enabling oxidative coupling between the 1,3-diene and an entering
unsaturated ligand. Examples of this behaviour have been docu-
mented (see Introduction).
precipitated, which proved to be pure Z-5l (72% isolated yield). Its 1H
NMR spectrum in benzene-d6 showed a characteristic one-proton
quintet at
4-position; the resonances due to the inner and outer diene protons
H1 and H2 appeared at
ꢃ0.06 (t) and 1.18 (dd), respectively. The
d
2.30 assignable to the endo-methine proton H6 at the
d
The
complexes
[Ru{h h
4-(Z)-cisoid-1,3-pentadiene}( 4-1,5-
NOESY showed a clear spin correlation between them and the inner
diene proton H1, consist with the presence of the Z-1,3-diene. E-5l
was obtained as the exclusive product in 25% yield from the mother
liquor, presumably owing to isomerisation of Z-5a during work-up.
The preferential precipitation of Z-5l owing to its poor solubility in
acetonitrile may promote the high Z selectivity. Similarly, after
treatment of 1 with (Z)-1,3-pentadiene in acetonitrile for 30 min at
room temperature and subsequent addition of P(OMe)3 or PMe3 at
room temperature, E/Z mixtures of 5h (E/Z ¼ 50/50) and 5j (E/Z ¼ 40/
60) were isolated in 75% and 99% yields, respectively.
COD)(L)] ( L ¼ MeCN, PR3) undergo irreversible Z to E isomer-
isation of the coordinated diene. The available evidence is consis-
tent with the sequence of events shown in Scheme 1, starting from
the acetonitrile complex Z-5a. Dissociation of the labile acetonitrile
generates a 16-electron intermediate that is in rapid equilibrium
with its favoured 16-electron counterpart E-5a; each of these
species is rapidly trapped by tertiary phosphines to give the cor-
responding Z-5 and E-5 complexes. The binding constant K4 of PPh3
to the Z-intermediate must be small enough to allow dissociation of
PPh3 from Z-5l, whereas the corresponding binding constant K5 to
the E-intermediate is probably larger, thus accounting for the
irreversibility of the isomerisation. Under the reaction conditions
described, the more compact ligands P(OMe)3 and PMe3 give
mixtures of the corresponding Z- and E-complexes, 5h and 5j,
respectively, in ca. 1:1 ratio; the fact that this ratio does not
subsequently change, even at higher temperature, suggests that, for
these ligands, both K4 and K5 are large. In contrast, for the bulky
ligand PCy3, the Z isomer is not detectable, indicating that, in this
case, K4 is close to zero and K5 is large. Qualitatively, bulkier P-
donor ligands apparently do not bind strongly to the intermediate
derived from Z-5a, probably owing to steric repulsion between
the endo-methyl group of the coordinated 1,3-diene and the
substituents on the phosphorus atom, whereas all P-donors bind
relatively strongly to the intermediate derived from E-5a, regard-
less of the bulk of the substituents.
It is notable that the E/Z ratio of 5j remained unchanged when
the benzene-d6 solution was set aside for 2 days at room temper-
ature or when it was heated to 70 ꢀC. Similar treatment of 1 with
(Z)-1,3-pentadiene in acetonitrile solution at room temperature
followed by addition of PCy3 resulted in precipitation of E-5m in
69% yield and the mother liquor also contained E-5m, which was
isolated in 25% yield. The stereochemistry was confirmed by the
NOESY spectrum. In this case, the E-diene complex was obtained,
both in the precipitate and in solution. In benzene-d6 at 30 ꢀC
complex Z-5l isomerised spontaneously to E-5l. This process was
easily monitored by the decay of the 31P{1H} NMR singlet due to Z-
5l at d 65.9 and the growth of the singlet at d 60.8 due to E-5l. Fig. 5
shows that the isomerisation obeys good first-order kinetics with
an observed rate constant of 2.89(0.06) ꢂ 10ꢃ4 sꢃ1 in benzene-d6 at
30 ꢀC. The observed rate constant was approximately doubled in
dichloromethane-d2 (6.0(0.4) ꢂ 10ꢃ4
s
ꢃ1). The process was signif-
icantly retarded by added PPh3: in the presence of 1 equiv of PPh3
The interconversion of the Z- and E-intermediates (equilib-
rium K2 in Scheme 1) requires a formal rotation about the C]C
the rate constant decreased to 2.8(1.0) ꢂ 10ꢃ6 sꢃ1
.

M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
53
Scheme 1.
bond. Nelson and his co-workers have shown that the E/Z iso-
Scheme 2. The rapid 1,5-hydrogen shift that is characteristic of the
(Z)-1,3-pentadiene complexes cannot account for the Z/E isomer-
isation because the fluxionality is independent of E-5a. In the iso-
merisation of Z-5l to E-5l, the rate-determining loss of PPh3 must be
followed by other, more rapid steps and no insight into the mecha-
nism of the C]C bond rotation can be gained. Recently, we estab-
lished the existence of reversible E/Z-isomerisation in the complex
merisation of 1,3-pentadiene in its CpRh(I) complex occurs by
a 1,5-hydrogen shift that involves an (h
3-1-vinylallyl)hydrido-
intermediate and isomerisation through the rotation of the vinyl
group (Scheme 2) [41].
In the present case, we have firm evidence for the 1,5-hydrogen
shift in the (Z)-1,3-pentadiene complex as shown in Table 6,
corresponding to the process between A and A0 going through B in
[Ru(
h
4-cisoid-1,3-pentadiene)(
h
2-transoid-1,3-pentadiene)( 4-1,5-
h
*
*
*
*
M
H M
M
H M
A
B
D
C
*
M
A'
1,5-hydrogen shift mechanism
*
*
*
*
M
M
M
M
H
H
A
B
D
C
1,1-hydrogen shift mechanism
Scheme 2. E/Z isomerisation by hydrogen shift mechanisms.

54
M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
COD)] [12]. EXSY measurements [34] ruled out the “envelope shift”
mechanism that appears to be widelyaccepted to account for the E/Z
isomerisation in other 1,3-diene complexes [30e32] but were
distilled over sodium benzophenone ketyl, pentane was distilled
over potassium benzophenone ketyl, and dichloromethane and
acetonitrile were distilled from Drierite; ethanol was dried over
calcium chloride and distilled under nitrogen from magnesium
ethoxide. These solvents were stored under a nitrogen atmosphere.
Butadiene (99.0% pure) was purchased from Takachiho Chemical
consistent with an initial
induced by metal-carbon bond rupture (either heterolytic or
homolytic) in the ene-diyl form of the
4-diene; rotation about the
h h
4ꢃ-diene to 3-allylic transformation
h
CeC bond in the resulting carbanion or radical would then lead to Z/
E isomerisation of the diene, as illustrated in Scheme 3. A mecha-
nism of this type was first proposed by Erker, Berke et al. [26] to
account for the stepwise E/Z isomerisation of the 1,4-substituents in
Industry and used as received. [Ru(h h
6-naphthalene)( 4-1,5-COD)]
(1) was prepared according to the literature procedure [2]. All other
reagents were obtained from commercial suppliers (Wako Pure
Chemical Industry, Aldrich, or TCI) and used as received. Benzene-
d6 and toluene-d8 were dried over sodium wire, acetonitrile-d3 was
the 1,3-diene unit of [ZrCp2(h
4-transoid-1,4-disubstituted-1,3-
butadiene)], and we suggest that it may operate also in [Ru(h4
-
dried over Drierite, and dichloromethane-d2 was dried over P4O10,
cisoid-1,3-pentadiene)(
h
4-1,5-COD)(L)] (L ¼ MeCN, PR3).
these solvents being stored under vacuum. The NMR spectra were
recorded on Varian Gemini 300 (1H at 300 MHz, 13C at 75.4 MHz)
and Varian XL 200 (31P at 80.96 MHz) spectrometers (Canberra),
and on JEOL LA300 (1H at 300.4 MHz, 31P at 75.5 MHz) and JEOL
ECX400P (1H at 399.8 MHz, 13C at 100.5 MHz, 31P at 161.8 MHz)
spectrometers (Tokyo). Tetramethylsilane was used as the internal
reference for 1H and 13C spectra, external 85% H3PO4 for 31P spectra.
IR spectra were measured on PE 683 and JASCO FT/IR-410 spec-
trometers (Canberra and Tokyo, respectively). EI-mass spectra were
measured at 70 eV on a VG Micromass 7070 instrument (Canberra).
Elemental analyses were performed on a PerkineElmer 2400 series
II, CHN analyser (Tokyo) and by the staff of the Research School of
Chemistry (Canberra).
For the reversible E/Z isomerisation in [Ru(h
4-cisoid-1,3-
pentadiene)(h h
2-transoid-1,3-pentadiene)( 2-1,5-COD)], we could
not completely rule out the possibility of a 1,1-hydrogen shift
mechanism (Scheme 2). However, a 1,1-hydrogen shift (i.e. between
A and B, and between A0 and B0, in Scheme 2) is necessarily involved
in the rapid, reversible 1,5-hydrogen shift, which, as discussed
above, cannot be responsible for the observed isomerisation. A 1,1-
hydrogen shift can therefore also be excluded in the present case.
4. Conclusion
In summary, we have described a general procedure for the
preparation, under mild conditions, of an extensive series of
conjugated diene complexes of ruthenium(0). For the 1,3-
pentadiene complexes, the observed irreversible Z to E isomer-
isation seems to require the generation of a vacant site by release of
an ancillary ligand from the metal atom. The binding constant
between the coordinatively unsaturated (Z)-1,3-pentadiene
complex and a P-donor, K4, decreases with increasing bulk of the
P-donor, while that between the (E)-1,3-pentadiene complex and P-
donor, K5, is always large regardless of the steric congestion. Our
study should provide a basis for a fundamental understanding of
the stereochemistry of coordinated 1,3-diene transformations.
Spectroscopic and physical data only for the butadiene complex
2a, the 2,3-dimethylbutadiene complex 3a and the (E)- and (Z)-1,3-
pentadiene complexes 5 are described in this section. 1H NMR data
for the butadiene fragments are listed in Table 1. Those data for the
other complexes are deposited as Supplementary Material.
5.2. Butadiene complex 2
5.2.1. [Ru(h h
4-cisoid-butadiene)( 4-1,5-COD)(NCMe)] (2a)
An orange slurry of freshly prepared 1 (300 mg, 0.890 mmol) in
acetonitrile (10 ml) was treated with a saturated solution of buta-
diene in benzene (20 ml) at room temperature. The mixture was
evaporated to dryness under reduced pressure as quickly as
possible. Some of the naphthalene was removed under vacuum
(2e10 mm Hg) from the solid residue at or below 0 ꢀC on to a cold-
finger cooled in liquid nitrogen. The resulting brown sticky solid
was extracted with hexane (20 ml) and the solution was filtered.
Concentration under reduced pressure and cooling for 2 d in a dry-
ice bath gave 2a as air-sensitive, thermally unstable brown crystals
5. Experimental
5.1. General procedures
All manipulations and reactions were performed under dry
nitrogen with use of standard Schlenk and vacuum line techniques.
Benzene, toluene, hexane, tetrahydrofuran (THF) and Et2O were
(92 mg, 0.30 mmol, 34% yield). 1H NMR (300 MHz, RT, C6D6)
d 0.85
(br s, 3H, NCMe), 2.15, 2.32, 2.61, 2.77 (each m, 2H, CH2 of COD),
3.29, 3.68 (each m, 2H, ¼CH of COD). 13C{1H} NMR (75.4 MHz, r.t.,
C6D6)
d
31.7 (1JCeH ¼ 123 Hz, CH2 of COD), 35.2 (1JCeH ¼ 123 Hz, CH2
Me
H
K
2
of COD), 37.2 (1JCeH ¼ 152 Hz, 1- and 4-CH of C4H6), 71.3
(1JCeH ¼ 151 Hz, ¼CH of COD), 75.0 (1JCeH ¼ 150 Hz, ¼CH of COD),
91.9 (1JCeH ¼ 166 Hz, 2- and 3-CH of C4H6); MeCN resonances were
not observed. Anal. Calcd. for C14H21NRu: C, 55.24; H, 8.95; N, 4.60.
Found: C, 53.46; H, 7.12; N, 3.48.
H
Me
Ru
Ru
intermediate-Z
intermediate-E
All other conjugated diene complexes were prepared by
a similar procedure.
5.3. 2,3-Dimethylbutadiene complex 3
5.3.1. [Ru(h h
4-cisoid-2,3-dimethylbutadiene)( 4-1,5-COD)](NCMe)] (3a)
Me
Me
+
H
+
H
rotation
Grey crystals. Yield: 33%. 1H NMR (300 MHz, 20 ꢀC, C6D6): 0.72
(br s, 3H, NCMe), 1.85e2.22 (br s, 4H, CH2 of COD), 2.40e2.70 (br s,
4H, CH2 of COD), 2.78 (m, 2H, ¼CH of COD), 3.72 (m, 2H, ¼CH of
H
Me
H
Me
Ru
Ru
Ru
Ru
COD). 13C{1H} NMR (75.4 MHz, r.t., C6D6):
d
19.8 (1JCꢃH ¼ 125 Hz, 2-
and 3-CMe), 32.0 (1JCꢃH ¼ 125 Hz, CH2 of COD), 33.5 (1JCꢃH ¼ 126 Hz,
Scheme 3. .
CH2 of COD), 42.0 (1JCꢃH
¼
152 Hz, 1- and 4-CH2), 72.2

M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
55
(1JCꢃH ¼ 153 Hz, ¼CH of COD), 78.3 (1JCꢃH ¼ 151 Hz, ¼CH of COD),
100.9 (2- and 3-CMe) and signals assignable to NCMe were not
observed. MS: m/z ¼ 291 (Mþ-NCMe), 41 (NCMe). IR (KBr, cmꢃ1):
2220 (nCN). Anal. Calcd for C16H25NRu: C, 57.81; H, 7.58; N, 4.21%.
Found: C, 57.93; H, 7.77; N, 4.30%.
COD), 3.35 [d, J ¼ 10.1 Hz, 9H, P(OMe)3], 3.54e3.57 (m, 2H, COD),
3
5.05 (t, JHꢃH ¼ 6.4 Hz, 1H, 3-CH), 5.12 (m, 1H, 2-CH).
5.4.6. [Ru{h h
4-(E)-cisoid-1,3-pentadiene}( 4-1,5-COD){P(OPh)3}]
(Eꢃ5i)
Pale brown powder. Yield: 98%. 1H NMR (400 MHz, r.t., C6D6):
5.4. 1,3-Pentadiene complexes 5
d
0.08 (dd, 3JHꢃP ¼ 14.5, 3JHꢃH ¼ 7.1 Hz,1H,1-CHendo),1.03 (overlapped,
1H, 4-CHendo), 1.07 (m,, 3H, 5-Meexo), 1.08 (overlapped, 1H, 1-CHexo),
1.84e1.93 (m, 2H, COD), 1.99e2.08 (m, 1H, COD), 2.17e2.23 (m, 3H,
COD), 2.54e2.64 (m, 2H, COD), 2.86e2.96 (m,1H, COD), 3.22e3.37 (m,
2H, COD), 3.54 (m, 1H, COD), 5.00 (m, 1H, 2-CH), 5.11 (m, 1H, 3-CH),
5.4.1. [Ru{
h
4-(E)-cisoid-1,3-pentadiene}(
h
4-1,5-COD)(NCMe)] (Eꢃ5a)
Reddish brownpowder. Yield: 100%.1H NMR (400 MHz, r.t., C6D6):
d
0.30 (d, 3JHꢃH ¼ 8.3 Hz, 1H, 1-CHendo), 0.75 (s, 3H, NCMe), 1.24e1.27
(distorted multiplet, 1H, 4-CHendo), 1.30 (distorted d, 3JHꢃH ¼ 5.0 Hz,
3H, 5-Meexo), 1.61 (d, 3JHꢃH ¼ 6.9 Hz, 1H, 1-CHexo), 2.02e2.18 (m, 3H,
COD), 2.34e2.44 (m, 2H, COD), 2.53e2.78 (m, 3H, COD), 3.10e3.14 (m,
6.78 [t, JHꢃH ¼ 7.3 Hz, 3H, peP(OPh)3], 6.93 [t, JHꢃH ¼ 7.8 Hz, m-
3
3
P(OPh)3]. 7.20 [d, JHꢃH ¼ 7.8 Hz, 6H, o-P(OPh)3]. 31P{1H} NMR
3
(162 MHz, r.t., C6D6): signals were not observed. 1H NMR (400 MHz,
3
3
2H, COD), 3.55 (td, JHꢃH ¼ 7.9, JHꢃH ¼ 3.5 Hz, 1H, COD), 3.71 (td,
17 ꢀC,C6D5CD3):
d
ꢃ0.01 (dd, 3JHꢃP ¼ 15.2, 3JHꢃH ¼ 7.3 Hz, 1H, 1-CHendo),
3JHꢃH ¼ 8.1, 3JHꢃH ¼ 3.4 Hz,1H, COD), 5.05(q, 3JHꢃH ¼ 6.9 Hz,1H, 2-CH),
0.93 (partly overlapped, 1H, 4-CHendo) 0.99 (d, 3JHꢃH ¼ 5.5 Hz, 1H, 1-
CHexo), 1.03 (m, 3H, 5-Meexo), 1.83 (br, 2H, COD), 2.01 (m, 1H, COD),
2.15 (m, 3H, COD), 2.53 (m, 2H, COD), 2.85 (m, 1H, COD), 3.18 (m, 1H,
COD), 3.25 (m,1H, COD), 3.48(br,1H, COD), 4.95(br,1H,1H, 2-CH), 5.07
(br, 1H, 3-CH), 6.77 [t, 3JHꢃH ¼ 6.9 Hz, 3H, peP(OPh)3], 6.92 [slightly
3
5.12 (t, JHꢃH ¼ 6.2 Hz, 1H, 3-CH). 1H NMR (400 MHz, r.t., CD3CN):
d
ꢃ0.22 (d, 3JHꢃH ¼ 8.3 Hz,1H,1-CHendo), 0.9 (m,1H, 4-CHendo),1.00 (d,
3JHꢃH ¼ 6.0 Hz, 3H, 5-Meexo), 1.01 (overlapped, 1-CHexo), 1.77e2.2 (m,
5H, COD), 2.3e2.5 (m, 3H, COD), 2.67 (m, 2H, COD), 3.00 (td,
3JHꢃH ¼ 8.2, JHꢃH ¼ 3.2 Hz, 1H, COD), 3.39 (m, 1H, COD), 4.75 (q,
broad t, JHꢃH ¼ 7 Hz, m-P(OPh)3], 7.15 [d, JHꢃH ¼ 8.2 Hz, 6H, o-
3
3
3
3JHꢃH ¼ 6.9 Hz, 1H, 2-CH), 4.96 (dd, 3JHꢃH ¼ 7.8, 5.0 Hz, 1H, 3-CH).
P(OPh)3]. 13C{1H} NMR (100.5 MHz, 18 ꢀC, C6D5CD3):
d 15.0 (s, 5-Me),
30.9 (s, COD), 31.6 (s, COD), 32.3 (s), 34.0 (s), 35.0 (s), 47.5 (s, 4-CHMe),
68.0(d, JCꢃP ¼ 8Hz, COD), 71.0 (d, JCꢃP ¼ 8Hz, COD), 71.7(d, JCꢃP ¼ 8Hz,
COD), 75.9 (d, JCꢃP ¼ 7 Hz, COD), 84.2 (s, 2- or 3-CH), 93.9 (s, 3- or 2-
CH), 120.9 [d, 2JCꢃP ¼ 4 Hz, o-P(OPh)],123.7 [s, peP(OPh)], 129.5 [s, m-
P(OPh)], 153.8 [d, 1JCꢃP ¼ 13 Hz, ipso-P(OPh)]. 31P{1H} NMR (162 MHz,
5.4.2. [Ru{h h
4-(Z)-cisoid-1,3-pentadiene}( 4-1,5-COD)(NCMe)] (Z-5a)
This compound was formed in situ and was characterised by 1H
NMR and 1H-1H COSY analyses. 1H NMR (400 MHz, r.t., CD3CN):
d
0.8e1.2 (br, 5H,1-CHendo,1-CHexo and 5-Meendo),1.7e2.2 (overlapped,
4-CHexo, COD), 2.3 (br, 2H, COD), 2.7 (br, 2H, COD), 3.0 (br, 2H, COD),
17 ꢀC, C6D5CD3):
5.4.7. [Ru{
d 127.6 (s).
3
4.67 (t, JHꢃH ¼ 6 Hz, 1H, 3-CH), 4.8e5.2 (br, 1H, 2-CH). 1H NMR
(400 MHz, ꢃ40 ꢀC, CD3CN):
d
0.74(d, 3JHꢃH ¼ 6.9 Hz, 3H, 5-Meendo),1.02
h
4-(E)-cisoid-1,3-pentadiene}(
h
4-1,5-COD)(PMe3)] (Eꢃ5j)
(d, 3JHꢃH ¼ 8.7 Hz,1H,1-CHendo),1.29 (d, 3JHꢃH ¼ 7.3 Hz, 1H, 1-CHexo),1.7
(overlapped, 4-CHexo), 1.75e1.77 (overlapped, COD), 1.88e1.98 (over-
lapped, COD), 2.1 (m,1H, COD), 2.23e2.33 (m, 2H, COD), 2.36e2.48 (m,
1H, COD), 2.52e2.57 (m, 1H, COD), 2.64e2.68 (m, 1H, COD), 2.92 (td,
3JHꢃH ¼ 6, 3 Hz, 1H, COD), 3.06 (td, 3JHꢃH ¼ 5, 3 Hz, 1H, COD), 4.68 (t,
3JHꢃH ¼ 6.0 Hz, 1H, 3-CH), 4.95 (q, 3JHꢃH ¼ 8 Hz, 1H, 2-CH).
Dark brown solid. Yield: 100%. 1H NMR (400 MHz, r.t., C6D6):
d
ꢃ0.83 (dd, 3JHꢃP ¼ 13.1, 3JHꢃH ¼ 7.1 Hz, 1H, 1-CHendo), ꢃ0.02 (qui,
3JHꢃH ¼ 6.2 Hz, 1H, 4-CHendo), 0.90 (br dd, JHꢃH ¼ 6, JHꢃP ¼ 1 Hz,
3H, 5-Meexo), 0.90 (overlapped, 1H, 1-CHexo), 1.19 (d, 2JHꢃP ¼ 7.3 Hz,
9H, PMe), 1.86e2.02 (m, 2H, COD), 2.1e2.3 (m, 6H, COD), 2.4e2.5
(m, 1H, COD), 2.56e2.59 (m, 1H, COD), 2.80e2.89 (m, 1H, COD),
3.24e3.31 (m,1H, COD), 4.99e5.03 (m,1H, 2-CH), 5.05e5.08 (m,1H,
3
4
5.4.3. [Ru{
h
4-(E)-cisoid-1,3-pentadiene}(
h
4-1,5-COD)(CO)] (Eꢃ5e)
3-CH). 31P{1H} NMR (162 MHz, r.t., C6D6):
d
5.78 (s).
This compound was produced by exposure of E-5a to CO in an
NMR tube and characterised by its NMR spectrum. Yield: 76%. 1H
5.4.8. [Ru{
h
4-(Z)-cisoid-1,3-pentadiene}(
h
4-1,5-COD)(PMe3)] (Z-5j)
NMR (400 MHz, r.t., C6D6):
d
ꢃ0.01 (dd, 3JHꢃH ¼ 6.7, 2JHꢃH ¼ 2.5 Hz,1H,
This compound was formed in situ and was characterised by its
1-CHendo), 0.78 (m,1H, 4-CHendo), 0.82 (s, 3JHꢃH ¼ 5.9 Hz, 3H, 5-Meexo),
0.89 (m,1H,1-CHexo),1.71e2.1 (m, 6H, COD), 2.34e2.43 (m,1H, COD),
2.52e2.61 (m, 1H, COD), 2.65e2.70 (m, 1H, COD), 3.20e3.24 (m, 1H,
COD), 3.42e3.52 (m, 2H, COD), 4.76e4.80 (m, 2H, 2- and 3-CH).
1H NMR spectrum. 1H NMR (400 MHz, r.t., C6D6):
d
0.61 (br dd,
3JHꢃP ¼ 12.1, JHꢃH ¼ 7.1 Hz, 1H, 1-CHendo), 0.83 (dd, JHꢃH ¼ 7.1,
4JHꢃH ¼ 2.5 Hz, 3H, 5-Meendo), 1.1 (overlapped, 1H, 4-CHexo), 1.23 (d,
2JHꢃP ¼ 7.4 Hz, 9H, PMe3), 1.38 (br d, 3JHꢃH ¼ 7.4 Hz, 1H, 1-CHexo), 1.5
(m, 1H, COD), 2.0e2.5 (m, 8H, COD), 2.65e2.71 (m, 1H, COD),
2.97e3.06 (m, 1H, COD), 4.94 (m, 1H, 3-CH), 5.01e5.06 (m, 1H, 2-
3
3
5.4.4. [Ru{h h
4-(E)-cisoid-1.3-pentadiene}( 4-1,5-COD){P(OMe)3}]
(Eꢃ5h)
CH). 31P{1H} NMR (162 MHz, r.t., C6D6):
d
6.24 (s).
Yellow brown oil. Yield: 70%. 1H NMR (400 MHz, r.t., C6D6):
3
3
d
ꢃ0.26 (dd, JHꢃP ¼ 13.8, JHꢃH ¼ 7.4 Hz, 1H, 1-CHendo), 0.78 (qui,
5.4.9. [Ru{
h
4-(E)-cisoid-1,3-pentadiene}( 4-1,5-COD)(PPh3)] (E-5l)
h
3JHꢃH ¼ 6.2 Hz, 1H, 4-CHendo), 1.07 (m, 3H, 5-Meexo), 1.08 (over-
White powder. Yield: 88%. 1H NMR (400 MHz, r.t., C6D6):
d
ꢃ0.67
3
3
lapped, 1H, 1-CHexo), 1.95e2.34 (m, 6H, COD), 2.52e2.80 (m, 3H,
(qui, JHꢃH ¼ 6.2 Hz, 1H, 4-CHendo), ꢃ0.53 (dd, JHꢃP ¼ 12,
3
COD), 3.12e3.32 (m, 2H, COD), 3.35 [d, JHꢃP ¼ 10.3 Hz, 9H,
3JHꢃH ¼ 6.2 Hz,1H,1-CHendo), 0.92 (dd, 3JHꢃH ¼ 6.0, 4JHꢃP ¼ 1.4 Hz, 3H,
3
P(OMe)3], 3.46 (m, 1H, COD), 5.0e5.06 (m, 1H, 2-CH), 5.09e5.11 (m,
5-Meexo), 0.86e0.93 (m, 1H, COD), 1.60 (d, JHꢃH ¼ 6.0 Hz, 1H, 1-
1H, 3-CH). 31P{1H} NMR (162 MHz, r.t., C6D6):
d
141.4 (s).
CHexo), 1.60e1.87 (m, 4H, COD), 2.02e2.10 (m, 1H, COD), 2.25e2.40
3
(m, 2H, COD), 2.67 (q, JHꢃH ¼ 8.2 Hz, 1H, COD), 2.88 (br dd,
5.4.5. [Ru{
h
4-(Z)-cisoid-1.3-pentadiene}(
h
4-1,5-COD){P(OMe)3}]
3JHꢃH ¼ 9, 3JHꢃH ¼ 6 Hz, 1H, COD), 3.47 (m, 1H, COD), 3.54e3.62 (m,
1H, COD), 5.1 (m, 2H, 2- and 3-CH), 7.01e7.03 (m, 9H, PPh3),
(Z-5h)
This compound was formed in situ and was characterised by its
1.03 (dd,
7.64e7.68 (m, 6H, PPh3). 31P{1H} NMR (162 MHz, r.t., C6D6):
d
60.8 (s).
1H NMR spectrum. 1H NMR (400 MHz, r.t., C6D6):
d
3JHꢃP ¼ 6.9, 3JHꢃH ¼ 2.8 Hz, 3H, 5-Meendo), 1.07 (dd, 3JHꢃH ¼ 6.0, 2.8,
1H, 1-CHendo), 1.42 (dt, 3JHꢃH ¼ 7.3, 3JHꢃH ¼ 1.9 Hz, 1H, 1-CHexo), 1.60
(qui, 3JHꢃH ¼ 6.9 Hz,1H, 4-CHexo),1.71e1.78 (m,1H, COD), 2.00e2.07
(m, 1H, COD), 2.27e2.37 (m, 2H, COD), 2.41e2.50 (m, 1H, COD),
2.57e2.65 (m, 2H, COD), 2.75e2.85 (m, 1H, COD), 3.22e3.25 (m, 1H,
5.4.10. [Ru{h h
4-(Z)-cisoid-1,3-pentadiene}( 4-1,5-COD)(PPh3)] (Z-5l)
White powder. Yield: 88%. 1H NMR (400 MHz, r.t., C6D6):
d
ꢃ0.06
(t, 3JHꢃH ¼ 8.2 Hz,1H, 1-CHendo), 0.51 (dd, 3JHꢃH ¼ 6.9, 4JHꢃP ¼ 3.2 Hz,
3
3H, 5-Meendo), 0.6e0.7 (m, 1H, COD), 1.18 (dd, JHꢃH ¼ 7.8,
3JHꢃP ¼ 2.3 Hz, 1H, 1-CHexo), 1.45e1.54 (m, 1H, COD), 1.6e1.7 (m, 2H,

56
M. Hirano et al. / Journal of Organometallic Chemistry 708-709 (2012) 46e57
Table 7
Crystallographic data and refinement details for 2a, E-5l, 8a, and 9a.
2A
E-5l
8A
9A
Formula
C14H21NRu
304.40
Monoclinic
P21/c (No. 14)
11.936(2)
C31H35PRu
539.66
Orthorhombic
Pbca (No. 61)
17.007(2)
C26H29NRu
456.59
Triclinic
C18H29NRu
360.50
Monoclinic
C2/c (No. 15)
21.439(8)
8.404(3)
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Pꢃ1(No. 2)
11.6098(17)
11.6436(18)
16.109(3)
96.191(3)
91.165(3)
92.298(4)
4931.1(10)
4
8.4800(10)
13.5494(18)
29.094(4)
9.9659(10)
19.443(8)
a
b
g
(deg)
(deg)
(deg)
110.250(6)
106.217(4)
V (Å3)
1286.7(4)
4
4931.1(10)
8
3364(3)
8
Z
Temp. (K)
Crystal size (mm)
Colour
200.0
200.0
200.0
200.0
0.458 ꢂ 0.285 ꢂ 0.086
Light brown
624.00
0.35 ꢂ 0.25 ꢂ 0.25
Colourless
2240.00
0.719
0.320 ꢂ 0.212 ꢂ 0.070
0.789 ꢂ 0.545 ꢂ 0.443
Yellow
Brown
F(000)
944.00
0.736
1504.00
0.924
m
(mmꢃ1
)
1.192
Absorption correction
Radiation
Diffractometer
Measurement method
Reflections (total)
Parameters
NUMABS
psi-scan
NUMABS
NUMABS
Mo K
a
(
l
¼ 0.71075 Å)
Mo K
a
(
l
¼ 0.7107 Å)
Mo K
a
(
l
¼ 0.71075 Å)
Mo K
a
(
l
¼ 0.71075 Å)
Rigaku AFC7R-Mercury II
u
2905
145
Rigaku AFC7R
u
5652
333
Rigaku AFC7R-Mercury II
u
9744
505
Rigaku AFC7R-Mercury II
u
3702
181
Goodness of fit
R (wR)
0.831
0.0373(0.1009)
0.884
0.0285 (0.0953)
0.726
0.0330 (0.0961)
0.604
0.0241(0.0642)
2
2
R ¼ S[jFojꢃjFcj]/SjFoj. Rw ¼ [Sw(jFoj ꢃjFcj )2/SwjFo]2]1/2
.
3
COD), 1.91e2.06 (m, 2H, COD), 2.30 (qui, JHꢃH ¼ 7.2 Hz, 1H, 4-
CHexo), 2.26e2.44 (m, 2H, COD), 2.68e2.75 (m, 2H, COD), 3.23 (m,
1H, COD), 3.67 (m, 1H, COD), 5.04 (t, 3JHꢃH ¼ 7 Hz, 1H, 3-CH), 5.19 (q,
3JHꢃH ¼ 7.5 Hz, 1H, 2-CH), 7.02e7.04 (m, 9H, PPh3). 7.66e7.72 (m,
collected data were solved by direct methods (SIR92), and refined
by a full-matrix least square procedure using SHELXL for 2a, 8a and
9a [42], and CrystalStructure programs for E-5l [43]. All non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were placed in calculated positions
and were not refined. The crystallographic and physical data are
listed in Table 7.
6H, PPh3). 31P{1H} NMR (162 MHz, r.t., C6D6):
d 65.9 (s).
5.4.11. [Ru{h h
4-(E)-cisoid-1,3-pentadiene}( 4-1,5-COD)(PCy3)] (E-5m)
Pale yellow powder. Yield: 97%. 1H NMR (400 MHz, r.t., C6D6):
3
d
ꢃ0.43 (t, JHꢃH
¼
3JHꢃP ¼ 8.7 Hz, 1H, 1-CHendo), 0.39 (qui,
Acknowledgements
3JHꢃH ¼ 6.2 Hz, 1H, 4-CHendo), 1.17e1.40 (m, 12 H, PCy3), 1.2 (over-
lapped, 3H, 5-Meexo), 1.36 (overlapped, 1H, 1-CHexo), 1.64e2.1 (m,
24 H, COD and PCy3), 2.31e2.4 (m, 4H, COD), 2.52e2.60 (m, 2H,
COD), 3.15 (q, 3JHꢃH ¼ 7.8 Hz, 1H, COD), 3.3e3.44 (m, 2H, COD), 4.91
A part of this work was financially supported by a Grant-in-Aid
for Scientific Research from the Ministry of Education, Culture,
Science and Technology, Japan. The authors are grateful to Ms. S.
Kiyota for elemental analyses in Tokyo.
(m, 1H, 2-CH), 5.10 (t, JHꢃH ¼ 6.0 Hz, 1H, 3-CH). 31P{1H} NMR
3
(162 MHz, r.t., C6D6):
d 30.3 (s).
Appendix A. Supplementary material
5.5. Isomerisation of Z-5l to E-5l
A Supplementary data related to this article can be found online
at doi:10.1016/j.jorganchem.2012.02.018.
A sealed capillary containing PPh3 in C6D6 as an internal stan-
dard was placed in an NMR tube, into which complex Z-5l (3.7 mg,
0.0069 mmol) and C6D6 (500
m
L) were transferred. The 31P{1H}
References
NMR spectrum of this solution was measured immediately and the
time-course of isomerisation was monitored at 30 ꢀC. The observed
[1] G. Vitulli, P. Pertici, P. Salvadori, J. Chem. Soc. Dalton Trans. (1984) 2255.
[2] M.A. Bennett, H. Neumann, M. Thomas, Q. X-Wang, P. Pertici, P. Salvadori,
G. Vitulli, Organometallics 10 (1991) 3237.
rate constant was estimated to be 2.89 ꢁ 0.06 x 10ꢃ4 sꢃ1
.
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2.8 ꢁ 1.0 x 10ꢃ6 sꢃ1
.
5.7. X-ray analyses of 2a, E-5l, 8a, and 9a
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a
radiation (
l
¼ 0.71069 Å) were
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