Synthesis of chiral chelating N-heterocyclic carbene complexes of ruthenium

Article abstract of DOI:10.1016/j.jorganchem.2005.05.036

The first 9-membered chiral chelating bidentate imidazol-2-ylidene ruthenium (II) benzylidene complexes based on a cyclopentane backbone were synthesised and characterised via NMR and HRMS.

Full text of DOI:10.1016/j.jorganchem.2005.05.036

Journal of Organometallic Chemistry 690 (2005) 3970–3975
www.elsevier.com/locate/jorganchem
Synthesis of chiral chelating N-heterocyclic carbene complexes
of ruthenium
*
Colin Marshall , Mark F. Ward, William T.A. Harrison
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen, AB24 3UE, Scotland, United Kingdom
Received 13 April 2005; received in revised form 25 May 2005; accepted 26 May 2005
Available online 11 July 2005
Abstract
The first 9-membered chiral chelating bidentate imidazol-2-ylidene ruthenium (II) benzylidene complexes based on a cyclopen-
tane backbone were synthesised and characterised via NMR and HRMS.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Chiral; Carbene complexes; Ruthenium
1. Introduction
tate NHC complexes designed for asymmetric synthesis
[9,10].
In recent years, synthetic efforts towards transition
metal complexes containing N-heterocyclic carbene li-
gands (NHC) have been the subject of intense interest
[1–3]. Major stimuli for the renewed appeal of these
complexes lie in their use as catalysts, where they often
display significant advantages over the analogous phos-
phane-containing compounds [4–6]. As NHC ligands
appear not to dissociate easily from the metal centre
of the catalyst this makes them particularly suitable
candidates for asymmetric induction reactions [7].
Development of air and moisture stable ruthenium
based olefin metathesis catalysts of type 1 [8] with
mixed NHC phosphane ligands have received much
attention due to their increased activity when com-
pared to the parent compound Grubbs catalyst. The
literature abounds with examples of chiral monoden-
Me
Ar
Ar
Me
Ph
Ph
iPr
N
N
N
Cl
Ph
N
N
Ru
Cl
i
Cl
Cl
Ph
Pr
Ru
N
Ar
Me
Me
Ar
PCy3
1
2
Herrmann et al. [4] have previously demonstrated
that active olefin metathesis catalysts 2 were produced
by substituting monodentate NHCs for both phos-
phines. To date no chiral chelating bidentate NHC
ruthenium alkylidene complexes have been prepared
for asymmetric metathesis reactions. In contrast, highly
efficient metathesis catalysts of molybdenum and tung-
sten have been synthesised that utilise chiral bidentate
ligands. The disadvantage of these catalysts are that
they require to be handled under inert atmospheres
and used in anhydrous solvents [11]. With this in mind,
*
Corresponding author. Tel.: +44 01224 272943; fax: +44 01224
272921.
E-mail addresses: c.marshall@abdn.ac.uk, che.522@abdn.ac.uk (C.
Marshall).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.05.036

C. Marshall et al. / Journal of Organometallic Chemistry 690 (2005) 3970–3975
3971
we began the synthesis of air stable chiral chelating
NHC ruthenium alkylidene complexes with a chiral
cyclopentane backbone to use in asymmetric ring clos-
ing metathesis.
dazol-2-thiones and a puckered cyclopentane ring. The
carbon sulphur bond lengths are consistent with litera-
ture imidazol-2-thiones [15].
Reduction of the dithiones 5a–b, by an alloy of
potassium and sodium in hot toluene was monitored
by TLC and revealed a clean reaction. After consump-
tion of the thione, the metal sulphide by-product was
filtered to leave a colourless solution of the free
dicarbenes 6a–b. This solution remains colourless for
several hours once separated from the reducing agent.
However, a deep red colour develops slowly after this
time. Removal of the solvent only accelerates this col-
our change and subsequent analysis of the residue re-
veals no typical carbene signal indicating the free
dicarbene is stable in solution for a few hours only.
Addition of the freshly prepared colourless dii-
midazol-2-ylidene solution to a toluene solution of
Grubbs catalyst gave access to the chelating bidentate
NHC ruthenium benzylidene complexes 7a–b. The
deep purple colour of Grubbs catalyst in solution
quickly abates to green/brown when the NHC solution
was added indicating a reaction. Upon work-up of the
complexation reaction the chelates were produced in
yields of 60–84%, as green air-stable solids.
2. Results and discussion
Employing methods of Yamamoto et al. [13] both
enantiomers of bis(menthyl)-1,2-cyclopentanedicarb-
oxylate were prepared [12]. Manipulation of this ester
by conventional methods furnished the dibromide 3.
When 3 was heated with 1-alkylimidazoles the salts
4a–b were produced in almost quantitative yields as
glassy solids. Employing modified methods by Karkh-
anis et al. [14] these glassy solids were converted to their
corresponding bis-imidazol-2-thiones 5a–b by deproto-
nation in the presence of sulphur (Scheme 1). The dithi-
ones were synthesised in yields of 76–93% and
characterised by HRMS and their typical C@S reso-
nance in the 13C NMR. Crystals of a phenyl derivative
were obtained from methanol. Interestingly the asym-
metric unit contains two independent half molecules
(Fig. 1) with the same chirality (C3 and C16 with R con-
figuration). Each complete molecule is generated by a
twofold symmetry axis passing through C1 and the
C3/C3i (symmetry code i = 1 ꢀ x, ꢀy, z) bisector for
molecule A and through C14 and the C16/C16ii (ii = ꢀx,
ꢀy, z) bisector for molecule B.
The chelates were characterised by NMR spectros-
copy and HRMS. Although the benzylidene carbon
(Ru = CHPh) was not detected from the 13C NMR
spectra, the attached proton had a resonance between
1
19.91 and 19.71 ppm in the H NMR. The 13C NMR
The structure determination of the solid dithione re-
vealed both forms of the molecule contain planar imi-
spectra of 7a–b revealed the configuration of the com-
plex to be similar to catalyst 2 with the Ru–C signals
at 185 ppm indicating a trans spanning configuration
[4]. Analysis by MS gave matching isotopic distribu-
tions with that expected of the theoretical. As NHC
ruthenium alkylidene complexes are known to be ac-
tive metathesis catalysts, it is anticipated the chiral
chelates 7a–b will allow stereodifferentiating alkene
metathesis reactions.
i
ii
N
N
N
N
2Br
=S S=
Br
Br
N
R
N
R
N
R
N
R
3. Summary
3
4a-b
5a-b
iii
The new chiral ligands (1S,2S) and (1R,2R)-1,2-bis-
(1-alkylimidazol-2-ylidene-3-methyl)cyclopentane were
prepared and used in situ to synthesise the first chiral
9-membered HNC ruthenium chelates. This was
achieved by elaboration of a chiral cyclopentane dibro-
mide backbone to the bisimidazolium salt. Conversion
of the salt to the crystalline bis(imidazol-2-thione) re-
vealed existence of two forms of the molecule in the
asymmetric unit with the same chirality. Reduction of
the thione functionality gave access to the bis(imidazol-
2-ylidene), which when reacted with Grubbs catalyst af-
fords the air stable chiral chelating bidentate NHC
ruthenium benzylidene complexes.
N
N
R
N
N
Cl
Cl
Ph
iv
N
N
Ru
N
R
N
R
R
R= Me (a),Cy (b)
7a-b
6a-b
Scheme 1. Synthesis of dicarbene ruthenium complex 7a–b. (i) 1-R-
imidazole, (ii) DBU, S, MeOH, C5H5N, (iii) Na/K, MePh, (iv)
(PCy3)2RuCl2CHPh, MePh.

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C. Marshall et al. / Journal of Organometallic Chemistry 690 (2005) 3970–3975
Fig. 1. ORTEP views of the two independent molecules of 5(30% displacement ellipsoids, arbitrary spheres for H atoms). Symmetry codes: (i) 1 ꢀ x,
˚
ꢀy, z, (ii) ꢀx, ꢀy, z. Selected bond lengths (A) and angles (ꢁ); molecule A: N1–C7 1.356 (3), C7–S1 1.683 (3), C7–N2 1.370 (3), N1–C7–N2 105.0 (2),
C4–C3–C2 114.3 (2), C4–C3–C3i 113.17 (17), C4–C3–C3i–C4i ꢀ70.9 (3); molecule B: N4–C20 1.372 (3), C20–S2 1.686 (3), C20–N3 1.363 (3), N3–
C20–N4 105.4 (2), C15–C16–C17 115.1 (2), C17–C16–C16ii 117.2 (2), C17–C16–C16ii–C17ii ꢀ65.0 (3).
4. Experimental
microscope and are uncorrected. Polarimetry was car-
ried out on a Bellingham and Stanley P20 polarimeter
and the values are given in 10ꢀ1 deg cm2 gꢀ1
.
4.1. General procedures
Starting materials were used as supplied by Lancas-
ter synthesis and Aldrich without further purification.
Reactions involving air sensitive reagents were carried
out in an atmosphere of nitrogen or argon using stan-
dard Schlenk techniques. Toluene was dried and dis-
tilled before use from sodium and benzophenone.
NMR spectra were recorded using a Bruker AC 250
4.2. Synthesis of Dichloro-(1S,2S) and (1R,2R)-1,2-
bis(1-methylimidazol-2-ylidene-3-methyl)cyclopentane
benzylidene ruthenium (II) 7a and b
4.2.1. (1S,2S)-1,2-Bis(1-methylimidazolium-3-
methyl)cyclopentane dibromide [(1S, 2S)5a]
A mixture of 1-methylimidazole (0.32 g, 3.9 mmol)
and (1S,2S)-1,2-Bis(bromomethyl)cyclopentane (0.5 g,
1
spectrometer. All H and 13C NMR spectra were ob-
tained at 250 and 62.9 MHz, respectively. Chemical
shifts are reported in ppm relative to Me4Si and were
1.96 mmol) was heated at 100 ꢁC for 6 h to give the dibr-
23
omide salt (0.82 g, 100%) as a light yellow glass; ½aꢁ
D
determined by reference to the residual H or 13C sol-
ꢀ17.5 (c 0.02 in H2O); mmax (KBr)/cmꢀ1 3140 (CH),
3101 (CH), 3065 (CH), 2955 (CH), 2866 (CH), 1449
(CH), 1338 (CH); dH(250 MHz; DMSO) 1.32–1.34
(2H, m, CH2CH2CH2), 1.54–1.70 (4H, m, CH2CH2),
2.16 (2H, m, CH), 3.87 (6H, s, NCH3), 4.05–4.32 (4H,
m, NCH2), 7.74–7.85 (4H, 2 · s, NCH), 9.35 (2H, s,
N2CH); dC(62.9 MHz; DMSO) 23.4 (CH2), 29.2
(CH2), 35.9 (NCH3), 42.4 (CH), 51.9 (NCH2), 122.3
1
vent peaks. Coupling constants, J, given in Hz. Infra-
red spectra were recorded as KBr pellets using an ATI
Mattson Genesis series FTIR instrument and reported
in cmꢀ1. Mass spectrometry was recorded by the
EPSRC National Mass Spectrometry Service Centre,
University of Wales, Swansea. Melting point determi-
nations were carried out using a Kufler hot-stage

C. Marshall et al. / Journal of Organometallic Chemistry 690 (2005) 3970–3975
3973
(NCH), 123.6 (NCH), 136.8 (N2CH); (ESI), 341.0 (12%,
[M ꢀ Br79]+), 339.0 (11%, [M ꢀ Br81]+), 129.9 (100%,
[M ꢀ 2Br]2+).
1.38 (2H, m, CH2CH2CH2), 1.54–1.60 (2H, m,
CH2CH2), 1.71–1.79 (2H, m, CH2CH2) 2.30–2.32 (2H,
m, CH), 3.54 (6H, s, NCH3), 3.84–3.90 (2H, dd, J 4.8
and 5.3, NCH2), 3.98–4.08 (2H, dd,J 5.3 and 4.8,
NCH2), 6.62 (2H, s, NCH), 6.82 (2H, s, NCH); dC
(62.9 MHz; CDCl3) 23.9 (CH2), 30.4 (CH2), 35.2
(NCH3), 43.1 (CH), 51.7 (NCH2), 117.5 (NCH), 117.7
(NCH), 162.3 (C@S; m/z (ESI) 323.1363 [M + H]+),
C15H22N4S2requires 323.1364, (ESI), 323.1 (100%,
[M + H]+).
(1R,2R)-1,2-Bis(1-methylimidazolium-3-methyl)-
cyclopentane dibromide [(1R, 2R)5a]
The procedure for the synthesis of (1S,2S)-5a was fol-
lowed using 1-methylimidazole (0.59 g, 3.9 mmol) and
(1R,2R)-1,2-Bis(bromomethyl)cyclopentane (0.5 g,
1.96 mmol) to give the dibromide salt (1.09 g, 100%) as
23
D
a light yellow glass; ½aꢁ 17.0 (c 0.02 in H2O).
(1R,2R)-1,2-bis(1-methylimidazol-2-thio-3-methyl)-
cyclopentane [(1R, 2R)6a]
4.2.2. (1S,2S)-1,2-Bis(1-cyclohexylimidazolium-3- methyl)-
cyclopentane dibromide [(1S, 2S)5b]
The procedure for the synthesis of (1S,2S )-5a was
followed using 1-cyclohexylimidazole (0.7 g, 4.66 mmol)
and (1S,2S)-1,2-Bis(bromomethyl)cyclopentane (0.6 g,
The procedure for the synthesis of [(1S, 2S) 6a] using
(1R,2R)-1,2-bis(1-methylimidazolium-3-methyl)cyclo-
pentane dibromide (0.77 g, 1.84 mmol), sulphur (0.18 g,
5.53 mmol), methanol (10 cm3), pyridine (0.9 g,
11.0 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene
2.33 mmol) to give the dibromide salt (1.3 g, 100%) as
23
D
a light yellow glass; ½aꢁ 5.4 (c 0.02 in H2O); 3126
(1.21 g, 8.10 mmol) gave the dithione (0.45 g, 76%) as
25
colourless crystals; m.p. 154 ꢁC (from methanol); ½aꢁ
(CH), 3075 (CH), 3043 (CH), 2931 (CH), 2857 (CH),
1449 (CH), 1365 (CH); dH(250 MHz; DMSO) 1.08–
1.90 (22H, m, CH2), 2.06 (4H, m, CH2CH2), 2.20 (2H,
m, CH), 4.09 (2H, m, NCH), 4.25 (4H, m, NCH2),
7.90–7.93 (4H, d,J 7, NCH), 9.61 (2H, s, N2CH);
dC(62.9 MHz; DMSO) 23.4 (CH2), 24.4 (CyCH2), 24.5
(CyCH2), 29.2 (CH2), 32.4 (CyCH2), 42.4 (CH), 52.0
(NCH2), 58.6 (NCH), 121.2 (NCH), 122.3 (NCH),
135.1 (N2CH). (ESI), 477.2 (100%, [M ꢀ Br79]+), 475.2
(98%, [M ꢀ Br81]+).
D
ꢀ35.8 (c 1.0 in CH2Cl2).
4.2.4. (1S,2S)-1,2-bis(1-cyclohexylimidazol-2-thio-3-
methyl) cyclopentane [(1S, 2S)6b]
The procedure for the synthesis of [(1S, 2S) 6a] using
(1S,2S)-1,2-bis(1-cyclohexylimidazolium-3-methyl)cyclo-
pentane dibromide (1.18 g, 2.12 mmol), sulphur (0.20 g,
6.35 mmol), methanol (15 cm3), pyridine (1.5 g,
19 mmol)
and
1,8-diazabicyclo[5.4.0]undec-7-ene
(1R,2R)-1,2-bis(1-cyclohexylimidazolium-3-methyl)-
cyclopentane dibromide [(1R, 2R)5b]
The procedure for the synthesis of (1S,2S)-5a was fol-
lowed using 1-cyclohexylimidazole (0.59 g, 3.9 mmol)
and (1R,2R)-1,2-bis(bromomethyl)cyclopentane (0.5 g,
(1.41 g, 9.42 mmol) gave the residue, which was purified
by column chromatography (SiO2, ethyl acetate: petro-
leum ether-1:1, loaded as a dichloromethane solution)
to give the dithione (0.90 g, 93%) as a colourless solid;
24
m.p. 86 ꢁC; ½aꢁ 31.42 (c 1.5 in CH2Cl2); mmax (KBr)/
D
1.96 mmol) to give the dibromide salt (1.09 g, 100%) as
cmꢀ1 2927 (CH), 2854 (CH); dH(250 MHz; CDCl3)
1.06–1.94 (26H, m, CH2), 2.22–2.30 (2H, m, CH),
3.78–4.03 (4H, dddd, J 6, 7.5 and 11, NCH2), 4.54–
4.63 (2H, m, NCH), 6.62 (2H, d,J 2.3, NCH), 6.78
(2H, d,J 2.3, NCH); dC(62.9 MHz; CDCl3) 23.77
(CH2), 25.3 (CyCH2), 25.4 (CyCH2), 30.3 (CH2), 32.5
(CyCH2), 42.3 (CH), 50.9 (NCH2), 56.1 (NCH), 113.7
(NCH), 117.6 (NCH), 160.8 (C@S); m/z (ESI)
459.2616 ([M + H]+, C25H38N4S2requires 459.2616),
(FAB), 481.4 (23%, [M + Na]+), 459.4 (100%, [M +
H]+), 458.4 (76%, [M]+).
23
D
a light yellow glass; ½aꢁ ꢀ5.6 (c 0.02 in H2O).
4.2.3. (1S,2S)-1,2-bis(1-methylimidazol-2-thio-3-methyl)-
cyclopentane [(1S, 2S)6a]
A mixture of (1S,2S)-1,2-bis(1-methylimidazolium-3-
methyl)cyclopentane dibromide (1.44 g, 3.4 mmol), sul-
phur (0.33 g, 10.3 mmol), methanol (20 cm3), pyridine
(1.8 g, 22.8 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-
ene (2.27 g, 15.2 mmol) was heated at 65 ꢁC for 6 h.
Once cooled to room temperature the mixture was
opened to water (100 cm3) and extracted with dichloro-
methane (3 · 30 cm3). The combined extracts were
washed with 8% (aq) HCl (2 · 50 cm3) before being
dried over magnesium sulphate, filtered and concen-
trated under reduced pressure to leave an orange
residue. The residue was purified by column chromatog-
raphy (SiO2, ethyl acetate, loaded as a dichloromethane
solution) to give the dithione (0.87 g, 79%) as a colour-
(1R,2R)-1,2-bis(1-cyclohexylimidazol-2-thio-3-methyl)-
cyclopentane [(1R, 2R)6b]
The procedure for the synthesis of [(1S, 2S) 6a]
using (1R,2R)-1,2-bis(1-cyclohexylimidazolium-3-methyl)
cyclopentane dibromide (1.03 g, 1.86 mmol), sulphur
(0.18 g, 5.53 mmol), methanol (10 cm3), pyridine (0.9 g,
11.13 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene
(1.23 g, 8.11 mmol) gave the residue, which was purified
by column chromatography (SiO2, ethyl acetate: petro-
leum ether-1:1, loaded as a dichloromethane solution)
less solid which was recrystallised from methanol to give
colourless crystals; m.p. 152 ꢁC (from methanol); ½aꢁ
23
D
36.4 (c 2.5 in CH2Cl2); mmax (KBr)/cmꢀ1 2956 (CH),
2928 (CH), 2867 (CH); dH(250 MHz; CDCl3) 1.34–
to give the dithione (0.81 g, 95%) as a colourless solid;
25
D
m.p. 86 ꢁC; ½aꢁ ꢀ30.23 (c 1.2 in CH2Cl2).

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C. Marshall et al. / Journal of Organometallic Chemistry 690 (2005) 3970–3975
4.2.5. Dichloro(1S,2S)-1,2-bis(1-methylimidazol-2-
ylidene-3-methyl)cyclopentane benzylidene ruthenium
(II) [(1S, 2S)7a]
plex(0.17 g, 63%) as a light green solid; m.p. 180 ꢁC (de-
comp); mmax (KBr)/cmꢀ1 2927 (CH), 2854 (CH);
dH(250 MHz; CDCl3) 1.10–2.45 (28H, br m, CH2, CH),
4.06 (4H, br m, NCH2), 4.58 (2H, br m, NCH), 6.96
(2H, s, NCH), 6.99 (2H, s, NCH), 7.25–7.55 (4H, m,
ArH), 8.26 (1H, br m, ArH), 19.71 (1H, s, Ru@CH);
dC(62.9 MHz; CDCl3) 25.4 (CH2), 25.7 (CH2), 25.9
(CH2), 29.9 (CH2), 30.0 (CH2), 30.5 (CH2), 30.6 (CH2),
34.8 (CH2), 34.9 (CH2), 45.6 (CH), 46.8 (CH), 54.2
(NCH2), 54.6 (NCH2), 59.0 (NCH), 59.1 (NCH) 118.4
(NCH), 118.6 (NCH), 124.0 (NCH), 124.1 (NCH),
128.9 (Co/m), 129.3 (Cp), 130.1 (Co/m), 131.4 (Co/m),
153.5 (Ci), 185.9 (N2CRu); m/z (ESI) 621.2310
([M ꢀ Cl]+, C32H44N4RuCl requires 621.2298), (ESI),
621.2 (100%, [M ꢀ Cl]+).
Oil free sodium (86 mg, 3.7 mmol) and potassium
(0.33 g, 8.37 mmol) was heated gently under vacuum to
yield an alloy. To this alloy was added (1S,2S)-
1,2-bis(1-methylimidazol-2-thio-3-methyl)cyclopentane
(0.2 g, 0.62 mmol) and toluene (20 cm3). The suspension
was heated to 60 ꢁC for 4 h before cooling to room tem-
perature. The colourless dicarbene solution was filtered
from the solid metal sulphide residue and had Dichloro-
tris(tricyclohexylphosphine)benzylidene ruthenium (II)
(0.46 g, 0.56 mmol) in toluene (30 cm3) added. An
immediate colour change was observed. The mixture
was stirred at room temperature for 3 h, filtered and
concentrated to ꢂ1 cm3. Addition of petroleum ether
(10 cm3) resulted in a green precipitate, which was fil-
tered, dissolved in toluene and reprecipitated by petro-
leum ether. This procedure was repeated three times
to give the bidentate carbene complex(0.25 g, 84%) as a
green solid; m.p. 215 ꢁC (decomp); mmax (KBr)/cmꢀ1
2935 (CH), 2863 (CH), 2852 (CH); dH(250 MHz;
CDCl3) 1.23–2.28 (8H, m, CH2, CH), 3.47 (6H, s,
NCH3), 3.54–4.25 (4H, m, NCH2), 6.91 (2H, s, NCH),
6.99 (2H, s, NCH), 7.25–7.48 (4H, m, ArH), 8.26 (1H,
d,J 7.5, ArH), 19.91 (1H, s, Ru@CH); dC(62.9 MHz;
CDCl3) 26.4 (CH2), 26.8 (CH2), 27.0 (CH2), 34.8
(CH), 35.8 (CH) 38.1 (NCH3), 45.4 (NCH2), 122.5
(NCH), 122.6 (NCH), 123.4 (NCH), 123.6 (NCH),
126.5 (Cp), 127.6 (Co/m), 128.7 (Co/m), 153.2 (Ci), 185.4
(N2CRu); m/z (ESI) 485.1052 ([M ꢀ Cl]+, C22H28-
N4RuCl requires 485.1046), (ESI), 485.1 (100%,
[M ꢀ Cl]+).
Dichloro(1R,2R)-1,2-bis(1-cyclohexylimidazol-2-yli-
dene-3-methyl)cyclopentane benzylidene ruthenium (II)
[(1R, 2R)7b]
The procedure for the synthesis of [(1S, 2S) 7a] was
followed using sodium (18 mg, 0.8 mmol), potassium
(64 mg, 1.64 mmol), (1R,2R)-1,2-bis(1-cyclohexylimi-
dazol-2-thio-3-methyl)cyclopentane (56 mg, 0.12 mmol)
in toluene (10 cm3) and Dichlorotris(tricyclohexylphos-
phine)benzylidene ruthenium (II) (100 mg, 0.12 mmol)
in toluene (10 cm3) to give the bidentate carbene com-
plex (48 mg, 60%) as a light green solid.
4.3. X-ray structure analysis
Crystallographic data (excluding structure factors)
for the structure in this paper have been deposited
with the Cambridge Crystallographic Data Centre as
supplementary publication numbers CCDC 265305.
Copies of the data can be obtained free of charge
on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, fax: +44 0 1223 336033, or e-mail: depos-
it@ccdc.cam.ac.uk. Crystal data for 5: empirical
formula C25H26N4S2, formula weight 446.64, tempera-
Dichloro(1R,2R)-1,2-bis(1-methylimidazol-2-ylidene-
3-methyl)cyclopentane benzylidene ruthenium (II) [(1R,
2R)7a]
The procedure for the synthesis of ([1S, 2S) 7a] was
followed using sodium (43 mg, 1.9 mmol), potassium
(0.16 g, 4.09 mmol), (1R,2R)-1,2-bis(1-methylimidazol-
2-thio-3-methyl)cyclopentane (0.1 g, 0.31 mmol) in
toluene (10 cm3) and Dichlorotris(tricyclohexylphos-
phine)benzylidene ruthenium (II) (0.23 g, 0.28 mmol)
in toluene (15 cm3) to give the bidentate carbene com-
plex(0.12 mg, 81%) as a green solid.
˚
ture 298 (2) K, wavelength 0.71073 A, orthorhombic,
space group P21212 (No. 18), unit cell dimensions
˚
˚
a = 12.6595 (7) A, b = 17.5962 (9) A, c = 10.41211
3
ꢀ3
˚
˚
(5) A, V = 2319.4 (2) A , Z = 4, Dc = 1.279 Mg m
,
absorption coefficient 0.249 mmꢀ1, F(000) = 944, crys-
tal size 0.52 · 0.24 · 0.22 mm, theta range for data col-
lection 1.98–25.01ꢁ, index ranges ꢀ11 ꢂ h ꢂ 15,
ꢀ20 ꢂ k ꢂ 20, ꢀ12 ꢂ l ꢂ 12, reflections collected
13123, independent reflections 4094 [Rint = 0.031],
completeness to h = 25.01ꢁ, 99.7%, max. and min.
transmission = 0.881 and 0.947, refinement method
full-matrix least-squares on F2, data/restraints/parame-
ters 4094/0/281, goodness-of-fit on F2 = 0.962, final R
indices [I > 2r(I)], R1 = 0.036, wR2 = 0.083, R indices
(all data), R1 = 0.053, wR2 = 0.088, absolute structure
4.2.6. Dichloro(1S,2S)-1,2-bis(1-cyclohexylimidazol-2-
ylidene-3-methyl)cyclopentane benzylidene ruthenium
(II) [(1S, 2S)7b]
The procedure for the synthesis of [(1S, 2S) 7a] was
followed using sodium (60 mg, 2.6 mmol), potassium
(0.23 g, 5.9 mmol), (1S,2S)-1,2-bis(1-cyclohexylimi-
dazol-2-thio-3-methyl)cyclopentane (0.2 g, 0.44 mmol)
in toluene (30 cm3) and Dichlorotris(tricyclohexylphos-
phine)benzylidene ruthenium (II) (0.33 g, 0.4 mmol) in
toluene (30 cm3) to give the bidentate carbene com-
parameter ꢀ0.ꢀ034 (9), largest diff. peak and hole 0.36
˚
and ꢀ0.16 e A
.

C. Marshall et al. / Journal of Organometallic Chemistry 690 (2005) 3970–3975
3975
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