A novel cis-push-pull effect in cycloruthenated azobenzene thiocarbonyl-containing complexes: Crystal and molecular structures of [RuX(CS)(η2-C,N-C6H4N=NPh)(PPh 3)2](X = Cl, I)

Article abstract of DOI:10.1016/S0022-328X(00)00692-6

Treatment of [RuHCl(CS)(PPh₃)₃] with Hg(o-C₆H₄N=NC₆H₅)₂ affords [RuCl(CS)(η²C,N-o-C₆H₄N=NC ₆H₅)(PPh₃)₂] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered chelate ring. Reaction of 1 with AgNO₃ followed by NaBr or NaI affords the chloride-exchanged products [RuX(CO)(η²C,N-o-C₆H₄N=NC₆H ₅)(PPh₃)₂] (2, 3), whereas reaction of 1 with AgOC(O)Me or NaS₂CNEt₂·2H₂O gives the halide mono-phosphine-substituted complexes [Ru(CS)(LL)(η²C,N-o-C₆H₄NNC ₆H₅)(PPh₃)] (4, 5). In the solid-state structures of 1 and 3 there are significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These are discussed, with the aid of spectroscopic and crystallographic data, in terms of a cis-push-pull effect.

Full text of DOI:10.1016/S0022-328X(00)00692-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 620 (2001) 60–68
A novel cis-push–pull effect in cycloruthenated azobenzene
thiocarbonyl-containing complexes: crystal and molecular
structures of [RuX(CS)(h2-C,N-C6H4NꢀNPh)(PPh3)2](X=Cl, I)
K.R. Flower *, R.G. Pritchard
Department of Chemistry, UMIST, PO Box 88, Manchester M60 1QD, UK
Received 17 July 2000; received in revised form 31 August 2000
Abstract
Treatment of [RuHCl(CS)(PPh3)3] with Hg(o-C6H4NꢀNC6H5)2 affords [RuCl(CS)(h2C,N-o-C6H4NꢀNC6H5)(PPh3)2] (1) in
good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered
chelate ring. Reaction of 1 with AgNO3 followed by NaBr or NaI affords the chloride-exchanged products [RuX(CO)(h2C,N-o-
C6H4NꢀNC6H5)(PPh3)2] (2, 3), whereas reaction of 1 with AgOC(O)Me or NaS2CNEt2·2H2O gives the halide mono-phosphine-
substituted complexes [Ru(CS)(LL)(h2C,N-o-C6H4NNC6H5)(PPh3)] (4, 5). In the solid-state structures of 1 and 3 there are
significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These
are discussed, with the aid of spectroscopic and crystallographic data, in terms of a cis-push–pull effect. © 2001 Elsevier Science
B.V. All rights reserved.
Keywords: Azobenzene; Crystal structure; Ruthenium; Thiocarbonyl
bond lengths around the azo-group as well as the CꢁC
bonds in the metallated phenyl ring [4]. We recently
reported the preparation of some azo-containing phos-
phines and explored the well-known [5] azo/hydrazone
tautomeric process and this alerted us to the structural
changes observed on going from the azo to hydrazone
tautomeric form [6]. In a recent paper we drew atten-
tion to the similarity in the structural changes that
occur on cyclometallation of azobenzene and the tau-
tomeric process and suggested the presence of a cis-
push–pull effect [7]. Caulton and coworkers have
published a series of papers concerning p-stabilised
unsaturation in transition metal complexes [8], and
during the course of this work they have shown that the
p-acid CO is able to stabilise p-donation in 18 valence
electron species, because of its special acceptor capabil-
ities, through a push–pull effect [8b]. In this paper we
show that the thiocarbonyl ligand is equally capable of
stabilising p-donation in 18 valence electron
organometallics, in this instance through a novel cis-
push–pull process.
1. Introduction
Roper and Wright first reported the transfer of or-
ganic groups to ruthenium or osmium using
organomercurials in 1977 [1], and since then Roper and
coworkers have developed extensive chemistry based
upon this methodology [2]. For example, compounds
that contain chelating C,N systems such as
[MCl(CO)(h2-C,N-2-C6H4-Py)(PPh3)2] (M=Ru, Os)
and [OsCl(CO)(h2-C,N-Qn)(PPh3)2] (Qn=8-quinolyl)
have been reported and their chemistry investigated
[2e–h]. Transition metal complexes that contain an
azobenzene ligand or derivatives of it are well known,
and there are several coordination modes documented
[3]. One particularly noteworthy structural characteris-
tic of complexes containing a cyclometallated azoben-
zene ligand is the perturbation of the CꢁN and NꢀN
* Corresponding author. Tel.: +44-161-2004538.
E-mail address: k.r.flower@umist.ac.uk (K.R. Flower).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00692-6

K.R. Flower, R.G. Pritchard / Journal of Organometallic Chemistry 620 (2001) 60–68
61
2. Results and discussion
tion of the crude reaction mixture with hot hexane
removed the azobenzene and PPh3; subsequent recrys-
tallisation of the remaining the material from CH2Cl2–
Et2OH afforded 1. The reactivity of 1 has been
investigated and is summarised in Scheme 1.
Treatment of [RuHCl(CS)(PPh3)3] with Hg(o-
C6H4NꢀNC6H5)2 in refluxing toluene afforded [Ru-
Cl(CS)(h2-C,N-o-C6H4NꢀNC6H5)(PPh3)2] (1) in good
yield according to Eq. (1).
(1)
After removal of elemental mercury by filtration and
removal of the solvent under reduced pressure, extrac-
All of the new compounds 1–5 have been character-
ised by elemental analysis (C, H, N, S), infrared spec-
Scheme 1. (i) AgNO3, CH2Cl2, EtOH, H2O; (ii) NaX (X=Br, I); (iii) AgOC(O)Me, CH2Cl2; (iv) NaS2CNEt2·2H2O, CH2Cl2, EtOH, H2O.
Table 1
Physicala and analytical datab and infrared datac for complexes 1–5
Complex
Colour
Yield (%)
M.p. (°C)
Microanalytical data (%)
w(CS) (cm−1
)
Others (cm−1
)
C
H
N
S
1
Purple
Purple
Purple
Red
85
87
92
72
66
211
202
195
190
195
66.1
(66.4)
61.0
(61.1)
59.8
(60.2)
61.0
(61.2)
58.4
(58.7)
4.0
(4.4)
4.2
(4.2)
4.0
(4.0)
4.1
(4.2)
4.5
(4.7)
3.0
(3.2)
2.9
(2.9)
2.9
(2.9)
4.5
(4.3)
5.3
(5.7)
3.2
(3.6)
3.0
(3.3)
3.0
(3.3)
5.3
(4.9)
12.5
(13.0)
1267s
1268s
1276s
1271s
1275s
2·0.5CH2Cl2
3
4
5
1524m,1389m
1485msh
Red
a All compounds soften before melting.
b Calculated values in parentheses.
c Spectra recorded as KBr discs; s, strong, m, medium, sh, shoulder, br, broad.

62
K.R. Flower, R.G. Pritchard / Journal of Organometallic Chemistry 620 (2001) 60–68
Table 2
31P{1H}-NMRa and protonb data for complexes 1–5
Complex
31P (l, ppm)
1H (l, ppm)
1
2
25.8
24.7
7.9 (bd, JHH 8.0, 1H, aryl H); 7.5–6.8 (bm 37H, aryl H); 6.2 (bt, 1H, JHH 7.0, aryl H)
7.9 (bd, JHH 8.0, 2.0, 1H, aryl H); 7.5–7.0 (bm 37H, aryl H); 6.2 (bt, 1H, JHH 8.0, aryl H); 5.29 (s, 0.5H,
CH2Cl2)
3
4
5
23.0
50.2
40.5
7.9 (bd, JHH 8.0, 1H, aryl H); 7.5–6.5 (bm 37H, arylH); 6.7 (m, 1H, arylH); 6.2 (bt, 1H, JHH 8.0, arylH)
8.2 (bd, JHH 8.0, 1H, aryl H); 7.7–6.8 (bm, 23H, aryl H); 0.9 (s, 3H, CH3)
8.2 (dd, JHH 8.0, 2.0, 1H, aryl H); 7.9 (bd, JHH 8.0, 1H, aryl H); 7.5–6.8 (bm 22H, aryl H); 3.4 (m, 4H, CH2);
1.0 (t, JHH 7.1, 3H, CH3); 0.8 (t, JHH 7.1, 3H, CH3)
a Spectra recorded in CDCl3 (298 K) and referenced to 85% H3PO4.
b Spectra recorded in CDCl3 (298 K) and referenced to CHCl3, J in hertz; s, singlet, d, doublet, t, triplet, m, multiplet, b, broad.
troscopy, 1H-, 31P{1H}-, and 13C{1H}-NMR spec-
troscopy (Tables 1–3). Compounds 1 and 3 have been
further characterised by single crystal X-ray diffraction
studies; see Table 4 for data collection and processing
parameters and Table 5 for selected bond lengths.
ORTEP representations of the molecular structures of 1
and 3, are presented as Figs. 1 and 2, showing the
atomic numbering scheme. Both structures are best
described as being slightly distorted octahedral with the
two PPh3 ligands mutually trans and axial, and with the
ortho-metallated azobenzene, thiocarbonyl and halide
in the equatorial plane. The greatest deviation from the
idealised geometry is in the C(3)ꢁRuꢁN(1) angle,
75.7(2)° 1, 75.8(4)° 3. This is commonly observed in
complexes containing ortho-metallated azobenzene lig-
ands, and is a result of the tight bite angle of the ligand
[4], and this has the obvious knock-on effect of opening
up of other angles in the equatorial plane from 90°. The
most significant structural features of 1 and 3 relate to:
(i) the Ru to azobenzene bond lengths; (ii) the bond
lengths within the ortho-metallated azobenzene ligand;
and (iii) the CS bond lengths: a detailed discussion that
relates these data to the w(CS) follows later.
stronger p-donating halide (Cl) affects the lowest w(CS),
suggesting that the w(CS) is dependent upon the p-do-
nating power of the halide even though they have a cis
rather than trans disposition. The relative values for the
w(CS) of 4 and 5, when taken as a pair, are also
consistent with this interpretation.
The 31P{1H}-NMR spectra of 1–5 (Table 1) all show
a singlet resonances, which for 1–3 suggest mutually
trans-PPh3 ligands. Slight shifts in resonance were ob-
served on exchange of chloride by bromide or iodide.
More significant shifts (20 ppm) occurred for 4 and 5,
where substitution of the chloride ligand and displace-
ment of one of the PPh3 ligands has taken place.
The 1H-NMR spectra of 1–5 are consistent with
their formulation (Scheme 1) and are also almost iden-
tical to those obtained for the analogous compounds
[RuCl(CO)(h2-C,N-o-C6H4NNPh)(PPh3)2] [7]. The aro-
matic region is complex, with overlapping multiplets
leaving individual proton assignment difficult; however,
the doublet of doublets observed at ca 7.9 ppm can be
assigned to the proton ortho to the ruthenated carbon
of the azobenzene and integrates as expected to the
remaining protons. The orientation of the chelating
azobenzene, two phosphine and halide ligands is the
same as has been observed in the analogous ruthenium
The infrared spectra of 1–5 (Table 1) all display a
strong w(CS) around 1270 cm−1 and complex finger-
print regions. Compound 4 displays w(CO2) at 1524 and
1389 cm−1, which implies a chelating coordination
mode for the acetate ligand [9]. In 5 the w(CN) for the
coordinated diethyldithiocarbamate ligand is tentatively
complex
[RuCl(CO)(h2-C,N-o-C6H4CNPh)(PPh3)2],
which contains an orthometallated imine rather than
azobenzene [10]. The data for 4 are also consistent
(integration of OC(O)CH3 to aryl-H) with the infrared
data and suggest the acetate ligand is coordinated in a
bidentate fashion as opposed to being bound monoden-
tate in the related CO-containing complex [Ru{h1-
assigned to a band observed at 1485 cm−1
.
Caulton and coworkers reported [8b] in an infrared
study to assess the degree of p-stabilisation in unsatu-
rated complexes of the type [RuHX(CO)(PtBu2Me)2]
that the w(CO) was dependent upon the p-donor power
of the ligand X. They also showed that this was also
true in the coordinatively saturated pyridine containing
adducts [RuHX(CO)(py)(PtBu2Me)2], although to a
slightly lesser extent, and that this formally forbidden
p-donation was possible because a trans-push–pull ef-
fect facilitated by the p-accepting properties of the CO
ligand. Careful inspection of the w(CS) stretching fre-
quencies in 1–3, Table 1, shows a similar pattern: the
OC(O)Me}(CO)(h2-C,N-o-C6H4NꢀNPh)(PPh3)2]
[7].
For compound 5 the integration suggests that the
dithiocarbamate ligand is also coordinated in a biden-
tate fashion. The methyl protons of the ethyl groups
appear as two ‘triplets’ and the methylene protons as a
complex second-order multiplet, and this is consistent
with its structure (Scheme 1) since there is no plane of
symmetry through the CN bond. It is also directly
comparable to the structurally characterised osmium

Table 3
13C {1H}-NMR dataa for 1–5
Compound
CS
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
Others
/
1
2
3
4
5
306.7
t(15.6)
306.9
t(16.1)
307.6
t(16.5)
292.2
d(19.1)
303.2
d(18.1)
184.6
t(9.6)
184.8
t(9.0)
185.2
t(8.6)
168.5
d(8.0)
187.7
d(9.0)
138.0
138.1
138.2
139.7
139.4
132.0
132.0
132.0
132.8
132.8
126.8
126.6
126.5
128.8
126.8
124.8
125.0
125.4
124.5
124.5
160.3
160.6
161.2
164.5
162.3
153.4
153.3
153.2
151.4
151.6
121.8
121.9
122.1
123.3
122.4
127.8
127.8
127.9
129.8
127.8
130.8
131.1
131.4
130.6
129.0
132.3
t(20.6)
132.5
t(22.1)
132.7
t(22.1)
131.1
134.3
t(5.0)
134.4
t(5.0)
134.7
t(5.0)
134.6
d(13.1)
133.6
d(10.0)
127.4
t(5.0)
127.4
t(5.0)
127.3
t(5.0)
128.3
d(13.1)
127.9
d(10.0)
129.3
129.3
129.3
130.4
129.8
185.2 CO
22.5 CH3
209.7 CS
44.3, 44.0 CH2
12.2,12.0 CH3
d(45.2)
134.0b
a Spectra recorded in CDCl3 at 298 K, JCP in hertz, t, triplet, d, doublet.
b Doublet expected but not observed, presumably because of signal overlap.
620
(
6

64
K.R. Flower, R.G. Pritchard / Journal of Organometallic Chemistry 620 (2001) 60–68
Table 4
comparable with the values for the CO-containing ana-
logues [7]. All of the other resonances were assigned
using substituent effects and previous assignments in
related systems [11].
Data collection and processing parameters
Compound
1
3
Confirmation of the solid-state structures of 1 and 3
were obtained from single crystal X-ray diffraction
studies and the most significant structural features re-
late to the ortho-metallated azobenzene ring and the
Ru(CS) moiety. The bond lengths in the ortho-ruthen-
ated azobenzene are significantly different than those
observed for uncoordinated azobenzene I [12] (Table 5).
Formula
C
886.34
293(2)
Monoclinic
P21/c
10.140(2)
17.525(4)
22.906(3)
97.22(3)
4038.3(13)
4
1.458
5.274
1816
3.18–65.13
7265
49H39ClN2P2RuS C49H39IN2P2RuS
Molecular weight
Temperature (K)
Crystal system
Space group
977.79
293(2)
Monoclinic
P21/c
10.339(2)
17.415(3)
22.771(2)
96.99(2)
4069.5(11)
4
1.596
1.312
1960
1.80–24.98
14102
7061
0.0871
0.25×0.25×0.20
0.7793, 0.7350
1.019
,
a (A)
,
b (A)
,
c (A)
i (°)
,
The RuꢁC(3) bond lengths at 2.029(7) A 1 and
3
,
V (A )
Z
,
2.045(9) A 3 are at the short end of the observed range
,
(2.01–2.20 A) for complexes containing an RuꢁC s-
aryl bond and are both longer than that observed for
Dcalc (Mg m−3
)
v (mm−1
F(000)
)
[RuCl(CO)(h2-C,N-o-C6H4NNPh)(PPh3)2]
II
of
,
q (min–max) (°)
Refections collected
Independent reflections 6840
Rint
,
2.021(7) A [7]. The RuꢁN(1) bond lengths at 2.232(6) A
,
,
1 and 2.242(8) A 2 are longer than in II, 2.184(6) A. In
common with other structures containing an ortho-
metallated azobenzene, the phenyl ring on the bonded
nitrogen twists away from the plane defined by Ru,
C(3), C(2), N(1), N(2) by approximately 40°. In a
related paper [7] we showed that the perturbations of
the bond lengths around the azobenzene moiety were
akin to the well-known hydroxyazo/ketohydrazone tau-
tomerisation observed in ortho-hydroxyazobenzenes,
Scheme 2 [5,13–16], and was the result of a cis-push–
pull effect. A similar argument can be invoked here to
explain the bond length perturbations observed in 1
and 3. A p-donation from the halide trans to the
metallated carbon induces an electron flow around the
ortho-ruthenated azobenzene and results in p-donation
by the azo-nitrogen to the ruthenium centre, which is
stabilised by the p-acid CS ligand, Fig. 4.
0.0683
Crystal size
0.25×0.25×0.07
0.7091, 0.3523
1.117
0.0612
0.1829
A (min, max)
Goodness of fit on F2
R (observed data)
wR2 (all data)
0.693
0.1960
0.995, −1.290
Difference map (min,
1.923, −1.059
max) (e−
A
)
−3
,
complex [Os(CO)(h2-C,N-C6H4-2-C5H4N)(S2CNMe2)-
(PPh3)] reported by Roper and coworkers that has this
structure [2g].
The 13C{1H}-NMR spectra for 1–5 were very helpful
in confirming their structures; see Fig. 3 for numbering
scheme. For compounds 1–3 (Table 3) the mutually
trans-PPh3 ligands couple to the CS, and ruthenated
carbon of the ortho-metallated azobenzene ligand and
split the signals into triplets. Further, the resonances for
the PPh3 ligand carbon atoms appear as virtual triplets.
For compounds 4 and 5, which contain one PPh3
ligand, the CS, ortho-ruthenated and PPh3 signals are
doublets. The molecular asymmetry also causes two sets
of carbon signals for the ethyl groups in 5. The ortho-
metallated carbon resonances 168.5–187.7 ppm are at
much lower field than might be expected when com-
pared with the metallated carbon resonance for [Ru-
Cl(Ph)(CO)(PtBu2Me)2] (155.7 ppm) [8c] but are
Theoretical calculations by Richards [17] suggested
that the CS ligand has the capability of being both a
better s-donor and p-acceptor than the ubiquitous CO
ligand in transition metal complexes; further, the possi-
bility of CS behaving as a p-donor to a metal centre has
been raised [18]. It seems reasonable to expect that if
CS is a stronger p-acceptor than CO then the RuꢁC(3)
and RuꢁN(1) bond lengths in 1 would be shorter than
those reported for II; this is obviously not the case,
since both bonds are longer (Table 5). Care has to be
exercised here since the bond length differences are
within the 3| level of certainty; however, there is a
Table 5
Selected bond lengths for 1, 3, I and II
Compound C(3)ꢁM
C(3)ꢁC(2)
C(2)ꢁN(2) N(2)ꢁN(1) N(1)ꢁC(8)
N(1)ꢁM
RuꢁC(E)
CE
RuX
Ref.
1
3
I
2.029(7)
2.045(9)
1.405(10)
1.407(13)
1.395
1.393(8)
1.402(12)
1.429
1.277(7)
1.265(11)
1.241
1.454(8)
1.444(12)
1.429
2.232(6)
2.242(8)
1.788(6)
1.806(11)
1.572(6)
1.520(11)
2.4855(18)
2.7136(12)
This work
This work
[12]
II
2.021(7)
1.426(10)
1.363(9)
1.273(8)
1.427(9)
2.184(6)
1.834(8)
1.134(9)
2.4990(19)
[7]

K.R. Flower, R.G. Pritchard / Journal of Organometallic Chemistry 620 (2001) 60–68
65
Fig. 1. ORTEP representation of 1 showing the atomic numbering scheme.
Fig. 2. ORTEP representation of 3 showing the atomic numbering scheme.
trend, and it is supported by the spectroscopic data.
The perturbations in the cycloruthenated azobenzene
bond lengths relative to free azobenzene are, however,
good evidence for p-donation by the halide, and p-ac-
ceptance by the CS ligand is facilitated by the cy-
cloruthenated azobenzene and results in a cis-push–pull
effect. This observation is similar to that observed in
analogous CO-containing complexes and was discussed
at length in Ref. [7]. The magnitude of the cis-push–
pull effect should be affected by the p-donor power of
the halide and would be expected to be observable in
the crystal structures. The RuꢁC(3) and RuꢁN(1) bond
lengths for 1 should be shorter than for 3 because Cl is
known to be a stronger p-donor than I [19]; they are,
however, within the 3| level of certainty. More signifi-
cant though are the bond length differences between 3
and II, where the CO ligand has been replaced by CS
too. This suggests that there is a moderation of the
effect dependent not only on the p-donor strength of
the halide but the p-acceptor capabilities of the accep-

66
K.R. Flower, R.G. Pritchard / Journal of Organometallic Chemistry 620 (2001) 60–68
4. Experimental
All solvents were dried by refluxing over an appropri-
ate drying agent and distilled prior to use. [RuH-
Cl(CS)(PPh3)3] and Hg(o-C6H4NꢀNPh)2 were prepared
according to literature procedures [21,22]; all other
chemicals were obtained from commercial sources and
used as received, except for RuCl3 which was loaned by
Johnson Matthey. Melting points were measured on a
Griffin melting point apparatus and are uncorrected.
Infrared spectra were recorded as KBr discs on a
Fig. 3.
1
Perkin Elmer spectrometer. H-NMR (200.2 MHz) and
31P{1H}-NMR (81.3 MHz) spectra were recorded on a
Bruker AC200 spectrometer and 13C{1H}-NMR
(100.55 MHz) spectra were recorded on a Brucker
AC400 spectrometer. 1H- and 13C{1H}-NMR spectra
were referenced to CHCl3 (l=7.26) and CHCl3 (l=
77.0) and 31P{1H}-NMR spectra were referenced exter-
nally to 85% H3PO4. Elemental analyses (C, H, N, S)
were performed by the Microanalytical Service, Depart-
ment of Chemistry, UMIST; solvates of crystallisation
were confirmed by repeated elemental analysis and by
NMR. The syntheses of all complexes were carried out
under a dinitrogen atmosphere using standard Schlenk
techniques. Work-ups were generally carried out in the
open unless stated otherwise.
Scheme 2. Azo/hydrazone tautomerisation.
Fig. 4. Numbering scheme for 13C-NMR data.
tor. The differences in the CꢁS bond lengths (Table 5)
suggest that there is moderation of the effect depending
upon the donor strength, and this is substantiated by
the infrared data. The significant lengthening of the
RuꢁN(1) bond length for 1 relative to II is presumably
due to the increased trans influence of the CS ligand,
and the stronger trans influence of the CS versus CO
ligand has been clearly shown in cis-cis-trans-
[OsCl2(CO)(CS)(PPh3)2], where the OsꢁCl trans to CS is
longer than that trans to CO [20]. The relevance of this
is that the longer RuꢁN bond means there is less
potential for the side-on overlap necessary for the for-
mation of the RuꢁN p-interaction that is stabilised by
the CS ligand. This will have the net effect of reducing
the ability of the cycloruthenated azobenzene to facili-
tate stabilisation p-donation from the halide donor;
hence the longer bond lengths in 1 relative to II suggest
a weaker cis-push–pull effect.
4.1. Complex syntheses
4.1.1. [RuCl(CO)(p2-C,N-C6H4NꢀNPh)(PPh3)2] (1)
Caution: use of an organomercury reagent.
To [RuHCl(CS)(PPh3)2] (1 g, 1.03 mmol) suspended
in toluene (40 cm3) was added Hg(o-C6H4NꢀNPh)2
(0.62 g, 1.15 mmol) and the solution was heated to
reflux under N2 with continuous stirring for 6 h. After
cooling, the solution was filtered to remove Hg (Cau-
tion) and the solvent removed under reduced pressure.
The crude material was then extracted with hot hexane
(3×25 cm3) to remove the azobenzene and PPh3. Re-
crystallisation of the remaining purple solid from
CH2Cl2–EtOH afforded 1 in good yield; see Table 1 for
physical and analytical data.
4.1.2. [RuBr(CO)(p2-C,N-C6H4NꢀNPh)(PPh3)2] (2)
and 3
To 1 (0.1 g, 0.11 mmol) dissolved in CH2Cl2 (10 cm3)
was added AgNO3 (0.017 g, 0.11 mmol) dissolved in
H2O–EtOH and the solution was stirred for 5 min. The
solution was filtered to remove AgCl and to the filtrate
was added NaBr (0.02 g, 0.2 mmol) dissolved in H2O–
EtOH and the solution stirred for 10 min. Reduction of
the solvent under reduced pressure induced crystallisa-
tion of crude 2. Recrystallisation from CH2Cl2–EtOH
afforded 2·0.5CH2Cl2; see Table 1 for physical and
analytical data.
3. Conclusion
It has been shown by a combination of infrared
spectroscopy and X-ray crystallography that the CS
ligand is capable of stabilising a cis-push–pull effect in
18 valence electron cycloruthenated azobenzene-con-
taining complexes. It appears that the magnitude of the
cis-push–pull effect appears to be less than in the
corresponding CO-containing complexes as a direct
result of the stronger trans influence of the CS ligand.

K.R. Flower, R.G. Pritchard / Journal of Organometallic Chemistry 620 (2001) 60–68
67
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C.E.L. Hedford, W.R. Roper, L.J. Wright, V.P.D. Yap, Inorg.
Chim. Acta 220 (1994) 261. (c) G.R. Clark, M.M.P. Ng, W.R.
Roper, L.J. Wright, J. Organomet. Chem. 491 (1995) 219. (d)
G.R. Clark, C.E.F. Rickard, W.R. Roper, L.J. Wright, V.P.D.
Yap, Inorg. Chim. Acta 251 (1996) 65. (e) A.M. Clark, C.E.F.
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C.E.F. Rickard, W.R. Roper, L.J. Wright, Organometallics 18
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Complex 3 was prepared in an analogous manner;
see Table 1 for physical and analytical data.
4.1.3.
[Ru(p2-O2CMe)(CO)(p2-C,N-C6H4NꢀNPh)(PPh3)2] (4)
and 5
To 1 (0.1 g, 0.1 mmol) dissolved in CH2Cl2 (10 cm3)
was added AgOC(O)CH3 (0.017 g, 0.11 mmol) and the
solution was stirred for 20 h. Filtration of the solution
to remove AgCl and addition of hexane (20 cm3) fol-
lowed by slow evaporation of the CH2Cl2 afforded 4;
see Table 1 for physical and analytical data.
Complex 5 was prepared in an analogous manner;
see Table 1 for physical and analytical data.
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4.2. Crystallography
Suitable crystals of 1 and 3 were grown by the slow
diffusion of ethanol into a solution of either 1 or 3
dissolved in CH2Cl2.
For 1 the data were collected on a Rigaku AFC6S
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,
diffractometer using Cu–Ka (1.541 78 A) radiation and
for 3 the data were collected on a Nonius Mach 3
,
diffractometer using Mo–Ka (0.710 73 A) radiation.
For both 1 and 3 the lattice constants were obtained
from the setting angles of 25 accurately centred reflec-
tions. Reflection intensities were corrected for Lorenz
polarisation and absorption. The SHELX97 suite of pro-
grams [23] was used to solve the structures by direct
methods using full-matrix least-squares based on F2.
All non-hydrogen atoms were allowed to refine an-
isotropically and the hydrogen atoms were confined to
chemically reasonable positions. See Table 4 for crystal
data, collection parameters and refinement details
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5. Supplementary material
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[10] K. Hiraki, Y. Kinoshita, H. Ushiroda, S. Koyama, H. Kawano,
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All crystallographic data have been deposited at
Cambridge Crystallographic Data Centre CCDC nos.
146923, 1, and 146924, 3. Copies of information can be
obtained free of charge from: The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44-
1123-336033; e-mail: deposit@ccdc.ac.uk or www:
http://www.ccdc.cam.ac.uk).
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Acknowledgements
[14] J. Kelemen, S. Moss, H. Sauter, T. Winkler, Dyes Pigments 3
(1982) 27.
We thank Johnson Matthey for the loan of RuCl3.
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