Ruthenium(II) complexes containing 4-ferrocenylphenylisocyanide ligands. Crystal structure of trans, trans, trans-[RuCl2(POMe-P)2(FcC6H4NC)2] (POMe=PPh2C6H4OCH3</

Article abstract of DOI:10.1016/S0022-328X(01)00887-7

The ruthenium complexes trans, trans, trans-[RuCl₂(POMe-P)₂(FcC₆H₄NC)₂] (1) (POMe=PPh₂C₆H₄OCH₃; Fc=ferrocenyl) and trans, trans, trans-[RuCl₂(PC2

Full text of DOI:10.1016/S0022-328X(01)00887-7

Journal of Organometallic Chemistry 637–639 (2001) 145–150
www.elsevier.com/locate/jorganchem
Ruthenium(II) complexes containing 4-ferrocenylphenylisocyanide
ligands. Crystal structure of trans, trans,
trans-[RuCl2(POMeꢀP)2(FcC6H4NC)2] (POMe=PPh2C6H4OCH3;
Fc=ferrocenyl)
Olivier Clot a, Michael O. Wolf a,*, Glenn P.A. Yap b
a Department of Chemistry, Uni6ersity of British Columbia, 2036 Main Mall, Vancou6er, British Columbia, Canada V6T 1Z1
b Department of Chemistry, Uni6ersity of Ottawa, Ottawa, Canada K1N 6N5
Received 12 August 2000; received in revised form 6 February 2001; accepted 6 February 2001
Abstract
The ruthenium complexes trans, trans, trans-[RuCl2(POMeꢀP)2(FcC6H4NC)2] (1) (POMe=PPh2C6H4OCH3; Fc=ferrocenyl)
and trans, trans, trans-[RuCl2(PC2OMeꢀP)2(FcC6H4NC)2] (2) (PC2OMe=PPh2CH2CH2OCH3) have been prepared by reaction
of FcC6H4NC with [RuCl2(POMeꢀP,O)2] (5) and [RuCl2(PC2OMeꢀP,O)2] (6), respectively. The mixed carbonyl–isocyanide
complexes trans, trans, trans-[RuCl2(POMeꢀP)2(CO)(FcC6H4NC)] (3) and trans, trans, trans-[RuCl2(PC2OMeꢀP)2-
(CO)(FcC6H4NC)] (4) were prepared by sequential reaction of 5 and 6 with carbon monoxide and FcC6H4NC, respectively. These
complexes have all been characterized by 1H-NMR, 31P-NMR and infrared spectroscopies as well as microanalysis. The solid-state
structure of 1 was determined by X-ray crystallography. All three pairs of ligands are trans in this complex, and the ferrocenyl
groups are tilted with respect to the phenyl ring plane by 28°. Cyclic voltammetry of these complexes reveals essentially no
electronic interaction occurs between the ferrocenyl groups and the Ru. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Isocyanide; Ruthenium; Ferrocene; Cyclic voltammetry
1. Introduction
allowing the identification of units which facilitate or
impede charge transport.
Transition metal-containing polymers in which the
metals are linked by p-conjugated bridges are an impor-
tant class of materials [1]. The contribution of the metal
to the electronic properties of such polymers may result
in novel functions and applications. These materials are
related to p-conjugated organic polymers [2], which
become conductive upon doping, and so the question of
which structural elements are prerequisites for similar
properties in metal-bearing polymers is an important
one. One approach to this issue is to build and study
model complexes which can be used to probe charge
delocalization across metal and organic bridges, thus
We and others have previously investigated the
charge delocalization over metal groups which span
two ferrocenyl moieties [3–8]. In these studies, the
ferrocenyl groups serve as redox probes, and are se-
lected because of their stability in dual redox states as
well as their synthetic manipulability. For instance, in a
series of ruthenium bis(ferrocenylacetylide) complexes
delocalization of charge between the two ferrocenyl
groups is observed both by cyclic voltammetry and
near-IR spectroscopy [5].
In this paper, we report the preparation and charac-
terization of complexes in which
a
ruthenium
bis(phenylisocyanide) bridge spans two ferrocenyl
groups (1 and 2), as well as two carbonyl derivatives 3
and 4. Cyclic voltammetry of 1–4 is used to probe
possible charge delocalization between metal centers.
* Corresponding author. Tel.: +1-604-822-1702; fax: +1-604-822-
2847.
E-mail address: mwolf@chem.ubc.ca (M.O. Wolf).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00887-7

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O. Clot et al. / Journal of Organometallic Chemistry 637–639 (2001) 145–150
2. Experimental
2.3. trans, trans,
2.1. General
trans-[RuCl2(PC2OMeꢀP)2(FcC6H4NC)2] (2)
A solution of 6 (94 mg, 0.14 mmol) and FcC6H4NC
(80 mg, 0.28 mmol) in dry CH2Cl2 (15 ml) was stirred
at 25 °C under nitrogen for 2.5 h. The red solution was
concentrated to ca. 1 ml and hexanes added until the
solution became cloudy. The product slowly crystallized
from this solution at 25 °C to yield brick red microcrys-
tals. Yield: 108 mg (63%). 1H-NMR (200 MHz,
CDCl3): l=7.86 (m, 4H, o-PC6H5), 7.28 (m, 8H, m,p-
PC6H5 and FcC6H4NC), 6.65 (d, JHH=8.50 Hz, 2H,
FcC6H4NC), 4.60 (t, JHH=1.80 Hz, 2H, C5H4), 4.35 (t,
[RuCl2(POMeꢀP,O)2] (5) (POMe=PPh2C6H4OCH3)
[9], [RuCl2(PC2OMeꢀP,O)2] (6) (PC2OMe=PPh2-
CH2CH2OCH3) [10], and 4-FcC6H4NC (Fc=ferro-
cenyl) [11,12] were all prepared using literature proce-
dures. All other reagents were purchased from either
Strem Chemicals or Aldrich and used as received. IR
spectra were obtained on a Bomem MB-series spec-
trometer in CH2Cl2 solution or CsI pellets. 1H- and
31P{1H}-NMR experiments were performed on
a
Bruker CPX-200 spectrometer. Spectra were referenced
to residual solvent (1H) or external 85% H3PO4 (31P).
Samples for elemental analysis were kept under vacuum
for several days in order to completely remove trace
solvents and water. Electrochemical measurements were
conducted on a Pine AFCBP1 bipotentiostat using a Pt
disc working electrode, Pt coil wire counter electrode
and a silver wire reference electrode. An internal refer-
ence (decamethylferrocene) was added to correct the
measured potentials with respect to saturated calomel
electrode (SCE). The supporting electrolyte was 0.1 M
[(n-Bu)4N]PF6, which was purified by triple recrystal-
lization from EtOH and dried at 90 °C under vacuum
for 3 days. Methylene chloride used in cyclic voltamme-
try was dried by refluxing over CaH2.
JHH=1.80 Hz, 2H, C5H4), 4.01 (s, 5H, Cp), 3.56 (m,
2H, PCH2), 3.13 (s, 3H, OCH3), 3.08 (m, 2H,
CH2OCH3). 31P{1H}-NMR (81.015 MHz, CDCl3): l=
15.03 (s). Anal. Found: C, 61.87; H, 4.97; N, 2.16. Calc.
for C64H60Cl2N2O2P2Fe2Ru: C, 62.24; H, 4.86; N,
2.27%.
2.4. trans, trans,
trans-[RuCl2(POMeꢀP)2(CO)(FcC6H4NC)] (3)
Carbon monoxide was bubbled through a solution of
5 (40 mg, 0.053 mmol) in CH2Cl2 (15 ml) for 40 min at
25 °C. The mixture was then filtered through Celite and
nitrogen was bubbled through the solution for 2 h.
FcC6H4NC (15 mg, 0.053 mmol) was then added and
the resulting solution stirred at 25 °C for 1 h. The
mixture was concentrated to 1–2 ml and hexanes added
to precipitate 3 as brick red microcrystals. Yield: 31 mg
2.2. trans, trans,
trans-[RuCl2(POMeꢀP)2(FcC6H4NC)2] (1)
1
(55%). H-NMR (200 MHz, CDCl3): l=8.00 (m, 8H,
A solution of 5 (105 mg, 0.14 mmol) and FcC6H4NC
(80 mg, 0.28 mmol) in dry CH2Cl2 (50 ml) was stirred
at 25 °C under nitrogen for 2.5 h. The ruby-red solution
was then concentrated to ca. 5 ml and hexanes added
until the solution became cloudy. The product slowly
crystallized from this solution at 25 °C yielding dark
o-PC6H5), 7.31 (m, 16H, m,p-PC6H5, PC6H4OCH3),
7.22 (d, JHH=8.50 Hz, 2H, FcC6H4NC), 6.87 (m, 4H,
PC6H4OCH3), 6.35 (d, JHH=8.50 Hz, 2H, FcC6H4NC),
4.58 (t, JHH=1.80 Hz, 2H, C5H4), 4.35 (t, JHH=1.80
Hz, 2H, C5H4), 4.00 (s, 5H, Cp), 3.57 (s, 6H, OCH3).
31P{1H}-NMR (81.015 MHz, CDCl3): l=26.21 (s).
Anal. Found: C, 62.63; H, 4.24; N, 1.13. Calc. for
C56H47Cl2NO3P2FeRu: C, 62.74; H, 4.39; N, 1.31%.
1
orange microcrystals. Yield: 121 mg (65%). H-NMR
(200 MHz, CDCl3): l=8.14 (m, o-PC6H5, 4H), 7.28
(m, 6H, m,p-PC6H5 and PC6H4OCH3), 7.21 (d, JHH
8.54 Hz, 2H, FcC6H4NC), 6.85 (m, 2H, PC6H4OCH3),
6.41 (d, JHH=8.54 Hz, 2H, FcC6H4NC), 4.58 (t, JHH
=
2.5. trans, trans,
trans-[RuCl2(PC2OMeꢀP)2(CO)(FcC6H4NC)] (4)
=
1.79 Hz, 2H, C5H4), 4.33 (t, JHH=1.79 Hz, 2H, C5H4),
4.01 (s, 5H, Cp), 3.51 (s, 3H, OCH3). 31P{1H}-NMR
(81.015 MHz, CDCl3): l=3D 29.72 (s). Anal. Found:
C, 65.10; H, 4.66; N 2.01. Calc. for C72H60Cl2-
N2O2P2Fe2Ru: C, 64.96; H, 4.51; N, 2.11%.
Carbon monoxide was bubbled through a solution of
6 (54.3 mg, 0.082 mmol) in dry CH2Cl2 (15 ml) for 5
min at 0 °C. Nitrogen was then bubbled through the
solution for 30 min at 0 °C. The mixture was then

O. Clot et al. / Journal of Organometallic Chemistry 637–639 (2001) 145–150
147
Table 1
diffractometer using 0.3° ꢀ-scans at 0, 90, and 180° in
ƒ. Unit-cell parameters were determined from 60 data
frames collected at different sections of the Ewald
sphere. Systematic absences in the diffraction data and
unit-cell parameters were consistent with space groups
Cc and C2/c. Solution in the centric option yielded
chemically reasonable and computationally stable re-
sults of refinement. Absorption correction based on
redundant data [13] was initially applied but later ig-
nored when the resulting Tmin/Tmax ratio was unity. The
structure was solved by direct methods, completed with
difference Fourier syntheses and refined with full-ma-
trix least-squares procedures based on F2. The molecule
is located at an inversion center. All non-hydrogen
atoms were refined with anisotropic displacement
parameters. All hydrogen atoms were treated as ideal-
ized contributions. All scattering factors and anoma-
lous dispersion factors are contained in the SHEXTL
5.10 program library [14]. Crystal data and refinement
parameters are summarized in Table 1.
Crystallographic and structural refinement data for 1·6CH2Cl2
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C78H72Cl14Fe2N2O2P2Ru
1840.39
203(2)
0.71073
Monoclinic
C2/c
,
Unit cell dimensions
,
a (A)
34.631(4)
12.007(9)
22.278(6)
90
117.976(7)
90
8181(6)
4
1.494
1.075
3736
0.10×0.10×0.10
1.33–22.50
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (Mg m−3
)
Absorption coefficient (mm−l
F(000)
)
Crystal size (mm)
Theta range for data collection
(°)
Limiting indices
−375h532, 05k512,
05l523
Reflections collected/unique
Completeness to 2q=22.50
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)]
R indices (all data)
9996/5338 [Rint=0.0943]
99.8%
3. Results
None
Full-matrix least-squares on F2
2385/0/391
3.1. Synthesis and structure of 1 and 2
1.022
The complexes 1 and 2 were synthesized by reaction
of 4-ferrocenylphenylisocyanide (FcC6H4NC) with 5
and 6, respectively (Scheme 1). The oxygen of the
hemilabile phosphine–ether ligand is displaced by the
isocyanide while the phosphorus remains coordinated
to the ruthenium. The structure of 1·6CH2Cl2 was
unambiguously determined by X-ray crystallography
(Fig. 1). The ruthenium in 1 is in a slightly distorted
octahedral environment and lies at an inversion center,
with the three pairs of ligands oriented trans to each
other. Both ferrocenyl groups are tilted with respect to
the phenyl ring plane with a dihedral angle of 28° (Fig.
2).
R1=0.0690, wR2=0.1925
R1=0.0962, wR2=0.2060
1.054 and −0.993
Largest different peak and hole
3
,
(e A )
allowed to warm to 25 °C, and FcC6H4NC (23.5 mg,
0.07 mmol) added. The resulting solution was stirred
for 1 h. The mixture was concentrated to 1–2 ml and
hexanes added to precipitate 4 as an orange powder.
Yield: 55 mg (69%). 1H-NMR (200 MHz, CDCl3):
l=7.77 (m, 8H, o-PC6H5), 7.30 (m, 12H, m,p-PC6H5),
7.23 (d, JHH=8.42 Hz, 2H, FcC6H4NC), 6.49 (d,
The 31P-NMR spectrum of 2 consists of a singlet at
l=29.7 and the IR spectrum contains one band in the
NꢁC stretching region at wNC=2092 cm−1. An all-trans
product was also obtained by others when 5 was re-
acted with t-BuNC [15]. The spectral data obtained for
2 indicates that this complex also has an all-trans
configuration. Lindner has previously reacted t-BuNC
with 6 and proposed that the obtained product is
[RuCl2(PC2OMeꢀP)2(t-BuNC)2] with the phosphine
and chloro ligands both in a cis orientation, based on
the presence of an assymetric (310 cm−1) and symmet-
ric (262 cm−1) RuꢀCl2 stretch in the infrared region
[16]. The far-IR spectra of 1 and 2 both contain a
medium strength absorption at ca. 315 cm−1 which we
assign to a trans RuCl2 stretch. In addition there are
several weak absorptions in this region (see Table 2)
and a band at 310 cm−1 which is present in the spectra
JHH=8.42 Hz, 2H, FcC6H4NC), 4.61 (t, JHH=1.76
Hz, 2H, C5H4), 4.37 (t, JHH=1.76 Hz, 2H, C5H4), 4.00
(s, 5H, Cp), 3.51 (m, 4H, PCH2), 3.17 (s, 6H, OCH3),
3.01 (m, 4H, CH2OCH3). 31P{1H}-NMR (81.015 MHz,
CDCl3): l=3D 13.80 (s). Anal. Found: C, 58.74; H,
4.88; N, 1.32. Calc. for C48H47Cl2NO3P2FeRu: C,
59.07; H, 4.82; N, 1.44%.
2.6. Crystallographic study
A suitable crystal of 1 which had been crystallized
from layered CH2Cl2 and hexanes was selected,
mounted on a thin glass fiber using paraffin oil and
cooled to the data collection temperature. Compound 1
consistently yields small, multiple crystals and this data-
set represents the best obtained after several trials. Data
were collected on a Bruker AX SMART 1k CCD

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O. Clot et al. / Journal of Organometallic Chemistry 637–639 (2001) 145–150
Scheme 1.
,
Fig. 1. Chem 3D representation of 1. Hydrogen atoms are omitted for clarity. Selected bond lengths (A): RuꢀCl(1)=2.4249(19), RuꢀC(20)=
1.978(8), RuꢀP(1)=2.383(2), C(20)ꢀN(1)=1.138(8), and N(1)ꢀC(26)=1.394(7). Selected bond angles (°): Cl(1)ꢀRuꢀCl(1A)=180.00(8),
C(20)ꢀRuꢀC(20A)=180.0(4), P(1)ꢀRuꢀP(1A)=180.00(8), Cl(1)ꢀRuꢀP(1)=87.32(7), RuꢀC(20)ꢀN(1)=178.6(6), and C(20)ꢀN(1)ꢀC(26)=
176.9(7).
of 1–4 as well as in other Ru carbonyl complexes and
is therefore likely a RuꢀC stretch. The similarities be-
tween the spectra of 1 and 2 support the assignment of
2 as an all trans isomer.
equilibrium mixture of the monocarbonyl and dicar-
bonyl complexes in both cases. Bubbling nitrogen
through this mixture drives the equilibrium to the
monocarbonyl complex, to which FcC6H4NC is added
yielding complexes 3 and 4, respectively (Scheme 1).
The 31P-NMR spectra of 3 and 4 contain only one
singlet which indicates that the phosphorus nuclei are
equivalent. The IR spectra of these complexes contain
3.2. Synthesis and structure of 3 and 4
Reaction of 5 or 6 with carbon monoxide yields an

O. Clot et al. / Journal of Organometallic Chemistry 637–639 (2001) 145–150
149
Fig. 2. ORTEP projection of 1 (30% probability ellipsoid shown) along
the NCꢀRuꢀCN axis. The phosphine and chloro ligands are omitted
for clarity.
two bands between 1900 and 2200 cm−1 (Table 1). The
higher energy band in each case is assigned to the CO
stretch and the lower energy band is assigned to the NC
stretch, and these bands appear close to those previ-
ously observed for trans, trans, trans-[RuCl2-
(PC2OMe)2(CO)(t-BuNC)] by Lindner [16]. The far-IR
spectra of 3 and 4 contain medium strength absorptions
at 327 and 325 cm−1, respectively, indicating the chloro
ligands are oriented trans in these complexes. The far-
IR spectra of trans, trans, trans-[RuCl2(POMe)2-
(CO)(t-BuNC)] and trans, trans, trans-[RuCl2-
(PC2OMe)2(CO)(t-BuNC)] have bands at 324 and 320
cm−1, respectively [15,16].
Fig. 3. Cyclic voltammogram of (a) 1 and (b) 3 in CH2Cl2 containing
0.1 M[(n-Bu)4]PF6. Scan rate=50 mV s−1
.
assigned to the oxidation of the ferrocenyl group. The
higher potential wave corresponds to the RuII/III oxida-
tion, shifted positive relative to the corresponding wave
in 1 and 2 due to the presence of the electron withdraw-
ing carbonyl group.
3.3. Cyclic 6oltammetry
The cyclic voltammograms (CVs) of both 1 (Fig. 3a)
and 2 contain two reversible oxidation waves (Table 2).
The lower potential wave for both complexes is approx-
imately twice the intensity of the second wave, and is
consequently assigned to the simultaneous oxidation of
the two ferrocenyl groups. The second wave is then
assigned to the reversible RuII/III oxidation. The CVs of
3 (Fig. 3b) and 4 also contain two reversible waves of
equal area, and the lower potential wave is again
4. Discussion and conclusions
The electrochemical data for these complexes may be
used to assess the degree of interaction between the
ferrocenyl groups. In complexes 1 and 2, the simulta-
neous oxidation of the two ferrocenyl groups indicates
that interaction between these groups over the rigid Ru
bis(phenylisocyanide) bridge is small. This is in contrast
with the relatively large interaction observed for bis-
Table 2
Infrared and cyclic voltammetric data for 1–4
Complex
Selected IR a and FIR b bands c (cm−1
)
E1/2(Fe) d (V)
E1/2(Ru) d (V)
1
2
3
4
2098 (s, CN), 317 (m, RuCl2)
2092 (s, CN), 315 (m, RuCl2)
2001 (s, CO), 2166 (s, CN), 327 (m, RuCl2)
1983 (s, CO), 2178 (s, CN), 325 (m, RuCl2)
0.51
0.51
0.53
0.54
0.73
0.90
1.03
1.19
a In CH2Cl2.
b In CsI, additional far-IR bands (cm−1): 1, 310 (m), 291 (w); 2, 310 (sh), 297 (w); 3, 310 (m); and 4, 312 (m) (s, strong; m, medium; w, weak;
sh, shoulder).
c
95 cm−1
90.01 V.
.
d

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O. Clot et al. / Journal of Organometallic Chemistry 637–639 (2001) 145–150
5. Supplementary material
(ferrocenylacetylide) complexes of Ru, in which the
difference in the oxidation potentials of the ferrocenyl
centers is between 90 and 220 mV [5], however in
these complexes the bridge between the metal centers
is shorter. A second indication that the electronic in-
teraction across the phenylisocyanide bridge is small,
comes from the observation that the ferrocenyl oxida-
tion potential of the ligand is invariant to the change
in the ligand trans to it on the Ru. The ferrocenyl
oxidation potential is essentially the same when the
trans ligand is a donor (RNC in 1 and 2) or an
acceptor (CO in 3 and 4). This same change results in
a ca. 0.3 V increase in the oxidation potential of the
Ru, and a substantial shift in the CN stretching fre-
quency of the coordinated ferrocenylphenylisocyanide.
It is possible that the lack of interaction between
metal centers is a consequence of poor coupling be-
tween the substituted phenyl ring and the NC bond.
This has been previously observed by Cotton who
showed that in a series of metal complexes containing
para-substituted phenylisocyanides, the substituents
on the phenyl group had almost no effect on the NC
frequency either in the free isocyanides or in the lig-
ands [17]. Furthermore, in the solid-state the phenyl
ring plane is tilted with respect to the ferrocenyl
group by 28° (Fig. 2), suggesting that p-conjugation
between these rings is also not optimal. On the other
hand, an electrochemical study of the chromium com-
plex [(FcNC)Cr(CO)5] in which the ferrocenyl group
in the ligand is directly attached to the isocyanide
group, showed no shift in the ferrocenyl oxidation
potential relative to FcNC [11]. This suggests that in
complexes where the isocyanide is a s-donor, with no
back-bonding from the metal, there is effectively no
conjugation between the metal and ligand preventing
electronic interaction between the ferrocenyl group
and the metal center. The greater degree of interac-
tion observed for the acetylide complexes may there-
fore be due to the back-bonding which occurs in
many cases, thus allowing dp–pp conjugation.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 153354. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
We thank the Natural Science and Engineering Re-
search Council of Canada for support of this research.
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