Syntheses and characterization of cyano-bridged homo and hetero bimetallic complexes containing η5 and η6-cyclic hydrocarbons

Article abstract of DOI:10.1016/j.jorganchem.2005.05.044

The reactions of [(ind)Ru(PPh₃)₂CN] (ind = η⁵-C₉H₇) (1) and [CpRu(PPh ₃)₂CN] (Cp = η⁵-C₅H₅) (2) with [(η⁶-p-cymene)Ru(bipy)Cl]Cl (bipy = 2,2′-bipyridine) (3) in the presence of AgNO₃/NH ₄BF₄ in methanol, respectively, yielded dicationic cyano-bridged complexes of the type [(ind)(PPh₃)₂Ru(μ- CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (4) and [Cp(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)] (BF₄)₂ (5). The reaction of [CpRu(PPh₃) ₂CN] (2), [CpOs(PPh₃)₂CN] (6) and [CpRu(dppe)CN] (7) with the corresponding halide complexes and [(η⁶-p-cymene)RuCl₂]₂ formed the monocationic cyano-bridge complexes [Cp(PPh₃)₂Ru(μ-CN) Os(PPh₃)₂Cp](BF₄) (8), [Cp(PPh ₃)₂Os(μ- CN)Ru(PPh₃)₂Cp](BF ₄) (9) and [Cp(dppe)Ru(μ-CN)Os(PPh₃) ₂Cp](BF₄) (10) along with the neutral complexes [Cp(PPh₃)₂Ru(μ-CN)Ru (η⁶-p-cymene) Cl₂] (11), [Cp(PPh₃)₂Os(μ-CN) Ru(η⁶-p-cymene)Cl₂] (12), and [Cp(dppe) Ru(μ-CN)Ru(η⁶-p-cymene)Cl₂] (13). These complexes were characterized by FT IR, ¹H NMR, ³¹P{¹H} NMR spectroscopy and the molecular structures of complexes 4, 8 and 11 were solved by X-ray diffraction studies.

Full text of DOI:10.1016/j.jorganchem.2005.05.044

Journal of Organometallic Chemistry 690 (2005) 3990–3996
www.elsevier.com/locate/jorganchem
Syntheses and characterization of cyano-bridged homo
and hetero bimetallic complexes containing
g5 and g6-cyclic hydrocarbons
a
a,
b
R. Lalrempuia , Mohan Rao Kollipara *, Patrick J. Carroll ,
c
c
Glenn P.A. Yap , K.A. Kreisel
a
Department of Chemistry, North Eastern Hill University, Shillong 793 022, India
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
Department of Chemistry and Biochemistry, University of Delaware, Delaware, Newark, DE 19716, USA
b
c
Received 2 January 2005; received in revised form 28 May 2005; accepted 28 May 2005
Available online 18 July 2005
Abstract
The reactions of [(ind)Ru(PPh3)2CN] (ind = g5-C9H7) (1) and [CpRu(PPh3)2CN] (Cp = g5-C5H5) (2) with [(g6-p-cym-
ene)Ru(bipy)Cl]Cl (bipy = 2,20-bipyridine) (3) in the presence of AgNO3/NH4BF4 in methanol, respectively, yielded dicationic
cyano-bridged complexes of the type [(ind)(PPh3)2Ru(l-CN)Ru(bipy)(g6-p-cymene)](BF4)2 (4) and [Cp(PPh3)2Ru(l-CN)Ru(bi-
py)(g6-p-cymene)](BF4)2 (5). The reaction of [CpRu(PPh3)2CN] (2), [CpOs(PPh3)2CN] (6) and [CpRu(dppe)CN] (7) with the
corresponding halide complexes and [(g6-p-cymene)RuCl2]2 formed the monocationic cyano-bridge complexes [Cp(PPh3)2Ru-
(l-CN)Os(PPh3)2Cp](BF4) (8), [Cp(PPh3)2Os(l- CN)Ru(PPh3)2Cp](BF4) (9) and [Cp(dppe)Ru(l-CN)Os(PPh3)2Cp](BF4) (10) along
with the neutral complexes [Cp(PPh3)2Ru(l-CN)Ru (g6-p-cymene)Cl2] (11), [Cp(PPh3)2Os(l-CN)Ru(g6-p-cymene)Cl2] (12), and
[Cp(dppe) Ru(l-CN)Ru(g6-p-cymene)Cl2] (13). These complexes were characterized by FT IR, 1H NMR, 31P{1H} NMR spectros-
copy and the molecular structures of complexes 4, 8 and 11 were solved by X-ray diffraction studies.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Cyano-bridged complexes; Hetero bimetallic complexes; Ruthenium; Osmium; p-Cymene; Cyclopentadiene
1. Introduction
strated the nucleophilic character of the terminal nitro-
gen of the cyano ligand of the M–CN fragment to
afford cationic complexes of the type M–CN–M+ or iso-
nitrile complexes M+–CNR by reacting such metal com-
plexes with alkyl halides (RX). This synthetic strategy
has been often utilized to provide a general route to syn-
thesize cationic dinuclear cyano-bridged complexes. In
continuation of our previous work on some cyano-
bridged complexes [3b,3c], we would like to describe
here the synthesis of cyano-bridged complexes (dicat-
ionic, cationic and neutral) formed from the reaction
between the appropriate [M] ꢀ CN and [M] ꢀ X
fragments.
Cyanide has been used frequently as a ligand to
bridge two metal centers and such complexes have inter-
esting magnetic properties [1]. Cyano-bridged, dinuclear
transition metal complexes have seen application in the
areas of electron delocalization and charge transfer
studies [2]. Baird et al. [3a] have successfully demon-
*
Corresponding author. Tel.: +91 364 272 2620; fax: +91 364 255
0076.
E-mail address: kmrao@nehu.ac.in (M.R. Kollipara).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.05.044

R. Lalrempuia et al. / Journal of Organometallic Chemistry 690 (2005) 3990–3996
3991
2. Experimental
3.4. Preparation of [Cp(L)2M(l-CN)Ru(Cl2)(g6-p-
cymene)] (M = Ru, L = PPh3 (11), M = Os, L = PPh3
(12); M = Ru (13), L2 = dppe)
All chemicals were obtained from commercial
sources. Infrared spectra were recorded as KBr pellets
using a Perkin-Elmer model-983 spectrophotometer.
1H NMR spectra were recorded on a Bruker ACF 300
spectrometer and referenced to external TMS. 31P{1H}
NMR chemical shifts were recorded relative to H3PO4
(85%). Elemental analyses were performed by the Regio-
nal Sophisticated Instrumentation Centre, NEHU, Shil-
long. [CpOs(PPh3)2CN] [4], [(ind)Ru(PPh3)2CN] [5],
[CpRu(PPh3)2CN] [6], [CpRu(dppe)CN] [7] and [(g6-p-
cymene)RuCl2]2 [8] were prepared according to the liter-
ature procedures.
A suspension of equimolar amounts of [(g6-p-cym-
ene)Ru(Cl2)]2 and the cyano-complexes (2, 6, 7) in meth-
anol was refluxed for 2 h. Removal of the solvent in
vacuo afforded the desired complexes as orange-red
crystalline powder.
4. Structure analysis and refinement
X-ray intensity data were collected on a Rigaku Mer-
cury CCD area detector employing graphite-monochro-
˚
mated Mo Ka radiation (k = 0.71069 A). In the case of
3. Preparation of the complexes
complex 4, Enraf Nonius Cad-4 was employed. Indexing
was performed from a series of twelve 0.5ꢁ rotation
images with exposures of 30 s. Rotation images were
processed using crystal clear [9], producing a listing of
unaveraged F2 and r(F2) values, which were then passed
on to the crystal structure [9] program package for fur-
ther processing and structure solution on a Dell Pentium
III computer. The intensity data were corrected for Lor-
entz and polarization effects and for absorption using
the REQAB program [10]. The structure was solved by di-
rect methods (SIR97) [11]. Refinement was performed by
a full-matrix least squares method based on F2 using
SHELXL 97 [12]. All reflections used during refinement
(F2ꢀs that were experimentally negative were replaced
by F2 = 0). Non-hydrogen atoms were refined aniso-
tropically, while hydrogen atoms were refined using a
‘‘riding’’ model. Refinement converged at a final value
of R1 = 0.0363, 0.0384 and 0.0935 for the complexes
11, 8, and 4, and at values of wR2 = 0.1145, 0. 0948
and 0.2553 for complexes 11, 8 and 4, respectively (for
unique data F2).
3.1. Preparation of [(g6-p-cymene)Ru(bipy)Cl]Cl (3)
A
suspension of [(g6-p-cymene)RuCl2]2 (0.1 g,
0.163 mmol) and 2,20-bipyridine (0.063 g, 0.407 mmol)
in methanol (15 ml) was stirred at room temperature
for 1 h. Methanol was removed on a rotary evaporator
and the residue was extracted with acetone. Subsequent
concentration and addition of excess hexane afforded
the orange-red microcrystalline compound.
3.2. Preparation of [(L)(PPh3)2Ru(l-CN)Ru(bipy)-
(g6-p-cymene)](BF4)2 [L = ind (4), L = Cp (5)]
A suspension of [(L)Ru(PPh3)2CN] (1.22 mol), [(g6-
p-cymene)Ru(bipy)Cl]Cl (1.22 mmol), AgNO3 (2.44
mmol) and NH4BF4 (3.66 mmol) in distilled acetone
(25 ml) was refluxed for 2 h. The resulting solution was
filtered and concentrated to ꢁ5 ml. Addition of excess
hexane to this solution gave the yellow microcrystalline
compounds.
Table 2 listed the cell information, data collection
parameters and refinement data. Figs. 1–3 are ORTEP
[13] representations of complexes 4, 8 and 11, respec-
tively. Selected bond lengths and angles are given in
Tables 3–5 for the complexes 4, 8 and 11, respectively.
3.3. Preparation of [Cp(PPh3)2Ru(l-CN)Os(PPh3)2-
Cp]BF4 (8), [Cp(PPh3)2Os(l-CN)Ru(PPh3)2Cp]-
BF4 (9) and [Cp(dppe)Ru(l-CN)Os(PPh3)2Cp]BF4
(10)
A suspension of equimolar amounts of the cyano-
complexes and the corresponding halide complexes
and a slight excess of NH4BF4 in distilled methanol
(20 ml) was refluxed for 3 h (1 h for 8). The color of
the solution changed to greenish yellow. The solvent
was removed on a rotary evaporator and the residue
was extracted with dichloromethane, whereupon the
white insoluble material was filtered off. The solution
was concentrated to ꢁ5 ml and addition of excess
hexane gave the compounds 8 and 9 as a light green
5. Results and discussion
5.1. Dicationic complexes
Treatment of the cyano-complexes (1, 2) with the
halo complex (3) in refluxing conditions in the presence
of AgNO3 (as a halide scavenger) after work up, affor-
ded the dicationic complexes, [(ind)(PPh3)2Ru(l-
CN)Ru(bipy)(g6-p-cymene)]2+ (4) (ind = g5-C9H7) and
[Cp(PPh3)2Ru(l-CN)Ru(bipy)(g6-p-cymene)]2+ (5) (Cp =
g5-C5H5). These two complexes were isolated as tetra-
fluoroborate salts (Scheme 1).
and as
a pale yellow orange crystalline solid,
respectively.

3992
R. Lalrempuia et al. / Journal of Organometallic Chemistry 690 (2005) 3990–3996
These two new dimetallic cations 4 and 5 exhibit med-
shifts mCN to a higher frequency [15]. This shift to higher
frequency upon bridging has also been explained on the
basis of force field arguments [16]. Very strong broad-
bands assignable to m(BF) of BF4 are observed at
1080 cmꢀ1 for both the complexes beside other absorp-
tion bands characteristic of triphenyl-phosphines.
ium intensity IR bands assignable to m(C@N) at 2085 and
2075 cmꢀ1 which are slightly shifted toward higher ener-
gies as compared to the parent mononuclear cyano-
complexes (1) [m(C@N) 2065 cmꢀ1] and (2) [m(C@N)
2070 cmꢀ1]. The high energy shift of mCN band on coor-
dination to second metal maybe explained [14] in terms
of removal of electron density from the lowest filled CN
r*(s) orbital on the coordinating nitrogen of the cyanide
group. Moreover, upon ꢁbridgeꢀ formation, there is a
simple mechanical constraint on the CN motion im-
posed by the presence of the second metal center which
The complexes were also characterized by 1H and
31P{1H} NMR spectroscopy. The NMR data are pre-
sented in Table 1. The proton NMR spectra of these
complexes exhibit characteristic peaks for all functional
groups. The 31P NMR spectra of these complexes exhi-
bit only one singlet suggesting that the both the P atoms
Table 1
Spectroscopic data of the complexes
Complexes
(CN)
2085
1H NMR (ppm)
31P{1H} NMR (ppm)
4
9.84 (d, 1H, 6), 8.63 (d, 1H, 9), 8.14 (t, 1H, 6), 7.82 (t, 1H, 6), 7.45–6.59 (m, 34H),
6.28 (d, 1H, 6), 5.96 (d, 1H, 6), 5.75 (m, 2H), 4.67 (t, 1H, 2), 4.07 (d, 2H, 2), 2.21
(sept, 1H), 0.83 (d, 6H, 9)
49.39 (s)
5
2075
9.45 (d, 2H, 6), 8.44 (t, 2H, 6), 8.20 (t, 2H, 6), 8.05 (d, 2H, 6), 7.88–6.79 (m, 30H),
6.20 (d, 1H, 6), 6.09 (d, 1H, 9), 6.02 (d, 1H, 6), 5.81 (d, 1H, 9), 4.38 (s, 5H), 2.4 (sept,
1H), 2.1 (s, 3H), 1.08 (d, 6H, 9).
50.42 (s)
8
9
2077
2069
2080
2110
7.25–7.00 (m, 60H), 4.25 (s, 5H), 4.23 (s, 5H)
7.25–7.00 (m, 60H), 4.32 (s, 5H), 4.10 (s, 5H).
7.77–6.85 (m, 40H), 4.7 (s, 5H), 3.79 (s, 5H), 2.93–2.71 (m, 4H)
7.35–7.17 (m, 30H), 5.49 (d, 1H, 6), 5.35 (d, 1H, 3), 5.24 (d, 1H, 6), 5.04 (d, 1H, 6),
4.40 (s, 5H), 2.90 (sept, 1H), 2.18 (s, 3H), 1.23 (d, 6H, 9).
48.56 (s), 0.50 (s)
42.94 (s), 2.00 (s)
82.63 (s), 0.50 (s)
49.32 (s)
10
11
12
13
2105
2103
7.35–7.17 (m, 30H), 5.42 (d, 1H, 6), 5.33 (d, 1H, 3), 5.16 (d, 1H, 6), 5.12 (d, 1H, 6),
4.52 (s, 5H), 2.82 (sept, 1H), 2.00 (s, 3H), 0.98 (d, 6H).
7.41–7.11 (m, 20H), 4.65 (s, 5H), 2.89–2.71 (m, 4H), 6.12 (d, 2H, 6), 6.07 (d, 2H, 6),
4.23 (s, 5H), 2.93–2.71 (m, 4H), 2.4 (sept, 1H), 2.21 (s, 3H), 1.02 (d, 6H, 9).
1.32 (s)
83.4 (s)
Table 2
Summary of structure determination of compounds 11, 8 and 4
Empirical formula
Formula weight
Temperature (K)
C
1022.9
120(2)
0.71073
Monoclinic
C2/c
52H51Cl2NP2Ru2
C83BH70NP4F4OsRu
1583.36
143(2)
0.71069
Monoclinic
C2/c
C66H59B2F8N3P2Ru2
1331.86
293(2)
1.54178
Monoclinic
P21/c
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
˚
a (A)
25.485(5)
20.779(4)
20.931(4)
124.913(2)
25.510(4)
13.863(2)
20.050(3)
93.430(3)
13.9100(10)
23.0670(10)
19.7260(10)
108.46
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
3
˚
9089(3)
7078(2)
6003.6(6)
Z
4
4
4
Dcalc (Mg/m3)
F(0 0 0)
1.495
4160
1.486
3184
1.474
2704
Crystal size
h range for data collection (ꢁ)
Limiting indices
0.40 · 0.29 · 0.18
1.38–28.29
0.46 · 0.20 · 0.10
5.02–54.96
0.1 · 0.2 · 0.4
3.04–70.83
0 6 h 6 16, 0 6 k 6 8,
ꢀ23 6 l 6 22
10,787/10,787 [Rint = 0. 0000]
ꢀ33 6 h 6 33, ꢀ26 6 k 6 26,
ꢀ31 6 h 6 30, ꢀ12 6 k 6 17,
ꢀ27 6 l 6 26
ꢀ25 6 l 6 18
Reflections collected/unique
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
50,186/10,540 [Rint = 0.0238]
Full-matrix least-squares on F2
10,540/0/532
22,729/7619 [Rint = 0.0315]
7619/0/406
1.089
10,787/9/732
0.757
1.073
Final R indices [I > 2r(I)]
R indices (all data)
Largest difference peak and hole
R1 = 0.0363, wR2 = 0.1145
R1 = 0.0399, wR2 = 0.1188
3.670 and ꢀ0.453
R1 = 0.0384, wR2 = 0. 0948
R1 = 0.0505, wR2 = 0.0987
+2.183 and ꢀ0.591
R1 = 0.0935, wR2 = 0.2553
R1 = 0.1038, wR2 = 0.2693
1.475 and ꢀ2.809

R. Lalrempuia et al. / Journal of Organometallic Chemistry 690 (2005) 3990–3996
3993
Fig. 1. Thermal ellipsoid (drawn at the 30% probability level) plot of [(ind)(PPh3)2Ru(l-CN)Ru(bipy)(g6-p-cymene)]+2 (4) with BF4 group, phenyl
ꢀ
groups of PPh3 and hydrogens omitted for clarity.
C24
C23
C21
C5
C6
C18
C35
C36
C19
C4
C25
C22
C7
C17
C16
C37
C20
C3
C2
C14
C33
C13
C12
C11
C34
C15
C32
P1
P2
C8
C27
C26
C1(N1)
C31
C30
C9
Os(Ru)
C10
C42
C41
C28
C29
C38
C40
C39
Fig. 3. Thermal ellipsoid (drawn at the 30% probability level) plot of
Fig. 2. ORTEP drawing of the [Cp(PPh3)2Ru(l-CN)Os(PPh3)2Cp]BF4
(8) with 30% probability thermal ellipsoids. BF4 anion and hydrogens
[Cp(PPh3)2Ru(l-CN)RuCl2(g6-p-cymene)]BF4 (11) with BF4 anion
ꢀ
ꢀ
and all the hydrogens being omitted for clarity.
omitted for clarity.
Table 3
6
˚
Selected bond lengths (A) and bond angles (ꢁ) for the complex [(ind)(PPh3)2Ru(l-CN)Ru(bipy)(g -p-cymene)](BF4)2 (4) (estimated standard
deviations are shown in parenthesis)
Bond lengths
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–C(23)
Ru(1)–C(25)
Ru(1)–C(27)
Ru(2)–P(1)
Ru(2)–C(01)
Ru(2)–C(03)
Ru(2)–C(09)
2.055(12)
2.071(13)
2.21(2)
2.177(13)
2.21(2)
2.341(4)
2.201(15)
2.218(16)
2.441(15)
Ru(1)–N(2)
Ru(1)–C(22)
Ru(1)–C(24)
Ru(1)–C(26)
Ru(2)–C(10)
Ru(2)–P(2)
Ru(2)–C(02)
Ru(2)–C(04)
C(10)–N(1)
2.165(16)
2.17(2)
2.130(17)
2.143(17)
1.957(13)
2.362(3)
2.170(15)
2.367(15)
1.111(17)
Bond angles
N(1)–Ru(1)–N(3)
N(3)–Ru(1)–N(2)
N(1)–C(10)–Ru(2)
83.5(5)
79.0(6)
168.0(11)
N(1)–Ru(1)–N(2)
Ru(1)–N(1)–C(10)
C(10)–Ru(2)–P(1)
83.5(5)
170.3(12)
85.7(4)

3994
R. Lalrempuia et al. / Journal of Organometallic Chemistry 690 (2005) 3990–3996
Table 4
˚
Selected bond lengths (A) and bond angles (ꢁ) for the complex [Cp(PPh3)2Ru(l-CN)Os(PPh3)2Cp]BF4 (8) (estimated standard deviations are shown
in parenthesis)
Bond lengths
Os(Ru)–P2
C1(N1)–C1(N1)*
2.3328(9)
1.139(6)
Os(Ru)–C1(N1)
Os(Ru)–P1
2.058(3)
2.3327(9)
Bond angles
C1–Os(Ru)–P2
C1–Os(Ru)–P1
89.73(9)
95.70(8)
C1(N1)*–C1(N1)–Os(Ru)
172.1(4)
Table 5
6
˚
Selected bond lengths (A) and bond angles (ꢁ) for the complex [Cp(PPh3)2Ru(l-CN)RuCl2(g -p-cymene)]BF4 (11) (estimated standard deviations are
shown in parenthesis)
Bond lengths
Ru(1)–C(42)
Ru(2)–N(1)
Ru(2)–Cl(2)
1.975(3)
2.048(3)
2.4235(9)
Ru(1)–P(1)
C(42)–N(1)
2.2976(8)
1.153(4)
Ru(1)–P(2)
Ru(2)–Cl(1)
2.2973(8)
2.4230(9)
Bond angles
Ru(1)–C(42)–N(1)
P(1)–Ru(1)–C(42)
Ru(2)–N(1)–C(42)
N(1)–Ru(2)–Cl(2)
169.7(3)
88.77(9)
168.7(3)
85.02(8)
P(1)–Ru(1)–P(2)
P(2)–Ru(1)–C(42)
N(1)–Ru(2)–Cl(1)
Cl(1)–Ru(2)–Cl(2)
102.55(3)
91.52(9)
84.68(8)
88.03(3)
(BF )2
4
N
N
+
Ru
N
N
AgNO
3
Ru
Ru
CN
Ru
+
Cl
CN
Ph P
3
Ph P
3
NH BF
4
4
PPh
PPh
3
3
=
,
5
4
Scheme 1.
of the triphenylphosphine ligands are in similar chemical
environments.
trated acetone solution of the compound. An ORTEP
[13] representation is shown in Fig. 1 and a summary
of X-ray structure determination is given in Table 2. Be-
cause of the poor quality of the data obtained from the
It is worth mentioning that in a compound such as
[(g6-arene)Ru(N,N0)Cl]+, the arene (specifically p-cym-
ene) ligand tended to be very labile during attempts to
substitute the chloride ligand and often resulted in the
displacement of the arene from the coordination sphere.
Even though some arene-ruthenium(II) complexes con-
taining tripodal nitrogen donor ligands have been synthe-
sized [17], to our knowledge, complexes 4 and 5 offer the
only examples of complexes having an [(g6-arene)Ru]
fragment, where the other available coordination sites
are occupied by bipyridine and a nitrogen donor ligand.
complex
[(ind)(PPh3)2Ru(l-CN)Ru(bipy)(g6-p-cym-
ene)](BF4)2 (5), discussion of the geometrical data will
be only for the sake of comparison. The disposition of
the bridging cyano ligand is such that the four atoms
Ru(1), N(1), C(10), and Ru(2) are almost collinear with
an angle of 170.3ꢁ at nitrogen and 168ꢁ at carbon. The
˚
Ru(1)–N(1) bond length of 2.055(12) A is slightly shorter
˚
than the value of 2.15 A noted in [Cp(dppe)Ru(l-
CN)Ru(PPh3)2Cp]+ [3] and the value of 2.165 A noted
˚
in typical ruthenium N-donor systems like [(g4-
C8H12)RuCl2(CO)(NCM2)] [18]. This supports the
charge distribution Ru+–N„C–Ru with the positive
charge being localized on the metal bearing nitrogen.
5.2. X-ray structure of [(ind)(PPh3)2Ru(l-CN)-
Ru(bipy)(g6-p-cymene)][BF4]2 (4)
˚
Crystals suitable for an X-ray structure analysis were
obtained via slow diffusion of hexane into a concen-
The C–N bond length of 1.111(17) A is also slightly
˚
shorter than the value of 1.14(2) A noted in [Cp(dppe)-

R. Lalrempuia et al. / Journal of Organometallic Chemistry 690 (2005) 3990–3996
3995
Ru(l-CN)Ru(PPh3)2Cp]+. The Ru(2)–C(10) bond
N1 atoms so that it is not possible to differentiate the
Ru atom from the Os atom or the N1 atom from the
C1 atom. In addition, the BF4 ion is disordered over
at least three areas and could not be reliably modeled.
˚
length of 1.957(13) A is also shorter than the Ru–C
˚
bond length of 2.03 A found in [Cp(dppe)Ru(l-CN)-
Ru(PPh3)2Cp]+ [3], being closer to the values found in
˚
ruthenium-isonitrile complexes like [RuCl2(CO)(PPh3)2-
The C1(N1)–C1(N1)* bond length of 1.139(6) A in (8)
˚
˚
(CNC6H4Me-p)] Æ EtOH (1.94 A) [19] and [RuI2(CO)-
is close to the value of 1.14(2) A observed in
t
(PPh3){CH(NMe)C6H4Me-p}(CNBu )] (1.998 A) [20].
[Cp(dppe)Ru(l-CN)Ru(PPh3)2Cp]+, being longer than
˚
that of 5.
5.3. Mono-cationic complexes
5.5. Neutral complexes
Reactions of the cyanide complexes 2, 6 and 7 with
the corresponding halo-complexes were also investi-
gated, offering an example of heterobimetallic cyano-
bridged species (Scheme 2). In comparison with those
of 4 and 5, the stretching frequency of the bridging cya-
no-ligand in these complexes 8–10 differs very little from
those of the parent cyano-complex (shifted to a higher
wave number by around 5 cmꢀ1). Here, the CN stretch-
ing frequency may not be the ideal gauge to determine
whether coordination has taken place since the absorp-
tion of the bridging cyano group is generally in a higher
region than in these complexes. The 1H NMR spectrum
clearly indicates the presence of the cyclopentadienyl li-
gands in all the complexes. In the case of complex 8,
however, the two Cp peaks are closely spaced and ap-
pear almost like a doublet for which an unambiguous
assignment could not be made. The 31P NMR spectra
of these complexes show two singlets, one at the high
field region assigned to the resonance of the P atoms at-
tached to osmium metal (Table 1).
It is well known that the complex [(g6-p-cym-
ene)RuCl2]2 is a versatile starting material for synthetic
manipulations. The chloride bridges may be easily
cleaved to give a mono-nuclear compound or else the
p-cymene ligand may be replaced under forcing condi-
tions. Thus, the reaction of the cyano-complexes 2, 6
and 7 with [(g6-p-cymene)RuCl2]2 afforded neutral
bimetallic cyano-bridged complexes (Scheme 3) as
anticipated.
Infrared spectroscopy affords an ideal gauge to deter-
mine whether the coordination of the second metal has
taken place or not. The infrared spectra of the com-
plexes 11, 12 and 13 exhibit strong bands assignable to
m(C@N) at 2110, 2105 and 2103 cmꢀ1, respectively. The
stretching frequency of the cyanide band is shifted by
about 30 cmꢀ1, quite a significant shift when compared
to that observed in the previous cationic complexes. It
is apparent that the chloride ligands participate to en-
hance donation of the electron lone pairs from both
the atoms in the CN moiety towards the ruthenium me-
tal center, which are in fact anti-bonding with respect to
C@N bond. Hence the m(C@N) frequency increases with
increasing donation of these lone pairs [14].
5.4. X-ray structure of [Cp(PPh3)2Ru(l-CN)Os-
(PPh3)2Cp]BF4 (8)
Crystals suitable for an X-ray structure analysis were
obtained via slow diffusion of hexane into a concen-
trated dichloromethane solution of the compound. The
ORTEP representation of complex (8) is shown in
Fig. 2 and a summary of the X-ray structure determina-
tion is given in Table 2. The molecule lies on a crystallo-
graphic center of symmetry; the midpoint of the C1–N1
bond is on the center at 1/4, 1/4, 1/2. This serves to com-
pletely disorder the Os and Ru atoms and the C1 and
The 1H and 31P{1H} NMR spectral data are given in
Table 1. The proton NMR spectra of these complexes
exhibit a strong resonance for Cp protons at around
4.5 ppm, while the p-cymene resonance appears in the
usual range as a doublet, singlet and septet for the iso-
propyl methyl groups, methyl group and proton of iso-
propyl group, respectively. The 31P NMR spectrum
exhibits a sharp singlet for the triphenylphosphine phos-
phorus atoms.
BF
4
Cl
L'
L'
Cl
Cl
Cl
Cl
Ru
Ru
M
L
Ru
M
L
+
CN
CN
M
L
M
L
X
M'
CN M'
CN
+
L
L
Cl
L
L'
L
'
L
8 - 10
11 - 13
L
2
M
M'
L
M
M'
X
2
L
M
2
Ru Os
(PPh )
Br
(2) (PPh )
Ru Os
(8)
(9)
2
3
3 2
(11) (PPh
(12) (PPh
(13) dppe
)
)
Ru
Os
Ru
3 2
(6) (PPh )
Os Ru Cl
Ru Os Br
(PPh )
dppe
Os Ru
Ru Os
2
3
3 2
3 2
(7)
dppe
(10)
Scheme 2.
Scheme 3.

3996
R. Lalrempuia et al. / Journal of Organometallic Chemistry 690 (2005) 3990–3996
5.6. X-ray structure of [Cp(PPh3)2Ru(l-CN)RuCl2-
(g6-p-cymene)]BF4 (11)
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lengths are again more or less similar, being 2.2976(8)
˚
and 2.2973(8) A, respectively, but slightly shorter than
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respectively. The m(C@N) frequency increases with
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˚
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6. Supplementary material
Crystallographic data for the structural analyses have
been deposited at the Cambridge Crystallographic Data
Centre (CCDC) at CCDC No. 257427 for complex 11,
257428 for complex 8 and 257429 for complex 4. Copies
of this information 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).
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R.L. is grateful to the Council of Scientific and Indus-
trial Research, Government of India, New Delhi for
providing financial assistance by way of the SRF Grant
No. (9/347/(164)/2004/EMRI). Thanks are due to Prof.
R.H. Duncan Lyngdoh for help in preparation of this
manuscript.
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