Synthesis and reactivity of homo-bimetallic Rh and Ir complexes containing a N,O-donor Schiff base

Article abstract of DOI:10.1016/j.jorganchem.2009.05.026

Binuclear complexes [{(η⁵-C₅Me₅)RhCl}₂(μ-bsh)] (1) and [{(η⁵-C₅Me₅)IrCl}₂(μ-bsh)] (2) containing N,N′-bis(salicylidine)hydrazine (H₂bsh) are reported. The c

Full text of DOI:10.1016/j.jorganchem.2009.05.026

Journal of Organometallic Chemistry 694 (2009) 3084–3090
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and reactivity of homo-bimetallic Rh and Ir complexes
containing a N,O-donor Schiff base
Ashish Kumar Singh a, Sudhakar Dhar Dwivedi a, Santosh Kumar Dubey a, Sanjay Kumar Singh a,
b
b,
*
Sanjeev Sharma a, Daya Shankar Pandey a, , Ru-Qiang Zou , Qiang Xu
*
a Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP, India
b National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
a r t i c l e i n f o
a b s t r a c t
Binuclear complexes [{(g l-bsh)] (1) and [{(g l-bsh)] (2) containing N,
5-C5Me5)RhCl}2( 5-C5Me5)IrCl}2(
Article history:
N0-bis(salicylidine)hydrazine (H2bsh) are reported. The complexes 1 and 2 reacted with EPh3 (E = P, As)
Received 6 August 2008
Received in revised form 19 May 2009
Accepted 21 May 2009
to afford cationic complexes [(
(4), [(
5-C5Me5)Ir(PPh3)( 2-Hbsh)]PF6 (5), and [(
lated as their hexafluorophosphate salts. Representative complexes 3 and 5 have been used as a metal-
lo-ligand in the synthesis of binuclear complexes [( -bsh)Ru(
5-C5Me5)RhCl( 6-C10H14)Cl]PF6 (7) and
[( -bsh)Ru(
5-C5Me5)IrCl( 6-C10H14)Cl]PF6 (8). The complexes under study have been fully character-
g
5-C5Me5)Rh(PPh3)(
j
2-Hbsh)]PF6 (3), [(
g
j
5-C5Me5)Rh(AsPh3)(
j
2-Hbsh)]PF6
g
j
g
5-C5Me5)Ir(AsPh3)(
2-Hbsh)]PF6 (6) which were iso-
Available online 27 May 2009
g
l
g
Keywords:
Homo-bimetallic
Rhodium
Iridium
Pentamethylcyclopentadienyl
Schiff base
g
l
g
ized by analytical and spectral (FAB/ESI-MS, IR, NMR, electronic and emission) studies. Molecular struc-
tures of 1, 2, 3 and 5 have been determined crystallographically. Structural studies on 1 and 2 revealed
the presence of extensive inter- and intra-molecular C–HꢀꢀꢀO and C–Hꢀꢀꢀ
p weak bonding interactions.
The complexes 1, 2, 3 and 5 moderately emit upon excitation at their respective MLCT bands.
Weak interactions
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
N,N0-bis(salicylidine)hydrazine (H2bsh) derived from the
reaction of salicylaldehyde with hydrazine possesses four donor
sites in the form of phenalato oxygen and imine nitrogen and
can act as a mono-, bi-, tri- or tetradentate ligand. Generally, it
The chloro-bridged dimeric complexes [{(
l-Cl)Cl}2] (M = Rh or Ir) have attracted attention of many research
g
5-C5Me5)M
(
groups as these are indispensable organometallic precursors [1,2].
These undergo chloro-bridge cleavage reactions leading to the for-
mation of a series of interesting neutral and cationic mononuclear
half sandwich complexes of the type (C5Me5)MLnX [3]. The half
sandwich complexes based on Rh and Ir have proved to be very
important because of their involvement in a number of stoichiom-
etric and catalytic reactions including activation of carbon-hydro-
gen bonds and alkene oligomerisation and polymerisation [4–9].
Reactions of the chloro-bridged rhodium and iridium complexes
interacts with metal ions as
a
tetradentate ligand through
both the bis-chelating N,O-donor sites in j2
:j
2-mode after dissoci-
ation of the phenolic protons. In some cases, H2bsh interacts with
metal ions through only one of the bis-chelating donor sites in a
j
2-mode and acts as a bidentate ligand (Scheme 1) [19,20]. It also
interacts with the metal ions in an unusual j2
:j
1-coordination
mode and acts as tridentate ligand. Recently we have
a
reported arene ruthenium(II) complexes in which two ruthenium
centres are bridged by two bsh2ꢁ groups in an unusual j2 1-mode
:j
[{(
g
5-C5Me5)MCl(
l
-Cl)}2] [M = Rh, Ir] have been studied exten-
[18].
sively with a variety of Lewis bases, N,N0 and N,O-donor Schiff
bases and N-heterocyclic ligands [10–17]. Despite extensive
Because of our interests in this area we devoted our efforts to-
wards reactivity of the chloro-bridged dimeric rhodium and irid-
studies on reactivity of the complexes [{(
g
5-C5Me5)MCl(
l-Cl)}2]
ium complexes [{(
In this paper, we report reproducible syntheses, spectral properties
and reactivity of the homo-nuclear bimetallic complexes [{(g5
C5Me5)MCl}2(
2-bsh)] (M = Rh 1, Ir 2) with EPh3 and crystal struc-
tures of [{( -bsh)] 1, [{( -bsh)]
5-C5Me5)RhCl}2( 5-C5Me5)IrCl}2(
2, [(
5-C5Me5)Rh(PPh3)( 2-Hbsh)]PF6 3 and [( 5-C5Me5)Ir(PPh3)
2-Hbsh)]PF6 5. Also we describe herein the results of our preli-
g l-Cl}2] [M = Rh, Ir] with H2bsh.
5-C5Me5)MCl(
[M = Rh, Ir] with a variety of ligands, their reactions with N2O2 do-
nor Schiff base ligands like, N,N0-bis(salicylidine)hydrazine
(H2bsh), N,N0-bis(salicylidine)-p-phenylenediamine (H2bsp) and
N,N0-bis(salicylidine)-p-biphenylenediamine (H2bsb) have seldom
been investigated [18].
-
j
g
l
g
l
g
j
g
(j
minary studies on application of representative complexes 3 and
5 as metallo-ligand in the synthesis of hetero-bimetallic complexes
7 and 8.
* Corresponding authors. Tel.: +91 542 2307321x105 (D.S. Pandey).
E-mail address: dspbhu@bhu.ac.in (D.S. Pandey).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.05.026

A.K. Singh et al. / Journal of Organometallic Chemistry 694 (2009) 3084–3090
3085
PF6
PF6
M
PPh3
O
O
O
O
M
PPh3
O
N
N
KOH/Methanol/50oC
M
M
M
M
N
N
N
N
N
N
O
[{η6-C10H14)Ru(µ-Cl)Cl}2]
N
N
Cl Ru
M
OH
O
HO
O
M = Rh (3); Ir (5)
M = Rh (7); Ir (8)
Scheme 4.
2
1
2
κ 2
κ 2
:κ
κ :κ
synthon in the development of hetero-bimetallic systems. To ex-
plore the possibility of their use as synthon for the construction
of homo/hetero-bimetallic complexes, 3 and 5 were treated with
Scheme 1.
chloro-bridged dimeric arene ruthenium complex [{(g6
-
2. Results and discussion
Reactions of the chloro-bridged dimeric complexes [{(g5
C10H14)Ru(l-Cl)Cl}2] in methanol. It led in the formation of binu-
-
clear complexes 7 and 8, respectively (Scheme 4).
C5Me5)MCl( -Cl}2] (M = Rh, Ir) with potassium derivative of
l
The complexes 1–8 gave satisfactory analyses for C, H and N.
The formations of 1, 2, 7 and 8 have also been supported by mass
spectral studies. FAB mass spectra of 1 and 2 exhibited peaks at m/z
H2bsh (obtained from the reaction of H2bsh with KOH in MeOH)
under stirring conditions at room temperature afforded neutral
binuclear complexes 1 and 2, respectively (Scheme 2). Synthesis
and spectral characterization of the complex 1 have already been
reported by us [18]. Attempts were made to prepare hetero-bime-
tallic complexes containing both the Ru and Rh centres from the
749 (750) and 928 (928), respectively, corresponding to [{(g5
-
C5Me5)MCl}(l-bsh)(g
5-C5Me5)M}] (M = Rh; Ir) moieties, resulting
from the loss of one chloro group from the molecular units. The
presence of peaks at m/z 477 (476) and 565 (566), respectively in
the FAB mass spectra of 1 and 2, corresponding to the monometal-
reactions of [{(
g
6-arene)RuCl(
-Cl}2] with potassium derivative of
l-Cl)}2] (arene = p-cymene or ben-
l
lic moieties [{(g j
5-C5Me5)MCl}( 2-bsh)] (M = Rh; Ir) further sup-
zene) and [{(
g
5-C5Me5)RhCl(
H2bsh in methanol under analogous conditions. Surprisingly such
a reaction yielded complex 1 as the major product with some
unidentified side products. The formation of 1 as major product
ported formation of the complexes. The presence of various
peaks in the ESI-MS spectra of 7 and 8 corroborated well to the for-
mulation of these complexes (Figs. S1 and S2).
over the homo-bimetallic ruthenium complex [{(
Ru}2(
2-bsh)] or hetero-bimetallic complex containing both the Ru
and Rh [{(
6-arene)Ru}( 2-bsh){( 5-C5Me5)RhCl}] may be attrib-
g
6-arene)-
IR spectra of 1 and 2 displayed shift in the position of bands cor-
responding to mC@N and phenolic C–O by ꢂ17 and ꢂ67 cmꢁ1
,
j
g
j
g
respectively as compared to that in the uncoordinated H2bsh
(1621 and 1273 cmꢁ1) [18,19]. It suggested coordination of the li-
gand H2bsh through imine nitrogen and phenolic oxygen after
deprotonation. The band associated with N–N stretching vibration
appeared at 1020 cmꢁ1. Coordination of H2bsh to the metal centre
uted to higher stability of the homo-bimetallic rhodium complex 1.
Complexes 1 and 2 upon treatment with EPh3 (E = P, As) in
methanol in presence of NH4PF6 under refluxing conditions affor-
ded monometallic complexes 3–6 in reasonably good yields
(Scheme 3). Further, reactions of one equivalent of 1 or 2 with
two equivalents of EPh3 could not give bsh2- bridged bimetallic
in
j
2-mode and formation of monometallic complexes were also
supported by IR spectra of the respective complexes. IR spectra
of the monometallic complexes exhibited two distinct bands asso-
ciated with mC@N at ꢂ1596 and ꢂ1465 cmꢁ1, respectively as com-
pared to that in the respective precursor complexes 1 and 2. The
band at ꢂ1596 cmꢁ1 may be attributed to the pendent C@N group,
while the one at ꢂ1465 cmꢁ1 to the coordinated C@N. Similarly,
the bands at ꢂ1190 and ꢂ1150 cmꢁ1 may be assigned to the pen-
dent and coordinated phenolic C–O groups, respectively. The pres-
ence of characteristic vibrations associated with mP–F (at
ꢂ842 cmꢁ1) suggested cationic nature of the complexes 3–8 [21].
1H NMR spectral data of the complex 1 has already been re-
ported [18] and data for 2–8 is recorded in Section 3. In the 1H
NMR spectrum of 2 protons of the ligand (bsh2ꢁ) resonated at d
9.69, 7.39 (d, J = 7.8 Hz), 7.31–7.24 (m), 7.03 (d, J = 8.4 Hz) and
6.61 (t, J = 7.2 Hz) ppm. The singlet at d 9.69 ppm has been as-
signed to the protons associated with [–C(H)@N–], while the reso-
nances at d 7.39 (d, J = 7.8 Hz), 7.31–7.24 (m), 7.03 (d, J = 8.4 Hz)
and 6.61 (t, J = 7.2 Hz) ppm to aromatic protons of the ligand.
complexes [{(g l-bsh)](PF6)2. Rather, it led in
5-C5Me5)M(EPh3)}2(
the cleavage of bsh2ꢁ bridged binuclear complexes to afford cat-
ionic monometallic complexes. The formation of monometallic
complexes may be attributed to the steric hindrance resulting from
the presence of two bulky EPh3 groups.
The presence of uncoordinated bis-chelating N,O-donor sites in
3–6 offers an unique opportunity for these molecules to behave as
M
Cl
O
HO
[Cp*MCl2]2
N
N
N
N
KOH, methanol, rt
O
OH
Cl
M
[M = Rh 1; Ir 2]
Scheme 2.
The
g
5-C5Me5 protons resonated as a singlet at d 1.43 ppm. The po-
sition and integrated intensity of various signals corroborated well
to the proposed formulation of the complex 2. The presence of a
singlet at d 9.69 corresponding to aldehydic protons in 1H NMR
spectra of 1 and 2 supported proposed formulations and suggested
an equivalent electronic environment about both the metal cen-
tres. Reactions of 1 and 2 with EPh3 (E = P, As) disrupts symmetric
coordination of H2bsh with the metal centres and results in mono-
metallic complexes 3–6. The asymmetric mode of coordination is
evidenced by presence of two singlet corresponding to –C(H)@N–
proton in the 1H NMR spectra of complexes 3–6. The metal coordi-
PF6
M
EPh3
O
M
Cl
O
EPh3/NH4PF6
N
N
N
N
Methanol/Reflux
OH
O
Cl
M
E=P, As
M = Rh, E=P (3); As (4)
M = Ir, E=P (5); As (6)
Scheme 3.

3086
A.K. Singh et al. / Journal of Organometallic Chemistry 694 (2009) 3084–3090
nated imine proton resonated at d ꢂ10.0 ppm, while the pendent
imine proton displayed an up-fielded shift (d ꢂ7.7 ppm). Aromatic
protons of EPh3 resonated as broad multiplet in the region d ꢂ7.3–
acceptor. Absorption spectra of 1 and 2 in dichloromethane are
shown in Fig. S3 and resulting data is recorded in Section 3. Low
energy transitions in the UV–Vis spectra of 1 and 2 at 552 and
7.2 ppm. Methyl protons of
g
5-C5Me5 in 3–6 resonated at almost
528 nm, respectively have been assigned to Md ? Lp metal to li-
ꢃ
p
same position as in the respective precursor complexes 1 and 2.
gand charge transfer transitions, while the higher energy transi-
tions at ca. 311 nm to the intra-ligand
1H NMR spectrum of 7 exhibited distinct resonances corre-
p–
p* transitions. It further
sponding to [–C(H)@N–] and aromatic phenyl protons of bsh2ꢁ
.
suggested that the low energy transitions are localized at metal
centre with the differences in absorptions attributed to electronic
interaction between two metal centres [22]. The electronic spectra
of monometallic complex 3 displayed absorptions at 463, 338,
262 nm and 5 at 415, 345 and 268 nm (Fig. S4). On the basis of
its position and intensity the low energy bands at 463 and
415 nm, respectively have been assigned to the MLCT transitions
These were displayed as a singlet at d 9.32 (s, 2H), and as broad
multiplet at d 6.51 (d, J = 7.8 Hz), 6.93 (d, J = 8.4 Hz), 7.02 (t,
J = 6.3 Hz), 7.14 (t, J = 6.9 Hz) ppm. The
g
5-C5Me5 protons in this
complex exhibited a downfield shift and resonated as a singlet at
d 1.47 ppm as compared to that in the complex 3 (d 1.37 ppm).
The downfield shift in the position of
attributed to the coordination of {Ru(
g
5-C5Me5 protons may be
g
6-C10H14)Cl} moiety
[M(III) ? p
* bsh]. The high intensity absorption bands in the region
through pendant bis-chelating site of Hbshꢁ in complex 3. The p-
cymene protons resonated at d 0.91 (d, J = 6.6 Hz, 6H), 2.61 (m,
1H), 5.12 (m, 2H), 5.34 (m, 2H) ppm. The position and integrated
intensity of various signals corroborated well to the proposed for-
mulation of 7. The 1H NMR spectrum of 8 followed the trends ob-
served in that of 7.
335–345 nm (338 nm in 3 and 345 nm in 5) and 260–270 nm
(262 nm in 3 and 268 nm in 5) nm have been assigned to the in-
tra-ligand transitions. One can see that upon reaction with EPh3
the bsh2ꢁ bridged complexes 1 and 2 afforded cationic complexes
3–6. The formation of monometallic species from bimetallic one,
leads to a blue shift (ꢂ100 nm) in the position of MLCT transitions
while intra-ligand transitions exhibited a red shift (ꢂ25 nm). The
shifts in the position of various transitions may result from disrup-
tion of the bsh2ꢁ bridged structure [23].
Complexes 1–3 and 5 upon excitation at their respective MLCT
transitions exhibited moderate emissions centred at 538 (1), 548
(2), 560 (3) and 565 nm (5). The observed red shift in the position
of emission bands for iridium complexes compared to the analo-
13C NMR spectral data of the complexes 3–6 provided valuable
information about bonding in these complexes. In the 13C NMR
spectra of these complexes resonances corresponding to methyl
carbons of C5Me5 appeared at ꢂ8.8 ppm, while the ring carbons
resonated at ꢂ97–100 ppm. Resonances corresponding to the aro-
matic carbons of triphenylphosphines/arsine and Hbshꢁ appeared
at d ꢂ125–135 ppm. An interesting feature of the 13C NMR spectra
of these complexes is the presence of two peaks associated with
the imine carbons at ꢂ161–172 ppm. The peak at ꢂ161–165 ppm
has been attributed to the signal associated with free imine carbon,
while the one at ꢂ168–172 ppm to the imine carbon coordinated
to the metal centre. The coordination of PPh3 to metal centre in 3
and 5 is further supported by the presence of signals associated
with 31P nuclei at d 30.70 and d 16.09 ppm, respectively. The 31P
nuclei of the counter anion PF6ꢁ resonated in its characteristic sep-
tet pattern at ꢂꢁ130.0 ppm and supported the cationic nature of
complexes 3 and 5.
gous rhodium complex is consistent with the fact that dp orbitals
of Rh(III) are more stable than those of Ir(III). The observed red shift
in 3 and 5 may be attributed to destabilisation of the ground state
by coordination of triphenylphosphine in place of chlorine (Supple-
mentary material Fig. S5).
Molecular structures of 1, 2, 3 and 5 have been determined crys-
tallographically. Details about data collection, solution and refine-
ment is summarized in Table 1, selected geometrical parameters
are listed in Table 2 and CCDC Mercury ellipsoid plots (at 30% prob-
ability) are depicted in Figs. 1–4. Relative configuration of these
pseudo-tetrahedral metal complexes is R, if viewed along the M–
The metal centre rhodium/iridium provides filled orbitals of
proper symmetry to interact with relatively low lying p* orbitals
of the ligand bsh2ꢁ. It is expected to give a band associated with
Cct axis (Fig. S6). In the complexes 1 and 2, two [(
g
5-C5Me5)MCl]
moieties are bridged by bsh2ꢁ in j2 2 mode, where both the metal
:j
metal to ligand charge transfer (MLCT) transition (t2g ?
p
*) whose
centres adopt a typical piano-stool geometry. Coordination geome-
position varies with the nature of metal ion and ligand acting as a
p
try about the metal centres is completed by imine nitrogen and
Table 1
Selected crystallographic data for 1, 2, 3 and 5.
1
2
3
5
Chemical formula
Formula weight
Color, habit
Space group
Crystal system
a (Å)
C17H20ClNORh
392.70
Red, blocks
P21/n
Monoclinic
7.6593(15)
13.543(3)
15.543(3)
90
C17H20ClNOIr
481.99
Red, blocks
P21/n
Monoclinic
7.7523(16)
13.564(3)
15.328(3)
90
C42H41F6N2O2P2Rh
884.62
Orange, blocks
Pna21
Orthorhombic
21.119(4)
13.141(3)
14.589(3)
90.00
C42H41F6N2O2P2Ir
973.91
Orange red, blocks
Pca21
Orthorhombic
21.109(4)
10.827(2)
17.507(4)
90.00
b (Å)
c (Å)
a
(°)
b (°)
97.30(3)
90
1599.3(5)
4
97.48(3)
90
1598.1(6)
4
90.00
90.00
4048.8(14)
4
1.451
293(2)
31 087
502
0.0546
0.0428
0.1304
0.1158
1.082
90.00
90.00
4001.4(14)
4
1.617
293(2)
33 630
502
0.0481
0.0390
0.0954
0.0871
0.973
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
T (K)
)
1.631
2.003
293 (2)
10 913
195
0.1050
0.0862
0.1462
0.1388
1.296
293 (2)
12 155
196
0.0337
0.0310
0.0950
0.0902
0.620
Number of reflections
Number of parameters
R factor all
R factor [I > 2
WR2
r
(I)]
WR2 [I > 2
Goodness-of-fit (GOF)
r
(I)]

A.K. Singh et al. / Journal of Organometallic Chemistry 694 (2009) 3084–3090
3087
phenolate oxygen from bsh2ꢁ, the chloro group and C5Me5 ring
coordinated in
5-manner. Both the metal centres are equivalent
Table 2
Important bond parameters for 1, 2, 3 and 5.
g
in terms of overall geometry and arrangement of various groups.
The metal centres occupy special position and only half of the mol-
ecule is labelled. Intermetallic distances in 1 and 2 are 5.264 and
5.233 Å, respectively. The salicylidimine moieties of bsh2ꢁ in both
the complexes are planar. The N–N bond lengths in 1 and 2 are
1.436 and 1.417 Å, respectively, which are slightly longer than that
in the free ligand (1.386 Å). This distance falls in the normal range
for N–N bond [24–29]. Metal to phenalato oxygen bond distances
in 1 and 2 are 2.092 and 2.102 Å. These are comparable to the val-
ues reported in literature [30]. The Rh–N and Ir–N and bond dis-
tances of 2.156 and 2.147 Å are in the normal range [31,32] as
1
2
3
5
M–Cav
M–Cct
C–C
C–CH3
M–O
M–Cl/P
M–N
2.153
1.774
1.436
1.497
2.092(6)
2.420(2)
2.156(6)
1.307(10)
1.436(12)
88.09(18)
84.0(2)
91.40(18)
2.155
1.774
1.438
1.495
2.102(4)
2.4022(15)
2.147(4)
1.312(7)
1.417(8)
84.45(13)
83.33(15)
89.57(12)
2.187
1.821
1.427
1.472
2.100(4)
2.3665(11)
2.091(4)
1.294(6)
1.416(6)
2.207
1.838
1.430
1.507(12)
2.092(5)
2.3482(15)
2.096(5)
1.316(8)
1.405(7)
C1–O
N–N#1
O–M–Cl
O–M–N
N–M–Cl/P
O–M–P
C7–N–N–C8
O–C1–C6–C7
O2–C–C–C
85.45(15)
91.78(12)
87.71(11)
ꢁ58.0(6)
177.2(5)
ꢁ2.4(8)
85.45(19)
90.59(14)
85.12(16)
ꢁ52.0(7)
ꢁ2.0(10)
7.8(11)
the M–Cl bond distances [Rh–Cl 2.378(5) Å in
2.395(3) Å in 2] [33–36]. The metal chelate bite angles [84.0 (1)
and 83.33° (2)] are almost same in both the complexes. The g5
1 and Ir–Cl
180.0(5)
178.6(9)
180.00(44)
178.6(6)
-
C5Me5 ring is essentially planar and coordinated to rhodium and
iridium centres almost symmetrically. The M–C bond distances
are almost equal with an average bond distance of 2.153 Å [range
2.14(4)–2.20(4) Å] in 1 and 2.155 Å [range 2.14(4)–2.20(4) Å] in
2. The M-(g
5-C5Me5)ct distances (1.774 Å) are similar for the metal
centres rhodium and iridium in 1 and 2 [32,35–37].
Coordination geometry about the metal centre Rh in 3 is com-
pleted by imine nitrogen and phenolate oxygen from the bsh2ꢁ
,
phosphorus from triphenylphosphine and C5Me5 ring coordinated
in
g
5-manner. An analogous arrangement of various groups has
been observed about the metal centre Ir in 5. The Rh–C average
bond distance is 2.186(5) Å [range 2.169(5)–2.208(5) Å] in 3 while,
Ir–C average bond distance in 5 is 2.205(4) Å [range, 2.217(4)–
2.201(4) Å]. Metal to centroid of the C5Me5 distances in 3 and 5
are 1.821 and 1.838 Å, respectively. These are longer than those
in 1 and 2 (1.77 Å). Metal to phenalato oxygen distances are
2.100(4) and 2.091 Å, respectively in 3 and 5, while metal to imine
nitrogen bond distances are almost equal and are 2.090(4) and
2.095 Å. These values are comparable to those in the precursor
complexes 1 and 2 and are consistent with the values reported in
literature [32–37]. The metal to phosphorus distance is
2.366(11) Å in complex 3 and 2.348 Å in 5. These distances are con-
sistent with the earlier reports [38].
Weak interaction studies in 1 and 2 revealed that two C–HꢀꢀꢀO
intermolecular contacts between methyl substituents of g5
-
C5Me5 and phenalato oxygen results in a ladder like motif along
the b-axis (Fig. S7). Significant interaction parameters along with
the symmetry are listed in Table 3. Furthermore, methyl protons
Fig. 1. Molecular structure of complex 1.
of C5Me5 ring are intramolecularly involved in long range C–Hꢀꢀꢀ
p
interactions with the phenalato ring. In complex 1, the methyl car-
bon C13 approaches to C1–C2 bond of the phenalato ring with a
contact distance of 2.776 Å (Hꢀꢀꢀ
p
2.776 Å, Cꢀꢀꢀ
p
3.523 Å, C–Hꢀꢀꢀ
p
135.23°), whereas in complex 2 the methyl carbon located at the
same position as in complex 1 is involved in a long range interac-
tion with C1–C6 bond of the phenalato ring (Hꢀꢀꢀ
3.503 Å, C–Hꢀꢀꢀ 111.86°) [22,23]. Further, crystal structures of 3
and 5 revealed the presence of extensive inter-molecular C–HꢀꢀꢀX
(X = F and ) interactions. It is well established that these types
p
3.030 Å, Cꢀꢀꢀ
p
p
p
of interactions plays an important role in the construction of huge
supramolecular architectures [22,23]. In complex 3, C–HꢀꢀꢀF
(C33–H33ꢀꢀꢀF5; 2.599 Å and C4–H4ꢀꢀꢀF3; 2.538 Å), one C–HꢀꢀꢀC–H
(C21–H21ꢀꢀꢀC6–H6, 2.397 Å) and FꢀꢀꢀC (C4ꢀꢀꢀF3, 3.140 Å) types of
interactions are present. In this molecule hydrogen atom of coordi-
nated phenyl ringꢁof one molecule is attached to the F3 from the
counter anion PF6 and hydrogen of phenyl ring of another mole-
cule is attached with F3 of the same anion leading to zig-zag chains
(Fig. S8). In complex 5, five cationic units are locked by five C–HꢀꢀꢀF
ꢁ
type interactions involving PF6 anion to form a spiral type of
architecture by weak interactions along ‘c’-axis (Fig. S9). Hexa-
Fig. 2. Molecular structure of complex 2.
fluorophosphate anions are embedded in this motif. The pendant

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A.K. Singh et al. / Journal of Organometallic Chemistry 694 (2009) 3084–3090
Table 3
Matrices for weak-interactions in 1, 2, 3 and 5.
D–HꢀꢀꢀA d(D–H) Å d(HꢀꢀꢀA) Å
d(DꢀꢀꢀA) Å
\(DHA)°
1
C(7)–H(7)ꢀꢀꢀCla
0.93
0.96
2.64
2.60
3.381(8)
3.462(11)
137
150
C(17)–H(17c)ꢀꢀꢀOb
2
C(7)–H(7)ꢀꢀꢀCla
0.93
0.96
2.64
2.56
3.3481(5)
3.469(8)
134
158
C(17)–H(17c)ꢀꢀꢀOb
3
C(4)–H(4)ꢀꢀꢀF(3)
C(32)–H(32)ꢀꢀꢀO(1)
C(38)–H(38)ꢀꢀꢀO(1)
0.93
0.93
0.93
2.55
2.56
2.47
3.1349
3.1916
3.2673
122
125
144
5
O(2)–H(2)ꢀꢀꢀN(2)
C(6)–H(6)ꢀꢀꢀF(1)A
C(7)–H(7)ꢀꢀꢀF(2)A
C(17)–H(17)ꢀꢀꢀF(6)C
C(26)–H(26)ꢀꢀꢀO(1)
C(32)–H(32)ꢀꢀꢀO(1)
C(41)–H(41A)ꢀꢀꢀF(1)B
C(41)–H(41C)ꢀꢀꢀN(2)
0.82
0.93
0.93
0.93
0.93
0.93
0.96
0.96
1.92
2.49
2.41
2.41
2.60
2.59
2.53
2.60
2.6391
3.2075
3.3325
3.2253
3.0783
3.3551
3.3587
3.2926
147
134
172
147
113
140
145
129
a
ꢁx, ꢁy, ꢁz.
b
1 + x, y, z.
A
ꢁ1/2 + x,1ꢁy,z.
B
1/2ꢁx,y,ꢁ1/2 + z.
Fig. 3. Molecular structure of complex 3.
C
1/2ꢁx,ꢁ1 + y,ꢁ1/2 + z.
coordinated C5Me5 and PPh3. These molecules also have chiral cen-
tre about each metal ion. Since priority order of the ligands for the
Rh/Ir centre falls in the order Cp* > O > N > Cl/PPh3 [39]. Therefore,
the complexes 7 and 8 exhibits R configuration about the Rh/Ir cen-
tres. Same configuration is also, observed about the Ru centre.
3. Experimental
3.1. Materials and physical measurements
All chemicals were obtained from commercial sources and used
directly without further purifications. Pentamethylcyclopentadi-
ene, hydrated rhodium(III) chloride, iridium(III) chloride, triphen-
ylphosphine, triphenylarsine, ammonium hexafluorophosphate
(all Aldrich) salicylaldehyde and hydrazine (s.d. fine chem.) were
used as received. The ligand N,N0-bis(salicylidine)hydrazine
(H2bsh) and the precursor complexes [{(g l-Cl}2]
5-C5Me5)MCl(
[M = Rh, Ir] were prepared following literature procedures [40,41].
Elemental analyses on the complexes were performed by
Microanalytical Laboratory, Sophisticated Analytical Instrument
Facility, Central Drug Research Institute, Lucknow. Electronic and
emission spectra in dichloromethane were obtained on a Shimadzu
UV-1700 and Perkin Elmer-LS 45 Luminescence spectrometer,
respectively. Infrared spectra were recorded on a Perkin El-
mer-3100 FT-IR spectrometer in KBr pellets. 1H, 13C and 31P NMR
spectra were recorded on a JEOL AL300 FT-NMR spectrometer in
d-chloroform at 298 K. FAB mass spectra was obtained on a JEOL
SX 102/DA-6000 mass spectrometer system using Xenon as the
FAB gas (6 kV, 10 mA).
Fig. 4. Molecular structure of complex 5.
hydroxy group of the uncoordinated N,O-donor site is involved in
the intra-molecular H bonding with azine nitrogen [19].
Reactions of the complexes [{(g l-Cl}2] (M = Rh,
5-C5Me5)MCl(
Ir) with potassium derivative of H2bsh (obtained from the reaction
of H2bsh with KOH in MeOH) in methanol under stirring conditions
at room temperature afforded neutral binuclear complexes with
the formulations [{(g l-bsh)]. The complexes can
5-C5Me5)MCl}2(
exist as diastereomers but all efforts to separate the diastereomers
were unsuccessful at our hands. Throughout this work we have ta-
ken into account only the major isomer. Further, the complexes 3–
6 were obtained by interaction of 1 and 2, respectively with EPh3.
From the crystal structures, it is clear that the complexes 1, 2, 3 and
5 adopted R configuration about the metal centre (Fig. S6). Due to
the presence of uncoordinated bis-chelating N,O-donor sites 3 and
5 were used as synthon to produce chiral rhodium/ruthenium (7)
and iridium/ruthenium (8). In these complexes the Rh/Ir is bonded
to N,O-donor bis-chelating ligand as the Ru centre, along with
3.2. Syntheses
3.2.1. Preparation of [{(
g
5-C5Me5)RhCl}2(
j
2-bsh)] 1
[{(g
5-C5Me5)RhCl(
l-Cl}2] (155 mg, 0.25 mmol) was added to a
deprotonated solution of H2bsh [(obtained by stirring H2bsh
(60 mg, 0.25 mmol) and KOH (0.50 mmol, 30 mg) in 25 mL of
methanol)] and stirred for 4 h at room temperature. Slowly, it dis-
solved and a dark red product separated which was filtered,
washed with methanol (2 ꢄ 10 mL), distilled water (10 mL), meth-

A.K. Singh et al. / Journal of Organometallic Chemistry 694 (2009) 3084–3090
3089
anol (2 ꢄ 10 mL), diethyl ether (2 ꢄ 10 mL) and dried under vac-
uum. Yield: 157 mg, 80%. Anal. Calc. for C34H40N2O2Cl2Rh2: C,
51.99; H, 5.13; N, 3.57. Found: C, 51.82; H, 5.15; N, 3.66%. UV–
C–H), 171.2 (coordinated C–H), 156.7, 142.4 (C, PPh3), 138.4,
131.3, 130.1, 125.7, 125.5, 121.2 (C, aromatic), 96.8 (C, C5Me5),
8.9 (CH3, C5Me5). 31P NMR (CDCl3, d ppm): 16.09, ꢁ137 (sep.).
Vis. {CH2Cl2, k nm (
e
)}: 511 (5.01 ꢄ 103), 424 (1.29 ꢄ 104), 313
UV–Vis. {CH2Cl2, k nm (
e
)}: 463 (1.66 ꢄ 104), 338 (1.51 ꢄ 104),
(1.25 ꢄ 104). FAB-MS: m/z 749 (750), [M]ꢁCl, 40%; 477 (476),
262 (2.37 ꢄ 104). IR (cmꢁ1, KBr pellet): 1597 (
mC@N), 1530 (mC@C),
[M]ꢁ[(
g
5-C5Me5)RhCl]ꢁCl, 35%.
1465 (
m
C@N), 1437 (
m
P–Ph), 1305 (dO–H), 1269 (
m
N–N), 1196 (
m
C–O),
1152 (
m
C–O), 842 (
m
P–F), 755 (dC–Hph), 679 (dC–H).
3.2.2. Preparation of [{(
It was prepared following the above procedure adopted for 1
except that [{( -Cl}2] (200 mg, 0.25 mmol) was
5-C5Me5)IrCl(
used in place of [{( -Cl}2]. Yield: 195 mg, 81%.
5-C5Me5)RhCl(
g j
5-C5Me5)IrCl}2( 2-bsh)] 2
3.2.6. Preparation of complex [(
g
5-C5Me5)Ir(AsPh3)(
j
2-Hbsh)]PF6
6
g
l
It was prepared following the procedure adopted for 5, using
AsPh3 in place of PPh3. Yield: 221 mg, 87%. Anal. Calc. for
C42H41N2O2PAsIrF6: C, 49.60; H, 4.04; N, 2.76. Found: C, 49.68; H,
3.98; N, 2.73%. 1H NMR (CDCl3, d ppm): 9.99 (s, 1H), 7.68 (s, 1H),
7.42 (s, 1H), 7.35 (s, 1H), 7.31–7.24 (m, 15H, AsPh3), 7.03 (d, 1H,
J = 8.1 Hz), 6.72 (t, 2H, J = 7.2 Hz), 6.56 (t, 2H, J = 7.5 Hz), 6.39 (s,
1H), 1.46 (s, 15H, C5Me5). 13C NMR (CDCl3, d ppm): 161.7 (free
C–H), 172.6 (coordinated C–H), 155.4, 141.2 (C, PPh3), 133.9,
132.7, 130.2, 130.1, 127.2, 121.4 (C, aromatic), 95.8 (C, C5Me5),
9.0 (CH3 C5Me5).
g
l
Anal. Calc. for C34H40N2O2Cl2Ir2: C, 42.36; H, 4.18; N, 2.91. Found:
C, 42.30; H, 4.15; N, 3.06%. 1H NMR (CDCl3, d ppm): 9.69 (s), 7.39
(d, J = 7.8 Hz), 7.31–7.24 (m), 7.03 (d, J = 8.4 Hz), 6.61 (t,
J = 7.2 Hz), 1.43 (s). UV–Vis. {CH2Cl2, k nm (
e
)}: 511 (6.02 ꢄ 103),
480 (4.87 ꢄ 103), 346 (7.91 ꢄ 103), 311 (1.24 ꢄ 104), 262
(1.62 ꢄ 104). FAB-MS: m/z 928 (928), [M]ꢁCl, 50%; 565 (566),
[M]ꢁ[(
g
5-C5Me5)IrCl]ꢁCl, 75%.
3.2.3. Preparation of complex [(g j 3
5-C5Me5)Rh(PPh3)( 2-Hbsh)]PF6
To a suspension of 1 (195 mg, 0.25 mmol) in methanol (25 mL),
PPh3 (65 mg, 0.25 mmol) and NH4PF6 (40 mg, 0.25 mmol) were
added and the contents of the flask were refluxed for 5 h. It was
cooled to room temperature and the reaction mixture was evapo-
rated to dryness under vacuum and the residue was extracted with
CH2Cl2. After filtration, the filtrate was saturated with petroleum
ether (60–80) and the solution left undisturbed in a refrigerator.
A microcrystalline product separated within a few hours. It was fil-
tered washed with diethyl ether, dried under vacuum and recrys-
tallized using dichloromethane/diethyl ether. Yeild: 188 mg, 85%
Anal. Calc. for C42H41N2O2P2RhF6: C, 57.01; H, 4.63; N, 3.16. Found:
C, 57.06; H, 4.65; N, 3.18%. 1H NMR (CDCl3, d ppm): 10.48 (s, 1H),
7.73 (s, 2H), 7.49 (d, 1H, J = 6.6 Hz), 7.45 (s, 1H) 7.31–7.24 (m,
15H, PPh3), 7.16 (d, 1H, J = 7.8 Hz), 7.07 (d, 1H, J = 8.4 Hz), 6.97 (t,
2H, J = 7.8 Hz), 6.86 (d, 1H, J = 6.6 Hz), 6.6 (t, 1H, J = 8.4 Hz), 1.37
(s, 15H, C5Me5). 13C{1H} NMR (CDCl3, d ppm): 162.9 (free C–H),
169.9 (coordinated C–H), 157.8, 134.6 (C, PPh3), 132.2, 130.4,
127.9, 127.8, 121.2, 115.8 (C, aromatic) 98.9 (C, C5Me5), 8.75
(CH3, C5Me5).31P NMR (CDCl3, d ppm): 30.7, ꢁ130.32 (sep.). UV–
3.2.7. Preparation of complex [(
Cl]PF6
To a solution of 3 [(obtained by stirring 3 (221 mg, 0.25 mmol)
and KOH (15 mg, 0.25 mmol,) in 25 mL of methanol)], [{(g6
C10H14)Ru( -Cl)Cl}2] (77 mg, 0.125 mmol) was added and stirred
g l-bsh) Ru(g )
5-C5Me5)RhCl( 6-C10H14
7
-
l
for 4 h at 50 °C. Slowly, it dissolved and a dark brown product sep-
arated which was filtered, washed with methanol (2 ꢄ 10 mL), dis-
tilled water (10 mL), methanol (2 ꢄ 10 mL), diethyl ether
(2 ꢄ 10 mL) and dried under vacuum. The crude product was puri-
fied by column chromatography Yield: 216 mg, 75%. Anal. Calc. for
C52H54N2O2ClRhRuP2F6: C, 54.10; H, 4.71; N, 2.43. Found: C, 53.92;
H, 4.77; N, 2.38%. (CDCl3, d ppm): 9.32 (br, s, 2H), 7.32–7.78 (m,
15H, PPh3), 7.14 (t, J = 6.9 Hz, 2H), 7.02 (t, J = 6.3 Hz, 2H), 6.93 (d,
J = 8.4 Hz, H), 6.51 (d, J = 7.8 Hz, 2H), 5.34 (m, 2H), 5.12 (m, 2H),
2.61 (m, 1H), 2.10 (s, 3H), 1.47 (s, 15H), 0.91 (d, J = 6.6 Hz, 6H).
ESI-MS: m/z 710.9 (711.6), [M]ꢁClꢁPF6ꢁPPh3, 8%; 477 (476),
[M]ꢁ[(g
6-C6H14)RuCl]ꢁClꢁPF6ꢁPPh3, 100%.
3.2.8. Preparation of complex [(
Cl]PF6
g l-bsh) Ru(g )
5-C5Me5)IrCl( 6-C10H14
Vis. {CH2Cl2, k nm (
e
)}: 486 (2.22 ꢄ 103), 415 (6.14 ꢄ 103), 345
8
(1.61 ꢄ 104), 268 (2.36 ꢄ 104), 246 (2.36 ꢄ 104). IR (cmꢁ1, KBr pel-
It was prepared following the above procedure adopted for 7,
except that 5 (243 mg, 0.25 mmol) was used in place of 3. Yield:
227 mg, 73%. Anal. Calc. for C52H54N2O2ClIrRuP2F6: C, 50.22; H,
4.38; N, 2.25. Found: C, 50.00; H, 4.15; N, 2.13%. 1H NMR (CDCl3,
d ppm): 9.66 (br, s, 2H), 7.36–7.82 (m, 15H, PPh3), 7.23 (t,
J = 8.1 Hz, 2H), 7.14 (t, J = 7.5 Hz, 2H), 7.03 (d, J = 7.5 Hz, H), 6.63
(d, J = 8.1 Hz, 2H), 5.77 (m, 2H), 5.42 (m, 2H), 2.78 (m, 1H), 2.23
(s, 3H), 1.39 (s, 15H), 1.01 (d, J = 6.9 Hz, 6H). ESI-MS: m/z 1208.2
(1209.0), [M]ꢁCl, 8%; 1063.2 (1066.9), [M]ꢁClꢁPF6, 15%;
801(802), [M]ꢁClꢁPF6ꢁPPh3, 40%.
let), 1597 mC@N), 1527 ( C@C), 1465 (mC@N), 1436 (mP–Ph), 1308 (dO–H),
m
1269 (mN–N), 1193 (mC–O), 1151 (mC–O), 842 (PF6), 757 (dC–Har) and
696 (dC–H).
3.2.4. Preparation of complex [(g j 4
5-C5Me5)Rh(AsPh3)( 2-Hbsh)]PF6
It was prepared by following the above procedure adopted for 3
except that AsPh3 was used in place of PPh3. Yield: 197 mg, 83%.
Anal. Calc. for C42H41N2O2PAsRhF6: C, 54.21; H, 4.41; N, 3.02.
Found: C, 54.26; H, 4.45; N, 3.06%. 1H NMR (CDCl3, d ppm): 10.23
(s, 1H), 7.65 (s, 2H), 7.38 (d, 1H, J = 6.3 Hz), 7.32 (s, 1H), 7.28–
7.12 (m, 15H AsPh3), 7.02 (d, 1H, J = 7.5 Hz), 6.95 (d, 1H,
J = 7.8 Hz), 6.82 (t, 2H, J = 8.1 Hz), 6.72 (d, 1H, J = 6.0 Hz), 6.55 (t,
2H, J = 8.1 Hz), 1.42 (s, 15H, C5Me5). 13C NMR (CDCl3, d ppm):
164.2 (free C–H), 169.8 (coordinated C–H), 154.6, 140.2 (C, PPh3),
135.2, 132.3, 130.3, 127.9, 127.4, 118.2 (C, aromatic), 99.3 (C,
C5Me5), 8.8 (CH3, C5Me5).
3.3. X-ray crystallography
Crystals suitable for single crystal X-ray data collection for 1
and 2 were obtained by slow diffusion of a deprotonated solution
of H2bsh in methanol into the dichloromethane solution of [{(g5
-
C5Me5)MCl(l-Cl}2] [M = Rh, Ir] and for 3 and 5 crystals were
obtained by slow diffusion using dichloromethane/diethyl ether.
X-ray data on 1, 2, 3 and 5 were collected on a R-AXIS RAPID II
3.2.5. Preparation of complex [(
g
5-C5Me5)Ir(PPh3)(
j
2-Hbsh)]PF6
5
This complex was prepared following the procedure used for 3
using complex 2 in place of 1. 204 mg, 84%. Anal. Calc. for
C42H41N2O2P2IrF6: C, 46.00; H, 4.16; N, 1.66. Found: C, 45.96; H,
4.15; N, 1.68%. 1H NMR (CDCl3, d ppm): 10.37 (s, 1H), 7.71 (s,
1H), 7.5 (s, 1H), 7.4 (s, 1H), 7.31–7.24 (m, 15H, PPh3), 7.06 (d, 1H,
J = 8.1 Hz), 6.69 (t, 2H, J = 7.2 Hz), 6.61 (t, 2H, J = 7.5 Hz), 6.47 (s,
1H), 1.36 (s, 15H, C5Me5). 13C NMR (CDCl3, d ppm): 162.1(free
diffractometer at room temperature with Mo Ka radiation
(k = 0.71073 Å). Structures were solved by direct methods (SHELXS
97) and refined by full-matrix least squares calculations on F2 (SHELX
97) [42]. All the non-H atoms were treated anisotropically.
H-atoms attached to the carbon were included as fixed contribu-
tion and were geometrically calculated and refined using the SHELX
riding model.

3090
A.K. Singh et al. / Journal of Organometallic Chemistry 694 (2009) 3084–3090
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In this work, we have described the synthesis, spectral and
structural characterization of bsh2- bridged complexes [{(g5
-
C5Me5)RhCl}2(
studies supported our earlier viewpoint that reaction of [{(g5
C5Me5)MCl(
-Cl}2] [M = Rh, Ir] with potassium derivative of bsh2ꢁ
j g j
2-bsh)] and [{( 5-C5Me5)IrCl}2( 2-bsh)]. Structural
-
l
(obtained from H2bsh and KOH in MeOH) in methanol leads to
homo-bimetallic complexes where the ligand interacts through
both the chelating sites. Further, it has been shown that reaction
of the bsh2- bridged complexes with EPh3 leads to stable monome-
tallic complexes containing one vacant bis-chelating site which can
be employed in the synthesis of homo/hetero-binuclear
complexes.
Acknowledgements
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We thank the Department of Science and Technology, New Del-
hi for financial assistance through the scheme SR/S1/IC-15/2006
and the Council of Scientific and Industrial Research, New Delhi
for the award of a Senior Research Fellowship to SKS (9/13(97)/
2006-EMR-I). We are also thankful to the Head, Department of
Chemistry, Banaras Hindu University, Varanasi (UP) India and Na-
tional Institute of Advanced Industrial Science and Technology
(AIST), Osaka, Japan for extending facilities and SAIF, Central Drug
Research Institute, Lucknow (UP), India for providing analytical
and spectral data.
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Appendix A. Supplementary material
CCDC 656456, 656457, 692962 and 692963 contain the supple-
mentary crystallographic data for 1, 2, 3 and 5, respectively. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.05.026.
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