Study of half sandwich platinum group metal complexes containing tetradentate N-donor ligand bearing two di-pyridylamine units linked by an aromatic spacer

Article abstract of DOI:10.1016/j.jorganchem.2010.09.060

A general approach for the preparation of dinuclear η⁵- and η⁶-cyclic hydrocarbon platinum group metal complexes, viz. [(η⁶-arene)₂Ru₂(NN∩NN)Cl ₂]²⁺ (arene = C₆H₆

Full text of DOI:10.1016/j.jorganchem.2010.09.060

Journal of Organometallic Chemistry 696 (2011) 702e708
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Study of half sandwich platinum group metal complexes containing tetradentate
N-donor ligand bearing two di-pyridylamine units linked by an aromatic spacer
,
Gajendra Gupta a, Sairem Gloria a, Bruno Therrien b, Babulal Das c, Kollipara Mohan Rao a
*
a Department of Chemistry, North Eastern Hill University, Shillong 793022, India
b Service Analytique Facultaire, Université de Neuchâtel, Case Postale 158, CH-2009 Neuchâtel, Switzerland
c Department of Chemistry, Indian Institute of Technology, Guwahati, India
a r t i c l e i n f o
a b s t r a c t
A general approach for the preparation of dinuclear h h
5- and 6-cyclic hydrocarbon platinum group metal
Article history:
complexes, viz. [(
h
6-arene)2Ru2(NNXNN)Cl2]2þ (arene ¼ C6H6, 1; p-iPrC6H4Me, 2; C6Me6, 3), [(h5
-
-
Received 8 September 2010
Received in revised form
23 September 2010
Accepted 24 September 2010
Available online 26 October 2010
C5Me5)2M2(NNXNN)Cl2]2þ (M ¼ Rh, 4; Ir, 5), [(
h
5-C5H5)2M2(NNXNN)(PPh3)2]2þ (M ¼ Ru, 6; Os, 7), [(h5
C5Me5)2Ru2(NNXNN)(PPh3)2]2þ (8) and [(
h
5-C9H7)2Ru2(NNXNN)(PPh3)2]2þ (9), bearing the bis-bidentate
ligand 1,2-bis(di-2-pyridylaminomethyl)benzene (NNXNN), which contains two chelating di-pyridyl-
amine units connected by an aromatic spacer, is reported. The cationic dinuclear complexes have been
isolated as their hexafluorophosphate or hexafluoroantimonate salts and characterized by use of
a combination of NMR, IR and UVevis spectroscopic methods and by mass spectrometry. The solid state
structure of three derivatives, [2][SbF6]2, [3][PF6]2 and [4][PF6]2, has been determined by X-ray structure
analysis.
Keywords:
Arene ruthenium compounds
Cp rhodium complexes
*
1,2-Bis(di-2-pyridylaminomethyl)benzene
ligand
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
[8e10]. The loss of this proton is believed to result in a planar
ligand configuration in the complexes [11]. Palladium(II) and
The coordination chemistry of 2,2-di-pyridylamine (dpa) and
its derivatives has been the focus of a considerable number of
investigations. For example, mono-, di- and tri-dpa derivatives
have been reported in which the secondary nitrogen of each dpa
is directly bound to an aryl core with such species being
employed in studies that range from metal coordination to
supramolecular chemistry [1,2] and the synthesis of new lumi-
nescent materials [3e5]. The use of Ag(I) in a range of metal
complex and supramolecular materials has received increasing
attention, in part due to the coordination flexibility of this d10 ion
and its well documented tendency to form strong complexes
with nitrogen donor ligands. It is well established that upon
coordination with the metal centers pyridyl rings of dpa adopt
either nearly co-planar or inclined pyridyl ring planes. This
property of dpa and its derivatives induces either electronically
or stereo chemically in the systems and have been observed in
a number of metal complexes [6,7]. Furthermore, the amine
proton of dpa becomes more acidic upon complexation to the
metal centre and both protonated as well as deprotonated (dpaꢀ)
complexes based on a number of metal ions have been studied
platinum(II) complexes of both the dpa and its extended deriv-
atives have also been investigated as potential anticancer agents
due to their structural similarity to cisplatin [12e14].
Chloro-bridged dimeric arene ruthenium, rhodium and
iridium complexes and monomeric arene ruthenium triphenyl-
phosphine complexes played a vital role in organometallic
chemistry [15e18]. While the reactivity of these valuable
precursors with a variety of nitrogen ligands has been reported by
our group [19e27], however the study with di-pyridylamine
derivative containing an aromatic spacer unit such as 1,2-bis(di-
2-pyridylaminomethyl)benzene (NNXNN) has not yet been
explored. This ligand has formed mononuclear, dinuclear, tri-
nuclear and tetra-nuclear complexes with metals [28] and it also
possesses the ability to form poly-pyridyl cages with silver and
other metals by varying the spacer units. But surprisingly in the
case of arene ruthenium and Cp* (pentamethylcyclopentadienyl)
rhodium or iridium systems, it only forms dinuclear complexes
despite of varying the metal ligand ratio. In this paper, we describe
slight modified procedure of synthesis of the ligand which has
been previously reported by Steel and coworkers [28], and the
synthesis of nine novel dinuclear h5- and 6-cyclic hydrocarbon
h
platinum group metal complexes bearing the ligand 1,2-bis(di-
2-pyridylaminomethyl)benzene (NNXNN) (Chart 1).
* Corresponding author.
E-mail address: mohanrao59@gmail.com (K. Mohan Rao).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.09.060

G. Gupta et al. / Journal of Organometallic Chemistry 696 (2011) 702e708
703
Chart 1. NNXNN tetradentate ligand 1,2-bis(di-2-pyridylaminomethyl)benzene and
1,4-bis{bis(pyrazolyl-methyl)}benzene.
2. Results and discussion
The synthesis of the ligand 1,2-bis(di-2-pyridylaminomethyl)
benzene (NNXNN), which has been previously reported by Steel and
coworkers [28], wasre-examined. Thisnew method hasanadvantage
over the previous method as it saves considerable amount of time as
compared to that of the reported procedure (2 days). The ligand
structure was confirmed by proper comparison with the literature
[28] and the detailed procedure is given in Experimental section.
Fig. 1. Molecular structure of [(
at 50% probability level. Hydrogen atoms and hexafluoroantimonate anions are
omitted for clarity.
h
6-p-iPrC6H4Me)2Ru2(NNXNN)Cl2](SbF6)2 ([2](SbF6)2)
841 cmꢀ1 due to the nPeF bond of the counter ions for complexes 1
and 3 whereas for complex 2 it shows a strong band at around 661
cmꢀ1 due to the nSbeF bond of the counter ion.
In the proton NMR spectra of 1e3, the ligand signals shift to the
downfield region as compared to that of the free ligand. The free
2.1. Dinuclear arene ruthenium, rhodium and iridium complexes
1e5
The dinuclear arene ruthenium complexes [(h m-Cl)
6-arene)Ru(
Cl]2 react with the NNXNN tetradentate bis(dipyridylaminomethyl)
ligand exhibits two doublets at around
at 7.56 and 6.88 corresponding to the different protons of the
pyridyl groups. It also shows another doublet at 7.27 and
a pseudo-triplet at 7.05 corresponding to the protons of the
phenyl group of the ligand. In addition to this, a singlet is also
observed at 5.52 which is due to the CH2 protons of the ligand.
However, after metallation, these peaks are shifted downfield in the
range 9.01e5.77. In addition to the ligand signals mentioned in
Experimental section, the 1H NMR spectrum of complex 2 exhibit
doublets at around 5.64 and 5.42 corresponding to the aromatic
CH protons of the p-cymene ring. It also exhibits a singlet at 1.81,
a doublet at 1.31 and a septet at 2.75 for the protons of the
d 8.32 and 7.25, two triplets
d
benzene ligand in methanol to afford the cationic dinuclear
complexes [(
h
6-arene)2Ru2(NNXNN)Cl2]2þ (arene
¼
C6H6, 1;
d
p-iPrC6H4Me, 2; C6Me6, 3), isolated as their hexafluorophosphate or
hexafluoroantimonate salts (Scheme 1). Compounds [2][SbF6]2 and
[3][PF6]2 are yellow in color, while [1][PF6]2 is brown. These salts
are non-hygroscopic and stable in air as well as in solution. They are
sparingly soluble in polar solvents like dichloromethane, chloro-
form, acetone and acetonitrile but are insoluble in non-polar
solvents like hexane, diethylether and petroleum ether. All
compounds are characterized by 1H NMR and IR spectroscopy and
mass spectrometry. In the mass spectra, they show the expected
molecular ion peaks m/z at 871.3, 851.4 and 1042.4, corresponding
to [1]2þ, [2]2þ and [3]2þ respectively. All these halogenated
complexes also displayed prominent peaks corresponding to the
loss of both chloride ions from the molecular ion peak [M-(PF6)2]þ,
but the loss of arene group is not observed indicating the stronger
bond of metal to arene group. The IR spectra of these complexes
exhibit a sharp band due to chelated NNXNN tetradentate ligand
between 1601 and 1465 cmꢀ1 corresponding to the different nC]C
and nC]N bond of these complexes (see Experimental section). In
addition, the infrared spectra contained a strong band at around
d
d
d
d
d
d
d
methyl and isopropyl groups of the p-cymene ligands. Interestingly
the methyl group protons moved upfield compare to the starting
dimer and also observed a single doublet for isopropyl protons
instead of two doublets observed in other cases. However in the
case of 1, the proton NMR spectrum displays a singlet at
d 6.06
which corresponds to the protons of the benzene groups of the
complex. The proton NMR spectrum of complex 3 exhibits a sharp
singlet at
towards high field in comparison to the starting complex [(h6
C6Me6)Ru( -Cl)Cl]2 which shows at around 2.04. The molecular
d 1.95 for the hexamethylbenzene ligand, which is shifted
-
m
d
Scheme 1.

704
G. Gupta et al. / Journal of Organometallic Chemistry 696 (2011) 702e708
these complexes exhibit a singlet at d 1.59 and 1.56 corresponding to
the protons of the pentamethylcyclopentadienyl group of these
complexes.
The m/z values of all these complexes and their ion peaks
obtained from the ESI mass spectra, as listed in Experimental
section, which are in good agreement with the expected values.
ESI mass spectra of the complexes displayed prominent peaks
corresponding to the molecular ion fragment. These halogenated
complexes displayed the prominent peak corresponding to the loss
of chloride ion from the molecular ion peak, but the loss of Cp*
group is not observed indicating the stronger bond of metal to this
group and remains intact. The molecular structure of representa-
tive compound 4 is solved by single crystal X-ray diffraction study
and the structure is discussed later (Fig. 3).
2.2. Dinuclear cyclopentadienyl ruthenium and osmium complexes
6e9
Fig. 2. Molecular structure of [(h
6-C6Me6)2Ru2(NNXNN)Cl2](PF6)2 ([3](PF6)2$H2O.
(CH3)2CO) at 50% probability level. Hydrogen atoms, water, acetone and hexa-
fluorophosphate anions are omitted for clarity. (Symmetry code: ꢀx, y, ½ ꢀ z).
Two equivalents of mononuclear cyclopentadienyl complexes
[(Cp)M(PPh3)2Cl] (M ¼ Ru, Os; Cp ¼
h h h
5-C5H5, 5-C9H7, 5-C5Me5)
react with NNXNN in refluxing methanol to give the corresponding
dinuclear complexes 6e9 which are isolated as their hexa-
fluorophosphate salts (Scheme 3). In this case also, our attempt to
make mononuclear complexes with the variation of metal to ligand
ratio was unsuccessful. The cationic complexes 6e9 are soluble in
halogenated solvents and polar organic solvents such as tetrahy-
drofuran, methanol or dimethylsulfoxide but are insoluble in non-
polar solvents. All these complexes are stable in solid state as well as
in solution. All complexes were characterized by IR,1H NMR, 31P{1H}
NMR spectroscopy and mass spectrometry. The analytical data of
these compounds are consistent with the formulations. Besides the
IR bands as mentioned in Experimental section, these complexes
also displaya strong band between 842 and 846 cmꢀ1 due tothe nPeF
stretching frequency of the counter ion of these complexes. The 1H
and 31P{1H} NMR spectra of complexes were recorded in CDCl3 and
spectral data are summarized in Experimental section. Shift in the
position of signals associated with protons of ligand NNXNN, sug-
gested coordination of nitrogen atom to the metal centre ruthenium
and osmium in bidentate fashion. The protons of the ligand in these
complexes 6e9 showa downfield shift with respect tothe protons of
the uncoordinated ligand. The 1H NMR spectrum of the uncoordi-
structures of the representative complexes 2 and 3 have been
solved by single crystal X-ray diffraction study and the structures
are presented in Figs. 1 and 2.
The reaction of the dimeric chloro complexes of [(h m-
5-C5Me5)M(
Cl)Cl]2 (M ¼ Rh or Ir) with one equivalent of tetradentate ligand
NNXNN in methanol results in the formation of the yellow air stable
dicationic dinuclear complexes [(
and [(
5-C5Me5)2Ir2(NNXNN)Cl2]2þ (5) which are isolated as their
h
5-C5Me5)2Rh2(NNXNN)Cl2]2þ (4)
h
hexafluorophosphate salts (Scheme 2). Complexes 4 and 5 are
characterized by 1H NMR, IR and mass spectroscopy. The infrared
spectra of both the complexes exhibit sharp bands due to chelated
NNXNN tetradentate ligand and are given in Experimental section.
Recently, we have reported a series of novel mono and binuclear
complexes of platinum group metals with a similar type of NNXNN
tetradentate ligand 1,4-bis{bis(pyrazolyl-methyl)}benzene (see
Chart 1) [29], where in the case of rhodium and iridium, we are able
to synthesize both mono and binuclear complexes with the varia-
tion in metal to ligand ratio. But here in this case, only binuclear
complexes are formed by the reaction of the metal complexes with
the NNXNN ligand, irrespective of the metal to ligand ratio. Several
attempts to make mononuclear complexes by varying the metal
complex ratio as well as changing different solvents were unsuc-
cessful. The 1H NMR spectra of these complexes show ligand peaks
a downfield shift in the position of signals associated with protons of
ligand NNXNN compared to that of the uncoordinated ligand sug-
gesting coordination of the nitrogen atoms to the metal center in
a bidentate fashion. Beside the different proton peaks for the ligand
as mentioned in Experimental section, the proton NMR spectra of
nated ligand displays peaks in between
the case of the metal complexes this peaks shifts to the downfield
region at 9.37 and 5.54 respectively. In addition to the aromatic
protons mentioned in Experimental section, complexes 6 and 7
show a singlet at 4.57 and 4.59 which corresponds to the cyclo-
d 8.26 and d 5.52, whereas in
d
d
d
d
pentadienyl ring protons, indicating a downfield shift from the
starting complexes. This downfield shift in the position of the
cyclopentadienyl protons might result from a change in the electron
density on the metal center due to the chelation of the NNXNN
Scheme 2.

G. Gupta et al. / Journal of Organometallic Chemistry 696 (2011) 702e708
705
with the atom labeling scheme are shown in Fig. 1e3 and selected
bond lengths and angles are presented in Table 1. The overall
geometry of all these structures corresponds to the characteristic
piano-stool configuration. All complexes contain two metal centers
bonded to a
tetradentate NNXNN ligand through nitrogen atoms. The distance
between the rhodium atom and the center of the
5-C5Me5 ring is
h h
5-C5Me5 or 6-arene ligands, which are bridged by the
h
1.759 Å in 4, whereas the corresponding RueC6Me6 and Ru-p-
cymene distances in 2 and 3 are shorter (1.687e1.697 Å). These
bond lengths are comparable to those in related complexes
[19e27]. The NeN and M-N bond distances in these complexes are
comparable to each other, i.e., not much variation is observed. The
MeCl bond lengths are 2.3821(12) and 2.4028(11) in 2, 2.3971(9) in
3 and 2.395(4) Å in 4, which are closely similar to reported poly-
pyridyl metal complexes [30,31].
In the crystal packing of [3](PF6)2$H2O$(CH3)2CO, the acetone
molecule sits in the cavity of the dinuclear complex with the oxygen
atom pointing down, see Fig. 4. The shortest CeH.O distances
between the dinuclear complex 3 and the oxygen atom of the
acetone molecule are respectively 2.444 Å with the C6Me6 ligand
and 2.785 Å with the CH2 groups. In addition to these interactions
between the acetone molecule and the dinuclear complex, weak
hydrogen bonds are observed between the water, the hexa-
fluorophosphate anions and the complex.
Fig. 3. Molecular structure of [(h
6-C5Me5)2Rh2(NNXNN)Cl2](PF6)2 ([4](PF6)2) at 25%
probability level. Hydrogen atoms and hexafluorophosphate anions are omitted for
clarity. (Symmetry code: ꢀx, y, ½ ꢀ z).
ligand through nitrogen atoms. While in the case of complex 8 it
displays a singlet at
the pentamethylcyclopentadienyl ligand. These complexes also
show multiplets in the range of 7.66e7.21 due to the protons of the
coordinated triphenylphosphine ligands. Complex 9 exhibits three
sets of signals, triplet at 4.39, doublets at 4.95 and 4.80 corre-
d 2.04 corresponding to the methyl protons of
d
d
d
d
2.4. UVevis spectroscopy
sponding to the protons of the indenyl group. The protons of the
triphenylphosphine ligands exhibit a large multiplet centered at
d
7.33. In the 31P{1H} NMR spectra of the complexes 6, 8 and 9, the 31
P
UVevis spectra of the complexes 1e4, 6 and 7 were acquired in
acetonitrile and spectral data are summarized in Table 2. The low
spin d6 configuration of these dinuclear complexes provides filled
orbitals of proper symmetry at the metal centers which can interact
with the low lying p* orbital of the ligands. One should therefore
expect a band attributable to the metal to ligand charge transfer
nuclei of the coordinated PPh3 resonated as a sharp singlet in the
range of 57.1e49.7 respectively whereas in the starting precursors
d
the signal appears in the upfield region. In the case of complex 7 the
31P{1H} NMR spectrum displays a sharp singlet at
compared to the starting complex which is found at
d
ꢀ0.27 as
d
ꢀ6.29. In
/
p* transition in their electronic spectra [32,33]. The
addition to this, the 31P{1H} NMR spectrum of all these complexes
(MLCT) t2g
electronic spectra of these complexes display a medium intensity
band in the UVevis region. The lowest energy absorption bands in
the electronic spectra of these complexes in the visible region
w419e378 nm have been tentatively assigned on the basis of their
shows a septet at
d
ꢀ143 corresponding to the phosphorus atom
present in the PF6 counter ions. The m/z values of all these complexes
and their stable ion peaks obtained from the ZQ mass spectra, as
listed in Experimental section, are in good agreement with the
theoretically expected values. ESI mass spectra of the complexes
also displayed prominent peaks corresponding to the molecular ion
fragment.
intensity and position to t2g
the high energy side at w305e232 nm for the complexes 1e4, 6
and 7, have been assigned to ligand-centered
p*/n / p*
/
p* MLCT transitions. The bands on
p
/
transitions [34,35]. In general, these complexes follow the normal
trends observed in the electronic spectra of the nitrogen-bonded
2.3. Molecular structures of [2](SbF6)2, [3](PF6)2.H2O.(CH3)2CO
and [4](PF6)2
metal complexes, which display a ligand-based
p /
p* transition
for pyrazolyl pyridazine ligands in the UV region and metal to
ligand charge transfer transitions in the visible region.
The complexes 3 and 4 crystallize in the space group C2/c, while
complex 2 crystallizes in the space group P21/n. ORTEP drawings
Table 1
Selected bond lengths and angles for complexes [2](SbF6)2, [3](PF6)2.H2O.(CH3)2CO
and [4](PF6)2.
[2](SbF6)2
[3](PF6)2
[4](PF6)2
Ru(1)
Ru(2)
Ru(1)
Rh(1)
Inter atomic distances (Å)
MeM
10.296(1)
2.091(4)
2.091(4)
2.3821(12)
1.692
11.654(1)a
2.091(3)
2.097(3)
2.397(9)
1.697
11.580(3)a
2.084(10)
2.076(10)
2.395(4)
1.759
MeN
2.108(3)
2.093(3)
2.4028(11)
1.687
MeN
MeCl
M-centroidb
Angles (ꢁ)
NeMeN
NeMeCl
NeMeCl
82.47(14)
86.33(10)
85.88(9)
80.76(13)
87.44(9)
88.02(9)
80.40(10)
86.84(7)
86.98(8)
81.0(4)
89.4(3)
88.5(3)
a
symmetry code -x, y, ½-z;
b
Calculated centroid-to-metal distances (h h
6-C6 or 5-C5 coordinated aromatic ring).
Scheme 3.

706
G. Gupta et al. / Journal of Organometallic Chemistry 696 (2011) 702e708
Fig. 4. Capped Sticks representation of [3](PF6)2.H2O.(CH3)2CO showing the weak hydrogen-bonded network in the crystal.
3. Conclusions
4.2. Single-crystal X-ray structures analyses
In summary, here we described an easy and time saving proce-
dure for the synthesis of the ligand 1, 2-bis(di-2-pyr-
idylaminomethyl)benzene (NNXNN) which has been previously
Crystals of complexes [2](SbF6)2, [3](PF6)2/H2O/(CH3)2CO and
[4](PF6)2 were mounted on a Stoe Image Plate Diffraction system
equipped with a
ochromated radiation (
4 circle goniometer, using Mo-Ka graphite mon-
reported, followed by the synthesis of nine dinuclear
h
5- and h6
-
l
¼ 0.71073 Å) with range 0e200ꢁ. The
cyclic hydrocarbon metal complexes bearing ligand NNXNN, which
are stable in the solid state and in solution have been successfully
synthesized in good yield. The ligand has ability to form mono-
nuclear, dinuclear and also tri- and tetra-nuclear complexes by
variation of metal ligand ratio, however arene ruthenium and Cp*Rh
and Cp*Ir reactions yielded dinuclear complexes only.
structures were solved by direct methods using the program
SHELXS-97 [46]. Refinement and all further calculations were
carried out using SHELXL-97 [46]. The H-atoms were included in
calculated positions and treated as riding atoms using the SHELXL
default parameters. The non-H atoms were refined anisotropically,
using weighted full-matrix least-square on F2. Crystallographic
details are summarized in Table 3 and selected bond lengths and
angles are presented in Table 1. Fig.1e3 were drawn with ORTEP-32
[47], while Fig. 4 was drawn with Mercury 2.3 [48].
4. Experimental
4.1. Physical measurements
4.3. Preparation of ligand 1,2-bis(di-2-pyridylaminomethyl)
benzene (NNXNN)
Infrared spectra were recorded on a PerkineElmer Model 983
spectrophotometer with the sample prepared as KBr pellets. The
NMR spectra were obtained using Bruker Advance II 400 spec-
trometer in CDCl3 for complexes using TMS as an internal standard.
Mass spectra were obtained from a Waters ZQ - 4000 mass spec-
trometer by the ESI method. All chemicals used were of reagent
grade. Elemental analyses of the complexes were performed on
a PerkineElmer 2400 CHN/S analyzer. All reactions were carried
out in distilled and dried solvents. The ligand NNXNN was
prepared by modification of a reported procedure [28] and is
Di-2-pyridylamine (1.00 g, 5.84 mmol) and potassium hydroxide
(1.33 g, 23.7 mmol) were stirred in DMSO (5 ml) for 1 h; 1,2-bis
(bromomethyl)benzene (0.70 g, 2.65 mmol) was added and the
reaction mixture was stirred for a further 4e5 h. The yellow
precipitate that formed was isolated and purified by column chro-
matography (hexane/acetone 1:2) to give the desired product as
a yellowsolid which was recrystallized from acetone/diethylether to
yield crystalline C28H24N6. Yield, 0.31 g (26%); mp 144e147 ꢁC.
Found: C, 75.37; H, 5.38; N, 19.04. Calc. for C28H24N6: C, 75.69; H,
described below. The precursor complexes [(
h
6-arene)Ru(
h
6-C5Me5)M(
m
m
-Cl)Cl]2
-Cl)Cl]2
5.52; N, 18.88%. 1H NMR (400 MHz, CDCl3):
(t, 4H, py), 7.27 (d, 2H, ph), 7.22 (d, 4H, py), 7.06 (t, 2H, ph), 6.88 (dd,
4H, py), 5.63 (s, 4H, CH2).
d
¼ 8.32 (d, 4H, py), 7.56
(arene ¼ C6H6, p-iPrC6H4Me and C6Me6), [(
(M
¼
Rh, Ir) [36e40], [(
h
5-C5H5)Ru(PPh3)2Cl], [(
h
5-C5H5)Os
(PPh3)2Br], [(
h
5-C5Me5)Ru(PPh3)2Cl] and [(
h
5-C9H7)Ru(PPh3)2Cl]
were prepared by following the literature methods [41e45].
4.4. Preparation of [(
h
6-arene)2M2(NNXNN)Cl2](PF6)2 {M ¼ Ru,
arene ¼ C6H6 [1](PF6)2,
h
6-p-iPrC6H4Me [2](SbF6)2, C6Me6 [3](PF6)2,
Table 2
UVevis absorption data in acetonitrile at 298 K.
M ¼ Rh, arene ¼ C5Me5 [4](PF6)2 and M ¼ Ir, arene ¼ C5Me5 [5]
(PF6)2
}
Complex
lmax/nm (e )
/10ꢀ4 Mꢀ1 cmꢀ1
1
2
3
4
6
7
232(0.65)
233(0.61)
235(0.99)
233(0.68)
233(1.10)
249(0.58)
255(0.66)
259(0.72)
263(1.00)
299(0.49)
304(0.57)
305(0.94)
298(1.03)
399(0.03)
394(0.04)
419(0.05)
397(0.06)
397(0.10)
378(0.05)
A mixture of [(
h
6-arene)M(
m
-Cl)Cl]2 (M ¼ Ru, Rh and Ir) (0.09
mmol), NNXNN (40 mg, 0.09 mmol) and two equivalents of NH4PF6
(NaSbF6 for complex 2) was stirred in dry methanol (30 ml) for 4 h at
room temperature. The yellow compound which formed was
filtered, washed with ethanol, diethyletherand dried under vacuum.
261(0.96)
281(0.42)

G. Gupta et al. / Journal of Organometallic Chemistry 696 (2011) 702e708
707
Table 3
Crystallographic and structure refinement parameters for complexes [2](SbF6)2, [3](PF6)2.H2O.(CH3)2CO and ([4](PF6)2.
[2](SbF6)2
[3](PF6)2.H2O.acetone
[4](PF6)2
Chemical formula
Formula weight
Crystal system
Space group
Crystal color and shape
Crystal size
a (Å)
C48H52Cl2F12N6Ru2Sb2
1457.50
C55H70Cl2F12N6O3P2Ru2
1426.15
C48H54Cl2F12N6P2Rh2
1281.63
Monoclinic
P21/n (no. 14)
Orange block
0.23 ꢂ 0.21 ꢂ 0.19
12.4524(6)
35.6140(11)
13.0152(6)
115.073(3)
5228.1(4)
Monoclinic
C2/c (no. 15)
Orange block
0.22 ꢂ 0.19 ꢂ 0.18
26.655(2)
13.7261(9)
17.2504(13)
110.207(6)
5922.8(8)
Monoclinic
C2/c (no. 15)
Red block
0.22 ꢂ 0.20 ꢂ 0.17
26.221(5)
13.460(3)
16.810(3)
110.69(3)
5550.2(19)
4
b (Å)
c (Å)
b
(ꢁ)
V (Å3)
Z
4
4
T (K)
203(2)
1.852
1.775
203(2)
1.599
0.741
173(2)
1.534
0.827
Dc (g cmꢀ3
)
m
(mmꢀ1
)
Scan range (ꢁ)
Unique reflections
Reflections used [I > 2
Rint
1.82 <
14115
9942
q
< 29.22
1.63 <
7046
5288
q
< 28.35
2.33 <
5093
2735
q < 26.01
s
(I)]
0.0769
0.0529
0.0542
Final R indices [I > 2
R indices (all data)
Goodness-of-fit
s
(I)]a
0.0496, wR2 0.00954
0.0841, wR2 0.1052
1.020
0.947, ꢀ1.504
0.0463, wR2 0.1404
0.0620, wR2 0.1519
1.057
1.029, ꢀ0.710
0.1061, wR20.3151
0.1500, wR20.3341
1.099
1.543, ꢀ0.968
Max, Min Dr/e (Åꢀ3
)
a
Structures were refined on F20: wR2 ¼ [S[w(F20 ꢀ F2c)2]/Sw(F02)2]1/2, where wꢀ1 ¼ [S(F20) þ (aP)2 þ bP] and P ¼ [max(F02, 0) þ 2F2c]/3.
4.4.1. Compound [1](PF6)2
3.97; N 5.43. IR (KBr pellets, cmꢀ1): 1622 (nC]C); 1415 (nC]N); 842
nPeF); 1H NMR (400 MHz, CDCl3):
Py), 7.61 (d, 2H, Ph), 7.41 (t, 4H, Py), 7.39e7.23 (m, 6H, Py and Ph),
5.83 (s, 4H, CH2), 1.56 (s, 30H, C5Me5); ESI-MS (m/z): 1169.8 [M-
(PF6)2]þ, 1098.4 [M-(PF6)2-Cl2]þ.
Yield: 145 mg, 74.7%. Elemental Anal (%) Calc. for
C40H36Cl2F12N6P2Ru2: C 41.29; H 3.13; N 7.21; found: C 41.58; H
3.55; N 6.92; IR (KBr pellets, cmꢀ1): 1601 (nC]C); 1466 (nC]N); 843
(
d
¼ 8.74 (dd, 4H, Py), 8.01 (dt, 4H,
(
nPeF); 1H NMR (400 MHz, CDCl3):
d
¼ 9.01 (dd, 4H, Py), 8.05 (dt, 4H,
Py), 7.51 (d, 2H, Ph), 7.47e7.43 (m, 6H, Py and Ph), 7.41 (t, 4H, Py),
6.06 (s, 12H, C6H6), 5.83 (s, 4H, CH2); ESI-MS (m/z): 871.3 [M-
(PF6)2]þ, 800.3 [M-(PF6)2-Cl2]þ.
4.5. Preparation of [(
h
5-Cp)2M2(NNXNN)(PPh3)2](PF6)2 {Cp ¼
C5H5, M ¼ Ru [6](PF6)2, Os [7](PF6)2, Cp ¼ C5Me5, M ¼ Ru [8](PF6)2
and Cp ¼ C9H7, M ¼ Ru [9](PF6)2}
4.4.2. Compound [2](SbF6)2
Yield: 136 mg, 73%. Elemental Anal (%) Calc. for
C38H38Cl2F12N6Sb2Ru2: C 39.99; H 3.37; N 7.35; found: C 40.44; H
3.66; N 7.15. IR (KBr pellets, cmꢀ1): 1600 (nC]C); 1467 (nC]N); 661
A mixture of [(
h
5-Cp)M(PPh3)2X] {M ¼ Ru, X ¼ Cl and M ¼ Os, X
¼ Br} (0.18 mmol), NNXNN (40 mg, 0.09 mmol) and two equiva-
lents of NH4PF6 in dry methanol (30 ml) were refluxed for 12 h until
the color of the solution changed from pale yellow to orange. The
solvent was removed under vacuum, the residue was dissolved in
dichloromethane (10 ml), and the solution filtered to remove
ammonium halide. The orange solution was concentrated to 5 ml,
upon addition of diethylether the orangeeyellow complex was
precipitated, which was separated and dried under vacuum.
(
nSbeF); 1H NMR (400 MHz, CDCl3):
d
¼ 8.68 (d, 4H, Py), 7.89 (dt, 4H,
Py), 7.38 (d, 2H, Ph), 7.34 (d, 4H, Py), 7.25 (t, 2H, Ph), 7.15 (t, 4H, Py),
5.77 (s, 4H, CH2), 5.64 (d, 4H, Arpecy), 5.42 (d, 4H, Arpecy), 2.75 (sept.
2H), 1.81 (s, 6H), 1.31 (d, 12H).
4.4.3. Compound [3](PF6)2
Yield: 143 mg, 71.8%. Elemental Anal (%) Calc. for
C52H60Cl2F12N6P2Ru2: C 46.87; H 4.57; N 6.30; found: C 47.08; H
4.89; N 6.04. IR (KBr pellets, cmꢀ1): 1597 (nC]C); 1465 (nC]N); 843
4.5.1. Compound [6](PF6)2
Yield: 163 mg, 74.4%. Elemental Anal (%) Calc. for
C74H64F12N6P4Ru2: C 55.86; H 4.06; N 5.26; found: C 56.11; H 4.37;
N 5.02. IR (KBr pellets, cmꢀ1): 1596 (nC]C); 1436 (nC]N); 842 (nPeF);
(
nPeF); 1H NMR (400 MHz, CDCl3):
d
¼ 8.52 (dd, 4H, Py), 7.89 (dt, 4H,
Py), 7.35 (d, 2H, Ph), 7.28 (t, 4H, Py), 7.22 (t, 2H, Ph), 6.92 (t, 4H, Py),
5.77 (s, 4H, CH2), 1.95 (s, 36H, C6Me6); ESI-MS (m/z): 1042.4 [M-
(PF6)2]þ, 971.4 [M-(PF6)2-Cl2]þ.
1H NMR (400 MHz, CDCl3):
d
¼ 8.59 (dd, 4H, Py), 7.93 (dt, 4H, Py),
7.55 (d, 2H, Ph), 7.33e7.21 (m, 30H, PPh3), 7.18 (t, 4H, Py), 7.12 (t, 2H,
Ph), 6.87 (t, 4H, Py), 5.73 (s, 4H, CH2), 4.57 (s, 10H, C5H5); ESI-MS (m/
4.4.4. Compound [4](PF6)2
z): 1301.1 [M-(PF6)2]þ; 31P{1H} NMR (CDCl3,
d): 50.85 (s, PPh3), ꢀ143
Yield: 159 mg, 76.8%. Elemental Anal (%) Calc. for
C48H54Cl2F12N6P2Rh2: C 45.01; H 4.27; N 6.55; found: C 45.37; H
4.49; N 6.23. IR (KBr pellets, cmꢀ1): 1616 (nC]C); 1445 (nC]N); 842
(sept, PF6).
4.5.2. Compound [7](PF6)2
(
nPeF); 1H NMR (400 MHz, CDCl3):
d
¼ 8.68 (dd, 4H, Py), 7.93 (dt, 4H,
Yield: 160 mg, 75.1%. Elemental Anal (%) Calc. for
C74H64F12N6P4Os2: C 50.24; H 3.65; N 4.74; found: C 50.59; H 3.92;
N 4.56. IR (KBr pellets, cmꢀ1): 1615 (nC]C); 1465 (nC]N); 842 (nPeF);
Py), 7.41 (d, 2H, Ph), 7.38 (t, 4H, Py), 7.33e7.21 (m, 6H, Py and Ph),
5.78 (s, 4H, CH2), 1.59 (s, 30H, C5Me5); ESI-MS (m/z): 991.5 [M-
(PF6)2]þ, 920.4 [M-(PF6)2-Cl2]þ.
1H NMR (400 MHz, CDCl3):
d
¼ 8.66 (dd, 4H, Py), 7.97 (dt, 4H, Py),
7.53 (d, 2H, Ph), 7.39e7.26 (m, 30H, PPh3), 7.15 (t, 4H, Py), 7.07 (t, 2H,
Ph), 6.65 (t, 4H, Py), 5.66 (s, 4H, CH2), 4.59 (s,10H, C5H5); ESI-MS (m/
4.4.5. Compound [5](PF6)2
Yield: 109 mg, 72.2%. Elemental Anal (%) Calc. for
C48H54Cl2F12N6P2Ir2: C 39.48; H 3.75; N 5.75; found: C 40.05; H
z): 1479.1 [M-(PF6)2]þ; 31P{1H} NMR (CDCl3,
ꢀ143 (sept, PF6).
d): ꢀ0.27 (s, PPh3),

708
G. Gupta et al. / Journal of Organometallic Chemistry 696 (2011) 702e708
[14] S. Fakih, W.C. Tung, D. Eierhoff, C. Mock, B. Krebs, Z. Anorg. Allg. Chem. 631
(2005) 1397e1402.
[15] P. Stĕpnicka, J. Ludvík, J. Canivet, G. Süss-Fink, Inorg. Chim. Acta 359 (2006)
2369e2374 and references therein.
[16] B. Therrien, Coord. Chem. Rev. 253 (2008) 493e519.
[17] E. Wong, C.M. Giandomenico, Chem. Rev. 99 (1999) 2451e2466.
[18] R.H. Crabtree, The Organometallic Chemistry of the Transition Metals, fourth
ed.. John Wiley and Sons, Hoboken, NJ, 2005.
4.5.3. Compound [8](PF6)2
Yield: 161 mg, 74.2%. Elemental Anal (%) Calc. for
C84H84F12N6P4Ru2: C 58.27; H 4.89; N 4.83; found: C 58.63; H 5.19;
N 4.59. IR (KBr pellets, cmꢀ1): 1642 (nC]C); 1401 (nC]N); 844 (nPeF);
ꢀ
ꢀ
1H NMR (400 MHz, CDCl3):
d
¼ 9.32 (dd, 4H, Py), 8.65 (dt, 4H, Py),
8.32 (d, 2H, Ph), 7.66e7.49 (m, 30H, PPh3), 7.38 (t, 4H, Py), 7.31 (t,
2H, Ph), 6.98 (t, 4H, Py), 5.63 (s, 4H, CH2), 2.04 (s, 30H, C5Me5). ESI-
[19] G. Gupta, G.P.A. Yap, B. Therrien, K. Mohan Rao, Polyhedron 28 (2009)
844e850.
[20] K.S. Singh, Y.A. Mozharivskyj, P.J. Carroll, K. Mohan Rao, J. Organomet. Chem.
689 (2004) 1249e1256.
[21] G. Gupta, K.T. Prasad, B. Das, G.P.A. Yap, K. Mohan Rao, J. Organomet. Chem.
694 (2009) 2618e2627.
[22] G. Gupta, B. Therrien, K. Mohan Rao, J. Organomet. Chem. 695 (2010)
753e759.
[23] G. Gupta, K.T. Prasad, B. Das, K. Mohan Rao, Polyhedron 29 (2010) 904e910.
[24] G. Gupta, C. Zheng, P. Wang, K. Mohan Rao, Z. Anorg. Allg. Chem. 636 (2010)
758e764.
[25] K.T. Prasad, G. Gupta, M.P. Pavan, A.K. Chandra, K. Mohan Rao, J. Organomet.
Chem. 695 (2010) 707e716.
[26] G. Gupta, K.T. Prasad, A.V. Rao, S.J. Geib, B. Das, K. Mohan Rao, Inorg. Chim.
Acta 363 (2010) 2287e2295.
[27] G. Gupta, S. Gloria, B. Das, K. Mohan Rao, J. Mol. Struct. 979 (2010) 205e213.
[28] B. Antonioli, D.J. Bray, J.K. Clegg, K. Gloe, K. Gloe, O. Kataeva, L.F. Lindoy, J.C. Mc
Murtrie, P.J. Steel, C.J. Sumby, M. Wenzel, J. Chem. Soc. Dalton Trans. (2006)
4783e4794.
MS (m/z): 1441.2 [M-(PF6)2]þ; 31P{1H} NMR (CDCl3,
PPh3), ꢀ143 (sept, PF6).
d): 49.7 (s,
4.5.4. Compound [9](PF6)2
Yield: 163 mg, 76.8%. Elemental Anal (%) Calc. for
C82H68F12N6P4Ru2: C 58.24; H 4.07; N 4.95; found: C 58.59; H 4.40;
N 5.27. IR (KBr pellets, cmꢀ1): 1616 (nC]C); 1415 (nC]N); 846; 1H
NMR (400 MHz, CDCl3):
d
¼ 9.37 (dd, 4H, Py), 8.72 (dt, 4H, Py), 8.31
(d, 2H, Ph), 7.65e7.20 (m, 38H, PPh3 and indenyl), 7.07 (t, 4H, Py),
6.97 (t, 2H, Ph), 6.81 (t, 4H, Py), 5.54 (s, 4H, CH2), 4.95 (d, 2H,
indenyl), 4.80 (d, 2H, indenyl), 4.39 (t, 2H, indenyl). ESI-MS (m/z):
1401.1 [M- (PF6)2]þ; 31P{1H} NMR (CDCl3,
(sept, PF6).
d
): 57.10 (s, PPh3), ꢀ143
[29] K.T. Prasad, B. Therrien, K. Mohan Rao, J. Org. Chem. 695 (2010) 1375e1382.
[30] B. Therrien, C.S. -Mohamed, G. Süss-Fink, Inorg. Chim. Acta 361 (2008)
2601e2608.
[31] P. Govindaswamy, J. Canivet, B. Therrien, G. Süss-Fink, P. Stepnicka, J. Ludvík,
J. Organomet. Chem. 692 (2007) 3664e3675.
[32] A.B.P. Lever, Inorganic Electronic Spectroscopy. Elsevier, Amsterdam, 1968.
[33] M. Gerloch, E.C. Constable, Transition Metal Chemistry: The Valence Shell in
d-Block Chemistry. VCH, 1994.
[34] P. Didier, I. Ortmans, A.K.D. Mesmacker, R.J. Watts, Inorg. Chem. 32 (1993)
5239e5245.
Appendix A. Supplementary material
ꢀ
ꢀ
ꢀ
CCDC-790563 ([2](SbF6)2), 790564 ([3](PF6)2/H2O/(CH3)2CO)
and 790565 ([4](PF6)2) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/data_request/cif.
[35] B.P. Sulliran, D.J. Salmon, T.J. Meyer, Inorg. Chem. 17 (1978) 3334e3341.
[36] M.A. Bennett, T.N. Huang, T.W. Matheson, A.K. Smith, Inorg. Synth. 21 (1982)
74e78.
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