Synthetic, spectral and structural aspects of some mono- and binuclear (homo/hetero) Ru(II) hydrido carbonyl complexes

Article abstract of DOI:10.1016/S0022-328X(01)01470-X

Reactions of the poly-pyridyl bridging ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine; 2,3-bis(2-pyridyl)-pyrazine and 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (referred hereafter as tptz, bppz and bptz respectively) with [RuH(CO)Cl(PPh₃)₃] in methanol, gave highly stable cationic complexes with the formulation [RuH(CO)(PPh₃)₂(L)]⁺. Further, the mononuclear complex [RuH(CO)(PPh₃)₂(bppz)]PF₆ reacted with K₂PtCl₄, [PdCl₂(benzonitrile)₂], [RuH(CO)(PPh₃)₂(bppz)PdCl₂]PF ₆, [RuH(CO)(PPh₃)₂(bppz)(η ⁶-C₁₀ H₁₄)RuCl](PF₆) ₂, [RuH(CO)(PPh₃) ₂(bppz)(η ⁶-C₆Me₆)Cl₂Ru](PF ₆)₂, [RuH(CO)(PPh₃)₂ (bppz)(η⁵-C₅H₅) (PPh ₃)Ru](PF₆)₂ and [RuH(CO)(PPh ₃)₂(bppz)Rh(η⁵-C₅ Me₅)Cl](PF₆)₂ in quantitative yield. The reaction products have been characterized by elemental analyses, IR, ¹H-, ¹H-¹H-COSY, ¹³C-, ³¹P-NMR, ESMS, FAB mass spectroscopy, electronic spectra and cyclic voltammetry. Molecular structure of the representative mononuclear complex [RuH(CO)(PPh₃)₂(tptz)]BF₄ has been confirmed by X-ray crystallography. Crystal structure determination revealed η²-coordination of the ligand tptz with the metal center. Crystal data: monoclinic, P2₁/n, a = 17.810(6) A?, b = 22.233(9) A?, β = 90.06(3)°, Z = 4, R = 0.078.

Full text of DOI:10.1016/S0022-328X(01)01470-X

Journal of Organometallic Chemistry 648 (2002) 39–48
www.elsevier.com/locate/jorganchem
Synthetic, spectral and structural aspects of some mono- and
binuclear (homo/hetero) Ru(II) hydrido carbonyl complexes
Manish Chandra a, Abhaya Nand Sahay a, Daya Shankar Pandey a,*,
M. Carmen Puerta b, Pedro Valerga b
a Department of Chemistry, Awadhesh Pratap Singh Uni6ersity, Rewa (M.P.)-486 003, India
b Departmento de Quimica Inorganica, Uni6ersidad de Cadiz, Apartado 40, Puerto Real 11510, Spain
Received 28 May 2001; accepted 30 November 2001
Abstract
Reactions of the poly-pyridyl bridging ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine; 2,3-bis(2-pyridyl)-pyrazine and 3,6-bis(2-
pyridyl)-1,2,4,5-tetrazine (referred hereafter as tptz, bppz and bptz respectively) with [RuH(CO)Cl(PPh3)3] in methanol, gave
highly stable cationic complexes with the formulation [RuH(CO)(PPh3)2(L)]+. Further, the mononuclear complex
[RuH(CO)(PPh3)2(bppz)]PF6 reacted with K2PtCl4, [PdCl2(benzonitrile)2], [{Ru(h6-C10H14)(m-Cl)Cl}2], [{Ru(h6-C6Me6)(m-
Cl)Cl}2], [RuCl(h5-C5H5)(PPh3)2] and [{Rh(h5-C5Me5)(m-Cl)Cl}2] in methanol under refluxing conditions to give bppz bridged
binuclear
complexes
with
the
formulation
[RuH(CO)(PPh3)2(bppz)PtCl2]PF6,
[RuH(CO)(PPh3)2(bppz)PdCl2]PF6,
[RuH(CO)(PPh3)2(bppz)(h6-C10H14)RuCl](PF6)2, [RuH(CO)(PPh3)2(bppz)(h6-C6Me6)Cl2Ru](PF6)2, [RuH(CO)(PPh3)2(bppz)(h5-
C5H5)(PPh3)Ru](PF6)2 and [RuH(CO)(PPh3)2(bppz)Rh(h5-C5Me5)Cl](PF6)2 in quantitative yield. The reaction products have been
characterized by elemental analyses, IR, H-, H–1H-COSY, 13C-, 31P-NMR, ESMS, FAB mass spectroscopy, electronic spectra
and cyclic voltammetry. Molecular structure of the representative mononuclear complex [RuH(CO)(PPh3)2(tptz)]BF4 has been
confirmed by X-ray crystallography. Crystal structure determination revealed h2-coordination of the ligand tptz with the metal
center. Crystal data: monoclinic, P21/n, a=17.810(6) A, b=22.233(9) A, c=12.156(4) A, i=90.06(3)°, Z=4, R=0.078.
© 2002 Elsevier Science B.V. All rights reserved.
1
1
,
,
,
Keywords: Poly-pyridyl ligands; Metallo-ligands; Synthon; Supramolecules
states play a very significant role in the photosubstitu-
tion and intramolecular energy transfer reactions [2a–
c]. In this regard, bridging ligands viz. 2,3-
1. Introduction
Synthesis and characterization of ruthenium com-
plexes containing poly-pyridyl bridging ligands have
received considerable recent attention, owing to their
interesting photophysical and photochemical proper-
ties, their possible use in photochemical molecular
devices and as light sensitive probes in biological sys-
tems [1a–g]. The polyazine ligands in general, have
energetically low lying p* orbitals, which can accept a
lone pair of electrons from filled metal d orbitals of p
symmetry. As a consequence, they exhibit reversible
reduction processes and very intense solvatochromic
charge transfer bands in the visible region. In addition,
properly tuned metal ligand charge transfer excited
bis(2-pyridyl)-pyrazine
(bppz),
3,6-bis(2-pyridyl)-
1,2,4,5-tetrazine (bptz), 2,4,6-tris(2-pyridyl)-1,3,5-tria-
zine (tptz) and other related diimines have drawn
special attention and have extensively been used in the
synthesis of mono- and polynuclear, homo- and het-
erometallic complexes possessing interesting spectro-
scopic, photophysical and photochemical properties
[3a–g].
Because of current interests in the poly-pyridyl lig-
ands and in continuation of our studies towards synthe-
sis of metallo-ligands/synthons based on organometallic
systems, which could be employed in the synthesis of
homo/hetero bi- or polynuclear complexes [4], we have
made a detailed study on reactivity of the poly-pyridyl
bridging ligands viz. 2,3-bis(2-pyridyl)-pyrazine, 3,6-
* Corresponding author. Tel.: +91-766-240-740.
E-mail
addresses:
dsprewa@yahoo.com
(D.S.
Pandey),
carmen.puerta@uca.es (M.C. Puerta).
bis(2-pyridyl)-1,2,4,5-tetrazine,
2,4,6-tris(2-pyridyl)-
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01470-X

40
M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
1,3,5-triazine with the ruthenium(II) complex [RuH-
(CO)Cl(PPh3)3]. We found that such a reaction led in
the formation of mononuclear complexes with the gen-
eral formulation [RuH(CO)(PPh3)2(L)]+. Further, to
evaluate applicability of the mononuclear complexes as
building blocks in the synthesis of homo/hetero binu-
clear complexes, we have reacted the representative
complex [RuH(CO)(PPh3)2(bppz)]PF6, with different
molecules ranging from K2PtCl4, [PdCl2(benzonitrile)2],
chloro-bridged dimeric arene ruthenium complexes
[{Ru(h6-arene)(m-Cl)Cl}2] (arene=p-cymene or hexam-
ethylbenzene), [RuCl(h5-C5H5)(PPh3)2] and [{Rh(h5-
C5Me5)(m-Cl)Cl}2]. We found that the mononuclear
complex [RuH(CO)(PPh3)2(bppz)]PF6 behaves as a po-
tential metallo-ligand and led in the formation of binu-
clear complexes. In this paper we report reproducible
syntheses and spectral characterization of mononuclear
complexes [RuH(CO)(PPh3)2(L)]+ (L=tptz, bppz or
and bptz) and homo and hetero binuclear bppz bridged
complexes [RuH(CO)(PPh3)2(bppz)PtCl2]PF6, [RuH-
(CO)(PPh3)2(bppz)PdCl2]PF6, [RuH(CO)(PPh3)2(bppz)-
(h6-C10H14)RuCl](PF6)2, [RuH(CO)(PPh3)2(bppz)(h6-
systems behave as potential metallo-ligands, which
could be employed as building blocks in the synthesis
of supramolecular systems. Reaction of complex 3 with
K2PtCl4, [PdCl2(benzonitrile)2], [{Ru(h6-C10H14)(m-Cl)-
Cl}2], [{Ru(h6-C6Me6)(m-Cl)Cl}2], [RuCl(h5-C5H5)-
(PPh3)2] and [{Rh(h5-C5Me5)(m-Cl)Cl}2], in methanol
under refluxing conditions gave binuclear complexes
[RuH(CO)(PPh3)2(bppz)PtCl2]PF6
(5),
[RuH(CO)-
(PPh3)2(bppz)PdCl2]PF6 (6), [RuH(CO)(PPh3)2(bppz)-
(h6-C10H14)RuCl](PF6)2 (7), [RuH(CO)(PPh3)2(bppz)-
(h6-C6Me6)RuCl](PF6)2 (8), [RuH(CO)(PPh3)2(bppz)-
(h5-C5H5)(PPh3)Ru](PF6)2 (9) and [RuH(CO)(PPh3)2-
(bppz)Rh(h5-C5Me5)Cl](PF6)2 (10) in quantitative yield.
Carbon, hydrogen and nitrogen analyses of all the
complexes conformed well to their formulations. Fur-
ther information about composition of the complexes
has also been obtained from ESMS, which is one of the
recent techniques being used as a powerful tool for
characterization of the complex systems [5a,b] and FAB
mass spectrometry (FABMS), ESMS spectra of com-
plexes 1 and 2 showed prominent peaks at m/z 967.2
(100%) and 891 (100%), respectively, corresponding to
C6Me6)RuCl](PF6)2,
[RuH(CO)(PPh3)2(bppz)(h5-C5-
[RuH(CO)(PPh3)2(tptz)]+
and
[RuH(CO)(PPh3)2-
H5)(PPh3)Ru](PF6)2, and [RuH(CO)(PPh3)2(bppz)Rh-
(h5-C5Me5)Cl](PF6)2. Also, we present herein, single
crystal X-ray structure of the representative mononu-
clear complex [RuH(CO)(PPh3)2(tptz)]BF4.
(bppz)]+, which is consistent with our formulations. In
the FABMS of complex 1 the molecular ion peak
corresponding to [RuH(CO)(h2-tptz)(PPh3)2]+ ap-
peared at m/z 967 (calc. 967). Presence of the peaks at
m/z 704 (calc. 704), m/z 675 (calc. 675), m/z 414 (calc.
413) corresponding to [RuH(CO)(h2-tptz)(PPh3)]+,
[Ru(h2-tptz)(PPh3)]2+ and [Ru(h2-tptz)]2+ moieties in
the FABMS of the complex 1 further supported formu-
lation of the complex.
2. Results and discussion
The cationic mononuclear complexes with the general
formulation [RuH(CO)(PPh3)2(L)]+ (L=tptz, bptz or
bppz) could easily be prepared in quantitative yield by
reaction of [RuH(CO)Cl(PPh3)3] with the bridging lig-
ands in methanol in 1:1 molar ratio.
FABMS of the complexes 5, 7, 8 and 10 displayed
prominent peaks at m/z 889 (calc. 889); 1309 (calc.
1306); 1160 (calc. 1157); 1333 (calc. 1333) and 1155
(calc. 1154), respectively, corresponding to the cationic
species [RuH(CO)(PPh3)2(bppz)PtCl2]+, {[RuH(CO)-
(PPh3)2(bppz)(h6-C10H14)RuCl](PF6)}+, {[RuH(CO)-
(PPh3)2(bppz)(h6-C6Me6)RuCl](PF6)}+ and {[RuH-
(CO)(PPh3)2(bppz)Rh(h5-C5Me5)](PF6)}+. Presence of
these peaks in the FAB mass spectra of the respective
complexes and overall fragmentation patterns are con-
sistent with the formulation of the binuclear complexes.
Infrared spectra of the complexes exhibited charac-
teristic bands due to coordinated ligands tptz, bppz,
bptz, PPh3, CO and hydride group in the respective
complexes. Interestingly, the position of w(CꢀO) and
w(RuꢁH) in the IR spectra of the complexes shifted
toward higher and lower frequency. It indicated a de-
crease in the metal to carbonyl carbon interaction and
an increase in the RuꢁH bond order.
The mononuclear complexes [RuH(CO)(PPh3)2-
(tptz)]BF4 (1), [RuH(CO)(PPh3)2(bppz)]BF4 (2), [RuH-
(CO)(PPh3)2(bppz)]PF6 (3) and [RuH(CO)(PPh3)2-
(bptz)]PF6 (4) are bright yellow to golden orange, air-
stable, non-hygroscopic shiny crystalline solids. These
are sparingly soluble in dichloromethane, chloroform,
methanol and ethanol, highly soluble in acetone, aceto-
nitrile, dimethylsulfoxide, and dimethylformamide, and
insoluble in benzene, petroleum ether, and diethyl
ether. These exhibit 1:1 conductance behavior in ni-
tromethane. Our preliminary studies on reactivity of the
complexes [RuH(CO)(PPh3)2(L)]+ indicated that these
1
The H-NMR spectra of the complexes have been
assigned using the atom numbering scheme shown in
1
Fig. 1. H-NMR data of all these complexes are given
in Section 3. To facilitate assignment of the resonances,

M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
41
1H–1H-COSY experiment was carried out and the re-
sulting spectrum of complex 1 is shown in Fig. 2. The
doublets are assigned to the protons at 3 and 6 posi-
tions and triplets to the protons at 4 and 5 positions.
have been assigned to H3 proton by comparison of
JHꢁH values in free tptz ligand. The resonance at l 8.14,
7.92, and 7.72 ppm have been assigned to H%5+H4, H4%
and H5 protons, respectively. The broad singlet at l
7.52 ppm has been assigned to H6 proton. Upfield shift
of this signal could be attributed to the shielding of this
proton from p back-bonding ability of Ru(II) which
increases electron density on metal bound nitrogen and
on adjacent atoms [3f]. In the 1H-NMR spectra of
complex 2, distinct resonances are displayed at l 9.15,
8.62, 8.16 and 6.62 ppm and overlapping resonance in
the region 7.91–7.18 ppm. In its 1H-NMR spectra,
doublets are expected for the protons at 3, 6 and 3%, 6%
1
The H-NMR spectra of the complex 1 exhibited dis-
tinct signals at l 8.92 (d, 1H, 4.2 Hz), 8.60 (d, 1H, 7.8
Hz), 8.14 (t, 3H, 6.6 Hz), 7.92 (t, 1H, 6.6 Hz), 7.72 (t,
1H, 7.2 Hz), and 7.52 (br s, 1H) along with a broad
multiplet due to aromatic protons of PPh3 in the region
l 7.27–7.33 ppm and a triplet in the high field side at
−11.3 ppm. The lowest field doublet at l 8.92 ppm
with JHꢁH value of 4.2 Hz have been assigned to H6% and
the doublet at l 8.60 ppm with JHꢁH value of 7.8 Hz
Fig. 1. Numbering of protons in the complex cations of 1, 3 and 4.
Fig. 2. 1H–1H-COSY spectrum of complex 1.

42
M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
filled orbitals of proper symmetry on d6 Ru(II), with
the low lying p* orbital of the ligands tptz, bppz or
bptz should provide MLCT transition (t2g“p*) in the
electronic spectra of these complexes, with the transi-
tion energy varying with nature of the ligands acting as
a p acceptor. In the electronic spectra of complex 1,
three strong absorption were observed at about 441,
389, and 335 nm. On the basis of the intensity and
position of the lowest energy absorption, it has been
assigned to MLCT transition [8], while the one at
ꢀ389 nm may be of MLCT character, but the possibil-
ity of s bond to ligand charge transfer SBLCT cannot
be ruled out [9]. The high-energy band has been as-
signed to intra-ligand p“p* transition or p (phenyl) to
p* (phenyl) transition [10]. Electronic spectra of the
bimetallic complexes in acetonitrile at room tempera-
ture are shown in Fig. 3. These displayed intense peaks
throughout the ultra-violet and visible region of the
spectrum. The mononuclear ruthenium complex 3,
[RuH(CO)(PPh3)2(bppz)]PF6, from which the binuclear
complexes have been prepared, displayed bands at 426,
336 and 298 nm. The low energy band at 426 nm has
been assigned to Ru“bppz CT transition, while the
one at 336 nm has been assigned to intra-ligand p“p*
transition. It was further observed that Ru“bppz CT
transition of complex 3, upon interaction with another
metal center through bridge formation on the bppz
ligand, exhibited significant red shifts [complex 5, 480;
6, 472; 7, 475; 8, 493; 9, 544 and 10, 465 nm] as
compared to that in the mononuclear complex 3. The
red shift in the position of Ru“bppz CT transition
towards lower energy in these complexes may result
from stabilization of bppz p* orbital upon coordination
of the second metal center. In general, the coordination
of another metal ion at the remote coordination site
results in stabilization of the p* level of the bridging
ligand leading to enhanced p–p*overlap [11]. This ef-
fect lowers the HOMO–LUMO gap, which results in a
lower energy shift of the MLCT bands in the binuclear
complexes. The stabilization of the bppz p* also leads
to a red shift of the ligand based p“p* transitions.
These observations strongly support the formation of
the binuclear complexes and are consistent with other
reports [3f].
Fig. 3. Electronic spectra of the binuclear complexes 3, 5–10 in
acetone.
position, triplets are expected for the protons at 4, 5
and 4%, 5% positions, while the protons 1 and 2 are
expected to show one signal each and split as doublets.
Interestingly, the protons 1 and 2 appeared as doublets
at l 7.77 and 7.63 ppm. The doublets at l 9.16 and 8.16
have been assigned to H3 and H6 protons overlapping
resonance in the region 7.91–7.31 ppm could not be
precisely assigned, since this region is highly crowded
by aromatic protons of PPh3 ligand. The doublet at l
6.62 ppm has been assigned H%6 proton. It showed an
upfield shift and is consistent with the shielding of
protons adjacent to metal bound nitrogen [6a–b].
In the 1H-NMR spectra of complex 4, the doublets at
l 8.92, 8.78, and 8.74 and 8.70 ppm have been assigned
to H6+H6% and H3+H%3 protons, while the triplets at l
8.11, 8.20, 7.95 and 7.02 ppm have been assigned to H5,
H5% and H4, H4% protons. Aromatic protons of PPh3
ligand resonated as a broad multiplet in the region l
7.52–7.18 ppm.
1
An interesting feature of the H-NMR spectra of the
complexes 1, 2 and 3 are the hydrido resonance in the
high field side at l −11.93 (JPꢁH=29.4 Hz), −11.7
(JPꢁH=30.1 Hz) and −12.18 ppm (26.7 Hz), respec-
tively. The presence of a triplet corresponding to the
1
metal bound hydride proton in the H-NMR spectra of
these complexes suggested that the hydride group be
coupled with two equivalent 31P nuclei [7].
The 31P{1H}-NMR spectra of these complexes 1, 2
and 3 displayed sharp singlets at l 46.54, 50.95 and
48.6 ppm, respectively. It indicated that both the
triphenylphosphine ligands in these complexes are
equivalent and are mutually trans disposed.
2.2. Electrochemistry
The cyclic voltammograms for the mononuclear
complexes 1, 2 and 4 are shown in Fig. 4. The plots of
the peak currents versus square root of the scan rates
are linear for all the complexes, indicating that diffu-
sion controlled processes occur at the electrodes. On the
cathodic side of the CV scan all the complexes exhibit
one or more ligand centered reductions, localized over
polyimine ligands. These are invariably observed at
more negative potentials than the former. The
2.1. Electronic spectra
Electronic spectra of the complexes follow typical
trends observed in ruthenium polyazine complexes,
which display ligand based p“p* transitions for each
polyazine ligand in the ultra-violet region and metal to
ligand charge transfer MLCT transitions for each ac-
ceptor ligand in the visible region. Interaction of the

M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
43
versus Ag ꢀ AgCl arises from oxidation of the metal
center [i.e. Ru(II)“Ru(III) processes]. Thus the oxida-
tion can be described as below.
analogous poly-pyridyl centered reductions in
[(bipy)2Ru(poly-py)]2+ are observed between −1.0 and
−1.5 V versus Ag/AgCl under similar conditions [12a–
c]. The ligand centered reduction in the complexes 1, 2
and 4 are observed at −0.73, −0.61 and −0.66 V
versus Ag ꢀ AgCl in acetonitrile, respectively [3f]. It
therefore indicates that the MꢁL s bond is stronger in
these complexes.
The binuclear complex 8 exhibits a quasi-reversible
oxidation wave at Ep +1.30 V and an irreversible
reduction wave at −0.80 V versus SCE in acetonitrile.
These waves seem to arise from [(C6Me6)Ru(II/III)] and
electron transfer to the coordinated bppz moieties, re-
spectively. However, if the cathodic scan is preceded by
the anodic scan, an additional irreversible reduction
wave appears at Ep −0.50 V versus SCE. It seems that
(h6-C6Me6)RuCl moiety in complex 8 undergoes a
metal centered oxidation followed by the dissociation
of the oxidized fragment. This solvated-oxidized frag-
ment is subsequently undergoing reduction at Ep
−0.50 V.
On the anodic side of the CV scan, these complexes
exhibit two consecutive oxidation waves. Analogous
phosphine complexes [Ru(PPh3)2(CO)Cl] are known to
catalyze electro-oxidation of CO to CO2 in solution
[13]. The second oxidation wave at 1.1 V versus
Ag ꢀ AgCl is expected to arise due to electron transfer
from coordinated CO. The first oxidation at 0.48 V
However, if the anodic scan is taken with the switch-
ing potential (Eu) −1.50 V versus SCE, an additional
reversible reduction wave is observed at E1/2 −1.07 V
versus SCE. This wave seems to arise from the Ru(II)/
Ru(III) process centered at [(PPh3)2RuH(bppz)] moiety.
2.3. Single crystal X-ray structure of the complex
[RuH(CO)(PPh3)2(tptz)]BF4
Structure of complex 1 has been confirmed by single
crystal X-ray diffraction analysis. An ORTEP view of the
complex cation along with the atom numbering is
shown in Fig. 5. Selected bond angles and bond lengths
are recorded in Tables 2 and 3, respectively. Geometry
about the Ru(II) center is distorted octahedron formed
by N(1) and N(4) from the ligand tptz, P(1) and P(2)
from the triphenylphosphine ligands, carbonyl carbon
C(1) and the hydride ligand H(1). The nitrogen atoms
N(1), N(4), C(1) and H(1) form the equatorial base and
the phosphine ligands are in axial position. The triazine
ring and coordinated pyridyl ring are co-planar and the
Ru(II) ion is contained in the least squares plane
through the atoms N(1), C(2), N(3), C(3), N(2), C(4),
C(5), C(6), C(7), C(8), C(9), and N(4) (mean deviation
Fig. 4. Cyclic voltammograms of the complexes 1, 2 and 4 in
,
acetonitrile.
0.0581 A). The uncoordinated pyridyl groups are out of

44
M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
and it is slightly larger than the Ru(II) to coordinated
,
pyridyl nitrogen N(4) [2.168(10) A]. These are compara-
ble to those reported for Ru(II) poly pyridyl complexes.
The triphenylphosphine ligands lie in trans position as
indicated by the P(1)ꢁRu(1)ꢁP(2) angle of 173.4(1)°.
The Ru(1)ꢁP(1) and Ru(1)ꢁP(2) distances are 2.347(4)
,
and 2.385(4) A, respectively. These are essentially
equivalent and comparable to those in other related
complexes [14]. The Ru(1)ꢁC(1) bond length is 1.81(1)
,
A, which is normal for Ru(II) carbonyls [15a,b]. The
,
Ru(1)ꢁH(1) distance in the complex cation is 1.458 A.
It is slightly shorter than those found in
[RuH(H2O)(CO)2(PPh3)2]+ (1.7 A), [RuHCl(PPh3)3]
,
,
(1.7 A), and other related systems [16a–c].
The average CꢁC bond length within the ring is
,
1.375(2) A, while, the average intra-ring CꢁN bond
length is 1.34(2) A. These values are comparable with
average CꢁC bond distances of 1.39 A and CꢁN bond
distances of 1.34 A.
,
,
,
It is well established that the ligand tptz is susceptible
for metal-promoted hydrolysis and gives 2-pyridylcar-
bonylamide anion (bpca) and 2-picolinamide [17]. In
this regard, complex 1 is highly stable, even after reflux-
ing for 48 h in ethanol–water (1:1), it did not show any
metal promoted hydrolysis. At the same time, metal
induced hydroxylation at the carbon atom of the tria-
zine ring has also not been observed with complex 1.
The present study clearly revealed that the mononu-
clear complex [RuH(CO)(PPh3)2(bppz)]PF6 acts as a
synthon and offers a unique opportunity of behaving as
a potential metallo-ligand in the synthesis of homo/het-
ero binuclear complexes. The analytical, NMR,
FABMS, electronic spectral and electrochemical data of
complexes 5–10 provide strong evidence in favor of
formation of binuclear complexes starting from com-
plex [RuH(CO)(PPh3)2(bppz)]PF6. However, at this
Fig. 5. ORTEP view of the complex cation of 1 (hydrogen atoms and
BF4 anion has been removed for clarity).
Table 1
Summary of crystal data and crystal structure analysis for complex 1
Empirical formula
Formula weight
Color, shape
Crystal size (mm)
Crystal system
Space group
C55H43BF4N6OP2Ru
1053.81
Orange, plate
0.35×0.25×0.10
Monoclinic
P21/n
,
a (A)
17.810(6)
22.233(9)
12.156(4
90.06(3)
4813(2)
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
4
Dcalc (g cm−3
)
1.454
4.45
2152.00
7181(Rint=0.1082)
3626
421
0.0784
0.0916
Table 2
m(Mo–Ka) (cm−1
F(000)
)
Selected bond angles (°) for complex 1 (estimated S.D.s are given in
parentheses)
Unique reflections
Observed reflections (I\3|)
Number of parameters
P(1)ꢁRu(1)ꢁP(2)
P(1)ꢁRu(1)ꢁN(4)
P(1)ꢁRu(1)ꢁH(1)
P(2)ꢁRu(1)ꢁN(4)
P(2)ꢁRu(1)ꢁH(1)
N(1)ꢁRu(1)ꢁC(1)
N(4)ꢁRu(1)ꢁC(1)
C(1)ꢁRu(1)ꢁH(1)
173.4(1)
95.3(3)
94.4151
86.7(3)
79.2516
104.5(6)
178.7(6)
88.3770
P(1)ꢁRu(1)ꢁN(1)
P(1)ꢁRu(1)ꢁC(1)
P(2)ꢁRu(1)ꢁN(1)
P(2)ꢁRu(1)ꢁC(1)
N(1)ꢁRu(1)ꢁN(4)
N(1)ꢁRu(1)ꢁH(1)
N(4)ꢁRu(1)ꢁH(1)
93.4(3)
85.8(5)
93.2(3)
92.2(5)
76.1(4)
165.4153
90.9514
a
R
Rw (w=|−F 2
)
b
Goodness-of-fit
Max/min residuals (e A
2.312
+1.26, −1.16
−3
,
)
a R=S(Fo−Fc)/SFo.
b Rw=[Sw(Fo2−F2c)2/S(Fo2)]1/2
.
Table 3
,
the above plane. The N(1)ꢁRu(1)ꢁN(4) angle of
76.1(4)° suggested inward bending of the coordinated
pyridyl group. The smaller value of N(1)ꢁRu(1)ꢁN(4)
bite angle 76.1(4)° as compared to the ideal value of 90°
is probably the source of observed distortion. The
Selected bond lengths (A) for the complex 1 (estimated S.D.s are
given in parentheses)
Ru(1)ꢁP(1)
Ru(1)ꢁN(1)
Ru(1)ꢁC(1)
2.347(4)
2.25(1)
1.81(1)
Ru(1)ꢁP(2)
Ru(1)ꢁN(4)
Ru(1)ꢁH(1)
2.385(4)
2.1688(10)
1.4582
,
Ru(1) to central triazine N(1) bond length is 2.25(1) A

M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
45
stage it has not been possible for us to confirm the
3.2. Preparation of the complexes
structure of any of the binuclear complexes by single
crystal X-ray diffraction studies. More detailed work in
this direction is in progress in our laboratory.
3.2.1. Preparation of [RuH(CO)(PPh3)2(tptz)]BF4 (1)
A suspension of [RuH(CO)Cl(PPh3)3] (955 mg, 1
mmol) in MeOH (60 ml) was treated with tptz (312 mg,
1 mmol) and the resulting solution was heated under
reflux for ꢀ20 h. The precursor complex
[RuH(CO)Cl(PPh3)3] slowly dissolved and gave a bright
orange–red solution. It was cooled to r.t. and filtered
through celite to remove any solid residue. Saturated
solution of NH4BF4 in methanol (25 ml) was added to
the filtrate, rotaporated to about 25 ml, and was left in
3. Experimental
All the reactions were carried out under nitrogen
atmosphere and with deaerated solvents. The solvents
were of AR grade and were purified by standard proce-
dures prior to their use. Electrochemical data of the
complexes were obtained in MeCN which was pre-
passed through activated neutral alumina (previously
dried at 110 °C for 24 h). 2,3-Bis(2-pyridyl)-pyrazine,
3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, 2,4,6-tris(2-pyridyl)-
1,3,5-triazine, ammonium tetrafluoroborate, ammo-
nium hexafluorophosphate, ruthenium(III) chloride
hydrate (all Aldrich) and tetrabutylammonium perchlo-
rate (Fluka) were used as received without further
purification. The precursor complex [RuH(CO)Cl-
(PPh3)3] was prepared and purified following the litera-
ture procedure [18].
a
refrigerator for slow crystallization. Crystalline
product appeared in a couple of days quantitatively.
The crystals were separated by filtration, washed with
MeOH, Et2O, and dried in vacuo. Yield: 80% (868 mg);
Anal. Found: C, 62.95; H, 4.13; N, 7.60. Calc. for
C55H43BF4N6OP2Ru: C, 62.67; H, 4.08; N, 7.97%.
ESMS (m/z): 967.2 Calc. for [RuH(CO)(PPh3)2(tptz)]+
(968). FABMS m/z obs. (calc.): 967 (967), 704 (704),
675 (675), 414 ( 413); IR (cm−1, nujol): 2005 w(RuꢁH),
1955 w(CO), 1635, 1575, 1537, 1500, 1433, 1363, 1311,
1155, 1033, 995, 848, 746, 696 (bands due to tptz, PPh3,
1
and counter anion BF4−); H-NMR (l ppm, acetone-d6,
300 MHz, 25 °C): 8.92 (d, 1H, 4.2 Hz), 8.60 (d, 1H, 7.8
Hz), 8.14 (t, 3H, 6.6 Hz), 7.92 (t, 1H, 6.6 Hz), 7.72 (t,
1H, 7.2 Hz), 7.52 (s, 1H), −11.93 (t, 1H, 29.4 Hz);
31P{1H}: 46.54 (s); UV–vis (umax nm): 441, 389, 335.
3.1. Physical measurements
Microanalyses were performed by the micro-analyti-
cal section of the Regional Sophisticated Instrumenta-
tion Centre, Central Drug Research Institute,
Lucknow. Conductivity measurements were made on a
Systronics-306 conductivity bridge. Infrared spectra
and electronic spectra were recorded on Shimadzu-
8201PC and Shimadzu-UV-160 spectrophotometers, re-
spectively. 1H-, 1H–1H-COSY, 13C- and 31P-NMR
spectra were recorded on a Bruker DRX-300 NMR
instrument. The ESMS were recorded on a Micromass-
Quattro-II triple quadrupole mass spectrometer. The
samples were introduced into the ESI source through a
syringe pump at 0.4 ml h−1. The ESI capillary was 3.5
kV and cone-voltage 25–50 V. The spectra were col-
lected in 4 s scans and print outs are averaged spectra
of 5–10 scans. FAB mass spectra were recorded on a
JEOL SX 102/DA 6000 mass spectrometer using Xenon
(6 kV, 10 mA) as the FAB gas. The accelerating voltage
was 10 kV and the spectra were recorded at room
temperature (r.t.) with m-nitrobenzyl alcohol as the
matrix. The cyclic voltammograms were recorded on a
Solartron-1287 electrochemical system in deaerated
MeCN in presence of 0.1 M tetrabutylammonium per-
chlorate as supporting electrolyte using three electrode
assembly at different scan rates, with Pt working elec-
trode, Pt wire counter electrode and Ag ꢀ AgCl refer-
ence electrodes.
3.2.2. Preparation of [RuH(CO)(PPh3)2(bppz)]BF4 (2)
Complex 2 was prepared by the same method as
described for complex 1 starting from [RuH(CO)Cl-
(PPh3)3] (477 mg, 0.5 mmol) and bppz (117 mg, 0.5
mmol). The complex separated as bright yellow needles.
Yield: 75% (366 mg, 0.75 mmol); Anal. Found: C,
63.16; H, 4.23; N, 5.34. Calc. for C51H41BF4N4OP2Ru:
C, 62.76; H, 4.20; N, 5.74%. ESMS (m/z): 889.1 (Calc.
for [RuH(CO)(PPh3)2(bppz)]+ (889); IR (cm−1, nujol):
2003 w(RuꢁH), 1960 w(CO), 1590, 1572, 1555, 1548,
1520, 1445, 1365, 1315, 1252, 1160, 1030, 986, 840, 735,
690, (bands due to bppz, PPh3 and counter anion BF−4 );
1H-NMR (l ppm, acetone-d6, 300 MHz, 25 °C): 9.15
(d), 8.62 (d), 8.16 (m), 8.12–7.8 (m), 7.62–7.59 (m),
7.42–6.96 (br, m), −11.3 (t); 31P{1H} l 50.95 ppm (s);
UV–vis (umax nm): 426, 336, 298.
3.2.3. Preparation of [RuH(CO)(PPh3)2(bppz)]PF6 (3)
Complex 3 was prepared by the same method as
described for complex 2 starting from [RuH(CO)Cl-
(PPh3)3] (477 mg, 0.5 mmol) and bppz (117 mg, 0.5
mmol). It separated as bright yellow needles. Yield:
75% (366 mg, 0.75 mmol); Anal. Found: C, 58.69; H,
4.21; N, 5.25. Calc. for C51H41F6N4OP3Ru: C, 59.24; H,
3.96; N, 5.42%. FABMS (m/z): 889.1 (Calc. for
[RuH(CO)(PPh3)2(bppz)]+ (889); UV–vis (umax nm):
426, 336, 298.

46
M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
3.2.4. Preparation of [RuH(CO)(PPh3)2(bptz)]PF6 (4)
Complex 4 was prepared following the above proce-
dure starting from [RuH(CO)Cl(PPh3)3] (477 mg, 0.5
mmol) and bptz (118 mg, 0.5 mmol). Red–brown crys-
tals separated out. Yield of the complex was found to
be very poor, ꢀ40% (390 mg, 0.4 mmol). Anal. Found:
C, 56.7; H, 3.76; N, 7.35. Calc. for C49H39F6N6OP3Ru:
C, 56.7; H, 3.96; N, 8.10%. IR (cm−1, nujol): 2000
w(RuꢁH), 1949 w(CO), 1627, 1575, 1539, 1502, 1477,
1433, 1359, 1311, 1255, 1184, 1159, 1091, 840, 746, 698
(characteristic bands due to bptz, PPh3, and counter
3.2.7. Preparation of
[RuH(CO)(PPh3)2(bppz)(p6-C10H14)RuCl](PF6)2 (7)
Complex 7 was prepared by reaction of [RuH(CO)-
(PPh3)2(bppz)]PF6 (517 mg, 0.5 mmol) in MeOH (20
ml) with [{Ru(h6-C10H14)(m-Cl)Cl}2] following the
above procedure. It appeared in the form of a brown–
red crystalline solid. Yield: 88%; Anal. Found: C, 48.85;
H, 3.91; N, 3.71. Calc. for C61H55ClF12N4OP4Ru2: C,
49.07; H, 3.79; N, 3.86%. FABMS (m/z): 1307, (calc.
for {[RuH(CO)(PPh3)2(bppz)(h6-C10H14)RuCl](PF6)}+
1304); 1H-NMR (l ppm, CDCl3, 300 MHz, 25 °C): 9.26
(d), 8.84 (d), 8.48 (m), 8.17–7.88 (m), 7.84–7.36 (m),
7.40–6.92 (br, m), 5.59–5.33 (dd), 2.92 (sep), 2.13 (s)
1.25 (dd), −10.50 (t); 31P{1H}: l 50.82 ppm (s); UV–
vis (umax nm): 475, 360, 315.
1
anion PF−6 ); H-NMR (l ppm, CDCl3, 300 MHz, 25
°C): 8.92 (d), 8.78 (d), 8.74 (d), 8.70 (d), 8.11 (t), 8.20
(t), 7.4–7.18 (br, m), 7.02 (t), −12.8 (t, RuꢁH);
13C{1H}: l 204 (carbonyl carbon), 153.89, 150.95,
138.77, 137.85, 128.98, 128.22, 127.08, 126.83 ppm (car-
bons of the bptz ligand); 31P{1H}: l 48.6 ppm (s);
UV–vis (umax nm): 399, 394, 241.
3.2.8. Preparation of
[RuH(CO)(PPh3)2(bppz)(p6-C6Me6)RuCl](PF6)2 (8)
It was prepared by reaction of [RuH(CO)(PPh3)2-
(bppz)]PF6 (517 mg, 0.5 mmol) complex in MeOH (20
ml) with [{Ru(h6-C6Me6)(m-Cl)Cl}2]. It separated as
dark tan-colored microcrystals. Yield: 70%. Anal.
Found: C, 49.76; H, 4.04; N, 3.79. Calc. for
C63H59ClF12N4OP4Ru2: C, 50.15; H, 3.99; N, 3.78%.
FABMS (m/z); 1333, (calc. for {[RuH(CO)(PPh3)2-
(bppz)(h6-C6Me6)RuCl](PF6)}+ 1333); 1H-NMR (l
ppm, CDCl3, 300 MHz, 25 °C), 9.26 (d), 8.84(d), 8.48
(m), 8.17–7.88 (m), 7.84–7.36 (m), 7.40–6.92 (br, m),
5.59–5.33 (dd), 2.92 (sep), 2.13 (s) 1.25 (dd), −10.50
(t); 31P{1H}: l 50.82 ppm (s); UV–vis (umax nm): 475,
360, 315.
3.2.5. Preparation of
[RuH(CO)(PPh3)2(bppz)PtCl2]PF6 (5)
Complex 3 [RuH(CO)(PPh3)2(bppz)]PF6 (517 mg, 0.5
mmol) was dissolved in MeOH (20 ml) and filtered to
remove any solid residue. To the filtrate K2PtCl4 (208
mg, 0.5 mmol) was added and the solution was heated
under reflux for 24 h. It was cooled to r.t. and filtered.
To the red–brown solution thus obtained, a solution of
NH4PF6 (163 mg, 1 mmol) dissolved in methanol (10
ml) was added. It was rotaporated to 10 ml and left
overnight. A brownish red colored microcrystalline
complex appeared. These were filtered, washed with
MeOH, Et2O and dried in vacuo. Yield 78%; Anal.
Found: C, 54.51; H, 3.77; N, 5.04. Calc. for
C51H41Cl2F6N4OP3PtRu: C, 54.07; H, 3.36; N, 4.75%.
FABMS (m/z); 1155 (calc. for [RuH(CO)(PPh3)2-
(bppz)PtCl2]+, 1154); IR (cm−1, nujol): 2006 w(RuꢁH),
1955 w(CO), 1585, 1575, 1550, 1540, 1520, 1440, 1365,
1312, 1250, 1160, 1035, 986, 845, 735, 690, (bands due
3.2.9. Preparation of
[RuH(CO)(PPh3)2(bppz)(p5-C5H5)(PPh3)Ru](PF6)2 (9)
Complex 9 was prepared by reaction of [RuH(CO)-
(PPh3)2(bppz)]PF6 (517 mg, 0.5 mmol) complex in
MeOH (20 ml) with [RuCl(h5-C5H5)(PPh3)2] (364 mg,
0.5 mmol). It separated as a dark black colored com-
plex. Yield 70%. Anal. Found: C, 55.20; H, 3.82; N,
3.45. Calc. for C74H61F12N4OP5Ru2: C, 55.22; H, 3.79;
1
to bppz, PPh3 and counter anion PF−6 ); H-NMR (l
1
N, 3.48%. H-NMR (l ppm, DMSO-d6, 300 MHz, 25
ppm, acetone-d6, 300 MHz, 25 °C): 9.20 (d), 8.65 (d),
8.16 (m), 8.12–7.80 (m), 7.65–7.52 (m), 7.40–6.94 (br,
m), −11.3 (t); 31P{1H}: l 51.20ppm (s); UV–vis (umax
nm): 480, 381, 315.
°C): 9.60 (d), 9.17 (d), 8.18 (m), 8.12–7.80 (m), 7.88–
6.94 (br, m), 5.4 (sharp s, Cp), −11.9 (t); UV–vis.
(umax nm): 544, 362, 315.
3.2.10. Preparation of
[RuH(CO)(PPh3)2(bppz)Rh(p5-C5Me5)Cl](PF6)2 (10)
Complex 10 was prepared following the above proce-
dure from [RuH(CO)(PPh3)2(bppz)]PF6 (517 mg, 0.5
mmol) and [{(h5-C5Me5)RhCl2}2] (314 mg, 0.5 mmol).
It separated as a red microcrystalline solid. Yield: 75%;
Anal. Found: C, 49.72; H, 3.88; N, 3.87. Calc. for
C61H56ClF12N4OP4RhRu: C, 50.41; H, 3.85; N, 3.85%.
FABMS (m/z): 1309, (calc. for {[RuH(CO)(PPh3)2-
(bppz)Rh(h5-C5Me5)Cl](PF6)}+, 1307); 1H-NMR (l
ppm, DMSO-d6, 300 MHz, 25 °C): 9.16 (d), 8.82 (d),
3.2.6. Preparation of
[RuH(CO)(PPh3)2(bppz)PdCl2](PF6) (6)
Complex 6 was prepared by the above procedure
starting from [RuH(CO)(PPh3)2(bppz)]PF6 (517 mg, 0.5
mmol) and [PdCl2(benzonitrile)2] (207 mg, 0.5 mmol). It
separated as black crystalline product. Yield: 72%;
Anal. Found: C, 50.53; H, 3.38; N, 4.62. Calc. for
C92H76F6N4OP5PdRu2: C, 50.03; H, 3.42; N, 4.72%.
UV–vis (umax nm): 472, 352, 315.

M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
47
8.45 (m), 8.13–7.81 (m), 7.84–7.36 (m), 7.36–6.94 (br,
m), 1.60(s, C5Me5) −11.2 (t); 31P{1H}: l 50.62 ppm (s);
UV–vis (umax nm): 465, 360, 315.
and the Head, Department of Chemistry, Awadhesh
Pratap Singh University, Rewa for extending labora-
tory facilities.
3.3. X-ray structure determination of
[RuH(CO)(PPh3)2(tptz)]BF4
References
A crystal suitable for X-ray diffraction analysis was
mounted onto a glass fiber and transferred to an
AFC6S-Rigaku automatic diffractometer (T=290 K,
Mo–Ka radiation, graphite monochromator, u=
[1] (a) K. Kalyansundaram, Photochemistry of Polypyridine and
Porphyrin Complexes, Academic Press, London, 1991;
(b) V. Balzani, F. Scandola, Supramolecular Photochemistry,
Horwood, Chichester, UK, 1991;
(c) J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim,
1995;
,
0.71073 A). Accurate unit cell parameters and an orien-
tation matrix were determined by least-squares fitting
from the settings of 25 high-angle reflections. Crystal
data and details on data collection and refinements are
given in Table 1. Data were collected by the ꢀ/2q scan
method. Lorentz and polarization corrections were ap-
plied. Decay and semi-empirical absorption correction
(„ method) were also applied. Patterson methods and
subsequent expansion of the models using DIRDIF [19]
solved the structure. Reflections having I\3|(I) were
used for structure refinement. Ru, N and C atoms of
the N, N%ꢁC15H12N6 ligand were anisotropically refined
and the remaining non-hydrogen atoms were isotropi-
cally refined. The H(1) was localized in a regular differ-
ence Fourier map and the remaining hydrogen atoms
included at idealized positions. The hydrogen atoms
were not refined. All calculations for data reduction,
structure solution, and refinement were carried out on a
VAX 3520 computer at the Servicio Central de Ciencia
y Technologia de la Universidad de Cadiz, using the
TEXSAN [20] software system and ORTEP [21] for plot-
(d) V. Balzani, A. Juris, M. Venturi, S. Campagna, S. Serroni,
Chem. Rev. 96 (1996) 96;
(e) A. Kirsch-De Mesmaeker, G.P. Leconte, G.M. Kelly, Top.
Curr. Chem. 177 (1996) 25;
(f) L. De Cola, P. Belser, Coord. Chem. Rev. 117 (1998) 301;
(g) F. Bargiletti, L. Flamigni, Chem. Soc. Rev. 29 (2000) 1.
[2] (a) R.E. Dessy, J.C. Charkoundian, T.P. Abeles, A.L. Rhein-
gold, J. Am. Chem. Soc. 92 (1970) 3947;
(b) C. Cruetz, N. Sutin, B.S. Brunschwis, J. Am. Chem. Soc.
101 (1979) 1297;
(c) G.M. Brown, B.S. Brunschwis, C. Creutz, J.N. Endicoff, N.
Sutin, J. Am. Chem. Soc. 101 (1979) 1298.
[3] (a) N. Gupta, N. Grover, G.A. Neyhart, P. Singh, H.H. Thorp,
Inorg. Chem. 32 (1993) 310;
(b) E. Brauns, W. Sumner, J.A. Clark, S.M. Molnar, Y.
Kawanishi, K.J. Brewer, Inorg. Chem. 36 (1997) 2861;
(c) J.-D. Lee, L.M. Vrana, E.R. Bullock, K.J. Brewer, Inorg.
Chem. 37 (1998) 3575;
(d) C. Ceroni, F. Paolucci, S. Roffia, S. Serroni, S. Campagna,
A.J. Bard, Inorg. Chem. 37 (1998) 2829;
(e) A. Klein, V. Kasack, R. Reinhardt, S. Torsten, T. Scheiring,
S. Zalis, J. Fiedler, W. Kaim, J. Chem. Soc. Dalton Trans. 0
(1999) 575;
(f) P. Paul, B. Tyagi, A.K. Bilakhia, D. Parthsarthi, E. Suresh,
Inorg. Chem. 39 (2000) 14;
ting. Maximum and minimum peaks in the final differ-
−3
,
ence Fourier mass were +1.26 and −1.16 e A
.
(g) G. Albano, P. Belser, C. Dual, Inorg. Chem. 40 (2001)
1408.
[4] D.S. Pandey, A.N. Sahay, M.G. Walwalkar, J. Organomet.
Chem. 613 (2000) 250 and references therein.
[5] (a) B. Hasenknopf, J.-M. Lehn, N. Boumediene, G.A. Dupont,
A. Van Dorsselaer, B. Kneisel, D. Fenske, J. Am. Chem. Soc.
119 (1997) 10956;
(b) E. Ishow, A. Gourdon, J.-P. Launay, C. Chiroboli, F.
Scandola, Inorg. Chem. 38 (1999) 1504.
[6] (a) R.P. Thummel, Y. Jahng, Inorg. Chem. 25 (1986) 2527;
(b) G.S. Hanan, C.R. Arana, J.-M. Lehn, G. Baum, D. Fenske,
Chem. Eur. J. 2 (1996) 1292.
4. Supplementary material
Crystallographic data for the structural analysis in
CIF format have been deposited with the Cambridge
Crystallographic Data Centre, CCDC no. 140169 for
the complex [RuH(CO)(PPh3)2(tptz)]BF4. 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).
[7] D.K. Gupta, O.S. Sisodia, A.N. Sahay, D.S. Pandey, Synth.
React. Inorg. Metal-Org. Chem. 28 (1998) 355.
[8] P. Didier, I. Ortmans, A. Kirsch- De Mesmaeker, R.J. Watts,
Inorg. Chem. 34 (1993) 5239.
Acknowledgements
[9] R.M. Berger, D.D. Elis II, Inorg. Chim. Acta 241 (1996) 1.
[10] B.P. Sullivan, D.J. Salmon, T.J. Meyer, Inorg. Chem. 17 (1978)
3334.
[11] R. Rillema, K.B. Mack, Inorg. Chem. 21 (1982) 3849.
[12] (a) L. Vogler, B. Scott, K.J. Brewer, Inorg. Chem. 36 (1993)
898;
Thanks are due to University Grants Commission,
New Delhi for providing financial assistance (F-12-21/
97). Thanks are also due to RSIC, Central Drug Re-
search Institute, Lucknow, for providing analytical and
spectral facilities, Dr. P.C. Pandey, Department of
Chemistry, B.H.U. Varanasi for electrochemical data
(b) S.M. Molnar, K.R. Nevile, G.E. Gensen, K.J. Brewer, In-
org. Chim. Acta 206 (1993) 69;
(c) S.D. Earnst, W. Kaim, Inorg. Chem. 28 (1989) 1520.

48
M. Chandra et al. / Journal of Organometallic Chemistry 648 (2002) 39–48
[13] (a) H. Ishida, K. Tanaka, T. Tanaka, Chem. Lett. (1995) 405;
(b) H. Ishida, K. Tanaka, T. Tanaka, Organometallics 6 (1987)
181;
(c) C.M. Bollinger, B.P. Sullivan, D. Conrad, J.A. Gilbert, N.
Storg, T.J. Meyer, J. Chem. Soc. Chem. Commun. (1985) 796.
[14] P. Ghosh, A. Chakravorty, Inorg. Chem. 36 (1997) 64 and
references therein.
L.A. Oro, J. Chem. Soc. Dalton Trans. (1995) 2171;
(c) M.R. Churchill, K.M. Keil, F.V. Bright, S. Pandey, G.A.
Baker, J.B. Keister, Inorg. Chem. 39 (2000) 5807.
[17] A. Cantarero, J.M. Amigo, J. Faus, M. Julve, T. Debaerde-
maeker, J. Chem. Soc. Dalton Trans. (1988) 2033.
[18] N. Ahmad, J.J. Levison, S.D. Robinson, M.F. Uttley, Inorg.
Synth. 15 (1974) 45.
[15] (a) M.F. McGuiggan, L.H. Pignolet, Inorg. Chem. 21 (1982)
2523;
[19] P.T. Beursken, DIRDIF, Technical Report 1984/1, Crystallogra-
phy Laboratory Toernooiveld, 1984.
(b) A. Sahajpal, S.D. Robinson, M.A. Mazid, M. Motevalli,
M.B. Hursthouse, J. Chem. Soc. Dalton Trans. (1990) 2119.
[16] (a) G.J. Philip, J.R. Steven, C.-L- Lee, B.R. Jamer, Inorg. Chem.
30 (1991) 4617;
[20] TEXSAN, Single-Crystal Structure Analysis Software, Version 5.0,
Molecular Structure Corporation, Houston Texas, TX,
1989.
[21] C.K. Johnson, ORTEP, A Thermal Ellipsoid Plotting Program,
Oak Ridge National Laboratory, Oak Ridge, TN, 1965.
(b) R. Atencio, B. Christina, M.A. Esteruelas, J.L. Fernando,