Paramagnetic ruthenium(III) ortho-metallated complexes. Synthesis, spectroscopic and redox properties

Article abstract of DOI:10.1016/S0022-328X(99)00261-2

The reaction of (CS)Cl(PPh₃)₂Ru^II (μ-Cl)₂ Ru^II (PPh₃)₂Cl(CS), A with the phenolic Schiff base ligands o-(OH)C₆H₄C(H)=N-C₆H₄(R), (R=p-OMe, Me, H, Cl, NO₂; H₂L¹-H₂L⁵) in methanol under aerobic conditions afforded the complexes Ru^III(HL)₂(PPh₃)Cl, 1 and Ru^III(L)(PPh₃)(CH₃OH)Cl, 2. In complexes 1 both the ligands (HL^-) are bound to the metal center at the deprotonated phenolic oxygen and azomethine nitrogen and in the complexes 2 the L^2- is in tridentate C,N,O mode where cyclometallation takes place from the ortho carbon atom of the amine fragment of H₂L. During the reaction the metal ion is oxidized from the starting Ru^II in A to Ru^III in the products 1 and 2. The complexes (1 and 2) are nonconducting and behave as one-electron paramagnets. Complexes display rhombic EPR spectra that have been analyzed to furnish values of axial (?) and rhombic (V) distortion parameters as well as energies of the two expected ligand field transitions (ν₁ and ν₂) within the t₂ shell. One of the transitions (ν₂) has been observed in the predicted region. The complexes exhibit moderately strong ligand-to-metal charge-transfer transition in the visible region and intraligand transitions in the UV region. The complexes are electroactive and show ruthenium (IV)-ruthenium(III) (E_1/2, 0.75-0.88 V vs. Ag/AgCl) and ruthenium(III)-ruthenium(II) (E_1/2, -0.42 to -0.59 V) couples. The E_1/2 values vary linearly with the Hammett constant of the substituents R. The role of coordination of phenolato function in stabilizing the unusual paramagnetic ruthenium(III) oxidation state in the complexes 2 is noted.

Full text of DOI:10.1016/S0022-328X(99)00261-2

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Journal of Organometallic Chemistry 586 (1999) 176–183
Paramagnetic ruthenium(III) ortho-metallated complexes.
Synthesis, spectroscopic and redox properties
Pradip Munshi, Ramapati Samanta, Goutam Kumar Lahiri *
Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
Received 3 March 1999; received in revised form 5 May 1999
Abstract
The reaction of (CS)Cl(PPh3)2RuII (m-Cl)2 RuII (PPh3)2Cl(CS), A with the phenolic Schiff base ligands o-(OH)C6H4C(H)ꢀN-
C6H4(R), (R=p-OMe, Me, H, Cl, NO2; H2L1–H2L5) in methanol under aerobic conditions afforded the complexes
RuIII(HL)2(PPh3)Cl, 1 and RuIII(L)(PPh3)(CH3OH)Cl, 2. In complexes 1 both the ligands (HL−) are bound to the metal center
at the deprotonated phenolic oxygen and azomethine nitrogen and in the complexes 2 the L2− is in tridentate C,N,O mode where
cyclometallation takes place from the ortho carbon atom of the amine fragment of H2L. During the reaction the metal ion is
oxidized from the starting RuII in A to RuIII in the products 1 and 2. The complexes (1 and 2) are nonconducting and behave
as one-electron paramagnets. Complexes display rhombic EPR spectra that have been analyzed to furnish values of axial (ꢀ) and
rhombic (V) distortion parameters as well as energies of the two expected ligand field transitions (w1 and w2) within the t2 shell.
One of the transitions (w2) has been observed in the predicted region. The complexes exhibit moderately strong ligand-to-metal
charge-transfer transition in the visible region and intraligand transitions in the UV region. The complexes are electroactive and
show ruthenium (IV)–ruthenium(III) (E1/2, 0.75–0.88 V vs. Ag/AgCl) and ruthenium(III)–ruthenium(II) (E1/2, −0.42 to −0.59
V) couples. The E1/2 values vary linearly with the Hammett constant of the substituents R. The role of coordination of phenolato
function in stabilizing the unusual paramagnetic ruthenium(III) oxidation state in the complexes 2 is noted. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Ruthenuim(III); Ortho-metallation; Schiff base; Paramagnetic; EPR
to report the syntheses of a group of such complexes of
the type RuIII(C, N, O)(PPh3)(Cl)(CH3OH) (2). The
complexes 2 are formed along with the noncyclometal-
lated complex of the type RuIII(O,N)2(PPh3)Cl (1) via
the cleavage of bridging chloride groups of the m-
dichlorodiruthenium starting complex (A) in the pres-
ence of phenolic Schiff base ligand H2L. Herein the
synthesis, spectroscopic characterization and electron-
transfer properties of the complexes (1 and 2) have been
described.
1. Introduction
Ruthenium cyclometallated complexes are virtually
restricted to the diamagnetic bivalent ruthenium(II)
oxidation state inspite of the fact that the variable
valence property pervades the chemistry of ruthenium
[1–17]. Although the coordination chemistry of triva-
lent ruthenium(III) has been developed tremendously in
recent years, the corresponding paramagnetic rutheniu-
m(III) organometallic species are rare [18]. Only a few
authentic paramagnetic trivalent ruthenium organo-
metallic complexes are known up to now [19–34].
The present work originates from our interest to
generate a new class of paramagnetic ruthenium(III)
cyclometallated complexes. In this article we would like
2. Results and discussion
2.1. Synthesis and characterization of the complexes
The reaction of phenolic Schiff base ligand H2L with
the dichloro bridged diruthenium starting complex A in
a ratio of 5:1 in boiling methanol for 5 h results in a
* Corresponding author. Fax: +91-22-5783480.
E-mail address: lahiri@ether.chem.iitb.ernet.in (G. Kumar Lahiri)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00261-2

P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
177
green solution. Chromatographic purification of the
green solution on a silica gel column yield yellowish
green colored cyclometallated complex 2 along with the
bluish green noncyclometallated complex 1 in the pure
solid state (Scheme 1).
methanol group of 2 can be replaced by other
monodentate ligands such as carbon monoxide,
triphenylphosphine or pyridine.
The microanalytical data of the complexes are in
good agreement with the calculated values (Table 1).
The conductivity measurements of the complexes in
acetonitrile, dimethylformamide and methanol indicate
that all the complexes (1 and 2) are electrically non-
conducting.
The formations of complexes 1 and 2 involve the
cleavage of m-chloro bonds of A followed by the re-
placement of one phosphine, thiocarbonyl (CS) and
terminal chloride from the resultant monomeric ruthe-
nium species by two (HL−) and one L2−, respectively.
Here in the course of the reaction one metal–carbon
s-bond has been formed in 2 from the pendant phenyl
ring of the coordinated ligand L2−. During this conver-
sion process the ruthenium ion is oxidized from its
starting bivalent state in A to the trivalent state in both
the products 1 and 2. Since the reaction (Scheme 1)
takes place preferentially under atmospheric conditions,
the oxygen in air may be responsible for the metal
oxidation (see later). It may be noted that the cleavage
of m-chloro bonds of A and the partial or full replace-
ment of PPh3, CS and terminal Cl− by the azopyridine,
2-2%-bipyridine or phenanthroline ligands have been
observed recently [35,36]. The formation of four and
five membered stable rutheniumꢁcarbon s-bond from
the pendant phenyl ring of azo and imine based ligands
have been documented in the literature [15,16,31,
33,34,37].
The FAB mass spectra of two representative com-
plexes of each class (1a, 1b, and 2a, 2b) were recorded.
The representative spectra are shown in Fig. 1. The
maximum peaks are observed at m/z, 790, 819, 626, 639
for the complexes 1a, 1b, 2a and 2b, respectively, which
match well with the corresponding calculated masses
(calculated molecular weight: 1a, 790.6; 1b, 818.6; 2a,
625.6; 2b, 639.6).
Thermogravimetric analyses (TGA) of one represen-
tative complex of each class (1d and 2d) were studied.
The complexes 1d and 2d show three- and four-step
decomposition patterns respectively. The three succes-
sive decompositions take place for 1d near 175, 288 and
440°C corresponding to the weight loss of one chlorine,
one phosphine and two ligands (HL−), respectively.
The TGA of complex 2d shows one additional decom-
position step due to the coordinated methanol. The
four successive decompositions take place at 85, 170,
290 and 450°C corresponding to the weight loss of one
each CH3OH, Cl−, PPh3 and L2− respectively. The
differential thermal analyses (DTA) of the complexes
(1d and 2d) further confirm the above decomposition
patterns. It display successive three and four exothermic
peaks for 1d and 2d, respectively, as expected.
To generalize the reaction in Scheme 1 five substi-
tuted ligands (abbreviated as H2L1ꢁH2L5) have been
used. The conversion of isolated complex 1 to 2 in
methanol solution and the transformation of isolated
complex 2 to 1 in the presence of excess H2L did not
take place even under heating condition. However, the
Scheme 1.

178
P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
Table 1
Microanalytical, selected infrared and electronic spectral data
Compound
Elemental analysis (%) a
IR b, wmax (cm−1
)
Electronic spectral data c
C
H
N
CꢀN
RuꢁCl
u (nm) (m, dm3 mol−1 cm−1
)
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
65.77(65.81)
67.28(67.11)
66.85(66.79)
63.91(64.00)
63.31(63.19)
60.19(60.32)
61.70(61.82)
61.37(61.29)
58.23(58.10)
57.05(57.19)
4.51(4.54)
4.60(4.63)
4.55(4.46)
4.18(4.15)
4.05(4.09)
4.67(4.75)
4.81(4.87)
4.72(4.66)
4.29(4.26)
4.18(4.20)
3.32(3.41)
3.31(3.48)
3.47(3.54)
3.49(3.39)
5.11(5.02)
2.22(2.13)
2.02(2.18)
2.38(2.23)
2.25(2.12)
4.31(4.17)
1595
1597
1597
1594
1598
1596
1597
1598
1594
1595
330
335
337
337
335
340
342
339
337
339
617(6810), 359(56370), 304(67822)
622(5972), 354(41818), 304(48770)
619(4545), 345(34793), 304(34839)
651(2082), 346(11112), 301(15294)
690(8222), 345(23019), 304(23535)
621(3950), 404(10577), 304(21056)
635(5509), 369(33779), 304(56158)
686(4581), 346(21695), 301(24582)
690(4004), 345(19304), 304(18608)
674(3544), 359(40835), 305(43589)
a Calculated values are in parentheses.
b In KBr disk.
c In dichloromethane.
All our attempts to grow suitable single crystals for
X-ray characterization of 2 have failed. However, ele-
mental analysis and all other physical data are in
agreement with the gross formulation of 2.
2.3. Magnetism, EPR and near-IR spectra
The complexes (1 and 2) are uniformly paramagnetic
with magnetic moments correspond to one unpaired
electron at 298 K (low-spin RuIII, t25g). The data are set
out in Table 2. The X-band EPR spectra of the com-
plexes in glassy 1:1 chloroformꢁtoluene solution (77 K)
is rhombic in nature with three distinct signals. The
representative spectra are shown in Fig. 3 and the g
values are listed in Table 2.
2.2. IR, UV–6is and NMR spectra
Selective IR frequencies are listed in Table 1. The
wCꢀN stretching frequency of the free ligands (H2L)
appears near 1650 cm’1, which has been shifted to
ꢀ1590 cm−1 in the complexes 1 and 2 in accordance
with the coordination of the azomethine function to the
metal ion [38]. Phosphine vibrations for the complexes
appear around 700 and 520 cm−1 [39]. A sharp band
near 340 cm−1 has been observed for all the complexes
due to wRuꢁCl stretching frequency.
The complexes (1 and 2) display one moderately
intense band in the region 600–700 nm (Table 1, Fig.
2). The position and intensity of the bands are sensitive
to the nature of the substituents present in the ligands
(Table 1). The observed visible-region band is believed
to represent ligand-to-matal charge-transfer (LMCT)
transition as is expected for low-spin ruthenium(III)
complexes of unsaturated ligands [40–42]. In the UV
region the complexes systematically exhibit two very
intense bands (Table 1), possibly due to ligand based
transitions [35].
The theory of EPR spectra of distorted octahedral
2
low-spin d5 (idealized t25g ground term T2g) complexes
is documented in the literature [31,33–35,37–39,42–
48]. The distortion of the pseudooctahedral complexes
can be expressed as the sum of axial (ꢀ) and rhombic
(V) components. The t2 orbital consists of the compo-
nents t02 (xy), t2+ (xz) and t2− (yz). The degeneracy of
the t2 orbital is partially removed by axial distortion
(ꢀ), which places t20 (b) above t2+/t2− (e). The superim-
posed rhombic distortion (V) then splits (e) further into
t2+ and t2−.
The analysis of the EPR spectrum using the g-tensor
theory of low-spin d5 ions provides the distortion
parameters (ꢀ and V) of the complex and energies of
two ligand field transitions (w1 and w2) that arise due to
optical transitions from ground to upper Kramers dou-
blets [31].
1H-NMR spectra of the complexes (1 and 2) in
CDCl3 solvent display very broad signals due to the
paramagnetic nature of the complexes, which has pre-
cluded the identification of the individual protons of
the complexes. However, a direct comparison of the
observed integration of the aliphatic proton signals
with that of the aromatic region signals reveals the
presence of the calculated number of aromatic protons.
31P-NMR spectra of both the complexes in CDCl3
solvent display one sharp signal near 30 ppm.
The EPR experiments provide only the absolute g
values and so neither their signs nor the correspondence
of g1, g2 or g3 to gx, gy or gz. are known. There are 48
possible combinations depending on the labeling of x,
y, z and signs chosen for the experimentally observed
EPR g values. In the present complexes we have consid-
ered the particular combination where g1 and g2 are
negative, g3 is positive and the order of magnitude
g1\g2\g3. This particular combination results in a
reasonable value of k (orbital reduction factor B1.0,

P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
179
Fig. 1. FAB mass spectra of (a) RuIII(HL2)2(PPh3)Cl, 1b and RuIII(L2)(PPh3)(CH3OH)Cl, 2b.
Table 2). The value of k for all other combinations of
g parameters does not satisfy the limit of k (kB1.0),
and is therefore not acceptable. The computed values
of axial distortion (ꢀ), rhombic distortion (V) and the
two ligand field transitions (w1 and w2) for the com-
plexes are listed in Table 2. The value for the spin–or-
bit coupling constant of ruthenium(III) is taken as
1000 cm−1 [42].
The calculated values of w1 and w2 are observed near
4000 and 9000 cm−1, respectively (Table 2). Experi-
mentally by near-IR spectra the w2 band is observed in
the expected positions (Table 2). In view of the ap-
proximations involved in the theory, the agreement
between the experimental and theoretical w2 values
(Table 2) is excellent. Due to the instrumental wave-
length scan limitation (maximum up to 2200 nm) it
has not been possible to check the w1 band properly.
However, the increase of absorption starting further
from 2000 nm for all the complexes gives clear indica-
tion of the presence of w1 band near the calculated
region. In general, here the axial distortion is 20–25%
more than the rhombic distortion. The complexes 1
and 2 thus behave as model ruthenium(III) complexes
possessing rhombic symmetry.
The complexes of type 1 exhibit one quasi-reversible
oxidative couple in the range 0.78–0.88 V and one
quasi-reversible reductive response in the range
−0.48“ −0.58 V [the difference between the oxida-
tion and reduction peak potentials (DEp) is observed
to be in the range 90–100 mV]. The one-electron na-
ture of the oxidative couple at the positive side of
Ag/AgCl is established with the help of constant po-
tential coulometry (Table 3). The oxidized complexes
1+ display cyclic voltammograms that are superpos-
able to those of the corresponding starting trivalent
complexes 1, suggesting that the oxidation process
here may be stereoretentive in nature. Thus the oxida-
tion process is assigned to ruthenium(III)ꢁ
ruthenium(IV) couple (Eq. (1)).
2.4. Redox properties
The redox properties of the complexes have been
studied in dichloromethane solution by cyclic voltam-
metry and differential pulse voltammetry using a plat-
inum working electrode. The complexes (1 and 2) are
electroactive with respective to the metal center only
and display the same two redox processes in the po-
tential range 91.5V vs. Ag/AgCl. Representative
voltammograms are shown in Fig. 4 and the potential
data are listed in Table 3.
Fig. 2. Electronic spectra of RuIII(HL4)2(PPh3)Cl, 1d (—) and
RuIII(L4)(PPh3)(CH3OH)Cl, 2d (---) in dichloromethane. Inset: elec-
tronic spectra of 1d (—) and 2d (---) in the range 2200–1000 nm.

180
P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
Table 2
Bulk magnetic moments a, g values b, distortion parameters and transition energies
Compound
veff, vB
g1
g2
g3
k
D (cm−1
)
V (cm−1
)
w1 (cm−1
)
w2 (cm−1
)
w2 (obs) (cm−1
)
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
1.97
1.99
1.99
1.95
1.93
1.95
1.94
1.95
1.99
1.96
−2.356
−2.370
−2.339
−2.371
−2.369
−2.339
−2.352
−2.325
−2.354
−2.352
−2.081
−2.099
−2.108
−2.107
−2.100
−2.067
−2.072
−2.082
−2.087
−2.100
1.874
1.897
1.896
1.891
1.903
1.852
1.900
1.887
1.882
1.881
0.648
0.741
0.699
0.735
0.759
0.579
0.691
0.628
0.667
0.675
6073
6834
6408
6482
7091
5462
7277
6267
6259
6053
5135
5832
4798
5242
6111
4464
6876
5067
5231
4700
3647
4043
4127
3987
4157
3384
3969
3864
3779
3834
8819
9909
8978
9271
10299
7892
10864
8974
9048
8583
8342 (110) c
(9471)(100) c
(8549)(90) c
(8988)(85) c
(9902)(80) c
c
(8100)(67)
(10410)(55) c
(8640)(68) c
(9530)(56) c
(9100)(72) c
a In solid state at 298 K.
b In 1:1 chloroformꢁtoluene glass at 77 K.
c Intensity (dm3 mol−1 cm−1) values are given in parantheses.
[RuIV(N,O)2(PPh3)Cl]+ +e− X [RuIII(N,O)2(PPh3)Cl]
Here for all the complexes (1 and 2) the separation in
1+
potential between the two successive redox processes
[Eqs. (1)/(2) and Eqs. (3)/(4)] is found to be around 1.3
V, which is in good agreement with the earlier observed
average potential difference between the RuIV/
RuIIIꢁRuIII/RuII couples (1.3–1.5 V) in mononuclear
ruthenium complexes having C, N, O, S, SR donor
centers [31,34,35,42,44,49].
The reduction potentials are sensitive to the nature of
the substituents present in the ligand frame. The plot of
E0298 vs. |R is linear (Fig. 5), where |R in the Hammett
constant of the substituents R.
1
(1)
Although the red–brown colored tetravalent rutheni-
um(IV) congener of 1 can be developed in solution by
bulk electrolysis, the 1+ species is not stable enough to
be isolated in the pure solid state at room temperature.
The one-electron nature of the reduction couple at
the negative side of Ag/AgCl is confirmed by a direct
comparison of the differential pulse current height of
this response with that of the previous one-electron
RuIII“RuIV process occurring at the positive side of
Ag/AgCl (Eq. (1)). The coulometric reduction of the
complexes 1 at a potential ꢀ200 mV negative to the
Epc of the corresponding reduction couple showed very
small coulomb count indicating that the reduced species
1− may be unstable even at the electrolysis time scale.
The reduction process is assigned to be rutheniu-
m(III)ꢁruthenium (II) reduction (Eq. (2)).
The coordination of the phenolato function in the
complexes possibly plays a crucial role to bring down
the ruthenium(III)ꢁruthenium(II) potential as low as
[RuIII(N,O)2(PPh3)Cl]+e− X [RuII(N,O)2(PPh3)Cl]−
1−
1
(2)
The complexes of type 2 display one oxidative and
one reductive quasi-reversible responses in the ranges
0.75“0.87 V and −0.43“ −0.60 V, respectively. The
one-electron nature of each of the couples is confirmed
with the help of constant potential coulometry (Table
3). The responses at positive and negative potentials are
respectively assigned to ruthenium(III)ꢁruthenium(IV)
and ruthenium(III)ꢁruthenium(II) couples, as in Eqs.
(3) and (4). The coulometrically generated oxidized
(2+) and reduced (2−) species are not stable at room
temperature.
[RuIV(C,N,O)(PPh3)(CH3OH)Cl]+e−
2+
X [RuIII(C,N,O)2(PPh3)(CH3OH)Cl]−
(3)
(4)
2
Fig. 3. X-band EPR spectra and t2 splittings of RuIII(HL1)2(PPh3)Cl,
1a (—) and RuIII(L1)(PPh3)(CH3OH)Cl, 2a (---) in chloroform–
toluene (1:1) glass at 77 K.
[RuIII(C,N,O)2(PPh3)(CH3OH)Cl]+e−
2
X [RuII(C,N,O)2(PPh3)(CH3OH)Cl]−
2−

P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
181
4. Experimental
The starting complex A was prepared according to the
reported procedure [36]. The ligands H2L1ꢁH2L5 were
synthesized by condensing salicylaldehyde with the ap-
propriate amines in methanol solvent. Other chemicals
and solvents were reagent grade and used as received.
Silica gel (60–120 mesh) used for chromatography was
purchased from S.D. Fine Chemicals, Bombay, India.
For spectroscopic and electrochemical studies HPLC
grade solvents were used. Commercial tetraethyl ammo-
nium bromide was converted to pure tetraethyl ammo-
nium perchlorate (TEAP) by following an available
procedure [50].
Fig. 4. Cyclic voltammograms of RuIII(HL1)2(PPh3)Cl, 1a (—) and
RuIII(L5)(PPh3)(CH3OH)Cl, 2e (---) in dichloromethane.
Solution electrical conductivity was checked using a
Systronic 305 digital conductivity-bridge. Electronic
spectra (700–200 nm) were recorded using a Shimadzu
UV 265 spectrophotometer. Near-IR spectra were
recorded by using a Hitachi 330 spectrophotometer.
Infrared (4000–400 cm−1) spectra were taken on a
Nicolet spectrophotometer with samples prepared as
KBr pellets. 1H- and 31P-NMR specta were checked with
the use of a 300 MHz Varian FT-NMR spectrometer.
Electrochemical measurements were carried out using a
PAR model 273A potentiostat/galvanostat. A platinum
wire working electrode, a platinum wire auxiliary elec-
trode and Ag/AgCl reference electrode were used in a
three-electrode configuration. TEAP was the supporting
electrolyte and the solute concentration was ꢀ10−3 M.
ꢀ −0.5 V. The low ruthenium(III)ꢁruthenium (II) po-
tential (ꢀ −0.5 V) might be responsible for the stabi-
lization of the complexes preferentially in the +3 state.
The bivalent species if formed as an initial product
might be oxidized by aerial oxygen.
3. Conclusions
We have observed ruthenium-mediated selective and
facile activation of the ortho-CꢁH bond of the pendant
phenyl ring of the ligand H2L, which in turn leads to the
formation of stable cyclometallated complexes 2. The
presence of coordinated phenolato oxygen function in
combination with metalꢁcarbon s bond in the com-
plexes 2 preferentially stabilizes the ruthenium ion in the
paramagnetic trivalent state.
The half-wave potential E° was set equal to 0.5
298
(Epa+Epc), where Epa and Epc are anodic and cathodic
cyclic voltammetric peak potentials, respectively. The
scan rate used was 50 mV s−1. A platinum wire gauze
working electrode was used in coulometric experiments.
Table 3
Electrochemical data at 298 K a
Compound
RuIVꢁRuIII couple
E0298 (V)
RuIIIꢁRuII couple
b
c
(DEp/mV)
n1
E0298 (V)
(DEp/mV)
n2
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
0.77
0.79
0.81
0.83
0.88
0.75
0.76
0.79
0.82
0.87
(100)
(99)
(98)
(100)
(100)
(90)
(95)
(97)
(100)
(90)
0.97
1.02
0.99
1.05
0.95
0.97
0.98
1.07
1.09
0.94
−0.58
−0.56
−0.54
−0.52
−0.49
−0.59
−0.57
−0.52
−0.49
−0.42
(90)
(95)
(100)
(100)
(85)
(95)
(97)
(90)
(95)
(100)
–
–
–
–
–
1.08
1.03
0.94
0.97
0.96
a Condition: solvent, dichloromethane; supporting electrolyte, TEAP; reference electrode Ag/AgCl; solute concentration, ꢀ10−3 M; working
electrode, platinum wire.
b n1=Q/Q% where Q% is the calculated coulomb count for 1e− transfer and Q is the columb count found after exhaustive coulometric oxidation
at +1.0 V.
c n1=Q/Q% where Q% is the calculated coulomb count for 1e− transfer and Q is the columb count found after exhaustive coulometric reduction
at −0.7 V.

182
P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
Fig. 5. Least-squares fit of E2098 vs |R of (a) RuIII(HL)2(PPh3)Cl, 1 and RuIII(L)(PPh3)(CH3OH)Cl, 2.
4.2. Synthesis
All experiments were carried out under dinitrogen at-
mosphere and are uncorrected for junction potentials.
The magnetic susceptibilities were measured on a PAR
155 vibrating-sample magnetometer. EPR measure-
ments were made with a Varian model 109 E-line
X-band spectrometer fitted with a quartz dewar for
measurements at 77 K (liquid nitrogen). The spectra
were calibrated by using radical anion of tetracya-
noethylene (TCNE) (g=2.0037). The elemental analy-
ses were carried out with a Carlo Eraba (Italy)
elemental analyzer. TGA–DTA experiments were per-
formed by using a Dupont 9900 machine. The FAB
mass spectra were recorded on a Jeol SX 102/DA-6000
mass spectrometer. The following Hammett | values
for para substituents were used: H, 0.00; Me, −0.17;
OMe, −0.27, Cl, +0.23; NO2, +0.78 [51].
Complexes (1 and 2) were prepared by following a
general method. Details are given for complexes 1a and
2a.
4.2.1. Bis-(N-phenylsalicylaldiminato)(triphenylphosphi-
ne)(chloro) ruthenium(III) (1a) and (N-phenylsalicylald-
iminato)(triphenylphosphine) (chloro) (methanol) ruthen-
ium(III) (2a)
The diruthenium starting complex [RuII(CS)(PPh3)2
Cl2]2 A (200 mg, 0.135 mmol) and the ligand H2L1 (135
mg, 0.685 mmol) were dissolved in 25 ml of methanol.
The resulting mixture was heated to reflux for a period
of 5 h. The initial reddish–brown solution was gradu-
ally turned to green color. The progress of the reaction
was monitored periodically by TLC. The solvent was
removed under reduced pressure. The crude product
was then purified by column chromatography on a
Silica gel (60–120 mesh) column. Unreacted excess
ligand was eluted first with benzene and was rejected.
The pure bluish–green colored complex 1a was eluted
with chloroform. The yellowish–green complex 2a was
eluted next with 10:1 ratio of chloroform and methanol
solvents. On removal of the solvents under reduced
pressure the complexes (1a and 2a) were obtained in the
4.1. Treatment of EPR data
An outline of the procedure can be found in our
recent publications [33–35,37–39,42–44]. We note that
a second solution also exists that is different from the
chosen one, having small distortions and w1, w2 values.
The experimentally observed near-IR results clearly
eliminate the solution as unacceptable.

P. Munshi et al. / Journal of Organometallic Chemistry 586 (1999) 176–183
183
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Yield: 64 mg, 30% for 1a and 68 mg, 40% for 2a.
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Acknowledgements
Financial support received from the Department of
Science and Technology, New Delhi, India, is gratefully
acknowledged. Special acknowledgement is made to the
Regional Sophisticated Instrumentation Center (RSIC),
Indian Institute of Technology, Bombay, for providing
NMR and EPR facilities and RSIC, Central Drug
Research Institute, Lucknow, for providing the FAB
mass spectra.
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