Unprecedented examples of double-addition of aromatic amines across a ruthenium(II)-coordinated nitrile function: Isolation and X-ray structures of ruthenium complexes of amidinate and cyclometalated amidine

Article abstract of DOI:10.1016/j.jorganchem.2006.02.033

The present report examplifies a novel type of aromatic amine addition reactions at a ruthenium(II) complexed acetonitrile. The electrophilic cationic complex, cis-[L₂Ru(CH₃CN)₂](ClO₄) ₂ (1) [L = 2-(phenylazo)pyridine] reacts with aromatic primary amines only in neat to produce a violet amidinate complex, [L₂Ru-N(Ar)-C(CH₃)-N(Ar)]⁺ (2) of ruthenium(II). Along with it a blue ortho-metalated ruthenium(II) amidine complex, [L₂Ru-N(H){double bond, long}C(CH₃)-N(H)Ar]⁺ (3) is also formed. X-ray structures of the two representative complexes are reported. The transformation 1 → 2 is unprecedented, involves multiple steps and occurs with addition of two equivalents of ArNH₂ across a coordinated nitrile function. In this complex, amidinate ligand binds to ruthenium(II) center as a σ,σ symmetrical bidentate chelate. The formation of 3 is a combination of nucleophilic amine addition and cyclometalation. ¹H and ¹³C NMR spectra of the products are examined, which are consistent with their formulations and structures. Optical spectra and redox properties of the newly synthesized complexes are reported. Visible range spectra of 2 and 3 are dominated by moderately intense metal-to-ligand charge transfer transitions. The complexes show multiple redox responses. The anodic potential response occurs at a high positive potential, which is attributed to a Ru(II)/Ru(III) couple. The cathodic potential responses are due to reductions of the coordinated diazo ligands.

Full text of DOI:10.1016/j.jorganchem.2006.02.033

Journal of Organometallic Chemistry 691 (2006) 2915–2923
www.elsevier.com/locate/jorganchem
Unprecedented examples of double-addition of aromatic amines
across a ruthenium(II)-coordinated nitrile function: Isolation and
X-ray structures of ruthenium complexes of amidinate and
cyclometalated amidine
a
a
b
a,
*
Priyabrata Banerjee , Srijit Das , Phillip E. Fanwick , Sreebrata Goswami
a
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science,
2A & 2B Raja S C Mullick Road, Kolkata, West Bengal 700 032, India
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana, IN 47907-2084, USA
b
Received 15 November 2005; received in revised form 16 February 2006; accepted 24 February 2006
Available online 3 March 2006
Abstract
The present report examplifies a novel type of aromatic amine addition reactions at a ruthenium(II) complexed acetonitrile. The elec-
trophilic cationic complex, cis-[L2Ru(CH3CN)2](ClO4)2 (1) [L = 2-(phenylazo)pyridine] reacts with aromatic primary amines only in neat
to produce a violet amidinate complex, [L2Ru–N(Ar)–C(CH3)–N(Ar)]+ (2) of ruthenium(II). Along with it a blue ortho-metalated ruthe-
nium(II) amidine complex, [L2Ru–N(H)@C(CH3)–N(H)Ar]+ (3) is also formed. X-ray structures of the two representative complexes are
reported. The transformation 1 ! 2 is unprecedented, involves multiple steps and occurs with addition of two equivalents of ArNH2
across a coordinated nitrile function. In this complex, amidinate ligand binds to ruthenium(II) center as a r,r symmetrical bidentate
chelate. The formation of 3 is a combination of nucleophilic amine addition and cyclometalation. 1H and 13C NMR spectra of the prod-
ucts are examined, which are consistent with their formulations and structures. Optical spectra and redox properties of the newly syn-
thesized complexes are reported. Visible range spectra of 2 and 3 are dominated by moderately intense metal-to-ligand charge transfer
transitions. The complexes show multiple redox responses. The anodic potential response occurs at a high positive potential, which is
attributed to a Ru(II)/Ru(III) couple. The cathodic potential responses are due to reductions of the coordinated diazo ligands.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Reactions of coordinated nitrile; Double-addition of aromatic amines; Ruthenium amidinates; Cyclometalated amidine
1. Introduction
nium(II)-complexed acetonitrile. The reaction resulted in
the formation of a ruthenium complex of amidinate ligand
directly due to double-amine fusion across a coordinated
nitrile function, along with it a cyclometalated amidine
complex is formed. The chemical transformations, con-
cerning us here, are shown in Scheme 1.
Amidinates, as ligand, have attracted considerable
attention in recent years not only because of their versatile
coordination abilities [5] but also some of their transition
metal complexes have been found to be useful [6,7]. We
wish to add here that while the chemistry associated with
the metal mediated addition of a variety of nucleophiles
to coordinated nitriles was 1:1 type, the observed addition
of two nucleophiles to metal coordinated one nitrile group
The nature of chemical reactions of organic substrates
can vastly be affected by their coordination to metal ions
[1]. It is now known that organonitriles are activated by
metal coordination toward addition reactions leading to
a variety of synthetic transformations of RCN species [2].
During the recent past we have been interested in the aro-
matic amine fusion reactions that are mediated by transi-
tion metal ions [3,4]. Herein we report an unprecedented
type of aromatic amine fusion reaction to a ruthe-
*
Corresponding author. Tel.: +91 33 2473 4971; fax: +91 33 2473 2805.
E-mail address: icsg@iacs.res.in (S. Goswami).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.02.033

2916
P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
is indeed scarce in the literature [8]. Furthermore, nucleo-
philic addition reaction to organonitriles coordinated to
bivalent ruthenium compounds is relatively uncommon [9].
2+
cis-
[RuL2 (CH3CN)2]
R
+
NH2 (neat)
1
2. Results and discussion
+
+
CH3
N
It is now known that organonitriles are activated toward
nucleophilic attack by coordination to metal ions and the
nitrile complexes undergo a variety of chemical transfor-
mations which otherwise do not occur [2a]. In our present
study a stable ruthenium(II) diacetonitrile complex, cis-
[L2Ru(CH3CN)2](ClO4)2 (1), was chosen as the reactant
[10]. Due to the presence of two excellent p-acceptor 2-
(phenylazo) pyridine (L) ligands, it was anticipated that
the metal complex would behave formally as an electron
deficient center for the promotion of nucleophilic addition
reaction. The complex, 1 reacted freely with neat aromatic
monoamines, ArNH2, on an oil bath (100–110 ꢁC). The ini-
tial brown color of 1 gradually became violet in 30 min; the
reaction was further continued for 1.5 h for completion.
The crude product, after initial work up, was purified
finally on a preparative TLC (silica gel) plate from which
two major bands; a violet (2) (yield: ca. 35%) and a blue
(3) (yield: ca. 30%) were isolated. Both the complexes, thus
obtained, are fairly soluble in common organic solvents
and their solutions behave as 1:1 electrolyte in acetonitrile.
Notably, the above reactions did not proceed at all in com-
mon organic solvents even in the presence of high excess
(>20 times) of aromatic amines. Our attempts to carry
out these reactions in solvents like acetonitrile, methanol,
2-methoxy ethanol and dimethyl formamide failed to pro-
duce the desired products. Thin layer chromatography
(TLC) experiment on the crude mass, obtained after sol-
Ar
N
H
N
C
II
II
L2Ru
L2Ru
H
-
CH3
N
Ar
2
R
H
2
3
3a
2a
2b
2c
R
CH
3b
3c
violet
3
3
OCH
blue
3
L=2-(phenylazo)pyridine
Scheme 1.
vent evaporation, showed the presence of several overlap-
ping minor bands which could not be purified and their
identities remained uncertain.
The ORTEP and atom numbering scheme for the cat-
ionic part of a representative complex 2b is shown in
Fig. 1 and its bond parameters are collected in Table 1.
Structural analysis reveals the coordination of an N-aryl
amidinate ligand, formed due to addition of two equiva-
lents of aryl amine to a coordinated acetonitrile. Associ-
ated with it are the two coordinated L ligands, which
complete six coordination around the central ruthenium(II)
ion. Bite angle of the amidinate chelate (62.13(9)ꢁ) is much
smaller than that of the L ligand (av. 76.99(9)ꢁ) but is sim-
ilar to those of reported amidinate complexes [6]. The two
˚
C–N bond lengths, N(31)–C(32) (1.329(4) A) and N(33)–
Fig. 1. ORTEP and atom numbering scheme for 2b. Hydrogen atoms are omitted for clarity.

P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
2917
Table 1
˚
Selected bond lengths (A) and angles (ꢁ) for the complexes 2b and 3b
2b
Ru–N(12)
Ru–N(212)
N(11)–N(12)
N(33)–C(331)
1.994(3)
2.036(2)
1.305(4)
1.414(4)
Ru–N(22)
Ru–N(33)
N(21)–N(22)
C(32)–N(33)
2.007(2)
2.110(2)
1.297(4)
1.337(4)
Ru–N(112)
Ru–N(31)
N(31)–C(32)
N(31)–C(311)
2.022(3)
2.088(2)
1.329(4)
1.416(4)
N(212)–Ru–N(22)
77.18(9)
N(112)–Ru–N(12)
76.79(10)
N(33)–Ru–N(31)
62.13(9)
3b
Ru–N(12)
Ru–N(31)
N(11)–N(12)
N(33)–C(331)
1.981(3)
2.073(3)
1.312(4)
1.411(4)
Ru–N(22)
2.145(3)
2.053(3)
1.265(4)
1.341(4)
Ru–N(112)
Ru–C(332)
N(31)–C(32)
C(331)–C(332)
2.035(3)
2.068(3)
1.298(4)
1.394(4)
Ru–N(212)
N(21)–N(22)
C(32)–N(33)
N(212)–Ru–N(22)
74.28(11)
N(12)–Ru–N(112)
76.35(11)
N(31)–Ru–C(332)
88.05(12)
˚
C(32) (1.337(4) A) are almost identical and are intermedi-
The two diazo lengths along with the two Ru–N (azo)
lengths are notably different. For example, the Ru–N(22)
bond (2.145(3) A), which is trans to the C-bonded aryl
˚
˚
ate between a typical C–N (1.47 A) and C@N (1.27 A),
which indicates strong delocalization of electronic charge
along the NCN skeleton. The coordination mode of the
amidinate ligand in 2b may best be described as r,r sym-
metrical bidentate chelate [5]. N-aryl bond lengths, viz.
N(31)–C(311) (1.416(4) A) and N(33)–C(331) (1.414(4) A)
are single bonds. Amongst the six metal–nitrogen bonds,
the two Ru–N(azo) lengths are short and notably the two
–N@N– lengths are elongated considerably due to strong
dp–pp interactions between ruthenium(II) and the p*(azo)
of the L ligand [11]. Consequently, the mN@N stretching
in these complexes appears at considerable low (ca.
1290 cmꢀ1) frequencies.
˚
group, is appreciably longer than the Ru–N(12) length,
˚
˚
1.981(3) A. Notably, the N(21)–N(22) length, 1.265(4) A
of one of the two coordinated L ligands is almost similar
˚
˚
˚
to that observed (1.258(5) A) in the uncoordinated salt
[HL]ClO4, however this length (N(11)–N(12), 1.312(4) A)
˚
in the second coordinated L ligand is elongated appreciably
[12b]. These may be attributed to the strong trans influence
of C-bonded aryl function, which is also responsible for
weaker Ru-azo back bonding interaction [14]. The Ru–N
(pyridyl) as well as Ru–N (imine) lengths are normal.
Due to unsymmetrical nature of the coordinated ami-
dine ligand, the symmetry in the complexes 3 is lost and
as a result a large number of resonances were observed in
their 1H NMR spectra due to the presence of several
unique protons [12]. Eight distinct pyridyl proton reso-
nances of the two coordinated L ligands were observed in
the range d, 8.5–7.3 (Table 2, Fig. 2b). Two broad singlet
resonances at d, 8.3 and 5.8 are assigned to the N–H
(imine) and N–H (amine) resonances of the amidine ligand,
respectively [9b,4a]. The C(333)–H resonance in 3b is a sin-
glet and it became doublet in the unsubstituted complex,
3a. This result further confirms ortho-metalation of the aryl
ring of the amidine ligand. While the complex, 3a displayed
a methyl resonance at d, 2.0 the complex, 3b, on the other
hand, showed two methyl resonances at d, 2.4 and 2.0. The
13C NMR of the complexes 3 (Supplementary Fig. S1),
showed a resonance systematically near d, 151 assignable
to the carbon bonded to ruthenium [15].
The synthetic reactions were carried out in neat ArNH2.
The primary step of these transformations involves
addition of one equivalent of the aromatic amine across
the ruthenium(II) coordinated acetonitrile function to yield
an amidine intermediate [A], [RuL2(CH3CN)[NH@C-
(CH3)N(H)Ar]2+ [9b]. The formation of the complex 2
from [A] involved several steps: addition of second equiva-
lent of aromatic amine at the intermediate [A], release
of ammonia and proton loss is the plausible steps involved
in this transformation [16]. Our proposal on the reaction
The X-ray structure of the compound 2b revealed that
there is a twofold axis of symmetry in this compound.
The H NMR spectra of 2 are resolved and data are col-
1
lected in Table 2, a representative spectrum is displayed
in Fig. 2a. The 1H NMR spectrum of 2a showed only
one methyl resonance at d, 2.0. The compound 2b, on the
other hand, displayed two methyl resonances at d, 2.3
and 2.0. The intensity of the methyl resonance at d, 2.3 is
twice that of the resonance at d, 2.0. Accordingly, the latter
resonance is assigned to amidinate methyl protons whereas
the former is assigned to aryl-methyl protons signal [12a].
The four-pyridyl proton signals appeared in the range d,
8.7–7.8. The resonance near d, 170 in the 13C NMR spectra
(Supplementary Fig. S1) of these complexes is assigned to
the middle carbon of NCN skeleton of the amidinate
ligand [13].
A view of cationic part of the molecule, 3b is shown in
Fig. 3. This is a mixed trischelate comprising of two biden-
tate neutral NꢂN donor ligands and an ortho-metalated
amidine ligand formed via ArNH2 addition to one of the
two coordinated CH3CN. The imine nitrogen of amidine
together with the ortho-carbon of the aryl ring binds to
the central metal atom forming a six member chelate ring.
Such a binding mode of an amidine ligand is rare [13b]. The
complex as a whole is monocationic, and the crystallo-
graphic asymmetric unit also contains one unit of perchlo-
rate. The bond parameters of 3b are collected in Table 1.

2918
P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
Table 2
1H NMR data of complexes 2 and 3 in CDCl3
Compound
N–H proton
Imine
Chemical shifta,b,c in ppm
Pyridyl proton
Amine
Aromatic proton
Methyl proton
2.0(s)
2a
8.70(d, 1H, J = 5.3),
8.49(d, 1H, J = 8.0),
8.20(t, 1H, J = 7.0),
7.87(t, 1H, J = 7.0)
7.38(t, 1H, J = 7.7),
7.15(m, 2H),
7.10(m, 2H),
7.01(t, 1H, J = 7.3),
6.58(d, 2H, J = 8.0),
6.20(d, 2H, J = 7.5)
3a
8.31(s) (1H)
8.32(s) (1H)
8.72(s) (1H)
5.88(s) (1H)
8.57(d, 1H, J = 5.6),
8.51(d, 1H, J = 8.0),
8.43(d, 1H, J = 8.0),
8.08(d, 1H, J = 5.0),
7.94(t, 1H, J = 7.0),
7.82(t, 1H, J = 7.2),
7.39(t, 1H, J = 7.4),
7.34(t, 1H, J = 6.0)
7.18(t, 2H, J = 7.9),
7.08(t, 2H, J = 7.8),
7.00(d, 2H, J = 7.9),
6.92(m, 2H),
6.71(t, 1H, J = 6.3),
6.29(d, 1H, J = 7.4)
2.0(s)
2b
3b
8.67(d, 1H, J = 5.2),
8.49(d, 1H, J = 8.0),
8.21(t, 1H, J = 7.9),
7.84(t, 1H, J = 6.2)
6.06(d, 2H, J = 8.2)
7.38(t, 1H, J = 7.5),
7.16(t, 2H, J = 7.8),
6.88(d, 2H, J = 8.1),
6.58(d, 2H, J = 8.0),
2.0(s), 2.3(s)d
2.0(s), 2.4(s)d
5.74(s) (1H)
8.56(d, 1H, J = 5.9),
8.50(d, 1H, J = 8.0),
8.45(d, 1H,J = 8.0),
8.08(d, 1H, J = 4.9),
7.94(t, 1H, J = 7.8),
7.83(t, 1H, J = 7.7),
7.47(t, 1H, J = 6.6),
7.39(t, 1H, J = 7.3)
7.17(t, 2H, J = 7.9),
7.08(t, 2H, J = 7.8),
6.99(d, 2H, J = 8.0),
6.86(d, 1H, J = 8.2),
6.70(d, 1H, J = 7.8),
6.07(s, 1H)
2c
3c
8.66(d, 1H, J = 5.4),
8.48(d, 1H, J = 8.0),
8.20(t, 1H, J = 7.2),
7.84(t, 1H, J = 6.0)
6.12(d, 2H, J = 8.7)
7.40(t, 1H, J = 7.4),
7.14(t, 2H, J = 7.9),
6.65(d, 2H, J = 6.9),
6.60(d, 2H, J = 7.8),
1.9(s), 3.76(s)e
2.0(s), 3.57(s)e
5.58(s) (1H)
8.55(d, 1H, J = 5.6),
8.49(d, 1H, J = 7.8),
8.43(d, 1H, J = 8.0),
8.12(d, 1H, J = 5.5),
7.94(t, 1H, J = 7.6),
7.81(t, 1H, J = 7.7),
7.44(t, 1H, J = 6.5),
7.38(t, 1H, J = 7.3)
7.14(m, 3H),
7.05(m, 2H),
6.89(d, 2H, J = 7.9),
6.42(d, 1H, J = 5.9),
5.82(s, 1H)
a
Solvent CDCl3.
b
c
Multiplicity (s, singlet; d, doublet; t, triplet; m, multiplet).
The coupling constant (J in Hz) are given in parentheses.
CH3 of toluidine.
d
e
OCH3 of anisidine.
pathways is based on the previous results on the similar
reactions of amines with organonitriles catalyzed by lan-
thanide(III) ions. However, our experimental conditions
did not allow us to detect ammonia in the gasses evolved
from the reference reaction mixture. The complex 3, on
the other hand, is a result of cyclometalation due to C–H
activation of the amidine intermediate. Successive steps
for the formation of the complexes 2 and 3 from the ami-
dine intermediate, [A] are shown in Scheme 2. The fact that
the compounds 2 and 3 are not inter-convertible also sup-
ports the proposed reaction scheme. Since the reactions
proceed only in neat aromatic amine it may be possible that
amine acts not only as a nucleophile but also as a suitable
solvent for these transformations.
Electronic spectra of the ruthenium complexes, recorded
in dichloromethane solution, showed several intense
absorptions in the visible and ultraviolet regions (Table
3). Two representative spectra of 2b and 3b are shown in
Fig. 4. The absorptions in the UV-region are assigned
to transitions within the ligand orbitals. The color of the

P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
2919
Fig. 2. 1H NMR spectra of (a) 2a and (b) 3a in CDCl3 at 298 K.
case is attributed to Ru(dp) ! p*(azo) MLCT transition
[17]. The donor Ru(dp) orbital of 2 is more stabilized than
that of 3 (see below) and is responsible for the red shift of
MLCT transition energy in moving from 2 to 3. We note
that MLCT band of both 2 and 3 are associated with a
shoulder at higher energy.
Electrochemical properties of the complexes were stud-
ied by cyclic voltammetry in dichloromethane (0.1 M
TBAP). Voltammetric data are collected in Table 3. The
complexes showed a reversible oxidative response on the
positive of SCE and two reversible reductive responses at
the negative potentials (Fig. 5). Notably, the anodic poten-
tial response of 2 is more anodic than that of 3 by 160–
170 mV. The cathodic potential responses are attributed
to successive reductions of L ligands while, the anodic
potential response is due to Ru(II)–Ru(III) oxidation
[17]. The oxidation of the present complexes occur at high
anodic potentials, making the ruthenium(III) species strong
oxidants and reactive. The color of the coulometrically oxi-
dized solutions of [2a]+ and [3a]+ are orange and brownish
pink, respectively. These are not stable enough for their
isolation. These transformed to a mixture of products,
which have not been characterized.
Fig. 3. ORTEP and atom numbering scheme for 3b. Hydrogen atoms are
omitted for clarity.
3. Conclusion
complex 2 is violet while that of 3 is blue. A strong visible
range transition for 2 appeared near 570 nm and that for 3
appeared near 600 nm. By analogy with the reported ruthe-
nium(II)–L systems, the lowest energy transition in each
We have presented the results of an unprecedented type
of organoamine addition reaction on a ruthenium(II)-coor-
dinated acetonitrile. Two excellent p-acceptor ancillary

2920
P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
R
+
2
2+
+
CH3
NH
CH3
NH
H
N
H
N
C
R
NH2
C
L
2Ru
-CH3CN
L2Ru
NH
+
CH3
NH
NCCH3
-H
C
L
2Ru
N
H2
R
N
C
R
3
[A]
CH3
R
+
2
R
R
N
+
N
-NH3
-CH CN,
H
CH3
L2Ru
-
CH3
C
+
- H
N
3
L2 Ru
N
H2
NH
N
C
R
CH3
R
2
Scheme 2.
Table 3
Electronic spectra and cyclic voltammetric data of complexes 2 and 3 in dichloromethane
Compound
Electronic spectraa
Cyclic voltammetryc,d
abs[kmax/nm (e/Mꢀ1 cmꢀ1)]
555 (7350), 465b (3510)
320 (27100), 235 (28500)
Oxidation E1/2/V (DEp/mV)
Reduction ꢀE1/2/V (DEp/mV)
0.37 (105)
2a
3a
2b
3b
2c
1.04 (100)
1.00 (85)
600 (8500), 485b (4420)
335 (30000), 235 (35950)
0.87 (90)
1.02 (100)
0.86 (80)
1.00 (80)
0.84 (100)
0.52 (70)
1.20 (100)
560 (10950), 470b (3350)
325 (29740), 230 (36900)
0.31 (95)
1.02 (80)
595 (6700), 480b (3425)
340 (23190), 235 (29400)
0.49 (90)
1.22 (80)
560 (9500), 480b (4200)
315 (26900), 230 (31850)
0.37 (90)
1.03 (70)
3c
595 (6270), 485b (3890)
340 (21575), 235 (28430)
0.53 (90)
1.24 (80)
a
Solvent, dichloromethane.
b
c
Shoulder.
Solvent, dichloromethane; supporting electrolyte, TBAP.
Potentials are referenced to SCE: scan rate, 50 mV sꢀ1
d
.
diazo ligands in the starting complex play the key role in
making the coordinated nitriles sufficiently electrophilic
for nucleophilic double-addition reactions. Such a chemical
transformation of coordinated organonitrile, to the best of
our knowledge, was not available in the literature. In the
present context we wish to note that nitriles in complexes
where the metal ion is in low oxidation state, e.g., Ru(II)
are sluggish addition reactions. Addition reactions in such
complexes are reported in the presence of additional Lewis
acids such as Ag+ or Cu2+ [18].

P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
2921
A Perkin–Elmer 240C elemental analyzer was used to col-
lect microanalytical data (C, H, N). Electrochemical mea-
surements were done under a dry nitrogen atmosphere on
a PAR 370-4 electrochemistry system as described before
[17]. All potentials in this work are referenced to the satu-
rated calomel electrode (SCE) and are uncorrected for
junction contribution. The value for the ferrocenium–ferro-
cene couple under our experimental condition was 0.40 V.
ESI mass spectra were recorded on a micro mass Q-TOF
mass spectrometer (serial no. YA 263).
4.3. Amine addition reactions to cis-[L2Ru(CH3CN)2]-
(ClO4)2, 1
The complexes 2 and 3 were isolated from the amine
fusion reaction of ArNH2 on cis-[L2Ru(CH3CN)2](ClO4)2
(1) in neat. Details are given below for the reaction of
cis-[L2Ru(CH3CN)2](ClO4)2 (1) with aniline.
A mixture of cis-[L2Ru(CH3CN)2](ClO4)2 (1) (100 mg,
0.135 mmol.) and freshly distilled aniline (1 ml) was heated
at 100–110 ꢁC on an oil-bath in argon atmosphere for
1.5 h. The initial reddish brown color of the mixture grad-
ually became violet. The product was washed thoroughly
with diethyl ether and was subjected to chromatography
on a preparative TLC plate using 20% acetonitrile–chloro-
form mixture as the eluent. Two major bands viz. a violet
and a blue was separated from the TLC plate. For purifica-
tion of the products, the TLC experiment need be repeated
thrice. Finally the two compounds were collected by com-
plete evaporation of the eluates. The violet compound 2a
was recrystallized from a tetrahydrofuran–hexane solvent
mixture.
Fig. 4. UV-vis spectra of 2b (---) and 3b (—) in dichloromethane.
Fig. 5. Segmented cyclic voltammograms of 2b (---) and 3b (—) in
2a Yield: 30%. Anal. Calc. for C36H31N8RuClO4: C,
55.65; H, 3.99; N, 14.42. Found: C, 55.68; H, 4.02; N,
14.40%. 13C NMR (298 K, CDCl3): d = 171.25 (amidinate-
carbon), 164.85, 155.79, 150.51, 138.26, 137.55, 131.61,
129.30, 129.13, 127.77, 127.44, 124.72, 123.47, 122.40,
16.90. IR (KBr disk): m 1620 (NCN), 1295 (N@N), 1100,
625 ðClO4ꢀÞ cmꢀ1. ESI-MS: m/z 676 [M ꢀ ClO4]+.
The blue compound 3a, was recrystallized from dichlo-
romethane–tetrahydrofuran–hexane solvent mixture.
3a Yield: 28%. Anal. Calc. for C30H27N8RuClO4: C,
51.47; H, 3.85; N, 15.99; Found: C, 51.45; H, 3.88; N,
16.01%. 13C NMR (298 K, CDCl3): d 166.39 (iminocar-
bon), 164.90, 157.97, 155.45, 153.75, 150.53, 148.32,
137.91, 137.15, 136.54, 135.80, 132.16, 129.81, 129.20,
128.74, 128.57, 125.51, 125.26, 124.81, 124.28, 123.58,
123.25, 122.63, 117.55, 117.39, 23.87. IR (KBr disk): m
3400 (N–H), 1600 (C@N), 1290 (N@N), 1125, 610
ðClO4ꢀÞ cmꢀ1. ESI-MS: m/z 600 [M ꢀ ClO4]+.
dichloromethane (0.1 M TBAP).
4. Experimental
4.1. Materials
The starting complexes cis-[L2Ru(H2O)2](ClO4)2 and
cis-[L2Ru (CH3CN)2](ClO4)2 were synthesized by the pub-
lished procedures [10]. Solvents and chemicals used for syn-
thesis were of analytical grade. Supporting electrolyte
(tetrabutylammonium perchlorate) and solvents for elec-
trochemical work were obtained as before [17].
Caution. Perchlorate salts of metal complexes can be
explosive. Although no detonation tendencies have been
observed, care is advised and handling of only small quan-
tities recommended.
4.2. Physical measurements
Compounds 2b, 3b, 2c and 3c were prepared similarly by
following the above procedure using the appropriate
substituted aromatic amines in place of aniline. Their yields
and characterization data are collected below.
A JASCO V-570 spectrometer was used to record elec-
tronic spectra. The IR spectra were obtained with a Per-
kin–Elmer 783 spectrophotometer. 1H and 13C NMR
spectra were recorded in CDCl3 on a Bruker Avance
DPV 300 spectrometer using TMS as the internal standard.
2b Yield: 35%. Anal. Calc. for C38H35N8RuClO4: C,
56.69; H, 4.35; N, 13.92. Found: C, 56.67; H, 4.38; N,
13.94%. 13C NMR (298 K, CDCl3): d 172.51 (amidinate-

2922
P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
Table 4
carbon), 166.89, 156.44, 151.38, 141.38, 139.35, 135.55,
132.61, 130.89, 130.18, 128.87, 128.27, 124.31, 123.53,
21.94, 17.74. IR (KBr disk) m 1610 (NCN), 1290 (N@N),
1100, 610 ðClO4ꢀÞ cmꢀ1. ESI-MS: m/z 704 [M ꢀ ClO4]+.
3b Yield: 30%. Anal. Calc. for C31H29N8RuClO4: C,
52.08; H, 4.06; N, 15.68. Found: C, 52.06; H, 4.08; N,
15.69%. 13C NMR (298 K, CDCl3): d 166.34 (iminocar-
bon), 164.90, 157.40, 155.42, 153.68, 151, 150.47, 148.23,
137.09, 135.76, 135.69, 132.25, 132.06, 129.79, 129.12,
128.63, 128.54, 127,54, 125.46, 125.36, 125.22, 124.14,
123.22, 122.58, 116.96, 23.54, 20.81. IR (KBr disk): m
3400 (N–H), 1590 (C@N), 1295 (N@N), 1125, 620
ðClO4ꢀÞ cmꢀ1. ESI-MS: m/z 615 [M ꢀ ClO4]+. 2c Yield:
35%. Anal. Calc. for C38H35N8RuClO6: C, 54.52; H,
4.18; N, 13.39. Found: C, 54.55; H, 4.20; N, 13.36%. 13C
Selected crystallographic data for compounds 2b and 3b
2b
3b
Empirical formula
Fw
C38H35N8RuClO4 C31H29N8RuClO4
804.28
220
714.15
150
T (K)
Crystal system
Monoclinic
P21/n (no. 14)
10.9838(2)
27.4166(5)
13.0687(2)
90
100.1170(10)
90
3874.29(12)
4
Monoclinic
P21/n (no. 14)
14.5163(11)
15.1004(6)
16.1254(11)
90
109.735(3)
90
3327.1(4)
4
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dc (Mg mꢀ3
)
1.379
0.28 · 0.35 · 0.38
1.43
Crystal size (mm)
0.13 · 0.30 · 0.41
2.1–27.9
0.71073
34090
NMR (298 K, CDCl3):
d 171.78 (amidinatecarbon),
h Range for data collections (ꢁ) 2.2–27.9
165.74, 156.79, 155.28, 150.31, 138.00, 135.81, 131.37,
128.76, 127.07, 126.23, 124.19, 122.35, 114.22, 55.45,
16.46. IR (KBr disk): m 1635 (NCN), 1295 (N@N), 1100,
630 ðClO4ꢀÞ cmꢀ1. ESI-MS: m/z 736 [M ꢀ ClO4]+.
˚
k (A)
0.71073
26875
9189
Reflections collected
Unique reflections
Absorption correction
Largest diff. between ꢀ3
7828
SCALEPACK
SCALEPACK
ꢀ0.87, 0.76
ꢀ1.01, 0.78
3c Yield: 30%. Anal. Calc. for C31H29N8RuClO5: C,
50.9; H, 4.0; N, 15.3. Found: C, 51.3; H, 4.2; N, 15.1%.
13C NMR (298 K, CDCl3): d 166.33 (iminocarbon),
164.94, 157.47, 155.47, 154.97, 153.72, 152.31, 150.76,
148.26, 137.05, 135.83, 132.13, 132.10, 129.82, 129.21,
128.65, 128.59, 125.44, 125.32, 124.28, 123.18, 122.63,
121.36, 118.18, 109.75, 55.13, 23.74. IR (KBr disk): m,
3450 (N–H), 1630 (C@N), 1290 (N@N), 1120, 625
ðClO4ꢀÞ cmꢀ1. ESI-MS: m/z 631 [M ꢀ ClO4]+.
˚
peak and hole (e A
)
Final R indices [I > 2r(I)]
R1
a
0.050
0.126
0.051
0.127
b
wR2
R indices (all data)
a
R1
wR2
0.084
0.138
472
0.086
0.139
417
b
Number of parameters (N)
Goodness-of-fitc
0.997
0.935
P
P
a
b
c
R1 ¼ jjF oj ꢀ jF cjj= jF oj.
P
P
2
1=2
wR2 ¼ ½ fwðF 2o ꢀ F c2Þ g= fwðF 2oÞgꢁ
.
P
GOF ¼ ½ fwðF 2o ꢀ F c2Þ g=ðM ꢀ NÞꢁ1=2, where M is the number of
2
4.4. X-ray crystallographic study
reflections and N is the number of parameters refined.
Crystallographic data for the compounds 2b and 3b are
collected in Table 4.
PACK was applied [19]. The structure solutions, refinement
as well as the crystallographic drawing were performed as
mentioned above.
2b X-ray quality crystals (0.38 · 0.35 · 0.28 mm3) of 2b
were obtained by slow diffusion of a tetrahydrofuran solu-
tion of the compound into hexane. The data were collected
on a Nonius Kappa CCD diffractometer equipped with a
graphite crystal, incident beam monochromator having
Acknowledgments
˚
Mo Ka radiation (k = 0.71073 A), and Lorentz and polar-
Financial support received from the Council of Scientific
and Industrial Research (CSIR) and the Department of
Science and Technology, New Delhi is gratefully acknowl-
edged. S.D. is also thankful to CSIR for his fellowship. We
are thankful to the Reviewers for their suggestions.
ization corrections were applied to the data. A total of
26875 reflections were collected of which 9189 were unique
(Rint = 0.041) and were used in subsequent analysis. An
empirical absorption correction using SCALEPACK was
applied [19]. The structure was solved using the structure
solution program PATTY in DIRDIF-99 [20a] and refined by
full-matrix least-squares based on F2. Refinement was per-
formed on a LINUX PC using SHELXL-97 [20b]. Crystallo-
graphic drawings were done using the programs ORTEP [21]
and PLATON [22].
Appendix A. Supplementary data
Crystallographic data for structural analysis have been
deposited with the Cambridge Crystallographic Data Cen-
ter, CCDC Nos. 264209 and 264210 for complexes 2b and
3b, respectively. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK, fax (int code):
+44 1223 336 033, or email: deposit@ccdc.cam.ac.uk or
www.ccdc.cam.ac.uk. 13C NMR (Fig. S1) of complexes
2b and 3b in CDCl3 is available as supporting information.
Supplementary data associated with this article can be
3b X-ray quality crystals (0.41 · 0.31 · 0.13 mm3) of 3b
were obtained by slow diffusion of a dichloromethane solu-
tion of the compound into tetrahydrofuran and hexane sol-
vent mixture. The data were collected as noted above. A
total of 34090 reflections were collected, of which 7828
were unique (Rint = 0.071) and were used in subsequent
analysis. An empirical absorption correction using SCALE-

P. Banerjee et al. / Journal of Organometallic Chemistry 691 (2006) 2915–2923
2923
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