Synthesis and characterization of cyclopentadienylruthenium(II) complexes containing N,N′-donor Schiff base ligands: Crystal and molecular structure of [(η5-C5H5)Ru(C5H 4N-2-CH=N-C6H4-p-OCH3)(PPh 3)]PF6

Article abstract of DOI:10.1016/j.poly.2004.03.007

Complexes of the formulae [(η⁵-C₅H ₅)Ru(PPh₃)(C₅H₅N-2-CH=N-C ₆H₄-p-X)]⁺ [X=H (2a), CH₃ (2b), OCH₃ (2c), Cl (2d), NO₂ (2e)] and [(η⁵- C₅H₅)Ru(PPh₃)(C₅H ₅N-2-CH=N-C₆H₁₁)]⁺ (3) were prepared by reacting para-substituted N-(pyrid-2-ylmethylene)-phenylamines (2-PP) and N-(pyrid-2-ylmethylene)cyclohexylamine (2-PC) with [(η⁵-C ₅H₅)Ru(PPh₃)₂Cl] (1) in methanol. These complexes have been isolated as hexa-fluorophosphate salts. Representative complex 2c has been established by single crystal X-ray diffraction analysis. Complex 2c crystallizes in the orthorhombic space group P_bcn, with a=21.1560 (11) A?, b=18.3972 (9) A? and c=17.5130 (9) A?, V=6816.3 (6) A?³ and z=8. All these complexes were characterized by FT-IR, ¹H NMR and ³¹P{¹H} NMR spectroscopy.

Full text of DOI:10.1016/j.poly.2004.03.007

Polyhedron 23 (2004) 1567–1572
www.elsevier.com/locate/poly
Synthesis and characterization of
cyclopentadienylruthenium(II) complexes containing N,N0-donor
Schiff base ligands: crystal and molecular structure of
q
[(g5-C5H5)Ru(C5H4N-2-CH@N–C6H4–p-OCH3)(PPh3)]PF6
a
b
P. Govindaswamy , Yurij A. Mozharivskyj , Mohan Rao Kollipara
a,
*
a
Department of Chemistry, North-Eastern Hill University, Shillong 793 022, India
b
Ames Laboratory, Iowa State University of Science and Technology, Ames, IA 50011, USA
Received 27 February 2004; accepted 15 March 2004
Available online 20 April 2004
Abstract
Complexes of the formulae [(g5-C5H5)Ru(PPh3)(C5H5N-2-CH@N–C6H4–p-X)]þ [X ¼ H (2a), CH3 (2b), OCH3 (2c), Cl (2d),
NO2 (2e)] and [(g5-C5H5)Ru(PPh3)(C5H5N-2-CH@N–C6H11)]þ (3) were prepared by reacting para-substituted N-(pyrid-2-ylm-
ethylene)-phenylamines (2-PP) and N-(pyrid-2-ylmethylene)cyclohexylamine (2-PC) with [(g5-C5H5)Ru(PPh3)2Cl] (1) in methanol.
These complexes have been isolated as hexa-fluorophosphate salts. Representative complex 2c has been established by single crystal
ꢀ
ꢀ
X-ray diffraction analysis. Complex 2c crystallizes in the orthorhombic space group Pbcn, with a ¼ 21:1560 (11) A, b ¼ 18:3972 (9) A
and c ¼ 17:5130 (9) A, V ¼ 6816:3 (6) A and z ¼ 8. All these complexes were characterized by FT-IR, H NMR and 31P{1H} NMR
3
1
ꢀ
ꢀ
spectroscopy.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Cyclopentadienyl; Schiff bases; Pyridine-2-carboxaldehyde; Ruthenium
1. Introduction
and catalytic activities [7]. Steric factors play an impor-
tant role compared to electronic factors in the structure
and chemistry of these complexes. We had earlier re-
ported the reaction of g5-indenylruthenium(II) [8] and
g6-arene-ruthenium(II) [9] with Schiff base ligands.
During the reactions involving the analogous pentam-
ethylcyclopentadienyl or indenyl systems, the products
did not show evidence of binding of these organic ligands,
simple coordination compounds being formed instead.
Although these groups can provide more electron density
to the metal for binding, their large bulk compared to the
cyclopentadienyl ligand prevents effective binding. This
observation indicates steric factors playing a major role
compared to electronic factors. However, relatively fewer
reports are available in the literature for the analogous
cyclopentadienylruthenium(II) Schiff base complexes
[10]. We report here the synthesis and characterization of
new cationic cyclopentadienylruthenium(II) complexes
with N,N0-donor Schiff base ligands, viz., various
As a part of our continuing investigation of the com-
plexes of g5-cyclopentadienyl-ruthenium(II) [1], g5-in-
denylruthenium(II) [2], g5-cyclopentadienylosmium(II)
[3] and g6-areneruthenium(II) [4] with a variety of ni-
trogen-based ligands, we here report the syntheses of
complexes of the cyclopentadienylruthenium(II) system
with some chelating Schiff base ligands. Considerable
interest has arisen in the chemistry of ruthenium (II)
complexes having Schiff bases [5] or chelating nitrogen
heterocyclic ligands [6] because of their photochemical
q Supplementary data associated with this article can be found, in the
online version, at doi: 10.1016/j.poly.2004.03.007.
* Corresponding author. Tel.: +91-364-272-2620; fax: +91-364-272-
1000.
E-mail addresses: kmrao@nehu.ac.in, mrkollipara@yahoo.com
(M. Rao Kollipara).
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.03.007

1568
P. Govindaswamy et al. / Polyhedron 23 (2004) 1567–1572
para-substituted N-(pyrid-2-ylmethylene) phenylamines
(2-PP) and N-(pyrid-2-ylmethylene)cyclohexylamine (2-
PC). The molecular structure of the complex [(g5-
C5H5)Ru(C5H4N-2-CH@N–C6H4–p-OCH3)(PPh3)]PF6
as solved by X-ray crystallography is reported here as
well.
2.3. Preparation of [(g5-C5H5)Ru(PPh3)(2-PC)] PF6
(3)
This complex was prepared in a similar manner to
that of the preparation of (2a–e), except that the ligand
2-PC was used instead of 2-PP to yield the dark brown
solid complex in 80% yield.
2. Experimental
3. Structure analysis and refinement
2.1. General remarks
X-ray quality crystals of the complex 2c were grown
by slow diffusion of hexane into a dichloromethane so-
lution. A brown crystal of complex 2c was mounted on a
Bruker Apex CCD diffractometer in a full reciprocal
sphere equipped with CCD detector and used for data
collection. X-ray intensity data were collected with
graphite mono-chromated Mo Ka radiation at
293(2) K, with 0.3° scans in x scan mode and 10-s ex-
posure time per frame. The intensity data were corrected
for Lorentz and polarization effects through the SAINT
program [13]. A summary of the crystal data, data col-
lection parameters and convergence results are compiled
in Table 3. An empirical absorption correction was
made by modeling a transmission surface by spherical
harmonics employing equivalent reflections with
I > 3rðIÞ (program SADABS) [14]. The structure was
solved by direct methods [15]. All the non-hydrogen
atoms were refined anisotropically using the full-matrix
least-squares technique on F 2 using the SHELXL 97
software [16]. All the hydrogen atom positions were
found from difference Fourier synthesis after four cycles
of anisotropic refinement and as ‘‘riding’’ model. Fig. 1
is the ORTEP [17] representation of the molecules with
50% probability thermal ellipsoids displayed. Refine-
ment coverage at a final value of R1 ¼ 0:0462 (for ob-
served data F) and at value of wR2 ¼ 0:1192,
respectively (for unique data F 2).
All reactions were carried out in distilled and dried
solvents under a dry nitrogen atmosphere. RuCl3 ꢀ 3H2O
was purchased from Arora Matthey Ltd. and used as
such. Pyridine-2-carboxaldehyde (Fluka) was purchased
and used as received. All liquid amines were reagent
grade and distilled prior to use, while solid amines were
used as such. Elemental analyses were performed in a
Perkin–Elmer-2400 CHN/O analyzer. Infrared spectra
were recorded on a Perkin–Elmer-model 983 spectro-
photometer with the sample prepared as KBr pellets.
Electronic spectra were recorded on a Hitachi-300
spectrophotometer. Conductivity measurements were
performed in Wayne Kerr automatic precision bridge B-
905. The 1H NMR spectra were recorded in CDCl3
solvent (with tetramethylsilane as the internal standard)
on a Bruker ACF-400 MHz spectrometer, coupling
constants J being given in hertz (hz). 31P{1H} NMR
chemical shifts were recorded relative to H3PO4 (85%).
The ligands C5H4N-2-CH@C6H4–p-X (where X ¼ H,
CH3, OCH3, Cl, NO2) [11], and the precursor complex
[(g5-C5H5)Ru(PPh3)2Cl] (1) [12] were prepared follow-
ing literature methods.
2.2. Preparation of [(g5-C5H5)Ru(PPh3)(C5H5N-2-
CH@N–C6H4–p-X)]PF6 (2a–e), (X ¼ H (2a), CH3
(2b), OCH3 (2c), Cl (2d), NO2 (2e)
4. Results and discussion
The following general procedure was used for prep-
aration of these five complexes:
The mixture of the starting complex [(g5-C5H5)
Ru(PPh3)2Cl] (0.1 g, 0.110 mmol), the appropriate Schiff
base ligand 2-PP (0.165 mmol) and NH4PF6 (0.165
mmol) was refluxed in methanol (40 ml) whereby the
orange color suspension gradually changed to a dark
brown solution. It was refluxed for 6 h, and the solvent
then rotary evaporated. The residue was dissolved in
dichloromethane and filtered through a short silica gel
column to remove insoluble material. The filtrate was
again concentrated to about 2 ml, whereupon addition
of excess hexane gave the desired complexes (2a–e) as
dark brown solids. The solid was washed with diethyl
ether and dried under vacuum to afford an 80–85% yield
of the complexes.
The synthetic reaction of the cyclopentadienyl com-
plex 1 with excess of N,N0-donor Schiff base ligands,
viz., 2-PP and 2-PC, in methanol under refluxing con-
dition resulted in the formation of brown colored and
air-stable cationic complexes of the type 2 (Scheme 1) by
dissociation of one of the triphenylphosphines and
chloride ligand. Here, we would like to point out that
when similar reactions were carried out with complexes
bearing the substituted analogue Cpꢁ and the indenyl
group instead, the resulting complexes had no organic
groups bound to the metal.
These complexes are highly soluble in polar solvents
such as chloroform, dichloromethane, etc., but insoluble
in non-polar solvents such as hexane, pentane, etc.

P. Govindaswamy et al. / Polyhedron 23 (2004) 1567–1572
1569
X
2-PP, NH PF
4
6
Ru
PPh
Cl
Ru
N
MeOH
P
Ph
3
P
3
Ph
3
N
1
X = H, CH , OCH , Cl, NO (2a-e)
3
3
2
2-PP = N-(pyrid-2-ylmethylene)phenylamine
Scheme 1.
These complexes were characterized by using analytical,
IR, 1H and 31P NMR spectroscopic techniques. The
data, as presented in Table 1, support the formation of
these complexes. The X-ray structure of the represen-
tative complex 2c was determined to confirm the struc-
ture of the complex. The IR spectra of these complexes
show a strong band in the range of 1602–1584 cmꢂ1 due
to the mC@N group of the Schiff base ligand. In addition,
the IR spectra contain strong bands due to the phenyl
groups of triphenylphosphine and a strong band at
840 cmꢂ1 due to the mP–F of the PF6 group. Complex 2e
shows the characteristic bands for mNO2 (asymmetric
stretch at 1523 cmꢂ1 and symmetric stretch 1346 cmꢂ1).
these complexes. The multiplet observed in the range
8.13–6.76 ppm is due to the phenyl protons of the tri-
phenylphosphine moiety, the amine group and the N-
heterocyclic ring of the ligands (2-PP or 2-PC). The 31P
NMR spectra of the complexes 2 and 3 exhibit a single
sharp resonance for triphenylphosphine around 47 ppm,
whereas the starting complex [(g5-Cp)Ru(PPh3)2Cl] (1)
exhibits it at 42 ppm for both triphenylphosphines in-
dicating the cationic nature of these complexes. The
ionic nature of these complexes was confirmed by car-
rying out conductivity measurements (Table 2).
The electronic spectra and conductivity data of these
complexes are shown in Table 2. The electronic spectra
of these complexes in dichloromethane exhibit bands in
the range of 428–461 nm. This low-energy absorption is
assigned to a Ru dp to ligand pꢁ metal-to-ligand charge
transfer (MLCT) transition. The molar conductivity of
the complexes in acetonitrile solvent ranges from 123.0
to 150.0 S cm2 molꢂ1, suggesting that these complexes
are ionically dissociated in the ratio of 1:1 [18].
1
In the H NMR spectra of these complexes, the cy-
clopentadienyl ring protons display a sharp singlet at
4.7 ppm. The presence of g-Cp, PPh3 and 2-PP or 2-PC
in a 1:1:1 ratio is inferred from the areas obtained upon
peak integration of the 1H NMR spectra. The resonance
of the ortho proton of the pyridine ring of the ligand is
observed as a doublet in the range 9.28–8.45 ppm in
Table 1
Analyticala, FT IR, 1H NMRb and 31P NMR of the complexes 2a–e and 3
Complex
IR (KBr Pellets, cmꢂ1
)
1H NMR d [multiplicity, nH, J (Hz)]
31P NMR (d)
Analyses %
C
H
N
2a
2b
55.6 (56.0)
4.0 (4.3)
3.7 (3.4)
1587(mC@N) 839(mP–F
1602(mC@N) 840(mP–F
)
)
9.28 (d, 1H, 5.48); 8.26 (d, 1H);
7.69–6.96 (m, 23H); 4.66 (s, 5H, Cp).
9.26 (d, 1H, 2.96); 8.23 (d, 1H);
7.65–6.91 (m, 22H); 4.67 (s, 5H, Cp);
2.36 (s, 3H).
46.91
47.09
56.1 (56.6)
55.0 (55.5)
4.1 (4.3)
4.1 (4.5)
3.6 (2.9)
3.6 (3.2)
2c
1598(mC@N) 837(mP–F
)
9.20 (d, 1H, 5.56); 8.23 (d, 1H);
7.69–6.76 (m, 22H); 4.68 (s, 5H, Cp);
3.84 (s, 3H)
47.25
2d
2e
3
53.2 (53.8)
52.5 (52.4)
55.3 (55.1)
3.7 (3.2)
3.6 (3.9)
4.6 (4.2)
3.5 (2.9)
5.3 (5.7)
3.7 (3.9)
1586(mC@N) 837(mP–F
1589(mC@N) 840(mP–F
1589(mC@N) 839(mP–F
)
)
)
9.21 (d, 1H, 5.44); 8.31 (d, 1H);
7.73–6.96 (m, 22H); 4.68 (s, 5H, Cp)
8.45 (d, 1H, 2.96); 8.11 (d, 1H);
7.83–6.93 (m, 22H); 4.69 (s, 5H, Cp)
9.06 (d, 1H, 7.04); 8.23 (d, 1H);
8.14–7.04 (m, 18H); 4.65 (s, 5H, Cp);
1.12–2.10 (m, 10H).
46.24
46.70
47.35
a Calculated values are in parentheses.
b In CDCl3; s singlet; d, doublet; m, multiplet; JðH–HÞ in Hz.

1570
P. Govindaswamy et al. / Polyhedron 23 (2004) 1567–1572
Table 2
UV–Vis and conductivity data of the complexes at room temperature
S. no.
Complexes
kmax (nm)
Conductivity, Km
(S cm2 molꢂ1
)
2a
2b
2c
2d
2e
3
[(g5-C5H5)Ru(PPh3)(C5H4N-2-CH@N–C6H4–p-H)]PF6
[(g5-C5H5)Ru(PPh3)(C5H4N-2-CH@N–C6H4–p-CH3)]PF6
[(g5-C5H5)Ru(PPh3)(C5H4N-2-CH@N–C6H4–p-CH3)]PF6
[(g5-C5H5)Ru(PPh3)(C5H4N-2-CH@N–C6H4–p-Cl)]PF6
[(g5-C5H5)Ru(PPh3)(C5H4N-2-CH@N–C6H4–p-NO2)]PF6
[(g5-C5H5)Ru(PPh3)(C5H4N-2-CH@N–C6H11)]PF6
454
452
454
458
461
428
150.00
126.02
143.90
137.91
136.79
123.80
Table 3
Summary of structure determination of complex [(g5-C5H5)Ru
(C5H4N-2-CH@N–C6H4–p-OCH3)]PF6 (2c)
Formula
C36H32F6N2OP2Ru
785.65
Formula weight
Crystal system
Space group
orthorhombic
Pbcn
Unit cell dimensions
ꢀ
a (A)
21.1560(11)
18.3972(9)
17.5130(3)
6816.3(6)
ꢀ
b (A)
ꢀ
c (A)
3
ꢀ
V ðA Þ
Z
Crystal size (mm)
8
0.3 ꢃ 0.3 ꢃ 0.6
1.531
3184
Dcalc (g cmꢂ3
F (0 0 0)
)
h range for data collection (°)
Index ranges
1.87–28.30
ꢂ28 6 h27, ꢂ23 6 k 6 24,
ꢂ23 6 l 6 23
57 254
Reflections collected
Independent reflections
8285 [Rint ¼ 0:0354]
0.619
Absorption coefficient (mmꢂ1
Absorption correction
Refinement method
)
Fig. 1. ORTEP drawing of compound 2c with 50% probability thermal
ellipsoids. Hydrogen atoms and PF6 omitted for clarity.
empirical (SADABS
)
full-matrix least-squares on F 2
8285/0/356
1.006
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I > 2rðIÞ]
R indices (all data)
R1 ¼ 0:0462; wR2 ¼ 0:1192
R1 ¼ 0:0594; wR2 ¼ 0:1286
ꢀ
C(04) and C(05), are shorter (2.191, 2.182 and 2.196 A)
than the other two bonds involving the C(01) and C(02)
ꢀ
carbon atoms (2.214 and 2.211 A). The average Ru–C
ꢀ
distance is 2.199 A, whereas the distance between the
ꢀ
ruthenium atom and the centroid of the ring is 1.837 A
Largest difference peak and hole 0.896 and )0.530
ꢂ3
ꢀ
(e A
)
at the axis x ¼ 0:0947, y ¼ 0:0534 and z ¼ 0:4796. The
ꢀ
Ru–P bond length is 2.3100 A, which is within the usual
5. Crystal structure of 2c
ꢀ
range of Ru–P bond distances (2.20–2.43 A) [19]. The
The structure of complex 2c is shown in Fig. 1.
Representative bond length and bond angle values are
listed in Table 4. The ruthenium atom is coordinated to
two nitrogen atoms of the Schiff base ligand, one tri-
phenylphosphine ligand and a pentahapto-bound cy-
clopentadienyl ligand. The geometry around the metal
atom can be regarded as distorted octahedral if the g5-
cyclopentadienyl group is assumed to occupy three fa-
cial coordinated positions.
The [(g5-C5H5)Ru(PPh3)(C5H5N-2-CH@N–C6H4–p-
OCH3)]PF6 complex crystallizes in the orthorhombic
space group Pbcn. The cyclopentadienyl group is clearly
bonded in a pentahapto fashion to the metal. Three of
the Ru–C bond lengths, viz., those involving the C(03),
ruthenium atom is directly coordinated to two nitrogen
atoms of the Schiff base ligand with an average distance
ꢀ
of 2.090 A. The bite angle of the chelating ligand is
76.42(8°), not very different from that in other related
complexes [20]. The geometry of the complex is octa-
hedral (of the piano-stool type) with the cyclopentadie-
nyl moiety occupying three coordination sites. This is
evident in the nearly 90° values for the bond angle N(1)–
Ru–P(1) between the non-cyclopentadienyl ligands
(90.39(6)°) and for the bond angle N(11)–Ru–P(1)
(92.67(6)°) at the metal centre. The orientation of the
phenyl group of the amine is similar to the observed
mutually perpendicular orientation found for similar
types of ligand in arene ruthenium complexes [9].

P. Govindaswamy et al. / Polyhedron 23 (2004) 1567–1572
1571
Table 4
ꢀ
Selected bond lengths (A) and bond angles (°) for [CpRu(PPh3)(C5H5N-2-CH@N–C6H4–p-OCH3)]PF6 (2c)
Bond lengths
Ru(1)–N(11)
Ru(1)–C(01)
Ru(1)–C(04)
P(1)–C(31)
N(1)–C(21)
Ru–Cpa
2.0801(13)
2.214(2)
2.182(2)
1.8570(12)
1.438(3)
1.837
Ru(1)–N(1)
Ru(1)–C(02)
Ru(1)–C(05)
P(1)–C(41)
2.110(2)
2.211(2)
2.196(2)
1.8363(12)
1.3900
Ru(1)–P(1)
Ru(1)–C(03)
P(1)–C(51)
N(1)–C(1)
2.3100(8)
2.191(2)
1.8357(12)
1.296(4)
1.3900
N(11)–C(12)
N(11)–C(16)
Bond angles
N(11)–Ru–N(1)
N(1)–Ru–P(1)
76.42(8)
90.39(6)
N(11)–Ru–P(1)
92.67(6)
a Ruthenium to centroid of Cp.
6. Conclusion
References
[1] (a) M.R. Kollipara, C.R.K. Rao, P.S. Zacharias, Polyhedron 16
(1997) 2369;
We have observed interesting phenomena in the
case of the cyclopentadienyl complex 1, which distin-
guish it from the analogous pentamethylcyclopenta-
dienyl or indenyl ruthenium systems. Unlike the case
of the complex 1, the reactions of Schiff bases with the
[(g5-Cpꢁ)Ru(PPh3)2Cl] and [(g5-ind.)Ru(PPh3)2Cl]
systems yield complexes without any organic group.
We suggest that in order to obtain complexes bound
to organic ligands for these cases, one has to start
from acetonitrile complexes. The reactions of [(g5-
Cp)Ru(PPh3)2Cl] with Schiff base ligands, viz, para-
substituted N-(pyrid-2-yl methylene)phenylamines and
N-(pyrid-2-ylmethylene)-cyclohexylamine, in methanol
yielded complexes 2a–e of the type [[(g5-Cp)Ru
(PPh3)(2-PP)]X and [(g5-Cp)Ru (PPh3)(2-PC)]X]. The
molecular structure of the representative complex 2c
has been characterized by single crystal X-ray dif-
fraction analysis.
(b) R. Lalrempuia, P. Govindaswamy, Y.A. Mozharivskyj, M.R.
Kollipara, Polyhedron 23 (2004) 1069;
(c) M.R. Kollipara, L. Mishra, U.C. Agarwala, Polyhedron 6
(1987) 1383.
[2] M.R. Kollipara, E.K. Rymmai, Polyhedron 22 (2003) 307.
[3] (a) R. Lalrempuia, P.J. Carroll, M.R. Kollipara, Polyhedron 22
(2003) 1391;
(b) R. Lalrempuia, Hemant Yennawar, Y.A. Mozharivskyj, M.R.
Kollipara, J. Organomet. Chem. 689 (2004) 539.
[4] (a) R. Lalrempuia, M.R. Kollipara, Polyhedron 22 (2003) 3155;
(b) M.R. Kollipara, P. Sarkhel, S. Chakraborty, R. Lalrempuia, J.
Coord. Chem. 56 (2003) 1085;
(c) Lalrempuia, P.J. Carroll, M.R. Kollipara, J. Coord. Chem. 56
(2003) 1499.
[5] S.A. Serron, C.M. Haar, S.P. Nolan, Organometallics 16 (1997)
5120.
[6] (a) C.W. Chang, G.H. Lee, Organometallics 22 (2003) 3107;
(b) M.R. Kollipara, E.K. Rymmai, Polyhedron 22 (2003) 307.
[7] (a) C.S. Hauser, C. Slugove, K. Mereiter, R. Schmid, K. Kirchner,
L. Xiao, W. Weissensteiner, J. Chem. Soc., Dalton Trans. (2001)
2989;
(b) U. Karllson, G.Z. Wang, J.-E. Backvall, J. Org. Chem. 59
(1994) 1196;
7. Supplementary material
(c) C. Ruppin, P.H. Dixneuf, S. Lewlier, Tetrahedron Lett. 20
(1998) 5365;
(d) B. Seiller, C. Bruneau, P.H. Dixneuf, J. Chem. Soc., Chem.
Commun. 493 (1994);
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre (CCDC), CCDC No. 231959 for complex 2c.
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; website: www: http://
www.ccdc.cam.ac.uk).
(e) V. Rotleng, R. Bertani, M. Pfeffer, C. Sirlin, J. Hirschinges,
Inorg. Chem. 40 (2001) 5117;
(f) C.A. Merlic, M.E. Pauly, J. Am. Chem. Soc. 18 (1996) 11319.
[8] S.S. Keisham, Y.A. Mozharivskyj, P.J. Carroll, M.R. Kollipara,
J. Organomet. Chem. 689 (2004) 1249.
[9] R. Lalrempuia, M.R. Kollipara, P.J. Carroll, Polyhedron 22
(2003) 605.
[10] S.K. Mandal, A.R. Chakravarty, Polyhedron 10 (1991) 2483.
[11] (a) R.N. Dominey, B. Hauser, J. Habbard, J. Dunham, Inorg.
Chem. 30 (1991) 4754;
(b) E.V. Dose, L.J. Wilson, Inorg. Chem. 17 (1978) 2660.
[12] M.I. Bruce, N.J. Windsor, Aust. J. Chem. 30 (1977) 1601.
[13] D. Becke, J. Chem. Phys. 98 (1993) 5648.
[14] XRD Single Crystal Software; Bruker Analytical X-ray systems,
Madison, WI, 2002.
Acknowledgements
We thank Professor R.H. Duncan Lyngdoh for his
help in preparing the manuscript. K.M.R. and P.G.
thank the Sophisticated Instruments Facility (SIF), In-
dian Institute of Science, Bangalore, for providing the
NMR facility.
[15] G.M. Sheldrick, SHELXS 86, Program for Crystal Structure
€
€
Solution, University of Gottingen, Gottingen, Germany, 1986.
[16] M. Sheldrick, SHELXS 97, Program for Crystal Structure Refine-
€
ment, University of Gottingen, Gottingen, Germany, 1997.
€

1572
P. Govindaswamy et al. / Polyhedron 23 (2004) 1567–1572
[17] C.K. Johnson, ORTEP II: A Fortran Thermal Ellipsoid Plot
Program for Crystal Structure Illustrations, ORNL-5138, 1976.
[18] J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[19] L.J. Guggenberger, Inorg. Chem. 12 (1973) 1317.
[20] S.K. Mandal, A.R. Chakravarty, Polyhedron 11 (1992)
823.