Pentamethylcyclopentadienyl ruthenium(II) complexes of para-substituted N-(pyrid-2-ylmethylene)-phenylamine ligands: Syntheses, spectral and structural studies

Article abstract of DOI:10.1016/j.poly.2004.11.021

The reaction of [(η⁵-C₅Me₅)Ru(PPh ₃)₂Cl] (1) with acetonitrile in the presence of excess NH₄PF₆ leads to the formation of the cationic ruthenium(II) complex [(η⁵-C₅Me₅) Ru(PPh₃)₂(CH₃CN)]PF₆ (2). The complex (2) reacts with a series of N,N′ donor Schiff base ligands viz. para-substituted N-(pyrid-2-ylmethylene)-phenylamines (ppa) in methanol to yield pentamethylcylopentadienyl ruthenium(II) Schiff base complexes of the formulation [(η⁵-C₅Me₅)Ru(PPh ₃)(C₅H₄N-2-CHN-C₆H ₄-p-X)]PF₆ [3a]PF₆-[3f]PF₆, where C₅Me₅ = pentamethylcylopentadienyl, X = H, [3a]PF ₆, Me, [3b]PF₆, OMe, [3c]PF₆, NO₂, [3d]PF₆, Cl, [3e]PF₆, COOH, [3f]PF₆. The complexes were isolated as their hexafluorophosphate salts. The complexes were fully characterized on the basis of elemental analyses and NMR spectroscopy. The molecular structure of a representative complex, [(η⁵-C ₅Me₅)Ru(PPh₃)(C₅H ₄N-2-CHN-C₆H₄-p-Cl)]PF₆ [3e]PF ₆, has been established by X-ray crystallography.

Full text of DOI:10.1016/j.poly.2004.11.021

Polyhedron 24 (2005) 391–396
www.elsevier.com/locate/poly
Pentamethylcyclopentadienyl ruthenium(II) complexes of
para-substituted N-(pyrid-2-ylmethylene)-phenylamine
ligands: syntheses, spectral and structural studies
a
Keisham Sarjit Singh , Patrick J. Carroll , Mohan Rao Kollipara
b
a,
*
a
Department of Chemistry, North-Eastern Hill University, Shillong 793022, India
Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
b
Received 8 November 2004; accepted 22 November 2004
Abstract
The reaction of [(g5-C5Me5)Ru(PPh3)2Cl] (1) with acetonitrile in the presence of excess NH4PF6 leads to the formation of the
cationic ruthenium(II) complex [(g5-C5Me5)Ru(PPh3)2(CH3CN)]PF6 (2). The complex (2) reacts with a series of N,N0 donor Schiff
base ligands viz. para-substituted N-(pyrid-2-ylmethylene)-phenylamines (ppa) in methanol to yield pentamethylcylopentadienyl
ruthenium(II) Schiff base complexes of the formulation [(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-p-X)]PF6 [3a]PF6–[3f]PF6,
where C5Me5 = pentamethylcylopentadienyl, X = H, [3a]PF6, Me, [3b]PF6, OMe, [3c]PF6, NO2, [3d]PF6, Cl, [3e]PF6, COOH,
[3f]PF6. The complexes were isolated as their hexafluorophosphate salts. The complexes were fully characterized on the basis of ele-
mental analyses and NMR spectroscopy. The molecular structure of a representative complex, [(g5-C5Me5)Ru(PPh3)(C5H4N-2-
CH@N-C6H4-p-Cl)]PF6 [3e]PF6, has been established by X-ray crystallography.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Keywords: Ruthenium; Pentamethylcyclopentadienyl; N-(pyrid-2-ylmethylene)-phenyl-amines; Pyridine-2-carboxaldehyde
1. Introduction
is one of the key routes to explore their chemistry. There
exist an extensive study on the chemistry of cyclopenta-
dienyl ruthenium(II) with a variety of ligands [5]. In con-
trast, the analogous pentamethylcyclopentadienyl
ruthenium(II) complexes have not been much studied.
The chemistry of the pentamethylcylopentadienyl ruthe-
nium fragment is largely based on the tetramer
[Cp*RuCl]4 [6] and on the tris-acetonitrile
[Cp*Ru(CH3CN)3]PF6 adduct [7], which upon addition
of monodentate ligands yield octahedral complexes
[Cp*RuX(L)2] [8,9] and [Cp*Ru(L)2(CH3CN)]PF6 [7],
respectively. However, to the best of our knowledge,
pentamethylcylopentadienyl ruthenium(II) phosphine
complexes chelated with N,N0 donor Schiff base ligands
are not known, although there is an extensive chemistry
available on arene and cyclopentadienyl ruthenium(II)
[3b,10–12] systems.
Half sandwich ruthenium(II) complexes have re-
ceived great attention in the past few decades owing to
their high reactivity ([1] and reference cited in) and cat-
alytic activity [2]. The syntheses, structures and reactiv-
ity of half sandwich ruthenium(II) complexes viz.,
cyclopentadienyl, indenyl and arene have been studied
in our laboratory. Our current interest has involved sub-
stitution of one triphenylphosphine and a chloride
ligand of the complex [Cp0Ru(PPh3)2Cl], where
Cp0 = ind., Cp*, Cp with N-donor ligands [3,4], which
*
Corresponding author. Tel.: +91 364 272 2620; fax: +91 364
2550076.
E-mail addresses: mrkollipara@yahoo.com, mrkollipara@rediff-
mail.com, kmrao@nehu.ac.in (M.R. Kollipara).
0277-5387/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.11.021

392
K.S. Singh et al. / Polyhedron 24 (2005) 391–396
This present work arises from our interest to synthe-
solid was filtered off and the filtrate was rotary evapo-
rated. The yellow residue was dissolved in dichlorome-
thane (5 ml) and filtered to remove excess NH4PF6.
The filtrate on concentration and addition of excess hex-
ane gave a yellow crystalline solid. The yellow solid was
collected and washed with hexane to afford 83% yield of
complex (2).
size various half sandwich ruthenium(II) complexes con-
taining N,N0 donor Schiff base ligands. Having this in
mind, we have previously described the syntheses of
indenyl, cyclopentadienyl and arene [3,10] ruthenium(II)
Schiff base complexes. In a continuation of our study,
herein we report the syntheses of a series of pentameth-
ylcyclopentadienyl ruthenium(II) Schiff base complexes
[3a]PF6–[3f]PF6. The elemental analyses, spectral and
structural characterization of the complexes is
presented.
1H NMR (CDCl3, d): 1.32 (s, 15H, Cp), 2.17 (s, 3H,
CH3CN), 6.78–7.83 (m, 30H).
31P{1H} NMR (CDCl3, d): 45.28 (s. 2P, PPh3), ꢀ143
(septet, PF6ꢀ).
2.3. Preparation of [(g5-C5Me5)Ru(PPh3)(C5H4N-2-
CH@N-C6H4-p-X)]PF6 [X = H [3a]PF6, Me [3b]PF6,
OMe [3c]PF6, NO2 [3d]PF6, Cl [3e]PF6, COOH [3f]
PF6
2. Experimental
2.1. General remarks
Reactions were carried out in distilled and dried
solvents under nitrogen atmosphere. The solvents were
purified according to the standard procedures. Ru-
Cl3 Æ3H2O was purchased from Arora Matthey (P)
Ltd. and used as such. Pyridine-2-carboxaldehyde
(Fluka) was used as received. All liquid aromatic
amines were reagent grade and were distilled prior to
use while solid aromatic amines were used as such.
Microanalyses (C, H, N) were done by Regional
Sophisticated Instrumentation Centre (RSIC), NEHU
using a Perkin–Elmer-2400 CHNS/O analyzer. FT-IR
spectra were recorded on a Perkin–Elmer-model 983
spectrophotometer with samples prepared as KBr
These complexes were prepared by using a general
method.
The complex (2), (0.1 g, 0.105 mmol) and the
appropriate ligand (0.210 mmol) were mixed in
20 ml of methanol. After a few minutes the yellow
solution turned into a dark brown suspension. The
mixture was refluxed for 1 h under nitrogen atmo-
sphere. The solution was cooled to room temperature
and solvent was removed in a rotary-evaporator to
dryness. The brown residue was dissolved in dichlo-
romethane (5 ml) and filtered through a short silica
gel column. The filtrate on subsequent concentration
and addition of excess diethyl ether gave complexes
[3a]PF6–[3f]PF6 as dark brown solids in 81–87%
yield.
pellets. Electronic spectra were recorded on
a
Hitachi-U-2300 spectrophotometer and conductivity
measurements were done by Wayne Kerr Automatic
Precession Bridge B905 using ca. 10ꢀ4 M solutions in
dry acetonitrile at room temperature (Km value in
S cm2 molꢀ1). The NMR spectra were obtained
in CDCl3 solution and recorded on a Bruker ACF-
300 MHz spectrometer. Chemical shifts are relative
to TMS (1H, 13C{1H}) and to 85% H3PO4
(31P{1H}); coupling constants are given in hertz. The
ligands (C5H4N-2-CH@N-C6H4-p-X), (where X = H,
Me, OMe, Cl, NO2, COOH) [13] were prepared by
the condensation of pyridine-2-carboxaldehyde with
the appropriate amines. The precursor complex [(g5-
C5Me5)Ru(PPh3)2Cl] [14] was prepared by following
the literature method.
2.4. Analytical and spectroscopic data
2.4.1. [(g5- C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H5)]-
PF6 [3a]PF6
Yield:
83%
(72
mg).
Anal.
Calc.
for
C40H40N2P2F6Ru: C, 58.13; H, 4.81; N, 3.39. Found:
C, 57.6; H, 5.01; N, 3.45%. IR (KBr, cmꢀ1): m(C@N)
ðPF6ꢀÞ
1600, m
844.
1H NMR (CDCl3, J Hz): d 1.31 (s, 15H, C5Me5); 7.14
(d, 2H, JH–H = 2.89); 7.18–7.64 (m, 21H); 8.25 (d, 1H,
2.64); 8.92 (d, 1H, 3.38).
13C{1H} NMR (CDCl3): d 9.31 (s, C5Me5(CH3));
88.73 (s, C5Me5 (ring)); 122.46–151.26 (phenyl and pyr-
idyl carbons); 157.83 (N@CH).
2.2. Preparation of [(C5Me5)Ru(PPh3)2(NCCH3)]PF6
[2]PF6
31P{1H} NMR: d 45.26 (s, PPh3); ꢀ141 (septet,
PF6ꢀ).
The complex was prepared by following the literature
method [15] as delineated here. The complex
[Cp*Ru(PPh3)2Cl] (0.1 g, 0.125 mmol) and NH4PF6
(0.041 g, 0.250 mmol) were refluxed in CH3CN (30 ml)
for 2 h. During this time the orange red suspension
turned yellow and a white solid appeared. The white
2.4.2. [(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-
p-Me)]PF6 [3b]PF6
Yield:
86%
(76
mg).
Anal.
Calc.
for
C41H42N2P2F6Ru: C, 58.59; H, 5.00; N, 3.33. Found:
C, 59.35; H, 4.99; N, 3.67%.
IR (KBr, cmꢀ1): m(C@N) 1598, m
844.
ðPF6ꢀÞ

K.S. Singh et al. / Polyhedron 24 (2005) 391–396
393
1H NMR (CDCl3, J Hz): d 1.31 (s, 15H, C5Me5); 2.38
(s, 3H); 7.07 (d, 2H, JH–H = 5.73); 7.18 (d, 2H, JH–H
2.4.6. [(g5- C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-
p-CO2H)]PF6 [3f]PF6
=
4.82); 7.29–7.62 (m, 18H); 8.22 (d, 1H, JH–H = 3.48);
8.92 (d, 1H, JH–H = 3.38).
Yield: 84% (77 mg). Anal. Calc. for C41H40N2O2P2-
F6Ru: C, 55.22; H, 4.60; N, 3.22. Found: C, 54.75; H,
4.83; N, 3.46%.
13C{1H} NMR (CDCl3): d 9.23 (s, C5Me5(CH3));
15.29 (s, Me); 88.47 (s, C5Me5 (ring)); 123.48–152.01
(phenyl and pyridyl carbons); 160.46 (N@CH).
31P{1H} NMR: d 46.55 (s, PPh3); ꢀ142 (septet,
PF6ꢀ).
IR (KBr, cmꢀ1): m(C@N) 1610, m
844.
ðPF6ꢀÞ
1H NMR (CDCl3, J Hz): d 1.31 (s, 15H, C5Me5); 6.64
(d, 2H, JH–H = 6.73); 7.37–8.05 (m, 17H); 8.02 (d, 2H,
JH–H = 4.02); 8.34 (d, 1H, JH–H = 2.63); 8.62 (s, 1H);
8.95 (d, 1H, JH–H = 5.22).
2.4.3. [(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-
p-OMe)]PF6 [3c]PF6
13C{1H} NMR (CDCl3): d 9.42 (s, C5Me5 (CH3));
88.86 (s, C5Me5 (ring)); 124.05–155.96 (phenyl and pyr-
idyl carbons); 160.46 (N@CH), 178.26 (C(CO2H)).
31P{1H} NMR: d 47.28 (s, PPh3); ꢀ145 (septet,
PF6ꢀ).
Yield: 87% (78 mg). Anal. Calc. for C41H42N2OP2-
F6Ru: C, 57.49; H, 4.91; N, 3.27. Found: C, 56.29; H,
4.97; N, 3.54%.
IR (KBr, cmꢀ1): m(C@N) 1602, m
844.
1H NMR (CDCl3, J Hz): d 1.32 (s, 15H, C5Me5);
3.84 (s, 3H); 6.77 (d, 2H, JH–H = 5.73); 7.13–7.65 (m,
ðPF6ꢀÞ
2.5. Structure analysis and refinement
20H); 8.24 (d, 1H, JH–H = 2.97); 8.87 (d, 1H, JH–H
5.10).
=
X-ray quality crystals of complex [3e]PF6 were grown
by slow diffusion of hexane into a dichloromethane solu-
tion of complex [3e]PF6. The X-ray intensity data were
collected on a Rigaku Mercury CCD area detector
employing graphite-monochromated Mo Ka radiation
13C{1H} NMR (CDCl3): d 9.24 (s, C5Me5(CH3));
88.42 (s, C5Me5 (ring)); 113.99 (s, OCH3); 125.48–
151.88 (phenyl and pyridyl carbons); 161.66 (N@CH).
31P{1H} NMR: d 46.63 (s, PPh3); ꢀ143 (septet,
PF6ꢀ).
˚
(k = 0.71069 A) at 143 K. Intensity data were corrected
for Lorentz and polarization effects and for absorption
correction using REQAB [16]. The structure was solved
by direct methods (SIR 97) [17] and refinement was by
2.4.4. [(g5- C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-
p-NO2)]PF6 [3d]PF6
full matrix least squares based on F2 using (SHELXL
-
97) [18]. The weighting scheme used was
Yield: 81% (74 mg). Anal. Calc. for C40H39N3O2P2-
F6Ru: C, 55.12; H, 4.47; N, 4.82. Found: C, 55.96; H,
4.73; N, 4.26%.
W ¼ 1=½r2ðF 20Þ þ 0:0822P2 þ 3:3880Pꢁ,
where
P ¼
ðF 20 þ 2F 2cÞ=3. The X-ray data were corrected for the
presence of disordered solvent using ‘‘SQUEEZE’’ [19].
Non-hydrogen atoms were refined anisotropically and
hydrogen atoms were refined using a ‘‘riding’’ model.
IR (KBr, cmꢀ1): m(C@N) 1608, mPF 844.
ꢀ
6
1H NMR (CDCl3; J Hz): d 1.32 (d, 15H, C5Me5
JP–H = 1.09); 6.93 (d, 2H, JH–H = 2.89); 7.18–7.96 (m,
18H); 8.15 (d, 2H, JH–H = 6.12); 8.41 (d, 1H, JH–H
=
3.34); 8.93 (d, 1H, 3.59).
13C{1H} NMR (CDCl3): d 9.45 (s, C5Me5(CH3));
88.91 (s, C5Me5 (ring)); 124.86–151.99 (phenyl and pyr-
idyl carbons); 162.38 (N@CH).
C21
C20
C22
C15
C16
C17
C19
31P{1H} NMR: d 47.23 (s, PPh3); ꢀ141 (septet,
Cl1
C10
C18
C9
C14
C13
C8
PF6ꢀ).
C39
C40
C35
C11
C12
Ru1
C33
C38
C29
2.4.5. [(g5- C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-
p-Cl)]PF6 [3e]PF6
C34
C7
C6
N2
C32
P1
C31
Yield:
87%
(76
mg).
Anal.
Calc.
for
C30
C37
N1
C40H39N2P2F6ClRu: C, 55.84; H, 4.53; N, 3.25. Found:
C, 54.20; H, 4.73; N, 3.12%.
C36
C23
C28
C1
C5
C24
IR (KBr, cmꢀ1): m(C@N) 1612, m
844.
ðPF6ꢀÞ
1H NMR (CDCl3, J Hz): d 1.32 (s, 15H, C5Me5); 6.83
(d, 2H, JH–H = 3.24); 6.94–7.67 (m, 20H); 8.29 (d, 1H,
JH–H = 1.98); 8.90 (d, 1H, JH–H = 4.73).
13C{1H} NMR (CDCl3): d 9.45 (s, C5Me5); 88.73 (s,
C5Me5 (ring)); 125.19–152.07 (phenyl and pyridyl car-
bons); 161.83 (N@CH).
C2
C4
C25
C3
C27
C26
Fig. 1. Molecular structure of complex [3e]PF6 with 30% thermal
ellipsoids. Hydrogen atoms and the PF6 ion have been omitted for
clarity.
31P{1H} NMR: d 46.53 (s, PPh3); ꢀ143 (septet,
PF6ꢀ).

394
K.S. Singh et al. / Polyhedron 24 (2005) 391–396
Refinement converged to R1 = 0.0444 and wR2 = 0.1267.
Fig. 1 is an ORTEP [20] representation of the molecule
with 30% thermal ellipsoids displayed.
dissociation of one of the triphenylphosphine ligands.
In fact, one triphenylphosphine can be readily substi-
tuted by diazonium salts from [Cp*Ru(PPh3)2Cl] irre-
spective of the solvent used (acetone or toluene), in
contrast the same substitution is only possible in the
analogous [CpRu(PPh3)2Cl] complex using toluene un-
der drastic conditions [21]. It is notable that the Cp* li-
gand is less stable as compared to the analogous Cp
ligand and that prolonged reaction under drastic condi-
tions results in removal of the Cp* ligand from the com-
plex. Very recently we have studied the reaction of
[Cp0Ru(PPh3)2Cl], [where Cp0 = ind., Cp*, Cp] with ste-
rically demanding the multidentate tetra-2-pyridyl-1,4-
pyrazine (tppz) ligand, where attempts to synthesis
Cp* and indenyl complexes chelated with the tppz li-
gand were unsuccessful, instead we isolated complexes
of the type [(tppz)Ru(PPh3)2X] [22]. However, when
the reaction was carried out with [CpRu(PPh3)2Cl], the
g5-bonded cyclopentadienyl group remained intact to
the metal thus forming a complex of the type
[CpRu(L2)(PPh3)]+ [5b]. This indicates the more labile
nature of the indenyl and Cp* ligands as compared to
the cyclopentadienyl ligand.
3. Results and discussion
While N-chelating cyclopentadienyl ruthenium(II)
complexes are well known [3b,5,10], only a few reports
about the analogous pentamethylcyclopentadienyl are
available in the literature [4]. Here we described the
preparation of six new monocationic pentamethylcyclo-
pentadienyl ruthenium(II) phosphine complexes
[3a]PF6–[3f]PF6 containing N,N0 donor Schiff base li-
gands, and their characterization with the help of ele-
mental analyses, IR and NMR (1H, 31P{1H}, 13C{1H})
spectroscopy. The molecular structure of a representa-
tive complex [3e]PF6 was determined by a single X-ray
study. To the best of our knowledge this complex is
the first structurally characterized pentamethyl-cyclo-
pentadienyl ruthenium(II) Schiff base complex contain-
ing a phosphine ligand. The complexes were obtained
in good yield, by reacting complex [2]PF6 with the
appropriate ligands in methanol as depicted in Scheme 1.
We have recently synthesized cyclopentadienyl ruthe-
nium(II) complexes of Schiff base ligands such as
[CpRu(PPh3)(ppa)]+ [3b] by reacting the ligand (ppa)
with the complex [CpRu(PPh3)2Cl]. However, in this
present case the complexes are readily obtained in high
yields by the reaction of the acetonitrile complex
[2]PF6 with the appropriate ligand. These complexes
can also be prepared in lower yield by the reaction of
complex (1) with the ligand over a longer period of time.
This suggests the acetonitrile complex [2]PF6 is a better
precursor than their chloro analog (1) for the prepara-
tion of these complexes [3a]PF6–[3f]PF6. This is due to
the cationic nature of the complex [2]PF6 which makes
ready coordination of the ligand to the metal atom com-
pared to the neutral chloro complex (1). It has been re-
ported that the pentamethylcyclopentadienyl complexes,
[Cp*Ru(PPh3)2Cl] are much more reactive than the
analogous cyclopentadienyl complexes, which is attrib-
uted to the electron rich nature of the Cp* ligand and
the presence of five sterically hindered methyl groups
associated with these complexes which facilitates ready
The complexes [3a]PF6–[3f]PF6 are highly soluble in
polar solvents but insoluble in non-polar solvents. The
conductivity measurement (10ꢀ4 in CH3CN) of the
complexes showed the complexes are ionically dissoci-
ated into a 1:1 electrolytic system [23]. The microanal-
yses data of the complexes are in good agreement with
that of their formulations. The IR spectra of the com-
plexes exhibit bands corresponding to mC@N of the
coordinatedꢀ ligands at 1598–1612 cmꢀ1, while mP–F
of the PF6 counter ion appears at 844 cmꢀ1. The
IR spectra showed a shift of the C@N stretching fre-
quency towards lower wavenumbers as compared with
the free base ligands (1598–1612 versus 1619–1638
cmꢀ1) indicating N-coordination of the C@N group
[24]. The complex ([3d]PF6) showed a characteristic
IR band for symmetric mNO and asymmetric mNO at
2
2
1348 and 1458 cmꢀ1, respectively, similar to those ob-
served for other reported compounds. The proton
NMR spectra of these complexes displayed a sharp
singlet (except [3d]PF6) at d 1.3 for the methyl protons
of the pentamethylcyclopentadienyl while for the com-
plex [3d]PF6 the resonance is observed as a doublet.
Scheme 1. X = H, [3a]PF6; Me, [3b]PF6; OMe, [3c]PF6; NO2, [3d]PF6; Cl, [3e]PF6; COOH, [3f]PF6.

K.S. Singh et al. / Polyhedron 24 (2005) 391–396
395
The doublet observed could be due to the coupling of
methyl protons of the Cp* moiety with the phospho-
rus of the triphenylphosphine. The resonance of ortho
proton of the pyridine ring of the ligand appeared as
a doublet in the range of d 8.87–8.95. The doublet ob-
served was probably due to coupling of the methine
proton with the proton of the aromatic ring of the
coordinated ligands. However, this proton appears as
singlet at d 8.6 in the case of the complex [3f]PF6.
We did not observe the resonance for the acidic pro-
ton CO2H in the proton NMR spectrum of the com-
plex [3f]PF6. The spectra of all these complexes also
contained multiple resonances for the aromatic pro-
tons in the range of d 6.94–8.05. The 13C{1H} NMR
spectra of the complexes contained resonances for
C5Me5 carbons at around d 9.49 for the methyl group
of Cp* and d 89.26 for the ring carbons. The reso-
nance observed at around d 161 could be due to the
imine carbon (CH@N) of the Schiff base ligand. The
13C{1H} NMR spectrum of complex [3f]PF6 showed
a singlet at d 178, which is assignable to the carbon
of COOH. The spectra also showed resonances in
the range of d 123.48–155.96 for the aromatic carbons
and carbons of the pyridyl ring. The 31P{1H} NMR
spectra of the complexes displayed a singlet in the
range of d 45.26–46.7 due to the triphenylphosphine
moiety as compared to d 38.5, observed in the neutral
precursor complex [Cp*Ru(PPh3)2Cl]. The spectra also
contained a septet in the range of d ꢀ141 to ꢀ145 for
fect of this disorder was removed from the data using
the ‘‘SQUEEZE’’ program, which was written to correct
data for the presence of disordered solvents [19]. The
perspective view of the cationic part of the complex with
the numbering scheme of the atoms is shown in Fig. 1.
Details of the crystallographic data collection are given
in Table 2. Selected bond lengths and angles are pre-
sented in Table 3.
The complex crystallized in the P21/c space group and
consists of complex cation and PF6 anions joined by col-
umbic forces. The ruthenium atom presents a pseudo-
octahedral environment with the Cp* ligand occupying
three facile coordination sites, p-bonded to the metal
in g5-fashion, while the remaining coordination positions
are occupied by the P atom of the triphenylphosphine
Table 2
Summary of structure determination of complex [3e]PF6
Formula
C40H39N2P2F6ClRu
Formula weight
Crystal class
Space group
Z
860.19
monoclinic
P21/c (#14)
4
Cell constants
˚
a (A)
˚
10.7236(5)
19.9676(9)
18.6390(9)
98.3575(4)
3948.7(3)
6.05
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
ꢀ
the PF6 counter ion. The electronic spectra of the
l (cmꢀ1
)
complexes in dichloromethane exhibited absorption
bands in the range of 475–493 nm (Table 1). These
low energy absorption bands present in all of these
complexes are characteristics of Ru(dp)–L(p*), metal
to ligand charge transfer transitions (MLCT).
Crystal size (mm)
Dc (g/cm3)
F(000)
0.40 · 0.35 · 0.30
1.447
1752
˚
Radiation
2h range
hkl collected
Mo Ka (k = 0.71069 A)
5.12–54.96
ꢀ13 6 h 6 13; ꢀ25 6 k 6 23;
ꢀ23 6 l 6 24
3.1. Crystal structure
Number of reflections measured
Number of unique reflections
Number of observed reflections
Number of reflections used in
refinement
24099
8816 (Rint = 0.0191)
7696 (F > 4r)
8816
The crystal structure determination was carried out
for the representative complex [3e]PF6. There is a disor-
dered area in the crystal, which was a combination of
PF6ꢀs and dichloromethane, the solvent of crystalliza-
tion. The space group has four symmetry-related posi-
tions in the unit cell, of which the PF6ꢀs ions occupy
two and the other two by the CH2Cl2 molecules. The ef-
Number of parameters
R indices (F > 4r)
R indices (all data)
445
R1 = 0.0444; wR2 = 0.1267
R1 = 0.0499; wR2 = 0.1332
1.052
GOF
Final difference peaks (e/A )
3
˚
+1.566, ꢀ0.656
Table 1
UV–Vis and conductivity data of the complexes at room temperature
No.
Complexes
kmax (nm)
Conductivity Km (S cm2 molꢀ1
)
1.
2.
3.
4.
5.
6.
[(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H5)]PF6 [3a]PF6
486
180
172
159
167
145
169
[(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-p-CH3)]PF6 [3b]PF6
[(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-p-OMe)]PF6 [3c]PF6
[(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-p-NO2)]PF6 [3d]PF6
[(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-p-Cl)]PF6 [3e]PF6
[(g5-C5Me5)Ru(PPh3)(C5H4N-2-CH@N-C6H4-p-CO2H)]PF6 [3f]PF6
490
475
482
493
478

396
K.S. Singh et al. / Polyhedron 24 (2005) 391–396
Table 3
Molecular structure of complex [3e]PF6 with 30% thermal ellipsoids
cle can be found, in the online version at doi:10.1016/
j.poly.2004.11.021.
˚
Bond lengths (A)
Ru–N(1)
Ru–N(2)
C*–Ru
2.106(2)
2.097(2)
1.8536(2)
Ru–P(1)
N(2)–C(6)
2.3593(7)
1.297(4)
References
C* = centroid of C(13), C(14), C(15), C(16), C(17)
[1] M.A. Bennett, K. Khan, E. Wenger, Comprehensive Organome-
tallic Chemistry, Elsevier, Oxford, 1995, p. 473 (Chapter 8).
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Kirchner, L. Xiao, W. Weissensteiner, J. Chem. Soc., Dalton
Trans. (2001) 2989;
Bond angles (ꢁ)
N(1)–Ru–N(2)
N(2)–Ru–P(1)
75.67(9)
92.84(6)
N(1)–Ru–P(1)
88.79(6)
Hydrogen atoms and the PF6 ion have been omitted for clarity.
¨
(b) A. FUrstner, M. Picquet, C. Bruneau, P.H. Dixneuf, Chem.
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(b) P. Govindaswamy, Y.A. Mozharivskyj, M.R. Kollipara,
Polyhedron 23 (2004) 1567.
and N atoms of the Schiff base ligand. The average bond
˚
distance of ruthenium to ring carbon is 2.2198 A,
whereas the distance between the ruthenium and the
˚
centroid of the ring is 1.8536(2) A. The Ru–P(1) bond
˚
length, 2.3593(7) A, is within the usual range of Ru–P
˚
bond distances (2.20–2.43 A) [25]. The ruthenium and
˚
nitrogen bond distances, 2.106(2) and 2.097(2) A, are
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(1997) 2369;
within the range of reported compounds. There is no
significant difference in the C–C bond lengths in the
cyclopentadienyl ring. The bond lengths falls within
(b) R. Lalrempuia, P. Govindaswamy, Yurij A. Mozharivskyj,
M.R. Kollipara, Polyhedron 23 (2004) 1069.
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(1988) 711;
˚
the range of 1.418(4)–1.452(4) A, suggesting the delocal-
(b) P.J. Fagan, M.D. Ward, J.V. Caspar, J.C. Calabrese, P.J.
Krusic, J. Am. Chem. Soc. 110 (1988) 2981;
(c) P.J. Fagan, W.S. Mahoney, J.C. Calabrese, I.D. Williams,
Organometallics 9 (1990) 1843.
ization of p-electrons in the ring. Further, the five-mem-
bered ring is planar as evident by the nearly equal bond
distances between the ruthenium and ring carbons. The
angle between N(1)–Ru(1)–N(2), 75.67(9)ꢁ, is very close
to those reported for the similar ligand in indenyl ruthe-
nium(II) complexes [3a]. The complex adopts the famil-
iar ‘‘piano stool’’ structure as evident by the nearly 90ꢁ
bond angles for N(1)–Ru–P(1) (88.79(6)ꢁ) and N(2)–
Ru–P(1) (92.84(6)ꢁ).
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¨
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(2003) 605.
4. Conclusions
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Chem. 30 (1991) 4754;
The present study describes the simple synthetic
methodology for the preparation of six new monocat-
ionic pentamethylcyclopentadienyl ruthenium(II) Schiff
base complexes. Complex [3e]PF6 provides a first insight
into the structural data of pentamethylcyclopentadienyl
ruthenium(II) Schiff base complexes containing a phos-
phine ligand.
(b) E.V. Dose, L.J. Wilson, Inorg. Chem. 17 (1978) 2660.
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Appl. Crystallogr. 32 (1999) 115.
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Crystal structures, University of Go¨ttingen, Go¨ttingen, Germany,
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Appendix A. Supplementary data
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[20] ORTEP-II: A Fortran Thermal Ellipsoid Plot Program for Crystal
Structure Illustrations, C.K. Johnson, 1976, ORNL-5138.
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684.
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre (CCDC), CCDC No. 252029 for complex 3e.
Copies of this information may be obtained free of
charge from the director, CCDC, 12 Union Road, Cam-
bridge, CB2 1EZ, UK (fax: +44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.ca-
m.ac.uk). Supplementary data associated with this arti-
[22] K.S. Singh, Yurij A. Mozharivskyj, M.R. Kollipara (unpublished
work).
[23] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
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