Ruthenium-carbonyl complexes with P/O or P/N donor ligands: Effect of the chelate ring size and donor atom

Article abstract of DOI:10.1016/j.poly.2012.05.016

Ruthenium(II) carbonyl complexes containing triarylphosphines and hybrid ligands PPh₂-X (X = o-dimethylaniline - P-N, o-pyridine - P-Py, or o-anisole - P-O) were synthesized and characterized. Six new complexes with the formula cis,trans-[RuCl<

Full text of DOI:10.1016/j.poly.2012.05.016

Polyhedron 42 (2012) 207–215
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Ruthenium-carbonyl complexes with P/O or P/N donor ligands: Effect
of the chelate ring size and donor atom
Francisco D. Fagundes a, Juliana P. da Silva a, Clebson L. Veber a, Andersson Barison a, Carlos B. Pinheiro b,
Davi F. Back c, Jackson R. de Sousa d, Márcio P. de Araujo a,
⇑
a Departamento de Química, UFPR, Centro Politécnico, CP 19081, CEP 81531-980, Curitiba, PR, Brazil
b Departamento de Física, ICEX, UFMG, Pampulha, CEP 31270-901, Belo Horizonte, MG, Brazil
c Departamento de Química, UFSM, CEP 97105-900, Santa Maria, RS, Brazil
d Departamento de Química Orgânica e Inorgânica, UFC, CEP 60455-970, Fortaleza, CE, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Ruthenium(II) carbonyl complexes containing triarylphosphines and hybrid ligands PPh2-X (X =
o-dimethylaniline – P–N, o-pyridine – P-Py, or o-anisole – P–O) were synthesized and characterized.
Six new complexes with the formula cis,trans-[RuCl2(CO)(PPh2-X)(PR3)] (X = o-dimethylaniline, R = Ph
1a; X = o-pyridine, R = Ph 2a; X = o-anisole, R = Ph 3a; X = o-dimethylaniline, R = p-tol 1b; X = o-pyridine,
R = p-tol 2b; and X = o-anisole, R = p-tol 3b) were obtained by starting from the appropriate precursors,
[RuCl2(CO)(DMF)(PPh3)2] or [RuCl2(CO)(DMF)(P{p-tol}3)2]. The two chlorine atoms are in cis position to
each other, and the monophosphine (PPh3 or P{p-tol}3) is in trans position to the nitrogen or oxygen of
the PPh2-X ligand. The synthesized complexes were characterized by 1D–1H, 31P{1H} and 2D-correlations
HMBC 31P–1H NMR, vibrational spectroscopy, elemental analysis, and X-ray diffraction structural deter-
mination (for complexes 1a, 2aÁCH2Cl2, 3a, and 3bÁCH2Cl2). Only the complexes containing the P–O ligand
(3a and 3b) reacted with carbon monoxide (at 1 atm and room temperature). The NMR (31P{1H}, 1H) data
was compatible with carbon monoxide coordination at the OCH3 position, which led to the formation of
dicarbonyl complexes [RuCl2(CO)2(P–O)(PR3)] (R = Ph 4a or p-tol 4b), and proved the hemilabile behavior
of the P–O ligand. In addition, the complexes underwent isomerization in solution when exposed to
ambient light, and the products were analyzed by 31P{1H} NMR. The X-ray structures and the chemical
shift in the 31P NMR spectra were correlated and discussed.
Received 28 February 2012
Accepted 16 May 2012
Available online 26 May 2012
Keywords:
Hybrid ligands
Phosphines
31P NMR
Ruthenium
Reactivity
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
ence of soft and hard donor atoms in the same ligand can lead to
labilization of the atom weakly bound to the metal center. The soft
The increasing demand for new transition metal complexes has
led to the use of ligands with different donor atoms in their struc-
tures and to the application of these new complexes as catalysts for
various organic transformations [1–6] and as chemical sensors
[7,8] for the determination of several analytes. The possibility of
generating a vacant coordination site allows the study of the inter-
action between these complexes and small molecules, such as H2,
CO, NO, N2, and H2S, aiming at their utilization in catalysis [1–6]
and biological systems [9–16], for instance.
donor atom is expected to form stronger bonds with soft metals,
such as Ru(II), Rh(I), Pd(II), and Pt(II), as compared to hard donor
atoms.
Herein we present the synthesis, characterization, reactivity
with carbon monoxide, and isomerization studies of six carbonyl
complexes with general formula [RuCl2(CO)(PPh2-X)(PR3)] (X =
o-dimethylaniline, R = Ph 1a; X = o-pyridine, R = Ph 2a; X = o-ani-
sole, R = Ph 3a; X = o-dimethylaniline, R = p-tol 1b; X = o-pyridine,
R = p-tol 2b; and X = o-anisole, R = p-tol 3b).
In this context, the idea of employing potentially hemilabile li-
gands, especially those containing phosphorus and nitrogen or
oxygen as donor atoms, can culminate in new exciting complexes
[7,17–20]. The hemilability phenomenon arises from the distinct
interactions of the two donor atoms with the metal center, as a
consequence of differences in their electronic properties. The pres-
2. Experimental methods
2.1. Measurements
The IR spectra were recorded on a FTIR Bomem-Michelson 102
spectrometer in the 4000–200 cmÀ1 region using solid samples
pressed in KBr pellets. The NMR experiments were carried out at
room temperature, using a Bruker AVANCE 400 NMR spectrometer
⇑
Corresponding author.
E-mail address: mparaujo@ufpr.br (M.P. de Araujo).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.05.016

208
F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
Table 1
Crystal data and structure refinement for the complexes [RuCl2(CO)(P–N)(PPh3)] (1a), [RuCl2(CO)(P-Py)(PPh3)]ÁCH2Cl2 (2aÁCH2Cl2), [RuCl2(CO)(P–O)(PPh3)] (3a), and
[RuCl2(CO)(P–O)(P{p-tol}3)]ÁCH2Cl2 (3bÁCH2Cl2).
1a
2aÁCH2Cl2
3a
3bÁCH2Cl2
Formula
Formula weight
T (K)
C39H35Cl2NOP2Ru
767.59
253(2)
C37H31Cl4NOP2Ru
810.44
150(2)
C38H32Cl2O2P2Ru
754.55
200(2)
C42H40O2P2Cl4Ru
811.55
293(2)
k (Å)
0.7107
1.5418
0.7107
0.7107
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
orthorhombic
P212121
triclinic
monoclinic
P121/c1
orthorhombic
P212121
ꢀ
P1
11.27565(14)
16.1691(2)
19.3071(2)
90.0
90.0
90.0
3520.03(8)
4
1.448
0.721
1568
9.8790(2)
13.2350(7)
14.1586(8)
106.373(5)
95.647(3)
93.083(3)
1761.07(14)
2
18.5036(4)
11.11630(10)
17.4554(3)
90.0
113.315(2)
90.0
3297.24(10)
4
1.52
10.6056(2)
17.7641(3)
21.7302(4)
90.0
90.0
90.0
4093.95(13)
4
1.430
0.757
1800
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
1.528
7.507
820
Absorption coefficient (mmÀ1
F(000)
)
0.769
1536
Crystal size (mm)
h range for data collection
Index ranges
0.93 Â 0.362 Â 0.24
2.78–26.37
À13 6 h 6 14
–20 6 k 6 20
–24 6 l 6 24
36045
7198 [Rint = 0.0339]
h = 26.37°, 99.8%
semi-empirical from
equivalents
1.00 and 0.717
0.31 Â 0.09 Â 0.03
3.28–63.69
À11 6 h 6 11
–15 6 k 6 15
–15 6 l 6 16
31722
5792 [Rint = 0.0321]
h = 63.69°, 99.8%
analytical
0.39 Â 0.31 Â 0.1
2.76–28.28
À24 6 h 6 24
–14 6 k 6 14
–22 6 l 6 21
58519
8071 [Rint = 0.0389]
h = 28.28°, 98.6%
semi-empirical from
equivalents
0.924 and 0.755
0.180 Â 0.17 Â 0.13
1.48–26.73
À13 6 h 6 12
–21 6 k 6 22
–27 6 l 6 22
35072
Reflections collected
Independent reflections
Completeness to
8690 [Rint = 0.0430]
99.9%
Absorption correction
GAUSSIAN
Maximum and minimum
transmission
0.806 and 0.205
0.9080 and 0.8758
Refinement method
full-matrix least-squares
on F2
full-matrix least-squares full-matrix least-squares
full-matrix least-squares
on F2
on F2
on F2
Data/restraints/parameters
7198/0/415
0.985
5792/0/415
1.091
8071/72/434
1.035
8690/0/448
1.056
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0203, wR2 = 0.0481
R1 = 0.0292,
wR2 = 0.0744
R1 = 0.0318,
wR2 = 0.0757
0.743 and À0.826
R1 = 0.0273, wR2 = 0.0644
R1 = 0.0460,
wR2 = 0.1240
R1 = 0.0562,
wR2 = 0.1315
1.247 and À0.930
R1 = 0.0242, wR2 = 0.0490
R1 = 0.0385, wR2 = 0.0669
1.203 and À1.297
Largest difference in peakand hole (eÀ Å3) 0.400 and À0.334
operating at 9.4 T and equipped with a 5-mm multinuclear direct
detection probe with z-gradient. 1H and 31P nuclei were observed
at 400.13 and 161.98 MHz, respectively.
by full-matrix least-squares on F2 with anisotropic displacement
parameters for all the non-hydrogen atoms. Hydrogen atoms
were included in the refinement in calculated positions. X-ray
diffraction data were also acquired on an Oxford-Diffraction
The 1H and 31P{1H} spectra were processed by applying an
exponential multiplication of the FIDs by a factor of 0.3 and
3 Hz prior to the Fourier transform, respectively. The 2D experi-
ments were processed by Fourier transform using square sine
apodization on both dimensions and zero-filling to 4 K Â 2 K data
points in f2 and f1, respectively. The NMR chemical shifts are
given in ppm in relation to TMS and H3PO4 85% at 0.00 ppm,
which were used as internal reference for 1H and 31P, respec-
tively. The coupling constants are presented in Hz. The pulse
program was supplied by Bruker BioSpin. The splitting of proton
and phosphorus resonances are defined as s, singlet; d, doublet;
br, broad; and m, multiplet. The microanalyses were performed
at the Microanalytical Laboratory at the Universidade Federal de
São Carlos, São Carlos, São Paulo, on a FISONS CHNS-O, mod. EA
1108 Element analyzer.
GEMINI diffractometer using graphite-Enhance Source Mo K
a
radiation (k = 0.7107 Å) or Enhance Source Cu radiation
K
a
(k = 1.5418 Å). Measurements were performed at different temper-
atures, as shown in Table 1. Data integration and scaling of the
reflections for all compounds were performed with the Crysalis
suite [22]. Final unit cell parameters were based on the fitting of
all the reflection positions. Analytical [23] and semi-empirical
[24] absorption corrections were also carried out with the aid of
Crysalis suite [22]. Program XPREP [21] was employed for space
group identification.
The structures of all compounds were solved by direct methods
using the SHELXS [21] program. For each compound, the positions of
all atoms could be unambiguously assigned on consecutive differ-
ence Fourier maps. Refinements were performed using SHELXL [21]
based on F2 through full-matrix least square routine.
2.2. X-ray diffraction data
Except for the hydrogen atoms, all atoms were refined with
anisotropic atomic displacement parameters. The hydrogen atoms
in the compounds were added in the structure in idealized posi-
tions and further refined according to the riding model [25].
In the cis,trans-[RuCl2(CO)(P–O)(PPh3)] 3a structure, the car-
bonyl group as well as the Cl atom were found to be disordered
around the Ru atom. The positions assigned Cl2B, C1A, and O1A
are the most likely ones (occupation probability 0.760(9)).
The data were collected using a Bruker APEX II CCD area-detec-
tor diffractometer and graphite-monochromatized Mo K
tion. The structures were solved by direct methods using SHELXS
[21]. Subsequent Fourier-difference map analyses provided the
positions of the non-hydrogen atoms. Refinements were carried
out with the SHELXL package [21]. All the refinements were made
a radia-

F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
209
Crystal data and more details on data collection and refinement
are summarized in Table 1.
Yield: 76% (0.021 g). Anal. Calc. for C41H38O2P2Cl2Ru: C, 61.81; H,
4.81. Found: C, 62.02; H, 4.96. 31P{1H} NMR (CDCl3): d 47.2 (d,
2
P{p-tol}3) 36.5 (d, PPh2) JP–P = 28.8 Hz. 1H NMR (CDCl3): d 6.5–
7.9 (26H, m, Ph), 4.5 (3H, s, OCH3) 2.2 (9H, s, Ph–CH3). FTIR mCO
3. Materials and methods
1974 cmÀ1
.
Commercially available RuCl3Á3H2O was donated by Johnson
Matthey plc. and was used as received. The monophosphines tri-
phenylphosphine (Aldrich) and tri-p-tolylphosphine (Aldrich) were
also used without prior purification. The ligands [o-(N,N-dimethyl-
amino)phenyl]diphenylphosphine (P–N) [26], 2-pyridyldiphenyl-
phosphine (P-Py) [27], and o-anisolediphenylphosphine (P–O)
[28], as well as the complexes [RuCl2(PPh3)3] [29], [RuCl2(P{p-
tol}3)3] [30], [RuCl2(CO)(DMF)(PPh3)2] [31], and [RuCl2(-
CO)(DMF)(P{p-tol}3)2] [31] were synthesized by literature meth-
ods. The solvents were dried before use. All the manipulations
involving solutions of the complexes were performed under argon
atmosphere. Yields are based on the metal. The first cis/trans desig-
nation refers to the relative position of the chloro ligands, while the
second designation refers to the position of the PR3 ligand relative
to the nitrogen or oxygen of the PPh2-X ligands.
3.2. Isomerization studies
Isomerization reactions were carried out in CDCl3 solutions, by
using an NMR tube equipped with a J-YoungÒ valve. The solutions
were exposed to ambient light, and the 31P{1H} NMR spectra were
recorded after 1–7 days of reaction time.
31P{1H} NMR data for the ‘‘in situ’’ analysis
cis,trans-[RuCl2(CO)(P–N)(PPh3)] (1a): CDCl3): d/ppm 46.5 (d)
2
2
17.6 (d) JP–P = 332 Hz; 38.2 (d) 16.4 (d) JP–P = 332 Hz.
cis,trans-[RuCl2(CO)(P-Py)(PPh3)] (2a): (CDCl3): d/ppm 36.6 (d)
2
2
À6.7 (d) JP–P = 349 Hz; d 24.2 (d) À26.2 (d) JP–P = 370 Hz.
cis,trans-[RuCl2(CO)(P–O)(PPh3)] (3a): (CDCl3) d/ppm 41.3 (d)
2
30.8 (d) JP–P = 344 Hz.
cis,trans-[RuCl2(CO)(P–N)(P{p-tol}3)] (1b): (CDCl3): d/ppm 46.2
3.1. Synthesis of the complexes
2
2
(d) 16.6 (d) JP–P = 334 Hz; 37.6 (d) 15.7 (d) JP–P = 359 Hz.
cis,trans-[RuCl2(CO)(P-Py)(P{p-tol}3)] (2b): (CDCl3): d/ppm 34.8
3.1.1. A representative synthesis is as follows
2
2
(d) À7.2 (d) JP–P = 348 Hz; d 22.7 (d) À26.7 (d) JP–P = 374 Hz.
[RuCl2(CO)(DMF)(PR3)2] and the ligand PPh2-X were dissolved
in degassed dichloromethane (20 mL) and stirred under argon for
18 h at room temperature. The resulting solution was concentrated
under vacuum (ꢀ5 mL), and n-hexane was added, yielding a yellow
or orange solid that was washed with diethylether and dried by
heating (ꢀ80 °C) the complex under vacuum overnight.
cis,trans-[RuCl2(CO)(P–O)(P{p-tol}3)] (3b): (CDCl3) d/ppm 40.4
2
(d) 29.6 (d) JP–P = 345 Hz.
3.3. Reactivity with carbon monoxide
The complexes cis,fac-[RuCl2(CO)(P–O)(PR3)] (10 mg) were
dissolved in degassed CDCl3 (0.5 mL) in an NMR tube equipped
with J-YoungÒ valve. Next, the tube was filled up with carbon
monoxide (1 atm), and the 31P{1H} and 1H NMR spectra were
recorded.
The same procedure can be applied for isolation of the
complexes, but using dichloromethane as solvent. The isolated
complexes are stable, and spectroscopic data agree with the
‘‘in situ’’ reaction.
cis,trans-[RuCl2(CO)(P–N)(PPh3)] (1a): [RuCl2(CO)(DMF)(PPh3)2]
(0.070 g; 0.088 mmol) and P–N (0.038 g; 0.101 mmol). Yield: 80%
(0.054 g). Anal. Calc. for C39H35NOP2Cl2Ru: C, 61.02; N, 1.82; H,
4.60. Found: C, 61.40; N, 1.90; H, 4.10. 31P{1H} NMR (CDCl3): d
36.6 (d, PPh3), 43.0 (d, PPh2) JP–P = 25.3 Hz. 1H NMR (CDCl3): d
2
6.6–7.8 (29H, m, Ph), 3.6 (3H, d, NCH3), 3.2 (3H, d, NCH3). FTIR
mCO 1964 cmÀ1
.
cis,trans-[RuCl2(CO)(P-Py)(PPh3)] (2a): [RuCl2(CO](DMF)(PPh3)2]
and (0.070 g; 0.088 mmol) and P-Py (0.029 g; 0.101 mmol). Yield:
76% (0.48 g). Anal. Calc. for C36H29NOP2Cl2Ru: C, 59.59; N, 1.93;
H, 4.03. Found: C, 59.12; N, 2.05; H, 4.04. 31P{1H} NMR (CDCl3): d
Relevant spectroscopic data
40.5 (d, PPh3) À13.5 (d, PPh2) JP–P = 23.2 Hz. 1H NMR (CDCl3): d
2
[RuCl2(CO)2(P–O)(PPh3)] (4a): 31P{1H} (CDCl3) d/ppm 19.5 (d)
9.1 (1H, br, PyH ) 7.9–7.0 (28H, m, Ph). FTIR mCO 1975 cmÀ1
.
a
2
10.7 (d) JP–P = 356 Hz; 1H NMR (400 MHz, CDCl3): d/ppm 3.63 (s,
cis,trans-[RuCl2(CO)(P–O)(PPh3)] (3a): [RuCl2(CO)(DMF)(PPh3)2]
(0.070 g; 0.088 mmol) and P–O (0.030 g; 0.102 mmol). Yield: 75%
(0.049 g). Anal. Calc. for C38H32O2P2Cl2Ru: C, 60.48; H, 4.27. Found:
C, 60.12; H, 4.10. 31P{1H} NMR (CDCl3): d 48.6 (d, PPh3) 36.0 (d,
OCH3); FTIR m
CO/cmÀ1 2059 and 1997.
[RuCl2(CO)2(P–O)(P{p-tol}3)] (4b): 31P{1H} (CDCl3) d/ppm 17.2 (d)
9.2 (d) 2JP–P = 358 Hz; 16.1 (s) 11.5 (s); 1H NMR (CDCl3): d/ppm 3.60
2
(s, OCH3), 2.34 (s, Ph–CH3); FTIR m
CO/cmÀ1 2054 and 1990.
PPh2) JP–P = 29.2 Hz. 1H NMR (CDCl3): d 6.51–8.08 (29H, m, Ph),
4.55 (3H, s, OCH3). FTIR mCO 1961 cmÀ1
.
cis,trans-[RuCl2(CO)(P–N)(P{p-tol}3)] (1b): [RuCl2(CO)(DMF)(P{p-
tol}3)2] (0.030 g, 0.037 mmol) and P–N (0.016 g, 0.041 mmol).
Yield: 72% (0.022 g). Anal. Calc. for C42H41NOP2Cl2Ru: C, 62.30; N,
1.73; H, 5.10. Found: C, 62.91; N, 1.65; H, 5.00. 31P{1H} NMR
4. Results and discussion
4.1. Synthesis and basic characterization
2
(CDCl3): d 35.1 (d, P{p-tol}3), 43.2 (d, PPh2) JP–P = 25.2 Hz. 1H
In this work, six new complexes were obtained by reaction of
the ligands [o-(N,N-dimethylamino)phenyl]diphenylphosphine
(P–N), 2-pyridyldiphenylphosphine (P-Py), or o-anisolediphenyl-
phosphine (P–O) with the ruthenium complexes [RuCl2(-
CO)(dmf)(PR3)2] (R = Ph or p-tol). The six new complexes were
synthesized according to Scheme 1 and had the general formula
cis,trans-[RuCl2(CO)(PPh2-X)(PR3)] (X = o-dimethylaniline, R = Ph
1a; X = o-pyridine, R = Ph 2a; X = o-anisole, R = Ph 3a; and X = o-
dimethylaniline, R = p-tol 1b; X = o-pyridine, R = p-tol 2b; and
X = o-anisole, R = p-tol 3b) (Scheme 1).
NMR (CDCl3): d 6.6–8.0 (26H, m, Ph), 3.6 (3H, d, NCH3), 3.2 (3H,
d, NCH3), 2.3 (9H, s, Ph-CH3). FTIR mCO 1965 cmÀ1
.
cis,trans-[RuCl2(CO)(P-Py)(P{p-tol}3)] (2b): [RuCl2(CO)(DMF)
(P{p-tol}3)2] (0.030 g, 0.037 mmol) and P-Py (0.011 g, 0.042 mmol).
Yield: 87%, (0.023 g). Anal. Calc. for C39H35NOP2Cl2Ru: C, 61.02; N,
1.82; H, 4.60. Found: C, 60.79; N, 1.79; H, 4.66. 31P{1H} NMR
2
(CDCl3): d 38.4 (d, P{p-tol}3) À12.4 (d, PPh2) JP–P = 22.3 Hz. 1H
NMR (CDCl3): d 9.1 (1H, br, PyH ) 7.9–6.9 (25H, m, Ph) 2.2 (9H, s,
a
Ph-CH3). FTIR mCO 1965 cmÀ1
.
cis,trans-[RuCl2(CO)(P–O)(P{p-tol}3)] (3b): [RuCl2(CO)(DMF)
(P{p-tol}3)2] (0.030 g, 0.037 mmol) and P–O (0.012 g, 0.041 mmol).
The reaction shown in Scheme 1 yielded only one isomer, in
which the chloro atoms are in cis position to each other, and the

210
F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
Two aspects are noteworthy, namely the effect of the donor
atom of the PPh2-X ligand ( -donor or -acceptor properties) and
r
p
the chelate ring size [39]. For the complexes containing the P–N
ligand, 1a and 1b, the chemical shifts of the phosphorus of the
PR3 ligand are more shielded in the 31P NMR spectrum than the
shifts of the phosphorus of the P–N ligand, which is in agreement
with other complexes exhibiting the same P–N ligand [40–43].
For the complexes with the P–O ligand, 3a and 3b, the chemical
shifts are inverted. In other words, the chemical shifts of the
phosphorus of the PR3 ligand are deshielded in comparison with
the shifts observed for the phosphorus of P–O. The same behavior
is noted for the complexes with P-Py, 2a and 2b, in which the
phosphorus atom of the PR3 ligand is deshielded when compared
to the phosphorus of P-Py. Interestingly, the chemical shift of the
phosphorus atom of the P-Py ligand is highly shielded as compared
to the phosphorus of the P–N and P–O ligands. This is because the
chelate ring size also exerts an important effect on the chemical
shift. The complexes [RuCl2(L)(PPh3)] and [RuCl2(L)(@C@CHPh)
Scheme 1. Synthetic route.
triarylphosphines (PPh3 or P{p-tol}3) are in trans position to the
nitrogen or oxygen atoms of the PPh2-X ligands. The complexes
were characterized by 1D–1H, 31P{1H} and 2D-correlations HMBC
31P–1H NMR, vibrational spectroscopy, elemental analysis, and X-
ray diffraction structural determinations (for complexes 1a,
2aÁCH2Cl2, 3a, and 3bÁCH2Cl2).
The band relative to m
CO can be detected in the 1961–1975 cmÀ1
range in the vibrational spectra of all the synthesized complexes.
This band is characteristic of ruthenium monocarbonyl complexes
[32–34].
Coordination of the P–N and P–O ligands (complexes 1a, 3a, 1b,
and 3b) to the ruthenium center afforded a five-membered chelate
ring, while the P-Py ligand (complexes 2a and 2b) afforded a four-
membered chelate ring. The presence of N- or O-donor atoms and
the chelate ring size are responsible for the differences found in the
31P NMR spectra, which will be discussed further.
(PPh3)]
(L = 2-[(diphenylphosphino)methyl]-6-methylpyridine)
[44], in which the ligand L produces a five-membered chelate ring
upon coordination, in this way, can be compared with complexes
containing P–N and P–O. These complexes ([RuCl2(L)(PPh3)] and
[RuCl2(L)(@C@CHPh)(PPh3)]) have the same behavior as the com-
plex [RuCl2(CO)(P–N)(PR3)] with respect to 31P NMR spectra; that
is, the PPh3 ligand is shielded when compared to the phosphorus
of the hybrid ligand L.
The integration of the resonances observed in the 1H NMR spec-
tra agrees with a PPh2-X/PR3 proportion of 1:1. The 31P{1H} NMR
spectra display two doublets, corresponding to the two magneti-
cally non-equivalent phosphorus atoms. The coupling constants
are in the range 23–30 Hz (see Table 2), which is compatible with
phosphorus in cis position [2,3,10,14,33]. For complexes 1a and 1b,
the presence of two resonances for the N-methyl hydrogen con-
firms a cis-dichloro arrangement. For obvious reasons, this analogy
cannot be drawn for the other complexes. On the other hand, the
long-range 1H–31P correlation experiments reveal a characteristic
correlation between the N-methyl hydrogen of the P–N or P–O li-
gands (complexes 1a, 1b, 3a and 3b) and the PR3 ligand [35], the
The shielding of the phosphorus nuclei of the PR3 ligands lo-
cated in trans position to the nitrogen atom of the P–N or P-Py li-
gands can be explained by the
r
-donor ability of the –N(CH3)2
substituents and the -donor/
r
p-acceptor ability of the pyridyl
group. Therefore, as will be discussed later, the Ru–PPh3 bond
lengths for complexes 1a and 2a are longer than those observed
for the complexes with P–O ligand, 3a and 3b. In the case of the
latter complexes, the weaker
accounts for the strengthening of the Ru–PR3 bond. For P-Py, the
-accepting character of pyridyl also causes weakening of the
Ru–PR3 bond, but the stronger -donor ability of the N(CH3)2
r-donating ability of the ligand
p
r
group causes a more pronounced structural trans effect [45]. As
discussed elsewhere [38,46], there is an inverse relation between
the Ru–P bond length and the chemical shift (see Fig. 1 for the
31P{1H} NMR and Figs. 2–5 for the Ru–P bond distance). The d31P
of the PR3 ligand becomes deshielded according to the sequence
of the PPh2-X ligand: P–N < P-Py < P–O (see 31P{1H} spectra in
Fig. 1 and NMR data in Table 2), while the Ru–PR3 bond length
(PR3 ligand is in trans position to the N or O of the PPh2-X ligand)
becomes longer in the sequence P–O < P-Py < P–N. Therefore, the
structural trans effect (STE) [45] increases according to the
sequence OCH3 < N(py) < N(CH3)2.
same correlation is observed for the
a-H of P-Py, indicating that
the PR3 ligand is in trans position to the N or O of the PPh2-X li-
gands. These observations are corroborated by the long range
1H–31P correlation experiments conducted for the P{p-tol}3 com-
plexes: besides correlating with the hydrogen atoms mentioned
above, the 31P nucleus of P{p-tol}3 also correlates with the hydro-
gen atoms of the p-CH3. In addition, the negative chemical shift
in the 31P{1H} spectra for the P atoms of the P-Py ligand (2a and
2b) reinforce the chelated coordination mode, as verified for other
systems [36–38].
Table 2
31P{1H} and 1H NMR, and mCO data.
4.2. X-ray crystallography for complexes 1a, 2aÁCH2Cl2, 3a, and
3bÁCH2Cl2
Complexes
31P, d/ppm d 1H, d/ppm (2J/Hz)
m
CO/cmÀ1
PR3; PPh2-X
(2J/Hz)
Suitable single-crystals were obtained by slow evaporation of a
dichloromethane solution of the complexes. The X-ray diffractions
studies reveal a distorted octahedron for all the complexes, as evi-
denced by their bond angles and bond lengths (see Figs. 2–5 for the
ORTEP plot and captions for selected bond lengths and angles).
The arrangement of the ligands around ruthenium (II) is in
agreement with the structure proposed on the basis of the NMR
experiments, in which the PR3 ligands are in trans position to the
nitrogen or oxygen atoms of the PPh2-X ligands and there is a
cis-dichloro arrangement.
1a
2a
3a
1b
36.6; 43.0
(26.4)
6.6–7.8 (29H, m, Ph), 3.6 (3H, d,
NCH3), 3.2 (3H, d, NCH3)
1964
40.5; À13.5
9.1 (1H, s, PyH ), 7.9–7.0 (28H, m, 1975
a
(23.3)
Ph)
48.6; 36.0
(29.3)
35.1; 43.2
(29.3)
6.51–8.08 (29H, m, Ph), 4.55 (3H, s, 1961
OCH3)
6.6–8.0 (26H, m, Ph), 3.6 (3H, d,
NCH3), 3.2 (3H, d, NCH3), 2.3 (9H, s,
Ph–CH3)
1965
2b
3b
38.4; À12.4
(29.3)
47.2; 36.5
(28.9)
9.1 (1H, s, PyH ), 7.9–6.9 (25H, m, 1965
a
Ph), 2.2 (9H, s, Ph–CH3)
6.5–7.9 (26H, m, Ph), 4.5 (3H, s,
OCH3), 2.2 (9H, s, Ph–CH3)
The Ru–P, Ru–Cl, Ru–C, and C–O bond lengths are in the same
range as reported for other complexes [14,33,34,46–52]. The C–O
bond length for complex 3bÁCH2Cl2 is short when compared with
1974

F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
211
Fig. 1. 31P{1H} NMR spectra showing the chemical shifts for the phosphorus atoms of the complexes cis,fac-[RuCl2(CO)(PPh2-X)(PR3)]. (A) R = ph and (B) R = p-tol. The hybrid
ligand is indicated in the corresponding spectrum.
the other complexes evaluated in this work (1.074(7) Å), but liter-
ature examples show that this is not unusual [34,53–57].
The Ru–PR3 bond lengths are 2.3546(5), 2.3330(7), 2.3102(5),
and 2.3009(12) Å, for complexes 1a, 2aÁCH2Cl2, 3a, and 3bÁCH2Cl2,
respectively. On the basis of these values, the strength of the struc-
tural trans effect (STE) [45] for the groups trans to the PR3 ligand
increases according to the sequence OCH3 < N(py) < N(CH3)2, as pre-
viously discussed.
It is well known that the C–P–C angle is usually related to the
31P chemical shifts, since the phosphorus becomes deshielded as
the C–P–C angle opens [39]. For complexes 1a, 2aÁCH2Cl2, 3a, and
3bÁCH2Cl2, the C–P–C angles are in the 99.12–107.41° range. The
average values for the C–P–C angles are 103.12, 105.68, 102.86
and 103.03° for 1a, 2aÁCH2Cl2, 3a, and 3bÁCH2Cl2, respectively.
The P-Py ligand has the highest C–P–C angle (average value), but
its phosphorus exhibits the lowest chemical shift (more shielded).
As mentioned elsewhere [38], the relation between the C–P–C an-
gles and the 31P chemical shifts only works for five-membered che-
lating ligands or ligands with larger rings; for four-membered
chelate rings, the larger the C–P–C angles, the more shielded the
phosphorus.
As expected, the variation of the bite angle (X–Ru–P) as a func-
tion of the chelate ring size ongoing from five-membered rings, in
the cases of the P–N (1a) and P–O (3a and 3bÁCH2Cl2) ligands, to

212
F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
Fig. 4. ORTEP view of the complex [RuCl2(CO)(P–O)(PPh3)] 3a, showing the atoms
labeling and the 50% probability ellipsoids. The hydrogen atoms have been omitted
for clarity. Bond lengths (Å): Cl2a–Ru 2.408(4), Cl2b–Ru 2.4014(12), Ru–C1a
1.832(5), Ru–C1b 1.84(2), Ru–O2 2.2559(13), Ru–P1 2.3102(5), Ru–P2 2.3169(5),
Ru–Cl1 2.4444(5), O2–C2 1.380(2), O1a–C1a 1.162(9), O1b–C1b 1.07(3). Bond
angles (°): C1a–Ru–O2 92.97(15), C1a–Ru–P(1) 94.83(15), C1b–Ru–P1 84.6(5), O2–
Ru–P1 171.19(4), C1a–Ru–P2 85.55(12), C1b–Ru–P2 92.8(4), O2–Ru–P2 80.36(4),
P1–Ru–P2 104.302(16), C1a–Ru–Cl2b 174.91(12), O2–Ru–Cl2b 84.14(5), O2–Ru–
Cl2a 84.88(12), P1–Ru–Cl2a 102.94(11), P2–Ru–Cl2a 83.60(8), P1–Ru–Cl2b
87.78(4), P2–Ru–Cl2b 98.05(4), O1a–C1a–Ru 175.8(3), O1b–C1b–Ru 176.8(16),
C7–P2–C14 105.98(9), C7–P2–C8 99.12(8), C14–P2–C8 103.48(8).
Fig. 2. ORTEP view of the complex [RuCl2(CO)(P–N)(PPh3)] 1a, showing the atoms
labeling and the 50% probability ellipsoids. The hydrogen atoms have been omitted
for clarity. Bond lengths (Å): Ru–C1 1.839(2), Ru–P1 2.2937(5), Ru–N1 2.3182(15),
Ru–P2 2.3546(5), Ru–Cl2 2.4502(5), Ru–Cl1 2.4651(5), O1–C1 1.130(2). Bond angles
(°): C1–Ru–P1 89.49(6), C1–Ru–N1 92.27(7), P1–Ru–N1 82.05(4), C1–Ru–P2
91.49(6), P1–Ru–P2 101.218(17), N1–Ru–P2 175.04(4), C1–Ru–Cl2 179.27(6) P1–
Ru–Cl2 89.784(18), N1–Ru–Cl2 87.63(4), P2–Ru–Cl2 88.651(18), C1–Ru–Cl1
87.22(6), P1–Ru–Cl1 167.844(18), N1–Ru–Cl1 86.39(4), P2–Ru–Cl1 90.569(18),
Cl2–Ru–Cl1 93.495(17), O1–C1–Ru 178.05(17), C7–P1–C14 100.95(9), C7–P1–C8
102.09(9), C14–P1–C8 106.31(9).
Fig. 5. ORTEP view of the complex [RuCl2(CO)(P–O)(P{p-tol}3)]ÁCH2Cl2 3bÁCH2Cl2,
showing the atoms labeling and the 50% probability ellipsoids. The hydrogen atoms
and the CH2Cl2 have been omitted for clarity. Bond lengths (Å): Ru–C41 1.875(6),
Ru–O1 2.264(4), Ru–P1 2.3009(12), Ru–P2 2.3267(13), Ru–Cl1 2.4303(14), Ru–Cl2
2.4356(14), C41–O2 1.074(7). Bond angles (°): C41–Ru–P1 90.15(16), O1–Ru–P1
177.42(11), C41–Ru–P2 87.16(16), O1–Ru–P2 77.67(11), P1–Ru–P2 99.85(4), C41–
Ru–Cl1 170.00(16), O1–Ru–Cl1 86.54(11), P1–Ru–Cl1 93.31(5), P2–Ru–Cl1
101.46(5), C41–Ru–Cl2 82.99(16), O1–Ru–Cl2 86.69(11), P1–Ru–Cl2 95.88(5), P2–
Ru–Cl2 161.44(5), Cl1–Ru–Cl2 87.32(5), C22–P2–C28 102.5(2), C22–P2–C34
103.8(2), C28–P2–C34 102.8(2).
Fig. 3. ORTEP view of the complex [RuCl2(CO)(P-Py)(PPh3)]ÁCH2Cl2 2aÁCH2Cl2, show-
ing the atoms labeling and the 50% probability ellipsoids. The hydrogen atoms and
the CH2Cl2 have been omitted for clarity. Bond lengths (Å): Ru–C1 1.847(3), Ru–N1
2.142(2), Ru–P1 2.3262(7), Ru–P2 2.3330(7), Ru–Cl2 2.4164(7), Ru–Cl1 2.4486(7),
C1–O1 1.147(4). Bond angles (°): C1–Ru–N1 89.25(11), C1–Ru–P1 91.10(9), N1–Ru–
P1 67.48(7), C1–Ru–P2 91.88(9), N1–Ru–P2 175.70(7), P1–Ru–P2 108.34(3), C1–
Ru–Cl2 89.56(9), N1–Ru–Cl2 92.43(7), P1–Ru–Cl2 159.88(3), P2–Ru–Cl2 91.73(3),
C1–Ru–Cl1 174.59(9), N1–Ru–Cl1 85.60(6), P1–Ru–Cl1 88.44(2), P2–Ru–Cl1
93.38(2), Cl2–Ru–Cl1 89.02(2), O1–C1–Ru 175.6(3), C13–P1–C7 103.15(13), C13–
P1–C6 106.49(13), C7–P1–C6 107.41(13).
also have a direct relation with the X–Ru–P bite angle. Indeed,
the chemical shift becomes shielded as the bite angle of coordi-
nated PPh2-X decreases; i.e., the smaller the angle, the more
shielded the phosphorus in the 31P{1H} NMR spectra (2a:
four-membered rings, as in the complex with P-Py (2aÁCH2Cl2), is
d
31P = À13.5 ppm, P–Ru–N(py) = 67.48°; 3b:
d
31P = 36.5 ppm,
more pronounced. In addition, the phosphorus chemical shifts

F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
213
and 0.627 Å, for the two chelated and the non-chelated P-Py,
respectively.
4.3. Isomerization reactions
When dissolved in dichloromethane and exposed to ambient
light, the complexes examined in this work isomerize, resulting
in the formation of two isomers. The isomerization process is not
complete for reactions times up to 7 days, as evidenced by
31P{1H} NMR.
According to Scheme 3, there are seven possible isomers for the
complexes with the general formula [RuCl2(CO)(PPh2-X)(PR3)].
Among these isomers, only two have the phosphorus atoms in mu-
tual trans position. 31P{1H} NMR analysis of the products obtained
after isomerization reveals the presence of three sets of signals,
namely two doublets relative to the (A) isomer (see Table 2 for
NMR data) and four doublets with coupling constants up to
374 Hz. This is compatible with the presence of two isomers with
phosphorus atoms in mutual trans position (isomers (E) and (G),
Scheme 3).
X = (CH3)2N-C; N; CH3O-C
Scheme 2. Bite angle and the d distance.
The isomerization of the complexes 1a and 1b, also yielded a
small amount of free triarylphosphines, which is compatible with
the weaker Ru–PR3 bond observed in the X-ray analysis for 1a –
see Fig. 2). In addition, singlets with chemical shifts in the 57–
64 ppm range can be observed, and they are probably due to the
presence of complexes with only one coordinated phosphorus
atom. The triarylphosphines release does not seem to be related
to the isomerization mechanism in the case of these complexes,
since the addition of excess triarylphosphines does not inhibit
the isomerization process. Triarylphosphines affect the formation
of complexes containing only one coordinated phosphorus atom.
The singlets, observed in the 57–64 ppm range in the absence of
triarylphosphine, disappear in its presence.
Besides the lack of reactivity with carbon monoxide verified for
the P–N- and P-Py-containing complexes investigated in this work
(as discussed later), the isomerization mechanism could involve
Ru-X bond cleavage (X = N or O), as proposed for other P–O com-
plexes [58] and reinforced by the fact that P–N ligands may form
non-chelated complexes [38,59,60].
P–Ru–O = 77.67°; 3a:
d
d
31P = 36.0 ppm, P–Ru–O = 80.36°; 1a:
31P = 43.0 ppm, P–Ru–N = 82.05°).
Worth of mentioning is the effect of the bite angle on the
distance of the phosphorus atom of the PPh2-X ligands from the
idealized plane, formed by ruthenium and the two carbon atoms
of the phenyl rings (carbon directly bound to the phosphorus
atoms – Cipso) (d distance – Scheme 2). These distances are 0.410,
0.412, and 0.411 Å for complexes 1a, 3a, and 3bÁCH2Cl2, respec-
tively, while this distance is 0.296 Å for complex 2aÁCH2Cl2. These
values could indicate that the hybridization on the phosphorus
atom of the PPh2-X is closer to sp2 in complex 2aÁCH2Cl2, which
is in agreement with the more shielded phosphorus in the 31P
NMR spectra (see Table 2). However, there is no evidence of such
hybridization when one considers the P–C bond lengths, since they
are essentially the same for complexes 1a, 2aÁCH2Cl2, 3a, and
3bÁCH2Cl2. The same behavior has been observed for other com-
plexes with chelated P-Py ligand. For example, the d distance is
0.375 Å for the complex [RhCl2(P-Py–P,N)2]PF6 [38] and 0.255 Å
for the complex [RhCl3(P-Py–P,N)(P-Py–P)] [38]. The distance from
the plane for the non-chelated P-Py in the case of the latter com-
plex is 0.583 Å [38]. According to the same reference [38], the com-
plex [RuCl(P-Py–P,N)2(P-Py–P)]Cl d distances are of 0.260, 0.273
4.4. Reactivity with carbon monoxide
In an attempt to verify the hemilability of the PPh2-X ligand, the
complexes assessed here were allowed to react with carbon mon-
oxide (1 atm) in dichloromethane or CDCl3 at room temperature.
Scheme 3. Possible isomers for the complexes [RuCl2(CO)(PPh2-X)(PR3)].

214
F.D. Fagundes et al. / Polyhedron 42 (2012) 207–215
Scheme 4. Possible isomers for the complexes [RuCl2(CO)2(P–O,P)(PR3)].
Only complexes 3a and 3b (with P–O ligand) react with carbon
monoxide in these conditions, resulting in complexes with phos-
phorus atoms in mutual trans position (major) and general formula
[RuCl2(CO)2(P–O, P)(PR3)] (R = Ph (4a); R = p-tol (4b)). The 31P{1H}
NMR spectra of the reaction products contain two doublets cen-
tered at 19.5 and 10.7 ppm 2J = 356 Hz for the reaction of 3a, and
17.2 and 9.2 ppm 2J = 358 Hz for the reaction of 3b. In addition to
the doublets, two unidentified singlets can be observed (minor)
in both reactions. The coupling constant indicates trans arrange-
ment of the phosphorus atoms, which is compatible with the struc-
tures (H) and (I) (see Scheme 4). The vibrational spectra display
two intense bands relative to carbonyl stretching at 2059 and
1997 cmÀ1 for the reaction of 3a and at 2054 and 1990 cmÀ1 for
3b. This suggests cis carbonyl arrangement for one of the products,
which is compatible with isomer (H). For both complexes, there is a
shoulder at ꢀ1950 cmÀ1, indicating the presence of another spe-
cies. These shoulders are probably associated with the singlets ver-
ified in the 31{1H} NMR spectra. The singlets remain irrespective of
the solvent (CDCl3, CD2Cl2, or C6D6) and experiment temperature
(25 to À80 °C). It is noteworthy that no free phosphine or phos-
phine oxides can be observed in the ‘‘in situ’’ 31P{1H} spectra.
Therefore, no singlets are expected, either.
chemical shift on the P–Ru–X angle was verified. Isomerization oc-
curred when the complexes were exposed to ambient light, which
led to the formation of isomers with phosphorus atoms in trans
configurations. Only complexes 3a and 3b (complexes with P–O)
presented reactivity in the presence of CO, which culminated in
dicarbonyl complexes and proved the hemilabile character of the
P–O ligand.
Acknowledgements
The authors are grateful to CNPq, CAPES (PROCAD/NF 2009 and
CAPES/UdelaR 2010), FINEP, and NENNAM (PRONEX F. Araucária/
CNPq protocolo 17378) for financial support, and to Johnson Mat-
they plc. for the loan of RuCl3 (to M.P.A.).
Appendix A. Supplementary data
CCDC 812457, 812459, 812458 and 800966 contain the supple-
mentary crystallographic data for [RuCl2(CO)(P–N)(PPh3)] 1a,
[RuCl2(CO)(P-Py)(PPh3)]ÁCH2Cl2 2aÁCH2Cl2, [RuCl2(CO)(P–O)(PPh3)]
3a, and [RuCl2(CO)(P–O)(P{p-tol}3)]ÁCH2Cl2 3bÁCH2Cl2. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.poly.2012.05.016.
1H NMR spectral analysis supports the hemilability of the ligand
P–O, since the chemical shift of the hydrogen of the OCH3 is
shielded, compared with the values recorded for complexes 3a
and 3b. In fact, these chemical shifts are close to the value regis-
tered for the free ligand (3.76 ppm).
5. Conclusions
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