Influence of ligands on the fac underover(?, Δ, h ν) mer isomerization in [RuCl3(NO)(P-P)] complexes.

Article abstract of DOI:10.1016/j.ica.2005.12.016

[RuCl₃(NO)(P-P)], [P-P = R₂P(CH₂)_nPR₂ (n = 1-3) and R₂P(CH₂)POR₂, PR₂-CH{double bond, long}CH-PR₂, R = Ph and (C₆H₁₁)₂P-(CH₂)₂- P(C₆H₁₁)₂] were obtained and characterized by ³¹P {¹H} NMR, IR spectroscopies and cyclic voltammetry. The structures of fac-[RuCl₃(NO)(P-P)], P-P = dppm (1), dppe (2), c-dppen (3) and dppp (4), mer-[RuCl₃(NO)(dcpe)] (6a) and mer-[RuCl₃(NO)(dppmO)] (7) have been determined by X-ray diffraction. Photochemical isomerization of fac- to mer-[RuCl₃(NO)(P-P)] was observed under white light in a CH₂Cl₂ solution and in solid state. The isomerization processes were followed by IR and ³¹P {¹H} spectra. The mer-[RuCl₃(¹⁵NO)(dppb)] isomer was used for the definition of the phosphorus atoms in the structure of the complex in solution. The electrochemical study shows that the oxidation/reduction processes observed in these complexes are dependent on both the isomer (fac or mer) and the solvent. In CH₂Cl₂, the NO⁺ reduction potentials are less negative for the mer-isomers than for the fac ones, while in CH₃CN solvent these potentials are, in general, very close for both isomers.

Full text of DOI:10.1016/j.ica.2005.12.016

Inorganica Chimica Acta 359 (2006) 2896–2909
www.elsevier.com/locate/ica
hm
Influence of ligands on the fac ꢀ mer isomerization in
D
[RuCl3(NO)(P–P)] complexes, [P–P = R2P(CH2)nPR2 (n = 1–3)
and R2P(CH2)POR2, PR2–CH@CH–PR2, R = Ph
and (C6H11)2P-(CH2)2-P(C6H11)2]
a,
a
a
Gustavo Von Poelhsitz *, Renata Cristina de Lima , Rose Maria Carlos ,
a
a,
b
Antonio Gilberto Ferreira , Alzir Azevedo Batista *, Alexandre Suman de Araujo ,
b
b
Javier Ellena , Eduardo Ernesto Castellano
a
Departamento de Quı´mica, Universidade Federal de Sa˜o Carlos, C.P. 676, CEP 13565-905, Sa˜o Carlos (SP), Brazil
Instituto de Fı´sica de Sa˜o Carlos, Universidade de Sa˜o Paulo, C.P. 369, CEP 13560-970, Sa˜o Carlos (SP), Brazil
b
Received 1 November 2005; accepted 11 December 2005
Available online 18 January 2006
Dedicated to Professor Brian R. James on his 70th birthday.
Abstract
[RuCl3(NO)(P–P)], [P–P = R2P(CH2)nPR2 (n = 1–3) and R2P(CH2)POR2, PR2–CH@CH–PR2, R = Ph and (C6H11)2P-(CH2)2-
P(C6H11)2] were obtained and characterized by 31P {1H} NMR, IR spectroscopies and cyclic voltammetry. The structures of fac-[RuCl3-
(NO)(P–P)], P–P = dppm (1), dppe (2), c-dppen (3) and dppp (4), mer-[RuCl3(NO)(dcpe)] (6a) and mer-[RuCl3(NO)(dppmO)] (7) have
been determined by X-ray diffraction. Photochemical isomerization of fac- to mer-[RuCl3(NO)(P–P)] was observed under white light in a
CH2Cl2 solution and in solid state. The isomerization processes were followed by IR and 31P {1H} spectra. The mer-[RuCl3(15NO)-
(dppb)] isomer was used for the definition of the phosphorus atoms in the structure of the complex in solution. The electrochemical study
shows that the oxidation/reduction processes observed in these complexes are dependent on both the isomer (fac or mer) and the solvent.
In CH2Cl2, the NO+ reduction potentials are less negative for the mer-isomers than for the fac ones, while in CH3CN solvent these
potentials are, in general, very close for both isomers.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Diphosphines; Nitrosyl complexes; Photochemical isomerization; Electrochemistry; X-ray structures
1. Introduction
have been seen as potential metalopharmaceutic drugs
[4,5]. In this perspective, ruthenium appears as a good can-
didate due to the high affinity of nitric oxide for this metal
[6,7]. In general the easiest accessible electroactive site in
nitrosyl complexes is the NO+ ligand and a number of
papers have described the NO labilization that can be pro-
moted by photochemical or electrochemical reduction reac-
tions [8–10]. As a strong p acid NO+ is able to promote the
stabilization of some metallic centers and, depending on
the electronic characteristics of the co-ligands in the metal
coordination sphere, a one electron reduction process
Nitric oxide is an interesting ligand for coordination
chemistry, mainly because of its versatility in coordination
to transition metals [1]. Also, NO is a very attractive and
fascinating molecule and its biological functions were rec-
ognized in the 1980s [2,3]. Since then, nitrosyl complexes
*
Corresponding authors. Tel.: +551633518285; fax: +551633518350.
E-mail addresses: gustavo@dq.ufscar.br (G. Von Poelhsitz), daab@
power.ufscar.br (A.A. Batista).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.12.016

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2897
involving the nitrosyl can be electrochemically reversible
[10] or irreversible [11].
In the last years our research group has been interested
in the nitrosyl ruthenium complexes containing
diphosphine ligands, with the general formula [RuCl3-
15N {1H} NMR spectra were recorded in CH2Cl2 using a
capillary of D2O to get the lock and H3PO4 (85%) and
CH3NO2 as external references, respectively. Cyclic vol-
tammetry (CV) experiments were carried out at room
temperature in CH2Cl2 or CH3CN containing 0.10 M
Bu4N+ClO4 (TBAP) (Fluka Purum) using a BAS-100B/
W Bioanalytical Systems Instrument; the working and aux-
iliary electrodes were stationary Pt foils; a Luggin capillary
probe was used and the reference electrode was Ag/AgCl.
In these conditions the ferrocene is oxidized at 0.43 V
(Fc+/Fc) in CH2Cl2 or in CH3CN. The microanalyses were
performed by Microanalytical Laboratory of Universidade
(NO)(P–P)]
[P–P = bis(diphenylphosphino)methane
(dppm), 1,2-bis(diphenylphosphino)ethane (dppe), cis-1,
2-bis(diphenyl- phosphino)ethylene (c-dppen), 1,3-bis
(diphenylphosphino)propane (dppp) and 1,4-bis(diph-
enylphosphino)butane (dppb)] [12–15]. Thus several com-
pounds with fac and/or mer geometries have been
synthesized and fully characterized including X-ray crystal-
lography analysis. These nitrosyl-compounds can be very
useful as precursors to synthesize a variety of derivatives
by substitution of the chlorides ligands as demonstrated
by the reactions between fac-[RuCl3(NO)(P–P)], P–
P = dppe or c-dppen, and 4,6-dimethyl-pyrimidine-2-thio-
late (‘SpymMe2’) to generate compounds with general
Federal de Sao Carlos, Sao Carlos (SP), using a FISIONS
˜
˜
CHNS, mod. EA 1108 micro analyser.
2.3. Synthesis
2.3.1. mer-[RuCl3(NO)(P–P)], P–P = dppm (1a), dppe
(2a), c-dppen (3a) and dppp (4a)
formula
[Ru(‘SpymMe2’,-N,-S)(‘SpymMe2’,-S)(NO)(P–
P)]+ [16]. Here we present a systematic route for the synthe-
sis of the mer-[RuCl3(NO)(P–P)] isomers starting from
the corresponding fac-isomers. Additionally, the electro-
chemical characterization of both fac and mer isomers is
presented. A new member of this series with P–P =
1,2-bis(dicyclohexylphosphino)ethane (dcpe) was obtained.
The X-ray structures of the fac-[RuCl3(NO)(dppm)] (1),
fac-[RuCl3(NO)(dppe)] (2), fac-[RuCl3(NO)(c-dppen)] (3),
fac-[RuCl3(NO)(dppp)] (4), mer-[RuCl3(NO)(dcpe)] (6a)
and mer-[RuCl3(NO)(dppmO)] (7) complexes are reported
here.
A CH2Cl2 (20 mL) solution/suspension of 50 mg
(@0.079 mmol) of the correspondent fac-complex was left
under magnetic stirring for two weeks in an ordinary glass
flask, not protected by light. Day by day the amount of sol-
ubilized complex increased as could be observed visually by
the intensity of the color of the solution. The end of the
reaction was confirmed by 31P {1H} NMR spectroscopy
and the volume of the solution was concentrated to ca.
1 mL and diethyl ether was added to give a yellow
precipitate.
(1a) Yield: 42 mg (84%). IR (CsI, cmꢀ1): mRu–Cl = 343;
286 w. UV–Vis (CH2Cl2) kmax nm (log e): 276 (4.17), 320
(3.73), 422 (2.63). Calc. for C25H22Cl3P2NORu: C, 48.29;
H, 3.57; N, 2.25. Found: C, 48.38; H, 3.54; N, 2.30%.
(2a) Yield: 45 mg (90%). IR (CsI, cmꢀ1): mRu–Cl = 345;
287 w. UV–Vis (CH2Cl2) kmax nm (log e): 276 (4.20), 324
(3.68), 420 (2.70). Calc. for C26H24Cl3P2NORu: C, 49.11;
H, 3.80; N, 2.20. Found: C, 48.95; H, 3.59; N, 2.19%.
(3a) Yield: 40 mg (80%). IR (CsI, cmꢀ1): mRu–Cl = 345;
288 w. UV–Vis (CH2Cl2) kmax nm (log e): 272 (4.17), 323
(3.61), 413 (2.69), 580 (2.07). Calc. for C26H22Cl3P2NORu:
C, 49.27; H, 3.50; N, 2.21. Found: C, 49.67; H, 3.45; N,
2.29%.
2. Experimental
2.1. Materials and methods
All the syntheses of the complexes were performed
under argon. Solvents were purified by standard methods.
All chemicals used were of reagent grade or comparable
purity. The RuCl3 Æ 3H2O was purchased from Degussa
or Aldrich and the diphosphine ligands were purchased
from Aldrich or Strem. The Na15NO2 (min. 98%) was pur-
chased from ISOTEC. The RuCl3NO Æ 2H2O, fac-[RuCl3-
(NO)(P–P)], P–P = dppm (1), dppe (2), c-dppen (3) and
dppp (4), mer-[RuCl3(dppb)(H2O)], fac (5) and mer (5a)-
[RuCl3(NO)(dppb)] were prepared according to the litera-
ture methods [12–14,17]. Yields are based on the metal.
(4a) Yield: 37 mg (74%). IR (CsI, cmꢀ1): mRu–Cl = 337;
291 w. UV–Vis (CH2Cl2) kmax nm (log e): 245 (4.27), 272
(4.07) sh, 326 (3.40) sh, 425 (2.32). Calc. for
C27H26Cl3P2NORu: C, 49.90; H, 4.03; N, 2.16. Found:
C, 49.86; H, 4.14; N, 2.19%.
2.2. Instrumentation
2.3.2. fac-[RuCl3(NO)(dcpe)] (6)
The infrared spectra were measured from powder sam-
ples diluted in CsI or in CH2Cl2 solutions using CaF2 win-
dows on an FTIR Bomem-Michelson 102 spectrometer in
the 4000–200 cmꢀ1 region for CsI samples and 4000–
1000 cmꢀ1 for solutions. UV–Vis spectra were recorded
in a Cary 500 spectrophotometer. All the NMR experi-
ments were recorded on a BRUKER equipment 9.4 T
(400 MHz for hydrogen frequency). The 31P {1H} and
To a deoxygenated CH3OH (25 mL) solution of the
RuCl3NO Æ 2H2O precursor (50 mg, 0.18 mmol) was added
84 mg (0.20 mmol) of the dcpe ligand. After 2 h of mag-
netic stirring under Ar atmosphere, the yellow solution
was filtered through celite. The resultant solution was con-
centrated until ca. 5 mL and diethyl ether was added to
give a beige precipitate. Yield: 85 mg (70%). IR (CsI, cmꢀ1):
m
Ru–Cl: 324; 279 w. UV–Vis (CH2Cl2) kmax nm (log e):

2898
G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
252 (4.19), 278 (4.01), 346 (3.37), 480 (2.24). Calc. for
C26H48Cl3P2NORu: C, 47.31; H, 7.33; N, 2.12. Found:
C, 47.61; H, 7.38; N, 2.29%.
For 6a, crystals were grown by slow evaporation of meth-
anol/diethyl ether solution. From the mother liquor of 1
were grown red crystals of 7.
The crystals were mounted on an Enraf-Nonius Kappa-
CCD diffractometer with graphite monochromated Mo Ka
(k = 0.71073 A) radiation. The final unit cell parameters
2.3.3. mer-[RuCl3(NO)(dcpe)] (6a)
Complex 6a was obtained as described above for 1a–4a
˚
starting with 6. Yield: 40 mg, (80%). IR (CsI, cmꢀ1): mRu–Cl
:
were based on all reflections. Data collections were made
using the COLLECT program [18]; integration and scaling
of the reflections were performed with the HKL Denzo-
Scalepack system of programs [19]. Absorption corrections
were carried out using the ‘‘multi-scan’’ method [20] for 1,
2, 4 and 7, integration [21] for 3 and gaussian [22] for 6a.
The structures were solved by direct methods with
SHELXS-97 [23]. The model was refined by full-matrix least
squares on F2 by means of SHELXL-97 [24]. All hydrogen
atoms were stereochemically positioned and refined with
the ridging model. Figs. 1–6 were prepared using ORTEP-3
for windows [25]. Hydrogen atoms of the aromatic rings
and CH2 were set isotropic with a thermal parameter
20% greater than the equivalent isotropic displacement
parameter of the atom to which each one is bonded. The
data collections and experimental details are summarized
in Tables 1–3. The crystal structures of the complexes are
shown in Figs. 1–6 and the selected bond distances and
angles are given in Tables 4–7.
338; 283 w. UV–Vis (CH2Cl2) kmax nm (log e): 269 (3.73),
320 (3.34), 421 (2.49). Calc. for C26H48Cl3P2NORu: C,
47.31; H, 7.33; N, 2.12. Found: C, 47.62; H, 7.29; N, 2.16%.
2.3.4. mer-[RuCl3(NO)(dppmO)] (7)
The liquor mother of a synthesis of 1 was recovered and
kept in a Becker cup at room temperature. After two days a
great amount of red crystals was obtained. These crystals
were identified as being 7. IR (CsI, cmꢀ1): mP@O = 1122 s;
m
Ru–Cl: 342; 289 w. UV–Vis (CH2Cl2) kmax nm (log e):
274 (3.91), 432 (1.94). Calc. for C25H22Cl3P2NO2Ru: C,
43.21; H, 3.35; N, 1.94. Found: C, 43.48; H, 3.33; N, 1.94%.
2.3.5. mer-[RuCl3(15NO)(dppb)] (8a)
To a deoxygenated CH2Cl2 (15 mL) solution of mer-
[RuCl3(dppb)(H2O)] (30 mg, 0.046 mmol) in a Schlenk
flask was added Na15NO2 (4.8 mg, 0.069 mmol) followed
by 15 mL of 0.1 mol Lꢀ1 HCl. The system was stopped
and submitted to a strong magnetic stirring to mix up the
two phases. After few seconds the color of the solution
changed from red to green, but the reaction was main-
tained for 1 h, after which the two phases were separated.
The organic phase containing the desired compound was
concentrated to ca. 3 mL and diethyl ether was added pre-
cipitating a green solid. The product was collected by filtra-
tion, washed with water, and dried in vacuo. Yield:
24.5 mg, 80%. IR (CsI, cmꢀ1): mRu–Cl = 340; 294 w. UV–
Vis (CH2Cl2) kmax nm (log e): 251 (4.34), 276 (4.19), 334
(3.49), 436 (2.27). Calc. for C28H28Cl3P215NORu: C,
50.58; H, 4.24; N, 2.26. Found: C, 50.64; H, 4.24; N, 2.06%.
3. Results and discussion
3.1. Synthesis
The RuCl3NO Æ 2H2O precursor reacts with stoichiome-
tric amount of the diphosphines dppm, dppe, c-dppen,
dppp and dcpe to form the corresponding fac isomers with
general formula [RuCl3(NO)(P–P)]. However, with the
dppb ligand, the reaction leads to the formation of a
2.3.6. fac-[RuCl3(15NO)(dppb)] (8)
The fac-[RuCl3(15NO)(dppb)] complex was synthesized
as previously reported for the synthesis of 5 [14]. Yield:
90%. IR (CsI, cmꢀ1): mRu–Cl: 330; 287 w. UV–Vis (CH2Cl2)
kmax nm (log e): 270 (4.27), 465 (1.95). Calc. for
C28H28Cl3P215NORu: C, 50.58; H, 4.24; N, 2.26. Found:
C, 50.66; H, 4.37; N, 2.08%.
2.4. X-ray crystallography
Compound 1 had previously been obtained in our
research group [12] but co-crystallized with the cis-
[RuCl2(dppm)2] complex. Compound 2 had also been
obtained before but crystallized in a different space group
[15]. The new structural results for these two compounds
are reported here and discussed together with other mem-
bers of the [RuCl3(NO)(P–P)] series.
Crystals of the 1–4 complexes were grown by slow
evaporation of dichloromethane/diethyl ether solutions.
Fig. 1. ORTEP view of 1 showing the atoms labeling and the 50%
probability ellipsoids.

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2899
Fig. 2. ORTEP view of 2 showing the atoms labeling and the 30%
probability ellipsoids.
Fig. 5. ORTEP view of 6a Æ CH3OH showing the atoms labeling and the
50% probability ellipsoids.
Fig. 3. ORTEP view of 3 showing the atoms labeling and the 50%
probability ellipsoids.
Fig. 6. ORTEP view of 7 Æ CH2Cl2 showing the atoms labeling and the
50% probability ellipsoids.
mixture of complexes detected by 31P {1H} NMR spectros-
copy. Using the aquo, mer-[RuCl3(dppb)(H2O)], previously
obtained in our laboratory [17], and bubbling NO gas, it
was possible to obtain 5a with a high level of purity, as
was shown by microanalysis data and a 31P {1H} spectrum.
The corresponding fac isomer 5 was isolated in quantitative
yield by heating 5a in methanol for 2 h. The mer-[RuCl3-
(dppb)(H2O)] was reacted with 15NO (generated from the
Na15NO2 and HCl 0.1 mol Lꢀ1) in a biphasic reaction, gen-
erating 8a. Following the same procedure described above,
complex 8 was also isolated.
Fig. 4. ORTEP view of 4 showing the atoms labeling and the 50%
probability ellipsoids.

2900
G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
Table 1
Crystallographic data and refinement details for 1, 2 and 4
1
2
4
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
C25H22Cl3NOP2Ru
621.80
120(2)
monoclinic
C2/c
C26H24Cl3NOP2Ru
635.82
293(2)
orthorhombic
Pbca
C27H26Cl3NOP2Ru
649.85
120(2)
monoclinic
P21/c
˚
a (A)
26.160(2)
15.433(1)
17.514(1)
16.1840(3)
15.1020(2)
22.5020(4)
16.4595(9)
10.8249(5)
16.4840(7)
˚
b (A)
˚
c (A)
b (ꢁ)
127.876(4)
5581.3(7)
8
1.480
0.981
115.259(2)
2656.2(2)
4
1.625
1.035
1312
0.08 · 0.02 · 0.01
2.73–25.00
ꢀ19 6 h 6 19
ꢀ12 6 k 6 12
ꢀ19 6 l 6 19
14318
3
˚
Volume (A )
Z
5499.73(16)
8
1.536
0.998
2560
0.15 · 0.70 · 0.45
1.81–27.5
ꢀ21 6 h6 21
ꢀ19 6 k 6 19
ꢀ29 6 k 6 28
55055
Density (calculated) (g cmꢀ3
)
Absorption coefficient (mmꢀ1
F(000)
)
2496
Crystal size (mm3)
0.22 · 0.18 · 0.10
3.74–25.00
ꢀ31 6 h6 31
ꢀ17 6 k 6 18
ꢀ20 6 l 6 20
8708
h Range for data collection (ꢁ)
Limiting indices
Reflections collected
Independent reflections (Rint
Data/restraints/parameters
Goodness-of-fit on F2
)
4891 (0.0321)
4891/0/298
1.047
6288 (0.0606)
6288/0/307
1.180
4675 (0.1089)
4675/0/317
1.091
Final R indices [I > 2r(I)]
R indices (all data)
R1 = 0.0485, wR2 = 0.1327
R1 = 0.0646, wR2 = 0.1447
0.568 and ꢀ0.814
R1 = 0.0423, wR2 = 0.1134
R1 = 0.0687, wR2 = 0.1414
0.999 and ꢀ1.417
R1 = 0.0521, wR2 = 0.1135
R1 = 0.0743, wR2 = 0.1221
0.979 and ꢀ1.126
ꢀ3
˚
Peak and hole/e A
Table 2
Crystallographic data and refinement details for 3
Super-cell
Sub-cell
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C26H22Cl3NOP2Ru
633.81
293
triclinic
P12
˚
a (A)
16.3710(6)
18.1210(5)
18.7200(5)
103.908(2)
97.384(2)
92.283(2)
5331.5(3)
8
16.3710(6)
11.3549(5)
14.5076(5)
88.081(2)
86.673(2)
82.084(2)
2665.8(2)
4
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Density (calculated) (g cmꢀ3
F(000)
)
1.579
2544
1272
Crystal size
Absorption coefficient (mmꢀ1
0.285 · 0.059 · 0.022
)
1.029
h Range for data collection (ꢁ)
1.81–27.51
0 6 h 6 21
ꢀ23 6 k 6 23
ꢀ24 6 l 6 24
24317
1.81–25
0 6 h 6 19
ꢀ13 6 k 6 13
ꢀ17 6 l 6 17
9407
Limiting indices
Reflections collected
Independent reflections (Rint
Data/parameters
)
24317 (0.000)
24317/1225
1.199
R1 = 0.0682, wR2 = 0.1588
R1 = 0.1432, wR2 = 0.2284
0.822 and ꢀ1.655
9407 (0.0630)
9407/705
1.262
R1 = 0.0423, wR2 = 0.1184
R1 = 0.0627, wR2 = 0.1582
0.708 and ꢀ1.385
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)ꢀ3
˚
Peak and hole (e A
)

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2901
Table 3
Crystallographic data and refinement details for 6a and 7
6a Æ CH3OH
7 Æ CH2Cl2
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
C26H48Cl3NOP2Ru
728.4
293(2)
triclinic
ꢀ
P
C25H22Cl3NO2P2Ru
722.72
293(2)
monoclinic
P21/n
˚
a (A)
12.2066(3)
15.5411(3)
17.5250(4)
10.4131(2)
16.0571(5)
17.6626(4)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
89.9580(10)
79.6110(10)
74.1000(10)
3140.79(12)
2
1.392
0.876
1365
90.6230(10)
3
˚
Volume (A )
2953.09(13)
4
1.626
1.117
1448
Z
Density (calculated) (g cmꢀ3
Absorption coefficient (mmꢀ1
F(000)
)
)
Crystal size
h Range for data collection (ꢁ)
Limiting indices
0.45 · 0.34 · 0.07
3.17–25.00
ꢀ14 6 h 6 14
ꢀ17 6 k 6 18
ꢀ20 6 l 6 20
20685
0.14 · 0.11 · 0.10
2.28–25.00
ꢀ12 6 h 6 12
18 6 k 6 19
ꢀ19 6 l 6 21
17134
Reflections collected
Independent reflections(Rint
Data/restraints/parameters
Goodness-of-fit on F2
)
11048 (0.0382)
11048/1/767
1.042
5184 (0.0462)
5184/0/335
1.180
Final R indices [I > 2r(I)]
R1 = 0.0532, wR2 = 0.1345
R1 = 0.0697, wR2 = 0.1449
0.798 and ꢀ1.171
R1 = 0.0618, wR2 = 0.1776
R1 = 0.0698, wR2 = 0.1816
0.913 and ꢀ0.653
R indices (all data)ꢀ3
˚
Peak and hole (e A
)
Table 4
˚
Selected bond distances (A) for 1, 2 and 4
1
2
4
Ru–N
1.787(6)
Ru–N
1.750(3)
2.3637(9)
2.3492(9)
1.128(5)
2.350(1)
2.429(1)
2.4356(9)
Ru–N
1.734(5)
Ru–P(1)
Ru–P(2)
O–N
Ru–Cl(1)
Ru–Cl(4)
Ru–Cl(2)
2.3488(12)
2.3582(11)
1.029(6)
2.3584(12)
2.4231(14)
2.4288(13)
Ru–P(1)
Ru–P(2)
O–N
Ru–Cl(1)
Ru–Cl(3)
Ru–Cl(2)
Ru–P(1)
Ru–P(2)
O–N
Ru–Cl(1)
Ru–Cl(3)
Ru–Cl(2)
2.3686(13)
2.3971(13)
1.152(5)
2.4180(13)
2.3679(13)
2.4068(13)
Under white light after a two weeks period the fac-
[RuCl3(NO)(P–P)] complexes, dissolved in CH2Cl2, isom-
erized to the mer species (Scheme 1).
(Scheme 2). When the isomerization of 1 is conducted
under totally deoxygenated atmosphere (under pure Ar)
the sole product formed is 1a.
Complex 7 was obtained from the liquor mother of 1,
but it was also obtained as a by-product during the fac to
mer photoisomerization of 1, as judged by a 31P {1H}
NMR spectrum. This result suggests that the oxidation
of the phosphorus in complex 1 had occurred during
the isomerization process, and it is worth pointing out
that this oxidation process was detected only for this
complex. The explanation for this may be the fact that
the four member chelate of the dppm complex is very
strained, generating a temporary ‘‘dangling’’ ligand and
in the presence of oxygen the non coordinated phospho-
rus atom is quickly oxidized. The dppmO ligand formed
is a five member chelate and it’s coordination to the
metal via P–O is favorable, allowing the formation of 7
There are a number of reports showing nitrosyl com-
plexes that are photoactive as NO0 donors [4,26–28]
but, however, this is not the case for the complexes stud-
ied in this work. Irradiations with white light do not pro-
duce any change that could be attributed to NO0
dissociation. As will be shown by IR and 31P {1H}
NMR spectroscopies, the photolysis of fac leads to forma-
tion of the mer isomers.
3.2. Characterization
3.2.1. Infrared spectra
There are in the literature reports on solid state effects
which cause split in the NO stretching band [29,30]. To

2902
G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
Table 5
Selected bond angles for (ꢁ) 1, 2 and 4
1
2
4
N–Ru–P(1)
N–Ru–P(2)
92.55(14)
93.27(14)
71.26(4)
175.93(14)
83.74(4)
83.96(4)
91.13(14)
99.59(5)
178.7(6)
170.00(5)
91.15(5)
92.09(15)
168.43(5)
97.90(5)
91.24(5)
90.90(5)
N–Ru–P(1)
N–Ru–P(2)
91.39(11)
92.62(10)
85.76(3)
176.94(11)
86.08(4)
92.07(10)
92.16(3)
83.96(4)
178.6(4)
174.91(4)
89.74(4)
91.91(11)
175.32(4)
90.77(4)
90.52(4)
91.04(4)
N–Ru–P(1)
N–Ru–P(2)
93.33(14)
94.44(15)
93.22(5)
90.13(14)
174.83(5)
90.34(5)
179.05(14)
86.27(5)
176.9(4)
84.73(5)
90.33(5)
90.76(14)
88.07(5)
174.56(5)
88.05(5)
90.08(5)
P(1)–Ru–P(2)
N–Ru–Cl(1)
P(1)–Ru–Cl(1)
P(2)–Ru–Cl(1)
N–Ru–Cl(4)
P(1)–Ru–Cl(4)
O–N–Ru
P(2)–Ru–Cl(4)
Cl(1)–Ru–Cl(4)
N–Ru–Cl(2)
P(1)–Ru–Cl(2)
P(2)–Ru–Cl(2)
Cl(1)–Ru–Cl(2)
Cl(4)–Ru–Cl(2)
P(1)–Ru–P(2)
N–Ru–Cl(1)
P(1)–Ru–Cl(1)
N–Ru–Cl(3)
P(1)–Ru–Cl(3)
P(2)–Ru–Cl(1)
O–N–Ru
P(2)–Ru–Cl(3)
Cl(1)–Ru–Cl(3)
N–Ru–Cl(2)
P(1)–Ru–Cl(2)
P(2)–Ru–Cl(2)
Cl(1)–Ru–Cl(2)
Cl(3)–Ru–Cl(2)
P(1)–Ru–P(2)
N–Ru–Cl(1)
P(1)–Ru–Cl(1)
P(2)–Ru–Cl(1)
N–Ru–Cl(3)
P(1)–Ru–Cl(3)
O–N–Ru
P(2)–Ru–Cl(3)
Cl(1)–Ru–Cl(3)
N–Ru–Cl(2)
P(1)–Ru–Cl(2)
P(2)–Ru–Cl(2)
Cl(1)–Ru–Cl(2)
Cl(3)–Ru–Cl(2)
Table 6
˚
Selected bond distances (A) and angles (ꢁ) for 3
Ru(1)–N(11)
Ru(1)–P(12)
Ru(1)–P(11)
Ru(1)–Cl(11)
Ru(1)–Cl(13)
Ru(1)–Cl(12)
O(11)–N(11)
1.738(4)
Ru(2)–N(21)
1.786(5)
2.3438(12)
2.3480(12)
2.3499(13)
2.4268(12)
2.4534(13)
1.143(6)
Ru(2)–P(21)
Ru(2)–P(22)
Ru(2)–Cl(23)
Ru(2)–Cl(21)
Ru(2)–Cl(22)
O(21)–N(21)
2.3476(12)
2.3496(13)
2.3514(13)
2.4185(14)
2.4280(13)
1.051(6)
N(11)–Ru(1)–P(12)
N(11)–Ru(1)–P(11)
P(12)–Ru(1)–P(11)
N(11)–Ru(1)–Cl(11)
P(12)–Ru(1)–Cl(11)
P(11)–Ru(1)–Cl(11)
N(11)–Ru(1)–Cl(13)
P(12)–Ru(1)–Cl(13)
P(11)–Ru(1)–Cl(13)
Cl(11)–Ru(1)–Cl(13)
N(11)–Ru(1)–Cl(12)
P(12)–Ru(1)–Cl(12)
P(11)–Ru(1)–Cl(12)
Cl(11)–Ru(1)–Cl(12)
Cl(13)–Ru(1)–Cl(12)
O(11)–N(11)–Ru(1)
92.61(14)
93.37(14)
84.26(4)
176.67(14)
87.49(5)
83.33(5)
93.14(14)
90.53(4)
171.84(5)
90.18(5)
89.33(14)
175.73(5)
91.83(5)
90.36(5)
93.16(5)
179.0(4)
N(21)–Ru(2)–P(21)
N(21)–Ru(2)–P(22)
P(21)–Ru(2)–P(22)
N(21)–Ru(2)–Cl(23)
P(21)–Ru(2)–Cl(23)
P(22)–Ru(2)–Cl(23)
N(21)–Ru(2)–Cl(21)
P(21)–Ru(2)–Cl(21)
P(22)–Ru(2)–Cl(21)
Cl(23)–Ru(2)–Cl(21)
N(21)–Ru(2)–Cl(22)
P(21)–Ru(2)–Cl(22)
P(22)–Ru(2)–Cl(22)
Cl(23)–Ru(2)–Cl(22)
Cl(21)–Ru(2)–Cl(22)
O(21)–N(21)–Ru(2)
93.82(14)
91.94(14)
84.45(4)
175.14(14)
84.94(4)
83.27(5)
95.13(15)
90.68(5)
171.67(5)
89.59(5)
88.15(15)
177.80(5)
94.52(5)
93.02(5)
90.12(5)
175.7(5)
avoid this effect, in this work the IR spectra were obtained
in CH2Cl2 solutions and CsI pellets (see Table 8).
The IR spectra of the complexes are dominated by the
strong NO stretching band (mNO) in the range of 1818–
1884 cmꢀ1 [31] depending on the isomer and the diphos-
phine. Important bands are also those involving the Ru
center and the chloride ligands in the low energy region
[32]. Comparing the fac and the mer isomers there is a
marked difference in the Ru–Cl stretching vibration
modes; the fac-ones are characterized by these bands
occurring in the range of 327–330 cmꢀ1 while in the mer
isomers the mRu–Cl bands are in the range of 337–
345 cmꢀ1. The other bands in the IR spectra are due to
the vibrational modes of the diphosphine ligands, being
only slightly affected by the coordination to the metal
center [33].
Comparing the mNO bands obtained in CsI pellets and
CH2Cl2 solutions for the same complex they are seen to
be generally different. In going from pellets to solutions
the mNO for the fac isomers shift to lower frequencies while
the mer isomers show opposite behavior. However the dif-
ferences are not constant, being dependent on the
compound.
Three of the mer-isomers (1, 2 and 3) show mNO values
smaller than those in the corresponding fac; however, the
opposite occurs for the pair 5/5a, and for the compounds
4/4a and 6/6a the mNO is independent of the isomer. Con-
sidering only electronic aspects, the mNO should shift to
lower frequencies in the mer than in the fac isomers because
the ruthenium center is expected to be electron richer in the
former (two chlorides in trans cause a strong competitive
effect). However this characteristic is not constant in this

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2903
Table 7
˚
Selected bond distances (A) and angles for (ꢁ) 6a and 7
6a
7
Ru(1)–N(1)
Ru(1)–P(2)
Ru(1)–P(1)
Ru(1)–Cl(11)
Ru(1)–Cl(13)
Ru(1)–Cl(12)
O(11)–N(11)
1.971(6)
Ru(2)–N(2)
Ru(2)–P(4)
Ru(2)–P(3)
Ru(2)–Cl(23)
Ru(2)–Cl(21)
Ru(2)–Cl(22)
O(21)–N(21)
1.940(5)
Ru–N
Ru–O(1)
Ru–P(2)
O–N
Ru–Cl(1)
Ru–Cl(3)
Ru–Cl(2)
O(1)–P(1)
N–Ru–O(1)
N–Ru–P(2)
O(1)–Ru–P(2)
N–Ru–Cl(1)
O(1)–Ru–Cl(1)
P(2)–Ru–Cl(1)
N–Ru–Cl(3)
O(1)–Ru–Cl(3)
1.713(6)
2.4015(12)
2.4563(12)
2.3748(14)
2.3723(12)
2.3759(16)
0.789(8)
2.3922(14)
2.4529(13)
2.3718(14)
2.3884(14)
2.3726(18)
0.866(7)
2.059(5)
2.3597(19)
1.147(9)
2.367(2)
2.3665(18)
2.404(2)
1.526(5)
N(1)–Ru(1)–P(2)
N(1)–Ru(1)–P(1)
P(2)–Ru(1)–P(1)
N(1)–Ru(1)–Cl(11)
P(2)–Ru(1)–Cl(11)
P(1)–Ru(1)–Cl(11)
N(1)–Ru(1)–Cl(13)
P(2)–Ru(1)–Cl(13)
93.1(2)
174.29(18)
84.26(4)
90.62(18)
92.88(5)
84.46(5)
93.94(18)
86.94(4)
N(2)–Ru(2)–P(3)
N(2)–Ru(2)–P(4)
P(3)–Ru(2)–P(4)
N(2)–Ru(2)–Cl(23)
P(3)–Ru(2)–Cl(23)
P(4)–Ru(2)–Cl(23)
N(2)–Ru(2)–Cl(21)
P(3)–Ru(2)–Cl(21)
171.95(16)
95.14(19)
83.86(4)
95.70(17)
92.25(5)
88.51(5)
89.00(17)
83.05(5)
176.1(3)
92.3(2)
83.94(14)
91.4(2)
88.13(15)
93.00(7)
94.7(2)
85.98(14)
cone angles which are bigger than in dppm, dppe and c-
dppen [34].
The sequence of IR spectra obtained during the solid
state fac to mer isomerization 1 in CsI pellets under irradi-
ation with white lamp is shown in Fig. 7.
All the complexes with fac geometry presented the
same behavior of solid state isomerization, but when
the mer isomers are irradiated following the same proce-
dure described above, there are no changes in the IR
spectra.
Cl
Ru
Cl
NO
NO
Cl
Cl
P
P
P
P
hν
CH2Cl2
Ru
Cl
Cl
fac 2-6
mer 2a-6a
Scheme 1. The fac to mer isomerization process for the fac-[RuCl3(NO)-
(P–P)] complexes.
In complexes 8 and 8a the NO stretching band is shifted
37 cmꢀ1 towards lower energy when compared with the
Cl
NO
Cl
14NO analogous,
5
and 5a; for both isomers
NO
Cl
Cl
P
P
NO
Cl
P
P
hν,O2
Ru
Ru
Ru
+
15
m1N4O=m ¼ 1:020, a value very close to the theoretical one
CH2Cl2
P
O
Cl
NO
P
Cl
calculated from the Hooke law (1.018) [35]. The mRu–N
and the dRu–N–O bands appear at 592 and 527 cmꢀ1 for 8
and 577 and 515 cmꢀ1 for 8a [32]. Similar differences are
found for the complex trans-[RuCl(NO)(das)2]Cl2 when
compared with the analogous 15NO [36].
Cl
Cl
mer 7
fac 1
mer 1a
Scheme 2. The fac to mer isomerization process for the fac-[RuCl3(NO)-
(dppm)] complex.
3.2.2. 31P {1H} and 15N {1H} NMR spectra
series probably because for some compounds, steric factors
may affect the properties of the coordinated NO. This is
apparent when considering that the compounds with oppo-
site behavior contain the more steric demanding diphos-
phines (dppp, dppb and dcpe), as can be seen by their
The 31P {1H} NMR spectra of the fac-[RuCl3(NO)(P–
P)] series are characterized by a singlet, indicating the mag-
netic equivalence of the phosphorus atoms [12]. For the
mer compounds a pair of doublets are observed in the spec-
Table 8
IR (mNO) bands (cmꢀ1) and 31P {1H} NMR data for the [RuCl3(NO)(P–P)] complexes
P–P
mNO
d
31P (ppm)
CH2Cl2
fac
CsI
fac
mer
mer
fac
mer
PA
PB
2JP–P (Hz)
dppm
dppe
c-dppen
dppp
dppb
dcpe
1872
1866
1883/1874
1870
1855
1838
1858
1851
1870
1880
1851
1878
1843
1876
1874
1884/1876
1875
1868
1834
1839
1828
1843
1868
1821
1858
1831
ꢀ15.3
46.9
55.3
15.6
22.8
62.9
ꢀ9.9
54.6
63.8
10.4
13.6
ꢀ32.1
35.6
46.8
0.78
10.1
68.2
23.6
12.8
49.8
37.5
18.2
23.0
36.9
1850
1838
67.1
44.0
dppmO
15NOdppb
a
67.9 (PIII
14.2
)
40.6 (PV)
10.7a
1818
1831
22.5
2JP–N = 72.2 Hz.

2904
G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
of the free phosphines, that is, the phosphorous atoms are
in these cases more shielded. For this reason the higher
field doublets can be attributed to the phosphorus trans
to the NO group. To verify this proposition the mer-
[RuCl3(15NO)(dppb)] (8a) was synthesized. The 31P {1H}
NMR spectrum shown in Fig. 8(A) presents two sets of sig-
nals, a doublet at lower field and a double doublet (dd) at
higher field, indicating an AMX spin system. The dd pat-
A
1876
B
C
2
tern indicates that PB is coupled to PA, with JP–
P = 36.9 Hz, and with the 15N of the 15NO group with
2JP–N = 72.2 Hz, which is a typical value for trans coupling
P–15N [38]. This result confirms the previous attribution to
the phosphorus chemical shifts in this class of compounds
[13,14]. In the 15N NMR spectrum of 8a, shown in
Fig. 8(B), an AX double doublet (dd) is observed at
1836
2
2
ꢀ30.0 ppm with JP–N = 72.2 Hz (trans) and JP–N
=
2200 2000 1800 1600 1400 1200 1000
Wavenumber (cm-1)
800
600
3.2 Hz (cis). The corresponding spectra for the fac isomer
8, given in Fig. 9, show that the spectrum lines become sim-
pler because the phosphorus are magnetically equivalent in
this case. In the 31P {1H} NMR of 8, a doublet appeared at
Fig. 7. Sequence of IR spectra (CsI) showing the fac (mNO at 1876) to mer
(mNO at 1836) isomerization of 1. Irradiation A–B: 20 min; A–C (90 min)
with a white lamp.
23.0 ppm with JP–N = 3.2 Hz (cis). In the 15N NMR spec-
2
tra of 8, an AB triplet system t(AB) is observed at
2
tra, showing that the phosphorus are trans to different
atoms, NO and Cl.
ꢀ54.0 ppm with JP–N = 3.2 Hz (cis); this pattern arises
due to the coupling between 15N with two almost equiva-
lent phosphorus. The slightly lower 15N chemical shift in
8 than in 8a indicates that in 8 there is a more linear nitro-
syl group and that in both complexes the chemical shifts
are typical of the 15NO+ ligand [39].
Fig. 10 is a graph correlating the NMR data for cou-
pling constants (Table 8) versus chemical shifts of the P
trans NO, suggesting a direct correlation between these
two phenomena in this series of mer-[RuCl3(NO)(P–P)]
complexes.
All the chemical shifts observed are in agreement with
the ring size effect in which the order of shielding is four >
six > seven > five member ring [37]. In spite of the fact that
compounds 2/2a, 3/3a and 6/6a have five member rings,
compounds 6/6a are more deshielded, possibly as a conse-
quence of the steric effect caused by the cyclohexyl rings,
which can distort more effectively the internal ring angle
of the P–Ru–P bite. For compounds 3/3a the main effect
is the electron-withdraw produced by the p orbitals from
the carbon-carbon double bond. Table 8 shows the 31P
{1H} NMR data for all the complexes and Fig. 10 shows
the NMR 31P {1H} data correlations (chemical shifts ver-
sus coupling constant) for the mer isomers.
3.3. Isomerization of mer to fac-isomers
Previous reports [12,13] have shown that 4a and 5a in
solution of CH2Cl2 undergo an isomerization process to
form the fac isomer; for 4a the conversion is total while
for 5a it is partial. The new mer complexes obtained in this
The phosphorus trans to the NO are more distant from
the metal center, as has been shown by X-ray analysis
[13,14]. Thus their chemical shifts become closer to the ones
PA
14.2 ppm
PB
10.7 ppm
Cl
15NO
PA
Ru
PB
Cl
Cl
-28.5
-29.0
-29.5
-30.0
-30.5
-31.0
-31.5
-32.0
16.0
14.0
12.0
10.0
8.0
δ (ppm)
δ (ppm)
A
B
Fig. 8. NMR spectra of 8a in CH2Cl2. (A) 31P {1H}. (B) 15N {1H}.

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2905
23.0 ppm
-54.0 ppm
15NO
Ru
Cl
Cl
P
P
Cl
-53.0
-53.5
-54.0
-54.5
-55.0
24.5
24.0
23.5
23.0
22.5
22.0
21.5
21.0
δ (ppm)
δ (ppm)
A
B
Fig. 9. NMR spectra of 8 in CH2Cl2. (A) 31P {1H}. (B) 15N {1H}.
70
60
50
40
30
20
10
0.10
0.05
1a
0.00
4a
-0.05
-0.10
5a
-0.15
2a
6a
-0.20
3a
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
E / V
-40
-20
0
20
40
60
Fig. 11. Cyclic voltammetric response for 2a in CH2Cl2 at 100 mV sꢀ1
.
δ (ppm) - P trans NO
Table 9
Fig. 10. Correlation between the coupling constants (Hz) and the
chemical shifts for the phosphorus trans NO in the mer-[RuCl3(NO)(P–
P)] series (R = 0.99).
Electrochemical data (V) for the series fac and mer [RuCl3(NO)(P–P)]
Complex
CH2Cl2
CH3CN
fac-Ecp
mer-Ecp
fac-Ecp/Eap
mer-Ecp/Eap
1
2
3
4
5
6
7
ꢀ0.79
ꢀ0.87
ꢀ0.73
ꢀ0.85
ꢀ0.92
ꢀ1.00
ꢀ0.64
ꢀ0.70
ꢀ0.64
ꢀ0.76
ꢀ0.80
ꢀ1.10
ꢀ0.75
ꢀ0.50/+1.42
ꢀ0.49/+2.03
ꢀ0.60/+2.06
ꢀ0.60/+ 2.15
ꢀ0.54/+2.08
ꢀ0.70/+1.80
ꢀ0.48/+ 1.89
ꢀ0.52/+1.88
ꢀ0.45/+1.89
ꢀ0.59/+1.81
ꢀ0.45/+1.90
ꢀ0.92/+1.76
ꢀ0.60/+1.77
work, 1a, 2a, 3a and 6a are stable in solution as demon-
strated by 31P {1H} NMR spectra of solutions followed
during a period of a month. Probably, due to steric rea-
sons, the complexes with the larger diphosphines, dppp
and dppb, adopt the fac geometry.
Ecp = RuII–NO+/RuII–NO0.
Eap = RuII–NO+/RuIII–NO+.
3.4. Electrochemistry
The cyclic voltammetric experiments on complexes 1–7
and 1a–6a were carried out in CH2Cl2 and CH3CN solu-
tions. In CH2Cl2, the CV responses are dominated by irre-
versible reduction waves, assigned to the reduction of the
NO+ group coordinated to Ru(II) [40,41]. Fig. 11 shows
a typical cyclic voltammogram for these complexes and
the potentials of the processes are shown in Table 9.
Electrochemical studies of Ru-NO+ containing com-
pounds have shown reversible reduction of the NO+ group
at more positive potentials than those observed in this
work [40]. For example, previous work from this group
[15] has shown that trans-[RuCl(NO)(dppe)2]2+ presents a
reversible reduction of the NO+ ligand at +0.10 V versus

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G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
Ag/AgCl. The more negative reduction potentials for the
NO+, measured for the [RuCl3(NO)(P–P)] complexes,
result from the replacement of two P atoms (p acceptor/
r-donor ligand) by two Clꢀ (r-/p-donor ligand). In this
case the ruthenium center becomes electronically richer
and consequently, it is more difficult to add an electron
to the NO+.
(reversible for 1 and 6a), a fact that has been attributed to
the oxidation of the ruthenium: RuII–NO+/RuIII–NO+
[42]. These characteristics can be observed in Fig. 12. The
high value for the RuII/RuIII potential is explained by the
presence of the NO+ (strong p acceptor) [7]. The dppm
complex shows the lowest potential for these processes,
which can be explained by the reduced size of this dipho-
shine when compared with the others. This fact turns the
RuIII oxidation state to be more favorable in this complex
than in the others, because the RuIII ion is slightly smaller
than RuII ion [43]. For all the compounds studied, except
for 1 and 6a, the oxidation of RuII to RuIII is irreversible
indicating that the RuIII–NO+ fragments are not stable.
After this oxidation, scanning for the cathodic region,
another irreversible wave appears. No further investiga-
tions were made to characterize this new specie.
The reduction of the coordinated NO+ group is accom-
panied by a rapid chemical reaction, hence, there is no sign
of a return wave even at low temperature (0 ꢁC) and at scan
rates of up to 5 V sꢀ1 for all compounds studied. In all
cases a plot of peak current versus the square root of the
scan rate gives a straight line, indicating that the elec-
tron-transfer process is diffusion controlled. Application
of a switching potential more negative than the NO+-based
reduction process results in new redox peaks in the cyclic
voltammogram, but no additional studies were made to
identify such a process.
Utilizing the coordinating solvent CH3CN in the CV
experiments, some other characteristics could be observed
(Fig. 12). The irreversible reduction under the NO+ in this
solvent occurred at a considerably less negative potential
(ca. 0.30 V) as shown in Table 9. This fact is an additional
evidence to confirm that this wave corresponds to the
reduction of the NO+ [40], because electrochemical pro-
cesses occurring over the ligands are more sensible to
changes in the medium.
The peak potential for the pair RuII/RuIII in the trans-
[RuCl(NO)(P–P)2]2+ complexes was not observed until
2.4 V [15]. For the complex [RuCl(NO)(bpy)2]2+, the
potential for this process was determined in liquid SO2 as
being 3.0 V [44], demonstrating the high electron deficient
metal center. Contraparty, this process is observed in the
[RuCl3(NO)(P–P)] complex showing, in this case, the
higher electron density on the metal center because of
the presence of two additional chlorides.
Scheme 3 shows the representative equations for the
above mentioned electrochemical processes involving the
coordinated nitrosyl ligand. In step 1 the compounds are
reduced at E1, ranging from ꢀ640 to ꢀ1000 mV, where
the site of reduction is the NO+ group giving the NO0 rad-
ical ligand. The reduced complexes are unstable and a chlo-
ride ligand is substituted by a neutral solvent CH3CN
molecule (step 2).
After the irreversible NO+ reduction, scanning to posi-
tive potential, a new dependent irreversible wave is
observed at +1.0 V for all the compounds. This process
can be ascribed to the oxidation of free chlorine present
in the solution [11]. Thus, reductions of all compounds
are accompanied by loss of chloride. At more positive
potentials, an irreversible wave appeared for all complexes
A similar redox induced substitution reaction has been
observed in the related compounds [trans-RuCl(NO)(cy-
clamꢀ)]2+ [45] and [RuCl2(dmso-O)(NO)L], L = Clꢀ or
NO2 [11]. The complex [RuCl2(P–P)(NO0)(CH3CN)] is
unstable and loses NOꢁ, producing the [RuCl2(P–
P)(CH3CN)2] compound (the processes for these species
were not identified).
0.30
0.4
0.3
II
+
III
+
Ru -NO --> Ru -NO
0.25
0.20
0.15
0.10
0.05
0.00
-0.05
The electronic density over the NO+ ligand can be esti-
mated by IR and electrochemical data [46]. There are in the
literature some good correlations between these two
parameters [47,48]. In this work such correlation between
the NO stretching in CH2Cl2 solutions and the Ecp for
the NO+ reduction in the same solvent was made and is
shown in Fig. 13. It is possible to observe a good linearity
of the data. The complex with the less energetic mNO, is that
with more electronic density over the NO and consequently
the reduction potential in this situation occurred at the
more negative value. The complex with the more basic
phosphine dcpe (pKa @ 10) [49] is the complex with this
characteristics. Following this series, the complex with
the more energetic mNO presents the lower reduction poten-
tial for the NO+, because the NO, in this case, has less elec-
tronic density, and addition of electrons on it is easier (less
negative potential).
0.2
1.0
1.2
1.4
1.6
1.8
2.0
2.2
0.1
2Cl- --> Cl2 + 2e-
E /V
0.0
-0.1
-0.2
(1)
-0.5
-1.0
0.0
0.5
E / V
1.0
1.5
2.0
Fig. 12. Cyclic voltammetric response for 2 in CH3CN at 100 mV sꢀ1
Inset. Same CV in the 1.0–2.2 V region.
.

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2907
[RuCl3(P-P)(NO)] + e-
[RuCl3(P-P)(NO )]- E1 (1)
0
[RuCl2(P-P)(NO )(CH3CN)] + Cl- (2)
0
[RuCl3(P-P)(NO )]- + CH3CN
0
.
0
[RuCl2(P-P)(CH3CN)2] + NO (3)
[RuCl2(P-P)(NO )(CH3CN)] + CH3CN
Scheme 3. Electrochemical processes involved in the [RuCl3(P–P)(NO)] complexes in CH3CN.
in the fac 1–4 isomers, trans to P in the mer 6a isomers
and trans to O in 7. The linearity of this group is consistent
with the NO stretching vibration band in the IR spectra,
both indicating that the NO group is formally bound to
the metal as NO+ [50,51]. The N–O bond lengths fall in
1880
1875
1870
1865
1860
1855
1850
3
1
˚
range from 1.029(6) to 1.152(5) A, being consistent with
4
other reported data [52–54]. In spite of the relatively large
differences in the NO distance, such trend is not reflected in
the NO stretching frequencies, because for similar values of
2
m
NO, very different N–O distances are found, as seen by
comparing the fac-[RuCl3(NO)(dppm)], mNO = 1875 cmꢀ1
/
˚
N–O = 1.029(6) A with the fac-[RuCl3(NO)(dppp)],
m
5
NO = 1875 cmꢀ1/N–O = 1.152(5) A.
The equatorial Ru–Cl bond lengths (2.41–2.43 A) for 1–
˚
˚
6
˚
4 are longer than the axial one (trans NO; 2.35–2.37 A) by
@0.07 A, consistent with the trans strength effect of the NO.
˚
-1000
-950
-900
-850
-800
-750
-700
In the related complexes fac-[RuCl3(NO)(bipy)] (bipy =
2,20-bipyridine) [55] and fac-[RuCl3(NO)(pdma)] (pdma =
o-phenylenebis(dimethyl-arsine)) [56], these differences are
E
cp (mV vs Ag/AgCl)
Fig. 13. Correlation between the NO+ reduction potential and the NO
strecthing band in CH2Cl2 solution for the fac-[RuCl3(NO)(P–P)] series
(R = 0.97).
˚
0.03 and 0.07 A, respectively, indicating that diphosphines
and the pdma ligand exert a greater trans labilizing influ-
ence on chloride than does bipy.
The Ru–P distances for 1–4 and 7 are in the usual range
for Ru–diphosphines complexes varying between 2.35 and
Comparing the series of isomers (fac and mer) the reduc-
tion of the NO+ in the mer ones should be less negative
than that observed for the fac species because the presence
of a phosphorus (p acceptor ligand) trans to NO in the mer
isomers creates a pathway to the distribution of the addi-
tional electron density when the NO+ is reduced to NO0,
consequently the reduction is more accessible. Analyzing
the values from Table 9 it is clear that this expected behav-
ior occurs, mainly with CH2Cl2 as solvent. The exception
are the compounds 6/6a in which the mer shows a more
negative potential, this happens because the dcpe diphos-
phine is much more basic than the other ones, not acting
as a good p acceptor.
˚
2.38 A, the same occurring for the Ru–Cl distances that are
˚
in the range 2.35–2.45 A [12–15]. The angles P–Ru–P (bite
angle) increase in the order of the chain length of the
diphosphines (dppm > c-dppen > dppe > dppp), ranging
from 71.26ꢁ until 93.22ꢁ.
The X-ray structure refinement of 6a shows a high
thermal parameter for the NO group, which results in
unusual values for the N–O and Ru–N distances. The
˚
Ru–P(1) distance [2.4563(12) A] is longer than the Ru–
˚
P(2) [2.4015(12) A], because the former is trans to the
NO+, a p acceptor ligand which competes for the same
electrons of the metal center with the phosphorus
atoms in trans. The same is observed for Ru–P(3) and
Ru–P(4).
Considering the oxidation process RuII/RuIII, in the mer
isomers such process should occur at lower potential than
for the corresponding fac compound, because the presence
of Clꢀ trans Clꢀ, due to the competitive effect, increases the
electron density in the ruthenium center. In fact, this is
experimentally observed for all compounds studied with
the exception of the dppm compounds.
This behavior in the structure of 6a had been previously
observed in the analogous mer-[RuCl3(NO)(dppb)] [13] and
mer-[RuCl3(NO)(diop)] [14], and in the cis-[Ru(dppe)-
(CO)2(OSO2CF3)2] [57]. This last one has a Ru–P distance
trans to CO longer than the other, trans to OSO2CF3,
showing the expected similar behavior of the CO when
compared with the NO ligand.
3.5. Structural studies
In complexes 2 and 7 the formed chelates are of five
members, this being the reason for the similarity of the bite
angles observed in their X-ray structures, 85.76ꢁ and
83.94ꢁ, respectively.
In all structures of this work the metal displays the
expected distorted octahedral coordination geometry
where the nitrosyl group is essentially linear, trans to Clꢀ

2908
G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
˚
[12] A.A. Batista, C. Pereira, S.L. Queiroz, L.A.A. de Oliveira, R.H.A.
Santos, M.T.P. Gambardella, Polyhedron 16 (1997) 927.
[13] A.A. Batista, C. Pereira, K. Wohnrath, S.L. Queiroz, R.H.A. Santos,
M.T.P. Gambardella, Polyhedron 18 (1999) 2079.
[14] G. Von Poelhsitz, M.P. de Araujo, L.A.A. de Oliveira, S.L. Queiroz,
J. Ellena, E.E. Castellano, A.G. Ferreira, A.A. Batista, Polyhedron
21 (2002) 2221.
The P@O distance of 1.526(5) A in 7 is approximately
the same as observed for tcc-[RuCl2(g2-dppmO)2]
(P@O = 1.50 A) [58]. The Ru–O distances of 2.059(5) A
in 7 is much shorter than that from the tcc-[RuCl2(g2-
dppmO)2] (2.20 A), reflecting the presence of the NO
ligand trans to the oxygen in the former.
˚
˚
+
˚
[15] R.C.L. Zampieri, G. Von Poelhsitz, A.A. Batista, O.R. Nascimento,
J. Ellena, E.E. Castellano, J. Inorg. Biochem. 92 (2002) 82.
[16] G. Von Poelhsitz, A.A. Batista, J. Ellena, E.E. Castellano, E.S.
Lang, Inorg. Chem. Commun. 8 (2005) 805.
4. Conclusions
We have shown that mer-[RuCl3(NO)(P–P)] isomers can
be obtained from the corresponding fac isomers in solid
state or in solution by using white light. The isomerization
processes were followed by IR (in solid state) and 31P {1H}
NMR spectra (in CH2Cl2 solution). The mer-[RuCl3-
(15NO)(dppb)] was used for the attribution of the phospho-
rus chemical shifts and it was used as a reference for the
other similar complexes. The reduction potential for the
NO+ group is dependent on the solvent used (CH2Cl2 or
CH3CN). There is a good correlation between the NO+
reduction potential and the NO stretching band in CH2Cl2
solution for the fac-[RuCl3(NO)(P–P)] series.
[17] L.R. Dinelli, A.A. Batista, K. Wohnrath, M.P. de Araujo, S.L.
Queiroz, M.R. Bonfadini, G. Oliva, O.R. Nascimento, P.W.
Cyr, K.S. MacFarlane, B.R. James, Inorg. Chem. 38 (1999)
5341.
[18] Enraf-Nonius, COLLECT, Nonius BV, Delft, The Netherlands, 1997–
2000.
[19] Z. Otwinowski, W. Minor, HKL Denzo Scalepack, in: C.W.
CarterJr., R.M. Sweet (Eds.), Methods in Enzymology, vol. 276,
Academic Press, New York, 1997, p. 307.
[20] R.H. Blessing, Acta Crystallogr. A51 (1995) 33.
[21] P. Coppens, in: F.R. Ahmed, S.R. Hall, C.P. Huber (Eds.),
Crystallographic Computing, Munksgaard, Copenhagen, 1970, p.
255.
[22] P. Coppens, L. Leiserowitz, D. Rabinovich, Acta Crystallogr. 18
(1965) 1035.
[23] G.M. Sheldrick, SHELXS-97. Program for Crystal Structure Resolu-
tion, University of Go¨ttingen, Go¨ttingen, Germany, 1997.
[24] G.M. Sheldrick, SHELXL-97. Program for Crystal Structures Analysis,
University of Go¨ttingen, Go¨ttingen, Germany, 1997.
[25] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[26] P.C. Ford, S. Wecksler, Coord. Chem. Rev. 249 (2005) 1382.
[27] A.K. Patra, P.K. Mascharak, Inorg. Chem. 42 (2003) 7363.
[28] V. Togniolo, R.S. da Silva, A.C. Tedesco, Inorg. Chim. Acta 316
(2001) 7.
5. Supplementary data
Coordinates and other crystallographic data have been
deposited with the CCDC, deposition code 287922–
287927, respectively for 3, 7, 2, 1, 4 and 6a. Copies of this
information may be obtained from The Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44
1233 336033; e-mail:deposit@ccdc.cam.ac.uk or www:http.
ccdc.cam.ac.uk).
[29] J.T. Mague, J.P. Mitchener, Inorg. Chem. 11 (1972) 2714.
[30] C.F. Fortney, S.J. Geib, F.T. Lin, R.E. Shepherd, Inorg. Chim. Acta
358 (2005) 2921.
[31] J.H. Enemark, R.D. Feltham, Coord. Chem. Rev. 13 (1974)
339.
Acknowledgement
[32] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4th ed., John Wiley & Sons, 1986.
[33] G.B. Deacon, J.H.S. Green, Spectrochim. Acta, A-M A 24 (1968)
845.
We thank CNPq, CAPES, FINEP, PRONEX and FA-
PESP for financial support.
[34] C.A. Tolman, Chem. Rev. 77 (1977) 313.
[35] D.A. Freedman, D.E. Janzen, J.L. Vreeland, H.M. Tully, K.R.
Mann, Inorg. Chem. 41 (2002) 3820.
References
[1] D.J. Hodgson, N.C. Payne, J.A. McGinnety, R.G. Pearson, J.A.
Ibers, J. Am. Chem. Soc. 90 (1968) 4486.
[36] P.G. Douglas, R.D. Feltham, H.G.J. Metzger, J. Am. Chem. Soc. 93
(1971) 84.
[2] R.M.J. Palmer, A.G. Ferrige, S. Moncada, Nature 327 (1987)
524.
[3] L.J. Ignarro, G.M. Buga, K.S. Wood, R.E. Byrns, Circ. Res. 61
(1987) 866.
[37] P.E. Garrou, Inorg. Chem. 14 (1975) 1435.
[38] L. Carlton, R. Weber, Inorg. Chem. 33 (1996) 5843.
[39] J. Mason, L.F. Larkworthy, E.A. Moore, Chem. Rev. 102 (2002)
913.
[4] E. Tfouni, M. Krieger, B.R. McGarvey, D.W. Franco, Coord. Chem.
Rev. 236 (2003) 57.
[5] R. Bakhtiar, R.E.I. Ochiai, Gen. Pharmacol. 32 (1999) 525.
[6] W.P. Griffith, The Chemistry of the Rarer Platinum Metals, Inters-
icence Publishers, New York, 1967.
[40] R.W. Callahan, T.J. Meyer, Inorg. Chem. 16 (1977) 574.
[41] F. Baumann, W. Kaim, L.M. Baraldo, L.D. Slep, J.A. Olabe, J.
Fiedler, Inorg. Chim. Acta 285 (1999) 129.
[42] D. Ooyama, N. Nagao, H. Nagao, Y. Sugimoto, F.S. Howell, M.
Mukaida, Inorg. Chim. Acta 261 (1997) 45.
[7] D.M.P. Mingos, D.J. Sherman, Adv. Inorg. Chem. 34 (1989)
293.
[8] M.J. Clarke, J.B. Gaul, Struct. Bond. 81 (1993) 147.
[9] P.C. Ford, J. Bourassa, K. Miranda, B. Lee, I. Lorkovic, S.
Boggs, S. Kudo, L. Laverman, Coord. Chem. Rev. 171 (1998)
185.
[43] D.D. Walker, H. Taube, Inorg. Chem. 20 (1981) 2828.
[44] D.W. Pipes, T.J. Meyer, Inorg. Chem. 23 (1984) 2466.
[45] D.R. Lang, J.A. Davis, L.G.F. Lopes, A.A. Ferro, L.C.G. Vascon-
cellos, D.W. Franco, E. Tfouni, A. Wieraszko, M.J. Clarke, Inorg.
Chem. 39 (2000) 2294.
[46] J.A. McCleverty, Chem. Rev. 79 (1979) 53.
[10] L.G.F. Lopes, A. Wieraszko, Y. El-Sherif, M.J. Clarke, Inorg. Chim.
Acta 312 (2001) 15.
[47] M.G. Sauaia, R.S. da Silva, Transition Metal Chem. 28 (2003)
254.
[11] B. Serli, E. Zangrando, E. Lengo, G. Mestroni, L. Yellowlees, E.
Alessio, Inorg. Chem. 41 (2002) 4033.
[48] L.G.F. Lopes, M.G. Gomes, S.S.S. Borges, D.W. Franco, Aust. J.
Chem. 51 (1998) 865.

G. Von Poelhsitz et al. / Inorganica Chimica Acta 359 (2006) 2896–2909
2909
[49] M. Rahman, H. Liu, K. Eriks, A. Prock, W. Giering, Organometallics
8 (1989) 1.
[54] H. Hadadzadeh, M.C. DeRosa, G.P.A. Yap, A.R. Rezvani, R.J.
Crutchley, Inorg. Chem. 41 (2002) 6521.
´
[50] G.B. Richter-Addo, P. Legzdins, Metal Nitrosyls, Oxford University
Press, New York, 1992.
[55] M. Haukka, T. Vena¨la¨inen, M. Ahlgren, T.A. Pakkanen, Inorg.
Chem. 34 (1995) 2931.
[51] H. Tomizawa, K. Harada, E. Miki, K. Mizumachi, T. Ishimori, A.
Urushiyama, A.M. Nakahara, Bull. Chem. Soc. Jpn. 66 (1993) 1658.
[52] R. Eisenberg, C.D. Meyer, Acc. Chem. Res. 8 (1975) 26.
[53] K.R. Coll, J.E. Fergusson, V. McKee, C.T. Page, W.T. Robinson,
T.S. Keong, Inorg. Chem. 26 (1987) 106.
[56] B.J. Coe, C.I. McDonald, R.L. Beddoes, Polyhedron 17 (1998) 1997.
[57] M.F. Mahon, M.K. Whittlesey, P.T. Wood, Organometallics 18
(1999) 4068.
[58] M.P. Felicissimo, A.A. Batista, A.G. Ferreira, J. Ellena, E.E.
Castellano, Polyhedron 24 (2005) 1063.