Dependence of the product on the P-P ligand in reactions of [RuCl3(NO)(P-P)] complexes (P-P = aromatic diphosphines) with 2-mercaptopyridine

Article abstract of DOI:10.1016/j.poly.2009.09.004

This study presents the syntheses and characterization of 2-mercaptopyridine (pyS^-) complexes containing ruthenium(II) with the following general formula [Ru(pyS)₂(P-P)], P-P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl₃(NO)(P-P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P-P ligand. The reaction of pyS^- with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)₂(NO)(η¹-dppbO-P)]PF₆ (5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1-5, and report the X-ray structures for 1 and 5.

Full text of DOI:10.1016/j.poly.2009.09.004

Polyhedron 29 (2010) 280–287
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Dependence of the product on the P–P ligand in reactions of [RuCl3(NO)(P–P)]
complexes (P–P = aromatic diphosphines) with 2-mercaptopyridine
b
c
d
Gustavo Von Poelhsitz a, , André L. Bogado , Luciano M. Lião , Antonio G. Ferreira ,
*
Eduardo E. Castellano e, Javier Ellena e, Alzir A. Batista d
a Departamento de Química, Universidade Federal de Goiás, Campus Catalão, CEP 75704-020, Catalão (GO), Brazil
b Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, CEP 38302-000, Ituiutaba (MG), Brazil
c Instituto de Química, Universidade Federal de Goiás, C.P. 131, CEP 74001-970, Goiânia (GO), Brazil
d Departamento de Química, Universidade Federal de São Carlos, C.P. 676, CEP 13565-905, São Carlos (SP), Brazil
e Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos (SP), Brazil
a r t i c l e i n f o
a b s t r a c t
This study presents the syntheses and characterization of 2-mercaptopyridine (pySꢀ) complexes contain-
ing ruthenium(II) with the following general formula [Ru(pyS)2(P–P)], P–P = (c-dppen) = cis-1,
2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-
bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes
were synthesized from the mer- or fac-[RuCl3(NO)(P–P)] precursors in the presence of triethylamine in
methanol solution with dependence of the product on the P–P ligand. The reaction of pySꢀ with a ruthe-
nium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling
Article history:
Available online 9 September 2009
Keywords:
Ruthenium nitrosyl complexes
Diphosphines
2-Mercaptopyridine
Dangling dppbO
coordinated dppbO-P, the [Ru(pyS)2(NO)(g
1-dppbO-P)]PF6 (5). In addition, this work also presents and
discusses the spectroscopic and electrochemical behavior of 1–5, and report the X-ray structures for 1
and 5.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
it is interesting to study the reactions between nitrosyl complexes
and ligands containing thiols residues, such as the complexes with
Nitric oxide (NO) is relevant for many physiological processes,
such as cytotoxicity, neural-transmission and blood pressure regu-
lation, and its imbalance relates to diseases, for example cancer,
epilepsy, diabetes and arthritis [1]. S-nitrosothiols (R-SNO) are be-
lieved to play an important role in storing, transporting, and releas-
ing NO in the human body [1]. The ability of transition metal
complexes to both scavenge and release NO has generated new
interest in such complexes as potential metallopharmaceuticals
[2]. As a non-innocent ligand that can be coordinated as NO+,
NO0 or NOꢀ, depending on the nature of the metal center and on
the coordination environment [3], nitric oxide promotes the for-
mation of complexes with unique properties [3,4]. Many nitrosyl
complexes have been utilized as metallodrugs and among them
ruthenium complexes are of great interest [2,5,6]. Ruthenium has
a high affinity for NO, and some complexes of this metal with coor-
dinated NO have therapeutic uses in the treatment of sepsis and in
the control of high blood pressure [2,7]. Considering the electro-
philic character of the coordinated NO in a wide range of com-
plexes, biological reducing agents, such as thiols, are able to
reduce the NO group promoting its labilization [8,9]. In this sense
general formula [Ru(‘SpymMe2’,–N,–S)(‘SpymMe2’,–S)(NO)(P–P)]+,
P–P = (dppe) or (c-dppen), ‘SpymMe2’,–N,–S = dimethylmercapto-
pyrimidine recently reported [10]. Ligands of the mercaptopyridine
type and their complexes are currently being investigated as anti-
viral, antimetabolite and antitumor drugs as well as for their inter-
esting photochemical properties [11–14]. These ligands are
ubiquitous S, N donors that form a wide variety of complexes with
different kinds of metals [15,16].
Herein are described the synthesis of mixed P–P and 2-mercap-
topyridine complexes containing ruthenium with general formula
[Ru(pyS)2(P–P)], P–P = c-dppen (1), dppe (2), dppp (3) or dppb (4)
and [Ru(pyS)2(NO)(g
1-dppbO-P)]PF6 (5), as well as a complete
characterization, including spectroscopic, electrochemical behav-
ior and elemental analysis. The X-ray crystals structures of the
complexes 1 and 5 are also reported and discussed.
2. Experimental
2.1. Materials and instrumentation
All manipulations were carried out under Ar using standard
Schlenk techniques. Reagent grade solvents were appropriately dis-
tilled and dried before use. RuCl3NOꢁ2H2O, mer-[RuCl3(H2O)
* Corresponding author. Tel.: +55 64 34415334; fax: +55 64 34415336.
E-mail address: gustvon@catalao.ufg.br (G. Von Poelhsitz).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.09.004

G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
281
(dppb)], mer-[RuCl3(NO)(dppb)] and fac-[RuCl3(NO)(P–P)], P–P = c-
dppen, dppe, dppp and dppb, were prepared following the proce-
dures described in the literature in earlier works from this group
[17–19]. NMR spectra were recorded on a Bruker DRX 400 – 9.4 T
spectrometer at 298 K using a 5 mm direct probehead. The spectra
were obtained at 400.21 MHz for 1H, 100.05 MHz for 13C and
162 MHz for 31P. 1H and 13C shifts were recorded using TMS as
internal standard. 31P shifts were referenced to H3PO4, 85%. The
proton phosphorus decoupled 1H{31P} NMR experiment was per-
(2) Anal. Calc. (%) for C36H32P2N2S2Ru: C, 60.06; H, 4.48; N, 3.89.
Found: C, 59.88; H, 4.65; N, 3.78%. Yield: 66.0 mg (58%). UV–Vis
(CH2Cl2) kmax, nm (log e
, molꢀ1 dm3 cmꢀ1): 318 (4.13), 392 (3.38),
445 (2.83). 31P{1H} NMR (d, ppm): 74.0 (s).
(3) Anal. Calc. for C37H34P2N2S2Ru: C, 60.56; H, 4.67; N, 3.82.
Found: C, 60.85; H, 4.32; N, 4.07%. Yield: 60.0 mg (53%). UV–Vis
(CH2Cl2) kmax, nm (log e
, molꢀ1 dm3 cmꢀ1): 322 (4.01), 390 (3.28),
441 (2.84). 31P{1H} NMR (d, ppm): 42.1 (s).
formed using a relaxation delay of 1.0 s, pulse width 3.5
ls for
2.2.3. [Ru(pyS)2(dppb)] (4) and [Ru(pyS)2(NO)(1-dppbO-P)]PF6 (5)
The precursor mer-[RuCl3(NO)(dppb)] (0.15 mmol, 100.0 mg)
was reacted with excess of the 2-mercaptopyridine ligand
(0.48 mmol, 54.0 mg) in methanol (20 mL) within 24 h. The ligand
was previously deprotonated with triethylamine (0.96 mmol,
0.13 mL) in methanol and added via cannula over the precursor
solution. After the reaction time a small amount of a yellow pow-
der was filtered off and identified as 4, and the red solution ob-
tained was concentrated to ca. 5 mL and NH4PF6 was added
(0.20 mmol, 32.6 mg). This solution was maintained in the freezer
at ꢀ10 °C and after 48 h a red powder identified as 5 was recov-
ered. The same reaction described above but utilizing the fac iso-
mer instead the mer resulted in the formation of the complex 5
as the sole product.
30°, sweep width of 8116 Hz, acquisition time 4.03 s and 16 tran-
sients for each spectrum. IR spectra were recorded on a Bomem
Michelson FT MB-102 spectrophotometer as CsI pellets. UV–Vis
spectra were recorded on a Varian-Cary 500 spectrometer using
quartz cells and are presented as kmax or shoulder (sh) (nm)/emax
(Mꢀ1 cmꢀ1). Cyclic voltammetric measurements were recorded
with a potentiostat BAS-100 B. A three-compartment cell was used
with an Ag/AgCl reference electrode separated from a Pt disk work-
ing electrode and Pt disk auxiliary electrode. Freshly distilled
dichloromethane was used as solvent in these measurements and
Bu4N+ClO4 (TBAP – Fluka Purum) was used as supporting electro-
lyte. Solutions containing 10ꢀ3 mol Lꢀ1 analyte (0.1 mol Lꢀ1 elec-
trolyte) were deoxygenated for 5 min by a vigorous Ar purge. All
E1/2 values were calculated from (Epa + Epc)/2 at a scan rate of
100 mV sꢀ1. Elemental analyses were performed by Microanalytical
Laboratory of Universidade Federal de São Carlos on a FISONS CHNS,
mod. EA-1108. The ESI analyses were done in a Micromass, triple-
quadrupole, ESI/APCI spectrometer utilizing CH2Cl2 as solvent.
(4) Anal. Calc. for C38H36P2N2S2Ru: C, 61.03; H, 4.85; N, 3.75.
Found: C, 61.32; H, 4.63; N, 3.65%. Yield: 16.0 mg (14%). UV–Vis
(CH2Cl2) kmax, nm (log e
, molꢀ1 dm3 cmꢀ1): 324 (4.00), 396 (3.15),
446 (2.69). 31P{1H} NMR (d, ppm): 49.1 (s).
(5) Anal. Calc. (%) for C38H36P2N3O2S2RuPF6: C, 48.60; H, 3.87; N,
4.48. Found: C, 48.30; H, 3.89; N, 4.76%. Yield: 76.0 mg (54%). UV–
2.2. Synthesis
Vis (CH2Cl2) kmax, nm (log e
, molꢀ1 dm3 cmꢀ1): 260 (4.69), 323
(3.85), 424 (2.75). 31P{1H} NMR (d, ppm): 31.4 (s); 35.9 (s). 1H
NMR (CDCl3, d, ppm): 2.32 (dt, J = 11.3; 8.1, 4H, CH2), 2.56–2.47
(m, 2H, CH2), 2.93–2.84 (m, 2H, CH2), 6.51 (ddd, J = 7.5; 5.8; 1.2,
2H, H5-pyS), 6.82 (dt, J = 8.2; 1.0, 2H, H3-pyS), 7.05 (ddt, J = 5.8;
1.4; 1.2, 2H, H4-pyS), 7.11 (dd, J = 8.2; 1.0, 2H, Ph), 7.29–7.38 (m,
4H, Ph), 7.40–7.46 (m, 4H, Ph), 7.70 (ddd, J = 8.2; 7.5; 1.6, 2H,
Ph), 7.75–7.81 (m, 8H, Ph), 8.42–8.45 (m, 2H, H6-pyS). 13C NMR
(CDCl3, d, ppm): 22.7 (CH2), 24.2 (CH2), 26.5 (CH2), 28.5 (CH2),
119.5 and 120.2 (C3-pyS), 125.7-133.4 (Ph), 127.4 and 127.5 (C5-
pyS), 139.6 and 140.3 (C4-pyS), 144.2 and 145.7 (C6-pyS), 173.6
and 178.4 (C2-pyS). ES mass spectrum (CH2Cl2, m/z): 795,
2.2.1. [Ru(pyS)2(c-dppen)] (1)
A solution of 2-mercaptopyridine (0.48 mmol, 54.0 mg) in
methanol (5 mL) with triethylamine (0.96 mmol, 0.13 mL) was
transferred via cannula in a Schlenk flask containing a methanolic
suspension (25 mL) of the fac-[RuCl3(NO)(c-dppen)] (0.16 mmol,
100 mg). The mixture was heated under reflux for 12 h providing
a yellow precipitate that was collected by filtration, washed with
methanol and ether, and dried under vacuum. Same results can
be achieved without refluxing if time reaction within 24 h. Anal.
Calc. for C36H30P2N2S2Ru: C, 60.24; H, 4.21; N, 3.90. Found: C,
60.43; H, 4.42; N, 3.82%. Yield: 62.0 mg (55%). UV–Vis (CH2Cl2)
[MꢀPF6 + H]+. IR (CsI, cmꢀ1):
m
NO = 1858 s,
m
CN = 1590 m; 1585
kmax, nm (log
e
, molꢀ1 dm3 cmꢀ1): 311 (4.13), 390 (3.45), 440
m, mP@O = 1187 m, mCS = 1144 w; 1139 w, mP–C(/) = 1100 m; also
(2.94). 31P{1H} NMR (CDCl3, d, ppm): 78.4 (s). 1H NMR (CDCl3, d,
ppm): 6.28 (dt, J = 8.1; 1.0 Hz, 2H, H3-pyS), 6.44 (ddt, J = 7.3; 5.4;
1.2 Hz, 2H, H5-pyS), 6.95 (ddd, J = 8.1; 7.3; 1.8 Hz, 2H, H4-pyS),
7.00–7.30 (m, 20H, Ph), 7.66 (ddd, J = 59.8; 37.8; 8.2 Hz, 2H,
CH@CH, 1H and 31P coupling), 8.02–8.06 (m, 2H, H6-pyS). 13C
NMR (CDCl3, d, ppm): 115.6 (C3-pyS), 124.9 (C5-pyS), 127.5–
134.5 (Ph), 133.9 (C4-pyS), 147.9 (C6-pyS), 149.9 (CH@CH), 181.7
(C2-pyS). 1H NMR (CD2Cl2, d, ppm): 6.36 (dt, J = 8.1; 1.0 Hz, 2H,
H3-pyS), 6.60 (ddt, J = 7.3; 5.4; 1.2 Hz, 2H, H5-pyS), 7.11 (ddd,
J = 8.1; 7.3; 1.8 Hz, 2H, H4-pyS), 7.13–7.44 (m, 20H, Ph), 7.80
(ddd, J = 59.8; 37.8; 8.2 Hz, 2H, CH@CH, 1H and 31P coupling),
8.15–8,19 (m, 2H, H6-pyS). 1H{31P} NMR (CD2Cl2, d, ppm): 6.36
(dt, J = 8.1; 1.0 Hz, 2H, H3-pyS), 6.60 (ddd, J = 7.3; 5.4; 1.2 Hz, 2H,
H5-pyS), 7.11 (ddd, J = 8.1; 7.3; 1.8 Hz, 2H, H4-pyS), 7.13–7.41
(m, 20H, Ph), 7.79 (s, 2H, CH@CH, no 1H and 31P coupling), 8.17
3105 w, 3058 w, 3018 w, 3012 w, 2931 w, 2904 w, 2890 w, 2869 w,
2829 w, 1557 m, 1487 w, 1445 s, 1437 s, 1429 s, 836 s, 759 s, 740 s,
719 s, 700 s, 690 s, 596 w, 549 s, 518 m, 507 m, 492 m, 425 w,
365 w.
Observation: the characterization data (1H and 13C NMR, IR and
UV–Vis spectroscopies, and elemental analysis) for complexes 2–4
were previously published by Lobana et al. [20] and will not be de-
scribed here again. Our data are in agreement with the previously
reported such a way we will only discuss the data not published,
mainly the 31P{1H} NMR.
2.3. X-ray structural determinations
Suitable crystals of 1 were grown by careful addition of diethyl
ether into dichloromethane solutions at room temperature. Red
crystals of 5 were obtained by cooling the reactional mixture of
(ddd, J = 5.4; 1.8; 1.0, 2H, H6-pyS). IR (CsI, cmꢀ1):
CS = 1135 s, P–C(/) = 1094 m; also 3071 w, 3047 w, 3014 w,
mCN = 1576 m,
ꢀ
m
m
the respective compound in the presence of PF6 anion. The crys-
3002 w, 2923 w, 1544 m, 1480 m, 1436 m, 1419 s, 747 s, 734 m,
tals were mounted on an Enraf-Nonius Kappa-CCD diffractometer
0
697 m, 529 m, 417 w, 377 w.
with graphite monochromated Mo K
a (k = 0.71073 ÅA) radiation.
The final unit cell parameters were based on all reflections. Data
collections were made using the COLLECT program [21]; integration
and scaling of the reflections were performed with the HKL Den-
zo-Scalepack system of programs [22]. Absorption corrections
2.2.2. [Ru(pyS)2(P–P)], P–P = dppe (2), dppp (3)
Same procedure described for 1 utilizing the corresponding pre-
cursor complexes.

282
G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
were carried out using the ‘‘semiempirical” [22] and ‘‘multi-scan”
[23] methods, respectively, for 1 and 5. The structures were solved
by direct methods with SHELXS-97 [24]. The model was refined by
full-matrix least squares on F2 by means of SHELXL-97 [25]. All
hydrogen atoms were stereochemically positioned and refined
with the ridging model. Figs. 1 and 2 were prepared using ORTEP-3
for windows [26]. Hydrogen atoms of the aromatic rings and CH
and CH2 were set isotropic with a thermal parameter 20% greater
Fig. 1. ORTEP view of
D
and
K
-[Ru(pyS)2(c-dppen)] (1) showing the atoms labeling and the 50% probability ellipsoids. Bond Lengths average from
D
and
K
isomers (Å): Ru–
and
N(2) 2.124(3), Ru–N(1) 2.141(4), Ru–P(1) 2.2571(10), Ru–P(2) 2.2603(11), Ru–S(1) 2.4278(11), Ru–S(2) 2.4313(11), C(1)–C(2) 1.322(7). Bond angles average from
D
K
isomers (°): N(2)–Ru–N(1) 85.13(13), N(2)–Ru–P(1) 170.60(9), N(1)–Ru–P(1) 98.15(9), N(2)–Ru–P(2) 93.72(10), N(1)–Ru–P(2) 172.23(9), P(1)–Ru–P(2) 84.20(4), N(2)–Ru–
S(1) 92.32(9), N(1)–Ru–S(1) 67.44(9), P(1)–Ru–S(1) 97.07(4), P(2)–Ru–S(1) 104.97(4), N(2)–Ru–S(2) 67.35(9), N(1)–Ru–S(2) 93.69(10), P(1)–Ru–S(2) 103.55(4), P(2)–Ru–S(2)
92.95(4).
Fig. 2. ORTEP view of [Ru(pyS)2(NO)(dppbO-P)]PF6 (5) showing the atoms labeling and the 50% probability ellipsoids. Bond lengths (Å): Ru–N(1) 1.714(9), Ru–N(21) 2.074(8),
Ru–N(11) 2.140(9), Ru–P(1) 2.383(3), Ru–S(1) 2.407(3), Ru–S(2) 2.418(3), O(1)–N(1) 1.154(10), P(2)–O(241) 1.469(7). Bond angles (°): N(1)–Ru–N(21) 171.3(4), N(1)–Ru–
N(11) 95.7(4), N(21)–Ru–N(11) 86.7(3), N(1)–Ru–P(1) 93.5(3), N(21)–Ru–P(1) 85.5(2), N(11)–Ru–P(1) 166.9(2), N(1)–Ru–S(1) 97.0(4), O(1)–N(1)–Ru 178.5(11), N(21)–Ru–
S(1) 91.6(2), N(11)–Ru–S(1) 68.2(3), P(1)–Ru–S(1) 101.51(11), N(1)–Ru–S(2) 102.9(4), N(21)–Ru–S(2) 68.6(3), N(11)–Ru–S(2) 94.5(3), P(1)–Ru–S(2) 92.49(11), S(1)–Ru–S(2)
154.88(10).

G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
283
Table 1
3. Results and discussion
3.1. Synthesis and structural characterization
Summary of X-ray parameters for the complexes 1 and 5.
1
5
Empirical formula
M
Space group
C36H30N2S2P2RuꢁCH3OH
C38H36N3O2P2S2RuꢁPF6
938.80
Pna21, orthorhombic
Previous studies in our laboratory showed that the products of
the reactions of complexes with general formula mer- or fac-
[RuCl3(NO)(P–P)], P–P = aromatic diphosphines, with the 2-mer-
captopyridine (pySꢀ), are dependent of the P–P ligand [27,28].
For dppm (bis(diphenylphosphine)methane) it was found that
selective oxidation of one phosphorus atom produces a nitrosyl
complex containing a dangling dppmO as ligand, the [Ru(pyS)2
749.79
ꢀ
P1, triclinic
a (Å)
b (Å)
c (Å)
11.5100(3)
12.2800(4)
12.3200(4)
79.087(2)
84.865(2)
87.970(2)
1702.69(9)
2
1.462
293
768
0.710
13.6400(5)
26.2180(5)
11.6330(11)
a
(°)
b (°)
c
(°)
U (Å3)
Z
4160.1(4)
4
1.499
293
1904
0.656
2.43–25.0
(NO)(g
1-dppmO-P)]PF6 [27]. However, with dppe or dppp the
products were identified by spectroscopic techniques (31P NMR,
IR and UV–Vis) and elemental analysis as the thiolate derivatives
[Ru(pyS)2(P–P)], which have previously been reported by Lobana
et al. [20,29]. In the present work the [Ru(pyS)2(P–P)] complexes
were obtained from mer or fac-[RuCl3(NO)(P–P)] precursors
whereas in the previously reported studies the compounds were
obtained from the addition of pySꢀ to cis-[RuCl2(P–P)2] complexes
with one diphosphine displacement (see Scheme 1). In previous
studies we noticed a partial oxidation of the [Ru(pyS)2(P–P)] com-
plexes, P–P = dppe or dppp, when in solution and exposed to air,
producing crystals with formulae [Ru(pySO2)0.33(pyS)1.67(dppe)]
and [Ru(pySO2)0.355(pyS)1.645(dppp)][28], as expected from the
well known sulfur-centered reactivity of transition metal thiolates
with dioxygen to produce sulfur oxygenates [30,31].
Dc (Mg mꢀ3
T (K)
)
F(0 0 0)
l
(mmꢀ1
)
2h limit (°)
h, k, l Ranges
1.69–27.03
ꢀ13 to 13, ꢀ14 to 14, ꢀ14 ꢀ15 to 15, ꢀ30 to 31, ꢀ13
to 14
10 867
to 13
20 059
Reflections
collected
Unique reflections
(Rint
Final R indices
(All data)
6025 (0.0165)
6892 (0.1449)
)
R = 0.0364, R0 = 0.1232
R = 0.0471, R0 = 0.1477
1.300
6025
0.679 and ꢀ1.468
R = 0.0571, R0 = 0.1172
R = 0.1317, R0 = 0.1585
1.201
Goodness-of-fit, S
No. of parameters
Peak and hole
549
0.539 and ꢀ0.842
(e Åꢀ3
)
In order to better explore this difference in reactivity, reactions
of the complexes fac-[RuCl3(NO)(c-dppen)] and mer-[RuCl3
(NO)(dppb)] were carried out with the 2-pySꢀ ligand. In these
reactions it distinct products depending on the P–P ligand were
obtained, the [Ru(pyS)2(c-dppen)] (1) and the [Ru(pyS)2(NO)
than the equivalent isotropic displacement parameter of the atom
to which each one is bonded. The data collections and experimen-
tal details are summarized in Table 1.
Scheme 1. Ruthenium nitrosyl complexes as starting material to prepare bis-mercaptopyridine derivatives.

284
G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
(dppbO-P)]PF6 (5). Interestingly, complex 5 contains a dangling
coordinated dppbO-P (see Scheme 1). Bis-phosphino monoxides
such as dppbO are hemilabile ligands due to the presence of the soft
(P) and hard (O) Lewis base centers on the same molecule [32].
These molecules are very interesting ligands for the preparation of
metal complexes for application in homogeneous catalysis [32].
The structures of 1 and 5 were determined by the X-ray diffrac-
tion method. The ORTEP view showing the atoms labeling and the
50% probability ellipsoids are presented in Figs. 1 and 2, and the
bond lengths and angles selected are described in the caption.
The structures adopt a six-coordinated structure with the thio-
late-sulfur donor atoms of two pyS- ligands occupying trans posi-
tion in relation to each other. In complex 1 the coordination
sphere is completed with a chelating c-dppen diphosphine with
P trans N, therefore there is a N2P2S2 set of donor atoms. Complex
1 crystallized as a racemate with no significative differences in
in such a way that the sulfur atom donates more electronic density
to the ruthenium in 1 and its
* transition is displaced to high-
er energy. It is interesting to mention that the strong bands for
p* transitions of the diphosphines ligands presented in the
nitrosyl precursors (around 260 nm) are absent in these deriva-
tives. The presence of a acceptor ligand trans positioned (N of
p
? p
p
?
p
2-pyS) justifies this observation, since that the competition for
electronic density between the phosphorus and the nitrogen atoms
makes the electronic density around the phosphorus smaller. Ana-
lyzing the spectrum of the nitrosyl derivative 5 we clearly noticed
three absorption bands. The most energetic of them arises around
250 nm and can be attributed to the
phine absorption bands due to the very high
p
?
p* intraligand diphos-
value. Still in the
e
ultraviolet region, a band at 323 nm was observed, similarly to
1–4 complexes, in such a way that it is attributed to the pyridinic
ligand as carried out in the earlier complexes. In the visible region
there is a band at 424 nm which probably arises from a d–d tran-
bond lengths and angles between the two enantiomers
D and K-
[Ru(pyS)2(c-dppen)] (see Fig. 1). In 5 a dangling dppb-O and a
NO molecule, both trans to the N of pyS ligands, complete the coor-
dination sphere. In the structures depicted here distortions from an
ideal octahedral geometry arise from the small bite angles of pySꢀ
(N–Ru–S = 67.34 (7) and 67.66 (7)), respectively, for 1 and 5. The
‘pyS’ ligands in 1 have C–S bond distances of 1.762(10) and
1.765(9) Å, which are significantly longer than the C@S double
bond distance of 1.62 Å, but shorter than a C–S single bond dis-
tance of 1.81 Å [33], suggesting that it has a partially double bound
character [34]. The coordination of 2-pyS promotes some varia-
tions on the ligand dimensions [35]. In the pyridine-2-thionate an-
ion the exocyclic thione (˜C@S) distance is increased from 1.695(2)
to 1.74 and 1.75 Å (av.), respectively, for 1 and 5. The thioamide
distance C–N decreases slightly, from 1.356(3) to 1.33 Å (av.) for
both 1 and 5, as does the N–C–S angle, which decreases from
120.6(1)° to 109.8 and 110.4° (av.), for 1 and 5, respectively. All
the observed changes in the pyS- dimensions are in agreement
sition due to the
trum of complex 5 is very similar to the previously reported
e
value of 500 Mꢀ1 L cmꢀ1. The electronic spec-
analogous [Ru(pyS)2(NO)(g
1-dppmO-P)]PF6 [27].
3.3. Infrared studies
The IR spectra for complexes 1–4 are very similar to each other
and are characterized by the typical vibrational modes of the aro-
matic diphosphines and the 2-pySꢀ ligand [20,41]. For the nitrosyl
complex 5, an intense m
NO band at 1858 cmꢀ1, which is typical of a
nitrosonium ligand bonded linearly to ruthenium, was observed
[42,43]. Since the two coordinated ‘pySꢀ’ ligands are not equiva-
lent, the IR spectrum of the complex shows a larger number of
vibrational modes from this ligand than in the spectrum of the
[Ru(pyS)2(P–P)] species[20]. The presence of a medium intensity
band at 1187 cmꢀ1 is characteristic of
mP@O. This value is similar
to the observed values for other ruthenium complexes containing
an oxidized dangling phosphorus [28,44]. For association purposes,
with the shift of p-electron density to the amide (C–N) portion of
the thioamide group, as well as with the concentration of the neg-
ative charge on the sulfur atom of the anion and with the enhance-
ment of the thionate character of this ligand [15]. The observed
distances related to the ruthenium center in 1 are close to that
encountered for the dppe and dppp analogous [28,36]. The struc-
ture of 5 shows a nearly linear Ru–N–O angle [174.2(7)°] and an
N–O distance of 1.154(10) Å, both indicating a {RuII–NO+} type
complex [27,37], as is also indicated by the IR spectrum. The Ru–
S distances of nearly 2.40 Å are essentially identical to those ob-
served in other complexes containing ‘pySꢀ’ ligands [27,38]. The
Ru–N (pySꢀ ligand) distance of N trans-NO of 2.080(7) Å is slightly
shorter than the N trans-P of 2.142(7) Å, which is probably due the
when the dppbO is bidentate through P and O atoms, the
creases from 1187 to 1120 cmꢀ1 as observed for the complexes
[RuCl2(
2-dppbO)(N–N)], N–N = bipy or phen [45].
mP@O de-
g
3.4. Electrochemical studies
The results of the cyclic voltammetric measurements for the
complexes 1–5 in CH2Cl2 solutions at room temperature are pre-
sented in Table 2. In the case of complexes 1–4 a reversible process
is observed with an E1/2 value in the range of 0.33 to 0.41 V. The ra-
tio between the anodic and cathodic half-wave peak currents is
close to unity, attesting to the reversible character of the oxidation
process. The difference between the values of the anodic and
cathodic peak potentials exceeds the theoretical value of 59 mV
for one-electron process, but such deviations are typical of revers-
ible RuIII/RuII pairs in nonaqueous media. The differences in E1/2
values among complexes 1–4 are related to the ability of electronic
delocalization from the diphosphines, thus the c-dppen, which has
fact that the NO acting as a strong
tance [39].
p-acid reduces the Ru–N dis-
In order to evaluate the NO+ character of the complex 5, a reac-
tion with the azide nucleophile was performed [40]. The 31P NMR
and IR data did not show any difference from that of the precursor
complex indicating that the coordinated NO, in this case, is not suf-
ficiently positive to be susceptible to nucleophilic attacks. The
same was observed for the analogous [Ru(pyS)2(NO)(g1
-
dppmO)]PF6 [27].
Table 2
Cyclic voltammetric and 31P{1H} NMR data for complexes 1–5.
3.2. UV–Vis studies
Complex
E1/2 (V)
D
E (Ea ꢀ Ec) (V)
31P{1H} NMR – d ppm (m)
Electronic spectra of complexes 1–4 are dominated by an in-
tense intraligand (
p* C–S) absorption band. This band occurs
in higher energy than that observed for the free ligand, since the
C@S bond order is lower with the sulfur coordination. The energy
of this band was 311 nm for 1 whereas for 2–4 it was in the range
318–324 nm. This difference reflects the greater electronic delocal-
ization of the c-dppen diphosphine when compared to the others,
1
2
3
4
0.41
0.35
0.33
0.34
ꢀ0.39
0.15
0.15
0.14
0.16
0.14
78.4 (s)
74.0 (s)
42.1 (s)
49.1 (s)
p
?
5
31.4 (s) PV; 35.9 (s) PIII
31.3 (s) PV; ꢀ16.2 (s) PIII
Free dppbO [32]
d, chemical shift, (m), multiplicity, (s), singlet.

G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
285
a double bond at the bridge between P atoms, helps to better sta-
bilize the metal center, increasing its redox potential.
electron acceptor characteristic of the phosphorus and ‘pyS’ ligands
that helps the distribution of electronic density added with the
reduction.
As expected, the nitrosyl complex 5 showed a different behavior
from the complexes 1–4. Complex 5 has a strong p-acceptor ligand
such as NO, which stabilizes the ruthenium (II) oxidation state,
providing an electrochemical process at the NO+ group [46]. The
electrochemical behavior of 5 (see Fig. 3) is similar to that observed
for other nitrosyl complexes described in the literature, with two
successive reduction waves centered at the coordinated nitrosyl
[27,46,47].
3.5. NMR characterization
As shown in Table 2, complexes 1–4 showed one singlet signal
in the 31P{1H} NMR spectra, indicating the magnetic equivalence of
the phosphorus atoms and consequently the trans configuration for
these complexes. Considering the variation of chemical shift, it can
be noticed that the protection order is in agreement with the delta
ring effect in which the five membered chelates (dppe and c-
dppen) are down field shifted, while the six and seven ones show
variable behavior. The c-dppen derivative shows an additional ef-
fect of electronic delocalization (the double bound), making the
phosphorus more deshielded than the dppe one. The same order
has been observed in the series [Pd(S2CNEt2)(P–P)]+ [49], trans-
[RuCl2(P–P)2] [50] and fac-[RuCl3(NO)(P–P)] [17], as ascribed in
the literature.
The first process at ꢀ0.39 V is reversible, corresponding to the
reduction of [Ru(pyS)2(NO)(dppbO-P)]+ to [Ru(pyS)2(NO)(dppbO-
P)]0 and the more cathodic wave (quasi-reversible) at ꢀ1.15 V cor-
responds to the reduction of [Ru(pyS)2-(NO)(dppbO-P)]0 to [Ru(-
pyS)2(NO)(dppbO-P)]ꢀ. A similar behavior was observed for the
[Ru(Cp)(P–P)(NO)]2+ series, P–P = dppe, dppm or dmpe [1,2-
bis(dimethylphosphine)ethane], which present two reversible
waves shifted to more anodic potentials when compared with 5
[48]. After the second reduction wave, a new anodic peak appears
close to 0.90 V. However, no additional study was carried out to
identify such species. The analogous with dppmO showed a very
similar behavior but with the first reversible process slightly dis-
placed to cathodic potential and with no additional waves after
the second reduction. In the utilized experimental condition the
Fc/Fc+ pair is shown at E1/2 = +0.43 V. The reversible one-electron
reduction process centered at the coordinated NO observed for 5
indicates a great stability of the reduced species promoted by the
The nitrosyl derivative 5 presents a different characteristic from
that aforementioned; one of the phosphorus is non-coordinated
and oxidized. Therefore, two singlet signals for this compound
can be observed, as shown in Fig. 4. For the dppm analogous, pre-
viously published, two doublets were observed [27]. Considering
that the coupling between phosphorus in these complexes will
happen just through chemical bonding instead of through d orbi-
tals from metallic center plus chemical bonding contributions, it
is possible to understand the small value of the coupling constant
in 5 and, consequently, the observation of singlet signals instead of
doublets. On the other hand, when the aliphatic group contains
only a CH2 between phosphorus the P–P scalar coupling is ob-
served, as is the case of the [Ru(pyS)2(NO)(dppmO-P)]+ complex
[27]. The more shielded signal is attributed to the oxidized phos-
phorus due to the almost coincidental signals of the complexes
and of the dioxidized free phosphine. There are some examples
of complexes with a chelated dppbO, as the [RuCl2(g
2-dppbO)(bi-
py)] [45], where two singlets appeared at 32.2 and 53.4 ppm,
respectively, corresponding to the PV and PIII oxidations state.
The 1H NMR spectrum of 1 presents an AA‘XX’ system for the
CH@CH protons of the c-dppen ligand. This system caused by cou-
pling between 1H and 31P generates a second-order pattern as
shown in Fig. 5. The multiplicity rules between 31P–1H and
1H–1H are the same, and a coupling constant could be observed
up to four bonds. A similar behavior was observed for the com-
plexes [ReOCl3(c-dppen)] and [ReOCl2(OEt)(c-dppen)] described
in the literature [51], for these cases a simulation was carried out
and a perfect fit was obtained. In our case, a different approach
to study this second-order system was chosen. We performed a
Fig. 3. Cyclic voltammogram of 5 in CH2Cl2 (TBAP – 100 mV sꢀ1).
Fig. 4. 31P{1H} spectrum of 5 in CDCl3 solution at room temperature.

286
G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
Fig. 5. 1H and 1H{31P} NMR spectra of 1 in CD2Cl2 solution at room temperature.
1H{31P} NMR experiment, in such a way that the coupling con-
stants of 1H with 31P were eliminated. The obtained spectrum
shown in Fig. 5 presented a singlet signal instead of the second-or-
der pattern signal for the CH@CH group, indicating the magnetic
equivalence of these protons. The other signals for the c-dppen li-
gand appeared as multiplets in the 7.13–7.41 ppm range. The two
pySꢀ ligands coordinated to ruthenium are equivalent and their
four hydrogens appeared as a deshielded doublet of a doublet of
doublet at 8.17, two others at 7.11 and 6.60 and a doublet of triplet
at 6.36 ppm. These chemical shift values are very similar to those
found for the analogous [Ru(pyS)2(P–P)] previously published [36].
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;
or e-mail: deposit@ccdc.cam.ac.uk
Acknowledgements
We thank FAPESP, CNPq, CAPES and FINEP for financial support.
References
[1] L.J. Ignarro, Nitric Oxide: Biology and Pathobiology, 1st ed., Academic Press,
San Diego, 2000.
[2] M.J. Clarke, Coord. Chem. Rev. 232 (2002) 69–93.
[3] R. Eisenberg, C.D. Meyer, Acc. Chem. Res. 8 (1975) 26–34.
[4] M.J. Clarke, J.B. Gaul, Struct. Bond. 81 (1993) 147–181.
[5] P.G. Zanichelli, A.M. Miotto, H.F.G. Estrela, F.R. Soares, D.M. Grassi-Kassisse,
R.C. Spadari-Bratfisch, E.E. Castellano, F. Roncaroli, A.R. Parise, J.A. Olabe, A. de
Brito, D.W. Franco, J. Inorg. Biochem. 98 (2004) 1921–1932.
[6] E. Tfouni, M. Krieger, B.R. McGarvey, D.W. Franco, Coord. Chem. Rev. 236
(2003) 57–69.
[7] S.P. Fricker, E. Slade, N.A. Powell, O.J. Vaughan, G.R. Henderson, B.A. Murrer, I.L.
Megson, S.K. Bisland, F.W. Flitney, Brit. J. Pharmacol. 122 (1997) 1441–1449.
[8] F. Bottomley, P.S. White, M. Mukaida, K. Shimura, H. Kakihana, J. Chem. Soc.,
Dalton Trans. (1978) 2965–2969.
[9] J.C. Toledo, B.S.L. Neto, D.W. Franco, Coord. Chem. Rev. 249 (2005) 419–431.
[10] G. Von Poelhsitz, A.A. Batista, J. Ellena, E.E. Castellano, E.S. Lang, Inorg. Chem.
Commun. 8 (2005) 805–808.
[11] A. Massey, Y.Z. Xu, P. Karran, Curr. Biol. 11 (2001) 1142–1146.
[12] R. Cini, G. Tamasi, S. Defazio, M. Corsini, P. Zanello, L. Messori, G. Marcon, F.
Piccioli, P. Orioli, Inorg. Chem. 42 (2003) 8038–8052.
4. Conclusions
This work presented a study on the dependence of the product
on the P–P ligand in the reactions of [RuCl3(NO)(P–P)] complexes
(P–P = aromatic diphosphines) with the 2-mercaptopyridine ligand
carried out in the same conditions. When the P–P ligand was c-
dppen, dppe or dppp, the sole product were the corresponding
[Ru(pyS)2(P–P)] complexes. However, with dppm and dppb a dif-
ferent pattern of reactivity was found and the main product was
identified as [Ru(pyS)2(NO)(g
1-P–PO)]PF6. In this sense, it is clear
that the reactivity was controlled by the chain length between
the phosphorus of diphosphines, in such a way that the small bite
angle of the dppm ligand (ꢂ72°) results in a ring strain which is
eased by ready dissociation of one of the P atoms from the Ru cen-
ter in the presence of the ‘pySꢀ’ ligand. For the dppb complex, the
explanation is the big bite angle (>90°) of this ligand, leaving the
phosphorus atoms more susceptible to break its bond with the
Ru center.
[13] C.K. Mirabelli, R.K. Johnson, C.M. Sung, L. Faucette, K. Muirhead, S.T. Crooke,
Cancer Res. 45 (1985) 32–39.
[14] F.B. Nascimento, G. Von Poelhsitz, F.R. Pavan, D.N. Sato, C.Q.F. Leite, H.S.
Selistre-de-Araújo, J. Ellena, E.E. Castellano, V.M. Deflon, A.A. Batista, J. Inorg.
Biochem. 102 (2008) 1783–1789.
[15] E.S. Raper, Coord. Chem. Rev. 153 (1996) 199–255.
[16] P.D. Akrivos, Coord. Chem. Rev. 213 (2001) 181–210.
[17] A.A. Batista, C. Pereira, S.L. Queiroz, L.A.A. de Oliveira, R.H.D. Santos, M.T.D.
Gambardella, Polyhedron 16 (1997) 927–931.
[18] 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) 5341–5345.
[19] 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) 2221–2225.
[20] T.S. Lobana, R. Singh, Polyhedron 14 (1995) 907–912.
[21] Enraf-Nonius, Collect, Nonius BV, Delft, The Netherlands, 1997–2000.
Supplementary data
CCDC 725472 and 725473 contain the supplementary crystallo-
graphic data for 1 and 5, respectively. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12

G. Von Poelhsitz et al. / Polyhedron 29 (2010) 280–287
287
[22] Z. Otwinowski, W. Minor, HKL Denzo and Scalepack, in: C.W. Carter Jr., R.M.
Sweet (Eds.), Methods in Enzymology, vol. 276, Academic Press, New York,
1997, pp. 307–326.
[23] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33–38.
[24] G.M. Sheldrick, SHELXS-97. Program for Crystal Structure Resolution, University
of Göttingen, Göttingen, Germany, 1997.
[25] G.M. Sheldrick, SHELXL-97. Program for Crystal Structures Analysis, University of
Göttingen, Göttingen, Germany, 1997.
[26] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[27] G. Von Poelhsitz, A.A. Batista, E.E. Castellano, J. Ellena, Inorg. Chem. Commun. 9
(2006) 773–776.
[36] T.S. Lobana, R. Verma, R. Singh, A. Castineiras, Trans. Metal Chem. 23 (1998)
25–28.
[37] G.B. Richter-Addo, P. Legzdins, Metal Nitrosyls, Oxford University Press, New
York, 1992.
[38] T.S. Lobana, R. Verma, A. Castineiras, Polyhedron 17 (1998) 3753–3758.
[39] B.J. Coe, S.J. Glenwright, Coord. Chem. Rev. 203 (2000) 5–80.
[40] P.G. Douglas, R.D. Feltham, J. Am. Chem. Soc. 94 (1972) 5254–5258.
[41] R. Martos-Calvente, V.A.D. O’Shea, J.M. Campos-Martin, J.L.G. Fierro, J. Phys.
Chem. A 107 (2003) 7490–7495.
[42] J.H. Enemark, R.D. Feltham, Coord. Chem. Rev. 13 (1974) 339–406.
[43] D.M.P. Mingos, D.J. Sherman, Adv. Inorg. Chem. 34 (1989) 293–377.
[44] M.I. Bruce, B.W. Skelton, A.H. White, N.N. Zaitseva, J. Organometal. Chem. 650
(2002) 141–150.
[28] G. Von Poelhsitz, B.L. Rodrigues, A.A. Batista, Acta Crystallogr., Sect. C 62 (2006)
M424–M427.
[29] E.R.T. Tiekink, T.S. Lobana, R. Singh, J. Crystallogr. Spec. Res. 21 (1991) 205–
208.
[45] P.W. Cyr, S.J. Rettig, B.O. Patrick, B.R. James, Organometallics 21 (2002) 4672–
4679.
[30] J.R. Dilworth, Y.F. Zheng, S.F. Lu, Q.J. Wu, Trans. Metal Chem. 17 (1992) 364–
368.
[46] R.W. Callahan, T.J. Meyer, Inorg. Chem. 16 (1977) 574–581.
[47] R.C.L. Zampieri, G. Von Poelhsitz, A.A. Batista, O.R. Nascimento, J. Ellena, E.E.
Castellano, J. Inorg. Biochem. 92 (2002) 82–88.
[48] L.F. Szczepura, K.J. Takeuchi, Inorg. Chem. 29 (1990) 1772–1777.
[49] G. Exarchos, S.D. Robinson, J.W. Steed, Polyhedron 19 (2000) 1511–1517.
[50] J.C. Briggs, C.A. McAuliffe, G. Dyer, J. Chem. Soc., Dalton Trans. (1984) 423–427.
[51] O. Sigouin, A.L. Beauchamp, Inorg. Chim. Acta 358 (2005) 4489–4496.
[31] C.A. Grapperhaus, M.Y. Darensbourg, Acc. Chem. Res. 31 (1998) 451–459.
[32] V.V. Grushin, Chem. Rev. 104 (2004) 1629–1662.
[33] J.D. Curry, R.J. Jandacek, J. Chem. Soc., Dalton Trans. (1972) 1120–1123.
[34] B.R. Penfold, Acta Crystallogr. 6 (1953) 707–713.
[35] M.M. Muir, S.I. Cuadrado, J.A. Muir, Acta Crystallogr., Sect. C 45 (1989) 1420–
1422.