Synthesis, characterization and reactivity of halides/pseudohalides and their complexes containing ruthenium II in the hydrogenation of cyclohexene

Article abstract of DOI:10.1016/j.poly.2017.08.013

In this paper, the influence of pseudohalide ligands coordinated to the ruthenium center on the hydrogenation of cyclohexene was investigated. The pseudohalide complexes containing ruthenium were synthesized from the cis-[RuCl₂(dppb)(N-N)] {whe

Full text of DOI:10.1016/j.poly.2017.08.013

Accepted Manuscript
Synthesis, Characterization and Reactivity of Halides/Pseudohalides and their
Complexes Containing Ruthenium II in the Hydrogenation of Cyclohexene
Murillo C. Ribeiro, Rodrigo S. Corrêa, Marília I.F. Barbosa, Javier Ellena,
André L. Bogado, Alzir A. Batista
PII:
S0277-5387(17)30544-2
DOI:
http://dx.doi.org/10.1016/j.poly.2017.08.013
POLY 12777
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
10 June 2017
1 August 2017
17 August 2017
Please cite this article as: M.C. Ribeiro, R.S. Corrêa, M.I.F. Barbosa, J. Ellena, A.L. Bogado, A.A. Batista, Synthesis,
Characterization and Reactivity of Halides/Pseudohalides and their Complexes Containing Ruthenium II in the
Hydrogenation of Cyclohexene, Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.2017.08.013
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Synthesis, Characterization and Reactivity of Halides/Pseudohalides and their
Complexes Containing Ruthenium II in the Hydrogenation of Cyclohexene
a
b
♯a
c
Murillo C. Ribeiro , Rodrigo S. Corrêa , Marília I. F. Barbosa , Javier Ellena , André
d
a
L. Bogado and Alzir A. Batista
a
Departamento de Química, Universidade Federal de São Carlos, Cx. Postal 676, CEP
3565-905, São Carlos – SP, Brazil
1
b
Departamento de Química, ICEB, Universidade Federal de Ouro Preto, CEP 35400-
00, Ouro Preto - MG, Brazil
0
c
Instituto de Física de São Carlos-USP, Cx. Postal 780, CEP 13560-970, São Carlos –
SP, Brazil
d
Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia,
Rua vinte, 1600, CEP 38304-402 Ituiutaba, MG, Brazil
Corresponding author: daab@ufscar.br (A.A. Batista), or bogado@ufu.br (A.L.
Bogado)
Present address:
♯
Instituto de Química, Universidade Federal de Alfenas, CEP 37130000, Alfenas -
MG. Brazil
1

Abstract
In this paper, the influence of pseudohalide ligands coordinated to the ruthenium
center on the hydrogenation of cyclohexene was investigated. The pseudohalide
complexes containing ruthenium were synthesized from the cis-[RuCl (dppb)(N-N))]
where N-N = 2,2′-bipyridine (bipy) (1A), 4,4′-dimethyl-2,2′-bipyridine (Me-bipy) (2),
or 4,4′-dimethoxy-2,2′-bipyridine (MeO-bipy) (3), dppb 1,4-
bis(diphenylphosphino)butane,} by chloride exchange to provide complexes with
2
{
=
−
−
general formula cis-[RuL
2
(dppb)(N-N)] {where L
2
= N
3
(4), (7) and (9) CN (5), (8)
−
and (10) or SCN (6) and (11)}. All complexes were characterized using spectroscopic,
electrochemical techniques, as well as elemental analyses to check their molecular
formulation and purity. Furthermore, crystal structure of the complexes cis-
[
(
Ru(N
3
)
2
(dppb)(bipy)] (4), cis-[Ru(CN)
2
(dppb)(bipy)] (5), cis-[Ru(SCN)
2
(dppb)(bipy)]
6), cis-[Ru(CN)
2
(dppb)(Me-bipy)] (8), and cis-[Ru(SCN)
2
(dppb)(MeO-bipy)] (11)
were determined by single-crystal X-ray diffraction, as well as the X-ray structure of the
solvate complex [RuCl(CH CN)(dppb)(bipy)](PF ) (1B). Dichloride and pseudohalide
complexes containing ruthenium were applied as pre-catalysts in the hydrogenation of
cyclohexene, after pre-established conditions using the cis-[RuCl (dppb)(bipy)] (1A) as
a target complex. The quantitative conversion of cyclohexene to cyclohexane was
obtained in 5h at 25 °C using 0.1 mol % of (1A) in methanol solution at 15 atm H . The
3
6
2
2
substituted bipy derivatives (2) and (3) were also effective pre-catalysts, but
pseudohalides were not under these conditions.
Keywords: Ruthenium complexes, pseudohalide, solvate complexes, hydrogenation of
cyclohexene, molecular structure.
2

1
. Introduction
The hydrogenation of simple or prochiral alkenes is a vital area of research, and
ruthenium catalysts have figured prominently in this area. The Wilkinson’s catalyst
RhCl(PPh ] is the best-known complex that activates the H molecule by oxidative
addition [1,2]. The [RuCl(dppb) (µ-Cl)] complex catalyzes the hydrogenation of
styrene [3], the transfer hydrogenation of acetophenone (from propan-2-ol) [4] and H
hydrogenation of imines [5]. The first reported “Ru(P-P)” enantioselective catalyst in
the hydrogenation of prochiral olefins was the [{RuCl(P-P)} -µ-(Cl) ] (P-P = chiraphos,
diop and binap) species [5]. Afterwards, many “Ru(P-P)” moieties containing
[
3
)
3
2
2
2
2
-
2
2
complexes {where P-P = chiral or non-chiral bisphosphine}, such as [Ru
2
Cl
4
(P-
+
+
P)
2
(NEt
8–10], [Ru(P-P)(π-allyl)
X = halogen) [5,6] and [RuX(P-P)]
3
)] [6], [Ru(OAc)
2
(binap)] [6,7], [RuCl(arene)(P-P)] [7], [RuH(P-P)(solvent)
3
]
[
(
2
] [11–13], [RuCl
2
(RCN)
2
(P-P)] [5,14], [RuX(P-P)]
2
-µ-(X) ]
2
2
(µ-X)
3
] [6,15] were used as catalysts in the
hydrogenation of functionalized olefins, dienes, and ketones [2,16] and certain prochiral
imines [17].
We reported that ruthenium (II) species are useful complexes as precursors in
the hydrogenation of apolar double bonds [18], transfer hydrogenation of polar double
bonds [19–21], hydroformylation – hydrogenation, hydroformylation – acetalization
[
22] and oxidation of alkenes [23,24].
Our group has been studying the various application of cis-[RuCl
1A) [25], which can be mentioned as an agent with cytotoxic activities [26,27], as an
2
(dppb)(bipy)]
(
aggregator agent to produce supramolecular species with gold nanoparticles [28–30], as
a sensor for electrochemical devices [28,29], as a precursor to prepare polymetallic
macrocylics [24], and as a precursor to synthesize vinylidene complexes with
photochemical and photophysical properties [31].
3

Thus, the objective of this study is to optimize the catalytic hydrogenation of
cyclohexene by varying bipyridine (bipy) derivatives, replacing the chloride for
pseudohalides, evaluating the dependence of the solvent and the pressure in the process.
Suitable crystals of cis-[Ru(N
3
)
2
(dppb)(bipy)](4), cis-[Ru(CN)
cis-[Ru(CN) (dppb)(Me-bipy)](8)
(dppb)(MeO-bipy)](11) were obtained and the X-ray structures are presented
CN)(dppb)(bipy)](PF )
2
(dppb)(bipy)](5), cis-
[
[
Ru(SCN)
Ru(SCN)
2
2
(dppb)(bipy)](6),
2
and cis-
here. The X-ray structure of the solvate complex [RuCl(CH
1B) was also determined and is presented in the same way.
3
6
(
2. Experimental
2.1. Reagents
All reactions were carried out under argon atmosphere using standard Schlenk
techniques. RuCl xH O, triphenylphosphine (PPh ), 1,4-bis(diphenylphosphino)butane
dppb), 2,2′-bipyridine (bipy), 4,4′-dimethyl-2,2′-bipyridine (Me-bipy), 4,4′-dimethoxy-
3
2
3
(
3
2,2′-bipyridine (MeO-bipy), sodium azide (NaN ), potassium cyanide (KCN),
potassium thiocyanate (KSCN) were purchased from Sigma – Aldrich and used as
received. Reagent grade solvents were distilled prior to use. The cis-
[
RuCl
2
(dppb)(bipy)] (1A), cis-[RuCl
2
2
(dppb)(Me-bipy)] (2) and cis-[RuCl (dppb)(MeO-
bipy)] (3) were prepared as described previously [25].
2
.2. Instrumentation
The NMR spectra of the compounds were performed at Federal University of São
Carlos, São Carlos (SP). They were acquired using a Bruker DRX-400 spectrometer
3
1
1
(
9.4 T) equipped with a 5 mm inverse probe head. Samples for P{ H} experiments
4

were prepared under inert atmosphere and measured at room temperature, with
methylene chloride (CH Cl ) as a solvent and a D O capillary. Chemical shifts were
reported regarding to the phosphorus signal in 85% phosphoric acid (H PO ).
2
2
2
3
4
The microanalyses were performed at the Federal University of São Carlos, São
Carlos (SP), using a FISONS CHNS-O, mod. EA 1108 Element analyzer.
The FTIR spectra of the powder complexes were recorded from KBr pellets in the
−1
4
000 – 200 cm range, in a Bomen − Michelson FT MB – 102 instrument.
The UV/Vis spectra of the complexes, in dichloromethane solution, concentration of
−3
−1
1
× 10 mol L , were recorded using a Hewlett Packard diode array − 8452 A.
Cyclic voltammetry (CV) experiments of the complexes, in solution, were
conducted in an electrochemical analyzer BAS model 100B Instrument. These
experiments were carried out at room temperature in CH Cl or in acetonitrile
(TBAP) (Fluka Purum) as a support electrolyte
using a one-compartment cell, where the working and auxiliary electrodes were
2
2
−1
containing 0.10 mol L Bu
4
NClO
4
−1
stationary Pt foils, and the reference electrode was Ag/AgCl, 0.10 mol L TBAP in
+
CH
2
Cl
2
. Under these conditions, ferrocene was oxidized at 0.43 V (Fc /Fc).
Gas chromatography analyses were run on a Shimadzu GC-17A instrument using an
Agilent HP-5 column (30 m, 0.32 mm diam., 0.25 µm film); carrier gas; N , flow rate;
2
−1
−2
−1
0
.9 mL min and hexadecane as an internal standard (1.0 × 10 mol L ).
2.3. X-ray diffraction data
Crystals of cis-[Ru(N
Ru(SCN) (dppb)(bipy)](6)
dichloromethane/diethyl ether solution. Meanwhile, crystals of cis-[Ru(CN)
3
)
2
(dppb)(bipy)](4), cis-[Ru(CN)
2
(dppb)(bipy)](5) and cis-
[
2
were grown by slow
evaporation of a
2
(dppb)(Me-
5

bipy)](8) and cis-[Ru(SCN) (dppb)(MeO-bipy)](11) were obtained from slow
2
evaporation of a dichloromethane/methanol solution containing one drop of water. The
crystals were mounted on an Enraf-Nonius Kappa-CCD diffractometer with graphite-
monochromated MoKα (λ = 0.71073 Å) radiation. The final unit-cell parameters were
based on all reflections. Data were collected using the COLLECT program [32]
integration and scaling of the reflections were performed with the HKL DENZO-
SCALEPACK software package [33]. Absorption corrections were carried out using the
Gaussian method [34]. The structures were determined by direct methods with
SHELXS-97 [35]. The model was refined by full-matrix least squares on F2 by means
of SHELXL-97 [36]. All hydrogen atoms were stereochemically positioned and refined
with a riding model. The figures were prepared with ORTEP-3 for Windows [37].
Hydrogen atoms on the aromatic rings were refined isotropically, each one with a
thermal parameter 20% greater than the equivalent isotropic displacement parameter of
the atom to which it was bonded. The data collection and experimental details are
summarized in Table 1S – 5S (see supplementary data), and the selected bond distances
and angles are given in Table 1.
In the crystal structure of (1B), a methanol molecule exhibited high thermal
motions and disorder on the solvation sphere of the complex. The disordered solvent
was subtracted from the overall diffraction data following a well-established method
called SQUEEZE [38], which showed a total solvent accessible area volume of c.a. 598
3
−
Å . SQUEEZE calculations indicated the presence of 18e per unit cell, which may be
attributed to one molecule of methanol present in each unit cell. The structure of (1B) is
also octahedrally distorted, as observed by the bond angles (see supplementary data),
which deviate from the ideal value (90°) in a monoclinic crystal system and P2
1
/n space
group (Table 6S).
6

2
.4. Preparation of ruthenium (II) complexes
RuCl(CH CN)(dppb)(bipy)](PF (1B): It was synthesized from the cis-
RuCl (dppb)(bipy)] (1A) [25] (80.0 mg, 0.10 mmol) in CH Cl (5 mL) with an excess
PF (0.025 mg, 0.16 mmol) was added to the
[
3
6
)
[
2
2
2
of acetonitrile (31.3 µL, 0.60 mmol). NH
4
6
ruthenium solution and then stirred for 24 h under an argon atmosphere. The volume
was reduced to approximately 2 mL and diethyl ether (15 mL) was added to precipitate
the product, which was filtered off and washed with water (2 x 10 mL) and diethyl ether
(
2 x 5 mL). Yield 81.5 mg of a yellow powder (90%). Crystals suitable for determining
the X-ray structure of the complex were produced from the CH Cl /Et O solution, by
slow evaporation. Anal. Calc. for C40 ClF Ru: exp. (cal.): C, 53.29 (53.07); H,
.50 (4.34); N, 4.75 (4.64). Molar conductivity (CH
2
2
2
H
39
N
3
6 3
P
−3
−1
−2
4
2
Cl
2
, 1.0 × 10 mol L ) Λ
m
(S cm
−1
-1
−1
III
II
mol ) 48.2. Cyclic voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 1.40. IR
−
1
31
1
(
(
(
cm ): (νCN) 2240 (s); (νP-F) 557 (s). P{ H} NMR (162 MHz, CD
3
CO, 298 K): δ
2
−5
−1
ppm) 40.7 (d) and 34.2 (d) JPP = 27.1 Hz. UV/Vis (CH
2
Cl
2
, 2.5 ×10 mol L ): λ/nm
−1
−1
4
3
ε/ mol L cm ) 290 (2.2 × 10 ); 415 (3.9 × 10 ).
−
−
−
2 3
cis-[Ru(L) (dppb)(N-N)], L = N , CN or SCN , N-N = bipy, Me-bipy or MeO-bipy
A typical experiment to prepare the pseudohalide complexes containing
ruthenium II (4) – (11), with general formula cis-[Ru(L) (dppb)(N-N)] is described as
follows for cis-[Ru(N (dppb)(bipy)](4): the precursor cis-[RuCl (dppb)(bipy)] (1A)
25] (42.0 mg, 0.055 mmol) was dissolved in the presence of NaN (11.0 mg, 0.165
mmol) in a mixture of CH Cl /methanol (1:1). The reaction mixture was stirred under
2
3
)
2
2
[
3
2
2
Ar atmosphere for 24 h. The final red solution was concentrated to ca. 5 mL and 10 mL
of diethyl ether was added to obtain a dark red precipitate, which was filtered off,
washed with water and dried under vacuum. Yield 40 mg of a red powder (96 %). Anal.
Calc. for C38
H
36
N
8
P
2
Ru.CH
3
OH: exp. (cal.): C, 58.91 (58.57); H, 4.89 (5.04); N, 14.40
7

−3
−1
−1
(
14.01). Molar conductivity (CH
2
Cl
2
, 1.0 × 10 mol L ) Λ
m
(µS cm ) 2.25. Cyclic
-1
−1
III
II
−1
voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 0.55. IR (cm ): (νasNNN
)
31
1
2
040 (s); (νsNNN) 1436 (w); (δ-NNN) 693 (w); (νRu-NNN) 431 / 409 (w). P{ H} NMR (162
2
MHz, CDCl
3
, 298 K): δ (ppm) 38.7 (d) and 38.1 (d) JPP = 32.8 Hz. UV/Vis (CH
2
Cl
2
,
−5
−1
−1
−1
4
3
3
1
0 mol L ): λ/nm (ε/ mol L cm ) 308 (1.8 × 10 ); 338 (5.0 × 10 ); 469 (2.3 × 10 ).
cis-[Ru(CN) (dppb)(bipy)] (5): KCN (10.0 mg, 0,165 mmol) and cis-
2
[
(
(
RuCl
94%). Anal. Calc. C40
7.61). Molar conductivity (CH
2
(dppb)(bipy)] (1A) [25](42.0 mg, 0.055 mmol). Yield 38 mg of a yellow powder
H
36
N
4
P
2
Ru
,
exp. (cal.); C, 65.20 (65.30); H, 4.75 (4.93); N, 7.31
−3
−1
−1
2
Cl
2
, 1.0 × 10 mol L ) Λ
m
(µS cm ) 2.25. Cyclic
-
1
−1
III
II
−1
voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 1.16. IR (cm ): (νCN
)
3
1
1
2
091/2072 (s); (νRu-CN) 427/416 (w); (νRu-P) 502 (m); ν(Ru-N) 455 (w). P{ H} NMR (162
2
MHz, CDCl
3
, 298 K): δ (ppm) 45.8 (d) and 25.2 (d) JPP = 23.4Hz. UV/Vis (CH
2
Cl
2
,
−5
−1
−1
−1
4
3
10
mol L ): λ/nm (ε/ mol L cm ) 303 (2,0 × 10 ); 412 (4.2 × 10 ).
cis-[Ru(SCN)
2
(dppb)(bipy)] (6): KSCN (16.0 mg, 0,165 mmol) and cis-
(dppb)(bipy)] (1A) [25] (42.0 mg, 0.055 mmol). Yield 41 mg of a yellow powder
94%). Anal. Calc. C40 RuS exp. (cal.); C, 60.27 (60.06); H, 4.67 (4.53); N,
.73 (7.00); S, 8.21 (7.67). Molar conductivity (CH
[
(
RuCl
2
H
36
N
4
P
2
2
−3
−1
6
2
Cl
2 m
, 1.0 × 10 mol L ) Λ (µS
−1
−1
cm ) 2.46. IR (cm ): (νCN) 2113/2103 (s); (νCS) 762/740 (w); (δNCS) 431. Cyclic
-
1
−1
III
II
31
1
voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 0,73. P{ H} NMR (162
2
−5
MHz, CDCl , 298 K): δ (ppm) 40.4 (d) and 35.9 (d) JPP = 32 Hz. UV/Vis (CH Cl , 10
3
2 2
−1
−1
−1
4
3
3
mol L ): λ/nm (ε/ mol L cm ) 307 (2.2 × 10 ); 447 (3.9 × 10 ); 492 (2.4 × 10 ).
cis-[Ru(N
3
)
2
(dppb)(Me-bipy)] (7): NaN
3
(11.0 mg, 0,165 mmol) and cis-
[
(
RuCl
2
(dppb)(Me-bipy)] (2) [25] (43.0 mg, 0.055 mmol). Yield 42 mg of a red powder
96%). Anal. Calc. C40
H
40
N
8
P
2
Ru: exp. (cal.); C, 59.89 (60.37); H, 5.05 (5.07); N,
8

−3
−1
−1
1
4.12 (14.08). Molar conductivity (CH
2
Cl
2
, 1.0 × 10 mol L ) Λ (µS cm ) 2.46. IR
m
−1
(
cm ): (νasNNN) 2037 (s); (νsNNN) 1431 (w); (δNNN) 696 (w); (νRu-NNN) 435/412 (w).
-1
−1
III
II
31
1
Cyclic voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 0.46. P{ H} NMR
2
(
(
(
162 MHz, CDCl
3
, 298 K): δ (ppm) 38.7 (d) and 37.2 (d) JPP = 32 Hz. UV/Vis
−5
−1
−1
−1
4
3
CH
2
Cl
2
, 10 mol L ): λ/nm (ε/ mol L cm ) 307 (2.1 × 10 ); 338 (9.8 × 10 ); 457
3
5.0 × 10 ).
cis-[Ru(CN)
RuCl (dppb)(Me-bipy)] (2) [25] (45.0 mg, 0.055 mmol). Yield 39 mg of a yellow
powder (94%). Anal. Calc. C42 Ru: exp. (cal.); C, 66.09 (66.04); H, 5.12 (5.27);
N, 7.21 (7.33). Molar conductivity (CH
2
(dppb)(Me-bipy)] (8): KCN (10.0 mg, 0,165 mmol) and cis-
[
2
40 4 2
H N P
−3
−1
−1
2
Cl
2
, 1.0 × 10 mol L ) Λ
m
(µS cm ) 2.46.
-1
−1
III
II
−1
Cyclic voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 1.40. IR (cm ): (νCN
)
3
1
1
2
091/2066 (s); (νRu-CN) 427/408 (w); (νRu-P) 495 (m); ν(Ru-N) 444 (w). P{ H} NMR (162
2
−5
MHz, CDCl
3
, 298 K): δ (ppm) 46 (d) and 25.9 (d) JPP = 24 Hz. UV/Vis (CH
2
Cl , 10
2
−1
−1
−1
4
3
mol L ): λ/nm (ε/ mol L cm ) 303 (2,0 × 10 ); 407 (4.4 × 10 ).
cis-[Ru(N
RuCl (dppb)(MeO-bipy)] (3) [25] (45.0 mg, 0.055 mmol). Yield 44 mg of a red
powder (94%). Anal. Calc. C40 Ru: exp. (cal.); C, 58.12 (58.04); H, 4.94
3
)
2
(dppb)(MeO-bipy)] (9): NaN
3
(11.0 mg, 0,165 mmol) and cis-
[
2
H
40
N
8
O
P
2 2
−3
−1
−1
(
4.87); N, 13.63 (13.54). Molar conductivity (CH
2
Cl
2
, 1.0 × 10 mol L ) Λ (µS cm )
m
−1
1
.96. IR (cm ): (νasNNN) 2038 (s); (νsNNN) 1434/1414; (δNNN) 710 (w); (νRu-NNN) 415/438
-
1
−1
III
II
31
1
(
w). Cyclic voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 0.46. P{ H}
2
NMR (162 MHz, CDCl
3
, 298 K): δ (ppm) 40.8 (d) and 37.8 (d) JPP = 32 Hz. UV/Vis
−5
−1
−1
−1
4
3
(
(
CH
2
Cl
2
, 10 mol L ): λ/nm (ε/ mol L cm ) 302 (2.1 × 10 ); 332 (9.4 × 10 ); 435
3
5.0 × 10 ).
9

cis-[Ru(CN)
RuCl (dppb)(MeO-bipy)] (3) [25] (43.0 mg, 0.055 mmol). Yield 41 mg of a yellow
powder (94%). Anal. Calc. C42 Ru: exp. (cal.); C, 63.29 (63.38); H, 5.12
2
(dppb)(MeO-bipy)] (10): KCN (10.0 mg, 0,165 mmol) and cis-
[
2
H
40
N
4
O
P
2 2
−3
−1
−1
(
5.07); N, 6.98 (7.04). Molar conductivity (CH
2
Cl
2 m
, 1.0 × 10 mol L ) Λ (µS cm )
−1
1
.96. IR (cm ): (νCN) 2097 (s); (νRu-CN) 424/415 (w); (νRu-P) 494 (m); (νRu-N) 449 (w).
-1
−1
III
II
31
1
Cyclic voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 1.34. P{ H} NMR
2
(
(
(
162 MHz, CDCl
3
, 298 K): δ (ppm) 46.0 (d) and 25.6 (d) JPP = 23.9 Hz. UV/Vis
−5
−1
−1
−1
4
3
CH
2
Cl
2
, 10 mol L ): λ/nm (ε/ mol L cm ) 302 (2.1 × 10 ); 332 (9.4 × 10 ); 435
3
5.0 × 10 ).
cis-[Ru(SCN)
RuCl (dppb)(MeO-bipy)] (3) [25] (42.0 mg, 0.055 mmol). Yield 41 mg of a yellow
powder (94%). Anal. Calc. C42 RuS :exp. (cal.); C, 58.41 (58.66); H, 4.75
4.69); N, 6.31 (6.51); S, 8.01 (7.30). Molar conductivity (CH
2
(dppb)(MeO-bipy)] (11): KSCN (16.0 mg, 0,165 mmol) and cis-
[
2
H
40
N
4
O
2
P
2
2
−3
−1
(
2
Cl
2
, 1.0 × 10 mol L )
−1
−1
Λ
m
(µS cm ) 1.96. IR (cm ): (νCN) 2112/2106 (s); (νCS) 700/689 (w); (δNCS) 435.
-1
−1
III
II
31
1
Cyclic voltammetry (CH
3
CN, TBAP 10 mol L ): V (Ru /Ru ): 0,89. P{ H} NMR
2
(
162 MHz, CDCl
3
, 298 K): δ (ppm) 43 (d) and 36.5(d) JPP = 31.8 Hz. UV/Vis (CH
2
Cl
2
,
−5
−1
−1
−1
4
3
3
10
mol L ): λ/nm (ε/ mol L cm ) 307 (2.3 × 10 ); 446 (4.0 × 10 ); 487 (2.5 × 10 ).
2.5. Hydrogenation of cyclohexene
Hydrogenation reactions were carried out in a stainless-steel autoclave Paar –
3
Model 4842 with a volume capacity of 100 cm equipped with an overhead magnetic
stirrer, a digital pressure indicator and a thermocouple to record temperature. The
autoclave was equipped with an electrical heating/cooling system to control the
temperature inside the vessel. In a typical reaction, the catalyst precursor (ruthenium
−3
complexes from (1) to (11), (7.0 × 10 mmol) was dissolved in 20 mL of the
appropriate solvent (isopropanol, methanol, ethanol, dimethylsulphoxide,
1
0

dichloromethane, acetonitrile or acetone) inside the autoclave in the presence of
cyclohexene (7.0 mmol) under Ar atmosphere. After that, the autoclave was flushed out
threefold with molecular hydrogen (H
2
), then the autoclave was pressurized with H
2
(
within 1 to 20 atm) and heated to a temperature of 25 – 80 °C, for 1 – 24 h. After the
reaction, the homogeneous reaction mixture was cooled down in an ice bath to room
temperature and the upper organic layer was analyzed by gas chromatography (GC-
−2
−1
FID). Hexadecane (1.0 × 10 mol L ) was used as an internal standard.
3. Results and discussion
3.1. Characterization of ruthenium complexes
−
−
2 3
The Ruthenium complexes cis-[Ru(L) (dppb)(N-N)] {where L = N , CN and
−
SCN , N-N = bipy, Me-bipy and MeO-bipy} were prepared by chloride exchange on
2 2 2
the cis-[RuCl (dppb)(N-N)] complexes in a mixture of CH Cl :MeOH (1:1) (see
Scheme 1). These compounds were characterized by spectroscopic and electrochemical
techniques, by elemental analyses, as well as by molar conductance. Moreover, they are
compatible with expectations for (4) - (11) complexes, suggesting the presence of
neutral compounds.
1
1

Scheme 1: General structure and numerical label of the ruthenium complexes [39].
The solvate complex [RuCl(CH
presence of an excess of CH CN in CH
1A). The X-ray structure of (1B) was determined and its structure is depicted in Fig. 1.
3
CN)(dppb)(bipy)]PF
6
(1B) was formed in
3
2
Cl solution of the cis-[RuCl
2
2
(dppb)(bipy)]
(
The structure is octahedral distorted, with the acetonitrile trans to N atom from the bipy
ligand. Additionally, the starting complex (1A) can provide a solvate complex in the
presence of methanol, but in this case the methanol molecule coordinates in the trans
position to phosphorus P atom of the dppb ligand. The X-ray structure of the complex
[
RuCl(CH
3
OH)(dppb)(bipy)](PF ) (1C) was determined in an octahedral distorted
6
1
2

environment such as previously published [30]. Crystal data and structure refinement
parameters for complex (1B) can be found in the supplementary material (Table 6S).
The crystals structures of complexes (4), (5), (6), (8) and (11) determined from
single-crystal X-ray diffraction are also shown in Fig. 1. Different from the case to
−
obtain (1B) and (1C), the two Cl ligands present in the precursor (1A) were exchanged
for two pseudohalides and the cis configuration was maintained in all complexes.
Selected bond lengths and angles are listed in Table 1. Crystal data and structure
refinement of complexes (4), (5), (6), (8) and (11) are described in the supplementary
material (Tables 1S – 5S).
The structures are octahedral distorted, as observed by the bond angles, which
deviate from the ideal value (90°), mainly in the Nbipy–Ru–Nbipy angle forming a five-
membered chelating ring. The Ru–P distances trans to pseudohalides are 2.2907(9),
2.4012(8), 2.3321(9), 2.3930(15) and 2.3234(9) Å for the complexes (4), (5), (6), (8)
and (11), respectively. These values are larger than those observed for the Ru–P bond
−
trans to Cl ligand in cis-[RuCl
2
(dppb)(bipy)] complex (2.279(3) A˚) [25]. Similarly,
the Ru–N (bipyridine) bond length for the ruthenium dichloride complex is shorter than
those observed for the five complexes reported here. These data are consistent with the
−
substitution of Cl ligand, a good σ and π donor by an π-acceptor ligand and can be
explained by the backbonding interaction involving the pseudohalide ligand and Ru (II),
as suggested by Brito et al [40].
1
3

Table 1: Selected bond lengths and angles of the crystal structures of the complexes (4),
5), (6), (8) and (11).
(
Complex
(5)
Bond lengths (Å)
P-Ru trans L
P-Ru trans bipy
(4)
(6)
(8)
(11)
2.2907(9)
2.3151(8)
2.085(2)
2.3151(8)
2.173(3)
2.111(3)
2.4006(8)
2.3321(9)
2.3930(15) 2.3234 (9)
2.2993(9)
2.171(2)
2.132(3)
2.030(3)
1.986(3)
2.3462(10) 2.2951(13) 2.3216(11)
N
bipy-Ru trans L
2.106(2)
2.121(3)
2.110(3)
2.070(3)
2.178(4)
2.133(4)
2.040(6)
1.987(6)
2.118 (2)
2.132(2)
2.102 (2)
2.048(3)
N
bipy-Ru trans P
L-Ru trans P
L-Ru trans Nbipy
N(1)-N(2)
N(2)-N(3)
N(4)-N(5)
N(5)-N(6)
N(1)-C(1)
N(2)-C(2)
S(1)-C(1)
S(2)-C(2)
1.182(3)
1.162(4)
1.182(4)
1.162(4)
1.156(4)
1.152(4)
1.144(4)
1.138(4)
1.626(3)
1.633(4)
1.15(1)
1.154(8)
1.150 (3)
1.159(4)
1.631(3)
1.619(4)
Bond angles (º)
P-Ru-P
94.20(3)
77.89(9)
87.95(10)
93.00(3)
76.10(10)
92.11(12)
94.33(3)
76.93(11)
91.56(10)
93.43(5)
75.81(16)
91.6(2)
94.42(3)
76.78 (9)
95.16(10)
N
bipy-Ru-Nbipy
L-Ru-L
Ru(1)-N(1)-N(2) 123.5(2)
Ru(1)-N(4)-(5)
Ru(1)-C(1)-N(1)
Ru(1)-C(2)-N(2)
Ru(1)-N(1)-C(1)
Ru(1)-N(2)-C(2)
N(1)-C(1)-S(1)
N(2)-C(2)-S(2)
L = pseudohalide N
133.9(2)
174.8(3)
175.9(3)
175.9(6)
172.9(6)
165.5(3)
162.7(3)
178.5(3)
178.6(3)
164.9(2)
160.4(3)
179.2(3)
176.6(3)
−
−
−
3
, CN or SCN . (4) = cis-[Ru(N
3
)
2
(dppb)(bipy)], (5) = cis-[Ru(CN)
cis-[Ru(CN) (dppb)(Mebipy)], (11)
2
(dppb)(bipy)],
cis-
(6)
=
cis-[Ru(SCN)
2
(dppb)(bipy)], (8)
=
2
=
[
Ru(SCN)
2
(dppb)(MeObipy)].
1
4

(
4)
(5)
(8)
(
6)
(
11)
(1B)
Fig. 1: ORTEP [37] view of the crystal structures showing main atoms labeling and
0% of probability ellipsoids. cis-[Ru(N (dppb)(bipy)] (4) cis-[Ru(CN) (dppb)(bipy)]
5) cis-[Ru(SCN) (dppb)(bipy)] (6) cis-[Ru(CN) (dppb)(Mebipy)] (8) cis-
Ru(SCN) (dppb)(MeObipy)] (11), and [RuCl(CH CN)(dppb)(bipy)] (1B).
3
3
)
2
2
(
[
2
2
+
2
3
1
5

As depicted in Table 1, the 4-substituted position in the bipyridine rings with the
methyl or methoxy group does not have an effective electronic influence on the Ru−L
−
−
−
bond length {L = pseudohalide N
3
, CN or SCN }. A bond length of 1.98 Å was
−
observed for the Ru−CN bond in complex (5), which has a CN group trans to the
−
nitrogen of the bipy ligand, while complex (8) has a CN group trans to the nitrogen of
the Me-bipy ligand. Similar behavior was detected for complexes (6) and (11), where
−
the Ru−NCS bond lengths of 2.070(3) and 2.048(3), were observed respectively.
Two different angles were observed in the Ru-N bonds in the crystal structure
3
of the complex (4), where the angles between the bonds Ru(1)-N(1)-N(2) and Ru(1)-
N(4)-(5) are 123.5(2)° and 133.9(2)°, respectively. These results can have two different
explanations. The first one is suggested to be a consequence of the steric hindrance of
−
the aromatic rings of the dppb over the N
3
. The second one finds support in the
−
−
molecular orbital of the N
3
molecule. The bonds in the free N
3
, with a linear shape,
3
have the same length, 1.16 Å. However, the HN molecule has a bent structure, where
the bond angle H–N–N is 112° [41]. This means that the extra electron from H must
occupy an antibonding molecular orbital, providing N–N bonds with significantly
different lengths, i.e. 1.24 Å and 1.13 Å. The bond orders are presumably 1.5 and 2
respectively [41]. The N–N–N bond lengths found in complex (4) fits well with what
was described above for the HN molecule. The N(1)-N(2) and N(4)-N(5) bonds, which
3
are closer to the metal center, have bond lengths of 1.182(3) Å and 1.182(4) Å
respectively, while bonds N(2)-N(3) and N(5)-N(6) are slightly shorter, 1.162(4) Å and
1.162(4) Å, respectively. These results also indicate different bond orders in the bonds
−
of the N
3
coordinated to ruthenium.
As the bond angle Ru–N–N in complex (4) is greater than H–N–N in the HN
3
−
molecule, it is reasonable to think that the N
3
is a weak π-acceptor, when it is compared
1
6

−
−
with the CN and SCN . The bond angles Ru(1)-C(1)-N(1) in (8), and Ru(1)-N(1)-C(1)
in (6) are 175.9° and 165.5°, respectively. These results indicate a double bond
−
−
character between ruthenium-CN and ruthenium- SCN ligands. Hence, a descending
order of π-acceptor electron density of the pseudohalide groups can be described as
−
−
−
31
1
3
follows: CN > SCN > N . This series is the same observed in the P{ H} NMR data
as described below, and it agrees with the spectrochemical series found in the literature
on inorganic chemistry [42].
The pseudohalide ligands present a strong band at FTIR spectra in the region
-1
around 2000 cm . The FTIR spectra of cis-[Ru(CN)
2
(dppb)(bipy)](5), cis-
[
Ru(CN) (dppb)(Mebipy)](8) and cis-[Ru(CN) (dppb)(MeObipy)](10) show two well-
2
2
−1
defined bands around 2090 and 2065 cm , due to the symmetric and antisymmetric
−
stretching mode combinations of the CN , while only one band was observed in the cis-
[
Ru(N
3
)
2
(dppb)(bipy)](4) and cis-[Ru(SCN)
spectra of cis-[Ru(SCN)
(dppb)(MeObipy)](11) present a N=C stretching peak around 2100 cm
2
(dppb)(bipy)](6) complexes [43,44]. The
FTIR
2
(dppb)(bipy)](6) and cis-
−1
[
Ru(SCN)
45,46]. The cis-[Ru(N
2
[
3
)
2
(dppb)(bipy)] complex also revealed a single band near to
-
1
−
2
000 cm , due to the antisymmetric stretching mode of the N
3
, as previously reported
for the similar complex, [Ru(N
3
)
2
(bipy) ] [47].
2
-5
2 2
The pseudohalide complexes (4) – (11) were dissolved in CH Cl (1.0 × 10 mol
-1
L ) and their electronic spectra at ultraviolet/visible region (UV/vis) were recorded,
which reveal two distinct bands. The higher energy bands are assigned to the N-N and
P-P donor groups, which present an electronic transition between molecular orbitals,
located in the ligands (π→π*), more appropriately known as an intraligand transition
(
IL). The lower energy bands are assigned to the metal-ligand charge transfer (MLCT),
which occurs in the visible region, corresponding to an electronic transition from a
1
7

metal based dπ orbital to a bipy ligand-based orbital π* [48–50]. Table 2 summarizes
the results observed in the UV/vis spectra of the complexes (4) – (11).
−5
Table 2: UV/vis data for the cis-[Ru(X)
mol L ).
2
(dppb)(N-N)] complexes in CH
2
Cl
2
(1.0 × 10
−1
Complex
λ (nm) π→π*
× 10 ε L mol cm )
308 (1.8)
λ (nm) dπ →π*
(× 10 ε L mol cm )
469 (2.3)
412 (4.2)
447 (3.9), 492 (2.4)
435 (5.0)
(
Ru)
−1
4
−1
−1
3
−1
(
(
(
(
(
(
(
4)
5)
6)
7)
8)
9)
303 (2.0)
307 (2.2)
307 (2.1)
304 (2.2)
412 (4.8)
435 (5.0)
302 (2.1)
(
(
10)
11)
303 (2.0)
307 (2.3)
407 (4.4)
446 (4.0), 487 (2.5)
The voltammetry studies for the complexes (4), (7) and (9) present an
III
II
irreversible process corresponding to the Ru /Ru couple with an anodic peak potential
pa) at 0.55 V for (4) and 0.46 for (7) and (9) (see Table 3). This shift to a cathodic
(
E
region in the cyclic voltammogram, when compared with the precursor cis-
-
[
RuCl
2
(dppb)(bipy)] (Epa = 0.7 V) can be attributed to the fact that the N
3
is a stronger
−
σ-donor ligand than Cl and it is a weak π-acceptor. In this case, there is an enrichment
of the electronic density in the metal center, which facilitates its oxidation process,
providing lower Epa. The second oxidation process observed for complexes (4), (7) and
-
(
9) at more anodic potentials (ca. 0.9 V), can be assigned to the oxidation of the N
3
−
ligand. The oxidation potential of the free N
3
ligand, in acetonitrile as a solvent, occurs
at 0.79 mV [43]. Complexes (4), (7) and (9) present a third electrochemical process at
III
II
about 1.2 V, which can be assigned to the Ru /Ru process belonging to the
+
[
Ru(N
3
)(CH
3
CN)(dppb)(N-N)] species, which was generated in an acetonitrile
solution. The cyclic and differential pulse voltammograms for the
Ru(N (dppb)(bipy)] can be found in the supplementary data (Fig. 1S).
[
3 2
)
1
8

Table 3: Cyclic voltammetry parameters to the complexes (4) − (11).
a
−
− b
Complex
E
½
(E, mV)
--- (550)
E
pa (V) N
0.93
---
---
0.89
---
0.90
---
3
*Epa (V) N
3
c
(
(
(
(
(
(
4)
5)
6)
7)
8)
9)
1.32
---
---
1.19
---
1.26
---
---
1.30 (280)
0.84(230)
c
--- (460)
1.29 (210)
c
--- (460)
(
(
10)
11)
1.26 (150)
0.80 (180)
---
a) E1/2 = half-wave potential (Epa-Epc/2); E = Epa-Epc, where Epa = anodic peak potential, Epc = cathodic
+
peak potential. b) *Epa related to the [Ru(N
3
)(CH
3
CN)(dppb)(N-N)] complex generated in acetonitrile
pa irreversible process. Complexes: (4) cis-
(dppb)(bipy)], (7) = cis-
(dppb)(Mebipy)], (9) = cis-[Ru(N (dppb)(MeObipy)],
(dppb)(MeObipy)] and (11) = cis-[Ru(SCN) (dppb)(MeObipy)].
solution in the CV experiment. c)
E
=
E
=
[
[
(
Ru(N
Ru(N
3
3
)
)
2
(dppb)(bipy)], (5) = cis-[Ru(CN)
2 2
(dppb)(bipy)], (6) = cis-[Ru(SCN)
2
(dppb)(Mebipy)], (8) = cis-[Ru(CN)
2
3 2
)
10) = cis-[Ru(CN)
2
2
Cyclic voltammetry of (5), (6), (8), (10) and (11) showed only one reversible
II
III
process, corresponding to the Ru /Ru couple, with half-wave potential (E1/2) values
between 0.80 − 1.30 (see Table 3). These values are considerable higher than the E1/2
normally observed in the dichloride ruthenium complexes with either trans or cis-
[
RuCl (P-P)(N-N)] {where: P-P= biphosphine and N-N=diimines} configuration, which
2
shows E1/2 values at around 0.60V [25]. This shift to an anodic region in the cyclic
voltammograms can be attributed to the presence of strong π-acceptor ligands, such as
−
−
CN and NCS .
3
1
1
2 2 2
The P{ H} NMR spectra of the complexes (4) – (11), in CH Cl /D O, exhibit
two doublets, as expected, due to the non-equivalence of phosphorus atoms from the
dppb ligand in the cis geometry of the complexes. It can be observed in Table 4 that
complexes (5), (8) and (10) present a doublet signal much more shielded than the
−
−
correlate complexes with N
3
and SCN ligands. This behavior provides a large
variation of the chemical shifts, between the doublets, labeled as ∆δ (ppm) (see Fig. 2).
−
The presence of a π-acceptor group (CN ) decreases the back donation towards the
−
phosphorus atoms. Therefore, the ∆δ value is around 20 ppm in the presence of CN
−
ligand, while in the presence of a weak π-acceptor, such as N
3
ligand, the ∆δ is much
1
9

lower, less than 3.0 ppm. This result is in agreement with the bond distance observed by
X-ray diffraction data, where the more shielded phosphorus atom provides a greater Ru-
P bond length.
3
1
1
Table 4: P{ H} NMR data of the complexes (4) – (11).
3
1
1
2
Complex δ P{ H} (ppm); JPP (Hz)
∆δ (ppm)
0.6
(
(
(
(
(
(
4)
5)
6)
7)
8)
9)
38.7, 38.1; 32.8
45.8, 25.2; 23.4
40.4, 35.9; 31.95
38.7, 37.2; 31.9
46.0, 25.9; 24.0
40.8, 37.8; 32.4
46.0, 25.6; 23.9
43.0, 36.5; 31.8
20.6
4.5
1.5
20.1
3.0
(
(
10)
11)
20.4
6.5
3
1
1
Fig. 2: P{ H} NMR data of pseudohalide complexes containing ruthenium in
CH
5). C) cis-[Ru(SCN)
each complex.
2
Cl
2
/D
2
O solution. A) cis-[Ru(N
3
)
2
(dppb)(bipy)] (4). B) cis-[Ru(CN)
2
(dppb)(bipy)]
(
2
(dppb)(bipy)] (6). The dashed circle is the amplified spectrum of
2
0

3.2. Hydrogenation of cyclohexene
Hydrogenation reactions of cyclohexene to produce cyclohexane were firstly
carried out in the presence of the dichloride complex containing ruthenium, cis-
RuCl (dppb)(bipy)] (1A), in different solvents, pressure of H , temperature, time and
[
2
2
molar ratio between the components. A series of reactions was performed in different
solvents to find a better homogeneous condition with a good yield of the saturated
product (see Table 5).
Table 5: Influence of the solvent on the hydrogenation of cyclohexene catalyzed by cis-
a
[
RuCl
2
(dppb)(bipy)] (1).
a
-1 c
Entry Solvent
% of cyclohexane
TOF (h )
b
±
RSD(%)
87 ± 2
99 ± 1
78 ± 5
4 ± 1
1
2
3
4
5
6
7
Isopropanol
18.13
20.83
16.25
< 1.00
13.96
Methanol
Ethanol
Dimethyl sulfoxide
Dichloromethane
Acetonitrile
Acetone
67 ± 8
3 ± 2
64 ± 6
< 1.00
13.33
Cyclohexene/(1) molar ratio = 500, at 25°C, within 24 h and 15 atm of H
2
. a) Determined by GC
analyses. b) Reactions were carried out in threefold analysis, RSD = relative standard deviation. c) TOF
−1
(
h ) = turnover frequency = nprod/(ncat × t); where nprod = mol number of product, ncat = mol number of
pre-catalyst and t = reaction time (h).
The results showed that 100 % of the hydrogenated product was obtained in
methanol (entry 2,Table 5), while in the presence of coordinating solvents, such as
dimethyl sulfoxide and acetonitrile, the yield of the product drastically decreased. In the
presence of other solvents, such as CH
product was less satisfactory, but it was still obtained with a good yield, at an average of
5%.
2 2
Cl or acetone, the amount of hydrogenated
6
2
1

Additionally, the hydrogenation reaction of cyclohexene by (1A) in the presence
of an excess of triphenylphosphine (PPh ), 10 times per mol of (1A), does not show any
3
conversion of the hydrogenation product. This result indicates that the real catalyst of
the reaction is formed inside the reaction system, and at least a vacant site on the
coordination sphere of ruthenium is necessary to promote the hydrogenation of
cyclohexene.
2
To estimate the better reaction time and H pressure, a series of experiments was
carried out (see Fig. 3). The time dependence of hydrogenation of cyclohexene by
complex (1A), in methanol solution, at room temperature and molar ratio
cyclohexene/(1A) = 500, showed an increase in the hydrogenated product with an
increase of time, with 20 atm of H
2
. After 5h of reaction, 98% of product (TOF = 98
h ) was obtained. The catalytic performance of (1A) in the methanol solution also
increased with the rise of H pressure until 15 atm, keeping constant at 20 atm, also
−1
2
producing 98% of the hydrogenated product, within 5h of reaction.
Fig. 3: A) Time dependence of hydrogenation of cyclohexene by (1A). B) Catalytic
performance of (1A) in the hydrogenation of cyclohexene with an increase of H
pressure.
2
2
2

The catalytic productivity of (1A) increases with the molar ratio between
cyclohexene and (1A) until 500. After that, the total amount of the product dropped, but
the pre-catalyst (1A) still worked at a high conversion rate, with 89 % of product, in the
−1
molar ratio at 1/2000, and TOF = 356 h . The temperature dependence of
hydrogenation of cyclohexene by (1A) showed a decrease in the percentage of the
hydrogenated product when the temperature was increased. At 25°C, the conversion
was quantitative, in the conditions set out above, but the amount of the hydrogenated
product decreased to 75% at 80°C. This unusual behavior was attributed to a thermal
instability of the complex (1A) in this applied condition.
As a protocol for the follow experiments, the hydrogenation reaction of
cyclohexene by complexes containing ruthenium (1A) – (11) was carried out in
methanol solution, with 15 atm of H
2
pressure, a molar ratio between
cyclohexene/ruthenium complex (S/[Ru]) = 1000, at 25°C, within 5h. Under these
conditions, complexes (1), (2) and (3) provide 100% of the hydrogenated product.
Based on the results obtained from (1) – (3) on the hydrogenation of
cyclohexene, the results obtained with the complexes (4) – (11) were no surprise, where
no catalytic activity was observed. Even after 24 h of reaction, in the best conditions
determined by (1A), no catalytic activity was observed. The exchange of chloride for
−
−
−
3
pseudohalide ligands (N , CN and SCN ) poisoned the catalyst formed inside the
system, and due to the strong coordination of these ligands in the ruthenium center, the
performance of the pre-catalysts fell drastically. The behavior attributed to the
pseudohalide complexes containing ruthenium on the hydrogenation reaction of
cyclohexene is practically the same as that described on the hydrogenation reaction with
3
dichloride complexes in the presence of excess of PPh . The available catalytic site is
lost and the determinant step must pass through an anionic ligand displacement. If this
2
3

step is prevented from happening, the remained species cannot catalyze the alkene
hydrogenation reaction.
4. Conclusion.
−
−
The ruthenium complexes cis-[Ru(L)
2
(dppb)(N-N)] {where L = N
SCN , N-N = bipy, Me-bipy or MeO-bipy} were prepared by chloride exchange on the
cis-[RuCl (dppb)(N-N)] complexes in a mixture of CH Cl :MeOH (1:1). The
pseudohalide complexes were characterized by spectroscopy and electrochemical
3
, CN and
−
2
2
2
techniques.
Appropriate
crystals
of
cis-[Ru(N
3
)
2
(dppb)(bipy)],
cis-
[
Ru(CN) (dppb)(bipy)], cis-[Ru(SCN)
2
2
(dppb)(bipy)] and cis-[Ru(SCN)
2
(dppb)(MeO-
bipy)] were obtained and the X-ray data were discussed. A total conversion of
cyclohexene to cyclohexane was obtain when the cis-[RuCl (dppb)(bipy)], cis-
RuCl (dppb)(Mebipy)] and cis-[RuCl (dppb)(MeObipy)] were used as pre-catalysts.
2
[
2
2
Exchanging chloride for pseudohalides was catastrophic as no catalytic activity was
observed. The catalytic poisoning of the compounds with pseudohalides originates from
the high stability of these anionic ligands, which prevents the formation of open sites in
the coordination sphere of the central atom. Mechanistic studies with compounds 1-3
are underway in our laboratory.
5. Acknowledgment
We would like to thank FAPESP, CNPq, CAPES, FAPEMIG, FINEP, RQ/MG and
GMIT for the financial support.
6
. Appendix A. Supplementary data.
CCDC 1522479 (4), 1522480 (5), 1522481 (6), 1522482 (8) , 1522483 (11) and
523559 (1B) contain the supplementary crystallographic data for the complexes cis-
1
2
4

[
[
[
Ru(N
3
)
2
(dppb)(bipy)](4),
cis-[Ru(CN)
cis-[Ru(CN)
(dppb)(MeO-bipy)](11) and [RuCl(CH
These data can be obtained
http://www.ccdc.cam.ac.uk/conts/retrieving.html or
2
(dppb)(bipy)](5),
(dppb)(Me-bipy)](8)
CN)(bipy)(dppb)](PF
cis-
cis-
Ru(SCN)
Ru(SCN)
2
2
(dppb)(bipy)](6),
2
3
6
)
(1B)
via
respectively.
free
of
the
charge
from
Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223 336 033; e-mail: deposit@ccdc.cam.ac.uk. Crystal data (Table 6S) and selected
o
bond lengths [Å] and angles [ ] for [RuCl(CH
3
CN)(bipy)(dppb)]PF
6
(1B) are described
in the supplementary data. Cyclic voltammogram and differential pulse (Fig.1S) of cis-
Ru(N (dppb)(bipy)] (4) are depicted in the supplementary data.
[
3 2
)
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