Heterobimetallic [Ru(II)/Fe(II)] complexes: On the formation of trans- and cis-[RuCl2(dppf)(diimines)]

Article abstract of DOI:10.1016/j.jorganchem.2007.08.038

The synthesis and characterization of trans/cis-[RuCl₂(dppf)(diimines)], dppf = 1,1′-bis(diphenylphosphino)ferrocene; diimines = 2,2′-bipyridine (trans/cis-(1)), the new complexes with 4,4′-dimethyl-2,2′-bipyridine (trans/cis-(2)) and 1,10-phen

Full text of DOI:10.1016/j.jorganchem.2007.08.038

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5447–5452
www.elsevier.com/locate/jorganchem
Heterobimetallic [Ru(II)/Fe(II)] complexes: On the formation
of trans- and cis-[RuCl2(dppf)(diimines)]
a
a
a
b
´
´
Tulio F. Gallatti , Andre L. Bogado , Gustavo Von Poelhsitz , Javier Ellena ,
b
a,
c,
*
*
´
Eduardo E. Castellano , Alzir A. Batista , Marcio P. de Araujo
a
Departamento de Quı´mica, Universidade Federal de Sa˜o Carlos, CP 676, CEP 13565-905, Sa˜o Carlos (SP), Brazil
b
Instituto de Fı´sica de Sa˜o Carlos, Universidade de Sa˜o Paulo, CEP 13560-970, Sa˜o Carlos (SP), Brazil
Departamento de Quı´mica, Universidade Federal do Parana´, CP 19081, CEP 81531-990, Curitiba (PR), Brazil
c
Received 13 June 2007; received in revised form 27 August 2007; accepted 31 August 2007
Available online 6 September 2007
Abstract
The synthesis and characterization of trans/cis-[RuCl2(dppf)(diimines)], dppf = 1,10-bis(diphenylphosphino)ferrocene; diimines =
2,20-bipyridine (trans/cis-(1)), the new complexes with 4,40-dimethyl-2,20-bipyridine (trans/cis-(2)) and 1,10-phenanthroline (cis-(3)) are
presented. The complexes were synthesized using two routes and the trans/cis-isomer formation is dependent upon conditions and
the precursor applied. The trans-isomer (kinetic) readily isomerizes to the cis-isomer (thermodynamic) when exposed to light (fluorescent)
and this process was followed by cyclic voltammetry and UV–vis. The electrochemical studies on these complexes reveal that Fe(III)/Fe(II)
couples are insensitive to the isomer (trans/cis) formed, but the Ru(III)/Ru(II) couples are dependent on the isomer. Transfer-hydrogena-
tion reactions for reduction of acetophenone were conducted using complexes cis-(1) and cis-(2) and the results are compared with that
obtained for similar complexes. X-ray structure for cis-(3) are presented and discussed.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Heterobimetallic; Dppf; Electrochemistry; Isomerization; Transfer-hydrogenation
1. Introduction
action of C@O or C@N groups with the ‘‘RuH–NH’’ unit
of the catalyst in an outer-sphere mechanism. In addition,
higher productivity and enantioselection are achieved.
The chemistry of dppf (1,10-bis[diphenylphosphino]fer-
rocene) is well documented [11] and the interest in such spe-
cies is mainly focused on structural [12,13], electrochemical
[14,15] and catalytical [16,17] studies. This diphosphine is a
very versatile ligand since it can be coordinated to a tran-
sition metal as a cis-chelate, trans-spanning and bridging,
leading to a great diversity of structures and properties
for its complexes [11].
Very recently, a work published by James and coworkers
[18] presented a series of complexes with dppf and diimines
or di- and triamines. Complexes with diamines were isolated
as trans-isomers (trans-dichlorides), but for the diimines
were only isolated as cis-isomers. The reason claimed for
the non-observation of trans-[RuCl2(dppf)(diimines)] (dii-
mines such as 2,2-bipyridine and phenanthroline) is the
The chemistry of ‘‘Ru(II)(P–P)(N–N)’’ (P–P = 1,4-bis-
(diphenylphosphino)butane-dppb, 2,20-bis(diphenylphos-
phino)-1,10-binaphthyl-binap and N–N = diamines or
diimines) has been widely studied and several complexes
containing this core have been synthesized [1–7]. The inter-
est in such system has strongly increased, mainly after the
works published by Noyori [8–10] and Morris [3–5] using
mixed ruthenium phosphine and diamine complexes. These
reactions lead themselves for selecting C@O or C@N bonds
over C@C bonds by a ligand-assisted mechanism, where an
ancillary ligand cis to the hydride must have an NH or OH
group [8–10]. The observed selection is due to the inter-
*
Corresponding authors. Tel.: +55 41 33613269 (M.P. de Araujo).
E-mail addresses: daab@power.ufscar.br (A.A. Batista), mparaujo@
quimica.ufpr.br (M.P. de Araujo).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.038

5448
T.F. Gallatti et al. / Journal of Organometallic Chemistry 692 (2007) 5447–5452
rigid character of such diimines in contrast with the flexible
character of diamines.
2.2. Synthesis of complexes
This fact was quite surprising for us, since we had syn-
thesized previously to the publication of James [18] the
trans-isomer using the same one-pot synthesis, but the
reaction was carried out in the dark and short period of
time.
Our group have been working with complexes trans/
cis-[RuCl2(P–P)(N–X)], where P–P is mono- or diphos-
phines and N–X is diimines, acetyl and benzoyl-pyri-
dines, with the interest in structural and isomerization,
transfer-hydrogenation and epoxidation [1,2,19–23]. In
these works we showed that the reaction condi-
tions are a key role for the isolation of desired isomer
[1,23].
In this work we present the syntheses, characterization,
and electrochemical studies of four complexes trans/cis-
[RuCl2(dppf)(diimines)]. In addition, we show that the
trans-isomer can be synthesized and isolated in disagree-
ment with the recently published work [18], and the iso-
merization trans ! cis was followed by cyclic voltammetry
and UV–vis spectroscopy. The catalytic activity of cis-
[RuCl2(dppf)(diimines)] complexes (N–N = 2,20-bipyridine
and 4,40-dimethyl-2,20-bipyridine) for reduction of aceto-
phenone was tested and the results are compared with anal-
ogous complexes. X-ray structure cis-[RuCl2(dppf)(phen)]
is presented and discussed.
2.2.1. trans-[RuCl2(dppf)(bipy)] trans-(1) and
trans-[RuCl2(dppf)(Me-bipy)] trans-(2)
A Schlenk flask containing a degassed dichloromethane
(10.0 mL) solution of [RuCl2(PPh3)3] (100 mg; 0.104 mmol)
and dppf (57.6 mg; 0.104 mmol) was stirred for 5 min, the
reaction was protected from exposure to light and the 2,20-
bipyridine (16.2 mg; 0.104 mmol) was added. The reaction
was stirred for additional 2 min and n-hexane was added
to yield a dark red solid. After filtration the solid was
washed with n-hexane and diethyl ether and dried under
vacuum. The resulting red solution was concentrated and
addition of diethyl ether afforded a red solid, which was col-
lected, washed with diethyl ether and dried under vacuum.
1
Yield: 87.4 mg (95%). H NMR: 3.87 (s, 4H, C5H4), 4.12
(s, 4H, C5H4), 6.50 (t, 2H, J 6.3, bipy), 6.78 (t, 8H, J 7.5,
Ph), 6.96 (t, 4H, J 7.2, Ph), 7.40 (t, 2H, J 7.4, bipy), 7.56
(br m, 8H, Ph), 7.76 (d, 2H, J 4.4, bipy), 8.38 (br d, 2H, J
4.4, bipy). IR (KBr pellet): 1602 m; 1481 m; 1471 m; 1433
s; 1384 w; 1309 w; 1188 w; 1155 m; 1086 m; 1035 m; 827
w; 745 s; 696 s; 640 m; 545 s; 516 s; 495 s; 476 m; 428 m;
330 w; 303 w; 281 w. Anal. Calc. for C44H36N2Cl2P2Fe-
Ru Æ H2O: C, 58.68; H, 4.25; N, 3.11. Found: C, 58.82; H,
4.05; N, 3.40%. UV–vis (CH2Cl2, 10ꢀ3 M): k/nm (e/
M
ꢀ1 cmꢀ1) 302 (14900), 351 (3600), 498 (2600).
Complex trans-(2) was synthesized following the same
procedure for the synthesis of trans-(1), but the reaction
was carried out in a NMR tube for direct analysis by 31P
NMR.
2. Experimental section
2.1. Material and instrumentation
2.2.2. cis-[RuCl2(dppf)(bipy)]cis-(1)
The cis-isomer can be isolated by two methods: Method
A: isomerization of trans-isomer in dichloromethane at
room temperature and exposure to light (fluorescent).
Method B: (A representative method for direct synthesis
of the cis-isomer is as follow), cis-[RuCl2(dppf)(bipy)]
cis-(1): A Schlenk flask containing degassed dichlorometh-
ane (20.0 mL) solution of cis-[RuCl2(PPh3)2(bipy)]
(100 mg; 0.117 mmol) and dppf (71.5 mg; 0.129 mmol)
was refluxed for 3 h. The resulting red solution was concen-
trated and addition of diethyl ether afforded a red solid,
which was collected, washed with diethyl ether and dried
All manipulations were carried out under purified argon
using standard Schlenk techniques. Reagent grade solvents
were appropriately distilled and dried before use. The
RuCl3 Æ 3H2O was supplied by Johnson Matthey Ltd. or pur-
chased from Aldrich. Triphenylphosphine (PPh3) (Aldrich),
1,4-bis(diphenylphosphino)butane (dppb) (Aldrich), 1,10-
bis(diphenylphosphino)ferrocene (Strem), 2,20-bipyridine
(bipy) (Aldrich), 1,10-phenanthroline (phen) (Aldrich) and
4,40-dimethyl-2,20-bipyridine (Me-bipy) (Aldrich) were used
as received. The [RuCl2(PPh3)3] [24] and [RuCl2(PPh3)2(dii-
mines)] [21] complexes were synthesized following published
procedures.
Cyclic voltammetry (CV) experiments were carried out
at room temperature in CH2Cl2 using a BAS-100B/W Bio-
analytical Systems Instruments; the working and auxiliary
electrodes were stationary Pt foils, and tꢀhe reference elec-
trode was Ag/AgCl, 0.10 M Bu4NþClO4 (TBAP) (Fluka
Purum), a medium in which ferrocene is oxidized at
0.43 V (Fc+/Fc). Elemental analyses were performed in
the Chemistry Department at Universidade Federal de
1
under vacuum. Yield: 82.8 mg (80%). H NMR: 3.41 (s,
1H, C5H4), 4.15 (s, 1H, C5H4), 4.24 (s, 1H, C5H4), 4.34
(s, 1H, C5H4), 4.47 (s, 2H, C5H4), 4.97 (s, 1H, C5H4),
5.98 (s, 1H, C5H4), 6.43 (t, 1H, J 6.5, bipy), 6.92 (t, 2H,
J 7.1, Ph), 6.99 (m, 2H, Ph), 7.11 (m, 8H, Ph), 7.38 (m,
4H, Ph), 7.48 (s, 1H, bipy), 7.61 (d, 1H, J 7.9, bipy), 7.64
(d, 1H, J 6.1, bipy), 7.68 (d, 1H, J 7.5, bipy), 7.74 (d,
1H, J 7.9, bipy), 7.83 (d, 1H, J 7.9, bipy), 8.12 (m, 2H,
Ph), 8.38 (t, 2H, J 8.1, Ph), 9.32 (d, 1H, J 5.0, bipy). IR
(KBr pellet): 1603 m; 1482 m; 1468 m; 1432 s; 1383 w;
1308 w; 1190 w; 1158 m; 1089 m; 1035 m; 816 w; 747 s;
696 s; 636 m; 546 s; 518 s; 499 s; 474 m; 427 m; 348 w;
319 w; 294 w. Anal. Calc. for C44H36N2Cl2P2FeRu: C,
59.88; H, 4.11; N, 3.17. Found: C, 60.13; H, 4.35; N,
Sao Carlos. All NMR experiments were recorded at
˜
298 K on a Bruker AVANCE 400 equipment operating
at 9.4 T, observing 1H at 400.13 MHz and 31P at
161.98 MHz.

T.F. Gallatti et al. / Journal of Organometallic Chemistry 692 (2007) 5447–5452
5449
3.23%. UV–vis (CH2Cl2, 10ꢀ3 M): k/nm (e/Mꢀ1 cmꢀ1) 300
(CH2Cl2, 10ꢀ3 M): k/nm (e/Mꢀ1 cmꢀ1) 271 (22500), 438
(15500), 351 (3600), 453 (2500), 530 (sh).
(3400), 521 (sh).
2.2.3. cis-[RuCl2(dppf)(Me-bipy)] cis-(2)
3. Results and discussion
Yield: 87.9 mg (85%). 1H NMR: 2.27 (s, 3H, CH3), 2.42
(s, 3H, CH3), 3.44 (s, 1H, C5H4), 4.17 (s, 1H, C5H4), 4.25
(s, 1H, C5H4), 4.35 (s, 1H, C5H4), 4.47 (m, 2H, C5H4),
4.98 (s, 1H, C5H4), 5.97 (d, 1H, J 1.2, C5H4), 6.29 (d,
1H, J 6.0, bipy), 6.85 (d, 1H, J 5.6, bipy), 6.94 (m, 2H,
Ph), 7.01 (m, 2H, Ph), 7.14 (m, 8H, Ph), 7.37 (m, 4H,
Ph), 7.57 (s, 1H, bipy), 7.67 (s, 1H, bipy), 7.89 (d, 1H, J
5.2, bipy), 8.15 (m, 2H, Ph), 8.41 (t, 2H, J 8.0, Ph), 9.20
(dd, 1H, J 8.6, 2.7, bipy). IR (KBr pellet): 1618 m; 1482
m; 1432 s; 1384 w; 1304 w; 1189 w; 1161 m; 1157 m;
1115 m; 1091 m; 1071 m; 1036 m; 816 w; 747 s; 696 s;
636 m; 546 s; 518 s; 499 s; 474 m; 427 m; 348 w; 319 w;
294 w. Anal. Calc. for C46H40N2Cl2P2FeRu: C, 60.67; H,
4.43; N, 3.08. Found: C, 60.35; H, 4.25; N, 3.15%. UV–
vis (CH2Cl2, 10ꢀ3 M): k/nm (e/Mꢀ1 cmꢀ1) 296 (8800),
441 (1500), 520 (sh).
In this work we present the synthesis, electrochemistry,
X-ray structure and preliminary transfer-hydrogenation
reactions studies of the heterobimetallic trans/cis-
[RuCl2(dppf)(diimines)], diimines = 2,20-bipyridine trans/
cis-(1), 4,40-dimethyl-2,20-bipyridine trans/cis-(2) and
1,10-phenanthroline cis-(3). These complexes were synthe-
sized by two methods: Starting from [RuCl2(PPh3)3], dppf
and diimines ligands for the synthesis of the trans-(1) and
trans-(2); and by phosphine exchange from the precursor
cis-[RuCl2(PPh3)2(diimines)]. When the starting compound
is cis-[RuCl2(PPh3)2(diimines)] [21], independently of the
conditions, only the cis-[RuCl2(dppf)(diimines)] complex
is obtained, which is in agreement with our previous work
with the dcype ligand [2]. When the starting compound is
the [RuCl2(PPh3)3], the conditions of the reaction can be
modified to isolate the trans- or the cis-isomer. The cis-con-
figuration was confirmed by 31P{1H} NMR. The spectra
were obtained in CH2Cl2 (with D2O capillary tube) and
presented a well defined AX spin system with chemical
shifts for cis-(1), cis-(2) and cis-(3) at 42.15, 36.50
(2JP–P = 30.7 Hz); 43.02, 36.90 (2JP–P = 31.6 Hz) and 43.6,
37.4 (2JP–P = 30.6 Hz), respectively. The trans-(1) (isolated)
and trans-(2) (in situ, NMR tube) were obtained by one-pot
reaction starting from [RuCl2(PPh3)3] in absence of light
and at short reaction time (2 min, after addition of dii-
mines). The 31P{1H} spectra present a singlet signal for
both complexes, which is in agreement with equivalent
phosphorus (trans-(1) and trans-(2), 41.91 and 42.47 ppm,
respectively). The isomerization trans(kinetic) ! cis(ther-
modynamic) for the complex trans-(1) was followed by cyc-
lic voltammetry and UV–vis spectroscopy and will be
discussed below (see Fig. 1).
2.2.4. cis-[RuCl2(dppf)(phen)] cis-(3)
1
Yield: 82.7 mg (80%). H NMR: 3.38 (m, 1H, C5H4),
4.15 (m, 1H, C5H4), 4.27 (m, 1H, C5H4), 4.37 (m, 1H,
C5H4), 4.42 (m, 1H, C5H4), 4.51 (m, 1H, C5H4), 5.07 (m,
1H, C5H4), 6.12 (m, 1H, C5H4), 6.78 (m, 4H, Ph), 6.83
(dd, 1H, J 8.1, 5.5, phen), 6.91 (m, 2H, Ph), 7.08 (m, 4H,
Ph), 7.19 (m, 4H, Ph), 7.40 (m, 4H, Ph), 7.70 (d, 1H, J
8.7, phen), 7.82 (d, 1H, J 8.7, phen), 7.95 (dd, 1H, J 8.1,
1.2, phen), 8.18 (dd, J 8.1, 1.5, 1H, phen), 8.22 (dd, 1H,
J 9.6, 1.5 phen), 8.28 (d, J 5.5, 1H, phen), 8.50 (t, J 8.6,
2H, Ph), 9.60 (m, 1H, phen). IR (KBr pellet): 1585 m;
1482 m; 1432 s; 1384 w; 1305 w; 1260 w; 1190 w; 1159 m;
1090 m; 1036 m; 840 w; 810 w; 745 s; 696 s; 640 m; 545
s; 518 s; 494 s; 472 m; 428 m; 336 w; 307 w; 281 w. Anal.
Calc. for C46H36N2Cl2P2FeRu Æ H2O: C, 59.76; H, 4.14;
N, 3.03. Found: C, 59.42; H, 4.02; N, 3.09%. UV–vis
0.32
A
B
dppf +/ dppf
0.24
cis
0.8
trans
0.16
0.08
0.00
0.4
-0.08
-0.16
300
375
450
525
600
675
200
400
600
800
1000
1200
Wavelenght (nm)
E / mV
Fig. 1. Isomerization process of trans-[RuCl2(dppf)(bipy)]. (A) Cyclic voltammetry (CH2Cl2 solution, 10ꢀ3 M, working and auxiliary electrodes were
stationary Pt foils, and the reference electrode was Ag/AgCl, 0.10 M Bu4N+ClO4ꢀ). (B) UV–vis spectroscopy (CH2Cl2 solution, 10ꢀ3 M).

5450
T.F. Gallatti et al. / Journal of Organometallic Chemistry 692 (2007) 5447–5452
The 1H NMR spectra of the cis-[RuCl2(dppf)(diimines)]
clusion, formation of trans- or cis-isomer is dependent
upon the starting complex and conditions of the reaction.
The electrochemical data obtained for the studied com-
plexes and for similar species from the literature are in
Table 1.
complexes showed signals for the phenyl groups of the
phosphine as a series of multiplets in the 6.80–8.50 ppm
region corresponding to 20 hydrogens. The ferrocenyl
hydrogens show resonances in the region d 3.40–6.10,
appearing as seven lines, one of them with twice the inten-
sity of the others for cis-(1) and cis-(2), however this is not
the case of cis-(3) in which eight lines are observed for these
hydrogens. This is a consequence of the non-equivalence of
the phosphorus atoms attached to the Cp rings, as
observed by the two doublets in the 31P{1H} NMR spectra.
The electrochemical behaviors of the trans/cis-
[RuCl2(dppf)(diimines)] complexes are similar to the
observed for trans/cis-[RuCl2(dppb)(bipy)] [1], but in this
case besides the Ru(III)/Ru(II) couples are also observed
the processes for Fe(III)/Fe(II) couples. The Ru(III)/Ru(II)
process for the trans-isomer is less anodic than for the
cis-isomer. This is in agreement with the observed for
the trans/cis-[RuCl2(dppb)(diimines)] species [1]. For the
Fe(III)/Fe(II) processes are observed only a negligible differ-
ence on E1/2 between trans- and cis-isomers (see Fig. 1).
This variation on potentials and the similarity with other
ruthenium complexes [1,2] allowed us to attribute the pro-
cesses centered on ruthenium as the lower potentials (less
anodic) and consequently the higher potentials to the iron
of the coordinated dppf ligand.
The trans- to cis-isomerization was accompanied by
spectral changes in the UV–vis spectra (Fig. 1(B)). The
bands in the UV–vis spectra initially at 301 nm slightly
change to 298 nm with an increase of intensity while the
360 nm band has its intensity greatly diminished. In the vis-
ible region the initial band at 500 nm was gradually substi-
tuted by a similar one at 452 nm with the formation of two
isosbestic points at 397 and 472 nm. The visible bands are
tentatively assigned to MLCT (Ru ! bipy) transitions and
the increase of the energy transition in the cis-isomer is in
agreement with the lowest electron density of this isomer
when compared with the trans species, as previously
showed in the electrochemical data.
3
In complex cis-(1) the expected JH–H coupling for the Cp
hydrogens is not resolved, and the resonances are seen as
singlets. This is in contrast with the pattern found for cis-
(2) and cis-(3), where for the first complex a multiplet is
observed at 4.47 and a doublet at 5.97 ppm, besides five
other singlet signals while for the other all the eight signals
are multiplets for the Cp hydrogens. The diimines (N–N)
hydrogens resonances are observed in the typical region.
For the complexes cis-(1) and cis-(3) the expected eight aro-
matic hydrogens environments (relative intensity 1H each)
appears as a series of doublets or double doublets in the
6.43–7.83 ppm region for cis-(1) and in the range 6.83–
8.28 ppm for cis-(3). Additionally, both complexes showed
the characteristic deshielded signal at 9.32 ppm for cis-(1)
and at 9.60 ppm for cis-(3), corresponding to one of the
ortho hydrogens of the (N–N) ligand. For the complex
cis-(2) the six aromatic hydrogens of Me-bipy are observed
as two singlets, three doublets and a double doublet at
9.20 ppm corresponding to one of the ortho hydrogens of
the pyridine rings. For the CH3 groups two singlets at
2.42 and 2.27 ppm are observed. In contrast with the cis-
(1) isomer the trans-(1) (trans-[RuCl2(dppf)(bipy)]) com-
1
plex has a C2 axis. This difference was reflected in the H
Recrystallization from dichloromethane/hexane solu-
tion led to formation of red single crystals of complex
cis-(3) which were analysed by X-ray diffraction. The
solved structure is presented in Fig. 2. Attempts to isolate
single crystals of the trans-isomer were unsuccessful leading
only to formation of single crystals of the cis-isomer.
The X-ray structure of the cis-(3) complex revealed that
the Ru(II) ion is in a distorted octahedral geometry, as evi-
denced by P–Ru–P 99.37ꢁ, Cl–Ru–Cl 86.85ꢁ and N–Ru–N
78.60ꢁ. The Ru–Cl, Ru–N, Ru–P distances found for the
cis-(3) are in the typical range reported in the literature
NMR spectrum which showed less signals than the cis
analogous. The aromatic hydrogens resonances are in the
range 6.78–7.56 ppm corresponding to 20 hydrogens. The
ferrocenyl hydrogens show singlet resonances at 3.87 and
4.12 ppm (relative intensity 4H each) suggesting that the
ferrocene rings are eclipsed and are essentially co-planar.
This is clearly contrasting with the seven resonances for
the similar hydrogens in the cis species. Finally, the bipy
hydrogens show resonances at 8.38 and 7.76 (doublets)
and at 7.40 and 6.50 (triplets) with relative intensity of
2H each, indicating that the two pyridyl rings are
equivalent.
As mentioned before the trans-[RuCl2(dppf)(diimines)]
can be selectively synthesized starting from [RuCl2(PPh3)3],
dppf and diimines. The key role for this is carrying out
the reaction in absence of light and at shortest reaction
time (2 min, after addition of diimines). The trans-
[RuCl2(dppf)(bipy)] (kinetic isomer) when exposed to light
readily isomerizes leading to the formation of cis-isomer
(thermodynamic isomer). This process is similar to the
observed for the trans-[RuCl2(dppb)(bipy)] complex [1].
This isomerization process was followed by cyclic voltam-
metry and UV–vis spectroscopy (see Fig. 1). Thus, in con-
Table 1
Electrochemical data (E1/2 in volts) for trans/cis-[RuCl2(P–P)(N–N)]
dppb [1]
dcype [2]
dppf a
Ru(III)/Ru(II) Ru(III)/Ru(II) Ru(III)/Ru(II) (Fe(III)/Fe(II) b
)
trans/bipy
cis/bipy
trans/phen
cis/phen
0.45
0.60
0.47
0.63
–
–
0.41
–
0.41
0.35
0.50 (0.97)
0.64 (0.98)
–
0.65 (1.00)
0.62 (0.99)
cis/Me-bipy
a
This work.
E1/2 for free dppf is 0.62 V.
b

T.F. Gallatti et al. / Journal of Organometallic Chemistry 692 (2007) 5447–5452
5451
Table 2
Crystal data and structure refinement for cis-(3)
Empirical formula
Formula weight
Temperature (K)
C46H36N2P2Cl2FeRu Æ 2CH2Cl2
1076.38
293(2)
0.71073
Monoclinic
C2/c
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
˚
a (A)
38.9410(9)
14.1620(3)
17.9160(5)
9078.1(4)
˚
b (A)
˚
c (A)
3
˚
Volume (A )
Z
8
Dcalc (Mg/m3)
1.575
1.113
4352
Absorption coefficient (mmꢀ1
F(000)
Crystal size (mm3)
)
0.24 · 0.16 · 0.06
3.42–26.40
ꢀ46 6 h 6 48, ꢀ17 6 k 6 16,
ꢀ22 6 l 6 22
27041
9040 [0.0448]
97.0%
0.855 and 0.733
Theta range for data collection (ꢁ)
Index ranges
Fig. 2. ORTEP [26] view of the complex cis-[RuCl2(dppf)(phe-
n)] Æ 2CH2Cl2, showing the atoms labelling and the 50% probability
ellipsoids. Bond lengths (A): Ru–N(1) 2.108(3), Ru–N(2) 2.122(3), Ru–P(2)
˚
Reflections collected
2.3210(8), Ru–P(1) 2.3664(8), Ru–Cl(1) 2.4206(8), Ru–Cl(2) 2.4621(8),
Fe–C(231) 2.019(3), Fe–C(131) 2.024(3), Fe–C(135) 2.024(3), Fe–C(232)
2.029(3), Fe–C(235) 2.037(3), Fe–C(132) 2.048(4), Fe–C(134) 2.056(4), Fe–
C(133) 2.058(4), Fe–C(234) 2.060(3), Fe–C(233) 2.064(4). Bond angles (ꢁ):
N(1)–Ru–N(2) 78.60(10), N(1)–Ru–P(2) 98.96(7), N(2)–Ru–P(2) 90.85(7),
N(1)–Ru–P(1) 98.68(8), N(2)–Ru–P(1) 169.73(7), P(2)–Ru–P(1) 99.37(3),
N(1)–Ru–Cl(1) 165.86(8), N(2)–Ru–Cl(1) 87.86(8), P(2)–Ru–Cl(1)
85.17(3), P(1)–Ru–Cl(1) 93.94(3), N(1)–Ru–Cl(2) 87.44(7), N(2)–Ru–
Cl(2) 82.95(7), P(2)–Ru–Cl(2) 170.07(3), P(1)–Ru–Cl(2) 87.05(3), Cl(1)–
Ru–Cl(2) 86.85(3).
Independent reflections [R(int)]
Completeness to theta = 27.50ꢁ
Maximum and minimum
transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
9040/0/577
1.042
R1 = 0.0491, wR2 = 0.1295
R1 = 0.0621, wR2 = 0.1399
Largest difference in peak and hole 0.675 and ꢀ1.024
ꢀ3
˚
(e A
)
[1,2,6,18,22]. As expected, the Ru–P bond length is longer
for the phosphorus trans to nitrogen than for the phospho-
rus trans-chloride, but the Ru–P bond lengths are longer
Table 3
Results for acetophenone reduction by mixed phosphines/diimines ruthe-
nium complexes
˚
for cis-(3) (Ru–P(av), 2.344 A) than for its analogue cis-
˚
[RuCl2(dppf)(bipy)] (Ru–P(av), 2.317 A) [18,25]. It is worth
Complexes
Conversiona (%) TOF30 min (hꢀ1
)
noting that the conformation for cis-(3) is synclinical stag-
gered, as previously discussed by Bandoli and Dolmella
[11], but the torsion angle P–C–C–P for cis-[RuCl2(dppf)-
(bipy)] is 19.70ꢁ and for cis-(3) is 35.54ꢁ and can be due
to the more rigid ring of phenanthroline than the bipyri-
dine (Table 2).
cis-[RuCl2(dppb)(bipy)] [2]
cis-[RuCl2(dppb)(bipy)] [2]
cis-[RuCl2(PPh3)2(bipy)] [2]
cis-[RuCl2(PPh3)2(Me-bipy)] [2]
cis-[RuCl2(dppf)(bipy)],d cis-(1)
78
86
90
81
47
760
940b
280
400
360c
120c
cis-[RuCl2(dppf)(Me-bipy)],d cis-(2) 33
a
Conditions: Acetophenone (10 mmol, 0.2 M) in 2-propanol, 1 mL of
KOH (0.2 M) in 2-propanol; precatalyst (10 lmol); P(H2(g)) = 1 atm,
temp. = 82 ꢁC, time = 3 h; acetophenone/precatalyst/KOH 1000:1:20.
The catalytic activities of cis-(1) and cis-(2) were tested
for reduction of acetophenone and the results are presented
in Table 3 with another complexes [2]. The complexes pre-
sented in this work and the ones in Table 3 do not present
an ‘‘NH’’ group, but they are active for converting
acetophenone in 1-phenylethanol in good yield. The dppf
complexes are less active than the [RuCl2(P–P)(diimines)]
(P–P = dppb or (PPh3)2) complexes for the reduction of
acetophenone as can be seen in Table 3 and Fig. 3, giving
low final conversions in 3 h (cis-(1), 47%; cis-(2), 33%) and
lower rates. The lower activity of dppf complexes can be
rationalized as a function of the bulkiness of the dppf
ligand when compared with dppb or PPh3. These com-
plexes (cis-(1) and cis-(2)) promote the reduction of aceto-
phenone via hydrogen transfer mechanism only in presence
of isopropanol and base. Similar results were found by
James [18] with the complexes cis-[RuCl2(dppf)(bipy)]
b
P(H2(g)) = 3 atm.
c
With H2(g) (1 atm) or without the results are the essentially the same.
This work.
d
and cis-[RuCl2(dppf)(phen)]. The presence of H2 in the
reaction system does not affect the activity of the catalysts
and the final conversion of the acetophenone. Quite the
opposite is observed for the complex cis-[RuCl2(dppb)-
(bipy)] [2] which has its activity improved under H2 atmo-
sphere (1 atm). In absence of H2 the reaction is very slow
achieving only 50% of conversion in 24 h, but under H2
(1 atm) this complex reduces acetophenone in 78% of con-
version in 3 h.

5452
T.F. Gallatti et al. / Journal of Organometallic Chemistry 692 (2007) 5447–5452
100
80
60
40
20
0
[RuCl2(dppf)(phen)]. The 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 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2007.08.038.
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0
20
40
60
80
100 120 140 160 180 200
Time (min)
cis-[RuCl (dppb)(bipy)]
cis-[RuCl (dppb)(bipy)] - 3 atm
[RuCl (PPh ) (bipy)
[RuCl (PPh ) (Mebipy)
[RuCl (dppf)(bipy)
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In this work we present the successful synthesis of the
trans/cis-[RuCl2(dppf)(diimines)] (diimines = 2,20-bipyri-
dine) (trans/cis-(1)), 4,40-dimethyl-2,20-bipyridine (trans/
cis-(2)) and 1,10-phenanthroline (cis-(3)) complexes and
their characterization by 31P{1H} and 1H NMR, cyclic vol-
tammetry, elemental analysis, UV–vis spectroscopy and X-
ray structures for two complexes, cis-(1) [25] and cis-(3). In
disagreement with stated in the recently published paper
[18] the trans-isomers (trans-[RuCl2(dppf)(diimines)], dii-
mines = bipy or Me-bipy) were synthesized. The isomeriza-
tion of the trans-[RuCl2(dppf)(bipy)] isomer was followed
using cyclic voltammetry and UV–vis. The precursor and
conditions applied are of fundamental importance for the
synthesis of the desired trans- or cis-isomer. The catalytic
activity of dppf complexes cis-(1) and cis-(2) was tested
and these complexes presented a low performance when
compared with other [RuCl2(P–P)(diimines)] complexes.
Improvement on these complexes should be made and
new dppf systems will be tested.
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Organometallics 23 (2004) 4836.
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B.R. James, T.Q. Hu, Organometallics 26 (2007) 846.
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945.
Acknowledgements
We thank CNPq, CAPES, FINEP, PRONEX and FA-
PESP for financial support and Johnson Matthey plc for
the loan of RuCl3 (to M.P.A).
[25] We also have solved the X-ray structure of cis-(1). This structure
was already reported (see Ref. [18]), due to this the complete
crystallographic data for this complex is presented in Supplementary
material.
Appendix A. Supplementary material
CCDC 632660 and 638566 contain the supplementary
crystallographic data for cis-[RuCl2(dppf)(bipy)] and cis-
[26] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.