Carbonyl and nitrosyl diruthenium compounds: Crystal structure of [Ru2(O2CMe)(DPhF)3(CO)]BF4 · CH2Cl2 and its isomorphous nitrosyl analogue

Article abstract of DOI:10.1016/j.jorganchem.2007.11.025

The reaction of [Ru₂(O₂CMe)(DPhF)₃(H₂O)]BF₄ (DPhF = N,N′-diphenylformamidinate) with CO gas leads to [Ru₂(O₂CMe)(DPhF)₃(CO)]BF₄ (1), that is the first isola

Full text of DOI:10.1016/j.jorganchem.2007.11.025

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1597–1604
www.elsevier.com/locate/jorganchem
Carbonyl and nitrosyl diruthenium compounds: Crystal structure
of [Ru2(O2CMe)(DPhF)3(CO)]BF4 ꢀ CH2Cl2 and its
isomorphous nitrosyl analogue
a
a
a,
b
*
´
M. Carmen Barral , Santiago Herrero , Reyes Jimenez-Aparicio , M. Rosario Torres ,
Francisco A. Urbanos a
a Departamento de Quı´mica Inorga´nica, Facultad de Ciencias Quı´micas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain
b Centro de Asistencia a la Investigacio´n de Rayos X, Facultad de Ciencias Quı´micas, Universidad Complutense de Madrid, Ciudad Universitaria,
28040 Madrid, Spain
Received 11 October 2007; received in revised form 14 November 2007; accepted 14 November 2007
Available online 22 November 2007
Abstract
The reaction of [Ru2(O2CMe)(DPhF)3(H2O)]BF4 (DPhF = N,N0-diphenylformamidinate) with CO gas leads to [Ru2(O2CMe)-
5+
(DPhF)3(CO)]BF4 (1), that is the first isolated carbonyl complex containing the Ru2 unit. The nitrosyl analogue [Ru2(O2CMe)-
(DPhF)3(NO)]BF4 (2) is prepared by reaction of Ru2Cl(O2CMe)(DPhF)3 with NOBF4. However, the attempts to obtain the cyanide
derivative by reaction of Ru2Cl(O2CMe)(DPhF)3 or [Ru2(O2CMe)(DPhF)3(H2O)]BF4 with NaCN were unsuccessful. The structure
of compounds 1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2 are described. Both compounds are isomorphous. The magnetic measurements at variable tem-
perature demonstrate that 1 is paramagnetic with one unpaired electron in all range of temperature, in contrast to the three unpaired
5+
electrons usually present in Ru2 complexes. The analogous nitrosyl compound 2 is diamagnetic.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Carbonyl complexes; Nitrosyl complexes; Ruthenium; Magnetism; Metal–metal bond
1. Introduction
cleavage by strong p acceptor ligands [7] and, therefore,
reports on diruthenium compounds with NO or CO
ligands are very scarce in the literature. The first two struc-
turally characterized nitrosyl complexes Ru2(O2CC2H5)4-
(NO)2 and Ru2(O2CCF3)4(NO)2 were prepared from the
corresponding tetracarboxylatodiruthenium(II) derivatives
The carbon monoxide (CO) has been extensively used as
ligand in organometallic chemistry [1]. Due to its r donor
and p acceptor character numerous metal complexes, espe-
cially with the metal in low oxidation state have been pre-
pared. The coordination chemistry of the nitrogen
monoxide (nitric oxide, NO) [2] has been less studied. How-
ever, because of its fundamental role as constituent of air
pollution [3] and in biochemical processes [4], the interest
of the chemistry of NO has largely increased [5].
2+
and were described as Ru2 compounds [8]. A formally
diruthenium(II) complex Ru2Cl(Fap)4(NO) (Fap = 2-(2-
fluoroanilino)pyridinate) containing a more basic equato-
rial ligand has also been published [9]. More recently,
two new nitrosyl compounds Ru2(DPhF)4(NO) and
Numerous paddlewheel diruthenium complexes with
different equatorial and axial ligands showing a large range
Ru2(DPhF)4(NO)2(DPhF = N,N0-diphenylformamidinate)
3+
proposed to be Ru2
and Ru22+, respectively, were
of basicities have been described [6]. However, it is known
also structurally characterized [10]. The reduction of
Ru2(DPhF)4(NO) under CO atmosphere gives the anion
[Ru2(DPhF)4(NO)(CO)]ꢁ. This species contains both
CO and NO axial ligands but the complex was not iso-
lated [10]. The number of carbonyl complexes containing
5+
that complexes containing Ru2
core are sensitive to
*
Corresponding author.
´
E-mail address: reyesja@quim.ucm.es (R. Jimenez-Aparicio).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.11.025

1598
M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
diruthenium cores reported in the literature is even lower
than of nitrosyl compounds. The unstable dicarbonyl com-
plex Ru2(N3Ph2)4(CO)2 has been briefly described [8] but
its crystal structure is unknown. The first stable carbonyl-
plex 1, [Ru2(O2CMe)(DPhF)3(NO)]BF4 (2), was prepared
by reaction of Ru2Cl(O2CMe)(DPhF)3 with NOBF4. Crys-
tals of 2 ꢀ CH2Cl2 were obtained similarly to 1 ꢀ CH2Cl2.
Regardless of the formal oxidation state of the diruthe-
nium core, there is one additional electron in 2 with
respect to 1. Presumably, the solvent is involved in this
reduction process and it could be related to the stabiliza-
tion of the p* orbitals upon coordination of NO+, which
makes the complex more oxidizing. The reduction of
dimetallic compounds in THF has been previously pointed
out [14].
diruthenium complex Ru2(DPhF)4(CO) containing
a
Ru24+ unit has four strongly basic equatorial ligands. This
compound can be converted by oxidation in the analogous
5+
Ru2 derivative but this latter complex was not isolated
[11].
In this paper we analyze the reaction of the neutral
and the cationic complexes Ru2Cl(O2CMe)(DPhF)3 and
[Ru2(O2CMe)(DPhF)3(H2O)]BF4 with NO+, CO, and
CNꢁ species. These reactions allow us to isolate and
characterize the new carbonyl and nitrosyl isomorphous
complexes [Ru2(O2CMe)(DPhF)3(CO)]BF4 (1) and [Ru2-
(O2CMe)(DPhF)3(NO)]BF4 (2). 1 represents the first
A different procedure, bubbling NO gas through a solu-
tion of Ru2Cl(Fap)4 (Fap = 2-(2-fluoroanilino)pyridinate),
was employed to obtain the related compound Ru2Cl-
(Fap)4(NO) [9].
5+
example of a carbonyl compound containing the Ru2
2.2. IR spectra
core.
The absorptions in the IR spectra of the complexes are
consistent with previous data observed for other diphenyl-
formamidinate complexes of Ru25+ where DPhFꢁ acts as a
bridge between the metal atoms. A detailed study of the IR
bands, in related compounds, has been published elsewhere
[15]. In compound 1 ꢀ CH2Cl2, the C–O normal mode of
vibration of the carbonyl group absorbs at 2016 cmꢁ1. This
value is very similar to the reported for the electrochemi-
cally generated species [Ru2(DPhF)4(CO)]+ in CH2Cl2
solution (2019 cmꢁ1). The CO stretching vibration bands
for the compound Ru2(DPhF)4(CO) and the electrochemi-
cally reduced species [Ru2(DPhF)4(CO)]ꢁ appear at 1929
and 1840 cmꢁ1, respectively. This difference is in agreement
with the variation of the electron density in the metal
centres and, consequently, with the back-donation to the
carbonyl ligand [11].
The m(CO) in 1 is sensitive to the solvent of crystalliza-
tion being higher in 1 ꢀ THF (2024 cmꢁ1). In accordance
with this behaviour, we have shown, very recently, how
small changes in the structure of the solids can modify
the electronic configuration of this kind of species [16].
The different population of the orbitals p* and d* may
change and affect the retrodonation of the electronic den-
sity to the axial ligand.
2. Results and discussion
2.1. Synthesis of the complexes
5+
The first neutral low spin complex of Ru2
,
6+
Ru2(CN)(DPhF)4 [12], and the oxidized Ru2 derivative
Ru2(CN)2(DPhF)4 [13] were isolated from the reaction
between Ru2Cl(DPhF)4 and an excess of NaCN. However,
the attempts to obtain the same kind of complexes by reac-
tion of Ru2Cl(O2CMe)(DPhF)3 or [Ru2(O2CMe)(DPhF)3-
(H2O)]BF4 with NaCN have been unsuccessful. It is
reasonable to think that the less donor carboxylate group
compare to the formamidinate ligand makes the complexes
unstable in the presence of cyanide species. This fact is
consistent with the difficulties found by numerous authors
to oxidize the [Ru2(O2CR)4]+ core and to isolate Ru2
carboxylates [6].
6+
The cationic species [Ru2(DPhF)4(CO)]+ was detected in
the electrochemical studies carried out on Ru2(DPhF)4(CO)
in CH2Cl2 solution [11], although the complex was not iso-
lated. However, the easy coordination of CO at the axial
position of [Ru2(O2CMe)(DPhF)3(H2O)]BF4 in dichloro-
methane solution allows the isolation of [Ru2(O2C-
Me)(DPhF)3(CO)]BF4 (1) in good yield. In contrast, when
CO was bubbled through a dichloromethane solution of
Ru2Cl(O2CMe)(DPhF)3, only the starting material was
recovered, in accordance with the high tendency of the
‘‘Ru2(O2CMe)(DPhF)3” moiety to coordinate only one axial
ligand.
The most important feature in the IR spectrum of
2 ꢀ CH2Cl2 is the absorption of the N–O bond that appears
at 1771 cmꢁ1, near to that found for Ru2(DPhF)4(NO)
(1773 cmꢁ1) despite the assigned oxidation state is lower
in this last compound [10]. However, the derivative Ru2Cl-
4+
(Fap)4(NO) [9], described as Ru2 complex, presents an
The easy isolation of the carbonyl complex 1 contrasts
to the difficulties found to obtain the cyanide derivative.
The lower basicity of CO with respect to CNꢁ may be
the reason why the fragment ‘‘Ru2(O2CMe)(DPhF)3”
endures the coordination of CO. Compound 1 is stable
absorption band at lower wavenumber (1740 cmꢁ1), close
to the bands detected for Ru2(DPhF)4(NO)2 at 1747 and
1727 cmꢁ1 [10]. It must be taken in consideration that the
n+
magnitude of the back-donation from the Ru2
unit
depends not only on the oxidation state of these units
but also on the donor character of the equatorial ligands.
Other complexes with formula Ru2(O2CR)4(NO)2,
R = Me, Et, Ph, CF3, present bands between 1722 and
1800 cmꢁ1 [8].
5+
to the air and constitutes the first example of a Ru2 car-
bonyl complex. Crystals of 1 ꢀ CH2Cl2 and 1 ꢀ THF were
obtained by crystallization from CH2Cl2/hexane and
THF/hexane, respectively. The nitrosyl analogue of com-

M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
1599
2.3. Mass spectra
The stability of the fragment [Ru2(L–L)4]+ has been
pointed out in mass-spectrometry studies on carboxylate
5+
complexes containing the Ru2
core [17]. The mass
spectrum of complex 1 also shows a strong signal
attributed to the fragment [Ru2(O2CMe)(DPhF)3]+, orig-
inated by the loss of the axial ligand. This fragment has
also been detected for Ru2Cl(O2CMe)(DPhF)3 [18],
Ru2(N3)(O2CMe)(DPhF)3,
Ru2(NCS)(O2CMe)(DPhF)3
[12], and [Ru2(O2CMe)(DPhF)3(H2O)]BF4 [19]. However,
in the mass spectrum of 2 only the peak assigned to the
[Ru2(O2CMe)(DPhF)3(NO)]+ fragment is displayed,
which indicates the strength of the Ru–NO bond in this
compound. A signal corresponding to [Ru2(Fap)4(NO)]+
was observed for Ru2Cl(Fap)4(NO) although other frag-
ments as [Ru2(Fap)4]+ and [Ru2(Fap)3]+ were also
detected [9]. The only fragment reported from the mass
spectra of the complexes Ru2(DPhF)4(NO) and
Ru2(DPhF)4(NO)2 was [Ru2(DPhF)4]+ [10].
Fig. 1. Electronic spectra in the solid state for Ru2Cl(O2CMe)(DPhF)3
(solid), 1 ꢀ CH2Cl2 (dots), and 2 ꢀ CH2Cl2 (dashed).
2.4. Magnetism
2.5. Electronic properties
Complexes of Ru25+ have been usually represented with
a (p*d*)3 configuration, with three unpaired electrons, due
to the accidental degeneration of the p* and d* orbitals
[6]. However, for some triazenido [20] and formamidinato
[12] complexes a HOMO p*3, with one unpaired electron,
have been proposed. In addition, more recently some form-
amidinate compounds with a magnetic moment intermedi-
ate between three and one unpaired electrons have been
published [15,16,19,21,22].
Complex 1 ꢀ CH2Cl2 shows a magnetic moment at room
temperature of 2.03 lB, corresponding to one unpaired
electron. The magnetic moment remains constant from
room temperature to 2 K as expected for a doublet ground
term. This magnetic behaviour contrasts with the three
unpaired electrons of the parent compound Ru2Cl(O2C-
Me)(DPhF)3 [18] and the intermediate behaviour of
[Ru2(O2CMe)(DPhF)3(H2O)]BF4 [19]. Moreover, the mag-
netic moment for 1 ꢀ THF is 2.24 lB at room temperature.
However, the difference of 0.21 lB for the same complex,
but crystallized with other solvent, is not a surprise in this
class of compounds where small changes, such as addi-
tional hydrogen bond interactions, may induce different
magnetic behaviour [16].
In Fig. 1, the visible spectra in the solid state of com-
plexes 1 and 2 are shown. The spectrum of the high spin
compound Ru2Cl(O2CMe)(DPhF)3 is also included for
comparison. The most noticeable differences between the
curves of Ru2Cl(O2CMe)(DPhF)3 and 1 are the presence,
in the latter, of a shoulder at 490 nm and the shift of its
maximum to lower energy (587 nm). A possible explana-
tion could be that the absorption at 528 nm for
Ru2Cl(O2CMe)(DPhF)3 corresponds to the sum of two
bands, due to the p ? p* and p* ? d* transitions [15].
The exchange of Clꢁ by CO as axial ligand produces a
stabilization of the p* orbital. This stabilization increases
the gap between the p* and d* orbitals and reduces the dis-
tance between the p and p* levels. In that case, for complex
1, the absorptions at about 490 and 587 nm can be attrib-
uted to the p* ? d* and p ? p* transitions, respectively.
The electronic spectrum of complex 2 shows the p* ? d*
band at 504 nm but does not display any absorption near
600 nm, as expected for a completely occupied p* orbital.
The other absorptions in the spectrum of 2 at lower ener-
gies should be related to transitions in which the r* orbital
is involved. This r* orbital must be strongly stabilized due
to the coordination of the NO ligand at the axial position
as evidenced by the elongated metal–metal bond distances
observed in this class of complexes [8–10].
Complex 2 is diamagnetic. This diamagnetism is com-
patible with two formulations, Ru24+(NO+) and
6+
Ru2 (NOꢁ), with electronic configurations r2p4d2(p*)4
and r2p4d2(d*)2, respectively. Nevertheless, the absorption
2.6. Cyclic voltammetry
band of NO at 1771 cmꢁ1 rejects the last configuration.
4+
Thus, a Ru2 core seems to be more probable although
The redox behaviour of compounds 1 and 2 has been
investigated by cyclic voltammetry.
Complex 1 shows two quasi-reversible cathodic pro-
cesses and two anodic peaks due to irreversible reductions
(Table 1). This voltammogram can be explained consider-
a Ru25+(NO) formulation with low spin configuration
r2p4d2(p*)3 and a strong antiferromagnetic coupling
5+
between the unpaired electrons of the Ru2 unit and the
NO radical cannot be discarded.

1600
M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
Table 1
Half-wave potentials of diruthenium complexes in CH2Cl2 solution under N2
Compound
Formal OE
1st oxid.
1st red.
2nd red.
Reference
5+
[Ru2(O2CMe)(DPhF)3(CO)]BF4
Ru2
0.93
0.61a
0.28
ꢁ0.11
ꢁ0.64a
ꢁ1.17
0.09
This workb
4+
Ru2(DPhF)4(CO)
[Ru2(O2CMe)(DPhF)3(NO)]BF4
Ru2(DPhF)4(NO)
a
Ru2
Ru2
Ru2
[11]
4+
ꢁ1.16
ꢁ1.24
This workb
[10]
3+
0.06
Potentials redox corresponding to the species [Ru2(O2CMe)(DPhF)3(CO)(BF4)].
The potential values were corrected to be compared with bibliographic data obtained vs. SCE.
b
˚
ing the presence of two species in equilibrium, [Ru2(O2C-
Me)(DPhF)3(CO)]+ and [Ru2(O2CMe)(DPhF)3(BF4)(CO)],
as described previously for similar compounds in the pres-
[1.148(11) A] bonds than 1 ꢀ CH2Cl2. These significant dif-
ferences can be attributed to a higher back-donation in
Ru2(DPhF)4(CO), richer in electron density than
1 ꢀ CH2Cl2. The same explanation could be inferred in
the comparison of Ru2(DPhF)4(NO) [10] and 2 ꢀ CH2Cl2.
However, the measurements of 2 ꢀ CH2Cl2 are quite similar
to those of Ru2(DPhF)4(NO) [10], despite the latter com-
ꢁ
ence of BF4 in high concentration [15]. The complex
[Ru2(O2CMe)(DPhF)3(CO)]+ is expected to be more diffi-
cult to oxidize and easier to reduce than [Ru2(O2C-
Me)(DPhF)3(BF4)(CO)]. Accordingly, the increase of
electrolyte concentration (NBu4BF4) reduces the intensity
of the cathodic process and the irreversible reduction that
appear at higher potentials. The electrochemical data of
3+
pound has been claimed as Ru2 species and contains a
fourth formamidinate group instead of the less donor ace-
tate ligand (Table 3). The Ru–N–O angle in 2 ꢀ CH2Cl2 is
closer to linearity [174.6(6)°] than in Ru2Cl(Fap)4(NO),
155.8(6)° [9], that has been formulated as Ru24+(NO+)
complex.
1
are also consistent with those described for
Ru2(DPhF)4(CO) taking into account the different oxida-
tion state of the diruthenium units in these complexes.
Complex 2 shows one quasi-reversible cathodic process
and one anodic peak due to an irreversible reduction
(Table 1). This behaviour is analogous to that observed
for Ru2Cl(O2CMe)(DPhF)3 [18] and Ru2Cl(O2CPh)-
(DPhF)3 [15]. Surprisingly, the redox potentials of 2 and
Ru2(DPhF)4(NO) are very similar in spite of the different
formal oxidation state proposed for these complexes. These
data confirm the difficulties to establish unequivocally the
oxidation states in nitrosyl compounds and that the
NO+–NOꢁ formalism seem to be also artificial.
Table 2
Crystallographic data for 1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2
1 ꢀ CH2Cl2
2 ꢀ CH2Cl2
Empirical formula
Formula weight
Crystal size (mm3)
Crystal system
Space group
C43H38BCl2F4N6O3Ru2 C42H38BCl2F4N7O3Ru2
1046.64
1048.64
0.15 ꢂ 0.18 ꢂ 0.19
0.17 ꢂ 0.23 ꢂ 0.26
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
˚
a (A)
11.7603(8)
12.2951(8)
17.0903(11)
105.4790(10)
90.4370(10)
111.2650(10)
2204.3(3)
2
11.7391(8)
12.2741(9)
17.0382(12)
105.4200(10)
90.2010(10)
111.3240(10)
2190.8(3)
2
˚
b (A)
2.7. X-ray crystallography
˚
c (A)
a (°)
b (°)
c (°)
Crystal data of complexes 1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2 are
given in Table 2. Selected geometric parameters of the com-
pounds are provided in Table 3.
3
˚
Volume (A )
Z
1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2 are isomorphous compounds
whose only constitutional difference is the atom linked at
the axial position of the diruthenium moiety, being carbon
in 1 ꢀ CH2Cl2 and nitrogen in 2 ꢀ CH2Cl2. Their molecular
structures are illustrated in Figs. 2 and 3, respectively. Both
complexes are constituted by eclipsed paddlewheel species
(Table 3) with three diphenylformamidinate and one ace-
tate ligands occupying the equatorial positions of the dime-
tallic units. An important feature of these structures is the
qcalc. (g cmꢁ3
)
1.577
0.869
1050
1.590
0.875
1052
l (mmꢁ1
F(000)
)
h Range (°)
Index ranges
1.86–23.28
ꢁ13 6 h 6 10,
ꢁ13 6 k 6 13,
ꢁ18 6 l 6 17
1.25–27.00
ꢁ14 6 h 6 14,
ꢁ15 6 k 6 10,
ꢁ20 6 l 6 21
13,318
Collected reflections 9883
Independent
6274 [0.0278]
9265 [0.0279]
reflections [Rint
Completeness (%) to 98.9–23.28
]
˚
96.9–27.00
9265/4/500
long Ru–Ru bond distances: 2.4502(9) and 2.4152(7) A for
h max (°)
1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2, respectively, although several
Data/restraints/
parameters
R1
6274/6/515
5+
4+
Ru2 [12,23] and Ru2 [9,11,24] complexes with d(Ru–
˚
Ru) > 2.40 A have been reported. In particular, the related
0.0722
0.2213
0.0648
0.2207
wR2 (all data)
complex Ru2(DPhF)4(CO) [11] has a very long Ru–Ru
˚
Largest differenceꢁi3n 2.225/ꢁ3.473
2.216/ꢁ2.481
bond distance (2.5544 A). This diruthenium(II) complex
˚
peak/hole (e A
)
˚
has shorter Ru–CO [1.913(10) A] and longer C–O

M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
1601
Table 3
Selected bond distances (A) and angles (°) for 1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2
˚
1 ꢀ CH2Cl2
2 ꢀ CH2Cl2
Ru2(DPhF)4(CO) [11]
Ru2(DPhF)4(NO) [10]
Ru(1)–Ru(2)
Ru(1)–Lax.
2.4502(9)
2.033(11)
1.105(12)
2.089(6)
2.061(6)
2.037(12)
1.997(12)
176.0(3)
177.3(9)
ꢁ0.7(2)
2.4152(7)
1.834(6)
1.148(8)
2.088(5)
2.084(4)
2.062(9)
1.981(9)
176.74(18)
174.6(6)
0.87(17)
2.5544(8)
1.913(10)
1.148(11)
2.4444(13)
1.809(11)
1.142(12)
X–O (Lax.
)
Ru(1)–O(1)
Ru(2)–O(2)
Ru(1)–Neq. (av.)
Ru(2)–Neq. (av.)
Ru(2)–Ru(1)–Lax.
Ru(1)–Xax.–O(3)
O(1)–Ru(1)–Ru(2)–O(2)
2.069(3)
2.028(3)
180
2.044
180
180
180
Selected bond distances and angles for Ru2(DPhF)4(CO) and Ru2(DPhF)4(NO) are given for comparison.
Fig. 2. PLUTO view of [Ru2(O2CMe)(DPhF)3(CO)](BF4) ꢀ CH2Cl2 (1 ꢀ CH2Cl2). Crystallization solvent molecule and hydrogen atoms are omitted for
clarity.
3. Conclusions
combined with the presence of a carboxylate bridging
ligand may be the reason why it was not possible to isolate
the cyanide derivative.
In this work, we have presented the first example of a
5+
Ru2 carbonyl complex isolated and structurally charac-
terized, 1 ꢀ CH2Cl2, which is air stable in the solid state
4. Experimental
and in solution. This Ru25+ compound completes the series
4+
of Ru22+, Ru23+, and Ru2 carbonyl derivatives. The iso-
4.1. Materials and equipment
morphous compound 2 ꢀ CH2Cl2 can be described as a
Ru24+(NO+) low spin complex taking into account its dia-
magnetism, IR and visible spectra, and its crystal structure.
The higher basicity of CNꢁ with respect to NO+ and CO
All reactions were carried out under nitrogen atmo-
sphere by using conventional Schlenk techniques and dried
solvents. Subsequent manipulations were carried out in

1602
M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
Fig. 3. PLUTO view of [Ru2(O2CMe)(DPhF)3(NO)](BF4) ꢀ CH2Cl2 (2 ꢀ CH2Cl2). Crystallization solvent molecule and hydrogen atoms are omitted for
clarity.
open air. Chemicals were purchased from commercial
sources and used without further purification. Ru2Cl(O2C-
Me)(DPhF)3 [18] and [Ru2(O2CMe)(DPhF)3(H2O)]BF4 ꢀ
0.5CH2Cl2 [19] were prepared by following published pro-
cedures. Elemental analyses were done by the Microanalyt-
ical Service of the Complutense University of Madrid. IR
spectra were obtained with a FT Midac prospect spectro-
photometer using KBr pellets. Electronic spectra of the
complexes in dichloromethane solution (ꢃ10ꢁ4 M) and in
the solid state (Nujol mulls) were acquired on a Cary 5G
spectrophotometer. Mass spectra were recorded on a Bru-
ker Esquire-LC with Electrospray Ionization. Nominal
molecular masses and distribution isotopic of all peaks
were calculated with the MASAS [25] computer program,
using a polynomial expansion based on natural abun-
dances of the isotopes. Variable-temperature magnetic sus-
ceptibility measurements were performed on a Quantum
Design MPMSXL SQUID magnetometer. All data were
corrected for the diamagnetic contribution to the suscepti-
bility of both the sample holder and the compound. Molar
diamagnetic corrections were calculated on the basis of
Pascal’s constants. The NMR spectra of 2 in CD2Cl2 solu-
tion were acquired on a Bruker Avance DPX 300 MHz in
the NMR Service of the Complutense University of
Madrid. Electrochemical measurements were done using
a MicroAutolab Type III potentiostat, with the general-
purpose electrochemical system (GPES) (EcoChemie
B.V.) electrochemical software. A three-electrode system
was used and consisted of a glassy carbon disk working
electrode, a platinum wire counter electrode, and a Ag/
AgCl reference electrode. The experiments were performed
at room temperature under a nitrogen atmosphere, in
dichloromethane solutions that contained 0.1 M NBu4BF4
as the supporting electrolyte, with a scan rate of
100 mV sꢁ1. Under our experimental conditions, the oxida-
tion of ferrocene was located at E1/2 = +0.625 V.
4.2. Synthesis of [Ru2(O2CMe)(DPhF)3(CO)](BF4) ꢀ
CH2Cl2 (1 ꢀ CH2Cl2) and [Ru2(O2CMe)(DPhF)3-
(CO)](BF4) ꢀ THF (1 ꢀ THF)
A
solution of [Ru2(O2CMe)(DPhF)3(H2O)](BF4) ꢀ
0.5CH2Cl2 (0.1040 g, 0.105 mmol) in freshly distilled
CH2Cl2 (10 mL) was bubbled with CO for 1 h at room tem-
perature until all the solvent was gone and the solid was
dried. The yield of 1 ꢀ CH2Cl2 was quantitative. Anal. Calc.
for C43H38BCl2F4N6O3Ru2: C, 49.34; H, 3.66; N, 8.03.
Found: C, 49.32; H, 3.58; N, 7.90%. IR (KBr): m (cmꢁ1
)
(intensity): 3058 (w), 2016 (vs), 1590 (m), 1530 (s), 1486
(vs), 1438 (m), 1316 (m), 1306 (m), 1212 (vs), 1068 (s),
1024 (s), 999 (m), 939 (m), 781 (m), 768 (s), 759 (s), 737
(m), 695 (s), 535 (w), 455 (m), 436 (m). Visible (Nujol): k
(nm) 390sh, 490sh, 587, 710sh, 860sh. Visible (CH2Cl2): k
(nm) 390sh, 485sh, 584, 650sh, 815sh. MS-ESI+ (CHCl3):

M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
1603
m/z 848 (M+ꢁCO, 100%). leff at r.t. (lB): 2.03. Crystals of
1 ꢀ CH2Cl2 suitable for X-ray analysis were obtained by dif-
fusion of hexane on a solution of the compound in CH2Cl2.
Compound 1 ꢀ THF was obtained when THF was used
instead of CH2Cl2 in the crystallization process. Anal.
Calc. for C46H44BF4N6O4Ru2: C, 53.44; H, 4.29; N, 8.13.
were refined for the fluorine atoms of BF4 and the chlorine
atoms of CH2Cl2. In 2 ꢀ CH2Cl2, only coordinates were
refined for the fluorine atoms of BF4, while the chlorine
atoms of CH2Cl2 were located in a Fourier synthesis,
included and fixed. In all cases, hydrogen atoms were
included in calculated positions and refined riding on the
respective carbon atoms.
Found: C, 53.46; H, 4.43; N, 7.92%. IR (KBr): m (cmꢁ1
)
(intensity): 3059 (w), 2024 (vs), 1591 (m), 1532 (s), 1487
(vs), 1437 (m), 1316 (s), 1212 (vs), 1065 (vs), 1025 (s), 999
(m), 939 (m), 780 (m), 759 (s), 695 (s), 535 (w), 453 (m),
436 (m). leff at r.t. (lB): 2.24.
Acknowledgement
We thank the financial support by the Spanish M. E. C.
(CTQ 2005-00397) and C. A. M. (S-0505-MAT-0303).
4.3. Synthesis of [Ru2(O2CMe)(DPhF)3(NO)](BF4) ꢀ
CH2Cl2 (2 ꢀ CH2Cl2)
Appendix A. Supplementary material
To a solution of Ru2Cl(O2CMe)(DPhF)3 (0.2003 g,
0.227 mmol) in freshly distilled THF (15 mL) was added
NOBF4 (0.0265 g, 0.227 mmol) in THF (10 mL). After
2 h of stirring, the volatile components were removed
and the solid was recrystallized from CH2Cl2/hexane.
CCDC 663295 and 663296 contain the supplementary
crystallographic data for 1 ꢀ CH2Cl2 and 2 ꢀ CH2Cl2. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this
article can be found, in the online version, at
doi:10.1016/j.jorganchem.2007.11.025.
Yield:
0.1619
(81%).
Anal.
Calc.
for
C42H38BCl2F4N7O3Ru2: C, 48.11; H, 3.65; N, 9.35.
Found: C, 48.09; H, 3.61; N, 9.32%. IR (KBr): m
(cmꢁ1) (intensity): 3059 (w), 1771 (vs), 1590 (m), 1526
(s), 1487 (vs), 1438 (m), 1309 (m), 1210 (vs), 1083 (s),
1028 (m), 940 (m), 780 (m), 760 (s), 695 (s), 452 (m),
436 (m). Visible (Nujol): k (nm) 504, 690, 850sh. Visible
(CH2Cl2): k (nm) 411, 494, 665. MS-ESI+ (CHCl3): m/z
878 (M+, 100%). 1H NMR (CD2Cl2, 23 °C) d: 9.22 (s,
2H, NCHN), 8.62 (s, 1H, NCHN), 7.25–7.45 (m, 15H),
7.15 (t, 1H), 7.08 (m, 4H), 7.02 (t, 2H), 6.92 (m, 4H),
6.78 (m, 2H), 6.42 (d, 2H), 2.52 (s, 3H, CH3). 13C{1H}
NMR (CD2Cl2, 24 °C) d: 190.37 (CO2), 173.97, 172.85
(NCHN), 154.74, 154.68, 154.47, 153.65, 130.90, 130.23,
129.92, 129.83, 128.32, 128.28, 127.61, 127.14, 123.25,
123.15, 122.83, 122.01 (NPh), 24.14 (CH3). Crystals of
2 ꢀ CH2Cl2 suitable for X-ray analysis were collected after
a slow diffusion of hexane over a dichloromethane solu-
tion of the compound.
References
[1] E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehensive
Organometallic Chemistry, Pergamon Press, Oxford, 1995.
[2] G. Wilkinson (Ed.), Comprehensive Coordination Chemistry, vol. 2,
Pergamon Press, Oxford, 1987.
[3] (a) G.B. Ritchter-Addo, P. Legzdins, Metal Nitrosyls, Oxford
University Press, New York, 1992;
(b) J.N. Armor (Ed.), Environmental Catalysis, ACS Symp. Ser., 1993.
[4] (a) M. Feelisch, J.S. Stamler (Eds.), Methods in Nitric Oxide
Research, Wiley, Chichester, UK, 1996;
(b) L.J. Ignaro (Ed.), Nitric Oxide: Biology and Pathobiology,
Academic Press, San Diego, CA, 2000;
(c) F.C. Fang (Ed.), Nitric Oxide and Infection, Kluwer Academic/
Plenum, New York, 1999.
[5] F. Roncaroli, M. Videla, L.D. Slep, J.A. Olabe, Coord. Chem. Rev.
251 (2007) 1903.
[6] F.A. Cotton, C.A. Murillo, R.A. Walton (Eds.), Multiple Bonds
between Metal Atoms, third ed., Springer Science and Business Media
Inc., New York, 2005.
4.4. X-ray structure determinations
[7] (a) F.A. Cotton, A. Yokochi, Inorg. Chim. Acta 275–276 (1998) 557;
´
(b) M.C. Barral, R. Jimenez-Aparicio, E.C. Royer, F.A. Urbanos,
Data collection for all compounds were carried out at
room temperature on a Bruker Smart CCD diffractometer
using graphite-monochromated Mo Ka radiation (k =
A. Monge, C. Ruiz-Valero, Polyhedron 10 (1991) 113.
[8] A.J. Lindsay, G. Wilkinson, M. Motevalli, M.B.J. Hursthouse, J.
Chem. Soc., Dalton Trans. (1987) 2723.
[9] J.L. Bear, J. Welhoff, G. Royal, E.V. Caemelbecke, S. Eapen, K.M.
Kadish, Inorg. Chem. 40 (2001) 2282.
[10] B. Han, J. Shao, Z. Ou, T.D. Phan, J. Shen, J.L. Bear, K.M. Kadish,
Inorg. Chem. 43 (2004) 7741.
[11] K.M. Kadish, B. Han, J. Shao, Z. Ou, J.L. Bear, Inorg. Chem. 40
(2001) 6848.
[12] M.C. Barral, R. Gonzalez-Prieto, S. Herrero, R. Jimenez-Aparicio,
J.L. Priego, E.C. Royer, M.R. Torres, F.A. Urbanos, Polyhedron
23 (2004) 2637.
[13] J.L. Bear, B. Han, S. Huang, K.M. Kadish, Inorg. Chem. 35 (1996)
3012.
˚
0.71073 A) operating at 50 kV and 10 mA. In all cases,
the data were collected over a hemisphere of the reciprocal
space by combination of three exposure sets, each exposure
was of 30 and 20 s for 1 and 2, respectively, and covered
0.3° in x. The first 50 frames were recollected at the end
of the data collection to monitor crystal decay. A summary
of the fundamental crystal and refinement data are given in
Table 2.
The structures were solved by direct methods and
refined by full-matrix least-square procedures on F2 [26].
All non-hydrogen atoms were refined anisotropically, with
some exceptions. Thus, in 1 ꢀ CH2Cl2 only coordinates
´
´
[14] F.A. Cotton, E.V. Dikarev, S. Herrero, Inorg. Chem. 37 (1998) 5862.
[15] M.C. Barral, T. Gallo, S. Herrero, R. Jimenez-Aparicio, M.R.
´
Torres, F.A. Urbanos, Inorg. Chem. 45 (2006) 3639.

1604
M.C. Barral et al. / Journal of Organometallic Chemistry 693 (2008) 1597–1604
´
[16] F.A. Cotton, S. Herrero, R. Jimenez-Aparicio, C.A. Murillo, F.A.
(b) G.-L. Xu, T. Ren, Organometallics 24 (2005) 2564;
(c) P. Angaridis, F.A. Cotton, C.A. Murillo, X. Wang, Acta
Crystallogr., Sect. C.: Cryst. Struct. Commun. 61 (2005) m71;
(d) M. Ebihara, N. Nagaya, N. Kawashima, T. Kawamura, Inorg.
Chim. Acta 351 (2003) 305;
´
Urbanos, D. Villagran, X. Wang, J. Am. Chem. Soc. 129 (2007) 12666.
[17] M.C. Barral, R. Jimenez-Aparicio, J.L. Priego, E.C. Royer, F.A.
´
Urbanos, Inorg. Chim. Acta 277 (1998) 76.
´
[18] M.C. Barral, S. Herrero, R. Jimenez-Aparicio, M.R. Torres, F.A.
Urbanos, Inorg. Chem. Commun. 7 (2004) 42.
(e) G.G. Briand, M.W. Cooke, T.S. Cameron, H.M. Farrell, T.J.
Burchell, M.A.S. Aquino, Inorg. Chem. 40 (2001) 3267;
(f) G. Xu, T. Ren, Inorg. Chem. 40 (2001) 2925;
´
[19] M.C. Barral, S. Herrero, R. Jimenez-Aparicio, M.R. Torres, F.A.
Urbanos, Angew. Chem. Int. Ed. 44 (2005) 305;
´
M.C. Barral, S. Herrero, R. Jimenez-Aparicio, M.R. Torres, F.A.
(g) C. Lin, T. Ren, E.J. Valente, J.D. Zubkowski, J. Organomet.
Chem. 579 (1999) 114.
Urbanos, Angew. Chem. 117 (2005) 309.
[20] (a) F.A. Cotton, L.R. Falvello, T. Ren, K. Vidyasagar, Inorg. Chim.
Acta 194 (1992) 163;
´
[24] (a) P. Angaridis, F.A. Cotton, C.A. Murillo, D. Villagran, X. Wang,
Inorg. Chem. 43 (2004) 8290;
(b) F.A. Cotton, A. Yokochi, Inorg. Chem. 37 (1998) 2723.
(b) F.A. Cotton, L.R. Falvello, T. Ren, K. Vidyasagar, Inorg. Chim.
Acta 194 (1992) 163;
´
[21] M.C. Barral, T. Gallo, S. Herrero, R. Jimenez-Aparicio, M.R. Torres,
F.A. Urbanos, Chem. Eur. J. (2007) (published on line – September
28, 2007). doi:10.1002/chem.200700494.
(c) F.A. Cotton, T. Ren, Inorg. Chem. 30 (1991) 3675;
(d) F.A. Cotton, M. Matusz, J. Am. Chem. Soc. 110 (1988) 5761.
[25] F.A. Urbanos, MASAS Program, Version 3.1, Complutense University
of Madrid, Madrid, Spain, 2002.
´
[22] P. Angaridis, F.A. Cotton, C.A. Murillo, D. Villagran, X. Wang, J.
Am. Chem. Soc. 127 (2005) 5008.
[23] (a) T.J. Burchell, T.S. Cameron, D.H. Macartney, L.K. Thompson,
M.A.S. Aquino, Eur. J. Inorg. Chem. (2007) 4021;
[26] G.M. Sheldrick, SHELX97, Program for Refinement of Crystal
Structure, University of Go¨ttingen, Go¨ttingen, Germany, 1997.