Ruthenium hydrides bearing SbPh3 and AsPh3 ligands: Characterization of the bis(dihydrogen) complexes [Cp*Ru(H2)2(EPh3)]+ (Cp* = C5Me5; E = Sb, As)

Article abstract of DOI:10.1016/S0022-328X(02)01965-4

Reaction of NaBH₄ with [Cp*RuCl₂(EPh₃)] (E = Sb 1a, As 1b) in THF/EtOH affords the trihydride complexes [Cp*RuH₃(EPh₃)] (E = Sb 2a, As 2b) in good yield. These trihydrides are protonated by HBF_4<

Full text of DOI:10.1016/S0022-328X(02)01965-4

Journal of Organometallic Chemistry 663 (2002) 151ꢄ157
/
www.elsevier.com/locate/jorganchem
Ruthenium hydrides bearing SbPh3 and AsPh3 ligands:
characterization of the bis(dihydrogen) complexes
[CpꢀRu(H2)2(EPh3)]ꢁ (Cpꢀꢂ
/
C5Me5; Eꢂ
/
Sb, As)
Halikhedkar Aneetha, Manuel Jime´nez Tenorio, M. Carmen Puerta, Pedro Valerga ꢀ
´ ´ ´ ´ ´
Departamento de Ciencia de Materiales e Ingenierıa Metalurgica y Quımica Inorganica, Facultad de Ciencias, Universidad de Cadiz, 11510 Puerto Real,
´
Cadiz, Spain
Received 31 May 2002; accepted 23 September 2002
This paper is dedicated to Professor Pascual Royo
Abstract
Reaction of NaBH4 with [CpꢀRuCl2(EPh3)] (Eꢂ
(EꢂSb 2a, As 2b) in good yield. These trihydrides are protonated by HBF4×
bis(dihydrogen) complexes [CpꢀRu(H2)2(EPh3)][BF4] (Eꢂ
/
Sb 1a, As 1b) in THF/EtOH affords the trihydride complexes [CpꢀRuH3(EPh3)]
/
/
OEt2 in CH2Cl2 at ꢃ80 8C furnishing the cationic
/
1
/
Sb 3a, As 3b), which were characterized in solution by T1 and JHD
?
measurements. These species are unstable and decompose at T ꢀ
/
0 8C. The reaction of [CpꢀRuCl(SbPh3)2] with H2 and NaBAr4 in
?
fluorobenzene yields the dihydride [CpꢀRuH2(SbPh3)2][BAr4] (5). Protonation of the monohydride [CpꢀRuH(SbPh3)2] (6) by
HBF4×
/
OEt2 in CH2Cl2 at ꢃ
/
80 8C generates the dihydrogen complex [CpꢀRu(H2)(SbPh3)2]ꢁ (7), which rearranges to its dihydride
tautomer 5 when the temperature is raised.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Hydride complexes; Dihydrogen complexes; Ruthenium; Stibine; Arsine
1. Introduction
dihydrogen ligand and two hydrides, hence it can be
formulated as [CpꢀOsH2(H2)(PPh3)][BF4] [8]. In the case
of ruthenium, attempts to protonate [CpꢀRuH3(PR3)]
The number of dihydrogen complexes bearing more
than one dihydrogen ligand is very limited. Accordingly
only a few bis(dihydrogen) complexes have been char-
acterized [1], and only four of them have been isolated:
[RuH2(H2)2(PCy3)2] [2], [TpꢀRuH(H2)2], [Tp?RuH(H2)2]
(PR3ꢂ
/
PPh3, PCy3) with HBF4×/Et2O immediately led to
extensive dihydrogen evolution and even dehydrogena-
tion of one cyclohexyl ring of the PCy3 ligand [9]. It has
been
previously
noted
for
the
derivatives
[CpꢀRuH3(PR3)], particularly those containing bulky
phosphine ligands such as PiPr3 or PCy3, the occurrence
of quantum exchange coupling (QEC). The hydride
signals in the 1H-NMR spectrum of compounds in
which QEC occurs exhibit large, temperature dependent
(Tpꢀꢂ
hydrotris(3-isopropyl-4-bromo-pyrazolyl)borate)
and very recently [RuH2(H2)2(PiPr3)2] [4]. Protonation
of the trihydride complexes [CpꢀMH3(PR3)] (MꢂRu,
Os) [5ꢄ7] is a route that should lead to complexes of
general formula [CpꢀMH4(PR3)]ꢁ. Thus, protonation
of [CpꢀOsH3(EPh3)] (EꢂP, As) with HBF4×Et2O
/
hydrotris(3,5ꢄ
/
dimethylpyrazolyl)borate; Tp?ꢂ
/
[3],
/
/
HꢄH coupling constants [6,10]. These quantum me-
/
chanical exchange couplings can be modulated through
hydrogen bonding. Thus, addition of various proton
donors such as methanol, indole, phenol, or hexafluor-
oisopropanol to [CpꢀRuH3(PCy3)] leads to an increase
of the quantum mechanical exchange couplings between
the hydride sites. This has been interpreted in terms of a
‘‘weak’’ interaction (hydrogen bonding) between
[CpꢀRuH3(PCy3)] and the proton donors added, with
/
/
yielded the corresponding [CpꢀOsH4(EPh3)][BF4] deri-
vatives. A neutron diffraction study performed on the
PPh3 complex showed it to contain one ‘‘elongated’’
ꢀ Corresponding author. Fax: ꢁ
/
34-956-016-288
E-mail address: pedro.valerga@uca.es (P. Valerga).
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 9 6 5 - 4

152
H. Aneetha et al. / Journal of Organometallic Chemistry 663 (2002) 151ꢄ
/157
˚
HÁ Á ÁH separations of 1.92 A as inferred from the
decrease in the value of the minimum longitudinal
relaxation time (T1)min [11]. More recently, the species
[CpꢀRuH4(PCy3)]ꢁ has been identified as a result of the
protonation of the hydrogen-bonded complex
[CpꢀRuH3(PCy3)]Á Á Á[HOR] (Rꢂ
by (CF3)2CHOH or (CF3)3COH in CDClF2/CDCF3 at
200 [12]. An analogous complex, [CpꢀRu-
/CH(CF3)2, C(CF3)3)
K
H4(PPhiPr2)]ꢁ, had already been postulated as one of
the species involved in the reaction of [CpꢀRuH3(P-
(PPhiPr2)] with CF3CH2OH [13]. T1 measurements for
[CpꢀRuH4(PCy3)]ꢁ are consistent with a dihydrido(di-
hydrogen) structure [CpꢀRuH2(H2)(PCy3)]ꢁ, although
a bis(dihydrogen) structure [CpꢀRu(H2)2(PCy3)]ꢁ can-
not be excluded [12].
Werner and co-workers have reported the preparation
of the ruthenium dihydrido(dihydrogen) complex
[RuH2(H2)(SbiPr3)3] [14], as well as a number of other
novel organometallic compounds bearing triisopropyl-
stibine as co-ligand [15,16]. It is known that despite the
poorer donor properties of stibines compared to phos-
phine or arsine ligands, they can otherwise form very
similar complexes [17], although these tend to adopt
higher coordination numbers (i.e. [RuCl2(SbPh3)4] ver-
sus [RuCl2(PPh3)3] [18]) as well as a reduced tendency to
dissociation in solution in contrast with their phosphine
homologues.
Scheme 1.
tively (Scheme 1). Thus, the validity of the synthetic
procedure for the preparation of trihydride derivatives
of the type [CpꢀRuH3(PR3)] is not only restricted to
phosphine ligands [5,6], and can be easily adapted for
the preparation of stibine and arsine hydride complexes.
Complexes 2a and 2b display strong n(RuH) absorption
bands near 2000 cmꢃ1 in their IR spectra. The hydride
ligands in these complexes give rise to one sharp
resonance in their 1H-NMR spectra. This resonance
does not experiment decoalescence when the tempera-
ture is lowered down to ꢃ90 8C, remaining relatively
/
sharp even at this temperature. A (T1)min of 210 ms was
measured for the hydride protons of 1a, the value being
190 ms for 2b (CD3C6D5, 400 MHz, 213 K in both
cases). These values point out to a formulation as RuIV
We have now shown that at variance with PPh3, both
SbPh3 and AsPh3 are effective co-ligands for the
stabilization of the rutheniumꢄ
complexes [CpꢀRu(H2)2(EPh3)][BF4] (Eꢂ
which are obtained by protonation of the trihydrides
[CpꢀRuH3(EPh3)] with HBF4×OEt2 in CD2Cl2 at
80 8C. The synthesis and spectral properties of these
/dihydrogen bond in
trihydrides like [CpꢀRuH3(PR3)] derivatives (PR3ꢂ
/
/
Sb, As),
PMe3, PPh3, PiPr3, PCy3) [5,6], rather than to hydri-
do(dihydrogen) complexes like [TpꢀRuH(H2)(PCy3)] [3]
/
or [TpRuH(H2)(PR3)] (Tpꢂ
/
Hydrotris(pyrazolyl)bo-
21]. It has been
ꢃ
/
rate, PR3ꢂ
/
PPh3, PCy3, PMeiPr2) [19ꢄ
/
species, as well as the study of the relative stability of
dihydride and dihydrogen tautomers of [CpꢀRu-
H2(SbPh3)2]ꢁ are presented in this work.
previously noted for the derivatives [CpꢀRuH3(PR3)]
the occurrence of quantum mechanical exchange cou-
pling (QEC) [6,10ꢄ12]. In the case of 1a or 1b, there is
/
no evidence for QEC at the lowest temperature mea-
sured (183 K). However, QEC cannot be observed in a
fluxional spectrum. Since the static spectrum was not
observed because the minimum temperature reached
was not low enough, the occurrence of QEC in these
complexes is therefore still possible. Consistent with
their formulation as ‘‘classical’’ RuIV trihydrides, com-
plexes 1a and 1b are quite stable towards thermal
reductive elimination of dihydrogen. Thus, they do not
react with unsaturated molecules such as ethylene,
phenylacetylene or thiophene. However, they react
slowly with chlorinated solvents such as dichloro-
methane, losing the hydride ligands as inferred from
NMR studies.
2. Results and discussion
[{CpꢀRuCl2}n] reacts with SbPh3 or AsPh3 in di-
chloromethane or acetone yielding the corresponding
derivatives [CpꢀRuCl2(EPh3)] (EꢂSb 1a, As 1b) in
good yield. These compounds are homologues of the
known phosphine complex [CpꢀRuCl2(PPh3)], which is
prepared in a similar fashion [5,6]. The derivative
[CpꢀRuCl2(SbiPr3)] has also been synthesized, and
unequivocally characterized by X-ray crystallography
/
[15]. Complexes 1a and 1b are redꢄorange paramagnetic
/
materials. Their effective magnetic moment value of 1.7
mB for 1a, and 1.9 mB for 1b in solution suggests the
presence of one unpaired electron, as expected.
Protonation of 2a and 2b in CD2Cl2 at ꢃ
HBF4×OEt2 generates in solution the bis(dihydrogen)
complexes [CpꢀRu(H2)2(EPh3)][BF4] (EꢂSb 3a, As 3b).
Attempts made to prepare the homologous PPh3
/
80 8C using
/
Both 1a and 1b react with NaBH4 in THFꢄethanol
/
affording the RuIV trihydride complexes [CpꢀRu-
H3(SbPh3)] (2a) and [CpꢀRuH3(AsPh3)] (2b), respec-
/

H. Aneetha et al. / Journal of Organometallic Chemistry 663 (2002) 151ꢄ
/157
153
compound [CpꢀRu(H2)2(PPh3)]ꢁ had been unsuccess-
ful, because this compound is unstable towards loss of
H2 [9]. The dihydrogen ligands in these complexes give
rise to one single resonance in their respective 1H-NMR
spectra at ꢃ
/
7.79 ppm for 3a, and ꢃ7.14 for 3b. These
/
resonances become broader when the temperature is
lowered, but no decoalescence is observed (Fig. 1). The
variation of T1 for the dihydrogen resonance in 3a and
3b with the absolute temperature is shown in Fig. 2.
From this plot, the corresponding (T1)min for 3a (11.2
ms at 210 K) and 3b (11.0 ms at 221 K) are obtained.
Fig. 2. Plot of the T1 values for 3a and 3b versus temperature (K).
Attempts to protonate 2aꢄ2b using HBF4/D2O in order
/
1
to determine the value of JHD failed. The dihydrogen
complex decomposes and apparently, species containing
coordinated D2O/HDO are generated. Alternatively, we
protonated the complexes [CpꢀRuD3(EPh3)] with
˚
H separation of 1.014(11) A in the
ture, with a Hꢄ
/
dihydrogen ligand. In this complex rapid scrambling
between hydride and dihydrogen sites occurs, and
decoalescence of the hydride resonance was only ob-
served for the derivative [CpꢀOsH2(H2)(AsPh3)][BF4] at
HBF4×
were able to generate the isotopomers [CpꢀRu-
(HD)(D2)(EPh3)]ꢁ (Eꢂ
Sb, As). The high-field NMR
/
OEt2 in CD2Cl2 at ꢃ
/
80 8C. In this fashion we
ꢃ
/
140 8C (in CDFCl2), suggesting a free energy of
/
activation of 6.0 kcal molꢃ1 for the hydrideꢄ
gen exchange in this case [8]. Consistent with this, the
/
dihydro-
resonance (Fig. 3) appears as a non-binomial septet for
both 3a and 3b, indicating the coupling to three
deuterium atoms and therefore confirming the presence
of four hydrogen atoms attached to ruthenium. The
1
values of (T1)min and JHD are averaged, as expected.
However, this behaviour has not been observed in the
case of 3a and 3b, which exhibit the shortest (T1)min
1
obs
HD
value of the averaged J
for 3a, and 9.9 Hz for 3b. Assuming that JHD
coupling constants is 9.3 Hz
2
1
values and the largest J
obs
HD
coupling constants among
the compounds shown in Table 1. Both the variation of
ꢁ0 Hz,
/
1
these values lead to a JHD coupling constant within
coordinated H-D of 27.9 Hz for 3a, and 29.7 Hz for 3b.
In Table 1 a compilation of NMR data is shown for
the known bis(dihydrogen) complexes, plus data for the
related complex [CpꢀOsH2(H2)(PPh3)][BF4]. Structural
characterization by neutron diffraction of [CpꢀOsH2-
(H2)(PPh3)][BF4] showed a dihydride(dihydrogen) struc-
1
T1 with temperature as well as the JHD coupling
constants point out to a formulation as bis(dihydrogen)
derivatives. If the equilibrium shown in Eq. (1) indeed
occurs in our system, it would be most likely shifted to
the left.
[CpꢀRu(H2)2(EPh3)]ꢁ X[CpꢀRuH2(H2)(EPh3)]ꢁ
(1)
The (T1)min value of 14.4 ms reported for the species
[CpꢀRuH4(PCy3)]ꢁ is close to ours for 3a and 3b, but in
that case it was not possible to measure JHD [12],
1
leaving doubts on its formulation either as
[CpꢀRuH2(H2)(PCy3)]ꢁ or [CpꢀRu(H2)2(PCy3)]ꢁ.
1JHD and (T1)min can be used for the determination of
the Hꢄ
/
H separation in these complexes. Thus using the
equation developed by Morris and co-workers [22],
rHH ꢂ1:42ꢃ0:0167(1JHD
)
(2)
˚
the calculated values for rHH are 0.95 A for 3a, and 0.92
˚
A for 3b. rHH can be also estimated using the equation
rHH ꢂK[(T1)min=n]1=6
(3)
(T1)min is in seconds, n is the frequency of the spectro-
meter in MHz, and K is a constant which takes the
values 5.815 if no rotation of the dihydrogen ligand is
considered, or 4.611 if there is a fast rotation of the
dihydrogen ligand [22,23]. In our case, for each of the
two possible situations the resulting rHH values are 1.01/
˚
0.80 A for both 3a and 3b. The rHH calculated using
Fig. 1. Variable temperature 1H-NMR spectra (400 MHz) in the high-
(T1)min assuming no rotation of the dihydrogen ligand
are closer to the values determined using 1JHD. In fact, it
field region of [CpꢀRu(H2)2(SbPh3)][BF4] (3a).

154
H. Aneetha et al. / Journal of Organometallic Chemistry 663 (2002) 151ꢄ157
/
1
Fig. 3. High field H-NMR signal of [CpꢀRuHD3(SbPh3)][BF4] (3a-d3) showing the expected non-binomial septet pattern (400 MHz, CD2Cl2, 263
K).
is recognized that only in a few cases is it necessary to
invoke the fast rotation model to produce a reasonable
of coordinatively unsaturated hydrides of the type
[CpꢀRuH2(EPh3)]ꢁ, formed upon dihydrogen elimina-
Hꢄ
using (T1)min data should consider static rotation
around the MꢄH2 axis [24].
/
H distance in the H2 ligand, and rHH determination
tion from 3aꢄ3b, prior to the rearrangement to the
/
sandwich species [CpꢀRu(h6-C6H5EPh2)]ꢁ, although
other possibilities, i.e. products of the reaction with
the solvent, species containing coordinated H2O coming
from the acid, etc., cannot be ruled out.
/
The complexes 3a and 3b are stable in CD2Cl2
solution up to 0 8C. Above this temperature, the
dihydrogen resonance disappears, and signals corre-
sponding to at least two new species appear (Fig. 1).
Several multiplet resonances between 5.0 and 6.0 ppm
are indicative of the formation of a p-arene complex,
most likely [CpꢀRu(h6-C6H5EPh2)]ꢁ, which is consis-
tent with the release of the dihydrogen ligands and
subsequent rearrangement of the coordinated EPh3
from h1 to h6 (Scheme 1). Apart from this, new hydride
Once it is clear that SbPh3 and AsPh3 ligands can
stabilize the rutheniumꢄdihydrogen bond in a manner
/
similar or even better than PPh3, it seems logical to
assume that species of the type [CpꢀRu(H2)(EPh3)2]ꢁ
(Eꢂ
/
Sb, As) might also be accessible, just like their
27]. We carried out
congeners [CpꢀRu(H2)(PR3)2]ꢁ [25ꢄ
/
the reduction with zinc dust of [{CpꢀRuCl2}n] in THF
in the presence of two equivalents of either SbPh3 or
AsPh3, in an attempt to prepare the chloro-complexes
[CpꢀRuCl(EPh3)2] as starting materials. The reaction
with AsPh3 gave a mixture of products, but from the
resonances appears near ꢃ8.4 ppm for both 3a and 3b.
/
It is not clear what these new hydridic species might be,
but they seem to be intermediates in the decomposition
of the bis(dihydrogen) complexes, since they also
disappear on standing, and complex mixtures are
obtained at room temperature. We can tentatively think
SbPh3 reaction yellowꢄorange [CpꢀRuCl(SbPh3)2] (4)
/
was isolated in pure form and in good yield. Halide
?
abstraction using NaBAr4 (Ar?ꢂ/3,5-C6H3(CF3)2) in
Table 1
Compilation of NMR data for bis(dihydrogen) complexes and related species
a
obs
Compound
d(H2) (ppm)
(T1)min (ms)
1JHD
(Hz)
Ref.
b
[RuH2(H2)2(PCy3)2]
[TpꢀRuH(H2)2]
[Tp?RuH(H2)2]
ꢃ7.9 (C6D6, 298 K)
45.0
ꢄ
/
[1,2]
[1,3]
ꢃ11.26 (C6D6, 298 K)
ꢃ11.82 (C6D6, 298 K)
ꢃ8.31 (THF-d8, 298 K)
ꢃ9.61 (CD2Cl2, 296 K)
ꢃ8.4 (CDClF2/CDF3, 200 K)
ꢃ7.79 (CD2Cl2, 193 K)
ꢃ7.14 (CD2Cl2, 193 K)
26
28
5.4
5.2
4.0
3.6
[3]
[4]
c
[RuH2(H2)2(Pi Pr3)2]
[CpꢀOsH2(H2)(PPh3)]ꢁ
[CpꢀRuH4(PCy3)]ꢁ
[CpꢀRu(H2)2(SbPh3)]ꢁ
[CpꢀRu(H2)2(AsPh3)]ꢁ
48.0
79.2
d
[8]
e
14.4
ꢄ/
9.3
9.9
[12]
This work
This work
11.2
11.0
a
All data extrapolated at 400 MHz, for comparison purposes.
60 ms at 500 MHz.
28 ms at 250 MHz.
b
c
d
e
99 ms at 500 MHz.
18 ms at 500 MHz.

H. Aneetha et al. / Journal of Organometallic Chemistry 663 (2002) 151ꢄ
/157
155
fluorobenzene under hydrogen gave the dihydride com-
?
kinetic stability of the dihydrogen tautomer is slightly
increased.
plex [CpꢀRuH2(SbPh3)2][BAr4] (5) (Scheme 2). Complex
5 is characterized by one sharp hydride resonance at
ꢃ8.51 ppm, with a minimum T1 of 1052 ms (400 MHz,
/
3. Experimental
CD2Cl2, 298 K). This compound is homologous of the
well-known dihydride derivatives [CpRuH2(P)2]ꢁ,
which have four-legged ‘‘piano stool’’ structures with
transoid disposition of hydride ligands [25,26]. Exactly
as it occurs with its PPh3 counterpart [CpꢀRuH2-
(PPh3)2]ꢁ, the dihydride is the most stable tautomeric
form. However, in the phosphine case the dihydrogen
tautomer [CpꢀRu(H2)(PPh3)2]ꢁ is accessible as the
kinetic product of the protonation of the neutral
monohydride [CpꢀRuH(PPh3)2] [27]. Hence the mono-
hydride complex [CpꢀRuH(SbPh3)2] (6) was prepared
by reaction of the dihydride 5 with a strong base such as
KOBut. This yellow material displays one strong
n(RuH) band at 1852 cmꢃ1, and one sharp hydride
All synthetic operations were performed under a dry
dinitrogen or Ar atmosphere by following conventional
Schlenk techniques. THF, Et2O and petroleum ether
(boiling point range 40ꢄ60 8C) were distilled from the
/
appropriate drying agents. Solvents were deoxygenated
?
immediately before use. {[CpꢀRuCl2}n] and NaBAr4
were prepared according to reported procedures [28,29].
SbPh3 and AsPh3 were purchased from Aldrich, and
used without further purification. IR spectra were
recorded in Nujol mulls on PerkinꢄElmer FTIR Spec-
/
trum 1000 spectrophotometer. NMR spectra were taken
on a Varian Unity 400 MHz or Varian Gemini 200 MHz
equipment. Chemical shifts are given in parts per million
from SiMe4. T1 measurements were made by the
signal at ꢃ
OEt2 in CD2Cl2 at ꢃ
/
11.33 ppm. Protonation of 6 using HBF4×
/
/
80 8C afforded the dihydrogen
inversionꢄrecovery method. Magnetic moments were
/
complex [CpꢀRu(H2)(SbPh3)2][BF4] (7) quantitatively.
This compound displays one dihydrogen resonance at
measured by the Evans’ method [30]. Microanalysis was
performed by the Serveis Cient´ıfico-Te`cnics, Universitat
de Barcelona.
1
8.32 ppm in its H-NMR spectrum. This signal has a
ꢃ
/
(T1)min of 17 ms (243 K, 400 MHz), which leads to HꢄH
/
˚
separations of 1.08/0.86 A for the no rotation/fast
spinning of the dihydrogen ligand. When temperature
is raised the dihydrogen complex 7 undergoes irrever-
sible tautomerization to its dihydride form 5, the
conversion being complete at room temperature
(Scheme 2). However, the rate of tautomerization of
3.1. [CpꢀRu(EPh3)Cl2] (EꢂSb 1a, As 1b)
/
To 0.31 g (1 mmol) of [{CpꢀRuCl2}n] in 15 ml of
CH2Cl2 or acetone, 1 mmol of either SbPh3 or AsPh3
was added. The reaction mixture was stirred for 1 h.
Solvent was removed to dryness. Addition of 10ꢄ
of EtOH gave a bright orange solid which was filtered,
washed with petroleum ether and dried. Yield 80ꢄ85%.
1a: Anal. Calc. for C28H30Cl2RuSb: C, 50.9; H, 4.54.
Found: C, 50.5; H, 4.62%. meff 1.7 mB (CD2Cl2
solution). 1b: Anal. Calc. for C28H30AsCl2Ru: C, 54.8;
/
15 ml
70
complexes [26,27], the half-life period being ca. 20 min
at 273 K (kobs
10ꢃ4 sꢃ1). We can there-
/5 is slower than those of analogous phosphine
/
ꢂ
/
(5.79
/
0.2)ꢅ
/
fore conclude that the system [CpꢀRuH2(SbPh3)2]ꢁ
behaves very much as its phosphorus counterpart, and
that the use of SbPh3 as co-ligand instead of PPh3 does
not alter the observed relative thermal stabilities of the
dihydride and dihydrogen tautomers, although the
ꢂ
/
H, 4.89. Found: C, 54.6; H, 4.77%. meff
solution).
ꢂ1.9 mB (CD2Cl2
/
3.2. [CpꢀRu(EPh3)H3] (EꢂSb 2a, As 2b)
/
To [CpꢀRu(EPh3)Cl2] (1 mmol) in THF, a solution
containing an excess of NaBH4 in EtOH was added. The
reaction mixture was stirred at room temperature for 1
h. The solvent was removed in vacuo and the residue
extracted with petroleum ether. Filtration, concentra-
tion and cooling to ꢃ20 8C gave an off white crystalline
/
solid. It was recrystallized from petroleum ether. Yield:
65%. 2a: Anal. Calc. for C28H33RuSb: C, 56.8; H, 5.57.
Found: C, 56.9; H, 5.89%. IR: n(RuH) 1925 (s), 2000
(w) cmꢃ1. H-NMR (400 MHz, CD3C6D5): d ꢃ
1
/
10.12
(s, 3H, RuH3, (T1)min 210 ms (400 MHz, 223 K)); 2.05
(s, C5(CH3)5); 7.12, 7.82 (m, Sb(C6H5)3). 13C{1H}-
¯
¯
¯
NMR (100.58 MHz, C6D6): d 13.1 (s, C5(CH3)5);
¯
104.9 (s, C5(CH3)5); 129.3, 129.9, 135.9, 137.2 (s,
¯
Scheme 2.
Sb(C6H5)3). 2b: Anal. Calc. for C28H33AsRu: C, 61.7;
¯

156
H. Aneetha et al. / Journal of Organometallic Chemistry 663 (2002) 151ꢄ157
/
H, 6.05. Found: C, 61.5; H, 5.95%. IR: n(RuH) 1939
1
9.70 (s, 3 H,
C5(CH3)5); 7.33, 7.40 (m, Sb(C6H5)3). 13C{1H}-NMR
cmꢃ1. H-NMR (400 MHz, C6D6): d ꢃ
RuH3, (T1)min 190 ms (400 MHz, 223 K)); 1.88 (s,
/
(100.58 MHz, CD2Cl2): d: 11.5 (s, C5(CH3)5); 99.8 (s,
¯
¯
¯
C5(CH3)5); 130.0, 130.3, 131.5, 136.9 (s, Sb(C6H5)3).
¯
¯
C5(CH3)5); 7.06, 7.66 (m, As(C6H5)3). 13C{1H}-NMR
¯
¯
¯
(100.58 MHz, C6D6): d 12.1 (s, C5(CH3)5); 94.7 (s,
¯
3.6. [CpꢀRuH(SbPh3)2] (6)
C5(CH3)5); 128.2, 129.0, 133.1, 140.8 (s, As(C6H5)3).
¯
¯
The deuterated derivatives [CpꢀRuD3(SbPh3)] (2a-d3)
and [CpꢀRuD3(AsPh3)] (2b-d3) were obtained following
an identical procedure, but using NaBD4 instead of
NaBH4.
To a solution of 5 (0.4 g, 0.22 mmol) in 10 ml of THF,
an excess of solid KOBut was added. The reaction
mixture was stirred for 1 h. The solvent was removed in
vacuo. The residue was extracted with petroleum ether
and filtered through celite. Concentration and cooling
gave a pale yellow residue. Yield 63%. Anal. Calc. for
C46H46RuSb2: C, 58.6; H, 4.88. Found: C, 58.2; H,
3.3. [CpꢀRu(H2)2(EPh3)][BF4] (EꢂSb 3a, As 3b)
/
1
4.50%. IR: n(RuH) 1852 cmꢃ1. NMR: H (400 MHz,
Both 3a and 3b were obtained and characterized in
solution by protonation of the corresponding trihy-
C6D6): d ꢃ11.33 (s, RuH); 1.79 (s, C5(CH3)5); 6.97,
/
13
7.65 (m, Sb(C6H5)3). C{ H}-NMR (100.58 MHz,
1
¯
¯
drides 2a or 2b in CD2Cl2 at ꢃ
/
80 8C using a slight
¯
excess of HBF4×OEt2. The isotopomers [CpꢀRu(HD)-
/
C6D6): d: 12.7 (s, C5(CH3)5); 87.2 (s, C5(CH3)5);
¯
¯
(D2)(SbPh3)][BF4] (3a-d3) and [CpꢀRu(HD)(D2)(As-
Ph3)][BF4] (3b-d3) were generated in analogous fashion
128.3, 128.6, 135.7, 138.6 (s, Sb(C6H5)3).
¯
by protonation of 2a-d3 or 2b-d3 in CD2Cl2 at ꢃ
using HBF4×OEt2. Yield: quantitative. 3a: NMR
(CD2Cl2, 193 K) H: d ꢃ
11.2 ms (400 MHz, 210 K), JoHbDs ꢂ
C5(CH3)5); 7.42, 7,49 (m, Sb(C6H5)3). 3b: NMR
/
808C
3.7. [CpꢀRu(H2)(SbPh3)2][BF4] (7)
/
1
/
7.79 (s, br, Ru(H2), (T1)min
The preparation of 7 is analogous to that for 3a, using
the monohydride 6 as starting material. Yield: quanti-
1
¯
/
9.3 Hz); 1.89 (s,
tative. 1H-NMR (400 MHz, CD2Cl2): d ꢃ
8.32 (s,
RuH2, (T1)min 17 ms (400 MHz, 243 K)); 1.75 (s,
/
1
¯
¯
(CD2Cl2, 193 K) H: d ꢃ
/
7.14 (s, br, Ru(H2), (T1)min
1
11.0 ms (400 MHz, 221 K), JoHbDs ꢂ
C5(CH3)5); 7.29, 7.46 (m As(C6H5)3).
/
9.9 Hz); 1.70 (s,
¯
C5(CH3)5); 7.33, 7.40 (m, Sb(C6H5)3). 13C{1H}-NMR
¯
¯
¯
(100.58 MHz, CD2Cl2): d: 11.5 (s, C5(CH3)5); 99.8 (s,
¯
¯
¯
C5(CH3)5); 130.0, 130.3, 131.5, 136.9 (s, Sb(C6H5)3).
¯
¯
3.4. [CpꢀRuCl(SbPh3)2] (4)
To [{CpꢀRuCl2}n] (0.31 g, 1 mmol) and SbPh3 (0.71
g, 2 mmol) in 30 ml of THF, an excess of zinc dust was
added. The reaction mixture was stirred for 1.5 h. It was
allowed to settle and then filtered over celite. THF was
removed in vacuo. The residue was repeatedly extracted
with Et2O. Filtration and solvent removal afforded a
Acknowledgements
We thank the Ministerio de Ciencia y Tecnolog´ıa of
Spain (DGICYT, Project BQU2001-4046) and Junta de
Andaluc´ıa (PAI FQM188) for financial support, Mr.
Juan Carlos Pe´rez-Arribas and Ms. Ma Dolores Pala-
cios-Tejero for assistance, and Johnson Matthey plc for
generous loans of ruthenium trichloride.
yellowꢄorange solid. Yield: 70%. Anal. Calc. for
/
C46H45ClRuSb2: C, 56.5; H, 4.60. Found: C, 56.1; H,
4.37%. 1H-NMR (400 MHz, CDCl3): d 1.40 (s,
C5(CH3)5); 7.14, 7.47 (m, Sb(C6H5)3). 13C{1H}-NMR
¯
¯
(100.58 MHz, CDCl3): d: 10.4 (s, C5(CH3)5); 83.3 (s,
¯
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