Approaches toward (η2-HX) (X = H, SiR (R = Me3 or Me2Ph), CH3) sigma-complexes of ruthenium

Article abstract of DOI:10.1016/j.jorganchem.2014.03.027

Two new Ru(II)-complexes [RuH(Tpms)(PPh₃)₂] 1 (Tpms = (C₃H₃N₂)₃CSO₃, tris-(pyrazolyl)methane sulfonate) and [Ru(OTf)(Tpms)(PPh₃) ₂] 2 (OTf = CF₃SO₃) have been synthesized and characterized wherein Ru-H and Ru-OTf are the key reactive centers. Reaction of 1 with HOTf results in the [Ru(η²-H₂)(Tpms)(PPh ₃)₂][OTf] complex 3, whereas reaction of 1 with Me ₃SiOTf affords the dihydrogen complex 3 and complex 1 through an unobserved σ-silane intermediate. In addition, an attempt to characterize the sigma methane complex via reaction of complex 1 with CH₃OTf yields complex 2 and free methane. On the other hand, reaction of [Ru(OTf)(Tpms)(PPh₃)₂] 2 with H₂ and PhMe ₂SiH at low temperature resulted in σ-H₂, 3 and a probable σ-silane complexes, respectively. However, no σ-methane complex was observed for the reaction of complex 2 with methane even at low temperature.

Full text of DOI:10.1016/j.jorganchem.2014.03.027

Journal of Organometallic Chemistry 762 (2014) 9e18
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Approaches toward (
sigma-complexes of ruthenium
h
2-HX) (X ¼ H, SiR (R ¼ Me3 or Me2Ph), CH3)
*
K.S. Naidu, Balaji R. Jagirdar
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new Ru(II)-complexes [RuH(Tpms)(PPh3)2] 1 (Tpms ¼ (C3H3N2)3CSO3, tris-(pyrazolyl)methane sul-
fonate) and [Ru(OTf)(Tpms)(PPh3)2] 2 (OTf ¼ CF3SO3) have been synthesized and characterized wherein
Received 11 February 2014
Received in revised form
25 March 2014
RueH and RueOTf are the key reactive centers. Reaction of 1 with HOTf results in the [Ru(h2
-
H2)(Tpms)(PPh3)2][OTf] complex 3, whereas reaction of 1 with Me3SiOTf affords the dihydrogen complex
3 and complex 1 through an unobserved esilane intermediate. In addition, an attempt to characterize
Accepted 26 March 2014
s
the sigma methane complex via reaction of complex 1 with CH3OTf yields complex 2 and free methane.
On the other hand, reaction of [Ru(OTf)(Tpms)(PPh3)2] 2 with H2 and PhMe2SiH at low temperature
Keywords:
Lithium tris(pyrazolyl)methane sulfonate
resulted in
seH2, 3 and a probable sesilane complexes, respectively. However, no semethane complex
s
s
s
eDihydrogen
eSilane
eMethane
was observed for the reaction of complex 2 with methane even at low temperature.
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
toward hydrolysis and an increased solubility in polar solvents [10].
It is a very good chelating tripodal ligand and shows dynamic k
2 and
Coordination of an HeX bond (X ¼ H, C, Si) to a transition metal
k3 modes of coordination. In addition, it behaves as a flexidentate
NNN and NNO donor, depending on the nature of the complex [11].
This versatile behavior of the Tpms ligand, motivated us to explore
the chemistry of ruthenium complexes for s-bond activation; to our
knowledge, very few results on CeH bond activation of benzene by
center in an h s-complexes has immense
2-fashion, in the so-called
importance in the field of catalysis [1e3]. Generally, these
are defined as metal complexes containing a ligand in which a
HeX (X ¼ H, C, Si, and B) acts as a two-electron donor to the metal
center, resulting in a 3 center-2-electron bond [1]. Particularly, the
H2 complexesformthebest-knowngroupof -complexes inwhich the
HeH bond is bound to the metal center in an
2-fashion. In addition,
several well characterized examples of
2-silane and 2-borane com-
plexes have also been reported [4]. In recent years, the carbon analogs
of these complexes in which alkanes are coordinated through
2-CeH
s
-complexes
s-bond,
se
metal complexes bearing the Tpms ligand are reported [12,13].
s
Severalsyntheticmethodsareavailabletoobtain
example, coordinatively unsaturated complexes or complexes having
highly labile groups react with HeX (X ¼ H, C, Si, and B) edonor
ligand resulting in the formation of -complexes. Another approach
s-complexes.For
h
h
h
s
s
h
involves reaction of metal-hydride ([M]eH) complexes with elec-
bonds to a metal center have been attracting immense attention from
trophiles such as HOTf, CH3OTf, and Me3SiOTf to lead to formation of
the standpoint of organometallic catalysis [5e8].
s
-complexes. In addition, metal-alkyl (or silyl) complexes also react
with Hþ to form
-complexes [14,15]. However, limited examples of
metal complexes that can stabilize all three -donor ligands (HeH,
These
such as hydrogenation, hydrosilylation, hydroboration and alkane
functionalization etc. Understanding the nature of the -complexes
s-complexes are key intermediates in catalytic processes
s
s
s
SieH, and CeH) have been reported; e.g., Kubas and co-workers re-
ported a metal complex wherein SieH, HeH, and agostic CeH bonds
provides an insight into the activation of HeX bonds by transition
metal centers. It is also important for fine catalyst design.
arebound tothesamemetalfragmentinan
widen the scope of these studies and to gain more insight into the
bonding nature and reactivity behavior of -H2, silane and methane
complexes, we employed two strategies to obtain these complexes in
solution. In the first, reactions of [RuH(Tpms)(PPh3)2],
(Tpms ¼ tris(pyrazolyl)methane sulfonate) with electrophilic re-
agentssuchasHOTf,Me3SiOTf, andCH3OTfandinthesecondstrategy,
reactions of [Ru(OTf)(Tpms)(PPh3)2] (OTf ¼ CF3SO3), 2 with H2,
PhMe2SiH, and CH4 (at 7 bar) at low temperature were carried out.
Herein, we describe these reactions in detail.
h
2 fashion [16]. In order to
Hydrotris(1-pyrazolyl)borate [HB(pz)3, Tp] and its derivative
hydrotris(3,5-dimethyl-1-pyrazolyl)borate [HB(3,5Me2pz), Tp0]
have been widely explored, however, in comparison, the chemistry
of tris(pyrazolyl)methane sulfonate (Tpms)-transition metal com-
plexes has been far less developed [9]. The Tpms bears a meth-
anesulfonate anionic moiety, which imparts very good stability
s
1
* Corresponding author.
E-mail address: jagirdar@ipc.iisc.ernet.in (B.R. Jagirdar).
http://dx.doi.org/10.1016/j.jorganchem.2014.03.027
0022-328X/Ó 2014 Elsevier B.V. All rights reserved.

10
K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
Results and discussion
variable-temperature spin-lattice relaxation time measurements
T1 and the observation of a large 1J(H,D) for the corresponding
Synthesis and characterization of [RuH(Tpms)(PPh3)2], 1 and
[Ru(OTf)(Tpms)(PPh3)2], 2 complexes
isotopomer [Ru(HD)(Tpms)(PPh3)2][OTf], 3-d1. The 1H NMR
spectrum of 3 in CD2Cl2 showed a broad signal at
d
ꢀ7.63 ppm
integrating to two hydrogen atoms. A T1 (min) value of 15.8 ms
(400 MHz) was obtained for the broad signal at ꢀ7.63 ppm at
243 K. The HeH distances dHH can be calculated from the T1 (min)
Reaction of [RuH2(PPh3)4] with LiTpms produced the yellow mon-
ohydride complex [RuH(Tpms)(PPh3)2] (eq (1)). Upon workup and
crystallization in CH2Cl2en-hexane solutions, yellow crystals of the
complex were obtained in 50% yield. The 1HNMRspectrumof1shows a
ꢀ
value [18] and are 1.08 and 0.85 A for slow and fast rotation re-
gimes of the bound H2 in 3. More definitive evidence for the
intact nature of the HeH bond in these derivatives was obtained
from the J(H,D) coupling for the HD isotopomer. We purged the
triplet for the hydride at
d
ꢀ13.35 due to coupling with 2 equivalent cis
phosphorus nuclei with a J(H,Pcis) of 27.7 Hz. The Tp analog
[RuH(Tp)(PPh3)2], reported by Lau and Jia exhibits very similar NMR
spectral features [17]. The 31P{1H} NMR spectrum is composed of only
CD2Cl2 solution containing the [Ru(
complex with HD gas (generated from NaH and D2O) at 243 K,
h
2-H2)(Tpms)(PPh3)2][OTf]
onesinglet at
d
65.8, indicating the cis disposition of the twophosphines.
which gave the h h
2-HD isotopomer [Ru( 2-HD)(Tpms)(PPh3)2]
[OTf]; it showed a 1:1:1 triplet (1J(HD) ¼ 31.6 Hz) of a 1:2:1
triplet (2J(HP) ¼ 6.6 Hz) centered at
d
ꢀ7.63 ppm in the 1H NMR
spectrum, after nullifying the
h
2-H2 peak at
d
ꢀ7.63 ppm by using
the inversion-recovery method with a delay time of 11 ms. The
HeH distance (dHH) calculated from the inverse relationship be-
ꢀ
tween dHH and J(H,D) of the HD isotopomer [19,20] is 0.86 A (see
Supporting information) which closely corresponds to the value
calculated from T1 for rapidly rotating H2. Dihydrogen complex 3
was found to be labile at room temperature; the bound H2 gets
replaced by the counter anion OTf and leads to the formation of
[Ru(OTf)(Tpms)(PPh3)2].
(1)
We also found that in dichloromethane, complex 1 slowly un-
dergoes hydride chloride exchange in days. In an attempt to pre-
(3)
pare
a five coordinate [Ru(Tpms)(PPh3)2][OTf] complex from
[Ru(Cl)(Tpms)(PPh3)2], we used AgOTf for the abstraction of chlo-
ride. Because of the high instability of the putative five coordinate
species upon chloride abstraction, it immediately reacts with the
triflate anion and affords [Ru(OTf)(Tpms)(PPh3)2], complex 2 (eq
(2)). Formation of complex 2 was evidenced by NMR spectroscopy
and X-ray crystallography. This product was crystallized from a
dichloromethane solution via slow diffusion of petroleum ether at
room temperature over a period of 2 days; yellow crystals were
obtained in 80% yield. Complex 2 is moderately soluble in toluene,
THF and completely soluble in chlorinated solvents. 19F NMR
spectrum confirmed the presence of a coordinated triflate ligand. In
particular, 19F NMR spectrum of 2 exhibits a singlet for CF3 at
Reaction of [RuH(Tpms)(PPh3)2], 1 with Me3SiOTf
In an attempt to obtain a ruthenium h2esilane complex, we
treated complex 1 with Me3SiOTf and monitored the reaction using
NMR spectroscopy. In this reaction at 193 K, instead of cationic h2
e
silane intermediate we observed peaks corresponding to the
dihydrogen complex 3 and hydride complex 1 (Scheme 1). On the
basis of these products we propose that the electrophile Me3Siþ
attacks complex 1 and forms a highly electrophilic unobservable
d
ꢀ76.6 ppm, downfield from free triflate ion (
d
ꢀ79.0 ppm). The 31
P
{1H} NMR spectrum displays a single peak at
d
36.6 ppm indicating
cationic [Ru(h
2-HSiMe3)(Tpms)(PPh3)2][OTf] species. This species
the cis disposition of the two equivalent phosphines.
rapidly undergoes hydrolysis due to the presence of residual water
in the solvent and forms dihydrogen complex 3 and Me3SiOH
(Scheme 1). Brookhart and his co-workers [15] noted that cationic
h2esilane complexes are quite sensitive to weak nucleophiles or
even non-nucleophilic counter ions such as BFꢀ4 , resulting in the
formation of R3SiF. Closely related system, for example, [Fe(Cp)(h2
-
HSiEt3)(CO)(PEt3)][BF4] is readily hydrolyzed by trace amount of
(2)
water and forms Et3SiOH and [Fe(
The appearance of a broad singlet at
spectrum and a singlet at
h
2-H2)(Cp)(CO)(PEt3)][BF4] [21].
d
ꢀ7.63 ppm in the 1H NMR
d
43.6 ppm in the 31P{1H} NMR spectrum
are consistent with the dihydrogen complex [Ru(h2
-
H2)(Tpms)(PPh3)2][OTf], 3 all other signals of complex 3 were also
observed and matched those of an authentic sample. In addition,
Me3SiOH shows a singlet at d
0.05 ppm for methyl protons in the 1H
Protonation of [RuH(Tpms)(PPh3)2]
NMR spectrum (Fig. 1). Another possibility is that the electrophilic
reagent reacts first with the water present in the solvent to
generate HOTf, which causes the protonation of the hydride com-
plex to form the dihydrogen complex 3 (see Supplementary
material). In order to trace generation of HOTf, we carried out an
independent reaction; reaction of Me3SiOTf and water leads to the
We carried out protonation of the monohydride complex,
[RuH(Tpms)(PPh3)2] with HOTf in dichloromethane which resul-
ted
H2)(Tpms)(PPh3)2][OTf], 3 at low temperature (243 K) (eq (3)).
The existence of the
2-H2 moiety in 3 was confirmed by
in
the
molecular
hydrogen
complex
[Ru(h2
-
h

K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
11
Scheme 1. Reaction of complex 1 with Me3SiOTf.
formation of HOTf (see Supplementary material). On the other
hand, cationic silane intermediate could also undergo nucleophilic
attack by counter ion OTf, leading to the formation of 1 and
Me3SiOTf. Identification of methyl signals in the NMR spectrum for
the eliminated Me3SiOTf was difficult due to excess Me3SiOTf
present in the reaction mixture. As is evident from the 1H NMR
spectral stack plot, the signal of the dihydrogen complex 3
remained intact up to 273 K and due to lower thermal stability of 3
at higher temperature (293 K) it eliminates H2 and forms complex 2
(see Supplementary material). Formation of complex 3 even at low
temperature is indicative of the highly reactive nature of the
this case, we observed complete conversion of the hydride complex
1 to acetonitrile complex [Ru(NCCH3)(Tpms)(PPh3)2][OTf], 8. These
observations suggest that Me3Siþ electrophile attacks the hydride
complex and forms the highly electrophilic cationic [Ru(h
2-HSi-
Me3)(Tpms)(PPh3)2][OTf] sigma silane complex. To this solution,
addition of acetonitrile results in elimination of free silane which is
observed in the NMR when acetonitrile substitutes for the silane.
Whereas, in the absence of acetonitrile, OTfꢀ acts as a nucleophile
and brings about the SieH bond cleavage leading to the formation of
hydride complex 1.
cationic
sesilane intermediate which undergoes SieH bond
Attempt to prepare [Ru(h
2-CH4)(Tpms)(PPh3)2][OTf]
cleavage by weak nucleophiles such as residual water.
From the VT 1H NMR spectral stack plot it is apparent that
(Fig. 1), the starting materials (complex 1 and Me3SiOTf) were
present throughout the temperature range (193e293 K). Another
possibility is that there is no reaction between complex 1 and
Me3SiOTf. To rule out this possibility, we carried out two indepen-
dent reactions of complex 1 (see Supplementary material). In the
first reaction, complex 1 was treated with acetonitrile, however no
reaction took place. In the second reaction, acetonitrile was added
to the solution of complex 1 and Me3SiOTf in dichloromethane; in
Brookhart and co-workers reported solution state NMR char-
acterization of sigma methane complex [(PONOP)Rh(CH4)]þ
at ꢀ110 ꢁC which strengthen our understanding of the binding of
the CeH bond of methane and its activation [6]. Recently, Weller
et al. characterized rhodium(I)
[8]. In addition, Perutz and co-workers reported Mnepropane and
Mnebutane ealkane complexes of [MnCp(CO)2] fragment which
sealkane complex in the solid state
s
was generated in situ from [MnCp(CO)3] photochemically at low
temperature with alkane as solvent [22]. Moreover, Ball
and his group recently reported the [(LOEt)Re(CO)2(alkane)]
(alkane
¼
cyclopentane, cyclohexane, pentane; LOEt
¼
cyclopentadienyltris(diethyl-phosphito)cobaltate(III)) species us-
ing both IR and NMR spectroscopies [23]. These results extend the
range of alkane complexes observable by NMR spectroscopy.
Following the Brookhart’s strategy, we attempted to generate
methane ligand directly bound in the coordination sphere of the
ruthenium metal by treating electrophilic reagent (CH3OTf or
CD3OTf) with hydride [RuH(Tpms)(PPh3)2] (Scheme 2). We found
that the reaction was quite slow at low temperature (203 K),
however, at 213 K complex 1 started reacting and eliminates CH4
(or CD3H) accompanied by the formation of complex 2. The sigma
methane intermediate was not observed even after w2 h at 213 K.
We noted signals for CH4 and CD3H at
respectively in the 1H NMR spectra. In addition, 31P{1H} NMR
spectrum shows a peak at 36.5 ppm for complex 2 (see
Supplementary material). Other minor products were [Ru(h2
d, 0.18 and 0.l6 ppm,
d
-
H2)(Tpms)(PPh3)2][OTf] (3) and [Ru(H2O)(Tpms)(PPh3)2][OTf] (6).
The possible pathway for the generation of these minor products is
through the hydrolysis of CH3OTf by residual water which gener-
ates HOTf which in turn protonates complex 1 and leads to the
Fig. 1. VT 1H NMR spectral stack plot for the reaction of [RuH(Tpms)(PPh3)2] with
Me3SiOTf.

12
K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
Scheme 2.
formation of complex 3. 31P{1H} NMR spectral stack plot (see
Supplementary material) suggests that complex 6 is formed
through complex 2. Even trace amount of moisture in rigorously
dried solvent causes the formation of the aqua complex. Since al-
kanes and in particular methane, are very poor electron donors and
acceptors, bind rather quite weakly to metal centers. Stronger
binding ability of OTf compared to CH4 or CD3H rendered the for-
mation and observation of only the triflate complex but not the
methane complex.
[Ru(Tpms)(PPh3)(h
3-HSiMe2Ph)] (4), [RuCl(Tpms)(PPh3)2] (7)
complexes and PhMe2SiOH, PhMe2SiOTf and [PPh3SiMe2Ph][OTf]
as evidenced by NMR spectroscopy (Scheme 3). This reaction was
found to be slow and took w24 h at room temperature to reach
completion. The spectral properties of 1, 4 and 7 matched those of
similar complexes reported in the literature [24,25] (see
Supplementary material). In order to get an insight into the
mechanistic aspects of the reaction, we carried out the same re-
action at low temperature and monitored the progress of the re-
action by using VT NMR spectroscopy. The VT partial 1H NMR
spectral stack plot of this reaction is shown in Fig. 2 and the cor-
responding 31P{1H} NMR spectral stack plot has been deposited in
the Supplementary material.
Reaction of [Ru(OTf)(Tpms)(PPh3)2] with H2
In the case of protonation reaction of complex 1 with HOTf, we
noted that complex 3 to be quite unstable at room temperature and
resulted in the formation of complex 2 and evolution of free H2 over
w10 min. However, complex 3 was found to be stable enough and
H2 was bound intact to the metal center at low temperature (243 K),
and no free H2 was observed. In an attempt to observe complex 3 at
RT, complex 2 was pressurized with 1 or 2 bar of H2 at 298 K which
resulted in the formation of a small amount of dihydrogen complex
Complex 2 contains a triflate, which is bound to the ruthenium
center opposite to one of the nitrogen atoms of the pyrazole of
Tpms ligand. Generally, silanes are good sigma donors when
compared to the HeH and CeH moieties [26]. In this reaction SieH
bond of HSiMe2Ph could replace the weakly coordinating triflate to
form highly reactive cationic intermediate [Ru(Tpms)(PPh3)2(h2
-
HSiMe2Ph)][OTf] 2.1 (see Scheme 4). It is well established that labile
[Ru(h
2-H2)(Tpms)(PPh3)2][OTf] (3) (Scheme 4) via the displace-
ment of the weakly bound OTf ion (see Supplementary material).
This indicates that H2 is not a better donor than OTf at room
temperature.
ligands in transition metal complexes can be displaced by free si-
lanes to form h
2-silane complexes [21]. The 1H NMR spectral data
displayed a low intensity broad singlet at ꢀ6.21 ppm and the 31P
{1H} NMR showed a signal at 47.2 ppm. These signals could be due
to the h
2-silane species 2.1 at 253 K. Appearance of a broad signal is
indicative of rapid exchange of coordinated silane with triflate in
the temperature range 253e223 K. Mechanistically, these reactions
may proceed via two main pathways. The first pathway wherein
intermediate species 2.1 undergoes rapid hydrolysis of SieH bond
Reaction of [Ru(OTf)(Tpms)(PPh3)2] with PhMe2SiH
Reaction of [Ru(OTf)(Tpms)(PPh3)2] (2) with PhMe2SiH at room
temperature resulted in the formation of [RuH(Tpms)(PPh3)2] (1),
Scheme 3.

K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
13
Scheme 4. Proposed mechanism of the reaction of complex 2 with PhMe2SiH.
due to the presence of residual water, leads to H2 gas evolution and
PhMe2SiOH formation. This process would take place until com-
plete consumption of residual water present in the solvent. At the
same time, very small amount of aqua complex 6 present in the
starting material also assists the hydrolysis of free silane via an
intermediate 2.1 and forms H2 and PhMe2SiOH. The hydrolysis
products H2 gas and PhMe2SiOH were noted in the 1H NMR spec-
rise to 3 as noted above. The appearance of a broad singlet at
43.6 ppm in the 1H and 31P{1H} NMR
d
ꢀ7.63 ppm and singlet at
d
spectra, respectively are consistent with the dihydrogen complex 3.
In order to understand the origin of H2, we carried out few inde-
pendent reactions; reaction of PhMe2SiH with residual water in
CD2Cl2 leads to no H2 evolution and silane hydrolysis even up to
w2 h. Once we add complex 2 to this solution, we noted instan-
trum as a singlet at
d
4.6 ppm and another singlet at 0.3 ppm for
taneous liberation of H2 (signal at d
4.6 ppm in 1H NMR spectrum),
methyl protons of PhMe2SiOH (see Supplementary material). Free
H2 generated in the reaction gets consumed by complex 2 giving
along with Me2PhSiOH (see Supplementary material). This in-
dicates an important role of complex 2 in the initiation of metal
complex assisted silane hydrolysis. Attempts to avoid all traces of
water from CD2C12 and PhMe2SiH to protect the cationic silane
intermediate 2.1 from hydrolysis were unsuccessful. Wide variety
of neutral transition metal sigma silane complexes have been
extensively studied although the cationic complex of type 2.1 is
limited due to its remarkable reactivity toward water and attack of
weakly coordinating anions such as BF4, OTf [15,27]. In the other
pathway, the intermediate 2.1 rapidly undergoes SieH bond
cleavage by weakly coordinating counter anion OTf to afford
hydride derivative [RuH(Tpms)(PPh3)2], 1 and PhMe2SiOTf as
observed in the NMR spectra. More importantly, from the 1H NMR
spectral stack plot we noted that hydrolysis was much more rapid
in comparison to SieH bond cleavage by counter anion OTf which
could be due to the better nucleophilicity of water than that of OTf.
The SieH bond cleaved product, PhMe2SiOTf was noted in the 1H
NMR spectrum as a singlet at
have been limited reports in the literature about heterolytic
cleavage of SiH bond, in which a -complex was observed as an
d 0.7 ppm for methyl groups. There
s
intermediate in the activation pathway [15,21,28]. Upon raising the
temperature of the reaction to 268 K, the spectral stack plots (Fig. 2)
show complexes 4 and 5 along with formation of [PPh3SiMe2Ph]
Fig. 2. VT 1H NMR spectral stack plot with temperature showing complexes 1, 3, 4 and
5 in the reaction of complex 2 with PhMe2SiH in CD2Cl2.
[OTf] species. Complex 4 shows a doublet at
d
ꢀ11.21 ppm (Ru-h3
-

14
K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
H2SiMe2Ph) which integrates to two protons in the 1H NMR spec-
trum; the doublet is flanked by 29Si satellite signals J(SiH) ¼ 22 Hz
indicating the presence of
d
h
2-silane ligand and a sharp singlet at
69.9 ppm in the 31P{1H} NMR spectrum. Similar complex of 4 with
Tp ligand was reported by Lau et al. by reacting
[TpRuH(CH3CN)(PPh3)] with PhMe2SiH at 90 ꢁC for 4 h [24]. In
addition, complex 5 shows a doublet at
d
ꢀ10.11 ppm (RuH-
h
2-H2)
d 70.19 ppm in the
in the 1H NMR spectrum and a sharp singlet at
31P{1H} NMR spectrum. The value of J(HP) ¼ 18 Hz and the peak
nature for the dihydrogen complex can be compared with the
analogous [TpRuH(h
2-H2)(PPh3)] complex [29]. It might be that
complex 2.1 undergoes subsequent intramolecular dissociation of
[PPh3SiMe2Ph][OTf] (Scheme 4) and formation of unobserved
complex [RuH(Tpms)(PPh3)], 3.1. In this reaction, the in-situ for-
mation of [PPh3SiMe2Ph][OTf] was not observed in the NMR
spectrum at low temperature because of its poor solubility. How-
ever at room temperature, the 1H NMR spectrum of [PPh3SiMe2Ph]
[OTf] shows a doublet at 2.78 ppm and the 31P{1H} NMR spectrum
displayed a signal at 21.2 ppm, which was further confirmed by
HSQC of 1He31P NMR spectrum (see Supplementary material). A
similar observation on the intramolecular dissociation was re-
ported wherein SieH bond gets cleaved at the metal center with
elimination of SieOH species [24]. Based on NMR spectral evidence,
it could be envisioned that formation of complexes 4 and 5 take
place via the intermediacy of a highly reactive five coordinated
neutral complex 3.1; this species could be a very short lived one and
reacts instantaneously with PhMe2SiH and free H2 present in the
solution. Apparently, we noted that the major product was 4
compared to 5 because it can also react with free silane (PhMe2SiH)
present in the solution to form 4. Additionally, to rule out the
possibility of formation of 4 and 5 via 1, we independently estab-
lished the reaction of 1 with PhMe2SiH at room temperature and
found that formation of a small amount of 4 and free PPh3 take
place after one week (see Supplementary material). On the other
hand, complex 3 is unstable at room temperature and slowly goes
back to [Ru(OTf)(Tpms)(PPh3)2] within a short time (w10 min).
Another plausible route for the formation of complex 3 is that H2
could be substituted by PhMe2SiH to give 2.1 (as mentioned earlier,
silane is a better donor than H2). Complex 1 is reactive toward
CD2Cl2 to form [RuCl(Tpms)(PPh3)2], 7 through a metathesis pro-
cess. Complex 7 shows a sharp singlet at 37.5 ppm in the 31P{1H}
NMR spectrum.
Fig. 3. ORTEP view of [RuH(Tpms)(PPh3)2] complex, 1 at the 50% probability level
showing selected atom labeling. Hydrogen atoms are omitted for clarity except for the
hydride H1.
pressurized complex 2 with 7 bar of CH4 at 298 K (Scheme 4), and
the reaction was monitored by VT NMR spectroscopy. We gradually
cooled down the NMR probe from 293
Supplementary material). However, under these conditions even at
183 K, we did not observe any signal for a emethane complex
spectroscopically. The sample was kept at 183 K for nearly 3 h to
find any trace amount of emethane complex formed in solution;
K to 183 K (see
s
s
however no signals were found. On the other hand, broadening of
the 31P{1H} NMR spectral signal was noted at 203e213 K along with
change in the pattern of proton signals of the aromatic region. Then
further cooling led to disappearance of the 31P{1H} NMR spectral
Attempted preparation of sigma methane complex from
[Ru(OTf)(Tpms)(PPh3)2] and CH4 at 7 bar
The lability of triflate in complex 2 is clearly demonstrated by its
reaction with acetonitrile and water which results in the formation
of [Ru(NCCH3)(Tpms)(PPh3)2][OTf], 8 and [Ru(H2O)(Tpms)(PPh3)2]
[OTf], 6 complexes, respectively. Structures for these two com-
plexes were determined unambiguously by X-ray crystallography
(Figs. 5 and 6). We found that in complex 2 the RueO bond distance
ꢀ
is 2.198(2) A, which is indicative of weakly coordinating nature of
the triflate ion. Generally, weakly coordinating triflate ion is ex-
pected to be a better leaving group in presence of strong donors
such as acetonitrile and water as mentioned earlier; however, for
very weakly coordinating ligands especially CeH bond of simple
alkanes, triflate behaves as strong ligand and remains tightly bound
to the metal center as we observed this when 2 was reacted with
CH4 at 7 bar. On the other hand, the reactions of complex 2 with H2
and PhMe2SiH, resulted in a
seH2 complex (3) and SieH bond
activation along with silane hydrolysis through an expected
s
e
silane intermediate 2a, respectively. As in the case of H2 and silane
reactions of complex 2, methane complexation with 2 at low
temperature and 7 bar of CH4 could be possible. In this context, we
Fig. 4. ORTEP view of [Ru(OTf)(Tpms)(PPh3)2] complex, 2 at the 50% probability level
showing selected atom labeling. Hydrogen atoms are omitted for clarity.

K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
15
Table 1
ꢁ
ꢀ
Selected bond distances (A) and angles ( ) for complexes 1, 2, 6 and 8.
1
2
6
8
Ru1eaL0
Ru1eN1
Ru1eN3
Ru1eN5
Ru1eP1
Ru1eP2
P2eRu1eP1
N1eRu1eN3
P2eRu1-L0
N3eRu1-L0
N1eRu1eP2
1.58(3)
2.154(2)
2.198(2)
2.077(2)
2.029(2)
2.104(2)
2.4037(8)
2.3858(8)
99.71(3)
85.48(9)
89.26(6)
170.17(8)
172.94(7)
2.126(3)
2.039(3)
2.125(3)
2.099(3)
2.3856(9)
2.3646(9)
101.84(3)
85.62(12)
91.19(9)
2.0319(16)
2.0688(16)
2.0967(16)
2.1214(16)
2.3739(5)
2.3946(5)
101.086(17)
86.74(6)
97.19(5)
87.93(6)
88.59(4)
2.1628(19)
2.116(2)
2.3169(8)
2.2910(9)
100.02(3)
82.10(8)
84.2(12)
173.8(12)
92.09(6)
86.38(12)
94.63(8)
L0 represents the atom of the monodentate ligand coordinated to Ru, L0 ¼ H (1),
a
OTf (2), H2O (6), CH3CN (8).
is low-lying and therefore, unsuitable for electron donation, and
the LUMO (s*) is high in energy and unsuitable for accepting
electron density and in addition, the dominant coordinating ability
of OTf in comparison to the weakly coordinating nature of methane,
could be the two reasons for not being able to observe interaction of
methane with complex 2.
X-ray structural studies of 1, 2, 6 and 8
Fig. 5. ORTEP view of [Ru(H2O)(Tpms)(PPh3)2] complex, 6 at the 50% probability level
showing selected atom labeling. Hydrogen atoms are omitted for clarity.
Molecular structures of 1, 2, 6 and 8 have been confirmed by an
X-ray crystallographic study. The molecular geometries of 1, 2, 6
and 8 are depicted in Figs. 3e6 and the crystallographic details and
selected bond distances and angles have been summarized in
Tables 1 and 2. The geometries of these four structures were found
to be quite similar to one another. The ruthenium center in all these
structures adopts an approximately octahedral geometry, with the
Tpms ligand occupying one face of the octahedron and the phos-
phines and L0 (L0 ¼ H, OTf, H2O, NCCH3) ligands occupying the
remaining positions. The RueN distance (L0 trans to N of pyrazolyl)
signal and reappearance of two separate broad signals at 183 K, and
again a clear change in the pattern of proton signals of aromatic
region at 183 K (see Supplementary material) which could be due to
weak interactions of phenyl protons of PPh3 competing with triflate
counter anion for binding at the metal center at low temperature
which are in rapid equilibrium.
H2 and silane are better donors as compared to methane
wherein H2 and silane
s-binding to metal center are governed by
ꢀ
in 1 was found to be slightly longer (2.1628(19) A) in comparison to
electron donation from
p
s
eHeH and SieH bonds to metal and the
ꢀ
ꢀ
ꢀ
-back bonding from metal to the respective s* orbitals of these
the other three (2.029(2) A), (2.039(3) A), (2.0688(16) A); 2, 6, 8,
respectively structures which could be attributed to the good sigma
donating ability of the hydride ligand trans to N. The distances
between the ruthenium atom and the metal bound pyrazolyl ni-
trogen atoms in all these structures compare well with those
ligands. In contrast, alkanes especially methane, notoriously
unreactive, interact with metals very weakly because the HOMO (
s
)
Table 2
Crystal data and refinement details for 1, 2, 6, 8.
1
2
6
8
Formula
C47H45Cl2N6 C49H43Cl4F3N6 C48H41Cl2F3N6 C60H58F3N7O8
O3P2RuS
Formula weight 1004.84
O6P2RuS2
1237.82
Triclinic
P ꢀ 1
O9P2RuS2
1200.92
Triclinic
P ꢀ 1
P2RuS2
1289.26
Triclinic
P ꢀ 1
Cryst syst
Space group
T (K)
Triclinic
P ꢀ 1
293(2)
100(2)
100(2)
100(2)
ꢀ
a, A
12.236(5)
13.134(5)
15.670(5)
94.504(5)
93.034(5)
115.329(5)
2258.7(15)
2
11.4609(10)
13.9020(12)
16.7287(14)
84.964(4)
79.137(4)
73.210(4)
2504.4(4)
2
1.641
0.742
0.71073
0.0525
0.1262
11.7928(5)
12.5404(5)
17.3718(7)
86.752(2)
75.499(2)
81.402(2)
2458.76(17)
2
1.622
0.650
0.71073
0.0654
0.1982
12.0652(7)
14.2645(8)
17.2149(9)
80.906(3)
85.682(3)
81.442(3)
2888.9(3)
2
1.482
0.471
0.71073
0.0389
0.0982
ꢀ
b, A
ꢀ
c, A
a
b
g
, deg
ꢀ
V, A
Z
dcalc, g cmꢀ3
1.477
0.631
m
(mmꢀ1
(A)
)
ꢀ
l
0.71073
0.0332
0.0919
P
Ra
Rw
P
P
P
a
2
Fig. 6. ORTEP view of [Ru(CH3CN)(Tpms)(PPh3)2] complex, 8 at the 50% probability
level showing selected atom labeling. Hydrogen atoms are omitted for clarity.
R ¼ (jFoj ꢀ jFcj)/ jFoj, Rw ¼ [ w(jFoj ꢀ jFcj)2/ wjFoj ]1/2 (based on reflections
with I > 2
s
(I)).

16
K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
observed in the structure of [RuCl(PPh3)2(Tpms)] [25]. The RueN
bond lengths of pyrazolyl ligand in 2, 6 and 8 complexes which are
trans to the phosphorus ligands (PPh3) are slightly longer than the
other RueN bond which is trans to OTf, H2O or CH3CN ligand. This
might indicate the trans influence of PPh3 ligand. The P1eRueP2
bond angle in all the four structures was found to be about 100ꢁ,
which is a consequence of the steric bulk of PPh3 ligands. The RueH
under an optical microscope and mounted on the Goniometer head
with paraffin oil coating. The unit cell parameters and intensity
data were collected at room temperature and 100 K using a Bruker
SMART APEX CCD diffractometer equipped with a fine focus Mo K
a
X-ray source (50 kV, 40 mA). The data acquisition was done using
SMART software and SAINT software was used for data reduction
[37]. The empirical absorption corrections were made using the
SADABS program [38]. The structure was solved and refined using
the SHELXL-97 program [39]. The ruthenium atom was located
from the Patterson map, and the non-hydrogen atoms and the
hydride were located from the difference Fourier map and refined
anisotropically. All other hydrogen atoms were fixed in idealized
positions and refined in a riding model.
ꢀ
bond length in 1 is 1.58(3) A which sits comfortably within the
range of distances generally observed in the hydride complexes
ꢀ
[30]. In complex 2, the RueO bond length is 2.198(2) A which is
i
ꢀ
longer than that in [Ru(Cp*)(OTf)(P Pr3)] [31] (2.136(2) A) and
shorter than that in [Ru(SO3CF3){C6H3(CH2NMe2)2-2,6)(C7H8)] [32]
ꢀ
complex (2.2327(16) A).
Conclusions
Synthesis of [RuH(Tpms)(PPh3)2], 1
In an attempt to stabilize and gain insights into the bonding
nature and reactivity behavior of various sigma ligands on a
[RuH2(PPh3)4] (0.400 g, 0.347 mmol) and LiTpms (0.102 g,
0.347 mmol) were dissolved in 20 mL of THF. The resulting yellow
solution was refluxed for 2 h to give a yellowish green suspension.
The mixture was filtered off and the filtrate was concentrated under
vacuum and washed with diethyl ether and then finally dried
under vacuum to obtain a yellow powder. Pure product of
[RuH(Tpms)(PPh3)2], 1 was obtained by recrystallization of the
residue from dichloromethane/n-hexane at room temperature for
overnight. Yield: 0.159 g, 50%. Anal. Calcd for C47H45Cl2N6O3P2RuS:
C, 56.01; H, 4.50; N, 8.34; S, 3.18. Found: C, 56.59; H, 4.28; N, 8.0; S,
ruthenium center [Ru(
h
2-HX)(Tpms)(PPh3)2][OTf], (X ¼ H, SiR
(R ¼ Me3 or Me2Ph) and CH3), we followed two strategies to
generate these complexes in solution. In the first strategy, reaction
of [RuH(Tpms)(PPh3)2] complex, 1 with electrophilic reagent HOTf
results in dihydrogen complex [Ru(
whereas the reaction of 1 with Me3SiOTf afforded the dihydrogen
complex 3 and complex 1 through an unobserved esilane inter-
h
2-H2)(Tpms)(PPh3)2][OTf] 3,
s
mediate. In addition, reaction of 1 with CH3OTf resulted in
[Ru(OTf)(Tpms)(PPh3)2] complex 2 and free methane through an
unobserved sigma methane species. In the second strategy, reac-
tion of [Ru(OTf)(Tpms)(PPh3)2] complex, 2 with H2, PhMe2SiH and
CH4 at low temperature were carried out. These reactions resulted
3.17. 1H NMR (400 MHz, CD2Cl2, 25 ꢁC):
d
ꢀ13.35 (t, 2J(HP) ¼ 27.7 Hz,
1H, RueH), 5.68 [t, 2H, H4(pz0)], 5.98 [t, 1H, H4(pz)], 6.45 [d, 1H,
H5(pz)], 6.92 [d, 2H, H5(pz0)], 7.02e7.26 [m, 30H, PC6H5], 8.74 [d, 2H,
H3(pz0)], 9.05 [d, 1H, H3(pz)] (pz ¼ pyrazolyl group trans to hydride,
pz0 ¼ pyrazolyl group trans to PPh3, all coupling constants for
pyrazolyl proton resonance were about 2.5 Hz). 31P{1H} NMR
in dihydrogen complex, a probable sesilane complex, and no re-
action between complex 2 and methane, respectively.
(161.70 MHz, CD2Cl2, 25 ꢁC):
d 65.8 (s).
Experimental section
Preparation of [Ru(OTf)(Tpms)(PPh3)2], 2
General procedures
[RuCl(Tpms)(PPh3)2] (0.200 g, 0.209 mmol) and AgOTf (0.052 g,
0.209 mmol) were dissolved in 20 mL of dichloromethane. The
yellow solution was stirred at room temperature for 30 min to give
a yellow suspension. The mixture was filtered through Celite and
washed with hexane and dried under vacuum to give a yellow
powder of [Ru(OTf)(Tpms)(PPh3)2], 2. Yield: 0.180 g, 80%. Anal.
Calcd for C47H43F3N6O6P2RuS2$2CH2Cl2: C, 47.54; H, 3.50; N, 6.79; S,
5.18. Found: C, 47.32; H, 3.32; N, 6.58; S, 5.14. 1H NMR (400 MHz,
CD2Cl2, 293 K): 5.06 [d, 1H, H3(pz)]; 5.36 [t, 2H, H4(pz0)]; 5.90 [t, 2H,
H4(pz)]; 7.24 [d, 2H, H5(pz0)]; 6.99e7.34 [m, 30H, P(C6H5)3]; 8.96 [d,
2H, H3(pz0)]; 9.10 [d, 1H, H5(pz)] (pz ¼ pyrazolyl group trans to OTf,
pz0 ¼ pyrazolyl group trans to PPh3; all coupling constants for
pyrazolyl proton resonance were about 2.5 Hz). 31P{1H} NMR
All reactions were carried out under N2 or Ar using standard
Schlenk and inert atmosphere techniques unless otherwise speci-
fied [33,34]. Reagent-grade solvents were dried and distilled under
N2 atmosphere from Na-benzophenone (hexane, petroleum ether,
THF, diethyl ether) just before use. Dichloromethane was first dried
and distilled using P2O5 and once again dried and distilled over
CaH2. Solvents for the reactions that involved the synthesis of
ruthenium complexes were thoroughly saturated with Ar or N2 just
before use. The 1H and 31P NMR spectral data were obtained using
an Avance Bruker 400 MHz instrument. All chemical shifts are re-
ported on the
d scale. The chemical shift of the residual protons of
the deuterated solvent was used as an internal reference.
Dichloromethane-d2 (CD2Cl2) was purchased from Cambridge-
Isotopes Limited, USA and distilled over CaH2 prior to use. Meth-
anol was dried and distilled under N2 atmosphere from Na.
Variable-temperature 1H T1 measurements were carried out at
(161.70 MHz, CDCl3, 293 K):
293 K):
ꢀ76.69 (s, 3F). EI-MS m/z ¼ 919[M-OTf].
d
36.6 (s). 19F NMR (376 MHz, CDCl3,
d
Protonation of [RuH(Tpms)(PPh3)2], 1
400 MHz using the inversion recovery method (180ꢁe e90ꢁ pulse
s
sequence at each temperature) [35]. All 31P NMR spectra were
proton-decoupled, unless otherwise stated. 31P NMR chemical
shifts have been measured relative to 85% H3PO4 (external) in
CD2Cl2. Lithium tris(pyrazolyl)methane sulfonate (LiTpms) and
[RuH2(PPh3)4], [RuCl(Tpms)(PPh3)2] complexes were prepared us-
ing literature procedures. [10,25,36].
[RuH(Tpms)(PPh3)2] (0.020 g, 0.021 mmol) was dissolved in
0.5 mL of CD2Cl2 in a 5 mm NMR tube that was capped with a
septum. The resulting solution was subjected to three cycles of
freezeepumpethaw degassing. The tube was cooled to 243 K. One
equivalent (ca. 2 mL, 0.028 mmol) of HOTf was added to this solution
immediately and then the sample was inserted into the NMR probe,
which was pre-cooled to 243 K. The 1H and 31P NMR spectra
recorded at 243 K showed the presence of the dihydrogen complex
X-ray structure determination of 1, 2, 6, and 8
3. 1H NMR (400 MHz, CD2Cl2, 243 K):
d
ꢀ7.63 [br s, 2H, Ru-(H2)];
Good quality crystals of complexes 1, 2, 6, and 8 suitable for X-
ray diffraction study were carefully selected after examination
5.90 [t, 1H, H4(pz); 5.94 [t, 2H, H4(pz0)]; 6.16 [d, 1H, H5(pz); 6.74 [d,
2H, H5(pz0)]; 7.11e7.71 (m, 30H, PC6H5); 9.04 [d, 2H, H3(pz0)]; 9.25

K.S. Naidu, B.R. Jagirdar / Journal of Organometallic Chemistry 762 (2014) 9e18
17
[d, 1H, H3(pz)] (pz ¼ pyrazolyl group trans to h2-H2, pz0 ¼ pyrazolyl
group trans to PPh3; all coupling constants for pyrazolyl proton
resonance were about 2.5 Hz). 31P{1H} NMR (161.70 MHz, CD2Cl2,
formation of [Ru(h
2-H2)(Tpms)(PPh3)2][OTf], 3 complex (5%) along
with starting material.
243 K):
signal were carried out by the inversion-recovery method using
standard 180ꢁe e90ꢁ pulse sequence. T1 (400 MHz, ms): 21.6
d 43.6 (s). Variable-temperature T1 measurements on the H2
Reaction of [Ru(OTf)(Tpms)(PPh3)2] with PhMe2SiH
s
Complex 2 (0.020 g, 0.018 mmol) was dissolved in 0.6 mL of
(193 K), 20.9 (203 K), 18.7 (213 K), 18.0 (223 K), 17.3 (233 K), 15.8
(243 K), 18.0 (253 K), 18.7 (263 K), 19.4 (273 K), 19.4 (283), 20.2
(293 K). T1(min) (400 MHz, 243 K): 15.8 ms.
CD2Cl2 in a 5 mm NMR tube and then the tube was cooled to 203 K
using slush bath (ethanol/liq N2). Next, 1 equiv of Me2PhSiH (3 mL,
0.018 mmol) was added at 203 K, immediately the sample was
inserted into the NMR probe, which was pre-cooled to 203 K. The
1H and 31P{1H} NMR spectra were recorded. The same reaction was
also carried out at room temperature and the products were
characterized by NMR spectroscopy.
Preparation of [Ru(HD)(Tpms)(PPh3)2][OTf]
In an attempt to prepare the HD isotopomer of [Ru(h2
H2)(Tpms)(PPh3)2][OTf], we purged the corresponding CD2Cl2 so-
-
lution containing the [Ru(h
2-H2)(Tpms)(PPh3)2][OTf] complex with
Reaction of [Ru(OTf)(Tpms)(PPh3)2] complex 2 with methane (7 bar)
in a pressure-stable NMR tube
HD gas (generated from NaH and D2O) at 243 K. The 1H NMR
spectrum of the resulting solution was then recorded at 243 K. The
2-HD signal (
d
ꢀ7.6 (tt), 1J(HD) ¼ 31.6 Hz, 2J(HP) ¼ 6.6 Hz) was
Complex 2 (0.020 g, 0.018 mmol) was dissolved in 0.6 mL of
CD2Cl2 in a high-pressure NMR tube. The solution was subjected to
one freezeepumpethaw degassing cycle, and then CH4 (7 bar) was
pressurized in the tube. The tube was closed by a Teflon valve, and
the progress of the reaction was monitored by using VT NMR
spectroscopy. 1H NMR spectroscopy did not reveal the formation of
h
observed after nullifying the
inversion-recovery method with a delay time of 11 ms.
h
2-H2 peak at
d
ꢀ7.6 using the
Reaction of complex 1 with Me3SiOTf
the [Ru(h semethane complex.
2-CH4)(Tpms)(PPh3)2][OTf]
This reaction was carried out using complex
1 (0.02 g,
0.021 mmol) and Me3SiOTf (8 mL, 0.043 mmol). The sealed NMR
Preparation of [Ru(L0)(Tpms)(PPh3)2][OTf] (L0 ¼ H2O(6), CH3CN(8))
tube with the frozen contents was inserted into the NMR probe pre-
cooled to 183 K and the 1H and 31P{1H} spectra were recorded as the
reaction progressed upon raising the temperature. In this case we
[Ru(OTf)(Tpms)(PPh3)2] (0.1 g, 0.092 mmol) and H2O (ca. 10 mL,
noted the formation of free Me3SiOH along with [Ru(h2
-
0.140 mmol) were dissolved in 10 mL of dichloromethane under
nitrogen atmosphere. The yellow solution was stirred at room
temperature for 5 min to give a light yellow solution. The yellow
product of [Ru(H2O)(Tpms)(PPh3)2][OTf] was obtained in a yield of
75 mg, 70%. 1H NMR (400 MHz, CDCl3, 293 K): 5.43 [d, 1H, H5(pz)];
5.59 [t, 1H, H4(pz)]; 5.72 [t, 2H, H4(pz0)]; 6.21[d, 2H, H5(pz0)]; 7.11e
7.89 [m, 30H, P(C6H5)3]; 8.78 [d, 2H, H3(pz0)]; 9.23 [d, 1H, H3(pz)]
(pz ¼ pyrazolyl group trans to H2O, pz0 ¼ pyrazolyl group trans to
PPh3; all coupling constants for pyrazolyl proton resonance were
H2)(Tpms)(PPh3)2]. 1H NMR (400 MHz, CD2Cl2, 193e293 K):
0.05 ppm [1H, Me3SiOH].
d
Attempt to prepare [Ru(h
2-CH4)(Tpms)(PPh3)2][OTf]
A flame-dried 5 mm Schlenk NMR tube was charged with
[RuH(Tpms)(PPh3)2] (0.020 g, 0.021 mmol) and ca. 0.5 mL of CD2Cl2
was added under nitrogen. The sample was cooled to 77 K, and then
about 2.5 Hz). 31P{1H} NMR (161.70 MHz, CD2Cl2, 293 K):
d 39.9 (s).
CH3OTf (4 mL, 0.036 mmol) was added and the tube was sealed
[Ru(NCCH3)(Tpms)(PPh3)2][OTf] compound was prepared using
above similar procedure. 1H NMR (400 MHz, CDCl3, 293 K): 2.71 (s,
3H, CH3CN), 5.52 [t, 1H, H4(pz); 5.98 [t, 2H, H4(pz0)]; 6.52 [d, 1H,
H5(pz)]; 6.74 [d, 2H, H5(pz0)]; 6.95e7.42 [m, 30H, P(C6H5)3]; 8.94 [d,
2H, H3(pz0)]; 9.16 [d, 1H, H3(pz)] (pz ¼ pyrazolyl group trans to
NCCH3, pz0 ¼ pyrazolyl group trans to PPh3; all coupling constants
for pyrazolyl proton resonance were about 2.5 Hz). 31P{1H} NMR
under vacuum. The sample was then inserted into the NMR probe
immediately, which was pre-cooled to 183 K. The progress of the
reaction was monitored by recording the 1H and 31P NMR spectra of
the sample over a temperature range 203e298 K. The 1H and 31P
{1H} NMR spectra recorded at 213 K showed the presence of free
methane, [Ru(OTf)(Tpms)(PPh3)2], 2 and [Ru(OH2)(Tpms)(PPh3)2],
6 complexes. 1H NMR (CD2Cl2, 213 K):
d 0.18 (s, 4H, CH4).
(161.70 MHz, CD2Cl2, 293 K):
d 39.1 (s).
Reaction of RuH(Tpms)(PPh3)2 complex 1 with CD3OTf
Appendix A. Supplementary material
This reaction was conducted in a similar manner to that of
CCDC 984250e984253 contain the supplementary crystallo-
graphic data for [RuH(Tpms)(PPh3)2] (1), [Ru(OTf)(Tpms)(PPh3)2]
(2), [Ru(H2O)(Tpms)(PPh3)2] (6) and [Ru(CH3CN)(Tpms)(PPh3)2]
(8). These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
complex
1
with CH3OTf starting with complex
1 (0.020 g,
0.021 mmol) and CD3OTf (ca. 4
mL, 0.030 mmol). The sealed NMR
tube with the frozen contents was inserted into the NMR probe pre-
cooled to 213 K and the 1H and 31P{1H} NMR spectra were recorded
as the reaction progressed upon raising the temperature. In this
case we found free CD3H along with [Ru(OTf)(Tpms)(PPh3)2], 2 and
[Ru(OH2)(Tpms)(PPh3)2], 6 complexes. 1H NMR (CD2Cl2, 213e
Appendix B. Supplementary data
293 K):
d 0.16 (sept, 1H, CD3H).
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2014.03.027.
Reaction of [Ru(OTf)(Tpms)(PPh3)2] with H2 at 298 K
Complex 1 (0.020 g, 0.018 mmol) was dissolved in 0.6 mL of
CD2Cl2 in a 5 mm high pressure NMR tube. Next, H2 (2 atm) was
pressurized for a period of 5 min. The 1H and the 31P NMR spectra of
the sample recorded immediately thereafter at 298 K showed the
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ꢀ
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