Catalytic hydrogen generation from the hydrolysis of silanes by ruthenium complexes

Article abstract of DOI:10.1021/om200256h

Dimeric Ru(II) complexes Ru₂(CO)₄L₂X ₄ (L = CO or PPh₃; X = Cl or Br) have been found to catalyze the hydrolysis of silanes to produce hydrogen gas and silanols with turnover numbers in excess of 10⁴ at room temperature. Deuteration and mass spectrometric studies have established that the hydrogen gas originates from one hydrogen atom from water and the other from silane. Ruthenium hydride intermediates have been detected in the NMR spectrum during the early stage of the reaction, while the FTIR spectra of more stable complexes such as Ru(CO)₂(PPh₃)(THF)Br₂ and Ru(CO) ₂(PPh₃)₂(H)Br have been recorded upon completion of catalysis. A mechanism has been proposed to account for the ruthenium-catalyzed silane hydrolysis based on the experimental data.

Full text of DOI:10.1021/om200256h

ARTICLE
pubs.acs.org/Organometallics
Catalytic Hydrogen Generation from the Hydrolysis of Silanes by
Ruthenium Complexes
Sze Tat Tan, Jun Wei Kee, and Wai Yip Fan*
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
S Supporting Information
b
ABSTRACT: Dimeric Ru(II) complexes Ru2(CO)4L2X4 (L =
CO or PPh3; X = Cl or Br) have been found to catalyze the
hydrolysis of silanes to produce hydrogen gas and silanols with
turnover numbers in excess of 104 at room temperature.
Deuteration and mass spectrometric studies have established
that the hydrogen gas originates from one hydrogen atom from water and the other from silane. Ruthenium hydride intermediates
have been detected in the NMR spectrum during the early stage of the reaction, while the FTIR spectra of more stable complexes
such as Ru(CO)2(PPh3)(THF)Br2 and Ru(CO)2(PPh3)2(H)Br have been recorded upon completion of catalysis. A mechanism
has been proposed to account for the ruthenium-catalyzed silane hydrolysis based on the experimental data.
’ INTRODUCTION
upon exposure to air. A mechanism has also been proposed to
account for the hydrolysis of silanes based on the experimental
data obtained.
Hydrogen gas has been extensively produced and used in
many applications. On an industrial scale, steam reforming,
which involves the reaction of hydrocarbons with steam to form
hydrogen gas, can be carried out efficiently at high tempera-
tures.1,2 Hydrogen is employed in the formation of ammo-
nia3 and methanol4 and is also essential in many chemical
syntheses.5,6 In fact hydrogen has even gained much attention
especially as an alternative energy source to replace fossil fuels.7
One of the energy-related areas being explored extensively is the
development of lighter and smaller alternatives for hydrogen
storage such as metal hydrides as a replacement for the currently
used large and heavy gas cylinders.8,9
’ RESULTS AND DISCUSSION
Halo-ruthenium carbonyl complexes16 Ru2(CO)4(PPh3)2Br4
(1), Ru2(CO)6Br4 (2), and Ru2(CO)6Cl4 (3) have been found
to activate the SiÀH bond toward the hydrolysis of silanes.
Syntheses of ruthenium complexes 1 and 2 are straightforward,
and their purification can be achieved easily. Complex 3 is
commercially available. The three complexes are stable toward
air and moisture at least for several weeks, as indicated by their
infrared spectra (Table 1).
Due to the widespread application of hydrogen gas, it is thus of
much interest to conduct fundamental studies on the various
methods of producing hydrogen with the purpose of improving
the efficiency. As the SiÀH bond is relatively weak, silanes are
good candidates as a hydrogen source for various applications. It
has been demonstrated that hydrogen formed via silane
hydrolysis10 can be used in hydrogenation reactions catalyzed
by palladium(II)11 or iridium(I)12 complexes. Although transi-
tion metal complex-catalyzed silane alcoholysis and, to a lesser
extent, silane hydrolysis have been extensively reported, few
quantitative studies have been carried out on hydrogen produc-
tion especially from silane hydrolysis.13 Recent reports have
shown that using cationic oxorhenium(V) complexes as a catalyst
can produce hydrogen gas from silane hydrolysis with reasonable
turnover number (TON).10,14 In addition, due to the ability to
generate hydrogen gas, silanes have been considered for devel-
opment in fuel cell technology.15
The molecular structure of 1 was determined using X-ray
crystallography from single crystals grown by slow evaporation of
solvent from a dichloromethane solution. 1 crystallizes in space
group P2(1)/n, with unit cell dimensions a = 9.88 Å, b = 16.11 Å,
c = 14.45 Å, β = 100.09°. The structure was refined using the
SHELXTL program, leading to a reasonable agreement factor,
R = 0.066. Disorders caused by the formation of isomers 1A and 1B
(Figure 1) during the synthesis of complex 1 were observed. The
existence of isomers is not surprising, as similar isomeric struc-
tures have also been observed for Ru2(CO)6Br4 previously.16 In
both isomers, the ruthenium center achieved a near octahedral
geometry, with the bulky phosphine group being located in the
equatorial plane. Such an orientation is expected, as it would
experience the least steric repulsion as compared to other
conformations. It was observed that the bond distance between
each ruthenium center and the bridging bromine atoms, Br(1)
2.5870(8) Å and Br(1A) 2.6090(8) Å, are slightly different. This
difference may be caused by the different extent of trans influence
exerted by the phosphine and carbonyl ligands.17 The difference
As such, we wish to report that the ruthenium complexes
Ru2(CO)4L2X4 (L = PPh3 or CO; X = Cl or Br) are able to
catalyze the production of hydrogen upon silane hydrolysis very
efficiently at room temperature. Turnover numbers in excess of
104 can be achieved with some of these ruthenium systems even
Received: March 24, 2011
Published: July 07, 2011
r
2011 American Chemical Society
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ARTICLE
between the bond distance of ruthenium and terminal bromine
atoms of each isomer [1A: Br(2) 2.5397(9) Å; 1B: Br(2K)
2.391(15) Å] is much more obvious. In these two cases, the Br
ligand is trans to either a CO or a bridging Br ligand, suggesting
that the difference in bond distance is due to a thermodynamic
trans effect. Being a stronger σ-donor than the bridging Br ligand,
the CO ligand tends to distort the electron density on Ru toward
itself, thereby weakening and lengthening the RuÀBr bond.18
The above-mentioned observations are in agreement with the
analogous Ru(CO)2(PPh3)2Br2 and Ru2(CO)6Br4 crystal
structures.19,20
When complex 1 was first added to a wet THF solution
containing triethylsilane, strong effervescence was immediately
observed (Table 2). The gaseous content of the reaction vessel
was analyzed using a mass spectrometer, which revealed an
intense signal at m/z = 2, corresponding to the production of
H2 gas. A carefully repeated experiment using dried THF as
solvent did not result in H2 evolution. Another setup carried out
with additional H2O produced significantly more H2. These
observations point toward water being one of the substrates. To
verify the observations further, the silane was allowed to react
with D2O, and indeed an intense signal at m/z = 3 (HD) was
observed. The signal at m/z = 2 remained low, and no signal was
seen at m/z =4 (D2). The H2 gas could not be generated if either
silane or the ruthenium catalyst is removed from the reaction
mixture. The data strongly indicated that the hydrogen gas was
formed from silane and water, from which one H atom was
supplied, which is similar to the work reported for the oxorhe-
nium complexes.14
Several cycles of addingfresh portions of silane or water into the
mixture containing complex 1 (of 0.05% mol loading) could be
accomplished with slight gradual loss of catalytic efficiency, leading
to a TON and TOF of about 103 and 16 minÀ1 determined over a
period of one hour (see entries 2À4, Table 2). In fact, the catalytic
rate involving either complex 2 or 3 was found to be even higher
Table 1. IR Values of Complexes 1À3 in Chloroform
complex
ν(CO)/cmÀ1
lit. values16/cmÀ1
than complex 1, with a TON and TOF of 104 and 40 minÀ1
,
Ru2(CO)4(PPh3)2Br2 (1) 2070 (s), 2012 (s) 2069 (s), 2011 (s)
respectively (entries 6 and 7, Table 2). However when two other
ruthenium complexes were used, no hydrogen was produced
(entries 8 and 9, Table 2)
Ru2(CO)6Br2 (2)
Ru2(CO)6Cl4 (3)
2138 (s), 2078 (s) 2136 (s), 2075 (s), 2013 (w)
2142 (s), 2083 (s) 2141 (s), 2079 (s), 2006 (w)
Figure 1. ORTEP view of solid-state structures 1a and 1b. Hydrogen atoms are removed for clarity. Pertinent bond distances (Å): Ru1ÀC1, 1.911(7);
Ru1ÀC2, 1.872(6); Ru1ÀP1, 2.3353(17); Ru1ÀBr1, 2.5870 (8); Ru1ÀBr1A, 2.6090(8); RuÀBr2, 2.5397(9); Ru1ÀC2K, 1.084(15); Ru1ÀBr2K,
2.391(15).
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Table 2. Product Details for the Hydrolysis of Triethylsilane Catalyzed by Some Ruthenium Complexesa
no.
silane
solvent
complex
time (min)
H2 yield (%)b
Et3SiOH yield (%)c
0
1
2
3
4
5
6
7
8
9
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Et3SiH
THF
THF
THF
THF
CHCl3
THF
THF
THF
THF
60
5
0
23
58
71
1.2
83
100
0
1
1
1
1
2
3
30
60
5
60
0d
75
94
0
5
5
Ru3(CO)12
60
60
Ru(CO)2(PPh3)2Br2
0
0
a Catalytic runs involve 2 mmol of silane and 20 mmol of H2O with 0.05% catalytic loading at 25 °C. b Total H2 yields were derived from a calibration
curve obtained from a known amount of H2. c 1H NMR yield calculated with respect to silane, using toluene as internal standard. d Organic product
obtained after 60 min is siloxane (yield = 14%).
Table 3. Product Details for the Hydrolysis of Silanes Cata-
lyzed by Complex 1a
no.
silane
H2 yield (%)b
1
2
3
4
5
6
Et3SiH
100
21
97
96
99
0
Ph3SiH
PhMe2SiH
b
Ph2SiH2
Me2(Cl)SiH
Et3SiH/PPh3
a Catalytic runs involve 2 mmol of silane and 20 mmol of H2O with
0.05% catalytic loading at 25 °C for 60 min. b Total H2 yields were
derived from a calibration curve obtained from a known amount of H2.
Figure 3. (a) FTIR spectrum obtained from the reaction of complex 1-
catalyzed hydrolysis of triethylsilane in thf solvent. Formation of two
ruthenium complexes [(A) 2030, 1961 cmÀ1 and (B) 2060, 1995 cmÀ1
]
was observed. (b) 1H NMR spectrum of the reaction mixture obtained
after catalysis showed a triplet, which is assigned to the complex
Ru(CO)2(PPh3)2(H)Br (A).
solvent such as THF is used to ensure good miscibility with
water. Upon removal of the catalyst and slow evaporation of
solvent after the reaction, a colorless liquid was obtained and
analyzed by NMR and mass spectrometry to be triethylsilanol.
On the other hand, the corresponding siloxanes, which result
from the reaction of silanol with silanes, were found to be
dominant in nonpolar solvents such as chloroform (Table 2,
entry 5).
Figure 2. 1H NMR spectrum obtained after the reaction of complex 1-
catalyzed hydrolysis of triethylsilane. Signals due to strongly shielded
protons suggest that metal hydride species are formed during the
reaction. An exact spectrum was observed when phenyl(dimethyl)silane
was used instead, which suggests that the complex does not contain any
silyl ligand.
The hydrolysis of different silanes catalyzed by complex 1 has
also been carried out, with the yields of hydrogen gas summarized
in Table 3. Generally, an increase in rate was observed when the
steric bulk on the silane molecule was decreased. However
addition of free phosphines such as PPh3 into the mixture
The H2 gas produced using complexes 1À3 can easily be
controlled by slowly titrating silane onto the catalytic system.
Once silane has been used up, H2 gas evolution ceases immedi-
ately. The hydrolysis is equally efficient when carried out in air or
under vacuum conditions. H2 gas evolution is faster if a polar
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Figure 4. Proposed mechanism for the hydrolysis of silane using complex 1 as the catalytic precursor.
prevented the generation of H2. An FTIR scan of the mixture
containing PPh3 reveals the formation of the bisphosphine
dibromoruthenium complex Ru(CO)2(PPh3)2Br2 (2056 and
1990 cmÀ1).21
and (B) 2060, 1995 cmÀ1 (Figure 3a). A literature search on
ruthenium carbonyl complexes suggests that peaks A are likely
due to the Ru(CO)2(PPh3)2(H)Br complex.24 The triplet
hydride signals obtained in the NMR spectrum can also be
assigned to this complex. To further confirm the assignment of
the complex, bromoform (CHBr3) was added to the reaction
mixture to allow a Br/H exchange with Ru(CO)2(PPh3)2-
(H)Br. Indeed, the dibromoruthenium complex Ru(CO)2-
(PPh3)2Br2 was formed in high yields. Peaks B have been
assigned to the Ru(CO)2(PPh3)(THF)Br2 complex. These
peaks can be reproduced easily if complex 1 is allowed to react
with THF as a substrate in CHCl3 solvent under room-
temperature conditions. Furthermore we have found that upon
addition of PPh3, the THF ligand can be displaced and also
leads to the formation of the bisphosphine ruthenium complex
Ru(CO)2(PPh3)2Br2.
We propose a mechanism that could account for the general
features of the experimental data using complex 1 as the catalytic
precursor. The reaction pathways are illustrated in Figure 4. The
first step involves dissociation of the dinuclear complex 1 into the
16-electron monomer Ru(CO)2(PPh3)Br2, which is immedi-
ately stabilized by THF to form Ru(CO)2(PPh3)(THF)Br2.
This [Ru]-THF complex is an important catalytic intermediate
that can be deactivated upon PPh3 substitution to afford
Ru(CO)2(PPh3)2Br2 (Table 3, entry 6). The silane then binds
weakly to the ruthenium center, most likely with the SiH bond
approaching in a σ-mode in order to reduce steric hindrance
caused by overcrowding of ligands.25,26 The subsequent step
involves the formation of either a (i) [Ru]-H intermediate with
elimination of silyl bromide (R3SiBr) or (ii) [Ru]-SiR3 inter-
mediate with elimination of HBr.22,23,26 From the NMR data, it
In order to understand the silane hydrolysis mechanism, 1H
NMR analysis of the reaction mixture of complex 1 in a sealed
tube during the early stage of catalysis was carried out. Inter-
estingly, the results revealed two sets of doublet signals (ca.
À5.7 and À11.7 ppm) in the strongly shielded region usually
assigned to metal hydrides (Figure 2). The splitting of J = 20 Hz
for both sets is consistent with the hydride coupling with an
adjacent phosphine ligand. The data suggest that at least two
metal hydride species containing the Ru(H)PPh3 moiety are
present in the catalytic mixture. The hydride signals persisted
even when different silanes were used or in the absence of water
in the mixture, indicating that the origin of the hydride is the
silane and that the two ruthenium hydride species most likely
do not contain silyl groups. This observation is consistent with
previous results that reported the occurrence of RuÀhalide/
SiÀH exchange.22,23 Unfortunately, the FTIR signals of these
intermediates could not be recorded presumably because of
their low concentrations or overlap with the much more intense
precursor signals, hence preventing further characterization.
When the mixture was analyzed at the completion of
catalysis, a triplet signal at À4.96 ppm was detected in the
NMR spectrum instead (Figure 3b). Both sets of doublet
signals of the hydride mentioned earlier have disappeared.
The splitting pattern (J = 19.2 Hz) is consistent with the
hydride coupling with two neighboring phosphine ligands.
Using FTIR spectroscopy, we have managed to obtain two
sets of carbonyl stretching vibrations at (A) 2030, 1961 cmÀ1
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ARTICLE
Scheme 1. An Alternate Pathway Involving Charge Separa-
tion Can Also Be Considered for Hydrogen Productiona
and the chemical shifts were referenced to tetramethylsilane. Hydrogen
gas was detected using a Balzer Prisma QMS 200 residual mass analyzer
and calibrated to known concentrations of pure hydrogen gas. The
organic product yields were calculated from the 1H NMR spectra using
reagent grade toluene as internal standard. Mass spectra of the organic
products are recorded with a Finnigan Mat 95XL-T spectrometer.
Complexes Ru2(CO)4(PPh3)2Br2 (1) and Ru2(CO)6Br2 (2) were
prepared according to literature methods and characterized by FTIR
spectroscopy.16,21,27 The complex Ru2(CO)6Cl4 (3) was obtained from
Strem and used without further purification.
a [Ru] may represent Ru(CO)2PPh3Br2.
Nonacarbonyltris(triphenylphosphine)triruthenium, Ru3-
(CO)9(PPh3)3. Ru3(CO)12 (0.5 g, 0.78 mmol) was refluxed with excess
PPh3 in hexane until a dark violet precipitate was formed. The residue
was recrystallized using CHCl3Àhexane to give needle-like crystals
(1 g, 0.75 mmol). IR ν(CO) (CHCl3): 2041 (vw), 1972 (sh), 1969 (vs).
Complex 1. Ru3(CO)9(PPh3)3 (0.5 g, 0.37 mmol) was dissolved in
cold benzene, before excess Br2 was added. The initial purple ruthenium
turned dark yellow immediately. The solvent and unreacted Br2 were
then removed under reduced pressure. At this point, the residue contains
a majority of Ru(CO)3(PPh3)Br2. This was redissolved in enough
CHCl3 to give a saturated solution, which was heated at 50 °C for 30
min. Hexane was then added to precipitate the product. The product was
recrystallized from a CHCl3Àhexane solvent pair to give the yellow
product 1 (0.35 g, 0.30 mmol). Anal. Found: C 41.3, H 2.7, Br 27.2.
C40H30O4Br4P2Ru2 requires: C 41.6, H 2.6, Br 27.4. 31P NMR: 41.3
ppm. The yellow product was also of sufficient quality to be used for
single-crystal X-ray analysis.
Complex 2. Ru3(CO)12 (0.2 g, 0.31 mmol) was dissolved in sufficient
benzene, before excess Br2 was added. The solution turned pale yellow
immediately. The solvent and unreacted Br2 were then removed under
reduced pressure. Hexane was added to the residue and heated at 50 °C
until a yellow precipitate formed. The yellow precipitate was collected
and recrystallized using CHCl3Àhexane as complex 2. Anal. Found: C
10.4, Br 46.4. C6O6Br4Ru2 requires: C 10.2, Br 46.3.
appears that at least two ruthenium hydride species have been
detected rendering pathway (i) to be highly possible. The
reactive 16-electron [Ru]-H monomer forms Ru(CO)2(PPh3)-
(H2O)(H)Br upon water coordination. Alternatively the mono-
mer undergoes dimerization to generate a dinuclear hydride
species Ru2(CO)4(PPh3)2(H)2Br2, analogous to complex 1.
Both of these ruthenium hydride species may have been the
carriers of the hydride signals in the NMR spectrum (Figure 2).
In fact the Ru(CO)2(PPh3)2(H)Br complex observed at the end
of catalysis is probably formed from one or both of these [Ru]-H
intermediates. In the next step, hydrogen gas could be produced
upon OÀH bond reaction with the hydride, leaving a hydroxide
ligand on the ruthenium center. Thus the H2 gas is comprised of
one H atom from silane and one from water. Finally, the silyl
bromide eliminated in an earlier step returns to coordinate to the
ruthenium center and produces silanol via a strong SiÀO
coupling. The bromide ligand is restored on the ruthenium,
hence completing the catalytic cycle.
Although the proposed mechanism is able to explain much of
our experimental data, it is by no means the only possible
pathway. Yang et al. proposed a pathway whereby a
[Et2OMe3Si]+ ion is formed upon reaction of the ether with a
η1-σ-trimethylsilane-coordinated iridium cationic complex.25d
By adopting their reaction, as shown in Scheme 1, hydrogen
can also be generated in our system if charge separation occurs.
However this process is almost certainly endothermic and may
not account for the efficiency of this ruthenium-based catalysis. It
is therefore difficult at this stage to be certain about the
mechanism until much more work has been carried out on the
system.
Typical Procedure for Catalytic Reaction. Silane (2 mmol, 1
equiv) was added into a THF (1 mL) solution containing the catalyst
(1 μmol) and excess H2O (20 mmol). The reaction mixture was stirred,
and evolution of gas was observed. Hydrogen gas was detected by
sampling the headspace above the catalytic mixture throughout the
reaction. A calibration curve using a known amount of pure hydrogen gas
was used for the yield measurement.
’ ASSOCIATED CONTENT
’ CONCLUSION
S
Supporting Information. This material is available free
b
Dinuclear ruthenium complexes 1À3 have been used for
catalytic silane hydrolysis, producing copious amounts of H2
gas. TONs in excess of 104 can be achieved with some of the
ruthenium systems used. The detection of ruthenium intermedi-
ates in the NMR and FTIR spectra has led to a proposed
mechanism for the silane hydrolysis. The high catalytic efficiency
and the ability of the system to control hydrogen production may
lead to potential applications.
of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*Fax: (+65) 6779-1691. E-mail: chmfanwy@nus.edu.sg.
’ ACKNOWLEDGMENT
’ EXPERIMENTAL SECTION
S.T.T. and J.W.K. thank NUS for research studentships. This
project was supported by research grant no. 143-000-430-112.
General Procedures. Triruthenium dodecacarbonyl, Ru3(CO)12
(Aldrich, 99%), was recrystallized from cyclohexane before use. Triethyl-
silane, diphenylsilane, triphenylsilane, and triphenylphosphine were
obtained from Aldrich and used without further purification. IR spectra
were collected with liquid samples in a cell with CaF2 windows and 0.1
mm path length, with a Shimadzu IR Prestige-21 spectrometer. NMR
(1H and 31P) spectra were recorded with a Bruker AMX 500 Fourier
transform spectrometer at room temperature, using CDCl3 as solvent,
’ REFERENCES
(1) (a) Hook, J. P. V. Catal. Rev.-Sci. Eng. 1980, 21, 1–51.
(b) Kugeler, K.; Kugeler, M.; Niessen, H. F.; Hammelmann, K. H. Nucl.
Eng. Des. 1975, 34, 129–145.(c) Rand, D. A. J.; Dell, R. M. Hydrogen
from Fossil Fuels and Biomass. In Hydrogen Energy: Challenges and
Prospects; The Royal Society of Chemistry, 2008; Chapter 2, p 34.
4012
dx.doi.org/10.1021/om200256h |Organometallics 2011, 30, 4008–4013

Organometallics
ARTICLE
(2) (a) Carrette, L.; Friedrich, K. A.; Stimming, U. Fuel. Cells 2001,
1, 5–39.(b) Rand, D. A. J.; Dell, R. M. Fuel Cells. In Hydrogen Energy:
Challenges and Prospects; The Royal Society of Chemistry, 2008; Chapter
6, p 179.
(3) Appl, M. Ammonia: Principles and Industrial Practice; Wiley-
VCH, 1999.
(23) (a) Chalk, A. J. J. Chem. Soc., Chem. Commun. 1969, 1207–1208.
(b) Chalk, A. J.; Harrod, J. F. J. Am. Chem. Soc. 1965, 87, 16–21.
(c) Kono, H; Wakao, N.; Ito, K. J. Organomet. Chem. 1977, 132, 53–67.
(24) (a) James, B. R.; Markham, L. D. Inorg. Nucl. Chem. Lett. 1971,
7, 373–377. (b) James, B. R.; Markham, L. D.; Hui, B. C; Rempel, G. L.
J. Chem. Soc., Dalton. Trans. 1973, 1972À1999, 2247–2252.
(25) (a) Kubas, G. J. Coordination and Activation of Si-H, Ge-H,
and Sn-H Bonds. In Metal Dihydrogen and σ-Bond Complexes; Fackler,
J. P. Jr., Ed.; Kluwer Academic/Plenum Publishers: New York, 2001; pp
327À364. (b) Corey, J. Y. Chem. Rev. 2011, 111, 863–1071. (c) Park, S.;
Brookhart, M. Organometallics. 2010, 29, 6057–6064. (d) Yang, J.;
White, P. S.; Brookhart, M. J. Am. Chem. Soc. 2008, 130, 17509–17518.
(26) Tuttle, T.; Wang, D.; Thiel, W.; Kohler, J.; Hofmann, M.; Weis,
J. Organometallics 2006, 25, 4504–4513.
(4) (a) Marschner, F.; Moeller, F. W. Applied Industrial Catalysis,
Vol. 2; Leach, B. E., Ed.; Acadamic Press: New York, 1984. (b) Dong,
Y.; Steinberg, M. Int. J. Hydrogen Energy 1997, 22, 971–977.
(5) (a) Speilmann, J.; Buch, F.; Harder, S. Angew. Chem., Int. Ed.
2008, 47, 9434–9438.(b) Claden, J.; Greeves, N.; Warren, S.; Wothers,
P. Organic Chemistry, 1st ed.; Oxford University Press: New York, 2001.
(6) (a) Caulton, K. G.; Mauthner, K.; Kirchner, K. J. Organomet.
Chem. 2000, 593À594, 342–353. (b) Scott, B. L.; Eckert, J.; Kubas, G. J.
Inorg. Chem. 1999, 38, 1069–1084. (c) Kuhlman, R.; Gusev, D. G.;
Eremenko, I. L.; Berke, H.; Huffman, J. C.; Caulton, K. G. J. Organomet.
Chem. 1997, 536À537, 139–147. (d) Kubas, G. J.; Nelson, J. E.; Bryan,
J. C.; Eckert, J.; Wisniewski, L.; Zilm, K. Inorg. Chem. 1994,
33, 2954–2960. (e) Bianchini, C.; Linn, K.; Masi, D.; Peruzzini, M.;
Polo, A.; Vacca, A.; Zanobini, F. Inorg. Chem. 1993, 32, 2366–2376.
(f) Sweany, R. L.; Moroz, A. J. Am. Chem. Soc. 1989, 111, 3577–3583.
(7) (a) Rand, D. A. J.; Dell, R. M. Why Hydrogen Energy. In Hydrogen
Energy: Challenges and Prospects; The Royal Society of Chemistry, 2008,
Chapter 1, p 1. (b) Bent, S. Hydrogen and Fuel Cells: Emerging Technologies
and Applications, 1st ed.; Elservier Academic Press, 2005.
(8) Rand, D. A. J.; Dell, R. M. Hydrogen Distribution and Storage. In
Hydrogen Energy: Challenges and Prospects; The Royal Society of
Chemistry, 2008; Chapter 5, p 146.
(27) Trovati, A.; Araneo, A.; Ugayagliati, P.; Zingales, F. Inorg. Chem.
1970, 9, 671–673.
(9) (a) Varin, R. A.; Czujko, T.; Wronski, Z. S. Nanomaterials for
Solid State Hydrogen Storage; Bansal, N. P., Ed.; Springer Science, 2009.
(b) Maeland, A. J. Hydrides for Hydrogen Storage. In Recent Advances in
Hydride Chemistry; Peruzzini, M.; Poli, R., Eds.; Elsevier Science:
Amsterdam, Chapter 18, p 531.
(10) Ison, E. A.; Corbin, R. A.; Abu-Omar, M. M. J. Am. Chem. Soc.
2005, 127, 11938–11939.
(11) Tour, J. M.; Cooper, J. P.; Pendalwar, S. L. J. Org. Chem. 1990,
55, 3452–3453.
(12) Wang, D. W.; Wang, D. S.; Chen, Q. A.; Zhou, Y. G. Chem.—
Eur. J. 2010, 16, 1133–1136.
(13) (a) Lukevics, E.; Dzintara, M. J. Organomet. Chem. 1985,
295, 265–315. (b) Lee, Y.; Seomoon, D.; Kim, S.; Han, H.; Chang, S.;
Lee, P. H. J. Org. Chem. 2004, 69, 1741–1743. (c) Lee, M.; Ko, S.; Chang,
S. J. Am. Chem. Soc. 2000, 122, 12011–12012. (d) Blackwell, J. M.;
Foster, K. L.; Beck, V. H.; Piers, W. E. J. Org. Chem. 1999,
64, 4887–4892. (e) Luo, X. K.; Crabtree, R. H. J. Am. Chem. Soc.
1989, 111, 2527–2535. (f) Blackburn, S. N.; Haszeldine, R. N.; Parish,
R. V.; Setchfield, J. H. J. Organomet. Chem. 1980, 192, 329–338.
(g) Dwyer, J.; Hilal, H. S.; Parish, R. V. J. Organomet. Chem. 1982,
228, 191–201. (h) Chang, S.; Scharrer, E.; Brookhart, M. J. Mol. Catal.
A.: Chem. 1998, 130, 107–119.
(14) Corbin, R. A.; Ison, E. A.; Abu-Omar, M. M. Dalton. Trans.
2009, 2850–2855.
(15) Spear, S. K.; Daly, D. T.; Swatloski, R. P.; Redemer, M. D.;
Paggi, R. E. PCT Int. Appl. WO 2007/019172 A2, 2007.
(16) Johnson, B. F. G.; Johnston, R. D.; Lewis, J. J. Chem. Soc. A
1969, 792–797.
(17) Chatt, J.; Duncanson, L. A.; Venanzi, L. M. J. Chem. Soc.
1955, 4456–4460.
(18) Miessler, G. L ; Tarr, D. A. Inorganic Chemistry, 3rd ed.; Pearson
Prentice Hall: NJ, 2004.
(19) Diz, E. L.; Therrien, B.; Neels, A.; S€uss-Fink, G. Acta Crystallogr.
2002, E58, m404–m405.
(20) Merlino, S.; Montagnoli, G. Acta Crystallogr. 1968, B24,
424–429.
(21) Piacenti, F.; Bianchi, M.; Benedetti, E.; Braca, G. Inorg. Chem.
1968, 7, 1815–1817.
(22) Ng, S. M.; Lau, C. P.; Fan, M. F.; Lin, Z. Organometallics. 1999,
18, 2484–2490.
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