Synthesis, characterization, and reactivity of Cp*Rh(III) complexes having functional N,O chelate ligands

Article abstract of DOI:10.1016/j.jorganchem.2017.02.015

Cp*Rh(III) complexes 1a and 1b (Cp* = 1, 2, 3, 4, 5-pentamethylcyclopentadienyl) having functional N,O chelate ligands have been synthesized and characterized by ¹H, ¹³C{¹H} NMR spectroscopy, elemental analysis, IR spectroscopy and X-ray diffraction. Reactivity of these complexes has been investigated towards dehydrogenation of alcohols and hydrogenation of ketones. It was found that these compounds are precursors to the formation of Rh nanoparticles which serve as catalysts, as evidenced by mercury poisoning of the catalysis and direct observation of the particles by TEM, EDX, and XRD.

Full text of DOI:10.1016/j.jorganchem.2017.02.015

Journal of Organometallic Chemistry xxx (2017) 1e5
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, characterization, and reactivity of Cp*Rh(III) complexes
having functional N,O chelate ligands
,
1
Lloyd Munjanja, Hongmei Yuan, William W. Brennessel, William D. Jones*
Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Cp*Rh(III) complexes 1a and 1b (Cp* ¼ 1, 2, 3, 4, 5-pentamethylcyclopentadienyl) having functional N,O
chelate ligands have been synthesized and characterized by 1H, 13C{1H} NMR spectroscopy, elemental
analysis, IR spectroscopy and X-ray diffraction. Reactivity of these complexes has been investigated to-
wards dehydrogenation of alcohols and hydrogenation of ketones. It was found that these compounds
are precursors to the formation of Rh nanoparticles which serve as catalysts, as evidenced by mercury
poisoning of the catalysis and direct observation of the particles by TEM, EDX, and XRD.
© 2017 Elsevier B.V. All rights reserved.
Received 3 October 2016
Received in revised form
10 February 2017
Accepted 11 February 2017
Available online xxx
Keywords:
Rhodium
Catalysis
Dehydrogenation
Non-innocent ligands
1. Introduction
Inspired by the eOH functionality of the Fujita catalysts, our group
has
developed
nickel
Tp'-stabilized
catalyst
(Tp':
incorporating
tris(3,5-
2-
With the rise in the need for liquid organic hydrogen storage
materials [1], acceptorless alcohol dehydrogenation (AAD) becomes
a favorable atom-economical approach for alcohol oxidation [2].
Alcohols and carbohydrates derived from renewable biomass pre-
sent an opportunity for such materials as they can be oxidized with
the concomitant release of hydrogen [3]. In addition, the carbonyl
compounds derived from the AAD process can be used for the
formation of imines, amides, and esters [4].
A significant number of catalysts have been discovered for this
process [5]. Cp*Ir (Cp* ¼ 1,2,3,4,5-pentamethylcyclopentadienyl)
catalysts bearing the functional N,O and C,N chelating ancillary li-
gands first developed by Fujita and co-workers caught our atten-
tion as useful catalysts [6a-b]. The Fujita Cp*Ir catalysts with N,O
and C,N chelating ligands were efficient for the reversible accept-
orless dehydrogenation of alcohols. The origin of the exceptional
reactivity of the iridium catalysts Cp*Ir(2-hydroxypyridine)Cl2, and
Cp*Ir[(2-OH-6-phenyl)pyridine]Cl (Ir-1. Fig. 1) was demonstrated
through the protic functional group on the ligand that promotes the
release of dihydrogen from the metal hydride intermediate.
dimethylpyrazolyl)borate)
hydroxypyridine [7]. These nickel catalysts with functional N, O
ligand were efficient in the acceptorless, reversible
dehydrogenation-hydrogenation of alcohols just as their iridium
analogs.
Employing the Fujita-Yamaguchi catalyst Cp*Ir[(2-OH-6-phenyl)
pyridine]Cl, Ir-1, we successful demonstrated a tandem catalytic
process upgrading ethanol to n-butanol with up 99% selectivity [8].
No reaction was observed with the unfunctionalized Cp*Ir(2-
phenylpyridine)Cl catalyst showing the significant role of hydrox-
yl (eOH) moiety on the Ir-1 catalyst in facilitating the dehydroge-
nation and hydrogenation steps [6]. With the success of the Ir-1
catalyst in both dehydrogenation of primary and secondary alco-
hols, we sought to synthesize the analogous rhodium catalyst, Rh-1
(Fig. 1) with similar hydroxyl (eOH) functionality to explore dif-
ferences in catalytic reactivity for the dehydrogenation of alcohols.
2. Results and discussion
2.1. Synthesis of Cp*Rh(III) complexes 1a and 1b
The attempted synthesis of Rh-1 following closely the synthetic
procedure used for preparation of Ir-1 was unsuccessful [6b]. The
reaction of [Cp*RhCl2]2 with 6-phenyl-2-pyridone in the presence
of NaOAc in dichloromethane at room temperature exclusively gave
* Corresponding author.
E-mail address: jones@chem.rochester.edu (W.D. Jones).
This article is dedicated to Professor John Gladysz on the occasion of his 65th
1
birthday.
http://dx.doi.org/10.1016/j.jorganchem.2017.02.015
0022-328X/© 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: L. Munjanja, et al., Journal of Organometallic Chemistry (2017), http://dx.doi.org/10.1016/
j.jorganchem.2017.02.015

2
L. Munjanja et al. / Journal of Organometallic Chemistry xxx (2017) 1e5
Single crystals suitable for X-ray diffraction were obtained for 1a by
layering a CH2Cl2 solution with pentane. The structure shows a
monomeric complex bearing Cp* and a N,O chelate ligand (Fig. 2).
In complex 1a the carboneoxygen bond is 1.295(3) Å, a distance in
between that expected for a single or double bond. Related N,O
chelate complexes of iridium and nickel show this delocalized
behavior [6a, 7].
Unfortunately, single crystals for 1b were challenging to obtain,
but addition of an excess of NaOAc to 1b in CH2Cl2 replaced the
chloride with an acetate ligand to give 1b'. Crystals of complex 1b'
were obtained by layering a CH2Cl2 in pentane. X-ray diffraction
confirms the N,O chelated complex with a monodentate acetate
ligand (Fig 3). The N1eRheO1 angle for the five membered met-
allacycle 1b' is 78.30ꢀ, much larger compared to 61.92ꢀ for the four
membered complex 1a. The RheO bonds are 2.1581 and 2.126 Å for
1a and 1b' respectively. In addition, the RheN bonds of 2.1357 and
2.090 Å are in the normal range of typical RheN bond lengths [10].
Fig. 1. Known catalyst Cp*Ir[(2-OH-6-phenyl)pyridine]Cl Ir-1 (left [6b]) and proposed
catalyst Cp*Rh[(2-OH-6-phenyl)pyridine]Cl, Rh-1 (right).
the N,O chelated complex 1a rather than the anticipated C,N
chelated product, Rh-1 (Scheme 1). Complex 1a was isolated as a
red solid that is stable indefinitely under air and moisture. To our
surprise, there has been no reported Cp*Rh catalyst with N,O
chelation.
Complexes 1a and 1b' both adopt
configuration.
a 3-legged piano stool
Employing stronger bases such as PhCO2Na to promote CeH
activation [9] of 6-phenyl-2-pyridone did not give the desired
product Rh-1. To confirm the preference for N,O chelation a sepa-
rate experiment was conducted with [Cp*RhCl2]2 and 8-
hydroxyquinoline in the presence of NaOAc in dichloromethane
at room temperature. Indeed, complex 1b was formed with N,O
chelation (eq (1)).
2.2. Rhodium vs. iridium selectivity
Davies and coworkers have reported formation of cyclo-
metalated rhodium and iridium complexes with various nitrogen
donor ligands using NaOAc to deprotonate the CeH bond [11].
Following Davies' synthetic approach, we have reported forma-
tion of C,N iridium and rhodium complexes from the reactions of
[Cp*MCl2]2 (M ¼ Ir, Rh) and substituted phenyl imines and 2-
phenypyridines [10]. Consequently, it was surprising for the re-
action of [Cp*RhCl2]2 with 6-phenyl-2-pyridone to favor the N,O
product 1a instead of the C,N product, Rh-1. DFT calculations
employed on the N,O chelated Rh complex 1a versus Rh-1 showed
that 1a is 12.6 kcal/mol more thermodynamically preferred than
Rh-1. Interestingly, the same trend is observed for iridium. The
N,O chelation product for iridium, 2a, is more favored than the C,N
chelation product Ir-1 by 8.1 kcal/mol (Scheme 2). On the basis of
these calculations one would expect to form N,O chelation com-
plexes for both iridium and rhodium and disfavor C,N chelation
products. However, experimentally, the exclusive formation of 1a
(N,O chelation product) is seen for rhodium and exclusive for-
mation of Ir-1 (C,N chelation product) is seen for iridium. A
plausible explanation for this significant difference in reactivity
(1)
Complexes 1a and 1b were characterized by 1H and 13C{1H}
NMR spectroscopy, elemental analysis, and infra-red spectroscopy.
The five-membered metallacycle 1b shows the Cp* resonance
further downfield at
d 1.71 compared to the four membered met-
allacycle 1a at
d
1.45 in the 1H NMR spectrum in CD2Cl2. Neither C]
O nor NeH stretches are observed in the solid state IR spectrum.
Fig. 2. Thermal ellipsoid drawing of the molecular structure of 1a. Ellipsoids are
shown at the 50% probability level. Selected bond lengths (Å) and angles [ꢀ]: Rh(1)-
O(1) 2.1581(15); Rh(1)-N(1) 2.1357(17); C(1) -O(1) 1.295(3); N(1)-C(1) 1.361(3); N(1)-
Rh(1)-O(1); 61.92(6); O(1)-C(1)-N(1) 112.53(18).
Scheme 1. Preferentially formation of N,O chelation complex 1a over C,N complex Rh-
1 from the reaction of 6-phenyl-2-pyridone and [Cp*RhCl2]2.
Please cite this article in press as: L. Munjanja, et al., Journal of Organometallic Chemistry (2017), http://dx.doi.org/10.1016/
j.jorganchem.2017.02.015

L. Munjanja et al. / Journal of Organometallic Chemistry xxx (2017) 1e5
3
system leads to C-Hb activation to give Ir-1 as the only product
(pathway B).
2.3. Catalytic activity of 1a and 1b
With the rhodium complexes 1a and 1b in hand, the dehydro-
genation of 1-phenylethanol to acetophenone with the release of
hydrogen was examined. First, the thermal stability of the com-
plexes was investigated by monitoring complex 1a or 1b at 150 ꢀC
in p-xylene by 1H NMR spectroscopy over 48 h. Approximately
30e40% of complex 1a slowly decomposed over that time period. In
contrast approximately 10% of 1b decomposed after 48 h. The
decomposition products were NMR silent making their identifica-
tion difficult.
Employing 10 mol% of catalyst 1a, 1-phenylethanol was heated
in toluene-d8 at 115 ꢀC, resulting in an 80% conversion of 1-
phenylethanol to acetophenone (79% yield). Lowering the catalyst
loading to 1 mol% of 1a did not affect the conversion and yield of
acetophenone. Changing the solvent to p-xylene and heating to
150 ꢀC for 24 h with 1 mol % catalyst 1a results in 100% conversion
of 1-phenylethanol to give 100% yield of acetophenone with the
release of hydrogen (eq (2)). In a separate experiment, 1 mol% of 1b
can yield 100% of acetophenone from 1-phenylethanol under
similar reaction conditions.
Fig. 3. Thermal ellipsoid drawing of the molecular structure of 1b'. Ellipsoids are
shown at the 50% probability level. Selected bond lengths (Å) and angles [ꢀ]: Rh (1)-
O(1) 2.126(4); Rh(1)-N(1) 2.090(4); C(1) -O(1) 1.323(7); N(1)-C(8) 1.380(6); C(1) -C(8)
1.428(7); N(1)-Rh(1)-O(1) 78.30(15); O(1)-C(1)-C(8) 118.2(5); C(1)-C(8)-N(1) 116.1(4);
C(8)-N(1)-Rh(1) 113.7(3).
(2)
To test the homogeneity of the system we ran the dehydroge-
nation reaction after the addition of 2 drops of mercury for 24 h
with 1 mol% of either 1a or 1b in p-xylene. For both catalysts we
observe a shutdown of the dehydrogenation reaction. Minimal
formation of acetophenone is observed in the 1H NMR spectrum
(<10%). To confirm if the reaction was indeed being catalyzed
heterogeneously, the formation of acetophenone was monitored
over 4 h by 1H NMR spectroscopy. A plot of the formation of ace-
tophenone over time does not display clean first order kinetics as
expected for
a homogeneous catalyst (see Supplementary
Information). These observations point to the involvement of
nanoparticles.
Additional evidence for nanoparticle formation was obtained by
examining the residue left after evaporation of the solution
following a dehydrogenation of 1-phenylethanol by TEM. EDX
spectroscopy confirmed the presence of rhodium in the particles.
The size of the particles was determined by XRD examination of the
material, which indicated a ~2 nm diameter (See Supporting In-
formation). Loss of a Cp* ligand to form an active transfer hydro-
genation catalyst has been observed previously [12], and rhodium
nanoparticles have recently been reported to dehydrogenate alco-
hols [13].
These results are quite surprising considering that the reported
iridium and nickel N,O complexes appear to be homogenous cata-
lysts in the dehydrogenation of alcohols to carbonyl compounds
[6a,7]. Rhodium nanoparticles have been reported previously to
facilitate dehydrogenation of ammonia-borane [14]. In addition
only a few homogeneous rhodium catalysts can participate in
acceptorless dehydrogenation [15,5b], though no rhodium N,O
complexes have been reported for dehydrogenation reactions to
our knowledge.
Scheme 2. Pathway for the preferential formation of N,O chelated Rh complex 1a.
can be traced back to the differences in electrophilicity of the
metal centers, with iridium being the more electrophilic of the
two.
Our group reported that the cationic [Cp*M(OAc)]þ species is
responsible for the electrophilic CeH activation of phenyl-
pyridines [10]. [Cp*M(OAc)]þ is generated in situ from the reaction
of [Cp*MCl2]2 and NaOAc. In using 6-phenyl-2-pyridone as the
chelating ligand we create two competing pathways for the
electrophilic metal centers (Scheme 2). Pathway A involves
deprotonation of the acidic phenol proton Ha to yield N,O chelated
complexes and pathway B involves C-Hb activation to give C,N
chelated complexes. We hypothesize that the exclusive formation
of 1a with the less electrophilic Rh occurs via that the favorable Ha
deprotonation (pathway A) by the acetate base to acetic acid
rather than CeH activation via Hb. However, in the case of the
Complex 1a was tested for hydrogenation catalysis. As shown in
equation (3), hydrogenation with 5 atm hydrogen at 150 ꢀC leads to
a product in which complete hydrogenation of both the ketone and
more electrophilic [Cp*Ir(OAc)]þ, interaction with the phenyl
p-
Please cite this article in press as: L. Munjanja, et al., Journal of Organometallic Chemistry (2017), http://dx.doi.org/10.1016/
j.jorganchem.2017.02.015

4
L. Munjanja et al. / Journal of Organometallic Chemistry xxx (2017) 1e5
the aromatic ring has taken place. A small quantity of cyclohexyl
methyl ketone is observed, indicating that hydrogenation of the
aromatic ring is more facile than hydrogenation of the ketone
moiety. This observation is consistent with the known reports that
heterogeneous rhodium catalysts can hydrogenate arenes to cy-
clohexanes [16-19]. Use of 1 atm of H2 in neat acetophenone pro-
duces a 1:1 ratio of these products after 24 h at 150 ꢀC.
evaporated under vacuum to obtain a red material. This solid was
washed with ~15 mL of pentane and dried further in vacuo to afford
the 1b (110 mg, 81%). 1H NMR (400 MHz, CD2Cl2):
d 8.55 (d,
J ¼ 4.7 Hz, 1H), 8.11 (d, J ¼ 8.4 Hz, 1H), 7.39 (dd, J ¼ 8.3, 4.8 Hz, 1H),
7.33 (t, J ¼ 8.0 Hz, 1H), 6.86 (d, J ¼ 7.9 Hz, 1H), 6.81 (d, J ¼ 7.4 Hz,1H),
1.71 (s, 15H). 13C{1H} NMR (126 MHz, CD2Cl2):
d 167.76 (s), 146.87
(s), 145.68 (s), 138.13 (s), 131.22 (s), 130.82 (s), 122.69 (s), 114.86 (s),
93.88 (s), 93.81(s), 9.14 (s). Anal. Calcd for C19H21ClNORh: C, 54.63;
H, 5.07; N, 3.35. Found: C, 53.61; H, 5.13; N, 3.15.
(3)
3.4. Dehydrogenation of 1-phenylethanol to acetophenone
Complex 1a or 1b (26
mmol) and 1-phenylethanol (2.6 mmol,
326 L) were mixed with 0.5 mL of p-xylene in a 3 mL flame-dried
m
ampoule. The solution color was light orange. The ampoule was
sealed and stirred at 150 ꢀC for 24 h. After the reaction, the solution
was cooled to room temperature, filtered through a short silica gel
column, and eluted with diethyl ether (0.3 mL). The resulting
filtrate was evaporated under vacuum to afford an oily residue. The
1H NMR spectrum in CDCl3 of the product showed acetophenone as
the only product. Dehydrogenation of 1-phenylethanol (1 mol %
catalyst 1a or 1b) in the presence of 2 drops of elemental mercury
shut down catalytic activity.
3. Experimental section
3.1. General considerations
Unless otherwise noted, all of the organometallic compounds
were prepared and handled under a nitrogen atmosphere using
standard Schlenk and glovebox techniques. Dry and oxygen-free
solvents (CH2Cl2, and pentane) were collected from an Innovative
Technology PS-MD-6 solvent purification system and used
throughout the experiments. Other solvents such as CD2Cl2 and
CDCl3 were used as received from commercial sources. 1H and 13C
{1H} NMR spectra were recorded on a Bruker Avance-400 NMR
spectrometer. Chemical shift values in 1H and 13C{1H} NMR spectra
were referenced internally to the residual solvent resonances.
Infrared spectra were recorded in the solid state on a Thermo Sci-
entific Nicolet 4700 FT-IR spectrometer equipped with smart orbit
diamond attenuated total refiectance (ATR) accessory. Elemental
analysis was performed by the University of Rochester using a
Perkin Elmer 2400 Series II elemental analyzer in CHN mode. TEM
images and EDX spectra were recorded on a FEI Tecnai F20 G2
Scanning Transmission Electron Microscope (S)TEM at the URNano
Center. XRD data were obtained on a Philips Powder X-ray
diffractometer in the Mechanical Engineering X-ray Analysis Lab-
oratory at the University of Rochester.
3.5. Hydrogenation of acetophenone at 1 atm and 5 atm H2
Complex 1a (42.8 mmol) and acetophenone (4.28 mmol, 500 mL)
were mixed in a 500 mL round bottom flask. The sample was placed
under 1 atm H2 heated at 150 ꢀC for ~24 h. After the reaction, the
solution was cooled to room temperature. The mixture was filtered
through Celite in a glass pipette, and the filtrate diluted with THF.
Examination of the product by GC showed the complete disap-
pearance of acetophenone and the appearance of both cyclohexyl
methyl ketone and 1-cyclohexylethanol in a 1:1 ratio.
Complex 1a (12.8 mmol) and acetophenone (1.28 mmol, 150 mL)
were mixed with 0.25 mL of p-xylene in a Teflon-lined Parr bomb
reactor (50 mL). The sample was placed under 5 atm H2 and heated
at 150 ꢀC for ~2 h. After the reaction, the solution was cooled to
room temperature and the reactor vented. The mixture was filtered
through Celite in a glass pipette, and the filtrate diluted with THF.
Examination of the product by GC showed the complete disap-
pearance of acetophenone and the appearance of both cyclohexyl
methyl ketone and 1-cyclohexylethanol in a 6:1 ratio.
3.2. Preparation of Cp*RhCl(6-phenylpyridone), 1a
[Cp*RhCl2]2 (50 mg, 0.081 mmol), 6-phenyl-2-pyridone (28 mg,
0.162 mmol), NaOAc (17 mg, 0.207 mmol), and 2 mL of dichloro-
methane was added to a flame-dried Schlenk flask. The resulting
red solution was stirred at room temperature for 24 h after which
the solution was filtered through Celite and the filtrate was evap-
orated under vacuum to obtain a red material. This solid was
washed with ~5 mL of pentane and ~1 mL of toluene and dried
further in vacuo to afford 1a (48 mg, 69%). 1H NMR (500 MHz,
4. Conclusions
In summary, we have demonstrated the synthesis of N,O
chelated Rh complexes 1a and 1b. The catalysts decompose upon
heating to give nanoparticles, which in turn can efficiently dehy-
drogenate 1-phenylethanol to give 100% yield of acetophenone
with the release of hydrogen. However, hydrogenation of aceto-
phenone leads to both cyclohexyl methyl ketone and 1-cyclo-
hexylethanol. The involvement of rhodium nanoparticles was
indicated by inhibition using elemental mercury and direct obser-
vation using TEM.
CD2Cl2):
4H, ArH), 6.54 (d, J ¼ 7.1 Hz, 2H, ArH), 6.06 (d, J ¼ 8.5 Hz, 2H, ArH),
1.45 (s, 15H, C5Me5); 13C{1H} NMR (126 MHz, CD2Cl2):
176.81 (CO),
d
7.92 (d, J ¼ 6.9 Hz, 2H, ArH), 7.53e7.34 (m, J ¼ 13.5, 7.4 Hz,
d
155.63 (ArC), 139.90 (ArC), 129.26 (ArC), 129.25 (ArC), 129.06 (ArC),
92.83 (ArC), 92.77 (ArC), 9.23 (C5Me5). Anal. Calcd for C21H8ClNORh:
C, 58.84; H, 1.88; N, 3.27. Found: C, 59.20; H, 1.73; N, 3.01.
3.3. Preparation of Cp*RhCl(8-hydroxylquinoline), 1b
Acknowledgments
[Cp*RhCl2]2 (200 mg, 0.324 mmol), 8-hydroxylquinoline (94 mg,
0.647 mmol), NaOAc (68 mg, 0.828 mmol), and 10 mL of
dichloromethane was added to a flame-dried Schlenk flask. The
resulting red solution was stirred at room temperature for 24 h
after which the solution was filtered through Celite. The filtrate was
Support for this work was provided by the National Science
Foundation grant CHE-1360985. L.M and H. Y would like to thank
Dr. Sarina Bellows for the computational calculations and insightful
discussions.
Please cite this article in press as: L. Munjanja, et al., Journal of Organometallic Chemistry (2017), http://dx.doi.org/10.1016/
j.jorganchem.2017.02.015

L. Munjanja et al. / Journal of Organometallic Chemistry xxx (2017) 1e5
559e563;
5
Appendix A. Supplementary data
~
(d) I. Mena, M.A. Casado, V. Polo, P. Garcia-Orduna, F.J. Lahoz, L.A. Oro, Angew.
Chem. Int. Ed. 51 (2012) 8259e8263;
X-ray crystallographic data for 1a and 1b' are included. CIF files
giving crystallographic information, including data collection pa-
rameters, bond lengths, fractional atomic coordinates, and aniso-
tropic thermal parameters, for complexes 1a and 1b' have been
deposited with the CCDC (1503278-1503279) and NMR spectra for
the complexes. GC traces for the hydrogenations are shown. TEM,
EDX, and XRD data for the nanoparticles.
(e) M. Bertoli, A. Choualeb, A.J. Lough, B. Moore, D. Spasyuk, D.G. Gusev, Or-
ganometallics 30 (2011) 3479e3482.
[6] (a) K.-I. Fujita, N. Tanino, R. Yamaguchi, Org. Lett. 9 (2007) 109e111;
(b) K.-I. Fujita, T. Yoshida, Y. Imori, R. Yamaguchi, Org. Lett. 13 (2011)
2278e2281;
(c) R. Kawahara, K.-I. Fujita, R. Yamaguchi, J. Am, Chem. Soc. 134 (2012)
3643e3646;
(d) R. Kawahara, K.-I. Fujita, R. Yamaguchi, Angew. Chem. Int. Ed. 51 (2012)
12790e12794;
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2017.02.015.
(e) G. Zeng, S. Sakaki, K.-I. Fujita, H. Sano, R. Yamaguchi, ACS Catal. 4 (2014)
1010e1020.
[7] S. Chakraborty, P.E. Piszel, C.E. Hayes, R.T. Baker, E.D. Jones, Organometallics
34 (2015) 5203e5206.
[8] S. Chakraborty, P.E. Piszel, C.E. Hayes, R.T. Baker, W.D. Jones, J. Am. Chem. Soc.
137 (2015) 14264e14267.
References
[9] A.P. Walsh, W.D. Jones, Organometallics 34 (2015) 3400e3407.
[10] L. Li, W.W. Brennessel, W.D. Jones, Organometallics 28 (2009) 3492e3500.
[11] (a) D.L. Davies, O. Al-Duaij, J. Fawcett, M. Giardiello, S.T. Hilton, D.R. Russell,
Dalton Trans. (2003) 4132e4138;
[1] M. Yadav, Q. Xu, Energy Environ. Sci. 5 (2012) 9698e9725.
[2] (a) G. Guillena, D.J. Ramon, M. Yus, Chem. Rev. 110 (2010) 1611e1641;
(b) C. Gunanathan, D. Milstein, Science 341 (2013) 1229712.
[3] (a) T.C. Jonson, D.J. Morris, M. Wills, Chem. Soc. Rev. 39 (2010) 81e88;
(b) M. Nielsen, A. Kammer, D. Cozzula, H. Junge, S. Gladiali, M. Beller, Angew.
Chem. Int. Ed. 50 (2011) 9593e9597;
ꢀ
(b) D.L. Davies, S.M.A. Donald, O. Al-Duaij, J. Fawcett, C. Little, S.A. Macgregor,
Organometallics 25 (2006) 5976;
(c) A.J. Davenport, D.L. Davies, J. Fawcett, D.R. Russell, J. Organomet. Chem. 691
(2006) 2221e2227;
(d) D.L. Davies, S.M.A. Donald, O. Al-Duaij, S.A. Macgregor, M. Polleth, J. Am.
Chem. Soc. 128 (2006) 4210e4211.
(c) M. Trincado, D. Banerjee, H. Grütmacher, Energy Environ. Sci. 7 (2014)
2464e2503.
[4] (a) G.E. Dobereiner, R.H. Crabtree, Chem. Rev. 110 (2009) 681e703;
ꢀ
~
(b) M.A. Esteruelas, N. Honczek, M. Olivan, E. Onate, M. Valencia, Organo-
metallics 30 (2011) 2468e2471;
[12] J. Campos, U. Hintermair, T.P. Brewster, M.K. Takase, R.H. Crabtree, ACS Catal. 4
(2014) 973e985.
(c) A. Maggi, R. Madsen, Organometallics 31 (2012) 451e455;
(d) J.W. Rigoli, S.A. Moyer, S.D. Pearce, J.M. Schomaker, Org. Biomol. Chem. 20
(2012) 1746e1749;
(e) E. Kossoy, Y. Diskin-Posner, G. Leitus, D. Milstein, Adv. Synth. Catal. 354
(2012) 497e504;
[13] L. Yao, J. Zhao, J.-M. Lee, ACS Sustain. Chem. Eng. (2017), http://dx.doi.org/
10.1021/acssuschemeng.6b02994.
€
[14] T. Ayvalı, M. Zahmakıran, S. Ozkar, Dalton Trans. 40 (2011) 3584e3591.
[15] D. Morton, D.J. Cole-Hamilton, J. Chem, Soc. Chem. Commun. (1987) 248e249.
[16] M. Ohde, H. Ohde, C.M. Wai, Chem. Commun. (2002) 2388e2389.
(f) A. Mukherjee, A.S. Nerush, G. Leitus, L.J.W. Shimon, Y.B. David, N.A.E. Jalapa,
D. Milstein, J. Am. Chem. Soc. 138 (2016) 4298e4301.
[5] (a) I. Dutta, A. Sarbajna, P. Pandey, S.M.W. Rahaman, K. Singh, J.K. Bera, Or-
ganometallics 35 (2016) 1505e1513;
ꢀ
[17] A. Sanchez, M. Fang, A. Ahmed, R.A. Sanchez-Delgado, Appl. Catal. A General
477 (2014) 117e124.
[18] H. Yang, H. Gao, R.J. Angelici, Organometallics 19 (2000) 622e629.
[19] P. Barbaro, C. Bianchini, V. Dal Santo, A. Meli, S. Moneti, R. Psaro, A. Scaffidi,
L. Sordelli, F. Vizza, J. Am. Chem. Soc. 128 (2006) 7065e7076.
(b) G. Zeng, S. Sakaki, K.-I. Fujita, H. Sano, R. Yamaguchi, ACS Catal. 4 (2014)
1010e1020;
(c) T. Zweifel, J.V. Naubron, H. Grützmacher, Angew. Chem. Int. Ed. 48 (2009)
Please cite this article in press as: L. Munjanja, et al., Journal of Organometallic Chemistry (2017), http://dx.doi.org/10.1016/
j.jorganchem.2017.02.015