A Ni0(η2-(Si-H))(η2-H2) Complex That Mediates Facile H Atom Exchange between Two σ-Ligands

Article abstract of DOI:10.1021/acs.organomet.5b00985

σ-adduct complexes of low-valent, late first-row metal complexes are highly unusual, and this is particularly true of d¹⁰ systems. We have discovered a nickel/phosphine/silyl system that undergoes reaction with H₂ in solution to gene

Full text of DOI:10.1021/acs.organomet.5b00985

Article
pubs.acs.org/Organometallics
A Ni0(η2‑(Si−H))(η2‑H2) Complex That Mediates Facile H Atom
Exchange between Two σ‑Ligands
Bridget A. Connor, Jonathan Rittle, David VanderVelde, and Jonas C. Peters*
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
S
* Supporting Information
ABSTRACT: σ-adduct complexes of low-valent, late first-row
metal complexes are highly unusual, and this is particularly true
of d10 systems. We have discovered a nickel/phosphine/silyl
system that undergoes reaction with H2 in solution to generate
a species best described as Ni0(η2-(Si−H))(η2-H2) on the basis
of multinuclear NMR studies. Theoretical calculations suggest
that the Ni center facilitates H atom exchange between the η2-(Si−H) and η2-H2 ligands via interconversion with a higher valent
NiII isomer. This exchange is exploited in the selective, catalytic deuteration of exogenous silanes.
INTRODUCTION
RESULTS AND DISCUSSION
■
■
Synthesis of [(SiP2)2O]Ni2 Synthons. The chemistry of
While homogeneous transition-metal catalysis has benefitted
enormously from the use of noble metals,1 there is significant
interest in developing catalysts that instead use earth-abundant
first-row transition metals without compromising the efficiency
and/or selectivity of their noble-metal counterparts.2 For
example, nickel has attracted recent attention as a catalyst for
the hydrosilylation3 and hydrogenation4 of various substrates.
Intermediates of such catalysis may include σ-silane and σ-
dihydrogen complexes of low-valent nickel. Whereas an
enormous body of work has highlighted the direct involvement
of σ-complexes in related catalytic cycles,5 σ-silane6 and σ-
dihydrogen7 complexes of Ni remain very rare and hence
largely unexplored. Zerovalent nickel is d10, and d10 systems,
irrespective of the transition metal and with very few
exceptions, do not generally form σ-adduct complexes with
either H2 or silanes;6a,c,g,h,7a they are instead prone to undergo
oxidative addition to form d8 dihydrides/silyl hydrides.7a,8
In this report, we describe the synthesis and characterization
of several η2-(Si−H) and η2-H2 complexes of zerovalent nickel.
Most interestingly, we have prepared a Ni0 complex with both
of these σ-ligands simultaneously coordinated to a single Ni0
center. To our knowledge there is only one other example of a
transition-metal complex featuring these two ligand types
bonded to a single metal center (Ru).9 Detailed NMR studies
support our assignment of this Ni0(η2-(Si−H))(η2-H2) species,
and theoretical studies suggest that the Ni center facilitates H
atom exchange between the η2-(Si−H) and η2-H2 ligands via
interconversion with a higher valent NiII isomer. This exchange
can be exploited in the selective, catalytic deuteration of
exogenous silanes. The results we report hence add to the
limited knowledge of the chemistry of H2 and silane adducts
with d10 transition metals and underscore Ni0 σ-adduct species
as broadly interesting in the context of homogeneous catalysis.
group 10 metals on [RPSiP] ligands (RPSiP = Si(R1)(2-PR2-
i
C6H4)2, R = Ph, Cy, Pr; R1 = Me, OH) has been investigated
by several groups, and some of these systems have shown
promise in the context of catalysis.10 We chose to explore the
chemistry of Ni on a binucleating variant of the [iPrPSiP] ligand,
initially hoping to explore cooperative reactivity with a
binucleating scaffold.11 Entry into this system was achieved
by the reaction of [(SiP2)2O]H2 with 2.1 equiv of NiX2·DME
(X = Cl, Br) in the presence of triethylamine to furnish
[(SiP2)2O]Ni2(X)2 (1-Cl, 1-Br) (eq 1).
2.1 equiv NiX2DME
[(SiP ) O]H2 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→ [(SiP ) O]Ni2(X)2
2 2
2 2
excess NEt3
1‐Cl, X = Cl
1‐Br, X = Br
(1)
Two distorted-square-planar Ni centers are observed in the
crystal structure of 1-Cl (Figure 1) with each Ni center
coordinated to two trans phosphine ligands (P−Ni−P angles
157.93(2), 160.12(2)°) in addition to the Cl− and silyl ligands
(d(Ni−Si) = 2.2166(5), 2.2189(5) Å). No metal−metal
interaction is observed (d(Ni···Ni) = 6.0473(6) Å). 1-Cl and
1-Br are diamagnetic complexes and display a single sharp
resonance in the 31P NMR spectrum (1-Cl, δ 60.2 ppm; 1-Br, δ
61.4 ppm) and triplets in the 29Si NMR spectrum (1-Cl, δ
2
2
43.55 ppm, JSi−P = 35.5 Hz; 1-Br, δ 45.84 ppm, JSi−P = 34.0
Hz).
The [(SiP2)2O] ligand framework was found to accom-
modate lower oxidation states of Ni. Reduction of [(SiP2)2O]-
Ni2(Br)2 (1-Br) with KC8 in THF yielded orange [(SiP2)2O]-
Ni2 (2) (eq 2). The crystal structure of 2 (Figure 1) revealed a
reorganization of the coordination environment presented by
[(SiP2)2O] to accommodate two formally NiI centers. The local
geometries of the two Ni centers are similar and can be
Received: December 2, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00985
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
unsymmetrical binding geometry of [(SiP2)2O] (refer to the
Supporting Information for spectra).
2.1 equiv KC8
[(SiP ) O]Ni2(Br)2 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→⎯ [(SiP ) O]Ni2
(2)
2 2
2 2
Reactivity of 2 with H2. On exposure of orange 2 to 1 atm
of H2, the solution color gradually faded to yellow over the
course of 6 h. Removal of the H2 atmosphere by three freeze−
pump−thaw cycles did not restore 2, even after prolonged
exposure to vacuum, as judged by multinuclear NMR
spectroscopy. Instead, a new species, formulated as [(SiP2)2O]-
Ni2(H)2 (3-2H) was observed (Scheme 1; the 3-2H label is
used to define the number of H atoms taken up to distinguish
this species from 3-4H and 3-6H (vide infra)). 3-2H displays a
1
hydride resonance in the H NMR spectrum at δ −4.00 ppm
that integrates to one proton per Ni. When the temperature is
lowered to −90 °C, this resonance splits into a triplet (2JP−H
=
45.3 Hz) indicating coupling to two equivalent phosphine
ligands. The solid-state IR spectrum of 3-2H displays a strong
ν(Ni−H) stretch at 1701 cm−1 which shifts to 1234 cm−1 on
deuterium substitution (via synthesis with D2 in place of H2),
consistent with a terminal Ni−H species. The relatively low
frequency of this vibration is most consistent with a hydride
positioned trans to the strongly trans influencing and electron
releasing silyl ligand.4f A 29Si chemical shift of δ 60.0 ppm was
observed, similar to the case for 1-Cl and 1-Br. It is noteworthy
that the preparation of terminal Ni−H complexes from the
direct reaction with H2 is uncommon, typically requiring the
action of cooperative ancillary ligand motifs.4a
Figure 1. X-ray diffraction crystal structures of 1-Cl and 2 with
thermal ellipsoids drawn at 50% probability. Hydrogen atoms have
been removed for clarity. The isopropyl substituents have been
rendered transparent to aid in visualization of the coordination
environment about Ni.
Reactivity of 3-2H with CO. Interested in exploring the
reactivity of 3-2H with L-type donor ligands, we exposed 3-2H
to 1 atm of CO and observed an immediate bleaching of the
solution color. The resulting species (4) displays a sharp triplet
in the 1H NMR spectrum (2H, δ −6.94 ppm, 2JP−H = 42.3 Hz)
as well as two prominent IR features at 1966 and 1769 cm−1
corresponding to ν(CO) and ν(Ni−H), respectively. A
1H−29Si HMBC experiment revealed a 29Si chemical shift of δ
described as distorted square planar, where each Ni center is
bound to two chemically inequivalent cis phosphines and one
silyl ligand. To complete the square plane, a short Ni−Ni
distance of 2.4169(2) Å was found, consistent with a Ni−Ni
single bond.6b,12 In accord with this interaction, 2 appeared
diamagnetic by NMR spectroscopy; its 31P{1H} NMR
spectrum features two resonances of equal integration (δ
43.35, 50.47 ppm); the 29Si spectrum shows a broad doublet (δ
2
70.19 ppm with JSi−H = 67.9 Hz. These data are consistent
with a hydrido-silyl species in which the hydride is positioned
trans to the silyl ligand and allow us to formulate 4 as
[(SiP2)2O]Ni2(CO)2(H)2, as drawn in Scheme 1. When it was
heated to 45 °C for 12 h under an N2 atmosphere, 4 was
observed to isomerize to complex 5. Complex 5 displays a
2
20.42 ppm) with JP−Si(trans) = 94.3 Hz (2JP−Si(cis) was not
resolved).13 1H and 13C NMR data are also consistent with the
Scheme 1. Synthesis of Ni Complexes Derived from the [(SiP2)2O]H2 Ligand
B
DOI: 10.1021/acs.organomet.5b00985
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Figure 2. (A) Behavior of 3-2H under H2 and (B−D) supporting 1H NMR spectra: (B) 1H NMR spectra of 3-2H under varying pressures of H2 (25
1
1
1
1
°C, C6D6); (C) H, H{2H}, and H{31P} NMR spectra of 3-2H under 3.9 atm of HD (−90 °C, C7D8); (D) H NMR spectra of 3-2H under
varying pressures of H2 (−90 °C, C7D8).
sharp triplet in its 1H NMR spectrum (2H, δ −2.40 ppm, 2JP−H
= 22.1 Hz) and ν(CO) at 1956 cm−1 in its IR spectrum, but
no features ascribable to a ν(Ni−H) are observed. The 1H−29Si
HMBC spectrum of 5 indicates strong coupling of the hydridic
those observed for 5 and establish the presence of an η2-(Si−
1
H) ligand. In addition, a H{31P} NMR spectrum (−90 °C)
under 3.9 atm of HD (Figure 2C, bottom) indicates that the
resonance at δ −3.01 ppm is coupled to phosphorus with 2JP−H
= 22.3 Hz. This coupling constant is nearly identical with that
observed in 5 (22.1 Hz) and differs dramatically from that
observed in 4 (42.3 Hz), again suggesting a close structural
analogy between the present dihydrogen adduct species and 5.
Multinuclear NMR data have established the coordination of
H2 by 3-2H and a structural rearrangement induced by this
binding event. However, the variable-pressure NMR data
(Figure 2B) suggest rather weak binding of H2 to Ni, which
we suggest can be understood by considering the interconver-
sion of compounds 3-2H, 3-4H, and 3-6H as depicted in
Figure 2A (the nomenclature defines the number of H atoms
bound). The relative populations of these rapidly interconvert-
ing species are dictated by the concentration of H2 in solution,
causing the trends in chemical shift and integration value
observed in Figure 2B. At low temperature, the interconversion
of 3-2H, 3-4H, and 3-6H is sufficiently slow to allow
observation of the spectroscopic features of both tetrahedral
Ni0 and square-planar NiII centers under intermediate H2
1
resonance in the H NMR to a silicon center with a chemical
shift of δ 8.98 ppm (1JSi−H = 122.5 Hz). These observations are
consistent with the presence of an η2-(Si−H) ligand. We
therefore assign complex 5 as [(SiHP2)2O]Ni2(CO)2, with a
σ(Si−H) interaction to each Ni0 center, as depicted in Scheme
1.
Dynamic Reactivity of 2 and 3-2H with H2. Compound
3-2H was found to support the coordination of H2 ligands, as
depicted in Figure 2A. On exposure of 3-2H to increasing
1
pressures of H2, the hydridic H resonance of the product
steadily shifted downfield while integrating to increasingly
larger values, as shown in Figure 2B. Similar results were
obtained by direct addition of varying H2 pressures to 2.
Notably, in all spectra, no peak corresponding to free H2 was
observed. This suggests that rapid exchange of the coordinated
hydride ligand/s with dissolved H2 leads to coalescence of their
1H NMR resonances.14 When the reaction mixture of 2 with
3.9 atm of H2 was cooled to −90 °C, the hydridic peak
observed in the room-temperature 1H NMR spectrum
decoalesced to give two hydridic signals (δ −1.84, −3.01
ppm) and a resonance corresponding to free H2 (Figure 2D,
top; also see the Supporting Information). Under 3.9 atm of
HD at −90 °C, the broad hydridic resonances sharpened
significantly and both appeared as triplets (Figure 2C, top).15
1
pressures. As shown in Figure 2D, the −90 °C H NMR
spectrum of 3-2H under 1 atm of H2 includes the features of
both 3-6H (top spectrum) and 3-2H (bottom spectrum).
Variable-pressure 29Si and 31P NMR data at −90 °C give similar
results (refer to the Supporting Information).
It is important to note that the equilibrium described in
Figure 2A treats each Ni center as acting independently of its
neighbor. We have no experimental or computational evidence
(vide infra) to suggest intramolecular metal−metal interactions
as facilitating this equilibrium. Hence, counter to our initial
intent, the use of this binucleating scaffold does not engender
cooperative bimetallic reactivity toward H2 between the Ni
centers, with a possible exception being the conversion of 2 to
3-2H. This ligand does, however, expose fascinating solution
equilibria between H2/Si−H ligands where cooperative and
reversible Ni−Si activations occur.
1
The low-temperature H{2H} NMR spectrum reveals that the
more downfield hydride resonance (δ −1.84 ppm) is coupled
to deuterium with 1JH−D = 34.2 Hz (Figure 2C, middle). Such a
large value of 1JH−D is consistent with an intact H−D ligand and
corresponds to an H−H distance of 0.87 Å on the basis of the
empirical correlation established by Luther and Heinekey.16
Upon H2 coordination to 3-2H, multinuclear NMR spectra
indicate that the Ni centers adopt a tetrahedral geometry
featuring an η2-(Si−H) ligand (Figure 2A), akin to the structure
observed for 5 (Scheme 1). A 29Si NMR resonance for 3-2H
under 3.9 atm of H2 was observed at δ 1.68 ppm at −90 °C
(1JSi−H = 102.0 Hz). These 29Si NMR parameters are similar to
Computational Studies of 3-6H. Given the transient
stability of a NiII isomer observed in the CO system (4), it is
C
DOI: 10.1021/acs.organomet.5b00985
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
reasonable to expect that the analogous H2 species is also
accessible. We probed the energetic feasibility of such a
structure using DFT calculations. The crystal structure of 1-Cl
provided the skeleton for initial geometry optimization of the
two isomers of 3-6H under consideration: isomer I, the
tetrahedral Ni0 structure featuring H2 and η2-(Si−H) ligands,
and isomer II, the trigonal-bipyramidal NiII hydride−
dihydrogen structure. Preliminary calculations carried out on
dimeric structures indicated no interaction between neighbor-
ing Ni centers; therefore, all further calculations were simplified
by considering only half of the dinuclear unit. The optimized
structure of isomer I features short H−H and Si−H distances
(0.90 and 1.80 Å, respectively), consistent with the
coordination of η2-H2 and η2-(Si−H) ligands. The bulky
phosphine groups define an angle of 128.0° with the Ni center,
in line with a distorted-tetrahedral geometry. Consistent with a
shift to a distorted-trigonal-bipyramidal structure, the P−Ni−P
angle of isomer II increases to 139.4°. An H2 ligand (H−H
distance 0.86 Å) completes the equatorial plane. The silyl and
hydride ligands are positioned trans to one another along the
axis (Si−Ni−H = 161.3°), located 2.24 and 1.52 Å from Ni,
respectively (see the Supporting Information for details). These
two optimized isomeric structures were found to be essentially
isoenergetic in the gas phase, lying just 0.06 kcal/mol apart.17
This energetic similarity suggests a pathway for H atom
exchange between the H2 and η2-(Si−H) ligands of 3-6H. As
outlined in Figure 3A, isomerization to structure II followed by
centers of [(SiP2)2O] under an H2 atmosphere might prove
useful in the context of catalytic studies. Facile scrambling of H2
and D2 to produce HD by 3-6H underscores this point. In a
preliminary study, we have explored whether the exchange of
atoms between σ ligands might be extended to related systems
in which the dihydrogen ligand is replaced by another σ ligand,
such as a silane. We thus studied the catalytic conversion of
Ph2SiH2 to Ph2SiD2 by 3-6H-d6. With a catalyst loading of 0.54
mol % of 2, we observed 85% conversion to Ph2SiD2 and 14%
conversion to Ph2SiHD after 12 h of stirring under 3.9 atm of
D2 at 22 °C (Scheme 2). No other major products were
Scheme 2. Proposed Catalytic Cycle for the Deuteration of
a
Silanes
a
Ligand framework omitted for simplicity.
observed by multinuclear NMR spectroscopy. In combination
with this system’s ability to exchange H and D atoms between
σ-silane and D2 ligands, we propose the catalytic cycle shown in
Scheme 2 to explain this reactivity.
Figure 3. (A) Pathway for the exchange of H atoms between the η2-H2
and η2-(Si−H) ligands of 3-6H. (B) Transition state for the
interconversion of isomers I and II located by DFT (Ni, green; P,
yellow; Si, red; H, white) including estimated energy values relative to
isomers I and II (see the Supporting Information for details).
CONCLUSION
■
In conclusion, we have described the synthesis and character-
ization of several species relevant to our fundamental
understanding of H2 and silane activation at low-valent Ni.
Among these compounds is [(SiHP2)2O]Ni2(H2)2 (3-6H),
which to our knowledge serves as the second well-defined
example of a complex with both σ(H−H) and σ(Si−H) bonds
coordinated to the same transition-metal center: in this case d10
Ni0. σ(H−H) and σ(Si−H) adducts of Ni0 are also extremely
rare, as oxidative cleavage of the σ bond most often occurs at
such electron-rich metal centers. Using DFT calculations, we
have provided evidence that isomerization of 3-6H to a higher
valent NiII(Si)(H)(H2) species provides a pathway for H atom
exchange between the Si−H and H2 ligands. This interchange
of atoms between σ-ligands was exploited to carry out the
catalytic deuteration of silanes. This study hence provides
fundamental insights into dihydrogen and silane activation at
low-valent Ni that may contribute to the future development of
catalytic chemistry with this base metal.
rotation of the H2 ligand and reisomerization to structure I
results in rearrangement of the H atoms. Consistent with this
mechanism, a low-lying transition state for interconversion of
the isomers was located 3.6 kcal/mol above isomer I (Figure
3B). This five-center transition state features elongated H−H
(1.696, 1.498, 2.632 Å) and Si−H distances (2.141 Å) and
short Ni−H (1.486, 1.487, 1.494 Å) and Ni−Si (2.240 Å)
distances, consistent with a formal NiIV formulation.6d The
interconversion of isomers I and II via this transition state is
conceptually related to a σ-bond metathesis pathway. The
transition state can also be compared to other computationally
studied metal hydride systems.18
Catalytic Deuteration of Silanes. The ability of 3-6H to
reversibly store and interchange hydrogen atoms on the silicon
D
DOI: 10.1021/acs.organomet.5b00985
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1313−1318. (c) Connelly, S. J.; Zimmerman, A. C.; Kaminsky, W.;
Heinekey, D. M. Chem. - Eur. J. 2012, 18, 15932−15934. (d) He, T.;
Tsvetkov, N. P.; Andino, J. G.; Gao, X.; Fullmer, B. C.; Caulton, K. G.
J. Am. Chem. Soc. 2010, 132, 910−911.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.5b00985.
■
S
(8) Flener Lovitt, C.; Frenking, G.; Girolami, G. S. Organometallics
2012, 31, 4122−4132.
(9) Sabo-Etienne, S.; Hernandez, M.; Chung, G.; Chaudret, B. New J.
Chem. 1994, 18, 175−177.
Experimental protocols, spectral data, catalysis data,
computational details, and crystallographic data (PDF)
Crystallographic data (CIF)
(10) (a) Suh, H.-W.; Guard, L. M.; Hazari, N. Polyhedron 2014, 84,
37−43. (b) Takaya, J.; Iwasawa, N. J. Am. Chem. Soc. 2008, 130,
15254−15255. (c) Mitton, S. J.; McDonald, R.; Turculet, L.
Organometallics 2009, 28, 5122−5136. (d) MacInnis, M. C.;
MacLean, D. F.; Lundgren, R. J.; McDonald, R.; Turculet, L.
Organometallics 2007, 26, 6522−6525. (e) Korshin, E. E.; Leitus, G.;
Shimon, L. J. W.; Konstantinovski, L.; Milstein, D. Inorg. Chem. 2008,
47, 7177−7189.
AUTHOR INFORMATION
Corresponding Author
*E-mail for J.C.P.: jpeters@caltech.edu.
Notes
■
(11) Rittle, J.; McCrory, C. C. L.; Peters, J. C. J. Am. Chem. Soc. 2014,
136, 13853−13862.
(12) Nova, A.; Suh, H.-W.; Schmeier, T. J.; Guard, L. M.; Eisenstein,
O.; Hazari, N.; Maseras, F. Angew. Chem., Int. Ed. 2014, 53, 1103−
1108.
(13) Shimada, S.; Rao, M. L. N.; Tanaka, M. Organometallics 1999,
18, 291−293.
(14) Exposure of 2 to 12.6 atm of H2 led to a hydride resonance at δ
1.64 ppm integrating to 10.6H, demonstrating a continuation of the
trend observed in Figure 2 (refer to the Supporting Information for
more details and spectra).
(15) Similar results were obtained in an experiment conducted using
3.9 atm of a mixture of H2 and D2, indicating rapid scrambling of H2
and D2 to give HD.
(16) Luther, T. A.; Heinekey, D. M. Inorg. Chem. 1998, 37, 127−132.
(17) We have presented extensive experimental evidence showing
that isomer I is favored over isomer II. However, DFT calculations
conducted using the BP86 functional slightly favor isomer II over
isomer I. Using the M06L functional, we obtained results consistent
with our experimental observations (isomer I is favored by 1.7 kcal/
mol) (see the Supporting Information for details).
(18) (a) Kubas, G. J. Metal Dihydrogen and σ-Bond Complexes:
Structure, Theory, and Reactivity; Kluwer Academic/Plenum Publishers:
New York, 2001; p 120. (b) Kubas, G. J. Metal Dihydrogen and σ-Bond
Complexes: Structure, Theory, and Reactivity; Kluwer Academic/Plenum
Publishers: New York, 2001; p 191.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the NSF Center for Chemical
Innovation Solar Fuels Grant CHE-1305124. We also acknowl-
edge the Gordon and Betty Moore Foundation for financial
support. B.A.C. acknowledges an Arthur R. Adams SURF
fellowship.
REFERENCES
■
(1) (a) Hartwig, J. F. Organotransition Metal Chemistry: From Bonding
to Catalysis; University Science Books: Mill Valley, CA, 2010;.
(b) Cornils, B.; Herrmann, W. A. Applied Homogeneous Catalysis
with Organometallic Compounds; Wiley-VCH: Weinheim, Germany,
2002.
(2) (a) Chirik, P. J.; Wieghardt, K. Science 2010, 327, 794−795. (b)
Catalysis Without Precious Metals; Bullock, R. M., Ed.; Wiley-VCH:
Weinheim, Germany, 2010.
(3) (a) MacMillan, S. N.; Harman, W. H.; Peters, J. C. Chem. Sci.
2014, 5, 590−597. (b) Chakraborty, S.; Krause, J. A.; Guan, H.
Organometallics 2009, 28, 582−586. (c) Kundu, S.; Brennessel, W. W.;
Jones, W. D. Inorg. Chem. 2011, 50, 9443−9453. (d) Tran, B. L.; Pink,
M.; Mindiola, D. J. Organometallics 2009, 28, 2234−2243. (e) Buslov,
I.; Becouse, J.; Mazza, S.; Montandon-Clerc, M.; Hu, X. Angew. Chem.,
Int. Ed. 2015, 54, 14523−14526.
(4) (a) Harman, W. H.; Peters, J. C. J. Am. Chem. Soc. 2012, 134,
5080−5082. (b) Angulo, I. M.; Kluwer, A. M.; Bouwman, E. Chem.
Commun. 1998, 2689−2690. (c) Angulo, I. M.; Bouwman, E. J. Mol.
Catal. A: Chem. 2001, 175, 65−72. (d) Wu, J.; Faller, J. W.; Hazari, N.;
Schmeier, T. J. Organometallics 2012, 31, 806−809. (e) Camacho-
Bunquin, J.; Ferguson, M. J.; Stryker, J. M. J. Am. Chem. Soc. 2013, 135,
5537−5540. (f) Lin, T. P.; Peters, J. C. J. Am. Chem. Soc. 2014, 136,
13672−13683. (g) Vasudevan, K. V.; Scott, B. L.; Hanson, S. K. Eur. J.
Inorg. Chem. 2012, 2012, 4898−4906.
(5) (a) Kubas, G. J. Catal. Lett. 2005, 104, 79−101. (b) Esteruelas,
M. A.; Oro, L. A. Chem. Rev. 1998, 98, 577−588. (c) Labinger, J. A.;
Bercaw, J. E. Nature 2002, 417, 507−514. (d) Perutz, R. N.; Sabo-
Etienne, S. Angew. Chem., Int. Ed. 2007, 46, 2578−2592.
(6) (a) Takaya, J.; Iwasawa, N. Dalton Trans. 2011, 40, 8814.
(b) Tanabe, M.; Yumoto, R.; Osakada, K. Chem. Commun. 2012, 48,
2125−2127. (c) Wu, S.; Li, X.; Xiong, Z.; Xu, W.; Lu, Y.; Sun, H.
Organometallics 2013, 32, 3227−3237. (d) Chen, W.; Shimada, S.;
Tanaka, M.; Kobayashi, Y.; Saigo, K. J. Am. Chem. Soc. 2004, 126,
8072−8073. (e) Iluc, V. M.; Hillhouse, G. L. Tetrahedron 2006, 62,
7577−7582. (f) Iluc, V. M.; Hillhouse, G. L. J. Am. Chem. Soc. 2010,
132, 11890−11892. (g) Tan, G.; Enthaler, S.; Inoue, S.; Blom, B.;
Driess, M. Angew. Chem., Int. Ed. 2015, 54, 2214−2218. (h) Hauf, C.;
Barquera-Lozada, J. E.; Meixner, P.; Eickerling, G.; Altmannshofer, S.;
Stalke, D.; Zell, T.; Schmidt, D.; Radius, U.; Scherer, W. Z. Anorg. Allg.
Chem. 2013, 639, 1996−2004.
(7) (a) Harman, W. H.; Lin, T.-P.; Peters, J. C. Angew. Chem., Int. Ed.
2014, 53, 1081−1086. (b) Tsay, C.; Peters, J. C. Chem. Sci. 2012, 3,
E
DOI: 10.1021/acs.organomet.5b00985
Organometallics XXXX, XXX, XXX−XXX