Phosphinite-Ni(0) Mediated Formation of a Phosphide-Ni(II)-OCOOMe Species via Uncommon Metal-Ligand Cooperation

Article abstract of DOI:10.1021/ja513112r

Reversible transformations are observed between a phosphide-nickel(II) alkoxide and a phosphinite-nickel(0) species via a P-O bond formation coupled with a 2-e^- redox change at the nickel center. In the forward reaction, the nickel(0) dinitrogen species (PP^OMeP)Ni(N₂) (2) and {(PP^OMeP)Ni}₂(μ-N₂) (3) were formed from the reaction of (PPP)NiCl (1) with a methoxy anion. In the backward reaction, a (PPP)Ni(II) moiety was regenerated from the CO₂ reaction of 3 with the concomitant formation of a methyl carbonate ligand in (PPP)Ni(OCOOMe) (7). Thus, unanticipated metal-ligand cooperation involving a phosphide based ligand is reported.

Full text of DOI:10.1021/ja513112r

Communication
pubs.acs.org/JACS
Phosphinite-Ni(0) Mediated Formation of a Phosphide-Ni(II)-
OCOOMe Species via Uncommon Metal−Ligand Cooperation
Yeong-Eun Kim, Seohee Oh, Seji Kim, Onnuri Kim, Jin Kim, Sang Woo Han, and Yunho Lee*
Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
S
* Supporting Information
platform in which the antimony ligand as a redox active ligand
ABSTRACT: Reversible transformations are observed
between a phosphide-nickel(II) alkoxide and a phosphin-
ite-nickel(0) species via a P−O bond formation coupled
with a 2-e− redox change at the nickel center. In the
forward reaction, the nickel(0) dinitrogen species
(PPOMeP)Ni(N2) (2) and {(PPOMeP)Ni}2(μ-N2) (3)
were formed from the reaction of (PPP)NiCl (1) with a
methoxy anion. In the backward reaction, a (PPP)Ni(II)
moiety was regenerated from the CO2 reaction of 3 with
the concomitant formation of a methyl carbonate ligand in
(PPP)Ni(OCOOMe) (7). Thus, unanticipated metal−
ligand cooperation involving a phosphide based ligand is
reported.
can be switched from an L to X to Z type ligand by successive
formal one-electron redox processes.8 With this in mind, we have
worked with an anionic PPP ligand (PPP− = P[2-PiPr2−
9
−
C6H4]2 ) previously reported in the literature in which a central
anionic phosphide moiety can be functionalized/defunctional-
ized with an alkoxy group via the reversible formation of a
phosphinite moiety, vide infra. Our strategy is to couple the
reversible phosphide/phosphinite interconversion of a PPP
ligand with a redox change that allows the central metal to go
from a square planar nickel(II) to tetrahedral nickel(0) with a π-
acidic ligand (Scheme 1). This chemistry is reminiscent of the
Scheme 1
etal−ligand cooperation is recently emphasized as a
Munique synthetic methodology to expand the role of
transition metal ions in multielectron catalytic reactions.1 As a
classical example, an FeIV(O) species supported by a cationic
porphyrin π-radical has been known as the key intermediate in
cytochrome P450.2 Various ligand types such as salicylaldimine
(salen) equipped with phenolate groups, catecholate, and
phenylenediamine along with their derivatives were reported as
redox-active ligands.1,3 Chirik and co-workers reported a series of
iron and cobalt complexes supported by aryl-substituted
bis(imino)pyridine ligands.4 Redox and chemically active ligands
assist transition metals to achieve catalysis for various bond-
forming reactions.4 More recently, metal−ligand cooperativity
mediated by aromatization/dearomatization is utilized as a
versatile methodology when working with group 10 transition
elements. Various catalytic reactions employing pincer type
ligands based on pyridine, acridine, and phenanthroline scaffolds
were demonstrated by Milstein and co-workers.5 In most of the
exemplified noninnocent ligands, a π-conjugated system is
employed in which the reasonable ligand activity can be coupled
with the metal’s redox change. While various phosphine ligands
have been widely utilized in organometallic chemistry, examples
of a “noninnocent” phosphine ligand are relatively rare. Recently,
Thomas and co-workers reported a new type of pincer ligand
containing a central cationic N-heterocyclic phosphenium
(NHP) donor.6 Its transition metal complexes of Pt, Pd, Cu,
and Co reveal the noninnocent behavior of an NHP unit with
interconversion of NHP+ and NHP−. Radosevich and co-workers
reported reversible PIII/PV redox cycling utilized for catalytic
transfer hydrogenation, along with E−H oxidative addition (E =
O, N) in a compound containing a three-coordinate phosphorus
previous example with a PNP pincer ligand (N[2-PiPr2-4-Me-
−
C6H3]2 ) in which oxidative addition of N−C and N−H bonds
occur at a low valent metal center, as reported by Ozerov and co-
workers.10
Herein, we report an uncommon transformation involving a
stable zerovalent nickel dinitrogen species, {(PPOMeP)Ni}2(μ-
N2) (3), obtained from the reaction of (PPP)NiCl (1) with a
methoxy anion via a P−O bond formation, coupled with a two-
electron reduction on nickel. In the reverse reaction, a nickel(II)-
methyl carbonate species, (PPP)Ni(OCOOMe) (7), was
successfully produced from the reaction of 3 with CO2, revealing
methoxy group transfer from a phosphinite moiety to a bound
CO2 ligand. This is a rare case where metal redox activity is tightly
coupled with a two-electron group transfer reaction via metal−
ligand cooperation within a phosphine−metal complex system.
Unanticipated production of a nickel(0) dinitrogen species
was accomplished by the addition of 1 equiv of NMe4OH to a red
purple solution of (PPP)NiCl (1) in THF/MeOH under N2
(Scheme 2). The resulting diamagnetic product was isolated as a
dark brown solid (83%); its C6D6 solution reveals the presence of
two nickel dinitrogen species (PPOMeP)Ni(N2) (2) and
{(PPOMeP)Ni}2(μ-N2) (3) detected as a mixture in the NMR
spectrum. When the same NMR sample was exposed to vacuum,
a set including a triplet at 132.37 ppm (JPP = 98.8 Hz) and a
Received: December 24, 2014
center.7 In fact, Gabbaı and co-workers reported a Ni/Sb
̈
© XXXX American Chemical Society
A
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Communication
as measured by the 1H NMR signals at ∼3.5 ppm (Scheme 2).
This equilibrium was also confirmed by 15N NMR spectroscopy
experiments (−50.0 and −71.7 ppm for 2 and −72.2 ppm for 3 at
−60 °C in toluene-d8; see Supporting Information). The
structural and spectroscopic data of 3 unambiguously reveal
the presence of a phosphinite moiety (P1 and P4 in Figure 1a). In
order to confirm the origin of a methoxy group, CD3OD was
used to synthesize {(PPOCD3P)Ni}2(μ-N2) (3-OCD3) under the
Scheme 2
1
same conditions. Both 31P and H NMR data suggest that the
identical species was obtained except for the absence of the signal
corresponding to a methoxy group at 3.69 ppm in the 1H NMR
spectrum. A deuterated 3-OCD3 species was also identified by
cold spray ionization mass spectrometry (Supporting Informa-
tion).
Conversion of (PPP)NiCl (1) to the corresponding
zerovalent nickel dinitrogen adducts (2 and 3) might occur via
ligand substitution at a divalent nickel center, resulting in the
formation of (PPP)Ni(OMe) followed by the reductive
elimination of a POMe moiety from a zerovalent nickel ion.
After the rebinding of a phosphinite group, the resulting Ni(0)
product is presumably further stabilized by a N2 ligand. This
scenario can be supported by the similar reductive elimination
behavior involved in the generation of the nickel(0) dicarbonyl
species with PNP pincer ligands (N(o-C6H4PR2)2− or N[2-PR2-
doublet at 60.60 ppm (JPP = 98.8 Hz) assigned to 3 was found to
have grown in 31P NMR spectrum. Another set that includes a
triplet at 139.34 ppm (JPP = 82.7 Hz) and a doublet at 61.55 ppm
(JPP = 83.6 Hz) was singly observed when a lower concentration
(0.54 mM) of 2 was present (Supporting Information). A similar
solution behavior of mono- and dinuclear species in equilibrium
was previously observed for an analogous nickel(0) dinitrogen
species {(PPMeP)Ni}2(μ-N2).11
The solid state structure of 3 confirms a dinuclear nickel end-
on bridging N2 adduct (Figure 1a). Its N−N distance of 1.112(5)
−
i
4-Me-C6H3]2 ; R = Ph or Pr) from the reaction of
corresponding nickel(II) species with excess CO(g).12 Involve-
ment of the direct addition of methoxide onto a phosphide
moiety cannot be ruled out.6d,13
Under a N2 atmosphere, the corresponding hypothesized
(PPP)Ni(OMe) could not be isolated due to the fast conversion
rate of the reaction at room temperature. However, under an Ar
atmosphere, an unknown species revealing a triplet at 91.32 ppm
(JPP = 8.3 Hz) and a doublet at 46.46 ppm (JPP = 8.1 Hz) in the
31P NMR spectrum was generated with other impurities from the
same reaction. This spectrum is clearly different from that of
zerovalent nickel species, but fairly similar to that of (PPP)Ni-
(OPh) (4; 99.22 ppm (t, JPP = 8.0 Hz), 48.61 ppm (d, JPP = 8.4
Hz)), vide infra. The intermediate species slowly disappeared
under the Ar atmosphere but was directly converted to 2 and 3
upon exposure to N2(g) indicating the presence of (PPP)Ni-
(OMe) (Supporting Information).
To attain further mechanistic insight into the formation of a
nickel(0) adduct, we sought to tune the stability/reactivity of the
corresponding nickel(II) alkoxide species. In the first instance,
phenoxide was utilized, in which less electron density can be
donated compared to alkoxides. The addition of NaOPh to the
solution of 1 produces (PPP)Ni(OPh) (4) in high yield (90%,
Scheme 2). Interestingly, the formation of the corresponding
nickel(0) dinitrogen species is not detected under the same
Figure 1. Displacement ellipsoid (50%) representation of (a)
{(PPOMeP)Ni}2(μ-N2) (3) and (b) (PPP)Ni(OPh) (4). Hydrogen
atoms and molecules of cocrystallization are omitted for clarity.
Å (Table 1) supports a triple bond character indicating weak
nickel-based π-back bonding. The bridging N2 ligand of 3 was
also confirmed by a N2 Raman vibration at 2038 cm−1 (Δ(15N2)
= −64 cm−1), similar to previously reported Ni(0)−μ-N2−Ni(0)
species.11 In the solution IR spectrum of 2, a peak at 2094 cm−1
(Δ(15N2) = −70 cm−1) was assigned to the vibration of the
terminal dinitrogen ligand (Supporting Information). The
apparent weak binding of N2 in both 2 and 3 suggests an
equilibrium under 1 atm of N2(g) at room temperature with the
estimated equilibrium constant as 34.0 9.2 in favor of 3 in C6D6
Table 1. Selected Bond Distances and Angles of 3, 4, 5-OPh, 5-OMe, and 7
a
b
Ni−P(1) (Å)
Ni−P(2, 3) (Å)
Ni−L (Å)
L−X (Å)
P(1)−Ni−L (deg)
P(2)−Ni−P(3) (deg)
{(PPOMeP)Ni}2(N2) (3)
(PPP)NiOPh (4)
2.098(1)
2.161(1), 2.171(1)
1.837(4)
1.112(5)
125.4(1)
128.54(5)
c
d
e
f
g
2.107(1)
2.173(1), 2.152(1)
2.1995(5), 2.1805(5)
2.2048(5), 2.1855(5)
2.1868(9), 2.1894(9)
2.1850(5), 2.1885(4)
2.180(1), 2.197(1)
1.839(4)
126.4(1)
131.91(5)
2.1506(5)
1.922(1)
1.321(2)
1.316(2)
1.163(4)
1.153(2)
1.273(5)
169.40(4)
162.43(2)
c
d
e
f
g
2.1494(5)
1.946(1)
171.53(4)
156.26(2)
(PPOPhP)NiCO (5-OPh)
(PPOMeP)NiCO (5-OMe)
(PPP)NiOCOOMe (7)
2.1231(9)
2.1332(5)
2.151(1)
1.746(4)
1.747(2)
1.940(3)
127.5(1)
128.81(5)
170.4(1)
123.64(4)
121.56(2)
162.71(5)
a
b
c
d
L = N for 3, O for 4 and 7, C for 5-OMe and 5-OPh. X = N for 3, C for 4 and 7, O for 5-OMe and 5-OPh. Distance for Ni(2)−P(4). Distance
e
f
g
for Ni(2)−P(5), Ni(2)−P(6). Distance for Ni(2)−N(2). Angle for P(4)−Ni(2)−N(2). Angle for P(5)−Ni(2)−P(6).
B
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Journal of the American Chemical Society
Communication
conditions; it is currently not clear why this is the case. However,
the generation of a zerovalent nickel species (PPOPhP)Ni(CO)
(5-OPh) was accomplished by the addition of carbon monoxide,
presumably via the similar reaction pathway described above
(Scheme 2 and Figure 1b). Instantaneously, 5-OPh was formed
upon addition of CO(g) at room temperature in C6D6 as
monitored by 31P NMR spectroscopy (Supporting Informa-
tion).14 Similarly a corresponding nickel monocarbonyl species
(PPOMeP)Ni(CO) (5-OMe) was also produced by the addition
of CO(g) to the C6H6 solution of 3. Both nickel(0) carbonyl
species were characterized by various spectroscopic techniques
including X-ray crystallography. Similar 31P NMR spectral signals
to those of the central phosphorus atom in 5-OPh and 5-OMe
were found to be positively shifted to 152.94 ppm (t, JPP = 72.1
Hz) and 162.40 ppm (t, JPP = 58.8 Hz), respectively, from that of
(PPP)NiCl (1, 114.80 ppm) and 4 (99.22 ppm) suggesting the
presence of an electron-deficient central P atom. The vibration at
1928 cm−1 is assigned to 5-OPh and supports coordination of a
single carbon monoxide ligand at a nickel(0) center. In the case
of 5-OMe, a carbonyl vibration appears at 1909 cm−1, due to
enhanced back-donation from the electron-rich Ni(0) center.
Both solid structures of 5-OPh and 5-OMe clearly reveal a
phosphinite coordination at the pseudotetrahedral nickel(0)
centers (τ4 = 0.78 and 0.77, respectively)15 where P−O bond
lengths of 1.676(2) and 1.645(1) Å were determined,
respectively (Figure 2). DFT analysis on both 5-OPh and 5-
Figure 3. Displacement ellipsoid (50%) representation of (a)
(PPP)Ni(OCOOMe) (7) and (b) {(PPMeP)Ni(I)}{I·MeOH} (8).
Hydrogen atoms and molecules of cocrystallization are omitted for
clarity.
(d, JPP = 9.9 Hz) ppm in 31P NMR spectroscopy in C6D6. In
addition, the 1H NMR spectrum reveals a signal at 3.43 ppm (d,
JPH = 14.2 Hz) in support of this species possessing a P−OMe
moiety (Supporting Information). This intermediate is reminis-
cent to the analogous species (PPMeP)Ni(η2-CO2) reported by
our group.11 However, this compound is not stable in CH3CN/
toluene at room temperature; consequently it was converted to 7
and the CO2 conversion reaction was completed within 5 h.
The X-ray structure of 7 reveals the CO2 incorporation as the
form of carbonate with a methoxy group migrated from
phosphinite (Figure 3). A methyl carbonato ligand is coordinated
to the nickel(II) center in which the Ni−O bond distance is
1.940(3) Å and two C−O bonds are 1.273(5) and 1.378(4) Å,
with the CO bond being 1.208(5) Å. A structurally
characterized nickel(II) methyl carbonato complex supported
by a tetraazacycloalkane ligand was reported by Ito and co-
workers.17
Other structurally characterized transition metal methyl
carbonato species were reported as well.18 In particular, several
metal−carbonato species were generated from the reaction of a
corresponding methoxide species with carbon dioxide.17,18b,19
However, there is no report revealing the metal methyl carbonato
Figure 2. Displacement ellipsoid (50%) representation of (a)
(PPOPhP)Ni(CO) (5-OPh) and (b) (PPOMeP)Ni(CO) (5-OMe).
Hydrogen atoms and molecules of cocrystallization are omitted for
clarity.
generation from such a phosphinito methoxide group.20
A
stoichiometric amount of methyl iodide was added to 7 resulting
in the formation of dimethyl carbonate (DMC) as detected by
1H NMR spectroscopy.21 According to our initial experiments,
the first methylation occurs at a central phosphide, not on the
carbonato ligand; the second addition of MeI results in the
formation of {(PPMeP)Ni(I)}{I·MeOH} (8, Figure 3) with
DMC (Supporting Information).
Herein, we report an unusual metal−ligand cooperation
employing a (PPP)Ni scaffold in which methoxy group transfer
occurs between a phosphide moiety of the ligand and the nickel
ion. This cooperation involves a two-electron Ni(0/II) redox
process, coupled with reversible P−O bond formation. The
electron-rich Ni-phosphide can react with alkoxide to produce
the phosphinite-nickel(0) dinitrogen species (2 and 3). The
formation of (PPP)Ni(OCOOMe) (7) from the reaction of 3
with CO2 reveals the regeneration of a divalent nickel center and
corresponding methyl carbonate formation via migratory
methoxy group transfer. Therefore, the (PPP)Ni scaffold
shows that the central phosphido P reveals phosphido-
phosphinite interconversion involving reversible P−O bond
formation coupled with anion metathesis at a nickel center.
OMe reveal that five highest filled orbitals have significant nickel
d-orbital character supporting the zerovalent nickel ion
(Supporting Information).16
To explore the oxidative migratory methoxy group transfer of
{(PPOMeP)Ni}2(μ-N2) (3) with small molecule chemistry, we
investigated carbon dioxide conversion. The addition of CO2 to
the CH3CN/toluene solution of 3 results in the formation of a
new divalent nickel complex (PPP)Ni(OCOOMe) (7) with
excellent conversion (>99%, Scheme 2 and Figure 3). The 31P
NMR data of the product reveal a new set of signals at 99.46 (t,
JPP = 9.0 Hz) and 51.02 (d, JPP = 8.6 Hz) ppm; these are shifted by
30 ppm from that observed for the central phosphorus atom of 3.
From a 13C-labeling experiment, the 13C enriched carbon dioxide
moiety in 7-13CO2 was detected by both 13C (158.10 ppm, s) and
1H (3.82 ppm, d, 3JCH = 3.6 Hz) NMR spectroscopy. According
to the IR data, a new carbonyl vibration was displayed at 1693
cm−1 (Δ(13CO2) = −56 cm−1); thus the formation of a methyl
carbonate moiety at the nickel center was ensured. In the CO2(g)
addition, the nickel-CO2 adduct, (PPOMeP)Ni(η2-CO2) (6)
might be formed as a reaction intermediate, revealing an
independent set of signals at 169.95 (t, JPP = 9.6 Hz) and 56.47
C
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Journal of the American Chemical Society
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(10) Ozerov, O. V.; Guo, C.; Papkov, V. A.; Foxman, B. M. J. Am. Chem.
Soc. 2004, 126, 4792−4793.
ASSOCIATED CONTENT
* Supporting Information
Figures, tables, and CIF files giving characterization data for 2−7,
and X-ray crystallographic data. This material is available free of
charge via the Internet at http://pubs.acs.org.
■
S
(11) Kim, Y.-E.; Kim, J.; Lee, Y. Chem. Commun. 2014, 50, 11458−
11461.
(12) (a) Yoo, C.; Kim, J.; Lee, Y. Organometallics 2013, 32, 7195−
7203. (b) Liang, L.-C.; Hung, Y.-T.; Huang, Y.-L.; Chien, P.-S.; Lee, P.-
Y.; Chen, W.-C. Organometallics 2012, 31, 700−708.
AUTHOR INFORMATION
Corresponding Author
*yunholee@kaist.ac.kr
Notes
(13) (a) Esteruelas, M. A.; Lop
Organometallics 2000, 19, 4650−4652. (b) Jorg, K.; Malisch, W.; Reich,
́
ez, A. M.; Tolosa, J. I.; Vela, N.
■
̈
W.; Meyer, A.; Schubert, U. Angew. Chem., Int. Ed. Engl. 1986, 25, 92−
93. (c) Weinand, R.; Werner, H. Chem. Ber. 1986, 119, 2055−2058.
(14) It is not clear that the migration of a PhO group occurs before or
after CO binding.
The authors declare no competing financial interest.
(15) Yang, L.; Powell, D. R.; Houser, R. P. Dalton Trans. 2007, 955−
ACKNOWLEDGMENTS
964.
■
(16) According to DFT analysis on (PPP)NiCl (1) and (PPP)NiOPh
(4), significant nickel d-orbital character can be found in HOMOs, while
This work was supported by Korea CCS R&D Center and the
National Research Foundation (NRF, No. 2010-0029149)
funded by the Ministry of Education, Science and Technology
and the Institute of Basic Science (IBS) in Korea. We thank Dr.
M. S. Seo, and Prof. W. Nam at Ewha Womans University for
mass data collection. Prof. J. Lee at Chonnam National
University is acknowledged for improving the X-ray data. Prof.
D. G. Churchill and Prof. S. Chang are also acknowledged for
insightful discussions concerning the reaction mechanism.
2
2
dx −y character was found in the LUMO, suggesting that both complexes
possess a d8 Ni(II) center. In fact, the HOMO for 1 and HOMO−1 for 4
possess the significant contribution of a central phosphorus atom
indicating the presence of a Ni(II)-bound electron-rich phosphide
moiety in both species; see Supporting Information. In addition, the
nickel’s oxidation state and the electronic nature of the central
phosphorus atom in 1−5 and 7 can be evaluated by comparing their
31P NMR and XRD data; see Table S7.
(17) Kato, M.; Ito, T. Bull. Chem. Soc. Jpn. 1986, 59, 285−294.
(18) (a) Peter, A.; Vahrenkamp, H. Z. Anorg. Allg. Chem. 2005, 631,
2347−2351. (b) Brombacher, H.; Vahrenkamp, H. Inorg. Chem. 2004,
43, 6042−6049. (c) Yan, Y.-K.; Koh, W.; Jiang, C.; Leong, W. K.; Hor, T.
S. A. Polyhedron 2000, 19, 641−647. (d) Ruf, M.; Vahrenkamp, H. Inorg.
Chem. 1996, 35, 6571−6578. (e) Mandal, S. K.; Ho, D. M.; Orchin, M.
Organometallics 1993, 12, 1714−1719. (f) Ishida, T.; Hayashi, T.;
Mizobe, Y.; Hidai, M. Inorg. Chem. 1992, 31, 4481−4485. (g) Kato, M.;
Ito, T. Inorg. Chem. 1985, 24, 509−514. (h) Immirzi, A.; Musco, A. Inorg.
Chim. Acta 1977, 22, L35−L36.
(19) (a) Truscott, B. J.; Nelson, D. J.; Slawin, A. M. Z.; Nolan, S. P.
Chem. Commun. 2014, 50, 286−288. (b) Arunachalampillai, A.;
Loganathan, N.; Wendt, O. F. Polyhedron 2012, 32, 24−29. (c) Ibrahim,
M. M.; Ichikawa, K.; Shiro, M. Inorg. Chem. Commun. 2003, 6, 1030−
1034. (d) Aresta, M.; Dibenedetto, A.; Pastore, C. Inorg. Chem. 2003, 42,
3256−3261.
REFERENCES
■
(1) (a) Luca, O. R.; Crabtree, R. H. Chem. Soc. Rev. 2013, 42, 1440−
1459. (b) Praneeth, V. K. K.; Ringenberg, M. R.; Ward, T. R. Angew.
Chem., Int. Ed. 2012, 51, 10228−10234. (c) Ketterer, N. A.; Fan, H.;
Blackmore, K. J.; Yang, X.; Ziller, J. W.; Baik, M.-H.; Heyduk, A. F. J. Am.
Chem. Soc. 2008, 130, 4364−4374. (d) Chaudhuri, P.; Verani, C. N.; Bill,
E.; Bothe, E.; Weyhermuller, T.; Weighardt, K. J. Am. Chem. Soc. 2001,
̈
123, 2213−2223. (e) See also Forum Articles on Redox-Active Ligands:
Inorg. Chem. 2011, 50, 9737−9914.
(2) (a) Rittle, J.; Green, M. T. Science 2010, 330, 933−937. (b) Poulos,
T. L. Chem. Rev. 2014, 114, 3919−3962.
(3) Lyons, C. T.; Stack, T. D. P. Coord. Chem. Rev. 2013, 257, 528−540.
(4) (a) Bart, S. C.; Lobkovsky, E.; Chirik, P. J. J. Am. Chem. Soc. 2004,
126, 13794−13807. (b) Bouwkamp, M. W.; Bowman, A. C.; Lobkovsky,
E.; Chirik, P. J. J. Am. Chem. Soc. 2006, 128, 13340−13341. (c) Sylvester,
K. T.; Chirik, P. J. J. Am. Chem. Soc. 2009, 131, 8772−8774.
(d) Tondreau, A. M.; Atienza, C. C. H.; Weller, K. J.; Nye, S. A.;
Lewis, K. M.; Delis, J. G. P.; Chirik, P. J. Science 2012, 335, 567−570.
(e) Gibson, V. C.; Redshaw, C.; Solan, G. A. Chem. Rev. 2007, 107,
1745−1776.
(20) There are several examples revealing alkoxide elimination from
the metal-phosphinite species. (a) Nakazawa, H.; Miyoshi, Y.;
Katayama, T.; Mizuta, T.; Miyoshi, K.; Tsuchida, N.; Ono, A.;
Takano, K. Organometallics 2006, 25, 5913−5921. (b) Nakazawa, H.;
Yamaguchi, Y.; Mizuta, T.; Miyoshi, K. Organometallics 1995, 14, 4173−
4182.
(5) (a) Gunanathan, C.; Milstein, D. Acc. Chem. Res. 2011, 44, 588−
602. (b) Langer, R.; Fuchs, I.; Vogt, M.; Balaraman, E.; Diskin-Posner,
Y.; Shimon, L. J. W.; Ben-David, Y.; Milstein, D. Chem.Eur. J. 2013,
19, 3407−3414. (c) Vogt, M.; Nerush, A.; Diskin-Posner, Y.; Ben-David,
Y.; Milstein, D. Chem. Sci. 2014, 5, 2043−2051.
(21) Product DMC (∼10%) generated from the reaction was detected
1
by H NMR spectroscopy in toluene with internal standard 1,1,2,2-
tetrachloroethane by comparison with an authentic sample of DMC; see
Supporting Information.
(6) (a) Day, G. S.; Pan, B.; Kellenberger, D. L.; Foxman, B. M.;
Thomas, C. M. Chem. Commun. 2011, 47, 3634−3636. (b) Pan, B.;
Bezpalko, M. W.; Foxman, B. M.; Thomas, C. M. Organometallics 2011,
30, 5560−5563. (c) Pan, B.; Xu, Z.; Bezpalko, M. W.; Foxman, B. M.;
Thomas, C. M. Inorg. Chem. 2012, 51, 4170−4179. (d) Pan, B.;
Bezpalko, M. W.; Foxman, B. M.; Thomas, C. M. Dalton Trans. 2012, 41,
9083−9090. (e) Knight, S. E.; Bezpalko, M. W.; Foxman, B. M.;
Thomas, C. M. Inorg. Chim. Acta 2014, 422, 181−187.
(7) (a) Dunn, N. L.; Ha, M.; Radosevich, A. T. J. Am. Chem. Soc. 2012,
134, 11330−11333. (b) McCarthy, S. M.; Lin, Y.-C.; Devarajan, D.;
Chang, J. W.; Yennawar, H. P.; Rioux, R. M.; Ess, D. H.; Radosevich, A.
T. J. Am. Chem. Soc. 2014, 136, 4640−4650. (c) Zhao, W.; McCarthy, S.
M.; Lai, T. Y.; Yennawar, H. P.; Radosevich, A. T. J. Am. Chem. Soc. 2014,
136, 17634−17644.
(8) Jones, J. S.; Wade, C. R.; Gabbaï, F. P. Angew. Chem., Int. Ed. 2014,
53, 8876−8879.
(9) Mankad, N. P.; Rivard, E.; Harkins, S. B.; Peters, J. C. J. Am. Chem.
Soc. 2005, 127, 16032−16033.
D
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