Chelating assistance of P-C and P-H bond activation at palladium and nickel: Straightforward access to diverse pincer complexes from a diphosphine-phosphine oxide

Article abstract of DOI:10.1021/om400042v

The diphosphine-phosphine oxide (DPPO) {[o-i-Pr₂P-(C ₆H₄)]₂P(O)Ph} (1) reacts with [Ni(cod) ₂] (cod = 1,4-cyclooctadiene) to give the diphosphine-phosphide oxide κ^P,P(O),P pincer complex 3. According to DFT calculations, the Ph-P(O) bond activation involves a three-center P,C_ipso,Ni transition state. Reaction of the DPPO ligand 1 with [(nbd)Pd(ma)] (nbd = 2,5-norbornadiene and ma = maleic anhydride) affords the [(DPPO)Pd(ma)] complex 4. Upon heating, the ma coligand is displaced and the κ^P,P(O),P palladium pincer complex 2 is obtained. The dinuclear complex {(DPPO)[Pd(ma)]₂} (6) has also been authenticated. X-ray diffraction analysis showed an original situation in which the oxygen atom of the central phosphine oxide moiety bridges the two palladium centers. Addition of trifluoromethanesulfonic acid to DPPO 1 affords the trifunctional phosphine-phosphine oxide-phosphonium derivative 7. Upon reaction with [Pd ₂(dba)₃], the palladium hydride κ^P,O(P),P pincer complex 8 is cleanly formed as the result of P⁺-H bond activation. Complex 8 is readily deprotonated by DBU (DBU = 1,8- diazabicycloundec-7-ene), and spontaneous oxidative addition of the Ph-P(O) bond gives the diphosphine-phosphide oxide κ^P,P(O),P pincer complex 2. Conversely, addition of trifluoromethanesulfonic acid on 2 does not give back the palladium hydride 8 but leads to the diphosphine-hydroxy phosphine κ^P,P(OH),P pincer complex 9.

Full text of DOI:10.1021/om400042v

Article
pubs.acs.org/Organometallics
Chelating Assistance of P−C and P−H Bond Activation at Palladium
and Nickel: Straightforward Access to Diverse Pincer Complexes
from a Diphosphine−Phosphine Oxide
Eric J. Derrah,†,∥ Carmen Martin,† Sonia Mallet-Ladeira,‡ Karinne Miqueu,§ Ghenwa Bouhadir,*,†
and Didier Bourissou*,†
†Universite
Toulouse, France
‡Universite
Paul Sabatier, Institut de Chimie de Toulouse (FR 2599), 118 route de Narbonne, 31062 Toulouse cedex 9, France
§Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Mater
iaux UMR-CNRS 5254, Universite de Pau
et des Pays de l’Adour, Helioparc, 2 avenue du President Angot, 64053 Pau Cedex 09, France
́
de Toulouse, UPS, LHFA, 118 route de Narbonne, 31062 Toulouse, France, and CNRS, LHFA, UMR 5069, 31062
́
́
́
́
́
S
* Supporting Information
ABSTRACT: The diphosphine−phosphine oxide (DPPO) {[o-i-Pr2P-(C6H4)]2P(O)Ph} (1) reacts with [Ni(cod)2] (cod = 1,4-
cyclooctadiene) to give the diphosphine−phosphide oxide κP,P(O),P pincer complex 3. According to DFT calculations, the Ph−
P(O) bond activation involves a three-center P,Cipso,Ni transition state. Reaction of the DPPO ligand 1 with [(nbd)Pd(ma)]
(nbd = 2,5-norbornadiene and ma = maleic anhydride) affords the [(DPPO)Pd(ma)] complex 4. Upon heating, the ma coligand
is displaced and the κP,P(O),P palladium pincer complex 2 is obtained. The dinuclear complex {(DPPO)[Pd(ma)]2} (6) has also
been authenticated. X-ray diffraction analysis showed an original situation in which the oxygen atom of the central phosphine
oxide moiety bridges the two palladium centers. Addition of trifluoromethanesulfonic acid to DPPO 1 affords the trifunctional
phosphine−phosphine oxide−phosphonium derivative 7. Upon reaction with [Pd2(dba)3], the palladium hydride κP,O(P),P pincer
complex 8 is cleanly formed as the result of P+−H bond activation. Complex 8 is readily deprotonated by DBU (DBU = 1,8-
diazabicycloundec-7-ene), and spontaneous oxidative addition of the Ph−P(O) bond gives the diphosphine−phosphide oxide
κ
P,P(O),P pincer complex 2. Conversely, addition of trifluoromethanesulfonic acid on 2 does not give back the palladium hydride 8
but leads to the diphosphine−hydroxy phosphine κP,P(OH),P pincer complex 9.
position, and the nature of the central moiety has been
INTRODUCTION
■
extensively varied (E = C,9 N,10 Si,11 B,12 ...). Notably, however,
PPP frameworks have been comparatively poorly explored,13,14
and complex 2 represents a rare example of a PP(O)P pincer
complex.15 This prompted us to explore further the
coordination of diphosphine−phosphine oxide ligands. DPPO
1 was found to remain intact and behave as a mono-, bi-, or
tridentate ligand upon coordination to gold, silver, and
rhodium.16 In this work, the coordination of 1 to Pd and Ni
has been comprehensively studied, with special interest paid to
the oxidative addition of the Ph−P(O) bond. The formation of
a palladium hydride complex by P+−H oxidative addition of a
phosphine−phosphine oxide−phosphonium derivative is also
described. Upon deprotonation of the palladium hydride
Over the past few years, our group has been investigating the
formation, electronic structure, and reactivity of transition-
metal complexes deriving from polyfunctional ligands. We are
particularly interested in ligands combining a central group 13,
14, or 15 element with phosphine buttresses.1−7 Such chelate
systems have proven extremely useful for the coordination of
Lewis acids as σ-acceptor ligands,1−4 and using the same
strategy, interesting results have been obtained recently on the
coordination and activation of σ bonds (Figure 1).5−7 In this
context, we have shown that the Ph−P(O) bond of the
diphosphine−phosphine oxide (DPPO) 1 readily undergoes
oxidative addition at palladium to give the diphosphine−
phosphide oxide complex 2 (Scheme 1).7
Thanks to their chelating rigid structure, pincer complexes
display unique properties, and over the last two decades, they
have attracted enormous interest.8 In this area, pincer
complexes derived from PEP ligands occupy a forefront
Received: January 18, 2013
© XXXX American Chemical Society
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those of the palladium complex 2, indicating that P(O)−Ph
bond activation had occurred similarly at Ni(0). In particular,
the 31P NMR spectrum displays a triplet at δ 134.6 ppm
(P(O)) and a doublet at δ 61.8 ppm (P(i-Pr)2) with a JPP
coupling constant of 43 Hz. Also diagnostic is the 13C NMR
signal observed at 158.2 ppm (doublet of triplets, JCP = 75 and
24 Hz) for the Cipso atom of the Ph group at Ni. C−X (X = I,
Br), C−O, and C−S bond activations at Ni are common,17 but
phosphines have only been occasionally reported to undergo
C−P bond cleavage at Ni,18 and to the best of our knowledge,
C−P(O) bond activation had not been observed so far with
this metal.19
To shed light on the C−P(O) bond activation leading to
complex 3, DFT calculations were performed on the actual
system.20 The energy profile computed for the Ni species
(Figure 2) very much resembles that found previously for Pd.7
The oxidative addition product 3* is favored thermodynami-
cally by 26 kcal/mol over the corresponding DPPO·Ni0
complex 4* (in which the low-valent Ni center is stabilized
by π coordination of the phenyl ring at the phosphine oxide).
The C−P(O) bond activation proceeds via a three-center
P,Cipso,Ni transition state, and the activation barrier from 4* to
3* is relatively low (9 kcal/mol).
Figure 1. Schematic representations of the different types of
complexes obtained upon coordination of PEP, PEEP, and PE(X)P
ligands (E = group 13−15 elements).
Scheme 1. Formation of the Diphosphine−Phosphide Oxide
Pd Pincer Complex 2 upon P(O)−Ph Bond Activation of 1
Complexes 2 and 3 are obtained directly upon reaction of the
DPPO ligand 1 with [Pd(Pt-Bu3)2] and [Ni(cod)2]. No
intermediate was detected spectroscopically before oxidative
addition of the Ph−P(O) bond occurred. To gain more insight
into the formation of the pincer complexes, we became
interested in the reaction of the DPPO 1 with other Pd(0)
precursors and turned our attention to [Pd(nbd)(ma)]21 (nbd
= 2,5-norbornadiene, ma = maleic anhydride). This choice was
stimulated by the labile character of the nbd coligand (in
comparison with Pt-Bu3) and the ability of ma to stabilize low-
valent Pd centers.22 The DPPO 1 was first treated with 1 equiv
of [Pd(nbd)(ma)] in dichloromethane at room temperature.
After 30 min, the new complex 5 was obtained predominantly
(∼90%, according to NMR) along with a small amount of the
side product 6 (∼10%) (Scheme 3). Complex 5 could be
obtained in pure form using a slight excess of DPPO (1.2 equiv
with respect to Pd). Its NMR data are consistent with the
complex, spontaneous Ph−P(O) bond activation occurs to give
the diphosphine−phosphide oxide complex 2.
RESULTS AND DISCUSSION
■
First, the DPPO ligand 1 was reacted with the nickel(0)
precursor Ni(cod)2 (cod = 1,4-cyclooctadiene) to substantiate
the generality of the P(O)−Ph bond activation process. After 3
days at room temperature in toluene, the pincer complex 3 was
obtained as the sole product (Scheme 2). After workup, it was
Scheme 2. P(O)−Ph Bond Activation of the Diphosphine−
Phosphine Oxide 1 at Nickel, Leading to the Pincer
Complex 3
1
general formula (DPPO)Pd(ma). According to H NMR, the
nbd coligand has been displaced but ma is retained. In addition,
the 31P NMR data indicate symmetric coordination of the two
phosphine moieties of DPPO to Pd: two singlets of relative
integrations 1:2 are observed at δ 39.1 and 34.8 ppm for the
P(O)Ph and Pi-Pr2 moieties, respectively. The molecular
structure of 5 was unambiguously assessed by X-ray diffraction
(Figure 3a). In agreement with the spectroscopic data, the
DPPO ligand 1 is intact and coordinates symmetrically to Pd
(P2−Pd = 2.388(1) and P3−Pd = 2.326(1) Å). The oxygen
atom of the central phosphine oxide moiety points toward the
metal but remains too far to interact significantly with it (O−Pd
isolated as a yellow powder (42% isolated yield) and fully
characterized. The spectroscopic data for 3 are very close to
Figure 2. P(O)−Ph bond activation at Ni, as calculated at the B3PW91/SDD+f (Ni) and 6-31G** (other atoms) level of theory.
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centers. The corresponding OPd distances (O−Pd1 = 2.219(2)
and O−Pd2 = 2.214(2) Å) fall in the higher range of those
observed in terminal phosphine oxide Pd complexes (1.968−
2.276 Å according to a Cambridge database search). Despite
the bridging coordination of DPPO, the two Pd centers are too
far away from each other to interact (Pd1−Pd2 distance
3.448(1) Å). The ability to bridge metal centers is well-
established for PS moieties23 but comparatively rare for P
O groups. Only a few examples of PO bridging coordination
have been reported to date with group 10 metals (all involving
Ni).24 Note that complex 6 can be obtained preparatively (33%
isolated yield) by reacting the free ligand DPPO 1 or the
mononuclear complex 5 with an excess of [Pd(nbd)(ma)].
As briefly discussed in the Introduction, chelating assistance
is a very useful method to support unusual metal−ligand
interactions and original bond activation processes. Also, pincer
complexes are now commonly prepared by E−H bond
activation (E = C,9 N,10 Si,11 B,12 P,13,14 ...) of polyfunctional
ligands. It is also well-known that oxidative addition of C−E
bonds (E = Si, O, S, N, ...)25 and E−E bonds (E = C, Si, ...)26
can be efficiently promoted by appending donor groups.
At this point, we became interested in taking advantage of
the chelating approach to promote P+−H bond activation and
thereby prepare hydride complexes, using DPPO as a precursor.
Tertiary phosphonium salts R3PH+,X− are stable and easy-to-
handle precursors for phosphines. Upon reaction with
transition metals in the presence of a base, they readily form
phosphine complexes, a route that is frequently used to
generate electron-rich Pd complexes.27 However, oxidative
addition of R3P+−H bonds at transition metals has only rarely
been observed. As far as Pd is concerned, Stephan recently
described the formation of a zwitterionic Pd hydride complex
upon oxidative addition of the phosphonium−borate Cy2P+H−
C6F4−B−F(C6F5)2 to [Pd(PPh3)4],28a while Caporaso and
Mecking reported a somewhat similar process starting from the
Scheme 3. Synthesis of the Mono- and Dinuclear Palladium
Complexes 5 and 6 and Thermal Activation of 5 Leading to
the Pincer Complex 2
distance 2.870(2) Å). η2 Coordination of ma completes the
coordination sphere of Pd (Pd−C8 = 2.096(2) and Pd−C5 =
2.125(3) Å).
Complex 5 simply results from the displacement of the nbd
coligand at Pd by the two phosphine moieties of DPPO. As the
result of this chelating coordination, the central phosphine
oxide fragment is positioned close to the metal, but ma
stabilizes the Pd(0) center and prevents oxidative addition of
the P(O)−Ph bond. In fact, ma dissociation and activation of
the DPPO ligand can be achieved upon heating, and 5 was
converted into the pincer complex 2 after 17 h of reflux in
toluene (spectroscopic yield of 80%).
We were intrigued by the aforementioned minor product 6
and also carried out an X-ray diffraction study to reveal its
structure (Figure 3b). Quite surprisingly, it is a dinuclear
complex in which a single DPPO ligand coordinates two Pd
atoms. Each metal center is surrounded by one i-Pr2P fragment
and a ma coligand. In addition, the oxygen atom of the central
phosphine oxide moiety bridges symmetrically the two Pd
phosphonium−sulfonate (o-An)2P+H−C6H4−SO3 and [Pd-
−
(Pt-Bu3)2].28b In order to study further such P+−H bond
activation processes, we envisioned converting our DPPO
ligand 1 into a trifunctional derivative combining phosphine,
Figure 3. Molecular view of complexes 5 (a, left) and 6 (b, right). For clarity, hydrogen atoms are omitted and isopropyl/phenyl groups at
phosphorus are simplified. Selected bond lengths (Å) and bond angles (deg) are as follows. 5: P2−Pd, 2.388(1); P3−Pd, 2.326(1); P1−O, 1.480(2);
Pd−C5, 2.125(3); Pd−C8, 2.096(2); C5−C8, 1.424(4); P2−Pd−P3, 111.48(2); C5−Pd−C8, 39.4(1). 6: P2−Pd1, 2.308(1); P3−Pd2, 2.283(1);
P1−O, 1.520(2); Pd1−C5, 2.062(4); Pd1−C8, 2.146(2); Pd2−C12, 2.065(4); Pd2−C9, 2.132(4); C5−C8, 1.425(6); C9−C12, 1.408(6); P2−
Pd1−O1, 95.21(6); P3−Pd2−O1, 94.01(6); C5−Pd1−C8, 39.5(2); C9−Pd2−C12, 39.2(2).
C
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phosphine oxide, and phosphonium fragments. Reaction of 1
with trifluoromethanesulfonic acid (1.1 equiv) in dichloro-
methane readily afforded the desired compound 7 (Scheme 4).
sphere is completed by the oxygen atom of the central
phosphine oxide moiety. The PO bond of 8 (1.512(2) Å) is
noticeably elongated in comparison to that of 5 (1.480(2) Å),
in which the phosphine oxide remains pendant. Also, despite
the strong trans influence of the hydride (O−Pd−H bond angle
179°), the O−Pd distance (2.116(2) Å) exceeds the sum of
covalent radii by only 5%.30
Scheme 4. Synthesis of the Phosphine−Phosphine Oxide−
Phosphonium Derivative 7 and Its Reaction with
[Pd2(dba)3]
The reaction of 7 with [Pd2(dba)3] thus proceeds via
oxidative addition of the P+−H bond at Pd, and the in situ
reconstituted DPPO ligand coordinates to Pd via the two lateral
phosphine groups as well as the central phosphine oxide
fragment. Such tridentate coordination is reminiscent of that
observed upon coordination of DPPO to [Rh(CO)]+,16 and the
Pd hydride complex 8 provides the second example of such a
PO(P)P pincer complex.
Formally, the cationic Pd hydride complex 8 differs from 2
only by a proton, raising the question of the possible
interconversion of these two species. It is known that strong
bases are able to depronotate palladium hydrides,31 and
accordingly, deprotonation of 8 was envisioned to generate
transiently a low-valent Pd(0) complex. At this stage, oxidative
addition of the P(O)−Ph bond should proceed spontaneously,
leading to the neutral Pd(II) complex 2. This hypothesis was
verified experimentally. Upon addition of 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU) in dichloromethane at
room temperature, complex 8 was converted quantitatively and
quasi-instantaneously into 2 (Scheme 5).
The reversibility of this transformation, that is reductive
elimination of P(O)−Ph at Pd upon protonation, was then
explored. To this end, complex 2 was treated with
trifluoromethanesulfonic acid in dichloromethane. A clean
reaction occurred immediately. According to NMR data, it did
not give back the Pd hydride 8 but led to the new complex 9,
whose structure was determined by X-ray crystallography
(Figure 4b). The overall structure of the precursor 2 is retained
in 9 (the Pd center is surrounded by the three phosphorus
atoms and the phenyl group, organized in a square-planar
arrangement), but the oxygen atom has been protonated so
that the central phosphide oxide of 2 has been converted into a
hydroxyphosphine moiety in 9. Such transformation of an X-
type into a L-type ligand upon protonation is rather common,
The protonation takes place at one of the P(i-Pr)2 moieties,
and three distinct signals are observed in the 31P NMR
spectrum. The signals are broad at room temperature but
sharpen at low temperature (− 40 °C), indicating that some
exchange occurs slowly on the NMR time scale. Compound 7
was then reacted with different Pd(0) precursors. Complex
mixtures of unidentified products were obtained with Pd[P(t-
Bu)3]2 and [Pd(nbd)(ma)], but 7 reacted cleanly with
[Pd2(dba)3] in acetonitrile at room temperature to give the
new complex 8. The 31P{1H} NMR spectrum of 8 displays a
doublet at δ 50.3 ppm for the two P(i-Pr)2 groups and a triplet
at δ 48.9 ppm for the central P(O)Ph moiety, with a JPP
coupling constant of 8 Hz. The presence of a hydride at Pd is
clearly apparent from the multiplet observed at δ −16.5 ppm in
1
the H NMR spectrum (the JPH coupling constants are too
small to be resolved). This chemical shift falls in the lower limit
of those reported for Pd hydrides (δ(1H) from −3 to −12
ppm).29
Crystals were obtained by diffusion of diethyl ether into an
acetonitrile solution of 8, and an X-ray diffraction study was
carried out (Figure 4a). Complex 8 adopts an ion pair structure,
and the Pd center is tetracoordinated. The two phosphine
fragments i-Pr2P coordinate symmetrically (P2−Pd = 2.299(1)
and P3−Pd = 2.279(1) Å). The hydrogen at Pd was
unambiguously located in the difference Fourier map, and the
Pd−H distance was refined at 1.50(2) Å. The coordination
Figure 4. Molecular view of complex 8 (a, left) and 9 (b, right). For clarity, the triflate counteranion and hydrogen atoms (except that at Pd for 8
and that at O for 9) are omitted and isopropyl/phenyl groups at phosphorus are simplified. Selected bond lengths (Å) and bond angles (deg) are as
follows. 8: P3−Pd, 2.279(2); P2−Pd, 2.299(2); P1−Pd, 2.934(2); O−Pd, 2.116(2); P1−O, 1.512(2); Pd−H, 1.50(2); P2−Pd−P3, 157.17(2); P3−
Pd−H, 88(1); P2−Pd−H, 93(1); P3−Pd−O1, 90.92(4); P2−Pd−O1, 88.52(4). 9: P2−Pd, 2.317(21); P3−Pd, 2.302(1); P1−Pd, 2.251(1); C13−
Pd, 2.079(2); P1−O1, 1.588(2); O1−H, 0.840(2); P2−Pd−P3, 160.88(2); P2−Pd−P1, 84.91(2); P3−Pd−P1, 85.72(2); P1−Pd−C13, 176.99(7);
P2−Pd−C13, 93.28(7); P3−Pd−C13, 96.69(7).
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Scheme 5. Synthesis of 2 by Deprotonation of the Palladium Hydride Complex 8 and Addition of Trifluoromethanesulfonic
Acid to 2 Giving the Diphosphine−Hydroxyphosphine Complex 9
including in pincer complexes.32 The conversion of 2 into 9
mass spectrometer. The DDPO ligand 1 was prepared as previously
described.7
provides the first example of this transformation happening via
Ni Complex 3. In a Schlenk flask containing Ni(cod)2 (55 mg, 0.20
mmol) was added a solution of diphosphine−phosphine oxide 1 (102
phosphide oxide protonation. The reverse transformation,
namely deprotonation of hydroxyphosphine complexes, is
mg, 0.20 mmol, 1 equiv) in toluene (2 mL). The progress of the
comparatively well-known.33 And actually, complex 8 gives
reaction was monitored by 31P{1H} NMR spectroscopy, and after ∼3
back 2 upon treatment with DBU.
days, most of the DPPO had been consumed. The solvent was
removed under vacuum, and trituration with pentane (2 × 5 mL)
CONCLUSION
followed by a pentane wash (3 × 5 mL) gave complex 3 (48 mg, 0.084
■
1
mmol, 42% yield) in ∼99% purity, as determined by H and 31P{1H}
Coordination of the diphosphine−phosphine oxide DPPO to
various Pd and Ni precursors has provided further insight into
the Ph−P(O) bond activation process. The reaction proceeds
similarly at Pd and Ni, involving a P,Cipso,M transition state.
The presence of a maleic anhydride coligand at Pd disfavors the
oxidative addition process, and complex 5, in which the two
phosphines are symmetrically coordinated but the P(O)Ph
moiety remains pendant, has been isolated. Complete
characterization of the dinuclear complex 6, obtained as a
byproduct of 5, revealed an original coordination mode for a
phosphine oxide moiety: namely, symmetric bridging of two
palladium centers.
1
NMR spectroscopy. H NMR (500.33 MHz, CDCl3): δ 8.27 (m, 2H,
H3), 7.98−7.82 (br, ω1/2 = 23 Hz, 1H, Ho), 7.72−7.62 (m, 2H, H6),
7.62−7.56 (m, 2H, H4), 7.55−7.47 (m, 2H, H5), 7.42−7.30 (br, 1H,
Ho), 7.07 (m, 2H, Hm), 6.89 (m, 1H, Hp). 2.85 (br, ω1/2 = 30 Hz, 2H,
H7), 2.66 (br, ω1/2 = 30 Hz, 2H, H7), 1.26 (m, 12H, H8), 0.95 (m, 6H,
H8), 0.79 (m, 6H, H8). 13C{1H} NMR (125.81 MHz, CDCl3): δ 158.2
(dt, 2JCP = 75 Hz, 2JCP = 24 Hz, Ci), 154.2 (AA′MX, N = 20 Hz, 2JPC
=
42 Hz, C2), 140.9 (br, ω1/2 = 15 Hz, Co), 137.6 (AA′MX, N = 19 Hz,
2JPC = 46 Hz, C1), 136.9 (br, ω1/2 = 12 Hz, Co), 130.9 (m, C4), 130.6
2
(d, JCP = 17.3 Hz, C6), 130.2 (s, C5), 129.7 (AA′X, N = 7 Hz, C3),
126.8 (br, ω1/2 = 16 Hz, Cm), 125.3 (br, ω1/2 = 16 Hz, Cm), 121.8 (s,
Cp), 27.3 (AA′X, N = 12 Hz, C7), 22.7 (AA′X, N = 12 Hz, C7), 19.2 (s,
C8), 18.1 (s, C8), 17.9 (s, C8), 17.6 (s, C8). 31P NMR (202.54 MHz,
CDCl3,): δ 134.6 (t, JPP = 43 Hz, 1P, P(O)Ph), 61.8 (d, JPP = 43 Hz,
2P, P(i-Pr)2).
Pd Complex 5. In a Schlenk flask containing a light yellow
suspension of Pd(nbd)(ma) (102 mg, 0.34 mmol) in dichloromethane
(2 mL) was added diphosphine-phosphine oxide 1 (211 mg, 0.41
mmol, 1.2 equiv) in dichloromethane (2 mL). The resulting mixture
was stirred for 30 min to give an orange solution with a black
precipitate. The suspension was filtered, and the solvent was
evaporated from the supernatant under vacuum. Trituration with
pentane (3 × 5 mL), followed by pentane wash (3 × 5 mL), gave
Pd(DPPO)(ma) (5; 235 mg, 0.33 mmol, 97% yield) as an orange
powder. 1H NMR (500.33 MHz, 253 K, CDCl3): δ 7.66−7.65 (m, 2H,
H6), 7.60 − 7.48 (m, 9H, H3, H5, Ho, Hm, Hp), 7.36 (AA′X, N = 7.3
Hz, 2H, H4), 4.22 (d, JHP = 5.0 Hz, 2H, =C−H ma), 2.86−2.81 (sept
The chelating approach was then extended to P+−H bond
activation. The original derivative 7 combining three different
phosphorus moieties (phosphine, phosphine oxide, and
phosphonium) was readily prepared by chemoselective
protonation of DPPO. Its coordination to Pd proceeds with
oxidative addition of the P+−H bond, and the ensuing hydride
complex 8 adopts a rare PO(P)P pincer structure. Upon
deprotonation, the palladium hydride complex 8 undergoes
spontaneous Ph−P(O) bond activation to afford the
diphosphine−phosphine oxide pincer complex 2, while
protonation of 2 selectively occurs at the oxygen atom to
give the diphosphine−hydroxyphosphine pincer complex 9.
This work substantiates the versatility of diphosphine−
phosphine oxide ligands such as 1. Indeed, a variety of
3
3
coordination modes, including κPO(P)P, κPP(O)P, and κPP(OH)P
,
br, JHH = 5.0 Hz, 2H, H7), 2.68−2.60 (sept br, JHH = 5.0 Hz, 2H,
3
3
H7), 1.29−1.24 (dd, JHP = 15.0 Hz, JHH = 5.0 Hz, 6H, H8), 1.16−
1.10 (m, 12H, H8), 0.91−0.87 (dd, 3JHP = 15.0 Hz, 3JHH = 5.0 Hz, 6H,
H8). 13C{1H} NMR (125.81 MHz, 253 K, CDCl3): δ 172.9 (s, C
have been authenticated in the ensuing pincer complexes.
Future work in our laboratory will seek to develop further the
chelating approach of bond activation, and the reactivity of the
ensuing complexes will be explored.
2
O), 138.6−138.5 (m, C2), 138.4 (AA′MX, N = 8 Hz, JPC = 99 Hz,
C1), 135.5 (d, 1JCP = 107 Hz, Ci), 134.8 (AA′MX, N = 4 Hz, 2JPC = 13
Hz, C3), 134.1 (d, JCP = 12 Hz, C6), 131.7 (s, Cp), 131.6 (d, 2JCP = 10
Hz, Co), 130.1 (s, Cm), 129.1 (d, 3JCP = 12 Hz, C5), 128.7 (d, 4JCP = 12
EXPERIMENTAL SECTION
■
Hz, C4), 51.4 (dt, JCP = 24 Hz, JCP = 12 Hz, =C−H ma), 30.0 (t, 1JCP
=
General Comments. All reactions and manipulations were carried
out under an atmosphere of dry argon using standard Schlenk
techniques. All solvents were sparged with argon and dried using an
2
10 Hz, C7), 23.8 (m, C7), 20.6 (t, JCP = 4 Hz, C8), 19.7 (s br, C8),
19.0 (m, C8), 17.4 (s br, C8). 31P{1H} NMR (202.54 MHz, 253 K,
CDCl3): δ 39.1 (s, 1P, P(O)Ph), 34.8 (s, 2P, P(i-Pr)2). HRMS (CI,
CH4): exact mass (monoisotopic) calcd for [M − ma]H+, 617.1483;
found, 617.1514. Mp: 184−186 °C.
MBRAUN Solvent Purification System (SPS). H, 13C, 19F, and 31P
1
NMR spectra were recorded on a Bruker Avance 500 or 300
spectrometer. Chemical shifts are expressed with a positive sign, in
parts per million, calibrated to residual 1H (7.24 ppm) and 13C (77.16
ppm) solvent signals, CFCl3 (0.00 ppm), and 85% H3PO4 (0 ppm),
respectively. Unless otherwise stated, NMR was recorded at 298 K.
Preparation of Complex 2 from 5. An orange solution of
Pd(DPPO)(ma) (5; 15 mg, 0.02 mmol) in toluene was heated at
reflux in a Schlenk flask. The progress of the reaction was monitored
over time by 31P{1H} NMR spectroscopy. After 17 h, all of the
Pd(DPPO)(ma) had been consumed to give complex 2 in 80% yield,
as determined by 31P{1H} NMR spectroscopy.
1
The N values corresponding to /2[J(AX) − J(A′X)] are provided
1
when second-order AA′X or AA′MX systems were observed in H or
13C NMR spectra.34 Mass spectra were recorded on a Waters LCT
E
dx.doi.org/10.1021/om400042v | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Preparation of Complex 6 from 5. In a Schlenk flask containing
a light yellow suspension of Pd(nbd)(ma) (5; 60 mg, 0.20 mmol, 3
equiv) in dichloromethane (1 mL) was slowly added a solution of
diphosphine−phosphine oxide 1 (34 mg, 0.067 mmol, 1 equiv) in
dichloromethane (3 mL). The resulting mixture was stirred for 1 h to
give an orange solution with a black precipitate. The reaction mixture
was filtered, the solvent was evaporated from the supernatant under
vacuum, and a pale yellow solid was obtained after trituration with
pentane (3 × 5 mL). The sample was recrystallized by slow diffusion
of diethyl ether (5 mL) into a concentrated solution of 6 in
dichloromethane (1 mL) to give yellow crystals with a small amount of
elemental palladium. The crystalline sample was redissolved in
dichloromethane and filtered to remove the remaining elemental
palladium. The solvent was removed under vacuum, and trituration
with pentane (3 × 5 mL) gave [(DPPO)(Pd(ma))2] (6; 20 mg, 0.022
residue was washed with ether (4 × 5 mL) to give 8 (92 mg, 0.12
mmol, 80% yield) in ∼99% purity. A portion of the sample (70 mg,
0.088 mmol) was dissolved in a minimal amount of acetonitrile and
recrystallized by solvent diffusion of diethyl ether (5 mL) to give
yellow crystals (36 mg, 0.047 mmol, 53% yield) suitable for X-ray
diffraction analysis. 1H NMR (500.33 MHz, 298 K, CD3CN): δ 8.03−
7.92 (m, 4H, H3 and H6), 7.87−7.84 (m, 2H, H4 or H5), 7.75−7.72
(m, 1H, Hp), 7.72−7.68 (m, 2H, H4 or H5), 7.58−7.54 (m, 2H, Hm),
7.40−7.36 (m, 2H, Ho), 2.92−2.86 (m, 2H, H7), 2.64−2.55 (m, 2H,
H7), 1.36−1.26 (m, 18H, H8), 0.89−0.84 (m, 6H, H8), −16.14 to
−16.17 (m, 1H, PdH); 13C{1H} NMR (125.81 MHz, 298K, CD3CN):
δ 136.1 (AA′MX, N = 4 Hz, 2JPC = 14 Hz, C3 or C6), 135.36 (AA′MX,
2
N = 6 Hz, JPC = 100 Hz, C1 or Cipso), 134.4 (d, JCP = 11 Hz, C3 or
C6), 133.8 (d, 4JCP = 3 Hz, Cp), 133.4−133.3 (m, C4 or C5), 132.5 (d,
2JCP = 11 Hz, Co), 130.4 (d, JCP = 13 Hz, C4 or C5), 129.99 (d, 1JCP
=
1
13 Hz, C2), 129.3 (d, 3JCP = 13 Hz, Cm), 114.5 (br, OTf), 27.5 (AA′X,
N = 11 Hz, C7), 21.2 (AA′X, N = 11 Hz, C7), 19.0 (br, C8), 18.7 (m,
C8), 18.4 (AA′X, N = 6 Hz, C8), the peak due to C1 or Cipso is not
mmol, 33% yield). H NMR (300.13 MHz, 295 K, CD2Cl2): δ 7.85−
7.75 (m, 2H, Hspacer), 7.73−7.60 (m, 4H, 3Hspacer and HPh), 7.51 (br,
ω1/2 ≈ 62 Hz, 2H, HPh), 7.36 (m, 3H, Hspacer), 6.86 (br, ω1/2 = 51 Hz,
2H, HPh), 3.80−4.40 (br, 4H, C−H ma), 2.38 (br, ω1/2 = 56 Hz,
4H, H7), 1.30−0.78 (m, 24H, H8). 31P{1H} NMR (121.44 MHz, 295
observed. 31P NMR (202.54 MHz, 298 K, CD3CN): δ 50.3 (dd, JPP
=
8 Hz, JPH = 4 Hz, 2P, P(i-Pr)2), 48.9 (td, JPP = 8 Hz, JPH = 2 Hz, 1P,
P(O)). 19F{1H} NMR (282.23 MHz, 298 K, CD3CN): δ −79.3 (s,
OTf).
K, CD2Cl2): δ 50.8 (br, ω1/2 = 45 Hz, 1P, P(O)Ph), 38.8 (br, ω1/2
115 Hz, 2P, P(i-Pr)2).
=
Phosphine−Phosphonium−Phosphine Oxide Derivative 7.
Neat trifluoromethanesulfonic acid (63 μL, 0.71 mmol, 1.1 equiv) was
added to a Schlenk flask containing a solution of diphosphine−
phosphine oxide 1 (330 mg, 0.64 mmol) in dichloromethane (2 mL).
The solution was stirred for 20 min, and the solvent was removed
under vacuum. Trituration with pentane (3 × 5 mL), followed by
pentane wash (3 × 5 mL), gave compound 7 (370 mg, 0.56 mmol,
88% yield) as a white powder in >99% purity. 1H NMR (500.33 MHz,
293 K, CD2Cl2): δ 8.40−7.90 (br, 1H, H11), 7.81 (br, ω1/2 = 23 Hz,
3H, H3, H12 and H14), 7.67 (m, 4H, H4, Ho and Hp), 7.58 (m, 2H,
Preparation of 2 from 8. In an NMR tube containing a colorless
solution of 8 (8 mg, 0.01 mmol) in d2-dichloromethane (0.5 mL) was
slowly added at room temperature neat 1,8-diazabicyclo[5.4.0]undec-
7-ene (1.6 μL, 0.01 mmol, 1 equiv). The 31P{1H} NMR spectrum
recorded immediately afterward showed that there was 100%
conversion of the starting material to the palladium complex 2.
Cationic Palladium Complex 9. In a Schlenk flask containing a
colorless solution of 2 (62 mg, 0.10 mmol) in dichloromethane (3
mL) was added at room temperature neat trifluoromethanesulfonic
acid (8.9 μL, 0.10 mmol, 1 equiv). The resulting mixture was stirred
for 15 min, the solution was condensed, and pentane (3−4 mL) was
added to give 9 (63 mg, 0.08 mmol, 80% yield) as a white crystalline
solid. 9 was crystallized in a 5/1 CH2Cl2/pentane mixture to give
1
Hm), 7.46−7.10 (br, 3H, H5, H6 and H13), 6.10 (d br, JPH = 408 Hz,
1H, (i-Pr2)PH+), 4.02 (br in baseline, 1H, H15), 3.46 (br in baseline,
1H, H15), 2.25 (br in baseline, 2H, H7), 1.75−0.60 (br, 24H, H8 and
1
3
1
H16). H NMR (500.33 MHz, 233 K, CD2Cl2): δ 8.20 (dd, JPH = 16
white crystals suitable for X-ray diffraction analysis. H NMR (500.33
MHz, 295 K, CDCl3): δ 9.5 (br, ω1/2 = 115 Hz, 1H, OH), 8.76 (dd,
Hz, 4JPH = 7 Hz, 1H, H11), 7.85−7.77 (m, 3H, H3, H12, and H14), 7.69
3
3
3
3JHP = 7 Hz, JHH = 7 Hz, 2H, H6), 7.86 (t br, JHH = 7 Hz, 2H, H5),
(t, JHH = 7 Hz, 1H, H4), 7.67−7.58 (m, 3H, Ho and Hp), 7.57−7.50
(m, 2H, Hm), 7.47−7.39 (m, 2H, H5 and H13), 7.15 (dd, 3JPH = 13 Hz,
7.85−7.73 (m, 6H, H3, H4 and Ho), 7.17 (m, 2H, Hm), 7.02 (t br, 3JHH
4JPH = 7 Hz, 1H, H6), 6.04 (dt, JPH = 414 Hz, JHH = 9 Hz, 1H, (i-
Pr2)PH+), 4.04 (br, 1H, H15), 3.52 (m, 1H, H15), 2.10 (m, 1H, H7),
2.04 (m, 1H, H7), 1.55 (dd, 3JPH = 22 Hz, 3JHH = 6 Hz, 3H, H16), 1.53
(dd, 3JPH = 22 Hz, 3JHH = 6 Hz, 3H, H16), 1.20 (dd, 3JPH = 22 Hz, 3JHH
= 7 Hz, 3H, H16), 1.00 (dd, 3JPH = 15 Hz, 3JHH = 7 Hz, 3H, H8), 0.95
(dd, 3JPH = 15 Hz, 3JHH = 6 Hz, 3H, H8), 0.76−0.65 (m, 6H, H16), 0.59
(dd, 3JPH = 12 Hz, 3JHH = 6 Hz, 3H, H16). 13C{1H} NMR (75.47 MHz,
1
3
= 7 Hz, 1H, Hp), 2.88 (m, 2H, H7), 2.59 (m, 2H, H7), 1.22 (dd, 3JHP
=
16 Hz, 3JHH = 7 Hz, 6H, H8), 1.19 (dd, 3JHP = 16 Hz, 3JHH = 7 Hz, 6H,
H8), 1.09 (dd, 3JHP = 17 Hz, 3JHH = 6 Hz, 6H, H8), 0.81 (dd, 3JHP = 17
Hz, JHH = 6.0 Hz, 6H, H8). 13C{1H} NMR (125.81 MHz, 295 K,
3
CDCl3): δ 153.2 (dt, 2JCP = 134 Hz, 2JCP = 7 Hz, Ci), 144.9 (AA′MX,
2
2
N = 16 Hz, JPC = 46 Hz, C2), 139.0 (AA′MX, N = 18 Hz, JPC = 70
Hz, C1), 133.0 (m, C5), 132.9−132.7 (m, C3, C4 and C6), 132.1 (d,
3JCP = 21 Hz, Co), 123.7 (s br, Cm and Cp), 115.5 (br, OTf), 27.4
(AA′X, N = 11 Hz, C7), 23.7 (AA′X, N = 11 Hz, C7), 18.9 (AA′X, N =
2 Hz, C8), 18.6 (AA′X, N = 2 Hz, CHCH3), 17.7 (s, C8), 17.5 (AA′X,
N = 2 Hz, C8). 31P{1H} NMR (202.54 MHz, 295 K, CDCl3, δ): 142.3
(t, JPP = 25 Hz, 1P, P(OH)), 62.8 (d, JPP = 25 Hz, 2P, PPri2). 19F{1H}
NMR (282.23 MHz, 298 K, CDCl3): δ −78.4 (br, ω1/2 = 30 Hz, OTf).
Mp: 249−251 °C.
Crystallographic Analyses. Crystallographic data were collected
at 193 K on a Bruker-AXS APEX-II QUAZAR diffractometer equipped
with an air-cooled microfocus source (5, 6, and 9) or on Bruker-AXS
SMART APEX-II (8), using Mo Kα radiation (λ = 0.71073 Å).
Semiempirical absorption corrections were employed.35 The structures
were solved by direct methods (SHELXS-97),36 and all non-hydrogen
atoms were refined anisotropically using the least-squares method on
F2. The molecular views were generated with ORTEP3.37
1
2
233 K, CD2Cl2): δ 142.8 (dd, JCP = 26 Hz, JCP = 12 Hz, C2), 140.7
(AA′X, N = 10 Hz, C11), 137.7 (dd, 1JCP = 108 Hz, 2JCP = 31 Hz, C1),
137.6 (dd, 1JCP = 99 Hz, 2JCP = 9 Hz, C9), 135.1 (dd, 2JCP = 11 Hz, 3JCP
= 2 Hz, C3), 134.5 (m, C6), 134.4 (m, C13), 134.3 (m, C14), 132.9 (m,
C12), 132.8 (m, C4), 132.7 (d, 4JCP = 3 Hz, Cp), 131.6 (d, 2JCP = 12 Hz,
Co), 131.3 (d, 1JCP = 107 Hz, Cipso), 129.2 (d, 3JCP = 9 Hz, Cm), 129.0
(d, 3JCP = 12 Hz, C5), 120.8 (dd, 1JCP = 80 Hz, 2JCP = 6 Hz, C10), 26.8
(d, 1JCP = 44 Hz, C15), 26.7 (dd, 1JCP = 44 Hz, 4JCP = 8 Hz, C15), 25.6
(d, 1JCP = 13 Hz, C7), 24.9 (d, 1JCP = 13 Hz, C7), 20.0 (d, 2JCP = 19 Hz,
2
2
C8), 19.9 (d, JCP = 17 Hz, C8), 19.9 (br, C16), 19.8 (d, JCP = 9 Hz,
C16), 19.7 (br, C16), 19.6 (d, 2JCP = 14 Hz, C8), 19.1 (br, C8), 18.2 (br,
C16). 31P{1H} NMR (121.44 MHz, 293 K, CD2Cl2): δ 57.6 (br, ω1/2
=
120 Hz, JPH = 440 Hz, 1P, (i-Pr2)PH+), 33.9 (br, ω1/2 = 83 Hz, 1P,
P(O)Ph), −2.5 (br, ω1/2 = 220 Hz, 1P, P(i-Pr)2). 31P{1H} NMR
(121.44 MHz, 233 K, CD2Cl2): δ 60.6 (d, 3JPP = 3 Hz, 1JPH = 440 Hz,
1P, PH(i-Pr)2), 33.2 (dd, 3JPP = 19 Hz, 3JPP = 5 Hz, 1P, P(O)Ph), −4.7
1
(d, JPP = 18 Hz, 1P, P(i-Pr)2). 19F{1H} NMR (282.23 MHz, 298 K,
3
ASSOCIATED CONTENT
CDCl3): δ −78.2 (s, OTf).
■
Palladium Hydride Complex 8. In a Schlenk flask containing a
dark red solution of Pd2(dba)3 (69 mg, 0.079 mmol) in acetonitrile (2
mL) was slowly added a colorless solution of compound 7 (100 mg,
0.15 mmol, 2 equiv) in the same solvent (2 mL). The resulting mixture
was stirred for 1 h and filtered via cannula to remove elemental Pd.
The solvent was removed from the supernatant under vacuum, and the
S
* Supporting Information
Figures, tables, text, and CIF files giving multinuclear NMR
spectra of 3−9, computational details and Cartesian coor-
dinates for the optimized structures, and X-ray crystallographic
data for CCDC 919850 (5), 919851 (6), 919852 (8), and
F
dx.doi.org/10.1021/om400042v | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(7) For Ph−P(O) bond cleavage at palladium, see: Derrah, E. J.;
Ladeira, S.; Bouhadir, G.; Miqueu, K.; Bourissou, D. Chem. Commun.
2011, 47, 8611.
919853 (9). This material is available free of charge via the
Internet at http://pubs.acs.org.
(8) (a) Van der Boom, M. E.; Milstein, D. Chem. Rev. 2003, 103,
1759. (b) The Chemistry of Pincer Ligands; Morales−Morales, D.,
Jensen, C. M., Eds.; Elsevier: Oxford, U.K., 2007. (c) Benito-Garagorri,
D.; Kirchner, K. Acc. Chem. Res. 2008, 41, 201.
AUTHOR INFORMATION
■
Corresponding Author
*Fax: 33 (0)5 61 55 82 04. Tel: 33 (0)5 61 55 68 03. E-mail:
dbouriss@chimie.ups-tlse.fr (D.B.).
(9) For selected references dealing with PCP pincer complexes
featuring a central aryl or alkyl moiety, see: (a) Gottker-Schnetmann,
̈
Present Address
I.; White, P. S.; Brookhart, M. Organometallics 2004, 23, 1766.
(b) Bolliger, J. L.; Blacque, O.; Frech, C. M. Chem. Eur. J. 2008, 14,
7969. (c) Schuster, E. M.; Botoshansky, M.; Gandelman, M. Angew.
Chem., Int. Ed. 2008, 47, 4555. (d) Azerraf, C.; Shpruhman, A.;
Gelman, D. Chem. Commun. 2009, 466. For PCP pincer complexes
featuring a central carbene moiety, see: (e) Weng, W.; Chen, C.-H.;
Foxman, B. M.; Ozerov, O. V. Organometallics 2007, 26, 3315.
(f) Steinke, T.; Shaw, B. K.; Jong, H.; Patrick, B. O.; Fryzuk, M. D.
Organometallics 2009, 28, 2830. (g) Burford, R. J.; Piers, W. E.; Parvez,
M. Organometallics 2012, 31, 2949.
∥Catalysis Research Laboratory (CaRLa), Universitat Heidel-
̈
berg, Im Neuenheimer Feld 584, D-69120 Heidelberg,
Germany.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The Centre National de la Recherche Scientifique (CNRS), the
(10) (a) Fan, L.; Yang, L.; Guo, C.; Foxman, B. M.; Ozerov, O. V.
Organometallics 2004, 23, 4778. (b) Masuda, J. D.; Jantunen, K. C.;
Ozerov, O. V.; Noonan, K. J. T.; Gates, D. P.; Scott, B. L.; Kiplinger, J.
L. J. Am. Chem. Soc. 2008, 130, 2408. (c) Liang, L. C.; Chien, P. S.;
Lee, P. Y. Organometallics 2008, 27, 3082. (d) van der Vlugt, J. I.;
Reek, J. N. H. Angew. Chem., Int. Ed. 2009, 48, 8832. (e) Calimano, E.;
Tilley, T. D. Dalton Trans. 2010, 39, 9250. (f) Lansing, R. B.;
Goldberg, K. I.; Kemp, R. A. Dalton Trans. 2011, 40, 8950.
(g) Venkanna, G. T.; M. Ramos, T. V.; Arman, H. D.; Tonzetich, Z.
Universite
́
Paul Sabatier (UPS), and the Agence Nationale de la
Recherche (ANR-10-BLAN-070901) are acknowledged for
financial support of this work.
REFERENCES
■
(1) For general reviews, see: (a) Fontaine, F. G.; Boudreau, J.;
Thibault, M. H. Eur. J. Inorg. Chem. 2008, 5439. (b) Kuzu, I.;
Krummenacher, I.; Meyer, J.; Armbruster, F.; Breher, F. Dalton Trans.
2008, 5836. (c) Bouhadir, G.; Amgoune, A.; Bourissou, D. Adv.
Organomet. Chem. 2010, 58, 1. (d) Amgoune, A.; Bourissou, D. Chem.
Commun. 2011, 47, 859.
J. Inorg. Chem. 2012, 51, 12789. (h) Gruger, N.; Wadepohl, H.; Gade,
̈
L. H. Dalton Trans. 2012, 41, 14028.
(11) (a) Brost, R. D.; Bruce, G. C.; Joslin, F. L.; Stobart, S. R.
Organometallics 1997, 16, 5669. (b) MacInnis, M. C.; MacLean, D. F.;
Lundgren, R. J.; McDonald, R.; Turculet, L. Organometallics 2007, 26,
6522. (c) MacLean, D. F.; McDonald, R.; Ferguson, M. J.; Caddell, A.
J.; Turculet, L. Chem. Commun. 2008, 5146. (d) Takaya, J.; Iwasawa,
N. J. Am. Chem. Soc. 2008, 130, 15254. (e) Takaya, J.; Iwasawa, N.
Organometallics 2009, 28, 6636. (f) Suh, H. W.; Schmeier, T. J.; Hazari,
N.; Kemp, R. A.; Takase, M. A. Organometallics 2012, 31, 8225.
(g) Korshin, E. E.; Leitus, G.; Shimon, L. J. W.; Konstantinovski, L.;
Milstein, D. Inorg. Chem. 2008, 47, 7177. (h) For PS(O)P complexes,
see: Suess, D. L. M.; Peters, J. C. Organometallics 2012, 31, 5213.
(12) (a) van der Vlugt, J. I. Angew. Chem., Int. Ed. 2010, 49, 252.
(b) Spokoyny, A. M.; Reuter, M. G.; Stern, C. L.; Ratner, M. A.;
Seideman, T.; Mirkin, C. A. J. Am. Chem. Soc. 2009, 131, 9482.
(c) Segawa, Y.; Yamashita, M.; Nozaki, K. Organometallics 2009, 28,
6234. (d) Hasegawa, M.; Segawa, Y.; Yamashita, M.; Nozaki, K. Angew.
Chem., Int. Ed. 2012, 51, 6956. (e) Ogawa, H.; Yamashita, M. Dalton
Trans. 2013, 42, 625.
(2) For the coordination of PBP ligands, see: (a) Bontemps, S.;
Gornitzka, H.; Bouhadir, G.; Miqueu, K.; Bourissou, D. Angew. Chem.,
Int. Ed. 2006, 45, 1611. (b) Bontemps, S.; Bouhadir, G.; Dyer, P. W.;
Miqueu, K.; Bourissou, D. Inorg. Chem. 2007, 46, 5149. (c) Sircoglou,
M.; Bontemps, S.; Mercy, M.; Saffon, N.; Takahashi, M.; Bouhadir, G.;
Maron, L.; Bourissou, D. Angew. Chem., Int. Ed. 2007, 46, 8583.
(d) Bontemps, S.; Sircoglou, M.; Bouhadir, G.; Puschmann, H.;
Howard, J. A. K.; Dyer, P. W.; Miqueu, K.; Bourissou, D. Chem. Eur. J.
2008, 14, 731. (e) Sircoglou, M.; Bontemps, S.; Mercy, M.; Miqueu,
K.; Ladeira, S.; Saffon, N.; Maron, L.; Bouhadir, G.; Bourissou, D.
Inorg. Chem. 2010, 49, 3983. (f) Conifer, C. M.; Law, D. J.; Sunley, G.
J.; White, A. J. P.; Britovsek, G. J. P. Organometallics 2011, 30, 4060.
(g) Harman, W. H.; Peters, J. C. J. Am. Chem. Soc. 2012, 134, 5080.
(h) Kameo, H.; Nakazawa, H. Organometallics 2012, 31, 7476. For the
coordination of PAlP and PGaP ligands, see: (i) Sircoglou, M.;
Bouhadir, G.; Saffon, N.; Miqueu, K.; Bourissou, D. Organometallics
2008, 27, 1675. (j) Sircoglou, M.; Mercy, M.; Saffon, N.; Coppel, Y.;
Bouhadir, G.; Maron, L.; Bourissou, D. Angew. Chem., Int. Ed. 2009,
48, 3454.
(3) For the coordination of PSiP and PSnP ligands, see: (a) Gualco,
P.; Lin, T. P.; Sircoglou, M.; Mercy, M.; Ladeira, S.; Bouhadir, G.;
Perez, L. M.; Amgoune, A.; Maron, L.; Gabbai, F. P.; Bourissou, D.
Angew. Chem., Int. Ed. 2009, 48, 9892. (b) Gualco, P.; Mercy, M.;
Ladeira, S.; Coppel, Y.; Maron, L.; Amgoune, A.; Bourissou, D. Chem.
Eur. J. 2010, 16, 10808.
(4) For the coordination of PSbP and PBiP ligands, see: (a) Wade, C.
R.; Gabbaï, F. P. Angew. Chem., Int. Ed. 2011, 50, 7369. (b) Wade, C.
R.; Ke, I. S.; Gabbaï, F. P. Angew. Chem., Int. Ed. 2012, 51, 478. (c) Lin,
T.-P.; Ke, I.-S.; Gabbaï, F. P. Angew. Chem., Int. Ed. 2012, 51, 4985.
(d) Tschersich, C.; Limberg, C.; Roggan, S.; Herwig, C.; Ernsting, N.;
Kovalenko, S.; Mebs, S. Angew. Chem., Int. Ed. 2012, 51, 4989.
(5) For the coordination of a σ-SiSi bond at copper, see: Gualco, P.;
Amgoune, A.; Miqueu, K.; Ladeira, S.; Bourissou, D. J. Am. Chem. Soc.
2011, 133, 4257.
(13) For triphosphine pincer complexes, see: (a) Jia, G.; Lee, H. M.;
Williams, I. D. Organometallics 1996, 15, 4235. (b) Meidine, F.;
Pombeiro, J. L.; Nixon, F. J. Chem. Soc., Dalton Trans. 1999, 3041.
(c) Goikhman, R.; Aizenberg, M.; Ben-David, Y.; Shimon, L. J. W.;
Milstein, D. Organometallics 2002, 21, 5060. (d) Fadini, L.; Togni, A.
Chem. Commun. 2003, 30. (e) Helmstedt, U.; Lonnecke, P.; Hey-
̈
Hawkins, E. Inorg. Chem. 2006, 45, 10300.
(14) For PP−P, PP+P, and PP+(O)P pincer complexes, see:
(a) Mazzeo, M.; Lamberti, M.; Massa, A.; Scettri, A.; Pellecchia, C.;
Peters, J. C. Organometallics 2008, 27, 5741. (b) Bauer, R. C.;
Gloaguen, Y.; Lutz, M.; Reek, J. N. H.; de Bruin, B.; van der Vlugt, J. I.
Dalton Trans. 2011, 40, 8822. (c) Pan, B.; Bezpalko, M. W.; Foxman,
B. M.; Thomas, C. M. Organometallics 2011, 30, 5560. (d) Day, G. S.;
Pan, B.; Kellenberger, D. L.; Foxman, B. M.; Thomas, C. M. Chem.
Commun. 2011, 47, 3634. (e) Pan, B.; Xu, Z.; Bezpalko, M. W.;
Foxman, B.; Thomas, C. M. Inorg. Chem. 2012, 51, 4170. (f) Gloaguen,
Y.; Jacobs, W.; de Bruin, B.; Lutz, M.; van der Vlugt, J. I. Inorg. Chem.
2013, DOI: 10.1021/ic302301h.
(6) For σ-bond activation of PSiSiP at gold, see: (a) Gualco, P.;
Ladeira, S.; Miqueu, K.; Amgoune, A.; Bourissou, D. Angew. Chem., Int.
Ed. 2011, 50, 8320. (b) Gualco, P.; Ladeira, S.; Miqueu, K.; Amgoune,
A.; Bourissou, D. Organometallics 2012, 31, 6001.
(15) A PP+(O)P complex has been recently obtained upon oxidation
of the corresponding PP+P complex.14c
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dx.doi.org/10.1021/om400042v | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(16) Derrah, E. J.; Martin, C.; Ladeira, S.; Miqueu, K.; Bouhadir, G.;
Bourissou, D. Dalton Trans. 2012, 41, 14274.
(17) For representative examples, see: (a) Hu, X. Chem. Sci 2011, 2,
(28) (a) Granville, S. L.; Welch, G. C.; Stephan, D. W. Inorg. Chem.
2012, 51, 4711. (b) Runzi, T.; Tritschler, U.; Roesle, P.; Gottker-
̈
̈
Schnetmann, I.; Moller, H. M.; Caporaso, L.; Poater, A.; Cavallo, L.;
̈
Mecking, S. Organometallics 2012, 31, 8388.
1867. (b) Wang, Z. X.; Liu, N. Eur. J. Inorg. Chem. 2012, 2012, 901.
(29) For representative 1H NMR chemical shifts of Pd hydride
complexes, see: (a) Wander, W. A.; Miedaner, A.; Noll, B. C.; Barkley,
R. M.; DuBois, D. L. Organometallics 1996, 15, 3360. δ −5 ppm for a
triphosphine cationic complex: (b) Johansson, R.; Wendt, O. F.
Organometallics 2007, 26, 2426. δ −4 ppm for a PCP pincer complex:
(c) Bruce, L. F.; Foxman, B. M.; Ozerov, O. V. Organometallics 2004,
23, 326. δ −11 ppm for a PNP pincer complex: (d) Gregor, L. C.;
Chen, C.-H.; Fafard, C. M.; Fan, L.; Guo, C.; Foxman, B. M.;
Gusevband, D. G.; Ozerov, O. V. Dalton Trans. 2010, 39, 3195.
(30) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.;
Echeverria, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans.
2008, 2832.
(c) Torres-Nieto, J.; Brennessel, W. W.; Jones, W. D.; Garciua, J. J. J.
̈
Am. Chem. Soc. 2009, 131, 4120. (d) Vicic, D. A.; Jones, W. D. J. Am.
Chem. Soc. 1999, 121, 7606. (e) Rosen, B. M.; Quasdorf, K. W.;
Wilson, D. A.; Zhang, N.; Resmerita, A. M.; Garg, N. K.; Percec, V.
Chem. Rev. 2011, 111, 1346.
(18) Garrou, P. E. Chem. Rev. 1985, 85, 171.
(19) Actually, phosphide oxide nickel complexes are relatively rare,
and none of them are derived from C−P bond cleavage: (a) Benito-
Garagorri, D.; Mereiter, K.; Kirchner, K. Eur. J. Inorg. Chem. 2006,
4374. (b) Zhang, J.; Medley, C. M.; Krause, J. A.; Guan, H.
Organometallics 2010, 29, 6393. (c) Paine, R. T.; Duesler, E. N.;
Moody, D. C. Organometallics 1982, 1, 1097.
(31) For an estimation of the pKa values of Pd hydride complexes,
see: Curtis, C. J.; Miedaner, A.; Raebiger, J. W.; DuBois, D. L.
Organometallics 2004, 23, 511.
(32) For selected examples, see: (a) Abdur-Rashid, K.; Clapham, S.
E.; Hadzovic, A.; Harvey, J. N.; Lough, A. J.; Morris, R. H. J. Am. Chem.
(20) Calculations were performed at the same level of theory as for
Pd: i.e., B3PW91/SDD+f (Ni) and 6-31G** (other atoms). See the
Supporting Information for computational details.
(21) Itoh, K.; Ueda, F.; Hirai, K.; Ishii, Y. Chem. Lett. 1977, 6, 877.
́ ́ ́
(22) (a) Gomez-de la Torre, F.; Jalon, F. A.; Lopez-Agenjo, A.;
Soc. 2002, 124, 15104. (b) Sandoval, C. A.; Ohkuma, T.; Muniz, K.;
̃
́
Manzano, B. R.; Rodrıguez, A.; Sturm, T.; Weissensteiner, W.;
Noyori, R. J. Am. Chem. Soc. 2003, 125, 13490. (c) He, T.; Tsvetkov,
N. P.; Andino, J. G.; Gao, X.-F.; Fullmer, B. C.; Caulton, K. G. J. Am.
Chem. Soc. 2010, 132, 910. (d) Gregor, L. C.; Chen, C.-H.; Fafard, C.
M.; Fan, L.; Guo, C.; Foxman, B. M.; Gusev, D. G.; Ozerov, O. V.
Dalton Trans. 2010, 39, 3195. (e) Zhu, Y.; Chen, C.-H.; Fafard, C. M.;
Foxman, B. M.; Ozerov, O. V. Inorg. Chem. 2011, 50, 7980. (f) Pan, B.;
Bezpalko, M. W.; Foxman, B. M.; Thomas, C. M. Dalton Trans. 2012,
41, 9083.
́
Martınez-Ripoll, M. Organometallics 1998, 17, 4634. (b) Selvakumar,
K.; Valentini, K.; Pregosin, P. S.; Albinati, A. Organometallics 1999, 18,
4591. (c) Iwasawa, T.; Komano, T.; Tajima, A.; Tokunaga, M.; Obora,
Y.; Fujihara, T.; Tsuji, Y. Organometallics 2006, 25, 4665. (d) Warsink,
S.; Hauwert, P.; Siegler, M. A.; Spek, A. L.; Elsevier, C. J. Appl.
Organomet. Chem. 2009, 23, 225. (e) Warsink, S.; Chang, I.-H.;
Weigand, J. J.; Hauwert, P.; Chen, J.-T.; Elsevier, C. J. Organometallics
2010, 29, 4555. (f) Warsink, S.; Bosman, S.; Weigand, J. J.; Elsevier, C.
J. Appl. Organomet. Chem. 2011, 25, 276. (g) Malacea, R.; Saffon, N.;
(33) (a) Beaulieu, W. B.; Rauchfuss, T. B.; Roundhill, D. M. Inorg.
Chem. 1975, 14, 1732. (b) Roundhill, D.; Sperline, R. P.; Beaulieu, W.
B. Coord. Chem. Rev. 1978, 26, 263. (c) Chan, E. Y. Y.; Zhang, Q.-F.;
Sau, Y.-K.; Lo, S. M. F.; Sung, H. H. Y.; Williams, I. D.; Haynes, R. K.;
Leung, W.-H. Inorg. Chem. 2004, 43, 4921.
(34) (a) Nuclear Magnetic Resonance Spectroscopy; Bovey, F. A., Ed.;
Academic Press: New York, 1969. (b) Abraham, R. J.; Bernstein, H. J.
Can. J. Chem. 1961, 39, 216.
Bourissou, D.; Gom
(23) For selected examples, see: (a) Cantat, T.; Ricard, L.; Le Floch,
P.; Mezailles, N. Organometallics 2006, 25, 4965. (b) Konu, J.; Chivers,
T. Chem. Commun. 2008, 4995. (c) Cantat, T.; Arliguie, T.; Noel, A.;
́
ez, M. Chem. Commun. 2011, 47, 8163.
́
̈
́ ́
Thuery, P.; Ephritikhine, M.; Le Floch, P.; Mezailles, N. J. Am. Chem.
́
Soc. 2009, 131, 963. (d) Nebra, N.; Saffon, N.; Maron, L.; Martın-
Vaca, B.; Bourissou, D. Inorg. Chem. 2011, 50, 6378. (e) Nebra, N.;
(35) SADABS; Bruker AXS Inc., Madison, WI, 2006 and 2008.
(36) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(37) ORTEP3: Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
́
Saffon, N.; Maron, L.; Martın-Vaca, B.; Bourissou, D. Chem. Eur. J.
2012, 18, 8474.
(24) (a) Campora, J.; Maya, C. M.; Matas, I.; Claasen, B.; Palma, P.;
Alvarez, E. Inorg. Chim. Acta 2006, 359, 3191. (b) Trush, E. A.;
Amirkhanov, V. M.; Ovchynnikov, V. A.; Swiatek-Kozlowska, J.;
Lanikina, K. A.; Domasevitch, K. V. Polyhedron 2003, 22, 1221.
(c) Akita, M.; Ma, D.; Hikichi, S.; Moro-oka, Y. J. Chem. Soc., Dalton
Trans. 1999, 987.
(25) For C−Si bond activation, see for example: (a) Fullmer, B. C.;
Fan, H.; Pink, M.; Huffman, J. C.; Tsvetkov, N. P.; Caulton, K. G. J.
Am. Chem. Soc. 2011, 133, 2571. For C−O bond activation, see for
example: (b) Kelley, P.; Lin, S.; Edouard, G.; Day, M. W.; Agapie, T. J.
Am. Chem. Soc. 2012, 134, 5480. For C−S and C−N bond activation,
see: (c) Sgro, M. J.; Stephan, D. W. Organometallics 2012, 31, 1584.
(26) For selected examples of C−C bond activation, see:
(a) Terheijden, J.; Van Koten, G.; Vinke, I. C.; Spek, A. L. J. Am.
Chem. Soc. 1985, 107, 2891. (b) Gozin, M.; Weisman, A.; Ben-David,
Y.; Milstein, D. Nature 1993, 364, 699. (c) Liou, S.-Y.; Gozin, M.;
Milstein, D. J. Am. Chem. Soc. 1995, 117, 9774. (d) Salem, H.; Ben-
David, Y.; Shimon, L. J. W.; Milstein, D. Organometallics 2006, 25,
2292. (e) Ruhland, K.; Obenhuber, A.; Hoffmann, S. D. Organo-
metallics 2008, 27, 3482. (f) Obenhuber, A.; Ruhland, K. Organo-
metallics 2011, 30, 171. (g) Obenhuber, A.; Ruhland, K. Organo-
metallics 2011, 30, 4039. For Si−Si bond activation, see:
(h) Murakami, M.; Yoshida, T.; Ito, Y. Organometallics 1994, 13,
2900. (i) Gilges, H.; Kickelbick, G.; Schubert, U. J. Organomet. Chem.
1997, 548, 57.
(27) For selected examples, see: (a) Netherton, M. R.; Fu, G. C. Org.
Lett. 2001, 3, 4295. (b) Ylijoki, K. E. O.; Kundig, E. P. Chem. Commun.
2011, 47, 10608. (c) Leibeling, M.; Werz, D. B. Chem. Eur. J. 2012, 18,
6138.
H
dx.doi.org/10.1021/om400042v | Organometallics XXXX, XXX, XXX−XXX