The coordination chemistry of pentafluorophenylphosphino pincer ligands to platinum and palladium

Article abstract of DOI:10.1002/chem.201304398

The synthesis of electron-poor PCP pincer ligands 1,3-((C₆F ₅)₂PO)₂C₆H₄, 1,3-((C ₆F₅)₂PCH₂)₂C ₆H₄, and 1-((C₆F₅) ₂PO)-3-(tBu₂PCH₂)C₆H₄, and their coordination chemistry to platinum and palladium is described. The most electron-poor ligand 1,3-((C₆F₅)₂PO) ₂C₆H₄ (POCOPH) reacts with Group10 metal chloride precursors to form a range of unusual cis, trans-dimers of the type κ²-P,P-[(POCOPH)MCl(L)]₂ (M=Pt, Pd; L=Cl, Me), which undergo metallation to form [(POCOP)MCl] pincer complexes only under prolonged thermolysis. The formation of such cis,trans-dimers during pincer complex formation can be mitigated through the use of starting materials with more strongly binding ancillary ligands, improving the overall rate of ligand metallation. Carbonyl complexes of the type [(PCP)M(CO)]⁺ were synthesised from the pincer chloride complexes by halide abstraction, and displayed large ν(C-O) values, from 2170-2111cm^-1, confirming the electron-poor nature of the compounds. The [(PCP)Pd(CO)]⁺ complexes also demonstrated the ability to reversibly bind carbon monoxide both in solution and the solid state, with the rate of decarbonylation increasing with increasing wavenumber for the C-O stretch. Back and forth: The electron-poor P(C₆F₅)₂ donor group was incorporated into the PCP pincer ligand motif to generate a range of poorly donating ligands. Palladium carbonyl complexes of these ligands demonstrated the ability to reversibly bind CO, with the ease of CO displacement increasing with increasing ν(CO) values (see figure). These ligands also displayed a reluctance to undergo metallation on Pt or Pd, which led to the formation of rare examples of cis,trans-dimers.

Full text of DOI:10.1002/chem.201304398

DOI: 10.1002/chem.201304398
Full Paper
&
CO Binding
The Coordination Chemistry of Pentafluorophenylphosphino
Pincer Ligands to Platinum and Palladium
Bradley G. Anderson* and John L. Spencer[a]
Abstract: The synthesis of electron-poor PCP pincer ligands
1,3-((C6F5)2PO)2C6H4, 1,3-((C6F5)2PCH2)2C6H4, and 1-((C6F5)2PO)-
3-(tBu2PCH2)C6H4, and their coordination chemistry to plati-
num and palladium is described. The most electron-poor
ligand 1,3-((C6F5)2PO)2C6H4 (POCOPH) reacts with Group 10
metal chloride precursors to form a range of unusual cis,
trans-dimers of the type k2-P,P-[(POCOPH)MCl(L)]2 (M=Pt,
Pd; L=Cl, Me), which undergo metallation to form [(PO-
COP)MCl] pincer complexes only under prolonged thermoly-
sis. The formation of such cis,trans-dimers during pincer
complex formation can be mitigated through the use of
starting materials with more strongly binding ancillary li-
gands, improving the overall rate of ligand metallation. Car-
bonyl complexes of the type [(PCP)M(CO)]+ were synthes-
ised from the pincer chloride complexes by halide abstrac-
tion, and displayed large n(CÀO) values, from 2170–
2111 cmÀ1, confirming the electron-poor nature of the com-
pounds. The [(PCP)Pd(CO)]+ complexes also demonstrated
the ability to reversibly bind carbon monoxide both in solu-
tion and the solid state, with the rate of decarbonylation in-
creasing with increasing wavenumber for the CÀO stretch.
Introduction
alysts with poorly donating ligands have demonstrated high
activities in a variety of addition reactions.[7] The choice of elec-
tron-withdrawing group on the donor atoms can also impart
other beneficial properties to the resultant complexes; for ex-
ample, the presence of pentafluorophenylphosphino groups
can dramatically increase solubility in supercritical CO2, a prop-
erty useful for “green” chemistry.[8] Thus, we aimed to synthe-
sise a range of PCP pincer ligands bearing P(C6F5)2 donor
groups, and assess how their electronic nature affected their
coordination chemistry, as well as the properties of the resul-
tant pincer complexes.
Over recent years, the pincer ligand motif has become an in-
creasing popular design for synthetic chemists. Their planar, tri-
dentate coordination geometry confers upon them high stabil-
ity, whereas the ability to incorporate different functionalities
while possessing the same general structure allows for sub-
stantial variety within the pincer ligand class.[1] These ligands
have been employed with great success in catalysis; pincer
complexes of ruthenium and iridium excel in acceptorless de-
hydrogenation,[2] and are at the forefront of research into
alkane metathesis.[3] Pincer complexes of Group 10 metals, es-
pecially those of palladium, are also effective catalysts for the
allylation of electrophiles, and cross-coupling reactions.[4]
Herein, we report the synthesis of the poorly donating PCP
pincer ligands 1,3-((C6F5)2PO)2C6H4 (POCOPH, 1a), 1,3-((C6F5)2-
PCH2)2C6H4 (PCCCPH, 1b), and 1-((C6F5)2PO)-3-(tBu2PCH2)C6H4
(POCCPH, 1c), and their coordination chemistry to platinum
and palladium metal centres. Owing to the difficulty in metal-
lating ligands 1a–1c, we observed the formation of a range of
dimeric structures with k2-P,P bridging ligands, and isolated
a number of rare examples of cis,trans-dimers. Prolonged ther-
molysis of these cis,trans-dimers yielded metallated PCP pincer
complexes; however, metallation could be made significantly
more facile by choosing ancillary ligands that disfavoured
dimer formation. We also describe the synthesis of the plati-
num and palladium carbonyl complexes of metallated ligands
1a–1c, and report facile, reversible carbon monoxide coordina-
tion to the electron-poor palladium metal centres.
Much of the research involving transition metal pincer com-
plexes has utilised very electron-rich, strongly donating li-
gands, such as di-tert-butyl phosphines, along with the phos-
phorus-carbon-phosphorus (PCP) coordination motif. The use
of poorly donating pincer ligands has so far been sparse, but
has revealed that electron-poor pincer ligands in some cases
possess a vastly different coordination chemistry to that of
their more electron-rich analogues.[5] The electronic character
of the pincer ligand also affects the reactivity and catalytic ac-
tivity of these compounds. An electron-poor iridium pincer
complex has displayed the ability to undergo ligand exchange
and catalytic hydrogenation within a single crystal,[6] while cat-
[a] Dr. B. G. Anderson, Prof. J. L. Spencer
School of Chemical and Physical Science
Victoria University of Wellington, Wellington (New Zealand)
E-mail: bganders1@gmail.com
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201304398.
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isolated as a pale yellow oil, which solidified into a cream-col-
oured solid on cooling to À158. The 31P NMR spectrum of 1c
displayed a quintet for the pentafluorophenyl phosphinite
moiety at 82.9 ppm (3JPÀF =35.5 Hz), and a singlet for the di-
tert-butyl phosphine group at 34.3 ppm.
Ligands 1a and 1c represent the only incorporation of the
bis(pentafluorophenyl)phosphinite moiety into the pincer
ligand framework to date.
Formation of dimeric metal complexes
Scheme 1. Synthesis of the pincer ligands 1a–1c. Reagents and conditions:
a) NEt3, Et2O; (C6F5)2PBr, Et2O, 08C–RT; b) [Mg(anth)(THF)3], THF; (C6F5)2PBr,
THF, À788C–RT; c) PBr3, THF/CH2Cl2, 08C–RT; HPtBu2, acetone, reflux; NEt3,
Et2O; d) NEt3, THF; (C6F5)2PBr, THF, 08C–RT.
Coordination chemistry of the most electron-poor ligand,
POCOPH ligand 1a, was initially explored with platinum(0).
There have been no reports on the reaction of PCP pincer li-
gands with Pt0 precursors. We were interested both in the co-
ordination mode of the electron-poor ligand 1a with Pt0 metal
centres, and whether the species formed could be forced to
oxidatively add the CÀH bond at C-2 of the ligand backbone
to form a metallated k3-PCP pincer complex.
Reactions between 1a and [Pt(nb)3] (where nb=norbor-
nene) produced predominantly the k2-P,P-bridged dimer, [(PO-
COPH)Pt(nb)]2 (2), along with minor amounts of a spectroscopi-
cally similar product, presumed to be a higher oligomer on the
basis of its low solubility in common solvents. The 31P NMR
data of 2 revealed one phosphorus environment, with a large
Pt–P coupling constant indicative of phosphorus coordination
Results and Discussion
Synthesis of pincer ligands 1a–1c
The synthesis of pincer ligands 1a–1c is summarised in
Scheme 1. These ligands were chosen as synthetic targets as
they offered a series of electron-poor ligands with similar steric
bulk, which varied slightly in electronic character. We were also
particularly interested the configuration of 1c, as it would pos-
sess mutually trans electron-donating and electron-withdraw-
ing donors once metallated. Moreover, the formation of bis(-
pentafluorophenyl)phosphinito donors (such as in 1a and 1c)
was desirable from a synthetic perspective, as the synthesis of
fluoroarylphosphine ligands can often be more difficult than
for the corresponding arylphosphine or alkylphosphine ana-
logues.[9] Therefore, by connecting the P(C6F5)2 moiety to the
ligand backbone with a phosphinite linkage, this synthetic dif-
ficulty could be circumvented.
1
trans to the norbornene (d=100.5 ppm, JPtÀP =4623 Hz). Com-
pound 2 was confirmed as a dimer by high resolution mass
spectrometry (HRMS), with [MÀnb+Na]+ observed at m/z
2087 amu. Attempts to promote oxidative addition of the
ligand backbone to produce the pincer species [(POCOP)PtR]
(where R=norbornyl or H) by thermolysis, protonolysis, or by
treatment of 2 with base were all unsuccessful.
The synthesis of the POCOPH ligand 1a was carried out by
the treatment of the phosphine halide (C6F5)2PBr with resorci-
nol, as is typical for the formation of phosphinite com-
pounds.[4c] Ligand 1a was isolated as a white solid, and dis-
Crystals of 2 suitable for single crystal X-ray diffraction were
grown from a dichloromethane solution layered with metha-
nol. The structure revealed two trigonal planar platinum cores,
bridged by two POCOPH ligands in a cis-k2-P,P fashion, with
the norbornene bound “in-plane” in a conventional h2 manner
(Figure 1). When compared to other structures possessing the
[P2Pt(nb)] coordination motif,[13] 2 displays a slightly shortened
norbornene C=C bond (1.434(3) ꢁ, compared to 1.460(11) and
1.469(8) ꢁ for reported structures), and slightly elongated PtÀC
bond (average of 2.146(4) ꢁ, compared to 2.109(15) and
2.113(10) ꢁ). This can be seen as a consequence of the poorly
donating P(C6F5)2 substituents reducing the amount of metal–
norbornene p-backbonding that can occur, leading to a more
weakly bound norbornene ligand when compared to struc-
tures with more electron-donating phosphine substituents.
The 13C NMR spectrum of 2 also supports the notion of a weak-
played a quintet in the 31P NMR spectrum at 87.1 ppm (3JPÀF
=
35.0 Hz).
The PCCCPH ligand 1b has previously been prepared by the
treatment of (C6F5)2PBr with the bis-Grignard reagent 1,3-
(ClMgCH2)2C6H4.[10] In replicating this procedure, the prepara-
tion of the Grignard reagent was found to be difficult and un-
reliable; however, using [Mg(anthracene)(THF)3][11] to generate
the bis-Grignard reagent resulted in consistently greater yields
of PCCCPH than for reactions in which the Grignard reagent
was generated using activated magnesium turnings. Purifica-
tion of the reaction mixture by column chromatography in air
afforded 1b as a white solid (d=À46.3 ppm), which was ob-
served to oxidise only gradually under ambient conditions.
The unsymmetrical POCCPH pincer ligand 1c was prepared
in a similar manner to that of the two previously published ex-
amples of phosphine-phosphinite pincer ligands.[12] The PtBu2
moiety was first installed by nucleophilic attack of di-tert-butyl-
phosphine at the benzylic carbon of 3-hydroxybenzyl bromide,
followed by formation of the phosphinite PÀO linkage by
treatment of the phenol functionality with (C6F5)2PBr, in an
almost identical manner to the synthesis of 1a. Ligand 1c was
1
ened metal–norbornene interaction, displaying a JPtÀC cou-
pling of 259 Hz, significantly lower than the corresponding
value of 344 Hz reported for the tert-butyl-substituted com-
pound [(dtbpe)Pt(nb)] (where dtbpe=tBu2PCH2CH2PtBu2).[13b]
The solid-state structure of 2 also displays a folding of the
aryl backbones to generate favourable “parallel displaced” p–p
interactions[14] (interplanar angle=0.08, interatomic distance=
3.321(3) ꢁ). This is somewhat unusual, as all similar cis-dimers
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Figure 2. 1H NMR spectra showing the effect of p–p interactions on the
chemical shift of the H2 proton environment of compounds 2, 3, and 4 in
[D6]acetone.
Figure 1. Crystal structure of [(POCOPH)Pt(nb)]2 (2), with 50% probability el-
lipsoids. Hydrogen atoms are omitted for clarity. Atoms denoted by the su-
perscripted “i” are generated from the asymmetric unit by inversion. Select-
ed bond lengths [ꢁ] and angles [8]: Pt1ÀC1, 2.153(2); Pt1ÀC2, 2.139(2); Pt1À
P1, 2.110(6); Pt1ÀP2, 2.2224(5); C1ÀC2, 1.434(3); P1-Pt1-P2, 108.04(2).
significant quantities of the desired [(PCP)PtMe] pincer com-
plexes.
Owing to the failure of [Pt(nb)3] and [PtMe2(hex)] to gener-
ate compounds that served as precursors to pincer complexes,
reactions with metal chloride precursors were examined, as
these have been shown to readily afford pincer complexes.[17]
Reactions between 1a and [PtCl2(hex)], [PtClMe(hex)], and
[PdCl2(NCMe)2], at low temperatures all yielded unusual k2-P,P-
bridged dimers possessing one cis-coordinated metal centre
and one trans-coordinated metal centre. This coordination
motif is very rare; only a handful of cis,trans-dimers have been
reported to date.[18]
reported have aromatic backbones canted towards each other
by at least 18.68, with the degree of canting seemingly inde-
pendent of the steric bulk of the phosphorus donor.[15] The
presence of p–p interactions in 2 may confer additional stabili-
ty to the dimeric structure, and account for the observation
that oligomeric species initially present in reaction mixtures ap-
peared to rearrange to form the dimer 2 over time.
The coordination chemistry of ligand 1a with [PtMe2(hex)]
(where hex=1,5-hexadiene) was also explored, with reactions
at room temperature yielding mixtures of the dimer cis-[(PO-
COPH)PtMe2]2 (3), and a higher oligomer cis-[(POCOPH)PtMe2]x
(4). Unlike many similar oligomeric species, 4 was sufficiently
soluble in CD2Cl2 for spectroscopic data to be obtained. Com-
pounds 3 and 4 possessed similar 31P NMR spectra, with small
Pt–P coupling values indicating coordination of phosphorus
These cis,trans-dimers were found to be the thermodynamic
product in each of the reactions, with in situ monitoring by
NMR spectroscopy revealing the formation of an initial coordi-
nation complex, then rearrangement or further reaction to
give the cis,trans-dimer (Scheme 2). None of the transient inter-
mediate species was isolated, and structures have been tenta-
tively proposed on the basis of 31P NMR data (Scheme 2). The
initial formation of a cis-species for the reaction with [PtCl2-
(hex)] was likely due a mutually trans-coordination being dis-
favoured for the p-accepting phosphinite groups, due to anti-
symbiotic effects.[19] The P-trans-P coordination was then ob-
served in the initial products of the [PtClMe(hex)] and [PdCl2-
(NCMe)2] reactions due to the preference of the methyl group
(with a strong trans-influence) to coordinate trans to the group
with the weakest trans-influence (the chloride), and also due
to the greater ionic character of metalÀligand bonding on pal-
ladium disfavouring cis-dichloride compounds due to electro-
static repulsion.[20]
1
trans to the methyl groups (3, d=89.9 ppm, JPtÀP =2202 Hz; 4,
1
d=90.9 ppm, JPtÀP =2150 Hz). HRMS confirmed that 3 was di-
meric, with the [M+Na]+ ion observed at m/z 2147 amu. The
nuclearity of 4 could not be determined by HRMS or LC-HRMS,
but was assumed to be a higher oligomer (x>2) on the basis
of its lower solubility than 3. As was observed for reactions
with [Pt(nb)3], longer reaction times in toluene (rather than di-
chloromethane) favoured the formation of the dimer 3 over
the oligomer 4. Proton NMR spectroscopy indicated the p-
stacking present in the crystal structure of 2 also occurs in so-
lution: the proton environment H2 of dimers 2 and 3 appeared
at about d=6.4 ppm in [D6]acetone, significantly upfield from
that of the oligomer 4 (d=7.1 ppm), which is unable to display
p-stacking of ligand backbones (Figure 2). Similar shielding of
aromatic protons by p-stacking has been observed for organic
compounds,[16] and in this instance the shielding of H2 allows
for ready discrimination between dimeric and oligomeric prod-
ucts. As for 2, subjecting 3 and 4 to thermolysis did not yield
The complexes cis,trans-[(POCOPH)PtCl2]2 (5), cis,trans-[(PO-
COPH)PtMeCl]2 (6), and cis,trans-[(POCOPH)PdCl2]2 (7), were all
confirmed as dimers by HRMS, and displayed similar NMR
spectra to each other. The mutually trans phosphorus environ-
ment of the compounds appeared at a 31P chemical shift close
to that of the free ligand 1a, at d=80.6, 90.3, and 88.7 ppm
for 5, 6, and 7, respectively, and displayed Pt–P coupling con-
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pnictogens,[21] poorly donating li-
gands may assist in the rear-
rangement to form cis,trans-
dimers from the initial kinetic
products formed in reaction mix-
tures.
Toluene solutions of cis,trans-
dimers 5, 6, and 7 underwent
thermolysis to cleanly produce
the desired [(PCP)MCl] pincer
compounds. This phenomenon
has not been widely reported:
examples of dimers undergoing
metallation possess either li-
gands that favour metallation
(through steric bulk[15c] or inter-
nal base functionality[22]), or
poorly donating ligands that
may be susceptible to rearrange-
ment to configurations from
which metallation is facile.[15a]
Where the ligands do not aid
metallation, dimers have been
Scheme 2. Reaction between ligand 1a and metal chloride precursors led to the formation of cis,trans-dimers 5–
7. In each reaction a transient intermediate species was observed, for which structures have been proposed on
1
the basis of the 31P NMR spectroscopy data shown. Numbers in brackets are JPtÀP values.
sistent with mutually trans phosphorus donors (1JPtÀP =3357 Hz
for 5, 4028 Hz for 6). The phosphorus environment trans to
a chloride was shifted significantly upfield for each compound,
and appeared at d=55.5, 62.1, and 78.5 ppm, respectively,
with large Pt–P coupling values signifying coordination of the
obtained as relatively inert by-products formed during the at-
tempted synthesis of pincer compounds.[15b,23]
Synthesis of PCP pincer complexes 8a–8c, 9a–9c
phosphorus trans to the low trans-influence chloride (1JPtÀP
=
From investigation of the coordination chemistry of 1a with
platinum and palladium starting materials, it was clear that the
metal chloride starting materials offered the most successful
route to the metallated pincer complex. Ligand metallation
studies were performed with 1a and [PtCl2(hex)], [PtCl2(COD)]
(where COD=1,5-cyclooctadiene), and [PtCl2(SEt2)2] to investi-
gate the effect of the ancillary ligand on both dimer and
pincer complex formation. After 120 h at reflux in toluene,
NMR spectroscopy revealed that the [PtCl2(SEt2)2] reaction was
complete, the [PtCl2(COD)] reaction contained approximately
75% product, and the [PtCl2(hex)] reaction contained approxi-
mately 50% metallated product. In situ NMR studies of the
metallation reaction revealed that the dimeric intermediate 5
was formed more slowly and in smaller quantities for the
faster reactions. This indicated that the ancillary ligand had
a significant effect on the rate of reaction, with the order of re-
activity being SEt2 >COD>hexadiene. This reactivity series also
correlated well with the binding strength of S-donors and al-
kenes on platinum.[24] Competitive displacement reactions be-
tween [PtCl2(COD)] and SEt2, and [PtCl2(SEt2)2] and COD were
performed, and qualitatively confirmed that SEt2 was more ef-
fective at displacing COD than COD was at displacing SEt2.
However, exact data were difficult to obtain owing to the low
solubility of [PtCl2(COD)] in [D6]benzene.
4582 Hz for 5, 5494 Hz for 6). The phosphorus coordinated
trans to the methyl group in 6 appeared at d=94.4 ppm with
1
a JPtÀP =2066 Hz, spectroscopically similar to the phosphorus
1
environments in the PtMe2 cis-dimer 3 (d=89.9 ppm, JPtÀP
=
1
2066 Hz). In this instance, JPtÀP coupling values were extremely
useful in establishing the coordination geometry around each
metal centre, with the palladium compound 7 assigned by
analogy to the platinum compounds 5 and 6. The structures of
1
these cis,trans-dimers were confirmed by H,31P HMBC experi-
ments, which established the connectivity of each of the phos-
phorus donors to the aromatic ligand backbone. Conventional
1H,13C HSQC and HMBC experiments were then used to estab-
lish the connectivity around the ligand backbone, and con-
firmed that both the cis- and trans-coordinated donors were in
the same compound.
The preference of platinum and palladium dimers of the
type [(POCOPH)M(L)2]2 to adopt a stable cis,trans configuration
is interesting, especially considering that 5, 6, and 7 represent
complexes both with and without a strongly trans-directing
methyl group, and are able to rearrange to form these asym-
metric dimers from both cis and trans complexes. For coordi-
nation complexes of the phosphinite ligand 1a the cis,trans-di-
meric structure must offer a balance between antisymbiotic
and electrostatic effects that is energetically favourable for all
compounds, despite the differences in metal centre and ancil-
lary ligand. It may be pertinent to note that all cis,trans-dimers
reported to date possess at least one diphenyl pnictogen
donor;[18] as aryl substitution decreases the s-donor ability of
Strongly binding ancillary ligands are likely to aid the metal-
lation reaction by stabilising k1-[(POCOPH)PtCl2L] intermediate
species, with more strongly binding ligands displaced from the
metal centre at temperatures closer to those required for met-
allation, minimising the build-up of dimer in solution
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brecht has published a crystal structure of a trans-k2-P,P-[(
PCPH)PtCl(L)]2 species in which the chloride ligands interact
strongly with the proton on C-2 of the ligand backbone, result-
ing in a weakened CÀH bond.[22] Such H···Cl interactions have
also been calculated to be favourable in the breaking of CÀH
bonds in Shilov reactions.[27]
The effect of the ligand on the metallation reaction was also
evaluated. The rate of ligand metallation was observed to in-
crease as the phosphine donors became more basic. In reac-
tions with [PdCl2(NCMe)2] at reflux in toluene, metallation of
the phosphinite ligand 1a was complete after 80 h, whereas
metallation of the phosphine ligand 1b took just 48 h. Replac-
ing a pentafluorophenylphosphino substituent of 1a with a di-
tert-butylphosphine (to give ligand 1c) allowed complete met-
allation after just 20 h. This is consistent with a recent study of
nickellation rates with PCP pincer ligands, in which more elec-
tron-rich ligands were observed to metallate much more readi-
ly than electron-poor ligands.[28] Reactions between ligands
1a–1c and platinum and palladium precursors gave the
[(PCP)MCl] pincer complexes 8a–8c and 9a–9c in moderate to
good yields (Scheme 4).
Scheme 3. Effect of ancillary ligand binding strength on dimer formation. Li-
gands that are more readily displaced from the k1-[(PCPH)PtCl2(L)] intermedi-
ate will favour dimer formation (top), while less readily displaced ligands will
favour monomer formation (bottom). Ligand metallation to form the pincer
complex is more facile from the monomer than the dimer.
(Scheme 3). Dimeric species, such as 5, hinder the metallation
reaction; since metallation is unlikely to occur readily from a di-
meric configuration, additional energy is required to rearrange
from the thermodynamically stable dimer into an arrangement
from which metallation can readily occur. The formation of di-
meric/oligomeric species during pincer complex synthesis is
less problematic when using ligands with fluoro-alkyl or -aryl
phosphine donors, as such ligands will have a lower energy
barrier to rearrangement than ligands with more basic phos-
phine donors. This has been reported in the literature, as start-
ing materials with strongly binding PPh3 ligands have resulted
in greater yields of pincer complex and less oligomer forma-
tion than reactions proceeding from MX2 or [MX2(nitrile)2] pre-
cursors.[25] Although the ancillary ligand effect has been little
discussed and often overlooked, by choosing starting materials
with less readily displaced ancillary ligands, oligomer/dimer
formation can be minimised, while pincer complex formation
can be made more facile.
Scheme 4. Synthesis of [(PCP)MCl] complexes.
Preliminary investigations into the effect of concentration on
the reactivity of the k1-[(POCOPH)PtCl2(SEt2)] intermediate
show that it does not react significantly faster when the con-
centration is doubled. While it may be anticipated that concen-
tration would play a greater role, the coordination of the
P(C6F5)2 moiety likely increases the affinity of the metal centre
for the remaining SEt2 ligand, making any dimerisation depen-
dent on SEt2 dissociation rather than the availability of uncoor-
dinated phosphinite donors in solution.
The NMR spectra of complexes 8a–8c and 9a–9c were all
consistent with the formation of tridentate pincer complexes;
31P NMR spectra displayed signals shifted downfield from those
of the free ligand and unmetallated intermediates, consistent
with deshielding of the phosphorus atoms upon coordination
to the metal centre, followed by the loss of an electron-rich
1
chloride from the metal centre upon metallation. The JPtÀP
values for 8a, 8b, and 8c ranged from 3088 to 3663 Hz, indica-
tive of mutually trans-coordinated phosphorus donors. Com-
plexes 8c and 9c, possessing the asymmetric POCCP ligand
The nature of the ionic ligand on the metal precursor has
a large effect on the ease of pincer complex formation; the
use of a platinum starting material with an internal base has
been shown to significantly lower the temperatures required
for ligand metallation.[26] However, such starting materials are
more difficult to prepare than [PtCl2(L)n] complexes. The
methyl chloride precursor [PtClMe(COD)] has been used to
good effect for the synthesis of [(PCP)PtCl] complexes,[15a,17a]
and we found that in reactions with 1a, [PtClMe(hex)] pro-
duced the desired pincer complex in less than half the time re-
quired when using dichloride precursor [PtCl2(hex)] (48 h com-
pared to >120 h). The efficacy of [PtClMe(hex)] as a starting
material was somewhat surprising, considering that reactions
between 1a and [PtMe2(hex)] only yielded trace amounts of
the desired [(PCP)PtMe] pincer complex. It is possible that in
these reactions the chloride assists with proton transfer from
the CÀH bond being cleaved on to the leaving group, as Al-
2
1c, displayed large JPÀP values (460–470 Hz), significantly
greater than the 388 Hz reported for a similar POCCP pincer
complex,[12a] suggesting the mutually trans arrangement of do-
nating and accepting ligands may provide a synergy that
strengthens the phosphorus–phosphorus coupling interaction.
The loss of a signal for the H2 proton environment was also
1
evident in the H NMR spectra of all compounds.
Synthesis and reactions of pincer carbonyl complexes 10a–
10c, 11a–11c
To quantify the electronic effect of ligands 1a, 1b, and 1c on
the metal centre, carbonyl complexes 10a–10c, 11 a–11 c were
prepared from the parent pincer chloride complexes 8a–8c,
9a–9c by chloride abstraction with AgSbF6 followed by treat-
ment with CO (Scheme 5). As expected, the observed magni-
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Scheme 5. Synthesis of [(PCP)M(CO)]+ complexes.
Table 1. Spectroscopic data for carbonyl complexes 10a–10c, 11 a–11 c.
Compound
n(CÀO) [cmÀ1
]
13C d(CO) (ppm)[a]
19F Ddm,p (ppm)[b]
10a
10b
10c
11 a
11 b
11 c
2145
2127
2111
2170
2148
2140
177.5
180.6[c]
180.1
176.0
177.9
179.7
15.8
13.3
13.8
15.1
13.4
13.9
Figure 3. Crystal structure of [(POCOP)Pt(CO)][SbF6] (10a), with 50% proba-
bility ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths [ꢁ] and angles [8]: Pt1ÀP1, 2.2748(6); Pt1ÀP2, 2.22829(6); Pt1ÀC1,
2.008(2); Pt1ÀC1a, 1.962(2); C1aÀO1a, 1.117(3); P1-Pt1-P2, 157.73(2); C1-Pt1-
C1a, 178.72(9); Pt1-C1a-O1a, 179.2(2).
[a] Recorded in [D2]dichloromethane. [b] Values are for the [(PCP)MCl]
compounds, to reflect that Ddm,p values may be used in lieu of carbonyl
CÀO stretches. [c] Recorded in [D6]acetone.
tude of n(CÀO) followed the pattern POCOP>PCCCP>POCCP;
the enhanced p-acceptor ability of the phosphinite POCOP
generated the most electron-poor metal centres, while the
strong s-donor ability of the tert-butyl phosphine in POCCP re-
sulted in the most electron-rich metal centres (Table 1). Of
note is that n(CÀO) values for compounds 10a, 11 a, and 11 b
were greater than that of free CO (2143 cmÀ1), suggesting that
negligible MÀCO p-backbonding is present in these carbonyl
complexes.[29]
solution of at room temperature. Compound 10a represents
the first example of
Group 10 [(POCOP)M(CO)]+ complex. The solid-state structure
revealed C-Pt-CO angle close to the expected 1808
a crystallographically characterised
a
(178.72(9)8), and a P-Pt-P angle of 157.73(2)8, smaller than that
commonly observed for platinum PCP pincer complexes (typi-
cally 161–1688,[15a,33] due to the steric constraints of the PCP
chelate; Figure 3). The small P-Pt-P angle in 10a was likely to
be due to the electron-poor phosphorus atoms polarising and
shortening the PÀO bonds (average bond length of 1.607(4) ꢁ,
compared to 1.644(10) ꢁ in a more electron-rich platinum
phosphinite),[33c] resulting in more strained five-membered che-
late rings. A similar effect is observed in iridium carbonyl
pincer complexes.[6] The CÀO and PtÀC bond lengths for the
carbonyl ligand of 10a (1.117(3) and 1.962(2) ꢁ) were consis-
tent with the IR data, and indicated CO coordination to an
electron-poor metal centre. Similar values were reported for an
electron-poor trifluoromethyl phosphine pincer compound
(1.114(6), 1.964(4) ꢁ, and 2143 cmÀ1, respectively),[15a] with a suf-
ficiently shorter CÀO bond and longer PtÀC bond than in the
more electron-rich isopropyl phosphine pincer complex
(1.131(4), 1.919(3) ꢁ, and 2080 cmÀ1).[33e]
Compounds 10a, 11 a, and 11 b all possess n(CÀO) values
higher than for any previously reported pincer complex,
(2141 cmÀ1 for a [(POCOP)Pd(CO)]+ complex,[30] and 2143 cmÀ1
for a [(PCCCP)Pt(CO)]+ complex),[15a] and are close to the
2174 cmÀ1 reported for the highly electrophilic [(dfepe)Pt(Me)(-
CO)]+ (where dfepe=(C2F5)2PCH2CH2P(C2F5)2).[31] As expected
the chemical shift of the carbonyl carbon in the 13C NMR spec-
tra of 10a–10c and 11 a–11 c is in broad agreement with the
corresponding CÀO stretching frequency; the greater the CÀO
stretching frequency the less electron density removed from
the CÀO bond by back-donation to the metal, and so the
more shielded (and further upfield) the resonance in the
13C NMR spectrum. A further measure of electronic character
for pentafluorophenyl-containing compounds is Ddm,p, the
chemical shift difference between meta and para fluorine envi-
ronments on the pentafluorophenyl ring.[10,32] This parameter
has been proposed as an approximation of the electronic char-
acter of the phosphorus donor, and therefore may be able to
provide insight into the electronic nature of these complexes
without having to synthesise the carbonyl derivatives. Howev-
er, for the platinum and palladium pincer complexes the Ddm,p
values of the [(PCP)MCl] complexes do not correlate well with
the observed n(CÀO) values of the carbonyl analogues
(Table 1).
All of the palladium carbonyl compounds underwent gradu-
al loss of bound carbon monoxide, as has been noted in the
literature for similar palladium species.[30,34] The decarbonylated
adducts of 11 a–11 c, [(PCP)Pd][SbF6] (12a–12c) gradually
formed over the course of months under ambient conditions
in the solid state. Infrared spectroscopy revealed that aside
from the absence of a CÀO stretch, these compounds were
almost identical to their parent carbonyl complexes, with the
observation of SbÀF stretches (n(SbÀF) approx. 650 cmÀ1) sug-
gesting the continued presence of the hexafluoroantimonate
counterion in 12a–12c (Figure 4).
Single crystals of 10a suitable for single crystal X-ray diffrac-
tion were grown by slow evaporation from a dichloromethane
The IR of 12b also displayed a sharp OÀH stretch at
3671 cmÀ1 (see the Supporting Information for IR spectra of
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monoxide was unable to be displaced from the metal centre.
This work, therefore, represents the first report of reversible
carbon monoxide uptake for a pincer complex.
The ease of decarbonylation of each of the carbonyl com-
plexes 12a–12c was investigated by passage of N2 through
CD2Cl2 solutions of carbonyl complexes 11 a–11 c for 30 min.
The proportion of decarbonylated species present was then as-
sessed by NMR spectroscopy. The ease of carbonyl displace-
ment was in broad agreement with n(CÀO) values for 11 a–
11 c; the larger the CÀO stretching frequency, the more readily
the decarbonylation occurred (Figure 5). However, while 11 b
and 11 c have n(CÀO) values that differ by only 8 cmÀ1 (2148
and 2140 cmÀ1, respectively), 11 c proved substantially harder
to decarbonylate than 11 b. This highlights the dramatic effect
that the electron-rich di-tert-butylphosphine group has in facili-
tating p-backbonding and stabilising the carbonyl ligand.
Carbon monoxide-releasing molecules (CO-RMs) are of phar-
maceutical significance,[36] as in vivo release of CO allows its
beneficial anti-inflammatory effects to be magnified, while re-
ducing its toxicity.[37] Whilst 11 a–11 c are not suited for use as
CO-RMs due to their high molecular weight and low water sol-
ubility, they indicate that the use of electron-deficient ligands
may be beneficial in the design of molecules with labile CO li-
gands.
Figure 4. IR spectra showing the formation and subsequent decarbonylation
of 11 b. The CÀO stretch of 11 b appears at 2148 cmÀ1, and SbÀF stretches
are observed around 650 cmÀ1 for 11 b and 12b, but not for the starting
material 9b.
11 b and 12b) indicating that in the solid state adventitious
water had replaced the CO on the palladium centre. However,
for solutions of 12b in CD2Cl2 NMR spectroscopy revealed no
indication of water coordination to the palladium, or of CÀ
F···Pd interactions from the pentafluorophenyl substituents sta-
bilising the decarbonylated species. Synthesis of the BF4
adduct of 12b from AgBF4 revealed no evidence of BF4 coordi-
nation to the metal centre in the 19F NMR spectrum (d=
À153 ppm: values of around À160 ppm have been reported
Conclusion
In this work, three electron-poor PCP pincer ligands 1a–1c
have been synthesised, and their coordination chemistry to
platinum and palladium examined. The electronic character of
ligands 1a–1c inhibited the cyclometallation reaction to form
the desired tridentate pincer complexes, instead displaying
a predisposition for the formation of bimetallic, k2-P,P-bridged
compounds. In reactions with 1a, three rare examples of cis,-
trans-dimers were isolated (5–7), all of which underwent metal-
lation upon prolonged thermolysis to yield the desired plati-
À
for coordinated BF4 ),[35] making it likely that compounds 12a–
12c are stabilised by solvent coordination in solution.
Quantitative regeneration of
the palladium carbonyl com-
plexes 11 a–11 c was achieved by
passage of CO through CD2Cl2
solutions of the decarbonylated
species 12a–12c for 15 min at
room temperature. This carbony-
lation was reversible, with the
CO displaced upon passage of
inert gas (Ar, N2, or CH4) through
solution; however, decarbonylat-
ed species 12a–12c slowly de-
composed over time in solution,
leading to palladium black for-
mation.
While the exchangeable bind-
ing of small gaseous molecules
(H2, N2, O2, NH3, and C2H4) in the
solid state has previously been
Figure 5. 31P NMR spectra showing the decarbonylation of compounds 11 a–11 c in CD2Cl2. Resonances arising
reported for an electron-poor
PCP iridium complex,[6] carbon from decarbonylated products are denoted with an asterisk.
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using Mercury (Version 2.4.5), and molecular drawings were gener-
ated using ORTEP3 (Version 1.0.3). CCDC-970819 (2) and -970820
(10a) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
num or palladium [(POCOP)MCl] pincer complexes. It was ob-
served during these ligand metallation reactions that the reac-
tion rate depended to some extent on the ancillary ligand of
the [PtCl2(L)n] precursor; using more strongly binding ancillary
ligands disfavoured the formation of the cis,trans-dimer 6, and
in doing so, improved the rate of ligand metallation.
Platinum and palladium carbonyl complexes of the metallat-
ed ligands 1a–1c were synthesised, and CO stretching fre-
quencies indicated that [(POCOP)Pd(CO)]+ (11 a) possessed
one of the most electron-poor metal centres of a pincer com-
pound reported to date. Consequently, the electron-poor palla-
dium compounds 11 a–11 c demonstrated the ability to reversi-
bly bind carbon monoxide, with decarbonylation proceeding
more rapidly for the compounds with larger CO stretching fre-
quencies. A subsequent report will outline the performance of
the palladium pincer compounds 9a–9c as catalysts in cross-
coupling reactions.
Synthesis and characterization
Synthesis of 1,3-[(C6F5)2PO]2C6H4 (POCOPH) (1a): Resorcinol
(1.00 g, 9.1 mmol) was suspended in a solution of triethylamine
(2.6 mL, 18.6 mmol) in diethyl ether (80 mL). The reaction mixture
was cooled on ice and a solution of BrP(C6F5)2 (4.1 mL, 18.2 mmol)
in diethyl ether (10 mL) was added dropwise. The reaction mixture
was stirred for 1 h on ice and 18 h at RT, and then filtered through
Celite. Removal of volatiles in vacuo and recrystallisation from tolu-
ene/hexane at À158C gave 1a as white needles (6.61 g, 87%).
1H NMR (500 MHz, CD2Cl2): d=7.24 (t, 3JH,H =7.8 Hz, 1H; H5), 6.86
3
4
(dd, JH,H =7.5 Hz, JH,H =1.6 Hz, 2H; H4,H6), 6.85 ppm (s, 1H; H2);
31P NMR (121 MHz, CD2Cl2): d=87.1 ppm (quint, 3JP,F =35.0 Hz);
19F NMR (282 MHz, CD2Cl2): d=À133.1 (m, 2F; o-C6F5), À148.6 (t,
3JF,F =19.7 Hz, 1F; p-C6F5), À160.6 ppm (m, 2F; m-C6F5); elemental
analysis calcd (%) for C30H4O2F20P2: C 42.98, H 0.48; found: C 42.86,
H 0.63; HRMS calcd for (C30H8NO4F20P2) [M+2O+NH4]+: m/z
887.9609, found 887.9618.
Experimental Section
General
All reactions were carried out under a nitrogen atmosphere using
standard Schlenk techniques unless otherwise stated. Dichlorome-
thane, diethyl ether, and THF were carefully dried and distilled
prior to use. Other solvents were degassed and stored over molec-
ular sieves. Unless otherwise stated, all other reagents were used
as obtained from commercial suppliers. The compounds (3-hydrox-
ybenzyl)di-tert-butyl phosphine,[12a] bis(pentafluorophenyl)bromo-
phosphine,[38] [PdCl2(NCMe)2],[39] [PtCl(N(SiMe3)2)(COD)],[26] [PtCl2-
(COD)],[40] [PtCl2(hex)],[41] [PtCl2(SEt2)2],[42] and [Pt(nb)3][43] were syn-
thesised according to literature procedures. NMR spectra were ob-
Synthesis of 1,3-[(C6F5)2PCH2]2C6H4 (PCCCPH) (1b): Magnesium
powder (0.10 g, 4.1 mmol) in THF (24 mL) was activated with 1,2-
dibromoethane (0.1 mL) and heated with a heat gun until rapid
bubbling was observed. After bubbling had ceased, anthracene
(1.4 g, 9.0 mmol) was added, and the reaction mixture was stirred
at RT for 4 days. The supernatant liquid was decanted, the solid
[Mg(anth)(THF)3] was resuspended in THF, and a solution of di-
chloro-m-xylene (350 mg, 2.0 mmol) in THF (6 mL) was added
dropwise and stirred, overnight. The supernatant was decanted
and cooled to À788C, and to it was added BrP(C6F5)2 (0.84 mL,
3.68 mmol) dropwise. The reaction mixture was allowed to warm
to RT, overnight, then the volatiles were removed in vacuo and the
remaining solid was extracted with hexane (4ꢂ50 mL) and filtered
through Celite. The solvent was removed under vacuum, and chro-
matography on silica in air (petroleum ether eluent, Rf =0.1) afford-
ed 1b as a white solid (1.03 g, 67%). Spectroscopic data matched
that previously reported for 1b.[10]
1
tained using a Varian Unity Inova 300 (300 MHz for H, 121 MHz for
1
31P, and 282 MHz for 19F), a Varian Unity Inova 500 (500 MHz for H
1
and 125 MHz for 13C), or a Varian DirectDrive 600 (600 MHz for H
and 150 MHz for 13C). Chemical shifts (d) are given in ppm, refer-
enced to the residual solvent peak (1H and 13C), or to H3PO4 or
CFCl3 (31P and 19F, respectively). NMR samples were prepared under
an inert atmosphere unless otherwise stated. Infrared spectra were
obtained with a PerkinElmer Spectrum One FT-IR spectrophotome-
ter using pressed KBr discs. Microanalyses were performed by the
Campbell Microanalytical Laboratory at the University of Otago.
Single-crystal X-ray diffraction data were obtained by the X-ray
Crystallography Laboratory at the University of Canterbury. Electro-
spray ionisation mass spectra were obtained using an Agilent 6530
Series Q-TOF mass spectrometer. Carbon-13 NMR data, as well as
infrared spectra for the decarbonylation of 11 b to form 12b are lo-
cated in the Supporting Information.
1-[(C6F5)2PO]-3-(tBu2PCH2)C6H4 (POCCPH) (1c): A solution of (3-hy-
droxybenzyl)di-tert-butyl phosphine (1.15 g, 4.56 mmol) and trie-
thylamine (1.4 mL, 10 mmol) in THF (50 mL) was cooled on ice, and
a solution of BrP(C6F5)2 (1.04 mL, 4.56 mmol) in THF (15 mL) was
added over 10 min. The solution was stirred on ice for a further
10 min, then at RT, overnight. The reaction mixture was filtered
through Celite, and the filter cake was washed with THF. The crude
material was dried in vacuo, and purified by extraction with
hexane (3ꢂ12 mL) at À788C, followed by filtration through Celite.
Removal of hexane in vacuo gave 1c as a viscous, pale yellow oil
(2.42 g, 86%). 1H NMR (500 MHz, C6D6): d=7.47 (s, 1H; H2), 7.02
(m, 3H; H4,H5,H6), 2.65 (d, 2JP,H =2.6 Hz, 2H; CH2), 0.99 ppm (d,
3JP,H =10.8 Hz, 18H; C(CH3)3); 31P NMR (121 MHz, C6D6): d=82.9
X-ray data measurements
Diffraction data were collected using Bruker CCD diffractometers
with MoKa radiation (l=0.71073 ꢁ) using Bruker SMART (Version
5.054), SAINT (Version 6.02A), and SADABS (Version 2.03) software.
The structures were solved using Patterson methods, and refined
using a full-matrix least squares method, with anisotropic thermal
motion parameters for all non-hydrogen atoms.[44] Hydrogen atoms
were placed in calculated positions and allowed to refine freely
using a riding model. OLEX2 (Version 1.1.5)[45] was used as a front-
end for the SHELX97 executables during structure solution and re-
finement. All relevant bond distances and angles were calculated
3
(quint, JP,F =35.5 Hz, 1P; P(C6F5)2), 34.3 ppm (s, 1P; PtBu2); 19F NMR
3
(282 MHz, C6D6): d=À133.2 (m, 4F; o-C6F5), À148.5 (t, JF,F
=
21.3 Hz, 2F; p-C6F5), À160.3 ppm (tm, 3JF,F =21.5 Hz, 4F; m-C6F5);
HRMS calcd for (C27H24OF10P2) [M+H]+: m/z 617.1215, found
617.1220; HRMS calcd for (C15H25OP) [MÀP(C6F5)2 +2H]+: m/z
253.1716, found 253.1756.
[(POCOPH)Pt(nb)]2 (2): A solution of Pt(nb)3 (117 mg, 0.25 mmol)
and 1a (204 mg, 0.24 mmol) in dichloromethane (7 mL) was
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heated at 408C for 36 h, at which point all volatiles were removed
in vacuo. The oily solid was washed with ice-cold pentane, then re-
dissolved in toluene (5 mL) and heated at 508C for 12 h. The
volume was reduced in vacuo to approximately 2 mL, with the ad-
dition of hexane to the toluene solution causing the precipitation
of 4 as a white solid, which was isolated by decantation of the su-
pernatant and washing with pentane (107 mg, 39%). Crystals suita-
ble for single crystal X-ray diffraction were obtained by solvent dif-
fusion at RT, with methanol layered above a dichloromethane solu-
C6D6): d=À126.9–130.5 (brm, 16F; o-C6F5), À141.0–142.3 (brm, 8F;
p-C6F5), À158.2–158.6 ppm (brm, 16F; m-C6F5); HRMS calcd for
(C60H8O4F40NaCl4P4Pt2) [M+Na]+: m/z 2230.6665, found 2230.6653.
Samples of 7 were contaminated with small amounts of cis-[(PO-
COPH)2PtCl2], preventing satisfactory elemental analysis data from
being obtained.
cis,trans-[(POCOPH)PtClMe]2 (6):
A solution of [PtClMe(hex)]
(101 mg, 0.30 mmol) and 1a (249 mg, 0.31 mmol) in toluene (5 mL)
was heated at 408C for 24 h, then stirred at RT for a further 8 h.
The solution was filtered through a short alumina column in air,
washing the column with toluene (3ꢂ2 mL). Volatiles were re-
moved in vacuo, and the crude product was purified by the precip-
itation of by-products from a toluene/hexane solution of 6 at
À158C. The supernatant was decanted and collected; removal of
the volatiles in vacuo followed by washing with pentane gave 6 as
a white, microcrystalline solid (65 mg, 20%). 1H NMR (600 MHz,
1
3
tion of 2. H NMR (500 MHz, CD2Cl2): d=6.85 (t, JH,H =8.1 Hz, 1H;
H5), 6.69 (d, 3JH,H =8.1 Hz, 2H; H4,H6), 6.12 (s, 1H; H2), 2.75 (d,
3
2
2JPt,H =70.8 Hz, J-H=10.7 Hz, 2H; nb C=CH), 2.20 (d, JH,H =10.0 Hz,
2H; nb C-CH), 1.44 (d, 2JH,H =7.3 Hz, 2H; nb H2C-CH2), 0.96 (d,
2JH,H =7.6 Hz, 2H; nb H2C-CH2), 0.42 (m, 1H; nb HC-CH2-CH),
0.15 ppm (d, JH,H =8.5 Hz, 1H; nb HC-CH2-CH); 31P NMR (121 MHz,
2
CD2Cl2): d=100.5 ppm (s, 1JPt,P =4623 Hz); 19F NMR (282 MHz,
CD2Cl2): d=À131.5 (m, 8F; o-C6F5), À149.3 (m, 4F; p-C6F5),
À160.8 ppm (m, 8F; m-C6F5); elemental analysis calcd (%) for
C74H28O4F40P4Pt2·CH2Cl2: C 38.50, H 1.29; found C 38.80, H 1.40;
HRMS calcd for (C60H8O4F40NaP4Pt2) [MÀ2nb+Na]+: m/z 2086.7886,
found 2086.7883.
3
C6D6): d=7.54 (s, 1H; H2), 7.34 (s, 1H; H2’), 6.68 (d, JH,H =7.9 Hz,
1H; H6), 6.62 (m, 3H; H5,H5’,H6’), 6.55 (d, 3JH,H =8.2 Hz, 1H; H4),
6.53 (d, 3JH,H =7.0 Hz, 1H; H4’), 1.27 (brm, 3H; CH3-trans-P),
0.26 ppm (brt, 3JP,H =6.6 Hz, 3H; CH3-trans-Cl); 31P NMR (121 MHz,
C6D6): d=94.4 (d, 1JPt,P =2066 Hz, 2JP,P =15.4 Hz, 1P; P-trans-CH3),
1
1
90.3 (s, JPt,P =4028 Hz, 2P; P-trans-P), 62.1 ppm (d, JPt,P =5494 Hz,
2JP,P =15.4 Hz, 1P; P-trans-Cl); 19F NMR (282 MHz, C6D6): d=À127.6–
129.5 (m, 16F; o-C6F5), À142.7–144.0 (m, 8F; p-C6F5), À158.2–
159.6 ppm (m, 16F; m-C6F5); HRMS calcd for (C64H17NO4F40P4ClPt2)
[MÀCl+NCMe]+: m/z 2170.8430, found 2170.8496. Accurate ele-
mental analysis data could not be obtained for 6.
cis-[(POCOPH)PtMe2]2 (3):
A solution of ligand 1a (200 mg,
0.24 mmol) and [PtMe2(hex)] (73.3 mg, 0.24 mmol) in toluene
(15 mL) was stirred at RT for 72 h. The solution was concentrated
in vacuo to approximately 3 mL, and the oligomeric by-product 4
precipitated out by the addition of 3 mL hexane to the solution.
Decantation and isolation of the supernatant, followed by removal
of the solvent in vacuo and washing with hexane afforded 3 as
a yellow, microcrystalline solid (199 mg, 78%). 1H NMR (300 MHz,
cis,trans-[(POCOPH)PdCl2]2 (7):
A
solution of
1
(101 mg,
0.12 mmol) and [PdCl2(NCMe)2] (32 mg, 0.12 mmol) in dichlorome-
thane (15 mL) was heated in an oil bath at 458C for 12 h, then con-
centrated in vacuo to a volume of approximately 2 mL. The super-
natant was decanted and retained; addition of hexane to the su-
pernatant gave a pale yellow precipitate, which was isolated and
washed with pentane, affording 7 as a pale yellow solid (101 mg,
83%). Samples of 7 were observed to undergo a degree of rear-
rangement to higher oligomers on standing in polar solvents such
as chloroform or acetone. 1H NMR (500 MHz, CD2Cl2): d=7.17 (s,
2H; H2), 7.16 (vt, 3JH,H =8.3 Hz, 2H; H5), 6.85 (dd, 3JH,H =8.3 Hz,
3
3
CD2Cl2): d=7.05 (t, JH,H =8.3 Hz, 2H; H5), 6.82 (d, JH,H =7.7 Hz, 4H;
2
H4,H6), 6.42 (s, 2H; H2), 0.21 ppm (brs, JPt,H =71.0 Hz, 12H; CH3);
31P NMR (121 MHz, CDCl3): d=89.9 ppm (s, 1JPt,P =2202 Hz);
19F NMR (282 MHz, CDCl3): d=À129.4 (brs, 16F; o-C6F5), À145.7
(brs, 8F; p-C6F5), À159.1 ppm (brs, 18F; m-C6F5); HRMS calcd for
(C64H20O4F40NaP4Pt2) [M+Na]+: m/z 2146.8825, found 2146.8855.
cis-[(POCOPH)PtMe2]x (4): The oligomeric species 4 could be isolat-
ed as a by-product during the synthesis of the dimer 3 as above,
with shorter reaction times in dichloromethane observed to in-
crease the yield of 4. A solution of ligand 1a (50 mg, 60 mmol) and
[PtMe2(hex)] (18.5 mg, 60 mmol) in dichloromethane (5 mL) was
stirred at RT for 24 h. The solvent was reduced to about 0.5 mL in
vacuo, and precipitation of the product with hexane followed be
decantation of the supernatant and washing with pentane afford-
ed 4 as a white solid (48 mg, 76%). Samples of 4 were found to be
contaminated with small quantities of the dimer 3. 1H NMR
(300 MHz, CD2Cl2): d=7.14 (t, 3JH,H =8.2 Hz, 1H; H5), 6.94 (s, 1H;
H2), 6.77 (d, 3JH,H =8.2, 2H; H4,H6), 0.42 ppm (vt, 2JPt,H =70.6 Hz,
3JPÀH =3.0 Hz, 6H; CH3); 31P NMR (121 MHz, CD2Cl2): d=90.9 ppm
(s, 1JPt,P =2150 Hz); 19F NMR (282 MHz, CD2Cl2): d=À129.0 (dm,
3JP,F =16.4 Hz, 8F; o-C6F5), À146.5 (tm, 3JF,F =20.8 Hz, 4F; m-C6F5),
À159.7 ppm (m, 8F; p-C6F5).
cis,trans-[(POCOPH)PtCl2]2 (5): A solution of ligand 1a (30 mg,
36 mmol) and [PtCl2(hex)] (12.5 mg, 36 mmol) in [D6]benzene was
heated at 908C for 3 min (to ensure dissolution of starting materi-
al), then left standing at RT for 12 h. The reaction mixture was
heated for a further 80 min at 908C, at which point NMR spectros-
copy revealed almost quantitative formation of 5. Removal of vola-
tiles in vacuo and repeated washing with hexane afforded the
3
4JH,H =2.0 Hz, 2H; H4), 6.55 ppm (d, JH,H =8.1 Hz, 2H; H6); 31P NMR
(121 MHz, CD2Cl2): d=88.7 (s, 2P; P-trans-P), 78.5 ppm (s, 2P; P-
trans-Cl); 19F NMR (282 MHz, CD2Cl2): d=À126.4 (s, 8F; o-C6F5),
À126.8 (s, 8F; o-C6F5), À141.7 (s, 4F; p-C6F5), À143.1 (s, 4F; p-C6F5),
À158.5 (t, 3JF,F =19.3 Hz, 8F; m-C6F5), À158.9 ppm (td, 3JF,F =21.7,
6.9 Hz, 8F; m-C6F5); elemental analysis calcd (%) for
C60H8O4F40P4Cl4Pd2: C 35.48, H 0.40; found C 35.64, H 0.38; HRMS
calcd for (C60H8O4F40P4Cl3Pd2) [MÀCl]+: m/z 1994.5881, found
1994.5869.
General procedure for the synthesis of pincer chloride com-
plexes 8a–8c, 9a–9c: A 1:1 mixture of metal precursor and pincer
ligand were heated to reflux in toluene for a sustained period of
time. At the conclusion of the reaction, all volatiles were removed
in vacuo, and the oily residue triturated with hexane to afford the
crude product. Any unmetallated, oligomeric species present pre-
cipitated from toluene/hexane solutions of the crude product by
the addition of hexane. The desired pincer complexes were then
purified by recrystallisation or precipitation from toluene/hexane
or dichloromethane/hexane mixtures at À158C.
[(POCOP)PtCl] (8a): A solution of [PtClMe(hex)] (79 mg, 0.24 mmol)
and 1a (203 mg, 0.24 mmol) in toluene (6 mL) for 48 h gave 8a as
a pale yellow solid (121 mg, 47%). 1H NMR (300 MHz, C6D6): d=
6.87 (t, 3JH,H =8.0 Hz, 1H; H5), 6.79 ppm (d, 3JH,H =7.8 Hz, 2H;
product
5
as
a
cream-coloured solid (8 mg, 20%). 1H NMR
3
(300 MHz, C6D6): d=7.38 (s, 2H; H2), 6.68 (d, JH,H =8.5 Hz, 2H; H6),
3
3
6.61 (vt, JH,H =8.2 Hz, 2H; H5), 6.53 ppm (d, JH,H =7.7 Hz, 2H; H4);
31P NMR (121 MHz, C6D6): d=80.6 (s, JPt,P =3357 Hz, 2P; P-trans-P),
H4,H6); 31P NMR (121 MHz, C6D6): d=107.8 ppm (s, JPt,P =3663 Hz);
1
1
55.5 ppm (s, 1JPtÀP =4582 Hz, 2P; P-trans-Cl); 19F NMR (282 MHz,
19F NMR (282 MHz, C6D6): d=À128.4 (dm, JP,F =22.2 Hz, 8F; o-C6F5),
3
Chem. Eur. J. 2014, 20, 1 – 13
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3
5
À141.8 (tt, JF,F =20.0 Hz, JF,F =6.8 Hz, 4F; p-C6F5), À157.6 ppm (m,
cantation of the supernatant and washing the precipitate with
hexane furnished the desired carbonyl complex. Where further pu-
rification was required, recrystallisation from dichloromethane/di-
ethyl ether mixtures was performed.
8F; m-C6F5); elemental analysis calcd for C30H3O2F20P2ClPt·CH2Cl2: C
H 0.44; found C 32.45, H 0.55; HRMS calcd for
(C30H3O2F20NaP2ClPt) [M+Na]+: m/z 1088.8502, found 1088.8513.
32.30,
[(PCCCP)PtCl] (8b): A solution of [PtClMe(hex)] (82 mg, 0.25 mmol)
and 1b (206 mg, 0.25 mmol) in toluene (5 mL) for 18 h afforded
[(POCOP)Pt(CO)][SbF6] (10a): Compound 8a (50 mg, 0.047 mmol)
and AgSbF6 (18 mg, 0.052 mmol) in dichloromethane (10 mL) gave
colourless rods of 10a (17.9 mg, 30%). Crystals of 10a suitable for
single crystal X-ray diffraction were grown from the slow evapora-
tion of a dichloromethane solution at RT. 1H NMR (300 MHz,
1
8b as an off-white solid (252 mg, 96%). H NMR (500 MHz, CDCl3):
2
d=7.11 (m, 3H; H4,H5,H6), 4.26 ppm (vt, 3JPt,H =29.8 Hz, JP,H
=
=
1
4.5 Hz, 4H; CH2); 31P NMR (121 MHz, CDCl3): d=11.5 ppm (s, JPt,P
3379 Hz); 19F NMR (282 MHz, CDCl3): d=À126.7 (m, 8F; o-C6F5),
À144.6 (t, 3JF,F =20.7 Hz, 4F; p-C6F5), À157.9 ppm (m, 8F; m-C6F5);
elemental analysis calcd for C32H7F20P2ClPt: C 36.13, H 0.66; found
C 36.13, H 0.88; HRMS calcd for (C34H10NF20P2Pt) [MÀCl+CH3CN]+:
m/z 1063.9568, found 1063.9564.
CD2Cl2): d=7.51 (t, 3JH,H =8.2 Hz, 1H; H5), 7.10 ppm (m, 2H;
1
H4,H6); 31P NMR (121 MHz, CD2Cl2): d=104.4 ppm (s, JPt,P
=
3345 Hz); 19F NMR (282 MHz, CD2Cl2): d=À129.1 (m, 8F; o-C6F5),
À139.3 (m, 4F; p-C6F5), À156.6 ppm (m, 8F; m-C6F5); IR (KBr): n˜ =
2145 cmÀ1 (CꢀO), elemental analysis calcd (%) for C31H3O3F26P2SbPt:
C
28.67, H 0.38; found C 28.73, H 0.23; HRMS calcd for
[(POCCP)PtCl] (8c): A solution of [PtCl2(SEt2)2] (191 mg, 0.43 mmol)
and 1c (265 mg, 0.24 mmol) in toluene (15 mL) for 64 h yielded 8c
(C32H8NO3F20P2Pt) [MÀCO+CH3CN+H2O]+: m/z 1090.9305, found
1
1090.9317.
as a yellow microcrystalline solid (181 mg, 50%). H NMR (500 MHz,
CDCl3): d=7.04 (vt, 3JH,H =7.6 Hz, 1H; H5), 6.95 (d, 3JH,H =7.3 Hz,
1H; H4), 6.76 (d, 4JPt,H =16.7 Hz, 3JH,H =7.9 Hz, 1H; H6), 3.42 (d,
[(PCCCP)Pt(CO)][SbF6] (10b): Compound 8b (50 mg, 0.047 mmol)
and AgSbF6 (17 mg, 0.049 mmol) in dichloromethane (10 mL) gave
2
3
1
3JPt,H =22.8 Hz, JP,H =10.3 Hz, 2H; CH2), 1.45 ppm (d, JP,H =14.3 Hz,
10b as an off-white, microcrystalline solid (20.0 mg, 33%). H NMR:
18H; C(CH3)3); 31P NMR (121 MHz, CDCl3): d=107.8 (d, JPt,P
=
(300 MHz, [D6]acetone) d=7.59 (m, 2H; H4,H6), 7.44 (m, 1H; H5),
5.06 ppm (t, 3JPt,H =36.6 Hz, 2JP,H =5.3 Hz, 4H; CH2); 31P NMR
(121 MHz, [D6]acetone): d=6.2 ppm (s, 1JPt,P =3056 Hz); 19F NMR
(282 MHz, [D6]acetone): d=À123.7 (m, 8F; o-C6F5), À140.0 (tt,
1
3294 Hz, 2JP,P =469 Hz, 1P; P(C6F5)2), 72.1 ppm (d, 1JPt,P =3088 Hz,
2JP,P =468 Hz, 1P; PtBu2); 19F NMR (282 MHz, CDCl3): d=À128.1 (m,
3
4F; o-C6F5), À144.6 (tm, JF,F =20.7 Hz, 2F; p-C6F5), À158.4 ppm (m,
4F, m-C6F5); HRMS calcd for (C27H27NOF10P2ClPt) [M+NH4]+: m/z
3JF,F =20.6 Hz, JF,F =6.7 Hz, 4F; p-C6F5), À154.5 ppm (m, 8F; m-C6F5);
4
864.0737, found 864.0720.
IR (KBr): n˜ =2127 cmÀ1 (CꢀO); HRMS calcd for (C33H7OF20P2Pt) [M]+:
m/z 1055.9298, found 1055.9038.
[(POCOP)PdCl] (9a):
A solution of [PdCl2(NCMe)2] (96.5 mg,
0.37 mmol) and 1a (316 mg, 0.38 mmol) in toluene (15 mL) for
80 h gave 9a as a pale yellow solid (291 mg, 80%). 1H NMR
(300 MHz, CDCl3): d=7.20 (t, 3JH,H =8.3 Hz, 1H; H5), 6.78 ppm (d,
3JH,H =7.9 Hz, 2H; H4,H6); 31P NMR (121 MHz, CDCl3): d=114.4 ppm
(s); 19F NMR (282 MHz, CDCl3): d=À127.0 (m, 8F; o-C6F5), À141.9
[(POCCP)Pt(CO)][SbF6] (10c): Compound 8c (50 mg, 0.059 mmol)
and AgSbF6 (22 mg, 0.064 mmol) in dichloromethane (10 mL) af-
forded 10c as
(300 MHz, CD2Cl2) d=7.38 (vt, JH,H =7.9 Hz, 1H; H5), 7.29 (d, JH,H
a
pale yellow solid (36.1 mg, 57%). 1H NMR
3
3
=
4
3
7.5 Hz, 1H; H4), 7.13 (d, JPt,H =11.6 Hz, JH,H =7.8 Hz, 1H; H6), 3.96
3
4
3
(tt, JF,F =20.9 Hz, JF,F =6.4 Hz, 4F; p-C6F5), À157.0 ppm (m, 8F; m-
C6F5); HRMS calcd for (C30H4O2F20P2ClPt) [M+H]+: m/z 976.8501,
found 976.8498.
(d, 3JPt,H =24.0 Hz, 2JP,H =10.1 Hz, 2H; CH2), 1.47 ppm (d, JP,H
=
15.4 Hz, 18H; C(CH3)3); 31P NMR (121 MHz, CD2Cl2): d=108.3 (d,
1
1JPt,P =2800 Hz, 2JP,P =326 Hz, 1P; P(C6F5)2), 91.4 ppm (d, JPt,P
=
2616 Hz, 2JP,P =324 Hz, 1P; PtBu2); 19F NMR (282 MHz, CD2Cl2): d=
À129.7 (m, 4F; o-C6F5), À140.2 (ttd, 3JF,F =20.7 Hz, 3JF,F =7.7 Hz,
5JP,F =1.9 Hz, 2F; p-C6F5), À156.7 ppm (tm, 3JF,F =20.1 Hz, 4F; m-
C6F5); IR (KBr): n˜ =2111 cmÀ1 (CꢀO).
[(PCCCP)PdCl] (9b):
A
solution of [PdCl2(NCMe)2] (59 mg,
0.23 mmol) and 1b (189 mg, 0.23 mmol) in toluene (6 mL) for 48 h
gave 9b as a yellow, microcrystalline solid (142 mg, 64%). Spectro-
scopic data matched that previously reported for 9b.[10]
[(POCOP)Pd(CO)][SbF6] (11a): Compound 9a (64.1 mg, 66 mmol)
and AgSbF6 (23.0 mg, 67 mmol) in dichloromethane (9 mL) afforded
11 a as an off-white solid (61.5 mg, 78%). 1H NMR (300 MHz,
[(POCCP)PdCl] (9c):
0.28 mmol) and 1c (172 mg, 0.28 mmol) in toluene (6 mL) for 20 h
afforded 9c as a bright yellow solid (115 mg, 55%). 1H NMR
(500 MHz, CDCl3): d=7.04 (vt, JH,H =7.7 Hz, 1H; H5), 6.95 (d, JH,H
7.6 Hz, 1H; H4), 6.76 (d, JH,H =7.8 Hz, 1H; H6), 3.47 (d, JP,H =9.5 Hz,
2H; CH2), 1.45 ppm (d, 3JP,H =14.4 Hz, 18H; C(CH3)3); 31P NMR
A solution of [PdCl2(NCMe)2] (71.9 mg,
3
3
3
CD2Cl2): d=7.46 (t, 3JH,H =8.1 Hz, 1H; H5), 7.03 ppm (d, JH,H
=
=
3
2
8.3 Hz, 1H; H4,H6); 31P NMR (121 MHz, CD2Cl2): d=119.4 ppm (s);
19F NMR (282 MHz, CD2Cl2): d=À129.5 (m, 8F; o-C6F5), À140.0 (tt,
5
2
3JF,F =20.6 Hz, JF,F =7.8 Hz, 4F; p-C6F5), À156.9 ppm (m, 8F; m-C6F5);
(121 MHz, CDCl3): d=111.5 (d, JP,P =460 Hz, 1P; P(C6F5)2), 83.5 ppm
2
IR (KBr): n˜ =2170 cmÀ1 (CꢀO).
(d, JP,P =460 Hz, 1P; PtBu2); 19F NMR (282 MHz, CDCl3): d=À127.8
3
3
(dm, JP,F =21.3 Hz, 4F; o-C6F5), À144.4 (t, JF,F =20.6 Hz, 2F; p-C6F5),
À158.3 ppm (m, 4F; m-C6F5); elemental analysis calcd (%) for
[(PCCCP)Pd(CO)][SbF6] (11b): Compound 9b (75 mg, 77 mmol) and
AgSbF6 (28 mg, 81 mmol) in dichloromethane (10 mL) gave 11 b as
a white microcrystalline solid (35 mg, 38%). 1H NMR (300 MHz,
C27H23OF10P2ClPd·1= CH2Cl2: C 41.38, H 3.03; found C 41.28, H 3.08;
2
2
HRMS calcd for (C29H26NOF10P2Pd) [MÀCl+CH3CN]+: m/z 758.0386,
CD2Cl2): d=7.34 (m, 3H; H4,H5,H6), 4.63 ppm (t, JP,H =5.6 Hz, 4H;
found 758.0357.
CH2); 31P NMR (121 MHz, CD2Cl2): d=7.1 ppm (s); 19F NMR
3
(282 MHz, CD2Cl2) d=À128.7 (m, 8F; o-C6F5), À142.5 (tt, JF,F
=
General procedure for the synthesis of pincer carbonyl com-
plexes 10a–10c, 11a–11c: A foil-wrapped flask containing the
pincer chloride complex and AgSbF6 was cooled to À788C and di-
chloromethane was added. The solution was stirred at À788C for
10 min, then carbon monoxide was bubbled through the solution
as the reaction mixture was allowed to warm to RT. After a further
60 min the reaction mixture was filtered through Celite, reduced in
volume to approximately 1 mL in vacuo, and the crude product
precipitated out by the addition of hexane or diethyl ether to the
dichloromethane solution saturated with carbon monoxide. De-
20.9 Hz, 5JF,F =6.3 Hz, 4F; p-C6F5), À157.1 ppm (m, 8F; m-C6F5); IR
(KBr): n˜ =2148 cmÀ1 (CꢀO).
[(POCCP)Pd(CO)][SbF6] (11c): Compound 9c (51.2 mg, 67 mmol)
and AgSbF6 (24.1 mg, 70 mmol) in dichloromethane (6 mL) yielded
11 c as a yellow solid (41.0 mg, 62%). 1H NMR (300 MHz, CD2Cl2):
d=7.33 (t, 3JH,H =7.7 Hz, 1H; H5), 7.19 (d, 3JH,H =7.6 Hz, 1H; H4),
7.06 (d, 3JH,H =7.9 Hz, 1H; H6), 3.85 (d, 2JP,H =10.0 Hz, 2H; CH2),
1.47 ppm (d, 3JP,H =15.3 Hz, 18H; C(CH3)3); 31P NMR: (121 MHz,
CD2Cl2): d=117.0 (brdq, 2JP,P =320 Hz, 3JP,F =16.7 Hz, 1P; P(C6F5)2),
&
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109.1 ppm (d, JP,P =320 Hz, 1P; PtBu2); 19F NMR (282 MHz, CD2Cl2):
[8] a) F. Zhao, Y. Ikushima, M. Chatterjee, O. Sato, M. Arai, J. Supercrit. Fluids
2003, 27, 65–72; b) S. Fujita, K. Yuzawa, B. M. Bhanage, Y. Ikushima, M.
Arai, J. Mol. Catal. A 2002, 180, 35–42.
[9] C. L. Pollock, G. C. Saunders, E. C. M. S. Smyth, V. I. Sorokin, J. Fluorine
Chem. 2008, 129, 142–166.
d=À130.0 (m, 4F; o-C6F5), À141.0 (tt, 3JF,F =20.6 Hz, 5JF,F =7.5 Hz,
2F; p-C6F5), À156.7 ppm (m, 4F; m-C6F5); IR (ATR film from CH2Cl2):
n˜ =2140 cmÀ1 (CꢀO).
Observation of [(PCP)Pd(CO)][SbF6] decarbonylation products
[(PCP)Pd][SbF6] (12a–12c): Compounds 12a, 12b, and 12c were
observed in solution arising from the decarbonylation of the
parent palladium carbonyl compounds 11 a, 11 b, and 11 c, respec-
tively, either by passage of inert gas through dichloromethane sol-
utions, or upon prolonged standing under ambient conditions.
[10] P. A. Chase, M. Gagliardo, M. Lutz, A. L. Spek, G. P. M. van Klink, G.
van Koten, Organometallics 2005, 24, 2016–2019.
[11] S. Harvey, P. C. Junk, C. L. Raston, G. Salem, J. Org. Chem. 1988, 53,
3134–3140.
[12] a) M. R. Eberhard, S. Matsukawa, Y. Yamamoto, C. M. Jensen, J. Organo-
met. Chem. 2003, 687, 185–189; b) R. Ahuja, B. Punji, M. Findlater, C.
Supplee, W. Schinski, M. Brookhart, A. S. Goldman, Nat. Chem. 2011, 3,
167–171.
[13] a) H. Petzold, H. Gçrls, W. Weigand, J. Organomet. Chem. 2007, 692,
2736–2742; b) N. Carr, B. J. Dunne, L. Mole, A. G. Orpen, J. L. Spencer, J.
Chem. Soc. Dalton Trans. 1991, 863–871.
[(POCOP)Pd][SbF6] (12a): 1H NMR (300 MHz, CD2Cl2): d=7.30 (t,
3JH,H =7.8 Hz, 1H; H5), 8.85 ppm (d, 3JH,H =8.0 Hz, 2H; H4,H6);
31P NMR (121 MHz, CD2Cl2): d=112.6 ppm (s); 19F NMR (282 MHz,
3
CD2Cl2): d=À129.9 (brs, 8F; o-C6F5), À141.0 (tm, JF,F =20.5 Hz, 4F;
3
[14] M. O. Sinnokrot, E. F. Valeev, C. D. Sherrill, J. Am. Chem. Soc. 2002, 124,
10887–10893.
p-C6F5), À157.5 ppm (tm, JF,F =18.9 Hz, 8F; m-C6F5).
1
[(PCCCP)Pd][SbF6] (12b): H NMR (300 MHz, CD2Cl2): d=7.15 (brs,
[15] a) J. J. Adams, A. Lau, N. Arulsamy, D. M. Roddick, Inorg. Chem. 2007, 46,
11328–11334; b) M. E. van der Boom, M. Gozin, Y. Ben-David, L. J. W.
Shimon, F. Frolow, H.-B. Kraatz, D. Milstein, Inorg. Chem. 1996, 35,
7068–7073; c) R. A. Baber, R. B. Bedford, M. Betham, M. E. Blake, S. J.
Coles, M. F. Haddow, M. B. Hursthouse, A. G. Orpen, L. T. Pilarski, P. G.
Pringle, R. L. Wingad, Chem. Commun. 2006, 3880–3882; d) E. E. Nifan-
tyev, E. N. Rasadkina, L. K. Vasyanina, V. K. Belsky, A. I. Stash, J. Organo-
met. Chem. 1997, 529, 171–176.
3H; H4,H5,H6), 4.38 ppm (t, 2JP,H =4.7 Hz, 4H; CH2); 31P NMR
(121 MHz, CD2Cl2): d=1.7 ppm (s); 19F NMR (282 MHz, CD2Cl2): d=
À129.7 (m, 8F; o-C6F5), À143.6 (tm, 3JF,F =20.4 Hz, 4F; p-C6F5),
3
À157.8 ppm (tm, JF,F =20.2 Hz, 8F; m-C6F5).
[(POCCP)Pd][SbF6] (12c): 1H NMR (300 MHz, CD2Cl2): d=7.13 (t,
3
3
3JH,H =7.6 Hz, 1H; H5), 7.03 (d, JH,H =7.3 Hz, 1H; H4), 6.81 (d, JH,H
=
=
2
3
8.0 Hz, 1H; H6), 3.47 (d, JP,H =9.9 Hz, 2H; CH2), 1.44 ppm (d, JP,H
14.5 Hz, 18H; C(CH3)3); 31P NMR (121 MHz, CD2Cl2): d=107.9 (brdq,
2JP,P =392 Hz, JP,F =16.5 Hz, 1P; P(C6F5)2), 87.7 ppm (d, JP,P =392 Hz,
1P; PtBu2); 19F NMR (282 MHz, CD2Cl2): d=À130.5 (m, 4F; o-C6F5),
À142.8 (t, 3JF,F =20.2 Hz, 2F; p-C6F5), À158.3 ppm (t, 3JF,F =18.9 Hz,
4F, m-C6F5).
[16] R. Nandy, M. Subramoni, B. Varghese, S. Sankararaman, J. Org. Chem.
2007, 72, 938–944.
3
2
[17] For representative example, see: a) M. A. Bennett, H. Jin, A. C. Willis, J.
Organomet. Chem. 1993, 451, 249–256; b) D. Morales-Morales, R. E.
Cramer, C. M. Jensen, J. Organomet. Chem. 2002, 654, 44–50; c) F. Gorla,
L. M. Venanzi, A. Albinati, Organometallics 1994, 13, 43–54.
[18] a) T. Even, A. R. J. Genge, A. M. Hill, N. J. Holmes, W. Levason, M. Web-
ster, J. Chem. Soc. Dalton Trans. 2000, 655–662; b) A. Babai, G. B.
Deacon, G. Meyer, Z. Anorg. Allg. Chem. 2004, 630, 399–402; c) J. Flap-
per, P. Wormald, M. Lutz, A. L. Spek, P. W. N. M. van Leeuwen, C. J. Elsevi-
er, P. C. J. Kamer, Eur. J. Inorg. Chem. 2008, 4968–4976; d) B. Drahos, Z.
Rohlik, J. Kotek, I. Cisarova, P. Hermann, Dalton Trans. 2009, 4942–4953.
[19] R. G. Pearson, Inorg. Chem. 1973, 12, 712–713.
Acknowledgements
We thank Rosie J. Somerville for her assistance in obtaining in-
frared data for 12b, and acknowledge the Tertiary Education
Commission of New Zealand for funding.
[20] J. N. Harvey, K. M. Heslop, A. G. Orpen, P. G. Pringle, Chem. Commun.
2003, 278–279.
[21] A. L. Fernandez, M. R. Wilson, A. Prock, W. P. Giering, Organometallics
2001, 20, 3429–3435.
[22] M. Albrecht, P. Dani, M. Lutz, A. L. Spek, G. van Koten, J. Am. Chem. Soc.
2000, 122, 11822–11833.
[23] a) S. Sjçvall, C. Andersson, O. F. Wendt, Inorg. Chim. Acta 2001, 325,
182–186; b) M. T. Johnson, O. F. Wendt, Inorg. Chim. Acta 2011, 367,
222–224; c) V. Pandarus, A. Castonguay, D. Zargarian, Dalton Trans.
2008, 4756–4761.
[24] a) P. Espinet, J. M. Martꢄnez-Ilarduya, C. Pꢅrez-Briso, A. L. Casado, M. A.
Alonso, J. Organomet. Chem. 1998, 551, 9–20; b) S. Otto, A. Roodt, J. Or-
ganomet. Chem. 2006, 691, 4626–4632.
Keywords: decarbonylation · metalation · palladium · pincer
complexes · platinum
[1] a) M. E. van der Boom, D. Milstein, Chem. Rev. 2003, 103, 1759–1792;
b) D. Benito-Garagorri, K. Kirchner, Acc. Chem. Res. 2008, 41, 201–213;
c) H. Nishiyama, Chem. Soc. Rev. 2007, 36, 1133–1141.
[2] C. Gunanathan, D. Milstein, Science 2013, 341.
[25] a) H. Rimml, L. M. Venanzi, J. Organomet. Chem. 1983, 259, C6–C7;
b) R. J. Cross, A. R. Kennedy, K. W. Muir, J. Organomet. Chem. 1995, 487,
227–233.
[26] A. Arunachalampillai, M. T. Johnson, O. F. Wendt, Organometallics 2008,
27, 4541–4543.
[27] P. E. M. Siegbahn, R. H. Crabtree, J. Am. Chem. Soc. 1996, 118, 4442–
4450.
[28] B. Vabre, M. L. Lambert, A. Petit, D. H. Ess, D. Zargarian, Organometallics
2012, 31, 6041–6053.
[29] A. S. Goldman, K. Krogh-Jespersen, J. Am. Chem. Soc. 1996, 118, 12159–
12166.
[30] J. L. Bolliger, O. Blacque, C. M. Frech, Chem. Eur. J. 2008, 14, 7969–7977.
[31] J. F. Houlis, D. M. Roddick, J. Am. Chem. Soc. 1998, 120, 11020–11021.
[32] A. D. Horton, J. de With, A. J. van der Linden, H. van de Weg, Organome-
tallics 1996, 15, 2672–2674.
[33] a) N. ꢆ. Espinosa-Jalapa, S. Hernꢇndez-Ortega, D. Morales-Morales, R. Le
Lagadec, J. Organomet. Chem. 2012, 716, 103–109; b) A. Arunachalam-
pillai, N. Loganathan, O. F. Wendt, Polyhedron 2012, 32, 24–29; c) Z.
Wang, S. Sugiarti, C. M. Morales, C. M. Jensen, D. Morales-Morales, Inorg.
[3] M. C. Haibach, S. Kundu, M. Brookhart, A. S. Goldman, Acc. Chem. Res.
2012, 45, 947–958.
[4] a) N. Selander, K. J. Szabꢃ, Chem. Rev. 2011, 111, 2048–2076; b) J. M. Ser-
rano-Becerra, D. Morales-Morales, Curr. Org. Synth. 2009, 6, 169–192;
c) D. Morales-Morales, Mini-Rev. Org. Chem. 2008, 5, 141–152.
[5] a) J. J. Adams, N. Arulsamy, D. M. Roddick, Organometallics 2011, 30,
697–711; b) E. Kossoy, B. Rybtchinski, Y. Diskin-Posner, L. J. W. Shimon,
G. Leitus, D. Milstein, Organometallics 2009, 28, 523–533; c) E. Kossoy,
M. A. Iron, B. Rybtchinski, Y. Ben-David, L. J. W. Shimon, L. Konstantinov-
ski, J. M. L. Martin, D. Milstein, Chem. Eur. J. 2005, 11, 2319–2326; d) C.
Barthes, C. Lepetit, Y. Canac, C. Duhayon, D. Zargarian, R. Chauvin,
Inorg. Chem. 2012, 51, 48–58.
[6] Z. Huang, P. S. White, M. Brookhart, Nature 2010, 465, 598–601.
[7] a) T. Korenaga, A. Ko, K. Uotani, Y. Tanaka, T. Sakai, Angew. Chem. 2011,
123, 10891–10895; Angew. Chem. Int. Ed. 2011, 50, 10703–10707; b) T.
Korenaga, R. Maenishi, K. Hayashi, T. Sakai, Adv. Synth. Catal. 2010, 352,
3247–3254; c) P. H. Lee, S. Kim, A. Park, B. C. Chary, S. Kim, Angew.
Chem. 2010, 122, 6958–6961; Angew. Chem. Int. Ed. 2010, 49, 6806–
6809.
Chem. Eur. J. 2014, 20, 1 – 13
www.chemeurj.org
11
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Chim. Acta 2006, 359, 1923–1928; d) J. J. Adams, N. Arulsamy, D. M.
Roddick, Inorg. Chim. Acta 2009, 362, 2056–2059; e) D. Vuzman, E. Po-
verenov, Y. Diskin-Posner, G. Leitus, L. J. W. Shimon, D. Milstein, Dalton
Trans. 2007, 5692–5700.
[40] D. Drew, J. R. Doyle, Inorg. Synth. 1990, 28, 346–349.
[41] K. A. Jensen, Acta Chem. Scand. 1953, 7, 868–870.
[42] M. Albrecht, R. A. Gossage, M. Lutz, A. L. Spek, G. van Koten, Chem. Eur.
J. 2000, 6, 1431–1445.
[34] a) J. L. Bolliger, O. Blacque, C. M. Frech, Angew. Chem. 2007, 119, 6634–
6637; Angew. Chem. Int. Ed. 2007, 46, 6514–6517; b) R. Gerber, T. Fox,
C. M. Frech, Chem. Eur. J. 2010, 16, 6771–6775.
[35] H. Salem, Y. Ben-David, L. J. W. Shimon, D. Milstein, Organometallics
2006, 25, 2292–2300.
[43] T. F. Vaughan, D. J. Koedyk, J. L. Spencer, Organometallics 2011, 30,
5170–5180.
[44] G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112–122.
[45] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H. Pusch-
mann, J. Appl. Crystallogr. 2009, 42, 339–341.
[36] R. Motterlini, L. E. Otterbein, Nat. Rev. Drug Discovery 2010, 9, 728–743.
[37] B. E. Mann, Organometallics 2012, 31, 5728–5735.
[38] E. P. Kꢈndig, C. Duprꢅ, B. Bourdin, A. Cunningham, D. Pons, Helv. Chim.
Acta 1994, 77, 421–428.
[39] F. R. Hartley, S. G. Murray, C. A. McAuliffe, Inorg. Chem. 1979, 18, 1394–
1397.
Received: November 10, 2013
Revised: March 4, 2014
Published online on && &&, 0000
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FULL PAPER
Back and forth: The electron-poor
P(C6F5)2 donor group was incorporated
into the PCP pincer ligand motif to gen-
erate a range of poorly donating li-
gands. Palladium carbonyl complexes of
these ligands demonstrated the ability
to reversibly bind CO, with the ease of
CO displacement increasing with in-
creasing n(CO) values (see figure). These
ligands also displayed a reluctance to
undergo metallation on Pt or Pd, which
led to the formation of rare examples of
cis,trans-dimers.
&
CO Binding
B. G. Anderson,* J. L. Spencer
&& – &&
The Coordination Chemistry of
Pentafluorophenylphosphino Pincer
Ligands to Platinum and Palladium
Chem. Eur. J. 2014, 20, 1 – 13
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13
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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These are not the final page numbers! ÞÞ