Electrochemically Driven and Acid-Driven Pyridine-Directed ortho-Phosphorylation of C(sp2)-H Bonds

Article abstract of DOI:10.1021/acs.organomet.0c00247

The key intermediate palladacycles (mono-, bi-, and tetranuclear) with phosphonate, acetate, and other counterions in C(sp2)-H phosphonation are analyzed in terms of their redox properties, mutual transitions, reactivity, and reaction pathways for the selective production of the desired products. It was found that, in the presence of pyridine, the reaction proceeds through a mononuclear palladacycle, which at a relatively high electrolysis potential gives the product of ortho-phosphonation of the arene with a C-P bond in good yield. Under acidic conditions, the process involves the tetrapalladium intermediate and leads to a product with a C-O-P bond. Phosphorous acid gives inorganic phosphoric derivatives of 2-phenylpyridine. The electrochemical data on the redox properties of key palladacycles 4 and 5 and their potentials and energy gaps are confirmed by DFT calculations.

Full text of DOI:10.1021/acs.organomet.0c00247

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Article
Electrochemically Driven and Acid-Driven Pyridine-Directed ortho-
Phosphorylation of C(sp2)−H Bonds
Tatyana V. Gryaznova, Mikhail N. Khrizanforov, Alina I. Levitskaya, Ildar Kh.Rizvanov,
Marina Yu. Balakina, Kamil A. Ivshin, Olga N. Kataeva, and Yulia H. Budnikova*
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ABSTRACT: The key intermediate palladacycles (mono-, bi-, and tetranuclear)
with phosphonate, acetate, and other counterions in C(sp2)−H phosphonation
are analyzed in terms of their redox properties, mutual transitions, reactivity, and
reaction pathways for the selective production of the desired products. It was
found that, in the presence of pyridine, the reaction proceeds through a
mononuclear palladacycle, which at a relatively high electrolysis potential gives
the product of ortho-phosphonation of the arene with a C−P bond in good yield.
Under acidic conditions, the process involves the tetrapalladium intermediate
and leads to a product with a C−O−P bond. Phosphorous acid gives inorganic
phosphoric derivatives of 2-phenylpyridine. The electrochemical data on the redox properties of key palladacycles 4 and 5 and their
potentials and energy gaps are confirmed by DFT calculations.
byproducts formed in these reactions are protons (H+) or
hydrogen (H2) under oxidative or reductive conditions,
1. INTRODUCTION
Palladium remains one of the most widely used transition
respectively, under ideal conditions with an electron as a
metals, catalyzing a large variety of reactions that occur both
traceless reagent, the strength of which is easily controlled by
under oxidizing and reducing, as well as seemingly redox
the potential of the electrode.4a,d−s
neutral, conditions.1 As a rule, it is believed that such universal
palladium reactivity is associated with several factors, primarily
with the ability to form diverse complexes in 0, I, II, III, or IV
oxidation states, which consequently can be easily involved in
one- and two-electron redox processes,2 facilitate substrate
binding and release through ligand exchange, and form
catalytically active high-order Pd intermediate clusters or
complexes that are mono- or polynuclear.2,3 Over the past
decade, metal-catalyzed functionalization of C−H bonds
including ligand-directed reactions has emerged as a powerful
strategy for the construction of important molecules, such as
pharmaceuticals, biologically active molecules, universal ligands
in catalytic reactions, and functional materials.1
Dehydrogenative (hetero)arene phosphonation triggered by
PdII and other metals, C(sp2)−H/P−H coupling, is an
important atom-economical and environmentally friendly
process.4 Phosphorus-containing moieties, such as the
phosphonic acid residue RP, comprise a part of numerous
structurally diverse natural compounds involved in different
biological reactions. Phosphonic acid moieties are also present
in many potential pharmaceutical agents having anticancer,
antibacterial, or antiviral activity, including anti-HIV potential,
increasing their bioavailability.4a In view of the synthetic value
of phosphorylated aromatics, the development of methods for
constructing C−P or C−OP bonds is of ongoing interest. The
electrochemical C−H/P−H cross-coupling methodology can
be regarded as environmentally friendly, since the only
Factors controlling the stability and reactivity of mono-
nuclear or binuclear Pd(II) complexes and palladacycles (as
catalyst precursors or intermediates) in C−H functionalization
catalysis have been investigated and established in each
particular case.5 However, the identification and character-
ization of the true catalytically active species and intermediates
are extremely difficult in many Pd-catalyzed transformations.
As a result, the identity of the active Pd structures in various
widely utilized cross-coupling and C−H functionalization
reactions still remains under active discussion. However,
there are a few papers in which all transformations are traced,
starting from electrosynthesis and mutual transformations of
intermediates, confirmed by physicochemical methods and
DFT calculations. Such methods include electrochemistry,
which gives experimental values of the redox potentials and
energies of the boundary molecular orbitals, information on
the stability of oxidized (reduced) forms, and the number of
participating electrons in each stage.4i,j,q,s
Received: April 8, 2020
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Scheme 1. ortho-Phosphorylation of 2-Phenylpyridine Involving Dipalladacycle Intermediates
Yu6 and Murakami4c reported catalytic ligand-directed
aromatic C−H phosphonation in 12−66% yields and showed
that dialkyl-H-phosphonates and α-hydroxyphosphonate were
phosphorylating reagents. However, these reactions required
high temperatures (120 °C), an excess of oxidants (expensive
silver salts), bases, and additives (N-methylmaleimide, 1,4-
benzoquinone, etc.) probably to promote a reductive
elimination step. One of the main problems arising in the
chemistry of Pd in the high oxidation state III/IV is that
applied co-oxidizing agents either are expensive (Ag or other
metal salts) or are hardly separable from the reaction mixture
(organic oxidants). In addition, all of them are insufficiently
selective. An electrochemical approach has several advantages
over conventional organic syntheses. Recently, an electro-
catalytic method for the phosphonation of 2-phenylpyridine
has been developed by the authors’ team, but apart from
obvious advantages such as room temperature and the absence
of traditional oxidizers, the best yields (up to 78%) have been
achieved only in the presence of additives: bases NaOAc (4
equiv) and benzoquinoline (2 equiv) or lutidine (4 equiv) and
2,2′-bpy (1 equiv).4i These conditions have been found
empirically, and they are difficult to explain in terms of
understanding the mechanism of the catalytic cycle. The desire
to simplify the reaction conditions, increase the yield of
phosphorylation products, and find out the nature of other
previously unidentified products stimulated further research.
This report demonstrates the possibility of managed,
controlled, and convenient production of organic and
inorganic phosphorylated derivatives of arenes under mild
Pd-catalyzed conditions of C(sp2)−H/P(O)−H cross-cou-
pling on the basis of a detailed analysis of the reactions of 2-
phenylpyridine as a model arene with dialkyl-H-phosphonates
or H3PO3, palladacyclic intermediates, and their redox
properties combined with computational confirmation of the
reactivity.
2. RESULTS AND DISCUSSION
2.1. Palladacycles. Traditional catalytic C−H functional-
ization is carried out by mixing reaction partners with the
catalyst, cocatalyst, oxidizer, and additives, followed by the
reaction stage under certain temperature conditions while
controlling the conversion of the original reagents. the
palladium reactivity is attributed also to its ability to form
catalytically active high-order aggregates (including Pd
clusters) of specific sizes.3,7 Low process selectivity and yields
may be associated with the divergence of the reaction paths
through different metal−organic intermediates with different
reactivities. Understanding how to eliminate unwanted
intermediates is very important for choosing the best
conditions. We have started the research by analyzing all
palladium derivatives, palladacycles, which are formed in a
three-component system used in C−H phosphonation:
palladium salt Pd(OAc)2 (existing as a trimer8 [Pd(OAc)2]3),
diethyl-H-phosphonate, and 2-phenylpyridine (1:1:1
Pd:P:phpy). Three palladacycles with different structures
have been identified from this reaction mixture (Scheme 1):
the clamshell Pd2(phpy)2(OAc)2 (3), the phosphonate-
bridged Pd2(phpy)2[P(O)(OEt)2]2 (4), and the unusual
tetranuclear Pd4(phpy)4[P(O)(OEt)2P(O)(OH)O] (5).
Their structures have been confirmed using X-ray single-
crystal diffraction (Figure 1). Monitoring the formation of
products and the consumption of precursors on the basis of 31P
NMR data dynamics, including the integrated signal intensity
in the 31P NMR spectrum of the reaction mixture, is a very
convenient method (see details in the Supporting Informa-
tion). The nature of each isolated product is then confirmed by
B
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Table 1. Electrochemical Data for Palladacycles 3−7:
a
Oxidation Potentials Ep (V vs Fc+/Fc)
complex
Pt4s
GC
CPE
0.42
0.80
0.55
0.99
0.99
1.44
0.17
1.08
Pd2(phpy)2(OAc)2 (3)
0.50
1.09
1.12
1.62
0.39
0.89
0.61
1.70
1.09
1.41
0.61
0.79
0.82
1.32
Pd2(phpy)2[P(O)(OEt)2]2 (4)
Pdbpy[P(O)(OEt)2]2 (6)
Pd-4 (5)
0.50
Pd(phpy)Py[P(O)(OEt)2] (7)
[phpyPd(H3PO3)] (11)
no crystal
0.25
1.07
a
Conditions: CH3CN; glassy carbon (GC), carbon paste (CPE), or
Pt electrodes.
at potentials of the first reduction peak is 2 times higher than
the current at potentials of the first oxidation peak, hence the
reduction is two-electron, PdII/0, and the oxidation is one-
electron at the first stage, PdII/II, as was previously
demonstrated and confirmed.4i,j,s,10,11 Thus, in a number of
binuclear palladacycles, acetate-bridged 3 is oxidized more
easily than diethylphosphonate-bridged 4. Among phospho-
nate palladacycles 4 and 5, the palladacycle with inorganic
phosphorus substitutes 5 (tetrapalladium complex) undergoes
the easiest oxidation. In order to confirm the more difficult
oxidation of palladium with a Pd−P(O)O(OEt)2 bond in
comparison to the easier oxidation of fragments with inorganic
substituents in palladium, the model compound bpyPd[P(O)-
(OEt)2]2 (6) has been synthesized. Its structure has been
confirmed by single-crystal XRD (Figure 2).
Figure 1. ORTEP drawings of Pd cycles 3 (top left),3f 4 (top right),4i
and 5 (bottom).
a combination of physicochemical methods, including X-ray
structural analysis.
Compound 3 gradually disappears (over 1 h, if (EtO)2PHO
is taken in excess) and completely turns into palladacycles with
phosphonate counterions. Since the formation of the pallada-
cycle releases the acid AcOH, it provokes some dealkylation of
dialkyl phosphorus fragments in palladium complexes during
aging. The addition of this acid to the reaction mixture
increases the content of 5. Despite the lack of Pd−Pd bonds
and π-stacking interactions between the aromatic substituents
at the palladium in 4 and 5 (in contrast to 3), they were
believed to enhance the stability of palladacycles;9 phospho-
nate-bridged 4 and tetranuclear 5 are stable and retain their
structure for a long time. The structures and NMR data for the
isolated crystals of 4 and 5 remain unchanged for at least 1
year.
The tetranuclear palladium complex 5 includes palladium in
different environments, two palladacycles and two palladium
atoms with the coordination bond Pd−N and two bonds Pd−
P, one of them with dealkylated phosphorus and one with
phosphorus with ethoxy substituents.
The study of the redox properties of palladacycles 3−5 using
cyclic voltammetry in both solution and solid form (using a
carbon-paste electrode, CPE) has shown that the oxidation
potential of Pd(II) is highly dependent on the nature of the
bridging ligand and the structure of the complex in general
(Table 1). Since potentials also depend on the electrode
nature, we conducted a study on two electrodes: Pt, which is
used in preparative synthesis, and glassy carbon, which is
usually similar in properties to carbon paste. The CPE was
mainly used for insoluble or poorly soluble complexes.
The electrochemical properties of complexes 3 and 4 were
first described in refs 4i, j, and s. Interestingly, oxidation of
complex 5 is noticeably easier than that of diphosphonate-
bridged dipalladacycles 4. This is somewhat surprising, as in
tetranuclear palladium complex 5 there are no Pd−Pd bonds
usually facilitating oxidation. The extension (blurring) of the
first oxidation peak for 5 is related to the presence of different
palladium ions with different environments. Since the current
Figure 2. ORTEP drawing of bpyPdP(O)(OEt)2 (6).
A voltammetric study of bpyPd[P(O)(OEt)2]2 (6) has
shown that it is oxidized at a relatively high potential of about
1.09 V (Table 1). The palladium complex obtained through
mixing phpy, Pd(OAc)2, and H3PO3, which does not produce
crystals suitable for X-ray structural analysis, is oxidized very
easily at 0.25 V (CPE), which confirms its instability and
propensity for oxidation even by oxygen in the air.
Thus, there are various palladium intermediatespallada-
cycles with different oxidation abilities in the mixture of arene,
phosphorylating agent (e.g., (EtO)2P(O)H), and the salt of the
palladium catalyst Pd(OAc)2 under conditions of C−H
phosphonation. Under conditions of chemical reaction with
4c,6
the added oxidizer K2S2O8
or under electrochemical
oxidation, this leads to a mixture of products of ortho-
substituted 2-phpy: cycle 3 will produce an ortho-acetoxylated
C
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product, cycle 4 (its Eox is above those of 3 and 5) ortho-
phosphonated 9, and cycle 5 a mixture of phosphorylation
products 9 and 10. Since the most easily oxidized cycles are
those undesired in terms of obtaining product 9, the yield of
the latter has never been very high: 12−66% in the papers of
Yu and 72−78% in our works.4c,i,6
The palladacycles 3 and 4 are the key intermediates of
electrocatalytic C−H functionalization, acetoxylation (3) and
phosphonation (4) of 2-phenylpyridine, which was previously
reported in refs 4i, j, s, and 11. It can be assumed that, in order
to increase the selectivity of the ortho-dialkylphosphonation
reaction, it is necessary to exclude the formation of cycles 3
and 5, as well as to provide conditions for the oxidation of key
intermediate 4, i.e. to use higher electrosynthesis potentials
corresponding to this process, or to choose stronger oxidizers
(in classical organic synthesis). To eliminate the presence of
acetate-bridged palladacycle 3, which gives the product of
aromatic C−H acetoxylation during oxidation (with low
potentials), it is necessary to age the mixture for some time
before oxidation (chemical or electrochemical) in order to turn
3 into phosphonate palladacycle 4, which is easy enough. The
next step should be neutralization of acetic acid, which was
released during the formation of phosphonate palladacycle 4.
For this purpose, oxidation processes were carried out in the
presence of a base (pyridine). When pyridine is added to the
bridge phosphonate palladacycle 4, the latter breaks down to
the monometallic palladacycle 7, which appears in the 31P
NMR spectrum as a singlet at δP 59.7 ppm in acetonitrile
solution. The assumption of the monomeric structure of the
intermediates with δP 69.5 (8) and 59 ppm (7) was proved by
the proximity of these values to the chemical shifts of other
mononuclear palladium phosphonate complexes, such as
Stockland’s arylpalladium complexes bu2bpyPd(Ar)(P(O)-
(OR)2) (δP 70.8−78.8 ppm).12 Monomerization of [(phpy)-
Pd(OEt)2P(O)]2 (4) into (phpy)Pd(CH3CN)[P(O)(OEt)2]
(8; the most likely structure) induced by an electron transfer
reaction is unusual and is described in ref 4j. Monomeric
palladium complexes are known to be oxidized usually at
potentials more positive than dimeric complexes with the same
ligand environment.4s,11,13, We assume and confirm that the
same trend is valid for phosphonate complexes (Table 1).
Indeed, the addition of pyridine to Pd2(phpy)2[P(O)(OEt)2]2
(4) results in the disappearance of its oxidation peaks on CVA
and the emergence of new peaks with more positive potentials
(Figure 3). We attribute these new peaks to the oxidation of
monometallic Pd(phpy)Py[P(O)(OEt)2] (7).
Figure 3. Cyclic voltammograms of palladacycle 4 (5 × 10−4 M) on a
GC electrode in CH3CN (a, red), in the presence of Py (1 × 10−4 M)
(b, blue), and in the presence of Py (1 × 10−3 M) (c, green).
Scheme 2
H3PO3 is completely absent, and there is a signal of the
product with δP 2.4 ppm. Registration of spectrum without
proton suppression revealed that compound 10 with δP 2.4
m.d. had a P−H bond (1JPH 650 Hz), i.e. a product with an
ortho-C(sp2)−O-P bond is formed (Scheme 3).
Scheme 3
Subsequent electrochemical oxidation of palladacycle 7
proceeds selectively with the formation of diethyl (2-
(pyridin-2-yl)phenyl)phosphonate (9) with a good yield
(86%) (Scheme 2).
Since dipalladium phosphonate-bridged complex 4 lies in
the way ofelectrocatalytic phosphorylation of 2-phenylpyridine
(1) with diethyl phosphite (2), we have assumed the formation
of a similar dipalladium complex when using phosphoric acid
H3PO3. Such s complex was formed during mixing of 2-
phenylpyridine (1), palladium acetate, and phosphoric acid.
However, on the basis of the analysis of 31P NMR spectra of
In the absence of base during electrolysis, the 31P NMR
spectrum shows two singlet signals with δP 16.2 and 2.3 (1JPH
=
626 Hz) ppm. Apparently, the presence of acetic acid in the
reaction mixture promotes the formation of tetranuclear
palladium complex 5, which breaks down into two products
with further electrochemical oxidation: ortho-phosphorylated
2-phenylpyridines 9 and 10 (Scheme 1).
To establish the possibility of obtaining inorganic
phosphorus derivatives of arenes under electrocatalytic
conditions, we performed phosphorylation of 2-phenylpiridine
1 using phosphorous acid H3PO3 as a phosphorylating reagent
(2F of electricity per mole of acid) and Pd(OAc)2 as catalyst.
In the 31P NMR spectrum of the reaction mixture, the original
1
the reaction mixture (δP 3.82 ppm, JPH = 637 Hz), one can
assume the formation of bridged dipalladium complex 11
having P−H fragments (Scheme 4). The dipalladium complex
11 is not very stable and is hardly soluble in organic solvents.
Aging in solvents such as DMSO and DMF over 1 day results
in the formation of a black powder sediment of Pd(0). After
the precipitate is filtered, the signal with δP 3.82 ppm
disappears in the 31P NMR spectrum of a solution of complex
11, and there is a new singlet with δP 1.89 ppm (splitting from
D
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performed a quantum chemical study of these phosphoric
palladacycles with known X-ray structures. Previously,
computational density functional theory was successfully
used to calculate the HOMO−LUMO energies, redox
potentials, stability of metal complexes, and factors controlling
the stability and reactivity of dimeric Pd(II) complexes,
including metal cycles of nickel and palladium.4s,5a,13,15
Structures of palladacycles 4 and 5 for the calculation of the
energy of frontier orbitals were taken from the X-ray diffraction
data. The calculations were performed in solvent (CH3CN) by
DFT using the M06L density functional,16 which has shown
itself well for the transition-metal energy calculations.17
Calculations of the energies of frontier orbitals of complex 4
were performed in the singlet ground state; the corresponding
HOMO and LUMO energies as well as the energy gap value,
ΔE, are given in Table 3. According to the presented data, the
computational level M06L/LACV3Psspp with the diffuse
functions included in the valence shell basis set provides
excellent agreement with the experimental data for ΔEg as well
as for the energies of the frontier orbitals.
Scheme 4
protons is not observed). Apparently, complex 11 is easily
oxidized by atmospheric oxygen in DMSO or DMF, which
leads to the release of Pd(0) and the formation of compound
12 (Scheme 4).
2.2. Electrochemical vs DFT Calculations. Electro-
chemical data for palladacycles 4 and 5 in the solid state
show that complex 5 oxidizes noticeably more easily than
diphosphonate-bridged dipalladacycles 4, and the value of its
electrochemical gap (Table 2 and Figure 4), associated with
The contour plots for the HOMO and LUMO are given in
Figure 5. HOMO orbital covers both Pd atoms, while the
LUMO is concentrated mostly on phosphonate groups.
For complex 5, the calculations performed with the
assumption that the complex ground state is a singlet gave
unreasonable estimations for ΔE. A study18 of the stability of
Pdn clusters in the gas phase established a state with
multiplicity, M, equal to 3 to have minimal energy for the
Pd2 and Pd4 clusters; at the same time the energy differences
between the cases M = 3 and M = 1 are 0.0018 and 0.017 eV,
respectively. As the difference for complex 4 is negligibly small
(an order of magnitude smaller than for M = 3), the presence
of ligands as well as solvent may change the most stable state of
the Pd2 cluster. We have examined this assumption and
obtained that for complex 4 the state with M = 1 is 2.7 eV
more stable than that with M = 3. The corresponding
calculations for complex 5 demonstrated that in this case, in
contrast, the state with M = 3 is more stable, though the energy
difference in this case is 0.12 eV. Thus, the calculated values of
ΔE and frontier orbital energies presented in Table 3
correspond to the state with M = 3. These data demonstrate
reasonable agreement with electrochemical data; the LUMO
energy is quite close to the value obtained on the basis of
electrochemical data. The ΔEg value for complex 5 estimated
on the basis of electrochemistry is shown to be notably smaller
than that for complex 4, and this tendency does hold for the
computational estimations: ΔEg is found to be 0.34 eV greater
for complex 4. The visualizations of the HOMO and LUMO
for complex 5 demonstrate that the HOMO covers mostly all
four Pd atoms, primarily the pair of Pd atoms bonded with
ortho-phosphonate fragments, while the LUMO is completely
placed on palladacycles.
Table 2. Electrochemical Data for Palladacycles 4 and 5 in
the Solid State: Oxidation and Reduction Peak Potentials
a
(Ep, V vs Fc+/Fc)
oxidation
reduction
electrochemical gap,
a c
a
c
complex
Ep , V
Ep , V
ΔEg = Ep − Ep , V
4
5
0.55
0.17
−2.20
−2.22
2.75
2.39
a
Conditions: carbon-paste electrode (graphite + ionic liquid +
palladacycle)14 in 2 mL of CH3CN (0.1 M Bu4NBF4).
CONCLUSION
Figure 4. CVs data for palladacycles 4 (upper CV) and 5 (at the
bottom) in carbon-paste electrodes (CPE): oxidation and reduction
peak potentials (Ep, V vs Fc+/Fc). Conditions: CPE (graphite + ionic
liquid + palladacycle)14 in 2 mL of CH3CN (0.1 M Bu4NBF4).
■
The key intermediates of ligand-directed aromatic phospho-
nation catalyzed by palladium, palladacycles, are distinguished
by their structure, chemical and electrochemical reactivities,
and redox properties, which determine the final products and
their yields. The reasons for the usually low yields of C−H
ortho-functionalization under oxidizing conditions, with
uncontrolled intermediates and the oxidizing power of the
reagents, have been established. The possibility of controlled
phosphorylation of an arene (2-phenylpyridine) in the
the energy difference between HOMO and LUMO orbitals, is
less than that for 5. That is, according to voltammetry, complex
5 is more easily polarizable and reactive. To confirm these
observations, to establish more stable forms, and to understand
the distribution of electron density in Pd complexes, we
E
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Table 3. Energies of Frontier Orbitals and the Energy Difference between Them (in eV) Calculated in Acetonitrile and
Estimated Electrochemically (Exp)
complex 4
complex 5
Exp
M06L/LACV3Pss
M06L/LACV3Psspp
Exp
M06L/LACV3Pss
M06L/LACV3Psspp
E(HOMO)
E(LUMO)
ΔEg
−5.35
−2.60
−2.75
−5.33
−2.52
−2.81
−5.35
−2.55
−2.80
−4.97
−2.58
−2.39
−4.99
−2.59
−2.40
−5.09
−2.63
−2.46
AUTHOR INFORMATION
Corresponding Author
■
Yulia H. Budnikova − Arbuzov Institute of Organic and
Physical Chemistry, FRC Kazan Scientific Center, Russian
Academy of Sciences, Kazan 420088, Russian Federation;
orcid.org/0000-0001-9497-4006; Email: yulia@iopc.ru
Authors
Tatyana V. Gryaznova − Arbuzov Institute of Organic and
Physical Chemistry, FRC Kazan Scientific Center, Russian
Academy of Sciences, Kazan 420088, Russian Federation
Mikhail N. Khrizanforov − Arbuzov Institute of Organic and
Physical Chemistry, FRC Kazan Scientific Center, Russian
Academy of Sciences, Kazan 420088, Russian Federation
Alina I. Levitskaya − Arbuzov Institute of Organic and Physical
Chemistry, FRC Kazan Scientific Center, Russian Academy of
Sciences, Kazan 420088, Russian Federation
Ildar Kh.Rizvanov − Arbuzov Institute of Organic and Physical
Chemistry, FRC Kazan Scientific Center, Russian Academy of
Sciences, Kazan 420088, Russian Federation
Marina Yu. Balakina − Arbuzov Institute of Organic and
Physical Chemistry, FRC Kazan Scientific Center, Russian
Academy of Sciences, Kazan 420088, Russian Federation
Kamil A. Ivshin − Arbuzov Institute of Organic and Physical
Chemistry, FRC Kazan Scientific Center, Russian Academy of
Sciences, Kazan 420088, Russian Federation
Olga N. Kataeva − Arbuzov Institute of Organic and Physical
Chemistry, FRC Kazan Scientific Center, Russian Academy of
Sciences, Kazan 420088, Russian Federation; orcid.org/
0000-0002-9763-5947
Figure 5. Contour plots for the HOMO and LUMO (M06L/
LACV3Psspp in ACN) of complexes 4 and 5.
direction of a reaction through the mononuclear palladacycle
in the presence of pyridine at high oxidation potentials has
been shown. It is possible to control the selectivity of
introduction of a phosphorus-containing substituent, giving
the diethyl arylphosphonate ArP(O)(OEt)2 with a yield of up
to 90% or the aryl phosphinic acid Ar−O−P(O)(H)(OH)
with a yield of up to 82% depending on the reaction
conditions. The reaction conditions (presence or absence or
pyridine base and ligand, anode potential) determine the
palladium intermediates through which electrolysis will go and
the general synthetic results.
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00247
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was partially supported by Russian Science
Foundation grant no. 19-13-00016. O.N.K. and K.A.I.
acknowledge financial support from the government assign-
ment for FRC Kazan Scientific Center of the RAS. The authors
gratefully acknowledge the CSF-SAC FRC KSC RAS for the
spectral (NMR, mass, etc.) studies.
ASSOCIATED CONTENT
■
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* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00247.
Experimental procedures for all experiments and
characterization, X-ray, electrochemical, and NMR data
(PDF)
REFERENCES
■
(1) For recent reviews and papers on Pd catalysis and C−H
activation, see: (a) James, J.; Jackson, M.; Guiry, P. J. Palladium-
Catalyzed Decarboxylative Asymmetric Allylic Alkylation: Develop-
ment, Mechanistic Understanding and Recent Advances. Adv. Synth.
Catal. 2019, 361, 3016−3049. (b) Hu, M.; Wu, W.; Jiang, H.
Palladium-Catalyzed Oxidation Reactions of Alkenes with Green
Oxidants. ChemSusChem 2019, 12, 2911−2935. (c) He, C.;
Whitehurst, W. G.; Gaunt, M. J. Palladium-Catalyzed C(sp3)-H
Bond Functionalization of Aliphatic Amines. Chem. 2019, 5, 1031−
Accession Codes
CCDC 1994142−1994144 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
F
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Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
1058. (d) Romero, A. H. Fused Heteroaromatic Rings via Metal-
Mediated/Catalyzed Intramolecular C-H Activation: A Comprehen-
sive Review. Top. Curr. Chem. 2019, 377, 21. (e) Kancherla, R.;
Muralirajan, K.; Sagadevan, A.; Rueping, M. Visible Light-Induced
Excited-State Transition-Metal Catalysis. Trends in Chemistry 2019, 1,
4382−4393. (e) Powers, D. C.; Ritter, T. Palladium(III) in Synthesis
and Catalysis. Top. Organomet. Chem. 2011, 35, 129−156.
(f) Racowski, J. M.; Sanford, M. S. Carbon-Heteroatom Bond-
Forming Reductive Elimination from Palladium (IV) Complexes. In
Higher Oxidation State Organopalladium and Platinum Chemistry.
Top. Organomet. Chem. 2011, 35, 61−84.
́
510−523. (f) Hagui, W.; Doucet, H.; Soule, J.-F. Application of
Palladium-Catalyzed C(sp2)-H Bond Arylation to the Synthesis of
Polycyclic (Hetero)Aromatics. Chem. 2019, 5, 2006−2078. (g) Dey,
A.; Sinha, S. K.; Achar, T. K.; Maiti, D. Accessing Remote meta- and
para-C(sp2)-H Bonds with Covalently Attached Directing Groups.
Angew. Chem., Int. Ed. 2019, 58, 10820−10843. (h) Szpera, R.;
Moseley, D. F. J.; Smith, L. B.; Sterling, A. J.; Gouverneur, V. The
Fluorination of C-H Bonds: Developments and Perspectives. Angew.
Chem., Int. Ed. 2019, 58, 14824−14848. (i) Li, J.; Yang, S.; Wu, W.;
Jiang, H. Palladium-Catalyzed Cascade Cyclization/Alkynylation
Reactions. Chem. - Asian J. 2019, 14, 4114−4128. (j) Tan, P. W.;
Seayad, J. Advances in amide and thioamide assisted C(sp3)-H
functionalization. Tetrahedron Lett. 2019, 60, 151338. (k) Kapdi, A.;
Maiti, D. Strategies for Palladium-Catalyzed Non-directed and Directed
C-H Bond Functionalization; Elsevier: 2017; ISBN: 9780128052549;.
(3) (a) Molnar, A. Efficient, selective, and recyclable palladium
catalysts in carbon- carbon coupling reactions. Chem. Rev. 2011, 111,
2251−2320. (b) Baumann, C. G.; De Ornellas, S.; Reeds, J. P.; Storr,
T. E.; Williams, T. J.; Fairlamb, I. J. S. Formation and propagation of
well-defined Pd nanoparticles (PdNPs) during C-H bond function-
alization of heteroarenes: are nanoparticles a moribund form of Pd or
an active catalytic species? Tetrahedron 2014, 70, 6174−6187.
(c) Fihri, A.; Bouhrara, M.; Nekoueishahraki, B.; Basset, J. M.;
Polshettiwar, V. Chem. Soc. Rev. 2011, 40, 5181−5203. (d) Notar
Francesco, I.; Fontaine-Vive, F.; Antoniotti, S. Synergy in the
Catalytic Activity of Bimetallic Nanoparticles and New Synthetic
Methods for the Preparation of Fine Chemicals. ChemCatChem 2014,
6, 2784−2791. (e) Moiseev, I. I.; Vargaftik, M. N. Pd cluster catalysis:
a review of reactions under anaerobic conditions. New J. Chem. 1998,
22, 1217−1227. (f) Powers, D. C.; Geibel, M. A. L.; Klein, J. E. M. N.;
Ritter, T. Bimetallic Palladium Catalysis: Direct Observation of
Pd(III)-Pd(III) Intermediates. J. Am. Chem. Soc. 2009, 131, 17050−
̈
(l) Sambiagio, C.; Schonbauer, D.; Blieck, R.; Dao-Huy, T.;
Pototschnig, G.; Schaaf, P.; Wiesinger, T.; Zia, M. F.; Wencel-
Delord, J.; Besset, T.; Maes, B. U. W.; Schnurch, M. A comprehensive
̈
́
̌
́
overview of directing groups applied in metal-catalysed C-H
functionalisation chemistry. Chem. Soc. Rev. 2018, 47, 6603−6743.
(m) Wu, Z. J.; Su, F.; Lin, W.; Song, J.; Wen, T. B.; Zhang, H. J.; Xu,
H. C. Scalable Rhodium (III)-Catalyzed Aryl C-H Phosphorylation
Enabled by Anodic Oxidation Induced Reductive Elimination. Angew.
Chem., Int. Ed. 2019, 58 (47), 16770−16774. (n) Yang, Q. L.; Li, Y.
Q.; Ma, C.; Fang, P.; Zhang, X. J.; Mei, T. S. Palladium-Catalyzed C
(sp3)-H Oxygenation via Electrochemical Oxidation. J. Am. Chem.
Soc. 2017, 139 (8), 3293−3298. (o) Jiao, K. J.; Xing, Y. K.; Yang, Q.
L.; Qiu, H.; Mei, T. S. Site-Selective C-H Functionalization via
Synergistic Use of Electrochemistry and Transition Metal Catalysis.
Acc. Chem. Res. 2020, 53 (2), 300−310. (p) Kakiuchi, F.; Kochi, T.;
Mutsutani, H.; Kobayashi, N.; Urano, S.; Sato, M.; Nishiyama, S.;
Tanabe, T. Palladium-catalyzed aromatic C- H halogenation with
hydrogen halides by means of electrochemical oxidation. J. Am. Chem.
Soc. 2009, 131 (32), 11310−11311. (q) Kakiuchi, F.; Kochi, T.
Selective CH Functionalizations by Electrochemical Reactions with
Palladium Catalysts. Isr. J. Chem. 2017, 57, 953−963. (r) Ackermann,
L. Metalla-electrocatalyzed C-H Activation by Earth-Abundant 3d
Metals and Beyond. Acc. Chem. Res. 2020, 53 (1), 84−104.
(s) Dhawa, U.; Tian, C.; Wdowik, T.; Oliveira, J. C. A.; Hao, J.;
Ackermann, L. Enantioselective Palladaelectro-Catalyzed C-H Acti-
vations by Transient Directing Groups: Expedient Access to
Helicenes. Angew. Chem., Int. Ed. 2020, DOI: 10.1002/
anie.202003826. (t) Meyer, T. H.; Oliveira, J. C. A.; Ghorai, D.;
Ackermann, L. Insights into Cobalta(III/IV/II)-Electrocatalysis:
Oxidation-Induced Reductive Elimination for Twofold C-H Activa-
tion. Angew. Chem., Int. Ed. 2020, 59. (u) Gryaznova, T. V.; Kholin, K.
V.; Nikanshina, E. O.; Khrizanforova, V. V.; Strekalova, S. O.;
Fayzullin, R. R.; Budnikova, Y. H. Copper or Silver-Mediated
Oxidative C(sp2)-H/N-H Cross-Coupling of Phthalimide and
Heterocyclic Arenes: Access to N-Arylphthalimides. Organometallics
2019, 38 (19), 3617−3628. (v) Budnikova, Y.; Bochkova, O.;
Khrizanforov, M.; Nizameev, I.; Kholin, K.; Gryaznova, T.; Laskin, A.;
Dudkina, Y.; Strekalova, S.; Fedorenko, S.; Kononov, A.; Mustafina, A.
Selective C (sp2)-H Amination Catalyzed by High-Valent Cobalt
(III)/(IV)-bpy Complex Immobilized on Silica Nanoparticles.
ChemCatChem 2019, 11 (22), 5615−5624.
17051. (g) Vana, J.; Hanusek, J.; Sedlak, M. Bi and trinuclear
complexes in palladium carboxylate-assisted C-H activation reactions.
Dalton Trans. 2018, 47, 1378−1382.
(4) (a) Budnikova, Yu. H.; Sinyashin, O. G. Phosphorylation of
aromatic C-H bonds involving metals and metal complexes. Russ.
Chem. Rev. 2015, 84, 917−951. (b) Qiao, H.; Sun, S.; Zhang, Y.; Zhu,
H.; Yu, X.; Yang, F.; Wu, Y.; Li, Z.; Wu, Y. Merging photoredox
catalysis with transition metal catalysis: site-selective C4 or C5-H
phosphonation of 8-aminoquinoline amides. Org. Chem. Front. 2017,
4, 1981−1986. (c) Li, C.; Yano, T.; Ishida, N.; Murakami, M.
Pyridine-Directed Palladium-Catalyzed Phosphonation of C(sp2)-H
Bonds. Angew. Chem., Int. Ed. 2013, 52, 9801−9804. (d) Budnikova,
Y. H. Opportunities and challenges for combining electro- and
organometallic catalysis in C(sp2)-H phosphonation. Pure Appl.
Chem. 2019, 91, 17−31. (e) Khrizanforova, V. V.; Kholin, K. V.;
Khrizanforov, M. N.; Kadirov, M. K.; Budnikova, Yu. H. Electro-
oxidative CH/PH functionalization as a novel way to benzo[b]-
phosphole oxides mediated by catalytic amounts of silver acetate. New
J. Chem. 2018, 42, 930−935. (f) Yurko, E. O.; Gryaznova, T. V.;
Kholin, K. V.; Khrizanforova, V. V.; Budnikova, Y. H. External
Oxidant-Free Cross-Coupling: Electrochemically Induced Aromatic
C-H Phosphonation of Azoles with Dialkyl-H-Phosphonates Under
Silver Catalysis. Dalton Trans. 2018, 47, 190−196. (g) Budnikova, Y.
H.; Dudkina, Y. B. Progress of electrochemical C(sp2)-H phospho-
nation. Phosphorus, Sulfur Silicon Relat. Elem. 2019, 194, 415−419.
(h) Budnikova, Y. H.; Gryaznova, T. V.; Grinenko, V. V.; Dudkina, Y.
B.; Khrizanforov, M. N. Eco-efficient Electrocatalytic C-P bond
Formation. Pure Appl. Chem. 2017, 89 (3), 311−330. (i) Grayaznova,
T. V.; Dudkina, Y. B.; Islamov, D.R.; Kataeva, O.N.; Sinyashin, O.G.;
Vicic, D.A.; Budnikova, Y. H. Pyridine-directed palladium-catalyzed
electrochemical phosphonation of C(sp2)-H bond. J. Organomet.
Chem. 2015, 785, 68−71. (j) Gryaznova, T.; Dudkina, Y.;
Khrizanforov, M.; Sinyashin, O.; Kataeva, O.; Budnikova, Y.
Electrochemical properties of diphosphonate-bridged palladacycles
and their reactivity in arene phosphonation. J. Solid State Electrochem.
2015, 19, 2665−2672. (k) Khrizanforov, M. N.; Strekalova, S. O.;
Kholin, K. V.; Khrizanforova, V. V.; Kadirov, M. K.; Gryaznova, T. V.;
Budnikova, Y. H. Novel approach to metal-induced oxidative
phosphorylation of aromatic compounds. Catal. Today 2017, 279,
133−141. (l) Khrizanforov, M. N.; Strekalova, S. O.; Kholin, K. V.;
Khrizanforova, V. V.; Grinenko, V. V.; Gryaznova, T. V.; Budnikova,
Y. H. One-stage Synthesis of FcP(O)(OC2H5)2 from Ferrocene and
α-Hydroxyethylphosphonate. RSC Adv. 2016, 6, 42701−42707.
(m) Strekalova, S.; Khrizanforov, M.; Sinyashin, O. G.; Budnikova,
Y. H. Catalytic Phosphorylation of Aromatic C-H Bonds: from
Traditional Approaches to Electrochemistry. Curr. Org. Chem. 2019,
(2) (a) Mirica, L. M.; Khusnutdinova, J. R. Coord. Chem. Rev. 2013,
́
́
257, 299−314. (b) Estevan, F.; Hirva, P.; Sanau, M.; ubeda, M.
Stability of Dinuclear Phosphane Palladium(III) Complexes: A DFT
Approach. Organometallics 2018, 37, 2980−2990. (c) Xu, L.-M.; Li,
B.-J.; Yang, Z.; Shi, Z.-J. Organopalladium(IV) chemistry. Chem. Soc.
Rev. 2010, 39, 712−733. (d) Camasso, N. M.; Canty, A. J.; Ariafard,
A.; Sanford, M. S. Experimental and Computational Studies of High-
Valent Nickel and Palladium Complexes. Organometallics 2017, 36,
G
https://dx.doi.org/10.1021/acs.organomet.0c00247
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
23, 1756−1770. (n) Strekalova, S.; Khrizanforov, M.; Budnikova, Y.
Evaluation of Transition Metal Catalysts in Electrochemically Induced
Aromatic Phosphonation. Molecules 2019, 24, 1823−1834. (o) Khri-
zanforov, M.; Strekalova, S.; Khrizanforova, V.; Dobrynin, A.; Kholin,
K.; Gryaznova, T.; Grinenko, V.; Gubaidullin, A.; Kadirov, M. K.;
Budnikova, Y. Cobalt-Catalyzed Green Cross-Dehydrogenative C-
(sp2)-H/P-H Coupling Reactions. Top. Catal. 2018, 61, 1949−1956.
(p) Budnikova, Y. H. Transition metal-promoted reactions of
diarylphosphine oxides as a synthetic method for organophosphorus
heterocyclic compounds. Chem. Heterocycl. Compd. 2018, 54, 269.
(q) Budnikova, Y. H.; Dudkina, Y. B.; Khrizanforov, M. N. Redox-
Induced Aromatic C-H Bond Functionalization in Metal Complex
Catalysis from the Electrochemical Point of View. Inorganics 2017, 5
(4), 70−88. (r) Yang, Q.-L.; Fang, P.; Mei, T.-S. Recent Advances in
Organic Electrochemical CH Functionalization. Chin. J. Chem.
2018, 36, 338−352. (s) Dudkina, Y. B.; Kholin, K. V.; Gryaznova, T.
V.; Islamov, D. R.; Kataeva, O. N.; Rizvanov, I. Kh.; Levitskaya, A. I.;
Fominykh, O. D.; Balakina, M. Yu.; Sinyashin, O. G.; Budnikova, Y.
H. Redox trends in cyclometalated palladium(II) Complexes. Dalton
Trans. 2017, 46, 165−177.
(5) (a) Haines, B. E.; Berry, J. F.; Yu, J.-Q.; Musaev, D. G. Factors
Controlling Stability and Reactivity of Dimeric Pd(II) Complexes in
C-H Functionalization Catalysis. ACS Catal. 2016, 6, 829−839.
(b) Le Bras, J.; Muzart, J. Dehydrogenative (Hetero)arene
Alkoxylations Triggered by PdIICatalyzed C(sp2)-H Activation and
Coordinating Substituent: PdII, III or PdIV Complex as Key
Intermediate? Eur. J. Org. Chem. 2017, 2017, 3528−3548. (c) Tay,
W. S.; Li, Y.; Pullarkat, S. A.; Leung, P.-H. Divergent Reactivity of
Phosphapalladacycles toward E-H (E = N, P, As) Bonds. Organo-
(12) (a) Kohler, M. C.; Stockland, R. A.; Rath, N. P. Steric and
electronic effects on arylphosphonate elimination from organo-
palladium complexes. Organometallics 2006, 25, 5746−5756.
(b) Kohler, M. C.; Grimes, T. V.; Xiaoping, W.; Cundari, T. R.;
Stockland, R. A. Arylpalladium phosphonate complexes as reactive
intermediates in Phosphorus-Carbon bond forming reactions.
Organometallics 2009, 28, 1193−1201. (c) Stockland, R. A., Jr.;
Levine, A. M.; Giovine, M. T.; Guzei, I. A.; Cannistra, J. C. Reductive
elimination from metal phosphonate complexes: Circumvention of
competing protonolysis reactions. Organometallics 2004, 23, 647−
656.
(13) Dudkina, Y. B.; Fayzullin, R. R.; Lyssenko, K. A.; Gubaidullin,
A. T.; Kholin, K. V.; Levitskaya, A. I.; Balakina, M. Yu.; Budnikova, Y.
H. Cyclometalated Nickel Complexes as Key Intermediates in
C(sp2)-H Bond Functionalization: Synthesis, Catalysis, Electro-
chemical Properties, and DFT Calculations. Organometallics 2019,
38 (6), 1254−1263.
(14) Carbon-paste electrode based on a phosphonium binder:
(a) Khrizanforov, M. N.; Arkhipova, D. M.; Shekurov, R. P.;
Gerasimova, T. P.; Ermolaev, V. V.; Islamov, D. R.; Miluykov, V.
A.; Kataeva, O. N.; Khrizanforova, V. V.; Sinyashin, O. G.; Budnikova,
Y. H. Novel paste electrodes based on phosphonium salt room
temperature ionic liquids for studying the redox properties of
insoluble compounds. J. Solid State Electrochem. 2015, 19 (9),
2883−2890. (b) Kataeva, O.; Metlushka, K.; Ivshin, K.; Kiiamov, A.;
Alfonsov, V.; Khrizanforov, M.; Budnikova, Y.; Sinyashin, O.;
Krupskaya, Y.; Kataev, V.; Buchner, B.; Knupfer, M. Electron Transfer
̈
and Unusual Chemical Transformations of F4-TCNQ in a Reaction
with Mn-Phthalocyanine. Eur. J. Inorg. Chem. 2018, 2018, 3344−
3353. (c) Taidakov, I.; Ambrozevich, S.; Saifutyarov, R.; Lyssenko, K.;
Avetisov, R.; Mozhevitina, E.; Khomyakov, A.; Khrizanforov, M.;
Budnikova, Y.; Avetissov, I. New Pt(II) complex with extra pure green
emission for OLED application: Synthesis, crystal structure and
spectral properties. J. Organomet. Chem. 2018, 867, 253−260.
(d) Gryaznova, T. V.; Khrizanforov, M. N.; Kholin, K. V.;
Vorotyntsev, M. A.; Gor’kov, K. V.; Talagaeva, N. V.; Dmitrieva, M.
V.; Zolotukhina, E. V.; Budnikova, Y. H. Palladium Nanoparticles-
Polypyrrole Composite as Effective Catalyst for Fluoroalkylation of
Alkenes. Catal. Lett. 2018, 148 (10), 3119−3125. (e) Khrizanforov,
M. N.; Fedorenko, S. V.; Mustafina, A. R.; Kholin, K. V.; Nizameev, I.
R.; Strekalova, S. O.; Grinenko, V. V.; Gryaznova, T. V.; Zairov, R. R.;
Mazzaro, R.; Morandi, V.; Vomiero, A.; Budnikova, Y. H. Silica-
supported silver nanoparticles as an efficient catalyst for aromatic C-H
alkylation and fluoroalkylation. Dalton Trans. 2018, 47, 9608−9616.
(f) Kadirov, M. K.; Minzanova, S. T.; Nizameev, I. R.; Mironova, L.
G.; Gilmutdinov, I. F.; Khrizanforov, M. N.; Kholin, K. V.;
Khamatgalimov, A. R.; Semyonov, V. A.; Morozov, V. I.; Kadirov,
D. M.; Mukhametzyanov, A. R.; Budnikova, Yu. H.; Sinyashin, O. G.
A nickel-based pectin coordination polymer as an oxygen reduction
reaction catalyst for proton-exchange membrane fuel cells. Inorg.
Chem. Front. 2018, 5 (4), 780−784.
(15) Matsui, T.; Kitagawa, Y.; Shigeta, Y.; Okumura, M. A Density
Functional Theory Based Protocol to Compute the Redox Potential
of Transition Metal Complex with the Correction of Pseudo-
Counterion: General Theory and Applications. J. Chem. Theory
Comput. 2013, 9, 2974−2980. Hughes, T. F.; Friesner, R. A.
Development of Accurate DFT Methods for Computing Redox
Potentials of Transition Metal Complexes: Results for Model
Complexes and Application to Cytochrome P450. J. Chem. Theory
Comput. 2012, 8, 442−459.
(16) Zhao, Y.; Truhlar, D. G. A new local density functional for
main-group thermochemistry, transition metal bonding, thermochem-
ical kinetics, and noncovalent interactions. J. Chem. Phys. 2006, 125,
194101.
́
̌
́
̌
metallics 2020, 39, 182−188. (d) Vana, J.; Bartacek, J.; Hanusek, J.;
́
́
Roithova, J.; Sedlak, M. C-H Functionalizations by Palladium
Carboxylates: The Acid Effect. J. Org. Chem. 2019, 84, 12746−
12754. (e) Davies, D. L.; Macgregor, S. A.; McMullin, C. L.
Computational Studies of Carboxylate-Assisted C-H Activation and
Functionalization at Group 8−10 Transition Metal Centers. Chem.
Rev. 2017, 117, 8649−8709.
(6) Feng, Ch.-G.; Ye, M.; Xiao, K.-J.; Li, S.; Yu, J.-Q. Pd (II)-
catalyzed phosphorylation of aryl C-H bonds. J. Am. Chem. Soc. 2013,
135, 9322−9325.
(7) (a) Beletskaya, I. P.; Cheprakov, A. V. Palladacycles in catalysis-a
critical survey. J. Organomet. Chem. 2004, 689, 4055−4082. (b) Phan,
N. T. S.; Van Der Sluys, M.; Jones, C. W. On the nature of the active
species in palladium catalyzed Mizoroki-Heck and Suzuki-Miyaura
couplings-homogeneous or heterogeneous catalysis, a critical review.
Adv. Synth. Catal. 2006, 348, 609−679. (c) Yin, L. X.; Liebscher, J.
Carbon- carbon coupling reactions catalyzed by heterogeneous
palladium catalysts. Chem. Rev. 2007, 107, 133−173. (d) Ananikov,
V. P.; Beletskaya, I. P. Toward the ideal catalyst: From atomic centers
to a “cocktail” of catalysts. Organometallics 2012, 31, 1595−1604.
(8) Skapski, A. C.; Smart, M. L. The Crystal Structure of Trimeric
Palladium(II) Acetate. J. Chem. Soc. D 1970, 11, 658b−659.
(9) (a) Powers, D. C.; Benitez, D.; Tkatchouk, E.; Goddard, W. A.,
III; Ritter, T. Bimetallic Reductive Elimination from Dinuclear
Pd(III) Complexes. J. Am. Chem. Soc. 2010, 132, 14092−14103.
(b) Powers, D. C.; Lee, E.; Ariafard, A.; Sanford, M. S.; Yates, B. F.;
Canty, A. J.; Ritter, T. Connecting Binuclear Pd(III) and
Mononuclear Pd(IV) Chemistry by Pd-Pd Bond Cleavage. J. Am.
Chem. Soc. 2012, 134, 12002−12009. (c) Powers, D. C.; Ritter, T.
Bimetallic Redox Synergy in Oxidative Palladium Catalysis. Acc. Chem.
Res. 2012, 45, 840−850.
(10) Dudkina, Yu. B.; Gryaznova, T. V.; Sinyashin, O. G.;
Budnikova, Yu. H. Ligand-directed electrochemical functionalization
of C(sp2)H bonds in the presence of the palladium and nickel
compounds. Russ. Chem. Bull. 2015, 64, 1713−1725.
(11) Dudkina, Y. B.; Mikhaylov, D. Y.; Gryaznova, T. V.; Tufatullin,
A. I.; Kataeva, O. N.; Vicic, D. A.; Budnikova, Y. H. Electrochemical
Ortho Functionalization of 2-Phenylpyridine with Perfluorocarboxylic
Acids Catalyzed by Palladium in Higher Oxidation States. Organo-
metallics 2013, 32, 4785−4792.
(17) Zhao, Y.; Truhlar, D. G. Calculation of semiconductor band
gaps with the M06-L density functional. J. Chem. Phys. 2009, 130,
074103.
H
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Organometallics
pubs.acs.org/Organometallics
Article
(18) Kalita, B.; Deka, R. C. Stability of small Pdn, n = 1−7··· clusters
on the basis of structural and electronic properties: A density
functional approach. J. Chem. Phys. 2007, 127, 244306.
I
https://dx.doi.org/10.1021/acs.organomet.0c00247
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