Acyl-carbene and methyl-carbene coupling via migratory insertion in palladium complexes

Article abstract of DOI:10.1021/om300462t

The migratory insertion reaction of a carbene into a palladium-acyl bond has been observed both for monoaminocarbenes and for methoxycarbenes. The acyl derivative [PdCl(COMe){C(NEt₂)Ph}(PPh₃)] undergoes an acyl-carbene coupling, leading to the enolate-type complex [PdCl{C(COMe) (NEt₂)Ph}(PPh₃)]₂ (2). This complex decomposes either by reductive elimination to give the iminium salt or by protonation of the enolate to give a ketoamine. In a similar fashion, the reaction of [Pd ₂(μ-Cl)₂(COMe)₂(SMe₂) ₂] with [W(CO)₅{C(OMe)Ph}] leads to an undetected palladium enolate that, after protonation, is stabilized by coordination to palladium ([PdCl₂{(OH)MeC=CPh(OMe}(SMe₂)], 8). The reaction of [Pd₂(μ-Cl)₂Me₂(SMe ₂)₂] with [W(CO)₅{C(OMe)-Ph}] leads to the migratory insertion of the carbene into the Pd-methyl group to give an alkyl palladium complex. The transfer of CO from tungsten, followed by insertion into the Pd-Me group, also occurs. This leads to the formation of a Pd-COMe group, which also undergoes migratory insertion of the carbene fragment. These results support that migratory insertion is a key C-C coupling step, as proposed for the new Pd-catalyzed transformations that use carbene precursors.

Full text of DOI:10.1021/om300462t

Article
pubs.acs.org/Organometallics
Acyl−Carbene and Methyl−Carbene Coupling via Migratory
Insertion in Palladium Complexes
Isabel Meana, Ana C. Albeniz,* and Pablo Espinet*
́
́
IU CINQUIMA/Química Inorganica, Universidad de Valladolid, 47071-Valladolid, Spain
ABSTRACT: The migratory insertion reaction of a carbene into a
palladium−acyl bond has been observed both for monoaminocarbenes
and for methoxycarbenes. The acyl derivative [PdCl(COMe){C(NEt2)-
Ph}(PPh3)] undergoes an acyl−carbene coupling, leading to the
enolate-type complex [PdCl{C(COMe)(NEt2)Ph}(PPh3)]2 (2). This
complex decomposes either by reductive elimination to give the
iminium salt or by protonation of the enolate to give a ketoamine. In a
similar fashion, the reaction of [Pd2(μ-Cl)2(COMe)2(SMe2)2] with [W(CO)5{C(OMe)Ph}] leads to an undetected palladium
enolate that, after protonation, is stabilized by coordination to palladium ([PdCl2{(OH)MeCCPh(OMe}(SMe2)], 8). The
reaction of [Pd2(μ-Cl)2Me2(SMe2)2] with [W(CO)5{C(OMe)-Ph}] leads to the migratory insertion of the carbene into the Pd−
methyl group to give an alkyl palladium complex. The transfer of CO from tungsten, followed by insertion into the Pd−Me
group, also occurs. This leads to the formation of a Pd−COMe group, which also undergoes migratory insertion of the carbene
fragment. These results support that migratory insertion is a key C−C coupling step, as proposed for the new Pd-catalyzed
transformations that use carbene precursors.
Scheme 2. Proposed Mechanism for the Multicomponent
Pd-Catalyzed Synthesis of Keto Derivatives
INTRODUCTION
■
New Pd-catalyzed transformations that use carbene precursor
reagents, such as diazoalkanes,1,2 tosylhydrazones,2,3 or group 6
metal carbenes,4 have been devised recently. In these reactions,
a migratory insertion in putative palladium carbene inter-
mediates is deemed responsible for the key C−C coupling step,
which leads to a new alkyl group on palladium, susceptible of
further functionalization (Scheme 1). As a result, the reactions
are highly efficient transformations often introducing at least
two different functional groups or building several C−C bonds
in one process.
Scheme 1. Key C−C Coupling Step for Pd-Catalyzed
Reactions That Use Carbene Precursors
into the Pd−acyl bond took place (Scheme 2). The migratory
insertion of carbene ligands into metal−acyl bonds is not
frequent, and only a few stoichiometric examples have been
reported for Mo and W complexes.7 In addition, this reaction
has been proposed to occur in the formation of cyclic ketones
from alkoxycarbene complexes of chromium,8 and the
formation of acylimidazolium salts from N,N-heterocyclic
palladium carbenes involves an acyl−carbene coupling.9
We have been interested in learning about this reaction by
checking in a more direct way whether, as proposed in the
many references above, carbenes do insert in Pd−acyl bonds
and can insert into other Pd−R bonds. We show here that
alkoxo- or aminocarbenes on Pd−acyl complexes indeed
undergo migratory insertion reactions. Moreover, the character-
ization of the key intermediates in this process support that
carbenes also insert in Pd−alkyl bonds.
Just a few years back, migratory insertion was unknown for
palladium carbene complexes [PdR(carbene)L2], but we
proved that this transformation did occur for R =
pentafluorophenyl.5 Another example was reported later by
Danopoulos et al., who synthesized a Pd complex containing a
chelating carbene−alkyl ligand and proposed that the alkyl
fragment had resulted from migratory insertion of an N-
heterocyclic carbene ligand into a Pd−Me bond.6
Among the new tandem transformations that use carbene
precursors and are believed to involve a migratory insertion
step, Wang et al. reported an interesting Pd-catalyzed synthesis
of keto derivatives from aryl iodides, CO, and diazoalkanes as
carbene precursors (Scheme 2).2 They proposed that a
carbonylation by CO and a migratory insertion of carbene
Received: May 25, 2012
Published: July 16, 2012
© 2012 American Chemical Society
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RESULTS
Scheme 3. Decomposition Pathways of Complexes 1
■
Our observations come from the study of the decomposition of
acyl−palladium amino- or methoxycarbenes. The experimental
protocol for these studies was the following: CDCl3 solutions of
a preformed acyl palladium aminocarbene or in situ generated
acyl palladium methoxycarbenes were monitored by NMR;
intermediate organometallic complexes and organic products
were spectroscopically characterized using multinuclear NMR
1
and H−13C NMR HMBC experiments. The results of these
experiments are described in detail below. Isolation of the
products was attempted by repeating the reactions in Schlenk
tubes, adjusting the reaction time to maximize the concen-
tration of the target species. Since mixtures of products were
produced in all cases, partial separation by chromatography was
carried out. In this way, the characterization of the involved
species was completed, but we failed to isolate pure species or
to obtain X-ray quality crystals for structure determination.
The complex trans-[PdCl(COMe){C(NEt2)Ph}(PPh3)]
(trans-1; trans refers to the relative phosphine−carbene
arrangement) was synthesized by reaction of [Pd2(μ-
Cl)2Me2(SMe2)2] with [W(CO)5{C(NEt2)Ph}], followed by
addition of PPh3, as reported before.10 This reaction involves
the transfer of carbene and CO from W to Pd, which leads to
the formation of the acyl group bound to palladium. trans-1
undergoes isomerization in solution (CDCl3) at room temper-
ature (Figure 1) to cis-1 (2JC,P = 5.0 Hz for the carbene carbon
disappearance of trans-1, as measured by initial rates, is first
order in the palladium complex and is independent of the
concentration of PPh3.
Complex 2 is an enolate derivative that shows a Pd-C 13C
NMR resonance at 111 ppm and 2JC,P = 5.0 Hz, consistent with
1
a cis alkyl−phosphine arrangement. The H NMR pattern for
the amino group shows chemical equivalence for the ethyl
groups (by fast rotation about the (Pd)C−N bond and
inversion of the lone pair on N), but diastereotopic methylene
protons (Figure 2). This is consistent with the structure
Figure 1. Kinetic profile for the evolution of complex trans-1 in CDCl3
solution (% of the carbene decomposition products vs time).
2
resonance in 13C NMR vs JC,P = 102.1 Hz for trans-1). Both
isomers bear the acyl group cis to the carbene ligand, and both
undergo migratory insertion to give 2 (Scheme 3).11
The decomposition of cis-1 is slower, and this complex stays
in solution for weeks, eventually decomposing to the same
products as trans-1. Complexes 1 also decompose at the
beginning of the reaction by direct hydrolysis of the carbene
moiety with adventitious water,12 to give diethylbenzamide (6)
and acetaldehyde.13 A kinetic profile of the whole process
monitored in an NMR tube is given in Figure 1. The
1
Figure 2. H NMR spectrum of 2 (a small amount of 5 is present).
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depicted for 2. Complex 2 undergoes two types of reactions: (i)
protonation to give the ketoamino derivative 3 and (ii)
reductive elimination to give the iminium salt 4, and
subsequent hydrolysis to the diketone 5. Protonation of
palladium enolate complexes is a very facile process,14 and
the acid generated in the formation of 6 or 5 can easily produce
3. The iminium derivative 4 was clearly identified by the
characteristic CN 13C NMR signal at 170 ppm, as well as the
MeCO resonance at 201.2 ppm. As expected, two non-
equivalent ethyl substituents on the nitrogen are observed for 4
in the 1H and 13C NMR spectra (see the Experimental
Section).
Finally, the reaction of [W(CO)5{C(OMe)Ph}] and the
methyl palladium complex [Pd2(μ-Cl)2Me2(SMe2)2] shows
reaction intermediates and products formed by migratory
insertion into both a Pd−Me and a Pd−acyl bond (Scheme 5).
Scheme 5. Migratory Insertion Reactions of a
Methoxycarbene into a Pd−Acyl and a Pd−Me Bond
In a similar study, the transmetalation of the analogous
methoxycarbene moiety from W to Pd, does not allow the
detection of the corresponding acyl palladium methoxycarbenes
A, because a subsequent fast migratory insertion reaction occurs
(Scheme 4). Thus, the reaction of [W(CO)5{C(OMe)Ph}]
Scheme 4. Migratory Insertion Reaction of a
Methoxycarbene into a Pd−Acyl Bond
The latter results from carbene plus CO transfer from tungsten
to palladium and CO insertion into the Pd−Me bond (path a,
Scheme 5). The reactivity is the same as that observed for the
acyl precursor in Scheme 4. This is the preferred pathway, and
7 accounts for 60% of the decomposition products. Although
the palladium carbene complex C could not be observed, it
must be formed, and the coupling of methyl and carbene also
occurs since the product of migratory insertion 9 could be
detected in solution (13C NMR Pd-C, 101.7 ppm). This
complex decomposes by β-H elimination to the enol ether 10,
and eventually by hydrolysis of 9 and 10 to the ketone 11.
Table 1 shows the percentages of the decomposition products
after 30 min and the final distribution.
and the acyl palladium complex [Pd2(μ-Cl)2(COMe)2(SMe2)2]
in CD3CN leads to the methoxyketone 7 (Scheme 4). The
formation of 7 must proceed via transmetalation to give the
palladium methoxycarbene (A), followed by migratory
insertion into the Pd−acyl moiety to give the enolato complex
B, in the same way it was described above for 1. Protonation of
B leads to 8, which finally releases 7. Complex 8 was detected
when the reaction was monitored by 1H NMR and was
characterized with the aid of 1H−13C NMR HMQC and
HMBC experiments. Complex 8 shows a hydroxoalkene ligand,
the enol tautomer of 7, coordinated to palladium. It is a mixture
of two isomers (81, major, and 82, minor), which we assign to
the E and Z isomers of the coordinated hydroxoalkene. Each
isomer shows characteristic signals at δ 5.71 (81) and 6.28 (82),
which are assigned to the hydroxy resonances. A 1H−13C NMR
HMBC experiment at low temperature shows long-range
coupling of the 1H OH and C-Me resonances to both
olefinic carbons at 143.5, 134.0 ppm (81) and 139.2, 133.2 ppm
(82). The reaction in Scheme 4 is faster than that for 1 (it is
complete in 9 h, compared with days for 1). As was the case for
the amino derivatives, the direct products of hydrolysis of the
palladium methoxycarbene (methyl benzoate and Pd(0)) were
also observed.
Table 1. Product Distribution (%) for the Reaction in
Scheme 5
compound or pathway
30 min
9 h
[Pd2(μ-
Cl)2Me2(SMe2)2]
21.4
pathway a
pathway b
38.8 (7, 3.5; 8, 35.2)
35.4 (9, 9.9; 10, 13.4; 11, 12.1) 35.4 (11)
4.4 (PhC(O)Me) 4.9 (PhC(O)Me)
59.7 (7)
a
hydrolysis
a
Hydrolysis of the carbene fragment in A or C.
DISCUSSION
■
The results obtained clearly show that both amino- and
methoxycarbenes insert into Pd−acyl bonds to give keto
derivatives as final products. All the steps in this transformation
have been proved by characterization of the intermediates
involved, as shown in the discussion. These results strongly
support Wang’s mechanistic proposal for the multicomponent
coupling of diazo derivatives and arylhalides in the presence of
CO (Scheme 2).2
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The reported examples of coupling of R groups on palladium
complexes with monoamino-5 or diaminocarbenes15 usually
leads to iminium salts as final products. This reaction is
indistinguishable from a reductive elimination. The character-
ization of 2 shows that, at least for monoaminocarbenes, the
coupling is a migratory insertion reaction, followed, when
iminium salts are formed, by a reductive decomposition. The
R−carbene coupling occurs by the same process for
monoamino- or alkoxocarbenes, although at a much faster
rate for the more electrophilic methoxycarbenes. This prevents
the detection of the intermediate methoxycarbene palladium
complexes that should form by transmetalation, whereas they
have been characterized when no migratory insertion can
follow.13 Although the different nature of the L ligand
coordinated to palladium could have some influence on the
rate of migratory insertion (L = PPh3 for 1 or L = μ-Cl, SMe2
for A or C), this difference is small compared to the change in
nature of the carbene ligand, as shown in our former work with
R = C6F5,5b,c and as suggested by the fact that none of the
methoxycarbene complexes could be detected.
A β-H elimination process, frequent for many palladium
alkyls, is not possible for 2. On the other hand, this alkyl group
is an enolate-type ligand that, as expected, undergoes
electrophilic attack by H+ to the oxygen atom, which is the
more nucleophilic center. Palladium enolates can show different
coordination modes, such as C-bonded,14,16,17 O-bonded,17,18
and η3-oxoallyl-type.19 Most of them are C-bonded, and this is
the case of 2. However, an equilibrium with molecules showing
the other bonding types, transient or in undetectable
concentration, could be responsible for the reactivity observed.
Complex 8 is the result of protonation and shows that the enol
form is strongly stabilized by coordination. We believe that the
characterization of 8 indicates that the protonation of 2 via an
O-bonded enolate intermediate is the least plausible route in
this case, since a fast decoordination should be expected in the
presence of other competing ligands, such as SMe2, or
acetonitrile as solvent. On the other hand, if protonation
occurs on the carbonyl group of the C-bonded palladium
enolate or, better, on the more basic oxygen of an η3-oxoallyl,
the resulting vinyl alcohol product is already coordinated to the
metal (Scheme 6). Although the η3-oxoallyl form is not a
coordination mode commonly observed for palladium, it
should be carefully considered to explain enolate reactivity.
Me bond has also been supported by the characterization of
complex 9. These findings show that the migratory insertion in
palladium carbenes is fairly general and includes Pd−Ar (Ar =
C6F5),5 Pd−acyl, and Pd−alkyl bonds. This means that it is
certainly a most plausible fundamental step in palladium-
catalyzed transformations whenever palladium carbene inter-
mediates can be formed.
EXPERIMENTAL SECTION
■
1
General Methods. H, 13C{1H}, 19F, and 31P{1H} NMR spectra
were recorded on Bruker AC-300, ARX-300, and AV-400
spectrometers. Chemical shifts (in δ units, parts per million) were
referenced to Me4Si (1H and 13C) and 85% H3PO4 (31P). The spectral
data were recorded at 293 K unless otherwise noted. GC-mass spectra
were recorded on a Thermo Scientific Focus DSQII system.
All the manipulations were carried out under an atmosphere of
nitrogen using standard Schlenk techniques. Solvents were dried using
a solvent purification system SPS PS-MD-5 or distilled from
appropriate drying agents under nitrogen, prior to use. Complexes
[Pd(μ-Cl)Me(SMe2)]2,20 [Pd(μ-Cl)COMe(SMe2)]2,10,21 trans-[PdCl-
(COMe){C(NEt2)Ph}(PPh3)] (1),10 and [W(CO)5{C(OMe)Ph}]22
were prepared according to literature methods. Compounds 5, 6, 10,
11, and Ph(CO)OMe are known and commercial. They were
completely characterized in the reaction mixtures or compared with
authentic samples, but their spectroscopic data are not included here.
Decomposition of trans-[PdCl(COMe){C(NEt2)Ph}(PPh3)] (trans-
1). A solution of trans-1 (0.008, 0.008 mmol) in CDCl3 (0.6 mL) was
prepared in a 5 mm NMR tube under nitrogen at room temperature.
1
The solution was monitored by H and 31P{1H}NMR spectroscopy
over a period of days. The decomposition products were characterized
in the mixture, and percentages of products are shown in Figure 1.
The reaction was repeated using 50 mg of trans-1. Partial separation
of the products was carried out as follows: cis-1 was obtained by
precipitation in Et2O of the mixture kept at room temperature for 3
days; 2 and 3 were separated from the mother liquors by preparative
TLC using Et2O as eluent.
1
cis-1: H NMR (400 MHz, δ, CDCl3): 7.50−7.28 (m, 18H; PPh3),
7.19 (m, 3H; Hmeta Ph, Hpara Ph), 6.67 (m, 2H; Hortho Ph), 5.31 (m,
1H; CHH), 4.39 (m, 1H; CHH), 3.46 (m, 2H; CH′2), 1.97 (s, 3H;
C(O)Me), 1.70 (t, J = 7.2 Hz, 3H; CH3), 1.01 (t, J = 7.2 Hz, 3H;
1
CH′3). H NMR (400 MHz, δ, CDCl3, 243 K): 7.50−7.28 (m, 18H;
PPh3), 7.20 (m, 3H; Hmeta Ph, Hpara Ph), 6.58 (br, 2H; Hortho Ph), 5.40
(m, 1H; CHH), 4.33 (m, 1H; CHH), 3.46 (m, 2H; CH′2), 1,90 (s,
3H; C(O)Me), 1.71 (t, J = 7.2 Hz, 3H; CH3), 1.02 (t, J = 7.2 Hz, 3H;
CH′3). 31P{1H} NMR (161.97 MHz, δ, CDCl3): 25.33 (s). 31P{1H}
NMR (161.97 MHz, δ, CDCl3, 243 K): 25.42 (s). 13C{1H} NMR
(100.61 MHz, δ, CDCl3, 243 K): 230.4 (d, 2JC,P = 5.0 Hz, Pd-Ccarbene),
221.7 (s, C(O)Me), 139.2 (s, Cipso Ph), 134.4 (d, 2JC,P = 12.1 Hz, Cortho
PPh3), 131.1 (s, Cpara PPh3), 130.5−128.0 (12C, Cipso PPh3, Cmeta
PPh3, Cmeta Ph, Cpara Ph), 125.1 (s, Cortho Ph), 57.3 (s, CH2), 47.4 (s,
Scheme 6. Protonation of Different Isomeric Forms of
Palladium Enolates
3
C′H2), 36.7 (d, JC,P = 28.2 Hz, C(O)Me), 13.0 (s, CH3), 11.9 (s,
C′H3).
2: 1H NMR (400 MHz, δ, CDCl3): 7.68 (m, 6H; Hortho PPh3), 7.43
(m, 3H; Hpara PPh3), 7.39 (m, 6H; Hmeta PPh3), 7.29 (m, 3H; Hmeta Ph,
Hpara Ph), 7.14 (m, 2H; Hortho Ph), 3.35 (m, 2H, CHH, CH2), 2.35 (m,
2H, CHH, CH2), 1.88 (t, J = 7.2 Hz, 6H; CH3), 1.42 (s, 3H; C(O)
1
Me). H NMR (400 MHz, δ, CDCl3, 243 K): 7.65 (m, 6H; Hortho
PPh3), 7.50 (m, 3H; Hpara PPh3), 7.43 (m, 6H; Hmeta PPh3), 7.30 (m,
3H; Hmeta Ph, Hpara Ph), 7.13 (m, 2H; Hortho Ph), 3.31 (m, 2H, CHH,
CH2), 2.34 (m, 2H, CHH, CH2), 1.89 (t, J = 7.2 Hz, 6H; CH3), 1.42
(s, 3H; C(O)Me). 31P{1H} NMR (161.97 MHz, δ, CDCl3): 23.54 (s).
31P{1H} NMR (161.97 MHz, δ, CDCl3, 243 K): 23.82 (s). 13C{1H}
CONCLUSION
■
3
NMR (100.61 MHz, δ, CDCl3, 243K): 164.8 (d, JC,P = 3.02 Hz,
The migratory insertion reaction of both methoxy- and
monoaminocarbenes into a Pd−acyl group has been observed.
The characterization of relevant intermediates 2 and 8 clearly
shows the main steps of the decomposition pathway. The
migratory insertion reaction of a methoxycarbene into a Pd−
2
C(O)Me), 134.7 (d, JC,P = 11.1 Hz, 2C; Cortho PPh3), 133.7 (s, Cipso
1
Ph), 132.7 (s, 2C; Cortho Ph), 131.0 (s, Cpara PPh3), 128.5 (d, JC,P
=
53.3 Hz, Cipso PPh3), 128.3 (d, 3JC,P = 11.1 Hz, 2C; Cmeta PPh3), 127.5
(s, 2C; Cmeta Ph), 111.0 (d, JC,P = 5.0 Hz; Pd-C), 52.4 (d, JC,P = 2.0
Hz, 2C; 2CH2), 19.1 (s, C(O)Me), 13.5 (s, 2C; 2CH3).
2
4
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1
3: H NMR (400 MHz, δ, CDCl3): 7.50−7.25 (5H; Ph)*, 4.31 (s,
ACKNOWLEDGMENTS
■
1H; CH), 2.65 (m, 2H; CHH, 2CH2), 2.48 (m, 2H; CHH, 2CH2),
2.14 (s, 3H; C(O)Me), 0.99 (t, J = 7.2 Hz, 6H; 2CH3). 13C{1H} NMR
(100.61 MHz, δ, CDCl3, 243K): 209.2 (s, C(O)Me), 135.4 (s, Cipso
Ph), 129.2 (s, Corto Ph), 128.8 (s, Cpara Ph), 128.3 (s, Cmeta Ph)*, 77.2
(s, C-H), 42.4 (s, 2C; 2CH2), 26.4 (s, C(O)Me), 10.1 (s, 2C; 2CH3).
MS (EI) m/z (%): 205 (1) [M]+, 162 (100), 134 (12), 77 (10) (* =
signals overlap with signals of other compounds).
Financial support from the Spanish MINECO (DGI, grant
CTQ2010-18901/BQU; FPU fellowship to I.M.) and the Junta
de Castilla y Leon
edged.
́
(grant VA373A11-2) is gratefully acknowl-
REFERENCES
4: 1H NMR (400 MHz, δ, CDCl3, 243 K): 8.00 (m, 2H; Hortho Ph),
7.80−7.30 (m, 3H; Hmeta, Hpara Ph), 3.35 (q, J = 7.2 Hz, 2H; CH2),
3.28 (q, J = 7.2 Hz, 2H; CH′2), 2.09 (s, 3H; C(O)Me), 1.16 (t, J = 7.2
Hz, 3H; CH3), 1.10 (t, J = 7.2 Hz, 3H; CH′3). 13C{1H} NMR (100.61
MHz, δ, CDCl3, 243 K): 201.2 (s, C(O)Me), 170.0 (s, CN), 136.9
(s, Cpara Ph), 133.6 (s, Cipso Ph), 130.4 (s, Cortho Ph), 130.0 (s, Cmeta
Ph), 42.8 (s, CH2), 39.9 (s, C′H2), 21.8 (s, C(O)Me), 14.1 (s, CH3),
13.1 (s, C′H3).
■
(1) (a) Chen, Z.-S.; Duan, X.-H.; Zhou, P.-X.; Ali, S.; Luo, J.-Y.;
Liang, Y.-M. Angew. Chem., Int. Ed. 2012, 51, 1370−1374. (b) Zhang,
Z.; Liu, Y.; Ling, L.; Li, Y.; Dong, Y.; Gong, M.; Zhao, X.; Zhang, Y.;
Wang, J. J. Am. Chem. Soc. 2011, 133, 4330−4341. (c) Kudirka, R.;
Devine, S. K. J.; Adams, C. S.; Van Vranken, D. L. Angew. Chem., Int.
Ed. 2009, 48, 3677−3680. (d) Yu, W.-Y.; Tsoi, Y.-T.; Zhou, Z.; Chan,
A. S. C. Org. Lett. 2009, 11, 469−472. (e) Chen, S.; Wang, J. Chem.
Commun. 2008, 4198−4200. (f) Peng, C.; Wang, Y.; Wang, J. J. Am.
Chem. Soc. 2008, 130, 1566−1567. (g) Devine, S. K. J.; Van Vranken,
D. L. Org. Lett. 2008, 10, 1909−1911. (h) Kudirka, R.; Van Vranken,
D. L. J. Org. Chem. 2008, 73, 3585−3588. (i) Devine, S. K. J.; Van
Vranken, D. L. Org. Lett. 2007, 9, 2047−2049. (j) Greenman, K. L.;
Van Vranken, D. L. Tetrahedron 2005, 61, 6438−6441. (k) Greenman,
K. L.; Carter, D. S.; Van Vranken, D. L. Tetrahedron 2001, 57, 5219−
5225.
Reaction of [W(CO)5{C(OMe)Ph)] and [Pd(μ-Cl)(Me)(SMe2)]2.
[Pd(μ-Cl)(Me)(SMe2)]2 (0.0150 g, 0.0337 mmol) was added to a
solution of [W(CO)5{C(OMe)Ph)] (0.0300 g, 0.0675 mmol) in
CD3CN (0.6 mL). The solution was then examined by 1H NMR
spectroscopy, and the resulting products were identified. Product
ratios are given in the text. The separation of the products was carried
out by preparative TLC using Et2O as eluent.
The reaction of [W(CO)5{C(OMe)Ph)] and [Pd(μ-Cl)(COMe)-
(SMe2)]2 was carried out in the same way.
(2) Zhang, Z.; Liu, Y.; Gong, M.; Zhao, X.; Zhang, Y.; Wang, J.
Angew. Chem., Int. Ed. 2010, 49, 1139−1142.
́
(3) (a) Barluenga, J.; Valdes, C. Angew. Chem., Int. Ed. 2011, 50,
7: 1H NMR (400 MHz, δ, CD3CN): 7.38 (m, 5H; Ph), 4.71 (s, 1H;
CH), 3.33 (s, 3H; OMe), 2.07 (s, 3H; C(O)Me). 1H NMR (400 MHz,
δ, CD3CN, 243 K): 7.38 (m, 5H; Ph), 4.74 (s, 1H; CH), 3.26 (s, 3H;
OMe), 2.04 (s, 3H; C(O)Me). 13C{1H} NMR (100.61 MHz, δ,
CD3CN): 207.6 (s, C(O)Me), 137.7 (s, 2C; Cipso Ph), 129.7 (s, 2C;
Cmeta Ph), 129.4 (s, 2C; Cpara Ph), 128.2 (s, 2C; Cortho Ph), 89.9 (s,
CH), 57.6 (s, OMe), 25.8 (s, C(O)Me). MS (EI) m/z (%): 164 (1)
[M]+, 121 (100), 105 (18), 91 (42), 77 (86), 63 (5), 51 (14), 43 (11).
8: This complex is a mixture of two isomers, 81 and 82 (see text).
81: 1H NMR (400 MHz, δ, CD3CN): 7.63 (m, 2H; Hortho Ph), 7.33
(m, 2H; Hmeta Ph), 7.17 (m, 1H; Hpara Ph), 5.71 (s, OH), 3.39 (s, 3H;
7486−7500. (b) Chen, Z.-S.; Duan, X.-H.; Wu, L.-Y.; Ali, S.; Ji, K.-G.;
Zhou, P.-X.; Liu, X.-Y.; Liang, Y.-M. Chem.Eur. J. 2011, 17, 6918−
6921. (c) Zhou, F.; Ding, K.; Cai, Q. Chem.Eur. J. 2011, 17, 12268−
12271. (d) Zhou, L.; Ye, F.; Zhang, Y.; Wang, J. J. Am. Chem. Soc.
2010, 132, 13590−13591. (e) Zhao, X.; Jing, J.; Lu, K.; Zhang, Y.;
Wang, J. Chem. Commun. 2010, 46, 1724−1726. (f) Barluenga, J.;
Escribano, M.; Moriel, P.; Aznar, F.; Valdes
́
, C. Chem.Eur. J. 2009,
15, 13291−13294. (g) Xiao, Q.; Ma, J.; Yang, Y.; Zhang, Y.; Wang, J.
Org. Lett. 2009, 11, 4732−4735. (h) Barluenga, J.; Moriel, P.; Valdes
́
,
1
C.; Aznar, F. Angew. Chem., Int. Ed. 2007, 46, 5587−5590.
OMe), 2.27 (s, 6H; SMe2), 2.05 (s, 3H; C-Me). H NMR (400
(4) Lopez-Alberca, M. P.; Mancheno, M. J.; Fernandez, I.; Gom
́
́
́
ez-
̃
MHz, δ, CD3CN, 243 K): 7.63 (m, 2H; Hortho Ph), 7.33 (m, 2H; Hmeta
Ph), 7.16 (m, 1H; Hpara Ph), 6.15 (s, OH), 3.36 (s, 3H; OMe), 2.21 (s,
6H; SMe2), 2.03 (s, 3H; C-Me). 13C{1H} NMR (100.61 MHz, δ,
CD3CN, 243 K): 143.5 (s, (OH)Me-C), 134.9 (s, Cipso Ph), 134.0
(s, C-OMe(Ph)), 128.5 (s, 2C; Cortho Ph), 126.6 (s, 2C; Cmeta Ph),
126.1 (s, Cpara Ph), 58.9 (s, OMe), 21.3 (s, 2C; SMe2), 16.2 (s, C-
Gallego, M.; Sierra, M. A.; Torres, R. Org. Lett. 2007, 9, 1757−1759.
(5) (a) Albeniz, A. C.; Espinet, P.; Perez-Mateo, A. J. Organomet.
Chem. 2010, 695, 441−445. (b) Albeniz, A. C.; Espinet, P.; Perez-
Mateo, A.; Nova, A.; Ujaque, G. Organometallics 2006, 25, 1293−1297.
(c) Albeniz, A. C.; Espinet, P.; Manrique, R.; Per
ez-Mateo, A. Chem.
Eur. J. 2005, 11, 1565−1573. (d) Albeniz, A. C.; Espinet, P.; Manrique,
R.; Per
́
́
́
́
́
́
́
Me).
1
́
ez-Mateo, A. Angew. Chem., Int. Ed. 2002, 41, 2363−2366.
82: H NMR (400 MHz, δ, CD3CN): 7.80−7.25 (m, 4H; Hortho
Hmeta Ph), 7.17 (m, 1H; Hpara Ph), 6.28 (s, OH), 3.35 (s, 3H; OMe),
,
(6) (a) Danopoulos, A. A.; Tsoureas, N.; Green, J. C.; Hursthouse,
1
M. B. Chem. Commun. 2003, 756−757.
(7) Adams, H.; Bailey, N. A.; Tattershall, C. E.; Winter, M. J. J. Chem.
Soc., Chem. Commun. 1991, 912−914.
(8) (a) Zora, M.; Li, Y.; Herndon, J. W. Organometallics 1999, 18,
4429−4436. (b) Zora, M.; Herndon, J. W. Organometallics 1994, 13,
3370−3373. (c) Zora, M.; Herndon, J. W. Organometallics 1993, 12,
248−249.
(9) McGuinness, D. S.; Cavell, K. J. Organometallics 2000, 19, 4918−
4920.
2.21 (s, 6H; SMe2), 1.84 (s, 3H; C-Me). H NMR (400 MHz, δ,
CD3CN, 243 K): 7.80−7.25 (m, 4H; Hortho, Hmeta Ph), 7.22 (m, 1H;
Hpara Ph), 6.53 (s, OH), 3.30 (s, 3H; OMe), 2.27 (s, 6H; SMe2), 1.83
(s, 3H; C-Me). 13C{1H} NMR (100.61 MHz, δ, CD3CN, 243 K):
139.2 (s, (OH)Me-C), 134.2 (s, Cipso Ph), 133.2 (s, C-
Ph(OMe)), 130.0−125.0 (5C; Cortho, Cmeta, Cpara Ph), 57.7 (s,
OMe), 21.3 (s, 2C; SMe2), 15.4 (s, C-Me).
1
9: H NMR (400 MHz, δ, CD3CN): 7.65* (m, 2H; Hortho Ph),
7.47* (m, 3H; Hmeta, Hpara Ph), 3.13 (s, 3H; OMe), 2.21 (s, 6H;
1
SMe2), 1.48 (s, 3H; Me). H NMR (400 MHz, δ, CD3CN, 243 K):
(10) Meana, I.; Alben
4193−4198.
́
iz, A. C.; Espinet, P. Organometallics 2008, 27,
7.50−7.40 (m, 3H; Hmeta, Hpara Ph), 7.40−7.30 (m, 2H; Hortho Ph),
3.09 (s, 3H; OMe), 2.27 (s, 6H; SMe2), 1.45 (s, 3H; Me). 13C{1H}
NMR (100.61 MHz, δ, CD3CN, 243 K): 143.4 (s, Cipso Ph), 129.4 (s,
2C; Cortho Ph), 127.4 (s, 2C; Cmeta Ph), 126.5 (s, Cpara Ph), 101.7 (s,
Pd-C), 48.6 (s, OMe), 26.0 (s, Me), 21.3 (s, 2C; SMe2) (* = signal
overlaps with signals of other compounds).
(11) We are drawing in all the schemes the resonant form that better
represents the bonding in monoamino or monoalkoxo Pd−carbenes.
The molecular structures of palladium monoaminocarbenes show
short C−X bond lengths and Pd−C bond distances fully consistent
with a single bond (see, for example, refs 5b−d and 10). The reactivity
of palladium alkoxocarbenes characterized in solution also indicates
the strong contribution of the depicted resonant form (see ref 13).
(12) Note that the importance of this hydrolysis is exaggerated in
Figure 1 because the amount of reagent in the NMR tube is very small.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: albeniz@qi.uva.es (A.C.A.), espinet@qi.uva.es (P.E.).
(13) Meana, I.; Toledo, A.; Alben
2012, 18, 7658−7661.
(14) Albeniz, A. C.; Catalina, N. M.; Espinet, P.; Redon
Organometallics 1999, 18, 5571−5576.
́
iz, A. C.; Espinet, P. Chem.Eur. J.
Notes
́
́
, R.
The authors declare no competing financial interest.
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dx.doi.org/10.1021/om300462t | Organometallics 2012, 31, 5494−5499

Organometallics
Article
(15) (a) Normand, A. T.; Stasch, A.; Ooi, L.-L.; Cavell, K. J.
Organometallics 2008, 27, 6507−6520. (b) Graham, D. C.; Cavell, K.
J.; Yates, B. F. Dalton Trans. 2006, 1768−1775. (c) Graham, D. C.;
Cavell, K. J.; Yates, B. F. Dalton Trans. 2005, 1093−1100. (d) Cavell,
K. J.; McGuinness, D. S. Coord. Chem. Rev. 2004, 248, 671−681.
(16) (a) Cam
́
pora, J.; Maya, C. M.; Palma, P.; Carmona, E.;
Gutier
́
rez, E.; Ruiz, C.; Graiff, C.; Tiripicchio, A. Chem.Eur. J. 2005,
11, 6889−6904. (b) Tian, G.; Boyle, P. D.; Novak, B. M.
Organometallics 2002, 21, 1462−1465. (c) Vicente, J.; Arcas, A.;
́ ́
Fernandez-Fernandez, J. M.; Bautista, D. Organometallics 2001, 20,
2767−2774. (d) Ruiz, J.; Rodríguez, V.; Cutillas, N.; Pardo, M.; Per
́
ez,
J.; Lopez, G. Organometallics 2001, 20, 1973−1982. (e) Vicente, J.;
́
Abad, J. A.; Chicote, M. T.; Abrisqueta, M. D.; Lorca, J. A.; Ramírez de
Arellano, M. C. Organometallics 1998, 17, 1564−1568. (f) Veya, P.;
Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1993, 12,
4899−4907. (g) Suzuki, K.; Yamamoto, H. Inorg. Chim. Acta 1993,
208, 225−229. (h) Byers, P. K.; Canty, A. J.; Skelton, B. W.; Traill, P.
R.; Watson, A. A.; White, A. H. Organometallics 1992, 11, 3085−3088.
(i) Burkhardt, E.; Bergman, R. G.; Heathcock, C. H. Organometallics
1990, 9, 30−44. (j) Bertani, R.; Castellani, C. B.; Crociani, B. J.
Organomet. Chem. 1984, 269, C15−C18.
(17) (a) Culkin, D. A.; Hartwing, J. F. Organometallics 2004, 23,
3398−3416. (b) Culkin, D. A.; Hartwig, J. F. Acc. Chem. Res. 2003, 36,
234−245. (c) Culkin, D. A.; Hartwig, J. F. J. Am. Chem. Soc. 2001, 123,
5816−5817.
(18) (a) Sodeoka, M.; Tokunoh, R.; Miyazaki, F.; Hagiwara, E.;
Shibasaki, M. Synlett 1997, 463−466. (b) Bouaoud, S.-E.; Braunstein,
P.; Grandjean, D.; Matt, D.; Nobel, D. Inorg. Chem. 1988, 27, 2279−
2286. (c) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.;
Nobel, D. J. Chem. Soc., Chem. Commun. 1987, 7, 488−490. (d) Ito, Y.;
Nakatsuka, M.; Kise, N.; Saegusa, T. Tetrahedron Lett. 1980, 21, 2873−
2876.
(19) (a) Lemke, F. R.; Kubiak, C. P. J. Organomet. Chem. 1989, 373,
391−400. (b) Yanase, N.; Nakamura, Y.; Kawaguchi, S. Inorg. Chem.
1980, 19, 1575−1581. (c) Yanase, N.; Nakamura, Y.; Kawaguchi, S.
Chem. Lett. 1979, 5, 591−594. (d) Yoshimura, N.; Murahashi, S.-I.;
Moritani, I. J. Organomet. Chem. 1973, 52, C58−C60.
(20) Byers, P. K.; Canty, A. J.; Engelhardt, L. M.; White, A. H. J.
Chem. Soc., Dalton Trans. 1986, 1731−1986.
(21) Hayashi, Y.; Isobe, K.; Nakamura, Y.; Okeya, S. J. Organomet.
Chem. 1986, 310, 127−134.
(22) Fischer, E. O.; Kreissl, F. R. In Synthetic Methods of
Organometallic and Inorganic Chemistry; Herrmann, W. A., Ed.;
Georg Thieme Verlag: Stuttgart, 1997; Vol. 7, pp 129−131.
5499
dx.doi.org/10.1021/om300462t | Organometallics 2012, 31, 5494−5499