Heterometallic complexes by transmetalation of alkynyl groups from copper or silver to allyl palladium complexes: Demetalation studies and alkynyl homocoupling

Article abstract of DOI:10.1021/om4005498

The reaction of [Pd(η³-allyl)ClL] (L = AsPh₃, PPh₃) with [M(Ci - CR)]_n (M = Cu, Ag; R = ⁿBu, Ph) leads to transmetalation of the alkynyl group from M to Pd. However, the group 11 metal stays η²-bound to the new Pd-alkynyl fragment and heterometallic Pd-M complexes are formed with different nuclearities depending on M: [{Pd(η³-allyl)(alkynyl)L}CuCl] ₂ (3, 4) or [{Pd(η³-allyl)(alkynyl)L}₂AgCl] (5, 6). The M-containing fragment can be eliminated to give the actual transmetalation complex [Pd(η³-allyl)(alkynyl)L] by adding an excess of arsine or phosphine, whereas amines do not have this effect. Allyl-alkynyl reductive elimination is a slow process; therefore, complexes 3-6 cleanly decompose by dimerization (homocoupling) of the alkynyl group. In the decomposition process reversible alkynyl transmetalation from Pd to Cu has been observed.

Full text of DOI:10.1021/om4005498

Article
pubs.acs.org/Organometallics
Heterometallic Complexes by Transmetalation of Alkynyl Groups
from Copper or Silver to Allyl Palladium Complexes: Demetalation
Studies and Alkynyl Homocoupling
Isabel Meana, Pablo Espinet, and Ana C. Albeniz*
́
́
́
IU CINQUIMA/Quımica Inorganica, Universidad de Valladolid, 47071-Valladolid, Spain
S
* Supporting Information
ABSTRACT: The reaction of [Pd(η3-allyl)ClL] (L = AsPh3, PPh3)
with [M(CCR)]n (M = Cu, Ag; R = nBu, Ph) leads to
transmetalation of the alkynyl group from M to Pd. However, the
group 11 metal stays η2-bound to the new Pd−alkynyl fragment and
heterometallic Pd−M complexes are formed with different nuclearities
depending on M: [{Pd(η3-allyl)(alkynyl)L}CuCl]2 (3, 4) or [{Pd(η3-
allyl)(alkynyl)L}2AgCl] (5, 6). The M-containing fragment can be
eliminated to give the actual transmetalation complex [Pd(η3-
allyl)(alkynyl)L] by adding an excess of arsine or phosphine, whereas
amines do not have this effect. Allyl−alkynyl reductive elimination is a
slow process; therefore, complexes 3−6 cleanly decompose by
dimerization (homocoupling) of the alkynyl group. In the decomposition process reversible alkynyl transmetalation from Pd
to Cu has been observed.
Scheme 1. Synthesis of Heterometallic Cu−Pd and Ag−Pd
INTRODUCTION
■
Complexes
The transmetalation of alkynyl groups from copper to
palladium has been used in the synthesis of palladium alkynyls,1
and it is a crucial step in the classical Sonogashira reaction.2,3 In
both synthetic and catalytic reactions the copper alkynyl is
often formed in situ from the alkyne and the copper salt in the
presence of base. Although less common, silver alkynyls have
also been used for the same purposes.4 We have studied the
reaction of [M(alkynyl)]n (M = Cu, Ag) with palladium allylic
complexes. The allyl moiety is a good donor ligand which
introduces little steric hindrance, and it fixes a cis geometry for
the remaining ligands around Pd in [Pd(allyl)XL]. Since the
reductive elimination of allyl-R in [Pd(allyl)RL] complexes is
generally slow, as has been shown for R = aryl5 and also R =
alkynyl groups,6 we rationalized that other decomposition
pathways for the transmetalation product [Pd(allyl)(alkynyl)L]
could be studied. Indeed, we have observed that alkynyl
transmetalation takes place from Cu or Ag to Pd, but
interesting heterometallic derivatives, the result of a failed
elimination of the group 11 metal, could be isolated. We have
checked what types of ligands induce the elimination of Cu or
Ag and studied the decomposition of the complexes.
heterometallic structure, and only half of the silver added is
included in the heterometallic framework (5 and 6; Scheme 1).
Complexes 3−6 were completely characterized in solution. All
of them except 5 could be isolated in moderate or good yields
(60−90%). The molecular structures of 3b, 4a,b, and 6 were
determined by X-ray crystal diffraction. Figures 1 and 2 show
ORTEP drawings for complexes 3b, 4a, and 6. The molecular
structure of 4b is analogous to that of the other Cu complexes
and can be found in the Supporting Information.
The heterometallic Cu−Pd complexes show a centrosym-
metric structure and are formed by two [Pd(η3-allyl)(alkynyl)-
L] units linked by a Cu2Cl2 unit (Figure 1). The Cu is three
coordinated, bound to the alkynyl group in a η2 symmetric
fashion and two chloro atoms. This type of structural unit [(η2-
RESULTS AND DISCUSSION
■
Synthesis of Heterometallic Cu−Pd and Ag−Pd
Complexes. The reaction of a copper(I) alkynyl and the
allylic complexes 1 and 2 leads to the heterometallic allyl
alkynyl complexes 3 and 4, where all of the copper is
incorporated into the new derivatives (Scheme 1). The
analogous reaction with a silver alkynyl leads to a different
Received: June 13, 2013
Published: August 1, 2013
© 2013 American Chemical Society
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Figure 1. ORTEP drawings of the heterometallic complexes 3b (left) and 4a (right).
Figure 2. ORTEP drawings of the heterometallic Ag−Pd complex 6: (a) complete structure; (b) structure with aryl rings of PPh3 omitted for clarity.
MCCR)CuCl]2 has also been found for other heterometallic
complexes where M = Fe,7 Ru,8 Pt.9
Table 1. Selected Distances (Å) and Angles (deg) for
Complexes 3b, 4a, and 6
The silver derivative 6 shows two [Pd(η3-allyl)(alkynyl)-
(PPh3)] units bound through η2 M−alkynyls to the same silver
atom. The silver coordination sphere is completed by a Cl and
shows a trigonal-planar geometry (Figure 2). This structural
feature has been observed before for M = Pt.9c,10 Silver is
asymmetrically coordinated to each η2 M−alkynyl unit, and the
Ag−Cβ bond length (2.600(9) Å) is longer than the Ag−Cα
distance (2.374(7) Å).9c,10d,11 The dihedral angle for both (η2-
MCCR)Ag planes is 61.8°.
3b
4a
6
Pd(1)−C(1)
2.171(16)
2.18(2)
2.180(5)
2.142(7)
Pd(2)−C(10)
Pd(2)−C(11)
2.177(8)
2.135(8)
Pd(1)−
C(2A)
Pd(1)−
2.17(4)
2.131(14)
C(2B)
Pd(1)−C(3)
Pd(1)−C(4)
2.184(15)
2.039(13)
2.4175(18)
2.190(4)
2.036(4)
Pd(2)−C(12)
Pd(2)−C(13)
2.158(7)
2.058(8)
Pd(1)−
As(1)
The distances found in all the complexes fall within the
expected ranges (Table 1). The allylic moieties show a
disordered structure; thus, in all cases the structures were
refined with C2 occupying two positions with different
occupation factors. The alkynyl unit is somewhat bent, and
the angle Pd−C4−C5 has a value in the range 173−168° and
the angle C4−C5−C6 in the range 158−172°.
Pd(1)−P(1)
2.3009(11) Pd(2)−P(2)
2.295(12)
2.2843(15)
2.4788(19)
Cu(1)−
2.305(4)
2.315(4)
Ag(1)−Cl(1)
Cl(1)
Cu(1)-
Cl(1A)
2.316(13)
Cu(1)−C(4) 2.023(12)
Cu(1)−C(5) 2.036(14)
2.008(4)
2.036(4)
1.198(6)
172.9(4)
Ag(1)−C(13)
Ag(1)−C(14)
C(13)−C(14)
Pd(2)−
C(13)−
C(14)
2.374(7)
2.600(9)
1.124(10)
173.3(8)
C(4)−C(5)
Pd(1)−
C(4)−
C(5)
1.217(17)
The structures of complexes 3−6 show that the alkynyl
group is no longer σ-bound to Cu but to Pd and the
dissociation of the group 11 metal has not occurred.
Intermediates of this type (A and B, Scheme 2) have been
proposed for the transmetalation of alkynyl groups, assuming
that a good ligand such as an alkyne could play a role in
anchoring both reaction counterparts.12 Complexes 3−6 are
168.1(11)
C(4)−
C(5)−
C(6)
158.6(13)
164.6(5)
C(13)−
C(14)−
C(15)
172.0(11)
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elimination of Cu and the formation of 8. Palladium complexes
with arsine or phosphine ligands [PdCl2L2] are commonly used
in Sonogashira couplings, and according to our results, this is
beneficial to complete the transmetalation step. In other type of
catalysts such as the so-called “ligandless catalytic systems”
(simple palladium salts without other ligands present except for
the solvent, reagents and products) this effect is not possible.
Hierso el at. have reported that the use of a multidentate
ferrocenylphosphine complex of copper instead of CuI makes
Sonogashira couplings more efficient. The use of these ligands
may affect other steps of the catalytic cycle but also avoids
copper coordination to the alkynyl, leading to bimetallic
species.14
The evolution of complexes 3−6 with or without added
ligands was followed by 1H NMR. Since the reductive
elimination of the allyl and the alkynyl fragments is very
slow, the allyl−alkynyl coupling was not observed in any of the
experiments and conversely the homocoupling of alkynyl
fragments took place. This is a competitive reaction in alkynyl
cross-coupling processes but can also be synthetically useful
(Glaser reaction).15
Scheme 2. Simplified Steps in the Transmetalation of
Alkynyls
analogous to intermediate B and give strong support to the
general pathway for transmetalation shown in Scheme 2.
Decomposition of the Heterometallic Complexes. For
a successful classical Sonogashira coupling an efficient trans-
metalation step followed by a fast reductive elimination is
desirable and, at some point, elimination of the group 11 metal
atom needs to occur. Thus, we have carried out several
experiments to find out what types of ligands, usually present in
Sonogashira couplings, can eliminate the group 11 metal atom
in complexes 3−6. The addition of PPh3 to a solution of 4a or
6 in the ratio PPh3:Pd = 3:1 at 243 K leads to the elimination of
Cu or Ag and the formation of [Pd(η3-allyl)(CCn-Bu)-
(PPh3)] (7) and a solid identified as CuClPPh3 for 4a and AgCl
for 6. Complex 7 was synthesized independently by reaction of
2 and a 5-fold molar amount of SnBu3CCn-Bu. Figure 3
shows the 1H NMR spectra before and after addition of
phosphine and the comparison with 7.
The decomposition of 3a (L = AsPh3) at room temperature
is slow, and it is complete after 3 days. The products observed
n
by NMR are just the dialkyne BuCCCCnBu (9) and 1
(eq 1). The 1:9 molar ratio found in solution is 4:1. This is
Similar experiments were carried out with the arsine
complexes 3a and 5. Upon addition of AsPh3 to 3a in the
ratio AsPh3:Pd = 10:1, [Pd(η3-allyl)(CCnBu)(AsPh3)] (8)
and CuClAsPh3 (or AgCl for 5) were observed. Complex 8 was
synthesized as described above for 7, and it has been reported
before.6 In this case, a higher ligand to Pd ratio was necessary to
drive the equilibrium toward the formation of CuClL, due to
the lower coordination ability of AsPh3 in comparison to that of
PPh3.13 In the case of the silver heterometallic complexes the
elimination of the silver follows the same trend and the
decoordination of the η2-alkynyl from Ag is easier for the more
coordinating PPh3. The formation of AgCl as the final product
seems to be favored, and this is the solid observed.
different than the expected ratio (4:2) if all of the alkynyl
fragment of 3a results in the formation of 9. The remaining
alkyne fragment forms [Cu(CCnBu)]n, which precipitates
out and was characterized by IR. The formation of the copper
alkynyl clearly shows that Cu−Pd transmetalation is a reversible
process. This was also found by Osakada, Sakata, and
Yamamoto when they studied the equilibria between
[Pd(CCPh)Ar(PR3)2] and CuI.16 The same decomposition
pattern and product ratio was observed for 4a, 5, and 6. The
Other ligands do not have the same effect. Thus, the addition
of an excess of an amine (NEt3), commonly used as a base in
Sonogashira couplings, to complex 3a does not lead to the
Figure 3. Addition of PPh3 to 4a at 243 K: (a) 1H NMR of 4a before ligand addition; (b) 1H NMR after the addition of PPh3 (Pd:P = 1:3); (c) 1H
NMR of 7 obtained independently by reaction of 2 and SnBu3CCnBu (Pd:Sn = 1:5; an excess of stannane is present in the spectrum).
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decomposition of the triphenylphosphine complexes takes
longer for completion than that of the AsPh3 analogues (cf. 13
days for 4a vs 3 days for 3a or 16 h for 6 vs 10 min for 5). The
silver complexes are less stable than the copper derivatives.
Upon addition of an excess of AsPh3 to 3a (10-fold) and of
PPh3 to 4a (3-fold) at 243 K, copper demetalation takes place
as described above and complexes 8 and 7 formed. These
solutions were warmed to room temperature, and the
decompositions of the [Pd(allyl)(CCPh)(EPh3)] complexes
in the mixture were monitored (Scheme 3). In comparison to
quantities of water give an allylic alcohol (Scheme 3). When L
= PPh3, a reductive elimination of the phosphine and an allyl
group to give (CH2CHCH2PPh3)Cl occurs, although under
the reaction conditions, isomerization of the double bond takes
place and the thermodynamically more stable 11 is observed
(entries 2 and 4, Table 2).17,18 This process has been observed
before and has been proposed to occur in [Pd(σ-allyl)ClL2]
complexes.17 The phosphonium salt (CH2CHCH2PPh3)Cl
and 11 are also formed when an excess of PPh3 is added to 2,
and this has been checked in an independent experiment (see
the Supporting Information). The complex trans-[Pd(CCn-
Bu)Cl(PPh3)2] (10) was also observed in the experiments with
triphenylphosphine, and it eventually decomposes to 9 through
a plausible second alkynyl transmetalation, isomerization, and
reductive elimination. 10 is the result of an alkynyl transfer to
[PdCl2(PPh3)2], formed in the reaction media (CDCl3)
presumably by oxidation of PdLn species (Scheme 4). Alkynyl
Scheme 3. Decomposition Pathways for Complexes 7 and 8
Formed by Addition of L to Complexes 3−6
Scheme 4. Proposed Pathway for the Formation of 10 and
Its Decomposition to 9
palladium complexes analogous to 10 with other alkynyl groups
have been reported before,12,19,20 and we checked the identity
of 10 by reacting ClCCnBu21 and Pd(PPh3)4 as previously
described.20
It is noteworthy that, in the decomposition reactions in the
presence of excess of ligand, the 1H NMR spectra of complexes
1 and 2 show the typical fluxional behavior for allylic
compounds via fast exchange between (i) η3- and σ-allylic
complexes and (ii) free and coordinated ligand, as well as
neutral and cationic species. This kind of behavior has been
studied in detail elsewhere.22 In the presence of a large excess of
triphenylphosphine (for example PPh3:Pd = 10:1), the new
alkynyl complex 7 also shows syn−anti exchange for the
protons attached to C3 (cis to the phosphine ligand) as well as
exchange of free and coordinated phosphine. These fluxional
processes are faster as the concentration of L in the solution
becomes greater; therefore, it is observed that the appearance of
the reactions shown in eq 1, the presence of ligands increases
the rate of decomposition and the conversion of the alkynyl
fragment to 9 is quantitative: the expected molar ratio of allyl-
containing compounds to 9 of 2:1 is obtained. Along with 9,
the solution contains complex 1 or 2, allylic alcohol, and, in the
case of 4a, the phosphonium salt [PPh3(1-propenyl)]Cl (11).
Scheme 3 summarizes the decomposition processes, which are
analogous for the Cu and Ag complexes bearing the same L.
Alkynyl transfer from complexes 7 or 8 to Cu can occur, as
we observed for the decomposition of the heterometallic
complexes 3−6 in the absence of added ligand (eq 1). Complex
1 or 2 is observed in most decompostion mixtures (entries 1−
3, Table 2). The key intermediate in the formation of the final
alkynyl product 9 must be the cis-dialkynyl complex C, which
we did not detect, and it could be formed by two different
pathways: (i) ligand rearrangement in complex 7 (or 8); (ii)
transmetalation of an alkynyl fragment from [Cu(CCnBu)L]
to 7. A reductive elimination in C leads to 9. The excess ligand
induces the formation of cationic species [Pd(η3-C3H5)L2]+,
represented as a cation for C, where nucleophilic attack on the
allyl ligand is quite favorable; thus, the presence of small
1
the H NMR spectrum of the complexes (specially 7) changes
as the decomposition proceeds and L is released.
In conclusion, stable heterometallic Pd−Cu and Pd−Ag
complexes can be formed in the transmetalation of alkynyl
ligands from the group 11 metals to palladium. This is a stage of
transmetalation where the carrier metal stays bound to the
transferred fragment, and it can be completely eliminated by
addition of soft ligands such as phosphines and arsines. Amines
do not have the same effect, and elimination of the group 11
metal does not occur. A slow reductive elimination in
[PdR(CCnBu)L2] complexes, as is the extreme case with R
a
Table 2. Decomposition Data (%) for Complexes 3−6 in the Presence of an Excess of L
entry
complex
L
Pd:L (mol)
time
5 h
9
10
1 or 2
C3H5OH
11
1
2
3
4
3a
AsPh3
PPh3
1:10
1:3
34
33
31
22
38
38
52
28
17
17
6
b
4a
12 h
2 h
10
46
5
AsPh3
PPh3
1:10
1:3
b
6
7 days
18
a
b
Molar percentages were determined by integration of 1H NMR signals. A small amount of unidentified allylic compounds was detected, which is
responsible for the total percentage being lower than 100% (each unidentified compound less than 3%).
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(s, 3C; Cpara PPh3), 128.7 (d, 3JP−C = 10.1 Hz, 6C; Cmeta PPh3), 123.6
= η3-allyl, drives the reaction quite effectively to the
homocoupling of alkynyls, which is a major competitive process
in Sonogashira couplings.
2
2
(s, C5), 119.0 (d, JP−C = 6.0 Hz; C2), 90.2 (d, JP−C = 24.1 Hz; C4),
2
2
69.0 (d, JP−C = 3.0 Hz; C3), 68.3 (d, JP−C = 31.2 Hz; C1), 31.7 (s,
C7), 22.9 (s, C6), 21.8 (s, C8), 13.8 (s, C9).
4b: off-white solid; 75% yield. Anal. Calcd for C58H50P2Cl2Cu2Pd2:
C, 57.10; H, 4.14. Found: C, 57.42; H, 4.37. H NMR (400 MHz, δ,
1
EXPERIMENTAL SECTION
■
1
General Methods. H, 13C{1H}, and 31P{1H} NMR spectra were
CDCl3): 7.63−7.51 (m, 6H; Hortho PPh3), 7.50−7.37 (m, 9H; Hmeta
,
Hpara PPh3), 7.20−7.07 (m, 3H; Hmeta, Hpara Ph), 7.02 (m, 2H; Hortho
Ph), 5.46 (br, 1H; H2), 5.00 (br, 1H; H1syn), 3.53 (br, 1H; H3syn), 3.33
(br, 1H; H1anti), 2.90 (d, J = 12.4 Hz, 1H; H3anti); 31P{1H} NMR
(161.97 MHz, δ, CDCl3): 26.3 (s); 13C{1H} NMR (100.61 MHz, δ,
CDCl3, 243 K): 133.9 (d, 2JP−C = 12.1 Hz, 6C; Cortho PPh3), 132.4 (d,
1JP−C = 42.3 Hz, 3C; Cipso PPh3), 131.4 (s, 2C; Cortho Ph), 130.9 (s,
3C; Cpara PPh3), 128.9 (d, 3JP−C = 11.1 Hz, 6C; Cmeta PPh3), 128.1 (s,
2C; Cmeta Ph), 127.7 (s, 1C; Cpara Ph), 124.7 (s, 1C; Cipso Ph), 122.4
(s, C5), 119.4 (d, 2JP−C = 6.0 Hz; C2), 102.5 (d, 2JP−C = 24.1 Hz; C4),
recorded on Bruker AC-300, ARX-300, and AV-400 spectrometers.
Chemical shifts (in δ units, ppm) were referenced to Me4Si (1H and
13C) and H3PO4 (85%, 31P). The spectral data were recorded at 293 K
unless otherwise noted. Signal assignments were made with the aid of
1
heteronuclear H−13C HMQC and HMBC experiments. IR spectra
were recorded on Perkin-Elmer IR 883 and Perkin-Elmer FT-IR
1720X spectrophotometers. C, H, and N elemental analyses were
performed on a Perkin-Elmer 2400 CHN microanalyzer.
All of the manipulations were carried out under an atmosphere of
nitrogen using standard Schlenk techniques. Solvents were dried using
an SPS PS-MD-5 solvent purification system or distilled from
appropriate drying agents under nitrogen, prior to use. The
compounds copper(I) butylacetylide,23 copper(I) phenylacetylide,23
silver butylacetylide,4a,24 SnBu3(CCnBu),25,26 [{Pd(η3-C3H5)(μ-
Cl)}2],27 [Pd(η3-C3H5)Cl(AsPh3)] (1),22a,28 [Pd(η3-C3H5)Cl(PPh3)]
(2),28 and [PdCl2(PPh3)2]29 were prepared according to literature
methods. The complex [Pd(η3-C3H5)(CCnBu)(AsPh3)] (8) has
been described before.6 Allyl alcohol and 9 are commercially available
and their NMR spectra were compared with authentic samples.
Synthesis of the Heterometallic Complexes [CuCl{Pd(η3-
C3H5)(CCR)L}]2. [CuCl{Pd(η3-C3H5)(CCnBu)(AsPh3)}]2 (3a).
[Cu(CCnBu)]n (0.2706 g, 1.870 mequiv) was added to a solution
of [Pd(η3-C3H5)Cl(AsPh3)] (0.9147 g, 1.870 mmol) in CH2Cl2 (25
mL) at room temperature. The reaction mixture was stirred until the
copper(I) acetylide dissolved and the initial yellow solution slowly
turned dark reddish. After this time, the mixture was filtered through
activated carbon and Celite and then evaporated to dryness. Et2O (10
mL) was added to the residue, and a grayish solid was obtained, which
was filtered, washed with Et2O (2 × 5 mL), and air-dried. Yield:
0.9270 g (78%). The solid can be recrystallized from a mixture of
acetone and hexane at −20 °C. Anal. Calcd for C54H58As2Cl2Cu2Pd2:
2
69.8 (s, C3), 68.4 (d, JP−C = 31.2 Hz; C1).
Synthesis of the Heterometallic Complexes [AgCl{Pd(η3-
C3H5)(CCnBu)L}2]. Detection of [AgCl{Pd(η3-C3H5)(CCnBu)-
(AsPh3)}2] (5). [Pd(η3-C3H5)Cl(AsPh3)] (0.0200 g, 0.041 mmol) was
dissolved in CDCl3 (0.6 mL) under nitrogen at 243 K in a 5 mm NMR
tube. Silver butylacetylide (0.0085 g, 0.045 mequiv) was added to the
1
solution. The reaction was then monitored by H NMR spectroscopy
1
at 243 K, and the formation of complex 5 was observed. H NMR
(400 MHz, δ, CDCl3, 243 K): 7.60−7.45 (m, 6H; Hortho AsPh3), 7.44−
7.32 (m, 9H; Hmeta, Hpara AsPh3), 5.33 (m, J = 13.2, 6.0 Hz, 1H; H2),
4.67 (d, J = 6.5 Hz, 1H; H1syn), 3.78 (d, J = 6.5 Hz, 1H; H3syn), 3.25 (d,
J = 13.2 Hz, 1H; H1anti), 2.88 (d, J = 13.2 Hz, 1H; H3anti), 2.19 (t, J =
7.2 Hz, 2H; H6), 1.19 (m, 2H; H7), 1.06 (m, 2H; H8), 0.66 (t, J = 7.3
Hz, 3H; H9). 13C{1H} NMR (100.61 MHz, δ, CDCl3, 243 K): 134.4
(s, 3C; Cipso AsPh3), 133.4 (s, 6C; Cortho AsPh3), 130.1 (s, 3C; Cpara
AsPh3), 129.0 (s, 6C; Cmeta AsPh3), 123.9 (a, C5), 117.3 (s, C2), 79.5
(a, C4), 67.2 (s, C3), 64.8 (s, C1), 32.3 (s, C7), 21.8 (s, C6), 21.5 (s,
C8), 13.9 (s, C9).
Synthesis of [AgCl{Pd(η3-C3H5)(CCnBu)(PPh3)}2] (6). Silver
butylacetylide (0.06 g, 0.317 mequiv) was added to a solution of
[Pd(η3-C3H5)Cl(PPh3)] (0.1282 g, 0.288 mmol) in CH2Cl2 (10 mL)
at room temperature. The reaction mixture was stirred until total
dissolution of the silver acetylide occurred. The initial yellow
suspension slowly turned dark. The mixture was filtered through
activated carbon and Celite and then evaporated to dryness. Et2O (10
mL) was added to the residue, and a grayish solid was obtained which
was filtered, washed with Et2O (2 × 5 mL), and air-dried (62% yield).
The solid can be recrystallized from a mixture of acetone and hexane at
−20 °C. Anal. Calcd for C54H58AgClP2Pd2: C, 57.64; H, 5.21. Found:
1
C, 51.15; H, 4.62. Found: C, 50.95; H, 4.42. H NMR (300 MHz, δ,
CDCl3): 7.53−7.46 (m, 6H; Hortho AsPh3), 7.45−7.37 (m, 9H; Hmeta
,
Hpara AsPh3), 5.35 (br, 1H; H2), 4.95 (br, 1H; H1syn), 3.82 (br, 1H;
H3syn), 3.33 (d, J = 13.4 Hz, 1H; H1anti), 2.86 (d, J = 13.4 Hz, 1H;
H3anti), 2.20 (t, J = 7.2 Hz, 2H; H6), 1.32−1.08 (m, 4H; H7, H8), 0.73
(t, J = 7.2 Hz, 3H; H9); 13C{1H} NMR (75.4 MHz, δ, CDCl3, 243 K):
133.9 (s, 3C; Cipso AsPh3), 133.2 (s, 6C; Corto AsPh3), 130.2 (s, 3C;
Cpara AsPh3), 128.9 (s, 6C; Cmeta AsPh3), 124.4 (s, C5), 117.3 (s, C2),
88.5 (s, C4), 67.1 (s, C3), 66.9 (s, C1), 31.6 (s, C7), 22.8 (s, C6), 21.7
(s, C8), 13.6 (s, C9).
1
C, 57.78; H, 5.46. H NMR (400 MHz, δ, CDCl3, 243 K): 7.60−7.35
(m, 15H; PPh3), 5.39 (m, J = 12.4, 6.5 Hz, 1H; H2), 4.67 (t, J = 5.8
3
Hz, JP−H = 5.8 Hz, 1H; H1syn), 3.44 (d, J = 7.2 Hz, 1H; H3syn), 3.18
3
(dd, J = 11.6 Hz, JP−H = 11.6 Hz, 1H; H1anti), 2.85 (d, J = 13.2 Hz,
Complexes 3b and 4a,b were prepared in the same way by reacting
the corresponding palladium complex 1 or 2 and the copper alkynyl.
3b: off-white solid; 77% yield. Anal. Calcd for C58H50As2Cl2Cu2Pd2:
1H; H3anti), 2.15 (t, J = 6.8 Hz, 2H; H6), 1.15 (m, 2H; H7), 1.03 (m,
2H; H8), 0.66 (t, J = 7.2 Hz, 3H; H9). 31P{1H} NMR (161.97 MHz, δ,
CDCl3, 243 K): 25.5 (s). 13C{1H} NMR (100.61 MHz, δ, CDCl3, 243
K): 133.8 (d, 2JP−C = 12.1 Hz, 6C; Cortho PPh3), 132.3 (d, 1JP−C = 43.3
1
C, 53.27; H, 3.86. Found: C, 53.53; H, 4.19. H NMR (400 MHz, δ,
CDCl3): 7.53 (m, 6H; Hortho AsPh3), 7.46−7.35 (m, 9H; Hmeta, Hpara
AsPh3), 7.22−7.10 (m, 3H; Hmeta, Hpara Ph), 7.06 (m, 2H; Hortho Ph),
5.44 (br, 1H; H2), 5.07 (br, 1H; H1syn), 3.92 (br, 1H; H3syn), 3.41 (br,
1H; H1anti), 2.95 (br, 1H; H3anti); 13C{1H} NMR (100.61 MHz, δ,
CDCl3, 243 K): 134.1 (s, 3C; Cipso AsPh3), 133.4 (s, 6C; Cortho AsPh3),
131.3 (s, 2C; Cortho Ph), 130.2 (s, 3C; Cpara AsPh3), 129.1 (s, 6C; Cmeta
AsPh3), 128.1 (s, 2C; Cmeta Ph), 127.8 (s, 1C; Cpara Ph), 124.5 (s, 1C;
Cipso Ph), 123.2 (a, C5), 117.8 (s, C2), 100.7 (a, C4), 67.7 (s, C3), 67.4
(s, C1).
3
Hz, 3C; Cipso PPh3), 130.7 (s, 3C; Cpara PPh3), 128.7 (d, JP−C = 10.1
Hz, 6C; Cmeta PPh3), 123.9 (s, C5), 119.1 (d, 2JP−C = 5.0 Hz; C2), 77.9
(d, C4) (signals overlapped with solvent resonances), 69.2 (s, C3), 66.7
2
(d, JP−C = 33.2 Hz; C1), 32.3 (s, C7), 21.8 (s, C8), 21.5 (s, C6), 13.8
(s, C9).
Characterization of [Pd(η3-C3H5)(CCnBu)(PPh3)] (7). A 5 mm
NMR tube was charged with SnBu3(CCnBu) (0.0104 g, 0.028
mmol) and [Pd(η3-C3H5)Cl(PPh3)] (2; 0.0027 g, 0.006 mmol). Then
CDCl3 (0.6 mL) was added under nitrogen at 243 K. The reaction was
then monitored by 1H NMR spectroscopy at this temperature, and the
formation of complex 7 was observed. 1H NMR (400 MHz, δ, CDCl3,
243 K): 7.70−7.55 (m, 6H; PPh3), 7.45−7.33 (m, 9H; PPh3), 5.29 (m,
J = 13.6, 7.2 Hz, 1H; H2), 4.40 (t, 3JP−H = 6.8 Hz, 1H; H1syn), 3.22 (dd,
4a: off-white solid; 86% yield. Anal. Calcd for C54H58P2Cl2Cu2Pd2:
C, 54.97; H, 4.96. Found: C, 54.86; H, 4.79. H NMR (400 MHz, δ,
1
CDCl3): 7.60−7.47 (m, 6H; Hortho PPh3), 7.46−7.35 (m, 9H; Hmeta
,
Hpara PPh3), 5.39 (br, 1H; H2), 4.88 (a, 1H; H1syn), 3.45 (br, 1H;
H3syn), 3.26 (br, 1H; H1anti), 2.83 (d, J = 13.2 Hz, 1H; H3anti), 2.16 (t, J
= 7.2 Hz, 2H; H6), 1.21 (m, 2H; H7), 1.14 (m, 2H; H8), 0.71 (t, J =
7.2 Hz, 3H; H9); 31P{1H} NMR (161.97 MHz, δ, CDCl3): 26.4 (s);
13C{1H} NMR (100.61 MHz, δ, CDCl3, 243 K): 133.8 (d, 2JP−C = 13.1
Hz, 6C; Cortho PPh3), 132.2 (d, 1JP−C = 43.3 Hz, 3C; Cipso PPh3), 130.7
3
J = 7.2, 2.0 Hz, 1H; H3syn), 3.00 (dd, J = 13.5, JP−H = 10.7 Hz, 1H;
H1anti), 2.70 (d, J = 13.1 Hz, 1H; H3anti), 2.25 (t, J = 7.2 Hz, 2H; H6),
1.30−1.15 (m, 2H; H7), 1.14−0.95 (m, 2H; H8), 0.65 (t, J = 7.4 Hz,
3H; H9). 31P{1H} NMR (161.97 MHz, δ, CDCl3, 243 K): 24.6 (s).
5
dx.doi.org/10.1021/om4005498 | Organometallics 2014, 33, 1−7

Organometallics
Article
13C{1H} NMR (100.61 MHz, δ, CDCl3, 243 K): 134.1 (d, 2JP−C = 13.1
AUTHOR INFORMATION
Corresponding Author
*E-mail for A.C.A.: albeniz@qi.uva.es.
Notes
■
1
Hz, 6C; Cortho PPh3), 133.7 (d, JP−C = 41 Hz, 3C; Cipso PPh3), 130.7
(d, 4JP−C = 2 Hz, 3C; Cpara PPh3), 128.3 (d, 3JP−C = 10.1 Hz, 6C; Cmeta
2
2
PPh3), 118.8 (d, JP−C = 6.0 Hz; C2), 117.2 (s, C5), 92.3 (d, JP−C
=
24.1 Hz; C4), 67.8 (s, C3), 63.5 (d, JP−C = 34 Hz; C1), 32.4 (s, C7),
2
21.9 (s, C8), 21.4 (s, C6), 14.0 (s, C9).
The authors declare no competing financial interest.
In the presence of an excess of PPh3, 7 shows a fluxional behavior
that exchanges free and coordinated phosphine and H3 syn and anti
protons.
ACKNOWLEDGMENTS
Financial support from the Spanish MINECO (DGI, Grant
CTQ2010-18901/BQU), MEC (FPU fellowship to I.M.), and
■
7 in the Presence of PPh3 (Pd/PPh3 = 1/10). 1H NMR (400 MHz,
δ, CDCl3, 243 K): 8.00−7.00 (m, PPh3), 5.43 (m, 1H; H2), 4.60 (d, J
= 6.4 Hz, 1H; H1syn), 3.18 (d, J = 13.6 Hz, 1H; H1anti), 3.10 (b, 2H;
H3syn, H3anti) 2.45 (t, J = 7.2 Hz, 2H; H6), 1.40 (m, 2H; H7), 1.22 (m,
2H; H8), 0.83 (t, J = 7.2 Hz, 3H; H9). 13C{1H}NMR (100.61 MHz, δ,
CDCl3, 243 K): 138.0−128.0 (36C; PPh3), 119.0 (s, 2C; C2), 117.3 (s,
C5), 92.5 (s, C4), 68.1 (s, C3), 63.7 (s, C1), 32.6 (s, C7), 22.1 (s, C8),
21.6 (s, C6), 14.4 (s, C9).
the Junta de Castilla y Leon
acknowledged.
́
(Grant VA373A11-2) is gratefully
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an ORTEP figure for 4b and additional experiments and
selected spectra of complexes. This material is available free of
charge via the Internet at http://pubs.acs.org.
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