Cis -1,2-Bis(diphenylphosphino)ethylene copper(i) catalyzed C-H activation and carboxylation of terminal alkynes

Article abstract of DOI:10.1039/c7nj03038j

The reaction of cis-1,2-bis(diphenylphosphino)ethylene (dppet) with CuX (X = CN, SCN) in 1:1 M molar ratio in DCM-MeOH (50:50 V/V) under refluxing conditions gave two dimeric Cu(i) complexes, viz. [Cu₂(μ-CN)₂(κ²-P,P-dppet)₂] (1) and [Cu₂(μ₂-SCN)₂(κ²-P,P-dppet)₂] (2). These complexes have been characterized by elemental analyses, IR, ¹H and ³¹P NMR, and electronic absorption spectroscopies, and ESI-MS. The molecular structure of 2 was confirmed by single crystal X-ray diffraction, which indicated that 2 exists as a centrosymmetric dimer in which the two copper centers are bonded to two dppet ligands and two bridging thiocyanate groups in a μ₂-manner. The electrochemical properties of 1 and 2 were studied by cyclic voltammetry. Both the complexes exhibited strong luminescence properties in the solution state at ambient temperature. Both the complexes were found to be efficient catalysts for the conversion of terminal alkynes into propiolic acids with CO₂. Owing to their excellent catalytic activity, the reactions proceed at atmospheric pressure and ambient temperature (25 °C). The catalytic products were obtained in excellent yields (90-97%) by using the complex loading of 1 mol%.

Full text of DOI:10.1039/c7nj03038j

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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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cis-1,2-bis(diphenylphosphino)ethylene copper(I) catalyzed C-H
activation and carboxylation of terminal alkynes
Received 00th January 20xx,
Accepted 00th January 20xx
a*
c
a*
b
c*
Manoj Trivedi, Jacob R. Smreker, Gurmeet Singh, Abhinav Kumar, Nigam P. Rath
The reaction of cisꢀ1,2ꢀbis(diphenylphosphino)ethylene (dppet) with CuX (X = CN, SCN) in 1:1 M molar ratio in DCMꢀ
DOI: 10.1039/x0xx00000x
2
MeOH (50:50 V/V) under refluxing condition gave two dimeric Cu(I) complexes viz. [Cu
2
(
ꢀꢀCN)
2
(k ꢀP,Pꢀdppet)
2
] (1), and
www.rsc.org/
2
1
31
[Cu
2
(
2
ꢀ ꢀSCN)
2
(k ꢀP,Pꢀdppet)
2
] (2). These complexes have been characterized by elemental analyses, IR, H and P NMR,
electronic absorption spectroscopy and ESIꢀMS. The molecular structure of 2 was confimed by single crystal Xꢀray
diffraction which indicated that 2 exists as a centrosymmetric dimer in which the two copper centers are bonded to two
dppet ligands and two bridging thiocyanate groups in
2
ꢀ ꢀmanner. The electrochemical properties of 1 and 2 were studied by
cyclic voltammetry. Both the complexes exhibited strong luminescence properties in the solution state at ambient
temperature. Both the complexes were found to be efficient catalysts for the conversion of terminal alkynes into propiolic
2
acids with CO . Owing to their excellent catalytic activity, the reactions proceed at atmospheric pressure and ambient
temperature (25°C). The catalytic products were obtained in excellent yields (90ꢀ97%) by using the complex loading of 1
mol%.
Introduction
bis(diphenylphosphino) ethylene copper(I) complexes has
emerged from the finding that little had been explored in
Bidentate diphosphines have received significant research
interest due to their extensive applications as ligands for a wide
variety of transition metal catalysed transformations. In the
presented, we have chosen the rigid diphosphine cisꢀ1,2ꢀ
bis(diphenylphosphino) ethylene
transition metal complexes of cisꢀ1,2ꢀbis(diphenylphosphino)
ethylene (dppet) had displayed novel and markedly different
bonding properties when compared to complexes of other
diphosphines complexes having saturated backbone. For dppet
complexes, solution P NMR investigations , solid state
respect to the binuclear structural form of its complexes with
simple salts, particularly copper(I) salts and their application in
1
ꢀ3
1
4
catalysis . Previous reports of simple CuX: dppet (1:1) adducts
2
comprises of: CuI: dppet (1:1) (of the form [Cu (
µ
ꢀI)2(
κ ꢀP,Pꢀ
2
(dppet) ligand because
1
5
dppet) ] and [CuI(dppet)(CH CN)] but no structural report
2
3
had been published till date dealing with CuX: dppet (1:1) (X=
CN, SCN, Cl, Br). Similar adducts for HAuCl : dppet (1.5:1)
4
1
6
4
had been reported by Eggleston and coꢀworkers. Various
Cu(I) complexes containing phosphine, ꢀheterocyclic carbene,
imidazole, triazole, hybrid nitrogenꢀsulfur ligands have been
3
1
5ꢀ7
N
1
97
8
31
6,8
Au Mossbauer and P CPꢀMAS NMR studies and single
crystal Xꢀray structure determinations for [Cu(dppet) ]X for
]X for X=
1
7
found to be the versatile catalysts. Currently, the serious issue
of our generation is the emission of CO which causes global
warming and as a consequence imposes serious environmental
2
5
9
10
2
X=PF
SnPh
I , BF
6
,
BF
4
1
,
and CuCl
2
;
[Ag(dppet)
; [Au(dppet) ]X for X=PF
support the formation of stable
2
1
12
12
6
3
(NO
3
)
2
13
, ClO
4
, and BF
4
2
6
,
1
8
8
13
13
13
problems. One of the ways to mitigate this problem is by
using carbon dioxide as C building block in organic synthesis
because it is an abundant, renewable carbon source and an
4 4
, Cl , Br , and BPh
1
tetrahedral bis(chelated) cations in both solid as well as in
solution state. Recently another incentive to study cisꢀ1,2ꢀ
1
9
environmentally friendly chemical reagent. Significant efforts
have been devoted towards exploring the technologies for CO
2
transformation, but harsh and severe reaction condition is one
of the major limitations to implement these technologies for
1
9,20
practical applications.
efficient catalysts systems for CO
conditions is highly desired, especially for real world
applications. One of the best strategies for CO conversion is
the synthesis of propiolic acids through the CꢀH bond activation
Therefore, the development of
2
utilization under mild
2
2
1
2 1
of terminal alkynes with CO as a C building block because
the alkynyl carboxylic acid products can serve as important
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ARTICLE
Journal Name
2
2
ꢀ1
synthetic intermediates for further applications in medicinal M of complex versus Ag/AgCl at a scan rate of 100 mVs .
2
3
chemistry as well as in organic synthesis to give coumarins, GCMS studies were done with the Shimadzuꢀ2010 instrument
flavones, aminoalkynes, alkynylarenes, and arylidene containing a DBꢀ5/RtXꢀ5MSꢀ30Mt & 60Mt column of 0.25mm
oxindoles. Several procedures and catalysts, including both internal diameter. M is the mass of the cation.
2
4
+
2
1cꢀe,25
21a,26
homogenous
have been developed in this area, but either the reusability Complexes
problems or synthetic complications limits further application 1,2ꢀbis(diphenylphosphino)ethylene (dppet) was dissolved in
of these catalytic systems. Therefore design and syntheses of CH OH (15 mL), and CH Cl (15 mL) and a copper
and heterogeneous catalytic
systems, Syntheses of the complexes 1 and 2
, and were prepared as follows: 1 mmol of cis
1
2
ꢀ
3
2
2
efficient, inexpensive, and easy to prepare catalysts for these cyanide/thiocyanate (1 mmol) was then added. The resulting
types of reactions are urgently required. In the past decades, solution was refluxed for 24 hours. The resulting solution was
several interesting systems have been reported for metalꢀ filtered and left for slow evaporation. Yellow colour powder
2
7
28
mediated reductive carboxylation of alkynes , allenes , and and needle shaped crystals for complex
1
and
2 were obtained.
2
9
2
alkyenes with CO
2
to form carboxylic acids or esters. Synthesis of [Cu (µ-CN) (κ -P,P-dppet) ] (1).
2 2 2
However, most of those systems need either a stoichiometric
amount of transition metals as reactants or an excess amount of
organometallic reagents for transmetallation processes. An
alternative possibility to achieve the catalytic synthesis of
Yield: (0.776 g, 80%). Anal. Calc. for C54
44 2 4 2
H N P Cu : C,
6
6.74; H, 4.53; N, 2.88. Found: C, 66.82; H, 4.65; N, 2.92. IR
ꢀ1
(
cm , nujol):
ν
= 2960, 2923, 2873, 2112 (CN), 1990, 1733,
1
1
650, 1545, 1457, 1437, 1379, 1338, 1314, 1259, 1215, 1172,
carboxylic acid from CO
carboxylation. Recently, Nolan’s group had reported a goldꢀ
catalyzed CO carboxylation of CꢀH bonds of highly activated
2
is by direct CꢀH bond activation and
1
120, 1102 1069, 1025, 926, 879, 800, 746, 691, 662. H NMR
ppm, 400 MHz, CDCl , 298 K): 7.16ꢀ7.39 (m, 40H, J=3.0
Hz, Ph), 7.45ꢀ7.62 (m, 2H, CH=CH). P{ H}:
(
δ
3
2
31
ꢀ1
1
δ
11.23 (s)
3
0
arenes and heterocycles. The state of the art for the
3
ꢀ1
(
(
broad). UV/Vis:
5028). ESIꢀMS (m/z): 971.63 (M ).
λ
max
(
ε
[dm mol cm ]) = 284 (8777), 241
carboxylation of terminal alkynes has recently been published
+
2
1b
by Gooßen et al.
.
which suggests that it is possible to
2
Synthesis of [Cu
Yield: (0.725g, 70%). Anal. Calc. for C54
62.55; H, 4.25; N, 2.70; S, 6.18. Found: C, 62.79; H, 4.35; N,
2 2 2
(µ-SCN) (κ -P,P-dppet) ] (2).
perform carboxylation of terminal alkynes with various copper
and silver complexes, even at ppm loadings. Because of our
44 2 4 2 2
H N P S Cu : C,
3
1
interest in the area of copper chemistry , we decided to
investigate the catalytic transformation of CO to carboxylic
ꢀ1
2
.78; S, 6.32. IR (cm , nujol):
ν = 3734, 2373, 2341, 2109
2
(
1
SCN), 2066, 2042, 1652, 1540, 1474, 1431, 1304, 1259, 1182,
acids through CꢀH bond activation and carboxylation of
terminal alkynes in the presence copper(I) complexes
containing cisꢀ1,2ꢀbis(diphenylphosphino) ethylene (dppet) The
results of these investigations are presented herein.
1
091, 1023, 996, 727, 687, 608. H NMR (
δ ppm, 400 MHz,
CDCl , 298 K): 7.00ꢀ7.40 (m, 40H, J=6.8 Hz, Ph), 7.53ꢀ7.83
3
3
1
1
(
(
1
m, 2H, CH=CH). P{ H}: δ 30.03 (s) (sharp). UV/Vis: λ
max
3
ꢀ1
ꢀ1
ε
[dm mol cm ]) = 313 (28641), 241 (6017). ESIꢀMS (m/z):
+
035.78 (M ).
X-ray structure determination
Intensity data sets for was collected on a Bruker APEX II
CCD area detector diffractometer using graphite
monochromated MoꢀK radiation at 100(2) K. ApexII, and
Experimental section
2
a
Materials and Physical Measurements
α
All the synthetic manipulations were performed under oxygen SAINT software packages were used for data collection and
3
3
free nitrogen atmosphere. The solvents were purified and dried data integration for
2
.
The structure was solved by direct
3
2
before use by adopting the standard procedures. Copper(I) method using SHELXSꢀ97, and refined by full matrix leastꢀ
3
3
cyanide,
Copper(I)
thiocyanate
and
cisꢀ1,2ꢀ squares with SHELXLꢀ2014. The nonꢀhydrogen atoms were
bis(diphenylphosphino)ethylene (all Aldrich) were used as refined with anisotropic thermal parameters. All the hydrogen
received. Elemental analyses were performed on a Carlo Erba atoms were treated using appropriate riding models. PLATON
Model EAꢀ1108 elemental analyser and data for C, H, N and S was also used for analyzing the intermolecular interactions and
3
4
are within ±0.4% of calculated values. Infrared spectra were stacking distances.
recorded using PerkinꢀElmer FTꢀIR spectrophotometer. Structure (CCDC 1543220): C54
Electronic and emission spectra of the complexes were obtained monoclinic, a = 28.3225(15), b= 9.7812(5), c = 18.6050(9) Å,
2
44 2 4 2 2
H N P S Cu , M = 1035.99,
3
on a Perkin Elmer Lambdaꢀ35 and Horiba Jobin Yvon
U
= 4820.8(4) Å , T = 100(2) K, space group C2/c, Z = 4,
1
31
1
Fluorologꢀ3 spectrofluorometer, respectively. H, and P{ H} 70850 reflections measured, 11709 unique (Rint = 0.0719),
2
NMR spectra were recorded on a JEOL ALꢀ400 FTNMR which were used in all calculations. The final w
instrument using tetramethylsilane and phosphoric acid as 0.0960 (all data).
internal standards, respectively. Mass spectral data were
R(F ) was
General Experimental Procedure for Carboxylation of Terminal
recorded using
a
Waters micromass LCT Mass
Alkynes
Spectrometer/Data system. Electrochemical property of the
complexes were measured by cyclic voltammetry using CuX(X=CN, SCN)/complexes
2 3
1ꢀ2 (1 mol%) and Cs CO (1.5
platinum as working electrode and the supporting electrolyte mmol) were added to DMF (5 mL) in a reaction tube (10 mL).
was [NBu
4
]ClO
4
(0.1 M) in dichloromethane solution of 0.001 A CO
2
(balloon) and 1 mmol of terminal alkynes were
2
| J. Name., 2012, 00, 1-3
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introduced into the reaction mixture under stirring. The These chemical shifts are within the range and are comparable
6
progress of the reaction was monitored by TLC. After to copper(I) complexes containing chelating dppet ligands. The
completion of the reaction, the reaction mixture was diluted NMR data for
with water (15 mL) and the solid residue was separated via four equivalent phosphorus atoms. This means that the two
centrifugation. The mixture was washed with CH Cl and the different diphosphine bridges indicated in the Xꢀray structure of
aqueous layer was acidified with concentrated HCl to pH=1 at vide infra) become chemically similar in solution at room
1 and 2 are consistent with structure showing
2
2
2
(
low temperature and then extracted with ethyl acetate. The temperature. The electronic absorption spectroscopy in
combined organic layers were washed with saturated NaCl dichloromethane solution shows that both complexes exhibit
solution, dried over Na SO and filtered. The solvent was two bands at 284ꢀ313 nm and 241 nm in dichloromethane
2 4
removed in vacuum to obtain the carboxylic acid products.
solution (Fig. 1) which may be attributed to the charge transfer
transitions.
Results and discussion
Synthesis
The reactions of CuX (X= CN, SCN) with cisꢀ1,2ꢀ
bis(diphenylphosphino)ethylene
(dppet)
ligand
in
a
dichloromethane: methanol mixture (50:50 V/V) in equimolar
ratio under refluxing conditions gave neutral bimetallic
2
complexes with the formulations [Cu
2
(
µꢀX)
2
(
κ
ꢀ
P
,P
ꢀdppet)
2
]
(X= CN(1), SCN(2)) in good yield (Scheme 1).
Ph
Ph
Cu
Ph
Ph
Ph
Ph
P
P
P
X
ꢀ3
Fig. 1
.
UVꢀVis spectra of the complexes 1 and 2 in 10 DCM solution.
CH OH+CH Cl (1:1)
3
2
2
Cu
Ph
+
CuX
Refluxing
X
Both the complexes were non emissive when excited at 241 nm
However, on excitation at 284ꢀ313 nm the complexes exhibited
one broad emissions at 363ꢀ398 nm (Fig. 2). Consistent with
P
P
P
Ph
Ph
Ph
Ph
Ph
3
6
X= CN, SCN
the previously reported copper(I) complexes , we tentatively
assigned the emission of these Cu(I) complexes as being a
combination of a XLCT, and CC. But LC transitions may be
ruled out since metalꢀmetal bonding is negligible and cyanide
X= CN(1), X= SCN(2)
Scheme 1. Synthetic Routes to Complexes 1ꢀ2.
3
6b
and thiocyanide has a fairly large band gap. Pike et al.
reported that the emission band at 392 nm for CuCN should be
ascribed to invoke MC transitions of the type 3d→(4p,4s).
These complexes are airꢀstable, nonꢀhygroscopic solids and
soluble in dimethylformamide, dimethylsulfoxide and
halogenated solvents but insoluble in petroleum ether and
They also reported that the peak broadening for (CuCN)20(pip)
pip = piperazine), compared to that of CuCN, were due to the
7
(
diethyl ether. Infrared spectrum of complex
1 exhibited
incorporation of pip ligands and a heterogeneous array of
copper(I) centers. Taking the position and broad shape into
characteristic band corresponding to N of the bridging
νC≡
ꢀ1
†
cyanide group at 2112 cm (Fig. Sꢀ1, ESI ). The appearance
only one N band indicated the presence of only one type of
cyanide bridge between copper(I) centers. In
associated with bridging SCN group appeared at 2109 cm
account, the emission of
1 and 2 may also be reasonable and
νC≡
consistent with the MC transitions influenced by the existence
3
5
2
the band
3
6
of dppet ligands. The redox behaviour of the complexes were
studied through cyclic voltammetry (Fig. 3). The cyclic
voltammograms of both the complexes were first compared
with that of their respective ligand to identify whether any
redox phenomenon is arising specifically from the ligand and
ꢀ1
†
(
Fig. Sꢀ2, ESI ) which is in accordance with those reported in
3
5
1
literature for bridging pseudohalide groups. In H NMR
spectra of the complexes , and , the ꢀCH=CH protons of
dppet ligands resonated as a multiplet in the range of 7.45ꢀ
.83 ppm. The phenyl ring protons of dppet ligands resonated
as a multiplets at
the P{ H} NMR spectra of both the complexes showed a
single resonance ( 11.23(1), 30.03(2) ppm) for dppet ligands
1
2
δ
not from the copper(I) center. The complex
reversible oxidations at ꢀ1.03, ꢀ0.574, 0.081 and 1.88 V,
respectively. Complex exhibits similar behaviour with four
1 shows four quasiꢀ
7
†
δ 7.00ꢀ7.40 ppm (Fig. Sꢀ3 and Sꢀ4, ESI ). In
2
3
1
1
distinct and separate oxidation couples at ꢀ0.995, ꢀ0.655, 0.760
and 1.55 V. The oxidation wave at 1.55 to 1.88 V corresponds
to the copper(I/II) oxidation. The rest of the oxidation waves
are arising because of the structure of the chelating ligand
δ
indicating that all the phosphorus atoms were chemically
†
equivalent (Fig. Sꢀ5 and Sꢀ6, ESI ). This occurs downfield
3
1
compared to the P NMR signal of the free ligand (δ
P
for dppet
which possess C=C
π bonds.
4
31 63/65
is ꢀ21.95 ppm). The Pꢀ
Cu couplings were not resolved.
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P(1)=125.05(4)°, N(1)ꢀCu(1)ꢀP(2)=111.35(4)°, P(2)ꢀCu(1)ꢀ
#
1
#1
S(1) =118.442(18)°, P(1)ꢀCu(1)ꢀS(1) =104.955(16)°]. This is
because of the strained fourꢀmembered Cu (SCN) ring and due
The CuꢀS, CuꢀN
and CuꢀP bond distances are 2.3561(4) Å, 1.9524(13) Å and
2
2
5
,6,9,10,15
to steric hindrance of the dppet ligand.
2
.2520(4)ꢀ2.2495(4) Å, respectively and are comparable with
5
,6,9,10,15
other copper derivatives with dppet ligand.
The SꢀCꢀN
bond angle is 179.17(16) which confirmed that thiocyanate
groups are linearly coordinated to each copper(I) center. The Sꢀ
C and CꢀN bond distances fall in the range of 1.6472(16) Å and
1
.1575(19) Å, respectively. These distances are within the
3
8
reported range. The CꢀC distance in the ethylene bridge is
1
.327(2) Å and is within the range reported for the cis
ꢀ
3
9,16
ethylene bridged structure.
The PCH=CHP planes are
orthogonal to the copper centers. The dppet ligands adopts
essentially the same conformation with a pseudo twofold axis
of symmetry lying in the PCH=CHP plane and is perpendicular
Fig. 2. Emission spectra of complexes 1 and 2 in DCM at 284 to 313 nm.
to C=C. Crystal packing in complex
hydrogen bond interactions. The contact distance for CꢀH
interactions is 3.131Å (See Sꢀ10, ESI†).
2
is stabilised by CꢀH
⋯
⋯
S
S
Fig. 4. Molecular structure of 2. Selected bond lengths [Å] and angles [°]: Cu(1)ꢀN(1)
#
1
1
.9524(13), Cu(1)ꢀP(2) 2.2495(4), Cu(1)ꢀP(1) 2.2520(4), Cu(1)ꢀS(1) 2.3561(4), S(1)ꢀ
#
1
Cu(1) 2.3561(5), S(1)ꢀC(3) 1.6472(16), N(1)ꢀC(3) 1.1575(19), C(1)ꢀC(2) 1.327(2),
N(1)ꢀCu(1)ꢀP(2) 111.35(4), N(1)ꢀCu(1)ꢀP(1) 125.05(4), P(2)ꢀCu(1)ꢀP(1) 90.936(15),
#
1
#1
N(1)ꢀCu(1)ꢀS(1)
S(1) 104.955(16), N(1)ꢀC(3)ꢀS(1) 179.17(16).
106.43(4),
P(2)ꢀCu(1)ꢀS(1)
118.442(18),
P(1)ꢀCu(1)ꢀ
#
1
4 4
Fig. 3. Cyclic voltammogram for the complexes 1, and 2 in DCM/0.1 M [NBu ]ClO at
−1
1
00 mV s scan rate.
Catalytic Performances for the conversion of
terminal alkynes into propiolic acids with CO
2
Crystal Structure
The comparative catalytic activities of the CuX (X=CN, SCN)
and Cu(I) complexes ( and ) were assessed for CO fixation
The molecular structure of complex
2
with atomic numbering
crystallizes in
monoclinic system with C2/c space group. The molecular
structure of revealed a centrosymmetric dimeric unit with the
1
2
2
scheme is presented in Fig. 4. Complex
2
with terminal alkynes into propiolic acids. In the initial
investigation, the carboxylation of phenylacetylene as a model
reaction had been performed to study the influence of various
solvents, loadings, bases and reaction times on the reaction. It
can be seen that, without copper source, no reaction taken place
2
two thiocyanate groups bridging the two copper centers. The
structural chemistry of this copper(I) complex can be compared
with that of the analogous copper(I) complexes [Cu(dppet)
2
]X
(
Table 1, entry 1). Also no reaction occurred in the presence of
isolated dppet and dppe ligands (entry 2 & 3). Table 1 shows
the generation of 3ꢀphenylpropiolic acid from CO (1 atm) and
phenylacetylene at room temperature in the presence of CuX
X= CN, SCN) as well as complexes and . The yield in DMF
was found to be higher in comparison to those obtained in
DMSO, CH CN, chloroform, NMP, 1,4ꢀdioxane (entry 4, 8ꢀ
2). We have also checked the effects of catalyst loadings on
5
9
10
15
6 4 2 2
for X=PF , BF , CuCl , [Cu(ꢀꢀI)(dppet)]
and others
3
7
polymorphs of this compound. The tetrahedral coordination
around the copper atoms is defined by two P atoms of the
chelating dppet ligand [CuꢀP bond lengths = 2.2520(4) and
2
(
1
2
2
1
.2495(4) Å] and two thiocyanate groups [S(1)ꢀC(3)=
.6472(16) Å, N(1)ꢀC(3)= 1.1575(19) Å]. The P1ꢀCuꢀP2 bite
3
angle is 90.936(15)°, which is marginally larger than those
found in Cu(I) complexes containing dppet ligand.
other bond angles in are rather distorted [N(1)ꢀCu(1)ꢀ
1
5
,6,9,10,15
The
the outcome of the reaction in the presence of 1, 2, 3 and 5
2
4
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Journal Name
ARTICLE
mol% of CuCN (entry 4ꢀ7). For 1 mol% of CuCN, 3ꢀ cyclohexylacetylene, ethynyltrimethylsilane, 1ꢀheptyne and 1ꢀ
phenylpropiolic acid was obtained in good yields (50%). heptenꢀ6ꢀyne, the desired yield was 91ꢀ95%. In comparison to
However, significant decrease in yield was observed with the previously reported carboxylation methods for catalysis of
4
0ꢀ41
increase in the catalyst amount to 5 mol%. As shown in Table the carboxylation of terminal alkynes,
the present Cu(I)
1
, complexes and exhibited higher catalytic activity in complexes ( and ) appear to be more efficient than diPhPhenꢀ
1
2
1
2
4
0a
40b
comparison to CuX (X=CN, SCN). Furthermore, the catalytic Cu(PPh
performance of CuX (X=CN, SCN) containing 1,2ꢀ
bis(diphenylphosphino)ethane (dppe) was evaluated under
identical conditions. Interestingly, the CuX (X=CN, SCN)
containing dppe showed lower catalytic activity (entry 13 &
3
)
2
NO
3
and P(NHC)0.5(NHCꢀCuCl)0.5
.
Table 2. Synthesis of propiolic acid derivatives from CO
complex 2.
2
and terminal alkynes with
1
mol% Complex 2
R
+ CO
2
R
COOH
1
4). The catalytic activity of
1 was relatively inferior in
HCl
comparison to . The yield dropped to 27% when the base was
2
Entry
1.
Alkyne
Product
Yield
changed to K CO3 under similar conditions (entry 18). The
2
b
(
%)
other bases screened, NaOH, KOH, CsOH·H O, and Na CO ,
2
2
3
resulted in poor yields (entry 19 to 22). This indicates that
Cs CO is a superior base for this direct carboxylation reaction
2
3
97
COOH
of terminal alkynes with CO . With the optimized conditions
2
(
1.5 equiv Cs CO , 1 atm CO , DMF, 1 mol% catalyst, 25°C) in
2 3 2
hand, several typical alkyne substrates were subjected to this
carboxylation reaction (Table 2).
2
3
.
.
94
88
Cl
COOH
Cl
Table 1. Synthesis of 3ꢀphenylpropiolic acid from CO
2
and Phenylacetylene with
a
catalysts CuX(X=CN, SCN) and complexes 1ꢀ2.
F
F
COOH
CuX/Complex 1-2
+
CO
2
COOH
HCl
4
5
.
.
95
91
H
3
CO
COOH
b
H
3
CO
Entry
Catalyst
Solvent
DMF
DMF
DMF
DMF
DMF
DMF
DMF
Yield (%)
1.
2.
3.
4.
5.
6.
7.
8.
9.
No catalyst
dppet
dppe
0
0
0
3
H C
H C
3
COOH
1 mol% CuCN
50
40
25
20
20
35
10
5
2 mol% CuCN
3 mol% CuCN
6
.
92
5 mol% CuCN
O
1 mol% CuSCN
1 mol% CuSCN
1 mol% CuSCN
1 mol% CuSCN
2 mol% CuSCN
1 mol% CuCN/1 equiv. dppe
1 mol% CuSCN/1 equiv. dppe
1 mol% complex 1
1 mol% complex 2
1 mol% complex 2
1 mol% complex 2
1 mol% complex 2
1 mol% complex 2
1 mol% complex 2
1 mol% complex 2
3
CH CN
O
2
N
2
O N
DMSO
NMP
OH
1
1
1
1
1
1
1
0.
1.
2.
3.
4.
5.
6.
Dioxane
O
7
8
.
.
91
93
CHCl
3
10
25
30
91
97
0
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
OH
CH3
Si
CH
3
3
O
c
3
H C
Si
1
7.
H3C
d
OH
1
8
9
0
1
2
70
5
CH
e
CH
3
1
f
9.
95
94
COOH
2
4
4
g
2
h
2
3
a
Reaction conditions: Phenylacetylene (1.0 mmol), catalyst, Cs
2
CO
3
c
(1.5 mmol),
1
0.
COOH
b
CO
2
(1.0 atm), 25°C, solvent (5 mL), 12 h. Yield of isolated product. In absence of
d
e
f
g
h
CO2.
2 2 3 2
K CO3. NaOH. KOH. Na CO . CsOH.H O
a
Reaction conditions: alkyne (1.0 mmol), complex 2 (1 mol%), Cs
2
CO
3
(1.5
Under standard conditions, the corresponding products were
obtained in excellent yields (91ꢀ97%) when aromatic alkynes
b
mmol), CO
2
(1.0 atm), 25°C, DMF (5 mL), 12 h. Yield of isolated product.
with either electronꢀdonating (–CH
withdrawing (–Cl, ꢀF, –NO
) substituent’s were employed. It is known that copper acetylide is the key intermediate for
With nonꢀphenylacetyleneꢀbased
3 3
, –OCH ) or electronꢀ
2
alkynes
such
as copperꢀcatalyzed CꢀH activation of terminal alkynes and the
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ARTICLE
Journal Name
4
0ꢀ41
4
E.M. Mothi, H. StoeckliꢀEvans, K. Panchanatheswaran,
Synth. React. Inorg. Met-Org. Nano-Met. Chem. 2016, 46
371.
S.J. BernersꢀPrice, C. Brevard, A. Pagelot, P.J. Sadler, Inorg.
Chem. 1985, 24, 4278.
S.J. BernersꢀPrice, L.A. Colquhoun, P.C. Healy, K.A. Byriel,
J.V. Hanna, J. Chem. Soc., Dalton Trans. 1992, 3357.
S.J. BernersꢀPrice, P.J. Sadler, Inorg. Chem. 1986, 25, 3822.
P.C. Healy, B.T. Loughrey, G.A. Bowmaker, J.V. Hanna,
Dalton Trans. 2008, 3723.
CuꢀC bond is active for CO
2
insertion.
A possible reaction
,
mechanism for copperꢀcatalyzed carboxylation of terminal
alkynes with CO is proposed in Fig. 5. The copper center
activates the terminal alkyne with a base to form the copper
acetylide intermediate. Afterwards CO inserts into the CꢀCu
bond to form the carboxylic acid products, as previously
1
2
5
6
2
2
1c,21e
7
8
proposed.
9
1
1
1
1
1
P.C. Healy, B.T. Loughrey, M.L. Williams, Acta Crystallogr.
2
009, E65, m500.
0 P.C. Healy, J.C. McMurtrie, J. Bouzaid, Acta Crystallogr.
010, E66, m493.
2
1
D. Franzoni, G. Pelizza, G. Predieri, P. Tarasconi, C. Pellizi,
Inorg. Chim. Acta 1988, 150, 279.
2 C. Pettinari, A. Marinelli, A. Pizzabiocca, Effendy, B.W.
Skelton, A.H. White, Inorg. Chem. Commun. 2009, 12, 55.
3 P.C. Healy, B.T. Loughrey, M.L. Williams, P.G. Parsons, J.
Inorg. Biochem. 2010, 104, 625.
4 (
Chem.
Hikichi,
Organometallics 2000, 19, 3744; (
a
) P.T. Maragh, Annu. Rep. Prog. Chem., Sect. A: Inorg.
,
2009, 105, 416; ( ) M. Akita, M. Hashimoto, S.
b
Y.
Moroꢀoka
) A. Correa, Niꢀ and Feꢀ
c
Based CrossꢀCoupling Reactions. (Ed.), 2017.
5 P. Aslanidis, P.J. Cox, S. Divanidis, P. Karagiannidis,
Inorganica Chimica Acta, 2004, 357, 1063.
6 D.S. Eggleston,J.V. McArdle, G.E. Zuber, J. Chem. Soc.
Dalton Trans. 1987,677.
1
1
1
7 (
a) V. Rampazzi, A. Massard, P. Richard, M. Picquet, P.L.
Fig. 5. The proposed reaction mechanism for Cu(I) complex catalyzed CꢀH activating
Gendre, J.ꢀC. Hierso, ChemCatChem 2012,
Blake, N.R. Brooks, N.R. Champness, L.R. Hanton, P.
4
, 1828; ( ) A.J.
b
2
carboxylation of terminal alkynes with CO .
Hubberstey, Martin Schröder, Pure and Appl. Chem., 1998,
7
0
, 2351; (
T.S. Andy Hor, Dalton Trans. 2010, 39, 2631; (
Bai,L. Jiang, J.ꢀL. Zuo, T.S. Andy Hor, Dalton Trans. 2013,
42, 11319; ( ) S.ꢀQ. Bai, A.M. Yong, J.J. Hu, D.J. Young, X.
Zhang, Y. Zong, J. Xu, J.ꢀL. Zuo, T.S. Andy Hor,
CrystEngComm, 2012, 14, 961;( ) M. Beaupérin, E. Fayad, R.
Amardeil, H. Cattey, P. Richard, S. Brandès, P. Meunier, J.ꢀ
C. Hierso, Organometallics 2008, 27 1506; M.
Beaupérin, E. Fayad, R. Amardeil, H. Cattey, P. Richard,S.
c
) S.ꢀQ. Bai, J.Y. Kwang, L.L. Koh, D.J. Young,
d
) S.ꢀQ.
Conclusions
In summary, we have synthesized and characterized two Cu(I)
complexes containing dppet ligand and successfully established
the reaction conditions where copper(I) complexes comprising
e
f
2
of dppet ligand catalysed the transformation of CO to
,
(g)
carboxylic acids through CꢀH bond activation of terminal
alkynes. Various propiolic acids were synthesized in excellent
yields under ambient conditions. The most remarkable
advantage of this mild reaction system is its tolerance towards a
wide substrate scope. This protocol opens up the access to a
pool of highly functionalized propiolic acids from CO .
2
Acknowledgements
This project was financially supported by the Department of
Science and Technology, New Delhi, India (Grant No.
SR/FT/CSꢀ104/2011). We acknowledge funding from the
National Science Foundation (CHE0420497) for the purchase
of the APEX II diffractometer. The authors sincerely thank the
reviewers for their valuable suggestions and Prof. Pedro
Valerga from Universidad de Cádiz, Spain for his kind
encouragement.
Brandès, P. Meunier, J.ꢀC. Hierso. Organometallics 2008, 27
506.
8 M. Pervaiz, M. M. Sain, Resour. Conserv. Recycl. 2003, 39
25.
) R. Zevenhoven, S. Eloneva, S. Teir, Catal. Today, 2006,
15, 73; ( ) M. Aresta, A. Dibenedetto, I. Tommasi, Energy
Fuels, 2001, 15, 269; ( ) P. Tundo, M. Selva, Acc. Chem.
Res. 2002, 35, 706; ( ) G.A. Olah, Angew Chem., Int Ed.
) T. Aida, S. Inoue, Acc. Chem. Res. 1996,
) S.N. Riduan, Y. Zhang, Dalton Trans. 2010, 39
,
1
1
1
,
3
9 (
a
1
b
c
d
2
2
3
005, 44, 2636; (
, 39; (
347.
) H. Arakawa, M. Aresta, J.N. Armor, M.A. Barteau, E.J.
e
9
f
,
2
0 (
a
Beckman, A.T. Bell, J.E. Bercaw, C. Creutz, E. Dinjus, D.A.
Dixon, K. Domen, D.L. DuBois, J. Eckert, E. Fujita, D.H.
Gibson, W.A. Goddard, D.W. Goodman, J. Keller, G. J.
Kubas, H.H. Kung, J.E. Lyons, L.E. Manzer, T.J. Marks, K.
Morokuma, K.M. Nicholas, R. Periana, L. Que, J. Rostrupꢀ
Nielson, W.M.H. Sachtler, L.D. Schmidt, A. Sen, G.A.
Somorjai, P.C. Stair, B.R. Stults, W. Tumas, Chem. Rev.
Notes and references
2001, 101, 953; (
Rev. 2007, 107, 2365; (
b
) T. Sakakura, J.C. Choi, H. Yasuda, Chem.
) D.J. Darensbourg, Chem. Rev.
) N. Eghbali, C.ꢀJ. Li, Green Chem. 2007,
) S.N. Riduan, Y. Zhang, J.Y. Ying, Angew Chem.
) T. Sakakura, K. Kohon, Chem.
) L. Gu, Y. Zhang, J. Am. Chem.
) T. Kubota, I. Hayakawa, H. Mabuse,
c
1
F.A. Cotton, K.R. Dunbar, M.G. Verbruggen, J. Am. Chem.
Soc. 1987, 109, 5498.
2
007, 107, 2388; (
d
9
, 213; (
e
2
3
R.J. Puddephatt, Chem. Soc. Rev. 1983, 12, 99.
R.V. Kiress, R. Eisenberg, Inorg. Chem. 1989, 28, 3372.
Int. Ed. 2009, 48, 3322; (
Commun. 2009, 1312; (
Soc. 2010, 132, 914; (
f
g
h
6
| J. Name., 2012, 00, 1-3
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View Article Online
DOI: 10.1039/C7NJ03038J
Journal Name
ARTICLE
K. Mori, K. Ushikoshi, T. Watanabe, Masahiro Saito, Appl.
Organomet. Chem. 2001, 15, 121; ( ) I. Omae, Catal. Today
006, 115, 33.
) D.Y. Yu, M.X. Tan,Y.G. Zhang, Adv. Synth. Catal. 2012,
54, 969; ( ) F. Manjolinho, M. Arndt, K. Gooßen, L.J.
Gooßen, ACS Catal. 2012, 2, 2014; ( ) M. Arndt, E. Risto, T. 37 (
Krause, L.J. Gooßen, ChemCatChem 2012, 4, 484; ( ) D.Y. A.H. White, Dalton Trans., 2008, 5290; (
Yu, Y.G. Zhang, Green Chem. 2011, 13, 1275; ( ) X. Zhang,
W.Z. Zhang, X. Ren, L.L. Zhang, X.B. Lu, Org. Lett. 2011,
3, 2402; ( ) K. Inamoto, N. Asano, K. Kobayashi, M.
Yonemoto, Y. Kondo, Org. Biomol. Chem. 2012, 10, 1514;
) W. Zhang, W. Li, X. Zhang, H. Zhou, X.B. Lu, Org. Lett. 38 C.d. Nicola, C. Pettinari, M. Ricciutelli, B.W. Skelton, N.
Yoichi, I. Shoji, K. Noboru, Inorg. Chem. 2005, 44, 9667; (
C. Kutal, Coord. Chem. Rev. 1990, 99, 213; ( ) W.F. Fu, X.
Gan, C.M. Che, Q.Y. Cao, Z.Y. Zhou, N.N.Y. Zhu, Chem.
Eur. J. 2004, 10, 2228; ( ) S. Hu, A.ꢀJ. Zhou, Y.ꢀH. Zhang, S.
Ding, M.ꢀL. Tong, Crystal Growth & Design, 2006, 6, 2543.
) G.A. Bowmaker, J.V. Hanna, R.D. Hart, B.W. Skelton,
) C. Pettinari, C.d.
d)
i
,
e
2
2
1 (a
f
3
b
c
a
d
b
e
Nicola, F. Marchetti, R. Pettinari, B.W. Skelton, N. Somers,
A.H. White, W.T. Robinson, M.R. Chierotti, R. Gobetto, C.
1
f
Nervi, Eur. J. Inorg. Chem. 2008, 1974; (
c) S.K. Chawla, M.
Arora, K. Nättinen, K. Rissanen, Polyhedron, 2006, 25, 627.
(g
2
010, 12, 4748; (
h
) Y. Fukue, S. Oi, Y. Inoue, J. Chem. Soc.
Somers, A.H. White, Inorg. Chim. Acta 2005, 358, 4003.
Chem. Commun. 1994, 2091; (
i
) Z. Wu, L. Sun, Q. Liu, X. 39 P.G. Jones, Acta Crystallogr., Sect. B, 1980, 36, 2775.
Yang, X. Ye, Y. Hub, Y. Huang, Green Chem., 2017,19, 40 (
080; ( ) M. Cokoja, C. Bruckmeier, B. Rieger, W. A. Adv. Synth. Catal., 2010, 352, 2913;(
Herrmann, F. E. Kuhn, Angew. Chem., Int. Ed., 2011, 50, Proc. Natl. Acad. Sci. U. S. A., 2010, 107, 20184; (
Xie, B. Yu, Z.ꢀH. Zhou, H.ꢀC. Fu, N. Wang, L.ꢀN. He,
Tetrahedron Letters 2015, 56, 7059;( ) S. Wang, G. Dua, C.
Xi, Org. Biomol. Chem., 2016, 14, 3666.
) G.W. Ebert, W.L. Juda , R.H. Kosakowski , B. Ma , L.
Dong , K.E. Cummings , M.V.B. Phelps, A.E. Mostafa, J.
Luo, J. Org. Chem. 2005, 70, 4314; ( ) A.S. Hay, J. Org.
Chem. 1962, 27, 3320; (c) Y. Fukue, S. Oi, Y. Inoue, Chem.
Commun. 1994, 2091ꢀ2091; ( ) T. Tetsuo, U. Kazuo, S.
Takeo, Chem. Commun. 1974, 380; ( ) S. Adimurthy, C.C.
Malakar, U. Beifuss, J. Org. Chem. 2009, 74, 5648.
a
) L.J. Gooßen, N. Rodríguez, F. Manjolinho, P.P. Lange,
) D. Yu, Y. Zhang,
) J.ꢀN.
2
j
b
c
8
2
7
510; (k) H. Cheng, B. Zhao, Y. Yao, C. Lu, Green Chem.,
015, 17, 1675;(
l) J. Jover, F. Maseras, J. Org. Chem., 2014,
d
9, 11981.
2
2 (
6
a
) A. Correa, R. Martin, Angew. Chem. Int. Ed. 2009, 48, 41 (
201ꢀ6204; Angew. Chem. 2009, 121, 6317; ( ) F. Lehmann,
L. Lake, E.A. Currier, R. Olsson, U. Hacksell, K. Luthman,
Eur. J. Med. Chem. 2007, 42, 276; ( ) D. Bonne, M.
Dekhane, J. Zhu, Angew. Chem. Int. Ed. 2007, 46, 2485;
Angew. Chem. 2007, 119, 2537; ( ) D.M. D_Souza, A. Kiel,
D.P. Herten, F. Rominger, T.J.M_ller, Chem. Eur. J. 2008,
4, 529.
) J. Moon, M. Jeong, H. Nam, J. Ju, J.H. Moon, H.M. Jung,
S. Lee, Org. Lett. 2008, 10, 945; ( ) J. Moon, M. Jang, S.
) W. Jia, N. Jiao, Org.
a
b
b
c
d
d
e
1
3 (a
2
b
Lee, J. Org. Chem. 2009, 74, 1403; (
c
Lett. 2010, 12, 2000.
2
4 (
a
) B.M. Trost, F.D. Toste, K. Greenman, J. Am. Chem. Soc.
003, 125, 4518; ( ) T. Kitamura, Eur. J. Org. Chem. 2009,
111; ( ) M. Bararjanian, S. Balalaie, F. Rominger, B.
Movassagh, H.R. Bijanzadeh, J. Org. Chem. 2010, 75, 2806;
2
b
1
c
(d
) A.V. Dubrovskiy, R.C. Larock, Org. Lett. 2010, 12, 3117.
2
5 (
a
) L.J. Gooßen, N. Rodrŕguez, F. Manjolinho, P.P. Lange,
Adv. Synth. Catal. 2010, 352, 2913; (b) D.Y. Yu, Y.G. Zhang,
Proc. Natl. Acad. Sci. USA 2010, 107, 20184.
6 X.ꢀH. Liu, J.ꢀG. Ma, Z. Niu, G.ꢀM. Yang, P, Cheng, Angew.
Chem. Int. Ed. 2015, 54, 988.
2
2
7 (
Chem. Commun. 2004, 2568; (
Farnworth, T.N. Tekavec, J. Am. Chem. Soc. 2002, 124,
5188.
)M. Takimoto, Y. Nakamura, K. Kimura, M. Mori, J. Am.
Chem. Soc. 2004, 126, 5956; ( ) C.M. Williams, J.B.
a
) M. Aoki, M. Kaneko, S. Izumi, K. Ukai, N. Iwasawa,
b) J. Louie, J.E. Gibby, M.V.
1
2
8 (a
b
Johnson, T. Rovis, J. Am. Chem. Soc. 2008, 130, 14936.
9 J. Takaya, N. Iwasawa, J. Am. Chem. Soc. 2008, 130, 15254.
0 I.I.F. Boogaerts, S.P. Nolan, J. Am. Chem. Soc. 2010, 132,
2
3
8
1 (a
2
858.
) M. Trivedi, G. Singh, A. Kumar, N.P. Rath, Dalton Trans.
015, 44, 20874;( ) M. Trivedi, Bhaskaran, A. Kumar, G.
3
b
Singh, A. Kumar, N.P. Rath, New J. Chem. 2016, 40, 3109.
3
2 B.S. Furniss, A.J. Hannaford, V. Rogers, P.W.G. Smith, A.R.
Tatchell, 4 Edn., Vogel,s Textbook of Practical Organic
th
Chemistry, Longman, London, 1978.
3
3 G.M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
3
4 (
of Crystal Structures, University of Gottingen, Gottingen,
Germany, 1997; ( ) PLATON, A.L. Spek, Acta Cryst. 1990,
6A, C34.
a) G.M. Sheldrick, SHELXꢀ97; Programme for Refinement
b
4
3
5 K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4 edn., Wiley, New York 1981.
th
3
6 (
3
a
) P.C. Ford, E. Cariati, J. Bourassa, Chem. Rev. 1999, 99,
625; ( ) R.D. Pike, K.E. deKrafft, A.N. Ley, T.A. Tronic,
Chem. Commun. 2007, 3732;( ) A. Hiromi, T. Kiyoshi, S.
b
c
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Graphical Abstract: Synopsis and Pictogram
2
2
Copper(I) complexes [Cu
(
(
2
(µ-CN)
2
(
κ
-P,P-dppet)
2
](1), and [Cu
2
(µ-SCN)
2
(
κ
-P,P-dppet)
2
]
2), were prepared using CuX (X= CN, SCN) and cis-1,2-bis(diphenylphosphino)ethylene
dppet) in 1:1 molar ratio in DCM-MeOH (50:50 V/V) under reflux. Complexes 1-2 were
shown to be efficient catalysts in comparison to CuCN/CuSCN for the conversion of terminal
alkynes into propiolic acids with CO at room temperature.
2