[(PhBP3)Cu(PPh3)] as a surrogate of TpxCuL in homogeneous catalysis (PhBP3 = PhB(CH2PPh 2)3; Tpx = hydrotrispyrazolylborate)

Article abstract of DOI:10.1021/om201016b

The novel complexes [(PhBP₃)Cu(L)] (PhBP₃ = PhB(CH₂PPh₂)₃, L = PPh₃, 1; L = tetrahydrofuran, 2) have been synthesized and spectroscopically and, in the case of 1, structurally characterized. Both complexes undergo dissociation of the PPh₃ or THF ligand in solution to deliver the (PhBP₃)Cu unit, similar in geometry to and isoelectronic with Tp^xCu (Tp ^x = trispyrazolylborate ligand). A complete study of the catalytic properties of 1 has shown that it can be considered as a surrogate of Tp ^xCu. The study includes (a) olefin cyclopropanation, cyclopropenation, aziridination, halocarbon addition, and radical polymerization, (b) X-H (X = O, N) functionalization by carbene insertion, and (c) furan conversion into dihydropyridines. Since the observed activity is quite comparable to that already described for Tp^xCu complexes, this new catalytic system could become an alternative to the latter.

Full text of DOI:10.1021/om201016b

Article
pubs.acs.org/Organometallics
[(PhBP3)Cu(PPh3)] as a Surrogate of TpxCuL in Homogeneous
Catalysis (PhBP3 = PhB(CH2PPh2)3; Tpx = Hydrotrispyrazolylborate)
†
‡
,†
,†
́
́
M. Angeles Fuentes, Eleuterio Alvarez, Ana Caballero,* and Pedro J. Perez*
́
†Laboratorio de Catal
Centro de Investigacion
́ ́
isis Homogenea, Departamento de Química y Ciencia de los Materiales, Unidad Asociada al CSIC,
́
en Química Sostenible (CIQSO), Universidad de Huelva, Campus de El Carmen, 21007 Huelva, Spain
‡Instituto de Investigaciones Químicas, (CSIC-US), C/Americo Vespucio 49, 41092 Sevilla, Spain
S
* Supporting Information
ABSTRACT: The novel complexes [(PhBP3)Cu(L)] (PhBP3 = PhB(CH2PPh2)3,
L = PPh3, 1; L = tetrahydrofuran, 2) have been synthesized and spectroscopically
and, in the case of 1, structurally characterized. Both complexes undergo dissociation of
the PPh3 or THF ligand in solution to deliver the (PhBP3)Cu unit, similar in geometry
to and isoelectronic with TpxCu (Tpx = trispyrazolylborate ligand). A complete study of
the catalytic properties of 1 has shown that it can be considered as a surrogate of TpxCu.
The study includes (a) olefin cyclopropanation, cyclopropenation, aziridination,
halocarbon addition, and radical polymerization, (b) X−H (X = O, N) functionalization by carbene insertion, and (c) furan
conversion into dihydropyridines. Since the observed activity is quite comparable to that already described for TpxCu complexes,
this new catalytic system could become an alternative to the latter.
dienols have been achieved (Table 1, entries 11 and 12).10,11
INTRODUCTION
In the past decade, there has been a great development in the
chemistry of trispyrazolylborate complexes (Figure 1) both in
■
2
The same complexes induced the amidation of Csp −H and
3
Csp −H bonds by formal nitrene insertion reactions (Table 1,
entries 13−15).12−14 In an unprecedented reaction that
comprises four catalytic cycles in a one-pot fashion, furans
and PhINTs were converted into 1,2-dihydropyridines, an
example of concurrent catalysis catalyzed by both the copper
and silver Tpx-containing complexes (Table 1, entry 16).15
In a third type of transformation, TpxCu complexes have
been employed as catalysts for atom transfer radical addition
(ATRA) reactions (Table 1, entry 17),16 which consists of
Figure 1. Trispyrazolylborate ligands (Tpx).
the addition of a C−Cl bond of a polyhalohydrocarbon to
an olefin. The ATRP (atom transfer radical polymerization;
the synthesis of new ligands with certain properties and in their
Table 1, entry 18) process has also been promoted by TpxCu
use in catalytic transformations.1 Among them, complexes of
the type TpxM (M = Cu, Ag) have been found to promote
a number of different transformations, such as the diazo
decomposition and subsequent metal-catalyzed carbene transfer
to olefins or alkynes to give cyclopropanes or cyclopropenes
(Table 1, entries 1 and 2).2,3 Benzene has also been converted
into cycloheptatrienes in the TpxM-catalyzed (M = Cu, Ag;
Table 1, entry 3)4 Buchner reaction. The same methodology served
to functionalize N−H and O−H (Table 1, entries 4 and 5)5,6 as
well as an array of C−H bonds ranging from benzylic to alkylic
in different substrates such as 2,3-dimethylbutane, pentane, and
polyolefins (Table 1, entries 6−9).4,7,8 The culmination of this
tool has consisted of the catalytic conversion of methane into
ethyl propionate (Table 1, entry 10), recently described using
TpxAg complexes as catalysts.9
complexes.17
The availability of a large number of trispyrazolylborate
ligands with tunable steric and electronic properties has been
crucial for the success of the use of TpxCu complexes as
catalysts for the above transformations. However, the synthetic
route to these ligands, although simple (thermal reaction of
pyrazoles with KBH4),1 often displays problems due to the
formation of mixtures of products or unreacted starting materials,
requiring a purification process that is also somewhat complex.
It would be therefore useful to develop a similar system,
electronically and sterically tunable as well, but easier from a
preparative point of view. With this idea in mind, we have turned
to the tris(phosphino)borate ligand18−20 [PhB(CH2PPh2)3]−
(tris((diphenylphosphino)methyl)phenylborate, PhBP3),
which resembles the structure of trispyrazolylborate ligands to
a certain extent. Thus, as shown in Figure 2, this PhBP3 ligand
Nitrene transfer from hypervalent iodine reagents (ArNIPh)
or Chloramine-T (NaClNTs) has also been described with
TpxM as catalyst (M = Cu, Ag). The aziridination of plain
olefins and a regio- and diasteroselective aziridination of allylic
Received: October 21, 2011
Published: January 20, 2012
© 2012 American Chemical Society
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Table 1. Reactions Catalyzed by TpxM (M = Cu, Ag) Compounds
of stirring at room temperature, 1 equiv of PPh3 was added and
the mixture stirred for an additional 12 h (eq 1). After workup,
1 was obtained as a colorless crystalline material.
PhB(CH PPh ) Li(tmeda) + CuCl
2
2 3
(1) THF, room temp, 6 h
⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→ [PhB(CH PPh ) ]Cu(PPh )
2
2 3
3
Figure 2. PhB(CH2PPh2)3 and Tpx ligands.
(2) PPh , room temp, 12 h
3
1
−LiCl,−tmeda
(1)
is also anionic in nature, with three donor atoms, and provides
five electrons to the metal center (considering the neutral
electron counting formalism). Although several transition-metal
complexes bearing this PhBP3 ligand have been independently
reported by Tilley,19 Peters,20 and Nocera,18 its coordination
chemistry with copper is yet unknown, with the exception of
the related, but bidentate, Ph2BPtBu2 ligand that afforded
Ph2BPtBu2CuL complexes.21 It is worth mentioning that Marks
and co-workers have described a series of silver complexes of
composition BP3Ag(PR3).22 In this contribution we report the
synthesis and structural characterization of the complexes
[PhB(CH2PPh2)3]Cu(PPh3) (1) and [PhB(CH2PPh2)3]Cu-
(THF) (2) and the use of the former as a catalyst precursor for
an array of transformations previously described with TpxCuL as
the catalyst. The results obtained in this work allow us to
propose that PhBP3Cu(PPh3) serves as a surrogate for the latter,
opening up the development of related complexes that could
improve the catalytic performance in those transformations.
The 1H NMR spectrum showed the characteristic signals for
both the PhB(CH2PPh2)3 and PPh3 ligands, evidencing a C3
symmetry on the basis of the equivalency of the three arms of
the tripod ligand. In addition, the 31P{1H} NMR spectrum con-
sisted of two broad singlets centered at δ −4.81 and −5.82 ppm,
assigned respectively to the PPh3 and PPh2 groups of the ligands
(see the Supporting Information). The lack of observance of
coupling could be interpreted as a consequence of a fluxional
process in which the PPh3 ligand is undergoing a relatively fast
coordination−decoordination process. In order to ascertain the
exact structure of the molecules of 1, an X-ray diffraction study
was carried out with single, colorless crystals grown from THF
solutions. As shown in Figure 3, the structure of complex 1
consists of a distorted-tetrahedral geometry with a P4 copper
unit, one P donor from the coordinated PPh3 ligand and the
other three from the tridentate ligand PhBP3, in the first
example of a copper complex of this anionic PhBP3 ligand. The
distances Cu−P(PPh3) of 2.242(2) Å compares well with that
of 2.241(3) Å in the cationic complex [(triphos)Cu(PPh3)]PF6
(triphos = MeC(CH2PPh2)).23 The same similarity is observed
with the average of Cu−PPh2 distances 2.32 and 2.36 Å,
respectively, for 1 and the cationic complex.
RESULTS AND DISCUSSION
■
Synthesis of the Complex [(PhBP3)Cu(PPh3)] (1). This
compound was prepared by direct reaction of [(PhBP3)]Li-
(tmeda)18 and CuCl in tetrahydrofuran as the solvent. After 6 h
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one coordinated THF molecule. Elemental analyses confirmed
the composition of [PhB(CH2PPh2)3]Cu(THF) for this new
complex. It seems that, in THF solution, a ligand exchange
equilibrium takes place (eq 2), the PPh3 ligand being replaced
by the THF molecule. The synthesis of 1 was improved by
dissolving the reaction residue in methylene chloride and
crystallizing from this solvent. On the other hand, complex 2
can be prepared directly from [(PhBP3)]Li(tmeda) and CuCl
(eq 3), followed by further crystallization from THF.
[PhB(CH PPh ) ]Cu(PPh )
2
2 3
1
3
+THF
XooooooY [PhB(CH PPh ) ]Cu(THF) + PPh
3
2
2 3
−THF
(2)
(3)
2
PhB(CH PPh ) Li(tmeda) + CuCl
2
2 3
THF, room temp, 6 h
Figure 3. ORTEP view of the molecules of 1. Thermal ellipsoids are
drawn at the 50% probability level. H atoms have been omitted for
clarity.
⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→⎯ [PhB(CH PPh ) ]Cu(THF)
2
2 3
2
On the other hand, to gain information about the electronic
properties of the PhBP3 ligand, the carbonyl derivative
[(PhBP3)Cu(CO)] was generated upon bubbling of carbon
monoxide through a solution of 1 or 2 at room temperature.
Once the volatiles were removed, the IR of the resulting solid
showed one absorption at 2055 cm−1, a value slightly lower
than that reported for TpMe2Cu(CO) (ν(CO) 2060 cm−1).25
Therefore, the electron density of at the BP3 derivative seems
to be slightly higher than in the TpMe2Cu complex.
A comparison of the structures of the PhBP3Cu and
TpMe2Cu fragments (obtained by removal of the PPh3 ligand
from the corresponding TpMe2Cu(PPh3)24 and PhBP3Cu-
(PPh3) X-ray structures) is shown in Figure 4. The relative
At this point, we could conclude that the complex
[(PhBP3)Cu(PPh3)] displays some differences compared to
the TpMe2Cu complex. First, the potential catalytic pocket
available at complex 1 seems to be larger than that of the
TpMe2Cu unit. Second, from an electronic point of view, the
copper center at 1 possesses a higher electron density than in
TpMe2Cu. These features should be somewhat reflected in the
catalytic behavior, as discussed below.
Catalytic Activity of [(PhBP3)Cu(PPh3)] (1). (a).
Carbene Transfer Reactions. Once the complex [(PhBP3)Cu-
(PPh3)] was synthesized and characterized, it was employed as
the catalyst precursor in some of the organic transformations
shown in the Introduction (Table 1). On the basis of the
electronic properties mentioned above, complex 1 should be a
good catalyst for those reactions that do not require a
somewhat electron deficient metal center. We should not
therefore expect good results when employing this complex as
the catalyst in carbene or nitrene insertion reactions into C−H
bonds.7,12−14 On the other hand, those reactions in which a
relatively electron rich metal center is preferred, such as ATRA
or ATRP,16,17 should be induced catalytically by 1. The addition of
carbene or nitrene moieties to unsaturated substrates (olefins,
alkynes)2,3,26 is not greatly affected by the electronic density
(TpxCu complexes with an array of electron-deficient and
electron-rich Tpx ligands similarly catalyze those reactions),
suggesting that 1 could also induce them.
The first group of reactions, where the catalytic ability of the new
complex 1 was tested, was the addition of carbene units, from
ethyl diazoacetate, to unsaturated hydrocarbons, resulting in the
formation of cyclopropanes and cyclopropenes (Scheme 1). In the
cyclopropanation reaction of styrene, the catalyst/EDA/styrene
mixture (1/20/160 ratio) was stirred at room temperature
until no EDA was detected by GC (8 h), with a 70% yield. In
the case of the cyclopropenation reaction with 3-hexyne as
Figure 4. Front and side views of the PhB(CH2PPh2)3Cu (left) and
TpMe2Cu (right) fragments obtained by removal of the PPh3 ligand of
the corresponding PhB(CH2PPh2)3Cu(PPh3) and TpMe2Cu(PPh3)
X-ray structures.
position of the copper center with regard to the ancillary ligand
differs from one case to the other. In the P-containing ligand,
the metal center is somewhat aligned with the pendant phenyl
groups. However, the copper ion is slightly embedded in the
pocket originated by the pyrazolyl substituents. Therefore, the
catalytic pocket seems to be larger in the former, and this
feature should have the corresponding effect during catalysis.
During crystallization, white crystalline material was also
obtained that gave a unique resonance in the 31P{1H} NMR
spectrum, very similar to that of complex 1, but lacking in the
PPh3 resonance. The 1H NMR spectrum displayed the
resonances of the BP3 ligand along with those expected for
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Scheme 1. Catalytic Carbene Transfer from Ethyl Diazoacetate Catalyzed by 1
Scheme 2. Catalytic Carbene Insertion from EDA into N−H and O−H Bonds Catalyzed by 1
substrate, the diazo compound was added slowly, with the aid
of a syringe pump, for 15 h to avoid the formation of EDA-
coupling products (diethyl fumarate and maleate)27 to give
cyclopropene in 57% yield. The lower catalytic activity is due to
the high electron density at the metal center, since the diazo
compound decomposition is favored by electrophilic metal
catalysts.28 The cis/trans diastereoselectivity provided in the
cyclopropanation reaction was 20/80, opposite to that observed
with TpxCu complexes, since complex 1 gave a trans selectivity
higher than that for the TpMe2Cu complex.2b This result must
be related to the larger catalytic pocket in the PhBP3Cu unit
compared to that in TpMe2Cu shown in Figure 4. Thus, the
formation of the bulkier trans-cyclopropane is more favored by
complex 1.
O−H bond (Scheme 2). The yields obtained in both reactions
were at least comparable to those already reported for the
TpMe2Cu complex.5a,6 Nevertheless, when the new complex 1
was employed as catalyst in the carbene insertion reaction into
the C−H bonds of cyclohexane, no formation of the insertion
product was detected, in good agreement with the electron-rich
nature of the metal center. It is noteworthy that NMR spectra
of the residue obtained at the end of the catalytic reactions
showed the resonances of the initial catalyst, evidencing the
lack of noticeable decomposition along the process.
We have also explored the potential of the THF adduct 2 as a
catalyst for the above transformations. The results obtained
were quite similar in terms of activities and selectivities, in good
agreement with the proposal of a unique BP3Cu core as
responsible for the catalytic reaction. However, prolonged reaction
times showed in some cases a certain bluish coloration of the
reaction mixture, typical of copper oxidation. Therefore, we pre-
ferred to explore the catalytic potential with the phosphine adduct.
(b). Nitrene Transfer Reactions. A third group of reactions
based on the addition or insertion of nitrene units, with
PhINTs as the nitrene source, to unsaturated or saturated
hydrocarbons has been studied (Scheme 3). In the styrene
aziridination reaction, a [1]/[PhINTs]/[styrene] ratio of
1/20/100 gave the corresponding aziridine in 80% yield. Again,
however, as observed in the carbene insertion reactions, we did
not observe any product derived from nitrene insertion into the
C−H bonds of cyclohexane when complex 1 was used as
catalyst. It is worth mentioning that TpMe2Cu does not catalyze
the latter reaction either.
The above explanation is based on our assumption that the
active species during catalysis is the 14-electron “PhBP3Cu” unit.
To test this, we carried out two twin experiments only differing
in the amount of added excess of PPh3, as shown in eq 4.
The yield in cyclopropanes drastically decreased in the presence
of the large excess, indicating the decoordination of the PPh3
ligand from 1 as the first step in this catalytic transformation.
We have also studied the potential of this system toward
N−H and O−H functionalization (Scheme 2). Complex 1 catalyzed
the insertion of the CHCO2Et group, generated from EDA,
into the N−H bond of aniline, using a [Cu]/[EDA]/[aniline]
ratio of 1/40/100, respectively. In a similar manner, the use of
n-butanol as substrate afforded the insertion product into the
We have recently described a novel transformation where the
TpMe2Cu complex catalyzes the conversion of furans into
1-(3a,4,7,7a-tetrahydro-2,5-dimethyl-4-tosylfurol[3,2-b]pyridin-
7-yl)ethanone,15 the bicyclic compound shown in Scheme 4,
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Scheme 3. Catalytic Nitrene Transfer Reactions from
PhINTs Catalyzed by 1
CONCLUSIONS
■
We have synthesized and characterized the novel copper
complex [(PhBP3)Cu(PPh3)], containing a trisphosphinobo-
rate ligand. The catalytic behavior of this complex toward a
series of transformations already described with TpxCu has
been established. Collected data allow describing 1 as a good
surrogate of the TpxCu complexes for catalytic purposes. The
preparation of other PhBP3Cu complexes with the appropriate
substituent at the P donors could provide the required
electronic and/or steric properties to build a new family of
catalysts for a number of transformations.
EXPERIMENTAL SECTION
derived from two molecules of furan and one NTs fragment. The
use of 1 as catalyst precursor also induced this transformation,
in 40% yield (Scheme 4).
■
General Procedures. All preparations and manipulations were
carried out under an oxygen-free nitrogen atmosphere using
conventional Schlenk techniques or inside a glovebox. The solvents
were dried, distilled, and degassed before their use. All the reagents
were purchased from Aldrich and were used as received, with the
exception of the olefins for the radical reactions, which were filtered
through alumina before use. GC data were collected with a Varian
3900 instrument. NMR spectra were recorded on a Varian Mercury
400 MHz and gel permeation chromatography (GPC) on a Waters
GPC system. [PhB(CH2PPh2)3][Li(TMEDA)] was prepared accord-
ing to literature methods.18−20 For all the reactions previously reported
by our group, blank experiments in the absence of catalyst or ligand had
already been performed.2−17,26,27
Scheme 4. Conversion of 2,5-Dimethylfuran into
1,2-Dihydropyridines Catalyzed by 1
Synthesis of [PhBP3]Cu(PPh3) (1). Copper(I) chloride (49.5 mg,
0.5 mmol) was added to a solution of [PhB(CH2PPh2)3][Li-
(TMEDA)] (404 mg, 0.5 mmol) in tetrahydrofuran (10 mL). The
mixture was stirred for 6 h. Then, 1 equiv of PPh3 (131 mg, 0.5 mmol)
was added and the mixture stirred overnight. The solvent was removed
under reduced pressure to give a white powder that was washed with
petroleum ether (2 × 15 mL). The solid was dissolved in
tetrahydrofuran (10 mL), and 3 equiv of PPh3 was added to disfavor
the displacement of PPh3 by THF. After concentration and cooling
overnight at −20 °C, complex 1 was obtained as white crystals in 60%
yield, some of them suitable for X-ray studies. Crystallization from
dichloromethane was also successful, without the need of additional
(c). Atom Transfer Radical Reactions. Previous work from
our laboratory has shown that atom transfer radical addition
(ATRA) of polyhalogenated alkenes to olefins is catalyzed by
TpxCu complexes.16 The best results were obtained with
electron-donating Tpx ligands. Consequently, the complex
[(PhBP3)Cu(PPh3)] could be a good candidate to catalyze this
reaction. In a typical procedure, a solution of complex 1 in
CD2Cl2 containing 300 equiv of styrene and 1200 equiv of
CCl4 was maintained at 90 °C for 60 h. The final mixtures
contained the desired product in 85% yield (Scheme 5), a
conversion significantly higher than that already reported for
TpMe2Cu as the catalyst.16a We have also employed the
complex [(PhBP3)Cu(PPh3)] as a catalyst in ATRP reactions
with several olefins. As shown in Scheme 5, the conversions as
well as the PDI values are moderate. Matyjaswewski and co-
workers already described the use of TpMe2Cu as the catalyst
for styrene polymerization.17b At shorter reaction times (4 h),
yields of 75% were obtained. However, the polydispersity
value Mw/Mn = 3.82 was found, much higher than that
obtained with 1.
1
PPh3, but no single crystals could be grown. H NMR (400 MHz,
CD2Cl2): δ 7.52 (d, 2 H, o-PhB(CH2PPh2)3), 7.25 (m, 21 H,
PhB(CH2PPh2)3CuPPh3), 7.14 (m, 2 H, m-PhB(CH2PPh2)3), 7.06 (m,
7 H, PhB(CH2PPh2)3), 6.94 (t, 1 H, p-PhB(CH2PPh2)3), 6.84 (m,
17 H, PhB(CH2PPh2)3), 1.40 (br s, 6 H, PhB(CH2PPh2)3). 31P{1H}
NMR (162 MHz, CD2Cl2): δ −4.81 (br s, −CuPPh3), −5.82 (br s,
PhB(CH2PPh2)3). 13C{1H} NMR (100 MHz, CD2Cl2): δ 140.7 (m),
131.8, 127.4, 123.6 (PhB(CH2PPh2)3), 134.6, 134.4, 132,9, 132.8,
132.7, 130.2, 129.1, 128.9, 128.4 (PhB(CH2PPh2)3), 134.4, 134.2,
130.1, 129.1 (CuPPh3) 18.5 (m, PhB(CH2PPh2)3). Anal. Calcd for
C63H56BCuOP4: C, 74.82; H, 5.58. Found: C, 74.16; H, 5.86.
Synthesis of [PhBP3]Cu(THF) (2). Copper(I) chloride (49.5 mg,
0.5 mmol) was added to a solution of [PhB(CH2PPh2)3][Li-
(TMEDA)] (404 mg, 0.5 mmol) in tetrahydrofuran (10 mL). The
mixture was stirred for 6 h. The solution was filtered, and the solvent
was removed under vacuum to yield a white powder. The solid
was crystallized from THF solution at −20 °C in 60% yield. 1H NMR
Scheme 5. Atom Transfer Radical Reactions Catalyzed by 1.
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(400 MHz, CD2Cl2): δ 7.52 (d, 2 H, o-PhB(CH2PPh2)3), 7.25 (m,
6 H, PhB(CH2PPh2)3), 7.14 (m, 2 H, m-PhB(CH2PPh2)3), 7.06 (m,
7 H, PhB(CH2PPh2)3), 6.94 (t, 1 H, p-PhB(CH2PPh2)3), 6.84 (m, 17 H,
PhB(CH2PPh2)3), 3.70 (t, 2 H, −OCH2CH2), 1.83 (t, 2 H,
−OCH2CH2−), 1.40 (br s, 6 H, PhB(CH2PPh2)3). 31P{1H} NMR
(162 MHz, CD2Cl2): δ −5.82 (br s, PhB(CH2PPh2)3). 13C{1H} NMR
(100 MHz, CD2Cl2): δ 140.7 (m), 131.8, 127.4, 123.6 (PhB-
(CH2PPh2)3), 134.6, 134.4, 132.9, 132.8, 132.7, 130.2, 129.1, 128.9,
128.4 (PhB(CH2PPh2)3), 66.3 (−OCH2CH2), 22.9 (−OCH2CH2−),
18.5 (m, PhB(CH2PPh2)3). Anal. Calcd for C49H49BCuOP3: C, 71.67;
H, 6.01. Found: C, 71.77; H, 5.66.
reaction mixture was analyzed by GC and no ethyl diazoacetate was
detected.
Styrene Aziridination Reaction. Complex 1 (12.6 mg, 0.0125 mmol)
and styrene (143.2 μL, 1.25 mmol) were dissolved in dichloromethane
(5 mL), before PhINTs (93 mg, 0.25 mmol) was added in one
portion. The mixture was stirred for 8 h at room temperature; no solid
PhINTs was observed after that time. The volatiles were removed
under vacuum, and the residue was dissolved in CDCl3. 9-Anthra-
cenecarboxaldehyde was added as internal standard (12 mg, 0.06 mmol),
1
the conversion and yields being calculated by H NMR.
Reaction of 2,5-Dimethylfuran with PhINTs. Complex 1 (12.6 mg,
0.0125 mmol) and 2,5-dimethylfuran (1.07 mL, 10 mmol) were
dissolved in dichloromethane (5 mL), and PhINTs (93 mg, 0.25 mmol)
was added in one portion. After 8 h of stirring and removal of volatiles,
the residue was dissolved in CDCl3. 9-Anthracenecarboxaldehyde was
added as internal standard (9.4 mg, 0.045 mmol), the conversion and
Structure Determination. Crystal data for [PhBP3]Cu(PPh3):
C63H50BCuP4·C4H8O, Mr = 1077.36, orthorhombic, space group Pbca,
a = 20.3770(19) Å, b = 17.9161(17) Å, c = 33.864(3) Å, α = 90.00°,
β = 90.00°, γ = 90.00°, V = 12362.9(19) Å3, Z = 8, Dexptl = 1.158 Mg/m3,
μ(Mo Kα) = 0.496 mm−1. A crystal grown from THF, of size 0.40 ×
0.06 × 0.05 mm3, coated with dry perfluoropolyether was mounted on
a glass fiber and fixed in a cold nitrogen stream (T = 173(2) K). X-ray
diffraction data were collected on a Bruker-Nonius X8Apex-II CCD
diffractometer, operating with graphite-monochromated Mo Kα1
radiation, λ = 0.710 73 Å and a Kryoflex low-temperature device.
A total of 87 281 reflections were measured, 12 636 of which were
independent (Rint = 0.0802) and were used in all calculations. The data
were reduced up to θ = 26.44° by the program SAINT29 and corrected
for Lorentz−polarization and absorption effects by a multiscan method
applied by SADABS;29 the structure was solved by direct methods
(SIR-2002)30 and refined against all F2 data by full-matrix least-squares
1
yields being calculated by H NMR.
Atom Transfer Radical Addition (ATRA) of CCl4 to Styrene. A
solution of complex 1 (5 mg, 0.005 mmol), styrene (172 μL, 1.5 mmol),
and CCl4 (580 μL, 6 mmol) was prepared in CD2Cl2 (0.4 mL). The
solution was transferred into a pressure NMR tube with a Teflon cap.
The tube was removed from the glovebox and placed into an oil bath at
90 °C. Biphenyl was added as internal standard (62 mg, 0.30 mmol); the
1
conversion and yields were calculated by H NMR at the end of the
reaction.
Atom Transfer Radical Polymerization (ATRP) to Olefins. To a
solution of complex 1 (30.3 mg, 0.03 mmol) in the corresponding
olefin (9 mmol) was added p-toluenesulfonyl chloride (5.7 mg, 0.03 mmol),
with toluene (1 mL) as the solvent. The reaction was heated to 80 °C for
methyl methacrylate (MMA) or for styrene. The polymer was later
precipitated with methanol and was separated from solution. The resulting
solid was dried for 24 h. Conversions were determined by gravimetric
analysis previous to the GPC analysis.
techniques (SHELXL97)31 minimizing w[Fo − Fc2]2. All non-
2
hydrogen atoms were refined with anisotropic thermal parameters.
Hydrogen atoms were included in calculated positions and allowed to
ride on the attached carbon atoms with the isotropic temperature
factors (Uiso values) fixed at 1.2 times those Ueq values of the corresponding
carbon atoms. For F2 > 2σ(F2), the final R1 value was 0.0620 and the
final wR(F2) value was 0.1453. For all data, the final R1 value was
0.0938 and the final wR(F2) value was 0.1921. The goodness of fit
on F2 was 1.040, the largest difference peak and hole being 0.867
and −1.755 e Å−3, respectively.
ASSOCIATED CONTENT
■
S
* Supporting Information
Figures giving 1H and 31P NMR spectra of [(PhB-
(CH2CH2PPh2)3)Cu(PPh3)] and [(PhB(CH2CH2PPh2)3)Cu-
(THF)] and a CIF file giving X-ray data for the determination
of the structure of 1. This material is available free of charge via
the Internet at http://pubs.acs.org.
General Catalytic Experiments. Cyclopropanation of Styrene
with Ethyl Diazoacetate. Complex 1 (25.2 mg, 0.025 mmol) was
dissolved in dichloromethane (10 mL), styrene (458 μL, 4 mmol) and
ethyl diazoacetate (52.6 μL, 0.5 mmol) being added in one portion.
The mixture was stirred for 8 h at room temperature. The
consumption of ethyl diazoacetate was monitored by GC. Volatiles
were removed under reduced pressure and the crude reaction product
was dissolved in CDCl3. 9-Anthracenecarboxaldehyde was added as
internal standard (60 mg, 0.29 mmol), the conversion and yields being
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: ana.caballero@dqcm.uhu.es (A.C.); perez@dqcm.uhu.es
(P.J.P.).
1
calculated by H NMR.
Cyclopropenation of 3-Hexyne with Ethyl Diazoacetate.
Complex 1 (25.2 mg, 0.025 mmol) was dissolved in dichloromethane
(10 mL) along with 3-hexyne (284 μL, 2.5 mmol). A solution of ethyl
diazoacetate (105.2 μL, 1 mmol) in dichloromethane (10 mL) was
added slowly with the aid of a syringe pump over 15 h at room
temperature. The consumption of ethyl diazoacetate was monitored
by GC.
ACKNOWLEDGMENTS
■
We thank the MICINN (Proyecto CTQ2001-28942-CO2-01
and Consolider Ingenio CSD2006-0003)) for financial support.
M.A.F. also thanks the MICINN for a research fellowship.
N−H and O−H Functionalizations by Carbene Insertion. (a). N−H
Bond Functionalization. Complex 1 (25.2 mg, 0.025 mmol) was
dissolved in dichloromethane (10 mL). Aniline (228 μL, 2.5 mmol)
and ethyl diazoacetate (105.2 μL, 1 mmol) were added in one portion.
After 12 h of stirring at room temperature, no ethyl diazoacetate was
detected by GC. The solvent was removed under reduced pressure,
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