Synthesis, characterization, and olefin/CO exchange reactions of copper(I) derivatives containing bidentate oxygen ligands

Article abstract of DOI:10.1021/om050416r

New hexafluoroacetylacetonate (hfacac) and trifluoroacetato olefin complexes of copper(I) of the general formulas Cu(hfacac)(olefin) and Cu(CF ₃COO)(olefin) have been prepared from Cu₂O/hfacacH/olefin or Cu(CF₃COO)(toluene)_0.5/olefin systems. The structures of [Cu(hfacac)-(coe)], [Cu(hfacac)(van)], [Cu(μ-CF₃COO)(tbve)] _n, and [Cu(μ-CF₃COO)(van)]₂·C ₇H₈ have been determined by X-ray diffraction methods, where coe = cyclooctene, van = 4-vinylanisole, and tbve = tert-butyl vinyl ether. In the solid state, the 4-vinylanisole/trifluoroacetate complex [Cu(CF₃COO)(van)]₂ is dimeric with two carboxylato groups symmetrically bridging two copper atoms, while the tert-butyl vinyl ether derivative [Cu(μ-CF₃COO)(tbve)]_n is polymeric with single [CF₃COO]^- bridges between adjacent copper atoms. Olefin hfacac complexes are monomeric, and considering the two oxygen atoms and the midpoint of the double bond of the coordinated olefin, the copper atom lies in a nearly trigonal-planar environment. The carbonylation reactions of Cu(CF₃COO)(olefin), (olefin = tbve, van; 2Cu(CF₃COO) (olefin) + 2CO ? [Cu(CF₃COO)(CO)]₂ + 2(olefin)) and of Cu(hfacac)(olefin) (olefin = coe, 1,5-cyclooctadiene (cod), norbornene (nbe), van; Cu(hfacac)(olefin) + CO ? Cu(hfacac)(CO) + olefin) have been studied gas volumetrically, and the equilibrium constants for the displacement of the coordinated olefin by carbon monoxide have been determined at different temperatures. Some hypotheses on the copper-olefin bond have been formulated on the basis of structural, thermodynamic and spectroscopic (¹³C NMR) data.

Full text of DOI:10.1021/om050416r

Organometallics 2005, 24, 4475-4482
4475
Synthesis, Characterization, and Olefin/CO Exchange
Reactions of Copper(I) Derivatives Containing Bidentate
Oxygen Ligands
Guido Pampaloni,*,† Riccardo Peloso,† Claudia Graiff,‡ and Antonio Tiripicchio‡
Dipartimento di Chimica e Chimica Industriale, Universita` di Pisa, Via Risorgimento 35,
I-56126 Pisa, Italy, and Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica,
Chimica Fisica, Universita` di Parma, Parco Area delle Scienze 17/A, I-43100 Parma, Italy
Received May 26, 2005
New hexafluoroacetylacetonate (hfacac) and trifluoroacetato olefin complexes of copper(I)
of the general formulas Cu(hfacac)(olefin) and Cu(CF3COO)(olefin) have been prepared from
Cu2O/hfacacH/olefin or Cu(CF3COO)(toluene)0.5/olefin systems. The structures of [Cu(hfacac)-
(coe)], [Cu(hfacac)(van)], [Cu(µ-CF3COO)(tbve)]n, and [Cu(µ-CF3COO)(van)]2‚C7H8 have been
determined by X-ray diffraction methods, where coe ) cyclooctene, van ) 4-vinylanisole,
and tbve ) tert-butyl vinyl ether. In the solid state, the 4-vinylanisole/trifluoroacetate complex
[Cu(CF3COO)(van)]2 is dimeric with two carboxylato groups symmetrically bridging two
copper atoms, while the tert-butyl vinyl ether derivative [Cu(µ-CF3COO)(tbve)]n is polymeric
with single [CF3COO]- bridges between adjacent copper atoms. Olefin hfacac complexes are
monomeric, and considering the two oxygen atoms and the midpoint of the double bond of
the coordinated olefin, the copper atom lies in a nearly trigonal-planar environment. The
carbonylation reactions of Cu(CF3COO)(olefin), (olefin ) tbve, van; 2Cu(CF3COO)(olefin) +
2CO / [Cu(CF3COO)(CO)]2 + 2(olefin)) and of Cu(hfacac)(olefin) (olefin ) coe, 1,5-
cyclooctadiene (cod), norbornene (nbe), van; Cu(hfacac)(olefin) + CO / Cu(hfacac)(CO) +
olefin) have been studied gas volumetrically, and the equilibrium constants for the
displacement of the coordinated olefin by carbon monoxide have been determined at different
temperatures. Some hypotheses on the copper-olefin bond have been formulated on the
basis of structural, thermodynamic and spectroscopic (13C NMR) data.
Introduction
rich olefins. Moreover, to extend our knowledge about
the thermodynamics of CO/olefin exchange equilibria,
we have focused our attention on copper(I) hexafluoro-
acetylacetonate, Cu(hfacac), due to its ability to bind
both carbon monoxide and alkenes.2 Lewis base stabi-
lized copper(I) â-diketonates of the general formula Cu-
(â-diketonate)(L) (L ) alkenes, alkynes, phosphines)
were extensively studied in the past as precursors for
copper vapor deposition.2-4
In this paper we report the synthesis and full char-
acterization of two new trifluoroacetato derivatives of
copper(I) bearing electron-rich olefins, [Cu(µ-CF3COO)-
(tbve)]n and [Cu(µ-CF3COO)(van)]2, and the thermody-
namic parameters of their carbonylation reactions. The
study of CO/olefin exchange equilibria has been ex-
tended to the copper(I) hexafluoroacetylacetonate sys-
In the general context of CO/olefin competition ther-
modynamics1 (eq 1) we have recently investigated the
effect of the olefin ligand on the CO/olefin exchange
reaction of organometallic compounds containing early
or late transition elements, namely VCp2(CO)1a and Cu-
(CF3COO)(CO).1b The choice of the olefin was somewhat
ML(olefin) + CO / ML(CO) + olefin
(1)
limited by the fact that vanadocene does not coordinate
olefins containing electron-releasing substituents1a and
by the difficulties encountered in the preparation and
the purification of copper(I) trifluoroacetato derivatives
bearing electron-rich olefins, such as vinyl ethers and
alkoxystyrenes.
In an effort to show how the electronic character of
the coordinated olefin affects the stability of the olefin
derivative Cu(L)(olefin) with respect to the carbonyl
compound Cu(L)(CO), attempts have been made to
obtain trifluoroacetato copper(I) complexes of electron-
(2) Doyle, G.; Eriksen, K. A.; Van Engen, D. Organometallics 1985,
4, 830.
(3) (a) Chi, K. M.; Shin, H.-K.; Hampden-Smith, M. J.; Duesler, E.;
Kodas, T. T. Polyhedron 1991, 10, 2293. (b) Kumar, R.; Fronczek, F.
R.; Maverick, A. W.; Lai, W. G.; Griffin, G. L. Chem. Mater. 1992, 4,
577. (c) Gladfelter, W. L. Chem. Mater. 1993, 5, 1372. (d) Hampden-
Smith, M. J.; Kodas, T. T. Polyhedron 1995, 14, 699. (e) Kumar, R.;
Fronczek, F. R.; Maverick, A. W.; Kim, A. J.; Butler, G. Chem. Mater.
1994, 6, 587.
* To whom correspondence should be addressed. E-mail: pampa@
dcci.unipi.it. Tel: int. code + 050 2219 219. Fax: int. code + 050 2219
246.
(4) (a) Chi, K.-M.; Hou, H.-C.; Hung, P.-T.; Peng, S.-M.; Lee, G.-H.
Organometallics 1995, 14, 2641. (b) Rozenberg, G. G.; Steinke, J. H.
G.; Gelbrich, T.; Hursthouse, M. B. Organometallics 2001, 20, 400. (c)
Chen, T.-Y.; Vaissermann, J.; Doppelt, P. Inorg. Chem. 2001, 40, 616.
(d) Krisyuk, V. V.; Turgambaeva, A. E.; Rhee, S.-W. Polyhedron 2004,
23, 809. Herberhold, M.; Milius, W.; Akkus, N. Z. Naturforsch., B 2004,
59, 843.
† Universita` di Pisa.
‡ Universita` di Parma.
(1) (a) Calderazzo, F.; Guelfi, M.; Pampaloni, G. Organometallics
2004, 23, 1519. (b) Pampaloni, G.; Peloso, R.; Graiff, C.; Tiripicchio,
A. Organometallics 2005, 24, 819.
10.1021/om050416r CCC: $30.25 © 2005 American Chemical Society
Publication on Web 08/04/2005

4476 Organometallics, Vol. 24, No. 18, 2005
Pampaloni et al.
Table 1. Selected Bond Distances (Å) and Angles
a
(deg) in [Cu(µ-CF3COO)(tbve)]n
Cu(1)-O(1)
Cu(1)-O(3′)
Cu(1)-C(3)
Cu(1)-C(4)
1.972(3)
2.020(3)
2.001(4)
2.159(3)
Cu(1)-M(1)
C(1)-O(1)
C(1)-O(3)
C(3)-C(4)
1.967(5)
1.251(5)
1.224(5)
1.363(5)
O(1)-Cu(1)-O(3′)
95.10(13) O(3′)-Cu(1)-M(1) 133.67(14)
O(1)-Cu(1)-M(1) 131.23(14)
a M(1) is the midpoint of the C(3)-C(4) double bond. Symmetry
transformations used to generate equivalent atoms: (′) 1 - y + 1,
x - 1, z + 1/4; (′′) y + 1, -x + 1, z - 1/4.
Figure 1. View of a fragment of the molecular structure
of [Cu(µ-CF3COO)(tbve)]n with the atomic numbering
scheme. The chain develops along the crystallographic 41
axis.
tem, and the parameters of the carbonylation equilib-
rium have been determined for [Cu(hfacac)(L)] (L ) coe,
nbe, van, cod). Moreover, the crystal structures of [Cu-
(hfacac)(coe)] and [Cu(hfacac)(van)] have been deter-
mined.
Results and Discussion
Figure 2. View of the molecular structure of [Cu(µ-CF3-
COO)(van)]2‚C7H8 with the atomic numbering scheme.
Synthesis and Structural Studies. Trifluoroac-
etato olefin complexes of copper(I) have been prepared
5
from Cu(CF3COO)(toluene)0.5 by ligand exchange in
is asymmetrically bound to the olefin double bond, the
Cu-C bond distances being 2.001(4) and 2.159(3) Å.
The structure of [Cu(µ-CF3COO)(tbve)]n adds to the
restricted family of structurally characterized vinyl
ether complexes of transition elements6 and represents
the first example of a transition-metal complex of tbve7
characterized by X-ray diffractometry. Moreover, at
variance with most of the structurally characterized
polymeric copper(I) trifluoroacetato compounds, which
contain two bridging trifluoroacetates,1b the polymeric
chain in [Cu(µ-CF3COO)(tbve)]n is obtained through
single trifluoroacetate bridges between adjacent copper
atoms. It is noteworthy that the polymeric chain runs
around the crystallographic screw axis 41.
The copper(I) complex of van, [Cu(µ-CF3COO)(van)]2‚
C7H8, crystallizes with one molecule of disordered
toluene per dimeric unit. The molecular structure of
[Cu(µ-CF3COO)(van)]2‚C7H8 is shown in Figure 2; the
most significant bond distances and angles are listed
in Table 2. The complex is dimeric, the two carboxylate
ligands symmetrically bridging the two copper atoms
to form an eight-membered ring. The copper‚‚‚copper
separation is 3.100(2) Å, slightly longer than that found
toluene (eq 2). The olefin derivatives, soluble in aromatic
Cu(CF3COO)(toluene)0.5 + olefin f
Cu(CF3COO)(olefin) + 0.5(toluene) (2)
olefin ) tbve, van, nbe
or chlorinated hydrocarbons, have been characterized
(IR and NMR spectra and X-ray crystallography) as
containing η2-ligated olefins. Some difficulties have been
encountered in the isolation of Cu(CF3COO)(tbve), due
to its heat and light sensitivity. Although no particular
conditions must be adopted during the preparation, the
isolated complex darkens in the solid state with forma-
tion of unidentified compounds; for this reason, it has
to be stored in the dark and at low temperature. No
special precautions are necessary for the norbornene
derivative, while storing of Cu(CF3COO)(van) in a
refrigerator is highly recommended.
The structures of [Cu(µ-CF3COO)(tbve)]n and [Cu(µ-
CF3COO)(van)]2‚C7H8 have been fully elucidated by
X-ray crystallography. The structure of [Cu(µ-CF3COO)-
(tbve)]n is shown in Figure 1 together with the atomic
numbering scheme; a selection of bond distances and
angles is reported in Table 1. The complex is polymeric,
with the trifluoroacetato ligand bridging two adjacent
copper atoms (the Cu‚‚‚Cu separation is 3.075(2) Å). On
consideration of the two oxygen atoms of two [CF3COO]-
bridges and the midpoint of the CdC double bond of the
coordinated olefin, the coordination at copper can be
considered to be nearly trigonal planar. The copper atom
(6) Chang, T. C. T.; Foxman, B. M.; Rosenblum, M.; Stockman, C.
J. Am. Chem. Soc. 1981, 103, 7361. Planas, J. G.; Marumo, T.;
Ichikawa, Y.; Hirano, M.; Komiya, S. Dalton Trans. 2000, 2613. Elder,
R. C.; Pesa, F. Acta Crystallogr., Sect. B 1978, 34, 268. Sartori, F.;
Leoni, L. Acta Crystallogr., Sect. B 1976, 32, 145.
(7) Only a few examples of tbve derivatives have been reported in
the literature, namely trans-PtCl2L(tbve) (L ) py, p-toluidine: Laz-
zaroni, R.; Uccello-Barretta, G.; Bertozzi, S.; Salvadori, P. J. Orga-
nomet. Chem. 1985, 297, 117. Lazzaroni, R.; Mann, B. E. J. Organomet.
Chem. 1979, 164, 79), and [MCl2(tbve)]2 (M ) Pt, Pd: Wakatsuki, Y.;
Nozakura, S.; Murahashi, S. Bull. Chem. Soc. Jpn. 1972, 45, 3426.
Wakatsuki, Y.; Nozakura, S.; Murahashi, S. Bull. Chem. Soc. Jpn.
1971, 44, 786).
(5) Belli Dell’Amico, D.; Alessio, R.; Calderazzo, F.; Della Pina, F.;
Englert, U.; Pampaloni, G.; Passarelli, V. Dalton Trans. 2000, 2067.

Cu(I) Derivatives Containing Bidentate O Ligands
Organometallics, Vol. 24, No. 18, 2005 4477
Table 2. Selected Bond Distances (Å) and Angles
a
(deg) in [Cu(µ-CF3COO)(van)]2‚C7H8
Cu(1)-O(1)
Cu(1)-O(3)
Cu(2)-O(2)
Cu(2)-O(4)
C(1)-O(1)
C(1)-O(2)
C(3)-O(3)
C(3)-O(4)
1.961(2)
1.977(3)
1.984(3)
1.991(3)
1.246(4)
1.242(4)
1.245(4)
1.233(4)
Cu(1)-C(5)
Cu(1)-C(6)
Cu(1)-M(1)
C(5)-C(6)
Cu(2)-C(14)
Cu(2)-C(15)
Cu(2)-M(2)
C(14)-C(15)
2.010(4)
2.033(3)
1.904(4)
1.358(5)
2.021(3)
2.046(3)
1.913(4)
1.382(5)
O(1)-Cu(1)-O(3) 103.60(12) O(2)-Cu(2)-O(4) 103.40(11)
M(1)-Cu(1)-O(1) 129.02(13) M(2)-Cu(2)-O(2) 128.31(13)
M(1)-Cu(1)-O(3) 126.89(12) M(2)-Cu(2)-O(4) 128.14(13)
a M(1) and M(2) are the midpoints of the C(5)-C(6) and C(14)-
C(15) double bonds.
in [Cu(µ-CF3COO)(coe)]2 (2.898(1) Å).1b On consideration
of the two oxygen atoms of the [CF3COO]- bridges and
the midpoint of the olefin double bond, the coordination
at copper can be considered as nearly trigonal planar.
The Cu-C bond distances are in the range 2.010(4)-
2.046(3) Å. The two ethereal oxygen atoms O5 and O6
are involved in weak interactions with the copper atoms
of adjacent dimers (Cu2‚‚‚O5 ) 2.774(3) and Cu1‚‚‚O6
) 2.881(3) Å), forming polymeric chains along the
crystallographic b axis.
Figure 3. View of the molecular structure of [Cu(hfacac)-
(coe)] with the atomic numbering scheme.
Hexafluoroacetylacetonato derivatives of copper(I)
have been prepared by reaction of Cu2O with hexafluo-
roacetylacetone in dichloromethane or THF in the
presence of olefin or CO (eq 3).
Cu2O + 2hfacacH + 2(olefin) f
2Cu(hfacac)(olefin) + 2H2O (3)
L ) nbe, coe, van, cod
Due to the tendency to disproportionation in the
presence of basic solvents typical of copper(I) deriva-
tives8 (2Cu(I) f Cu + Cu(II)), and in particular of
hexafluoroacetylacetonato derivatives,2 the procedure
described by Doyle and co-workers2 has been modified
in some cases and dichloromethane was used instead
of THF. Nevertheless, some disproportionation (forma-
tion of a pale green solution and of a reddish solid) was
always observed, the amount of copper(II) being almost
negligible in the case of nbe and coe. On the other hand,
a separation procedure of Cu(hfacac)(van) from the
copper(II) complex Cu(hfacac)2(van), derived from the
disproportionation reaction, had to be devised (see
Experimental Section). The compound Cu(hfacac)2(van)
was identified as containing an O-coordinated van
ligand by analytical and infrared data (the O-CH3
stretching vibration shifts from 1248 to 1163 cm-1 on
complexation).
We have observed that the copper(I) disproportion-
ation occurs to a large extent in THF during the
preparation of Cu(hfacac)(cod),2 with formation of Cu-
(hfacac)2(THF)2 (vide infra). Furthermore, we could not
prepare tbve, diethyl fumarate, or methyl cinnamate
derivatives, due to the fact that disproportionation of
copper(I) was the main reaction even in hydrocarbon
solutions. These reactions were not investigated further.
Figure 4. View of the molecular structure of [Cu(hfacac)-
(van)] with the atomic numbering scheme.
Table 3. Selected Bond Distances (Å) and Angles
(deg) in [Cu(hfacac)(coe)]a
Cu(1)-C(6)
Cu(1)-C(7)
Cu(1)-M(1)
2.017(4)
2.013(4)
1.904(4)
C(6)-C(7)
Cu(1)-O(2)
Cu(1)-O(1)
1.363(6)
1.956(3)
1.961(3)
O(2)-Cu(1)-O(1)
94.19(13) O(2)-Cu(1)-M(1) 130.11(16)
O(1)-Cu(1)-M(1) 134.25(15)
a M(1) is the midpoint of the C(6)-C(7) double bond.
The compounds Cu(hfacac)(L) (L ) coe, nbe, van) have
been characterized by single-crystal X-ray diffraction;
due to the poor quality of the crystals of Cu(hfacac)-
(nbe), only the structures of [Cu(hfacac)(coe)] and of [Cu-
(hfacac)(van)] are described here, the structure of the
norbornene derivative being substantially similar as far
as coordination to copper is concerned.
Hexafluoroacetylacetonato olefin derivatives of cop-
per(I) are monomeric compounds, with the copper atom
lying in a nearly trigonal planar environment. The
structures of [Cu(hfacac)(coe)] and [Cu(hfacac)(van)] are
shown in Figures 3 and 4, and the most important bond
distances and angles are listed in Tables 3 and 4,
respectively. In [Cu(hfacac)(van)], two centrosymmetri-
cally related molecules are joined as dimers through
weak interactions between the ethereal oxygen atoms
and the copper atoms (Cu1‚‚‚O3 ) 2.658(3) Å) and
through face-to-face π-π stacking (approximately 3.7
(8) (a) Endicott, J. F.; Taube, H. Inorg. Chem. 1965, 4, 437. (b)
Caulton, K. G.; Davies, G.; Holt, E. M. Polyhedron 1990, 9, 2319. (c)
Jardine, F. H. Adv. Inorg. Chem. Radiochem. 1975, 17, 115. (d) Sloan,
W. H. J. Am. Chem. Soc. 1910, 32, 972 (cited in ref 8c). (e) Anders, U.;
Plambeck, J. A. Can. J. Chem. 1969, 47, 3055.

4478 Organometallics, Vol. 24, No. 18, 2005
Pampaloni et al.
Table 4. Selected Bond Distances (Å) and Angles
(deg) in [Cu(hfacac)(van)]a
Table 5. 13C NMR Resonances of the Olefinic
Carbon Atoms in CuL(olefin) compounds (C6D6, T
) 294 K)
Cu(1)-C(6)
Cu(1)-C(7)
Cu(1)-M(1)
2.008(4)
2.024(3)
1.894(3)
C(6)-C(7)
Cu(1)-O(1)
Cu(1)-O(2)
1.379(5)
1.975(3)
1.970(3)
Cu(L)(olefin)
L ) hfacac
L ) CF3CO2
O(2)-Cu(1)-O(1)
94.06(12) O(2)-Cu(1)-M(1) 130.61(13)
uncomplexed olefin
O(1)-Cu(1)-M(1) 134.49(13)
a
a
olefin
δ (ppm)
δ (ppm)
∆
δ (ppm)
∆
a M(1) is the midpoint of the C(6)-C(7) double bond.
cod
coe
nbe
van
128.8
115.1
100.2
103.2
102.5
72.2
13.7
30.1
32.3
34.3
39.2
115.7
102.6
104.6
106.6
76.5
13.1
27.7
30.9
30.2
34.2
130.3
135.5
136.8 (CHd)
111.4 (CH2d)
a ∆ ) δuncomplexed olefin - δcomplexed olefin, both measured in the same
solvent under the same conditions.
a CO atmosphere (eq 4). No disproportionation was
CuCl + Tl(hfacac) + CO f Cu(hfacac)(CO) + TlCl
(4)
observed under these experimental conditions, and
cooling the solution to -30 °C afforded Cu(hfacac)(CO)
as a colorless crystalline compound (ν˜CO: 2112 cm-1
,
Figure 5. Schematic view of the centrosymmetric [Cu-
(hfacac)(van)]2 dimeric units. Dashed lines indicate inter-
molecular contacts between copper and ethereal oxygen in
adjacent molecules.
Nujol mull) which quickly decomposed into a green
brown solid with loss of CO.
13C NMR Spectra and Some Ideas Concerning
the Copper(I)-Alkene Bond. The availability of two
classes of olefin copper(I) compounds (trifluoroacetates
and hexafluoroacetylacetonates) and their high solubil-
Å) between the aromatic rings of the olefins (see Figure
5). The Cu-C bond distances are almost identical in
both [Cu(hfacac)(coe)] (2.013(4) and 2.017(4) Å) and [Cu-
(hfacac)(van)] (2.008(4) and 2.024(4) Å) and comparable
to the corresponding distances found in the Cu(hfacac)-
(alkene) family (2.011(3) and 2.029(3) Å in Cu(hfacac)-
(7-tert-butoxy-2,5-norbornadiene)4a and 2.011(5) and
2.025(6) Å in Cu(hfacac)(vinyltrimethylsilane)).9
The preparation of the carbonyl derivative Cu(hfacac)-
(CO) deserves some additional comments. Attempts to
isolate Cu(hfacac)(CO) from THF according to the
procedure reported in the literature2 (eq 2) were not
successful, due to disproportionation and easy loss of
CO during the isolation procedures (evaporation of the
solvent in vacuo at room temperature or lower). Nev-
ertheless, a strong IR carbonyl band (ν˜CO: 2120 cm-1
(toluene); 2131 cm-1 (CH2Cl2)) confirmed the presence
of coordinated CO. During one preparation of Cu-
(hfacac)(CO), a green THF/heptane solution was cooled
at -30 °C, but the compound which separated out
consisted of pale green crystals of Cu(hfacac)2(THF)2,
formed by disproportionation of copper(I) in THF, which
was characterized by analysis, spectroscopy, and X-ray
diffraction.10
ity in non polar solvents prompted us to study their 13
C
NMR spectra. This study was of particular interest as
far as the interpretation of the nature of the copper-
alkene bond is concerned. Data are collected in Table
5. The general observation is that the resonances of the
olefin carbon atoms show high-field shifts on coordina-
tion, thus suggesting a shielding of the carbon atoms
on going from uncoordinated to ligated olefin. Similar
results have been reported in former studies on copper-
(I) complexes of the same type.12 The difference between
the resonances of the olefinic carbon atoms of coordi-
nated and uncoordinated cod (13.7 and 13.1 ppm for Cu-
(hfacac)(cod) and Cu(CF3COO)(cod) complexes, respec-
tively) is smaller than those observed for other olefins:
it has been ascribed to fluxionality processes which
average the chemical shifts of the coordinated and
uncoordinated olefin.
According to former contributions on similar sys-
tems,12 the Cufolefin π-back-donation will cause a
high-field shift of the 13C NMR spectra of coordinated
olefins with respect to the uncoordinated ones, whereas
a low-field shift of the corresponding resonance will be
expected due to olefinfCu σ-donation. Therefore, the
resulting NMR spectrum will be the combination of the
two contributions and we would observe low-field shifts
in the case of prevalence of the σ-contribution and high-
field shifts when the π-contribution is dominant.
On the basis of these considerations, data reported
in Table 5 suggest that the π-component dominates over
the σ-component in our systems. Similar conclusions
were obtained on cyclopentadienyl palladium(II) deriva-
tives containing substituted styrenes.13 The largest
Operating in the absence of basic species which may
induce disproportionation of copper(I), and considering
that water is formed in stoichiometric amounts accord-
ing to eq 3, we attempted the preparation of Cu(hfacac)-
(CO) by reacting CuCl and Tl(hfacac)11 in toluene under
(9) Chen, T. Y.; Omne`s, L.; Vaisserman, J.; Pascal, P. Inorg. Chim.
Acta 2004, 357, 1299.
(10) As the structure of Cu(hfacac)2(THF)2 (green crystals from THF/
heptane at -30 °C) is very similar to that of Cu(hfacac)2(H2O)2
(Maverick, A. W.; Fronczek, F. R.; Maverick, E. F.; Billodeaux, D. R.;
Cygan, Z. T.; Isovitsch, R. A. Inorg. Chem. 2002, 41, 6488) and the
two THF molecules are severely disordered, crystal data have been
submitted as Supporting Information.
(12) (a) Baum, T. H.; Larson, C. E.; May, G. J. Organomet. Chem.
1992, 425, 189. (b) Salomon, R. G.; Kochi, J. K. J. Am. Chem. Soc.
1973, 95, 1889. (c) Salomon, R. G.; Kochi, J. K. J. Organomet. Chem.
1974, 64, 135.
(11) Hartmann, F. A.; Jacobi, P. L.; Wojcicki, A. Inorg. Synth. 1970,
12, 81.

Cu(I) Derivatives Containing Bidentate O Ligands
Organometallics, Vol. 24, No. 18, 2005 4479
Table 6. Carbon-Carbon Double-Bond Distances
of Olefins as Uncomplexed Species and in the
Corresponding CuL(olefin) Derivatives
Scheme 1. Carbonylation of Cu(L)(olefin)
Derivatives
2Cu(CF3COO)(olefin)solv
+
complexed olefin
2COsolv a Cu2(CF3CO2)2(CO)2,solv + 2(olefin)
olefin
uncomplexed olefin
L ) hfacac
L ) CF3COO
cod
coe
van
1.312a
1.314d
1.303f
1.367(11)b
1.363(6)e
1.379(5)e
1.377(4)c
KCF COO ) [Cu2(CF3COO)2(CO)2,solv][olefinsolv]2/
1.367(7)c
3
1.382(5), 1.358(5)e
2
[Cu(CF3COO)(olefin)solv]2[COsolv
]
a Reference 14. b Reference 3a. c Reference 1b. d Reference 15.
e This work. f Reference 16.
olefin ) tbve, van
Cu(hfacac)(olefin)solv
COsolv a Cu(hfacac)(CO)solv + olefinsolv
Khfacac ) [Cu(hfacac)(CO)solv][olefinsolv]/
[Cu(hfacac)(olefin)solv][COsolv
olefin ) coe, nbe, van
+
high-field shift has been observed for Cu(L)(van) (L )
CF3COO, hfacac), thus suggesting a larger π-back-
donation contribution in the case of this olefin than in
the case of cod, nbe, and coe. In this connection, it is
interesting to observe that the largest increase of the
CdC bond distances on going from uncoordinated to
complexed olefin (see Table 6) is observed for van with
respect to cod and coe.
Table 6 data also suggest that the upfield shifts of
the olefin carbon resonances for the trifluoroacetato
derivatives are smaller than those found within the
hexafluoroacetylacetonato analogues. This observation
may be explained by considering that the π-component
to the Cu-olefin bond increases on increasing the
basicity of the ancillary ligand, which was reported to
increase in the order triflate < trifluoroacetate <
hexafluoroacetylacetonate < trifluoroacetylacetonate for
Cu(I)(cod) complexes.12
]
Data were collected by gas volumetric methods,19 and
the values of the equilibrium constants are reported in
Table 7 together with the enthalpy and entropy of the
reactions obtained from van’t Hoff plots.
Data of Table 7 (which lists also our previous results
on copper(I)1b) show the following.
(a) Reactions are exothermic; the negative values of
the reaction entropy are in agreement with the decreas-
ing number of gaseous species on going from left to right
in the equations reported in Scheme 1.
(b) On considering that the enthalpy of solution of
olefins is generally small and not largely dependent on
the nature of the olefin,20 we can observe that the
relative stability of the olefin complex with respect to
CuL(CO) increases in the order meci21 , defu < tbve <
van < coe < cod for L ) trifluoroacetate and in the order
van < coe < nbe < cod for L ) hexafluoroacetylaceto-
nate. The presence of some interactions between both
the double bonds of cod and copper, observed either in
the solid state3a or in the gas phase,22 may explain the
stability of Cu(hfacac)(cod) with respect to all of the
other derivatives of the same class.
(c) Once the difference of stoichiometry of the carbo-
nylation reactions is considered, the general trend is
that the stability of the olefin complexes with respect
to the corresponding carbonyl derivative depends on the
anionic ligand as well; i.e., the enthalpy variation of the
reactions reported in Scheme 1 is higher for trifluoro-
acetates than for the corresponding hexafluoroacetylac-
etonates.
Olefin/CO Exchange Reactions. In this section of
the paper we will discuss the results obtained on the
carbonylation reactions of trifluoroacetato and hexafluo-
roacetylacetonato olefin derivatives of copper(I).
Before presenting the results of the thermodynamic
study, some comments are required concerning the
nuclearity of the species present in solution. Since we
used the same experimental conditions as in our previ-
ous research on this subject,1b we will consider olefin
and carbonyl adducts of copper trifluoroacetate to be
present in toluene solution as mononuclear and di-
nuclear species, respectively. On the other hand, on the
basis of the fact that olefin adducts of copper(I) hexaflu-
oroacetylacetonate are generally mononuclear in the
solid state2,3a,b,4,17 (vide infra), a mononuclear formula-
tion for the diketonates (either olefin or carbonyl deriva-
tive) will be used in our calculations (Scheme 1). As
additional support to this hypothesis, bridging diketo-
nates have not been observed for copper, while the
bridging disposition is rather common for carboxylate
derivatives of transition elements.18
Concluding Remarks
(13) Miki, K.; Shiotani, O.; Kai, Y.; Kasai, N.; Kanatani, H.;
Kurosawa, H. Organometallics 1983, 2, 585.
This paper deals with olefin derivatives of copper(I)
containing fluorinated ancillary ligands. With respect
to our previous paper, we have reported new data
(14) Conquest version 1.7; Cambridge Crystallographic Data Centre,
Cambridge, U.K., 2004; CSD version 5.26 (Feb 2005). The value is the
average of the CdC bond distances observed in 3,4,7,8-tetrasubstituted
cyclooctadienes (CSD reference codes: MAPCTD, PIRKEG, RULTIB).
(15) Conquest version 1.7; Cambridge Crystallographic Data Centre,
Cambridge, U.K., 2004; CSD version 5.26 (Feb 2005). The value is the
average of the CdC bond distances observed in 5,6-disubstituted
cyclooctenes (CSD reference codes: ENADAY, FAQKIR, HAVGAM,
HAVGIU, HECDAU, JITMEE, SORCUX, WIRNUG).
(18) Oldham, C. Carboxylates, Squarates and Related Species. In
Comprehensive Coordination Chemistry; Wilkinson, G., Gillard, R. D.,
McCleverty, J. A., Eds.; Pergamon Press: London, 1987; Vol. 2, p 435.
(19) Calderazzo, F.; Cotton, F. A. Inorg. Chem. 1962, 1, 30.
(20) Saluja, P. P. S.; Young, T. M.; Rodewald, R. F.; Fuchs, F. H.;
Kohli, D.; Fuchs, R. J. Am. Chem. Soc. 1977, 99, 2949. Fuchs, R.;
Saluja, P. S. Can. J. Chem. 1976, 54, 3857. Lister, M. W. J. Am. Chem.
Soc. 1941, 63, 143.
(16) Byrn, M. P.; Curtis, C. J.; Hsiou, Y.; Khan, S. I.; Sawin, P. A.;
Tendick, S. K.; Terzis, A.; Strouse, C. E. J. Am. Chem. Soc. 1993, 115,
9480.
(17) Pettinari, C.; Marchetti, F.; Drodzov, A. â-Diketones and
Related Ligands. In Comprehensive Coordination Chemistry II; Mc-
Cleverty, J. A., Meyer, T. J., Eds.; Elsevier: Oxford, U.K., 2004; Vol.
1, p 97.
(21) The carbonylation of the methyl cinnamate (meci) adduct of
copper(I) trifluoroacetate is quantitative, even in the solid state.1b
(22) Hnyk, D.; Bu¨hl, M.; Brain, P. T.; Robertson, H. E.; Rankin, D.
W. H. J. Am. Chem. Soc. 2002, 124, 8078.

4480 Organometallics, Vol. 24, No. 18, 2005
Pampaloni et al.
Table 7. Equilibrium Constants and
Thermodynamic Parameters at 298 K for the
CO/Olefin Exchange Reported in Scheme 1
coe, cod, and nbe. Moreover, the stability of the Cu(CF3-
COO)(olefin) species decreases on increasing the electron-
withdrawing power, i.e., the π-acceptor capability, of the
olefin.
L ) CF3COO
The smaller carbonylation enthalpy observed for the
hfacac complexes with respect to the trifluoroacetates
probably depends on the relative stabilities of Cu-
(hfacac)(CO) and Cu(CF3CO2)(CO). Due to the presence
of the more donating hexafluoroacetylacetonate, the
π-back-donation in Cu(hfacac)(CO) is likely larger than
in Cu(CF3CO2)(CO), thus causing a decrease of stability
of the former (Cu(hfacac)(CO) is unstable with respect
to the CO loss). On the other hand, the stability of the
olefin complexes may be less affected by the ancillary
ligands, the alkenes behaving as better σ-donors than
CO.
∆H
∆S
olefin
coea
cod
KCF CO (M-1
)
(kJ mol-1
)
(J mol-1 K-1
)
ref
3
2
(6.3 ( 3.2) × 102 -71 ( 17
-189 ( 57
-131 ( 14
1b
1b
1b
12.6 ( 2.4
-46 ( 4
defu (1.1 ( 0.7) × 107 -112 ( 20 -248 ( 65
tbve (1.4 ( 0.4) × 104 -110 ( 12 -285 ( 38
this work
this work
van
(5.3 ( 1.0) × 103 -91 ( 7
-234 ( 25
L ) hfacac
∆H
∆S
olefin
Khfacac
(kJ mol-1
)
(J mol-1 K-1
)
ref
coe
nbe
cod
van
2.80 ( 0.40 -12.0 ( 0.2
-31.7 ( 0.7
-29 ( 2
nd
this work
this work
this work
this work
0.86 ( 0.15
0.40 ( 0.08
20 ( 3
-8.3 ( 0.7
ndb
-28 ( 2
-69 ( 7
Experimental Section
a Equilibrium constant at 293.2 K. b nd ) not determined.
General Procedures. Unless otherwise stated, all of the
operations were carried out under an atmosphere of prepuri-
fied argon. Solvents were dried by conventional methods prior
to use. Diethyl fumarate (Fluka), 1,5-cyclooctadiene (Aldrich),
cis-cyclooctene (Aldrich), and 4-vinylanisole (Aldrich) were
distilled under reduced pressure and stored at ca. -30 °C; tert-
butyl vinyl ether (Aldrich) was distilled at atmospheric pres-
sure and stored at ca. -30 °C; hfacacH (Aldrich), norbornene
(Aldrich), and Cu2O (Aldrich) were used as received. Cu(CF3-
COO)(toluene)0.55 and Tl(hfacac)11 were prepared according to
literature procedures. IR spectra were recorded on a FT-1725X
instrument on Nujol or polychlorotrifluoroethylene (PCTFE)
mulls prepared under rigorous exclusion of moisture and air.
NMR spectra (1H at 200 MHz and 13C at 50.31 MHz, with TMS
as reference; 19F at 188 MHz, with C6F6 as reference) were
recorded with a Varian Gemini 200BB spectrometer. The gas
volumetric measurements were performed with the apparatus
described by Calderazzo and Cotton.19
concerning hexafluoroacetylacetonato derivatives and
trifluoroacetato copper(I) complexes containing electron-
releasing olefins.
Mixed olefin trifluoroacetato derivatives have been
prepared by starting from Cu(CF3COO)(toluene)0.5 ac-
cording to a previously reported synthetic pathway. At
variance with the previously reported copper(I) trifluo-
roacetato olefin derivatives, the solid-state structure of
[Cu(µ-CF3COO)(tbve)]n consists of polymeric chains
formed by single trifluoroacetato bridges. The prepara-
tion of the mixed olefin hfacac derivatives (from the
readily available Cu2O, hfacacH, and olefin) is compli-
cated by the instability of Cu(hfacac), whose dispropor-
tionation to copper(0) and copper(II) may also be pro-
moted by the water formed in the reaction (see Scheme
2). We have found that disproportionation becomes an
important reaction with respect to olefin complexation
in the case of alkenes containing electron-withdrawing
substituents.
Preparation of Cu(CF3COO)(L) (L ) tbve, van, nbe).
Only the preparation of Cu(CF3COO)(tbve) is described in
detail, the other preparations being performed similarly. A
solution of Cu(CF3COO)(toluene)0.5 (1.83 g, 8.2 mmol) in
toluene (40 mL) was added to tbve (0.91 g, 9.1 mmol). A pale
yellow suspension formed. After 15 h of stirring at room
temperature, the pale yellow suspension was added to heptane
(150 mL). The colorless microcrystalline solid which separated
out was recovered by filtration and dried in vacuo at room
temperature, affording 1.62 g (71% yield) of Cu(CF3COO)(tbve)
as an air- and light-sensitive colorless solid, indefinitely stable
in sealed tubes at -30 °C. Anal. Found: C, 33.9; H, 3.9. Calcd
for C8H12CuF3O3: C, 34.7; H, 3.9. IR (Nujol and PCTFE): ν˜/
cm-1 3079 w, 1670 vs, 1639 vs, 1631 vs, 1615 s, 1548 m, 1529
m, 1459 vs, 1406 m, 1264 m, 1198 vs, 1155 vs, 1002 s, 884 s,
Scheme 2. Formation and Disproportionation
Pathways of Copper Hexafluoroacetylacetonates
Cu2O L, hfacacH, solvent8 2Cu(hfacac)L L′8
9
-H2O
Cu + Cu(hfacac)2L′n
(a) L ) nbe, coe; solvent ) CH2Cl2; L′ ) H2O
(b) L ) van; solvent ) CH2Cl2; L′ ) van
(c) L ) cod; solvent ) THF; L′ ) THF
1
847 m, 837 m, 789 m, 727 s. H NMR (C6D6): δ 6.20 (s, 1 H),
4.20 (s, 1 H), 3.64 (s, 1 H). 1.01 (s, 9 H, CH3).
The availability of two copper(I) systems containing
ancillary ligands featuring different electronic proper-
ties (trifluoroacetate and hexafluoroacetylacetonate) and
the choice of alkenes containing electron-releasing or
electron-withdrawing substituents have allowed some
hypotheses on the nature of the copper(I) olefin bond to
be formulated. In particular, we have added some new
evidence to the suggestions reported in the literature12
concerning the decrease of the stability of the copper
olefin derivatives on increasing the Cufolefin π-back-
donation. As a matter of fact, we have found that Cu-
(hfacac)(van) is the least stable complex within the
hfacac derivatives, whose spectral and X-ray data
suggest that van behaves as a better π-acid ligand than
Cu(CF3COO)(van) was obtained as a colorless crystalline
compound, sensitive to air, in 75% yield. Anal. Found: C, 42.8;
H, 3.6. Calcd for C11H10CuF3O3: C, 42.5; H, 3.2. IR (Nujol and
PCTFE): ν˜/cm-1 3138 w, 3096 w, 3072 w, 1867 w, 1679 vs,
1606 s, 1579 m, 1535 mw, 1507 s, 1500 s, 1456 vs, 1314 m,
1303 s, 1250 s, 1198 vs, 1172 vs, 1153 vs, 1041 w, 1024 s, 953
w, 928 s, 850 s, 845 s, 814 m, 788 m, 750 m, 724 s, 693 mw,
525 m. 1H NMR (C6D6): δ 6.95 (d, 2H, J ) 8.4 Hz, m-CH),
6.61 (d, 2H, J ) 8.4 Hz, o-CH), 5.30 (dd, 1H, Jtrans ) 16.4 Hz,
Jcis ) 9 Hz, CH)CH2), 4.13 (d, 1H, Jtrans ) 16.4 Hz, cis H),
3.53 (d, 1H, Jcis) 9 Hz, trans H). 13C NMR (C6D6): δ 160.6
(COCH3), 128.3 (ring CH), 127.9 (CCHdCH2), 114.7 (ring CH),
106.6 (CHdCH2), 76.5 (CHdCH2), 54.9 (OCH3).
Cu(CF3COO)(nbe) was obtained as a colorless crystalline
compound, very sensitive to air, in 80% yield, Anal. Found:

Cu(I) Derivatives Containing Bidentate O Ligands
Organometallics, Vol. 24, No. 18, 2005 4481
Table 8. Carbonylation Reactions of Cu(L)(olefin)
Complexes
C, 40.0; H, 3.6. Calcd for C9H10CuF3O2: C, 39.9; H, 3.7. IR
(Nujol and PCTFE): ν˜/cm-1 3082 w, 3045 w, 1678 vs, 1455 s,
1325 m, 1295 mw, 1277 mw, 1211 vs, 1146 vs, 1122 s, 971
mw, 945 w, 902 w, 889 m, 850 m, 846 m, 789 m, 729 s, 673 w,
T (K)
103[Cu(CF3COO)(tbve)]i
CO/Cu
103KCF COO (M-1
)
3
288.4
298.2
308.5
317.5
332.0
9.25
13.21
6.98
10.19
10.38
0.977
0.919
0.881
0.791
0.689
150
14
3
1
0.3
1
523 m, 451 m. H NMR (C6D6): δ 4.47 (s, 2 H, CHdCH), 2.62
(s, 2 H, CHCHdCH), 1.40-0.90 (m, 3 H), (d, 1 H, J ) 10 Hz),
0.70-0.30 (m, 3 H). 13C NMR (C6D6): δ 104.6 (CHdCH), 45.4
(CHCHd), 43.1 (CHCH2CH), 24.2 (CH2CH2).
Preparation of Cu(hfacac)(L) (L ) coe, nbe). Only the
preparation of Cu(hfacac)(coe) is described in detail, the other
being performed similarly. A solution of hfacacH (2.94 g, 14.1
mmol) in dichloromethane (20 mL) was dropped into a well-
stirred mixture of coe (1.59 g, 14.5 mmol) and Cu2O (1 g, 7.0
mmol) in dichloromethane (50 mL). A yellow-green suspension
was obtained, which was filtered. After elimination of the
solvent in vacuo at room temperature, the yellow-green liquid
residue was dissolved in heptane (5 mL) and the solution was
cooled to ca. -30 °C. The pale yellow crystalline solid was
recovered by filtration and dried in vacuo at room temperature,
affording 2.8 g (53% yield) of Cu(hfacac)(coe). Anal. Found: C,
40.8; H, 3.5. Calcd for C13H15CuF6O2: C, 41.1; H, 3.7. IR (Nujol
and PCTFE): ν˜/cm-1 1639 vs, 1598 m, 1553 s, 1526 s, 1473
vs, 1346 m, 1257 vs, 1207 vs, 1101 s, 984 w, 974 w, 799 s, 763
w, 743 w, 722 w, 672 s, 586 m, 528 w, 497 w. 1H NMR (C6D6):
δ 6.19 (s, 1 H, CHCdO), 4.35 (m, 2 H, CHdCH), 1.74 (s, 4 H,
CH2CHd), 1.12 (s, 8 H, (CH2)4). 13C NMR (C6D6): δ 177.9 (q,
JC-F ) 34 Hz, CF3CdO), 118.4 (q, JC-F ) 286 Hz, CF3CdO),
100.2 (CHdCH), 90 (CHCdO), 29.8 (CH2CHd), 26.1 ((CH2)4).
Cu(hfacac)(nbe) was obtained as a yellow crystalline
compound, slightly sensitive to air, in 60% yield. Anal.
Found: C, 39.4; H, 3.0. Calcd for C12H11CuF6O2: C, 39.6; H,
2.8. IR (Nujol and PCTFE): ν˜/cm-1 3085 w, 3042 w, 1639 vs,
1598 m, 1554 s, 1526 s, 1473 vs, 1345 m, 1323 m, 1257 vs,
1207 vs, 1149 vs, 1101 s, 967 w, 944 w, 903 w, 892 w, 799 s,
743 w, 672 s, 586 m, 528 w, 457 w. 1H NMR (C6D6): δ 6.19 (s,
1 H, CHCdO), 4.34 (s, 2 H, CHdCH), 2.53 (s, 2 H, CHCHd
CH), 1.02 (d, 2 H, J ) 7.4 Hz), 0.83 (d, 1 H, J ) 10 Hz), 0.60-
0.30 (m, 3 H). 13C NMR (C6D6): δ 178.0 (q, JC-F ) 34 Hz,
CF3CdO), 118.4 (q, JC-F ) 286 Hz, CF3CdO), 103.2 (CHdCH),
90.0 (CHCdO), 44.9 (CHCHd), 42.9 (CHCH2CH), 24.9
(CH2CH2).
T (K)
103[Cu(CF3COO)(van)]i
CO/Cu
103KCF COO (M-1
)
3
278.5
288.3
298.2
308.3
318.0
12.69
5.12
18.70
8.36
0.585a
0.953
0.859
0.863
0.729
70.9
18.2
5.3
2.5
0.42
8.96
T (K)
103[Cu(hfacac)(coe)]i
CO/Cu
Khfacac
278.6
288.5
298.3
308.0
317.8
16.22
11.37
12.78
11.14
18.52
0.723
0.748
0.703
0.703
0.593
4.09
3.35
2.80
2.47
2.13
T (K)
103[Cu(hfacac)(nbe)]i
CO/Cu
Khfacac
278.6
288.5
298.3
308.0
317.8
16.79
17.62
23.65
20.51
25.71
0.496
0.461
0.403
0.401
0.362
1.09
0.93
0.86
0.73
0.70
T (K)
103[Cu(hfacac)(van)]i
CO/Cu
Khfacac
278.5
288.4
298.3
307.9
318.0
11.96
14.48
19.09
13.95
19.03
0.717b
0.934
0.887
0.880
0.823
43
25
20
12
10
a [olefin]i ) 0.16 M. b [olefin]i ) 0.12 M.
Preparation of Cu(hfacac)(cod). The preparation has
been performed by a modification of the literature procedure.2
A solution of hfacacH (5.44 g, 26.1 mmol) in THF (30 mL) was
added dropwise over 30 min into a well-stirred mixture of cod
(2.82 g, 26.1 mmol) and Cu2O (1,87 g, 13.1 mmol) in THF (50
mL). After 18 h of stirring, the green suspension was filtered
to remove copper and unreacted Cu2O. After elimination of
the solvent in vacuo at room temperature, a yellow-green solid
was obtained, which was heated at 70 °C/10-2 mmHg. The
green sublimate was identified as Cu(hfacac)2(THF)2 by IR
spectroscopy (vide infra). Cu(hfacac)(cod) was obtained as a
yellow crystalline solid residue (3.29 g; 33%). 1H NMR (C6D6):
δ 6.16 (s, 1H, CHCdO), 5.05 (s, 4H, CHdCH), 1.77 (s, 8H,
CH2). 13C NMR (C6D6): δ 177.7 (q, JC-F ) 34 Hz, CF3CdO),
118.6 (q, JC-F ) 286 Hz, CF3CdO), 115.1 (CHdCH), 89.0
(CHCdO), 28.1 (CH2).
Attempted Preparation of Cu(hfacac)(CO): Prepara-
tion of Cu(hfacac)2(THF)2. According to the literature
procedure,2 a solution of hfacacH (4.7 g, 22.6 mmol) in THF
(25 mL) was dropped over 30 min under CO into a well-stirred
suspension of Cu2O (1.56 g, 10.9 mmol) in CO-saturated THF
(15 mL). The mixture was then filtered under CO to remove
metallic copper from the green solution. The volume of the
solution was reduced to 10 mL in vacuo at room temperature,
and heptane (50 mL) was added. The green solution was
saturated with CO and kept at -30 °C, affording Cu(hfacac)2-
(THF)2 as pale green crystals. Anal. Found: C, 33.9; H, 2.6.
Calcd for C18H18CuF12O6: C, 34.8; H, 2.9. IR (Nujol and
PCTFE): ν˜/cm-1 3289 w, 3148 w, 1640 vs, 1602 s, 1559 s, 1532
s, 1488 vs, 1464 s, 1353 s, 1257 vs, 1219 vs, 1201 vs, 1149 vs,
1107 s, 1050 s, 953 w, 918 m, 888 s, 815 m, 802 vs, 771 w, 745
Preparation of Cu(hfacac)(van). A solution of hfacacH
(5 g, 24.0 mmol) in dichloromethane (25 mL) was dropped over
30 min into a well-stirred mixture of van (3.23 g, 24.1 mmol)
and Cu2O (1.6 g, 11.2 mmol) in dichloromethane (25 mL). The
green suspension was filtered to remove insoluble materials.
After elimination of the solvent in vacuo at room temperature,
a yellow-green solid was obtained, which was heated at 55 °C/
10-2 mmHg. The compound Cu(hfacac)(van) was obtained as
a yellow crystalline solid residue (6.13 g; 68%). Anal. Found:
C, 40.8; H, 2.4. Calcd for C14H11CuF6O3: C, 41.5; H, 2.8. IR
(Nujol and PCTFE): ν˜/cm-1 3271 w, 1642 vs, 1607 s, 1583 m,
1550 m, 1525 s, 1506 s, 1486 s, 1442 s, 1342 m, 1313 m, 1256
vs, 1243 s, 1202 vs, 1186 s, 1177 vs, 1147 vs, 1095 s, 1044 m,
1023 s, 957 m, 911 m, 833 s, 797 s, 751 w, 741 w, 709 mw, 672
1
s, 587 m, 550 mw, 523 m, 453 w. H NMR (C6D6): δ 7.00 (d,
2H, J ) 7.4 Hz, m-CH), 6.58 (d, 2H, J ) 7.4 Hz, o-CH), 6.02
(s, 1H, CHCdO), 5.45 (dd, 1H, Jtrans ) 16.0 Hz, Jcis ) 9.6 Hz,
CHdCH2), 4.11 (d, 1H, Jtrans ) 16.0 Hz, cis H), 3.46 (d, 1H,
Jcis ) 9.6 Hz, trans H). 13C NMR (C6D6): δ 177.8 (q, JC-F ) 34
Hz, CF3CdO), 160.6 (C-OCH3), 128.3 (ring CH), 118.3 (q, JC-F
) 286 Hz, CF3CdO), 114.6 (ring CH), 102.5 (CHdCH2), 90.0
(CHCdO), 72.2 (CHdCH2), 54.7 (OCH3).
The green sublimate (ca. 300 mg) was identified as Cu-
(hfacac)2(van). Anal. Found: C, 36.8, H, 1.6. Calcd for C19H12-
CuF12O5: C, 37.3; H, 2.0. IR (Nujol and PCTFE): ν˜/cm-1 3251
w, 3082 w, 1640 vs, 1608 s, 1561 s, 1530 s, 1511 s, 1366 m,
1300 m, 1257 vs, 1211 vs, 1163 s, 1148 vs, 1110 m, 1043 m,
986 m, 832 s, 802 s, 769 w, 722 s, 680 s, 596 m, 528 mw.
Magnetic measurement: øMcorr ) 1.70 × 10-3 cgsu; diamagnetic
correction -286.40 × 10-6 cgsu; µeff(294 K) ) 2.01 µB.
corr
m, 721 w, 679 vs, 594 s, 528 w. Magnetic measurement: øM
) 1.23 × 10-3 cgsu; diamagnetic correction -262.30 × 10-6
cgsu, µeff(294 K) ) 1.71 µB.

4482 Organometallics, Vol. 24, No. 18, 2005
Pampaloni et al.
Table 9. Crystallographic Data for the Compounds [Cu(µ-CF3COO)(tbve)]n, [Cu(µ-CF3COO)(van)]2‚C7H8,
[Cu(hfacac)(coe)], and [Cu(hfacac)(van)]
[Cu(µ-CF3COO)(tbve)]n
[Cu(µ-CF3COO)(van)]2‚C7H8
[Cu(hfacac)(coe)]
[Cu(hfacac)(van)]
formula
C8H12CuF3O3
276.72
tetragonal
P41
9.495(3)
9.495(3)
12.168(5)
90
C22H20Cu2F6O6‚C7H8
713.59
C13H15CuF6O2
380.79
orthorhombic
Pbca
20.574(5)
13.856(3)
10.607(3)
90
C14H11CuF6O3
404.77
triclinic
P1h
formula wt
cryst syst
triclinic
space group
P1h
a, Å
12.714(5)
13.467(5)
9.236(3)
99.23(5)
101.09(5)
95.04(5)
1520.2(10)
2
9.926(4)
10.517(5)
9.211(4)
102.71(5)
106.81(5)
112.72(5)
786.8(6)
2
b, Å
c, Å
R, deg
â, deg
90
90
90
90
γ, deg
V, Å3
1097.0(7)
4
3023.8(13)
8
Z
Dcalcd, g cm-3
F(000)
1.675
1.559
1.673
1.708
560
724
1536
404
µ, cm-1
31.37
24.18
27.10
14.63
no. of rflns collected
no. of unique rflns
no. of obsd rflns (I > 2σ(I))
no. of params
final R indices (I > 2σ(I))a
4153
5725
2622
6003
1092 (Rint ) 0.0603)
1071
5710 (Rint ) 0.0522)
4456
2622 (Rint ) 0.000)
2204
2949 (Rint ) 0.0537)
2889
184
454
200
272
R1 ) 0.0295,
wR2 ) 0.0742
R1 ) 0.0301,
wR2 ) 0.0748
R1 ) 0.0496,
wR2 ) 0.1345
R1 ) 0.0643,
wR2 ) 0.1445
R1 ) 0.0557,
wR2 ) 0.1650
R1 ) 0.0643,
wR2 ) 0.1839
R1 ) 0.0535,
wR2 ) 0.1518
R1 ) 0.0545,
wR2 ) 0.1527
final R indices (all data)a
2
a R1 ) ∑||Fo| - |Fc||/∑(Fo); wR2 ) [∑[w(Fo2- Fc )2]/∑[w(Fo2)2]]1/2
.
Attempted Isolation of Cu(hfacac)(CO). A thin-walled
sealed glass container containing CuCl (0.36 g, 3.6 mmol) was
introduced into an Erlenmeyer flask equipped with a lateral
stopcock containing a solution of Tl(hfacac) (1.5 g, 3.6 mmol)
in toluene (50 mL). The system was connected to a gas
volumetric buret and saturated with CO at 292.3 K at 753
mmHg of total pressure. The container was broken by me-
chanical stirring, and the CO absorption was measured. After
3 days of stirring, the absorption of CO had become very slow
and corresponded to a CO/Cu molar ratio of 0.7. An IR
spectrum of the solution in the carbonyl stretching region
showed a strong absorption at 2120 cm-1. Solids (containing
ca. 30% of the copper introduced) were filtered off, and the
solution was partially evaporated in vacuo at room tempera-
ture. After saturation with CO, the solution turned colorless
and a strong absorption at 2120 cm-1 was present in the
infrared spectrum. The concentrated solution was then cooled
at ca. -30 °C, affording a small amount of colorless crystals
(ν˜CO, Nujol ) 2112 cm-1) which quickly decomposed with CO
loss.
Carbonylation Reactions of Cu(L)(olefin) (L ) CF3CO2,
olefin ) tbve, van; L ) hfacac, olefin ) coe, nbe, van).
IMPORTANT: In the case of a carbonylation reaction largely
shifted to the right such as in the cases of Cu(CF3CO2)(van)
and Cu(hfacac)(van) at 278.5 K, a certain amount of olefin,
[olefin]i, was added to the solution. In the following, the
carbonylation in the absence of added olefin is described.
Toluene (50 mL) and a thin-walled sealed glass container
containing the copper(I) derivative were introduced into an
Erlenmeyer flask equipped with a lateral stopcock. The system
was connected to a gas volumetric buret and saturated with
CO at atmospheric pressure at the temperature of the experi-
ment. The glass container was then broken by mechanical
stirring, and the absorption of gas was measured. The con-
centration of CO in toluene is assumed to be 7.5 × 10-3 M in
the range of temperature studied.1a The gas volumetric experi-
X-ray Structure Determination of [Cu(µ-CF3COO)-
(tbve)]n, [Cu(µ-CF3COO)(van)]2‚C7H8, [Cu(hfacac)(coe)],
and [Cu(hfacac)(van)]. Crystals were grown from toluene/
heptane ([Cu(µ-CF3COO)(tbve)]n, [Cu(µ-CF3COO)(van)]2‚C7H8,
[Cu(hfacac)(van)]) or by sublimation at 35 °C/10-2 mmHg ([Cu-
(hfacac)(coe)]). Data were collected at 173 K on an Enraf-
Nonius CAD 4 single-crystal diffractometer (Cu KR radiation,
λ ) 1.54183 Å). Details of the X-ray data collections are
collected in Table 9. The structures were solved by Patterson
and by direct methods with SHELXS-97 and refined against
F2 with SHELXL-97,23 with anisotropic thermal parameters
for all non-hydrogen atoms. In [Cu(µ-CF3COO)2(van)]2‚C7H8
the toluene molecule was disordered in two positions with an
occupancy factor of 0.5. The fluorine atoms of one of the two
trifluoroacetate groups in [Cu2(µ-CF3COO)2(van)]2‚C7H8 and
those of the hfacac anion in [Cu(hfacac)(van)] were disordered
and distributed over two positions.
Acknowledgment. Thanks are due to the Ministero
dell’Istruzione dell’Universita` e della Ricerca (MIUR,
Roma), Programma di Ricerca Scientifica di Notevole
Interesse Nazionale 2004-2005, for financial support, to
the COST Action D17/003 of the European Community
for promoting the scientific activity, and to Professor
Fausto Calderazzo, University of Pisa, for discussions.
Supporting Information Available: A full table of
equilibrium data at different temperatures (including van’t
Hoff plots) and X-ray crystallographic data for the compounds
[Cu(µ-CF3COO)(tbve)]n, [Cu(µ-CF3COO)(van)]2‚C7H8, [Cu(hfa-
cac)(coe)], [Cu(hfacac)(van)], and [Cu(hfacac)2(THF)2]; X-ray
data are also available as CIF files. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM050416R
ments were repeated twice, thus obtaining consistent COabsorbed
/
Cu molar ratios. The details of the experiments together with
the measured COabsorbed/Cu molar ratios (CO/Cu) at equilibri-
um, respectively, are reported in Table 8.
(23) Sheldrick, G. M., SHELX-97: Programs for Crystal Structure
Analysis (Release 97-2); University of Go¨ttingen, Go¨ttingen, Germany,
1997.