Synthesis of copper(I) ?-diketone complexes

Article abstract of DOI:10.1016/S0277-5387(01)00715-X

At room temperature, the reaction of metallic copper powder with 2-thenoyltrifluoroacetone (tfac) and selected phosphine ligands gives the new copper(I) complexes [Cu(PPh₃)₂(tfac)] (1), [Cu(dppm)-(tfac)]₂ (2), [Cu(dppe)(tfac)]₂ (3), [Cu(dppp)(tfac)](4), [Cu(dppb)-(tfac)]₂ (5), Ph₂P(CH₂)_nPPh₂ [n = 1 (dppm), 2 (dppe), 3 (dppp), 4 (dppb)]. These complexes have been characterized by physicochemical and spectroscopic methods. X-ray structure analysis of 1 and 3 shows that tfac behaves as a chelating ligand and dppe coordinates as a bridging bidentate ligand to Cu(I) atoms in the Cu(I) complexes.

Full text of DOI:10.1016/S0277-5387(01)00715-X

Polyhedron 20 (2001) 585–590
www.elsevier.nl/locate/poly
Synthesis of copper(I) b-diketone complexes
Rui-Na Yang a,b,*, Dong-Mei Wang a,b, Ying-Fan Liu a,b, Dou-Man Jin a,b
a Henan Institute of Chemistry, Zhengzhou 450002, People’s Republic of China
b State Key Laboratory of Coordination Chemistry, Nanjing Uni6ersity, Nanjing 210093, People’s Republic of China
Received 10 August 2000; accepted 24 October 2000
Abstract
At room temperature, the reaction of metallic copper powder with 2-thenoyltrifluoroacetone (tfac) and selected phosphine
ligands gives the new copper(I) complexes [Cu(PPh3)2(tfac)] (1), [Cu(dppm)–(tfac)]2 (2), [Cu(dppe)(tfac)]2 (3), [Cu(dppp)(tfac)] (4),
[Cu(dppb)–(tfac)]2 (5), Ph2P(CH2)nPPh2 [n=1 (dppm), 2 (dppe), 3 (dppp), 4 (dppb)]. These complexes have been characterized
by physicochemical and spectroscopic methods. X-ray structure analysis of 1 and 3 shows that tfac behaves as a chelating ligand
and dppe coordinates as a bridging bidentate ligand to Cu(I) atoms in the Cu(I) complexes. © 2001 Elsevier Science B.V. All
rights reserved.
Keywords: Copper; Complexes; Diketone; Crystal structure
describe an easy way to synthesize Cu(I) b-diketone(2-
thenoyltrifluoroacetone) (Cu(I) b-diketone(tfac)) com-
plexes using phosphine ligands (PPh3, dppm, dppe,
dppp, dppb) and metallic copper powder. Structural
results allowed us to interpret some properties of the
complexes, such as molecular weight and conductivity
measurements.
1. Introduction
Copper(I) displays wide diversity in its structural
chemistry, the copper coordination number ranging
from two to six. Procedures to synthesize Cu(I) com-
plexes are of great interest because of the variety of
products resulting from almost the same methodology.
Binuclear Cu(I) complexes containing diphosphine
ligands have been the focus of much investigation in the
last few years. In light of this growing interest [1], many
examples of complexes containing diphosphine ligands
are known with a variety of metals in differing oxida-
tion states and stereochemistry [2–4]. In general, bridg-
ing diphosphine ligands give an M2P4 core structure
with the two metal atoms held in close proximity to
each other (regardless of whether a metalꢀmetal bond is
present or not). This feature is presumably one of the
chief reasons for the unusual bonding, reactivity, and
catalytic properties of M2(diphosphine)2 compounds.
These compounds require additional ligands, since each
metal ion in the M2P2 framework is coordinatively
unsaturated. There are few reports concerning investi-
gations of the structure and properties of the
Cu2(dppe)2 framework [5]. In the present paper we
2. Experimental
2.1. General considerations
The compounds (dppm, dppe, dppp, and dppb) were
synthesized according to the literature [3]. All other
chemicals were of reagent grade quality obtained from
commercial sources and used without further purifica-
tion. All solvents were dried by standard methods.
Elemental analyses were performed on an ERBA-1106
instrument (Italy). Cu and P contents were determined
using a JA96-970 spectrometer. Molecular weight deter-
minations were made on CHCl3 solutions at 25°C using
a CORONA-117 analyzer (American instrument). IR
spectra were recorded on a Nicolet 170SX IR spec-
trophotometer. TG-DTA spectra were recorded on a
PE-TGS-2 instrument. Conductivity measurements
were carried out in acetone solutions thermostated at
* Corresponding author. Fax: +86-371-5723797.
E-mail address: yangrn@371.net (R.-N. Yang).
0277-5387/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(01)00715-X

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R.-N. Yang et al. / Polyhedron 20 (2001) 585–590
25°C using a Shanghai DDS-11A conductometer and
DJS-1 type platinum black electrode. Melting points
were determined on an electrothermal apparatus and
are uncorrected. Room temperature (r.t.) 31P NMR
spectra were taken on a DPX-400 NMR spectrometer,
and measured in CDCl3-d with 85% H3PO4 as external
reference. XPS spectra were recorded on a VG ES-
CALAB MK II instrument with Al Ka radiation.
Voltage, electric current and pressure were set at 12.5
kV, 20 mA and 6×10−6 Pa, respectively.
NMR (3, ppm): 1.750–2.597 (m, CH2, dppe); 6.444 (s,
CH, tfac); 7.206–7.829 (m, ph, C4H3S). H NMR (4,
1
ppm): 2.456–2.546 (m, CH2, dppp); 6.445 (s, CH,
1
tfac); 7.198–7.802 (m, ph, C4H3S). H NMR (5, ppm):
1.720–2.307 (m, CH2, dppb); 6.447 (s, CH, tfac);
7.184–7.748 (m, ph, C4H3S).
2.3. X-ray data collection and structure determination
A single crystal of each complex (1 and 3) was
selected and mounted on an automatic Enraf–Nonius
CAD-4 four-circle diffractometer equipped with a
graphite monochromator and Mo Ka radiation (u=
2.2. Synthesis of complexes 1–5
Dppe (2 mmol, 0.796 g) was added to a mixture of
metallic copper powder (2 mmol, 0.127 g) and tfac (2
mmol, 0.444 g) in acetone. The mixture was stirred at
r.t. for 48 h giving a yellow precipitate. The product
was collected by filtration and washed with acetone.
Yellow crystals were obtained by recrystallization of
the product from CHCl3 and THF. The crystals are
stable in air. The complex [Cu(dppb)(tfac)]2 (5) was
prepared by a similar method. Using an acetone and
THF solution, the complexes 1, 2, and 4 can be ob-
tained by the above-described method. 1H NMR (1,
ppm): 6.449 (s, CH, tfac); 7.191–7.829 (m, ph,
C4H3S). 1H NMR (2, ppm): 3.185 (s, CH2, dppm);
,
0.71073 A). Unit cell dimensions and intensity data
were measured at r.t. Reflections were collected using
ꢀ–2q scan (scan width 1.00+0.35 tan q). No signifi-
cant change was detected in the intensity of three
standard reflections. Lorentz, polarization, and ab-
sorption corrections (empirical method, c-scan) were
applied to the intensity data. The structure was solved
by direct methods and Fourier synthesis. The structure
was refined by full-matrix least-squares method. Com-
putations were performed using the SDP program on a
PDP11/44 computer. Details of the crystal data and
intensity collection are summarized in Table 1. Se-
lected bond lengths and angles are given in Table 2.
1
6.442 (s, CH, tfac); 6.937–7.728 (m, ph, C4H3S). H
Table 1
3. Results and discussion
Crystal data and structure refinement parameters
Empirical formula
Color
Crystal system
Space group
C44H33CuF3O2P2S Cu2C68H56P4O4S2F6
yellow
yellow
3.1. Preparation of the complexes
monoclinic
P21/n
monoclinic
C2/c
According to the color changes that accompany the
preparation of complexes 1–5, metallic copper powder
has reacted with the phosphine ligand and tfac to
form Cu(I) complexes. The direct use of metallic cop-
per powder and tfac is characteristic of the present
synthetic method. Molecular weights were measured in
CHCl3 solution, the complexes being soluble enough
for measurements. The results are quite reproducible
and seem to be scarcely influenced by concentration
changes in the accessible range. The molecular weight
determinations strongly suggest that the complexes 2,
3, and 5 are binuclear. The Cu(I) complexes (1–5) can
be obtained with high yields. The elemental analyses
of the five complexes agreed well with their formulae
(Table 3). Conductance data show that the complexes
are non-electrolytes. At room temperature, the title
complexes are crystalline, diamagnetic compounds, are
fairly stable in air in the solid state, are soluble in
organic solvents such as CH2Cl2, DMF, and CHCl3,
and are sparingly soluble in benzene, THF, and hex-
ane.
Unit cell dimensions
,
a (A)
11.012(2)
21.282(4)
17.241(3)
90
101.68(3)
90
3956.9(14)
4
1.357
25.215(6)
15.304(9)
18.851(6)
90
107.20(3)
90
6949.0(2)
4
1.375
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
Absorption coefficient 7.36
8.196
(cm−1
)
Crystal size (mm)
2q Range (°)
Index ranges
0.5×0.4×0.2
3.08–46
0BhB12,
−23BkB23,
−18BlB18
0.1×0.1×0.15
2–49
0BhB27, 0BkB18,
−22BlB22
Independent reflections 5484
Solution
Final R indices
6301
direct methods
direct methods
R=0.06682,
Rw=0.07326
[I\3|(I)]
0.842
R=0.0568,
Rw=0.1437
[I\2|(I)]
Largest difference peak 0.439
−3
,
and hole (e A
)

R.-N. Yang et al. / Polyhedron 20 (2001) 585–590
587
Table 2
,
Selected bond lengths (A) and angles (°) for 1 and 3
Complex 1
Bond lengths
CuꢀO(1)
CuꢀP(2)
2.059(5)
2.254(2)
CuꢀO(2)
O(2)ꢀC(2)
2.118(5)
1.261(10)
CuꢀP(1)
O(1)ꢀC(4)
2.2243(19)
1.232(9)
Bond angles
O(1)ꢀCuꢀO(2)
O(1)ꢀCuꢀP(2)
C(4)ꢀO(1)ꢀCu
89.0(2)
106.20(17)
125.6(6)
O(1)ꢀCuꢀP(1)
O(2)ꢀCuꢀP(2)
C(2)ꢀO(2)ꢀCu
114.37(16)
112.94(16)
120.0(5)
O(2)ꢀCuꢀP(1)
P(1)ꢀCuꢀP(2)
107.71(16)
121.87(8)
Complex 3
Bond lengths
Cu(1)ꢀP(1)
Cu(1)ꢀO(2)
2.236(2)
2.064(6)
Cu(1)ꢀP(2)
O(1)ꢀC(3)
2.244(3)
1.255(10)
Cu(1)ꢀO(1)
O(2)ꢀC(5)
2.096(6)
1.259(9)
Bond angles
P(1)ꢀCu(1)ꢀP(2)
P(2)ꢀCu(1)ꢀO(1)
Cu(1)ꢀP(1)ꢀC(1)
Cu(1)ꢀO(1)ꢀC(3)
Cu(1)ꢀP(2)ꢀC(31)
118.49(9)
106.3(2)
112.6(3)
126.8(6)
116.5(3)
P(1)ꢀCu(1)ꢀO(1)
P(2)ꢀCu(1)ꢀO(2)
Cu(1)ꢀP(1)ꢀC(11)
Cu(1)ꢀO(2)ꢀC(5)
Cu(1)ꢀP(2)ꢀC(41)
106.9(2)
115.0(2)
117.7(3)
124.4(6)
118.1(3)
P(1)ꢀCu(1)ꢀO(2)
O(1)ꢀCu(1)ꢀO(2)
Cu(1)ꢀP(1)ꢀC(21)
Cu(1)ꢀP(2)ꢀC(2)
Cu(1)ꢀO(1)ꢀC(3)
115.9(2)
88.7(2)
115.5(3)
110.9(3)
126.8(6)
Table 3
Analytical data and physical properties of the complexes
Complex
C
H (calc.%)
P
Cu
Yield (%)
m.p. (°C)
\
M (calc.)
Color
M
(S cm2 mol−1
)
1
2
3
4
5
65.44 (65.31)
59.48 (59.24)
59.63 (59.78)
60.15 (60.30)
60.77 (60.80)
3.98 (4.20)
4.01 (3.89)
4.27 (4.10)
4.58 (4.31)
4.35 (4.50)
7.8 (7.7)
9.6 (9.3)
8.8 (9.1)
9.1 (8.9)
8.9 (8.7)
8.1 (7.8)
9.3 (9.5)
9.0 (9.3)
8.9 (9.1)
9.1 (8.9)
76
71
79
66
81
116
225
248
110
234
5.2
1.2
4.9
5.6
3.8
807 (808.5)
1339 (1337)
1367 (1365)
695 (696.5)
1419 (1421)
yellow
orange
yellow
yellow
orange
Table 4
Absorption maxima and IR of the complexes
Complex
umax (nm)
31P a (ppm)
wcꢁo (cm−1
)
wcꢁc (cm−1
)
wMꢀO (cm−1
)
wMꢀP (cm−1
)
uem (nm)
1
2
3
4
5
326, 310, 213
327, 256, 243
320, 261, 240
325, 258, 239
323, 260, 242
1605
1610
1608
1610
1610
1545
1550
1552
1550
1535
300
290
298
300
300
195
196
198
200
198
540, 610
525
525
−13.6
−6.2
−3.2
−7.7
530
a 85% H3PO4 as an external reference.
3.2. IR data and 31P NMR spectra
In 31P NMR spectra of the complexes (Table 4), the
corresponding phosphorus resonance is shifted to
higher field compared to that of the free ligand (dppm:
−22.9; dppe: −12.6; dppp: −13.0; dppb: −11.9
ppm). 31P NMR spectra at room temperature only
display a single resonance showing that all phosphorus
atoms in each molecule are chemically equivalent [3].
The characteristic wcꢁo(1650 cm−1) of free tfac shifts
to lower frequency (1605–1610 cm−1) in the Cu(I)
complexes 1–5 (Table 4). b-Diketone(tfac) in the com-
plex is in the enol form and is bonded to the metal in
a chelate mode. The CꢁO and CꢁC stretching vibration
of the enol ring were assigned to absorptions at 1605–
1610 and 1535–1550 cm−1, respectively. The vibra-
tional absorption peak shape and intensity change were
obviously in the range 1000–1400 cm−1. The PꢀPh
absorption, at about 1100 cm−1, shows an increase in
frequency and intensity, which is characteristic of
Pꢀmetal coordination.
3.3. TG-DTA analysis and XPS spectra
The results of the thermogravimetric analyses of the
complexes, compared with those of free ligands, indi-
cate that the thermal stability of the phosphine com-
pounds increases upon complexation. The TG-DTA

588
R.-N. Yang et al. / Polyhedron 20 (2001) 585–590
thermogram of 1 reveals that the pyrolytic decomposi-
tion takes place in one step. This process in the 200–
500 range corresponds to a pronounced weight loss of
89% and is probably due to the decomposition of the
organic moiety (loss of weight calc. 90.2%), giving CuO
as final residue (exp.: 11.0%; calc.: 9.8%). The TG-DTA
pattern of complexes 2–4 is similar to that of complex
1.
The XPS data of the complexes give information
concerning copper–ligand binding. The binding energy
of the complexes 1, 2, and 3 are at C1s: 288.65 (1),
288.63 (2), 288.61 (3); O1s: 536.25 (1), 536.23 (2), 536.21
(3); S2p: 168.20 (1), 168.18 (2), 168.19 (3); P2p: 135.00
(1), 134.71 (2), 133.52 (3); and Cu2p: 936.85 (1), 936.30
(2), and 936.12 (3) eV, respectively. The binding energy
P2p of the phosphine ligand in the complexes 1–3 is
larger than the relative value of the free ligand (PPh3:
133.9 eV; dppm: 132.5 eV; dppe: 132.4 eV). This is
attributed to electronic density reduction of the P atom
because of the formation of a P“Cu bond in the
complexes.
as a metal-centered 3d94s1“3d10 transition [6]. In the
binuclear Cu(I) complex [(PPh3)Cu2Cl2(py)], a similar
type of assignment has been made [7]. Based on a
literature assignment of analogous compounds and our
experimental observation, the low-energy and long life-
time emission (525–540 nm) is most likely associated
with the metal-centered excited state 3d94s1 of Cu(I)
since the low-energy emission occurs at similar energies
for complexes 1–5, irrespective of the nature of the
phosphine ligand. Complex 1 also exhibits another
emission band maximum at ꢀ610 nm. The Cu(I) cen-
ter, a d10 system, is very electron rich in nature and can
be stabilized by ligands having p-acid character, viz.
PPh3, bpy, phen, CO, CN, etc. Complexes having the
general formula [Cu(PPh3)2(NN)]+ are known to ex-
hibit emission properties both at low and room temper-
ature. There are emissions at 608 nm for
[Cu(PPh3)(phen)]+ and at 620 nm for [Cu(PPh3)(bpy)]+
[9]. These emissions were tentatively assigned as metal-
to-ligand charge transfers (MLCT). Thus, the emission
band at ꢀ610 nm in 1 has also been assigned as
MLCT.
3.4. Luminescence properties
3.5. Crystal structures of complexes 1 and 3
The electronic absorption spectrum of the title com-
plexes in CH2Cl2 exhibit low-energy bands in the 310–
330 nm region. Excitation of solid samples of the
complexes at u=355 nm at room temperature produces
long-lived luminescence at u=525–540 nm. Lumines-
cence spectra of 1 are shown in Fig. 1. The room
temperature solid-state emission spectra of the com-
plexes 2–5 showed very similar patterns. There is exten-
sive literature on the emission of Cu(I) complexes [6–8].
In the trinuclear Cu(I) complex [Cu3(dpmp)2-
(MeCN)2Cl2]+, where dpmp is bis(diphenylphosphi-
nomethyl)methyl, an emission at 560 nm was assigned
The molecular structures of 1 and 3 are depicted in
Figs. 2 and 3, respectively. In complex 1 the copper ion
is four coordinate with a tetrahedral sphere of two
phosphorus atoms from PPh3 and two oxygen atoms
from tfac. The CuꢀP distances in [Cu(PPh3)2(tfac)] vary
,
from 2.2243(19) to 2.254(2) A, with a mean value of
,
2.239(2) A, in good agreement with the average value
,
of 2.2312(8) A found in [Cu(PPh3)2(NO3)] [10]. The
thiophene ring in 1 may rotate around the C(4) atom.
The solid-state 3 consists of a neutral dimeric molec-
ular unit with the two copper atoms bridged by a pair
Fig. 1. Luminescence spectrum of complex 1; excitation was performed at u=355 nm.

R.-N. Yang et al. / Polyhedron 20 (2001) 585–590
589
Fig. 2. Molecular structure of complex 1.
Fig. 3. Molecular structure of complex 3.
of dppe ligands. In addition, each copper atom is
bound by tfac in a chelating fashion. The two copper
atoms are doubly bridged by two dppe ligands to form
a ten-membered Cu2P4C4 ring. Each copper atom is
four coordinate, having a P2O2 donor set. The slightly
distorted tetrahedral coordination around copper is
completed by two phosphorus atoms from the dppe
ligand and two oxygen atoms from tfac. It has already
been observed that CuꢀP bond lengths in similar com-
pounds are mainly influenced by the number of phos-
phorus atoms bonded to the same copper atom. In the
present compound, the Cu(I) atom is coordinated by
two phosphorus atoms. The CuꢀP distances in 3 of
,
2.236(2) and 2.244(3) A are in good agreement with the

590
R.-N. Yang et al. / Polyhedron 20 (2001) 585–590
,
values of 2.240(6) and 2.249(6) A found in [Cu(S2CC6-
4. Supplementary material
H4MeꢀO)(dppm)]2 [11]. The CuꢀCu separation of
,
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 147876 and 147877 for com-
pounds 1 and 3, respectively. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
3.652(10) A is significantly longer than the range of
CuꢀCu bond lengths [2.494(5)–2.674(5) A] found in
,
H6Cu6(PPh3)6·DMF [12], suggesting that the copper
atoms in the present compound are not involved in
metalꢀmetal bonding interactions. The CꢀO and CꢀC
bond lengths in tfac are in the region expected for
localized symmetrical bonding of the b-diketone ligand
(tfac). The bond lengths of C(3)ꢀC(4), C(4)ꢀC(5),
C(3)ꢀC(6), and C(5)ꢀC(10) are 1.410(14), 1.381(4),
,
1.492(3), and 1.521(14) A, respectively. The bond
lengths of C(3)ꢀC(4) and C(4)ꢀC(5) are shorter than
Acknowledgements
those of C(3)ꢀC(6) and C(5)ꢀC(10) because C(3), C(4),
and C(5) form
a conjugated system. The bond
We thank NSFC (No. 29871009), Henan Province
Outstanding Youth and Natural Science Foundation
for the financial support of this research.
C(3)ꢀC(6), linking to the thiophene ring, falls within the
limits for single and double bond lengths. This certifies
that there is a conjugated system formed between the
chelating ring and the thiophene ring.
In each copper moiety, all of the distances between
the copper and donor atoms are different. The observed
References
,
CuꢀO distances of 2.096(6) and 2.064(6) A are com-
,
parable to the CuꢀO values [1.954(11) A] found for the
[1] R.J. Puddephatt, Chem. Soc. Rev. 12 (1983) 99.
[2] R.N. Yang, Y.A. Sun, X.Y. Hu, D.M. Jin, Chin. J. Chem. 17
complex [Cu(2,2%-bipy)(tfac)] [13]. Structural studies in-
volving binuclear phosphine species of other transition
metals (Mn [14], Mo [15]) are less common but, in
general, reveal linear PꢀMꢀP fragments and planar
M2P4 skeletal units. For d10 complexes, however, the
PꢀMꢀP units are distinctly non-linear [16,17]. X-ray
structural characterization of the complex [Cu-
(dppe)(tfac)]2, reported here, clearly reveals that the
PꢀMꢀP angles in the complex are not restricted by
steric crowding of dppe phenyl rings. The PꢀCuꢀP
angles in 3, in particular, are much more bent (118.49°)
than the corresponding PꢀMꢀP values (131.8°) found in
[Cu(dppm)(NO3)]2 [3], but similar to the corresponding
P(1)ꢀCuꢀP(2) angle of 119.9(1)° found in the related
binuclear (dppm)2 complex [Cu(dppm)(MeCN)2]2-
(ClO4)2 [18]. The two bis(diphenylphosphine)ethane lig-
ands in 3 are located on opposite sides of the complex
to minimize repulsion between the ligands.
(1999) 284.
[3] R.N. Yang, K.H. Lin, D.M. Jin, Transition Met. Chem. 22
(1997) 254.
[4] H.K. Shin, M.J. Hampden-Smith, T.T. Kodas, Polyhedron 10
(1991) 645.
[5] R.N. Yang, Y.M. Hou, X.Y. Hu, D.M. Jin, Chin. J. Chem. 18
(2000) 346.
[6] D. Li, H.K. Yip, C.M. Che, Z.Y. Zhou, T.C.W. Mak, S.T. Liu,
J. Chem. Soc., Dalton Trans. (1992) 2445.
[7] M. Henry, J.L. Wotton, S.I. Khan, J.I. Zink, Inorg. Chem. 36
(1997) 796.
[8] V.W. Yam, W. Lee, T.F. Lai, J. Chem. Soc., Chem. Commun.
(1993) 1571.
[9] S. Ranjan, S.K. Dikshit, Polyhedron 17 (1998) 3071.
[10] R.N. Yang, X.Y. Hu, D.M. Jin, Chin. J. Struct. Chem. 19 (2000)
126.
[11] A.M. Manotti Lanfredi, F. Ugozzoli, Inorg. Chim. Acta 99
(1985) 111.
[12] M.R. Churchill, S. Bezman, J.A. Osborn, Inorg. Chem. 11
(1972) 1818.
[13] D.M. Wang, B.Y. Xue, R.N. Yang, D.M. Jin, Chin. J. Struct.
In summary, we have prepared the following Cu(I)
Chem. 16 (1997) 287.
b-diketone
complexes
[Cu(PPh3)2(tfac)],
[Cu-
[14] C.J. Commons, B.F. Hoskins, Aust. J. Chem. 28 (1975) 1663.
[15] E.H. Abbott, K.S. Bose, F.A. Cotton, Inorg. Chem. 17 (1978)
(dppp)(tfac)], and [Cu(tfac)L]2 (L=dppm, dppe, dppb).
The doubly bridged bis(diphenylphosphine)ethane com-
plex [Cu(dppe)(tfac)]2 has been structurally character-
ized by single-crystal X-ray diffraction and found to
contain a folded Cu2P4 core. In addition, the M2(dppe)2
core in 3 is apparently quite flexible, exhibiting varying
degrees of folding along the M···M axis in the solid
state. The coordinative unsaturation of the dimer is
particularly intriguing in that this should facilitate the
binding of other species [19,20].
3240.
[16] R.N. Yang, X.Y. Hu, D.M. Jin, Transition Met. Chem. 25
(2000) 174.
[17] R.N. Yang, Y.M. Hou, X.Y. Hu, D.M. Jin, Inorg. Chim. Acta
304 (2000) 1.
[18] J.D.M. Pilar, J. Gimeno, J. Chem. Soc., Dalton Trans. (1987)
1275.
[19] R.N. Yang, K.H. Lin, Y.M. Hou, D.M. Jin, Polyhedron 16
(1997) 4033.
[20] R.N. Yang, Y.A. Sun, X.Y. Hu, D.M. Jin, Acta Chim. Sinica 58
(2000) 727.
.