Copper(I) complexes with conjugated dienes

Article abstract of DOI:10.1016/S0022-328X(00)00109-1

Three copper(I) complexes containing conjugated dienes and one containing the acetylenic analogue of isoprene, 2-methyl-1-butene-3-yne (isopropenylacetylene), have been prepared and characterised by means of crystal-structure determination. Direct reaction between isoprene (2-methylbutadiene) and copper(I) trifluoromethylsulfonate, using triphenylphosphine as a stabilising ligand, results in [Cu₂(PPh₃)₂{μ-(H₂C=CHC(CH ₃)=CH₂)}(O₃SCF₃)₂] (1), whereas reaction between copper(I) chloride and isopropenylacetylene, dimethylbutadiene, and trans-1,3-pentadiene yields the labile compounds [Cu₂Cl₂{μ-(H₂C=CHC(CH₃)CH)}] (2), [Cu₂Cl₂{μ-(H₂C=C(CH₃)C(CH ₃)=CH₂)}] (3) and [Cu₂Cl₂{μ-(trans-H₂C=CHCH=CH(CH ₃))}] (4), respectively. All four compounds are polymeric. Thus, the organic ligands bridge two copper(I) centres via the alkene or alkyne bonds, the conjugated dienes all assuming the s-trans conformation. Further bridging is effected by the trifluoromethylsulfonate ligands in 1 and by the chloride ligands in 2, 3 and 4. In 1, copper(I) has distorted tetrahedral geometry, whereas in 2, 3 and 4, copper(I) exhibits tetrahedral or trigonal pyramidal geometry with the C=C/CC linkage in the trigonal plane and an apical Cu-Cl bond. The nearly planar carbon skeleton of isoprene in 1 bonds to two copper(I) atoms from opposite faces of the diene. The Cu-C distances range from 2.085(6) to 2.220(6) A? [C(CH₃)] and the C=C bond lengths are 1.360(8) and 1.353(8) A?. Trifluoromethylsulfonate ligands bridge adjacent [Cu₂(PPh₃)₂{μ-(H₂C=CHC(CH ₃)=CH₂)}(O₃SCF₃)₂] units leading to the formation of chains, containing internal chair-shaped Cu₂S₂O₄ rings alternating with isoprene ligands, with peripheral triphenylphosphine ligands. The carbon skeleton of the isopropenylacetylene ligand in 2 and those of dimethylbutadiene in 3 and of trans-1,3-pentadiene in 4 are also approximately planar, but, unlike the situation in 1, in compounds 2-4, two copper(I) atoms are coordinated by C=C/CC from the same face of the ligand. In 2, Cu-C distances range from 2.005(11) to 2.158(9) A? [C(CH₃)] and the C=C and CC bond lengths are 1.373(13) and 1.200(14) A?, respectively. In 3, Cu-C distances range from 2.06(1) to 2.17(1) A? [C(CH₃)] and both C=C bonds are 1.35(1) A?. Dimeric [Cu₂Cl₂{μ-(H₂C=CHC(CH₃)CH)}] ₂ and [Cu₂Cl₂{μ-(H₂C=C(CH₃)C(CH ₃)=CH₂)}] units are linked by long Cu-Cl bonds leading to the formation of chains with peripheral isopropenylacetylene (2) and dimethylbutadiene (3) ligands. The crystal structure of 4 could be determined only with low precision, but can be described in terms of copper(I) chloride layers with peripheral trans-1,3-pentadiene ligands. Shifts in the infrared absorptions on coordination of the conjugated dienes (including butadiene and cis-1,3-pentadiene) to copper(I) are discussed in the light of the crystal structures of 2-4.

Full text of DOI:10.1016/S0022-328X(00)00109-1

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 602 (2000) 5–14
Copper(I) complexes with conjugated dienes
Mikael Ha˚kansson *1, Katarina Brantin, Susan Jagner *2
Department of Inorganic Chemistry, Chalmers Uni6ersity of Technology, SE-412 96 Go¨teborg, Sweden
Received 6 January 2000; received in revised form 4 February 2000
Abstract
Three copper(I) complexes containing conjugated dienes and one containing the acetylenic analogue of isoprene, 2-methyl-1-
butene-3-yne (isopropenylacetylene), have been prepared and characterised by means of crystal-structure determination. Direct
reaction between isoprene (2-methylbutadiene) and copper(I) trifluoromethylsulfonate, using triphenylphosphine as a stabilising
ligand, results in [Cu2(PPh3)2{m-(H2CꢀCHC(CH3)ꢀCH2)}(O3SCF3)2] (1), whereas reaction between copper(I) chloride and iso-
propenylacetylene, dimethylbutadiene, and trans-1,3-pentadiene yields the labile compounds [Cu2Cl2{m-(H2CꢀCHC(CH3)ꢁCH)}]
(2), [Cu2Cl2{m-(H2CꢀC(CH3)C(CH3)ꢀCH2)}] (3) and [Cu2Cl2{m-(trans-H2CꢀCHCHꢀCH(CH3))}] (4), respectively. All four com-
pounds are polymeric. Thus, the organic ligands bridge two copper(I) centres via the alkene or alkyne bonds, the conjugated
dienes all assuming the s-trans conformation. Further bridging is effected by the trifluoromethylsulfonate ligands in 1 and by the
chloride ligands in 2, 3 and 4. In 1, copper(I) has distorted tetrahedral geometry, whereas in 2, 3 and 4, copper(I) exhibits
tetrahedral or trigonal pyramidal geometry with the CꢀC/CꢁC linkage in the trigonal plane and an apical Cu–Cl bond. The nearly
planar carbon skeleton of isoprene in 1 bonds to two copper(I) atoms from opposite faces of the diene. The Cu–C distances range
,
,
from 2.085(6) to 2.220(6) A [C(CH3)] and the CꢀC bond lengths are 1.360(8) and 1.353(8) A. Trifluoromethylsulfonate ligands
bridge adjacent [Cu2(PPh3)2{m-(H2CꢀCHC(CH3)ꢀCH2)}(O3SCF3)2] units leading to the formation of chains, containing internal
chair-shaped Cu2S2O4 rings alternating with isoprene ligands, with peripheral triphenylphosphine ligands. The carbon skeleton of
the isopropenylacetylene ligand in 2 and those of dimethylbutadiene in 3 and of trans-1,3-pentadiene in 4 are also approximately
planar, but, unlike the situation in 1, in compounds 2–4, two copper(I) atoms are coordinated by CꢀC/CꢁC from the same face
,
of the ligand. In 2, Cu–C distances range from 2.005(11) to 2.158(9) A [C(CH3)] and the CꢀC and CꢁC bond lengths are 1.373(13)
,
,
and 1.200(14) A, respectively. In 3, Cu–C distances range from 2.06(1) to 2.17(1) A [C(CH3)] and both CꢀC bonds are 1.35(1)
,
A. Dimeric [Cu2Cl2{m-(H2CꢀCHC(CH3)ꢁCH)}]2 and [Cu2Cl2{m-(H2CꢀC(CH3)C(CH3)ꢀCH2)}] units are linked by long Cu–Cl
bonds leading to the formation of chains with peripheral isopropenylacetylene (2) and dimethylbutadiene (3) ligands. The crystal
structure of 4 could be determined only with low precision, but can be described in terms of copper(I) chloride layers with
peripheral trans-1,3-pentadiene ligands. Shifts in the infrared absorptions on coordination of the conjugated dienes (including
butadiene and cis-1,3-pentadiene) to copper(I) are discussed in the light of the crystal structures of 2–4. © 2000 Elsevier Science
S.A. All rights reserved.
Keywords: Isoprene; Isopropenylacetylene; Butadiene; Dimethylbutadiene; 1,3-Pentadiene; Alkene; Alkyne; Copper(I); Infrared spectroscopy;
Crystal structure
to copper(I), and this is restricted to isoprene
(2-methylbutadiene), namely the coordination of this
1. Introduction
ligand in [Cu2Cl2(m-C5H8)] [3] and in [Cu2-
Several structures of p-olefinic complexes of cop-
{(C6H5CH2N(C5H4N)2}2((m-C5H8)(O3SCF3)2] [4]. It was
per(I) have now been characterised and analysed [1,2].
here shown that the conjugated diene does not complex
Despite this, there is still relatively little information
available on the mode of bonding of conjugated dienes
the metal in the more usual h4, tetrahapto, mode [5,6]
but acts essentially as an h2 donor, bridging two cop-
per(I) centres [2,3]. In these two compounds, the ligand
1 *Corresponding author. Tel.:+46-31-772 2856; fax:+46-31-772
thus retains the s-trans conformation, demonstrated to
2846; e-mail: hson@inoc.chalmers.se
2 *Corresponding author. Tel.:+46-31-772 2852; fax:+46-31-772
2846; e-mail: susan@inoc.chalmers.se
be the more stable for the free isoprene ligand and its
non-methylated analogue butadiene [7].
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 0 ) 0 0 1 0 9 - 1

6
M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
The present investigation was undertaken in order
18°C, pale-yellow rods of 2 being deposited, in low
yield, after a few days. Crystals of 2 are unstable in
air decomposing with loss of the organic ligand
within a few seconds of exposure to the atmosphere.
Attempts to suppress acetylide formation by the addi-
tion of a small amount of hydrochloric acid [13] were
not successful and yielded a dark suspension of de-
composition products.
to provide more information on the bonding of con-
jugated dienes to copper(I), and encompasses butadi-
ene, isoprene, dimethylbutadiene and cis- and
trans-piperylene. In addition, we were interested in
preparing an acetylenic analogue of the isoprene com-
plex described earlier, [Cu2Cl2(m-C5H8)] [3], in order
to facilitate comparison of p-ethylenic and p-
acetylenic coordination within the same ligand. To
our knowledge, the only previous such example is di-
vinylacetylene complexed to copper(I) chloride [2,8].
In this compound the organic ligand bridges three
copper(I) centres [2,8].
2.4. Preparation of
[Cu2Cl2{v-(H2CꢀC(CH3)C(CH3)ꢀCH2)}] (3)
The compound was prepared according to the gen-
eral method described previously [9]. Thus, ca. 2.0
mmol (0.2 g) copper(I) chloride was added to 10 ml
of ethyl vinyl ketone at ambient temperature, yielding
a clear solution upon stirring. Dimethylbutadiene (10
ml) was added slowly to the solution at ambient tem-
perature. The solution was stored at −25°C, yellow
crystals of 3 being deposited, in quantitative yield,
overnight. The mother liquor was withdrawn at low
temperature and fresh dimethylbutadiene added. Crys-
tals of 3 decompose instantaneously, with loss of
dimethylbutadiene, on exposure to the atmosphere.
2. Experimental
2.1. General
All operations were carried out under argon using
standard Schlenk or special low-temperature tech-
niques [9]. Copper(I) triflate (trifluoromethylsulfonate)
was prepared using the method of Salomon and
Kochi [10]. Triphenylphosphine was recrystallised
from ethanol, and copper(I) chloride was purified ac-
cording to the method of Keller and Wycoff [11].
,
Solvents and ligands were dried with 3 or 4 A molec-
ular sieves, deoxygenated by means of freeze–pump–
thaw cycles and distilled immediately prior to use.
2.5. Preparation of
[Cu2Cl2{v-(trans-H2CꢀCHCHꢀCH(CH3))}] (4)
The compound was prepared according to the gen-
eral method described previously [9]. Thus, ca. 2.0
mmol (0.2 g) copper(I) chloride was added to 10 ml
of ethyl vinyl ketone at ambient temperature, yielding
a clear solution upon stirring. trans-1,3-Pentadiene
(4.0 ml) was added very slowly to the solution at
ambient temperature, yellow crystals of 4 being de-
posited overnight, in quantitative yield. The mother
liquor was withdrawn at low temperature and fresh
trans-1,3-pentadiene was added. trans-1,3-Pentadiene
is lost from 4 instantaneously on exposure of the
compound to the atmosphere.
2.2. Preparation of
[Cu2(PPh3)2{v-(H2CꢀCHC(CH3)ꢀCH2)}(O3SCF3)2] (1)
A solution of triphenylphosphine (0.11 g, 0.44
mmol) in 1 ml of isoprene was added slowly under
stirring to
a
suspension of copper(I) triflate
[Cu(O3SCF3)]2·C6H6 [10] in 2 ml of isoprene. The
dark-brown suspension rapidly changed colour, form-
ing a beige precipitate and a pale-yellow solution. A
further 5 ml of isoprene was added and stirring was
continued for a few hours. After centrifugation, the
clear, pale-yellow solution was separated from the
precipitate and cooled to 5°C, pale-yellow plates of 1
being deposited, in low yield, overnight. Crystals of 1
are relatively stable, decomposing only after 1–2 h
exposure to the atmosphere.
2.6. Preparation of a complex between
cis-1,3-pentadiene and copper(I) chloride (5)
Yellow crystals of 5 were obtained by an identical
procedure to that described above for 4, using cis-1,3-
pentadiene instead of trans-1,3-pentadiene. The com-
pound was obtained in quantitative yield. Crystals of
5 were, however, not of sufficiently good diffracting
quality to permit even an approximate structure de-
termination of the compound; they decompose instan-
taneously with loss of diene ligand on exposure to the
atmosphere.
2.3. Preparation of
[Cu2Cl2{v-(H2CꢀCHC(CH3)ꢁCH)}] (2)
Copper(I) chloride (0.1 g, 1.0 mmol) was dissolved
in 1 ml of isopropenylacetylene at room temperature
yielding a yellow solution. Almost immediately, a
bright yellow, flocculant precipitate (presumably the
copper(I) acetylide [12]) separated. The clear solution
was removed from the precipitate and stored at −

M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
7
2.7. Preparation of a complex between butadiene and
copper(I) chloride (6)
liquor was withdrawn at low temperature with a syringe
and 10 ml of cyclohexane, saturated with butadiene was
added. The compound decomposes immediately, with
loss of butadiene, on exposure to the atmosphere.
Ca. 2.0 mmol (0.2 g) copper(I) chloride was added to
10 ml of ethyl vinyl ketone at ambient temperature,
yielding a clear solution upon stirring. Introduction of
gaseous butadiene caused immediate precipitation of
microcrystalline 6, in quantitative yield. The mother
2.8. Infrared spectrometry
Measurements were performed on crystalline samples
of 1 and 2, mixed with Fluorolube®, and also on the
pure ligands placed between KBr discs, using a Mattson
Polaris FTIR spectrometer. Solid samples of 3–6 were
prepared at low temperature as described in Ref. [9] and
CaF2 mull windows were employed. Spectra were
recorded with a resolution of 2 cm−1, varying the num-
ber of scans from 10 to 100. For 1 the CꢀC stretching
frequencies were masked by stretches associated with
the phenyl groups, thus precluding observation of shifts
caused by coordination of isoprene to copper(I). For 2:
w(CꢁC) 1962 cm−1, w(CꢀC) 1525 cm−1 (tentative as-
signment). Corresponding frequencies for isopropeny-
lacetylene: 2103 and 1615 cm−1. For 3: w(CꢀC–CꢀC)
1551, 1514 cm−1; for dimethylbutadiene: w(CꢀC–CꢀC)
1601 cm−1; For 4: w(CꢀC–CꢀC) 1579, 1517 cm−1; cor-
responding frequencies for trans-1,3-pentadiene: 1650,
1603 cm−1. For 5: w(CꢀC–CꢀC) 1567, 1502 cm−1; cor-
responding frequencies for cis-1,3-pentadiene: 1646,
1595 cm−1. For 6: w(CꢀC–CꢀC) 1564, 1506 cm−1. For
Table 1
Crystallographic
CH2)}(O3SCF3)2] (1) and [Cu2Cl2{m-(H2CꢀCHC(CH3))CH)}] (2)
data
for
[Cu2(PPh3)2{m-(H2CꢀCHC(CH3)ꢀ
a
Compound
1
2
Formula
Mr
Crystal system
Space group
Unit cell dimensions
C43H38Cu2F6O6P2S2 C5H6Cu2Cl2
1017.9
264.1
Triclinic
Triclinic
(
(
P1
P1
,
a (A)
13.109(5)
17.629(4)
10.658(5)
96.58(3)
107.62(4)
70.70(2)
2215(1)
2
7.162(1)
8.772(2)
6.369(1)
108.13(2)
90.83(2)
102.80(1)
369.5(1)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.526
2.373
v(Mo–Ka) (cm−1
)
11.93
64.08
Temperature (°C)
No. observed reflections
22
−120
1003
butadiene w(CꢀC–CꢀC) 1595 cm−1
.
3709
No. parameters refined
550
106
R
Rw
0.038
0.043
0.048
0.060
2.9. NMR spectrometry
Rapid loss of ligand from 2 to 5 on attempted dissolu-
tion, prevented measurement of spectra for these com-
pounds. 1H-NMR spectra (400 MHz) for 1 and for
uncoordinated isoprene were recorded on a Varian XL
400 spectrometer, using TMS as internal standard (s,
singlet; d, doublet; dd, doublet of doublets). For 1 l
(ppm): methylic 1.84 (s, 3H); non-methylated olefinic
bond, internal vinylic 6.39 (dd, 1H), terminal vinylic
5.06 (d, 1H), 4.97 (d, 1H); methylated olefinic bond, ter-
minal vinylic 4.99 (s, 1H), 4.96 (s, 1H). For free iso-
prene: methylic 1.84 (s, 3H); non-methylated olefinic
bond, internal vinylic 6.45 (dd, 1H), terminal vinylic
5.18 (d, 1H), 5.07 (d, 1H); methylated olefinic bond, ter-
minal vinylic 5.00 (s, 1H), 4.98 (s, 1H).
a R=ꢀꢁꢁFoꢁ−ꢁFcꢁ/ꢀꢁFoꢁ; Rw=[(ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/ꢀwF2o)]1/2
.
Table 2
Crystallographic data for [Cu2Cl2{m-(H2CꢀC(CH3)C(CH3)ꢀCH2)}]
(3) and [Cu2Cl2{m-(trans-H2CꢀCHCHꢀCH(CH3))}] (4) a
Compound
3
4
Formula
Mr
C6H10Cu2Cl2
280.1
C5H8Cu2Cl2
266.1
Crystal system
Space group
Unit cell dimensions
Orthorhombic
Pbcn
Monoclinic
P21/a
,
a (A)
16.048(4)
8.709(2)
12.154(3)
90
1699(1)
8
6.543(6)
12.981(3)
8.994(3)
95.07(3)
760.9(8)
4
,
b (A)
,
c (A)
i (°)
V (A )
2.10. X-ray crystallography
3
,
Z
Crystal and experimental data are summarised in Ta-
bles 1 and 2. Crystals of 1–4 were mounted in glass
capillaries, 2–4 were mounted under argon, at
−155°C [9] and transferred at the same temperature to
a Rigaku AFC6R diffractometer. Diffracted intensities
were measured with a Rigaku AFC6R diffracto-
meter, using graphite-monochromated Mo–Ka (u=
Dcalc (g cm−3
)
2.19
55.8
2.32
62.2
v(Mo-Ka) (cm−1
)
Temperature (°C)
No. observed reflections
−140
904
−144
825
No. parameters refined
121
82
R
0.036
0.040
0.11
0.14
Rw
a R=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ; Rw=[(ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/ꢀwF2o)]1/2
.
0.710 73 A) radiation from a RU200 rotating
,

8
M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
anode operated at 9 kW (50 kV; 180 mA). The ꢀ–2q
scan mode was employed, and stationary background
counts were recorded on each side of the reflection, the
ratio of peak counting time to background counting
time being 2:1. Weak reflections (IB10.0|(I)) were
rescanned up to three times and counts accumulated to
improve counting statistics. The intensities of three
reflections were monitored regularly after measurement
of 150 reflections and indicated crystal stability in all
cases. Cell constants were obtained by least-squares
refinement from the setting angles of 25 reflections.
For 1, data were measured at 22°C for 5B2q B
50.1° from a pale-yellow plate-shaped crystal with di-
mensions ca. 0.35×0.30×0.20 mm, using the ꢀ–2q
scan mode with an ꢀ scan rate of 16° min−1 and a scan
width of (1.15+0.30 tan q)°. Correction was made for
Lorentz and polarisation effects; an empirical correc-
tion based on azimuthal scans for several reflections
was made for the effects of absorption (minimum/max-
imum transmission factors=0.88/1.00). Of the 7784
unique reflections measured (+h, 9k, 9l), 3709 had
I\3.0|(I) and were considered observed. The struc-
ture was solved by direct methods (MITHRIL [14]) and
refined using full-matrix least-squares calculations on F
for 3709 observed [I\3.0|(I)] reflections and 550
parameters, with anisotropic thermal displacement
parameters for all the non-hydrogen atoms and with
the hydrogen atoms included as a fixed contribution in
calculated positions. Final R: 0.038 (Rw=0.043); maxi-
unique reflections measured, (+h, +k, +l), 904 had
[I\3.0|(I)] and were considered observed. The struc-
ture was solved by direct methods (MITHRIL [14]).
Full-matrix least-squares refinement on F including an-
isotropic thermal displacement parameters for the non-
hydrogen atoms and positional parameters for the
hydrogen atoms gave R=0.036 (Rw=0.040) for 121
parameters and 904 reflections. The maximum and
minimum values in the final difference map were 0.63
and −0.59 e A−3, respectively.
,
For 4, data were measured at −144°C for 5B2qB
50° from a pale-yellow cube with dimensions ca. 0.15×
0.15×0.15 mm, using the ꢀ–2q scan mode with an ꢀ
scan rate of 16° min−1 and a scan width of (1.52+
0.30 tan q)°. Correction was made for Lorentz and
polarisation effects; an empirical correction for the
effects of absorption was made as for 1 (minimum/max-
imum transmission factors=0.72/1.00). Of the 1408
unique reflections measured, (+h, +k, 9l), 825 had
[I\3.0|(I)] and were considered observed. Full-matrix
least-squares refinement on F, including anisotropic
thermal displacement parameters for the non-hydrogen
atoms, gave R=0.11 (Rw=0.14) for 82 parameters.
The hydrogen atoms could not be located.
All calculations on 1–4 were carried out with the
TEXSAN program package [15]. Atomic scattering fac-
tors and anomalous dispersion correction factors were
taken from Ref. [16]. Structural illustrations have been
drawn with ORTEP [17]. Selected interatomic distances
and angles are given in Tables 3–5. Owing to the poor
precision of the structure determination of 4, despite
numerous attempts to collect better quality data, the
partial structure has been deposited (see below) and the
structural results will not be discussed in detail here.
mum and minimum residual electron density: 0.63,
−3
,
−0.38 e A
.
For 2, data were measured at −120°C for 5B2q
B50.1° from a pale-yellow plate-shaped crystal with
dimensions ca. 0.30×0.30×0.10 mm, using the ꢀ–2q
scan mode with an ꢀ scan rate of 32° min−1 and a scan
width of (1.42+0.30 tan q)°. Correction was made for
Lorentz and polarisation effects; an empirical correc-
tion for the effects of absorption was made as for 1
(minimum/maximum transmission factors=0.76/1.00).
Of the 1306 unique reflections measured, (+h, 9k,
9l), 1003 had [I\3.0|(I)] and were considered ob-
served. The structure was solved by direct methods
3. Results and discussion
The general preparative method described previously
[9], and also used to prepare the labile complexes
[Cu2Cl2{m-(H2CꢀCHC(CH3)ꢀCH2)}] [3], [Cu(CO)Cl]
[18] and [Cu2Cl2{m-(H2CꢀCH–CH2–CHꢀCH2)}] [19],
has been exploited to obtain novel complexes between
copper(I) chloride and the conjugated dienes butadiene,
dimethylbutadiene and cis- and trans-piperylene. Of
these compounds, Cu2Cl2{m-(H2CꢀC(CH3)C(CH3)ꢀ
CH2)}] (3) and [Cu2Cl2{m-(trans-H2CꢀCHCHꢀCH-
(CH3))}] (4) have been subjected to crystal-structure
determination, whereas the complexes between cop-
per(I) chloride and butadiene and cis-piperylene, 6 and
5, respectively, have been investigated solely by means
of infrared (IR) spectroscopy. By means of direct reac-
tion between copper(I) trifluoromethanesulfonate and
copper(I) chloride with isoprene and isopropenyl-
acetylene, respectively, two further complexes, 1 and 2
have been prepared and their crystal structures deter-
(MITHRIL [14]) and refined by means of full-matrix
least-squares calculations on F for 1003 observed [I\
3.0|(I)] reflections and 106 parameters, including an-
isotropic thermal parameters for the non-hydrogen
atoms and isotropic thermal parameters for the hydro-
gen atoms. Final R: 0.048 (Rw=0.060); maximum and
minimum values in the final difference map were 1.38
and −1.63 e A−3, respectively.
,
For 3, data were measured at −140°C for 5B2qB
50° from a pale-yellow rod with dimensions ca. 0.20×
0.10×0.05 mm, using the ꢀ–2q scan mode with an ꢀ
scan rate of 16° min−1 and a scan width of (1.42+
0.30 tan q)°. Correction was made for Lorentz and
polarisation effects but not for absorption. Of the 1746

M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
9
Table 3
Coordination occurs from opposite faces of the diene
(Fig. 1). This resembles the structure found for bridging
isoprene in [Cu2{(C6H5CH2)N(C5H4N)2}2{m-(H2Cꢀ
CHC(CH3)ꢀCH2)}(O3SCF3)2] [4], in which, as in 1,
there are bulky ligands on copper(I), hindering h2
coordination from the same face of the diene. Further
bridging is effected by the trifluoromethanesulfonate
ligand, leading to the formation of chains in which
isoprene and trifluoromethanesulfonate alternate as
linkages, the latter ligand participating in chair-shaped
Cu2S2O4 rings (Fig. 2). In contrast to the chloride-con-
taining compounds, the diene in 1 is embedded in the
chain, the carbon skeleton of the ligand (C(1)–C(4))
,
Selected bond distances (A) and angles (°) for [Cu2(PPh3)2(m-
C5H8)(O3SCF3)2] (1) a
Cu(1)–C(1)
Cu(1)–C(2)
Cu(1)–X(1)
C(1)–C(2)
C(2)–C(3)
Cu(1)–P(1)
Cu(1)–O(1)
Cu(1)–O(3i)
O(1)–S(1)
S(1)–O(3)
S(1)–O(4)
S(1)–C(6)
C(6)–F(1)
C(6)–F(2)
C(6)–F(3)
2.114(6)
2.179(6)
2.036
Cu(2)–C(3)
Cu(2)–C(4)
Cu(2)–X(2)
C(3)–C(4)
C(3)–C(5)
Cu(2)–P(2)
Cu(2)–O(2)
Cu(2)–O(6ii)
O(2)–S(2)
S(2)–O(5)
S(2)–O(6)
S(2)–C(7)
C(7)–F(4)
C(7)–F(5)
C(7)–F(6)
2.220(6)
2.085(6)
2.045
1.360(8)
1.440(8)
2.262(2)
2.079(4)
2.370(5)
1.444(4)
1.424(4)
1.421(4)
1.828(8)
1.337(8)
1.308(8)
1.288(8)
1.353(8)
1.543(9)
2.278(2)
2.091(4)
2.297(4)
1.450(4)
1.424(4)
1.440(4)
1.810(6)
1.326(7)
1.310(7)
1.324(7)
,
being planar to within 0.03 A. The copper(I) centres are
approximately tetrahedrally coordinated by phosphorus
of a triphenylphosphine, CꢀC and two triflate oxygen
donors from different anions (see Fig. 2 and Table 3).
The Cu–C bond lengths range from 2.085(6) to
O(1)–Cu(1)–C(1)
95.5(2)
O(2)–Cu(2)–C(4)
O(2)–Cu(2)–C(3)
P(2)–Cu(2)–C(4)
P(2)–Cu(2)–C(3)
O(6ii)–Cu(2)–C(4)
O(6ii)–Cu(2)–C(3)
P(2)–Cu(2)–O(2)
P(2)–Cu(2)–O(6ii)
O(2)–Cu(2)–O(6ii)
C(2)–C(3)–C(4)
C(4)–C(3)–C(5)
Cu(2)–O(2)–S(2)
S(2)–O(6)–Cu(2ii)
O(2)–S(2)–O(5)
O(2)–S(2)–O(6)
O(5)–S(2)–O(6)
O(2)–S(2)–C(7)
O(5)–S(2)–C(7)
O(6)–S(2)–C(7)
99.1(2)
133.8(2)
156.2(2)
121.2(2)
95.1(2)
102.9(2)
99.0(1)
100.3(1)
89.9(1)
121.0(6)
121.4(6)
137.2(3)
132.8(2)
115.9(3)
113.8(2)
115.3(3)
101.3(3)
105.1(3)
102.9(3)
O(1)–Cu(1)–C(2) 129.6(2)
P(1)–Cu(1)–C(1) 156.2(2)
P(1)–Cu(1)–C(2) 119.5(2)
,
2.220(6) A [C(CH3)] and are very similar to those in
O(3i)–Cu(1)–C(1)
95.6(2)
[Cu2Cl2{m-(H2CꢀCHC(CH3)ꢀCH2)}] [3], whereas corre-
sponding distances in the more stable compound,
[Cu2{(C6H5CH2) N(C5H4N)2}2 {m - (H2CꢀCHC (CH3)ꢀ
O(3i)–Cu(1)–C(2) 102.2(2)
P(1)–Cu(1)–O(1) 105.2(1)
P(1)–Cu(1)–O(3i)
93.7(1)
O(1)–Cu(1)–O(3i) 96.7(2)
,
CH2)}(O3SCF3)2], are ca. 0.1 A shorter [4], which may
C(1)–C(2)–C(3)
C(2)–C(3)–C(5)
127.2(7)
116.8(5)
indicate a stronger interaction between isoprene and
copper(I) in the latter compound. As in the two other
isoprene-containing copper(I) complexes [3,4], the metal
is closer to the terminal carbons of both double bonds,
the asymmetry in coordination being more pronounced
for the olefinic ligand carrying the methyl group. In
solution, 1 shows a net magnetic shielding, as indicated
Cu(1)–O(1)–S(1) 139.4(3)
S(1)–O(3)–Cu(1i) 129.5(3)
O(1)–S(1)–O(3)
O(1)–S(1)–O(4)
O(3)–S(1)–O(4)
O(1)–S(1)–C(6)
O(3)–S(1)–C(6)
O(4)–S(1)–C(6)
112.4(3)
116.8(3)
116.2(3)
101.2(3)
103.2(3)
104.4(4)
1
by upfield H-NMR shifts, of all the vinylic protons in
comparison with the free ligand. The somewhat larger
a Symmetry code: (i) −x, 1−y, −z; (ii) 1−x, −y, −z.
Table 4
mined. Although two isoprene complexes of copper(I),
namely [Cu2Cl2(m-C5H8)] [3] and [Cu2{(C6H5CH2N-
(C5H4N)2}2((m-C5H8)(O3SCF3)2] [4] have been fully
characterised previously, to the best of our knowledge,
complex 2 represents the first compound in which cop-
per(I) is coordinated by an isopropenylacetylene ligand.
All the conjugated dienes adopt the s-trans confor-
mation on coordination to copper(I), as has been ob-
served previously for isoprene [3,4]. This property of
copper(I) is unusual since the most prevalent bonding
mode of conjugated dienes to transition metals is the
tetrahapto, with the ligand in the s-cis conformation
[5,6], notable exceptions being the butadiene
,
Bond distances (A) and angles (°) for the non-hydrogen atoms in
[Cu2Cl2{m-(H2CꢀCHC(CH3)ꢁCH)}] (2) a
Cu(1)–C(1)
Cu(1)–C(2)
Cu(1)–X(1)
C(1)–C(2)
2.048(10) Cu(2)–C(3)
2.056(9)
2.005(10)
1.940
1.200(14)
1.480(13)
2.255(2)
2.293(3)
3.239(3)
2.158(9)
1.989
Cu(2)–C(4)
Cu(2)–X(2)
1.373(13) C(3)–C(4)
1.473(13) C(2)–C(5)
C(2)–C(3)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
Cu(1)–Cl(2i)
2.274(3)
2.322(2)
2.766(3)
Cu(2)–Cl(1ii)
Cu(2)–Cl(2)
Cu(2)–Cl(2ii)
Cl(1)–Cu(1)–C(1)
Cl(1)–Cu(1)–C(2)
Cl(2)–Cu(1)–C(1)
Cl(2)–Cu(1)–C(2)
Cl(2i)–Cu(1)–C(1)
Cl(2i)–Cu(1)–C(2)
Cl(1)–Cu(1)–Cl(2)
Cl(1)–Cu(1)–Cl(2i)
Cl(2)–Cu(1)–Cl(2i)
C(1)–C(2)–C(3)
105.6(3)
143.3(3)
138.5(3)
104.6(3)
108.2(3)
98.9(3)
107.0(1)
98.4(1)
91.9(1)
Cl(2)–Cu(2)–C(4)
Cl(2)–Cu(2)–C(3)
Cl(1ii)–Cu(2)–C(4)
Cl(1ii)–Cu(2)–C(3)
Cl(2ii)–Cu(2)–C(4)
Cl(2ii)–Cu(2)–C(3)
Cl(1ii)–Cu(2)–Cl(2)
Cl(1ii)–Cu(2)–Cl(2ii)
Cl(2)–Cu(2)–Cl(2ii)
C(2)–C(3)–C(4)
137.9(3)
105.1(3)
113.1(3)
146.5(2)
105.8(4)
97.8(3)
108.3(1)
82.4(1)
86.0(1)
derivatives:
[{Ni(C4H6)(C10H8N2)}2(C4H6)]
[20],
[{Mn(C5H5)(CO)}2(C4H6)] [21], [N(CH3)3(C2H5)]2-
[Pt2Cl6(C4H6)] [22] and [Os3(CO)10(C4H6)] [23]. In
Cp2Zr(C4H6), the butadiene ligand is, however, coordi-
nated to zirconium in the tetrahapto mode, despite
transoid ligand conformation [24].
119.6(9)
124.7(9)
168.0(10)
114.5(8)
C(1)–C(2)–C(5)
C(3)–C(2)–C(5)
In 1, the isoprene ligand bridges two copper(I) cen-
tres via h2 coordination involving both CꢀC bonds.
a Symmetry code: (i) −x, −y, 1–z; (ii) −x, −y, 2−z.

10
M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
Table 5
,
strong (2.079(4) and 2.091(4) A, respectively) and one
,
Bond distances (A) and angles (°) for the non-hydrogen atoms in
,
weaker (2.370(5) and 2.297(4) A, respectively) for each
[Cu2Cl2{m-(H2CꢀC(CH3)C(CH3)ꢀCH2)}] (3) a
copper(I) centre. This leads to distorted tetrahedral
coordination geometry for the metal, which geometry
Cu(1)–C(1)
Cu(1)–C(2)
Cu(1)–X(1)
C(1)–C(2)
C(2)–C(3)
C(2)–C(5)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
Cu(1)–Cl(2i)
2.07(1)
2.12(1)
1.98
1.35(1)
1.48(1)
1.52(1)
2.319(2)
2.307(3)
2.750(2)
Cu(2)–C(3)
Cu(2)–C(4)
Cu(2)–X(2)
C(3)–C(4)
C(3)–C(6)
2.17(1)
2.06(1)
2.00
1.35(1)
1.51(1)
Cu(2)–Cl(1)
Cu(2)–Cl(1ii)
Cu(2)–Cl(2ii)
2.448(2)
2.455(2)
2.319(2)
Cl(1)–Cu(1)–C(1)
Cl(1)–Cu(1)–C(2)
Cl(2)–Cu(1)–C(1)
Cl(2)–Cu(1)–C(2)
Cl(2i)–Cu(1)–C(1)
Cl(2i)–Cu(1)–C(2)
Cl(1)–Cu(1)–Cl(2)
Cl(1)–Cu(1)–Cl(2i)
Cl(2)–Cu(1)–Cl(2i)
C(1)–C(2)–C(3)
C(1)–C(2)–C(5)
C(3)–C(2)–C(5)
Cu(1)–Cl(1)–Cu(2)
Cu(1)–Cl(1)–Cu(2ii)
Cu(2)–Cl(1)–Cu(2ii)
138.2(3)
100.5(2)
118.2(3)
147.9(2)
95.6(3)
Cl(1)–Cu(2)–C(4)
Cl(1)–Cu(2)–C(3)
Cl(1ii)–Cu(2)–C(4)
Cl(1ii)–Cu(2)–C(3)
Cl(2ii)–Cu(2)–C(4)
Cl(2ii)–Cu(2)–C(3)
120.7(3)
105.0(3)
132.2(3)
104.8(2)
109.1(3)
145.4(2)
101.77(8)
96.07(8)
91.38(8)
121.2(8)
117.2(8)
120.0(9)
80.02(8)
85.56(8)
107.8(2)
100.28(8) Cl(1)–Cu(2)–Cl(2ii)
98.18(8) Cl(1ii)–Cu(2)–Cl(2ii)
93.13(8) Cl(1)–Cu(2)–Cl(1ii)
121.1(8)
119.7(9)
117.7(8)
C(2)–C(3)–C(4)
C(2)–C(3)–C(6)
C(4)–C(3)–C(6)
82.83(7) Cu(1)–Cl(2)–Cu(2ii)
77.03(7) Cu(1)–Cl(2)–Cu(1i)
88.62(8) Cu(1i)–Cl(2)–Cu(2ii) 106.86(8)
a Symmetry code: (i) 1−x, y, 1.5–z; (ii) 1−x, 1−y, 1−z.
Fig. 1. View of [Cu2(PPh3)2{m-(H2CꢀCHC(CH3)ꢀCH2)}(O3SCF3)2]
(1), showing the crystallographic numbering. Thermal ellipsoids en-
close 50% probability. In addition, Cu(1) is coordinated by O(3) of a
neighbouring triflate group and Cu(2) likewise by O(6) of a neigh-
bouring triflate ligand (see Table 3).
shifts for the terminal vinylic protons associated with
the non-methylated olefinic bond suggest the presence
of a somewhat larger back-bonding component for this
bond, as compared with the methylated linkage, which
would be consistent with electron release from the
methyl group tending to reduce the back-bonding com-
ponent to the latter. The bending back of C(3) from the
C(1)–C(2) bond (C(1)–C(2)–C(3)=127.2(7)°) is also
more pronounced than that of C(5) and C(2) from
C(3)–C(4) (121.4(6) and 121.0(6)°), respectively).
The CꢀC bond lengths do not differ significantly
from one another and are similar to those determined
previously for isoprene coordinated to copper(I) [3,4].
The lengthening on coordination is slight and corre-
sponding reduction in the IR absorption frequencies
impossible to ascertain, owing to the interference from
aromatic ring stretches in this crucial region.
Triflate is normally assumed to be a non-coordinat-
ing or
[Cu2{(C6H5CH2)N(C5H4N)2}2
a
very weakly coordinating anion. In
{m-(H2CꢀCHC(CH3)ꢀ
CH2)}(O3SCF3)2] [4], it is weakly coordinating and, as a
result, both copper(I) centres attain trigonal pyramidal
coordination with an apical triflate oxygen donor. Tri-
flate bridges containing two short Cu–O bonds, viz.
,
2.101(4) and 2.135(4) A, are, however, present in the
Fig.
2.
Part
of
a
chain
in
[Cu2(PPh3)2{m-
compound with a chelating 1,5-hexadiene ligand, in
which copper(I) is approximately tetrahedrally coordi-
nated [25]. In 1, the bridging Cu–O bonds indicate one
(H2CꢀCHC(CH3)ꢀCH2)}(O3SCF3)2] (1), showing the alternate bridg-
ing of copper(I) by isoprene and triflate (participating in
eight-membered Cu2S2O4 rings).

M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
11
like chain. Part of a chain of 5 is shown in Fig. 7, these
chains being further linked by long Cu···Cl interactions
,
(ca. 3 A) to form layers. Contrary to the situation in 1
and in [Cu2{(C6H5CH2)N(C5H4N)2}2{m-(H2CꢀCHC-
(CH3)ꢀCH2)}(O3SCF3)2] [4], the conjugated dienes in 3
and 4, bond to two copper(I) centres from the same
face of the ligand, as in [Cu2Cl2{m-(H2Cꢀ
CHC(CH3)ꢀCH2)}] [3].
A trigonal pyramid in which the trigonal plane com-
prises the CꢀC linkage and two chloride ligands with an
additional chloride forming the apex is the prevalent
coordination geometry for copper(I) in 2–4, but some
copper(I) centres exhibit tetrahedral coordination geo-
metry. Thus, in 2 both Cu(1) and Cu(2) are trigonal
pyramidally coordinated by two chloride ligands and a
Fig. 3. The basic dimeric [{Cu2Cl2{m-(H2CꢀCHC(CH3)ꢁCH)}}2] unit
in 2, showing the crystallographic numbering. Starred atoms are
related to the non-starred counterparts by −x, −y, 2−z (see Table
4). Thermal ellipsoids enclose 50% probability.
Fig. 4. Part of a chain of [Cu2Cl2{m-(H2CꢀCHC(CH3)ꢁCH)}] (2),
showing the connection of the dimers depicted in Fig. 3, which
contain chair-shaped Cu4Cl4 rings, by longer Cu···Cl contacts of
,
2.766(3) A (see Table 4). Note that the isopropenylacetylene ligands
are situated on the periphery of the copper–chloride framework.
Fig.
5.
The
basic
dimeric
unit
of
[{Cu2Cl2{m-
more closely approaches that of a trigonal pyramid for
Cu(2) than is the case for Cu(1).
(H2CꢀC(CH3)C(CH3)ꢀCH2)}}2] (3), showing the crystallographic
numbering. Thermal ellipsoids enclose 50% probability. For clarity
only the asymmetric unit has been labelled, the remaining atoms are
related by a centre of symmetry (1−x, 1−y, 1−z).
The copper(I) chloride complexes, 2–4 are similar in
that the basic copper(I) units bridged by the conjugated
diene in the s-trans conformation (3, 4) or by iso-
propenylacetylene (2) are further linked by long Cu···Cl
interactions to form chains (2, 3) or layers (4) in which
the organic ligands are positioned on the periphery.
These basic units, which are dimeric in 2 and 3, and
their linking to form chains are illustrated in Figs. 3
and 4 and Figs. 5 and 6, respectively. The basic dimeric
units in 2 and 3 are seen to be very similar if the long
ii
ii
,
Cu(2)–Cl(2 ) and Cl(2)–Cu(2 ) contacts of 3.239(3) A
are visualised as bonds. The linking of these dimeric
units to form chains differs, however. Thus in 2, the
chains are composed of alternate four-membered and
chair-shaped Cu4Cl4 eight-membered rings, whereas the
copper–chloride linking in 3 results in a pleated ribbon-
Fig. 6. Part of a chain in [Cu2Cl2{m-(H2CꢀC(CH3)C(CH3)ꢀCH2)}]
(3), illustrating the pleated ribbon-like copper–chloride chain with
peripheral dimethylbutadiene ligands.

12
M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
,
Cu(1)–C(2) distances are 2.06(3) and 2.07(3) A, respec-
tively, while Cu(2)–C(3) and Cu(2)–C(4)=2.11(4) and
,
2.12(2) A. The CꢀC bonds are unrealistically long at
,
1.46(4) and 1.50(4) A, which artefact is attributable to
the low precision and accuracy of the structure determi-
nation, since such lengthening is not mirrored by ex-
traordinary shifts in IR absorption frequencies (see
below).
IR absorption frequencies for compounds 2–6 are
compared with those of the free ligands in Table 6. As
has been noted previously, the conjugated dienes as-
sume the s-trans conformation and coordinate to cop-
per(I) in the h2 mode. The dienes are essentially
unchanged in geometry on coordination with marginal
lengthening of the CꢀC bonds, which is in accordance
with previous studies (see Refs. [1–4,19,25,27] and
Refs. therein). Weak interaction between the dienes and
copper(I) is evident from the magnitudes of the ob-
served shifts (70–100 cm−1), each diene acting essen-
tially as if it were composed of two localised h2 donors.
In the complex with the analogous non-conjugated 1,
4-pentadiene [Cu2Cl2({m-(H2CꢀCH–CH2–CHꢀCH2)}]
[19], where the ligand is a true localised h2 donor,
bridging two copper(I) centres via the two CꢀC func-
tionalities, marginally greater shifts are observed (Table
6), which are reflected in a reduced lability of
[Cu2Cl2({m-(H2CꢀCH–CH2–CHꢀCH2)}] [19] in com-
parison with 2–6. The similarity in the CꢀC–CꢀC shifts
for 5 and 6 to those of the other compounds suggest
that these are likely to possess similar structures with
the ligand in the s-trans conformation: 5 is therefore
tentatively formulated as ‘[Cu2Cl2(C5H8)]’ where
C5H8=cis-1,3-pentadiene and 6 as ‘[Cu2Cl2(C4H6)]’
where C4H6=1,3-butadiene. The vibrations at 1564
and 1506 cm−1 for 6 correspond well, moreover, to
those of the compound prepared from copper(I) chlo-
ride and liquid butadiene (1570 and 1507 cm−1) [30]
and that prepared by reducing cupric chloride with
organic phosphites in the presence of butadiene (1565
and 1500 cm−1) [31], suggesting that these butadiene
complexes of copper(I) chloride are identical, indepen-
dent of the preparative method. It is interesting that in
the complex between 1,5 hexadiene and copper(I) tri-
fluoromethanesulfonate the hexadiene ligand is chelat-
ing, rather than bridging [25]; yielding a compound in
which the Cu:diene stoichiometry is 1:1, in contrast to
the 2:1 stoichiometry exhibited by the compounds 1–4.
The copper(I) trifluoromethanesulfonate–1,5 hexadiene
complex is relatively stable [25], which indicates that
once a diene can be induced to bond to a single
copper(I) centre as a chelating ligand, enhanced stabil-
ity results.
Fig. 7. Part of chain in [Cu2Cl2{m-(trans-H2CꢀCHCHꢀCH(CH3))}]
(4) showing the overall structural features and the crystallographic
numbering. Such chains are further connected by long Cu···Cl con-
tacts to form layers with peripheral trans-1,3-pentadiene ligands.
CꢀC or CꢁC linkage comprising the basal plane with
,
long apical Cu···Cl contacts of 2.766(3) and 3.239(3) A,
,
respectively, copper(I) being displaced 0.32 and 0.02 A
towards the apices. The carbon skeleton (C(1)–C(4)) of
,
the ligand is planar to within 0.04 A. There is little
olefin sliding [26], and the midpoint of the CꢀC bond is
symmetrically placed with respect to the chloride lig-
ands in the trigonal plane (Cl–Cu–X(1)=121 and
125°). The CꢁC linkage is, however, less symmetrically
coordinated, with corresponding angles of 121 and
130°. The deviation of the C(2)–C(3)–C(4) angle
(168(1)°) from linearity is similar to values determined
previously for p-acetylenic complexes of copper(I) chlo-
ride [13,27]. Slight bending back of the methyl group
from the CꢀC bond is evident from the C(1)–C(2)–
C(5) and C(3)–C(2)–C(5) angles (Table 4).
In 3, Cu(2) has distorted tetrahedral coordination,
whereas Cu(1) is trigonal pyramidally coordinated, the
,
metal being displaced 0.31 A from the trigonal plane
,
towards the apical chloride situated at 2.750(2) A from
Cu(1). The discrepancy between the X(1)–Cu(1)–Cl(1)
and X(1)–Cu(1)–Cl(2) angles (119 and 134°, respec-
tively), indicate olefin sliding [26] in the trigonal plane.
There would not appear to be any appreciable bending
back of the methyl groups from CꢀC linkages (Table 5).
The diene backbone of the ligand (C(1)–C(4)) is planar
,
to within 0.05 A. In 4, both copper(I) centres exhibit
trigonal pyramidal coordination geometry, Cu(1) with
,
two chloride ligands at 2.283(7) A and a third at
,
2.905(9) A towards which the metal is displaced by 0.16
It has, thus, now been further established that the
preferential bonding mode of a conjugated diene to
copper(I) is as an h2 bridge between metal centres, the
diene assuming the s-trans conformation. Similar bond-
,
A and Cu(2) with two chloride ligands at 2.287(7) and
2.308(7) A and a third at 2.793(8) A towards which the
metal is displaced by 0.27 A. The Cu(1)–C(1) and
,
,
,

M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
13
ing is also observed for the acetylenic analogue of
isoprene: isopropenylacetylene. While it is unlikely
that back-bonding effects in such compounds are neg-
ligible [2,19,32], particularly since the trigonal pyrami-
dal coordination geometry relies on this component
for its stabilisation [19], the ready loss of organic lig-
and, if positioned on the peripheries of chains or lay-
ers, thus occupying unprotected or vulnerable
structural sites, is suggestive of a weak overall p-in-
teraction between the ligand and copper(I).
It is also possible to compare the effect on lability
of bridging chloride contra bridging trifluoromethane-
sulfonate in copper(I) complexes containing conju-
gated dienes: when isoprene is embedded in the chain,
as in 1, or protected by bulky ligands, as in [Cu2-
{(C6H5CH2N(C5H4N)2}2((m-C5H8)(O3SCF3)2] [4], rela-
tively stable compounds are obtained. When the diene
(or isopropenylacetylene) is situated on the periphery
of a copper(I)–chloride chain or layer, the organic
ligand is lost instantaneously on exposure to the at-
mosphere. A rationale for this has been proposed to
account for the resistance of [(Cu(OtBu)(CO))4] to de-
carbonylation [33]: namely, the unfavourable pyrami-
dal coordination geometry for copper(I) which would
result from the initial decarbonylation product [33].
Similar reasoning can be used to account for instan-
taneous loss of carbon monoxide from [Cu(CO)Cl] (s)
[18], which contains carbonyl groups peripherally
bonded to copper(I) centres participating in a cop-
per(I) chloride layer. Here tetrahedral coordination of
copper(I) by chloride following loss of carbon
monoxide is favoured by the proximity of chloride
ligands, the decomposition product being copper(I)
chloride. Similarly, in 2–4, the organic ligands are
unprotected on the periphery of a copper(I) chloride
framework, and initial loss of an organic ligand can
therefore result in rapid formation of copper(I) chlo-
ride.
4. Supplementary material
Crystallographic data (excluding structure factors)
for the structural analysis have been deposited with
the Cambridge Crystallographic Data Centre, CCDC
no. 138841 for compound 1, CCDC no. 138842 for
compound 2, CCDC no. 138843 for compound 3 and
CCDC no. 138844 for compound 4. Copies of the
data can be obtained free of charge from The Direc-
tor, CCDC, 12 Union Rd., Cambridge CB2 1EX,
UK (fax:+44-1223-336033; e-mail: deposit@ccdc.
com.ac.uk or www: http://www.ccdc.cam.ac.uk).
Table 6
Comparison of the shifts in IR absorption frequencies observed on coordination of some conjugated and non-conjugated dienes and
2-methyl-1-butene-3-yne to copper(I) a
Compound
Free ligand
ws
Complex
ws
was
was
Dws
Dwas
‘[Cu2Cl2(C4H6)]’
1643 a,b
1595
1564
1506
89
89
(Butadiene, 6)
[Cu2Cl2(C5H8)]
(Isoprene [1])
1640
1598
1603
1595
1601
1569
1579
1567
1551
1520
1517
1502
1514
71
78
86
93
87
[Cu2Cl2(C5H8)]
(trans-1,3-pentadiene, 4)
1650
71
‘[Cu2Cl2(C5H8)]’
(cis-1,3-pentadiene, 5)
1646
79
[Cu2Cl2(C6H10)]
1654 a,c
103
(dimethylbutadiene, 3)
wCꢀC
wCꢀC
DwCꢀC
[Cu2Cl2(C5H8)]
1639
1542
1532
97
107
(1,4-pentadiene [22])
wCꢀC
wCꢁC
wCꢁC
wCꢁC
DwCꢀC
DwCꢁC
[Cu2Cl2(C5H6)]
1615
2103
1525
1962
90
141
(2-methyl-1-butene-3-yne, 2)
a R, Raman.
b See Ref. [28].
c See Ref. [29].

14
M. Ha˚kansson et al. / Journal of Organometallic Chemistry 602 (2000) 5–14
[15] TEXSAN TEXRAY Structure Analysis Package, Molecular
—
Acknowledgements
Structure Corporation, The Woodlands, TX, 1989.
[16] International Tables for X-ray Crystallography, Vol. IV, Kynoch
Press, Birmingham, UK, 1974.
[17] C.K. Johnson, ORTEP, ORNL Report 3794, Oak Ridge National
Laboratory, Oak Ridge, TN, USA, 1965.
Financial support from the Swedish Natural Science
Research Council (NFR) is gratefully acknowledged.
[18] M. Ha˚kansson, S. Jagner, Inorg. Chem. 29 (1990) 5241.
[19] M. Ha˚kansson, S. Jagner, E. Clot, O. Eisenstein, Inorg. Chem.
31 (1992) 5389.
References
[20] W. Mayer, G. Wilke, R. Benn, R. Goddard, C. Kru¨ger,
Monatsch. Chem. 116 (1985) 879.
[21] M. Ziegler, Z. Anorg. Allgem. Chem. 355 (1967) 12.
[22] V.C. Adam, J.A.J. Jarvis, B.T. Kilbourn, P.G. Owston, J. Chem.
Soc. Chem. Commun. (1971) 467.
[23] C.G. Pierpont, Inorg. Chem. 17 (1978) 1976.
[24] G. Erker, J. Wicher, K. Engel, F. Rosenfeldt, W. Dietrich, C.
Kru¨ger, J. Am. Chem. Soc. 102 (1980) 6346.
[25] T. Nickel, K.-R. Po¨rschke, R. Goddard, C. Kru¨ger, Inorg.
Chem. 31 (1992) 4428.
[26] S.D. Ittel, J.A. Ibers, Adv. Organomet. Chem. 14 (1976) 33.
[27] M. Ha˚kansson, K. Wettstro¨m, S. Jagner, J. Organomet. Chem.
421 (1991) 347.
[28] Schorgyin, Izv. Akad. S.S.S.R. Ser. Fiz. 12 (1948) 576.
[29] E.G. Treshchova, V.M. Tatevskii, R. Ya. Levina, A.A. Fainzil-
berg, E.A. Viktorova, Zhur. Fiz. Khim. 26 (1952) 1266.
[30] P.J. Hendra, D.B. Powell, Spectrochim. Acta 18 (1962) 1195.
[31] B.W. Cook, R.G.J. Miller, P.F. Todd, J. Organomet. Chem. 19
(1969) 421.
[32] P.H.M. Budzelaar, P.J.J.A. Timmermans, A. Mackor, E.J.
Baerends, J. Organomet. Chem. 331 (1987) 397.
[33] R.L. Geerts, J.C. Huffman, K. Folting, T.H. Lemmen, K.G.
Caulton, J. Am. Chem. Soc. 105 (1983) 3503.
[1] A. Camus, N. Marsich, G. Nardin, L. Randaccio, Inorg. Chim.
Acta 23 (1977) 131.
[2] M.G. Mys’kiv, V.V. Oliinik, Russian J. Coord Chem. 21 (1995)
275.
[3] M. Ha˚kansson, S. Jagner, D. Walther, Organometallics 10
(1991) 1317.
[4] L. Song, W.C. Trogler, J. Organomet. Chem. 452 (1993)
271.
[5] H.W. Quinn, J.H. Tsai, Adv. Inorg. Radiochem. 12 (1969) 217.
[6] R.H. Crabtree, The Organometallic Chemistry of the Transition
Metals, 2nd ed., Wiley, New York, 1994.
[7] J.C. Tai, N.L. Allinger, J. Am. Chem. Soc. 98 (1976) 7928.
[8] M.G. Mys’kiv, P.Yu. Zavalii, B.M. Mykalichko, V.S. Fun-
damenskii, Koord. Khim. 14 (1988) 1619.
[9] M. Ha˚kansson, Inorg. Synth. 32 (1998) 222.
[10] R.G. Salomon, J.K. Kochi, J. Am. Chem. Soc. 95 (1973) 1889.
[11] R.N. Keller, H.D. Wycoff, Inorg. Synth. 2 (1946) 1.
[12] F.G. Schreiber, R. Stevenson, J. Chem. Soc. Perkin Trans.
(1977) 90.
[13] K. Brantin, M. Ha˚kansson, S. Jagner, J. Organomet. Chem. 474
(1994) 229.
[14] C.J. Gilmore, J. Appl. Crystallogr. 17 (1984) 42.
.