Synthesis and characterization of Cu(I) and Cu(II) complexes containing ketiminate ligands

Article abstract of DOI:10.1016/j.jorganchem.2007.08.028

A series of Cu(I) and Cu(II) complexes containing substituted ketiminate ligands was synthesized. Reaction of CuCl₂ with 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] in toluene generated dark green solid of Cu[OC(Me)CHC(Me)N(Ar)]₂ (1). Similarly, Cu(I) complex, {Cu[OC(Me)CHC(Me)N(Ar)]Li[OC(Me)CHC(Me)N(Ar)]}₂ (2) was synthesized by reacting 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] with CuCl in toluene at room temperature for 12 h. While the reaction of CuCl with Li[OC(Me)CHC(Me)N(Ar)] in the presence of triphenylphosphine in THF solution at room temperature, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)](PPh₃) (3) can be isolated in high yield. Replacing the PPh₃ of 3 with N-heterocarbene (NHC) generates Cu[OC(Me)CHC(Me)N(Ar)](NHC) (4) in low yield. Complexes 2, 3, and 4 were characterized by ¹H and ¹³C NMR spectroscopies and all molecules were structurally characterized by X-ray diffractometry. Two coordination modes of ketiminate ligands were found in the molecular structure of 2, one of which is copper-coordinated terminal ketiminates and the other is lithium-copper-coordinated bridging ketiminates.

Full text of DOI:10.1016/j.jorganchem.2007.08.028

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5421–5428
www.elsevier.com/locate/jorganchem
Synthesis and characterization of Cu(I) and Cu(II)
complexes containing ketiminate ligands
a
a
a
a
a
Shih-Hsien Hsu , Chen-Yi Li , Yi-Wen Chiu , Mei-Chun Chiu , Yu-Ling Lien ,
a
a
a,
b
Pei-Cheng Kuo , Hon Man Lee , Jui-Hsien Huang *, Cheu-Pyeng Cheng
a
Department of Chemistry, National Changhua University of Education, Changhua 50058, Taiwan
b
Department of Chemistry, National Ting-Hua University, Hsinchu, Taiwan
Received 21 June 2007; received in revised form 17 August 2007; accepted 23 August 2007
Available online 29 August 2007
Abstract
A series of Cu(I) and Cu(II) complexes containing substituted ketiminate ligands was synthesized. Reaction of CuCl2 with 2 equiv. of
Li[OC(Me)CHC(Me)N(Ar)] in toluene generated dark green solid of Cu[OC(Me)CHC(Me)N(Ar)]2 (1). Similarly, Cu(I) complex,
{Cu[OC(Me)CHC(Me)N(Ar)]Li[OC(Me)CHC(Me)N(Ar)]}2 (2) was synthesized by reacting 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)]
with CuCl in toluene at room temperature for 12 h. While the reaction of CuCl with Li[OC(Me)CHC(Me)N(Ar)] in the presence of tri-
phenylphosphine in THF solution at room temperature, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)](PPh3) (3) can be isolated in
high yield. Replacing the PPh3 of 3 with N-heterocarbene (NHC) generates Cu[OC(Me)CHC(Me)N(Ar)](NHC) (4) in low yield. Com-
1
plexes 2, 3, and 4 were characterized by H and 13C NMR spectroscopies and all molecules were structurally characterized by X-ray
diffractometry. Two coordination modes of ketiminate ligands were found in the molecular structure of 2, one of which is copper-coor-
dinated terminal ketiminates and the other is lithium–copper-coordinated bridging ketiminates.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Copper; NHC carbene; Ketiminate
1. Introduction
cules making these kinetically more stable. Therefore, we
adopted the strategy to use bidentate ligands with bulky
substituents on one side to protect the metal centers keep-
ing open ends on the other side to increase the activity of
the metal complexes. We have demonstrated the use of
substituted ketiminates [3] as ancillary ligands to form
compounds of group 13 [4] and early transition metals
[5]. We now have extended the metals from main group
and early transition metals to the late transition metals.
Herein we report the syntheses of a series of Cu(I) and
Cu(II) complexes containing ketiminate ligands, [OC(Me)-
CHC(Me)NH(Ar)] where Ar = 2,6-diisopropylphenyl and
measurements of their structures and magnetic properties.
The reactivities of b-diketiminate copper complexes have
also been studied extensively in the literature [6,7]. There-
fore, we also tried some reactions of the synthesized Cu
The coordination chemistry of using b-diketiminate
derivatives [1] bearing bulky substituents has been studied
with wide variety of metals due to easy accessibility of
ligands synthesis, inexpensive of the starting material,
and controllable of steric and electronic effects. The bulky
b-diketiminate ligands indeed work effectively in prevent-
ing the decomposition of metal complexes by protecting
the metal centers using their bulky substituents [2]. We con-
ceived that the bulky substituents of b-diketiminate might
prevent the reactions of metal complexes with other mole-
*
Corresponding author. Tel.: +886 4 7232105; fax: +886 4 7211190.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.028

5422
S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
complexes with other coordinating ligands and oxygen
molecule.
Noticeably, there are two coordination modes of ketimi-
nate ligands presented in the molecular structure of com-
plex 2, one of which is copper-coordinated terminal
ketiminates and the other is lithium–copper-coordinated
bridging ketiminates (Scheme 2). Therefore, the methine
protons for the backbone of the terminal and bridging keti-
minates were observed at d 4.90 and 4.47, respectively.
Again, the terminal ketiminate methine carbon is likely
to be sp2 hybridized with the chemical shift at d 96.4 and
JCH coupling constant at 154 Hz while the bridging ketimi-
nate methine carbon is more like a sp3 hybridized with the
chemical shift at d 69.3 where the value of JCH coupling
constant is 146 Hz [8]. While the reaction of CuCl and
Li[OC(Me)CHC(Me)N(Ar)] in 1:1 ratio with the presence
of triphenylphosphine in THF solution at room tempera-
ture, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)]-
(PPh3) (3) can be isolated in high yield. Compound 3 can
also be obtained by reacting 2 with PPh3 in solution; how-
ever, the isolation yield is low. Again, the copper atom of
complex 3 exists a d10 electronic configuration and there-
fore the complex is NMR active and EPR silent. Indeed,
the 1H and 13C NMR spectra of 3 show a distinct methine
resonance for the backbone of the substituted ketiminate
ligand at d 5.30 and 96.7, respectively. The methine and
methyl protons of the isopropyl groups appear as a septet
(d 3.39) and two doublets (d 0.81 and 1.14).
2. Results and discussion
2.1. Synthesis and characterization of complexes 1, 2, 3,
and 4
Reaction of CuCl2 with 2 equiv. of Li[OC(Me)CHC-
(Me)N(Ar)] [4b] in toluene generated dark green solid of
Cu[OC(Me)CHC(Me)N(Ar)]2 (1) in 63% yield (Scheme
1). Attempts to obtain mono-ketiminate copper complex
by reacting CuCl2 with 1 equiv. of Li[OC(Me)CHC(Me)-
N(Ar)], however, leading to the formation of complex 1
only. No NMR singles were observed for the paramagnetic
Cu(II) complex. However, we did observe EPR resonances
for 1 and the data will be discussed in next section.
The Cu(I) complex, {Cu[OC(Me)CHC(Me)N(Ar)]-
Li[OC(Me)CHC(Me)N(Ar)]}2 (2) was synthesized by
reacting 2:1 ratio of Li[OC(Me)CHC(Me)N(Ar)] and CuCl
in toluene at room temperature for 12 h. While the reaction
was performed at 1:1 ratio of Li[OC(Me)CHC(Me)N(Ar)]
and CuCl, 2 was the only product isolated; however, the
yield is much lower than that of using 2:1 ratio. Complex
1
2 was characterized by H and 13C NMR spectroscopy.
However, the NMR spectral data are very complicated
due to the unsymmetrical structure of 2. 13C DEPT and
Replacing phosphine ligand by NHC carbene in organo-
metallic complexes have been seen very often in the litera-
ture due to the probability of finding more active catalysts
[9]. Therefore we also tried the reactions of compound 3
1
1H-coupled spectra as well as 2-D H–13C HSQC spectra
obtaining from a 600 MHz NMR spectrometer were uti-
lized to illustrate the molecular structure of complex 2.
O
1/2 CuCl2
N
Cu
N
O
N
Li
O
1
CuCl
CuCl + PPh3
N
Cu
O
N
PPh3
N
O
O
Cu
Li
Li
PPh3
O
O
N
3
Cu
N
2
Scheme 1.

S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
5423
2.3. Reactivity study of complexes 2, 3, and 4
Ar
N
The reactions of Cu(I) complexes 2, 3, and 4 with oxy-
gen molecules are monitored with 1H NMR spectra in
C6D6 in J-Young NMR tubes. Detail procedures can be
seen in Section 3. The results show that complex 2 reacted
fast with oxygen molecules and color changed from yellow
to deep brown. The sharp resonances of 2 also became very
broad and only a few resonances at ca. d 2.0 were observed.
Similarly, complex 3 can also react with oxygen atoms fast
and color changed from yellow to deep brown too. Only
triphenylphosphine oxide resonances were observed. A
bulk reaction of 3 with O2 in CH2Cl2 in a Schlenk flask
results the isolation of black crystal of 1, which has been
confirmed by X-ray crystallography or NMR spectros-
copy. A large quantity of triphenylphosphine oxide was
also observed in the residual of the solution. No terminal
(Cu–O) or bridging (Cu–O–Cu) oxo compound was
observed or isolated. However, while complex 4 reacted
with oxygen molecules, the reaction remained unchanged
after one day. Apparently the NHC ligands binded to
Cu(I) atom strongly preventing the oxidization of Cu(I)
to Cu(II) by oxygen. Attempting to isolate the products
of complexes 2 and 3 with oxygen molecules is still in
processing.
Cu
Ar
N
O
O
Li
Li
O
O
N
Ar
Cu
N
copper-coordinated
terminal ketiminates
Ar
lithium-copper-coordinated
bridging ketiminates
Ar = 2,6-diisopropylphenyl
Scheme 2.
with NHC ligands. Reaction of 3 with NHC (N,N0-bis(2,6-
diphenyl)imidazol-2-ylidene) in THF results the PPh3
replaced by NHC to yield Cu[OC(Me)CHC(Me)N(Ar)]-
(NHC) (4) (Scheme 3). The low reaction yield may result
from the lost of the recrystallization and isolation. 1H
NMR spectrum of 4 shows that the methine proton of
ketiminate backbone and the CH@CH protons of the
NHC ring appeared at d 5.00 and 6.40, respectively. The
13C NMR spectrum for the CH@CH carbons of the NHC
ring exhibits a single resonance at d 122.6 with a very large
coupling constant (JCH = 194 Hz). Similarly the coordina-
tion NHC carbene is evidenced by higher field shift of
NCN carbon from d 211.0–188.3.
2.4. Molecular structures of 1, 2, 3, and 4
Crystal structures of complexes 1, 2, 3, and 4 were stud-
ied and the summaries of data collections and selected
bond lengths and angles were shown in Tables 1 and 2,
respectively. The dark green black cubic crystals of 1 were
obtained from a saturated toluene solution of the complex.
The crystal structure of 1 is shown in Fig. 1. Complex 1
represents a distorted square planar geometry, in which
two ketiminate bidentate ligands are held in trans positions
where the O(1)–Cu–O(1A) and N(1)–Cu–N(1A) angles are
153.42(7)ꢁ and 153.74(7)ꢁ, respectively. The dihedral angle
of the two copper–ketiminate chelate rings is 41.5ꢁ. The
trans arrangement around the Cu center avoids steric
repulsions of the bulky 2,6-diisoprolylphenyl groups. The
structure is similar to the reported copper ketiminate com-
plex [10].
2.2. EPR study of 1
At 25 ꢁC, the EPR spectrum of 1 in toluene can be inter-
preted by the presence of an unpair electron (giso = 2.1059)
interacting with a copper nucleus (ACu = 73.82 G) and
2 equiv. nucleus (AN = 11.60 G). When the solution is
immersed in a liquid nitrogen, the EPR spectrum was aniso-
tropic with the following parameters: gx = 2.2117, gy =
2.0349, gz = 2.0096; ACux = 173.4 G, ACuy = 24 G, ACuz
=
20 G; ANx = 10.4 G, ANy = 12 G, ANz = 10 G. Both the
solution and solid EPR parameters are consistent with the
assignment of the structure of 1.
Crystals of 2 were obtained from a concentrated toluene
solution at ꢀ20 ꢁC. There are two independent molecules
of 2 and two toluene molecules in form the asymmetrical
unit. One of the methyl groups of toluene molecules is dis-
ordered and was splitted by a 50/50 ratio. The geometries
and bond parameters of the two molecules are very similar;
therefore, only one of the structures is described here
(Fig. 2). The molecular structure of 2 contains two three-
coordinate terminal ketiminate–copper fragments and
two four-coordinate bridging ketiminate–lithium frag-
ments. The two four-coordinate bridging ketiminate–lith-
ium fragments form a Li2O2 square planar core in which
the lithium atoms were bound to the oxygen atoms of
the terminal ketiminate–copper fragments and the methine
N
N
O
N
N
Cu
3
N
4
Scheme 3.

5424
S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
Table 1
The summary of crystallographic data for complexes 1–4
1
2
3
4
Formula
Fw
C34H48CuN2O2
580.28
C78.5H106.5Cu2Li2N4O4
1131.14
C35H39CuNOP
584.18
C44H60CuN3O
710.49
Temperature (K)
Crystal system
Space group
150(2)
Monoclinic
C2/c
24.0933(13)
11.5163(6)
12.1798(7)
150(2)
Triclinic
150(2)
Monoclinic
P21/c
17.2066(19)
11.3098(14)
16.434(2)
150(2)
Monoclinic
P21/n
11.1842(3)
15.9524(5)
23.3328(6)
ꢀ
P1
˚
a (A)
8.8465(3)
˚
b (A)
19.1370(8)
22.7828(9)
93.298(2)
96.876(2)
98.984(2)
3770.9(3)/2
1.155
0.612
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
109.5180(2)
100.819(4)
96.5240(10)
3
˚
Volume (A )/Z
3185.3(3)/4
1.210
0.716
3141.2(6)/4
1.235
0.773
4136.0(2)/4
1.141
0.562
Density (calc.) (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
1244
1403
1232
1528
Crystal size (mm)
h Range (ꢁ)
0.42 · 0.25 · 0.17
1.79–28.97
23808
4232 (Rint = 0.0471)
0.8879 and 0.7529
4232/0/183
1.053
0.0341, 0.0821
0.0442, 0.0857
0.429 and ꢀ0.320
0.25 · 0.09 · 0.08
0.90–29.06
57726
20066 (Rint = 0.1058)
0.9527 and 0.8620
20066/0/846
0.963
0.0616, 0.1342
0.1561, 0.1707
0.836 and ꢀ0.439
0.43 · 0.36 · 0.26
2.17–29.13
27777
8333 (Rint = 0.0403)
0.8243 and 0.7323
8333/0/358
1.076
0.0379, 0.1011
0.0564, 0.1078
0.504 and ꢀ0.636
0.46 · 0.28 · 0.25
1.55–29.98
46742
Number of reflections collected
Number of independent reflections
Maximum and minimum transmission
Number of data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)], Ra1, wR2b
R indices (all data), Ra1, wR2b
10845 (Rint = 0.0254)
0.8722 and 0.7820
10,845/0/456
1.059
0.0464, 0.1219
0.0691, 0.1320
1.706 and ꢀ0.973
ꢀ3
˚
Largest difference in peak and hole (e A
)
P
P
a
R1 = jFoj ꢀ jFcj/ jFoj.
P
P
b
wR2 = [ [x(F2o ꢀ F2c)2]/ [x(F2o)2]1/2
.
carbons of the bridging ketiminate–lithium fragments were
connected to the copper atoms (Fig. 3). The lithium atoms
can be described as trigonal pyramidal while the geometry
about copper atoms were shown as T shaped geometries
where the C(20)–Cu(1)–N(1) is 158.43(13)ꢁ. A more careful
examination of the bond distances of the ketiminate back-
bones of complex 2, we have found that the bridging keti-
N(1)–Cu(1)–P(1), N(1)–Cu(1)–O(1), and O(1)–Cu(1)–P(1)
for complex 3 and N(1)–Cu(1)–P(1), N(1)–Cu(1)–O(1),
and O(1)–Cu(1)–P(1) for complex 4 are both very close
to perfect 360ꢁ. However, complex 3 is more like Y-shape
geometry and complex 4 can be describes as T-shape geom-
etry. Three-coordinated trigonal planar complexes of tran-
sition metals with partially filled d shell electrons form
T-shape and Y-shape geometries due to the electronic effect
or the differential charge donation from the ligands to the
metals [13]. Complexes 3 and 4 have the same bidentate
ketiminate ligands, filled d shell electrons, and similar aux-
iliary ligands (PPh3 and NHC), therefore, the geometries
differences between complexes 3 and 4 are attributed as
the steric effect of the bulkiness of PPh3 and NHC. The
ketiminates bind to copper atoms with similar angles
(96.48(6)ꢁ and 93.16(7)ꢁ for 3 and 4, respectively) and their
phenyl rings are perpendicular to the Cu–ketiminate
formed six-membered rings. The bond length of Cu(1)–
˚
minate backbones tend to exist with a C@O (ca. 1.268 A), a
3
˚
C@N (ca. 1.302 A) bond, and a sp hybrid methine carbon
atom. While examination of the terminal ketiminate
NCCCO backbones showed that the C–O and C–N bond
˚
˚
lengths (ca. 1.286 A and ca. 1.316 A, respectively) are
longer that the bridging ketiminates indicating bond order
less than double bonds. In searching the molecular struc-
tures of organo-cuprate complexes, there are numerous
‘‘LixCuy’’ aggregates structurally characterized [11] How-
ever, there is only one ‘‘Li2Cu2’’, Li2Cu2(CH2SiMe3)4,
aggregate found in the literature [12]. Comparing the struc-
tures of 1 with Li2Cu2(CH2SiMe3)4, the ‘‘Li2Cu2’’ array in
1 is more like a dimeric of ‘‘LiCu’’ unit with very long
˚
P(1) for complex 3 (2.1384(5) A) is in the average for
majority complexes of Cu(I)–triphenylphosphine bond
lengths [14]. Again, the bond length of Cu(I) to the carbon
˚
Cuꢁ ꢁ ꢁCu distance of 7.78 A where the ‘‘Li2Cu2’’ array in
˚
Li2Cu2(CH2SiMe3)4 forms a pseudo square planar with
atom of NHC for complex 4 (1.8946(19) A) is similar to
˚
short of Cuꢁ ꢁ ꢁCu distance of 2.984(1) A.
those of majority complexes of Cu(I)–NHC [15].
The molecular structures of 3 and 4 (Figs. 4 and 5) are
both exhibiting three-coordinated geometries and will be
discussed together. Both of the structures of complexes 3
and 4 are trigonal planar, with the ketiminate N,O atoms
and triphenylphosphine P atom or NHC carbon atom tak-
ing the trigonal positions. The sums of the bond angles
In conclusion, we have synthesized a series of Cu(I) and
Cu(II) complexes by using lithium salt of bulky ketiminate
ligand, Li[OC(Me)CHC(Me)N(Ar)]. Complexes 1–4 are
fully characterized by spectroscopic techniques and X-ray
structure determination. The weaker Cu(I)–P bonding in
complex 3 can be replaced by Cu(I)–NHC bonding as

S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
5425
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for complexes 1–4
Complex 1
Cu(1)–O(1A)
Cu(1)–N(1A)
O(1)–C(2)
1.8931(11)
Cu(1)–O(1)
Cu(1)–N(1)
N(1)–C(4)
C(4)–C(3A)
1.8931(11)
1.9743(12)
1.3213(19)
1.411(2)
1.9742(12)
1.2861(19)
1.378(2)
C(2)–C(3)
C(3)–C(4A)
1.411(2)
O(1A)–Cu(1)–O(1)
O(1)–Cu(1)–N(1A)
O(1)–Cu(1)–N(1)
153.42(7)
93.74(5)
92.24(5)
O(1A)–Cu(1)–N(1A)
O(1A)–Cu(1)–N(1)
N(1A)–Cu(1)–N(1)
92.25(5)
93.74(5)
153.74(7)
Complex 2
Cu(1)–N(1)
Cu(1)–O(1)
Li(1A)–N(2)
Li(1A)–O(2A)
N(1)–C(4)
C(2)–C(3)
Cu(1A)–N(1A)
N(2)–C(21)
C(19)–C(20)
Cu(1A)–O(1A)
Li(1)–N(2A)
N(1A)–C(4A)
N(2A)–C(21A)
C(19A)–C(20A)
C(2A)–C(3A)
Cu(2)–N(3)
1.915(3)
2.105(2)
2.029(6)
1.883(6)
1.316(4)
1.391(5)
1.915(3)
1.302(4)
1.420(5)
2.105(2)
2.029(6)
1.316(4)
1.302(4)
1.420(5)
1.391(5)
1.915(3)
2.110(2)
2.029(7)
1.867(6)
1.310(4)
1.384(4)
1.291(4)
1.430(5)
1.915(3)
2.110(2)
2.029(7)
1.310(4)
1.384(4)
Cu(1)–C(20)
Li(1A)–O(1)
Li(1A)–O(2)
Li(1)–O(2A)
C(3)–C(4)
2.027(3)
1.921(6)
1.964(6)
1.964(6)
1.418(5)
1.280(4)
2.027(3)
1.467(4)
1.268(4)
1.921(6)
1.883(6)
1.418(5)
1.467(4)
1.268(4)
1.280(4)
2.035(3)
1.909(6)
1.958(6)
1.867(6)
1.423(5)
1.283(4)
1.456(4)
1.261(4)
2.035(3)
1.909(6)
1.958(6)
1.423(5)
1.283(4)
O(1)–C(2)
Cu(1A)–C(20A)
C(20)–C(21)
O(2)–C(19)
Li(1)–O(1A)
Li(1)–O(2)
C(3A)–C(4A)
C(20A)–C(21A)
O(2A)–C(19A)
O(1A)–C(2A)
Cu(2)–C(54)
Li(2A)–O(3)
Li(2A)–O(4)
Li(2)–O(4)
Cu(2)–O(3)
Li(2A)–N(4)
Li(2A)–O(4A)
N(3)–C(38)
C(37)–C(38)
O(3)–C(36)
C(36)–C(37)
N(4A)–C(55A)
C(53A)–C(54A)
Cu(2A)–N(3A)
Cu(2A)–O(3A)
Li(2)–N(4A)
N(3A)–C(38A)
C(36A)–C(37A)
C(54A)–C(55A)
O(4A)–C(53A)
Cu(2A)–C(54A)
Li(2)–O(3A)
Li(2)–O(4A)
C(37A)–C(38A)
O(3A)–C(36A)
N(1)–Cu(1)–O(1)
96.16(10)
158.43(13)
92.1(3)
104.3(3)
96.16(10)
158.43(13)
92.1(3)
104.3(3)
127.8(3)
95.69(10)
158.70(12)
92.8(2)
C(20)–Cu(1)–O(1)
N(2)–Li(1A)–O(2A)
N(2)–Li(1A)–O(2)
N(2)–Li(1A)–O(1)
C(20A)–Cu(1A)–O(1A)
N(2A)–Li(1)–O(2)
N(2A)–Li(1)–O(2A)
N(2A)–Li(1)–O(1A)
O(2A)–Li(1A)–O(1)
C(54)–Cu(2)–O(3)
N(4)–Li(2A)–O(4)
N(4)–Li(2A)–O(4A)
104.55(11)
126.5(3)
91.4(3)
102.6(3)
104.55(11)
126.5(3)
91.4(3)
102.6(3)
127.8(3)
104.62(11)
91.8(3)
N(1)–Cu(1)–C(20)
O(2)–Li(1A)–O(2A)
O(1)–Li(1A)–O(2)
N(1A)–Cu(1A)–O(1A)
N(1A)–Cu(1A)–C(20A)
O(2A)–Li(1)–O(2)
O(1A)–Li(1)–O(2A)
O(2)–Li(1)–O(1A)
N(3)–Cu(2)–O(3)
N(3)–Cu(2)–C(54)
O(4)–Li(2A)–O(4A)
127.2(3)
Complex 3
Cu(1)–N(1)
Cu(1)–P(1)
1.9341(14)
2.1384(5)
Cu(1)–O(1)
1.9653(12)
143.19(5)
N(1)–Cu(1)–O(1)
O(1)–Cu(1)–P(1)
96.48(6)
120.33(4)
N(1)–Cu(1)–P(1)
Complex 4
Cu(1)–C(18)
Cu(1)–O(1)
1.8946(19)
2.0799(15)
Cu(1)–N(1)
1.9296(16)
161.96(7)
N(1)–Cu(1)–O(1)
O(1)–Cu(1)–C(18)
93.16(7)
104.85(7)
N(1)–Cu(1)–C(18)

5426
S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
Fig. 1. The molecular diagram for complex 1. The thermal ellipsoids were
drawn at 50% probability and all hydrogen atoms were omitted for clarity.
Fig. 4. The molecular structure of complex 3. The thermal ellipsoids were
drawn at 30% probability. The toluene molecules and all hydrogen atom
were omitted for clarity.
Fig. 2. The molecular structure of complex 2. The thermal ellipsoids were
drawn at 30% probability. The toluene molecules and all hydrogen atom
were omitted for clarity.
Fig. 5. The molecular structure of complex 4. The thermal ellipsoids were
drawn at 30% probability. The toluene molecules and all hydrogen atom
were omitted for clarity.
3. Experimental
3.1. General procedure
All reactions were performed under a dry nitrogen
atmosphere using standard Schlenk techniques or in a
glove box. Toluene, heptane, diethyl ether, and tetrahydro-
furan were dried by refluxing over sodium benzophenone
ketyl. CH2Cl2 was dried over P2O5. NHC (N,N0-bis(2,6-
diisopropylphenyl)imidazol-2-ylidene) was synthesis by fol-
low the published procedure [16]. All solvents were distilled
Fig. 3. The core structure of complex 2 including four ketiminate
backbones, two lithium atoms, and two copper atoms. All the other
atoms were omitted for clarity.
˚
and stored in solvent reservoirs which contained 4 A
1
molecular sieves and were purged with nitrogen. H and
13C NMR spectra were recorded on a Bruker Avance 300
1
showed in Scheme 3. Further studies on the chemistry of
complexes 1 and 2 including oxidation of Cu(I) and de-clu-
sterification of Cu(II) complexes and the isolation of reac-
tion products of complexes 2–4 with oxygen atoms are in
progress.
spectrometer. Chemical shifts for H and 13C spectra were
recorded in ppm relative to the residual protons and 13C of
C6D6 (d 7.16, 128.0). Elemental analyses were performed
on a Heraeus CHN–OS Rapid Elemental Analyzer at the
Instrument Center, NCHU.

S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
5427
3.2. Synthesis of Cu[OC(Me)CHC(Me)N(Ar)]2 (1)
mmol), and PPh3 (2.90 g, 11.02 mmol) was cooled to 0 ꢁC
and THF (80 mL) was added. The solution was stirred at
room temperature for 12 h. Volatiles were removed under
vacuum and the residues were extracted with toluene and
filtered through Celite. The filtrate was vacuum dried and
solid was washed with heptane to yield 4.89 g of final prod-
uct (76%). 1H NMR (C6D6): 0.81 (d, 6H, CHMe2), 1.14 (d,
6H, CHMe2), 1.70 (s, 3H, CMe), 2.28 (s, 3H, CMe), 3.39
(m, 2H, CHMe2), 5.30 (s, 1H, CMeCHCMe), 6.95 (m,
10H, phenyl CH), 7.10 (m, 2H, phenyl CH), 7.32 (m, 6H,
phenyl CH). 13C NMR (C6D6 ): 22.9 (q, JCH = 134 Hz,
A 50 mL Schleck flask was charged with CuCl2 (0.50 g,
3.72 mmol) and Li[OC(Me)CHC(Me)N(Ar)] (1.97 g,
7.43 mmol) and cooled to 0 ꢁC. To the flask 30 mL of tol-
uene was added and the solution was stirred at room tem-
perature for 12 h. The solution was filtered through Celite
and the filtrate was concentrated to small volume, stored at
ꢀ20 ꢁC to generate 1.33 g (68% yield) of dark green black
crystals. Anal. Calc. for C34H48N2O2Cu: C, 70.37; H,
8.34; N, 4.83. Found: C, 69.89; H, 8.85; N, 4.87%.
CMe), 23.5 (q, JCH = 131 Hz, CHMe2), 28.2 (d, JCH
=
3.3. Synthesis of {Cu[OC(Me)CHC(Me)N(Ar)]-
Li[OC(Me)CHC(Me)N(Ar)]}2 (2)
128 Hz, CHMe2), 28.8 (q, JCH = 127 Hz, CMe), 96.7 (d,
JCH = 157 Hz, CMeCHCMe), 123.8 (d, JCH = 154 Hz,
phenyl CH), 124.1 (d, JCH = 158 Hz, phenyl CH), 128.8
(d, JCH = 159 Hz, phenyl CH), 128.9 (d, JCH = 159 Hz,
phenyl CH), 129.8 (d, JCH = 159 Hz, phenyl CH), 133.1
A 100 mL Schleck flask was charged with CuCl (0.25 g,
2.45 mmol) and Li[OC(Me)CHC(Me)N(Ar)] (1.30 g, 4.90
mmol) and cooled to 0 ꢁC. To the flask 80 mL of toluene
was added and the solution was stirred at room tempera-
ture for 12 h. The solution was filtered through Celite
and the filtrate was concentrated to small volume, stored
at ꢀ20 ꢁC to generate 0.76 g (53% yield) of dark pale yel-
(s, phenyl Cipso), 133.6 (s, phenyl Cipso), 133.9 (d, JCH
=
160 Hz, phenyl CH), 134.2 (d, JCH = 160 Hz, phenyl
CH), 140.3 (s, phenyl Cipso), 148.7 (s, phenyl Cipso), 167.7
(s, CN), 184.3 (s, CO). Anal. Calc. for C35H39CuNOP: C,
71.96; H, 6.73; N, 2.40. Found: C, 71.55; H, 6.29; N, 2.10%.
1
low crystals. H NMR (C6D6): d 1.17 (d, 6H, CHMe2),
1.26 (d, 6H, CHMe2), 1.28 (d, 6H, CHMe2), 1.30 (d, 6H,
CHMe2), 1.35 (d, 6H, CHMe2), 1.36 (d, 6H, CHMe2),
1.37 (d, 6H, CHMe2), 1.39 (d, 6H, CHMe2), 1.48 (s, 6H,
CMe), 1.52 (s, 6H, CMe), 1.64 (s, 6H, CMe), 1.85 (s, 6H,
CMe), 3.18 (m, 2H, CHMe2), 3.28 (m, 4H, CHMe2), 3.44
(m, 2H, CHMe2), 4.47 (s, 2H, MeCCHCMe), 4.90 (s, 2H,
MeCCHCMe), 7.10–7.26 (m, 12H, phenyl CH). 13C
NMR (C6D6): 22.2 (q, JCH = 126 Hz, CMe), 23.0 (q,
JCH = 128 Hz, CMe), 23.4 (q, JCH = 125 Hz, CHMe2),
23.6 (q, JCH = 125 Hz, CHMe2), 23.7 (q, JCH = 125 Hz,
CHMe2), 23.8 (q, JCH = 130 Hz, CHMe2), 24.4 (q,
JCH = 130 Hz, CHMe2), 24.5 (q, JCH = 130 Hz, CHMe2),
24.7 (q, JCH = 128 Hz, CHMe2), 25.7 (q, JCH = 126 Hz,
CHMe2), 27.8 (d, JCH = 128 Hz, CHMe2), 28.1 (d,
JCH = 126 Hz, CHMe2), 28.3 (d, JCH = 129 Hz, CHMe2),
28.4 (d, JCH = 125 Hz, CHMe2), 28.5 (q, JCH = 125 Hz,
3.5. Synthesis of Cu[OC(Me)CHC(Me)N(Ar)](NHC)
(4)
A 30 mL Schleck flask charged with 3 (0.133 g,
0.22 mmol) and NHC (0.089 g, 0.222 mmol) was cooled
to 0 ꢁC and THF (10 mL) was added. The solution was
stirred at room temperature for 12 h and solvent was
removed under vacuum. The solid was recrystallized from
a diethyl ether solution to yield the final product (0.041 g,
27.5%). 1H NMR (CDCl3): 0.75 (d, 6H, CHMe2), 1.05
(d, 12H, CHMe2), 1.07 (d, 6H, CHMe2), 1.20 (d, 12H,
CHMe2), 1.50 (s, 3H, CMe), 2.04 (s, 3H, CMe), 2.97 (m,
6H, CHMe2), 5.00 (s, 1H, CMeCHCMe), 6.40 (s, 2H,
NCHCHN), 7.00–7.22 (m, 9H, phenyl CH). 23.3 (q,
JCH = 130 Hz, CMe and CHMe2), 23.82 (q, JCH = 126 Hz,
CHMe2), 23.87 (q, JCH = 126 Hz, CHMe2), 25.2 (q,
JCH = 126 Hz, CHMe2), 28.1 (d, JCH = 130 Hz, CHMe2),
28.6 (d, JCH = 126 Hz, CHMe2), 28.8 (q, JCH = 129 Hz,
CMe), 95.2 (d, JCH = 153 Hz, CMeCHCMe), 122.6 (d,
JCH = 194 Hz, NCHCHN), 123.1 (d, JCH = 150 Hz, phe-
nyl CH), 123.3 (d, JCH = 158 Hz, phenyl CH), 124.1 (d,
JCH = 158 Hz, phenyl CH), 128.7 (s, phenyl Cipso), 128.8
(s, phenyl Cipso), 129.7 (d, JCH = 159 Hz, phenyl CH),
134.0 (d, JCH = 160 Hz, phenyl CH), 134.3 (d,
JCH = 160 Hz, phenyl CH), 136.9 (s, phenyl Cipso), 139.9
(s, phenyl Cipso), 146.3 (s, phenyl Cipso), 149.3 (s, phenyl
Cipso), 166.6 (s, CN), 183.1 (s, CO), 188.3 (s, NCN).
CMe), 29.8 (q, JCH = 126 Hz, CMe), 69.3 (d, JCH
=
146 Hz, MeCCHCMe), 96.4 (d, JCH = 154 Hz, MeCCH-
CMe), 123.1 (d, JCH = 155 Hz, phenyl-CH), 123.2 (d,
JCH = 155 Hz, phenyl-CH), 123.6 (d, JCH = 155 Hz, phe-
nyl-CH), 123.7 (d, JCH = 155 Hz, phenyl-CH), 124.4 (d,
JCH = 155 Hz, phenyl-CH), 124.8 (d, JCH = 155 Hz, phe-
nyl-CH), 128.3 (s, phenyl Cipso), 128.8 (s, phenyl Cipso),
139.4 (s, phenyl Cipso), 140.0 (s, phenyl Cipso), 146.3 (s, phe-
nyl Cipso), 147.3 (s, phenyl Cipso), 168.9 (s,CN), 169.1
(s,CN), 181.6 (s,CO), 189.1 (s,CO). Anal. Calc. for
C68H96N4O4Cu2Li2: C, 69.54; H, 8.24; N, 4.77. Found:
C, 69.00; H, 8.70; N, 4.72%.
3.6. Reactivity studies of complexes 2, 3, and 4 with oxygen
molecules
3.4. Synthesis of Cu[OC(Me)CHC(Me)N(Ar)](PPh3)
(3)
Complexes 2–4 were dissolved in C6D6 in J-Young
NMR tubes and then the tubes were immersed in a liquid
nitrogen dewer to freeze the solutions. Vacuum was applied
A 100 mL Schleck flask charged with CuCl (1.10 g,
11.02 mmol), Li[OC(Me)CHC(Me)N(Ar)] (2.90 g, 11.02

5428
S.-H. Hsu et al. / Journal of Organometallic Chemistry 692 (2007) 5421–5428
(f) M. Cheng, A.B. Attygalle, E.B. Lobkovsky, G.W. Coates, J. Am.
Chem. Soc. 121 (1999) 11583–11584;
to the NMR tubes to remove the inert gas and then oxygen
gas was introduced into the NMR tubes. The pressure of
oxygen is no larger than 15 psi. H NMR spectrometer
(g) T.R. Younkin, E.F. Connor, J.I. Henderson, S.K. Friedrich,
R.H. Grubbs, D.A. Bansleben, Science 287 (2000) 460–462.
[4] (a) P.-C. Kuo, I.-C. Chen, J.-C. Chang, M.-T. Lee, C.-H. Hu, C.-H.
Hung, H.M. Lee, J.-H. Huang, Eur. J. Inorg. Chem. (2004) 4898–
4906;
1
was used to monitor the reactions.
3.7. X-ray structure determination
(b) R.-C. Yu, C.-H. Hung, J.-H. Huang, H.-Y. Lee, J.-T. Chen,
Inorg. Chem. 41 (2002) 6450–6455.
Crystal data collection, refinement parameter, and bond
lengths and angles were listed in Tables 1 and 2, respec-
tively. The crystals were mounted on a goniostat and were
collected at 150 K under liquid nitrogen stream. Data were
collected on a Bruker SMART CCD diffractometer with
graphite-monochromated Mo Ka radiation. Structural
determinations were made using the SHELXTL package of
programs. All refinements were carried out by full-matrix
least squares using anisotropic displacement parameters
for all non-hydrogen atoms. All the hydrogen atoms are
calculated.
[5] S.-H. Hsu, J.-C. Chang, C.-L. Lai, C.-H. Hu, H.M. Lee, G.-H. Lee,
S.-M. Peng, J.-H. Huang, Inorg. Chem. 43 (2004) 6786–6792.
[6] (a) N.W. Aboelella, S.V. Kryatov, B.F. Gherman, W.W. Brennessel,
V.G. Young, R. Sarangi, E.V. Rybak-Akimova, K.O. Hodgson, B.
Hedman, E.I. Solomon, C.J. Cramer, W.B. Tolman, J. Am. Chem.
Soc. 126 (2004) 16896–16911;
(b) N.W. Aboelella, E.A. Lewis, A.M. Reynolds, W.W. Brennessel,
C.J. Cramer, W.B. Tolman, J. Am. Chem. Soc. 124 (2002) 10660–
10661;
(c) D.J.E. Spencer, N.W. Aboelella, A.M. Reynolds, P.L. Holland,
W.B. Tolman, J. Am. Chem. Soc. 124 (2002) 2108–2109.
[7] (a) X. Dai, T.H. Warren, J. Am. Chem. Soc. 126 (2004) 10085–10094;
(b) D.S. Laitar, C.J.N. Mathison, W.M. Davis, J.P. Sadighi, Inorg.
Chem. 42 (2003) 7354–7356;
4. Supplementary material
(c) S. Yokota, Y. Tachi, S. Itoh, Inorg. Chem. 41 (2002) 1342–
1344;
(d) X. Dai, T.H. Warren, Chem. Commun. (2001) 1998–1999.
[8] R.M. Silverstein, F.X. Webster, Spectrometric Identification of
Organic Compounds, sixth ed. (Chapter 5).
[9] (a) L. Jafarpour, E.D. Stevens, S.P. Nolan, J. Organomet. Chem. 606
(2000) 49–54;
(b) J. Huang, H.-J. Schanz, E.D. Stevens, S.P. Nolan, Organomet-
allics 18 (1999) 2370–2375.
[10] D.V. Baxter, K.G. Caulton, W.-C. Chiang, M.H. Chisholm, V.F.
DiStasi, S.G. Dutremez, K. Folting, Polyhedron 20 (2001) 2589–
2595.
CCDC 638784, 638785, 638786 and 638787 contain the
supplementary crystallographic data for 1, 2, 3 and 4.
These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
[11] (a) G. van Koten, J.T.B.H. Jastrzebski, F. Muller, C.H. Stam, J. Am.
Chem. Soc. 107 (1985) 697–698;
(b) M.M. Olmstead, P.P. Power, J. Am. Chem. Soc. 111 (1989) 4135–
4136;
(c) H. Hope, D. Oram, P.P. Power, J. Am. Chem. Soc. 106 (1984)
1149–1150;
(d) S.I. Khan, P.G. Edwards, H.S.H. Yuan, R. Bau, J. Am. Chem.
Soc. 107 (1985) 1682–1684.
We thank the National Science Council of Taiwan for
financial support and the National Changhua University
of Education for supporting the NMR and X-ray
spectrometers.
[12] M.M. Olmstead, P.P. Power, Organometallics 9 (1990) 1720–1722.
[13] (a) N.A. Eckert, A. Dinescu, T.R. Cundari, P.L. Holland, Inorg.
Chem. 44 (2005) 7702–7704;
References
[1] (a) L. Bourget-Merle, M.F. Lappert, J.R. Severn, Chem. Rev. 102
(2002) 3031–3066;
(b) P.L. Holland, W.B. Tolman, J. Am. Chem. Soc. 121 (1999) 7270–
7271;
(b) N.J. Hardman, A.D. Phillips, P.P. Power, ACS Symp. Ser. 822
(2002) 2–15;
(c) C.-M. Che, J.-S. Huang, Coord. Chem. Rev. 242 (2003) 97–113;
(d) V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283–316.
[2] (a) P.L. Franceschini, M. Morstein, H. Berke, H.W. Schmalle, Inorg.
Chem. 42 (2003) 7273–7282;
(c) D.W. Randall, S. Debeer George, P.L. Holland, B. Hedman,
K.O. Hodgson, W.B. Tolman, E.I. Soloman, J. Am. Chem. Soc. 122
(2000) 11632–11648.
[14] (a) Q.T. Anderson, E. Erkizia, R.R. Conry, Organometallics 17
(1998) 4917–4920;
(b) F.A. Cotton, J. Takats, J. Am. Chem. Soc. 92 (1970) 2353–
2358;
(c) T.P. Hanusa, T.A. Ulibarri, W.J. Evans, Acta Crystallogr., Sect.
C 41 (1985) 1036–1038;
(d) D.J. Darensbourg, D.L. Larkins, J.H. Reibenspies, Inorg. Chem.
37 (1998) 6125–6128.
(b) J. Chai, H. Zhu, H.W. Roesky, C. He, H.-G. Schmidt, M.
Noltemeyer, Organometallics 23 (2004) 3284–3289;
(c) R.J. Wright, P.P. Power, B.L. Scott, J.L. Kiplinger, Organomet-
allics 23 (2004) 4801–4803.
[3] (a) M. Stender, B.E. Eichler, N.J. Hardman, P.P. Power, J. Prust,
M. oltemeyer, H.W. Roesky, Inorg. Chem. 40 (2001) 2794–2799;
(b) C.E. Radzewich, I.A. Guzei, R.F. Jordan, J. Am. Chem. Soc. 121
(1999) 8673–8674;
[15] (a) D.S. Laitar, E.Y. Tsui, J.P. Sadighi, Organometallics 25 (2006)
2405–2408;
(b) N.P. Mankad, D.S. Laitar, J.P. Sadighi, Organometallics 23
(2004) 3369–3371;
(c) H. Kaur, F.K. Zinn, E.D. Stevens, S.P. Nolan, Organometallics
23 (2004) 1157–1160;
(c) C.E. Radzewich, M.P. Coles, R.F. Jordan, J. Am. Chem. Soc. 120
(1998) 9384–9385;
(d) C. Cui, H.W. Roesky, H. Hao, H.-G. Schmidt, M. Noltemeyer,
Angew. Chem., Int. Ed. 39 (2000) 1815–1817;
(d) D.S. Laitar, P. Muller, J.P. Sadighi, J. Am. Chem. Soc. 127 (2005)
¨
(e) V.C. Gibson, P.J. Maddox, C. Newton, C. Redshaw, G.A. Solan,
A.J.P. White, D.J. Williams, Chem. Commun. (1998) 1651–1652;
17196–17197.
[16] J. Huang, S.P. Nolan, J. Am. Chem. Soc. 121 (1999) 9889–9890.