Syntheses and crystal structures of copper(II) and copper(I) dpp complexes, [Cu(dpp)Br2] and [Cu(dpp)2][CuBr2] (dpp = 2,9-diphenyl-1,10-phenanthroline)

Article abstract of DOI:10.1002/zaac.200500462

The complexes [Cu(dpp)Br₂] (1) and [Cu(dpp)₂] [CuBr₂] (2) (dpp = 2,9-diphenyl-1,10-phenanthroline) were synthesized and characterized by single-crystal X-ray diffraction methods. Reaction of copper(II) bromide with the dpp ligand in dichloromethane at room temperature afforded 1, which is a rare example of non-square planar four-coordinate copper(II) complexes. Complex 1 crystallizes in the monoclinic space group C2/c with a = 15.352(3), b = 13.192(3), c = 11.358(2) A, β= 120.61(3)°, V= 1979.6(7) A³, Z = 4, D_calc = 1.865 g cm^-3. The coordination geometry about the copper center is distorted about halfway between square planar and tetrahedral. The Cu-N distance is 2.032(2) Aand the Cu-Br distance 2.3521(5) A. Heating a CH ₂Cl₂ or acetone solution of 1 resulted in complex 2, which consists of a slightly distorted tetrahedral [Cu(dpp)₂]⁺ cation and a linear two-coordinate [CuBr₂]^- anion. 2 crystallizes in the triclinic space group P1 with a = 10.445(2), b = 11.009(2), c = 18.458(4) A, a = 104.72(3), β= 94.71(3), γ= 103.50(3)°, V = 1973.3(7) A³, Z = 2, D_calc = 1.602 g cm^-3. The four Cu(I)-N distances are between 2.042(3) and 2.067(3) A, the distance of Cu(2)-Br(1) 2.2268(8) A, and the disordered Cu(3)-Br(2) distances are 2.139(7) and 2.237(4) A, respectively. Complex 2 could also be prepared by directly reacting CuBr with dpp in CH₂Cl₂.

Full text of DOI:10.1002/zaac.200500462

DOI: 10.1002/zaac.200500462
Syntheses and Crystal Structures of Copper(II) and Copper(I) dpp Complexes,
[Cu(dpp)Br2] and [Cu(dpp)2][CuBr2] (dpp ؍ 2,9-diphenyl-1,10-phenanthroline)
Biao Wu*, Peiju Yang, Xiaojuan Huang, Yanyan Liu, Xiaofei Liu, and Chungu Xia
Lanzhou/P. R. China, State Key Laboratory for Oxo Synthesis & Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese
Academy of Sciences
Received November 24th, 2005.
Abstract. The complexes [Cu(dpp)Br2] (1) and [Cu(dpp)2][CuBr2]
(2) (dpp ϭ 2,9-diphenyl-1,10-phenanthroline) were synthesized and
characterized by single-crystal X-ray diffraction methods. Reaction
of copper(II) bromide with the dpp ligand in dichloromethane at
room temperature afforded 1, which is a rare example of non-
square planar four-coordinate copper(II) complexes. Complex 1
hedral [Cu(dpp)2]ϩ cation and a linear two-coordinate [CuBr2]Ϫ
¯
anion. 2 crystallizes in the triclinic space group P1 with a ϭ
˚
10.445(2), b ϭ 11.009(2), c ϭ 18.458(4) A, Ͱ ϭ 104.72(3), β ϭ
3
˚
94.71(3), γ ϭ 103.50(3)°, V ϭ 1973.3(7) A , Z ϭ 2, Dcalc ϭ 1.602 g
cmϪ3. The four Cu(1)-N distances are between 2.042(3) and
˚
˚
2.067(3) A, the distance of Cu(2)-Br(1) 2.2268(8) A, and the disor-
˚
crystallizes in the monoclinic space group C2/c with a ϭ 15.352(3),
dered Cu(3)-Br(2) distances are 2.139(7) and 2.237(4) A, respec-
3
˚
˚
b ϭ 13.192(3), c ϭ 11.358(2) A, β ϭ 120.61(3)°, V ϭ 1979.6(7) A ,
Z ϭ 4, Dcalc ϭ 1.865 g cmϪ3. The coordination geometry about the
copper center is distorted about halfway between square planar
tively. Complex 2 could also be prepared by directly reacting CuBr
with dpp in CH2Cl2.
˚
and tetrahedral. The Cu-N distance is 2.032(2) A and the Cu-Br
distance 2.3521(5) A. Heating a CH2Cl2 or acetone solution of 1
˚
Keywords: Copper; Crystal structure; 2,9-Diphenyl-1,10-phen-
resulted in complex 2, which consists of a slightly distorted tetra-
anthroline (dpp)
Introduction
The monovalent CuI ion has d10 electron configuration
and is generally four-coordinate with a nearly tetrahedral
geometry, while the d9-CuII ion usually adopts a five- or
six-coordinate, Jahn-Teller distorted geometry with diimine
ligands. Several synthetic approaches to four-coordinate
CuII phenanthroline compounds have been employed, in-
cluding the utilization of phenanthroline ligands with sub-
stituents in the 2- and 9-positions that can inhibit further
coordination. However, only few such complexes have been
reported so far; the first example has been the copper(II)
complex of 2,9-diphenyl-1,10-phenanthroline (dpp),
[Cu(dpp)2](ClO4)2, where the metal and ligand have a 1:2
ratio [18].
1,10-Phenanthroline and its derivatives have been exten-
sively used to form different composited complexes of tran-
sition metal ions (Mnϩ) in various oxidation states [1, 2].
Copper complexes of phenanthroline ligands having aryl
substituents in the 2- and 9-positions are of recent interest
for their long-lived excited states at room temperature
[3Ϫ10] and their potential application in selective func-
tionalization of carbon-hydrogen bonds [11]. These steri-
cally demanding ligands are also capable of providing a
highly protected, rigid coordination environment for metal
ions. A series of catenates, supramolecular complexes of
CuI with 2,9-disubstituted phenanthroline ligands, have
been synthesized by Sauvage and co-workers [12]. Not only
are these interlocked systems topologically novel, but they
also have a variety of interesting photochemical properties
and exhibit reasonably intense metal-to-ligand charge-
transfer (MLCT) bands in the visible region [13Ϫ17].
Recently we have succeeded in the isolation of a phen-
anthroline copper(II) complex, Cu(dpp)Br2 (1), which rep-
resents a very rare example of four-coordinate CuII com-
pounds with a 1:1 metal to phenanthroline ligand ratio and
the coordination sphere completed by two bromide anions.
To the best of our knowledge, the only other known com-
pound of this type is CuL1Br2 (L1 ϭ 2,9-bis(2,6-dimeth-
oxyphenyl)-1,10-phenanthroline) [2]. Unexpectedly, com-
plex 1 could readily undergo ligand redistribution, ac-
companied by the reduction of the CuII to CuI, when it is
heated in CH2Cl2 or acetone, to form [Cu(dpp)2][CuBr2]
(2). The CuI species 2 contains a 1:2 coordination cation
* Prof. Dr. B. Wu
Lanzhou Institute of Chemical Physics
Chinese Academy of Sciences
Lanzhou 730000
P. R. China
Tel./Fax: ϩϩ 86 931 4968286
E-mail: wubiao@lzb.ac.cn
Ϫ
and an interesting CuBr2 counter ion. Structurally anal-
ogous compounds of
2
include [Cu(dpp)2][CuCl2]·
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Z. Anorg. Allg. Chem. 2006, 632, 684Ϫ688

Syntheses and Crystal Structures of Copper(II) and Copper(I) dpp Complexes
2/3CH3CN [19] and [Cu(phen)2][CuBr2] (phen ϭ phen-
anthroline) [20]. Herein we report the syntheses and molec-
ular structures of 1 and 2.
Table 1 Crystallographic data and refinement details for com-
pounds 1 and 2
Compound
1
2
Empirical formula
M/g molϪ1
Crystal size/mm
Crystal description
Crystal color
T/K
Diffractometer
Scan type, θ range/°
h; k; l range
C24H16Br2CuN2
555.74
0.33 x 0.21 x 0.18
block
black
293(2)
Rigaku Raxis Rapid IP Rigaku Raxis Rapid IP
Oscillation, 2.18-27.47 Oscillation, 1.15-27.38
0, 19; 0, 17; Ϫ14, 12
monoclinic
C2/c
15.352(3)
13.192(3)
11.358(2)
90
120.61(3)
90
1979.6(7)
4
1.865
1092
5.154
0.6882/1.2845
11068
2262 [Rint ϭ 0.0438]
1860
C48H32Br2Cu2N4
951.68
0.21 x 0.18 x 0.17
block
red
293(2)
Experimental Part
Anhydrous CuBr2 and CuBr were commercially available and were
used without further purification. Solvents (diethyl ether and di-
chloromethane) were treated according to conventional methods.
The ligand 2,9-diphenyl-1,10-phenanthroline (dpp) was synthesized
as previously reported [21]. Elemental analyses were performed by
an Elementar VarioEL instrument. IR spectra were recorded on a
Bruker IFS 120HR spectrometer.
0, 13; Ϫ14, 13; Ϫ23, 23
Crystal system
Space group
triclinic
¯
P1
˚
a/A
10.445(2)
11.009(2)
18.458(4)
104.72(3)
94.71(3)
103.50(3)
1973.3(7)
2
1.602
952
3.143
0.8126/1.2803
21504
8779 [Rint ϭ 0.0420]
5423
512
0.0559; 0.1099
0.1061; 0.1304
1.054
˚
b/A
˚
c/A
Synthesis of Dibromo(2,9-diphenyl-1,10-phenanroline)-
copper(II) (1)
Ͱ/°
β/°
γ/°
3
˚
V/A
The ligand dpp (100 mg, 0.30 mmol) and anhydrous CuBr2 (67 mg,
0.30 mmol) were stirred in dichloromethane (50 mL) at room tem-
perature to form a brown solution. After filtration, the solution
was allowed to slowly evaporate to afford complex 1 as black crys-
tals (crystal yield 92 mg, 55 %). M.p. 220 °C. IR (KBr, ν/cmϪ1):
3046, 1620, 1586, 1549, 1506, 1487, 1358, 1156, 1021, 869, 851, 776,
741, 703, 658, 556. C24H16Br2CuN2 (555.74): calculated C 51.87, H
2.90, N 5.04; found C 51.98, H 3.00, N 4.99 %.
Z
Dcalc/g cmϪ3
F (000)
µ/mmϪ1
min/max transmission
Measured reflections
Unique reflections
Obs. refl. [I > 2σ(I)]
Parameters refined
133
[a]
R1;wR2 [I > 2σ(I)]
0.0302; 0.0775
0.0394; 0.0809
[a]
R1;wR2 (all refl.)
Goodness-of-fit on F2 [b] 1.041
Synthesis of [Bis(2,9-diphenyl-1,10-phenanroline)-
copper(I)]-dibromocuprate, (2)
Extinction coefficient
0.0034(3)
none
[a] R1 ϭ [Σ(ʈFoΗ - ΗFcʈ)/ΣΗFoΗ], wR2 ϭ [Σ[w(Fo - Fc2)2]/Σ[w(Fo2)2]]1/2
.
2
[b] Goodness-of-fit ϭ [Σ[w(Fo - Fc2)2]/(n-p)]1/2
2
Dpp (100 mg, 0.30 mmol) and anhydrous CuBr (43 mg, 0.30 mmol)
were refluxed in dichloromethane (50 mL) for 2 h, followed by fil-
tering of the reaction mixture. The product was obtained as an
orange powder by adding diethyl ether to the CH2Cl2 solution.
Yield 135 mg (94 %). X-ray quality red crystals were grown through
vapor diffusion of diethyl ether into a concentrated solution of the
product in dichloromethane. M.p. 238 °C. IR (KBr, ν/cmϪ1): 3052,
1623, 1584, 1504, 1486, 1355, 1149, 1022, 859, 842, 776, 741, 700,
601. C48H32Br2Cu2N4 (951.69): calculated C 60.58, H 3.39, N 5.89;
found C 60.41, H 3.47, N 5.87 %. Alternatively, complex 2 could
also be prepared by heating a CH2Cl2 solution of 1 to reflux for
about 1 h.
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Centre,
CCDC No. 283612 for 1 & No. 283613 for 2. Copies of this
information may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax:
ϩ44-1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
Results and Discussion
Syntheses
X-ray structure determination
As illustrated in Scheme 1, complex 1 was prepared by the
reaction of anhydrous copper(II) bromide with the dpp li-
gand in dichloromethane at room temperature. Elemental
analysis and X-ray structural study confirmed the forma-
tion of the Cu(dpp)Br2 product, which is stable in solid
state or CH2Cl2 solution at room temperature without any
change after several days. However, 1 can be easily con-
verted into complex 2, [Cu(dpp)2][CuBr2], by heating the
CH2Cl2 or acetone solution. Initially, this conversion took
place in carefully dried solvent under nitrogen; when the
heating procedure was performed in air, the same phenom-
enon was observed. Although the detailed mechanism of
this transformation is not yet clear, it seemed that the cop-
per(I) species with two dpp ligands (complex 2) is thermo-
dynamically more stable than the copper(II) compound
Diffraction data for both complexes were collected on a Rigaku
RAXIS-RAPID IP diffractometer at room temperature (293 K)
with graphite-monochromated Mo Kα radiation (λ ϭ 0.71073 A)
˚
using oscillation scan method. An empirical absorption correction
using SADABS [22] was applied for the data. Both structures were
solved by direct methods. All non-hydrogen atoms were refined an-
isotropically by full-matrix least-squares on F2 by the use of the
program SHELXL-97 structure solution package [23]. Hydrogen
atoms were placed in calculated positions according to idealized
geometries with C-H ϭ 0.93 and U(H) ϭ 1.2 Ueq(C). In complex
2, the bromine atom on one of the half dibromocupric anions is
disordered. By assignment of reasonable anisotropic thermal par-
ameters to the bromine atoms, the site occupation factors for the
atoms were refined and the model was finally adopted in an ap-
proximately 50:50 occupation ratio. Table 1 lists the crystallo-
graphic details for 1 and 2.
Z. Anorg. Allg. Chem. 2006, 684Ϫ688
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
zaac.wiley-vch.de
685

B. Wu, P. Yang, X. Huang, Y. Liu, X. Liu, C. Xia
Scheme 1
which contains only one dpp ligand (complex 1). 2 could
also be prepared in almost quantitative yield by directly re-
acting copper(I) bromide with dpp in refluxing dichloro-
methane (Scheme 1). The coordination of two dpp ligands
to the Cu(I) center in the complex cation [Cu(dpp)2]ϩ, to-
gether with the incorporation of a [CuBr2]Ϫ anion in the
compound, was supported by analysis results. 2 is quite
stable both in solid state and in solution.
X-ray structural analyses
Single crystals suitable for X-ray studies were obtained from
CH2Cl2 (complex 1) or by diffusion of Et2O to CH2Cl2
solution (complex 2). ORTEP [24] presentations of the mo-
lecular structures of 1 and 2 are depicted in Figs. 1 and 2,
respectively, while the selected bond lengths and bond
angles are given in Table 2.
The structural analysis of complex 1 shows that the
asymmetric unit contains half Cu(dpp)Br2 molecule with
the formula of C12H8BrCu0.5N. The copper atom is coordi-
nated by the two nitrogen donors of the dpp ligand and two
bromine atoms (Fig. 1a). The coordination environment of
the CuII ion can be described as flattened tetrahedral with
the dihedral angle of the N-Cu-N and Br-Cu-Br planes be-
ing 59.2° (about halfway between tetrahedral and square-
planar) (see Fig. 1b). Such flattening has also been reported
for bis(2,9-diphenyl-1,10-phenanthrolinato)copper(II) di-
perchlorate [18]. The molecule has a two-fold axis bisecting
the N-Cu-N and Br-Cu-Br angles. The intermolecular sep-
aration of copper with the bromine atom of the closest mol-
Fig. 1 Molecular structure of complex 1: (a) side view; (b) view
along b axis showing the flattened-tetrahedral geometry about Cu
atom. Thermal ellipsoids are shown at the 30 % possibility level.
Hydrogen atoms are omitted for clarity.
system with two ortho methoxy groups on each phenyl ring
˚
ecule is 4.433 A, ruling out the possibility of any interac-
is present [2].
tion. Therefore the CuII atom in 1 is definitely four-coordi-
nate. As mentioned above, non-square planar, four-coordi-
nate copper(II) complexes are uncommon. Among the
few structurally available examples, the compound
[Cu(dpp)2](ClO4)2 [18] has two dpp ligands that provide
sufficient steric shielding of the copper center to prevent
coordination of solvent or counterions. Although another
four-coordinate compound [Cu(phen)2](PF6)2 has also been
reported, the coordination sphere of the CuII atom may be
The Cu-N bond distance (2.032(2) A) in 1 is similar to
˚
those in the other CuII-phen compounds, e.g., Cu-N of
2.05 A in CuL Br2 (L1 ϭ 2,9-bis(2,6-dimethoxyphenyl)-
1
˚
˚
1,10-phenanthroline) [2], and 1.980(4)-1.997(4) A in
[Cu(dpp)2](ClO4)2 [18]. The Cu-Br distance in
1
˚
(2.3521(5) A), however, is significantly longer than that in
1
˚
the CuL Br2 compound (2.01 A), implying that the Cu-Br
coordinate bond is somewhat weakened; consequently, the
complex 1 could be readily converted to complex 2 at elev-
ated temperature. The N-Cu-N bond angle in 1 (82.43(12)°)
falls in the range of normal values for chelate copper phen-
anthroline complexes. In this structure, there is an intermo-
lecular π-stacking between two parallel C5N heterocycles
(dihedral angle 0.00°) of the phenanthroline moieties on ad-
jacent molecules with centroid-centroid separation of
˚
enhanced by a secondary interaction of Cu-F (2.75 A) [25].
It is significant that in complex 1 described here, the CuII
atom is surrounded by only one dpp ligand (and two bro-
mide ions) and yet the structure can be stabilized. In the
analogous 1:1 complex, CuL1Br2 (L1 ϭ 2,9-bis(2,6-dimeth-
oxyphenyl)-1,10-phenanthroline), however, bulkier ligand
686
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Z. Anorg. Allg. Chem. 2006, 684Ϫ688

Syntheses and Crystal Structures of Copper(II) and Copper(I) dpp Complexes
(2,9-dimethyl-1,10-phenanthroline-N,NЈ)-copper(I))
[27],
was not observed, possibly due to the bulkier phenyl sub-
stituents on dpp ligand.
The complex cation contains a copper(I) atom coordi-
nated by two dpp ligands in a slightly distorted tetrahedral
arrangement. The dihedral angle between the N(1)-Cu(1)-
N(2) and N(3)-Cu(1)-N(4) planes is 84.3° (Fig. 2). The Cu-
˚
N bond lengths (2.054 A, average) are similar to those in
the copper(I) phenanthroline complexes and are not further
discussed. For the CuN4 core, the intraligand N-Cu-N
angles are 82.24(14) and 82.67(13)°, respectively, while the
interligand N-Cu-N angles range 106.47(13)Ϫ138.20(14)°
(Table 2). These values are also similar to those in most of
the copper(I) phenanthroline complexes. The dihedral
angles between the phenanthroline systems and the phenyl
groups are 48.2, 80.7, 57.4 and 44.5°, respectively. It is note-
worthy that one phenyl group is almost perpendicular
(80.7°) to the phenanthroline plane to which it is attached,
permitting significant intramolecular π-stacking interaction
of this phenyl substituent with the central phenyl moiety
of the other dpp ligand. The centroid-centroid distance is
Fig. 2 Molecular structure of complex 2. Thermal ellipsoids are
shown at the 30 % possibility level. Two halves of [CuBr2]Ϫ anions
are shown. Hydrogen atoms are omitted for clarity.
˚
3.792 A, the vertical displacement between the stacking ring
˚
˚
Table 2 Selected bond lengths/A and bond angles/° for 1 and 2
centroids 1.546 A, and the dihedral angle is 0.0°. Similar
phenomenon has also been observed in [Cu(dpp)2](PF6)
[18]. Another interligand π-stacking interaction in 2 be-
tween phenyl group and phenanthroline central ring is
Complex 1
a
Cu-N
Cu-Br
N-Cu-N(A)
2.032(2)
2.3521(5)
82.43(12)
Br-Cu-Br(A)
N-Cu-Br(A)
N-Cu-Br
104.63(3)
101.13(6)
136.60(6)
a
˚
much weaker, with a centroid-centroid distance of 4.094 A,
a
˚
vertical displacement of 1.723 A and a dihedral angle of
25.8°.
Complex 2
One of the two halves CuBr2Ϫ counterions is slightly dis-
ordered while the other is not. Since the anions reside on a
2-fold axis, they are linear in geometry. In contrast, the
Cu(1)-N(1)
Cu(1)-N(2)
Cu(1)-N(3)
Cu(1)-N(4)
N(1)-Cu(1)-N(2)
N(4)-Cu(1)-N(1)
N(4)-Cu(1)-N(3)
N(1)-Cu(1)-N(3)
N(4)-Cu(1)-N(2)
2.042(3)
2.067(3)
2.066(3)
2.042(3)
82.24(14)
138.20(14)
82.67(13)
126.13(13)
121.58(13)
Br(1)-Cu(2)
Br(2)-Cu(3)
Br(2Ј)- Cu(3)
2.2268(8)
2.139(7)
2.237(4)
Ϫ
CuCl2 anion in [Cu(dpp)2][CuCl2] [19] is found to be
N(3)-Cu(1)-N(2)
Br(1)-Cu(2)-Br(1)
Br(2)-Cu(3)-Br(2)
Br(2)-Cu(3)-Br(2Ј)
Br(2Ј)-Cu(3)-Br(2Ј)
106.47(13)
180.00(3)
180.000(1)
12.5(2)
slightly bent with a Cl-Cu-Cl angle of 177.3(2)°. The bond
b
c
˚
distance of the non-disordered Cu(2)-Br(1) is 2.2268(8) A,
and those for the disordered Cu(3)-Br(2) are 2.237(4) and
c
180.00(13)
˚
2.139(7) A, respectively, which are compared to those in
˚
Symmetrical codes: a 1.5ϩx, 0.5ϩy, z; b Ϫx, Ϫy, Ϫz; c Ϫx, Ϫy, 1Ϫz.
[Cu(phen)2][CuBr2] (2.223(2) and 2.209(2) A) [20].
˚
˚
3.945 A and vertical displacement between ring centroids of
Conclusions
2.279 A [26]. The dihedral angle between the 1,10-phen-
anthroline moiety and the phenyl substituent encloses 46.5°.
In the ionic complex 2, [Cu(dpp)2][CuBr2], the asymmet-
ric unit consists of one bis(2,9-diphenylphenanthroline)-
cupric cation and two halves of the dibromocopper(I)
anions, which reside on a crystallographic 2-fold axis. The
crystallization of 2 is somewhat surprising. It appeared that
the single bromide ion did not match the [Cu(dpp)2]ϩ cat-
ion; instead, the ligand-dismutated CuBr2Ϫwas incorpor-
ated as the counterion. This novel anion system and its con-
gener CuCl2Ϫ have also been found as counterions for other
CuI phenanthroline complexes, e.g., [Cu(dpp)2][CuCl2] [19]
and [Cu(phen)2][CuBr2] [20]. On the other hand, com-
Copper(II) and copper(I) complexes of dpp (2,9-diphenyl-
1,10-phenanthroline) are
reported.
The
complex
[Cu(dpp)Br2] (1) could be prepared by the reaction of
CuBr2 with one equivalent of dpp ligand at room tempera-
ture. As mentioned in the Introduction, this compound rep-
resents a very rarely seen example of non-square planar,
four-coordinate copper(II) phenanthroline complexes.
Compared to the 1:2 compound [Cu(dpp)2](ClO4)2 [18],
where the four phenyl groups provide sufficient shielding
for the copper center, 1 has only one dpp ligand with two
phenyl substituents, indicating much less protection for the
CuII ion. This may attribute to the fact that 1 is thermo-
dynamically unstable at higher temperature and undergoes
ligand redistribution accompanied by reduction of the CuII
ion to afford [CuI(dpp)2][CuIBr2] (2). Complex 2 could also
be obtained by the reaction of CuBr with dpp. The cation
Ϫ
Ϫ
pounds with larger counterions such as PF6 and ClO4
,
[Cu(dpp)2](PF6) [18] and [Cu(phen)2](ClO4) [20], are
known. Furthermore, the formation of a dibromo-bridged
dimer, “(dpp)CuI(µ2-Br)2CuI(dpp)”, as in bis((µ-bromo)-
Z. Anorg. Allg. Chem. 2006, 684Ϫ688
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zaac.wiley-vch.de
687

B. Wu, P. Yang, X. Huang, Y. Liu, X. Liu, C. Xia
in 2 is typical for CuI phenanthroline compounds with a
tetrahedral geometry and interligand π-stacking interac-
tions between the phenyl rings and the phenanthroline moi-
eties. Further investigation on the detailed mechanism for
the transformation of 1 to 2 is in progress.
[13] F. Ibukuro, M. Fujita, K. Yamaguchi, J.-P. Sauvage, J. Am.
Chem. Soc. 1999, 121, 11014.
[14] J.-M. Kern, J.-P. Sauvage, J.-L. Weidmann, N. Armaroli, L.
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Acknowledgement. This work is supported by the ‘One Hundred
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