Copper(I) and silver(I) complexes containing the enantiopure N,N-bidentate 1,3-bis[4′-(S)-isopropyloxazolin-2′-yl]benzene ((S,S)-iPr-pheboxH) ligand

Article abstract of DOI:10.1016/j.poly.2015.04.014

Abstract The reaction of CuX (X = I, Br, Cl) with (S,S)-ⁱPr-pheboxH = 1,3-bis[4′-(S)-isopropyloxazolin-2′-yl]benzene in 2:1 molar ratio allows us to synthesize tetranuclear complexes [Cu₄X₄(k²-N,N-ⁱPr

Full text of DOI:10.1016/j.poly.2015.04.014

Polyhedron 94 (2015) 59–66
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Copper(I) and silver(I) complexes containing the enantiopure
0
0
N,N-bidentate 1,3-bis[4 -(S)-isopropyloxazolin-2 -yl]benzene
(
i
(S,S)- Pr-pheboxH) ligand
⇑
Esmeralda Vega, Eire de Julián, Gustavo Borrajo, Josefina Díez, Elena Lastra, M. Pilar Gamasa
Departamento de Química Orgánica e Inorgánica, Instituto de Química Organometálica ‘‘Enrique Moles’’ (Unidad Asociada al CSIC), Universidad de Oviedo, 33006 Oviedo, Spain
a r t i c l e i n f o
a b s t r a c t
i
0
0
Article history:
The reaction of CuX (X = I, Br, Cl) with (S,S)- Pr-pheboxH = 1,3-bis[4 -(S)-isopropyloxazolin-2 -yl]benzene
Received 5 February 2015
Accepted 11 April 2015
Available online 18 April 2015
2
i
in 2:1 molar ratio allows us to synthesize tetranuclear complexes [Cu
X
4 4
(r -N,N- Pr-pheboxH)
] (4) has been prepared by reaction
2
] (X = Cl
2
i
(
1), Br (2), I (3)). The polymeric species [Cu
4
I
4
(j
-N,N- Pr-pheboxH)
2 n
i
2
of CuI with (S,S)- Pr-pheboxH in 1.5:1 molar ratio. Also, polymeric silver species {[Ag(
j
-N,
(7c)) have been synthesized by reaction of the
corresponding silver salt and (S,S)- Pr-pheboxH in 1:1 molar ratio. The structures of the tetranuclear
i
n 3 3 6 6
N- Pr-pheboxH)][X]} (X = CF SO (7a), SbF (7b), PF
Keywords:
Copper(I) complexes
Silver(I) complexes
i
2
i
2
complexes 1–3 as well as of the polymeric species [Cu
N- Pr-pheboxH)][PF ]} (7c) have been determined by single crystal X-ray analysis.
4
4
I (
j
-N,N- Pr-pheboxH)
2 n
] (4) and {[Ag(j -N,
i
6 n
Enantiopure complexes
0
0
Ó 2015 Elsevier Ltd. All rights reserved.
1
,3-Bis[4 -(S)-isopropyloxazolin-2 -yl]
benzene ligand
Bis(oxazoline) ligand
1
. Introduction
Over the last two decades, enantiopure bis(oxazoline) deriva-
ligand. This study has permitted to access a variety of metal com-
plexes with great structural diversity. The crystal structures of
complexes 1, 2, 3, 4 and 7c have been determined by single-crystal
X-ray diffraction analysis. In accordance with the presence of an
enantiopure ligand, complexes 1–4 and 7c crystallize in chiral
space groups. The absolute structures have been confirmed by
refinement of the Flack parameter.
tives have been recognized as one of the most useful type of
ligands in metal-catalyzed asymmetric transformations. This fact
is not only a consequence of their high induction efficiency but also
on their ability to coordinate to a large number of metals [1,2].
Despite that bis(oxazoline) ligands wherein the two oxazoline
rings are connected by a one-carbon spacer are most commonly
employed, other systems containing spacer units with varied
nature, size, and flexibility have also been reported [1c,f,g].
Moreover, metal complexes containing monoanionic bisoxazoli-
nate ligands have been successfully employed in asymmetric
catalysis in the last years [3].
2. Experimental
2.1. General procedures
The reactions were performed under an atmosphere of dry
nitrogen using vacuum-line and standard Schlenk techniques.
Solvents were dried by standard methods and distilled under nitro-
On the other hand, the N,C,N-tridentate anionic ligands
0
0
i
t
2
,6-bis[4 -R-oxazolin-2 -yl)]phenyl (R-phebox, R = Pr, Ph, Bu, Me,
i
Bn) represent a related type of C -symmetric chiral ligands that
2
gen before use. (S,S)- Pr-pheboxH was prepared by reported
have been successfully employed in asymmetric catalysis in the
method [6]. Infrared spectra were recorded on a Perkin–Elmer
1720-XFT spectrometer. The conductivities were measured at
last years [4]. However, as far as we are aware, N,N-bidentate com-
ꢁ4
ꢁ1
0
0
plexes containing the enantiopure 1,3-bis[4 -R-oxazolin-2 -yl]ben-
zene (R-pheboxH) ligand have not been reported as yet [5].
Therefore, we herein report on the synthesis of copper(I) and
room temperature, in ca. 3 ꢀ 10 mol L
acetone or nitro-
methane solutions, with a Jenway PCM3 crison EC-meter Basic
30+ conductimeter. The C, H and N analyses were carried out with
a LECO CHNS-TruSpec and a Perkin–Elmer 240-B microanalyzers
i
silver(I) complexes containing the enantiopure (S,S)- Pr-pheboxH
(
(
inconsistent analyses were found for complex 4). Mass spectra
FAB) were recorded using a VG-AUTOSPEC spectrometer, operat-
⇑
Corresponding author. Fax: +34 985103446.
E-mail address: pgb@uniovi.es (M.P. Gamasa).
ing in the positive mode, and using 3-nitrobenzyl alcohol (NBA)
as the matrix (complexes 5, 6, 7a and 7b). NMR spectra were
http://dx.doi.org/10.1016/j.poly.2015.04.014
277-5387/Ó 2015 Elsevier Ltd. All rights reserved.
0

6
0
E. Vega et al. / Polyhedron 94 (2015) 59–66
2
i
obtained on Bruker spectrometers (AV 400 operating at 400.13
2.3. Synthesis and characterization of complex [Cu
4 4
I (r -N,N- Pr-
1
13
1
(
H) and 100.61 MHz ( C) or DPX300 operating at 300.13 ( H)
pheboxH) (4)
2 n
]
1
3
and 75.48 ( C) MHz). DEPT experiments were carried out for all
the compounds. Chemical shifts are reported in parts per million
and referenced to TMS as standard. Coupling constants J are given
i
To a solution of (S,S)- Pr-pheboxH (0.051 g, 0.173 mmol) in
dichloromethane (15 mL), CuI (0.049 g, 0.259 mmol) was added
and the mixture stirred at room temperature during 24 h. Then,
the reaction mixture was filtered via cannula and concentrated
under reduced pressure to ca. 2 mL and diethyl ether/n-hexane
1
in hertz. The following atom labels have been used for the H and
1
3
1
i
C{ H} spectroscopic data of the (S,S)- Pr-pheboxH.
(
1:2) (30 mL) was added. The resulting dark yellow solid was
washed with n-hexane (3 ꢀ 5 mL) and vacuum-dried. Yield: 96%
(
2
0.250 g). Color: dark-yellow. Molar conductivity (nitromethane,
2
ꢁ1
1
93 K, Sꢂcm ꢂmol ): 19.3. H NMR (400.13 MHz, CD
2 2
Cl , 298 K):
2
4,6
d = 8.97 (br s, 2H, H
C H
6 4
), 8.08 (d, JH,H = 7.6 Hz, 4H, H
6 4
C H ),
5
7
(
.57 (t, JH,H = 7.6 Hz, 2H, H
C H
6 4
), 4.53 (m, 4H, OCH
CH Pr), 2.06 (br s, 4H, CHMe
H,H = 6.8 Hz, 12H, CHMe
2
), 4.31–4.19
), 1.01 (d,
i
2
2m, 8H, OCH ,
2
J
2
), 0.94 (d, JH,H = 6.8 Hz, 12H, CHMe
2
).
1
3
1
C{ H} NMR (75.45 MHz, CD
2
Cl
2
, 298 K): d = 162.9 (s, OCN),
C H ), 126.3, 126.2 (2s, C
6 4
1
,3
4,6
2,5
1
C
(
30.4 (s, C
), 71.2 (s, OCH
).
C
6
H
4
), 128.2 (s, C
2
i
2
.2. Synthesis and characterization of complexes [Cu
X
4 4
(r -N,N- Pr-
i
6
H
4
2
), 69.4 (s, CH Pr), 32.2 (s, CHMe
2
), 17.8, 16.5
2
pheboxH) ] (X = Cl (1), Br (2), I (3))
2s, CHMe
2
i
To a solution of (S,S)- Pr-pheboxH (0.051 g, 0.173 mmol) in
2
i
2
.4. Synthesis and characterization of complex {[Cu(r -N,N- Pr-
dichloromethane (15 mL), the corresponding copper(I) salt CuX
X = Cl, Br, I) (0.347 mmol) was added and the mixture stirred at
4 n
pheboxH)][BF ]} (5)
(
room temperature during 24 h. Then, the reaction mixture was fil-
tered via cannula, concentrated under reduced pressure to ca. 2 mL
and diethyl ether/n-hexane (1:2) (30 mL) was added. The resulting
solid was washed with n-hexane (3 ꢀ 5 mL) and vacuum-dried.
i
To a solution of (S,S)- Pr-pheboxH (0.052 g, 0.173 mmol) in
tetrahydrofuran (15 mL), the complex [Cu(MeCN) ][BF ] (0.054 g,
.173 mmol) was added and the mixture stirred at room tempera-
4
4
0
ture during 1 h. The solvent was then evaporated under reduced
pressure, the solid residue was dissolved in dichloromethane and
the resulting solution filtered via cannula. Then, the solution
obtained was concentrated under reduced pressure to ca. 2 mL
and diethyl ether (30 mL) was added giving a white solid which
was washed with diethyl ether (3 ꢀ 5 mL) and vacuum-dried.
Yield: 82% (0.064 g). Color: White. Anal. Calc. for
2
i
2
.2.1. [Cu
Yield: 90% (0.161 g). Color: yellow. Anal. Calc. for
Cu Cl Cl : C, 42.18; H, 4.75; N, 5.39. Found: C,
ꢂ0.5CH
2.20; H, 4.66; N, 5.39. Molar conductivity (nitromethane, 293 K,
4 4 2
Cl (r -N,N- Pr-pheboxH) ] (1)
C
4
36
H
48
N
4
O
4
4
4
2
2
2
ꢁ1
1
Sꢂcm ꢂmol ): 9.1. H NMR (300.13 MHz, CD
2
Cl
2
, 298 K): d = 9.56
2
4,6
(
(
(
(
2
C
br s, 2H, H
t, JH,H = 7.6 Hz, 2H, H
br s, 4H, CHMe ), 1.08 (d, JH,H = 6.9 Hz, 12H, CHMe
d, JH,H = 6.8 Hz, 12H, CHMe
C
6
H
4
), 8.38 (d, JH,H = 7.6 Hz, 4H, H
C
6
H
4
), 7.63
, CH Pr), 2.31
), 1.02
C
5
[
(
18
H
24BCuF
4 2 2
N O : C, 47.96; H, 5.37; N, 6.21. Found: C, 47.64; H,
5
i
i
+
6 4 2
C H ), 4.57 (m, 12H, OCH
.89; N, 6.30. MS-FAB: m/z = 663.75 [Cu( Pr-pheboxH)
2
] , 363.32
) (vs). Molar conductivity
nitromethane, 293 K, Sꢂcm ꢂmol ): 64, (acetone, 293 K,
i
+
ꢁ
4
2
2
Cu( Pr-pheboxH)] . IR (KBr):
m
1063 (BF
13
1
2
ꢁ1
2
). C{ H} NMR (75.45 MHz, CD
2
Cl
2
,
1,3
4,6
98 K): d = 163.9 (s, OCN), 131.5 (s, C
C
6
H
4
), 128.9 (s, C
2
ꢁ1
1
Sꢂcm ꢂmol ): 117. H NMR (400.13 MHz, CD
2
Cl
2
, 298 K): d = 8.73
2
,5
i
2
4,6
5
H
6 4
), 125.5 (s, C
C
6
H
4
), 71.9 (s, CH Pr), 69.9 (s, OCH
2
), 31.2
(
br s, 1H, H
C
6
H
4
), 8.12 (m, 2H, H
C H ), 7.50 (m, 1H, H
6 4
(
s, CHMe
2
), 18.3, 16.1 (2s, CHMe ).
2
i
C
2
6
4
H ), 4.93 (m, 2H, OCH
2
), 4.57 (m, 4H, OCH
), 1.06 (m, 12H, CHMe
CD Cl , 298 K): d = 170.3 (s, OCN), 133.1 (s, C C H ), 130.4 (s,
2 2 6 4
6 4 6 4 6 4 2
C C H ), 127.5 (s, C C H ), 126.5 (s, C C H ), 73.3 (s, OCH ),
2
, CH Pr), 1.99 (m,
1
3
1
H, CHMe
2
2
). C{ H} NMR (100.61 MHz,
2
i
4,6
2.2.2. [Cu
4
Br
4
(r -N,N- Pr-pheboxH)
2
] (2)
5
2
1,3
Yield: 88% (0.190 g). Color: yellow. Anal. Calc. for
Cu Br Cl : C, 35.28; H, 4.00; N, 4.45. Found: C,
ꢂCH
5.20; H, 4.08; N, 4.37. Molar conductivity (nitromethane, 293 K,
i
C
3
36
H
48
N
4
O
4
4
4
2
2
2 2
70.7 (s, CH Pr), 32.2 (s, CHMe ), 18.2, 17.4 (2s, CHMe ).
2
ꢁ1
1
2
Sꢂcm ꢂmol ): 11.6.
H
NMR (400.13 MHz, CD
2
Cl
2
,
298 K):
), 7.55 (m,
, CH Pr), 2.74 (br s, 4H, CHMe ),
, 298 K):
), 126.7
), 18.1,
2 3 3 2
2.5. Synthesis and characterization of complex [Cu (CF SO ) (r -
2
4,6
i
d = 10.54 (br s, 2H, H
C
6
H
4
), 8.06 (br s, 4H, H
C
6
H
4
n
N,N- Pr-pheboxH)] (6)
5
i
2
0
H, H
C
6
H
4
), 4.51 (m, 12H, OCH
2
2
1
3
1
i
.96 (m, 24H, CHMe
2
). C{ H} NMR (75.45 MHz, CD
2
Cl
2
To a solution of (S,S)- Pr-pheboxH (0.052 g, 0.173 mmol) in
dichloromethane (15 mL), the compound 2Cu(CF SO )ꢂC H
1,3
4,6
d = 164.1 (s, OCN), 132.1 (s, C
C
H
6 4
), 129.6 (s, C
6
C H
4
3
3
7
8
2
,5
i
(
s, C
C
6
4
H ), 72.3 (s, CH Pr), 70.5 (s, OCH
2
), 31.6 (s, CHMe
2
(0.090 g, 0.173 mmol) was added and the mixture stirred at room
temperature during 24 h. Then, the reaction mixture was filtered
via cannula, concentrated under reduced pressure to ca. 2 mL and
diethyl ether/n-hexane (1:2) (30 mL) was added. The resulting yel-
low solid was washed with n-hexane (3 ꢀ 5 mL) and vacuum-
dried. Yield: 88% (0.110 g). Color: yellow. Anal. Calc. for
1
2
6.8 (2s, CHMe ).
2
i
2.2.3. [Cu
4 4
I
(r -N,N- Pr-pheboxH)
2
] (3)
Yield: 90% (0.223 g). Color: yellow. Anal. Calc. for
Cu Cl : C, 30.70; H, 3.48; N, 3.87. Found: C,
ꢂCH
0.64; H, 3.5; N; 3.88. Molar conductivity (nitromethane, 293 K,
C
3
36
H
48
N
4
O
4
I
4 4
2
2
C
20
H
24
N
2
O
8
Cu
2 6 2
F S : C, 33.11; H, 3.33; N, 3.86; S, 8.84. Found: C,
33.41; H, 3.87; N, 4.00; S, 8.64. MS-FAB: m/z = 575.36 [Cu
2
ꢁ1
1
i
Sꢂcm ꢂmol ): 9.1. H NMR (400.13 MHz, CD
2
Cl
2
, 298 K): d = 10.28
2
( Pr-
1257
2
4,6
+
i
+
(
J
br s, 2H, H
H,H = 7.6 Hz, 2H, H
H, CHMe ), 0.98 (d,
H,H = 6.8 Hz, 12H, CHMe
C
6
H
4
), 8.00 (d, JH,H = 7.6 Hz, 4H, H
C
6
H
4
), 7.54 (t,
, CH Pr), 2.68 (br s,
H,H = 7.2 Hz, 12H, CHMe ), 0.90 (d,
pheboxH)(CF
3
SO
3
)] , 363.31 [Cu( Pr-pheboxH)] . IR (KBr):
m
5
i
ꢁ1
C H
6 4
), 4.46 (m, 12H, OCH
2
(vs), 1160 (s), 1029 (s) (CF
3
SO
3
) cm . Molar conductivity (nitro-
2
ꢁ1
2
ꢁ1
4
2
J
2
methane, 293 K, Sꢂcm ꢂmol ): 7, (acetone, 293 K, Sꢂcm ꢂmol ):
13
1
1
2
J
2
). C{ H} NMR (100.61 MHz, CD
2
Cl
2
,
92. H NMR (400.13 MHz, CD
2
Cl
2
, 298 K): d = 9.36 (s, 1H, H
1,3
4,6
4,6
5
2
98 K): d = 163.7 (s, OCN), 132.7 (s, C
C
6
H
4
), 129.9 (s, C
6
C H
4
), 8.15 (m, 2H, H
2H, OCH
CHMe ), 0.90 (m, 6H, CHMe
C
6
H
4
), 7.60 (m, 1H, H
C H
6 4
), 4.82 (m,
), 1.88 (m, 2H,
2
,5
i
i
C
H
6 4
), 126.9 (s, C
C H
6 4
), 72.9 (s, CH Pr), 70.2 (s, OCH
).
2
), 31.7 (s,
2
), 4.64 (m, 2H, CH Pr), 4.52 (m, 2H, OCH
2
), 0.86 (m, 6H, CHMe ). C{ H} NMR
2
1
3
1
CHMe
2
), 18.8, 15.9 (2s, CHMe
2
2
2

E. Vega et al. / Polyhedron 94 (2015) 59–66
61
4
4
,6
(
C
7
100.61 MHz, CD
2
Cl
C
2
, 298 K): d = 169.0 (s, OCN), 133.8 (s, C
(3) into a solution of the complexes in dichloromethane (1-3) or
toluene (4). Crystals of complex 7c were obtained by slow diffusion
of hexane into a solution of the complex in acetone. The unit cell of
the complex 3 contains benzene and hexane (1:1:1). The crystal of
complex 4 contains hexane (1:0.5). In the crystal of complex 7c,
two acetone solvation molecules per four formula units of complex
were found. The most relevant crystal and refinement data are
collected in the Supplementary data (Tables S2 and S3).
5
2
1,3
H
6 4
), 130.7 (s, C
3.1 (s, OCH ), 71.1 (s, CH Pr), 32.5 (s, CHMe
).
6
H
4
), 127.3 (s, C
C H
6 4
), 126.9 (s, C
6
C H
),
i
2
2
), 18.5, 17.6 (2s,
CHMe
2
2
i
2
.6. Synthesis and characterization of complexes {[Ag(r -N,N- Pr-
pheboxH)][X]} (X = CF SO (7a), SbF (7b), PF (7c))
n
3
3
6
6
To a solution of the corresponding silver salt (0.145 mmol) in
dichloromethane (10 mL) an equivalent of the (S,S)- Pr-pheboxH
Diffraction data for 1, 2, 3 and 4 were recorded on an Oxford
Diffraction Xcalibur Nova single-crystal diffractometer, using Cu
i
(
44 mg, 0.145 mmol) was added. The reaction mixture was stirred
Ka radiation (l = 1.5418 Å). Images were collected at a 65 mm fixed
at room temperature in the absence of light for 2 h. Then, the
solution was exposed to the light for 1 h, filtered via cannula and
concentrated under reduced pressure to ca. 2 mL. The addition of
crystal-detector distance, using the oscillation method, with 1°
oscillation and variable exposure time per image. The data collec-
tion strategy was calculated with the program CrysAlis Pro CCD [7].
Data reduction and cell refinement was performed with the pro-
gram CrysAlis Pro RED [7]. An empirical absorption correction
was applied using the SCALE3 ABSPACK algorithm as implemented
in the program CrysAlis Pro RED [7].
Diffraction data for 7a were recorded on a Bruker Smart 6000
CCD diffractometer and Cu Ka radiation (k = 1.5418 Å) generated
by an Incoatec microfocus source equipped with Incoatec Quazar
MX optics. The software APEX2 was used for collecting frames of
data, indexing reflections and the determination of lattice parame-
ters, and SAINT [8] for integration of intensity of reflections, and
2
5 mL of diethyl ether afforded a pale pink solid which was washed
with diethyl ether (3 ꢀ 5 mL) and vacuum-dried.
2
i
2
.6.1. {[Ag(r -N,N- Pr-pheboxH)][CF
Yield: 69% (0.056 g). Color: pale pink. Anal. Calc. for
24AgF S: C, 40.95; H, 4.34; N, 5.03; S, 5.75. Found: C,
0.89; H, 4.57; N, 5.42; S, 5.20. MS-FAB: m/z = 406.9
3 3 n
SO ]} (7a)
C
4
[
19
H
3
N
2
O
5
i
+
Ag( Pr-pheboxH)] . IR (KBr): m 1264 (vs), 1177 (s), 1034 (vs)
ꢁ
1
2
ꢁ1
(
CF
3
SO
3
) cm . Molar conductivity (acetone, 293 K, Sꢂcm ꢂmol ):
2
1
C
1
2
04. 1H NMR (400.13 MHz, acetone-d
6
, 298 K): d = 8.53 (s, 1H, H
H
H, H
4
), 8.27 (d, JH,H = 8.0 Hz, 2H, H4
,6
C
6
H
4
), 7.29 (t, JH,H = 8.0 Hz,
), 4.58 (m,
2
), 1.04 (d, JH,H = 6.8 Hz, 6H,
6
SADABS [9] for scaling and empirical absorption correction. In all
cases the software package WINGX [10] was used for space group
determination, structure solution and refinement. The structure
for 1 was solved by Patterson interpretation and phase expansion
using DIRDIF [11]. The structure for the complexes 2, 3, 4 and 7c
were solved by direct methods using SIR2004 [12]. In the crystal
of 7c, the asymmetric unit contains four formula units and two
molecules of acetone. The cations of two formula units are disor-
dered in two positions with an occupancy factor of 0.5.
5
6 4 2 2
C H ), 4.79 (m, 2H, OCH ), 4.65 (m, 2H, OCH
H, CH Pr), 2.22 (m, 2H, CHMe
i
13
1
CHMe
(
C
1
2
), 0.97 (d,
100.61 MHz, acetone-d
J
H,H = 6.8 Hz, 6H, CHMe
2
).
C{ H} NMR
4
4
,6
6
, 298 K): d = 167.4 (s, OCN), 131.9 (s, C
5
), 127.3 (C2
SO ), 71.2 (s, OCH
), 17.7, 15.8 (2s, CHMe ).
1,3
H
6 4
), 129.4 (s, C
C
6
H
4
C
6
H
4
), 126.9 (s, C
6
C H
),
i
21.2 (q, JCF = 321 Hz, CF
3
3
2
, CH Pr), 31.5 (s,
CHMe
2
2
2
i
2
.6.2. {[Ag(r -N,N- Pr-pheboxH)][SbF
Yield: 58% (0.054 g). Color: Pale pink. Anal. Calc. for
24AgF Sb: C, 33.57; H, 3.76; N, 4.35. Found: C, 33.68; H,
.0; N, 4.19. MS-FAB: m/z = 407.0 [Ag( Pr-pheboxH)] . IR (KBr):
6
]}
n
(7b)
2
Isotropic least-squares refinement on F using SHELXL97 [13] was
performed. During the final stages of the refinements, all the posi-
tional parameters and the anisotropic temperature factors of the
non-H atoms were refined (except C, O, and N atoms for units
disordered in 7c which were refined isotropically). The H atoms
were geometrically placed riding on their parent atoms with iso-
tropic displacement parameters set to 1.2 times the Ueq of the
atoms to which they are attached (1.5 for methyl groups). The
C
4
6
18
H
6 2 2
N O
i
+
m
ꢁ
ꢁ1
60 (vs) (SbF
6
)
cm
.
Molar conductivity (acetone, 293 K,
2
ꢁ1
1
Sꢂcm ꢂmol ): 130. H NMR (400.13 MHz, acetone-d
6
, 298 K):
), 7.30
), 4.68 (m, 2H,
), 4.50 (m, 2H, CH Pr), 2.21 (m, 2H, CHMe ), 1.05 (d,
), 0.99 (d, H,H = 6.8 Hz, 6H, CHMe ).
C{ H} NMR (100.61 MHz, acetone-d , 298 K): d = 167.8 (s, OCN),
), 127.6 (C2
), 126.9 (s,
, CH Pr), 31.6 (s, CHMe ), 17.7, 15.7 (2s,
2
4,6
d = 8.50 (s, 1H, H C
6
H
4
), 8.26 (d, JH,H = 7.7 Hz, 2H, H
6 4
C H
5
(
6 4 2
t, JH,H = 7.7 Hz, 1H, H C H ), 4.81 (m, 2H, OCH
i
OCH
2
2
2
2
2
1/2
function minimized was ([
R
w(F
o
ꢁ F
c o
)/Rw(F )] , where w = 1/
J
H,H = 6.8 Hz, 6H, CHMe
2
J
2
2
2
2
[r
(F
o
) + (aP) + bP] (a and b values are collected in Tables S2 and
1
3
1
2
2
2
6
S3) with
r
(F
o
4
,6
5
1
C
31.7 (s, C
C
6
H
4
), 129.4 (s, C
C
6
H
4
6 4
C H
3
. The maximum residual electron density is located near heavier
atoms.
Atomic scattering factors were taken from the International
1
,3
i
C
6
H
4
), 71.3 (s, OCH
2
2
2
CHMe ).
Tables for X-Ray Crystallography International [14]. Geometrical
calculations were made with PARST [15]. The crystallographic plots
were made with PLATON [16].
2
i
2
.6.3. {[Ag(r -N,N- Pr-pheboxH)][PF
6 n
]} (7c)
Yield: 62% (0.050 g). Color: Pale pink. Anal. Calc. for
C
4
(
18
H24AgF
6
N
2
O
2
P: C, 39.08; H, 4.3; N, 5.06. Found: C, 39.07; H,
ꢁ
ꢁ1
.44; N, 4.80. IR (KBr):
m
831 (vs) (PF
6
) cm . Molar conductivity
2
ꢁ1
1
acetone, 293 K, Sꢂcm ꢂmol ): 106.
H
NMR (400.13 MHz,
3. Results and discussion
acetone-d
2
OCH
6
, 298 K): d = 8.51 (s, 1H, H2
), 7.32 (t, JH,H = 7.8 Hz, H, H
), 4.50 (m, 2H, CH Pr), 2.21 (m, 2H,
), 1.05 (d, JH,H = 6.8 Hz, 6H, CHMe ), 0.99 (d, JH,H = 6.8 Hz,
6
C H
4
), 8.25 (d, JH,H = 7.8 Hz,
4
,6
5
2
i
H, H
C
6
H
4
C
6
H
4
), 4.81 (m, 2H,
3.1. Synthesis of the tetranuclear complexes [Cu
pheboxH} ] (X = Cl (1), Br (2), I (3)) and the polymer species [Cu
N,N- Pr-pheboxH} (4)
4 4
X {r -N,N- Pr-
i
2
2
), 4.67 (m, 2H, OCH
2
2
4 4
I {r -
i
CHMe
H, CHMe
d = 167.6 (s, OCN), 131.7 (s, C
2
2
2 n
]
1
3
1
6
2
).
C{ H} NMR (100.61 MHz, acetone-d
6
,
H
298 K):
), 127.5
4,6
), 129.5 (s, C5
), 71.3 (s, OCH
), 17.7, 15.8 (2s, CHMe ).
C
6
H
4
C
6
4
i
The treatment of a suspension of CuX (X = Cl, Br, I) with
2
1,3
i
(
C
C
6
H
4
), 127.0 (s, C
C H
6 4
2
), 71.2 (s, CH Pr), 31.6
(S,S)- Pr-pheboxH (ca. 2:1 molar ratio), in dichloromethane at room
2
i
(
s, CHMe
2
2
temperature, leads to the complexes [Cu
4
X
4
{r -N,N- Pr-pheboxH}
2
]
(
1–3) in 88–90% yields (Scheme 1). Interestingly, the polymeric
2
i
2.7. X-ray data
4 4 2 n
species [Cu I {r -N,N- Pr-pheboxH} ] (4) is obtained (96% yield)
i
when the reaction of CuI with (S,S)- Pr-pheboxH is carried out
using larger molar ratio of the ligand (1.5:1) (Scheme 1).
However, the attempts to synthesize the analogous chlorine and
Crystals suitable for X-ray diffraction analysis were obtained by
slow diffusion of diethyl ether/hexane (1, 2, 4) or benzene/hexane

6
2
E. Vega et al. / Polyhedron 94 (2015) 59–66
Scheme 1. Synthesis of complexes 1–4.
2
i
4 4 2 n
bromine polymeric species [Cu X {r -N,N- Pr-pheboxH} ] (X = Cl,
Br) from CuX (X = Cl, Br) have been unsuccessful. Therefore, it
appears that the formation of this polymeric species requires both
the participation of the bulky iodide and an excess of the ligand.
The 1H and C NMR resonance signals (298 K) of complexes
Fig. 1. An ORTEP drawing of 1 showing atom-labeling scheme. Thermal ellipsoids are
shown at 10% probability. Hydrogen atoms are omitted for clarity.
13
1
–4 in CD
2 2 2
Cl are fully consistent with a time-averaged C symme-
13
1
try structure. Thus, single resonance C{ H} NMR signals were
0
0
0
i
observed for the C-5 (OCH
atoms of both oxazoline rings and for the carbon C-1/C-3 and C-
/C-6 of the phenyl ring. The structures of complexes 1–4 have
2
), C-2 (OCN) and C-4 (CH Pr) carbon
4
been determined by X-ray crystallography. The X-ray analyses
reveal the formation of the tetranuclear neutral complexes 1–3
and the polymeric species 4. However, the molar conductivity
ꢁ
4
ꢁ1
values in acetone solution (5 ꢀ 10 mol L , 293 K, 98 (1), 110
2
ꢁ1
(
2), 98 (3), 138 (4) Sꢂcm ꢂmol ) are indicative of the partial
halogen dissociation in this solvent, although the complexes show
very low conductivity in nitromethane solutions (in the range
2
ꢁ1
1
9.3–9.1 Sꢂcm ꢂmol ) [17].
2
i
3
4 4
.1.1. Structural determination of the complexes [Cu X {r -N,N- Pr-
2
pheboxH} ] (X = Cl (1), Br (2), I (3))
The ORTEP-type views of the complexes 1–3 are shown in
Figs. 1–3 and selected bonding data are collected in the
Supplementary data (Table S1). Complexes 1–3 crystallize in chiral
1 1 1 1
space groups P2 2 2 (1, 2) and P2 (3). Similarly, all complexes
whose structures are reported in this paper crystallize in chiral
space groups due to the presence of an enantiopure ligand. The
absolute structures have been confirmed by refinement of the
Flack parameter which is found to be nearly zero for all of them
Fig. 2. An ORTEP drawing of 2 showing atom-labeling scheme. Thermal ellipsoids are
shown at 10% probability. Hydrogen atoms are omitted for clarity.
(
see Tables S2 and S3, Supplementary data) [18]. The four copper
atoms in complexes 1–3 form a distorted tetrahedral skeleton with
each of the four triangular faces being formally capped by a
3
l -halogen atom revealing a cubane-type structure. Each copper
atom is formally coordinated to three halogen atoms and to one
oxazoline nitrogen atom. Thus, the Cu(1) and Cu(2) atoms of these
complexes are coordinated to the oxazoline nitrogens N(1) and N(2)
of one pheboxH ligand whereas Cu(3) and Cu(4) atoms are bonded
to the oxazoline nitrogens N(3) and N(4) of the other pheboxH
ligand. The Cu–N bond lengths (range: 1.996(3)–1.948(4) Å (for
3.0782(27)–2.628(2) Å (av. 2.8132 Å) (for 3). These distances are
found to be shorter (for 2) and longer (for 3) than those found in
various structurally characterized tetranuclear complexes
4 4
[CuBrL] (av. 2.943 Å) and [CuIL] (av. 2.710 Å) with L = N-ligand
[19] and are consistent with nonbonding Cuꢂ ꢂ ꢂCu contacts [20].
The cubane-type structures for complexes 2 and 3 are considerably
distorted with appreciable variations of both Cu–X–Cu and X–Cu–X
angles and are quite different from the idealized values of 90°. Thus,
the Cu–X–Cu angles vary from 76.245(19) to 62.391(6) (av.
68.874°) and from 69.79(6) to 56.46(5)° (av. 62.491°) for 2 and 3,
1
), 2.019(3)–1.987(3) (for 2), 2.043(9)–2.032(9) (for 3) are in good
agreement with those found in other cubane tetranuclear com-
plexes [CuXL]
(L = N-ligand) [19]. The Cuꢂ ꢂ ꢂCu bond distances are
in the ranges of 3.0585(7)–2.7125(7) Å (av. 2.886 Å) (for 2) and
4

E. Vega et al. / Polyhedron 94 (2015) 59–66
63
2
.3668(13)–2.2290(16) Å and the third one between 3.3007(14)
and 2.8783(14) Å. On the other hand, the complex shows the
Cu(1)ꢂ ꢂ ꢂCu(4) bond to be relatively short (2.8196(11) Å), while
the rest of Cuꢂ ꢂ ꢂCu bond distances are in the range of
3
.3529(10)–3.1385(9) Å. The torsion angles found for the
pheboxH ligands are N(1)–C(6)–C(7)–C(12) (ꢁ4.0(9)°), C(12)–
C(11)–C(13)–N(2) (ꢁ10.7(8)°), N(3)–C(24)–C(25)–C(30) (ꢁ2.5(7)°)
and C(30)–C(29)–C(31)–N(4) (24.9(7)°).
2
i
3.1.2. Structural determination of the complex [Cu
4 4
I {r -N,N- Pr-
pheboxH} (4)
2 n
]
The ORTEP-type view of the complex 4 is shown in Figs. 4 and 5,
and selected bonding data are collected in the Supplementary data
(
2
Table S1). Complex 4 crystallize in chiral space group C with the
Flack parameter being 0.004(5). Complex 4 is a polymeric species
in which the repeated unit consists of a cubane-type structure
i
C I
4 4
, as in the case of complexes 1–3, and two (S,S)- Pr-pheboxH
i
ligands. One of the Pr-pheboxH group is coordinated to the Cu(1)
and Cu(2) atoms of the Cu unit through the N(1) and N(2) oxa-
zoline nitrogen atoms, while the other Pr-pheboxH group is bond-
ing to the Cu(3) and Cu(4b) atoms of two different C units
4 4
I
i
4 4
I
through the N(3) and N(4) oxazoline nitrogen atoms, the Cu–N dis-
tances being similar for both pheboxH units. The Cuꢂ ꢂ ꢂCu bond dis-
tances (2.9934(16)–2.6605(16) Å) are in the range found for
complex 3 (2.924(3)–2.628(2) Å). The torsion angles for the
pheboxH bridging the Cu(1) and Cu(2) atoms of the unit C
N(1)–C(6)–C(7)–C(12) (16.5(12)°) and C(12)–C(11)–C(13)–N(2)
ꢁ15.4(12)°) are similar to those found in complex 3 while the tor-
sion angles for the pheboxH bridging to two Cu units are larger
N(3)–C(24)–C(25)–C(30) (165.3(9)°), C(30)–C(29)–C(31)–N(4)
152.29°). The structure of complex 4 in solid state is not main-
4 4
I
Fig. 3. An ORTEP drawing of 3ꢂC
6
H
6
ꢂC
6
H14 showing atom-labeling scheme. Thermal
ellipsoids are shown at 10% probability. Hydrogen atoms and the solvent molecules
are omitted for clarity.
(
4 4
I
respectively. The X–Cu–X angles are in the ranges of 119.17(2)–
(
9
1
4.95(2)° (av. 106.528°) (for 2) and 123.96(6)–98.71(7)° (av.
00.49°) (for 3). The variation in the copper–bromine and copper–
1
13
tained in solution since the H and C NMR resonance signals
298 K) of complex 4 are fully consistent with a time-averaged C
symmetry structure (see above).
(
2
iodine bond lengths for complexes 2 and 3 are in the ranges of
2
.7109(7)–2.4216(6) and 2.816(2)–2.6207(17) Å, respectively, and
indicates also a significant distorsion in the cubane geometry. The
non-planar skeleton of both pheboxH ligands show torsion angles
N(1)–C(6)–C(7)–C(12) (16.3(5) (2), ꢁ16.5(17)° (3)), C(12)–C(11)–
C(13)–N(2) (ꢁ6.1(5) (2), 19.4(17)° (3)), N(3)–C(24)–C(25)–C(30)
2
i
3.2. Synthesis of the complexes {[Cu{r -N,N- Pr-pheboxH}][BF ]} (5)
4
n
2
i
and [Cu (CF SO ) (r -N,N- Pr-pheboxH)] (6)
2
3
3 2
n
(
ꢁ6.5(5) (2), ꢁ10.5(18)° (3)) and C(30)–C(29)–C(31)–N(4) (5.4(5)
The room temperature reaction of an equimolecular amount of
i
(2), 19.3(19)° (3)).
(S,S)- Pr-pheboxH with [Cu(MeCN) ][BF ] or 2CuCF SO ꢂ1C H in
4
4
3
3
7
8
Complex 1 presents the most distorted structure with very
tetrahydrofuran (for 5) or dichloromethane (for 6) leads to the
complexes 5 (82% yield) and 6 (88% yield). The molar conductivity
unsymmetrical bridging of
3
l -Cl ligands. Thus, each chlorine
2
ꢁ1
atom shows two Cu–Cl bond lengths in the range of
value found for complex 5 (nitromethane solution, 64 Sꢂcm ꢂmol
;
Fig. 4. An ORTEP drawing of the unit [Cu
4
I
4
(pheboxH)
2
] present in the polymeric complex 4ꢂ0.5C
6
H14 showing atom-labeling scheme. Thermal ellipsoids are shown at 20%
probability. Hydrogen atoms and C 14 solvent molecule are omitted for clarity.
6
H

6
4
E. Vega et al. / Polyhedron 94 (2015) 59–66
Fig. 5. An ORTEP drawing of a portion of the polymeric complex 4ꢂ0.5C
Hydrogen atoms and C 14 solvent molecule are omitted for clarity.
6
H14 showing essential atom-labeling scheme. Thermal ellipsoids are shown at 10% probability.
6
H
2
ꢁ1
i
+
acetone solution, 117 Sꢂcm ꢂmol ) is in the range expected for 1: 1
363.31 ([Cu( Pr-pheboxH)] , 43%) (for 6). Unfortunately, an X-ray
analysis could not be performed since all attempts to crystallize
complexes 5 and 6, using different mixtures of various solvents
were unsuccessful [21].
electrolytes [17]. On the other hand, the molar conductivity values
2
ꢁ1
found for complex 6 (nitromethane solution, 7 Sꢂcm ꢂmol ; ace-
2
ꢁ1
tone solution, 92 Sꢂcm ꢂmol ) are indicative of a covalent interac-
tion between the triflate group and the copper center in
nitromethane solution whereas certain degree of triflate dissocia-
tion occurs in acetone. Selected spectroscopic data for complexes
2
i
3.3. Synthesis of complexes {[Ag(r -N,N- Pr-pheboxH)][X]}
(X = CF SO (7a), SbF (7b), PF (7c))
n
5
and 6 are the following: (i) the IR spectrum of complex 5 shows
the expected absorptions for the BF
3
3
6
6
ꢁ
ꢁ1
4
anion (1063 cm ) and the IR
spectrum of complex 6 exhibits strong bands of triflate at 1248,
The reaction of the corresponding silver salt AgX with an
equimolar amount of (S,S)- Pr-pheboxH in dichloromethane at
ꢁ1
13
1
i
1
168 and 1030 cm . (ii) The C{ H} NMR signals observed for
the phebox ligand are consistent with the presence of a C
2
symme-
room temperature gives rise to the complexes 7a–7c in moderate
yield (58–69%). Selected spectroscopic data for complexes 7a–7c
0
try axis. Thus, single resonance signals were observed for the C-5
0
0
i
13
1
(
OCH
2
), C-2 (OCN) and C-4 (CH Pr) carbon atoms of both oxazoline
are the following: (i) the C{ H} NMR signals observed for the
rings and for the C-1/C-3 and C-4/C-6 carbon atoms of the phenyl
pheboxH ligand are consistent with the presence of a C symmetry
2
1
3
1
ring in the C{ H} NMR spectra for complexes 5 and 6 (see
Section 2 for details). The C, H and N elemental analyses of 5 and
axis (see Section 2 for details). (ii) The molar conductivity value
found in acetone solutions are in the range expected for 1: 1 elec-
2
ꢁ1
6
are consistent with the proposed stoichiometry. In addition, mass
trolytes (104 (7a), 130 (7b) and 106 (7c) Sꢂcm ꢂmol ). (iii) The IR
i
spectra (FAB) show significant peaks at m/z = 663.75 ([Cu( Pr-
pheboxH)
and at m/z = 575.36 ([Cu
spectra of complexes 7a–7c show the expected absorptions for the
+
i
+
ꢁ
ꢁ
6
2
] , 95%) and 363.32 ([Cu( Pr-pheboxH)] , 43%) (for 5)
3 3
corresponding anions (CF SO , 1264, 1177, 1034 (7a); SbF , 660
(7b); PF , 831 cm (7c)).
6
i
+
ꢁ
ꢁ1
2
( Pr-pheboxH)(CF
3
SO
3
)] , 100%) and
Fig. 6. An ORTEP drawing of a portion of the zigzag chain present in the structure of complex 7cꢂ2Me
probability. Hydrogen atoms and Me CO solvent molecules are omitted for clarity.
2
CO showing atom-labeling scheme. Thermal ellipsoids are shown at 20%
2

E. Vega et al. / Polyhedron 94 (2015) 59–66
i
65
2
3
.3.1. Structural determination of the complex {[Ag(r -N,N- Pr-
rearrangement has allowed us to prepare the single-stranded poly-
meric species 7a–7c. Complex {[Ag(r -N,N- Pr-pheboxH)}][PF ]}
6 n
2
i
pheboxH)}][PF ]} (7c)
6
n
The structure of complex 7c has been confirmed by a single-
crystal X-ray analysis. The ORTEP-type view of the complex 7c is
shown in Fig. 6 and selected bonding data are collected in the
Supplementary data (Table S1). Complex 7c crystallize in chiral
(7c) presents a single-stranded polymeric structure with a zigzag
conformation in which each silver atom shows a near linearity envi-
ronment and is coordinated to the oxazoline nitrogen atoms of two
different pheboxH.
space group I4
refinement of the Flack parameter, which is 0.000(10). Complex
c exhibits a single-stranded polymeric structure with a zigzag
1
and the absolute structure was confirmed by
Acknowledgements
7
conformation in which the repeated unit consists of four silver
atoms and 4 Pr-pheboxH ligands. The silver atoms are coordinated
i
This work was supported by the MICINN of Spain (CTQ-2010-
7005 and CTQ2011-26481 and CONSOLIDER INGENIO CSD2007-
0006). E.V. thanks MICINN of Spain and E. de J. thanks FICYT
Principado de Asturias, Spain) for the award of the corresponding
PhD fellowships.
1
0
(
to the oxazoline nitrogen atoms of two different pheboxH and
show a near linearity environment with N–Ag–N angles in the
range of 174.9(6)–163.6(15)°. The Ag–N bond lengths are in the
range of 2.119(7)–1.968(11) Å (av. 2.068 Å). The pheboxH moiety
is non-planar as can be seen for the pheboxH bridging the Ag(1)
and Ag(2) atoms wherein torsion angles of N(2)–C(6)–C(7)–C(12)
of ꢁ31.2(12)° and C(12)–C(11)–C(13)–N(1) of ꢁ35.7(12)° are
observed.
Appendix A. Supplementary data
CCDC 1014371, 1014372, 1014373, 1014374, and 1014375 con-
tains the supplementary crystallographic data for compounds 1, 2,
3ꢂC H ꢂC H , 4ꢂ0.5C H , 7cꢂMe CO. These data can be obtained
3.3.2. Copper(I)-catalyzed addition of alkynes to imines
6
6
6
14
6
14
2
Enantioselective metal-catalyzed addition of terminal alkynes
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.
to imines [22], as well as the corresponding three-component reac-
tion of aldehydes, amines, and alkynes [23], provides direct access
to optically active propargylamines. These species are actually rec-
ognized as powerful synthetic intermediates for the construction
of privileged nitrogen-containing structures, particularly biologi-
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2015.04.014.
cally active compounds and natural products. We have tested the
2
capability of the new pheboxH–copper(I) complexes {[Cu(
j
-
i
2
i
References
N,N- Pr-pheboxH)][BF
pheboxH)] (6) to catalyze the addition of N-benzylideneaniline
to phenylacetylene. In a typical experiment, dried and deoxy-
genated CH Cl (0.5 mL) was placed in a three-neck Schlenk flask
]}
4 n
2 3 3 2
(5) and [Cu (CF SO ) (j -N,N- Pr-
n
[
1] For reviews see: (a) S. O’Reilly, P.J. Guiry, Synthesis 46 (2014) 722;
b) G. Desimoni, G. Faita, K.A. Jørgensen, Chem. Rev. 111 (2011) 284;
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(
2
2
(
(
(
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under a nitrogen atmosphere. Then, deoxygenated N-benzylide-
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and the mixture stirred under nitrogen (room temperature, 48 h)
to provide N-(1,3-diphenyl-2-propynyl)aniline. Despite moderate
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(
7
(
[2] Immobilization of chiral catalysts containing bis(oxazolines): (a) J.M. Fraile, J.I.
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(
b) D. Rechavi, M. Lemaire, Chem. Rev. 102 (2002) 3467.
[
[
3] S. Dagorne, S. Bellemin-Laponnaz, A. Maisse-François, Eur. J. Inorg. Chem.
(2007) 913.
4] (a) J. Ito, H. Nishiyama, Synlett 23 (2012) 509;
(
(
dentate
oxazoline-based
catalysts.
Whereas
excellent
enantiomeric excesses are obtained with copper(I) complexes con-
taining tridentate bis(oxazolinyl)pyridines (pybox) ligands, either
with in situ prepared [23a–c,24] or isolated [25] complexes, the
use of in situ prepared copper(I)/bidentate bis(oxazoline) com-
plexes lead to very low ee (<5% [24], <32% [26].
b) H. Nishiyama, J. Ito, Chem. Commun. 46 (2010) 203;
c) H. Nishiyama, Chem. Soc. Rev. 36 (2007) 1133.
0
[5] Silver complexes with non chiral 1,3-bis[oxazolin-2
-yl]benzene have been
recently reported: (a) Y. Zhao, L.-L. Zhai, G.-C. Lv, X. Zhou, W.-Y. Sun, Inorg.
Chim. Acta 392 (2012) 38;
(
b) Y. Zhao, L. Luo, C. Liu, M. Chen, W.-Y. Sun, Inorg. Chem. Commun. 14 (2011)
145.
1
[
[
6] Y. Kanazawa, Y. Tsuchiya, K. Kobayashi, T. Shiomi, J. Itoh, M. Kikuchi, Y.
Yamamoto, H. Nishiyama, Chem. Eur. J. 12 (2006) 63.
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9] G.M. Sheldrick, SADABS, University of Göttingen, Germany, 1996.
4
. Summary
We have synthesized enantiopure and structurally diverse
[
[
0
copper(I) and silver(I) complexes by reaction of 1,3-bis[4 -(S)-iso-
propyloxazolin-2 -yl]benzene with different copper(I) and
silver(I) precursors. Thus, tetramer cubane-type structures
0
[10] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[
11] P.T. Beurskens, G. Beurskens, R. De Gelder, J.M.M. Smits, S. García-Granda, R.O.
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Netherlands).
[15] M. Nardelli, Comput. Chem. 7 (1983) 95.
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Utrecht, The Netherlands, 2007.
2
i
[
Cu
4 4 2
X {r -N,N- Pr-pheboxH} ] (X = Cl (1), Br (2), I (3)) have been
resolved by X-ray diffraction analysis. Moreover, a new and inter-
esting polymeric species [Cu
been synthesized wherein the repeated structural unit consists of
2
i
4 4 2 n
I {r -N,N- Pr-pheboxH} ] (4) has
[
i
a cubane-type structure C
one of them is coordinated to two copper atoms of the Cu
and the second one is bonding to two copper atoms of different
units). On the other hand, the use of silver salts1 combined
I
4 4
and two (S,S)- Pr-pheboxH ligands
(
4 4
I
unit
[
(
4 4
C I
with the tendency of the silver cation to adopt
a lineal
[
1
No silver halides have been employed in the present study.
[17] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.

6
6
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(
(
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[
[
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(
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