Enantiospecific syntheses of copper cubanes, double-stranded copper/palladium helicates, and a (dilithium)-dinkkel coronate from enantiomerically pure bis-1,3-diketones - solid-state self-organization towards wirelike copper/palladium strands

Article abstract of DOI:10.1002/chem.200701537

Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H₂L^(S,S) (3a-c) with different substitution patterns. Reaction of these C₂-symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4-8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transitionmetal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu ₄(L^(SS)₂(OMe)₄] (4a-c) or dinuclear copper(II) helicates (P)-[Cu₂(L^(S,S)₂] (5) could be synthesized with square-pyramidal and squareplanar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (F)-[Pd₂(L ^(S,S))₂] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H₂L^(S,S) (3 a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(Li·MeOH) ₂C-{(Δ,Λ)-Ni₂(L^(S,S)) ₂(OMe)₂}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4-8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4a and palladium(II) helicate 6.

Full text of DOI:10.1002/chem.200701537

DOI: 10.1002/chem.200701537
Enantiospecific Syntheses of Copper Cubanes,Double-Stranded Copper/
Palladium Helicates,and a (Dilithium)–Dinickel Coronate from
Enantiomerically Pure Bis-1,3-diketones—Solid-State Self-Organization
Towards Wirelike Copper/Palladium Strands**
Rolf W. Saalfrank,*[a] Christine Spitzlei,[a] Andreas Scheurer,*[a] Harald Maid,[a]
Frank W. Heinemann,[a] and Frank Hampel[b]
Dedicated to Professor Ulrich Zenneck on the occasion of his 60th birthday
AHCTREUNG
Abstract: Enantiomerically pure, vici-
nal diols 1 afforded in a two-step syn-
thesis (etherification and subsequent
Claisen condensation) chiral bis-1,3-di-
ketones H2L(S,S) (3a–c) with different
substitution patterns. Reaction of these
C2-symmetric ligands with various tran-
sition-metal acetates in the presence of
alkali ions generated distinct polynuc-
lear aggregates 4–8 by diastereoselec-
tive self-assembly. Starting from cop-
per(II) acetate monohydrate and de-
pending on the ratio of transition-
metal ion to alkali ion to ligand, chiral
[Cu2(L(S,S))2] (5) could be synthesized
with square-pyramidal and square-
planar coordination geometry at the
metal center. In analogy to the last
case, with palladium(II) acetate
double-stranded helical systems (P)-
nickel(II) in combination with lithium
hydroxide monohydrate and chiral
ligand H2L(S,S) (3a) allowed the isola-
tion of enantiomerically pure dinuclear
nickel(II) coronate [(Li·MeOH)2ꢀ-
AHCTREUNG
G
G
[Pd2(L(S,S))2] (6,7) were accessible ex-
hibiting a linear self-organization of
ligand-isolated palladium filaments in
the solid state with short inter- and in-
tramolecular metal distances. Finally,
the introduction of hexacoordinate
lithium ions in the voids, defined by
the oxygen donors in the ligand back-
bone. The high diastereoselectivity, in-
duced by the chiral ligands, during the
self-assembly process in the systems 4–
8 could be exemplarily proven by circu-
lar dichroism spectroscopy for the syn-
thesized enantiomers of the chiral cop-
per(II) cubane 4a and palladium(II)
helicate 6.
AHCTREUNG
Keywords: chirality · circular di-
chroism · copper · helical structures ·
nickel
tetranuclear
copper(II)
cubanes
(C,C,C,C)-[Cu
A
)
ACHTREUNG
or dinuclear copper(II) helicates (P)-
Introduction
molecular squares and boxes, cubes, helicates, one- to three-
dimensional networks etc.). In addition to their appealing
structural design, the synthesis of these high-nuclearity coor-
dination complexes of transition metals is stimulated by
their electronic and magnetic properties, which predestine
them as metalloenzyme models,[2] nanoscale catalysts and
containers,[3] quantum computing components,[4] and molec-
ular magnets.[5] In the last case, it is an interesting challenge
to create chiral magnets, presenting at the same time mag-
netic circular dichroism (Faraday effect), natural circular di-
chroism (Cotton effect), and therefore possible cross-ef-
fects.[6] One synthetic approach, leading to these chiral
supramolecular architectures, is the combination of suitably
designed enantiomerically pure organic ligands and metal
ions,[7] which we used earlier for the diastereoselective syn-
thesis of copper(II) cubanes.[8]
Over the past two decades, major efforts were undertaken
to the metal-directed self-assembly[1] of highly organized ar-
chitectures (catenanes, rotaxanes, knots, grids, ladders, racks,
[a] Prof. Dr. R. W. Saalfrank, Dr. C. Spitzlei, Dr. A. Scheurer,
Dr. H. Maid, Dr. F. W. Heinemann
Institut für Anorganische Chemie
Universität Erlangen-Nürnberg, Egerlandstrasse 1
91058 Erlangen (Germany)
Fax: ( +49)9131-85-27396
E-mail: saalfrank@chemie.uni-erlangen.de
andreas.scheurer@chemie.uni-erlangen.de
[b] Dr. F. Hampel
Institut für Organische Chemie
Universität Erlangen-Nürnberg, 91054 Erlangen (Germany)
[**] Chelate Complexes, Part 38; for Part 37, see reference [26g].
1472
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Chem. Eur. J. 2008, 14, 1472 – 1481

FULL PAPER
Results and Discussion
In the course of our ongoing studies on supramolecular co-
ordination chemistry, we developed a stereospecific synthe-
sis for the copper(II) cubanes (C,C,C,C)-[Cu4(L(S,S)
)
ACHTREUNG
AHCTREUNG
AHCTREUNG
(4a) and (A,A,A,A)-[Cu4(L(R,R)
)
ACHTREUNG
from the chiral bis-1,3-diketones H2L(S,S) (3a) or H2L(R,R)
(ent-3a) through diastereoselective self-assembly.[8] Com-
pared to earlier results,[9] the presence of chiral centers in
the ligand appeared to be responsible for the transition
from a double-stranded copper(II) coronate to a copper(II)
cubane substructure. To evaluate, if we have found a general
method for the synthesis of chiral cubanes, enantiomerically
pure and differently substituted H2L(S,S) (3) ligands,[10] in
which the chirality is incorporated in the spacer backbone,
were generated from (2S,3S)-1,4-dimethoxy-2,3-butanediol
(1a), derived from l-tartaric acid,[11] or (S,S)-(ꢁ)-hydroben-
zoin (1b). Thus, etherification of diols 1 with ethyl bromo-
Scheme 2. Synthesis and schematic presentation of (C,C,C,C)-[Cu4-
A
N
ꢁ
ꢁ
metal separations in 4b are 2.97 (Cu1 Cu1’), 3.25 (Cu1
ꢁ
Cu2), and 3.29 Š (Cu1 Cu2’). Each copper ion has approxi-
A
mate square-pyramidal coordination, with a total of five
oxygen donors (two m1-O ions from the ligand and three m3-
OMe donors). Consequently, the two hexadentate ligands
bridge opposite edges of the copper tetrahedron
(Figure 1).[17,18]
afford diesters 2. Subsequent Claisen condensation of 2 with
sodium enolates, from acetophenone or 2-acetonaphthone
and sodium amide, led to C2-symmetric H2L(S,S) (3)
(Scheme 1).[12]
Scheme 1. Synthesis of the enantiomerically pure bis-1,3-diketones
Figure 1. Stereoview of copper(II) cubane 4b. C white, O dark grey, Cu
grey; disorder and hydrogen atoms omitted for clarity.
H2L(S,S) (3).
Reaction of one equivalent of 3a with two equivalents of
cesium acetate, followed by addition of two equivalents of
copper(II) acetate monohydrate, resulted in the formation
The circular dichroism (CD) measurements of copper(II)
cubanes 4a and ent-4a in dichloromethane further confirm
the opposite ground-state chirality and the enantiomeric
nature of these complexes. The CD spectrum of (C,C,C,C)-
AHCTREUNG
of (C,C,C,C)-[Cu4(L(S,S)
)2(OMe)4] (4a) in a yield of 84%
G
ACHTREUNG
(Scheme 2). Similarly, (A,A,A,A)-[Cu4(L(R,R)
)2(OMe)4] (ent-
H
4a) was prepared from H2L(R,R) (ent-3a) and characterized
by X-ray diffraction analysis.[8,13] In addition, reaction of one
equivalent of H2L(S,S) (3b,c) with two equivalents of alkali
acetate and subsequent addition of two equivalents of cop-
per(II) acetate monohydrate resulted in the formation of
[Cu4(L(S,S)
)2(OMe)4] (4a) exhibits two negative Cotton ef-
A
AHCTREUNG
fects at lmax =415 and 646 nm and a positive dichroic signal
centered at lmax =764 nm (dichroic crossover point at l=
714 nm), while ent-4a shows Cotton effects of the opposite
sign at the same wavelengths (Figure 2, top).
(C,C,C,C)-[Cu4(L(S,S)
)
C
Whereas reaction of one equivalent of H2L(S,S) (3b) with
two equivalents of potassium acetate and two equivalents of
copper(II) acetate monohydrate resulted in the formation of
ACHTREUNG
Cubane 4b is isostructural with 4a, exists as a single enan-
AHCTREUNG
tiomer, crystallizes in the chiral monoclinic space group C2,
(C,C,C,C)-[Cu4(L(S,S)
)2(OMe)4] (4b) (Scheme 2), unexpect-
A
[16]
and possesses a [Cu4(m3 O)4] cubane core unit consisting
A
edly, reaction of H2L(S,S) (3b) with five equivalents of potas-
sium acetate and one equivalent of copper(II) acetate mon-
ohydrate yielded the double-stranded helicate (P)-[Cu2-
ꢁ
of two interpenetrating tetrahedra: one made up of four
copper ions and one of four m3-OMe ligands. The metal–
Chem. Eur. J. 2008, 14, 1472 – 1481
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1473

R. W. Saalfrank, A. Scheurer et al.
may involve nonbonding stacking of two dx2ꢁy2 orbitals.[20]
The decisive role of the Cs+ and K+ ions for the formation
Table 1. Selected bond lengths [Š] and angles [8] for complexes 5–7.
5
6[a]
7
dav (M2+ O)
1.90
3.55
3.55
7.10
176.5
36.9
9.9
1.98 (1.99)
3.27 (3.23)
3.19 (3.23)
6.46 (6.46)
180.0 (180.0)
45.4 (39.9)
2.6 (3.9)
1.99
3.26
3.32
6.53
165.9
44.9
0.2
ꢁ
2+
2+
dintra (M2+
dinter (M2+
dinter aryl
M
)
)
ꢁ
ꢁ
M
angle (M2+-M2+-M2+
torsion angle[b]
angle[c] M2+
)
[a] Values for the disordered independent molecule in the unit cell (in
brackets). [b] Torsion angle of the nearly parallel coordination spheres
(averaged over the coordinating atoms). [c] Average angle, in which the
chelating planes at one metal center are twisted to each other.
AHCTREUNG
Figure 2. Top: CD spectrum of copper(II) cubanes (C,C,C,C)-[Cu4(L(S,S))2-
AHCTREUNG
A
N
thane, 258C, c=2.2·10ꢁ3 mollꢁ1). Bottom: CD spectrum of palladium(II)
A
ACHTREUNG
helicates (P)-[Pd2(L(S,S))2] (6) and (M)-[Pd2(L(R,R))2] (ent-6) (dichlorome-
thane, 258C, 6: c=6.4·10ꢁ4 mollꢁ1 and ent-6: c=1.0·10ꢁ3 mollꢁ1).
(L(S,S))2] (5) (Scheme 3). This was established by X-ray struc-
ture analysis on crystals, obtained by vapour diffusion of di-
AHCTREUNG
ethyl ether into a solution of (P)-[Cu2(L(S,S))2] (5) in metha-
nol/acetone (1:1).
AHCTREUNG
Figure 3. Stereoview of helicate (P)-[Cu2(L(S,S))2] (5). C white, O dark
grey, Cu grey; hydrogen atoms omitted for clarity.
of the cubanes 4 and helicate 5 is still in the dark. However,
in the absence of alkali ions, only polymeric material is iso-
lated, insoluble in standard solvents.[21]
The square-planar environment of the copper centers in 5
indicated that, in principle, it should be possible to generate
8
this type of complexwith second- and third-row d -transi-
tion metals too. Due to their electronic structure, these com-
plexes are diamagnetic and should enable the study of bulk
properties with NMR spectroscopy. Indeed, reaction of one
equivalent of H2L(S,S) (3a,c) and one equivalent of palladi-
G
dine[22] afforded the palladium(II) helicates (P)-[Pd2(L(S,S))2]
AHCTREUNG
Scheme 3. Synthesis and schematic presentation of (P)-[Cu2(L(S,S))2] (5),
(6) and (P)-[Pd2(L(S,S))2] (7) in 92 and 95% yield, respective-
ly (Scheme 3). 1H NMR spectroscopy of double-stranded
palladium(II) helicates[20c,23] 6 and 7 displayed only one set
of signals and variable-temperature experiments in
[D6]acetone and [D5]bromobenzene did not show any dy-
namic effects in these systems.[24] Final proof of the helical
structure and the trans–anti arrangement of the substituents
AHCTREUNG
(P)-[Pd2(L(S,S))2] (6), and (P)-[Pd2(L(S,S))2] (7), starting from H2L(S,S) (3a–
G
ACHTREUNG
c).
According to these analyses,[17,18] double-stranded cop-
per(II) helicate[9,19] 5 crystallizes in the chiral monoclinic
space group C2. Each copper ion has approximate square-
planar coordination, formed by the chelating 1,3-diketo
units of the ligands. Two phenyl substituents, each, of the
parallel coordination spheres at copper (torsion angle 378),
A
ACHTREUNG
in (P)-[Pd2(L(S,S))2] (6) and (P)-[Pd2(L(S,S))2] (7) was achieved
by X-ray structure analyses on single crystals obtained from
solutions of the compounds on prolonged standing in
[D6]acetone and [D5]bromobenzene, respectively.[17,18] Heli-
cates 5–7 are principally isostructural (Figure 3) and the
slight differences in bond lengths and angles of 5–7 are sum-
marized in Table 1. Solution-CD experiments of palladi-
are arranged in trans-positions, and the stereogenic centers
of ligand (L(S,S)
)
(3b)2ꢁ induce P-helicity, resulting in an
2ꢁ
overall D2 molecule symmetry of helicate
5 (Table 1,
Figure 3). The Cu2+–Cu2+ distances (dintra =dinter =3.55 Š) in
5 are rather short, indicating that the Cu2+–Cu2+ interaction
A
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Chem. Eur. J. 2008, 14, 1472 – 1481

Wirelike Copper/Palladium Strands
FULL PAPER
3a)[8]) in dichloromethane displayed a perfect mirror image
with an slightly bathochromic-shifted, enhanced absorption
at lmax =401 nm, compared to the free ligand (lmax =367 nm,
not shown), which is induced by the helicity of complexes
through d–d orbital interactions between the metal centers
into wirelike linear superstructures promises unique electro-
conductive, magnetic, and optical properties.[20,26] In the
cases of 61 and 71, the Pd2+–Pd2+ distances (Table 1) are of
length similar to the interatomic distances in metallic palla-
dium (2.74 Š),[27] but longer than the double effective ionic
radius of Pd2+ (1.72 Š)[27] and close to the double van der
Waals radius of palladium (3.26 Š).[28] These data suggest
substantial d8–d8 Pd2+–Pd2+ interactions.[20]
A
ACHTREUNG
(P)-[Pd2(L(S,S))2] (6) and (M)-[Pd2(L(R,R))2] (ent-6) (Figure 2,
bottom).[25]
Most interesting, in the solid-state helicates 5–7 self-or-
ganize into polymeric superstructures with linear threading
of the transition-metal ions, as exemplarily presented for
ACHTREUNG
(P)-[{Pd2(L(S,S))2}1] (71; Figure 4).[20d,f,26] The overlapping
van der Waals radii of the palladium ions emphasize the
close contacts of the metal ions. The intercomplexCu–Cu or
Pd–Pd van der Waals distances (dinter) amount to 3.55 (51),
3.19 (61), and 3.32 Š (71). The intercomplexaryl–aryl dis-
tances between individual cylinders are dinter =7.10, 6.46 and
6.53 Š for 51–71, respectively. In any case, no close p–p
contacts between the phenyl or naphthyl substituents in 51–
71 were observed. Stacking of planar transition complexes
In spite of oxygen donors present in the ligand backbone,
no encapsulation of alkali ions in helicates 5–7 was ob-
served, not even in solution.[10] To make accessible chiral
metallacoronates, we chose to put additional stress on the
system by varying the preferential coordination geometry at
the transition-metal center. Instead of penta- or tetracoordi-
nate copper(II) or palladium(II), we introduced hexacoordi-
N
nate nickel(II). Therefore, when H2L(S,S) (3a) was treated
with lithium hydroxide monohydrate and nickel(II) acetate
tetrahydrate in methanol at
room temperature, we isolated
neutral
heterochiral
(di-
lithium)–dinickel(II) coronate
[(Li·MeOH)2ꢀ
ACHTREUNG
AHCTREUNG
(L(S,S)
4).
)
ACHTREUNG
Crystals,
obtained
by
vapour diffusion of diethyl
ether into a solution of 8 in
methanol were subjected to
an X-ray structure analysis
(Table 1).[17,18] According to
this analysis, 8 crystallizes in
the chiral orthorhombic space
group P21212 and possesses a
dinuclear nickel(II) coronate
framework,[13b,29] composed of
2ꢁ
two ligands (L(S,S)
)
(3a)2ꢁ
and two nickel ions. Each
nickel ion has approximate oc-
tahedral coordination, consist-
ing of two m1-O donors and
two m2-O donors from each
ligand and two m2-(OMe)ꢁ
donors. Ni(1) has L- and
Ni(2) has D-configuration
(dNi–Ni =3.08 Š).[15] However,
because of the stereogenic
centers of (L(S,S))2ꢁ, 8 is not a
mesocate,[30] but rather exists
as a single enantiomer with
idealized C2 molecule symme-
try (C2 axis running through
the two nickel(II) centers).
The two halves of the nick-
el(II) coronate backbone, each
AHCTREUNG
Figure 4. Top: Stereoview of wire-like superstructure of helicate (P)-[{Pd2(L(S,S))2}n] (7n) (n=4, side view), ex-
hibiting an linear overlap of the palladium dz2 orbitals. Bottom: Stereoview of 7n (n=3, top view along the b
axis) of one independent molecule in the unit cell. C white, O grey, Pd light grey, van der Waals radii of Pd
light grey (dotted); hydrogen atoms omitted for clarity.
host a lithium cation (dLi–Li
=
6.14 Š) with approximate
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1475

R. W. Saalfrank, A. Scheurer et al.
Experimental Section
General techniques: Unless stated otherwise, all manipulations were car-
ried out under dry dinitrogen atmosphere and the solvents used were pu-
rified and dried according to standard procedures. All reagents employed
(high-grade purity materials) were commercially available and used as
supplied (Fluka, Aldrich, and Acros Organics). The enantiomerically
pure diols (2S,3S)-1,4-dimethoxy-2,3-butanediol (1a; 38715)[31] and its en-
antiomer ent-1a (38710) are available from Fluka, (S,S)-(ꢁ)-hydroben-
zoin (1b; 256269) from Aldrich. Flash chromatography was carried out
using silica gel 60 Š (230–400 mesh, Merck grade 9385). For thin-layer
chromatography (TLC), Merck silica gel 60 Š (layer: 0.20 mm) with fluo-
rescent indikator UV254 on aluminium sheets (5”10 cm) was used. Melt-
ing points were determined on a WAGNER-MUNZ apparatus and are
not corrected. IR spectra were recorded as films or powder films on a
ASI React IR-1000 spectrometer. NMR spectra were obtained from
dilute solutions in CDCl3 at approximately 258C, unless stated otherwise,
Scheme 4. Synthesis and schematic presentation of [(Li·MeOH)2ꢀ
Ni2(L(S,S) 2(OMe)2}] (8), starting from H2L(S,S) (3a).
{(D,L)-
ACHTREUNG
)
ACHTREUNG
square-pyramidal coordination of two carbonyl m2-O donors
2ꢁ
and two ether m2-O donors of one ligand (L(S,S)
)
and a m1-
and recorded on
a
JEOL EX400 spectrometer (1H 400.1 MHz, 13C
O donor of methanol (Figure 5).
100.5 MHz). The residual solvent signals were used as internal standards:
CDCl3 (1H d=7.27 ppm, 13C d=77.0 ppm), [D6]acetone (1H d=
2.05 ppm; 13C d=29.85 ppm), and [D5]bromobenzene (1H d=7.17 ppm,
13C d=122.51 ppm).[32] The resonance multiplicity is indicated as s (sin-
glet), d (doublet), t (triplet), q (quartet), and m (multiplet). In solution li-
gands H2L(S,S) (3) are present as a tautomeric mixture of the diketo, mon-
oenol, and bisenol species. Below, only signals of the dominating bisenol
form are listed. FAB-MS spectra were recorded on a Micromass ZAB-
Spec (Cs+) spectrometer with m-NBA as matrix. Circular dichroism
(CD) measurements were carried out on a JASCO J 710 spectropolarim-
eter (Xe-lamp) with optical grade solvents and quartz glass cuvettes with
a 5 mm path length. Optical rotations were measured on a Perkin Elmer
341 polarimeter. Elemental analyses were performed on a Carlo Erba
EA1110 CHN instrument and on a HERAEUS CHN-Mikroautomat.
Single-crystal X-ray structure analyses: Details of crystal data, data col-
lection and refinement are given in Table 2. X-ray data for 4b, and 5’[33]
were collected on a Nonius Kappa CCD area detector, with MoKa radia-
tion (l=0.71073 Š). The structures were solved by direct methods with
SHELXS-97[34] and refined with full-matrixleast-squares against F2 with
the SHELXL-97 program system.[35] Lorentz, polarization, and absorp-
tion corrections[36] were applied. All non-hydrogen atoms were refined
anisotropically. The positions of the hydrogen atoms were fixed in ideal
positions (riding model) and were included without refinement and with
fixed isotropic U. In case of 4b, C31–C34 of the aromatic ring are disor-
dered with a ratio of 65:35%. The occupation of the cocrystallizing
CHCl3 molecule was set to 50%, the carbon C100 of the solvate mole-
cule was refined only isotropically. In case of 5’, carbon atoms of the
phenyl substituent (C11–C16) showed disorder with an occupation of
51:49.
Figure 5. Stereoview of (dilithium)–dinickel(II) coronate [(Li·MeOH)2ꢀ-
{(D,L)-Ni2(L(S,S)
2(OMe)2}] (8), disorder and hydrogen atoms are omitted
for clarity. C white, O dark grey, Ni grey, Li light grey (dotted).
ACHTREUNG
A
)
ACHTREUNG
Conclusion
Starting from enantiomerically pure ligands H2L(S,S) (3), we
present in this contribution the efficient synthesis of three
different types of polynuclear complexes 4–8 through diaste-
reoselective self-organization. The nuclearity and the coordi-
nation geometry at the transition-metal centers of the chiral
cubic, helical, and metallacoronate systems 4–8 were con-
trolled by the appropriate choice and ratio of transition-
metal ion, alkali-metal ion, and ligand. Furthermore, heli-
cates 5–7 undergo polyassociation in the solid state to gener-
ate polymeric architectures containing linear arrays of cop-
per(II) and palladium(II) ions. The structures of complexes
4–8 were solved by the combination of mass spectrometry,
NMR spectroscopy, and single-crystal X-ray analyses. The
diastereoselectivity of the self-organization was demonstrat-
ed by circular dichroism measurements of the enantiomers
for complexes 4a and 6. Due to their optical purity and
their arrangement in the solid state, complexes 4–8 could
function as model systems for magnetochiral or electrocon-
ductive studies.
Data for 5–8 were collected on a Bruker-Nonius Kappa CCD diffractom-
eter with MoKa radiation (l=0.71073 Š), and a graphite monochromator.
The structures were solved by direct methods, and full-matrixleast-
squares refinements were carried out on F2 by using
SHELXTLNT6.12.[37] A semi-empirical absorption correction based on
multiple scans (SADABS)[38] was performed. All non-hydrogen atoms
were refined anisotropically. The hydrogen atoms were geometrically
positioned with isotropic displacement parameters being either 1.2 Ueq or
1.5 Ueq of the proceeding C atom. Disorder was found in structures 6 and
8. A number of restraints (SIMU and DFIX, respectively) were applied
in the treatment of this disorder. In the case of 6, one of the two inde-
pendent molecules showed disorder on the CH3OCH2 moiety with a re-
fined occupation of the two preferred orientations of 52.8(5) and
47.2(5)%. In 8, oxygen O3 was subjected to positional disorder with oc-
cupations of the two refined sites of 67(2)% for O3 and 33(2)% for O3’.
In addition, there was a disordered methanol solvate molecule located on
a crystallographic twofold rotation axis; no hydrogen atoms were includ-
ed for this in the structure model.
A
of (2S,3S)-1,4-dimethoxy-2,3-butanediol (S,S)-1a (4.00 g, 26.60 mmol) in
dry THF (100 mL) was added dropwise to a suspension of sodium hy-
1476
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 1472 – 1481

Wirelike Copper/Palladium Strands
FULL PAPER
Table 2. Crystal and structure refinement data for complexes 4b, 5–8.
4b
5
5’[33]
6
7
8
formula
C72H68Cu4O16·CHCl3 C68H56Cu2O12
C68H56Cu2O12
1192.21
C52H56O16Pd2
1149.77
C68H64O16Pd2
1349.99
C56H70Li2Ni2O20·0.5CH3OH
1210.44
Mr [gmolꢁ1
]
1562.88
1192.21
crystal size [mm3]
crystal system
space group
a [Š]
b [Š]
c [Š]
0.20”0.20”0.15
monoclinic
C2
0.14”0.12”0.09 0.15”0.10”0.10 0.08”0.07”0.05 0.32”0.18”0.11 0.24”0.12”0.10
monoclinic
C2
orthorhombic
I222
7.0923(5)
14.0724(6)
27.4167(18)
90
2736.3(3)
2
1.447
monoclinic
C2
orthorhombic
P21 212
29.890(3)
6.5297(4)
14.637(2)
90
2856.7(5)
2
1.569
orthorhombic
P21 212
25.555(3)
25.569(3)
8.8061(7)
90
5754.0(11)
4
1.397
28.1231(8)
6.9100(2)
21.2674(7)
114.794(2)
3751.9(2)
2
30.791(3)
7.0987(2)
27.586(2)
116.588(5)
5392.0(7)
4
29.222(2)
6.4592(3)
28.950(3)
119.578(5)
4752.3(7)
4
1.607
100(2)
0.831
b [8]
V [Š3]
Z
1calcd [Mg mꢁ3
T [K]
]
1.383
1.469
173(2)
100(2)
173(2)
0.845
100(2)
0.704
100(2)
0.730
m [mmꢁ1
]
1.288
0.858
F
(000)
1606
2472
1236
2352
1384
2548
q range [8]
indexranges
2.25 to 27.49
ꢁ35%h%36
ꢁ8%k%8
ꢁ27%l%27
8483
3.30 to 27.00
ꢁ39%h%39
ꢁ9%k%9
ꢁ35%l%35
47337
2.66 to 25.00
ꢁ8%h%8
ꢁ16%k%16
ꢁ32%l%32
2433
3.45 to 27.10
ꢁ37%h%37
ꢁ8%k%8
ꢁ37%h%37
42701
3.40 to 27.87
ꢁ39%h%39
ꢁ8%k%8
ꢁ19%l%18
26852
3.56 to 26.37
ꢁ31%h%31
ꢁ31%k%31
ꢁ10%l%10
52678
reflns collected
independent reflns
8483
11704
2433
10473
6762
11164
reflns observed [I>2s(I)] 7106
max/min transmission 0.8303/0.7828
[Rint
8341
0.926/0.823
0.0580
1978
0.9202/0.8837
0.0000
7250
0.874/0.959
0.0666
6058
0.930/0.764
0.0346
9790
0.930/0.772
0.0372
A
]
0.0000
data/parameters
8483/459
1.020
0.09(2)
0.0596
0.1720
1.305/ꢁ0.613
11704/739
1.013
0.03(2)
0.0654
0.1767
2433/202
1.014
10473/661
0.984
0.03(3)
0.0375
0.0757
6762/390
1.047
11164/751
1.134
0.05(2)
0.0501
0.1159
goodness-of-fit on F2
flack parameter[39]
final R1 [I>2s(I)]
wR2 (all data)
ꢁ0.05(3)
ꢁ0.01(2)
0.0431
0.0260
0.1220
0.413/ꢁ0.406
0.0550
0.385/ꢁ0.682
ꢁ3
largest residuals [eŠ
]
1.144/ꢁ0.545
0.439/ꢁ0.423
1.182/ꢁ0.540
dride (1.55 g, 59.00 mmol, 95%) in THF (100 mL), placed in a three-
necked, round-bottomed flask (500 mL) equipped with dropping
funnel, a refluxcondenser, and a nitrogen inlet. The reaction mixture
was stirred at room temperature for 1 h and then refluxed. After no prog-
ress of the reaction could be monitored by TLC (approx. 2 h), the sol-
vents were removed with a rotary evaporator. The crude reaction product
(yellowish oil) was further purified by column chromatography on silica
gel (i-hexane/ethyl acetate 80:20). Yield: 5.43 g (30%), colorless solid,
Rf =0.29 (i-hexane/ethyl acetate 80:20); m.p. 53–548C; [a]D =+43.7,
[a]25578 =+45.2, [a]25456 =+50.9, [a]42356 =+82.4, [a]24356 =+120.1 (c=0.01 in
CHCl3); 1H NMR: d=7.19–7.08 (m, 6H; Ar-CHmeta,para), 7.03–6.96 (m,
4H; Ar-CHortho), 4.72 (s, 2H; O-CH), 4.14 (d, J=16.4 Hz, 2H; O-
CHAHB), 4.14 (q, J=7.2 Hz, 4H; CH2-CH3), 4.06 (d, J=16.4 Hz, 2H; O-
CHAHB), 1.21 ppm (t, J=7.2 Hz, 6H; CH2-CH3) 13C NMR:[41] d=170.28
(C=O), 137.09 (Ar-Cipso), 127.99 (4C, Ar-CHmeta), 127.83 (Ar-CHpara),
127.78 (4C, Ar-CHortho), 85.95 (CH), 66.86 (O-CH2), 60.61 (O-CH2-CH3),
14.09 ppm (CH2-CH3); IR (film): n˜ =2997, 2985, 2944, 2914, 1752, 1445,
1418, 1376, 1198, 1133, 1027, 961, 702 cmꢁ1; MS: m/z (%): 387 (12)
[M+H]+, 283 (100) [MꢁOCH2CO2Et]+, 193 (93) [M/2]+, 179 (72)
a
funnel, a refluxcondenser, and a nitrogen inlet. The suspension was
stirred for further 30 min at room temperature and then a solution of
ethyl bromoacetate (6.5 mL, 58.60 mmol) in THF (100 mL) was added
slowly. After stirring overnight and refluxfor 1 h, the reaction mixture
was cautiously hydrolyzed by addition of distilled water (5 mL). The or-
ganic phase was removed (rotary evaporator, 408C) and the residue was
diluted with distilled water (20 mL). The aqueous phase was extracted
with n-pentane (3”50 mL) and the combined organic extracts were dried
over anhydrous sodium sulfate, filtered, and concentrated. The crude re-
action product was purified by vacuum distillation. Yield: 3.77 g (44%),
colorless oil; b.p. 210–2208C (ꢂ5.0·10ꢁ4 mbar); [a]D =+8.1, [a]52578 =+8.4,
25
[a]52456 =+9.4, [a]42536 =+17.2, [a] =+35.6 (c=0.01 in CHCl3); 1H NMR:
365
d=4.28 (d, J=16.8 Hz, 2H; O-CHAHB-CO), 4.26 (d, J=16.8 Hz, 2H; O-
CHAHB-CO), 4.15 (q, J=7.2 Hz, 4H; CH2-CH3), 3.77–3.72 (m, 2H; O-
CH),[40] 3.68 (pseudo dd, J=10.2, 3.0 Hz, 2H; CH-CH2),[40] 3.53 (pseudo
dd, J=10.2, 5.8 Hz, 2H; CH-CH2),[40] 3.31 (s, 6H; O-CH3), 1.23 ppm (t,
J=7.2 Hz, 6H; CH2-CH3); 13C NMR:[41] d=170.70 (C=O), 79.78 (O-CH),
72.82 (CH-CH2), 68.58 (O-CH2-C=O), 60.59 (CH2-CH3), 59.03 (O-CH3),
14.13 ppm (CH2-CH3); IR (film): n˜ =2988, 2930, 2837, 1733, 1451, 1374,
1351, 1200, 1108, 1023, 870 cmꢁ1; MS: m/z (%): 323 (71) [M+H]+, 291
(67) [MꢁOCH3]+, 277 (32) [MꢁOEt]+, 249 (21) [MꢁCO2Et]+, 161 (43)
[M/2]+, 115 (100) [M/2ꢁOEt]+; (ent-2a): Prepared in analogy to 2a,
[Mꢁ(OCH2CO2Et)2ꢁH]+;
elemental
analysis
calcd
(%)
for
C22H26O6·0.25H2O (390.95): C 67.59, H 6.83; found: C 67.51, H 6.85.
General procedure for the synthesis of H2L(S,S) (3):[9,13] A solution of
methyl ketone (35.3 mmol) in THF (50 mL) was added dropwise to a
stirred suspension of sodium amide (2.75 g, 70.4 mmol, 95%) in THF
(50 mL) at room temperature. After 10 min the resulting mixture was
treated with a solution of diester 2 (16.0 mmol) in THF (50 mL), which
was added dropwise over 5 min. The mixture was refluxed for 4 h and
after cooling the solution to room temperature, the solvent was removed.
The residue was hydrolyzed with 1m hydrochloric acid (100 mL) and ex-
tracted with ethyl acetate (3”100 mL). The combined extracts were
washed with distilled water (2”100 mL), dried over anhydrous sodium
sulfate, and filtered. Removal of the solvent afforded 3 as an oil which
crystallized at low pressure (oil pump).
starting from d-tartaric acid: [a]D =ꢁ8.0, [a]25578 =ꢁ8.1, [a]25456 =ꢁ9.3,
25
[a]24536 =ꢁ17.1, [a] =ꢁ35.5 (c=0.01 in CHCl3); elemental analysis calcd
365
(%) for C14H26O8·0.5 H2O (331.36): C 50.75, H 8.21; found: C 51.04, H
7.81.
(1S,2S)-1,2-Diphenyl-(1,2-ethylacetoxy)-ethane [(S,S)-2b]: Boron tri-
fluoride diethyl etherate (0.47 mL, 3.81 mmol) was added dropwise to a
cooled solution (08C) of (S,S)-(ꢁ)-1,2-diphenyl-1,2-ethanediol (S,S)-1b
(10.00 g, 46.60 mmol) and ethyl diazoacetate (11.7 mL, 93.20 mmol,
AHCTREUNG
ꢂ10% dichloromethane) in dichloromethane (100 mL), placed in
a
three-necked, round-bottomed flask (250 mL) equipped with a dropping
Chem. Eur. J. 2008, 14, 1472 – 1481
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1477

R. W. Saalfrank, A. Scheurer et al.
erence [8]. 1H NMR ([D5]bromobenzene): d=16.61 (brs, 2H; OH), 8.05
(dd, J=8.5, 1.3 Hz, 4H; Ar-CHortho), 7.47–7.40 (m, 2H; Ar-CHpara), 7.40–
7.33 (m, 4H; Ar-CHmeta), 6.91 (s, 2H; =CH), 4.58 (d, J=16.7 Hz, 2H; O-
CHACHB), 4.53 (d, J=16.7 Hz, 2H; O-CHACHB), 4.06–3.99 (m, 2H; O-
CH),[40] 3.82 (pseudo dd, J=10.4, 2.9 Hz, 2H; CH-CH2),[40] 3.74 (pseudo
dd, J=10.4, 6.0 Hz, 2H; CH-CH2),[40] 3.40 ppm (s, 6H; O-CH3);
13C NMR ([D5]bromobenzene):[41] d=194.93 (C=O), 183.10 (C-OH),
134.77 (Ar-Cipso), 132.51 (Ar-CHpara), 128.72 (4C, Ar-CHmeta), 127.33 (4C,
Ar-CHortho), 93.84 (=CH), 80.10 (O-CH), 72.78 (O-CH2), 72.51 (CH-
CH2), 59.11 ppm (O-CH3).
973, 845, 760, 703 cmꢁ1; MS: m/z (%): 1325 (23) [Cu2L2+Cs]+ (Cs+ from
the matrix), 1255 (73) [Cu3L2]+, 1215 (23) [Cu2L2+Na]+ (Na+ from the
matrix), 1193 (38) [Cu2L2]+, 721 (38) [Cu3L]+, 659 (62) [Cu2L]+, 597
(100) [CuL+H]+; elemental analysis calcd (%) for C72H68Cu4O16
(1443.50): C 59.91, H 4.75; found: C 60.15, H 4.55.
AHCTREUNG
A
N
124 mg (82%), green crystals from dichloromethane; m.p. >1998C
(decomp); IR: n˜ =3026, 2921, 2860, 2811, 1586, 1567, 1519, 1445, 1414,
1356, 1339, 1291, 1285, 1200, 1179, 1133, 1106, 1077, 1038, 976, 863, 780,
758 cmꢁ1; MS: m/z (%): 1397 (13) [Cu2L2+Cs]+ (Cs+ from the matrix),
1327 (47) [Cu3L2]+, 1287 (33) [Cu2L2+Na]+ (Na+ from the matrix), 1265
(100) [Cu2L2+H]+, 759 (25) [Cu3L]+, 695 (82) [Cu2L]+, 633 (61)
[CuL+H]+; elemental analysis calcd (%) for C72H76Cu4O20 (1515.56): C
57.06, H 5.05; found: C 56.85, H 4.92.
A
dione [(S,S)-3b]: Diester (S,S)-2b (6.18 g), acetophenone (4.12 mL);
yield: 1.80 g (21%), slightly pink-colored crystals from methanol, Rf =
0.29 (i-hexane/ethyl acetate 80:20); m.p. 108–1098C; [a]D =+108.5,
[a]25578 =+113.5, [a]52456 =+132.8, [a]42356 =+290.2 (c=0.01 in CHCl3);
1H NMR: d=15.91 (brs, 2H; OH), 7.85–7.78 (m, 4H; Ar-CHortho), 7.53–
7.45 (m, 2H; Ar-CHpara), 7.44–7.33 (m, 4H; Ar-CHmeta), 7.24–7.16 (m,
6H; CH-Ar-CHmeta,para), 7.12–7.03 (m, 4H; CH-Ar-CHortho), 6.81 (s, 2H; =
CH), 4.71 (s, 2H; O-CH), 4.24 (d, J=16.9 Hz, 2H; O-CHAHB), 4.09 ppm
(d, J=16.9 Hz, 2H; O-CHAHB); 13C NMR:[41] d=194.49 (C=O), 183.42
(C-OH), 136.97 (CH-Ar-Cipso), 134.39 (Ar-Cipso), 132.51 (Ar-CHpara),
128.53 (4C, Ar-CHortho meta), 128.24 (4C, CH-Ar-CHortho meta), 128.15
AHCTREUNG
(P)-[Cu2(L(S,S))2] (5)[33]: Tetraketone 3b (54 mg, 0.10 mmol) was dissolved
in boiling methanol (2 mL) in the presence of potassium acetate (49 mg,
0.50 mmol). After approximately 2 min, a solution of copper(II) acetate
monohydrate (20 mg, 0.10 mmol) in methanol (2 mL) was added drop-
wise and the reaction mixture was stirred after cooling to room tempera-
ture for further 30 min. After filtration over celite and dilution of the
mother liquor by addition of acetone (4 mL), green prisms suitable for
X-ray structure analysis were obtained by vapor diffusion of diethyl
ether. Yield: 57 mg (95%); m.p. >2358C (decomp); IR: n˜ =3069, 3034,
2922, 2891, 2833, 1594, 1563, 1513, 1486, 1455, 1420, 1378, 1336, 1258,
1173, 1131, 1089, 1027, 973, 842, 753, 703 cmꢁ1; MS: m/z (%): 1215 (100)
[Cu2L2+Na]+ (Na+ from the matrix), 1193 (18) [Cu2L2+H]+, 681 (26);
or
or
(CH-Ar-CHpara), 127.97 (4C, CH-Ar-CHortho or meta), 127.14 (4C, Ar-CHortho
meta), 93.70 (=CH), 86.44 (O-CH), 70.69 ppm (O-CH2); n˜ =3134, 3065,
or
3030, 2895, 2833, 1598, 1575, 1471, 1424, 1343, 1266, 1212, 1108, 1027,
695 cmꢁ1
;
MS: m/z (%): 536 (35) [M+H]+, 357 (100)
[MꢁOCH2COCH2COPh]+,
267
(41)
[M/2]+,
161
(43)
elemental analysis calcd (%) for C68H56Cu2O12·0.5H2O (1201.28):
C
[CH2COCH2COPh]+; elemental analysis calcd (%) for C34H30O6
(534.61): C 76.39, H 5.66; found: C 76.10, H 5.78.
67.99, H 4.78; found: C 68.15; H 4.63.
AHCTREUNG
General procedure for synthesis of helicates (P)-[Pd2(L(S,S))2] (6,7): Tetra-
ketone 3a or c (0.05 mmol) was dissolved in boiling methanol (2 mL) in
the presence of pyridine (16 mL, 0.20 mmol). After approximately 2 min,
(2S,3S)-1,1’-Di-(2-naphthyl)-4,4’-(1,4-dimethoxy-2,3-butanedioxy)dibu-
tane-1,3-dione [(S,S)-3c]: Diester (S,S)-2a (5.16 g), 2-acetonaphthone
(6.01 g); yield: 0.548 g (6%), beige microcrystalline material from metha-
nol, Rf =0.47 (i-hexane/ethyl acetate 60:40); m.p. 83–848C; [a]D =+16.1,
a
solution of palladium(II) acetate (23 mg, 0.10 mmol) in methanol
(2 mL) was added dropwise and the reaction mixture was stirred after
cooling to room temperature for further 2 h. After concentration of the
solvent (ca. 1 mL; rotary evaporator, 408C) and filtration over celite, an
orange microcrystalline material was obtained by vapor diffusion of di-
ethyl ether.
25
436
1
[a]52758 =+17.7, [a]25456 =+22.2, [a] =+79.3 (c=0.01 in CHCl3); H NMR:
d=15.95 (brs, 2H; OH), 8.40 (s, 2H; Ar-C-H), 7.87 (d, J=8.5 Hz, 2H;
Ar-C-H), 7.86 (d, J=8.8 Hz, 2H; Ar-C-H), 7.91–7.75 (m, 8H; Ar-C-H),
6.78 (s, 2H; =CH), 4.47 (d, J=16.6 Hz, 2H; O-CHAHB), 4.38 (d, J=
16.6 Hz, 2H; O-CHAHB), 3.91–3.85 (m, 2H; O-CH),[40] 3.74 (pseudo dd,
J=10.4, 2.8 Hz, 2H; CH-CH2),[40] 3.62 (pseudo dd, J=10.4, 5.6 Hz, 2H;
CH-CH2),[40] 3.41 ppm (s, 6H; O-CH3); 13C NMR:[41] d=194.68 (C=O),
182.68 (C-OH), 135.25 (Ar-Cipso), 132.63 (Ar-C), 131.60 (Ar-C), 129.28
(Ar-C-H), 128.35 (Ar-C-H), 128.09 (4C, Ar-C-H), 127.68 (Ar-C-H),
126.71 (Ar-C-H), 123.00 (Ar-C-H), 93.94 (=CH), 79.96 (O-CH), 72.74
(O-CH2), 72.09 (CH-CH2), 59.30 ppm (O-CH3); IR: n˜ =3058, 2892, 2848,
AHCTREUNG
(P)-[Pd2(L(S,S))2] (6): Bis-1,3-diketone 3a (24 mg); yield: 27 mg (92%);
yellow prisms suitable for X-ray analysis from [D6]acetone; m.p. >2208C
(decomp); 1H NMR ([D6]acetone):[24] d=7.62–7.52 (m, 6H; Ar-
CHortho,para), 7.41–7.33 (m, 4H; Ar-CHmeta), 5.27 (s, 2H; =CH), 4.38 (d, J=
17.6 Hz, 2H; O-CHACHB), 4.36–4.31 (m, 2H; O-CH),[40] 4.29 (d, J=
17.6 Hz, 2H; O-CHACHB), 3.81 (d, J=8.8 Hz, 2H; CH-CHAHB),[40] 3.50–
3.42 (m, 2H; CH-CHAHB, partially hidden by the singlet of OCH3),[40]
3.49 ppm (s, 6H; O-CH3); 13C NMR ([D6]acetone):[41] d=189.82 (Ar-C=
O), 177.72 (C=O), 135.84 (Ar-Cipso), 132.26 (Ar-CHpara), 128.80 (4C, Ar-
CHortho), 128.76 (4C, Ar-CHmeta), 93.96 (=CH), 79.86 (O-CH), 74.88 (O-
2819, 1602, 1590, 1567, 1453, 1387, 1328, 1273, 1227, 1111, 1048, 816 cmꢁ1
;
MS: m/z (%): 571 (31) [M+H]+, 211 (39) [CH2COCH2COC10H7]+, 197
(20) [COCH2COC10H7]+, 155 (100) [COC10H7]+; elemental analysis calcd
(%) for C34H34O8 (570.64): C 71.56, H 6.01; found: C 71.39, H 6.08.
CH2),
73.54
(CH-CH2),
59.81 ppm
(O-CH3);
1H NMR
AHCTREUNG
General procedure for synthesis of cubanes [Cu4(L(S,S)
)2(OMe)4] (4): A
A
([D5]bromobenzene):[24] d=7.80 (m, 4H; Ar-CHortho), 7.62–7.55 (m, 2H;
Ar-CHpara), 7.50–7.44 (m, 4H; Ar-CHmeta, partially hidden by solvent re-
sidual peaks), 5.33 (s, 2H; =CH), 4.80 (d, J=7.3 Hz, 2H; O-CH),[40] 4.67
(d, J=17.3 Hz, 2H; O-CHACHB), 4.47 (d, J=17.3 Hz, 2H; O-CHACHB),
4.18 (d, J=9.3 Hz, 2H; CH-CH2),[40] 3.77 (dd, J=9.3, 7.3 Hz, 2H; CH-
CH2),[40] 3.55 ppm (s, 6H; O-CH3); 13C NMR ([D5]bromobenzene):[41] d=
188.65 (Ar-C=O), 177.15 (C=O), 135.38 (Ar-Cipso), 128.39 (4C, Ar-
CHortho), (Ar-CHpara hidden by solvent residual peaks), 127.97 (4C, Ar-
CHmeta), 93.54 (=CH), 79.28 (O-CH), 74.55 (CH-CH2), 73.20 (O-CH2),
59.67 ppm (O-CH3); IR: n˜ =2980, 2903, 2810, 1590, 1567, 1513, 1486,
1455, 1417, 1336, 1274, 1204, 1274, 1204, 1139, 1112, 1081, 1031, 1000,
973, 953, 930, 865, 795, 753 cmꢁ1; MS: m/z (%): 1283 (2) [Pd2L2+Cs]+
(Cs+ from the matrix), 1255 (3) [Pd3L2]+, 1151 (100) [Pd2L2+H]+, 681
(14) [Pd2L]+, 575 (21) [PdL]+; elemental analysis calcd (%) for
C52H56O16Pd2·0.5 H2O (1158.81): C 53.90, H 4.96; found: C 53.96, H 4.98.
Complex ent-6 was prepared in analogy to 6 from H2L(R,R) (ent-3a).[8]
hot solution of copper(II) acetate monohydrate (80 mg, 0.40 mmol) in
methanol (8 mL) was added dropwise to a refluxing solution of H2L(S,S)
(3) (0.20 mmol) and cesium acetate (39 mg, 0.20 mmol) in methanol
(4 mL) (for the synthesis of 4b potassium acetate (39.3 mg; 0.40 mmol)
was used instead of cesium acetate). The reaction mixture was allowed to
cool to room temperature and stirred for 30 min. After removal of the
solvent (rotary evaporator, 408C), the deep green residue was treated re-
peatedly (6”) with methanol (12 mL), which was removed by evapora-
tion. The crude reaction product was suspended in methanol (12 mL),
and the turquoise powder was filtered off. After drying under vacuum
(oil pump), the solid material was crystallized from the indicated solvent
by layering with methanol.
A
ACHTREUNG
A
)
G
N
(ent-4a): For the experimental data of copper(II) cubanes 4a and ent-4a,
see reference [8].
R
ACHTREUNG
A
)
A
(P)-[Pd2(L(S,S))2] (7): Bis-1,3-diketone 3c (29 mg); yield: 32 mg (95%);
130 mg (90%), dark-green cuboids suitable for X-ray analysis from
chloroform; m.p. >2108C (decomp); IR: n˜ =3061, 3034, 2918, 2899, 2810,
1594, 1563, 1521, 1486, 1451, 1413, 1343, 1282, 1193, 1119, 1089, 1027,
yellow right parallelepipeds suitable for X-ray analysis from
[D5]bromobenzene;
m.p.
>2208C
(decomp);
1H NMR
([D5]bromobenzene):[24] d=8.25 (dd, J=8.7, 1.7 Hz, 2H; Ar-CH), 8.06 (d,
1478
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Wirelike Copper/Palladium Strands
FULL PAPER
J=8.7 Hz, 2H; Ar-CH), 8.00 (d, J=8.7 Hz, 2H; Ar-CH), 7.85 (s, 2H; Ar-
CH), 7.70–7.63 (m, 4H; Ar-CH), 7.62–7.55 (m, 4H; Ar-CH), 5.50 (s, 2H;
=CH), 4.92 (d, J=7.1 Hz, 2H; O-CH),[40] 4.78 (d, J=17.2 Hz, 2H; O-
CHACHB), 4.48 (d, J=17.2 Hz, 2H; O-CHACHB), 4.30 (d, J=9.2 Hz, 2H;
CH-CH2),[40] 3.96–3.89 (dd, J=9.2, 7.1 Hz, 2H; CH-CH2),[40] 3.68 ppm (s,
6H; O-CH3); 13C NMR ([D5]bromobenzene):[41] d=188.50 (Ar-C=O),
177.34 (C=O), 135.01 (Ar-Cipso), 133.12 (Ar-Cipso), 132.55 (Ar-Cipso),
131.80–122.20 (7 Ar-C-H-signals hidden by solvent residual peaks), 94.23
(=CH), 79.50 (O-CH), 74.44 (CH-CH2), 73.19 (O-CH2), 59.78 ppm (O-
CH3); IR: n˜ =3057, 2976, 2926, 2845, 2810, 1567, 1505, 1436, 1417, 1328,
1270, 1200, 1135, 1104, 1069, 978, 950, 857, 772, 753 cmꢁ1; MS: m/z (%):
1351 (100) [Pd2L2+H]+; elemental analysis calcd (%) for
C68H64O16Pd2·0.5 H2O (1359.05): C 60.10, H 4.82; found: C 60.07, H 4.88.
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AHCTREUNG
A
G
A
monohydrate (8 mg, 0.20 mmol) was added to a solution of tetraketone
3a (48 mg, 0.1 mmol) in methanol (2 mL). After stirring for approximate-
ly 2 min,
a
solution of nickel(II) acetate tetrahydrate (16 mg,
0.066 mmol) in methanol (2 mL) was added dropwise and the reaction
mixture was stirred for further 30 min at room temperature. After filtra-
tion of the turquoise solution over celite, green microcrystals were ob-
tained by vapor diffusion of diethyl ether. Yield: 19 mg (48%); green
right parallelepipeds suitable for X-ray analysis by recrystallization from
methanol and vapor diffusion of diethyl ether. M.p. >2108C (decomp);
IR: n˜ =2988, 2934, 2883, 2829, 1594, 1571, 1521, 1471, 1432, 1339, 1274,
1239, 1193, 1108, 1081, 1027, 977, 930, 853, 799, 764, 718, 695 cmꢁ1; MS:
m/z (%): 1543 (10) [Ni2L3+Li3]+, 1220 (27) [Ni3L2
(7) [Ni2L2
(OMe)2+Li2]+, 1097 (10) [Ni2L2
ACHTREUNG
A
ACHTREUNG
[Ni2L2+Li]+, 533 (38) [NiL+Li]+; elemental analysis calcd (%) for
C56H70Li2Ni2O20·0.5 H2O (1203.47): C 55.89, H 5.95; found: C 55.69, H
5.86.
Acknowledgements
This work was supported by the Deutsche Forschungsgemeinschaft SPP
1137 “Molecular Magnetism” (SA 276/26-1–3), SA 276/27-1–2, SA 276/
29-1, SFB 583, GK 312, the Bayerisches Langzeitprogrammm Neue
Werkstoffe, and the Fonds der Chemischen Industrie. The generous allo-
cation of premises by Prof. Dr. K. Meyer at the Institut für Anorganische
Chemie (Universität Erlangen-Nürnberg) is gratefully acknowledged.
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AHCTREUNG
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Chem. Eur. J. 2008, 14, 1472 – 1481

Wirelike Copper/Palladium Strands
FULL PAPER
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1
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3a,c as well as complexes 6 and 7 are consistent with a symmetrical
AA’BB’CC’ six-spin system.[8,11]
[33] If sodium acetate (0.50 mmol, 41.0 mg) was used instead of potassi-
um acetate in the synthesis of 5 (otherwise identical reaction condi-
tions),[21] a green solid material could be isolated by filtration after
stirring for further 30 min at room temperature. Dissolution of the
precipitate was achieved in a mixture of methanol/acetone/dichloro-
[41] Due to the C2 symmetry of compounds 2, 3, 6, and 7, each observed
resonance in the 13C spectra originates from two carbon atoms,
unless stated otherwise.
Received: September 28, 2007
Published online: January 9, 2008
Chem. Eur. J. 2008, 14, 1472 – 1481
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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