Shape takes the lead: Templating organic 3D-frameworks around organometallic sandwich compounds

Article abstract of DOI:10.1021/om200837t

The novel organic-organometallic crystalline compounds [(η⁵- C₅H₅)₂Co][(cis-deccaH)(cis-deccaH₂)] (1), [(η⁵-C₅H₅)₂Co][(cis- deccaH)(cis-deccaH₂)]?H₂O (2), [(η⁵- C₅H₅)₂Co][trans-deccaH] (3), [(η⁵-C₅H₅)₂Co][(trans-deccaH) (trans-deccaH₂)] (4), [(η⁵-C₅Me ₅)₂Co][cis-deccaH] (5), [(η⁵-C ₅Me₅)₂Co][trans-deccaH]?4H₂O (6), and [(η⁶-C₆H₆)₂Cr][trans- deccaH] (7) have been prepared by direct reaction of neutral [(η⁵-C₅H₅)₂Co], [(η⁵-C₅Me₅)₂Co], and [(η⁶-C₆H₆)₂Cr] with the organic compounds cis-9,10-dihydroanthracene-9,10-α,β-succinic acid anhydride and trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (cis-decca and trans-deccaH₂, respectively). The organic building blocks have been chosen because of their three-stem star-like shape and the difference in hydrogen-bonding capacity. It is shown that the formation of a honeycomb-type anionic arrangement around the organometallic cations does not require the assistance of strong hydrogen-bonding interactions. Depending on the stoichiometric ratio and on the presence of water molecules, rectangular and layered crystal packings are also obtained.

Full text of DOI:10.1021/om200837t

Article
pubs.acs.org/Organometallics
Shape Takes the Lead: Templating Organic 3D-Frameworks around
Organometallic Sandwich Compounds
Dario Braga,* Simone d’Agostino, and Fabrizia Grepioni
̀
Dipartimento di Chimica G. Ciamician, Alma Mater Studiorum Universita di Bologna,Via Selmi 2, 40126 Bologna, Italy
S
* Supporting Information
ABSTRACT: The novel organic−organometallic crystalline
compounds [(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)] (1),
[(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)]·H2O (2), [(η5-
C5H5)2Co][trans-deccaH] (3), [(η5-C5H5)2Co][(trans-
deccaH)(trans-deccaH2)] (4), [(η5-C5Me5)2Co][cis-deccaH]
(5), [(η5-C5Me5)2Co][trans-deccaH]·4H2O (6), and [(η6-
C6H6)2Cr][trans-deccaH] (7) have been prepared by direct
reaction of neutral [(η5-C5H5)2Co], [(η5-C5Me5)2Co], and
[(η6-C6H6)2Cr] with the organic compounds cis-9,10-dihy-
droanthracene-9,10-α,β-succinic acid anhydride and trans-9,
10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (cis-decca and trans-deccaH2, respectively). The organic building
blocks have been chosen because of their three-stem star-like shape and the difference in hydrogen-bonding capacity. It is shown
that the formation of a honeycomb-type anionic arrangement around the organometallic cations does not require the assistance
of strong hydrogen-bonding interactions. Depending on the stoichiometric ratio and on the presence of water molecules,
rectangular and layered crystal packings are also obtained.
number, and geometry of the −OH/−COOH/COO− groups
INTRODUCTION
■
around the cationic sandwich. The regular cylindrical shape of
these cations appeared to play a role in directing the assembly
of the anionic frameworks, also with the participation of C−
H···O interactions between the acceptor sites on the networks
and the C−H groups protruding from the complex surface.11
The relevance of interanionic hydrogen bonds sustained by the
presence of nonparticipating cations (such as the organo-
metallic sandwiches) has also been addressed by computational
studies.12 Early examples of this strategy are the compounds
[Co(η5-C5H5)2][(D,L-taH)·(D,L-taH2] and [Co(η5-C5H5)2]-
[L-taH], which were obtained with D,L- and L-tartaric acid
(D,L-taH2 and L-taH2) respectively.13 With oxalic acid (oxaH2),
compounds [Fe(η5-C5Me5)2][(oxaH)(oxaH2)0.5] and [Cr(η6-
C6H6)2][oxaH]·H2O were prepared,14 while compounds [Cr-
(η6-C6H6)2][sqaH] and {[Cr(η6-C6H6)2]}2[sqa]·6H2O were
prepared with squaric acid (sqaH2).15 With phthalic (paH2) and
terephthalic acids (tpaH2) the compounds {[Co(η5-C5H5)2]}4-
[(paH2)(pa)]·4H2O, [Cr(η6-C6H6)2][(paH)(paH2)], and
{[Co(η5-C5H5)2]}2[tpa]·6H2O were prepared,16 while with
trimesic acid (tmaH3) [Co(η5-C5H5)2][(tmaH2)(tmaH3)]·
2H2O was obtained,17 and with R-binaphtol (R-bnH2) were
prepared [Co(η5-C5H5)2][(R-bnH)(RbnH2)], and [Co(η5-
C5H5)2][(R-bnH)(R-bnH2)0.5].18,19
Making crystals by design is the paradigm of crystal engineering,
an area of solid-state chemistry that encompasses molecular
crystals and materials.1 The assembly of building blocks into
frameworks with predefined architectural (hence functional)
features requires control over the interactions that are chosen to
glue together the molecular or ionic components. It is un-
questionable that, although the attention of researchers has
been and is attracted by the whole range of possible supra-
molecular interactions, the hydrogen bond has taken the lion’s
share in crystal engineering studies.2 The role of strong π−π
stacking interactions in the stabilization of homochiral, helical
metal−organic frameworks has also been recently explored.3
The number of papers dealing with hydrogen-bonded organic,
inorganic, and organometallic building blocks is very large and
still increasing. The reason for this interest stems from the
potential applications of organometallic and metal−organic frame-
works in diverse areas such as gas storage4 and sensing,5 but
also catalysis6 and separations,7 among others.
We have contributed with a number of studies dealing with
hydrogen-bonded networks formed by organic or inorganic
molecules and ions templated by organometallic sandwich cations
such as [Co(η5-C5H5)2]+, [Cr(η6-C6H6)2]+, [Fe(η5-C5Me5)2]+,
and [Co(η5-C5Me5)2]+.8−10 In all these cases the design
criterion was based on the idea of confining all strong donor/
acceptor hydrogen-bonding groups on the organic or inorganic
(usually anionic) networks while excluding the organometallic
fragments (usually cationic) from the direct participation in the
hydrogen bonds. This strategy has led to hydrogen-bonded
superstructures, whose topology depends on the size, shape,
In this paper we report an extension of these studies aimed at
understanding the relationship between hydrogen-bonding
capability and shape of the building blocks and how the shape
Received: September 6, 2011
Published: February 13, 2012
© 2012 American Chemical Society
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Article
of the sandwich cation may act as a template for the aggrega-
tion of monoanions, all containing carboxylic and carboxylate
groups, in 3-D networks. In the cases discussed herein the
hydrogen-bonding interaction is confined either within the
discrete units (0-D bricks) or between ions in the formation of
1-D stripes and channels, while the global architecture depends
on shape recognition between building blocks. In other words,
we attempt to address the question of whether the absence of
extramolecular hydrogen-bonding capacity because of the for-
mation exclusively of intramolecular bonds of no hydrogen-
bonding capacity within organic dicarboxylic acids or anhy-
drates would lead, in the presence of the same sandwich cations
as used in all cases referred to above, to different architectures.
To this end we have selected and synthesized20 two organic
building blocks, namely, the dicarboxylic acid trans-9,
10-dihydroethanoanthracene-11,12-dicarboxylic acid (trans-
deccaH2) and the anhydrate cis-9,10-dihydroanthracene-9,10-
α,β-succinic acid anhydride (cis-decca). Sketches are provided
in Scheme 1. Upon hydrolysis, the latter generates the monoanion
exploited. More specifically the spontaneous oxidation by oxy-
gen of the neutral complexes cobaltocene, decamethyl cobal-
tocene, and bisbenzene chromium generates the strongly basic
anion O2−, which is able to fully or partially deprotonate the
polyprotic acids, depending on the stoichiometric ratio. Since
the oxidation products, namely, the cations [(η5-C5H5)2Co]+,
[Co(η5-C5Me5)2]+, and [(η5-C6H6)2Cr]+, are not suitable for
coordination by the −COO− groups, self-assembly of the
neutral or deprotonated polycarboxylic acid moieties is promoted.
RESULTS AND DISCUSSION
■
Table 2 summarizes chemical information for the compounds
part of this study. A brief description of the salient structural
features will be provided in the following.
Table 1
formula
no.
[(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)]
[(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)]·H2O
[(η5-C5H5)2Co][trans-deccaH]
[(η5-C5H5)2Co][(trans-deccaH)(trans-deccaH2)]
[(η5-C5Me5)2Co][cis-deccaH]
[(η5-C5Me5)2Co][(trans-deccaH)]·4H2O
[(η6-C6H6)2Cr][(trans-deccaH)]
1
2
3
4
5
6
7
Scheme 1. (Left) 9,10-Dihydroanthracene-9,10-α,β-succinic
a
Acid Anhydride; (Right) trans-9,10-Dihydro-
ethanoanthracene-11,12-dicarboxylic Acid (trans-deccaH2)
The anhydrous [(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)]
(1) and the monohydrate [(η5-C5H5)2Co][(cis-deccaH)(cis-
deccaH2)]·H2O (2) crystalline salts share similar features and
will be discussed together. In both crystalline 1 and 2 a neutral
diacid molecule and a monodeprotonated unit interact via an
−
O(H)COOH···OCOO hydrogen bond [O···O distances 2.604(2)
and 2.691(3) Å for 1 and 2, respectively], thus forming the
supramolecular anion [(cis-deccaH)(cis-deccaH2)]− shown in
Figure 1. These supramolecular anions are all connected via
a
We name the corresponding cis-acid as cis-deccaH2.
−
cis-9,10-dihydro-9,10- ethanoanthracene-11-carboxylate-12-carboxylic
acid (cis-deccaH)−.
In order to promote assembly around the organometallic
cations, a combination of redox and acid−base processes are
intermolecular hydrogen bonds of the kind O(H)COOH···OCOO
[O···O distances 2.595(2), 2.666(3), and 2.619(3) Å for 1 and
2, respectively], originating tape motifs that extend along the
crystallographic a-axis, as shown in Figure 2. The two moieties
Table 2. Crystal Data and Details of Measurements for Compounds 1−7
1
2
3
4
5
6
7
formula
C46H37O8Co
triclinic
C46H39O9Co
orthorhombic
Pnma
4
C28H23O4Co
monoclinic
Cc
C46H37O8Co
monoclinic
P21/n
C76H86O8 Co2
triclinic
C38H51O8Co
monoclinic
C2/c
C30H25O4Cr
monoclinic
Cc
cryst syst
space group
Z
P1
̅
2
P1
̅
2
4
4
4
4
a (Å)
6.9519(2)
8.8643(4)
30.6884(9)
87.744(3)
87.644(2)
77.553(3)
776.69
12.948
32.013
9.058
15.9614(9)
9.8616(5)
14.7153(9)
90
9.446(2)
22.886(4)
17.238(3)
90
12.5536(6)
14.6337(7)
17.4280(8)
88.839(4)
89.410(4)
79.904(4)
1245.31
3151.32(1)
1.312
14.0376(7)
19.4515(6)
14.9838(7)
90
16.3726(9)
9.9754(6)
14.5407(8)
90
b (Å)
c (Å)
α (deg)
90
β (deg)
90
105.083(7)
90
100.653(18)
90
118.555(6)
90
104.215(6)
90
γ (deg)
90
fw
V (Å3)
Dcalc (Mg/m3)
μ (mm−1)
no. of collected reflns
no. of indep reflns
794.70
3754.6
1.406
481.39
2236.5(2)
1.433
776.69
3662(1)
1.409
693.72
3593.7(3)
1.286
501.50
2302.1(2)
1.447
1844.2(1)
1.399
0.523
0.517
0.801
0.527
0.584
0.528
0.534
40 270
27 427
3914
5109
13 743
7207
25 385
10 720
4063
17 557
7472
8892
3042
14 115
a
2
R1[on Fo , I > 2σ(I)]
0.0543
0.1415
0.0412
0.0833
293
0.0524
0.1011
293
0.0909
0.0643
0.1798
293
0.0487
0.0941
293
wR2 (all data)
0.1091
0.4494
293
0.2633
T (K)
293
150
a
Crystal data for this compound were not of high quality; part of the reason is probably the heavy disorder shown by the structure (see above).
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Figure 1. (a) Ball-and-stick representation of the supramolecular anion
[(cis-deccaH)(cis-deccaH2)]− in crystalline 1 and 2 (only one of the
possible images due to COOH/COO− disorder is shown here for 2).
HCH is omitted for clarity.
are oriented differently with respect to each other within the
two supramolecular anions (Figure 1); this is probably a
consequence of the presence of one water molecule in 2, which
participates in the hydrogen bonds along the tape (Figure 2b).
Figure 3. Space-filling representation of the juxtaposition of phenyl
groups on adjacent tapes in 1 (top) and 2 (bottom). HCH atoms are
omitted for clarity.
Figure 4. Projections along the crystallographic a-axis of the crystalline
packing in 1 (a) and 2 (b); the walls and channels generated via tape
interlocking are filled with the [(η5-C5H5)2Co] cations. On the right
side of each figure the cations (carbon atoms in orange) have been
artificially removed, to show the anionic superstructures; HCH atoms
are omitted for clarity. The cations in 2 are disordered over two
equivalent positions.
Figure 2. Ball-and-stick representation of the hydrogen-bonded tapes
extending along the crystallographic a-axis in (a) anhydrous (1) and
(b) monohydrated (2) [(η5-C5H5)2Co][(cis-deccaH)(cis-
deccaH2)]·H2O (only one of the possible images due to COOH/
COO− groups disorder is shown here for 2). Blue spheres in 2 represent
water molecules. HCH atoms are omitted for clarity.
In the crystal architecture of [(η5-C5H5)2Co][(trans-
deccaH)] (3) the organic superstructure recalls a honeycomb
scaffold with large and almost hexagonal channels extending
along the c-axis. The channels are occupied by columnar piles
of organometallic cations, as represented in Figure 5.
One of the two COO(H) groups on the two moieties in 2
(which are related by symmetry) is affected by disorder over
two positions; only one of the possible images of the supra-
molecular anion is shown in both Figures 1b and 2b.
The tapes are interlocked, taking advantage of the shape
factor: the aromatic rings belonging to adjacent tapes are
juxtaposed, so that geometrical complementarity is satisfied; no
π-stacking interactions, though, are present, as in 1 and 2 the
distance between the phenyl groups is 3.7 and 3.9 Å, re-
spectively, therefore much larger than the one usually associated
with π-stacking interactions21 (see also Figure 3). This is not
surprising, as the interacting dimers are both negatively charged;
that is, their interaction has to be repulsive.
The tape interlocking generates walls and channels, in which
the cations are accommodated in infinite piles that run along
the a-axis (see Figure 4). In compound [(η5-C5H5)2Co][(cis-
deccaH)(cis-deccaH2)]·H2O (2), which is affected by orienta-
tional disorder of the cobalticinium moieties, the channels
are wider and accommodate the disordered cations with their
molecular axes perpendicular to the channel direction (see
Figure 4b).
Figure 5. (a) Space-filling representation of the channels formed by
the [trans-deccaH]− anions in crystalline 3; (b) the channels are
accommodating the cobalticinium piles extending along the c-axis. HCH
atoms are omitted for clarity.
The carboxylic and carboxylate groups do not participate in
significant interactions between the anions, but are involved in
−
a short intramolecular hydrogen bond (OCOO ···OCOOH
=
2.473(6) Å; see Figure 6); in this respect the system behaves
quite differently from other geometrically related systems, i.e.,
tartaric, terephthalic, etc.,13,16 in which intermolecular hydrogen
bonds are responsible for the generation of the 3-D superanion
networks. Contrary to what was observed earlier in the case
of the adduct between cobalticinium and D,L-tartaric acid, for
Crystallization in the presence of one equivalent or an excess
(two equivalents) of anhydride invariably results in the forma-
tion of 2, and it has not been possible, so far, to obtain a salt in
which the neutral form of the acid is absent.
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cobalticinium cations fit within each cavity with their axes per-
pendicular to the a-axis direction.
In the case of compound [(η5-C5Me5)2Co][cis-deccaH] (5)
there are two independent cations and two anions of (cis-
deccaH)− in the asymmetric unit. The decamethylcobalticinium
cations are much more demanding in terms of space with
respect to the smaller cobalticinium ones. This results in a dif-
ferent superstructure consisting of adjacent cationic [(η5-C5Me5)2-
Co]+ piles forming an almost layered packing alternated by
organic anionic planes. In addition to this, the carboxylic/
carboxylate functions, localized on the anion, form very short
Figure 6. Intramolecular hydrogen bond observed in the (trans-
deccaH)− anion. HCH is omitted for clarity.
−
intramolecular hydrogen bonds [OCOOH···OCOO = 2.395(8)
and 2.384(10) Å]. See Figure 9.
In the crystal structure of compound [(η5-C5Me5)2Co]-
[(trans-deccaH)]·4H2O (6) we observe the presence of an R4
cyclic water tetramer (shown in blue in Figure 10)22 held to-
gether by hydrogen bonds [Ow···Ow distances in the range
2.882(10)−2.992(8) Å, Ow···Ow···Ow angles in the range
101.7(4)−103.9(7)° and 71.1(5)−74.0(6)°], in a sort of
“butterfly” conformation (dihedral angle ca. 151°). To the
best of our knowledge this conformation is unusual because (i)
it strongly deviates from planarity and (ii) two angles are much
smaller than those usually observed for these kinds of clusters.
The majority of water tetramers either predicted23 or ob-
served24 are planar or quasi-planar, with angles ranging from ca.
90° to ca. 125°. In crystalline 6 H-atoms could not be directly
located from a Fourier difference map, but a possible distri-
bution is presented in Figure 10: as it can be seen, the small
Ow···Ow···Ow angles are possible because the tetramer is also
example, where the honeycomb superstructure is held together
by interanionic hydrogen bonds, in the case of 3 it is only the
combination of the shape of the cation (a cylinder) and of the
anionic three-spike stars that yields the honeycomb structure.
A comparison (see Figure 7) between the two packings shows
the strong analogy between the two compounds.
−
hydrogen bonded to the anion [Ow···OCOO /COOH distances
3.025(4) and 2.788(6) Å], and no acute H−O−H angles are
actually present.
Figure 7. (a) Comparison of the packings for crystalline 3 (a) and
[Co(η5-C5H5)2][(D,L-taH)·(D,L-taH2] (b), showing how the same
honeycomb motif is generated only by the matching shapes of cations
and anions in 3, while it is sustained by the presence of interanionic
hydrogen bonds in [Co(η5-C5H5)2][(D,L-taH)·(D,L-taH2]. HCH atoms
are omitted for clarity.
This tetramer, in turn, interacts through a net of hydrogen
bonds, with the [trans-deccaH]− monoanion. The small water
clusters act as “reinforcement” units along the anionic chain
−
[OCOOH···OCOO = 2.471(2) Å; Ow···OCOOH = 2.987(5) Å], as
it is shown in Figure 10.
Yellow spheres represent Hwater and HCOOH atoms. Blue solid
lines represent intermolecular H-bonds involving water molec-
ules; red solid lines represent anion···anion H-bonds: here the
H-atom has been arbitrarily assigned to one of the COO
groups.
As it can be seen in Figure 11, these infinite chains are
arranged to form almost hexagonal channels that run along the
[1 0 1] direction, which are filled by stacks of [(η5-C5Me5)2-
Co]+ cations. In projection the overall structure is closely
reminiscent of that of compound 3.
If the cobalticinium cation [(η5-C5H5)2Co]+ is crystallized in
the presence of two equivalents of trans-deccaH2, the cocry-
stalline derivative [(η5-C5H5)2Co][(trans-deccaH)(trans-
deccaH2)] (4) is obtained, analogously to what is observed in the
case of the cis-decca derivative (2). In crystalline [(η5-C5H5)2-
Co][(trans-deccaH)(trans-deccaH2)] (4) we observe the pre-
sence of supramolecular anions held together by intermolecular
−
hydrogen bonds (OCOO ···OCOOH = 2.603(6) Å). The super-
anions, in turn, participate in a hydrogen-bonded network
−
(OCOO ···OCOOH = 2.557(6)−2.759(7) Å) that yields conne-
The role of the water molecules may be that of enlarging, via
hydrogen bonds formation, the size of the channels formed by
cted cavities along the a-axis, as shown in Figure 8. Two
Figure 8. (a) Ball-and-stick representation of the supramolecular anion [(cis-deccaH)(cis-deccaH2)]− in crystalline 4; (b) hydrogen-bonding
interaction network and (c) how the cations fit inside the niches, both viewed along the a-axis. HCH atoms are omitted for clarity.
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Figure 9. (a) Space-filling representation of the layered structure of compound [(η5-C5Me5)2Co][cis-deccaH] (5) viewed along the b-axis; (b)
projection along the a-axis of the cationic piles formed by the decamethylcobalticinium cations; and (c) the intramolecular hydrogen bond observed
in the (cis-deccaH)− anion. HCH atoms are omitted for clarity.
Figure 10. Ribbon formed by water tetramers and (trans-deccaH)−
anions in crystalline 6. For the sake of clarity only the HOOC−C−C-
COO− fragments are shown for the anions. HCH atoms are omitted for
Figure 12. (a) Space-filling representation of the honeycomb
framework formed by the [trans-deccaH]− anions; (b) space-filling
clarity.
representation of how the cationic piles fit inside the channels
extending along the c-axis. HCH atoms are omitted for clarity.
other porous structures that could accommodate the organo-
metallic cations [Co(η5-C5H5)2]+, [Cr(η6-C6H6)2]+, [Fe(η5-
C5Me5)2]+, and [Co(η5-C5Me5)2]+. The regular cylindrical
shape of these cations appeared to play a role in directing the
assembly of the anionic frameworks, also with the participation
of C−H···O interactions between the acceptor −COOH/
COO− sites on the networks and the C−H groups protruding
from the complex surface.11
In this paper we have shown that, although the “hydrogen-
bonding confinement” strategy is essentially correct and can be
extended to more complex dicarboxylic acids, such as cis-9,10-
dihydroanthracene-9,10-α,β-succinic acid anhydride (cis-decca)
and trans-9,10-dihydro-9,10- ethanoanthracene-11,12-dicarbox-
ylic acid (trans-deccaH2), leading to novel architectures, the
hydrogen bond is not the key structure-directing interaction. In
compounds 1, 2, and 4, in which the organometallic/organic
stoichiometric ratio is 1:2, the hydrogen-bonding donor/
acceptor ratio is larger compared to that in compounds 3, 5,
6, and 7, formation of interanionic hydrogen bonds is possible,
and the resulting structures show extended network patterns
and self-assembly around the cations of the type observed
before. In compounds 3, 5, 6, and 7, where deprotonation leads
to intramolecular hydrogen bonds, hence forbids interanionic
hydrogen bonding, alternative solutions are adopted. In
compounds 3 and 7 the three-stem star-like shape of the
anions takes the lead and generates the observed close-packing
arrangement thanks to a perfect match in terms of size and
shape with the small sandwich organometallic cations [Co(η5-
C5H5)2]+ and [Cr(η6-C6H6)2]+. Compounds 5 and 6, on the
other hand, provide a sort of proof of concept because the
larger shape of the cations does not allow an equivalent efficient
arrangement; hence the crystal structure of 5 adopts a columnar
organization, while 6 drags in four water molecules as space
fillers to generate a honeycomb arrangement similar to that in
3 and 7.
Figure 11. (a) Projection along the [1 0 1] direction of the channels
formed by the anions (trans-deccaH)− and the water tetramers in solid
6; (b) view along the same direction filled by cationic stacks. H atoms
omitted for clarity.
the organic anions, thus allowing the bulky cations to fit inside.
In the absence of water molecules the [trans-deccaH]− anions
could not fold around the [(η5-C5Me5)2Co]+ cations, as ob-
served in compound 3.
Crystalline [(η6-C6H6)2Cr][(trans-deccaH)] (7), the only
derivative of bis-benzene chromium reported in this paper,
provides a further example of how a hexagonal honeycomb-type
arrangement of the organic moieties unsustained by strong
hydrogen bonds can be organized around the organometallic
cations. The packing is shown in Figure 12 and ought to be
compared with those shown above in Figures 7 and 11. The
intramolecular hydrogen bond within the [trans-deccaH]−
monoanion is comparable to those observed in the other com-
−
pounds of this series (OCOOH···OCOO 2.457(3) Å).
CONCLUSIONS
■
In previous studies we have reported several examples of
organic−organometallic superstructures obtained with the idea
that confinement of all strong donor/acceptor hydrogen-bonding
groups on the organic or inorganic networks would lead to
spontaneous self-assembly of the anions in the honeycomb or
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material, and kept in the dark. Recrystallization of the bright yellow
powder from water yielded single crystals suitable for X-ray diffraction.
Anal. Calcd for C46H39O9Co: C, 69.52; H, 4.95. Found: C, 69.82;
H, 4.67.
The use of organometallic building blocks in the preparation
of two-dimensional (2-D) and three-dimensional (3-D)
framework materials has obvious potential; yet, in spite of the
large efforts in crystal engineering, it remains an area that is
relatively underdeveloped. The observation that the same
topology can be attained by selecting molecular/ionic com-
ponents on the basis of their shape, rather than their supra-
molecular bonding capacity, might affect the way we look at the
engineering of metal−organic frameworks. All in all, the series
of compounds examined in this study shows how difficult it still
is to “make crystals by design”, because of the complex
interplay of different and not always converging factors/inter-
actions such as hydrogen bonding, shape, charge balance, and
space filler solvent molecules in the formation of stable
crystalline aggregates. However, the analysis of differences be-
tween crystal structures obtained with structurally similar
molecules may indicate ways to obtain polymorphs of the
same compound or ways to interconvert crystal forms by adding/
removing solvent molecules. A study of this type is under way.
Synthesis of [(η5-C5H5)2Co][trans-deccaH] (3). A 30 mg (0.16
mmol) portion of [(η5-C5H5)2Co] was suspended in ca. 15 mL of
nitromethane and oxidized by bubbling oxygen into the suspension
until a dark yellow solution was obtained. Then 47 mg (0.16 mmol) of
trans-deccaH2 were added to the solution, which was kept under
stirring for two hours, and the solution was filtered, to remove un-
reacted material, and kept in the dark. Pale brown crystals suitable for
X-ray diffraction were obtained by slow evaporation of the solvent at
RT. Anal. Calcd for C28H23O4Co: C, 69.71; H, 4.81. Found: C, 69.54;
H, 4.43.
Synthesis of [(η5-C5H5)2Co][(trans-deccaH)(trans-deccaH2)]
(4). The same procedure used for the synthesis of 1 was repeated
here, but using two equivalents of trans-deccaH2 (94 mg; 0.31 mmol).
Yellow crystals suitable for X-ray diffraction were obtained by slow
evaporation of the solvent at RT. Solid 4 can also be obtained directly
in the solid state by manually grinding solid 3 for 10 min with one
equivalent of trans-deccaH2. Anal. Calcd for C46H37O8Co: C, 71.13; H,
4.80. Found: C, 71.45; H, 4.96.
EXPERIMENTAL SECTION
Synthesis of [(η5-C5Me5)2Co][cis-deccaH] (5). A 36.5 mg (0.11
mmol) amount of [(η5-C5Me5)2Co] was suspended in ca. 20 mL of
nitromethane. Oxygen was bubbled into the suspension until a dark
yellow solution was obtained. Then 26.1 mg (0.11 mmol) of cis-decca
was added to the solution, which was kept under stirring for two
hours; the solution was then filtered, to remove unreacted material,
and kept in the dark. Pale brown crystals suitable for X-ray diffraction
were obtained by slow evaporation of the solvent at RT. Anal. Calcd
for C38H43O4Co: C, 73.30; H, 6.96. Found: C, 73.11; H, 6.74.
Synthesis of [(η5-C5Me5)2Co][trans-deccaH]·4H2O (6). A
40.7 mg (0.12 mmol) sample of [(η5-C5Me5)2Co] was suspended in ca.
15 mL of bidistilled water. The suspension was stirred until a bright
yellow solution was obtained. Then 37 mg (0.13 mmol) of trans-
deccaH2 was added to the solution, which was kept under stirring for
two hours; the solution was then filtered, to remove unreacted
material, and placed in the dark. Pale brown crystals suitable for X-ray
diffraction were obtained by slow evaporation of water at RT. Anal.
Calcd for C38H51O8Co: C, 65.69; H, 7.40. Found: C, 65.37; H, 7.31.
Synthesis of [(η6-C6H6)2Cr][(trans-deccaH)] (7). A 20 mg (0.10
mmol) amount of [(η6-C6H6)2Cr] was suspended in ca. 15 mL of
nitromethane and oxidized by bubbling oxygen into the suspension
until a dark yellow solution was obtained. Then 28 mg (0.10 mmol) of
trans-deccaH2 was added to the solution, which was kept under stirring
for two hours; the solution was filtered, to remove unreacted material,
and placed in the dark. Pale brown crystals suitable for X-ray
diffraction were obtained by slow evaporation of the solvent at RT.
Anal. Calcd for C30H25O4Cr: C, 71.85; H, 5.02. Found: C, 71.59;
H, 5.35.
X-ray Diffraction. Single-crystal data for compounds 1−7 were
collected on an Oxford X’Calibur S CCD diffractometer equipped with
a graphite monochromator (Mo Kα radiation, λ = 0.71073 Å) and
operating at room temperature except for compound 5, which was
collected at 150 K. Crystal data and details of measurement for all
compounds are listed in Table 2. All non-hydrogen atoms were refined
anisotropically; HOH atoms were either directly located or added
in calculated positions; HCH atoms for all compounds were added in
calculated positions and refined riding on their respective carbon
atoms. SHELX9725a was used for structure solution and refinement
on F2; PLATON25b and SCHAKAL9925c were used for hydrogen
bonding analysis and molecular graphics, respectively.
■
The neutral compound [(η5-C5H5)2Co], bought from Alfa-Aesar, and
all reactants and reagents, purchased from Sigma-Aldrich, were used
without further purification. Reagent-grade solvents and bidistilled
water were used. 1H NMR spectra were recorded on a Varian
Mercury400, and chemical shifts of 1H NMR signals were expressed in
parts per million (δH) using internal standard TMS (δH = 0.00).
Synthesis of trans-deccaH2. Dioxane (25 mL) was added to a
mixture of fumaric acid (0.645 g, 5.6 mmol) and anthracene (3.0 g,
17 mmol). After refluxing for 3 days at 104 °C the solvent was removed
by rotary evaporation under reduced pressure. A saturated solution
(100 mL) of Na2CO3 was added, and the mixture was stirred for half a
day. The mixture was filtered (in order to remove the unreacted
anthracene), and concentrated HCl was added to the clear solution to
pH = 1. The solid product was recovered by filtration of the hot
solution. Yield = 90%. Mp = 251−252 °C (lit. mp = 252.5 °C). Anal.
1
Calcd for C18H14O4: C, 73.46; H, 4.79. Found: C, 73.12; H, 4.34. H
NMR (400 MHz, DMSO-d6, TMS) δH: 12.52 (s, 2H, COOH),
7.065−7.371 (m, 8H, aromatic CH), 4.707 (s, 2H, methine CH) and
3.549 (s, 2H, methine CH).
Synthesis of cis-decca. p-Xylene (30 mL) was added to a mixture
of maleic anhydride (0.346 g; 5.3 mmol) and anthracene (0.62 g; 3.56
mmol). The mixture was refluxed at 135 °C for 1 h. The resulting
solution was allowed to cool to room temperature, yielding a white
powder, which was removed by filtration and washed with a few
milliliters of ethyl acetate. Solid cis-decca was recrystallized from hot
ethyl acetate. Colorless prismatic crystals formed upon cooling the
ethyl acetate solution. Yield = 80%. Mp = 262 °C (lit. mp = 262−263 °C).
Anal. Calcd for C18H12O3: C, 78.25; H, 4.38. Found: C, 78.36; H, 4.54.
1H NMR (400 MHz, CDCl3-d1, TMS) δH: 7.41 (m, 8H, aromatic
CH), 4.87 (s, 2H, methine CH) and 3.55 (s, 2H, methine CH).
Synthesis of [(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)] (1). A
30 mg (0.16 mmol) amount of [(η5-C5H5)2Co] was suspended in ca.
15 mL of nitromethane. Oxygen was bubbled into the suspension until
a dark yellow solution was obtained. Then 44 mg (0.16 mmol) of
trans-deccaH2 was added to the solution, which was kept under stirring
for two hours. The solution was then filtered, to remove unreacted
material, and kept in the dark. Pale brown crystals suitable for X-ray
diffraction were obtained by slow evaporation of the solvent at RT.
Anal. Calcd for C46H37O8Co: C, 71.13; H, 4.80. Found: C, 71.33; H,
4.92.
Synthesis of [(η5-C5H5)2Co][(cis-deccaH)(cis-deccaH2)]·H2O
(2). A 30 mg (0.16 mmol) sample of [(η5-C5H5)2Co] was suspended
in ca. 10 mL of water. Oxygen was bubbled into the suspension until a
bright yellow solution was obtained. Then 44 mg (0.16 mmol) of
trans-deccaH2 was added to the solution, which was kept under stirring
for two hours. The solution was then filtered, to remove unreacted
X-ray powder data were collected on a Philips X’Pert automated
diffractometer with Cu Kα radiation. The program PowderCell25d was
used for calculation of X-ray powder patterns on the basis of single-
crystal data. The identity between bulk materials and single crystals
was always verified by comparing calculated and experimental powder
diffraction patterns.
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(7) (a) Pan, L.; Olson, D. H.; Ciemnolonski, L. R.; Heddy, R.; Li, J.
Angew. Chem., Int. Ed. 2005, 45, 616−619. (b) Chen, B.; Liang, C.;
Yang, J.; Contreras, D.; Clancy, Y.; Lobkovsky, E.; Yaghi, O. M.; Dai, S.
Angew. Chem., Int. Ed. 2006, 45, 1390−1393. (c) Dybtsev, D.; Chun,
H.; Yoon, S.; Kim, D.; Kim, K. J. Am. Chem. Soc. 2004, 126, 32−33.
(d) Custelcean, R.; Gorbunova, M. J. Am. Chem. Soc. 2005, 127,
16362−16363. (e) Bourrelly, S.; Llewellyn, P.; Serre, C.; Millange, F.;
Loiseau, T.; Ferey, G. J. Am. Chem. Soc. 2005, 39, 13519−13521.
(8) Braga, D.; Grepioni, F.; Desiraju, G. R. Chem. Rev. 1998, 98,
1375−1405.
ASSOCIATED CONTENT
■
S
* Supporting Information
Ortep drawings and CIF files for compounds 1−7. This
material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Fax: +39 051 2099456. E-mail: dario.braga@unibo.it.
(9) Braga, D.; Giaffreda, S.; Grepioni, F.; Pettersen, A.; Maini, L.;
Curzi, M.; Polito, M. Dalton Trans. 2006, 1249−1263.
(10) Braga, D.; Grepioni, F. Coord. Chem. Rev. 1999, 183, 19.
(11) Braga, D.; Grepioni, F. Acc. Chem. Res. 2000, 33, 601−608.
(12) (a) Braga, D.; Bazzi, C.; Grepioni, F.; Novoa, J. J. New J. Chem.
1999, 23, 577−579. (b) Braga, D.; Grepioni, F.; Tagliavini, E.; Novoa,
J. J.; Mota, F. New J. Chem. 1998, 22, 755−757. (c) Novoa, J. J.;
Nobeli, I.; Grepioni, F.; Braga, D. New J. Chem. 2000, 24, 5−8.
(d) Braga, D.; Maini, L.; Grepioni, F.; Mota, F.; Rovira, C.; Novoa, J. J.
Chem.Eur. J. 2000, 6, 4536−4551. (e) Braga, D.; D’Oria, E.;
Grepioni, F.; Mota, F.; Novoa, J. J.; Rovira, C. Chem.Eur. J. 2002, 8,
1173−1180. (f) Braga, D.; Grepioni, F.; Novoa, J. J. Chem. Commun.
1998, 1959−1960.
ACKNOWLEDGMENTS
■
We thank University of Bologna and MiUR for financial
support.
REFERENCES
■
(1) (a) Desiraju, G. R., Ed. Crystal Engineering: The Design of Organic
Solids; Elsevier: Amsterdam, 1989. (b) Blake, A. J.; Champness, N. R.;
Hubberstey, P.; Li, W. S.; Withersby, M. A.; Schroder, M. Coord.
Chem. Rev. 1999, 183, 117−138. (c) Braga, D. J. Chem. Soc., Dalton
Trans. 2000, 3705−3713. (d) Moulton, B.; Zaworotko, M. J. Chem.
Rev. 2001, 101, 1629−1658. (e) Braga, D. Chem. Commun. 2003,
2751−2754. (f) Braga, D.; Desiraju, G. R.; Miller, J.; Orpen, A. G.;
Price, S. CrystEngComm 2002, 4, 500−509. (g) Hollingsworth, M. D.
Science 2002, 295, 2410−2413. (h) Hosseini, M. W. CrystEngComm
2004, 6, 318−322. (i) Brammer, L. Chem. Soc. Rev. 2004, 33, 476−
489. (j) Braga, D.; Brammer, L.; Champness, N. CrystEngComm 2005,
7, 1. (k) Desiraju, G. R. Angew. Chem., Int. Ed. 2007, 46, 8342−8356.
(l) Braga, D.; Grepioni, F.; Maini, L. Chem. Commun. 2010, 46, 6232−
6242.
(2) (a) Desiraju, G. R.; Steiner, T., Eds. The Weak Hydrogen Bond in
Structural Chemistry and Biology; Oxford University Press: Oxford,
1999. (b) Braga, D.; Grepioni, F.; Biradha, K.; Pedireddi, V. R.;
Desiraju, G. R. J. Am. Chem. Soc. 1995, 117, 3156−3166. (c) Calhorda,
M. .J. Chem. Commun. 2000, 801−809. (d) Nangia, A. J. Chem. Sci.
2010, 122, 295−310. (e) Thalladi, V. R.; Goud, B. S.; Hoy, V. J.; Allen,
F. H.; Howard, J. A. K.; Desiraju, G. R. Chem. Commun. 1996, 401−
402. (f) Braga, D.; Brammer, L.; Champness, N. L. CrystEngComm
2005, 7, 1−19. (g) Desiraju, G. Cryst. Growth Des. 2011, 11, 896−898.
(3) Reger, D. L.; Horger, J.; Smith, M. D.; Long, G. J. Chem.
Commun. 2009, 6219−6221.
(4) (a) Roswell, J. L.; Yaghi, O. M. Angew. Chem., Int. Ed. 2005, 44,
4670−4679. (b) Collins, D.; Zhou, H. C. J. Mater. Chem. 2007, 17,
3154−3160. (c) Kitagawa, S.; Matsuda, R. Coord. Chem. Rev. 2007,
251, 2490−2509. (d) Dybtsev, D.; Chun, H.; Yoon, S. H.; Kim, D.;
Kim, K. J. Am. Chem. Soc. 2004, 126, 5666−5667. (e) Dinca, M.; Long,
J. Angew. Chem., Int. Ed. 2008, 47, 6766−6779. (f) Belof, J.; Stern, A.;
Eddaoudi, M.; Space, B. J. Am. Chem. Soc. 2007, 129, 15202−15210.
(5) (a) Chen, B.; Yang, Y.; Zapata, F.; Lin, G.; Qian, G.; Lobkovsky,
E. Adv. Mater. 2007, 19, 1693−1696. (b) Wong, K. L.; Law, G. L.;
Yang, Y. Y.; Wong, W. T. Adv. Mater. 2006, 18, 1051−1054.
(c) Maspoch, D.; Ruiz-Molina, D.; Wurst, K.; Domingo, N.; Cavallini,
M.; Biscarini, F.; Tejada, J.; Rovira, C.; Veciana, J. Nat. Mater. 2003, 2,
190−195. (d) Halder, G.; Kepert, C.; Moubaraki, B.; Murray, K.;
Cashion, J. Science 2002, 298, 1762−1765.
(6) (a) Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. J. Am. Chem.
Soc. 1994, 116, 1151−1152. (b) Seo, J.; Whang, D.; Lee, H.; Jun, S.;
Oh, J.; Jeon, Y.; Kim, K. Nature 2000, 404, 982−986. (c) Wu, C. D.;
Hu, A.; Zhang, L.; Lin, W. J. Am. Chem. Soc. 2005, 127, 8940−8941.
(d) Wu, C. D.; Lin, W. Angew. Chem., Int. Ed. 2007, 46, 1075−1078.
(e) Dybtsev, D.; Nuzhdin, A.; Chun, H.; Bryliakov, K.; Talsi, E. P.;
Fedin, V. P.; Kim, K. Angew. Chem., Int. Ed. 2006, 45, 916−920.
(f) Cho, S. H.; Gadzikwa, T.; Afshari, M.; Nguyen, S.; Hupp, J. Eur. J.
Inorg. Chem. 2007, 31, 4863−4867. (g) Cho, S. H.; Ma, B.; Nguyen, S.
T.; Hupp, J. T.; Albrecht-Schmitt, T. E. Chem. Commun. 2006, 24,
2563−2565. (h) Alkordi, M.; Liu, Y.; Larsen, R.; Eubank, J.; Eddaoudi,
M. J. Am. Chem. Soc. 2008, 130, 12639−12641.
(13) (a) Braga, D.; Angeloni, A.; Grepioni, F.; Tagliavini, E. Chem.
Commun. 1997, 1447−1448. (b) Braga, D.; Angeloni, A.; Grepioni, F.;
Tagliavini, E. Organometallics 1997, 16, 5478−5485.
(14) Braga, D.; Eckert, M.; Fraccastoro, M.; Maini, L.; Grepioni, F.;
Caneschi, A.; Sessoli, R. New J. Chem. 2002, 26, 1280−1286.
(15) Braga, D.; Maini, L.; Prodi, L.; Caneschi, A.; Sessoli, R.;
Grepioni, F. Chem.Eur. J. 2000, 6, 1310−1317.
(16) Braga, D.; Angeloni, A.; Maini, L.; Gotz, A. W.; Grepioni, F. New
̈
J. Chem. 1999, 23, 17−24.
(17) Braga, D.; Angeloni, A.; Tagliavini, E.; Grepioni, F. J. Chem. Soc.,
Dalton Trans. 1998, 1961−1968.
(18) (a) Grepioni, F.; Gladiali, S.; Scaccianoce, L.; Ribeiro, P.; Braga,
D. New J. Chem. 2001, 25, 690−695.
(19) (a) Braga, D.; Giaffreda, S.; Grepioni, F.; Maini, L.; Polito, M.
Coord. Chem. Rev. 2006, 250, 1267−1285. (b) Braga, D.; Maini, L.;
Polito, M.; Tagliavini, E.; G. Coord. Chem. Rev. 2003, 246, 53−71.
(c) Braga, D.; Maini, L.; Polito, M.; Scaccianoce, L.; Cojazzi, G.;
Grepioni, F. Coord. Chem. Rev. 2001, 216−217, 225−248. (d) Braga,
D.; Grepioni, F. Coord. Chem. Rev. 1999, 183, 19−41.
(20) (a) Bachman, W. E.; Scott, L. B. J. Am. Chem. Soc. 1948, 70 (4),
1458−1461. (b) Weber, E.; Csoregh, I.; Ahrendt, J.; Finge, S.; Czugler, M.
J. Org. Chem. 1988, 53 (25), 5831−5839. (c) Diaz de Delgado, G.; Belkis
Ramirez, V, B.; Velas
o501−o503.
(21) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885−3896 , and
references therein.
̀
quez, W.; Rodriguez, P. Acta Crystallogr. 2002, E58,
(22) (a) Infantes, L.; Motherwell, S. CrystEngComm 2002, 4, 454−
461. (b) Infantes, L.; Chisholm, J.; Motherwell, S. CrystEngComm
2003, 5, 480−486. (c) Mascal, M.; Infantes, L.; Chisholm, J. Angew.
Chem., Int. Ed. 2006, 45, 32−36.
(23) (a) Ludwig, R. Angew. Chem., Int. Ed. 2001, 40, 1808−1827.
(b) Masella, M.; Gresh, N; Flament, J.-P. J. Chem. Soc., Faraday Trans.
1998, 94, 2745−2753.
(24) (a) Supriya, S.; Das, S. K. CrystEngComm 2008, 10, 1743−1746.
(b) Chacko, K. K.; Saenger, W. J. Am. Chem. Soc. 1981, 103, 1708−
1715. (c) Zabel, V.; Saenger, W.; Mason, S. A. J. Am. Chem. Soc. 1986,
108, 3664−3673. (d) Stephens, F. C.; Vagg, R. S. Inorg. Chim. Acta
1982, 57, 43−49. (e) Xu, J.; Radkov, E.; Ziegler, M.; Raymond, K. N.
Inorg. Chem. 2000, 39, 4156−4164. (f) Favas, M. C.; Kepert, D. L.;
Skelton, B. W.; White, A. H. J. Chem. Soc., Dalton Trans. 1980, 454−
458. (g) Supriya, S.; Das, S. K. New J. Chem. 2003, 27, 1568−1574.
(h) Long, L. S.; Wu, Y. R.; Huang, R. B.; Zheng, L. S. Inorg. Chem. 2004,
43, 3798−3800. (i) Fabelo, O.; Pasan
́
, J.; Canadillas-Delgado, L.;
̃
Delgado, F. S.; Labrador, A.; Lloret, F.; Julve, M.; Ruiz-Per
́
ez, C.
CrystEngComm 2008, 10, 1743−1746. (j) Zuhayra, M.; Kampen, W. U.;
1694
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Organometallics
Article
Henze, E.; Soti, Z.; Zsolnai, L.; Huttner, G.; Oberdorfer, F. J. Am. Chem.
Soc. 2006, 128, 424−425.
(25) (a) Sheldrick, G. M. SHELXL97, Program for Crystal Structure
Determination; University of Gottingen: Gottingen, Germany, 1997.
̈
̈
(b) Speck, A. L. PLATON. Acta Crystallogr. Sect. A 1990, 46, C34.
(c) Keller, E. SCHAKAL99, Graphical Representation of Molecular
Models; University of Freiburg: Freiburg, Germany, 1999. (d) Kraus,
W.; Nolze, G. PowderCell; BAM: Berlin; subgroups developed by
Muller, U.; Universitat Gh Kassel: Kassel, Germany.
̈
̈
1695
dx.doi.org/10.1021/om200837t | Organometallics 2012, 31, 1688−1695