Syntheses and Crystal Structures of Two Cadmium Methanetetrabenzoates Featured by Open Framework and Infinite Layers

Article abstract of DOI:10.1002/zaac.201900089

Colorless single crystals of Cd₂[μ₈-MTB]·3H₂O·DMF (1) were prepared in DMF/H₂O solution [1: space group C2/c (no. 15) with a = 1821.30(6), b = 2175.08(6), c = 1269.87(4) pm, β = 129.684(1)°]. The connection between the methane-p-benzoate tetraanions (MTB^4–) and the Cd²⁺ cations leads to a three-dimensional framework with channels extending along [110] and [110] with openings of 670 pm × 360 pm. The channel-like voids accommodate water molecules and N,N-dimethylformamide (DMF) molecules not bound to Cd²⁺. Colorless single crystals of [Cd₄(2,2′-bipy)₄(μ₇-MTB)₂]·7DMF (2) were prepared in DMF in the presence of 2,2′-bipyridine [2: space group P1 (no. 2) with a = 1224.84(4), b = 1418.85(5), c = 2033.49(4) pm, α = 85.831(2)°, β = 88.351(2)°, γ = 68.261(1)°]. The coordination of MTB^4– to Cd²⁺ results in infinite layers parallel to (001). The layers, not connected by any hydrogen bonds, contain small openings of about 320 pm × 340 pm.

Full text of DOI:10.1002/zaac.201900089

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201900089
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Syntheses and Crystal Structures of Two Cadmium
Methanetetrabenzoates Featured by Open Framework and Infinite
Layers
Sven Harms,[a] Roberto Köferstein,[b] Helmar Görls,[a] and Christian Robl*[a]
2
+
Abstract. Colorless single crystals of Cd
were prepared in DMF/H O solution [1: space group C2/c (no. 15) [Cd
with a = 1821.30(6), b = 2175.08(6), c = 1269.87(4) pm, β = presence of 2,2Ј-bipyridine [2: space group P1 (no. 2) with a =
29.684(1)°]. The connection between the methane-p-benzoate tet- 1224.84(4), b = 1418.85(5), c = 2033.49(4) pm, α = 85.831(2)°, β =
2
[μ
8
-MTB]·3H
2
O·DMF (1) molecules not bound to Cd . Colorless single crystals of
2
4
(2,2Ј-bipy) (μ -MTB) ]·7DMF (2) were prepared in DMF in the
4
7
2
¯
1
4–
2+
4–
2+
raanions (MTB ) and the Cd cations leads to a three-dimensional 88.351(2)°, γ = 68.261(1)°]. The coordination of MTB to Cd re-
¯
framework with channels extending along [110] and [110] sults in infinite layers parallel to (001). The layers, not connected by
with openings of 670 pmϫ360 pm. The channel-like voids any hydrogen bonds, contain small openings of about
accommodate water molecules and N,N-dimethylformamide (DMF) 320 pmϫ340 pm.
Introduction
been reported for the connection between the methanetetra-p-
4–
2+
2+
2+
benzoate anion (MTB ) and metal cations (Ni , Co , Cu ,
Porous coordination polymers, often called metal-organic
frameworks (MOFs), have attracted much attention due to their
potential application e.g. as catalyst, ion exchanger, and in
gas storage and separation processes.[ Hereby, polycarboxyl-
ate ligands are able to coordinate metal ions in flexible modes,
2+
2+
4+
2+ [12,13,16–24]
Zn , Cd , Zr , Pb ).
Several transition metal
methane-p-benzoates show selective gas adsorption
[
1]
[2]
[12,17,18,19,25]
behavior for CO , H , and O .
Additionally,
2
2
2
3]
[
Ni (cyclam) (MTB)]·8H O·4DMF (DMF = dimethylform-
2
2
2
amide, cyclam = 1,4,8,11-tetraazacyclotetradecane) can be
used to produce palladium nanoparticles, whereas
resulting in various interesting complexes with one-, two, and
three-dimensional structure motives.[
4–8]
Building blocks with
[
Ni (μ -MTB) (μ -H O) (H O) ]·10DMF·11H O
and
4
6
2
2
2
4
2
4
2
tetrahedrally directed functional groups will very likely build
up frameworks related to the structure of diamond. Such dia-
mond-like frameworks, often called diamondoid, have been
veryfied in the crystal structure of methanetetraacetic acid
[
Pb (μ -MTB) (H O) ]·5DMF·H O act as catalysts in Knoev-
4
8
2
2
4
2
[17,18,26]
enagel condensation reactions.
Herein, we report on the crystal structures of two cad-
mium(II) methanetetra-p-benzoates with a three-dimensional
open framework (Cd [μ -MTB]·3H O·DMF) and a two-di-
(
3,3-bis(carboxymethyl)glutaric acid) and adamantane-1,3,5,7-
2
8
2
[9,10]
tetracarboxylic acid.
These compounds feature interpen-
mensionally polymeric structure ([Cd (2,2Ј-bipy) (μ -MTB) ]·
4
4
7
2
etrating networks. If it is possible to avoid interpenetrating
structures, open frameworks will result. Common examples are
the mineral melanophlogite and various porous silica modifica-
7DMF), respectively.
tions. A platinum coordination compound with adamantoid Results and Discussion
11]
cages has been reported very recently.[ Further three-dimen-
sional and porous coordination polymers have been prepared Cd [μ -MTB]·3H O·DMF (1)
2
8
2
using tetrahedral building units, like the anions of meth-
In Cd [μ -MTB]·3H O·DMF (1) there are two crystallo-
2
8
2
anetetra-p-benzoic acid and tetrakis(4-carboxy-phenyl)-
graphically independent Cd2+ cations. Cd(1) occupies a crys-
tallographic inversion center (Wyckoff position 4c), whereas
Cd(2) lies on a twofold crystallographic axis of space-group
C2/c (Wyckoff position 4e). Cd(1) is sixfold coordinated in a
slightly distorted octahedral manner by four carboxylate oxy-
gen atoms [2ϫ O(2), 2ϫO(4)], from four crystallographically
silane.[12–15]
A few three-dimensional open frameworks have
*
Prof. Dr. C. Robl
Fax: +49-3641-948152
E-Mail: crr@uni-jena.de
[
[
a] Institute of Inorganic and Analytical Chemistry
Friedrich-Schiller-University Jena
Humboldtstrasse 8
4–
equivalent methanetetra-p-benzoate tetraanions (MTB ) and
twice by the water molecule O(1w) (Figure 1a). The Cd–O
distances range from 221.2(3) to 231.3(3) pm (Table 1,
Table 2). The bond angles within the octahedron differ margin-
ally from the ideal values, except the angles between the oxy-
gen atoms O(2) and O(4). Thus, the octahedron can be de-
scribed by D2d symmetry in good approximation. Cd(2) is sur-
0
7743 Jena, Germany
b] Institute of Chemistry, Inorganic Chemistry
Martin Luther University Halle-Wittenberg
Kurt-Mothes-Strasse 2
06120 Halle, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201900089 or from the au-
thor.
Z. Anorg. Allg. Chem. 0000, ᭿,0–0
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Journal of Inorganic and General Chemistry
ARTICLE
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Table 1. The coordination of Cd2+ in Cd
[μ -MTB]·3H O·DMF (1).
2 8 2
Distance /pm
Cd(1)–O(2)
Cd(1)–O(4)
Cd(1)–O(1w)
228.7(3)
231.3(3)
221.2(3)
2x
2x
2x
Cd(2)–O(1)
Cd(2)–O(3)
Cd(2)–O(4)
221.3(3)
235.4(3)
241.1(3)
2x
2x
2x
Bond angle /°
#
1
#4
O(1w) –Cd(1)–O(1w)
O(1w)–Cd(1)–O(2)#
180.0
O(1) –Cd(2)–O(3)
98.89(11)
107.59(15)
86.88(10)
137.52(11)
102.14(10)
81.94(16)
54.85(10)
112.07(10)
164.78(13)
#
4
#5
92.10(12)
87.90(12)
88.15(13)
91.85(13)
99.12(10)
180.0
O(1) –Cd(2)–O(1)
1
#5
O(1w)–Cd(1)–O(2)
O(1) –Cd(2)–O(4)
#1
#2
#3
#5
O(1w) –Cd(1)–O(4)
O(1) –Cd(2)–O(3)
#1
#4
O(1w) –Cd(1)–O(4)
O(2)–Cd(1)–O(4)#
O(2)–Cd(1)–O(2)#
O(1) –Cd(2)–O(4)
2
#6
O(3) –Cd(2)–O(3)
1
O(3)–Cd(2)–O(4)
O(3)–Cd(2)–O(4)
O(4)–Cd(2)–O(4)
#3
#6
O(2)–Cd(1)–O(4)
80.88(10)
180.00(16)
#
2
#3
#6
O(4) –Cd(1)–O(4)
Symmetry codes: #1: –x+0.5; –y+0.5; –z, #2: –x;–y;–z, #3: x+0.5;y+0.5;z, #4: –x+0.5;y–0.5;–z–0.5, #5: x–0.5;y–0.5;z, #6: –x–1;y;–z–0.5.
rounded by six carboxylate oxygen atoms stemming from four Table 2. Selected bond lengths and angles of the MTB4– anion in
4
–
2 8 2
Cd [μ -MTB]·3H O·DMF (1).
equivalent MTB anions with bond lengths between 221.3(3)
and 241.1(3) pm. The coordination polyhedron strongly devi-
ates from an ideal octahedron as well as from an ideal trigonal
prism (Figure 1b, Table 1). Thus the Cd(2) polyhedron can be
Distance /pm
C(8)–O(1)
C(8)–O(2)
127.6(5)
124.7(5)
151.0(5)
154.5(4)
C(15)–O(3)
C(15)–O(4)
C(12)–C(15)
C(1)–C(9)
125.4(5)
127.0(5)
149.5(5)
155.3(4)
best described as a distorted intermediate between an octahe- C(5)–C(8)
C(1)–C(2)
dral and a trigonal prismatic coordination. Employing the
method of Brese and O’Keeffe[27] the bond valence sum for Bond angle /°
Cd(1) and Cd(2) is calculated to 2.24 and 1.97, respectively.
Neighboring Cd(1) and Cd(2) polyhedra are linked by a com-
mon corner [O(4)] leading to sinusoidal infinite polyhedra C(9)–C(1)–C(9) 108.6(4)
chains along [101] (Figure 1c). The shortest Cd(1)···Cd(2) con-
O(1)–C(8)–O(2) 124.9(3)
O(2)–C(8)–C(5) 119.1(3)
O(3)–C(15)–O(4) 120.9(4)
O(3)–C(15)–C(12) 120.0(4)
#
7
#7
C(2)–C(1)–C(2)
C(2)–C(1)–C(9)
107.5(4)
110.34(18)
#
7
C(2)–C(1)–C(9)
110.02(18)
tact is 387.53(2) pm.
Symmetry code: #7: –x;y; –z + 0.5.
127.6(5) pm. The carboxylate groups with C(8) are nearly co-
planar to the C rings [torsion angle 2.3(3)°] and the carboxyl-
6
ate groups with C(15) are slightly twisted by 9.7(4)°. More-
over, the phenyl rings are twisted against each other by
6
3.3(1)° to 74.2(2)°. Each MTB4– anion connects eight cad-
mium cations and adopts a μ coordination mode (Figure 2a).
8
All carboxylate oxygen atoms are involved in the coordination
Figure 1. (a,b) The coordination environment of Cd(1) and Cd(2) in
Cd [μ -MTB]·3H O·DMF (1). (c) The connection between the Cd(1)
2 8 2
and Cd(2) polyhedra leads to infinite chains (hydrogen atoms are omit-
ted for clarity).
Chun et al.[20] reported on a tetragonal three-dimensionally
connected cadmium methanetetra-p-benzoate complex
(
[Cd (MTB) (DMF) ]·4DMF·4H O), in which the sevenfold
4 2 4 2
+
2
coordinated Cd cations form tetranuclear clusters and all
carboxylate groups act as chelate ligands.
The tetraanion of the methanetetra-p-benzoic acid (MTB )
is situated on a twofold axis. The C–O bond lengths in the
Figure 2. (a) The connection between the tetraanion of the meth-
4–
4–
2+
anetetra-p-benzoic acid (MTB ) and the Cd cations in 1. (b) New-
man projection of the N,N-dimethylformamide (DMF) molecule along
carboxylate groups are in the range between 124.7(5) and N(1A)–C(1A).
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2
+
to Cd . The carboxylate groups with C(15) are bonded to
Cd(1) in a monodentate and to Cd(2) in a bidentate manner.
2
1
The coordination leads to a μ -η :η connection mode.
2
Whereas the carboxylate groups with C(8) show only a mono-
2
+
1
1
dentate coordination to Cd with a μ -η :η mode.
2
The cadmium centered polyhedra chains are linked by
4
–
MTB anions to an open three-dimensional framework (Fig-
4
–
ure 3, Figure 4). Each MTB anion connects three Cd-polyhe-
dra chains (Figure S1, Supporting Information). Channel-like
¯
voids extend along [110] and [110]. The openings of these
channels are approximately 670 pmϫ360 pm with van der
Waals radii[ of the framework atoms taken into account. The
channels accommodate in a disordered manner water mol-
ecules [O(2w), O(3w)] and N,N-dimethylformamide (DMF)
28]
2
+
molecules not bound to Cd . Figure 2b shows the Newman
projection of the DMF molecule along the N(1A)–C(1A) bond.
The torsion angles between C(2A)/O(1A) and C(3A)/O(1A) of
1
2(4)° and 170(2)° are comparable with values found in gas-
[29]
eous DMF.
The DMF molecules are only connected to the
framework by weak C–H···O contacts to the phenyl rings
Table 3). Furthermore, the coordinated water molecule O(1w)
acts as donator in medium and strong hydrogen bonds to the
uncoordinated water molecules [O(2w), O(3w)] and to the Figure 4. Space-filling model of the framework of 1. (a) View along
(
¯
110], (b) view along [110]. DMF molecules and uncoordinated water
molecules are omitted.
[
carboxylate oxygen atom O(1). The water molecule O(2w)
builds up a weak hydrogen bond to the DMF oxygen atom
O(1A).
Table 3. Hydrogen bonds in 1.
d(O···O) /pm
Angle (O–H···O) /°
O(1w)–H(1w1)···O(2w)
O(1w)–H(1w1)···O(3w)
O(1w)–H(2w1)···O(1)MTB
O(2w)–H(2wB)···O(1A)DMF
262.3(10)
258.2(10)
269.8(5)
143(1)
159(1)
169(1)
136(1)
264.4(10)
d(C···O) /pm)
Angle (C–H···O) /°
C(11)MTB–H(11A)···O(1A)DMF 374.3(10)
147(1)
Table 4. The coordination of Cd2+ in Cd
4
4 7 2
(2,2Ј-bipy) (μ -MTB) ]·
7DMF (2).
Distance /pm
Cd(1)–O(1)
Cd(1)–O(2)
Cd(1)–O(3)
Cd(1)–O(4)
Cd(1)–O(5)
Cd(1)–O(6)
Cd(1)–N(1)
284.3(7)
224.4(5)
238.9(5)
254.9(5)
254.7(5)
233.2(5)
231.9(6)
234.9(6)
Cd(2)–O(1)
Cd(2)–O(3)
Cd(2)–O(6)
Cd(2)–O(7)
Cd(2)–O(8)
Cd(2)–N(3)
Cd(2)–N(4)
227.0(6)
225.1(5)
266.9(6)
246.3(6)
234.3(6)
231.5(7)
234.8(8)
Figure 3. Crystal structure of Cd
from [110]. Hydrogen atoms are omitted for clarity.
2
[μ
8 2
-MTB]·3H O·DMF (1) viewed
¯
[
Cd (2,2Ј-bipy) (μ -MTB) ]·7DMF (2)
4 4 7 2
In 2, the cadmium cations occupy general positions of space Cd(1)–N(2)
¯
group P1. Cd(1) is surrounded by two nitrogen atoms [N(1),
N(2)] from the 2,2Ј-bipyridine (bipy) molecule (I) and six
carboxylate oxygen atoms from three crystallographically
Bond angle /°
O(2)–Cd(1)–N(2)
154.5(2)
170.81(18)
146.3(2)
83.15(18)
125.37(18)
155.1(2)
N(3)–Cd(2)–N(4)
70.8(3)
100.76(19)
53.7(2)
144.1(2)
153.0(2)
149.5(2)
#2
#1
#1
#2
#3
#3
O(4) –Cd(1)–O(5)
O(3) –Cd(2)–O(7)
4
–
#2
#3
equivalent MTB anions. The Cd(1)–N distances are 231.9(6) N(1)–Cd(1)–O(3)
O(8) –Cd(2)–O(7)
#1
O(6) –Cd(1)–N(2)
O(1)–Cd(2)–N(4)
and 234.9(6) pm, respectively (Table 4). The Cd(1)–O bond
lengths to O(2), O(3), O(4), O(5), and O(6) are in the range
between 224.4(5) and 254.9(5) pm, whereas the bond to O(1)
is 284.3(7) pm. Although this Cd–O bond is weak, it is signifi-
cantly shorter than the sum of the van der Waals radii.
#2
#2
O(3) –Cd(1)–O(5)
N(2)–Cd(1)–O(1)
O(3) –Cd(2)–N(3)
#1
#3
O(6) –Cd(2)–O(7)
Symmetry codes: #1: x+2;y–1;z, #2: x–1;y;z, #3: –x;–y+1; –z+1.
A similar situation was reported with several Cd com- proximately described as a distorted two-capped octahedron.
plexes.[
28,30,31–37]
The resulting coordination (7+1) can be ap- As seen in Figure 5a, the equatorial plane is spanned by N(1),
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2
O(3), O(4), and O(5) deviating slightly from planarity with an coordinates in a μ -η mode, whereas the remaining carboxyl-
1
2
1
average and maximum deviation of 4.4(3) pm and 5.2(7) pm, ate groups show a μ -η :η connection. The C–O bonds are
2
respectively. The axial positions are occupied by the nitrogen between 121.4(12) and 128.7(9) pm (Table 5). The carboxylate
atom N(2) and the carboxylate oxygen atom O(2).
groups with C(8) and C(15) are slightly tilted to the C rings
6
[torsion angles 7.0(5)°, 3.9(4)°], whereas the carboxylate
Figure 5. (a,b) The coordination spheres of Cd2+ in [Cd
(2,2Ј-
4
bipy)
Cd(1) polyhedra.
4
(μ
7
-MTB)
2
]·7DMF (2). (c) Connection between the Cd(1) and
Figure 6. The connection between the [MTB]4– tetraanion and the cad-
mium cations in 2.
Alternatively, the coordination polyhedron might also be
considered as a monocapped pentagonal bipyramid with O(1)
as the capping atom. However, the pentagonal equatorial plane 2,2Ј-bipyridine molecules in Cd (2,2Ј-bipy) (μ -MTB) ]·7DMF (2).
Table 5. Selected bond lengths and angles of the MTB4– anion and the
4
4
7
2
through N(1), O(3), O(4), O(5) and O(6) deviates considerably
from planarity [average 20.6(4) pm] with a maximum devia-
tion of 35.3(6) pm for O(6). The coordination sphere of Cd(2)
is built up by two nitrogen atoms [N(3), N(4)] from the 2,2Ј-
Distance /pm
MTB4–
C(8)–O(1)
C(8)–O(2)
124.9(10)
C(22)–O(5)
C(22)–O(6)
C(29)–O(7)
C(29)–O(8)
C(12)–C(15)
C(26)–C(29)
C(1)–C(16)
C(1)–C(23)
124.9(10)
127.5(9)
125.5(11)
121.4(12)
149.0(10)
152.4(10)
155.2(9)
154.2(9)
128.3(10)
128.7(9)
124.3(9)
148.9(10)
151.7(10)
156.0(9)
152.7(9)
bipyridine molecule (II) and five carboxylate oxygen atoms C(15)–O(3)
[
O(1), O(3), O(6), O(7), O(8)] stemming from four crystallo- C(15)–O(4)
4
–
C(5)–C(8)
C(19)–C(22)
C(1)–C(2)
C(1)–C(9)
graphically equivalent MTB anions. The coordination envi-
ronment (cn = 7) forms a strongly distorted monocapped octa-
hedron with O(7) as the capping atom (Figure 5b). The bond
lengths are 231.5(7) and 234.8(8) pm for Cd(2)–N and
2,2Ј-Bipyridine I
225.1(5)–266.9(6) pm for Cd(2)–O. The bond angles within
N(1)–C(30)
133.5(11)
135.4(10)
138.3(11)
N(2)–C(39)
N(2)–C(35)
131.6(11)
134.4(9)
the Cd(1) and Cd(2) polyhedra differ significantly from those N(1)–C(34)
C(33)–C(34)
in an ideal octahedron (Table 4). According to Brese and
O’Keeffe[ the bond valence sum for Cd(1) and Cd(2) was 2,2Ј-Bipyridine II
27]
calculated to 2.14 and 2.15, respectively.
N(3)–C(40)
N(3)–C(44)
C(44)–C(45)
132.2(12)
134.1(11)
149.9(13)
N(4)–C(49)
N(4)–C(45)
132.4(13)
135.0(11)
As shown in Figure 5c, neighboring Cd(1) and Cd(2) poly-
hedra share a common face [O(1), O(3), O(6)] leading to di-
meric polyhedra units. The Cd(1)···Cd(2) distance is 347.32(7)
pm.
Bond angle /°
MTB4–
O(1)–C(8)–O(2)
O(3)–C(15)–O(4)
O(1)–C(8)–C(5)
O(5)–C(22)–C(19)
4
–
123.3(7)
120.9(7)
119.1(7)
119.8(7)
113.5(5)
113.1(6)
102.7(5)
O(5)–C(22)–O(6) 123.4(7)
O(7)–C(29)–O(8) 123.5(8)
O(3)–C(15)–C(12) 118.5(6)
O(7)–C(29)–C(26) 118.2(8)
C(9)–C(1)–C(2)
C(9)–C(1)–C(16)
C(2)–C(1)–C(16)
The methanetetra-p-benzoate anion (MTB ) lies on a gene-
ral crystallographic position. The phenyl rings within the
4
–
MTB anion are twisted against each other by 58.4(2)° to
8
7.4(2)°. As seen in Figure 6 each tetraanion bridges seven C(9)–C(1)–C(23)
cadmium cations. All carboxylate groups are bound to Cd(2) C(23)–C(1)–C(2)
C(23)–C(1)–C(16)
101.8(5)
113.1(6)
113.1(5)
–
in a monodentate manner, except the COO group with C(29),
which coordinates in a bidentate mode only to Cd(2). The 2,2Ј-Bipyridine I/II
N(1)–C(34)–C(35)
116.1(7)
116.9(7)
N(2)–C(35)–C(34) 116.5(6)
N(4)–C(45)–C(44) 116.1(8)
Cd(1) cations are exclusively bidentately coordinated by the
N(3)–C(44)–C(45)
carboxylate groups. Thus, the carboxylate group with C(29)
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groups with C(22) and C(29) are twisted by 23.9(3)° and
5.5(5)°.
1
The two crystallographically independent 2,2Ј-bipyridine
molecules (I, II) are planar with small torsion angles between
the C N rings of 1.9(3)° and 3.3(3)°, respectively
5
4
–
In 2, the coordination of the MTB tetraanions to the Cd(2)
cations leads to infinite layers extending in the (001) plane
(
Figure 7 and Figure 8) with honeycomb-like pattern. The con-
4
–
nection between Cd(1) and MTB leads to a stabilization of
the structure by compensating the resulting negative charge of
the layers. Each MTB anion is linked to four dimeric Cd(1)/
Cd(2) polyhedra units (Figure S2, Supporting Information).
4
–
2
+
The 2,2Ј-bipyridine molecules bound to Cd are not essential
for the two-dimensionally infinite connection, but they com-
plete the Cd coordination sphere. This obviously prevents from
formation of a three-dimensional framework. The 2,2Ј-bipyr-
idine molecule I extends into the openings of the layer acting
as void filling group (Figure 7). The cavities along [001] (see
inset in Figure 7) have dimensions of about 320 pmϫ340 pm
[28]
(
inclusive van der Waals radii ).
Figure 8. View along [100] in 2. DMF molecules are drawn as sticks.
Hydrogen atoms are omitted for clarity.
situated within the layers as well as intercalated between adja-
cent layers (Figure 8, Figure S3, Supporting Information). The
partly disordered DMF molecules form weak and medium C-
H···O hydrogen bonds to the phenyl rings of MTB4– and to the
C N-rings of the 2,2Ј-bipyridine molecules (Table 6). Some C–
5
N–C–O torsion angles of the DMF molecules [0(3)°-12(4)°],
differ considerably from the values found in gaseous DMF
4 4 7 2
Figure 7. Crystal structure of [Cd (2,2Ј-bipy) (μ -MTB) ]·7DMF (2)
viewed on (001). Hydrogen atoms and uncoordinated DMF molecules
are omitted for clarity. The inset shows a space-filling model including
hydrogen atoms.
The layers are stacked in a …AA… sequence along the
[001] direction. Neighboring layers are not connected by any
interlayer hydrogen bonds. On the other hand, the layers are
confined by the 2,2Ј-bipyridine molecules (I) coordinated to
Cd(1) pointing towards the interlayer space. As seen in Fig-
ure 9, the 2,2Ј-bipyridine molecules (I) are parallel to the 2,2Ј-
¯
bipyridine molecules (I) of the neighboring layer along [110].
The distance between these 2,2Ј-bipyridine molecules is
348 pm indicating a very close π–π interaction between the
bipyridine rings, which additionally stabilizes the crystal struc-
ture.[
38,39]
Within each layer, neighboring 2,2Ј-bipyridine mol-
ecules (II) bound to Cd(2) are parallel to each other with a
distance of 345 pm. There are five crystallographically inde-
pendent DMF molecules (I–V) not bound to Cd , which are and uncoordinated DMF molecules are omitted for clarity.
Figure 9. Crystal structure of 2 viewed from [110]. Hydrogen atoms
2
+
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Figure S4, Supporting Information).[29] The small torsion while slowly heated to room temperature After adding of half concen-
(
trated HCl the THF was distilled. The white residue was dissolved in
angles of 4(2)° in DMF II and 0(3)° in DMF III are probably
caused by the formation of strong C–H···O hydrogen bonds
with short C···O contacts.
aqueous NaOH and filtered through diatomaceous earth. The filtrate
was acidified with HCl. The formed precipitate of methanetetra-p-ben-
zoic acid [tetrakis(4-carboxyphenyl)methane] was collected and dried.
Yield: 71%. EA: (molecular weight 496.46): C 68.78 (calcd. 70.16);
Table 6. Hydrogen bonds in 2.
1
13
H 4.51% (4.06%). H NMR ([D
6
]DMSO): δ (ppm) = 7.29, 7.85;
C
d(C···O) /pm
Ͻ(C–H···O) /°
NMR ([D ]DMSO): δ (ppm) = 65.2, 128.9, 129.3, 130.5, 149.8, 166.9.
6
C(24)MTB–H(24A)···O(1DA)DMF–I 338.6(16)
C(21)MTB–H(21A)···O(1DA)DMF–I 356.6(15)
147(1)
168(1)
157(1)
132(1)
123(1)
124(1)
170(1)
142(1)
154(1)
134(1)
Cd
Cd(NO
2
[μ
8
-MTB]·3H
·4H
2
O·DMF (1):[42]
2
O (0.4 mmol) were dissolved in 5 mL DMF (N,N-di-
4
H MTB (0.2 mmol) and
C(4)MTB–H(4A)···O(1DB)DMF–II
C(6)MTB–H(6A)···O(1DE)DMF–V
351.4(12)
355(2)
3
)
2
methylformamide) and 2 mL deionized water. The mixture was kept
at about 50 °C in a drying oven. After several days, colorless crystals
of 1 appeared.
C(40)MTB–H(40A)···O(1DE)DMF–V 320(3)
C(47)bipy–H(47A)···O(1DA)DMF–I
327.6(17)
C(31)bipy–H(31A)···O(1DB)DMF–II 326.4(19)
C(37)bipy–H(37A)···O(1DC)DMF–III 318(3)
C(38)bipy–H(38A)···O(1DD)DMF–IV 377(3)
C(48)bipy–H(48A)···O(1DD)DMF–IV 388(3)
]·7DMF (2):[42]
[Cd
4
(2,2Ј-bipy)
4
(μ
7
-MTB)
2
H
4
MTB (0.2 mmol), 2,2Ј-
bipyridine (0.8 mmol), and Cd(NO ) ·4H O (0.4 mmol) were dis-
solved in 7 mL DMF. The mixture was kept at about 70 °C in a drying
3 2 2
oven. Colorless crystals of 2 appeared after several days.
X-ray Diffraction: The intensity data were collected with a Nonius
KappaCCD diffractometer, using graphite-monochromated Mo-K ra-
α
diation. Data were corrected for Lorentz and polarization effects; ab-
Conclusions
We reported on the synthesis and structural properties of
sorption was taken into account on a semi-empirical basis using mul-
Cd [μ -MTB]·3H O·DMF (1) and [Cd (2,2Ј-bipy) (μ -MTB) ]·
[43–45]
2
8
2
4
4
+
7
2
tiple-scans.
(
The structures were solved by direct methods
2
7
DMF (2). In 1 the connection between the Cd cations and
[46]
2
SHELXS ) and refined by full-matrix least-squares techniques
4
–
the MTB tetra-anions leads to an open three-dimensional
[46]
against |F
o
| (SHELXL-97 ). The hydrogen atoms bound to the water
¯
framework with channels along [110] and [110]. The channels
accommodate uncoordinated DMF and water molecules. Com-
Table 7. Crystallographic data.
pound 2 was synthesized with 2,2Ј-bipyridine as an additional
2
+
4–
ligand. The Cd cations are linked by MTB anions to form
1
2
infinite layers parallel to (001). The layers contain small open-
Empirical formula
C
32
H
29NCd
2
O
12
C
119 113 4 23
H N15Cd O
ings. The 2,2Ј-bipyridine molecules act as N-donor ligands Crystal system
monoclinic
C2/c (no.15)
triclinic
2
+
Space group
Lattice constants
a /pm
P 1¯ (no.2)
completing the coordination environment of Cd . π–π interac-
tions between 2,2Ј-bipyridine rings of neighboring layers obvi-
ously contribute to stabilize the structure. The results confirm
1821.30(6)
2175.08(6)
1269.87(4)
90
129.684(1)
90
3.8714(2)
4
844.36
1224.84(4)
1418.85(5)
2033.49(4)
85.831(2)
88.351(2)
68.261(1)
3.27391(17)
1
b /pm
that ligands with tetrahedrally directed functional groups favor c /pm
α /°
β /°
γ /°
the formation of diamondoid arrangements as expected and
encourage further use of these buildings blocks in the synthesis
of open framework structures.
Cell volume /nm3
Formulas in unit cell
–1
Formula weight /g·mol
2570.84
1.304
Density (calcd.) /g·cm–3 1.449
Experimental Section
Synthesis of Tetrakis(4-bromophenyl)methane:[40] Tetraphenyl-
methane (54 mmol) synthesized as described elsewhere, was slowly
dropped in 60 mL bromine in a round-bottomed flask under ice-cool-
ing and stirred for 45 min. Afterwards, 150 mL ethanol was added
Wavelength /pm
71.073
Absorption coefficient / 1.153
0.709
[
41]
–1
mm
Numerical absorption
correction
min./max. transmit-
tance 0.6841/0.7456
min./max. transmit-
tance 0.6539/0.7456
Temperature /K
Crystal size /mm
F(000)
Θ range /°
Limiting indices
183 (2)
0.104ϫ0.094ϫ0.084 0.088ϫ0.082ϫ0.076
(
cooling with ice). The precipitate formed was collected by filtering
and dried. The solid was dissolved in 500 mL CHCl and washed with
aqueous Na SO solution. The organic phase was distilled and the
3
1680
1308
2
3
1.87–27.47
h: –23/+23; k: –28/
2.09–27.45
white product formed was recrystallized from a dioxane/ acetonitrile
mixture. Yield 63%. EA: (molecular weight 636.01): C 46.46 (calcd.
4
δ (ppm) = 6.99, 7.37. C NMR ([D
1
h: –15/14; k: –15/
+18; l: –26/+26
20389
+28; l: –16/+15
1
7.21); H 2.30 (2.54); Br 51.24% (50.25%). H NMR ([D
6
]DMSO):
Reflections collected
Independent reflections
Structure refinement
Refined parameters
Goodness-of-fit on |F|2
Residuals (all data)
13612
13
6
]DMSO): δ (ppm) = 63.6, 120.8,
4427 (Rint = 0.0314)
14138 (Rint = 0.0341)
Full-matrix least-squares on |F|2
31.1, 132.4, 144.4.
219
767
Synthesis of Methanetetra-p-benzoic Acid (H
4
MTB):[42] The reac-
1.079
1.039
tion was carried out in an argon atmosphere. Tetrakis(4-bromophenyl)
methane (7.9 mmol) was dissolved in 500 mL dried THF. Buthylli-
thium was slowly dropped into the THF solution at –70 °C. The solu-
tion was stirred for 10 min. Afterwards, CO
into the solution whilst stirring and the reaction mixture was mean-
R
1
= 0.0479, wR
2
=
1 2
R = 0.1191, wR =
0
.1166
0.2633
Max. features in last Dif- 1255 and –646
ference Fourier synthe-
sis /e·nm–3
5869 and –2312
2
was introduced for 2 h
Z. Anorg. Allg. Chem. 0000, 0–0
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
molecule O(1 W) of 1 were located by difference Fourier synthesis
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2
[
46]
non-hydrogen atoms were refined anisotropically.
used for structure representations.
piled in Table 7.
DIAMOND was
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Copies of the data can be obtained free of charge on quoting the de-
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3
Keywords: Methanetetra-p-benzoic acid; Cadmium; Coordi-
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Z. Anorg. Allg. Chem. 0000, 0–0
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
S. Harms, R. Köferstein, H. Görls, C. Robl* ................... 1–8
Syntheses and Crystal Structures of Two Cadmium Meth-
anetetrabenzoates Featured by Open Framework and Infinite
Layers
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