5,5′-Dicyano-2,2′-bipyridine silver complexes: Discrete units or co-ordination polymers through a chelating and/or bridging metal-ligand interaction

Article abstract of DOI:10.1039/a807450j

The ambidentate ligand 5,5′-dicyano-2,2′-bipyridine (L) was found to function as a bi-, tri- or tetra-dentate chelate or chelate/bridging ligand in the co-ordination of silver ions. The mode of co-ordination depends on the anion and the crystallization conditions and was elucidated by single crystal X-ray diffractometry. With metal-co-ordinating anions such as NO₃^- and CF₃SO₃^- a tridentate co-ordination mode of L is observed which involves the two bipyridine nitrogen donor atoms and one cyano group. The latter bridges to a neighboring silver center so that a one-dimensional co-ordination polymer results. For NO₃^- this co-ordination polymer forms a 2₁ helix. With less co-ordinating anions such as BF₄^- and PF₆^- monomeric bis-chelate complexes are obtained, where L assumes a bidentate co-ordination mode involving only the bipyridine nitrogen donor atoms. In the case of the PF₆^- anion a variation in the solvent of crystallization also produced a two-dimensional hexagonal co-ordination polymer where L functions as a tetradentate ligand using all four nitrogen donor atoms in chelation and bridging to the silver centers.

Full text of DOI:10.1039/a807450j

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5
,5Ј-Dicyano-2,2Ј-bipyridine silver complexes: discrete units or
co-ordination polymers through a chelating and/or bridging
metal–ligand interaction
a
a
b
b
He-Ping Wu, Christoph Janiak,* Gerd Rheinwald and Heinrich Lang
a
Institut für Anorganische und Analytische Chemie, Universität Freiburg, Albertstr. 21,
D-79104 Freiburg, Germany. E-mail: janiak@uni-freiburg.de
Institut für Chemie, Zehrstuhl für Anorganische Chemie, Technische Universität Chemnitz,
Strasse der Nationen 62, D-09111 Chemnitz, Germany
b
Received 24th September 1998, Accepted 6th November 1998
The ambidentate ligand 5,5Ј-dicyano-2,2Ј-bipyridine (L) was found to function as a bi-, tri- or tetra-dentate chelate
or chelate/bridging ligand in the co-ordination of silver ions. The mode of co-ordination depends on the anion and
the crystallization conditions and was elucidated by single crystal X-ray diffractometry. With metal-co-ordinating
Ϫ
Ϫ
anions such as NO3 and CF SO3 a tridentate co-ordination mode of L is observed which involves the two
3
bipyridine nitrogen donor atoms and one cyano group. The latter bridges to a neighboring silver center so that a
Ϫ
one-dimensional co-ordination polymer results. For NO this co-ordination polymer forms a 2 helix. With less
3
1
Ϫ
Ϫ
co-ordinating anions such as BF4 and PF6 monomeric bis-chelate complexes are obtained, where L assumes a
bidentate co-ordination mode involving only the bipyridine nitrogen donor atoms. In the case of the PF6 anion
Ϫ
a variation in the solvent of crystallization also produced a two-dimensional hexagonal co-ordination polymer
where L functions as a tetradentate ligand using all four nitrogen donor atoms in chelation and bridging to the
silver centers.
5
Introduction
co-ordination polymers. A highlighted example is the co-
ordination of TEB with AgSO CF in benzene that led to the
isolation of the compound [Ag(CF SO )(TEB)]ؒ2C H , which
exhibits 15 Å channels and is porous to benzene exchange.
We investigate here the co-ordination chemistry of 5,5Ј-
dicyano-2,2Ј-bipyridine (L). This ambidentate ligand can be
thought of as combining the ligating properties of the chelating
3
3
Metal complexes of chelating 2,2Ј-bipyridine or bridging
6
3
3
6
6
4
,4Ј-bipyridine or derivatives thereof are of constant and
1
general interest in metal co-ordination chemistry. 4,4Ј-Bipyr-
idine has recently gained considerable interest in the synthesis
of (rectangular) two-dimensional network structures. The
2
generation of such frameworks is a promising path in the search
for stable microporous metal–organic networks that exhibit
reversible guest exchange and possibly selective catalytic
2
,2Ј-bipyridine and the bridging 4,4Ј-dicyanobiphenyl ligand.
The idea behind the use of such ambidentate ligands is to have
cross-connecting blocks (tectons) for co-ordination polymers
based on the endo chelation of two ligands with an appropriate
metal center (1) or to supply functional donor atoms within the
walls of the co-ordination polymer when the ligands are solely
exo bridging (2).
3,4
activity.
N
N
N
N
Our research has been concerned with the utilization of ambi-
dentate endo-chelating/exo-bridging modified 2,2Ј-bipyridine
CN
7
ligands such as 5,5Ј-diamino-2,2Ј-bipyridine or 2,2Ј-dimethyl-
8
4
,4Ј-bipyrimidine and ligands of the tris(pyrazolyl)borate
9,10
type for the assembly of metal co-ordination polymers.
In
this paper we describe the results of synthetic and structural
studies of metal complexes with the ligand 5,5Ј-dicyano-2,2Ј-
bipyridine (L) and try to elucidate the factors which lead to
bridging, chelating or simultaneous bridging/chelating metal
co-ordination. As a metal we have chosen silver() which
together with copper() is a preferred ligand linker because of
NC
CN
5,11–13
their favored tetrahedral co-ordination mode.1
In addition,
3
silver can also assume a linear co-ordination and would thus
NC
CN
be ideal for testing the formation of cross-linkers as depicted in 1.
Results and discussion
NC
CN
The synthesis of 5,5Ј-dicyano-2,2Ј-bipyridine as reported in the
literature is the reaction of 2,2Ј-bipyridine-5,5Ј-dicarboxamide
with POCl in CHCl under sonication (50 kHz) to give the
N
N
Ligands containing CN-donors such as 4,4Ј-dicyanobi-
phenyl, 1,3,5-tris(4-cyanophenylethynyl)benzene (TEB) and
others are also excellent bridging ligands to synthesize porous
3
3
14
product in 86% yield. Another method is the sublimation
of a mixture of 2,2Ј-bipyridine-5,5Ј-dicarboxamide and P O
4
10
J. Chem. Soc., Dalton Trans., 1999, 183–190
183

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NC
CN
2
H N(O)C
C(O)NH2
N
N
N
N
N
N
C
M
(F3CCO)2O
pyridine
dioxane
N
Crude
product
P4O
C
0
.2 mbar
N
2
00 °C
1
NC
CN
(1)
N
N
is obtained in high yield. This crude product was then
N
again dehydrated with P O at 0.2 mbar/200 ЊC to give the
4
10
M
NC
CN
M
final product in 43% yield. This method has the advantage of
N
15
a higher yield (compared to the literature), the possibility
N
C
N
C
of starting with an increased amount of the dicarboxamide,
and the use of a lower sublimation temperature.
The reaction routes of 5,5Ј-dicyano-2,2Ј-bipyridine (L) with
silver metal salts are summarized in Scheme 1. The reaction of
silver nitrate or silver trifluoromethane sulfonate with L in a
N
N
2
:1 metal-to-ligand stoichiometry in ethanol or toluene,
respectively, led to the formation of compounds which feature a
:1 metal-to-ligand ratio (3 and 4). Both reactions were carried
N
N
1
out by heating the mixture of reactants to 95 ЊC for 24 h
C
N
C
N
and then slowly cooling to room temperature (RT) at a rate of
N
Ϫ1
1
ЊC h .
M
NC
CN
M
Treating L with an excess of silver salts of less co-ordinating
N
tetrafluoroborate or hexafluorophosphate anions (again with
:1 metal-to-ligand stoichiometry) at room temperature gave
2
2
silver complexes with a 1:2 (5 and 6) or a 1:1 metal-to-ligand
ratio (7). The outcome of these latter reactions could be subtly
affected by a change in solvents. For BF4 as the anion an
15
Ϫ
under vacuum at a temperature of 300 ЊC. However, a two-
fold dehydration treatment and a two-fold sublimation of the
crude (sublimed) product was found necessary to obtain the
product in satisfactory purity. This finally gave the dicyanobi-
pyridine in a low yield of only 29%. Furthermore, if more than
ethanol–tetrahydrofuran mixture gave the same isostructural
complex composition 5 as an acetonitrile–ethanol–methylene
chloride or toluene mixture as shown by X-ray powder dif-
Ϫ
fractometry. For PF6 as anion the inclusion of acetonitrile
0
.5 g of the dicarboxamide was used in the dehydration reaction
in the solvent mixture led to a 1:1 metal–ligand compound
7 instead of the 1:2 complex 6. All compounds were obtained
in yields above 50%. Characterization was mainly based on
X-ray diffraction studies.
The metal–ligand co-ordination modes elucidated from
single-crystal structure determinations are depicted in Figs. 1,
with P O this resulted in a further decrease of the yield of the
4
10
product. Thus, we report here a modified method which is based
on a two-times dehydration treatment of the dicarboxamide,
first with a trifluoroacetic anhydride–pyridine system and
then with P O [eqn. (1)]. The initial dehydrated crude product
4
10
1[Ag(NO3)(µ-L)]
∞1 [Ag(CF3SO3)(µ-L)]
∞
3
4
AgNO3
3 3
Ag(CF SO )
ethanol
5 °C to RT
toluene
95 °C to RT
9
AgBF4
ethanol/THF
or
CH3CN/ethanol/
CH2Cl2(toluene)
[Ag(L)2]BF4
NC
CN
5
N
N
L
ethanol/THF
or
CH3CN/ethanol/
toluene
AgPF6
AgPF6
ethanol/CH Cl /
2
2
toluene
2[Ag(µ-L)]PF6 · 1/2 C6H5Me
∞
[Ag(L)2]PF6
6
7
Scheme 1
1
84
J. Chem. Soc., Dalton Trans., 1999, 183–190

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Ϫ
Ϫ
3
, 5, and 7 for the 1-D co-ordination polymers 3 and 4, the
NO3 and CF SO3 in 3 and 4, respectively, still co-ordinate
3
bis-chelate complexes 5 and 6, and the 2-D framework 7,
respectively. The structural studies revealed that the anions
to a metal center with one of the oxygen atoms (Figs. 1 to 4).
They serve as terminal ligands and occupy one position in the
distorted tetrahedral co-ordination sphere of the silver ions. At
the same time, the dicyanobipyridine ligand chelates a silver
atom in 3 and 4 through the bipyridine moiety and bridges to a
neighboring silver center through one of the exodentate cyano
groups. Hence, the silver co-ordination sphere consists of
an oxygen atom, two bipyridine nitrogen atoms and a cyano
nitrogen atom. The planes of the two pyridine rings within a
bipyridine ligand deviate by 9.1(1) (3) and 16.9(3)Њ (4) from
coplanarity. The potentially tetradentate dicyanobipyridine
group functions as a tridentate ligand only; the other cyano
group is not involved in metal co-ordination even though a
twofold excess of metal over ligand has been offered during
the reaction. The bridging action of the ligand L gives rise to
1
one-dimensional co-ordination polymers, [Ag(NO )(µ-L)]
∞
3
1
3
and [Ag(CF SO )(µ-L)] 4, whose metal–ligand arrange-
∞ 3 3
ment is depicted in Figs. 1 and 3, respectively. While the chain
in 4 is oriented rather straight with the metal and bipyridine
ligands lying all in one plane, it is noteworthy that the strand
for the silver nitrate complex 3 assumes a 2 -helical conform-
1
ation. These chain conformations together with the packing
of neighboring strands are further illustrated in Figs. 2 and 4
with the help of stereoplots. The chains run parallel in the
Fig. 1 Section of the one-dimensional co-ordination polymer of
1
[
Ag(NO )(µ-L)] 3.
∞
3
1
Fig. 2 (a) Stereoplot of the chain structure of [Ag(NO )(µ-L)] 3 illustrating the helical nature and the intertwining of neighboring 2 helices (view
∞
3
1
along a) and (b) schematic representation of the interdigitation of adjacent strands in 3.
J. Chem. Soc., Dalton Trans., 1999, 183–190
185

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case of 4. For 3 neighboring strands are of opposite helicity
and interlock or interdigitate as is schematically depicted in
Fig. 2(b). Bipyridine ligands from adjacent strands mutually
intrude into the openings within the chain. The interdigitated
bipyridine moieties form π–π stacks with an interplane distance
of 3.47 Å. In the orientation of neighboring chains a weakly
cation π contact might play a small role in 3, as the Ag ؒ ؒ ؒ C
distances are 3.497 (to C3), 3.596 (to C4), and 3.716 Å (to C5).
Silver is known to have a remarkably high affinity for some
16
aromatic π-donor systems.
When silver salts of only weakly co-ordinating anions
Ϫ
Ϫ
such as BF4 and PF6 are employed, as in the isostructural
Ϫ
Ϫ
8,17
bridging mode of the NO3 and CF SO3 anions may play a
compounds 5 and 6, respectively,
the metal co-ordination
3
role. Interchain non-bonding Ag ؒ ؒ ؒ O contacts are 3.001 Å
(
to O1) in 3 and 3.370 and 3.590 Å (to O2 and O3, respectively)
in 4. In addition, an interchain silver–pyridine or electrostatic
Fig. 3 Metal–ligand arrangement in a segment of the one-dimen-
Fig. 5 Molecular structures of the bis-chelate complex [AgL ]BF 5
2 4
1
sional co-ordination polymer of [Ag(CF SO )(µ-L)] 4.
(shown) and of the isostructural [AgL ]PF 6.
∞
3
3
2 6
1
∞
Fig. 4 Stereoplot of the chain structure of [Ag(CF SO )(µ-L)] 4 to show the parallel alignment of the chains in contrast to those of 3. View along a.
3
3
Ϫ
Fig. 6 Stereoscopic partial cell plot of complex 5 to illustrate the packing of the bis-chelate complexes. The BF4 anion has been omitted for clarity.
View approximately along b.
1
86
J. Chem. Soc., Dalton Trans., 1999, 183–190

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2
1
–
Fig. 9 Partial cell plot of [Ag(µ-L)]PF ؒ
C H Me 7 viewed along the
6 5
∞
6
2
ab plane to show the . . . BAABAA . . . sequence of the metal–ligand
2
Fig. 7 Section of the two-dimensional framework of ∞[Ag(µ-L)]PF6ؒ
(A) and toluene–PF (B) layers which were separately depicted in Figs. 7
and 8.
6
1
–
C H Me 7. View along c. The toluene molecule and two of the three
2
6
5
Ϫ
crystallographically different PF6 anions are not shown for clarity (see
Fig. 8 for these remaining moieties and Fig. 9 for the complete
ensemble). Owing to space requirements the ligand is not fully labelled.
Symmetry equivalent positions: Ϫ2 = Ϫy ϩ 1, x Ϫ y Ϫ 1, z; Ϫ3 =
Ϫx ϩ y ϩ 1, Ϫx ϩ 1, z; Ϫ7 = Ϫx ϩ 1, Ϫy ϩ 1, Ϫz.
the ionic bis-chelate complexes through a bipyridine π–π inter-
action of neighboring molecules with an interplane distance of
3
.76 Å.
The working hypothesis that the co-ordination of the
exodentate cyano nitrogen atoms would be exercized only when
the simultaneous endodentate co-ordination of two chelating
bipyridine moieties was not possible, was proven wrong with
the structure elucidation of complex 7. In this two-dimensional
2
co-ordination polymer of formula [Ag(µ-L)]PF ؒ¹C H Me the
∞
6
6
5
¯
²
dicyanobipyridine ligand chelates a silver ion and bridges to
two other metal centers with both of the exodentate cyano
groups (Fig. 7). Two types of C -symmetrical triangular open-
3
ings are thus created in this framework. In the larger ones one
of the three crystallographically different PF anions is partly
6
immersed. The other two PF anion sites lie within a layer
6
together with the toluene solvent molecules (Fig. 8). The metal–
ligand layer (A, together with one PF ) and the toluene–PF6
6
layer (B) are stacked along the c direction in a . . . BAABAA . . .
sequence as is illustrated in Fig. 9. Clearly, a silver–toluene or
electrostatic cation π contact is present in 7, as rather short
Ag ؒ ؒ ؒ C distances of 2.815 (to C18) and 2.830 Å (to C17) are
2
Fig. 8 The toluene–PF layer in the crystal structure of ∞[Ag(µ-L)]-
6
1
PF6ؒ
–
C H Me 7 which contains two of the three crystallographically
different PF6 sites. One of these anions P3 sits on a special position
and is disordered. View along c as in Fig. 7.
2
6
5
Ϫ
16
encountered. The remaining silver–toluene contacts are 3.381
(
to C16), 3.771 (to C15), 3.769 (to C14), and 3.335 Å (to C13).
The two pyridine rings are strongly twisted by 21.0(1)Њ in 7,
more than in the other compounds 3–6. The metal environment
is again almost halfway between tetrahedral and square planar.
The interplane angle between the five-membered chelate ring
and the plane formed by the cyano nitrogen atoms with the
silver center is 25.5(2)Њ.
sphere is fully constructed from the ligand donor atoms (Figs.
5
and 6). However, only the endodentate bipyridine nitrogen
atoms serve as donor atoms towards silver; the exodentate
cyano groups are not involved in metal co-ordination even
though a twofold molar excess of metal over ligand has again
been offered during the reaction. The results are cationic bis-
ϩ
Ϫ
4
Ϫ
Selected bond distances and angles for compounds 3–6 are
summarized in Table 1.
chelate complexes of the type [AgL ] with BF (5) and PF6
2
(
6) as the anion. The non-involvement of the cyano groups is
ϩ
remarkable in view of their known high affinity towards Ag
18
ions. The cyano nitrogen atom is perhaps a somewhat weaker
donor atom when compared with a pyridine nitrogen atom.
The co-ordination of the latter is definitely enhanced further
through the chelate effect of the bipyridine unit. Two chelating
ligands construct a strongly distorted environment, almost
halfway between tetrahedral and square planar as is evident
from the graphical presentation in Figs. 5 and 6. The interplane
angle between the two five-membered chelate rings formed by
Ag–N1–C5–C6–N2 and their symmetry equivalent atoms is
Conclusion
In the ambidentate ligand 5,5Ј-dicyano-2,2Ј-bipyridine (L) both
the bipyridine nitrogen and the exodentate cyano nitrogen
atoms can function as donors towards a silver metal center. The
choice of metal co-ordination was found to depend on the
8,19
counter anion
or the solvent of crystallization. When a co-
ordinating anion was present in the silver co-ordination sphere
L acted as a tridentate ligand, chelating through the bipyridine
moiety and bridging through one of the cyano groups. With
non-co-ordinating anions the silver co-ordination sphere
was solely constructed from the ligand nitrogen donors. Either
the formation of bis-chelate silver complexes through bis-
bipyridine nitrogen co-ordination could be observed with L
as a bidentate ligand, or, with a slight change in the solvent
mixture for crystallization, L could also become tetradentate
5
5.34(5)Њ for 5 and 56.31(5)Њ for 6. The origin of this distortion
is not clearly apparent as the nearest non-co-ordinating atoms
are fluorine atoms, which are, however, 3.12 (5) and 3.16 Å (6)
away. The two pyridine rings of the bipyridine ligand remain
essentially coplanar to within 3Њ for 5 or 5Њ for 6 (based on the
torsion angles N1–C5–C6–N2 and C4–C5–C6–C7). A stereo-
scopic cell plot of 5 in Fig. 6 serves to illustrate the packing of
J. Chem. Soc., Dalton Trans., 1999, 183–190
187

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Table 1 Selected bond distances (Å) and angles (Њ) for complexes 3–7
1
∞
1
∞
2
∞
1
–
Compound
[Ag(NO )(µ-L)] 3
[Ag(CF SO )(µ-5)] 4
[AgL ]BF 5
[AgL ]PF 6
[Ag(µ-L)]PF6ؒ2C H Me 7
6 5
3
3
3
2
4
2
6
Ag1–N1bipy
Ag1–N2bipy
Ag1–N3CN
Ag1–N4CN
Ag1–O1
N3–C11
N4–C12
2.339(2)
2.453(2)
2.349(6)
2.322(4)
2.356(2)
2.312(2)
2.325(2)
2.378(3)
2.377(6)
2.444(6)
g: 2.375(7)
h: 2.294(7)
a: 2.425(3)
2.371(2)
1.143(4)
1.148(4)
c: 2.156(5)
2.689(5)
1.139(7)
1.116(8)
1.139(4)
1.137(4)
1.140(5)
1.144(5)
1.134(10)
1.146(10)
Within the anions
O1–N5 1.277(3)
O2–N5 1.236(3)
O3–N5 1.240(3)
O1–S1 1.438(5)
O2–S1 1.438(5)
O3–S1 1.430(5)
B1–F1 1.389(4)
B1–F2 1.374(4)
P1–F1 1.596(2)
P1–F2 1.599(3)
P1–F3 1.596(2)
P1–F 1.539(7)–1.569(9)
P2–F 1.576(10)–1.601(11)
P3–F 1.40(4)–1.54(4)
N1–Ag1–N2
N1–Ag1–O1
N2–Ag1–O1
N1–Ag1–N4
N2–Ag1–N4
O1–Ag1–N4
C12–N4–Ag1
X–O1–Ag1
68.42(7)
148.69(8)
129.38(8)
a: 106.44(8)
a: 90.32(8)
a: 99.54(9)
b: 148.4(2)1
X = N5; 103.0(2)
70.6(2)
105.5(2)
118.3(2)
c: 129.2(2)
c: 144.3(2)
c: 87.3(2)
d: 168.3(6)
X = S1: 110.8(3)
N1–Ag1–N2
N1–Ag1–N1
N2–Ag1–N2
N1–Ag1–N2
N1–Ag1–N3
N1–Ag1–N4
N2–Ag1–N3
N2–Ag1–N4
N3f–Ag1–N4g
71.12(8)
e: 136.5(1)
e: 165.7(1)
e: 114.57(8)
70.75(9)
f: 170.5(1)
f: 135.3(1)
f: 113.12(9)
68.38(19)
g: 88.4(2)
h: 164.6(3)
g: 144.9(3)
h: 101.7(3)
94.5(3)
Symmetry transformations apply to the last atom in the bond or angle definition if not assigned otherwise: a = Ϫx ϩ 0.5, y Ϫ 0.5, Ϫz ϩ 0.5;
b = Ϫx ϩ 0.5, y ϩ 0.5, Ϫz ϩ 0.5; c = Ϫx ϩ 1, y ϩ 0.5, Ϫz ϩ 1.5; d = Ϫx ϩ 1, y Ϫ 0.5, Ϫz ϩ 1.5; e = Ϫx, y, Ϫz ϩ 0.5; f = Ϫx ϩ 1, y, Ϫz ϩ 1.5;
g = Ϫy ϩ 1, x Ϫ y Ϫ 1, z = _2 in Fig. 7; h = Ϫx ϩ y ϩ 1, Ϫx ϩ 1, z = _3 in Fig. 7.
utilizing all four nitrogen donor atoms in chelating and
bridging co-ordination between three metal centers. Pyridine
π–π interactions and silver–pyridine or –toluene cation π
contacts were controlling factors in the non-bonded crystal
organization.
1540m, 1468s, 1373s, 1292m, 1240s, 1170w, 1130w, 1053w,
1030s, 948w, 850s, 795w, 776w, 751m, 726m, 652m and 554m
cm .
Modified method. Trifluoroacetic anhydride (2.5 ml, 18.4
mmol) was added dropwise to a stirred ice-cooled suspension
of 2,2Ј-bipyridine-5,5Ј-dicarboxamide (2.0 g, 8.4 mmol) in
anhydrous 1,4-dioxane (150 ml) and anhydrous pyridine
Ϫ1
Experimental
(
1.5 ml, 18.4 mmol). Over the period of the addition the
The NMR spectra were collected on a Varian O-300 spec-
temperature was kept below 5 ЊC. The reaction mixture was
then allowed to warm to room temperature and stirred for
10 h. Then 100 ml of distilled water were added, the solid prod-
uct was removed by filtration and washed with water to obtain
1.5 g of crude product. A 0.2 g amount of this was heated
together with 0.5 g of P O in a sublimator at 0.2 mbar/180 ЊC
1
13
trometer (300.0 MHz for H, 75.4 MHz for C) and calibrated
1
13
against the solvent signal (d -THF: H, δ 1.73; C, δ 25.2), IR
8
spectra on a Perkin-Elmer 783 spectrophotometer as KBr disks
or as Nujol mulls. Elemental analyses were carried out with
a Perkin-Elmer Elemental Analyzer E 240 C. X-Ray powder
diffractograms were obtained with a Siemens powder diffract-
ometer D5000 using Cu-Kα radiation. All crystallizations of
the silver complexes were carried out in the dark.
4
10
until sublimation had ceased. The solid was purified by resub-
limation to obtain 0.12 g of a colorless solid (L) (43% yield), mp
275.4–276.2 ЊC. The IR spectrum was identical to that of the
1
above sample. H NMR (d -THF): δ 8.34 (dd, 2 H, H4, H4Ј,
8
Preparations
J = 8.3, 2.1), 8.57 (dd, 2 H, H3, H3Ј, J = 8.2, 0.8 Hz) and 8.9 (br,
13
2
H, H6, H6Ј). C NMR (d -THF): δ 111.63 (C5, C5Ј), 117.49
8
2
,2Ј-Bipyridine-5,5Ј-dicarboxamide. A mixture of 3.0 g of
(
1
CN), 122.38 (C3, C3Ј), 142.33 (C4, C4Ј), 153.40 (C6, C6Ј) and
57.75 (C2, C2Ј).
diethyl 2,2Ј-bipyridine-5,5Ј-dicarboxylate, 100 ml of ethanol
and 100 ml of ethylene glycol was saturated with ammonia
and heated in a sealed round bottom flask in an oil-bath at
1
∞
(
ì-5,5Ј-Dicyano-2,2Ј-bipyridine)nitratosilver(I),
[Ag(NO )-
3
9
5 ЊC for 48 h. The precipitate formed was collected and
washed with hot ethanol and ethylene glycol. 1.9 g (79%) of
,2Ј-bipyridine-5,5Ј-dicarboxamide was obtained, mp >280 ЊC
(
(
ì-L)] 3. In a 50 ml round bottom flask an ethanolic solution
10 ml) of L (21 mg, 0.10 mmol) was added to an ethanolic
2
15
solution (15 ml) of silver nitrate (34 mg, 0.20 mmol). A yellow
precipitate immediately formed. The flask was sealed and
heated to 95 ЊC for 24 h. The reaction mixture was then cooled
(
lit. >310 ЊC). IR: 3375s, 3170s, 1660s, 1634s, 1599s, 1548m,
1
1
6
480w, 1410s, 1370m, 1285w, 1252m, 1165w, 1132m, 1118w,
055w, 1028m, 955w, 860m, 810w, 790m, 760w, 720m, 665m,
59m, 638m, 600w and 535w cm .
Ϫ1
Ϫ1
to room temperature at a rate of 1 ЊC h . Well formed yellow
rod-like crystals were produced, collected by filtration, washed
with water and ethanol and dried under vacuum. Yield: 28 mg
5
,5Ј-Dicyano-2,2Ј-bipyridine (L). This compound was pre-
(
76%, based on L) (Found: C, 38.07; H, 1.56; N, 17.92. Calc. for
pared by two methods. 1
5
C H AgN O : C, 38.30; H, 1.60; N, 18.60%). IR: 3440m,
Literature method.
2,2Ј-Bipyridine-5,5Ј-dicarboxamide
12
6
5
3
3
1
110w, 3062w, 3030w, 2240m, 1725w, 1598s, 1540w, 1478s,
(
0.2 g, 0.8 mmol) and 0.5 g (1.7 mmol) of P O were placed into
4 10
468m, 1387s, 1316m, 1240m, 1249w, 1030m, 849m, 735m, 651s
a sublimator and kept at 0.2 mbar/300 ЊC until the sublimation
had ceased. The crude product which easily absorbs water from
the air was resublimed to obtain 0.1 g of a colorless solid. This
was repurified with 0.2 g of P O in a sublimator at 0.2 mbar/
00 ЊC followed by resublimation to give 0.05 g of L (29%
yield), mp 275.9–276.6 ЊC (lit. 269–271, 284–285 ЊC ). IR:
Ϫ1
and 555w cm .
(ì-5,5Ј-Dicyano-2,2Ј-bipyridine)(trifluoromethanesulfonato)-
4
10
1
∞
3
silver(I), [Ag(CF SO )(ì-L)] 4. In a 50 ml round bottom
3
3
15
14
flask a solution of Ag(CF SO ) (56 mg, 0.22 mmol) in 5 ml of
3 3
3
420w, 3070w, 2240s, 1985w, 1898w, 1796w, 1720s, 1597s,
88 J. Chem. Soc., Dalton Trans., 1999, 183–190
toluene was added to 15 ml of a toluene solution of L (21 mg,
1

View Online
0
.1 mmol). A white precipitate immediately formed. The flask
16.85%). IR: 3435m, 3139w, 3064w, 3036w, 2238m, 1728w,
was sealed and heated to 95 ЊC for 24 h, followed by cooling to
room temperature at 1 ЊC h . The well formed colorless to pale
1600s, 1560w, 1540w, 1480s, 1466m, 1388s, 1380m, 1323m,
1250m, 1150w, 1033m, 947w, 860m, 850w, 830m, 788w, 733w,
670w, 650w and 562w cm .
Slow concentration of a mixture of solutions of AgPF6
in ethanol and of L in THF (or dichloromethane and toluene)
in the mole ratio of 1:1 (or 2:1) also gave complex 6, with
the yield being about 57%. The identity was based on IR
spectroscopy and X-ray powder diffractometry.
Ϫ1
Ϫ1
green crystals were collected by filtration, washed with ethanol
and dried under vacuum. Yield 31 mg (67%) (Found: C, 33.37;
H, 1.26; N, 11.86. Calc. for C H AgF N O S: C, 33.69; H,
13
6
3
4
3
1
2
1
5
.29; N, 12.10%). IR: 3440m, 3120w, 3070w, 3138w, 2270w,
240m, 1598s, 1540m, 1480m, 1468s, 1374m, 1260s, 1240m,
188w, 1160s, 1035s, 1030s, 945w, 850s, 705m, 650m, 634m,
Ϫ1
80w, 555m and 520m cm .
(
ì -5,5Ј-Dicyano-2,2Ј-bipyridine)silver(I)
hexafluorophos-
C H Me 7. A solu-
3
2
1
–
phatehemitoluene solvate, ∞[Ag(ì -L)]PF ؒ
Bis(5,5Ј-dicyano-2,2Ј-bipyridine)silver(I)
tetrafluoroborate,
3
6
2
6
5
tion of 27 mg (0.11 mmol) of AgPF in a mixture of 1 ml of
[
AgL ]BF 5. A solution of AgBF (21 mg, 0.10 mmol) in 10 ml
6
2
4
4
acetonitrile and 2 ml of ethanol was overlayered in a test-tube
with a solution of 10 mg (0.05 mmol) of L in 6 ml of toluene.
After 8 d at room temperature (in the dark) pale yellow crystals
had formed. Yield 16 mg (64% based on L) (Found: C, 36.66;
of ethanol was carefully overlayered in a test-tube with a
solution of L (10 mg, 0.05 mmol) in 10 ml of tetrahydrofuran.
After 10 d at room temperature, well formed orange crystals
had appeared at the boundary between ethanol and THF.
They were collected, washed with water and ethanol and dried
under vacuum. Yield 8 mg (66% based on L) (Found: C, 47.40;
H, 1.97; N, 18.38. Calc. for C H AgBF N : C, 47.54; H, 1.98;
H, 1.93; N, 11.40. Calc. for C15.5H AgF N P: C, 36.8; H, 1.98;
10
6
4
N, 11.90%). IR: 3440m, 3108w, 3070w, 2240m, 1730w, 1598s,
1
1
5
550w, 1540s, 1478s, 1467s, 1374m, 1280w, 1240s, 1088s, 1054w,
030s, 950m, 850s (br), 776m, 734m, 695m, 650m, 565s and
55m cm .
24
12
4
8
N, 18.48%). IR: 3440m, 3124w, 3064w, 3235w, 2239m, 1725w,
Ϫ1
1
1
8
598s, 1560w, 1540w, 1478s, 1467m, 1388s, 1376m, 1320m,
241m, 1126m, 1088m, 1070s, 1050s, 1030s, 1000m, 946w, 938w,
69m, 850w, 735m, 670w, 650w, 560w and 522w cm .
Even when stored in the dark, compound 7 slowly turned
dark and appeared to be more sensitive to decomposition than
the other four complexes 3–6.
Ϫ1
When a solution of AgBF (10 mg, 0.05 mmol) in 0.5 ml of
4
acetonitrile and 4 ml of ethanol was carefully overlayered in a
test-tube with a solution of L (21 mg, 0.10 mmol) in 10 ml of
dichloromethane (or toluene) orange crystals were obtained
after 5 d. Yield 15 (18) mg [49% (58%)]. The crystals were
identified as complex 5 based on an identical IR spectrum.
Furthermore, they were shown to be isotypic from their
X-ray powder diffractograms which in addition matched the
calculated pattern from the single crystal data.
Structure determinations
Data were collected on a Bruker Smart CCD diffractometer
with Mo-Kα radiation (λ = 0.71073 Å) and the use of a
graphite monochromator. The crystal specimens were cooled to
173(2) K. Structure solution was performed by direct methods
20
2
(SHELXL 97). Refinement: full-matrix least squares on F
(SHELXL 97); all non-hydrogen positions found and refined
with anisotropic thermal parameters. The hydrogen atoms of
complexes 3, 5 and 6 were found and refined, including the
thermal parameter. Calculated hydrogen positions were added
in the structures of 4 and 7, refined as riding atoms on the
bonded carbon atom position. With respect to data quality it
should be noted that the crystal of 4 was very small. The
refinement of the heavily disordered fluorine atoms in the third
hexafluorophosphate anion of 7 (P3, cf. Fig. 8) is a rough
approximation, the electron density related to the fluorine
Bis(5,5Ј-dicyano-2,2Ј-bipyridine)silver(I) hexafluorophosphate,
[
AgL ]PF 6. A solution of AgPF (28 mg, 0.11 mmol) in 10 ml
2
6
6
of ethanol was carefully overlayered in a test-tube with a
solution of L (10 mg, 0.05 mmol) in 10 ml of tetrahydrofuran.
After 12 d at room temperature, the well formed orange crystals
were collected, washed with water and ethanol and dried under
vacuum. Yield 19 mg (57% based on L) (Found: C, 42.81; H,
1
.59; N, 16.51. Calc. for C H AgF N P: C, 43.31; H, 1.80; N,
24 12 6 8
Table 2 Crystal data for compounds 3–7
3
4
5
6
7
Formula
M
C H AgN O
376.09
C H AgF N O S
463.15
C H AgBF N
607.10
C H AgF N P
665.26
C15.5H AgF N P
505.11
1
2
6
5
3
13
6
3
4
3
24 12
4
8
24 12
6
8
10
6
4
Crystal system
Space group
Crystal size/mm
Monoclinic
Monoclinic
Monoclinic
C2/c
0.3 × 0.15 × 0.1
4.0–62.3
Monoclinic
C2/c
0.3 × 0.2 × 0.05
4.1–57.5
Hexagonal
P2 /n
P2 /c
P6 /m
1
1
3
0.4 × 0.2 × 0.1
4–62.1
0.15 × 0.1 × 0.02
4.3–57.8
0.4 × 0.3 × 0.3
2.6–60.4
2
θ range/Њ
h; k; l range
Ϫ10, 11; Ϫ10, 7; Ϫ29, 24 Ϫ11, 12; Ϫ5, 21; Ϫ9, 12 Ϫ17, 31; Ϫ10, 9; Ϫ21, 22 Ϫ28, 25; Ϫ4, 10; Ϫ10, 10 Ϫ24,17;Ϫ8,24;Ϫ27,9
a/Å
b/Å
c/Å
β/Њ
8.2230(2)
7.5328(2)
20.3896(5)
93.308(1)
1260.87(5)
4
9.4946(5)
15.8010(8)
10.3381(5)
92.242(2)
1549.78(14)
4
21.9430(3)
7.5298(1)
15.7431(2)
112.676(1)
2400.10(5)
4
21.8760(1)
8.2210(2)
15.8848(3)
115.277(1)
2583.24(8)
4
17.8017(3)
17.8017(1)
19.6142(1)
90
5383.0(1)
12
3
V/Å
Z
Ϫ3
D /g cm
1.981
1.985
1.680
1.711
1.870
c
F(000)
µ/cm
736
16.17
904
14.91
1200
9.02
1312
9.17
2964
12.80
Ϫ1
Measured reflections
Unique reflections
9319
3703 (0.0586)
5664
2813 (0.0836)
7335
3420 (0.0416)
4895
2649 (0.0298)
22491
5094 (0.0538)
(
Rint
Observed reflections
I > 2σ(I )]
Parameters refined
)
3269
1634
2561
2286
3491
[
214
226
197
206
277
Ϫ3 a
∆
ρ/e Å
R1; wR2 [I > 2σ(I )]
all reflections)
0.537; Ϫ1.361
0.0337; 0.0796
0.0403; 0.0839
0.616; Ϫ0.960
0.0522; 0.0874
0.1188; 0.1094
0.562; Ϫ0.808
0.0440; 0.0925
0.0693; 0.1035
0.369; Ϫ0.593
0.0384; 0.0852
0.0486; 0.0907
1.694; Ϫ2.171
0.0753; 0.1882
0.1104; 0.2037
(
a
Largest difference peak and hole.
J. Chem. Soc., Dalton Trans., 1999, 183–190
189

View Online
T. G. Scharmann, W. Günther, F. Girgsdies, H. Hemling, W.
atoms forming an almost perfect shell around P3. Crystal data
are listed in Table 2. Graphics were prepared with ORTEP 3
and PLATON/PLUTON 97 for Windows.
CCDC reference numbers 186/1235.
See http://www.rsc.org/suppdata/dt/1999/183/ for crystallo-
graphic files in .cif format.
Hinrichs and D. Lentz, Chem. Eur. J., 1995, 1, 637.
21
10 See for example: F.-Q. Liu and T. D. Tilley, Chem. Commun., 1998,
1
03; H. Li, C. E. Davis, T. L. Groy, D. G. Kelley and O. M. Yaghi,
J. Am. Chem. Soc., 1998, 120, 2186; C. J. Kepert and M. J.
Rosseinsky, Chem. Commun., 1998, 31; B. F. Hoskins, R. Robson
and D. A. Slizys, Angew. Chem., Int. Ed. Engl., 1997, 36, 2752;
R. W. Saalfrank, O. Struck, M. G. Davidson and R. Snaith, Chem.
Ber., 1994, 127, 2489.
1 C. Kaes, M. W. Hosseini, C. E. F. Rickard, B. W. Skelton and
A. H. White, Angew. Chem., Int. Ed. Engl., 1998, 37, 920;
P. K. Bowyer, K. A. Porter, A. D. Rae, A. C. Willis and S. B. Wild,
Chem. Commun., 1998, 1153; K. A. Hirsch, S. R. Wilson and
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D. W. v. Gudenberg, D. M. Proserpio and A. Sironi, Chem.
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D. A. Lemenovskii, W.-S. Li and M. Schröder, Chem. Commun.,
Acknowledgements
This work was supported by the Alexander von Humboldt
Foundation (fellowship for H.-P. W.), the Fonds der Chemi-
schen Industrie, and the Deutsche Forschungsgemeinschaft.
1
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