6
W. Chen, F. Liu / Journal of Organometallic Chemistry 673 (2003) 5ꢂ12
/
ne) ] [Ag I ] (2), which was purified by recrystallization
2
[Ag(carbene)2]ꢀ complexes. The AgÃ
[2.091(7) and 2.088(7) A] are consistent with other
/C bond distances
2
4 6
˚
from hot DMSO. The tetranuclear complex [Ag(carbe-
ne) ] [Ag I ] (3) was obtained similarly from the reac-
reported silverꢂ
/
carbene complexes [10ꢂ
/17]. The build-
2
2
2 4
2
ꢁ
tion of N-allyl-N?-methylimidazolium iodide with
ing unit [Ag I ] is linked by two AgÃ
/
I bonds. Within
the chain the Ag(I) ions have distorted tetrahedral
4
6
Ag O, and isolated directly from its CH Cl solution.
2
2
2
Both 2 and 3 are poorly soluble in common organic
solvents once they were isolated, but they can dissolve in
hot DMSO. When a suspension of 3 in DMSO was
heated at 80 8C for a few hours, a new coordination
geometry when the AgÃAg interactions are not taken
/
into account, which are coordinated by four iodide ions.
The I(1) and I(2) ions link three neighboring Ag atoms,
whereas I(3) acts as a bridge between two Ag atoms. The
polymer 4 with the formula [Ag(carbene)][AgI ] was
afforded. Complex 4 does not dissolve in any solvent
once it was crystallized from hot DMSO.
AgÃ
/
I bond distances range between 2.7959(9) and
˚
2
2.9488(9) A. The AgÃ
/
Ag bond distances within the
2
ꢁ
˚
building unit [Ag I ]
are around 3.0 A, which are
shorter than the sum of the van der Waals radii,
suggesting some metalꢂmetal interaction. Furthermore,
the cations and anionic chains are connected each other
via Ag(3)ÃI(3) interaction forming two-dimensional
network structure (Fig. 2). The Ag(3)ÃI(3) separation
(3.757 A) is relatively long when compared to the
4
6
These silverꢂcarbene complexes were fully character-
/
1
ized by elemental analysis and H-NMR spectroscopy.
/
1
In the H-NMR spectrum of 1, a peak at low field (9.80
1
ppm) indicates the presence of an acidic CH proton. H-
/
NMR spectra of 2 and 3 in DMSO-d6 showed the
complete disappearance of the acidic 2H-imidazolium
/
˚
2
ꢁ
protons, indicating the formation of silverꢂ
/carbene
corresponding values of [Ag I ] , showing weak inter-
4 6
complexes. Because of the poor solubility in DMSO at
action between the cations and anionic chain. It was
(kꢁl)ꢁ
1
3
room temperature, C-NMR spectra of 2ꢂ
recorded. The structures of complexes 2ꢂ4 were deter-
mined by X-ray diffraction analysis.
/
4 were not
known that the type of anionic complexes [Ag X ]
k
l
/
formed is strongly influenced by the countercation and
the nature of the halide [18]. In the case of iodide, the
2
ions [AgI3] , [Ag I ] , and [Ag I ]
ꢁ
2ꢁ
4ꢁ
have been
new anionic
complex form and exists as an one-
2 4
4 8
2
ꢁ
reported. Thus [Ag I ]
is
a
4
6
2
.2. Molecular structure of 2
(
kꢁl)ꢁ
[
Ag X ]
l
k
dimensional polymer.
It is noted that N,N?-dimethylimidazolium chloride
and N,N?-dimethylimidazolium bromide reacted with
The structure of 2 is shown in Fig. 1. Complex 2 is a
ionic coordination polymer, consisting of the cation
ꢀ
[
[
Ag(carbene) ] and one-dimensional infinite anionic
2
2
Ag I ] chain. Selected bond distances and angles are
ꢁ
Ag O to afforded one-dimensional polymers, which are
2
4
6
ꢀ
ꢁ
composed of alternating [Ag(carbene)2] and [AgX2]
associated through AgÃAg interactions at a distance of
given in Table 1. The cation has a typical linear
ꢀ
/
conformation of [Ag(carbene)2] with a CÃ
/
AgÃ
/
C angle
˚
ca. 3.19 A [15].
.3. Molecular structure of 3
Crystals suitable for X-ray crystallography of 3 were
of 170.6(3)8, comparable with other examples of linear
2
obtained by slow cooling of a hot DMSO solution of the
complex. As has been revealed by X-ray diffraction
analysis, complex 3 crystallizes as a tetranuclear com-
pound of the formula [Ag(carbene) ] [Ag I ] that is
2
2
2 4
symmetric about an inversion center. One half of the
molecule comprises the asymmetric unit of the structure.
The structure of the silverꢂcarbene complex of 3 is
/
shown in Fig. 3 and selected bond distances and angles
are listed in Table 2. The complex consists of two
ꢀ
2ꢁ
[
Ag(carbene)2] and one [Ag2I4] units, which are held
together by AgÃAg interactions. The geometry at the
Ag(1) atom is nearly linear or T-shaped when the
Ag(1)ÃAg(2) interaction is taken into consideration,
which is bi-coordinated by two carbene carbon atoms
C bond
/
/
with a CÃ
/
AgÃ
/
C angle of 172.8(3)8. The AgÃ
/
˚
lengths are 2.103(9) and 2.081(9) A, which are slightly
longer than those values in complex 2. These values are
quite normal when compared to the same values
Fig. 1. ORTEP diagram of 2 in the crystal state with 50% probability
ꢀ
ellipsoids.
reported for other [Ag(carbene)2] complexes [10ꢂ14].
/
Chen, Wanzhi
