[Pd(CH3COO)2]n from X-ray powder diffraction data

Article abstract of DOI:10.1107/S0108270104016129

The synthesis and crystal structure of [Pd(C₂H₃O ₂)₂]_n was analyzed. X-ray powder diffraction technique was used to determine the crystal structure of the compound. It was found that palladium acetate complexes were connected into a polymeric in which two Pd atoms were bridged by two acetate groups. It was observed that Pd atom occupied the special position (0,1/2,1/2) and formed rows with a Pd....Pd distance of 2.9192(I)A.

Full text of DOI:10.1107/S0108270104016129

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
[Pd(CH3COO)2]n from X-ray powder
diffraction data
Sergei D. Kirik,* Ruslan F. Mulagaleev and Alexander I.
Blokhin
Institute of Chemistry and Chemical Technology, 660049 Krasnoyarsk, Russia
Correspondence e-mail: kirik@icct.ru
Received 1 June 2004
Accepted 1 July 2004
Online 21 August 2004
Figure 1
Observed (dots), calculated (superimposed solid line) and difference
pro®les after Rietveld re®nement. The re¯ection positions are marked by
ticks.
The water-insoluble title compound, catena-poly[palla-
dium(II)-di-ꢀ-acetato-ꢁ4O:O0], [Pd(C2H3O2)2]n, was obtained
from a nitratopalladium solution and acetic acid as a pale-pink
powder. Ab initio crystal structure determination was carried
out using X-ray powder diffraction techniques. Patterson and
Fourier syntheses were used for atom location and the Riet-
veld technique was applied for the ®nal structure re®nement.
The structure consists of palladium acetate complexes
connected into polymeric chains running along b, in which
two Pd atoms are bridged by two acetate groups that are in a
cis con®guration with respect to one another. The unique Pd
atom lies on a site with 2/m symmetry and the acetate moieties
have imposed m symmetry; these are joined into in®nite
chains running along the b direction. The shortest PdÁ Á ÁPd
Ê
distance in the row is 2.9192 (1) A. The planes of adjacent
palladium complexes are inclined towards each other, the
angle between the planes being approximately 30ꢀ.
Figure 2
The crystal structure of polymeric [Pd(CH3COO)2]n.
Comment
Palladium acetate complexes have been extensively investi-
gated because they have some useful properties, especially for
catalyst preparation (Stephenson et al., 1965; Romm et al.,
1992; Pandey & Henry, 1974). Crystal data have been reported
for palladium acetate and some adducts, for example,
[Pd3(CH3COO)6] (Lyalina et al., 1993), [Pd3(CH3COO)6]Á-
0.5H2O (Scapski & Smart, 1970), [Pd3(CH3COO)6]Á0.5CH2Cl2
(Cotton & Han, 1985) and [Pd3(CH3COO)6]Á0.5C6H6 (Cotton
& Han, 1983). In all of these compounds, palladium forms a
triangular cluster, with two acetate groups in bridging posi-
tions on each side of the triangle. In the present work, a
including the Cambridge Structural Database (Allen, 2002).
However, it seems to be the most easily obtained form,
although it has not yet been characterized because of the
absence of a single-crystal sample. We have obtained the
structure solution using X-ray powder diffraction techniques.
The main structural units of (I) are the [Pd(CH3COO)2]
1
2
1
2
complexes. Pd atoms occupy the special position (0, , ) and
Ê
form rows along b, with a PdÁ Á ÁPd distance of 2.9192 (1) A;
this distance is less than those reported for the triangular
clusters, in which the PdÁ Á ÁPd distances range from 3.098 to
Ê
3.196 A (Lyalina et al., 1993). All acetate groups in (I) are of
the bridging type. Each PdÁ Á ÁPd contact is formed by two
acetate groups in cis positions with respect to one another. In
spite of the bridging character of the acetate groups, the
palladium coordination is square planar, since the Pd atom is
located on an inversion centre; by contrast, [Pd3(CH3COO)6]
(Lyalina et al., 1993) is only approximately planar. Because of
the tension in the chemical bonding, the coordination planes
polymeric form of palladium acetate, (I), was investigated. We
did not ®nd any mention of this form in the literature,
Acta Cryst. (2004). C60, m449±m450
DOI: 10.1107/S0108270104016129
# 2004 International Union of Crystallography m449

metal-organic compounds
Table 1
Selected geometric parameters (A, ).
of neighboring Pd atoms are not parallel, being inclined
towards one another with an angle between the planes of
approximately 30ꢀ. In contrast, the angle between the [PdO4]
planes in the trimer cluster is about 60ꢀ (Lyalina et al., 1993).
As noted above, the larger angle in the trimer is comple-
mented by a longer PdÁ Á ÁPd distance. The differences in these
two geometric features can be attributed to the higher ther-
modynamic stability of the polymeric form of palladium
acetate. A similar chain arrangement was found previously in
some acetate-containing palladium compounds with addi-
tional donor ligands. In particular, [Pd3(CH3COO)4{S[CH2-
CH(CH3)2]}2(C8H10}2] (Fuchita et al., 1996), [Pd3(CH3COO)4-
{(SbPh3)2Ph2}] (Barton et al., 1990) and [Pd3(CH3COO)4(C13-
H21O4)2] (Ukhin et al., 1981) demonstrate planar palladium
coordination with acetate groups in cis positions; the PdÁ Á ÁPd
ꢀ
Ê
PdÐO11
PdÐO21
O11ÐC11
O21ÐC21
2.050 (8)
2.017 (8)
1.31 (2)
1.28 (2)
C11ÐC12
C21ÐC22
PdÐPdi
1.44 (3)
1.41 (3)
2.9192 (1)
O21ÐPdÐO11
O11ÐPdÐO21
O11iiÐC11ÐO11
89.9 (3)
90.1 (3)
116.6 (7)
O21ÐC21ÐO21ii
PdiiiÐPdÐO11
PdiiiÐPdÐO21
111.5 (4)
80.3 (3)
78.5 (2)
Symmetry codes: (i) x; y 21; 1 z; (ii) x; 23 y; z; (iii) x; 12 ‡ y; 1 z.
re®ning using programs described by Visser (1969) and Kirik et al.
(1979). The space group was determined from the analysis of
systematic absences. The intensities of 120 re¯ections were estimated
from the powder pattern by means of a full-pro®le ®tting procedure
(Le Bail et al., 1988) and used in Patterson synthesis. Pd atoms were
located directly from the Patterson map, and the positions of O and C
atoms were de®ned from difference Fourier syntheses. H atoms were
not located but were included in the re®ned structure model, rigidly
connected to their C atoms and taking into account special positions
of the C atoms. The ®nal re®nement was carried out by the Rietveld
(1969) method.
Ê
distances are 2.98 (2), 3.01 (8) and 2.9 (2) A, respectively.
In summary, palladium acetate can form at least two
isomers, viz. trimeric and polymeric. The Pd atoms in both
forms have square-planar coordination. The higher thermo-
dynamic stability of the polymeric form is related to the
mutual orientation of the [PdO4] planes of adjacent
complexes, which provides stronger PdÁ Á ÁPd interactions.
Data collection: DRON-4 data collection software; cell re®nement:
POWDER (Kirik et al., 1979); program(s) used to solve structure:
modi®ed version of DBWM (Wiles & Young, 1981); program(s) used
to re®ne structure: modi®ed version of DBWM; molecular graphics:
XP (Siemems, 1989).
Experimental
The synthesis of (I) was carried out by adding acetic acid to a solution
of palladium dissolved in nitric acid. The solution was heated at
393 K. The precipitated pale-pink product was ®ltered off, washed
with water and dried in air.
X-ray powder diffraction data preparation was supported
by the ICDD (Grand-in-Aid No. 9310).
Crystal data
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SK1735). Services for accessing these data are
described at the back of the journal.
[Pd(C2H3O2)2]
Mr = 224.51
Monoclinic, P21=m
Cu Kꢃ radiation
Ê
ꢄ = 1.5418 A
ꢀ = 21.21 mm
T = 293 K
1
Ê
Ê
a = 7.4467 (1) A
b = 5.8383 (1) A
Pale yellow
Specimen shape: circular ¯at plate
20.0 Â 20.0 Â 0.5 mm
Ê
c = 7.9900 (1) A
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ꢂ = 93.46 (1)ꢀ
V = 346.74 (1) A
3
Ê
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Data collection
DRON-4 powder diffractometer
ꢅ/2ꢅ scans
Specimen mounting: packed powder
pellet
Specimen mounted in re¯ection
mode
321 measured re¯ections
321 independent re¯ections
ꢅmax = 45ꢀ
h = 0 ! 6
k = 0 ! 5
l = 6 ! 7
2ꢅmin = 5.0, 2ꢅmax = 90.0ꢀ
Increment in 2ꢅ = 0.02ꢀ
Re®nement
Re®nement on F2
Rp = 0.108
Rwp = 0.152
Rexp = 0.117
RB = 0.047
Pro®le function: Pearson VII
41 parameters
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(Á/ꢆ)max = 0.1
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ꢁ
m450 Sergei D. Kirik et al.
[Pd(C2H3O2)2]
Acta Cryst. (2004). C60, m449±m450