Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270105027095/sq1216sup1.cif | |
Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108270105027095/sq1216Isup2.rtv |
CCDC reference: 288617
The synthesis of (I) was carried out by adding acetic acid to a solution of palladium nitrate in nitric acid. The solution was heated at 378 K. The precipitated yellow product was filtered off, washed with water and dried in air.
The sample was prepared by top-loading the standard quartz sample holder. Corundum was used as the external standard. X-ray powder diffraction data are deposited in JCPDS-ICDD PDF2 data base. Cell parameters were obtained from d-spaces by indexing and refining 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 85 reflections were estimated from the powder pattern by means of the full-profile fitting procedure (Le Bail et al., 1988) and used in the Patterson synthesis. The Pd atoms were located directly from the Patterson map. The positions of light atoms O, N and C were obtained from a difference Fourier synthesis. H atoms were not located, but they were included in the refined structure models and rigidly connected to their C atoms having in view the special positions of C atoms. The final refinement was carried out by the Rietveld (1969) method.
Nitroso–acetate and nitrito–acetate complexes of palladium are, frequently, intermediate compounds in the synthesis of palladium acetate, which is an important industrial catalyst. They can be obtained at various ratios of acetate and nitroso groups and present an example of stable cluster complexes with various palladium nucleation numbers. Therefore, these compounds are rather interesting models for studying polynuclear complexes. A search of the Cambridge Structural Database (Allen, 2002) for palladium acetate compounds with NO- or NO2- ligands revealed structures of [Pd3(CH3COO)5NO2] (Chiesa et al., 1990), [Pd6(CH3COO)8(NO)2] (Chiesa et al., 1990) and [Pd4(CH3COO)6(NO)2]·CH2Cl2 (Podberezskaya et al., 1981), as well as one nitroso–acetate compound of platinum, [Pt4(CH3COO)6(NO)2]·2CH3COOH (Meester & Skapski, 1973). In the present paper, the crystal structure of the novel octanuclear complex compound [Pd8(CH3COO)8(NO)8], (I), as determined from powder diffraction data (Fig. 1), is communicated.
The [Pd8(CH3COO)8(NO)8] structure is of molecular type with relatively large molecules consisting of 48 non-H atoms (Fig. 2). The skeleton of the molecule is constructed as a tetragonal prism with Pd in the vertices. However, the eight Pd atoms are not directly bonded in a single cluster unit. Rather, there are four Pd2 fragments in vertical edges of the prism. The 2.8648 (10) Å Pd···Pd contacts in the fragments can be considered as metal–metal bonds. These Pd2 groups are connected via NO- ligands, which form the eight horizontal edges of the prism. The Pd···Pd bonds are enforced by two acetate groups positioned across the bond in a bridging mode and cis oriented to each other.
The nitroso groups demonstrate the bidentate bonding mode in the compound, coordinating one Pd atom by the O atom and another by the N atom. The exact positions of the NO- ligands are not coincident with the lines connecting the Pd atoms. Rather, they lie a little higher or lower than this line, allowing the Pd coordination geometry to remain very close to ideal square planar (Table 1). The very short N—O distance, 1.06 (3) Å, is consistent with the triple bond expected in a negatively charged NO- anion. The packing arrangement in the crystal conforms to an I-centered cell with the centers of the Pd8(CH3COO)8(NO)8] molecules situated on the lattice points and the molecules rotated approximately 60° around the z axis with respect to the Pd8 cages (Fig. 3). This packing results in the formation of columns from stacked complexes with 3.9856 (10) Å intermolecular Pd···Pdiii distances along the z direction (symmetry operation iii is x,y,-z).
The known nitroso-acetate compounds of palladium and platinum can be separated into two groups in terms of the number of metal atoms in the cluster. The compounds Pd2(CH3COO)2(NO)2, [Pd4(CH3COO)6(NO)2]·CH2Cl2 and [Pt4(CH3COO)6(NO)2]·2CH3COOH have two atoms in clusters with the Pd—Pd bond shorter than 2.92 Å. [Pd3(CH3COO)5NO2] and [Pd6(CH3COO)8(NO)2] have triangular clusters with the Pd···Pd contact in the range 3.03–3.20 Å. In this respect, [Pd8(CH3COO)8(NO)8] can be related to first group. Another point of classification is the coordination of the NO- groups. Bidentate bonding of NO- is a specific feature of the studied structure. The title compound is the first example of such coordination in the family of nitroso–acetate compounds of palladium and platinum.
Data collection: DRON-4 data collection software; cell refinement: POWDER (Kirik et al., 1979); data reduction: ?; program(s) used to solve structure: Modified DBWM (Wiles & Young, 1981); program(s) used to refine structure: Modified DBWM; molecular graphics: XP (Siemens, 1989).
[Pd8(C2H3O2)8(NO)8] | Cell parameters are obtained from the Rietveld refinement |
Mr = 1563.79 | Dx = 2.461 Mg m−3 |
Tetragonal, I4/m | Cu Kα radiation |
Hall symbol: -I 4 | T = 293 K |
a = 17.5504 (3) Å | Particle morphology: thin powder |
c = 6.8504 (2) Å | yellow |
V = 2110.04 (8) Å3 | circular flate plate, 20.0 × 20.0 mm |
Z = 2 | Specimen preparation: Prepared at 293 K and 101 kPa, cooled at 0 K min−1 |
F(000) = 1472.0 |
DRON-4 powder diffractometer | Specimen mounting: packed powder pellet |
Radiation source: conventional sealed tube | Data collection mode: reflection |
Graphite monochromator | 2θmin = 5.0°, 2θmax = 90.0°, 2θstep = 0.02° |
Refinement on F2 | Profile function: Pearson VII |
Least-squares matrix: full | 45 parameters |
Rp = 0.106 | 0 restraints |
Rwp = 0.146 | 0 constraints |
Rexp = 0.105 | H-atom parameters constrained |
RBragg = 0.053 | Weighting scheme based on measured s.u.'s |
R(F2) = 0.040 | (Δ/σ)max = 0.05 |
Excluded region(s): none | Preferred orientation correction: March-Dollase correction |
[Pd8(C2H3O2)8(NO)8] | V = 2110.04 (8) Å3 |
Mr = 1563.79 | Z = 2 |
Tetragonal, I4/m | Cu Kα radiation |
a = 17.5504 (3) Å | T = 293 K |
c = 6.8504 (2) Å | circular flate plate, 20.0 × 20.0 mm |
DRON-4 powder diffractometer | Data collection mode: reflection |
Specimen mounting: packed powder pellet | 2θmin = 5.0°, 2θmax = 90.0°, 2θstep = 0.02° |
Rp = 0.106 | R(F2) = 0.040 |
Rwp = 0.146 | 45 parameters |
Rexp = 0.105 | 0 restraints |
RBragg = 0.053 | H-atom parameters constrained |
Refinement. Shift/su_max coeficient related with positional coordinates. R_prof-backgr = 0.106 |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Pd | 0.1956 (2) | 0.0365 (2) | 0.2909 (1) | 0.0091* | |
C11 | 0.319 (1) | −0.043 (2) | 0.5 | 0.0267* | |
C12 | 0.386 (1) | −0.087 (2) | 0.5 | 0.0290* | |
O1 | 0.289 (1) | −0.025 (2) | 0.3341 (5) | 0.0295* | |
H12A | 0.40186 | −0.09606 | 0.63209 | 0.0800* | 0.50 |
H12B | 0.42544 | −0.06016 | 0.43144 | 0.0800* | 0.50 |
H12C | 0.37642 | −0.1348 | 0.43647 | 0.0800* | 0.50 |
C21 | 0.281 (2) | 0.164 (1) | 0.5 | 0.0361* | |
C22 | 0.324 (1) | 0.232 (1) | 0.5 | 0.0372* | |
O2 | 0.257 (1) | 0.131 (1) | 0.3398 (6) | 0.0305* | |
H22A | 0.33486 | 0.24669 | 0.36791 | 0.0800* | 0.50 |
H22B | 0.29594 | 0.27187 | 0.56351 | 0.0800* | 0.50 |
H22C | 0.37091 | 0.22336 | 0.56858 | 0.0800* | 0.50 |
O3 | 0.104 (1) | 0.101 (1) | 0.2519 (4) | 0.0283* | |
N | 0.135 (1) | −0.054 (1) | 0.2611 (5) | 0.0310* |
Pd—O1 | 1.99 (2) | O3i—N | 1.06 (3) |
Pd—O2 | 2.01 (2) | Pd—Pdii | 2.8648 (10) |
Pd—O3 | 1.98 (2) | C12—H12A | 0.96 |
Pd—N | 1.92 (2) | C12—H12B | 0.96 |
O1—C11 | 1.29 (2) | C12—H12C | 0.96 |
O2—C21 | 1.31 (2) | C22—H22A | 0.96 |
C11—C12 | 1.41 (3) | C22—H22B | 0.96 |
C21—C22 | 1.41 (3) | C22—H22C | 0.96 |
O2—Pd—O1 | 88.9 (6) | C11—C12—H12A | 109.4 |
O2—Pd—O3 | 89.2 (6) | C11—C12—H12B | 109.4 |
O3—Pd—N | 90.5 (6) | C11—C12—H12C | 109.4 |
O1—Pd—N | 91.3 (7) | C21—C22—H22A | 109.4 |
O1—C11—O1ii | 123.2 (2) | C21—C22—H22B | 109.4 |
O2—C21—O2ii | 113.8 (3) | C21—C22—H22C | 109.4 |
Symmetry codes: (i) y, −x, z; (ii) x, y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Pd8(C2H3O2)8(NO)8] |
Mr | 1563.79 |
Crystal system, space group | Tetragonal, I4/m |
Temperature (K) | 293 |
a, c (Å) | 17.5504 (3), 6.8504 (2) |
V (Å3) | 2110.04 (8) |
Z | 2 |
Radiation type | Cu Kα |
Specimen shape, size (mm) | Circular flate plate, 20.0 × 20.0 |
Data collection | |
Diffractometer | DRON-4 powder diffractometer |
Specimen mounting | Packed powder pellet |
Data collection mode | Reflection |
Scan method | ? |
2θ values (°) | 2θmin = 5.0 2θmax = 90.0 2θstep = 0.02 |
Refinement | |
R factors and goodness of fit | Rp = 0.106, Rwp = 0.146, Rexp = 0.105, RBragg = 0.053, R(F2) = 0.040, χ2 = 1.932 |
No. of parameters | 45 |
H-atom treatment | H-atom parameters constrained |
Computer programs: DRON-4 data collection software, POWDER (Kirik et al., 1979), Modified DBWM (Wiles & Young, 1981), Modified DBWM, XP (Siemens, 1989).
Pd—O1 | 1.99 (2) | O2—C21 | 1.31 (2) |
Pd—O2 | 2.01 (2) | C11—C12 | 1.41 (3) |
Pd—O3 | 1.98 (2) | C21—C22 | 1.41 (3) |
Pd—N | 1.92 (2) | O3i—N | 1.06 (3) |
O1—C11 | 1.29 (2) | Pd—Pdii | 2.8648 (10) |
O2—Pd—O1 | 88.9 (6) | O1—Pd—N | 91.3 (7) |
O2—Pd—O3 | 89.2 (6) | O1—C11—O1ii | 123.2 (2) |
O3—Pd—N | 90.5 (6) | O2—C21—O2ii | 113.8 (3) |
Symmetry codes: (i) y, −x, z; (ii) x, y, −z+1. |
Nitroso–acetate and nitrito–acetate complexes of palladium are, frequently, intermediate compounds in the synthesis of palladium acetate, which is an important industrial catalyst. They can be obtained at various ratios of acetate and nitroso groups and present an example of stable cluster complexes with various palladium nucleation numbers. Therefore, these compounds are rather interesting models for studying polynuclear complexes. A search of the Cambridge Structural Database (Allen, 2002) for palladium acetate compounds with NO- or NO2- ligands revealed structures of [Pd3(CH3COO)5NO2] (Chiesa et al., 1990), [Pd6(CH3COO)8(NO)2] (Chiesa et al., 1990) and [Pd4(CH3COO)6(NO)2]·CH2Cl2 (Podberezskaya et al., 1981), as well as one nitroso–acetate compound of platinum, [Pt4(CH3COO)6(NO)2]·2CH3COOH (Meester & Skapski, 1973). In the present paper, the crystal structure of the novel octanuclear complex compound [Pd8(CH3COO)8(NO)8], (I), as determined from powder diffraction data (Fig. 1), is communicated.
The [Pd8(CH3COO)8(NO)8] structure is of molecular type with relatively large molecules consisting of 48 non-H atoms (Fig. 2). The skeleton of the molecule is constructed as a tetragonal prism with Pd in the vertices. However, the eight Pd atoms are not directly bonded in a single cluster unit. Rather, there are four Pd2 fragments in vertical edges of the prism. The 2.8648 (10) Å Pd···Pd contacts in the fragments can be considered as metal–metal bonds. These Pd2 groups are connected via NO- ligands, which form the eight horizontal edges of the prism. The Pd···Pd bonds are enforced by two acetate groups positioned across the bond in a bridging mode and cis oriented to each other.
The nitroso groups demonstrate the bidentate bonding mode in the compound, coordinating one Pd atom by the O atom and another by the N atom. The exact positions of the NO- ligands are not coincident with the lines connecting the Pd atoms. Rather, they lie a little higher or lower than this line, allowing the Pd coordination geometry to remain very close to ideal square planar (Table 1). The very short N—O distance, 1.06 (3) Å, is consistent with the triple bond expected in a negatively charged NO- anion. The packing arrangement in the crystal conforms to an I-centered cell with the centers of the Pd8(CH3COO)8(NO)8] molecules situated on the lattice points and the molecules rotated approximately 60° around the z axis with respect to the Pd8 cages (Fig. 3). This packing results in the formation of columns from stacked complexes with 3.9856 (10) Å intermolecular Pd···Pdiii distances along the z direction (symmetry operation iii is x,y,-z).
The known nitroso-acetate compounds of palladium and platinum can be separated into two groups in terms of the number of metal atoms in the cluster. The compounds Pd2(CH3COO)2(NO)2, [Pd4(CH3COO)6(NO)2]·CH2Cl2 and [Pt4(CH3COO)6(NO)2]·2CH3COOH have two atoms in clusters with the Pd—Pd bond shorter than 2.92 Å. [Pd3(CH3COO)5NO2] and [Pd6(CH3COO)8(NO)2] have triangular clusters with the Pd···Pd contact in the range 3.03–3.20 Å. In this respect, [Pd8(CH3COO)8(NO)8] can be related to first group. Another point of classification is the coordination of the NO- groups. Bidentate bonding of NO- is a specific feature of the studied structure. The title compound is the first example of such coordination in the family of nitroso–acetate compounds of palladium and platinum.