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Crystal structure of AgPF6 and AgAsF6 at ambient temperatures
Solid State Sciences 2 (2000) 237 – 241
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Crystal structure of AgPF6 and AgAsF6 at ambient temperatures Rika Hagiwara a,* , Kouichi Kitashita a, Yasuhiko Ito a, Osamu Tamada b b
a Department of Fundamental Energy Science, Kyoto Uni6ersity, Sakyo-ku, Kyoto 606 -8501, Japan Graduate School of Human and En6ironmental Study, Kyoto Uni6ersity, Sakyo-ku, Kyoto 606 -8501, Japan
Received 18 June 1999; received in revised form 26 November 1999; accepted 28 November 1999
Abstract AgPF6 dissolved in anhydrous HF crystallizes in space group Fm3m with a0 = 755.08(7) pm, V =4.3051(12)×108 pm3 at 25°C, z= 4. The structure was determined with the aid of Fourier map and refined to conventional R and Rw values of 0.0812 and 0.0644, respectively. The Ag+ and PF− 6 ions form a rock salt structure with a threefold orientational disorder of the anion. The distortion of PF− 6 was scarcely observed. The PF(1) and PF(2) bond lengths are 156 and 159 pm, respectively. AgAsF6 prepared in the same manner is isostructural with AgPF6; a0 = 775.48(21) pm, V =4.6634(37) ×108 ´ ditions scientifiques et me´dicales Elsevier SAS. All rights reserved. pm3 at 25°C, z=4, R=0.0707, Rw=0.0495. © 2001 E Keywords: Silver hexafluorophosphate; Silver hexafluoroarsenate; AgPF6; AgAsF6; Structure; Disorder
1. Introduction Hexafluorophosphates (V) of univalent metals except lithium, M(I)P(V)F6, have cubic lattices at room temperature [1 – 4]. The array of cations and anions is rock salt type, variation of the structure arising from the orientations of PF− 6 [1 – 3,5,6]. On the other hand, only the silver salt is known to have a cubic lattice at ambient temperatures [4] among hexafluoroarsenates (V), M(I)As(V)F6. The authors have recently reported [8] that, at ambient temperatures, NaPF6 is isostructural with NaSbF6 [7] in which the P (or Sb)FNa array is straight. Furthermore, they determined the structures of the heavier alkaline metal salts containing a fourfold disorder in the orientation of anions. In the present study, structures of AgPF6 and AgAsF6 were * Correspondence and reprints: Tel.: + 81-75-7535822; fax: + 81-75-7535906. E-mail address: [email protected] (R. Hagiwara)
determined by means of X-ray diffraction single crystallography.
2. Experimental
2.1. Preparation of single crystals Since AgPF6 and AgAsF6 are moisture-sensitive, handling was made in an argon glove box with a gas purifier. AgPF6 and AgAsF6 (Ozark Mahoning, purity 99%) were used as supplied. Using a T-shaped FEP (Perfluoroethylene-propylene copolymer) tube equipped with a SUS316 stainless steel valve, a saturated solution was prepared in one end of the tube by condensing anhydrous HF (ca. 2 ml) on the sample and decanted into the other end of the tube. Single crystals were grown at room temperature by eliminating HF very slowly from the solution with cooling the other end of the FEP tube by water. The tube was kept in the dark during the crystal growth.
1293-2558/00/$ - see front matter © 2001 E´ditions scientifiques et me´dicales Elsevier SAS. All rights reserved. PII: S 1 2 9 3 - 2 5 5 8 ( 0 0 ) 0 0 1 2 4 - 2/FLA
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
238
In 4 days, cubic single crystals with 0.3–1 mm of edge lengths were formed in the bottom of the HF solution. The solution was decanted to the other end and the tube was evacuated through a soda lime trap by a vacuum pump. Monitoring by a microscope equipped with a CCD camera, the single crystals were recovered in the argon atmosphere. A selected crystal was transferred and fixed in the pre-sealed narrower end of a quartz capillary. The capillary was tentatively plagued with silicone grease, and then flame-sealed outside the glove box using a microburner.
2.2. X-ray diffraction single crystallography A sealed capillary was fixed on a small brass pin with adhesive to mount on a goniometer head. In order to check the quality of crystal, oscillation photographs were recorded with the aid of a Weissenberg camera (Stoe, 3.10.1) using CoKa radiation (40 kV, 25 mA) from an X-ray generator (Philips, PW1729). Weissenberg photographs of 0, 1 and 2nd layer was obtained to determine Laue symmetry and an approximate cell dimension. The same crystal was mounted on a Rigaku AFC5S diffractometer and data collection was performed at room temperature using MoKa radiation (50 kV, 20 mA). Single crystal data analysis was performed by RADY [9].
3. Results and discussion
3.1. AgPF6 A colorless cubic single crystal with the edge length of 0.5 mm was chosen for X-ray data collection after checked by preliminary camera works. The
space group Fm3m, assumed by the camera works was confirmed from the analysis of intensity data as well as the systematic extinctions. The structure refinement was made using 52 reflections (2u B60°, Fo\ 5s). In all the face-centered cubic structures of MPF6 reported so far, M+ and PF− 6 ions form a rock salt array [1–3,5–7]. It has been shown in the present study that AgPF6 was not the exception. The positions of fluorine atoms were searched with the aid of Fourier maps around the phosphorus atom at 0,0,0 in Fig. 1. They were found at around x,x,0(48h) and 0,0,z(24e). This implies that there is a disorder in the orientations of PF− 6 ions rotated by 45° around one of the crystal axes from the original position found in the NaSbF6 structure [7,8] in which all the fluorine atoms are located at x,0,0, etc.(24e). Thus the threefold disorder arises by the choice of crystal axis with 1/3 atomic occupancy at each site. The result of the refinement is shown in Tables 1 and 3. In the temperature factors anisotropically determined for fluorine atoms, b11 and b22, are identical and fairly large compared with b33 in the case of F(1) atom. These values are similar to that of b33 determined for F(2) atom that is also much larger than b11 and b22 of it. In parameters for both the fluorine atoms, b11 and b22 are identical. This suggests that the PF− 6 ion is librating and/or precessing around the z-axis with the position of phosphorus atom as a fixed point. The refinement introducing another disorder by placing F(1) atom at x%,x%,z or x%,0,z with increasing the numbers of nonequivalent fluorine atoms slightly decreased the R values. However, the distortion of PF− 6 molecule was too serious to be ascribed to the consequence of the difference in the number of coordinating cations around fluorine atoms bound to a phosphorus atom, or, the require-
Table 1 Positional parameters of cubic AgPF6 Atom Ag P F(1) F(2) F(1) F(2)
Wyckoff 4b 4a 24e 48h b11 1051(76) 250(17)
Occup. 1.00 1.00 0.33 0.33 b22 1051(76) 250(17)
x
y
0.500 0.000 0.000 0.149(3) b33 78(32) 1005(52)
0.000 0.000 0.000 0.149(3) b12 0 −75(25)
z
Beq (104pm2)
0.000 0.000 0.207(7) 0.000
6.6(2) 3.5(2) 16.6(8) 11.5(5)
b23 0 0
b31 0 0
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
239
Fig. 1. Fourier maps around (0,0,0) of AgPF6 and AgAsF6 lattices. Contributions of the electron density of the phosphorus atom is zapped from the maps of z= 0.00−0.08.
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
240
Table 2 Positional parameters of cubic AgAsF6 Atom
Wyckoff
Ag As F(1) F(2)
4b 4a 24e 48h
F(1) F(2)
b11 708(39) 324(15)
Occup. 1.00 1.00 0.33 0.33 b22 708(39) 324(15)
x
y
0.500 0.000 0.000 0.154(2) b33 119(25) 689(33)
ment for the closer packing of ions. The structure was not acceptable again when the refinement was made placing the F(1) atom at a general position. The PF− 6 ion is a regular octahedron. The F(1) atom is coordinated by one Ag+ while F(2) is coordinated by two of them. The AgF(1) distance is larger than that based on the sum of the averaged ionic radii estimated taking account the coordination number (196 pm, by Shannon [10]). This is probably due to the AgF(2) distance, not much longer than that estimated for the coordination of eight nearest neighbors (261 pm [10]). The F(2) atoms should be included in the coordinating atoms around Ag+ when the averaged coordination numbers are discussed (Table 3).
3.2. AgAsF6 The structure determination of AgAsF6 was made in the same manner. The refinement was made using 73 reflections (2u B75°, Fo \5s). Fourier maps around the phosphorus atom at 0,0,0 shown in Fig. 1 are quite similar with those of AgPF6. The refinement was made placing the fluorine atoms at the same position found in AgPF6 structure. The final result is shown in Tables 2 and 3. The anisotropically determined temperature factors exhibit the same tendency found for AgPF6. The refinement introducing further disorders described in the case of AgPF6 did not converge with realistic values of parameters. It is concluded that AgPF6 and AgAsF6 are isostructural at ambient temperatures.
0.000 0.000 0.000 0.154(2) b12 0 −157(33)
z
Beq (104pm2)
0.000 0.000 0.214(5) 0.000
8.04(18) 3.71(9) 12.3(5) 10.7(4)
b23 0 0
b31 0 0
3.3. The unusual coordination numbers and formula 6olumes of the sil6er salts The coordination number of fluorine atoms around the cation in MAF6 changes with the size of the cation. Hexafluorometallates of the metals with smaller ionic radii than that of silver (Li, Na) have the coordination number of six regardless the hexafluorometallate anion [11,12]. On the other hand, hexafluorometallates of the metals with larger ionic radii than that of potassium (Tl, Rb, Cs) possess a coordination number of 12 [11,12]. Coordination numbers of potassium salts sprit in two groups, 12 for small fluorometallate anions and eight for large fluorometallate anions, respectively [8,11,12]. For the silver salts, only the coordination number of eight has been reported. The averaged coordination number of ten for AgPF6 and AgAsF6 found in this study is unique although it is still in harmony with Table 3 Structural parameters of AgPF6 and AgAsF6 AgPF6 R Rw Lattice constant (pm) AF bond length (pm) FAF bond angle (°) Averaged C.N. of F around Ag AgF distance (pm)
AgAsF6
0.0812 0.0707 0.0644 0.0495 755.08(7) 775.48(21) F(1) 156(5) F(1) 166(4) F(2) 159(3) F(2) 169(2) 90 90 10 F(1) 2 10 F(1) 2 10 F(2) 8 10 F(2) 8 F(1) 222(5) F(1) 222(4) F(2) 288(3) F(2) 294(2)
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
the relation between the cation size and coordination numbers of this series. It should be noted that the formula volume of AgPF6 (1.076 ×108 pm3) is slightly smaller than that of NaPF6 (1.104 × 108 pm3, [8]) in spite of the larger ionic radius of the cation. The AgF(1) bond distance shorter than that found in AgF (246 pm) suggests increasing of the covalent character in the bond, which could cause this volume irregularity. Another possible explanation is that the size of the sodium cation having a coordination number of fluorine atoms, six, in NaPF6 [8]. The size of the cation could be too small against the PF− 6 ion to have a higher coordination numbers like found in AgPF6 (ten) which enables a closer approach of the cations and anions by increasing the number of the bonds. At the same time, it could be too large to decrease the lattice volume effectively by the size of itself. Such a halfway size of the sodium cation in the salt might cause a bulky structure for NaPF6. At this moment, it is hard to tell which is the right reason and which lattice volume is irregular, NaPF6 or AgPF6 in the series of hexafluorophosphates. The formula volume of the AgAsF6 (1.166×108 pm3) is only slightly larger than that of the sodium salt (1.149 ×108 pm3), exhibiting the similar tendency, although it is not as remarkable as in the case of hexafluorophosphates.
.
241
Acknowledgements The authors thank the Ministry of Education, Science, Sports and Culture for financial support by a Grant-in-Aid for Scientific Research. RADY in the program library of Data Processing Center, Kyoto University was applied for analysis of single crystal data.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
H. Bode, H. Clausen, Z. Anorg. Chem. 265 (1951) 229. H. Bode, G. Teufer, Z. Anorg. Chem. 268 (1952) 20. H. Bode, G. Teufer, Z. Anorg. Chem. 268 (1952) 129. J. Cox, J. Chem. Soc. (1956) 876. R.B. English, A.M. Heyns, J. Crystallogr. Spectrosc. Res. 14 (1984) 531. A.M. Heyns, C.W.F.T. Pistorius, Spectrochim. Acta 30A (1974) 99. G. Teufer, Acta Cryst. 9 (1956) 539. K. Kitashita, R. Hagiwara, Y. Ito, O. Tamada, J. Fluor. Chem. 101 (2000) 173. S. Sasaki, KEK Internal, National Laboratory of High Energy Physics, Tsukuba, 1987, vol. 3. R.D. Shannon, Acta Cryst. A32 (1976) 751. R.D.W. Kemmitt, D.R. Russell, D.W.A. Sharp, J. Chem. Soc., (1963) 4408, and references therein. D. Babel, Structural Chemistry of Octahedral Fluorocomplexes of the Transition elements, in: Structure and Bonding, vol 3, C.K. Jorgensen, J.B. Neilands, R.S. Nyholm, D. Reinen, R.J.P. Williams (Eds), Springer-Verlag, New York, 1967, pp. 1, and references therein.
www.elsevier.com/locate/ss
Crystal structure of AgPF6 and AgAsF6 at ambient temperatures Rika Hagiwara a,* , Kouichi Kitashita a, Yasuhiko Ito a, Osamu Tamada b b
a Department of Fundamental Energy Science, Kyoto Uni6ersity, Sakyo-ku, Kyoto 606 -8501, Japan Graduate School of Human and En6ironmental Study, Kyoto Uni6ersity, Sakyo-ku, Kyoto 606 -8501, Japan
Received 18 June 1999; received in revised form 26 November 1999; accepted 28 November 1999
Abstract AgPF6 dissolved in anhydrous HF crystallizes in space group Fm3m with a0 = 755.08(7) pm, V =4.3051(12)×108 pm3 at 25°C, z= 4. The structure was determined with the aid of Fourier map and refined to conventional R and Rw values of 0.0812 and 0.0644, respectively. The Ag+ and PF− 6 ions form a rock salt structure with a threefold orientational disorder of the anion. The distortion of PF− 6 was scarcely observed. The PF(1) and PF(2) bond lengths are 156 and 159 pm, respectively. AgAsF6 prepared in the same manner is isostructural with AgPF6; a0 = 775.48(21) pm, V =4.6634(37) ×108 ´ ditions scientifiques et me´dicales Elsevier SAS. All rights reserved. pm3 at 25°C, z=4, R=0.0707, Rw=0.0495. © 2001 E Keywords: Silver hexafluorophosphate; Silver hexafluoroarsenate; AgPF6; AgAsF6; Structure; Disorder
1. Introduction Hexafluorophosphates (V) of univalent metals except lithium, M(I)P(V)F6, have cubic lattices at room temperature [1 – 4]. The array of cations and anions is rock salt type, variation of the structure arising from the orientations of PF− 6 [1 – 3,5,6]. On the other hand, only the silver salt is known to have a cubic lattice at ambient temperatures [4] among hexafluoroarsenates (V), M(I)As(V)F6. The authors have recently reported [8] that, at ambient temperatures, NaPF6 is isostructural with NaSbF6 [7] in which the P (or Sb)FNa array is straight. Furthermore, they determined the structures of the heavier alkaline metal salts containing a fourfold disorder in the orientation of anions. In the present study, structures of AgPF6 and AgAsF6 were * Correspondence and reprints: Tel.: + 81-75-7535822; fax: + 81-75-7535906. E-mail address: [email protected] (R. Hagiwara)
determined by means of X-ray diffraction single crystallography.
2. Experimental
2.1. Preparation of single crystals Since AgPF6 and AgAsF6 are moisture-sensitive, handling was made in an argon glove box with a gas purifier. AgPF6 and AgAsF6 (Ozark Mahoning, purity 99%) were used as supplied. Using a T-shaped FEP (Perfluoroethylene-propylene copolymer) tube equipped with a SUS316 stainless steel valve, a saturated solution was prepared in one end of the tube by condensing anhydrous HF (ca. 2 ml) on the sample and decanted into the other end of the tube. Single crystals were grown at room temperature by eliminating HF very slowly from the solution with cooling the other end of the FEP tube by water. The tube was kept in the dark during the crystal growth.
1293-2558/00/$ - see front matter © 2001 E´ditions scientifiques et me´dicales Elsevier SAS. All rights reserved. PII: S 1 2 9 3 - 2 5 5 8 ( 0 0 ) 0 0 1 2 4 - 2/FLA
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
238
In 4 days, cubic single crystals with 0.3–1 mm of edge lengths were formed in the bottom of the HF solution. The solution was decanted to the other end and the tube was evacuated through a soda lime trap by a vacuum pump. Monitoring by a microscope equipped with a CCD camera, the single crystals were recovered in the argon atmosphere. A selected crystal was transferred and fixed in the pre-sealed narrower end of a quartz capillary. The capillary was tentatively plagued with silicone grease, and then flame-sealed outside the glove box using a microburner.
2.2. X-ray diffraction single crystallography A sealed capillary was fixed on a small brass pin with adhesive to mount on a goniometer head. In order to check the quality of crystal, oscillation photographs were recorded with the aid of a Weissenberg camera (Stoe, 3.10.1) using CoKa radiation (40 kV, 25 mA) from an X-ray generator (Philips, PW1729). Weissenberg photographs of 0, 1 and 2nd layer was obtained to determine Laue symmetry and an approximate cell dimension. The same crystal was mounted on a Rigaku AFC5S diffractometer and data collection was performed at room temperature using MoKa radiation (50 kV, 20 mA). Single crystal data analysis was performed by RADY [9].
3. Results and discussion
3.1. AgPF6 A colorless cubic single crystal with the edge length of 0.5 mm was chosen for X-ray data collection after checked by preliminary camera works. The
space group Fm3m, assumed by the camera works was confirmed from the analysis of intensity data as well as the systematic extinctions. The structure refinement was made using 52 reflections (2u B60°, Fo\ 5s). In all the face-centered cubic structures of MPF6 reported so far, M+ and PF− 6 ions form a rock salt array [1–3,5–7]. It has been shown in the present study that AgPF6 was not the exception. The positions of fluorine atoms were searched with the aid of Fourier maps around the phosphorus atom at 0,0,0 in Fig. 1. They were found at around x,x,0(48h) and 0,0,z(24e). This implies that there is a disorder in the orientations of PF− 6 ions rotated by 45° around one of the crystal axes from the original position found in the NaSbF6 structure [7,8] in which all the fluorine atoms are located at x,0,0, etc.(24e). Thus the threefold disorder arises by the choice of crystal axis with 1/3 atomic occupancy at each site. The result of the refinement is shown in Tables 1 and 3. In the temperature factors anisotropically determined for fluorine atoms, b11 and b22, are identical and fairly large compared with b33 in the case of F(1) atom. These values are similar to that of b33 determined for F(2) atom that is also much larger than b11 and b22 of it. In parameters for both the fluorine atoms, b11 and b22 are identical. This suggests that the PF− 6 ion is librating and/or precessing around the z-axis with the position of phosphorus atom as a fixed point. The refinement introducing another disorder by placing F(1) atom at x%,x%,z or x%,0,z with increasing the numbers of nonequivalent fluorine atoms slightly decreased the R values. However, the distortion of PF− 6 molecule was too serious to be ascribed to the consequence of the difference in the number of coordinating cations around fluorine atoms bound to a phosphorus atom, or, the require-
Table 1 Positional parameters of cubic AgPF6 Atom Ag P F(1) F(2) F(1) F(2)
Wyckoff 4b 4a 24e 48h b11 1051(76) 250(17)
Occup. 1.00 1.00 0.33 0.33 b22 1051(76) 250(17)
x
y
0.500 0.000 0.000 0.149(3) b33 78(32) 1005(52)
0.000 0.000 0.000 0.149(3) b12 0 −75(25)
z
Beq (104pm2)
0.000 0.000 0.207(7) 0.000
6.6(2) 3.5(2) 16.6(8) 11.5(5)
b23 0 0
b31 0 0
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
239
Fig. 1. Fourier maps around (0,0,0) of AgPF6 and AgAsF6 lattices. Contributions of the electron density of the phosphorus atom is zapped from the maps of z= 0.00−0.08.
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
240
Table 2 Positional parameters of cubic AgAsF6 Atom
Wyckoff
Ag As F(1) F(2)
4b 4a 24e 48h
F(1) F(2)
b11 708(39) 324(15)
Occup. 1.00 1.00 0.33 0.33 b22 708(39) 324(15)
x
y
0.500 0.000 0.000 0.154(2) b33 119(25) 689(33)
ment for the closer packing of ions. The structure was not acceptable again when the refinement was made placing the F(1) atom at a general position. The PF− 6 ion is a regular octahedron. The F(1) atom is coordinated by one Ag+ while F(2) is coordinated by two of them. The AgF(1) distance is larger than that based on the sum of the averaged ionic radii estimated taking account the coordination number (196 pm, by Shannon [10]). This is probably due to the AgF(2) distance, not much longer than that estimated for the coordination of eight nearest neighbors (261 pm [10]). The F(2) atoms should be included in the coordinating atoms around Ag+ when the averaged coordination numbers are discussed (Table 3).
3.2. AgAsF6 The structure determination of AgAsF6 was made in the same manner. The refinement was made using 73 reflections (2u B75°, Fo \5s). Fourier maps around the phosphorus atom at 0,0,0 shown in Fig. 1 are quite similar with those of AgPF6. The refinement was made placing the fluorine atoms at the same position found in AgPF6 structure. The final result is shown in Tables 2 and 3. The anisotropically determined temperature factors exhibit the same tendency found for AgPF6. The refinement introducing further disorders described in the case of AgPF6 did not converge with realistic values of parameters. It is concluded that AgPF6 and AgAsF6 are isostructural at ambient temperatures.
0.000 0.000 0.000 0.154(2) b12 0 −157(33)
z
Beq (104pm2)
0.000 0.000 0.214(5) 0.000
8.04(18) 3.71(9) 12.3(5) 10.7(4)
b23 0 0
b31 0 0
3.3. The unusual coordination numbers and formula 6olumes of the sil6er salts The coordination number of fluorine atoms around the cation in MAF6 changes with the size of the cation. Hexafluorometallates of the metals with smaller ionic radii than that of silver (Li, Na) have the coordination number of six regardless the hexafluorometallate anion [11,12]. On the other hand, hexafluorometallates of the metals with larger ionic radii than that of potassium (Tl, Rb, Cs) possess a coordination number of 12 [11,12]. Coordination numbers of potassium salts sprit in two groups, 12 for small fluorometallate anions and eight for large fluorometallate anions, respectively [8,11,12]. For the silver salts, only the coordination number of eight has been reported. The averaged coordination number of ten for AgPF6 and AgAsF6 found in this study is unique although it is still in harmony with Table 3 Structural parameters of AgPF6 and AgAsF6 AgPF6 R Rw Lattice constant (pm) AF bond length (pm) FAF bond angle (°) Averaged C.N. of F around Ag AgF distance (pm)
AgAsF6
0.0812 0.0707 0.0644 0.0495 755.08(7) 775.48(21) F(1) 156(5) F(1) 166(4) F(2) 159(3) F(2) 169(2) 90 90 10 F(1) 2 10 F(1) 2 10 F(2) 8 10 F(2) 8 F(1) 222(5) F(1) 222(4) F(2) 288(3) F(2) 294(2)
R. Hagiwara et al. / Solid State Sciences 2 (2001) 237–241
the relation between the cation size and coordination numbers of this series. It should be noted that the formula volume of AgPF6 (1.076 ×108 pm3) is slightly smaller than that of NaPF6 (1.104 × 108 pm3, [8]) in spite of the larger ionic radius of the cation. The AgF(1) bond distance shorter than that found in AgF (246 pm) suggests increasing of the covalent character in the bond, which could cause this volume irregularity. Another possible explanation is that the size of the sodium cation having a coordination number of fluorine atoms, six, in NaPF6 [8]. The size of the cation could be too small against the PF− 6 ion to have a higher coordination numbers like found in AgPF6 (ten) which enables a closer approach of the cations and anions by increasing the number of the bonds. At the same time, it could be too large to decrease the lattice volume effectively by the size of itself. Such a halfway size of the sodium cation in the salt might cause a bulky structure for NaPF6. At this moment, it is hard to tell which is the right reason and which lattice volume is irregular, NaPF6 or AgPF6 in the series of hexafluorophosphates. The formula volume of the AgAsF6 (1.166×108 pm3) is only slightly larger than that of the sodium salt (1.149 ×108 pm3), exhibiting the similar tendency, although it is not as remarkable as in the case of hexafluorophosphates.
.
241
Acknowledgements The authors thank the Ministry of Education, Science, Sports and Culture for financial support by a Grant-in-Aid for Scientific Research. RADY in the program library of Data Processing Center, Kyoto University was applied for analysis of single crystal data.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
H. Bode, H. Clausen, Z. Anorg. Chem. 265 (1951) 229. H. Bode, G. Teufer, Z. Anorg. Chem. 268 (1952) 20. H. Bode, G. Teufer, Z. Anorg. Chem. 268 (1952) 129. J. Cox, J. Chem. Soc. (1956) 876. R.B. English, A.M. Heyns, J. Crystallogr. Spectrosc. Res. 14 (1984) 531. A.M. Heyns, C.W.F.T. Pistorius, Spectrochim. Acta 30A (1974) 99. G. Teufer, Acta Cryst. 9 (1956) 539. K. Kitashita, R. Hagiwara, Y. Ito, O. Tamada, J. Fluor. Chem. 101 (2000) 173. S. Sasaki, KEK Internal, National Laboratory of High Energy Physics, Tsukuba, 1987, vol. 3. R.D. Shannon, Acta Cryst. A32 (1976) 751. R.D.W. Kemmitt, D.R. Russell, D.W.A. Sharp, J. Chem. Soc., (1963) 4408, and references therein. D. Babel, Structural Chemistry of Octahedral Fluorocomplexes of the Transition elements, in: Structure and Bonding, vol 3, C.K. Jorgensen, J.B. Neilands, R.S. Nyholm, D. Reinen, R.J.P. Williams (Eds), Springer-Verlag, New York, 1967, pp. 1, and references therein.