Inougtrnic Chemistry, Vol. 9, No. 10, 1970 2259
SYNTHETIC SPOIIIOSITES
CONTRIBUTION FROM THE DEPARTMENTS OF CHEMISTRY A X D PHYSICS, POLYTECHNIC INSTITUTE OF BROOKLYN, BROOKLYN, NEW YORK 11201
The Crystal Structures of Synthetic Spodiosites. Ca2V04C1and Ca2As0,C11 B Y E. BANKS, M. GREENBLATT,
AND
B. POST
Received October 2 . 1969 The crystal structures of Ca;.V04Cl and CazAsO4Cl isomorphous with the spodiosite analogs CazPOdCl and CazCrOaCl have been determined. Both compounds crystallize in the orthorhombic system space group Dehl1-Pbcrn, with F u r molecules per unit cell. The cell constants are as follows: for CanVOaCl, a = 6.311 (5), b = 7.140 (5), c = 11.052 (5) A; for CazAs04C1, a = 6.318 (a), b = 7.108 (2), c = 11.058 (3) A. Refinement of the atomic coordinates was carried out by full-matrix leastsquares procedures (final R is 0.021 for CaZV04Cl and 0.023 for CazAs04Cl). The structures are made up of discrete XO4stetrahedra held together by calcium ions. The x04'- tetrahedra are significantly distorted from ideal tetrahedral symmetry in all four crystals.
Introduction The syntheses and crystal structure determination of CazP04C1 and CazCrO&l have been reported previously.2 These compounds are isomorphous with the mineral spodiosite, CazP04F.3 Recently, two new analogs of spodiosite, Ca2V04C1and CazAs04C1,have been ~ r e p a r e d . ~ The determination of the crystal structures of CazP04C1 and CazCr04Cl showed that both the Po43-and CrOd3- tetrahedra are significantly distorted from the ideal symmetry and that the distortion of the chromate tetrahedron is significantly greater than that of the phosphate. This effect was attributed to electronic ordering in the croq3--,in which the single d electron occupies the d,, orbital in a fashion analogous to the Jahn-Teller effect.j In vo43-there are no electrons in the d orbitals (ground state), and AsOq3- also has a closed-shell electronic configuration. The absence of unpaired electrons should exclude the possibility of electronic ordering of the type apparently present in the chromate, and any additional distortion in Ca2V04Cl and CazAsO4C1 as compared to the phosphate tetrahedron would presumably be due to size effects. The analysis of the crystal structures of Ca2V04C1 and Ca2As04C1was undertaken to make possible detailed comparisons of the X043- ions in the spodiosite series. Experimental Section Preparation.-Single crystals of Ca2V04C1 and CasAsOaCl were grown from a melt containing excess CaC12. The starting materials were thoroughly mixed, fired overnight in platinum crucibles a t 900' in air, and cooled a t 14'/hr to 300-400". Wellformed, colorless, needlelike crystals of CasVOaCl and CanAsO4Cl were obtained. This stoichiometry is based on data reported previously.4 Crystal Data .-Single-crystal photographic studies with preces(1) Work supported by Army Research Office (Durham) Contract No. i)A-31-124-AKO(D)-71 and National Institutes of Health Grant No. D E 02.577. ( 2 ) M . Greenblatt, E. Banks, and B. Post, A d a Cvyslallogf,., 23, 166 (1967). (3) H. Berman, C. Frondel, and C. Palache, "Dana's System of Mineralogy," Vol. 11, Wiley, New York, N. Y . , 1951, p 848. (4) E. Banks, M. Greenblatt, and 11. W. Schwartz, IWJUY. Chem., 7, 1230 il9tiS) 15) E. Banks, bI. Greenblatt, and R , I < , McGarvey, J . Chem. Phys., 41, 3772 ( 1 Y t i i ) .
sion and Weissenberg cameras confirmed that these compounds are isostructural with Ca2P04Cl and CasCrOaCl. Crystal data for the four spodiosite phases are given in Table I. The lattice constants of CanAsOaCl were determined by leastsquares refinement of the setting angles of 12 reflections measured on a Picker full-circle automatic diffractometer with manual control; each reflection was carefully centered. The lattice constants of CazV04C1 were computed from higher order powder reflections obtained using a Norelco diffractometer. Collection and Treatment of X-Ray Intensity Data. Ca2V04Cl. -A single crystal of CazVOaCl was ground to spherical shape (radius 0.018 =I=0.001 cm). Complete three-dimensional X-ray intensity data were collected on a PAILRED automatic singlecrystal diffractometer, using graphite-monochromatized Mo K a radiation. The integrated intensity was measured by an w scan of l"/min over a 3.8" range, and background was counted for 24 sec on each side of the peak. The intensities of 912 reflections in the levels h0Z to h9Z were measured. Integrated intensities were calculated from the function Inet
=
Imeasd
-
(BI
+ Bz) T 2
k)
where Imeasd is the total count, BI and Bz are the background counts, T is the total time spent scanning the reflection, and t g is the time spent for each background count. Of the 912 reflections, 799 were accepted as statistically above background (i.e., I n n e twas positive). The data were corrected for Lorentz and polarization factors in the usual way. In the case of the vanadate where the incident beam was monochromatized (monochromator angle 3.078'), the corrections for Lorentz and polarization effects are those given by Ladell.6 A spherical crystal absorption correction was applied using the linear absorption coefficient p>f0K~ = 44.8 cm-1 and p R = 0.80; the transmission factor range was 3.15-2.55.7 A standard reflection checked each day for intensity drift did not change more than l-2yo during the entire data collection period. CanAsOaC1.-A single crystal of CanAsOdCl was ground into a small spherical shape of radius 0.016 zt 0.001 cm. Threedimensional X-ray data were collected on a Picker full-circle automatic diffractometer using zirconium-filtered Mo K a radiation. The intensities of 1390 independent reflections were recorded in one octant using the 8-28 scan technique. All independent reflections to 20 = 80' were measured. The peaks were scanned at 1' 28/min for 100 sec, and backgrounds were estimated by (6) J. Ladell, Trans. Amer. Cuyslallogv. Ass., 1, 110 (1965). (7) "International Tables for X-Ray Crystallography," Vol. 11, Kynoch Press, Birmingham, England, 1962, p 302 I
2260
Inorgnnic Chemistry, 1’01, 9 , -Vo, 10, 1970 TABLE I CRYSTALDATA CaZPOLI
Crystal system Space group a,A b, A c,
CazVOnCl
Orthorhombic Pbcm 6.185=!=0.002 6 . 9 8 3 i 0.002 10.816 f 0.004 2.995 2.993
A
Density (measd), g cm-3 Density (X-ray), g ~ m - ~ No. of molecules per unit cell Color Habit
Orthorhombic Pbcm 6.311 =!= 0.005 7 . 1 4 0 i 0.005 11.052 f 0.00A 3.06 3.07 4 Colorless Needles elongated along c
4
Colorless Seedles elongated along c
TABLE I1 ATOMIC
P O S I T I O S A L PARAMETERS I N Y
X
Ca(1) Ca(2)
c1 v
0(1) O(2)
0.6218(1) 0.1395(1) 0.4886(1) 0.126F(1) 0.0345(2) 0.7103(2:
4(c)
4(d) 4(d) 4(~) 8(e) 8(e)
Caz\rOaC1a 2
0
‘/4
0.4717(1) 0.1944(1) ‘/4
0.7308(2) 0.5652(2)
l/g
0 0.3762(1) 0.5285(1)
C a C r OaCl
Ca?AsOCI
Orthorhombic Pbcm 6.259 f 0.005 7.124& 0.005 1 0 . 9 9 i 0.005 3.14 3.14 4 Dark green h-eedles elongated along b
Orthorhombic Pbcm 6 . 3 1 8 2 ~0.002 7 . 1 0 8 h 0.002 i i . 0 5 8 f 0,003 3.42 3.41 4 Colorless Needles elongated along c
maining 1147 observed reflections were used for the final refine ment. Refinement of the Structure. CasVO4Cl.--The structure was refined by least-squares procedures using our version of the Busing, Martin, and Levy* program. The atomic parameters determined for CaaCrOaCl were used as a starting point.2 Akfter three cycles of refinement in which anisotropic temperature factors were used and in which the scattering factors of Ca, V, and CI werecorrected for dispersion effects,@R (=ZIIF,l - ~ T ~ F ~ , ~ ~ / Z ~ F ~ I ) the discrepancy factor, dropped to slightly above 8(5.
TABLE 111“ ATomc THERMAL PARAMETERS IN Ca2V04Clb A.
Anisotropic Thermal Factors
PI1
8>2
P33
0.0028 (1) 0.0059 ( 1 ) 0.0079 (1) 0.0022 (1) 0.0046(3) 0.0047(2)
0.0030 (1) 0.0033 (1) 0.0090 (1) 0.0023(1) 0.0053(2) 0.0031 ( 2 )
0.00204(3) 0.00116(3) 0.00175 (4) 0.00076 ( 3 ) 0.0012 ( 1) 0.0024 ( 1 )
B.
812
0 0 0 0 0.0005 ( 1)
0
Rms Displacement along Principal Axes of Thermal Elkipsoids 2
1
P?8
Bl8
0 - 0.0004 ( 1 ) 0.0038 (1) 0 0.0011 ( 2 ) -0.0006 (1)
0.00052 (3) 0 0
-0.00011 ( 2 0 0.0003 ( 1 )
(A) 3
0.075 ( 2 ) 0.083 (1) 0.116 ( 1 ) 0.085 ( 1) 0.091 (1) 0.110 ( 1 ) O.lOl(1) 0.104 (1) 0.171 ( 1 ) 0.078 ( 1 ) 0.067 (1) 0.068 (1) 0.122(2) 0.076 (3) 0.097 (3) 0.123 ( 2 ) 0.083(3) 0,101 (2) 5 Estimated standard deviations (in parentheses) in this and following tables occur in the last significant digit in each case. form of the anisotropic temperature expression is exp[ - ( P I @ Paak2 p J 2 2p12hk 2p,,hl 2pz3kl)].
+
counting for 10 sec at 0.8” from peak maxima. A standard reflection was measured after every 20 reflections, to check on stability of operation. Total variation in the standard intensity was less than 57, during the data collection. Deviations were erratic ( ; . e . , intensity of standard reflection fluctuated between a minimum and maximum value, probably due to instability of Xray intensity or slight movement of the pulse-height analyzer’s window or a combination of both and other operational factors). These variations were corrected by scaling the intensities as follows. W e assumed a linear correction between monitored standards, and then these were scaled to the maximum standard. T h e total discrepancy was less than 57, between the maximum and minimum values of the intensity of standard reflection, and the average was much less. Data reduction was carried out as described above for CasVOaCl. For the absorption correction the linear absorption coefficient p\rolca = 96 and p R = 1.57 were used. The transmission factor range was 8.51-4.31. Of the 1390 recorded reflections, 30 were found to equal zero after data refinement, and 213 additional reflections were removed as these were too weak to be statistically reliable. The re-
+
+
+
+
The
It was observed in an independent experiment that crystals from this batch exhibited large extinction and multiple diffraction effects.1° Furthermore, me noticed that F, was systematically larger than F, for all strong reflections, indicating large extinction effects. The structure was then refined further by applyinR estinction corrections to minimize the effects of both extinctioii and multiple diffraction in the form first suggested by Zachariasen and incorporated by Coppens and Hamilton into their leastsquares program at the Brookhaven riational Laboratories.” After two more cycles of refinement using isotropic extinction corrections and a weighting scheme, w = 1/[36 0.015FL],the conventional R factor decreased t o 0.021. The weighted R , , ( = [ Z w ( l F , l - I F c 1 ) 2 / 2 w ~ F o ~ 2was0.032. ]1’z) Plots of 4Fos. F,, and v s . sin 0 yield approximately a constant value using our
+
(8) W. K.Busing, K. 0. Martin, and H . A. Levy, “ORPIS, a Fortran Crystallographic Least-Squares Program,” Report OKh~I,-TX-305,Oak Ridge Sational Laboratory, Oak Ridge, Tenn., 1962. (9) “International Tables for X-Ray Crystallography,” Vol. 111, Rynoch Press, Birmingham, England, 1862, pp 215, 216. (10) B. Post, private communications. (11) P. Coppensand W. C . Hamilton, Acta C?’wla?lloni., A26, 71 (lL470).
SYNTHETIC SPODIOSITES
Iriorgcinic Chemistry, Vol. 9, No. 10, 1970 2261 TABLE IV CALCULATED AND OBSERVED STRUCTURE FACTORS FOR Ca2V04CP 0b
65
64
1 2
11 11
3 4
11 9
12 11 11
5 7
9
12
0
10
1 2
6 5
l i 6
4 4
7
5 v 1
5
n -
9 10 11 10 6
0
6
L FOBS FC*I*. 0
74
.'O
2 b
20 77
21
6
22
28
7:
1E0
66 19
l2
59 20
20
1 1 4 0
23 67
59
13
14
1
20
19
2
6 11
j
50
0 2 0 0
57 29 62 18 I, 15 8 11
I 0
1 2
3 0 0
: 11 50 5c 29
Gi) 10
L? 16 i 11
30
30
2
12 9
1
3
9
; $ 1;
5 5 15 . I 5 9
0 2
n =
I FOBS FCALC 0 23 23 13 I3 6 1 6 8 13 13
9
10
H
=
2
12
7 9
4 6
8
n
D
10
L FOBS F
6
W I1
'i
P 0
11 L FOBS FCALC =
26 24 1 16 2
2':
6
10
0
a
10
12 17
Scale factor is 10.54; F, = Fo/scale factor.
TABLE V ATOMICPOSITIONAL PARAMETERS IN CazAsOlCl Y
X
Ca(1) Ca(2) c1 As O(1) O(2)
4(c) 4(d) 4(d) 4(~)
8(e) 8(e)
0.6252(1) 0.1384(1) 0.4958(1) 0.12909(3) 0.0297(2) 0.7100(2)
2
l/4
0
0.4764(1) 0.2007(1)
l/*
'/4
0 0.3774(1) 0.5272(1)
0.7352(2) 0.5669(2)
weighting scheme. The standard deviation of an observation of unit weight is 0.8439. The isotropic extinction parameter which multiplies Fo is 1.320 (41) X cm-l. The largest extinction correction is equal to 0.29 for (004) in CaZVOaCl. The atomic
parameters and their estimated standard deviations are listed in Tables I1 and 111. Calculated and observed structure factors are listed in Table I V . The refinement of the crystal structure of CalAsOaCl proceeded in much the same way. Starting with the positional parameters of Ca2VOaC1, three cycles of least-squares refinement yielded R = 0.071. Two more cycles of refinement with isotropic extinction corrections gave a discrepancy coefficient of 0.023. The weighted R, value was 0.024, using the weighting scheme w = l/(ar2 0.004F2) where cr is the fractional standard deviation in the intensity of each reflection calculated by the function
+
BI
+ B2
TABLE VI ATOMIC THERMAL PARAMETERS IN Ca2As0,C1
A. 011
C 4 1) C42) c1 As O(1) O(2)
0,0038 (1) 0.0060 (1) 0.0082 (1) 0.00308 (4) 0.0061 (2) 0.0051 ( 2 ) B.
Anisotropic Thermal Factors
P22
Paa
0.0028 (1) 0.0031 (1) 0.0081 (1) 0.00232 (3) 0.0049 (2) 0.0027 ( 2 )
0.00202(3) 0.00143 (3) 0.00185(3) 0.00108 ( 2) 0.0013(1) 0.0027 (1)
811
BiI
0 - 0.0005 ( 1) 0.0035 ( 1) 0
0.0009 ( 2 ) -0.0011 ( 2 )
0 0 0 0
0.0007 ( 1) 0
Rms Displacement along Principal Axes of Thermal Ellipsoids 1
0.083(1) 0.088 (1) 0.102(1) 0.0761 ( 6 ) 0.084 (3) 0.074 (3)
2
0.088 ( 1) 0.094 (1) 0.107 (1) 0.0789 ( 5 ) 0.103 (2) 0.108 (2)
iaY8
0,00036 ( 3 ) 0 0 - 0.00009 ( 2 ) 0.0002 (1) 0.0003 (1)
(A) 3
0.114(1) 0.111 (1) 0.164 (1) 0.0825 ( 6 ) 0.123 (2) 0.129 (2)
TABLE VI1 CALCULATED AND OBSERVED STRUCTURE FACTORS FOR Ca2As04CP 1 8
8 . 0
1: L m n S W 1 9
U8 110
0 2 I22 0 4 279 69 0 6 0 8 218 0 10 39 2 0 1 e 2 1 13 2 2 l 6 4
6 5 1 u 61112 219. 1 1 3 40 L 14 1 7 9 2 0 1 3 2 1 15922 212 3 n 2 4 11 l 6 2 5 131 133 2 6 28 4 2 7 116 K O 2 8 6 6 2 9 103 106 2 10 12 K 2 U 58 6 3 2 1 2 TI 73 2 13 223 218 Q 14 15 1 4 3 0 85 8431
z
E2 25
2 6 2 7 2 8 2 9 2 10 2 U 212 2 14 '1 0
4
1
4 2
:2
b2 64
633 5 693 6
31 8 1 4 6 9 9 10 55
4u
18
4l2
84
4 6 6 6 6 6 6 6
1 4 35 o u 2 1 4 2 147 4 69 5 16 6 U9 7 12 6 8 71 6 9 6 6 1 0 SS 612 p 6 1 3 10 6 14 59 8 0 13
8 1 8 2
:8 25
39
8 7
8 8 8 9 810 all
IO
62 P
B Y
41
8 13 8 14
17 48
10 0
10 1 i o 2
n 3 9 57 3 10
183U
3313 S 3 14 u 2 4 0 2 4 149 4 69'1 114 1204 u 4
1 2 3 4 5 6
7248
60 15
;E;
?9
io 5 l o 6
17 69
10
20
I
46
56
24 ~ O K4 K O 43 Y 1 15 12 2 51 K 3 13 1 2 4 36 12 6 51 1 2 7 20
10412 60 4 1 3 73 4 14 405 0 1 1 5 1
2 4 5 4 6 7 5 5 3 8 5 6 6 1 5 1 2 8 5 8 625 9 P S I 0 415U 17 5 Y 41 5 13 59 6 0 14 6 1 1862
17 6 6
6 8 6 7 20 6 8 466 9 56 6 10 24 6 U 28612 44613 14 6 14 n 7 2 127 3
$?': 2 1 1 7
I
8
44
32
32;:
o 14
21 50 23 65
20 8 4 8 8 2 4 8 6 3 8
63
34
62812 34 8 14
10
109 0
1 1 1 1 1 1
a
2 3 4 5 6 7
,pB
458 1 6 1 8 9
9 9 2 4 2 9 3 21 9 4 10 9 5 21 9 8 25 9 U 14 9 1 2 9 914 33 10 0 117 10 I 41 10 2 6 8 10 3 30 10 4 8410 5 27 10 7 5 10 8 15 10 9 64 10 10 23 io u 27 10 12 15ll 0 4lU 2
u 3 9 u 18 u 30
10
31 x2 o 3912 1 3312 2 1912 3 1012 4
2112 5 3612 6 15 t 20 K L
35 19 19 31 7L 10 20 19 11 23 14 85 15 14 12
61 20
0 0
I 10 1U 112
I 18
18 8 27 7 29 P 26 47 25 39 29 25 22
26
6 29 28 P 46
38
25 2L 29 21 24 31 23 40 17 18 5 18 37
31 16 5 25
3:
9 37 10
38 4 10
17 3
25
5 7 5 8 7 t
13 53
9
20
410 4 11
It
7 3 5 23 3 6 24 3 8 1 9 3 13 6 4 0 16 4 2
1) I3 414 5 5 3 103 5 1 8 5 2 -4 5 3 18
3:;
ig
5 i 51 5 13
5 ' 8
11 111
11 5 :1 111 5 11 27 5 1 2 ? 513
9
- 13
2:
lj
6
7 14
23 is 11 7
t8 e 61 8
s :
8 40
2
8
e
e
8
1 :
11 2
2 I
5 6 5
17
15 11 11
? 1; 1,
13 32
14
--
11
c
2
8 6 "
c 9 - 1
: j
r3
5 7 6
r o a 5
:a
0 1" 0 12 1 0
1 1 1 2 1 3
27 36 25 42 19 24 119 24 0 16
8 1 4 14 1 5
e5
1 6
76 6
25
1 3 1 7 38 1 8 24 I 9 48 113 19 1 11 9112 17 1 I3 3e 1 +3 21
1 -4
25 2 s 1 7 2 1 3 1 2 2 1 3 2 3
5 2 4 1 2 2 5
31
89 26
41 9
6 7
2:;
10 3
10 4 l l
5 7
11
6
18 4 12 4 4 I3 25 4 1 4
5
7 74 28
81 23 51 24
18 3 7
21
77
12
1114
-F
i
L
j
6
~
411' 1
P 5 c.
119 10 6D 45
28 I*
13
6 '9 6 10 6 3 6
6
2 i
7
17 ii 23 19 15
63
19 6 11 111612 62 7 0
10
1 0 7 1
15 7
25 I.
2 L 7 2 11 21 77 64
7 7
9 62 3: 13 52
1 2 e :
52 8
6
4 8 8
33
3 3 6 9 7 9 0 5 - 9 1 9 "
a
d
7 L SOB5 F c m B =
33
3*
25 30 12 15 8 21 13 9
6
11
7 17 12 4
8
17 18 52 2 21 22
4 9 4 13 411
9 3 19412 5 5 1 t 5 3
9
11
5
5
-
5 5 5 23 5 ' 2 6 5 8 3 4 5 9 25 14 5 10 29 28 6
3
Y
6 15 10 7
85
I: d 3
10
64 7 46
11 11 6
5 7 7
8 47
8
1
7
8 8 : 2 c 9 0
6
9
23
9 Y
17
16 e o 0
5
4 0 e o 0
2
16
LB
IL 45 15
44 14 9
e
5 71 62 5 64 53 5 51 39
3
8
2191 112 111
2
13 13 15 11
17 29 11
13 18 13 10
11 23 15
13
18 16 10
9
9
8
13 9 12
; 13 12 7
?.I 11 7
4 25
8
4
c
13 11
6 5
25
e
7
7 6
15 12
'
14 11 _.
10
10
7
5 10 4
8
11 f
1 6 7 1 51 7 2
27
5 28
12
12
c
53 0 :7 ;5 ;
7
f
4 H - 1 0 14 K L FOBS PCMC 1 1 0 6 2 3 7 0 8 10 10 4 1 0 4a 41 8 1 1 10 11 4 0 1 2
4 0 1 3 60 1 L 38 1 5 57 1 D 35 1 7 49 I 8 5 2 1 9 2 2 11 2 3 6 2 4 1 0 2 5 7 2
6
47 2 7 1 6 2 8 48 3 0 1 4 3 2
4 5 3 : 14 3 4 " 3 5 1 3 3 6 9 3 7 8 3 8
4
4a 12
5;
45
14
32 29 11 9 5 25 12 6 41
%
51 6
48
48 K 52
7 45 13
35 29 10 8
4 25 11 5 4
9 7 50 5 48 5
0
7 33 I6
2
b
4 5 0
11
7
5
42
1
10
42 11
;; 3 ;; ; ; 1;
32
15 4 11
3;
5; 5; 6 1 13 13 1 7 6 2 7 7 29 H = 11 10 K I FOBS Ic*Ic 12 0 0 33 33 1 8 0 2 8 8 Ij 0 4 21 27 9 1 2 5 4 l o 1 3 7 6 14 1 4 12 11 2 ? 2 0 12 13 5 2 2 21 20 2 0 2 4 8 7 9 3 0 8 1 7 3 2 5 4 9 12
8 20
Y4 2 10 7
10 11
li
12 2 1 1 6 3 0 68 3 1
9 16
1 16 9
a
17
25 15 6
29 20 21 18 25 15 5 13 18 15 11
6
6 2 2 18 2 3 6 2 6
16
29 20 21
3270
1 2 2 1
10
2
3 3 3 4 3 5 3 6 3 7 3 8 3 9 3 lo 3 3 11 14 4 1 6 4 2 6 4 7 4 2 6 4 5 1 0 4 6 1 0 4 9 6 410 7 5 0 11 5 1 5 5 2 1 1 5 3 7 5 L e o 5 5 1 9 5 6 4 5 5 21 5 8 75 5 9 1 5 6 1 41 6 3 2 0 6 1 65 1 3 (.6 8
H = 9 L FOBS IC.A I c 4 13 4 0 2 11 14 1 1 4 4 9 9 5 6 111 5
a%
3 7 I1 13 6 67
9 31
0
19 6 9 22 7
118 7 1 10 11 53 1 12 13 1 13 2 i 1 14 22 2 0
52 I2
2
: e 2
e
:; i"-
7
20 e 4 9 8 5 : e 6
13
7 1 5
16 41
7
6 8 3
7
19 12 6 18
74
L
13 i
23
22
21
15
4 8 0
4
8 I115
49 5
Y L F03S 1"AD2 0 10 3 6 0 0 94 9 5 1 0 33 1 1 91 1 2 33 P I 3 e Bi 81 1 4 27 27 1 5 65 1 6 65 24 23 1 7 6 1 1 16 16 1 8 14 1 9 5 1 2 13 9 1 10 5 1 3 9
I
I 11 5 12
38 59
6 - 3
7
1 5 1 2 1 6 6 1 7
10
5 10
33
, I:
8
11 18 6 2II 2 3 6 6 2 0 6 8 17
9 'i= 8
25 3 2 2 0 0 4 i3 0 6 It 0 7 $ 10 21 0 12 14 0 14
5
? 2 4 ' 2 2
7
"9
8
4 4 i u
5
26 34 25
24 8 10 93 6 11 16 9 0 € 6 9 2 9 3 , 9 L e 9 5 85 9 6 2 0 9 1 6 3 9 9
229 30 1 08 4 312 4 014 8 1 3 7 1 2 5 1 3 7 1 5 li 1 6 7 1 7 4 1 8 4 110 76 11: 28 114 83 2 3 20 2 1 51 2 2 2 L 2 3 77 2 1 20 2 5
2
4 6 3
16 i 10 13 3 3 8 8 2 1 3 8 2 E 2 8 3 35 8 1
1 1;
3 4 5 a
- 6 1
21 1 ;7 ;9 :
11 5
8 9 22 7
1 2 6 2
12
I17 2 33 45 1 ' 3 6
is 4 1
0
9
15 6 8
-8 4
9 22
23
e
23 2 3 0 1 1 5 3 2 1 3 3
23
3
71 6 10
41 51
13 13
8
8
70 62 5 64 53 6
14 37 2 10 12 31 2 13
-8
1 : 5 13
1.4 16
50
9
e
0
11
K
~
510 5 I1 I 5 1 2 15 5 I3
9 7
6
75
8 I7
1)
2;
10
3 1L
6
19 0 2 19 0 4 b3 0 6
i 43 26 3 5 2 2 3 b ~
e ae
50
t4 22
1.7
38 2 11 36212 8 3 0 20 3 1 28 3 2
18 122 21
e 1 7
4
42
e
9
11
19
20
I 3 6 e 2 23 8 3 4 2 8 5 2-
29
r
71
:
19
; ;: ;-: ; :p
5 23
8
1 6 1 1 "
1 2 4 5 6 8 9
10 3 6 33 96 5 3 10 30 3 u 5
11
5 5
714 35
2
;; 7
35
30
6
ir
11 16 10
33
Ir
86l2 13 9
2
23 5 15 4
e
e
18 i b 1 5 6 7 i l 6 9 11 6 10
7
10 li
1 3 4 ) 13 L 4 4 4 :
le ~i 9 Bo 4 1 0 10 4 11 t 2 4 12
5 1 2 7 2 9 2 1 8 2 45 2 7 2 9 2
19 45
22
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113 114 2 0 2 2 2 2 2
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25 64 9 20 6
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5 3 8 *68 23 i 9 211 31 3 10 71 n 3 11 1 3 4 3 1 2 43 14 3 13 16 44 3 14 54 14 4 0 29 16 7 44 21 269
8 25 11 16
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Scale factor is 3.350; F, = Fo/scale factor.
The standard deviation of an observation of unit weight is 0.6668. The isotropic extinction parameter applied to F, is 0.733 (16) X 10-4 cm-1. The largest extinction correction is 0.35 for (004) in CazAsOaCl. The atomic parameters are listed in Tables V and V I . Calculated and observed structure factors are listed in Table 1'11.
the vanadate and arsenate tetrahedra are illustrated i n Figure 2, produced by Johnson's thermal ellipsoid plot program.13
Discussion
The spodiosite structure projected along the a axis is shown in Figure 1. Interatomic distances and interbond angles for Ca2PO4C1,Ca2V04Cl, CazCr04C1, and CanAsOC1 are listed in Table VIII. The standard deviations reported were derived from the complete variance-covariance matrices using the function and error program of Busing, et a1.12 The dimensions of
The spodiosite structure is made up of discrete XOa3tetrahedra, arranged along the c axis one above the other; members of each pair are related by a mirror plane a t z = l/,$. They are apparently held together by the positively charged calcium ions. The coordination around both calcium ions is eight, with six nearest oxygens and two chlorines, in an irregular polyhedron. The chlorines appear to fill available holes in the structures. Evidently the spodiosite structure requires the
(12) W. R. Busing, K. 0. Martin, and H. A. Levy, "ORFFE, a Foitran Crystallographic Function a n d Error Program," Report OKhTI.-TM-306, Oak Ridge National Laboratory. Oak RidRe, T e n n 1964.
(13) C. K. Johnson, "ORTEP, a Fortran Thermal-Ellipsoid Plot Program for Crystal Structure Illustrations," Report ORNLH794, Oak KirlKe N a tional Taboratory. Oak Ridxe, Tenn., 1966.
Results
SYNTHETIC Sponrosrms
rnorgunic Chemistry, Vol. 9, No. 10, 1970 2263
0 n
0 0
0
0
00
0
0
0
0 0
O
0
O
00 67 0
0 Q
0 0 O
0 Figure 1.-The unit cell contents of CaZX04C1 projected along Q (X = P, V, Cr, As): large open circles, C1; atoms shaded up and down, X ; double circles, Ca; smaller open circles, 0. Bonds between the atoms in X043- tetrahedra are represented by broken lines.
TNTERATOMIC
TABLE VI11 DISTANCES AND BONDA k ~ ~ ~ ~ ~ ‘ L
Ca?POCI
CazVOaCl
Ca( 1)-O( 1) Ca( 1)-O(2) Ca(2)-0( 1) Ca(2>-0(2) c1-c1 C1-0( 1) Cl-0(2) x-O( 1) X-0(2) O(1)-O(2’) O( 1‘)-0(2’) O(2)-O(2’) O(1)-O(1’)
Distances, A 2.538 (2) 2.568 (1) 2.491 ( 2 ) 2.496 (1) 2.424 (2) 2.409 (1) 2.655 (2) 2.638 (1) 3.4990 (1) 3.5729 (1) 3.263(2) 3.327(1) 3.191(2) 3.243(1) 1.547 (2) 1.711 (1) 1.534 (2) 1.703 (1) 2.481 (2) 2.724(2) 2.578 (2) 2.902 (2) 2.477(3) 2.713(2) 2.495(3) 2.751(2)
O( l)-X-O(2’) 0(1’)-X-0(2) 0(2)-X-0(2’) O(1)-X-O(1’) O(l)-X-O(2) O( l’)-X-0(2’)
107.3 (1) 107.3(1) 107.7(1) 105.7(1) 113.6(1) 113.6 (1)
Angles, deg 105.9 (1) 105.9(1) 105.6(1) 107.0(1) 116.4(1) 116.4 (1)
CanCrOXl
CnrAsOd3
2.515 (3) 2.464 (3) 2.425 (3) 2.593 (3) 3.5707 ( 2 ) 3.331(3) 3.227(3) 1.710 (3) 1.689 (3) 2.694(4) 2.931 (4) 2.670(5) 2.719(5)
2.570 (1) 2.504 (1) 2.416 (1) 2.661 (1) 3.5545 ( 0 ) 3.322(1) 3.239(1) 1.690 (1) 1.679 (1) 2.678(2) 2.873 (2) 2.672(2) 2.720(2)
104.8 (1) 104.8(1) 104.4(2) 105.3(2) 119.2(1) 119.2 (1)
105.3 (1) 105.3(1) 105.5(1) 107.2(1) 117.1(1) 117.1 (1)
presence of a large anion such as C1- or Br- in these positions. Except for the mineral CazP04F which gives its name t o this structure, there are no spodiosites with these ions absent, and, significantly, no phase of this composition exists in the Ca3(P04)2-CaF2 system. Comparison of tetrahedral radii for V5f and As5f in these compounds with those listed by Shannon and Prewitt14 shows a discrepancy of about 0.05 A. We (14) K.D Shannon and C. T.Prewitt, Acta Crysfallogv., Swt,R , , 80, 98.5 (1969).
Figure 2.-Dimensions
of vanadate and arsenate tetrahedra.
believe that this contradicts the statement by Shannon and Prewitt that radii are independent of structure type. However, these authors point out that this independence must be modified by considerations of covalency and repulsive forces. It would appear that the effect of these differences between the structures reported here and those chosen by Shannon and Prewitt as standards is sufficient to modify the apparent radii to this extent, which is significantly greater than experimental error. The tetrahedra are considerably distorted from ideal configuration for all four structures ; the only element of symmetry left is a twofold axis. A significant aspect of this study is the relative distortion of XOd3- tetrahedra. It is now clear that the most significant angular distortions occur in The electronic configuration of Cr(V) in Cr043- is d’. Results of the electron spin resonance measurements made in diluted single showed that the unpaired crystais of Caz(PO~,Cr04)C1 electron is in a d,a orbital.6 We suggested that, in additinn to the distortion due to crystal lattice effects
clearly present in the phosphate tetrahedron, a JahnTeller type of electronic ordering takes place in the case of CrOh3- tetrahedron, nearly doubling the extent of distortion. I n V043-there is no electron in the d orbitals (ground state). Bond distances in V043- are similar to those in CrOh3-, but bond angles fall approximately between the values in the phosphate and chromate. The increased distortion in the vanadate tetrahedron as compared to P043-is tentatively attributed to the lowering of the interatomic force constants and vibration frequencies due to the increased mass. As the chromium(V) and vanadium(V) ions are not expected to differ appreciably in size the larger distortion in the Cr0d3tetrahedron appears t o be electronic in nature. However, the excess distortion in v0d3- may also be due to the mixing of low-lying excited states in the d manifold. This should be investigated spectroscopically. Similarly, in AsOa3-, there are no unpaired electrons (ground state) ; the crystal structure shows the distortion t o be intermediate between the V0,3- and Cr043-. On the basis of size considerations alone we might have expected the distortion of the arsenate to be smaller than
that of the vanadate ion; although the differences between the distortions of the two tetrahedra are small, the arsenate is distorted t o a significantly greater extent than the vanadate. The reasons are not clear. Conclusion Spodiosites with the general formula CaZX04C1, with X = P, V, Cr, and As, have been prepared. Detailed crystal structure analyses of all four show that the XOk3- tetrahedra are considerably distorted from T d symmetry. Interatomic distances are normal, and the distortions cannot be explained by considerations of crystal packing alone. The largest distortion is exhibited by the CrOh3- tetrahedron ; this was attributed to electronic ordering of the lone electron in the d orbi- not contain untal. Po43-, V043-, and A s O ~ ~do paired electrons and the observed distortions are notably smaller than in Cr043-. Acknowledgment.-We wish to thank S . J. La Placa of the Chemistry Department of Brookhaven National Laboratories for his help in connection with the use of the computer programs a t the Brookhaven National Laboratories.
COSTRIBUTION FROM
THE
BELLTELEPHONE LABORATORIES, INC., MURRAY HILL,NEWJERSEY 07971
The Crystal Structure of the 1:1 Molecular Addition Compound Xenon Difluoride-Iodine Pentafluoride, XeF,. IF, BY G. R. JOKES, R. D. BURBASK, ASD S E I L BXRTLETT
Received September 11, 1969 The crystal structure of the 1: 1 molecular addition compound xenon difluoride-iodine pentafluoride, XeF2.IFb,has been determined from three-dimensional X-ray data. The material crystallizes in the tetragonal system, with four molecules in a cell of dimensions a = 7.65 (1)and c = 10.94 (1) A. -4 satisfactory refinement was obtained in the space group I4/m, with a final conventional R factor of 0.034 for 403 nonzero reflections. The structure has established the existence of discrete XeFz and IF5 molecules, linear and square-based pyramidal, respectively. The alignment of the XeFg molecules, with each fluorine ligand directed t:ward the iodine atoms of neighboring IF6 molecules, and the shortness of those interatomic distances (3.142 ( u = 0.007) A ) suggest that the ordered crystal lattice is largely a consequence of electrostatic attractions between the different components
Introduction Xenon difluoride is a fluoride ion dot10r~-~ and forms salts with arsenic pentafluoride and strong fluoride ion acceptor metal pentafluorides. It also forms a 1 : l compound with iodine pentafluoride which Bartlett and Sladky4concluded was a molecular adduct on the basis of Raman spectroscopic evidence. The crystal structure of the compound confirms this representation, the geometry of each molecule being only slightly different from that of the “free” species. (1) F. 0. Sladky, P.A. Bulliner, N. Bartlett, B. G. De Boer, and A. Zalkin, Chem. Commun., 1048 (1968); F. 0.Sladky, P. A. Bulliner, and N. Bartlett, J . Chem. SOC.A , 2179 (1969). (2) V. M.McRae, R . D. Peacock, and D. R. Russell, Chem. Commum., 62 (1969). (3) J. G. Knowles and J. H. Holloway, J . Chem. SOC.A , 756 (1969). (4) N.Bartlett and F. 0. Sladky, ibid., A , 2188 (1969).
The nature of the alignment of the molecules in the crystal lattice is consistent with coulombic attraction of negatively charged fluorine ligands of the XeFa molecules to the positively charged iodine atoms of nearest IF6 molecules. This is similar to the 1 : 1 molecular adduct6 XeFz.XeF4and like the situations found6a7in crystalline XeFz and XeF4. ( 5 ) J. H. Burns, R. D. Ellison, and H. A. Levy, Acta Crystallogv., 18, 11 (1965); J. Phys. Chem., 67, 1569 (1963): “Noble-Gas Compounds,” H. H. Hyman, Ed., University of Chicago Press, Chicago, Ill., 1963, p 226. (6) H. A. Levy and P. A. Agron, “Noble-Gas Compbunds,” fl. H. Hyman, Ed., University of Chicago Press, Chicago, Ill., 1963, p 221; J . Amer. Chem. Soc., 85, 241 (1963); P. A. Agron, G. M. Begun, H. A. Levy, A. A. Mason, C. G. Jones, a n d D. F. Smith, Science, 189, 842 (1963). (7) D. H. Templeton, A. Zalkin, J. D. Forrester, and S. M. Williamson. J . Amev. Chem. Soc., 85, 242 (1963); “Noble-Gas Compounds,” H. H. Hyman, Ed., University of Chicago Press, Chicago, Ill., 1963, p 203; W.C. Hamilton and J. A. Ibers, ibid., p 195; J. H. Burns, P. A. Agron, a n d H. A . Levy, ibid., p 211; Science, 189,1208 (1963); J. A. Ibers and W. C. Hamilton, %bid.,139, 106 (1963).
