CRYSTAL STRUCTURE OF SODIUM NITROPRUSSIDE1043
Vol. 2, No. 5, October, 1963 NEW
CONTRIBUTION FROM THE CHEMISTRY DEPARTMENTS OF COLUMBIA UNIVERSITY, NEWY O R K , AND BROOKHAVEN NATIONAL LABORATORY, UPTON, NEW Y O R K
YORK,
The Crystal Structure of Sodium Nitroprusside1 BY P. T. MANOHARAW
AND
WALTER C. HAMILTON
Received June 21, 1963 The crystal structure of sodium nitroprusside, Na2Fe(CN),( NO).2H20, has been determined by an analysis of three-dimensional X-ray diffraction data. The crystal is orthorhombic, space group Pnnm. The nitroprusside ion lies on the mirror C-N, 1.16 f 0.02 plane and has approzimate Clv symmetry. The important distances are Fe-C, 1.90 f 0.02 Fe-N, 1.63 =t0.02 A , ; N-0, 1.13 f 0.02 A. The ligands are colinear with the metal atom, which is displaced slightly in the direction of the NO group from the plane of the four pseudo-equivalent CN groups. Each sodium ion lies a t the center of a distorted octahedron composed of four CN groups and two water molecules. These octahedra share edges in such a way that eaFh CN group is coordinated to two N a + ions, as is each water molecule; the Na+-ligand distance is approximately 2.5 A. in every case. The nitroso group is coordinated only t o Fe+*. The water molechles do not lie near enough to other electronegative atoms to permit significant hydrogen bonding.
w.;
Introduction The coordination of the NO group to transition metals is of great theoretical i n t e r e ~ t , ~but - ~ X-ray diffraction data on inorganic nitroso compounds are rather sparse. In particular, the linearity of the M-N0 linkage, which has important implications as t o the nature of the metal-nitrogen bond, is open to question. Johansson and Lipscomb' have carried out a structure determination of Roussin's black salt, CsFe4F3(NO)7.Hz0,and Thomas, Robertson, and Cox8 have determined the structure of Roussin's red ethyl ester, (N0)4FeSz(CzH&. The Fe-N distances in these compounds vary from 1.57 to 1.71 A., suggesting a large amount of double-bond character for the Fe-N bond. Such double bonding would seem to force linearity on the Fe-N-0 link. However, values of 167.7 f 3.5' and 167.2 f 3.5' are ascribed t o the Fe-N-0 angles in the ester, and a value as small as 160' may be calculated for one such angle in the black salt. Johansson and Lipscomb consider these deviations to be indicative of crystalline packing forces rather than of any unusual electronic structure. Alderman, et al.,9z10have reported a rather more severe departure from linearity in the compound Co(NO)[SzCN(CH&]2. The Co atom lies above the plane of the four sulfur atoms, and the N-0 bond is reported to make an angle of about 140' with the approximate fourfold axis of the FeS4 configuration, with its mid-point approximately on this axis. This investigation was based on two-dimensional data only. The three preceding compounds all involve rather unusual coordination about the metal atoms. Two (1) Research performed under the auspices of the U. S. Atomic Energy Commission. (2) Participant in Brookhaven National Laboratory summer student program, 1962. (3) H. B. Gray and C. J. Ballhausen, J . Chem. Phys., 36, 1151 (1962). (4) C. J. Ballhausen and H. B. Gray, Inovg. Chem., 2, 426 (1963). (6) H. B. Gray, I. Bernal, and E. Billig, J . A m . Chem. Soc., 84, 3404 (1962). (6) J. Lewis, Sci. Pvogu., 47, 506 (1959). (7) G. Johansson and W. N. Lipscomb, Acta Cvyst., 11, 594 (1958). (8) J. T . Thomas, J. H. Robertson, and E. G. Cox, ibid., 11, 599 (1958). (4) 1'. R. H. Alderman and P. G. Owston, Nature, 178, 1071 (1956). (10) P. It. H. Alderman, P. G. Owston, and J. M. Rowe, J . Chem. Soc., 668 (1962).
w.;
octahedral complexes of ruthenium have been the subjects of two-dimensional X-ray diffraction investigations.l1,l2 Values of 150 and 153' are found for the RuN-0 angles in [ R u ( N H ~ ) ~ ( N O ) ( O H ) and ] C ~ ~[Ru("&(NO) (OH) ICL. In view of the fact that these determinations are either of nontypical structures or are of limited accuracy, we decided to undertake a three-dimensional X-ray diffraction study of the geometrically simple and extensively studied sodium nitroprusside, Na*Fe(CN)5N 0 . 2 H z 0 . A preliminary report's of the structure of the isostructural Na2Co(CN),N0.2H20 indicated a distorted octahedral arrangement about the Co atom but gave no further information regarding the linearity of Co-N-0. No further work on this structure has been published. Preliminary results of a neutron diffraction investigation of another octahedral ruthenium salt, Naz [Ru(NO2)4(NO)(OH)]e2H20, indicate a linear Ru-N-0 bond and a Ru-N bond length of about 1.67 A.14 Crystallographic Data Sodium nitroprusside is orthorhombic, space group Dzh12-Pnnm. The cell constants were determined to b e a = 6.17 % 0.03, b = 11.84 f 0.06, a n d c = 15.43 0.08 A., in satisfactory agreement with those reported by Cooke15: 6.22, 11.8, and 15.52 A. The X-ray density calculated for four formula weights per unit cell is 1.76 g. cm.+, in good agreement with the macroscopically observed value of 1.72 g. ~ r n . - ~ .
*
Experimental Equi-inclination Weissenberg photographs of seven reciprocal lattice nets perpendicular to u were obtained from a needle-like crystal with approximate dimensions 0.5 X 0.25 X 0.25 mm.3 The observed absences, (Okl) for k I odd and (h01) for h I odd, indicated t h a t the probable space groups are the centro-
+
+
(11) G. B. Bokii and N. A. Parpiev, Sooiet Phys.-Cryst., 2, 681 (1957). (12) N. A. Parpiev and M. A. Porai-Koshits, ibid., 4, 26 (1959). (13) Y. Okaya, R. Pepinsky, Y . Takeuchi, H. Kuroya, A. Shimada, P. Gallitelli, N. Stemple, and A. Beevers, Acta Cryst., 10, 798 (1957). (14) S. H. Simonsen and M. H. Mueller, paper to be presented a t meeting of International Union of Crystallography, Rome, September, 1963. (15) P. W. Cooke, Netum, 167, 518 (1946).
1044
c. HAMILTON
P.T. hxANOHARAN AND WALTER
Inorganic Chemistry
TABLE 10 OBSERVED ASD CALCULATED STRUCTURE FACTORS IN E L E C T R O N S / ~ N CELL I T FOR SODIUM NITROPRUSSIDE
..... ..... ..... ..... = 0
//
K
L
FZ
c
4
62 51 104 50 71
c
t
1 C C
IC
8
Li c I& c it C IF
b3 49
F0
FC
X
L
FP
98 L
27 70 23 20 19
30
5 9
0 2
54
59
31
3
c
21
?
7
33 Ih
4
9
5
13
$
t
46
5
7
33
26 -12 4H -32
19 I7 I9
29 20
9
9 P 9 IC 9 17
41
41
5 5 5 5 t t t
54 21 35
5t 28 3'
68
213 I t4 99 I 14 I 52
?I it
7
17
9
It 30 22 57 bo 0 72 52 50 12
I 13 i
4
?
6
2 i
ir
P
? I? 14 16 IP
2 2 2 2 2
20 72 2 24
38
29 33 21 35
18
20 2R 24 2v
33 15 -9 33 -82
-79
-L s
1'
41
i
R
9 28
4
*
IC 12
27
I2
21 79 52 3t
8
s
I i 10 11 I ? I1 14
5 1
11 I 6 12 1 I2 3
76 7G 46
26
12
5
Ib
-17
2s
-30 -23
I2
12 1 12 9 I2 11 12 I 3 I? 0 13 2 13 5 13 h
11
13
16
40
36
13
23 I9 22
-18 14
7
-19
8
-15
9 IC
-73 11 45 8 29 23
$
12 14 18 3 4
5
IC
4
14
19
-12
4
It
47 78
40
6 7 8 9
II 24 -19
17
-tL 76 -115 40 -47 17 -19 54 -71 21 -29 4h
s
25 11
27 LR
7 9
25
1 3 1'. I4 I 14 ? 14 5 14 7 14 9 14 11 I4 I 3 :4 15
?4
?4 2v
32 25
23 27 25
20
1P 5 3
If9
62
-88
I
24
'> 5 5 7 5 9 5 11
IC
31
-30
16
3
72
19
18
11
24
I2 I3
7
21
38
-44
lt It It
5
33 12 4c It 32
45 12
-44
35 15
19
I7 I8
4
Et
I?
18
5 15 5 17
I1
'i
5 19 b
o
6 e 6
7 4 6
t 14
"
38 15
28 17 74 69
?I
25 56 96 s
24
LO
3
15 It
36
-3t -22 -37
19 21 23 25
-34
-23 -I3 i -31
0
13 17
-17
1
57
-77
1
3
?8
1
5
7
7
51 t5 51
-2t -56 -55
e
12
-11
10
30
-28
11
41 14 25 16 64
-41 -34
I2 I3
-24 -'I 7 6t S
14
33
-33 I3 -10
10
I*
7 9 1 11 1 11 7 I5 7 17 7 ir 1 2 1 C
C
8
2
d
3'
r
t
18
12
-8
-83
e e
"
4V
IC
72
52 -19
9 $
1 3
46
45
55
1 9 9
5 7 9
51 ?4 ?5
th 5c 32 32
Li
52
53
9 13 9 15 V 17 9 19
42
4 21 IC 0 IC 4 IC n i c LO
21
46
*C 24 2c 24 25 56
I3
IO
42
43 -6 18
Y
1L
11 I1 I1
It 1 ?
24 20 27
17 22 52 47
s
4
I
5 c 7
22 37 28 22
i
E
3v 0 49
39 t i 45
32
28
72
20 I? 24 51 -25 -19
I4
-14
-27
38 11
-41 -11
I1 5c 8
-I? -55 1
LO
-l?
8
-11
17 I8 10 1
I7 26
-?I -6 -15
9
34
74
LI9
4c 1c 27 28 29
69
9V I
10 49
28
49
49 41 33
-56 I -25 -24
6
1
e 6 6
4 6 5
24 54 21 15
12 1 4 LJ
1
13
3 5
I3 I3
7
13
q
1 3 11 I 3 13 1 3 I5
i ;
-18
6
9
34
-26 -15 -24 -27
t 15 t 11 I C 1 2 1 3 7 4 7 6 1 1 1 8 7 IC
70
28 24 31
22 78
-23 40
21 30 21 2n 25
7 I2 14
72
4
!b
31
8
9
t
20
16
P
IP
2
I,, I4
36
39 28 20 63 42 23 44
20 45
32 -20 63 -18 -11
-3t -28 -I7 -25 -38 -28
. .
27 18
4
0
77
4 4
7 3
I6
4
4
4 4 4
5 t 7
36 13 29 2R.
4 8 4 LO 4 11
9 LO 30
I7
73
31 -54 31 -15 -IC -21 -7 -23
-t -28 -53 -I7 2c -1 9
14
5 9 5 11 5 11
31 36
74 1 11 55
LO
-15
4
8
-24
4
9
-23 -12 -77 I -22 -LE S -4c -59
4
IC
17 11 14
4 4
11
50
I?
17
4
I3 4 14
35
I 15
31 29
76
53 19 50 I8
52 25 40
12 31 19 23 23 13 16
20 19 26 20 39
8
'i
I3
Y
15
23 24 25 I7 3R
36
I7 34
12 I C l i 14 I! 1
24 20 21 16 27 I6
h
-29 -18 -2t lt
1
2
e
3
c
5
6
6
c
7
24
6
9
41
c I I h I? t I5
23 22 I9
36 ?L
22 74 -1t -38 -I7 -31 -26
e
I7
18
I 7 7 1 7 l 7 7
C 1 2 3 4 t 1 P
59
I
-21 -35 -23 -21
9 38
15 iP 21
17 4h 41
IC
21
58 26 30 18 24
7 c
Lb 43
-14 41
26 61
7 F
7 P
14 37
i
l
15 39
-18
11
-10
5 1c 5 14
20 21
-75
F 16
18
-20 30
; , = I . FR
1
52
C
67
c
5 1
L
9
43
C 11
46
37
18
14
21 33
41 I d
45 48
2
4
2 2 2
5 t
72 28 11 38 28
7
54
e
10 5b 20 24
9
2 I? 2 15 2 17
2 19 2 21 3 3 3
C 2
16
29 36 45 22
....
FC 112 128 1 39 49 45
34
7'. 24 12
r le IC ? LC 1 IC 3 IC 5 11: 1 I IC I 3 11 0 11 ?
I1 .I
4 t
I8 -37 11
I' 13 13
4
-46
14
-28 -6 , .-12
I 3
I' % .~
-6C
15
I8 -23 12 -28 -33 -38 -21
I
14 I4
It it It 1
4
C
t
C C
IC
-19
0
24 -51
c
c
H 12 I4
I6
LP
-35 -42. -25 -35 -23 -21 21 -54
c 2
-16
3 1 J
3 4 7
-I2
?
P
-11 -41
11
2Y
33 ?3
31 36 18
36 I7 27
38
32 34 17
2X -33 -15
29 42 29
-35 -41
I?
7 7
t e
32
-33
34
-33
7
IC
?2
7 12 1 I4
38
-20 -35 -?7
61
-12 4c -17 -13
I3
29
21 47 3c
1
11
LI
E 8
?S 26
C
-5
-28
-18
3 11 F C 9 1 9 2
20 2?
1c
10
25
4 5
e
-25 -2r
21 35
I P
-1t 34
72
15
10
4 6
32 63
27 38
I3 Ib
7 P
14
8 5 IC ,I 0
12 14 27
29
t t
-12 -I3 -IC
-23
13 -16 -I3
11 11 11 12
4
41
-43
t
24
8 1
28
13 13
2 5
-24 -2b -27 75
12 t I4 7 c I
,
1 7 7 7
1 5 7 9
7 11 7 I3
15
I9 I8 17 23
20
-18
47 23 I3
-20 -49 -2) -I2
I(
L
FZ
FC
4
%A
-2t
c C
6
C
8
24 15 21
3t 12
7
23
19
2 6
11 18
-15
14
10
15
5
"
I
37
IC
c
e
31
24
25 25 76
25
?I
LI LI
c I
17 31
I1
3
41
4J 44 33
23 71
22
23 23 28 29
19
26
24 21
23
28
I7
23
I1 24 21 2t
