CRYSTAL STRVCTURES OF BISMUTHHALIDE COMPLEX SALTS
3531
The Crystal Structures of Bismuth Halide Complex Salts. I.
2-Picolinium
Tetrabromobismuthate(II1) and Tetraiodobismuthate(III)1
by B. Ken Robertson,2 W. Gant McPherson, and Edward A. Meyers Department of Chemistry, Texas A & M University, College Station, Texas
(Received April 25, 1967)
2-Picolinium tetrabromobismuthate(II1) and tetraiodobismuthate(II1) are isomorphous. The anions in both structures show distorted octahedral packing of halogen atoms around bismuth, with two pairs of halogen bridges linking neighboring bismuth atoms. The two unshared bromine atoms are located a t 2.63 f 0.02 and 2.65 f 0.02 A from Bi, and the Br-Bi-Br angle is 93.2 f 0.6". The corresponding values for the iodine structure are 2.87 f 0.02 and 2.90 f 0.02 A, and the I-Bi-I angle is 93.7 f 0.5". There is little evidence for the influence of the Bi "lone pair'' upon the coordination around Bi in either structure. The various bond angles and distances in the halogen bridges are irregular, but the total Pauling bond order for the bismuth-halogen bonds is close to 3 for both structures.
Introduction
morphous, and that they were monoclinic with systematic absences for (h01) with 1 odd and for (OkO) with Many amine salts of group V halogen complexes k odd, characteristic of P21/c-Czb.5 For convenience, have been prepared by Whealy and his c o - w o r k e r ~ . ~ ~ ~ the reflections were indexed on the basis of B-centered Since relatively little X-ray structural work has been P close to 90". The equivalent posicells which made done on bismuth compounds, the ready availability tions in these cells of the (nonconventional) space of a number of amine salts of bismuth-halogen com*((z,Y,z); f(x,'/2 Y,'/~ 2); group B2dc are: plexes made a study of some of these materials seem * ( ' / z x,'/z y,z). The cell +('/2 x,Y,'/z 2 ) ; attractive. Moreover, the structural work done on a number of salts of antimony(II1) halogen complexes6-* dimensions and densities are as follows. BiBr4: a = 24.66 f 0.04; b = 13.40 f 0.03, c = 7.63 f 0.02 A; had indicated that interesting structural effects were P = 90.0 f 0.5"; dobsd (flotation) = 3.25 f 0.08 g/cc; apparent, presumably due to the presence of the "lone dcalcd = 3.28 g/cc for 2 = 8. For Bi14: a = 26.14 f: pair" of electrons on the antimony atom. The 20.04; b = 14.06 f 0.03; c = 8.03 f 0.02 A; = picolinium salts of BiBr4'-(III) and Bi141-(III) were selected for study because good single crystals were easily produced and because the presence of a bulky (1) This paper was presented at the Joint Southeast-Southwest organic cation was expected to make the resolution of Regional Meeting of the American Chemical Society, Memphis, the heavy atoms relatively easy and the absorption Tenn., Dec 2, 1965. effects relatively small. (2) Submitted to the Graduate College of Texas A & M University
+
Experimental Section The preparations of 2-picolinium BiBr4(III) and BiL(II1) have been described p r e v i o ~ s l y . ~Needle~~ shaped single crystals of the salts were grown from water-acetone or water-isopropyl alcohol mixtures that contained the appropriate halogen acid. Examination of the crystals with filtered 310 X radiation revealed that the crystals of the two compounds were iso-
+
+
+
in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Aug 1965. (3) J. F. Osborn, Master's Thesis, Texas A & M University, 1960. (4) J. C. Scott, Master's Thesis, Texas A & M University, 1960. (5) A. Bystrom and K. A. Wilhelmi, Arkiv Kemi, 3, 461 (1951). (6) A. Bystrom, 5. Backlund, and K. A. Wilhelmi, ibid., 4, 175 (1952). (7) A. Brystrom, S. BacMund, and K. A. Wilhelmi, ibid., 6, 77 (1953). (8) M. Edstrand, M . Inge, and N. Ingri, Acta Chem. Seand., 9, 122 (1955).
Volume 71, Number 11
October 1967
B. K. ROBERTSON, W. G. MCPHERSON, AND E. A. MEYERS
3532
0.5’; dobsd (pycnometer) = 3.63 f 0.05 g/cc; 3.60 g/cc for Z = 8. For each compound, a slender needle-shaped crystal enclosed in a thin-walled glass capillary was mounted on the Buerger precession camera and timed exposures were made of a number of zones with the use of Zr filtered 110 X radiation, (A = 0.7107 A). For BiL, Weissenberg data for the (hkO) zone were also collected by means of Ni-filtered Cu radiation (A = 1.5418 A) and a multiple film pack. The intensities were read with a Welch Densichron, >lode1 I. Lorentz and polarization corrections were applied to the intensity and approximate corrections were made for absorption by the nearly cylindrical crystals. For BiBr,, ( ~ L R ) M =~ 4.0; for Bi14, ( ~ R ) = x ~1.2 and (pR)cU = 5.4. Approximately 2SO reflections were available for each structure. These data were obtained from the (h01), ( O M ) , (h&l),(hkh) and (hkh) zones for B i B s and from the (hOZ), (OM) and (hh-0)zones for BiI,. Patterson syntheses were calculatedg for the [OlO] and [loo] projections and their interpretation was straightforward. The trial coordinates for the bismuth and halogen atoms were refined by least-squares techniques, lo and appropriate Fourier and difference Fourier syntheses9 were examined. With the use of individual at om isotropic temperature factors and the inclusion of only bismuth and halogen atom parameters, Rz = ( Z ( j F o l - / F , ~ ) 2 / 2 ~ F o ~ 2=) ”0.155 2 for the BiBr4 structure, and Rz = 0.138 for the BiII structure The atomic scattering factors used were taken from the International Tables for X-Ray Diffraction, Volume 111, Mynoch Press, 1962, pp 206-207 for Br, p 211 for I, and p 212 for Bi. The placement of the 2-picolinium group was accomplished primarily by packing considerations in the BiBr, structure. The results were supported by the appearance of several difference Fourier syntheses and by improvement in RP when light atom contributions were included in F,. The coordinates for the light atoms were transferred from the BiBr, to the BiL structure, and a number of attempts mere made to refine the positions of the light atoms in both structures by means of least-squares techniques. In the attempted refinements. large oscillations in the light atom parameters occurred, and it was at first decided to use the coordinates obtained from packing considerations and to abandon the effort to refine them further. The final values of R2, with the light atoms included, were 0.112 and 0.126 for BiBr, and BiL, respectively. I n the final refinements of the heavy atoms, the lightatom scattering factors mere all taken to be that of carbon, and their temperature factors were all assigned a value of B = 7 . 5 A2.
90.4
f
dealed =
The Journal of Physical Chemistry
At the suggestion of a referee, a number of other analyses were performed upon the data. (1) The least-squares programlo was modified to permit the introduction of a convergence factor’l in order to damp the oscillations in the refinement of the light-atom coordinates. A weighting scheme was also adopted, in which w = 1, lFo1(600; w = 0.25, 600 (IF01(900; w = 0, IFol) 900 for the BiI, structure, and in which w = 1, IFo1(450; w = 0.25, 450 (/Fol(G50; w = 0, IF01)650 for the BiBa structure. After more than 24 cycles of refinement, for each structure, all parameter shifts were less then 10% of their estimated standard errors. There were no significant changes in any of the bond distances or angles that involved the Bi and halogen atoms, when compared to the values obtained with unit weights, and with the light atoms fixed by packing considerations. (2) The least-squares programlo was also modified to permit the calculation of structure factors in which the effect of anomalous dispersion was included (both real and imaginary parts). Again with unit weights and light atoms fixed by packing, no significant changes were found. I n addition to the above, calculations were made (a) in which the light atoms were fixed by packing and (b) in which the light atoms were excluded completely from the calculations. I n order to make a fair comparison, the weighting scheme described above in (1) was used. The only result was, again, to alter slightly the uncertainties in the bond distances and angles among the heavy atoms, but to leave their calculated values essentially unchanged. The net result of the various calculations is probably the generation of more confidence in the values given in Tables I and I1 for the heavy atom parameters and related properties which are the topics of interest in this study. The values given in Tables I and I1 are based upon unit weights, no correction for anomalous dispersion, and with the light-atom coordinates fixed by packing. The uncertainties in bond angles and distances that involve light atoms refined by procedure 1 above are so large as to make their values unreliable (estimated error in bond distances approximately 0.4 -4,estimated error in bond angles approximately 25’).
(9) W. G. Sly, D. P. Shoemaker, and J. H. Van den Hende, “Two and Three-Dimensional Crystallographic Fourier Sunlmation Program for the IBM 7090 Computer,” CBRL-22M-62, Massachusetts Institute of Technology, Esso Research and Engineering Co., 1962. (10) W. R. Busing, K. 0. Martin, and H . A . Levy, “OR FLS, A Fortran Crystallographic Least-Squares Program,” ORNL-Thf-305, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1962. (11) J. 9. Rollett, Ed., “Computing Xethods in Crystallography,” Pergamon Press, London, 1962, p 80.
CRYSTAL STRIJCTURES OF BISMUTH HALIDE COMPLEX SALTS
3533
Table I : Atomic Coordinates from Least-Squares Refinement (Uncertainties Are in Parentheses and Apply to the Last Digits of a Number.) z//b
z/a
B . .12
z/c
0.1194 (2) 0.0637 (8) 0.0457 (9) 0.1851 (12) 0.1885 (12) 0.442 0.390 0.351 0.306 0,299 0.335 0.381
2-Picolinium Tetrabromobismuthate(II1) 0.1658 (4) 0.4630 ( 6 ) 0.0078 (13) 0.3664(14) 0.3029 (11) 0.2425 (16) 0,3527 (10) 0.6388 (16) 0,0592 (10) 0.6529 (16) 0.134 0.405 0.338 0.055 0.422 -0.023 -0.103 0.383 0.281 - 0.105 0.220 -0.025 0.254 0 . 0.53
0.1209 (2) 0.0618 (4) 0.0163 (4) 0.1859 (4) 0.1938 (4) 0.436 0.387 0.331 0.308 0.301 0.335 0.379
2-Picolinium Tetraiodobismuthate(II1) 0.1613 ( 5 ) 0.0007 (10) 0.3127 (9) 0.3487 (8) 0.0452 (10) 0,397 0.333 0.414 0.377 0,280 0.221 0.2.54
0.4490 (8) 0.3431 (15) 0.2310(16) 0.6248 (19) 0.6276 ( 2 2 ) 0 122 0.0.51 -0.02.; -0.101 -0.101 -0,023 0,051
3.06 (11) 4.36 (31) 4.10 (31) 4.01 (34) 4.10 (34) 7.5
-.(
e?
“ I .a
7 .3 7 .3 7,5 7.5 2.19(10) 3 , 3 6 (21) 3.39 (21) 2 . 7 5 (21) 3.82 (27) m
-
i . ;)
7.5
” I ..I
7.5 7..i 7.5 7.5
m,
Discussion I n both the BiBr4and the Bi14structures it was found that each Bi atom was surrounded by an irregular octahedron of halogen neighbors and that four halogen bridges connected adjacent Bi atoms. The configuration of the octahedral unit in BiBr4 is shown in Figure 1, and the relevant bond angles and distances12 are listed in Table I1 for BiBr4 and Bi14. An electron diffraction study of BiBrs(g)13has given __ 0.02 A, Br-Bi-Br = 100 4”. This BiBr = 2.63 __ distance compares well with BiBr(1) = 2.63 It 0.02 A and BiBr(4) -- 2.65 A 0.02 A, but the angle is considerably differect, since Br(l)-Bi-Br(4) = 93.2 f 0.6”. The structure of BiI,(s) has been determined most recently by electron diff raction,14 and the results indicate that each Bi atom is surrounded by an octahedron of I atoms, with B T = 3.07 .4, = 4.33 A. Each Bi atom is linked to three other Bi atoms through three pairs of halogen bridges. The earlier X-ray diffraction ~ t u d i e s ~ give ~ , ’ ~similar coordination of I around Bi, and nearly the same interatomic distances. By means of Pauling’s equation for bond order”
*
*
~
m’
d, =
cll
- 0.6 log n
it is possible to estimate the value of cll for if it is assumed that the bond order n in Bi13(s) is The value of the single bond bismuth-iodine length is calculated to be 2.89 ,4,which is very close to the values of zI(1) = 2.87 f 0.02 A and KI(4) = 2.90 f 0.02 A. The longer bonds in both structures involve halogen atoms that are linked to __ two Bi atoms. In one rectangle in BiBr4,the bonds BiBr(3’) = 2.97 0.2 h and __ BiBr(2) = 3.08 h form the bridge to an adjacent Bi atom at 4.43 f 0.01 A. In the other rectangle, E&@’)= 2.83 f 0.02 A and m(3) = 3.27 i: 0.02 A. The longest bonds are directly opposite the shortest bonds in the structures. This-~ is similar to the situation in (SHJzSbCls,* where the SbCl bond opposite the
*
(12) W.R. Busing, K. 0. Xartin, and H. A. Levy, “OR F F E , A Fortran Crystallographic Function and Error Program,” ORNLTM-306, Oak Ridge National Laboratory, Onk Ridge, Tenn,, 1964. (13) H. A. Skinner and L E. Sutton, Tians. Fatarlay Soc., 36, 681 (1941). (14) Z. G. Pinsker, Try.Inst. Kristallogi. Akarl. .\-auk SSSR. 7, 35 (1952); Slruct. Rept., 17, 356 (1953). (15) H. Braekken, 2. Rrzst., 74, 67 (1930). (16) J. Backer in L. Vegnrd, Shifter S o i s k e T’idenskaps-Akad OSZO. I . Mat. Saturs. Kl., 2, 73 (1947). (17) L. Pauling, J . Am. Chem. Soc., 69, 542 (1947).
Volume 713 Siimber 11 October 1967
B. K. ROBERTSON, W. G . MCPHERSON, AND E. A. MEYERS
3534
Table I1 Bond distmen. A
Bond
B iX(1) __ BiX(2) BiX(3) BiX(4) __ BiX(2)‘ ___ BiX(3)’ __ BiBi’ ~
~
BiBn
Bil.
2.63 + 0.02 3.08 zt 0.02 3.27 *n.m 2.65 f 0.03 2.83 f 0.02 2.97*0.02 4.43 + 0.01
2.87 z t n . 0 1 3.31 f n . 0 2 3.45 f 0.01 2.90 * o m 3.11f0.02 3.09 0.02 4.73 ztO.01
Bond a n ~ l e ade.Anile
X(I)-Bi-X(2) X(l)-Bi-X(4) X(I)-Bi-X(2)‘ X (1)-Bi-X(3)‘ X(Z)-Bi-X(3) X(Z)-Bi-X(2)’ X(Z)-Bi-X(3)‘ X(3)-Bi-X(4) X(3)-Bi-X(2)‘ xi3j-Bi-xi3 jf X(4)-Bi-X(2)’ X(4)-Bi-X(3)’ Bi-X(Z)-Bi’
BiI3I.C
BiL-
91.1 f 0 . 6 93.2zt0.6 89.7f0.6 89.1 f O . 6 93.4 f 0 . 6 86.8 zt 0.6 85.2 f 0.6 82.5 f 0 . 5 X4.0 f 0 . 5 97.8 f 0 . 8 94.6zt0.6 93.5+n0.6 97.0*n0.7 90.4 zt 0.7
92.3 zt 0.4 93.7 0 . 5 89.4 0 . 4 90.4 0.4 90.1f0.4 R6.lf0.3 86.9 f 0.4 X4.1 f 0 . 4 84.1 3 ~ 0 . 4 96.4 0.4 95.1 f 0 . B 91.9 f 0 . 5 94.8f0.4 92.4 f 0 . 4
*
+
* *
Figure 1. Schematic reprcqentation of BiBrhshowing infinite chain 6tructiire. 0
“lone pair” of electrons - is 2.36 A compared to 2.62 A for the other four SbCl bonds and compared to the value found for SbCI, in SICll(g), of 2.325 f 0.005 A.“ However, even the longest distance in BiBr, corresponds to an appreciable bond, certainly greater than that observed on the “lone pair” side in SbF4,1.’ SbFs,’ or SbCls.B Indeed, the outstanding characteristic of the structures of BiBr, and BiI,, as well as BiL, appears to be the lack of influence that the “lone pair” of Bi appears to have in the determination of the coordination number around Bi. A very similar result has been found in the preliminary results that we have obtained for 2-picolinium SbL, crystals of which are isomorphous with the BiBr, and BiI, crystals examined in this study. The position of the 2-picolinium group was obtained by packing considerations and the placement of this group is shown in Figure 2, a projection along the e axis of BiBr4. The ring-to-ring contact distances are 3.3 A or greater. With the exception of C(3), all distances from ring atoms to heavy atoms in BiBr, are 3.55 A or greater. C(3), which should correspond to N , has been placed 3.27 A from the closest Br(3) and 3.53 A from the closest Br(4). The ring distances are 1.39 0.02 A, the C(l)-C(2) distance is 1.56 A, and the ring angles are 120 f 2’. The Jour&
OJ
Phyaical Chemistry
0.5
b-
10
Figure 2. Schematic projection of stnictiire nn (001) Picolinium ring placed by packing considerations.
Acknoiukdqments. The financial support of The Robert A. Welch Foundation is gratefully acknowledged. The facilities of the Data Processing Center (18) P. Kiiuik. J . Chm. Phya.. 22. 86 (1854).
3535
LIQUID-LIQUID PHASE SEPARATION IN ALKALI RfETAL-AMMONIA SOLUTIONS
of the Texas -4& -11 University System have been used extensively in the course of this research. Dr. Roger
D. Whealy has kindly supplied us with samples of the compounds studied.
Liquid-Liquid Phase Separation in Alkali Metal-Ammonia Solutions. 111. Sodium with Added Sodium Bromide and Azide
by Patricia White Doumaux' and Andrew Patterson, Jr. Sterling Chemistry Laboratory, Y a l e Unioersitv, New Haven, Connecticut Accepted and Transmitted by T h e Faraday Society
06620
(February 20, 1.967)
Experimental data are given for the effect on phase separation in sodium-liquid ammonia solutions of adding varying ?mounts of sodium salts. Xeasurements were made a t -32.90' with sodium azide and at -32.90 and -56.39' with added sodium bromide. The data are compared with previously reported measurements on sodium iodide. The additions all raise the consolute temperature, broaden the temperature-composition curve, and alter the distribution of components: at a given temperature as the total salt is increased, the salt migrates to the dilute phase and the sodium metal to the concentrated phase. The magnitude of these effects varies, approximately linearly, with the amount of salt added, but depends also on the salt used in the order KaI > N a y 3 > SaBr, the most effective listed first.
Introduction In a previous paper,* the effect of adding sodium iodide on liquid-liquid phase separation in sodiuniammonia solutions was examined. It was not found possible to explain the results in terms of a simple common ion effect. On extending these measurements to include salts with other anionic constituents as reported in this paper, one finds that although the concentration of the salt is a significant factor, it is principally the anion of the salt which influences the results. This finding is further supported by data on phase separation in the sodium-potassium-ammonia system which are reported separately.3
Experimental Section In preliminary measurements, sodium thiocyanate, sodium sulfide, sodium chloride, sodium cyanide, and sodium tetraphenylborate additions were tested. The
first two reacted with the metal-ammonia solution, and the remainder were too insoluble to bring about phase separation a t temperatures of -33" and below for which data on sodium iodide were available for comparison. Sodium bromide and azide suffered none of these failings; they were studied in detail by a procedure which was essentially that of Schettler and Patterson,2 with minor modifications. Samples were taken of the separated phases, the ammonia was quantitatively removed, and aqueous solutions of the residues were analyzed for base and salt by successive titrations (1) This paper contains material taken from a dissertation submitted by P. W. Doumaux to the Graduate School, Tale University, in partial fulfillment of the requirements of the degree of Doctor of Philosophy, Sept 1966. (2) P. D. Schettler and A. Patterson, J . P h y s . Chem., 6 8 , 2870 (1964).
(3) P. W. Doumaux and A. Patterson, ibid., 7 1 , 3540 (1967).
Volume 7 1 , S u m b e r 11 October 1967
