CRYSTAL STRUCTURE OF SODIUM TETRACHLOROFERRATE(III)
aluminum ion is often more evident than that of the oxide ion ( e . g . , in adsorption of butene). Adsorption on an aluminum ion should cause partial electron withdrawal froin an adsorbed molecule. Proton transfer iiiey then occur froiii the adsorbed molecule to an adjoining oxide ion, provided that the resulting anion and hydroxyl ion can be suitably held by the surface. Present results suggest that butene isomerization may occur through transient formation of a carbanion. Attempts to relate total ammonia retention on alu-
239
mina to catalytic activity appear destined toveryliiiiited success. Ammonia adsorption on chlorided alumina provides, at best, ambiguous evidence on acidity because S H z - can readily replace chloride ions.
Acknowledgments. The cooperation of Dr. R. B. Hannan, who performed the experiments involving deconiposition of ammonia over alumina, and of A h . J. Kekich, who assisted in most of the experimental work, is gratefully acknowledged.
The Crystal Structure of Sodium Tetrachloroferrate( 111)
by R. Ronald Richards and N. W. Gregory Department of Chemistry, Unirersity of Washington, Seattle, Washington
(Eeceived July 30g1964)
The crystal structure of NaFeC14 is found to be orthorhombic, P2'2'2', with unit cell dimensions a0 = 10.304, bo = 9.880, co = 6.235 d. The crystal contains slightly distorted tetrahedral FeCIBgroups; sodium atoms are surrounded by six chlorine atoms a t distances between 2.78 and 3.09 A. Bond distances, angles, and packing characteristics are discussed.
I n conjunction with a thermodynamic study' we have determined the crystal structure of sodium tetrachloroferra t e (II I). Crystallographic data for compounds of the type 31FeC14have not been found in the literature. However Friedman and Taube,2 and on the basis of visible and ultraviolet spectra and melting point data, suggest that the iron in such substances is in the form of an FeC14- ion. Friedman also concluded, from magnetic susceptibility nieasurenients, that the FeC14- ion is tetrahedral and noted that the visible spectra of FeCI4- in ether and of KFeCI4 solid are siiiiilar. A tetrahedral arrangeiiient in solution is also indicated by Ranian ~ p e c t r a . ~ Magnetic susceptibility iiieasurenierits arid optical and Alossbauer spectra indicate that the iron in ( p ~ H ) ~ F e ~ C(py 1 9 = pyridine) is present in the form of tetrahedral FeCll- i011s.~ The crystal structure of XaAlCl,, which appears to be isomorphous with XaFeCI?, has been reported by Baenziger.
Experimental NaFeC14was formed by subliming FeC13,prepared by reaction of Mallinckrodt A.R. iron wire (99.95%) with commercial tank chlorine at 425' in a vacuum system, onto an equimolar amount of B and A reagent grade NaCl, which had been dried under high vacuum a t 500'. The mixture was melted (1ii.p. 163')' in an ampoule, sealed off from the vacuum line, and cooled slowly. Large crystals (1-2-mm. cubes or plates) were observed to grow a t the surface of the melt as the mass (1) R. R. Richards and N. W. Gregory, J . Phys. Chem., 6 8 , 3089 (1964). (2) H. L. Friedman and H. Taube, J . Am. Chem. Soc., 72, 2236 (1950).
(3) (4) (5) (6) (7)
H. L. Friedman, ibid.,74, 5 (1952). J. A. Woodward and ,M.J. Taylor, J . Chem. SOC.,4473 (1960). A. P. Ginsberg and M.B. Robin, Inorg. Chem., 2 , 817 (1963). N. C . Baensiger, Acta Cryst., 4, 216 (1951). C. M .Cook and W. E. Dunn. J . Phys. Chem., 6 5 , 1505 (1961).
volume 69, Number 1 J a n u a r y 1966
R. RONALD RICHARDS -4KD
240
s.\v. GREGORY
Table I : Structure Factors and Phase Angles for Sodium Tetrachloroferrate(II1)
10lF"l
101F,l
Phase angle, mcyoles
10IFoI
H 0, 0 2 4 6 10 12
1063 636 656 483 214
2 3 5
315 963 1000 475 394 245
936 616 635 468 211
I
9 11
500 750 750 750 750 750
H . 2, 0 0 2 3 4 5 6 8 9 10
1073 1185 78 1057 305 283 343 150 264
1 2 3 4 5 6 7 11
H , 3, 0 678 688 375 373 404 381 269 281 14,54 1422 299 284 449 458 245 248
0 1 2 4 a
6 8 10
1000 1119 74 1045 306 242 367 209 236
H , L> 0 1443 1479 533 538 803 784 305 316 140 147 244 270 171 1.50 200 2-51
4 1 * I
I' 10
240 184 522 337
244 184 5f34 J29
43,5
474
36.5 331 163
3% .3.54
16j
250 000 750 500 750 500
-. IO0
3 4 5 6 7 8 9 11
-_ so I
600 750 300 1 .I0 750 750 500
-_
Thc Joicrnal of Ph~lisicaiChemistry
1332 323 459 213 313 188 266
381 180 446 296 225 163 171 178
384 188 472 261 184 122 165 154
Phase angle, mcycles
4
8
262 381 438 212
280 388 397 157
750 500 750 500 750 500 750 750 750 000 000 500
H,9, 0 4 5 6 7
137 289 388 203 221
0 1 2
429 234 144
2 3
148 174
152 278 417 198 224
250 500 750 500 750
H , 10, 0 388 250 178
000 750 000
H , 11, 0 102 180
0 1 2 3 4 5 6 8
321 719 925 398 247 132 181 325
1 2
529 517 205 630 235 640 162
346 707 892 370 262 111 158 329
3 4 5 6 7
540 495 203 597 208 629 178
989 ,508 698 979 600 999 030
500 750
H , 4, 1 1 2 3 4 5 7 8 9
211 263 327 153 279 228
222 268 346 183 268 198
a
-
6 I
8 10
446 1011 558 143 364 329 267 198
408 923 538 125 348 327 256 190
456 502 307 205 268 165 184 187
311 802 229 062 172 528 717 735
H , 5, 1 0 1 2 3 4 5 7 8
213 264 498 606 315 187 293 222
231 282 495 628 332 218 261 203
0 1 2 6
HI 6, 1 454 478 501 543 209 177 250 242
4 6
221 284
250 468 982 978 910 84 1 528 050
2 3 4 6 9
504 824 413 201 338
469 761 371 190 343
500 500 500 000 500
2 3 5 6 7 9 10
570 294 225 381 327 162 252
H , 1, 2 5S8 278 226 382 336 153 244
886 100 294 669 296 113 193
0 1 2 4 5 6 7 11
106 614 383 253 953 176 251 190
117 629 372 271 886 156 247 158
500 022 544 518 506 186 488 544
0 1 2 3 4 5 7 8 9
280 523 480 487 496 123 143 194 239
H , 3, 2 302 537 477 474 476 108 153 218 209
750 253 738 297 750 607 212 189 228
0 1 2 3 4 5 7
278 114 292 281 272 461 158
0 1 2 5 6 7 10
845 280 210 204 321 274 227
H,2, 2
H,4, 2 250 250 750 250 750 7 50
H,1, 1 2 3 4
420 491 284 214 284 178 200 184
10lF,I
Phase angle, mcycles
H,0, 2 000 276 752 307 295 172 144 737
H , 3, 1
H , 0, 1 2 5 6 7 9 11
10lF"l
H , 2, 1 000 750 000 750 000 250 500
H , 8, 0 1 2
750
000 750 000 000 250 000 500 5 00
1332 308 418 177 345 184 276
H , 7, 0
1
H , 5, 0 1 2 3
000 000 750 000 750 000 500 250 500
0 1 2 5 6 9 10
101F,l
10IFO
H,6, 0 000 500 000 500 500
H 1,0 320 923 971 500 411 236
101Fc1
Phase angle, mcycles
944 038 04 1 924 075 608 912 933
000 253 161 816
H, 7, 1 243 275
984 080
H , 8, 1 1 2 3 4 5
214 280 258 176 182
238 337 243 158 168
399 799 318 901 078
301 114 316 275 291 468 184
500 082 507 405 299 490 562
H,5, 2 884 271 196 218 317 255 210
750 506 807 223 806 296 266
CRYSTAL STRUCTURE OF SODIUM TETRACHLOROFERRATE(III)
24 1
Table I (Continued) Phase angle, 1 0 ~ F O ' 1 0 I F c ~ mcycles
1 2
3 4 9
194 193 350 281 210
H , 6, 2 193 224 355 285 189
490 505 407 462 505
1
2 3
358 204 275 137
389 220 290 157
750 391 872 193
H,8, 2 173 233 161 362
155 254 147 367
500 098 272 519
H,9, 2 2 4
165 172
150 181
829 770
H,10, 2 3
179
166
335
H,11, 2 0 1
235 186
237 154
8
11430 234 335 377 427 314
1327 217 355 366 423 314
0 1 2 3 4 5 6 7 8 10
750 505
2 3
423 352
390 341
487 028
142 365 900 490 140 148 201 161 501 203
498 074 531 499
713 677 698 766 947 814 670
128 373 919 482 136 147 132 134 505 179
750 095 519 046 515 942 451 367 502 507
H,4, 3 483 163 523 326 240 256 206
750 750 750 750 250 750
H,1, 3
356 144 515 387
101FOI
6 7 8
496 182 559 319 239 265 220
805 647 767 627 575 720 831
423 159 314
426 174 341
402 208 216
493 221 465
1 2 3 4 5 6 7
197 280 622 200 135 206 211
208 284 636 208 177 203 219
618 609 714 623 761 846 293
H,7, 3 194 168 198 271 152 212 232
205 201 226 286 162 225 235
750 120 557 097 487 533 506
H,8, 3 1 2
355 148
350 167
741 551
H,9, 3 1 2
212 249
214 296
123 557
H,0, 4 353 315 189 222
347 356 153 186
000 000 500 000
H,1, 4
H,5, 3 1 2 4
419 202 282
Phase angle, 10/FcI mcycles
H,6, 3
H,3, 3
H,0, 3 3 4 5 6 7
10lF,(
360 172 523 408
HI 2, 3 867 870 365 346 446 455 374 364 113 97 242 264 227 186
H,7, 2 0
10IF01
Phase angle, mcycles
018 616 571
solidified. A crystal suitable for X-ray analysis was obtained by crushing the solid (in a drybox) and selecting fragments. Fragments were placed in separate Lindeman glass capillary tubes (0.4 mm. o.d., wall thickness 0.015 inni.) and, after evacuation and subsequent addition of ca. 0.7 atni. of argon, anchored in a small piece of hpiezon W wax (by melting and then cooling the wax). In spite of all the precautions, evidence of slight surface reaction, presumably with traces of moisture, could be seen on the hygroscopic crystal. There was no indication that this had any observable effect on the X-ray data. The external form of the crystal, ea. 0.6 mm. long
210 158 327 277
235 174 320 269
187 633 305 648
101F0;
6 7
174 177
0 1 2 3 7
309 241 251 188 174
0 1 2 3 7 9
274 332 169 277 192 200
10IFc1
166 189
Phase angle, mcycles
714 809
H,2, 4 357 268 247 198 167
000 02 1 905 872 067
H,3, 4
,.,_ .
277 319 181 277 173 171
250 721 333 824 707 736
,
H,4, 4 0 1 2 3
165 291 235 197
0 2 3 4 5 7
272 152 164 277 234 193
2 3 4
196 168 185
0 2
195 199
190 285 212 189
H,6
000 923 967 056
4
263 166 172 279 235 143
750 334 956 252 778 644
H,6, 4 186 168 196
956 718 004
H,8, 4 201 202
000 802
and 0.09 by 0.15 mni. wide, approximated that of a parallelepiped split diagonally along two mutually perpendicular faces and resembled the end of a blunt knife. The capillary was oriented so the crystal could be rotated along its e-axis. Unit cell dimensions (ao = 10.301, bo = 9.880, eo = 6.235 ( = t O . O l -1.)) were determined from rotation and Weissenberg photographs on which were superiniposed rotation patterns of SaCl (a0 = 5.640 A,). Copper K a radiation (1.54178 8.) was used for determination of cell dimensions. T o mininiize film shrinkage errors, the distances between sodium chloride lines were used to calibrate the camera Volume 69, Number 1
January 1965
R. RONALD RICHARDS A N D S.W. GREGORY
242
radius for the rotation photograph; points along the zero-layer line were used for the Weissenberg. The lattice was found to be orthorhombic, with hOO and OkO reflections extinct for odd values of h and k , respectively. 001 reflections were not observed for rotation about c, but the space group was assumed to be P212121, with four equivalent positions (5,y, z; z, -y, l ’ 2 2; 2 2, ‘ 1 2 - y, - 2 ; -z, ‘ 1 2 y, l I 2 - z ) hy analogy with the structure reported for SaAlC1, which has very similar cell dimensions.6 The density, experinlentally determined as 2.25 g. cm. --3 by weighing a calibrated tube filled with solidified melt, compared favorably with the value 2.31 g. calculated on the basis of four molecules in the unit cell. Using zirconium-filtered molybdenum radiation (Ka 0.7107 A.) , integrated photographic intensity data were collected for the first five levels (hkO to hk4) with a Sonius-integrating, equi-inclination Weissenberg camera. Multiple films (except for the fourth level) and timed exposures were used. A uniform 1-mil sheet of brass was inserted between the films. The relative irit erisities of the same reflections indicated a film-brass-film ratio of 3.59. The small variation of absorption due to different beam angles for the first, second, arid third levels, as compared with the zero levels, was ignored. Camera integration was in one direction c d y , and each spot was scanned in the perpendicular direction with a Moll-type densitometer which was used in conjunction with a Leeds and Sorthrup amplifier and recorder with logarithmic slide wire. The area under each curve was assumed proportional to the intensity. Forty of the weaker reflections of the zero, first, and third levels were estimated by eye; weak reflections on the second film were used as standards, and intensity values were assigned to these by dividing the first film-photometered intensity by the film ratio. In the find calculations 286 reflections were used. S o correction was applied for absorption. To obtain statistically better data and to average out absorption effects, the entire film for the zero and first levels and for both lower half-quadrants of the second through fourth levels were photometered. The SahlC1, atomic coordinates of Baeriziger were used for thi. initial trial structure.6 Calculations were performed on an I B l I 709 computer using the “Xray 63” program of the crystallographic group a t the Univei*sity of Washington. The level-to-level scaling was initially taken as proportional to the exposure time but was finally used as a parameter in the refinement program. Scattering factors and dispersion corrections were based on data taken from the
+
+
The Journal oj’ Physical Chemistry
+
“International Tables for X-Ray Crystallography.”s,q The structure was refined using a full matrix leastsquares program by Busing, Martin, and Levy,’O modified for the “X-ray 63” system by Professor J. 31. Stewart. The residual minimized was 2whk1(i F,i / F , j ) 2where whiclis the weight of a particular reflection. A Hughes weighting scheme was used” although the same atomic positions, but with slightly higher standard deviations, were obtained with unitary weight,ing factors. Twenty-nine parameters were varied : eighteen atomic positions, six isotropic temperature factors, and five scale factors. The final value of R = B ( / F , / - l F c ] ) , / 2 / F o lwas 0.058. A detailed list of calculated and observed structure factors may be found in Table I. Of ca. 160 unobserved reflections in the observable range, none of the F , values were significantly above the observed threshold value.
Results and Discussion The atomic and thermal parameters are listed in Table 11. The thermal parameters are not indicative of the actual thermal motion since temperature factors are not independent of the level-to-level scaling.
Table 11: Atomic and Thermal Parameters for NaFeC14(s) Atom
z/aa
y /bo
z/c
0
B
Fe
Position Std. dev. X 103
0.03816 0.4886 0.29 0 44
0.2127 0.62
Na
Position Std. dev. X lo3
0.1187 1.26
0.2138 1 27
0.6970 6.04 2.64 310
c11
Position Std. dev. X
0.03392 0.4924 0.61 0.88
0.5622 4.04 1.42 150
Position Std. dev. X 103
0.1804 0.67
0.3118 0.65
0.1131 3.79 1.49 170
C ~ I I I Position Std. dev. X l o 3
0 3413 0.56
0 01793 0.9238 3.84 0.74 1.15 140
C l l ~ Position Std. dev. X lo3
0.3718 0 67
0.3274 0.66
Clr~
lo3
2.87 90
0.8732 3 61 1.56 160
The crystal contains discrete, slightly distorted, tetrahedral FeCh groups, with the sodium atoms located in some of the empty spaces between tetrahedra. The atomic positions are not displaced greatly from those reported for NaA1CL6 A projection of the unit (8) “International Tables for X-Ray Crystallography,” Vol. 11, Kynoch Press, Birmingham, England, 1959, p. 236. (9) See ref. 8, Val. 111, 1962, p. 215. (10) W. R. Busing, K. 0. Martin. and H. A. Levy, O R N L T M - 3 0 5 . August 1962. (11) E. Q. Hughes, J . Am. Chem. Soc., 63, 1737 (1941).
CRYSTAL STRUCTURE OF SODIUM
TETRACHLOROFERRATE(III)
243
0.09
M
Figure 1. Projection of FeC1,- tetrahedra on (001).
Table 111: Interatomic Distances within the FeC14- Tetrahedron
(A.) and Angles
Distance,
Fe-C1I Fe-Clri Fe -Clr 1 I Fe-Cliv CllClII ClICllIl CllClIv C1I1C11l1 ClIl Clrv ClrrrClrv
A.
2.180 2.184 2.200 2.218 3.530 3.624 3.662 3.608 3.580 3,504
Figure 2. Bond distances and angles in KaFeC14 crystal.
Std. dev., A,
0.010 0.008 0,008 0.008 0.013 0.013 0.012 0.010 0,010 0.010
Other distances
Na-C1I Xa-ClI Na-ClII Xa-Cl~r Pl;a-C1111 Xa-ClIlI Sa-C1Iv Sa-ClIv
CllFeClII c11FeClr11 CIIFeClrv C1I I F ~ C I I I I ClllFeClIv C1I IrFeClIT
3.007 3.084 2.788 3.781 2.883 3.318 2.943 3.078
cell on (001) is shown in Figure 1. The four tetrahedra in the unit cell are arranged so that each has a face nearly parallel to the (001) plane. The elevation of this face and the elevation of the sodiuin atoms (represented as circles) are indicated on the figure. All of the tetrahedra along the a-axis ( b = 0) point below the plane of the paper and those at b = 0..5 point above the plane. Some interatoinic distances and angles are listed in Table 111. The standard deviations represent the coiiibined uncertainty of the atomic positions and cell dimensions. The average Iie-Cl distance is 2.196 '1. This value is considerably shorter than the Fe-C1 distance (2.48 A.) in ferric chloride.I2 However, in the latter case, the iron atoin is octahedrally coordinated to six chlorine atoms. Only one sodium-chlorine distance (2.788 is shorter than the sodium-chlorine distance in sodium chloride (2.82 Each sodium atom has six chlorine neighbors 2.788-3.084 -1. distant atid one slightly farther away at 3.318 The distances arid angles within the IirCl1 group are also shown in Figure 2 . The ClIIrFeClIv angle of 104.9'
K.)
Interatomic angle, deg.
Std. dev., deg.
107.98 111.64 112.70 110.77 108.81 104.93
0.44 0.47 0.48 0.42 0.39 0.38
z.
(12) N. \vooster, Krist., 83, 35 (1932): N. \T,Gregory, .J. A m . Chem. Soc., 73, 472 (1951).
Volume 69, .Yumher 1
January 1966
TERRY B. SWANSON AND VICTOR W. LAURIE
244
differs froni the tetrahedral angle of 109.47' by twelve times the standard deviation. The ClIFeClrv angle is nearly seven standard deviations larger than 109.47'. The remaining ClFeCl angles lie between the two extremes. The irregularities appear to be associated with electrostatic interactions as a Jahn-Teller distortion would not be expected for tetrahedral d6 Fe(111). The sodium atom approximately midway between Clr11 and C l ~ vmay be largely responsible for the small 104.9' angle (see Figure 2; C ~ I IisI above the plane of the other three chlorines). A void between adjacent tetrahedra exists in a location such that movement of C ~ towards I the void would cause the ClIFeClIv angle and the ClIClIv distance to be larger than
normal.
The attraction of the two sodium atoms near
c11and the repulsion of the neighboring chlorine atoms would be expected to contribute to this shift. The drawing together of C ~ I Iand I ClIv may also contribute to the large value of the ClIFeClIv angle. The values of the remaining angles follow qualitatively from these considerations. Acknowledgments. We wish to express our thanks and appreciation to Professor Lingafelter's group for use of and for assistance with the computer programs, and in particular to Dr. C. H. L. Kennard. Financial support was received from the U. S. Army Research Office (Durham) which we acknowledge with thanks.
Electron Magnetic Resonance and Electronic Spectra of Tetrachloroferrate(111) Ion in Nonaqueous Solution'
by Terry B. Swanson and Victor W. Laurie2 Department of Chemistry, Stanford University, Stanford, California
(Received July 80,1964)
Solutions of FeC13in various organic solvents including pyridine, N,S-dimethylformamide, acetonitrile, acetone, and dimethyl sulfoxide have been shown to contain the tetrachloroferrate (FeCL-) ion by studies of the electron magnetic resonance (e.m.r.) and electronic spectra. It is found that the amount of FeC14- formed is solvent dependent. E.m.r. line widths are also found to be strongly solvent dependent. Addition of LiCl or raising the temperature increases the F e C k concentration. Studies of the temperature dependence of the e.m.r. intensity have been used to determine thermodynamic quantities for the reaction 2FeC13 $ FeC12+ FeC14- in pyridine. Equilibrium constants for this reaction in a number of solvents are given. E.m.r. g-values and electronic oscillator strengths have been measured for some solutions.
+
Ultraviolet and visible spectroscopy in particular, and also infrared spectroscopy, have been utilized extensively in the study Of solutions. Afore recently, nuclear The Journal of Physical Chemistry
(1) Presented in part a t the 144th National Meeting of the American Chemical Societv. LOSAnneles. Calif.. March 1963. (2) Alfred p . Sloan Fellow.
