Volume 4 Number 5
Inorganic Chemistry Q Cogyrighl 1965 by :be Amrrican Chemical Socirly
April 30, 1965
CONTRIBUTION FROM THE CHEMISTRY DEPARTMENT, BROOKHAVEN NATIONAL LABORATORY, UPTON,NEWYORK 11973
Structure of Di(tetramethylammonium)bis(maleonitrile dithiolate)nickelate(II)l BY RICHARD EISENBERGa AND JAMES A. IBERS
Received December 30. 1964 The crystal and molecular structure of di(tetramethylammonium)bis(maleonitrile dithiolate)nickelate( 11) has been determined from three-dimensional X-ray data collected from a single crystal. The material crystallizes in space group ci of the triclinic system, with two molecules in a eel1 of dimensions a = 10.18, b = 15.79, c = 8.04 A., a = 87.1, p = 113.4, and y = 91.9'. Although the NiSa portion of the anion is required by crystallographic symmetry to beplanar, the eiitire anion need have only Ci symmetry; the anion is found to be essentially planar and to have symmetry very near toDSh. The cation has its expected tetrahedral shape.
Introduction Subsequent to our study the structures of other anions of the series Since the initial reporta on the preparation of Co2+ and Ni2+ complexes containing as the ligand the diI anion of maleonitriledithiol (MNT), there has been considerable activity in the preparation and characterization of a number of presumably square-planar complexes of the transition metals. The d i s ~ o v e r y ~ - ~ that these compounds readily undergo reversible electron-transfer reactions to yield a wide variety of complexes with total charges of 0, -1, or -2 is of importance since it makes possible the study of similar comhave been determined (M = Co, p = -211; M = plexes of transition metals in a series of formal oxidation c u , q = - 1 1 2 ; M = Ni, p = - - l I 3 ) . The series is states. Extensive physical measurements on the M N T in fact remarkable, for the geometry of the anion apsystems7~* as well as on related systemsQhave been repears to be independent of the metal M and the charge ported recently. I n an earlier communicationlo we 4. provided the first crystallographic proof that in one of these compounds, namely ( (CH3)4N)2Ni(MNT)2, Collection and Reduction of the X-Ray Data the anion is indeed very nearly square-planar. In this The orange-red crystals of ( (CH3)4N)2Ni(MNT)2 paper we describe in detail the structure determinawere examined optically and by precession and Weissention. berg techniques and were found to belong to the triclinic (1) Research performed under t h e auspices of t h e U. S. Atomic Energy system. A Delaunay reduction performed on our initial Commission. triclinic cell failed to suggest hidden symmetry. (2) Participant in t h e Brookhaven Summer Student Program. (3) H. B. Gray, R. Williams, I. Bernal, and E. Billig, J . A m . Chem. Soc., The cell chosen for the indexing of the Weissenberg 84, 3596 (1982). photographs is a C-centered one, with a = 10.18 i. (4) H . B. Gray and E. Billig, ibid., 86, 2019 (1963). (5) A. Davison, N. Edelstein, R. H. Holm, a n d A. H. Maki, ibid., 86, 0.03, b = 15.79 =k 0.03, c = 8.04 f 0.02 A., a: = 87.1 2029 (1963). 0 1,/3 = 113.4 0.1, y = 91.9 f 0.2', cellvolume = ( 8 ) A. Davison, N. Edelstein, R. H . Holm, and A. H . Maki, Inorg. Chem., 2, 1227 (1963). 1185 A.3. The observed density of 1.35 g . / ~ m is .~ (7) E. Billig, R . Williams, I. Bernal, J. H. Waters, and H. B. Gray, ibid., in good agreement with the density of 1.37 g . / ~ m . ~ 8 , 663 (1964).
*
(8) A. H. Maki, N. Edelstein, A. Davison, and R. H . Holm, J . A m . Chem. Soc., 86, 4580 (1964). (9) A. Davison, N. Edelstein, R. H. Holm, and A. H. Maki, Inorg. Chem., 8 , 814 (1964). (10) R. Eisenberg, J. A. Ibers, R. J. H. Clark, and H. B. Grey, J . A m . Chem. Soc., 86, 113 (1964).
(11) J. D. Forrester, A. Zalkin, and D. H . Templeton, Inorg. Chem., 3, 1500 (1964). (12) J. D. Forrester, A. Zalkin, and D. H. Templeton, zbid., 3, 1507 (1964). (13) C. J. Fritchie, Jr., Abstract K-10, American Crystallographic Association Meeting, Bozeman, Mont., July 25-31, 1964; Acta Cryst , in press.
605
606 RICHARD EISENBERG AND
JAXES
A. IBERS
Inorganic Chemistry
TABLEI FINAL PARAMETER VALUESFOR (( CHl)aN)nNi(MNT)2 Atom
Y
X
0 0.1851 ( 4 ) a 0.1349 (4) 0.329 (1) 0.470 (1) 0.581 (2) 0.310 (1) 0.423 (2) 0.515 (2) 0.034 (1) 0.064 (2) 0.136 (3) -0.107 (2) 0,038 (2)
Ni SI SZ
c1 C2 XI CI
c 4
A-2
Scat Clcat Czcat CBcat C4cat
2
0 -0.0715(3) 0 ~ 1 0 0 0(3) -0.008 (1) -0.040 (1) -0.065 (1) 0.065 (1) 0.117 (1) 0.160 (1) -0,178 (1) -0.226 (2) -0.106 (2) -0.139 (2) -0.240 (2)
0 0.1794 (5) -0.0410 (5) 0.182 ( 2 ) 0.288 (2) 0.369 ( 2 ) 0.087 (2) 0.088(2) 0,095 (2) -0.389 (1) -0,208 (3) -0.374 ( 4 ) -0.458 (3) -0.530 (3)
13, h.z 3.7 (1)b 4.9 ( 1 ) b
5 . 0 (1)‘ 4 . 5 (3) 4 . 7 (3) 7 . 1 (3) 4.4(3) 5 . 2 (3) 7 . 3 (3) 4 . 4 (2) 9.4 ( 5 ) 11.4 ( 7 ) 9 . 1 (5) 8 . 2 (5)
P ! 1c 82% Pss 812 Pia 828 0.0144 (3) 0.0037 (2) 0.0133 (4) 0.0026 (2) 0.0064(3) 0.0004 ( 2 ) 0.0142 (5) 0.0044(3) 0.0214 (7) 0.0022 (3) 0 0048 ( 5 ) 0.0019 (3) Sn 0.0157(5) 0.0052 (3) 0.0214 (7) 0.0025(3) 0.0074 (5) 0.0036 (3) a The estimated standard deviation in the least significant figure is given in parentheses here and in subsequent tables. * From the isotropic refinement. The general form for the anisotropic temperature factor is exp( -Pllh2 - &k2 - Pa# - 2P12hk - 2bl3Frl 2P38kl). Atom
Ni SI
calculated for two molecules in this centered cell. A very sensitive piezoelectric test14 was negative, and this provides reasonable evidence that the space group is Ci, rather than C1. The satisfactory agreement ultimately obtained is also taken as support for the choice of CT. (The equivalent positions of C i are zt ( x , y, 2; ‘/z x,l / 2 y , z).) Intensity data were collected a t room temperature by the equi-inclination Weissenberg technique. Zirconium-filtered Mo KCY radiation was employed. The layers h0Z to h1Ol were photographed. The intensities of 996 independent reflections accessible within the angular range OLIO 5 22.2’ were estimated visually. Because of the triclinic symmetry the intensity estimates were necessarily made from both the top and bottom portions of the films, and no corrections were applied for spot elongation. The usual Lorentzpolarization factor was applied to the intensities to yield Fo2 values (where Fa is the observed structure amplitude) and these were then corrected for absorption. I n order to carry out the absorption correction the 12 crystal faces were identified by optical goniometry and the dimensions of the faces were carefully measured. (It turns out that the volume of the crystal used in the X-ray study is approximately 0.23 mm.3 and has a calculated weight of 315 pg.) Csing a n absorption coefficient of 11.7 cm.-l we find the resultant transmission coefficients range from about 0.39 to 0.61.15 The Fo values were subsequently brought to an approximate common scale through a modification of Wilson’s procedure.
+
+
Solution of the Structure With two molecules in C i the Ni atoms may be placed a t the special positions (000) and (1/21/20) (14) W e are indebted t o F. Holtzherg f o r performing this measurement for us. (15) T h e programs for t h e I B M 7090 used in this work were local modifications of Burnham’s GNABS absorption program, Zalkin’s F O R D A P Fourier program, and t h e Busing-Levy O R F L S least-squares program.
and the NiSb portion of the anion is necessarily planar. These features make the solution of an oth:rwise simple problem trivial. A complete trial structure was readily found from the usual combination of three-dimensional Patterson and difference Fourier maps and was refined by the least-squares procedure. The function minimized was Z w ( F o - F J 2 , where the weights w were assigned in the following n-ay: F 5 10 e, w = F2/100; 10 < F < 30 e, w = 1; F 2 30e, w = 900/F2. The atomic scattering factors for the neutral atoms tabulated by IbersI6 were used. The anomalous parts of the Ni and S scattering factors were obtained from Templeton’s t a b ~ l a t i o n ’and ~ were included in the calculated structure factors.l8 The contributions of the hydrogen atoms to the structure factors were ignored, since no clear indication of their positions was obtained. Initially the iefinement was carried out in which all atoms were assigned individual isotropic thermal parameters. This refinement of 53 positional and thermal parameters converged to a conventional R factor (R = Zl1F.l - ~ F c ~ / / 2 ~ofF o0.15 ~ ) and to a weighted R factor R‘ (R’= (Zw(F,- F , ) 2 / 2 ~ F o 2 ) 1 ~ 2 ) of 0,180. A difference Fourier based on this refinement exhibited electron density as high as 2 9 e/K.j (about 75% of the height of a carbon atom in this structure). There was clear indication of significant anisotropic thermal motion in the vicinity of the heavy atoms. In a second round of calculations the Ni and S atoms were allowed to vibrate anisotropically, while the other atoms were restricted to isotropic vibration. This refinement of 68 positional and thermal parameters converged to the values R = 0.107and R‘ = 0.130. (16) J. A. Ibers, “International Tables for X-ray Crystallography,” Kynoch Press, Birmingham, England, 1 9 6 2 , 1’01. 3, Table 3.3.1A. (17) D. H. Templeton, ibid., Table 3.3.2‘2. (18) J. A. Ibers and W. C. Hamilton, Acta C i y s t . , 17, 781 (1964).
VoZ. 4 , No. 5, May 1965
~I(TETRAMETHYLAMMONIUM)BIS(MALEONITRILEDITHIOLATE)NICKELATE(II)
607
TABLE I1 OBSERVEDAND CALCULATED STRUCTURE AMPLITUDES( X 10) FOR (( CHs)aN)2Ni(MNT)2 n L
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n L
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225 205 158 b63 242 223 211 19
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0
o.
I01
233 1113
21B
18 1.6 59
298 28P .2b 6bO 2'1
75 2. 111 25,
lee
213
significant shifts of the positional parameters away from the positions found in the previous refinement. Moreover, the improvement in the value of R' is significant a t only about the 25y0 levellg and there is thus little justification for this refinement of additional thermal parameters. Accordingly in Table I we list as final parameters for this structure those that were obtained from the second calculation in which only the Ni and S atoms were allowed to vibrate anisotropically. The final values of F, are based on these parameters: in Table I1 we list 10Foand 101Fcl (in electrons) for the 996 observed reflections. Since (20) Since the scale factors of t h e separate layers were also adjusted in t h e least-squares procedure, i t is n o t possible t o carry o u t a complete anisotropicrefinement. As long as a reasonable fraction of the atoms are restricted t o isotropic vibration there is little correlation between the scale factors and t h e values of pz2 of those atoms t h a t are vibrating anisotropically.
Inorganic Chemistry
608 RICHARD EISENBERG AND JAMES A. IBERS
consists of the packing of essentially planar anions and tetrahedral cations. The anions are well-separated, the closest Ni-Ni approach being the lattice repeat of 5.04 A. All intermolecular contacts appear to be normal and give no indication of unusual anion-cation interactions. The closest intermolecular contacts of the Ni are three methyl carbons from each of the cations a t a distance of about 4 *&. The dimensions of the Ni(MNT)22- ion are shown in Figure 1 and tabulated in Table IV. The equation of TABLEIV INTRAMOLECULAR DISTANCES AND ANGLES PRINCIPAL Distance, Atoms
A.
Ni-Sl Si-&
2.174(6) 2.156(6) 1.74 ( 2 ) 1.76(1) 1.33(2) 1.44(2) 1.38(2) 1.13(2) 1 . 1 3( 2 )
Anion
s1-c1 &-c3
c1-c3 c1-c2
Figure 1.-A sketch of the Ni(MNT)22-ion showing approximate dimensions and angles and also the electron density in the best least-squares plane through the anion. The electron density map was drawn by the cathode ray tube*plotter on-line to the IBM 7094. The lowest contour is 1.46 e/A.3 and contours above 5.10 e/d4.3 have been omitted. The contour interval of 0.73 e/A.B nicely displays the density of the light atoms, but is too small to allow the heavy-atom contours to be resolved. The dots in the centers of the heavy atoms designate the atomic centers.
c3-c4
Cz-s.1 c4-sz
none of the intensities calculated for the unobserved b u t accessible reflections exceeds our estimate of a minimum observable intensity value, F,[ values for unobserved reflections are omitted from Table 11. The final R value of 0.107 is somewhat higher than we would normally expect, and we attribute this mainly to intensity errors arising from spot elongation and contraction. The anisotropic thermal parameters (Table I) lead t o the root-mean-square amplitudes of vibration along the principal axes of the thermal ellipsoids tabulated in Table 111. The orientations of the principal axes, which can be worked out from the data of Table I, lead us to conclude that the translational motion of the anion as a whole is somewhat smaller than motion resulting from rocking. No analysis of these vibrations in terms of a rigid-body approximation has been attempted. Description of the Structure The crystal structure described by the space group, the parameters of Table I, and the cell parameters TABLE I11 O F VIBRATION ( I N
A. )
Atom
Minimum
Intermediate
Maximum
Ni
0.180 (3) 0.198(5) 0.197 ( 5 )
0.189 (3) 0.265(5) 0.257 (4)
0.276 (3) 0.274(5) 0.301 (6)
s1 s2
91.5 ( 2 ) 1 0 4 , 5(6) 119 (1) 122(1) 103.1 (5) 118(1) 177 ( 2 ) 123 (1) 121 (1) 117 (1) 179 (1)
Sl-Ni-S2 Ni-Sz-Ca Sz-C3-C1 c3-c1-s1
Cl-S1-Ni Sz-C3-C4 Ca-Ca-Nz
c4-c3-c1 Cz-C1-C3 S1-C1-C2 C1-CrN1 Cation
S-Ct
s-cz N-C3 s-c4
ROOT-MEAN-SQUARE -1MPLITUDES
Angle, deg.
Atoms
1.331
Mean C-S
1 53(3) 1.50(3) 1.47(2) 1.55(2)
113 (1) 111 (1) 110 ( 2 ) 104 (2) 110 (1) 109 (1)
C1-X-Cz CI-N-CB Cl-?;-C4 c2-s-c3
~1,512
Cz-N-C? Ca-Ii-Ca -
Mean angle
109.4
the best least-squares planez1 through the anion is 3.741% - 8 . 0 1 1 ~- 7.1222 = 0 (triclinic coordinate system). The deviations of the individual atoms from this plane (Table V) are small and presumably
(x.)
DEVIATIOXS
TABLE V
FROM THE
LEAST-SQUARES PLASE
THROUGH THE A S I O N Atom
Deviation
u (deviation)
SI
-0,012
s2
-0.004 -0.001 0.016 0,024 0.014 0.065 -0.036
0.004 0.004 0.016 0.016 0.016 0.017 0.017 0.017
c1
C3
cz
c 4
S I S Z
result from packing distortions. Although the molecule is required to have only the symmetry C;, the symmetry closely approximates D 2 h . The geometry of the anion differs insignificantly from that of the Co(NLSIT)Z~-,~' Cu(?vlNT)z-,12and Ni(MNT)2- 1 B anions. The tetramethylammonium cation has its expected tetrahedral shape (Table IV). (21) W.C. Hamilton, Acta C r $ s l . , 1 4 , 189 (1961).
