Abstract
Full Text
UDC 548
CRYSTALLOGRAPHY
B. M. SHCHEDRIN, Academician N. V. BELOV, L. P. ZHIDKOV,
M. A. PORAI-KOSHITS, A. E. SHVELASHVILI
THE CRYSTAL STRUCTURE OF NITROBIS(ETHYLENEDIAMINE)NICKEL CHLORIDE \([\mathrm{Nien}_2\mathrm{NO}_2]\mathrm{Cl}\)
Crystals of \(\mathrm{Nien}_2\mathrm{NO}_2\mathrm{Cl}\) were synthesized at the Institute of General and Inorganic Chemistry of the USSR Academy of Sciences in the form of violet octahedra elongated along the (short) \(y\) axis. There, in the crystal-chemical laboratory, all the experimental X-ray material was obtained from a single crystal ground into a sphere of \(\varnothing 0.15\)—\(0.20\) mm (Mo-\(K_\alpha\) radiation, KFOR X-ray goniometer). The orthorhombic cell \((a = 18.321 \pm 0.003,\ b = 8.777 \pm 0.001,\ c = 13.025 \pm 0.003\ \text{Å})\) contains \(Z = 8\) units of the indicated composition. The acentric (diamond) Fedorov group is \(Fdd2 = C_{2v}^{19}\). On an MF-2 microphotometer, the blackenings of the film were estimated from the difference between the instrument readings when set on a reflection and on the background near it, at a constant slit width somewhat larger than the size of the reflections. The transition to intensities was made according to a calibrated blackening scale. The array used in the structural analysis consisted of 212 structure factors differing from zero and derived from the intensities with allowance only for the angular factor \(Lp\) \((\sin \vartheta/\lambda < 0.65)\). The structure determination was carried out entirely at the Computing Center of Moscow University by the material-point method recently developed there \((^1)\).
The group \(Fdd2\) fixes the atoms Ni, Cl, and N (from \(\mathrm{NO}_2\)) on twofold axes and permits the position of one of these atoms (Ni) to be taken as the origin of coordinates. Patterson synthesis on the same twofold axis also brings out the atom \(\mathrm{Cl}(00z)\).
The limited experience of previous structure determinations made probable for Ni an octahedral coordination of Cl and five N \((^2)\), with four N from two ethylenediamine ligands having to form a rectangle with semidiagonals \(\mathrm{Ni}—\mathrm{N} = 2.1\ \text{Å}\) at an angle of \(\sim 86^\circ\). This pseudosquare must lie in the \(xOy\) plane, i.e., be perpendicular to the \(z\) axis. The distances from Ni to the fifth N (on a twofold axis) are \(\sim 2.0\ \text{Å}\), and to the Cl atom (on the same axis) \(\sim 2.5\ \text{Å}\). To be determined were the azimuth of one of the four N and the azimuth of the \(\mathrm{NO}_2\) triangle \((\mathrm{N}—\mathrm{O} \sim 1.3\ \text{Å})\), which remains in the plane passing through the twofold axis, and, in addition, the 6 coordinates of two independent C atoms (Fig. 1).
Accordingly—in the rigid conditions indicated—the first stage of the solution did not give an acceptable result, and the discrepancy factor varied only within small limits around 60%.
At the second stage the atoms on the twofold axes \((\mathrm{Cl}\) and \(\mathrm{N}(\mathrm{O}_2))\) were loosened, and the restrictions on the O atoms were also removed; however, the pseudosquare of four N atoms remained rigidly fixed in the \(xOy\) plane. Under the relaxed conditions the material-point method immediately destroyed the proposed coordination scheme. The \(\mathrm{Ni}—\mathrm{Cl}\) distance increased to \(4.5\ \text{Å}\), and \(\mathrm{Ni}—\mathrm{N}(\mathrm{O}_2)\) to \(2.45\ \text{Å}\), i.e., the halogen atom left the first coordination sphere entirely, while the \(\mathrm{NO}_2\) group, with respect to the central Ni, “turned over” and became attached to this Ni by both of its O atoms; the \(R\) factor fell sharply to 24% at \(B_0 = -2\), but further refinement did not reduce it.
The electron-density synthesis constructed at the conclusion of this stage did not reveal one pair of ethylenediamine N atoms, which now appears to be a natural consequence of placing the Ni octahedron “on an edge” \(\mathrm{O}—\mathrm{O}\), to which there must correspond (along the \(z\) axis) a parallel upper edge of the ...
Fig. 1. A priori model of the complex \([\mathrm{Nien}_2\mathrm{NO}_2\mathrm{Cl}]\). \(\mathrm{en}=\mathrm{NH}_2—\mathrm{CH}_2—\mathrm{CH}_2—\mathrm{NH}_2;\ Z=8;\ a=18.321\pm0.003\ \text{Å},\ b=8.877\pm0.001\ \text{Å},\ c=13.025\pm0.005\ \text{Å};\ Fdd2\)
Fig. 2. Real bidentate structure of the complex chloride \([\mathrm{Nien}_2\mathrm{NO}_2]^+\mathrm{Cl}^-\)
two N(en), sharply emerging from the \(xOy\) plane. Thus, an important consequence of the halogen leaving the coordination octahedron was the change from the trans configuration of the two en groups to the cis configuration.
At the third stage of the determination, by the same method of the material point, all forced parametrization was discarded (apart from that dictated by the group \(Fdd2\) and by the number \(Z = 8\) of units in the cell), and only the initial coordinates—for continuous variation—were taken from the second stage. The factor \(R\) fell to 13.5% at \(B_0 = -2.5\). In the electron-density synthesis at the variable specified position, one of the C atoms did not appear, but a new position for it was indicated sufficiently clearly, to which it was transferred.
Table 1
Coordinates of the atoms of the \(\mathrm{Nien_2NO_2Cl}\) structure and “errors” in the determination of the coordinates
| Atoms | Coordinates | Isotropic structural factors \(B\) | “Errors” | Atoms | Coordinates | Isotropic structural factors \(B\) | “Errors” |
|---|---|---|---|---|---|---|---|
| Ni | 000 | 2.49 | 0.02 | \(\mathrm{N_2(en)}\) | \(x\ -0.05332\) \(y\ 0.21321\) \(z\ 0.00450\) |
2.50 | 0.00098 0.00021 0.00074 0.20 |
| Cl | \(x\ 0\) \(y\ 0\) \(z\ 0.34795\) |
2.74 | 0.00094 0.13 |
O | \(x\ 0.05177\) \(y\ 0.04954\) \(z\ 0.13458\) |
2.50 | 0.00011 0.00011 0.00100 0.60 |
| \(\mathrm{N(O_2)}\) | \(x\ 0\) \(y\ 0\) \(z\ -0.19424\) |
2.52 | 0.00105 0.12 |
\(\mathrm{C_1(en)}\) | \(x\ -0.03182\) \(y\ 0.28178\) \(z\ 0.10256\) |
3.68 | 0.00273 0.00065 0.00254 0.40 |
| \(\mathrm{N_1(en)}\) | \(x\ 0.06909\) \(y\ 0.10968\) \(z\ 0.10965\) |
2.50 | 0.00057 0.00032 0.00095 0.20 |
\(\mathrm{C_2(en)}\) | \(x\ 0.05350\) \(y\ 0.27000\) \(z\ 0.11363\) |
3.68 | 0.00129 0.00718 0.00858 0.40 |
As a result of introducing isotropic individual temperature factors, the final value of \(R\) was obtained in the range 8.2–8.6%. Its change by 0.2–0.4% within the indicated interval was regarded as a random effect, especially since the use of correcting weight functions (1) led to results that fluctuated only slightly around the mean values. Therefore the solution giving the best N—C and C—C distances in the ethylenediamine group was accepted as final (Tables 1 and 2).
Table 2
Interatomic distances and valence angles in the complex \([\mathrm{Nien_2NO_2}]^{+} + \mathrm{Cl}^{-}\)
| Distance | Value | Distance | Value | Angle | Value | Angle | Value |
|---|---|---|---|---|---|---|---|
| Ni—Cl | 4.532 Å | Ni—\(\mathrm{N_1(en)}\) | 2.142 Å | \(\mathrm{ON(O_2)O}\) | 106°44′ | \(\mathrm{NiN_1C_2}\) | 110°39′ |
| Ni—\(\mathrm{N(O_2)}\) | 2.530 | Ni—\(\mathrm{N_2(en)}\) | 2.131 | \(\mathrm{ONiO}\) | 61°36′ | \(\mathrm{NiN_2C_1}\) | 105°36′ |
| \(\mathrm{N(O_2)}\)—O | 1.303 | \(\mathrm{N_2}\)—\(\mathrm{C_1}\) | 1.469 | \(\mathrm{N_1NiN_1}\) | 96°22′ | \(\mathrm{N_1C_2C_1}\) | 104°54′ |
| O—O | 2.091 | \(\mathrm{N_1}\)—\(\mathrm{C_2}\) | 1.452 | \(\mathrm{N_2NiN_2}\) | 176°50′ | \(\mathrm{N_2C_1C_2}\) | 108°34′ |
| Ni—O | 2.041 | \(\mathrm{C_1}\)—\(\mathrm{C_2}\) | 1.573 | \(\mathrm{N_1NiN_2}\) | 81°18′ |
The scatter in the coordinates over 7 variants with correcting functions may be taken as an objective estimate of the “errors” of the solution.
Figure 2 shows the complex \([\mathrm{Nien_2NO_2}]^{+}(\mathrm{Cl}^{-})\) in the form of an octahedron placed on the shortest edge, O—O = 2.09 Å; the upper edge is \(N(\mathrm{en})—N(\mathrm{en}) = 3.24\) Å, to which correspond the angles \(\mathrm{ONiO} = 61^\circ36′\) and \(\mathrm{N(en)NiN(en)} = 96^\circ22′\). Accordingly, two other \(N(\mathrm{en})\) emerge from the \(xOy\) plane (“rise”) up to the angle \(N'(\mathrm{en})NiN'(\mathrm{en}) = 176^\circ50′\).
The angle (valence angle) in the ONO group is \(106^\circ44'\) for bond lengths \(N—O = 1.30\) Å. The distances are \(Ni—O = 2.04\) Å, \(Ni—N(\mathrm{en}) = 2.14\) and \(2.13\) Å, and \(Ni—N(O_2) = 2.53\) Å, \(N—C = 1.47\) and \(N—C_2 = 1.45\) Å for \(C_1—C_2 = 1.57\) Å. All interatomic distances and angles within the complex are collected in Table 2.
The four atoms of the ethylenediamine group deviate from the plane of the best least-squares fit by \(\pm 0.2—0.3\) Å. The C atoms deviate from the plane \(Ni\)—two \(N(\mathrm{en})\) by 0.5 and 0.3 Å. The angle of inclination of the \(C_1—C_2\) direction to the \(z\) axis is \(84^\circ\). The distances between Cl and the atoms O, N, C, as well as between atoms of neighboring enantiomorphic complexes, are close to the corresponding sums of intermolecular radii.
One may emphasize the parallelism of the established orientation of the octahedral complex—namely, along the \(N(\mathrm{en})—N(\mathrm{en})\) axis in the \(xOy\) plane—to the corresponding morphological feature of the octahedral crystals \([\mathrm{Nien}_2\mathrm{NO}_2]\mathrm{Cl}\), which was noted at the beginning of the article.
Moscow State University
named after M. V. Lomonosov
Received
30 VIII 1966
CITED LITERATURE
- B. M. Shchedrin, N. V. Belov, N. P. Zhidkov, DAN, 170, No. 5 (1966).
- A. E. Shvelashvili, X-ray structural study of several diacidodiethylenediamine nickel compounds of the type \(\mathrm{Nien}_2XY\), Dissertation, Moscow, 1965.