CRYSTAL STRUCTURE OF THE COMPLEX OF 1,2-BIS[2-(o-HYDROXYPHENOXY)ETHOXY]ETHANE 1041
In the crystal structure of I, the molecules of the
complex [NH4(SCN)L] formed, as already noted, by
hydrogen bonding exist not as isolated species but as
infinite (along y axis) polymeric chains, which are
also formed by hydrogen bonds but of a different
type: between the hydrogen atoms of both OH groups
of L and N atom of the SCN anion (see H bonds
O1 HO1 N* and O16 H16 N* in the figure and in
Table 4).
gen atoms. For the structure refinement, we used al-
most all the reflections from the working set [includ-
ing very weak reflections with I < 2 (I)], except sev-
eral reflections for which the measured and calculated
F2 values were poorly consistent.
From the E synthesis (direct method), we revealed
the disordered SCN anion and the ordered molecule
of podand L. However, after anisotropic refinement of
the ordered structure of I (taking into account all the
hydrogen atoms), the detailed analysis of the peaks
of the check differential electron density synthesis
showed that the S and hence C atoms of the SCN
anion are disordered each over two close positions A
and B, and in podand L the atoms of its chain CH2
O10 CH2 CH2 are also disordered each over two
relatively close positions considerably differing, how-
ever, in the occupancy (see above discussion). Then,
when refining the parameters of all the atoms of I, we
imposed soft equality conditions of the SADI and
DFIX types [5] on the structurally equivalent 1,2 and
1,3 interatomic distances involving the disordered
atoms. The total occupancies of the positions of the
disordered atoms were also refined by the least-
squares method.
All the other short interatomic contacts between
molecules of I in the crystal are close to, or slightly
shorter than the sums of the corresponding van der
Waals atomic radii.
EXPERIMENTAL
Complex I was prepared as follows. Podand L and
ammonium thiocyanate NH4SCN (molar ratio 1 : 1)
were dissolved in an acetone water mixture (5 : 1),
and the solvent was allowed to evaporate until a crys-
talline precipitate formed. Colorless transparent crys-
tals of I of X-ray quality were obtained by recrystalli-
zation of this precipitate from ethanol at room temper-
ature.
The unit cell parameters and three-dimensional set
of reflection intensities were obtained with an Enraf
Nonius CAD-4 autodiffractometer (MoK radiation,
graphite monochromator). Crystals of I are monoclin-
The four disordered hydrogen atoms of the NH4+
cation and almost all the hydrogen atoms of podand L
were objectively localized in the intermediate differen-
tial electron density synthesis. Then, in the course
of the least-squares refinement of the structure of I,
the coordinates of almost all the hydrogen atoms of
podand L (except the HO1 and H16 atoms of two OH
groups), including those at the disordered carbon
atoms, were calculated geometrically using the rider
model [5], wth the individual isotropic thermal param-
eters Uiso being refined. For the hydrogen atoms of
the NH+4 cation and for the HO1 and H16 atoms of
podand L, the coordinates (and individual parameters
Uiso) were refined by the least-squares method as for
free atoms.
ic: C18H22O6 NH4SCN, M 410.48; a 13.222(3), b
3
8.865(2), c 17.772(5)
;
93.98(2) , V 2078.1(9)
,
3
1
Z 4, dcalc 1.312 g cm , (MoK ) 1.93 cm , space
group P21/n.
The intensities of 3660 reflections were measured
in the reciprocal space quadrant (2
48 ) in the /2
scanning mode using a 0.15 0.34 1.00-mm single
crystal of I. When measuring the intensities, we used
a special mode in which the final scanning was per-
formed for all, including very weak, reflections. After
exclusion of 256 systematically absent reflections and
averaging of the intensities of 157 pairs of equivalent
reflections 0kl and 0kl (Rint 0.029), the working set
of the measured F2(hkl) and (F2) consisted of 3247
unique reflections.
For the exposed crystal of I, we also refined by the
least-squares method the isotropic extinction coeffi-
cient: g 0.0019(5) [5]. In the last cycle of the full-
matrix refinement of the structure of I, the absolute
shifts of all the 354 varied parameters were less than
0.001 . The final coordinates and thermal parameters
of the atoms are listed in Tables 5 and 6.
The structure of I was solved by the direct method
using the SHELXS 97 program [5] and refined by the
full-matrix least-squares method (with respect to F2)
using the SHELXL 97 program [5] in the approxima-
tion of anisotropic thermal vibrations of all nonhydro-
The final R factors are as follows: R1 0.036 and
wR2 0.092 for 2500 observed reflections with I
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004
Chekhlov
