research papers
ence on the shape of the dimer and it does not hinder phenyl±
phenyl interactions between adjacent dimers.
The effect of adding a branch to the propyl chain is bigger as
shown by the Iv index for (IV)/(V.) A hydrogen at the second
C atom of the n-propyl group is replaced by a methyl group in
(IV). One of these H atoms is directed towards the thioureide
group and is sterically hindered. Therefore, the additional
methyl group in (IV) replaces the other hydrogen, which
points upwards in Fig. 9. This changes the external surface of
the dimer [compared with (V)] and causes a noticeable
increase in the a axis (Table 5). (The new CÐCH3 bond is
approximately parallel with the a axis.)
The isostructurality indices show that structure (I) is less
similar to (V) than (IV) (Table 6). The Iv value for (I)/(V)
being larger than that for (I)/(IV) indicates that the nature of
the distortion from the reference structure is different in (I)
and (IV). Indeed, the b axis is elongated in (I), but the a axis in
(IV) (Table 5). The reason for a longer b axis is clear from the
packing diagram of (I) (Fig. 6). The phenylethyl group
protrudes parallel to this axis and increases the size of the (I)
dimers.
Figure 11
The crystal packing of (a) (VIII) and (b) (IX).
Even though the unit-cell dimensions of (II) are similar to
those of (V), the Iv index for this pair is smaller than for (I)
and (V). This is apparently the consequence of their molecular
constitutions. While the ethyl part and the ®rst aromatic C
atom of the PhEt substituent of (I) completely overlap with
are related to each other by translation in the triclinic struc-
tures and by screw axes with different relative orientations in
(VIII) and (IX). The prevalence of the column motif suggests
this to be the energetically preferred arrangement of dimers.
n
the Pr moiety of (V), only one atom can be in an identical
position in the substituents of (II) (Ph) and (V) (nPr).
The only compound that crystallizes with the space group
4. Conclusions
ꢀ
P1 without being isostructural with (I) and (II) is (VII) (R =
Me). In this structure (Fig. 10), a similar grid of dimers is
assembled to those of the other triclinic crystals. The short-
ening of the alkyl chain generates a hollow region on the
surface of the dimers (cf. Fig. 9). In (VII) (Fig. 10) the `methyl
arms' of the dimers are inserted between two arms of the next
molecule in the same row and the `N-phenyl arms' between
the arms of the following molecule in the same column. The
role of arms in holding together the rows and columns is the
opposite in (I), (II) and (IV)±(VI). The unusual row structure
of (VII) is stabilized by the interaction of `upper' and `lower'
molecules of adjacent dimers. A shift perpendicular to the ac
plane ensures that the hollows at the methyl groups are ®lled
by the O3 phenyl moiety from the neighboring dimer.
Compounds (III), (VIII) and (IX) crystallize with the space
group P21/c. It is a common feature of their molecules that the
®rst C atom of their alkyl chain bears at least one branching
methyl group. Nevertheless, the crystal structure of (III) is
closer to that of (VII) than to (VIII) and (IX). Structures (III)
and (VII) are built up from similar rows (Figs. 8 and 10), but
the adjacent rows are antiparallel in (III) and parallel in (VII).
Again the formation of these rows can be attributed to the
shortness of the alkyl fragment.
Three (N-phenylthioureidoalkyl- and -aryl)phosphonates
have been synthesized and their crystal and molecular struc-
tures examined. The comparative analysis was carried out with
literature data. It can be seen that the different packing
arrangements of (N-phenylthioureidoalkyl- and -aryl)pho-
sphonates are all based on the formation of characteristic
dimers and can be described in terms of the packing of the
dimers. In these arrangements common motifs were identi®ed,
which helped in understanding the relationship of molecular
and crystal structures and in the identi®cation of preferred
interactions. The resemblances between the analyzed struc-
tures result in one-dimensional or three-dimensional
isostructurality.
 Â
Financial support from the University of èodz (grant No.
505/675 2003) and OTKA (grant No. T034985) is gratefully
acknowledged.
References
Allen, F. H. (2002). Acta Cryst. B58, 380±388.
Allen, F. H., Bird, C. M., Rowland, R. S. & Raithby, P. R. (1997). Acta
Cryst. B53, 680±695.
Birum, G. H. (1976). Chem. Abstr. 84, 59745; US Patent 3,920,733.
Birum, G. H. (1977a). Chem. Abstr. 86, 155794; US Patent 4,003,965.
Birum, G. H. (1977b). Chem. Abstr. 87, 135932; US Patent
4,032,601.
The one-dimensional-isostructurality of (VIII) and (IX) has
Â
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already been noted (CheÎcinska, Sieron et al., 2003). Interest-
ingly, this relationship can be extended to also include (I), (II),
(IV), (V) and (VI). In all these seven structures, identical
columns are built from the dimers (Figs. 6, 7 and 11). Columns
ꢀ
Î
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Acta Cryst. (2004). B60, 211±218
Checinska et al.
(N-phenylthioureidoalkyl- and -aryl)phosphonates 217
Checinska, Lilianna
