Favoured conformations of methyl isopropyl, ethyl isopropyl, methyl tert-butyl, and ethyl tert-butyl 2-(tri-phenylphosphoranylidene)malonate

Article abstract of DOI:10.1107/S0108270108018246

The conformations of organic compounds determined in the solid state are important because they can be compared with those in solution and/or from theoretical calculations. In this work, the crystal and mol-ecular structures of four closely related diesters, namely methyl isopropyl 2-(triphenyl- phosphoranylidene)malonate, C25H25O4P, ethyl isopropyl 2-(triphenyl- phosphoranylidene)malonate, C26H27O4P, methyl tert-butyl 2-(triphenyl- phosphoranylidene)malonate, C26H27O4P, and ethyl tert-butyl 2-(triphenyl- phosphoranylidene)-malonate, C27H29O4P, have been analysed as a preliminary step for such comparative studies. As a result of extensive electronic delocalization, as well as intra- and inter-molecular inter-actions, a remarkably similar pattern of preferred conformations in the crystal structures results, viz. a syn-anti conformation of the acyl groups with respect to the P atom, with the bulkier alk-oxy groups oriented towards the P atom. The crystal structures are controlled by nonconventional hydrogen-bonding and intra-molecular inter-actions between cationoid P and acyl and alk-oxy O atoms in syn positions.

Full text of DOI:10.1107/S0108270108018246

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
keto or ester group, there is a strong interaction between
cationoid phosphorus and the syn acyl O atom (Wilson &
Tebby, 1972; Zeliger et al., 1969), but syn±syn diesters have
never been observed and are not shown, as in the ®rst scheme
for syn±anti and anti±anti mixtures. The crystal conformation
is controlled by minor changes in the diester groups because
the dimethyl ester is a 1:1 anti±anti/syn±anti mixture, in the
methyl ethyl diester the acyl O atom of the methyl ester group
is syn and that of the ethyl ester group is anti (CastanÄeda,
Jullian et al., 2007), and in the diethyl ester both acyl O atoms
are anti to the P atom (CastanÄeda et al., 2005). This limited
evidence indicates that acyl groups can adopt either geometry,
but the bulkier alkoxy group tends to be syn to P.
ISSN 0108-2701
Favoured conformations of methyl
isopropyl, ethyl isopropyl, methyl
tert-butyl, and ethyl tert-butyl 2-(tri-
phenylphosphoranylidene)malonate
Fernando Castaneda,a* Paul Silva,a Clifford A. Bunton,b
Ä
c
d
Â
Marõa Teresa Garland and Ricardo Baggio
a
Â
Â
Â
Departamento de Quõmica Organica y Fisicoquõmica, Facultad de Ciencias
Â
Â
Quõmicas y Farmaceuticas, Universidad de Chile, Casilla 233, Santiago, Chile,
bDepartment of Chemistry and Biochemistry, University of California, Santa Barbara,
c
Â
Â
CA 93106, USA, CIMAT, Departamento de Fõsica, Facultad de Ciencias Fõsicas y
Â
Matematicas, Universidad de Chile, Casilla 487-3, Santiago de Chile, Chile, and
d
Â
Â
Â
Â
Departamento de Fõsica, Comision Nacional de Energõa Atomica, Avenida Gral Paz
1499, 1650 Buenos Aires, Argentina
Correspondence e-mail: fcastane@ciq.uchile.cl
Received 4 May 2008
Accepted 16 June 2008
Online 28 June 2008
The conformations of organic compounds determined in the
solid state are important because they can be compared with
those in solution and/or from theoretical calculations. In this
work, the crystal and molecular structures of four closely
related diesters, namely methyl isopropyl 2-(triphenyl-
phosphoranylidene)malonate, C25H25O4P, ethyl isopropyl
2-(triphenylphosphoranylidene)malonate, C26H27O4P, methyl
tert-butyl 2-(triphenylphosphoranylidene)malonate, C26H27-
O4P, and ethyl tert-butyl 2-(triphenylphosphoranylidene)-
malonate, C27H29O4P, have been analysed as a preliminary
step for such comparative studies. As a result of extensive
electronic delocalization, as well as intra- and intermolecular
interactions, a remarkably similar pattern of preferred
conformations in the crystal structures results, viz. a syn±anti
conformation of the acyl groups with respect to the P atom,
with the bulkier alkoxy groups oriented towards the P atom.
The crystal structures are controlled by nonconventional
hydrogen-bonding and intramolecular interactions between
cationoid P and acyl and alkoxy O atoms in syn positions.
A series of diesters with methoxy, ethoxy, isopropoxy and
tert-butoxy groups, namely the methyl isopropyl-, (Ia), ethyl
isopropyl-, (Ib), methyl tert-butyl-, (IIa), and ethyl tert-butyl
2-(triphenylphosphoranylidene)malonate diesters,
(IIb),
Ph3P C(CO2R1)CO2R2 (where R1 = Me or Et and R2 = iPr or
tBu), have been prepared and their structures analysed. Figs. 1,
3, 5 and 7 show the molecular structures of the compounds,
while Figs. 2, 4, 6 and 8 present the corresponding packing
views. Selected bond distances for (Ia), (Ib), (IIa) and (IIb)
are given in Tables 1, 3, 5 and 7, respectively. Tables 2, 4, 6, 8
and 9 show the nonbonding interactions and short contacts
relevant to the packing discussion.
Comment
The conformations of crystalline triphenylphosphonium ylides
stabilized by electron-withdrawing groups such as ester, keto
or cyano depend on the balance between electronic delocali-
zation and intra- and intermolecular nonbonding interactions
(CastanÄeda et al., 2003; CastanÄeda, AcunÄa et al., 2007). The
bond between P and the ylidic C atom allows free rotation at
ambient temperatures on the NMR time scale, indicating the
inadequacy of a structure with a classical C P double bond
(Bachrach & Nitsche, 1994). In ylides stabilized by a single
In the crystals of these diesters, the bulkier alkoxy groups
are oriented towards, and the smaller alkoxy groups away
from, the P atom. The ester groups have Z conformations, as is
typical of carboxylic esters (Eliel & Wilen, 1994), and are
1
approximately in the ylidic plane. The H and 13C NMR
spectra of these diesters indicate that the conformations are
Acta Cryst. (2008). C64, o405±o410
DOI: 10.1107/S0108270108018246
# 2008 International Union of Crystallography o405

organic compounds
the same in solution and the solid state, as detailed elsewhere
(CastanÄeda et al., 2008). The geometries of the crystalline
diesters are governed by the balance between ylidic resonance
and intra- and intermolecular interactions. As is generally the
360ꢀ. In earlier observations of ylidic diesters with methoxy or
ethoxy substituents, we found that the bulkier alkoxy group
was oriented towards the P atom (CastanÄeda, Jullian et al.,
2007), and the present results ®t this generalization. In the
crystal structure, bulky alkoxy groups oriented away from the
P atom would interfere both intra- and intermolecularly. Both
isopropoxy and tert-butoxy groups are oriented towards the
face of the phenyl group which is approximately orthogonal to
the C P bond, as shown by the H NMR signals in solution
(CDCl3). The bond lengths between ylidic and acyl C atoms
are between those typical of single and double bonds, as are
those in the acyl groups (Howells et al., 1973).
Elsewhere, we show that computed interatomic distances
and angles for isolated molecules are generally similar to those
in the crystal structure (CastanÄeda, Jullian et al., 2007).
Computations indicate that the conformations of isolated
ylidic diesters have minor effects on their computed energies,
indicating the role of intermolecular interactions in controlling
conformation. Intramolecular interactions in the crystal
structure, and probably also in solution, involve interactions
between cationoid P and acyl and alkyl O atoms in the syn
position, which slightly lengthens the acyl group syn to P
relative to the anti-acyl group, as shown by the relative lengths
of O4ÐC3 and O2ÐC2. This generalization fails for the
methyl tert-butyl diester, (IIa). There are also, in some
diesters, intramolecular interactions between methyl H atoms
and anti acyl O atoms. There are always intermolecular
interactions between phenyl H atoms and the acyl O atoms of
an adjacent molecule (Desiraju & Steiner, 1999). These
interactions between phenyl H atoms and acyl O atoms are
generally important and play key roles in determining the
conformations of individual molecules and crystal structures
(CastanÄeda, Jullian et al., 2007).
. . .
case, the C P bond lengths are between those characteristic
of single and double bonds (Howells et al., 1973), and in
1
solution the H and 13C NMR signals indicate free rotation
about this bond. However, in the crystal structure, the orien-
tations of the phenyl groups are similar in the four ylides and
are apparently insensitive to the bulkiness of the alkoxy ester
groups.
To a ®rst approximation, the bonds between the ylidic and
acyl C atoms are in the same plane, consistent with important
ylidic resonance. Some angles at these C atoms differ from the
expected 120ꢀ, but the sum of the angles is approximately
1
. . .
Figure 1
A molecular diagram of (Ia), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. H atoms
have been omitted for clarity. Cg1, Cg2 and Cg3 denote ring centroids.
Intramolecular interactions (PÁ Á ÁO contacts and CÐHÁ Á Áꢀ bonds) are
shown as single dashed lines. The minor component of the disordered
methyl group is shown by double dashed bonds and dashed ellipsoids.
Figure 3
A molecular diagram of (Ib), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. H atoms
have been omitted for clarity. Cg1, Cg2 and Cg3 denote ring centroids.
Intramolecular interactions (PÁ Á ÁO contacts and CÐHÁ Á Áꢀ bonds) are
shown as single dashed lines. The minor component of the disordered
ethyl group is shown by double dashed bonds and dashed ellipsoids.
Figure 2
A packing diagram for (Ia), showing the weakly connected dimeric
structure. Intermolecular CÐHÁ Á ÁO and intramolecular CÐHÁ Á Áꢀ bonds
are shown as dashed lines. The symmetry codes are as in Table 2.
ꢁ
o406 Castaneda et al.
C25H25O4P, C26H27O4P, C26H27O4P and C27H29O4P
Acta Cryst. (2008). C64, o405±o410
Ä

organic compounds
In the crystal structure of (Ib) (Fig. 4), one alkoxy group syn
to P is directed towards the face of a phenyl group which is
approximately orthogonal to the ylidic CÐP bond. The
consequent CÐHÁ Á Áꢀ interaction should be modestly stabi-
lizing (Nishio et al., 1995; Nishio & Hirota, 1989) and is seen in
a variety of diesters and keto esters. In the other ester residue,
the syn-acyl group is oriented between two phenyl groups, and
independent evidence indicates that for some diester ylides
the geometries are similar for isolated molecules and in the
crystal structure.
PÁ Á ÁO contacts and one further CÐHÁ Á Áꢀ hydrogen bond
between the terminal methyl H atom (C5ÐH5C) and the
phenyl ring C31±C36 (Cg3) (entries 1±3 in Tables 2, 4, 6 and 8).
There are, however, differences in the intermolecular inter-
actions and the derived packing schemes. In (Ia) and (Ib),
there is one nonconventional intermolecular CÐHÁ Á ÁO bond
between the C21±C26 phenyl ring (Cg2) and atom O4, but it
Due to the common skeleton, all four ylides exhibit
analogous weak intramolecular interactions, viz. two short
Figure 6
Figure 4
A packing diagram for (IIa), showing the three-dimensional structure.
Intermolecular CÐHÁ Á ÁO bonds are shown as dashed lines. Intra-
molecular hydrogen bonds have been omitted for clarity. The symmetry
codes are as in Table 6.
A packing diagram for (Ib), showing the weakly connected chains
running along the b axis. Intermolecular CÐHÁ Á ÁO and intramolecular
CÐHÁ Á Áꢀ bonds are shown as dashed lines. The symmetry codes are as in
Table 4.
Figure 7
Figure 5
A molecular diagram of (IIb), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. H atoms
have been omitted for clarity. Cg1, Cg2 and Cg3 denote ring centroids.
Intramolecular interactions (PÁ Á ÁO contacts and CÐHÁ Á Áꢀ bonds) are
shown as dashed lines. The minor component of the disordered ethyl
group is shown by double dashed bonds and dashed ellipsoids.
A molecular diagram of (IIa), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. H atoms
have been omitted for clarity. Cg1, Cg2 and Cg3 denote ring centroids.
Intramolecular interactions (PÁ Á ÁO contacts and CÐHÁ Á Áꢀ bonds) are
shown as dashed lines.
ꢁ
Acta Cryst. (2008). C64, o405±o410
Castaneda et al.
C25H25O4P, C26H27O4P, C26H27O4P and C27H29O4P o407
Ä

organic compounds
follows. A solution of methyl or ethyl chloroformate (20 mmol) in dry
benzene (8 ml) was added slowly to isopropyl or tert-butyl 2-(tri-
i
phenylphosphoranylidene)acetate (Ph3P CHÐCO2R, R = Pr or
tBu; 40 mmol) in dry benzene (100 ml) under a dry atmosphere. The
resulting solution was stirred for 4 h at room temperature and a white
solid separated. The carboalkoxy methyltriphenylphosphonium
i
t
chloride (Ph3P+ÐCH2ÐCO2R Cl ; R = Pr or Bu) was removed by
®ltration and the solvent evaporated, giving a solid or an oil.
Recrystallization from ethyl acetate gave the title novel diester ylides.
For methyl isopropyl 2-(triphenylphosphoranylidene)malonate, (Ia):
yield 82%; m.p. 393 K; analysis calculated for C25H25O4P: C 71.42, H
5.99%; found: C 71.70, H 6.22%. For ethyl isopropyl 2-(triphenyl-
phosphoranylidene)malonate, (Ib): yield 78%; m.p. 397 K; analysis
calculated for C26H27O4P: C 71.88, H 6.26%; found: C 72.15, H 6.35%.
For methyl tert-butyl 2-(triphenylphosphoranylidene)malonate, (IIa):
yield 70%; m.p. 460 K; analysis calculated for C26H27O4P: C 71.88,
H 6.26%; found: C 72.12, H 6.30%. For ethyl tert-butyl 2-(tri-
phenylphosphoranylidene)malonate, (IIb): yield 65%; m.p. 412 K;
analysis calculated for C27H29O4P: C 72.31, H 6.52%; found: C 72.45,
1
H 6.80%. H NMR spectra in solution were monitored on a Bruker
DRX 300 spectrometer referenced to trimethylsilane. IR spectra
were obtained with a KBr disk on a Bruker IFS 56 FT spectrometer.
Elemental analyses were carried out with a Fison EA 1108 analyser.
Spectroscopic data are available in the archived CIF.
Compound (Ia)
Crystal data
C25H25O4P
Mr = 420.42
Triclinic, P1
a = 9.8033 (6) A
b = 10.4492 (7) A
Ê
c = 11.2169 (7) A
ꢁ = 100.573 (2)ꢀ
ꢂ = 94.878 (2)ꢀ
ꢃ = 102.446 (3)ꢀ
V = 1093.64 (12) A
Z = 2
3
Ê
Ê
Mo Kꢁ radiation
Figure 8
1
Ê
ꢄ = 0.15 mm
T = 273 (2) K
A packing diagram for (IIb), showing the dimeric structures (at site A)
connected into chains (at site B). Intermolecular CÐHÁ Á Áꢀ and ꢀ±ꢀ
interactions are shown as dashed lines. Intramolecular interactions have
been omitted for clarity. The symmetry codes are as in Tables 8 and 9.
0.20 Â 0.17 Â 0.14 mm
Data collection
Bruker SMART CCD area-detector
diffractometer
9176 measured re¯ections
Re®nement
R[F2 > 2ꢅ(F2)] = 0.052
wR(F2) = 0.134
S = 1.01
4675 re¯ections
282 parameters
4675 independent re¯ections
3133 re¯ections with I > 2ꢅ(I)
Rint = 0.025
gives dissimilar packing schemes: in (Ia), hydrogen-bonded
dimers are built up around a group of symmetry centres
(Fig. 2), while for (Ib) it results in the formation of a chain
around the screw axis running along the unique b axis (Fig. 4).
In ylides (IIa) and (IIb), these interactions differ, viz. in (IIa)
the preferred intermolecular contacts are nonconventional
CÐHÁ Á ÁO bonds (Table 6), while in (IIb) they are mainly CÐ
HÁ Á Áꢀ (Table 8) and ꢀ±ꢀ bonds (Table 9), and the crystal
structures differ. In (IIa), the predominant CÐHÁ Á ÁO bonds
are spread uniformly in four directions (Fig. 6), generating a
homogeneously connected three-dimensional structure. In
(IIb), dimeric structures are built up around a group of
symmetry centres [at (0, 12, 0), zone A in Fig. 8], connected into
[111] chains by rather weak ꢀ±ꢀ bonds around the inversion
2 restraints
H-atom parameters constrained
3
Ê
Áꢆmax = 0.27 e A
3
Ê
0.17 e A
Áꢆmin
=
Table 1
Selected bond lengths (A) for (Ia).
Ê
P1ÐC1
O2ÐC2
O4ÐC3
1.7388 (19)
1.208 (2)
1.211 (2)
C1ÐC3
C1ÐC2
1.436 (3)
1.443 (3)
1
centre at (12, 1, ) (B in Fig. 8). Finally, weak hydrogen bonds
Table 2
Hydrogen-bond geometry (A, ) for (Ia).
2
ꢀ
Ê
with atom O2 as an acceptor link these chains, with their [100]
translated homologues, into a two-dimensional structure
parallel to the (011) plane.
Cg3 is the centroid of the C31±C36 ring.
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
P1Á Á ÁO1
2.799 (2)
3.030 (2)
3.657 (3)
3.430 (3)
Experimental
P1Á Á ÁO4
C5ÐH5CÁ Á ÁCg3
0.96
0.93
2.89
2.56
138
156
The title isopropyl and tert-butyl diesters of triphenylphosphonium
ylides, viz. (Ia), (Ib), (IIa) and (IIb), were synthesized by trans-
Â
ylidation (Cristau & Plenat, 1994). The general procedure was as
C23ÐH23Á Á ÁO4i
Symmetry code: (i) x; y ‡ 1; z ‡ 1.
ꢁ
o408 Castaneda et al.
C25H25O4P, C26H27O4P, C26H27O4P and C27H29O4P
Acta Cryst. (2008). C64, o405±o410
Ä

organic compounds
Compound (Ib)
Table 5
Selected bond lengths (A) for (IIa).
Ê
Crystal data
3
P1ÐC1
O2ÐC2
O4ÐC3
1.7451 (16)
1.211 (2)
1.188 (2)
C1ÐC3
C1ÐC2
1.434 (2)
1.447 (2)
Ê
V = 2318.0 (5) A
C26H27O4P
Mr = 434.45
Z = 4
Mo Kꢁ radiation
Monoclinic, P21=c
1
Ê
a = 12.5175 (16) A
ꢄ = 0.15 mm
T = 140 (5) K
Ê
b = 9.1555 (12) A
Ê
c = 20.351 (3) A
0.18 Â 0.16 Â 0.16 mm
Table 6
Hydrogen-bond geometry (A, ) for (IIa).
ꢂ = 96.342 (2)ꢀ
ꢀ
Ê
Cg3 is the centroid of the C31±C36 ring.
Data collection
Bruker SMART CCD area-detector
diffractometer
19001 measured re¯ections
5252 independent re¯ections
2713 re¯ections with I > 2ꢅ(I)
Rint = 0.053
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
P1Á Á ÁO1
2.729 (2)
2.986 (2)
3.788 (3)
3.424 (2)
3.255 (3)
3.511 (3)
3.455 (3)
P1Á Á ÁO4
C5ÐH5CÁ Á ÁCg3
C23ÐH23Á Á ÁO2i
C25ÐH25Á Á ÁO4ii
C34ÐH34Á Á ÁO2iii
C13ÐH13Á Á ÁO3iv
0.96
0.93
0.93
0.93
0.93
2.99
2.56
2.39
2.59
2.54
141
154
155
171
166
Re®nement
R[F2 > 2ꢅ(F2)] = 0.057
wR(F2) = 0.140
S = 0.86
5252 re¯ections
300 parameters
7 restraints
H-atom parameters constrained
3
Ê
Áꢆmax = 0.33 e A
1
2
1
2
3
Symmetry codes: (i) x; y; z ‡ 1; (ii) x ‡ 1; y; z ‡ 1; (iii) x
;
y ‡ 12; z
;
Ê
0.27 e A
Áꢆmin
=
(iv) x ‡ 12; y ‡ 12; z
.
1
2
Table 3
Selected bond lengths (A) for (Ib).
Compound (IIb)
Ê
Crystal data
P1ÐC1
O2ÐC2
O4ÐC3
1.741 (2)
1.188 (3)
1.228 (3)
C1ÐC3
C1ÐC2
1.425 (3)
1.441 (3)
C27H29O4P
Mr = 448.47
Triclinic, P1
ꢃ = 105.338 (2)ꢀ
V = 1209.55 (16) A
Z = 2
3
Ê
Ê
a = 8.9616 (7) A
b = 10.3589 (8) A
Mo Kꢁ radiation
ꢄ = 0.14 mm
T = 140 (5) K
0.20 Â 0.18 Â 0.14 mm
1
Ê
Ê
c = 14.5644 (11) A
ꢁ = 97.388 (2)ꢀ
ꢂ = 107.705 (3)ꢀ
Table 4
Hydrogen-bond geometry (A, ) for (Ib).
ꢀ
Ê
Cg3 is the centroid of the C31±C36 ring.
Data collection
Bruker SMART CCD area-detector
diffractometer
10154 measured re¯ections
5183 independent re¯ections
3919 re¯ections with I > 2ꢅ(I)
Rint = 0.019
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
P1Á Á ÁO1
2.953 (2)
2.809 (2)
3.663 (4)
3.323 (3)
P1Á Á ÁO4
Re®nement
C5ÐH5CÁ Á ÁCg3
0.96
0.93
2.93
2.40
134
172
C25ÐH25Á Á ÁO4i
R[F2 > 2ꢅ(F2)] = 0.050
wR(F2) = 0.136
S = 1.03
5183 re¯ections
299 parameters
3 restraints
H-atom parameters constrained
Symmetry code: (i) x ‡ 2; y ‡ 12; z ‡ 21.
3
Ê
Áꢆmax = 0.35 e A
3
Ê
0.16 e A
Áꢆmin
=
Compound (IIa)
Table 7
Selected bond lengths (A) for (IIb).
Crystal data
Ê
3
Ê
C26H27O4P
Mr = 434.45
Monoclinic, P21=n
V = 2402.0 (5) A
Z = 4
P1ÐC1
O2ÐC2
O4ÐC3
1.7383 (14)
1.2080 (18)
1.2174 (19)
C1ÐC3
C1ÐC2
1.429 (2)
1.448 (2)
Mo Kꢁ radiation
1
Ê
Ê
a = 9.8140 (7) A
ꢄ = 0.14 mm
T = 140 (5) K
b = 15.889 (2) A
Ê
c = 15.404 (2) A
0.16 Â 0.16 Â 0.16 mm
ꢂ = 90.413 (2)ꢀ
Table 8
Hydrogen-bond geometry (A, ) for (IIb).
ꢀ
Ê
Data collection
Cg2 is the centroid of the C21±C26 ring and Cg3 is the centroid of the C31±
C36 ring.
Bruker SMART CCD area-detector
diffractometer
19840 measured re¯ections
5292 independent re¯ections
4501 re¯ections with I > 2ꢅ(I)
Rint = 0.021
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
P1Á Á ÁO1
2.877 (2)
2.877 (2)
3.944 (2)
3.712 (2)
3.168 (2)
Re®nement
P1Á Á ÁO4
C5ÐH5CÁ Á ÁCg3
C34ÐH34Á Á ÁCg2i
C12ÐH12Á Á ÁO2ii
Symmetry codes: (i) x; y ‡ 1; z; (ii) x 1; y; z.
0.96
0.93
0.93
3.07
2.90
2.57
152
146
123
R[F2 > 2ꢅ(F2)] = 0.052
wR(F2) = 0.144
S = 1.04
284 parameters
H-atom parameters constrained
3
Ê
Áꢆmax = 0.59 e A
3
Ê
0.45 e A
5292 re¯ections
Áꢆmin
=
ꢁ
Acta Cryst. (2008). C64, o405±o410
Castaneda et al.
C25H25O4P, C26H27O4P, C26H27O4P and C27H29O4P o409
Ä

organic compounds
Table 9
ꢀ±ꢀ contacts (A, ) for (IIb).
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: AV3152). Services for accessing these data are
described at the back of the journal.
ꢀ
Ê
Cg1 and Cg3 are as de®ned in Fig. 7. DA is the mean slippage angle, IPD is the
mean interplanar distance and CCD is the centre-to-centre distance (for
details, see Janiak, 2000).
References
DA (ꢀ)
Ê
IPD (A)
Ê
CCD (A)
Group 1
Group 2
Allen, F. H. (2002). Acta Cryst. B58, 380±388.
Bachrach, S. M. & Nitsche, C. I. (1994). The Chemistry of Organophosphorus
Compounds, edited by F. R. Hartley, Vol. 3, ch. 4, pp. 273±302. Chichester:
Wiley.
Cg1
Cg3
Cg1ii
Cg3i
0
0
3.386
3.663
3.974 (2)
3.937 (2)
Bruker (2001). SMART-NT (Version 5.624) and SAINT-NT (Version 6.04).
Bruker AXS Inc., Madison, Wisconsin, USA.
Symmetry codes: (i) x; 1 y; z; (ii) 1 x; 2 y; 1 z.
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2554.
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Acta Cryst. C61, o496±o499.
H atoms were placed in idealized positions and allowed to ride on
Ê
their parent atoms, with CÐH = 0.93 (aromatic), 0.97 (CH2) or 0.96 A
(CH3), and with Uiso(H) = 1.2Ueq(C) for aromatic H and CH2, or
1.5Ueq(C) for CH3.
CastanÄeda, F., Jullian, C., Bunton, C. A., Garland, M. T. & Baggio, R. (2007).
Acta Cryst. C63, o267±o270.
Some terminal groups were disordered over two different orien-
tations and accordingly were re®ned with a geometrically restrained
split model; these were the methoxy group in (Ia) and the ethoxy
groups in (Ib) and (IIb). The re®nements converged to ®nal occu-
pancies of 0.66 (2)/0.34 (2), 0.616 (4)/384 (4) and 0.747 (4)/0.253 (4)
using two, seven and three restraints, respectively.
CastanÄeda, F., Silva, P., Garland, M. T., Shirazi, A. & Bunton, C. A. (2008).
Phosphorus Sulfur Silicon Relat. Elem. Submitted.
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Â
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For all four compounds, data collection: SMART-NT (Bruker,
2001); cell re®nement: SAINT-NT (Bruker, 2001); data reduction:
SAINT-NT; program(s) used to solve structure: SHELXS97 (Shel-
drick, 2008); program(s) used to re®ne structure: SHELXL97
(Sheldrick, 2008); molecular graphics: SHELXTL-NT (Sheldrick,
2008); software used to prepare material for publication: SHELXTL-
NT and PLATON (Spek, 2003).
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The authors acknowledge the Spanish Research Council
(CSIC) for providing a free-of-charge licence to the
Cambridge Structural Database (Allen, 2002).
ꢁ
o410 Castaneda et al.
C25H25O4P, C26H27O4P, C26H27O4P and C27H29O4P
Acta Cryst. (2008). C64, o405±o410
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