Hexaphenyl-hexa-phosphinane benzene solvate

Article abstract of DOI:10.1107/S0108270107067248

In the mol-ecular crystal of hexa-phenyl-hexa-phosphinane benzene solvate, C₃₆H₃₀P₆·C₆H₆, representing the trigonal form of phospho-benzene as a solvate, the six-membered ring of P atoms adopts a chair conformation wherein the six phenyl groups are located in equatorial positions. The mol-ecules [mol-ecular symmetry (C 3i )] are stacked infinitely along the c-axial direction.

Full text of DOI:10.1107/S0108270107067248

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
A displacement ellipsoid drawing of (I) is shown in Fig. 1
with the corresponding numbering scheme. The centers of
both the (PPh)6 and the benzene molecules are located on the
threefold axis as well as the symmetry center, and thus the ring
ISSN 0108-2701
Hexaphenylhexaphosphinane benzene
solvate
Jan J. Weigand,a* Andreas Deckenb and Neil Burfordc
aWWU Munster, Institut fur Anorganische und Analytische Chemie, Corrensstrasse
È
È
28/30, Munster D-48149, Germany, bDepartment of Chemistry, University of New
È
Brunswick, Fredericton, New Brunswick, Canada E3B 6E2, and cDepartment of
Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B4H 4J3
Correspondence e-mail: jweigand@uni-muenster.de
entities are constructed from a single unique PÐPh fragment
for the (PPh)6 molecule and a unique C-atom position for the
solvate. The molecules of the cyclohexamer contain an all-
phosphorus ring framework adopting a chair conformation
with the phenyl groups located in equatorial positions, as
required by the 3 symmetry. X-ray investigation shows that the
Received 25 August 2007
Accepted 16 December 2007
Online 22 January 2008
Ê
In the molecular crystal of hexaphenylhexaphosphinane
benzene solvate, C36H30P6ÁC6H6, representing the trigonal
form of phosphobenzene as a solvate, the six-membered ring
of P atoms adopts a chair conformation wherein the six phenyl
groups are located in equatorial positions. The molecules
[molecular symmetry 3 (C3i)] are stacked in®nitely along the c-
axial direction.
PÐP length of 2.2207 (8) A does not signi®cantly differ from
those reported for the other four crystalline forms, with an
Ê
average value of 2.237 (3) A. The average aromatic CÐC
bond length found in the phenyl ring attached to the P atom is
Ê
1.384 (2) A and the C atoms of the phenyl group do not
deviate signi®cantly from a regular hexagon. Similar to the
trigonal form of solvent-free (PPh)6 (Daly, 1965), a slight
deviation of the molecule from 3m (D3d) symmetry is
observed. The PÐPÐC values differ slightly by 1.62 (5)ꢀ from
each other, the phenyl ring makes an angle of 7.6 (3)ꢀ with the
3 axis of the puckered central ring, and the P atom deviates
Comment
Oligophosphines (Baudler & Glinka, 1994), such as hexa-
phenylhexaphosphinane (PPh)6, provide analogies with
cycloalkanes since the CR2 methylene unit is isolobal with the
phosphine (PR) unit. The familiar cationic phosphonium
center is also isolobal with this unit and is obtained, for
example, through methylation reactions of phosphines
(Burford et al., 2005). catena-Phosphorus cations represent a
newly developing family of compounds and we are currently
establishing a comprehensive series of high yielding and facile
methods for the synthesis of prototypical polyphosphonium
salts from oligophosphines (Weigand et al., 2007). Recently, we
reported the synthesis and crystal structures of cyclohexa-
phosphorus dications, containing a P6 homocycle composed of
two phosphonium centers (1,4-positions) and four phosphine
centers (Weigand et al., 2006). In further investigations, we
attempted the synthesis of hexaphenylhexaphosphinane,
(PPh)6, according to a modi®cation of the procedure of
Henderson et al. (1963). The (PPh)6 hexamer exists in at least
four crystalline forms (Daly, 1965, 1966; Daly & Maier, 1964,
1966). However, for the title solvate, (I), only the cell
dimensions of the trigonal crystal system were reported, with
Ê
from the phenyl ring plane by 0.041 (2) A. Distances and
angles for the benzene molecule are also presented in Table 1.
Ê
Ê
a = 12.68 A and c = 20.96 A (Daly & Maier, 1964). Therefore,
we have reinvestigated the crystal structure of hexaphenyl-
hexaphosphinane benzene solvate, which is, to our knowledge,
only the second crystallographic characterization of a
solvated cyclooligophosphine after (2,5-Me2C6H3)6P6ÁCHCl3
(Schmutzler et al., 1993).
Figure 1
A view of the molecular structure of (I), showing the atom-labeling
scheme. Displacement ellipsoids are drawn at the 50% probability level
and H atoms are shown as small spheres of arbitrary radii. [Symmetry
1
3
codes: (i) x y, x, z + 1; (ii) y, x + y, z + 1; (iii) x y + 13, x
,
z + 23;
1
2
(iv) y + , x + y+23, z + .]
3
3
o64 # 2008 International Union of Crystallography
DOI: 10.1107/S0108270107067248
Acta Cryst. (2008). C64, o64±o66

organic compounds
Speci®c interactions between the (PPh)6 molecules and the
benzene solvent molecules are not observed. All inter-
molecular distances are longer than the sum of the appro-
priate van der Waals radii.
theless, this packing is surprisingly similar to that of the
unsolvated trigonal (PPh)6. The difference lies mainly in a
more effective layer stacking of the latter caused by the
absence of solvent molecules.
Fig. 2 presents the packing arrangement of the molecules in
the unit cell, depicted along the b and c axes. All hexamers in
this structure are positioned with their molecular threefold
axes parallel to the c axis. The packing of the cyclo-
polyphosphine molecules in (I) corresponds to layers in a
hexagonal arrangement. These body-centered packing layers
have an ABC sequence separated by the benzene molecules,
which also form layers and are located in the `octahedral
holes'. Thus, the benzene is surrounded by six individual
(PPh)6 molecules arranged in a pseudo-octahedron. Short van
Experimental
All manipulations were performed under an inert atmosphere of
argon. To a solution of PhPCl2 (179 mg, 1 mmol) in benzene (6 ml)
was added PhP(SiMe3)2 (254 mg, 1 mmol) in one portion and the
solution stirred for 6 h. From the reaction mixture, very small
amounts of colorless block-shaped crystals were obtained after two
weeks and crystallographically identi®ed as the title compound, (I).
The analytical data for the 31P{1H} NMR shift (ꢀ = 26.4 p.p.m.) is in
agreement with that previously reported (Henderson et al., 1963).
Ê
der Waals contacts of less than 4.0 A are observed between the
phenyl groups and the solvent molecule. However, there are
Crystal data
Ê
no contacts of less than 4.0 A involving the P atom. Never-
C36H30P6ÁC6H6
Mr = 726.53
Trigonal, R3
Z = 3
Mo Kꢁ radiation
ꢂ = 0.32 mm
T = 173 (1) K
1
Ê
a = 12.533 (5) A
Ê
c = 20.763 (6) A
0.45 Â 0.40 Â 0.15 mm
3
Ê
V = 2824.4 (18) A
Data collection
Bruker SMART1000/P4
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.871, Tmax = 0.954
6465 measured re¯ections
1426 independent re¯ections
1279 re¯ections with I > 2ꢃ(I)
Rint = 0.048
Re®nement
R[F2 > 2ꢃ(F2)] = 0.030
wR(F2) = 0.088
S = 1.10
73 parameters
H-atom parameters constrained
3
Ê
Áꢄmax = 0.48 e A
3
Ê
0.18 e A
1426 re¯ections
Áꢄmin
=
Table 1
Selected geometric parameters (A, ).
ꢀ
Ê
P1ÐC1
1.8446 (15)
P1ÐP1i
P1iÐP1ÐP1ii
2.2207 (8)
98.17 (2)
C1ÐP1ÐP1i
C1ÐP1ÐP1ii
97.83 (5)
96.21 (5)
Symmetry codes: (i) x y; x; z ‡ 1; (ii) y; x ‡ y; z ‡ 1.
H atoms were included in calculated positions, with distances ®xed
Ê
at 0.95 A and isotropic displacement parameters corresponding to
1.2Ueq of the carrier C atom. The data set was truncated at 2ꢅ = 55ꢀ as
only statistically insigni®cant data were present above the limit. The
largest residual electron-density peaks were found within 0.83 and
Ê
1.02 A of atoms C1 and P1, respectively.
Data collection: SMART (Bruker, 1999); cell re®nement: SMART;
data reduction: SAINT (Bruker, 2006); program(s) used to solve
structure: SHELXS97 (Sheldrick, 1997); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics:
DIAMOND (Brandenburg, 2000); software used to prepare material
for publication: SHELXTL (Sheldrick, 2000).
The authors thank the Natural Sciences and Engineering
Research Council of Canada, the Killam Foundation, the
Canada Research Chairs Program and the Alexander von
Humboldt-Stiftung (Humboldt Fellowship for JJW, Lynen
Return Program) for funding.
Figure 2
Views along (a) the b axis and (b) the c axis, showing the packing of (I) in
its molecular structure. H atoms have been omitted for clarity. Light gray
denotes phenyl C atoms, medium gray denotes benzene C atoms and
black denotes P atoms.
ꢁ
Acta Cryst. (2008). C64, o64±o66
Weigand et al. C36H30P6ÁC6H6 o65

organic compounds
Daly, J. J. (1965). J. Chem. Soc. pp. 4789±4799.
Daly, J. J. (1966). J. Chem. Soc. pp. 428±439.
Daly, J. J. & Maier, L. (1964). Nature (London), 203, 1167±1168.
Daly, J. J. & Maier, L. (1966). Nature (London), 208, 383±384.
Henderson, W. A., Epstein, M. Jr & Seichter, F. S. (1963). J. Am. Chem. Soc.
85, 2462±2466.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GA3071). Services for accessing these data are
described at the back of the journal.
Schmutzler, R., Heuer, L. & Schomburg, D. (1993). Phosphorus Sulfur Silicon,
83, 149±156.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of
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o66 Weigand et al.
C36H30P6ÁC6H6
Acta Cryst. (2008). C64, o64±o66