Iodophosphane selenides: Building blocks for supramolecular soft-soft chain, helix, and base-pair arrays

Article abstract of DOI:10.1002/(SICI)1521-3765(19990104)5:1<385::AID-CHEM385>3.0.CO;2-D

Structure determinations on di-tert-butyliodophosphane selenide 1 and c- hexyldiiodophosphane selenide 2 reveal that intermolecular donor-acceptor interactions between nucleophilic selenium atoms and electrophilic iodine atoms lead to chains or helices that are interconnected by Se ··· Se contacts, building up layer structures. In the adduct of 1 with molecular iodine (3), 1 acts as donor through Se(=P) and as weak acceptor through I(- P). These interactions lead to base-pair-like dimers [tBu₂P(Se-I-I)I]₂ that are interconnected by additional Se ··· Se contacts.

Full text of DOI:10.1002/(SICI)1521-3765(19990104)5:1<385::AID-CHEM385>3.0.CO;2-D

FULL PAPER
Iodophosphane Selenides: Building Blocks for Supramolecular Soft ± Soft
Chain, Helix, and Base-Pair Arrays
Jörg Jeske, Wolf-W. du Mont,* and Peter G. Jones[a]
Abstract: Structure determinations on di-tert-butyliodophosphane selenide 1 and c-
hexyldiiodophosphane selenide 2 reveal that intermolecular donor± acceptor
Keywords: donor± acceptor interac-
interactions between nucleophilic selenium atoms and electrophilic iodine atoms
tions ´ iodine ´ iodophosphane se-
lead to chains or helices that are interconnected by Se ´´´ Se contacts, building up
lenides ´ selenium ´ supramolecular
layer structures. In the adduct of 1 with molecular iodine (3), 1 acts as donor through
chemistry
ˆ
Se( P) and as weak acceptor through I( P). These interactions lead to base-pair-like
dimers [tBu2P(Se I I)I]2 that are interconnected by additional Se ´´´ Se contacts.
Introduction
Iodine atoms adjacent to s4l5-phosphonium centres behave as
soft electrophiles. With iodide anions as nucleophiles, anion ±
cation donor± acceptor I ´´´ I interactions of I with electro-
‡
philic iodine atoms of iodophosphonium ions RnPI4 leadÐ
n
depending on the number of iodine atoms bound to phos-
phorusÐto spoke structures with approximately linear P I ´´´
I units (n ˆ 3; R3PI2),[1±5] to rings, helices and zigzag chains (n
ˆ 2, R2PI3),[6±9] or to interpenetrating puckered layers and 3D
Scheme 1. Se I and I I donor± acceptor interactions in the neighborhood
of s4l5 phosphorus.
networks (n ˆ 1, RPI4).[10] The above kind of cation ± anion
soft ± soft donor± acceptor interactions could lead to a novel
kind of soft ± soft building blocks for supramolecular chem-
istry, when soft donor and acceptor functions are expressed in
reactions of tri-tert-butylphosphane selenide with varying
amounts of iodine revealed that the ability of this phosphane
one type of molecule. Such bifunctional molecules should
selenide to act as a soft donor towards iodine is very similar to
adopt properties related to base-pairing building blocks.
that of iodide ions.[13] Compared with tBu3P Se, Ph3P Se is a
ˆ
ˆ
Selenium is a suitable soft donor atom for designing such
building blocks, because its electronegativity is very similar to
that of iodine and because selenium ligands are better donors
towards iodine than are related sulfur ligands.[11] We selected
slightly weaker donor towards molecular iodine, and amino-
[14]
ˆ
phosphane selenides (R2N)3P Se are slightly better donors.
The simplest combination of a s4l5-P I acceptor function
ˆ
and a P Se donor function within one molecule should be
ˆ
the phosphane selenide (P Se) group as the first selenium
ˆ
expressed in iodophosphane selenides RnP( Se)I3 n; how-
donor function designed to coordinate to iodine atoms
ever, structures of this type of molecule have not yet been
bonded to s4l5 phosphorus (Scheme 1). Phosphane selenides
determined. As building blocks for intermolecular interac-
[11, 12]
ˆ
R3P Se are known to react with molecular iodine,
but
ˆ
tions, we regard compounds R2P( Se)I as soft ± soft equiv-
structure determinations on products from such reactions
have been carried out only recently.[13, 14]
ˆ
alents of phosphinic acids R2P( O)OH (Scheme 2). Depend-
ing on their organic substituents, the latter crystallise as
P O ´´´ H O P-bridged dimers or polymers.
solid phosphoryl chloride and bromide exhibit weak inter
A study of the structures of the products tBu3PSe I I,
[15±17]
ˆ
Similarly,
‡
‡
[(tBu3PSe)2I] [I3] and [{(tBu3PSe)2I}2] [2/x(I5)x] from the
[a] Prof. W.-W. du Mont, J. Jeske, Prof. P. G. Jones
Institut für Anorganische und Analytische Chemie
der Technischen Universität Braunschweig, Postfach 3329
D-38023 Braunschweig (Germany)
Fax: (‡49)531-391-5387
Scheme 2. Phosphinic acid derivatives interacting with hard and soft
donors and acceptors.
E-mail: w.du-mont@tu-bs.de
Chem. Eur. J. 1999, 5, No. 1
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385

W.-W. du Mont et al.
FULL PAPER
ˆ
molecular P O ´´´ X P interactions (O ´´´ Cl 305 pm, O ´´´ Br
325 pm) leading to infinite chains.[18] For iodophosphane
ˆ
selenides, we expected a novel type of P Se ´´´ I P bridging.
Like O ´´´ H O bridges, Se ´´´ I P bridges should be close to
linear. In the following, syntheses and the first solid-state
structures of iodophosphane selenides and of an iodophos-
phane selenide adduct with molecular iodine are presented.
Results and Discussion
Syntheses and NMR spectra: Crystalline iodophosphane
ˆ
ˆ
selenides (tBu)2P( Se)I (1) and c-C6H11P( Se)I2 (2) were
prepared from the related iodophosphanes with elemental
selenium. It was sufficient to prepare the iodophosphanes in
situ from chloro- or bromophosphanes with excess sodium
iodide in toluene and to add selenium powder to the crude
iodophosphanes. Yellow 1 was recrystallised from hexane,
red-orange 2 crystallised from toluene solution. Addition of
iodine to a toluene solution of 1 furnished the iodine adduct
[(tBu)2P(Se I I)I] (3); diffusion of hexane into the toluene
solution furnished brown-black single crystals of pure 3.
Figure 1. Molecular structure and secondary contacts of 1 (H atoms are
omitted). Symmetry operators for equivalent atoms: x, y 0.5, z ‡ 0.5
(A); x, y ‡ 0.5, z ‡ 0.5 (B).
being approximately linearly coordinated, is consistent with
the expectations for typical Se(donor) !I(acceptor) interac-
tions [aP1-I1-Se2 158.62(4)8, aP2-I2-Se1' 167.68(4)8; sym-
metry operator: x, y 0.5, z ‡ 0.5].
ˆ
Similar reactions of 2 and the related compound tBuP( Se)I2
with iodine in dichloromethane led to insoluble, amorphous
black solids that are apparently not straightforward 1:1
adducts.
A surprising feature of the structure of 1 are additional
intermolecular contacts between the two symmetry-equiva-
lent selenium atoms Se2 and Se2' (Se2 ´´´ Se2' 359.4(2) pm;
symmetry operator: x, y ‡ 1, z ‡ 1); the P Se ´´´ Se P
arrangement is not far from linear [aP Se Se 173.73(6)8].
This additional secondary cross-link between the chains
arising from PSe ´´´ IP interactions is associated with the
above-mentioned slight elongation of d(P2 Se2) compared
with d(P1 Se1): Se1 does not participate in intermolecular
Se ´´´ Se interactions (Figure 1). Cross-linking of the PSe ´´´ IP
chains by PSe ´´´ SeP interactions leads to layers that are
separated by regions containing the tert-butyl groups from
adjacent layers (Figure 2).
In the 31P-NMR spectra of 1 ± 3, satellites arising from
1
77
31
[19]
ˆ
J( Se, P) are well-resolved. Compared with tBu3P Se,
the magnitude of 1J(77Se,31P) of iodophosphane selenide 1
(775 Hz) is about 60 Hz larger. The couplings of diiodophos-
phane selenides 2 (755 Hz) and tBuP( Se)I2 (747 Hz), how-
ˆ
ever, are about 20 ± 30 Hz smaller than that of 1. As in the case
of the reactions of R3PSe with iodine,[13, 14] coordination of 1
with iodine leads to a decrease of 1J(77Se,31P) and to an upfield
shift of d31P, and no separate signals of free and iodine-
coordinated phosphane selenide were resolved in 31P NMR
spectrum at room temperature, that is, 3 is kinetically labile.
The NMR parameters of 3 are solvent-dependent: the change
from dichloromethane to benzene (in which it is less soluble)
Because crystals of the related diiodophosphane selenide
ˆ
tBuP( Se)I2 were not suitable for a structure determination,
leads to a further significant decrease of J(77Se,31P) and to a
the comparable c-hexyl compound 2 was isolated and inves-
1
slight deshielding of the 31P nucleus.
tigated. Like 1, compound 2 contains a P Se donor function
ˆ
ˆ
ˆ
[2: d(P Se) 209.2(2) pm: shorter than both P Se bonds in 1];
however, two electrophilic iodine atoms are attached to the
phosphorus atom of 2. As in compound 1, L-shaped P Se ´´´
I P donor± acceptor interactions (Se ´´´ I: 347.59(8) pm) form
one motif of the supramolecular structure of 2 and P Se ´´´
Se P contacts (361.23(14) pm) the other (Figure 3).
Structure determinations: Iodophosphane selenide 1 crystal-
lises with two independent molecules in the unit cell. Bond
angles and lengths within the two molecules of 1 are very
similar; the most significant deviation between molecules I
and II of 1 is the slightly larger P Se distance in molecule II.
(P1 Se1: 210.4(2) pm, P2 Se2: 212.1(2) pm). P I bond
Interconnection of two stacks of molecules of 2 by L-shaped
P Se ´´´ I P bridges leads to staircaselike helices; layers are
built up by connection of these helices through Se ´´´ Se
contacts. In contrast to 1, all selenium atoms of 2, but only one
iodine atom of each molecule participate in building up layers
from helices. The stacking of these layers allows cyclohexyl
groups and iodine atoms from terminal P I groups to
approach in a herringbone pattern, creating domains of
iodine atoms and of cyclohexyl groups from two adjacent
layers (Figure 4, p. 388).
‡
lengths are very similar to those of {[(tBu)2PI2] [I] }n, which
is a chain polymer as a result of P I ´´´ I ´´´ I P bridging.[7]
Compound 1 can be described as a helical chainlike polymer if
intermolecular P Se ´´´ I P contacts are taken into consider-
ation (Figure 1). These secondary Se ´´´ I contacts (Se1 I2'
369.04(9) and Se2 I1 384.38(9) pm; symmetry operator: x,
y ‡ 0.5, z ‡ 0.5) are only slightly shorter than the sum of the
van der Waals radii of selenium and iodine,[20] and are even
longer than those found in the diselenide ± diiodine interca-
lation compound [(TIP2Se2)2I2].[21] However, the L-shaped
As expected, iodophosphane selenides exhibit intermolec-
ular L-shaped P Se ´´´ I P donor± acceptor interactions;
ˆ
geometry of the P Se ´´´ I P bridges, with the iodine atoms
386
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Chem. Eur. J. 1999, 5, No. 1

Iodophosphane Selenides
385±389
The structure of the iodine
adduct 3 can to a first approx-
imation be described as a mo-
lecular 1:1 complex of the io-
dophosphane selenide 1 donor
with iodine as acceptor. Com-
pared with tBu3PSe I I, the
Se I bond length within the
monomeric unit of 3 is slightly
longer and the I I bond length
is slightly shorter, that is, 1 is a
somewhat weaker donor than
tBu3PSe[13] towards molecular
iodine and should be compared
with Ph3PSe[14] (Table 1, p. 388).
However, the monomeric units
of 3 exhibit secondary I ´´´ I con-
tacts [d(I1 I3') 370.32(11) pm;
symmetry operator:
x ‡ 1,
Figure 2. Packing diagram of 1.
y ‡ 1, z] that lead to the for-
mation of dimeric units, which
can alternatively be regarded as
two molecules of 1 bridged by
two molecules of molecular
iodine (Figure 5, p. 388). In this
respect, the resulting ten-mem-
bered ring of 21 and 2I2 mole-
cules, all acting as donors and as
acceptors, shows a coordination
pattern that is very similar to
that of the dimeric adduct of
Ph2Se2 with I2.[23]
Between the ten-membered
cyclic dimers, additional PSe ´´´
SeP contacts (382.9(2) pm, re-
sembling those in 1 and 2) and
further I ´´´ I contacts [d(I3-I3')
379.83(14) pm; symmetry oper-
ator: x ‡ 2, y ‡ 1, z] lead
to a layer structure through the
base-pair-like dimers (Figure 6,
p. 388).
Figure 3. Molecular structure and secondary contacts of 2 (H atoms are omitted). Symmetry operators for
equivalent atoms: x 0.5, y ‡ 1.5, z (A); x ‡ 0.5, y ‡ 0.5, z (B); x ‡ 0.5, y ‡ 1.5, z (C).
Conclusion
however, in the case of 1 and 2 these interactions do not lead
to base-pair-like dimers, but to chains. If the factor preventing
dimers in solid 1 and 2 were unfavourable steric interactions
between linearly coordinated acceptor iodine atoms of two
adjacent L-shaped moieties, relief from this kind of strain
might be provided by increasing the distance between the two
donor± acceptor systems. Such an increase of distance should
be achieved by inserting iodine molecules between two
molecules of 1. From the solid-state structures of iodine[22]
and of the dimeric adduct of Ph2Se2 with I2[23] it is known that
I2 molcules may act as both acceptor and donor at the same
time: when one iodine atom behaves as electrophile, the
donor properties of the other iodine atom become more
pronounced.
Addition of selenium to alkyl(iodo)phosphanes RnPI3 n led to
the isolation of the first iodophosphane selenides
ˆ
RnP( Se)I3 (1: R ˆ tBu, n ˆ 2; and 2: R ˆ c-Hex, n ˆ 1)
n
and the determination of their structures. Increasing the
number of iodine atoms bonded to phosphorus (at the
expense of alkyl groups) from one to two leads to a slight
ˆ
decrease of the P Se bond length. Solid 1 and 2 exhibit
ˆ
intermolecular P Se(donor) !I P(acceptor) [n !s*] inter-
actions leading to infinite chains. Addition of iodine to 1 can
be understood as insertion of an iodine molecule into such a
donor± acceptor system, leading to Se(donor) !I I !I P-
(acceptor) brigding. From two such bridges, a novel soft ± soft
base pair (dimeric 3) is built up. Becoming two-coordinate by
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387

W.-W. du Mont et al.
FULL PAPER
Figure 5. Molecular structure and secondary contacts of 3 (H atoms are
omitted).
Figure 4. Packing diagram of 2.
Table 1. Selected bond lengths and secondary contacts (<400 pm) of compounds
with C P Se I moieties.
Experimental Section
d(P Se)
d(P I)
d(I I)
d(Se I)
d(Se Se)
31P NMR spectra were run on a Bruker AM 200 spectrometer
(81.0 MHz) with CH2Cl2 as solvent, if not otherwise specified. J values
are given in Hz. Melting points were determined on a Kofler hot-stage
microscope. All values are uncorrected. Elemental analyses were
carried out by the Analytisches Laboratorium des Instituts für
Anorganische und Analytische Chemie, Technische Universität
Braunschweig. Solvents were dried by distillation under nitrogen
from the appropriate drying agent, glassware was flame-dried and
cooled under a stream of nitrogen.
tBu2P(Se)I (1)
210.4(2)
212.1(2)
209.2(2)
245.35(14)
244.6(2)
244.3(2)
243.9(2)
243.1(2)
369.04(9)
384.38(9) 359.4(2)
347.59(8) 361.23(14)
c-HexP(Se)I2 (2)
tBu2P(SeI I)I (3)
217.3(2)
287.83(9) 278.19(11) 382.9(2)
379.83(14)
370.32(11)
tBu3PSeI I[13]
219.50(10)
219.39(11)
215.6(4)
291.44(8) 276.02(8) 352.70(12)
291.42(10) 276.51(11)
‡
[13]
[(tBu3PSe)2I] [I3]
Ph3PSeI I[14]
288.1(2)
280.3(3)
ˆ
weak P Se !I interactions, selenium
atoms of 1 and 2 tend to exhibit further
ˆ
ˆ
weak P Se ´´´ Se P interactions that link
the base-pair dimers of 3 and cross-link
the chains of 1 and 2. In compound 1, the
Se ´´´ Se interaction is associated with
slight elongation of the participating
ˆ
P Se bonds. This type of Se ´´´ Se inter-
action, which is not observed in ordinary
phosphane selenides, indicates a certain
electrophilicity of two-coordinate sele-
nium atoms bonded to phosphonium
centres; it is also related to Se ´´´ Se
interactions in trigonal selenium and in
certain solid diselenides.[21, 24] For future
molecular architecture with iodophos-
phane selenides, besides packing of the
organic substituents, directed L-type
ˆ
P Se !I P and approximatedly linear
ˆ
ˆ
P Se ´´´ Se P interactions should be
taken into consideration.
Figure 6. Packing diagram of 3.
388
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Chem. Eur. J. 1999, 5, No. 1

Iodophosphane Selenides
385±389
2
Di-tert-butyliodophosphane selenide (1): Di-tert-butylchlorophosphane
(9.03 g 50 mmol) was added to a suspension of sodium iodide (14.9 g,
100 mmol) in toluene (50 mL). After stirring for 4 d the solid was removed
by filtration, half of the solvent was evaporated under reduced pressure,
and powdered grey selenium (3.20 g, 40 mmol) was added. After stirring
for 3 d unconsumed selenium was removed by filtration, the solvent was
evaporated under reduced pressure, and the yellowish residue was
recrystallised from hexane. Compound 1 (11.45 g, 65%) was isolated as
yellow crystals. M.p. 838C; 31P NMR: d ˆ 126 (s, 1J(77Se,31P) ˆÆ 775 Hz);
C8H18PSeI (351.07): calcd C 27.37, H 5.17; found C 29.11, H 5.28.
anisotropically by full-matrix least squares on jF j . Rigid methyl groups
were employed. The final wR(F2) was 0.1167, with conventional
R(F) 0.0426, for 124 parameters (highest peak 1633, deepest hole
1626 epm 3).
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie for financial support. Dipl.-Chem. F. Ruthe assisted
in preparing the manuscript.
Crystal structure determination of 1:[24] C8H18IPSe, M ˆ 351.05, P21/c, a ˆ
756.9(2),
b ˆ 1375.7(4),
c ˆ 2388.1(2) pm,
b ˆ 90.334(10)8,
Vˆ
2.4864(9) nm3, Z ˆ 8, 1calcd ˆ 1.876 Mgm 3, m ˆ 5.583 mm 1, Tˆ 143 K. A
yellow prism (0.75 Â 0.40 Â 0.30 mm) was mounted in inert oil. 4517 re-
flections were measured (2V 6 ± 508, w/V scans, 9 < h < 9, 16 < k < 12,
28 < l < 28; index ranges not complete, data are composed of independ-
ent set plus some Friedel pairs) with MoKa radiation (graphite monochro-
mator) on a Stoe STADI-4 diffractometer. After absorption correction (psi
scans, min. and max. transmission: 0.386, 0.646), 4372 reflections were
unique (Rint ˆ 0.0279) and 4368 were used for all calculations (program
SHELXL-93[26]). The structure was solved by direct methods and refined
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2
anisotropically by full-matrix least squares on jF j . Rigid methyl groups
were employed. The final wR(F2) was 0.0942, with conventional
R(F) 0.0396, for 211 parameters and 96 restraints (highest peak 1399,
deepest hole 1556 epm 3).
[6] M. Bätcher, W.-W. du Mont, S. Pohl, W. Saak, Abstracts of Papers, XI.
Int. Conf. on Phosphorus Chemistry, Tallinn, 1989, Abstract 1 ± 23;
Phosphorus, Sulfur, Silicon 1990, 49/50, 147.
c-Hexyldiiodophosphane selenide (2): A bromochlorocyclo-c-hexylphos-
phane mixture (18.36 g, about 80 mmol, Cl:Br ratio about 2:1), which had
been obtained by distillation from the reaction of c-hexylmagnesium
bromide with phosphorus trichloride, was added to a suspension of sodium
iodide (30 g, 200 mmol) in toluene (40 mL). The mixture was heated under
reflux for 1 h. After further 18 h at room temperature, the solid was
removed by filtration, and powdered grey selenium (6.40 g, 80 mmol) was
added. After 1 d at room temperature, the mixture was heated to 908C for
30 min to complete the reaction. After filtration of the hot solution, slow
cooling led to crystallisation of 18.23 g (about 50%) 2 as red-orange prisms.
M.p. 748C; 31P NMR: d ˆ 79 (s, 1J(77Se,31P) ˆÆ 755 Hz); C6H11PSeI2
(446.90): calcd C 16.13, H 2.48; found C 17.84, H 2.66.
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[9] R. Binnewies, R. Kopitzky, unpublished results; R. Kopitzky, Ph.D.
thesis, Universität Hannover, 1996.
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Saak, M. Bätcher, Inorg.Chem. 1994, 33, 1502.
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Inorg. Chem. 1963, 2, 192.
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du Mont, P. G. Jones, Abstracts of Papers, VII. Int. Conf. on the
Chemistry of Selenium and Tellurium, Vaalsbroek Castle (The
Netherlands)/Aachen (Germany), 1997.
Crystal structure determination of 2:[24] C6H11I2PSe, M ˆ 446.88, Pbca, a ˆ
812.3(2), b ˆ 1289.9(2), c ˆ 2143.7(3) pm, Vˆ 2.2460(6) nm3, Z ˆ 8, 1calcd
ˆ
2.643 Mgm 3, m ˆ 8.925 mm 1, Tˆ 173 K. A orange prism (0.38  0.28 Â
0.20 mm) was mounted in inert oil. 3442 reflections were measured (2V 6 ±
[14] S. M. Godfrey, S. L. Jackson, C. A. McAuliffe, R. G. Pritchard, J.
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[15] D. Fenske, R. Mattes, J. Löns, K.-F. Tebbe, Chem. Ber. 1973, 106, 1139.
[16] M. E. Druyan, A. H. Reis, E. Gebert, S. W. Peterson, G. W. Mason,
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[18] A. F. Wells, Structural Inorganic Chemistry, Clarendon, Oxford, 1984,
p. 848.
[19] W.-W. du Mont, Z. Naturforsch. B 1985, 40, 1453.
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4847.
[22] H. Krebs, Angew. Chem. 1958, 70, 615; F. van Bolhuis, P. B. Koster, T.
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[24] Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC-101426. Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax:
(‡44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
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p. 199.
508, w scan,
9 < h < 6,
15 < k < 13,
3 < l < 25; index ranges not
complete, data are composed of independent set plus some Friedel pairs)
with MoKa radiation (graphite monochromator) on a Siemens P4 diffrac-
tometer. After absorption correction (psi scans, min. and max. trans-
mission: 0.411, 0.953), 1976 reflections were unique (Rint ˆ 0.0373) and were
used for all calculations (program SHELXL-93[26]). The structure was
solved by direct methods and refined anisotropically by full-matrix least
2
squares on jF j . All hydrogen atoms were refined with a riding model. The
final wR(F2) was 0.0731, with conventional R(F) 0.0296, for 92 parameters
and 48 restraints (highest peak 858, deepest hole 681 epm 3).
Di-tert-butyliodophosphane selenide-diiodine (3): Iodine (0.76 g,
3.0 mmol) was added to a solution of 1 (1.20 g, 3.4 mmol) in toluene
(10 mL). Stirring was continued until all iodine had dissolved. Subsequently
10 mL of hexane were carefully added and allowed to diffuse into the
toluene solution. This led to the separation of black-brown crystals of 3
(1.45 g, 80%). M.p. 968C (decomp); 31P NMR (CH2Cl2): d ˆ 117 (s,
1J(77Se,31P) ˆÆ 696 Hz), 31P NMR (C6H6): d ˆ 129 (s, 1J(77Se,31P) ˆ
Æ 600 Hz); C8H18PSeI3 (604.88): calcd C 15.89, H 3.00; found C 15.23, H 2.83.
Crystal structure determination of 3:[24] C8H18I3PSe, M ˆ 604.85, P21/c, a ˆ
926.6(2), b ˆ 1132.8(3), c ˆ 1512.3(3) pm, b ˆ 91.165(8)8, Vˆ 1.5870(6) nm3,
Z ˆ 4, 1calcd ˆ 2.532 Mgm 3, m ˆ 8.271 mm 1, Tˆ 173 K. A brown plate
(0.75 Â 0.38 Â 0.03 mm) was mounted in inert oil. 4022 reflections were
measured (2V 6 ± 558, w scans, 11 < h < 12, 14 < k < 11, 19 < l < 19;
index ranges not complete, data are composed of independent set plus
some Friedel pairs) with MoKa radiation (graphite monochromator) on a
Siemens P4 diffractometer. After absorption correction (psi scans, min. and
[26] G. M. Sheldrick, SHELXL-93,
A Program for Crystal Structure
max. transmission: 0.313, 0.818), 3384 reflections were unique (Rint
0.0319) and 3379 reflections were used for all calculations (program
SHELXL-93[26]). The structure was solved by direct methods and refined
ˆ
Refinement, Göttingen, 1993.
Received: April 22, 1998 [F1111]
Chem. Eur. J. 1999, 5, No. 1
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