Reactions of Ph4Se4Br4 with tertiary phosphines. Structural isomerism within a series of R3PSe(Ph)Br compounds

Article abstract of DOI:10.1039/b516784a

The synthesis and characterisation of Ph₄Se₄Br ₄ (1) directly from the reaction of Ph₂Se₂ with dibromine is reported. The solid-state structure of 1 consists of four PhSeBr units linked by weak seleni

Full text of DOI:10.1039/b516784a

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Reactions of Ph4Se4Br4 with tertiary phosphines. Structural isomerism within
a series of R3PSe(Ph)Br compounds
Nicholas A. Barnes, Stephen M. Godfrey,* Ruth T. A. Halton, Imrana Mushtaq, Robin G. Pritchard and
Shamsa Sarwar
Received 11th November 2005, Accepted 1st February 2006
First published as an Advance Article on the web 14th February 2006
DOI: 10.1039/b516784a
The synthesis and characterisation of Ph4Se4Br4 (1) directly from the reaction of Ph2Se2 with
dibromine is reported. The solid-state structure of 1 consists of four PhSeBr units linked by weak
˚
selenium–selenium bonds [3.004(2)–3.051(2) A] into a Se4 square, and is structurally analogous to the
previously reported Ph4Te4I4. The reactions of Ph4Se4Br4 with a variety of tertiary phosphines have
been undertaken, resulting in the formation of compounds of formula R3PSe(Ph)Br. X-Ray
crystallographic analysis of three of the compounds reveals different structural isomers. Ph3PSe(Ph)Br
˚
(2) is a charge-transfer (CT) compound [Se–Br 3.0020(8) A], with an essentially linear P–Se–Br bond
angle, 172.15(4)◦ and T-shaped geometry at selenium. Me3PSe(Ph)Br (5) also contains the selenium
atom in a T-shaped geometry, consistent with a CT formulation, although the Se–Br distance of
˚
3.327(3) A is considerably longer than observed for 2. In contrast, Cy3PSe(Ph)Br (6) is an ionic
phosphonium salt, [Cy3PSePh]Br with no short Se–Br interactions. Geometry at selenium is bent, as
expected for an ionic compound. These results are discussed with reference to the previously reported
iodo-compounds Ph3PSe(Ph)I and [(Me2N)3PSe(Ph)]I.
Introduction
The structural characterisation of dihalogen derivatives of organic
molecules containing a group 16 donor atom has attracted
considerable interest from a variety of research groups.1–4 It has
now been clearly established that the solid-state structure of
the resultant adducts depends upon the nature of the organic
groups bound to the group 16 atom, the group 16 atom itself
and the identity of the dihalogen. Thioamide,5 selenoamide6 and
tertiary phosphine sulfide7 and selenide8 systems have all been
extensively studied. In addition, structural studies of thioethers,9
selenoethers10 and telluroethers11 have been reported, with the ma-
jority of reports focusing upon selenium/tellurium(IV) R2EX2,12
or REX3 systems.13 Related REX species (E = Se, Te), also
exhibit structural diversity. For example, the reaction of Ph2Se2
with diiodine produces a compound of stoichiometry “PhSeI”,
the solid-state structure of which is a centrosymmetric dimer,
(Ph2Se2I2)2, Fig. 1.14 One selenium atom acts as a donor towards
Fig. 1 Solid-state structures of (Ph2Se2I2)2,14 and Ph4Te4I4.15
ionic product results, [(Me2N)3PSePh]I, exhibiting bent geometry
at the selenium centre [P–Se–C 94.1(3)◦]. A weak contact to the
˚
iodide anion of 3.825(1) A is observed, with a P–Se–I angle
of 114.5(2)◦.16 This phenylselenylphosphonium salt is analogous
to the [R3PSeMe]OTf compounds obtained when phosphine
selenides are reacted with methyl triflate,17 and the magnitude
˚
iodine, [Se–I 2.992 A], whilst the other behaves as a weak acceptor,
˚
[Se–I 3.588 A]. In contrast, reaction of Ph2Te2 with diiodine
1
of the J(SeP) coupling (494 Hz) is also consistent with values
produces “PhTeI” which displays an unusual “square” structure,
Ph4Te4I4, in the solid state, Fig. 1. Unlike (Ph2Se2I2)2 it is not
a CT compound, but instead contains individual PhTeI units
linked together through weak tellurium–tellurium bonds [Te–Te
observed for the triflate salts. In contrast, reaction with the less
basic Ph3P produces a CT compound, Ph3PSe(Ph)I with a near
linear P–Se–I angle of 176.09(5)◦, and a Se–I bond of 3.2564(5)
15
˚
˚
A. Here, the selenium centre displays T-shaped geometry, P–Se–
2.799(2)–2.830(2) A].
C 93.59(9)◦, C–Se–I 88.84(5)◦.18 In view of the often observed
structural sensitivity of group 16 halogen compounds to the
identity of the halogen we have now extended our studies to the
reactivity of the analogous phenylselenyl bromide with phosphine
donors. Herein, we report the solid-state structure of the reagent
“PhSeBr” and its subsequent reaction with a variety of tertiary
phosphines of differing basicities and steric bulk to investigate the
effect these factors have on the resulting structures.
We have previously reported that (Ph2Se2I2)2 may bereacted with
donor molecules such as tertiary phosphines, with cleavage of the
selenium–selenium bonds to form compounds of stoichiometry
R3PSe(Ph)I. With the very basic tertiary phosphine (Me2N)3P, an
School of Chemistry, The University of Manchester (North Campus),
Manchester, PO Box 88, UK M60 1QD. E-mail: stephen.godfrey@
manchester.ac.uk; Fax: +44 (0)161 200 4559; Tel: +44 (0)161 200 4525
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The Se–Se–Se angles are however close to the anticipated 90◦ for a
square motif, ranging between 89.92(6) and 90.51(6)◦, forming an
essentially planar ring. The conformation of the Se4 square is such
that the Se–Br bonds lie in the Se4 plane with two phenyl rings lying
above the plane, and two below. The selenium atom therefore lies
in a pseudo-trigonal bipyramidal “see-saw” geometry. The weak
Se–Se bonds in 1 are considerably longer than the Se–Se bonds in
Results and discussion
Solid-state structure of Ph4Se4Br4
Phenylselenyl bromide, PhSeBr, is a familiar synthetic reagent
which is commercially available and used in a wide variety of
organic transformations.19 The synthesis of PhSeBr is achieved
by the direct reaction of Ph2Se2 with dibromine in a 1 : 1 ratio
in diethyl ether. The solid was recrystallised from refluxing 1 :
1 dichloromethane–diethyl ether solution. On cooling to room
temperature a large crop of amber crystals were obtained, one of
which was selected for analysis by single-crystal X-ray diffraction.
The structure of the material was revealed to be Ph4Se4Br4 (1), as
shown in Fig. 2.
20
14
˚
˚
Ph2Se2 [Se–Se 2.29(1) A], and in Ph2Se2I2 [Se–Se 2.347 A].
The extended structure of 1 is further linked into a planar sheet
(again as observed for Ph4Te4I4) through long-range bromine–
bromine contacts, Fig. 3. In this fashion a network consisting of
small Se4 squares and larger, weakly linked Br4 squares, is formed.
The Br4 squares contain weak bromine–bromine linkages, ranging
˚
from 3.693(2) to 3.798(2) A, all of which are around, or slightly
larger than the sum of the van der Waals radii for two bromine
˚
atoms (3.70 A). The sheets are remarkably planar and further
stack on top of one another, as shown in Fig. 4.
Fig. 3 Extended solid-state structure of Ph4Se4Br4 (1) showing Se–Se
and Br–Br contacts. Phenyl rings are omitted for clarity. Selected contact
◦
˚
distances (A) and angles ( ): Br(1_3)–Br(2) 3.798(2), Br(2)–Br(3_3)
3.716(2), Br(3_3)–Br(4) 3.693(2), Br(4)–Br(1_3) 3.749(2); Br(2)–Br(1_3)–
Br(4) 88.99(8), Br(2)–Br(1_3)–Se(1_3) 151.61(8), Br(4)–Br(1_3)–Se(1_3)
119.40(8).
Fig. 2 Molecular structure of Ph4Se4Br4 (1). Thermal ellipsoids are
shown at the 30% probability level, and hydrogen atoms are omitted for
◦
˚
clarity. Selected bond lengths (A) and angles ( ): Se(1)–Se(2) 3.014(2),
Se(2)–Se(3) 3.048(2), Se(3)–Se(4) 3.051(2), Se(4)–Se(1) 3.004(2), Se(1)–
Br(1) 2.390(2), Se(2)–Br(2) 2.391(2), Se(3)–Br(3) 2.381(2), Se(4)–Br(4)
2.381(2), Se(1)–C(1) 1.929(15), Se(2)–C(7) 1.901(14), Se(3)–C(13)
1.914(14), Se(4)–C(19) 1.895(14); Br(1)–Se(1)–Se(4) 172.61(9), Br(1)–
Se(1)–Se(2) 94.60(7), C(1)–Se(1)–Br(1) 94.9(4), C(1)–Se(1)–Se(2) 97.0(4),
C(1)–Se(1)–Se(4) 89.8(4), Se(2)–Se(1)–Se(4) 90.51(6), Se(1)–Se(2)–Se(3)
89.82(6), Se(2)–Se(3)–Se(4) 88.99(6), Se(3)–Se(4)–Se(1) 89.96(6).
1
The 77Se{ H} NMR spectrum of 1 displays a resonance at
866.5 ppm, consistent with literature reports for PhSeBr (867
ppm),21 and strongly suggests that Ph4Se4Br4 breaks down to
1
monomeric “PhSeBr” units in solution, the 77Se{ H} NMR
chemical shift being typical for selenium(II) RSeBr compounds.
This contrasts with the situation observed for Ph2Se2I2 where a
peak is observed at 485.3 ppm in CDCl3, close to the chemical shift
of Ph2Se2 (461 ppm),22 suggestive of the presence of an equilibrium
between Ph2Se2 and Ph2Se2I2.
That the solid-state structure displayed by PhSeBr is a “square”
motif, analogous to Ph4Te4I4, is perhaps surprising since we had
expected a centrosymmetric dimer, isostructural with du Mont’s
(Ph2Se2I2)2.14 Ph4Se4Br4 is structurally similar to the previously
reported Ph4Te4I4, as four PhSeBr units are linked together by
weak selenium–selenium bonds to form a Se4 square. There is slight
asymmetry in the Se–Se distances, with two shorter bonds, Se(4)–
Reactivity of Ph4Se4Br4 with tertiary phosphines
In view of the different solid-state structures exhibited by
Ph4Se4Br4 and (Ph2Se2I2)2 it was of interest to compare their
reactivity towards a series of tertiary phosphines, and to determine
whether adducts of formula R3PSe(Ph)Br could be formed,
˚
˚
Se(1) 3.004(2) A/Se(1)–Se(2) 3.014(2) A, and two longer bonds,
˚
˚
Se(2)–Se(3) 3.048(2) A/Se(3)–Se(4) 3.051(2) A, being observed.
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NMR spectrum suggests that the bromide analogue 7 exhibits the
same ionic structure as [(Me2N)3PSePh]I. Since the magnitude of
1
the J(SeP) coupling for 4 to 9 is consistent with similar values
reported for Se–P single bonds in phosphonium cations,17,23 it
seems likely that all these compounds display an ionic structure in
CDCl3 solution. We were unable to observe any selenium satellites
for the resonances of compounds 2 and 3, and since a similar
situation was observed for the CT compound Ph3PSe(Ph)I,18 we
believe that 2 and 3 may also adopt CT structures in the solid state
and do not ionise in solution, since the J(SeP) coupling indicative
of the phosphonium salts should be observed. Compounds 2 and
3 appear to be fluxional in solution at room temperature, with a
rapid equilibrium, R3PSePhBr ↔ R3P + PhSeBr, being set up, with
1
resultant loss of J(SeP) coupling. Similarly, the 77Se{ H} NMR
spectra of compounds 4–9 display resonances between 146.7 and
329.8 ppm, whilst no signal could be resolved for 2 or 3.
In order to ascertain whether the structural assignments sug-
gested by the spectroscopic evidence were correct we decided
to crystallographically characterise three of the R3PSe(Ph)Br
compounds. Crystals of Ph3PSe(Ph)Br, 2, were prepared from
refluxing a diethyl ether–dichloromethane (1 : 1) solution of the
solid, which upon cooling to room temperature produced a large
crop of yellow crystals. The structure obtained is shown in Fig. 5.
Fig. 4 Stacks of the sheet networks built up from Se4 and Br4 squares in
Ph4Se4Br4. Phenyl rings are omitted for clarity.
analogous to the R3PSe(Ph)I [R3 = Ph3, N(Me2)3] systems.16,18
We therefore decided to undertake a comprehensive study of the
reaction of Ph4Se4Br4 with a range of tertiary phosphines, see
Scheme 1.
Scheme 1 Synthesis of R3PSe(Ph)Br compounds from Ph4Se4Br4.
Ph4Se4Br4 was reacted with four molar equivalents of tertiary
phosphine in anhydrous diethyl ether for 24 h. In all cases the
red-brown colour of Ph4Se4Br4 faded rapidly with precipitation
of white solids. Elemental analyses in all cases supported an
Fig. 5 Molecular structure of Ph3PSe(Ph)Br (2). Thermal ellipsoids
˚
are shown at the 30% probability level. Selected bond lengths (A)
and angles (◦): Se(1)–P(1) 2.2601(14), Se(1)–Br(1) 3.0020(8), Se(1)–C(19)
1.929(5), P(1)–C(1) 1.797(4), P(1)–C(7) 1.786(5), P(1)–C(13) 1.796(5);
P(1)–Se(1)–Br(1) 172.15(4), P(1)–Se(1)–C(19) 93.29(17).
1
empirical formula of R3PSe(Ph)Br. The 31P{ H} NMR spectrum
of each of the compounds was recorded in CDCl3 solution, the
shifts ranging from 33.8 to 62.2 ppm. The resonances for all
the compounds except 2 and 3 display selenium satellites, the
magnitude of the coupling varying between 412 and 497 Hz.
Ph3PSe(Ph)Br is the first R3PSe(Ph)Br compound to be crystal-
lographically characterised, and exhibits a CT motif, analogous
to Ph3PSe(Ph)I, which is consistent with the spectroscopic data.
The P(1)–Se(1)–Br(1) angle of 172.15(4)◦ is slightly distorted from
linearity, cf. P–Se–I 176.09(5)◦ for Ph3PSe(Ph)I.18 The Se(1)–Br(1)
1
The 31P{ H} NMR spectrum for (Me2N)3PSe(Ph)Br, 7, displays a
signal at 61.6 ppm, 1J(SeP) = 494 Hz, the chemical shift and J(SeP)
coupling being identical to that observed for the ionic compound,
1
[(Me2N)3PSePh]I.16 The presence of the same cation in the 31P{ H}
bond in 2 [3.0020(8) A] lies well within the sum of the van der
˚
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˚
Me3P yielded a CT adduct, and suggests that steric effects may
also be important in determining the structural motif adopted
by R3PSe(Ph)X adducts. There is evidence from the extended
structure, Fig. 7, that the bromine atom participates in extensive
hydrogen bonding with five different protons from methyl groups.
Individual molecules pack head-to-tail, with five short Br · · · H
Waals radii for a bromine and selenium atom (3.75 A), although is
considerably lengthened compared to Ph4Se4Br4. The P(1)–Se(1)
distance of 2.2601(14) A is consistent with a phosphorus–selenium
single bond, and similar to the P–Se bond of 2.2585(9) A observed
˚
˚
for Ph3PSe(Ph)I.18 Geometry at selenium is T-shaped [P(1)–Se(1)–
C(19) 93.29(17)◦, C(19)–Se(1)–Br(1) 89.57(16)◦]. There are four
short Br · · · H interactions present in the extended structure,
˚
interactions varying between 2.80 and 2.98 A. Two of the
˚
interactions are from methyl protons of adjacent stacks whilst the
other three are from the next molecule in the same stack. These
interactions appear to drive the molecular packing and are set up
by the linear P–Se–Br arrangement and may contribute towards
the preference of the CT motif. It appears from the spectroscopic
data that the CT structure of 5 does not survive in solution and
ionisation to [Me3PSePh]Br occurs, in contrast to 2. This is likely
to be a consequence of the much weaker selenium–bromine bond
in 5, and suggests that the structural motif adopted by some of the
adducts is different between the solid state and solution.
varying between 2.79(7) and 2.96(7) A, compared to the sum of
˚
the van der Waals radii of bromine and hydrogen of 3.05 A.
For comparative purposes we also decided to recrystallise
Me3PSe(Ph)Br 5, a compound containing a much more basic
and less sterically demanding phosphine. Compound 5 was
of particular interest as a highly basic phosphine would be
expected to favour an ionic structure as suggested by the 31P{ H}
1
NMR data. Crystals of 5 were obtained from a refluxing 1 : 1
dichloromethane–diethyl ether solution of the solid, the structure
being shown in Fig. 6.
Fig. 6 Molecular structure of Me3PSe(Ph)Br (5). Thermal ellipsoids
˚
are shown at the 30% probability level. Selected bond lengths (A)
and angles (◦): Se(1)–P(1) 2.234(4), Se(1)–Br(1) 3.327(3), Se(1)–C(4)
1.912(17), P(1)–C(1) 1.778(17), P(1)–C(2) 1.79(2), P(1)–C(3) 1.82(2);
P(1)–Se(1)–Br(1) 176.30(12), P(1)–Se(1)–C(4) 93.8(6).
Fig.
7
Short Br · · · H interactions in the extended structure of
˚
Me3PSe(Ph)Br. Contact distances (A): Br(1) · · · H(1b) 2.86, Br(1) · · · H(2c)
Perhaps surprisingly, considering the basicity of Me3P, the
selenium atom in 5 adopts a T-shaped geometry which would
be consistent with a CT compound, similar to 2, in contrast to the
ionic structure suggested by the NMR data. The P(1)–Se(1)–Br(1)
angle in 5, [176.30(12)◦], is essentially linear, although the Se–Br
2.88, Br(1) · · · H(3c) 2.98, Br(1) · · · H(1a) 2.80, Br(1) · · · H(1c) 2.86.
In order to ascertain the effect of a very basic and bulky tertiary
phosphine, we recrystallised Cy3PSe(Ph)Br, 6, in an identical
manner to that described for 2 and 5; the crystal structure of
Cy3PSe(Ph)Br is illustrated in Fig. 8.
˚
bond [3.327(3) A] is considerably longer than that of 3.0020(8)
˚
A observed for 2, reflecting the increased donor strength of
Me3P compared with Ph3P. Similarly, the P(1)–Se(1) bond length
In contrast to 5, Cy3PSe(Ph)Br is an ionic species, [Cy3PSePh]Br,
with no close interaction between the selenium and bromine atoms
˚
[2.234(4) A] is typical for a P–Se single bond, although shorter than
˚
˚
the P–Se bond of 2.2601(14) A in Ph3PSe(Ph)Br. A shorter P–Se
(closest approach is 4.562 A). The ionic formulation is supported
1
bond and longer Se–Br bond would be consistent with the electron
donating properties of Me3P, although considering the ionic struc-
ture displayed by [(Me2N)3PSePh]I it was a surprise to observe that
by the 31P{ H} NMR data, d 62.2, 1J(SeP) = 438 Hz, and contrasts
the solid-state CT motif observed for 5. As expected, the selenium
atom adopts a bent geometry [C(19)–Se(1)–P(1) 102.20(18)◦], with
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phines used were purchased commercially (Aldrich/Strem), and
diphenyl diselenide (Aldrich) and bromine (Aldrich) were used
as supplied. Elemental analyses were performed by the UMIST
Chemistry Department Microanalytical service. Raman spectra
were recorded as solid samples on a Nicolet-Nexus combined FT-
1
IR/FT-Raman spectrometer. 1H and 13C{ H} NMR spectra were
recorded on a Bruker DPX400 spectrometer operating at 399.9
1
1
and 100.6 MHz, respectively. 31P{ H} and 77Se{ H} NMR spectra
were recorded on a Bruker DPX200 spectrometer operating at 81.8
and 38.2 MHz, respectively. Peak positions are quoted relative to
external TMS (1H/13C), Me2Se (77Se), and 85% H3PO4 (31P), using
the high frequency positive convention throughout.
Crystallographic details
Details of the structural analyses for compounds 1, 2, 5 and 6 are
summarised in Table 1. Compound 5 crystallised as stacks of ex-
tremely thin crystals. The crystal obtained was a non-merahedral
twin (twin axis 0 0 1, twin components ratio 6 : 4). Despite
allowing for the major twin component the diffraction pattern was
extremely heavily streaked, suggesting further misaligned minor
components. Despite omitting the 40 reflections with the worse
agreements the final R-factors still converged to relatively high
values. Diffraction data were recorded on a Nonius MAC3 CAD4
diffractometer (1), or Nonius j-CCD four-circle diffractometer
(2, 5, 6), using graphite-monochromated Mo-Ka radiation (k =
Fig. 8 Molecular structure of [Cy3PSePh]Br (6). Thermal ellipsoids are
shown at the 30% probability level, and hydrogen atoms are omitted for
◦
˚
clarity. Selected bond lengths (A) and angles ( ): Se(1)–P(1) 2.2260(16),
Se(1)–C(19) 1.953(7), P(1)–C(1) 1.836(6), P(1)–C(7) 1.841(7), P(1)–C(13)
1.816(7), Se(1) · · · Br(1) 4.562(8); P(1)–Se(1)–C(19) 102.20(18).
˚
a P–Se bond of 2.2260(16) A, considerably shorter than in 2, and
˚
slightly shorter than the P–Se distance [2.234(4) A] observed for 5,
reflecting the even higher basicity of Cy3P. There are no significant
interactions present in the crystal packing of 6.
˚
0.71073 A). Structural data were solved by direct methods, with
full-matrix least squares refinement on F2 using the SHELX-
97 program.24 Absorption corrections by the multiscan method
were applied with the SORTAV program. Non-hydrogen atoms
were refined with anisotropic thermal parameters. All hydrogen
atoms in compounds 1, 5 and 6 were allowed for as riding atoms.
In compound 2 the H atom (H2) on C2 was allowed for as a
riding atom and all others were refined isotropically. Figures were
generated using ORTEP-3 for Windows.25
Conclusion
In common with R3PSe(Ph)I compounds, the analogous series
of R3PSe(Ph)Br compounds exhibit structural isomerism (CT vs.
ionic) dependent upon the R groups bound to the phosphorus
centre. It would appear that electronic factors are important,
with highly basic phosphines favouring the ionic phosphonium
salt structure, whilst more weakly donating phosphines tend to
favour the CT structure. However, there are exceptions to this
generalisation, since the adduct with the highly basic trimethyl
phosphine, Me3PSe(Ph)Br adopts a CT structure in the solid
state, hence steric factors and crystal packing interactions may
CCDC reference numbers 279360 and 290834–290836.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b516784a
Synthesis of Ph4Se4Br4
be significant factors also. Finally, it appears that 31P{ H} NMR
1
Ph4Se4Br4, 1. 2.485 g (7.96 × 10−3 mol) of Ph2Se2 was dissolved
in 50 cm3 of freshly distilled diethyl ether under a nitrogen
atmosphere. Bromine (0.409 cm3, 7.96 × 10−3 mol) was added
dropwise to the solution which turned deep red–brown in colour.
The reaction was allowed to stir for 48 h, after which time the
solution was reduced in volume with gradual precipitation of
a red–brown solid which was isolated using standard Schlenk
techniques. Yield = 88.4%, mp 60–62 ◦C. Calc. for C24H20Se4Br4:
spectroscopy is a useful tool in predicting the structural motif
as the phosphonium salts appear to display J(SeP) coupling.
Caution must however be applied in assigning a structural motif
by spectroscopic data alone as CT adducts appear to fall into
two groupings: adducts with relatively strong selenium–halogen
bonds, such as 2 and 3, which are fluxional in solution, and
those with much weaker selenium–halogen interactions, such as 5
(and probably 4 also), where the weak bond is broken in solution
resulting in ionisation to phenylselenylphosphonium salts.
1
C, 30.5; H, 2.1; Br, 33.9; Found: C, 30.7; H, 2.0; Br, 33.7%. H
NMR (CDCl3): d 7.35–7.48 [m, Ar, 3H], 7.72–7.90 [m, Ar, 2H].
1
1
13C{ H} NMR (CDCl3): d 135.6 [s], 130.8 [s], 130.0 [s]. 77Se{ H}
NMR (CDCl3): d 866.5 [s]. Raman (cm−1): 3057, 1572, 1663, 1020,
997, 237, 206.
Experimental
Reagents and physical measurements
Most of the compounds described here are air and mois-
ture sensitive, therefore all procedures were carried out un-
der strict anhydrous and anaerobic conditions. Diethyl ether
was purchased commercially (BDH) and freshly distilled from
sodium/benzophenone ketyl before use. All the tertiary phos-
General method of synthesis of R3PSe(Ph)Br adducts, 2–9
To a dry diethyl ether solution containing one equivalent of
Ph4Se4Br4 was added four equivalents of the tertiary phosphine
with immediate loss of the deep red colouration and rapid
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Table 1 Crystallographic parameters for compounds 1, 2, 5 and 6
Ph4Se4Br4, 1
Ph3PSePhBr, 2
Me3PSePhBr, 5
Cy3PSePhBr, 6
Empirical formula
Mr
C6H5BrSe
235.97
C24H20BrPSe
498.24
C9H14BrPSe
312.04
C24H38BrPSe
516.38
Color, habit
Crystal system
Space group
Crystal size/mm
Amber, plate
Monoclinic
Cc (no. 9)
0.07 × 0.20 × 0.25
13.172(2)
13.183(2)
15.724(3)
101.47(2)
2675.9(8)
203(2)
Pale yellow, plate
Orthorhombic
Pbca (no. 61)
0.05 × 0.15 × 0.30
14.0231(7)
16.7384(8)
18.1228(8)
Pale yellow, plate
Monoclinic
P21/c (no. 14)
0.02 × 0.20 × 0.25
6.8100(11)
9.5140(18)
18.657(4)
92.469(7)
1207.7(4)
150(2)
Pale yellow, plate
Monoclinic
Cc (no. 9)
0.15 × 0.15 × 0.15
10.1891(4)
16.3115(6)
14.8944(6)
105.165(2)
2389.24(16)
150(2)
˚
a/A
˚
b/A
˚
c/A
b/◦
3
˚
V/A
T/K
Z
4253.9(3)
150(2)
8
1.556
0.71073
16
2.343
0.71073
11.470
4
4
Dc/Mg m−3
1.716
0.71073
6.502
608
3.68–25.25
3058 (1990)
0.1132/0.2876
0.135/0.3133
2.51, −2.131
1.436
0.71073
3.318
1064
2.87–27.47
9984 (4934)
0.0536/0.1175
0.0872/0.1329
0.798, −0.642
˚
k/A
l(Mo-Ka)/mm−1
F(000)
3.725
1984
1760
2h Range/◦
2.21–24.99
4663 (4663)
0.0541/0.1022
0.0859/0.1132
0.832, −0.727
3.67–26.34
20089 (4248)
0.0505/0.1034
0.0805/0.1174
0.781, −0.746
No. of reflections (unique)
R1/wR2 (I > 2rI)
R1/wR2 (all data)
−3
˚
Largest diff. peak, hole/e A
formation of white solids. The solutions were stirred for ca. 24 h,
before isolation via standard Schlenk techniques. Characterising
data for compounds 2–9 is given below.
5.1; Br, 26.1; P, 9.4%. 1H NMR (CDCl3): d 2.49 [d, CH3, 2J(PH) =
14.0 Hz], 7.37–7.45 [m, Ar], 7.48–7.57 [m, Ar], 7.60–7.67 [m, Ar].
1
13C{ H} NMR (CDCl3): d 14.3 [d, PCH3, 1J(PC) = 45.8 Hz], 118.9
[d, Ph, 2J(PC) = 8.0 Hz], 131.3 [d, Ph, J(PC) = 2.1 Hz], 132.1 [d,
Ph3PSe(Ph)Br, 2. Yield = 64.2%. White solid. Calc. for
1
Ph, J(PC) = 2.9 Hz], 138.0 [d, Ph, J(PC) = 2.9 Hz]. 31P{ H} NMR
C24H20PSeBr: C, 57.8; H, 4.0; Br, 16.1; P, 6.2; Se, 15.8; Found:
1
(CDCl3): d 37.3 [s, 1J(SeP) = 412 Hz]. 77Se{ H} NMR (CDCl3): d
1
C, 57.6; H, 4.0; Br, 15.7; P, 6.1; Se, 15.4%. H NMR (CDCl3): d
295.8 [d, 1J(SeP) = 412 Hz].
7.15 [m, Ar], 7.26 [m, Ar], 7.37 [m, Ar], 7.49–7.56 [m, Ar], 7.60–
1
7.66 [m, Ar], 7.75–7.80 [m, Ar]. 13C{ H} NMR (CDCl3): d 119.0 [d,
Cy3PSe(Ph)Br, 6. Yield = 80.1%. Cream solid. Calc. for
PPh3, 1J(PC) = 77.0 Hz], 120.1 [s, SePh], 129.4 [d, PPh3, 2J(PC) =
13.1 Hz], 129.5 [s, SePh], 132.0 [s, SePh], 134.2 [d, PPh3, 3J(PC) =
C24H38PSeBr: C, 55.8; H, 7.4; Br, 15.5; P, 6.0; Se, 15.3; Found:
1
C, 55.6; H, 7.1; Br, 15.4; P, 6.1; Se, 15.4%. H NMR (CDCl3): d
1
10.9 Hz], 136.1 [d, PPh3, 4J(PC) = 2.2 Hz], 138.3 [s, SePh]. 31P{ H}
0.99–1.33 [m, CH2], 1.46–1.50 [m, CH2], 1.63 [m, CH2], 1.76 [m,
CH2], 2.47 [m, PCH, 2J(PH) = 11.3 Hz, 3J(HH) = 10.2 Hz], 7.25
NMR (CDCl3): d 36.5 [s, br].
1
[m, Ar], 7.34 [m, Ar], 7.47 [m, Ar]. 13C{ H} NMR (CDCl3): d 25.3
Ph2MePSe(Ph)Br, 3. Yield = 58.3%. White solid. Calc. for
[s, PCHCH2CH2CH2], 26.4 [d, PCHCH2, 2J(PC) = 12.4 Hz], 28.1
[d, PCHCH2CH2, 3J(PC) = 4.4 Hz], 34.3 [d, PCH, 1J(PC) = 24.7
C19H18PSeBr: C, 52.3; H, 4.1; Br, 18.3; Found: C, 51.8; H, 4.2;
1
2
Br, 19.3%. H NMR (CDCl3): d 3.01 [d, CH3, J(PH) = 12.8
2
Hz], 117.9 [d, Ph, J(PC) = 7.3 Hz], 131.1 [s, Ph], 132.1 [s, Ph],
Hz], 7.18 [m, Ar], 7.35 [m, Ar], 7.44–7.62 [m, Ar], 7.65–7.83 [m,
1
138.2 [s, Ph]. 31P{ H} NMR (CDCl3): d 62.2 [s, 1J(SeP) = 438 Hz].
Ar], 7.90–7.92 [m, Ar]. 13C{ H} NMR (CDCl3): d 13.8 [d, PCH3,
1
1
77Se{ H} NMR (CDCl3): d 146.7 [d, 1J(SeP) = 438 Hz].
1J(PC) = 47.2 Hz], 119.4 [s, SePh], 120.2 [d, PPh2, 1J(PC) = 82.3
2
Hz], 130.7 [d, PPh2, J(PC) = 13.1 Hz], 131.0 [s, SePh], 131.8 [s,
(Me2N)3PSe(Ph)Br, 7. Yield = 73.2%. White solid. Calc. for
SePh], 133.4 [d, PPh2, 3J(PC) = 10.9 Hz], 135.6 [s, PPh2], 138.0 [s,
C12H23N3PSeBr: C, 36.1; H, 5.8; N, 10.5; Br, 20.1; P, 7.8; Se, 19.8;
SePh]. 31P{ H} NMR (CDCl3): d 35.8 [s, br].
1
1
Found: C, 36.5; H, 6.1; N, 10.3; Br, 20.1; P, 8.4; Se, 19.8%. H
3
NMR (CDCl3): d 2.75 [d, NCH3, J(PH) = 11.3 Hz], 7.34–7.49
PhMe2PSe(Ph)Br, 4. Yield = 73.6%. White solid. Calc. for
1
[m, Ar], 7.58–7.67 [m, Ar]. 13C{ H} NMR (CDCl3): d 38.7 [d,
C14H16PSeBr: C, 44.9; H, 4.3; Br, 21.4; Found: C, 44.5; H, 4.5; Br,
NCH3, 2J(PC) = 2.9 Hz], 119.6 [d, Ph, 2J(PC) = 8.0 Hz], 130.9 [d,
Ph, J(PC) = 2.9 Hz], 131.6 [d, Ph, J(PC) = 2.9 Hz], 138.0 [d, Ph,
1
2
21.1%. H NMR (CDCl3): d 2.57 [d, CH3, J(PH) = 13.9 Hz],
7.08 [m, Ar], 7.22–7.24 [m, Ar], 7.33–7.37 [m, Ar], 7.41–7.46 [m,
1
J(PC) = 4.4 Hz]. 31P{ H} NMR (CDCl3): d 61.6 [s, 1J(SeP) = 494
Ar]. 13C{ H} NMR (CDCl3): d 13.6 [d, PCH3, 1J(PC) = 45.8 Hz],
1
1
Hz]. 77Se{ H} NMR (CDCl3): d 288.6 [d, 1J(SeP) = 494 Hz].
2
1
119.4 [d, SePh, J(PC) = 6.5 Hz], 121.1 [d, PPh, J(PC) = 75.6
2
Hz], 130.2 [d, PPh, J(PC) = 13.8 Hz], 130.9 [s, SePh], 131.6 [s,
(Et2N)3PSe(Ph)Br, 8. Yield = 82.9%. White solid. Calc. for
SePh], 132.0 [d, PPh, 3J(PC) = 11.6 Hz], 135.2 [d, PPh, 4J(PC) =
C18H35N3PSeBr: C, 44.7; H, 7.2; N, 8.7; Br, 16.6; P, 6.4; Se, 16.4;
2.9 Hz], 137.8 [d, SePh, J(PC) = 2.2 Hz]. 31P{ H} NMR (CDCl3):
1
1
Found: C, 44.3; H, 7.4; N, 8.4; Br, 16.1; P, 6.3; Se, 15.8%. H
d 33.8 [s, 1J(SeP) = 427 Hz]. 77Se{ H} NMR (CDCl3): d 320.2 [d,
1
NMR (CDCl3): d 1.13 [t, NCH2CH3, 3J(HH) = 7.2 Hz], 3.15 [dq,
1J(SeP) = 427 Hz].
3
3
NCH2, J(PH) = 6.0 Hz, J(HH) = 7.2 Hz], 7.36–7.51 [m, Ar],
1
Me3PSe(Ph)Br, 5. Yield = 69.3%. Cream solid. Calc. for
7.62–7.69 [m, Ar]. 13C{ H} NMR (CDCl3): d 13.8 [d, NCH2CH3,
C9H14PSeBr: C, 34.6; H, 4.5; Br, 25.6; P, 9.9; Found: C, 35.2; H,
3J(PC) = 2.2 Hz], 41.5 [d, NCH2, 2J(PC) = 2.9 Hz], 120.6 [d, Ph,
1522 | Dalton Trans., 2006, 1517–1523
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2J(PC) = 8.7 Hz], 131.0 [d, Ph, J(PC) = 2.9 Hz], 131.7 [d, Ph,
8 See, for example: S. M. Godfrey, S. L. Jackson, C. A. McAuliffe and
R. G. Pritchard, J. Chem. Soc., Dalton Trans., 1997, 4499; S. M.
Godfrey, S. L. Jackson, C. A. McAuliffe and R. G. Pritchard, J. Chem.
Soc., Dalton Trans., 1998, 4201; E. Seppa¨la¨, F. Ruthe, J. Jeske, W.-W.
du Mont and P. G. Jones, Chem. Commun., 1999, 1471.
9 C. Rømming, Acta Chem. Scand., 1960, 14, 2145; A. J. Blake, R. O.
Gould, C. Radek and M. Schro¨der, J. Chem. Soc., Chem. Commun.,
1993, 1191; B. Regelman, K. W. Klinkhammer and A. Schmidt,
Z. Anorg. Allg. Chem., 1997, 623, 1633; A. J. Blake, F. Cristiani, F. A.
Devillanova, A. Garau, L. M. Gilby, R. O. Gould, F. Isaia, V. Lippolis,
S. Parsons, C. Radek and M. Schro¨der, J. Chem. Soc., Dalton Trans.,
1997, 1337; A. J. Blake, F. A. Devillanova, A. Garau, L. M. Gilby, R. O.
Gould, F. Isaia, V. Lippolis, S. Parsons, C. Radek and M. Schro¨der,
J. Chem. Soc., Dalton Trans., 1998, 2037; A. J. Blake, F. A. Devillanova,
A. Garau, F. Isaia, V. Lippolis, S. Parsons and M. Schro¨der, J. Chem.
Soc., Dalton Trans., 1999, 525.
1
J(PC) = 2.9 Hz], 137.6 [d, Ph, J(PC) = 3.6 Hz]. 31P{ H} NMR
1
(CDCl3): d 59.2 [s, 1J(SeP) = 494 Hz]. 77Se{ H} NMR (CDCl3): d
326.7 [d, 1J(SeP) = 494 Hz].
(Pr2N)3PSe(Ph)Br, 9. Yield = 67.5%. White solid. Calc. for
C24H47N3PSeBr: C, 50.8; H, 8.3; N, 7.4; Br, 14.1; P, 5.5; Se, 13.9;
1
Found: C, 50.9; H, 8.2; N, 7.1; Br, 14.4; P, 5.7; Se, 14.6%. 31P{ H}
1
1
NMR (CDCl3): d 59.4 [s, J(SeP) = 497 Hz]. 77Se{ H} NMR
(CDCl3): d 329.8 [d, 1J(SeP) = 497 Hz].
Acknowledgements
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We are grateful to EPSRC for a research studentship to R. T. A. H.,
and also for the UMIST FT IR-Raman facility (Grant No:
GR/M30135), NMR facility (Grant No: GR/L52246), and X-
ray facility (Research Initiative Grant).
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