Reactivity of a heterocyclic As-Se compound with metal salts: Syntheses and structures of the first copper complexes and of new alkali metal salts containing As-Se anions

Article abstract of DOI:10.1039/b715947a

The structures of the new compounds [Cu₈(Ph₂As ₂Se₂)₂(PhAsSe₂)₂(dppm) ₄] (1) (dppm = bis-diphenylphosphinomethane), [Cu₄(Ph ₂As₂Se₂)₂(PPh₃) ₄] (2), [{K(18-crown-6)}₂(PhAsSe₃)] (3), [Na₁₂(PhAsSe₃)₆(15-crown-5)₆] (4) and 1/×[Na₂(PhAsSe₃)(thf)(H₂O) ₃]_× (5) are reported. 2-5 were prepared by reactions of metal thiolates with [(PhAs)₂(μ-Se)(μ-Se₂)]. The Royal Society of Chemistry.

Full text of DOI:10.1039/b715947a

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PAPER
www.rsc.org/dalton | Dalton Transactions
Reactivity of a heterocyclic As–Se compound with metal salts: syntheses and
structures of the first copper complexes and of new alkali metal salts
containing As–Se anions†
Thomas Zell,a Weifeng Shi,a Robert Langer,a Lukasz Ponikiewskia and Alexander Rothenberger*a,b
Received 16th October 2007, Accepted 27th November 2007
First published as an Advance Article on the web 13th December 2007
DOI: 10.1039/b715947a
The structures of the new compounds [Cu8(Ph2As2Se2)2(PhAsSe2)2(dppm)4] (1) (dppm =
bis-diphenylphosphinomethane), [Cu4(Ph2As2Se2)2(PPh3)4] (2), [{K(18-crown-6)}2(PhAsSe3)] (3),
[Na12(PhAsSe3)6(15-crown-5)6] (4) and 1/×[Na2(PhAsSe3)(thf)(H2O)3]× (5) are reported. 2–5 were
prepared by reactions of metal thiolates with [(PhAs)2(l-Se)(l-Se2)].
These investigations are part of ongoing efforts aimed at
Introduction
providing novel wet-chemistry routes to semiconducting metal
Since the late 1950s it is known that minerals containing vari-
phases containing group 15/16 anions and are built on recent
results in related P–S and P–Se systems.29–33
ous mixtures of metals, arsenic and chalcogenide elements are
semiconducting compounds.1,2 This knowledge has driven many
of the activities in the field of metal chalcoarsenates. There
are several different synthetic research directions, which directed
towards the preparation of compounds containing the structural
fragment As–Se-metal. The oldest approach uses the ‘heat and
beat method’ and gave rise to copper and alkali metal salts
of various As–Se anions.3–5 More recently, the majority of the
compounds known in this area have been produced by solven-
tothermal methods.6–14 Another route to metal chalcoarsenates
was established by preparations in chalcoarsenate fluxes and in
salt melts.15–20 Synthesis of these compounds by wet-chemistry
methods is also well-documented.21–23 Most of the efforts involve
the fragmentation of binary As–Se compounds and incorporation
of As–Se fragments into transition metal complexes or direct
oxidation of As(III)–metal complexes to As(V)Se–metal complexes
by addition of Se.24–27
In contrast to the group 15 element phosphorus, which forms
organo-chalcogen transfer reagents with phosphorus in the oxida-
tion state +V ([ArP(S)(l-S)]2, Ar = 4-anisyl, Lawesson’s reagent;34
[tolSP(S)(l-S)]2, tol = C7H7, Davy’s reagent;35 [PhP(Se)(l-Se)]2,
Woollins’ reagent36,37), attempts to produce similar arsenic-based
reagents failed. Instead [(PhAs)2(l-Se)(l-Se2)] was obtained by
the reaction of phenylarsonic acid PhAs(O)(OH)2 with Na2Se in
concentrated hydrochloric acid (Scheme 1). The reaction generates
H2Se in situ and is safe to handle in the fume hood. Pure
[(PhAs)2(l-Se)(l-Se2)] was obtained by recrystallisation of the
solid residue from DME.
Similar to previously described investigations of the related As–
S system, investigations of the reactivity of [(PhAs)2(l-Se)(l-Se2)]
were performed (Scheme 2).38
Results and discussion
Here, an alternative synthetic pathway to the ones outlined above
is described, in which the neutral precursor [(PhAs)2(l-Se)(l-Se2)]
(Scheme 1) was reacted with copper and alkali metal thiolates,
providing a route to metal complexes containing the structural
fragment As–Se-metal.28
Scheme 2 Synthesis of 1–5 (dppm = bis-diphenylphosphino-methane).
Scheme 1 Synthesis of [(PhAs)2(l-Se)(l-Se2)].
These reactivity studies were initially aimed at fragmentation
reactions, breaking the As–Se bond and generating complexes with
Cu · · · Se contacts. From earlier experiments it is known however,
that phosphines play a crucial role in this type of reactions and
do not solely act as donor molecules to the coinage metal.38,39 The
main role of the phosphines in the reactions in Scheme 2 is the
deselenisation of the starting material. Tertiary phosphines PR3
are oxidised to R3P(Se) and arsenic-containing intermediates will
aInstitut fu¨r Anorganische Chemie der Universita¨t Karlsruhe, Geb. 30.45,
Engesserstr 15a, 76131, Karlsruhe, Germany
bInstitut fu¨r Nanotechnologie, Forschungszentrum Karlsruhe GmbH, Post-
fach 3640, 76021, Karlsruhe, Germany. E-mail: ar252@chemie.uni-
karlsruhe.de
† CCDC reference numbers 664248–664252. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b715947a
932 | Dalton Trans., 2008, 932–937
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act as ligands to metals present in the reaction. The fact that solid
samples of 1 and 2 were contaminated with tertiary phosphine se-
lenides and possibly other copper complexes explains that crystals
of 1 and 2 could only be characterised by X-ray crystallography.
The complexity of the reaction mixture became apparent when
only PEt3 was reacted with [(PhAs)2(l-Se)(l-Se2)]. In the EIMS of
a previously heated toluene solution of both compounds, a range
of ions was detected including [Ph3As3Se2]+. This indicates that
in the gas phase a variety of intermolecular reactions of arsenic-
containing species take place. The findings indicate further, that
the presence of an additional Cu salt makes matters even more
complicated. This was indeed the case in the reaction leading to
the formation of 1. X-Ray analysis of red crystals of 1 showed
that fragmentation of [(PhAs)2(l-Se)(l-Se2)] into the two anions
[Ph2As2Se2]2− and [PhAsSe2]2− had occurred (Fig. 1). The eight
Cu atoms present in [Cu8(Ph2As2Se2)2(PhAsSe2)2(dppm)4] (1) all
exhibit distorted tetrahedral coordination environments. They are
held together by a centrosymmetric arrangement of two inner
[PhAsSe2]2−ions and two terminal [Ph2As2Se2]2− anions. Se(1) and
Se(2) bridge two copper atoms each whilst Se(3) is coordinating
four copper atoms. The arsenic(III) centres As(1,1a) in 1 exhibit
a stereochemically active lone-pair. All other As atoms are four-
coordinated and involved in metal bonding with Cu–As distances
in the expected range.40
Fig. 2 Solid-state structure of 2 (C atoms of PPh3 are omitted;
only one of the two independent molecules is displayed). Selected
◦
˚
bond lengths (A) and angles ( ): As(1)–Se(1) 2.359(3) As(2)–Se(2)
2.355(3), As(1)–As(2) 2.444(3), As(2)–Cu(2) 2.441(3), Cu(1)–Se(1)
2.386(3), Cu(1)–Se(2A) 2.373(3), Cu(2)–Se(1A) 2.499(3), Cu(2)–Se(2A)
2.428(3) Cu(1)–P(1) 2.221(5), Cu(2)–P(2) 2.242(5), Se(1)–As(1)–As(2)
94.81(9), Se(2)–As(2)–Cu(2) 115.59(11), Se(2)–As(2)–As(1) 103.86(10),
Cu(2)–As(2)–As(1) 114.99(10), P(1)–Cu(1)–Se(2A) 116.89(17), P(1)–
Cu(1)–Se(1) 126.36(17), Se(2A)–Cu(1)–Se(1) 116.09(11), P(2)–Cu(2)–
Se(2A) 115.12(16), P(2)–Cu(2)–As(2) 112.10(17), Se(2A)–Cu(2)–As(2)
115.02(11), P(2)–Cu(2)–Se(1A) 109.00(16), Se(2A)–Cu(2)–Se(1A)
105.68(11), As(2)–Cu(2)–Se(1A) 98.12(10); A: −x + 1, −y, −z + 1.
[Cu4(Ph2As2S2)2(PEt3)4].38 The phenyl substituents at As(1,2) are
in gauche-conformation and form the organic shell of 2 together
with phenyl substituents of the tertiary phosphine. Se(1) and
Se(2) each bridge two Cu atoms. Cu(1) is three-coordinated by
Se atoms and one phosphine ligand. The lone-pair at As(1) is
not involved in metal coordination and is pointing towards the
periphery of the arrangement. Cu(2) is four-coordinated by As(2),
two Se atoms and one phosphine ligand. Crystals of 2 were of
poor quality and just about good enough to establish the structure
(Table 1). The formation of the new [Ph2As2Se2]2− and [PhAsSe2]2−
anions found in the solid-state structures of 1 and 2 shows that
deselenisation of [(PhAs)2(l-Se)(l-Se2)] by tertiary phosphines
may give rise to a greater variety of novel As–Se anions. The
downside of the synthetic route chosen clearly is its non-selectivity
and practical aspects (e.g., polymerisation of starting material,
decomposition into yet unknown compounds and elemental
selenium).
This prompted us to attempt similar reactions of [(PhAs)2(l-
Se)(l-Se2)] and alkali metal thiolates, now, in the absence of
tertiary phosphines. It turned out however, that side reactions still
do occur. Amongst solid and semi-solid precipitates which were
impossible to unequivocally identify, crystals of 3 were obtained
(Scheme 2, Fig. 3). 3 consists of a new example of rare se-
lenoarsenate dianions and two [K(18-cr.-6)]+ cations. [PhAsSe3]2−
anions coordinate potassium in bis-chelating mode analogous
to the alkali metal coordination in [Cs2(MeAsSe3)·2H2O].7,41
Remarkable is the formation of the [PhAsSe3]2− anion in 3 and
PhAs(StBu)2 (verified by GC-MS) from [(PhAs)2(l-Se)(l-Se2)] and
KStBu (Scheme 2). It is likely that the metal ion is playing a
crucial role in the nucleophilic break-up of [(PhAs)2(l-Se)(l-Se2)].
Fig. 1 Solid-state structure of 1 (C atoms of phosphine ligands are
◦
˚
omitted). Selected bond lengths (A) and angles ( ): Cu–P 2.212(2)–
2.263(3), Cu–Se 2.4132(14)–2.8787(15), As(3)–Cu(2A) 2.3861(14), Cu(2)–
As(3A) 2.3860(14), Cu(3)–As(2) 2.4523(13), As(1)–Se(1) 2.3645(12),
As(2)–Se(2) 2.3653(12), As(3)–Se(4) 2.3407(13), As(3)–Se(3) 2.3960(12),
As(1)–As(2) 2.4887(13), P–Cu–Se 106.41(7)–119.81(8), Se–Cu–Se
85.51(4)–123.94(5), As–Cu–Se 92.98(4)–122.87(5), P(4)–Cu(3)–As(2)
102.76(7), P(4)–Cu(3)–Se(3) 118.34(7), P(2)–Cu(4)–P(3) 119.57(9), Se(1)–
As(1)–As(2) 98.20(4), Se(2)–As(2)–Cu(3) 107.12(4), Se(2)–As(2)–As(1)
103.12(4), Cu(3)–As(2)–As(1) 124.00(5), Se(4)–As(3)–Cu(2A) 118.02(5),
Se(4)–As(3)–Se(3) 100.01(4), Cu(2A)–As(3)–Se(3) 107.48(5), A: −x + 1,
−y + 1, −z + 1.
When [(PhAs)2(l-Se)(l-Se2)] is reacted with the Cu(I) thio-
late CuSEt in the presence of the tertiary phosphine PPh3,
[Cu4(Ph2As2Se2)2(PPh3)4] (2) is formed in low yield (Scheme 2,
Fig. 2). The structural analysis showed that 2 forms a centrosym-
metric arrangement of four [Cu(PPh3)] units held together by two
[Ph2As2Se2]2− anions. 2 is isostructural to the previously reported
˚
The K · · · Se distances in 3 are almost 1 A longer than Cu · · · Se
distances found in 1 and 2. This weak coordination may allow the
formation of the [PhAsSe3]2− anion in 3 whereas more covalent
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Table 1 Details of the X-ray data collection and refinements
Compound
1
2
3
4
5
Formula
Formula weight
T/K
C140H126As6Cl8Cu8P8Se8
3929.29
100(2)
Triclinic
¯
P1
18.8226(7)
20.8206(8)
21.6135(9)
76.153(3)
70.301(3)
69.693(3)
7406.8(5)
2
C108H104As4Cu4O3P4Se4
2443.47
150(2)
Monoclinic
P2/n
24.736(5)
15.659(3)
26.355(5)
90
105.85(3)
90
9820(3)
4
3.792
C36H68AsK2O15Se3
1130.90
150(2)
Monoclinic
P21/n
8.9580(18)
28.590(6)
19.330(4)
90
99.29(3)
90
4885.7(17)
4
3.160
C102H162.67As6Na12O31Se18
4031.67
100(2)
Trigonal
¯
R3
32.3388(19)
32.3388(19)
12.6601(6)
90
90
120
11466.1(11)
3
5.677
C10H19AsNa2O4Se3
561.03
203(3)
Monoclinic
P2/c
19.9887(15)
6.9605(8)
14.3162(15)
90
110.304(13)
90
1868.1(3)
4
7.717
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
l/mm−1
4.699
F(000)
3848
59429
30240
0.0589
1255
0.1618
0.0605
4880
53681
17285
0.2432
857
0.2131
0.1077
2308
19956
9299
0.1763
517
0.1156
0.0697
5894
15805
4952
0.0641
244
0.1029
0.0391
1072
12655
3623
0.0856
188
0.1293
0.0471
Reflections collected
Unique data
Rint
Parameters
wR2 (all data)
R1 [I > 2r(I)]
˚
Fig. 3 Solid-state structure of 3. Selected bond lengths (A) and an-
gles (◦): As(1)–Se(1) 2.2988(13), As(1)–Se(2) 2.2843(16), As(1)–Se(3)
2.2858(18), Se(1)–K(1) 3.384(3), Se(1)–K(2) 3.373(3), Se(2)–K(1)
3.519(2), Se(3)–K(2) 3.452(2), K–O 2.822(10)–3.100(9), Se(2)–As(1)–Se(3)
115.27(6), Se(2)–As(1)–Se(1) 112.14(6), Se(3)–As(1)–Se(1) 112.48(7),
As(1)–Se(1)–K(2) 89.98(6), As(1)–Se(1)–K(1) 87.94(6), K(2)–Se(1)–K(1)
169.75(7), As(1)–Se(2)–K(1) 84.91(6), As(1)–Se(3)–K(2) 88.24(6).
Fig. 4 Solid-state structure of 4 (only a-C atoms of phenyl groups
and O atoms of 15-crown-5 are displayed). Selected bond lengths (A)
˚
and angles (◦): As(1)–C(1) 1.969(5), As(1)–Se(1) 2.2907(8), As(1)–Se(2)
2.2795(8), As(1)–Se(3) 2.3001(8), Se(1)–Na(1) 3.196(2), Se(1)–Na(2)
3.008(2), Se(2)–Na(1) 3.105(2), Se(3)–Na(2) 3.030(2), Na(1)–O(4)
2.416(5), Na(1)–O(3) 2.475(5), Na(1)–O(1) 2.521(5), Na(1)–O(2)
2.528(4), Na(1)–O(5) 2.574(5), Na(2)–O(5) 2.578(4), C(1)–As(1)–Se(2)
106.59(17),
C(1)–As(1)–Se(1)
107.93(16),
Se(2)–As(1)–Se(1)
110.77(3), C(1)–As(1)–Se(3) 106.97(17), Se(2)–As(1)–Se(3) 112.48(3),
Se(1)–As(1)–Se(3) 111.79(3).
metal–Se bonds give rise to new As–Se anions similar to those
observed in 1 and 2. [PhAsSe3]2− anions can be prepared from
[(PhAs)2(l-Se)(l-Se2)] and a range of other alkali metal thiolates
and other donating solvents. This is in the following exemplified by
compounds 4 and 5 which were obtained according to Scheme 2.
For the synthesis of 4 the principal starting materials used are
analogous to those employed for the preparation of 3. The solid-
state structure of 4 consists of a cyclic hexameric arrangement of
[PhAsSe3]2− anions held together by sodium ions (Fig. 4). There
are two types of sodium ions. Na(1) is complexed by the O atoms
of a 15-crown-5 molecule, Se(1) and Se(2). Na(2) is complexed
by two l-O atoms of two different 15-crown-5 molecules and by
4 Se atoms of two different [PhAsSe3]2− anions. The formation
of the macrocyclic arrangement found in 4 is a consequence of
the bridging coordination mode of O(1) and O(5) of 15-crown-5.
Bridging O atoms in 15-crown-5 are rare but may allow in future
the preparation of a larger range of macrocyclic compounds.42,43
Further insight in potential ways of assembling [PhAsSe3]2− anions
was gained, when traces of water were present in the reaction
between [(PhAs)2(l-Se)(l-Se2)] and NaStBu (Scheme 2). It turned
out that [PhAsSe3]2− anions are stable in the presence of water and
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assembly of [PhP(O)Se2]2− anions.44 In 5, however, oxygen of
water is not present within the anion and As–Se bonds remain
intact.
Conclusion
In future more investigations are necessary in order to get a clearer
picture of the reactivity of [(PhAs)2(l-Se)(l-Se2)] and other group
15/16 reagents. Here, three new As–Se anions and their metal
complexes are described. A key in the preparative investigations is
the use of further metal salts and to limit the number of reactions
occurring between reactants. On the other hand solubility is a
key issue. In order to dissolve coinage metal compounds in the
future, it is planned to use donor reagents, e.g., tertiary arsines and
stibines, which are less reactive than phosphines towards group
15 chalcogen transfer reagents. For the alkali metal derivatives
the picture is much clearer. The synthesis of the [PhAsSe3]2−
anion from [(PhAs)2(l-Se)(l-Se2)] and alkali metal thiolates is
straightforward and the byproduct PhAs(StBu)2 was identified by
GC-MS. It remains a challenge to produce compounds in better
yield so their physical properties can be studied in depth. This
is particularly the case for 5 because the thermal removal of both
water and THF could give rise to new types of porous compounds.
Experimental
All operations were carried out in an atmosphere of purified
dinitrogen. Solvents were dried and freshly distilled prior to use.
Crystallography
The crystal structures were solved and refined with the SHELXTL
program package.45 The Squeeze option in Platon was used to
correct for heavily disordered solvent molecules in 1, 2 and 4.46,47
In 1 and 2 phenyl groups were refined as rigid hexagons (afix 66).
Disordered components and lattice-bound solvent were refined
using isotropic temperature factors. Crystallographic details are
listed in Table 1.
Fig. 5 Solid-state structure of a section of 2D-polymeric 5 (top) and
section of the outer 2D-polymeric layer of [PhAsSe3]2− anions held
together by Na+ ions (bottom). Only a-C atoms of phenyl groups and
O atoms of THF ligands are displayed. Symmetry operations: −x + 1,
[(PhAs)2(l-Se)(l-Se2)]: 4.00 g (19.8 mmol) PhAs(O)(OH)2 were
dissolved in 100 mL of concentrated hydrochloric acid. The
solution was cooled to 0 ◦C and a solution of 3.75 g (30.0 mmol)
Na2Se in 120 mL distilled water was added dropwise. The orange
precipitate was washed with three times with hexane (10 mL) and
dried under reduced pressure. The product was stored in a brown
screwcap bottle in a glove box. It can be recrystallised from DME.
3.60 g, yield 67%. EI-MS (70 eV) m/z: 541.5 (M+, 19%), 383.7
(34), 311.8 (44), 229.0 (100), 226.9 (92), 154.8 (87), 151.9 (41), 77.0
˚
−y, −z + 2 (A), −x + 1, y, −z + 3/2 (B). Selected bond lengths (A)
and angles (◦): As(1)–C(1) 1.963(8), As(1)–Se(2) 2.2851(10), As(1)–Se(1)
2.2916(10), As(1)–Se(3) 2.2942(11), Na(1)–O(3) 2.341(6), Na(1)–O(1A)
2.366(6), Na(1)–O(4) 2.441(6), Na(1)–O(1) 2.448(6), Na(1)–O(2) 2.456(6),
Na(1)–Se(1) 3.172(3), Na(2)–Se(1A) 3.035(4), Na(2)–Se(2B) 3.182(4),
Se(1)–Na(2A) 3.034(4), Se(2)–Na(2B) 3.182(4), O(1)–Na(1A) 2.366(6),
O(2)–Na(1B) 2.456(6), O(3)–Na(1B) 2.341(6), C(1)–As(1)–Se(2) 104.8(2),
C(1)–As(1)–Se(1) 108.5(2), Se(2)–As(1)–Se(1) 114.12(4), C(1)–As(1)–Se(3)
102.4(2), Se(2)–As(1)–Se(3) 114.39(4), Se(1)–As(1)–Se(3) 111.47(4).
◦
(81), 51.0 (47), 39.0 (8); dH (400 MHz, CDCl3, 23 C) 7.30–7.90
(m, 10H, ArH); dC (100 MHz, CDCl3, 23 ◦C) 128.2–140.9 (ArC);
dSe (76,31 MHz, CDCl3, 23 ◦C, Me2Se) 497, 680 (s).
a 2D polymeric arrangement was found in 5 (Fig. 5). 5 consists
of a 1D polymeric strand of Na+ ions bridged by water (O atoms
1, 2, 3). This 1D polymer and parallel 1D arrangements in the
extended crystal lattice are sandwiched between two lipophilic
outer layers consisting of a 2D arrangement of [PhAsSe3]2−
anions and [Na(thf)]+. A section of one lipophilic outer layer
displayed at the bottom of Fig. 5 shows a net-like composition
in which each Se atom of [PhAsSe3]2− anions coordinates to one
Na(thf)-unit. This arrangement bears a remarkable resemblance
to a similar structural motif observed earlier in a 2D polymeric
1. 135 mg (0.25 mmol) of [(PhAs)2(l-Se)(l-Se2)] was dissolved
in 10 mL THF and a solution of 70 mg (0.50 mmol) [CuOtBu]
was added. After 10 min, a colour change of the solution from
yellow to deep red was observed. The reaction was stirred for
12 h at room temperature and a solution of 193 mg (0.50 mmol)
dppm in 5 mL THF was added. The mixture was stirred again
for 12 h at room temperature. After filtration the solvent was
removed under reduced pressure at room temperature and the
solid residue washed with 5 mL diethyl ether, dried and dissolved
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in 10 mL CH2Cl2. The resulting orange solution was reduced to
approximately 3 mL and layered with hexane (15 mL). Storage
of the solution at room temperature for one week produced a
colourless precipitate with a few orange crystals of 1. The reaction
was repeated and the unit cell repeatedly determined from crystals
of different batches. A few red crystals that could not be separated
from the rest of the precipitate of dppmSe, etc. were also found.
Yield < 10% (estimated). Investigation of the mother liquor: GC
MS: m/z 384 (Ph2As2Se+, 30%), 229 (Ph2As+, 100%) retention
time: 15 min, 384 (dppm+, 40%) retention time: 20 min.
Acknowledgements
We thank the Dfg Centre for Functional Nanostructures (W. S.)
and the Forschungszentrum Karlsruhe for financial support. A. R.
thanks Prof. Dieter Fenske for his support.
Notes and references
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3 R. Blachnik and G. Kurz, J. Solid State Chem., 1984, 55, 218–224.
4 H. J. Whitfield, J. Solid State Chem., 1981, 39, 209–214.
5 B. Eisenmann and H. Scha¨fer, Z. Anorg. Allg. Chem., 1979, 456,
87–94.
6 D. X. Jia, A. M. Zhu, J. Deng, Y. Zhang and J. Dai, Dalton Trans.,
2007, 2083–2086.
7 T. van Almsick and W. S. Sheldrick, Z. Anorg. Allg. Chem., 2006, 632,
1409–1412.
8 T. van Almsick and W. S. Sheldrick, Z. Anorg. Allg. Chem., 2005, 631,
1746–1748.
2. 135 mg (0.25 mmol) [(PhAs)2(l-Se)(l-Se2)] and 63.0 mg
(0.50 mmol) CuSEt were dissolved in 10 mL THF and stirred at
rt for 1 d. To the resulting brown suspension 262 mg (1.00 mmol)
PPh3 were added and the reaction was stirred for 1 d and filtered.
The dark red solution was concentrated to 6 mL under reduced
pressure and layered with 5 mL of a hexane–THF mixture (ratio
1 : 2). Storage of the reaction for two weeks produced a few red
crystals, which were contaminated with Ph3PSe. Yield < 10%
(estimated). dP (162 MHz, CDCl3, 23 ◦C, 65% H3PO4) −4.7 (s,
CuPPh3), 35.5 (s, Ph3PSe) + 1JPSe satellites, dSe (76,31 MHz, CDCl3,
23 ◦C, Me2Se) −269.1 (d, Ph3PSe, 1JSeP = 729.7 Hz)
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6 and 270 mg (0.50 mmol) [(PhAs)2(l-Se)(l-Se2)] were dissolved in
DME (10 mL) and stirred at rt overnight. The orange suspension
was filtered. The pale yellow solution was layered with 3 mL of
a DME–hexane mixture in the following order: 1. DME : hexane
5 : 1, 1 : 1, 1 : 5. Finally the mixture was carefully layered with
hexane (40 mL). After six weeks yellow crystals of 3 were isolated.
Yield 294 mg, 52%. Despite repeated attempts, elemental analysis
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◦
19 J. Beck, S. Hedderich and K. Ko¨llisch, Inorg. Chem., 2000, 39, 5847–
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5850.
◦
H), 3.6 (s, O–CH2), dc (100 MHz, d6-DMSO, 23 C) ◦148–128 (s,
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(PhAs(StBu)2 , 30%), retention time: 11 min.
+
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1 : 1, 1 : 5. Finally the mixture was carefully layered with hexane
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(PhAs(StBu)2 , 27%), retention time: 11 min.
+
30 W. Shi and A. Rothenberger, Eur. J. Inorg. Chem., 2005, 2935–2937.
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mixture was carefully layered with hexane (50 mL). Over the course
of almost four months, traces of water gave rise to 5, which has
yet to be reproduced. For future work, however, it is important to
note the stability of the [PhAsSe3]2− anion in the presence of water.
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936 | Dalton Trans., 2008, 932–937
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This journal is
The Royal Society of Chemistry 2008
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