Lewis base sequestered chalcogen dihalides: Synthetic sources of ChX 2 (Ch = Se, Te; X = Cl, Br)

Article abstract of DOI:10.1002/chem.200901000

The synthesis and comprehensive characterization of a series of base-stabilized ChX₂ (Ch = Se, Te; X = Cl, Br) is reported using aryl-substituted diazabutadiene and 2,2'-bipyridine (bipy) as the ligands. In stark contrast to free ChX₂

Full text of DOI:10.1002/chem.200901000

FULL PAPER
DOI: 10.1002/chem.200901000
Lewis Base Sequestered Chalcogen Dihalides: Synthetic Sources of ChX2
(Ch=Se, Te; X=Cl, Br)
Jason L. Dutton, Gregory J. Farrar, Michael J. Sgro, Taylor L. Battista, and
Paul J. Ragogna*[a]
Abstract: The synthesis and compre-
hensive characterization of a series of
base-stabilized ChX2 (Ch=Se, Te; X=
Cl, Br) is reported using aryl-substitut-
ed diazabutadiene and 2,2’-bipyridine
(bipy) as the ligands. In stark contrast
to free ChX2 the complexes display ex-
cellent thermal stability. Their use as
viable ChX2 reagents that may be
stored for later use is demonstrated in
principle. The syntheses are simple and
high-yielding from commercially avail-
able or easily synthesized reagents. The
bipy complexes are exceedingly rare
examples of this ubiquitous ligand
being utilized within Group 16 chemis-
try; the Se examples are the first to be
characterized by X-ray crystallography,
and the Te species are only the second.
Keywords: chalcogens · heterocy-
cles
· N ligands · selenium ·
tellurium
Introduction
for only mere minutes before substantial decomposition
ensues, rendering these reagents very difficult to use in a
straightforward fashion.[9] There exist several different meth-
ods for making SeX2 and all suffer from the drawback that
the resultant selenium dihalide must be used in situ, and
cannot be stored for later use.[9–11] Complicating matters,
there is no simple method of readily ascertaining exactly
what is present in solution—that is, how pure the SeCl2 is
after, for example, 4 or 5 h. Selenium-77 NMR spectroscopy
is relatively simple using modern spectrometers, but obtain-
ing a reasonable 77Se NMR spectrum in a short timeframe is
The coordination chemistry of the heavy chalcogens is un-
derdeveloped when compared with the majority of the peri-
odic table.[1] The primary reason for this lack of activity is
likely because the obvious electrophilic Group 16 starting
reagents, the tetrahalides (ChX4; Ch=Se, Te; X=Cl, Br, I),
typically undergo redox reactions in the presence of
common ligands (imine, phosphine, N-heterocyclic car-
bene).[2] These processes result in a reduction of the chalco-
gen atom to the +2 oxidation state, coupled with the elimi-
nation of reactive X2. The released dihalogen often partici-
pates in undesirable side reactions, leading to difficulty in
controlling the reaction outcome.[3,4] The X2 can be seques-
tered by the addition of a third species (i.e., cyclohexene,
SnCl2), provided the additional reagent does not interfere
with the targeted reactions.[5,6] Within our laboratory we
have found that starting with a ChII source appears to large-
ly circumvent this problem.[7,8] Unfortunately, the selenium
dihalides (SeX2; X=Cl, Br) are highly unstable with respect
to disproportionation. Selenium dichloride must be synthe-
sized and used within a matter of hours, and SeBr2 is stable
1
not as facile as it is for other routine nuclei (e.g., H, 13C,
31P, 19F). Moreover, a 5–10% impurity is not easily observed
in a routine sample analyzed by 77Se NMR spectroscopy,
even though it may be a significant detriment to any at-
tempted transformations. Another restriction is that SeX2 is
only compatible with certain organic solvents (e.g., THF,
MeCN), whereas other common solvents such as CH2Cl2
cannot be used.
Base-stabilized SeX2 derivatives have been reported and
include the products from the oxidative addition of X2 to
phosphine selenides or selenoureas, which formally contain
a SeX2 fragment (e.g., 1; Scheme 1).[12–17] Direct reaction of
S-based ligands with SeX2 has also been used to sequester
this reactive fragment.[9,18,19] To the best of our knowledge,
no further chemistry has been described using any of these
as a source of SeX2. The corresponding tellurium binary hal-
ides are known only as transient species in the gas
phase.[20,21] Base-stabilized TeX2 (X=Cl, Br, I; for example,
1, 2) compounds have also been reported but they have not
[a] J. L. Dutton, G. J. Farrar, M. J. Sgro, T. L. Battista, Prof. P. J. Ragogna
Department of Chemistry
The University of Western Ontario
1151 Richmond St.
London, ON, N6A 5B7 (Canada)
Fax : (+1)519-661-3022
E-mail: pragogna@uwo.ca
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Results and Discussion
The 1:1 stoichiometric reaction of Dipp-DAB or Dipp-
BIAN with SeCl2 (prepared from Se0 and SO2Cl2) in THF
results in a red solution. Removal of the solvent in vacuo
gives a bright orange (Dipp-DAB) or deep red (Dipp-
BIAN) powder. A sample of each of the powders redis-
1
solved in CDCl3 for H NMR spectroscopy revealed a set of
Scheme 1. Representative examples of known base-stabilized ChX2
ACHTUNGTRENNUNGspecies.
signals indicative of a single, pure diazabutadiene-containing
product, with an apparent retention of the ligand symmetry.
The diagnostic resonance arising from the protons in the
ligand backbones were shifted downfield from the free
ligand in both cases (Dipp-DAB: Dd=0.7 ppm; Dipp-
BIAN: Dd=0.14 ppm). Single crystals for X-ray diffraction
studies were obtained for the Dipp-BIAN analogue, which
revealed the Dipp-BIAN chelate of SeCl2 (4Cl). Despite
many repeated efforts, we were unable to obtain single crys-
tals from solutions of the bulk powder. Elemental analysis
(C, H, N) gave results indicative of a molecular formula
containing only Dipp-DAB and SeCl2 (C26H36N2Cl2Se),
which is also consistent with the total mass of material re-
covered from the reaction (96% yield). Based on these
data, the compound was assigned as being the Dipp-DAB
chelate of SeCl2 (3Cl).
yet been utilized in the delivery of the tellurium dihalide,
with the exception of a hydrated thiourea-ligated TeCl2 frag-
ment.[4,22–25]
These combined issues call for a system in which a func-
tional equivalent of ChX2 can be stored for an indefinite
period of time, its purity easily ascertained, and demon-
strates the ability to cleanly deliver the chalcogen dihalide.
In this context, we have discovered that a-diimine ligands
featuring aryl N-substituents (Dipp-DAB, Dipp-BIAN;
Dipp=2,6-diisopropylphenyl;
DAB=diazabutadiene;
BIAN=bisaryliminoacenaphthene) or the 2,2’-bipyridyl
(bipy) ligand can easily sequester ChX2 in a stable form (3–
ꢀ
6). If one views the Ch N linkage as a formally dative inter-
The same compounds may also be made from SeCl2 gen-
erated in situ from SeCl4 and SbPh3 in THF, in which the
Ph3SbCl2 byproduct is easily removed by washing with Et2O,
and the complexed SeCl2 remains insoluble. Both 3Cl and
4Cl are stable in the solid state (>1 year under an N2 at-
mosphere) at room temperature, and for days in solution,
which is in distinct contrast to free SeCl2, which readily dis-
proportionates. Remarkably, the compounds show no evi-
dence of decomposition in the solid state until after at least
sixty days if left open to the ambient atmosphere of the lab-
oratory, as monitored by FT-Raman spectroscopy, whereas
molecular SeCl2 reacts almost instantaneously if exposed to
the open air. In solution, 3Cl and 4Cl decompose within
five minutes of exposure to ambient conditions. The materi-
als are also compatible with a range of common organic sol-
vents (alkanes (insoluble), ethers such as Et2O (insoluble)
and THF (soluble), arenes (slight soluble), chloroalkanes
(soluble), MeCN (soluble)), provided the solvents are dried
to the typical standards required for handling moderately
moisture-sensitive materials (H2O<100 ppm).
Selenium dibromide is considered to be significantly less
stable than SeCl2; however, the successful trapping of SeCl2
indicated that it might be possible to do the same for the
bromide congener. The 1:1 stoichiometric reaction of SeBr2
with Dipp-DAB or Dipp-BIAN in THF results in the imme-
diate generation of a very dark red solution. Removal of the
THF under vacuum gave dark brown (Dipp-DAB) or
purple (Dipp-BIAN) solids. The proton NMR spectra of
samples of both solids were essentially identical to those ob-
served for 3Cl and 4Cl, and indicated successful complexa-
tion of the SeBr2. Single crystals for X-ray diffraction analy-
sis were obtained for the Dipp-BIAN analogue, which re-
vealed the expected Dipp-BIAN chelate to SeBr2 (4Br). Al-
action, it has an intrinsic lability and should therefore be in-
clined to quantitative release of the ChX2 fragment, which
can be utilized as a synthetic equivalent of the chalcogen di-
halide. The syntheses may easily be performed on a large
scale, thus they are amenable to preparatory reactions. Al-
though 2,2’-bipyridine has been synonymous with a wide
range of transition metal and p-block complexes, com-
pounds 5 and 6 are exceedingly rare examples of this ubiqui-
tous ligand being utilized within Group 16 chemistry.[26,27]
Indeed, the Se–bipy complexes are the first structurally
characterized bipy chelates of that element, and a derivative
of 6 represents only the second example of a Te–bipy mole-
cule characterized by X-ray diffraction studies.[28]
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Chalcogen Dihalides
FULL PAPER
ternatively, the compounds can be prepared in quantitative
yields by means of halide metathesis of 3Cl or 4Cl using
(CH3)3SiBr. Compound 4Br shows no signs of decomposi-
tion if stored under N2 at room temperature; 3Br decom-
poses within 2 weeks at room temperature under inert con-
ditions. In contrast with the chlorine derivatives, both bro-
mine analogues are quite sensitive to the ambient atmos-
phere of the laboratory in the solid state, decomposing in
minutes.
mosphere, but they do decompose within an hour if opened
to ambient air.
In contrast with the reactivity observed for Se, the direct
reaction of alkyl-substituted DAB ligands and TeX4 does
not result in a reduction of the Te atom from TeIV to TeII. In-
stead simple [TeACHTNUTRGNE(NUG dab)X4] coordination complexes are
formed (Scheme 3).[6] Unfortunately, all attempts to reduce
The 1:1 stoichiometric reaction of a freshly prepared solu-
tion of SeX2 (X=Cl, Br) with 2,2’-bipyridine resulted in the
immediate precipitation of yellow solids. The solids were
separated from the supernatant, washed with Et2O, and
dried in vacuo. For X=Cl, the material was found to be in-
soluble in a variety of solvents for NMR spectroscopy
(C6D6, CDCl3, CD3CN), but was sufficiently soluble in
[D6]acetone, enabling the acquisition of 1H NMR spectro-
scopic data. The spectrum showed a set of resonances con-
sistent with a single product containing the bipy framework.
The yield of material recovered was essentially equal to the
total expected based on SeCl2 and bipy, and therefore the
identity of the compound was tentatively assigned as the
bipy chelate of SeCl2 (5Cl). Decomposition of a solution of
the compound in acetone was observed within minutes
Scheme 3. Previous synthesis of TeX4–diimine coordination complex
using the tert-butyl DAB ligand.
the Te to the +2 oxidation state in these compounds result-
ed in the immediate deposition of elemental tellurium.
Cowley et al. showed that the direct reaction of the Dipp-
BIAN ligand with TeI4 did result in a redox process, gener-
ating the TeI2 chelate of Dipp-BIAN.[23] This compound ap-
pears to have the potential to be used as a TeII source al-
though no further chemistry utilizing the compound as a
TeI2 synthon has been reported. Very recently our group has
reported the use of a Dipp-BIAN-stabilized pseudohalide of
ACHTUNGTRENNUNG(<20 min), which precluded the growth of single crystals for
X-ray analysis, and a definitive assignment of the bonding.
The bromine derivative was found to be significantly more
soluble, with single crystals readily grown from a solution of
the bulk powder in CH2Cl2. Subsequent X-ray diffraction
studies revealed the [SeACTHNUTRGNE(NUG bipy)Br2] complex (5Br). A more
soluble derivative of 5Cl was generated by means of halide
Te (TeACTHUNTGRNE(UNG OTf)2) to generate a series of Te-centered dicat-
ions.[29] However, a viable source of TeCl2 remains unknown.
We have found that the direct reaction of TeX4 (X=Cl, Br)
with either Dipp-DAB or Dipp-BIAN gives a complicated
mixture of products, and trying to mediate the redox process
using SbPh3 or SnCl2 also results in complex mixtures with
concomitant deposition of Te metal. Given the successful
complexation of SeX2 using the bipy ligand, we were
prompted to investigate the use of bipy as a potential stabi-
lizing agent for TeX2.
abstraction (Scheme 2) using one stoichiometric equivalent
The 1:1 stoichiometric reaction of TeX4 (X=Cl, Br) with
bipy results in the immediate generation of a yellow (X=
Cl) or bright orange (X=Br) precipitate. After separation
from the supernatant and drying under vacuum, bright
yellow (X=Cl) or orange (X=Br) powders are isolated.
Both solid materials are highly insoluble in all common
NMR spectroscopic solvents, with the exception of
[D6]acetone; 1H NMR spectra of both materials in
[D6]acetone showed resonances indicative of a single bipy-
containing product. As in the above case with SeCl2, the
compounds decompose readily in acetone. Results from
CHN combustion analysis allowed the assignment of the
compounds as bipy chelates of TeX4 (8Cl and 8Br). Related
compounds of the formula RTeCl3bipy (R=o-cresol, m-
cresol, p-cresol, o-chlorophenol) have been described as a
Scheme 2. Derivation of 5Cl by means of halide metathesis.
of TMS-OTf (TMS-OTf=trimethylsilyltrifluoromethanesul-
fonate), in CH2Cl2, which resulted in a color change of the
solid from pale yellow to colorless. After isolation, a sample
1
of the powder was dissolved in CD3CN for H NMR spec-
troscopy. The resonances were consistent with a single prod-
uct containing the bipy ligand. To obtain definitive identifi-
cation of the material single crystals were grown from a sa-
turated solution of the bulk powder in CH3CN by means of
vapor diffusion of Et2O. X-ray diffraction studies revealed
cation–anion pair ([TeACHTNUTGRNEUNG
(bipy)Cl2R][Cl]).[27] No structural evi-
dence was obtained, but conductivity measurements were
consistent with a 1:1 electrolyte. Conductivity experiments
on 8Cl and 8Br in acetone showed similar conductivity as
the compound to be the salt [Se
ACHUTNGTRENNUG(bipy)Cl]ACHUTNGTREN[NUGN OTf] (OTf=trif-
ACHTUNGTRENNUNG
bipyridine ligand. Compounds 5Cl and 5Br are indefinitely
stable in the solid state at room temperature under an N2 at-
the above report, therefore an ionic formula ([Te
[X]) is also proposed for these compounds.
ACHTUNGTNER(NUNG bipy)X3]
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P. J. Ragogna et al.
No reaction is detectable between bipy and TeI4, which
was also observed in attempted reactions with alkyl-substi-
tuted diazabutadiene ligands. The TeCl4 congener may be
cleanly reduced to the TeCl2 species (6) using Ph3Sb, which
gives a green powder upon workup (Scheme 4). The powder
a yellow slurry. After warming the mixture to room temper-
ature, the THF was removed in vacuo and the residue was
extracted with n-hexane. After filtration and removal of the
n-hexane, an 1H NMR spectrum of the gel-like material
showed resonances arising from the free Dipp-BIAN ligand,
as well as other overlapping sig-
nals in the phenyl region. A
77Se{1H} NMR spectrum of the
same sample revealed only one
signal at d=416 ppm, consistent
with SePh2. The phenylselenide
may be easily separated from
the Dipp-BIAN by column
Scheme 4. Reduction of 8Cl, which gave a base-stabilized form of TeCl2 (6) and subsequent derivation by
halide abstraction for positive identification.
chromatography (silica gel;
98.5:1.5 hexane/ethyl acetate)
and recovered in an overall
yield of 70–75%, which is com-
may be dissolved in CD3CN in sufficient quantities for
1H NMR spectroscopic studies, which gave a clean spectrum
of a single bipy-containing compound, and combustion anal-
ysis of the bulk powder was consistent with the molecular
formula containing TeCl2 and bipy. Although this material is
stable in acetonitrile, we have been unable to obtain crystals
of sufficient quality for X-ray diffraction analysis. A halide-
abstraction reaction from the TeCl2 using one stoichiometric
equivalent of TMS-OTf gives a derivative for which single
crystals could be obtained. X-ray diffraction analysis of a
parable to the literature report for the direct reaction. An
essentially identical procedure may be used to generate
ꢀ
SeBz2 from BzMgCl (Bz= CH2Ph), with the exception that
3Cl was used as the SeCl2 source. The [Se
A
5 also reacts with the Grignard reagents to form aryl sele-
nides. The primary difference from the DAB congeners is
that the released bipy ligand forms an insoluble complex
with the MgCl2 byproduct, thereby eliminating the need for
column chromatography.[31] Most interesting is that com-
pound 6 serves as a functional equivalent of TeCl2. This is a
significant discovery as the free binary halide is unknown in
the condensed phase, and thus the reactivity of the tellurium
dihalides is completely unexplored. Diaryl telluriudes may
be formed by the reaction of 6 with either PhMgCl or
BzMgCl in good yields with only a simple workup (60–
70%). Compound 6 may also be utilized as a TeCl2 synthon
in a ligand-exchange reaction with a stronger Lewis base
(e.g., N-heterocyclic carbene; NHC=2,5-diisopropylimida-
zole-3,4-dimethyl-2-ylidene). The reaction of one equivalent
of NHC with 6 in THF gives compound 10 in a good yield
(70%) after a short workup. A previous investigation by
Kuhn and co-workers generated the I2 congener of this com-
pound through the direct reaction of TeI4 with the carbene,
coupled with the reductive elimination of I2.[4] They were
unable to synthesize the lighter halide analogues due to the
much higher reactivity of the released Cl2 or Br2, which gave
complex mixtures. Using a source of TeII rather than TeIV ap-
pears to have circumvented this issue, highlighting the possi-
ble utility of 6 as an effective source of TeCl2.
single crystal revealed the expected [TeACTHNUGRTENUNG(bipy)Cl] cation
paired with a triflate anion (9), thereby allowing us to infer
that the formulation of 6 was indeed correct.
Preliminary reactivity studies: The above compounds repre-
sent novel complexes within chalcogen–nitrogen chemistry,
but to act as functional equivalents of ChX2, they must
cleanly release the chalcogen dihalide and the ligand by-
product must be readily removed from the new material.
Aryl Grignard reagents react with SeCl2 in a 2:1 stoichiome-
try to give the corresponding aryl selenides.[30] This appeared
to be an ideal reaction to test our ability to use the above
compounds as a source of SeCl2 (Scheme 5). The reaction of
4Cl with two equivalents of PhMgCl in THF at ꢀ788C gives
X-ray crystallography: Compounds 4, 5Br, 7, 9, and 10 have
been characterized by single-crystal X-ray diffraction stud-
ies. Views of the solid-state structures are shown in Figures 1
to 6, and pertinent refinement details may be found in
Table 1. Key bond lengths and angles are summarized in
Table 2.
An examination of the metrical parameters for 4Cl re-
veals a square–planar Se center (Figure 1), which is consis-
tent with an AX4E2 electron-pair geometry, indicative of
two lone pairs at Se, and retention of the +2 oxidation of
Scheme 5. Selected reactions utilizing the base-stabilized ChX2 species as
synthetic equivalents of ChX2.
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Chalcogen Dihalides
FULL PAPER
Table 2. Selected bond lengths [ꢁ] and angles [8] for compounds 4, 5Br,
7, and 9.
4Cl
4Br
5Br
7
9
ꢀ
Ch(1) N(1)
2.263(3) 2.290(3)
2.314(5) 2.358(3)
2.293(2) 2.4367(7) 2.673(1)
2.326(2) 2.4677(8) 2.640(1)
1.301(8) 1.286(5)
1.286(8) 1.279(5)
1.490(9) 1.496(6)
2.099(6)
2.090(5)
1.970(3) 2.171(6)
N/A 2.288(6)
2.710(1) 2.492(2)
N/A N/A
1.359(5) 1.36(1)
N/A 1.347(9)
1.451(8) 1.46(1)
ꢀ
Ch(1) N(2)
ꢀ
Ch(1) X(1)
ꢀ
Ch(1) X(2)
ꢀ
N(1) C(1)
1.360(8)
1.348(8)
1.45(1)
ꢀ
N(2) C(2)
ꢀ
C(1) C(2)
X(1)-Ch(1)-X(2) 98.56(8) 97.91(2)
94.51(4)
N/A
N/A
X(2)-Ch(1)-N(2) 95.1(2)
N(2)-Ch(1)-N(1) 74.4(2)
N(1)-Ch(1)-X(1) 91.9(2)
95.96(8)
73.6(1)
92.54(9)
94.36(15) N/A
N/A
73.1(2)
88.9(2)
77.0(2)
80.1(2)
94.19(15) 94.1(1)
Figure 1. Solid-state structure of 4Cl. Ellipsoids are drawn to 50% proba-
bility level and hydrogen atoms are omitted for clarity.
ꢀ
the metal. The Se N bonds are considerably elongated
ꢀ
ꢀ
(Se(1) N(1), 2.263(3); Se(1) N(2), 2.314(5) ꢁ) relative to a
[32]
ꢀ
typical Se N single bond (1.8–1.9 ꢁ).
best designated as coordinative in nature, which is supported
These bonds are
by their labile character, and thus the ease with which di-
ꢀ
G
were also elongated by virtue of the coordination of the
ꢀ
ꢀ
ligand into the Se Cl s* orbitals (Se(1) Cl(1), 2.293(2);
[33]
ꢀ
ꢀ
Se(1) Cl(2), 2.326(2) ꢁ). The endocyclic N C bonds are
short (1.286–1.301 ꢁ), reflective of their imine character,
ꢀ
and the C C bond in the N2C2Se heterocycle is consistent
Figure 2. Solid-state structure of 4Br. Ellipsoids are drawn to 50% prob-
ability level and hydrogen atoms are omitted for clarity.
with a single bond (1.490(9) ꢁ). This is in contrast to what is
reported for coordination of Dipp-BIAN or Dipp-DAB with
the pnictogen halides, whereby an internal two-electron
transfer from the central element into the LUMO of the
plexes of the 2,2’-bipyridine ligand. In 5Br (Figure 3), the
ꢀ
DAB ligand imposes a pnictenium architecture containing
square–planar N2SeBr2 motif is again observed, and the Se
[34,35]
ꢀ
ꢀ
ꢀ
N C and C=C functionalities.
Compound 4Br (Figure 2) is isostructural with 4Cl, where
N bonds (Se(1) N(1), 2.099(5); Se(1) N(2), 2.090(5) ꢁ) are
significantly shorter as compared with those in 4Br, which
reflects the greater Lewis basicity of the less sterically en-
ꢀ
ꢀ
the main difference was even longer Se N bonds (Se(1)
ꢀ
ꢀ
ꢀ
N(1), 2.290(3); Se(1) N(2), 2.358(3) ꢁ). Compounds 5Br
cumbered bipy ligand. The Se Br bonds are long (Se(1)
Br(1), 2.673(1); Se(1) Br(2), 2.640(1) ꢁ) and likely reflect a
ꢀ
and 7 represent the first structurally characterized Se com-
Table 1. Crystal data for compounds 4, 5Br, 7, 9, and 10.
4Cl
4Br
5Br
7
9
10
formula
Mr
C36H40Cl2N2Se1
650.56
C36H40Br2N2Se1
739.48
C10H8Br2N2Se1
394.96
C11H8Cl1F3N2O3S1Se1
419.66
C11H8Cl1F3N2O3S1Te1
468.30
C11H20Cl2N2Te1
378.79
crystal system
space group
a [ꢀ]
b [ꢀ]
c [ꢀ]
orthorhombic
Pbca
11.5069(5)
21.4507(8)
27.0071(8)
90
orthorhombic
Pbca
11.602(2)
21.673(4)
27.103(5)
90
monoclinic
P21/c
8.649(2)
10.005(2)
13.623(3)
90
monoclinic
I2/m
5.794(1)
12.932(3)
19.246(4)
90
monoclinic
P21/c
9.586(2)
38.269(8)
8.510(2)
90
monoclinic
C2/c
10.846(2)
12.207(2)
12.046(2)
90
a [8]
b [8]
90
90
90
90
6815(2)
1.441
0.0508
100.54(3)
90
1159.0(4)
2.264
0.0593
0.1588
93.76(3)
90
1439.0(5)
1.937
0.0426
0.0981
109.90(3)
90
2935(1)
2.119
0.0623
0.1788
110.37(3)
90
1495.2(5)
1.683
0.0262
0.0670
g [8]
V [ꢁ3]
6666.2(4)
1.296
0.0716
1calcd [mgmꢀ3
]
R [I>2s(I)][a]
wR2 (F2)[b]
0.1971
0.1367
[a] R(F
[I>2s(I)])=SjjFo jꢀjFc jj/SjFo j ; wR
E
G
varied). [b] w=1/[s2(Fo2)+(aP)2 +bP] in which P=(F2o +2Fc2)/3 and a and b are constants suggested by the refinement program.
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P. J. Ragogna et al.
Figure 3. Solid-state structure of 5Br. Thermal ellipsoids are drawn to the
50% probability level and hydrogen atoms are omitted.
Figure 5. Solid-state structure of 9. One of two independent cation–anion
pairs in the asymmetric unit is shown. Thermal ellipsoids are drawn to
the 50% probability level and hydrogen atoms are omitted.
degree of ionic character for the molecule. For compound 7
(Figure 4), a dicationic dimer is formed between two {Se-
ꢀ
(bipy)Cl} moieties by means of very long Se Cl interactions
(2.710(1) ꢁ). Within the asymmetric unit, the Se center is T-
Compound 10 (Figure 6) is isostructural with its recently
reported Se counterpart.[2] The Te C bond is 2.103(3) ꢁ,
ꢀ
[36]
ꢀ
similar to other representative Te C single bonds, and the
Figure 4. Solid-state structure of 7 showing the dicationic dimer formed
by two units. Thermal ellipsoids are drawn to the 50% probability level;
hydrogen atoms and triflate anions are omitted.
Figure 6. Solid-state structure of 10. Thermal ellipsoids are drawn to the
50% probability level and hydrogen atoms are omitted for clarity. Select-
ꢀ
ꢀ
ed bond lengths [ꢁ] and angles [8]: Te(1) C(1) 2.103(3), Te Cl(1)
ꢀ
ꢀ
ꢀ
ꢀ
2.5522(9); C(1) Te(1) Cl(1) 85.69(2), Cl(1) Te(1) Cl(1A) 171.38(3).
shaped (AX3E2), and the chloride atom from the neighbor-
ing unit fills the vacant coordination site, imposing a
ꢀ
ꢀ
square–planar geometry. The Se N bonds are somewhat
Te Cl bonds are slightly elongated from those in 9 at
shortened in comparison with 5Br at 1.970(3) ꢁ. No signifi-
cant cation–anion interactions are present between the Se
centers and the OTf anions. The solid-state structure of
compound 9 (Figure 5) is very different from that of the se-
lenium analogue, in that no dimeric arrangement is formed;
rather a long contact is present between the Te center and
2.5522(9) ꢁ.[34] Unlike the TeI2 analogue reported by Kuhn
et al. and the Et3P–TeX2 species by Chivers et al., there are
ꢀ
no significant Te X intermolecular contacts in the solid
state.[4,22]
ꢀ
an O atom from the triflate anion (Te(1) O(1), 2.836(6) ꢁ).
Conclusion
ꢀ
ꢀ
The Te N bonds are asymmetric (Te(1) N(1), 2.171(6);
ꢀ
Te(1) N(2), 2.288(6) ꢁ), reflecting the trans influence of the
chlorine atom bound to Te (Te(1) Cl(1), 2.492(2) ꢁ). The
We have described a facile synthetic route to diimine se-
questered forms of ChX2, which show remarkable stability
in contrast to the free binary halides. Furthermore we have
demonstrated that, in principle, these compounds may act as
a source of ChII for further transformations, possibly open-
ing new opportunities in the study of low-valent chalcogen
chemistry. This report underscores the utility of binary
ꢀ
overall geometry about Te is T-shaped, which is consistent
with the assignment of the +2 oxidation state for the telluri-
um center. Compound 9 represents only the second Te–bipy
compound to be characterized by X-ray diffraction stud-
ies.[26]
10268
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 10263 – 10271

Chalcogen Dihalides
FULL PAPER
d=163.0, 141.5, 141.2, 138.6, 132.3, 130.9, 128.8, 128.3, 126.9, 125.4, 123.3,
68.0, 29.2, 23.9 ppm; FT-Raman (ranked intensity): n˜ =89 (4), 145 (3),
204 (6), 236 (1), 273 (10), 290 (18), 443 (19), 508 (14), 625 (12), 686 (20),
831 (16), 957 (9), 1047 (15), 1127 (17), 1187 (11), 1244 (7), 1436 (8), 1576
(2), 1597 (5), 1661 cmꢀ1 (13); FTIR (ranked intensity): n˜ =266 (4), 760
(7), 781 (3), 799 (5), 833 (10), 936 (16), 1050 (11), 1086 (17), 1187 (12),
1252 (14), 1286 (9), 1324 (13), 1365 (6), 1377 (2), 1435 (1), 1575 (8), 1641
cmꢀ1 (15); elemental analysis calcd (%) for 4Cl: C 67.16, H 5.75, N 4.82;
found: C 66.44, H 6.20, N 4.92.
chalcogen halides as electrophilic reagents, which has re-
mained largely unexplored due to their instability (Se) or
complete unavailability (Te).
Experimental Section
Manipulations were performed using an N2-filled MBRAUN Labmaster
130 glove box in 4 dr. vials affixed with Teflon-lined screw caps, or using
standard Schlenk techniques. Dichloromethane, THF, Et2O, n-pentane,
and n-hexane were obtained from Caledon Laboratories and dried using
an MBRAUN SPS. The dried solvents were stored in Strauss flasks
under an N2 atmosphere, or over 4 ꢁ molecular sieves in the glove box.
Solvents for NMR spectroscopy were purchased from Cambridge Isotope
Laboratories, dried by stirring for 3 d over CaH2, distilled prior to use,
and stored in the glove box over 4 ꢁ molecular sieves. Selenium tetra-
chloride, SeBr4, TeCl4, TeBr4, TMS-OTf, benzyl magnesium chloride, and
2,2’-bipyridine were purchased from Alfa Aeasar and used as received.
Phenyl magnesium chloride, SO2Cl2, SbPh3, and elemental selenium were
obtained from the Aldrich Chemical Company. The Dipp-DAB and
Dipp-BIAN ligands, as well as SeCl2 and SeBr2 were prepared according
to literature procedures.[9–11,37,38]
Synthesis of 3Br: A freshly prepared solution of SeBr2 (0.572 mmol;
THF 5 mL) was added to a solution of Dipp-DAB (0.214 g, 0.572 mmol;
THF 5 mL) immediately, which resulted in a color change to deep red.
The mixture was stirred for 15 min. The solvent was then removed in
vacuo, which gave 3Br as a brown powder. Yield: 0.351 g (100%); d.p.
868C; 1H NMR (CDCl3); d=8.16 (br, 2H), 7.55 (br), 7.22 (br) 2.95 (br,
4H), 1.22 ppm (br, 24H); FT-Raman (ranked intensity): n˜ =109 (4), 142
(2), 160 (5), 218 (12), 236 (3), 503 (16), 535 (15), 575 (19), 836 (18), 867
(13), 887 (20), 1001 (11), 1045 (9), 1173 (6), 1242 (7), 1353 (10), 1492 (1),
1587 (8), 2960 (17), 3054 cmꢀ1 (14); FTIR (ranked intensity): n˜ =291
(10), 457 (13), 682 (8), 728 (3), 754 (9), 800 (5), 995 (16), 1059 (20), 1175
(19), 1328 (12), 1353 (15), 1365 (7), 1386 (18), 1436 (2), 1466 (6), 1475
(4), 1492 (14), 2870 (17), 2928 (11), 2960 cmꢀ1 (1).
Synthesis of 4Br: A freshly prepared solution of SeBr2 (2.47 mmol; THF
5 mL) was added to a solution of Dipp-BIAN (1.236 g, 2.47 mmol; THF
15 mL), which immediately resulted in a color change to deep purple.
The mixture was allowed to stir for 15 min. The solvent was then re-
moved in vacuo, which gave 4Br as a very deep purple powder. Yield:
1.60 g (100%); d.p. 1898C; 1H NMR (CDCl3): d=7.91 (d, 3JH,H =8.4 Hz,
2H), 7.38 (t, 3JH,H =7.2 Hz, 2H), 7.27 (overlaps residual CHCl3 signal),
Nuclear magnetic resonance spectra were recorded using an INOVA
400 MHz spectrometer (77Se=76.26 MHz; 13C=100.52 MHz) at room
temperature (258C). 77Se NMR spectra were externally referenced to
Me2Se (d=0.00 ppm using SeO2 in D2O; d=ꢀ1302 ppm), and
125Te{1H} NMR spectra were referenced to Me2Te (d=0.00 ppm using
H2TeO4 in D2O; d=712 ppm). Proton and 13C{1H} NMR spectra were
referenced relative to Me4Si using the NMR spectroscopic solvent (1H:
CHCl3, d=7.26 ppm; 13C{1H}: CDCl3 d=77.2 ppm).
3
3
3
6.66 (d, JH,H =7.2 Hz, 2H), 3.02 (sept, JH,H =7.2 Hz, 4H), 1.24 (d, JH,H
=
7.2 Hz, 12H), 0.95 ppm (d, 3JH,H =6.6 Hz, 12H); 13C{1H} NMR (CH2Cl2):
d=162.19, 142.78, 138.03, 133.66, 131.47, 130.83, 128.53, 127.7, 125.30,
124.22, 29.19, 23.93 ppm; FT-Raman (ranked intensity): n˜ =89 (8), 108
(10), 125 (7), 160 (9), 183 (2), 206 (6), 216 (4), 507 (18), 622 (19), 830
(20), 956 (13), 1000 (12), 1122 (17), 1187 (14), 1243 (15), 1435 (11), 1578
(1), 1596 (3), 1611 (6), 3055 cmꢀ1 (12); FTIR (ranked intensity): n˜ =457
(12), 541 (13), 683 (5), 729 (4), 760 (9), 781 (3), 799 (13), 833 (7), 995
(16), 1053 (10), 1188 (11), 1257 (19), 1286 (8), 1328 (15), 1364 (18), 1385
(17), 1436 (1), 1579 (6), 2868 (20), 2962 cmꢀ1 (2); elemental analysis calcd
(%) for 4Br: C 58.45, H 5.45, N 3.79; found: C 58.37, H 5.59, N 3.81.
Samples for FT-Raman spectroscopy were packed in capillary tubes,
flame-sealed, and data were collected using a Bruker RFS 100/S spec-
trometer with a resolution of 4 cmꢀ1. FTIR spectra were collected on
samples as CsI pellets using a Bruker Tensor 27 spectrometer with a reso-
lution of 4 cmꢀ1. Decomposition/melting points were recorded in flame-
sealed capillary tubes using a Gallenkamp Variable Heater. Suitable
single crystals for X-ray diffraction studies were individually selected
under oil (Paratone-N), mounted on nylon loops, and immediately placed
in a cold stream of N2 (150 K). Data were collected using a Bruker
Nonius Kappa CCD X-ray diffractometer using graphite-monochromated
MoKa radiation (l=0.71073 ꢁ). The solution and subsequent refinement
of the data were performed using the SHELXTL suite of programs.[39]
Synthesis of 5Cl: A solution of bipy (0.071 g, 0.452 mmol; THF 5 mL)
was added to a freshly prepared solution of SeCl2 (0.452 mmol; THF
5 mL), which resulted in the immediate precipitation of a light yellow
solid. The supernatant was decanted and the solids washed with Et2O
(2ꢂ5 mL), then dried in vacuo, which gave 5Cl as a pale yellow powder.
Yield: 0.117 g (85%); d.p. 260–2708C; 1H NMR (C2D6O); d=9.04 (br,
2H), 8.90 (br, 2H), 8.43 (br, 2H), 7.91 ppm (br, 2H); FT-Raman (ranked
intensity): n˜ =128 (2), 218 (5), 266 (12), 365 (7), 766 (10), 1016 (4), 1056
(11), 1161 (13), 1251 (15), 1275 (14), 1329 (3), 1494 (8), 1557 (6), 1604
(1), 3073 cmꢀ1 (9); FTIR (ranked intensity): n˜ =635 (13), 655 (12), 711
(9), 761 (1), 995 (15), 1013 (3), 1153 (11), 1168 (10), 1310 (7), 1431 (4),
1446 (2), 1468 (5), 1526 (14), 1584 (6), 1600 cmꢀ1 (8); elemental analysis
calcd (%) for 5Cl: C 39.64, H 2.43, N 9.01; found: C 39.22, H 2.64, N
9.15.
Synthesis of 3Cl: A freshly prepared solution of SeCl2 (7.33 mmol; THF
10 mL) was added to a solution of Dipp-DAB (2.89 g, 7.33 mmol; THF
15 mL) at ꢀ788C, which resulted in an orange slurry. The mixture was al-
lowed to warm to room temperature, which gave a red solution. After
stirring at RT for 20 min, the THF was removed in vacuo, which gave
3Cl as a bright orange powder. Yield: 3.88 g (96%); decomposition point
1
(d.p.) 1458C; H NMR (CDCl3): d=8.78 (brs, 2H), 7.23 (br, overlaps re-
sidual CHCl3 signal), 2.83 (br, 4H), 1.22 ppm (d, 3JH,H =6.4 Hz, 24H);
FT-Raman (ranked intensity): n˜ =84 (10), 121 (15), 143 (3), 169 (11), 189
(12), 236 (1), 308 (13), 582 (9), 841 (19), 888 (20), 1040 (18), 1052 (17),
1175 (4), 1243 (5), 1355 (7), 1488 (2), 1588 (6), 2868 (14), 2961 (16),
3061 cmꢀ1 (8); FTIR (ranked intensity): n˜ =212 (8), 279 (19), 453 (17),
579 (20), 722 (14), 755 (6), 801 (3), 867 (15), 939 (18), 1058 (11), 1100
(10), 1176 (9), 1266 (13), 1325 (7), 1354 (5), 1364 (2), 1377 (1), 1486 (4),
1589 (16), 3057 cmꢀ1 (12); elemental analysis calcd (%) for 3Cl: C 58.87,
H 7.19, N 5.73; found: C 59.30, H 6.90, N 5.32.
Synthesis of 5Br: A solution of bipy (0.140 g, 0.900 mmol; THF 5 mL)
was added to a freshly prepared solution of SeBr2 (0.900 mmol; THF
5 mL), which resulted in the immediate precipitation of a yellow solid.
The supernatant was decanted and the solids washed with Et2O (2ꢂ
5 mL), then dried in vacuo, which gave 5Br as a bright yellow powder.
Yield: 0.325 g (90%); d.p. 232–2368C; 1H NMR (CDCl3): d=9.00 (d,
Synthesis of 4Cl: A freshly prepared solution of SeCl2 (0.626 mmol; THF
10 mL) was added to a solution of Dipp-BIAN (0.407 g, 0.626 mmol;
THF 15 mL) at room temperature, which resulted in a red solution.
After stirring at RT for 20 min, the THF was removed in vacuo, which
gave 4Cl as a deep red powder. Yield: 0.503 g (100%); d.p. 1898C;
1H NMR (CDCl3): d=8.03 (d, 3JH,H =8 Hz, 2H), 7.47 (t, 3JH,H =8 Hz,
2H), 7.37 (t, 3JH,H =8 Hz, 6H), 6.67 (d, 3JH,H =8 Hz, 2H), 3.02 (sept,
3JH,H =8 Hz, 4H), 1.34 (d, 3JH,H =8 Hz, 12H), 0.94 ppm (d, 3JH,H =8 Hz,
12H); 77Se{1H} NMR (CDCl3): d=1523 ppm; 13C{1H} NMR (CH2Cl2):
3
3JH,H =4.8 Hz, 2H), 8.43 (d, 3JH,H =8 Hz, 2H), 7.98 (t, JH,H =7.2 Hz, 2H),
3
7.46 ppm (t, JH,H =4.8 Hz, 2H); FT-Raman (ranked intensity): n˜ =86 (7),
108 (10), 127 (13), 168 (3), 202 (8), 765 (12), 1013 (5), 359 (6), 1057 (14),
1159 (15), 1326 (2), 1393 (11), 1557 (4), 1602 (1), 3069 cmꢀ1 (9); FTIR
(ranked intensity): n˜ =412 (14), 631 (9), 650 (10), 710 (6), 764 (1), 1009
(2), 1107 (13), 1160 (8), 1169 (7), 1248 (15), 1311 (5), 1425 (11), 1442 (3),
1464 (12), 1598 cmꢀ1 (4); elemental analysis calcd (%) for 5Br: C 30.41,
H 1.93, N 6.99; found: C 30.39, H 2.04, N 7.09.
Chem. Eur. J. 2009, 15, 10263 – 10271
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10269

P. J. Ragogna et al.
Synthesis of 6: A solution of Ph3Sb (0.090 g, 0.255 mmol; CH2Cl2 5 mL)
was added to a slurry of 8Cl (0.108 g, 0.255 mmol; CH2Cl2 5 mL), which
resulted in an immediate color change from yellow to dark green. Et2O
(10 mL) was added and the supernatant was decanted. The solids were
washed with Et2O (2ꢂ5 mL) and the solids dried in vacuo, which gave 6
348 (15), 370 (8), 765 (6), 1018 (1), 1064 (10), 1181 (13), 1275 (14), 1325
(3), 1495 (4), 1558 (5), 1603 (2), 3089 cmꢀ1 (9); FTIR (ranked intensity):
n˜ =412 (14), 517 (8), 573 (13), 634 (2), 712 (12), 768 (6), 1025 (4), 1065
(15), 1168 (5), 1230 (1), 1293 (3), 1321 (11), 1445 (7), 1476 (9), 1603 cmꢀ1
(10).
as a dark green powder. Yield: 0.065 g (72%); d.p. 2258C; 1H NMR
Synthesis of 10: A solution of NHC (0.050 g, 0.280 mmol; THF 5 mL)
was added to a slurry of 6 (0.099 g, 0.2804 mmol; THF 5 mL), which re-
sulted in the immediate generation of a black slurry. After stirring for
10 min, the solvent was stripped in vacuo. The solids were then washed
with Et2O (2ꢂ5 mL), and then CH2Cl2 (10 mL) was added. The dark
mixture was centrifuged, which gave a yellow solution over a small
amount of black solid. The solution was decanted and the CH2Cl2 was re-
moved in vacuo, which gave 10 as a green-yellow powder. Yield: 0.072 g
(68%); d.p. 2058C (solid turns brown); 1H NMR (CDCl3): d=5.77 (br,
2H), 2.39 (s, 6H), 1.69 ppm (d, 3JH,H =7.2 Hz, 12H); 13C{1H} NMR
(CH2Cl2): d=128.1, 59.4, 20.9, 10.2 ppm; 125Te{1H} NMR (CH2Cl2): d=
902 ppm; FT-Raman (ranked intensity): n˜ =108 (7), 142 (10), 247 (1), 282
(3), 889 (12), 1279 (6), 1360 (15), 1408 (11), 1446 (8), 1572 (13), 1590
(14), 1618 (9), 2936 (2), 2963 (5), 2982 cmꢀ1 (4); FTIR (ranked intensity):
n˜ =750 (9), 765 (12), 906 (11), 1025 (15), 1114 (5), 1138 (10), 1217 (4),
1335 (14), 1370 (2), 1382 (3), 1412 (1), 1443 (6), 1618 (8), 2935 (13),
2980 cmꢀ1 (7); ESI-MS: m/z: 304 [TeIM]ꢀ, 414 [TeIMCl3]ꢀ, 793
[Te2IM2Cl5]ꢀ.
3
(CD3CN): d=9.31 (brs, 2H), 8.59 (d, 3JH,H =8.4 Hz; 2H), 8.36 (t, JH,H
=
3
7.6 Hz; 2H), 7.85 ppm (t, JH,H =6.4 Hz, 2H); FT-Raman (ranked intensi-
ty): n˜ =81 (1), 122 (3), 141 (2), 358 (7), 762 (9), 1010 (5), 1319 (6), 1485
(8), 1555 (11), 1598 (4), 3069 cmꢀ1 (10); FTIR (ranked intensity): n˜ =414
(8), 634 (12), 649 (11), 717 (5), 766 (1), 1010 (3), 1068 (14), 1114 (13),
1164 (9), 1248 (15), 1310 (7), 1439 (2), 1468 (6), 1597 (4), 3100 cmꢀ1 (10);
elemental analysis calcd (%) for 8Cl: C 34.26, H 2.27, N 7.14; found: C
33.84, H 2.27, N 7.90.
Synthesis of 7: Neat TMS-OTf (80.1 uL, 0.448 mmol) was added to a
slurry of 5Cl (0.137 g, 0.448 mmol; CH2Cl2 5 mL) and stirred at room
temperature for 10 min, which gave a colorless slurry. The solids were al-
lowed to settle, and the supernatant was decanted. The solids were then
dried in vacuo, which gave 7 as a colorless powder. Yield: 0.152 g (81%);
d.p. 200–2108C; 1H NMR (CD3CN): d=9.61 (d, 3JH,H =6.0 Hz, 2H), 8.84
3
(d, 3JH,H =8.4 Hz, 2H), 8.57 (t, 3JH,H =8.4 Hz, 2H), 8.11 ppm (t, JH,H
=
6.4 Hz, 2H); FT-Raman (ranked intensity): n˜ =85 (3), 124 (1), 260 (8),
322 (6), 381 (11), 667 (12), 767 (10), 1030 (2), 1058 (13), 1337 (7), 1505
(5), 1557 (9), 1608 (4), 3083 cmꢀ1 (14); FTIR (ranked intensity): n˜ =518
(8), 574 (11), 638 (3), 664 (14), 784 (5), 1027 (2), 1057 (12), 1134 (15),
1158 (6), 1182 (4), 1224 (7), 1261 (1), 1428 (13), 1470 (9), 1607 cmꢀ1 (10);
ESI-MS: m/z: 271 [M]+.
Synthesis of Ph2Se from 4Cl: A solution of PhMgCl (1.22 mL, 2m in
THF, 2.44 mmol) was added to a solution of 4Cl (0.7932 g, 1.22 mmol;
THF 50 mL) at ꢀ788C, which resulted in the generation of a light orange
slurry over 30 min. The mixture was allowed to warm to room tempera-
ture, and the solvent was removed in vacuo, which gave a sticky orange
gel. Hexane (50 mL) was added and the mixture was filtered. The filtrate
was reduced in volume to approximately 3 mL and was loaded onto a
silica gel column (eluent: 98.5:1.5 n-hexane/ethyl acetate). The yellow
Ph2Se eluted first and a yellow oil was recovered (0.206 g, 72%) after re-
moval of the solvent under vacuum. Purity and identity were confirmed
Synthesis of 8Cl: A solution of bipy (0.059 g, 0.371 mmol; THF 5 mL)
was added to a solution of TeCl4 (0.100 g, 0.371 mmol; THF 5 mL), which
resulted in the precipitation of a yellow solid over five minutes. The solu-
tion was stored at ꢀ308C for one hour. The supernatant was then deca-
nted and the solids dried in vacuo, which gave 8Cl as a bright yellow
powder. Yield: 0.145 g (90%); d.p. 2108C (solid turns brown); 1H NMR
1
by H and 77Se{1H} NMR spectroscopy.[40]
3
(C2D6O): d=9.11 (brs, 2H), 8.83 (d, 3JH,H =7.6 Hz, 2H), 8.60 (t, JH,H
=
3
8.0 Hz, 2H), 8.06 ppm (t, JH,H =6.0 Hz, 2H); FT-Raman (ranked intensi-
ty): n˜ =113 (3), 225 (7), 275 (4), 360 (13), 765 (15), 995 (6), 1020 (14),
1236 (11), 1302 (10), 1319 (2), 1446 (9), 1482 (12), 1572 (5), 1593 (1),
3074 cmꢀ1 (8); FTIR (ranked intensity): n˜ =412 (7), 636 (3), 646 (4), 713
(11), 763 (2), 1012 (1), 1062 (12), 1097 (13), 1247 (14), 1314 (5), 1441 (6),
1367 (9), 1494 (10), 1561 (15), 1593 cmꢀ1 (8); elemental analysis calcd
(%) for 8Cl: C 26.21, H 2.14, N 5.97; found: C 28.20, H 1.89, N 6.58;
Synthesis of Ph2Se from 5Cl: A solution of PhMgCl (0.432 mL, 2m in
THF, 0.866 mmol) was added to a solution of 4Cl (0.132 g, 0.433 mmol;
THF 5 mL) at ꢀ788C and was allowed to warm to room temperature,
which resulted in a yellow slurry. The mixture was centrifuged and the so-
lution was decanted. The THF was stripped in vacuo giving a sticky
yellow gel. The gel was washed with n-pentane (3ꢂ5 mL), the washings
were combined, and the solvent was removed in vacuo, which gave a
yellow oil. The oil was dissolved in CH2Cl2 (2 mL) and passed through a
small plug of silica gel. The CH2Cl2 was removed in vacuo, which gave
Ph2Se as a yellow oil. The amount of Ph2Se recovered was 0.082 g (82%).
molar conductivity: 59 ohmꢀ1 cm2 molꢀ1
.
Synthesis of 8Br: A solution of bipy (0.026 g, 0.164 mmol; THF 5 mL)
was added to a slurry of TeBr4 (0.074 g, 0.164 mmol; THF 5 mL), which
resulted in the precipitation of an orange solid over five minutes. The
mixture was stored at ꢀ308 for one hour, and then the supernatant was
decanted. The solids were dried in vacuo, which gave 8Br as a bright
Synthesis of Bz2Se from 3Cl: A solution of BzMgCl (2.3 mL, 1.2m in
THF, 2.76 mmol) was added to a solution of 3Cl (0.725 g, 1.38 mmol;
THF 50 mL) at ꢀ788C, which resulted in the generation of a light orange
slurry over 30 min. The mixture was allowed to warm to room tempera-
ture, and the solvent was removed in vacuo, which gave a yellow gel.
Hexane (50 mL) was added and the mixture was filtered. The filtrate was
reduced in volume to approximately 3 mL and was loaded onto a silica
gel column (eluent: 50:50 n-hexane/CH2Cl2). The yellow Bz2Se eluted
first and a yellow powder was recovered (0.128 g, 48%) after removal of
the solvent under vacuum. Purity was confirmed by 1H and
77Se{1H} NMR spectroscopy.[40]
1
orange powder. Yield: 0.080 g (80%); d.p. 2058C; H NMR (C2D6O): d=
9.20 (brs, 2H), 8.85 (d, 3JH,H =8.0 Hz, 2H), 8.60 (t, 3JH,H =7.6 Hz, 2H),
8.05 ppm (brs, 2H); FT-Raman (ranked intensity): n˜ =105 (5), 155 (1),
166 (2), 351 (7), 410 (15), 764 (14), 1015 (6), 1062 (9), 1156 (12), 1270
(13), 1314 (3), 1492 (11), 1562 (10), 1591 (4), 3066 cmꢀ1 (8); FTIR
(ranked intensity): n˜ =408 (8), 449 (12), 632 (3), 645 (6), 713 (4), 762 (1),
969 (15), 1006 (2), 1063 (10), 1243 (14), 1310 (7), 1437 (5), 1463 (9), 1490
(13), 1589 cmꢀ1 (11); elemental analysis calcd (%) for 8Br: C 19.89, H
1.18,
N 4.55; found: C 19.89, H 1.34, N 4.64; molar conductivity:
Synthesis of Bz2Se from 5Cl: A solution of BzMgCl (1.09 mL, 1.2m in
THF, 1.358 mmol) was added to a solution of 4Cl (0.207 g, 0.679 mmol;
THF 5 mL) at ꢀ788C and allowed to warm to room temperature, which
resulted in a dark brown slurry. The THF was stripped in vacuo, which
gave a brown solid. The solid was washed with Et2O (2ꢂ15 mL), the
washings were combined, and the solvent was removed in vacuo, which
gave Bz2Se as a light yellow powder. The amount of Bz2Se recovered was
0.147 g (83%).
110 ohmꢀ1 cm2 molꢀ1
.
Synthesis of 9: Neat TMS-OTf (19 uL, 0.107 mmol) was added to a slurry
of 6 (0.038 g, 0.107 mmol; CH2Cl2 5 mL). The mixture was stirred for two
hours, and then the volatiles were stripped in vacuo. Acetonitrile (5 mL)
was added and the mixture was centrifuged. The yellow supernatant was
decanted and Et2O (15 mL) was added, which resulted in a yellow precip-
itate. The solids were allowed to settle, the supernatant was decanted,
and the solids were dried in vacuo, which gave 9 as a yellow powder.
Yield: 0.033 g (66%); m.p. 198–2008C; 1H NMR (CD3CN): d=9.47 (d,
3JH,H =5.6 Hz, 2H), 8.81 (d, 3JH,H =7.6 Hz, 2H), 8.46 (t, 3JH,H =8.4 Hz,
2H), 8.00 ppm (t, 3JH,H =7.6 Hz, 2H); 19F{1H} NMR (CD3CN): d=
ꢀ78.4 ppm; FT-Raman (ranked intensity): n˜ =142 (12), 211 (11), 258 (7),
Synthesis of Ph2Te from 6: A solution of PhMgCl (0.436 mL, 2m in THF,
0.873 mmol) was added to a slurry of 6 (0.155 g, 0.436 mmol; THF 5 mL)
at ꢀ788C and allowed to warm to room temperature resulting in a
yellow slurry. The mixture was centrifuged and the solution was de-
AHCTUNGERTGcNNUN anted. The THF was stripped in vacuo, which gave a sticky yellow gel.
10270
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Chem. Eur. J. 2009, 15, 10263 – 10271

Chalcogen Dihalides
FULL PAPER
The gel was washed with n-pentane (3ꢂ5 mL), the washings were com-
bined, and the solvent was removed in vacuo, which gave Ph2Te as a
yellow oil (0.085 g, 70%). Purity and identity were confirmed by 1H and
125Te{1H} NMR spectroscopy.[41]
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Synthesis of Bz2Te from 6: A solution of BzMgCl (0.360 mL, 1.2m in
THF, 0.420 mmol) was added to a slurry of 6 (0.075 g, 0.211 mmol; THF
10 mL) at ꢀ788C and allowed to warm to room temperature, which gave
a dark red solution. The solvent was removed in vacuo, which gave a
dark red gel. The gel was washed with n-pentane (3ꢂ5 mL) and the
washings were combined. The volume of n-pentane was reduced to ap-
proximately 2 mL in vacuo and cooled to ꢀ608C, which resulted in the
precipitation of a light yellow powder. The mother liquor was decanted
and the precipitate was dried, which gave Bz2Te as a yellow powder
1
(0.038 g, 58%). Purity and identity were confirmed by H NMR spectros-
copy.[42] The 125Te{1H} chemical shift of Bz2Te was found to be d=
608 ppm.
[27] K. K. Verma, R. Dahiya, D. Soni, Synth. React. Inorg. Met.-Org.
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We thank NSERC, the Canadian Fund for Innovation, the Ontario Min-
istry for Research and Innovation, and the University of Western Ontario
for their generous funding. We are extremely grateful to Dr. Jiju Joseph
for obtaining the conductivity data for compounds 8Cl and 8Br, and the
referee who correctly suggested the ionic formulation for those com-
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Received: April 15, 2009
Published online: August 26, 2009
Chem. Eur. J. 2009, 15, 10263 – 10271
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10271