Structure of "bis(methoxymagnesium)diselenide": A reagent for the introduction of selenium into organic molecules

Article abstract of DOI:10.1007/s10870-006-9156-7

The reaction of magnesium and selenium in dry methanol has been reported to yield a reagent tentatively identified as bis(methoxymagnesium) diselenide. The dark red-brown solution obtained from this reaction yielded red crystals that crystallized in the monoclinic space group C2/c, a=17.391(4) A, b=15.823(3) A, c=21.626(4) A, β=110.71(3)°, V=5566.5(19) A³, Z=4, R=0.0350, wR₂=0.0850 for 4930 reflections. X-ray crystallographic analysis of this reagent showed it to be dodecamethanol-tetramethoxy-di(μ₄-hydroxy)tetra(μ₃- methoxy)hexamagnesium hexaselenide, Mg₆(μ₄-OH) ₂(μ₃-OCH₃)₄(OCH₃) ₄(CH₃OH)₁₂]Se₆·2CH ₃OH (1), not the bis(methoxymagnesium) diselenide as previously described. The structure of 1 is composed of six magnesium ions and six bridging oxygen-containing ligands in a face-sharing cubic arrangement.

Full text of DOI:10.1007/s10870-006-9156-7

ꢀ
C
Journal of Chemical Crystallography, Vol. 37, No. 2, February 2007 ( 2006)
DOI: 10.1007/s10870-006-9156-7
Structure of “bis(methoxymagnesium)diselenide”:
A reagent for the introduction of selenium
into organic molecules
Rajashree Sathyamurthy,(1) Julia L. Brumaghim,(1)∗ and Donald G. VanDerveer(1)
Received August 10, 2006; accepted September 20, 2006
Published Online November 9, 2006
The reaction of magnesium and selenium in dry methanol has been reported to yield
a reagent tentatively identified as bis(methoxymagnesium) diselenide. The dark red-
brown solution obtained from this reaction yielded red crystals that crystallized in
the monoclinic space group C2/c, a = 17.391(4) Å, b = 15.823(3) Å, c = 21.626(4) Å,
β = 110.71(3)◦, V = 5566.5(19) Å3, Z = 4, R = 0.0350, wR2 = 0.0850 for 4930 reflec-
tions. X-ray crystallographic analysis of this reagent showed it to be dodecamethanol-
tetramethoxy-di(µ4-hydroxy)tetra(µ3-methoxy)hexamagnesium hexaselenide, Mg6(µ4-
OH)2(µ3-OCH3)4(OCH3)4(CH3OH)12]Se6 · 2CH3OH (1), not the bis(methoxymagnesium)
diselenide as previously described. The structure of 1 is composed of six magnesium ions
and six bridging oxygen-containing ligands in a face-sharing cubic arrangement.
KEY WORDS: methoxymagnesium selenide reagent; polyselenide; methoxymagnesium cluster.
Introduction
Many synthetic approaches for the intro-
number of synthetic approaches have employed
elemental selenium to yield a metal-diselenide
species. On further reaction with organic halides,
these reagents yield the desired organic dise-
lenides. Typically, these types of reactions in-
volve treating elemental selenium with a Grig-
nard reagent5 or with alkali metals as shown in
Fig. 1.6,7 These approaches also use highly re-
active alkali metals and require multiple steps to
isolate and purify the desired diselenide.6
However, Gu¨nther reported the synthesis
of a bis(methoxymagnesium) diselenide reagent
that avoids the disadvantages of other dise-
lenide synthesis.8 This reagent is synthesized by
treating elemental selenium with magnesium in
dry methanol, and the resulting reagent adds
a diselenide moiety directly to organic halides
via nucleophilic displacement.8 Thus, with this
reagent, organic diselenides can be generated in a
duction of diselenide into organic molecules are
based on converting elemental selenium into a
nucleophilic species, a transformation achieved
either through the formation of various inorganic
selenium compounds such as potassium seleno-
cyanate1 and potassium selenosulfate,2 or through
the formation of selenium compounds with a pro-
tective organic group such as benzyl selenol3 or
selenourea.4 These methods often involve mul-
tiple steps to generate the selenium-containing
product and subsequently yield the desired or-
ganic diselenide compounds. More recently, a
(1)
Department of Chemistry, Clemson University, Clemson South
Carolina 29634-0973.
To whom correspondence should be addressed; e-mail: bru-
∗
magh@clemson.edu
109
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1074-1542/07/0200-0109/0 2006 Springer Science+Business Media, LLC

110
Sathyamurthy, Brumaghim, and VanDerveer
cat. PhC
CPh
2 R-X
2 Se + 2 M
R-Se-Se-R + R-Se-R
M2Se2
M= Li, Na, K
Fig. 1. Reaction of elemental selenium with alkali metals as a precursor to the formation of
organic diselenides.
minimum number of steps with good yield (Fig.
2), while avoiding the use of reactive alkali met-
als. Based on the amount of gas evolved by the
reaction of magnesium and methanol in the pres-
ence and absence of selenium, and on elemen-
tal analysis, this reagent was tentatively identified
as a diselenide with the formula (MeOMg)2Se2.
Since this reagent has broad applications in syn-
thesizing organic diselenides and its composi-
tion was uncertain, we crystallized this com-
pound to determine its structure. Instead of the
reported bis(methoxymagnesium) diselenide, the
X-ray structure revealed the compound to be a
much more complex methoxymagnesium cluster
cation with a hexaselenide anion.
until all solids dissolved. The resultant dark
red-brown solution was cooled to − 20◦C for
24 hrs to yield red crystals of 1.
Synthesis of dibenzyl diselenide. Dibenzyl
diselenide was synthesized from 1 as reported
by Gu¨nther8 using benzyl chloride (6.3 g, 0.05
mole) and a methanolic solution of 1 (from 0.05 g-
atom of selenium). After 10 min stirring, wa-
ter (100 mL) and concentrated hydrochloric acid
(5 mL) were added, the solution was cooled, and
the black solid was collected by filtration. This
black solid was then extracted with ethanol to
yield a bright yellow solution which, upon sol-
vent removal, gave a yellow crystalline product.
The 1H NMR of the yellow solid (in CDCl3) was
identical to that of commercially available diben-
zyl diselenide.
Experimental
X-ray structure determination of 1. A single
crystal of 1 was mounted on a glass fiber and
cooled to − 100◦C in a cold nitrogen stream on a
Rigaku AFC8 diffractometer. Data were collected
with an area detector using the measurement pa-
rameters listed in Table 1. Systematic absences
for h k l (h + k = 2n) and h 0 l (l = 2n) were only
consistent with space groups Cc and C2/c. The
centrosymmetric space group C2/c was chosen
based on the average values of the normalized
structure factors. The measured intensities were
reduced to structure factor amplitudes and were
corrected for absorption using REQAB9 multi-
scan technique, background and Lorentz and
Preparation of [Mg6(µ4-OH)2(µ3-OCH3)4
(OCH3)4(CH3OH)12]Se6 · 2CH3OH (1). The
bis(methoxymagnesium) diselenide reagent (1)
was synthesized as reported8 except that the
reaction was carried out under argon. Magnesium
turnings (3.0 g) and a small crystal of iodine were
added to a Schlenk flask and activated by heating
briefly over a flame. The flask was flushed with
argon, dry methanol (150 mL) was added, and
the flask was fitted with a reflux condenser and
a magnetic stirrer. After the yellow iodine color
had been discharged, selenium powder (7.9 g)
was added, and the mixture was stirred overnight
R-X
"(MeOMg)2Se2"
Mg + CH3OH + Se
R-Se-Se-R
(1)
Fig. 2. General reactions of an organic halide with the “(MeOMg)2Se2” reagent (1)
to afford organic diselenide compounds (R = benzylic, aliphatic groups; X = Br, Cl;
range of yields = 55–85%).8

Structure of “bis(methoxymagnesium)diselenide”
111
Table 1. Crystallographic data and structure refinement for 1
rameters were set equal to 1.5 times Ueq of the
attached carbon atom. Eight molecules of non-
coordinating methanol were also found in the unit
cell. Final refinement parameters for the struc-
ture of 1 are given in Table 1. The highest peak
in the final Fourier difference map (1.08 Å3)
was located 1.19 Å from Se(3) and the lowest
peak ( − 0.48 Å3) was located at a distance of
0.79 Å from Se(3). The final analysis of variance
between observed and calculated structure factors
showed no apparent errors.
Empirical formula
Formula weight (amu)
CCDC #
C22H82O24Mg6Se6
1350.50
615359
Temperature
Wavelength, λ (Å)
Crystal system,
Space group
a (Å)
173(2) K
0.71073
Monoclinic
C2/c
17.391(4)
15.823(3)
21.626(4)
110.71(3)
5566.5(19)
4
b (Å)
c (Å)
β (◦)
V (Å3)
Z
Crystal size (mm)
0.31 × 0.26 × 0.24
calc (g cm−3
1.611
Results and discussion
D
)
Absorption coefficient, µ
4.077
(mm−1
θ range, ◦
)
In 1967, Gu¨nther reported that the reaction
of activated magnesium and selenium in
dry methanol yielded a reagent tentatively
identified as bis(methoxymagnesium) diselenide
(1).8 Although use of air-sensitive techniques
is not mentioned in the reported synthetic
procedure, we repeated the synthesis under
argon due to the reported instability of 1 to
oxygen and water.8 Cooling the resultant dark
red solution to − 20◦C yielded red crystals of
2.76–25.10
0.4412 and 0.3646
23234
0.0421
4930/0/281
1.068
Max. and min. transmission
Reflections collected
Reflections unique (Rint
)
Data/restraints/parameters
Goodness of fit on F2
R1a, wR2 [I > 2σ(I)]
0.0350, 0.0850
0.0501, 0.0899
a
b
R1 wR2 (all data)
ꢀ
ꢀ
aR1
=
ꢂ Fo–|Fc ꢂ )/ |Fo| for observed data (I > 2σ(I)).
ꢀ
bwR2 = { [w(Fo2–Fc2)2]/[w(Fo2)2]}1/2 for all data.
–
–
[Mg6(µ4 OH)2(µ3 OCH3)4(OCH3)4(CH3OH)12]
Se6 · 2CH3OH (1), the structure of which was
solved by X-ray analysis.
polarization effects using Crystal Clear.10 Sys-
tematically absent reflections were removed and
symmetry equivalent reflections were averaged
to yield the set of unique data. The struc-
ture solution, refinement, and calculation of
derived results were performed using direct
methods with SHELXTL.11 Subsequent least-
squares refinement and difference Fourier calcu-
lations revealed the positions of non-hydrogen
The asymmetric unit of 1 is shown in Fig. 3,
and selected bond distances and angles are given
in Table 2. The structure of the entire ion pair is
shown in Fig. 4, and consists of a methoxymagne-
sium cluster cation, a hexaselenide (Se62−) anion,
and two non-coordinating methanol molecules.
The methoxymagnesium cluster cation of 1 is
unique in that it consists of six magnesium ions
and six bridging oxygen ligands in a face-sharing
cubic arrangement. In addition, different coordi-
nation environments are observed for Mg(1) as
compared to Mg(2) and Mg(3) (Fig. 5). Despite
the differences in coordination, each magnesium
ion has Mg-O coordination in distorted octahe-
dral geometry. To distinguish the methoxy and
methanol ligands, hydrogen atoms bonded to oxy-
gen atoms were located based on geometries of
peaks found in electron density maps. Mg(1) is
bound to two quadruply-bridging OH groups, two
atoms. The quantity minimized by the least-
ꢀ
2
2 2
squares program was
w = (Fo –Fc ) , where
2
w = {[σ2(Fo )] + (0.0460P)2 + 7.7633P}−1 and
2
2
P = (Fo + 2Fc )/3]. The analytical approxima-
tions to the scattering factors were used, and all
structure factors were corrected for both real and
imaginary components of anomalous dispersion.
In the final cycle of least squares, independent
anisotropic displacement factors were refined for
the non-hydrogen atoms and the methyl hydrogen
atoms were fixed in “idealized” positions with
–
C H = 0.96 Å. Their isotropic displacement pa-

112
Sathyamurthy, Brumaghim, and VanDerveer
Fig. 3. The asymmetric unit of 1. The 40% probability density surfaces are shown.
nesium this distance is 2.08 Å,13 and in
triply-bridging OCH3 groups, and two terminal
OCH3 groups. Mg(2) and Mg(3) are each co-
ordinated to three terminal CH3OH groups, one
quadruply-bridging OH group, and two triply-
bridging OCH3 groups. Mg(1) differs from the
other two magnesium ions in the cation since it
has no terminal CH3OH coordination.
Mg(OCH3)2 · 3.5CH3OH the distance of
–
triply-bridging Mg OCH3 bonds vary from 2.05–
2.14 Å.14 Mg(1) is unique in its coordination
to terminal methoxy groups, with an average
terminal Mg(1)–OCH3 bond distance of 2.03 Å.
This bond distance is comparable to the 2.01–
The methoxymagnesium cation of 1 lies aro-
und an inversion center at 0, 0.5, 0 as derived
from the atomic coordinates. In 1, the average
bond distance of triply bridging methoxy groups,
–
2.09 Å distances reported for terminal Mg OCH3
bonds in Mg(OCH3)2 · 3.5CH3OH.14
Two quadruply-bridging hydroxyl groups
(containing O2 and O2A) lie across the inver-
sion center with Mg-O bond distances from 2.12–
2.24 Å. The average distance of the terminal Mg–
O(H)CH3 bonds is 2.06 Å, somewhat less than the
2.15 Å12 and 2.14 Å13 average bond distances for
terminal Mg–O(H)CH3 bonds reported for similar
magnesium clusters. The Mg-Mg bond distances
in 1 range from 3.05 to 3.19 Å.
–
–
Mg(2) OCH3 and Mg(3) OCH3 is 2.05 Å,
–
whereas that of Mg(1) OCH3 is slightly longer
–
at 2.140(3) Å. The triply bridging Mg OCH3
distances observed for 1 are comparable to
those in the few reported methoxymagnesium
clusters: the average distance of triply-bridging
Mg-OCH3 bonds in tetrakis(µ3-methoxo)tetrakis
(acetylacetonato-O,O’-tetrakis(methanol-O)tetr-
amagnesium reported by Kessler et al. is
2.07 Å,12 in tetrakis(µ3-methoxo)(2,2,6,6-tetra-
methylheptane-3,5-dionato)(methanol-O) mag-
The structure of the hexaselenide (Se62−) an-
ion in 1 has a helical conformation similar to
that reported for polyselenide compounds with
organic counterions.15,16 The average Se-Se bond

Structure of “bis(methoxymagnesium)diselenide”
113
Table 2. Selected bond lengths (Å) and angles (◦) for 1
–
–
Se(2) Se(3)
2.3111(8)
2.024(2)
2.117(2)
Se(1) Se(2)
2.3167(8)
2.029(2)
2.122(3)
2.138(2)
3.1665(15)
3.1915(16)
3.0552(15)
2.3657(13)
3.1481(15)
2.051(2)
2.188(2)
2.050(2)
2.117(2)
2.063(3)
2.071(3)
2.035(3)
110.73(10)
95.56(9)
87.86(10)
87.48(10)
83.17(9)
95.55(10)
162.02(9)
82.34(9)
85.07(7)
43.90(7)
126.63(8)
134.39(8)
81.95(7)
39.86(6)
57.71(4)
57.96(4)
121.1(2)
96.25(10)
99.18(9)
106.07(10)
94.32(9)
93.29(9)
122.48(19)
96.22(9)
–
–
Mg(1) O(4)
–
Mg(1) O(2)
–
Mg(1) O(1)
–
Mg(1) Mg(3)
–
Mg(1) Mg(2)
–
Mg(2) Mg(3)
–
Se(3) Se(3)#2
–
Mg(3) Mg(1)#1
–
O(1) Mg(3)
–
O(2) Mg(3)#1
–
O(3) Mg(2)
–
O(3) Mg(1)#1
–
O(7) Mg(2)
–
O(9) Mg(3)
–
O(11) Mg(3)
– –
O(5) Mg(1) O(4)
– –
O(4) Mg(1) O(3)#1
– –
O(4) Mg(1) O(2)
– –
O(5) Mg(1) O(2)#1
– –
O(3)#1 Mg(1) O(2)#1
– –
O(5) Mg(1) O(1)
– –
O(3)#1 Mg(1) O(1)
– –
O(2)#1 Mg(1) O(1)
– –
O(4) Mg(1) Mg(3)#1
– –
O(2) Mg(1) Mg(3)#1
– –
O(1) Mg(1) Mg(3)#1
– –
O(4) Mg(1) Mg(3)
– –
O(2) Mg(1) Mg(3)
– –
O(1) Mg(1) Mg(3)
– –
Mg(3)#1 Mg(1) Mg(1)#1
– –
Mg(2)#1 Mg(1) Mg(1)#1
– –
C(1) O(1) Mg(2)
Mg(1) O(5)
–
Mg(1) O(3)#1
–
Mg(1) O(2)#1
2.130(2)
–
Mg(1) Mg(3)#1
3.1481(15)
3.1771(19)
3.398(2)
3.1771(19)
2.188(2)
2.053(2)
2.130(2)
2.238(3)
2.054(2)
–
Mg(1) Mg(2)#1
–
Mg(1) Mg(1)#1
–
Mg(2) Mg(1)#1
–
Mg(3) O(2)#1
–
O(1) Mg(2)
–
O(2) Mg(1)#1
–
O(2) Mg(2)
–
O(3) Mg(3)
–
O(6) Mg(2)
2.066(2)
2.050(3)
2.071(2)
–
O(8) Mg(2)
–
O(10) Mg(3)
–
–
Se(3) Se(1) Se(2)
110.07(2)
94.40(10)
161.41(10)
83.06(9)
161.78(11)
73.93(10)
94.87(10)
82.73(9)
134.27(8)
40.25(6)
82.29(7)
84.93(7)
126.71(7)
43.55(6)
114.90(4)
57.19(3)
57.55(4)
124.49(19)
112.69(19)
98.20(10)
93.84(10)
94.07(9)
–
–
–
O(5) Mg(1) O(3)#1
–
O(5) Mg(1) O(2)
–
–
O(3)#1 Mg(1) O(2)
–
–
–
–
–
O(4) Mg(1) O(2)#1
–
O(2) Mg(1) O(2)#1
–
O(4) Mg(1) O(1)
–
O(2) Mg(1) O(1)
–
–
O(5) Mg(1) Mg(3)#1
–
–
–
–
O(3)#1 Mg(1) Mg(3)#1
O(2)#1 Mg(1) Mg(3)#1
–
–
O(5) Mg(1) Mg(3)
–
–
–
–
O(3)#1 Mg(1) Mg(3)
O(2)#1 Mg(1) Mg(3)
Mg(3)#1 Mg(1) Mg(3)
–
–
–
–
–
Mg(3) Mg(1) Mg(1)#1
–
Mg(2) Mg(1) Mg(1)#1
–
–
–
– –
Mg(2) O(1) Mg(3)
– –
Mg(2) O(1) Mg(1)
– –
Mg(1) O(2) Mg(1)#1
– –
Mg(1)#1 O(2) Mg(3)#1
– –
Mg(1)#1 O(2) Mg(2)
– –
C(2) O(3) Mg(2)
– –
Mg(2) O(3) Mg(3)
C(1) O(1) Mg(3)
–
C(1) O(1) Mg(1)
–
–
–
–
Mg(3) O(1) Mg(1)
–
Mg(1) O(2) Mg(3)#1
–
Mg(1) O(2) Mg(2)
–
–
Mg(3)#1 O(2) Mg(2)
167.08(12)
120.84(18)
–
–
C(2) O(3) Mg(3)
Symmetry transformations used to generate atoms #1–x, –y–1, –z #2 –x, –y, –z + 1/2.
spectively) in 1. It is interesting to note the Se(2)–
distance of 2.331 Å in 1 is comparable to the
2.3351 Å Se-Se distance found in [NMe4]2Se6.
Se(3)–Se(3A) bond angle of 105.66(3)◦ is sim-
17
2−
ilar to the bond angles found for known Se5
One characteristic feature of polychalcogenide
complexes (104.5◦–106.6◦),17 but smaller than
2−
Sex anions is that the two outer Se-Se bonds
2−
the corresponding bond angle for the Se6 moi-
are shorter than the innermost Se-Se bond, likely
ety in [Me4N]2Se6◦(110.1◦). However, the bond
due to pπ – dπ bonding.17 Accordingly, the cen-
–
angle of 110.05(3) between Se(1) Se(2)–Se(3)
–
tral Se(3) Se(3A) bond length of 2.3657(13) Å is
atoms is comparable to that seen for [Me4N]2Se6
slightly longer the Se(1)–Se(2) and Se(1)–Se(3)
bond distances (2.3111(8) and 2.3167(8) Å, re-
(109.3◦).17

114
Sathyamurthy, Brumaghim, and VanDerveer
Fig. 4. Structure of 1. Hydrogen atoms and non-coordinating methanol molecules have been
removed for clarity. The 40% probability density surfaces are shown.
The crystal packing of 1 viewed along the
lenides into organic halides. Although the cal-
culated elemental analysis values for Gu¨nther’s
proposed (CH3OMg)2Se2 · 4CH3OH formula and
the actual structure of 1 are similar, neither corre-
spond exactly to the questionable elemental anal-
ysis data reported in his 1967 paper. Despite
an excess of selenium found in the elemental
c-axis is depicted in Fig. 6. The cluster cation,
selenide anion, and the methanol of crystallization
are connected by three hydrogen bonds: between
Se(1) and O(8) from a terminal methanol group
(Se-O distance 3.264 Å), Se(1) and O(15) with
the non-coordinating methanol molecule (Se-O
distance 3.310 Å), and O(15) and O(11) of a
coordinating methanol molecule (O-O distance
2.592 Å). When viewed along the c-axis, the
hexaselenide anions are seen along the four cor-
ners of the unit cell at coordinates (a = 0, b = 0),
(0,1), (1,0), and (1,1) and at the middle of the cell
(a = 1/2, b = 1/2). The methoxymagnesium clus-
ter cations are stacked along the center of each
side of the unit cell at coordinates (1/2, 0), (0,
1/2), (1, 1/2), and (1/2, 1/2).
analysis, G
u¨nther assumed the reagent to be a
diselenide, and explained that the higher value
of selenium found during analysis was likely
due to the formation of triselenide chains in the
reagent.8 Despite the inaccuracy of the reported
elemental analysis data, we successfully repeated
the synthesis of dibenzyl diselenide from benzyl
chloride and 1 according to Gu¨nther’s reported
procedure.
By measuring the amount of gas evolved
u¨nther arrived
Gu¨nther likely identified the reagent 1 as a
diselenide because it is used to introduce dise-
from the reaction mixture, G
at the stoichiometry of three molecules of

Structure of “bis(methoxymagnesium)diselenide”
115
Fig. 5. Structure of the hexamagnesium cluster in 1, showing the varied magnesium ion
coordination.
methanol reacting with two atoms each of
magnesium and selenium. As he states, this
stoichiometry neither satisfies the simple
valence of the elements involved in synthesis
of the reagent nor corresponds to his proposed
formula for 1.8 These results, however, do
correspond well to the actual structure of 1,
degree of complexity than the (CH3OMg)2Se2
structure originally proposed by Gu¨nther.
Conclusion
Gu¨nther reported the reaction of magnesium
and selenium in refluxing dry methanol to yield
a reagent tentatively identified as bis(methoxy-
magnesium) diselenide. X-ray crystallographic
analysis of this reagent instead showed it to be
–
–
[Mg6(µ4 OH)2(µ3 OCH3)4(OCH3)4(CH3OH)12]
Se6 · 2CH3OH. From this formula, four equiva-
lents of hydrogen (to form the eight methoxide
ligands) and one equivalent of ethane (to form
the two hydroxide ligands) would be generated
during the reaction, requiring ten equivalents of
methanol for every six of magnesium or selenium.
This 3.3 to 2 ratio found for the formation of 1 is
much closer to the reported experimental results
than the 1:1 ratio expected for the formation of
(CH3OMg)2Se2. Thus, upon structural analysis,
our reported structure of 1 reveals a much greater
–
–
[Mg6(µ4 OH)2(µ3 OCH3)4(OCH3)4(CH3OH)12]
Se6 · 2CH3OH (1). The crystal structure of 1
reveals the compound to be a hexaselenide anion
with a cationic methoxymagnesium cluster, and
our reported structure better agrees with previous
characterization than the structure reported
by Gu¨nther. In 1, the structure of the cationic
cluster is unique, having a face-sharing cubic

116
Sathyamurthy, Brumaghim, and VanDerveer
b
0
c
a
Fig. 6. Packing diagram of 1 viewed along the c-axis of the unit cell. Hydrogen atoms are
omitted for clarity. Dotted lines show hydrogen bonding between Se(1)–O(15), Se(1)–O(8) and
O(11)–O(15).
cation with varied coordination to magnesium
ions. The hexaselenide anion has the expected
helical conformation. This reagent can be used
to synthesize many types of organic diselenides
from the corresponding organic halides in good
yields.
Acknowledgements
We thank the NSF for research grant CHE-
0545138 and for grant CHE-9808165 (CRIF) to
support the X-ray diffractometer.
References
Supplementary material: Additional data of the X-ray struc-
ture reported in this paper have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary publications,
CCDC number 615359. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, United Kingdom (fax: + 44–1223–336033, email: de-
posit@ccdc.cam.ac.uk).
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