Aryl(trimethylsilyl)selenides as reagents for the synthesis of mono- and diselenoesters

Article abstract of DOI:10.1021/om200768m

Silylated organoselenium reagents react undermild conditions with acid chlorides to provide a high yield route to aromatic selenoesters. The synthesis, structures, and spectroscopic properties of the selenoesters C ₆H₅SeC(O)R(R=CH₂CH₃, 1; p-CH ₃C₆H₄, 2; p-C6Me4Br, 3; p-C6Me4C-(O)SeC ₆H₅, 4) and RC(O)SeFcSeC(O)R (Fc = Fe(C5H4)2;R=CH ₂CH₃, 5; p-CH₃C₆H₄, 6; p-BrC6Me4, 7) and RC(O)Se(C6H4)nSeC(O)R (n = 1, R=CH₂CH₃, 8a; n = 2, R =CH₂CH₃, 8b; n = 1, R= p-CH₃C ₆H₄, 9a; n = 2, R=p-CH₃C₆H ₄, 9b; n=1,R=p-C6Me4Br, 10a; n=2, R = p-C6Me4Br, 10b) andC ₆H₅SeC(O)CH₂CH₂C(O)SeC ₆H₅ 11 are discussed. Although 11 can be prepared in high yield from the reaction of C₆H₅SeSiMe3 and ClC(O)CH ₂CH₂C(O)Cl in tetrahydrofuran solvent, similar reactions in the absence of solvent led to the competitive formation of both 11 and (C₆H₅Se)3CCH₂CH₂C(O)OSiMe3 12. The new selenoesters have been characterized by multinuclear NMR (¹H, ¹³C, ⁷⁷Se), IR, and UV-vis spectroscopies, electrospray mass spectrometry, and, for complexes 2, 4, 7, 10b, and 12, single-crystal X-ray diffraction. 2011 American Chemical Society.

Full text of DOI:10.1021/om200768m

ARTICLE
pubs.acs.org/Organometallics
Aryl(trimethylsilyl)selenides as Reagents for the Synthesis
of Mono- and Diselenoesters
Deeb Taher†,§ and John F. Corrigan*,†,‡
†Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
‡Centre for Advanced Materials and Biomaterials Research, The University of Western Ontario, London, ON,
Canada N6A 3K7
S Supporting Information
b
ABSTRACT: Silylated organoselenium reagents react under mild conditions
with acid chlorides to provide a high yield route to aromatic selenoesters.
The synthesis, structures, and spectroscopic properties of the selenoesters
C6H5SeC(O)R(R=CH2CH3, 1;p-CH3C6H4, 2;p-C6Me4Br, 3;p-C6Me4C-
(O)SeC6H5, 4) and RC(O)SeFcSeC(O)R (Fc = Fe(C5H4)2; R = CH2CH3,
5; p-CH3C6H4, 6; p-BrC6Me4, 7) and RC(O)Se(C6H4)nSeC(O)R (n = 1,
R = CH2CH3, 8a; n = 2, R = CH2CH3, 8b; n = 1, R = p-CH3C6H4, 9a; n = 2,
R = p-CH3C6H4, 9b; n = 1, R = p-C6Me4Br, 10a; n = 2, R = p-C6Me4Br, 10b) and C6H5SeC(O)CH2CH2C(O)SeC6H5 11 are discussed.
Although 11 can be prepared in high yield from the reaction of C6H5SeSiMe3 and ClC(O)CH2CH2C(O)Cl in tetrahydrofuran solvent,
similar reactions in the absence of solvent led to the competitive formation of both 11 and (C6H5Se)3CCH2CH2C(O)OSiMe3 12. The
new selenoesters have been characterized by multinuclear NMR (1H, 13C, 77Se), IR, and UVꢀvis spectroscopies, electrospray mass
spectrometry, and, for complexes 2, 4, 7, 10b, and 12, single-crystal X-ray diffraction.
’ INTRODUCTION
telluroesters, C6H5TeC(O)Ar, via the formation of Me3SiCl.23
Severengiz and du Mont demonstrated similar reactivity with
Te(SiMe3)2.24 Aryl(trimethylsilyl)selenides offer a convenient,
easily handled source of “ArSeꢀ” in the synthesis of metalꢀ
selenolate complexes.25 To date, the reaction chemistry of
ArSeSiMe3 has not been similarly developed for the formation of
selenoesters, although we recently reported the preparation of
trans-Pd(PBu3)2(SeC(O)Et)2 from the reaction of trans-Pd-
(PBu3)2(SeSiMe3)2 with ClC(O)Et.26 Herein, we demonstrate
the straightforward and efficient preparation of a variety of
selenoesters from the reaction of acid chlorides and readily
prepared aryl(trimethylsilyl)selenides. This includes examples
of bis(trimethylsilylselenium) complexes of the type Me3SiSe-
Ar-SeSiMe3 that have recently been reported (Ar = 1,4-C6H4;
4,40-C6H4-C6H4; (C5H4)2Fe).27
The development of convenient and efficient methods for the
synthesis of selenoesters has attracted considerable attention, due to
the importance of these Se systems in organic synthesis.1zꢀ3
Acyl selenides and selenoesters can produce acyl radicals under
mild conditions, which can be used in a large variety of inter-
and intramolecular reactions.4 Acyl selenides are also useful
synthetic intermediates and are employed as building blocks
for the synthesis of heterocyclic compounds,5 in asymmetric aldol
reactions,6 and as precursors for acyl radical chemistry.7,8 Sele-
noesters can also be converted to their corresponding acids,9
esters,9 amides,9a ketones,10 aldehydes,11 and alkenyl selenides.12
Methods to prepare selenoesters include the reaction of acyl halides
with selenols, or alkali metal selenide salts,13,14 transition-metal-
catalyzed carbonylation,15 and the Pd-catalyzed coupling of
stannyl/silyl selenide and acyl halides.16 They have also been
prepared by the reaction of aldehydes, acyl halides, or esters with
organoselenolato reagents, such as C6H5SeTl,17 Hg(SeR)2
(R = alkyl, aryl),18 and Me2AlSeMe,9a,c as well as reactions
between acyl chlorides and C6H5SeSeC6H5 mediated by
indium iodide19 or RhCl(PPh3)3.20 Zhang and co-workers
have also reported novel syntheses of selenoesters by using
SmI2,21a Sm/TMSCl/H2O,21b TiCl4-Sm,21c Sm/CrCl3,21d and
Sm/CoCl221e as reducing agents. Other methods include treating
aryl selenocyanates with carboxylic acids,22a and α,β-unsaturated
selenoesters can be prepared by the reaction of acylzirconocene
chlorides with electrophilic selenium bromides.22b
’ RESULTS AND DISCUSSION
We have found that a range of structurally diverse alkyl and
aryl acid chlorides undergo reactions with phenylselenotri-
methylsilane (eq 1), 1,10-bis(trimethylsilylseleno)ferrocene (eq 2),
phenylene-1,4-bis(trimethylsilylselenium) (eq 3), and biphenylene-
4,40-bis(trimethylsilylselenium) (eq 4), in good yields. The
results are summarized in Tables 1 and 2. Reactions of
propionyl chloride proceed under mild conditions; however,
reactions with the more sterically restricted (aromatic) acid
chlorides are comparatively slow and need higher temperatures
It has been demonstrated by Ogura and co-workers that the
heavier congener tellurium reagent C6H5TeSiMe3 reacts directly
with acyl chlorides under ambient conditions to yield a variety of
Received: August 17, 2011
Published: October 13, 2011
r
2011 American Chemical Society
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Table 1. Synthesis of Aryl- and Ferrocenylselenoestersa
a Yields refer to those of pure isolated products characterized by IR and 1H, 13C, and 77Se NMR spectroscopies.
to proceed.
with reagents containing two ꢀSeSiMe3, namely, 1,10-bis-
(trimethylsilylseleno)ferrocene, 1,4-bis(trimethylsilylseleno)-
phenylene, and biphenylene-4,40-bis(trimethylsilylselenium),
under reaction conditions similar to those for 1 afforded the
corresponding selenoesters (5, 8a, and 8b, respectively) in good
yield (Tables 1 and 2). Similar reactions with aromatic p-toluoyl
chloride proceeded only at higher temperatures (40 °C over 5 h) to
give the corresponding selenoesters 2, 6, 9a, and 9b in 78ꢀ85%
yields (entries 2, 6 in Table 1; entries 3, 4 in Table 2). Reactions
with a more sterically encumbered aryl chloride also proceed
without any difficulty, although more forcing conditions were
required. Thus, 1,4-C6Me4BrC(O)Cl reacted cleanly with arylse-
lenotrimethylsilanes (neat) at 85 °C to furnish the corresponding
selenoesters in good yield (entries 3, 7 in Table 1; entries 6, 7
in Table 2). Furthermore, when 1,4-benzenedicarbonyldichloride-
2,3,5,6-tetramethyl was treated with 2 equiv of phenylselenotri-
methylsilane at 85 °C for 5 h, the di(selenoester) 1,4-(C6H5SeC-
(O))2C6Me4 4 was generated in 87% yield. No reaction was
observed between 1,4-(ClC(O))2C6Me4 and PhSeSiMe3 in solu-
tions of tetrahydrofuran, even at higher temperatures (reflux).
PhSeSiMe3 þ RCðOÞCl f PhSeCðOÞR þ Me3SiCl
ð1Þ
1; 10-Feðη5-C5H4SeSiMe3Þ2 þ 2RCðOÞCl
f 1; 10-Feðη5-C5H4SeCðOÞRÞ2 þ 2Me3SiCl
ð2Þ
ð3Þ
1; 4-Me3SiSe-C6H4-SeSiMe3 þ 2RCðOÞCl
f 1; 4-RðOÞCSe-C6H4-SeCðOÞR þ 2Me3SiCl
4; 40-Me3SiSe-ðC6H4Þ2-SeSiMe3 þ 2RCðOÞCl
f 4; 40-RðOÞCSe-ðC6H4Þ2-SeCðOÞR þ 2Me3SiCl ð4Þ
Thus, when propionyl chloride, CH3CH2C(O)Cl, was re-
acted with phenylselenotrimethylsilane at ꢀ10 °C in THF for
2 h, C6H5SeC(O)CH2CH3 122 was obtained in 80% yield after
workup at room temperature. Treatment of propionyl chloride
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Table 2. Synthesis of Aryl- and Ferrocenylselenoestersa
a Yields refer to those of pure isolated products characterized by IR and 1H, 13C, and 77Se NMR.
Table 3. Selected Spectroscopic Data for theSelenoesters1ꢀ11
compound
for the aromatic derivatives 2ꢀ4, 6, 7, 9, and 10 (δ = 189.1ꢀ
200.6).28ꢀ30
IR (cmꢀ1) νCO
77Se{1H} NMR ppm
13C (CO) ppm
The nature of some of the structures of the selenoesters in the
solid state was confirmed by X-ray crystallographic analysis for 2,
4, 7, and 10b. Crystallographic data and data collection para-
meters are summarized in Table 4. Complex 2 crystallizes in the
monoclinic space group P2(1)/n, and the molecular structure of
2 together with a summary of relevant intermolecular bond
distances and angles are provided in the caption of Figure 1. The
selenoester 2 is monomeric and exists in the Z-configuration, as
do the sulfur and tellurium analogues.30ꢀ32 The C(1)ꢀSe(1)
[1.953(5) Å] and C(12)ꢀSe(1) [1.911(6) Å] distances are
typical for seleniumꢀcarbon single bonds and the carbonyl
C(1)ꢀO(1) distance [1.190(6) Å] is in the range observed for
common esters and thioesters. The dihedral angle Se1ꢀC1ꢀ
C2ꢀC3 is 89.8°, but the C6H5 ring is rotated 6.5° from an
orthogonal angle with C12ꢀSe1ꢀC1. The two aromatic rings
are nearly parallel, with an angle of 8.8° between them.
The structural parameters for the centrosymmetric diseleno-
ester C6H5SeC(O)C6Me4C(O)SeC6H5 4 (monoclinic, P2(1)/n,
Figure 2) are similar to those for 3, although the two crystal-
lographically equivalent C6H5 rings are more markedly twisted
away from the central C6Me4 ring in 4, at an angle of 52.3°.
Ferrocenyl selenoesters FcSeC(O)R have been previously
prepared from Li[FcSe] and RC(O)Cl,33 and structural details
have been reported for isomeric FcC(O)SeR.35 X-ray quality
crystals of the ferrocenyl diselenoester BrC6H4C(O)SeFcSeC-
(O)C6H4Br 7 were obtained from concentrated solutions,
and the molecular structure of 7 is illustrated in Figure 3.
1
2
1723
1691
1702
1707
1702
1632
1632
1719
1719
1685
1680
1709
1706
1700
648
634
701
701
577
549
612
646
643
632
628
695
695
658
200.9
192.7
200.6
200.6
203.1
194.2
189.1
200.3
200.9
192.1
192.7
199.7
200.6
198.2
3
4
5
6
7
8a
8b
9a
9b
10a
10b
11
Selected spectroscopic data for the selenoesters are listed in
Table 3. The νCO absorption in the infrared spectra is observed
between 1632 and 1723 cmꢀ1. The absorption for the aliphatic
substituted carbonyl complexes appears at higher wavenumbers
(1719ꢀ1723 cmꢀ1) than those of the aromatic derivatives
(1632ꢀ1709 cmꢀ1).28 The carbonyl carbon chemical shifts are
observed between δ 189ꢀ203 in their respective 13C NMR
spectra, where the signals of the aliphatic derivatives 1, 5, and 8
(δ = 200.3ꢀ203.1) generally appear downfield to those observed
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Table 4. Crystallographic Data
2
4
7
10b
12
formula
formula weight
space group
crystal system
Z
C17H17BrOSe
396.18
C24H22O2Se2
C32H32Br2FeO2Se2
822.17
C34H32Br2O2Se2 CH2Cl2 C25H28O2Se3Si
3
500.34
monoclinic
P 2(1)/n
2
875.26
625.44
monoclinic
P 2(1)/n
4
monoclinic
P 2(1)/c
2
triclinic
P1
orthorhombic
P 2(1) 2(1) 2(1)
4
2
a (Å)
12.0338(8)
5.8357(3)
22.778(2)
90
8.4304(3)
8.4811(4)
14.8491(6)
90
21.5761(8)
5.6000(2)
12.6532(6)
90
7.9348(6)
11.5667(7)
19.5538(9)
103.036(4)
94.354(3)
102.575(3)
1691.6(2)
1.718
10.5264(4)
15.3887(4)
16.0798(6)
90.0
b (Å)
c (Å)
α (°)
β (°)
γ (°)
volume (A3)
98.951(3)
90
100.941(2)
90
95.295(2)
90
90.0
90.0
1580.1(2)
1.665
1042.20(7)
1.594
1522.3(1)
1.794
2604.7(2)
1.595
F
cal (mg cmꢀ1
)
temperature (K)
200(2)
784
200(2)
500
200(2)
200(2)
200(2)
F(000)
808
864
1240
μ (Mo Kα, mmꢀ1
θ min, θ max (°)
h, k, l (min; max)
total reflns
)
4.898
3.564
5.539
4.737
4.301
1.81, 27.53
2.59, 27.49
1.90, 27.48
1.86, 27.45
1.83, 27.49
ꢀ15, ꢀ7, ꢀ29; 15, 7, 29 ꢀ10, ꢀ11, ꢀ19; 10, 11, 19 ꢀ28, ꢀ7, ꢀ16; 27, 7, 16 ꢀ10, ꢀ14, ꢀ25; 9, 14, 25 ꢀ13, ꢀ19, ꢀ20; 13, 19, 20
6730
4248
6358
10 953
5949
unique reflns
R(int)
3630
2390
3482
7666
4452
0.0945
0.0302
0.0498
0.0551
0.118
data/restraints/parameter
goodness of fit on F2
R1, wR2 [I g 2σ(I)]
R1, wR2 (all data)
1748/0/185
0.926
1933/0/129
1.049
2380/0/182
1.048
3946/0/396
0.966
4452/0/283
1.077
0.0485, 0.0961
0.1507, 0.1268
0.579, ꢀ0.700
0.0345, 0.0848
0.0463, 0.0903
0.426, ꢀ0.764
0.0487, 0.1167
0.0824, 0.1290
1.118, ꢀ1.318
0.0540, 0.1063
0.1467, 0.1336
0.681, ꢀ0.804
0.0895, 0.2482
0.1217, 0.2228
2.602, ꢀ2.056
max., min. peaks
in final Fourier map (e Åꢀ3
)
Figure 2. Thermal ellipsoid plot (40% probability level) of 4 with the
atom numbering scheme. The diselenoester resides about a crystal-
lographic inversion center relating the two halves of the molecule.
Selected bond distances (Å) and angles (°): Se1ꢀC1 1.944(3), Se1ꢀC7
1.913(3), C1ꢀO1 1.197(3); C1ꢀSe1ꢀC7 100.4(1), C2ꢀC1ꢀSe1
124.2(2), C2ꢀC1ꢀSe1ꢀC12 174.7, C1ꢀSe1ꢀC7ꢀC8 123.4.
Figure 1. Thermal ellipsoid plot (40% probability level) of 2 with the
atom numbering scheme. Selected bond distances (Å) and angles (°):
Se1ꢀC1 1.953(5), Se1ꢀC12 1.911(6), C1ꢀO1 1.190(6); C1ꢀSe1ꢀ
C12 100.7(2), C(2)ꢀC1ꢀSe1 109.2(4), C2ꢀC1ꢀSe1ꢀC12 166.2.
formation of yellow crystals. The molecular structure of 10b and
selected bond distances and angles are shown in Figure 4. The
structure consists of two BrC6Me4C(O)Se centers linked by the
biphenylene unit. The two phenylene rings in 10b are non-
coplanar in the solid state (rotated by 22.7°), with a CipsoꢀCipso
bond length of 1.500(7) Å between the two rings.27a,c
Treatment of succinyl chloride in THF solution with phenyl-
(trimethylsilyl)selenide (1:2) at 40 °C produced the di(seleno-
ester) C6H5SeC(O)CH2CH2C(O)SeC6H5 11 in excellent yield
(Scheme 1).
The organometallic 7 sits about a crystallographic inversion
center in the monoclinic space group P2(1)/c. The two selenoe-
ster groups are held in a trans configuration in the solid state with
the two Cp rings adopting a staggered conformation. The Fe
atom sits on a crystallographic inversion center with the planes of
the cyclopentadienyl rings parallel and the selenium atoms lying
slightly below the C5 rings, toward the iron center. The C6 and
C5 rings are not coplanar (rotated 24°), and the dihedral angle
between C1ꢀSe1ꢀC6 and Se1ꢀC6ꢀO1 is 10.5°.
The 1H NMR spectra for 11 display the expected singlet for
the equivalent methylene groups at δ 3.05, and the 13C{1H}
NMR spectrum for the equivalent carbonyl units gives rise to one
signal at 198.2 ppm. However, when the same reaction was
Structural information of the related di(selenoester) BrC6-
Me4C(O)Se(C6H4)2SeC(O)C6Me4Br 10b was also obtained by
a single-crystal X-ray structure determination. Slow evaporation
of the dichloromethane solutions of 10b at 25 °C led to the
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repeated in the absence of solvent at 80 °C for 5 h, 11 was isolated
together with the unsymmetrical tri(selenoether) (C6H5Se)3-
CCH2CH2C(O)OSiMe3 12. The formation of 12 at the expense
of 11 under these more forcing conditions occurs via addition of
two additional PhSe to the carbonyl moiety and, presumably,
HOSiMe3 generated from adventitious water reacting with any
ClSiMe3 present. The identity of 12 was assigned via NMR data,
with a singlet observed at 536.8 ppm in the 77Se{1H} NMR spec-
trum at a much higher field than that observed for 11 (657.9 ppm),
1
while the H NMR spectrum indicated the retention of one
trimethylsilyl group in the compound, with a singlet resonance
present at 0.21 ppm and two resonances observed for inequi-
valent CH2 centers.
The molecular structure of 12 was confirmed by X-ray analysis
of a weakly scattering crystal and is illustrated in Figure 5 together
with a summary of bond distances and angles. All SeꢀC distances
are identical at the level of the data (Se1ꢀC1 1.98(1) Å, Se2ꢀC1
1.97(1) Å, and Se3ꢀC1 1.97(1) Å).
The ferrocenyl selenoesters 5ꢀ7 all show electrochemical
responses due to the Fe(II/III) couple. The reversibility and
relative oxidation potentials of the redox processes in these
compounds were determined by cyclic voltammetry (CV) in
THF solutions containing 0.1 M [(n-Bu)4N]ClO4 (TBAP) as
the supporting electrolyte. The ferrocenyl selenoesters show one
oxidation wave for each of at E1/2 = 242 mV (5), E1/2 = 236 mV
(6), and at E1/2 = 275 mV (7), respectively, vs ferrocene and
assigned to the Fe(II/III) redox couple. The cyclic voltammo-
gram for these compounds showed a well-defined single electron
Figure 3. Two thermal ellipsoid plots of the molecular structure of 7
(40% probability level) with the atom numbering scheme. The molecule
resides about a crystallographic inversion center. Selected bond dis-
tances (Å) and angles (°): Se1ꢀC1 1.889(4), Se1ꢀC6 1.944(4),
C6ꢀO1 1.202(5); C1ꢀSe1ꢀC6 99.7(2), C2ꢀC1ꢀSe1 124.7(3),
C1ꢀSe1ꢀC6ꢀC7 170.1.
Figure 4. Molecular structure of 10b with the atom numbering scheme.
Thermal elipsoids are drawn at the 40% probability level. Selected bond
distances (Å) and angles (°): Se1ꢀC1 1.907(5), Se1ꢀC7 1.949(6),
C7ꢀC8 1.485(7), Se2ꢀC18 1.912(5), Se2ꢀC24 1.952(6), C24ꢀC25
1.493(7); C1ꢀSe1ꢀC7 99.1(2), Se1ꢀC7ꢀC8 110.2(4), C1ꢀSe1ꢀ
C7ꢀC8 174.7.
Figure 5. Molecular structure of 12 (40% probability level) with the
atom numbering scheme (the hydrogen atoms are omitted for clarity).
Selected bond distances (Å) and angles (°): Se(1)ꢀC(1) 1.98(1),
Se(2)ꢀC(1) 1.97(1), Se(3)ꢀC(1) 1.97(1); Se(2)ꢀC(1)ꢀSe(1)
104.3(5), Se(3)ꢀC(1)ꢀSe(1) 114.5(5), Se(2)ꢀC(1)ꢀSe(3)
104.7(5), Si(1)ꢀO(2)ꢀC(4)ꢀC(3) 178.3.
Scheme 1
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Scheme 2
wave that was reversible in nature with ic/ia ∼ 1, as observed for
other ferrocenylselenoesters.34 The potential of the E1/2 is
dependent on the electron density of the selenoester bridge on
the ferrocenyl unit,35 and the E1/2 values for 5ꢀ7 are consider-
ably more positive than the corresponding value for ferrocene, in
keeping with the electron-withdrawing nature of the ꢀC(O)SeR
groups. Within the series 5ꢀ7, however, E1/2 values show depen-
dence on the electronic nature of R. The differences in the 77Se
NMR chemical shifts (ppm) for 5ꢀ7 are also consistent with the
observed changes in the values of E1/2 higher oxidation potentials
correlatingwith an upfield chemical shift, in agreement with reports
by Singh and co-workers34 and Burgess and Morley.35
The facile synthesis of 7 suggested that condensation reactions
with the di(acid chloride) p-ClC(O)C6Me4C(O)Cl and Fe-
(η5-C5H4SeSiMe3)2 might allow for the formation of oligomeric
complexes.36 Molecules containing repeating ferrocenyl units in
the main chain have been the focus of intense research efforts,
due, in part, to the attractiveness of incorporating this electro-
chemically active and stable fragment into polymer backbones.37
After heating a 1:1 molar ratio of Fe(η5-C5H4SeSiMe3)2 and
p-ClC(O)C6Me4C(O)Cl at 85 °C in a vacuum-sealed glass tube,
[(SeC5H4)Fe(C5H4Se)C(O)C6Me4C(O)]x 13 (x ≈ 5) is ob-
tained as an orange solid that is reasonably soluble in organic
solvents (Scheme 2). In a typical experiment, after about 18 h, the
poly(ferrocenyldiselenoester) 13 was isolated in ∼40% yield
after precipitation from THF solutions with hexane. The 1H, 13C,
and 77Se NMR and IR spectroscopies and elemental analysis are
in agreement with the proposed oligomeric structure of 13.
Qualitatively, the 13C{1H} NMR spectrum of 13 is similar to
that observed for monomeric 7. A signal for the ꢀSeC(O)ꢀ
moieties is detected as a resonance at 202.5 ppm for 13
(δ = 189.1 for 7), and an additional, weak carbonyl signal at
170.9 ppm is assigned to ꢀC6Me4C(O)Cl end groups. An
estimate of the molecular weight (Mn) of several samples was
obtained from relative integration of the two carbonyl signals and
indicate that 13 displays moderate degrees of oligomerization
(Xn, x = 5, Mn = 2900). The chlorine content, as determined via
elemental analysis, is also in agreement with this end-group
analysis. 77Se{1H} NMR spectra of molecular 7 display a sharp
signal at 611.7 ppm, and a somewhat broader signal is observed
for oligomeric 13 at δ = 611.1 (W1/2 = 29 Hz), in addition to
weaker, broadened resonances at 611.8 and 612.3 ppm. Whereas
the intense signal for 13 is assigned to ꢀSeC(O)C6Me4C(O)Seꢀ
units, the additional signals are assigned to (SeC(O)C6Me4-
C(O)Cl) centers. For comparison, 77Se{1H} NMR spectra of
samples prepared with a 1:2 ratio of Fe(η5-C5H4SeSiMe3)2/
p-ClC(O)C6Me4C(O)Cl display a much stronger signal for the
peak at 611.8 ppm (and a marked decrease in the intensity of the
signal observed at 611.1 ppm). Similarly, 13C{1H} NMR spectra
of these samples display a strong signal at δ = 170.9 ppm and a
much weaker signal at δ = 202.5 ppm. The 1H NMR spectra of 13
(Supporting Information) are also in agreement with the pro-
posed structure via integration of methyl resonances at δ =
2.20 and 2.22 ppm (C6Me4C(O)Cl) versus an intense, broad
signal at δ = 2.16 ppm. Infrared spectra of 13 display a strong
carbonyl stretch at 1699 cmꢀ1 assigned to SeꢀC(O)ꢀC, and a
weaker band at 1792 cmꢀ1 assigned to terminal C(O)Cl. The
cyclic voltammogram of 13 (Supporting Information) consists
of a single, reversible one-electron wave with E1/2 = 0.31 V
(vs ferrocene), consistent with no electrochemical communica-
tion between the spatially separated Fe centers.
’ CONCLUSIONS
ArSeSiMe3 react under mild conditions with acid chlorides to
provide a route to selenoesters in good yields. Diselenoesters can
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be prepared from reactions of PhSeSiMe3 with di(acid chlorides)
or the reaction of acid chlorides with reagents containing two
ꢀSeSiMe3 groups. This reactivity led to the formation of oligo-
meric [(SeC5H4)Fe(C5H4Se)C(O)C6Me4C(O)]x 13 (x ≈ 5).
13 represents, to the best of our knowledge, the first reported
oligoselenoester complex.
ꢀ78 °C, and dry CO2 was bubbled through the reaction mixture for
30 min. Hydrochloric acid (0.5 M, 100 mL) was added, and the solution was
extracted with diethyl ether (3 ꢁ 50 mL). The combined fractions were
dried over magnesium sulfate, and the solvent was removed by rotary
evaporation to yield a colorless powder (1,4-C6Me4(C(O)OH)2). The
acid was suspended in thionyl chloride (100 mL) as described for the
preparation of 1,4-C6Me4BrC(O)Cl (vide supra). After a similar work-
up, 1,4-C6Me4(C(O)Cl)2 was isolated as a colorless, air stable solid.
Yield: 3.5 g (14 mmol, 87%). 1HNMR (CDCl3, δ): 2.29 (s, 6H, CH3).
Preparation of 122. C6H5SeSiMe3 (258 mg, 1.12 mmol) was
dissolved in tetrahydrofuran (20 mL). An equimolar amount of
CH3CH2C(O)Cl (103 mg, 0.10 mL, 1.1 mmol) was added in one
portion at ꢀ10 °C and stirred for 2 h. After removal of the solvent in
vacuo, 1 was isolated as a yellow oil. Yield: 0.19 g (0.90 mmol, 80%). 1H
NMR (CDCl3, δ): 7.54ꢀ7.23 (5H, C6H5), 2.74 (q, 2H, JHH = 8 Hz,
CH2), 1.22 (t, 3H, JHH = 8 Hz, CH3). 13C{1H}: 200.9 (CO), 136.5 (Ar,
Cipso), 135.7 (Ar), 129.2 (Ar), 128.7 (Ar), 40.9 (CH2), 9.4 (CH3).
’ EXPERIMENTAL SECTION
All syntheses were carried out under an atmosphere of high-purity
dried nitrogen using standard double-manifold Schlenk line techniques
and nitrogen-filled glove boxes. Solvents were dried and collected using
an MBraun MB-SP Series solvent purification system. Chloroform-d was
dried and distilled over P2O5. NMR spectra [1H (399.763 MHz),
13C{1H} (100.522 MHz), 77Se{1H} (76.217 MHz)] were recorded
1
on a Varian Inova 400 NMR spectrometer. The H and 13C NMR
chemical shifts were referenced internally to SiMe4 using the residual
proton and carbon signal of the deuterated solvent, respectively. 77Se-
{1H} spectra are reported relative to Me2Se at 0 ppm. Ultravioletꢀ
visible spectroscopy was performed on a Varian Cary 100 spectrometer.
Mass spectra and exact mass determinations were performed on a
Finnigan MAT 8200 instrument. Single-crystal X-ray diffraction mea-
surements were completed on an Enraf-Nonius KappaCCD diffracto-
meter. Molecular structures were determined via direct methods using
the SHELXTL suite of crystallographic programs.41 All non-hydrogen
atoms, with the exception of disordered carbon centers, were refined
with anisotropic thermal parameters. Hydrogen atoms were included as
riding on their respective carbon atoms. Crystals of 12 were invariably
small and weakly diffracting. For 12, the refined Flack parameter was
0.00(3). Cyclic voltammetry measurements (concentration = 0.1 ꢁ
10ꢀ3 M) were performed at a scan rate of 100 mV/s using a standard
three-electrode cell with a gold working electrode, a platinum flag
counter electrode, and a silver wire reference electrode in tetrahydrofur-
an with NBu4ClO4 (0.1 M) as the supporting electrolyte. Potentials are
referenced internally to ferrocene (0.00 V) added at the end of the
experiments.
77Se{1H}: 648.7. IR (NaCl): νCO 1723 cmꢀ1
.
Synthesis of 2. To C6H5SeSiMe3 (0.38 mL, 0.35 g, 1.52 mmol)
dissolved in 20 mL of tetrahydrofuran, 1 equiv of CH3C6H4C(O)Cl
(0.20 mL, 0.23 g, 1.52 mmol) was added in one portion at 25 °C. After
12 h of stirring at 40 °C, all volatiles were removed in vacuo and the
resulatant white solid residue was washed with 30 mL of n-pentane. After
removal of the solvents, the residue was crystallized from n-pentane
at ꢀ25 °C. The white precipitate was dried in vacuo. Yield: 0.35 g
(1.27 mmol, 84%). Anal. Found: C, 61.04; H, 4.26; C14H12SeO
(275.05). Calcd: C, 61.08; H, 4.40%. IR (NaCl): υCO 1691 cmꢀ1. 1H
NMR (CDCl3, δ): 7.83 (d, 4H, JHH = 8 Hz, C6H4), 7.60 (m, 2H, C6H5),
7.43 (m, 3H, C6H5), 7.28 (d, 4H, JHH = 8 Hz, C6H4), 2.42 (s, 3H, CH3).
13C{1H}: 192.7 (CO), 144.9 (Ar, Cipso), 136.3 (Ar), 136.0 (Ar, Cipso),
129.6 (Ar), 129.3 (Ar), 129.0 (Ar), 127.4 (Ar), 125.9 (Ar, Cipso), 21.8
(CH3). 77Se{1H}: 634.
Synthesis of 3. p-C6Me4BrC(O)Cl (0.2 g, 0.73 mmol) was mixed
with equimolar amounts of C6H5SeSiMe3 (0.17 g, 0.18 mL, 0.73 mmol)
at 25 °C in a Schlenk tube, and the sample was placed in a preheated
(85 °C) oven. After 12 h, the sample was cooled, Me3SiCl was removed
in vacuo, and the residue was washed with n-pentane. Crystallization
from n-pentaneꢀdichloromethane gave colorless crystals of 3 in 85%
yield (0.24 g, 0.61 mmol). Anal. Found: C, 51.73; H, 3.93; C17H17SeOBr
Materials. 1,4-Dibromo-2,3,5,6-tetramethylbenzene,38 phenyl(tri-
methylsilyl)selenide,39 phenylene-1,4-bis(trimethylsilylselenium),27a bi-
phenylene-4,40-bis(trimethylsilylselenium),27a and bis(trimethylsilyl-
seleno)ferrocene27b were synthesized according to literature proce-
dures. p-Toluoyl chloride and propionyl chloride were used as received
from the Aldrich Chemical Co.
(396.18). Calcd: C, 51.54; H, 4.33%. IR (NaCl): υCO 1702 cmꢀ1
.
1H NMR (CDCl3, δ): 7.58 (m, 2H, C6H5), 7.41 (m, 3H, C6H5), 2.39
(s, 6H, CH3), 2.34 (s, 6H, CH3). 13C{1H}: 200.6 (CO), 140.8 (Ar, Cipso),
135.6 (Ar), 135.0 (Ar, Cipso), 130.7 (Ar, Cipso), 129.4 (Ar), 129.3 (Ar,
Cipso), 126.9 (Ar, Cipso), 20.6 (CH3), 17.9 (CH3). 77Se{1H}: 701.
Synthesis of 4. A 0.2 g portion of 1,4-C6Me4(C(O)Cl)2 (0.77
mmol) was reacted with 0.35 g (0.38 mL, 1.54 mmol) of C6H5SeSiMe3,
as described for the preparation of 3. After a similar workup, 4 was
isolated as colorless, air stable crystals. Yield: 0.33 g (0.70 mmol, 87%).
Anal. Found: C, 58.02; H, 4.16; C24H22Se2O2 (500.09). Calcd: C, 57.59;
Synthesis of 1,4-C6Me4BrC(O)Cl. To a stirring solution of 1,4-
dibromodurene (5 g, 17.13 mmol) in diethyl ether (100 mL) at ꢀ78 °C,
tBuLi (1.7 M, 200.05 mL, 64.26 mmol) was added dropwise over 10 min.
The resultant white suspension was stirred at this temperature for 1.5 h,
and dry CO2 was then bubbled through the reaction mixture for 30 min.
Hydrochloric acid (0.5 M, 50 mL) was added, and the solution was
extracted with diethyl ether (3 ꢁ 50 mL). The combined fractions were
dried over magnesium sulfate, and the solvent was removed by rotary
evaporation, yielding a colorless powder. The acid 1,4-C6Me4BrC-
(O)OH was suspended in thionyl chloride (100 mL) and heated to
reflux overnight during which time all of the solid dissolved to yield a
brown solution. SOCl2 was removed in vacuo, leaving a brown solid.
Colorless crystals (3.9 g, 14 mmol, 90%) were isolated after vacuum
sublimation (80 °C, 0.01 mmHg). NMR (CDCl3, δ) 1H: 2.41 (s, 6H,
CH3), 2.33 (s, 6H, CH3). 13C{1H}: 171.4, 139.2, 135.2, 13.4, 128.7,
20.6, 18.1. 275.97 (M+, rel. intens. 15).
1
H, 4.43%. IR (NaCl): υCO 1707 cmꢀ1. H NMR (CDCl3, δ): 7.59
(m, 4H, C6H5), 7.42 (m, 6H, C6H5), 2.27 (s, 12H, CH3). 13C{1H}:
200.6 (CO), 142.7 (Ar, Cipso), 135.6 (Ar), 129.4 (Ar), 129.3 (Ar), 129.1
(Ar), 126.8 (Ar, Cipso), 16.4 (CH3). 77Se{1H}: 701.
Preparation of 5. To a solution of Fe(C5H4SeSiMe3)2 (150 mg,
0.386 mmol) in 20 mL of tetrahydrofuran was slowly added CH3CH2-
C(O)Cl (71.43.0 mg, 0.07 mL, 0.772 mmol) in 10 mL of tetrahydrofuran
at ꢀ10 °C. After stirring for 2 h at this temperature, the reaction mixture
was gradually warmed to 25 °C and all volatiles were removed
in vacuo. The yellow residue was dissolved in 20 mL of n-pentane
and filtered through a pad of dried Celite. Removal of the solvent
under vacuum left 5 as a yellow oil in 70% yield (123 mg, 0.27 mmol).
Exact mass Calcd. for C16H18FeO2Se2: (M+) 457.89936. Found:
457.89995. IR (NaCl): υCO 1702 cmꢀ1. UVꢀvis: λmax = 435 nm (ε =
200 L molꢀ1 cmꢀ1). 1H NMR (CDCl3, δ): 4.34 (br s, 4H, C5H4), 4.30
Synthesis of 1,4-C6Me4(C(O)Cl)2. In a modification of the
published procedure,36a tBuLi (1.7 M, 40.3 mL, 68.5 mmol) was added
to a solution of 1,4-dibromodurene (5.0 g, 17.1 mmol) in diethyl ether
(100 mL) at ꢀ78 °C. The resultant white suspension was stirred at this
temperature for 1.5 h, and the reaction mixture was then warmed to
room temperature overnight. The reaction mixture was again cooled to
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(br s, 4H, C5H4), 2.61 (q, 4H, JHH = 8 Hz, CH2), 1.12 (t, 6H, JHH = 8 Hz,
CH2). 13C{1H}: 203.1 (CO), 76.3 (C5H4), 71.7 (C5H4), 67.9 (Cp,
Cipso), 40.3 (CH2), 9.2 (CH3). 77Se{1H}: 557.
Synthesis of 6. Fe(C5H4SeSiMe3)2 (0.3 g, 0.77 mmol) was
dissolved in tetrahydrofuran (20 mL), and 2 equiv of p-CH3C6H4COCl
(0.23 g, 0.21 mL, 1.54 mmol) were added in one portion at 25 °C. After
12 h of stirring, all volatiles were removed in vacuo and the residue
obtained was washed with n-pentane. Crystallization from n-pentane/
dichloromethane (8:1) gave yellow crystals of 6 in 80% yield (0.35 g,
0.60 mmol). Anal. Found: C, 54.16; H, 3.52; FeC26H22Se2O2 (580.22).
13C{1H}: 192.1 (CO), 145.3 (Ar, Cipso), 137.1 (Ar), 136.1 (Ar, Cipso),
129.9 (Ar), 127.7 (Ar), 127.5 (Ar, Cipso), 21.8 (CH3). 77Se{1H}: 632.
Synthesis of 9b. A 0.3 g portion of p-CH3C6H4COCl (0.65 mmol)
was reacted with 0.20 g (0.1.3 mmol) of 4,40-(C6H4SeSiMe3)2, as
described for the preparation of 9a (see above). After appropriate
workup, 9b was isolated as pale yellow, air stable crystals. Yield: 0.30 g
(0.55 mmol, 85%). Anal. Found: C, 61.03; H, 3.98; C28H22Se21O2
(548.09). Calcd: C, 61.30; H, 4.05%. IR(NaCl): υCO 1680 cmꢀ1. H
NMR (CDCl3, δ): 7.84 (d, 4H, JHH = 8 Hz, C6H4), 7.66 (m, 8H, C6H4),
7.29 (d, 4H, JHH = 8 Hz, C6H4), 2.42 (s, 6H, CH3). 13C{1H}: 192.7
(CO), 145.0 (Ar, Cipso), 141.1 (Ar, Cipso), 136.7 (Ar), 135.9 (Ar, Cipso),
129.6 (Ar), 128.1 (Ar), 127.5 (Ar), 125.4 (Ar, Cipso), 21.8 (CH3).
77Se{1H}: 628.
Synthesis of 10a. A 0.144 g portion of C6Me4BrC(O)Cl (0.52 mmol)
was mixed with 100 mg (0.26 mmol) of 1,4-C6H4(SeSiMe3)2 as solids at
25 °C in a Schlenk tube. The sample was placed in a preheated (85 °C)
oven, whereupon the solids melted to yield a yellow, free-flowing liquid.
After 12 h, the mixture became solid and was cooled to room tempera-
ture. Me3SiCl was removed in vacuo, and the residue was washed with
n-pentane. Crystallization from n-pentaneꢀdichloromethane gave yellow,
air stable crystals of 10a. Yield: 0.18 g (0.23 mmol, 73%). Anal. Found:
C, 46.81; H, 3.91; C28H28Se2O2Br2 (714.25). Calcd: C, 47.08; H, 3.95%.
IR (NaCl): νCO 1709 cmꢀ1. 1H NMR (CDCl3, δ): 7.61 (s, 4H, C6H4),
2.40 (s, 6H, CH3), 2.34 (s, 6H, CH3). 13C{1H}: 199.7 (CO), 140.6 (Ar,
Cipso), 136.1 (Ar), 135.1 (Ar, Cipso), 129.4 (Ar, Cipso), 128.3 (Ar, Cipso),
20.6 (CH3), 18.0 (CH3). 77Se{1H}: 698.
Calcd: C, 53.82; H, 3.82%. IR (NaCl): υCO 1632 cmꢀ1. UVꢀvis: λmax
=
471 (ε = 300 L molꢀ1 cmꢀ1). 1H NMR (CDCl3, δ): 7.79 (d, 4H, J = 8
Hz), 7.26 (d, 4H, J = 8 Hz), 4.45 (vt, 4H, J = 2 Hz, C5H4), 4.41 (vt, 4H,
J = 2 Hz, C5H4), 2.41 (s, 6H, CH3). 13C{1H}: 194.2 (CO), 144.7 (Ar,
Cipso), 135.7 (Ar, Cipso), 129.5 (C6H4), 127.3 (C6H4), 76.6 (C5H4), 71.8
(C5H4), 68.5 (Cp, Cipso), 21.7 (CH3). 77Se{1H}: 549.
Synthesis of 7. Fe(C5H4SeSiMe3)2 (0.1 g, 0.26 mmol) was mixed
with 2 equiv of C6Me4BrC(O)Cl (0.14 g, 0.52 mmol) as solids in a
Schlenk tube. The sample was placed in a preheated (85 °C) oven,
whereupon the solids melted, forming an orange-red, free-flowing liquid.
After 12 h, the mixture became solid and was cooled to room tempera-
ture. Me3SiCl was removed in vacuo, and the residue was washed with
n-pentane. Crystallization from n-pentaneꢀdichloromethane gave yellow
crystals of 6 in 80% yield (0.17 g, 0.21 mmol). Anal. Found: C, 47.08;
H, 3.48; FeC326H32Se2O2Br2 (821.83). Calcd: C, 46.75; H, 3.92%. IR
(NaCl): υCO 1632 cmꢀ1. UVꢀvis: λmax = 435 (ε = 250 L molꢀ1 cmꢀ1).
1H NMR (CDCl3, δ): 4.34 (bs, 4H, C5H4), 4.31 (bs, 4H, C5H4), 2.35
(s, 12H, CH3), 2.25 (s, 12H, CH3). 13C{1H}: 189.1 (CO), 134.9
(Ar, Cipso), 131.0 (Ar, Cipso), 130.5 (Ar, Cipso), 129.2 (Ar, Cipso), 76.0
(C5H4), 71.8 (C5H4), 69.8 (Cp, Cipso), 20.5 (CH3), 17.9 (CH3).
77Se{1H}: 612.
Synthesis of 10b. A 0.18 g portion of C6Me4BrC(O)Cl (0.65
mmol) was reacted with 0.15 g (0.325 mmol) of 4,40-Me3SiSe-
(C6H4)2SeSiMe3, as described for the preparation of 10a (see above).
After appropriate workup, 10b was isolated as pale yellow, air stable
crystals. Yield: 0.18 g (0.23 mmol, 70%). Anal. Found: C, 51.73; H, 3.93;
C28H22Se2O2Br2 (790.34). Calcd: C, 51.67; H, 4.08%. IR (NaCl): υCO
Synthesis of 8a. To 1,4-C6H4(SeSiMe3)2 (100 mg, 0.26 mmol) in
20 mL of tetrahydrofuran, 2 equiv of CH3CH2C(O)Cl (49 mg,
0.046 mL, 0.52 mmol) was added in one portion at ꢀ10 °C and warmed
to room temperature. After 2 h of stirring at room temperature, the
reaction mixture was filtered through a pad of Celite. All volatiles were
removed under vacuum, and the residual solid was dissolved in
n-pentane (10 mL) and stored at ꢀ25 °C to form pale yellow, platelike
crystals of 8a. Yield: 0.063 g (0.18 mmol, 70%). Anal. Found: C, 41.66;
H, 4.36; C28H22Se2O2.CH2Cl2 (348.16). Calcd: C, 41.40; H, 4.05%. IR
1
1706 cmꢀ1. H NMR (CDCl3, δ): 7.65 (m, 8H, C6H4), 2.40 (s, 6H,
CH3), 2.36 (s, 6H, CH3). 13C{1H}: 200.6 (CO), 141.2 (Ar, Cipso), 140.7
(Ar, Cipso), 135.9 (Ar), 135.1 (Ar, Cipso), 130.8 (Ar, Cipso), 129.4 (Ar, Cipso),
128.2 (Ar), 126.4 (Ar, Cipso), 20.6 (CH3), 18.0 (CH3). 77Se{1H}: 695.
Synthesis of 11 (Method 1). ClC(O)CH2CH2C(O)Cl (0.1 mL,
0.89 mmol) was added in one portion to C6H5SeSiMe3 (1.8 mmol) in
tetrahydrofuran (30 mL) at 25 °C. After 12 h of stirring at 40 °C,
the solution was cooled to room temperature and all volatiles were
removed in vacuo. The colorless solid residue was washed with 20 mL of
n-pentane, and the residue was crystallized from n-pentane/dichloro-
methane (ratio 30:1) at ꢀ25 °C. Yield: 0.30 g (0.76 mmol, 85%). Anal.
Found: C, 48.55; H, 3.52; C16H14Se2O2 (396.2). Calcd: C, 48.50; H,
3.564%. IR(NaCl): υCO 1700 cmꢀ1. 1H NMR (CDCl3, δ): 7.51 (m, 4H,
C6H4), 7.36 (m, 6H, C6H5), 3.05 (s, 4H, CH2). 13C{1H}: 198.2 (CO),
135.8 (Ar), 129.4 (Ar), 129.1 (Ar), 125.8 (Ar, Cipso), 41.8 (CH2).
77Se{1H}: 658.
1
(NaCl): υCO 1719 cmꢀ1. H NMR (CDCl3, δ): 7.49 (s, 4H, C6H4),
2.73 (q, 4H, JHH = 8 Hz, CH2), 1.21 (t, 6H, JHH = 8 Hz, CH3). 13C{1H}:
200.3 (CO), 136.3 (Ar), 127.4 (Ar, Cipso), 41.1 (CH2), 9.41 (CH3).
77Se{1H}: 646.
Synthesis of 8b. A 0.10 g portion of 4,40-(C6H4SeSiMe3)2 (200 mg,
0.44 mmol) was reacted with 81 mg (0.08 mL, 0.88 mmol) of
CH3CH2C(O)Cl, as described for the preparation of 8a (see above).
After appropriate workup, 8b was isolated as yellow, air stable crystals in
75% yield (130 mg, 0.31 mmol). IR (NaCl): υCO 1719 cmꢀ1. 1H NMR
(CDCl3, δ): 7.58 (m, 8H, C6H4), 2.75 (q, 4H, JHH = 8 Hz, CH2), 2.36
(t, 6H, JHH = 8 Hz, CH3). 13C{1H}: 200.9 (CO), 141.2 (Ar, Cipso), 140.7
(Ar, Cipso), 136.1 (Ar), 127.9 (Ar), 125.7 (Ar, Cipso), 41.0 (CH2), 9.4
(CH3). 77Se{1H}: 643. EI-MS [m/e (rel. intens.)]: 426 (M+, 90).
Synthesis of 9a.40 p-CH3C6H4COCl (1.4 mL, 1.06 mmol) was
added in one portion to 1,4-C6H4(SeSiMe3)2 (0.2 g, 0.53 mmol) and
tetrahydrofuran (30 mL) at 25 °C. After 12 h of stirring at 40 °C, the
solution was cooled and all volatiles were removed in vacuo. The
colorless solid residue was washed with 20 mL of n-pentane. After
removal of the solvents, the residue was crystallized from n-pentane/
dichloromethane (15:2) at ꢀ25 °C. The white precipitate was dried in
vacuo. Yield: 0.20 g (0.42 mmol, 78%). Anal. Found: C, 55.82; H, 3.95;
C22H18Se2O2 (472.06). Calcd: C, 55.92; H, 3.84%. IR(NaCl): υCO
1685 cmꢀ1. 1H NMR (CDCl3, δ): 7.82 (d, 4H, JHH = 8 Hz, C6H4), 7.62
(s, 4H, SeC6H4Se), 7.30 (d, 4H, JHH = 8 Hz, C6H4), 2.42 (s, 6H, CH3).
Synthesis of 11 (Method 2) and 12. C6H5SeSiMe3 (1.8 mmol)
was mixed with Cl(O)CCH2CH2C(O)Cl (0.1 mL, 0.89 mmol) at 25 °C
in a Schlenk tube. The sample was placed in a preheated (80 °C) oven.
After 5 h, the mixture became solid. Me3SiCl was removed in vacuo, and
the residue was washed with n-pentane. Crystallization from n-penta-
neꢀdichloromethane (30:1) gives colorless crystals of 11 (20% yield)
and 12 (30% yield), which were manually separated. Anal. Found for 12:
C, 48.51; H, 4.51; C25H28Se3SiO2 (625.45). Calcd: C, 48.01; H, 4.51%.
IR(NaCl): νCO 1667 cmꢀ1. Data for 12 1H NMR (CDCl3, δ):
7.74ꢀ7.72 (m, 6H, C6H5), 7.40ꢀ7.30 (m, 9H, C6H5), 2.63 (m,
2H, CH2), 2.29 (m, 2H, CH2), 0.21 (s, 9H, SiMe3). 13C{1H}: 172.8
(CO), 135.9 (Ar), 129.4 (Ar), 129.3 (Ar), 125.9 (Ar, Cipso), 52.0
(CCH2CH2CO), 38.0 (CCH2CH2CO), 34.1 (CCH2CH2CO), ꢀ0.3
(SiCH3). 77Se{1H}: 537.
Synthesis of 13. ClC(O)C6Me4C(O)Cl (0.13 g, 0.51 mmol)
was mixed as powder with equimolar amounts of Fe(C5H4SeSiMe3)2
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(0.25 g, 0.51 mmol) in a thick-walled glass tube and flame-sealed in
vacuo. The sample was placed in a preheated (85 °C) oven. After 18 h,
the mixture became solid. Me3SiCl was removed under vacuum, and the
residue was dissolved in a minimum amount of tetrahydrofuran. Cold
hexanes were added rapidly to precipitate the oligomer as an orange
solid. The hexanes-soluble fraction was removed and 13 remained (0.12 g,
40%) as a yellow glassy solid after drying. Anal. Found: C, 49.29; H, 3.80;
Cl, 2.54; C122H112Fe5Se10O12Cl2 (2908.57). Calcd: C, 50.33; H, 3.88;
(5) (a) Alvarez-Ibarra, C.; Mendoza, M.; Orellana, G.; Quiroga, M. L.
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UVꢀvis: λmax = 456 nm. 1H NMR (CDCl3, δ): 4.35 (s, C5H4, 12H),
4.30 (br s, C5H4, 18H), 2.22 (s, C6(CH3)4C(O)Cl, 6H), 2.20 (s,
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’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic information
b
files for 2, 4, 7, 10b, and 12 in CIF format and 1H NMR spectra
and cyclic voltammogram of 13. This material is available free of
charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: corrigan@uwo.ca.
Present Address
§Current address: Department of Chemistry, The University of
Jordan, Amman, Jordan.
’ ACKNOWLEDGMENT
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We thank the Natural Sciences and Engineering Research
Council (NSERC) of Canada for financial support of this work in
the form of discovery and equipment grants and the Canada
Foundation for Innovation and The University of Western
Ontario for equipment funding. We thank Prof. Mark S. Workentin
for the use of his electrochemical equipment and Prof. Derek P.
Gates (UBC) and Kevin Noonan (UBC) for helpful discussions
regarding this work. Daniel G. MacDonald and Michael C.
Jennings are thanked for collecting the X-ray diffraction data.
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