(Selenocarbamoyl)silanes and -germanes: Their synthesis using (selenocarbamoyl)lithium and characterization

Article abstract of DOI:10.1021/om100290h

Deprotonation of the selenoformyl group in N,N-dibenzyl selenoformamide with LDA, followed by silylation and germylation of the resulting anion with Me₃SiCl and Me₃GeCl, gives (selenocarbamoyl)silane and -germane in moderate to good

Full text of DOI:10.1021/om100290h

2400 Organometallics 2010, 29, 2400–2402
DOI: 10.1021/om100290h
(Selenocarbamoyl)silanes and -germanes: Their Synthesis Using
(Selenocarbamoyl)lithium and Characterization
Toshiaki Murai,* Rumi Hori, Toshifumi Maruyama, and Fumitoshi Shibahara
Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
Received April 10, 2010
Scheme 1
Summary: Deprotonation of the selenoformyl group in N,N-
dibenzyl selenoformamide with LDA, followed by silylation
and germylation of the resulting anion with Me3SiCl and
Me3GeCl, gives (selenocarbamoyl)silane and -germane in
moderate to good yields. The molecular structures of these
products and the starting selenoformamide were characterized
by using X-ray analyses.
Studies of selenocarbonyl compounds have provided fruit-
ful results for over 40 years.1 Owing to their lability, seleno-
aldehydes and -ketones2 have been generated in situ
and trapped by their reactions with dienes. In order to
stabilize these substances, bulky substituents are typically
incorporated at the selenocarbonyl group.3 Although being
dependent on their exact nature, heteroatom-containing
functional groups, such as amino, alkoxy, sulfenyl, and
selenenyl groups, introduced at the selenocarbonyl carbon
also bring about stabilization of these compounds.4 As a
result, selenoamides,5 selenoic acid O-esters,6 and their
sulfur and selenium counterparts6,7 have been widely stu-
died. In contrast, investigations probing the effects of silyl
and germyl groups on the properties of selenocarbonyl
compounds have not been conducted,8 owing in part to the
lack of methods for the introduction of these functional
groups. One of the most promising ways to introduce these
groups is via the generation of selenocarbonyl anions
and their reaction with silyl and germyl halides. However,
only a limited number of examples of compounds bearing
a selenoformyl group are known. As part of a long-range
program to study selenocarbonyl compounds,9 we recently
developed a convenient method for the synthesis of seleno-
formamides by the reaction of formamides, elemental sele-
nium, trichlorosilane, and amines.10 Below, we describe
the results of an effort that takes advantage of this metho-
dology in routes for the synthesis of the first examples
of (selenocarbamoyl)silanes and -germanes via (selenocarba-
moyl)lithium. In addition, we have structurally characteri-
zed the (selenocarbamoyl)silanes and -germanes by using
X-ray crystallographic and theoretical methods.
*To whom correspondence should be addressed. Tel: 81-58-293-2614.
Fax: 81-58-293-2614. E-mail: mtoshi@gifu-u.ac.jp.
(1) For reviews: (a) Murai, T.; Kato, S. In Topics in Current Chem-
istry; Wirth, T., Ed.; Springer-Verlag: Berlin, 2000; Vol. 208, p 177.
(b) Grobe, J.; Le Van, D. J. Fluorine Chem. 2004, 125, 801.
(2) For reviews and recent examples of the generation and reaction of
selenoaldehydes and -ketones: (a) Guziec, F. S., Jr.; Guziec, L. J. In
Organoselenium Chemistry: A Practical Approach; Back, T. G., Ed.;
Oxford University Press: Oxford, U.K., 1999; p 193. (b) Guziec, L. J.;
Guziec, F. S., Jr. In Comprehensive Organic Functional Group Transfor-
mations, Katritzky, A. R., Taylor, R. J. K., Eds.; Elsevier: Oxford, U.K.,
2005; Vol. 3, p 397. (c) Okuma, K; Izaki, T.; Kubo, K.; Shioji, K.;
Yokomori, Y. Bull. Chem. Soc. Jpn. 2005, 78, 1121. (d) Shioji, K.;
Matsumoto, A.; Takao, M.; Kurauchi, Y.; Shigetomi, T.; Yokomori, Y.;
Okuma, K. Bull. Chem. Soc. Jpn. 2007, 80, 743. (e) Okuma, K.; Mori, Y.;
Shigetomi, T.; Tabuchi, M.; Shioji, K.; Yokomori, Y. Tetrahedron Lett.
2007, 48, 8311. (f) Okuma, K.; Koda, M.; Shigetomi, T. Phosphorus, Sulfur
Silicon Relat. Elem. 2008, 183, 1057.
In exploratory studies we observed that treatment of N,N-
dibenzyl selenoformamide (1) with LDA at -78 °C for 2 h
generates (selenocarbamoyl)lithium 2 (Scheme 1). Addition
of chlorotrimethylsilane to the reaction mixture followed by
stirring at -78 °C for 24 h and chromatographic purification
(3) Tokitoh, N.; Okazaki, R. Pol. J. Chem. 1998, 72, 971.
(4) (a) Wu, R.; Barr, M. E.; Hernandez, G. O.; Charles, C. C.; Silks,
L. A. Recent Res. Dev. Org. Bioorg. Chem. 1998, 2, 29. (b) Wu, R.;
Hernandez, G.; Dunlap, R. B.; Odom, J. D.; Martinez, R. A.; Silks, L. A.
Trends Org. Chem. 1998, 7, 105. (c) Bricklebank, N. Recent Res. Dev.
Inorg. Organomet. Chem. 2001, 1, 25. (d) Guziec, L. J.; Guziec, F. S., Jr. In
Comprehensive Organic Functional Group Transformations; Katritzky,
A. R., Taylor, R. J. K., Eds.; Elsevier: Oxford, U.K., 2005; Vol. 6, p 573.
(5) For reviews: (a) Moore, A. J. In Comprehensive Organic Func-
tional Group Transformations; Katritzky, A. R., Taylor, R. J. K., Eds.;
Elsevier: Oxford, U.K., 2005; Vol. 5, p 519. (b) Flynn, C.; Haughton, L. In
Comprehensive Organic Functional Group Transformations; Katritzky,
A. R., Taylor, R. J. K., Eds.; Elsevier: Oxford, U.K., 2005; Vol. 5, p 571.
(c) Murai, T. In Topics in Current Chemistry; Kato, S., Ed.; Springer-
Verlag: Heidelberg, Germany, 2005; Vol. 251, p 247. (d) Koketsu, M.;
Ishihara, H. Curr. Org. Synth. 2007, 4, 15. (e) Koketsu, M.; Ishihara, H. In
Handbook of Chalcogen Chemistry: New Perspectives in Sulfur, Sele-
nium, Tellurium; Devillanova, F. A., Ed.; Royal Society of Chemistry:
Cambridge, U.K., 2007; p 145. (e) Hua, G.; Woollins, J. D. Angew. Chem.,
Int. Ed. 2009, 48, 1368.
(7) For reviews: (a)Murai, T. Synlett 2005, 1509. (b) Ishii, A.; Nakayama,
J. In Topics in Current Chemistry; Kato, S., Ed.; Springer-Verlag: Heidelberg,
Germany, 2005; Vol. 251, p 227.
(8) In situ generation of selenoacylsilane and its trapping by a diene
has been reported: Segi, M.; Koyama, T.; Nakajima, T.; Suga, S.; Murai,
S.; Sonoda, N. Tetrahedron Lett. 1989, 30, 2095.
(9) For recent examples, see: (a) Murai, T.; Aso, H.; Kato, S. Org.
Lett. 2002, 4, 1407. (b) Tani, Y.; Murai, T.; Kato, S. J. Am. Chem. Soc. 2002,
124, 5960. (c) Murai, T.; Ishizuka, M.; Suzuki, A.; Kato, S. Tetrahedron
Lett. 2003, 44, 1343. (d) Mutoh, Y.; Murai, T. Org. Lett. 2003, 5, 1361.
(e) Murai, T.; Fujishima, A.; Iwamoto, C.; Kato, S. J. Org. Chem. 2003, 68,
7979. (f) Mutoh, Y.; Murai, T. Organometallics 2004, 23, 3907. (g) Mutoh,
Y.; Murai, T.; Yamago, S. J. Organomet. Chem. 2007, 692, 129. (h) Murai,
T.; Nogawa, S.; Mutoh, Y. Bull. Chem. Soc. Jpn. 2007, 80, 2220.
(10) Shibahara, F.; Sugiura, R.; Murai, T. Org. Lett. 2009, 11, 3064.
(6) For a review: Wirth, T. Sci. Synth. 2005, 22, 181.
r
pubs.acs.org/Organometallics
Published on Web 05/04/2010
2010 American Chemical Society

Communication
Organometallics, Vol. 29, No. 11, 2010 2401
Figure 1. ORTEP drawings of selenoformamide 1 (left), (selenocarbamoyl)silane 3 (center), and (selenocarbamoyl)germane 4 (right).
on silica gel led to production of the (selenocarbamoyl)silane
3 as an air-stable solid.11 Similar treatment of the in situ
generated (selenocarbamoyl)lithium 2 with chlorotrimethyl-
germane results in the production of (selenocarbamoyl)-
germane 4.12 It is important to note that 2 does not react in
a similar fashion with chlorotrimethylstannane; rather, the
starting selenoformamide 1 is recovered along with several
unidentified products after aqueous workup.
To determine the structural properties of 1, 3, and 4, X-ray
crystallographic analyses were performed. ORTEP plots of
the data are shown in Figure 1, and selected bond lengths and
Figure 2. Representative bond lengths and angles of 1 and 3-5.
Table 1. Representative Spectroscopic Properties of 1 and 3-5
(11) To a solution of the diisopropylamine (0.29 mL, 2.1 mmol) in
THF (5 mL) was added n-butyllithium (1.6 M solution in hexane,
1.3 mL, 2.1 mmol) at -78 °C under an Ar atmosphere followed by stirring
for 30 min. To the mixture was added a solution of N,N-dibenzylseleno-
formamide (1; 0.29 g, 1.0 mmol) in THF (1 mL) at -78 °C followed by
stirring for 2 h. To the mixture was added chlorotrimethylsilane (0.27 mL,
2.1 mmol) at -78 °C. The resulting mixture was stirred for 24 h, poured
into water, and extracted with Et2O. The organic layer was dried over
MgSO4, filtered, and concentrated in vacuo, giving a residue which was
subjected to column chromatography on silica gel (hexane/EtOAc 8/1) to
give N,N- bis(phenylmethyl)trimethylsilanecarboselenoamide (3; 0.23 g,
0.62 mmol, 63%, Rf = 0.56) as an orange solid. Mp: 71-73 °C. IR (KBr):
2958, 2927, 1450, 1422, 1351, 1240, 1210, 873, 839, 743, 697 cm-1 1H
.
NMR (CDCl3): δ 0.00 (s, 9H, SiCH3), 4.40 (s, 2H, CH2), 5.01 (s, 2H, CH2),
6.69 (d, J = 7.0 Hz, 2H, Ar), 6.78 (d, J = 6.0 Hz, 2H, Ar), 6.85-6.98 (m,
6H, Ar). 13C NMR (CDCl3): δ 2.00, 56.4, 58.8, 126.6, 127.5, 127.8, 128.1,
128.6, 129.0þ, 134.3, 134.5, 230.9. 77Se NMR (CDCl3): δ 827.1. MS (EI):
m/z 361 [M ]. Anal. Calcd for C18H23NSeSi: C, 59.98; H, 6.43; N, 3.89.
Found: C, 59.79; H, 6.48; N, 3.90.
a Measured in CDCl3. b Measured in CHCl3.
angles are given in Figure 2. Bond lengths and angles derived
from the theoretical calculations at the B3LYP level with a
6-311G(d) basis set13 are shown in parentheses in Figure 2.
The results of a theoretical treatment of selenoamide 5,9 in
which a tert-butyl group is present on the CdSe carbon, are
also included in Figure 2. Analysis of the results shows that 1
and 3-5 are isostructural, but elongation of the CdSe bond
length occurs in a similar manner when the hydrogen atom in
1 is replaced by tert-butyl, silyl, and germyl groups. No
striking differences are observed in the CdSe bond lengths in
3-5. Finally, the Se-C-N bond angles were also found to
decrease on going from 1 to 3-5.
The spectroscopic properties of 1 and 3-5 were also
determined (Table 1). Analysis of 13C NMR spectra shows
that tert-butyl, silyl, and germyl groups deshield the CdSe
carbon, exemplified by the greater than 35 ppm downfield
shift for the carbons in 3 and 4 as compared with that of 1.
The introduction of silyl and germyl groups to the carbonyl
carbons of formamides is known to cause a slight shift to
(12) To a solution of the diisopropylamine (0.15 mL, 1.1 mmol) in THF
(5 mL) was added n-butyllithium (1.6 M solution in hexane, 0.66 mL, 1.1
mmol) at -78 °C under an Ar atmosphere followed by stirring for 30 min.
To the mixture was added a solution of N,N-dibenzylselenoformamide (1;
0.14 g, 0.5 mmol) in THF (1 mL) at -78 °C followedby stirring for 10 min.
To the reaction mixture was added chlorotrimethylgermane (0.13 mL, 1.1
mmol) at -78 °C. The resulting mixture was stirred for 24 h, poured into
water, and extracted with Et2O. The organic layer was dried over MgSO4,
filtered, and concentrated in vacuo, giving a residue which was subjected to
column chromatography on silica gel (hexane/EtOAc 20/1) to give N,N-
bis(phenylmethyl)trimethylgermanecarboselenoamide (4; 0.086 g, 0.21
mmol, 42%, Rf = 0.43) as a yellow solid. Mp: 76-78 °C. IR (KBr):
2960, 1601, 1494, 1422, 1350, 1199, 989, 834, 742, 696, 597, 567 cm-1. 1H
NMR (CDCl3): δ 0.08 (s, 9H, GeCH3), 4.33 (s, 2H, CH2), 4.98 (s, 2H,
CH2), 6.66 (d, J =7.4Hz, 2H, Ar), 6.77 (d, J =6.4Hz, 2H, Ar), 6.83-6.96
(m, 6H, Ar). 13C NMR (CDCl3): δ 2.54, 56.4, 59.3, 126.7, 127.7, 128.0,
128.2, 128.7, 129.1, 134.3, 134.6, 231.4. 77Se NMR (CDCl3): δ 785.1
(SedC). MS (EI): m/z 405 [Mþ]. Anal. Calcd for C18H23GeNSe: C,
53.38; H, 5.72; N, 3.46. Found: C, 53.62; H, 5.87; N, 3.39.
(13) The computations were done using Gaussian 03. The hybrid
density functional B3LYP along with the 6-311þG(d) basis set was used
for the structure optimization and energy calculations. Further technical
details are provided in the Supporting Information.

2402 Organometallics, Vol. 29, No. 11, 2010
Murai et al.
The HOMO and LUMO energy levels of 1 and 3-5 are
shown in Figure 3. In all cases, the HOMO corresponds to
the orbital containing the lone pair of the CdSe sele-
nium atom, while π* orbitals of CdSe double bonds serve
as LUMOs. In contrast to 1, introduction of silyl and
germyl groups increases the energy of the HOMO and
lowers that of the LUMO. The HOMO and LUMO energy
differences decrease on going from 1 to 5, 4, and 3, a finding
that is in accord with the trend observed in the UV-visible
spectra.
In summary, in this effort the first examples of silicon- and
germanium-substituted selenocarbonyl compounds have
been synthesized and structurally and spectroscopically
characterized. Elongation of the CdSe bonds and red shifts
of n-π* transitions in UV-visible spectra were observed to
take place by the introduction of the silicon and germanium
substituents. Particularly interesting is the fact that the effect
of the silyl group on the spectroscopic properties is greater
than that of the germyl group. Further studies probing appli-
cations of (selenocarbamoyl)silanes and -germanes as well as
(selenocarbamoyl)lithium17 are in progress.
Figure 3. Energy levels of the HOMO and LUMO of com-
pounds 1 and 3-5 at the B3LYP/6-311þG(d) level.
lower fields of CdO carbon resonances.14,15 A series of sulfur
isologues of 3 and 4 display downfield shifts similar to those
with HC(S)Bn2 (6),16 but the carbon resonances of 3 and 4
are more greatly shifted to lower fields. Likewise, downfield
shifts are observed in the 77Se NMR spectra for 3-5 as
compared to 1. The chemical shifts of 77Se in 3 and 4 occur at
greater than 210 ppm lower fields compared with that of 1.
The absorption band ascribed to an n-π* transition in the
UV-visible spectrum of 1 occurs at a maximum at 408.5 nm.
The corresponding n-π* absorptions of 3-5 are red-shifted,
with that of 3 occurring at the longest wavelength.
Acknowledgment. This work was supported in part by
a Grant-in-Aid for Scientific Research from the Ministry
of Education, Culture, Sports, Science and Technology of
Japan.
Supporting Information Available: Text and tables giving
experimental procedures and spectral data for new compounds
and a CIF file giving crystallographic data for 1, 3, and 4.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(14) For recent examples of carbamoylsilanes: (a) Cunico, R. F.;
Motta, A. R. Org. Lett. 2005, 7, 771. (b) Chen, J.; Pandey, R. K.; Cunico,
R. F. Tetrahedron: Asymmetry 2005, 16, 941. (c) Cunico, R. F.; Pandey,
R. K. J. Org. Chem. 2005, 70, 5344. (d) Cunico, R. F.; Pandey, R. K. J. Org.
Chem. 2005, 70, 9048. (e) Cunico, R. F.; Pandey, R. K.; Chen, J.; Motta, A. R.
Synlett 2005, 3157. (f) Cunico, R. F.; Motta, A. R. J. Organomet. Chem.
2006, 691, 3109. (g) Canac, Y.; Aniol, G. E.; Conejero, S.; Donnadieu, B.;
Bertrand, G. Eur. J. Inorg. Chem. 2006, 5076.
(15) For examples of carbamoylgermanes: (a) Bravo-Zhivotovskii,
D. A.; Pigarev, S. D.; Kalikhman, I. D.; Vyazankina, O. A.; Vyazankin,
N. S. J. Organomet. Chem. 1983, 248, 51. (b) Seleznev, A. V.; Bravo-
Zhivotovskii, D. A.; Vakul'skaya, T. I.; Voronkov, G. Polyhedron 1990, 9, 227.
(16) For comparison of the properties of 3 and 4 with those of their
sulfur isologues, Me3SiC(S)NBn2 (7) and Me3GeC(S)NBn2 (8) were
prepared from HC(S)NBn2 (6) in a procedure that is similar to that used
to prepare 3 and 4. The CdS carbons of 6-8 resonate at δ 189.5, 224.2,
and 225.1, respectively (see the Supporting Information).
(17) In contrast to the generation of carbamoyllithiums18 and
thiocarbamoyllithiums,19 no studies of their selenium isologues have
been reported.
(18) (a) Banhidai, B.; Schollkopf, U. Angew. Chem., Int. Ed. Engl.
1973, 12, 836. (b) Schollkopf, U.; Beckhaus, H. Angew. Chem., Int. Ed.
Engl. 1976, 15, 293. (c) Fletcher, A. S.; Smith, K.; Swaminathan, K. J. Chem.
Soc., Perkin Trans. 1 1977, 1881. (d) Hiiro, T.; Mogami, T.; Kambe, N.;
Fujiwara, S.; Sonoda, N. Synth. Commun. 1990, 20, 703.
(19) Seebach, D.; Luboch, W.; Enders, D. Chem. Ber. 1976, 109,
1309.