Synthesis and structure of the first 1,2σ5-selenaphosphirane

Article abstract of DOI:10.1021/ja026107z

A 1,2σ⁵-selenaphosphirane bearing the Martin ligand was synthesized. Its structure in both the solid and the solution state was established by X-ray crystallographic analysis and NMR measurements, respectively. The selenaphosphirane has a polar

Full text of DOI:10.1021/ja026107z

Published on Web 07/30/2002
Synthesis and Structure of the First 1,2σ5-Selenaphosphirane
Shohei Sase, Naokazu Kano, and Takayuki Kawashima*
Department of Chemistry, Graduate School of Science, The UniVersity of Tokyo, 7-3-1 Hongo, Bunkyo-ku,
Tokyo 113-0033, Japan
Received March 6, 2002
Three-membered-ring compounds containing phosphorus have
been studied for four decades both experimentally and theoretically
in view of their interesting structural features and high strain
energies.1 Many examples bearing a tri- and tetracoordinate
phosphorus atom, such as phosphiranes, as well as those containing
another heteroatom in the ring were synthesized, and their structures
and properties were established.2 In contrast, there are only limited
reports on three-membered-ring compounds bearing a phosphorus
atom with a coordination number higher than four.3,4 Although some
σ5(P)-phosphirenes bearing a C-C double bond in the ring were
synthesized and some of them were crystallographically charac-
terized,3c only a few compounds bearing a pentacoordinate phos-
Figure 1. ORTEP drawing of 4 with thermal ellipsoid plot (30%
phorus atom located in the saturated three-membered ring have been
probability). Selected bond lengths (Å) and bond angles (deg): P(1)-Se-
(1) 2.4540(10), P1-O(1) 1.706(2), P(1)-C(1) 1.767(2), P(1)-C(2) 1.806-
reported to date. Furthermore, no X-ray crystal structure is available
for these saturated ring compounds. In this communication, we
report the synthesis of the first selenaphosphirane involving a
pentacoordinate phosphorus atom by taking advantage of the
stabilizing effect of the Martin ligand, together with its structure
in solid and solution state.5
Heterolytic cleavage of the P-F bond of fluorophosphorane 1
bearing the Martin ligand with 1.1 equiv of trimethylsilyl triflate
in ether at room temperature gave the corresponding phosphonium
triflate 2 quantitatively.6 Deprotonation of 2 with 1.2 equiv of 2,4,6-
trimethylphenyllithium (MesLi) in THF at -72 °C provided
phosphorus ylide 3 in 83% yield. Treatment of 3 with 1.6 equiv of
elemental selenium in THF at room temperature successfully
afforded selenaphosphirane 4 as a colorless solid in 96% yield
(Scheme 1).7,8 The selenaphosphirane 4 is highly moisture-sensitive.
(2), P(1)-C(3) 1.803(2), C(1)-Se(1) 1.998(2), O(1)-P(1)-Se(1) 155.82(6),
O(1)-P(1)-C(1) 102.61(10), O(1)-P(1)-C(2) 90.26(9), O(1)-P(1)-C(3)
97.65(9), C(1)-P(1)-Se(1) 53.53(8), P(1)-C(1)-Se(1) 81.13(10), C(1)-
Se(1)-P(1) 45.35(7).
angle (155.82(6)°) and the O1-P1-C1 angle (102.61(10)°) are far
from those of a TBP structure (%TBP f SP: 56).10 Judging from
the value of %TBP character, 4 exhibits an intermediate structure
between TBP and square pyramidal. The C1-Se1 bond length
(1.998(2) Å) roughly agreed with the sum of the corresponding
covalent bond radii (1.94 Å).11 The P-Se bond length (2.4540(10)
Å) is much shorter than the sum of van der Waals radii of
phosphorus and selenium (3.9 Å), which apparently indicates the
interaction between the phosphorus and selenium atoms of 4 in
the crystalline state. Although the P-Se bond length is longer than
the sum of the covalent bond radii (2.27 Å), such an elongation is
a typical feature of the apical bond of hypervalent compounds. The
P1-C1-Se1 angle (81.13(10)°) is significantly reduced from the
bond angle of a tetrahedral structure (109.5°), and the C1-P1-
Se1 angle (53.53(8)°) apparently deviates from a TBP structure
(90°), respectively. These structural features clearly suggest the
formation of the P-C-Se three-membered-ring structure of 4. This
is the first example of an X-ray structural analysis not only of a
selenaphosphirane but also of a saturated three-membered-ring
compound involving a pentacoordinate phosphorus atom.
Scheme 1
In the solid-state 31P{1H} NMR spectrum, the selenaphosphirane
4 showed a singlet at δP -26.1, the value of which is in the range
of the 31P NMR chemical shifts of typical pentacoordinate
phosphorus compounds. This result also proves the pentacoordinate
state of the phosphorus atom of 4 in the solid state. In the C6D6
solution, the signal of 4 in the 31P{1H} NMR spectrum was observed
at δP -26.6 as a singlet, which is almost the same value as that in
the solid state, suggesting the pentacoordinate state of the phos-
phorus atom of 4 to persist also in C6D6. In the 77Se{1H} NMR
spectrum (C6D6), 4 showed a singlet at δSe 147.5, which differs
from that of a selenaphosphirane bearing a tricoordinate phosphorus
atom (δSe -130.4).2f Although the coupling constant between the
It is purified by recrystallization from hexane in an argon
atmosphere. The molecular structure of 4 was established by X-ray
crystallographic analysis (Figure 1), and it was found that 4 has a
highly distorted trigonal bipyramidal (TBP) structure with an
oxygen and a selenium atom at the apical positions and three carbon
atoms at the equatorial positions, respectively.9 The O1-P1-Se1
* Corresponding author. E-mail: takayuki@chem.s.u-tokyo.ac.jp.
9
9706
J. AM. CHEM. SOC. 2002, 124, 9706-9707
10.1021/ja026107z CCC: $22.00 © 2002 American Chemical Society

C O M M U N I C A T I O N S
Table 1. NMR Spectral Data of 4 in Several Solvents and
Acceptor Number of the Solvents
Supporting Information Available: Details of experimental
procedures of all compounds (PDF) and data for X-ray crystallographic
analysis of 4 (CIF). This material is available free of charge via the
Internet at http//:www.acs.org.
a
δH
solvent
δP
δSe
acceptor number
C6D6
-26.6
-20.2
-19.3
-13.6
147.5
144.3
138.3
129.9
8.97
9.04
9.08
9.11
8.2
18.9
20.4
23.1
CD3CN
CD2Cl2
CDCl3
References
(1) (a) Mathey, F. Chem. ReV. 1990, 90, 997. (b) Mathey, F.; Regitz, M. In
ComprehensiVe Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W.,
Scriven, E. F. V., Eds.; Pergamon: Amsterdam, 1996; Vol. 1A, pp 277-
304. (c) Mathey, F.; Regitz, M. In Phosphorus-Carbon Heterocyclic
Chemistry: The Rise of a New Domain; Mathey, F., Ed.; Pergamon:
Amsterdam, 2001; pp 17-55. (d) Ikeda, H.; Inagaki, S. J. Chem. Phys. A
2001, 105, 10711.
(2) For heteraphosphiranes involving a tri- and tetracoordinate phosphorus
atom, see: (a) Niecke, E.; Wildbredt, D.-A. J. Chem. Soc., Chem.
Commun. 1981, 72. (b) Caira, M.; Neilson, R. H.; Watson, W. H.; Wisian-
Neilson, P.; Xie, Z.-M. J. Chem. Soc., Chem. Commun. 1984, 698. (c)
Niecke, E.; Bo¨ske, J.; Krebs, B.; Dartmann, M. Chem. Ber. 1985, 118,
3227. (d) Niecke, E.; Symalla, E. Chimia 1985, 39, 320. (e) Xie, Z.-M.;
Wisian-Neilson, P.; Neilson, R. H. Organometallics 1985, 4, 339. (f)
Appel, R.; Casser, C. Chem. Ber. 1985, 118, 3419. (g) Bauer, S.; Marinetti,
A.; Ricard, L.; Mathey, F. Angew. Chem., Int. Ed. Engl. 1990, 29, 1166.
(h) Driess, M.; Pritzkow, H. Angew. Chem., Int. Ed. Engl. 1992, 31, 751.
(i) Ma¨rkl, G.; Ho¨lzl, W.; Kallmu¨nzer, A. Tetrahedron Lett. 1992, 33, 4421.
(j) Streubel, R.; Kusenberg, A.; Jeske, J.; Jones, P. G. Angew. Chem., Int.
Ed. Engl. 1994, 33, 2427. (k) Toyota, K.; Takahashi, H.; Shimura, K.;
Yoshifuji, M. Bull. Chem. Soc. Jpn. 1996, 69, 141. (l) Ruf, S. G.; Dietz,
J.; Regitz, M. Tetrahedron 2000, 56, 6259. (m) Vlaar, M. J. M.; Ehlers,
A. W.; de Kanter, F. J. J.; Schakel, M.; Spek, A. L.; Lutz, M.; Sigal, N.;
Apeloig, Y.; Lammertsma, K. Angew. Chem., Int. Ed. 2000, 39, 4127.
phosphorus and the selenium nuclei was observed in the cases of
1,2σ3-selenaphosphiranes,2d,f,l 4 showed no coupling between these
two nuclei. The reason for the absence of the coupling of 4 is
unclear at present. In the 1H NMR spectrum (C6D6), the ortho proton
of the Martin ligand (Ha) showed a high downfield shift (δH 8.97),
a
which is a typical feature of the compounds bearing the Martin
ligand with TBP and pseudo-TBP structures. It has been already
reported that the downfield shift of Ha is attributed to magnetic
deshielding by a polar apical bond.12 Therefore, the downfield shift
of Ha of 4 suggests that 4 has a polar P-Se bond and that the
selenium atom seems to be close to the C-Ha bond.
In the solution state, the selenaphosphirane 4 showed an
interesting behavior depending on the solvent. The results are
summarized in Table 1, together with acceptor numbers of the
solvents. Since the 31P resonances of 4 in these solvents still
appeared at high field, the phosphorus atom of 4 should retain the
pentacoordinate state in these solvents.13 A rough correlation was
found between the acceptor numbers of the solvents and the 31P
and 77Se NMR shifts of 4.14 The larger the acceptor number
becomes, the lower field the signal of 4 appeared in the 31P NMR
spectrum and the higher field the signal of 4 in the 77Se NMR
spectrum, respectively. Moreover, the signal of Ha is shifted to lower
field in the 1H NMR spectra as the acceptor number increases. These
results show that the negative charge on the selenium atom and
the positive charge on the phosphorus atom increase with increasing
acceptor number of the solvent, that is, the polarization of the P-Se
bond depends on the acceptor number of the solvent. Considering
the rough correlation of the acceptor number of the solvents with
the chemical shifts of 4 and its significance as an indicator of the
electrophilic property of the solvent, an interaction between the
negatively charged selenium atom of 4 and the solvent should exist
in the solution state.
Treatment of 4 with 2 equiv of methyl triflate in CDCl3 gave
the highly air-sensitive R-(methylseleno)alkyl phosphonium triflate
5 in 76% yield. The formation of 5 was reasonably explained by
the electrophilic attack of methyl triflate on the negatively charged
selenium atom of 4 and the subsequent dissociation of the P-Se
bond, reflecting the polarized character of the P-Se bond.
In summary, we have succeeded in the isolation of the first stable
1,2σ5-selenaphosphirane, 4, and elucidated its three-membered-ring
structure with a polarized P-Se bond. Further studies on its
reactivity are in progress.
(3) For three-membered-ring compounds bearing a pentacoordinate phosphorus
atom, see: (a) Burger, K.; Fehn, J.; Thenn, W. Angew. Chem., Int. Ed.
Engl. 1973, 12, 502. (b) Campbell, B. C.; Denny, D. B.; Denny, D. Z.;
Shih, L. S. J. Chem. Soc., Chem. Commun. 1978, 854. (c) Ehle, M.;
Wagner, O.; Bergstra¨sser, U.; Regitz, M. Tetrahedron Lett. 1990, 31, 3429.
(d) Abdou, W. M.; Yakout, E.-S. M. A. Tetrahedron 1993, 49, 6411. We
could not reproduce the result of ref 3d.
(4) For dioxaphosphiranides involving a hexacoordinate phosphorus atom,
see: Nakamoto, M.; Akiba. K.-y. J. Am. Chem. Soc. 1999, 121, 6958.
(5) Perozzi, E. F.; Michalak, R. S.; Figuly, G. D.; Stevenson, W. H., III;
Dess, D. B.; Ross, M. R.; Martin, J. C. J. Org. Chem. 1981, 46, 1049.
(6) Sase, S.; Kano, N.; Kawashima, T. Chem. Lett. 2002, 268.
(7) 4: colorless crystals, mp 94.1-96.2 °C (dec); 1H NMR (500 MHz, C6D6)
3
3
δ 1.78 (d, JPH ) 6.3 Hz, 3H), 1.86 (d, JPH ) 7.4 Hz, 3H), 6.95-7.10
3
(m, 5H), 7.33 (brt, 1H), 8.07-8.12 (m, 2H), 8.97 (dd, JPH ) 13.2 Hz,
3JHH ) 7.8 Hz, 1H); 13C{1H}NMR (126 MHz, C6D6) δ 14.0 (d, JPC
)
1
1
93 Hz, PCSe), 28.65 (s), 28.73 (s), 122.4 (q, JFC ) 288 Hz), 122.7 (q,
1JFC ) 287 Hz), 124.6 (d, 3JPC ) 15 Hz), 127.5 (d, 3JPC ) 15 Hz), 131.2
(d, 4JPC ) 3 Hz), 131.5 (d, 3JPC ) 14 Hz), 134.7 (d, 4JPC ) 3 Hz), 134.9
(d, 2JPC ) 11 Hz), 136.0 (d, 2JPC ) 20 Hz), 139.1 (d, 2JPC ) 8 Hz), three
signals due to quaternary carbons were not observed; 19F NMR (254 MHz,
4
4
C6D6) δ -74.3 (q, JFF ) 9.1 Hz, 3F), -74.9 (q, JFF ) 9.1 Hz, 3F);
31P{1H} NMR (109 MHz, C6D6) δ -26.6 (s); 77Se{1H} NMR (95 MHz,
C6D6) δ 147.5 (s); LRMS (EI): m/z 472 (M+). Anal. Calcd for C18H15F6-
OPSe: C, 45.88; H, 3.21. Found: C, 45.26; H, 4.00.
(8) For reactions of phosphorus ylides with elemental selenium, see: (a) Erker,
G.; Hock, R.; Nolte, R. J. Am. Chem. Soc. 1988, 110, 624. (b) Okuma,
K.; Sakata, J.-i.; Tachibana, Y.; Honda, T.; Ohta, H. Tetrahedron Lett.
1987, 28, 6649. (c) Okuma, K.; Komiya, Y.; Kaneko, I.; Tachibana, Y.;
Iwata, E.; Ohta, H. Bull. Chem. Soc. Jpn. 1990, 63, 1653.
(9) Crystallographic data for 4: C18H15F6OPSe, FW ) 471.24, T ) 173 K,
monoclinic, P21/n, a ) 14.306(2), b ) 8.6454(8), and c ) 16.0518(13)
Å, â ) 109.0760(9)°, V ) 1876.3(3) Å3, Z ) 4, Dcalc ) 1.668 g cm-3
.
The final cycle of full-matrix least squares refinement was based on all
3796 observed reflections and 304 variable parameters and converged at
R1 ) 0.033 (I > 2.00σ(I)) and wR2 ) 0.080 (all data) with GOF ) 1.13.
(10) Holmes, R. R.; Deiters, J. A. J. Am. Chem. Soc. 1977, 99, 3318.
(11) Pauling, L. In The Nature of the Chemical Bond, 3rd ed.; Cornell
University: New York, 1960; p 224.
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science and Technology of Japan. We are grateful
to Dr. T. Sasaki of the University of Tokyo for technical assistance
in the solid-state NMR studies and for helpful comments. We also
thank Central Glass, Tosoh Finechem Corporation, and Shin-etsu
Chemical Co., Ltd. for gifts of organofluorine compounds, alkyl-
lithiums, and organosilicon compounds, respectively.
(12) Granoth, I.; Martin, J. C. J. Am. Chem. Soc. 1981, 103, 2711.
(13) (a) Wilker, S.; Laurent, C.; Sarter, C.; Puke, C.; Erker, G. J. Am. Chem.
Soc. 1995, 117, 7293. (b) Puke, C.; Erker, G.; Aust, N. C.; Wu¨rthwein,
E.-U.; Fro¨hlich, R. J. Am. Chem. Soc. 1998, 120, 4863.
(14) (a) Mayer, U.; Gutmann, V.; Gerger, W. Monatsh. Chem. 1975, 106, 1235.
(b) Mayer, U.; Gerger, W.; Gutmann, V. Monatsch. Chem. 1977, 108,
489. (c) Parker, A. J.; Mayer, U.; Schmid, R.; Gutmann, V. J. Org. Chem.
1978, 43, 1843.
JA026107Z
9
J. AM. CHEM. SOC. VOL. 124, NO. 33, 2002 9707