J. Am. Chem. Soc. 2001, 123, 6443-6444
6443
Scheme 1
Dimeric Triarylbismuthane Oxide: A Novel Efficient
Oxidant for the Conversion of Alcohols to Carbonyl
Compounds
Yoshihiro Matano* and Hazumi Nomura
Department of Chemistry
Graduate School of Science, Kyoto UniVersity
Sakyo-ku, Kyoto 606-8502, Japan
ReceiVed March 5, 2001
The oxidation of organic compounds by metal-oxo or het-
eroatom-oxo species has received much attention because of its
importance in organic synthesis, biological systems, and industrial
processes.1 Such oxidants exist in monomeric, dimeric, or
oligomeric forms, and their oxidizing abilities differ considerably,
depending on the central elements as well as on the attached
ligands. Triorganylbismuthane oxides (R3BidO), formally bearing
a Bi(V)dO bond, are attractive oxidants due to the potent
oxidizing ability of the pentavalent bismuth2 and also because of
the low toxicity of bismuth.3 Despite this interest, however, the
chemistry of bismuthane oxides has been much less explored than
that of lighter pnictogen counterparts, probably due to the limited
access to this class of compounds.4 All bismuthane oxides
prepared thus far have been polymeric substances in the solid
state,5,6 and there are no well-characterized examples. We report
herein the first synthesis of a dimeric bismuthane oxide that was
structurally characterized by X-ray crystallography. In marked
contrast to the lighter pnictogen counterparts, this bismuthane
oxide readily oxidizes alcohols to aldehydes or ketones with high
efficiency under mild conditions.
and CH2Cl2 but insoluble in acetonitrile, diethyl ether, and
benzene. Its structure was characterized by NMR, IR, and FAB
mass spectrometry as well as by a chemical transformation. The
FAB mass spectrum of 2 showed a strong fragment ion peak at
m/z 969, attributable to a cation with a dimeric framework
(Ar5Bi2O+). When treated with 0.5 equiv of acetic anhydride, 2
was converted to µ-oxobis[tris(2-methoxyphenyl)bismuth] diac-
etate in a ca. 80% yield. These findings suggest that bismuthane
oxide 2 would exist for the most part in dimeric form. When
triphenylbismuth dichloride (1c) or diacetate (1d) was used instead
of 1a, triphenylbismuth dihydroxide4b or its µ-oxo-bridged dimer
(3, n ) 0 or 1) was formed as the initial product. As in a previous
finding,4b 3 was dehydrated in vacuo to give an amorphous
powder, insoluble in most organic solvents. On the basis of the
spectral and analytical data, we have characterized this powder
as polymeric triphenylbismuthane oxide.11 Thus, the o-methoxy
groups in 2 are likely to prevent both hydration and polymerization
of the Bi(V)dO bond.
Treatment of tris(2-methoxyphenyl)bismuth dichloride7 (1a) or
diacetate8 (1b) with 2 equiv of KO-t-Bu in the presence of 5 equiv
of water in CH2Cl2 at 0 °C afforded tris(2-methoxyphenyl)-
bismuthane oxide (2) as a pale yellow solid (Scheme 1).9 The
present method is simple and efficient for obtaining 2, which is
otherwise difficult to prepare.10 Compound 2 is soluble in CHCl3
The structure of 2 was further determined by X-ray crystal-
lography.12 As shown in Figure 1, oxide 2 exists, at least in the
solid state, in a dimeric form with a four-membered Bi2O2 ring.
Each bismuth center adopts a distorted trigonal bipyramidal
geometry with two ipso carbon and one oxygen atom at the
equatorial sites and one ipso carbon and one oxygen at the apical
sites. The Bi-Oap bond is longer than the Bi-Oeq bond over 0.3
Å, and the Bi-Oap/Bi-Oeq bond length ratio (1.147) is slightly
larger than the Sb-Oap/Sb-Oeq ratio (1.074-1.078) observed for
an analogous triphenylstibane oxide dimer.13 The Bi-Obridge single
bond lengths of known µ-oxo-bridged dinuclear organobismuth
compounds range from 2.02(3) to 2.12(3) Å.14,15 Thus, the
Bi-Oeq bond length of 2.013(5) Å is at the shorter end of this
range and would be best represented as a Bi-O single bond. It
is likely that two molecules of the oxide monomer with a polarized
Bi+-O- bond aggregate to attain electrostatic stabilization.
Bismuthane oxide 2 was found to possess remarkable oxidizing
ability (Scheme 2). Primary and secondary alcohols are oxidized
by 2 (1.0-1.2 equiv) within 10 min at room temperature to
aldehydes and ketones, respectively, in excellent yields (Table
(1) (a) ComprehensiVe Organic Synthesis; Trost, B. M., Ed.; Pergamon:
New York, 1991; Vol. 7. (b) Sheldon, R. A.; Kochi, J. K. Metal-Catalyzed
Oxidation of Organic Compounds; Academic Press: New York, 1981. (c)
Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley: New
York, 1988.
(2) (a) Kitchin, J. P. In Organic Synthesis by Oxidation with Metal
Compounds; Mijs, W. J., deJonge, C. R. H. I., Eds.; Plenum: New York,
1986; Chapter 15, pp 817-837. (b) Postel, M.; Dun˜ach, E. Coord. Chem.
ReV. 1996, 155, 127-144.
(3) (a) Maeda, S. In The Chemistry of Organic Arsenic, Antimony and
Bismuth Compounds; Patai, S., Ed.; Wiley: New York, 1994; Chapter 19, pp
725-759. (b) Reglinski, J. In Chemistry of Arsenic, Antimony and Bismuth;
Norman, N. C., Ed.; Blackie Academic and Professional: London, 1997;
Chapter 8, pp 403-440.
(4) Most attempts to prepare triarylbismuthane oxides have been unsuc-
cessful. (a) Challenger, F.; Goddard, A. E. J. Chem. Soc. 1920, 117, 762-
773. (b) Challenger, F.; Richards, O. V. J. Chem. Soc. 1934, 405-411. (c)
Monagle, J. J. J. Org. Chem. 1962, 27, 3851-3855. (d) Agolini, F.; Bonnett,
R. Can. J. Chem. 1962, 40, 181-183. (e) Brandes, D.; Blaschette, A. J.
Organomet. Chem. 1974, 73, 217-227. (f) Glidewell, C. J. Organomet. Chem.
1976, 116, 199-209. (g) ElSheikh, S. I. A.; Patel, M. S.; Smith, B. C.; Waller,
C. B. J. Chem. Soc., Dalton Trans. 1977, 641-644. (h) Suzuki, H.; Ikegami,
T.; Matano, Y.; Azuma, N. J. Chem. Soc., Perkin Trans. 1 1993, 2411-
2415.
(5) Metathesis of Ph3BiX2 (X ) Cl or CN) with silver or mercury oxide:
(a) Goel, R. G.; Prasad, H. S. J. Organomet. Chem. 1972, 36, 323-332. (b)
Goel, R. G.; Prasad, H. S. J. Organomet. Chem. 1973, 50, 129-134.
(6) Oxygenation of Ar3Bi (Ar ) Ph, p-Tol) with iodosylbenzene: Suzuki,
H.; Ikegami, T.; Matano, Y. Tetrahedron Lett. 1994, 35, 8197-8200.
(7) Matano, Y.; Nomura, H.; Shiro, M.; Suzuki, H. Organometallics 1999,
18, 2580-2582.
(8) Combes, S.; Finet, J.-P. Synth. Commun. 1996, 26, 4569-4575.
(9) For details, see Supporting Information.
(10) An attempt to prepare 2 using tris(2-methoxyphenyl)bismuthane and
iodosylbenzene resulted in the formation of tetrakis(2-methoxyphenyl)-
bismuthonium salts. Suzuki, H.; Ikegami, T.; Azuma, N. J. Chem. Soc., Perkin
Trans. 1 1997, 1609-1616.
(11) This insoluble powder was reversibly converted to 3 on treatment with
water in CH2Cl2.
(12) Space group P1h, a ) 10.4018(6) Å, b ) 12.1622(8) Å, c ) 9.0988(6)
Å, R ) 108.935(3)°, â ) 104.073(3)°, γ ) 104.779(2)°, V ) 983.7(1) Å3, Z
) 1, Dc ) 1.845 g cm-3, T ) 23 °C.; 9056 collected and 4446 observed
reflections (I > -10.00σ(I)) refined to R ) 0.072, R1 ) 0.044, GOF ) 1.07.
(13) Bordner, J.; Doak, G. O.; Everett, T. S. J. Am. Chem. Soc. 1986, 108,
4206-4213.
(14) Bi(V) compounds: (a) Ph3BiOBiPh3(ClO4)2 [2.065(15), 2.062(14)
Å]: March, F. C.; Ferguson, G. J. Chem. Soc., Dalton Trans. 1975, 1291-
1294. (b) Ph3BiOBiPh3(OTf)2 [2.091(8), 2.039(8) Å]: Matano, Y.; Azuma,
N.; Suzuki, H. J. Chem. Soc., Perkin Trans. 1 1994, 1739-1747. (c) Ar3-
BiOBiAr3Cl2; Ar ) 4-Me2NC6H4, [2.12(3), 2.02(3) Å]: Hassan, A.; Breeze,
S. R.; Courtenary, S.; Deslippe, C.; Wang, S. Organometallics 1996, 15, 5613-
5621.
(15) Mes2BiOBiMes2 (Mes ) 2,4,6-Me3C6H2) [2.075(8), 2.064(7) Å]: Li,
X.-W.; Lorberth, J.; Ebert, K. H.; Massa, W.; Wocadlo, S. J. Organomet.
Chem. 1998, 560, 211-215.
10.1021/ja010584k CCC: $20.00 © 2001 American Chemical Society
Published on Web 06/08/2001