Synthesis and stereochemical behavior of unsymmetrical tetraarylbismuthonium salts

Article abstract of DOI:10.1021/om990597v

The synthesis and stereochemical behavior of unsymmetrical tetraarylbismuthonium salts were investigated. Two methods (tin and boron methods) for synthesizing unsymmetrically substituted tetraarylbismuthonium salts were developed. In the tin method, successive treatment of triarylbismuth difluorides (1; Ar¹₃BiF₂) with trimethylsilyl cyanide and aryltrin-butylstannanes (2; Bu₃SnAr²) in the presence of a Lewis acid (BF₃·OEt₂ or Me₃SiOTf) in boiling dichloromethane afforded tetraarylbismuthonium salts (3, [Ar¹₃Ar²Bi⁺][BF₄ ^-], or 5, [Ar¹₃Ar²Bi⁺][OTf^-]) in 44-85% yield. In contrast, in the boron method, similar treatment of 1 with arylboronic acids (4; Ar²B(OH)₂) in the presence of BF₃·OEt₂ afforded the tetrafluoroborates 3 in 55-99% yield at room temperature. Both methods were used to synthesize unsymmetrical tetraarylbismuthonium salts (9; [Ar¹Ar²Ar³Ar⁴Bi⁺][BF ₄^-]) starting from unsymmetrical triarylbismuth difluorides 8. The boron method was also used to synthesize unsymmetrical tetraarylbismuthonium tetrafluoroborates 14 bearing an oxazoline group at the ortho position ([(4-MeOC₆H₄)(4-CF₃C₆H ₄)(2-OxC₆H₄)ArBi⁺][BF ₄^-]; Ox = 4,4-dimethyl-3,4-dihydrooxazol-2-yl; a, Ar = 4-MeC₆H₄; b, Ar = 2-C₄H₃S). The reaction of bismuthonium tetrafluoroborate 14b with ammonium tosylate afforded bismuthonium tosylate 15, which, on treatment with sodium halides, was converted to the corresponding halides 16 ([(4-MeOC₆H₄)(4-CF₃C₆H ₄)(2-OxC₆H₄)(2-C₄H ₃S)Bi⁺][X^-]; a, X = Cl; b, X = Br; c, X = I). Tetrafluoroborates 14 and tosylate 15 are thermally stable, but halides 16 are unstable and underwent ligand coupling in solution. The X-ray diffraction analysis of a tetrafluoroborate 20 ([(4-MeC₆H₄)₃(2-OxC₆H ₄)Bi⁺][BF₄^-]) revealed a distorted tetrahedral geometry at the bismuth center, which was coordinated by the neighboring oxazoline nitrogen atom. The stereochemical behavior of the synthesized bismuthonium salts was investigated. The signals due to the diastereotopic geminal methyl groups on the oxazoline ring of 14 and 15 did not coalesce in the ¹H NMR spectra in 1,2-dichlorobenzene-d₄ (up to 150 °C), in DMSO-d₆ (up to 135 °C), and in pyridine-d₅ (up to 110 °C), whereas those of chloride 16a and bromide 16b coalesced in pyridine-d₅, 1,2-dichlorobenzene-d₄, chlorobenzene-d₅, and toluene-d₈. The coalescence temperature (T_c) depended on the nucleophilicity of the counteranions as well as on the polarity of the solvents; T_c decreased as the nucleophilicity of the counteranions increased or as the polarity of the solvent decreased. Thus, the configuration at bismuth in tetrafluoroborates 14 and tosylate 15 was found to be stable, whereas that in halides 16 strongly depended on the solvent polarity. The observed permutation of bismuthonium halides, [Ar¹Ar²Ar³Ar⁴Bi⁺][X ^-], can be explained by a pseudorotation mechanism involving a nonionic pentacoordinate species of the type Ar¹Ar²Ar³Ar⁴BiX.

Full text of DOI:10.1021/om990597v

5668
Organometallics 1999, 18, 5668-5681
Syn th esis a n d Ster eoch em ica l Beh a vior of
Un sym m etr ica l Tetr a a r ylbism u th on iu m Sa lts
Yoshihiro Matano,* Shameem Ara Begum,1 Takashi Miyamatsu, and
Hitomi Suzuki2
Department of Chemistry, Graduate School of Science, Kyoto University,
Sakyo-ku, Kyoto 606-8502, J apan
Received J uly 29, 1999
The synthesis and stereochemical behavior of unsymmetrical tetraarylbismuthonium salts
were investigated. Two methods (tin and boron methods) for synthesizing unsymmetrically
substituted tetraarylbismuthonium salts were developed. In the tin method, successive
treatment of triarylbismuth difluorides (1; Ar1 BiF2) with trimethylsilyl cyanide and aryltri-
3
n-butylstannanes (2; Bu3SnAr2) in the presence of a Lewis acid (BF3‚OEt2 or Me3SiOTf) in
boiling dichloromethane afforded tetraarylbismuthonium salts (3, [Ar1 Ar2Bi+][BF4-], or 5,
3
[Ar1 Ar2Bi+][OTf-]) in 44-85% yield. In contrast, in the boron method, similar treatment of
3
1 with arylboronic acids (4; Ar2B(OH)2) in the presence of BF3‚OEt2 afforded the tetrafluo-
roborates 3 in 55-99% yield at room temperature. Both methods were used to synthesize
unsymmetrical tetraarylbismuthonium salts (9; [Ar1Ar2Ar3Ar4Bi+][BF4-]) starting from
unsymmetrical triarylbismuth difluorides 8. The boron method was also used to synthesize
unsymmetrical tetraarylbismuthonium tetrafluoroborates 14 bearing an oxazoline group at
the ortho position ([(4-MeOC6H4)(4-CF3C6H4)(2-OxC6H4)ArBi+][BF4-]; Ox ) 4,4-dimethyl-
3,4-dihydrooxazol-2-yl; a , Ar ) 4-MeC6H4; b, Ar ) 2-C4H3S). The reaction of bismuthonium
tetrafluoroborate 14b with ammonium tosylate afforded bismuthonium tosylate 15, which,
on treatment with sodium halides, was converted to the corresponding halides 16 ([(4-
MeOC6H4)(4-CF3C6H4)(2-OxC6H4)(2-C4H3S)Bi+][X-]; a , X ) Cl; b, X ) Br; c, X ) I).
Tetrafluoroborates 14 and tosylate 15 are thermally stable, but halides 16 are unstable and
underwent ligand coupling in solution. The X-ray diffraction analysis of a tetrafluoroborate
20 ([(4-MeC6H4)3(2-OxC6H4)Bi+][BF4-]) revealed a distorted tetrahedral geometry at the
bismuth center, which was coordinated by the neighboring oxazoline nitrogen atom. The
stereochemical behavior of the synthesized bismuthonium salts was investigated. The signals
due to the diastereotopic geminal methyl groups on the oxazoline ring of 14 and 15 did not
1
coalesce in the H NMR spectra in 1,2-dichlorobenzene-d4 (up to 150 °C), in DMSO-d6 (up to
135 °C), and in pyridine-d5 (up to 110 °C), whereas those of chloride 16a and bromide 16b
coalesced in pyridine-d5, 1,2-dichlorobenzene-d4, chlorobenzene-d5, and toluene-d8. The
coalescence temperature (Tc) depended on the nucleophilicity of the counteranions as well
as on the polarity of the solvents; Tc decreased as the nucleophilicity of the counteranions
increased or as the polarity of the solvent decreased. Thus, the configuration at bismuth in
tetrafluoroborates 14 and tosylate 15 was found to be stable, whereas that in halides 16
strongly depended on the solvent polarity. The observed permutation of bismuthonium
halides, [Ar1Ar2Ar3Ar4Bi+][X-], can be explained by a pseudorotation mechanism involving
a nonionic pentacoordinate species of the type Ar1Ar2Ar3Ar4BiX.
In tr od u ction
and organoarsenic compounds bearing this type of
chirality have been studied in detail,4 the bismuth
counterparts have not. Since Bras et al. reported the
first example of unsymmetrical bismuthanes in 1981,5
attention in this area has been focused mainly on
organobismuth(III) compounds.6 Akiba and Yamamoto
reported7 that inversion at the trivalent bismuth center
bearing a Martin ligand8 proceeds via the edge inversion
mechanism, which was earlier predicted by Dixon and
The chirality of a heteroatom center in organic
compounds has long been the subject of numerous
studies in structural as well as synthetic organic
chemistry because it provides valuable information on
the stereochemical behavior around the central het-
eroatom.3 In the group 15 family, this type of chirality
can be constructed by simply attaching different ligands
to the heteroatom. Although many organophosphorus
(1) Current address: Department of Chemistry, Faculty of Physical
Sciences, Shahjalal University of Science and Technology, Sylhet,
Bangladesh.
(2) Current address: Department of Chemistry, School of Science,
Kwansei Gakuin University, Uegahara, Nishinomiya 662-8501, J apan.
(3) (a) Holms, R. R. Chem. Rev. 1990, 90, 17. (b) Yamamoto, Y.;
Akiba, K.-y. In Chemistry of Hypervalent Compounds; Akiba, K.-y.,
Ed.; Wiley: New York, 1998; Chapter 9, pp 279-294. (c) Kawashima,
T. In Chemistry of Hypervalent Compounds; Akiba, K.-y., Ed.; Wiley:
New York, 1998; Chapter 6, pp 171-210, and references therein.
10.1021/om990597v CCC: $18.00 © 1999 American Chemical Society
Publication on Web 12/02/1999

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5669
Arduengo on the basis of ab initio calculations.9 Re-
cently, Murafuji et al. successfully isolated the first
optically active bismuthane by introducing a chiral
iminoferrocenyl group as a coordinating ligand.10 How-
ever, little information is available as yet for unsym-
metrical organobismuth(V) compounds that possess
chirality at bismuth, and there is a need to determine
the factors that affect the permutation process at the
bismuth(V) center.11
atom. For the preparation of alkyltriarylbismuthonium
salts, we recently reported a general methodology that
is based on the Lewis acid-promoted reaction of triaryl-
bismuth difluorides with organosilanes or organostan-
nanes.15 Due to the certainty in its selective Bi-Calkyl
bond formation, in the current study we applied this
methodology to the selective Bi-Caryl bond formation
to obtain unsymmetrically substituted tetraarylbismu-
thonium salts.
Here we report the synthesis and stereochemical
behavior of tetraarylbismuthonium salts bearing four
different aryl ligands.16 One aim of our current study
was to obtain unsymmetrical tetraarylbismuthonium
salts that can be used for the direct NMR study on the
permutation process. The other aim was to determine
the factors that affect the activation energy for the
permutation at the bismuth(V) center.
For better understanding of the overall stereochemical
behavior around the bismuth(V) center, unsymmetri-
cally substituted tetraarylbismuthonium salts of the
type [Ar1Ar2Ar3Ar4Bi+][X-] (X ) an anionic species) are
considered a good model not only because they would
possess reasonable stability for use in kinetic and
thermodynamic studies but also because much struc-
tural and spectroscopic information is available for
compounds of the symmetrical type [Ar4Bi+][X-]. There-
fore, first a general method must be established for
preparation of unsymmetrical bismuthonium salts bear-
ing different aryl ligands, and then the structures and
stereochemical behavior of these prepared salts must
be determined.12 Although symmetrical tetraarylbis-
muthonium salts have been prepared by several meth-
ods,13 compounds of the mixed type [Ar3Ar′Bi+][X-] have
only been synthesized by a process that involves the
Bi-C bond cleavage of the corresponding pentaarylbis-
muth (Ar3Ar′2Bi).14 This method, however, does not
seem to ensure selective Bi-C bond cleavage when four
or five similar aryl ligands are attached to the bismuth
Resu lts
To accomplish our research aims, first we established
two methods involving organotin and organoboron
reagents, respectively, for the synthesis of tetraaryl-
bismuthonium salts of the type [Ar3Ar′Bi+][X-].
These methods then were applied to the preparation
of unsymmetrical bismuthonium salts of the type
[Ar1Ar2Ar3Ar4Bi+][X-], and finally we investigated, us-
ing variable-temperature (VT) NMR spectroscopy, the
stereochemical behavior of unsymmetrical tetraarylbis-
muthonium salts bearing an oxazoline group.
Syn th esis of Tetr a a r ylbism u th on iu m Sa lts. Com-
pounds of the type [Ar3Ar′Bi+][X-] were prepared as
shown in Scheme 1 and Table 1. In the tin method,
successive treatment of triphenylbismuth difluoride (1a )
with trimethylsilyl cyanide (Me3SiCN) and aryltri-n-
butylstannanes (2) in the presence of a Lewis acid,
BF3‚OEt2, in CH2Cl2 afforded aryltriphenylbismutho-
(4) For example, see: (a) Luckenbach, R. Phosphorus 1972, 1, 223,
229, 293. (b) Cristau, H.-J .; Ple´nat, F. In The Chemistry of Organo-
phosphorus Compounds; Hartley, F. R., Ed.; Wiley: Chichester, 1994;
Vol. 3, Chapter 2, p 45. (c) Wild, S. B. In The Chemistry of Organic
Arsenic, Antimony and Bismuth Compounds; Patai, S., Ed.; Wiley:
Chichester, 1994; Chapter 3, p 89. (d) Horner, L.; Fuchs, H. Tetrahe-
dron Lett. 1963, 1573. (e) Horner, L.; Dickerhof, K. Phosphorus Sulfur
1983, 15, 213. (f) Ionov, L. B.; Kornev, V. I.; Kunitskaya, L. A. Zh.
Obshch. Khim. 1976, 46, 64. (g) Ionov, L. B.; Kunitskaya, L. A.;
Mukanov, I. P.; Gatilov, Y. F. Zh. Obshch. Khim. 1976, 46, 68. (h) Allen,
D. G.; Roberts, N. K.; Wild, S. B. J . Chem. Soc., Chem. Commun. 1978,
346. (i) Allen, D. G.; Raston, C. L.; Skelton, B. W.; White, A. H.; Wild,
S. B. Aust. J . Chem. 1984, 37, 1171, and references therein.
(5) They reported the synthesis of bismuthanes of the types ArAr′Ar-
′′Bi and ArAr′BiBr. (a) Bras, P.; Herwijer, H.; Wolters, J . J . Organomet.
Chem. 1981, 212, C7. (b) Bras, P.; Van der Gen, A.; Wolters, J . J .
Organomet. Chem. 1983, 256, C1.
(6) We also have reported the synthesis and properties of unsym-
metrical bismuthanes bearing three different ligands. (a) Suzuki, H.;
Murafuji, T. J . Chem. Soc., Chem. Commun. 1992, 1143. (b) Suzuki,
H.; Murafuji, T.; Azuma, N. J . Chem. Soc., Perkin Trans. 1 1993, 1169.
(c) Suzuki, H.; Murafuji, T.; Matano, Y.; Azuma, N. J . Chem. Soc.,
Perkin Trans. 1 1993, 2969. (d) Murafuji, T.; Mutoh, T.; Satoh, K.;
Tsunenari, K.; Azuma, N.; Suzuki, H. Organometallics 1995, 14, 3848.
(e) Matano, Y.; Miyamatsu, T.; Suzuki, H. Organometallics 1996, 15,
1951.
(7) (a) Yamamoto, Y.; Chen, X.; Akiba, K.-y. J . Am. Chem. Soc. 1992,
114, 7906. (b) Yamamoto, Y.; Chen, X.; Kojima, S.; Ohdoi, K.; Kitano,
M.; Doi, Y.; Akiba, K.-y. J . Am. Chem. Soc. 1995, 117, 3922. (c) Chen,
X.; Yamamoto, Y.; Akiba, K.-y. Heteroatom Chem. 1995, 6, 293.
(8) 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.
(9) (a) Dixon, D. A.; Arduengo, A. J ., III; Fukunaga, T. J . Am. Chem.
Soc. 1986, 108, 2461. (b) Dixon, D. A.; Arduengo, A. J ., III. J . Phys.
Chem. 1987, 91, 3195. (c) Dixon, D. A.; Arduengo, A. J ., III. J . Am.
Chem. Soc. 1987, 109, 338.
(12) For leading reviews on the chemistry of organobismuth com-
pounds, see: (a) Gmelin Handbuch der Anorganischen Chemie, Bisumut-
Organische Verbindungen; Wieber, M., Ed.; Springer-Verlag: Berlin,
l977; Band 47. (b) Freedman, L. D.; Doak, G. O. Chem. Rev. 1982, 82,
15. (c) Finet, J .-P. Chem. Rev. 1989, 89, 1487. (d) Akiba, K.-y.;
Yamamoto, Y. In The Chemistry of Organic Arsenic, Antimony and
Bismuth Compounds; Patai, S., Ed.; Wiley: New York, l994; Chapter
20, pp 761-812. (e) Matano, Y.; Suzuki, H. Bull. Chem. Soc. J pn. 1996,
69, 2673. (f) Suzuki, H.; Matano, Y. In Chemistry of Arsenic, Antimony
and Bismuth; Norman, N. C., Ed.; Blackie Academic and Profes-
sional: London, 1998; Chapter 6, pp 283-343.
(13) For example, see: (a) Wittig, G.; Clauss, K. Liebigs Ann. Chem.
1952, 578, 136. (b) Doak, G. O.; Long, G. G.; Kakar, S. K.; Freedman,
L. D. J . Am. Chem. Soc. 1966, 88, 2342. (c) Ptitsyan, O. A.; Gurskii,
M. E.; Mariorova, T. D.; Reutov, O. A. Izv. Akad. Nauk SSSR, Ser.
Khim. 1971, 2618. (d) Beaumont, R. E.; Goel, R. G. J . Chem. Soc.,
Dalton Trans. 1973, 1394. (e) Barton, D. H. R.; Charpiot, B.; Dau, E.
T. H.; Motherwell, W. B.; Pascard, C.; Pichon, C. Helv. Chim. Acta
1984, 67, 586. (f) Barton, D. H. R.; Bhatnagar, N. Y.; Blazejewski, J .-
C.; Charpiot, B.; Finet, J .-P.; Lester, D. J .; Motherwell, W. B.; Papoula,
M. T. B.; Stanforth, S. P. J . Chem. Soc., Perkin Trans. 1 1985, 2657.
(g) Barton, D. H. R.; Finet, J .-P.; Motherwell, W. B.; Pichon, C. J . Chem.
Soc., Perkin Trans. 1 1987, 251. (h) Hassan, A.; Breeze, S. R.;
Courtenay, S.; Deslippe, C.; Wang, S. Organometallics 1996, 15, 5613.
(i) Suzuki, H.; Ikegami, T.; Azuma, N. J . Chem. Soc., Perkin Trans. 1
1997, 1609. (j) Hoppe, S.; Whitmire, K. H. Organometallics 1998, 17,
1347.
(14) Hellwinkel, D.; Bach, M. Liebigs Ann. Chem. 1968, 720, 198.
(15) (a) Matano, Y.; Azuma, N.; Suzuki, H. Tetrahedron Lett. 1993,
34, 8457. (b) Matano, Y.; Azuma, N.; Suzuki, H. J . Chem. Soc., Perkin
Trans. 1 1994, 1739. (c) Matano, Y.; Azuma, N.; Suzuki, H. J . Chem.
Soc., Perkin Trans. 1 1995, 2543. (d) Matano, Y.; Yoshimune, M.;
Suzuki, H. Tetrahedron Lett. 1995, 36, 7475. (e) Matano, Y.; Yoshimune,
M.; Azuma, N.; Suzuki, H. J . Chem. Soc., Perkin Trans. 1 1996, 1971.
(16) Preliminary results, see: (a) Matano, Y.; Miyamatsu, T.; Suzuki,
H. Chem. Lett. 1998, 127. (b) Matano, Y.; Begum, S. A.; Miyamatsu,
T.; Suzuki, H. Organometallics 1998, 17, 4332.
(10) Murafuji, T.; Satoh, K.; Sugihara, Y.; Azuma, N. Organome-
tallics 1998, 17, 1711.
(11) Akiba et al. synthesized unsymmetrical hypervalent organo-
bismuth compounds bearing a Martin ligand and monitored the
stereochemical behavior by using VT-NMR technique. The inversion
energy at the bismuth center was estimated to be higher than 21 kcal
mol-1. Chen, X.; Ohdoi, K.; Yamamoto, Y.; Akiba, K.-y. Organometallics
1993, 12, 1857.

5670 Organometallics, Vol. 18, No. 26, 1999
Matano et al.
Sch em e 1
the reaction was carried out for 24 h with an excess of
the reagents, 3-nitrophenyl and 4-acetylphenyl groups
also could be transferred in 55-56% yield (entries 14,
15). Sterically hindered aryl groups, such as mesityl and
1-naphthyl, as well as heteroaryl groups, such as
2-thienyl and 2-furyl, were all efficiently transferred to
the bismuth atom (entries 16-19). The 4-vinylphenyl
group remained intact throughout the reaction (entry
20). Although para-substituted triarylbismuth difluo-
rides 1b-d all reacted similarly with 4a , tris(2-meth-
ylphenyl)bismuth difluoride 1e failed to afford the
expected onium salt (entries 21-24). Tris(4-methylphe-
nyl)bismuth dichloride and 2a did not react in the
presence of BF3‚OEt2 even after 24 h at room temper-
ature.
When a different Lewis acid, trimethylsilyl trifluo-
romethanesulfonate (Me3SiOTf), was used, the corre-
sponding bismuthonium triflate 5 was obtained (eq 1).
No Bi-Caryl coupling occurred in the absence of the
given Lewis acid.
Tetraarylbismuthonium salts 3 and 5 are colorless
solids that are thermally stable and readily soluble in
CH2Cl2, CHCl3, MeCN, and DMSO, but are almost
insoluble in toluene and Et2O. The IR spectra of these
salts show strong absorption at around 1150-900 cm-1
due to the counteranion (BF4- or OTf-). The FAB mass
spectra show a strong fragment peak due to [Ar13Ar2-
Bi+] ([M+ - X]; X ) BF4, OTf). These data support the
onium nature of the bismuth center in 3 and 5. Tet-
raphenylbismuthonium salts bearing similar counter-
anions are known to have an ionic nature.13
Syn th esis of Un sym m etr ical Bism u th on iu m Salts
Bea r in g F ou r Differ en t Ar yl Liga n d s. Both the tin
and boron methods were used to synthesize bismutho-
nium salts that bear four different aryl ligands. Unsym-
metrical triarylbismuthanes 6, prepared from mixed
diarylbismuth triflate-HMPA complexes and Grignard
reagents as reported,6e were reacted with sulfuryl
chloride to afford triarylbismuth dichlorides 7. When
treated with an excess of potassium fluoride in EtOH/
H2O, dichlorides 7 were converted to the corresponding
difluorides 8 in 66-84% yield (Scheme 2).
Successive treatment of 8 with Me3SiCN and aryl-
stannanes 2 in the presence of BF3‚OEt2 in boiling CH2-
Cl2 afforded the desired unsymmetrical tetraarylbis-
muthonium salts 9 in 60-71% yield. When boronic acids
4 were used instead of stannanes 2, these salts were
obtained in better yield (95-97%) within 1 h at room
temperature (Scheme 3). The results are summarized
in Table 2. Attempts to obtain single crystals of 9 for
X-ray analysis failed.
nium tetrafluoroborates (3) in 44-85% yield. Because
the reaction proceeded very slowly at room temperature,
the reaction mixture was heated at gentle reflux for 17-
42 h. The boron trifluoride was converted to tetrafluo-
roborate, and thus the counteranion in 3 came from the
Lewis acid. Addition of Me3SiCN was required to obtain
high-purity onium salts.17 In the absence of Me3SiCN,
tetraphenylbismuthonium tetrafluoroborate was formed
as a contaminant. Only electron-rich aryl ligands, such
as tolyl, anisyl, and thioanisyl groups, were transferred
efficiently by using the tin method. Electron-deficient
and sterically hindered aryl ligands, such as 4-chlo-
rophenyl, 1-naphthyl, and mesityl, were not transferred
efficiently.
In the boron method, we used arylboronic acids (4)
because they are more effective as the aryl ligand
source.18,19 Thus, treatment of difluorides 1 with aryl-
boronic acids 4 in the presence of BF3‚OEt2 in CH2Cl2
afforded the corresponding tetraarylbismuthonium tet-
rafluoroborates 3 within 2 h at room temperature.20
These were easily isolated by recrystallization from CH2-
Cl2/Et2O (1:10). By the boron method, a variety of
ligands could be connected to the bismuth center in high
yield. Aryl ligands bearing an electron-donating or
electron-withdrawing substituent were transferable
with similar ease and efficiency (entries 7-13). When
(17) A combination of Me3SiCN and organostannanes was succsess-
fully employed for the synthesis of iodonium salts, see: Williamson,
B. L.; Tykwinski, R. R.; Stang, P. J . J . Am. Chem. Soc. 1994, 116, 93,
and references therein.
Treatment of 9a with a large excess of (d)-camphor-
10-sulfonic acid sodium salt supported on a silica gel
afforded the corresponding bismuthonium camphorsul-
fonate 10 as a pasty solid in 64% yield (eq 2). Despite
the presence of two chiral centers, one each at the
bismuth and the counteranion, compound 10 showed a
(18) Ochiai et al. reported the synthesis of aryl- and alkenyliodonium
salts by the Lewis acid-promoted reaction of (diacetoxyiodo)benzene
with the corresponding boronic acids: Ochiai, M.; Toyonari, M.;
Nagaoka, T.; Chen, D.-W.; Kida, M. Tetrahedron Lett. 1997, 38, 6709.
(19) Morgan and Pinhey used arylboronic acids for the in situ
generation of aryllead triacetates: Morgan, J .; Pinhey, J . T. J . Chem.
Soc., Perkin Trans. 1 1990, 715.
(20) The 1H NMR monitoring of this reaction using a 0.050 mmol
scale of the reagents and 0.5 mL of CD2Cl2 revealed that the Bi-C
coupling is complete within a few minutes at room temperature.
1
single set of peaks in the H NMR spectrum that could
not be resolved even by the use of a shift reagent,

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5671
Ta ble 1. Syn th esis of Tetr a a r ylbism u th on iu m Tetr a flu or obor a tes 3
entry
methoda
1
2/4
conditions
bismuthonium tetrafluoroborate (3)
yield (%)
1
2
3
4
5
6
7
8
T
T
T
T
T
T
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
2f
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
reflux, 17 h
reflux, 32 h
reflux, 17 h
reflux, 24 h
reflux, 42 h
reflux, 28 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 24 h
rt, 24 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 2 h
rt, 2 h
[Ph3(4-MeC6H4)Bi+][BF4-] (3a )
[Ph3(4-MeOC6H4)Bi+][BF4-] (3b)
[Ph3(2-MeOC6H4)Bi+][BF4-] (3c)
[Ph3(2-i-PrOC6H4)Bi+][BF4-] (3d )
[Ph3(4-MeSC6H4)Bi+][BF4-] (3e)
[Ph3(2-MeSC6H4)Bi+][BF4-] (3f)
[Ph4Bi+][BF4-] (3g)
76
77
85
60
79
44
95
97
97
96
95
96
97
55
56
98
93
98
96
95
98
99
95
3a
9
[Ph3(2-MeC6H4)Bi+][BF4-] (3h )
3b
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
3e
[Ph3(4-FC6H4)Bi+][BF4-] (3i)
[Ph3(4-ClC6H4)Bi+][BF4-] (3j)
[Ph3(3-NO2C6H4)Bi+][BF4-] (3k )
[Ph3(4-MeCOC6H4)Bi+][BF4-] (3l)
[Ph3(2,4,6-Me3C6H2)Bi+][BF4-] (3m )
[Ph3(1-C10H7)Bi+][BF4-] (3n )
[Ph3(2-C4H3S)Bi+][BF4-] (3o)
[Ph3(2-C4H3O)Bi+][BF4-] (3p )
[Ph3(4-CH2dCHC6H4)Bi+][BF4-] (3q)
[(4-MeC6H4)3PhBi+][BF4-] (3r )
[(4-MeOC6H4)3PhBi+][BF4-] (3s)
[(4-ClC6H4)3PhBi+][BF4-] (3t)
no Bi-C coupling
4m
4n
4a
4a
4a
4a
rt, 2 h
rt, 2 h
rt, 2 h
rt, 24 h
a
T: (i) BF3‚OEt2, 0 °C, 1 h; (ii) Me3SiCN, 0 °C, 1 h; (iii) 2, reflux, 17-42 h. B: (i) BF3‚OEt2 and 4, rt, 2-24 h; (ii) NaBF4aq, rt, 20 min.
Sch em e 2
expected to reflect the stability of configuration at
bismuth.22 If the configuration is stable on the NMR
time scale, these gem-methyl peaks should be diaste-
1
reotopic in the H NMR spectra.
Scheme 4 illustrates the synthesis of the target
compounds 14. Reaction of tris(4-methoxyphenyl)bis-
muthane with triflic acid in the presence of HMPA and
subsequent treatment with 2-(4,4-dimethyl-3,4-dihy-
drooxazol-2-yl)phenylmagnesium bromide afforded 2-(4,4-
dimethyl-3,4-dihydrooxazol-2-yl)phenylbis(4-methox-
yphenyl)bismuthane (11) in 73% yield. Selective Bi-
Canisyl bond cleavage of 11 with triflic acid and subsequent
treatment with an excess of 4-(trifluoromethyl)phenyl-
magnesium bromide in THF at 0 °C afforded unsym-
metrical bismuthane 12 in 60% yield after fractional
recrystallization from benzene/MeOH. As expected, the
geminal methyl peaks of 12 were diastereotopic, thus
indicating that the bismuth center in 12 possesses a
stable configuration on the NMR time scale.23 Oxidative
fluorination of 12 with xenon difluoride in MeCN/CH2-
Cl2 afforded the corresponding difluoride 13 as a crys-
talline solid in 87% yield. The BF3‚OEt2-promoted
reaction of 13 with arylboronic acids 4b,l afforded
tetraarylbismuthonium tetrafluoroborates 14a ,b in 97%
and 72% yield, respectively. Compound 14a was a pasty
solid, whereas 14b was a crystalline solid as obtained
by recrystallization from CH2Cl2/Et2O. In contrast, the
BF3‚OEt2-promoted reaction of 13 with Me3SiCN/aryl-
stannane 2a afforded a complex mixture after 24 h in
boiling CH2Cl2.
Sch em e 3
europium tris(heptafluorobutanoylpivaloylmethanate).
Attempts to separate diastereomers by fractional re-
crystallization also failed due to the poor crystallinity
of 10. At present, we have no direct evidence for the
occurrence of chirality at bismuth in camphorsulfonate
10.
Treatment of tetrafluoroborate 14b with a large
excess of tetraethylammonium tosylate in CH2Cl2 af-
(21) Meyers, A. I.; Temple, D. L.; Haidukewych, D.; Mihelich, E. D.
J . Org. Chem. 1974, 39, 2787.
(22) This type of oxazoline group has been widely used in asym-
metric organic synthesis. (a) Peer, M.; deJ ong, J . C.; Kiefer, M.; Langer,
T.; Rieck, H.; Schell, H.; Sennhenn, P.; Sprinz, J .; Steinhagen, H.;
Wiese, B.; Helmchen, G. Tetrahedron 1996, 52, 7547. (b) von Matt, P.;
Pfaltz, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 566. (c) Dawson, G.
J .; Frost, C. G.; Williams, J . M. J .; Coote, S. J . Tetrahedron Lett. 1993,
34, 3149, and references therein.
Therefore we next synthesized unsymmetrical bis-
muthonium salts that bear prochiral substituents in the
neighborhood of the bismuth center. In this synthesis,
we chose the 2-(4,4-dimethyl-3,4-dihydrooxazol-2-yl)-
phenyl group21 as the aryl ligand, because the two
geminal methyl groups on the oxazoline ring were
(23) δ 1.11 (s, 3H) and 1.13 (s, 3H) in CDCl3.

5672 Organometallics, Vol. 18, No. 26, 1999
Ta ble 2. Syn th esis of Tetr a a r ylbism u th on iu m Tetr a flu or obor a tes 9
Matano et al.
entry
methoda
8
2/4
[Ar1Ar2Ar3Ar4Bi+][BF4-] (9)
yield (%)
1
2
3
4
5
6
7
T
B
T
T
B
B
T
8a
8a
8a
8a
8a
8b
8c
2b
4d
2d
2e
4e
4l
[(2-MeOC6H4)(4-MeC6H4)(4-ClC6H4)(4-MeOC6H4)Bi+][BF4-] (9a )
9a
71
97
65
60
97
95
70
[(2-MeOC6H4)(4-MeC6H4)(4-ClC6H4)(2-i-PrOC6H4)Bi+][BF4-] (9b)
[(2-MeOC6H4)(4-MeC6H4)(4-ClC6H4)(4-MeSC6H4)Bi+][BF4-] (9c)
9c
[(4-MeOC6H4)(2-MeC6H4)(4-ClC6H4)(2-C4H3S)Bi+][BF4-] (9d )
[(2-i-PrOC6H4)(4-MeC6H4)(4-ClC6H4)(4-MeOC6H4)Bi+][BF4-] (9e)
2b
a
T: (i) BF3‚OEt2, 0 °C, 1 h; (ii) Me3SiCN, 0 °C, 1 h; (iii) 2, reflux, 20 h. B: (i) BF3‚OEt2 and 4, rt, 1 h; (ii) NaBF4aq, rt, 20 min.
Sch em e 4
60
Sch em e 5
they decomposed with surprising exclusively to bis-
muthane 17 and the corresponding haloarene 18a ,b (eq
3). In contrast, tetrafluoroborates 14 and tosylate 15
were thermally stable and showed no sign of decomposi-
tion up to 150 °C.
Although solid-state structures of 14, 15, and 16 could
not be determined, the structure of a bismuthonium salt
20, synthesized from difluoride 19 and boronic acid 4b
according to eq 4, was characterized by X-ray diffraction
analysis. Crystal data and collection parameters are
given in Table 3. An ORTEP diagram is shown in Figure
1, and selected bond distances and angles are listed in
Table 4.
forded the corresponding tosylate 15 in 83% yield.
Compound 15 was further converted to chloride 16a ,
bromide 16b, and iodide 16c by treatment with the
respective sodium halides in CH2Cl2/H2O (Scheme 5).
Chloride 16a and bromide 16b were isolated as powders
by recrystallization from CH2Cl2/hexane. Iodide 16c was
also obtained as a powder that was approximately 95%
1
pure (based on H NMR).
Unsymmetrical tetraarylbismuthonium salts 14, 15,
and 16 were characterized using spectroscopic analyses.
For all prepared salts, the geminal methyl groups on
the oxazoline ring appeared as a pair of diastereotopic
1
singlet peaks in the H NMR spectra at room temper-
The bismuth center in 20 possesses a significantly
distorted tetrahedral geometry with an average C-Bi-C
ature (in CDCl3). This appearance indicates the stable
configuration at bismuth on this NMR time scale.24
The halides 16a ,b were thermally unstable; when
heated in 1,2-dichlorobenzene-d4 or chlorobenzene-d5,
(24) δ 0.74 (s, 3H), 0.76 (s, 3H) for 14a ; δ 0.77 (s, 3H), 0.84 (s, 3H)
for 14b; δ 0.80 (s, 3H), 0.83 (s, 3H) for 15 in CDCl3.

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5673
Ta ble 3. Cr ysta l Da ta for 20
widened C-Bi-C bond angles [112.9(4)-119.2(5)°] be-
tween the bismuth and the respective C(1), C(12), and
C(19) atoms.
formula
a (Å)
b (Å)
C32H33BBiF4NO‚CH2Cl2
10.215(2)
18.268(3)
18.667(1)
94.730(10)
3471.6(8)
52.70
The solid-state structure of 20 seems to be similar to
the structure in solution, because the gem-methyl
groups on the oxazoline ring were observed relatively
c (Å)
â (deg)
V (Å3)
1
µ(Mo KR) (cm-1
space group
Z value
)
upfield (δ 0.75 in CDCl3, vs δ 1.41 for 18b) in the H
P21/c
4
NMR spectrum. This upfield resonance probably is due
to the ring-current effect from the neighboring p-tolyl
groups. Unsymmetrical bismuthonium tetrafluorobo-
rates 14a ,b also showed the diastereotopic methyl peaks
at δ 0.74-0.84 in CDCl3, suggesting similarity in the
structures of 14 and 20.
Tetrafluoroborate 20 was further converted to the
corresponding bromide 21, a pale yellow solid, by
treatment with an excess of sodium bromide (eq 5).
Tetrafluoroborate 20 was only slightly soluble in toluene
and Et2O, whereas bromide 21 was soluble. Thus, in
the solvents that have lower polarity, the ionic nature
of 21 would be considerably less than that of 20.
D
calc (g cm-3
)
1.585
T (°C)
26.0
no. of reflns collected
8408
no. of unique reflns
7965
Rint
0.054
no. of observations (I > 2.00σ(I))
no. of variables
3094
389
R
Rw
0.045
0.064
goodness of fit
1.18
Although tetrafluoroborate 20 was stable up to 150
°C in 1,2-dichlorobenzene-d4, bromide 21 decomposed
completely to tris(4-methylphenyl)bismuthane (22) and
bromoarene 18b (eq 6). The decomposition rate of 21 in
either 1,2-dichlorobenzene-d4 or toluene-d8 obeyed first-
order kinetics, suggesting that bismuthane 22 and
bromoarene 18b were afforded by the ligand-coupling
reaction. The observed rate constants k depended on the
ET values26 of the solvents: 1.6 × 10-3 s-1 in 1,2-
dichlorobenzene-d4 (ET ) 38.0) and 2.2 × 10-3 s-1 in
toluene-d8 (ET ) 33.9) at 22 °C. Bromide 21 did not
decompose over 3 days at 22 °C in DMSO-d6 (ET ) 45.1).
Thus, the decay rate constant increased as the polarity
decreased.
F igu r e 1. ORTEP drawing of 20 (30% probability el-
lipsoids) with the atom-numbering scheme. Dichloromethane
is omitted for clarity.
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 20
Bi-C(1)
2.21(1)
2.18(1)
2.20(1)
2.21(2)
2.77(1)
C(1)-Bi-C(12)
C(1)-Bi-C(19)
C(1)-Bi-C(26)
C(12)-Bi-C(19)
C(12)-Bi-C(26)
C(19)-Bi-C(26)
119.2(5)
112.9(4)
98.3(5)
115.5(5)
105.8(5)
101.3(5)
Bi-C(12)
Bi-C(19)
Bi-C(26)
Bi‚‚‚N(1)
bond angle of 108.8°. The tetrafluoroborate anion is
spatially separated from the bismuth cation. The mea-
sured Bi-C bond lengths, 2.18(1)-2.21(2) Å, are within
the reported range for symmetrical tetraarylbismutho-
nium compounds.13b,e,h-j The oxazoline ring-nitrogen
atom is coordinated weakly to the bismuth center with
a separation of 2.77 Å, which is longer than the sum of
their respective covalent radii (2.16 Å) but much shorter
than that of their respective van der Waals radii (ca.
3.6 Å).25 The oxazoline ring is nearly coplanar with the
adjacent benzene ring (dihedral angle is 6.55°), and thus
the two geminal methyl groups are located above the
neighboring two tolyl rings. These tolyl groups are bent
away from the oxazoline moiety, as indicated by the
Ster eoch em ica l Beh a vior of Un sym m etr ica l Tet-
r a a r ylbism u th on iu m Sa lts Bea r in g th e Oxa zolin e
Gr ou p . The two geminal oxazoline methyl peaks of 14,
15, and 16 were used as probes for VT-NMR monitoring
of the permutation process around the bismuth center
in these onium salts. Halides 16a ,b were separately
monitored in five organic solvents of different polarity
(DMSO-d6, pyridine-d5, 1,2-dichlorobenzene-d4, chlo-
robenzene-d5, and toluene-d8 ), whereas tetrafluorobo-
rates 14 and tosylate 15 were monitored in the first
three of these solvents because they are insoluble in
chlorobenzene-d5 and toluene-d8. The diastereotopic
appearance of the gem-methyl peaks of tetrafluorobo-
(25) Bondi, A. J . Phys. Chem. 1964, 68, 441. Because the van der
Waals radius of bismuth is not yet known, we postulated this value to
be similar to that of antimony.
(26) (a) Dimroth, K.; Reichardt, C.; Siepmann, T.; Bohlmann, F.
Liebigs Ann. Chem. 1963, 661, 1. (b) Marcus, Y. Chem. Soc. Rev. 1993,
409.

5674 Organometallics, Vol. 18, No. 26, 1999
Matano et al.
a
Ta ble 5. Tc a n d ∆Gqb of 14, 15, a n d 16a ,b
Tc (∆Gq)
DMSO-d6
pyridine-d5
1,2-Cl2C6D4
[38.0 (3.0)]c
ClC6D5
toluene-d8
salt
[45.1 (29.8)]c
[40.5 (33.1)]c
[36.8 (3.3)]c
[33.9 (0.1)]c
14a
14b
15
16a
16b
>135 (>22.5)
>135 (>21.0)
>110 (>20.8)
>110 (>19.2)
>110 (>20.3)
90 (19.4)
>150 (>23.0)
>150 (>21.4)
>150 (>22.5)
88 (19.4)
>135 (>21.2)
>135 (>21.0)
85 (19.2)
<25 (-)
<25 (-)
75 (18.9)
73 (18.8)
a
b
Coalescence temperature (°C). Activation energy at Tc (kcal mol-1) estimated from the equation ∆Gq ) 4.57 × 10-3Tc[10.32 + log(Tc
2/π∆ν)], where ∆ν (Hz) is a difference in the resonance between two gem-methyl peaks at room temperature. c ET (DN), where ET is the
solvent polarity (see ref 26) and DN is the donor number (see ref 26).
x
Sch em e 6
rates 14a ,b was discrete up to 135 °C in DMSO-d6, 110
°C in pyridine-d5, and 150 °C in 1,2-dichlorobenzene-
d4, although the difference in frequencies (δν) between
the two peaks narrowed at high temperatures. These
results show that the configuration at the bismuth
center in 14 is stable within the temperature ranges
considered here.27 Similarly, the diastereotopic appear-
ance of the gem-methyl groups of tosylate 15 was
discrete up to 110 °C in pyridine-d5 and 150 °C in 1,2-
dichlorobenzene-d4. Therefore, we estimated the thresh-
old values for the activation free energy (∆Gq) of the
permutation process in 14 and 15 by assuming that the
oxazoline methyl peaks had coalesced at the highest
observable temperature in each solvent (Table 5).28
The geminal oxazoline methyl peaks of halides 16a ,b
coalesced in pyridine-d5, 1,2-dichlorobenzene-d4, chlo-
robenzene-d5, and toluene-d8 at the temperature shown
in Table 5, but did not coalesce in DMSO-d6 up to 135
°C. The coalescence temperature (Tc) decreased with
decreasing ET of the solvents in the following order;
pyridine-d5 > 1,2-dichlorobenzene-d4 > chlorobenzene-
d5. In toluene-d8, the gem-methyl groups appeared as a
single broad peak, even at room temperature. The Tc
was independent of the concentration of 16a ,b in the
range 0.008-0.035 M, suggesting that the observed
coalescence reflected the intramolecular ligand permu-
tation process. For all solvents, bromide 16b coalesced
at lower temperatures than did chloride 16a . At tem-
peratures near Tc, halides 16a ,b also underwent ligand
coupling, thus producing haloarenes 18a ,b and bis-
muthane 17. The thermal stability of 16 depended on
the solvent polarity; for a given temperature, the
obtain bismuthonium salts that bear four different aryl
ligands (Scheme 6): oxidative arylation of a triarylbis-
muthane (route A), Bi-C bond cleavage of a pentaaryl-
bismuth (route B), and Bi-C bond construction from a
triarylbismuth(V) dihalide and an arylmetal reagent
(route C).
Route A may not be generally applicable because a
pair of unshared electrons in triarylbismuthane has low
nucleophilicity.12,15b For instance, the reaction of tris-
(4-methylphenyl)bismuthane and 4-nitorophenyldiazo-
nium tetrafluoroborate affords a mixture of triarylbis-
muthanes [(4-MeC6H4)n(4-NO2C6H4)3-nBi; n ) 1 and 2]
instead of the onium salt.29 The late transition metal-
catalyzed arylation, which works well for the prepara-
tion of arylphosphonium salts,30 is unlikely to occur
because the Bi-C bonds of bismuthanes are readily
cleaved by these transition metal complexes.31 As
mentioned in the Introduction, route B was effective
for the synthesis of mixed compounds of the type
[Ar3Ar′Bi+][X-].14 However, this methodology does not
seem to ensure the selective cleavage of the Bi-C bond
when similar aryl ligands are attached to the bismuth
atom. Our results demonstrate that route C is the most
general and most reliable for preparing bismuthonium
salts that bear four different aryl ligands, because this
route is free from the uncertainties involved in routes
A and B. In route C, however, a suitable arylating agent
must be chosen. Early attempts by Challenger to
prepare tetraphenylbismuthonium halides from triph-
enylbismuth dihalides and phenyl Grignard reagents
resulted in the formation of a mixture of phenylbis-
muthanes PhnBiX3-n (n ) 1, 2, 3; X ) halide) and
halobenzene.32 The Grignard reagents apparently are
too reactive to control selective Bi-C bond formation.
In contrast, both arylstannanes 2 and arylboronic acids
lifetime of 16a in decreasing order was pyridine-d5
>
1,2-dichlorobenzene-d4 > chlorobenzene-d5 > toluene-
d8. Thus, the stability of halides 16 increased as the
solvent polarity increased.
An equimolar pyridine-d5 solution of tetraethylam-
monium bromide and either tetrafluoroborate 14 or
tosylate 15 showed coalescence of the gem-methyl peaks
at around 80 °C, thus leading to gradual formation of
bismuthane 17 and bromoarene 18b. This formation
indicated the facile conversion of 14 and 15 to bromide
16b.
Discu ssion
(29) Barton, D. H. R.; Bhatnagar, N. Y.; Finet, J .-P.; Motherwell,
W. B. Tetrahedron 1986, 42, 3111.
(30) (a) Cassar, L.; Fao, M. J . Organomet. Chem. 1974, 74, 75. (b)
Horner, L.; Mummenthey, G.; Moser, H.; Beck, P. Chem. Ber. 1966,
99, 2782.
Syn th esis of Un sym m etr ica l Tetr a a r ylbism u -
th on iu m Sa lts. There are three possible routes to
(27) Because the upper limit of the variable-temperature unit was
150 °C, we did not monitor the NMR peaks above 150 °C.
(31) For example, see: (a) Barton, D. H. R.; Ozbalik, N.; Ramesh,
M. Tetrahedron 1988, 44, 5661. (b) Cho, C. S.; Yoshimori, Y.; Uemura,
S. Bull. Chem. Soc. J pn. 1995, 68, 950, and references therein.
(32) (a) Challenger, F. J . Chem. Soc. 1914, 105, 2210. (b) Challenger,
F.; Goddard, A. E. J . Chem. Soc. 1920, 117, 762.
(28) The ∆Gq threshold values were estimated by assuming that the
methyl peaks had coalesced at 135 °C in DMSO-d6, 110 °C in pyridine-
d5, and 150 °C in 1,2-dichlorobenzene-d4. See Experimental Section.

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5675
Sch em e 7
The thermal stability of bismuthonium salts in solu-
tion also depends on the nucleophilicity of the counter-
anions involved. The observed instability and the de-
composition mode of 16 agree with the general trends
reported for tetraphenylbismuthonium halides, i.e.,
rapid decomposition to halobenzene and triphenylbis-
muthane via the ligand coupling.13a The instability of a
Bi(V) compound has recently been confirmed by theo-
retical analysis.35 The exclusive formation of bismuth-
anes 17 and 22 from the respective bromides 16 and
21 indicates that the electropositive ipso carbon atom
of the oxazoline-substituted phenyl group is much more
reactive than other ipso carbons.
4 are milder nucleophilic reagents that can interact with
difluorides 1, but only in the presence of a Lewis acid.
A plausible pathway for the boron method is depicted
in Scheme 7. A BF3 molecule coordinates to a fluorine
atom in 1 to enhance the electrophilicity of the bismuth
center, and the aryl group is transferred from the boron
to the bismuth center via simultaneous ligand exchange
with fluorine.
Evidence that the high affinity of boron toward
fluorine is the key in promoting the Bi-Caryl bond
formation is that no reaction occurs when tris(4-meth-
ylphenyl)bismuth dichloride is used instead of difluo-
rides 1.33 An additional feature of the present tin and
boron methods is that tetrafluoroborate and triflate
anions are formed directly from the respective Lewis
acids used. These weakly coordinating anions guarantee
the thermal stability of the resulting bismuthonium
salts (see the following section).
On the basis of our results, the boron method has four
advantages over the tin method: (a) a variety of
arylboronic acids are readily available,34 (b) Bi-C bond
formation occurs under mild conditions, (c) a wide range
of aryl ligands are transferable, and (d) inorganic wastes
are not toxic. The advantages of the boron method over
the tin method are well demonstrated in the synthesis
of unsymmetrical bismuthonium salts 14 bearing the
oxazoline group ortho to the bismuth atom, where the
latter method failed to afford the desired product 14.
Ster eoch em ica l Beh a vior a r ou n d th e Bism u th
Cen ter . Our results on the VT-NMR monitoring re-
vealed that both the nucleophilicity of counteranions
and the polarity of solvents strongly affect the stereo-
chemical behavior around the bismuth center. Although
accurate ∆Gq values could not be obtained for 14 and
15, we can qualitatively discuss these two factors based
on our results and previous results in the literature. The
diastereotopic appearance of the geminal methyl peaks
of tetrafluoroborates 14 and tosylate 15 revealed that
the ligand permutation in these compounds proceeds
very slowly on the NMR time scale. We could not
differentiate 14 from 15 in this respect. Conversion of
the counteranions to halides, however, brought a dra-
matic change in the stereochemical stability of bismu-
thonium salts. The observed findings suggest the ac-
celeration of permutation is due to counteranions that
have higher nucleophilicity toward the cationic bismuth
center.
The stereochemical behavior of unsymmetrical tet-
raarylbismuthonium salts seems closely related to the
coordination geometry at bismuth. Barton et al.13e and
also Doak and Freedman13b observed that tetraphenyl-
bismuth(V) compounds of the type Ph4BiZ can change
the central geometry depending on the coordinating
ability of an anionic group Z. Both studies showed that
weakly coordinating counteranions favor the tetracoor-
dinate (tetrahedral) onium-type geometry, whereas
strongly coordinating anions favor the pentacoordinate
(trigonal bipyramidal) structure. Beaumont and Goel
investigated the physical properties of several tetraphe-
nylbismuth(V) compounds by IR and Raman spec-
troscopies and molecular weight and conductance
measurements.13d They found that a tetrafluoroborate
behaves as a 1:1 electrolyte in acetonitrile and nito-
methane, whereas a trichloroacetate is nonionic. The
observations from these three studies clearly show that
counteranions that have higher nucleophilicity are
prone to bond tightly with the cationic bismuth atom
(either in the solid state or in solution) to favor the
pentacoodinate geometry over the ionic tetrahedral
structure. Thus, for halides 16, the bismuth center
would readily reorganize its geometry to the nonionic
pentacoordinate geometry at high temperatures, whereas
in tetrafluoroborates 14 it would maintain the original
tetrahedral geometry up to high temperatures.
Honer and Hofer reported that optically active arso-
nium halides racemize with decreasing ease in the order
iodide > bromide > chloride, but those salts containing
counteranions that have lower nucleophilicity appar-
ently are stable.36 These results can be explained by a
mechanism involving Berry pseudorotation37 of a tran-
sient pentacoordinate halogenoarsenic(V) intermediate.4c
Our observed counteranion effect may also be explained
in similar terms; the higher the nucleophilicity of a
halide, the faster the permutation. A plausible mecha-
nism for the permutation and ligand coupling of halides
16 is depicted in Scheme 8.
At high temperatures, the halide anion moves closer
to the cationic bismuth center to generate a pentacoor-
dinate species A or A′ as a transient intermediate. This
intermediate then undergoes either several pseudoro-
(33) The B-F bond energy in BF3 is 646 kJ mol-1, see: Cotton, F.
A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th ed.; Wiley: New
York, 1988; p 172, Table 6-2.
(34) (a) Matteson, D. S. Tetrahedron 1989, 45, 1859. (b) Suzuki, A.
Pure Appl. Chem. 1994, 66, 213. (c) Miyaura, N.; Suzuki, A. Chem.
Rev. 1995, 95, 2457, and references therein.
(35) Moc, J .; Morokuma, K. J . Am. Chem. Soc. 1995, 117, 11790.
BiH5 (D3h) is thermodynamically unstable with respect to BiH3 + H2
by over 70 kcal mol-1. A zwitterionic transition state with axial(-)
-
equatorial(+) polarization is proposed for this ligand-coupling process.
(36) Horner, L.; Hofer, W. Tetrahedron Lett. 1965, 3281.
(37) Berry, R. S. J . Chem. Phys. 1960, 32, 933.

5676 Organometallics, Vol. 18, No. 26, 1999
Matano et al.
Sch em e 8
Sch em e 9
tations (route a) or reductive coupling (route b).38 The
transition-state structures in these stereochemical pro-
cesses should be similar to the intermediate A (A′) and
would be less polarized compared with the ground-state
structure. Recently, Moc and Morokuma carried out ab
initio calculations on the stereochemical processes of a
series of MH5 compounds (M ) P, As, Sb, Bi) and
estimated an energy barrier of the Berry pseudorotation
spectra of unsymmetrical tetraarylbismuthonium salts
bearing the oxazoline group at the ortho-position clearly
show the stability of the configuration at bismuth in
solution. The stereochemical as well as thermal stability
of this class of compounds strongly depends on the
nucleophilicity of the counteranions as well as on the
polarity of the solvents. Tetrafluoroborates and tosylate
salts possess stable configuration, whereas halide salts
do not. The permutation of bismuthonium halides,
[Ar1Ar2Ar3Ar4Bi+][X-], probably occurs via the ligand
reorganization at the bismuth(V) center involving pseu-
dorotations of a nonionic pentacoordinate species of the
type Ar1Ar2Ar3Ar4BiX.
of BiH5 to be ca. 2 kcal mol-1 35
This value implies that
.
the interconversion between A and A′ proceeds smoothly
with a small activation energy. Therefore, the ∆Gq
values that we estimated in this study may represent
the energy necessary to reorganize the coordination
geometry of the bismuth from tetracoordinate to pen-
tacoordinate. The relationship between the Tc and the
solvent polarity (ET) also supports this interpretation.
The activation energy for the permutation of 16 in-
creases as the polarity of solvents is increased, probably
because the ground state of 16 is polarized and becomes
stabilized more efficiently relative to the transition state
in polar solvents (Scheme 9).
The observed solvent-polarity effect significantly dif-
fers from the effect involved in the edge inversion
process of unsymmetrical bismuthanes, where nucleo-
philic solvents such as pyridine and DMSO dramatically
stabilize the transition state by coordinating to the
trivalent bismuth center.7 For the bismuth(V) systems
that we studied, the donor ability of solvents seems to
be less important than the polarity. In fact, no coales-
cence was observed in DMSO-d6 for any bismuthonium
salt 14, 15, and 16.
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions with air-sensitive
compounds were carried out under an atmosphere of argon.
All melting points were determined on a Yanagimoto hot-stage
apparatus and are uncorrected. 1H and 13C NMR spectra were
recorded on a Varian Gemini-200 or a J EOL FX400 spectrom-
eter using CDCl3 as the solvent unless otherwise noted.
Chemical shifts are reported as the relative value versus
tetramethylsilane, and coupling constants J are given in Hz.
Variable-temperature NMR measurements were carried out
using a J EOL FX400 spectrometer equipped with a temper-
ature control unit. IR spectra were observed as KBr pellets
on a Shimadzu FTIR-8100S spectrophotometer (see Supporting
Information for full data of IR spectra). FAB mass spectra were
obtained on a J EOL J MS-HS110 spectrometer using 3-ni-
trobenzyl alcohol as a matrix. Elemental analyses were
performed at the Microanalytical Laboratory of Kyoto Uni-
versity. Column chromatography was performed on silica gel
(Wakogel C200). Dichloromethane (CH2Cl2) was distilled from
CaH2 under argon before use. Tetrahydrofuran (THF) and
diethyl ether (Et2O) were distilled from sodium benzophenone
ketyl under argon before use.
Con clu sion s
The Lewis acid-promoted reaction of triarylbismuth
difluorides with arylstannanes or arylboronic acids
provides convenient routes to afford unsymmetrically
substituted tetraarylbismuthonium salts. The 1H NMR
Ma ter ia ls. Triarylbismuth difluorides 1a ,b were prepared
according to reported procedures.39,15b Difluorides 1c-e were
obtained quantitatively from triarylbismuthanes and XeF2 in
CH2Cl2 at 0 °C. Aryltributylstannanes 2 were synthesized from
chlorotri-n-butylstannane and the corresponding aryllithium
or aryl Grignard reagents.40 Arylboronic acids 4a ,c,h ,i,n were
(38) If the species A and A′ possess trigonal bipyramidal structure
with the numbering scheme as illustrated in Scheme 8, the intercon-
version between A and A′ should involve more than two pseudorotation
processes. We believe that the activation energies for all the processes
between A and A′ are very small. See ref 3b.
(39) Challenger, F.; Wilkinson, J . F. J . Chem. Soc. 1922, 121, 91.
(40) Wardell, J . L.; Ahmed, S. J . Organomet. Chem. 1974, 78, 395.

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5677
purchased from Aldrich. Other arylboronic acids were prepared
from B(OR)3 (R ) Me, i-Pr) and the corresponding aryllithium
or aryl Grignard reagents according to reported procedures.19,41
Other reagents were used as commercially received.
Tr is(4-m eth oxyp h en yl)bism u th d iflu or id e (1c): pasty
solid; 1H NMR (200 MHz) δ 3.82 (s, 9H), 7.14 (d, 6H, J ) 8.6),
8.12 (d, 6H, J ) 8.6); FABMS m/z 549 (M+ - F).
7.55-7.90 (m, 17H); IR νmax 1150-950 (BF4-) cm-1; FABMS
m/z 575 (M+ - BF4), 421, 363, 344, 286, 209. Anal. Calcd for
C
27H26BBiF4O: C, 48.97; H, 3.96. Found: C, 48.74; H, 3.96.
(4-Meth ylth ioph en yl)tr iph en ylbism u th on iu m tetr aflu -
1
or obor a te (3e): mp 141-143 °C; H NMR (200 MHz) δ 2.49
(s, 3H), 7.46 (d, 2H, J ) 8.6), 7.55-7.82 (m, 17H); IR νmax
1150-900 (BF4-) cm-1; FABMS m/z 563 (M+ - BF4), 409, 363,
332, 286, 209. Anal. Calcd for C25H22BBiF4S: C, 46.17; H, 3.41.
Found: C, 45.93; H, 3.49.
Tr is(4-ch lor op h en yl)b ism u t h d iflu or id e (1d ): pasty
solid; 1H NMR (200 MHz) δ 7.64 (d, 6H, J ) 8.7), 8.16 (d, 6H,
J ) 8.7); FABMS m/z 561 (M+ - F; 35Cl × 3).
(2-Meth ylth ioph en yl)tr iph en ylbism u th on iu m tetr aflu -
or obor a te (3f): glassy solid; 1H NMR (200 MHz) δ 2.27 (s,
3H), 7.55-7.90 (m, 19H); FABMS m/z 563 (M+ - BF4), 409,
363, 332, 286, 209. This compound was further transformed
into hexafluorophosphate by treatment with aqueous am-
monium hexafluorophosphate: mp 207-209 °C; 1H NMR (200
MHz) δ 2.30 (s, 3H), 7.60-7.92 (m, 19H); IR νmax 900-800
(PF6-) cm-1; FABMS m/z 563 (M+ - PF6), 409, 363, 332, 286,
Compounds 1c,d were used for the synthesis of 3s,t without
further purification.
Tr is(2-m eth ylp h en yl)bism u th d iflu or id e (1e): mp 165-
166 °C (decomp); 1H NMR (200 MHz) δ 2.65 (s, 9H), 7.4-7.55
(m, 9H), 7.82 (m, 3H); FABMS m/z 501 (M+ - F). Anal. Calcd
for C21H21BiF2: C, 48.47; H, 4.07. Found: C, 48.36; H, 4.04.
Syn th esis of Tetr a a r ylbism u th on iu m Tetr a flu or obo-
r a tes 3. F r om Ar ylsta n n a n es 2 (Tin Meth od ). Gen er a l
P r oced u r e. To a stirred CH2Cl2 solution (5 mL) containing
triphenylbismuth difluoride 1a (478 mg, 1.0 mmol) and BF3‚
OEt2 (0.13 mL, 1.0 mmol) was added Me3SiCN (0.13 mL, 1.0
mmol) at 0 °C. After 1 h, aryltri-n-butylstannane 2 (1.0 mmol)
was added, and the resulting mixture was heated under gentle
reflux for 17-42 h to complete the reaction. Evaporation of
the solvent under reduced pressure left an oily residue, which
was washed with hexane (5 mL × 3), purified by passing
through a short silica gel column with CH2Cl2 as the eluent,
and crystallized from Et2O/CH2Cl2 (10:1) to give aryltriph-
enylbismuthonium tetrafluoroborate 3 as a solid. When Me3-
SiOTf (0.19 mL, 1.0 mmol) was used instead of BF3‚OEt2, the
bismuthonium triflate 5 was obtained.
F r om Ar ylbor on ic Acid s 4 (Bor on Meth od ). Gen er a l
P r oced u r e. To a CH2Cl2 solution (5 mL) containing triaryl-
bismuth difluoride 1 (0.50 mmol) and arylboronic acid 4 (0.50
mmol) was added BF3‚OEt2 (65 µL, 0.50 mmol) at 0 °C. The
mixture was stirred for 2 h at room temperature. An aqueous
solution (20 mL) of NaBF4 (500 mg, 4.55 mmol) was then
added, and the resulting two-phase solution was vigorously
stirred for a further 20 min. The aqueous phase was separated
and extracted with CH2Cl2 (5 mL × 2). The combined organic
extracts were dried over MgSO4 and passed through a short
silica gel column. The eluted solution was evaporated under
reduced pressure to leave an oily residue, which was crystal-
lized from Et2O/CH2Cl2 (10:1) to give compound 3 as a
crystalline or glassy solid.
209. Anal. Calcd for
C25H22BBiF6PS: C, 42.38; H, 3.13.
Found: C, 42.55; H, 3.09.
Tetr a p h en ylbism u th on iu m tetr a flu or obor a te (3g): mp
243-244 °C (lit.,42 236 °C); 1H NMR (200 MHz) δ 7.5-7.8 (m,
20H); 13C NMR (50 MHz) δ 132.5, 132.6, 135.1, 137.3; FABMS
m/z 517 (M+ - BF4).
(2-Met h ylp h en yl)t r ip h en ylb ism u t h on iu m t et r a flu o-
1
r obor a te (3h ): mp 197-198 °C; H NMR (200 MHz) δ 2.44
(s, 3H), 7.40-7.90 (m, 19H); IR νmax 1150-950 (BF4-) cm-1
;
FABMS m/z 531 (M+ - BF4), 377, 363, 300, 286, 209. Anal.
Calcd for C25H22BBiF4: C, 48.57; H, 3.59. Found: C, 48.55;
H, 3.48.
(4-F lu or op h en yl)t r ip h en ylb ism u t h on iu m t et r a flu o-
r obor a te (3i): mp 172-173 °C; 1H NMR (400 MHz) δ 7.36 (t,
2H, J ) 8.4), 7.62 (t, 3H, J ) 7.2), 7.68 (t, 6H, J ) 7.4), 7.79
(d, 6H, J ) 7.6), 7.84 (dd, 2H, J ) 8.4, 5.5); IR νmax 1150-950
(BF4-) cm-1; FABMS m/z 535 (M+ - BF4), 209. Anal. Calcd
for C24H19BBiF5: C, 46.33; H, 3.08. Found: C, 46.36; H, 3.02.
(4-Ch lor op h en yl)t r ip h en ylb ism u t h on iu m t et r a flu o-
1
r obor a te (3j): mp 123-124 °C; H NMR (200 MHz) δ 7.56-
7.86 (m, 19H); IR νmax 1150-900 (BF4-) cm-1; FABMS m/z 551
(M+ - BF4; 35Cl), 363, 286, 209. Anal. Calcd for C24H19
BBiClF4: C, 45.14; H, 3.00. Found: C, 45.39; H, 2.98.
-
(3-Nitr op h en yl)tr ip h en ylbism u th on iu m tetr a flu or ob-
or a te (3k ): mp 218-220 °C; 1H NMR (200 MHz) δ 7.64 (t,
3H, J ) 7.3), 7.69 (t, 6H, J ) 7.3), 7.81 (d, 6H, J ) 7.4), 7.86
(t, 1H, J ) 7.8), 8.29 (d, 1H, J ) 7.5), 8.41 (d, 1H, J ) 7.9),
-
8.50 (s, 1H); IR νmax 1524 (NO2), 1345 (NO2), 1200-950 (BF4
)
(4-Met h ylp h en yl)t r ip h en ylb ism u t h on iu m t et r a flu o-
cm-1; FABMS m/z 562 (M+ - BF4), 546, 408, 363, 286, 209.
Anal. Calcd for C24H19BBiF4NO2: C, 44.40; H, 2.95; N, 2.16.
Found: C, 44.92; H, 2.90; N, 2.40.
1
r obor a te (3a ): mp 138-139 °C; H NMR (200 MHz) δ 2.44
(s, 3H), 7.49 (d, 2H, J ) 8.0), 7.57-7.83 (m, 17H); IR νmax
1150-950 (BF4-) cm-1; FABMS m/z 531 (M+ - BF4), 377, 363,
300, 286, 209. Anal. Calcd for C25H22BBiF4: C, 48.57; H, 3.59.
Found: C, 48.70; H, 3.61.
(4-Acet ylp h en yl)t r ip h en ylb ism u t h on iu m t et r a flu o-
r obor a te (3l): mp 166-168 °C; 1H NMR (200 MHz) δ 2.64 (s,
3H), 7.60-7.88 (m, 15H), 7.95 (d, 2H, J ) 8.3), 8.20 (d, 2H, J
) 8.3); IR νmax 1686 (CdO), 1150-950 (BF4-) cm-1; FABMS
m/z 559 (M+ - BF4), 405, 363, 328, 286, 209. Anal. Calcd for
(4-Meth oxyp h en yl)tr ip h en ylbism u th on iu m tetr a flu o-
r obor a te (3b): glassy solid; 1H NMR (200 MHz) δ 3.86 (s, 3H),
7.20 (d, 2H, J ) 8.7), 7.58-7.82 (m, 17H); IR νmax 1150-900
(BF4-) cm-1; FABMS m/z 547 (M+ - BF4), 393, 363, 316, 286,
209. Anal. Calcd for C25H22BBiF4O: C, 47.34; H, 3.50. Found:
C, 47.23; H, 3.48.
C
26H22BBiF4O: C, 48.32; H, 3.43. Found: C, 48.27; H, 3.37.
Mesityltr iph en ylbism u th on iu m tetr aflu or obor ate (3m ):
1
mp 219-220 °C; H NMR (200 MHz) δ 2.33 (s, 6H), 2.36 (s,
3H), 7.17 (s, 2H), 7.52-7.70 (m, 9H), 7.80-7.90 (m, 6H); IR
(2-Meth oxyp h en yl)tr ip h en ylbism u th on iu m tetr a flu o-
1
ν
max 1150-950 (BF4-) cm-1; FABMS m/z 559 (M+ - BF4), 363,
r obor a te (3c): mp 130-131 °C; H NMR (200 MHz) δ 3.86
(s, 3H), 7.28 (t, 1H, J ) 8.0), 7.37 (d, 1H, J ) 8.0), 7.60-7.83
328, 286, 209. Anal. Calcd for C27H26BBiF4: C, 50.18; H, 4.05.
Found: C, 50.31; H, 3.99.
(m, 17H); IR νmax 1150-900 (BF4-) cm-1; FABMS m/z 547 (M+
- BF4), 393, 363, 316, 286, 209. Anal. Calcd for C25H22
BBiF4O: C, 47.34; H, 3.50. Found: C, 47.43; H, 3.48.
-
(1-Na p h t h yl)t r ip h en ylb ism u t h on iu m t et r a flu or ob o-
r a te (3n ): mp 163-164 °C; 1H NMR (400 MHz) δ 7.52 (dd,
1H, J ) 7.0, 8.2), 7.60-7.75 (m, 12H), 7.83 (d, 6H, J ) 7.0),
7.97 (d, 1H, J ) 7.0), 8.07 (d, 1H, J ) 8.2), 8.18 (d, 1H, J )
(2-Isopr opoxyph en yl)tr iph en ylbism u th on iu m tetr aflu -
1
or obor a te (3d ): mp 170-172 °C; H NMR (200 MHz) δ 0.99
8.2); IR νmax 1150-950 (BF4-) cm-1; FABMS m/z 567 (M+
-
(d, 6H, J ) 6.0), 4.71 (sept, 1H, J ) 6.0), 7.20-7.35 (m, 2H),
BF4), 363, 336, 286, 209. Anal. Calcd for C28H22BBiF4: C, 51.40;
H, 3.39. Found: C, 51.62; H, 3.38.
(41) (a) Howthorne, M. F. J . Am. Chem. Soc. 1958, 80, 4291. (b)
Brown, H. C.; Campbell, J . B. J . Org. Chem. 1980, 45, 389. (c) Chan,
K. S.; Zhou, X.; Au, M. T.; Tam, C. Y. Tetrahedron 1995, 51, 3129. (d)
Cullen, K. E.; Sharp, J . T. J . Chem. Soc., Perkin Trans. 1 1995, 2565.
(e) Thompson, W. J .; Gaudino, J . J . Org. Chem. 1984, 49, 5237.
(42) Pitsyan, O. A.; Gurskii, M. E.; Maiorova, T. D.; Reutov, O. A.
Izv. Akad. Nauk SSSR, Ser. Khim. 1971, 2618.

5678 Organometallics, Vol. 18, No. 26, 1999
Matano et al.
Tr ip h en yl(2-th ien yl)bism u th on iu m tetr a flu or obor a te
(3o): mp 181-182 °C; 1H NMR (400 MHz) δ 7.43 (dd, 1H, J )
4.5, 3.4), 7.52 (d, 1H, J ) 3.4), 7.61 (t, 3H, J ) 7.3), 7.68 (t,
Syn th esis of Tr ia r ylbism u th Diflu or id es (8). Gen er a l
P r oced u r e. A mixture of 7 (1.0 mmol), KF (581 mg, 10 mmol),
EtOH (5 mL), and water (0.25 mL) was stirred vigorously for
12 h at room temperature. The mixture was then diluted with
water (5 mL), and EtOH was removed under reduced pressure.
The aqueous phase was extracted with CH2Cl2 (5 mL × 4),
and the combined organic extracts were concentrated under
reduced pressure. An oily residue was again reacted with KF
(290 mg, 5.0 mmol), EtOH (5 mL), and water (0.25 mL) for 6
h. A similar workup of the mixture gave a crystalline residue,
which was recrystallized from CH2Cl2/hexane (1:5) to yield
difluoride 8 as colorless crystals.
6H, J ) 7.3), 7.85-7.95 (m, 7H); IR νmax 1150-900 (BF4-) cm-1
;
FABMS m/z 523 (M+ - BF4), 369, 363, 286, 209. Anal. Calcd
for C22H18BBiF4S: C, 43.30; H, 2.97. Found: C, 43.57; H, 2.90.
(2-F u r yl)t r ip h en ylb ism u t h on iu m t et r a flu or ob or a t e
(3p ): mp 154-155 °C; 1H NMR (400 MHz) δ 6.72 (dd, 1H, J )
3.7, 2.1), 6.99 (d, 1H, J ) 3.7), 7.60 (t, 3H, J ) 7.7), 7.67 (t,
6H, J ) 7.8), 7.91 (d, 1H, J ) 2.1), 7.93 (d, 6H, J ) 8.0); IR
ν
max 1150-950 (BF4-) cm-1; FABMS m/z 507 (M+ - BF4), 363,
353, 286, 276, 209. Anal. Calcd for C22H18BBiF4O: C, 44.47;
H, 3.05. Found: C, 44.65; H, 3.03.
(4-Ch lor op h en yl)(2-m eth oxyp h en yl)(4-m eth ylp h en yl)-
bism u th d iflu or id e (8a ): 66%; mp 167-170 °C (decomp); 1H
NMR (200 MHz) δ 2.44 (s, 3H), 3.76 (s, 3H), 7.12-7.19 (m,
2H), 7.47 (dt, 1H, J ) 7, 1.4), 7.51 (d, 2H, J ) 8), 7.61 (d, 2H,
J ) 7), 7.66 (d, 1H, J ) 8), 8.12 (d, 2H, J ) 8), 8.25 (d, 2H, J
) 8); FABMS m/z 537 (M+ - F; 35Cl), 427, 411, 407, 339, 335,
320, 319, 316, 300, 209. Anal. Calcd for C20H18BiClF2O: C,
43.14; H, 3.26. Found: C, 42.98; H, 3.25.
Tr ip h en yl(4-vin ylp h en yl)bism u th on iu m tetr a flu or ob-
or a te (3q): mp 108-110 °C; 1H NMR (200 MHz) δ 5.41 (d,
1H, J ) 10.8), 5.85 (d, 1H, J ) 17.6), 6.72 (dd, 1H, J ) 17.6,
10.8), 7.55-7.85 (m, 19H); IR νmax 1150-1000 (BF4-) cm-1
;
FABMS m/z 543 (M+ - BF4), 389, 363, 312, 286, 209. Anal.
Calcd for C26H22BBiF4: C, 49.55; H, 3.52. Found: C, 49.69;
H, 3.53.
(4-Ch lor op h en yl)(4-m eth oxyp h en yl)(2-m eth ylp h en yl)-
bism u th d iflu or id e (8b): 84%; mp 119-120 °C; 1H NMR (200
MHz) δ 2.60 (s, 3H), 3.86 (s, 3H), 7.20 (d, 2H, J ) 9.2), 7.35-
7.50 (m, 3H), 7.66 (d, 2H, J ) 8.8), 7.67 (d, 1H, J ) 8.8), 8.20
Tr is(4-m eth ylp h en yl)p h en ylbism u th on iu m tetr a flu o-
r obor a te (3r ): mp 149-150 °C; 1H NMR (200 MHz) δ 2.44 (s,
9H), 7.49 (d, 6H, J ) 8.1), 7.55-7.80 (m, 11H); IR νmax 1150-
900 (BF4-) cm-1; FABMS m/z 559 (M+ - BF4), 391, 377, 300,
286, 209. Anal. Calcd for C27H26BBiF4: C, 50.18; H, 4.05.
Found: C, 50.41; H, 4.01.
Tr is(4-m eth oxyp h en yl)p h en ylbism u th on iu m tetr a flu -
or obor a te (3s): glassy solid; 1H NMR (200 MHz) δ 3.85 (s,
9H), 7.21 (d, 6H, J ) 8.4), 7.50-7.80 (m, 11H); IR νmax 1150-
950 (BF4-) cm-1; FABMS m/z 607 (M+ - BF4), 316, 209. Anal.
Calcd for C27H26BBiF4O3: C, 46.71; H, 3.77. Found: C, 46.79;
H, 3.75.
(d, 2H, J ) 9.2), 8.27 (d, 2H, J ) 8.8); FABMS m/z 537 (M+
-
F; 35Cl), 427, 411, 407, 339, 335, 320, 319, 316, 300, 209. Anal.
Calcd for C20H18BiClF2O: C, 43.14; H, 3.26. Found: C, 42.89;
H, 3.24.
(4-Ch lor op h en yl)(2-isop r op oxyp h en yl)(4-m et h ylp h e-
n yl)bism u th d iflu or id e (8c): 80%; mp 135-147 °C (decomp);
1H NMR (200 MHz) δ 1.06 (d, 6H, J ) 5.9), 2.44 (s, 3H), 4.59
(sept, 1H, J ) 5.9), 7.00-7.70 (m, 8H), 8.15 (d, 2H, J ) 8),
8.28 (d, 2H, J ) 9); FABMS m/z; 565 (M+ - F; 35Cl), 455, 435,
411, 344, 320, 300, 209. Anal. Calcd for C22H22BiClF2O: C,
45.18; H, 3.79. Found: C, 44.95; H, 3.69.
Tr is(4-ch lor op h en yl)p h en ylbism u th on iu m tetr a flu o-
r obor a te (3t): mp 156-157 °C; 1H NMR (200 MHz) δ 7.63
-
(d, 6H, J ) 8.7), 7.65-7.80 (m, 11H); IR νmax 1150-900 (BF4
)
cm-1; FABMS m/z 619 (M+ - BF4; 35Cl × 3), 431, 397, 320,
286, 209. Anal. Calcd for C24H17BBiCl3F4: C, 40.74; H, 2.42.
Found: C, 40.93; H, 2.37.
Syn th esis of Bism u th on iu m Sa lts Bea r in g F ou r Dif-
fer en t Ar yl Liga n d s 9. These compounds were prepared from
8 by the tin or boron method similarly to the synthesis of 3.
The reaction conditions and yields of 8 are listed in Table 2.
(2-Met h oxyp h en yl)t r ip h en ylb ism u t h on iu m t r iflu o-
r om eth a n esu lfon a te (5): mp 98-99 °C; 1H NMR (200 MHz)
δ 3.85 (s, 3H), 7.28 (t, 1H, J ) 8.1), 7.37 (d, 1H, J ) 8.1), 7.58-
7.83 (m, 17H); IR νmax 1300-1200 (OTf-), 1200-1100 (OTf-)
cm-1; FABMS m/z 547 (M+ - OTf), 393, 363, 316, 286, 209.
Anal. Calcd for C26H22BiF3O4S: C, 44.84; H, 3.18. Found: C,
44.66; H, 3.13.
Syn th esis of Tr ia r ylbism u th Dich lor id es (7). Gen er a l
P r oced u r e. To a solution of triarylbismuthane 6 (2.0 mmol)
in CH2Cl2 (10 mL) was added sulfuryl chloride (0.18 mL, 2.2
mmol) at 0 °C, and the resulting mixture was stirred for 2-3
h at this temperature. The volatiles were evaporated under
reduced pressure to leave dichloride 7 as a crystalline solid in
a quantitative yield. (4-Chlorophenyl)(2-isopropoxyphenyl)(4-
methylphenyl)bismuth dichloride (7c) was converted to the
corresponding fluoride 8c without purification.
(4-Ch lor oph en yl)(2-m eth oxyph en yl)(4-m eth oxyph en yl)-
(4-m eth ylp h en yl)bism u th on iu m tetr a flu or obor a te (9a ):
1
pasty solid; H NMR (400 MHz) δ 2.45 (s, 3H), 3.84 (s, 3H),
3.87 (s, 3H), 7.20 (d, 2H, J ) 9.0), 7.25-7.33 (m, 2H), 7.49 (d,
-
2H, J ) 8.1), 7.57-7.75 (m, 10H); IR νmax 1150-950 (BF4
cm-1; FABMS m/z 625 (M+ - BF4; 35Cl). Anal. Calcd for C27H25
BBiClF4O2: C, 45.50; H, 3.53. Found: C, 45.45; H, 3.49.
)
-
(4-Ch lor op h en yl)(2-isop r op oxyp h en yl)(2-m eth oxyp h e-
n yl)(4-m et h ylp h en yl)b ism u t h on iu m t et r a flu or ob or a t e
1
(9b): mp 160-166 °C; H NMR (200 MHz) δ 0.99 (d, 6H, J )
6.1), 2.47 (s, 3H), 3.86 (s, 3H), 4.72 (sept, 1H, J ) 6.1), 7.2-
7.8 (m, 16H); IR νmax 1150-950 (BF4-) cm-1; FABMS m/z 653
(M+ - BF4; 35Cl), 455, 451, 435, 427, 411, 408, 344, 316, 300,
209. Anal. Calcd for C29H29BBiClF4O2: C, 47.02; H, 3.95.
Found: C, 46.78; H, 3.85.
(4-Ch lor op h en yl)(2-m eth oxyp h en yl)(4-m eth ylp h en yl)-
(4-m et h ylt h iop h en yl)b ism u t h on iu m t et r a flu or ob or a t e
(9c): glassy solid; H NMR (400 MHz) δ 2.45 (s, 3H), 2.51 (s,
3H), 3.83 (s, 3H), 7.27 (dt, 1H, J ) 1, 7.2), 7.30 (d, 1H, J )
8.1), 7.48 (d, 2H, J ) 8.5), 7.49 (d, 2H, J ) 7.3), 7.60 (d, 2H, J
) 8.3), 7.60-7.68 (m, 6H), 7.70 (d, 2H, J ) 8.3); IR νmax 1150-
900 (BF4-) cm-1; FABMS m/z 641 (M+ - BF4; 35Cl), 332, 320,
316, 300, 209. Anal. Calcd for C27H25BBiClF4OS: C, 44.50; H,
3.46. Found: C, 44.45; H, 3.38.
(4-Ch lor op h en yl)(2-m eth oxyp h en yl)(4-m eth ylp h en yl)-
bism u th d ich lor id e (7a ): mp 175-178 °C; 1H NMR (200
MHz) δ 2.44 (s, 3H), 3.86 (s, 3H), 7.17 (t, 1H, J ) 7.3), 7.22 (d,
1H, J ) 7.3), 7.45-7.52 (m, 3H), 7.64 (d, 2H, J ) 8.9), 7.70 (d,
1H, J ) 7.3), 8.45 (d, 2H, J ) 8.4), 8.58 (d, 2H, J ) 8.9);
FABMS m/z 553 (M+ - Cl; 35Cl × 2), 427, 411, 407, 351, 335,
320, 316, 300, 209. Anal. Calcd for C20H18BiCl3O: C, 40.74;
H, 3.08. Found: C, 40.65; H, 3.07.
(4-Ch lor op h en yl)(4-m eth oxyp h en yl)(2-m eth ylp h en yl)-
bism u th d ich lor id e (7b): mp 152-156 °C; 1H NMR (200
MHz) δ 2.62 (s, 3H), 3.88 (s, 3H), 7.19 (dt, 2H, J ) 9.2, 2.0),
7.32-7.48 (m, 3H), 7.65 (dt, 2H, J ) 8.8, 2.0), 7.66 (d, 1H, J )
8.0), 8.59 (dt, 2H, J ) 9.2, 2.0), 8.64 (dt, 2H, J ) 8.8, 2.0);
FABMS m/z 553 (M+ - Cl; 35Cl × 2), 427, 411, 407, 351, 335,
320, 316, 300, 209. Anal. Calcd for C20H18BiCl3O: C, 40.74;
H, 3.08. Found: C, 41.05; H, 3.17.
1
(4-Ch lor op h en yl)(4-m eth oxyp h en yl)(2-m eth ylp h en yl)-
(2-th ien yl)bism u th on iu m tetr a flu or obor a te (9d ): glassy
solid; 1H NMR (400 MHz) δ 2.50 (s, 3H), 3.87 (s, 3H), 7.19 (d,
2H, J ) 8.8), 7.40 (dd, 1H, J ) 4.9, 3.7), 7.43-7.64 (m, 5H),
7.64 (d, 2H, J ) 8.5), 7.86 (d, 2H, J ) 8.8), 7.89 (d, 2H, J )
8.5), 7.90 (d, 1H, J ) 4.9); IR νmax 1150-900 (BF4-) cm-1
;
FABMS m/z 601 (M+ - BF4; 35Cl), 320, 316, 300, 292, 209.

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5679
Anal. Calcd for C24H21BBiClF4OS: C, 41.85; H, 3.07. Found:
C, 41.74; H, 3.08.
(13). To a 50 mL Teflon reaction vessel containing bismuthane
12 (0.95 g, 1.5 mmol), CH2Cl2 (5 mL), and CH3CN (5 mL) was
added xenon difluoride (0.25 g, 1.5 mmol) at -20 °C. The
mixture was stirred for 2 h, during which time it was warmed
to room temperature. Evaporation of the solvents under
reduced pressure left an oily residue, which was crystallized
from CH2Cl2/hexane (1:10) to yield difluoride 13 (0.88 g, 87%)
(4-Ch lor op h en yl)(2-isop r op oxyp h en yl)(4-m eth oxyp h e-
n yl)(4-m et h ylp h en yl)b ism u t h on iu m t et r a flu or ob or a t e
(9e): glassy solid; 1H NMR (200 MHz) δ 1.02 (d, 6H, J ) 5.9),
2.45 (s, 3H), 3.88 (s, 3H), 4.70 (sept, 1H, J ) 5.9), 7.18-7.27
(m, 4H), 7.49 (d, 2H, J ) 8.1), 7.66-7.77 (m, 10H); IR νmax
1150-1000 (BF4-) cm-1; FABMS m/z 653 (M+ - BF4; 35Cl),
455, 451, 435, 427, 411, 408, 344, 316, 300, 209. Anal. Calcd
for C29H29BBiClF4O2: C, 47.02; H, 3.95. Found: C, 46.89; H,
3.98.
1
as a colorless solid: mp 199-201 °C (decomp); H NMR (200
MHz) δ 0.93 (s, 6H), 3.86 (s, 3H), 4.15 (s, 2H), 7.16 (d, 2H, J
) 9.0), 7.52-7.76 (m, 3H), 7.88 (d, 2H, J ) 7.8), 8.08 (dd, 1H,
J ) 7.3, 1.4), 8.19 (d, 2H, J ) 9.0), 8.43 (d, 2H, J ) 7.8);
FABMS m/z 654 (M+ - F), 528, 490, 402, 383, 209. Anal. Calcd
for C25H23BiF5NO2: C, 44.59; H, 3.44; N, 2.08. Found: C, 44.80;
H, 3.33; N, 2.06.
(4-Ch lor oph en yl)(2-m eth oxyph en yl)(4-m eth oxyph en yl)-
(4-m eth ylp h en yl)bism u th on iu m (d )-Ca m p h or -10-su lfon -
a te (10). Treatment of 9a (356 mg, 0.499 mmol) adsorbed on
silica gel with an aqueous solution (30 mL) of (d)-camphor-
10-sulfonic acid sodium salt (2.54 g, 10 mmol) followed by
extraction with CH2Cl2 gave the corresponding bismuthonium
(d)-camphor-10-sulfonate 10 (273 mg, 64%) as a pasty solid.
The 1H NMR spectrum of 10 in CDCl3 showed no diaste-
reotopic peaks. Added europium tris(heptafluorobutanoylpiv-
aloylmethanate) failed to cause the peak separation: 1H NMR
(200 MHz) δ 0.65 (s, 3H), 0.96 (s, 3H), 1.11-2.28 (m, 7H), 2.41
(s, 3H), 2.45-2.85 (m, 2H), 3.74 (s, 3H), 3.84 (s, 3H), 7.09-
7.85 (m, 16H); IR νmax 1383 (SO2), 1181 (SO2) cm-1; FABMS
m/z 625 (M+ - OSO2R; 35Cl). Although spectroscopic data
supported a high state of purity of 10, we could not obtain the
satisfactory analytical data within an accuracy of (0.4%.
[2-(4,4-Dim eth yl-3,4-d ih yd r ooxa zol-2-yl)p h en yl]bis(4-
m eth oxyp h en yl)bism u th a n e (11). To a mixture of tris(4-
methoxyphenyl)bismuthane (2.65 g, 5.0 mmol), HMPA (1.78
mL, 10.2 mmol), MeOH (1 mL), and CH2Cl2 (30 mL) was added
Me3SiOTf (0.99 mL, 5.2 mmol) at 0 °C, and the resulting
solution was stirred for 2 h at room temperature. The volatiles
were removed under reduced pressure, and an oily residue was
thoroughly dried under vacuum to leave a colorless solid. At
-20 °C, a THF solution (20 mL) of this solid was added slowly
to a solution of 2-(4,4-dimethyl-3,4-dihydrooxazol-2-yl)phenyl-
magnesium bromide, generated from 1-bromo-2-(4,4-dimethyl-
3,4-dihydrooxazol-2-yl)benzene (1.91 g, 7.5 mmol), magnesium
(194 mg, 8.0 mmol), and THF (35 mL). The resulting mixture
was stirred for 15 min, during which time it was warmed to
room temperature. The mixture was then poured into a
saturated aqueous NH4Cl solution (40 mL) at 0 °C. The organic
phase was separated, and the aqueous phase was extracted
with benzene (20 mL × 2). The combined organic extracts were
washed with brine (20 mL), dried over MgSO4, and concen-
trated under reduced pressure to leave an oily residue, which
was crystallized from benzene/MeOH (1:4) to give bismuthane
11 as a colorless crystalline solid (2.21 g, 73%): mp 139-141
Syn th esis of Un sym m etr ica l Tetr a a r ylbism u th on iu m
Sa lts Bea r in g th e Oxa zolin e Gr ou p (14). These compounds
were synthesized from difluoride 13, BF3‚OEt2, and boronic
acids 4b,l according to a similar procedure (boron method) used
for the preparation of 3.
[2-(4,4-Dim eth yl-3,4-d ih yd r ooxa zol-2-yl)p h en yl](4-m e-
th ylp h en yl)(4-m eth oxyp h en yl)(4-tr iflu or om eth ylp h en yl-
)bism u th on iu m tetr aflu or obor ate (14a): glassy solid (97%);
1H NMR (400 MHz) δ 0.74 (s, 3H), 0.76 (s, 3H), 2.44 (s, 3H),
3.87 (s, 3H), 4.22 (s, 2H), 7.19 (d, 2H, J ) 8.8), 7.48 (d, 2H, J
) 8.0), 7.60 (d, 2H, J ) 8.0), 7.64 (d, 2H, J ) 8.8), 7.6-7.7 (m,
1H), 7.76-7.85 (m, 2H), 7.86 (s, 4H), 8.29 (dd, 1H, J ) 7.0, 2);
IR νmax 1646 (CdN), 1100-950 (BF4-) cm-1; FABMS m/z 726
(M+ - BF4), 528, 490, 474, 383, 209. Anal. Calcd for C32H30
-
BBiF7NO2: C, 47.25; H, 3.72; N, 1.72. Found: C, 47.04; H,
3.76; N, 1.68.
[2-(4,4-Dim eth yl-3,4-dih ydr ooxazol-2-yl)ph en yl](4-m eth -
oxyp h en yl)(2-t h ien yl)(4-t r iflu or om et h ylp h en yl)b ism u -
th on iu m tetr a flu or obor a te (14b): crystals (72%), mp 224-
1
226 °C; H NMR (400 MHz) δ 0.77 (s, 3H), 0.84 (s, 3H), 3.88
(s, 3H), 4.25 (s, 2H), 7.20 (d, 2H, J ) 9.0), 7.38 (dd, 1H, J )
3.6, 4.9), 7.49 (d, 1H, J ) 3.6), 7.75-7.85 (m, 6H), 7.89 (d, 2H,
J ) 8.0), 8.02 (d, 2H, J ) 8.0), 8.29 (m, 1H); IR νmax 1638 (Cd
N), 1200-1000 (BF4-) cm-1; FABMS m/z 718 (M+ - BF4), 528,
490, 466, 383, 209. Anal. Calcd for C29H26BBiF7NO2S: C, 43.25;
H, 3.25; N, 1.74. Found: C, 43.16; H, 3.07; N, 1.74.
[2-(4,4-Dim eth yl-3,4-dih ydr ooxazol-2-yl)ph en yl](4-m eth -
oxyp h en yl)(2-t h ien yl)(4-t r iflu or om et h ylp h en yl)b ism u -
th on iu m Tosyla te (15). A mixture of 14b (0.19 g, 0.23 mmol),
tetraethylammonium tosylate (0.69 g, 2.3 mmol), and CH2Cl2
(10 mL) was stirred at room temperature for 8 h. Water (10
mL) was then added, and the organic phase separated was
again treated with the ammonium tosylate (0.69 g, 2.3 mmol)
for 16 h. The separated organic phase was dried over MgSO4
and concentrated under reduced pressure to leave an oily
residue, which was washed with CH2Cl2/Et2O (1:2) to yield
bismuthonium tosylate 15 as a pasty solid (0.17 g, 83%): 1H
NMR (400 MHz) δ 0.80 (s, 3H), 0.83 (s, 3H), 2.28 (s, 3H), 3.85
(s, 3H), 4.13 (s, 2H), 6.89 (d, 2H, J ) 8.1), 7.10 (d, 2H, J )
9.0), 7.20 (d, 2H, J ) 8.1), 7.26 (m, 1H), 7.41 (d, 1H, J ) 3.2),
7.54-7.62 (m, 2H), 7.68-7.80 (m, 2H), 7.75 (d, 2H, J ) 8.1),
8.00-8.10 (m, 3H), 8.14 (d, 2H, J ) 7.9); IR νmax 1646 (CdN),
1325 (SO2), 1168 (SO2) cm-1; FABMS m/z 718 (M+ - OTs),
528, 490, 466, 383, 209. Although spectroscopic data supported
a high state of purity of 15, we could not obtain the analytical
data within an accuracy of (0.4%.
Syn th esis of [2-(4,4-Dim eth yl-3,4-d ih yd r ooxa zol-2-yl)-
p h en yl](4-m et h oxyp h en yl)(2-t h ien yl)(4-t r iflu or om et h -
ylp h en yl)bism u th on iu m Ha lid es (16). Gen er a l P r oce-
d u r e. A mixture of 15 (55 mg, 0.062 mmol), a saturated
aqueous NaX solution (10 mL, X ) Cl, Br, I), and CH2Cl2 (5
mL) was stirred for 10 min at room temperature. The organic
phase was then separated and treated with a new portion of
saturated aqueous NaX solution (10 mL). The separated
organic phase was dried over MgSO4 and concentrated under
reduced pressure to leave an oily residue, which was crystal-
lized from CH2Cl2/hexane (1:4) to give bismuthonium halide
1
°C; H NMR (200 MHz) δ 1.14 (s, 6H), 3.78 (s, 6H), 3.98 (s,
2H), 6.88 (d, 4H, J ) 8.5), 7.22-7.46 (m, 2H), 7.62 (d, 4H, J )
8.5), 7.82 (d, 1H, J ) 7.0), 7.99 (d, 1H, J ) 7.3). Anal. Calcd
for C25H26BiNO3: C, 50.26; H, 4.39; N, 2.34. Found: C, 50.33;
H, 4.32; N, 2.37.
[2-(4,4-Dim eth yl-3,4-dih ydr ooxazol-2-yl)ph en yl](4-m eth -
oxyp h en yl)(4-tr iflu or om eth ylp h en yl)bism u th a n e (12).
This compound was synthesized from bismuthane 11 (1.79 g,
3.0 mmol) and 1-bromo-4-(trifluoromethyl)benzene (0.63 mL,
4.5 mmol) according to a similar procedure used for the
preparation of 11. Bismuthane 12 was obtained as a colorless
crystalline solid (1.14 g, 60%) by fractional recrystallization
from benzene/MeOH (1:4): mp 148-150 °C; 1H NMR (200
MHz) δ 1.11 (s, 3H), 1.13 (s, 3H), 3.78 (s, 3H), 4.00 (s, 2H),
6.90 (d, 2H, J ) 8.3), 7.33 (t, 1H, J ) 7.0), 7.42 (t, 1H, J )
7.5), 7.53 (d, 2H, J ) 7.6), 7.60 (d, 2H, J ) 8.3), 7.79 (d, 1H, J
) 7.3), 7.85 (d, 2H, J ) 7.6), 8.01 (d, 1H, J ) 7.3); IR νmax
1649 (CdN) cm-1; FABMS m/z 528, 490, 383, 209. Anal. Calcd
for C25H23BiF3NO2: C, 47.25; H, 3.65; N, 2.20. Found: C, 47.36;
H, 3.47; N, 2.18.
[2-(4,4-Dim eth yl-3,4-dih ydr ooxazol-2-yl)ph en yl](4-m eth -
oxyp h en yl)(4-tr iflu or om eth ylp h en yl)bism u th Diflu or id e

5680 Organometallics, Vol. 18, No. 26, 1999
Matano et al.
16 as a colorless (16a ) or pale yellow (16b) solid. Iodide 16c
was obtained as a yellow solid that was approximately 95%
pure (based on 1H NMR).
(M+ - F), 474, 402, 383, 300, 209. Anal. Calcd for C25H26BiF2-
NO: C, 49.76; H, 4.34; N, 2.32. Found: C, 49.62; H, 4.24; N,
2.37.
Ch lor id e (16a ): 58%, mp 142-144 °C; 1H NMR (400 MHz)
δ 0.86 (s, 3H), 0.88 (s, 3H), 3.84 (s, 3H), 4.13 (s, 2H), 7.06 (d,
2H, J ) 9.1), 7.15-7.28 (m, 2H), 7.58 (dt, 1H, J ) 1.3, 7.6),
7.62-7.68 (m, 2H), 7.75 (d, 2H, J ) 8.1), 7.81 (d, 1H, J ) 7.6),
8.10 (dd, 1H, J ) 7.6, 1.3), 8.30 (br-d, 2H), 8.39 (br-d, 2H); IR
νmax 1646 (CdN) cm-1; FABMS m/z 718 (M+ - Cl), 490, 466,
383, 209. Anal. Calcd for C29H26BiClF3NO2S: C, 46.19; H, 3.48;
N, 1.86. Found: C, 45.98; H, 3.75; N, 1.69.
[2-(4,4-Dim eth yl-3,4-d ih yd r ooxa zol-2-yl)p h en yl]tr is(4-
m et h ylp h en yl)b ism u t h on iu m Tet r a flu or ob or a t e (20).
This compound was prepared from 19 (301 mg, 0.50 mmol),
4b (68 mg, 0.50 mmol), and BF3‚OEt2 (65 µL, 0.50 mmol)
according to a similar procedure (boron method) used for the
synthesis of 3. Yield: 340 mg, 91%; mp 216-218 °C; 1H NMR
(400 MHz) δ 0.75 (s, 6H), 2.44 (s, 9H), 4.22 (s, 2H), 7.46 (d,
6H, J ) 7.8), 7.54 (d, 6H, J ) 7.8), 7.64 (d, 1H, J ) 7.3), 7.73-
7.90 (m, 2H), 8.30 (d, 1H, J ) 7); 13C NMR (50 MHz) δ 21.60,
27.58, 68.11, 81.39, 130.32, 131.14, 132.88, 133.11, 134.99,
135.59, 136.52, 137.73, 139.22, 142.88, 163.09; IR νmax 1646
(CdN), 1150-975 (BF4-) cm-1; FABMS m/z 656 (M+ - BF4),
474, 383, 300, 209. Although spectral data supported a high
state of purity of compound 20, satisfactory analytical results
were not available probably due to the persistent adhesion of
the solvent used for recrystallization.
Br om id e (16b): 53%, mp 133-135 °C; 1H NMR (400 MHz)
δ 0.89 (s, 3H), 0.90 (s, 3H), 3.85 (s, 3H), 4.14 (s, 2H), 7.06 (d,
2H, J ) 9.0), 7.19 (dd, 1H, J ) 4.7, 3.5), 7.27 (d, 1H, J ) 3.5),
7.58 (dt, 1H, J ) 1.3, 7.6), 7.63-7.72 (m, 2H), 7.75 (d, 2H, J )
8.3), 7.80 (d, 1H, J ) 7.5), 8.10 (dd, 1H, J ) 7.1, 1.2), 8.28
(br-d, 2H), 8.36 (br-d, 2H); IR νmax 1646 (CdN) cm-1; FABMS
m/z 718 (M+ - Br), 528, 490, 466, 383, 209. Anal. Calcd for
C
29H26BiBrF3NO2S: C, 43.62; H, 3.28; N, 1.75. Found: C,
[2-(4,4-Dim eth yl-3,4-d ih yd r ooxa zol-2-yl)p h en yl]tr is(4-
m eth ylp h en yl)bism u th on iu m Br om id e (21). A mixture of
20 (132 mg, 0.178 mmol), a saturated aqueous NaBr solution
(10 mL), and CH2Cl2 (5 mL) was vigorously stirred for 5 min
at room temperature, and the aqueous layer was removed by
decantation. This treatment was repeated twice, and then the
separated organic phase was dried over MgSO4 and concen-
trated under reduced pressure. Recrystallization of an oily
residue from CH2Cl2/hexane (1:2) yielded bromide 21 as a pale
yellow solid (90 mg, 69%): mp 113-115 °C; 1H NMR (400
MHz) δ 0.78 (s, 6H), 2.42 (s, 9H), 4.16 (s, 2H), 7.41 (d, 6H, J
) 8.1), 7.69 (d, 6H, J ) 8.1), 7.7-7.8 (m, 3H), 8.18-8.28 (m,
1H); 13C NMR (50 MHz) δ 21.59, 27.72, 68.14, 81.24, 129.54,
130.81, 131.26, 132.46, 132.56, 135.24, 135.45, 135.91, 137.52,
142.31, 162.93; IR νmax 1646 (CdN) cm-1; FABMS m/z 656 (M+
- Br), 474, 383, 300, 209. Anal. Calcd for C32H33BiBrNO: C,
52.19; H, 4.52; N, 1.90. Found: C, 51.56; H, 4.47; N, 1.78.
Th er m a l Decom p osition of Br om id e 21. A solution of
43.86; H, 3.05; N, 1.71.
1
Iod id e (16c): H NMR (400 MHz) δ 0.89 (s, 3H), 0.90 (s,
3H), 3.85 (s, 3H), 4.18 (s, 2H), 7.08 (d, 2H, J ) 8.8), 7.23 (dd,
1H, J ) 4.7, 3.5), 7.36 (d, 1H, J ) 3.5), 7.62 (t, 1H, J ) 7.6),
7.65-7.72 (m, 2H), 7.76 (d, 2H, J ) 7.9), 7.79 (d, 1H, J ) 7.5),
8.13 (m, 1H), 8.16 (d, 2H, J ) 8.8), 8.27 (d, 2H, J ) 7.6);
FABMS m/z 718 (M+ - I), 528, 490, 466, 383, 209.
VT-NMR Mea su r em en t . Bismuthonium salt 14, 15, or
16a ,b was dissolved in a solvent in an NMR tube under an
argon atmosphere, and the tube was sealed with a cap. The
coalescence temperatures (Tc) of the geminal oxazoline-methyl
peaks are summarized in Table 5. Activation energies at Tc
for the permutation of 16a ,b were calculated from the equation
∆Gq ) 4.57 × 10-3Tc[10.32 + log(Tc 2/π∆ν)]. The other
43
x
T
c
∆Gq threshold values in Table 5 were estimated by assuming
that the gem-methyl peaks had coalesced at the highest
observable temperatures in the respective solvents (135 °C in
DMSO-d6; 110 °C in pyridine-d5; 150 °C in 1,2-dichlorobenzene-
d4). When allowed to stand in 1,2-dichlorobenzene-d4, chlo-
robenzene-d5, or toluene-d8, 16a ,b decomposed to (4-methox-
yphenyl)(2-thienyl)(4-trifluoromethylphenyl)bismuthane 17 and
the corresponding haloarenes 18a ,b in a quantitative NMR
yield. Unsymmetrical bismuthane 17 could not be isolated,
because it underwent facile disproportionation during at-
tempted purification by recrystallization and column chroma-
tography. It was therefore characterized on the basis of the
1H NMR and FABMS data of a crude product. Compounds
18a ,b were identified by direct comparison with the authentic
specimens.
1
bromide 21 in a deuterio solvent was monitored by H NMR
at a given temperature. Bismuthane 22 and bromoarene 18b
were formed quantitatively. The methyl groups on the oxazo-
line ring in 21 and 18b were used for the estimation of rate
constants. A half-life period of 21 did not depend on its
concentration over 0.005-0.035 M. Compound 22: 1H NMR
(200 MHz) δ 2.32 (s, 9H), 7.18 (d, 6H, J ) 7.6), 7.62 (d, 6H, J
1
) 7.6); H NMR (200 MHz; in 1,2-dichlorobenzene-d4) δ 2.20
(s, 9H), 7.07 (d, 6H, J ) 7.4), 7.62 (d, 6H, J ) 7.4). Compound
18b: 1H NMR (200 MHz) δ 1.41 (s, 6H), 4.13 (s, 2H), 7.20-
7.37 (m, 2H), 7.57-7.72 (m, 2H).
X-r a y Diffr a ction An a lysis of Com p ou n d 20. A colorless
crystal of dimensions 0.14 × 0.14 × 0.20 mm, grown from CH2-
Cl2/Et2O (1:2) at room temperature, was used for X-ray
diffraction. Data were recorded on a Rigaku AFC7S diffrac-
tometer, with graphite-monochromated Mo KR (λ ) 0.71069
Å) radiation, using the ω-2θ scan technique to a maximum
2θ value of 55.3°. Scans of (0.94 + 0.30 tan θ)° were made at
a speed of 4.0° min-1. An empirical absorption correction based
on azimuthal scans of several reflections was applied, which
resulted in transmission factors ranging from 0.92 to 1.00. The
data were corrected for Lorentz and polarization effects. A
correction for secondary extinction was applied. The structure
was solved by the Patterson methods45 and expanded using
the Fourier techniques.46 The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included but not
refined. Neutral atom scattering factors were taken from
Bism u th a n e 17: 1H NMR (400 MHz; in 1,2-dichloroben-
zene-d4) δ 3.60 (s, 3H, OMe), 6.84 (d, 2H, J ) 8.3, MeOC6H4),
7.08 (dd, 1H, J ) 4.6, 3.5, C4H3S), 7.29 (d, 1H, J ) 3.5, C4H3S),
7.46 (d, 2H, J ) 8.3, MeOC6H4), 7.54 (d, 1H, J ) 4.6, C4H3S),
7.63 (d, 2H, J ) 7.8, CF3C6H4), 7.82 (d, 2H, J ) 7.8, CF3C6H4);
FABMS m/z 461 [(4-MeOC6H4)(4-CF3C6H4)Bi+], 437 [(4-
CF3C6H4)(2-C4H3S)Bi+], 399 [(4-MeOC6H4)(2-C4H3S)Bi+], 209
(Bi+).
[2-(4,4-Dim eth yl-3,4-d ih yd r ooxa zol-2-yl)p h en yl]bis(4-
m eth ylp h en yl)bism u th Diflu or id e (19). This compound
was synthesized from [2-(4,4-dimethyl-3,4-dihydrooxazol-2-yl)-
phenyl]bis(4-methylphenyl)bismuthane44 (766 mg, 1.4 mmol)
and xenon difluoride (237 mg, 1.4 mmol) according to a similar
procedure used for the synthesis of 13. Yield: 830 mg, 98%;
mp 184-187 °C (decomp); 1H NMR (400 MHz) δ 0.92 (s, 6H),
2.40 (s, 6H), 4.10 (s, 2H), 7.45 (d, 4H, J ) 8.0), 7.53 (dt, 1H, J
) 1.6, 7.4), 7.60-7.76 (m, 2H), 8.05 (dd, 1H, J ) 1.2, 7.6), 8.13
(d, 4H, J ) 8.0); IR νmax 1653 (CdN) cm-1; FABMS m/z 584
(45) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bos-
man, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla,
C. The DIRDIF program system; Technical Report of the Crystal-
lography Laboratory; University of Nijmegen: The Netherlands, 1992.
(46) DIRDIF94: Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J . M. M. The DIRDIF-
94 program system; Technical Report of the Crystallography Labora-
tory; University of Nijmegen: The Netherlands, 1994.
(43) (a) Kessler, H. Angew. Chem. 1970, 82, 237. (b) Buono, G.;
Llinas, J . R. J . Am. Chem. Soc. 1981, 103, 4532.
(44) Ikegami, T.; Suzuki, H. Organometallics 1998, 17, 1013.

Unsymmetrical Tetraarylbismuthonium Salts
Organometallics, Vol. 18, No. 26, 1999 5681
Cromer and Waber.47 Anomalous dispersion effects were
Ack n ow led gm en t. This work was supported by
Grants-in-Aid (Nos. 10133225 and 09740469) from the
Ministry of Education, Science, Sports and Culture of
J apan. We thank Mr. Yoshinori Kitahara for X-ray
diffraction analysis.
48
included in Fcalc
;
the values for ∆f ′ and ∆f′′ were those of
Creagh and McAuley.49 The values for the mass attenuation
coefficients are those of Creagh and Hubbel.50 All calculations
were performed using the teXsan51 crystallographic software
package of Molecular Structure Corporation. Further details
are provided as Supporting Information.
Su p p or tin g In for m a tion Ava ila ble: Tables of experi-
mental details for an X-ray diffraction study, atomic coordi-
nates, thermal parameters, bond distances and angles, torsion
angles, nonbonded contacts, and figures giving additional
views and unit cell packing for 20, and full IR data (νmax) of
all the new compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
(47) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography, Vol. IV; The Kynoch Press: Birmingham, England,
1974; Table 2.2A.
(48) Ibers, J . A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(49) Creagh, D. C.; McAuley, W. J . International Tables for Crystal-
lography; Wilson, A. J . C., Ed.; Kluwer Academic Publishers: Boston,
1992; Vol. C, Table 4.2.6.8, pp 219-222.
(50) Creagh, D. C.; Hubbell, J . H. International Tables for Crystal-
lography; Wilson, A. J . C., Ed.; Kluwer Academic Publishers: Boston,
1992; Vol. C, Table 4.2.4.3, pp 200-206.
(51) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corporation: 1985 and 1992.
OM990597V