Unexpected formation of highly stabilized tetrakis-(2-alkoxyphenyl)bismuthonium salts in the oxidation of tris-(2-alkoxyphenyl)bismuthanes with iodosylbenzene

Article abstract of DOI:10.1039/a700379j

Treatment of tris-(2-alkoxyphenyl)bismuthanes 1 with iodosylbenzene in methylene dichloride at 40°C led to none of the expected bismuthane oxides 2 but, quite unexpectedly, gave tetrakis-(2-alkoxyphenyl)bismuthonium chlorides 3 in moderate to good yields. In some cases, bismuthonium formates 4 accompanied the main reaction products. Similar treatment in benzene in the presence of benzyl bromide, ethyl bromide, or 2,2,2-trifluoroethyl iodide led to the corresponding bismuthonium bromides 7 and iodides 8. Through anion exchange, a variety of bismuthonium salts including formate 4, tetrafluoroborate 11, toluene-p-sulfonate 12, bromide 7, iodide 8 and perchlorate 13 were prepared from the salt 3 in good yields. In contrast to the known tetraphenylbismuthonium salts, all of these new bismuthonium salts exhibited high thermal stability. The molecular structure of compound 7a was elucidated by X-ray analysis, where the four neighbouring oxygen atoms are found to surround the bismuth atom tetrahedrally via a weak through-space interaction with the metal, making the bismuth centre less susceptible to nucleophilic attack of the halide anion.

Full text of DOI:10.1039/a700379j

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Unexpected formation of highly stabilized tetrakis-
(2-alkoxyphenyl)bismuthonium salts in the oxidation of
tris-(2-alkoxyphenyl)bismuthanes with iodosylbenzene
Hitomi Suzuki,*,a Tohru Ikegamia and Nagao Azuma b
a
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku,
Kyoto 606-01, Japan
b Department of Chemistry, Faculty of Science, Ehime University, Bunkyo-cho,
Matsuyama 790-77, Japan
Treatment of tris-(2-alkoxyphenyl)bismuthanes 1 with iodosylbenzene in methylene dichloride at 40 ЊC
led to none of the expected bismuthane oxides 2 but, quite unexpectedly, gave tetrakis-(2-
alkoxyphenyl)bismuthonium chlorides 3 in moderate to good yields. In some cases, bismuthonium
formates 4 accompanied the main reaction products. Similar treatment in benzene in the presence of
benzyl bromide, ethyl bromide, or 2,2,2-trifluoroethyl iodide led to the corresponding bismuthonium
bromides 7 and iodides 8. Through anion exchange, a variety of bismuthonium salts including formate 4,
tetrafluoroborate 11, toluene-p-sulfonate 12, bromide 7, iodide 8 and perchlorate 13 were prepared from the
salt 3 in good yields. In contrast to the known tetraphenylbismuthonium salts, all of these new
bismuthonium salts exhibited high thermal stability. The molecular structure of compound 7a was
elucidated by X-ray analysis, where the four neighbouring oxygen atoms are found to surround the
bismuth atom tetrahedrally via a weak through-space interaction with the metal, making the bismuth
centre less susceptible to nucleophilic attack of the halide anion.
under reduced pressure left a brown oily residue which could be
Introduction
crystallized out from CH2Cl2–Et2O as a light brown solid. More
conveniently, the reaction mixture was concentrated to a syrup,
which was diluted with ethyl acetate to separate the same com-
pound as a microcrystalline solid melting at 195–197 ЊC with
decomposition. Elemental analysis of this compound showed a
In contrast to well documented triorganylpnicogen oxides
derived from lighter 15-group elements, R Pn᎐O (Pn = N, P, As
᎐
3
and Sb), the oxides of triorganylbismuthanes as yet remain to
be characterized.1 These compounds are of interest because of
their high potential as precursors to a variety of organobis-
muth() compounds. However, the literature to date contains
only a few papers dealing with somewhat conflicting results.
Many attempts by previous workers to obtain triarylbismuth-
ane oxides by direct oxidation of triarylbismuthanes 1 have so
far met with failure; attempted oxidation of triphenylbismuth-
ane with hydrogen peroxide,2 dinitrogen trioxide,3 potassium
permanganate,4 selenium dioxide,5 and cyclic nitrones6 all led to
none of the expected product.
Recently, we have found that iodosylbenzene was effective as
an oxidant for this purpose; under ultrasonic irradiation or gen-
tle heating in an appropriate organic solvent, some triarylbis-
muthanes were smoothly converted to the corresponding oxides
in good yield.7 However, we could not isolate these oxides due
to their high sensitivity towards moisture and carbon dioxide;
during the course of evaporation under reduced pressure, the
oxides were readily decomposed to intractable polymeric
substances.
1
composition C28H30BiClO5. Its H NMR spectrum in CDCl3
exhibited a broad 2 H absorption at δ 2.2, a singlet due to the
methoxy group at δ 3.66, and two peak clusters at δ ~7.22–7.32
and 7.55–7.75 due to aromatic protons. The broad resonance at
high field suggests the presence of one water molecule, which
was confirmed by an IR absorption at 3450 cmϪ1. The 13C
NMR spectrum exhibited absorptions at δC 56.46, 112.59,
124.50, 127.20 (Bi–C), 134.20, 134.79 and 159.74 (MeO–C),
showing the presence of four intact 2-methoxyphenyl moieties.
A peak at δC 127.20, assigned to the ipso carbon attached to the
bismuth atom, was shifted 15.6 ppm upfield as compared with
that of the parent bismuthane 1a. Such a noticeable upfield
shift of the signal due to the ipso carbon atom attached to a
positively charged heteroatomic centre is generally observed for
various heteroatom onium compounds.9 Thus the new com-
pound may safely be formulated as a bismuthonium compound
3a (2-MeOC6H4)4BiClؒH2O, which was further supported by a
fast-atom-bombardment (FAB) mass spectrum showing diag-
nostic fragment peaks at m/z 637 (Ar4Bi), 423 (Ar2Bi), 316
(ArBi) and 209 (Bi). Formation of compound 3a in a hydrated
form may be attributed to adventitious water in the commercial
solvent used for the work-up.
The present new oxidation reaction of triarylbismuthanes
was highly dependent on the solvent system employed; in
chloroform, only a trace amount of the onium salt 3a was
obtained and 50% of starting bismuthane 1a was recovered
intact, while in ethylene dichloride the salt 3a was obtained in
43% yield. In benzene, the reaction did not proceed in the
expected way; anisole and iodobenzene (phenyl iodide) were the
major products with a recovery of 59% of initial bismuthane
1a, no other organobismuth compounds being detected in the
product mixture. Since iodosylbenzene is known to dis-
Results and discussion
Since the 2-methoxy- and 2,6-dimethoxy-phenyl groups have
been shown by PM3 calculations to stabilize the bismuthonium
cation more effectively than the phenyl or 4-methoxyphenyl
group,8 we came to the idea of obtaining tris-(2-methoxyphen-
yl)bismuthane oxide 2a by the oxidation of tris-(2-methoxy-
phenyl)bismuthane 1a with iodosylbenzene, expecting that the
2-alkoxyphenyl ligand might work effectively to stabilize the
polar bismuth oxide function. Treatment of bismuthane 1a with
an excess of iodosylbenzene in boiling methylene dichloride led
to rapid disappearance of the oxidizing agent to give an orange-
coloured solution or suspension. Evaporation of the solution
J. Chem. Soc., Perkin Trans. 1, 1997
1609

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proportionate to iodylbenzene and iodobenzene on heating,10
low-boiling methylene dichloride was apparently the solvent of
choice. Even in the presence of added water, the oxidation in
methylene dichloride proceeded smoothly to give the onium salt
3a in a similar or slightly reduced yield.
Tris-(2-ethoxyphenyl)bismuthane 1c, tris-(2-isopropoxyphen-
yl)bismuthane 1d, and tris-(2-methoxy-4-methylphenyl)bis-
muthane 1e were all similarly oxidized by the present procedure
to give the corresponding bismuthonium chlorides 3c–e in
moderate yield (Scheme 1). In the case of bismuthane 1c, how-
ane 1a (44%) and tris-(2-methoxyphenyl)bismuth dichloride 5a
(23%). This result was similar to that observed in the ozone
oxidation of triphenylbismuthane in methylene dichloride, in
which triphenylbismuth dichloride was obtained in 42% yield.
Supposedly, this oxidation reaction would proceed via the
intermediacy of a bismuthane ozonide.11
It would be pertinent to mention here that tris-(2-methoxy-
phenyl)stibane 912a was smoothly oxidized with iodosylbenzene
in benzene at reflux to give the expected oxide 1012b in almost
quantitative yield (Scheme 2). Stibane oxides are more stable
Me
OMe
OMe
OMe
Me
BiCl2
BiCl
i
MeO
Bi=O
Sb
Sb=O
3
3
2
3
3
Me
2b
9
10
6g
5f
Scheme 2 Reagents and conditions: i, PhI᎐O, PhH, 80 ЊC
᎐
i
i
i
against moisture as compared with the corresponding bismuth-
ane oxides 2.7
Onium salts 2 are readily soluble in methylene dichloride,
chloroform, acetone, acetonitrile and ethanol, but almost
insoluble in ethyl acetate, diethyl ether, hexane and benzene.
When chlorides 3a,c–e were treated with silver() tetrafluorobo-
rate in acetonitrile, the corresponding tetrafluoroborates 11a,c–
e were obtained in good yield (Scheme 3). Similarly, the chlor-
R1
R2
Bi
3
R4
R3
1
OR1
Bi+ X–
ii
i
4
R2
OR1
OMe
Bi+ X–•H2O
R1
11a,c–e X = BF4
12c; X = OTs
13a; X = ClO4
i
Bi+ Cl–•H2O
Bi+ Cl–•H2O
4
4
4
R2
OR1
R3
3a; c–e
7a (X = Br)
8a (X = I)
3a,c–e
+
Bi+ X–•H2O
OEt
4
R2
Bi+ OCHO–•H2O
a; R1 = OMe, R2 = R3 = R4 = H
b; R2 = OMe, R1 = R3 = R4 = H
c; R1 = OEt, R2 = R3 = R4 = H
d; R1 = OPri, R2 = R3 = R4 = H
e; R1 = OMe, R2 = R4 = H, R3 = Me
f; R1 = R2 = R4 = Me, R3 = H
g; R1 = CH2OMe, R2 = R3 = R4 = H
4c; X = HCO2
7a; X = Br
8a; X = I
4
4c
a; R1 = Me, R2 = H; c; R1 = Et, R2 = H; d; R1 = Pri, R2 = H; e; R1 = R2 = Me
Scheme 3 Reagents and conditions: i, MX (AgBF4, HCO2Na, NaOTs,
NaBr, NaI or AgClO4), water–CH2Cl2(CHCl3), room temp.
Scheme 1 Reagents and conditions: i, PhI᎐O, CH2Cl2, 40 ЊC; ii, PhI᎐O,
᎐
᎐
RX (EtBr, PhCH2Br, CF3CH2I), PhH, 40–50 ЊC
ide 3c was converted to the formate 4c and tosyl ester 12c by
treatment with an aqueous solution of sodium formate or
toluene-p-sulfonate. All of these new bismuthonium com-
pounds 3a,c–e, 4c, 11a,c–e and 12c were thermally stable; they
did not show any significant sign of degradation after 3 months
storage under ambient conditions.
The first preparation of tetraphenylbismuthonium chloride
and bromide was reported by Wittig and Clauss, who obtained
them by treating pentaphenylbismuth with hydrogen chloride
or bromine.13 They described how these salts decomposed with-
in several minutes at room temperature, producing the triphe-
nylbismuthane and corresponding halogenobenzenes (phenyl
halides). Hence, all stable bismuthonium salts so far known
carry low-nucleophilic, bulky counter-anions such as perchlor-
ate, tetrafluoroborate, trifluoromethanesulfonate and tetra-
phenylborate.14–18 Beaumont and Goel have prepared a variety
of bismuth() compounds, Ph4BiX, by anion-exchange reaction
between tetraphenylbismuthonium chloride and appropriate
metal salts.14 They observed that the nature of Ph4BiX changes
depending on the anions involved; when X was ClO4, BF4 or
ever, bismuthonium formate 4c was obtained as the major
product. The 3c:4c ratio was estimated as 1:3.3 by H NMR
1
analysis. Tris-(4-methoxyphenyl)bismuthane 1b and tris-(2-
methylphenyl)bismuthane behaved quite differently toward
iodosylbenzene under similar reaction conditions; the former
was converted to a presumed oxide 2b, while the latter resisted
oxidation. Interestingly, tris-(2,4,6-trimethylphenyl)bismuthane
1f was converted to the corresponding dichloride 5f in 80%
yield, while tris-[2-(methoxymethyl)phenyl]bismuthane 1g gave
bis-[2-(methoxymethyl)phenyl]bismuth chloride 6g in 22%
yield. From these findings, it became clear that the alkoxy
grouping attached to the position ortho to the bismuth atom is
indispensable to stabilization of tetraarylbismuthonium salts 2
in the oxygen-transfer oxidation of bismuthanes 1 by iodosyl-
benzene.
The ozone oxidation of bismuthane 1a was also examined;
bismuthane 1a was added to a solution of ozone in methylene
dichloride at Ϫ40 ЊC, which was then gradually warmed to
room temperature to afford a mixture of unchanged bismuth-
1610
J. Chem. Soc., Perkin Trans. 1, 1997

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1
Table 1 Selected H, 13C NMR (δ/ppm), and IR (νmax/cmϪ1) spectral
PF6, the compounds showed an ionic nature, while when X was
NO3, Cl3CCO2, NCO or NCS, they took a non-ionic pentaco-
ordinate structure. An X-ray crystallographic study of tetra-
phenylbismuthonium perchlorate demonstrated that the bis-
muth centre possesses a tetrahedral onium structure.15 When X
was N3 or NCSe, the corresponding bismuth() compounds
were thermolabile at room temperature and readily decomposed
to triphenylbismuthane and other products.
data of tetraarylbismuthonium salts obtained
Compound 1H NMR (RO) 13C NMR (RO, C-Bi)
IR (RO-Ar)
3a
11a
7a
8a
13a
3c
3.67
3.66
3.67
3.67
56.46, 127.20
56.49, 127.40
56.66, 127.36
56.76, 127.33
1244, 1044
1244
1244, 1044
1244, 1044
1244, 1044
1242, 1044
1242, 1044
1244, 1040
1240, 1042
1240
3.66
56.39, 127.19
We were also successful in obtaining the isolable bismutho-
nium bromide 7 and iodide 8 from the chloride 3 by anion
exchange. Shaking of a chloroform solution of bismuthonium
salt 3a with aq. sodium bromide gave the corresponding brom-
ide 7a as crystals in 74% yield. Similar treatment with sodium
iodide gave the iodide 8a in 74% yield. Both salts 7a and 8a are
remarkably stabilized and decompose only above 200 ЊC. Simi-
larly for the chloride 3a and tetrafluoroborate 11a, they do not
show any sign of degradation when stored at room temperature.
Compounds 7a and 8a constitute the first example of tetraaryl-
bismuthonium halides of indefinite shelf-life. These halides
were also readily available by the oxidation of bismuthane 1a
with iodosylbenzene in benzene in the presence of the corres-
ponding alkyl halides; bismuthane 1a was oxidized in the pres-
ence of ethyl or benzyl bromide at 40–50 ЊC to give compound
7a in 39 and 42% yield, respectively. In the latter case, the for-
mation of benzaldehyde as by-product was observed. Similar
oxidation of bismuthane 1a in the presence of 2,2,2-
trifluoroethyl iodide afforded compound 8a in 13% yield
(Scheme 1).
In connection with the anion exchange, the metathetical reac-
tion of tris-(2-methoxyphenyl)bismuth dichloride 5a with silver
perchlorate was re-examined in both acetone18 and butan-2-
one.14 In acetone, tris-(2-methoxyphenyl)(2-oxopropyl)bis-
muthonium perchlorate 14a was obtained in 55% yield, while in
butan-2-one the formation of a dark tarry substance was pre-
dominant, tetrakis-(2-methoxyphenyl)bismuthonium perchlor-
ate 13a being obtained in only a slight amount (~1%) (Scheme
4). Treatment of the salt 14a with brine gave bismuthane 1a
0.81, 3.98
0.81, 3.97
0.80, 3.98
0.79, 3.97
0.84, 4.60
0.83, 4.60
3.62
13.72, 64.97, 127.19
not determined
13.73, 64.99, 127.28
not determined
20.96, 71.13, 128.31
20.96, 71.10, 128.30
not determined
56.45, 127.15
4c
11c
12c
3d
11d
3e
1242, 1038
1250, 1042
1248
11e
3.61
OCH2Cl
Cl
i
Ar3Bi=O
Ar3Bi
Ar3Bi
1a,c–e
+ PhI=O
2a,c–e
16a,c–e
ii
Cl
Ar3Bi
Cl
Cl
Ar3Bi
OCH2Cl
BiAr3
–HCHO
BiAr3
O
O
18a,c–e
17a,c–e
Ar4BiCl•H2O +
Ar2Bi(=O)Cl
3a,c–e
Scheme 5 Reagents: i, CH2Cl2; ii, Ar3Bi᎐O
᎐
11a showed additional broad IR absorption due to the BF4
anion (Table 1). The IR spectrum of salt 4c contained a strong
carbonyl absorption at 1632 cmϪ1, which falls within the carb-
oxylate anion region, endorsing the ionic structure for this salt.
Spectral data showed that these bismuthonium salts have a
similar ionic structure with a long separation between the bis-
muth atom and the corresponding anions, the decomposition
of these salts via a ligand-coupling mode thereby being
suppressed.
OMe
i
Bi+CH2COCH3 ClO4
–
3
OMe
14a
ii
BiCl2
13a
3
OMe
BiOH•3H2O
5a
iii
X-Ray structure analysis of compound 7a
4
In order to get some insight into the extraordinarily enhanced
thermal stability of tetrakis-(2-alkoxyphenyl)bismuthonium
salts, an X-ray crystallographic analysis was performed for com-
pound 7a. As shown in Fig. 1 and Table 2, the bismuth centre has
a tetrahedral geometry with the Bi᎐C bond lengths 2.194(8)–
2.207(9) Å and C᎐Bi᎐C bond angles 105.9(3)–114.7(3)Њ.
The values are in accordance with those of the previously
reported tetraarylbismuthonium salts.15,20 Compound 7a is sub-
ject to the interactions between Bi and four oxygen atoms and
the intramolecular Bi᎐O distances are intermediate between the
sum of their covalent radii (2.10 Å) and that of the estimated
van der Waals radii (3.72 Å).21 All methoxy groups are found to
lean slightly toward the bismuth atom with a deviation of about
5Њ from the standard sp2 bond angle of 120Њ. A similar type
of Bi᎐O interaction has been observed for tris-(2,6-
dimethoxyphenyl)bismuthane.8 A large separation between the
bismuth and bromine atoms [6.752(3) Å] is in accord with the
ionic nature of compound 7a. Since the previously reported
bismuth–bromine covalent bond lengths are around 3 Å,22 we
may safely conclude that there is little or no direct interaction
between the bismuthonium moiety and the bromide anion.
15a
Scheme 4 Reagent and conditions: i, AgClO4, Me2CO, room temp.; ii,
AgClO4, MeCOEt, room temp.; iii, Ag2O, CH2Cl2, 40 ЊC
(100%), probably via the intermediacy of a pentacoordinate
bismuth compound. Metathesis of compound 5a with silver()
oxide in benzene–water gave bismuthane 1a in a low yield, while
the same reaction in methylene dichloride gave tetrakis-(2-
methoxyphenyl)bismuthonium hydroxide 15a, which probably
arose from the metathesis of the initially formed chloride 3a
with silver() oxide. A trace amount of the formate 4a was also
detected by 1H NMR monitoring. The likely source of the for-
mate anion is formaldehyde, derived from methylene dichloride
according to the sequence shown in Scheme 5. By treatment
with tetrafluoroboric acid in acetonitrile–water, hydroxide 15a
was converted to tetrafluoroborate 11a in good yield. A similar
conversion of iodonium chloride to the tetrafluoroborate has
previously been reported.19
Onium salts 3a, 7a, 8a, 11a and 13a were all similar in their
1H and 13C NMR and IR spectral patterns, although the salt
J. Chem. Soc., Perkin Trans. 1, 1997
1611

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Table 2 Selected bond lengths (Å) and angles (Њ) for compound 7a,
with estimated standard deviations in parentheses. Crystallographic
numbering scheme (Fig. 1) is used
ucts by subsequent disproportionation reaction. Although
compounds of type 18 have been reported previously,1a their
exact nature has not been established well to date. So we with-
hold detailed discussion on the mode of the formation of bis-
muthonium compounds 3a,c–e at the present time.
Bond length
Bond angle
To further the above mechanistic considerations, the follow-
ing experiments were carried out. First, a possible involvement
of aryl radical species is ruled out, since no aryl–aryl coupling
products were detected from any of the present reactions; the
oxidation proceeded smoothly even in the presence of a radical
scavenger, 1,1-diphenylethylene. Oxidation of an equimolar
mixture of bismuthanes 1a and 1e with an excess of iodosyl-
benzene gave a mixture of all four possible bismuthonium
chlorides 3a, 3e, Ar1 Ar2BiCl, and Ar1Ar2 BiCl (Ar1 = 2-
Bi᎐C(1)
Bi᎐C(8)
2.201(9)
2.194(8)
2.203(9)
2.207(9)
6.752(3)
2.968(7)
3.099(2)
2.968(6)
3.091(6)
C(1)᎐Bi᎐C(8)
112.4(3)
105.9(3)
107.7(3)
114.7(3)
107.7(3)
108.2(3)
114.2(6)
124.0(7)
116.7(7)
121.6(7)
115.0(7)
124.0(7)
117.0(7)
122.1(7)
114.2(8)
127.0(9)
116.8(8)
125.4(9)
114.0(9)
125.9(9)
116.1(8)
124.6(9)
C(1)᎐Bi᎐C(15)
C(1)᎐Bi᎐C(22)
C(8)᎐Bi᎐C(15)
C(8)᎐Bi᎐C(22)
C(15)᎐Bi᎐C(22)
Bi᎐C(1)᎐C(2)
Bi᎐C(15)
Bi᎐C(22)
Bi ؒ ؒ ؒ Br
Bi ؒ ؒ ؒ O(1)
Bi ؒ ؒ ؒ O(2)
Bi ؒ ؒ ؒ O(3)
Bi ؒ ؒ ؒ O(4)
Bi᎐C(1)᎐C(6)
Bi᎐C(8)᎐C(9)
Bi᎐C(8)᎐C(13)
Bi᎐C(15)᎐C(16)
Bi᎐C(15)᎐C(20)
Bi᎐C(22)᎐C(23)
Bi᎐C(22)᎐C(27)
O(1)᎐C(2)᎐C(1)
O(1)᎐C(2)᎐C(3)
O(2)᎐C(9)᎐C(8)
O(2)᎐C(9)᎐C(10)
O(3)᎐C(16)᎐C(15)
O(3)᎐C(16)᎐C(17)
O(4)᎐C(23)᎐C(22)
O(4)᎐C(23)᎐C(24)
3
3
methoxy-4-methylphenyl, Ar2 = 2-methoxyphenyl), as was con-
firmed by FAB-mass spectroscopy. This observation is consist-
ent with the formation and subsequent decomposition of the µ-
oxo-type intermediates 17 and 18. The main product from the
oxidation of bismuthane 1c was bismuthonium formate 4c (vide
supra). This result may be taken to support the elimination of a
formyl moiety from the intermediate 17. In accord with this
observation, benzaldehyde was detected in the oxidation of
bismuthane 1a with iodosylbenzene in benzene in the presence
of benzyl bromide.† In the present oxidation leading to bismu-
thonium compounds, alkyl halides including methylene dichlo-
ride should have worked not only as a halide anion source but
also as an oxygen acceptor.
The formation of bismuthonium salt 15a in the metathesis
between dichloride 5a and silver() oxide is also suggestive of
the formation of the corresponding µ-oxo-type intermediate 18.
The conversion of triarylbismuth dichlorides 5 to the corres-
ponding µ-oxo-type compounds have previously been reported
by Goel and Prasad.1a However, Doak et al. had earlier
reported that the reaction between triphenylbismuth dichloride
and silver perchlorate in anhydrous ethanol gave a good yield
of tetraphenylbismuthonium perchlorate.17 Additional conflict-
ing results, also reported by Goel,14 suggest the possibility that
the µ-oxo-type compound 18 may be converted to the bismu-
thonium salt 3 under certain conditions. With the intention of
verifying the reaction pathway shown in Scheme 5, we
attempted to prepare the µ-oxybis[tris-(2-methoxyphenyl)bis-
muth] dichloride 18a by a few different approaches including the
anion-exchange reaction of µ-oxybis[tris-(2-methoxyphenyl)-
bismuth]di(perchlorate) or di(trifluoromethanesulfonate) have
been made. As has been mentioned above, the reaction of
dichloride 5a with silver perchlorate gave three different type of
products, 13a, 14a and 15a, but any expected µ-oxybis[tris-
(2-methoxyphenyl)bismuth] di(perchlorate) could not be
obtained. The reaction was carried out in a benzene–water mix-
ture, a typical reaction condition used to obtain a µ-oxo-type
compound from the corresponding dichloride; however, the
product was bismuthonium salt 13a in 18% yield. A newly
developed preparative method for µ-oxybis(triarylbismuth)
di(trifluoromethanesulfonate)23 was also applied to the present
purpose; dichloride 5a was treated successively with trimethyl-
silyl trifluoromethanesulfonate and hexamethyldisiloxane, but
the reaction gave a mixture of at least four compounds includ-
Fig. 1 ORTEP drawing of compound 7a, with crystallographic num-
bering scheme. The percentage probability level of the ellipsoids in this
drawing is 50%.
Possible mechanism for the formation of bismuthonium salts 3
The mechanism of the formation of the salts 3 is not clear at
present. However, one possible pathway leading to compounds
3 may be depicted as shown in Scheme 5. Of course, other
possible mechanisms could not be ruled out.
1
Bismuthanes 1a,c–e undergo oxygen-transfer reaction with
iodosylbenzene to give the corresponding oxides 2a,c–e as the
initial product, which is assumed to react with methylene
dichloride to form a pentacoordinate intermediate 16a,c–e.
Insertion of another molecule of oxide 2 into the bismuth–
chlorine bond of this intermediate 16a,c–e would result in the
formation of a µ-oxo-type intermediate 17a,c–e. Elimination of
a formaldehyde molecule from products 17a,c–e would give
another µ-oxo-type intermediate 18a,c–e, in which one of the
aryl groups may migrate toward the neighbouring bismuth
atom to form the corresponding bismuthonium chloride 3a,c–e.
The counterpart of the bismuth moieties is supposed to be
transformed into the triarylbismuthane 1a,c–e and other prod-
ing bismuthonium salt (checked by H NMR analysis). By
treatment of this mixture with brine, we could isolate the bis-
muthonium salt 3a by chromatography over silica gel. These
findings are highly suggestive of the ease of conversion of
the µ-oxybis[tris-(2-methoxyphenyl)bismuth] derivative into
tetrakis-(2-methoxyphenyl)bismuthonium salt. At present, the
preparation of the µ-oxobis[tris-(2-methoxyphenyl)bismuth]
compound is not successful and the development of more
promising methodology for our purpose is under way.
† One referee suggested the possibility of direct formation of benzalde-
hyde from the adduct of type 16 formed from benzyl bromide and the
corresponding bismuthane oxide.
1612
J. Chem. Soc., Perkin Trans. 1, 1997

View Article Online
Some of these stabilized bismuthonium salts have been found
to exhibit prominent in vitro antimicrobial activity against Heli-
cobacter pylori, and relevant biological data will be published
elsewhere.
cm3) and heated to reflux for 3 h. The resulting white suspen-
sion was filtered through a Celite bed to remove any insoluble
materials and the filtrate was evaporated under reduced pres-
sure to give a product (476 mg), the composition of which was
estimated by 1H NMR spectroscopy as follows; 3a (0.01 mmol),
anisole (0.48 mmol), 2-chloroanisole (0.1 mmol), iodobenzene
(0.67 mmol) and substrate 1a (0.57 mmol).
Experimental
All oxidation reactions were carried out under argon. All solv-
ents were distilled from CaH2 and were stored over molecular
sieves 4 Å. Triarylbismuthanes were prepared from the corres-
ponding arylmagnesium bromides or aryllithiums with bis-
muth() chloride and were recrystallized from benzene–
methanol. Iodosylbenzene was prepared according to the
reported procedure24 and was stored at Ϫ20 ЊC. Other com-
mercially available reagents were used without further purific-
ation. Column chromatography was performed on silica gel
(Wakogel, 200 mesh). All mps were determined on a Yanagi-
moto hot-stage apparatus and are uncorrected. 1H and 13C
NMR spectra were recorded on a Varian Gemini-200 (200
MHz) spectrometer for solutions in CDCl3 with tetramethyl-
silane as internal standard. Coupling constants (J values) are
given in Hz. IR spectra were recorded on a Shimadzu FTIR-
8100 spectrophotometer. FAB-mass spectra were obtained on a
JEOL JMS-HS 110 spectrometer with 3-nitrobenzyl alcohol as
the matrix. Elemental analyses were performed at the Micro-
analytical Laboratory, Institute of Chemical Research, Kyoto
University.
Tetrakis-(2-methoxyphenyl)bismuthonium chloride monohy-
drate 3a. Yield 68%; mp 195–197 ЊC (decomp.); δH 2.19 (2 H, br
s), 3.67 (12 H, s), 7.22–7.32 (8 H, m) and 7.55–7.75 (8 H, m); δC
56.46, 112.59, 124.50, 127.20 (Bi–C), 134.20, 134.79 and 159.74;
νmax(KBr)/cmϪ1 3450 br, 1472, 1433, 1277, 1242, 1043, 785 and
760; m/z (FAB) 637 (Ar4Bi), 423 (Ar2Bi), 316 (ArBi) and 209
(Bi) (Found: C, 48.84; H, 4.28. C28H30BiClO5 requires C, 48.66;
H, 4.34%).
Tetrakis-(2-ethoxyphenyl)bismuthonium chloride monohydrate
3c. A product mixture from a similar oxidation of bismuthane
1c was dissolved in chloroform (20 cm3) and the solution was
stirred vigorously with brine (20 cm3) for 1 h. The organic layer
was separated and the aqueous layer was extracted with chloro-
form (10 cm3 × 4). The combined extracts were dried (MgSO4)
and evaporated to give salt 3c (28%), mp 212–214 ЊC (decomp.);
δH 0.81 (12 H, t, J 7.0), 2.65 (2 H, br s), 3.98 (8 H, q, J 7.0),
7.18–7.30 (8 H, m) and 7.55–7.75 (8 H, m); δC 13.72, 64.97,
112.69, 124.20, 127.19 (Bi–C), 134.21, 134.86 and 159.15;
νmax(KBr)/cmϪ1 3450br, 1482, 1464, 1443, 1277, 1242, 1044,
1032 and 762; m/z (FAB) 693 (Ar4Bi), 451 (Ar2Bi), 330 (ArBi)
and 209 (Bi) (Found: C, 51.43; H, 5.23. C32H38BiClO5 requires
C, 51.45; H, 5.13%).
Triarylbismuthanes
Compound 1a. Mp 159–161 ЊC (lit.,25 167–169 ЊC); δH 3.76 (9
H, s), 6.87 (3 H, dt, J 7.3 and 1.0), 6.99 (3 H, dd, J 8.1 and 1.0),
7.32 (3 H, ddd, J 8.1, 7.3 and 1.7) and 7.45 (3 H, dd, J 7.3 and
1.7); δC 55.49, 109.73, 123.99, 129.12, 139.05, 142.81 (BiC)
and 162.14.
Tetrakis-(2-isopropoxyphenyl)bismuthonium chloride mono-
hydrate 3d. Yield 39%; mp 225–227 ЊC (decomp.); δH 0.84 (24 H,
d, J 6.0), 2.17 (2 H, br s), 4.60 (4 H, hept, J 6.0), 7.15–7.25 (8 H,
m) and 7.55–7.75 (8 H, m); δC 20.96, 71.13, 113.01, 123.72,
128.31 (Bi–C), 134.11, 135.58 and 157.96; νmax
(KBr)/cmϪ1
Compound 1c. Mp 123–124 ЊC (lit.,26 121–122 ЊC); δH 1.25 (9
H, t, J 7.0), 3.99 (6 H, q, J 7.0), 6.85 (3 H, dt, J 7.2 and 1.0), 6.96
(3 H, dd, J 8.1 and 1.0), 7.28 (3 H, ddd, J 8.1, 7.2 and 1.7) and
7.50 (3 H, dd, J 7.2 and 1.7); δC 14.74, 63.74, 110.72, 123.75,
128.86, 139.09, 143.55 (Bi–C) and 161.49.
3450br, 1582, 1468, 1443, 1275, 1240, 1125, 1103, 947 and 758;
m/z (FAB) 749 (Ar4Bi), 479 (Ar2Bi), 344 (ArBi) and 209 (Bi)
(Found: C, 53.80; H, 5.68. C36H46BiClO5 requires C, 53.83; H,
5.73%).
Tetrakis-(2-methoxy-4-methylphenyl)bismuthonium chloride
dihydrate 3e. Yield 29%; mp 210–212 ЊC (decomp.); δH 2.19 (4
H, br s), 2.34 (12 H, s), 3.62 (12 H, s), 7.18 (4 H, br d, J 8), 7.30 (4
H, br s) and 7.43 (4 H, br d, J 8); νmax(KBr)/cmϪ1 3450br, 1487,
1281, 1250, 1146, 1042, 1011, 806 and 729 (Found: C, 50.46; H,
5.10. C32H40BiClO6 requires C, 50.26; H, 5.23%).
Compound 1d. Mp 101–102 ЊC; δH 1.21 (18 H, d, J 6.0), 4.50
(3 H, hept, J 6.0), 6.82 (3 H, dt, J 7.2 and 1.0), 6.96 (3 H, d, J
8.1), 7.25 (3 H, ddd, J 8.1, 7.2 and 1.7) and 7.53 (3 H, dd, J 7.2
and 1.7); δC 22.13, 70.01, 111.88, 123.55, 128.66, 139.56, 145.04
(Bi–C) and 160.47 (Found: C, 52.65; H, 5.44. C27H33BiO3
requires C, 52.77; H, 5.41%).
Compound 1e. Mp 151–153 ЊC; δH 2.13 (9 H, s), 3.72 (9 H, s),
6.89 (3 H, d, J 8.2), 7.10 (3 H, ddd, J 8.2, 2.2 and 0.7) and 7.29
(3 H, d, J 1.6); δC 20.59, 55.69, 109.63, 129.47, 132.84, 139.47,
142.5 (Bi–C) and 160.24 (Found: C, 50.42; H, 4.81. C24H27BiO3
requires C, 50.35; H, 4.72%).
Oxidation of tris-[2-(methoxymethyl)phenyl]bismuthane 1g
A mixture of tris-[2-(methoxymethyl)phenyl]bismuthane 1g
(572 mg, 1 mmol), iodosylbenzene (330 mg, 1.5 mmol) and
methylene dichloride (50 cm3) was heated to reflux for 1 h to
obtain a bright yellow solution, which was filtered through a
Celite bed and the filtrate was evaporated to leave a brown
residue (910 mg), which was chromatographed on alumina,
with CH2Cl2 as the eluent to give unchanged bismuthane
1g (40% recovery) and bis-[2-(methoxymethyl)phenyl]bismuth
chloride 6g (22%), mp 140–142 ЊC; δH 3.45 (6 H, s), 4.60 (2 H, d,
J 12), 4.78 (2 H, d, J 12), 7.33–7.55 (6 H, m) and 8.59 (2 H, d, J
7.6); νmax(KBr)/cmϪ1 1453, 1208, 1088, 1046, 957, 760 and 737
(Found: C, 39.90; H, 3.87. C16H18BiClO2 requires C, 39.47; H,
3.70%).
Preparation of tetrakis-(2-alkoxyphenyl)bismuthonium chloride
monohydrates 3
In methylene dichloride. General procedure. Tris-(2-alkoxy-
phenyl)bismuthane 1 (1 mmol) and freshly prepared iodosyl-
benzene (330–440 mg, 1.5–2 mmol) were suspended in methy-
lene dichloride (50 cm3) and heated to reflux until substrate 1
was consumed (usually 0.5–1.5 h). When a part of starting bis-
muthane 1 remained unchanged, an additional amount of
iodosylbenzene was introduced to complete the reaction. The
resulting solution or suspension was filtered through a Celite
bed to remove any insoluble materials and the filtrate was con-
centrated under reduced pressure to give an oily residue. Ethyl
acetate (20–30 cm3) was added to the residue and the separated
microcrystalline salt 3 was collected, washed with a minimum
amount of the same solvent, and dried in vacuo. Further
crystallization from CH2Cl2–EtOAc (1:5) gave pure compound
3, the yield of which was calculated on the basis of bismuth.
In chloroform. Typical procedure. Tris-(2-methoxyphenyl)-
bismuthane 1a (530 mg, 1 mmol) and freshly prepared iodosyl-
benzene (330 mg, 1.5 mmol) were suspended in chloroform (30
Ozone oxidation of bismuthane 1a in methylene dichloride
Ozonized oxygen (10 mmol hϪ1) was passed into methylene
dichloride (50 cm3) at Ϫ70 ЊC for 1 h to obtain a blue solution,
to which was added a solution of the bismuthane 1a (530 mg, 1
mmol) in the same solvent (15 cm3) in one portion. The result-
ing pale yellow suspension was allowed to warm to room
temperature during the course of 30 min to give an orange
suspension, which was filtered through a Celite bed. The filtrate
was evaporated under reduced pressure to leave a brown
residue, which was chromatographed on silica gel, with
J. Chem. Soc., Perkin Trans. 1, 1997
1613

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CH2Cl2–EtOH (1:0–50:1) as the eluent, to give unchanged
bismuthane 1a (224 mg, 44% recovery) and tris-(2-methoxy-
phenyl)bismuth dichloride 5a (137 mg, 23%). Compound 5a had
mp 196–197 ЊC; δH 3.87 (9 H, s), 7.20–7.28 (6 H, m), 7.50 (3 H,
dt, J 7.7 and 1.5) and 8.13 (3 H, dd, J 8.2, 1.6); δC 56.33, 113.36,
123.34, 132.53, 133.44, 151.65 and 157.65; νmax(KBr)/cmϪ1
1588, 1472, 1431, 1273, 1248, 1046, 1019, 1001 and 750 (Found:
C, 42.22; H, 3.51. C21H21BiCl2O3 requires C, 41.95; H, 3.52%).
This compound was also prepared by treating bismuthane 1a
with sulfuryl dichloride in methylene dichloride at 0 ЊC.
Tris-(2-ethoxyphenyl)bismuth dichloride 5c was similarly
obtained, mp 190 ЊC (decomp.); δH 1.10 (9 H, t, J 7.0), 4.14
(6 H, q, J 7.0), 7.15–7.30 (6 H, m), 7.46 (3 H, t, J 7.9) and 8.13
(3 H, d, J 8.4); νmax(KBr)/cmϪ1 1584, 1480, 1466, 1441, 1397,
1279, 1248, 1163, 1125, 1044, 1003, 922 and 758 (Found: C,
44.73; H, 4.20. C24H27BiCl2O3 requires C, 44.81; H, 4.23%).
1441, 1279, 1248, 1150, 1097, 1061, 1011, 820 and 729 (Found:
C, 49.06; H, 4.60. C32H36BBiF4O4 requires C, 49.25; H, 4.65%).
Preparations of bismuthonium formate 4c, tosyl ester 12c,
bromide 7a and iodide 8a
Tetrakis-(2-ethoxyphenyl)bismuthonium formate monohydrate
4c. To a solution of compound 3c (52 mg, 0.07 mmol) in chloro-
form (15 cm3) was added aq. sodium formate (1 g in 5 cm3) and
the resulting mixture was stirred vigorously for 2 h at room
temperature. The organic layer was separated and the aqueous
layer was extracted with chloroform (5 cm3 × 4). The combined
organic phase was dried (MgSO4) and evaporated to give for-
mate 4c (37 mg, 70%), mp 153–155 ЊC (decomp.); δH 0.81 (12 H,
t, J 7.0), 3.84 (2 H, br s), 3.97 (8 H, q, J 7.0), 7.18–7.30 (8 H, m)
7.55–7.75 (8 H, m) and 8.80 (1 H, s); νmax(KBr)/cmϪ1 1632,
1582, 1461, 1443, 1277, 1242, 1044 and 762 (Found: C, 52.92;
H, 5.47. C33H39BiO7 requires C, 52.38; H, 5.16%).
Oxidation of tris-(2-methoxyphenyl)stibane 9 with
Tetrakis-(2-ethoxyphenyl)bismuthonium toluene-p-sulfonate
12c. Similarly obtained from compound 3c (192 mg, 0.257
mmol) and sodium toluene-p-sulfonate (0.68 g per 15 cm3). The
product was chromatographed on silica gel, with CH2Cl2–
EtOH (1:0–10:1) as eluent, to give tosyl ester 12c (152 mg,
68%), mp 272–273 ЊC; δH 0.79 (12 H, t, J 7.0), 2.29 (3 H, s), 3.97
(8 H, q, J 7.0), 7.09 (2 H, d, JAB 8.3), 7.15–7.28 (8 H, m), 7.55–
7.75 (8 H, m) and 7.90 (2 H, d, JAB 8.3); νmax(KBr)/cmϪ1 1584,
1464, 1445, 1275, 1240, 1217, 1204, 1121, 1042, 1034, 1013, 762
and 681; m/z 693 (Ar4Bi), 451 (Ar2Bi), 330 (ArBi) and 209 (Bi)
(Found: C, 54.07; H, 5.01. C39H43BiO7S requires C, 54.17; H,
5.01%).
iodosylbenzene
A mixture of tris-(2-methoxyphenyl)stibane 912a (443 mg, 1
mmol), iodosylbenzene (242 mg, 1.1 mmol) and benzene (50
cm3) was heated to reflux for 1 h to give a pale yellow suspen-
sion, which was filtered through a Celite bed while hot. The
filtrate was concentrated under reduced pressure to give a mix-
ture (556 mg) of phenyl iodide and tris-(2-methoxyphenyl)-
stibane oxide 10. Trituration of this mixture with hexane gave
pure oxide 10 (454 mg, 99%), mp 247–249 ЊC (lit.,12b 247 ЊC); δH
3.78 (9 H, s), 7.00 (3 H, dd, J 8.3 and 1.0), 7.12 (3 H, dt, J 7.4
and 1.0), 7.44 (3 H, ddd, J 8.3, 7.4 and 1.7) and 7.88 (3 H, dd, J
7.4 and 1.7).
Tetrakis-(2-methoxyphenyl)bismuthonium bromide monohy-
drate 7a. To a solution of compound 3a (235 mg, 0.34 mmol) in
methylene dichloride (10 cm3) was added aq. sodium bromide
(2 g in 10 cm3) and the resulting mixture was stirred vigorously
for 30 min at room temperature. Usual work-up gave compound
7a (184 mg, 74%) as fine crystals, mp 220–223 ЊC (decomp.); δH
1.67 (2 H, br s), 3.67 (12 H, s), 7.22–7.32 (8 H, m) and 7.55–7.75
(8 H, m); δC 56.66, 112.75, 124.63, 127.36 (Bi–C), 134.31, 134.92
and 159.87; νmax(KBr)/cmϪ1 3450br, 1470, 1435, 1277, 1244,
1044, 781 and 760 (Found: C, 46.00; H, 3.93. C28H30BiBrO5
requires C, 45.71; H, 4.08%).
Tetrakis-(2-methoxyphenyl)bismuthonium iodide monohydrate
8a. Similarly obtained from compound 3a (235 mg, 0.34 mmol)
and sodium iodide (2 g) in 74% yield (198 mg), compound 8a
had mp 202–204 ЊC (decomp.); δH 1.61 (2 H, br s), 3.67 (12 H,
s), 7.22–7.32 (8 H, m) and 7.55–7.75 (8 H, m); δC 56.76, 112.76,
124.66, 127.33 (Bi–C), 134.30, 134.92 and 159.84; νmax(KBr)/
cmϪ1 3450br, 1470, 1435, 1277, 1244, 1044, 781 and 760
(Found: C, 42.73; H, 3.72. C28H30BiIO5 requires C, 42.97; H,
3.84%).
Preparation of bismuthonium tetrafluoroborates 11
An acetonitrile solution (5 cm3) of silver() tetrafluoroborate
(200 mg) was added to a solution of salt 3a (517 mg, 0.75
mmol) in the same solvent (10 cm3) and the resulting mixture
was stirred in the dark under ambient conditions. After 2 h
silver() chloride was filtered off and the filtrate was evaporated
to leave a brown solid, which was extracted with methylene
dichloride (10 cm3 × 3). The combined extracts were evaporated
and then treated with EtOAc (20 cm3) to give tetrakis-(2-
methoxyphenyl)bismuthonium tetrafluoroborate 11a (468 mg,
86%) as fine crystals, mp 268–270 ЊC; δH 3.66 (12 H, s), 7.22–
7.32 (8 H, m) and 7.55–7.75 (8 H, m); δC 56.49, 112.67, 124.60,
127.40 (Bi–C), 134.28, 134.94 and 159.92; νmax(KBr)/cmϪ1 1472,
1433, 1279, 1244, 1097, 1061, 1009 and 762 (Found: C, 46.00;
H, 3.84. C28H28BBiF4O4 requires C, 46.43; H, 3.90%).
Compound 3c (0.154 mmol, 115 mg) was similarly converted
to compound 11c (104 mg, 87%). Compounds 3d (0.138 mmol,
111 mg) and 3e (0.25 mmol, 186 mg) gave the corresponding
tetrafluoroborates 11d (107 mg, 92%) and 11e (156 mg, 80%),
respectively, as fine crystals.
Tetrakis-(2-ethoxyphenyl)bismuthonium tetrafluoroborate 11c.
Mp >300 ЊC; δH 0.80 (12 H, t, J 7.0), 3.98 (8 H, q, J 7.0), 7.15–
7.30 (8 H, m) and 7.50–7.70 (8 H, m); δC 13.73, 64.99, 112.73,
124.20, 127.28 (Bi–C), 134.21, 134.90 and 159.25; νmax(KBr)/
cmϪ1 1584, 1466, 1445, 1244, 1279, 1063, 1040 and 772 (Found:
C, 48.95; H, 4.62. C32H36BBiF4O4 requires C, 49.25; H, 4.65%).
Tetrakis-(2-isopropoxyphenyl)bismuthonium tetrafluoroborate
11d. Mp >300 ЊC; δH 0.83 (24 H, d, J 6.1), 4.60 (4 H, hept, J
6.1), 7.15–7.25 (8 H, m) and 7.55–7.75 (8 H, m); δC 20.96, 71.10,
113.00, 123.67, 128.30 (Bi–C), 134.08, 135.57 and 157.97;
νmax(KBr)/cmϪ1 1584, 1468, 1277, 1242, 1125, 1105, 1055, 1038,
947 and 754 (Found: C, 51.63; H, 5.28. C36H44BBiF4O4 requires
C, 51.69; H, 5.30%).
Oxidation of bismuthane 1a with iodosylbenzene
In benzene in the presence of alkyl halides: typical procedure.
A mixture of bismuthane 1a (530 mg, 1 mmol), iodosylbenzene
(330 mg, 1.5 mmol), benzyl bromide (171 mg, 1 mmol) and
benzene (50 cm3) was stirred at 40–50 ЊC for 5 h. The resulting
suspension was filtered through a Celite bed and the filtrate was
evaporated to give an oily residue (597 mg), which was passed
through a short column of silica gel to give an oily mixture (278
1
mg), the composition of which was estimated by H NMR
analysis as follows; bismuthane 1a (0.09 mmol), anisole (0.09
mmol), benzyl bromide (0.74 mmol), phenyl iodide (0.45 mmol)
and benzaldehyde (0.02 mmol). The solid residue retained on
the Celite bed was extracted with methylene dichloride (20
cm3 × 4) and the combined extracts were evaporated to give
bismuthonium salt 7a (309 mg, 42%). Similar oxidation of bis-
muthane 1a in the presence of ethyl bromide and 2,2,2-
trifluoroethyl iodide gave the bismuthonium bromide 7a and
the corresponding iodide 8a in 39 and 13% yield, respectively.
Tetrakis-(2-methoxy-4-methylphenyl)bismuthonium
tetrafluoroborate 11e. Mp 183–184 ЊC; δH 2.33 (12 H, s), 3.61
(12 H, s), 7.17 (4 H, d, J 8.4) 7.31 (4 H, br s) and 7.43 (4 H, ddd,
J 8.4, 1.8 and 0.7); δC 20.70, 56.45, 112.32, 127.15 (Bi–C),
134.25, 134.59 134.74 and 157.82; νmax(KBr)/cmϪ1 1601, 1487,
1614
J. Chem. Soc., Perkin Trans. 1, 1997

View Article Online
Metathetical reaction of tris-(2-methoxyphenyl)bismuth
dichloride 5a with silver(I) perchlorate
(286 mg, 1.3 mmol), 1,1-diphenylethylene (2 mmol, 360 mg)
and methylene dichloride (50 cm3) was heated to reflux, and
after 1.5 h it was filtered through a Celite bed. Usual work-up
gave the salt 3a (299 mg, 43%). 1,1-Diphenylethylene was
recovered unchanged from the mother liquor from which the
salt 3a had separated out.
In acetone. To a solution of compound 5a in acetone (50 cm3)
was added commercial silver() perchlorate (460 mg, 2 mmol;
from Wako Pure Chemical Industries, Ltd.; content 90%) in the
same solvent (10 cm3) and the resulting suspension was stirred
at room temperature in the dark. After 1 h the precipitated
silver chloride was filtered off and the filtrate was concentrated
under reduced pressure to leave a dark brown oily residue,
which was triturated with a mixture of acetone (2 cm3) and
benzene (20 cm3) to give tris-(2-methoxyphenyl)(2-oxopropyl)-
bismuthonium perchlorate 14a as light brown crystals (375 mg,
55%), mp 149–150 ЊC (decomp.); δH 2.48 (3 H, s), 3.82 (9 H, s),
5.09 (2 H, s), 7.15–7.30 (6 H, m) and 7.50–7.65 (6 H, m); δC
30.28, 51.79, 56.54 (Bi–CH2), 112.19, 124.34, 126.23 (Bi–C),
Cross-over experiment between bismuthanes 1a and 1e during
oxidation with iodosylbenzene
A mixture of bismuthanes 1a (265 mg, 0.5 mmol) and 1e (286
mg, 0.5 mmol), iodosylbenzene (330 mg, 1.5 mmol) and meth-
ylene dichloride (50 cm3) was heated to reflux for 1 h. Usual
work-up gave a mixture of bismuthonium salts (284 mg), which
was found by FAB-MS analysis to contain compounds 3a, 3e,
tris-(2-methoxyphenyl)(2-methoxy-4-methylphenyl)bismuthon-
ium and (2-methoxyphenyl)tris-(2-methoxy-4-methylphenyl)-
bismuthonium chlorides; m/z 693 (Ar1 Bi), 679 (Ar1 Ar2Bi), 651
134.07, 135.14, 159.97 and 202.99 (C᎐O); νmax(KBr)/cmϪ1 1458,
᎐
1429, 1233, 1092, 1049, 1021 and 758 (Found: C, 41.96; H, 3.77.
C24H26BiClO8 requires C, 41.97; H, 3.82%).
4
3
(Ar1Ar2 Bi), 637 (Ar2 Bi), 451 (Ar1 Bi), 437 (Ar1Ar2Bi), 423
3
4
2
(Ar2 Bi), 330 (Ar1Bi), 316 (Ar2Bi), and 209 (Bi) (1Ar = 2-
Treatment of salt 14a with an excess of brine in chloroform
at room temperature readily gave bismuthane 1a quantitatively.
In butan-2-one. Dichloride 5a in butan-2-one (50 cm3) was
treated with silver() perchlorate (460 mg, 2 mmol; from Wako
Pure Chemical Industries, Ltd.; content 90%). Usual work-up
gave a dark brown oily residue, which was triturated with a
mixture of MeOH (2 cm3) and EtOAc (20 cm3) to give tetrakis-
(2-methoxyphenyl)bismuthonium perchlorate 13a as light brown
crystals (8 mg, 1%), mp 250–251 ЊC; δH 3.66 (12 H, s), 7.25–7.35
(8 H, m) and 7.55–7.75 (8 H, m); δC 56.39, 112.58, 124.51,
127.19 (Bi–C), 134.20, 134.86 and 159.79; νmax(KBr)/cmϪ1 1472,
1435, 1279, 1244, 1098, 1044 and 762; m/z 637 (Ar4Bi), 423
(Ar2Bi), 316 (ArBi) and 209 (Bi) (Found: C, 45.67; H, 3.80.
C28H28BiClO8 requires C, 45.62; H, 3.80%).
2
methoxy-4-methylphenyl, 2Ar = 2-methoxyphenyl).
Attempt to prepare ì-oxybis[tris-(2-methoxyphenyl)bismuth]
di(trifluoromethanesulfonate)
To a suspension of dichloride 5a (601 mg, 1 mmol) in dry
methylene dichloride (8 cm3) was added trimethylsilyl trifluoro-
methanesulfonate (0.19 cm3, 1 mmol) at 0 ЊC, and the mixture
was stirred at room temperature for 20 h. To the resulting
yellow solution was added hexamethyldisiloxane (0.11 cm3, 0.5
mmol) and the whole was stirred for 48 h at room temperature
to give a brown solution, which was evaporated under reduced
1
pressure to obtain a grey solid (680 mg). The H NMR spec-
trum of the mixture showed that the mixture contained at least
four products, including bismuthonium salt. The starting
material 5a was found to have been consumed completely. The
residue was dissolved in methylene dichloride (15 cm3) and
shaken with brine vigorously for 3 h. After extractive work-up,
a dark brown solid (245 mg) was obtained. The residue was
chromatographed on silica gel with methylene dichloride–
ethanol (1:0–10:1) as eluent to give dichloride 5a (68 mg, 11%)
and bismuthonium salt 3a (113 mg, 16%).
Reaction of dichloride 5a with silver(I) oxide in methylene
dichloride
To a suspension of silver() oxide, freshly prepared from 4 mmol
of silver() nitrate and sodium hydroxide in methylene dichlo-
ride (5 cm3), was added a solution of dichloride 5a (601 mg, 1
mmol) in the same solvent (45 cm3) and the resulting suspension
was heated at reflux in the dark. After 4 h, the mixture was
filtered through a Celite bed and the filtrate was evaporated
under reduced pressure to leave a light yellow solid, which con-
tained tetrakis-(2-methoxyphenyl)bismuthonium hydroxide tri-
hydrate 15a and bismuthane 1a. The presence of a formate in
X-Ray crystallography of compound 7a
A crystal of dimensions 0.45 × 0.38 × 0.20 mm, grown from a
mixture of EtOH–EtOAc (1:5) at room temperature, was
sealed in a glass capillary and used for X-ray crystallography.
Crystal data. C28H28BiBrO4, M = 717.41. Monoclinic. Space
group P21/c, a = 11.466(4), b = 19.802(9), c = 12.369(5) Å,
β = 103.30(3)Њ, V = 2733(2) Å3, Z = 4, Dc = 1.743 g cmϪ3. Prisms,
1
the product mixture was detected by H NMR spectroscopy.
The mixture was recrystallized from CH2Cl2–EtOAc (1:5) to
deposit compound 15a (271 mg, 38% based on Bi). Compound
15a, mp 155–160 ЊC (decomp.); δH 2.77 (6 H, br s), 3.67 (12 H,
s), 7.22–7.32 (8 H, m) and 7.55–7.75 (8 H, m); OH group was
not observed; νmax(KBr)/cmϪ1 3450br, 1586, 1566, 1471, 1277,
1244, 1044, 1009, 783 and 760 (Found: C, 47.53; H, 4.60.
C28H35BiO8 requires C, 47.46; H, 4.94%).
Compound 15a was also obtained by the reaction of salt
3a and silver() oxide as follows; to a suspension of salt 3a in
tetrahydrofuran (THF) (30 cm3) [prepared from bismuthane
1a (1 mmol, 530 mg) and iodosylbenzene (2 mmol, 440 mg)]
was added a suspension of silver() oxide [prepared from
silver nitrate (1.1 mmol) and sodium hydroxide] in water (5 cm3)
and the resulting suspension was stirred for 40 min in the
dark under ambient conditions. Organic solvent was removed
under reduced pressure and the aqueous layer was extracted
with methylene dichloride (20 cm3 × 4). The combined extracts
were dried (MgSO4) and evaporated under reduced pressure to
leave compound 15a (392 mg, 55%).
µ(Mo-Kα, λ = 0.710 69 Å) = 79.08 cmϪ1
.
Data collection and processing. Intensity data were collected
on a Rigaku AFC5R diffractometer using graphite-mono-
chromated Mo-Kα radiation from a 12 kW rotating anode gen-
erator using the ω–2θ scan technique to a maximum 2θ-value of
55.0Њ. Scans of (0.79 ϩ 0.30 tan θ)Њ were made at a speed of 16.0
deg min-1 (in omega). Data were corrected for Lorentz and
polarization effects. Of the 6754 reflections which were col-
lected, 6446 were unique (Rint = 0.074). The intensities of three
representative reflections which were measured after every 150
reflections declined by 5.7%. A linear correction factor was
applied to the data to account for this phenomenon. An empir-
ical absorption correction, based on azimuthal (ψ) scans of
several reflections, was applied which resulted in correction fac-
tors ranging from 0.53 to 1.00.
Treatment of compound 15a with 42% tetrafluoroboric acid
in acetonitrile at 0–5 ЊC gave the corresponding tetrafluoro-
borate 11a (mp 268 –270 ЊC) in 91% yield.
Structure analysis and refinement. The structure was solved
by direct methods. The non-hydrogen atoms were refined aniso-
tropically. The positions of hydrogen atoms were calculated
from those of the non-hydrogen atoms and were included in the
Fc calculation. The final cycle of full-matrix least-squares
refinement, Σw(|Fo| Ϫ |Fc|)2 where w = 1/σ2(Fo), was based on
Oxidation of compound 1a in the presence of a radical scavenger
A mixture of bismuthane 1a (530 mg, 1 mmol), iodosylbenzene
J. Chem. Soc., Perkin Trans. 1, 1997
1615

View Article Online
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3547 observed reflections [I > 2.50σ(I)] and 308 variable
parameters and converged with unweighted and weighted
agreement factors of R = 0.042 and Rw = 0.036. The weighting
scheme w = 1/σ2(Fo) was employed. The standard deviation of
an observation of unit weight was 1.17,‡ and the maximum peak
and minimum trough in the final ∆F syntheses surpluses which
are 0.80 and Ϫ1.34 ÅϪ3. All calculations were performed using
the TEXSAN 27 crystallographic software package of the
Molecular Structure Corporation. The ORTEP 28 program was
used to obtain the drawing in Fig. 1. Selected bond lengths and
bond angles are given in Table 2.§
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Acknowledgements
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22 W. Clegg, M. R. J. Elsegood, V. Graham, N. C. Norman, N. L.
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We acknowledge support of this work by Grant in Aid (No.
07740496) from the Ministry of Education, Sports and Culture,
Japan. We would like to thank Dr A. Kita (Kyoto University)
for her help with the X-ray experiments. T. I. thanks the Japan
Society for the Promotion of Science for the fellowship (No.
6710).
‡ Atomic coordinates, thermal parameters, and bond lengths and angles
have been deposited at the Cambridge Crystallographic Data Centre
(CCDC). See Instructions for Authors, J. Chem. Soc., Perkin Trans. 1,
1997, Issue 1. Any request to the CCDC for this material should quote
the full literature citation and the reference number 207/109.
§ Standard deviation of an observation of unit weight: [Σw(|Fo| Ϫ |Fc|)2/
¹

(No Ϫ Nv)]² where No = number of observations and Nv = number of
variables.
23 Y. Matano, N. Azuma and H. Suzuki, J. Chem. Soc., Perkin Trans. 1,
1994, 1739.
24 H. Saltzman and J. G. Sharefkin, Org. Synth., 1973, Coll. Vol. 5,
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27 TEXSAN-TEXRAY Structure Analysis Package, Molecular
Structure Corporation, The Woodlands, Texas, 1985.
28 ORTEP: C. K. Johnson; ORTEPII. Report, ORNL-5138, Oak
Ridge National Laboratory, Oak Ridge, Tennessee, 1976.
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Paper 7/00379J
Received 15th January 1997
Accepted 25th February 1997
1616
J. Chem. Soc., Perkin Trans. 1, 1997