Synthesis, structure, and reactions of triaryl(methyl)bismuthonium salts

Article abstract of DOI:10.1021/om000095d

Treatment of triarylbismuth difluorides 2 (Ar₃BiF₂; a, Ar = Ph; b, Ar = 4-MeC₆H₄; c, Ar = 4-MeOC₆H₄; d, Ar = 2-MeOC₆H₄) with methylboronic acid (3) in the presence of BF₃·OEt₂ in CH₂Cl₂ afforded the corresponding triaryl(methyl)bismuthonium tetrafluoroborates 4a-d ([Ar₃MeBi⁺][BF₄^-]) in 42-91% yield. X-ray crystallographic analysis of compound 4d revealed that the bismuth center possesses a distorted tetrahedral geometry with C-Bi-C bond angles of 106.1(3)-113.6(3)° and Bi-C bond lengths of 2.182(7)-2.195(8) angstrom. Compound 4a transferred the methyl group to Ph₃E (E = P, As, Sb), tris(4-methylphenyl)bismuthine, ROH (R = Me, Et, i-Pr, PhCH₂), water, sodium benzenesulfinate, sodium benzoate, N,N-dimethylformamide (DMF), and thioacetamide to give the corresponding methylated products with a good recovery of triphenylbismuthine. The pseudo-first-order rate constant (k_obsd = 2.9 × 10^-4 s^-1) observed for the reaction between 4a and benzyl alcohol (5d) was about twice as large as that (k_obsd = 1.3 × 10^-4 s^-1) between MeOTf and 5d (in CDCl₃ at 23°C; [4a] or [MeOTf] = 0.062 M; [5d] = 0.97 M). The observed reactivity of 4a clearly demonstrates the high nucleofugality of the triphenylbismuthonio group.

Full text of DOI:10.1021/om000095d

2258
Organometallics 2000, 19, 2258-2263
Syn th esis, Str u ctu r e, a n d Rea ction s of
Tr ia r yl(m eth yl)bism u th on iu m Sa lts
Yoshihiro Matano†
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku,
Kyoto 606-8502, J apan
Received February 3, 2000
Treatment of triarylbismuth difluorides 2 (Ar3BiF2; a , Ar ) Ph; b, Ar ) 4-MeC6H4; c, Ar
) 4-MeOC6H4; d , Ar ) 2-MeOC6H4) with methylboronic acid (3) in the presence of BF3‚OEt2
in CH2Cl2 afforded the corresponding triaryl(methyl)bismuthonium tetrafluoroborates 4a -d
([Ar3MeBi+][BF4-]) in 42-91% yield. X-ray crystallographic analysis of compound 4d revealed
that the bismuth center possesses a distorted tetrahedral geometry with C-Bi-C bond angles
of 106.1(3)-113.6(3)° and Bi-C bond lengths of 2.182(7)-2.195(8) Å. Compound 4a
transferred the methyl group to Ph3E (E ) P, As, Sb), tris(4-methylphenyl)bismuthine, ROH
(R ) Me, Et, i-Pr, PhCH2), water, sodium benzenesulfinate, sodium benzoate, N,N-
dimethylformamide (DMF), and thioacetamide to give the corresponding methylated products
with a good recovery of triphenylbismuthine. The pseudo-first-order rate constant (kobsd
)
2.9 × 10-4 s-1) observed for the reaction between 4a and benzyl alcohol (5d ) was about twice
as large as that (kobsd ) 1.3 × 10-4 s-1) between MeOTf and 5d (in CDCl3 at 23 °C; [4a ] or
[MeOTf] ) 0.062 M; [5d ] ) 0.97 M). The observed reactivity of 4a clearly demonstrates the
high nucleofugality of the triphenylbismuthonio group.
Sch em e 1
In tr od u ction
Methylated onium salts of the general formula
[RnMeE+][X-] (E ) group 15 and 16 elements; X-
)
counteranion) have attracted considerable attention
because of their importance in organic synthesis.1 The
reactivity of these onium salts differs considerably
depending on the nature of the central element. How-
ever, very little information is available concerning
methylbismuthonium salts ([R3MeBi+][X-]) due to the
limited access to this class of compounds.2 As shown in
Scheme 1, there are two possible methods for the
synthesis of the methylbismuthonium salts: addition
of a methyl cation equivalent to a triorganylbismuthine
(method A) and metathesis of a methyl anion equivalent
to a triorganylbismuth dihalide (method B). In 1994,
Wallenhauer and Seppelt prepared tetramethylbismu-
thonium triflate by treating trimethylbismuthine with
methyl triflate in acetonitrile.3 In contrast, an earlier
attempt by Henry and Wittig to prepare a methyltriph-
enylbismuthonium salt by the reaction of triphenylbis-
muthine with trimethyloxonium tetrafluoroborate4
([Me3O+][BF4-]) in liquid sulfur dioxide was unsuccess-
ful.5 Thus, method A has been applicable only to the
synthesis of the tetramethylbismuthonium salt. Nev-
ertheless, no attention has been paid to method B thus
far. For practical use, triaryl(methyl)bismuthonium
salts are preferable substrates because triarylbismuth-
ines that would be produced in their reactions are much
easier to handle than air-sensitive trimethylbismuth-
ine.6 Recently, the metathesis of triarylbismuth difluo-
rides with organometallic reagents has proven to be a
reliable method for the synthesis of various types of
alkyltriarylbismuthonium salts.7 Encouraged by these
(4) Meerwein, H.; Hinz, G.; Hofmann, P.; Kroning, E.; Pfeil, E. J .
Prakt. Chem. 1937, 147, 257.
(5) Henry, M. C.; Wittig, G. J . Am. Chem. Soc. 1960, 82, 563. The
authors reported that triphenylbismuthine reacts with the oxonium
salt but does not produce a bismuthonium salt. They also reported
that triphenylstibine reacts readily with the same oxonium salt to yield
methyltriphenylstibonium tetrafluoroborate.
(6) (a) Gmelin Handbuch der Anorganischen Chemie, Bismut-
Organische Verbindungen; Wieber, M., Ed.; Springer-Verlag: Berlin,
l977; Band 47. (b) Freedman, L. D.; Doak, G. O. Chem. Rev. 1982, 82,
15.
(7) (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.
(f) Matano, Y.; Suzuki, H. Bull. Chem. Soc. J pn. 1996, 69, 2673. (g)
Matano, Y.; Rahman, M. M.; Yoshimune, M.; Suzuki, H. J . Org. Chem.
1999, 64, 6924.
† E-mail: matano@kuchem.kyoto-u.ac.jp. Fax: +81-75-753-4000.
Phone: +81-75-753-4042.
(1) For monographs and reviews, see: (a) J ohnson, A. W. Ylides and
Imines of Phosphorus; Wiley: New York, 1993. (b) Lloyd, D.; Gosney,
I.; Ormiston, R. A. Chem. Soc. Rev. 1987, 16, 45. (c) Lloyd, D.; Gosney,
I. In The Chemistry of Organic Arsenic, Antimony and Bismuth
Compounds; Patai, S., Ed.; Wiley: New York, 1994; Chapter 16, pp
657-693. (d) Trost, B. M.; Melvin, L. S., J r. Sulfur Ylides; Academic
Press: New York, 1975. (e) J ohnson, C. R. Acc. Chem. Res. 1973, 6,
341. (f) J ohnson, A. W. Ylide Chemistry; Academic Press: New York,
1966.
(2) Arbuzov et al. postulated the formation of an intermediary
methyltriphenylbismuth cation in the reaction between triphenylbis-
muthine and a sulfonium ylide. However, their attempt to isolate a
methyltriphenylbismuthonium salt was not successful. Arbuzov, B. A.;
Belkin, Y. V.; Polezhaeva, N. A.; Buslaeva, G. E. Izv. Akad. Nauk SSSR
1978, 1643.
(3) Wallenhauer, S.; Seppelt, K. Angew. Chem., Int. Ed. Engl. 1994,
33, 976.
10.1021/om000095d CCC: $19.00 © 2000 American Chemical Society
Publication on Web 05/06/2000

Triaryl(methyl)bismuthonium Salts
Organometallics, Vol. 19, No. 12, 2000 2259
Sch em e 2
results, I aimed to prepare triaryl(methyl)bismutho-
nium salts based on method B and to elucidate their
reactivity.
Reported here are the synthesis, structure, and reac-
tions of triaryl(methyl)bismuthonium salts. The BF3‚
OEt2-promoted reaction of triarylbismuth difluorides
with methylboronic acid has been found to be effective
for constructing the Bi(V)-Me bond. Methyltriphenyl-
bismuthonium tetrafluoroborate behaves as the methyl
cation equivalent due to the remarkable nucleofugality
of the triphenylbismuthonio group.
sired product 4a usually was isolated in 42-58% yields
by fractional recrystallization from CH2Cl2/Et2O. Dif-
luoride 2a also was recovered in 30-40% yields. The
formation of the tetraphenylbismuthonium salt could
not be suppressed completely, and its yield increased
with increasing reaction time.14 Difluoride 2a did not
react with 3 in the absence of BF3‚OEt2, and triphenyl-
bismuth dichloride did not react with 3 even in the
presence of BF3‚OEt2. Presumably, BF3 enhances the
electrophilicity of the bismuth(V) center of 2a by coor-
dinating to the apical fluorine atom. Substituted tri-
arylbismuth difluorides 2b-d similarly underwent the
BF3‚OEt2-promoted reaction with 3 to afford the corre-
sponding triaryl(methyl)bismuthonium tetrafluorobo-
rates 4b-d in 72-91% yields (Scheme 2). To the best
of my knowledge, this is the first use of the boronic acid
3 in the synthesis of methylated onium salts.15
Resu lts a n d Discu ssion
Syn th esis of Tr iar yl(m eth yl)bism u th on iu m Salts.
First, to confirm the earlier observation by Henry and
Wittig,5 the reaction of triphenylbismuthine (1a ) to-
gether with the trimethyloxonium salt was reexamined.
Treatment of 1a with [Me3O+][BF4-] in CH2Cl2/CH3CN
at room temperature afforded a significant amount of
insoluble substance with N-methylacetamide8 (ca. 80%),
benzene,9 and a small amount of unassigned bismuth
compound.10 As reported by Henry and Wittig, the
desired methyltriphenylbismuthonium salt was not
formed at all. The combined use of methyl iodide and
silver tetrafluoroborate instead of [Me3O+][BF4-] gave
a similar result. Methyl triflate also did not transfer a
methyl group to bismuthine 1a after 1 week in CDCl3
or in acetonitrile at room temperature. The observed
reactivity of bismuthine 1a is in marked contrast to
those of Ph3E (E ) P, As, Sb), which readily react
with [Me3O+][BF4-] under similar conditions to yield
the corresponding methylated onium salts, [Ph3MeE+]-
[BF4-].5,11 Thus, methyltriphenylbismuthonium salts
are much more difficult to prepare by method A than
the lighter pnictogen counterparts. Apparently, this is
due to the low nucleophilicity of the lone electron pair
of triphenylbismuthine 1a .12
Compounds 4 were characterized by 1H NMR, IR, and
MS spectroscopy as well as by elemental analysis. In
the 1H NMR spectra (in CDCl3), the methyl group bound
to the bismuth was observed at δ 3.17-3.29. The
FABMS spectra of compounds 4 showed a strong frag-
ment peak due to the [M+ - BF4] cation, and their IR
-
spectra showed a broad absorption due to the BF4
anion. These spectral data are consistent with the
onium nature of the bismuth center in 4. These com-
pounds are soluble in CHCl3, CH2Cl2, and CH3CN, but
insoluble in Et2O and toluene. When kept in open air,
compounds 4 gradually were hydrolyzed by atmospheric
moisture. Under a dry condition or in dry CDCl3,
however, they did not decompose over a month.
Next, method B was examined using methylboronic
acid as the methyl anion equivalent.13 As shown in
Scheme 2, treatment of triphenylbismuth difluoride (2a )
with an excess of methylboronic acid (3) in the presence
of BF3‚OEt2 in CH2Cl2 at room temperature for 12 h
afforded a mixture of methyltriphenylbismuthonium
tetrafluoroborate (4a ), difluoride 2a , and a trace amount
of tetraphenylbismuthonium tetrafluoroborate. The de-
The structure of 4d was further elucidated by X-ray
crystallographic analysis. The crystal data and collection
parameters are given in Table 1, and an ORTEP dia-
gram is shown in Figure 1 with selected bond lengths
and angles. The bismuth center in 4d possesses a dis-
torted tetrahedral geometry with C-Bi-C bond angles
of 106.1(3)-113.6(3)°. The Bi-C(1) bond length of
2.195(8) Å and the Bi-CAr bond lengths of 2.182(7)-
2.189(7) Å in 4d are almost identical with the
reported values for the Bi-CMe bonds of [Me4Bi+][OTf-]3
[2.210(7)-2.230(10) Å] and the Bi-CAr bonds of [(2-
MeOC6H4)4Bi+][Br-]16 [2.194(8)-2.207(9) Å]. Three meth-
oxy groups lean ca. 5° toward the bismuth center from
the ideal sp2 bond angle, and intramolecular distances
[2.993(5)-3.031(6) Å] between the bismuth and oxygen
atoms are shorter than the sum of their van der Waals
(8) N-Methylacetamide was most likely formed via the Ritter
reaction of acetonitrile. Ritter, J . J .; Minieri, P. P. J . Am. Chem. Soc.
1948, 70, 4045.
(9) Benzene was most likely formed via the Bi-C bond cleavage of
1a by a generated protonic acid.
(10) This compound showed phenyl protons in the 1H NMR spectrum
(in CDCl3) at δ 7.7-7.8 (m, m- and p-H) and 8.26 (d, J ) 7.9 Hz, o-H).
It also showed
a strong ion peak in the FABMS spectrum (in
3-nitrobenzyl alcohol) at 516 that could be assigned to the [Ph2-
BiOCH2C6H4-3-NO2]+ ion. These spectral features suggest a Ph2BiX
type of structure.
(11) Parris, G. E.; Long, G. G.; Andrews, B. C.; Parris, R. M. J . Org.
Chem. 1976, 41, 1276.
(12) For example, see: (a) Carty, A. J .; Taylor, N. J .; Coleman, A.
W.; Lappert, M. F. J . Chem. Soc., Chem. Commun. 1979, 639. (b)
Godfrey, S. M.; McAuliffe, C. A.; Mackie, A. G.; Pritchard, R. G. In
Chemistry of Arsenic, Antimony and Bismuth; Norman, N. C., Ed.;
Blackie Academic and Professional: London, 1998; Chapter 4, pp 159-
205.
(13) Recently, aryl- and alkenylboronic acids were found to be potent
reagents for preparing aryl- and alkenylbismuthonium salts. (a)
Matano, Y.; Begum, S. A.; Miyamatsu, T.; Suzuki, H. Organometallics
1998, 17, 4332. (b) Matano, Y.; Begum, S. A.; Miyamatsu, T.; Suzuki,
H. Organometallics 1999, 18, 5668.
(14) When the reaction was performed for 48-72 h, the tetraphe-
nylbismuthonium salt was formed in ca. 5-10% yield.
(15) This method was not applicable to the Bi-Bu bond formation;
no Bi-C coupling took place between n-butylboronic acid and 2a in
the presence of BF3‚OEt2.
(16) Suzuki, H.; Ikegami, T.; Azuma, N. J . Chem. Soc., Perkin Trans.
1 1997, 1609.

2260 Organometallics, Vol. 19, No. 12, 2000
Matano
Sch em e 3
Sch em e 4
Sch em e 5
F igu r e 1. ORTEP diagram for 4d (30% probability el-
lipsoids). Selected bond lengths (Å) and angles (deg): Bi-
C(1), 2.195(8); Bi-C(2), 2.185(7); Bi-C(9), 2.189(7); Bi-
C(16), 2.182(7); C(1)-Bi-C(2), 107.5(3); C(1)-Bi-C(9),
111.6(3); C(1)-Bi-C(16), 113.6(3); C(2)-Bi-C(9), 108.5-
(3); C(2)-Bi-C(16), 106.1(3); C(9)-Bi-C(16), 109.3(3);
O(1)-C(7)-C(2), 115.1(7); O(2)-C(14)-C(9), 114.9(7); O(3)-
C(21)-C(16), 114.0(7).
Ta ble 2. Rea ction of 4a w ith Alcoh ols 5a
Ta ble 1. Cr ysta l Da ta for 4d
entry
alcohol (5)
ether (7)
yield/%b
formula
a (Å)
b (Å)
C22H24BBiF4O3
11.505(1)
12.358(1)
8.696(1)
102.072(8)
100.232(10)
87.028(8)
1189.8(2)
74.47
1
2
3
4
MeOH (5a )
EtOH (5b)
MeOMe (7a )
EtOMe (7b)
69
74
82
95
i-PrOH (5c)
PhCH2OH (5d )
i-PrOMe (7c)
PhCH2OMe (7d )
c (Å)
R (deg)
a
â (deg)
Reaction was carried out in CDCl3 at room temperature.
Yields refer to the NMR yield. Bismuthine 1a and pyridinium
salt 8 were formed quantitatively.
b
γ (deg)
V (Å3)
µ(Mo KR) (cm-1
space group
Z value
)
P1h
2
1.765
muthonium salt 4a is thermodynamically much less
stable than the lighter pnictogen counterparts.
D
calc (g cm-3
)
no. of reflns collected
5825
An interesting equilibrium was observed between 4a
and tris(4-methylphenyl)bismuthine (1b) (Scheme 4).
Treatment of 4a with an equimolar amount of 1b in
CDCl3 at room temperature slowly afforded 4b and 1a
at the initial stages of the reaction. After 24 h, however,
an equilibrium mixture of four triaryl(methyl)bismu-
thonium salts 4a ,b,e,f was formed.19 The mixed type of
compounds 4e,f were assigned on the basis of the
bismuth-bound methyl peaks in the 1H NMR spectra
and by the [PhnTol3-nMeBi+] (n ) 0-3) ion peaks in the
FABMS spectra. Reaction between 4b and 1a afforded
a similar equilibrium mixture after 24 h. In contrast,
tetrakis(4-methylphenyl)bismuthonium tetrafluorobor-
ate did not react with 1a under the same conditions.
The observed equilibrium is therefore characteristic of
the methylbismuthonium salts 4, but the reaction
course is not clearly understood at present.20
Methylbismuthonium salt 4a reacted with alcohols 5
in the presence of 2,6-di-tert-butyl-4-methylpyridine (6)
to yield alkyl methyl ethers 7 as the exclusive coupling
product with good recovery of bismuthine 1a and
pyridinium salt 8 (Scheme 5, Table 2). When treated
with methanol (5a ), ethanol (5b), 2-propanol (5c), and
benzyl alcohol (5d ), 4a transferred the methyl group to
afford dimethyl ether (7a ), ethyl methyl ether (7b),
isopropyl methyl ether (7c), and benzyl methyl ether
no. of unique reflns
Rint
no. of observations (I > 2.00σ(I))
no. of variables
R
Rw
5464
0.023
3992
281
0.036
0.048
1.11
goodness of fit
radii (ca. 3.8 Å).17 Thus, the interaction between the
cationic bismuth center and the oxygen atoms should
be attractive. This type of interaction between the
positively charged bismuth(V) and neighboring oxygen
atoms was also observed for [(2-MeOC6H4)4Bi+][Br-]16
and (2-MeOC6H4)3BidNCOCCl3.18
Reaction s of Tr iar yl(m eth yl)bism u th on iu m Salts.
To investigate the reactivity of triaryl(methyl)bismu-
thonium salts 4 toward nucleophiles, 4a was reacted
with Ph3E (E ) P, As, Sb), tris(4-methylphenyl)bis-
muthine, alcohols, water, sodium benzenesulfinate,
sodium benzoate, DMF, and thioacetamide.
Treatment of 4a with triphenylphosphine (1 equiv),
triphenylarsine (1 equiv), and triphenylstibine (5 equiv)
in CDCl3 at room temperature afforded the methylated
phosphonium, arsonium, and stibonium tetrafluoro-
borates, respectively, together with bismuthine 1a
(Scheme 3). The methyl transfer was complete within
a minute in all cases, suggesting that the methylbis-
(17) (a) Dean, J . A. Lange’s Handbook of Chemistry, 11th ed.;
McGraw-Hill: New York, 1973; Tables 3-9. (b) Emsley, J . The
Elements, 3rd ed.; Oxford University Press: Oxford, 1998.
(18) Matano, Y.; Nomura, H.; Shiro, M.; Suzuki, H. Organometallics
1999, 18, 2580.
(19) A small amount of insoluble substance was also formed.
(20) Unidentified trace components in the reaction mixture might
cause disproportionation of 1a ,b to 1e,f. It is likely that 4a ,b transfer
the methyl group to these unsymmetrical bismuthines 1e,f to afford
4e,f.

Triaryl(methyl)bismuthonium Salts
Organometallics, Vol. 19, No. 12, 2000 2261
Sch em e 6
Sch em e 7
(7d ), respectively. Oxidation products such as acetal-
dehyde (from 5b), acetone (from 5c), and benzaldehyde
(from 5d ) were not produced at all. The sterically
hindered pyridine 6 behaved as a non-nucleophilic base
to trap fluoroboric acid. Thus, in the absence of 6, 4a
reacted with 5 to afford an insoluble substance and
benzene in addition to 7. In this reaction, the Bi-C
bonds of 1a would be cleaved by the generated fluo-
roboric acid. No reaction took place between alcohols 5
and methyltriphenylphosphonium or methyltriphenyl-
stibonium tetrafluoroborate under the same reaction
conditions, suggesting the remarkable nucleofugality of
the triphenylbismuthonio group.
Compound 4a also reacted with water; treatment of
4a with an excess of water (5 equiv) in the presence of
6 afforded methanol (5a ) and dimethyl ether (7a ) in 30%
and 16% yields, respectively (eq 1). In the initial stages
of this reaction, 5a was the sole coupling product. Ether
7a likely is formed by the reaction of the initially
produced 5a with the remaining bismuthonium salt 4a .
much higher temperatures (100-120 °C).21 When water
was added to the resulting solution, 9 was readily
hydrolyzed to yield methyl formate and a dimethylam-
monium salt.22 Compound 4a also reacted with thioac-
etamide to afford 1-(methylthio)ethyleneiminium salt
1023 quantitatively.
In summary, a new method for the synthesis of
triaryl(methyl)bismuthonium salts based on the BF3‚
OEt2-promoted reaction of triarylbismuth difluorides
with methylboronic acid has been developed. The bis-
muth center in the tris(2-methoxyphenyl)(methyl)bis-
muthonium salt possesses a distorted tetrahedral ge-
ometry. The methyltriphenylbismuthonium salt has
been found to transfer the methyl group to various
nucleophiles under mild conditions. The observed reac-
tivity of the methyltriphenylbismuthonium salt differs
considerably from that of lighter pnictogen counterparts.
This is attributed to the high nucleofugality of the
triphenylbismuthonio group.
To compare the leaving ability of the triphenylbis-
muthonio group with that of triflate, kinetic studies
were carried out for the reactions of 5d with 4a and
methyl triflate (MeOTf) separately (Scheme 6). In the
presence of an excess of 5d (15 equiv), both 4a and
MeOTf were consumed according to first-order kinetics.
The pseudo-first-order rate constants (kobsd) observed
under the same conditions (in CDCl3 at 23 °C, [4a ] or
[MeOTf] ) [6] ) 0.063 M; [5d ] ) 0.96 M) were 2.9 ×
10-4 s-1 for 4a and 1.3 × 10-4 s-1 for MeOTf, respec-
tively. The kobsd did not depend on the concentration of
the pyridine 6 in the range of 0.063-0.32 M (1-5 equiv),
suggesting that 6 is not involved in the rate-determining
step of the reaction. These observations indicate that
the leaving ability of the triphenylbismuthonio group
is about twice as large as that of triflate in the ether
formation.
Compound 4a transferred its methyl group to several
O- and S-nucleophiles with quantitative recovery of
bismuthine 1a (Scheme 7). Reaction of 4a with sodium
benzenesulfinate or sodium benzoate in DMF at room
temperature afforded methyl phenyl sulfone or methyl
benzoate after aqueous workup. Due to the competing
side-reaction with the solvent, the yields of these
products were only 30-54%. Actually, 4a reacted with
DMF in CDCl3 at room temperature to afford meth-
oxymethyleneiminium salt 921 quantitatively. This is in
contrast to a similar N-methylation using methyldiphe-
nylsulfonium tetrafluoroborate, which proceeds only at
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions with air-sensitive com-
pounds 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 spectrometer (200 MHz for
1H and 50 MHz for 13C) using CDCl3 as the solvent. Chemical
shifts are reported as the relative value vs tetramethylsilane.
IR spectra were observed as KBr pellets on a Shimadzu FTIR-
8100S spectrophotometer. FABMS spectra were obtained on
a J EOL J MS-HS110 spectrometer using 3-nitrobenzyl alcohol
as a matrix. Elemental analyses were performed at the
Microanalytical Laboratory of Kyoto University. Dichlo-
romethane (CH2Cl2) was distilled from CaH2 before use.
Diethyl ether (Et2O) was distilled from sodium benzophenone
ketyl before use. DMF and CH3CN were distilled from CaH2
and stored over 4 Å molecular sieves.
Ma ter ia ls. Triarylbismuth difluorides 2a -c were prepared
according to reported procedures.7b,13b,24 Tris(2-methoxyphen-
yl)bismuth difluoride (2d ) was prepared from tris(2-methoxy-
phenyl)bismuthine and xenon difluoride. Methylboronic acid
3 was purchased from Aldrich. Other reagents were used as
commercially received.
Tr is(2-m eth oxyp h en yl)bism u th d iflu or id e (2d ): mp
1
215-220 °C (decomp); H NMR δ 3.87 (s, 9H), 7.20-7.30 (m,
(22) Due to the high water-solubility, methyl formate and the
ammonium salt could not be recovered in the reactions with sodium
sulfinate and benzoate.
(23) Casadei, M. A.; Rienzo, B. D.; Moracci, F. M. Synth. Commun.
1983, 13, 753.
(21) J ulia, M.; Mestdagh, H. Tetrahedron 1983, 39, 433.
(24) Challenger, F.; Wilkinson, J . F. J . Chem. Soc. 1922, 121, 91.

2262 Organometallics, Vol. 19, No. 12, 2000
Matano
6H), 7.46-7.56 (m, 3H), 8.02 (dd, 3H, J ) 1.7, 7.7 Hz); FABMS
Rea ction of 4a w ith P h 3E (E ) P , As, Sb). To a mixture
of 4a (11.4 mg, 0.021 mmol) and triphenylphosphine (5.8 mg,
0.022 mmol) was added CDCl3 (0.50 mL) in an NMR tube at
room temperature, and the resulting colorless solution was
measured by 1H NMR. The reaction was complete within a
minute, and triphenylbismuthine (1a ) and methyltriphe-
nylphosphonium tetrafluoroborate were formed quantitatively.
Triphenylarsine (6.8 mg, 0.022 mmol) and triphenylstibine (35
mg, 0.10 mmol) also reacted with 4a (11.4 mg, 0.021 mmol)
within a minute in CDCl3 (0.50 mL) to afford the corresponding
arsonium and stibonium salts, respectively. These onium salts
were characterized by comparison with an authentic specimen.
m/z 549 (M+ - F), 423, 316, 209. Anal. Calcd for C21H21
-
BiF2O3: C, 44.38; H, 3.72. Found: C, 44.17; H, 3.78.
Rea ction of Tr ip h en ylbism u th in e (1a ) w ith Tr im eth yl-
oxon iu m Tetr a flu or obor a te. To a CH2Cl2/CH3CN solution
(1 mL:1 mL) of 1a (44 mg, 0.10 mmol) was added [Me3O+][BF4
]
-
(15 mg, 0.10 mmol) at 0 °C, and the resulting mixture was
stirred at room temperature. As the reaction proceeded, white
insoluble substances were gradually deposited. After 12-14
h, the latter were filtered through Celite and the filtrate was
evaporated under reduced pressure to leave an oily residue
(21 mg), in which unreacted bismuthine 1a , a bismuth
compound of the type Ph2BiX, benzene, and N-methylaceta-
mide were observed by 1H NMR spectroscopy. The yields of
1a and the amide were about 20% and 80%, respectively. A
similar result was obtained when methyl iodide and silver
tetrafluoroborate were used instead of [Me3O+][BF4-]. Under
the same conditions, triphenylphosphine, triphenylarsine, and
triphenylstibine smoothly reacted with [Me3O+][BF4-] to give
the corresponding onium salts.
Meth yltr ip h en ylp h osp h on iu m tetr a flu or obor a te:25 1
H
NMR δ 2.88 (d, 3H, J HP ) 13.3 Hz), 7.55-7.85 (m, 15H); IR
νmax 1200-1000 (BF4-) cm-1; FABMS m/z 277 (M+ - BF4).
Meth yltr iph en ylar son iu m tetr aflu or obor ate:26 1H NMR
-
δ 2.84 (s, 3H), 7.60-7.85 (m, 15H); IR νmax 1200-1000 (BF4
)
cm-1; FABMS m/z 321 (M+ - BF4).
Meth yltr iph en ylstibon iu m tetr aflu or obor ate:26 1H NMR
δ 2.55 (s, 3H), 7.50-7.75 (m, 15H); FABMS m/z 369 (M+
-
BF4; 123Sb), 367 (M+ - BF4; 121Sb).
Rea ction of 1a w ith Meth yl Tr ifla te. To a CDCl3 solution
(0.50 mL) of 1a (10 mg, 0.023 mmol) was added methyl triflate
(11 µL, 1.0 mmol) at room temperature, and the resulting
solution was monitored by 1H NMR spectroscopy. No bismuth-
derived compound except for 1a was detected after 1 week at
room temperature.
Rea ction of 4a ,b w ith Tr ia r ylbism u th in es 1b,a . A
mixture of 4a (10.6 mg, 0.020 mmol), 1b (9.4 mg, 0.020 mmol),
and CDCl3 (0.50 mL) was allowed to stand in a sealed NMR
tube at room temperature, and the reaction course was
monitored by 1H NMR spectroscopy at several intervals. After
24 h, an equilibrium mixture consisting of four triaryl(methyl)-
bismuthonium salts 4a ,b,e,f (ca. 1:2:3:4) was formed with a
small amount of insoluble substance. Treatment of 4b (11.5
mg, 0.020 mmol) with 1a (8.6 mg, 0.020 mmol) in CDCl3 (0.50
mL) gave a similar equilibrium mixture after 24 h. Compounds
4e,f were assigned only by 1H NMR and FABMS spectroscopy
and have not been isolated. In the 1H NMR spectra of the
equilibrium mixtures, the bismuth-bound methyl peaks of 4a ,
4e, 4f, and 4b were observed at δ 3.25, 3.23, 3.21, and 3.19,
Syn th esis of Tr ia r yl(m eth yl)bism u th on iu m Tetr a flu o-
r obor a tes 4. Gen er a l P r oced u r e. To a stirred mixture of
triarylbismuth difluoride 2 (3.0 mmol), methylboronic acid 3
(2-3 equiv), and CH2Cl2 (40 mL) was added BF3‚OEt2 (0.46
mL, 3.5 mmol) at -20 °C. The mixture was stirred vigorously
for 12-14 h, during which time the temperature was gradually
warmed to room temperature. An aqueous solution (10 mL)
of NaBF4 (2.2 g, 20 mmol) was then added, and the resulting
two-phase solution was vigorously stirred for 30 s. The organic
phase was immediately separated, dried over MgSO4, and
evaporated under reduced pressure to leave an oily residue.
Fractional recrystallization of the residue from Et2O/CH2Cl2
(2:1) twice afforded triaryl(methyl)bismuthonium tetrafluo-
roborate 4 as a colorless solid. Meth yltr ip h en ylbism u th o-
respectively. In the FABMS spectra, the [Phn(4-MeC6H4)3-n
-
MeBi+] ion peaks derived from 4a , 4e, 4f, and 4b were
observed at 455 (n ) 3), 469 (n ) 2), 483 (n ) 1), and 497 (n
) 0). No reaction took place between tetrakis(4-methylphenyl)-
bismuthonium tetrafluoroborate and 1a in CDCl3 at room
temperature.
1
n iu m tetr a flu or obor a te (4a ): mp 137-139 °C; H NMR δ
Tetr a k is(4-m eth ylp h en yl)bism u th on iu m tetr a flu or o-
bor a te: mp 205-206 °C; 1H NMR δ 2.44 (s, 12H), 7.48 (d, 8H,
J ) 8.1 Hz), 7.64 (d, 8H, J ) 8.1 Hz); IR νmax 1487, 1447, 1391,
3.29 (s, 3H), 7.50-7.85 (m, 15H); 13C NMR δ 17.36, 131.82,
132.00, 135.67, 136.21; IR νmax 3050, 1568, 1474, 1429, 1325,
1298, 1200-950 (BF4-), 729, 695, 534, 523, 446 cm-1; FABMS
1312, 1280, 1210, 1188, 1150-950 (BF4-), 799, 519, 475 cm-1
;
m/z 455 (M+ - BF4), 363, 286, 209. Anal. Calcd for C19H18
BBiF4: C, 42.09; H, 3.35. Found: C, 42.02; H, 3.22.
-
FABMS m/z 573 (M+ - BF4), 391, 300, 209. Anal. Calcd for
28H28BBiF4: C, 50.93; H, 4.27. Found: C, 51.00; H, 4.24. This
C
Meth yltr is(4-m eth ylp h en yl)bism u th on iu m tetr a flu o-
r obor a te (4b): pasty solid; 1H NMR δ 2.42 (s, 9H), 3.23 (s,
3H), 7.41 (d, 6H, J ) 8.0 Hz), 7.59 (d, 6H, J ) 8.0 Hz); IR νmax
1576, 1561, 1487, 1450, 1437, 1391, 1306, 1279, 1240, 1177,
compound was synthesized from BF3‚OEt2, 1b, and 4-meth-
ylphenylboronic acid according to the reported procedure.13
Rea ction of 4a w ith Alcoh ols. Gen er a l P r oced u r e.
Alcohol 5 (0.15 mmol) was added to a mixture of 4a (11.4 mg,
0.021 mmol), 2,6-di-tert-butyl-4-methylpyridine 6 (4.6 mg,
0.022 mmol), and CDCl3 (0.50 mL) in an NMR tube, and the
1150-900 (BF4-), 830, 816, 785, 579, 534, 519, 469 cm-1
;
FABMS m/z 497 (M+ - BF4), 391, 300, 209. Due to the low
crystallinity of 4b, a trace amount of the tetrakis(4-meth-
ylphenyl)bismuthonium salt could not be removed completely.
1
resulting clear solution was monitored by H NMR spectros-
copy at 23 °C. The reaction was complete after 4-7 h.
Bismuthine 1a and pyridinium salt 8 were formed quantita-
tively. Ethers 7 were identified by NMR spectroscopy.
Tr is(4-m eth oxyph en yl)(m eth yl)bism u th on iu m tetr aflu -
or obor a te (4c): mp 156-159 °C (decomp); 1H NMR δ 3.17 (s,
3H), 3.84 (s, 9H), 7.10 (d, 6H, J ) 8.8 Hz), 7.63 (d, 6H, J ) 8.8
Hz); IR νmax 1585, 1487, 1440, 1389, 1307, 1296, 1210, 1200-
950 (BF4-), 791, 560, 532, 521, 480, 473, 430 cm-1; FABMS
1
Dim eth yl eth er (7a ): H NMR δ 3.32 (s, 6H).
Eth yl m eth yl eth er (7b):27 1H NMR δ 1.17 (t, 3H, J ) 7.0
Hz), 3.33 (s, 3H), 3.43 (q, 2H, J ) 7.0 Hz).
m/z 545 (M+ - BF4), 423, 316, 209. Anal. Calcd for C22H24
BBiF4O3: C, 41.80; H, 3.83. Found: C, 42.03; H, 3.80.
-
Isop r op yl m eth yl eth er (7c):27 1H NMR δ 1.16 (d, 6H,
J ) 6.0 Hz), 3.31 (s, 3H), 3.48 (sept, 1H, J ) 6.0 Hz).
Ben zyl m eth yl eth er (7d ):28 1H NMR δ 3.38 (s, 3H), 4.45
(s, 2H), 7.25-7.42 (m, 5H).
Tr is(2-m eth oxyph en yl)(m eth yl)bism u th on iu m tetr aflu -
or obor a te (4d ): 1H NMR δ 3.29 (s, 3H), 3.87 (s, 9H), 7.18
(dt, 3H, J ) 1.1, 7.4 Hz), 7.21 (d, 3H, J ) 8.4 Hz), 7.43 (d, 3H,
J ) 7.6 Hz), 7.61 (m, 3H); IR νmax 1570, 1460, 1428, 1298, 1269,
1231, 1175, 1157, 1150-900 (BF4-), 785, 752, 565, 534, 521,
475, 436 cm-1; FABMS m/z 545 (M+ - BF4), 423, 316, 209.
Anal. Calcd for C22H24BBiF4O3: C, 41.80; H, 3.83. Found: C,
41.59; H, 3.67. Compound 4d did not show a definite melting
point.
(25) Winter, C. H.; Veal, W. R.; Garner, C. M.; Arif, A. M.; Gladysz,
J . A. J . Am. Chem. Soc. 1989, 111, 4766.
(26) Schiemenz, G. P. J . Organomet. Chem. 1973, 52, 349.
(27) Nakao, R.; Fukumoto, T.; Tsurugi, J . J . Org. Chem. 1972, 37,
4349.
(28) Kotsuki, H.; Ushio, Y.; Yoshimura, N.; Ochi, M. J . Org. Chem.
1987, 52, 2594.

Triaryl(methyl)bismuthonium Salts
Organometallics, Vol. 19, No. 12, 2000 2263
2,6-Di-ter t-b u t yl-4-m et h ylp yr id in iu m t et r a flu or ob o-
r a te (8): 1H NMR δ 1.55 (s, 18H), 2.65 (s, 3H), 7.5 (s, 2H),
11.5 (s, 1H, NH).
1-(Meth ylth io)eth ylen eim in iu m tetr aflu or obor ate (10):
1H NMR δ 2.66 (s, 3H), 2.72 (s, 3H), 9.8 (br-s, 2H).
X-r a y Cr ysta llogr a p h ic An a lysis of Com p ou n d 4d . A
23
Rea ction of 4a w ith Wa ter . Water (2.0 µL, 0.11 mmol)
was added to a mixture of 4a (11.4 mg, 0.021 mmol), 6 (4.6
mg, 0.022 mmol), and CDCl3 (0.50 mL) in an NMR tube, and
the resulting solution was allowed to stand at room temper-
ature. After 33 h, methanol (5a ) and dimethyl ether (7a ) were
formed in 30% and 16% yield, respectively. Bismuthine 1a and
pyridinium salt 8 were formed quantitatively.
Kin etic Mea su r em en t on th e Rea ction of 5d w ith 4a
a n d MeOTf. Compound 4a (17.0 mg, 0.0314 mmol), 5d (50
µL, 0.483 mmol; 15 equiv), 6 (6.5 mg, 0.032 mmol), and CDCl3
(0.50 mL) were mixed well in an NMR tube. The reaction was
monitored at 23 °C by 1H NMR spectroscopy using the methyl
peaks of 4a and 7d as probes. The reaction followed pseudo-
first-order kinetics for up to 3-4 half-lives, and the pseudo-
first-order rate constant (kobsd) was estimated to be 2.9 × 10-4
s-1 (r2 ) 0.998). The reaction rate did not depend on the
concentration of 6 in the range of 0.063-0.32 M. Similar
pseudo-first-order kinetics were observed for the reaction of
MeOTf (3.6 µL, 0.032 mmol) with 5d (15 equiv) in the presence
of 6 (1 equiv) under the same conditions, and the kobsd was
estimated to be 1.3 × 10-4 s-1 (r2 ) 0.996).
colorless crystal of dimensions 0.20 × 0.20 × 0.08 mm, grown
from CH2Cl2/Et2O (1:1) at 4 °C, was used for X-ray crystal-
lographic analysis. Data were recorded at 27 °C on a Rigaku
AFC7S diffractometer with graphite-monochromated Mo KR
(λ ) 0.71069 Å) radiation, using the ω-2θ scan technique to
a maximum 2θ value of 55.0°. Scans of (1.05 + 0.30 tan θ)°
were made at a speed of 8.0° min-1. The intensities of three
representative reflections were measured after every 150
reflections. Over the course of data collection, the standards
decreased by 14.1%. A linear correction factor was applied to
the data to account for this phenomenon. An empirical
absorption correction based on azimuthal scans of several
reflections was applied, which resulted in transmission factors
ranging from 0.62 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
methods29 and expanded using the Fourier techniques.30 The
non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included but not refined. Neutral atom scattering
factors were taken from Cromer and Waber.31 Anomalous
32
dispersion effects were included in Fcalc
;
the values for ∆f ′
and ∆f′′ were those of Creagh and McAuley.33 The values for
the mass attenuation coefficients are those of Creagh and
Hubbel.34 All calculations were performed using the teXsan35
crystallographic software package of Molecular Structure
Corporation. Further details of the crystal structure are
provided as Supporting Information.
Rea ction of 4a w ith Sod iu m Ben zen esu lfin a te. A
mixture of 4a (28 mg, 0.052 mmol), sodium benzenesulfinate
dihydrate (52 mg, 0.26 mmol), and DMF (1 mL) was stirred
at room temperature for 2 h. Water (3 mL) and Et2O (3 mL)
were added, and the resulting two-phase solution was stirred
vigorously. The organic phase was separated, and the aqueous
phase was extracted with Et2O (3 mL × 2). The combined
organic extracts were washed with water (2 mL), dried over
MgSO4, and evaporated to leave a mixture of bismuthine 1a
(20.8 mg, 91%) and methyl phenyl sulfone (4.4 mg, 54%).
Rea ction of 4a w ith Sod iu m Ben zoa te. A mixture of 4a
(33 mg, 0.061 mmol), sodium benzoate (83 mg, 0.58 mmol),
and DMF (2 mL) was stirred at room temperature for 2 h.
Water (3 mL) and Et2O (3 mL) were added, and the resulting
two-phase solution was stirred vigorously. The organic phase
was separated, and the aqueous phase was extracted with
Et2O (3 mL × 2). The combined organic extracts were washed
with water (2 mL), dried over MgSO4, and evaporated to leave
a mixture of bismuthine 1a (26 mg, 97%) and methyl benzoate
(2.5 mg, 30%).
Ack n ow led gm en t. This work was partially sup-
ported by a Grant-in-Aid (No. 11120224) from the
Ministry of Education, Science, Sports and Culture of
J apan. The author thanks Mr. Hazumi Nomura for
X-ray crystallographic analysis.
Su p p or tin g In for m a tion Ava ila ble: Detailed X-ray crys-
tallographic data for 4d . This material is available free of
charge via the Internet at http://pubs.acs.org.
OM000095D
(29) 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.
(30) 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.
(31) Cromer, D. T.; Waber, J . T. In International Tables for X-ray
Crystallography, Vol. IV; The Kynoch Press: Birmingham, England,
1974; Table 2.2A.
(32) Ibers, J . A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(33) Creagh, D. C.; McAuley, W. J . In International Tables for
Crystallography, Vol. C; Wilson, A. J . C., Ed.; Kluwer Academic
Publishers: Boston, 1992; Table 4.2.6.8, pp 219-222.
Rea ction of 4a w ith DMF . A mixture of 4a (15.1 mg,
0.0279 mmol), DMF (10 µL, 0.26 mmol), and CDCl3 (0.50 mL)
was allowed to stand in an NMR tube at room temperature.
The reaction was complete within 1 h, and compound 9 and
bismuthine 1a were formed quantitatively.
1-Meth oxy-N,N-d im eth ylm eth ylen eim in iu m tetr a flu o-
r obor a te (9):21 1H NMR δ 3.22 (d, 3H, J ) 1.1 Hz), 3.44 (d,
3H, J ) 0.8 Hz), 4.43 (s, 3H), 8.56 (br s, 1H). When water (5
µL) was added to the resulting solution, 9 was immediately
converted to dimethylammonium salt and methyl formate.
Rea ction of 4a w ith Th ioa ceta m id e. To a CDCl3 solution
(0.50 mL) of 4a (14.5 mg, 0.0268 mmol) was added thioaceta-
mide (2.9 mg, 0.039 mmol), and the resulting mixture was
shaken quickly at room temperature. The reaction was com-
plete within a minute, and compound 10 and bismuthine 1a
were formed quantitatively.
(34) Creagh, D. C.; Hubbell, J . H. In International Tables for
Crystallography, Vol. C; Wilson, A. J . C., Ed.; Kluwer Academic
Publishers: Boston, 1992; Table 4.2.4.3, pp 200-206.
(35) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corporation: 1985 and 1992.