Bismuth(III) bis(trifluoromethanesulfonyl)amide

Article abstract of DOI:10.1016/S0022-1139(02)00122-7

Bismuth(III) bis(trifluoromethanesulfonyl)amide (Bi(NTf₂)₃, 3) has been prepared from the reaction of protiodemetallation of tri-p-tolylbismuth by a stoichiometric amount of bis(trifluoromethanesulfonyl)amine (1). The intermediates BiPh_3-n(NTf₂)_n (n=2 (4), 1 (5)) resulting from the reaction of 1 with triphenylbismuth have also been isolated. The amide 3 was able to catalyze the benzoylation and the benzenesulfonylation of toluene.

Full text of DOI:10.1016/S0022-1139(02)00122-7

Journal of Fluorine Chemistry 116 (2002) 129±134
Bismuth(III) bis(tri¯uoromethanesulfonyl)amide
a
Alexandre Picot , Sigrid R e pichet , Christophe Le Roux ,
a
a,*
a
Jacques Dubac , Nicolas Roques
b
a
Universit e Paul-Sabatier, H e t e rochimie fondamentale et appliqu e e (UMR-CNRS 5069),
18 route de Narbonne, 31062 Toulouse Cedex 04, France
Rhodia Chimie, Centre de Recherche de Lyon, 85avenue des FreÁres-Perret, 69192 Saint-Fons Cedex, France
1
b
Received 1 March 2002; received in revised form 16 May 2002; accepted 23 May 2002
Abstract
2 3
Bismuth(III) bis(tri¯uoromethanesulfonyl)amide (Bi(NTf ) , 3) has been prepared from the reaction of protiodemetallation of tri-p-
tolylbismuth by a stoichiometric amount of bis(tri¯uoromethanesulfonyl)amine (1). The intermediates BiPh3 (NTf ) (n ˆ 2 (4), 1 (5))
Àn
resulting from the reaction of 1 with triphenylbismuth have also been isolated. The amide 3 was able to catalyze the benzoylation and the
2 n
benzenesulfonylation of toluene.
#
2002 Elsevier Science B.V. All rights reserved.
Keywords: Bis(tri¯uoromethanesulfonyl)amine; Bismuth bis(tri¯uoromethanesulfonyl)amides; Methylbenzophenone; Methyldiphenyl sulfone; Triphenyl-
bismuth; Tri-p-tolylbismuth
1
. Introduction
2. Results and discussion
Initially synthesized in 1984 by DesMarteau and cow-
orkers [1a], bis(tri¯uoromethanesulfonyl)amine (Tf NH
First, we used the methods previously known for the
preparation of the alkaline earth, scandium and lanthanide
derivatives of 1 [2c,d,k]. But the reactions of 1 with Bi(III)
oxide or acetate in boiling water failed as no incorporation of
2
(
concerning the use of its metal derivatives [M(NTf ) ] as
1), Tf ˆ CF3SO2) has been the subject of numerous works
2
n
catalysts for organic reactions [1b,2]. In some cases, such
catalysts were more active than their tri¯ate analogues
the Tf N ligand at bismuth occured, even after prolonged
2
reaction time (12 h). The same result was obtained at a lower
temperature, in a water±ethanol mixture, a process used with
success for the preparation of 2 from Bi O [7].
[M(OTf) ], owing to a stronger Lewis acidity. Concur-
n
rently, our laboratories, and others, were involved in the
2
3
use of bismuth(III) tri¯uoromethanesulfonate (Bi(OTf) , 2)
3
Another method for the preparation of 2 is based on the
cleavage of the weak bismuth±carbon bonds in triphenyl-
as catalyst for organic reactions [3,4], and it has been
shown that 2 exhibits a higher catalytic activity than many
other metal tri¯ates. Thus, it seems likely that bismuth(III)
bis(tri¯uoromethanesulfonyl)amide [Bi(NTf ) (3)] could
bismuth by tri¯ic acid [8]. The reaction of 1 with Ph Bi in
3
3:1 molar ratio did not lead to the expected formation of 3
but to the mixed compound 4 (Scheme 1). In addition, when
2 (or 1) eq. of 1 were used, 4 (or 5) was produced.
2
3
be an ef®cient Lewis acid. The use of 3 (among many other
analogous derivatives) has been recently reported as a
catalyst for some organic reactions [2o,5]. However,
neither experimental procedure for its preparation nor its
characteristics were given. In this paper, we report our
results concerning the preparation of 3, and its use as
catalyst for the benzoylation and the benzenesulfonylation
of toluene [6].
These results indicate that the selective cleavage of the
two ®rst Bi±Cbonds in Ph 3Bi by 1 is possible (such
selectivity has already been observed with TfOH) [8,9],
but that 1, under the conditions used, is unreactive towards
the third Bi±Cbond present in 4 [10]. Amine 1 might not be
1
acidic enough to cleave this last Bi±Cbond. Effectively, the
1
Triflic acid is a ``superacid'' (H0 ˆ À14:1) [11]. For trifluorometha-
nesulfonyl analogues (CF
3
SO
2
)
n
XH (X ˆ O, N (1), C; n ˆ 1,2,3 res-
pectively), the acidity order in gas phase is Tf3CH > 1 > TfOH [12].
In liquid phase, this order is reversed [13], and 1 has a pK in water of
1.7 [1b] which is considerably higher than TfOH estimated to be
a
*
Corresponding author. Tel.: ‡33-561-55-6557; fax: ‡33-561-55-8204.
E-mail address: leroux@chimie.ups-tlse.fr (C.L. Roux).
around À10 [14].
0022-1139/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 1 2 2 - 7

130
A. Picot et al. / Journal of Fluorine Chemistry 116 (2002) 129±134
Scheme 1.
addition of 1 on PhBi(OTf) (6) led to unchanged products
2
would be due to a strong tendency to hydrolysis of the
3
‡
after standing 72 h at RT, conversely to TfOH which is able
to substitute this last phenyl group giving 2 [8]. However,
under the same conditions, TfOH was unable to substitute
the last phenyl group in 4. This shows that the electron
withdrawing power of the Tf N ligands in 4 deactivates
2
the phenyl group more strongly than the TfO ligands in 6.
In addition, steric crowding around the bismuth center due
Bi
cations (pKh > 4) [17], such as Li , Mg , C a , Ba
cation (pKh ˆ 1:09) [16]. With non-hydrolysable
‡ 2‡ 2‡ 2‡
,
Sc , Zn , or Ln [16], metal derivatives of 1 are water
3
‡
2‡
3‡
stable [2a,c,d,h,k,13]. In the case of compound 3 in the
‡
presence of water, the formation of H O ions resulting from
3
3‡
the hydrolysis of Bi cation (Eq. (2)) [7,16], leads to the
À
protonation of the Tf N anion with formation of 1:
2
to two bulky Tf N ligands and hypervalent interactions
2
3
‡
ꢀ3xÀy†‡
y
‡ yH‡
On the contrary, owing to the stronger acidity of TfOH
between the bismuth and sulfonyl oxygen atoms would
probably contribute to the enhanced stability of 4.
xBi ‡ yH O „ ‰Bi ꢀOH† Š
(2)
2
x
It is known that the electrophilic demetallation of electron
rich aromatic groups occurs more easily than that of a non-
activated phenyl group [15]. We tried the reaction of 1 with
tri-p-tolylbismuth in 3:1 molar ratio, under the same experi-
mental conditions, i.e. in dichloromethane as solvent and at
moderate temperature (À78 8Cto RT). This reaction was
complete, leading to the substitution of the three tolyl groups
À
with respect to that of Tf NH, TfO anion is not protonated
2
in the same conditions. Consequently, the synthesis of 2
becomes possible in the presence of water because, despite
the hydrolysis of the Bi cation, this salt is recoverable
either by elimination of water [7], or from concentrated
solution of TfOH [18].
3
‡
Compound 3 shows characteristic spectral data of analo-
gous metal amides [1b,2]: strong infrared absorptions at
bonded to bismuth by the Tf N ligands (Eq. (1)):
2
À1
CH2Cl2
1450 and 1230 cm assigned to the SO stretching, and
2
typical 13Cand 19F NMR signals of tri¯uoromethyl groups
ꢀ
p-MeC H † Bi ‡ 3Tf NH
!
BiꢀNTf † ‡ 3PhMe
6
4 3
2
1
2 3
ꢁ
À78 Cto RT
3
(see below). In this respect, silicon derivatives of 1 with
(1)
bulky trialkylsilyl substituents can exist in the tautomeric
O-silyl form [2m]. As compounds 3±5 show only one 19F
NMR signal one can predict that they exist in the N-bismuth
form in which the tri¯uoromethyl groups are equivalents.
This is the usual form of metal derivatives of 1 [2].
Bismuth amide 3 is an highly moisture sensitive com-
pound, fuming in air, which decomposes in the presence of
water with the formation of 1. This sensitivity, which
explains the previous failures in the presence of water,
Fig. 1. Catalysis of the benzoylation of toluene. Conditions: temperature 110 8C(oil bath); reactants: (PhCO)
in methylbenzophenone (10).
2
O, 1 eq.; toluene, 10 eq.; catalyst, 0.1 eq. Yield

A. Picot et al. / Journal of Fluorine Chemistry 116 (2002) 129±134
131
3
Fig. 2. Catalysis of the benzoylation of toluene. Conditions: temperature 110 8C (oil bath); reactants: PhCOCl, 1 eq., toluene, 10 eq.; catalyst: Bi(OTf) and
Bi(NTf ) , 0.1 eq.; AgNTf and Tf NH, 0.3 eq. Yield in methylbenzophenone (10).
2 3 2 2
Consequently, any synthesis or study of 3 (or other Bi-
derivatives of 1), must be carried out in strictly anhydrous
conditions. In preliminary experiments, the catalytic activity
of bismuth amides 3 and 4 has been tested in the benzoyla-
tion of toluene, a more dif®cult acylation than that of
aromatic ethers [20]. We observed that methylbenzophenone
AgOTf, are known to give this ligand exchange with an acid
halide (Eq. (3)) [3b,4f,21]. Effectively, the two kinetic
curves for 3 and 7 were similar (Fig. 2).
MꢀNTf † ‡ n PhCOCl ! MCl ‡ n PhCONTf
(3)
2 n
n
2
8
(
re¯ux for 5 h with benzoic anhydride in the presence of 3
10) was produced in 80% yield when toluene was reacted at
n ˆ 3, M ˆ Bi (3); n ˆ 1, M ˆ Ag (7).
In the second step, amide 8 would be responsible for the
benzoylation of toluene with formation of 1 (Scheme 2). The
regeneration of 8 (Step 3) could be achieved either by
reaction of 1 with PhCOCl (proton mediated pathway) or
(
toluene/(PhCO) O/3 ˆ 4/1/0.1 (mol)).
2
An excess of toluene with respect to the acylating agent
10/1) allowed a rather slow and easily monitored reaction.
In these conditions, using (PhCO) O as reagent (Fig. 1), 4
(
with BiCl
, via 3 (and/or mixed species Bi(NTf
)3Àn Cl
,
n
2
3
2
appeared as a better catalyst than 6, in agreement with their
relative Lewis acid strength. However, activities of 2 and 3
2
were similar. On the contrary, using benzoyl chloride as
reagent, a discrimination between 2 and 3 was observed
n ˆ 1 or 2; metal mediated pathway) (Scheme 3) [3b,4f].
An additional experiment was carried out in the presence
of 1 (30 mol%). The reaction was slower than in the pre-
sence of 3, but the yield after 4 h heating was similar (Fig. 2).
This result shows that: (i) the exchange reaction 3 is faster
than the reaction between 1 and PhCOCl; (ii) in the 3 (or 7)-
catalyzed reaction, the proton mediated pathway is predo-
minant or the only one.
(
Fig. 2). Following our mechanistic study of Friedel-Crafts
acylation in the presence of 2 [4f], we think that a ligand
exchange occurs between 3 and BzCl, giving BiCl and
3
N,N-bis(tri¯uoromethanesulfonyl)benzamide (8; Step 1;
3
Eq. (3)). This latter, acylation agent less powerful than a
For a reaction in which 1 is not a catalyst, only the metal
mediated pathway would be involved. We have found such
an example using benzenesulfonyl chloride instead of ben-
zoyl chloride. The 3-catalyzed benzenesulfonylation of
À
À
mixed anhydride as PhCOOTf (formed by TfO /Cl
exchange between 2 and PhCOCl [3b,4f]), gave a slower
rate of benzoylation. Weight was given to this hypothesis by
comparing the catalytic activity of 3 (10 mol%) with that of
toluene (toluene:PhSO
Cl:3 ˆ 10:1:0.05 (mol); re¯ux,
2
AgNTf (7; 30 mol%). Silver salts of this type, such as
2
5 h) led to methyldiphenyl sulfone (11) in 40% yield,
whereas 1 (15 mol%) appeared inactive under the same
conditions. In this case, the active species formed (analogous
to 8) from the bismuth mediated pathway would be the
sulfonamide PhSO NTf (9; Scheme 2) [21c], and the
2
An intermolecular carbonyl±bismuth interaction has been observed
O and 3 by 13C NMR. The mixture showed a down-
between (PhCO)
field shift of the 13CO signal from 164 ppm ((PhCO)
2
2
2
2
O alone) to
78 ppm (solvent nitromethane). A comparable deshielding has also
mechanism could be comparable to that previously
described for the same reaction in the presence of 2 [3f].
The use of 7 (15 mol%) gave only 15% yield, corresponding
to the amount of 9 due to the reaction between 7 and
1
been observed for a (PhCO)
2
O/2 mixture (Dd ˆ 13 ppm) [3b].
3
À
À
The Tf
Bi(NTf
(3) ‡ p-MeC
MeC COCl on the other hand, using nitromethane as solvent. The
substitution has been characterized by 1H NMR at RT (internal
standard CD NO ): aromatic protons: p-MeC COCl, d 7.32 and
CONTf , d 7.46 and
2
N /Cl ligand exchange was identified from mixtures,
2
)
3
6
H
4
COCl on one hand and AgNTf
2
ꢀ7† ‡ p-
6
H
4
PhSO Cl, and consequently, without possibility of a silver
2
mediated pathway.
As a result of this work, and also of our recent mechanistic
studies about the behavior of 2 in Friedel-Crafts acylation
3
2
6 4
H
3
7
8
.92 ppm (doublets, J ˆ 8:2 Hz); p-MeC
6
H
4
2
3
.15 ppm (doublets, J ˆ 7:8 Hz).

132
A. Picot et al. / Journal of Fluorine Chemistry 116 (2002) 129±134
Scheme 2.
Scheme 3.
À1
and related reactions [4f], it is evident from this that for
À
obtained as a beige solid. IR (CCl ): nꢀcm † ˆ 1450 (s),
4
À
À
reactions involving a Cl /TfO or Tf N ligand exchange
2
1440 (sh), 1348 (m), 1304 (m), 1251 (sh), 1230 (vs), 1218
(sh), 1132 (vs), 1109 (sh), 1047 (m), 894 (w), 855 (m), 656
between 2 or 3 and a chlorinating agent, the catalytic systems
BiCl /3 TfOH or BiCl /3 Tf NH led to similar results as those
(w), 608 (s), 573 (sh), 502 (m). NMR (acetone-d ): 13C
3
3
2
6
1
ˆ 321 Hz); 19F
obtained with 2 or 3, respectively. However, the synthesis of
these two compounds becomes necessary in all other cases,
and further studies of their catalytic activity in organic
reactions is currently in progress in our laboratories.
(50.3 MHz): d ˆ 120 ppm (quad., J
13C=19
F
(75.4 MHz): dꢀfrom CF COOH† ˆ À1:77 ppm; ¯uorine
3
content (18 atoms per mol) was determined using tri¯uor-
otoluene as 19F-standard.
3.2. Gravimetric determination of bismuth content in 3
3
. Experimental
An indirect but ef®cient method was applied. We have
found that chlorotrimethylsilane reacted quantitatively with
The following experiments have been carried out under
dry atmosphere (argon or nitrogen) using a glove box and
vacuum line technique.
3 in toluene to give BiCl and Me SiNTf (12) via a ligand
3
3
2
exchange reaction (Eq. (4)). After hydrolysis, bismuth(III)
chloride gave bismuth oxychloride (BiOCl) as an insoluble
powder that was weighted.
3
.1. Bismuth(III) bis(trifluoromethanesulfonyl)amide (3)
Toluene; RT
!
In a 100 ml Schlenck tube were introduced 480 mg
1 mmol) of tri-p-tolylbismuth [19] and 10 ml of anhydrous
BiꢀNTf2† ‡ 3Me3SiCl
BiCl3 ‡ 3Me3SiNTf2 (4)
12
n
(
dichloromethane. The ¯ask was immersed in an acetone/dry
ice bath and 850 mg (3 mmol) of 1 dissolved in 15 ml of
anhydrous dichloromethane were introduced under mag-
netic stirring via a syringe. After 10 min the bath was
removed and the reaction was stirred at RT for 10 h. Then
In a Schlenck tube, were successively introduced 15 ml of
anhydrous toluene and 1.480 g (1.41 mmol) of 3. An excess
of chlorotrimethylsilane (3 ml) was added dropwise under
stirring via a syringe. The 29Si NMR monitoring indicated
the formation of 12 [2i,m]. After 1 h of stirring at RT, the
volatile materials were eliminated under reduced pressure.
The residue was hydrolyzed (NaOH 1 M), and the mixture
was centrifuged. The white powder formed was extracted,
washed twice with distillated water and acetone, and dried at
5
0 ml of anhydrous pentane were added and the supernate
removed via a syringe. This procedure was repeated twice.
The solvents were eliminated under reduced pressure and,
after 1 h heating at 50 8C, 3 (1.01 g; 96% yield) was

A. Picot et al. / Journal of Fluorine Chemistry 116 (2002) 129±134
133
(
(
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j) N. Kuhnert, J. Peverley, J. Robertson, Tetrahedron Lett. 39 (1998)
1
3
00 8Cunder reduced pressure. Mass of BiO Cl obtained:
68 mg. Bi% for 3: calcd., 19.91; found, 19.95.
3
215±3216;
k) K. Mikami, O. Kotera, Y. Motoyama, M. Tanaka, Inorg. Chem.
(
3.3. Phenylbismuth bis(trifluoromethanesulfonyl)
amide (4) and diphenylbismuth
bis(trifluoromethanesulfonyl)amide (5)
Commun. 1 (1998) 10±11;
(l) J. Nishido, H. Nakajima, T. Saeki, A. Ishii, K. Mikami, Synlett
(
1998) 1347±1348;
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06±512;
(
5
Using the same procedure as above, triphenylbismuth and 2
or 1) eq. of 1, the product 4 (resp. 5) has been isolated in
(
(
n) J. Nie, J. Xu, G. Zhou, J. Chem. Res. S (1999) 446±447;
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(
almost quantitative yield as a white powder. 4: NMR (acet-
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Laporterie, J. Dubac, Tetrahedron Lett. 38 (1997) 8871±8874;
1
one-d ): H (400 MHz): aromatic protons, d ˆ 7:60 (H para,
6
(
b) S. R e pichet, C. Le Roux, J. Dubac, J.-R. Desmurs, Eur. J. Org.
Chem. (1998) 2743±2746;
c) B. Garrigues, F. Gonzaga, H. Laurent-Robert, J. Dubac, J. Org.
1
8
H, J ˆ 7:5 and 1.2 Hz), 8.32 (H meta, 2 H, J ˆ 7:5 and
13
.3 Hz), 9.21 ppm (H ortho, 2 H, J ˆ 8:3 and 1.2 Hz); C :
13
C=
(
1
d ˆ 120 ppm (quad., CF , J 19 ˆ 321 Hz), aromatic car-
3
F
Chem. 62 (1997) 4880±4882;
1
9
bons: 130.7, 135.1, 138.8 ppm (C
not observed); F:
(d) H. Laurent-Robert, C. Le Roux, J. Dubac, Synlett (1998) 1138±
ipso
1
1
140;
e) C. Le Roux, L. Ciliberti, H. Laurent-Robert, A. Laporterie, J.
Dubac, Synlett (1998) 1249±1251;
f) S. R e pichet, C. Le Roux, J. Dubac, J. Org. Chem. 64 (1999)
d ˆ À2:1 ppm. 5: NMR (acetone-d ): H: aromatic protons,
6
(
d ˆ 7:50 (H para, 2 H, J ˆ 7:5 and 1.2 Hz), 7.89 (H meta,
4
H, J ˆ 7:8 and 7.5 Hz), 8.52 ppm (H ortho, 4 H, J ˆ 7:8
(
1
3
1
13
and 1.2 Hz); C: d ˆ 121 ppm (quad., CF ,
J
21 Hz), aromatic carbons: 131.3, 133.7, 138.6 ppm (C
19
ˆ
3
C=
F
6479±6482;
3
(g) A. Orita, C. Tanahashi, A. Kakuda, J. Otera, Angew Chem. Int.
Ed. 39 (2000) 2877±2879;
ipso
1
9
not observed); F: d ˆ À1:79 ppm.
(
h) H. Laurent-Robert, B. Garrigues, J. Dubac, Synlett (2000) 1160-
162; Err. (2001) 564;
i) Y. Torisawa, T. Nishi, J.-i. Minamikawa, Org. Process Res. Dev. 5
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1
3
.4. Benzoylation and benzenesulfonylation of toluene
(
(
These reactions were carried out under experimental
1
conditions similar to that previously described using 2 as
catalyst [3b,f]. Methylbenzophenone (10) and methyldiphe-
nyl sulfone (11) were obtained as mixtures of isomers: o-10/
m-10/p-10 ˆ 16/4/80 (from PhCOCl), 20/4/76 (from
(
Mohan, Synthesis (2001) 2091±2094.
[
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11, Pergamon Press, New York, 1995, pp. 487±513;
(
PhCO) O) and o-11/m-101p-11 ˆ 39/6/55 (from PhSO Cl).
2
2
(
(
(
(
b) H. Suzuki, T. Ikegami, Y. Matano, Synthesis (1997) 249±267;
c) J.A. Marshall, Chemtracts 10 (1997) 1064±1075;
d) S. Vidal, Synlett (2001) 1194±1195;
Acknowledgements
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Support of this work by the Centre National de la
Recherche Scienti®que and Rhodia Organique Fine are
gratefully acknowledged.
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