A new convenient synthesis of triarylbismuthanes bearing three different aryl groups by the grignard arylation of unsymmetrical diarylbismuth triflate-hexamethylphosphoric triamide (HMPA) complexes

Article abstract of DOI:10.1021/om9509709

Triarylbismuthanes bearing three different aryl groups, Ar¹Ar²Ar³Bi (4), have been conveniently synthesized by the action of aryl Grignard reagent Ar³-MgBr on unsymmetrical diarylbismuth triflate-HMPA complexes Ar¹Ar²BiOTf(HMPA)₂ (8), which are readily accessible by the selective cleavage of triarylbismuthanes Ar¹₂Ar²Bi (7; Ar¹ is more fugacious than Ar²) with trimethylsilyl triflate in the presence of HMPA.

Full text of DOI:10.1021/om9509709

Organometallics 1996, 15, 1951-1953
1951
Notes
A New Con ven ien t Syn th esis of Tr ia r ylbism u th a n es
Bea r in g Th r ee Differ en t Ar yl Gr ou p s by th e Gr ign a r d
Ar yla tion of Un sym m etr ica l Dia r ylbism u th
Tr ifla te-Hexa m eth ylp h osp h or ic Tr ia m id e (HMP A)
Com p lexes
Yoshihiro Matano,* Takashi Miyamatsu, and Hitomi Suzuki*,†
Department of Chemistry, Graduate School of Science, Kyoto University,
Sakyo-ku, Kyoto 606-01, J apan
Received December 18, 1995X
Sch em e 1
Summary: Triarylbismuthanes bearing three different
aryl groups, Ar1Ar2Ar3Bi (4), have been conveniently
synthesized by the action of aryl Grignard reagent Ar3-
MgBr on unsymmetrical diarylbismuth triflate-HMPA
complexes Ar1Ar2BiOTf(HMPA)2 (8), which are readily
accessible by the selective cleavage of triarylbismuthanes
Ar12Ar2Bi (7; Ar1 is more fugacious than Ar2) with
trimethylsilyl triflate in the presence of HMPA.
In tr od u ction
In the present work, this selective dearylation-
rearylation methodology for the synthesis of chiral
triarylbismuthanes has been further elaborated into the
use of diarylbismuth triflate-HMPA (HMPA ) hexa-
methylphosphoric triamide) complexes 6 and 8 as the
key intermediate (Scheme 2). These triflates are readily
accessible in a high state of purity by the cleavage of
the respective triarylbismuthanes 5 and 7 with tri-
methylsilyl triflate in the presence of HMPA. They are
stable enough to be handled in open air, are soluble in
most common organic solvents, and can be stored
without change in a refrigerator.
Although many examples have been reported of chiral
organophosphorus(III), organoarsenic(III), and orga-
noantimony(III) compounds, the literature to date con-
tains very few descriptions of chiral organobismuth(III)
compounds.1,2 This would mainly be due to the lack of
reliable approaches to such compounds because of their
greater instability as compared with those derived from
other pnicogen elements.
In 1983, Bras et al. first prepared tertiary bismuth-
anes having three different organyl substituents by the
reaction of ArAr′BiBr with an appropriate aryl Grignard
reagent, but their isolated yields were low to moderate
(10-55%).1a We have recently reported a general
methodology for the synthesis of chiral triarylbismuth-
anes 4 based on intramolecular coordination by a
sulfonyl group.1b In this method, the 2-(tert-butylsul-
fonyl)phenyl group ()Ar ) plays an important role, in
which this auxiliary aryl group not only assures the
selective iododearylation of triarylbismuthane (1) to
diarylbismuth iodide (2) but leaves preferentially from
bismuthane 3 in the final ligand exchange step, leading
to the required chiral triarylbismuthane 4 (Scheme 1).
Resu lts a n d Discu ssion
Syn th esis of Diar ylbism u th Tr iflate-HMP A Com -
p lexes 6. Bismuth compounds of the type Ar2BiX have
usually been prepared by the redistribution reaction
between Ar3Bi and BiX3, where X denotes a halogen
atom other than fluorine.3 Although quite easy to effect,
this methodology has an intrinsic disadvantage; it is
based on the equilibration among four different bismuth
compounds ArnBiX3-n (n ) 0-3) in a given solution;
thus, it is often difficult to obtain the required Ar2BiX
in high yield and in a high state of purity.4
An alternative approach to this type of compound
involves the selective cleavage of triarylbismuthanes
with an appropriate acid reagent. Although some-
what limited in scope, this methodology can provide the
required Ar2BiX in a 100% pure form. As an acid
reagent, trimethylsilyl triflate (Me3SiOTf) proved to be
† E-mail: suzuki@kuchem.kyoto-u.ac.jp.
X Abstract published in Advance ACS Abstracts, March 1, 1996.
(1) ArAr′Ar′′Bi type of compounds: (a) Bras, P.; Van Der Gen, A.;
Wolters, J . J . Organomet. Chem. 1983, 256, C1. (b) Suzuki, H.;
Murafuji, T. J . Chem. Soc., Chem. Commun. 1992, 1143.
(2) ArAr′BiX (X ) halogen or oxygen) type of compounds: (a) Bras,
P.; Herwijer, H.; Wolters, J . J . Organomet. Chem. 1981, 212, C7. (b)
Yamamoto, Y.; Chen, X.; Kojima, S.; Ohdoi, S.; Kitano, M.; Doi, Y.;
Akiba, K.-y. J . Am. Chem. Soc. 1995, 117, 3922. (c) Chen, X.; Ohdoi,
K.; Yamamoto, Y.; Akiba, K.-y. Organometallics 1993, 12, 1857. (d)
Yamamoto, Y.; Chen, X.; Akiba, K.-y. J . Am. Chem. Soc. 1992, 114,
7906. (e) Chen, X.; Yamamoto, Y.; Akiba, K.-y.; Yoshida, S.; Yasui, M.;
Iwasaki, F. Tetrahedron Lett. 1992, 33, 6653. (f) Murafuji, T.; Mutoh,
T.; Satoh, K.; Tsunenari, K.; Azuma, N.; Suzuki, H. Organometallics
1995, 14, 3848. (g) Murafuji, T.; Azuma, N.; Suzuki, H. Organometallics
1995, 14, 1542. (h) Suzuki, H.; Murafuji, T.; Matano, Y.; Azuma, Y. J .
Chem. Soc., Perkin Trans. 1 1993, 1169.
(3) For a review, see: Freedman, L. D.; Doak, G. O. Chem. Rev. 1982,
82, 15.
(4) For example, stirring a 2:1 mixture of tris(4-methylphenyl)-
bismuthane and BiCl3 in diethyl ether for 5 h at room temperature
gave the corresponding diarylbismuth chloride, arylbismuth dichloride,
and unreacted bismuthane in the ratio 74:7:19.
0276-7333/96/2315-1951$12.00/0 © 1996 American Chemical Society

1952 Organometallics, Vol. 15, No. 7, 1996
Notes
Sch em e 2
the former methodology to construct the bismuthane
unit Ar12Ar2Bi (7). Treatment of 6 with an excess of
Ar2MgBr in THF at 0 °C readily gave 7 in good yield
(Scheme 2). Although the reaction was accompanied to
some extent by concurrent disproportionation of bis-
muthanes, the analytically pure product was easily
obtained by recrystallization from MeOH. The previ-
ously unknown bismuthanes Ar12Ar2Bi (7) were char-
acterized by NMR, MS, and IR.
Syn th esis of Un sym m etr ica l Dia r ylbism u th Tr i-
fla te-HMP A Com p lexes 8. Mixed triarylbismuth-
anes 7 were easily transformed into unsymmetrical
diarylbismuth triflates 8, as shown in Scheme 2. The
more electron-rich aryl group was preferentially re-
moved from 7, in accord with the general pattern of the
nucleophilic exchange of aromatic ligands. The spectral
features of 8 are almost the same as those of 6,
suggesting that compound 8 also possesses the pseudo
trigonal bipyramidal structure at the bismuth center.
The triflates 8 are stable in the solid state, but they
undergo slow redistribution in solution.
Syn th esis of Un sym m etr ica l Tr ia r ylbism u th -
a n es 4. Unsymmetrical diarylbismuth triflate-HMPA
complexes 8 were treated with an excess of an appropri-
ate aryl Grignard reagent in THF at 0 °C in a manner
similar to that used for the synthesis of mixed triaryl-
bismuthanes 7. Disproportionation of bismuthanes
during the Grignard arylation was insignificant, and the
required bismuthanes 4 were easily isolated in pure
form by recrystallization from MeOH.
Attempts to convert these bismuthanes into bismu-
thonium compounds bearing four different aryl groups
attached to the bismuth atom and resolve the latter into
the respective optical antipodes for the first time are
now under way.
In conclusion, triarylbismuthanes 4 having three
different aryl groups were conveniently prepared by the
action of an appropriate aryl Grignard reagent on the
unsymmetrical diarylbismuth triflate-HMPA com-
plexes. This new approach circumvents the use of
diarylbismuth halides, which are moisture-sensitive and
often difficult to obtain in a high state of purity.
the most satisfactory for our purpose. Thus, the reac-
tion of Ar13Bi (5) with Me3SiOTf in the presence of two
equiv of HMPA in CH2Cl2/MeOH at room temperature
led to the quantitative formation of Ar12BiOTf(HMPA)2
6 within a few hours (Scheme 2). In this reaction, triflic
acid, generated in situ from Me3SiOTf and MeOH,
cleaves the C-Bi bond of 5 to give 6.
The complexes 6 are stable colorless crystals or oils,
readily soluble in CH2Cl2, CHCl3, benzene, THF, and
MeOH without decomposition. When left in air, some
of these complexes slowly absorbed moisture to form the
monohydrate Ar12BiOTf(HMPA)2(H2O). A similar reac-
tion carried out in the absence of HMPA afforded the
Ar12BiOTf-MeOH complexes, which were less stable in
open air as compared to 6. The HMPA ligand is
apparently more effective in protecting the triflates from
hydrolysis by atmospheric moisture.
The compounds 6 exhibited some characteristic spec-
1
tral features; H NMR spectra showed a signal due to
the ortho protons of the aromatic rings at appreciably
lower field (δ 8.17-8.37) as compared to those of 5 (δ
7.6-7.8). The methyl protons of HMPA in 6 were
observed at slightly higher field (δ 2.42-2.53) than those
of free HMPA (δ 2.63). In the IR spectra, broad intense
bands due to the triflate group appeared in the range
1350-1100 cm-1. FAB mass spectra displayed a strong
peak due to the M+-OTf and/or M+-(OTf, HMPA)
fragments in support of the cationic nature of the
bismuth center. Norman et al. have earlier reported the
synthesis of a similar type of complex Ph2BiBF4-
(HMPA)2 and elucidated its X-ray structure, in which
the central bismuth atom was found to possess a pseudo
trigonal bipyramidal structure.5 On the basis of the
spectral features as well as structural analogy, the
geometry around the bismuth center of 6 may be taken
to be pseudo trigonal bipyramidal, with two aryl groups
and a pair of electrons at the equatorial positions and
two HMPA ligands at both axial positions. Then, the
complex 6 would provide another example of a cationic
trivalent bismuth compound with a slightly nucleophilic
counteranion.
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions were carried out under
an argon atmosphere. Dichloromethane (CH2Cl2) and tetrahy-
drofuran (THF) were distilled under argon from CaH2 and
sodium benzophenone ketyl, respectively, before use. Other
reagents were used as commercially received. All melting
points were determined on a Yanagimoto hot-stage apparatus
and are uncorrected. 1H NMR was recorded on a Varian
Gemini-200 (200 MHz) or J EOL J NM R 500 (500 MHz)
spectrometer in CDCl3 with tetramethylsilane as an internal
standard. Coupling constants are given in Hz. IR spectra
were observed on a Shimadzu FTIR-8100S spectrophotometer.
EIMS spectra at 70 eV were obtained on a Shimadzu GCMS-
QP2000A spectrometer and FABMS spectra 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.
Syn th esis of Mixed Tr ia r ylbism u th a n es 7. Mixed
triarylbismuthanes of the type Ar12Ar2Bi (7) have been
prepared by a reaction between Ar12BiX and Ar2M or
between Ar12BiM and Ar2X, where X is a halogen and
M is Li, Na, K, or MgBr.3 In the present study, we used
(5) (a) Carmalt, C. J .; Norman, N. C.; Orpen, A. G.; Stratford, S. E.
J . Organomet. Chem. 1993, 460, C22. (b) Carmalt, C. J .; Cowley, A.
W.; Decken, A.; Norman, N. C. J . Organomet. Chem. 1995, 496, 59. (c)
Clegg, W.; Elsegood, M. R. J .; Errington, R. J .; Fisher, G. A.; Norman,
N. C. J . Mater. Chem. 1994, 891. (d) Clegg, W.; Errington, R. J .; Fisher,
G. A.; Flynn, R. J .; Norman, N. C. J . Chem. Soc., Dalton Trans. 1993,
637. (e) Clegg, W.; Errington, R. J .; Fisher, G. A.; Hockless, D. C. R.;
Norman, N. C.; Orpen, A. G.; Stratford, S. E. J . Chem. Soc., Dalton
Trans. 1992, 1967.
P r ep a r a tion of Dia r ylbism u th Tr ifla te-HMP A Com -
p lexes 6. Gen er a l P r oced u r e. To a stirred solution of the
bismuthane 5 (10 mmol) in HMPA (3.5 mL, 20 mmol)/CH2Cl2
(50 mL)/MeOH (5 mL) was added Me3SiOTf (1.9 mL, 10 mmol)
at 0 °C, and the resulting mixture was stirred for 0.5-2 h at
room temperature to complete the reaction. The solvent was

Notes
Organometallics, Vol. 15, No. 7, 1996 1953
removed under reduced pressure to give pure 6 as an oily
residue or a crystalline solid in quantitative yield.
Hz); EIMS (m/ z) 322, 320, 316, 209; IR (KBr) 1568, 1460, 1426,
1269, 1230, 1177, 1161, 1115, 1090, 1051, 1020, 1005, 810, 785,
Dip h en ylbism u th tr ifla te-HMP A com p lex (6a ): yield
100%. 1H NMR δ 2.52 (d, 36H, J ) 9.7 Hz), 7.38 (t, 2H, J )
7.4 Hz), 7.70 (t, 4H, J ) 7.6 Hz), 8.29 (d, 4H, J ) 7.9 Hz);
FABMS (m/ z) 721 (M+ - OTf), 542, 465, 388, 363, 286, 209,
180, 179, 135; IR (KBr) 2900, 1500-1430, 1330-1290, 1260-
756, 714 cm-1
. Anal. Calcd for C20H18BiClO2: C, 44.92; H,
3.39. Found: C, 45.32; H, 3.34.
P r ep a r a tion of Un sym m etr ica l Dia r ylbism u th Tr i-
fla te-HMP A Com p lexes 8. Compounds 8a ,b were prepared
from 7a ,b according to the same procedure used for the
preparation of 6.
1050, 1032, 990, 752, 733, 696, 639 cm-1
C
.
Anal. Calcd for
25H46BiF3N6O5P2S: C, 34.49; H, 5.33; N, 9.65. Found: C,
34.00; H; 5.17; N, 9.48.
(4-Ch lor op h en yl)(2-m eth ylp h en yl)bism u th tr ifla te-
HMP A com p lex (8a ): yield 100%. 1H NMR δ 2.52 (d, 36H, J
) 9.6 Hz), 2.67 (s, 3H), 7.33 (dt, 1H, J ) 1.6, 7.4 Hz), 7.43 (dt,
1H, J ) 1.5, 7.6 Hz), 7.60 (dd, 1H, J ) 1.6, 7.6 Hz), 7.65 (d,
2H, J ) 8.3 Hz), 8.20 (d, 2H, J ) 8.3 Hz), 8.35 (dd, 1H, J )
Bis(2-m eth ylp h en yl)bism u th tr ifla te-HMP A com p lex
(6b): yield 100%. 1H NMR δ 2.42 (d, 36H, J ) 9.7 Hz), 2.65
(s, 6H), 7.36 (dt, 2H, J ) 1.4, 7.4 Hz), 7.44-7.64 (m, 4H), 8.32
(dd, 2H, J ) 1.4, 7.4 Hz); FABMS (m/ z) 570 (M+ - OTf,
HMPA), 479, 391, 388, 300, 209, 180, 179, 135; IR (KBr) 1464,
1.5, 7.4 Hz); FABMS (m/ z) 771 (M+ - OTf, 37Cl), 769 (M+
-
OTf, 35Cl), 592, 590, 501, 499, 479, 413, 411, 388, 209, 179; IR
(neat) 1470, 1294, 1267, 1192, 1163, 1090, 1036, 990, 810, 752,
714 cm-1. Anal. Calcd for C26H47BiClF3N6O5P2S + H2O: C,
33.32; H, 5.26; N, 8.96. Found: C, 33.18; H, 5.16; N, 9.26.
1300-1250, 1200-1150, 1034, 981, 750, 638 cm-1
. Anal.
Calcd for C27H50BiF3N6O5P2S: C, 36.08; H, 5.61; N, 9.35.
Found: C, 35.82; H, 5.52; N, 9.26.
Bis(4-m eth ylp h en yl)bism u th tr ifla te-HMP A com p lex
(6c): yield 100%. 1H NMR δ 2.33 (s, 6H), 2.53 (d, 36H, J )
9.7 Hz), 7.49 (d, 4H, J ) 7.8 Hz), 8.17 (d, 4H, J ) 7.8 Hz);
FABMS (m/ z) 749 (M+ - OTf), 570, 479, 391, 388, 300, 209,
180, 179, 135; IR (KBr) 1487, 1458, 1330-1290, 1260-1050,
1032, 990, 797, 752, 639 cm-1. Anal. Calcd for C27H50BiF3-
N6O5P2S + H2O: C, 35.38; H, 5.71; N, 8.99. Found: C, 35.16;
H, 5.47; N, 9.31.
(4-Ch lor op h en yl)(2-m eth oxyp h en yl)bism u th tr ifla te-
HMP A com p lex (8b): yield 100%. 1H NMR δ 2.53 (d, 36H,
J ) 9.6 Hz), 3.93 (s, 3H), 7.16 (m, 1H), 7.25-7.41 (m, 2H),
7.65 (d, 2H, J ) 8.4 Hz), 8.16 (d, 2H, J ) 8.4 Hz), 8.32 (d, 1H,
J ) 7.3 Hz); FABMS (m/ z) 787 (M+ - OTf, 37Cl), 785 (M+
-
OTf, 35Cl), 608, 606, 501, 499, 495, 429, 427, 388, 209, 179; IR
(neat) 1572, 1462, 1431, 1296, 1269, 1192, 1163, 1094, 1034,
988, 810, 752, 714 cm-1
. Anal. Calcd for C26H47BiClF3-
Bis(2-m eth oxyp h en yl)bism u th tr ifla te-HMP A com -
p lex (6d ): yield 100%. mp 93-100 °C dec; 1H NMR δ 2.42 (d,
36H, J ) 9.8 Hz), 3.89 (s, 6H), 7.22-7.46 (m, 6H), 8.37 (dd,
2H, J ) 1.7, 7.2 Hz); FABMS (m/ z) 602 (M+ - OTf, HMPA),
495, 423, 388, 316, 209, 180, 179, 135; IR (KBr) 1570, 1466,
1428, 1350-1260, 1250-1100, 1034, 982, 752, 640 cm-1. Anal.
Calcd for C27H50BiF3N6O7P2S + H2O: C, 34.18; H, 5.52; N,
8.85. Found: C, 33.76; H, 5.18; N, 9.22.
P r ep a r a tion of Mixed Tr ia r ylbism u th a n es 7. Gen er a l
P r oced u r e. To a stirred solution of 6 (10 mmol) in THF (50
mL) was added at 0 °C a solution of an appropriate Ar2MgBr
compound (prepared from Ar2Br (15-25 mmol) and Mg (15-
25 mmol)) in THF (60 mL), and the resulting mixture was
stirred at the same temperature for 1-2 h to complete the
reaction. The mixture was poured into ice-cold saturated
aqueous NH4Cl (30 mL), and the insoluble materials were
filtered off through a Celite bed. The organic phase was
extracted with benzene (10 mL × 5), and the combined extracts
were washed with brine (10 mL × 5), dried (Na2SO4), and
concentrated under reduced pressure to leave an oily residue,
which was crystallized from benzene/MeOH (1/5) to afford 7
as colorless crystals.
(4-Ch lor op h en yl)bis(2-m eth ylp h en yl)bism u th a n e (7a ):
yield 85%; mp 88-91 °C (lit.1a 80-83 °C). 1H NMR δ 2.41 (s,
6H), 7.11 (dt, 2H, J ) 1.4, 7.1 Hz), 7.23-7.40 (m, 6H), 7.54-
7.60 (m, 4H); EIMS (m/ z) 322, 320, 300, 209; IR (KBr) 1557,
1470, 1455, 1375, 1088, 1046, 1007, 806, 745, 713 cm-1. Anal.
Calcd for C20H18BiCl: C, 47.77; H, 3.61. Found: C, 47.86; H,
3.56.
(4-Ch lor op h e n yl)b is(2-m e t h oxyp h e n yl)b ism u t h a n e
(7b): yield 86%; mp 93-95 °C. 1H NMR δ 3.76 (s, 6H), 6.92
(dt, 2H, J ) 1.0, 7.2 Hz), 7.02 (d, 2H, J ) 7.2 Hz), 7.23-7.40
(m, 4H), 7.49 (dd, 2H, J ) 1.7, 7.2 Hz), 7.56 (d, 2H, J ) 8.3
N6O6P2S: C, 33.39; H, 5.06; N, 8.98. Found: C, 33.62; H, 5.07;
N, 8.95.
P r ep a r a tion of Un sym m etr ica l Tr ia r ylbism u th a n es 4.
Compounds 4a ,b were prepared by the reaction of 8a ,b with
(4-methoxyphenyl)- and (4-methylphenyl)magnesium bro-
mides, respectively, according to the same procedure used for
the preparation of 7.
(4-Ch lor op h en yl)(4-m eth oxyp h en yl)(2-m eth ylp h en yl)-
bism u th a n e (4a ): yield 80%; mp 120-123 °C. 1H NMR δ 2.39
(s, 3H), 3.79 (s, 3H), 6.92 (d, 2H, J ) 8.6 Hz), 7.13 (dt, 1H, J
) 1.7, 8.4 Hz), 7.22-7.38 (m, 4H), 7.53-7.65 (m, 5H); EIMS
(m/ z) 322, 320, 316, 300, 209; IR (KBr) 1578, 1487, 1374, 1279,
1242, 1181, 1084, 1057, 1024, 1003, 810, 745, 710 cm-1. Anal.
Calcd for C20H18BiClO: C, 46.30; H, 3.50. Found: C, 46.47;
H, 3.46.
(4-Ch lor op h en yl)(2-m eth oxyp h en yl)(4-m eth ylp h en yl)-
bism u th a n e (4b): yield 70%; mp 99-102 °C. 1H NMR δ 2.32
(s, 3H), 3.77 (s, 3H), 6.94 (dt, 1H, J ) 7.3, 0.9 Hz), 7.02 (d, 1H,
J ) 7.7 Hz), 7.19 (d, 2H, J ) 7.3 Hz), 7.28 (d, 2H, J ) 8.3 Hz),
7.35 (t, 1H, J ) 9.1 Hz), 7.55 (d, 1H, J ) 7.4 Hz), 7.56 (d, 2H,
J ) 8.2 Hz), 7.60 (dt, 2H, J ) 1.7, 8.3 Hz); EIMS (m/ z) 429,
427, 407, 322, 320, 316, 300, 209; IR (KBr) 1570, 1458, 1428,
1370, 1300, 1220, 1170, 1085, 1050, 1025, 1005, 795, 756, 710
cm-1
.
Anal. Calcd for C20H18BiClO: C, 46.30; H, 3.50.
Found: C, 46.41; H, 3.50.
Ack n ow led gm en t. We acknowledge support of this
work by Grants-in-Aid for Scientific Research (No.
07740496 and 05236101) from the Ministry of Educa-
tion, Science, Sports and Culture of J apan.
OM9509709