Synthesis and Structure of Monoorganobismuth Compounds Bearing Pyridinedimethoxide Ligands

Article abstract of DOI:10.1021/om990683v

Monoorganobismuth compounds bearing pyridinedimethoxide ligands [2,6-C₅H₃N-(CR¹₂O)₂] ^2- (R¹ = Me, Et, ⁱPr) have been synthesized. The ligand exchange reaction of PhBi-(OEt)₂, which was in situ generated from PhBiBr₂ and 2 equiv of NaOEt, with [2,6-C₅H₃N(CR¹₂OH)₂] (1a, R¹ = Me; 1b, R¹ = Et; 1c, R¹ = ⁱPr) gave PhBi[2,6-C₅H₃N(CR¹₂O)₂] (5a, R¹ = Me; 5b, R¹ = Et; 5c, R¹ = ⁱPr) in 57-78% yields. A similar reaction of MeBi(OEt)₂ with 1a gave MeBi[2,6-C₅H₃N(CMe₂O)₂] (5d) in 96% yield. (EtO)Bi[2,6-C₅H₃N(CEt₂O)₂] (5e) was also synthesized by the reaction of Bi(OEt)₃ with 1b in 61% yield. The structures of 5a-5c and 5e were characterized by X-ray structure analysis. Compounds 5a-5c and 5e form dimers in the solid state through the intermolecular coordination of the oxygen atoms to the bismuth atoms. The intermolecular Bi-O distances highly depend on the bulkiness of R¹ groups and range from 2.699(2) ? (5a) to 3.581(3) ? (5c). In solution at room temperature, on the other hand, 5a-5e exist as monomers judging from NMR spectra in CDCl₃ and/or toluene-d₈.

Full text of DOI:10.1021/om990683v

Organometallics 2000, 19, 931-936
931
Syn th esis a n d Str u ctu r e of Mon oor ga n obism u th
Com p ou n d s Bea r in g P yr id in ed im eth oxid e Liga n d s
Shigeru Shimada, Maddali L. N. Rao, and Masato Tanaka*
National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305-8565, J apan
Received August 24, 1999
Monoorganobismuth compounds bearing pyridinedimethoxide ligands [2,6-C5H3N-
(CR1 O)2]2- (R1 ) Me, Et, iPr) have been synthesized. The ligand exchange reaction of PhBi-
2
(OEt)2, which was in situ generated from PhBiBr2 and 2 equiv of NaOEt, with [2,6-
i
C5H3N(CR1 OH)2] (1a , R1 ) Me; 1b, R1 ) Et; 1c, R1 ) Pr) gave PhBi[2,6-C5H3N(CR1 O)2]
2
2
(5a , R1 ) Me; 5b, R1 ) Et; 5c, R1 ) iPr) in 57-78% yields. A similar reaction of MeBi(OEt)2
with 1a gave MeBi[2,6-C5H3N(CMe2O)2] (5d ) in 96% yield. (EtO)Bi[2,6-C5H3N(CEt2O)2] (5e)
was also synthesized by the reaction of Bi(OEt)3 with 1b in 61% yield. The structures of
5a -5c and 5e were characterized by X-ray structure analysis. Compounds 5a -5c and 5e
form dimers in the solid state through the intermolecular coordination of the oxygen atoms
to the bismuth atoms. The intermolecular Bi-O distances highly depend on the bulkiness
of R1 groups and range from 2.699(2) Å (5a ) to 3.581(3) Å (5c). In solution at room
temperature, on the other hand, 5a -5e exist as monomers judging from NMR spectra in
CDCl3 and/or toluene-d8.
In tr od u ction
ligands, similar to those used by Lee and Martin,5 allow
introduction of substituent R1 in the proximity of the
oxygen atoms, which enhances the solubility. In addi-
tion, intramolecular coordination of the nitrogen atom
to the bismuth atom may serve to weaken the intermo-
lecular coordination between oxygen and bismuth at-
Since bismuth generally is believed to be a nontoxic
element,1 we have become interested in organic syn-
thesis using organobismuth reagents.2 However, their
application to organic synthesis is still limited.1,3 Most
organobismuth(III) reagents so far used in organic
synthesis are triaryl- and trialkylbismuth compounds.
The presence of three reactive Bi-C bonds in a molecule
makes their chemistry complicated, and a mechanistic
study is not straightforward. In this context monoor-
ganobismuth dialkoxides appear to be suitable com-
pounds for the investigation on the reactivity of a Bi-C
bond. However, a survey of the literature reveals that
most of monoorganobismuth dialkoxides so far reported
have very low solubility in common organic solvents
presumably because of the formation of oligomeric or
polymeric structures due to the strong intermolecular
Bi-O interactions.4 Furthermore, these compounds are
moisture-sensitive, and some of them are thermally
unstable. To obtain monoorganobismuth dialkoxides
possessing improved solubility and stability, we have
oms. Here we report the synthesis and the structure of
i
R2Bi[2,6-C5H3N(CR1 O)2] (R1 ) Me, Et, Pr; R2 ) Ph,
2
Me, OEt).
Resu lts a n d Discu ssion
Syn th esis. Pyridinedimethanols [2,6-C5H3N(CR1 -
2
OH)2] 1a -1c were synthesized by the reaction of 2,6-
C5H3N(CO2Me)2 with an excess of Grignard reagent as
described in the literature (Scheme 1).6 Methyl (1a ) and
ethyl (1b) derivatives were obtained in satisfactory
yields, while the bulkier isopropyl compound (1c) was
obtained only in 19% yield. An initial attempt to
synthesize 5a by the sequence of lithiation of 1a with 2
equiv of n-BuLi and the subsequent reaction with
PhBiBr2 failed. An alternative procedure involving the
conversion of PhBiBr2 to PhBi(OEt)2 (2)4a by 2 equiv of
NaOEt and the subsequent ligand exchange reaction
between 2 and 1a successfully afforded desired com-
pound 5a in 78% yield (Scheme 2). Compounds 5b and
5c were similarly prepared in 57% and 62% yields,
respectively. Similar procedures gave methyl derivative
5d in 96% yield from 1a and MeBi(OEt)2 (3)4c and
ethoxy compound 5e in 61% yield from 1b and Bi(OEt)3
(4).7 Starting 3 or 4 was generated in situ from MeBiCl2
or BiCl3, respectively, with NaOEt (2 equiv for MeBiCl2
designed alkoxide ligands [2,6-C5H3N(CR1 O)2]2-. These
2
(1) Suzuki, H.; Ikegami, T.; Matano, Y. Synthesis 1997, 249-267.
(2) Rao, M. L. N.; Shimada, S.; Tanaka, M. Org. Lett. 1999, 1, 1271-
1273.
(3) (a) Doak, G. O.; Freedman, L. D. Organometallic Compounds of
Arsenic, Antimony, and Bismuth; Wiley-Interscience: New York, 1970.
(b) Freedman, L. D.; Doak, G. O. Chem. Rev. 1982, 82, 15-57. (c) Wada,
M.; Ohki, H. Yuki Gosei Kagaku Kyokaishi 1989, 47, 425-435. (d)
Finet, J .-P. Chem. Rev. 1989, 89, 1487-1501. (e) Wardell, J . L. In
Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G.
A., Abel, E. W., Eds.; Pergamon: Oxford, U.K., 1982; Chapter 13. (f)
Wardell, J . L. In Comprehensive Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U.K.,
1995; Chapter 8.
(4) (a) Wieber, M.; Baudis, U. Z. Anorg. Allg. Chem. 1976, 423, 40-
46. (b) Wieber, M.; Baudis, U. Z. Anorg. Allg. Chem. 1976, 423, 47-
52. (c) Wieber, M.; Baudis, U. Z. Anorg. Allg. Chem. 1978, 439, 139-
144.
(5) Lee, D. Y.; Martin, J . C. J . Am. Chem. Soc. 1984, 106, 5745-
5746.
(6) Lukes, R.; Perga´l, M. Collect. Czech. Chem. Commun. 1959, 24,
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(7) Mehrotra, R. C.; Rai, A. K. Indian J . Chem. 1966, 4, 537.
10.1021/om990683v CCC: $19.00 © 2000 American Chemical Society
Publication on Web 02/09/2000

932 Organometallics, Vol. 19, No. 5, 2000
Shimada et al.
Sch em e 1
Bi-N distances (2.34-2.35 Å) are longer than the
known Bi-N single bond (2.12-2.28 Å),11 but shorter
than those reported for the bismuth compounds bearing
pentadentate pyridine ligands (2.44-2.47 Å).12,13 The
intermolecular Bi-O distances, 2.699(3) and 2.761(3)
Å, are much longer than the intramolecular ones and
are in the range observed for coordinative Bi-O dis-
tances.14 The pyridine ring and Bi1, O1, O2, C2, C3
atoms are almost coplanar, and the maximum deviation
(for O2) from the least-squares plane is 0.061(4) Å. As
shown in the crystal packing diagram of 5a (Figure 2),
only one of the two independent dimers is connected to
two H2O molecules through hydrogen bonds, forming
an indefinite chain along the a axis. The other dimer
does not have any interaction with H2O while it also
forms an independent column in the crystal.
Sch em e 2
As shown in Figures 3 and 4, 5b and 5c also form
dimers in the solid state. Compound 5b crystallizes in
the C2/c space group, and the two apical phenyl groups
in the dimer point to the same side (syn), while 5c
crystallizes in the P1h space group and the two apical
phenyl groups are directed to the opposite side (anti),
as observed for 5a . The intramolecular Bi-O, Bi-N, and
Bi-C distances of 5b and 5c are similar to those of 5a .
On the other hand, the intermolecular Bi-O distances
highly depend on the bulkiness of the substituent R1
and are 2.907(5) Å for 5b and 3.581(3) Å for 5c.
Although, the distance for 5c is close to the sum of the
van der Waals radii (3.67 Å),15 the intermolecular Bi-O
interaction seems to still exist in 5c judging from its
crystal structure. The N1-Bi1-C1 angles also depend
of the bulkiness of the substituent R1 and range from
93.3(2)° (5a ) to 105.4(1)° (5c). The planarities of Bi-
containing fused rings also decrease in 5b and 5c. The
maximum deviations from the least-squares plane are
0.176(5) Å (O1) for 5b and 0.314(6) Å (one of the carbon
atoms in the pyridine ring) for 5c.
and 3 equiv for BiCl3). Compounds 5a -5e are soluble
in common organic solvents such as toluene, THF, and
CH2Cl2. As expected, the solubility increases in the
order 5a < 5b < 5c. Organobismuth compounds 5a -
5d are stable at least for several days to air in the solid
state, while they hydrolyze in solution upon exposure
to air. Ethoxy compound 5e hydrolyzes even in the solid
state upon exposure to air for a few hours.
Cr ysta l a n d Molecu la r Str u ctu r es. The crystal
structures of 5a -5c and 5e were determined by X-ray
structure analysis. Crystallographic data are sum-
marized in Table 1. Selected bond distances and angles
are listed in Table 2. In case of 5a , needle-type crystals
containing THF molecules were easily obtained by the
recrystallization from THF, although the quality was
not good enough for X-ray analysis. Fortunately, X-ray-
quality crystals of 5a were obtained from an NMR
sample in C6D6. Interestingly, the crystals contained one
molecule of H2O per every two molecules of 5a . The H2O
molecule is presumed to have come from the solvent.
In the asymmetric unit of 5a , two independent mol-
ecules exist, both of which form dimers in the solid state
through the Bi-O intermolecular coordination. The
molecular structure of one of the dimers is shown in
Figure 1. The geometry at the bismuth atom can be
described as highly distorted square pyramid, in which
a stereoactive lone pair of electrons probably occupies
the vacant position trans to the phenyl group. A very
similar arrangement has been reported for bis(1-oxopy-
ridine-2-thiolato)phenylbismuth,8 although it is a mon-
omeric compound. The intramolecular Bi-O distances
(2.21-2.30 Å) and the Bi-C distances (2.26-2.27 Å) are
comparable to those found in the literatures.9,10 The
As Figure 5 shows, 5e has a dimeric structure similar
to that of 5a . The EtO group occupies the apical position,
and its oxygen atom does not have intermolecular
(10) Suzuki, H.; Murafuji, T.; Azuma, N. J . Chem. Soc., Perkin
Trans.
1 1993, 1169-1175. Murafuji, T.; Mutoh, T.; Satoh, K.;
Tsunenari, K.; Azuma, N.; Suzuki, H. Organometallics 1995, 14, 3848-
3854. Hassan, A.; Breeze, S. R.; Courtenay, S.; Deslippe, C.; Wang, S.
Organometallics 1996, 15, 5613-5621. Matano, Y.; Kurata, H.; Mu-
rafuji, T.; Azuma, N.; Suzuki, H. Organometallics 1998, 17, 4049-
4059.
(11) Veith, M.; Bertsch, B. Z. Anorg. Allg. Chem. 1988, 557, 7-22.
Clegg, W.; Compton, N. A.; Errington, R. J .; Norman, N. C.; Wishart,
N. Polyhedron 1989, 8, 1579-1580. Clegg, W.; Compton, N. A.;
Errington, R. J .; Fisher, G. A.; Green, M. E.; Hockless, D. C. R.;
Norman, N. C. Inorg. Chem. 1991, 30, 4680-4682. Burford, N.;
Macdonald, C. L. B.; Robertson, K. N.; Cameron, T. S. Inorg. Chem.
1996, 35, 4013-4016.
(12) (a) Battaglia, L. P.; Corradi, A. B.; Pelosi, G.; Tarasconi, P.;
Pelizzi, C. J . Chem. Soc., Dalton Trans. 1989, 671-675. (b) Battaglia,
L. P.; Corradi, A. B.; Pelizzi, C.; Pelosi, G.; Tarasconi, P. J . Chem. Soc.,
Dalton Trans. 1990, 3857-3860.
(13) After submission of this paper, Akiba et al. have reported tri-
and pentavalent azabismocines. The B-N distances of the trivalent
ones range from 2.76 to 2.78 Å. See: Minoura, M.; Kanamori, Y.;
Miyake, A.; Akiba, K.-y. Chem. Lett. 1999, 861-862.
(14) Rogers, R. D.; Bond, A. H.; Aguinaga, S. J . Am. Chem. Soc.
1992, 114, 2960-2967. Rogers, R. D.; Bond, A. H.; Aguinaga, S.; Reyes,
A. J . Am. Chem. Soc. 1992, 114, 2967-2977. Asato, E.; Katsura, K.;
Arakaki, T.; Mikuriya, M.; Kotera, T. Chem. Lett. 1994, 2123-2126.
Asato, E.; Kamamuta, K.; Akamine, Y.; Fukami, T.; Nukada, R.;
Mikuriya, M.; Deguchi, S.; Yokota, Y. Bull. Chem. Soc. J pn. 1997, 70,
639-648.
(15) Alcock, N. W. In Advances in Inorganic Chemistry and Radio-
chemistry; Emele´us, H. J ., Sharpe, A. G., Eds.; Academic Press: New
York, 1972; Vol. 15; pp 1-58.
(8) Curry, J . D.; J andacek, R. J . J . Chem. Soc., Dalton Trans. 1972,
1120-1123.
(9) (a) Matchett, M. A.; Chiang, M. Y.; Buhro, W. E. Inorg. Chem.
1990, 29, 358-360. (b) Hegetschweiler, K.; Ghisletta, M.; Gramlich,
V. Inorg. Chem. 1993, 32, 2699-2704. (c) Diemer, R.; Keppler, B. K.;
Dittes, U.; Nuber, B.; Seifried, V.; Opferkuch, W. Chem. Ber. 1995,
128, 335-342.

Monoorganobismuth Compounds
Organometallics, Vol. 19, No. 5, 2000 933
Ta ble 1. Su m m a r y of Cr ysta l Da ta for Com p ou n d s 5a , 5b, 5c, a n d 5e
5a
5b
5c
5e
formula
fw
C
17H20BiNO2‚1/2H2O
C21H28BiNO2
535.44
C25H35BiNO2‚CH2Cl2
675.47
C17H28BiNO3
503.39
488.34
cryst size, mm
a, Å
b, Å
0.25 × 0.12 × 0.20
10.859(1)
15.024(2)
10.5933(9)
94.287(8)
91.922(8)
88.003(9)
1651.7(9)
triclinic
P1h (No. 2)
4
0.12 × 0.10 × 0.23
0.25 × 0.25 × 0.20
10.726(3)
13.653(1)
10.643(2)
90.98(1)
119.28(2)
83.13(1)
1348.2(6)
triclinic
P1h (No. 2)
2
0.15 × 0.15 × 0.10
10.068(3)
11.882(3)
8.346(3)
93.32(3)
111.14(2)
91.49(2)
928.5(5)
triclinic
P1h (No. 2)
2
22.304(3)
11.130(4)
16.807(3)
c, Å
R, deg
â, deg
γ, deg
V, Å3
94.07(1)
4161(1)
monoclinic
C2/c (No. 15)
8
cryst syst
space group
Z
D
calc, g cm-3
1.88
1.71
1.66
1.80
F(000)
932.00
102.30
Mo KR
296
2080.00
84.70
Mo KR
223
666.00
67.47
Mo KR
203
488.00
94.89
Mo KR
193
µ (Mo KR), cm-1
radiation
T, K
scan type
2θmax, deg
no. of rflns measd
no. of unique rflns
no. of rflns used, Io > 3.0σ(Io)
no. of variables
R, Rw
ω-2θ
ω-2θ
ω-2θ
ω-2θ
55.0
55.0
54.9
55.2
8164
7862 (Rint ) 0.016)
6243
389
0.026, 0.033
1.30
4946
4779 (Rint ) 0.022)
3277
222
0.030, 0.039
1.04
6465
6136 (Rint ) 0.031)
5599
290
0.029, 0.039
1.41
4488
4242 (Rint ) 0.050)
3127
199
0.041, 0.049
1.32
GOF
diff peak, hole, e Å-3
0.83, -1.38
0.61, -0.67
1.16, -2.10
0.90, -2.60
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5a , 5b, 5c, a n d 5e
5a
5b
5c
5e
Bi1-O1
Bi1-O2
Bi1-O3
Bi1-O1*
Bi1-N1
Bi1-C1
2.215(3), 2.212(3) 2.223(4) 2.201(3) 2.184(6)
2.230(3), 2.297(3) 2.243(4) 2.189(3) 2.223(6)
2.099(8)
2.761(3), 2.699(3) 2.907(5) 3.581(3) 2.709(5)
2.349(4), 2.338(4) 2.317(5) 2.330(3) 2.334(7)
2.261(5), 2.269(5) 2.240(7) 2.263(4)
O1-Bi1-O2 140.3(1), 139.9(1) 140.4(2) 138.6(1) 139.9(2)
O1-Bi1-O3
86.1(3)
O1-Bi1-O1* 71.8(1), 69.6(1)
O1-Bi1-N1 70.3(1), 70.6(1)
70.4(2) 92.79(9) 68.4(2)
70.9(2) 70.4(1)
90.9(2) 88.9(1)
70.5(2)
94.0(3)
O1-Bi1-C1
O2-Bi1-O3
89.8(2), 90.9(2)
O2-Bi1-O1* 147.8(1), 150.5(1) 149.0(1) 128.36(8) 151.6(2)
O2-Bi1-N1 70.1(1), 69.3(1)
70.4(2) 70.5(1)
88.4(2) 88.8(1)
69.4(2)
93.0(3)
O2-Bi1-C1
O3-Bi1-N1
N1-Bi1-C1
90.3(2), 90.0(2)
93.3(2), 93.3(2)
100.9(2) 105.4(1)
F igu r e 2. Crystal packing of 5a (a) along the c direction
and (b) along the a direction. Dashed lines indicate
hydrogen bonds.
O2, N1, C2, C3 atoms of 5e are almost coplanar. The
maximum deviation from the least-squares plane is
0.05(1) Å (C3). The apical Bi1-O3 distance (2.099(8) Å)
is much shorter than the Bi1-O1 and Bi1-O2 dis-
tances, as observed in other square pyramidal bismuth
compounds.9a,12b,16
F igu r e 1. Molecular structure of the dimeric pair of 5a
(30% probability).
interaction with the bismuth atom. The intermolecular
Bi-O distance of 5e (2.709(5) Å) is almost the same as
that of 5a . Similarly to 5a , pyridine rings and Bi1, O1,

934 Organometallics, Vol. 19, No. 5, 2000
Shimada et al.
F igu r e 6. Methyl proton signals in the VT-1H NMR
spectra of 5a in CD2Cl2.
F igu r e 3. Molecular structure of the dimeric pair of 5b
Ta ble 3. 1H NMR Ch em ica l Sh ifts of P h en yl
P r oton s of 5a -5c, P h 3Bi, a n d Som e Oth er
P h en ylbism u th Com p ou n d s in CDCl3
(30% probability).
compound
o-H/ppm
m-H/ppm
p-H/ppm
5a
5b
5c
Ph3Bi
8.59
8.50
8.56
7.79
7.62
7.64
7.69
7.43
7.20
7.20
7.21
7.36
PhBi(OCOCHdCHCOO)a,b 8.53-8.76 7.66-7.98 7.21-7.44
c,d
PhBiCl2
PhBiBr2
8.99
9.14
8.15
7.96
7.94
7.60
7.43
7.44
7.32
c,d
PhBi(SCH2CH2S)e
a
b
Phenylbismuth maleate, ref 13. In DMSO-d6. c Reference 14.
In acetone-d6. e Reference 4b. The values shown here were
d
obtained by ourselves.
and broadened by lowering the temperature. The dif-
ference between the chemical shift value due to this
methyl group at 20 °C and the value at -80 °C was
-0.24 ppm (the minus sign in the chemical shift
difference means upfield shift). On the other hand, the
corresponding difference between the values due to the
other methyl group was only -0.06 ppm. The chemical
shifts of the phenyl proton signals were also tempera-
ture dependent, the differences between the values at
20 °C and at -80 °C being 0.19, -0.03, and -0.03 ppm
for o-, m-, and p-protons, respectively. The differences
for the pyridine protons, which behaved similarly, were
respectively 0.12 and 0.07 ppm for 3- and 4-protons.
Larger chemical shift differences were observed for the
protons nearer to the bismuth center. This presumably
suggests that although a rapid monomer-dimer inter-
change occurs even at -80 °C, the relative concentration
of the dimer increases with lowering of the temperature.
F igu r e 4. Molecular structure of the dimeric pair of 5c
(30% probability).
F igu r e 5. Molecular structure of the dimeric pair of 5e
(30% probability).
1
Table 3 shows the H NMR chemical shifts of phenyl
protons of 5a -5c along with those of relevant phenyl
bismuth compounds. The signals of the ortho protons
of 5a -5c are considerably downfield shifted, as com-
pared with that of Ph3Bi. The meta protons of 5a -5c
also show downfield shifts to smaller extents, while the
signals for the para protons are slightly upfield shifted.
Other phenylbismuth dicarboxylate,17 dihalide,18 and
dithiolate4b also show similar downfield shifts for ortho
and meta protons. Table 4 summarizes the 13C NMR
chemical shifts of the bismuth-bound carbons with
1
NMR Sp ectr a . H and 13C NMR spectra of 5a -5e
in CDCl3 at room temperature displayed only the
signals assignable for the monomeric species, suggesting
that the integrity of the dimeric structures is not
retained in solution. Variable-temperature 1H NMR
study of 5a in CD2Cl2 or toluene-d8 did not show any
new signal even at -80 °C. However, as shown in Figure
6, the higher field signal arising from one of the two
methyl groups of 5a in CD2Cl2 largely upfield shifted
(16) Massiani, M.-C.; Papiernik, R.; Hubert-Pfalzgraf, L. G.; Daran,
J . C. Polyhedron 1991, 10, 437-445. J ones, C. M.; Burkart, M. D.;
Whitmire, K. H. Angew. Chem., Int. Ed. Engl. 1992, 31, 451-452.
J ones, C. M.; Burkart, M. D.; Bachman, R. E.; Serra, D. L.; Hwu, S.-
J .; Whitmire, K. H. Inorg. Chem. 1993, 32, 5136-5144.
(17) Georgiades, A.; Latscha, H. P. Z. Naturforsch. 1980, 35b, 1000-
1001.
(18) Becker, G.; Egner, J .; Mundt, O.; Stadelmann, H. In Synthetic
Methods of Organometallic and Inorganic Chemistry; Herrmann, W.
A., Ed.; Thieme: Stuttgart, 1996; Vol. 3; pp 210-214.

Monoorganobismuth Compounds
Organometallics, Vol. 19, No. 5, 2000 935
Ta ble 4. 13C NMR Ch em ica l Sh ifts of th e Ca r bon s
Dir ectly Atta ch ed to Bism u th Atom s in CDCl3
27.0 g of dimethyl 2,6-pyridinedicarboxylate (0.138 mol) in 5
portions over a period of 20 min with ice-cooling. The resulting
wine red suspension was gradually heated to 105 °C (2.5 h)
with concurrent removal of ether. After cooling, water (400
mL) was carefully added to the mixture with ice-cooling, and
then 300 mL of EtOAc was added. The mixture was filtered
through Celite under reduced pressure, and the remaining
solid was washed with EtOAc (6 × 100 mL). The filtrate was
separated, and the organic layer was washed with water (2 ×
100 mL). The aqueous layer was extracted with EtOAc (2 ×
100 mL), and the extract was washed with water (2 × 80 mL).
The combined organic layers were dried over Na2SO4, filtered,
and then concentrated in vacuo. The crude mixture was
purified by chromatography on silica gel (hexane/iPrOH ) 27:
1) to give 1b (20.8 g, 60%) as a slightly yellow oil. 1H NMR
(CDCl3, 499.1 MHz): δ 0.63 (12H, t, J ) 7), 1.83 (8H, q, J )
7), 4.23 (2H, s, OH), 7.20 (2H, d, J ) 8), 7.67 (1H, t, J ) 8).
13C NMR (CDCl3, 125.4 MHz): δ 7.65, 34.66, 77.09, 117.72,
137.48, 161.75.
compound
chemical shift/ppm
∆δ/ppmb
Ph3Bi
5a
5b
5c
Me3Bi
5d
(Me3Si)2CHBiCl2
155.26
206.97
208.85
210.43
-6.71
63.89
51.71
53.59
55.17
70.60
a
69.69
a
b
In C6D6. The difference in chemical shift between 5a -5c and
Ph3Bi or 5d and Me3Bi.
reference to the relevant data for Ph3Bi or Me3Bi. For
5a -5c, large downfield shifts were observed as com-
pared with Ph3Bi. Compound 5d also showed large
downfield shifts relative to Me3Bi. Since the 13C NMR
signals of bismuth-bound carbons are extremely weak
or not observed due to the adjacent bismuth atoms, their
chemical shift data are sorely lacking in the literature.
However, our observations for 5a -5d are in agreement
with a recent paper reporting an alkylbismuth dichlo-
ride, (Me3Si)2CHBiCl2, which also shows a considerable
downfield shifts for the CBi signal.19
2,6-P yr id in ebis(d iisop r op ylm eth a n ol) (1c). To a mix-
ture of 800 mL of an ether solution of isopropylmagnesium
chloride (2.0 M, 1.6 mol) and 700 mL of toluene was added
69.2 g of dimethyl 2,6-pyridinedicarboxylate (0.355 mol) in 5
portions over a period of 30 min with ice-cooling. The resulting
wine red suspension was gradually heated to 110 °C (3.5 h)
accompanied by the removal of ether and then kept at this
temperature for 10 h. After cooling, the reaction mixture was
hydrolyzed by pouring onto crushed ice. After addition of
hexane (1 L), the mixture was filtered through Celite under
reduced pressure. The remaining solid was washed with
hexane (3 × 200 mL) and THF (5 × 200 mL). The filtrate was
separated, and the organic layer was washed with water (3 ×
150 mL). The aqueous layer was extracted with hexane (250
mL), and the extract was washed with water (3 × 100 mL).
The combined organic layers were dried over Na2SO4, filtered,
and then concentrated in vacuo. The crude mixture was
purified by chromatography on silica gel (hexane/EtOAc/iPrOH
) 100:4:1). The resulting product was further purified by
recrystallization from heptane to give 1c in the form of
Con clu sion
Monoorganobismuth compounds bearing 2,6-py-
ridinedimethoxide ligands are easily prepared in moder-
ate to excellent yields by the ligand exchange reaction
of phenylbismuth diethoxide or methylbismuth diethox-
ide with corresponding pyridinedimethanols 1a -1c.
These compounds form dimers through the intermo-
lecular oxygen coordination to bismuth in the solid state.
Each unit in the dimeric form adopts a distorted square
pyramidal configuration with the organic ligand placed
at the apical positions. The intermolecular Bi-O dis-
tances very much depended on the bulkiness of the
pyridinedimethoxy ligands. Compounds 5a -5d are
soluble in common organic solvents, but the dimeric
structures do not persist in solution. The compounds will
be useful to investigate the reactivity of the Bi-C bond
and related synthetic reactions.
1
colorless prisms (20.3 g, 19%). H NMR (CDCl3, 499.1 MHz):
δ 0.75 (12H, d, J ) 7), 0.80 (12H, d, J ) 7), 2.34 (4H, septet,
J ) 7), 7.24 (2H, d, J ) 8), 7.66 (1H, t, J ) 8). 13C NMR (CDCl3,
125.4 MHz): δ 16.72, 17.48, 34.39, 80.42, 119.07, 136.15,
159.79. IR (KBr): 3428, 3202, 2966, 2878, 1578, 1464, 1412,
1383, 1369, 1303, 1238, 1147, 1106, 1085, 1000, 917, 857, 806,
764, 669, 497. Anal. Calcd for C19H33NO2: C, 74.22; H, 10.82;
N, 4.56. Found: C, 74.42; H, 11.22; N, 4.60.
Exp er im en ta l Section
P h Bi[2,6-C5H3N(CMe2O)2] (5a ). To an EtOH solution (160
mL) of PhBiBr2 (17.1 g, 38.4 mmol) was added an EtOH
solution of NaOEt (2.0 M, 38.6 mL, 77 mmol) at -30 °C. The
mixture was gradually warmed to -15 °C over a period of 1 h
and then cooled again to -30 °C. An EtOH solution of 1a (7.50
g, 38.4 mmol) was added. The mixture was gradually warmed
to room temperature over a period of 5 h. EtOH was removed
under reduced pressure (up to 1 × 10-3 Torr), and CH2Cl2 (150
mL) was added to the residue. The mixture was filtered
through Celite, and the filtrate was evaporated in vacuo. To
the residual solid contaminated by unreacted 1a and a red-
brown-colored material was added THF (100 mL), and the
mixture was refluxed for ca. 5 min. After cooling to room
temperature, the white solid was filtered and washed with
THF (3 × 30 mL) and dried under reduced pressure at room
temperature for 24 h. Yield: 78% (14.3 g). 1H NMR (CDCl3,
300.1 MHz): 1.46 (6H, s), 1.51 (6H, s), 7.20 (1H, br t, J ) 7.5,
p-H in Ph), 7.24 (2H, d, J ) 7.5, 3-H in Py), 7.62 (2H, t, J )
7.5, m-H in Ph), 7.89 (1H, t, J ) 7.5, 4-H in Py), 8.59 (2H, dd,
J ) 1, 7.5, o-H in Ph). 13C NMR (CDCl3, 75.5 MHz): 34.73,
34.84, 73.97, 120.19 (2C), 128.02, 130.72 (2C), 136.08 (2C),
139.45, 171.75, 206.97 (Bi-C). Anal. Calcd for C17H20BiNO2:
C, 42.60; H, 4.21; N, 2.92. Found: C, 42.13; H, 4.43; N, 2.83.
Gen er a l P r oced u r es. All manipulations of air-sensitive
materials were carried out under a nitrogen atmosphere using
standard Schlenk tube techniques. Toluene was distilled from
Na/benzophenone ketyl. All other anhydrous solvents were
purchased from Kanto Chemicals or Aldrich and were used
as received. Compound 1a ,6 PhBiBr2,18,20 and MeBiCl2 were
21
prepared according to literature procedures. BiCl3 was pur-
chased from Kojundo Chemical Laboratory and used as
received. 1H and 13C NMR spectra were recorded on Bruker
ARX300 and J EOL LA500 spectrometers. Chemical shifts are
given in ppm and are referenced to tetramethylsilane. Cou-
pling constants are reported in hertz.
2,6-P yr id in ebis(d ieth ylm eth a n ol) (1b). The procedure
reported by Lukes and Perga´l was slightly modified as follows.6
To a mixture of 210 mL of an ether solution of ethylmagnesium
chloride (3.0 M, 0.63 mol) and 300 mL of toluene was added
(19) Althaus, H.; Breunig, H. J .; Ro¨sler, R.; Lork, E. Organometallics
1999, 18, 328-331.
(20) 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, 1967-1974.
(21) Marquardt, A. Chem. Ber. 1887, 20, 1516-1523.

936 Organometallics, Vol. 19, No. 5, 2000
Shimada et al.
1
P h Bi[2,6-C5H3N(CEt2O)2] (5b). The compound was pre-
pared as described for 5a from 12.0 g (26.9 mmol) of PhBiBr2
and 6.76 g (26.9 mmol) of 1a . Recrystallization of the crude
product from 1,2-dichloroethane/hexane gave colorless crystals
(8.25 g, 57% yield). 1H NMR (CDCl3, 499.1 MHz): 0.55 (6H, t,
J ) 7), 0.88 (6H, t, J ) 7), 1.73-2.01 (8H, m), 7.20 (1H, tt, J
) 1, 7, p-H in Ph), 7.22 (2H, d, J ) 7, 3-H in Py), 7.64 (2H, t,
J ) 7, m-H in Ph), 7.92 (1H, t, J ) 7, 4-H in Py), 8.50 (2H, br
d, J ) 7, o-H in Ph). 13C NMR (CDCl3, 125.4 MHz): 8.04, 8.61,
36.43, 38.46, 78.98, 120.69 (2C), 128.50, 130.82 (2C), 135.05
(3.11 g, 61%). H NMR (CDCl3, 499.1 MHz): δ 0.41 (6H, t, J
) 7), 0.86 (6H, t, J ) 7), 1.05 (3H, t, J ) 7), 1.70-1.94 (8H,
m), 4.45 (2H, q, J ) 7), 7.29 (2H, d, J ) 7.5), 8.00 (1H, t, J )
7.5). 13C NMR (CDCl3, 125.4 MHz): δ 7.86, 8.44, 21.73, 36.90,
38.39, 58.92, 79.52, 120.53, 139.72, 170.47. Anal. Calcd for
C
17H28BiNO3: C, 40.56; H, 5.61; N, 2.78. Found: C, 40.59; H,
5.71; N, 2.95.
X-r a y Cr ysta llogr a p h y. Crystal data, data collection
details, and solution and refinement procedures are collected
in Table 1. Data were collected on a Rigaku AFC7R diffrac-
tometer. All calculations were performed using teXsan crystal-
lographic software package22 unless otherwise noted. Addi-
tional comments specific to each structure follow.
(2C), 139.40, 169.64, 208.85 (Bi-C). Anal. Calcd for C21H28
-
BiNO2: C, 47.11; H, 5.24; N, 2.62. Found: C, 46.71; H, 5.33;
N, 2.50.
P h Bi[2,6-C5H3N(CiP r 2O)2] (5c). The compound was pre-
pared as described for 5a from 9.00 g (20.2 mmol) of PhBiBr2
and 6.13 g (19.9 mmol) of 1c. Recrystallization of the crude
product from a 1,2-dichloroethane/heptane mixture gave color-
less crystals (7.30 g, 62%). 1H NMR (CDCl3, 499.1 MHz): 0.36
(6H, d, J ) 7), 0.64 (6H, d, J ) 7), 0.98 (6H, d, J ) 7), 1.07
(6H, d, J ) 7), 2.34 (2H, sept, J ) 7), 2.45 (2H, sept, J ) 7),
7.21 (1H, tt, J ) 1, 7, 4-Ph), 7.28 (2H, d, J ) 8, 3-Py), 7.69
(2H, t, J ) 7.5, 3-Ph), 7.88 (1H, t, J ) 8, 4-Py), 8.56 (2H, dd,
J ) 1, 8, 2-Ph). 13C NMR (CDCl3, 125.4 MHz): 16.84, 18.19,
18.41, 18.59, 36.90, 37.89, 82.89, 121.51 (2C), 128.61 (1C),
130.60 (2C), 135.33 (2C), 137.48 (1C), 167.17 (2-Py), 210.43
(Bi-C). Anal. Calcd for C25H36BiNO2: C, 50.76; H, 6.13; N,
2.37. Found: C, 50.55; H, 6.25; N, 2.26.
MeBi[2,6-C5H3N(CMe2O)2] (5d ). To an EtOH solution (40
mL) of MeBiCl2 (3.00 g, 10.2 mmol) was added an EtOH
solution of NaOEt (2.13 M, 9.55 mL, 20.3 mmol) at 0 °C. The
mixture was stirred for 40 min at 0 °C and for 80 min at room
temperature. After cooling to 0 °C, an EtOH (15 mL) solution
of 1a (1.97 g, 10.1 mmol) was added to the mixture, which
was stirred for 220 min at 0 °C and then at room temperature
overnight. After removal of volatiles under reduced pressure,
the crude product was dissolved in dichloromethane, and the
solution was filtered through Celite. Removal of the solvent
under reduced pressure gave 5d as a slightly brown-colored
powder (4.04 g, 96%). 1H NMR (CDCl3, 499.1 MHz): 1.21 (3H,
s, Bi-Me), 1.50 (6H, s), 1.52 (6H, s), 7.27 (2H, d, J ) 7.6, 3-Py),
7.94 (1H, t, J ) 7.6, 4-Py). 13C NMR (CDCl3, 125.4 MHz):
34.04, 35.76, 63.89 (Bi-C), 73.53, 120.02, 139.44, 172.19. Anal.
Calcd for C12H18BiNO2: C, 34.54; H, 4.35; N, 3.36. Found: C,
34.65; H, 4.23; N, 3.22.
5a ‚0.5H2O. Small amounts of crystals were obtained from
a saturated C6D6 solution used for NMR measurement. The
crystals contained a half molecule of H2O per 5a molecule. All
non-hydrogen atoms were refined anisotropically. Hydrogen
atoms of H2O were refined anisotropically, and the other
hydrogen atoms were included in fixed positions.
5b. Crystals were obtained by recrystallization from hep-
tane. One of the CEt2 parts is disordered in two positions. The
ratio of the population in the two positions was refined using
SHELX97 crystallographic software package.23 The final re-
finement was performed by using the teXsan crystallographic
software package with fixed population values for the disor-
dered atoms. Hydrogen atoms were not located on the disor-
dered carbons. The disordered carbon atoms were refined
isotropically, and the other non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included in fixed posi-
tions.
5c‚CH2Cl2. Crystals were obtained by recrystallization from
CH2Cl2. All non-hydrogen atoms were refined anisotropically,
and all hydrogen atoms were included in fixed positions.
5e. Crystals were obtained by recrystallization from hep-
tane. All non-hydrogen atoms were refined anisotropically, and
all hydrogen atoms were included in fixed positions.
Ack n ow led gm en t. We are grateful to the J apan
Science and Technology Corporation (J ST) for financial
support through the CREST (Core Research for Evolu-
tional Science and Technology) program and for a
postdoctoral fellowship to M.L.N.R.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement, atomic coordinates, anisotropic
thermal parameters, and bond lengths and angles for 5a , 5b,
5c, and 5e and a table of hydrogen-bonding geometry for 5a
(PDF). This material is available free of charge via the Internet
at http://pubs.acs.org.
EtOBi[2,6-C5H3N(CEt2O)2] (5e). To an EtOH solution (80
mL) of BiCl3 (3.17 g, 10.1 mmol) was added an EtOH solution
of NaOEt (2.13 M, 14.1 mL, 30 mmol) at 0 °C. After stirring
at 0 °C for 50 min, an EtOH (20 mL) solution of 1b (2.54 g,
10.1 mmol) was added to the mixture, which was stirred for
20 min at 0 °C and then for 7 h at room temperature. After
removal of volatiles under reduced pressure, 1,2-dichloroet-
hane (20 mL) and heptane (10 mL) were added to the residue.
The mixture was centrifuged, and the supernatant was
separated. Removal of the solvent under reduced pressure and
recrystallization from heptane gave 5e as colorless crystals
OM990683V
(22) teXsan, Crystal Structure Analysis Package; Molecular Struc-
ture Corporation, 1985 and 1992.
(23) Sheldrick, G. M. SHELX-97; Universita¨t Go¨ttingen, 1997.