Syntheses, structures and properties of kinetically stabilized distibenes and dibismuthenes, novel doubly bonded systems between heavier group 15 elements

Article abstract of DOI:10.1246/bcsj.75.661

The first stable distibene (RSb=SbR) and dibismuthene (RBi=BiR) were successfully synthesized by taking advantage of steric protection using an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). Since it is quite difficult to investigate the reactivities of the distibene (TbtSb=SbTbt) and dibismuthene (TbtBi= BiTbt) in solution due to their extremely low solubility values, similarly overcrowded distibene and dibismuthene, BbtE=EBbt (E = Sb, Bi), with sufficiently high solubility were also synthesized using another bulky substituent, 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl group (Bbt). The crystallographic analysis and spectroscopic studies of these stable dipnictenes led to the systematic comparison of structural parameters and physical properties for all homonuclear doubly bonded systems between heavier group 15 elements. In addition to these experimentally obtained results, theoretical calculations for these doubly bonded systems also revealed the intrinsic character of dipnictenes.

Full text of DOI:10.1246/bcsj.75.661

c. Jpn.
© 2002 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 75, 661–675 (2002)
661
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Headline Articles
Syntheses, Structures and Properties of Kinetically Stabilized Distibenes
and Dibismuthenes, Novel Doubly Bonded Systems between Heavier
Group 15 Elements.
02
1
5
SJA8
09-2673
384
Syntheses of Distibenes and Dibismuthene
T. Sasamori et al.
Takahiro Sasamori,# Yoshimitsu Arai,† Nobuhiro Takeda, Renji Okazaki,†,## Yukio Furukawa,††
Masahiro Kimura,†††,### Shigeru Nagase,††† and Norihiro Tokitoh*
01
01
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011
†Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033
††Department of Chemistry, School of Science and Engineering, Waseda University,
3-4-1 Okubo, Shinjyuku-ku, Tokyo 169-8555
†††Institute for Molecular Science, Myodaiji, Okazaki 444-8585
(Received October 26, 2001)
The first stable distibene (RSbwSbR) and dibismuthene (RBiwBiR) were successfully synthesized by taking advan-
tage of steric protection using an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt).
Since it is quite difficult to investigate the reactivities of the distibene (TbtSbwSbTbt) and dibismuthene (TbtBiwBiTbt)
in solution due to their extremely low solubility values, similarly overcrowded distibene and dibismuthene, BbtEwEBbt
(E = Sb, Bi), with sufficiently high solubility were also synthesized using another bulky substituent, 2,6-bis[bis(trimeth-
ylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl group (Bbt). The crystallographic analysis and spectroscopic stud-
ies of these stable dipnictenes led to the systematic comparison of structural parameters and physical properties for all
homonuclear doubly bonded systems between heavier group 15 elements. In addition to these experimentally obtained
results, theoretical calculations for these doubly bonded systems also revealed the intrinsic character of dipnictenes.
The syntheses of stable compounds containing multiple
bonds between heavier main group elements have been among
the frontiers of great interest in chemical research.1 The histo-
ry of heavier congeners of azo-compounds dates back to 1877,
when Köller and Michaelis reported that condensation reaction
of PhPCl2 and PhPH2 resulted in the formation of a compound
formulated as “C6H5PwPC6H5”, which they dubbed “phospho-
benzene”.2 However, subsequent X-ray diffraction studies
have revealed that this product has a pentameric or hexameric
structure in the solid state.3 A similar mistake arose in the case
of arsenic. The structure of the chemotherapeutic drug “Salvar-
san” was first formulated as a monomeric diarsene structure by
Ehrlich,4 but here again, X-ray crystallographic work on the
compound of the empirical composition C6H5As revealed their
oligomeric character.5 These failures developed a concept that
compounds featuring double bonds between the heavier main
group elements would not be isolable, which has been some-
times referred to as “the classical double-bond rule”.6 The pio-
neering syntheses and isolation of reactive doubly bonded sys-
tems stemmed from a realization that the steric bulk of suffi-
ciently large ligands makes it possible to avoid the oligomer-
ization of these reactive multiple bonds. Namely, the first dis-
ilene (Mes2SiwSiMes2; Mes = mesityl)7 and the first diphos-
phene (Mes*PwPMes*; Mes* = 2,4,6-tri-t-butylphenyl)8 were
successfully synthesized by the kinetic stabilization of reactive
double-bonds using bulky ligands in 1981. The synthesis of
these compounds is a significant landmark in the chemistry of
doubly bonded systems between the heavier main group ele-
ments. Nowadays, as for the heavier dipnictene series,
numerous examples of kinetically stabilized diphosphenes
(RPwPR),9 diarsenes (RAswAsR),10 and phosphaarsenes
(RPwAsR)11 have been isolated and fully characterized, and
their various chemical properties have been revealed.
#
Graduate School of Science, Kyushu University, 6-10-1
Hakozaki, Higashi-ku, Fukuoka 812-8581
##
Present address: Department of Chemical and Biological
Sciences, Faculty of Science, Japan Women’s University, 2-8-1
Mejirodai, Bunkyo-ku, Tokyo 112-0015
###
Although distibene (RSbwSbR) and dibismuthene
(RBiwBiR) should be the key compounds of great importance
Graduate School of Science, Tokyo Metropolitan University,
Hachioji, Tokyo 192-0397

662 Bull. Chem. Soc. Jpn., 75, No. 4 (2002)
HEADLINE ARTICLES
in the systematic elucidation of the intrinsic nature of low-co-
ordinated compounds of heavier group 15 elements, no stable
doubly bonded compound between two antimony atoms or two
bismuth atoms had been reported so far except for a few transi-
tion-metal complexes,12 in which the multiple bond was sup-
ported by metal bridging, until our successful syntheses and
isolation of the first stable distibene13 and dibismuthene14 uti-
lizing a very effective and bulky substituent, 2,4,6-tris[bis(tri-
methylsilyl)methyl]phenyl group (denoted as Tbt hereafter),15
which we developed during the course of our investigation on
the kinetic stabilization of low-coordinated highly reactive
species. The synthetic route of these Tbt-substituted distibene
and dibismuthene was based on an indirect way, that is, the de-
selenation reaction of the six-membered precursors, (TbtESe)3
(E = Sb and Bi). At this stage, however, we could not suffi-
ciently elucidate the reactivities of these new dipnictenes in so-
lution due to their extremely low solubility in organic solvents.
Later on, Power and co-workers also synthesized another type
of stable distibenes and dibismuthenes substituted by bulky
2,6-Ar2C6H3 groups (Ar = mesityl or 2,4,6-triisopropylphen-
yl) via simple reductive coupling reaction of the corresponding
dihalide precursors, which is the traditional method for the
synthesis of homonuclear double-bond compounds between
the heavier group 15 elements.16 On the other hand, we have
developed another bulky aromatic substituent, 2,6-bis[bis(tri-
methylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (de-
noted as Bbt) group,17 which is expected to be a potentially
more useful steric protection group than Tbt group. Indeed,
the first stable stibabismuthene (BbtSbwBiBbt), a novel hetero-
nuclear double-bond compound between antimony and bis-
muth, has been synthesized by taking advantage of the Bbt
group.18 The syntheses of a Bbt-substituted distibene and di-
bismuthene were examined in the hope of obtaining a stable
distibene and dibismuthene which would have different solu-
bility from the Tbt-substituted ones. The Bbt-substituted dist-
ibene and dibismuthene were successfully synthesized via sim-
ple and direct reductive coupling reaction of the corresponding
dibromide precursors.19 In this paper, we present the details of
the syntheses of these distibenes and dibismuthenes, which are
kinetically stabilized by Tbt or Bbt groups, together with their
chemical and physical properties.
into the corresponding divalent analogues in solution. On the
other hand, ab initio calculations have suggested that the
heavier group 15 elements, Sb or Bi, can form a compound
with rather high double-bond character and REwER (E = Sb
or Bi) should be stable enough to be isolated if the reactive
EwE double bond is kinetically protected from dimerization by
sufficiently large substituents.24
The natural and simple approach to the synthesis of a dist-
ibene may be that based on the methods used in the syntheses
of diphosphenes and diarsenes, that is, the coupling reactions
of dihalostibines. However, unsuccessful attempts to synthe-
size distibenes with some bulky substituents,12,25 which were
used in the synthesis of diphosphenes and diarsenes, prompted
us to choose other types of bulky substituents as steric protec-
tion groups. We chose first Tbt as a steric protection group,
since we have already succeeded in the synthesis of stable dis-
ilene,26 silaaromatic compounds (2-silanaphthalene,27 silaben-
zene,28 and 9-silaanthracene29), and a variety of compounds
having a double bond between the heavier group 14 and 16 el-
ements (heavy ketones)30 by taking advantage of kinetic stabi-
lization using a Tbt group (Chart 1). These examples clearly
show that the Tbt group is a very effective steric protection
group to stabilize these highly reactive compounds, in particu-
lar, compounds with a multiple bond containing fifth row ele-
ments or sixth row elements such as Sn, Te, and Pb. From
these points of view, we expected that Tbt-substituted distibene
and dibismuthene would be isolated as stable doubly bonded
systems protected by two Tbt groups effectively.
Chart 1.
Synthesis of Tbt-Substituted Distibene and Dibismuth-
ene. Dichlorostibine 1a and dichlorobismuthine 2a bearing a
Tbt group TbtECl2 (1a; E = Sb, 2a; E = Bi) were readily syn-
thesized by the reaction of TbtLi with SbCl3 or BiCl3, respec-
tively, where neither Tbt2ECl nor Tbt3E was obtained, proba-
bly due to the bulkiness of the Tbt group. In the initial stage of
the investigation, the simplest approach to distibenes, i. e., the
attempted coupling reactions of dichlorostibine 1a using vari-
ous reducing reagents such as magnesium, lithium, lithium
Results and Discussion
As described above, the first stable diphosphene having a
PwP double bond was synthesized and isolated utilizing steric
protection afforded by bulky Mes* groups.8 Using a similar
synthetic approach, diarsenes (RAswAsR) have also been suc-
cessfully synthesized and isolated.10 These compounds bear
considerable structural similarity to azo compounds, i. e., their
lighter congeners. For example, their P–P and As–As double
bonds are shorter than the corresponding single bonds (by
about 7–10%), and they have an almost planar trans geometry.
As for the counterparts of group 14 elements, i. e., Si and Ge
analogues of ethylene, disilenes (R2SiwSiR2)20 and digermenes
(R2GewGeR2),21 can be isolated by taking advantage of kinetic
stabilization like diphosphenes and diarsenes. By contrast, the
heavier Sn and Pb atoms are reluctant to form doubly bonded
systems, distannenes (R2SnwSnR2)20–22 and diplumbenes
(R2PbwPbR2),20–23 because of the high tendency to dissociate
Scheme 1.

T. Sasamori et al.
Bull. Chem. Soc. Jpn., 75, No. 4 (2002) 663
naphthalenide, and so on resulted in the recovery of a small
amount of starting materials together with the formation of a
small amount of TbtH. The reason why distibene could not be
isolated via this simple reductive coupling method will be ex-
plained later.
12 h, the solution turned purple, and then the expected dibis-
muthene 6a was precipitated on cooling and isolated in 68%
yield as deep-purple single crystals by filtration as in the case
of 4a. Thus, the first stable distibene and dibismuthene, i. e.,
the long-sought doubly bonded compounds consisting of anti-
mony and bismuth, were synthesized and isolated as stable
compounds. Fortunately, the extremely low solubility of 4a
and 6a in common organic solvents made their isolation quite
simple.
Desulfurization reaction of novel sulfur-containing antimo-
ny compounds synthesized by the reaction of TbtSbH2 with el-
emental sulfur (Scheme 1)31 was also examined as another
synthetic approach to a distibene. However, no distibene was
observed in the reaction of 1,3,2,4-dithiadistibetane with hex-
amethylphosphorous triamide (HMPT) in toluene-d8 at 120
°C. Also, the desulfurization of 1,3,5,2,4,6-trithiatristibane
(TbtSbS)3 with triphenylphosphine did not proceed even under
severe reaction conditions (130 °C for 30 h in toluene). These
unsuccessful results of desulfurization reactions of cyclic anti-
mony-sulfur compounds turned our attention to the possible
deselenation reaction of an appropriate selenium-containing
compound, because selenium is known to be removed more
easily than sulfur in the case of chalcogenadiphosphirane de-
rivatives.32
A six-membered ring precursor, 1,3,5,2,4,6-triselenatrist-
ibane 3a, was synthesized by the reaction of TbtSbCl2 1a with
Li2Se in THF at room temperature (Scheme 2). The structure
of 3a was supported by 1H and 77Se NMR, elemental analysis,
and molecular weight measurement. When a toluene solution
of 3a and excess amount of HMPT was heated at 110 °C in a
sealed tube, distibene TbtSbwSbTbt (4a) was precipitated from
the mixture on cooling and was isolated as deep green single
crystals in 94% yield by filtration in a glovebox filled with ar-
gon (Scheme 3). This roundabout deselenation synthetic route
to distibene 4a was expected to be also applicable to the syn-
thesis of the first stable dibismuthene. Indeed, treatment of
TbtBiCl2 (2a) with Li2Se in THF afforded a bismuth- and sele-
nium-containing six-membered ring compound, (TbtBiSe)3
(5a). The first example of the heaviest congener of azo-com-
pounds, i. e., dibismuthene 6a, was also successfully synthe-
sized by a similar method, namely, the deselenation reaction of
1,3,5,2,4,6-triselenatribismane 5a with an excess amount of
HMPT in toluene at 110 °C in a sealed tube. After heating for
In the final step in the synthesis of distibene 4a, that is, the
deselenation reaction of 3a, it is reasonable to postulate the ini-
tial formation of stibinidene 9a, i. e., a monovalent species of
antimony, as an intermediate.33 We tried the trapping reaction
of the intermediate in this deselenation reaction. When 3a was
treated with HMPT in the presence of isoprene in toluene at
110 °C in a sealed tube for 22 h, Tbt-substituted stibolene de-
rivative 7a was obtained as a main product (62%) together with
a small amount of green crystals of distibene 1 (26%). Sti-
bolene 8a was also obtained (65%) in a similar deselenation
reaction of 3a using 2,3-dimethyl-1,3-butadiene instead of iso-
prene (Scheme 4). On the other hand, thermolysis of the iso-
lated distibene 4a in the presence of 2,3-dimethyl-1,3-butadi-
ene (in toluene, at 150 °C) did not give such [1 + 4]cycload-
duct of stibinidene 8a but resulted in an almost quantitative re-
covery of 4a. These results suggest that distibene 4a is not
thermally dissociated into stibinidenes 9a, because 9a should
be trapped as stibolene derivative 8a if generated. Taking ac-
count of the above-mentioned results, we can reasonably ex-
plain the formation of 7a and 8a as a main product in the dese-
lenation reactions of 3a by the initial formation of an interme-
diary stibinidene 9a and its subsequent [1 + 4]cycloaddition
reactions with butadienes. Furthermore, thermolysis of a tolu-
ene-d8 solution of the isolated stibolene 7a in the presence of
excess amount of 2,3-dimethyl-1,3-butadiene at 120 °C in a
Scheme 4.
Scheme 2.
Scheme 3.
Scheme 5.

664 Bull. Chem. Soc. Jpn., 75, No. 4 (2002)
HEADLINE ARTICLES
sealed tube resulted in the formation of the diene-exchange ad-
duct 8a in 74% yield. Thermolysis of 8a in toluene-d8 in the
presence of an excess amount of isoprene also afforded the
corresponding diene-exchanged product 7a in 78% yield.
These results indicate that the stibinidene 9a was regenerated
by the thermal retrocycloaddition of both stibolenes 7a and 8a.
In addition, thermolysis of 7a in the absence of any trapping
reagents afforded distibene 4a in 55% yield, suggesting the
dimerization of the thermally generated stibinidene intermedi-
ate 9a (Scheme 5). These facts indicate that this reaction can
be used as another synthetic method for distibene 4a.
Fig. 1. Selected bond lengths (Å) and bond angles (°) for
distibene 4a and dibismuthene 6a.
In the case of deselenation of (TbtBiSe)3 (5a) in the pres-
ence of either isoprene or 2,3-dimethyl-1,3-butadiene, no di-
ene-adduct of the corresponding bismuthinidene intermediate
was obtained, probably due to the weakness of the Bi–C bonds
in the diene-adducts and/or the extremely high reactivity of the
bismuthinidene intermediate toward dimerization.
lengths for HEwEH and H2E–EH2 (E = group 15 elements) are
summarized in Table 1.36
The observed Sb–Sb–C bond angle of 101.4(1)° in 4a and
the Bi–Bi–C bond angle of 100.5(2)° in 6a deviate greatly
from the ideal sp2 hybridized bond angle (120°). These exper-
imental results indicate that the heavy atoms like antimony and
bismuth atoms have a lower tendency to form a hybridized or-
bital and prefer to maintain the (ns)2(np)3 valence electron con-
figuration. The size-difference and energy-gap between the
valence s and p orbitals are known to increase upon going from
N to Bi atoms (the significant 6s orbital contraction originates
mostly from the relativistic effect).37 Theoretical calculations
for HEwEH (Table 1) also show the E–E–H angles get closer to
90° as the center element “E” goes from N to Bi, because the
use of these three orthogonal 6p orbitals without significant
hybridization leads to a bond angle of approximately 90° at
bismuth. Although the experimental values of C–Sb–Sb angle
in 4a and C–Bi–Bi angle in 6a which are larger than 90° are
not consistent with those obtained by the theoretical calcula-
tions for HEwEH models, the results of DFT calculations for
sterically congested systems of REwER lead us to a reasonable
Molecular Structures of Tbt-Substituted Distibene and
Dibismuthene. The molecular geometries and the definitive
structural parameters for SbwSb and BiwBi bonds of distibene
4a and dibismuthene 6a are of great interest. In particular, it is
a very interesting question to be answered whether 6a has a
“true” double bond between bismuth atoms because 6a is the
first compound containing a bismuth-bismuth double bond, the
heaviest doubly bonded system among those which consist of
non-radioactive elements in the periodic table. The definitive
structures of 4a and 6a were determined by X-ray crystallo-
graphic analysis. These molecules have trans configuration
with the Tbt groups perpendicular to the C–E–E–C plane. The
X-ray crystallographic structural analyses of distibene 4a and
dibismuthene 6a revealed important parameters of EwE dis-
tances and C–E–E angles, which are shown in Fig. 1. The Sb–
Sb bond length [2.642(1) Å] in 4a is 7% shorter than the re-
ported Sb–Sb single bond length for Ph2Sb–SbPh2 (2.837 Å).34
As in the case of antimony, obvious bond shortening (7%) of
the Bi–Bi bond length [2.8206(8) Å] of 6a as compared with
that of Ph2Bi–BiPh2 (2.990 Å)35 agrees with the calculated
bond-shortening of 6–8% from H2Bi–BiH2 to HBiwBiH ob-
tained at the MP2, B3LYP, and QCISD levels. It is interesting
that the observed bond-shortenings of the SbwSb and BiwBi
bonds are comparable with those reported for diphosphenes;
the experimentally observed bond-shortening is 8% from the
P–P single bond in (PhP)5 [2.217(6) Å]3 to the PwP double
bond in Mes*PwPMes* [2.034(2) Å].8 The calculated bond
understanding.
The optimized structural parameters of
PhEwEPh and PhEwEH models are summarized in Table 2.36
In any pnictogen systems (E = P, As, Sb, Bi), all the optimized
structures for HEwEH, PhEwEPh, and PhEwEH systems show
very similar EwE bond lengths to each other, and they are com-
parable to the experimentally obtained values of the corre-
sponding double-bond compounds. By contrast, the bond an-
gles at the pnictogen atom are sensitive to the substituents on
the central pnictogen atoms. As for PhEwEPh systems, the
bond angles at the pnictogen atoms reasonably become smaller
with increasing the atomic number [from P (99.7°) to Bi
Table 1. The Calculated Values of the Bond Lengths and Angles for HEwEH and H2E–EH2 [Basis Sets:
TZ(2d) (DZ(p) for H)]
E–E bond lengths/Å
H–E–E bond angles/°
Compounds
MP2
2.048
2.279
2.674
2.794
B3LYP
2.045
2.270
2.656
2.767
QCISD
2.047
2.278
2.676
2.795
MP2
94.1
92.1
90.5
89.1
B3LYP
94.2
92.6
91.2
90.4
QCISD
94.6
92.7
91.3
90.2
HPwPH
HAswAsH
HSbwSbH
HBiwBiH
H2P–PH2
2.227
2.496
2.867
2.984
2.255
2.500
2.895
3.007
2.241
2.488
2.887
3.009
H2As–AsH2
H2Sb–SbH2
H2Bi–BiH2

T. Sasamori et al.
Bull. Chem. Soc. Jpn., 75, No. 4 (2002) 665
Table 2. The Calculated Values of the Bond Lengths and Angles for
PhEwEPh and PhEwEH
bond angles/°
Compounds E–E bond lengths/Å
C–E–E
H–E–E
PhPwPPh
2.049
2.271
2.659
2.770
99.7
97.4
95.4
94.5
PhAswAsPh
PhSbwSbPh
PhBiwBiPh
PhPwPH
2.046
2.270
2.657
2.768
100.3
97.7
95.9
94.9
93.4
92.1
90.7
90.2
PhAswAsH
PhSbwSbH
PhBiwBiH
B3LYP/TZ(2d) (6-31G(d) for C and H).
The phenyl groups are fixed perpendicularly to the C–E–E plane.
Table 3. UV/Vis Spectral Data for the Double-Bond Com-
pounds between Heavier Group 15 Elements
Compounds
λ1/nm (ε) n → π* λ2/nm (ε) π → π*
Mes*PwPMes*
TsiPwPTsi
Mes*PwPDis
Mes*PwPMes
TsiPwAsTsi
DisPwAsMes*
Mes*AswAsDis
TsiAswAsTsi
TbtSbwSbTbt
TbtBiwBiTbt
460(1360)
484(62.8)
427(370)
456(220)
497(20)
340(7690)
353(9474)
325(13000)
326(2500)
361(7900)
354(8400)
368(6960)
380(5000)
466(5200)
525(4000)
431(220)
449(180)
505(10)
Fig. 2. The theoretically optimized structural parameters of
dibismuthenes.
559(170)
660(100)
(94.5°)] as in the case of HEwEH systems. However, they are
clearly wider than those of HEwEH models. On the other
hand, the optimized structures of PhEwEH systems, which
have a relatively bulky phenyl group on the only one side,
show that the C–E–E angles for all heavier pnictogen atoms (E
= P, As, Sb, Bi) are widened like PhEwEPh, and that the H–E–
E angles are similar to those of HEwEH systems. Furthermore,
the optimized structural parameters for TbtBiwBiTbt (Fig. 2),
which was calculated as a representative of the sterically con-
gested systems (TbtEwETbt; E = P, As, Sb, Bi), was found to
have almost the same structural parameters (BiwBi: 2.7854 Å,
C–Bi–Bi: 100.5°) as experimentally obtained values [BiwBi:
2.806(8) Å, C–Bi–Bi: 100.5(2)°]. In addition, the C–Bi–Bi an-
gle of HBiwBiTbt model (Fig. 2.), which has only one bulky
Tbt group on the bismuth atom, was also found to be widened
to ca. 100°. Taking these results of theoretical calculations
into account, it can be concluded that the wider angles at the
antimony and bismuth atoms observed in the X-ray crystallo-
graphic analysis of 4a and 6a are probably not due to the pack-
ing force or steric repulsion between the two bulky substituents
but are due to the steric repulsion between the bulky Tbt group
and the central EwE moiety.
Mes* = 2,4,6-Tri-t-butylphenyl, Tsi = C(SiMe3)3,
Dis = CH(SiMe3)2.
transitions. The absorption of π → π* transition is much more
intense than that of n → π* transition. Distibene 4a is the first
example of a stable antimony-antimony doubly bonded sys-
tem, and the green solution of 4a in hexane showed two ab-
sorption maxima at 466 (ε 5200) and 599 nm (ε 170), which
correspond to the π → π* and n → π* transitions of the SbwSb
chromophore respectively. Dibismuthene 6a is also a new
member of the doubly bonded systems between group 15 ele-
ments and 6a is purple in hexane. The π → π* and n → π*
transitions of the BiwBi chromophore of 6a appeared as ab-
sorption maxima at 525 (ε 4000) and 660 nm (sh, ε 100), re-
spectively. The typical examples of absorption maxima report-
ed for the double-bond compounds between group 15
elements9–11 are shown in Table 3, together with those of 4a
and 6a. The experimentally observed red-shifts of 4a and 6a
relative to the values reported for diphosphenes and diarsenes
agree with the decreasing trend in the calculated values [HF/
DZ(d,p)] of the frontier orbital energy gaps of HEwEH (E = P,
As, Sb, and Bi).24 Power and co-workers also reported the
synthesis of ArSbwSbAr and ArBiwBiAr with bulky m-terphe-
nyl ligands (Ar = 2,6-Mes2C6H3 or 2,6-Tip2C6H3; Tip = 2,4,6-
triisopropylphenyl).16 Their ArEwEAr systems also show ab-
sorption at longer wavelengths for the π → π* transition; 451
nm (ε 5450; E = Sb, Ar = 2,6-Mes2C6H3), 470 nm (ε 6570; E
= Sb, Ar = 2,6-Tip2C6H3), 505 nm (ε 5010; E = Bi, Ar = 2,6-
Physical Properties of Tbt-Substituted Distibene and Di-
bismuthene. Generally, the heavier congeners of azo-com-
pounds are intensely colored. Their color arises from the EwE
double-bond chromophore, which appears as the two absorp-
tion maxima at wavelengths longer than 300 nm. These ab-
sorption maxima can reasonably be assigned as the symmetry
allowed π → π* and symmetry forbidden n → π* electron

666 Bull. Chem. Soc. Jpn., 75, No. 4 (2002)
HEADLINE ARTICLES
Table 4. The Calculated Values of the Harmonic Vibrational
Frequencies (cm−1) of HEwEH and H2E–EH2 [Basis Sets:
TZ(2d) (DZ(p) for H)]
Compounds
MP2
B3LYP
QCISD
HPwPH
606.4
331.4
213.7
150.8
615.2
343.6
223.8
159.9
626.4
337.6
216.7
152.9
HAswAsH
HSbwSbH
HBiwBiH
H2P–PH2
448.1
254.3
172.7
125.3
418.8
239.9
163.0
118.6
436.4
244.9
167.4
119.5
H2As–AsH2
H2Sb–SbH2
H2Bi–BiH2
Scheme 6.
Mes2C6H3), and 518 nm (ε 6920; E = Bi, Ar = 2,6-Tip2C6H3).
These UV–vis spectral data indicate that 4a and 6a feature
SbwSb and BiwBi double bonds, respectively, even in solution,
as in the case of diphosphenes, diarsenes, and phosphaarsenes.
In order to identify the double-bond characters of the central
EwE bonds in distibene 4a and dibismuthene 6a, the frequen-
cies of the SbwSb and BiwBi stretching vibrations were mea-
sured by resonance Raman spectroscopy. Distibene 4a showed
a characteristic strong Raman shift at 207 cm−1 (solid; excita-
tion, He–Ne laser 632.8 nm) which is higher than the frequen-
cies observed for distibanes (e.g. Ph2Sb–SbPh2 141 cm−1).34
The calculated values of the harmonic vibrational frequency of
HSbwSbH obtained at MP2, B3LYP, and QCISD/TZ(2d)
(DZ(p) for H) levels are shown in Table 4, and these values
agree with the experimentally observed value for 4a. The
diphosphene (Mes*PwPMes*) is known to show the vibration-
al frequency for its PwP double bond at 610 cm−1 in the
Raman spectra,38 and the assignment was confirmed by the
theoretically calculated values shown in Table 4. Meanwhile,
a strong band attributable to the BiwBi stretching was observed
at 134 cm−1 for 6a (solid; excitation, He–Ne laser 632.8 nm).
This is higher by 31 cm−1 than the Bi–Bi stretching frequency
of Ph2Bi–BiPh2 (103 cm−1),39 agreeing with the frequency
shift of 34 cm−1 calculated for HBiwBiH (153 cm−1) and
H2Bi–BiH2 (119 cm−1) at the QCISD level. These results in
Raman spectra suggest that 4a and 6a feature stronger EwE
bonds as compared with the corresponding E–E single bonds
(E = Sb, Bi), indicating that 4a and 6a has considerable dou-
ble bond character in the solid state.
Introduction of Bbt-groups to Distibene. Synthesis of
the First Stable Selenadistibirane. Although the first stable
distibene 4a and dibismuthene 6a have been synthesized and
isolated by taking advantage of the kinetic stabilization using
Tbt groups, the extremely low solubility of 4a and 6a in com-
mon organic solvents (e.g., hexane, benzene, toluene, CHCl3,
CH2Cl2, THF, Et2O, etc.) prevented further studies on their
chemical properties in solution. On the other hand, we have
developed a new bulky aromatic substituent, 2,6-bis[bis(tri-
methylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (de-
noted as Bbt) group,17,18 which is expected to be a potentially
more useful steric protection group than Tbt group. Taking ac-
count of the empirical fact that TbtH has very low solubility
while BbtH is comparatively more soluble than TbtH, the syn-
thesis of a Bbt-substituted distibene 4b was examined in the
hope of obtaining a new distibene which has higher solubility
than 4a.
When a 1,3,5,2,4,6-triselenatristibane derivative 3b bearing
three Bbt groups on the antimony atoms, prepared by the reac-
tion of BbtSbBr2 1b with Li2Se in THF, was treated with
HMPT (excess) in toluene at 130 °C in a sealed tube in a man-
ner similar to that used for the transformation of the Tbt ana-
logue 3a into distibene 4a, the color of the reaction mixture
turned deep red. The UV–vis spectrum of this reaction mix-
ture showed two characteristic absorption maxima at 490 and
594 nm, attributable to the π → π* and n → π* transitions, re-
spectively, of the expected distibene 4b (BbtSbwSbBbt) as in
the case of distibene 4a. Strangely, no distibene 4b was ob-
served on concentration of the reaction mixture, but a new an-
timony-containing three-membered ring compound, selenadis-
tibirane derivative 10, was isolated as air-stable orange crystals
in 85% yield. Selenadistibirane 10 showed satisfactory spec-
tral data and the molecular geometry of 10 was definitively de-
termined by X-ray structural analysis.40 The selenadistibirane
ring skeleton of 10 is an almost isosceles triangle with the nor-
mal Sb–Sb bond length [2.852(2) Å] and the two Bbt groups
are oriented in trans configuration with regard to the central se-
lenadistibirane ring.
On the other hand, the deselenation reaction of 3b with an
excess amount of HMPT in the presence of 2,3-dimethyl-1,3-
butadiene afforded the stibolene derivative 8b (70%) together
with 10 (30%)(Scheme 6). The formation of 8b as a major
product strongly suggests the initial generation of intermediary
stibinidene 9b in the deselenation reaction of 3b, as in the case
of the deselenation reaction of Tbt derivative 3a, since 10 is al-
most inert toward 2,3-dimethyl-1,3-butadiene even at 130 °C
in toluene-d8 for a long time. Taking into consideration the
previously mentioned results in the thermolysis of Tbt-substi-
tuted stibolene derivative 7a and 8a, the stibolene 8b is expect-
ed to be a good precursor of Bbt-substituted distibene 4b. In-
deed, the diene adduct 8b was found to readily undergo ther-
mal retrocycloaddition in toluene-d8 at 130 °C for 64 h in a
sealed tube to give the deep red solution of expected distibene
4b, which has indubitably higher solubility than 4a, probably
via dimerization of intermediary stibinidene 9b. The UV–vis
spectrum of 4b thus obtained was identical with that obtained
from the direct deselenation of 3b with HMPT; the two charac-
teristic absorption maxima of SbwSb moiety of 4b were ob-

T. Sasamori et al.
Bull. Chem. Soc. Jpn., 75, No. 4 (2002) 667
Scheme 7.
served at 490 (ε 6000) and 594 nm (ε 200).
In order to elucidate the formation mechanism of the selena-
distibirane 10, the reaction of distibene 4b, prepared from 8b,
with an excess of phosphine selenide (Me2N)3PwSe in toluene
at room temperature was examined. Removal of the solvent
and (Me2N)3P generated in the reaction from the reaction mix-
ture resulted in the almost quantitative formation of selenadist-
ibirane 10, while the reaction of isolated 10 with an excess of
HMPT in toluene-d8 at 120 °C for 2 h gave a solution of 4:1
Scheme 8.
Scheme 9.
1
mixture of 4b and 10 as judged by H NMR (Scheme 7).
These results are important as experimental evidence for the
equilibrium between 4b plus (Me2N)3PwSe and 10 plus
(Me2N)3P, which may be a key factor in the final step for the
formation of 10 in the deselenation reaction of 3b.
hexane. Removal of inorganic salts and subsequent evapora-
tion of hexane gave the expected distibene 4b almost quantita-
tively. This efficient synthetic method is also applicable to
Bbt-substituted dibismuthene 6b (Scheme 9). Treatment of
BbtBiBr2 2b with Mg in THF at room temperature afforded
purple powder of 6b, which has the desired solubility in com-
mon organic solvents, in almost quantitative yields. The for-
mation of 6b was readily confirmed by its two characteristic
absorption maxima at 537 (ε 6000) and 670 nm (sh, ε 20) in
hexane, which are similar to those of Tbt-substituted dibis-
muthene 6a. Thus, it was found that the traditional synthetic
method for heavier dipnictenes, i. e., reductive coupling reac-
tion of the corresponding dihalide precursor, is also applicable
even to antimony and bismuth analogues. These results also
reveal a reason why we could isolate Tbt-substituted distibene
and dibismuthene not via simple direct reduction of their ha-
lide precursors but via a more roundabout route. In our initial
experiments where TbtSbCl2 or TbtSbBr2 was treated with me-
tallic Mg as reducting reagents, the green powder generated, i.
e., distibene 4a had been removed together with inorganic salts
by filtration. Unfortunately, we could not realize at first that
the green powder is distibene 4a, which has extremely low sol-
ubility.
As mentioned above, the deselenation reactions of over-
crowded 1,3,5,2,4,6-triselenatristibanes, (TbtSbSe)3 (3a) and
(BbtSbSe)3 (3b), which are very similar to each other, afforded
quite different types of reaction products, i. e., distibene (4a)
and selenadistibirane (10), respectively. These facts are very
interesting since the initial formation of the stibinidene inter-
mediates 9a and 9b has been confirmed by the trapping experi-
ments with dienes in both reactions. The unexpected great dif-
ference in the deselenation between 3a and 3b is most likely
interpreted in terms of the remarkable insolubility of 4a in
common organic solvents, which may prevent 4a from under-
going further transformation into its selenadistibirane deriva-
tive via redistribution of a selenium atom between the initially
formed distibene and (Me2N)3PwSe on concentration (Scheme
8).
Thus, it was found that Bbt-substituted distibene 4b cannot
be isolated by the deselenation reaction of 3b but can be pre-
pared and isolated as a stable compound by the stepwise trans-
formation via stibolene derivative 8b. As for its bismuth ana-
logue, 1,3,5,2,4,6-triselenatirbismane (BbtBiSe)3 is not stable
enough to be isolated, unfortunately. It is necessary to investi-
gate other synthetic methods for the soluble dibismuthene.
Synthesis of Bbt-Substituted Distibene and Dibismuth-
ene. Since Bbt-substituted distibene 4b was found to be sol-
uble in hexane, the direct reductive coupling reaction was ex-
amined for the synthesis of 4b. Bbt-substituted dibromostib-
ine 1b was treated with Mg metal in THF at room temperature
for 30 min and then the reaction mixture was extracted with
In addition to the solubility, Tbt-substituted distibene 4a and
Bbt-substituted distibene 4b are also different in color; 4a is
green crystals while 4b is a deep red solid. In UV–vis spectra
of these distibenes and dibismuthenes, the characteristic ab-
sorption maxima corresponding to the π → π* electron transi-
tions of Bbt-substituted compounds are observed at longer

668 Bull. Chem. Soc. Jpn., 75, No. 4 (2002)
HEADLINE ARTICLES
Fig. 5. Selected bond lengths (Å) and bond angles (°) for
distibene 4b and dibismuthene 6b.
Scheme 10.
Dibismuthene. The definitive structural parameters of 4b
and 6b in the solid state were determined by the X-ray crystal-
lographic structural analysis. These molecular geometries and
selected bond lengths and angles are shown in Figs. 3, 4, and 5,
which reveal that 4b and 6b have quite similar structures to
those of 4a and 6a, respectively. The SbwSb [2.7037(6) Å]
and BiwBi [2.8699(6) Å] double bond lengths of 4b and 6b are
considerably shorter than the typical Sb–Sb and Bi–Bi single
bond lengths (Ph2Sb–SbPh2; 2.837 Å34 and Ph2Bi–BiPh2;
Fig. 3. ORTEP drawing of BbtSbwSbBbt (4b) with thermal
ellipsoid plot (50% probability).
2.990 Å35), respectively.
The previous discussion for
TbtEwETbt suggests that the C–E–E angles of 4b
[105.38(10)°] and 6b [104.15(12)°] may be widened due to the
steric repulsion between the Bbt group and the central EwE
moiety, as in the case of 4a and 6a, respectively. The structural
optimization at B3LYP level of HBiwBiBbt model shows the
C–Bi–Bi angle (104.8°) to be very close to that of 6b (104.1°)
and shows the reasonable BiwBi bond length of 2.777 Å. A
small difference between structures of Tbt-substituted and Bbt-
substituted distibenes is found in the Sb–Sb bond length and
the C–Sb–Sb angle. Distibene 4b has a longer Sb–Sb bond
length by 0.07 Å and a larger C–Sb–Sb angle by 3° than 4a. In
the case of Bi analogues, 6b also has a longer Bi–Bi bond by
0.05 Å and a larger C–Bi–Bi angle by 4° than 6a. This tenden-
cy might indicate that the Bbt group is bulkier than Tbt group
due to the difference of the substituents at p-position. The
greater steric repulsion of Bbt group slightly elongates the
EwE bonds and enlarges the C–E–E angles.
Chemical Properties of the Distibenes and the Dibis-
muthenes. Distibenes 4a,b and dibismuthenes 6a,b are quite
stable compounds at room temperature in the absence of air in
the solid state and are inert to photolysis (100 W medium pres-
sure Hg lamp/ Pyrex filter/ in a sealed tube) in C6D6 solution.
Furthermore, 4b and 6b are surprisingly inert to deoxygenated
water and MeOH even at 100 °C for a long time in a sealed
tube in C6D6 solution. On the other hand, the distibenes 4a,b
and dibismuthenes 6a,b lose their color upon exposure to air.
Furthermore, during the course of our studies on the reactivity
Fig. 4. ORTEP drawing of BbtBiwBiBbt (6b) with thermal
ellipsoid plot (50% probability).
wavelengths than those of Tbt-substituted ones by 24 nm for
distibenes and 12 nm for dibismuthene. These bathochromic
shifts, which mean lower degree of interaction between p or-
bitals, may be indicative of the longer E–E bond lengths of 4b
and 6b than of 4a and 6a, respectively, in solution.
Molecular Structures of Bbt-Substituted Distibene and

T. Sasamori et al.
Bull. Chem. Soc. Jpn., 75, No. 4 (2002) 669
ture was finally confirmed to be 1,3,2,4-dioxadistibetane 11a
and 1,3,2,4-dioxadibismetane 12a, respectively. We have al-
ready reported in detail that the oxidation process of 4a in the
crystalline phase was successfully monitored by repeated mea-
surements of the cell dimensions using an X-ray diffraction
technique with an imaging plate Weissenberg diffractome-
ter.13 Although the oxidation process of 6a was not monitored
by this method, dibismuthene 6a might also undergo the crys-
talline-state oxidation reaction to give 1,3,2,4-dioxadibismet-
ane 12a. Figures 6 and 7 show the ORTEP drawing of 12a and
selected bond lengths and angles of 11a and 12a, respectively.
The geometries of 11a and 12a are very similar to each other;
they have a completely flat four-membered ring of 1,3,2,4-di-
oxadistibetane and 1,3,2,4-dioxadibismetane, respectively.
The intramolecular distance between the two antimony atoms
of 11a was found to be increased by about 0.4 Å, and the C–
Sb–Sb angle was widened by 6° compared to distibene 4a.
1,3,2,4-Dioxadibismetane 12a also has similar features; 12a
has an elongated intramolecular distance between the two bis-
muth atoms [3.133(2) Å] and widened C–Bi–Bi angle
[104.8(3)°] compared to dibismuthene 6a. Such unique reac-
tivity in the crystalline-state as observed for 4a and 6a is most
likely interpreted in terms of the combination of the high reac-
tivity of the SbwSb and BiwBi double bond moieties toward
oxygen with the loose packing structure of the crystals, con-
sisting of overcrowded molecules bearing very bulky Tbt
group. On the other hand, 4b and 6b also reacted with atmo-
spheric oxygen in the crystalline state to give colorless crys-
tals. In contrast to the case of 4a and 6a, however, the oxida-
tion reactions gave only very complicated mixtures containing
BbtH. In solution, 4b and 6b reacted with atmospheric oxygen
very rapidly to give again complex mixtures containing BbtH.
Although the corresponding 1,3,2,4-dioxadistibetane and
1,3,2,4-dioxadibismetane derivatives 11b and 12b may be gen-
erated in these oxidation reactions, we have not succeeded in
clarifying the fate of the oxidized products. They may easily
undergo over-oxidation and decomposition in solution due to
their high solubility, in contrast to 11a and 12a which are al-
most insoluble.
Fig. 6. ORTEP drawing of 12a with thermal ellipsoid plot
(30% probability).
Conclusion
Following the pioneering work on stable diphosphenes and
diarsenes, the first stable distibenes and dibismuthenes were
successfully synthesized by taking advantage of kinetic stabili-
zation using bulky Tbt and Bbt groups. Thus, the doubly
bonded compounds between heavier group 15 elements are no
more imaginary species but are those with real existence which
are stable, even in the heaviest non-radioactive element of bis-
muth, when they are appropriately protected by bulky substitu-
ents. The construction of a series of doubly bonded systems
between group 15 elements in the present work revealed the
feature of the core-like nature of the ns electron, namely, the
so-called “inert s-pair effect” or “non-hybridization effect” of
the heavier group 15 elements. Although it is difficult to inves-
tigate the reactivities of 4a and 6a in solution due to their ex-
tremely low solubility values, the syntheses of soluble dist-
ibene 4b and dibismuthene 6b have made it possible for us to
elucidate their reactivity in solution, which will be described
elsewhere in the near future. Furthermore, theoretical calcula-
Fig. 7. Selected bond lengths (Å) and bond angles (°) for
11a and 12a.
with oxygen of distibenes and dibismuthene, a unique and in-
teresting reactivity of 4a and 6a with oxygen was found. Crys-
talline dipnictenes 4a and 6a reacted with atmospheric oxygen
to give the corresponding 1,3,2,4-dioxadistibetane and 1,3,2,4-
dioxadibismetane derivatives 11a and 12a, which are rather
stable in the solid state in open air (Scheme 10). Thus, the
crystals of 4a remained dark green for several hours, but they
slowly reacted with atmospheric oxygen to give 11a quantita-
tively. Similarly, the purple color of the crystals of 6a gradual-
ly faded in open air to give 12a as colorless crystals. Single
crystals of these compounds suitable for X-ray crystallograph-
ic analysis were obtained by a unique method of leaving the
single crystals of 4a and 6a in air for a few days, and the struc-

670 Bull. Chem. Soc. Jpn., 75, No. 4 (2002)
HEADLINE ARTICLES
dures.
Preparation of {2,4,6-Tris[bis(trimethylsilyl)methyl]phen-
tions showed that the bond angles of C–E–E of these doubly
bonded systems between heavier group 15 elements were con-
siderably widened by bulky substituents, which are indispens-
able to isolate these compounds, while the EwE bond lengths
were not so influenced by the steric congestion.
The concept of kinetic stabilization should certainly be of
great use for the construction of these unprecedented chemical
bondings. Also, matching of theoretical calculations with ex-
periments has been shown to be very important to elucidate the
intrinsic nature of new inter-element linkages of heavier main
group elements. We hope the successful application of the ki-
netic stabilization to the chemistry of heavier dipnictenes will
lead to further progress in the synthesis and properties of a
unique class of low-coordinated main group elements in fu-
ture.
yl}dichlorostibine (1a). To a solution of TbtBr (5.05 g, 8.00
mmol) in THF (120 mL) was added t-butyllithium (1.6 M pentane
solution, 11.0 mL, 17.6 mmol) at −78 °C. After 30 min, a solu-
tion of SbCl3 (2.82 g, 12.3 mmol) in THF (40 mL) was added.
The reaction mixture was warmed to room temperature and stirred
for 2 h. The solvents were evaporated under reduced pressure and
100 mL of hexane was added to the residue. Insoluble inorganic
salts were removed by filtration through Celite®. After removal of
the solvent from the filtrate, the residue was reprecipitated from
CH2Cl2/isopropyl alcohol to afford TbtSbCl2 (1a, 4.13 g, 69%).
1a: pale yellow crystals, mp 128–129 °C (decomp). Found: C,
42.89; H, 7.80; Cl, 9.88%. Calcd for C27H59Cl2SbSi6: C, 43.53; H,
7.98; Cl, 9.52%. 1H NMR (500 MHz, CDCl3) δ 0.05 (s, 18H),
0.09 (s, 36H), 1.36 (s, 1H), 2.44 (s, 1H), 2.53 (s, 1H), 6.36 (s, 1H),
6.52 (s, 1H). 13C NMR (125 MHz, CDCl3) δ 0.67 (q), 0.75 (q),
0.97 (q), 30.1 (d), 31.36 (d), 31.40 (d), 123.5 (s), 128.2 (d), 145.3
(d), 148.3 (s), 151.8 (s), 152.6 (s). HRMS (FAB) Found: m/z
744.1651 ([M]+). Calcd for C27H59Cl2SbSi6 ([M]+): 744.1703.
Preparation of {2,4,6-Tris[bis(trimethylsilyl)methyl]phen-
yl}dichlorobismuthine (2a). To a solution of TbtBr (3.16 g,
5.00 mmol) in THF (45 mL) was added t-butyllithium (1.6 M pen-
tane solution, 6.9 mL, 11.0 mmol) at −78 °C. After 30 min, a so-
lution of BiCl3 (2.37 g, 7.5 mmol) in THF (15 mL) was added.
The reaction mixture was warmed to room temperature and stirred
for 12 h. The solvents were evaporated under reduced pressure
and 100 mL of hexane was added to the residue. Insoluble inor-
ganic salts were removed by filtration through Celite®. The re-
moval of the solvent from the filtrate gave 2.0 g of a lemon yellow
solid, which contained TbtBiCl2 (2a, 42%) and TbtH (9%) with
the ratio of 9:2 as estimated by 1H NMR spectrum. This mixture
was used for the next reaction without further purification. 2a:
lemon yellow crystals, mp 235–250 °C (decomp). 1H NMR (500
MHz, CDCl3) δ 0.05 (s, 18H), 0.10 (s, 36H), 1.34 (s, 1H), 2.27 (s,
1H), 2.31 (s, 1H), 7.05 (s, 1H), 7.25 (s, 1H). HRMS (FAB)
Found: m/z 832.2487 ([M]+). Calcd for C27H59BiCl2Si6 ([M]+):
832.2384.
Experimental
Theoretical Calculations. All theoretical calculations were
carried out using the Gaussian 98 program.41 The triple zeta basis
set ([3s3p])42 augmented by two sets of d polarization functions
for P (d exponents 0.537 and 0.153), As (d exponents 0.434 and
0.129), Sb (d exponents 0.277 and 0.088), and Bi (d exponents
0.229 and 0.069) and double zeta basis ([2s2p]) set for Si were
used with an effective core potential. The 6-31G(d) basis set
(PhEwEPh and HEwEPh) and the 3-21G basis set (the others)
were used for C and H. In geometrical optimization of PhEwEPh
and HEwEPh, the phenyl groups were fixed perpendicularly to the
C–E–E plane.
General Procedure. All experiments were performed under
an argon atmosphere unless otherwise noted. Solvents were dried
by standard methods and freshly distilled prior to use. 1H NMR
(500, 300, or 270 MHz) and 13C NMR (125, 75, or 68 MHz) spec-
tra were measured in CDCl3 or C6D6 with a Bruker AM-500,
Bruker DRX-500, JEOL JNM-A500, JEOL AL-300, or JEOL EX-
1
270 spectrometer. In H NMR signals due to CHCl3 (7.25 ppm)
and C6D5H (7.15 ppm) were used as references, and those due to
CDCl3 (77 ppm) and C6D6 (128 ppm) were used in 13C NMR.
Multiplicity of signals in 13C NMR spectra was determined by
DEPT technique. 77Se NMR (95 MHz) spectra were measured in
CDCl3 or C6D6 with a JEOL JNM-A500 spectrometer using
diphenyl diselenide as an external standard (480 ppm). High- and
low-resolution mass spectral data were obtained on a JEOL JMS-
SX102 spectrometer. Molecular weights were measured by vapor
pressure osmometry in CHCl3 with HITACHI 117. GPLC (gel
permeation liquid chromatography) was performed on an LC-908
(Japan Analytical Industry Co., Ltd.) equipped with JAIGEL 1H
and 2H columns (eluent: chloroform or toluene). Electronic spec-
tra were recorded on a JASCO V530 UV/VIS or JASCO Ubest-50
UV/VIS spectrometer. Raman spectra were measured at room
temperature on a Raman spectrometer consisting of a Spex 1877
Triplemate and an EG & G PARC 1421 intensified photodiode ar-
ray detector. An NEC GLG 108 He-Ne laser (632.8 nm) was used
for Raman excitation. All melting points were determined on a
Yanaco micro melting point apparatus and are uncorrected. Ele-
mental analyses were carried out at the Microanalytical Laborato-
ry of the Department of Chemistry, Faculty of Science, The Uni-
versity of Tokyo or at the Microanalytical Laboratory of the Insti-
tute for Chemical Research, Kyoto University. 1-Bromo-2,4,6-
tris[bis(trimethylsilyl)methyl]benzene (TbtBr)15 and 1-bromo-2,6-
bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]ben-
zene (BbtBr)17 were prepared according to the reported proce-
Preparation of 2,4,6-Tris{2,4,6-tris[bis(trimethylsilyl)meth-
yl]phenyl}-1,3,5,2,4,6-triselenatristibane (3a). To
a suspen-
sion of selenium (23.8 mg, 0.30 mmol) in THF (1 mL) was added
a THF solution (0.67 mL) of LiB(C2H5)3H (1.0 M, 0.67 mmol) at
room temperature. After 15 min, a solution of TbtSbCl2 1a (224
mg, 0.30 mmol) in THF (5 mL) was added and the reaction mix-
ture was stirred for 1 h. The solvent was evaporated under re-
duced pressure and 30 mL of hexane was added to the residue. In-
soluble inorganic salts were removed by filtration through Celite®.
After removal of the solvent from the filtrate, the residue was puri-
fied by GPLC and reprecipitation from CH2Cl2/EtOH to afford
(TbtSbSe)3 (3a, 154 mg, 68%) 3a: yellow crystals, mp 284–286
°C. Found: C, 42.77; H, 7.62; Se, 10.33%. Calcd for
C81H177Sb3Se3Si18: C, 43.06; H, 7.89; Se, 10.48%. 1H NMR (500
MHz, CDCl3) δ 0.03 (s, 54H), 0.06 (s, 54H), 0.08 (s, 54H), 1.30
(s, 3H), 2.69 (s, 6H), 6.30 (s, 3H), 6.42 (s, 3H). 13C NMR (125
MHz, CDCl3) δ 0.72 (q), 0.87 (q), 1.13 (q), 30.38 (d), 32.32 (d),
32.71 (d), 122.8 (d), 127.6 (d), 139.6 (s), 144.8 (s), 150.9 (s),
151.1 (s). 77Se NMR (95 MHz, CDCl3) δ 179. Molecular weight
(osmometry in CHCl3) Found: 2146. Calcd for C81H177Sb3Se3Si18:
2259.
Synthesis and Isolation of Bis{2,4,6-tris[bis(trimethylsi-
lyl)methyl]phenyl}distibene (4a). To a toluene solution (5 mL)
of 3a (338 mg, 0.15 mmol) was added 0.29 mL of P(NMe2)3 (1.5

T. Sasamori et al.
Bull. Chem. Soc. Jpn., 75, No. 4 (2002) 671
mmol), and the reaction mixture was heated at 110 °C in a sealed
tube for 12 h. Green crystals, which were precipitated by cooling
the mixture to room temperature, were filtered in a glovebox filled
with argon to afford Tbt2Sb2 4a (284 mg, 94%). 4a: green crys-
tals, mp > 300 °C. Found: C, 47.50; H, 8.70%. Calcd for
C54H118Sb2Si12: C, 48.11; H, 8.82%. 1H NMR (500 MHz, CDCl3)
δ 0.128 (s, 36H), 0.132 (s, 36H), 0.15 (s, 36H), 1.44 (s, 2H), 2.75
(s, 2H), 2.94 (s, 2H), 6.54(s, 2H), 6.64 (s, 2H). UV–vis (hexane)
599 (ε 170), 466 nm (ε 5200). FT-Raman (solid, excitation; He–
Ne laser 632.8 nm) 207 cm−1 (νSbwSb).
Preparation of 2,4,6-Tris{2,4,6-tris[bis(trimethylsilyl)meth-
yl]phenyl}-1,3,5,2,4,6-triselenatribismane (5a). To a suspen-
sion of selenium (31.6 mg, 0.40 mmol) in THF (1 mL) was added
a THF solution (0.84 mL) of LiB(C2H5)3H (1.0 M, 0.84 mmol) at
room temperature. After 15 min, a solution of TbtBiCl2 2a (332
mg, 0.4 mmol) in THF (5 mL) was added and the reaction mixture
was stirred for 1 h. After removal of the solvent from the filtrate,
the residue was purified by GPLC to afford (TbtBiSe)3 (5a, 94.5
mg, 28%) 5a: orange crystals, mp 262–265 °C. HRMS (FAB)
Found: m/z 1967.3241 ([M−Tbt]+), 1890.4158 ([M + H−Tbt]+).
Calcd for C54H118Bi378Se80Se2Si12 ([M−Tbt]+): 1967.338,
C54H119Si12Bi380Se2 ([M + H−Tbt]+): 1890.4286. 1H NMR (500
MHz, CDCl3) δ 0.03 (s, 54H), 0.07 (s, 118H), 1.28 (s, 3H), 2.42
(s, 2H), 2.44 (s, 2H), 2.51 (s, 2H), 6.65 (s, 2H), 6.68 (s, 2H), 6.75
(s, 2H).
Synthesis and Isolation of Bis{2,4,6-tris[bis(trimethylsi-
lyl)methyl]phenyl}dibismuthene (6a). To a toluene solution
(0.5 mL) of 5a (20.8 mg, 0.008 mmol) was added 0.02 mL of
P(NMe2)3 (0.1 mmol), and the reaction mixture was heated at 110
°C in a sealed tube for 12 h. Deep-purple crystals, which were
precipitated by cooling the mixture to room temperature, were fil-
tered in a glovebox filled with argon to afford Tbt2Bi2 6a (12.8
mg, 68%). 6a: purple crystals, mp > 300 °C. Found: C, 42.37; H,
7.77%. Calcd for C54H118Bi2Si12: C, 42.60; H, 7.81%. UV–vis
(hexane) 660 (sh, ε 100), 525 nm (ε 4000). FT-Raman (solid, ex-
citation; He–Ne laser 632.8 nm) 134 cm−1 (νBiwBi).
Deselenation Reaction of (TbtSbSe)3 (3a) with P(NMe2)3 in
the Presence of Isoprene. To a toluene solution (4 mL) of 3a
(217 mg, 0.10 mmol) were added 0.18 mL of P(NMe2)3 (1.0
mmol) and 1.0 mL of isoprene (10.0 mmol), and the reaction mix-
ture was heated at 110 °C in a sealed tube for 12 h. Green crys-
tals, which were precipitated by cooling the mixture to room tem-
perature, were filtered in a glovebox filled with argon to afford
Tbt2Sb2 4a (16 mg, 26%). The filtrate was separated by GPLC to
give the stibolene 7a (133 mg, 62%). 7a: colorless powder, mp
123–125 °C (decomp). Found: C, 50.61; H, 8.72%. Calcd for
C32H67SbSi6•H2O: C, 50.56; H, 9.14%. 1H NMR (500 MHz,
CDCl3) δ 0.31 (s, 54H), 1.27 (s, 1H), 1.81 (s, 3H), 1.97 (s, 1H),
2.03 (s, 1H), 2.34–1.47 (m, 2H), 3.05–3.10 (m, 2H), 5.89 (br s,
1H), 6.26 (s, 1H), 6.40 (s, 1H). 13C NMR (125 MHz, CDCl3) δ
0.74 (q), 1.02 (q), 21.4 (d), 23.6 (t), 28.6 (t), 29.9 (q), 30.8 (d),
31.0 (d), 121.8 (d), 126.7 (d), 127.4 (d), 133.3 (s), 142.0 (s), 142.7
(s), 150.5 (s), 150.7 (s).
65%). 8a: colorless powder, mp 141–143 °C (decomp). Found:
C, 51.64; H, 8.99%. Calcd for C33H69SbSi6•H2O: C, 51.20; H,
1
9.24%. H NMR (500 MHz, CDCl3) δ 0.00 (s, 54H), 1.26 (s, 1H),
2
1.66 (s, 6H), 1.93 (s, 1H), 1.99 (s, 1H), 2.43 (d, JHH = 14.4 Hz,
2H), 3.18 (d, 2JHH = 14.4 Hz, 2H), 6.24 (s, 1H), 6.38 (s, 1H). 13C
NMR (125 MHz, CDCl3) δ 0.73(q), 1.03 (q), 20.3 (d), 29.9 (q),
30.7 (t), 30.8 (d), 31.1 (d), 121.8 (d), 126.7 (d), 132.1 (s), 132.2
(s), 142.5 (s), 150.4 (s), 150.5 (s).
Thermolysis of Stibolene 7a in the Presence of 2,3-Dimeth-
yl-1,3-butadiene. 7a (22.3 mg, 0.03 mmol) and 2,3-dimethyl-
1,3-butadiene (34 µL, 0.30 mmol) were dissolved in toluene-d8
(0.7 mL), and the solution was degassed and sealed in an NMR
tube. After the reaction mixture was heated at 90 °C for 4.5 h, no
change was observed by 1H NMR. Furthermore, after the solution
was heated at 120 °C for 20 h, the signals of 7a disappeared and
the signals assignable to 8a were observed by 1H NMR. The reac-
tion mixture was separated by GPLC to give 8a (16.7 mg, 74%).
Thermolysis of Stibolene 8a in the Presence of Isoprene.
8a (22.8 mg, 0.03 mmol) and isoprene (30 µL, 0.30 mmol) were
dissolved in toluene-d8 (0.7 mL), and the solution was degassed
and sealed in an NMR tube. After the solution was heated at 120
°C for 23 h and 130 °C for 12 h, the signals of 8a disappeared and
the signals assignable to 7a were observed by 1H NMR. The reac-
tion mixture was separated by GPLC to give 7a (17.4 mg, 78%).
Thermolysis of Stibolene 7a. 7a (21.0 mg, 0.03 mmol) was
dissolved in toluene-d8 (0.6 mL), and the solution was degassed
and sealed in an NMR tube. After the solution was heated at 120
1
°C for 19 h, the signals of 7a found by H NMR disappeared.
Green crystals, which were precipitated by cooling the mixture to
room temperature, were filtered to afford Tbt2Sb2 4a (10.3 mg,
55%).
Preparation
of
{2,6-Bis[bis(trimethylsilyl)methyl]-4-
[tris(trimethylsilyl)methyl]phenyl}dibromostibine (1b). To a
solution of BbtBr (3.52 g, 5.00 mmol) in THF (50 mL) was added
t-butyllithium (1.6 M pentane solution, 7.0 mL, 12.0 mmol) at
−78 °C. After 30 min, a solution of SbBr3 (2.74 g, 7.60 mmol) in
THF (15 mL) was added. The reaction mixture was warmed to
room temperature and stirred for 12 h. The solvents were evapo-
rated under reduced pressure and 100 mL of hexane was added to
the residue. Insoluble inorganic salts were removed by filtration
through Celite®. After removal of the solvent from the filtrate, the
residue was reprecipitated from CH2Cl2/isopropyl alcohol to af-
ford BbtSbBr2 (1b, 3.05 g, 67%). 1b: pale yellow crystals, mp
128–130 °C (decomp). 1H NMR (500 MHz, CDCl3) δ 0.14 (s,
36H), 0.26 (s, 27H), 2.64 (s, 2H), 6.83 (s, 2H). 13C NMR (125
MHz, CDCl3) δ 1.46 (q), 5.41 (q), 23.16 (s), 32.23 (d), 127.99 (d),
143.13 (s), 149.84 (s), 151.51 (s). HRMS (FAB) Found: m/z
906.1048 ([M]+). Calcd for C30H6779Br81BrSi7123Sb ([M]+):
906.1016.
Preparation of 2,4,6-Tris{2,6-bis[bis(trimethylsilyl)methyl]-
4-[tris(trimethylsilyl)methyl]phenyl}-1,3,5,2,4,6-triselenatrist-
ibane (3b). To a suspension of selenium (63.4 mg, 0.80 mmol)
in THF (2 mL) was added a THF solution (1.7 mL) of
LiB(C2H5)3H (1.0 M, 1.70 mmol) at room temperature. After 10
min, a solution of BbtSbBr2 (1b) (730 mg, 0.80 mmol) in THF (12
mL) was added and the reaction mixture was stirred for 1.5 h. The
solvent was evaporated under reduced pressure and 30 mL of hex-
ane was added to the residue. Insoluble inorganic salts were re-
moved by filtration through Celite®. After removal of the solvent
from the filtrate, the residue was purified by GPLC and reprecipi-
tation from CHCl3/isopropyl alcohol to afford (BbtSbSe)3 (3b,
484 mg, 73%) 3b: yellow crystals, mp 293–296 °C (decomp).
Deselenation Reaction of (TbtSbSe)3 (3a) with P(NMe2)3 in
the Presence of 2,3-Dimethyl-1,3-butadiene. To a toluene so-
lution (3 mL) of 3a (136 mg, 0.06 mmol) were added 0.10 mL of
P(NMe2)3 (0.6 mmol) and 0.7 mL of 2,3-dimethyl-1,3-butadiene
(6.0 mmol), and the reaction mixture was heated at 120 °C in a
sealed tube for 15 h. Green crystals, which were precipitated by
cooling the mixture to room temperature, were filtered in a glove-
box filled with argon to afford Tbt2Sb2 4a (14.5 mg, 12%). The
filtrate was separated by GPLC to give the stibolene 8a (88.3 mg,

672 Bull. Chem. Soc. Jpn., 75, No. 4 (2002)
HEADLINE ARTICLES
Found: C, 43.44; H, 7.89%. Calcd for C90H201Sb3Se3Si21: C,
43.67; H, 8.18%. 1H NMR (500 MHz, CDCl3) δ 0.13 (s, 108H),
0.26 (s, 81H), 2.75 (brs, 6H), 6.80 (s, 6H). 13C NMR (125 MHz,
CDCl3, 323 K) δ 1.79 (q), 5.47 (q), 22.48 (s), 34.16 (d), 127.50
(d), 143.38 (s), 146.77 (s), 151.06 (s). Molecular weight (osmom-
etry in CHCl3) Found: 2447. Calcd for C90H201Sb3 Se3Si21: 2475.
Deselenation Reaction of (BbtSbSe)3 (3b) with P(NMe2)3.
3b (50.2 mg, 0.02 mmol) and P(NMe2)3 (0.02 mL, 0.08 mmol)
were dissolved in toluene-d8 (0.6 mL), and the solution was de-
gassed and sealed in an NMR tube. After the solution was heated
at 130 °C for 33 h, the signals of the selenadistibirane 10 and
0.04 mL of P(NMe2)3 (0.16 mmol), and then the solution was de-
gassed and sealed in an NMR tube. The signals of 10 and 4b were
observed in the ratio of 1:1 in the 1H NMR spectrum at room tem-
perature. After the reaction mixture was heated at 120 °C for 2 h,
1
the signals of 10 and 4b were observed in the ratio of 1:4 by H
NMR. Even after the solution was further heated at 120 °C for 15
h and at 150 °C for 23 h, no change of the ratio was observed in
the 1H NMR spectra.
Synthesis
[tris(trimethylsilyl)methyl]phenyl}distibene (4b) via Reductive
Coupling Reaction of BbtSbBr2 (1b) with Mg Metal. To a
of
Bis{2,6-bis[bis(trimethylsilyl)methyl]-4-
1
BbtSbwSbBbt 4b were observed in the ratio of 6:1 by H NMR.
THF solution (4 mL) of BbtSbBr2 1b (378 mg, 0.09 mmol) was
added Mg metal (31.2 mg, 1.28 mmol) at room temperature. After
the reaction mixture was stirred for 30 min, the color of the solu-
tion changed to deep red. The solvent was evaporated under re-
duced pressure and 30 mL of hexane was added to the residue. In-
soluble inorganic salts were removed by filtration through Celite®.
The removal of the solvent from the filtrate gave a deep red solid
of distibene 4b (64.0 mg, quant.).
Deep red crystals, which were precipitated by cooling the mixture
to room temperature, were filtered to afford the selenadistibirane
10 (25.1 mg, 52%). The filtrate was separated by GPLC to give 10
(15.7 mg, 33%) and starting material 3b (1.9 mg, 4%). 10: orange
crystals, mp 215–220 °C (decomp). Found: C, 46.13; H, 8.37; Se,
4.56%. Calcd for C60H134Sb2SeSi14: C, 45.86; H, 8.60; Se, 5.02%.
1H NMR (500 MHz, CDCl3) δ 0.37(s, 54H), 0.41 (s, 72H), 3.00 (s,
4H), 6.99 (s, 4H). 13C NMR (125 MHz, CDCl3, 323 K) δ 2.01 (q),
2.13 (q), 5.65 (q), 22.30 (s), 36.98 (d), 127.00 (d), 142.19 (s),
146.05 (s), 150.89 (s). 77Se NMR (95 MHz, C6D6) δ −182. Mo-
lecular weight (osmometry in CHCl3) Found: 1491. Calcd for
C60H134Sb2SeSi14: 1571.
Deselenation Reaction of (BbtSbSe)3 (3b) with P(NMe2)3 in
the Presence of 2,3-Dimethyl-1,3-butadiene. To a toluene so-
lution (4 mL) of 3b (263 mg, 0.11 mmol) were added 0.40 mL of
P(NMe2)3 (1.6 mmol) and 1.2 mL of 2,3-dimethyl-1,3-butadiene
(10.0 mmol), and the reaction mixture was heated at 130 °C in a
sealed tube for 38 h. The reaction mixture was separated by
GPLC to give the selenadistibirane 10 (80.1 mg, 30%) and the sti-
bolene 8b (192.7 mg, 70%). 8b: colorless powder, mp 104–106
Preparation
of
{2,6-Bis[bis(trimethylsilyl)methyl]-4-
[tris(trimethylsilyl)methyl]phenyl}dibromobismuthine (2b).
To a solution of BbtBr (2.10 g, 3.00 mmol) in THF (30 mL) was
added t-butyllithium (1.65 M pentane solution, 4.3 mL, 7.6 mmol)
at −78 °C. After 30 min, a solution of BiCl3 (2.74 g, 7.60 mmol)
in THF (15 mL) was added. After the reaction mixture was stirred
at −78 °C for 2 h, LiBr (6.75 g, 77.7 mmol) was added. The reac-
tion mixture was warmed to room temperature and stirred for 12
h. The solvents were evaporated under reduced pressure and 100
mL of hexane was added to the residue. Insoluble inorganic salts
were removed by filtration through Celite®. After removal of the
solvent from the filtrate, the residue was recrystallized from hex-
ane to afford BbtBiBr2 (2b, 653 mg, 22%). 2b: yellow crystals,
1
°C (decomp).
Found: C, 51.42; H, 8.85%.
Calcd for
mp 150–155 °C (decomp). H NMR (500 MHz, CDCl3) δ 0.15 (s,
C36H77SbSi7•0.5H2O: C, 51.64; H, 9.39%. 1H NMR (500 MHz,
CDCl3) δ 0.07 (s, 36H), 0.23 (s, 27H), 1.66 (s, 6H), 1.98 (s, 2H),
36H), 0.26 (s, 27H), 2.32 (s, 2H), 7.54 (s, 2H). HRMS (FAB)
Found: m/z 992.1752 ([M]+). Calcd for C30H67Bi79Br81BrSi7
([M]+): 992.1778.
2
2
2.40 (d, JHH = 13.9 Hz, 2H), 3.31(d, JHH = 13.9 Hz, 2H), 6.67
(s, 2H). 13C NMR (125 MHz, CDCl3) δ 1.50 (q), 5.40 (q), 20.18
(s), 21.40 (q), 31.42 (t), 32.22 (d), 126.31 (d), 131.73 (s), 137.45
(s), 144.03 (s), 149.92 (s).
Synthesis
of
Bis{2,6-bis[bis(trimethylsilyl)methyl]-4-
[tris(trimethylsilyl)methyl]phenyl}dibismuthene (6b) via Re-
ductive Coupling Reaction of BbtBiBr2 (2b) with Mg Metal.
To a THF solution (4 mL) of BbtBiBr2 (2b) (200 mg, 0.20 mmol)
was added Mg metal (70.0 mg, 2.88 mmol) at room temperature.
After the reaction mixture was stirred for 30 min, the color of the
solution changed to violet. The solvent was evaporated under re-
duced pressure and 30 mL of hexane was added to the residue. In-
soluble inorganic salts were removed by filtration through Celite®.
The removal of the solvent from the filtrate gave dibismuthene 6b
(167 mg, quant.) as a violet solid. 6b: violet powder, mp 250.5–
252.0 °C (decomp). Found: C, 43.34; H, 8.00%. Calcd for
C60H134Bi2Si14: C, 43.23; H, 8.10%. 1H NMR (500 MHz, C6D6) δ
0.34 (s, 72H), 0.38 (s, 54H), 1.46 (s, 4H), 7.33 (s, 4H). 13C NMR
(125 MHz, C6D6) δ 3.11 (q), 5.75 (q), 14.29(s), 46.60 (d), 124.44
(d), 147.40 (s), 154.36 (s), 162.42 (s). UV–vis (hexane) 670 (sh, ε
20), 537 nm (ε 6000).
Thermolysis of Stibolene 8b. 8b (50.2 mg, 0.06 mmol) was
dissolved in toluene-d8 (0.6 mL), and the solution was degassed
and sealed in an NMR tube. After the solution was heated at 130
°C for 64 h, the disappearance of the signals of 8b was confirmed
1
by H NMR and only the signals assignable to distibene 4b and
2,3-dimethyl-1,3-butadiene were observed by 1H NMR. After the
solvent and the generated diene were evaporated under reduced
pressure in a glovebox filled with argon, the residue (52.5 mg) was
found to contain distibene 4b as the main product (> 90%). 4b:
deep red solid, mp 201–205 °C (decomp). Found: C, 47.88; H,
9.21%. Calcd for C60H134Sb2Si14: C, 48.29; H, 9.05%. 1H NMR
(500 MHz, C6D6) δ 0.32 (s, 72H), 0.41 (s, 54H), 2.49 (s, 4H), 7.19
(s, 4H). 13C NMR (125 MHz, C6D6) δ 2.27 (q), 5.77 (q), 22.24 (s),
39.42 (d), 126.97 (d), 146.81 (s), 147.15 (s), 150.37 (s). UV–vis
(hexane) 594 (ε 200), 490 nm (ε 6000).
X-ray Crystallographic Analyses of 4b and 6b.
Crystal
Reaction of Distibene 4b with SewP(NMe2)3. A toluene so-
lution (1 mL) of 4b (9.9 mg, 0.01 mmol) and SewP(NMe2)3 (8.2
mg, 0.03 mmol) was concentrated. The reaction mixture was dis-
solved in C6D6 and then the solution was degassed and sealed in
an NMR tube. Only the signals for 10 along with those of excess
SewP(NMe2)3 were observed in the 1H NMR measurement.
Reaction of Selenadistibirane 10 with P(NMe2)3. To a tolu-
ene-d8 solution (0.6 mL) of 10 (24.8 mg, 0.02 mmol) was added
data of 4b and 6b are shown in Table 5. Single crystals of these
compounds suitable for X-ray analysis were obtained by slow re-
crystallization from hexane in a refrigerator at −40 °C fixed in a
glovebox filled with argon. The intensity data were collected on a
Rigaku R-AXIS RAPID imaging plate detector (for 4b) and
Rigaku/MSC Mercury CCD diffractometer (for 6b) with graphite
monochromated Mo Kα radiation (λ = 0.71069 Å) at −180 °C to
2θmax = 50°. The structures were solved by direct methods

T. Sasamori et al.
Bull. Chem. Soc. Jpn., 75, No. 4 (2002) 673
Table 5. Crystal Data for 4b and 6b
4b
6b
Formula
C60H134Sb2Si14
1492.44
deep red, prismatic
0.30×0.20×0.15
−180°C
C60H134Bi2Si14
1666.89
violet, prismatic
0.20×0.10×0.10
−180°C
Formula weight
Crystal color, habit
Crystal dimensions/mm
Temperature
Crystal system
Space group
Lattice parameters
a/Å
triclinic
P1 (#2)
triclinic
P1 (#2)
12.5987(6)
17.9474(12)
9.3011(6)
93.096(2)
98.8541(16)
88.764(3)
2074.8(2)
1
9.2869(18)
12.5191(13)
18.122(2)
88.841(5)
87.697(4)
81.2683(14)
2080.6(5)
1
b/Å
c/Å
α/°
β/°
γ/°
V/Å3
Z
Dcalc/g cm−3
Independent reflections
No. of parameters
R1 (I > 2σ(I))
wR2 (all data)
Goodness of fit
1.194
6633
364
0.044
0.132
1.031
1.330
7285
364
0.040
0.098
1.092
Table 6. Crystal Data for 12a
could not be obtained because of its insolubility in any organic
solvent.
Formula
Formula weight
Crystal color, habit
Crystal dimensions/mm
Temperature
Crystal system
Space group
Lattice parameters
C54H118Bi2O2Si12
1554.51
pale yellow, prismatic
0.50×0.20×0.10
23°C
X-ray Crystallographic Analysis of 12a. Crystal data of
12a are shown in Table 6. Single crystals of 12a suitable for X-
ray analysis were obtained by leaving the single crystals of 6a in
open air for a few days. The intensity data were collected on a
Rigaku AFC5R diffractometer with graphite monochromated Mo
Kα radiation (λ = 0.71069 Å) at 23 °C to 2θmax = 55°. The struc-
tures were solved and refined by using the program package teX-
san.45
X-ray crystallographic files in CIF format for 4b, 6b, and 12a
have been deposited as document No. 75018 at the office of the
Editor of Bull. Chem. Soc. Jpn. and also deposited at the CCDC,
12 Union Road, Cambridge CB21EZ, UK and copies can be ob-
tained on request, free of charge, by quoting the publication cita-
tion and the deposition numbers 177271–177273.
triclinic
P1 (#2)
a/Å
b/Å
c/Å
12.848(3)
18.236(6)
9.333(2)
93.83(2)
108.43(2)
105.84(2)
1967.5(10)
1
α/°
β/°
γ/°
V/Å3
Z
This work was partially supported by a Grant-in-Aid for
COE research on Elements Science (No. 12CE2005) and a
Grant-in-Aid for Scientific Research on Priority Area (A) (No.
11166250) from the Ministry of Education, Culture, Sports,
Science and Technology. T. S. thanks Research Fellowships of
the Japan Society for the Promotion of Science for Young Sci-
entists. We also thank Shin-etsu Chemical and Tosoh Akzo
Co., Ltds. for their generous gifts of chlorosilanes and alkyl-
lithiums, respectively.
Dcalc/g cm−3
Observed reflections
[I > 3.00σ(I)]
No. of parameters
R
1.312
3108
316
0.069
0.062
2.19
Rw
Goodness of fit
(SIR9743 or SHELXS-9744) and refined by full-matrix least-
squares procedures on F2 for all reflections (SHELXL-9744). All
hydrogens were placed using AFIX instructions.
References
Oxidation of Dibismuthene 6a. Purple crystals of dibis-
muthene 6a were taken out of the glovebox to be exposed to open
air. On standing for 20 h, the purple color of 6a faded to give col-
orless crystals of Tbt2Bi2O2 12a quantitatively. 12a: colorless
crystals, mp 187–191 °C. Found: C, 39.66; H, 7.74%. Calcd for
C54H118Bi2O2Si12: C, 41.72; H, 7.65%. NMR spectral data of 12a
1
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