A convenient route to distannanes, oligostannanes, and polystannanes

Article abstract of DOI:10.1139/V10-130

The quantitative conversion of the tertiary stannane (ν;-Bu) ₃SnH (2) into (ν-Bu)₆Sn₂ (4) was achieved by heating the neat hydride material under low pressure or under closed inert atmosphere conditions. A 31% conversion of Ph3SnH (3)to Ph₆Sn ₂ (5) was also observed under low pressure; however, under closed inert atmosphere conditions afforded Ph4Sn (6) as the major product. A mixed distannane, (ν-Bu)₃SnSnPh₃ (7), can also be prepared in good yield utilizing an equal molar ratio of 2 and 3 and the same reaction conditions used to prepare 4. This solvent-free, catalyst-free route to distannanes was extended to a secondary stannane, (ν-Bu)₂SnH ₂ (8), which yielded evidence (NMR) for hydride terminated distannane H(ν-Bu)₂SnSn(ν-Bu)₂H(9), the polystannane [(ν-Bu)₂Sn] ' (10), and various cyclic stannanes [(ν- Bu)₂Sn]_ν=5,6=5,6 (11, 12). Further evidence for 10 was afforded by gel permeation chromatography (GPC) where a broad, moderate molecular weight, but highly dispersed polymer, was obtained (M_w = 1.8 × 10⁴ Da, polydispersity index (PDI) = 6.9) and a characteristic UV-vis absorbance (1_max)of ν370 nm observed.

Full text of DOI:10.1139/V10-130

1046
A convenient route to distannanes,
oligostannanes, and polystannanes
Aman Khan, Robert A. Gossage, and Daniel A. Foucher
Abstract: The quantitative conversion of the tertiary stannane (n-Bu)3SnH (2) into (n-Bu)6Sn2 (4) was achieved by heating
the neat hydride material under low pressure or under closed inert atmosphere conditions. A 31% conversion of Ph3SnH
(3) to Ph6Sn2 (5) was also observed under low pressure; however, under closed inert atmosphere conditions afforded
Ph4Sn (6) as the major product. A mixed distannane, (n-Bu)3SnSnPh3 (7), can also be prepared in good yield utilizing an
equal molar ratio of 2 and 3 and the same reaction conditions used to prepare 4. This solvent-free, catalyst-free route to
distannanes was extended to a secondary stannane, (n-Bu)2SnH2 (8), which yielded evidence (NMR) for hydride termi-
nated distannane H(n-Bu)2SnSn(n-Bu)2H (9), the polystannane [(n-Bu)2Sn]n (10), and various cyclic stannanes [(n-
Bu)2Sn]n=5,6 (11, 12). Further evidence for 10 was afforded by gel permeation chromatography (GPC) where a broad, mod-
erate molecular weight, but highly dispersed polymer, was obtained (Mw = 1.8 Â 104 Da, polydispersity index (PDI) =
6.9) and a characteristic UV–vis absorbance (lmax) of &370 nm observed.
Key words: solvent free, catalyst free, dehydrogenation, stannanes, polystannanes.
´
´
´
Resume : On a effectue la conversion quantitative du stannane tertiaire (n-Bu)3SnH (2) en (n-Bu)6Sn2 (4) par chauffage
`
´
´
de l’hydrure net, a basse pression ou dans des conditions atmospheriques inertes, sans contact avec l’exterieur. On a aussi
´
observe une conversion de 31 % du Ph3SnH (3) en Ph6Sn2 (5) dans des conditions de basse pression; toutefois, dans des
´
´
conditions atmospheriques inertes sans contact avec l’exterieur, le produit majeur est le Ph4Sn (6). Un distannane mixte
ˆ
´
´
´
`
´
(n-Bu)3SnSnPh3 (7) peut aussi etre prepare avec un bon rendement en utilisant un rapport molaire egal a l’unite des com-
´
ˆ
´
´
´
´
poses 2 et 3 dans les memes conditions que celles utilisees pour preparer le compose 4. On a etendu cette nouvelle voie
´
de preparation des distannanes, sans solvant et sans catalyseur, pour obtenir un distannane secondaire, le (n-Bu)2SnH2 (8)
´
`
qui, sur la base de donnees de RMN, contient aussi un distannane a hydrure terminal, H(n-Bu)2SnSn(n-Bu)2H (9), du po-
lystannane, [(n-Bu)2Sn]n (10), et divers stannanes cycliques [(n-Bu)2Sn]n=5,6 (11, 12) dans lesquels n = 5 et 6. La chroma-
´
´
´
´
tographie par permeation de gel (CPG) a aussi permis d’obtenir des donnees mettant en evidence la presence d’un
polymere de poids moleculaire modere, mais hautement disperse (Mw = 1,8 Â 104 Da, indice de polydispersion (IPD) =
`
´
´ ´
´
´
6,9) et d’observer une absorbance caracteristique dans le spectre UV–vis avec un lmax & 370 nm.
´
´
´
Mots-cles : sans solvant, sans catalyseur, deshydrogenation, stannanes, polystannanes.
´
[Traduit par la Redaction]
Distannanes can be synthesized directly from the dehydro-
genative dimerization of tin hydrides (e.g., 2 and 3) with ei-
ther amines or alkoxides acting as the catalyst.8 Organotin
hydrides can also be dehydrogenatively coupled using tran-
sition metal catalysts such as Pd(PPh3)4, PdCl2(NCMe)2,9 or
ruthenium–allenylidene complexes.10 Electrochemical prepa-
rations of R3SnSnR3 (e.g., R = n-C4H9 (4), C6H5 (5), p-
CH3C6H4–, or C6H5CH2–) compounds involving the reduction
of R3SnX (X = Cl, NO3, H, SPh, OCHO, OCOCH3, etc.)
have also been reported.11,12 Stoichiometrically, 5 can be
prepared via the reductive coupling of triphenyltin deriva-
Introduction
Hexaorganodistannanes are a convenient source of stannyl
radicals and have found applications in organic chemistry in
a variety of reduction reactions,1 in addition to their utility
in palladium-catalyzed cross-coupling processes.2 Distan-
nanes also serve as useful models for polystannanes.3 Indus-
trially, distannanes show considerable antibacterial and
fungicidal activity and were previously used as wood preser-
vatives.4 The distannane class of compounds are the tin ana-
logues of ethanes but possess a Sn–Sn bond that is
comparatively weaker (154 vs 356 kJ/mol) and longer (2.80
tives (Ph3SnX, where
X = Cl, I, or OH) in a
5,6
˚
THF / aq NH4Cl solution containing Zn metal.13,14 The first
high yield synthesis of 4 was reported by Sawyer15 from the
treatment of distannoxane 1 with 2 at 100 8C for several
days (Scheme 1).
vs 1.54 A) than typical C–C bonds. Organodistannanes are
generally thermally stable but are chemically sensitive to the
presence of oxygen (more so than that of water, mild acids,
or alkalis) and can readily decompose to form stannoxanes
(i.e., R3Sn–O–SnR3) such as 1 (Fig. 1).7
Alternative methods for the synthesis of 4 from 1 include
Received 22 June 2010. Accepted 29 July 2010. Published on the NRC Research Press Web site at canjchem.nrc.ca on 7 October 2010.
A. Khan, R.A. Gossage, and D.A. Foucher.1 Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto,
ON M5B 2K3, Canada.
1Corresponding author (e-mail: daniel.foucher@ryerson.ca).
Can. J. Chem. 88: 1046–1052 (2010)
doi:10.1139/V10-130
Published by NRC Research Press

Khan et al.
1047
Fig. 1. Various stannanes.
Scheme 1.
reactions with formic acid,16 or reductions utilizing Mg, Na,
Scheme 2.
or K metal in THF17 solution; NaBH4 or SmI2 in hexam-
ethylphosphoramide (HMPA) has also been used. Recently,
an improvement in the synthesis of 420 was reported, which
involves a high temperature (200 8C), catalyst-free protocol
using 1 and 2 at a molar ratio of 1:2.2. This method gives 4
in a quantitative yield. Interestingly, these same authors also
reported a lower yield (52%) of 4 by simply heating 2 at a
lower temperature (150 8C) for 6 h under vacuum
(Scheme 2).
18
19
under a nitrogen atmosphere. Analysis by 119Sn NMR
showed a small peak for 2 after 5 h, which was completely
consumed after heating for an additional 1 h (Fig. 2). There
was no evidence of redistribution products, which were re-
ported when 2 was thermally dehydrocoupled in the pres-
ence of group 4 or 6 transition metal complexes.21
Similar dehydrocoupling conditions were used for hydride
3. After 6 h at reflux (200 8C) under reduced pressure, anal-
ysis by NMR showed that approximately 31% of the starting
material had converted to distannane 5, with most of the re-
mainder represented by the starting material 3 in addition to
a significant fraction of the redistribution product (24%)
Ph4Sn (6). Product 5 precipitated from the reaction mixture
as a crystalline solid as it cooled and could be easily recov-
ered from the starting material by recrystallization. The re-
action was also repeated in a heated (200 8C) and sealed
Schlenk flask under static vacuum. The 119Sn NMR spec-
trum showed evidence of a thermal redistribution reaction
with the bulk of the material converted (87%) to 6 and a
considerably lower fraction of 5 (10%), in addition to a trace
of grayish sediment, which was attributed to elemental tin
(3%).
Utilizing closed, reduced-pressure reaction conditions, an
equimolar mixture reaction of 2 and 3 was heated (200 8C)
for 5 h. Analysis by 119Sn NMR spectroscopy (Fig. 3) re-
vealed resonances at d –145.8 and –67 ppm consistent with
the formation of 7.22 The NMR evaluation of the reaction
mixture also indicated that compound 7 was present in a
36.6% yield. Traces of the starting materials, along with 4
(11.9%) and 5 (37.6%), the redistribution product 6
(12.9%), recovered tin metal (1.2%), and two unassigned
peaks were also noted. These unidentified materials may be
other higher molecular weight redistribution products.
The solvent-free, catalyst-free reaction N2(g) conditions
were also employed with the secondary stannane, (n-
Bu)2SnH2 (8; Scheme 3). After 6 h of heating (160 8C),
119Sn NMR spectroscopic analysis of the bright yellow oily
solid material revealed a multitude of resonances.
In this study, we reinvestigate the solvent and catalyst-
free dehydrocoupling of 2 to produce 4 in an effort to identify
the optimum reaction conditions for a variety of distannanes.
This direct approach was thus extended to the aryl tin hy-
dride (3) to obtain Ph3SnSnPh3 (5). We also report on the
catalyst-free reactions involving equimolar ratios of alkyl
(2) and aryl (3) tin hydrides. Finally, we present evidence
that this approach can be extended to alkyl dihydrostannanes
for the production of both oligostannanes and polystannanes.
Results and discussion
The reaction conditions for both 2 and 3 to produce dis-
tannanes 4 and 5 are listed in Table 1. An attempt to distill
2 (200 8C, in vacuo) using a long path distillation condenser
was initiated with the intention to further purify 2. Surpris-
ingly, the product of this distillation was not 2, but a nearly
quantitative conversion (1H and 119Sn NMR, yield: 97%) to
distannane 4. We investigated the impact of heating 2 to re-
flux temperature (200 8C) under reduced pressure using a
1
long path reflux condenser. After 6 h, analysis by H and
119Sn NMR indicated a 75% conversion of 2 into 4. The
sample was further heated (6 h) under these conditions, but
NMR analysis showed virtually no change in the proportions
of the product and starting material. A plausible reason for
this observation is that the more volatile hydride is retained
by the cool portion of the reflux condenser rather than in
close proximity to the heat source. To improve this conver-
sion, 2 was heated (200 8C) under static vacuum conditions
in a sealed Schlenk flask. An analysis (119Sn NMR) of a
small aliquot of the reaction mixture taken every hour
revealed that after 5 h, 2 had completely converted to the
distannane 4. A single 119Sn resonance (d –83.6 ppm) was
Clearly identifiable in this spectrum, however, was a reso-
nance at d & –208 ppm, which is attributed to the hydride
terminated distannane (n-Bu2SnH)2 (9).23 Additionally, a res-
onance at d & –189 ppm can be assigned to linear dibutyl-
119SnÀ117Sn
observed for 4, with characteristic Sn satellites (J
1280 Hz), which is in agreement with reported literature val-
ues.20 The reaction was also carried out in a sealed flask
=
Published by NRC Research Press

1048
Can. J. Chem. Vol. 88, 2010
Table 1. Catalyst- and solvent-free thermal couplings of tin hydrides.
Starting
material
Reaction
time (h)
Yield
(%)
Reaction conditions
Product
2
200 8C, N2
6
4
97
200 8C, reflux/reduced pressure
200 8C, static/reduced pressure
200 8C, reflux/reduced pressure
200 8C, static/reduced pressure
200 8C, static/reduced pressure
12
5
6
4
5
4
4
5, 6
5, 6
4
75
95
31, 24
10, 87
12
3
2 and 3
5
37
6
13
7
37
Scheme 3.
Fig. 2. 119Sn NMR spectra of the products from the dehydrocou-
pling of 2 at (A) 4 h at 200 8C and (B) 5 h at 200 8C under static
reduced pressure.
lar weight polystannane (Mw = 1.8 Â 104 Da, polydispersity
index (PDI) = 6.9), along with a considerable fraction of
lower molecular weight linear and cyclic products. A UV–
vis spectrum (Fig. 4) of the mixture containing the polymer
10 displayed a broad absorbance with a lmax centered at
&370 nm. This absorbance can be attributed to the s–s* of
the polystannane, which is in good agreement with reported
values.24
When the dehydrocoupling of 8 was attempted at a higher
temperature (200 8C, 6 h), evidence of multitude of alkyl re-
distribution products was found (Scheme 4). Analysis by
119Sn NMR spectroscopy showed resonances attributed to 2,
as well as to dimeric 4 and higher tributylstannane termi-
nated oligomers (i.e., 13 and 14), which were identified by
comparison to literature values.16 A large unassigned reso-
nance was observed at +156 ppm. This downfield shift is
characteristic of a four-coordinate dialkyl tin alkoxide spe-
cies, e.g., R2Sn(OR)2, which typically have resonances in
the range of +90 to +200 ppm.27 There is no evidence of cy-
clic products nor hydride terminated oligomers.
Fig. 3. 119Sn NMR spectrum of the products from the dehydrocou-
pling of 2 and 3 at 200 8C for 5 h. Peaks with an asterisk are unas-
signed.
Mechanistic considerations
The catalyst- and solvent-free, presumably radically
driven, dehydrocoupling reactions described herein
(Scheme 5) are apparently activated through the thermolysis
of the relatively weak Sn–H bonds of R3SnH (R = n-Bu3,
Ph). The small differences between the ground state bond
dissociation energies for known stannanes (e.g., Me3SnH =
305 17 kJ/mol, Me3SnEt = 284 17 kJ/mol, Me3SnPh =
339 21 kJ/mol, and Me3SnSnMe3 = 317 25 kJ/mol) pro-
vides little insight to identifying clear redistribution trends
with these systems.28
In the case of 3, additional redistribution reactions to
yield products such as 6 also occur. The Sn–aryl bonds also
appear to be thermally labile at 200 8C and redistribution
chemistry is competitive with dehydrogenation. In contrast,
trialkyl stannanes seem less active towards such redistribu-
tion at this temperature. To maximize yields of distannanes
and reduce the potential of unwanted redistribution products,
it is essential to identify the optimum reaction conditions
polystannane (10).24 Two cyclic species (11 and 12) were
identified by comparison with the literature 119Sn chemical
shift values.25,26 The assignments of the rest of the minor
signals has not yet been made but these are likely due to
the presence of higher molecular weight hydride terminated
oligomers (e.g., n-Bu2SnH(n-Bu2Sn)nSnHn-Bu2). Analysis of
this material by gel permeation chromatography (GPC)
showed a broad polymer distribution and a modest molecu-
Published by NRC Research Press

Khan et al.
1049
Scheme 4.
(e.g., temperature and duration of the reaction). Closed reac-
tion vessels under slight reduced pressure produce the high-
est yields for all products (4, 5, and 7). A likely driving
force in these reactions is the liberation of H2(g) along with
the formation of the persistent tin alkyl and aryl radicals that
later combine to form distannanes. Attempts to carry out de-
hydrocoupling reactions at higher temperatures (>200 8C)
resulted in the decomposition of the starting materials and
(or) lower product yields. Reaction of the secondary stan-
nane 8 at lower temperatures (160 8C) resulted in the forma-
tion of linear and cyclic polystannane species including a
modest molecular weight polymer (10). The broad polydis-
persity found for this sample is typical of other radical poly-
mers prepared from an uncontrolled polymerization process.
The mechanism of propagation for this species is unclear,
but may occur through the coupling of two growing oligo-
meric species that contain active radical end groups. When
8 is heated at 200 8C, redistribution to tributylstannyl termi-
nated species are dominant but no evidence for cyclics or
polymers was noted.
Scheme 5.
mined by gel permeation chromatography (GPC) using a
Viscotek Triple Model 302 detector system equipped with a
refractive index detector (RI), a four capillary differential
viscometer (VISC), a right angle (908) laser light scattering
detector (l0 = 670 nm), and a low angle (78) laser light scat-
tering detector. GPC columns were calibrated versus poly-
styrene standards (American Polymer Standards). A flow
rate of 1.0 mL/min was used with ACS grade THF as the
eluent. GPC samples were prepared using 3–10 mg of poly-
mers per mL THF, and filtered using a 0.45 mm filter. All
samples were run with and without ultraviolet absorbers
(UVA; concn & 0.001 mol/L) for comparison. All reactions
were carried out under a nitrogen atmosphere using Schlenk
techniques unless otherwise described. Thermally driven de-
hydrocoupling reactions were performed under a variety of
conditions in Schlenk flasks, including in an inert N2 atmos-
phere, or in a sealed Schlenk flask placed under a static re-
duced pressure (closed), or finally in a Schlenk flask
exposed to dynamic reduced pressure (open). Pressures
were measured using a mercury manometer attached to the
Schlenk line.
Conclusion
Compound 4 was successfully synthesized in a high yield
from the thermally driven dehydrocoupling of the tertiary
stannane 2 under a variety of catalyst- and solvent-free con-
ditions. Compound 5 was also obtained in a similar way
with lower conversion from the tertiary stannane 3. A mixed
distannane 7 was also prepared from the equimolar reaction
of 2 and 3 under similar conditions. Evidence for the redis-
tribution product 6 was found when aryl stannane (3) was
used. Solvent- and catalyst-free dehydrogenative coupling
of the secondary distannane 8 at 160 8C resulted in the for-
mation of a modest molecular weight polystannane (10) and
other linear and cyclic stannanes, but favours only redistrib-
ution products at 200 8C. This work has demonstrated that
dehydrocoupling of stannanes in the absence of a catalyst
under a variety of conditions may provide a viable route to
valuable organic radical sources. Future efforts will be di-
rected to the coupling of tertiary and secondary stannanes
using other metal-free routes, including the use of light and
microwave mediated coupling processes.
Materials
(n-Bu)3SnH (2, 99%), Ph3SnH (3, 97%), (n-Bu)2SnCl2
(97%), LiAlH4 (1.0 mol/L in ether), and anhydrous CaCl2
were purchased commercially and used without further puri-
fication. (n-Bu)6Sn2 (4) and Ph6Sn2 (5) were purchased from
Strem and used as reference samples. (n-Bu)2SnH2 (8) was
prepared from (n-Bu)2SnCl2 and LiAlH4 according to litera-
ture preparation.24,25 Solvents were dried by standard proce-
dures prior to use.
Large-scale thermal dehydrocoupling of 2 under reduced
pressure (open system)
The tin hydride 2 (50 g, 0.17 mol) was added to a
100 mL round-bottom flask connected to a long path distil-
lation condenser (13 cm) and the volatile components dis-
tilled at 200 8C under reduced pressure (&1 Â 10–2 mm
Hg; 1 mm Hg = 133.32 Pa). The product of this distillation
Experimental methods
was then analyzed by NMR spectroscopy. The H and 119Sn
1
Equipment and procedures
1H, 13C{1H}, and 119Sn{1H} NMR spectra were recorded
NMR spectra revealed that 2 had been consumed and con-
verted (recovered yield: 97%) into 4. The NMR data pro-
vided here are in good agreement with literature
values.18,20,22
1
on a Bruker Avance 400 MHz NMR spectrometer. H spec-
tra were referenced to the residual solvent peaks in the deu-
terated solvents, whereas the 13C spectra are referenced
internally to the deuterated solvent resonances, which are in
turn referenced to SiMe4 (d 0 ppm), whereas 119Sn was ref-
erenced to SnMe4 (d 0 ppm). UV–vis measurements were
carried out in THF solutions using a PerkinElmer Lamda 40
spectrometer. Molecular weights of polymers were deter-
Small-scale thermal dehydrocoupling of 2 under reduced
pressure (open system)
To a 25 mL round-bottom flask equipped with long path
reflux condenser (20 cm), was added tin hydride 2 (1.0 g,
Published by NRC Research Press

1050
Can. J. Chem. Vol. 88, 2010
Fig. 4. UV–vis (THF) spectrum of the mixture containing 10.
3.44 mmol). The sample was heated to reflux temperature
(200 8C) under reduced pressure (&2 Â 10–2 mm Hg) for
6 h. Analysis (1H and 119Sn NMR spectroscopy) of a small
aliquot of the reaction mixture revealed 75% conversion of
2 into 4, while the remainder was unreacted 2. Additional
heating for 6 h under these conditions showed no further re-
actant conversion (NMR).
CH3CH2CH2CH2–Sn), 1.66 (2H, m, CH3CH2CH2CH2–Sn).
13C{1H} NMR (C6D6, ppm) d: 10.49 (1JC–Sn (CH3CH2CH2CH2–
2
Sn) = 120.3 Hz and JC–Sn (CH3CH2CH2CH2–Sn–Sn) =
19.6 Hz), 14.01 (CH3CH2CH2CH2–Sn), 27.98 (3JC–Sn
(CH3CH2CH2CH2–Sn)
=
26.5
Hz),
31.23
(2JC–Sn
(CH3CH2CH2CH2–Sn) = 8.1 Hz). 119Sn{1H} NMR (C6D6, ppm)
119SnÀ117Sn
v: –83.6 (J
= 1280 Hz).
Small-scale thermal dehydrocoupling of 2 under reduced
pressure (closed system)
Small-scale thermal dehydrocoupling of 3 under reduced
pressure (open system)
To a 25 mL Schlenk flask equipped with a glass stopper
was added 2 (530 mg, 1.82 mmol). The neat hydride was
placed under static reduced pressure (&5 Â 10–1 mm Hg),
the vessel was then sealed and subsequently heated
(200 8C) for 5 h. Analysis (1H and 119Sn NMR spectro-
scopy) showed that the majority of 2 had been consumed
and was converted to 4 (recovered yield: 95%).
Compound 3 (471 mg, 1.34 mmol) was added to a 25 mL
round-bottom flask equipped with a long path reflux con-
denser (20 cm). The sample was heated (200 8C) under re-
duced dynamic pressure (&1 Â 10–3 mm Hg) for 6 h.
During this time period, clear and colourless crystals formed
on the sides of the reaction flask that were then collected
and analyzed (1H and 119Sn NMR spectroscopy). These data
indicated that a considerable fraction of 3 (41%) was un-
reacted. Approximately 59% of 3 was consumed and was
converted to both 5 (31%),29 6 (24%),30 and Sn metal (4%).
Small-scale thermal dehydrocoupling of 2 under inert
atmosphere (open system)
1
Major product 5: H NMR (CDCl3, ppm) d: 7.28–7.36 (12H,
Compound 2 (530 mg, 1.82 mmol) was added to a 25 mL
Schlenk flask equipped with a long path (20 cm) reflux con-
denser that was open to a N2(g) atmosphere. The flask was
then heated (200 8C) for 6 h. Analysis (1H and 119Sn NMR
spectroscopy) of the reaction mixture indicated that 2 had
been consumed and was converted to 4 (recovered yield:
97%). 1H NMR (C6D6, ppm) d: 0.97 (3H, t, CH3CH2CH2CH2–
Sn), 1.16 (2H, m, CH3CH2CH2CH2–Sn), 1.42 (2H, m,
m), 7.39–7.52 (12H, m), 7.60–7.63 (6H, m). 13C{1H} NMR
(CDCl3, ppm) d: 139.24 (C1), 137.61 (C2, C6), 128.82 (C3,
C5), 128.94 (C4). 119Sn{1H} (CDCl3, ppm) d: –143.7.
Small-scale thermal dehydrocoupling of 3 under reduced
pressure (closed system)
To a 50 mL Schlenk flask equipped with a glass stopper
Published by NRC Research Press

Khan et al.
1051
was added 3 (394 mg, 1.12 mmol). The neat hydride was
kept under static reduced pressure (&5 Â 10–1 mm Hg), the
flask sealed, and heated (200 8C) for 4 h. Analysis (1H and
119Sn NMR) of the reaction mixture indicated that 3 had
been consumed and was converted to both 6 (yield: 87%),30
5 (yield: 10%),29 and Sn metal (3%). Major product 6:
13C{1H} NMR (CDCl3, ppm) d: 138.04 (C1), 137.39 (C2,
C6), 128.79 (C3, C5), 128.28 (C4). 119Sn{1H} NMR
(CDCl3, ppm) d: –129.6.
References
(1) (a) Chabaud, L.; Landais, Y.; Renaud, P. Org. Lett. 2002, 4
(24), 4257. doi:10.1021/ol026824y. PMID:12443072.; (b)
Harendza, M.; Leßmann, K.; Neumann, W. P. Synlett 1993,
283. doi:10.1055/s-1993-22433.; (c) Verlhac, J. B.; Chanson,
E.; Jousseaume, B.; Quintard, J. P. Tetrahedron Lett. 1985,
26 (49), 6075. doi:10.1016/S0040-4039(00)95129-3.
(2) (a) McIntee, J. W.; Sundararajan, C.; Donovan, A. C.;
Kovacs, M. S.; Capretta, A.; Valliant, J. F. J. Org. Chem.
2008, 73 (21), 8236. doi:10.1021/jo8013287. PMID:
18826327.; (b) Ha, Y.-H.; Kang, S. K. Org. Lett. 2002, 4
(7), 1143. doi:10.1021/ol025557t. PMID:11922803.
Small-scale thermal dehydrocoupling of 2 and 3 under
reduced pressure (closed system)
¨
(3) Adams, S.; Drager, M. Angew. Chem. Int. Ed. Engl. 1987, 26
To a 50 mL Schlenk flask equipped with a glass stopper
was added 2 (291 mg, 1.00 mmol) and 3 (351 mg,
1.00 mmol). Neat tin hydrides were then placed under static
reduced pressure (&5 Â 10–1 mm Hg), sealed, and heated
(200 8C) for 5 h. Analysis (1H and 119Sn NMR) of the reac-
tion products indicated the conversion of 2 and 3 into a mix-
ture containing 4 (12%), 5 (37%), 6 (13%), 7 (37%), and
trace of elemental tin (1%).
(12), 1255. doi:10.1002/anie.198712551.
(4) Crowe, A. J.; Hill, R.; Smith, P. J.; Cox, T. R. G. Int. J.
Wood. Preserv. 1979, 1, 119.
(5) Windus, T. L.; Gordon, M. S. J. Am. Chem. Soc. 1992, 114
(24), 9559. doi:10.1021/ja00050a040.
(6) Jacobsen, H.; Ziegler, T. J. Am. Chem. Soc. 1994, 116 (9),
3667. doi:10.1021/ja00088a001.
(7) See, for example: Podlech, J. Compounds of Group 14 (Ge,
Sn, Pb); In Science of Synthesis: Houben–Weyl Methods of
Molecular Transformation — Category 1: Organometallics;
Moloney, M. G., Thieme, G., Eds.; Verlag: Stuttgart, 2003;
Vol. 5, pp 273–283.
Small-scale thermal dehydrocoupling of 8 under nitrogen
(open system)
To a 50 mL Schlenk flask equipped with a glass stopper
was added 8 (428 mg, 1.82 mmol). The flask containing 8
was then placed under an atmosphere of N2 and heated
(160 8C) for 6 h. Analysis (1H and 119Sn NMR spectro-
scopy) of a small aliquot of the reaction mixture indicated
the conversion of 8 to a mixture containing 9, 10, 11, and
12 along with unassigned oligomers. UV–vis lmax (nm):
370. 119Sn{1H} NMR (C6D6, ppm) d: 10: –189.3; 12: –202.1;
8: –203.2; 9: –207.9; others: –195.6, –209.5, –220.1. Analy-
sis by GPC revealed a molecular weight of Mw = 1.8 Â
104 Da, PDI = 6.9.
(8) Smith, P. J. In Comprehensive Organometallic Chemistry;
Abel, E. W., Ed.; Pergamon Press: Oxford, 1982; Vol. 2,
Chapter 11, p 591.
(9) Bumagin, N. A.; Gulevich, Y. V.; Beletskaya, I. P. Bull.
Acad. Sci. USSR Div. Chem. Sci. (Engl. Transl.) 1984, 33
(5), 1044. doi:10.1007/BF01141722.
(10) Maddock, S. M.; Finn, M. G. Angew. Chem. Int. Ed. 2001,
40
(11),
2138.
doi:10.1002/1521-3773(20010601)
40:11<2138::AID-ANIE2138>3.0.CO;2-6.
(11) Nokami, J.; Nose, H.; Okawara, R. J. Organomet. Chem.
1981, 212 (3), 325. doi:10.1016/S0022-328X(00)85658-2.
(12) Savall, A.; Lacoste, G.; Mazerolles, P. J. Appl. Electrochem.
1981, 11 (1), 61. doi:10.1007/BF00615323.
(13) von Gyldenfeldt, F.; Marton, D.; Tagliavini, G. Organome-
tallics 1994, 13 (3), 906. doi:10.1021/om00015a025.
(14) Ma˛kosza, M.; Grela, K. Synth. Commun. 1998, 28 (14),
2697. doi:10.1080/00397919808004840.
Small-scale thermal dehydrocoupling of 8 under reduced
pressure (open system)
To a 50 mL Schlenk flask equipped with a glass stopper
was added 8 (500 mg, 2.12 mmol). The flask containing 8
was then placed under an atmosphere of N2 and heated
(200 8C) for 6 h. Analysis (1H and 119Sn NMR spectro-
scopy) of a small aliquot of the reaction mixture indicated
the conversion of 8 to a mixture containing 2, 4, 13, and 14
along with other unassigned peaks. 119Sn{1H} NMR (C6D6,
ppm) d: 14: –75.3, –213.4; 13: –76.2, –227.0; 4: –83.2;
2: –87.3; others: +155.9, –57.7, –66.6, –210.2.
(15) Sawyer, A. K. J. Am. Chem. Soc. 1965, 87 (3), 537. doi:10.
1021/ja01081a025.
(16) Jousseaume, B.; Chanson, E.; Bevilacqua, M.; Saux, A.;
Pereyre, M.; Barbe, B.; Petraud, M. J. Organomet. Chem.
1985, 294 (3), C41. doi:10.1016/0022-328X(85)87458-1.
(17) Jousseaume, B.; Chanson, E.; Pereyre, M. Organometallics
1986, 5 (6), 1271. doi:10.1021/om00137a042.
(18) McAlonan, H.; Stevenson, P. J. Organometallics 1995, 14
(8), 4021. doi:10.1021/om00008a058.
(19) Handa, Y.; Inanaga, J.; Yamaguchi, M. J. Chem. Soc. Chem.
Commun. 1989, 298. doi:10.1039/C39890000298.
(20) Darwish, A.; Chong, J. M. Synth. Commun. 2004, 34 (10),
1885. doi:10.1081/SCC-120034172.
Supplementary data
1
Supplementary data of H and 119Sn{1H} NMR spectra
for compounds 4, 5, 6, and the products of the dehydrocou-
pling of 8 at two different temperatures are provided.
(21) Woo, H.-G.; Song, S.-J.; Kim, B.-K. Bull. Korean Chem.
Soc. 1998, 19, 1161.
(22) Lee, A. S.-Y.; Zhang, S.-L.; Pan, O.-G. J. Chin. Chem. Soc
1997, 44, 625.
(23) Sharma, H. K.; Arias-Ugarte, R.; Metta-Magana, A. J.;
Pannell, K. H. Angew. Chem. Int. Ed. 2009, 48 (34), 6309.
doi:10.1002/anie.200902327.
(24) Imori, T.; Tilley, T. D. J. Chem. Soc. Chem. Commun. 1993,
1607. doi:10.1039/c39930001607.
Acknowledgment
Drs. Foucher and Gossage would like to thank the Natural
Sciences and Engineering Research Council of Canada
(NSERC) Discovery Grants program and the Ryerson
Dean’s startup fund program for support of this research. A.
Khan would like to thank the Molecular Sciences Program
at Ryerson University for a graduate student award.
Published by NRC Research Press

1052
Can. J. Chem. Vol. 88, 2010
(25) Imori, T.; Lu, V.; Cai, H.; Tilley, T. D. J. Am. Chem. Soc.
1995, 117 (40), 9931. doi:10.1021/ja00145a001.
(28) Davies, A. G. Organotin Chemistry, 2nd ed.; Davis, A. G.,
Ed.; Wiley-VCH: Weinheim, 2004; p 426.
(26) Pannell, K. H. In Tin Chemistry: Fundamentals, Frontiers
and Applications; Davies, A. G., Tickink, E. R. T., Eds.; Wi-
ley: New York, 2008; pp 371–387, and refs. cited therein.
(27) Yergey, A. L.; Lampe, F. W. J. Am. Chem. Soc. 1965, 87
(18), 4204. doi:10.1021/ja01096a046.
(29) King, B.; Eckert, H.; Denney, D. Z.; Herber, R. H. Inorg.
Chim. Acta 1986, 122 (1), 45. doi:10.1016/S0020-1693(00)
81265-7.
(30) Wharf, I.; Simard, M. G. J. Organomet. Chem. 1997, 532
(1–2), 1. doi:10.1016/S0022-328X(96)06782-4.
Published by NRC Research Press