A nearly planar stannene with a reactive tin-carbon double bond

Article abstract of DOI:10.1002/ejic.200701277

Bis(2,4,6-triisopropylphenyl)-2,7-di-tert-butylfluorenylidene stannane, Tip₂Sn=CR₂, an isolable stannene that displays a deep-purple colour, was synthesized by dehydrofluorination of the corresponding fluorostannane by tert-butyllith

Full text of DOI:10.1002/ejic.200701277

FULL PAPER
DOI: 10.1002/ejic.200701277
A Nearly Planar Stannene with a Reactive Tin–Carbon Double Bond
Abdoul Fatah,[a,b] Rami El Ayoubi,[a] Heinz Gornitzka,[a] Henri Ranaivonjatovo,*[a] and
Jean Escudié*[a]
Keywords: Stannenes / Tin / Cycloaddition / Ene reaction
Bis(2,4,6-triisopropylphenyl)-2,7-di-tert-butylfluorenylidene
stannane, Tip2Sn=CR2, an isolable stannene that displays a
deep-purple colour, was synthesized by dehydrofluorination
of the corresponding fluorostannane by tert-butyllithium. It
exhibits the shortest Sn=C distance [2.003(5) Å] and the
slightest twisting around this unsaturation (10°) among the
known stannenes. Its reaction with benzaldehyde according
to a [2+2] cycloaddition and that with α-ethylenic aldehydes
and ketones such as crotonaldehyde and methyl vinyl ketone
by a [2+4] cycloaddition proceeded in near-quantitative
yield. With acetone, an ene reaction occurred. The four-
membered ring 1,2-oxastannacyclobutane obtained with
benzaldehyde underwent a ring expansion with a second
molecule of benzaldehyde to afford the six-membered ring
dioxastannacyclohexane.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
The significant contribution of the opposite limit form B
accounts for the NMR spectroscopic data and the X-ray
structures of the products obtained from an electrophilic
cryptodiborylcarbene and stannylenes (Scheme 1).[3–6]
The chemistry of the Sn=C bond has been sparsely ex-
plored. Only punctual studies of the reactions of long-lived
stannenes with protic reagents,[3,7,8] benzophenone,[14]
Introduction
Over the past 25 years, dramatic and exciting progress
has been made in the field of the heavier congeners of het-
eroalkenes ϾM=CϽ (M = Si, Ge, Sn). It is particularly true
for silenes[1] and (to a lesser extent) for germenes[2] regard-
ing the number of reports about their synthesis, their
physicochemical characteristics and theoretical studies.
Also, their chemical behaviour is now well known. By con-
trast, relatively few stable Sn=C compounds have been pre-
pared[3–9] (Scheme 1). The main synthetic methods consist
in stannylene–carbene coupling[3–6] or in dehydrohalogena-
tion of halostannanes[7–9] with lithium compounds as bases.
Noteworthy is the accurate description of the reaction out-
comes of nucleophilic carbenes (imidazol-2-ylidenes, cyclo-
propylidenes) with stannylenes as the ylidic resonance
structure A.[10–12] Their 119Sn chemical shifts at low fre-
quency [δ(119Sn) = –59.4,[10] –44.7 ppm[12]], their geometries
and their large Sn–C separation,[10–12] which is markedly
longer than the standard single bond length, differ greatly
from those expected for true alkene analogues. A similar
bonding situation was reported for the unique formal stan-
naketenimine,[13] which is better described as a Lewis acid–
base adduct of a stannylene (Lewis acid) with isocyanide.
2,3-dimethylbutadiene,[8] methyl iodide,[7b] reduction by
[7b]
LiAlH4
along with their head-to-tail dimerization have
been reported.[7] Investigation of the chemical behaviour of
the transient stannene Me2Sn=C(SiMe3)2
[15]
has been lim-
ited to its reaction with alkenes, dienes, azides and phen-
yllithium.
The dehydrohalogenation method allowed us to prepare
the first stannapentafulvene 1 some years ago.[7] This stan-
nene possesses the Sn=C bond as the principal reaction site
and seemed to fit well for the study of the chemical behav-
iour of this unsaturation. However, it converts readily into
its head-to-tail dimer, the corresponding 1,3-distannacyclo-
butane, above 0 °C,[7] which makes the extensive study of
its reactivity less convenient than with a stannene stable at
room temperature. Therefore, it was characterized only by
some trapping reactions and by tin NMR spectroscopy. Re-
cently, Tokitoh succeeded in preparing the first stable stan-
napentafulvene 2 by increasing the steric hindrance on the
tin atom while keeping the fluorenylidene group.[8] We then
became interested in probing the reverse steric shielding of
the Sn=C bond to stabilize it, that is, by enlarging the steric
hindrance on the fluorenylidene unit by substituting the
2,7-positions by two tert-butyl groups. Indeed, the stanna-
pentafulvene skeleton presents the advantage of easier
crystallization and enhanced stabilization by conjugation of
the Sn=C with the fluorenylidene system.
[a] Hétérochimie Fondamentale et Appliquée, UMR-CNRS 5069,
Université Paul Sabatier,
118 route de Narbonne, 31062 Toulouse Cedex 09, France
Fax: +33-561558204
E-mail: ranaivon@chimie.ups-tlse.fr
escudie@chimie.ups-tlse.fr
[b] Laboratoire de Chimie Organique, Faculté des Sciences, Uni-
versité d’Antsiranana,
B. P. 0, 201 Antsiranana, Madagascar
Eur. J. Inorg. Chem. 2008, 2007–2013
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2007

Abdoul Fatah, R. El Ayoubi, H. Gornitzka, H. Ranaivonjatovo, J. Escudié
FULL PAPER
Scheme 1.
Here we report the synthesis of the stable stannene changed when heated at 120 °C for 15 h in a sealed tube.
namely bis(2,4,6-triisopropylphenyl)-2,7-di-tert-butylfluor-
enylidene stannane 3 and the first aspects of its reactivity
toward some carbonyl compounds.
Its decomposition occurred only after 20 h at 150 °C to give
still-unidentified derivatives.
Stannene 3 was characterized by a 119Sn NMR signal at
the expected field for a double-bond tin compound (δ =
277 ppm). This chemical shift is very close to those pre-
viously reported for similar stannenes with a fluorenylidene
group [δ(119Sn) = 288 and 270 ppm for 1[7] and 2,[8] respec-
tively] and for a stable stannanaphthalene [δ(119Sn) =
264 ppm].[9] Thus, it seems that the introduction of two tert-
butyl groups increases dramatically the thermal stabiliza-
tion of the stannene, but has practically no influence on the
tin chemical shift. The great difference in chemical shifts
observed with stannenes derived from the electrophilic
cryptodiborylcarbene (647–835 ppm[3,4]) is rationalized by
the more positive tin nuclei due to noticeable contribution
of the resonance structure B (Scheme 1). The introduction
of aryl groups on tin in such adducts shifts the 119Sn signal
to lower frequency (δ = 374 ppm[5]).
Results and Discussion
The best synthetic route to stannene 3 appeared to be, as
in the case of 1[7] and 2,[8] the dehydrofluorination of (di-
tert-butylfluorenyl)fluorostannane 4. The latter was pre-
pared from 2,7-di-tert-butylfluorene,[16] n-butyllithium and
bis(2,4,6-triisopropylphenyl)difluorostannane[7a] (Scheme 2).
Deprotonation of fluorenylfluorostannane 4 by tert-butyl-
lithium at –78 °C gave immediately a red coloration due to
the related lithium compound. A deep-purple colour ap-
peared around –10 °C indicating the formation of stannene
3.
The sp2 Sn=C carbon atom resonates at δ = 146.9 ppm,
which is a 13C chemical shift comparable to those reported
for analogous stannapentafulvenes (δ = 133.85 ppm in 1[7a]
and 144.9 ppm in 2[8]). In the UV/Vis spectrum, the absorp-
tion maximum was observed at 560 nm, close to that re-
ported by Tokitoh for stannene 2 (552 nm).[8]
The molecular structure of 3 (Figure 1) displays the
shortest Sn=C bond [2.003(5) Å] ever reported. This Sn–C
separation is even shorter than that of the previous stable
stannapentafulvene 2 (dSn=C = 2.016 Å),[8] which was re-
ported to be the shortest Sn=C bond length among those
known (2.025–2.032 Å).[3–5] This value of 2.003(5) Å is in
agreement with the computed value (1.95–2.06 Å[8,17] de-
pending on the basis set used). The shortening, in relation
Scheme 2. Synthesis of stannapentafulvene 3.
Stannene 3 was isolated from a Et2O/pentane mixture as
extremely air- and moisture-sensitive, but thermally stable, to the Sn–C single bond (2.14–2.15 Å)[18] is about 7%.
purple crystals. Et2O solutions of 3 were recovered un- Furthermore,
a completely trigonal planar geometry
2008
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Eur. J. Inorg. Chem. 2008, 2007–2013

A Nearly Planar Stannene with a Reactive Tin–Carbon Double Bond
around the Sn1 and C1 atoms is observed (sum of bond nearly quantitative and occurred around –20 °C, as shown
angles of 360° in both cases) with a very small torsion angle by the loss of the characteristic purple colour of starting
(10°) between the planar fluorenylidene and the C22–Sn1– stannene 3. The reactions are regioselective, with the oxygen
C37 plane. It is the smallest twisting ever reported for such atom bonded to the tin atom, as expected from the well-
heavier metallaalkenes, comparable to that of 5.9° observed known oxophilic character of tin and the polarities of the
for the germene Mes2Ge=CRЈ2 (CRЈ2 = 9-fluorenylidene tin–carbon double bond (Snδ+=Cδ–) and of the carbonyl de-
group),[19] whereas a larger angle was observed for stannap- rivatives. The regioselectivity is also proved by the fragment
entafulvene 2 (28.5°).[8] Depending on the groups on the tin at m/z = 543 corresponding to [Tip2SnO + 1] in the mass
atom, cryptodiborylcarbene–stannylene adducts display a spectra of compounds 5, 7 and 8. The cleavage leading to
twist angle (11.9°) comparable to that of 3 Ϫ with a trans Tip2Sn=CR2 is also observed. The 13C NMR spectrum of
bending structure and a bent angle of 13.2 (Sn) and 9.7° (C) oxastannacyclobutane 5 displays, as expected, a signal at δ
[6]
Ϫ or even greater twist angle ranging from 36 to 61°.[3–5] = 81.5 ppm for the carbon atom bonded to the oxygen atom
2
117/119Sn,C
with J
coupling constants of 80.0/86.1 Hz.
Scheme 3. Reactivity of stannapentafulvene 3.
Figure 1. X-ray molecular structure of stannene 3 (50% probability
level). H atoms and disorder are omitted for clarity. Selected bond
lengths [Å] and angles [°]: Sn1–C1 2.003(5), Sn1–C22 2.138(4),
Sn1–C37 2.156(4), C1–C2 1.457(6), C1–C13 1.464(6), C22–Sn1–
C37 124.69(17), C22–Sn1–C1 119.04(18), C37–Sn1–C1 116.27(18).
As a result of the very high steric hindrance, a slow rota-
tion, as proved by the presence of broad signals, is generally
observed for the Tip groups, which renders the o-iPr groups
inequivalent. As derivatives 5, 6 and 7 have also at least one
asymmetric carbon atom, the two Tip groups and the Me
groups of every iPr are diastereotopic. Thus, for example in
the case of 7, 13 doublets (12 for the Me of iPr groups and
Thus, stannene 3 exhibits the geometric parameters
(planarity, amount of bond shortening) that are the closest
to those of the ideal double bond in alkenes and predicted
by theoretical calculations.
1
1 for the Me on the ring) are observed in the H NMR
spectrum.
In four-membered ring derivative 5 and in six-membered
heterocycles 6 and 7, the Sn–C(R2) bond lengths (2.217 to
2.223 Å) are slightly longer than the standard Sn–C dis-
tance (2.14–2.15 Å)[18] and the endocyclic Sn–C(Tip) bonds
(2.15 to 2.18 Å) probably for steric reasons. Sn–O bond
lengths (2.003 to 2.038 Å) lie in the normal range. In oxa-
Reactivity of Stannene 3
Despite the steric hindrance, stannene 3 is very reactive, stannacyclobutane 5 and in oxastannacyclohexene 7, the
particularly toward carbonyl compounds. It underwent sum of angles on the tin atom with the three bonded carbon
[2+2] cycloaddition with the C=O group of benzaldehyde atoms is surprisingly close to 360° (356.72 and 357.53°,
leading to 1,2-oxastannacyclobutane 5 (Scheme 3). A ring- respectively) like in starting stannene 3. In the six-mem-
expansion reaction was observed by addition of a second bered ring of 7, the four C1, Sn, O and C4 atoms lie practi-
equivalent of benzaldehyde to the highly strained four- cally in a plane (C1SnO1C4 = 0.05°) (Figures 2, 3 and 4).
membered heterocycle 5: the six-membered ring compound,
Unlike methyl vinyl ketone, acetone underwent an ex-
1,2,4-dioxastannacyclohexane 6, was obtained due to the clusive ene reaction with stannene 3 to afford vinyloxystan-
insertion of the C=O moiety of benzaldehyde into the Sn– nane 9 (Scheme 4). This air- and moisture-sensitive com-
O bond of 5. [2+4] Cycloadditions with α-ethylenic alde- pound rapidly hydrolyzes to give hydoxystannane 10, which
hydes and ketones such as crotonaldehyde and methyl vinyl is also quantitatively obtained by direct hydrolysis of stan-
ketone occurred with stannene 3 to form 1,2-oxastannacy- nene 3. Vinyloxystannane 9 is easily characterized by 119Sn
clohexenes 7 and 8. An ene reaction with methyl vinyl (δ = –96.3 ppm), 13C (OC=CH2 δ = 160.2 and 86.5 ppm)
1
ketone has not been observed. All these cycloadditions are and H NMR (=CH2: δ = 3.83 and 3.88 ppm) spectra. Un-
Eur. J. Inorg. Chem. 2008, 2007–2013
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2009

Abdoul Fatah, R. El Ayoubi, H. Gornitzka, H. Ranaivonjatovo, J. Escudié
FULL PAPER
like its germene analogue Mes2Ge=CR2,[20] it does not un-
dergo a Lutsenko-like rearrangement, which would give
Tip2Sn(CH2COMe)CHR2.
Figure 2. Molecular structure of oxastannacyclobutane 5 (50%
probability level); H atoms, noncoordinated solvent molecules (1/2
THF) and disorder are omitted for clarity. Selected bond lengths
[Å] and angles [°]: Sn1–C8 2.223(5), Sn1–O1 2.038(3), O1–C1
1.419(6), C1–C8 1.559(7), Sn1–C29 2.168(5), Sn1–C44 2.182(5),
C29–Sn1–C44 123.98(18), C29–Sn1–C8 119.80(18), C44–Sn1–
C8 112.94(18), O1–Sn1–C8 68.43(16), Sn1–C8–C1 83.8(3), C8–C1–
O1 107.4(4), C1–O1–Sn1 94.5(3).
Scheme 4. Reactivity of stannapentafulvene 3.
Conclusions
The introduction of two tert-butyl groups in the 2,7-posi-
tions on the fluorenylidene group dramatically increases the
stability of the related nearly planar stannene, which, how-
ever, still remains very reactive. The study of its chemical
behaviour is under active investigation.
Experimental Section
General Information: All experiments were carried out in flame-
dried glassware under an argon atmosphere by using high-vacuum-
line techniques. Solvents were dried and freshly distilled from so-
dium benzophenone ketyl and carefully deoxygenated on a vacuum
line by several “freeze–pump–thaw” cycles. Unless otherwise men-
tioned, CDCl3 was the NMR solvent. NMR spectra were recorded
with the following spectrometers: 1H, Bruker Avance 300
(300.13 MHz); 13C{1H}, Bruker Avance 300 (75.47 MHz) (refer-
ence TMS); 19F, Bruker AC200 (188.30 MHz) (reference CFCl3);
119Sn{1H}, Bruker Avance 300 (111.92 MHz) (reference Me4Sn).
Melting points were determined with a Wild Leitz-Biomed appara-
tus. Mass spectra were obtained with a Hewlett–Packard 5989A
spectrometer by electron impact (EI) at 70 eV and with a Nermag
R10–10 spectrometer by chemical ionization (CI).
Figure 3. Molecular structure of dioxastannacyclohexane 6 (50%
probability level); H atoms, noncoordinated solvent molecules
(pentane) and disorder are omitted for clarity. Selected bond
lengths [Å] and angles [°]: Sn1–C1 2.217(5), Sn1–O1 2.003(4), O1–
C2 1.383(7), C2–O2 1.424(6), O2–C9 1.436(6), C1–C9 1.551(7),
Sn1–C36 2.176(6), Sn1–C51 2.150(5), C36–Sn1–C51 103.8(2), C36–
Sn1–C1 109.06(19), C51–Sn1–C1 134.5(2), O1–Sn1–C1 95.84(18).
Starting compounds were synthesized according to the literature:
Tip2SnF2,[7a] and 2,7-di-tert-butylfluorene.[16] The carbon atoms of
the fluorenyl group are labelled as mentioned in Scheme 2.
Bis(2,4,6-triisopropylphenyl)-2,7-di-tert-butylfluorenylfluorostan-
nane (4): To
a solution of 2,7-di-tert-butylfluorene (1.70 g,
6.11 mmol) in THF (10 mL) cooled to –78 °C was added a solution
of nBuLi (1.6  in hexane, 3.8 mL 6.11 mmol); the solution turned
immediately red. After stirring for 15 min, this solution was added
dropwise to a solution of Tip2SnF2 (3.44 g, 6.11 mmol) in THF
(15 mL) cooled to –78 °C. The brown reaction mixture was slowly
warmed to room temperature and then turned light yellow. After
removal of the solvents under reduced pressure, pentane (20 mL)
was added, and the lithium salts were removed by filtration. White
crystals of fluorostannane 4 (3.76 g, 75%) were obtained from pen-
Figure 4. Molecular structure of oxastannacyclohexene 7 (50%
probability level); H atoms and disorder are omitted for clarity.
Selected bond lengths [Å] and angles [°]: Sn1–C1 2.220(4), Sn1–O1
2.027(3), O1–C4 1.329(6), C4–C3 1.339(7), C3–C2 1.514(7), C2–C1
1.560(6), Sn1–C41 2.166(4), Sn1–C26 2.164(5), C41–Sn1–
C26 103.57(18), C41–Sn1–C1 119.07(19), C26–Sn1–C1 134.89(18),
O1–Sn1–C1 96.53(15).
1
tane at –20 °C. M.p. 153 °C. H NMR (300.13 MHz, CDCl3): δ =
3
3
0.75 (d, JH,H = 6.6 Hz, 12 H, o-CHMeMeЈ), 0.84 (d, JH,H
=
3
6.6 Hz, 12 H, o-CHMeMeЈ), 1.07 (s, 18 H, tBu), 1.11 (d, JH,H
= 6.6 Hz, 12 H, p-CHMe2), 2.41 (sept., JH,H = 6.6 Hz, 4 H, o-
3
3
CHMeMeЈ), 2.77 (sept., JH,H = 6.6 Hz, 2 H, p-CHMe2), 4.69 (s,
1 H, CHR2), 6.87 (s, 4 H, arom H of Tip), 7.25 (dd, 3JH,H = 8.0 Hz,
2010
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Eur. J. Inorg. Chem. 2008, 2007–2013

A Nearly Planar Stannene with a Reactive Tin–Carbon Double Bond
4
4JH,H = 1.1 Hz, 2 H, H on C3 and C6), 7.35 (d, JH,H = 1.1 Hz, 2
CHMeMeЈ), 6.68 (s, 1 H, OCH), 6.79–6.95 (m, 7 H), 7.05 (dd,
3JH,H = 6 Hz, 1 H), 7.15–7.25 (m, 3 H), 7.28–7.33 (m, 2 H), 7.58
3
H, H on C1 and C8), 7.68 (d, JH,H = 8.0 Hz, 2 H, H on C4 and
C5) ppm. 13C NMR (75.47 MHz, CDCl3): δ = 23.9 (p-CHMe2), (dd, JH,H = 6.0 Hz, JH,H = 1.0 Hz, 1 H) and 7.70 (dd, JH,H
=
3
4
3
24.7 and 24.8 (o-CHMeMeЈ), 31.5 (CMe3), 34.1 (JSn,C = 5.7 Hz, p-
6.0 Hz, 4JH,H = 0.5 Hz, 1 H, arom H) ppm. 13C NMR (75.47 MHz,
CHMe2), 34.7 (CMe3), 37.9 (d, 4JC,F = 3.3 Hz, 3JSn,C = 35.2 Hz, o-
CDCl3): δ = 23.9, 24.0, 24.1, 25.8, 26.4 and 34.5 (o- and p-
CHMeMeЈ), 50.47 (1JSn,C = 152.5 Hz, CHR2), 122.2 (3JSn,C
=
CHMeMeЈ and CHMeMeЈ), 31.4 and 31.6 (CMe3), 34.6 and 34.8
2
(CMe3), 78.9 (CR2), 81.5 (2J
= 80.0 Hz, J
117Sn,C
119Sn,C
= 86.1 Hz,
57.4 Hz, m-CH of Tip), 119.6, 121.1 and 123.7 (other arom CH),
154.7 (2J = 51.3 Hz, 2J
= 53.6 Hz, o-C of Tip), 137.9
(JSn,C = 24.9 Hz), 140.3, 144.0, 149.1 (JSn,C = 13.1 Hz) and 151.1
(JSn,C = 11.9 Hz, other arom C) ppm. 19F NMR (188.30 MHz,
OCH), 118.6, 118.9, 119.6 (JSn,C = 24.2 Hz), 122.2, 122.3, 122.5,
122.8 and 122.9 (m-C of Tip and arom CH of CR2), 124.5 and
126.9 (o- and m-CH of Ph), 125.4 (p-CH of Ph), 135.5, 136.0, 137.9,
117Sn,C
119Sn,C
1
1
117Sn,F
119Sn,F
= 2428.0 Hz)
CDCl3): δ = –184.6 (s, J
= 2320.9 Hz, J
139.3, 144.9, 145.4, 145.8, 147.5 (JSn,C = 16.6 Hz), 148.6 (JSn,C
21.1 Hz), 150.8 (JSn,C = 13.6 Hz) and 151.1 (JSn,C = 13.6 Hz) (arom
2428.0 Hz) ppm. MS (EI, 70 eV): m/z (%) = 803 (2) [M – F], 561 C) ppm. 119Sn NMR (111.92 MHz, CDCl3): δ = 16.0 ppm. MS
(7) [M – Tip – tBu + 1], 545 (100) [Tip2SnF], 525 (12) [Tip2Sn – (FAB): m/z (%) = 908 (8) [M], 803 (50) [M – PhCHO + 1], 543 (70)
1], 321 (12) [TipSn – 2], 277 (60) [CHR2], 262 (40) [CHR2 – Me]. [Tip2SnO + 1], 525 (82) [Tip2Sn – 1], 321 (100) [TipSn – 2], 277
=
ppm. 119Sn NMR (111.92 MHz, CDCl3): δ = –22.4 (d, J
=
1
119Sn,F
C51H71FSn (821.81): calcd. C 74.54, H 8.71; found C 74.38, H 8.50.
(40) [CHR2]. C58H76OSn (907.93): calcd. C 76.73, H 8.44; found C
76.97, H 8.52.
Stannene 3: To a solution of fluorostannane 4 (1.00 g, 1.22 mmol)
in Et2O (20 mL) cooled to –78 °C was slowly added by syringe a
solution of tBuLi (1.6  in pentane, 0.76 mL, 1 equiv.). The reac-
tion mixture turned immediately deep red. After 10 min, the reac-
tion mixture was warmed to room temperature; it turned deep pur-
ple around –10 °C. A 119Sn NMR analysis showed the nearly quan-
titative formation of stannene 3. The solvents were removed under
vacuum and replaced by pentane (20 mL). The lithium salts were
filtered out, and the purple residue was crystallized from pentane
at –20 °C to afford deep purple crystals of 3 (0.76 g, 78%). M.p.
140 °C. 1H NMR (300.13 MHz, C6D6): δ = 1.22 (s, 18 H, tBu),
Dioxastannacyclohexane 6 [from Stannene 3 and Benzaldehyde
(2 equiv.)]: Brown crystals from pentane. Yield: 0.40 g, 80%. M.p.
1
135 °C. H NMR (300.13 MHz, CDCl3): δ = 0.71–1.80 (m, 36 H,
CHMeMeЈ), 1.72–3.51 (m, 6 H, CHMeMeЈ), 6.52–8.14 (m, 20 H,
arom H) ppm. 13C NMR (75.47 MHz, CDCl3): δ = 22.6, 22.8, 23.0,
23.4, 23.8, 23.9, 24.0, 24.1, 24.4, 24.7, 24.9, 25.7, 31.1, 31.4, 34.1,
34.2, 34.3 and 36.6 (CHMeMeЈ), 31.2 and 31.5 (CMe3), 34.5 and
34.9 (CMe3), 65.6 (CR2), 83.8 (OCHPh), 101.4 (OCO), 119.0,
119.2, 121.7, 122.9, 123.3, 123.7, 124.2, 124.6, 125.6, 125.6, 125.9,
126.1, 126.1, 126.7, 126.9 and 127.1 (arom CH), 136.4, 137.2, 137.8,
3
3
1.25 (d, JH,H = 6 Hz, 24 H, o-CHMe2), 1.27 (d, JH,H = 6 Hz, 12 138.4, 141.0, 142.7, 143.2, 144.3, 146.6, 147.6, 148.7, 150.4, 150.5,
H, p-CHMe2), 2.71 (sept., 2 H, p-CHMe2), 2.82 (sept., 4 H, o-
152.8, 154.7 and 155.1 (arom C) ppm. 119Sn NMR (111.92 MHz,
3
CHMe2), 7.15 (s, 4 H, arom H of Tip), 7.25 (dd, JH,H = 8.0 Hz, CDCl3): δ = –84.8 ppm. MS (FAB): m/z (%) = 907 (100) [M –
4
4JH,H = 1.5 Hz, 2 H, H on C3 and C6), 7.58 (d, JH,H = 1.5 Hz, 2
PhCHO – 1], 863 (53) [M – PhCHO – iPr – 2], 802 (50) [M – 2
PhCHO], 647 (48) [M – CR2 – PhCH – 1], 525 (82) [Tip2Sn – 1].
3
H, H on C1 and C8), 7.88 (d, JH,H = 8.0 Hz, 2 H, H on C4 and
C5) ppm. 13C NMR (75.47 MHz, C6D6): δ = 23.8, 24.4 and 25.5 C65H82O2Sn (1014.05): calcd. C 76.99, H 8.15; found C 77.21, H
(o- and p-CHMe2 and p-CHMe2), 31.4 (CMe3), 43.0 (o-CHMe2),
117.8, 118.6 and 119.4 (arom CH of CR2), 122.5 (m-CH of Tip),
154.6 (o-C of Tip), 131.3, 143.6, 145.7, 146.5 and 152.0 (other arom
C), 146.9 (Sn=C) ppm. 119Sn NMR (111.92 MHz, C6D6): δ =
277.4 ppm. UV/Vis (pentane, r.t.): λ (ε, –1 cm–1) = 560 (8000) nm.
MS (EI, 70 eV): m/z (%) = 802 (1) [M], 745 (0.5) [M – tBu], 599
(2) [M – Tip], 543 (33) [M – Tip – tBu + 1], 525 (21) [Tip2Sn – 1],
482 (1) [Tip2Sn – iPr – 1], 321 (16) [TipSn – 2], 277 (100) [CHR2].
C51H70Sn (801.80): calcd. C 76.40, H 8.80; found C 76.65, H 8.91.
8.30.
Oxastannacyclohexene 7 (from Stannene 3 and Crotonaldehyde):
Light-brown needles from Et2O. Yield: 1.25 g, 95%. M.p. 237 °C.
1H NMR (300.13 MHz, CDCl3): δ = –0.10, 0.17, 0.24, 0.35, 0.44,
3
0.65, 1.10, 1.13, 1.20, 1.22, 1.29, 1.43 and 1.54 (13 d, JH,H = from
5.2 to 6.8 Hz, 39 H, CHMeMeЈ and =CHMe), 0.95 (s, 9 H, tBu),
1.36 (s, 9 H, tBu), 2.71, 2.84 and 3.11 (3 sept., 3JH,H = 5.8 Hz, 3ϫ1
H, CHMeMeЈ), 3.20–3.31 (m, 1 H, CHMeMeЈ), 3.82–4.03 (m, 2
H, CHMeMeЈ), 4.41–4.44 (m, 1 H, =CH-CHMe), 6.71 (s, 4JSn,H
=
General Procedure for the Reactions of Tip2Sn=CR2: Crude solu-
tions of stannene 3 (containing LiF) prepared from fluorostannane
4 (1.00 g) were used without purification. After 0.5 h at room tem-
perature, the solution containing the stannene was cooled again to
–50 °C and the carbonyl compound (1 equiv.) was slowly added
by syringe. The reaction mixture turned immediately brown. After
warming to room temperature, 119Sn NMR spectroscopic analysis
showed in all cases the disappearance of the starting stannene and
the formation of only one compound. After evaporation of the sol-
vents under vacuum and addition of pentane (20 mL), the lithium
salts were removed by filtration; the crude brown residue was crys-
tallized at –20 °C from Et2O or pentane (see the solvent used in
each case).
12 Hz, 2 H, H of Tip), 6.88 (s, 2 H, H of Tip), 6.94 (s, 1 H, arom
H of CR2), 7.12–7.30 (m, 2 H, H of CR2), 7.42, 7.72 and 7.79 (3
dd, 3JH,H = 8.2 Hz, 4JH,H = 1.5 Hz, 3ϫ1 H, arom H of CR2), 8.22
(s, 1 H, CHO) ppm. 13C NMR (75.47 MHz, CDCl3): δ = 22.7, 22.8,
23.2, 23.3, 23.8, 23.9, 24.0, 24.1, 24.9, 25.0, 25.6, 26.2, 34.1, 34.3,
34.5, 34.9, 35.5, 36.9, 39.8 and 41.9 (o- and p-CHMeMeЈ and
CHMeCR2), 31.2 and 31.7 (CMe3), 34.9 (CMe3), 60.2 (CR2), 106.1
(OCH =CH), 118.7, 118.9, 121.3, 121.5, 122.0, 122.5, 122.7, 123.1,
123.3 and 123.6 (arom CH), 137.2, 138.6, 141.1, 144.2, 147.4, 148.1,
148.6, 149.3, 150.2, 150.3, 152.4, 153.9, 154.9 and 155.0 (arom C),
148.7 (OCH=CH) ppm. 119Sn NMR (111.92 MHz, CDCl3): δ =
–52.7 ppm. MS (EI, 70 eV): m/z (%) = 802 (2) [M – crotonalde-
hyde], 669 (3) [M – Tip], 611 (5) [M – Tip – tBu – 1], 597 (4) [M –
Tip – tBu – Me], 543 (35) [Tip2SnO + 1], 525 (34) [Tip2Sn – 1],
322 (100) [TipSn – 1], 57 (67) [tBu]. C55H76OSn (871.89): calcd. C
75.77, H 8.79; found C 76.05, H 8.92.
Oxastannacyclobutane
5 [from Stannene 3 and Benzaldehyde
(1 equiv.)]: Brown crystals from pentane. Yield: 0.83 g, 75%. M.p.
1
145 °C. H NMR (300.13 MHz, CDCl3): δ = 1.20–1.40 (very br. s
due to coalescence, 24 H, CHMeMeЈ), 1.26, 1.27, 1.36 and 1.37 (4
d, 3JH,H = 6 Hz, 4ϫ3 H, CHMeMeЈ), 0.95 (s, 9 H, tBu), 1.15 (s, 9
H, tBu), 2.71–2.98 (m, 2 H, o-CHMeMeЈ), 2.89 and 2.99 (2 sept.,
3JH,H = 6 Hz, 2ϫ1 H, p-CHMeMeЈ), 3.27–3.55 (m, 2 H, o-
Oxastannacyclohexene 8 (from Stannene 3 and Methyl Vinyl
Ketone): Brown-yellow needles from Et2O. Yield: 0.90 g, 70%. M.p.
213 °C. 1H NMR (300.13 MHz, CDCl3): δ = –0.05 (br. s, 3 H),
0.32 (br. s, 6 H), 0.54 (br. s, 3 H), 0.67 (br. s, 3 H) and 0.79–1.55
Eur. J. Inorg. Chem. 2008, 2007–2013
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2011

Abdoul Fatah, R. El Ayoubi, H. Gornitzka, H. Ranaivonjatovo, J. Escudié
FULL PAPER
(m, 41 H, CHMeMeЈ, CH2 and tBu), 2.01 (s, 3 H, OCMe), 2.69– OC(Me)=CH2], 583 (55) [M – CHR2 – OC(Me)=CH2], 543 (12)
2.95 (m, 3 H), 3.10–3.29, 3.45–3.67 and 3.80–3.92 (3 m, 3ϫ1 H, [Tip2SnO + 1], 525 (45) [Tip2Sn – 1], 482 (3) [Tip2Sn – iPr – 1],
CHMeMeЈ), 4.63 (t, JH,H = 6.0 Hz, 1 H, CHCH2), 6.74 (br. s, 2 321 (70) [TipSn – 2], 277 (100) [CHR2]. C54H76OSn (859.88): calcd.
3
H), 6.85–7.05 (m, 2 H), 7.15–7.50 (m, 3 H), 7.69–7.90 (m, 2 H) and
8.10 (br. s, 1 H, arom H of Tip and CR2) ppm. 13C NMR
(75.47 MHz, CDCl3): δ = 22.8, 23.9, 24.7, 25.7, 31.2, 31.5, 34.3 (o-
and p-CHMe2, CH2R2 and OCMe), 23.9 (CMe3), 33.2 (CMe3),
54.1 (CH2CR2), 92.8 (3JSn,C = 46.8 Hz, CH=CMe), 118.9, 121.1,
121.9, 122.2, 122.5, 123.3 and 123.6 (br. and small s, arom CH),
148.5, 149.0, 150.3 (2JSn,C = 11.3 Hz), 154.0, 155.4 and 156.4 (arom
C and OCMe) ppm. 119Sn NMR (111.92 MHz, CDCl3): δ =
–57.5 ppm. MS (EI, 70 eV%): m/z (%) = 872 (5) [M], 802 (10) [M –
methyl vinyl ketone], 595 (4) [M – CR2], 543 (15) [Tip2SnO + 1],
525 (45) [Tip2Sn – 1], 322 (100) [TipSn – 1], 57 (67) [tBu].
C55H76OSn (871.89): calcd. C 75.77, H 8.79; found C 75.85, H 8.83.
C 75.43, H 8.91; found C 75.40, H 9.03.
Hydroxystannane 10 (from Stannene 3 and Water): White crystals
from Et2O. Yield: 0.75 g, 75%. M.p. 160 °C. 1H NMR
(300.13 MHz, CDCl3): δ = 0.85, 0.93 and 1.19 (3 d, JH,H = 6 Hz,
3
3ϫ12 H, CHMeMeЈ), 1.15 (s, 18 H, tBu), 2.68–2.90 (m, 6 H,
CHMeMeЈ), 4.86 (s, 2J
= 105.0 Hz, 1 H, CHR2), 6.94 (s,
119Sn,H
4J
= 24.0 Hz, 4 H, arom H of Tip), 7.33 (dd, JH,H = 6 Hz,
3
119Sn,H
4JH,H = 1.3 Hz, 2 H, H on C3 and C6), 7.39 (br. s, 2 H, H on C1
3
and C8), 7.75 (d, JH,H = 6 Hz, 2 H, H on C4 and C5) ppm. 13C
NMR (75.47 MHz, CDCl3): δ = 24.0, 24.4, 24.8 (o- and p-
CHMeMeЈ), 30.7 (CMe3), 34.3 (p-CHMeMeЈ), 34.8 (CMe3), 37.6
(3J
= 35.6 Hz, o-CHMeMeЈ), 49.5 (CHR2), 119.3, 121.3 and
119Sn,C
Vinyloxystannane 9 (from Stannene 3 and Acetone): White crystals
from Et2O. Yield: 0.65 g, 61%. M.p. 172 °C. 1H NMR
123.3 (arom CH of CR2), 122.1 (m-CH of Tip), 137.7, 141.7, 144.6,
148.7 and 150.6 (arom C of CR2, ipso- and p-C of Tip), 154.8
3
(300.13 MHz, CDCl3): δ = 0.70, 0.86 and 1.24 (3 d, JH,H = 6 Hz,
(2J
= 49.8 Hz, o-C of Tip) ppm. 119Sn NMR (111.92 MHz,
119Sn,C
36 H, CHMeMeЈ), 1.19 (s, 18 H, tBu), 1.92 (s, 3 H, OCMe), 2.55
CDCl3): δ = –61.1 ppm. MS (EI, 70 eV): m/z (%) = 803 (3) [M –
OH], 599 (5) [M – Tip – 1], 543 (55) [Tip2SnOH], 525 (25) [Tip2Sn –
1], 321 (27) [TipSn – 2], 277 (100) [CHR2]. C51H72OSn (819.82):
calcd. C 74.72, H 8.85; found C 74.97, H 9.08.
(very br. s, half width: 30 Hz, 2 H, p-CHMeMeЈ), 2.82 (sept., 3JH,H
2
= 6 Hz, 4 H, o-CHMeMeЈ), 3.83 (d, JH,H = 2.2 Hz, 1 H, H trans/
2
Me of CHHЈ=COMe), 3.88 (d, JH,H = 2.2 Hz, 1 H, H cis/Me of
CHHЈ=COMe), 4.86 (s, 2J117Sn,H = 126.0, 2J119Sn,H = 135.0 Hz, 1 H,
CHR2), 6.87 (s, 4 H, arom H of Tip), 7.28 (br. s, 2 H, H of CR2),
X-ray Structural Determination: All data for all structures repre-
7.55 (br. s, 2 H, H of CR2), 7.75–7.79 (m, 2 H, H of CR2) ppm. sented in this paper were collected at low temperatures by using
13C NMR (75.47 MHz, CDCl3): δ = 22.8, 23.1, 23.6, 28.7, 30.5,
36.7 and 37.4 (o- and p-CHMeMeЈ and OCMe), 30.7 (CMe3), 33.7
an oil-coated shock-cooled crystal with a Bruker-AXS CCD 1000
diffractometer with Mo-Kα radiation (λ = 0.71073 Å). The struc-
(CMe3), 45.3 (CHR2), 86.5 (CH2=CO), 118.0, 120.8 and 121.3 tures were solved by direct methods[21] and all non hydrogen atoms
(arom CH), 121.8 (m-CH of Tip), 136.4, 140.7, 147.4, 148.9, 152.7
were refined anisotropically by using the least-squares method on
and 153.0 (arom C), 160.3 (=C–O) ppm. 119Sn NMR (111.92 MHz, F2.[22] ADP- and distances restraints were used to refine several
CDCl3): δ = 96.3 ppm. MS (EI, 70 eV): m/z (%) = 803 (10) [M –
Table 1. Crystal data for compounds 3, 5, 6 and 7.
disorders: a rotation disorder of a tBu group and an iPr for 3, two
3
5
6
7
Empirical formula
Formula weight
Temperature [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C51H70Sn
801.76
173(2)
monoclinic
P21/c
14.817(1)
26.652(2)
12.457(1)
–
110.920(2)
–
C60H80O1.5Sn
943.93
173(2)
monoclinic
C2/c
23.109(2)
12.996(1)
35.439(2)
–
91.618(1)
–
10638.8(12)
8
C70H94O2Sn
1086.14
173(2)
C55H76OSn
871.85
173(2)
orthorhombic
Pbca
11.073(1)
25.256(1)
35.368(2)
–
triclinic
¯
P1
12.508(1)
13.686(1)
21.076(2)
71.094(2)
75.049(2)
68.321(2)
3132.4(6)
2
–
–
γ [°]
Volume [Å3]
Z
4595.1(6)
4
9891.3(9)
8
0.552
Absorption coefficient [mm–1] 0.587
0.519
0.449
Reflections collected
Independent reflections
R(int)
Absorption correction
Min./max. transmission
Data
20354
6530
0.0909
semiempirical
0.759050
6530
23239
7564
0.0838
semiempirical
0.748219
7564
13999
8863
0.0682
semiempirical
0.297743
8863
42206
7025
0.1236
semiempirical
0.767978
7025
Restraints
105
554
1.013
81
642
1.071
64
720
0.988
60
558
1.055
Parameters
Goodness-of-fit on F2
Final R indices
[IϾ2σ(I)]
R1
wR2
0.0485
0.0777
0.0567
0.0931
0.0625
0.1059
0.051
0.0764
R indices (all data) R1
wR2
0.0947
0.0884
0.523/–0.362
0.0955
0.1032
0.621/–0.664
0.1153
0.1221
0.996/–0.909
0.1017
0.0884
0.474/–0.662
Largest diff. peak/hole [eÅ–3]
2012
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Eur. J. Inorg. Chem. 2008, 2007–2013

A Nearly Planar Stannene with a Reactive Tin–Carbon Double Bond
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Acknowledgments
A. F. is grateful to the Service de Coopération et d’Action Sociale
of the French Embassy in Antananarivo (Madagascar) for a grant.
The authors thank the Centre National de la Recherche Sci-
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Received: November 28, 2007
Published Online: March 19, 2008
Eur. J. Inorg. Chem. 2008, 2007–2013
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2013