Versatile reactivity of stannene Tip2Sn=CR2 with unsaturated compounds

Article abstract of DOI:10.1021/om3004916

The stannene Tip₂Sn=CR₂ (1; Tip = 2,4,6-triisopropylphenyl, CR₂ = 2,7-di-tert-butylfluorenylidene) gives [2 + 2] cycloadditions with phenyl isocyanate and diphenylketene (by the C=O bond) and phenyl isothiocyanate (by the C=S bond) to afford the corresponding four-membered heterocycles. [2 + 3] cycloadditions are observed between 1 and N-tert-butyl α-phenyl nitrone and methyl (benzylideneamino)acetate. Very different reactions occur with nitriles: an insertion of a C-H bond of acetonitrile across the Sn=C double bond and a [2 + 2] cycloaddition between Sn=C double bond and C≡N unsaturation of pivalonitrile.

Full text of DOI:10.1021/om3004916

Article
pubs.acs.org/Organometallics
Versatile Reactivity of Stannene Tip2SnCR2 with Unsaturated
Compounds
§
§
Abdoul Fatah,†,‡ Dumitru Ghereg,† Jean Escudie,† Nathalie Saffon, Sonia Ladeira,
́
and Henri Ranaivonjatovo*,†
†Universite
́
de Toulouse, UPS, LHFA, 118 Route de Narbonne, F-31062 Toulouse, France CNRS, LHFA, UMR 5069, F-31062
Toulouse cedex 09, France
‡Laboratoire de Chimie Organique, Faculte
́
des Sciences, Universite
́
d’Antsiranana, B.P. 0, 201 Antsiranana, Madagascar
§Institut de Chimie de Toulouse, ICT-FR 2599, Universite
́
Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse cedex 09, France
S
* Supporting Information
ABSTRACT: The stannene Tip2SnCR2 (1; Tip = 2,4,6-triisopro-
pylphenyl, CR2 = 2,7-di-tert-butylfluorenylidene) gives [2 + 2]
cycloadditions with phenyl isocyanate and diphenylketene (by the
CO bond) and phenyl isothiocyanate (by the CS bond) to afford
the corresponding four-membered heterocycles. [2 + 3] cyclo-
additions are observed between 1 and N-tert-butyl α-phenyl nitrone
and methyl (benzylideneamino)acetate. Very different reactions occur
with nitriles: an insertion of a C−H bond of acetonitrile across the
SnC double bond and a [2 + 2] cycloaddition between SnC double bond and CN unsaturation of pivalonitrile.
and sulfur compounds such as isocyanates, isothiocyanates,
nitrones, imino esters, nitriles, and ketenes.
INTRODUCTION
■
Great progress has been made over the past 25 years in the field
of heavier congeners of heteroalkenes >MC< (M = Si, Ge,
Sn). Such derivatives, called metallaalkenes, are now important
building blocks in organometallic and heterocyclic chemistry,
owing to the great reactivity of the MC double bond. Silenes
>SiC< are the most studied derivatives,1 followed by
germenes >GeC<.1c,d,h,k,l,2 Stannenes >SnC< (for reviews
see refs 1c,k,l and 2c,e) are more difficult to stabilize as
monomers, and limited syntheses are known.3−9 We have
recently described the synthesis of stannene 1,10 which is
stabilized by the large steric hindrance caused by two Tip groups
(Tip = 2,4,6-triisopropylphenyl) on tin and particularly the
presence of two tert-butyl groups at the 2- and 7-positions of the
fluorenylidene (Scheme1). The chemical behavior of stannenes
has begun to be well-documented,3,7,8,10−13 except toward
compounds with a CS or a CN double bond.
RESULTS AND DISCUSSION
■
Phenyl Isocyanate, Phenyl Isothiocyanate, and Diphe-
nylketene. Addition of phenyl isocyanate, phenyl isothiocya-
nate, and diphenylketene to stannene 1 at −78 °C led by a [2 + 2]
cycloaddition between the SnC and CO or CS double
bonds to the four-membered rings 2−4, respectively, in nearly
quantitative yields. The regioselectivity of the reaction is easily
explained from the polarity of the reagents (Snδ+Cδ−) and
Cδ+Oδ− (or Sδ−) and the high Sn−O and Sn−S bond energy
(Scheme 2). Under the experimental conditions, addition of the
stannene to the CN or CC double bond was never
observed. Derivatives 2−4 were characterized by the expected
Scheme 2
We present in this paper the reactivity of the bis(2,4,6-
triisopropylphenyl)-2,7-di-tert-butylfluorenylidene stannane
Tip2SnCR2 toward various multiply bonded nitrogen, oxygen,
Scheme 1. Synthesis of Stannene 1
Received: June 1, 2012
© XXXX American Chemical Society
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low-field shift for the sp2 carbon atom of the four-membered ring
(2, 174.24 ppm; 3, 168.56 ppm; 4, 161.26 ppm). Mass
spectroscopy confirms the regioselectivity of the cycloaddition
owing to the typical cleavage [4] → [2] + [2] of the four-
membered rings 2−4: some of the main fragments are the
ketenimine R2CCNPh and allene R2CCCPh2 togeth-
er with Tip2SnO and Tip2SnS.
to give the five-membered rings 5 and 6, respectively (Scheme 3).
Such a result with the formation of the 1,2,5-oxazastannacyclo-
pentane 5 could reasonably be expected. 6 is the first α-stannyl-
substituted α-amino ester.
Scheme 3
The four-membered heterocycles 2−4 present a good thermal
stability under an inert atmosphere despite the high ring strain.
Such heterocycles are stabilized by the great steric hindrance.
However, a free rotation of the Tip group occurs, proved by the
equivalence of iPr, and only two signals are observed for the
diastereotopic Me groups on every iPr. The formation of the 1,2-
thiastannacyclobutane 3 is unambiguously proved by an X-ray
structure determination (Figure 1).
We can explain the formation of cycloadduct 6 by a [2 + 3]
cycloaddition between stannene 1 and the 1,3-dipolar
azomethine ylide 7 formed from PhCHNCH2COOMe by a
prototropic shift which could be assisted by the lithium salt
(Scheme 4).
Scheme 4
Note that a similar reaction has been reported between methyl
(benzylideneamino)acetate and the germene Mes2GeCR′2.17
In contrast, a completely different reaction occurs with the
phosphagermaallene Tip(t-Bu)GeCPMes* (Tip = 2,4,6-
triisopylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl); in this case an
ene reaction leads to an acyclic azadienyl germyl ether18 (Scheme
5).
Figure 1. Molecular structure of 3. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms are omitted for clarity.
Relevant bond lengths (Å), bond angles (deg), and torsion angles (deg):
Sn1−S1 = 2.4691(4), Sn1−C1 = 2.223(2), Sn1−C23 = 2.149(2), Sn1−
C38 = 2.176(2), C1−C2 = 1.524(2), C2−S1 = 1.793(2), N1−C2 =
1.264(2), C1−C3 = 1.510(2), C1−C14 = 1.497(2); Sn1−C1−C2 =
92.28(8), C1−C2−S1 = 111.42(10), C2−S1−Sn1 = 78.41(5), S1−
Sn1−C1 = 71.38(4), S1−C2−N1 = 128.31(11), C1−C2−N1 =
120.27(12), Sn1−C1−C14 = 113.92(10), Sn1−C1−C3 = 117.01(9);
C1−Sn1−S1−C2 = 14.69, S1−C2−C1−Sn1 = 24.21; angle between
four-membered ring and fluorenylidene ring 81.90.
Scheme 5
Similar [2 + 2] cycloadditions involving the GeC and CO
(or CS) double bonds were observed between the germene
Mes2GeCR′2 (Mes = 2,4,6-trimethylphenyl, CR′2 = fluo-
renylidene) and phenyl isocyanate and methyl isothiocyanate.14
In contrast, the germanimine Ph2GeNPh gives a [2 + 2]
cycloaddition with the CN double bond of phenyl
isocyanate15 and both the CN and CS double bonds of
methyl isothiocyanate.15
While the acyclic Sn−C(Tip) bond lengths are in the normal
range16 (2.149(2) Å for Sn1−C23 and 2.176(2) Å for Sn1−
C38), the intracyclic Sn−CR2 bond length is slightly elongated
due to the large steric hindrance (2.223(2) Å for Sn1−C1). The
four-membered ring is not planar, with rather large torsion angles
from 14.69 to 24.21°.
Because of the presence of the chiral carbon atom of the
C(H)Ph unit, the two Tip groups are, as expected, non-
equivalent. Due to a hindered rotation of the two Tip groups (on
1
the H NMR time scale), eight doublets were observed in the
case of 6 for the eight methyls of the o-iPr groups. In contrast, for
5, only four doublets could be determined for these eight methyl
groups, the four other expected doublets being unobservable due
to a coalescence phenomenon caused by the slow rotation of one
of the Tip groups. The great difference in their chemical shifts
from −0.21 to +1.60 ppm shows their various positions in
relation to the fluorenylidene group.
The structures of derivatives 5 and 6 have been unambiguously
determined by an X-ray study (5, Figure 2; 6, Figure 3). In 6 the
phenyl and COOMe groups are in a cis disposition
(pseudoequatorial position), which shows that one of the main
features of this reaction, besides its regioselectivity, is its
N-tert-Butyl α-Phenyl Nitrone and Methyl
(Benzylideneamino)acetate. The reactions of stannene 1
with N-tert-butyl α-phenyl nitrone and methyl
(benzylideneamino)acetate proceed by [2 + 3] cycloadditions
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(Scheme 6). Adduct 8 was evidenced in the 1H NMR spectrum
by the presence of a CHR2 unit (δ(CH) 4.92 ppm, 2JSnH = 75.3
Scheme 6
Figure 2. Molecular structure of 5. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms and solvent are omitted for
clarity. Relevant bond lengths (Å) and angles (deg): Sn1−C33 =
2.160(2), Sn1−C48 = 2.186(2), Sn1−C1 = 2.202(2), Sn1−O1 =
2.015(2), C1−C22 = 1.568(2), C22−N1 = 1.491(2), N1−O1 =
1.484(2); Sn1−O1−N1 = 109.58(8), O1−N1−C22 = 103.83(12),
N1−C22−C1 = 106.43(13), C22−C1−Sn1 = 97.11(9), C1−Sn1−O1
= 84.25(5); angle between five-membered ring Sn1−C1−C22−N1−
O1 and fluorenylidene ring 88.5.
Figure 4. Molecular structure of 8. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms and solvent are omitted for
clarity. Relevant bond lengths (Å) and angles (deg): Sn1−C1 =
2.225(2), Sn1−C22 = 2.193(2), Sn1−C24 = 2.177(2), Sn1−C39 =
2.178(2), C22−C23 = 1.439(4), C23−N1 = 1.148(3); Sn1−C1−C2 =
109.79(14), Sn1−C1−C13 = 104.54(14), C1−Sn1−C22 = 99.28(8),
C24−Sn1−C39 = 104.15(8), C1−Sn1−C24 = 109.36(8), C1−Sn1−
C39 = 123.29(8), C22−C23−N1 = 176.8(3).
Figure 3. Molecular structure of 6. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms, except for H1, and the
solvent are omitted for clarity. Relevant bond lengths (Å) and angles
(deg): Sn1−C1 = 2.262(3), Sn1−C37 = 2.178(3), Sn1−C22 =
2.177(3), Sn1−C59 = 2.230(3), C1−C52 = 1.573(4), C52−N1 =
1.474(4), N1−C59 = 1.460(4), C59−C60 = 1.492(5); Sn1−C1−C52 =
94.8(2), C1−C52−N1 = 108.5(3), C52−N1−C59 = 115.8(3), N1−
C59−Sn1 = 103.0(2), C59−Sn1−C1 = 84.03(12), Sn1−C59−C60 =
106.4(2), N1−C59−C60 = 111.7(3); angle between five-membered
ring Sn1−C1−C52−N1−C59 and fluorenylidene ring 75.1°.
Hz) and by an X-ray structural study (Figure 4). In the case of
pivalonitrile, such a reaction could not occur and exclusive [2 +
2] cycloaddition leading to the 2-aza-3-stannacyclobut-1-ene 9
was observed. The latter was characterized by 1H, 13C, and 119Sn
NMR: for example, by a signal at very low field (δ(13C) 195.96
ppm) for the carbon atom doubly bonded to the nitrogen atom.
In mass spectroscopy, the molecular peak could not be observed:
the four-membered ring decomposes to give again the starting
stannene. Similar reactions between the germene Mes2Ge
CR′2 and acetonitrile or pivalonitrile have been reported.19
complete diastereoselectivity, since only one isomer is obtained.
In the oxazastannacyclopentane 5 and the azastannacyclopen-
tane 6, the five-membered rings are slightly distorted: the carbon
atom bonded to the phenyl group is 0.759 Å (5) and 0.766 Å (6)
from the mean plane constituted by the other four atoms.
Pivalonitrile and Acetonitrile. With a nitrile such as
acetonitrile, two reactions could occur: an addition of the SnC
double bond onto the CN triple bond or an insertion of a C−
H bond across the SnC double bond. In fact, only the insertion
of a C−H bond across the SnC double bond was observed
CONCLUSION
■
Stannene 1 is highly reactive, despite the very large steric
hindrance necessary for its stabilization (two Tip groups on Sn
and two t-Bu groups at the 2- and 7-positions of the
fluorenylidene). Reactions occur generally at low temperature
and can be easily followed by the rapid disappearance of the deep
purple color of the starting stannene. [2 + 2] cycloadditions are
C
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General Procedure for the Reactions of Tip2SnCR2 (1). In a
typical experiment, a crude solution of stannene 1 (containing LiF) was
prepared as described above from Tip2SnFCHR2 (0.82 g, 1.00 mmol)
and cooled to −78 °C. An equimolar amount of reactant (in neat form
when liquid at room temperature or dissolved in 5 mL of Et2O in the
case of N-tert-butyl α-phenyl nitrone) was added by syringe. The
reaction mixture was warmed to room temperature, and its color slowly
turned from purple to yellow or brown. After overnight stirring, the
solvent was removed in vacuo and replaced by 10 mL of pentane; LiF
was filtered out. Crystallization at −20 °C afforded the discussed
products in pure form as a powder or crystalline compound.
Synthesis of oxastannacyclobutane 2: Reaction of Stannene
1 with PhNCO. Yield: 0.65 g, 71%,. Mp: 182 °C. 1H NMR: δ 0.59
and 0.89 (2d, 3JHH = 6.0 Hz, 2 × 12H, o-CHMeMe′), 1.14 (s, 18H, CMe3
of CR2), 1.20 (d, 3JHH = 6.0 Hz, 12H, p-CHMeMe′), 2.31−2.41 (broad s,
4H, o-CHMeMe′), 2.83 (sept, 3JHH = 6.8 Hz, 2H, p-CHMeMe′), 6.95 (s,
4JSnC = 26.4 Hz, 4H, m-CH of Tip), 7.21 (t, 3JHH = 7.5 Hz, 1H, p-CH of
observed with heterocumulenes such as phenyl isocyanate,
methyl isothiocyanate, and diphenylketene (only CO and C
S double bonds are involved, the CN and CC bonds being
inert in these reactions) and [2 + 3] cycloadditions with N-tert-
butyl α-phenyl nitrone and methyl (benzylideneamino)acetate.
The versatile behavior of stannene 1 is particularly illustrated in
its reactions with nitriles: whereas a [2 + 2] cycloaddition occurs
with pivalonitrile (the sole reaction which needs heating), only
the insertion of a C−H bond across the SnC double bond is
observed with acetonitrile. In conclusion, 1 appears as a powerful
building block in heterocyclic tin chemistry with, in particular,
the easy synthesis in rather good yields of novel types of four- and
five-membered-ring tin derivatives.
EXPERIMENTAL SECTION
■
Ph), 7.33 (dd, 3JHH = 8.1 Hz, 4JHH = 1.5 Hz, 2H, H3 and H6 of CR2), 7.38
(d, 4JHH = 0.9 Hz, 2H, H1 and H8 of CR2), 7.42 (3JHH = 7.5 Hz, 2H, m-
CH of Ph), 7.73 (d, 3JHH = 8.1 Hz, 2H, H4 and H5 of CR2), 7.81 (d, 3JHH
= 7.5 Hz, 2H, o-CH of Ph). 13C NMR: δ 23.89 (p-CHMeMe′), 24.32 and
24.86 (o-CHMeMe′), 31.41 (CMe3 of CR2), 34.23 (p-CHMeMe′), 34.79
(CMe3 of CR2), 40.10 (3JSnC = 36.4 Hz, o-CHMeMe′), 78.56 (C9 of
CR2), 119.55 (4JSnC = 2.6 Hz, C4 and C5 of CR2), 120.19 (3JSnC = 5.5 Hz,
C1 and C8 of CR2), 122.86 (3JSnC = 57.1 Hz, m-CH of Tip), 124.07 (o-
CH of Ph), 124.23 (p-CH of Ph), 124.38 (C3 and C6 of CR2), 128.44
(m-CH of Ph), 137.07 (C12 and C13 of CR2), 140.07 (ipso-C of Tip),
All experiments were carried out in flame-dried glassware under a
nitrogen or argon atmosphere using high-vacuum-line techniques.
Solvents were dried and freshly collected using an SPS-800MB system.
NMR spectra were recorded (with CDCl3 as solvent) on a Bruker
Avance 300 spectrometer at the following frequencies: 1H, 300.13 MHz;
13C, 75.47 MHz (reference TMS); 119Sn, 111.92 MHz (reference
Me4Sn). Melting points were determined on a Wild Leitz-Biomed
apparatus. Mass spectra were obtained on a Hewlett-Packard 5989A
spectrometer by EI at 70 eV and on a Nermag R10-10 spectrometer by
CI. Elemental analyses were performed by the “Service de Microanalyse
de l′Ecole de Chimie de Toulouse”. NMR spectra have been elucidated
using COSY, HMBC, and HSQC techniques.
143.03 (ipso-C of Ph), 145.01 (C10 and C11 of CR2), 148.91 (4JSnC
=
16.3 Hz, C2 and C7 of CR2), 151.73 (4JSnC = 12.4 Hz, p-C of Tip),
154.09 (2JSnC = 51.7 Hz, o-C of Tip), 174.24 (CN). MS (m/z, %): 921
(M, 12), 717 (M − Tip − H, 1), 658 (Tip2SnCR2 − 2 t-Bu, 3), 542
(Tip2SnO, 14), 526 (Tip2Sn, 45), 482 (TipSn − iPr − H, 17), 379
(R2CCNPh, 35), 321 (TipSn − 2, 67), 277 (CR2 + H, 43), 57 (t-
Bu, 100). Anal. Calcd for C58H75NOSn (920.92): C, 75.65; H, 8.21.
Found: C, 75.51; H, 8.44.
1
For the H and 13C NMR study, the carbon atoms of the fluorenyl
group are numbered as shown in Chart 1.
Chart 1
Synthesis of Thiastannacyclobutane 3: Reaction of Stannene
1 with PhNCS. Yield: 0.72 g, 77%. Mp: 201 °C. 1H NMR: δ 0.73
and 0.91 (2 broad s, 2 × 12H, o-CHMeMe′), 1.20 (d, 3JHH = 6.0 Hz, 12H,
p-CHMeMe′), 1.22 (s, 18H, CMe3 of CR2), 2.50−2.80 (very broad s,
4H, o-CHMeMe′), 2.82 (sept, 3JHH = 6.9 Hz, 2H, p-CHMeMe′), 6.93 (s,
4H, m-CH of Tip), 6.92 (d, 3JHH = 7.9 Hz, 2H, o-CH of Ph), 7.12 (t, 3JHH
= 7.5 Hz, 1H, p-CH of Ph), 7.34 (dd, 3JHH = 8.1 Hz, 4JHH = 0.6 Hz, 2H,
H3 and H6 of CR2), 7.37 (t, 3JHH = 7.5 Hz, 2H, m-CH of Ph), 7.73 (d,
3JHH = 7.8 Hz, 2H, H4 and H5 of CR2), 7.79 (s, 2H, H1 and H8 of CR2).
13C NMR: δ 23.87 (p-CHMeMe′), 24.38 and 25.03 (o-CHMeMe′),
31.53 (CMe3 of CR2), 34.20 (p-CHMeMe′), 34.88 (CMe3 of CR2),
39.59 (broad, o-CHMeMe′) 89.62 (C9 of CR2), 119.57 (4JSnC = 9.8 Hz,
C4 and C5 of CR2), 120.60 (3JSnC = 22.6 Hz, C1 and C8 of CR2), 121.05
(o-CH of Ph), 122.49 (3JSnC = 52.8 Hz, m-CH of Tip), 123.98 (p-CH of
Ph), 124.32 (5JSnC = 15.1 Hz, C3 and C6 of CR2), 128.42 (m-CH of Ph),
135.67 (3JSnC = 16.6 Hz, C12 and 13 of CR2), 139.65 (ipso-C of Tip),
146.52 (2JSnC = 36.2 Hz, C10 and C11 of CR2), 149.19 (4JSnC = 15.1 Hz,
C2 and C7 of CR2), 150.62 (ipso-C of Ph), 151.09 (4JSnC = 12.1 Hz, p-C
of Tip), 154.17 (2JSnC = 50.5 Hz, o-C of Tip), 168.56 (CN). MS (m/z,
%): 938 (M + H, 4), 659 (M − CR2 − 1, 10), 558 (Tip2SnS, 58), 524
(Tip2Sn − 2, 35), 379 (R2CCNPh, 100), 321 (TipSn − 2, 5). 119Sn
NMR: δ −90.0. Anal. Calcd for C58H75NSSn (936.99): C, 74.35; H,
8.07. Found: C, 74.50; H, 8.24.
X-ray Structure Determinations for 3, 5, 6, and 8. The data of
the structures for compounds 3, 5, 6, and 8 (Table 1, Supporting
Information) were collected on a Bruker-AXS SMART APEX II
diffractometer (5 and 6) and on a Bruker-AXS kappa APEX II Quazar
diffractometer (3 and 8) at a temperature of 193(2) K using an oil-
coated, shock-cooled crystal with Mo Kα radiation (wavelength 0.710
73 Å) by using ψ and ω scans. The data were integrated with SAINT,
and an empirical absorption correction with SADABS was applied.20,21
The structures were solved by direct methods (SHELXS-97)22 and
refined against all data by the full-matrix least-squares methods on F2
(SHELXL-97).23 For 3, 5, 6, and 8, all non-hydrogen atoms were refined
with anisotropic displacement parameters. The hydrogen atoms were
refined isotropically on calculated positions using a riding model with
their Uiso values constrained to 1.5Ueq of their pivot atoms for terminal
sp3 carbon atoms and 1.2Ueq for all other carbon atoms.
Synthesis of Oxastannacyclobutane 4: Reaction of Stannene
1 with Ph2CCO. Oxastannacyclobutane 4 was sparingly soluble in
pentane and was isolated by washing the precipitate with CH2Cl2 (10
mL) and subsequent crystallization at −20 °C. Yield: 0.81 g, 81%. Mp:
Synthesis of Stannene 1. Stannene 1 was prepared as previously
described10 by slow addition of 1 equiv of a solution of t-BuLi 1.7 M in
1
188 °C. H NMR: δ 0.50−0.85 (broad s, 12H, o-CHMeMe′), 1.11 (s,
10
18H, CMe3 of CR2), 1.15−1.25 (broad s, 12H, o-CHMeMe′), 1.26 and
1.27 (2d, 3JHH = 6.9 Hz, 2 × 6H, p-CHMeMe′), 2.40−2.90 (very broad s,
4H, o-CHMeMe′), 2.89 (sept, 3JHH = 6.9 Hz, 2H, p-CHMeMe′), 6.12
(dd, 3JHH = 8.1 Hz, 4JHH = 0.9 Hz, 2H, o-CH of Pha), 6.38 (t, 3JHH = 7.5
Hz, 2H, m-CH of Pha), 6.55 (tt, 3JHH = 7.5 Hz, 4JHH = 1.2 Hz, 1H, p-CH
of Pha), 7.03 (t, 3JHH = 7.5 Hz, 1H, p-CH of Phb), 7.04 (s, 4H, m-CH of
Tip), 7.10 (dd, 3JHH = 8.1 Hz, 4JHH = 0.9 Hz, 2H, H3 and H6 of CR2),
pentane (0.59 mL) to a solution of fluorostannane Tip2Sn(F)C(H)R2
(0.82 g, 1.00 mmol) in Et2O (20 mL) cooled to −78 °C. The reaction
mixture turned immediately deep red. After 10 min, the reaction mixture
was warmed to room temperature; it turned deep purple around −10
°C. A 119Sn NMR analysis showed the nearly quantitative formation of
stannene 1 (δ 277.4 ppm). Reactions were carried out with crude
solutions of stannene in Et2O containing LiF.
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7.22 (t, 3JHH = 7.5 Hz, 2H, m-CH of Phb), 7.31 (s, 2H, H1 and H8 of
CR2), 7.33 (d, 3JHH = 7.5 Hz, 2H, H4 and H5 of CR2), 7.83 (d, 3JHH = 7.2
Hz, 2H, o-CH of Phb). 13C NMR: δ 23.88 and 23.94 (p-CHMeMe′),
24.22 and 25.81 (o-CHMeMe′), 31.42 (CMe3 of CR2), 34.28 (p-
CHMeMe′), 34.56 (CMe3 of CR2), 39.11 (broad, o-CHMeMe′) 80.02
(C9 of CR2), 112.28 (CPh2), 118.73 (4JSnC = 15.2 Hz, C4 and C5 of
CR2), 120.60 (3JSnC = 26.3 Hz, C1 and C8 of CR2), 122.68 (3JSnC = 47.3
Hz, m-CH of Tip), 122.74 (C3 and C6 of CR2), 123.43 and 124.53 (p-
CH of Ph), 125.86 and 127.11 (m-CH of Ph), 127.47 and 132.16 (o-CH
of Ph), 135.06 (C12 and 13 of CR2), 136.26 (ipso-C of Ph), 138.90 (ipso-
C of Tip), 141.42 (ipso-C of Ph), 146.39 (C10 and C11 of CR2), 148.19
(C2 and C7 of CR2), 151.37 (p-C of Tip), 154.94 (o-C of Tip), 161.26
(OCC). 119Sn NMR: δ 37.4. MS (m/z, %): 997 (M + H, 4), 794 (M −
Tip + H, 12), 525 (Tip2Sn − H, 15), 454 (R2CCCPh2, 5), 321
(TipSn − 2, 65), 277 (CR2 + H, 33), 57 (t-Bu, 100). Anal. Calcd for
C65H80OSn (996.03): C, 78.38; H, 8.10. Found: C, 78.53; H, 8.34%.
Synthesis of Oxazastannacyclopentane 5: Reaction of
Stannene 1 with N-tert-Butyl α-Phenyl Nitrone. Yield: 0.65 g,
31.81 (CMe3 of CR2), 34.02 and 34.35 (p-CHMeMe′), 34.52 and 35.29
(CMe3 of CR2), 37.85 (3JSnC = 22.6 Hz, o-CHMeMe′), 38.89 (3JSnC
=
33.2 Hz, o-CHMeMe′), 40.27 (3JSnC = 35.5 Hz, o-CHMeMe′), 41.56
1
(3JSnC = 27.2 Hz, o-CHMeMe′), 51.20 (OMe), 56.83 ( J
= 150.9
119
SnC
1
Hz, J SnC = 144.1 Hz, CHCO), 62.29 (C9 of CR2), 71.47 (2JSnC = 39.2
Hz, CHPh), 118.77 and 118.96 (C4 and C5 of CR2), 121.70 and 121.80
(m-CH of Tip(a)), 122.12 (C6 of CR2), 122.73 (C8 of CR2), 122.85
(C3 of CR2), 122.99 and 123.01 (m-CH of Tip(b)), 124.48 (C1 of
CR2), 126.56 (o-CH of Ph), 126.65 (p-CH of Ph), 127.11 (m-CH of
Ph), 137.78 and 137.82 (C12 and C13 of CR2), 138.05 (ipso-C of Ph),
141.49 and 142.91 (ipso-C of Tip), 146.06 (JSnC = 6.0 Hz), 146.59 (JSnC
= 13.1 Hz), 147.08 (JSnC = 9.6 Hz) and 148.12 (JSnC = 9.7 Hz) (C2, C7,
C10 and C11 of CR2), 150.08 (4JSnC = 11.2 Hz, p-C of Tip), 150.24
(4JSnC = 10.1 Hz, p-C of Tip), 153.21, 153.71, 153.84, and 154.24 (o-C of
Tip), 176.71 (CO). 119Sn NMR: δ 32.6. MS (m/z, %): 979 (M + H,
1), 802 (Tip2SnCR2, 2), 776 (M − Tip, 3), 573 (M − 2Tip, 12), 526
(Tip2Sn, 25), 454 (M − Tip2Sn + H, 77), 351 (R2CCHPh − Me, 100),
366 (R2CCHPh, 61), 321 (TipSn − 2, 81), 277 (CR2 + H, 30), 118
(PhCHNHCH, 5), 57 (t-Bu, 31). Anal. Calcd for C61H81NO2Sn
(979.00): C, 74.84; H, 8.34. Found: C, 74.51; H, 8.24.
117
1
3
69%. H NMR: δ 0.44, 0.49, and 0.55 (3d, JHH = 6.6 Hz, 3 × 3H, o-
CHMeMe′), 0.82 (s, 9H, CMe3 of CR2), 1.07 (d, 3JHH = 6.6 Hz, 6H, p-
CHMeMe′), 1.08 (s, 9H, NCMe3), 1.10 and 1.11 (2d, 3JHH = 6.9 Hz, 2 ×
Synthesis of Stannane 8: Reaction of Stannene 1 with
1
3
3
Acetonitrile. Yield: 0.54 g, 64%. H NMR: δ 0.86 (d, JHH = 6.6 Hz,
12H, o-CHMeMe′), 1.12 (d, 3JHH = 6.6 Hz, 12H, o-CHMeMe′), 1.21 (s,
18H, CMe3 of CR2), 1.24 (d, 3JHH = 6.9 Hz, 12H, p-CHMeMe′), 1.42 (s,
2H, CH2), 2.52−2.80 (m, 4H, o-CHMeMe′), 2.85 (sept, 3JHH = 6.9 Hz,
2H, p-CHMeMe′), 4.92 (s, 1JSnH = 75.3 Hz, SnH), 6.99 (s, 4JSnH = 21.9
Hz, 4H, m-CH of Tip), 7.38 (dd, 3JHH = 8.1 Hz, 4JHH = 1.5 Hz, 2H, H3
and H6 of CR2), 7.40 (broad s, H1 and H8 of CR2), 7.81 (d, 3JHH = 8.1
Hz, 2H, H4 and H5 of CR2). 119Sn NMR: δ −97.9. Anal. Calcd for
C53H73NSn (842.85): C, 75.53; H, 8.73. Found: C, 75.31; H, 8.54.
Synthesis of Azastannacyclobutene 9: Reaction of Stannene
1 with Pivalonitrile. A sealed tube containing a mixture of crude
stannene 1 (prepared from 1.00 mmol of Tip2Sn(F)C(H)R2),
pivalonitrile (0.083 mg, 1.00 mmol), and Et2O (20 mL) was heated to
60 °C overnight. The tube was opened, and the volatiles were removed
in vacuo; addition of 10 mL of pentane to the residue led to a white
precipitate, which was filtered and washed with CH2Cl2. Crystallization
at −20 °C afforded azastannacyclobutene 9 as a crystalline compound.
Yield: 0.39 g, 44%. Mp: 167 °C. 1H NMR: δ 0.72 and 1.05 (2d, 3JHH = 6.0
Hz, 2 × 12H, o-CHMeMe′), 0.76 (s, 9H, NCMe3), 1.12 (s, 18H, CMe3
of CR2), 1.21 and 1.22 (2d, 3JHH = 6.0 Hz, 2 × 6H, p-CHMeMe′), 2.60−
3H, p-CHMeMe′), 1.27 (d, JHH = 6.6 Hz, 3H, o-CHMeMe′), 1.32 (s,
9H, CMe3 of CR2), 2.70 (sept, 3JHH = 6.9 Hz, 2H, p-CHMeMe′), 2.89
3
(sept, JHH = 6.6 Hz, 1H, o-CHMeMe′) (due to slow rotation, some
signals of one Tip group are in the baseline and cannot be observed),
3
5.06 (s, 1H, JSnH = 30.0 Hz, CHPh), 6.30−6.75 (m, 5H, Ph), 6.89
(broad s, 3H, m-CH of Tip), 6.82 (d, 4JHH = 1.5 Hz, 1H, m-CH of Tip),
6.90 (dd, 3JHH = 8.1 Hz, 4JHH = 1.5 Hz, 1H, H6 of CR2), 6.99 (d, 4JHH
=
1.5 Hz, 1H, H8 of CR2), 7.29 (dd, 3JHH = 8.1 Hz, 4JHH = 2.1 Hz, 1H, H3
of CR2), 7.35 (d, 3JHH = 8.1 Hz, 1H, H5 of CR2), 7.55 (d, 3JHH = 8.1 Hz,
1H, H4 of CR2), 8.81 (d, 4JHH = 2.1 Hz, 1H, H1 of CR2). 13C NMR: δ
22.90 and 23.69 (o-CHMeMe′), 23.89, 23.93, 24.02, and 24.11 (p-
CHMeMe′), 25.82 and 28.09 (o-CHMeMe′), 28.34 (NCMe3), 31.35 and
31.73 (CMe3 of CR2), 34.19 and 34.29 (p-CHMeMe′), 34.46 and 35.11
(CMe3 of CR2), 39.40 (3JSnC = 27.0 Hz, o-CHMeMe′), 40.56 (3JSnC
34.4 Hz, o-CHMeMe′), 61.25 (3JSnC = 17.3 Hz, NCMe3), 65.03 (1J
=
119SnC
1
= 329.9 Hz, C9 of CR2), 79.8 (2JSnC = 18.2 Hz,
117SnC
= 345.2 Hz, J
CHPh), 118.50 (4JSnC = 8.4 Hz, C4 of CR2), 118.86 (4JSnC = 8.4 Hz, C5
of CR2), 121.20 (3JSnC = 21.3 Hz, C8 of CR2), 121.97, 122.17, and
122.24 (2 m-CH of Tip and C6 of CR2), 123.67 (5JSnC = 12.1 Hz, C3 of
CR2), 125.39 (3JSnC = 16.6 Hz, C1 of CR2), 125.80 and 126.43 (m- and p-
CH of Ph), 126.83 (m-CH of Tip), 129.41 (o-CH of Ph), 130.79 (m-CH
of Tip), 136.63 (3JSnC = 21.4 Hz, C13 of CR2), 137.35 (ipso-C of Ph),
137.83 (3JSnC = 22.8 Hz, C12 of CR2), 141.19 and 143.03 (ipso-C of
Tip), 145.18 (2JSnC = 17.0 Hz, C10 of CR2), 147.59 (4JSnC = 25.1 Hz, C2
of CR2), 147.64 (4JSnC = 12.2 Hz, C7 of CR2), 148.25 (2JSnC = 12.2 Hz,
C11 of CR2), 149.96 (4JSnC = 11.2 Hz, p-C of Tip), 150.38 (4JSnC = 12.5
Hz, p-C of Tip), 153.16 (2J119SnC = 69.1 Hz, 2J117SnC = 66.2 Hz, o-C of
Tip), 154.69 (2JSnC = 39.5 Hz, o-C of Tip). 119Sn NMR: δ −18.9. MS (m/
z, %): 978 (M, 2), 802 (Tip2SnCR2, 4), 718 (M − Tip − t-Bu − H, 1),
541 (Tip2SnO − H, 2), 525 (Tip2Sn − H, 52), 321 (TipSn − 2, 65), 277
(CR2 + H, 40), 161 (PhCH-N-t-Bu, 10), 57 (t-Bu, 100). Anal. Calcd for
C62H85NOSn (979.05): C, 76.06; H, 8.75. Found: C, 76.31; H, 8.74.
Synthesis of Azastannacyclopentane 6: Reaction of Stannene
3
2.75 (broad s, 4H, o-CHMeMe′), 2.83 (sept, JHH = 6.9 Hz, 2H, p-
CHMeMe′), 6.95 (s, 4JSnC = 22.2 Hz, 4H, m-CH of Tip), 7.20 (d, 4JHH
=
1.2 Hz, 2H, H1 and H8 of CR2), 7.26 (dd, 2H, 3JHH = 8.1 Hz, 4JHH = 1.2
Hz, H3 and H6 of CR2), 7.72 (d, 3JHH = 8.1 Hz, 2H, H4 and H5 of CR2).
13C NMR: δ 23.94 (p-CHMeMe′), 24.46 and 25.96 (o-CHMeMe′),
29.77 (NCMe3), 31.45 (CMe3 of CR2), 34.20 (p-CHMeMe′), 34.65
(CMe3 of CR2), 38.77 (3JSnC = 38.3 Hz, o-CHMeMe′) 44.64 (NCMe3),
87.73 (C9 of CR2), 119.44 (4JSnC = 11.8 Hz, C4 and C5 of CR2), 120.77
(3JSnC = 23.6 Hz, C1 and C8 of CR2), 122.34 (m-CH of Tip), 122.85
(5JSnC = 17.7 Hz, C3 and C6 of CR2), 134.46 (C12 and C13 of CR2),
140.67 (ipso-C of Tip), 145.32 (C10 and C11 of CR2), 148.29 (C2 and
C7 of CR2), 150.44 (4JSnC = 11.5 Hz, p-C of Tip), 154.84 (2JSnC = 46.2
Hz, o-C of Tip), 195.96 (CN). 119Sn NMR: δ −75.1. MS (m/z, %):
802 (Tip2SnCR2, 3), 658 (Tip2SnCR2 − 2 t-Bu, 2), 526 (Tip2Sn,
80), 361 (M − Tip2Sn, 20), 321 (TipSn − 2, 92), 277 (CR2 + H, 100).
Anal. Calcd for C56H79NSn (884.93): C, 76.01; H, 9.00. Found: C,
76.31; H, 8.94.
1
1 with PhCHNCH2COOMe. Yield: 0.80 g, 82%. Mp: 235 °C. H
NMR: δ −0.21, −0.12, 0.03, 0.38, 0.54, 1.19, 1.48, and 1.60 (8d, 3JHH
=
6.3 Hz, 8 × 3H, o-CHMeMe′), 0.87 and 1.43 (2s, 2 × 9H, CMe3 of CR2),
1.02, 1.03, 1.14, and 1.15 (4d, 3JHH = 6.9 Hz, 4 × 3H, p-CHMeMe′), 1.43,
1.45, 2.63, and 3.83 (4sept, 3JHH = 6.6 Hz, 4 × 1H, o-CHMeMe′), 2.74
3
and 2.84 (2sept, JHH = 6.9 Hz, 2 × 1H, p-CHMeMe′), 3.34 (s, 3H,
ASSOCIATED CONTENT
OMe), 3.60 (dd, 3JHH = 7.2 and 9.6 Hz, 1H, NH), 4.88 (d, 3JHH = 7.2 Hz,
2JSnH = 19.8 Hz, 1H, CHCO), 5.25 (d, 3JHH = 9.6 Hz, 3JSnH = 25.8 Hz,
1H, CHPh), 6.60 and 7.15 (2d, 4JHH = 1.5 Hz, 2 × 1H, m-CH of Tip(a)),
6.63 and 6.71 (2d, 4JHH = 1.5 Hz, 2 × 1H, m-CH of Tip(b)), 6.66−6.80
(m, 5H, H of Ph), 6.99 (d, 4JHH = 1.5 Hz, 1H, C8 of CR2), 7.02 (dd, 3JHH
■
S
* Supporting Information
CIF files and a table giving crystallographic data for 3, 5, 6, and 8.
This material is available free of charge via the Internet at http://
pubs.acs.org.
= 7.8 Hz, 4JHH = 1.5 Hz, 1H, H6 of CR2), 7.17 (dd, 3JHH = 8.1 Hz, 4JHH
=
1.5 Hz, 1H, H3 of CR2), 7.40 (d, 3JHH = 7.8 Hz, 1H, H5 of CR2), 7.45 (d,
3JHH = 7.8 Hz, 1H, H4 of CR2), 8.72 (d, 4JHH = 1.5 Hz, 1H, H1 of CR2).
13C NMR: δ 22.76, 23.02, 23.18, 23.68, 24.39, 24.64, 25.42, and 27.98 (o-
CHMeMe′), 23.83, 23.99, 24.01, and 24.17 (p-CHMeMe′), 31.42 and
AUTHOR INFORMATION
■
Notes
The authors declare no competing financial interest.
E
dx.doi.org/10.1021/om3004916 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(15) Lacrampe, G.; Lavayssier
Trav. Chim. Pays-Bas 1983, 102, 21−34.
(16) Mackay, K. M. In The Chemistry of Organic Germanium, Tin and
Lead Compounds; Patai, S., Ed.; Wiley: Chichester, U.K., 1995; Vol. 1,
Chapter 2.
(17) Ech-Cherif El Kettani, S.; Escudie, J.; Couret, C.; Ranaivonjatovo,
́
H.; Lazraq, M; Soufiaoui, M.; Gornitzka, H.; Cretiu Nemes, G. Chem.
Commun. 2003, 1662−1663.
̀ ̀ ́
e, H.; Riviere-Baudet, M.; Satge, J. Recl.
ACKNOWLEDGMENTS
■
A.F. is grateful to the “Service de Cooper
́
ation et d’Action
Sociale” of the French Embassy in Antananarivo (Madagascar)
and to the “Agence Universitaire pour la Francophonie” for a
grant. We are grateful to the Agence Nationale pour la Recherche
(contract ANR-08-BLAN-0105-01) for financial support.
(18) Ghereg, D.; Gornitzka, H.; Escudie,
2010, 49, 10497−10505.
(19) Ech-Cherif El Kettani, S.; Lazraq, M.; Ranaivonjatovo, H.;
Escudie, J.; Couret, C.; Gornitzka, H.; Merceron, N. Organometallics
́
J.; Ladeira, S. Inorg. Chem.
DEDICATION
■
Dedicated to the memory of Dumitru Ghereg, a brilliant young
chemist who died prematurely.
́
2004, 23, 5062−5065.
(20) SAINT-NT; Bruker AXS Inc., Madison, WI, 2000.
(21) SADABS, Program for data correction; Bruker AXS Inc., Madison,
WI.
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dx.doi.org/10.1021/om3004916 | Organometallics XXXX, XXX, XXX−XXX