Reactions of an Isolable Dialkylstannylene with Propynoates and Benzyne

Article abstract of DOI:10.1021/acs.organomet.8b00197

The reactions of stable monomeric dialkylstannylene 1 with methyl and ethyl propynoates give the corresponding 1:2 adducts, alkenyl(alkynyl)stannane 2 and 3 in high yields, while 1 does not react with parent acetylene or common mono- and disubstituted acetylenes such as phenylacetylene, trimethylsilylacetylene, diethyl 2-butynedioate, etc. Notably, 2 and 3 have the Z-configuration of the alkenyl moieties, in contrast to similar adducts obtained by the known reactions of silylenes with terminal acetylenes. It is suggested that the formation of a carbonyl oxygen-coordinate cyclic zwitterion as a key intermediate is essential for the reactions. Stannylene 1 adds to in situ generated benzyne, forming a 1:1 adduct having a unique 3-stanna-1-silaindane ring system.

Full text of DOI:10.1021/acs.organomet.8b00197

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Reactions of an Isolable Dialkylstannylene with Propynoates and
Benzyne
Jian Xu, Xu-Qiong Xiao, Chenting Yan, Zhifang Li,* Qiong Lu, Qian Yang, Guoqiao Lai,*
and Mitsuo Kira*
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University,
Hangzhou, 311121, Zhejiang, People’s Republic of China
*
S Supporting Information
ABSTRACT: The reactions of stable monomeric dialkyl-
stannylene 1 with methyl and ethyl propynoates give the
corresponding 1:2 adducts, alkenyl(alkynyl)stannane 2 and 3
in high yields, while 1 does not react with parent acetylene or
common mono- and disubstituted acetylenes such as
phenylacetylene, trimethylsilylacetylene, diethyl 2-butyne-
dioate, etc. Notably, 2 and 3 have the Z-configuration of the alkenyl moieties, in contrast to similar adducts obtained by
the known reactions of silylenes with terminal acetylenes. It is suggested that the formation of a carbonyl oxygen-coordinate
cyclic zwitterion as a key intermediate is essential for the reactions. Stannylene 1 adds to in situ generated benzyne, forming a
1
:1 adduct having a unique 3-stanna-1-silaindane ring system.
uch attention has been focused on the comparative
Scheme 1. Reactions of an Equilibrated Stannylene with
Strained Alkynes
M
chemistry of heavy congeners of carbenes, R E (E = Si,
2
1
Ge, Sn, and Pb). Knowledge and understanding of the
chemistry of robust germylenes and stannylenes are however
still limited in comparison to those of silylenes, while a number
of isolable germylenes and stannylenes have been synthesized1
and their unique structures and reactions have been disclosed
2
since the pioneering works of Lappert et al. One of the most
intriguing difference in the reactivity between silylenes,
germylenes, and stannylenes has been found in their reactivity
toward alkenes and alkynes. While silylenes and germylenes are
known to smoothly add to alkenes and alkynes giving the
corresponding three-membered ring compounds, only a few
addition reactions of stannylenes with alkenes and alkynes have
1
been investigated. The reactions of neither transient nor
isolable stannylenes with simple alkenes and alkynes have been
1
e
reported to date. Theoretical studies have shown that the
addition reactions are almost thermo-neutral and an addition-
dissociation equilibrium will be attained between the
Though the 1,2-distannacyclobutenes would be formed by
the consecutive addition of the stannylene molecules to the
acetylene, direct [2 + 2] addition of the corresponding
distannenes toward the strained alkynes is not ruled out; a
number of stable heavy unsaturated tin−tin bonds have been
found to react with various strained and less-strained alkynes,
3
stannylene and the unsaturated C−C bonds.
In 1988, Sita and his co-workers have first reported that
well-known Lappert’s stannylene, Sn[CH(SiMe ) ] equili-
4
3
2 2
2
6
brated with the corresponding distannene, reacts with a highly
strained alkyne, 3,3,7,7-tetramethyl-6-thiacycloheptyne, giving
a 1:1 adduct, the corresponding stannacyclopropene, at −16
giving the corresponding 1,2-distannacyclobutenes. Recently,
7
Wesemann et al. have also reported that both a non-
dissociative distannene and a nondimerizable bis(stannylene)
afford the corresponding distannacyclobutenes during the
reactions with alkynes (Scheme 2).
°
C as shown in Scheme 1. At elevated temperatures, it
dissociates into the corresponding stannylene and the alkyne.
A similar reaction of the stannylene with a strained, but less
sterically hindered, cyclooctyne was found to give the
As a part of our recent studies on the reactivity of isolable
8
dialkylstannylene 1 that is monomeric and does not form the
9
,10
4b
corresponding dimer in solution,
we have intended to shed
corresponding 1,2-distannacyclobutene.
Similarly, Veith et al. have reported that an N-heterocyclic
stannylene reacts with the strained alkyne, giving the
corresponding 1,2-distannacyclobut-3-ene (eq 1).
Received: April 4, 2018
5
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00197
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Organometallics
Article
Scheme 2. Reactions of Phenylacetylene with a Distannene and a Bis(stannylene)
Scheme 3. Reactions of Stannylene 1 with Propynoates and Benzyne
light on the generality of the reactivity of stannylenes toward
alkynes. Unprecedentedly, stannylene 1 reacts with propynoate
esters to afford the corresponding 1:2 adducts 2 and 3
138.0 ppm, and at δ 152.9 and 134.4 ppm, respectively, and
their alkynyl carbon signals are at 102.8 and 96.3 ppm and at
1
19
101.5 and 98.6 ppm. A Sn NMR signal appears at −52.2 and
(
Scheme 3), while no reaction of 1 occurs with gaseous
−52.9 ppm for 2 and 3, respectively.
acetylene, phenylacetylene, trimethylsilylacetylene, 1,2-diphe-
The molecular structures of 2 and 3 determined by X-ray
single-crystal analysis are consistent with the proposed. Yellow
single crystals of 2 and 3 suitable for X-ray crystallography
were obtained by slowly evaporating the solvent from their
pentane solutions. The ORTEP drawings of the single crystals
of 2 and 3, which have the Pn and C2/c space groups,
respectively, are depicted in Figures 1 and 2, together with
pertinent structural parameters. Four independent molecules
were found in an asymmetric unit of 2; see the Supporting
Information for the details. Because the molecular structures of
11
nylacetylene, or diethyl 2-butynedioate. The reaction of 1
with in situ generated benzyne affords 4 with a unique 3-
stanna-1-silaindane ring system, being accompanied by 1,4-silyl
migration (Scheme 3).
RESULTS AND DISCUSSION
■
Reactions of Dialkylstannylene 1 with Methyl and
Ethyl Propynoates. When 1 was treated with two molar
amounts of methyl and ethyl propynoates in hexane at room
temperature, the deep red color of 1 disappeared within 5 min,
affording the corresponding 1:2 adducts, alkenyl(alkynyl)-
stannanes 2 and 3, in 85% and 90% isolated yields, respectively
1
2
(
Scheme 4). In the similar conditions, 1 does not react with
Scheme 4. Reactions of Stannylenes 1 with Ethynylcarbonyl
Compounds in Hexane at rt
dimethyl 2-butynedioate even after a prolonged reaction time
(
5 h), probably owing to the severe steric hindrance during the
reaction. Benzoylethyne reacts with 1 but gives a complex
mixture.
1
The structures of 2 and 3 were fully characterized by H,
C, Si, and Sn NMR spectroscopies, MALDI-TOF-MS,
Figure 1. Molecular structure of 2. Hydrogen atoms are omitted for
clarity. Thermal ellipsoids are shown at the 30% probability level.
Selected bond lengths (Å) and angles (deg): Sn(1)−C(17) =
1
3
29
119
1
and finally X-ray crystallography. The H NMR spectra of 2
and 3 show two doublet signals at 7.39 and 6.86 ppm and at
2
.142(5), Sn(1)−C(21) = 2.151(5), Sn(1)−C(4) = 2.204(5),
Sn(1)−C(1) = 2.196(5), Sn(1)−O(3) = 2.848(4), C(19)−O(1) =
1.167(7), C(23)−O(3) = 1.213(6), C(17)−C(18) = 1.180(7),
C(21)−C(22) = 1.308(7), C(1)−Sn(1)−C(4) = 91.82(19),
C(17)−Sn(1)−C(21) = 101.23(19), O(3)−Sn(1)−C(4) =
7
3
alkenyl protons with vicinal coupling constants ( J
1
around the CC double bond that is confirmed by the X-ray
crystallography (vide infra). Their 13C NMR spectra clearly
show the presence of the C−C double and triple bonds. The
alkenyl carbon resonances of 2 and 3 appear at δ 149.3 and
1
73.8(12), C(18)−C(17)−Sn(1) = 169.1(5), C(17)−C(18)−
C(19) = 179.2(7), C(22)−C(21)−Sn(1) = 124.7(4), C(21)−
C(22)−C(23) = 121.5(8). Dihedral angle (deg): Sn(1)−C(21)−
C(22)−C(23) = 1.61(8), C(21)−C(22)−C(23)−O(3) = −4.42(9).
B
DOI: 10.1021/acs.organomet.8b00197
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Organometallics
Article
14
silylenes with phenylacetylene have recently been reported.
Interestingly, the geometry around the double bonds of 2 and
adopts Z-configuration, though in the above silylene
3
14
reactions, the corresponding (E)-phenylethenylsilanes are
produced. To figure out reasonable pathways for rather
unexpected formation of 2 (and 3), optimized structures and
free energies of possible products and intermediates for the
model reaction of stannylene 1′ with methyl propynoate were
determined using the dispersion-corrected DFT calculations
(
B3PW91-GD3) in heptane and THF; all the trimethylsilyl
15
groups of 1 were replaced to trihydrosilyl groups in 1′. As
shown in Scheme 5, while the optimized structures of (Z)-2′(s-
cis) with the Sn···O(CO) distance of 2.62 Å in heptane
(
(
2.63 Å in THF) are similar to that of 2 observed in the crystal
Figure 1), the isomer is 3−6 kcal/mol less stable than the
other three isomers; no large difference is observed in the
relative free energies among the other three structures. It is
suggested that the extra-coordination of carbonyl oxygen
toward tin does not contribute to stabilizing the system. The
reaction of 1′ + 2(methyl propynoate) giving 2′ is highly
exergonic with the ΔG larger than −28 kcal/mol in the two
solvents.
Figure 2. Molecular structure of 3. Hydrogen atoms are omitted for
clarity. Thermal ellipsoids are shown at the 30% probability level.
Selected bond lengths (Å) and angles (deg): Sn(1)−C(17) =
2
.119(6), Sn(1)−C(22) = 2.123(7), Sn(1)−C(4) = 2.170(5),
Sn(1)−C(1) = 2.197(6), Sn(1)···O(1) = 2.767(5), C(19)−O(1) =
.197(8), C(19)−O(2) = 1.314(7), C(24)−O(3) = 1.174(9),
C(24)−O(4) = 1.298(9), C(17)−C(18) = 1.322(9), C(22)−C(23)
1
The mechanism for the formation of 2 (and 3) would be
similar to that for the reactions of the NHC-stabilized silylenes
=
1.191(9), C(1)−Sn(1)−C(4) = 91.5(2), C(17)−Sn(1)−C(22) =
9
1
1
9.4(2), O(1)−Sn(1)−C(1) = 173.7 (2), C(18)−C(17)−Sn(1) =
24.4(5), C(17)−C(18)−C(19) = 119.7(6), C(23)−C(22)−Sn(1) =
68.7(6), C(22)−C(23)−C(24) = 179.1(8). Dihedral angle Sn(1)−
14
with phenylacetylene. Thus, the 1:2 adduct 2 (and 3) may be
formed via the initial nucleophilic attack of 1 on a propynoate
ester, giving an alkenyl anion-tin cation zwitterionic
intermediate (A), which abstracts an acidic proton of the
second propynoate ester, followed by combining the resulting
alkynyl anion and the cationic tin atom (Scheme 6). The
formation of the cyclic zwitterion A is indispensable for
producing the Z-isomer of 2 and 3.
C(17)−C(18)−C(19) = −2.75(9), C(17)−C(18)−C(19)−O(1) =
−
3.33(10).
2
and 3 are very similar to each other, we discuss herein only
the structural characteristics of 2. The Z configuration around
the CC double bond and the s-cis enone conformation are
shown by the small dihedral angles Sn(1)−C(21)−C(22)−
C(23) [1.61(8)°] and C(21)−C(22)−C(23)−O(3)
Scheme 6. A Plausible Mechanism for the Formation of 2
(
and 3) by the Reactions of 1 with Propynoate Esters
[
−4.42(9)°]. Though the s-cis conformation, the Sn···O
distance of 2.848(4) Å, which is significantly smaller than
the sum of van der Waals radii of Sn (2.25 Å) and O atoms
1
3
(
1.55 Å), and the O(3)−Sn(1)−C(4) angle of 173.8(2)° are
suggestive of a trigonal bipyramidal pentacoordinate tin
structure of 2. A theoretical study suggests however that the
stabilization by the coordination may be unimportant (vide
infra). The stannacyclopentane ring of 2 adopts an envelope
conformation with one of the ring CH groups out of a plane
2
formed by the other four ring atoms. The C21−C22 and C17−
C18 bond lengths, 1.308(7) and 1.180(7) Å, indicate the
existence of one CC double bond and one CC triple
bond.
The reactions of stannylenes with terminal acetylenes giving
the corresponding 1:2 adducts have never been known up to
date, while similar 1:2 addition reactions of base-stabilized
Relative stabilities of possible model 1:1 adducts of 1′ to
methyl propynoate, A′, B′, and C′ are calculated in heptane
15
and THF as shown in Scheme 7. In accord with the
experimental results, the cyclic zwitterionic intermediate A′
with the Sn···O distance of 2.23 Å in heptane (2.20 Å in THF)
Scheme 5. Relative Free Energies (kcal/mol) of the Isomers of a Model Stannylene-Methyl Propynoate 1:2 Adduct in Heptane
and THF (Italics)
C
DOI: 10.1021/acs.organomet.8b00197
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Article
a
Scheme 7. Relative Stabilities of A′−C′ in Reference to 1′ + Methyl Propynoate
a
Relative free energies (ΔG in kcal/mol) in heptane and THF (italics) are shown in parentheses.
is located as a minimum. Intermediate A′ is 1.4 and 2.4 kcal/
mol more stable than stannacyclopropene B′ in heptane and
THF, respectively. Compounds A′ and B′ are more than 10
kcal/mol less stable than CH insertion product C′ in the two
solvents. The formation of A as the key intermediate would be
essential for the reactions of 1 with propynoates, and it may
explain why only the (Z)-isomers of the products 2 and 3 are
formed and why phenyl- and other common terminal
acetylenes do not react with 1.
The theoretical calculations show that the reactions of 1′ +
methyl propynoate giving A′ and B′ are both highly
endergonic at 298.15 K (Scheme 7), suggesting that, without
the subsequent addition of the secondary propynoate to the
intermediates, the reactions may not proceed.
Another pathway in which the reaction occurs via the initial
insertion of 1 into the C−H bond of the propynoate, followed
by the hydrostannation of the resulting hydrostannane C with
the second propynoate (eq 2), is improbable because neither
the CH-insertion nor the hydrostannation without catalysts or
activators has been known. Actually, our studies showed that
neither the insertion of 1 into the acetylenic CH bond of
phenylaceylene nor the hydrostannation of diphenyldihydros-
tannane to methyl propynoate was observed.
Figure 3. Molecular structure of 4. Hydrogen atoms are omitted for
clarity. Thermal ellipsoids are shown at the 30% probability level.
Selected bond lengths (Å) and angles (deg): Sn(1)−C(1) = 2.162(3),
Sn(1)−C(4) = 2.203(3), Sn(1)−C(14) = 2.173(3), Sn(1)−C(20) =
2
.150(3), C(19)−Si(4) = 1.887(4), C(20)−Si(4) = 1.853(4),
C(14)−C(19) = 1.409(4), C(14)−C(15) = 1.386(5), C(20)−
Sn(1)−C(14) = 93.74(13), C(1)−Sn(1)−C(4) = 88.56(11),
C(15)−C(14)−Sn(1) = 128.10(2), C(19)−C(14)−Sn(1) =
1
=
12.7(2), Si(4)−C(20)−Sn(1) = 107.33(2), C(14)−C(19)−Si(4)
120.5(2), C(20)−Si(4)−C(19) = 105.669(14).
Scheme 8. Pathway Proposed for the Reaction of Stannylene
with Benzyne
1
Reaction of Dialkylstannylene 1 with Benzyne. When
1
was treated with benzyne generated by the reaction of 2-
(
trimethylsilyl)phenyl trifluoromethanesulfonate with cesium
1
6
fluoride at −15 °C, the reaction took place smoothly, and the
color of the mixture changed from deep green to colorless
within 10 min and yielded 4 in 75% isolated yield (eq 3).
The product was fully characterized by multinuclear NMR
spectroscopy, elemental analysis, and finally confirmed by
single crystal X-ray diffraction studies. The molecular structure
of 4 determined by X-ray single-crystal analysis is shown in
Figure 3 together with pertinent structural parameters.
The reaction pathway is not fully understood, but a plausible
mechanism is proposed as follows (Scheme 8): Stannacyclo-
propene D would initially form through the reaction of 1 with
benzyne having a strained and hence highly reactive triple
bond. Intermediate D may then form the ring-opened 1,3-
zwitterionic intermediate E, in which stannylene tin and phenyl
ortho-carbon are positively and negatively charged. 1,4-
Trimethylsilyl migration to the anionic carbon gives stannene
F. Final product 4 would be formed via the insertion of the
17
CSn bond of F into a C−H bond of a trimethylsilyl group.
Optimized structures of D′, F′, and 4′, as models of D, F,
and 4 in Scheme 8 were determined using the B3PW91-GD3
calculations in heptane and THF. Relative free energies of
these compounds are compared with those of the starting 1′′ +
benzyne in Scheme 9; in stannylene 1′′, one silyl group of 1′
was replaced to a methylsilyl group. Expectedly, all the
reactions giving D′, F′, and 4′ from 1′′ + benzyne are found to
be highly exergonic. Several attempts to locate E′ as a
minimum failed and were terminated by the formation of D′.
Compound E′ may be in a shallow minimum between D′ and
F′ or may not be formed as an intermediate. Further works are
D
DOI: 10.1021/acs.organomet.8b00197
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Hz, 3H), 1.26 (t, J = 8 Hz, 3H), 0.25 (s, 18H), 0.10 (s, 18H); 13C
Scheme 9. A Pathway for the Reaction of Stannylene 1′′
a
NMR (101 MHz, CDCl ) δ 168.4, 157.2, 152.9, 134.4, 101.5, 98.6,
with Benzyne Giving 4′
3
2
9
6
1.9, 61.3, 34.2, 14.2, 14.0, 13.8, 3.5, 3.0; Si NMR (79 MHz,
1
19
CDCl ) δ 4.86, 3.70; Sn NMR (187 MHz, CDCl ) δ −52.9;
3
3
MALDI-TOF-MS m/z Calcd for C H O Si Sn: 660; Found:660;
2
6
52
4
4
Anal. Calcd for C H O Si Sn: C, 47.33; H, 7.94; O, 9.70. Found: C,
2
6
52
4
4
4
7.26; H, 7.89; O, 9.72.
Reaction of Stannylene 1 with Benzyne. Cesium fluoride
0.164 g, 1.08 mmol) was charged into a Schlenk tube and dried with
(
a heat gun under reduced pressure. The tube was cooled to room
temperature under an argon atmosphere. To the tube were added 18-
crown-6 ether (0.57 g, 2.15 mmol) and dry THF (6 mL). The
resulting solution was stirred at −15 °C for 10 min. To the solution
was quickly added a solution of 2-(trimethylsilyl)phenyl trifluor-
omethanesulfonate (0.161 g, 0.540 mmol) in dry THF (1 mL), and
the mixture was stirred for 20 min at −15 °C. Then stannylene 1 (0.1
g, 0.216 mmol) in THF (1 mL) was added to the mixture. After the
reaction mixture was stirred for half an hour at −15 °C, the solvent
was removed under vacuum. The residue was purified by preparative
silica column chromatography, giving 3-stanna-1-silaindane 4 in the
yield of 75%.
a
Relative free energies (ΔG in kcal/mol) of the intermediates D′, F′,
and product 4′ in heptane and in THF are given in parentheses
(
heptane, THF in italics). E′ is not located as an energy minimum.
1
White solid (83.4 mg); mp: 205.3−206.5 °C; H NMR (400 MHz,
required for obtaining the reasonable profile for the whole
reaction.
In conclusion, not only strained C−C triple bonds like
benzyne but also polar mono-alkoxycarbonyl-substituted
acetylenes have been found to react with isolable dialkyl-
stannylene 1. In the latter reactions giving the corresponding
C D ) δ 7.86 (d, J = 8 Hz, 1H), 7.46 (d, J = 8 Hz, 1H), 7.20−7.24 (m,
6
6
2
H), 2.34−2.38 (m, 2H), 1.55−1.67(m, 2H), 0.36 (s, 3H), 0.31 (s,
3H), 0.29 (t, J = 6 Hz, 1H), 0.20 (s, 9H), 0.10 (s, 9H), 0.02−0.06 (m,
13
2H), −0.02 (s, 9H); C NMR (101 MHz, C D ) δ 152.3, 151.5,
6
6
137.2, 133.5, 128.7, 128.4, 34.7, 32.8, 17.2, 16.0, 2.7, 2.0, 1.4, 1.1, 0.0,
1
19
−
6.8; Sn NMR (187 MHz, C D ) δ 148.1; MALDI-TOF-MS m/z
6 6
Calcd for C H Si Sn: 540; Found:540; Anal. Calcd for C H Si Sn:
1
:2 adducts, a neighboring alkoxycarbonyl substituent is
22 44
4
22 44
4
C, 48.97; H, 8.22. Found: C, 48.89; H, 8.15.
essential to facilitate the initial nucleophilic attack of 1,
forming the key zwitterionic intermediate due to the
intramolecular coordination of the carbonyl oxygen to the
tin center.
DFT Calculations. All calculations were performed using the
Gaussian 09 package. Geometry optimizations and vibrational
frequency calculations of all stationary points were performed using
a dispersion-corrected DFT method, B3PW91-GD3 using the basis
sets of 6-31+G(d,p) for C, H, O, and Si atoms + SDD for Sn. To
evaluate the effects of a polar solvent in the reactions investigated, all
the calculations were performed in heptane and THF as well as in gas
EXPERIMENTAL SECTION
■
All synthetic experiments were performed under argon or nitrogen in
a standard vacuum system unless otherwise noted. H (400 MHz),
18
1
phase using the polarizable continuum model (PCM). See the
Supporting Information for the calculation details and full reference of
Gaussian 09.
13
29
119
C (100 MHz), Si (79 MHz), and Sn (187 MHz) NMR were
1
13
29
recorded using tetramethylsilane ( H, C, and Si) and tetrame-
thyltin (119Sn) as external standards on a BRUKER AV-400 MHz
X-ray Structure Determination. The X-ray diffraction data were
collected on a Bruker Smart Apex CCD diffractometer with graphite
monochromated Mo−Kα radiation (λ = 0.71073 Å) using the ω-2θ
scan mode. The structures were solved by direct methods and refined
instrument. GC−MS spectra were measured with an Agilent 7890a
gas chromatography instrument coupled to an Agilent 5975c mass
spectrometer. Mass spectra were measured with a Bruker Daltonics
Autoflex II TM MALDI-TOF spectrometer. Elemental analyses were
performed on a VARIO EL-III instrument. Stannylene 1 was prepared
according to the literature procedures. Stannylene 1 and other air-
sensitive materials were handled in an MBraun glovebox.
2
19
on F by full-matrix least-squares methods using SHELX-2000. The
crystal and refinement data are described in the SI. The
supplementary crystallographic data for 2, 3, and 4 are deposited
with the CCDC; the nos. are 1817474, 1817475, and 1817473,
respectively.
8
1
13
29
119
The full H, C, Si, and
Sn NMR spectra of all new
compounds (2−4) are provided in the Supporting Information (SI).
Reaction of 1 with Methyl and Ethyl Propynoates. When
methyl propynoate (75.6 mg, 0.9 mmol) or ethyl propynoate (88.2
mg, 0.9 mmol) was added dropwise into a hexane (5 mL) solution of
stannylene 1 (200 mg, 0.432 mmol) at room temperature, the color of
the reaction mixture turned quickly from red to green, and 1 h later,
to yellow. Removal of the solvent under vacuum and then preparative
silica column chromatography gave pure 2 or 3 in the yield of 85%
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00197.
■
*
S
1H, 13C, 29Si, and 119Sn NMR spectra of 2−4 and X-ray
crystallography of compounds 2−4 and details of the
theoretical calculations (PDF)
and 90%, respectively.
1
2
: white solid (232 mg); mp:104−106 °C; H NMR (400 MHz,
CDCl ) δ 7.39 (d, J = 12 Hz, 1H), 6.86 (d, J = 12 Hz, 1H), 3.87 (s,
3
3
H), 3.70 (s, 3H), 2.17−2.04 (m, 4H), 0.26 (s, 18H), 0.10 (s, 18H);
Cartesian coordinates (XYZ)
13
C NMR (101 MHz, CDCl ) δ 165.1, 152.9, 149.3, 138.0, 102.8,
3
2
9
9
4
6.3, 52.6, 51.9, 34.7, 17.4, 3.7, 3.4; Si NMR (79 MHz, CDCl ) δ
3
Accession Codes
.91, 3.74; 1 Sn NMR (187 MHz, CDCl ) δ −52.2; MALDI-TOF-
19
3
CCDC 1817473−1817475 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
MS m/z Calcd for C H O Si Sn: 632; Found:632; Anal. Calcd for
24
48
4
4
C H O Si Sn: C, 45.63; H, 7.66; O, 10.13. Found: C, 45.58; H,
24
48
4
4
7
.57; O, 10.08.
: white solid (257 mg); mp:107−108 °C; H NMR (400 MHz,
CDCl ) δ 7.38 (d, J = 12 Hz, 1H), 7.84 (d, J = 12 Hz, 1H), 4.34 (q, J
1
3
3
=
8 Hz, 2H), 4.15 (q, J = 8 Hz, 2H), 2.16−2.04 (m, 4H), 1.36 (t, J = 8
E
DOI: 10.1021/acs.organomet.8b00197
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Bond That Is Stable Both in the Solid State and in Solution. J. Am.
Chem. Soc. 2006, 128, 11643−11651. (c) Peng, Y.; Ellis, B. D.; Wang,
X.; Fettinger, J. C.; Power, P. P. Reversible Reactions of Ethylene with
Distannynes Under Ambient Conditions. Science 2009, 325, 1668−
AUTHOR INFORMATION
Corresponding Authors
E-mail: zhifanglee@hznu.edu.cn (Z.L.).
E-mail: gqlai@hznu.edu.cn (G.L.).
■
*
*
*
1
670. (d) Hardwick, J. A.; Baines, K. M. The Addition of Nitriles to a
E-mail: mitsuo.kira.e2@tohoku.ac.jp (M.K.).
Molecular Digermene: Reversible Addition and Comparison to
Surface Reactivity. Angew. Chem., Int. Ed. 2015, 54, 6600−6603.
ORCID
(
7) Schneider, J.; Henning, J.; Edrich, J.; Schubert, H.; Wesemann,
Zhifang Li: 0000-0002-9548-2158
Notes
The authors declare no competing financial interest.
L. Reversibility in Reactions of Linker-Bridged Distannenes with
Terminal Alkynes at Ambient Temperature. Inorg. Chem. 2015, 54,
6020−6027.
(8) (a) Kira, M.; Yauchibara, R.; Hirano, R.; Kabuto, C.; Sakurai, H.
ACKNOWLEDGMENTS
Synthesis and X-ray Structure of the First Dicoordinate Dialkyl-
stannylene That Is Monomeric in The Solid State. J. Am. Chem. Soc.
■
This work was supported by the National Natural Science
Foundation of China (Grant Nos. 21472032, 21771048) and
the Natural Science Foundation of Zhejiang Province (Grant
No. LY17B010002). We are grateful to Prof. Takeaki Iwamoto,
Department of Chemistry, Tohoku University, for helping us
perform theoretical calculations at the B3PW91-GD3 level.
1
991, 113, 7785−7787. (b) Kira, M.; Ishida, S.; Iwamoto, T.;
Yauchibara, R.; Sakurai, H. New Synthesis of a Stable Dialkylstanny-
lene and Its Reversible Complexation with Tetrahydrofuran. J.
Organomet. Chem. 2001, 636, 144−147. (c) Iwamoto, T.; Masuda,
H.; Ishida, S.; Kabuto, C.; Kira, M. Addition of Stable Nitroxide
Radical to Stable Divalent Compounds of Heavier Group 14
Elements. J. Am. Chem. Soc. 2003, 125, 9300−9301. (d) Kira, M.;
Ishida, S.; Iwamoto, T. Comparative Chemistry of Isolable Divalent
Compounds of Silicon, Germanium, and Tin. Chem. Rec. 2004, 4,
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DOI: 10.1021/acs.organomet.8b00197
Organometallics XXXX, XXX, XXX−XXX

Organometallics
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G
DOI: 10.1021/acs.organomet.8b00197
Organometallics XXXX, XXX, XXX−XXX