The chemical behavior of the silaoxine C22H34OSi3 and silaazetidine C25H43NSi4 towards CO2

Article abstract of DOI:10.1515/znb-2016-0157

When 4,4a-dihydro-3,3-dimethyl-1-phenyl-4,4-bis(trimethylsilyl)-3H-2-oxa-3-sila-naphthaline (silaoxine C₂₂H₃₄OSi₃ (3); orthorhombic, space group Pna2₁, Z=4) was thermolized in a CO₂ atmosphere, the co

Full text of DOI:10.1515/znb-2016-0157

Z. Naturforsch. 2016; 71(12)b: 1219–1224
Inge Sänger, Michael Bolte and Hans-Wolfram Lerner*
The chemical behavior of the silaoxine C22H34OSi3
and silaazetidine C25H43NSi4 towards CO2
DOI 10.1515/znb-2016-0157
Received July 6, 2016; accepted July 26, 2016
implies that the π bonds in phosphinoboranes [8] are
similar to those in silenes [9–12].
The parent Wiberg-type silene Me2Si=C(SiMe3)2 (2)
could be conveniently generated either by retro Diels-
Alder reaction from the silaoxine 3 or by [2ꢀ+ꢀ2] cyclorever-
sion from the silaazetidine 4 (see Scheme 1 and footnote1)
[9, 10, 13–16]. It should also be noted that the reactivity of
the Brook-type is distinguished significantly from that of
the Wiberg-type silenes [9, 10, 17, 18].
Following the approaches of Wiberg we synthesized
the silaoxine 3 [14] and the silaazetidine 4 [15] to make
a comparison of the reaction behavior of Wiberg-type
silenes with that of the related phosphinoboranes. As
an example we have investigated the reactions of 3 and
4 with carbon dioxide. In addition we present here the
structure of the silaoxine 3, the silaazetidine 4, and the
olefin Ph2C=C(SiMe3)2. The latter one was obtained from
the silaoxetane 5 by [2ꢀ+ꢀ2] cycloreversion.
Abstract: When 4,4a-dihydro-3,3-dimethyl-1-phenyl-
4,4-bis(trimethylsilyl)-3H-2-oxa-3-sila-naphthaline
(silaoxine C22H34OSi3 (3); orthorhombic, space group
Pna21, Zꢀ=ꢀ4) was thermolized in a CO2 atmosphere, the
corresponding oxasilacyclobutane (silaoxetane) 5 was
quantitatively formed. The [2ꢀ+ꢀ2] cycloreversion of the
silaoxetane 5 occurred at temperatures higher than 120°C
to give exclusively Ph2C=C(SiMe3)2 and (Me2SiO)n. Single
crystals of Ph2C=C(SiMe3)2 (6; monoclinic, space group
C2/c, Zꢀ=ꢀ8) were isolated from this reaction. When the
azasilacyclobutane (silaazetidine) C25H43NSi4 (4; mono-
clinic, space group P21/n, Zꢀ=ꢀ4) was reacted with an excess
of CO2 at 100°C an unknown intermediate was formed
along with the benzophenonimine Ph2C=N(SiMe3). The
NMR resonances of this intermediate indicates the for-
mation of the β-silalactone (silaoxetanone) C10H24O2Si3
(7). At temperatures higher than 120°C the silaoxetanone
7 decomposed to give (Me3Si)2C=C=O and (Me2SiO)n,
respectively.
2 Results and discussion
Keywords: carbon dioxide; silene; X-ray structure analysis.
As noticed above heating of the silaoxine 3 to a tempera-
ture higher than 100°C leads to the formation of the silene
2 along with benzophenone (cf. Scheme 1). However, when
the silaoxine 3 was thermolized in a CO2 atmosphere, the
silaoxetane 5 was quantitatively formed at this tempera-
ture. In this case the Lewis acid CO2 solely catalyzed the
rearrangement of the silaoxine 3 to the silaoxetane 5, as
depicted in Scheme 2 (see footnote2). This implies that the
[2ꢀ+ꢀ2] cycloadduct of 2 with Ph2C=O is apparently more
stable than that with CO2.
At a temperature higher than 120°C the [2ꢀ+ꢀ2] cyclo-
reversion of the silaoxetane 5 occurred to give exclusively
Ph2C=C(SiMe3)2 and (Me2SiO)n (see Scheme 2). Single crys-
tals of the olefin 6 were isolated from this reaction.
When the silaazetidine 4 was treated with an excess
of CO2 at 100°C an unknown intermediate was formed
along with the benzophenonimine Ph2C=N(SiMe3). The
1 Introduction
In the past decade the reactivity of frustrated Lewis pairs
(FLPs) [1, 2] towards small molecules such as dihydrogen
[3, 4] or carbon dioxide [5, 6] has been extensively studied.
Previously we have reported that the phosphinoborane 1
(phosphaboradibenzofulvene; Fig. 1) reacts fast with H2
[7]. In addition to the reaction of 1 with gaseous H2, the
compound 1 reacts also with acetonitrile, benzophenone,
and 2,3-dimethylbutadiene [7].
The structural analogy of phosphinoboranes R2B=PR2
and isoelectronic Wiberg-type silenes (Fig. 2) evidently
*Corresponding author: Hans-Wolfram Lerner, Institut für
Anorganische Chemie, Goethe-Universität Frankfurt am Main,
Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany,
Fax: ++49-69-79829260, E-mail: lerner@chemie.uni-frankfurt.de
Inge Sänger and Michael Bolte: Institut für Anorganische Chemie,
Goethe-Universität Frankfurt am Main, Max-von-Laue-Straße 7,
60438 Frankfurt am Main, Germany
1ꢁFor the reactivity of silaazetidines, see ref. [13].
2ꢁRearrangement of 3 to 5 also takes place in the presence of Me3SiCl
see ref. [14].
Brought to you by | University Paris-Sud
Authenticated
Download Date | 5/19/19 9:59 AM

ꢀꢀꢀꢁ
1220ꢀ ꢀI. Sänger et al.: The chemical behavior of the silaoxine C22H34OSi3 and silaazetidine C25H43NSi4 towards CO2
Me2Si
O
C(SiMe3)2
tBu
tBu
B
P
Ph
3
1
[CO2]
Fig. 1:ꢀPhosphaboradibenzofulvene 1.
100°C
Me2Si
C(SiMe3)2
CPh2
OR
OR
O
i
S
C
i
S
C
i
S
i
S
C
C
5
120°C
Brook type
Wiberg type
Me3Si
SiMe3
Ph
Me
iMe
Me3Si
OSiMe3
S
Me
Me
3
.
.
1 764
1 702
Å
Å
C
C
Si
O
+
i
S
C
i
S
C
Me
i
3S
iMetBu
S
Me
Ph
2
6
(Me2SiO)n
Scheme 2:ꢀThermolysis of the silaoxine 3 in the presence of CO2.
Fig. 2:ꢀWiberg-type and Brook-type silenes.
Me2Si
O
Me2Si
C(SiMe3)2
CPh2
C(SiMe3)2
(Me3Si)N
4
+
−
Ph
CO2
=
3
Ph
)
2C
N(SiMe3
100°C
−
Ph
2CO
Me2Si
O
C(SiMe3)2
Me2Si
C(SiMe3)2
C
O
2
4
7
− Ph2C=N(SiMe3)
120°C
Me2Si
C(SiMe3)2
CPh2
Me3Si
SiMe3
Me
Me
Si
C
C
(Me3Si)N
+
O
O
Scheme 1:ꢀSynthesis of the silene Me2Si=C(SiMe3)2 (2) by cyclo-
reversion of 3 and 4 at 100°C.
8
(Me2SiO)n
Scheme 3:ꢀReaction of the silaazetidine 4 with CO2.
NMR resonances of this intermediate indicates the for-
mation of silaoxetanone 7. This reaction reveals that the
parent Wiberg-type silene 2 which was generated from the
silaazetidine 4, activates carbon dioxide. Unfortunately, of one of two enantiomers (selected bond lengths are
we were not able to isolate 7. As also shown in Scheme 3, reported in the caption of Fig. 3) and indicates a central
the silaoxetanone 7 decomposed at higher temperatures C4OSi heterocycle with an annelated C6 ring. The C4OSi
to give the literature-known bis(trimethylsilyl)ketene 8 heterocycle in 3 adopts a screw-chair conformation and
[19, 20] and (Me2SiO)n (see Scheme 3).
reveals a dihedral angle with the attached phenyl ring
The silaoxine 3 crystallizes in the orthorhombic space of 36.1(1)° (atoms used to define the ring planes: Si(1),
group Pna21 as a racemate. Fig. 3 represents the structure O(1), C(1), C(2), C(7), C(8), and C(81), C(82), C(83), C(84),
Brought to you by | University Paris-Sud
Authenticated
Download Date | 5/19/19 9:59 AM

ꢁꢀꢀꢀ
I. Sänger et al.: The chemical behavior of the silaoxine C22H34OSi3 and silaazetidine C25H43NSi4 towards CO2ꢂ
ꢂ1221
Fig. 4:ꢀMolecular structure of the silaazetidine 4 in the solid state.
Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and bond angles (deg): C(1)–C(2) 1.647(2), C(1)–Si(4) 1.909(1),
C(1)–Si(1) 1.917(1), C(1)–Si(2) 1.933(1), C(2)–N(3) 1.501(1), C(2)–C(61)
1.533(2), C(2)–C(51) 1.553(2), N(3)–Si(4) 1.734(1), N(3)–Si(3) 1.740(1),
Si(4)–C(42) 1.875(1), Si(4)–C(41) 1.878(2), Si(1)–C(12) 1.875(2),
Si(1)–C(13) 1.882(2), Si(1)–C(11) 1.882(2); C(2)–C(1)–Si(4) 84.4(1),
C(2)–C(1)–Si(1) 118.2(1), Si(4)–C(1)–Si(1) 120.5(1), C(2)–C(1)–Si(2)
117.7(1), Si(4)–C(1)–Si(2) 105.8(1), Si(1)–C(1)–Si(2) 108.5(1), N(3)–
C(2)–C(61) 113.4(1), N(3)–C(2)–C(51) 108.6(1), C(61)–C(2)–C(51)
109.6(1), N(3)–C(2)–C(1) 98.2(1), C(61)–C(2)–C(1) 111.2(1), C(51)–
C(2)–C(1) 115.6(1), C(2)–N(3)–Si(4) 95.3(1), C(2)–N(3)–Si(3) 131.7(1),
Si(4)–N(3)–Si(3) 131.1(1), N(3)–Si(4)–C(42) 119.4(1).
Fig. 3:ꢀSolid-state structure of one enantiomer of the silaoxine
3. Selected bond lengths (Å) and bond angles (deg): O(1)–C(8)
1.369(2), O(1)–Si(1) 1.677(1), Si(1)–C(11) 1.859(2), Si(1)–C(12)
1.862(2), Si(1)–C(1) 1.887(2), C(1)–C(2) 1.612(2), C(1)–Si(2) 1.914(2),
C(1)–Si(3) 1.917(2), Si(2)–C(21) 1.879(2), Si(2)–C(23) 1.882(2),
Si(2)–C(22) 1.898(2), C(2)–C(3) 1.517(2), C(2)–C(7) 1.533(2),
Si(3)–C(31) 1.884(2), Si(3)–C(33) 1.887(2), C(3)–C(4) 1.333(3),
C(4)–C(5) 1.448(3), C(5)–C(6) 1.349(2), C(6)–C(7) 1.448(2), C(7)–C(8)
1.365(2), C(8)–C(81) 1.475(2); C(8)–O(1)–Si(1) 127.2(1), O(1)–Si(1)–
C(11) 106.0(1), O(1)–Si(1)–C(12) 102.7(1), C(11)–Si(1)–C(12) 107.7(1),
O(1)–Si(1)–C(1) 105.2(1), C(11)–Si(1)–C(1) 116.9(1), C(12)–Si(1)–C(1)
116.8(1), C(2)–C(1)–Si(1) 100.5(1), C(2)–C(1)–Si(2) 112.6(1), Si(1)–
C(1)–Si(2) 111.6(1), C(2)–C(1)–Si(3) 111.9(1), Si(1)–C(1)–Si(3) 108.4(1),
Si(2)–C(1)–Si(3) 111.4(1), C(3)–C(2)–C(7) 112.1(1), C(3)–C(2)–C(1)
114.3(1), C(7)–C(2)–C(1) 113.0(1), C(3)–C(4)–C(5) 121.3(2), C(6)–
C(5)–C(4) 120.4(2), C(5)–C(6)–C(7) 122.3(2), C(8)–C(7)–C(6) 121.1(2),
C(8)–C(7)–C(2) 119.3(2), C(6)–C(7)–C(2) 119.5(1), C(7)–C(8)–O(1)
120.9(2).
to the monoclinic space group P21/n. The compound
4 consists of a four-membered ring with a Si–C and a
Si–N bond of 1.909(1) Å and 1.734(1) Å, respectively. This
C2NSi heterocycle is nearly planar (r.m.s. deviation 0.045
Å). The H atoms bonded to the C atoms were geometri-
cally positioned and refined using a riding model. The
phenyl rings form dihedral angles with the heterocycle
of 72.4(1)° and 53.7(4)°. All endocyclic bond angles in
the heterocycle are significantly narrowed [C(2)–C(1)–
Si(4) 84.4(1)°, N(3)–C(2)–C(1) 98.2(1)°, C(2)–N(3)–Si(4)
C(85), C(86), respectively). Furthermore the angle Si(1)– 95.3(1)°, N(3)–Si(4)–C(1) 81.5(1)°].
O(1)–C(8) is widened to 127.2(1)°. The bicyclic ring system
Furthermore we could isolate single crystals of the
is characterized by alternating C–C single and double olefin 6 from the reaction mixture. The compound crys-
bonds [C(2)–C(3) 1.517(2) Å, C(3)–C(4) 1.333(3) Å, C(4)–C(5) tallizes in the monoclinic space group C2/c. As shown
1.448(3) Å, C(5)–C(6) 1.349(2) Å, C(6)–C(7) 1.448(3) Å, in Fig. 5, its structure features a central C=C bond. Due
C(7)–C(8) 1.365(2) Å]. The endocyclic single bond C(1)– to the bulky substituents, this double bond is elongated
C(2) [1.612(2) Å] is significantly elongated and is therefore to 1.360(8) Å. The bond angle between the two ipso ring
comparable to that in the corresponding tBu-substituted atoms at C(2) [C(11)–C(2)–C(21) 112.1(5)°] is significantly
silaoxine [1.624(12) Å] [21].
narrowed whereas the bond angles at C(1) are all close to
Crystals of the silaazetidine 4 (see Fig. 4) were 120° [Si(1)–C(1)–Si(2) 118.4(3)°, Si(1)–C(1)–C(2) 120.8(5)°,
grown from pentane at room temperature, and belong Si(2)–C(1)–C(2) 120.8(5)°].
Brought to you by | University Paris-Sud
Authenticated
Download Date | 5/19/19 9:59 AM

ꢀꢀꢀꢁ
1222ꢀ ꢀI. Sänger et al.: The chemical behavior of the silaoxine C22H34OSi3 and silaazetidine C25H43NSi4 towards CO2
recrystallization from a 1:1 mixture of Et2O and pentane. –
1H NMR (300.032 MHz; C6D6; Me4Si): δꢀ=ꢀ0.18 (s; SiMe3), 0.24
(s; SiMe), 0.32 (s; SiMe3), 0.42 (s; SiMe), 4.37 (m; CH), 5.84
13
(m; =CH), 7.25 ppm (m; o/m/p-H of Ph). – C NMR (62.9
MHz; C6D6; Me4Si): δꢀ=ꢀ2.0 (SiMe), 3.1 (SiMe3), 3.6 (SiMe), 4.1
(SiMe3), 14.4 (CSi3), 39.1 (CH), 115.2/118.3/124.4/126.9/128.1
(C=C), 128.2/129.5/130.9/137.6 (C-Ph), 152.9 ppm (=CO). –
29Si NMR (59.6 MHz; C6D6; Me4Si): δꢀ=ꢀ–1.3 (SiMe3), 1.2
(SiMe3), 14.4 ppm (SiMe2).
3.2 Synthesis of the silaazetidine 4
The silaazetidine 4 was prepared according to the pub-
lished procedure [15]. Single crystals were grown from a
pentane solution at room temperature. – 1H NMR (300.032
MHz; C6D6; Me4Si): δꢀ=ꢀ0.04 (s; SiMe3), 0.11 (s; NSiMe3), 0.65
13
(s; SiMe2), 7.14 ppm (m; o/m/p-H of Ph). – C NMR (62.9
MHz; C6D6; Me4Si): δꢀ=ꢀ3.2 (NSiMe3), 5.7 (SiMe3), 8.9 (SiMe2),
36.1 (CSi3), 79.4 (CN), 126.5/127.0/129.7/148.0 ppm (C-Ph). –
29Si NMR (59.6 MHz; C6D6; Me4Si): δꢀ=ꢀ–3.8 (SiMe3), 16.4 ppm
(SiMe2).
Fig. 5:ꢀMolecular structure of the olefin 6 in the solid state.
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å)
and bond angles (deg): Si(1)–C(3) 1.862(7), Si(1)–C(5) 1.867(6),
Si(1)–C(4) 1.883(8), Si(1)–C(1) 1.901(7), Si(2)–C(7) 1.860(8),
Si(2)–C(8) 1.864(7), Si(2)–C(6) 1.883(8), Si(2)–C(1) 1.894(6),
C(1)–C(2) 1.360(8), C(2)–C(21) 1.502(8), C(2)–C(11) 1.503(8);
C(3)–Si(1)–C(5) 109.2(4), C(3)–Si(1)–C(4) 108.4(4), C(5)–Si(1)–
C(4) 102.5(4), C(3)–Si(1)–C(1) 112.0(3), C(5)–Si(1)–C(1) 114.4(3),
C(4)–Si(1)–C(1) 109.8(4), C(7)–Si(2)–C(8) 109.6(4), C(7)–Si(2)–
C(6) 108.7(4), C(8)–Si(2)–C(6) 104.2(4), C(7)–Si(2)–C(1) 112.9(3),
C(8)–Si(2)–C(1) 112.7(3), C(6)–Si(2)–C(1) 108.3(4), C(2)–C(1)–Si(2)
120.8(5), C(2)–C(1)–Si(1) 120.8(5), Si(2)–C(1)–Si(1) 118.4(3).
3.3 Reaction of 3 with CO2
An NMR tube was charged with the silaoxine 3 [14] (40
mg, 0.1 mmol), benzene (0.6 mL) and CO2 (0.1 mmol) and
sealed, and the reaction mixture was heated for 24 h to
1
13
100°C. The H, C, and 29Si NMR spectra of the reaction
solution revealed signals which could be assigned to
the silaoxetane 5 (NMR data of 5 see below). In addition
a signal which is attributable to CO2 [13C NMR (62.9 MHz;
C6D6; Me4Si): δꢀ=ꢀ124.9 ppm] could be recognized. Heating
of the reaction mixture for additional 24 h to 120°C yielded
quantitatively the olefin 6 and (Me2SiO)n, as monitored by
NMR spectroscopy. Crystals of 6 were grown from the reac-
tion solution after 1 week at room temperature (yield: 10
mg, 31%).
3 Experimental section
The solvents Et2O, tetrahydrofuran, pentane, benzene,
and C6D6 were stirred over sodium/benzophenone and
distilled prior to use. Me2SiBr–CBr(SiMe3)2 [22] and
Me2SiF–CBr(SiMe3)2 [15] were prepared according to the
published procedures. All other starting materials were
purchased from commercial sources and used without
further purification. The NMR spectra were recorded on
Bruker AM 250, DPX 250, Avance 400, and Avance 500
spectrometer. NMR chemical shifts are reported in ppm.
A JASCO FT/IR 4200 spectrometer was used for recording
the IR spectra.
1
5: H NMR (300.032 MHz; C6D6; Me4Si): δꢀ=ꢀ–0.01 (s;
SiMe3), 0.48 (s; SiMe2), 7.10 ppm (m; o/m/p-H of Ph). – 13C
NMR (62.9 MHz; C6D6; Me4Si): δꢀ=ꢀ5.3 (SiMe3), 7.5 (SiMe2),
3 7.0 ( CSi3), 89.7 (CO), 126.9/128.0/130.1/149.5 ppm (C-Ph). –
29Si NMR (59.6 MHz; C6D6; Me4Si): δꢀ=ꢀ–3.2 (SiMe3), 34.8 ppm
(SiMe2).
6: M.p. 99°C. – 1H NMR (300.032 MHz; C6D6;
Me4Si): δꢀ=ꢀ0.06 (s; SiMe3), 7.20 ppm (m; o/m/p-H of
Ph). – 13C NMR (62.9 MHz; C6D6; Me4Si): δꢀ=ꢀ2.7 (SiMe3),
3.1 Synthesis of the silaoxine 3
The silaoxine 3 was prepared according to the pub- 127.6/127.6/129.7/147.6 (C-Ph), 144.4 (Si2C=C), 169.6 ppm
lished procedure [14]. Single crystals were obtained by (Si2C=C). – 29Si NMR (59.6 MHz; C6D6; Me4Si): δꢀ=ꢀ–5.9 ppm
Brought to you by | University Paris-Sud
Authenticated
Download Date | 5/19/19 9:59 AM

ꢁꢀꢀꢀ
I. Sänger et al.: The chemical behavior of the silaoxine C22H34OSi3 and silaazetidine C25H43NSi4 towards CO2ꢂ
ꢂ1223
Table 1:ꢀCrystal data and refinement of 3, 4, and 6.
ꢁ
3
ꢁ
4
ꢁ
6
Empirical formula
ꢃ
C22H34OSi3
398.76
ꢃ
ꢃ
C25H43NSi4
ꢃ
ꢃ
C20H28Si2
Mr
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
469.96
324.60
Crystal size, mm3
0.38ꢁ×ꢁ0.26ꢁ×ꢁ0.12ꢃ
0.47ꢁ×ꢁ0.42ꢁ×ꢁ0.15ꢃ
Monoclinic
P21/n
0.40ꢁ×ꢁ0.27ꢁ×ꢁ0.18
Monoclinic
C2/c
Crystal system
Orthorhombic
Pna21
26.678(1)
9.0415(6)
9.3342(5)
90
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
Space group
a, Å
b, Å
c, Å
β,°
9.5402(5)
17.6007(6)
16.3546(8)
91.806(4)
2744.8(2)
4
24.290(5)
9.0423(19)
18.338(3)
101.391(15)
3948.4(13)
8
V, Å3
Z
2251.5(2)
4
D
calcd., g cm−3
1.176
1.137
1.092
μ(MoKα), mm−1
F(000), e
0.220
0.229
0.176
864
1024
1408
hkl range
−33/30, 11, 11 ꢃ
13, 25, 23
0.7154
28, 10, 21
0.5953
((sinθ)/λ)max, Å−1
Refl. measured
Refl. unique/Rint
Param. refined
0.6315
22 328
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
62 267
16 425
4690/0.034
235
8369/0.041
271
3314/0.085
199
R(F)a (observed refls.) ꢃ
0.0306
0.0470
0.1619
wR(F2)b (all refls.)
GoF (F2)c
ꢃ
ꢃ
0.0681
0.1191
0.2338
0.987
1.057
1.087
a/bb (weight. scheme)ꢃ
0.0474/0.0
0.03(8)
0.0814/0.1553
–
0.0821/4.8877
–
Flack parameter x
ꢃ
ꢃ
Δρfin (max/min), e Å−3
0.17/–0.21
0.43/–0.47
0.29/–0.46
2
2
2
2
2
aR(F)ꢁ=ꢁΣ||Fo|–|Fc||/Σ|Fo|; bwR(F2)ꢁ=ꢁ[Σw(Fo –Fc2)2/Σw(Fo )2]1/2, wꢁ=ꢁ[σ2(Fo )ꢁ+ꢁ(aP)2ꢁ+ꢁbP]−1, where Pꢁ=ꢁ(Max(Fo , 0)ꢁ+ꢁ2Fc2)/3; cGoFꢁ=ꢁSꢁ=ꢁ[Σw(Fo –Fc2)2/
(nobs–nparam)]1/2
.
(SiMe3). – Anal. for C20H28Si2 (324.61): calcd. C 74.00, H 15.7 (CSi3), 167.5 ppm (CO). – 29Si NMR (59.6 MHz; C6D6;
8.69; found C 73.75, H 8.47.
Me4Si): δꢀ=ꢀ–3.8 (SiMe3), –1.6 (SiMe3), 22.8 ppm (SiMe2) (see
footnote3).
Ph2C=N(SiMe3): 1H NMR (300.032 MHz; C6D6;
Me4Si): δꢀ=ꢀ0.19 (s; SiMe3), 7.20 ppm (m; o/m/p-H of Ph).
3.4 Reaction of 4 with CO2
–
13C NMR (62.9 MHz; C6D6; Me4Si): δꢀ=ꢀ0.7 (NSiMe3),
An NMR tube was charged with the silaazetidine 4 [15] 127.9/128.1/128.2/141.9 (C-Ph), 174.9 ppm (C=N). – 29Si NMR
(23 mg, 0.05 mmol), benzene (0.6 mL) and CO2 (0.1 mmol) (59.6 MHz; C6D6; Me4Si): δꢀ=ꢀ–0.6 ppm (SiMe3).
and sealed. The reaction mixture was heated for 24 h to
1
13
100°C. The H, C, and 29Si NMR spectra of the reaction
solution revealed signals which could be assigned to the 3.5 Crystal structure determinations
silaoxetanone 7 (NMR data see below) and the benzophe-
nonimine Ph2C=N(SiMe3) (NMR data see below). In addi- Data were collected on a STOE IPDS II two-circle diffrac-
tion a signal which is attributable to CO2 [13C NMR (62.9 tometer with graphite-monochromatized MoKα radiation
MHz; C6D6; Me4Si): δꢀ=ꢀ124.9 ppm] was detected. Heating (λꢀ=ꢀ0.71073 Å) and corrected for absorption with an empir-
of the reaction mixture for additional 24 h to 120°C yielded ical absorption correction using the program Platon [23].
quantitatively the literature-known bis(trimethylsilyl) The structures were solved by Direct Methods using the
ketene 8 [IR: νꢀ=ꢀ2084.4 cm−1 (CCO); cf. ref. [18] (νꢀ=ꢀ2085 program Shelxs and refined against F2 with full-matrix
cm−1)] and polysiloxanes (Me2SiO)n, as monitored by NMR least-squares techniques using the program Shelxl-97
and IR spectroscopy.
1
7: H NMR (300.032 MHz; C6D6; Me4Si): δꢀ=ꢀ0.16 (s;
SiMe3), 0.27 (s; SiMe3), 0.45 ppm (s; SiMe2). – 13C NMR (62.9
3ꢁDue to butterfly-like structures of cyclobutanone derivatives sub-
MHz; C6D6; Me4Si): δꢀ=ꢀ1.3 (SiMe3), 5.6 (SiMe3), 7.5 (SiMe2), stituents attached to the same atom are unequal.
Brought to you by | University Paris-Sud
Authenticated
Download Date | 5/19/19 9:59 AM

ꢀꢀꢀꢁ
1224ꢀ
ꢀI. Sänger et al.: The chemical behavior of the silaoxine C22H34OSi3 and silaazetidine C25H43NSi4 towards CO2
[9] H.-W. Lerner, ChemInform 2005, 36; DOI 10.1002/
[24]. The compound 3 is a racemate crystallizing in a non-
centrosymmetric space group (Pna21). As a consequence
of that, the absolute structure could be determined with
the Flack x parameter being 0.03(8). Details of the crystal
structure analyses are summarized in Table 1.
chin.200540290.
[10] H.-W. Lerner, Recent Res. Dev. Org. Chem. 2004,
8, 159.
[11] N. Wiberg, G. Wagner, G. Müller, Angew. Chem., Int. Ed. Engl.
1985, 24, 229.
CCDC 948710 (3), 948709 (4), and 954167 (6) contain [12] A. G. Brook, S. C. Nyburg, F. Abdesaken, B. Gutekunst,
G. Gutekunst, R. K. M. R. Kallury, Y. C. Poon, Y.-M. Chang,
the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
W. Wong-Ng, J. Am. Chem. Soc. 1982, 104, 5667.
[13] F. Schödel, I. Sänger, M. Bolte, H.-W. Lerner, Z. Anorg. Allg.
bridge Crystallographic Data Centre via www.ccdc.cam.
Chem. 2016, 642, 96.
ac.uk/data_request/cif.
[14] N. Wiberg, G. Preiner, K. Schurz, G. Fischer, Z. Naturforsch.
1988, 43b, 1468.
[15] N. Wiberg, G. Preiner, G. Wagner, H. Köpf, G. Fischer, Z. Natur-
forsch. 1987, 42b, 1055.
References
[16] N. Wiberg, G. Preiner, G. Wagner, H. Köpf, Z. Naturforsch. 1987,
42b, 1062.
[1] D. W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2015, 54, 6400.
[2] G. C. Welch, R. R. S. Juan, J. D. Masuda, D. W. Stephan, Science
2006, 314, 1124.
[17] M. Bedikov, S. R. Quadt, O. Rabin, Y. Apeloig, Organometallics
2002, 21, 3930.
[18] F. Meyer-Wegner, J. H. Wender, K. Falahati, T. Porsch, T. Sinke,
M. Bolte, M. Wagner, M. C. Holthausen, H.-W. Lerner, Chem.
Eur. J. 2014, 20, 4681.
[3] P. Spies, G. Erker, G. Kehr, K. Bergander, R. Fröhlich, S. Grimme,
D. W. Stephan, Chem. Commun. 2007, 5072.
[4] G. C. Welch, D. W. Stephan, J. Am. Chem. Soc. 2007, 129, 1880.
[5] C. M. Mömming, E. Otten, G. Kehr, R. Fröhlich, S. Grimme, D. W.
Stephan, G. Erker, Angew. Chem. Int. Ed. 2009, 48, 6643.
[6] D. Voicu, M. Abolhasani, R. Choueiri, G. Lestari, C. Seiler, G.
Ménard, J. Greener, A. Guenther, D. W. Stephan, E. Kumacheva,
J. Am. Chem. Soc. 2014, 136, 3875.
[7] J. M. Breunig, A. Hübner, M. Bolte, M. Wagner, H.-W. Lerner,
Organometallics 2013, 32, 6792.
[8] S. J. Geier, T. M. Gilbert, D. W. Stephan, J. Am. Chem. Soc. 2008,
130, 12632.
[19] D. F. Sullivan, R. P. Woodbury, M. W. Rathke, J. Org. Chem.,
1977, 42, 2038.
[20] L. L. Shchukovskaya, A. I. Koltsov, A. N. Lazarev, Dokl. Akad.
Nauk. SSSR, 1968, 179, 892.
[21] N. Wiberg, H.-S. Hwang-Park, H.-W. Lerner, S. Dick, Chem. Ber.
1996, 129, 471.
[22] N. Wiberg, G. Preiner, O. Schieda, G. Fischer, Chem. Ber. 1981,
114, 3505.
[23] A. L. Spek, J. Appl. Crystallogr. 2003, 36, 7.
[24] G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112.
Brought to you by | University Paris-Sud
Authenticated
Download Date | 5/19/19 9:59 AM