Lactamomethylsilanes – Synthesis, Structures, and Reactivity towards CO2 and Phenylisocyanate

Article abstract of DOI:10.1002/zaac.201800424

Lactamomethylsilanes of γ-butyrolactam, δ-valerolactam, ε-caprolactam, and 1-isoindolinone (phthalimidine) with up to three methyl moieties were synthesized according to the chemical formula Me_xSiLac_(4–x) (x = 0, 1, 2, and 3). Using the lactams as starting materials four synthetic routes were tested: salt elimination, transsilylation, transamination, and metallation of the lactames followed by reaction with methylchlorosilanes. All products were analyzed by NMR (¹H, ¹³C and ²⁹Si) and RAMAN spectroscopy. Selected solid products were crystallized and the molecular structure was determined by single-crystal X-ray diffraction. The reactivity of the lactamomethylsilanes towards phenylisocyanate and CO₂ was studied.

Full text of DOI:10.1002/zaac.201800424

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201800424
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Lactamomethylsilanes – Synthesis, Structures, and Reactivity
towards CO and Phenylisocyanate
2
Marcus Herbig,[a] Uwe Böhme,*[a] and Edwin Kroke*[a]
Dedicated to Professor Dr. Thomas Fässler on the Occasion of his 60th Birthday
1
Abstract. Lactamomethylsilanes of γ-butyrolactam, δ-valerolactam,
ε-caprolactam, and 1-isoindolinone (phthalimidine) with up to three
with methylchlorosilanes. All products were analyzed by NMR ( H,
1
3
29
C and Si) and RAMAN spectroscopy. Selected solid products were
methyl moieties were synthesized according to the chemical formula crystallized and the molecular structure was determined by single-crys-
Me SiLac(4–x) (x = 0, 1, 2, and 3). Using the lactams as starting materi- tal X-ray diffraction. The reactivity of the lactamomethylsilanes
towards phenylisocyanate and CO was studied.
x
als four synthetic routes were tested: salt elimination, transsilylation,
transamination, and metallation of the lactames followed by reaction
2
Introduction
Si–O bond but less reactive than a Si–Cl bond. The Si–N bond
is prone towards hydrolysis and alkoholysis. Additionally,
some substances containing Si–N bonds react with heteroall-
Lactames are common structural motifs in the synthesis of
polyamide 6 from ε-caprolactam or β-lactam antibiotics. As
state of the art, a trialkylsilyl moiety is attached to the lactam
nitrogen atom as protecting group to metallate the α-carbon
for further reactions.[
enes like CO and isocyanates via insertion reactions yielding
2
useful products such as ureas, carbamates, and polysiloxanes,
among others.[
23–26]
Therefore, in the presented study we have
1–10]
Silylated lactames can react with or-
synthesized lactamomethylsilanes of the type Me SiLac
x
(4–x)
ganic acid chlorides, phosphorchlorides or methanal to form an
(x = 0, 1, 2, and 3) [Lac = γ-butyrolactam, δ-valerolactam, ε-
N–C bond.[
11,12]
With strong nucleopilic bases, such as lithium
caprolactam, and 1-isoindolinone (phthalimidine)] in order to
investigate their structures and reactivities.
organyls, imines can be synthesized starting with silylated
lactams.[
3,13]
The silylation of ε-caprolactam and afterwards
the polymerization leads to new inorganic-organic hybrid
materials.[
14]
Results and Discussion
An early report about the silylation of lactams was published
by Rühlmann and Rupprich.
[15]
A selection of 16 lactamomethylsilanes was synthesized by
different routes. They are listed in Table 1.
N-Trimethylsilyl-ε-caprolac-
tam is a multifunctional reagent for the anionic polymerization
of ε-caprolactam.[ Vinyl containing silyllactams have been
copolymerized. It was shown that the introduction of silicon-
containing monomers into the main chain of polystyrols and
polyacrylates causes improved thermostability and processabil-
16]
2.1 Synthesis
Four different synthetic procedures were used to prepare the
The acylation of N-trimethylsilyl lact- compounds 1–16. The synthesis of the lactamosilanes is pos-
[
17]
ity of the polymers.
ams is important for the synthesis of polymers.[ N-Trimeth- sible from lactams with triethylamine and chloromethylsilanes.
18]
ylsilyl lactams were used as substrates for phosphorylation re- Other synthesis routes are transamination, using bis(diethylam-
actions,[ and lactamosilanes were utilized to generate penta- ino)dimethylsilane (for SiN2), tri(pyrrolidino)methylsilane or
19]
coordinate hydrochlorosilanes.[
12]
tri(isopropylamino)methylsilane (for SiN3) and tetra(isoprop-
Due to its reactivity, the Si–N bond is interesting for dif- ylamino)silane (for SiN4), and transsilylation using the SiN1
ferent potential applications, e.g. the synthesis of precursors derivative and chloromethylsilanes of the type Me SiCl
x
(4–x)
[21,22]
for Si/C/O or Si/C/N materials.
It is more reactive than a (x = 0, 1 and 2).
*
*
*Dr. Uwe Böhme
E-mail: uwe.boehme@chemie.tu-freiberg.de
Prof. Dr. E. Kroke
2
.1.1 Synthesis Starting with Lactams, Chloromethylsilanes,
and Triethylamine
E-Mail: kroke@.tu-freiberg.de
[
a] Institut für Anorganische Chemie
TU Bergakademie Freiberg
Leipziger Str. 29
The silylation of lactams with chlorosilanes in presence of a
base like triethylamine is a simple and easy route to synthesize
lactamomethylsilanes (Scheme 1).
0
9599 Freiberg, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201800424 or from the au-
thor.
Many aminosilanes were synthesized via this route in non-
polar solvents like n-hexane or n-pentane.[
23,27–38]
The used
Z. Anorg. Allg. Chem. 2019, 645, 377–387
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Table 1. Synthesized lactamomethylsilanes with their numbering in this article and appearance at room temperature.
Lac =
γ-Butyrolactam
δ-Valerolactam
ε-Caprolactam
1-Isoindolinone
SiN1
1
5
9
13
Me
SiN2
Me SiLac
3
SiLac
colorless liquid
2
colorless liquid
3
colorless liquid
6
colorless liquid
7
colorless liquid
10
colorless liquid
11
yellow solid
14
yellow solid
15
2
2
SiN3
MeSiLac
SiN4
3
white solid
4
white solid
8
white solid
12
yellow solid
16
SiLac
4
white solid
white solid
white solid
yellow solid
Scheme 1. Synthesis of lactamomethylsilanes via elimination of trieth-
ylamine hydrochloride, exemplified for product 1.
Scheme 2. Synthesis of 2 via transamination with bis(diethylamino)-
dimethylsilane.
The most well-known reaction of this type is the trimethyl-
silylation of amines with hexamethyldisilazane (HMDS) liber-
ating ammonia. Ammonium sulfate is frequently used to cata-
lyze these reactions.
The substitution is supported by having a more basic leaving
amine, to catch the proton, and a less basic entering amine, to
release the proton. Ammonium salts catalyze the reaction by
protonating the nitrogen atom of the leaving amine and there-
fore, lowering the strength of the Si–N bond.
Heating γ-butyrolactam with bis(diethylamino)dimethyl-
silane without any solvent yields pure di-γ-butyrolactamodi-
methylsilane. The same reaction with δ-valerolactam leads to
a brown undefined solid. Because of the good results with the
SiN2 derivative of γ-butyrolactam, transamination was used to
synthesize the SiN3 and SiN4 derivatives. Tripyrrolidino-
methylsilane was used as reactant and the reaction was per-
lactams as well as the synthesized lactamomethylsilanes are
not soluble in these solvents. Triethylamine hydrochloride is
formed as a side product and is difficult to be separated from
the lactamosilanes. Therefore, a slightly more polar solvent
than hexane must be used in order to separate the product from
the triethylamine hydrochloride. We tested dichloromethane,
ethyl ether, and THF. The best results for SiN1 and SiN2 deriv-
atives of γ-butyrolactam are obtained in ethyl ether; and for
SiN3 and SiN4 THF turned out to be most suitable. All δ-
valerolactam and ε-caprolactam derivatives are synthesized in
ethyl ether with good yields. Compound 13 was synthesized
in dichloromethane due to the solubility of the 1-isoindolinone.
The SiN2, SiN3, and SiN4 derivatives of 1-isoindolinone were
obtained in boiling THF.
A common problem of all synthesis routes starting with the
lactams is the presence of small amounts of lactams in the
product. Compounds 1, 2, and 9 are purified by distillation in
vacuo, whereas all 1-isoindolinone derivatives are recrys-
tallized from chloroform. The compounds 5 to 8 (δ-vale-
formed in CHCl by heating half an hour. Afterwards, all vola-
tiles were removed in vacuo. NMR analysis shows several re-
action products.
For the synthesis of silanes of type SiN4 with γ-butyrolac-
tam, δ-valerolactam, and 1-isoindolinone tetrakis-(isoprop-
3
rolactam) turned red in solution upon standing at room tem- ylamino)silane was used due to the low boiling point of iso-
perature. It is assumed, that ring-opening-polymerization has propylamine. The reactions with γ-butyrolactam were used to
started due to the presence of new signals in the spectra as to find the best synthesis conditions: either THF or CHCl as
3
see in the Supporting Information.
solvent and heating under reflux or standing several days. Stir-
ring the reaction mixture in THF for several days leads to the
best results with the lowest amount of side-products.
All reactions yielded the disubstituted product di(γ-butyrol-
actamo)-di(isopropylamino)silane 17 according to NMR spec-
tra, which was also structurally analyzed by single crystal
2.1.2 Transamination
Transamination means the substitution of an amino moiety XRD (see below). A reaction time of 5 days leads to the
bonded to the silicon with another amine (Scheme 2).
formation of tri(γ-butyrolactamo)-(isopropylamino)silane side
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by side to the disubstituted product 17. Even with a longer
reaction time no evidence of 4 could be found.
The reaction of the lactams with nBuLi solution leads to
many undefined products. Metallation with freshly prepared
lithium-diisopropylamide (LDA) shows impure products, too.
Attempts to synthesize SiN3-type products of γ-butyrolactam
2.1.3 Transsilylation
after metallation with sodium methoxide shows signals of
typical transsilylation reaction is shown in methoxy moieties in 13C- and H-NMR spectra. Therefore,
1
A
Scheme 3.
metallation reactions like this are not suitable for the synthesis
of lactamosilanes.
2.1.5 Comparison of Synthetic Routes
The most efficient and adaptable synthetic route to the title
Scheme 3. Synthesis of 10 via transsilylation.
compounds is the silylation with chlorosilanes. Unfortunately,
the liquid products are frequently obtained containing the start-
ing material, i.e. the lactams, as impurities. Using transsil-
ylation, the products can be synthesized in case both – the
lactams and the lactamosilanes – are thermally stable. Trans-
amination is suitable to synthesize mixed amino-lactamo-si-
lanes like 17 and 18 (see below). Metallation of the lactams
with sodium methoxide, LDA or butyllithium appears not to
be suitable for the synthesis of lactamomethylsilanes.
Often trimethylsilylated amines react with a chloromethyl-
silane of the formula Me SiCl
(x Ͻ 3). In this case, chloro-
(4–x)
x
trimethylsilane is leaving the reaction mixture (which usually
can be distilled off) and the amine is transferred to the silane
with less methyl groups. This reaction type can again be cata-
lyzed by ammonium salts.
We studied the transsilylation as a procedure to synthesize
the target compounds of type SiN1 to SiN4 from lactamotri-
methylsilanes using the ε-caprolactamo derivatives 9–12 as
testing substances. These transsilylations were successful as
2
.2 Spectroscopic Data
2
9
confirmed by Si-NMR spectra where the desired products
were identified by an intense signal. However, the obtained
solutions turned out to be product mixtures which could not
be separated.
In the H- and 13C-NMR spectra, the signals of the lactames
1
can be found at almost the same chemical shift as the starting
materials, which was expected. Additionally, a signal of the
methyl moieties bound to the silicon atom can be found.
All 29Si-NMR shifts of the synthesized lactamomethylsil-
anes are shown in Table 2. The signals of derivatives of type
2.1.4 Metallation
Lactamomethylsilanes and the corresponding lactams SiN1 to SiN3 are shifted to higher values due to the electronic
showed similar solubility in many solvents. Therefore, separat- influence of the carbonyl moiety. There is no homologue series
ing of both substances is generally a problem, which can be of the chemical shifts and a general influence of the ring sizes
avoided using metallation as a synthesis route. Metallated lact- of the lactams. It seems to be more important if the number of
ams were used in a different approach to synthesize the deriva- carbon atoms in the ring is even or odd. The benzene ring of
tives of type SiN4 of γ-butyrolactam and δ-valerolactam 1-isoindolinone has little influence of the electronic situation
(Scheme 4).
at the silicon atom.
2.3 Molecular Structures
Information about the structural features of the prepared
compounds was drawn from the data of the single crystal struc-
ture analyzes. Suitable crystals for single-crystal X-ray diffrac-
tion experiments were obtained from the compounds 3, 11, 13,
14, 16, 17, and 19.
Scheme 4. Trimethylsilylation of sodium γ-butyrolactam as an exam-
ple for aminosilane synthesis via metallated lactams.
Table 2. 29Si NMR shift of all synthesized lactamomethylsilanes and the four corresponding pyrrolidinosilanes for comparison.
Lac =
SiN1
γ-Butyrolactam
δ-Valerolactam
ε-Caprolactam
1-Isoindolinone
Pyrrolidine
1
8.6
2
–2.1
3
5
9.4
6
0.0
9
8.9
10
–1.0
11
13
9.8
14
–1.1
15
Me
SiN2
Me SiLac
3
SiLac
2.5 [49]
–8.1 1
2
2
SiN3
7
MeSiLac
SiN4
3
–19.9
4
–45.5
–20.0
8
no signal
–19.2
12
–43.5
–17.9
16
–42.9
–24.6 1
–43.3 a)
SiLac
4
a) See Experimental Section of this work.
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Compound 3 crystallizes in the monoclinic space group complete molecule is generated by a threefold rotation around
P2 /n with three crystallographically independent molecules in the axis Si1–C1. The molecule itself is not chiral, whereas
1
the asymmetric unit. These molecules have different orienta- the 6 axis generates chirality in the solid-state structure. The
3
tion of the γ-butyrolactam rings at the silicon atoms. However, absolute structure parameter was determined to 0.05(5) during
the bond lengths and angles are very similar in all three mol- refinement. The molecule structure is shown in Figure 2 and
ecules, therefore only molecule A is discussed here in detail. essential geometric parameters in Table 3. The tetrahedral ar-
The molecule is shown in Figure 1, essential geometric param- rangement at the silicon atom is distorted. The bond angles N–
eters are listed in Table 3. The overall arrangement of the com- Si–N are 105.37(5) and the bond angles N–Si–C 113.31(5)°.
pound can be characterized as distorted tetrahedral with bond The bond lengths Si–N and Si–C are somewhat longer than in
angles at the silicon atom between 105.83(9) and 112.8(1)°. 3, but still in the normal range for these types of bonds. The
The Si–N bond lengths are between 1.742(2) to 1.745(2) Å. ring pucker of the seven membered ring (N1–C2–C3-C4–C5–
This is in the range for typical Si–N bond lengths.[
37–40]
The C6-C7) was analyzed according to reference . The least-
[42]
3
Si–C bond is 1.834(3) Å. This is a typical value for a Si-C(sp ) squares plane of these seven atoms in crystal coordinates is
bond.[ Ring Puckering Analysis
40]
[41]
of 3 shows that the five- given by 3.4549x + 1.1750y – 8.7332z = 1.3223. The out-of-
membered rings in molecule A adopt different conformations: plane displacements of the ring atoms in Å are 0.2357 N1,
The γ-butyrolactam ring N1A–C5A is twisted on C4A and 0.2075 C2, –0.4309 C3, 0.2754 C4, –0.1068 C5, 0.2537 C6,
C5A. These two atoms are about 0.1 Å above and below the and –0.4347 C7. These displacements hint to the presence of
least-squares plane formed by the atoms N1A, C1A, C2A, a chair or twist chair conformation. A quantitative description
C3A, C4A, and C5A. The five-membered ring N2A–C9A is of the ring pucker parameters with PLATON[ gave the pa-
planar. All ring atoms deviate less than 0.04 Å from the least- rameters q = 0.445 Å and q = 0.654 Å. This corresponds to
43]
2
3
squares plane. The ring N3A–C13A adopts an envelope con- a chair conformation according to reference[ . Figure 3 sup-
formation on C12A. This atom is 0.165(2) Å out of the least- ports this finding.
squares plane of the five ring atoms.
44]
Figure 1. Molecular structure of one crystallographically independent
Figure 2. Molecular structure of 11. Anisotropic displacement param-
molecule of 3. Anisotropic displacement parameters are depicted at the
eters are depicted at the 50% probability level.
50% probability level.
The compounds 13, 14, and 16 contain the 1-isoindolinone
ligand and are discussed here together. Compound 13 crys-
tallizes in the orthorhombic space group Pbcn, 14 and 16 in
Table 3. Selected geometric parameters /Å,° of silanes 3 and 11.
3
the monoclinic space group P2 /c. 13 and 14 have each one
1
Si1A–N1A
Si1A–N3A
1.742(2)
1.743(2)
Si1A–N2A
Si1A–C1A
1.745(2)
1.834(3)
molecule in the asymmetric unit. Compound 16 crystallizes
with four molecules chloroform in the asymmetric unit
N1A–Si1A–N3A 109.21(10)
N1A–Si1A–N2A 106.91(9)
N3A–Si1A–N2A 105.83(9)
N1A–Si1A–C1A
N3A–Si1A–C1A
N2A–Si1A–C1A
112.83(12)
109.22(12)
112.56(13)
(
16·4CHCl ). Three of the chloroform molecules are disor-
3
dered. The molecule structures are shown in Figure 4, Fig-
ure 5, and Figure 6, essential geometric parameters are summa-
rized in Table 4. The coordination arrangement at the silicon
atoms is tetrahedral distorted in all three compounds (see
Table 4). The Si–C bond lengths in 13 and 14 are around
1
1
Si1–N1
N1–Si1–N1A
1.7701(12)
105.37(5)
Si1–C1
N1–Si1–C1
1.848(3)
113.31(5)
Compound 11 crystallizes in the hexagonal space group P63 1.85 Å and the Si–N bond lengths are around 1.76 Å. In com-
with one third of the molecule in the asymmetric unit. The pound 16 the latter ones are shorter with values between
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Figure 3. Asymmetric unit of 11 showing the chair conformation of
the seven membered ring. Anisotropic displacement parameters are
depicted at the 50% probability level.
1.721(4) to 1.733(5) Å. The 1-isoindolinone ligand is planar in
Figure 6. Molecular structure of 16. The co-crystallizing chloroform
all three compounds.
molecules are omitted for clarity. Anisotropic displacement parameters
are depicted at the 50% probability level.
Table 4. Selected geometric parameters /Å,° of 13, 14, and 16.
1
3
Si1–N1
Si1–C9
1.7608(19)
1.848(3)
Si1–C10
Si1–C11
1.850(3)
1.851(3)
N1–Si1–C9
N1–Si1–C10
N1–Si1–C11
109.59(12)
109.21(13)
105.17(11)
C9–Si1–C10
C9–Si1–C11
C10–Si1–C11
111.24(17)
110.89(17)
110.56(17)
1
4
Si1–N1
Si1–N2
N1–Si1–N2
N1–Si1–C18
N2–Si1–C18
1.7596(15)
1.7632(15)
107.44(7)
107.29(8)
111.41(8)
Si1–C18
Si1–C17
N1–Si1–C17
N2–Si1–C17
C18–Si1–C17
1.8493(19)
1.854(2)
111.23(8)
106.88(8)
112.51(9)
Figure 4. Molecular structure of 13. Anisotropic displacement param-
eters are depicted at the 50% probability level.
1
6
Si1–N3
Si1–N1
N3–Si1–N1
N3–Si1–N2
N1–Si1–N2
1.721(4)
1.731(5)
112.2(2)
106.10(19)
108.00(19)
Si1–N2
Si1–N4
N3–Si1–N4
N1–Si1–N4
N2–Si1–N4
1.730(4)
1.733(5)
111.3(2)
107.3(2)
111.9(2)
ents. This leads to differences in the bonding mode of both
substituents: The bond lengths to the γ-butyrolactam nitrogen
atoms are longer than the bond lengths to the isopropylamino
nitrogen atoms (see Table 5). Furthermore, the tetrahedral ar-
rangement at the silicon atom is strongly distorted. The bond
Figure 5. Molecular structure of 14. Anisotropic displacement param-
eters are depicted at the 50% probability level.
The disubstituted diamino-dilactamosilane 17 obtained by angle N3A–Si1A–N4A between the two isopropylamino
transamination (see above) crystallizes in the monoclinic space groups is expanded to 120.18(16)°. This is due to the sterically
group P2 /n with two crystallographically independent mol- demanding isopropyl groups. Other angles incorporating the
1
ecules in the asymmetric unit. The molecules A and B differ flat γ-butyrolactam are compressed to values between 110 to
mainly in the orientation of the isopropyl groups. All other 103°. Ring Puckering Analysis[ shows that both five mem-
geometric features (i.e. bond lengths and angles) are very sim- bered rings of the γ-butyrolactam units in molecule A adopt
ilar. Therefore, only molecule A will be discussed here. The envelope conformations. The ring N1A–C1A–C2A–C3A–C4A
molecule structure of 17A is shown in Figure 7 and essential forms an envelope on C3A. This atom is 0.181(3) Å out of the
geometric parameters in Table 5. Two different nitrogen sub- least-squares plane of the five ring atoms. The ring N2A–
stituents are bound to the central silicon atom in 17. There is C5A–C6A–C7A–C8A forms an envelope on C7A. This atom
the γ-butyrolactam bound via the nitrogen atoms N1A and is 0.196(3) Å out of the least-squares plane of the five ring
N2A to the silicon atom. The silicon bound nitrogen atoms atoms. The same envelope conformations are found in mol-
N3A and N4A are components of the isopropylamino substitu- ecule B.
41]
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The insertion of CO into the Si–N bond is tested with com-
2
pound 1 and 3. CO does not insert into the Si–N bond, even
2
under slightly higher pressure (4 bar). In contrast, PhNCO is
able to insert but leads to product mixtures. The 29Si NMR
spectra of 1 with PhNCO show unreacted 3 and 1 and some
minor signals. The insertion of PhNCO into 5, 9, and 13 leads
to new signals in the 29Si NMR spectra at δ = 13.8 ppm (inser-
tion into 9) and 14.2 ppm (insertion into 5), next to the signals
of 5 and 9, respectively, which are in the typical range for
insertion products of this type.[ The C and H NMR spec-
tra show more new signals, which cannot be assigned. Further-
more, the molecular structure of the hydrolysis product 19 of
the insertion into 1 could be determined by single-crystal
X-ray diffraction. The insertion products of phenylisocyanate
seem to be more prone towards hydrolysis than the lactamosil-
anes.
24]
13
1
¯
Compound 19 crystallizes in the triclinic space group P1
molecule of 17. Anisotropic displacement parameters are depicted at with two molecules in the asymmetric unit (Figure 8). The ar-
Figure 7. Molecular structure of one crystallographically independent
the 50% probability level.
rangements of molecule A and B are very similar. Therefore,
only molecule A will be discussed here. Bond lengths and
[
46]
angles are in the usual range for organic molecules.
The
Table 5. Selected geometric parameters /Å,° of 17.
molecule is composed of γ-butyrolactam, an urea unit and a
phenyl group. The nitrogen atom N1A is part of the γ-butyrol-
actam and the urea unit. All three units are nearly coplanar to
each other. The dihedral angle between the least-squares plane
of the γ-butyrolactam and the urea unit is 2.6(1)°, the dihedral
angle between urea unit and the phenyl group is 3.8(1)°. Intra-
molecular hydrogen bonds between the oxygen atoms O1A,
Si1A–N1A
Si1A–N2A
N2A–Si1A–N1A 108.23(14)
N4A–Si1A–N1A 103.83(14)
N3A–Si1A–N1A 110.35(14)
1.759(3)
1.758(3)
Si1A–N3A
Si1A–N4A
N4A–Si1A–N3A 120.18(16)
N4A–Si1A–N2A 110.65(15)
N3A–Si1A–N2A 103.27(14)
1.685(3)
1.682(3)
The Si···O distances of the structurally characterized lactam-
osilanes are summarized in Table S2 (Supporting Information).
All these distances are below the sum of van der Waals radii
O2A, and neighboring hydrogen atoms stabilize this molecule
41]
(
see Table 6). Ring Puckering Analysis[ shows that the five
[45]
membered ring of the γ-butyrolactam unit in molecule A
adopts an envelope conformation on C4A. This atom is
with 1.52 Å (O) + 2.10 Å (Si) = 3.62 Å.
Thus, these weak
Si···O interactions contribute to the stabilization and the con-
formation of the lactamosilanes not only in the solid state, but
also in the liquid states and in solutions.
0.075(1) Å out of the least-squares plane of the five ring
atoms.
2.4 Insertion Reactions
It is known that heteroallenes can insert into the Si–N bond
of aminosilanes. We investigated the insertion behavior of CO2
and phenylisocyanate (PhNCO, Scheme 5) into the Si–N bond
of the synthesized lactamosilanes.
Figure 8. Molecular structure of one crystallographically independent
molecule of 19. Anisotropic displacement parameters are depicted at
the 50% probability level.
Scheme 5. Insertion of phenylisocyanate (PhNCO) into 1.
Table 6. Intramolecular hydrogen bonds of 19 /Å,°.
D–H···A
d(D–H)
d(H···A)
d(D···A)
Ͻ(DHA)
N2A–H2A···O2A
C7A–H7A···O1A
N2B–H2B···O2B
C7B–H7B···O1B
0.93(2)
0.95(2)
0.90(2)
0.95(2)
1.89(2)
2.30(2)
1.89(2)
2.29(2)
2.6859(17)
2.901(2)
2.6672(17)
2.888(2)
141.7(19)
121.0(19)
143.4(18)
120.6(19)
Z. Anorg. Allg. Chem. 2019, 377–387
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
(
(
CH
vs), 2955 (s), 2903 (vs), 2865 (m), 2703 (vw), 1445 (w), 1407 (vw),
) ppm. 29Si NMR: δ = –45.5 ppm. RAMAN: ν˜ = 3347 (w), 2969
3
3
Conclusions
We have synthesized lactamomethylsilanes of γ-butyro- 1324 (vw), 1301 (vw), 1123 (vw), 928 (vw), 853 (w), 714 (w), 429
–
1
lactam, δ-valerolactam, ε-caprolactam, and 1-isoindolinone (w), 248 (w), 194 (w) cm .
phthalimidine) with up to three methyl moieties according to
the chemical formula Me SiLac
(0 Յ x Յ 3). In most cases Tri(isopropylamino)methylsilane: Yield 7.06 g (92%), colorless li-
(
x
(4–x)
1
3
quid; bp = 192 °C. H NMR: δ = 1.06 (d, JH,H = 6.4 Hz, 18 H, CH
3
3
),
.12 (m, 3 H, CH), 0.46 (br., 3 H, NH) ppm. C NMR: δ = 42.4
CH), 28.2 (CH
) ppm. 29Si NMR: δ = –26.9 ppm. RAMAN: ν˜ = 3399
vw), 2961 (s), 2928 (s), 2903 (vs), 2868 (vs), 2708 (vw), 1457 (vw),
reactions of the lactams with chlorosilanes in the presence of
triethylamine as base are appropriate but leave a small amount
of unreacted lactam in the product. Transamination can be used
to synthesize lactamosilanes of type SiN1 and SiN2, otherwise
the substitution is not complete. Transsilylation reactions gave
inseparable product mixtures. Single crystal structures of
mono- (13), di- (14, 17), tri- (3, 11), and tetralactamosilanes
1
3
(
(
3
1
8
447 (vw), 1399 (vw), 1168 (vw), 1121 (vw), 1013 (vw), 932 (vw),
57 (vw), 664 (vw), 435 (w), 307 (vw), 236 (w) cm .
–1
(
16) indicate atomic distances and angles in the expected ran-
4.2 Synthesis of Sec-aminomethylsilanes
ges, with weak contacts between the O atoms of the carbonyl
groups and the Si atoms, which are all below the sum of the Example bis(diethylamino)dimethylsilane: To a stirred solution of di-
van der Waals radii (see Supporting Information). Silanes of ethylamine (12.71 g, 174 mmol) in 150 mL n-pentane at 0 °C (ice-
δ-valerolactam are quite fragile and tend to polymerize in solu- water) was added dropwise dichlorodimethylsilane (4.92 g,
3
8.1 mmol). The suspension was allowed to reach room temperature
tion. Insertions into the Si–N bond are possible, if PhNCO is
used, but only product mixtures are obtained and the products
are more prone to hydrolysis than the alkylaminosilanes.
and was stirred overnight. The mixture was filtered through a G4-fritt
to remove the diethylamine hydrochloride and volatiles were removed
in vacuo resulting in 6.12 g (30.2 mmol, 79%) of a colorless liquid.
Bis(diethylamino)dimethylsilane: 1H NMR: δ = 2.77 (q, 3
.0 Hz, 8 H, CH ), 0.93 (t, J = 7.0 Hz, 12 H, CH ), 0.0 (s, 6 H, SiMe
All reactions were carried out in a dry argon atmosphere using standard ppm. C NMR: δ = 39.5 (CH ), 15.8 (CH ), –1.0 (SiMe ) ppm. Si
H,H
J =
4
Experimental Section
7
2
3
2
)
1
3
29
2
3
2
Schlenk-techniques. Table S1 (Supporting Information) shows the
NMR: δ = –5.6 ppm.
source and purification of the used chemicals.
1
Di(pyrrolidino)dimethylsilane: H NMR: δ = –0.01 (s, 6 H, SiMe),
NMR spectra were measured with a BRUKER DPX 400 (frequencies:
13
1
.63 (m, 8 H, CH
2 2
), 2.89 (m, 8 H, NCH ) ppm. C NMR: δ = 46.8
1
13
29
H: 400.13 MHz; C: 100.61 MHz; Si: 79.49 MHz) or BRUKER
29
(NCH ), 26.9 (CH
2
2
), –3.3 (SiMe) ppm. Si NMR: δ = –8.1 ppm.
1
13
AVANCE III 500 MHz (frequencies: H: 500.13 MHz;
25.76 MHz; 29Si: 99.36 MHz) spectrometer in CDCl
with TMS as
internal standard.
C:
1
3
1
Tri(pyrrolidino)methylsilane: H NMR: δ = –0.01 (s, 3 H, SiMe),
1
3
1
.63 (m, 12 H, CH
2 2
), 2.93 (m, 12 H, NCH ) ppm. C NMR: δ = 46.7
2
9
(NCH ), 26.9 (CH
2
2
), –5.5 (SiMe) ppm. Si NMR: δ = –24.6 ppm.
RAMAN-spectra were measured with Bruker FT-Raman spectrometer
RFS 100/S. The device works with an air-cooled Nd:YAG-Laser with
a wavelength of 1064 nm and a nitrogen-cooled detector. The samples
were filled in glass tubes and sealed with PTFE-paste. The intensities
are listed as follows: vs. (very strong) 80–100% of the highest signal,
s (strong), m (medium), w (weak), vw (very weak) next 20% respec-
tively.
1
Tetra(pyrrolidino)silane: H NMR: δ = 1.68 (m, 16 H, CH
2
), 3.00
1
3
(
m, 16 H, NCH
2
) ppm. C NMR: δ = 46.8 (NCH
2 2
), 26.9 (CH ) ppm.
2
9Si NMR: δ = –43.3 ppm.
4
.3 Synthesis of 1-Isoindolinone
Mass spectra were measured with an Advion expression CMS mass
spectrometer.
The syntheses were based on a literature report.[48] A suspension of
phthalimide (30.10 g; 205 mmol) and tin powder (50.80 g, 495 mmol)
in 150 mL acetic acid and 75 mL conc. hydrochloric acid were heated
to reflux for 2 h. The suspension was filtered and concentrated by
distillation. Dichloromethane (200 mL) was added and the solution
was stirred overnight. The phases were separated and the aqueous layer
was extracted three times with 50 mL dichloromethane. The combined
organic layers were extracted one time with 50 mL of a sodium hy-
droxide solution (about 20%) and afterwards washed three times with
saturated sodium chloride solution. The organic solution was dried
with sodium sulfate. Volatiles were removed in vacuo yielding a yel-
Boiling points of liquid samples were measured as described in the
literature.[
47]
4.1 Synthesis of Methyl-isopropylaminosilanes
As example: tetra(isopropylamino)silane: To a stirred solution of iso-
propylamine (27.93 g, 472 mmol) in 250 mL ethyl ether at 0 °C (ice-
water) was added dropwise tetrachlorosilane (5.00 g, 29.4 mmol). The
suspension was allowed to reach room temperature and was stirred
overnight. The mixture was filtered through a G4-fritt to remove the
isopropylamine hydrochloride and volatiles were removed in vacuo
resulting in 7.06 g (27.1 mmol, 92%) of a white solid.
1
low solid. Mp = 153 °C. H NMR: δ = 8.55 (br., 1 H, NH), 7.89–7.46
1
3
(
1
=
m, 5 H, Ar), 4.48 (s, 2 H, CH
2
) ppm. C NMR: δ = 172.1 (C=O),
43.8, 132.3, 131.6, 127.94, 123.3 (Ar), 45.9 (CH ) ppm. RAMAN: ν˜
3061 (vs), 3017 (w), 2932 (vs), 2865 (w), 1652 (m), 1594 (m), 1449
2
Tetra(isopropylamino)silane: Yield 7.06 g (92%), white solid; m.p.
(m), 1387 (m), 1322 (w), 1212 (m), 1179 (w), 1144 (w), 1015 (m),
1
3
7
4
3 °C. H NMR: δ = 1.06 [d, J(H,H) = 6.4 Hz, 24 H, CH
3
], 3.12 (m, 847 (m), 797 (w), 772 (s), 564 (m), 498 (m), 292 (m), 182 (m), 95 (s)
–1
H, CH), 0.41 (br., 4 H, NH) ppm. 13C NMR: δ = 2.4 (CH), 28.2 cm .
Z. Anorg. Allg. Chem. 2019, 377–387
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
1
4
.4 General Procedure for Preparing Lactamomethylsilanes
yellow liquid of high viscosity; b.p. = 266 °C (760 Torr). H NMR: δ
γ
β
3
=
=
2
0.0 (s, 6 H, Me Si), 1.25–1.34 (m, 8 H, H and H ), 1.88 (t, JH,H
6.8 Hz, 4 H, H ), 2.91 (t, JH,H = 5.9 Hz, 4 H, H ) ppm. C NMR:
δ = 173.1 (C=O), 45.3 (C ), 33.3 (C ), 23.9 (C ), 21.7 (C ), 0.0 (Me
ppm. Si NMR: δ = 0.0 ppm. RAMAN: ν˜ = 2949 (vs), 2905 (vs),
809 (vw), 2730 (vw), 2689 (vw), 1673 (vw), 1623 (vw), 1449 (vw),
277 (vw), 1150 (vw), 1073 (vw), 967 (vw), 834 (vw), 660 (vw), 612
vw), 531 (vw), 458 (vw), 356 (vw), 284 (vw), 201 (vw), 132 (vw)
This procedure is described for the example of compound 1.
α
3
δ
13
δ
α
γ
β
2
Si)
To a stirred solution of γ-butyrolactam (4.15 g, 48.7 mmol) and trieth-
ylamine (4.83 g, 47.7 mmol) in 50 mL dichloromethane at 0 °C (ice-
water) was added dropwise chlorotrimethylsilane (5.33 g, 49.0 mmol) .
The suspension was allowed to reach room temperature and was stirred
overnight. The mixture was filtered through a G4-fritt to remove the
triethylamine hydrochloride and volatiles were removed in vacuo. The
resulting suspension was filtered though a syringe filter (PTFE,
2
9
2
1
(
–
1
cm .
Tri(δ-valerolactamo)methylsilane (7): Ethyl ether was used as sol-
vent instead of dichloromethane. The product was not distilled. Yield
.98 g (30%) light red solid; m.p. decomp. starting at about 60 °C. H
NMR: δ = 0.70 (s, 3 H, MeSi), 1.91–1.55 (m, 12 H, H and H ), 2.39–
2.27 (m, 6 H, H ), 3.40–3.23 (m, 6 H, H ) ppm. C NMR: δ = 172.2
(C=O), 44.1 (C ), 32.1 (C ), 23.0 (C ), 20.6 (C ), –0.8 (MeSi) ppm.
Si NMR: δ = –20.0 ppm. RAMAN: ν˜ = 2955 (vs), 2905 (s), 2678
(vw), 1613 (vw), 1449 (vw), 1341 (vw), 1279 (vw), 1177 (vw), 1075
(vw), 1025 (vw), 971 (vw), 892 (vw), 838 (vw), 666 (vw), 616 (vw),
0.20 μm) and the filtrate was distilled in vacuo resulting in 1.83 g
(11.6 mmol, 24%) of a colorless liquid.
1
1
γ
β
γ-Butyrolactamotrimethylsilane (1): Yield 1.83 g (24%) colorless li-
quid; bp = 213 °C (760 Torr). H NMR: δ = 0.05 (s, 9 H, Me
α
δ
13
1
3
Si),
δ
α
γ
β
γ
3
α
3.19–3.12 (m, 2 H, H ), 2.09 (t, JH,H = 8.2 Hz, 2 H, H ), 1.87–1.77
2
9
β
13
γ
α
(m, 2 H, H ) ppm. C NMR: δ = 182.9 (C=O), 46.1 (C ), 32.4 (C ),
β
29
[50]
2
8
1.3 (C ), –1.6 (Me
3
Si) ppm. Si NMR: δ = 8.6 ppm (δ =8.7 ppm
.8 ppm[ ). RAMAN: ν˜ = 2963 (m), 2899 (vs), 2793 (vw), 2724
51]
5
27 (vw), 460 (vw), 381 (vw), 331 (vw), 273 (vw), 203 (vw), 143
(
(
(
vw), 2681 (vw), 2620 (vw), 1677 (vw), 1488 (vw), 1426 (vw), 930
vw), 709 (vw), 633 (w), 537 (vw), 390 (vw), 259 (vw), 205 (vw), 153
vw), 101 (vw) cm .
–
1
(
vw), 95 (vw) cm .
–1
Tetra(δ-valerolactamo)silane (8): The general procedure for prepar-
Di(γ-butyrolactamo)dimethylsilane (2): Ethyl ether was used as sol-
ing lactamomethylsilanes was not suitable for the synthesis of this
vent instead of dichloromethane. The product was not distilled. The compound.
product contains some lactam, which could not be removed. Yield
1
6
=
3
(
.42 g (73%) pale yellow liquid; bp = 296 °C (760 Torr). H NMR: δ
ε-Caprolactamotrimethylsilane (9): Ethyl ether was used as solvent
γ
α
2
0.15 (s, 6 H, Me Si), 1.79–1.66 (m, 4 H, H ), 1.95 (m, 4 H, H ), instead of dichloromethane. The product was not distilled. Yield 6.52 g
.20–3.12 (m, 4 H, H ) ppm. C NMR: δ = 183.0 (C=O), 46.1 (75%); b.p. = 177 °C (760 Torr). H NMR: δ = 3.02 (m, 2 H, H ),
β
13
1
ε
γ
α
β
29
α
δ
γ
β
C ), 31.8 (C ), 21.1 (C ), –3.3 (Me
RAMAN: ν˜ = 2978 (s), 2905 (vs), 2839 (vw), 1673 (vw), 1488 (vw),
426 (vw), 1231 (vw), 1011 (vw), 930 (w), 855 (vw), 797 (vw), 678
w), 537 (w), 394 (vw), 300 (vw), 223 (vw), 176 (vw), 103 (vw)
2
Si) ppm. Si NMR: δ = –2.1 ppm.
2.32 (m, 2 H, H ), 1.35–1.55 (m, 6 H, H , H and H ), 0.04 (s, 9 H,
1
3
ε
α
SiMe ) ppm. C NMR: δ = 183.0 (C=O), 44.3 (C ), 37.6 (C ), 30.2
(C ), 29.6 (C ), 23.2 (C ), –0.12 (SiMe ) ppm. Si NMR: δ = 8.9 ppm
3
(δ =8.8 ppm ). RAMAN: ν˜ = 2899 (vs), 2859 (w), 2809 (vw), 2691
3
δ
γ
β
29
1
(
[
9]
–1
cm . MS: 210.155 (M-CH
4
).
(vw), 1638 (vw), 1445 (vw), 1333 (vw), 1260 (vw), 1083 (vw), 1025
(
(
vw), 844 (vw), 770 (vw), 689 (vw), 606 (w), 550 (vw), 429 (vw), 315
vw), 251 (vw), 196 (vw) cm . MS: 139 (M+CH CN+Na).
3
Tri(γ-butyrolactamo)methylsilane (3): Ethyl ether was used as sol-
vent instead of dichloromethane. The solid product was not distilled
but washed several times with ethyl ether. Yield 2.98 g (69%), white
crystals, suitable for X-ray diffraction (CCDC 1865087). M.p. 75 °C.
–1
Di(ε-caprolactamo)dimethylsilane (10): Ethyl ether was used as sol-
vent instead of dichloromethane. The product was not distilled but
stored at –28 °C and afterwards filtered to remove remaining ε-caprol-
actam. Yield 7,04 (65%) pale yellow liquid; b.p. = 184 °C (760 Torr).
1
γ
H NMR: δ = 0.07 (s, 3 H, MeSi), 2.13–1.98 (m, 6 H, H ), 2.32 (t,
3JH,H = 8.1 Hz, 6 H, H ), 3.49 (t, JH,H = 6.9 Hz, 6 H, H ) ppm.
α
3
β
13
C
γ
α
β
NMR: δ = 184.1 (C=O), 46.4 (C ), 32.4 (C ), 21.9 (C ), –4.2 (MeSi)
1
ε
α
H NMR: δ = 3.03 (m, 4 H, H ), 2.25 (m, 4 H, H ), 1.41 (m, 12 H,
ppm. 29Si NMR: δ = –19.9 ppm. RAMAN: ν˜ = 2982 (vs), 2928 (s),
δ
γ
β
13
2
H , H and H ), –0.17 (s, 6 H, SiMe ) ppm. C NMR: δ =
1
1
1
2
663 (w), 1484 (vw), 1430 (vw), 1387 (vw), 1283 (vw), 1231 (vw),
011 (vw), 930 (w), 851 (vw), 701 (w), 649 (vw), 533 (w), 369 (vw),
82 (vw), 211 (vw), 151 (vw), 109 (w) cm . MS: 318 [M + Na].
ε
α
δ
γ
β
83.0 (C=O), 44.5 (C ), 37.7 (C ), 29.7 (C ), 29.5 (C ), 23.2 (C ), –0.7
29
[52]
(SiMe
2
) ppm. Si NMR: δ = –1.0 ppm (–0.7 ppm
). RAMAN: ν˜
–1
=
2967 (m), 2907 (vs), 2857 (m), 2693 (vw), 2240 (vw), 1626 (vw),
1
7
1
445 (vw), 1333 (vw), 1260 (vw), 1085 (vw), 1027 (vw), 845 (vw),
72 (vw), 718 (vw), 610 (w), 548 (vw), 415 (vw), 365 (vw), 261 (vw),
90 (vw), 143 (vw), 97 (vw) cm .
Tetra(γ-butyrolactamo)silane (4): The general procedure for prepar-
ing lactamomethylsilanes was not suitable for the synthesis of this
compound.
–
1
Tri(ε-caprolactamo)methylsilane (11): Ethyl ether was used as sol-
vent instead of dichloromethane. The product was not distilled but
washed several times with ethyl ether. Yield 4.01 g (32%) pale yellow
solid suitable for X-ray diffraction (CCDC 1865086); m.p. 80 °C
δ-Valerolactamotrimethylsilane (5): Ethyl ether was used as solvent
instead of dichloromethane. Yield 1.3 g (47%) colorless liquid; bp =
1
2
05 °C (760 Torr). H NMR: δ = 0.00 (s, 9 H, Me
3
Si), 1.58–1.38 (m, 4
γ
β
3
α
3
H, H and H ), 2.07 (t,
.0 Hz, 2 H, H ) ppm. C NMR: δ = 176.5 (C=O), 43.7 (C ), 31.2
C ), 22.9 (C ), 20.4 (C ), –0.7 (Me Si) ppm. Si NMR: δ = 9.4 ppm
3
δ = 8.8 ppm . RAMAN: ν˜ = 2953 (s), 2901 (vs), 1626 (vw), 1461
JH,H = 6.7 Hz, 2 H, H ), 2.95 (t,
J
H,H
=
1
ε
α
δ
13
δ
(subl.). H NMR: δ = .20 (m, 6 H, H ), 2.50 (m, 6 H, H ), 1.67 (m,
5
(
(
δ
γ
β
13
α
γ
β
29
18 H, H , H and H ), 0.66 (s, 3 H, SiMe) ppm. C NMR: δ = 183.4
ε
α
δ
γ
β
[9
(C=O), 45.1 (C ), 38.3 (C ), 30.2 (C ), 29.7 (C ), 23.5 (C ), –0.4
2
9
[52]
(
SiMe) ppm. Si NMR: δ = –19.2 ppm (–19.2 ppm ). RAMAN: ν˜
= 2978 (w), 2934 (vs), 2857 (m), 2791 (vw), 2699 (vw), 2631 (vw),
628 (vw), 1445 (w), 1401 (vw), 1337 (vw), 1295 (vw), 1237 (vw),
1088 (vw), 1029 (vw), 967 (vw), 849 (vw), 786 (vw), 714 (vw), 616
vent instead of dichloromethane. The product was not distilled and (vw), 543 (vw), 439 (vw), 361 (vw), 317 (vw), 259 (vw), 213 (vw),
(
5
vw), 1412 (vw), 1279 (vw), 1073 (vw), 834 (vw), 689 (vw), 641 (vw),
33 (vw), 458 (vw), 346 (vw), 199 (vw), 132 (vw) cm .
–1
1
Di(δ-valerolactamo)dimethylsilane (6): Ethyl ether was used as sol-
–
1
+
4
contains some lactam which could not be removed. Yield 5.62 g (53%) 165 (vw), 122 (vw) cm . MS: 397 (M+NH ).
Z. Anorg. Allg. Chem. 2019, 377–387
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Tetra(ε-caprolactamo)silane (12): Yield 1.55 g (11%) white solid; 5 mmol) and ammonium sulfate as catalyst in about 20 mL THF for
1
ε
α
m.p. 195 °C. H NMR: δ = 3.21 (m, 8 H, H ), 2.47 (m, 8 H, H ), 1.69
60 min. Volatiles were removed in vacuo. The reaction yielded an
undefined product mixture.
δ
γ
β
13
(
(
m, 24 H, H , H and H ) ppm. C NMR: δ = 183.9 (C=O), 46.1
ε
α
δ
γ
β
29
C ), 38.4 (C ), 30.4 (C ), 29.7 (C ), 23.7 (C ) ppm. Si NMR: δ =
43.5 ppm (–43.5 ppm [14]). RAMAN: ν˜ = 2998 (w), 2936 (vs), 2857 This reaction was also performed in chloroform with 1-isoindolinone
–
(
(
m), 2693 (vw), 1621 (vw), 1443 (w), 1331 (vw), 1289 (vw), 1231 and an undefined product mixture without signals of isopropylamine
vw), 1087 (vw), 1027 (vw), 844 (vw), 766 (vw), 718 (vw), 620 (vw), in the NMR spectra was obtained.
5
35 (vw), 427 (vw), 390 (vw), 359 (vw), 176 (vw), 134 (w), 86 (vw)
–1
SiN4 Synthesis with Tetra(isopropylamino)silane: γ-Butyrolactam
1 g, 12 mmol) was stirred with tetrakis(isopropylamino)silane (1.31 g)
and ammonium sulfate (0.01 g) for 12 h in THF. Volatiles were re-
cm . MS: 363 (M-caprolactam).
(
Phthalimidinotrimethylsilane (13): Yield 0.95 g (50%) yellow crys-
tals suitable for X-ray diffraction (CCDC 1865088); m.p. 65 °C. H moved in vacuo yielding a colorless liquid, which partly crystallizes
NMR: δ = 0.41 (s, 9 H, Me Si), 4.35 (s, 2 H, H ), 7.38–7.79 (m, 4 H, after several days. The reaction was repeated in chloroform with the
3
H
1
7
2
–5
13
6
1
) ppm. C NMR: δ = 175.4 (C=O), 144.8 (C ), 133.4 (C ), 131.2
same yield. Heating the reaction mixture to the boiling point of the
solvent for 2 h and distilling of the isopropylamine leads to more side
products.
4
3
2
5
7
(
C ), 127.5 (C ), 123.2 (C ), 122.7 (C ), 48.8 (C ), –1.3 (Me
3
Si) ppm.
Si NMR: δ = 9.8 ppm. RAMAN: ν˜ = 3059 (m), 3023 (vw), 2961
s), 2930 (s), 2899 (vs), 1659 (w), 1596 (w), 1449 (w), 1414 (vw),
2
9
(
1378 (vw), 1303 (vw), 1218 (vw), 1023 (w), 847 (vw), 801 (w), 747 Di(γ-butyrolactamo)-di(isopropylamino)silane (17): The product
(
2
vw), 695 (vw), 624 (m), 575 (vw), 367 (vw), 315 (vw), 269 (vw), was identified in the product mixture with γ-butyrolactam. The white
–1
21 (w), 167 (vw), 132 (w), 99 (m) cm .
crystals were suitable for X-ray diffraction (CCDC 1865092). m.p.:
1
3
7
3 °C (decomp.). H NMR: δ = 0.78 (d, JH,H = 6.36 Hz, 12 H, CH
3
),
Di(phthalimidino)dimethylsilane (14): Yield 2.33 g (89%) yellow
crystals suitable for X-ray diffraction (CCDC 1865091); m.p. 127 °C
decomp. H NMR: δ = 1.82 (s, 6 H, Me
7
1
–
γ
3
α
1.65 (m, 4 H, H ), 2.02 (t, JH,H = 6.4 Hz, 4 H, C ), 2.93 (m, 2 H,
3
β
13
CH), 3.05 (t, JH,H = 6.98 Hz, 4 H, H ) ppm. C NMR: δ = 182.9
1
7
2
Si), 4.65 (s, 4 H, H ), 7.38–
γ
α
β
(
C=O), 46.2 (C ), 41.4 (CH), 33.6 (C ), 27.2 (CH
3
), 21.4 (C ) ppm.
Si NMR: δ = –48.6 ppm. RAMAN: ν˜ = 2973 (vs), 2920 (vs), 2710
vw), 1673 (w), 1493 (vw), 1459 (w), 1426 (w), 1123 (vw), 1009 (vw),
2–5
13
6
.75 (m, 8 H, H ) ppm. C NMR: δ = 176.1 (C=O), 145.5 (C ),
29
1
4
3
2
5
7
32.7 (C ), 131.9 (C ), 127.8 (C ), 123.6 (C ), 123.1 (C ), 49.6 (C ),
(
2.64 (Me
2
Si) ppm. 29Si NMR: δ = –1.0 ppm; The measured RAMAN
–1
932 (w), 892 (w), 809 (vw), 701 (w), 587 (w), 473 (w) cm .
spectra shows no sharp bands.
Tri(γ-butyrolactamo)-(isopropylamino)silane (17a): The product
was identified in the product mixture with γ-butyrolactam and 17. H
Tri(phthalimidino)methylsilane (15): Yield 0.17 g (15%) of a waxy
1
1
7
yellow solid. H NMR: δ = 1.18 (s, 3 H, MeSi), 4.77 (s, 6 H, H ),
3
β
NMR: δ = 0.61 (d, JH,H = 6.28 Hz, 6 H, CH
3
), 1.51 (m, 6 H, H ),
2
–5
13
7
(
(
.42–7.82 (m, 12 H, H ) ppm. C NMR: δ = 176.3 (C=O), 146.0
α
1
J
.89 (m, 6 H, C ), 2.70 (m, 1 H, CH), 2.93 (m, 2 H, CH), 3.00 (t,
H,H = 6.88 Hz, 6 H, H ) ppm. C NMR: δ = 182.6 (C=O), 46.8
C ), 42.6 (CH), 33.9 (C ), 26.0 (CH
6
1
4
3
2
5
C ), 132.5 (C ), 132.0 (C ), 127.9 (C ), 123.9 (C ), 123.2 (C ), 49.4
C ), –3.9 (MeSi) ppm. Si NMR: δ = –17.9 ppm; The measured
3
γ
13
7
29
γ
β
α
29
(
3
), 21.3 (C ) ppm. Si NMR:
RAMAN spectra shows no sharp bands.
δ = –47.0 ppm.
Tetra(phthalimidino)silane (16): Yield 0.29 g (28%, pure crystals)
Di(phthalimidino)-di(isopropylamino)silane (18): The product was
yellow crystals suitable for X-ray diffraction (CCDC 1865090); m.p.
1
7
identified in a mixture with phthalimidine. The white crystals were
1
63 °C decomp. H NMR: δ = 5.02 (s, 8 H, H ), 7.43–7.79 (m, 16
1
2–5
13
6
1
suitable for X-ray diffraction (see above). m.p. 178 °C subl.. H NMR:
H, H ) ppm. C NMR: δ = 176.7 (C=O), 146.8 (C ), 132.8 (C ),
31.3 (C ), 127.9 (C ), 124.0 (C ), 123.5 (C ), 49.5 (C ) ppm. Si
3
4
3
2
5
7
29
δ = 1.22 (d,
J
H,H = 6.03 Hz, 12 H, CH
3
), 3.71 (m, CH), 2.02 (t,
), 7.30–7.90 (m, aryl) ppm.
C NMR: δ = 180–170 (C=O), 150–120 (aryl), 45.8 (CH ), 42.8
) ppm. Si NMR: δ = –46.9 ppm. RAMAN: ν˜ = 3061
vs), 3017 (vw), 2932 (vs), 2865 (w), 1594 (m), 1472 (w), 1449 (m),
1
3
α
J
3
H,H = 6.4 Hz, 4 H, C ), 4.50 (s, 2 H, CH
2
NMR: δ = –42.9 ppm. The measured RAMAN spectrum shows no
sharp bands.
1
2
2
9
(
(
CH), 25.8 (CH
3
4
.5 Transsilylation
1322 (w), 1212 (m), 1179 (w), 1144 (w), 1015 (s), 847 (m), 772 (vs),
64 (m), 496 (s), 292 (m), 273 (m), 213 (s), 182 (m), 107 (s), 95 (vs)
cm .
5
The transsilylation was tested with the ε-caprolactamosilanes. 9 (2 g,
0 mmol) with (NH SO (0.24 g) in about 20 mL of THF was heated
with dichlorodimethylsilane (0.65 g, 5 mmol) , trichlormethylsilane
0.54 g, 3.6 mmol), and silicon tetrachloride (0.44 g, 2.5 mmol),
–
1
1
4
)
2
4
(
4.7 Metallation with n-Butyllithium
respectively, for 4 h. The mixture was stirred overnight, filtered, and
volatiles removed in vacuo. All reactions lead to a product mixture.
This reaction was carried out in order to synthesize 4. To a stirred
solution of γ-butyrolactam in ethyl ether at –78 °C a solution of nBuLi
(
2.5 m in hexanes) was added. The reaction mixture was allowed to
4
.6 Transamination
reach room temperature and was stirred half an hour. Afterwards sili-
con tetrachloride was added at 0 °C. The resulting suspension was
stirred overnight, filtered, and volatiles were removed in vacuo re-
Di(γ-butyrolactamo)dimethylsilane (2): Bis(diethylamino)dimeth-
ylsilane (5 g, 25 mmol) was heated with γ-butyrolactam (4.29 g,
5
0 mmol) without solvent for 30 min distilling continuously the sulting in a product mixture.
formed diethylamine at 54 °C. Pure 2 was formed in quantitative yield
5.63 g). The same reaction with δ-valerolactam yielded an undefined
product mixture.
(
4.8 Metallation with Sodium Methoxide
Tri(δ-valerolactamo)methylsilane (7): δ-Valerolactam (1.45 g, The reactions were carried out in order to synthesize 3. No pure prod-
5 mmol) was heated with tris(isopropylamino)methylsilane (1.06 g, uct could be synthesized with the procedures described below.
1
Z. Anorg. Allg. Chem. 2019, 377–387
www.zaac.wiley-vch.de 385
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Procedure 1: To a solution of γ-butyrolactam in diglyme a solution 4.12 Determination of Molecular Structures using Single
of 20% sodium methoxide was added dropwise. After addition, the
methanol was distilled from the reaction mixture. To the resulting solu-
tion stoichiometric amounts of trichloromethylsilane was added drop-
wise. The resulting suspension was stirred overnight, filtered, and the
solvent was removed in vacuo.
Crystal X-ray Diffraction
Data collections for the structures discussed in this publication were
performed with a STOE IPDS-2T image plate diffractometer equipped
with a low-temperature device with Mo–K
using ω and φ scans. Software for data collection: X-AREA, cell re-
finement: X-AREA and data reduction: X-RED.
α
radiation (λ = 0.71073 Å)
[
53]
Procedure 2: To a solution of sodium methoxide in methanol (20%)
γ-butyrolactam was added. The mixture was refluxed for 1 h and after-
wards all volatiles were removed in vacuo. The residue was suspended
Preliminary struc-
[
54]
ture models were derived by direct methods
refined by full-matrix least-squares calculations based on F for all
and the structures were
2
in ethyl ether and trichloromethylsilane added. The resulting mixture reflections using SHELXL.[55] Hydrogen atoms were included in the
was stirred overnight, filtered, and volatiles removed in vacuo.
models in calculated positions and were refined as constrained to the
bonded atoms. The absolute structure parameter of 11 was determined
to 0.05(5) during refinement. Compound 14 was refined as twin with
matrix (–1 0 0, 0 –1 0, 0 0 1) and BASF 0.14. Compound 16 crys-
tallized with four molecules chloroform in the asymmetric unit. Three
of the chloroform molecules were disordered, which makes refinement
difficult. An extinction coefficient of 0.019(5) was refined for 19. Fur-
ther crystallographic data are listed in Tables S3 and S4 (Supporting
Information).
Procedure 3: To a solution of sodium methoxide in methanol (20%)
γ-butyrolactam was added. After the addition all volatiles were re-
moved slowly in vacuo. The residue was suspended in ethyl ether and
trichloromethylsilane added. The resulting mixture was stirred over-
night, filtered, and volatiles were removed in vacuo.
4.9 Metallation with Freshly Prepared Lithium
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1865086, CCDC-1865087, CCDC-1865088, CCDC-
Diisopropylamide
To a stirred solution of diisopropylamine in THF at –78 °C a solution
of nBuLi (20% in hexane/cyclohexane) was added. The solution was
allowed to reach room temperature. The γ-butyrolactam was added to
the solution dropwise forming immediately a white solid. Volatiles
were removed in vacuo. The white residue was suspended in ethyl
ether and cooled to 0 °C. Silicon tetrachloride was added dropwise.
The reaction mixture was stirred overnight, filtered and volatiles were
removed in vacuo. The product was analyzed by NMR spectroscopy
showing no signals of the desired product 4.
1865089, CCDC-1865090, CCDC-1865091, and CCDC-1865092
(
Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk, http://
www.ccdc.cam.ac.uk)
Supporting Information (see footnote on the first page of this article):
The supporting information contains information about the origin and
purification of used chemicals, additional NMR-spectra, and a table
with Si...O distances.
4.10 Insertion of CO2
The trimethyllactamosilane was dissolved in THF and CO
from a gas Acknowledgements
2
cylinder was passed through the solution at 0 °C for 20 min. After-
wards all volatiles were removed in vacuo. No reaction took place.
The authors thank TU Bergakademie Freiberg (Freiberg, Germany) for
financial support. Part of this work was performed within the research
group “Chemical utilization of carbon dioxide with aminosilanes
Further experiments were carried out in an autoclave. A solution of
0.26 g 1 in about 2 mL of THF was placed in an open vessel in the
(CO –Sil)” that is financially supported by the European Union
2
2
autoclave. The apparatus was filled with CO with a pressure of 4 bar (European regional development fund), the Ministry of Science and
and stored overnight. The reaction mixture was transferred into a Art of Saxony (SMWK) and the Sächsische Aufbaubank (SAB).
round-bottom-flask and all volatiles were removed in vacuo yielding
.26 g of 1. The same results were obtained with 3 and 8 bar of
CO pressure.
K. Kraushaar is acknowledged for measuring the MS spectra.
0
2
Keywords: N-aminosilanes; Lactames; Silylation; Insertion
reaction
4.11 Insertion of PhNCO
Half a gram of the trimethyllactamosilane was dissolved in 5 mL of
chloroform. At room temperature stoichiometric amounts of PhNCO
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Published Online: February 5, 2019
Z. Anorg. Allg. Chem. 2019, 377–387
www.zaac.wiley-vch.de 387
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim