New cyclic and spirocyclic aminosilanes

Article abstract of DOI:10.1515/mgmc-2021-0007

New cyclic and spirocyclic aminosilanes were synthesised using ethylenediamine, 2-aminoben-zylamine, 1,8-diaminonaphthalene, o-phenylenediamine, and trans-cyclohexane-1,2-diamine as starting material. These diamines were converted into aminosilanes using

Full text of DOI:10.1515/mgmc-2021-0007

Main Group Met. Chem. 2021; 44: 51–72
Research Article
Open Access
Marcus Herbig, Henrik Scholz, Uwe Böhme*, Betty Günther, Lia Gevorgyan, Daniela Gerlach,
JNöreg Wwaglcery*,cSlaincdraaSnchdwarszepr,iarnod EcdywicnlKirockeaminosilanes
https://doi.org/10.1515/mgmc-2021-0007
received November 25, 2020; accepted February 13, 2021
1 Introduction
Aminosilanes, i.e., silicon organic compounds with
Abstract: New cyclic and spirocyclic aminosilanes
at least one Si–NR2 bond (R = H, hydrocarbyl), are the
were synthesised using ethylenediamine, 2-aminoben-
topic of research for several decades. They are often
zylamine, 1,8-diaminonaphthalene, o-phenylenediamine,
synthesised in non-polar aprotic solvents, such as
and trans-cyclohexane-1,2-diamine as starting material.
pentane and hexane (Böhme et al., 2000, 2003a, 2003b;
These diamines were converted into aminosilanes using
Herzog et al., 1998; Huber and Schmidbaur, 1999; Huber
silicon tetrachloride and dimethyldichlorosilane directly
et al., 1997a, 1997b; Meinel et al., 2014, 2015; Schlosser
and via the N,N’-bis(trimethylsilylated) amino deriva-
et al., 1994; Tamao et al., 1994; Trommer et al., 1997). Up
tives. 15 new compounds of the type (diamino)(SiMe3)2,
to four amino moieties can be bound to one silicon atom.
(diamino)2Si, (diamino)SiMe2, and (diamino)SiCl2 have
Besides hydrolysis, alcoholysis and other substitution
been prepared. The formation of two cyclotrisilazane
reactions, the Si–N bond can undergo insertion
derivatives was observed starting from (N,N’-2-aminoben-
reactions with heteroallenes (Barluenga et al., 1989;
zylamino)dichlorosilane by trimerisation. All synthesised
Degl’Innocenti et al., 1992; Glidewell and Rankin, 1970;
compounds have been characterised with NMR-, Raman-,
Herbig et al., 2018a; Kirilinet al., 2009; Kraushaar et al.,
or IR-spectroscopy, mass-spectrometry, and boiling or
2017; Wolff et al., 1978). For example, CO2 can insert into
melting point. Single-crystal X-ray structure analyses of
the Si–N bond to form a carbamoic moiety (Kraushaar
several derivatives have been performed.
et al., 2012, 2014).
The degree of substitution with trimethylsilyl groups
Siloxanes as derivatives of silanediols are studied
in the final compounds depends on the ring size of the
for decades (e.g., Jaçoviç, 1957). The corresponding
spirocycles. It was shown with quantum chemical cal-
diaminosilanes (and aminosilanes with three or four
culations on the M062X/6-31G(d) level that trimethylsi-
Si–NR2 moieties) are less researched (Armitage, 1982).
lyl groups have a stabilising effect on 5-membered ring
Interesting structural motifs for this class of aminosilanes
systems and a destabilising effect on 6-membered rings in
are cyclic and oligocyclic structures. So far, many cyclic
these compounds.
aminosilanes having two Si–N bonds per cycle are known
(e.g., Herbig et al., 2018b). But only in a few compounds
Keywords: spiro compound, spirocyclic, aminosilane,
the silicon atom is part of one or two independent cyclic
silazane
systems without sterically demanding substituents
(Kaßner et al., 2016; Kummer and Rochow, 1963). Most
of the known spirocyclic aminosilanes contain ethylene
bridges like in Figure 1. The substituents R are either
aliphatic (Me, Et – Yoder and Zimmermann (1964);
* Corresponding author: Uwe Böhme, Institut für Anorganische
Chemie, TU Bergakademie Freiberg, Leipziger Str. 29, 09599
iPr – Schlosser et al. (1994)) or feature aryl groups (benzyl –
Yoder and Zimmermann (1964); p-methylphenyl – Rong et
al. (1998); benzenesulfonyl, tosyl – Schlosser et al. (1994).
Wannagat and Eisle (1978) have synthesised compounds
with either Me or TMS moieties on each ring. Cyclic
aminosilanes with exocyclic silyl moieties starting from
ethylenediamine are also known (Auner et al. 1992; Böhme
et al., 2007; Daniéle et al., 2001; Diedrich et al., 2002).
Freiberg, Germany, e-mail: uwe.boehme@chemie.tu-freiberg.de
* Corresponding author: Jörg Wagler, Institut für Anorganische
Chemie, TU Bergakademie Freiberg, Leipziger Str. 29, 09599
Freiberg, Germany, e-mail: joerg.wagler@chemie.tu-freiberg.de
Marcus Herbig, Henrik Scholz, Betty Günther, Lia Gevorgyan,
Daniela Gerlach, Sandra Schwarzer and Edwin Kroke: Institut für
Anorganische Chemie, TU Bergakademie Freiberg, Leipziger Str. 29,
09599 Freiberg, Germany
Open Access. © 2021 Marcus Herbig et al., published by De Gruyter.
Attribution alone 4.0 License.
This work is licensed under the Creative Commons

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52ꢀ
M. Herbig et al.
Prout et al. (1994) reported cyclic aminosilanes starting 2.1 Syntheses of N,N’-bis(trimethylsilyl)ated
from o-phenylenediamine. Other compounds having a Si
atom as spiro atom are derivatives of o-phenylenediamine
aminosilanes
and 2-aminobenzylamine (Kaßner et al., 2016; Kummer The N,N’-bis(trimethylsilyl)ated products (derivatives
and Rochow, 1963) or spirosilazanes (Schlingmann and 1a-5a) were obtained in high yields by reacting the
Wannagat, 1976a), a series of heavier congeners of the amine with chlorotrimethylsilane in the presence of
latter of which has also been studied (Schlingmann and triethylamine (Scheme 1). Silylation reactions of that kind
Wannagat, 1976b).
are often carried out in nonpolar solvents like n-pentane
In this work new cyclic and spirocyclic aminosilanes or n-hexane to support the separation (i.e., precipitation)
according to Figure 1 are described. We set out to prepare of the amine hydrochloride formed as by-product. In the
these compounds in order to obtain an overview about current case, however, THF was used because of the better
the preparative accessibility to this class of compounds solubility of some of the diamines in this solvent.
and to use them later for further derivatisation reactions.
The amines shown in Figure 2 were used for the
investigations.
2.2 Syntheses of cyclic and spirocyclic
derivatives
Two different routes are pursued for the synthesis of
cyclic and spirocyclic aminosilanes: The reaction of the
diamines 1-5 with the chlorosilane in the presence of
triethylamine as base is denoted as method A (Scheme 2).
The reaction of the N,N’-bis(trimethylsilyl)ated diamine
derivatives 1a-5a with the corresponding chlorosilane and
triethylamine is denoted as method B (Scheme 2).
Synthesised spirocyclic compounds are labelled with
the number of the parent diamine and the suffix b. Two
types of cyclic aminosilanes were synthesised: Derivatives
with the suffix c contain two methyl groups bound to
the endocyclic silicon atom. Derivatives d contain two
chlorine atoms at the endocyclic silicon atom. Additional
trimethylsilyl groups at the nitrogen atoms are indicated
by the suffix -TMS and the number of these moieties per
molecule.
2 Results
The outcome of numerous reactions is summarised in
Sections 2.1, 2.2, and 3.1 in order to provide a coherent
overview for the reader. NMR spectroscopic data are
condensed in Section 3.2. Molecular structures are
discussed in detail in Section 3.3, in order to understand
the diversity of the obtained structures. The results of
quantum chemical calculations in Section 3.4 help to
understand the formation of different products.
2
2
2
R
R
R
3
N
N
R
N
1
1
1
Si
Si
R
R
R
3
R
N
N
N
2.2.1 Syntheses with 1 and 1a
2
2
2
R
R
R
Compounds 1 and 1a are colourless liquids. The
reactions and experiments are shown in Scheme 3. All
attempts to synthesise cyclic and spirocyclic silicon
Figure 1: Generic structures of cyclic and spirocyclic aminosilanes
in this work (with R1 = ethylene, o-phenylene, 1,2-cyclohexanediyl,
benzyl-2-yl, 1,8-naphthylene; R2 = H, SiMe3; R3 = Me, Cl).
Figure 2: Amines used as starting materials.

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ53
compounds starting with 1 lead to product mixtures trimethylsilyl moieties retained. Compound 1d-TMS2
from which no products could be isolated. Starting was synthesised by our group and published earlier
with the bis-trimethylsilylated derivative 1a cyclic and (Böhme et al., 2007). The substance 1b-TMS4 is also a
spirocyclic compounds could be synthesised with all solid while 1c-TMS2 is a colourless liquid, the structure
of which is confirmed by NMR spectroscopy and the
molar mass by cryoscopy.
2.2.2 Syntheses with 2 and 2a
The attempts to synthesise aminosilanes with
o-phenylenediamine
mixtures in reactions with silicon tetrachloride and
dichlorodimethylsilane (see Scheme 4). In reactions with
2
gave intractable product
Scheme 1: Synthesis of derivatives a from amines and
chlorotrimethylsilane in the presence of triethylamine.
Method B
Method A
2
R
3
3
H
N
+ Cl SiR
+ Cl SiR
2
2
2
2
3
SiMe
NH
NH
N
R
3
2
+2 Et N
+2 Et N
3
3
1
1
1
R
Si
R
R
3
-2 Et NHCl
-2 Et NHCl
3
3
R
N
H
SiMe
3
N
2
2
R
1 - 5
1a - 5a
Scheme 2: Synthesis of cyclic aminosilanes with method A and B.
Scheme 3: Experiments with and reactions of ethylenediamine (1).

ꢀ
54ꢀ
M. Herbig et al.
Scheme 4: Experiments with and reactions of o-phenylenediamine (2).
Scheme 5: Experiments with and reactions of 1,2-diaminocyclohexane (3).
2a half of the trimethylsilyl moieties are preserved in poor yield only. Thus, details related to the reactions of
the cyclic and spirocyclic compounds. The compounds 3a can be found in Supplementary material and have not
2b-TMS2 and 2d-TMS were crystallised and the molecular been included in the discussion.
structures were determined. Earlier, 2d-TMS2 was reported
as product of the reaction of 2a with SiCl4 and triethylamine
in toluene (Wagler and Roewer, 2007). Obviously, changing 2.2.4 Syntheses with 4 and 4a
the solvent alters the reactivity of 2a significantly.
The outcome of the reactions of 4 are different from those
of 1 to 3 because the cycle to be created is a 6-membered
ring unlike the 5-membered one in the previous target
products (see Scheme 6). The reactions with the amine
2.2.3 Syntheses with 3 and 3a
Compound3gaveintractableproductmixturesinreactions 4 gave isolable products (4b and 4c). Compound 4e is
with silicon tetrachloride and dichlorodimethylsilane. formed together with 4c. Therein, two molecules of 4c
Even though silylation of 3 afforded 3a in good yield are connected via a Me2Si moiety at the aliphatic amine N
(Scheme 5), further reactions of 3a with SiCl4 and Me2SiCl2 atom. A changed reactivity pattern is also observed in the
afforded mixtures of products from which individual reaction which aimed at formation of the SiCl2 containing
compounds could not be isolated or have been isolated in derivative 4d. The expected product was not obtained,

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ55
but the cyclotrisilazane compounds 4f and 4g formed are preserved. All cyclic and spirocyclic derivatives of
by subsequent substitution of Si–Cl bonds for Si–N 4 were crystallised and their molecular structures were
with the aliphatic amine group. Both 4f and 4g contain determined (see Section 3.3).
6-membered silazane rings in the centre supplemented
by three 2-aminobenzylamine moieties fused to this ring.
Both compounds, which are isomers, are obtained from 2.2.5 Syntheses with 5 and 5a
the same reaction batch and vary only in the arrangement
of the diamine moieties.
The results of the reactions with 5 are similar to the
Starting with 4a the synthesis of 4b-TMS2 is possible. reactions of 4. Starting with 5, the spirocyclic and
The trimethylsilyl moieties on the aliphatic amine N atom cyclic products 5b and 5c are obtained (Scheme 7). The
Scheme 6: Experiments with and reactions of 2-aminobenzylamine (4).
Scheme 7: Experiments with and reactions of 1,8-diaminonaphthalene (5).

ꢀ
56ꢀ
M. Herbig et al.
29
dichloro derivative 5d-TMS was synthesised, preserving 3.2 Si NMR data of the synthesised
one of the two trimethylsilyl groups from 5a. Further
condensation reactions (as encountered with derivatives
compounds
of 4) were not observed. One reason is the lower reactivity All successfully synthesised and isolated compounds
due to the absence of any aliphatic amine moiety in 5. have been characterised in various ways such as NMR-,
The compounds 5b, 5c, and 5d-TMS were crystallised Raman-, and mass spectroscopy as well as melting
and their molecular structures were determined points if possible. 29Si NMR data of the new compounds
(see Section 3.3).
are summarised in Table 1. In the literature, many other
ethylenediamine derivatives are known. Table 2 shows a
compilation of their 29Si NMR shifts. The comparison of
the 29Si NMR data is in support of the assignment of the
silicon containing moieties in the new products.
No data for comparison are known in literature for the
aminosilanes 1a, 2a, 3a, and 4a. Only for 5a the 29Si NMR
shift of 3.7 ppm (Gade et al., 2002) can be found, which
is close to the shift we recorded. The 29Si NMR shift for
3 Discussion
3.1 Discussion of the outcome of the
syntheses
Our current observations indicate that for the syntheses compound 4b found in literature has the value -48.9 ppm
of spiro-compounds with 6-membered rings the synthetic (Lange A., Cox G., Wolf H., Csihony S., Spange S., Kaßner L.
routestartingwiththeamine(methodA)ismorefavourable et al., 2014, Stickstoffhaltige Kompositmaterialien, deren
while compounds containing 5-membered rings should be Herstellung und Verwendung. World patent, 2015086461)
synthesised starting from the trimethylsilyl derivatives a andisalsoveryclosetothedataobtainedinourexperiment.
29
(method B). This fact can be explained with steric aspects. The Si NMR shifts of derivatives b, c, and d (cyclic and
If method B is applied for the synthesis of 4b, 4c, 5b, and spirocyclic compounds) reveal a clear difference between
5c side products are observed, as outlined in Schemes 6 6-membered and 5-membered rings. The silicon nuclei of
and 7. In fact, within the same reaction time, no indication derivatives of amines 1, 2, and 3 are less shielded while
29
of spirocyclic compounds b or c can be found in the NMR the Si NMR signals of derivatives of the amines 4 and 5
spectra. Nevertheless, using method A for the synthesis are high field shifted. All TMS moieties exhibit a chemical
of 5-membered silacycles, the formation of oligo- and shift similar to that of hexamethyldisilazane (2.4 ppm).
polymers as main products is indicated in the NMR spectra
by sets of very broad signals.
It must be pointed out that the synthesised spirocyclic 3.3 Molecular structures
aminosilanes show a tendency for polymerisation. So it
happened regularly, that an already isolated substance Compound 2b-TMS2 crystallises in the monoclinic space
formed a gelatinous compound shortly after being group C2/c with a half molecule in the asymmetric unit.
dissolved in solvents like CDCl3. Most likely, ring opening Compound 2d-TMS crystallises in the orthorhombic
reactions or further reactions with NH-functions took space group P212121 with one molecule in the asymmetric
place. Polymerisations were not further investigated, unit. The molecular structures are shown in Figures 3
since we were interested in the preparation of molecular and 4, essential geometric parameters in Table 3. The
compounds as precursors for insertion reactions. The 1,2-diaminobenzene units in both compounds carry one
results of insertion reactions will be reported in a trimethylsilylgroupeach. Thiswasalreadyconcludedfrom
forthcoming paper.
the NMR data. The bonds Si1–N1 are longer than the bonds
Table 1:ꢁ29Si NMR data of the synthesised compounds
Amine
Derivative a
Derivative b
Derivative c
Derivative d
1
2
3
4
5
3.7
15.3 (TMS: 1.6)
-24.6 (TMS: 4.2)
exact assignment impossible
-49.0
12.1 (TMS: 1.4)
15.1 (TMS: 2.1)
10.6 (TMS: -1.3)
-1.7
-18.6 (TMS: 6.2) (Böhme et al., 2007)
-23.5 (TMS: 6.8)
3.8
1.6
1.6, 5.5
3.6
-20.7 (TMS: 3.7)
derivative not synthesised
-37.5
-59.1
-5.6
TMS: Trimethylsilyl moieties.

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ57
Table 2:ꢁ29Si NMR data of compounds taken from literature
Amine Substituents on endocyclic Substituents Literature
Chemical shift of endocyclic Chemical shift of exocyclic
silicon atom
on N
silicon atom
silicon atom
2
2
2
1
1
1
1
1
1
1
1
1
Ph, Ph
H
Prout et al., 1994
11.8
-0.7
-18.1
14.0
-9.4
-18.6
-16.7
-17.4
-17.0
-15.2
-38.7
17.7
--
Ph, Me
H
Prout et al., 1994
--
Cl, Cl
TMS
TMS
TMS
TMS
SiMePh2
SiMe2Ph
Wagler and Roewer, 2007
Auner et al., 1992
Auner et al., 1992
Böhme et al., 2007
Wagler and Roewer, 2007
Diedrich et al., 2002
Diedrich et al., 2002
Diedrich et al., 2002
Diedrich et al., 2002
Diedrich et al., 2002
6.5
Me, CH(SiMe3)CH(Me)2
1.3 (NTMS), 3.0 (CTMS)
Vi, Ph
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, H
2.8
6.2
-8.4
-1.4
10.0
9.1
t
SiMe2 Bu
t
SiMe2 Bu
t
Br, Br
SiMe2 Bu
9.9
0.8
iPr, iPr
TMS
Figure 4: Molecular structure of 2d-TMS including numbering
scheme. The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level.
Figure 3: Molecular structure of 2b-TMS2 including numbering
scheme. The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level.
Si1–N2. This is attributed to the substitution of N1 with Table 3:ꢁSelected geometric parameters (Å, °) of 2b-TMS2 and 2d-TMS
the trimethylsilyl group. As a result of the five-membered
2b-TMS2
2d-TMS
1.7362(17) Si(1)–N(1)
1.7172(18) Si(1)–N(2)
1.7654(18) Si(1)–Cl(1)
Si(1)–Cl(2)
ring(s), the coordination sphere about silicon atom Si1 is
rather distorted tetrahedral. The intra-chelate bond angle
N1–Si1–N2 (93.06(8)° in 2b-TMS2 and 95.47(9)° in 2d-TMS)
is noticeably smaller than the other angles at Si1. All other
bond angles are expanded to values between 115.52(8)
to 121.31(12)° in 2b-TMS2 and 113.75(7)° to 115.48(6)° in
2d-TMS (see Table 3). The (N,N’-o-phenylenediamino)
silicon units (involving the atoms C1 to C6, N1, N2, and
Si1) are essentially planar in both molecules. The two
(N,N’-o-phenylenediamino)silicon units in 2b-TMS2
intersect at an angle of 83.32(4)°. This deviation from
orthogonality can be explained with the steric bulk of the
two trimethylsilyl groups within the molecule. However,
Si(1)–N(1)
Si(1)–N(2)
Si(2)–N(1)
1.7259(16)
1.6983(19)
2.0480(7)
2.0435(7)
Si(2)–N(1)
1.7756(17)
N(2)–Si(1)–N(1)
N(2)–Si(1)–N(1A) 115.52(8)
N(1A)–Si(1)–N(1) 120.78(13) N(1)–Si(1)–Cl(1) 114.43(6)
N(2A)–Si(1)–N(2) 115.52(8)
N(2A)–Si(1)–N(1)
N(1A)–Si(1)–N(1) 121.31(12) N(1)–Si(1)–Cl(2) 115.48(6)
N(2A)–Si(1)–N(2) 120.78(13)
N(1A)–Si(1)–N(1) 121.31(12) N(2)–Si(1)–Cl(1) 113.75(7)
N(2)–Si(1)–Cl(2) 114.54(7)
93.06(8)
N(2)–Si(1)–N(1)
Cl(2)–Si(1)–Cl(1) 103.68(3)
95.47(9)

ꢀ
58ꢀ
M. Herbig et al.
this value is very similar to the structural analogous thio
compound Si[S2(o-C6H4)]2, where partial planarisation
was already observed without additional substituents
(Herzog et al., 2000). Partial planarisation of the silicon
coordination sphere in spirocyclic tetrathiosilanes was
explained with the high s-character of the Si–S-bonds
(Wojnowski et al., 1985). The dihedral angle between the
(N,N’-o-phenylenediamino)silicon unit in 2d-TMS and
the plane Cl1–Si1–Cl2 is 89.89(3)°. The Si1–Cl bonds in
2d-TMS are 2.0480(7) and 2.0435(7) Å. These values are
very similar to the Si–Cl bonds in analogous compounds
(Böhme et al., 2007; Schlosser et al., 1994; Wagler and
Roewer, 2007).
R
R=SiMe ,
3
Ph,
N
Cl
Cl
CH -Ph,
2
Si
Si(Ph) Me
2
N
R
Figure 5: Previously published derivatives of 1d.
The single crystal structures of four derivatives
of 1d have been published previously, see Figure 5. In
2,2-dichloro-1,3-bis(trimethylsilyl)-1,3-diaza-2-silacyclopentane
(Böhme et al., 2007), 1,3-dibenzyl-2,2-dichloro-1,3-diaza-2-
silacyclopentane (Schlosser et al., 1994), and 2,2-dichloro-
1,3-bis(methyldiphenylsilyl)-1,3-diaza-2-silacyclopentane
(Wagler and Roewer, 2007) the ethylenediamine unit
(N–C–C–N) adopts a torsion angle of 32° to 34°. In contrast,
in 2,2-dichloro-1,3-diphenyl-1,3-diaza-2-silacyclopentane
this torsion angle is 0° due to a crystallographically
imposed Cs-symmetry (Schlosser et al., 1994).
Compound 3d-TMS2 has a similar topology like
derivatives of 1d. As the bond precision of this structure
suffers from disorder effects and thus does not contribute
to the discussion, this structure is presented in
Supplementary material only.
Figure 6: Molecular structure of 4b-TMS2 including numbering
scheme. The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level.
Table 4:ꢁSelected geometric parameters (Å, °) of 4b-TMS2
Compound 4b-TMS2 crystallises in the monoclinic
space group C2/c with a half molecule in the asymmetric
unit. The molecular structure is shown in Figure 6,
essential geometric parameters in Table 4. In accord
with NMR data, there is a trimethylsilyl group bound at
nitrogen atom N2. The coordination geometry at silicon
atom Si1 is roughly tetrahedral and, with bond angles
ranging from 102.00(6)° to 116.69(7)°, less distorted than
in case of compound 2b-TMS2. Unlike the latter, this
molecule bears two different kinds of amine moieties:
Si(1)–N(2)
1.7103(12)
1.7315(13)
1.7477(12)
113.64(8)
116.69(7)
102.00(6)
106.22(9)
Si(1)–N(1)
N(2)–Si(2)
N(2A)–Si(1)–N(2)
N(2A)–Si(1)–N(1)
N(2)–Si(1)–N(1)
N(1A)–Si(1)–N(1)
C(1)–N(1)–Si(1)
C(1)–N(1)–H(1)
Si(1)–N(1)–H(1)
C(7)–N(2)–Si(1)
C(7)–N(2)–Si(2)
123.29(10)
114.4(15)
114.9(15)
115.48(10)
113.87(9)
Si(1)–N(2)–Si(2) 125.69(7)
N1 bound to the aromatic ring whereas N2 is benzylic. trimethylsilyl groups might explain the deviation of
This and the different additional substituents cause both nitrogen atoms´ environments from planarity in
slightly different Si–N bond lengths for the central silicon order to fit into the conformation of the six-membered
atom Si1. The coordination spheres about the nitrogen ring. As to the latter, ring puckering analysis reveals a
atoms are noticeably planarised albeit not completely boat conformation for the ring containing the atoms
planar, as the sum of bond angles around nitrogen Si1–N1–C1–C6–C7–N2 with the parameters θ = 101.1(2)°,
atoms N1 and N2 are 352.59° and 355.04°, respectively. φ = 70.8(1)°, and a ring puckering amplitude Q = 0.549(2) Å.
This was rather unexpected for nitrogen atom N1, which Ideal parameters for a boat conformation are θ = 90.0°;
is substituted with a phenyl group and a silicon atom, φ = k . 60° (Cremer and Pople, 1975), (Boeyens, 1978). The
because with this substitution pattern it was expected presence of the CH2-group at C7 prevents the formation of
to be planar (Meinel et al., 2014, 2015). Further steric a planar 6-membered ring as it was found in 5b and 5c
requirements by the spirocycle and the additional (see below).

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New cyclic and spirocyclic aminosilanes
ꢀ59
Compound 5b co-crystallises with one unit of
triethylammonium chloride and one molecule of
chloroform per two molecules of 5b in the triclinic space
group P-1. Essential intermolecular interactions between
these components are summarised in the Supplementary
Information. Compound 5c crystallises in the monoclinic
space group P21/c. Two crystallographically independent
aminosilane molecules are present in the crystal structures
of both compounds. The molecular structures are shown
in Figures 7 and 8, essential geometric parameters
in Table 5. Since these have very similar geometric
parameters, only one molecule will be discussed here as
representative. No trimethylsilyl groups remained at the
nitrogen atoms of both molecules (see Figures 7 and 8).
The 1,8-diaminonaphthalene unit is bound to a silicon
atom via both nitrogen atoms, thus forming six-membered
diazasilacyclohexane rings. These heterocycles are planar
in both molecules. The dihedral angle between both
six-membered rings in 5b is 88.58(5)°. The Si–N bond
lengths in 5b range from 1.696(2) (Si1A–N4A) to 1.712(2) Å
(Si1A–N2A). This is rather short for Si–N-bonds and in
accord with sp2-hybridisation at the nitrogen atoms. Mean
bond lengths have been determined from X-ray structural
data with 1.713 Å for Si–N(sp2)- and 1.739 Å for Si–N(sp3)-
bonds (Kaftory et al., 1998). This view is supported by the
presence of planar nitrogen atoms in both molecules. The
silicon atoms in both molecules are located in distorted
tetrahedral coordination environments. The smallest
bond angles at silicon are found inside the six-membered
rings, i.e., 99.75(8)° for N1A–Si1A–N2A and 100.46(8)°
for N3A–Si1A–N4A of compound 5b; and 99.14(9)° for
Figure 7: Molecular structure of 5b including numbering scheme.
The thermal displacement ellipsoids of the non-hydrogen atoms are
drawn at the 50% probability level.
Figure 8: Molecular structure of 5c including numbering scheme.
The thermal displacement ellipsoids of the non-hydrogen atoms are
drawn at the 50% probability level.
N1A–Si1A–N2A of compound 5c. All other angles at the Table 5:ꢁSelected geometric parameters (Å, °) of 5b and 5c
silicon atoms in 5b and 5c range between 110° and 115°.
5b
5c
Compound 5d-TMS crystallises in the monoclinic
space group P21/c with one molecule in the asymmetric
unit. The molecular structure is shown in Figure 9,
essential geometric parameters in Table 6. The
1,8-diaminonaphthalene unit is bound via both nitrogen
atoms at silicon atom Si1 forming a planar six-membered
diazasilacyclohexane ring. One additional trimethylsilyl
group is located at nitrogen atom N1. This was already
concluded from the NMR data. The Si1–Cl bond lengths
are 2.0462(5) and 2.0470(5) Å. These values are similar
to the Si–Cl bonds in 2d-TMS. The Si-N bond lengths in
Si(1A)–N(1A)
Si(1A)–N(2A)
Si(1A)–N(3A)
Si(1A)–N(4A)
1.7036(16) Si(1A)–N(1A)
1.7123(17) Si(1A)–N(2A)
1.7035(17) Si(1A)–C(11A)
1.6965(16) Si(1A)–C(12A)
1.7217(18)
1.7220(19)
1.849(3)
1.848(2)
N(1A)–Si(1A)–N(2A) 99.75(8)
N(1A)–Si(1A)–N(2A)
99.14(9)
N(3A)–Si(1A)–N(1A) 115.48(9) C(12A)–Si(1A)–C(11A) 109.31(14)
N(3A)–Si(1A)–N(2A) 113.65(9) N(1A)–Si(1A)–C(11A) 112.38(11)
N(4A)–Si(1A)–N(1A) 115.46(8) N(2A)–Si(1A)–C(11A) 110.75(11)
N(4A)–Si(1A)–N(2A) 112.74(8) N(1A)–Si(1A)–C(12A) 110.63(10)
N(4A)–Si(1A)–N(3A) 100.46(8) N(2A)–Si(1A)–C(12A) 114.38(12)
5d-TMS are 1.6977(12) (Si1–N1) and 1.6702(13) Å (Si1–N2). Cl1–Si–Cl2 with 103.21(2)°. This is a very similar value as
This is rather short for Si–N-bonds and hints again at in compound 2d-TMS. The bond angle N1–Si1–N2 within
sp2-hybridisation at the nitrogen atoms (see discussion the six-membered diazasilacyclohexane ring is 107.29(6)°.
above). The bond Si2–N1 to the trimethylsilyl group is This is larger than the corresponding bond angles in 5b
substantially longer with 1.7871(12) Å. The coordination and 5c with values at 99°. The dihedral angle between
geometry at silicon atom Si1 can be interpreted as the diazasilacyclohexane ring and the plane Cl1–Si1–Cl2
distorted tetrahedral. The smallest bond angle is is 86.613(3)°.

ꢀ
60ꢀ
M. Herbig et al.
Figure 9: Molecular structure of 5d-TMS including numbering
scheme. The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level. The methyl groups at
C11 and C12 are rotationally disordered. Their alternative positions
C11A and C12A have been omitted for clarity.
H
N
Si
N
Si
N
Si
N
H
Table 6:ꢁSelected geometric parameters (Å, °) of 5d-TMS
Figure 10: Molecular structure of 4e including numbering scheme
(top). The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level. Schematic formula
drawing of 4e (bottom).
Cl(1)–Si(1)
2.0462(5)
2.0470(5)
1.6977(12)
1.6702(13)
1.7871(12)
107.29(6)
103.21(2)
110.69(5)
113.37(4)
108.53(5)
113.70(4)
Cl(2)–Si(1)
Si(1)–N(1)
Si(1)–N(2)
Si(2)–N(1)
N(2)–Si(1)–N(1)
Cl(1)–Si(1)–Cl(2)
N(2)–Si(1)–Cl(1)
N(1)–Si(1)–Cl(1)
N(2)–Si(1)–Cl(2)
N(1)–Si(1)–Cl(2)
Table 7:ꢁSelected geometric parameters (Å, °) of 4e
Si(1)–N(1)
1.737(2)
1.724(2)
1.867(2)
1.866(2)
102.58(8)
111.75(9)
112.01(10) N(3)–Si(2)–C(18)
115.80(9) N(4)–Si(2)–C(17)
106.88(10) N(3)–Si(2)–C(17)
Si(2)–N(3)
1.745(2)
Si(1)–N(2)
Si(2)–N(4)
1.729(2)
Si(1)–C(15)
Si(1)–C(16)
N(2)–Si(1)–N(1)
N(2)–Si(1)–C(15)
N(1)–Si(1)–C(15)
N(2)–Si(1)–C(16)
N(1)–Si(1)–C(16)
Si(2)–C(17)
Si(2)–C(18)
N(4)–Si(2)–N(3)
N(4)–Si(2)–C(18)
1.858(2)
1.863(2)
101.52(8)
113.51(9)
112.83(9)
113.39(10)
109.10(10)
Compound 4e crystallises in the monoclinic space
group I2/c with one molecule in the asymmetric unit. The
overall composition of this molecule is surprising: Six-
membereddiazasilacyclohexaneringshaveformed, butan
additional dimethylsilyl group bridges two such units via
the benzylamino nitrogen atoms N2 and N4 (see Figure 10).
All three silicon atoms are situated in distorted tetrahedral
coordination spheres. The smallest bond angles at silicon
are found inside the diazasilacyclohexane rings with
102.6(1)° for N2–Si1–N1 and 101.5(1)° for N4–Si2–N3
C(15)–Si(1)–C(16) 107.71(10) C(18)–Si(2)–C(17) 106.54(11)
N(2)–Si(3)
N(4)–Si(3)
Si(3)–C(19)
Si(3)–C(20)
1.737(2)
1.740(2)
1.860(2)
1.863(2)
N(2)–Si(3)–N(4)
N(2)–Si(3)–C(19)
N(4)–Si(3)–C(19)
N(2)–Si(3)–C(20)
N(4)–Si(3)–C(20)
110.82(8)
108.57(9)
108.73(10)
110.02(10)
108.61(9)
C(19)–Si(3)–C(20) 110.09(12)
(Table 7). The other bond angles at Si1 and Si2 adopt values The coordination sphere of silicon atom Si3 has a more
between 106.5(2)° and 115.8(1)°. Interesting in this context “relaxed” geometry with bond angles between 108.6(1)°
is the comparison between coordination geometries of the to 110.8(1)°, which is close to the angles of an ideal
silicon atoms Si1 and Si2, which are part of six-membered tetrahedron (109.5°). The Si–C bonds in this molecule
rings, and the silicon atom Si3, which is not part of a ring. have lengths close to 1.860 Å, which is the mean bond

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ61
length for such bonds (Kaftory et al., 1998). There are two analysis (see Table 9) shows that the silazane ring is in
different types of nitrogen atoms in 4e: The atoms N1 and twist-boat conformation while the fused non-aromatic
N3 are bound each to an aromatic ring, to one hydrogen rings are in boat or screw-boat conformation. Compound
atom, and to one silicon atom. The atoms N2 and N4 are 4g crystallises in the monoclinic space group P21/n with
bound each to two different silicon atoms and a CH2-
group. This has implications for the bond lengths from
these nitrogen atoms. The bonds Si1–N1, Si2–N3, Si3–N2,
Table 8:ꢁSelected geometric parameters (Å, °) of 4f and 4g
and Si3–N4 have lengths around 1.74 Å. This corresponds
to Si-N(sp3) bonds (Kaftory et al., 1998). The bonds Si1–
N2 and Si2–N4 are slightly shorter with lengths of 1.724(2)
and 1.729(2) Å, respectively.
4f
4g
Cl(1)–Si(1)
Cl(2)–Si(2)
Cl(3)–Si(3)
Si(1)–N(2)
Si(1)–N(1)
Si(1)–N(6)
Si(2)–N(3)
Si(2)–N(4)
Si(2)–N(2)
Si(3)–N(4)
Si(3)–N(6)
Si(3)–N(5)
N(2)–Si(1)–N(1)
N(2)–Si(1)–N(6)
N(1)–Si(1)–N(6)
N(2)–Si(1)–Cl(1)
N(1)–Si(1)–Cl(1)
N(6)–Si(1)–Cl(1)
N(3)–Si(2)–N(4)
N(3)–Si(2)–N(2)
N(4)–Si(2)–N(2)
N(3)–Si(2)–Cl(2)
N(4)–Si(2)–Cl(2)
N(2)–Si(2)–Cl(2)
N(4)–Si(3)–N(6)
N(4)–Si(3)–N(5)
N(6)–Si(3)–N(5)
N(4)–Si(3)–Cl(3)
N(6)–Si(3)–Cl(3)
N(5)–Si(3)–Cl(3)
2.0629(8)
2.0736(7)
2.0625(8)
1.6979(18)
1.7047(18)
1.7050(19)
1.7000(19)
1.7041(17)
1.7050(17)
1.6960(17)
1.6994(19)
1.7089(19)
104.57(9)
109.02(9)
117.97(9)
112.74(7)
106.58(7)
106.12(7)
104.72(9)
115.51(9)
109.43(8)
106.45(7)
112.93(6)
107.89(7)
111.35(9)
117.43(9)
103.84(9)
106.05(7)
113.30(7)
104.94(8)
Cl(1)–Si(2)
Cl(2)–Si(3)
Cl(3)–Si(3)
Si(1)–N(5)
Si(1)–N(1)
Si(1)–N(2)
Si(1)–N(6)
Si(2)–N(3)
Si(2)–N(2)
Si(2)–N(4)
Si(3)–N(4)
Si(3)–N(6)
2.0644(15)
2.0435(16)
2.0410(15)
1.706(4)
1.706(4)
1.712(4)
1.729(4)
1.684(4)
1.710(4)
1.715(4)
The aromatic rings C1–C6 and C8–C13 are planar. The
six-membereddiazasilacyclohexaneringsarefusedtothese.
Conformational analysis has been performed. This reveals a
boat conformation for the ring containing the atoms Si1–N1–
C1–C6–C7–N2 with the parameters θ = 77.4(4)°, φ = 244.0(4)°,
and a ring puckering amplitude Q = 0.430(3) Å. Ideal
parameters for a boat conformation are θ = 90.0°; φ = k . 60°
(Boeyens, 1978; Cremer and Pople, 1975). The six-membered
ringwiththeatomsSi2-N3-C8-C13-C14-N4hastheparameters
θ = 65.7(3)°, φ = 269.3(3)°, and a ring puckering amplitude
Q = 0.595(3) Å. This corresponds to a screw-boat
conformation with ideal parameters θ = 67.5° and
φ = k . 60° + 30°.
On the attempt to synthesise compound 4d, two
unexpected compounds crystallised: 4f and 4g. Selected
geometric parameters can be found in Table 8. Both
compounds are structural isomers with a six-membered
silazane ring in the centre. The nitrogen atoms of the
2-aminobenzylamino units (N2, N4, N6) are integrated into
the silazane ring. Isomer 4f crystallises in the monoclinic
space group P21/c with one molecule in the asymmetric
unit (see Figure 11). The compound co-crystallises with
one molecule diethyl ether. The coordination geometries
at the silicon atoms of 4f are roughly tetrahedral with bond
angles between 103.84(9)° and 117.97(9)°. The bond lengths
of the Si–N (about 1.70 Å) bonds and the Si–Cl bonds (about
2.06 Å) are quite similar to the corresponding bonds of the
other structures discussed in this paper. Ring-puckering
1.679(4)
1.699(4)
N(5)–Si(1)–N(1)
N(5)–Si(1)–N(2)
N(1)–Si(1)–N(2)
N(5)–Si(1)–N(6)
N(1)–Si(1)–N(6)
N(2)–Si(1)–N(6)
N(3)–Si(2)–N(2)
N(3)–Si(2)–N(4)
N(2)–Si(2)–N(4)
N(3)–Si(2)–Cl(1)
N(2)–Si(2)–Cl(1)
N(4)–Si(2)–Cl(1)
N(4)–Si(3)–N(6)
N(4)–Si(3)–Cl(3)
N(6)–Si(3)–Cl(3)
N(4)–Si(3)–Cl(2)
N(6)–Si(3)–Cl(2)
108.21(19)
120.72(19)
101.92(17)
101.82(17)
120.15(19)
105.20(17)
115.94(18)
103.63(18)
110.75(17)
108.03(14)
107.51(12)
110.95(13)
108.23(17)
110.72(13)
111.77(13)
110.32(14)
111.59(12)
Cl(3)–Si(3)–Cl(2) 104.21(7)
Table 9:ꢁRing puckering analysis of structures 4f and 4g
molecule
ring atoms
Θ [°]
φ [°]
Q [Å]
conformation
4f
Si(1)–N(2)–Si(2)–N(4)–Si(3)–N(6)
Si(1)–N(2)–C(7)–C(6)–C(1)–N(1)
Si(2)–N(4)–C(14)–C(13)–C(8)–N(3)
Si(3)–N(6)–C(21)–C(20)–C(15)–N(5)
Si(1)–N(2)–Si(2)–N(4)–Si(3)–N(6)
Si(1)–N(2)–C(7)–C(6)–C(1)–N(1)
Si(1)–N(6)–C(21)–C(20)–C(15) –N(5)
Si(2)–N(4)–C(14)–C(13)–C(8)–N(3)
107.9(2)
110.1(2)
103.64(19)
70.4(2)
260.1(2)
79.3(2)
0.3312(13)
0.532(2)
0.586(2)
0.557(2)
0.644(3)
0.545(4)
0.578(4)
0.554(4)
twist–boat
twist–boat
boat
screw–boat
boat
screw–boat
boat
boat
72.95(18)
260.7(2)
108.6(2)
258.5(4)
247.4(4)
245.8(4)
4g
93.4(3)
71.8(4)
79.0(4)
82.1(4)

ꢀ
62ꢀ
M. Herbig et al.
two independent silazane molecules in the asymmetric
unit (see Figure 12). Only one of the two silazane
molecules in the asymmetric unit of 4g is discussed in the
further course. The constitution of 4f is more symmetric
than the constitution of 4g. Both substances differ in
the topology of one 2-aminobenzylamino moiety. One
2-aminobenzylamino moiety is inverted with respect to
the topology of 4f. This results in silicon atoms with three
different coordination spheres in the structure of 4g. Si1 is
bound to four nitrogen atoms (marked green in Figure 12)
and has the most distorted tetrahedral coordination
geometry with bond angles from 101.82(17)° to 120.72(19)°.
Si2 is bound to one chlorine atom and three nitrogen
atoms (marked blue in Figure 12). This atom features a
more “relaxed” tetrahedral geometry with bond angles
between 103.63(18)° and 115.94(18)°. The atom Si3 is
bound to two chlorine and two nitrogen atoms (marked
red in Figure 12). The coordination geometry of this atom
is even less distorted with bond angles between 104.21(7)°
and 111.77(13)°. The Si-N bond length decreases with the
increasing degree of chlorine substitution. Ring puckering
analyses shows that the silazane ring is in twist-boat
conformation while the fused non-aromatic rings have
screw-boat or boat conformation (see Table 9).
NH
Si Cl
N
Cl
HN Si
N
N
Si
HN
Cl
Figure 11: Molecular structure of 4f including numbering scheme
(top). The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level. Schematic formula
drawing of 4f (bottom).
3.4 Quantum chemical calculations
For a better understanding of the preferred number of
TMS moieties remaining in the synthesised molecules
(when starting from amines 1a-5a), quantum chemical
calculations were performed. As example, the
trimethylsilylation of compounds 2b (as a representative
with 5-membered ring) and 4b (as a representative with
6-membered ring) with hexamethydisilazane (HMDS)
were compared (Scheme 8). The results are shown in
Table 10. This hypothetical reaction has been chosen,
since it is an isodesmic reaction in which the total number
of each bond type is identical in the reactants and products
H
N
NH
Cl
HN Si
Si
N
Si
N
N
Cl
Cl
Figure 12: Molecular structure of 4g including numbering scheme
(top). The thermal displacement ellipsoids of the non-hydrogen
atoms are drawn at the 50% probability level. Schematic formula
drawing of 4g (bottom). The bonding situation of the silicon atoms
is colour coded (see text for explanation).
Scheme 8: The model reaction used for comparison of the relative
stability of different silylation states of 2b with quantum chemical
calculations. The reaction of 2b → 2b-TMS2 is shown here as an
example.

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ63
Table 10:ꢀCalculated Gibbs free energies and enthalpies for the
silylation reactions of 2b and 4b with HMDS, calculated at the
M062X/6-31G(d) level in THF solution with the PCM model
in case of the derivatives of 1 and 2, which feature
5-membered rings. Therefore, the energy necessary for
the planarisation of 1b has been calculated with quantum
chemical methods. The planar form has D2d symmetry
and is 6.1 kJ/mol higher in Gibbs free energy than the
same compound with bent ethylene diamine units (for
details see Supplementary material). In contrast to that,
the global minimum for compound 2b is planar on both
(N,N’-o-phenylenamino)silicon units. The annelation
of the phenylene group makes the planar form more
favourable. This was indeed observed in the solid state
structures of 2b-TMS2 and 2d-TMS.
Model reaction
Gibbs free energy
(kJ/mol)
Enthalpy
(kJ/mol)
Reactions of 2b
2b → 2b-TMS2
2b-TMS2 → 2b-TMS4
2b→ 2b-TMS4
-6.2
-21.9
-28.1
-15.8
-27.1
-42.9
Reactions of 4b
4b → 4b-TMS2 (aliph.)
4b → 4b-TMS2 (arom.)
4b-TMS2 (aliph.) → 4b-TMS4
4b-TMS2 (arom.) → 4b-TMS4
4b → 4b-TMS4
15.6
72.4
58.3
1.5
-1.7
49.7
33.8
-17.5
32.1
Further on, the stabilities of the two isomers 4f and 4g
were compared on the B3LYP/6-31G(d) level of theory. At
298 K (1 atm) the less symmetric derivative 4g is 14.2 kJ/mol
lower in energy. This small energy difference can be
73.9
(Foresmann and Frisch, 2015). Isodesmic reactions are overcome by solvation effects and crystallisation energies.
useful to predict ΔH and ΔG of chemical reactions. In effect both isomers crystallised side by side from one
It is obvious that the silylation of 2b is exergonic in all reaction batch.
reactions. Therefore, it must be assumed, that the sterical
hindrance of the TMS moieties prevents the formation of
2b-TMS4. Instead 2b-TMS2 is formed in our experiments.
4 Comparative reflections and
Additionally, all silylation reactions of 4b are endergonic.
The silylation of the aliphatic nitrogen atoms is less
endergonic than the silylation of the aromatic nitrogen
conclusions
atoms. The silylation reaction of the aliphatic nitrogen As a result of the accomplished experiments, the
atoms is only slightly endergonic (15.6 and 1.5 kJ/mol, aminosilanes 1a-5a, spirocyclic aminosilanes 1b-5b,
respectively).
and several other cyclic aminosilanes were successfully
Further effects might play a role in the experiments synthesised, isolated, and characterised. Spirocyclic
which have been performed in the laboratory. These aminosilanes with six-membered rings were obtained only
are for instance: reaction conditions like boiling under from direct reactions of the amines with tetrachlorosilane
reflux, thus fostering the formation of the volatile Me3SiCl, (method A). Spirocyclic aminosilanes with five-membered
solvation effects, solubility of formed intermediates, or rings are obtained from reactions of tetrachlorosilane with
crystallisation enthalpies of products. All these effects trimethylsilyl substituted amines (method B).
are not taken into account in the model reaction used
Comparison of the angles N–Si–N in the crystal
for the calculations. The calculated Gibbs enthalpy, structures show smaller angles in the five-membered rings
which is slightly positive, could be turned to a negative than in the six-membered rings, as one would expect.
value by such effects. This explains why 4b-TMS2 could Derivatives b, the spirocyclic compounds, exhibit smaller
be crystallised. In accord with the preferred retention of bite angles than the derivatives c and d. The TMS moieties
SiMe3 groups at the aliphatic amine N atoms, the silicon widen that angle. This could explain why derivatives
atom of the bridging SiMe2 moiety in 4e is also bound to of amines 1-3 only could be synthesised by method B.
the benzylamine N atoms, and cyclosilazane formation The wider angle N–Si–N lowers the ring-strain in the
via benzylamine N atoms in 4f and 4g indicates the same products. Additionally, the steric hindrance caused by
trend. The results of the quantum chemical calculations the TMS moieties lowers the tendency of polymerisation.
of both example systems show the stabilising effect Furthermore, the TMS moieties lower the nucleophilicity
of TMS moieties to five-membered ring systems and of the lone pair of the nitrogen atom, thus suppressing
the destabilising effect on six-membered rings. These side reactions, and the cyclic products can be obtained.
results are in agreement with the observed preparative
accessibility of spirocyclic compounds.
It was surprising, that the degree of substitution with
trimethylsilyl groups differs noticeably between the final
Furthermore, we were interested to understand the products. Quantum chemical calculations gave insight
occurrence of planar and nonplanar ring conformations into the thermodynamic reasons for this phenomenon.

ꢀ
64ꢀ
M. Herbig et al.
The degree of substitution with trimethylsilyl groups filtered through a fritted glass filter (G4), and the solid was
depends on the ring size of the spirocycles: Trimethylsilyl washed with THF (2 × 20 mL). From the combined filtrate
groups have a stabilising effect on five-membered ring and washings all volatile compounds were removed by
systems and a destabilising effect on six-membered rings distillation under reduced pressure. The residue (10.35 g,
in this type of compounds.
89%) was an orange liquid which was identified as N,N’-
The prepared compounds are useful as substrates for bis(trimethylsilyl)-1,2-diaminobenzene (2a).
further investigations. These might be insertion reactions
with carbon dioxide and with other heteroallenes
N,N’-Bis(trimethylsilyl)-1,2-ethylenediamine (1a)
into Si–N bonds, ring opening polymerisations, or the
1
NMR solvent: CDCl3. H NMR: δ [ppm] = -0.04 (s, 18 H,
preparation of macrocyclic ligands in the coordination
SiMe3), 0.58 (s, 2 H, NH), 2.59 (s, 4 H, CH2). 13C NMR:
sphere of silicon.
29
δ [ppm] = -0.1 (SiMe3), 45.7 (CH2). Si NMR: δ [ppm] = 3.7.
bp: 35°C (0.35 mbar).
Experimental
N,N’-Bis(trimethylsilyl)-1,2-diaminobenzene (2a)
1
All reactions were carried out under argon using NMR solvent: CDCl3. H NMR: δ [ppm] = 0.21 (s, 18 H,
Schlenk technique (Böhme, 2020; Herzog and Dehnert, SiMe3), 3.06 (s, 2 H, NH), 6.71 (m, 2 H, Ar), 6.80 (m, 2 H,
1964). NMR spectra were recorded in CDCl3 or C6D6 with Ar). 13C NMR: δ [ppm] = 0.4 (SiMe3), 119.7, 120.2, 137.6 (Ar).
TMS as internal standard either on a BRUKER DPX 29Si NMR: δ [ppm] = 3.8. Raman: ν [cm-1] = 3367 (vw), 3059
400 spectrometer at 400.13, 100.61, and 79.49 MHz for (w), 2958 (m), 2899 (vs), 1598 (w), 1499 (vw), 1410 (vw),
1H, 13C, and 29Si, or on a BRUKER AVANCE III 500 MHz 1300 (vw), 1250 (vw), 1189 (vw), 1156 (vw), 1044 (w), 920
1
13
spectrometer at 500.13, 125.76, and 99.36 MHz for H, C, (vw), 827 (vw), 780 (vw), 740 (vw), 689 (vw), 616 (m). MS:
and 29Si, respectively. Raman spectra were measured with m/z = 253.2 g/mol [M+H]+. bp: 236°C (975 mbar).
a FT-Raman spectrometer RFS/100S from BRUKER using
an air-cooled Nd:YAG-laser with a wavelength of 1064 nm
N,N’-Bis(trimethylsilyl)-( )-trans-1,2-
and a nitrogen-cooled germanium detector. Melting points
diaminocyclohexane (3a)
were measured using a Polytherm A hot stage microscope
The substance was synthesised like 2a using 9.51 g
from Wagner and Munz with an attached 52II thermometer
(83 mmol) 3, 16.95 g (167 mmol) NEt3 and, 18.10 g
from Fluke. The measurement of boiling points was
(167 mmol) Me3SiCl. The reaction and workup afforded a
performed with an apparatus which has been published
colourless liquid (14.34 g, 67%).
by Herbig and Kroke (2017). Mass spectra were recorded
1
NMR solvent: CDCl3. H NMR: δ [ppm] = 0.00 (s, 18
on a expressionL CMS from Advion using ESI (sample
H, SiMe3), 0.67 (s, 2 H, N–H), 1.03 (m, 2 H, ring), 1.19 (m,
was dissolved in acetonitrile). The setup for cryoscopy is
2 H, ring), 1.57 (m, 2 H, ring), 1.81 (m, 2 H, ring), 2.15 (d,
described in the Supplementary material (section S5).
3
13
2 H, JH,H = 7.0 Hz). C NMR: δ [ppm] = 0.9 (SiMe3), 25.5,
36.7, 58.8 (ring). 29Si NMR: δ [ppm] = 1.6. Raman: ν [cm-1] =
2954 (m), 2939 (m), 2897 (vs), 2856 (m), 1445 (vw),
1408(vw),1347(vw),1114(vw),1044(vw),849(vw),784(vw),
742 (vw), 685 (vw), 617 (m). MS: m/z = 259.23 g/mol [M+H]+.
bp: 229°C (975 mbar).
Synthesis of trimethylsilylated amines
The synthesis of the trimethylsilylated derivatives 1a-5a
is shown for compound 2a as example. The other four
substances are synthesised in the same manner. Variation
from this general method are pointed out in the paragraph N,N’-Bis(trimethylsilyl)-2-aminobenzylamine (4a)
of the related compound.
The substance was synthesised like 2a using 5.00 g
In a 2-necked round-bottomed flask, 5.01 g (46 mmol) (41 mmol) 4, 8.40 g (83 mmol) NEt3, and 9.00 g (83 mmol)
of o-phenylenediamine and 9.42 g (93 mmol) triethylamine Me3SiCl. The reaction and workup afforded a yellow liquid
were dissolved in about 150 mL of dry THF. The solution (6.48 g, 59%).
was stirred while cooling in an ice-water bath, and
1
NMR solvent: CDCl3. H NMR: δ [ppm] = 0.12 (s, 9 H,
10.00 g (92 mmol) Me3SiCl were added to the mixture SiMe3–NAr), 0.30 (s, 9 H, SiMe3-NAliph), 0.51 (s, 1H, NAliph–H),
3
dropwise. After complete addition, the suspension was 3.84 (d, 2 H, JH,H = 6.0 Hz, CH2), 5.20 (s, 1 H, NAr–H), 6.65
heated under reflux for 2 h, followed by stirring at room (m, 1 H, Ar), 6.77 (m, 1 H, Ar), 7.02 (m, 1 H, Ar), 7.08 (m, 1 H,
temperature overnight. Thereafter, the suspension was Ar). 13C NMR: δ [ppm] = -0.4 (SiMe3–NAr), 0.4 (SiMe3-NAliph),

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New cyclic and spirocyclic aminosilanes
ꢀ65
45.5 (CH2), 115.9, 117.1, 128.1, 128.1, 129.5, 147.3 (Ar). 29Si NMR: ice-water bath, 2.13 g (17 mmol) Me2SiCl2 was added
δ[ppm]=1.6(SiMe3–NAliph),5.5(SiMe3–NAr).Raman:ν[cm-1]= dropwise. The reaction mixture was heated under reflux
3056 (w), 2957 (m), 2898 (vs), 1606 (vw), 1583 (vw), 1496 for 2 h, followed by stirring at room temperature overnight.
(vw), 1458 (vw), 1410 (vw), 1296 (vw), 1248 (vw), 1187 The resulting suspension was filtered through a fritted
(vw), 1158 (vw), 1045 (w), 915 (vw), 840 (vw), 776 (vw), glass filter (G4), and the solid was washed with dry THF
749 (vw), 708 (vw), 690 (vw), 626 (m), 603 (w), 553 (vw), (2 × 20 mL). From the combined filtrate and washings all
432 (vw). MS: m/z = 267.65 g/mol [M+H]+. bp: >300°C volatile compounds were removed by distillation under
(974 mbar).
reduced pressure. Further purification steps are pointed
out below.
N,N’-Bis(trimethylsilyl)-1,8-diaminonaphthalene (5a)
The substance was synthesised like 2a using 7.30 g
(46 mmol) 5, 9.33 g (92 mmol) NEt3, and 10.50 g (97 mmol)
Me3SiCl. The reaction and workup yielded a dark red solid
(12.52 g, 90%).
Synthesis of derivatives d – example 1d
In dry THF (100 mL), 3.27 g (16 mmol) 1a and 3,63 g
(36 mmol) triethylamine were dissolved. While cooling
in an ice-water bath, 2.9 g (17 mmol) SiCl4 was added
dropwise. The reaction mixture was heated under reflux
for 2 h, followed by stirring at room temperature overnight.
The resulting suspension was filtered through a fritted
glass filter (G4), and the solid was washed with dry THF
(2 × 20 mL). From the combined filtrate and washings all
volatile compounds were removed by distillation under
reduced pressure. Further purification steps are pointed
out below.
1
NMR solvent: CDCl3. H NMR: δ [ppm] = 0.23 (s, 18 H,
SiMe3), 5.49 (s, 2 H, N–H), 6.65 (m, 2 H, Ar), 7.14 (m, 2 H, Ar),
7.21 (m, 2 H, Ar). 13C NMR: δ [ppm] = 0.1 (SiMe3), 115.4, 120.4,
29
121.3, 125.7, 137.4, 144.4 (Ar). Si NMR: δ [ppm] = 3.6. MS:
m/z = 302.40 g/mol [M]+. mp: 42-44°C.
Synthesis of cyclic and spirocyclic compounds
(derivatives b, c, and d)
For the synthesis of cyclic and spirocyclic compounds,
two methods are used: method A starts from the amines
1-5 and method B starts from the bis-trimethylsilylated
derivatives 1a-5a. To synthesise the different derivatives,
the composition of the reaction mixtures is varied. First,
the preparation of 1b, 1c, and 1d are given as examples.
All following syntheses differ in the workup of the
products. Therefore, the workup procedures are given in
the subsequent sections for each compound individually.
spiro-Bis(N,N’-1,2-ethylene-bis-(trimethylsilylamino))
silane (1b-TMS4)
This compound was synthesised by using method B:
60 mL dry n-heptane, 2.50 g (12 mmol) 1a, 2.40 g
(24 mmol) NEt3, 1.00 g (6 mmol) SiCl4 were used. The silicon
tetrachloride was also dissolved in dry n-heptane (20 mL).
The mixture was heated for 7 h. The compound received
after removing volatiles in vacuo was recrystallised from
n-pentane yielding a yellow substance (2.40 g, 40%).
The obtained compound contains four trimethylsilyl
moieties.
Synthesis of derivatives b – example 1b
In dry n-heptane (80 mL), 2.43 g (12 mmol) 1a and 2.38 g
NMR solvent: CDCl3. 1H NMR: δ [ppm] = 0.07 (s, 36 H,
(24 mmol) triethylamine were dissolved. While cooling in SiMe3), 3.02 (s, 8 H, CH2). 13C NMR: δ [ppm] = -0.2 (SiMe3),
an ice-water bath, a solution of 1.02 g (6 mmol) SiCl4 in 43.8 (CH2). 29Si NMR: δ [ppm] = 1.7 (SiMe3), 15.3 (Si). Raman:
about 20 mL of n-heptane was added dropwise. Thereafter, ν [cm-1] = 2956 (s), 2897 (vs), 2863 (w), 2682 (vw), 1471 (vw),
the reaction mixture was heated under reflux for 7 h, 1411 (vw), 1254 (vw), 1230 (vw), 838 (vw), 750 (vw), 684
followed by stirring at room temperature overnight. The (vw), 634 (w), 460 (w). MS: m/z = 433.33 g/mol [M+H]+.
resulting suspension was filtered through a fritted glass mp: 131°C.
filter (G4), and the solid was washed with dry n-heptane
(2 × 20 mL). From the combined filtrate and washings all
(N,N’-1,2-ethylene-bis-(trimethylsilylamino))
volatile compounds were removed by distillation under
dimethylsilane (1c-TMS2)
reduced pressure. Further purification steps are pointed
This compound was synthesised by using method B:
out below.
3.25 g (16 mmol) 1a, 3.7 g (36 mmol) NEt3, 2.13 g (17 mmol)
Me2SiCl2, and 70 mL THF as solvent were used. The silicon
Synthesis of derivatives c – example 1c
tetrachloride was used neat. The mixture was heated for
In dry THF (70 mL), 3.25 g (16 mmol) 1a and 3.7 g (36 mmol) 4 h. The compound received after removing volatiles in
triethylamine were dissolved. While cooling in an vacuo was distilled at 0.2 mbar (bp = 35°C), yielding a

ꢀ
66ꢀ
M. Herbig et al.
colourless liquid (1.794 g, 43%). The obtained compound N,N’-(N-trimethylsilyl-o-phenylenediamino)
contains two trimethylsilyl moieties.
dimethylsilane (2c-TMS)
NMR solvent: CDCl3. 1H NMR: δ [ppm] = 0.08 (s, 18 H, This compound was synthesised by using method
13
SiMe3), 0.13 (s, 6 H, SiMe2), 3.00 (s, 4 H, CH2). C NMR: B: 4.99 g (20 mmol) 2a, 4.05 g (40 mmol) NEt3, 3.40 g
δ [ppm] = 0.4 (SiMe3), 3.7 (SiMe2), 46.9 (CH2). 29Si NMR: (20 mmol) Me2SiCl2, and THF (80 mL) as solvent were
δ [ppm] = 1.4 (2 Si, SiMe3), 12.8 (1 Si, SiMe2). Raman: used. A light brown compound mixture of the product and
ν [cm-1] = 2955.0 (m), 2899.0 (vs), 2836.0 (w), 2662.0 triethylammonium chloride was yielded. The obtained
(vw), 1464.0 (vw), 1409.0 (vw), 1351.0 (vw), 1249.0 (vw), compound contains one trimethylsilyl moiety.
1
1222.0 (vw), 1075.0 (vw), 749.0 (vw), 703.0 (vw), 626.0
NMR solvent: CDCl3. H NMR: δ [ppm] = 0.32 (s, 9 H,
(vw), 523.0 (m), 369.0 (vw), 346.0 (vw), 327.0 (vw), SiMe3), 0.36 (s, 6H, SiMe2), 6.51-6.73 (m, 4H, Ar). 13C NMR:
288.0 (vw), 248.0 (vw), 180.0 (vw), 120.0 (vw). MS: δ [ppm] = 0.9 (SiMe3), 4.6 (SiMe2), 110.5, 113.4, 117.0, 118.6
261 g/mol [M+H]+. bp: 210°C (963 mbar). molecular (Ar), 140.0, 142.1(Aripso). 29Si NMR: δ [ppm] = 15.1 (SiMe2), 2.1
mass: cryoscopy (see Supplementary material) calc. (SiMe3). Raman: ν [cm-1] = 3252 (vw), 3233 (vw), 3057 (m),
206 g/mol, found 240 g/mol.
2998 (m), 2980 (s), 2901 (m), 1594 (m), 1557 (w), 1505 (w),
1480 (w), 1464 (m), 1366 (w), 1337 (w), 1277 (m), 1160 (w),
1034 (s), 905 (w), 763 (m), 705 (w), 687 (w), 614 (w), 579
(w), 550 (w), 502 (w), 464 (w), 344 (w), 331 (w), 203 (m),
128 (m), 109 (m).
Dichloro-(N,N’-bis(trimethylsilyl)-N,N’-1,2-
ethylendiamino)silane (1d-TMS2)
This compound was published earlier (Böhme et al.,
2007).
Dichloro-N,N’-(N-trimethylsilyl-o-phenylenediamino)
silane (2d-TMS)
spiro-Bis(N,N’-o-phenyleneamino(trimethylsilylamino))
silane (2b-TMS2)
This compound was synthesised by using method B: 8.45 g
(33 mmol) 2a, 5.69 g (33 mmol) SiCl4, 6.68 g (66 mmol)
Et3N, and THF as solvent were used. The crude product
was dissolved in a mixture of CHCl3/n-hexane (1:3 volume
parts, 60 mL in total) and crystallises after serval days at
4°C as a light brown solid (3.43 g, 37.5%).
This compound was synthesised by using method B: 5.02 g
(20 mmol) 2a, 4.05 g (40 mmol) NEt3, 1.54 g (9.1 mmol)
SiCl4, and THF as solvent were used. The crude product
was dissolved in diethyl ether, and after addition of
n-pentane and storage for several days at 4°C a light brown
solid (0.55 g, 16%) was yielded. The obtained compound
contains two trimethylsilyl moieties.
1
NMR solvent: CDCl3. H NMR: δ [ppm] = 0.47 (s, 9 H,
SiMe3), 4.65 (br, 1 H, NH), 6.69 – 6.90 (m, 4 H, Ar). 13C
NMR: δ [ppm] = 0.3 (SiMe3), 111.5, 113.9, 118.9, 120.0 (Ar),
137.2, 136.5 (Aripso). 29Si NMR: δ [ppm] = 6.8 (SiMe3), -23.5
(SiCl2). IR: ν [cm-1] = 3411, 3030, 2957, 2899, 2833, 2604,
1598, 1583, 1530, 1448, 1459, 1410, 1365, 1352, 132, 1254,
1229, 1202, 1184, 1111, 1047, 1033, 1018, 995, 901, 846, 814,
762, 742, 690, 677, 625, 576, 569, 559 527, 476, 447, 432.
EA: C: 33.63% (calc. 38.98%), H: 5.92% (calc. 5.09%), N:
9.00% (calc. 10.10%). mp: 128-130°C (decomp.). UV/VIS
(0.00099 mol/L, d = 0.999 cm, in CHCl3): [nm] 212.68
(ε = 1640.93 mol L-1 cm-1), 246.94 (ε = 2381.47 mol L-1 cm-1),
290.16 (ε = 1780.97 mol L-1 cm-1), 960.58 (ε = 477.65 mol L-1
cm-1).
1
NMR solvent: CDCl3. H NMR: δ [ppm] = 0.23 (s, 18 H,
SiMe3), 4.28 (s, 2 H, NH), 6.75 (m, 10 H, Ar). 13C NMR: δ [ppm]
= -0.06 (SiMe3), 110.8, 113.7, 118.2, 119.4, 136.2, 137.2 (Ar). 29Si
NMR: δ [ppm] = -24.6 (Si), 4.2 (SiMe3). (The integral of the
multiplet indicates the existence of not converted starting
material or products of hydrolysis.) Raman: ν [ppm] = 3460
(vw), 3400 (vw), 3080 (w), 3059 (m), 3013 (w), 2958 (m),
2900 (vs), 1598 (m), 1586 (w), 1489 (w), 1461 (vw), 1366 (m),
1309(vw),1266(m),1222(vw),1200(vw),1156(w),1112(vw),
1032 (s), 948 (vw), 925 (vw), 845 (vw), 815 (vw), 752 (vw),
616 (m), 440 (vw), 403 (w). MS: m/z = 384.11 g/mol [M]+.
mp: 124°C. UV/VIS (0.00108 mol/L, d = 0.999 cm,
in chloroform): [nm] 253.03 (ε = 2265.14 mol L-1 cm-1),
288.11 (ε = 2279.78 mol L-1 cm-1).
Crystals suitable for X-ray-diffraction were received
from a solution of the crude product in chloroform/
n-hexane (1:3 volume parts) and storing at 4°C for
several days.
Crystals suitable for X-ray-diffraction were received
from a solution in diethyl ether after addition of n-pentane
and storing at 4°C for several days.
The received substance is unknown in literature, but spiro-Bis(N,N’-2-aminobenzylamino)silane (4b)
a similar compound was synthesised by Kummer and This compound was synthesised by using method A:
Rochow (1963).
4.32 g (35 mmol) 4, 7.20 g (71 mmol) NEt3, and 2.99 g

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ67
(18 mmol) SiCl4 and about 150 mL THF as solvent were for X-Ray diffraction, were obtained. mp = 97°C. EA: C:
used. The reaction mixture was not heated and stirred 57.86% (calc. 58.20%), H: 7.65% (calc. 7.81%), N: 14.60%
21 h. A colourless substance (2.18 g, 46%) was received (calc. 13.57%).
1
after filtration and removal of all volatiles.
4c: NMR solvent: CDCl3. H NMR: δ [ppm] = 0.17 (s,
1
NMR solvent: CDCl3. H NMR: δ [ppm] = 1.66 (s, 2 H, 6 H, SiMe2), 1.05 (s (br), 1 H; NH), 3.57 (s (br), 1 H, NH), 3.87
3
NH), 3.88 (s, 2 H, NH), 4.08 (qd, 4 H, JH,H = 14.8 Hz, (s, 2 H, CH2) 6.49 (m, 1 H, Ar), 6.62 (m, 1 H, Ar), 6.85 (m, 1 H,
3JH,H = 5.5 Hz, CH2), 6.61 (d, 4 H, 3JH,H = 7.8 Hz, Ar), 6.72 (m, Ar), 6.99 (m, 1 H, Ar). 13C NMR: δ [ppm] = 0.5 (SiMe2), 44.2
3
2 H, Ar), 6.93 (d, 2 H, JH,H = 7.3 Hz, Ar), 7,04 (m, 2 H, Ar). (CH2), 117.4, 117.5, 126.3, 127.4, 128.0, 145.5 (Ar). 29Si NMR: δ
13C NMR: δ [ppm] = 44.5 (CH2), 117.91, 118.9, 126.5, 127.6, [ppm] = -1.7. bp 270°C (963 mbar). mp = 52°C. MS: m/z =
29
127.9, 144.9 (Ar). Si NMR: δ [ppm] = -49.0 (-48.9; Kaßner 178 g/mol [M+H]+.
et al., 2016). Raman: ν [cm-1] = 3057 (vs), 3046 (vs), 3032
(m), 2938 (m), 2881 (vw), 1607 (s), 1585 (w), 1455 (vw),
Silazanes 4f and 4g
1300 (vw), 1279 (vw), 1257 (w), 1221 (vw), 1194 (vw), 1158
These compounds was synthesised by using method A:
(w), 1037 (m), 760 (s), 594 (vw). MS: m/z = 310.00 g/mol
0.98 g (8 mmol) 4, 1.69 g (17 mmol) NEt3, 1.53 g (9 mmol)
[M+AcN+H]+. Decomposition: 155-160°C (Kaßner et al.,
SiCl4, and 40 mL diethyl ether as solvent were used.
2016).
During the addition of the silicon tetrachloride, the
reaction mixture was cooled in a dry-ice/iso-propanol
bath. Afterwards the mixture was allowed to attain room
temperature and stirred overnight. A part of the solvent
spiro-Bis(N-trimethylsilyl-N,N’-2-aminobenzylamino)
silane (4b-TMS2)
This compound was synthesised by using method B: was removed in vacuo and from the resulting mixture 4f
1.34 g (11 mmol) 4, 2.30 g (23 mmol) NEt3, 1.02 g (6 mmol) and 4g crystallised in the course of several weeks.
SiCl4, and about 100 mL dry THF as solvent were used. The
reaction mixture was heated for 8 h under reflux. From the
product mixture in THF a few crystals of 4b-TMS2 were spiro-Bis(N,N’-1,8-diaminonaphthalenyl)silane (5b)
obtained after several weeks.
This compound was synthesised by using method A:
5.63 g (36 mmol) 5, 7.26 g (72 mmol) NEt3, 2.89 g
(17 mmol) SiCl4, and about 200 mL of dry THF as solvent
were used. After removing volatiles in vacuo a dark
red compound (9.97 g) was obtained, which contained
residual THF (ca. 80 mol%) according to the NMR spectra.
(N,N’-2-aminobenzylamino)dimethylsilanes (4c and 4e)
These compounds was synthesised by using method
A: 4.64 g (38 mmol) 4, 7.82 g (77 mmol) NEt3, 6.464 g
(38 mmol) Me2SiCl2, and about 150 mL of dry THF as
solvent were used. A yellow substance was received after
removing all volatiles in vacuo. After distillation under
reduced pressure a residue and a distillate were obtained.
The residue is 4e (0.635 g) which crystallised from the
melt with small amounts of CDCl3, and the distillate is 4c
(0.748 g).
1
NMR solvent: CDCl3. H-NMR: δ [ppm] = 4.44 (s, 4 H,
3
N–H), 6.22 (d, 4 H, JH,H = 6.1 Hz, Ar), 7.00 (s, 8 H, Ar).
13C NMR: 108.6, 115.3, 117.9, 127.0, 136.5, 143.4. 29Si NMR:
δ [ppm] = -59.1. MS: m/z = 341.06 g/mol [M+H]+.
Decomposition: 124°C. Raman: the Raman spectrum does
not show sharp bands most likely due to luminescence
effects of the compound.
4e: NMR solvent: CDCl3. 1H NMR: δ [ppm] = 0.19 (s, 6 H,
Si-exocyclic), 0.30 (s, 12 H, Si-endocyclic), 3.56 (s (br), 2 H;
NH), 3.93 (s, 4 H, CH2) 6.59-6.66 (m, 4 H, Ar), 6.8 (m, 2 H, Ar),
7.04-7.08 (m, 2 H, Ar). 13C NMR: δ [ppm] = 1.5 (Si-exocyclic),
2.7 (Si-endocyclic), 45.2 (CH2), 116.4, 117.6, 126.7, 127.7, 127.8,
Crystals suitable for X-ray-diffraction were received
from the crude product with small amounts of CDCl3 and
storing at room temperature for several days.
145.9 (Ar). 29Si NMR: δ [ppm] = -2.2 (Si-endocyclic), -3.6 (N,N’-1,8-diaminonaphthalenyl)dimethylsilane (5c)
(Si-exocyclic). Raman: ν [cm-1] = 3358 (w), 3063 (w), 3048 This compound was synthesised by using method A:
(s), 2969 (s), 2903 (vs), 2834 (w), 1599 (w), 1586 (vw), 1455 12.18 g (77 mmol) 5, 15.62 g (155 mmol) NEt3, 13.08 g
(vw), 1368 (vw), 1339 (vw), 1306 (vw), 1277 (vw), 1200 (77 mmol) Me2SiCl2, and 200 mL of dry benzene as
(vw), 1156 (w), 1114 (vw), 1038 (w), 1009 (vw), 899 (vw), solvent were used. The crude product was dissolved in
732 (vw), 716 (w), 616 (w), 523 (w), 450 (vw), 350 (w), 311 10 mL THF and stored at 4°C. After filtration and removal
(vw), 213 (w), 132 (m), 91 (w). After standing several days of volatiles in vacuo 14.39 g (87%) of this light pink product
standing with small amount of CDCl3, crystals, suitable were obtained.

ꢀ
68ꢀ
M. Herbig et al.
1
NMR solvent: CDCl3. H-NMR: δ [ppm] = 0.35 (s, 6 H, Crystal structure determination
SiMe2), 3.95 (s (br), 2 H, NH), 6.40 (d, 2 H, 3JH,H = 7.3 Hz, Ar),
7.08 (d, 2 H, 3JH,H = 8.3 Hz, Ar), 7.15 (t, 2 H, 3JH,H = 7.7 Hz, Ar). Single crystal X-ray diffraction data of 2b-TMS2 and
13C NMR: 2.6 (SiMe2), 108.7 (Ar–H), 114.8 (Ar-quart), 117.6 2d-TMS were collected on a BRUKER NONIUS X8 APEX2
(Ar–H), 126.9 (Ar-H), 136.7 (Ar-quart.), 142.9 (Ar-quart.). CCD diffractometer using graphite monochromated Mo
29Si NMR: δ [ppm] = -5.6. Raman: ν [cm-1] = 3364 (vw), 3345 Kα radiation (λ = 0.71073 Å) using φ- and ω-scans. Data
(vw), 3059 (m), 3023 (w), 2965 (vw), 2895 (w), 2157 (vw), collections for the structures 3d-TMS2, 4b-TMS2, 4e, 4f,
.
2145 (vw), 2060 (vw), 1580 (s), 1518 (vw), 1466 (m), 1445 4g, 5b [Et3NH]Cl.HCCl3, 5c, and 5d-TMS were performed on
(w), 1397 (vw), 1366 (vs), 1256 (m), 1169 (vw), 1125 (w), a STOE IPDS-2T image plate diffractometer equipped with a
1088 (w), 1067 (w), 845 (vw), 817 (w), 755 (vw), 682 (vw), low-temperaturedevicewithMo-Kα radiation(λ=0.71073Å)
641 (w), 547 (s), 473 (w), 454 (w), 363 (w), 317 (w), 169(w), using ω-scans. Software for data collection: X-AREA, cell
113 (m). EA: C: 67.22% (calc. 67.24%), H: 6.68 (calc. 6.58%), refinement: X-AREA and data reduction: X-RED (Stoe
N: 12.82 (calc. 13.07%). mp: 114°C.
& Cie, 2009, X-RED and X-AREA. Stoe & Cie, Darmstadt,
Crystals suitable for X-ray-diffraction were obtained Germany). Preliminary structure models were derived by
from the crude product with small amounts of CDCl3 upon direct methods (Sheldrick, 2008) and the structures were
storing at room temperature for several days.
refined by full-matrix least-squares calculations based
on F2 for all reflections using SHELXL (Sheldrick, 2015).
The positions of N-H-atoms have been refined without
constraints. All other hydrogen atoms were included in
the models in idealised positions and were refined as
constrained to the pivot atoms. 2d-TMS crystallises in the
chiral space group P212121. The molecule itself is not chiral.
The absolute structure parameter was refined to a value
of -0.01(2). There are rotational disorders at the methyl
groups C11 and C12 in 5d-TMS. These have been refined
with split atom models. Further crystallographic data are
listed in Table 11.
CCDC-2033885 (2b-TMS2), 2033886 (2d-TMS),
2043741 (3d-TMS2), 2033889 (4b-TMS2), 2033888 and
2043739 (4e), 2043742 (4f ⋅ Et2O), 2043740 (4g), 2033887
(5b ⋅ Et3NHCl ⋅ CHCl3), 2033890 (5c), and 2043742 (5d-TMS)
contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The
Cambridge Crytallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
Dichloro-(N-trimethylsilyl-N,N’-1,8-diaminonaphthalenyl)
silane (5d)
Toasolutionof1,8-diaminonaphthalene(5.00g,31.6mmol)
and triethylamine (7.98 g, 79.0 mmol) in toluene (100 mL)
at room temperature a solution of chlorotrimethylsilane
(7.90 g, 72.7 mmol) in toluene (10 mL) was added dropwise
with stirring, whereupon the mixture was heated and
stirred under reflux for 2 h. Upon cooling to room
temperature the triethylamine hydrochloride precipitate
was filtered off and washed with toluene (36 mL).
From the combined filtrate and washings the solvent and
other volatiles were removed under reduced pressure. The
remaining oily residue was dissolved in toluene (50 mL),
stirred at room temperature, and triethylamine (7.34 g,
72.7 mmol) as well as a solution of SiCl4 (5.64 g, 33.2 mmol)
in toluene (6 mL) were added. This mixture was heated
and stirred under reflux for 10 h. Upon cooling to room
temperature the triethylamine hydrochloride precipitate
was filtered off and washed with toluene (20 mL). From
the combined filtrate and washings the solvent and other Quantum chemical calculations
volatiles were removed under reduced pressure, and the
solid residue was placed on a fritted glass filter and was The quantum chemical calculations have been performed
extracted with n-hexane (70 mL). From the hexane extract with GAUSSIAN 16 (Frisch et al., 2016). The molecules
the crude product crystallised in fine colourless needles, have been optimised with M062X/6-31G(d) (Francl et
which, upon storage at 6°C overnight, were filtered off, al., 1982; Hariharan and Pople, 1973; Zhao and Truhlar,
washed with hexane (2 mL) and dried in vacuo. Yield: 7.46 g 2008). The calculation of Hessian-matrices verified the
(22.8 mmol, 72%).
presence of local minima on the potential energy surface
1
NMR solvent: CDCl3. H-NMR: δ [ppm] = 0.57 (s, 9 H, with zero imaginary frequencies. The solvent THF was
SiMe3), 4.69 (s (br), 1H, NH), 6,46-7,32 (m, 6H, Ar). 13C included into these calculations by placing the molecules
NMR: 2.7 (SiMe3), 109.7, 115.0, 117.8, 119.9, 121.5, 125.9, 126.6, in a cavity within the solvent reaction field. This method
136.4, 139.3, 141.2 (Ar). 29Si NMR: δ [ppm] = 8.5 (SiMe3); is described in the literature as Polarizable Continuum
-35.5 (SiCl2). EA: C: 47.73% (calc. 47.70%), N: 8.43% (calc. Model (PCM). See Tomasi et al. (2005) for a review about
8.56%), H: 5.04% (calc. 4.93%). mp = 122°C.
relevant literature. Enthalpy (H) and Gibbs free energy (G)

ꢀ
New cyclic and spirocyclic aminosilanes
ꢀ69
Table 11:ꢁCrystal data and structure refinement
2b-TMS2
2d-TMS
3d-TMS2
Empirical formula
C18H28N4Si3
384.71
C9H14Cl2N2Si2
277.30
93
Orthorhombic, P212121
7.8056(12)
9.0025(14)
18.713(2)
90
C12H28Cl2N2Si3
355.53
Formula weight
T (K)
93
200
Crystal system, space group
Monoclinic, C2/c
15.0990(13)
14.1234(12)
10.5762(10)
90
114.400(4)
90
Monoclinic, P21/n
9.6940(6)
12.1485(7)
17.4157(9)
90
105.242(4)
90
a (Å)
b (Å)
c (Å)
α (°)
β (°)
90
90
γ (°)
Volume (Å3)
2053.9(3)
4
1315.0(3)
4
1978.9(2)
4
Z
ρcalc (g/cm3)
1.244
1.401
1.193
µMoKα (mm-1)
0.240
0.647
0.501
F(000)
824
576
760
Crystal size (mm)
Reflections collected / unique
0.530 × 0.280 × 0.260
15493 / 2359
[R(int) = 0.0647]
2359 / 0 / 120
R1 = 0.0491,
wR2 = 0.1323
R1 = 0.0613,
wR2 = 0.1494
0.400 × 0.300 × 0.160
17564 / 3174
[R(int) = 0.0295]
3174 / 0 / 143
R1 = 0.0224,
wR2 = 0.0574
R1 = 0.0236,
wR2 = 0.0579
0.400 × 0.300 × 0.150
17820 / 4772
[R(int) = 0.0240]
4772 / 15 / 197
R1 = 0.0375,
wR2 = 0.0939
R1 = 0.0497,
wR2 = 0.1049
Data / restraints / parameters
Final R indices [I > 2sigma(I)]
R indices (all data)
4b-TMS2
4e
4f . Et2O
4g
Empirical formula
C20H32N4Si3
412.76
C20H32N4Si3
412.76
C25H31Cl3N6OSi3
622.18
200
Monoclinic, P21/c
10.4899(4)
10.2209(6)
28.1420(13)
90
91.244(4)
90
C21H21Cl3N6Si3
548.06
180
Monoclinic, P21/n
10.3542(7)
16.5306(8)
29.913(2)
90
Formula weight
T (K)
153
200
Crystal system, space group
Monoclinic, C2/c
16.4390(11)
14.2531(12)
9.8574(6)
90
94.821(5)
90
Monoclinic, I2/c
20.2108(13)
10.4857(4)
23.7581(14)
90
113.392(5)
90
a (Å)
b (Å)
c (Å)
α (°)
β (°)
99.590(5)
90
γ (°)
Volume (Å3)
2301.5(3)
4
4621.1(5)
8
3016.6(3)
4
5048.5(5)
8
Z
ρcalc (g/cm3)
1.191
1.187
1.370
1.442
µMoKα (mm-1)
0.219
0.218
0.454
0.529
F(000)
888
1776
1296
2256
Crystal size (mm)
Reflections collected / unique
0.450 × 0.400 × 0.340
20017 / 2650
[R(int) = 0.0381]
2650 / 0 / 130
R1 = 0.0332,
wR2 = 0.0821
R1 = 0.0404,
wR2 = 0.0888
0.450 × 0.300 × 0.250
35511 / 5313
[R(int) = 0.0277]
5313 / 0 / 258
R1 = 0.0430,
wR2 = 0.1082
R1 = 0.0632,
wR2 = 0.1205
0.400 × 0.250 × 0.150 0.400 × 0.060 × 0.030
35175 / 6581
[R(int) = 0.0288]
6581 / 4 / 373
R1 = 0.0377,
wR2 = 0.0912
R1 = 0.0555,
wR2 = 0.1005
39071/8882
[R(int) = 0.1097]
8882/0/614
R1 = 0.0498,
wR2 = 0.0947
R1 = 0.1246,
wR2 = 0.1154
Data / restraints / parameters
Final R indices [I > 2sigma(I)]
R indices (all data)
(continued)

ꢀ
70ꢀ
M. Herbig et al.
Table 11:ꢁ(continued)
.
5b [Et3NH]Cl.HCCl3
5c
5d-TMS
Empirical formula
C47H49Cl4N9Si2
937.93
C12H14N2Si
214.34
C13H16Cl2N2Si2
327.36
Formula weight
T (K)
153
153
180
Crystal system, space group
Triclinic, P-1
12.1354(6)
14.1506(7)
15.1245(8)
102.395(4)
98.013(4)
Monoclinic, P21/c
14.0807(5)
9.4389(2)
17.4383(6)
90
100.415(3)
90
Monoclinic, P21/c
14.2310(4)
9.4966(2)
12.2393(4)
90
108.065(2)
90
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
109.180(4)
2333.0(2)
Volume (Å3)
2279.47(12)
8
1572.56(8)
4
Z
2
ρcalc (g/cm3)
1.335
1.249
1.383
µMoKα (mm-1)
0.350
0.174
0.553
F(000)
980
912
680
Crystal size (mm)
Reflections collected / unique
0.450 × 0.380 × 0.300
50078 / 10055
[R(int) = 0.0427]
10055 / 18 / 635
R1 = 0.0393,
wR2 = 0.0902
R1 = 0.0555,
wR2 = 0.1016
0.380 × 0.280 × 0.210
28952 / 5234
[R(int) = 0.0327]
5234 / 0 / 291
R1 = 0.0496,
wR2 = 0.1040
R1 = 0.0653,
wR2 = 0.1170
0.300 × 0.200 × 0.150
27189 / 3791
[R(int) = 0.0318]
3791 / 0 / 182
R1 = 0.0292,
wR2 = 0.0740
R1 = 0.0336,
wR2 = 0.0762
Data / restraints / parameters
Final R indices [I > 2sigma(I)]
R indices (all data)
data derived from the calculations correspond to 298.15 K review and editing, investigation; Sandra Schwarzer:
and 1 atmosphere of pressure.
funding acquisition, supervision; Edwin Kroke: funding
acquisition, writing – review and editing.
Acknowledgements:ꢀFurther data can be found as
electronic Supplementary material for this publication. Conflict of interest:ꢀOne of the authors (Jörg Wagler)
The authors gratefully acknowledge help from Beate is a member of the Editorial Board of Main Group Metal
Kutzner (NMR), Regina Moßig (Raman), Konstantin Chemistry.
Kraushaar (MS), and Ute Groß (EA). The authors thank
the Computing Centre of the TU Bergakademie Freiberg Data availability statement:ꢀData of the crystal structures
for computing time at the high-performance computing reported in this paper (in CIF format) can be obtained
(HPC) cluster.
free of charge from The Cambridge Crytallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Further
Funding information:ꢀPart of this work was performed data can be found as electronic Supplementary material
within the research group “Chemical utilization of carbon for this publication.
dioxide with aminosilanes (CO2-Sil)” that is financially
supported by the European Union (European social fund,
ESF), the Ministry of Science and Art of Saxony (SMWK),
and the Sächsische Aufbaubank (SAB).
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