Formation of Alkynylgermyl-Substituted Germylenes via a Catenation of Ge Atoms

Article abstract of DOI:10.1021/acs.inorgchem.0c01244

Reactions of amidinate-stabilized germylene chlorides R1Ge(:)Cl (R1 = PhC(NtBu)2) and R2Ge(:)Cl (R2 = PhC(NCy)2, Cy = cyclohexanyl) with trimethylsilylethynyl lithium salt (LLi, L = a'C?f‰CTMS) afforded alkynylgermylsubstituted germylenes R1(:)Ge-GeL3 (1) and [R2GeL2]2Ge(:) (2), respectively. Both of them may undergo the formation of Gea'Ge single bonds with a concomitant 1,2-shift of ethynyl groups. DFT calculations determined the reaction pathways where two possible intermediates (:)GeL2 and RGe(:)L (R = R1, R2) are proposed, which were consistent with the trapping reactions of (:)GeL2 toward IAra(:)GeL2 (3, IAr = :C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3). The reaction of 1 with N3TMS gave a new aminogermylene R1(:)Gea'N(TMS)-GeL3 (4), indicating a reactive Gea'Ge bond.

Full text of DOI:10.1021/acs.inorgchem.0c01244

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Article
Formation of Alkynylgermyl-Substituted Germylenes via a
Catenation of Ge Atoms
Chenghuan Liu, Keke Zhu, Weichun Han, Xue Liu, Zheng-Feng Zhang, Ming-Der Su,* Di Wu,*
and Yan Li*
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ABSTRACT: Reactions of amidinate-stabilized germylene chlorides R1Ge(:)Cl (R1 =
PhC(NtBu)2) and R2Ge(:)Cl (R2 = PhC(NCy)2, Cy = cyclohexanyl) with
trimethylsilylethynyl lithium salt (LLi, L = −CCTMS) afforded alkynylgermyl-
substituted germylenes R1(:)Ge-GeL3 (1) and [R2GeL2]2Ge(:) (2), respectively. Both
of them may undergo the formation of Ge−Ge single bonds with a concomitant 1,2-
shift of ethynyl groups. DFT calculations determined the reaction pathways where two
possible intermediates (:)GeL2 and RGe(:)L (R = R1, R2) are proposed, which were
consistent with the trapping reactions of (:)GeL2 toward IAr−(:)GeL2 (3, IAr
=
:C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3). The reaction of 1 with N3TMS gave a new
aminogermylene R1(:)Ge−N(TMS)-GeL3 (4), indicating a reactive Ge−Ge bond.
Ge atoms has not been extensively investigated in recent
research.7,15 In this context, we were intrigued to explore if
such Ge catenation can be employed in developing new
structures possessing active Ge(II)−C bonds. In this work, we
present the syntheses and mechanistic studies of alkynylgerm-
yl-substituted germylenes, which undergo a catenation of Ge
atoms.
INTRODUCTION
■
Monomeric germylenes (R2Ge(:)) are reactive organometallic
building blocks for germanium-containing compounds with
unique electronic structures, owing to the lone pair of electrons
and vacant p orbital on the Ge atom.1 Their synthetic
strategies have been extensively documented including the
metathesis reactions, the reduction of germanium halide
precursors with alkali metals, or the activation of the
noninnocent ligand skeletons.2 Polygermanes (R2Ge)n con-
taining catenated Ge atoms are widely explored as optoelec-
tronic materials,3 which can be considered as the polymeric/
oligomeric form of monomeric germylenes. They are mainly
synthesized via Wurtz-type coupling reactions, reaction of
Grignard reagents with organogermanium halides, Lewis acid-
catalyzed rearrangement of oligogermylsilanes, and hydro-
germolysis reactions.4 Several radical-mediated coupling
reactions of monomeric germylenes toward digermylenes
were also reported.2c,d,4d Notably, a polyhalogermane com-
pound IAr-GeCl2−(:)Ge(GeCl3)2 (IAr = :C{N(Ar)CH}2, Ar =
2,6-iPr2C6H3) with a branched Ge4 core containing Ge centers
in formal oxidation states of 0, +2, and +3 was synthesized by
Rivard and co-workers via sequential additions of [(:)GeCl2]
units.5 Synthesis of similar structure Me2EtN-SiCl2−(:)Si-
(SiCl3)2 was also achieved through amine-induced dispropor-
tionation of Si2Cl6 under low temperatures.6 Theoretical
calculations supported both reactions proceeding through a
consecutive halide migration to construct a catenated E−E (E
= Si, Ge) structure, which paves a way to access novel group 14
heavier analogues of hydrocarbons. Through a surveying of the
literature, formation of the polygermanes containing low-valent
RESULTS AND DISCUSSION
■
It is well-known that reactions of germylene chlorides with
alkynyllithium salts afford RGe(:)−CCR′ (R, R′ = organic
groups) as routine substituted products.2e,8−10 Interestingly,
treatment of an amidinate-stabilized germylene R1Ge(:)Cl (R1
= PhC(NtBu)2) with the solid of trimethylsilylethynyl lithium
salt LLi (prepared in advance, L = −CCTMS)16 in a molar
ratio of 1:1 in Et2O did not give product R1Ge(:)L; instead, a
mixture of unreacted R1Ge(:)Cl and a new compound
R1(:)Ge-GeL3 (1) was obtained, confirmed by the H NMR
1
spectrum. When the reaction molar ratio was changed to 2:3,
compound 1 was exclusively isolated as colorless crystals in
51% yield (Scheme 1). Using Et2O as a solvent is advantageous
over THF and toluene since the yields of 1 in the latter two
Received: April 26, 2020
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1
substitution was not isolated. The H NMR spectrum of 2
shows multiple singlets of TMS-Me at a range of δ 0.11−0.37
ppm, and 29Si NMR shows four singlets at δ −19.0, −19.4,
−19.6, and −20.2 ppm, indicative of different −SiMe3
environments.
Scheme 1. Syntheses of Compounds 1 and 2
In contrast to compound 1, the molecular structure of 2
shows a Ge−Ge−Ge chain,14b which can be considered as a
base-stabilized bis(dialkynylgermyl) germylene (Figure 2). The
solvents are low. The 1H NMR spectrum of 1 shows the tBu-H
(δ 1.17 ppm) of an amidinate ligand and ethynyl TMS-Me (δ
0.08 ppm) resonances. X-ray crystallography of 1 exhibits a tri-
(TMS)ethynylgermyl-substituted germylene structure (Figure
1). The Ge1 atom is pyramidalized due to the presence of a
Figure 2. Molecular structure of 2 (H atoms are omitted for clarity).
Selected bond lengths (Å) and angles (deg): Ge(1)−Ge(3)
2.4310(4), Ge(2)−Ge(3) 2.4373(5), Ge(1)−N(2) 1.895(2),
Ge(2)−N(3) 1.906(2), Ge(3)−N(4) 2.260(2); N(2)−Ge(1)−
Ge(3) 107.63(7), N(3)−Ge(2)−Ge(3) 101.38(7), Ge(1)−Ge(3)−
N(4) 91.55(6), Ge(2)−Ge(3)−N(4) 76.08(6), Ge(1)−Ge(3)−
Ge(2) 94.728(15).
central Ge3 atom adopts significantly pyramidalized geometry
(∑°Ge3 = 262.36°) showing the presence of a lone pair. Each
Ge1 and Ge2 atom is substituted with two TMS−ethynyl
groups. The two Ge−Ge bond distances (2.4310(4) Å and
2.4373(5) Å) fall in the range of a Ge−Ge single bond,1a,4a
which are obviously shorter than that of 1 (ca. 2.5068(8) Å).
The N1 atom shows weak interaction toward the Ge3 center,
owing to the much longer Ge3−N1 distance (ca. 2.519 Å)
than that of the Ge3−N4 coordinative bond (2.260(2) Å).
The Ge3 chain is almost rectangular (Ge1−Ge3−Ge2 angle:
94.728(15)°), which is close to that (Ge−Ge−Ge angle:
90.46(3)°) of the [(:)Ge(GeCl3)2] fragment in the poly-
halogermane IAr-GeCl2−(:)Ge(GeCl3)2 (IAr = :C{N(Ar)CH}2,
Ar = 2,6-iPr2C6H3),5 while it is more acute than those found in
the functionalized Ge3 species (cAAC)Ge(GeR1)2
Figure 1. Molecular structure of 1 (H atoms are omitted for clarity).
Selected bond lengths (Å) and angles (deg): Ge(1)−Ge(2)
2.5068(8), N(1)−Ge(1) 1.986(3), N(2)−Ge(1) 1.976(3); N(1)−
Ge(1)−N(2) 65.38(13), N(1)−Ge(1)−Ge(2) 92.49(9), N(2)−
Ge(1)−Ge(2) 93.87(9).
lone pair (∑°Ge1 = 251.74°). The Ge1−Ge2 bond distance
(ca. 2.5068(8) Å) of 1 is slightly longer than ordinary Ge−Ge
single bonds (2.41−2.48 Å)1a,4a and is comparable to that
(2.5439(7) Å) of the alkylgermyl germylene 2,6-
Mes2C6H3Ge−GetBu3 (Mes = mesityl).11 To the best of our
knowledge, compound 1 is the first isolated germylene with
alkynylgermyl substitutent.
It is anticipated that the possible generation of (:)GeL (L =
−CCTMS) moiety in the formation of 1 triggers bonding
activations, and we were curious to know if any new reaction
arises when the amidinate ligand is varied. Therefore,
treatment of R2Ge(:)Cl (R2 = PhC(NCy)2, Cy = cyclo-
hexanyl) with LLi in a molar ratio of 3:412 in Et2O facilely
afforded compound [R2GeL2]2Ge(:) (2) as colorless crystals in
56% yield (Scheme 1). Product R2Ge(:)-L through simple
(107.65(2)°; cAAC = cyclic alkyl(amino) carbene; R1
=
PhC(NtBu)2)13 and trigermaallene (RGe)2Ge (122.61(6)°; R
= [CC(TMS)2]2).14a
Compounds 1 and 2 demonstrate a structural character of
double or triple catenation of Ge atoms. Two possible key
intermediates RGe(:)L (R = R1 or R2) and (:)GeL2 are
generated at the beginning of reactions, on the basis of which a
formal insertion reaction of Ge(II) atoms into Ge(II)−Csp
bonds is then proposed via the formation of Ge−Ge single
bonds with concomitant transfer of L groups.15
To get a better understanding of the mechanism, DFT
calculations were performed at the M06-2X/def2-TZVP//
M06-2X/def2-SVP level.16 As shown in Figure 3, the
stoichiometric reactions of RGe(:)Cl (R = R1 or R2) with
B
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Figure 3. Proposed mechanisms for the formation of 1 and 2. Free energy data are given in each step at the M06-2X/def2-TZVP/SMD//M06-2X/
def2-SVP and M06-2X/def2-SVP (in bracket) levels of theory. (The energy of LiCl is for the gas phase.)
LLi in molar ratios of 2:3 and 3:4 give two intermediates,
RGe(:)L and (:)GeL2, in an equivalent molar ratio by
eliminating LiCl and LLi, which is energetically favored by
18.5 and 39.2 kcal/mol, respectively. For the former case,
R1Ge(:)L interacts readily (2.9 kcal/mol) with (:)GeL2 via a
transition state of TS1, where the Ge−Csp bond of R1Ge(:)L is
weakened and a Ge2C three-membered ring is built in a
concerted manner. Then, formation of a Ge−Ge bond occurs
with an intermolecular transfer of the L group from R1Ge(:)L
to (:)GeL2 leading to product 1, showing energetic preference
by 35.2 kcal/mol. In contrast, a different formation route is
shown in the case of compound 2 (Figure 3). The interaction
between R2Ge(:)L and (:)GeL2 forms a Ge2C three-membered
ring (TS2), where the Ge−Csp bond cleavage of (:)GeL2
instead of R2Ge(:)L happens. A subsequent migration of the L
group as well as the formation of a Ge−Ge bond lead to
intermediate R2GeL2−(:)GeL (Int) with a substantial total
free energy change of 44.9 kcal/mol (calculated by considering
one remaining R2Ge(:)L molecule). Furthermore, the Int
reacts with another molecule of R2Ge(:)L in solution through
similar concerted Ge2C three-membered ring (TS3) by
conquering a barrier of 39.1 kcal/mol to obtain product 2.
Due to the large excess energy of 76.1 kcal/mol obtained by
the decay from reactants (3RGe(:)Cl + 4LLi) to Int (with one
R2Ge(:)L molecule), the above energy barrier can be easily
surmounted. Theoretical results estimated that the relative
energy of the final product 2 is −87.0 kcal/mol, with respect to
the corresponding reactants (3RGe(:)Cl + 4LLi). Accordingly,
the present theoretical findings suggest that both reactions
given in Figure 3 can readily proceed since all the relative
energies of the critical points (such as TS1, 1, and TS2, Int,
TS3, 2) are calculated to be lower than those of their
corresponding reactants.17 Such germylene formation is rare,
which is comparable to the reported carbene-supported
(GeCl2)x oligomers via formal Ge(II) insertion into the
Ge(II)−Cl bonds.5
Numerous attempts to isolate intermediates RGe(:)L (R =
R1, R2) were not successful. But the existence of key
intermediate (:)GeL2 can be evidenced by the reactions of
RGe(:)Cl (R = R1 and R2) with LLi in the presence of N-
heterocyclic carbene IAr (:C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3)
as a trapping reagent (Scheme 2). Dialkynylgermylene
compound IAr−(:)GeL2 (3) was successfully isolated as
colorless plates from both reactions, yielding 31% and 34%,
respectively. A similar (:)Ge(CCPh)2 species was postulated
as intermediate in the formation of lithium germinate
[{(PhCC)3Ge}3GeLi(Et2O)3].9 Compound 3 can be
Scheme 2. Trapping Reactions of (:)GeL2 Intermediate and
the Alternative Synthesis of Compound 3
C
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alternatively synthesized by stoichiometric reaction of IAr−
(:)GeCl2 and LLi in 75% yield.16 The X-ray structure of 3
shows two types of configurations in one asymmetric unit
(Figure S1 in Supporting Information), where the (:)GeL2
moiety in one molecule is distorted probably due to the crystal
packing effect.18
To investigate the reactivity of the newly synthesized
germylenes, compound 1 was treated with organic azide
N3TMS in a molar ratio of 1:1 in toluene. Compound
R1(:)Ge−N(TMS)−GeL3 (4) was smoothly afforded as
colorless crystals in 90% yield (Scheme 3). The X-ray
CONCLUSION
■
In summary, alkynylgermyl-substituted germylenes 1 and 2
were synthesized by reactions of amidinate-stabilized germy-
lene chlorides RGe(:)Cl (R = R1, R2) with TMS−CCLi salt,
which may undergo the formation of Ge−Ge single bonds with
concomitant 1,2-shifts of ethynyl groups. The mechanisms
were supported by DFT calculations and the capture reactions
of the key intermediate (:)GeL2. The amidinate scaffolds may
have an important influence upon dictating the Ge catenation
style. It is assumed that the Cy group has less steric hindrance
than tBu, which could facilitate the addition of another Ge unit
in 2. Compound 1 exhibits unique reactivity toward N3TMS to
form an aminogermylene 4, which was rarely reported in the
reaction modes of germylenes with organic azides. Exploration
of other catenated Ge species containing the Ge−Csp bond and
relevant reactivity studies toward small molecules are currently
under way.
Scheme 3. Synthesis of Compound 4
EXPERIMENTAL SECTION
■
All manipulations were carried out under a dry argon or nitrogen
atmosphere by using Schlenk line and glovebox techniques. Organic
solvents Et2O, THF, toluene, and n-hexane were dried by refluxing
with Na/K under N2 prior to use. R1GeCl (R1 = PhC(NtBu)2),2c IAr
crystallography of 4 clearly shows an aminogermylene
structure (Figure 4), where the Ge1 atom adopts pyrami-
(:C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3),21 and IArGeCl2 were
22
synthesized according to the literature. TMSCCH (LH, L =
TMSCC−) and N3TMS were dried by CaH2 prior to use. R2GeCl
(R2 = PhC(NCy)2, Cy = cyclohexanyl) was prepared in the same
manner as R1GeCl and was used directly. LLi (L = TMSCC−) was
prepared in advance by the treatment of LH with n-BuLi (1.05 equiv)
in n-hexane at room temperature, which was used directly as white
powder.23 1H NMR spectra were recorded on a Bruker Avance II 400
spectrometer, and 13C{1H} and 29Si spectra were recorded on a
Bruker Avance II 500 spectrometer. Elemental analysis was performed
on a Thermo Quest Italia SPA EA 1110 instrument. Commercial
reagents were purchased from TCI and J&K Chemical Co.
Synthesis of 1. At −78 °C, Et2O (25 mL) was added to a mixture
of R1GeCl (0.68 g, 2.0 mmol) and LLi (0.33 g, 3.0 mmol). The
mixture was allowed to warm to room temperature and stirred
overnight. The suspension was filtered and the filtrate was dried under
a vacuum to give an oily solid. The residue was extracted with n-
hexane (ca. 5 mL), and colorless crystals of 1 were grown at 0 °C.
Yield: 0.34 g (51% based on R1GeCl). mp: 143 °C (dec.). Elemental
analysis calcd (%) for C30H50Ge2N2Si3 (668.26, the solvent n-hexane
was removed after drying the crystals): C, 53.92; H, 7.54; N, 4.19.
Figure 4. Molecular structure of 4 (H atoms are omitted for clarity).
Selected bond lengths (Å) and angles (deg): N(1)−Ge(1) 2.011(3),
N(2)−Ge(1) 2.020(3), N(3)−Ge(1) 1.913(2), N(3)−Si(4)
1.738(3), N(3)−Ge(2) 1.818(2); N(1)−Ge(1)−N(3) 106.30(11),
N(2)−Ge(1)−N(3) 104.96(11), N(2)−Ge(1)−N(3) 64.443(11),
Ge(1)−N(3)−Ge(2) 106.45(11), Ge(1)−N(3)−Si(4) 133.77(13),
Ge(2)−N(3)−Si(4) 119.78(13).
1
Anal. found: C, 53.60; H, 7.42; N, 3.89. H NMR (400 MHz, C6D6,
298 K, ppm): δ 7.93 (m, 1H, PhH), 7.13−6.95 (m, 4H, PhH), 1.17
(s, 18H, tBuH), 0.08 (s, 27H, SiMe3). 13C{1H} NMR (125 MHz,
C6D6, 298 K, ppm): δ = 165.1(PhCN2), 135.2, 131.6, 129.4, 127.7,
(PhC) 114.1(CSi), 110.6(GeC), 53.1(CMe3), 31.4(CMe3),
0.4(SiMe3). 29Si{1H} NMR (99 MHz, C6D6, 298 K, ppm): δ −19.9.
Synthesis of 2. At−78 °C, Et2O (25 mL) was added to a mixture
of R2GeCl (0.59 g, 1.5 mmol) and LLi (0.22 g, 2.0 mmol). The
mixture was allowed to warm to room temperature and stirred
overnight. The suspension was filtered, and the filtrate was dried
under a vacuum to give an oily solid. The residue was extracted with
n-hexane (ca. 5 mL), and colorless crystals of 2 were grown at room
temperature. Yield: 0.33 g (56% based on R2GeCl). mp: 130 °C
(dec.). Elemental analysis calcd (%) for C58H90Ge3N4Si4 (1173.62):
C, 59.36; H, 7.73; N, 4.77. Anal. found: C, 59.52; H, 7.18; N, 4.56. 1H
NMR (400 MHz, C6D6, 298 K, ppm): δ 7.75 (m, 1H, PhH), 7.38−
6.85 (m, 4H, PhH), 3.31−0.72 (m, 44H, CyH), 0.37−0.11 (m, 36H,
SiMe3). 13C{1H} NMR (125 MHz, C6D6, 298 K, ppm): δ 167.8
(PhCN2), 137.0, 135.4, 126.5, 125.6 (PhC), 118.3, 116.7 (CSi),
115.1, 111.0 (GeC), 66.0, 60.9, 60.4, 54.3, 36.6, 36.5, 35.1, 33.8,
33.6, 27.1, 26.7, 26.5, 26.2, 25.9, 25.8, 25.3 (CyC), 1.5, 1.1, 0.4, 0.0
(SiMe3). 29Si{1H} NMR (99 MHz, C6D6, 298 K, ppm): δ −19.0,
−19.4, −19.6, −20.2 (SiMe3).
dalized geometry (∑°Ge1 = 275.70°) indicating the presence
of a lone pair. The formation of 4 may undergo a possible
germanimine19 R1Ge(NTMS)−GeL3, accompanied by a
migration of the −GeL3 group from the GeGeN atom to the
NGeN atom, showing a reactive Ge−Ge bond in compound
1.19 This reaction mode contrasts markedly with the
ubiquitous formation of stable GeN species or azagermanes
containing Ge2N, GeN4, and Ge2N2 rings.20 A similar reaction
was not reported in the alkylgermyl germylene 2,6-
Mes2C6H3Ge−GetBu3 (Mes = mesityl) system with the strong
electron-donating −GetBu3 substituent.11 The related reaction
of compound 2 with N3TMS shows the formation of a product
mixture containing unknown species transpired, which is still
under investigation now.
D
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Trapping Reactions of GeL2 toward IArGeL2 (3). (A) At room
temperature, Et2O (30 mL) was added to a mixture of R1GeCl (0.34
g, 1.0 mmol), LLi (0.11 g, 1.0 mmol), and IAr (0.39 g, 1.0 mmol). The
mixture was allowed to warm to room temperature and stirred
overnight. The suspension was filtered, and the filtrate was dried
under a vacuum to give an oily solid. Colorless plates of 3 were grown
slowly from a mixture of THF/n-hexane solvents at room temper-
ature. Yield: 0.20 g (31%). (B) At room temperature, Et2O (30 mL)
was added to a mixture of R2GeCl (0.39 g, 1.0 mmol), LLi (0.11 g, 1.0
mmol), and IAr (0.39 g, 1.0 mmol). The mixture was allowed to warm
to room temperature and stirred overnight. The suspension was
filtered, and the filtrate was dried under a vacuum to give an oily solid.
Colorless plates of 3 were grown slowly from a mixture of THF/n-
hexane solvents at room temperature. Yield: 0.22g (34%).
Normal University, Hangzhou 311121, China; orcid.org/
0000-0001-7703-6560; Email: yli@hznu.edu.cn
Ming-Der Su − Department of Applied Chemistry, National
Chiayi University, Chiayi 60004, Taiwan; Department of
Medicinal and Applied Chemistry, Kaohsiung Medical
University, Kaohsiung 80708, Taiwan; orcid.org/0000-
0002-5847-4271; Email: midesu@mail.ncyu.edu.tw
Di Wu − College of Material, Chemistry and Chemical
Engineering, Hangzhou Normal University, Hangzhou 311121,
China; Email: wudi@hznu.edu.cn
Authors
Chenghuan Liu − Key Laboratory of Organosilicon Chemistry
and Material Technology of Ministry of Education, Hangzhou
Normal University, Hangzhou 311121, China
Keke Zhu − Key Laboratory of Organosilicon Chemistry and
Material Technology of Ministry of Education, Hangzhou
Normal University, Hangzhou 311121, China
Weichun Han − Key Laboratory of Organosilicon Chemistry
and Material Technology of Ministry of Education, Hangzhou
Normal University, Hangzhou 311121, China
Xue Liu − Key Laboratory of Organosilicon Chemistry and
Material Technology of Ministry of Education, Hangzhou
Normal University, Hangzhou 311121, China
Alternative Synthesis of 3. At room temperature, Et2O (30 mL)
was added to a mixture of IArGeCl2(0.53 g, 1.0 mmol) and LLi (0.21
g, 2.0 mmol). The mixture was allowed to warm to room temperature
and was stirred overnight. The suspension was filtered, and the filtrate
was concentrated under a vacuum to give colorless crystals of 3. Yield:
0.49 g (75%). mp: 154 °C (dec.). Elemental analysis calcd (%) for
C37H54GeN2Si2 (655.66): C, 67.78; H, 8.30; N, 4.27. Anal. found: C,
1
67.52; H, 8.13; N, 4.06. H NMR (400 MHz, C6D6, 298 K, ppm): δ
3
7.18−6.90 (m, 6H, PhH), 6.25 (s, 2H, CH), 2.70 (sept, 4H, JHH
=
8.0 Hz, CHMe2), 1.42 (d, 12H, 3JHH = 8.0 Hz, CHMe2), 0.95 (d, 12H,
3JHH = 8.0 Hz, CHMe2), 0.00 (s, 18H, SiMe3). 13C{1H} NMR (125
MHz, C6D6, 298 K, ppm): δ 174.7 (NCN), 145.0, 133.6, 130.0, 126.9
(PhC), 123.4 (CSi), 113.0 (GeC), 28.2 (CHMe2), 24.3, 22.8
(CHMe2), 0.0 (SiMe3). 29Si{1H} NMR (99 MHz, C6D6, 298 K, ppm):
δ −24.0 (SiMe3).
Zheng-Feng Zhang − Department of Applied Chemistry,
National Chiayi University, Chiayi 60004, Taiwan
Synthesis of 4. At room temperature, N3TMS (0.15 mL, 1.0
mmol) was added to the solution of 1 (0.67 g, 1.0 mmol) in toluene
(25 mL). The mixture was stirred overnight. The insoluble materials
were removed by filtration, and the filtrate was dried under a vacuum
to give a gray oil. The oil was extracted with n-hexane (8 mL), and the
extract was kept at 0 °C for 12 h to give colorless crystals of 4. Yield:
0.68 g (90%). mp: 146 °C (dec.). Elemental analysis calcd (%) for
C33H59Ge2N3Si4 (755.46): C, 52.47; H, 7.87; N, 5.56. Anal. found: C,
Complete contact information is available at:
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
1
52.98; H, 7.34; N, 5.85. H NMR (400 MHz, C6D6, 298 K, ppm): δ
This work is funded by the NSF of China (No. 21801055),
Zhejiang Provincial Natural Science Foundation (No.
LY20B020009 and LQ20B010007). Y.L. acknowledges the
support from the open fund of State Key Laboratory of
Physical Chemistry of Solid Surfaces, Xiamen University (No.
201916). Z.-F.Z. and M.-D.S. are grateful to the National
Center for High-Performance Computing of Taiwan for
generous amounts of computing time, and the Ministry of
Science and Technology, Taiwan for the financial support. We
thank greatly Dr. Xuqiong Xiao for the X-ray crystallographic
assistance.
8.01 (m, 1H, PhH), 7.33 (m, 1H, PhH), 7.08−6.83 (m, 3H, PhH),
1.32 (s, 6H, tBuH), 1.22 (s, 12H, tBuH), 0.83 (s, 3H, NSiMe3), 0.78
(s, 6H, NSiMe3), 0.11 (s, 9H, CSiMe3), 0.08 (s, 18H, CSiMe3).
13C{1H} NMR (125 MHz, C6D6, 298 K, ppm): δ 165.0 (PhCN2),
136.7, 130.0, 128.1, 127.9 (PhC), 114.3, 113.8 (CSi), 112.1, 110.2
(GeC), 54.3 (CMe3), 32.9, 32.6 (CMe3), 5.8, 5.5 (NSiMe3), 0.1, 0.0
(CSiMe3). 29Si{1H} NMR (99 MHz, C6D6, 298 K, ppm): δ 10.22
(NSiMe3), −18.5 (CSiMe3).
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c01244.
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sı
REFERENCES
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Accession Codes
CCDC 1974194−1974197 contain the supplementary crys-
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AUTHOR INFORMATION
Corresponding Authors
Yan Li − Key Laboratory of Organosilicon Chemistry and
Material Technology of Ministry of Education, Hangzhou
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