A Simple Catalytic Route for Alkynylgermanes

Article abstract of DOI:10.1002/ejic.201501110

We report a new one-pot, iridium(I)-catalyzed direct method for the synthesis of alkynyl-substituted germanium compounds with various functional groups from commercially available reagents. More than 25 compounds were obtained and spectroscopically charac

Full text of DOI:10.1002/ejic.201501110

DOI: 10.1002/ejic.201501110
Full Paper
Alkynylgermanes
A Simple Catalytic Route for Alkynylgermanes
Monika Rzonsowska,[a] Bartosz Woźniak,[a] Beata Dudziec,*[a] Jadwiga Pyziak,[a]
Ireneusz Kownacki,[b] and Bogdan Marciniec*[a,c]
Abstract: We report a new one-pot, iridium(I)-catalyzed direct culations were performed to study the mechanism of the cata-
method for the synthesis of alkynyl-substituted germanium
compounds with various functional groups from commercially
available reagents. More than 25 compounds were obtained
and spectroscopically characterized. Moreover, detailed DFT cal-
lytic cycle of the germylative coupling. The results confirm our
assumptions that the rate-determining step of the germylative
coupling process is the product-formation step.
Introduction
lytic methods for alkynylgermane syntheses have been far less
documented.[6a,8b]
Elemental germanium and its organic derivatives exhibit a
During the course of our previous studies, we discovered two
multitude of interesting properties that favor various applica- independent catalytic coupling reactions of terminal alkynes to
tions. The use of germanium as a semiconductor in the elec- form the analogous R3E–C≡ C–R′ (E = Si, Ge) moieties mediated
tronic industry is general.[1] New applications for organoger- by either ruthenium or iridium complexes (Scheme 1).[11,12,13]
manes are broad and are still under development through the We revealed a new and elegant method for the synthesis of a
variation of the functionality of the organic substituents. Alkyn- variety of functionally substituted alkynylgermanes through the
ylgermanes are a group of compounds that exhibit many inter- coupling of iodogermanes with terminal alkynes (Scheme 1).[13]
esting applications. They are versatile precursors for the prepa- This process is far more universal than the ruthenium-catalyzed
ration of a diverse collection of alkenylgermane derivatives reaction, which is limited by the use of aliphatic terminal alk-
through their hydrometallation (e.g., hydrostannylation[2] or ynes (owing to the dimerization of alkynes containing aromatic
hydroboration).[3] The (cyclo)addition reactions of alkynylger- groups under catalytic conditions).[14]
manes are also well documented, for example, with tetrazines,
imines, or azides to form heterocycles,[4] as is their use in the
chemistry of functionalized boron[5] and tin compounds.[2] The
important utilization of trialkylgermanes as protecting groups
for terminal alkynes should also be mentioned.[6] The different
reactivities of alkynylsilanes and alkynylgermanes under acidic,
electrophilic,[7] or fluoridic[8] conditions are an advantage and
enable their exploitation in the preparation of nonsymmetri-
cally substituted dialkyne-containing molecules.[6a,9]
Scheme 1. Ruthenium- and iridium-mediated coupling reactions leading to
The synthetic procedures for the synthesis of alkynylgerm-
anes are still under development. A significant number of re-
ports concerns the use of lithium or magnesium reagents to
obtain alkynyl-substituted germanes.[5b,8,10] All of these reac-
tions are stoichiometric, often multistep processes that are non-
selective in many cases and provide low isolated yields. Cata-
functionalized alkynylmetalloids.
Our recent reports on the successful use of chlorosilanes[15]
in one-pot coupling reactions to obtain their alkynyl derivatives
encouraged us to explore the reactivity of chlorogermanes in
the analogous catalytic coupling with terminal alkynes.
Here, we present our results on a one-pot reaction sequence
of chlorogermanes with terminal alkynes in the presence of
[{Ir(μ-Cl)(CO)2}2] (the precursor of the actual catalyst), a metal
iodide as a source of iodine, and an amine to scavenge hydro-
gen iodide (Scheme 2).
[a] Department of Organometallic Chemistry, Faculty of Chemistry,
A. Mickiewicz University in Poznan,
Umultowska 89B, 61-614 Poznan, Poland
E-mail: beata.dudziec@gmail.com
Bogdan.Marciniec@amu.edu.pl
www.chemia.amu.edu.pl
[b] The Laboratory of the Chemistry and Technologies of Inorganic Polymers,
Faculty of Chemistry, A. Mickiewicz University in Poznan,
Umultowska 89B, 61-614 Poznan, Poland
[c] Center for Advanced Technologies, A. Mickiewicz University in Poznan,
Umultowska 89C, 61-614 Poznan, Poland
Scheme 2. One-pot germylative coupling reaction sequence from chloro- to
alkynylgermanes.
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The great advantage of this procedure would be the expan- aforementioned processes to proceed with the best efficiency,
sion of the scope of the synthesized products as the chloro-
a series of germylative coupling tests were performed
germanes are far more readily commercially available than their (Scheme 3). The coupling reaction between chlorotriethyl-
iodo analogues.
germane with 1-octyne/phenylacetylene was chosen as the
model system for optimization.
The examined parameters that affected either the Finkelstein
reaction or the germylative coupling, that is, the type of
acetylene (aryl or alkyl), the solvent polarity, the metal iodide,
the reaction temperature, and the reagent stoichiometry, are
presented in Table 1.
Results and Discussion
We began our study by examining the possibility of using chlo-
rogermanes under the standard catalytic reaction conditions
elaborated for their iodo derivatives.[13] As for the chloro-
silanes,[15] the iridium(I) catalytic system works smoothly only if
an R3Ge–I bond is present in the organogermane substrate
(Table 1, Entries 3 and 7). Similarly, we were interested in meth-
ods that would enable the synthesis of catalytically reactive
R3Ge–I moieties,[16] for example, by exploiting the substitution
of a chlorine atom by an iodine atom. The nucleophilic substitu-
tion of a chlorine atom for an iodine atom in a polar solvent
system with the use of inorganic salts (alkali metal iodides),
known in organic chemistry as the Finkelstein reaction,[17] was
the best choice. This process was successfully applied for the
elaboration of the reactive catalytic system through the combi-
nation of a sequence of two reactions in a one-pot procedure,
that is, the creation of an iodogermane in situ and its subse-
quent conversion to an alkynylgermane derivative through an
iridium-mediated reaction. If the iridium(I) complex was not
used, we did not observe the alkynyl-substituted product. To
find the optimized reaction conditions that would allow both
The tested system features presented in Table 1 elaborated
the optimized reaction conditions (Table 1, Entries 5 and 9) that
enabled the most efficient synthesis of the desired alkynyl-
germane. Lithium iodide was selected as the iodating agent
as it facilitated the highest conversion of R3Ge–Cl; as the Cl/I
nucleophilic substitution requires a polar solvent, α,α,α-tri-
fluorotoluene was the preferred option, and it also enables the
germylative coupling.[13] The presence of an inorganic salt has
no deactivating effect on the efficiency of the coupling process.
Furthermore, the use of a higher amount of lithium iodide is
not required, as was shown for the one-pot reaction of chloro-
silanes.[15]
As the germylative coupling proceeds with the in situ gener-
ated iodogermane derivative, we observed here the same trend
for the catalyst loading, time, temperature, and amine as dis-
cussed previously.[13] We investigated the scope of this reaction
under our optimized conditions and used selected commer-
cially available chlorogermanes and terminal alkynes. The versa-
tility of the one-pot procedure to obtain a wide range of corre-
sponding functionalized alkynylgermanes is demonstrated in
Table 2.
All of the applied terminal alkynes and chlorogermanes gave
the expected alkynylgermanium products in moderate to very
good isolated yields (45–94 %). The nature of the substituent(s)
attached to the germanium atom and the terminal alkynes was
investigated. The nature of the group at the ethynyl moiety
proved to be insignificant to the reaction outcome. For the
Scheme 3. Germylative coupling of 1-octyne/phenylacetylene performed by
a one-pot protocol.
Table 1. Coupling of chlorotriethylgermane with 1-octyne/phenylacetylene.
Entry
R′
Reaction conditions
[R3GeCl]/[alkyne]/[MI]/[NEt(iPr)2]/[Ir]
Conversion of Et3GeCl [%]
MI
[a]
[a]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
Ph
LiI
LiI
–
6[b]
10[c]
0
1:1.5:0:1.5:2 × 10–2
[a]
KI
82
[a]
LiI
LiI
LiI
LiI
LiI
LiI
LiI
LiI
–
37[d]
75
1:1.5:1.5:1.5:0.5 × 10–2
1:1.5:1.5:1.5:10–2
82
85[e]
78[f]
81
[a]
[a]
1:1.5:1.2:2:2 × 10–2
1:1.5:1.8:1.5:2 × 10–2
88
98
0
79
[a]
1:1.5:0:1.5:2 × 10–2
[a]
Ph
Ph
KI
LiI
[a]
99
[a] Reaction conditions: [R3GeCl]/[alkyne]/[MI]/[NEt(iPr)2]/[Ir] = 1:1.5:1.5:1.5:2 × 10–2, C6H5CF3, closed system, Ar, 80 °C, 24 h. The conversion was determined
by GC analysis with the solvent as an internal standard. [b] N,N-Dimethylformamide (DMF) as the solvent. [c] Tetrahydrofuran (THF) as the solvent. [d] Reaction
time 12 h. [e] At 60 °C. [f] At 120 °C.
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Table 2. Synthesis of alkynyl-substituted germanium compounds by a one-
pot procedure.[a]
germanium compounds, we used alkyl- and aryl-substituted
chlorogermanes to measure the impact of their bulkiness and
electronic properties on the reaction efficiency.
Sterically more encumbered aliphatic substituents at germa-
nium (Table 2, Entries 25 and 26) do not favor the coupling
reaction nor does the presence of aromatic groups (Table 2,
Entries 27–30), but longer reaction times gave satisfactory re-
sults. Most of the alkynylgermanes obtained were isolated and
characterized spectroscopically. Products 4–6, 9–12, 19–22, and
27–28 are classified as new compounds. The literature con-
cerning the synthesis of dialkynyl-substituted germanes and
alkynyl-substituted germanes with another unsaturated func-
tional group with possible catalytic reactivity is scarce.[6a,9,18]
Positive results for the one-pot protocol elaborated for mono-
acetylenes prompted us to perform preliminary tests for the
one-pot germylative coupling of 1,4-diethynylbenzene with
chlorogermane to explore its utility toward the synthesis of the
above-mentioned systems. The reaction conditions developed
for this reaction included the establishment of the optimal rea-
gent stoichiometry and concentration in C6H5CF3. The germ-
ylation of 1,4-diethynylbenzene by chlorotriethylgermane with
a 2.2-fold excess of germane substrate gives 1,4-bis[(triethyl-
germyl)ethynyl]benzene (32) in a high yield and selectivity
(Scheme 4). For equimolar amounts of chlorogermane and 1,4-
diethynylbenzene, it was possible to obtain 1-ethynyl-4-[(tri-
ethylgermyl)ethynyl]benzene (31) in high yield with only traces
of dialkynylgermyl-substituted benzene.
Scheme 4. Synthesis of mono- and dialkynyl-substituted germanes.
In our previous paper, we proposed a reasonable mechanism
for the germylative coupling of terminal alkynes with iodo-
germanes on the basis of stoichiometric reactions with iridium
complexes.[13] The real catalyst that initiates the reaction be-
tween iodogermanes and alkynes is the iridium(I) complex
[Ir(CO)(CCR)(NR′′3)2], as was also confirmed for iodosilanes.[15] As
the first step of the developed one-pot protocol for the germ-
ylative coupling of alkynylgermanes involves the creation of an
iodogermane in situ, the actual catalytic coupling concerns the
iridium-mediated coupling of iodogermanes with terminal
alkynes. Our next step to verify and prove the catalytic mecha-
nism of this process was theoretical calculations for the germ-
ylative coupling of iodogermanium derivatives with alkynes.
After reviewing the available literature on the subject, we de-
cided to perform the theoretical calculations for the model re-
action of prop-1-yne with iodotrimethylgermane (Scheme 5)
and trimethylamine and employed the three exchange-correla-
tion potential DFT (B3LYP)[19] and the hybrid M06 functional of
Truhlar and Zhao.[20] The SDD[21] and LANL2DZ basis sets of
[a] [R3GeCl]/[alkyne]/[MI]/[NEt(iPr)2]/[Ir]
(0.25 ), closed system, Ar, 80 °C, 24 h. [b] Measured by GC. [c] 48 h.
= , C6H5CF3
1:1.5:1.5:1.5:2 × 10–2
M
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Scheme 5. The catalytic cycle of the germylative coupling of terminal alkynes with iodogermanes catalyzed by the IrI complex A0; the transitions states (TS)
for the DFT calculations are shown.
triple-valence and double-valence quality were checked to see
if they provided similar results.
Both DFT methods resulted in comparable conclusions
(Table 3). The catalytic data obtained for the reaction of termi-
nal alkynes with iodogermanes show that the formation of the
product, that is, alkynylgermane elimination form complex A2,
is the rate-determining step for the process. The structures of
the respective A2 and A3 and the transition state TSA2–A3 at
the optimized energies obtained with B3LYP(LANL2DZ) are pre-
sented in Figure 1.
The energy profile for the A1–A6 process is shown in Fig-
ure 2. It is clear that the product elimination step is the energet-
ically most demanding process.
The energy barrier for the alkynylgermane, that is, the reac-
tion product elimination step, is 18.8 kcal/mol, which is 6.0 kcal/
mol higher than the energy for the insertion of iodotrimethyl-
Figure 1. Structures of A2 and A3 and the transition state TSA2–A3. Color
code: nitrogen blue, iridium dark blue, germanium light blue, oxygen red,
iodine violet, carbon gray, hydrogen white. All distances are in Å.
germane into the iridium complex. The DFT calculations indi- step in the catalytic cycle, that is, the insertion of the terminal
cated that the fastest step for this reaction is the second to last alkyne, the activation energy of which is only 6.8 kcal/mol.
Table 3. Calculated activation energies [kcal/mol] for selected stages of the coupling reaction.
Process
B3LYP/LANL2DZ
M06/SDD
Oxidative addition of trimethyliodogermane
Alkynylgermane elimination
12.8
18.8
6.8
13.4
19.6
7.3
Oxidative addition of alkyne
Ammonium salt elimination
15.1
17.3
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Computational Details: The methodology used in this study is sim-
ilar to that used in our previous studies of the Ru-catalyzed reac-
tion.[23] All geometry optimizations were performed with the
B3LYP[24] and M06 functionals.[20] Basis sets of triple-valence and
double-valence quality SDD[21] and LANL2DZ (the sets were used
to represent the investigated elements) were checked to see if they
provided similar results. Frequency calculations at the same level of
theory were also performed to confirm the characteristics of all of
the optimized structures as minima or transition states. Thermal
corrections to Gibbs free energies calculated at 298 K were in-
cluded. All computations were performed with Gaussian 09.[25]
Figure 2. Energy profiles for germylative coupling of iodogermanes with ter-
minal alkynes. The relative free energies are given in kcal/mol.
1
1-(Triethylgermyl)oct-1-yne (1): H NMR (500 MHz, CDCl3, 25 °C):
δ = 2.24 (t, J = 7.2 Hz, 2 H), 1.55–1.28 (m, 8 H), 1.10–1.07 (m, 9 H),
0.90 (t, J = 7 Hz, 3 H), 0.85–0.81 (m, 6 H) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 107.8 (–CC–), 80.8 (–CC–), 31.3 (–CH2–), 29.0
(–CH2–), 28.4 (–CH2–), 22.5 (–CH2–), 19.9 (–CH2–), 14.0 (–CH3), 8.9
(–GeEt3), 5.8 (–GeEt3) ppm. MS (EI): m/z (%) = 269.8 (0.2), 240.8
(100), 212.8 (41), 184.7 (6), 108.8 (21), 86.8 (6). Compound known
from the literature.[26]
Conclusions
We have presented a new one-pot catalytic method for the
synthesis of functionalized alkynyl-substituted germanium
compounds. This protocol has significant advantages over the
previously used procedure[13] as it allows the direct application
of commercially available chlorogermanes with terminal alk-
ynes in a single batch for the generation of the corresponding
iodogermanium derivatives without any additional operations.
DFT calculations showed that the rate-determining step for the
catalytic cycle of the germylative coupling of the terminal alk-
ynes with iodogermanes is the product-formation step, that is,
Trimethyl{1-[(triethylgermyl)ethynyl]cyclohexyloxy}silane (2):
1H NMR (500 MHz, CDCl3, 25 °C): δ = 1.86–1.84 (m, 2 H), 1.66–1.49
(m, 6 H), 1.09 (t, J = 7.9 Hz, 9 H), 0.85 (q, J = 7.8 Hz, 6 H), 0.20 (s, 9
H) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ = 110.4 (–CC–), 87.1
(–CC–), 70.4 (Ci), 41.5 (–CH2–), 25.3 (–CH2–), 23.4 (–CH2–), 9.0
(–GeEt3), 5.7 (–GeEt3), 2.1 [–Si(CH3)3] ppm. 29Si NMR (99 MHz, CDCl3,
25 °C): δ = 12.75 ppm. MS (EI): m/z (%) = 256.2 (5), 328.2 (11), 299.2
alkynylgermane elimination forms the catalytically active irid- (9), 195.2 (33), 161.1 (26), 157.0 (13), 143.0 (20), 133.0 (26), 128.9
(16), 103.0 (22), 75.1 (64), 73.1 (100), 59.0 (14). These assignments
ium species. Preliminary tests performed for 1,4-diethynylbenz-
ene have demonstrated the potential of this synthetic method-
ology, which will be developed in future studies.
are in good accordance with those reported previously.[11a]
1
1-(Triethylgermyl)-2-phenylethyne (3): H NMR (300 MHz, CDCl3,
25 °C): δ = 7.50–7.46 (m, 2 H), 7.31–7.29 (m, 3 H), 1.19–1.13 (m, 9
H), 0.98–0.91 (m, 6 H) ppm. 13C NMR (70 MHz, CDCl3, 25 °C): δ =
131.9 (–Ph), 128.1 (–Ph), 128.0 (–Ph), 123.7 (–Ph), 106.0 (–CC–), 92.0
(–CC–), 9.0 (–GeEt3), 5.8 (–GeEt3) ppm. MS (EI): m/z (%) = 260.3 (3),
233.1 (88), 205.1 (51), 175.1 (100), 177.0 (81), 98.9 (22), 77.1 (5).
Compound known from the literature.[26]
Experimental Section
Methods and Materials: All solvents were dried by standard meth-
ods and distilled before use. Reactions were performed under argon
by using standard Schlenk techniques. The iridium complex was
prepared according to a literature method.[22] The NMR spectra
were recorded at 25 °C with Bruker Ultra Shield (600 MHz), Varian
Mercury (300 MHz), Bruker Avance II (400 MHz), and Bruker Av-
ance III (500 MHz) spectrometers; CDCl3 was used as the solvent
and as internal deuterium lock. The chemical shifts are reported in
ppm with reference to the residual solvent (CHCl3) peaks for 1H and
13C and to tetramethylsilane (TMS) as an external standard for 29Si.
Mass spectra (EI-MS) were recorded with a Varian Saturn 2100 T
instrument by using electron-impact ionization at 70 eV. The chemi-
cals were purchased from the following sources: IrCl3·3H2O from
Pressure Chemicals; cis-cyclooctene, CDCl3, and α,α,α-trifluorotolu-
ene from Sigma–Aldrich; chlorogermanes and NEt(iPr)2 from ABCR;
and CO from Linde Gas.
3,3-Dimethyl-1-(triethylgermyl)-3-(trimethylsiloxy)prop-1-yne
1
(4): H NMR (500 MHz, CDCl3, 25 °C): δ = 1.48 (s, 6 H), 1.08 (t, J =
7.9 Hz, 6 H), 0.84 (q, J = 7.9 Hz, 6 H), 0.19 (s, 9 H) ppm. 13C NMR
(126 MHz, CDCl3, 25 °C): δ = 111.6 (–CC–), 84.4 (–CC–), 66.8 (Ci), 33.4
(–CH3), 8.9 (–GeEt3), 5.6 (–GeEt3), 1.93 [–Si(CH3)3] ppm. 29Si NMR
(99 MHz, CDCl3, 25 °C): δ = 13.10 ppm. MS (EI): m/z = 301.3 (26),
287.1 (10), 257.2 (13), 229.2 (12), 200.6 (8), 159.3 (26), 156.4 (12),
147.1 (90), 131.0 (20), 118.0 (24), 102.9 (14), 75.0 (100), 59.0 (20).
3,3-Diphenyl-1-(triethylgermyl)-3-(trimethylsiloxy)prop-1-yne
1
(5): H NMR (500 MHz, CDCl3, 25 °C): δ = 7.62 (d, J = 7.6 Hz, 4 H),
7.31–7.24 (m, 6 H), 1.15 (t, J = 7.3 Hz, 9 H), 0.97–0.92 (m, 6 H), 0.15
(s, 9 H) ppm. 13C NMR (126 MHz, CDCl3, 25 °C): δ = 147.0 (–Ph),
127.8 (–Ph), 126.9 (–Ph), 126.0 (–Ph), 108.6 (–CC–), 91.1 (–CC–), 76.6
(Ci), 9.0 (–GeEt3), 5.7 (–GeEt3), 1.64 [–Si(CH3)3] ppm. 29Si NMR
(99 MHz, CDCl3, 25 °C): δ = 17.02 ppm. MS (EI): m/z (%) = 411.2 (5),
359.2 (2), 279.2 (58), 159.0 (36), 133.0 (26), 105.0 (100), 91.1 (23),
88.8 (18), 77.1 (11), 73.1 (82), 59.1 (6).
General Synthetic Procedure for the Germylative Coupling of
Terminal Alkynes: A glass Schlenk reactor equipped with a mag-
netic stirring bar was evacuated and flushed with argon. A given
amount of LiI was placed in the reactor under a flow of argon;
then, α,α,α-trifluorotoluene and a precise amount of NEt(iPr)2 were
added. Next, appropriate amounts of terminal alkyne, chloroger-
mane, and [{Ir(μ-Cl)(CO)2}2] were added. The reaction was con-
ducted in a closed system at 80 °C with stirring for 24 h (or 48 h).
After the completion of the reaction, the solvent and any excess of
1-[Dimethyl(isopropyl)silyl]-2-(triethylgermyl)ethyne (6): 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 1.10 (t, J = 7.21 Hz, 9 H), 1.01 (d,
J = 7.2 Hz, 6 H), 0.85 (q, J = 8.1 Hz, 6 H), 0.17–0.14 (m, 1 H), 0.11 (s,
6 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 112.5 (–CC–), 112.0
(–CC–), 17.3 (–CH3), 14.0 (–CH–), 9.0 (–GeEt3), 5.7 (–GeEt3), –3.6
other reagents were removed under reduced pressure. The crude [–Si(CH3)2] ppm. 29Si NMR (79 MHz, CDCl3, 25 °C): δ = –13.00 ppm.
product was isolated after purification by column chromatography
(SiO2) with hexane as the eluent.
MS (EI): m/z (%) = 286.1 (0.8), 256.8 (100), 228.7 (40), 156.8 (9), 126.7
(9), 102.7 (7), 86.6 (9), 72.9 (14), 58.9 (15).
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1-(Triethylgermyl)-2-(triethylsilyl)ethyne (7): 1H NMR (500 MHz,
CDCl3, 25 °C): δ = 1.10 (t, J = 8.5 Hz, 9 H), 1.00 (t, J = 7.6 Hz, 9 H),
0.88–0.83 (m, 6 H), 0.62–0.57 (m, 6 H) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 112.6 (–CC–), 111.2 (–CC–), 8.9 (–GeEt3), 7.5
(–SiCH2CH3), 5.8 (–GeEt3), 4.5 (–SiCH2CH3) ppm. 29Si NMR (99 MHz,
1-(Tributylgermyl)-2-(triethylsilyl)ethyne (15): 1H NMR (500 MHz,
CDCl3, 25 °C): δ = 1.48–1.32 (m, 12 H), 1.00 (t, J = 8 Hz, 3 H), 0.92–
0.84 (m, 15 H), 0.61–0.57 (m, 6 H) ppm. 13C NMR (125 MHz, CDCl3,
25 °C): δ = 113.7 (CC), 111.1 (CC), 27.4 (–GeBu3), 26.0 (–GeBu3),
14.2 (–GeBu3), 13.7 (–GeBu3), 7.4 (–SiEt3), 4.5 (–SiEt3) ppm. 29Si NMR
CDCl3, 25 °C): δ = –8.82 ppm. MS (EI): m/z (%) = 300.0 (0.5), 270.8 (99 MHz, CDCl3, 25 °C): δ = –8.91 ppm. MS (70 eV): m/z (%) = 299.2
(100), 242.7 (38), 212.8 (21), 184.8 (20), 158.6 (13), 128.6 (17), 100.7 (20), 271.3 (100), 269.3 (85), 209.5 (16). These assignments are in
(7). These assignments are in good accordance with those reported good accordance with those reported previously.[13]
previously.[11a]
4-Phenyl-1-(tributylgermyl)but-1-yne (16): 1H NMR (500 MHz,
1,2-Bis(triethylgermyl)ethyne (8): 1H NMR (500 MHz, CDCl3,
25 °C): δ = 1.10 (t, J = 7.9 Hz, 9 H), 0.84 (q, J = 7.9 Hz, 6 H) ppm.
13C NMR (125 MHz, CDCl3, 25 °C): δ = 110.8 (–CC–), 8.9 (–GeEt3), 5.8
(–GeEt3) ppm. MS (EI): m/z (%) = 343.7 (0.3), 314.7 (100), 286.7 (32),
256.8 (23), 228.6 (18), 198.7 (15), 170.6 (30), 102.8 (25).
N-Benzyl-N-methyl-3-(triethylgermyl)prop-2-yn-1-amine (9): 1H
NMR (500 MHz, CDCl3, 25 °C): δ = 7.34–7.28 (m, 5 H), 3.59 (s, 2 H),
3.35 (s, 2 H), 2.35 (s, 3 H), 1.07 (t, J = 7.93 Hz, 9 H), 0.93–0.85 (m, 6
H) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ = 138.5 (–Ph), 129.3
(–Ph), 128.2 (–Ph), 127.1 (–Ph), 100.6 (–CC–), 87.2 (–CC–), 59.8
(–CH2–), 45.9 (–CH2–), 41.8 (–CH3), 9.1 (–GeEt3), 5.78 (–GeEt3) ppm.
CDCl3, 25 °C): δ = 7.25–7.16 (m, 5 H), 2.81 (t, J = 7.5 Hz, 2 H), 2.50
(t, J = 7.5 Hz, 2 H), 1.40–1.28 (m, 12 H), 0.88 (t, J = 6.7 Hz, 9 H),
0.81–0.78 (m, 6 H) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ = 140.9
(–Ph), 128.5 (–Ph), 128.2 (–Ph), 126.1 (–Ph), 106.5 (–CC–), 82.8 (–CC–
), 35.5 (–CH2–), 27.3 (–GeBu3), 26.2 (–GeBu3), 22.2 (–CH2–), 14.1
(–GeBu3), 13.8 (–GeBu3) ppm. MS (70 eV): m/z (%) = 373.0 (4), 317.0
(29), 259.1 (82), 187.2 (45), 129.1 (28). These assignments are in
good accordance with those reported previously.[13]
1
1-[(Tributylgermyl)ethynyl]cyclohexanol (17): H NMR (500 MHz,
CDCl3, 25 °C): δ = 2.18 (s, 1 H), 1.69–1.54 (m, 11 H), 1.45–1.34 (m,
12 H), 0.92–0.84 (m, 15 H) ppm. 13C NMR (125 MHz, CDCl3, 25 °C):
MS (EI): m/z (%) = 319.2 (2), 290.2 (4), 158.1 (51), 120.1 (14), 91.1 δ = 110.0 (–CC–), 86.7 (–CC–), 69.2 (Ci), 40.2 (–CH2–), 27.4 (–GeBu3),
(100), 77.0 (4).
26.0 (–GeBu3), 25.2 (–CH2–), 23.5 (–CH2–), 14.1 (–GeBu3), 13.8 (–Ge-
Bu3) ppm. MS (70 eV): m/z (%) = 367.5 (2), 293.3 (9), 255.3 (100),
181.3 (43). These assignments are in good accordance with those
reported previously.[13]
Dimethyl(phenyl)[(tributylgermyl)ethynyl]silane (18): 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 7.69–7.66 (m, 2 H), 7.39–7.36 (m, 3 H),
1.49–1.35 (m, 12 H), 0.94–0.88 (m, 15 H), 0.42 (s, 6 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C): δ = 137.6 (–Ph), 133.7 (–Ph), 129.2 (–Ph),
127.7 (–Ph), 115.05 (–CC–), 111.47 (–CC–), 27.4 (–GeBu3), 26.0
(–GeBu3), 14.1 (–GeBu3), 13.7 (–GeBu3), –0.6 [–Si(CH3)2] ppm. 29Si
NMR (79 MHz, CDCl3, 25 °C): δ = –23.49 ppm. MS (EI): m/z (%) =
347.5 (9), 291.5 (100), 288.5 (79), 243 (23), 219.5 (10), 189.5 (55).
6-(Triethylgermyl)hex-5-ynenitrile (10): 1H NMR (300 MHz, CDCl3,
25 °C): δ = 2.52 (t, J = 7.45 Hz, 2 H), 2.43 (t, J = 6.5 Hz, 2 H), 1,92–
1.82 (m, 2 H), 1.07 (t, J = 7.7 Hz, 9 H), 0.83 (q, J = 7.8 Hz, 6 H) ppm.
13C NMR (75 MHz, CDCl3, 25 °C): δ = 119.3 (–CN), 104.0 (–CC–), 83.7
(–CC–), 24.8 (–CH2–), 18.9 (–CH2–), 15.9 (–CH2–), 8.9 (–GeEt3), 5.6
(–GeEt3) ppm. MS (EI): m/z (%) = 224.2 (100), 196.2 (74), 166.0 (77),
114.0 (37), 101.9 (6), 94.1 (6), 74.0 (14).
4-Phenyl-1-(triethylgermyl)but-1-yne (11): 1H NMR (300 MHz,
CDCl3, 25 °C): δ = 7.32–7.19 (m, 5 H), 2.87 (t, J = 7.5 Hz, 2 H), 2.56
(t, J = 7.5 Hz, 2 H), 1.09 (t, J = 7.8 Hz, 9 H), 0.85 (q, J = 7.9 Hz, 6 H)
ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 140.8 (–Ph), 128.5 (–Ph),
128.2 (–Ph), 126.1 (–Ph), 106.6 (–CC–), 81.9 (–CC–), 35.5 (–CH2–), 22.2
(–CH2–), 8.9 (–GeEt3), 5.7 (–GeEt3) ppm. MS (EI): m/z (%) = 288.3
1-(Tributylgermyl)-2-(triisopropylsilyl)ethyne (19): 1H NMR
(600 MHz, CDCl3, 25 °C): δ = 1.48–1.43 (m, 6 H), 1.39–1.33 (m, 6 H),
(0.2), 261.2 (60), 259.2 (48), 233.1 (23), 203.1 (25), 199.0 (11), 91.1 1.11–1.04 (m, 21 H), 0.91–0.84 (m, 15 H) ppm. 13C NMR (150 MHz,
(100), 77.1 (7), 65.1 (34).
CDCl3, 25 °C): δ = 114.1 (–CC–), 109.7 (–CC–), 27.5 (–GeBu3), 26.0
(–GeBu3), 18.6 (–CH3), 14.3 (–GeBu3), 13.8 (–GeBu3), 11.2 (–CH–)
ppm. 29Si NMR (79 MHz, CDCl3, 25 °C): δ = –3.41 ppm. MS (EI): m/z
(%) = 383.0 (89), 270.0 (40), 268.9 (76), 368.8 (64), 326.1 (11), 313.0
(42), 271.0 (100), 256.9 (8), 188.9 (15), 182.9 (23), 170.8 (63), 156.8
(64), 133.9 (18), 128.7 (61).
6-(Tributylgermyl)hex-5-ynenitrile (20): 1H NMR (300 MHz, CDCl3,
25 °C): δ = 2.51 (t, J = 7.3 Hz, 2 H), 2.42 (t, J = 7.3 Hz, 2 H), 1.91–
1.82 (m, 2 H), 1.46–1.25 (m, 12 H), 0.96–0.80 (m, 15 H) ppm. 13C
NMR (79 MHz, CDCl3, 25 °C): δ = 119.2 (–CN), 103.8 (–CC–), 84.6
(–CC–), 27.4 (–GeBu3), 26.1 (–GeBu3), 24.8 (–CH2–), 19.0 (–CH2–), 15.9
(–CH2–), 14.1 (–GeBu3), 13.7 (–GeBu3) ppm. MS (EI): m/z (%) = 280.2
(37), 224.1 (85), 222.4 (28), 166.0 (100), 131.0 (6), 55.1 (17).
1-(Cyclohexenyl)-2-(triethylgermyl)ethyne
(12):
1H
NMR
(300 MHz, CDCl3, 25 °C): δ = 6.15–6.13 (m, 1 H), 2.16–2.07 (m, 4 H),
1.66–1.55 (m, 4 H), 1.09 (t, J = 7.64 Hz, 9 H), 0.90–0.82 (m, 6 H) ppm.
13C NMR (75 MHz, CDCl3, 25 °C): δ = 135.1 (–CH–), 121.0 (Ci), 108.1
(–CC–), 88.3 (–CC–), 29.4 (–CH2–), 25.6 (–CH2–), 22.3 (–CH2–), 21.5
(–CH2–), 8.6 (–GeEt3), 5.7 (–GeEt3) ppm. MS (EI): m/z (%) = 264.1 (4),
237.2 (100), 209.1 (70), 181.1 (83), 105.0 (39), 97.0 (20), 81.1 (3).
1-(Tributylgermyl)oct-1-yne (13): 1H NMR (500 MHz, CDCl3, 25 °C):
δ = 2.24 (t, J = 7 Hz, 2 H), 1.54–1.50 (m, 6 H), 1.46–1.28 (m, 17 H),
0.92–0.89 (m, 9 H), 0.83 (t, J = 7 Hz, 2 H) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 107.6 (–CC–), 81.7 (–CC–), 31.4 (–CH2–), 28.9
(–CH2–), 28.4 (–CH2–), 27.4 (–GeBu3), 26.2 (–GeBu3), 22.6 (–CH2–),
19.9 (–CH2–), 14.2 (–GeBu3), 14.0 (–CH3), 13.8 (–GeBu3) ppm. MS
Tributyl(cyclohexen-1-ylethynyl)germane
(21):
1H
NMR
(70 eV): m/z (%) = 297.3 (50), 241.3 (56), 199.2 (25), 183.2 (80), 169.2 (300 MHz, CDCl3, 25 °C): δ = 6.14–6.12 (m, 1 H), 2.16–2.08 (m, 4 H),
(47), 153.2 (45), 109.2 (55). These assignments are in good accord- 1.65–1.55 (m, 4 H), 1.49–1.29 (m, 12 H), 0.93–0.83 (m, 15 H) ppm.
ance with those reported previously.[13]
13C NMR (75 MHz, CDCl3, 25 °C): δ = 134.9 (–CH–), 121.1 (Ci), 107.9
(–CC–), 89.2 (–CC–), 29.4 (–CH2–), 27.4 (–GeBu3), 26.1 (–GeBu3), 25.6
(–CH2–), 22.3 (–CH2–), 21.5 (–CH2–), 14.1 (–GeBu3), 13.8 (–GeBu3)
ppm. MS (EI): m/z (%) = 293.3 (25), 237.2 (29), 179.0 (42), 161.1 (100),
105.1 (43), 96.9 (8).
Tributyl(phenylethynyl)germane (14): 1H NMR (500 MHz, CDCl3,
25 °C): δ = 7.45–7.43 (m, 2 H), 7.26 (m, 3 H), 1.50–1.44 (m, 6 H),
1.41–1.33 (m, 6 H), 0.93–0.89 (m, 15 H) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 131.9 (–Ph), 128.1 (–Ph), 127.9 (–Ph), 123.8 (–Ph),
105.8 (–CC–), 92.6 (–CC–), 27.4 (–GeBu3), 26.1 (–GeBu3), 14.2 (–Ge- 3-Methyl-1-(tributylgermyl)-3-(trimethylsiloxy)but-1-yne (22):
Bu3), 13.8 (–GeBu3) ppm. MS (EI): m/z (%) = 347.5 (4), 289.3 (100),
1H NMR (300 MHz, CDCl3, 25 °C): δ = 1.48 (s, 6 H), 1.45–1.40 (m, 6
232.8 (40), 203.5 (83), 189.5 (82) 101.3 (13). These assignments are H), 1.38–1.32 (m, 6 H), 0.92–0.84 (m, 15 H), 0.20 (s, 9 H) ppm. 13C
in good accordance with those reported previously.[13]
NMR (75 MHz, CDCl3, 25 °C): δ = 111.4 (–CC–), 85.3 (–CC–), 66.8 (Ci),
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33.4 [–(CH3)2], 27.4 (–GeBu3), 26.1 (–GeBu3), 14.0 (–GeBu3), 13.7
(–GeBu3), 1.95 [–Si(CH3)3] ppm. MS (EI): m/z (%) = 385.1 (6), 287.0
(58), 230.9 (100), 228.9 (79), 156.8 (8), 146.9 (63), 88.8 (18), 73.0 (53).
Acknowledgments
The authors gratefully acknowledge financial support from the
National Science Centre (Poland) (PRELUDIUM Project No. DEC-
2012/05/N/ST5/00759 and MAESTRO Project No. DEC-2011/02/
A/ST5/00472). This research was supported in part by the PL-
Grid Infrastructure.
1-(Tributylgermyl)-2-(triethylgermyl)ethyne (23): MS (EI): m/z
(%) = 401.1 (18), 371.1 (64), 373.2 (41), 342.8 (7), 313.1 (33), 286.1
(24), 259.0 (19), 229.0 (27), 201.0 (33), 172.8 (62), 57.0 (100). Com-
pound known from the literature.[27]
Tributyl{[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phen-
yl]ethynyl}germane (24): MS (EI): m/z (%) = 415.3 (31), 358.3 (39),
301.4 (25), 244.8 (11), 229.4 (23), 187.1 (14), 129.1 (38), 84.0 (100),
72.5 (7), 57.0 (80).
Keywords: Alkynes · Organocatalysis · Germanium ·
Iridium · Density functional calculations
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1-(tert-Butyldimethylgermyl)-2-(triethylsilyl)ethyne (25): MS (EI):
m/z (%) = 298.3 (0.7), 283.3 (1.3), 270.6 (1.2), 225.4 (13), 223.3 (100),
195.1 (56), 167.0 (39), 139.9 (7), 113.0 (21), 85.0 (88).
1-Phenyl-2-(triisopropylgermyl)ethyne (26): MS (EI): m/z (%) =
306.20 (100), 303.3 (7), 289.2 (23), 263.3 (3), 228.2 (21), 215.2 (14),
202.1 (8), 176.5 (2), 144.7 (11), 91.0 (3), 77.1 (17).
(Cyclohexen-1-ylethynyl)dimethyl(phenyl)germane (27): 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 7.62–7.59 (m, 2 H), 7.40–7.37 (m, 3 H),
6.23–6.20 (m, 1 H), 2.18–2.10 (m, 4 H), 1.66–1.58 (m, 4 H), 0.59 (s, 6
H) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 139.1 (–Ph), 135.9
(–CH–), 133.1 (–Ph), 128.8 (–Ph), 128.1 (–Ph), 120.8 (Ci), 107.82 (–CC–
), 88.62 (–CC–), 29.2 (–CH2–), 25.6 (–CH2–), 22.2 (–CH2–), 21.4 (–CH2–
), –0.9 [–Ge(CH3)2] ppm. MS (EI): m/z (%) = 284.1 (16), 271.1 (100),
182.1 (37), 175.1 (10), 166.2 (22), 149.0 (26), 94.9 (8), 91.1 (31), 77.1
(35).
6-[Dimethyl(phenyl)germyl]hex-5-ynenitrile (28): 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 7.53–7.50 (m, 2 H), 7.35–7.33 (m, 3 H),
2.52–2.41 (dt, J = 18.3 Hz, 2 H), 1.90–1.81 (m, 2 H), 0.52 (s, 6 H) ppm.
13C NMR (75 MHz, CDCl3, 25 °C): δ = 138.6 (–Ph), 132.8 (–Ph), 128.8
(–Ph), 128.0 (–Ph), 119.1 (–CN), 103.9 (CC), 84.2 (CC), 24.4 (–CH2–),
18.8 (–CH2–), 15.9 (–CH2–), –1.2 (–CH3) ppm. MS (EI): m/z (%) = 258.1
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1-(Cyclohexen-1-yl)-2-(triphenylgermyl)ethyne (29): MS (EI): m/z
(%) = 410.2 (12), 333.2 (25), 303.2 (15), 255.1 (3), 227.2 (93), 175.1
(14), 151.0 (100), 105.3 (7), 95.0 (8), 77.0 (48), 72.0 (8).
1-Phenyl-2-(triphenylgermyl)ethyne (30): 1H NMR (300 MHz,
CDCl3, 25 °C): δ = 7.81–7.21 (m, 20 H), 2.16–2.08 (m, 4 H), 1.65–1.55
(m, 4 H), 1.49–1.29 (m, 12 H), 0.93–0.83 (m, 15 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C): δ = 135.2 (–Ph), 134.6 (–Ph), 132.2 (–Ph),
129.5 (–Ph), 128.8 (–Ph), 128.7 (–Ph), 128.4 (–Ph), 128.2 (–Ph), 108.1
(–CC–), 88.7 (–CC–) ppm. MS (EI): m/z (%) = 406.3 (30), 329.3 (35),
303.4 (6), 251.8 (18), 227.2 (100), 149.2 (90), 173.0 (40), 93.3 (5), 77.2
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Triethyl[(4-ethynylphenyl)ethynyl]germane (31): 1H NMR
(500 MHz, CDCl3, 25 °C): δ = 7.41 (s, 4 H), 3.15 (s, 1 H), 1.15 (t, J =
7.8 Hz, 9 H), 0.94 (q, J = 7.6 Hz, 6 H) ppm. 13C NMR (125 MHz, CDCl3,
25 °C): δ = 131.9 (–Ph), 131.8 (–Ph), 124.2 (–Ph), 121.6 (–Ph), 105.3
(–CC–), 93.7 (–CC–), 83.3 (–CC–), 78.7 (–CC–), 9.00 (–GeEt3), 5.75
(–GeEt3) ppm. MS (EI): m/z (%) = 285.4 (7), 256.8 (100), 228.9 (55),
200.8 (63), 198.8 (80), 131.7 (2), 123.0 (14), 100.8 (11), 74.8 (7).
1
1,4-Bis[(triethylgermyl)ethynyl]benzene (32): H NMR (300 MHz,
CDCl3, 25 °C): δ = 7.38 (s, 4 H), 1.15 (t, J = 7.7 Hz, 18 H), 0.94 (q, J =
7.6 Hz, 12 H) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 131.7
(–Ph), 123.3 (–Ph), 105.6 (–CC–), 94.1 (–CC–), 9.0 (–GeEt3), 5.7 (–
GeEt3) ppm. MS (EI): m/z (%) = 444.2 (15), 415.2 (100), 387.1 (30),
359.1 (29), 330.1 (15), 303.1 (6), 273.0 (17), 133.0 (23), 103.0 (25),
75.1 (5).
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Received: September 29, 2015
Published Online: January 4, 2016
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