Reactivity of germanium(II) hydride with nitrous oxide, trimethylsilyl azide, ketones, and alkynes and the reaction of a methyl analogue with trimethylsilyl diazomethane

Article abstract of DOI:10.1039/b914164b

The reactions of stable β-diketiminate germanium(II) hydride LGeH (1) [L = HC(CMeNAr)₂, Ar = 2,6-iPr₂C₆H₃] with nitrous oxide, trimethylsilyl azide, ketones, and alkynes are described. 1 reacts with nitrous oxide to yield the germanium(II) hydroxide LGeOH (2), and with trimethylsilyl azide affords in toluene at room temperature the germanium(II) azide LGeN₃ (3), and also the germanium(IV) diamide L′Ge(NHSiMe₃)₂ (L′ = CH{(CCH₂) (CMe)(2,6-iPr₂C₆H₃N) ₂}) (4). Ketones (PhCOCF₃, 2-C₄H₃SCOCF₃) and 1 generated the germanium(II) alkoxides (5-6) in high yield. The activated terminal alkyne (HCCCO₂Me) and disubstituted alkyne (EtO₂ CCCCO₂Et) react with 1 to form the germanium(II) substituted alkenes (vinyl germylene) (7-8). Further reaction of the methylgermanium(II) compound LGeMe (9) with trimethylsilyl diazomethane resulted in the formation of germanium(IV) amide L′Ge(Me)NHNCHSiMe₃ (10). Compounds 2-8, and 10 were characterized by microanalysis and multi-nuclear NMR spectroscopy. Furthermore compounds 3-6, and 8 are confirmed by X-ray structural analysis. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/b914164b

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Reactivity of germanium(II) hydride with nitrous oxide, trimethylsilyl azide,
ketones, and alkynes and the reaction of a methyl analogue with trimethylsilyl
diazomethane†
Anukul Jana,a Herbert W. Roesky*a and Carola Schulzkeb
Received 15th July 2009, Accepted 11th September 2009
First published as an Advance Article on the web 5th October 2009
DOI: 10.1039/b914164b
The reactions of stable b-diketiminate germanium(II) hydride LGeH (1) [L = HC(CMeNAr)2, Ar =
2,6-iPr2C6H3] with nitrous oxide, trimethylsilyl azide, ketones, and alkynes are described. 1 reacts with
nitrous oxide to yield the germanium(II) hydroxide LGeOH (2), and with trimethylsilyl azide affords in
toluene at room temperature the germanium(II) azide LGeN3 (3), and also the germanium(IV)
=
diamide L¢Ge(NHSiMe3)2 (L¢ = CH{(C CH2)(CMe)(2,6-iPr2C6H3N)2}) (4). Ketones (PhCOCF3,
2-C4H3SCOCF3) and 1 generated the germanium(II) alkoxides (5–6) in high yield. The activated
≡
≡
terminal alkyne (HC CCO2Me) and disubstituted alkyne (EtO2CC CCO2Et) react with 1 to form
the germanium(II) substituted alkenes (vinyl germylene) (7–8). Further reaction of the
methylgermanium(II) compound LGeMe (9) with trimethylsilyl diazomethane resulted in the
=
formation of germanium(IV) amide L¢Ge(Me)NHN CHSiMe3 (10). Compounds 2–8, and 10 were
characterized by microanalysis and multi-nuclear NMR spectroscopy. Furthermore compounds 3–6,
and 8 are confirmed by X-ray structural analysis.
the metal–metal bond to generate metal oxygen compounds.7
Introduction
However there is no reaction known of group 14 metal hydride
with nitrous oxide to form the metal hydroxide. Herein we are
reporting the reaction of LGeH with nitrous oxide under the
formation of LGeOH (2) in almost quantitative yield (Scheme 1).
Compound 2 was previously reported by our group by the
reaction of LGeCl with water in the presence of 1,3-di(2,4,6-
The chemistry of divalent germanium compounds has received
considerable attention due to their carbene like properties.1 Such
compounds are generally reactive and tend to oligomerize or poly-
merize. However, Ge(II) compounds can be stabilized kinetically
by sterically demanding ligands and/or thermodynamically by
inter- and intramolecular coordination. Compounds of divalent
germanium bonded to small substituents (such as H, Me, Et, and
nBu) are highly reactive and therefore exist only as intermediates.
Organometallics hydrides of group 14 play an important role
in various metathesis reactions and therefore the reactivity of
hydrides like R3SiH, R3GeH, and R3SnH is well studied.2 To
overcome these difficulties our group reported the syntheses and
structures of LGeR (R = H, Me, and nBu; L = HC(CMeNAr)2,
Ar = 2,6-iPr2C6H3).3,4 More recently we also communicated the
reactivity of LGeH with some unsaturated compounds including
carbon dioxide and trimethylsilyl diazomethane.5,6 Herein we
report the reactivity of LGeH (1) with nitrous oxide, trimethylsilyl
azide, ketones, and alkynes. Furthermore, we also describe the
reactivity of LGeMe with trimethylsilyl diazomethane.
Me3C6H2)-2-ylidene8 or alternatively by the reaction of L¢Ge (L¢ =
9
=
CH{(C CH2)(CMe)(2,6-iPr2C6H3N)2}) with water.
Scheme 1 Preparation of compound 2
Recently we reported on the reactivity of 1 with diazoalkane by
formation of germanium(II) substituted hydrazone derivatives.6
Subsequently we became interested in studying the reactivity of 1
with trimethylsilyl azide. In 2005 our group communicated the
first end-on azide insertion into an Al–C bond of an alumi-
nacyclopropene and the formation of aluminaazacyclobutene.10
Trimethylsilyl diazomethane and trimethylsilyl azide are isoelec-
tronic and both exhibit 1,3-dipolar properties. Therefore we ex-
pected that the azide might also insert end-on into the germanium–
hydrogen bond of 1. However the reaction of 1 with trimethylsilyl
azide at room temperature afforded two products in a ratio of 1:1
(Scheme 2).
Results and discussion
Syntheses and characterization
It is well known that nitrous oxide acts as a mono oxygen source.
It can supply the oxygen to the low valent metal center or to
aInstitut fu¨r Anorganische Chemie, Universita¨t Go¨ttingen, Tammannstrasse
4, 37077, Go¨ttingen, Germany. E-mail: hroesky@gwdg.de; Fax: +49-551-
393373
bSchool of Chemistry, Trinity College Dublin, Dublin 2, Ireland
One is the germanium(II) azide (3), and the other is the germa-
nium(IV) diamide (4). Compound 3 was formed by metathesis
reaction of 1 with Me3SiN3 under elimination of Me3SiH. In
† CCDC reference numbers 713790, 715866, 730408, 738339, and 730403
for 3, 4, 5, 6, and 8 respectively. For crystallographic data in CIF or other
electronic format see DOI: 10.1039/b914164b
132 | Dalton Trans., 2010, 39, 132–138
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Scheme 2 Preparation of compounds 3 and 4
the literature only two germanium(II) azides are reported by
nucleophilic substitution reaction using NaN3 and germanium(II)
chloride precursors,11 whereas compound 4 was generated by
elimination of dinitrogen from azide, with the resulting nitrene
inserting into the germanium–hydrogen bond. The final oxidative
addition of another nitrene is followed by simultaneous hydrogen
transfer from one methyl group, which is attached to the hetero-
cyclic ring backbone. A few reactions of group 14 compounds with
divalent elements and organic azides have been reported.12 The
initial dinitrogen elimination from Me3SiN3 is generally accepted,
and supported by experimental observations.13
Fig. 1 Molecular structure of 3. Thermal ellipsoids are shown at 50%
probability. H atoms are omitted for clarity reasons. Selected bond lengths
◦
˚
[A] and angles [ ]: Ge1–N3 2.002(3), N3–N4 1.198(4), N4–N5 1.149(4),
Ge1–N1 1.980(2), Ge1–N2 1.973(2); Ge1–N3–N4 121.5(3), N3–N4–N5
176.3(4), N1–Ge1–N2 90.69(11).
The formation of the imide LGe(F)NSiMe3 was observed by
elimination of dinitrogen from Me3SiN3 followed by oxidative
addition to the germanium(II) center of LGeF,14 whereas LGeMe
reacted with Me3SiN3 under dinitrogen elimination, oxidative
addition, followed by intramolecular hydrogen transfer from one
methyl group of the ring backbone to yield L¢Ge(Me)NHSiMe3.4
Subsequently we propose a reasonable pathway for the formation
of 4 (Scheme 3).
Fig. 2 Molecular structure of 4. Thermal ellipsoids are shown at 50%
probability. H atoms except N3–H and N4–H and the iso-propyl grou◦ps
Scheme 3 Proposed pathway for the formation of 4
˚
are omitted for clarity reasons. Selected bond lengths [A] and angles [ ]:
Ge1–N1 1.8416(14), Ge1–N2 1.8413(15), Ge1–N3 1.8011(14), Ge1–N4
1.8224(15); N1–Ge1–N2 101.59(6), N1–Ge1–N3 112.77(7), N3–Ge1–N4
111.24(8), N2–Ge1–N4 111.54(7).
Compound 3 crystallizes in the triclinic space group P-1 from
n-hexane at room temperature. There are three independent
molecules in the unit cell (Fig. 1). The IR spectrum of 3 exhibits a
band at 2068 cm-1, which is assigned to the N3 stretching frequency.
4 is a colorless solid soluble in benzene, THF, n-hexane, and
n-pentane respectively and shows no decomposition on exposure
to dry air. 4 was characterized by 1H and 29Si NMR spectroscopy,
EI mass spectrometry, elemental analysis, and X-ray structural
analysis. The 1H NMR spectrum of 4 shows a singlet (d 0.01 ppm),
which can be assigned to the Si(CH3)3 protons.
from the supporting ligand, and two others from the imide groups,
featuring a distorted tetrahedral geometry. The four Ge–N bond
lengths are almost similar. The Ge–N bond lengths of 2 and 3 and
those of 4 are quite different due to the non-equal oxidation states
of the germanium atoms. The formation of 4 requires the oxidation
of germanium(II) to germanium(IV). Therefore the synthesis of 4
also involves a unprecedented oxidative addition–insertion with
nitrene (:NSiMe3), which is formed in situ from trimethylsilyl
azide by elimination of dinitrogen, and insertion into the Ge(II)–
H bond, which leads to the formal conversion of the GeH hydride
to a NH proton.
Maintaining a n-hexane solution of 4 for two days at -32 ◦C
resulted in colorless single crystals suitable for X-ray structural
analysis. 4 crystallizes in the monoclinic space group P21/n, with
one molecule of 4 in the asymmetric unit. 4 exists as a monomer
in the solid state (Fig. 2). There are no intermolecular hydrogen
bonds observed in the crystal lattice. The coordination polyhedron
around the germanium atom comprises four nitrogen atoms, two
Surprisingly there is no precedent reaction of group 14 known
where nitrene is added and inserted simultaneously at the same
element. We were not able to isolate any intermediate of this
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reaction. No evidence was found for any tautomeric equilibrium
of 4.
are upfield shifted when compared with that of LGeOC(O)H
(d 8.64 ppm).5 The assignment of the chemical shift for the CH
proton of LGeOC(O)H should be downfield instead of upfield
when compared with that of LGeH (d 8.08 ppm).5 The 19F
NMR resonance arises as a doublet (d -75.76 (5) and -76.29
(6) ppm) with the same coupling constant of 8 and 7 Hz
respectively. The four isopropyl groups of 5 and 6 are showing
four different resonances, and even the two methyl groups in the
ring backbone exhibit two different signals each in the 1H NMR
spectra.
In a preliminary publication we have shown some reactions
of 1 with unsaturated molecules.5 So far we used no ketone,
which might generate the germanium(II) alkoxide by nucleophilic
addition reaction to the carbon oxygen double bond. Although
1 displayed no reactivity toward acetone or benzophenone at
room temperature, it reacts cleanly with activated ketones namely
2,2,2-trifluoro acetophenone and 2,2,2-trifluoroacetothiophene.
Treatment of 1 with 2,2,2-trifluoroacetophenone and 2,2,2-
trifluoroacetothiophene leads quantitatively to the germylene
alkoxides 5 and 6 respectively with a Ge(II)–O–C framework
that is formed by nucleophilic hydride addition to the respective
carbon of the carbonyl group (Scheme 4). Compounds 5 and 6
Single crystals of 5 and 6 suitable for X-ray structural analysis
were obtained from n-hexane solutions. 5 and 6 crystallize in
the triclinic space group P-1 and monoclinic space group P21/c
respectively (Table 1). The molecular structures of 5 and 6 are
shown in Figs. 3 and 4. The asymmetric unit of 5 and 6 contains one
formula unit of the compound, and there are two of the molecules
1
were monitored by H NMR spectra. Sharp resonances in the
1H NMR spectra of 5 and 6 gave the initial indication that the
1
products have been formed in high yield.
in each unit cell. As predicted, based on the H NMR spectrum
and EI mass spectrum, compounds 5 and 6 contain a Ge(II)–
O–CH core. The three coordinate germanium atom is surrounded
by two N atoms of the b-diketiminato ligand, and an exocyclic
˚
˚
O atom. The Ge–O bond lengths (1.862 A, 1.855 A) are compara-
8
˚
ble with those of compound 2 (1.828 A). The O–C bond distances
of 5 and 6 are in a narrow range of each other (1.407 A and
1.417 A).
The hydrogermylation of alkynes has been well known for
˚
˚
nearly 50 years and follows a polar or a free radical pathway
depending on the substituents, catalyst, solvent, and conditions.15
In contrast to this result the present hydrogermylation reaction
of alkynes with 1 proceeds without any catalyst. 1 reacts with
Scheme 4 Preparation of compounds 5 and 6
Compounds 5 and 6 have one CF3 group each and both display
1
an interesting NMR spectrum. The H NMR spectra of 5 and 6
≡
≡
HC CCO2Me and EtO2CC CCO2Et respectively at room tem-
perature to form the vinyl germylenes 7 and 8 (Scheme 5). 7 and 8
are obtained by the 1,2-addition of 1 to the carbon–carbon triple
bond.
exhibit a quartet each (d 4.73 and 5.04 ppm) which corresponds
to the quaternary CH proton and its coupling with the three
F-atoms of the CF3 group (3J(19F-1H) = 8 and 7 Hz respectively).
The CH resonances of 5 (d 4.73 ppm) and 6 (d 5.04 ppm)
Table 1 Crystallographic data for the structural analysis of 3, 4, 5, 6, and 8
Parameters
3
4
5
6
8
Empirical formula
Mol. Wt.
C29H41GeN5
532.26
triclinic
C35H60GeN4Si2
665.64
monoclinic
P21/n
10.389(2)
32.555(7)
12.216(2)
90
112.28(3)
90
3823.0(13)
4
1.158
0.891
1432
0.5 ¥ 0.4 ¥ 0.4
1.91–25.84
30291/7365
[R(int) = 0.0476]
7365/0/405
0.0304, 0.0725
0.0373, 0.0748
1.033
C37H47F3GeN2O
665.36
triclinic
C35H45F3GeN2OS
671.38
monoclinic
P21/c
12.142(2)
8.7405(17)
32.073(6)
90
98.61(3)
90
3365.5(11)
4
1.325
C37H52GeN2O4
661.40
monoclinic
P21/c
11.837(2)
17.042(3)
17.895(4)
90
103.69(3)
90
3507.3(12)
4
1.253
0.913
1408
0.38 ¥ 0.15 ¥ 0.08
1.67–26.96
31646/7613
[R(int) = 0.0585]
7613/0/413
0.0341, 0.0738
0.0472, 0.0777
1.016
Crystal system
Space group
P-1
P-1
˚
a [A]
16.697(3)
17.006(3)
17.763(4)
101.17(3)
116.15(3)
100.60(3)
4229.2(15)
6
10.833(2)
11.879(2)
14.500(3)
79.54(3)
83.10(3)
69.63(3)
1717.0(6)
2
1.287
0.939
700
0.29 ¥ 0.20 ¥ 0.19
1.85–27.09
15959/7458
[R(int) = 0.1029]
7458/0/411
0.0724, 0.1880
0.0968, 0.2109
1.102
˚
b [A]
˚
c [A]
a [◦]
b [◦]
g [◦]
3
˚
V [A ]
Z
rcalc [Mg m-3]
1.254
1.112
1692
m [mm-1]
1.018
1408
F(000)
Crystal Size (mm)
0.33 ¥ 0.30 ¥ 0.29
1.54–27.01
41106/18275
[R(int) = 0.0442]
18275/0/979
0.0449, 0.0905
0.0900, 0.1019
0.999
0.47 ¥ 0.43 ¥ 0.37
1.28–25.91
25583/6486
[R(int) = 0.0561]
6486/0/388
0.0537, 0.1363
0.0578, 0.1385
1.199
q range [◦]
Reflections Collected/unique
Data/restraints/parameters
R1, wR2 [I > 2s(I)]a
R1, wR2 (all data)a
GoF
-3
˚
Residual density max./min. [e A ]
0.445/0.417
0.376/-0.617
0.873, -1.444
1.115, -0.607
0.384, -0.317
2
a R1 = RꢀFo| - |Fcꢀ/R|Fo|. wR2 = [Rw(Fo - Fc2)2/Rw(Fo2)2]0.5
134 | Dalton Trans., 2010, 39, 132–138
.
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Scheme 5 Preparation of compounds 7 and 8
Fig. 3 Molecular structure of 5. Anisotropic displacement parameters are
depicted at the 50% probability level and all restrained refined hydrogen
atoms and the isopropy◦l groups are omitted for clarity. Selected bond
˚
lengths [A] and angles [ ]; Ge1–O1 1.862(3), Ge1–N1 2.002(4), O1–C1
1.407(6); N1–Ge1–N2 88.77(15), N1–Ge1–O1 97.52(15), Ge1–O1–C1
112.8(3).
Fig. 5 Molecular structure of 8. Anisotropic displacement parameters are
depicted at the 50% probability level and all restrained refined hydrog◦en
˚
atoms are omitted for clarity. Selected bond lengths [A] and angles [ ];
Ge1–C5 2.1083(18), Ge1–N1 2.0177(15), C4–C5 1.338(3); N1–Ge1–N2
91.07(6), N1–Ge1–C5 92.07(6), Ge1–C5–C4 122.03(14).
Compound 8 crystallizes in the monoclinic space group P21/c,
with one monomer in the asymmetric unit, and with two molecules
in the unit cell. Single crystals were obtained from a saturated n-
hexane solution at -32 ◦C in a freezer after two days (Table 1). The
coordination polyhedron around the germanium atom features a
distorted tetrahedral geometry with a stereochemically active lone
pair.
Moreover we conducted the reaction of LGeMe (9)4 with
trimethylsilyl diazomethane, which resulted in the formation of
[L¢Ge(Me)(NHNCHSiMe3)] (10), instead of nitrogen elimination
=
and creation of LGe(Me) CHSiMe3 (Scheme 6). The reaction
Fig. 4 Molecular structure of 6. Anisotropic displacement parameters are
depicted at the 50% probability level and all restrained refined hydrogen
proceeds with migration of a hydrogen atom from a methyl group
of the ligand backbone to the end-on nitrogen atom of the diazo
group. In the 1H NMR spectrum of 10 the resonances clearly show
the existence of NH (d 6.76 ppm) CH (d 5.78 ppm), and the CH2
moiety (d 3.83 and 3.21 ppm). The NH proton of 10 is upfield
˚
atoms are omitted for clarity. Selected bond lengths [A] and angles
[◦]; Ge1–O1 1.855(2), Ge1–N1 2.011(3), O1–C1 1.417(4); N1–Ge1–N2
88.45(11), N1–Ge1–O1 96.69(11), Ge1–O1–C1 112.8(2).
7 and 8 are yellow solids soluble in benzene, THF, n-hexane,
and n-pentane, respectively and show no decomposition on
exposure to air. 7 and 8 were characterized by multinuclear
NMR spectroscopy, EI mass spectrometry, and elemental analysis.
Furthermore 8 was characterized by X-ray structural analysis
(Fig. 5). The 1H NMR spectrum of 7 exhibits two broad resonances
(d 6.20 and 5.82 ppm) which correspond to the two alkenyl
protons.
Scheme 6 Preparation of compound 10
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shifted when compared with that of the GeH (d 8.08 ppm) proton
of LGeH (1), which is similar to those in the case of compounds
LGeN(H)NCHCO2Et (d 7.25 ppm).6
The formation of 10 may be compared with that of 4. In both
compounds an oxidation of the Ge(II) to Ge(IV) occurred and
a migration of a hydrogen atom from a methyl group of the
ligand backbone to the end-on nitrogen of the diazo group is
observed.
(d, 6H, CH(CH3)2), 1.05 (d, 6H, CH(CH3)2) ppm; IR (Nujol,
-1
˜
KBr, cm ): n = 2068 (N3); EI-MS (70 eV): m/z (%): 491 (100)
[M - N3]+. Found C, 64.06; H, 8.11%. Calcd for C29H41GeN5
(532.26), C, 65.43; H, 7.76%.
4. Yield: 0.37 g (28%); mp 200 ◦C; 1H NMR (500 MHz, C6D6):
d 7.21 (s, 2H, NH), 7.04-7.13 (m, 6H, Ar-H), 5.29 (s, 1H, g-
CH), 3.87 (s, 1H, CH), 3.86 (sept, 2H, CH(CH3)2), 3.74 (sept,
2H, CH(CH3)2), 3.28 (s, 1H, CH), 1.58 (s, 6H, CH3), 1.32 (d, 6H,
CH(CH3)2), 1.18 (d, 12H, CH(CH3)2), 1.15 (d, 6H, CH(CH3)2),
Experimental
1
1.05 (d, 6H, CH(CH3)2), 0.01 (s, 18H, Si(CH3)3) ppm; 29Si{ H}
NMR (125.77 Hz, C6D6): d 5.53 (Si(CH3)3) ppm; EI-MS (70 eV):
m/z (%): 651 (100) [M - Me]+. Found C, 64.83; H, 8.36%. Calcd
for C35H60GeN4Si2 (665.64), C, 63.15; H, 9.08%.
General considerations
All manipulations were performed in a dry and oxygen-free
atmosphere (N2 or Ar) by using Schlenk-line and glove-box
techniques. Solvents were purified with the M-Braun solvent
drying system. Compounds LGeH5 and LGeMe4 were prepared
by literature methods. Other chemicals were purchased and used
as received.1H, 13C, 19F, and 29Si NMR spectra were recorded on
a Bruker 500 MHz instrument and referenced to the deuterated
Synthesis of [{HC(CMeNAr)2}GeOCHPhCF3] (Ar = 2,6-
iPr2C6H3) (5).
A solution of 2,2,2-trifluoroacetophenone
(0.175 g, 1.00 mmol in 5 mL toluene) was added by cannula to
a solution of 1 (0.49 g, 1.00 mmol in toluene 20 mL) at room
temperature. After 12 h all volatiles were removed in vacuum, and
the remaining residue was extracted with n-hexane (25 mL). The
solution was concentrated and kept in a freezer to obtain 5 as
yellow crystals, which are suita◦ble for X-ray diffraction analysis.
1
solvent in the case of the H and 13C NMR spectra. 19F and 29Si
NMR spectra were referenced to CFCl3. and to SiMe4 respectively.
Elemental analyses were performed by the Analytisches Labor
des Instituts fu¨r Anorganische Chemie der Universita¨t Go¨ttingen.
Mass spectra were obtained on a Finnigan Mat 8230 instrument.
Melting points were measured in a sealed glass tube with a Bu¨chi
melting point B 540 instrument and are not corrected.
1
Yield: 0.545 g (82%); mp 182 C; H NMR (500 MHz, C6D6):
d 6.74–7.28 (m, 11H, Ar-H), 4.73 (q, 1H, CH), 4.65 (s, 1H,
g-CH), 3.73 (sept, 2H, CH(CH3)2), 3.29 (sept, 1H, CH(CH3)2),
3.07 (sept, 1H, CH(CH3)2), 1.60 (d, 3H, CH(CH3)2), 1.50 (d, 3H,
CH(CH3)2), 1.48 (s, 3H, CH3), 1.41 (s, 3H, CH3), 1.35 (d, 3H,
CH(CH3)2), 1.21 (d, 3H, CH(CH3)2), 1.15 (d, 3H, CH(CH3)2),
1.11 (d, 3H, CH(CH3)2), 1.02 (d, 3H, CH(CH3)2), 0.72 (d,
Synthesis of [{HC(CMeNAr)2}GeOH] (Ar = 2,6-iPr2C6H3) (2).
1
3H, CH(CH3)2) ppm; 13C{ H} NMR (125.77 MHz, C6D6): d
Dry N2O was bubbled into a solution of 1 (0.49 g, 1.00 mmol)
in toluene (20 mL) at room temperature. After 30 min the gas
flow of N2O was disconnected, and all the volatiles were removed
in vacuum. The residue was treated with n-hexane (40 mL)
and after filtration and drying in vacuum, 2 was obtained as a
164.71, 164.39 (CN), 145.03–124.59 (Ar-C), 96.38 (g-C), 75.84 (q,
CH), 29.00 (CH(CH3)2), 28.90 (CH(CH3)2), 28.77 (CH(CH3)2),
28.63 (CH(CH3)2), 26.61 (CH(CH3)2), 25.71 (CH(CH3)2),
24.86 (CH(CH3)2), 24.81 (CH(CH3)2), 24.79 (CH(CH3)2), 24.56
(CH(CH3)2), 24.19 (CH3), 23.99 (CH(CH3)2), 22.62 (CH3), 22.51
1
yellow microcrystalline powder. Yield: 0.480 g (95%). H NMR
1
(CH(CH3)2) ppm; 19F{ H} NMR (188.29 MHz): d -75.76 (d,
(500 MHz, C6D6): d 7.09-7.17 (m, 6H, Ar-H), 4.91 (s, 1H, g-
CH), 3.71 (sept, 2H, CH(CH3)2), 3.31 (sept, 2H, CH(CH3)2),
1.65 (s, 1H, OH), 1.60 (s, 6H, CH3), 1.30 (d, 6H, CH(CH3)2),
1.28 (d, 6H, CH(CH3)2), 1.20 (d, 6H, CH(CH3)2), 1.11 (d,
3
3F, CF3, J (19F-1H) = 8 Hz) ppm; EI-MS (70 eV): m/z (%):
666 (100) [M]+. Found: C, 66.65; H, 7.24; N, 4.12%. Calcd for
C37H47F3GeN2O (665.36), C, 66.78; H, 7.12; N, 4.21%.
1
6H, CH(CH3)2) ppm. 13C{ H} NMR (125.77 MHz, C6D6): d
Synthesis of [{HC(CMeNAr)2}GeOCH(2-C4H3S)CF3] (Ar =
161.48 (CN), 142.75, 141.22, 125.82, 123.55 (Ar-C), 94.24 (g-C),
29.16 (CH(CH3)2), 28.60 (CH(CH3)2), 26.69 (CH(CH3)2), 24.73
(CH(CH3)2), 24.58 (CH(CH3)2), 24.08 (CH(CH3)2), 23.25 (CH3)
ppm. For comparison see ref. 8.
2,6-iPr2C6H3) (6).
A solution of 2,2,2-trifluorothiophene
(0.175 g, 1.00 mmol in 5 mL toluene) was added by cannula
to a solution of 1 (0.49 g, 1.00 mmol in toluene 20 mL) at
room temperature. After 12 h all volatiles were removed in
vacuum, and the remaining residue was extracted with n-hexane
(25 mL). The extract was concentrated to about 15 mL and
stored in a -30 ◦C freezer. Yellow crystals of 6 suitable for
X-ray diffraction analysis had formed after two days. Yield:
0.570 g (85%); mp 171 ◦C; 1H NMR (500 MHz, C6D6): d
6.93–7.12 (m, 6H, Ar-H), 6.67 (d, 1H, C4H3S), 6.45 (dd, 1H,
C4H3S), 6.26 (d, 1H, C4H3S), 5.04 (q, 1H, CH), 4.66 (s, 1H,
g-CH), 3.69 (sept, 1H, CH(CH3)2), 3.63 (sept, 1H, CH(CH3)2),
3.28 (sept, 1H, CH(CH3)2), 3.15 (sept, 1H, CH(CH3)2), 1.58
(d, 3H, CH(CH3)2), 1.48 (s, 3H, CH3), 1.42 (s, 3H, CH3), 1.41
(d, 3H, CH(CH3)2), 1.32 (d, 3H, CH(CH3)2), 1.20–1.14 (m, 6H,
CH(CH3)2), 1.12 (d, 3H, CH(CH3)2), 1.07 (d, 3H, CH(CH3)2), 0.98
Synthesis of [{HC(CMeNAr)2}GeN3] (3) and [HC(CCH2)-
(CMe)(NAr)2Ge(NHSiMe3)2] (Ar = 2,6-iPr2C6H3) (4). An excess
of trimethylsilyl azide was slowly added drop by drop to a
20 mL toluene solution of 1 (0.98 g, 2 mmol). Then the reaction
mixture was stored overnight. After that the solvent and excess
trimethylsilyl azide were removed in vacuum. The residue was
extracted with n-hexane (35 mL) and the extract concentrated to
about 20 mL. After one day at room temperature colorless crystals
of 3 are formed. Then the residual extract is stored in a freezer at
-30 ◦C. After two days colorless crystals of 4 had formed.
3. Yield: 0.34 g (32%); mp 190 ◦C; 1H NMR (500 MHz,
C6D6): d 7.04-7.13 (m, 6H, Ar-H), 4.98 (s, 1H, g-CH), 3.73
(sept, 2H, CH(CH3)2), 3.10 (sept, 2H, CH(CH3)2), 1.53 (s, 6H,
CH3), 1.32 (d, 6H, CH(CH3)2), 1.18 (d, 12H, CH(CH3)2), 1.15
1
(d, 3H, CH(CH3)2) ppm; 13C{ H} NMR (125.77 MHz, C6D6): d
164.65, 164.34 (CN), 145.21-123.54 (Ar-C), 96.49 (g-C), 75.43 (q,
136 | Dalton Trans., 2010, 39, 132–138
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CH), 28.93 (CH(CH3)2), 28.88 (CH(CH3)2), 28.76 (CH(CH3)2),
28.59 (CH(CH3)2), 26.46 (CH(CH3)2), 25.96 (CH(CH3)2),
24.89 (CH(CH3)2), 24.65 (CH(CH3)2), 24.45 (CH(CH3)2), 24.28
(CH(CH3)2), 24.05 (CH(CH3)2) 23.40 (CH(CH3)2), 22.68 (CH3),
CH(CH3)2), 1.16 (d, 3H, CH(CH3)2), 1.05 (d, 3H, CH(CH3)2),
1
0.17 (s, 9H, Si(CH3)3) ppm; 29Si{ H} NMR (125.77 Hz, C6D6): d
-8.76 (Si(CH3)3) ppm; EI-MS (70 eV): m/z (%): 605 (25) [M -
Me]+, 491 (100) [M-Me, NHNCHTMS]+. Found: C, 65.81; H,
9.14%. Calcd. for C34H54GeN4Si (619.54), C, 65.91; H, 8.79%.
1
22.56 (CH3) ppm; 19F{ H} NMR (188.29 MHz): d -76.29 (d, 3F,
3
CF3, J (19F-1H) = 7 Hz) ppm; EI-MS (70 eV): m/z (%): 672
Crystallographic details for compounds 3, 4, 5, 6, and 8. Suit-
able crystals of 3, 4, 5, 6, and 8 were mounted on a glass fiber and
data was collected on an IPDS II Stoe image-plate diffractometer
(100) [M]+. Found: C, 62.58; H, 6.68; N, 4.17; S, 5.33%. Calcd for
C35H45F3GeN2OS (671.38), C, 62.61; H, 6.76; N, 4.17; S, 4.78%.
˚
(graphite monochromated Mo Ka radiation, l = 0.71073 A) at
Synthesis of [{HC(CMeNAr)2}GeC(CO2Me)CH2] (Ar = 2,6-
133(2) K. The data was integrated with X-Area. The structures
were solved by Direct Methods (SHELXS-97)16 and refined by
full-matrix least square methods against F2 (SHELXL-97).16 All
non-hydrogen atoms were refined with anisotropic displacement
parameters. Crystallographic data are presented in Table 1.
≡
iPr2C6H3) (7). A solution of HC CCO2Me (0.085 g, 1.00 mmol
in 5 mL toluene) was added drop by drop by cannula to a solution
of 1 (0.490 g, 1.00 mmol in toluene 15 mL) at room temperature.
After overnight constant stirring at ambient temperature all
volatiles were removed in vacuum, and the remaining residue
was extracted with n-hexane (15 mL) and after removal of all
the volatiles compound 7 was obtained as a yellow powder. Yield:
0.49 g (85 %); mp 161 ◦C. 1H NMR (500 MHz, C6D6): d 7.09–7.16
(m, 6H, Ar-H), 6.20 (br, 1H, CH2), 5.82 (br, 1H, CH2), 4.88 (s,
1H, g-CH), 3.70 (sept, 2H, CH(CH3)2), 3.47 (s, 3H, CO2CH3), 3.46
(sept, 2H, CH(CH3)2), 1.58 (s, 6H, CH3), 1.31 (d, 6H, CH(CH3)2),
1.27 (d, 6H, CH(CH3)2), 1.18 (d, 6H, CH(CH3)2), 1.15 (d, 6H,
CH(CH3)2) ppm; EI-MS: m/z (%) 576 (100) [M]+. Found: C,
68.89; H, 8.16; N, 4.20%. Calcd for C33H46GeN2O2 (575.37), C,
68.89; H, 8.06; N, 4.87%.
Conclusion
Germanium(II) hydroxide has been prepared by the reaction
of LGeH with nitrous oxide as a mono oxygen source. The
corresponding reaction of LGeH with trimethylsilyl azide resulted
in the formation of two compounds, the terminal germanium(II)
azide and germanium(IV) diamide. Germanium(II) alkoxides
have been prepared by the reaction of LGeH with activated
ketones with the outcome of compounds containing the Ge(II)–
O–CH core. Furthermore LGeH reacts with terminal and internal
alkynes generating the vinyl substituted germylene, rather than
the elimination of dihydrogen in the case of terminal alkynes.
Compounds 2, 3, 5–8 represent a unique new class of germylene
compounds with an electron lone pair on germanium(II) that is
prone for complexation reaction with transition metal fragments.
Moreover it is interesting to mention that most of the compounds
are stable in air and moisture and highly soluble in common
organic solvents. Finally it was shown that the trimethylsilyl
diazomethane coordinates end-on to the germanium atom under
migration of a hydrogen atom from a methyl group of the ligand
backbone to the coordinate N atom.
Synthesis of [{HC(CMeNAr)2}GeC(CO2Et)CHCO2Et] (Ar =
2,6-iPr2C6H3) (8). A solution of diethylacetylene dicarboxylate
(0.170 g, 1.00 mmol in 5 mL toluene) was added drop by drop
by cannula to a solution of 1 (0.490 g, 1.00 mmol in toluene
15 mL) at room temperature. After 24 h under constant stirring at
ambient temperature the red solution turned yellow. All volatiles
were removed in vacuum, and the remaining residue was extracted
with n-hexane (25 mL) and concentrated to about 15 mL and
stored in a -30 ◦C freezer. Yellow crystals of 8 suitable for X-ray
diffraction analysis are formed after two days. Yield: 0.53 g (80
%); mp 117 ◦C. 1H NMR (500 MHz, C6D6): d 7.07–7.15 (m, 6H,
Ar-H), 6.68 (s, 1H, CH), 4.91 (s, 1H, g-CH), 3.99 (q, 2H, CH2),
3.91 (sept, 2H, CH(CH3)2), 3.82 (q, 2H, CH2), 3.34 (sept, 2H,
CH(CH3)2), 1.63 (s, 6H, CH3), 1.34 (d, 6H, CH(CH3)2), 1.29 (d,
6H, CH(CH3)2), 1.21 (d, 6H, CH(CH3)2), 1.14 (d, 6H, CH(CH3)2),
1.05 (t, 3H, CH2CH3), 0.74 (t, 3H, CH2CH3) ppm. EI-MS: m/z
(%) 633 (100) [M-Et]+. Found: C, 68.25; H, 9.83; N, 4.53%. Calcd
for C37H52GeN2O4 (661.40), C, 69.29; H, 8.21; N, 4.75%.
Acknowledgements
This work was supported by the Deutsche Forschungsgemein-
schaft.
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