Novel derivatives of hypervalent germanium: Synthesis, structure, and stability

Article abstract of DOI:10.1039/b901885a

Syntheses of a series of novel germanium complexes, viz. RN(CH ₂CH₂NC₆F₅)₂GeHal ₂ (1, R = Me, Hal = Cl; 2, R = Me, Hal = Br; 3, R = PhCH₂, Hal = Cl; 4, R = PhCH₂, Hal

Full text of DOI:10.1039/b901885a

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www.rsc.org/dalton | Dalton Transactions
Novel derivatives of hypervalent germanium: synthesis, structure,
and stability†
El’mira Kh. Lermontova,a MengMeng Huan,b Andrei V. Churakov,a Judith A. K. Howard,c Maxim V. Zabalov,d
Sergey S. Karlov*b and Galina S. Zaitsevab
Received 29th January 2009, Accepted 31st March 2009
First published as an Advance Article on the web 6th May 2009
DOI: 10.1039/b901885a
Syntheses of a series of novel germanium complexes, viz. RN(CH2CH2NC6F5)2GeHal2 (1, R = Me,
Hal = Cl; 2, R = Me, Hal = Br; 3, R = PhCH2, Hal = Cl; 4, R = PhCH2, Hal = Br), as well as
MeN[CH2(2-C4H3N)]2GeHal2 (5, Hal = Cl; 6, Hal = Br), by the reaction of GeHal4 with dilithium salts
of corresponding triamines 7–9 are presented. PhCH2N(CH2CH2NSiMe3)2GeCl2 (10) was prepared
analogously from triamine 11. Other approaches to the synthesized compounds were also tested.
Unexpected complexes [N(CH2CH2NSiMe3)2Ge(Hal)]2 (12, Hal = Cl; 13, Hal = Br) were obtained by
the reaction of GeHal4 with dilithium salt of Me3SiN(CH2CH2NHSiMe3)2 (14). DFT calculations on
this reaction were carried out and discussed. Composition and structures of the novel compounds were
established by elemental analyses, 1H, 13C, and 19F NMR spectroscopy. The X-ray structural studies of
1–4 and 12 clearly indicated the presence of a transannular interaction N(ax)→Ge for all studied
compounds.
were prepared by the metathetical reaction of dilithium salts of
Introduction
corresponding triamines with SnCl4.19 The structure of the former
Aminodialkyldiamide ligands based on diethylenetriamines have
of them was confirmed by X-ray data. However, no germanium
enjoyed intense interest of transition metal chemists due to utility
derivatives were reported to date.
of the complexes with these ligands in organic chemistry.1–11
Schrock et al. and others have prepared alkylidyne and dinitrogen
As a part of our investigation program to study the com-
plexes of main group elements as well as transition metals with
2-
3-
complexes of different transition metals. The derivatives of Zr
were found to be effective catalysts for olefin polymerization.
Yttrium complexes are catalysts for hydroamination reactions.
Using these ligands, main group element analogues of these
complexes have already been prepared for different group 13
elements. These derivatives catalyzed the polymerization of lactide.
The structural chemistry of these compounds was also studied.12–15
In contrast, the coordination chemistry of 14 group elements
with these ligands is sparse, despite the importance of these
elements’ derivatives for many technological applications, e.g. as
an elemental semiconductor and in optics and ceramics in the case
of germanium.
There are four papers devoted to compounds of 14 group
elements based on the ligands in question.16–19 Several silicon
derivatives were prepared by the transamination reaction of sil-
icon dialkyldiamides with diethylenetriamines.16–18 Tin complexes,
MeN(CH2CH2NSiMe3)2SnCl2 and MeN(CH2CH2NiPr)2SnCl2
Y(CH2CH2Z)2 and N(CH2CH2Z)3 ligands (Y = AlkN, ArN;
Z = O, NSiMe3, NAlk),20–30 we report herein the synthesis and crys-
tal structures of the first examples of germanium complexes based
on diethylenetriamine type ligands—1,3,6,2-triazagermocanes or
“azagermocanes”. An unusual intramolecular dehalosilylation
process was found and discussed.
Results and discussion
Three general approaches were used for construction of the target
complexes’ skeleton: the reaction of halogermanes with dilithium
salts of the corresponding diethylenetriamines, transamination
reaction of diethylenetriamines with aminogermanes and amin-
odehalogenation of halogermanes with corresponding diethylen-
etriamines in the presence of Et3N. Our synthetic efforts are
summarized in the Schemes 1 and 2.
Triamines 8 and 11 are novel and were prepared according to
the synthetic procedures presented in Experimental.
aN. S. Kurnakov Institute of General and Inorganic Chemistry RAS, Leninskii
pr. 31, 119991, Moscow, Russia. E-mail: churakov@igic.ras.ru
The reaction of the dilithium salt of triamines 7–9 with
tetrahalogermanes expectedly led to the target compounds 1–6.
Complex 1 was also obtained by the corresponding transamina-
tion reaction. Although the second route gave the higher yield
of the target compound (55% vs. 48%) the first route is more
preferable since tetrahalogermanes are easier to handle than
GeHal2(NMe2)2. In addition, our attempts to prepare 5 via the
transamination route failed (see Experimental). The reactions of
GeCl2(NMe2)2 with 9 and 14 as well as Ge(NMe2)4 with 7, 9, and
14 were also unsuccessful.
bChemistry Department, Moscow State University, B-234 Leninskie Gory,
119899, Moscow, Russia. E-mail: sergej@org.chem.msu.ru
cDepartment of Chemistry, University of Durham, South Road, Durham,
UK DH1 3LE. E-mail: j.a.k.howard@durham.ac.uk
dN. N. Semenov Institute of Chemical Physics RAS, Kosygina str. 4, 119991,
Moscow, Russia. E-mail: zabalov@mail.ru
† Electronic supplementary information (ESI) available: Calculated Carte-
sian coordinates of transition states and stable compounds, electronic ener-
gies, numbers of imaginary frequencies. CCDC reference numbers 718433–
718437 for the structures of 1–4 and 12. For ESI and crystallographic data
in CIF or other electronic format see DOI: 10.1039/b901885a
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expected “Me3SiN(CH2CH2NSiMe3)2GeHal2”. To gain a better
understanding of the driving force behind these unusual reactions
we carried out density functional calculations at the PBE level of
theory on a geometry of 12 and Me3SiN(CH2CH2NSiMe3)2GeCl2
(15). The structure of hypothetical N(CH2CH2NSiMe3)2Ge(Cl)
(16) with covalent N–GeIV bond was also optimized (see Table 1).
It was found that the most thermodynamically stable molecule
among the three studied species is digermanium derivative 12.
We can suppose that 15 forms in the course of reaction but due
to instability transforms into 12. The calculation results on 16
confirm that this compound is a believable intermediate in the
transformation 15 → 12. The activation energy of this process
(28.99 kcal mol-1) demonstrates that this reaction may take place
at room temperature. The value of Eact for the second transition
state (TS2) is expectedly low. Thus, this process falls into a very
rare transformation of transannular bond (in 15) into covalent
bond (in 16) and back into transannular bond (in 12).
We believe that the main driving force for this reaction is steric
proximity of the halogen atom and Me3Si group bound to the
nitrogen atom of N(CH2. . .)2 which appears due to the formation
of transannular Ge–N bond. It should be noted that the covalent
Si–N bond in Me3SiN group weakens also due to the presence of
transannular bond.
Scheme 1 Synthesis of Ge complexes 1–6.
In order to estimate the ability of the prepared dihaloger-
manium complexes to serve precursors for the preparation of
novel germanium compounds we studied the reactions of 1
with MeN(CH2CH2NLiC6F5)2, PhCH2N(CH2CH2OSiMe3)2, and
n-BuLi. It was found that Ge–Cl bond in 1 is unreactive towards
MeN(CH2CH2NLiC6F5)2 and PhCH2N(CH2CH2OSiMe3)2, while
the reaction with n-BuLi leads to destruction of “ocane” skeleton.
This behaviour is similar to the previously found for azagerma-
tranes with bulky substituents at the equatorial nitrogen atoms,
for example, for N(CH2CH2NC6F5)3GeCl.31
The structure of the prepared compounds was confirmed by
NMR spectroscopy and elemental analysis data. The structures of
1–4 and 12 in the solid state were studied by X-ray crystallography.
The molecular structures of 1–4 and 12 are shown in Fig. 1–5,
respectively. Tables 2 and 3 summarize the significant geometrical
parameters of these compounds.
Scheme 2 Synthesis of compound 10 and digermanium derivatives 12
and 13.
The coordination polyhedron of the Ge atom in compounds
1–4 represents a distorted trigonal bipyramid with N(1) (for
compound 1–3) or N(11) (for compound 4) and halogen atoms
Cl(1) (for 1 and 3), Br(1) (for 2) or Br(11) (for 4) occupying
the axial positions. The two nitrogen atoms and one halogen
atom form the equatorial plane in each molecule. The Ge–
Hal(ax) bond is expectedly longer than the Ge–Hal(eq) bond in
the same molecule. This is in accordance with the hypervalent
bond theory. The strength of the intramolecular transannular
Compound 10 was prepared via the “lithium” method. This
complex also formed in the reaction of 11 with GeCl4 in the
presence of Et3N. It should be noted that compound 10 is very
unstable. Its structure was confirmed by NMR data.
Unlike the reactions described above, the treatment of tetra-
halogermanes with dilithium salt of 14 as well as with 14 in
the presence of Et3N gave very unusual results. Digermanium
derivatives 12 and 13 formed in both processes instead of the
Table 1 DFT calculations on 12, 15, and 16a
System
E/Hartree
DE/kcal mol-1
15 (two molecules)
-9090.472254
-9090.379871
-9090.455830
-9090.446120
-9090.490413
11.40
TS1 (15 → 16 + Me3SiCl) (two pairs of molecules)
16 (two molecules) + 2Me3SiCl
TS2 (2 16 → 12) + 2Me3SiCl
12 + 2Me3SiCl
40.39 (Eact 15→16 = 28.99)
21.70
27.79 (Eact 16→12 = 6.09)
0.00
a See ESI for details of structure calculations†
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Fig. 1 Molecular structure of complex 1. Hydrogen atoms are omitted
for clarity. Displacement ellipsoids are shown at the 50% probability level.
Fig. 3 Molecular structure of complex 3. Hydrogen atoms are omitted
for clarity. Displacement ellipsoids are shown at the 50% probability level.
Fig. 2 Molecular structure of complex 2. Hydrogen atoms are omitted
for clarity. Displacement ellipsoids are shown at the 50% probability level.
interaction (in this case N(ax)→Ge) in the hypervalent main
group element derivatives is the most intriguing aspect of their
structure. For compounds 1–4 these distances vary within the
Fig. 4 Molecular structure of complex 4. Hydrogen atoms are omitted
for clarity. Displacement ellipsoids are shown at the 50% probability level.
˚
˚
range 2.118(2) A (1) to 2.169(3) A (4). These values testify to the
presence of strong hypervalent interactions in these compounds
This conclusion is supported by X-ray data obtained early for
three azagermatranes. The N(ax)→Ge bond distances in these
compounds vary in broad interval due to varying of the equa-
and are close to those previously found in dihalogermocanes,
22
˚
MeN(CH2CH2O)2GeBr2, 2.166(5) A, PhN(CH2CH2O)2GeHal2,
23
31
˚
˚
˚
2.202(4) A (Hal = Cl), 2.202(2) A (Hal = Br). At the same
torial groups at Ge atom: N(CH2CH2N6F5)3GeCl (2.148(7) A),
˚
time N(ax)→Ge distances in 1–4 are significantly shorter than
N(CH2CH2NMe)3Ge–Cl (2.167(4) A), N(CH2CH2NSiMe3)3GeCl
32
20
˚
˚
that in iso-BuN(CH2CH2CH2)2GeCl2 (2.389(4) A). Therefore,
(2.278(2) A).
the nature of groups bound to germanium atom in dihaloger-
mocanes crucially influences the N(ax)→Ge bond length, while
the nature of substituent at the N(ax) atom is not so important.
The coordination polyhedron of the N(eq) atoms in compounds
1–4 is a slightly distorted trigonal plane while the environment
of the N(ax) atoms is approximately tetrahedral. For these
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◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for 1–4 [RN(ax)(CH2CH2N(eq)C6F5)2Ge(Hal(eq))Hal(ax)]
1 (R = Me, Hal = Cl)
2 (R = Me, Hal = Br)
3 (R = PhCH2, Hal = Cl)
4a (R = PhCH2, Hal = Br)
N(ax)→Ge
Ge–Hal(ax)
Ge–Hal(eq)
N(eq)–Ge
2.118(2)
2.2400(6)
2.1719(6)
1.833(2)
1.839(2)
2.132(6)
2.414(1)
2.333(1)
1.834(6)
1.848(6)
2.157(2)
2.2269(7)
2.1798(8)
1.832(2)
1.836(2)
2.161(4)
2.4100(7)
2.3442(7)
1.834(4)
1.837(4)
2.169(3)
2.4226(7)
2.3328(7)
1.831(4)
1.842(4)
N(ax)→Ge–Hal(ax)
N(ax)→Ge–Hal(eq)
N(ax)→Ge–N(eq)
174.35(6)
92.24(6)
82.37(8)
83.11(8)
118.60(6)
113.11(6)
94.15(6)
95.52(6)
12655(8)
93.34(3)
175.0(2)
92.3(2)
82.4(2)
81.8(2)
120.5(2)
113.4(2)
95.1(2)
96.1(2)
124.1(3)
92.69(4)
176.91(7)
90.01(7)
82.41(9)
82.8(1)
120.30(8)
113.90(8)
95.85(7)
96.16(8)
123.5(1)
93.07(3)
177.0(1)
91.0(1)
82.0(2)
82.8(2)
122.0(1)
114.1(1)
95.6(1)
97.0(1)
121.8(2)
91.83(2)
171.7(1)
94.0(1)
81.9(2)
81.6(2)
121.0(1)
113.2(1)
93.3(1)
95.8(1)
124.1(2)
94.27(2)
N(eq)→Ge–Hal(eq)
N(eq)→Ge–Hal(ax)
N(eq)→Ge–N(eq)
Hal(eq)→Ge–Hal(ax)
a Two independent molecules.
◦
a
˚
compounds, the axial nitrogen atoms are displaced from
the plane defined by the three carbon atoms toward the
germanium atom.
The same structural trends discussed above for 1–4 were found in
compound 12. It should be especially noted that the transannular
N(ax)→Ge distance in 12 is the shortest among those found
for studied azagermocanes and azagermatranes.33 This short
bond corresponds to long covalent bond Ge(1)–N(13A), thus
compound 12 should be considered as two mesomeric forms
(Scheme 3).
Table 3 Selected bond lengths (A) and angles ( ) for 12
Ge(1)–N(13)
Ge(1)–N(13)#1
Ge(1)–N(12)
Ge(1)–N(11)
Ge(1)–Cl(1)
2.118(3)
1.949(3)
1.832(3)
1.836(3)
Ge(2)–N(23)
Ge(2)–N(23)#2
Ge(2)–N(21)
Ge(2)–N(22)
2.113(3)
1.945(3)
1.833(3)
1.840(3)
2.2837(9)
2.2872(9) Ge(2)–Cl(2)
N(13)–Ge(1)–Cl(1)
N(12)–Ge(1)–N(11)
171.57(7) N(23)–Ge(2)–Cl(2)
171.08(7)
123.4(1)
123.6(1)
N(21)–Ge(2)–N(22)
N(21)–Ge(2)–N(23)#2 118.9(1)
N(22)–Ge(2)–N(23)#2 114.5(1)
N(21)–Ge(2)–N(23)
N(22)–Ge(2)–N(23)
N(12)–Ge(1)–N(13)#1 120.0(1)
N(11)–Ge(1)–N(13)#1 113.2(1)
N(12)–Ge(1)–N(13)
N(11)–Ge(1)–N(13)
85.9(1)
85.7(1)
86.2(1)
85.7(1)
N(13)#1–Ge(1)–N(13) 80.2(1)
N(23)#2–Ge(2)–N(23) 80.0(1)
98.22(9) N(21)–Ge(2)–Cl(2) 98.65(9)
N(12)–Ge(1)–Cl(1)
N(11)–Ge(1)–Cl(1)
98.00(9) N(22)–Ge(2)–Cl(2)
97.67(9)
91.08(8)
N(13)#1–Ge(1)–Cl(1) 91.41(8) N(23)#2–Ge(2)–Cl(2)
#1 -x + 1, -y + 1, -z + 1; #2 -x, -y + 1, -z. a Two independent molecules.
Scheme 3 Two mesomeric forms for 12.
Conclusions
We have prepared and structurally characterized a novel class of
germanium complexes—azagermocanes. The strong hypervalent
interaction N→Ge was found in these compounds. In the course of
the preparation of tris(silyl) derivatives an unusual intramolecular
dehalosilylation process was found. The DFT calculation data
support the suggestion about consecutive order of bond trans-
formation during this reaction: hypervalent bond–covalent bond–
hypervalent bond.
Experimental
All manipulations were performed under dry, oxygen-free ar-
gon atmosphere using standard Schlenk techniques. Solvents
were dried by standard methods and distilled prior to use.
GeHal4 (Cl, Br) (Aldrich) were distilled prior to use. Start-
ing materials MeN(CH2CH2NHC6F5)2 (7),2 bis-pyrrol deriva-
tive (9),34 Me3SiN(CH2CH2NHSiMe3)2 (14),35 Ge(NMe2)4,36
Fig. 5 Molecular structure of complex 12. Hydrogen atoms are omitted
for clarity. Displacement ellipsoids are shown at the 50% probability level.
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Cl2Ge(NMe2)4,37 PhCH2N(CH2CH2OSiMe3)2,29 and N,N-bis(2-
phthalimidoethyl)amine38 were prepared according to the litera-
ture. C6D6 was obtained from Deutero GmbH and dried over
sodium. 1H, 13C, and 19F NMR spectra were recorded with
Bruker AC300 and Bruker Avance 400 spectrometers at room
temperature. 1H and 13C chemical shifts are reported in ppm
relative to Me4Si as external standard; in 19F NMR experiments
CFCl3 was used as an external standard. Elemental analyses were
carried out by the Microanalytical Laboratory of the Chemistry
Department of the Moscow State University. Mass spectra (EI-
MS) were recorded on a VARIAN CH-7a device using electron
impact ionization at 70 eV; all assignments were made with
reference to the most abundant isotopes.
PhCH2N(CH2CH2NHSiMe3)2 (11). To a stirred solution of
PhCH2N(CH2CH2NH2)2 (1.90 g, 9.8 mmol) in 20 ml of toluene
12.25 ml of a 1.6 M n-BuLi solution (19.6 mmol) in hexane was
added dropwise at -78 ◦C. The reaction mixture was stirred for 1 h
and allowed to warm to room temperature. The reaction mixture
was chilled to -78 ◦C and Me3SiCl (2.14 g, 19.6 mmol) was added
with stirring. After an additional stirring within 24 h at room
temperature a white precipitate of LiCl was separated by filtration.
The precipitate was extracted with toluene (50 ml) and organic
solutions were combined. The volatiles were evaporated in vacuum
and the residue◦was fractionated. Yield: 2.17 g (66%), yellow oil.
1
Bp = 105–107 C (0.3 mmHg). H NMR (C6D6, 400 MHz) d =
7.30–7.32, 7.17–7.21, 7.07–7.10 (m, 5H, Ph), 3.43 (s, 2H, PhCH2),
2.75 (q, 4H, NH2), 2.37 (t, 4H, NH2), 0.07 (s, 18H, SiMe3). 13C
NMR (C6D6, 100 MHz) d = 140.26, 128.97, 128.25, 126.94 (Ph),
59.42, 58.28 39.81 (PhCH2, NCH2), 0.06 (SiMe3).
PhCH2N(CH2CH2NHC6F5)2 (8)
A mixture of HN(CH2CH2NHC6F5)2 (12.07 g, 0.028 mol), K2CO3
(21.30 g, 0.150 mol), PhCH2Cl (4.20 g, 0.033 mol), and 120 ml
CH3CN was stirred at 60 ◦C for two weeks. All volatiles were
removed under vacuum. Water (200 ml) was added to the residue
and the mixture was extracted with ethyl acetate (3 ¥ 200 ml).
Combined organic extracts were dried over MgSO4. All volatiles
were removed under vacuum to give 8 as a deep-brown oil which
MeN(CH2CH2NC6F5)2GeCl2 (1)
Method 1. To a stirred solution of 7 (2.40 g, 5.3 mmol) in 30 ml
of toluene was 7.50 ml of a 1.6 M n-BuLi solution (12.0 mmol) in
hexane added dropwise at -78 ◦C. The reaction mixture was stirred
for 1 h and allowed to warm to room temperature. The reaction
mixture was chilled to -78 ◦C and GeCl4 (1.14 g, 5.3 mmol) in
10 ml of toluene was added with stirring. After an additional
stirring within 24 h at room temperature a white precipitate of
LiCl was separated by filtration. The precipitate was extracted
with toluene (50 ml) and organic solutions were combined. Half of
the volatiles were evaporated in vacuum and 30 ml of diethyl ether
were added. A white crystalline solid was separated by filtration,
washed by cold diethyl ether (3 ¥ 5 ml) and dried in vacuum. Yield:
1.50 g (48%). 1H NMR (C6D6, 300 MHz) d = 2.77–2.83 (m, 2H,
CH2), 2.69–2.75 (m, 2H, CH2), 2.20–2.26 (m, 2H, CH2), 1.92–1.98
(m, 2H, CH2), 1.93 (s, 3H, Me). 13C NMR (C6D6, 75 MHz) d =
50.99, 45.04, (CH2), 43.37 (Me). 19F NMR (C6D6, 376.4 MHz) d =
-163.60–-163.14 (m, 2F), -157.54 (t, 1F), -146.52–-146.47 (m,
1F), -146.05–-145.97 (m, 1F). EI m/z 252 (M–GeCl2–CH2NC6F5,
100%). Anal. calcd for C17H11Cl2F10GeN3 (590.79): C, 34.57; H,
1.88. Found: C, 34.65; H, 2.06%.
1
was used without further purification. Yield: 10.41 g (71%). H
NMR (C6D6, 300 MHz) d = 7.02–7.20 (m, 5H, Ph), 3.82 (br s,
2H, NH), 3.11 (s, 2H, NH2Ph), 2.91–2.96 (m, 4H, NH2), 2.15–
2.19 ’(m, 4H, NH2). An analytically pure sample (colourless oil)
was obtained after chromatography (eluent: hexane). Refluxing
of a reaction mixture (first stage) led to the crude 8 (yield =
58%), which contained a considerable amount of undesirable
PhCH2OOCN(CH2CH2NHC6F5)2 (X-ray data).39
PhCH2N(CH2CH2NHSiMe3)2 (11)
Benzyl-bis(2-phthalimidoethyl)amine.
A mixture of N,N-
bis(2-phthalimidoethyl)amine (7.27 g, 0.020 mol), Na2CO3 (2.12 g,
0.020 mol) and PhCH2Cl (3.16 g, 0.025 mol) in EtOH (abs., 300 ml)
was refluxed for 25 h. The warm solution was filtered and chilled
(-30 ◦C). A white precipitate was separated by filtration and
dried in vacuum. Yield: 6.08 g (67%). 1H NMR (C6D6, 400 MHz)
d = 7.39–7.42, 7.07–7.12, 6.93–6.95, 6.85–6.89 (m, 13H, aromatic
protons), 3.55 (t, 4H, NH2), 3.43 (s, 2H, PhCH2), 2.58 (t, 4H, NH2).
13C NMR (C6D6, 100 MHz) d = 167.80 (CO), 139.36, 133.11,
132.93, 129.34, 128.20, 126.92, 122.78, (aromatic carbons), 58.28
(CH2Ph), 52.02, 35.80 (NCH2).
An analogous reaction of GeCl4 (0.60 g, 2.8 mmol) with two
equivalents of 7 (2.52 g, 5.6 mmol) and 7.00 ml of a 1.6 M n-BuLi
solution (11.2 mmol) gave 1. Yield: 0.40 g (24%).
Method 2. A mixture of 7 (2.25 g, 5.0 mmol) and Cl2Ge(NMe2)2
(1.16 g, 5.0 mmol) was heated at 130 ◦C for 25 h. Toluene (15 ml)
was added to the mixture at room temperature. White solid was
separated by filtration, washed by cold diethyl ether (3 ¥ 5 ml) and
dried in vacuum. Yield: 1.62 g (55%).
PhCH2N(CH2CH2NH2)2.
A
suspension of benzyl-bis(2-
phthalimidoethyl)amine (3.70 g, 8.0 mmol) in 36% HCl (aq.) was
refluxed for 25 h. Two thirds of the volatiles were evaporated
in vacuum and the precipitate was filtered off. The filtrate was
evaporated in vacuum and the residue was refluxed for 5 h in a
solution of NaOH (2.4 g, 0.060 mol) in 50 ml H2O. Two thirds
of the volatiles were evaporated in vacuum and the residue was
extracted with toluene (3 ¥ 30 ml). Combined organic extracts
were dried over MgSO4. All volatiles were removed under vacuum
to give a yellow oil which was used without further purification.
MeN(CH2CH2NC6F5)2GeBr2 (2)
The procedure was analogous to that for 1, Method 1: reaction
of 7 (1.79 g, 4.0 mmol) with 5.13 mL of a 1.6 M n-BuLi solution
(8.2 mmol) in hexane and then with GeBr4 (1.57 g, 4.0 mmol) gave
2 as a beige solid. Yield: 0.79 g (29%). 1H NMR (C6D6, 300 MHz)
d = 2.68–2.80 (m, 4H, CH2), 2.14–2.20 (m, 2H, CH2), 1.90–1.96
(m, 2H, CH2), 1.85 (s, 3H, Me). 13C NMR (C6D6, 75 MHz) d =
50.48, 45.27, (CH2), 43.64 (Me). 19F NMR (C6D6, 376.4 MHz)
d = -163.34–-163.05 (m, 2F), -156.82 (t, 1F), -146.03–-145.98
(m, 1F), -145.14–-145.22 (m, 1F). EI m/z 599 (M–Br, 4%), 485
1
Yield: 1.03 g (65%). H NMR (C6D6, 400 MHz) d = 7.23–7.25,
7.14–7.19, 6.99–7.12 (m, 5H, Ph), 3.49 (br s, 4H, NH2), 3.34 (s,
2H, PhCH2), 2.51 (q, 4H, NH2), 2.25 (t, 4H, NH2).
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(M–CH2NC6F5, 3%)+, 252 (M–GeCl2–CH2NC6F5, 100%). Anal.
calcd for C17H11Br2F10GeN3 (679.69): C, 30.05; H, 1.63; N, 6.18.
Found: C, 30.37; H, 1.81; N, 5.85%.
PhCH2N(CH2CH2NSiMe3)2GeCl2 (10)
Method 1. The procedure was analogous to that for 1, Method
1: reaction of 11 (0.32 g, 1.0 mmol) with 1.25 mL of a 1.6 M
n-BuLi solution (2.0 mmol) in hexane and then with GeCl4 (0.20 g,
PhCH2N(CH2CH2NC6F5)2GeCl2 (3)
1
1.0 mmol) gave a red oil which contained 10 according to H
NMR. Yield (crude): 0.21 g (43%). All attempts to purify or
investigate this compound with other analytical methods failed.
1H NMR (C6D6, 300 MHz) d = 7.09–7.14 (m, 3H, Ph), 6.82–
6.86 (m, 2H, Ph), 3.61 (s, 2H, PhCH2), 2.65–2.88 (m, 4H, NCH2),
2.29–2.39 (m, 2H, NCH2), 1.68–1.79 (m, 2H, NCH2), 0.40 (s, 18H,
SiMe3).
Method 2. To a stirred solution of GeCl4 (0.49 g, 2.3 mmol)
in 10 ml of toluene a solution of 14 (0.76 g, 2.3 mmol) and
Et3N (0.47 g, 4.6 mmol) in toluene (10 ml) was added dropwise
at -78 ◦C. The stirring reaction mixture was allowed to warm
to room temperature overnight. The precipitate (Et3N·HCl) was
separated by filtration. Volatiles were evaporated in vacuum. A
red oil contained 10 according to 1H NMR.
The procedure was analogous to that for 1, Method 1: reaction of
8 (4.29 g, 8.0 mmol) with 10.13 mL of a 1.6 M n-BuLi solution
(16.2 mmol) in hexane and then with GeCl4 (1.70 g, 8.0 mmol) gave
3 as a beige solid. Yield: 1.17 g (22%). 1H NMR (C6D6, 300 MHz)
d = 6.99–7.12 (m, 3H, Ph), 6.64–6.66 (m, 2H, Ph), 3.84 (s, 2H,
PhCH2), 2.88–2.93 (m, 2H, NCH2), 2.77–2.82 (m, 2H, NCH2),
2.21–2.36 (m, 4H, CH2). 13C NMR (C6D6, 75 MHz) d = 131.64,
130.71, 129.26, 128.51 (Ph), 56.74 (PhCH2), 45.81, 45.03 (NCH2).
19F NMR (C6D6, 376.4 MHz) d = -164.04–-163.72 (m, 2F),
–157.89 (t, 1F), -147.16 (br s, 1F), -146.61–-146.54 (m, 1F). Anal.
calcd for C23H15Cl2F10GeN3 (666.88): C, 41.42; H, 2.27; N, 6.30.
Found: C, 40.97; H, 2.43; N, 5.92%.
PhCH2N(CH2CH2NC6F5)2GeBr2 (4)
The procedure was analogous to that for 1, Method 1: reaction
of 8 (2.80 g, 5.0 mmol) with 6.38 mL of a 1.6 M n-BuLi solution
(10.2 mmol) in hexane and then with GeBr4 (1.97 g, 5.0 mmol)
[N(CH2CH2NSiMe3)2Ge(Cl)]2 (12)
Method 1. The procedure was analogous to that for 1, Method
1: reaction of 14 (2.95 g, 9.0 mmol) with 11.25 mL of a 1.6 M
n-BuLi solution (18.0 mmol) in hexane and then with GeCl4
(1.93 g, 9.0 mmol) gave 12 as a white solid (after recrystallisation
1
gave 4 as a beige solid. Yield: 0.50 g (13%). H NMR (C6D6,
300 MHz) d = 6.99–7.12 (m, 3H, Ph), 6.64–6.66 (m, 2H, Ph),
3.86 (s, 2H, PhCH2), 2.92–2.87 (m, 2H, NCH2), 2.79–2.85 (m, 2H,
1
NCH2), 2.35–2.41 (m, 2H, NCH2), 2.24–2.30 (m, 2H, NCH2). 13
C
from toluene). Yield: 1.12 g (35%). H NMR (C6D6, 300 MHz)
d = 3.23–3.29 (m, 4H, CH2), 2.94–3.00 (m, 4H, CH2), 2.74–2.80
NMR (C6D6, 75 MHz) d = 131.65, 130.37, 129.40, 128.95 (Ph),
56.98 (PhCH2), 45.29 (2NCH2). 19F NMR (C6D6, 376.4 MHz) d =
-164.22–-164.03 (m, 2F), -157.91 (t, 1F), -146.51–-146.46 (m,
1F), -145.83–-145.85 (m, 1F). Anal. calcd for C23H15Cl2F10GeN3
(755.79): C, 36.55; H, 2.00; N, 5.56. Found: C, 36.23; H, 2.21; N,
5.31%.
(m, 4H, CH2), 2.06–2.12 (m, 4H, NCH2), 0.38 (s, 36H, SiMe3). 13
C
NMR (C6D6, 75 MHz) d = 51.62 (CH2), 43.28 (CH2), 3.63 (SiMe3).
EI m/z 352 (1/2M, 4%), 252 (1/2M - CH2NSiMe3, 9%); 237 (16)
(1/2M - CH2CH2NSiMe3, 16%). Anal. calcd for C20H52Cl2Ge2N6
(705.13): C, 34.07; H, 7.43; N, 11.92. Found: C, 34.41; H, 7.70; N,
11.65%.
Method 2. To a stirred solution of GeCl4 (0.99 g, 4.6 mmol) in
10 ml of toluene a solution of 14 (1.47 g, 4.6 mmol) and Et3N
(0.93 g, 9.2 mmol) in toluene (20 ml) was added dropwise at
-78 ◦C. The stirring reaction mixture was allowed to warm to
room temperature. The precipitate (Et3N·HCl) was separated by
filtration. Half of the volatiles were evaporated in vacuum and
10 ml of diethyl ether were added. A white crystalline solid was
separated by filtration, washed by cold diethyl ether (3 ¥ 5 ml) and
dried in vacuum. Yield: 1.00 g (62%).
MeN(CH2–C4H3N)2GeCl2 (5)
The procedure was analogous to that for 1, Method 1: reaction
of 9 (0.62 g, 3.0 mmol) with 3.81 mL of a 1.6 M n-BuLi solution
(6.1 mmol) in hexane and then with GeCl4 (0.70 g, 3.0 mmol) gave
3 as a beige solid. Yield: 0.52 g (52%). 1H NMR (C6D6, 300 MHz)
d = 7.50–7.51 (m, 2H, pyrrole ring protons), 6.27–6.31 (m, 2H,
pyrrole ring protons), 5.91–5.95 (m, 2H, pyrrole ring protons),
2.78–3.01 (dd, 4H, NCH2), 1.73 (s, 3H, Me). 13C NMR spectrum
was not registered due to very low solubility in C6D6. Anal. calcd
for C11H13Cl2GeN3 (330.76): C, 39.94; H, 3.96; N, 12.70. Found:
C, 40.07; H, 3.81; N, 12.98%.
[N(CH2CH2NSiMe3)2Ge(Br)]2 (13)
The procedure was analogous to that for 1, Method 1: reaction of
14 (2.11 g, 6.6 mmol) with 8.25 mL of a 1.6 M n-BuLi solution
(13.2 mmol) in hexane and then with GeCl4 (2.60 g, 6.6 mmol)
gave 13 as a white solid (after recrystallisation from toluene) Yield:
1.12 g (35%). 1H NMR (C6D6, 300 MHz) d = 3.23–3.28 (m, 4H,
CH2), 2.95–3.02 (m, 4H, CH2), 2.75–2.81 (m, 4H, CH2), 1.99–
2.04 (m, 4H, NCH2), 0.40 (s, 36H, SiMe3). 13C NMR spectrum
was not registered due to very low solubility in C6D6. EI m/z 397
(1/2M, 1%), 296 (1/2M - CH2NSiMe3, 9%), 217 (16) (1/2M -
Br - CH2NSiMe3, 5%), 147 (1/2M - Br - SiMe3 - CH2NSiMe3,
100%). Anal. calcd for C20H52Br2Ge2N6 (794.04): C, 30.25; H, 6.60;
N, 10.58. Found: C, 30.75; H, 7.03; N, 10.93%.
MeN(CH2–C4H3N)2GeBr2 (6)
The procedure was analogous to that for 1, Method 1: reaction
of 9 (1.09 g, 6.0 mmol) with 7.63 mL of a 1.6 M n-BuLi solution
(12.2 mmol) in hexane and then with GeBr4 (2.26 g, 6.0 mmol) gave
3 as a beige solid. Yield: 0.41 g (16%). 1H NMR (C6D6, 300 MHz)
d = 7.50–7.51 (m, 2H, pyrrole ring protons), 6.27–6.31 (m, 2H,
pyrrole ring protons), 5.91–5.95 (m, 2H, pyrrole ring protons),
2.78–3.01 (dd, 4H, NCH2), 1.73 (s, 3H, Me). 13C NMR (C6D6,
75 MHz) d = 129.38, 123.83, 112.00, 107.76 (pyrrole ring), 52.66
(CH2), 44.20 (Me). Anal. calcd for C11H13Br2GeN3 (419.66): C,
31.48; H, 3.12; N, 10.01. Found: C, 31.44; H, 3.30; N, 9.82%.
4700 | Dalton Trans., 2009, 4695–4702
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Reaction of Ge(NMe2)4 with 7
and then with 1 (0.75 g, 1.3 mmol) resulted (according 1H NMR
spectroscopy data) in only starting materials.
The mixture of 7 (1.51 g, 3.0 mmol) and Ge(NMe2)4 (0.84 g,
3.0 mmol) was heated at 130 ◦C for 72 h. According to 1H
NMR spectroscopy data, only starting materials were found in
the reaction mixture.
Reaction of 1 with PhCH2N(CH2CH2OSiMe3)2
A
solution of 1 (0.04 g, 0.07 mmol) and PhCH2N-
(CH2CH2OSiMe3)2 (0.02 g, 0.07 mmol) in toluene (15 ml) was
refluxed for 15 h resulting (according to 1H NMR spectrum) in a
complex mixture of products which were difficult to separate and
to identify.
Reaction of Cl2Ge(NMe2)2 with 9
The mixture of 9 (0.19 g, 1.0 mmol) and Cl2Ge(NMe2)2 (0.23 g,
◦
1
1.0 mmol) was heated at 80 C for 24 h. According to H NMR
spectroscopy data, only starting materials were found in the
reaction mixture.
Reaction of 1 with n-BuLi
To a suspension of 1 (0.10 g, 0.17 mmol) in toluene (10 ml) 0.21 ml
of a 1.6 M n-BuLi solution (0.34 mmol) in hexane was added
dropwise at -78 C. The reaction mixture was allowed to warm
Reaction of Ge(NMe2)4 with 9
◦
The mixture of 9 (0.19 g, 1.0 mmol) and Ge(NMe2)4 (0.25 g,
1.0 mmol) was heated at 80 ◦C for 24 h. According to 1H
NMR spectroscopy data, only starting materials were found in
the reaction mixture.
to room temperature and stirred for further 24 h (1 dissolved in
40 min after the treatment). A precipitate of LiCl was filtered
off. The filtrate was evaporated resulting (according to 1H NMR
spectrum) in a complex mixture of products which were difficult
to separate and to identify.
Reaction of Cl2Ge(NMe2)2 with 14
Computational procedure
To a stirred solution of Cl2Ge(NMe2)2 (0.58 g, 2.5 mmol) in 25 ml
of toluene 14 (0.8 g, 2.5 mmol) was added. The reaction mixture
was refluxed for 72 h resulting (according to 1H NMR spectrum)
in a complex mixture of products which were difficult to separate
and to identify.
Density functional (DFT) study was carried out using the ab initio
generalized gradient approximation and the PBE40 functional
with the TZ2P basis set and “Priroda” software.41 Geometry
optimization was carried out for all stable compounds and for
the structures corresponding to the saddle points (in the case
of transition states, TS). The types of the stationary points
were confirmed by the vibrational frequency analysis. For the
saddle points, the reaction coordinates were also calculated. All
computations were performed for the gas phase.
Reaction of Ge(NMe2)4 with 14
The mixture of 14 (0.35 g, 1.0 mmol) and Ge(NMe2)4 (0.27 g,
◦
1.0 mmol) was heated at 130 C for 24 h resulting (according to
1H NMR spectrum) in a complex mixture of products which were
difficult to separate and to identify.
X-Ray crystallography
Crystal data and details of X-ray analyses are given in Table 4.
All experimental datasets were collected on a Bruker SMART
diffractometer using graphite monochromatized Mo-Ka radia-
Reaction of 1 with MeN(CH2CH2NLiC6F5)2
The procedure was analogous to that for 1, Method 1 except
1 was used instead of GeCl4: reaction of 7 (0.57 g, 1.3 mmol)
with 1.63 mL of a 1.6 M n-BuLi solution (2.6 mmol) in hexane
˚
tion (l = 0.71073 A) at 120 K. Absorption correction based on
measurements of equivalent reflections was applied. The structures
Table 4 X-Ray structure determination summary
Compound
1
2
3
4
12
Formula
M
C27.5H23Cl2F10Ge1N3
728.98
Monoclinic
C27.5H23Br2F10Ge1N3
817.90
Orthorhombic
C33.5H27Cl2F10Ge1N3
805.07
Monoclinic
C24.75H17Br2F10Ge1N3
778.82
Triclinic
¯
P1
C20H52Cl2Ge2N6Si4
705.12
Monoclinic
Crystal system
Space group
P21/c
Pbca
P21/c
P21/c
˚
a/A
7.4562(6)
22.0794(17)
17.7878(14)
90
90.241(2)
90
2928.4(4)
4
1.317
14.4325(5)
21.6686(8)
19.2039(7)
90
90
90
6005.7(4)
8
3.768
35 449
5583 (0.0748)
0.0667
7.3340(5)
19.8573(12)
22.7800(14)
90
90.994(2)
90
3317.0(4)
4
1.171
7.7668(5)
16.6310(10)
20.6711(12)
83.241(1)
80.160(1)
87.979(1)
2612.2(3)
4
4.326
15 498
9391 (0.0343)
0.0424
0.0946
16.744(3)
14.569(2)
13.503(2)
90
90.501(4)
90
3293.9(9)
4
2.154
˚
b/A
˚
c/A
a/◦
b/◦
g ◦
3
˚
V/A
Z
m/mm-1
Data collected
Unique data (Rint
R1 [I > 2s(I)]
wR2 (all data)
19 274
6279 (0.0285)
0.0338
17 319
7198 (0.0371)
0.0462
18 868
7896 (0.0428)
0.0466
)
0.0846
0.1791
0.1111
0.1179
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were solved by direct methods42 and refined by full-matrix least-
squares on F243 with anisotropic thermal parameters for all
non-hydrogen atoms (except disordered toluene molecules). All
measured structures contain solvent toluene molecules disordered
over crystallographic inversion centres. All hydrogen atoms were
placed in calculated positions and refined using a riding model.
In the monoclinic structures 1, 3 and 12, b angles are close to
90◦ and they may emulate the orthorhombic crystal system. The
possibility of pseudo-merohedric twinning for these structures
was checked, however, no twinning behaviour was observed. 12
contains two crystallographically independent pseudo-symmetric
molecules. The refinement of 12 in higher symmetry space group
Pbca was found to be unsatisfactory.
20 P. L. Shutov, S. S. Karlov, K. Harms, A. V. Churakov, J. A. K. Howard,
J. Lorberth and G. S. Zaitseva, Eur. J. Inorg. Chem., 2002, 2784.
21 P. L. Shutov, D. A. Sorokin, S. S. Karlov, K. Harms, Yu. F. Oprunenko,
A. V. Churakov, M. Yu. Antipin, G. S. Zaitseva and J. Lorberth,
Organometallics, 2003, 22, 516.
22 S. S. Karlov, E. Kh. Yakubova, E. V. Gauchenova, A. A. Selina, A. V.
Churakov, J. A. K. Howard, D. A. Tyurin, J. Lorberth and G. S.
Zaitseva, Z. Naturforsch., B: Chem. Sci., 2003, 58, 1165.
23 E. Kh. Lermontova, A. A. Selina, S. S. Karlov, A. V. Churakov, J. A. K.
Howard, Yu. F. Oprunenko, M. Yu. Antipin, J. Sundermeyer and G. S.
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24 S. S. Karlov, E. Kh. Lermontova, M. V. Zabalov, A. A. Selina, A. V.
Churakov, J. A. K. Howard, M. Yu. Antipin and G. S. Zaitseva, Inorg.
Chem., 2005, 44, 4879.
25 P. L. Shutov, S. S. Karlov, K. Harms, D. A. Tyurin, A. V. Churakov, J.
Lorberth and G. S. Zaitseva, Inorg. Chem., 2002, 41, 6147.
26 P. L. Shutov, S. S. Karlov, K. Harms, O. Kh. Poleshchuk, J. Lorberth
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27 E. V. Gauchenova, S. S. Karlov, A. A. Selina, E. S. Chernyshova, A. V.
Churakov, J. A. K. Howard, N. A. Troitsky, S. N. Tandura, J. Lorberth
and G. S. Zaitseva, J. Organomet. Chem., 2003, 676, 8.
28 P. L. Shutov, S. S. Karlov, K. Harms, A. V. Churakov, J. Lorberth and
G. S. Zaitseva, Eur. J. Inorg. Chem., 2004, 2123.
29 K. V. Zaitsev, S. S. Karlov, A. A. Selina, Yu. F. Oprunenko, A. V.
Churakov, B. Neumu¨ller, J. A. K. Howard and G. S. Zaitseva,
Eur. J. Inorg. Chem., 2006, 1987.
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4702 | Dalton Trans., 2009, 4695–4702
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©