Reaction of RGeBr3 (R = iPr2C6H3NSiMe3) with ammonia to give (RGe)2(NH2)4(NH): A compound containing terminal NH2 groups

Article abstract of DOI:10.1002/(SICI)1521-3773(19990215)38:4<522::AID-ANIE522>3.0.CO;2-N

The surprisingly facile preparation of (RGe)₂(NH₂)₄(NH) (1; R = iPr₂C₆H₃NSiMe₃), which contains one NH and four NH₂ groups, is achieved by the introduction of gaseous

Full text of DOI:10.1002/(SICI)1521-3773(19990215)38:4<522::AID-ANIE522>3.0.CO;2-N

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[18] a) D. Touchard, S. Guesmi, M. Bouchaib, P. Haquette, A. Daridor,
P. H. Dixneuf, Organometallics 1996, 15, 2579 ± 2581; b) review: M. I.
Bruce, Chem. Rev. 1991,91, 197 ± 257.
[19] a) M. I. Bruce, A. G. Swincer, Aust. J. Chem. 1980, 33, 1471 ± 1483;
b) C. Bianchini, J. A. Casares, M. Peruzzini, A. Romerosa, F.
Zanobini, J. Am. Chem. Soc. 1996, 118, 4585 ± 4594, and references
therein; c) M. L. Buil, M. A. Esteruelas, A. M. Lopez, E. Onate,
Organometallics 1997, 16, 3169 ± 3177.
To obtain a suitable reagent for the synthesis of an amino
derivative, we first prepared tribromogermanium compounds
of the type RGeBr3. The compound iPr2C6H3NSiMe3GeBr3
(1) was obtained by reaction of iPr2C6H3NSiMe3Li with GeBr4
in diethyl ether at 788C under elimination of LiBr. The
reaction of 1 in liquid ammonia, which was performed analogous
to the synthesis of RSi(NH2)3 derivatives,[1, 3] proved to be
unsuccessful; due to condensation reactions no definitive
product could be isolated. If 1 is dissolved at room temper-
ature in diethyl ether and ammonia is passed through the
reaction solution, however, (RGe)2(NH2)4(NH) (2) is ob-
tained in good yield (Scheme 1).
[20] This species was originally detected in an inseparable mixture of
complexes resulting from a metal-mediated degradation of methyl
formate.[6]
[21] Crystal data for [PPN]-4c: Monoclinic, space group P21/n; a ˆ
29.322(4), b ˆ 15.558(2), c ˆ 9.656(2) Š, b ˆ 92.77(2), Vˆ 4400(2) Š3;
R ˆ 0.046, Rw ˆ 0.050.[11b]
[22] a) R. M. Bullock, J. Chem. Soc. Chem. Commun. 1989, 165 ± 167.
[23] Carbenoid species derived from simple carbonyl-chloro RuII com-
plexes have been recently proposed by Murai et al. as intermediates in
the construction of polycyclic ring systems from enynes.[4a]
Reaction of RGeBr3 (R ˆ iPr2C6H3NSiMe3)
with Ammonia To Give (RGe)2(NH2)4(NH):
A Compound Containing Terminal NH2
Groups**
Karsten Wraage, Lutz Lameyer, Dietmar Stalke, and
Herbert W. Roesky*
Scheme 1. Synthesis of 2 from 1.
In memory of Jean Rouxel
Compound 2 was studied by NMR spectroscopy, mass
spectrometry, and structure analysis. In the 1H NMR spectrum
the characteristic signals for the NH and NH2 protons are
recognizable as broad singlets (d ˆ 0.65 for (RGe)2(NH2)4-
(NH) and d ˆ 0.75 for (RGe)2(NH2)4NH). The IR spectrum
shows three N H bands in the bond stretching region (3325 ±
In the past few years Power et al.,[1] Schnick et al.,[2] and
others[3, 4] have shown that amino and imino derivatives
containing silicon can undergo interesting reactions. In this
respect they resemble the oxygen derivatives to some extent,
but they can also differ from them quite considerably.[5] For
example, RSi(NH2)3 compounds react with AlMe3 and
[Cp*TiMe3] (Cp* ˆ C5Me5) with elimination of methane to
form interesting, new, soluble heterocycles. We were inter-
ested in finding out whether there is a similar successive
chemistry for germanium derivatives. We quickly discovered
that the preferred starting compound for the reaction with
ammoniaÐnamely, RGeCl3 (R ˆ iPr2C6H3NSiMe3)Ðis not
accessible in a pure form. Until now, only one monoamino-
germanium compound with the composition Mes3GeNH2
(Mes ˆ Me3C6H2) was known which is stable with regard to
condensation reactions.[6] We report here on the preparation
and structure of an amino-iminogermanium compound with
free amino groups that have not undergone condensation
reactions.
1
1
3402 cm ), and the bands at 1540 and 1578 cm have been
provisionally assigned to the NH2 bending vibrations.
Single crystals of 2 are obtained on recrystallization from n-
hexane. Compound 2 crystallizes in the space group P1;[11] two
Å
RGe(NH2)2 fragments bridged by a NH group are shown in
the asymmetric unit in Figure 1a. In spite of their compara-
tively large spatial requirement, both of the N-(2,6-diisopro-
pylphenyl)-N-(trimethylsilyl)amino groups are located on one
side of the molecule and the four NH2 groups on the opposite
side. This cisoid arrangement is the result of a network of
bridging hydrogen bonds (Figure 1b). The centrosymmetric
dimer has four weak N ´´´ H-N bridges.[7] The N ´´´ H distances
are 250.5 pm (H21 ´´´ N5A, H21A ´´´ N5; Figure 1b) and
267.8 pm (H31 ´´´ N2A, H31A ´´´ N2; Figure 1b). All the
Ge N bond lengths to the hydrogen-substituted nitrogen
atoms N1, N2, N3, N5, and N6 lie in the range from 181.1(2) to
182.4(2) pm, the bonds to the aryl-substituted nitrogen atoms
N4 and N7 (both 184.2(2) pm) are about 3 pm longer.
[*] Prof. H. W. Roesky, Dipl.-Chem. K. Wraage
Institut für Anorganische Chemie der Universität
Tammannstrasse 4, D-37077 Göttingen (Germany)
Fax: (‡49)551-393-373
The Ge N bond lengths all lie in the expected region.
Similar derivatives, such as the NH-bridged compound
[Me2Si(NtBu)2Ge(tBu)]NH[(C5H4N)Ge(NtBu)2SiMe2] de-
scribed by Veith et al. and the cyclotris(dithiolato)germanium
imide [{(tBuS)2Ge(NH)}3] described by George et al., have
E-mail: hroesky@gwdg.de
Dipl.-Chem. L. Lameyer, Prof. D. Stalke
Institut für Anorganische Chemie der Universität Würzburg
(Germany)
[**] This work was supported by the Deutsche Forschungsgemeinschaft.
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Angew. Chem. Int. Ed. 1999, 38, No. 4

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diethyl ether (80 mL) was added slowly to the GeBr4 solution at 788C.
After the mixture was warmed slowly and stirred for about 12 h, the solvent
was removed under reduced pressure and the residue taken up in n-hexane
(70 mL). Insoluble components were filtered off, and the product
subsequently recrystallized from n-hexane (5 mL). Yield: 7.5 g (80%) of
1. C15H26Br3GeNSi (M ˆ 560.8 gmol 1); sublimation at 150 ± 1608C;
1H NMR (200 MHz, C6D6, TMSext.): d ˆ 0.32 (s, 9H; Si(CH3)3), 1.15 (d,
3J(H,H) ˆ 6.9 Hz, 6H; CH(CH3)2), 1.25 (d, 3J(H,H) ˆ 6.9 Hz, 6H;
CH(CH3)2), 3.45 (sept, 2H; CH(CH3)2), 7.05 (m, 3H; Harom.); 29Si NMR
(49 MHz, C6D6, TMSext.): d ˆ 13.1 (Si(CH3)3); MS (EI, 70 eV): m/z (%):
‡
‡
560.9 (100) [M ], 545.8 (90) [M
CH3]; correct elemental analysis.
2: iPr2C6H3NSiMe3GeBr3 (1, 0.56 g, 1 mmol) was dissolved in diethyl ether
(10 mL). Ammonia (120 mLmin 1) was introduced under continuous
stirring at room temperature. After 1 min the originally orange solution
had turned colorless and a white precipitate formed. The reaction mixture
was stirred for a further 0.5 h, and the precipitate then filtered off and
recrystallized from n-hexane (5 mL). Yield: 0.3 g (81%) of 2. C30H61Ge2N7-
Si2 (M ˆ 721.3 gmol 1); m.p. 1398C; 1H NMR (250 MHz, CDCl3, TMSext.):
d ˆ 0.07 (s, 18H; Si(CH3)3), 0.65 (s, 1H; (H2N)2GeNHGe(NH2)2), 0.75 (s,
8H; (H2N)2GeNHGe(NH2)2), 1.15 (dd, 24H; CH(CH3)2), 3.45 (sept, 4H;
CH(CH3)2), 7.05 (m, 6H; Harom.); 29Si NMR (79 MHz, CDCl3, TMSext.): d ˆ
4.9 (Si(CH3)3); IR (KBr): nÄ ˆ 1540, 1578, 3325, 3389, 3402 cm 1; MS (EI,
‡
‡
70 eV): m/z (%): 705 (2) [M
CH3], 473 (100) [M
iPr2C6H3NSiMe3];
correct elemental analysis.
Received: September 28, 1998 [Z12457]
German version: Angew. Chem. 1999, 111, 542 ± 544
Keywords: amides ´ bromine ´ germanium ´ imides
Figure 1. a) Structure of 2 in the crystal. Selected bond lengths [pm] and
angles [8]: Ge1 N1 181.8(2), Ge1 N2 181.8(2), Ge1 N3 181.5(2), Ge1 N4
184.2(2), Ge2 N1 181.1(2), Ge2 N5 182.4(2), Ge2 N6 181.4(2), Ge2 N7
184.2(2); Ge1-N1-Ge2 120.89(9), N1-Ge1-N4 108.61(8), N2-Ge1-N3
101.80(10), N1-Ge2-N7 109.55(8), N5-Ge2-N6 104.54(11). b) Bridging
hydrogen bonds between two molecules of 2. Distances [pm] and angles [8]
(the hydrogen atom positions were determined by difference Fourier
synthesis and freely refined): H21 ´´´ N5A 250.5, H31 ´´´ N2A 267.8; N2-
H21 ´´´ N5A 164.28, N3-H31 ´´´ N2A 174.08.
[1] K. Ruhlandt-Senge, R. A. Bartlett, M. M. Olmstead, P. P. Power,
Angew. Chem. 1993, 105, 459; Angew. Chem. Int. Ed. Engl. 1993, 32,
425.
[2] H. Huppertz, W. Schnick, Angew. Chem. 1997, 109, 2765; Angew.
Chem. Int. Ed. Engl. 1997, 36, 2651.
[3] K. Wraage, A. Künzel, M. Noltemeyer, H.-G. Schmidt, H. W. Roesky,
Angew. Chem. 1995, 107, 2954; Angew. Chem. Int. Ed. Engl. 1995, 34,
2645.
[4] C. Rennekamp, A. Gouzyr, A. Klemp, H. W. Roesky, C. Brönneke, J.
Kärcher, R. Herbst-Irmer, Angew. Chem. 1997, 109, 413; Angew.
Chem. Int. Ed. Engl. 1997, 36, 404.
Ge N bond lengths similar to those in 2.[8, 9] In the NtBu-
bridged amide [{tBuN(CH2)2NtBu}(Me)Si]N(tBu)[Ge{N(H)-
SiMe3}(OSiMe3){OCH2N(CH3)2}], which contains sterically
more demanding substituents on the nitrogen atom, the
Ge N bond is 184.2 pm long, and thus lies in the same range
[5] R. Murugavel, A. Voigt, M. G. Walawalkar, H. W. Roesky, Chem. Rev.
1996, 96, 2205.
Á
Á
[6] M. Riviere-Baudet, A. Morere, J. Organomet. Chem. 1992, 423, C5.
[7] a) J. Emsley, Chem. Soc. Rev. 1980, 9, 91; b) G. R. Desiraju, Angew.
Chem. 1995, 107, 2541; Angew. Chem. Int. Ed. Engl. 1995, 34, 2328.
[8] M. Veith, E. Werle, V. Huch, Z. Anorg. Allg. Chem. 1993, 619, 641.
[9] C. George, A. P. Purdy, Acta Crystallogr. Sect. C 1996, 52, 2489.
[10] M. Veith, A. Rammo, Z. Anorg. Allg. Chem. 1997, 623, 861.
[11] Crystal structure analysis of 2: C30H61Ge2N7Si2, Mr ˆ 721.22, triclinic,
as the Ge NAr(SiMe3) bond lengths in
2 (Ge1 N4,
Ge2 N7).[10] The dimers exist in the solid as isolated
molecules, however, and there are no bridging intermolecular
hydrogen bonds.
Å
space group P1, a ˆ 1035.0(2), b ˆ 1264.3(3), c ˆ 1556.7(3) pm, a ˆ
101.59(3), b ˆ 90.86(3), g ˆ 109.39(3)8, Vˆ 1.8749(6) nm3, Z ˆ 2,
1calcd ˆ 1.278 Mgm 3, F(000) ˆ 764, l ˆ 71.073 pm, Tˆ 173(2) K, ab-
sorption coefficient 1.696 mm 1. Crystal size: 0.40 Â 0.30 Â 0.30 mm3,
measured q region 2.09 ± 25.998; of 26875 reflections measured, 6810
were independent (Rint ˆ 0.1052); 62 restraints, 408 refined parame-
ters, R values [I > 2s(I)]: R1 ˆ 0.0290, wR2 ˆ 0.0741, R values (for all
The synthesis of 2 demonstrates that stable amino-imino-
germanium derivatives can be prepared through the ammo-
nolysis of a RGeBr3 compound. Compound 2 contains
reactive hydrogen atoms which should prove predestined for
the synthesis of heterocycles containing germanium. The
reaction of 2 with trimethylaluminum leads to the formation
of a six-membered (GeN)3 heterocycle and methane. Termi-
nal NH2 groups are located on each of the germanium atoms
in the ring. The high hydrogen content should favor the
elimination of the organic groups in 2, so that new Ge N
phases should become accessible.
data): R1 ˆ 0.0354, wR2 ˆ 0.0764; weighting scheme w ˆ 1 [s2(F 2) ‡
/
o
(0.0560P)2] with P ˆ (max(F 2,0) ‡ 2F 2) 3; max./min. residual electron
/
o
c
density: 559/ 734 enm 3. All non-hydrogen atoms were refined
anisotropically. The hydrogen atoms on N2, N3, N5, and N6 (H21,
H22, H31, H32, H51, H52, H61, and H62) were localized by difference
Fourier syntheses and freely refined using distance restraints. The
ideal geometrical positions of all the other hydrogen atoms were
calculated and refined using a riding model. Crystallographic data
(excluding structure factors) for the structure reported in this paper
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-103202. Copies of
the data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB21EZ, UK (fax: (‡44)1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
Experimental Section
1: GeBr4 (5.2 g, 16.6 mmol) was dissolved in diethyl ether (100 mL). A
solution of iPr2C6H3NSiMe3Li (3.8 g, 14.9 mmol, 0.9 equiv.) dissolved in
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