Synthesis and characterization of gallium(III) and germanium(II) chlorides bearing the C6F5-substituted β-diketiminate HC[(CMe)(NC6F5)]2 ligand

Article abstract of DOI:10.1002/zaac.200800087

The germanium(II) and gallium(III) organochlorides containing the C ₆F₅-substituted β-diketiminate ligand LGeCl (2) and LGaCl₂ (3) (L = HC[(CMe)(NC₆F₅)]₂) were synthesized. Salt elimination

Full text of DOI:10.1002/zaac.200800087

DOI: 10.1002/zaac.200800087
Synthesis and Characterization of Gallium(III) and Germanium(II) Chlorides
Bearing the C6F5-Substituted β-Diketiminate HC[(CMe)(NC6F5)]2 Ligand
Zhi Yanga, Xiaoli Maa, Herbert W. Roesky*,a, Ying Yanga,b, Hongping Zhua, Jörg Magulla, and Arne Ringea
a Göttingen, Institut für Anorganische Chemie der Georg-August-Universität Göttingen
b Changsha /P. R. China, College of Chemistry and Chemical Engineering, Central South University
Received February 7th, 2008.
Dedicated to Professor Achim Müller on the Occasion of his 70th Birthday
Abstract. The germanium(II) and gallium(III) organochlorides
containing the C6F5-substituted β-diketiminate ligand LGeCl (2)
and LGaCl2 (3) (L ϭ HC[(CMe)(NC6F5)]2) were synthesized. Salt
elimination reactions of the C6F5-substituted β-diketiminato lith-
ium salt with the corresponding germanium(II) and gallium(III)
chlorides led to the organochlorides respectively. Compounds 2
and 3 were characterized by spectroscopic and elemental analyses,
and 2 was further investigated by single crystal X-ray structural
analysis.
Keywords: Gallium; Germanium; C6F5-substituted; β-Diketimin-
ate ligand
Introduction
boronϪoxygen double bond using this ligand [8], and they
also reported on the single crystal X-ray structure of the
ligand (LH) and on LLi·(OEt2), LAlMe2, and LGaMe2
respectively [9]. Recently LAlBr2, LAl(Me)Cl, LAl(Me)I,
and (LAlMe)2(μ-O) were reported from our group [10]. In
these papers, it was demonstrated that this ligand exhibits
very interesting reaction properties. Until now there are still
no germanium and gallium halides reported with this
ligand. Herein, we describe the synthesis and characteriz-
ation of germanium and gallium chlorides supported by the
HC[(CMe)(NC6F5)]2 ligand.
Germanium and gallium halides are involved in most of
the germanium and gallium containing reactions. They are
important for germanium and gallium chemistry [1, 2]. Re-
duction of gallium halides can result in GaI or Ga-Ga bond
containing compounds [3]. Hydrolysis of germanium and
gallium halides lead to gallium and germanium terminal
hydroxide compounds [4, 5]. Recent research in our group
showed that organic germanium chloride reacts with
H3Al·NMe3 to result in an unusual monomeric ger-
manium(II) compound with terminal hydride [6]. Bulky en-
cumbered β-diketiminate ligands are usually used to stabil-
ize the metal center due to their electronic and/or steric
properties. The bulky ligands can avoid the condensation of
molecules to form oligomeric compounds. A noticeable
point is the ability of these ligands to stabilize low coordi-
nation numbers at the metal atoms, rare coordination
geometries, or low oxidation states owing to their ability to
tune properly between the steric and electronic factors.
Using this kind of ligands, we can selectively change
the functionalities on the metal center, design and control
the reaction process. In 2002, Power et al. reported
Experimental Section
General Procedures. All manipulations were carried out under a
purified nitrogen atmosphere using Schlenk techniques or inside a
Mbraun MB 150-GI glovebox. All solvents were distilled from Na/
benzophenone ketyl prior to use. Commercially available chemicals
were purchased from Aldrich or Fluka and used as received. LH
[7] was prepared as described in the literature. Elemental analyses
were performed by the Analytisches Labor des Instituts für Anor-
ganische Chemie der Universität Göttingen. 1H, 13C, and
19F NMR spectra were recorded on Bruker AM 300 and 500 spec-
trometers and IR spectra on a Bio-Rad Digilab FTS-7 spec-
trometer. EI mass spectra were measured on a Finnigan MAT 8230
or a Varian MAT CH5 instrument. Melting points were measured
in sealed glass tubes and were not corrected.
on
HC[(CMe)(NC6F5)]2 (L) [7]. Moreover Cowley et al.
prepared Lewis acid stabilized compound with
a
new C6F5 substituted β-diketiminate ligand
a
a
* Prof. Dr. Dr.h.c. H. W. Roesky
Institut für Anorganische Chemie der
Georg-August-Universität Göttingen
Tammannstrasse 4
D-37077 Göttingen / Germany
Fax: (ϩ49) 551-39-3373
HC[(CMe)(NC6F5)]2GeCl (2)
To a toluene solution (20 mL) of LH (0.43 g, 1 mmol) at 0 °C was
added drop by drop n-BuLi (2.5 M, 0.4 mL, 1 mmol). The mixture
was stirred and allowed to warm to room temperature. After ad-
E-mail: hroesky@gwdg.de
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© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2008, 634, 1490Ϫ1492

Gallium(III) and Germanium(II) Chlorides
ditional stirring for 12 h, the solution was cooled to 0 °C and
GeCl2 ·dioxane (0.23 g, 1 mmol) in toluene (10 mL) was added.
The resulting solution was allowed to warm to room temperature
and stirred for 12 h. After workup, the insoluble LiCl was removed
by filtration and the filtrate was dried in vacuum and washed with
cold n-hexane twice to yield solid 2. Yield: (0.45 g, 84 %). Mp
183 °C. Anal. Calcd for C17H7ClF10GeN2 (Mr ϭ 537.29): C, 38.00;
H, 1.31; N, 5.21. Found C, 39.05; H, 1.67; N, 4.97 %.
Single Crystal X؊ray Structure Determination and
Refinement
The crystallographic data for compound 2 was collected on a Stoe
IPDS II-array detector system with graphite-monochromated
˚
MoKa radiation (λ ϭ 0.71073 A). This structure was solved by di-
rect methods (SHELXS-96) [11] and refined against F2 using
SHELXL-97 [12]. All non-hydrogen atoms were located by differ-
ence Fourier synthesis and refined anisotropically, and hydrogen
atoms were included using the riding model with Uiso related to the
Uiso of the parent atoms.
1H NMR (300.13 MHz, CDCl3, 298 K, ppm): δ 2.08 (s, 6 H, β-Me), 5.67 (s,
1 H, γ-CH). 13C NMR (75.48 MHz, CDCl3, 298 K, ppm): δ 23.43 (β-Me),
103.22 (γ-C), 119.22, 137.54, 138.55, 139.15, 139.88, 142.19 (C6F5), 167.27
(CN). 19F NMR (188.28 MHz, CDCl3, 298 K, ppm): Ϫ141.83 (m, 2 F, o-F),
Ϫ146.63 (m, 2 F, o-F), Ϫ154.23 (t, 2 F, p-F), Ϫ159.94 (m, 2 F, m-F), Ϫ160.52
(m, 2 F, m-F). EI-MS: m/z (%) 538 (59, [Mϩ]), 503 (100, [MϩϪCl].
Results and Discussion
According to the outline given in Scheme 1, compounds
LGeCl (2) and LGaCl2 (3) were prepared by lithium salt
elimination with the corresponding germanium and gallium
chloride. The toluene solution of LLi prepared from LH
and n-BuLi was used in situ for the reaction with
GeCl2 ·dixone and GaCl3 respectively (The structure of
LLi·OEt2 in ether has been reported by Cowley et al. [9a].).
Both compounds were characterized by EI-MS, 1H, 13C,
and 19F NMR measurements as well as by elemental analy-
HC[(CMe)(NC6F5)]2GaCl2 (3)
To a toluene solution (40 mL) of LH (4.31 g, 10 mmol) at 0 °C was
added drop by drop n-BuLi (2.5 M, 4 mL, 10 mmol). The mixture
was stirred and allowed to warm to room temperature. After ad-
ditional stirring for 12 h, the solution was cooled to 0 °C and
GaCl3 (1.73 g, 10 mmol) in toluene (20 mL) was added. The re-
sulting solution was allowed to warm to room temperature and
stirred for 12 h. After workup, the insoluble LiCl was removed by
filtration and the filtrate was dried in vacuum and washed with n-
hexane twice to yield solid 3. Yield: (4.67 g, 82 %). Mp 242 °C.
Anal. Calcd for C17H7Cl2F10GaN2 (Mr ϭ 569.87): C, 35.83; H,
1.24; N, 4.92. Found C, 35.60; H, 1.74; N, 4.61 %.
1
sis. In the H NMR spectrum compounds 2 and 3 exhibit
each one resonance for the γ-C-H proton around 5.5 ppm,
and one signal for Me protons around 2.0 ppm with the
intensity of 1:6, showing the characteristic β-diketiminate
resonances. The 19F NMR spectrum of compound 2 shows
five resonances in the ratio of 1:1:1:1:1, while 3 exhibits
three resonances in the ration of 2:1:2. These differences
can be attributed to the symmetric arrangement of 3 and
the asymmetric structure of 2 due to the non-coordinate
lone-pair of the germanium atom. In the EI-MS spectra,
the most intense peak of compounds 2 and 3 is attributed to
1H NMR (300.13 MHz, CDCl3, 298 K, ppm): δ 2.05 (s, 6 H, β-Me), 5.47 (s,
1 H, γ-CH). 13C NMR (125.77 MHz, C6D6, 298 K, ppm): δ 23.82 (β-Me),
100.14 (γ-C), 117.06, 137.08, 139.13, 139.91, 141.78, 143.75 (C6F5), 173.93
(CN). 19F NMR (188.28 MHz, C6D6, 298 K, ppm): δ Ϫ144.24 (m, 4 F, o-F),
Ϫ153.35 (t, 2 F, p-F), Ϫ160.02 (m, 4 F, m-F). EI-MS: m/z (%) 570 (100,
[Mϩ]).
Scheme 1
Z. Anorg. Allg. Chem. 2008, 1490Ϫ1492
© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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Z. Yang, X. Ma, H. W. Roesky, Y. Yang, H. Zhu, J. Magull, A. Ringe
β-diketiminate ligand HC[(CMe)(NC6F5)]2GeCl (2) and
HC[(CMe)(NC6F5)]2GaCl2 (3). To our knowledge com-
pound 2 is the first germanium compound supported by
this ligand. The germanium(II) compound (2) has carbene-
like properties and is therefore a promising candidate for
the preparation of other germanium derivatives either
by electron donor-acceptor reactions or by chloride met-
athesis reactions.
Acknowledgment. We are grateful for financial support by the
Deutsche Forschungsgemeinschaft, Fonds der Chemischen Indus-
trie, and the Göttinger Akademie der Wissenschaften.
References
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2000, 1991Ϫ1992:
Figure 1 Molecular structure of 2. Thermal ellipsoids are drawn at
50 % level, and the hydrogen atoms are omitted for clarity.
[4] L. W. Pineda, V. Jancik, H. W. Roesky, D. Neculai, A. M.
Neculai, Angew. Chem. 2004, 116, 1443Ϫ1445; Angew. Chem.
Int. Ed. 2004, 43, 1419Ϫ1421.
˚
Table 1 Selected bond distances/A and angles/° for compound 2
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Chem. 2006, 4029Ϫ4032.
[6] L. W. Pineda, V. Jancik, K. Starke, R. B. Oswald, H. W. Roe-
sky, Angew. Chem. 2006, 118, 2664Ϫ2667; Angew. Chem. Int.
Ed. 2006, 45, 2602Ϫ2605.
Ge(1)-N(1)
Ge(1)-Cl(1)
N(1)-Ge(1)-Cl(1)
1.998(2)
2.299(1)
98.78(6)
Ge(1)-N(2)
N(1)-Ge(1)-N(2)
N(2)-Ge(1)-Cl(1)
2.000(2)
89.01(8)
94.50(6)
[7] A. Panda, M. Stender, R. J. Wright, M. M. Olmstead, P.
K l av i ns, P. P. Powe r, Inorg. Chem. 2002, 41, 3909Ϫ3916.
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the molecular ion [Mϩ] (m/z 538, 570) with correct isotopic
pattern. In 2, the ion at m/z ϭ 503 was assigned to
[MϪCl]ϩ.
Pale yellow single crystals of compound 2 were obtained
from saturated toluene solution at Ϫ28 °C, and were sub-
mitted to X-ray diffraction studies to determine the molecu-
lar structure. The structure of 2 shows mononuclear ar-
rangement with germanium at the center that coordinates
to the chelating β-diketiminate ligand with the C6F5 groups
attached to the ring. Compound 2 crystallizes in the tri-
[10] Z. Yang, H. Zhu, X. Ma, J. Chai, H. W. Roesky, C. He, H.-G.
Schmidt, M. Noltemeyer, Inorg. Chem. 2006, 45, 1823Ϫ1827.
[11] G. M. Sheldrick, SHELXS-90, Program for Structure Solu-
tion. Acta Crystallogr. Sect. A 1990, 46, 467Ϫ473.
[12] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
Refinement; University of Göttingen, Germany, 1997.
[13] Crystal data for 2: C17H7ClF10GeN2, Mr ϭ 537.29, triclinic,
¯
clinic space group P1 with one molecule in the asymmetric
unit [13]. The molecular structure of 2 is shown in Figure
1. In 2, the germanium atom is coordinate to two nitrogen
atoms of the monoanionic ligand and a terminal chloride
atom, resulting in a pyramidal coordination sphere. The
˚
˚
¯
space group P1, a ϭ 11.0621(6) A, b ϭ 12.0853(7) A, c ϭ
˚
15.4740(8) A, Ͱ ϭ 112.788(4)°, β ϭ 93.632(4)°, γ ϭ 96.160(5)°,
˚
3
˚
Ge-N bond length (av. 1.999 A) is similar to that (av.
V ϭ 1883.90(18) A , Z ϭ 4, ρcalcd ϭ 1.894 gcmϪ3, F(000) ϭ
˚
1048, 1.84 Յ θ Ն 24.77, of 28409 reflections collected, 6048
1.993 A) in compound LЈGeCl (LЈ ϭ HC[(CMe)(NAr)]2,
˚
were independent, R(int) ϭ 0.0479, R1 ϭ 0.0260, wR2
ϭ
Ar ϭ 2,6-iPr2C6H3) [14]. The Ge-Cl bond length (2.299 A)
0.0627 (I > 2σ(I)); The residual electron density: 0.893/
˚
is comparable to that of LЈGeCl (2.295 A).
Ϫ0.906 e AϪ3. The CCDC reference number 670516. Copies
˚
of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB2IEZ, UK; fax:
(ϩ44) 1223-336-033; or deposit@ccdc.cam.ac.uk.
Conclusion
In summary we report on the synthesis of a germanium and
[14] Y. Ding, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt,
Organometallics 2001, 20, 1190Ϫ1194.
a
gallium chloride containing the C6F5 substituted
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© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2008, 1490Ϫ1492