Synthesis and characterization of β-diketiminate germanium(II) and tin(II) bromides

Article abstract of DOI:10.1016/j.ica.2010.07.051

The equimolar reaction of a β-diketiminate lithium salt LLi(OEt ₂) [L = HC(CMeNAr)₂; Ar = 2,6-iPr₂C ₆H₃] with either GeBr₂ or SnBr₂ in diethyl ether affords the synthetically use

Full text of DOI:10.1016/j.ica.2010.07.051

Inorganica Chimica Acta 363 (2010) 4408–4410
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Note
Synthesis and characterization of b-diketiminate germanium(II) and tin(II) bromides
*
Anukul Jana, Gerald Schwab, Herbert W. Roesky , Dietmar Stalke
Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 22 July 2010
The equimolar reaction of a b-diketiminate lithium salt LLi(OEt2) [L = HC(CMeNAr)2; Ar = 2,6-iPr2C6H3]
with either GeBr2 or SnBr2 in diethyl ether affords the synthetically useful monomeric b-diketiminate-
element halides LGeBr (1) and LSnBr (2), respectively. Both are soluble in hydrocarbon solvents, stable
in inert atmosphere, and have been characterized by elemental analysis, NMR spectroscopy, and single-
crystal X-ray diffraction analysis.
Dedicated to Professor Achim Müller
Keywords:
Germanium
Tin
Ó 2010 Elsevier B.V. All rights reserved.
Bromide
X-ray
b-Diketiminate
1. Introduction
2. Result and discussion
Halides of group 14 elements are important precursors for a
variety of new reactions. Dihalogermylenes, GeX2 (X = F, Cl, Br, I),
were the first known divalent species that had been studied and
reviewed as starting materials and intermediates in organogerma-
The reaction of the b-diketiminato lithium salt LLi(OEt2) with
GeBr2 and SnBr2 in diethyl ether gave the monomeric compounds
LMBr (M = Ge (1); M = Sn (2)) with three-coordinate metal atoms
(Scheme 1).
*
nium chemistry in 1973 [1]. Cp GeCl was the first example of a
Compounds 1 and 2 are well soluble in common organic sol-
vents, including benzene, THF, n-hexane, and n-pentane. Com-
pounds 1 and 2 are characterized by NMR spectroscopy, EI-mass
spectrometry, and elemental analysis. The 119Sn NMR spectrum
of 2 exhibits a singlet at d ꢁ180.47 ppm. In Table 1 we summarise
the 119Sn NMR data of all four halogen derivatives of tin(II) com-
pounds with the same b-diketiminate ligand. These data are in
the expected range for the high field fluorine compound and low
field iodine derivative.
The molecular structures of 1 and 2 are shown in Figs. 1 and 2.
The X-ray single-crystal structures of 1 and 2 show that they are
monomeric and isostructural. The metal atoms adopt three-coordi-
nate sites, and reside in a distorted-tetrahedral environment with
one vertex occupied by a lone pair of electrons. The structural fea-
ture of 1 and 2 is similar to the corresponding chloro derivative
[13]. In compounds 1 and 2 the backbone of the chelating ligand
is essentially planar and the metal atom is slightly shifted from
the best C3N2-plane (23.5° in 1 and 23.7° in 2). However, the bond
angle of N(1)–Ge(1)–N(2) (90.80(6)°) in 1 is larger than the corre-
sponding angle in 2 (N(1)–Sn(1)–N(2) 85.33(5)°), indicating the
even lower tendency of tin to hybridize [14]. The bond length of
N–Ge (1.9824(14) and 1.9934(14) Å) in 1 is slightly shorter than
monohalide with the general composition RMX (M = Ge, Sn; R =
organic group; X = halide) prepared in 1987 [2], followed by the
tin analogue RSnCl (R = C(SiMe3)2C5H4N-2) in 1988 [3]. After
10 years Filippou et al. were successful in preparing a germanium
bromide dimer, [Cp*GeBr]2 [4]. In 2006 our group reported the
synthesis and structure of the first monomeric chloro silylene
[{PhC(NtBu)2}SiCl] [5]. More recently we described the synthesis
of a Lewis base (NHC) stabilised dichloro silylene [6], which has
the potential for further reactions and may have the same impact
like GeCl2ꢀdioxane. Filippou et al. published the N-heterocyclic car-
bene adduct of dibromosilylene [7]. In the literature there are
numerous reports known on the synthesis of fluoro, chloro, and
iodo derivatives of compounds with low valent group 14 elements.
This is in contrast to the corresponding bromo derivatives [8].
Independently, Lappert et al. and we reported on the b-diketiminate
of lead(II) bromo derivative [9,10], and very recently So et al.
described the synthesis of monomeric bromo silylene
[{PhC(NtBu)2}SiBr] [11], by the reaction of the silicon(I) compound
[{PhC(NtBu)2}Si]2 [12] with elemental bromine. Herein we outline
the preparation and characterization of the monomeric LGeBr (1)
and LSnBr (2) [L = HC(CMeNAr)2; Ar = 2,6-iPr2C6H3] compounds.
the corresponding N–Sn bond length in
2 (2.1758(13) and
2.1883(13) Å), as expected. This indicates that the ionic interactions
of the central metal atom with the ligand decrease from Ge to Sn
due to the difference of the atomic radii (Ge(II) 0.93 Å, Sn(II) 1.12 Å).
* Corresponding author. Fax: +49 551 393373.
E-mail address: hroesky@gwdg.de (H.W. Roesky).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.07.051

A. Jana et al. / Inorganica Chimica Acta 363 (2010) 4408–4410
4409
Scheme 1. Preparation of compounds 1 and 2.
Table 1
119Sn NMR data of Sn(II) compounds.
Compounda
119Sn NMR (d, ppm)
LSnF [15]
LSnCl [13]
ꢁ371.52
ꢁ224
LSnBr [this work] ꢁ180.47
LSnI [15]
ꢁ107.33
a
Fig. 2. Molecular structure of 2. Anisotropic displacement parameters are depicted
at the 50% probability level and all hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (°): Sn1–Br1 2.6373(2), Sn1–N1 2.1758(13), N1–C25
1.337(2); N1–Sn1–N2 85.33(5), N1–Sn1–Br1 93.35(3), and Sn1–N1–C25
123.82(10).
L = HC(CMeNAr)2; Ar = 2,6-iPr2C6H3.
Mat 8230 instrument. Melting points were measured in a sealed
glass tube and are not corrected.
4.1. LGeBr (1)
A solution of LLi(OEt2) (0.498 g, 1.0 mmol) in diethyl ether
(20 mL) was added drop by drop to a stirred suspension of GeBr2
(0.230 g, 1.0 mmol) in diethyl ether (10 mL) at ꢁ78 °C. The reaction
mixture was warmed to room temperature and was stirred for an-
other 12 h. The precipitate was filtered off, and the solvent was
partially reduced (ca. 15 mL). Storing the solution in a freezer at
ꢁ32 °C overnight afforded colorless crystals of 1, which are suit-
able for X-ray diffraction analysis. Yield: 0.480 g (85%). M.p.
214 °C. 1H NMR (500 MHz, C6D6): d 7.03–7.18 (m, 6H, Ar-H), 5.22
(s, 1H, c-CH), 4.01 (sept, 2H, CH(CH3)2), 3.13 (sept, 2H, CH(CH3)2),
1.59 (s, 6H, CH3), 1.48 (d, 6H, CH(CH3)2), 1.20 (q, 12H, CH(CH3)2),
1.00 (d, 6H, CH(CH3)2) ppm. EI-MS (70 eV): m/z (%): 570 (100)
[M]+. Anal. Calc. for C29H41BrGeN2(570.17): C, 61.09; H, 7.25; N,
4.91. Found: C, 60.46; H, 7.10; N, 4.87%.
Fig. 1. Molecular structure of 1. Anisotropic displacement parameters are depicted
at the 50% probability level and all hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (°): Ge1–Br1 2.5064(3), Ge1–N1 1.9934(14), N1–C25
1.326(2); N1–Ge1–N2 90.80(6), N1–Ge1–Br1 92.58(4), and Ge1–N1–C25
124.91(11).
4.2. LSnBr (2)
3. Conclusion
A solution of LLi(OEt2) (0.498 g, 1.0 mmol) in diethyl ether
(20 mL) was added drop by drop to a stirred suspension of SnBr2
(0.280 g, 1.0 mmol) in diethyl ether (10 mL) at ꢁ78 °C. The reaction
mixture was warmed to room temperature and was stirred for
another 12 h. The precipitate was filtered off, and the solvent
was partially reduced (ca. 20 mL). Storage of the remaining solu-
tions in a freezer at ꢁ32 °C overnight afforded colorless crystals
of 2 suitable for X-ray diffraction analyses. Yield: 0.490 g (80%).
M.p. 206 °C. 1H NMR (500 MHz, C6D6): d 7.02–7.17 (m, 6H, Ar-H),
In summary we have prepared the b-diketiminate germa-
nium(II) and tin(II) bromides. These two compounds are prone to
be the potential precursors for the preparation of compounds with
low valent germanium and tin atoms.
4. Experimental
5.11 (s, 1H,
c-CH), 3.99 (sept, 2H, CH(CH3)2), 3.11 (sept, 2H,
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. Compound LLiꢀOEt2 was prepared by literature
procedure [13]. Other chemicals were purchased and used as re-
ceived. 1H, 19F, and 119Sn NMR spectra were recorded on a Bruker
instrument and referenced to the deuterated solvent in the case
of 1H NMR spectra. 19F and 119Sn NMR spectra were referenced
to CFCl3 and SnMe4. Elemental analyses were performed by the
Analytisches Labor des Instituts für Anorganische Chemie der
Universität Göttingen. Mass spectra were obtained on a Finnigan
CH(CH3)2), 1.61 (s, 6H, CH3), 1.44 (d, 6H, CH(CH3)2), 1.19 (q, 12H,
CH(CH3)2), 1.03 (d, 6H, CH(CH3)2) ppm. 119Sn {1H} NMR
(186.50 Hz, C6D6): d ꢁ180.47 ppm. EI-MS (70 eV): m/z (%): 616
(100) [M]+. Anal. Calc. for C29H41BrN2Sn (616.15): C, 56.52; H,
6.71; N, 4.55. Found: C, 55.58; H, 6.55; N, 4.42%.
4.3. Crystallographic studies
The data sets of 1 and 2 were collected on a Bruker TXS-Mo
rotating anode equipped with INCOATEC Helios mirror optics

4410
A. Jana et al. / Inorganica Chimica Acta 363 (2010) 4408–4410
Table 2
Appendix A. Supplementary material
Crystallographic data for the structural analyses of compounds 1 and 2.
1
2
CCDC 743152 and 743153 contain the supplementary crystallo-
graphic data for compounds 1 and 2. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.07.051.
Empirical formula
T (K)
Crystal system
Space group
a (pm)
C
29H41BrGeN2
C29H41BrN2Sn
100(2)
triclinic
100(2)
triclinic
P1
ꢀ
ꢀ
P1
1026.07(7)
1221.77(9)
1223.14(9)
88.5760(10)
69.8670(10)
72.0860(10)
1.36422(17)
2
1.388
2.606
592
1.76–26.37
32510
1034.47(8)
1206.01(9)
1236.28(9)
89.9690(10)
72.4870(10)
71.0940(10)
1.38346(18)
2
1.479
2.387
628
1.74–26.37
16293
b (pm)
c (pm)
a
(°)
References
b (°)
c
(°)
V (nm3)
[1] P. Jutzi, H.J. Hoffmann, D.J. Brauer, C. Krüger, Angew. Chem. 85 (1973) 1116–
1117. Angew. Chem., Int. Ed. Engl. 12 (1973) 1002–1003.
[2] F.X. Kohl, P. Jutzi, J. Organomet. Chem. 329 (1987) C17.
[3] L.M. Engelhardt, B.S. Jolly, M.F. Lappert, C.L. Raston, A.H. White, J. Chem. Soc.,
Chem. Commun. (1988) 336–338.
[4] J.G. Winter, P. Portius, G. Kociok-Köhn, R. Steck, A.C. Filippou, Organometallics
17 (1998) 4176–4182.
[5] C.-W. So, H.W. Roesky, J. Magull, R.B. Oswald, Angew. Chem. 118 (2006) 4052–
4054. Angew. Chem., Int. Ed. 45 (2006) 3948–3950.
Z
Dcalc. (Mg mꢁ3
)
l
(mmꢁ1
)
F(0 0 0)
h range (°)
Reflections collected
Independent reflections
Data/restraints/parameters
5574
5617
5574/0/308
0.0213/0.0542
0.0243/0.0557
1.046
5617/0/308
0.0170/0.0400
0.0184/0.0405
1.036
[6] R.S. Ghadwal, H.W. Roesky, S. Merkel, J. Henn, D. Stalke, Angew. Chem. 121
(2009) 5793–5796. Angew. Chem., Int. Ed. 48 (2009) 5683–5686.
[7] A.C. Filippou, O. Chernov, G. Schnakenburg, Angew. Chem. 121 (2009) 5797–
5800. Angew. Chem., Int. Ed. 48 (2009) 5687–5690.
[8] S. Nagendran, H.W. Roesky, Organometallics 27 (2008) 457–492.
[9] M. Chen, J.R. Fulton, P.B. Hitchcock, N.C. Johnstone, M.F. Lappert. A.V.
Protchenko, Dalton. Trans. (2007) 2770–2778.
R1/wR2 [I > 2r
(I)]a
R1/wR2 (all data)a
Goodness-of-fit (GOF)
D
q(max),
D
q
(min) (e Åꢁ3
)
0.424, ꢁ0.287
0.363, ꢁ0.2860
ꢂ
ꢃ
0:5
ꢀ
ꢁ
ꢀ
ꢁ
2
2
P
P
P
P
F2o ꢁ F2c
=
w
Fo2
.
a
R1
¼
kFoj ꢁ jFck= jFoj and wR2
¼
w
[10] L.W. Pineda, V. Jancik, S. Nembenna, H.W. Roesky, Z. Anorg. Allg. Chem. 633
(2007) 2205–2209.
[11] H.-X. Yeong, K.-C. Lau, H.-W. Xi, K.H. Lim, C.-W. So, Inorg. Chem. 49 (2010)
371–373.
[12] S.S. Sen, A. Jana, H.W. Roesky, C. Schulzke, Angew. Chem. 121 (2009) 8688–
8690. Angew. Chem., Int. Ed. 48 (2009) 8536–8538.
[13] Y. Ding, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt, P.P. Power,
Organometallics 20 (2001) 1190–1194.
[14] S. Wingerter, H. Gornitzka, R. Bertermann, S.K. Pandey, J. Rocha, D. Stalke,
Organometallics 19 (2000) 3890–3894.
[15] A. Jana, H.W. Roesky, C. Schulzke, A. Döring, T. Beck, A. Pal, R. Herbst-Irmer,
Inorg. Chem. 48 (2009) 193–197.
[16] (a) T. Kottke, D. Stalke, J. Appl. Crystallogr. 26 (1993) 615–619;
(b) T. Kottke, R.J. Lagow, D. Stalke, J. Appl. Crystallogr. 29 (1996) 465–468;
(c) D. Stalke, Chem. Soc. Rev. 27 (1998) 171–178.
(Mo K
a k = 0.71073 Å). The crystals were mounted in a shock-
cooled oil drop at the tip of a fibre [16]. The data were integrated
with SAINT V7.23A [17] and an empirical absorption correction
(SADABS V2.10) was applied [18]. The structures were solved by di-
rect methods (SHELXS) [19] and refined on F2 using the full-matrix
least-squares methods of SHELXL [20]. All non-hydrogen atoms were
refined with anisotropic displacement parameters. All hydrogen
atoms were assigned ideal positions and refined using a riding
model with Uiso constrained to 1.2 (1.5) times the Ueq value of
the parent carbon atom. Crystallographic data, details of data
collection, and refinement are given in Table 2.
[17] SAINT v7.46A in Bruker APEX v2.2-0, Bruker AXS Inst. Inc., Madison, WI, USA,
2005.
[18] G.M. Sheldrick, SADABS 2008/1, Göttingen, 2007.
[19] G.M. Sheldrick, SHELXS in SHELXTL v6.10, Bruker AXS Inst. Inc., Madison, WI, USA,
2000.
Acknowledgment
[20] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
This work was supported by the Deutsche Forschungsgemein-
schaft.