Synthesis and structures of germanium(II) fluorides and hydrides

Article abstract of DOI:10.1021/om010358j

Treatment of [{HC(CMeNAr)₂}GeCl] (Ar = 2,6-iPr₂C₆H₃ (1), 2,6-Me₂C₆H₃ (2)) with Me₃-SnF in dichloromethane at room temperature afforded the corresponding fluoride [{HC-

Full text of DOI:10.1021/om010358j

4806
Organometallics 2001, 20, 4806-4811
Syn th esis a n d Str u ctu r es of Ger m a n iu m (II) F lu or id es
a n d Hyd r id es†
Yuqiang Ding, Haijun Hao, Herbert W. Roesky,* Mathias Noltemeyer, and
Hans-Georg Schmidt
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received May 2, 2001
Treatment of [{HC(CMeNAr)2}GeCl] (Ar ) 2,6-iPr2C6H3 (1), 2,6-Me2C6H3 (2)) with Me3-
SnF in dichloromethane at room temperature afforded the corresponding fluoride [{HC-
(CMeNAr)2}GeF] (Ar ) 2,6-iPr2C6H3 (3), 2,6-Me2C6H3 (4)), while with NaBH4 in THF under
reflux for 12 h gave the hydride [{HC(CMeNAr)2}GeH(BH3)] (Ar ) 2,6-iPr2C6H3 (5), 2,6-
Me2C6H3 (6)). Reaction of 3 with Me3SiN3 in toluene provided [{HC(CMeNAr)2}Ge(F)NSiMe3]
(Ar ) 2,6-iPr2C6H3 (7)). The BH3 in 5 can be removed with Me3P to afford [{HC(CMeNAr)2}-
GeH] (Ar ) 2,6-iPr2C6H3 (8)). Treatment of 5 with tBuLi in diethyl ether led to [{HC(C(CH2)-
NAr)CMeNAr}Ge(H)BH3]Li(Et2O)3 (Ar ) 2,6-iPr2C6H3 (9)), in which a hydrogen of one of
the Me groups was eliminated, and this consequently resulted in the formation of a methylene
group. Compounds 3-6 are the first examples of structurally characterized germanium(II)
fluorides and hydrides. Single-crystal X-ray structural analyses indicate that compounds 3,
5, and 9 are monomeric and the germanium center resides in a trigonal-pyramidal
environment in 3 and in distorted-tetrahedral environments in 5 and 9.
In tr od u ction
of Ge(IV) chemistry encouraged us to synthesize Ge(II)
fluorides and hydrides. The related lower valent deriva-
tives of group 14 elements can be stabilized with bulky
substituents,6 and therefore we have prepared a stable
germanium(II) chloride (1) containing a bulky diketimi-
nato ligand,7 as well as other related compounds using
this ligand.8 Moreover, we have recently shown that the
use of a bulky ligand enables the synthesis and char-
acterization of a monomeric Al(I) compound.9 Conse-
quently we became interested in the preparation of the
germanium(II) fluoride and hydride by using such bulky
diketiminato ligands. Herein, we report on the synthesis
and characterization of [{HC(CMeNAr)2}GeCl] (Ar )
2,6-Me2C6H3 (2)), [{HC(CMeNAr)2}GeF] (Ar ) 2,6-
iPr2C6H3 (3)), [{HC(CMeNAr)2}GeF] (Ar ) 2,6-Me2C6H3
(4)), [{HC(CMeNAr)2}GeH(BH3)] (Ar ) 2,6-iPr2C6H3
(5)), and [{HC(CMeNAr)2}GeH(BH3)] (Ar ) 2,6-Me2C6H3
(6)), as well as the resulting derivatives [{HC-
(CMeNAr)2}Ge(F)NSiMe3] (Ar ) 2,6-iPr2C6H3) (7)),
[{HC(CMeNAr)2}GeH] (Ar ) 2,6-iPr2C6H3 (8)), and
[{HC(C(CH2)NAr)CMeNAr}Ge(H)BH3]Li(Et2O)3 (Ar )
2,6-iPr2C6H3 (9)). Compounds 3, 5, and 9 have been
Organometallic fluorides and hydrides of the heavier
group 14 elements are important due to their industrial
applications, synthetic methodology, and theoretical
implications.1 To the best of our knowledge, the known
compounds involve the metal preferentially in the +4
oxidation state. Currently, only two dimeric Sn(II)
fluorides2 and a dimeric Sn(II) hydride3 have been
reported as stable molecules. Although several Ge(IV)
fluorides have been structurally characterized,4 only one
Ge(II) fluoride, [PhGeF],5 was studied as a reactive
intermediate. Moreover, there has also been a growing
interest in Ge(IV) hydrides, after the germanium hy-
drides had been neglected for a long time compared to
the silicon and tin hydrides.1 This rapid development
† Dedicated to Professor Max Herberhold on the occasion of his 65th
birthday.
(1) Selected examples: (a) Murphy, E. F.; Murugavel, R.; Roesky,
H. W. Chem. Rev. 1997, 97, 342. (b) Roesky, H. W.; Haiduc, I. J . Chem.
Soc., Dalton Trans. 1999, 2249. (c) Roesky, H. W. Inorg. Chem. 1999,
38, 5934. (d) Barrow, M. J .; Ebsworth, E. A. V.; Harding, M. M.;
Rankin, D. W. H. J . Chem. Soc., Dalton Trans. 1980, 603. (e) Giese,
B. Silicon, Germanium, Tin, Lead Compd. 1986, 9, 99. (f) Brelie`re, C.;
Carre´, F.; Corriu, R. J . P.; Royo, G. Organometallics 1988, 7, 1006. (g)
Chatgilialoglu, C. Acc. Chem. Res. 1992, 25, 188. (h) Chatgilialoglu,
C. Chem. Rev. 1995, 95, 1229. (i) Chatgilialoglu, C.; Newcomb, M. Adv.
Organomet. Chem. 1999, 44, 67. (j) Riedmiller, F.; Wegner, G. L.;
J ockisch, A.; Schmidbaur, H. Organometallics 1999, 18, 4317. (k) Veith,
M.; Schu¨tt, O.; Huch, V. Angew. Chem. 2000, 112, 614; Angew. Chem.,
Int. Ed. 2000, 39, 601.
(6) Selected recent reviews of low-coordinate group 14 compounds:
(a) Brook, A. G.; Brook, M. A. Adv. Organomet. Chem. 1996, 39, 71.
(b) Okazaki, R.; West, R. Adv. Organomet. Chem. 1996, 39, 232. (c)
Weidenbruch, M. Eur. J . Inorg. Chem. 1999, 373. (d) Power, P. P.
Chem. Rev. 1999, 99, 3463. (e) J utzi, P.; Keitemeyer, S.; Neumann,
B.; Stammler, A.; Stammler, H.-G. Organometallics 2001, 20, 42. (f)
Lappert, M. F.; Rowe, R. S. Coord. Chem. Rev. 1990, 100, 267.
(7) Ding, Y.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.; Power,
P. P. Organometallics 2001, 20, 1190.
(8) (a) Akkari, A.; Byrne, J . J .; Saur, I.; Rima, G.; Gornitzka, H.;
Barrau, J . J . Organomet. Chem. 2001, 622, 190. (b) Dove, A. P.; Gibson,
V. C.; Marshall, E. L.; White, A. J . P.; Williams, D. J . Chem. Commun.
2001, 283. (c) Ayers, A. E.; Klapo¨tke, T. M.; Dias, H. V. R. Inorg. Chem.
2001, 40, 1000.
(2) Chorley, R. W.; Ellis, D.; Hitchcock, P. B.; Lappert, M. F. Bull.
Soc. Chim. Fr. 1992, 129, 599.
(3) Eichler, B. E.; Power, P. P. J . Am. Chem. Soc. 2000, 122, 8785.
(4) (a) Brauer, D. J .; Bu¨rger, H.; Eujen, R. Angew. Chem. 1980, 92,
859; Angew. Chem., Int. Ed. Engl. 1980, 19, 836. (b) Brauer, D. J .;
Wilke, J .; Eujen, R. J . Organomet. Chem. 1986, 316, 261. (c) Lukevics,
E.; Belyakov, S.; Arsenyan, P.; Popelis, J . J . Organomet. Chem. 1997,
549, 163.
(5) (a) Rivie`re, P.; Satge´, J .; Castel, A.; Normant, H. C.R. Acad. Sci.
Paris 1976, 282, 971. (b) Rivie`re, P.; Satge´, J .; Castel, A.; Normant,
H. C.R. Acad. Sci. Paris 1977, 284, 395. (c) Castel, A.; Rivie`re, P.; Satge´,
J .; Cazes, A.; Normant, H. C.R. Acad. Sci. Paris 1978, 287, 205.
(9) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao,
H.; Cimpoesu, F. Angew. Chem. 2000, 112, 4444; Angew. Chem., Int.
Ed. 2000, 39, 4274.
10.1021/om010358j CCC: $20.00 © 2001 American Chemical Society
Publication on Web 10/13/2001

Germanium(II) Fluorides and Hydrides
Organometallics, Vol. 20, No. 23, 2001 4807
Sch em e 1
solution of 3 and trimethylsilyl azide in toluene for 3 h
gave the pale yellow compound 7, [{HC(CMeNAr)2}Ge-
(F)NSiMe3] (Ar ) 2,6-iPr2C6H3). Compound 7 was
characterized by MS, multinuclear (19F, 29Si, and 1H)
NMR, and elemental analysis. In the mass spectrum
the molecular ion M+ was observed at m/e 597 (10%)
followed by [M - F]+ (m/e 578, 100%) with the correct
isotope pattern. The 19F NMR chemical shift of 7 is
found at low field (71.04 ppm) compared with that of
the starting material 3 (50.58 ppm). The 29Si NMR
resonates at 13.79 ppm. The 1H NMR spectrum and
elemental analysis are in accordance with the proposed
formula of 7.
Sch em e 2
Germanium(IV) hydrides generally were prepared by
the substitution of X- by H-. Treatment of 1 with
LiAlH4 in diethyl ether at room temperature did not give
the expected Ge(II) hydride, but instead the known
aluminum hydride [{HC(CMeNAr)2}AlH2] (Ar ) 2,6-
iPr2C6H3)12 was formed by a metathesis reaction. How-
ever, reflux of the suspension of 1 and NaBH4 in THF
for 12 h enabled us to get the adduct of germanium
hydride with BH3, [{HC(CMeNAr)2}Ge(H)BH3] (Ar )
2,6-iPr2C6H3 (5)) (Scheme 1). After removal of all the
volatiles of the reaction mixture the residue was ex-
tracted with diethyl ether. Storage of the slightly green
extract at -32 °C for 24 h afforded colorless crystals of
5 suitable for single-crystal X-ray analysis. Compound
6, [{HC(CMeNAr)2}Ge(H)BH3] (Ar ) 2,6-Me2C6H3), was
prepared in a similar manner.
There is current interest in the base behavior of
monomeric low-coordinated group 14 element com-
pounds with reference to Lewis acids. Several such
examples using carbene, silylene, and stannylene13 were
reported. Lappert et al. have published the first example
of a Lewis acid (BH3) adduct of a monomeric intramo-
lecularly base-stabilized germylene,14 and Dias et al.
reported on the adduct of a germylene with BPh3.15
Compounds 5 and 6 feature the adduct with BH3 and
that of a hydride containing germane.
characterized by single-crystal X-ray structure analyses.
The structures of 3 and 5 are the first examples of such
species.
Resu lts a n d Discu ssion
We have reported the preparation and solid structure
of [{HC(CMeNAr)2}GeCl] (Ar ) 2,6-iPr2C6H3 (1)). The
compound [{HC(CMeNAr)2}GeCl] (Ar ) 2,6-Me2C6H3
(2)), an analogue of 1, was prepared in a way similar to
that of 1. With the change of the substituent on the aryl
from isopropyl to methyl, compound 2 became less
soluble than that of 1. Both 1 and 2 are soluble in polar
solvents (such as CH2Cl2, and THF), while 1 is soluble
but 2 shows only limited solubility in hydrocarbons.
However, compound 2 is soluble in hot (70 °C) toluene.
Treatment of 1 and 2, respectively, with Me3SnF in
dichlormethane at ambient temperature for 2 days
smoothly afforded the corresponding fluorides [{HC-
(CMeNAr)2}GeF] (Ar ) 2,6-iPr2C6H3 (3), 2,6-Me2C6H3
(4)) in high yield (88% and 80%) (Scheme 1). Colorless
crystals of 3 suitable for single-crystal X-ray analysis
were obtained from a hexane solution at room temper-
ature. Both 3 and 4 are thermally stable. No decomposi-
tion was observed at temperatures below the corre-
sponding melting points (182-184 and 186-189 °C,
respectively) under an inert atmosphere. EI-MS of 3 and
4 both gave the corresponding monomeric molecular ion
peak M+. The 19F NMR spectrum consisted of a singlet
resonance for Ge-F (50.58 and 54.46 ppm, respectively).
The IR spectra exhibit Ge-F stretching frequencies (543
Both 5 and 6 were characterized by elemental analy-
1
1
sis, EI-MS, IR, and H and 11B NMR. In the H NMR
spectra of 5 and 6 the protons of the backbone ligand
can be clearly distinguished, while the resonance was
silent for the proton on the germanium atom, even at
1
low temperature (193 K). The H NMR spectrum of 5
exhibits a broad resonance for BH (toluene-d8, 0.78 ppm)
and indicates that there are three hydrogen atoms on
the boron atom (213 K). The 11B NMR spectra of 5 (C6D6,
δ -41.94, q, J (11B-1H) ) 95 Hz) and 6 (C6D6, δ -43.04,
q, J (11B-1H) ) 95 Hz) are similar to that of the complex
reported by Lappert,14 confirming that there are three
hydrogen atoms on the boron atom. The IR absorptions
at 1928 cm-1 for 5 and 1949 cm-1 for 6, however, are
indicative for the existence of GeH. The reason for the
and 539 cm-1, respectively) close to those found in
-
[(CF3)GeF2] (545 cm-1 4b
)
and [GeF6]2- (563 cm-1).10
1
The H NMR spectra and elemental analyses are also
in accordance with 3 and 4 as formulated.
1
undistinguishable GeH resonance in the H NMR prob-
We preliminarily examined the reactivity of 3 with
trimethylsilyl azide (Scheme 2). The reactions of ger-
mylenes with trimethylsilyl azide have been well-
studied and established as a route to compounds
containing the GedN double bond.11 Refluxing the
(12) Cui, C.; Roesky, H. W.; Hao, H.; Schmidt, H.-G.; Noltemeyer,
M. Angew. Chem. 2000, 112, 1888; Angew. Chem., Int. Ed. 2000, 39,
1815.
(13) (a) Arduengo, A. J .; Dias, H. V. R.; Calabrese, J . C.; Davidson,
F. J . Am. Chem. Soc. 1992, 114, 9724. (b) Kuhn, N.; Henkel, G.; Kratz,
T.; Kreutzberg, J .; Boese, R.; Maulitz, A. H. Chem. Ber. 1993, 126,
2041. (c) Kuhn, N.; Kratz, T.; Bla¨ser, D.; Boese, R. Chem. Ber. 1995,
128, 245. (d) Li, X.-W.; Su, J .; Robinson, G. H. Chem. Commun. 1996,
2683. (e) Metzler, N.; Denk, M. Chem. Commun. 1996, 2657.
(14) Drost, C.; Hitchcock, P. B.; Lappert, M. F. Organometallics
1998, 17, 3838.
(10) Begun, G. M.; Rutenberg, A. C. Inorg. Chem., 1967, 6, 2212.
(11) (a) Pfeiffer, J .; Maringgele, W.; Noltemeyer, M.; Meller, A.
Chem. Ber. 1989, 122, 245. (b) Veith, M.; Becker, S.; Huch, V. Angew.
Chem. 1990, 102, 186; Angew. Chem., Int. Ed. Engl. 1990, 29, 216. (c)
Veith, M.; Rammo, A. Z. Anorg. Allg. Chem. 1997, 623, 861. (d) Barrau,
J .; Rima, G.; El Amraoui, T. J . Organomet. Chem. 1998, 570, 163.
(15) Dias, H. V. R.; Wang, Z. J . Am. Chem. Soc. 1997, 119, 4650.

4808 Organometallics, Vol. 20, No. 23, 2001
Ding et al.
Sch em e 3
Sch em e 4
F igu r e 1. Molecular structure of 3 in the crystal (50%
probability thermal ellipsoids).
ably is due to the rapid hydrogen exchange on the NMR
time scale, or there is an overlap of the resonance with
those of the aryl protons. Although the exact mechanism
F igu r e 2. Molecular structure of 5 in the crystal (50%
probability thermal ellipsoids).
of the formation of 5 is unclear, H- migration from BH4
-
to the germanium(II) center may be involved. The
formula of 5 was confirmed by the crystal structure
(Figure 2).
Although several adducts of monomeric low-valent
group 14 element compounds with Lewis acids have
been prepared,13-15 the reactivity of these compounds
has not been studied so far. We were preferentially
interested in removing the Lewis acids of these adducts
to obtain the free base. For this purpose PMe3 was used.
Treatment of a solution of 5 in hexane with PMe3 at
room temperature was accompanied by a smooth color
change from pale yellow to orange. After removal of the
solvent, the resulting Me3PBH3 was trapped as a white
solid. The composition of Me3PBH3 was confirmed by
1H, 11B, and 31P NMR. Recrystallization of the residue
with n-hexane afforded orange crystals of 8 (Scheme 3).
Compound 8 was characterized by elemental analysis,
MS, IR, and multinuclear NMR (1H, 11B, 31P). The 11B
and 31P NMR was silent, as expected. Interestingly, the
F igu r e 3. Molecular structure of 9 in the crystal (50%
probability thermal ellipsoids).
1
GeH resonance was found (δ 8.04) in the H NMR of 8.
The IR absorption at 1726 cm-1 was assigned to the
Ge-H stretching frequency.
the germanium center. Compound 9 was characterized
The reactivity of compound 5 was preliminarily
studied with tBuLi (Scheme 4). Treatment of a solution
of 5 in diethyl ether with tBuLi at room temperature
led to the formation of [{HC(C(CH2)NAr)CMeNAr}Ge-
(H)BH3] (Ar ) 2,6-iPr2C6H3) (9). The reaction proceeds
with elimination of a hydrogen atom from a methyl
group of the ligand backbone and formation of a meth-
ylene moiety. This may be due to the relative inertness
of the Ge-H bond or due to the bulky ligand protecting
by elemental analyses, MS, and multinuclear (1H, 11B,
1
7Li) NMR. In the H NMR spectrum of 9 (toluene-d8)
the resonances clearly show the existence of GeH (δ
6.70, b, 1 H), the â-CH2 moiety (δ 3.92, s, 1 H and δ
3.20, s, 1 H), and the BH3 group (δ -0.65 to -1.15, b, 3
H), as well as the coordinated diethyl ether molecule (δ
2.85, q, 12 H, OCH2Me and δ 0.79, t, 18 H, OCH2Me).
Colorless crystals of 9 suitable for X-ray diffraction
analysis were obtained from a diethyl ether solution at

Germanium(II) Fluorides and Hydrides
Organometallics, Vol. 20, No. 23, 2001 4809
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p ou n d s 3, 5, a n d 9
3
5
9
formula
fw
C
29H41FGeN2
C29H45BGeN2
505.07
C41H73BGeLiN2O3
732.35
509.23
color
colorless
colorless
colorless
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
13.805(3)
16.060(4)
14.408(3)
90
116.580(15)
90
2856.7(10)
4
triclinic
P1h
monoclinic
P21/n
11.245(2)
19.132(5)
21.115(10)
90
92.52(2)
90
4538(3)
4
10.713(2)
15.306(3)
20.340(4)
105.11(3)
101.30(3)
100.68(3)
3057.6(11)
4
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
dcalcd (g cm-3
)
1.184
1.096
1080
1.097
1.019
1080
1.072
0.709
1588
µ (mm-1
F(000)
)
cryst size (mm)
2θ range (deg)
index range
1.10 × 0.30 × 0.30
3.54-25.05
-16 e h e 16
-14 e k e 19
-17 e l e 17
9557
5040 (R(int) ) 0.0201)
0.0359, 0.0849
0.0475, 0.0917
1.051
0.60 × 0.40 × 0.20
3.51-25.00
-12 e h e 11
-16 e k e 15
-16 e l e 21
9237
8487 (R(int) ) 0.1173)
0.0640, 0.1530
0.0959, 0.1826
1.064
1.10 × 0.80 × 0.80
3.52-25.04
-13 e h e 12
-8 e k e 22
-9 e l e 25
7135
7100 (R(int) ) 0.1543)
0.0689, 0.1705
0.1106, 0.2043
1.041
no. of rflns collected
no. of indep rflns
R1, wR2 (I > 2σ(I))
R1, wR2 (all data)
goodness of fit, F2
no. of data/restaints/params
5040/0/308
0.503 to -0.333
8479/9/621
1.188 to -0.897
7100/1/481
0.585 to -1.001
largest diff peak, e Å-3
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for Com p ou n d s 3, 5, a n d 9
-32 °C within 2 days. Although the mechanism for the
formation of 9 is unclear, the most likely one is given
in Scheme 4.
Compound 3
Ge(1)-N(1)
Ge(1)-N(2)
Ge(1)-F(1)
C(1)-N(1)
C(1)-C(2)
1.977(19)
1.978(18)
1.805(17)
1.333(3)
1.387(3)
C(2)-C(3)
C(1)-C(4)
C(3)-C(5)
C(3)-N(2)
1.393(3)
1.508(3)
1.510(3)
1.3334(3)
Another important finding for compounds 5, 6, 8, and
9 is their distinct difference in the NMR and IR spectra
compared to the Ge(IV) congeners. In the 1H NMR
spectra the GeIVH resonances are generally observed in
the range of 4-6 ppm,1f,j,16 whereas in 8 (8.04 ppm,
C6D6) and 9 (6.70 ppm, toluene-d8) they are shifted to
lower field. The GeH resonances of 5 and 6 probably
appeared in the range of 6.9-7.2 ppm, overlapping with
those of the aryl protons. The low-field shift of the GeH
resonance in 5, 6, 8, and 9 compared to those of Ge(IV)
compounds indicates the distinct influence of the free
electron pair on the hydrogen atom of the Ge(II)
compounds. As a consequence, the Ge-H bond in the
Ge(II) compounds is more covalent compared to that in
the corresponding Ge(IV) species, due to the higher
electron density around the Ge(II). This is also seen in
the IR spectra comparing the Ge-H stretching frequen-
cies. In the compound Mes2HGe(Li-crown-4),16 the
electron density is increased compared to neutral GeIVH
compounds exhibiting a low Ge-H absorption at 1980
cm-1. The germanium(II) hydrides 5, 6, and 8 show
absorptions even at lower wavenumbers (1927, 1949,
and 1726 cm-1). This applies especially to compound 8,
without the coordinating BH3.
N(1)-Ge(1)-N(2)
N(1)-Ge(1)-F(1)
N(2)-Ge(1)-F(1)
91.04(8)
93.67(8)
93.16(8)
Ge(1)-N(1)-C(1)
Ge(1)-N(2)-C(3)
126.12(15)
125.85(16)
Compound 5
Ge(1)-N(1)
Ge(1)-N(2)
Ge(1)-H(1)
Ge(1)-B(1)
C(1)-N(1)
1.917(4)
1.933(4)
1.110
2.015(7)
1.355(7)
C(1)-C(2)
C(2)-C(3)
C(1)-C(5)
C(3)-C(5)
C(3)-N(2)
1.390(8)
1.398(8)
1.499(9)
1.513(8)
1.325(7)
N(1)-Ge(1)-N(2)
N(1)-Ge(1)-B(1)
N(2)-Ge(1)-B(1)
94.5(2)
118.3(3)
117.9(3)
Ge(1)-N(1)-C(1)
Ge(1)-N(2)-C(3)
120.3(4)
120.8(4)
Compound 9
Ge(1)-N(1)
Ge(1)-N(2)
Ge(1)-B(1)
B(1)-Li(1)
C(1)-N(1)
1.875(4)
1.879(4)
2.016(8)
2.382(14)
1.377(7)
C(1)-C(2)
C(2)-C(3)
C(1)-C(4)
C(3)-C(5)
C(3)-N(2)
1.443(8)
1.380(7)
1.384(9)
1.480(8)
1.380(7)
N(1)-Ge(1)-N(2)
N(1)-Ge(1)-B(1)
N(2)-Ge(1)-B(1)
96.41(19)
115.8(3)
116.7(3)
G(1)-B(1)-Li(1)
Ge(1)-N(1)-C(1)
Ge(1)-N(2)-C(3)
161.0(6)
119.8(3)
117.6(3)
X-r a y Diffr a ction An a lysis for 3, 5, a n d 9. The
solid-state structures of compounds 3, 5, and 9 were
determined by single-crystal X-ray diffraction and are
shown in Figures 1-3. Crystallographic data are given
in Table 1, and selected bond lengths and bond angles
are listed in Table 2; additional bond distances and
angles are included in the Supporting Information.
Figures 1-3 show that compounds 3, 5, and 9 are
monomeric. The germanium center is three- (in 3) and
four-coordinated (in 5 and 9). The sum of the angles at
the metal center in 3 (277.87°) deviates strongly from
the sp3 tetrahedral value. Thus, the geometry of 3 may
be described pyramidal rather than distorted tetra-
hedral. However, the sums of the angles N(1)-Ge(1)-
N(2), N(1)-Ge(1)-B(1), and N(2)-Ge(1)-B(1) around
the metal center in 5 (330.7°) and in 9 (328°) are
tetrahedral.
The order of the corresponding N-Ge-N angles is 9
(96.41(19)°) > 5 (94.5(2)°) > 3 (91.04(8)°) > 1 (90.89-
(10)°), while the order of the Ge-N bond lengths is 9
(16) Castel, A.; Riviere, P.; Satge´, J .; Ko, H. Y. Organometallics 1990,
9, 205.

4810 Organometallics, Vol. 20, No. 23, 2001
Ding et al.
ether (20 mL) was reacted at -78 °C with GeCl2‚(dioxane)
(0.271 g, 1.0 mmol) to yield 2. Pure 2 was obtained after
extraction with hot (70 °C) toluene (15 mL). Yield: 60%. Mp:
221-224 °C. Anal. Calcd for C21H25ClGeN2: C, 61.00; H, 6.09;
Cl, 8.57; N, 6.77. Found: C, 61.05; H, 6.03; Cl, 8.62; N, 6.70.
EI-MS: m/e 414 (M+), 379 ([M - Cl]+). 1H NMR (CDCl3): δ
1.85 (s, 6 H, â-Me), 2.17 (s, 6 H, Ar Me), 2.49 (s, 6 H, Ar Me),
5.50 (s, 1 H, γ-CH), 7.08-7.29 (m, 6 H, Ar H).
[{HC(CMeNAr )2}GeF ] (Ar ) 2,6-iP r 2C6H3 (3)). A solution
of 1 (0.526 g, 1.0 mmol) in dichloromethane (20 mL) was added
to a stirred suspension of Me3SnF (0.201 g, 1.1 mmol) in
dichloromethane (10 mL), and the reaction mixture was stirred
at room temperature for 2 days. After removal of all volatiles
the residue was extracted with n-hexane (20 mL). Storage of
the extract at -32 °C for 24 h afforded colorless needle-shaped
crystals of 2 (yield 0.45 g, 88%). Mp: 182-184 °C. Anal. Calcd
for C29H41FGeN2: C, 66.21; H, 7.79; N, 5.32. Found: C, 66.01;
H, 7.97; N, 5.22. EI-MS: m/e 510 (M+), 475 ([M - Me - F]+).
1H NMR (C6D6): δ 1.07 (d, 6 H, CHMe2), 1.17 (d, 6 H, CHMe2),
1.22 (d, 6 H, CHMe2), 1.40 (d, 6 H, CHMe2), 1.60 (s, 6 H, â-Me),
3.05-3.20 (sept, 2 H, CHMe2), 3.70-3.82 (sept, 2 H, CHMe2),
5.05 (s, 1 H, γ-CH), 7.05-7.10 (m, 6 H, 2,6-iPr2C6H3). 19F NMR
(C6D6): δ 50.58. IR (Nujol): 543 cm-1 (GeF).
(1.875(4), 1.879(4) Å) < 5 (1.917(4), 1.933(4) Å) < 3
(1.977(19), 1.979(18) Å) < 1 (1.988(2), 1.997(3) Å). This
indicates that the metal center in 9 is more closely
bound to the ligand. This perhaps results from the
coordination of the Lewis acid (BH3) to the germanium
center in 9 and 5 combined with the weak electron-
withdrawing property of the chlorine atom in 1 com-
pared to the fluorine atom in 3.
Veith17 and Lappert8c et al. have reported that the
coordinative NfGe bonds in the intramolecular NfGe
complexed germylene are longer (2.045-2.110 Å) than
those related GeIV-N bonds. However, the Ge-N bond
lengths observed in 3 (1.997(19), 1.978(18) Å), in 5
(1.917(4), 1.933(4) Å), and in 9 (1.875(4), 1.879(4) Å) are
comparable to σ GeIV-N bonds. Similar results were
observed in close analogues of 3, 5, and 9 in which
conjugated ligand backbones are involved.8c,15 Previous
studies have suggested that the conjugated ligand
backbones play an important role in improving the
stability.18 The same applies to compounds 1-9 and
affects the Ge-N bond lengths in 3, 5, and 9. Because
of the delocalization of the electrons in the backbones
of the ligand, the bond length differences of the C-C
bond (0.006 Å in 3, 0.002 Å in 5, 0.064 Å in 9), the C-N
bond (0.001 Å in 3, 0.030 Å in 5, 0.003 Å in 9), and the
Ge-N bond (0.002 Å in 3 and 0.016 Å in 5 and 0.004 Å
in 9) are very small.
The C(1)-C(4) (1.384(9) Å) bond length is much
shorter than that of C(3)-C(5) (1.480(8) Å) in 9 and
those in 3 (1.508(3), 1.510(3) Å) and 5 (1.499(9), 1.513-
(8) Å). This indicates that C(1)-C(4) and C(2)-C(3)
bonds in 9 have double-bond character! The B-Li
distance in 9 is longer than the covalent radius (2.03
Å). The observed Ge-F bond length (1.805(17) Å) in 3
is in the normal range (1.781-1.835 Å),4b,c although
there is no germanium(II) fluoride available for com-
parison with 3. The Ge-B bond lengths of 5 and 9
(2.015(7) and 2.016(8) Å, respectively) are slightly
shorter than that of a comparable adduct of a germylene
with BH3 (2.041(11) Å).14
[{HC(CMeNAr )2}GeF ] (Ar ) 2,6-Me2C6H3 (4)). The pro-
cedure is the same as that described for 3. Yield: 80%. Mp:
186-189 °C. Anal. Calcd for C21H25FGeN2: C, 63.53; H, 6.35;
N, 7.06. Found: C, 63.59; H, 6.31; N, 7.15. EI-MS: m/e 398
1
(M+), 379 ([M - F]+). H NMR (CDCl3): δ 1.83 (s, 6 H, â-Me),
2.13 (s, 6 H, Ar Me), 2.41 (s, 6 H, Ar Me), 5.40 (s, 1 H, γ-CH),
7.05-7.15 (m, 6 H, Ar H). 19F NMR (CDCl3): δ 54.46. IR
(Nujol): 539 cm-1 (GeF).
[{HC(CMeNAr )2}GeH(BH3)] (Ar ) 2,6-iP r 2C6H3 (5)). A
solution of 1 (0.526 g, 1.0 mmol) in THF (20 mL) was added to
a stirred suspension of NaBH4 (excess) in THF (10 mL), and
the reaction mixture was refluxed for 12 h. After removal of
all volatiles the residue was extracted with diethyl ether (20
mL). Storage of the slightly green extract in a -32 °C freezer
for 24 h afforded colorless crystals of 5 (yield 0.44 g, 87%).
Mp: 193-195 °C. Anal. Calcd for C29H49BGeN2: C, 68.96; H,
8.98; N, 5.55. Found: C, 68.89; H, 9.03; N, 5.67. EI-MS: m/e
491 ([M - BH3 - H]+). 1H NMR (C6D6): δ 1.06 (d, 6 H, CHMe2),
1.09 (d, 6 H, CHMe2), 1.25 (d, 6 H, CHMe2), 1.45 (s, 6 H, â-Me),
1.47 (d, 6 H, CHMe2), 2.85-3.05 (sept, 2 H, CHMe2), 3.25-
3.45 (sept, 2 H, CHMe2), 4.88 (s, 1 H, γ-CH), 6.95-7.15 (m, 6
H, 2,6-iPr2C6H3). 11B NMR (C6D6): δ -41.94. IR (Nujol): 2370,
2333, 1927 cm-1 (BH3, GeH).
Exp er im en ta l Section
[{HC(CMeNAr )2}Ge(H)BH3] (Ar ) 2,6-Me2C6H3 (6)). The
procedure is the same as that for 5. Yield: 81%. Mp: 184-
187 °C. Anal. Calcd for C21H29BGeN2: C, 64.20; H, 7.44; N,
7.13. Found: C, 64.37; H, 7.51; N, 7.18. EI-MS: m/e 379 ([M
Gen er a l Con sid er a tion s. All manipulations were carried
out using standard Schlenk techniques or in a glovebox under
a nitrogen atmosphere. Diethyl ether was freshly distilled from
Na and n-hexane from K prior to use. Elemental analyses were
performed by the Analytisches Labor des Instituts fu¨r Anor-
ganische Chemie der Universita¨t Go¨ttingen. A Bruker AM 200
instrument was used to record 1H (200.1 MHz), 19F (188.3
MHz), 11B (80.25 MHz), and 7Li (97.21 MHz) NMR spectra,
with reference to TMS, BF3‚OEt2, and LiCl, respectively. Mass
spectra were obtained on a Finnigan Mat 8230. IR spectra
were recorded on a Bio-Rad Digilab FTS-7 spectrometer as
Nujol mulls on KBr plates. The compound [HC(CMeNAr)2]Li‚
OEt2 was prepared by literature procedures.7 Other chemicals
were purchased from Aldrich and used as received.
1
- BH3]+). H NMR (CDCl3): δ 1.82 (s, 6 H, â-Me), 2.24 (s, 6
H, Ar Me), 2.26 (s, 6 H, Ar Me), 5.32 (s, 1 H, γ-CH), 7.08-7.15
(s, 6 H, Ar H). 11B NMR (C6D6): δ -43. IR (Nujol): 2351, 2327,
1949 cm-1 (BH3, GeH).
[{HC(CMeNAr )2}Ge(F )NSiMe3] (Ar ) 2,6-iP r 2C6H3 (7)).
A solution of 3 (0.510 g, 1.0 mmol) and Me3SiN3 (0.115 g, 1.0
mmol) in toluene (25 mL) was refluxed for 3 h. After removal
of all volatiles, washing of the residue with n-hexane (2 × 5
mL) afforded a pale yellow powder of 7. Storage of the slightly
yellow solution of 7 in a -32 °C freezer gave pale yellow
crystals of 7 (yield 0.471 g, 79%). Mp: 167-169 °C. EI-MS:
1
m/e 597 (M+), 578 ([M - F]+). H NMR (C6D6): δ 0.00 (s, 9 H,
[{HC(CMeNAr )2}GeCl] (Ar ) 2,6-Me2C6H3 (2)). A solu-
tion of [HC(CMeNAr)2Li(OEt2)] (0.412 g, 1.0 mmol) in diethyl
SiMe3), 1.11 (d, 6 H, CHMe2), 1.21 (d, 6 H, CHMe2), 1.23 (d, 6
H, CHMe2), 1.51 (d, 6 H, CHMe2), 1.54 (s, 6 H, â-Me), 3.08-
3.12 (sept, 2 H, CHMe2), 3.72-3.78 (sept, 2 H, CHMe2), 4.98
(s, 1 H, γ-CH), 7.04-7.08 (m, 6 H, 2,6-iPr2C6H3). 19F NMR
(C6D6): δ 71.05. 29Si NMR (C6D6): δ 13.85.
[{HC(CMeNAr )2}GeH] (Ar ) 2,6-iP r 2C6H3 (8)). A solution
of PMe3 (2 mL, 1.0 M in toluene) was added to a solution of 5
(1.052 g, 2.0 mmol) in n-hexane (30 mL) at room temperature
and stirred for 12 h. The color turned from pale yellow to
(17) (a) Veith, M.; Becker, S.; Huch, V. Angew. Chem. 1989, 101,
1287; Angew. Chem., Int. Ed. Engl. 1989, 28, 1237. (b) Veith, M.;
Becker, S.; Huch, V. Angew. Chem. 1990, 102, 186; Angew. Chem., Int.
Ed. Engl. 1990, 29, 216.
(18) (a) Driess, M.; Gru¨tzmacher, H. Angew. Chem. 1996, 108, 900;
Angew. Chem., Int. Ed. Engl. 1996, 35, 828. (b) Heinemann, C.;
Herrmann, W. A.; Thiel, W. J . Organomet. Chem. 1994, 475, 73. (c)
Boehme, C.; Frenking, G. J . Am. Chem. Soc. 1996, 118, 2039.

Germanium(II) Fluorides and Hydrides
Organometallics, Vol. 20, No. 23, 2001 4811
orange. After removal of all volatiles, the residue was extracted
with n-hexane (20 mL). Storage of the extract in a -32 °C
freezer for 24 h afforded orange crystals of 8 (yield 0.776 g,
79%). Mp: 173-175 °C. Anal. Calcd for C29H42GeN2: C, 70.90;
H, 8.62; N, 5.70. Found: C, 70.51; H, 8.65; N, 5.67. EI-MS:
m/e 491 ([M -1]+), (100%). 1H NMR (C6D6): δ 1.15 (d, 6 H,
CHMe2), 1.17 (d, 6 H, CHMe2), 1.27 (d, 6 H, CHMe2), 1.35 (d,
6 H, CHMe2), 1.54 (s, 6 H, â-Me), 3.24-3.42 (sept, 2 H, CHMe2),
3.43-3.62 (sept, 2 H, CHMe2), 4.92 (s, 1 H, γ-CH), 7.02-7.15
(m, 6 H, 2,6-iPr2C6H3), 8.08 (s, 1 H, GeH). IR (Nujol): 1726
cm-1 (GeH).
X-r a y Cr ysta llogr a p h y. Single crystals of 3, 5, and 9 were
taken from the flask under nitrogen gas and mounted on a
glass fiber in rapidly cooled perfluoropolyether.19 Diffraction
data were collected on a Stoe-Siemens-Huber four-circle dif-
fractometer coupled to a Siemens CCD area detector at 200-
(2) K with graphite-monochromated Mo KR radiation (λ )
0.710 73 Å). The structures were solved by direct methods
(SHELXS-96)20 and refined against F2 using SHELXL-97.21 All
non-hydrogen atoms were refined anisotropically with similar-
ity and rigid bond restraints. All hydrogen atoms were
included in the refinement in geometrically ideal positions.
[{HC(C(CH2)NAr )CMeNAr }Ge(H)BH3]Li(Et2O)3 (Ar )
2,6-iP r 2C6H3 (9)). A solution of tBuLi (2 mL, 1 M in toluene)
was added to a solution of 5 (1.012 g, 2.0 mmol) in diethyl
ether (30 mL) at -78 °C, and the reaction mixture was warmed
to room temperature. After the mixture was stirred for an
additional 3 h and stored in a -32 °C freezer for 2 days,
colorless crystals of 9 were obtained (yield 1.039 g, 71%). Mp:
138-140 °C. Anal. Calcd for C41H73BGeLiN2O3: C, 67.24; H,
10.05; N, 3.82. Found: C, 67.31; H, 9.98; N, 3.91. EI-MS: m/e
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie.
Su p p or tin g In for m a tion Ava ila ble: Tables giving full
details of the crystallographic data and data collection param-
eters, atom coordinates, bond distances, bond angles, aniso-
tropic thermal parameters, and hydrogen coordinates for 3,
5, and 9. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
491 ([M - Li(Et2O)3 - H]+) (100%). H NMR (toluene-d8): δ
-0.65 to -1.15 (b, 3 H, BH3), 0.79 (t, 18 H, OCH2Me), 1.30-
1.50 (m, 24 H, CHMe2), 1.70 (s, 3 H, â-Me), 2.85 (q, 12 H, OCH2-
Me), 3.19 (s, 1 H, â-CH2), 3.65 (sept, 2 H, CHMe2), 3.75 (sept,
2 H, CHMe2), 3.92 (s, 1 H, â-CH2), 3.97 (sept, 2 H, CHMe2),
4.05 (sept, 2 H, CHMe2), 5.38 (s, 1 H, γ-CH), 6.70 (b, 1 H, GeH),
7.04-7.10 (m, 6 H, 2,6-iPr2C6H3). 11B NMR (toluene-d8): δ
OM010358J
(19) Kottke, T.; Stalke, D. J . Appl. Crystallogr. 1993, 26, 615.
(20) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(21) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1997.
7
-43.68. Li NMR (toluene-d8): δ -1.41.