Synthesis, decomposition, and structural studies in the gas phase and solid state of N,N-Dimethylaminoxygermane

Article abstract of DOI:10.1021/ic0007409

N,N-Dimethylaminoxygermane, H₃GeONMe₂, was prepared by the reaction of H₃GeBr with LiONMe₂ in dimethyl ether at -96 °C. The identity of H₃GeONMe₂ was proven by gas-phase IR and solution NMR spectroscopy (¹H, ¹³C, ¹⁵N, ¹⁷O). It is an unstable volatile liquid compound. It decomposes by cleavage of a Ge-O and a Ge-H bond giving HONMe₂ and an insoluble germanium hydride polymer (GeH₂)_n. This decomposition reaction has been modeled at the MP2/6-311G(d,p) level of theory by the homodesmotic reaction H₃GeONMe₂ + Ge₂H₆ → Ge₃H₈ + HONMe₂, which is predicted slightly exothermic by 14 kJ mol^-1. The molecular structure of H₃GeONMe₂ was determined by gas-phase electron diffraction supported by an ab initio geometry [MP2/6-311G(d,p)] and a force field [MP2/6-31G(d)]. The structure of the compound in the crystal lattice was determined by low-temperature crystallography using a single crystal of H₃GeONMe₂ grown in situ [C₂H₉NOGe, orthorhombic, Pnma, Z = 4, a = 8.1280(12) A, b = 9.7037(15) A, c = 7.0722(12) A]. Important bond lengths and angles (gas phase/solid state, A/deg) are Ge-O 1.785(2)/1.815(1), O-N 1.462(7)/1.460(2), N-C 1.460(4)/1.453(2), Ge-O-N 105.2(5)/104.6(1), O-N-C 105.8(5)/105.8(1), C-N-C 110.8(9)/111.2(2), Ge···N 2.587(6)/2.601(1). In the solid state the compound forms infinite chains by intermolecular Ge···O contacts of 2.808 A. The question of the attraction between Ge and N atoms is discussed with respect to reference Ge/O and N/O compounds, which have wider angles at oxygen than H₃GeONMe₂. For comparison the structures of the compounds H₃CONMe₂, H₃SiONMe₂, and H₃SnONMe₂ were also calculated to reflect the influence of the group 14 atom on the structure and to discuss the occurrence of weak E···N interactions in the compounds H₃EONMe₂.

Full text of DOI:10.1021/ic0007409

Inorg. Chem. 2001, 40, 661-666
661
Synthesis, Decomposition, and Structural Studies in the Gas Phase and Solid State of
N,N-Dimethylaminoxygermane
Norbert W. Mitzel,*,† Udo Losehand,† Sarah L. Hinchley,‡ and David W. H. Rankin‡
Anorganisch-chemisches Institut, Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
85747 Garching, Germany, and Department of Chemistry, University of Edinburgh,
West Mains Road, Edinburgh EH9 3JJ, U.K.
ReceiVed July 5, 2000
N,N-Dimethylaminoxygermane, H3GeONMe2, was prepared by the reaction of H3GeBr with LiONMe2 in dimethyl
ether at -96 °C. The identity of H3GeONMe2 was proven by gas-phase IR and solution NMR spectroscopy (1H,
13C, 15N, 17O). It is an unstable volatile liquid compound. It decomposes by cleavage of a Ge-O and a Ge-H
bond giving HONMe2 and an insoluble germanium hydride polymer (GeH2)n. This decomposition reaction has
been modeled at the MP2/6-311G(d,p) level of theory by the homodesmotic reaction H3GeONMe2 + Ge2H6 f
Ge3H8 + HONMe2, which is predicted slightly exothermic by 14 kJ mol-1. The molecular structure of H3GeONMe2
was determined by gas-phase electron diffraction supported by an ab initio geometry [MP2/6-311G(d,p)] and a
force field [MP2/6-31G(d)]. The structure of the compound in the crystal lattice was determined by low-temperature
crystallography using a single crystal of H3GeONMe2 grown in situ [C2H9NOGe, orthorhombic, Pnma, Z ) 4, a
) 8.1280(12) Å, b ) 9.7037(15) Å, c ) 7.0722(12) Å]. Important bond lengths and angles (gas phase/solid state,
Å/deg) are Ge-O 1.785(2)/1.815(1), O-N 1.462(7)/1.460(2), N-C 1.460(4)/1.453(2), Ge-O-N 105.2(5)/
104.6(1), O-N-C 105.8(5)/105.8(1), C-N-C 110.8(9)/111.2(2), Ge‚‚‚N 2.587(6)/2.601(1). In the solid state
the compound forms infinite chains by intermolecular Ge‚‚‚O contacts of 2.808 Å. The question of the attraction
between Ge and N atoms is discussed with respect to reference Ge/O and N/O compounds, which have wider
angles at oxygen than H3GeONMe2. For comparison the structures of the compounds H3CONMe2, H3SiONMe2,
and H3SnONMe2 were also calculated to reflect the influence of the group 14 atom on the structure and to discuss
the occurrence of weak E‚‚‚N interactions in the compounds H3EONMe2.
Introduction
gaseous Me3SiONMe2, Me3GeONMe2,4 and Me3SnONMe2.5
The germanium compound turned out to have the widest
The chemistry of germanium is often viewed as very similar
to that of silicon, but is far less well developed, because
germanium is much more expensive. The acceptor quality of
the carbon group elements is generally seen as increasing from
carbon to lead, but a closer look at listed electronegativities of
the elements shows germanium to be an exception to a steady
decrease of electronegativity, i.e., it is slightly more electroneg-
ative than silicon on various scales (Pauling, Mulliken, Allen).1
However, the atomic and covalent radii of silicon (1.17 Å) and
germanium (1.22 Å) are similar.2
There are not very many compounds that allow a direct
comparison of the acceptor qualities of carbon, silicon, germa-
nium, and tin. For example, the bipyridyl adducts of SiF4, GeF4,
and SnF4 have been investigated by crystal structure determina-
tions,3 but there is no reference material for estimation of the
structural changes that occur upon adduct formation, and a direct
comparison of element-nitrogen distances is not possible due
to the different element radii.
E-O-N angle in this series, but there was a substantial
discrepancy between the experimental values for this parameter
[108.9(7)°] and Ge‚‚‚N distance [2.682(11) Å] and those
theoretically predicted at the MP2/6-31G(d) level [102.9°, 2.595
Å]. By contrast, in the molecule Me3SnONMe2 a Sn‚‚‚N
attraction leads to a small angle of 102.5(8)° in the gas phase
and a markedly distorted geometry at the Sn atom, while in the
solid state an additional intermolecular Sn‚‚‚O contact leads to
[4 + 2]-coordination at an even more distorted tin center.5 The
interactions between E and N centers in such compounds were
recently investigated in considerable detail and were found to
be predominantly electrostatic with interactions between group
dipole moments playing a major role. This was proven by the
gas-phase structure determination of two conformers (gauche
and anti) of ClH2SiONMe2, which reveal drastically different
strengths in their Si‚‚‚N interactions.6 Even in the electronically
extreme case of F3SiONMe2, with an extremely short Si‚‚‚N
distance [1.963(1) Å in the crystal, SiON 77.1(1)°], there is
no covalent contribution to the Si‚‚‚N secondary bond.7
We have recently determined the molecular structures of a
series of compounds with intramolecular E‚‚‚N interactions, i.e.,
(4) Mitzel, N. W.; Losehand, U.; Richardson, A. D. Inorg. Chem. 1999,
38, 5323.
(5) Mitzel, N. W.; Losehand, U.; Richardson, A. Organometallics 1999,
18, 2610.
(6) (a) Mitzel, N. W.; Losehand, U. J. Am. Chem. Soc. 1998, 120, 7320.
(b) Mitzel, N. W.; Losehand, U.; Bauer, B. Inorg. Chem. 2000, 39,
1998.
(7) Mitzel, N. W.; Losehand, U.; Wu, A.; Cremer, D.; Rankin, D. W. H.
J. Am. Chem. Soc. 2000, 122, 4471.
* Author to whom correspondence should be addressed. E-mail:
N.Mitzel@lrz.tum.de.
† Technische Universita¨t Mu¨nchen.
‡ University of Edinburgh.
(1) Allen, L. C. J. Am. Chem. Soc. 1989, 111, 9003.
(2) Emsley, J. The Elements; Clarendon Press: Oxford, 1991.
(3) Adley, A. D.; Bird, P. H.; Fraser, A. R.; Onyszchuk, M. Inorg. Chem.
1972, 11, 1402.
10.1021/ic0007409 CCC: $20.00 © 2001 American Chemical Society
Published on Web 01/06/2001

662 Inorganic Chemistry, Vol. 40, No. 4, 2001
Table 1. Crystallographic Data for 1
Mitzel et al.
and vibrational frequency calculations were performed from analytic
first and second derivatives at the SCF and MP2 levels of theory.
Different basis sets of increasing size were employed, namely, the
standard basis sets 3-21G(d), 6-31G(d), and 6-31G(d,p) as well as the
more extended 6-311G(d,p) basis set.14 For calculations involving tin
atoms 3-21G(d) and a basis set of double-ú quality by Dunning were
employed.15
C2H9NOGe
fw 135.69
space group Pnma
T ) 153(2) K
λ ) 0.71073 Å
Fcalc ) 1.616 g cm-3
5.350 mm-1
a ) 8.1280(12) Å
b ) 9.7037(15) Å
c ) 7.0722(12) Å
V ) 557.8(2) Å3
Z ) 4
R1(Fo) ) 0.0249
2
wR2(Fo ) ) 0.0638
Results and Discussion
The stoichiometrically simple N,N-dimethylaminoxygermane,
H3GeONMe2 (1), was prepared from bromogermane and N,N-
dimethylaminoxy lithium (eq 1). Due to the instability of
monohalogenogermanes, the preparation of N,N-dimethylami-
noxygermane (1) had to be conducted at -96 °C. Dimethyl ether
(bp -24 °C) was advantageously applied as a solvent, as its
volatility exceeds that of all starting materials and products and
thus allows complete separation. H3GeONMe2 is obtained as a
To reduce the steric and electronic influences at the germa-
nium center, we decided to study the simplest possible GeON
compound that can be prepared, H3GeONMe2. The absence of
steric repulsion in this compound and its C, Si, and Sn
homologues allows comparison of the E‚‚‚N distances and
E-O-N angles and so the assessment of the influence of the
group 14 atom on the molecular structure of the E-O-N units.
Experimental Section
H3GeBr + LiONMe2 f LiBr + H3GeONMe2
(1)
General. The experiments were carried out using a standard Schlenk
line or a vacuum line with greaseless stopcocks (Young taps), directly
attached to the gas cell in an FTIR spectrometer (Midac Prospect FTIR).
All NMR spectra were recorded at 21 °C on a JEOL JNM-LA400 spec-
trometer in sealed tubes with C6D6 as solvent directly condensed onto
the sample from K/Na alloy. Bromogermane was prepared according
to a literature procedure from GeH4 and HBr in the presence of AlBr3.8
(N,N-Dimethylaminoxy)germane (1). At -50 °C n-butyllithium
(0.3 g, 5 mmol, 1.8 M in hexane) was added dropwise to a solution of
N,N-dimethylhydroxylamine (0.6 mL, 0.5 g, 8 mmol) in pentane (25
mL). The mixture was slowly warmed to ambient temperature, and
all volatiles were pumped off. Dimethyl ether (30 mL) and 0.86 g
of bromogermane (5.5 mmol) were condensed onto the remaining
LiONMe2 (0.33 g, 4.9 mmol). The mixture was stirred for 10 h at -96
°C while H3GeBr was carefully washed off the flask wall. (N,N-
Dimethylaminoxy)germane was isolated in low yield as a colorless,
air and temperature sensitive liquid (mp -22 °C) by fractionated
condensation through a series of cold traps held at -20, -96, -196
colorless liquid in moderate yield by trap-to-trap distillation. It
is highly sensitive to air and unstable at ambient temperature.
Decomposition of the compound can be observed even near
the melting point of -22 °C by the occurrence of a yellow-
brownish color and later by formation of a red-brown precipitate.
The compound has been identified by gas-phase IR spec-
troscopy and NMR spectroscopy of the nuclei 1H, 13C, 15N, and
17O. The Ge-H stretching vibrational mode corresponds to an
absorption at 2101 cm-1 in the IR spectrum, and correct relative
intensities of the proton signals and the occurrence of the
expected quartet of quartet splitting in the proton-coupled 13C
NMR proved the identity of H3GeONMe2. An attempt to record
a
73Ge NMR spectrum failed as well as attempts to obtain a
mass spectrum and a reliable elemental analysis.
Despite having the different elements bound to the ONMe2
unit, the 15N and 17O NMR chemical shifts of H3GeONMe2
(-234.0 and 112 ppm) and H3SiONMe2 (-237.9 and 113
ppm)16 are surprisingly similar. This indicates that the bonding
situations in the two compounds are similar.
The decomposition of H3GeONMe2 can be monitored by
recording proton NMR spectra at suitable time intervals. Figure
1 displays two spectra of a freshly prepared sample in C6D6
°C. The product was retained in the -96 °C trap. 1H NMR: δ ) 2.41
1
(s, 6H, H3C), 5.11 (s, 3H, H3Ge). 13C NMR: δ ) 49.6 (q q, JCH
)
3
134.4 Hz, JCNCH ) 5.7 Hz, CH3). 15N{1H} NMR: δ ) -237.9 (s).
17O{1H} NMR: δ ) 113 (s). IR (gas): 2101 cm-1 (s, νGeH).
Crystal Structure Determination of 1. A single crystal of 1 was
grown in situ by slowly cooling the melt in sealed capillaries after
generation of a suitable seed crystal. The crystal and refinement data
are listed in Table 1.
Gas-Phase Electron Diffraction of 1. Electron scattering intensity
data for 1 were recorded on Kodak Electron Image plates using the
Edinburgh electron diffraction apparatus and a wavelength of 0.06016
Å.9 Scattering data for benzene were recorded concurrently and used
to calibrate the electron wavelength and camera distances. Three
exposures were taken at each camera distance. Data were obtained in
digital form using the microdensitometer at the Institute of Astronomy
at Cambridge.10 The data analysis followed standard procedures, using
established data reduction and least-squares refinement programs11 and
the scattering factors established by Fink and co-workers.12 The
experimental conditions are summarized in Table 2. The refined
molecular parameters, their definitions and the applied restraints, a list
of selected interatomic distances including vibrational amplitudes and
applied restraints, and elements of the correlation matrix are given in
Tables 2, 4, and 6.
(12) Ross, A. W.; Fink, M.; Hilderbrandt, R. In International Tables for
X-Ray Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Dordrecht, Boston, 1992; Vol. C., p 245.
(13) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts,
R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C.
Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.;
Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.; Gonzalez, C.;
Head-Gordon, M.; Replogle, E. S.; Pople, J. A., Gaussian 98, revision
A.7; Gaussian, Inc.: Pittsburgh, PA, 1998.
(14) (a) Binkley, J. S.; Pople, J. A.; Hehre W. J. J. Am. Chem. Soc. 1980,
102, 939. (b) Gordon, M. S.; Binkley, J. S.; Pople, J. A.; Pietro, W.
J.; Hehre W. J. J. Am. Chem. Soc. 1982, 104, 2797. (c) Pietro, W. J.;
Francl, M. M.; Hehre, W. J.; Defrees, D. J.; Pople, J. A.; Binkley J.
S. J. Am. Chem. Soc. 1982, 104, 5039. (d) 6-31G(d): Hariharan, P.
C.; Pople J. A. Theor. Chim. Acta 1973, 28, 213. (e) Hariharan, P. C.;
Pople, J. A. Chem. Phys. Lett. 1972, 66, 217. (f) 6-311G(d): Krishnan,
R.; Frisch, M. J.; Pople, J. A. Chem. Phys. 1980, 72, 4244.
(15) Dunning, T. H. Unpublished work.
Ab Initio Calculations. Ab initio molecular orbital calculations were
carried out using the Gaussian 98 program.13 Geometry optimizations
(8) Dennis, L. M.; Judi, P. R. J. Am. Chem. Soc. 1929, 51, 2321.
(9) Huntley, C. M.; Laurenson G. S.; Rankin, D. W. H. J. Chem. Soc.,
Dalton Trans. 1980, 945.
(10) Lewis, J. R.; Brain P. T.; Rankin, D. W. H. Spectrum 1997, 15, 7.
(11) Mitzel, N. W.; Brain, P. T.; Rankin, D. W. H. ED96, version 2.0,
1998. A program developed on the basis of formerly described ED
programs: Boyd, A. S. F.; Laurenson, G. S.; Rankin, D. W. H. J.
Mol. Struct. 1981, 71, 217.
(16) Mitzel, N. W.; Losehand, U. Angew. Chem., Int. Ed. Engl. 1997, 36,
2807.

N,N-Dimethylaminoxygermane
Inorganic Chemistry, Vol. 40, No. 4, 2001 663
a
Table 2. Geometric Parameters, Their Values (ra), and Parameter Restraints for the GED Refinements of H3GeONMe2
GED (ra ,
)
a
parameter
value
restraint
MP2/6-311G**
XRD
p1
p2
p3
p4
p5
p6
p7
p8
r(Ge-H4)
r(Ge-H5/6)
r(Ge-O)
1.547(8)
1.548(8)
1.785(2)
1.462(7)
1.460(4)
1.100(7)
1.105(7)
1.109(7)
105.2(5)
105.8(5)
110.8(9)
102.9(14)
108.4(15)
109.1(12)
108.6(12)
111.4(12)
-188.9(29)
49.5(30)
-67.4(34)
62.2(29)
2.587(6)
1.533
1.532
1.816
1.459
1.458
1.091
1.094
1.100
104.2
105.0
110.6
103.9
109.4
109.0
108.3
111.3
-177.4
64.1
1.45(5)
1.37(2)
1.815(1)
1.460(2)
1.453(2)
1.02(3)
p1 - p2 ) 0.001(5)
r(O-N)
r(N-C)
p4 - p5 ) 0.001(10)
r(C7-H9)
r(C7-H10)
r(C7-H11)
(Ge-O-N)
(O-N-C)
(C-N-C)
(O-Ge-H4)
(OGeH5/6)
(NC7H9)
p7 - p6 ) 0.003(5)
p8 - p6 ) 0.009(5)
0.95(3)
0.95(2)
p9
104.64(8)
105.76(9)
111.2(2)
107.2(10)
101.0(15)
107.2(16)
107.3(15)
115(2)
-178.7(25)
67.3(25)
-57.1(24)
59.7(23)
2.6013(14)
p10
p11
p12
p13
p14
p15
p16
p17
p18
p19
p20
p21
p17 ) 103.9(15)
p13 - p12 ) 5.5(5)
(NC7H10)
(NC7H11)
τ(C8NC7H9)
τ(CNC7H10)
τ(CNC7H11)
τ(NOGeH5)
r(Ge1‚‚‚N3)
p15 - p14 ) 0.009(5)
p16 - p14 ) 0.009(5)
p17 ) -177.4(50)
p18 - p17 ) 241.5(30)
p19 - p17 ) 120.5(30)
p20 ) 60.9(30)
-56.9
60.9
2.592
b
a The geometrical parameter values determined in the ab initio calculations [MP2/6-311G(d,p)] are listed for comparison. Distances are given in
Å, angles and torsion angles in deg. b Dependent parameter.
Figure 1. 1H NMR spectra of a freshly prepared solution of 1 in C6D6 (1 min) and of the same sample after 120 min at room temperature.
recorded at 21 °C 1 and 120 min after removing the liquid nitro-
gen coolant. After 120 min at ambient temperature the decom-
position is almost complete and the signals of H3GeONMe2 at
2.42 (methyl protons) and 5.11 ppm (germyl protons) have
disappeared. New signals have appeared at 2.40 and 8.65
ppm and are identified as HONMe2, which is further veri-
fied by 13C, 15N, and 17O NMR experiments, which reproduce
the literature data for this compound.17 A new broad signal at
3.8 ppm is typical of the decomposition products of GeH3
compounds and is usually assigned as (GeH2)n polymer,
which fulfills the stoichiometry of the proposed decomposition
reaction
of reactants such as cyclohexene (germacyclopropane formation)
failed, i.e., so far we have no evidence that H3GeONMe2 could
serve as a clean source for the simplest germylene GeH2.
This decomposition reaction seems thermodynamically sur-
prising as a relatively strong Ge-O bond and a Ge-H bond
are broken, while a Ge-Ge and an O-H bond are formed. To
understand the energetic contributions involved in this reaction
we have estimated the energy difference occurring in the
homodesmotic reaction in eq 3, which mimics the insertion of
the germylene unit of H3GeONMe2 into the Ge-Ge backbone
of the (GeH2)n polymer. Fully optimized geometries for all four
H3GeONMe2 + H3Ge-GeH3 f
H3GeONMe2 f HONMe2 + (1/n)(GeH2)n
(2)
HONMe2 + H3Ge-GeH2-GeH3 (3)
compounds were calculated at the MP2/6-311G(d,p) level of
theory (Figure 2). The energies were calculated at the same level
and corrected for zero-point vibration estimated from frequency
calculations at SCF/6-31G(d) calculations. The result favors the
products HONMe2 and H3Ge-GeH2-GeH3 by 14 kJ mol-1
No hydrogen or other gas evolution is observed, but after a few
hours a brown precipitate is formed. Attempts to trap a proposed
intermediate germylene GeH2 by decomposition in the presence
(17) Mitzel, N. W.; Schmidbaur, H. Z. Anorg. Allg. Chem. 1994, 620, 1087.

664 Inorganic Chemistry, Vol. 40, No. 4, 2001
Mitzel et al.
in Figure 4. The model for least-squares refinement had Cs
symmetry, with the mirror plane passing through the atoms Ge,
O, and N. The geometrical model is thus defined by 20
independent parameters, which are listed in Table 4. Applying
the principles of the SARACEN21 procedure to overcome the
usual limitations of the GED technique, the refinement was
supported by 12 restraints. These were applied to the O2-Ge1-
H4 angle, the torsional angles C8-N3-C7-H9 and N3-O2-
Ge1-H5, the differences between the N-O and N-C distances,
and various differences between parameters of similar nature
(see Table 2). Fifteen vibrational amplitudes were refined
simultaneously under the action of 10 restraints. These ampli-
tudes represent all pairs of scatterers with a contribution
exceeding 5% of the Ge-O scatterer pair. The restraints were
taken from a MP2/6-31G(d) force field and transformed into
amplitudes by means of the program ASYM4022 after scaling
it by an overall factor of 0.93 previously used in connection
with the SARACEN method.23 The success of the refinement
can be assessed from the molecular scattering intensity curves
and the radial distribution curve displayed in panels a and b of
Figure 5. The most important geometrical parameter is the
Ge-O-N angle, which is 105.2(5)° in the gas phase and 104.6-
(1)° in the crystal. This is a smaller valence angle than in most
Ge-O compounds studied in the gas phase, such as (H3Ge)2O
[126.5(3)°],24 slightly smaller than in the methyl derivative
Me3GeONMe2 [gas: 108.9(7)°],4 and almost identical to that
in gaseous Cl3GeONMe2 [104.0(11)°].25 There is to the best of
our knowledge no suitable Ge-O-C compound which could
be used for a comparison of Ge-O-N and Ge-O-C angles.
The only crystal structure of an open chain germanium(IV)
alkoxide is that of a cage Si/Ge/N compound with a terminal
EtO group at the Ge atom,26 which is surrounded by three
additional N atoms. In this case a Ge-O-C angle of 120.0°
was observed, which might serve as a coarse value for com-
parison with the Ge-O-N angle in our simple H3GeONMe2
compound.
Figure 2. Molecular geometries of the reference molecules used in
the homodesmotic reaction (eq 3). Distances are in Å, angles in deg.
Figure 3. Contents of a unit cell of 1 showing the intermolecular
Ge‚‚‚O contacts 2.808(2) Å in length and the geometry of the molecules
of 1 in the solid state.
over the starting materials H3GeONMe2 and H3Ge-GeH3,
which does not represent a great driving force for the decom-
position, but proves its thermodynamical feasibility.
27
Structure Determination in the Gas Phase and in the Solid
State. Crystal Structure. Utilizing in situ techniques, growth
of a single crystal of 1 from the melt at -22 °C was successfully
performed. This was despite the fact that decomposition of 1
starts at this temperature, which means that crystal growth had
to be achieved within ca. 15 min, before the higher-melting
decomposition products caused problems as competitive crystal
seeds. The single-crystal specimen allowed successful deter-
mination of the solid-state structure of 1 by X-ray diffraction.
Geometrical results are included in Table 2, and the contents
of the unit cell are presented in Figure 3.
In the crystal lattice (Pnma) the molecules form infinite chains
of molecules of 1 connected by weak intermolecular Ge‚‚‚O
contacts of 2.808(2) Å distance with the O‚‚‚Ge-O unit
adopting an angle of 177.0(1)° at the germanium atom. These
contacts are similar to the intermolecular Si‚‚‚O contacts in solid
H3SiONMe2,16 MeOSiH3,18 (H3Si)2O,19 and (H3Si)2NOMe.20
The intramolecular structure will be compared with the gas-
phase structure.
In the crystalline phase of Cl2Ge(ONMe2)2 smaller
Ge-O-N angles [102.0(1)°] were found than in solid 1. The
theoretical prediction of the Ge-O-N angle in 1 is 104.2° at
the MP2/6-311G(d,p) level. These calculations thus provide an
adequate description of the molecular geometry. The Ge‚‚‚N
distance has been determined in the gas phase to be 2.587(6) Å
and in the solid state to be 2.601(1) Å.
The Ge-O distance in 1 is 1.815(1) Å in the solid state and
1.785(2) Å in the gas phase, which is a relatively large difference
even considering the fact that two different methods have been
applied. The gas-phase value is somewhat larger than in gaseous
(H3Ge)2O [1.766(4) Å],24 gaseous Cl3GeONMe2 [1.759(6) Å],25
and solid Cl2Ge(ONMe2)2 [1.745(2) and 1.753(2) Å],27 but
(21) (a) Blake, A. J.; Brain, P. T.; McNab, H.; Miller, J.; Morrison, C. A.;
Parsons, S.; Rankin, D. W. H.; Robertson H. E.; Smart, B. A. J. Phys.
Chem. 1996, 100, 12280. (b) Brain, P. T.; Morrison, C. A.; Parsons,
S.; Rankin, D. W. H. J. Chem. Soc., Dalton Trans. 1996, 4589.
(22) Hedberg, L.; Mills, I. M. ASYM20, ASYM40, Programs for Force
Constants and Normal Coordinate Analysis, version 3.0, June 1994;
see also: Hedberg, L.; Mills, I. M. J. Mol. Spectrosc. 1993, 160, 117.
(23) This scaling factor fits well with the generally accepted scaling factor
of 0.9496 for MP2-fc/6-311G(d,p): Scott, A. P.; Radom L. J. Phys.
Chem. 1996, 100, 16502.
(24) (a) Glidewell, C.; Rankin, D. W. H.; Robiette, A. G.; Sheldrick, G.
M.; Beagley, B.; Cradock, S. J. Chem. Soc. A 1970, 315. (b) Glidewell,
C.; Rankin, D. W. H.; Robiette, A. G.; Sheldrick, G. M.; Cradock, S.;
Ebsworth, E. A. V.; Beagley, B. Inorg. Nucl. Chem. Lett. 1969, 5,
417.
Gas-Phase Structure. The high volatility of 1 allowed a gas-
phase electron-diffraction experiment to be performed. The
experimental conditions are described in Table 3, and the
geometry including the atomic numbering scheme is presented
(18) Barrow, M. J.; Ebsworth, E. A. V.; Harding, M. M. Acta Crystallogr.,
Sect. B 1979, 35, 2093.
(19) Blake, A. J. Dyrbush, M.; Ebsworth, E. A. V.; Henderson, S. G. D.
Acta Crystallogr., Sect. C 1988, 44, 1.
(20) Mitzel, N. W.; Breuning, E.; Blake, A. J. Robertson, H. E.; Smart, B.
A.; Rankin, D. W. H. J. Am. Chem. Soc. 1996, 118, 2664.
(25) Losehand, U.; Mitzel, N. W.; Rankin, D. W. H. J. Chem. Soc., Dalton
Trans. 1999, 4291.
(26) Veith, M.; Detempke, A.; Huch, V. Chem. Ber. 1991, 124, 1135.
(27) Losehand, U.; Mitzel, N. W. Eur. J. Inorg. Chem. 1998, 2023.

N,N-Dimethylaminoxygermane
Inorganic Chemistry, Vol. 40, No. 4, 2001 665
Table 3. Experimental Conditions (Camera Distances [mm], Electron Wavelengths [Å], Nozzle and Sample Temperatures [°C]), Data Ranges
and Trapezoidal Weighting Functions [Å-1], Correlation Parameters, Scale Factors, and Final R Factors for the GED Experiments and
Refinements of H3GeONMe2
T
correlation
data set
camera dist
wavelength
nozz
samp
∆s
smin
s1
s2
smax
param
scale factor
R1
Rg
1
2
285.51
128.21
0.06016
0.06016
20
20
-30
-16
0.2
0.4
2.0
9.2
4.0
11.2
11.8
30.0
13.8
31.2
0.3503
0.2746
0.761(12)
0.705(64)
0.0728
0.1678
0.0967
Figure 4. Molecular structure of 1 in the gas phase as determined by
electron diffraction, with the atom-numbering scheme.
Table 4. Distances, Amplitudes, and Restraints for the GED
Refinements of H3GeONMe2
no.
atom pair
distancea
amplitudea
restraint
d1
d2
d3
d4
d5
d6
d7
d8
Ge1-H4
Ge1-H5
Ge1-O2
O2-N3
1.547(8)
1.548(8)
1.785(2)
1.462(7)
1.460(4)
1.100(7)
1.105(7)
1.109(7)
2.587(6)
3.587(5)
2.331(6)
2.404(17)
3.424(25)
0.102(9)
0.102(10)
0.050(6)
0.058(5)
0.055(4)
0.087(7)
0.088(8)
0.089(8)
0.091(6)
0.156(5)
0.073(6)
0.073(7)
0.254(24)
0.174(16)
0.181(17)
u2/u1 ) 1.000(50)
u4/u5 ) 1.059(53)
u5/u1 ) 0.538(27)
u6 ) 0.077(15)
u7/u6 ) 1.004(50)
u8/u6 ) 1.014(51)
N3-C7
C7-H9
C7-H10
C7-H11
Ge1‚‚‚N3
Ge1‚‚‚C7
O2‚‚‚C7
C7‚‚‚C8
Ge1‚‚‚H9
d9
d10
d11
d12
d13
d14
d15
u12/u11 ) 0.994(50)
u13 ) 0.257(26)
u14 ) 0.182(18)
u15 ) 0.190(19)
Ge1‚‚‚H10 4.175(33)
Ge1‚‚‚H11 4.433(22)
a Distances and amplitudes are given in Å.
similar to the Ge-O distance in gaseous (Me3Ge)2O [1.770-
(10) Å].28 The N-O distance in 1 is 1.462(7) Å in the gas phase
and 1.460(2) Å in the solid state. This is similar to the value in
other E-O-N units with weak E‚‚‚N interactions [H3SiONMe2
147.1(1) Å] and relatively small in comparison to those in
systems with electronegative substituents at the E atom, such
as ClH2SiONMe2 [anti conformer, solid state 1.490(1) Å]6 and
F3SiONMe2 [solid state 1.508(1) Å].7 Other structural param-
eters require no detailed comments.
Figure 5. (a) Molecular intensity and difference curve and (b) radial
distribution and difference curve for the electron diffraction refine-
ment of 1. Vertical lines in the radial distribution curve indicate
atom pairs with their height being proportional to their scattering
contribution.
Table 5. Molecular Geometry Parameters for H3EONMe2 with E )
C, Si, Ge, and Sn Calculated at Different Levels of Theorya
(E-O-N) [deg]
r(E‚‚‚N) [Å]
MP2
B3LYP
MP2
B3LYP
Comparison of the H3EONMe2 Compounds (E ) C, Si,
Ge, Sn). For a comparison of the interactions between the
elements E ) C, Si, Ge, and Sn and the N atoms in geminal
position of an EON unit, we have calculated the structures of
the compounds H3EONMe2 at two levels of theory, MP2/
6-311G(d,p) and B3LYP/6-311G(d,p). The results for the angles
E-O-N and the E‚‚‚N distances are listed in Table 5. The
values for the E-O-N angles show that the MP2 results are
closer to experimental parameters for E ) C,29 Si,16 and Ge
than the DFT results, which give slightly too large E-O-N
angles. The deviation between experiment and DFT theory
becomes greater with increasing strength of the secondary
interaction, as has already been shown for F3SiONMe2, which
has an Si-O-N angle of 94.3(9)° in the gas phase. In this case
B3LYP/6-311++G(d,p) calculations predict 105.5°, whereas
MP2/6-31G(d,p) predicts correctly 94.1°.7
H3CONMe2
H3SiONMe2
H3GeONMe2
H3SnONMe2
107.6
102.5
104.2
98.2
109.2
106.9
107.5
103.9
2.304
2.454
2.592
2.664
2.335
2.532
2.650
2.757
a The basis set 6-311G(d,p) was used for E ) C, Si, and Ge, while
a basis set of double-ú quality was used for calculations on the Sn
compound.15
In the series E ) C, Si, Ge, Sn the E-O-N angles become
smaller from C to Si, become slightly wider from Si to Ge, and
reach a minimum at Sn. This parallels the electronegativities
for the elements of the carbon group, which also do not decrease
monotonically, but feature Ge as an exception with a higher
electronegativity than Si.
To gauge the effect of a Me2N substituent at an oxygen atom
we calculated the molecular structure of Me2NONMe2 up to
the MP2/6-311G(d,p) level of theory. The results of these
calculations are shown in Figure 6. Two Me2N groups lead to
a valence angle at oxygen (106.4°), which is slightly smaller
(28) Vilkov, L. V.; Tarasenko, N. A. Zh. Strukt. Khim. 1969, 10, 1102.
(29) Riddell, F. G.; Turner, E. S.; Rankin, D. W. H.; Todd, M. R. J. Chem.
Soc., Chem. Commun. 1979, 72.

666 Inorganic Chemistry, Vol. 40, No. 4, 2001
Mitzel et al.
a
Table 6. Elements of the Least-Squares Correlation Matrix (×100) for H3GeONMe2
p1
p4
p6
p9
p11
p12
p14
p15
p17
u1
u2
u3
u4
u5
u6
u7/8
p2
p5
p7
80
-54
73
73
p8
p9
-57
57
-57
p13
p15
p16
p18
p19
u2
94
-58
-53
90
91
82
56
62
86
78
67
83
u3
u4
u5
u6
u7/8
u20
u21
k2
73
59
72
75
82
58
55
80
52
56
53
82
62
-64
-57
78
71
91
84
89
59
a Only elements with absolute values greater 50 are shown. p, u, and k denote parameters, amplitudes, and scale factors, which can be identified
in Tables 1 and 3.
In the series E ) C, Si, Ge (H3EONMe2) the charge at the N
atom is almost unchanged as is shown by the Mulliken charges
calculated at the MP2/6-311G(d,p) level (C -0.27, Si -0.29,
Ge -0.28 e), but the charges on the E atoms are very different
(C 0.05, Si 1.11, Ge 0.95 e). This reflects again the more
electropositive character of Si as compared with Ge and is
consistent with the E‚‚‚N interaction being weaker for the Ge
system than for the Si system.
Figure 6. Calculated molecular geometries of Me2NONMe2 (MP2/
dzp). Shown are the ground state of C2 symmetry and a transition state
of C2V symmetry. Distances are given in Å, angles in deg.
However, much care is needed in a final assessment of the
strength of this Ge‚‚‚N interaction in H3GeONMe2 (1). Other
compounds such as ClH2GeONMe2 or F3GeONMe2 have to be
synthesized and studied to obtain a more detailed insight into
the details of bonding in the Ge-O-N system.
H3GeONMe2 (1).
than the tetrahedral angle, but still significantly larger than in
In contrast, germyl substitution at an oxygen center in general
Acknowledgment. This work was supported by the Bay-
erisches Staatsministerium fu¨r Wissenschaft, Forschung und
Kunst (Bayerischer Habilitationsfo¨rderpreis 1996 for N.W.M.),
leads to a marked widening of its valence angle [e.g., (H3Ge)2O24
126.5(3)°, (Me3Ge)2O28 141(1)°, ((F3C)3Ge)2O30 151.5(15)°],
whereas alkyl substitution does not grossly affect the valence
the Deutsche Forschungsgemeinschaft, the Fonds der Chemis-
angle at oxygen. This and the knowledge about systems with
chen Industrie, the Leonhard-Lorenz-Stiftung, and the EPSRC
(Grant GR/K44411). Dr. H. E. Robertson and Dr. C. A.
Morrison (both Edinburgh) are thanked for their assistance with
the GED data collection. Generous support from Prof. H.
stronger E‚‚‚N interactions in EON units (ClH2SiONMe2,6
F3SiONMe2,7 Me3SnONMe2)5 leads us to the conclusion that
H3GeONMe2 (1) with a mixed germyl and Me2N substitution
at oxygen contains a very weak attractive force between the
Schmidbaur (Garching) is gratefully acknowledged. Prof. R.
Ge and N atoms.
Gillespie (Hamilton) is thanked for many helpful comments.
Electrostatic forces are of major importance for the E‚‚‚N
interactions.7 Apart from the more complicated group dipole
interactions, the attraction between negatively charged N atoms
and positively charged E atoms is an important contribution.
Supporting Information Available: An X-ray crystallographic file,
in CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
(30) Eujen, R.; Laufs, F. E.; Oberhammer, H. Z. Anorg. Allg. Chem. 1988,
561, 82.
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