Stabilized germylenes based on dialkanolamines: Synthesis, structure, chemical properties

Article abstract of DOI:10.1016/j.jorganchem.2012.01.018

A series of novel low valent germanium compounds RN(CHR²CR ¹R³O)(CHR⁴CHR⁵O)Ge 1-13 (R = Me, Ph, Bn; R¹, R², R³, R⁴, R⁵ = H, Me, Ph, (CH₂)₃, (CH₂)₄, CH ₂(C₆H₄)) was obtained via the reaction between Ge[N(SiMe₃)₂]₂ and various dialkanolamines. All new compounds were characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy and in several cases by X-ray diffraction analysis (1, 3, 8, 10). The compounds 1, 3, 8 are dimeric in the solid state due to the formation of intermolecular Ge-O bonds, the complex 10 is monomeric, all compounds possess a transannular Ge-N bond. The reactivity of the germylenes synthesized was investigated in reactions of oxidative insertion (with halogenation reagents, MeI, disulfides), [1 + 4]-cycloaddition, oxidation and in reactions with water and acetic anhydride. Some reactions were investigated by DFT calculations.

Full text of DOI:10.1016/j.jorganchem.2012.01.018

Journal of Organometallic Chemistry 706-707 (2012) 66e83
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Stabilized germylenes based on dialkanolamines: Synthesis, structure, chemical
properties
,
a
b
Mengmeng Huang a, Marina M. Kireenko a, Kirill V. Zaitsev a , Yuri F. Oprunenko , Andrei V. Churakov ,
*
Judith A.K. Howard c, Maxim V. Zabalov d, Elmira Kh. Lermontova a b, Jörg Sundermeyer e,
,
,
a
Thomas Linder e, Sergey S. Karlov a , Galina S. Zaitseva
*
a Chemistry Department Moscow State University, B-234 Leninskie Gory, 119991 Moscow, Russia
b Institute of General and Inorganic Chemistry, Russian Acad. Sci., Leninskii pr., 31, 119991 Moscow, Russia
c Department of Chemistry, University of Durham, South Road, DH1 3LE Durham, UK
d N.N. Semenov Chem. Phys. Inst., Russian Acad. Sci., Kosygin st. 4, 119991 Moscow, Russia
e Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35032 Marburg/Lahn, Federal Republic of Germany
a r t i c l e i n f o
a b s t r a c t
A series of novel low valent germanium compounds RN(CHR2CR1R3O)(CHR4CHR5O)Ge 1e13 (R ¼ Me, Ph,
Bn; R1, R2, R3, R4, R5 ¼ H, Me, Ph, (CH2)3, (CH2)4, CH2(C6H4)) was obtained via the reaction between Ge
[N(SiMe3)2]2 and various dialkanolamines. All new compounds were characterized by elemental analysis,
1H and 13C NMR spectroscopy and in several cases by X-ray diffraction analysis (1, 3, 8, 10). The
compounds 1, 3, 8 are dimeric in the solid state due to the formation of intermolecular GeeO bonds, the
complex 10 is monomeric, all compounds possess a transannular GeeN bond. The reactivity of the
germylenes synthesized was investigated in reactions of oxidative insertion (with halogenation reagents,
MeI, disulfides), [1 þ 4]-cycloaddition, oxidation and in reactions with water and acetic anhydride. Some
reactions were investigated by DFT calculations.
Article history:
Received 17 October 2011
Received in revised form
11 January 2012
Accepted 25 January 2012
Keywords:
Germanium
Dialkanolamines
X-ray analysis
Germylenes
Ó 2012 Elsevier B.V. All rights reserved.
Chemical properties
1. Introduction
stabilization may be caused by using N-heterocyclic carbenes (NHC)
[4d,e] or b-diketiminate [5], amidinate [6], aminotroponimine [7]
The low valent derivatives of group IVA elements (Si, Ge, Sn)
attract much attention because of interest in “heavy” carbon analogs
[1]. The carbene center is very reactive, while some “heavy carbenes”
are more stable due to the known “inert pair” effect and may be used
as precursors for the synthesis of various metalloorganic compounds
and intermediates. Especial interest may be aroused by application
of such derivatives as ligands in coordination chemistry [2].
The stabilization of highly reactive “heavy carbene” centers may
be accomplished using two approaches. The kinetic stabilization
may be caused by the introduction of sterically demanding groups to
the central atom in MR2 (M ¼ Si, Ge, Sn, R ¼ t-Bu, N(SiMe3)2, 2,6-(i-
Pr)2C6H3) [3]. The thermodynamic stabilization may be achieved by
donation of electron density from substituents to a vacant orbital of
ligands). However application of tridentate ligands for the
synthesis of stabilized germylenes is very rare [8,9]. It is evident that
stabilization of Ge(II) centers with dialkanolamine dianions
(RN(CH2CH2Oꢀ)2) as ligands is achieved by all these ways. So these
germylenes with such ligands have to be high stable compounds. It
should be noted that these germylenes may possess either a mono-
meric or a dimeric structure with GeeO intermolecular coordination.
At the same time it is important to investigate the chemical a reac-
tivity of these new complexes to find out the difference in chemical
behavior between monomeric and dimeric species. In the present
work we used substituted diethanolamines for the synthesis of
stable germylenes and performed a systematic investigation of the
chemical and structural properties of these compounds.
the central atom (n- and
p-donation as in Ge[N(SiMe3)2]2 or N-
heterocyclic germylenes (NHGe) [4a,b,c]), or by intra- or intermo-
lecular interaction with electron donors (for example, this type of
2. Results and discussion
2.1. Synthesis of dialkanolamines
* Corresponding authors. Tel.: þ7 095 9393887; fax: þ7 095 932 8846.
The dialkanolamines used in this work were synthesized
according to the procedures published (see Experimental part) and
E-mail
addresses:
zaitsev@org.chem.msu.ru
(K.V.
Zaitsev),
sergej@
org.chem.msu.ru (S.S. Karlov).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.01.018

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
67
Ph
Ph
H3N
MeOH
H2CO
aq
HN[CHPhCHPhOH]2
83 %
MeN[CHPhCHPhOH]2
68 %
HCO2H
O
erythro-,erythro-
erythro-,erythro-
trans-
Scheme 1.
include derivatives with various substituents. The new compound
erythro,erythro-MeN[CH(Ph)CH(Ph)OH]2 containing sterically vol-
uminous substituents was obtained in two steps using the condi-
tions (formalin as a source of methyl group, formic acid as
a reductant) of the EschweilereClarke reaction (Scheme 1). The
target compound was isolated as a mixture of two diastereomers.
We believe that the formation of the strong intramolecular GeeN
and GeeO bonds in 1 (the latter due to dimerization) is a driving
force of this reaction. It should be noted that there is not appre-
ciable GeeN interaction in PhN(CH2CH2O)GeMe2 [11].
We investigated the possibility of the synthesis of germylenes
by the reduction of corresponding dihalogermocanes by KC8. This
reduction occurs under mild conditions at stirring in THF at room
temperature and gives the desired germylene with moderate yield
(Scheme 5).
2.2. Synthesis of germylenes
The most suitable method for synthesis of Ge(OR)2 is a reaction
of alkoxydesamination of [(Me3Si)2N]2Ge with appropriate alcohols
[10]. An alternative variant in which the unstable Ge(OEt)2 * xEtOH
is used seems undesirable [8]. Using first approach we synthesized
with high yield target germanium compounds 1e13 (Scheme 2),
containing the ligands with various substituents. The compounds
2e13 are novel. The previously known germylene 1 [8] was
prepared for structural studies. For synthesis of 6, 7, 11e13 one
diastereomer of corresponding dialkanolamine was used; in the
case of compound 10 the enantiomerically pure dialkanolamine
was used.
2.3. Investigation of the structure
There are two main methods to investigate the structure of
germylenes: NMR spectroscopy (1H, 13C) in solution and X-ray
analysis in the solid state. The basic question regarding the
structural chemistry of low valent germanium compounds is
establishing the coordination number of the Ge atom and inves-
tigating how the geometry depends on the nature of substituents
of the central atom or the ligand (electronic and steric properties).
Germylenes can be associated due to forming dimers or coordi-
nation polymers. The degree of oligomerization and the coordi-
nation geometry around the central atom in germylenes in our
opinion should determine chemical properties of these
compounds.
The desired compounds were obtained at long stirring (4 days)
of a mixture of the corresponding reagents in toluene at room
temperature. The yields of the target compounds (see Scheme 2)
depend on the ligand structure.
In our work we establish that (Me2N)2Ge can also be used as
a source of germanium for the synthesis of alkanolamine deriva-
tives (Scheme 3). It should be noted that this approach is less
favorable in spite of the high yield due to the fact that (Me2N)2Ge is
more difficult of access than [(Me3Si)2N]2Ge.
According to general considerations and quantum chemical
calculations performed for simple germylenes (GeH2, GeMe2, GeF2)
[12], germylenes may exist in three possible structures (IeIII)
where M ¼ Ge has oxidation state equal to þ2 [13] (Fig. 1).
Structure I is monomeric; structure II is dimeric with the GeeGe
interaction; structure III is dimeric, in which dimerization is
observed due to OeGe coordination. In this case there are two
Also we show the possibility of germylene synthesis in the
reaction of a derivative of Ge(IV) with GeCl2*C4H8O2 (Scheme 4).
R4
R4
2
2
H
R
H
R
R5
R3
R5
R
R
CH(R4) CH(R5)
R3
OH
N
N
[(Me3Si)2N]2Ge
- 2 (Me3Si)2NH
[(Me3Si)2N]2Ge
R
N
R1
R1
- 2 (Me3Si)2NH
CH(R2) C(R1)(R3)
OH
H
H
Ge
Ge
O
O
O
O
2
1 - 8, 11 - 13
9, 10
1. R = Ph, R1 = R2 = R3 = R4 = R5 = H (63%)
2. R = Bn, R1 = R2 = R3 = R4 = R5 = H (53%)
3. R = Me, R1 = R2 = R3 = R4 = R5 = H (89%)
4. R = Me, R1= R2 = R4 = R5=H, R3 = Me (29%)
5. R = Me, R1= R22= R4 = R5=H, R3 = Ph (71%)
6. R = Me, R1 = R = Ph, R3 = R4 = R5 = H (erythro-) (86%)
7. R = Me, R2 = R3 = Ph, R1 = R4 = R5 = H (threo-) (61%)
8. R = Me, R1 = R3 = Ph, R2 = R4 = R5= H (96%)
9. R = Me, R1 = R2 = R4 = R5 = Ph, R3 = H (erythro-, erythro-) (42%)
10. R = Me, R1 = R3 = Ph, R5 = (R)-Ph, R2 = H, R4 = (S)-Me (78%)
11. R = Me, R1, R2 = (CH2)3, R3 = R4 = R5 = H (threo-) (64%)
12. R = Me, R1, R2 = (CH2)4, R3 = R4 = R5 = H (threo-) (60%)
13. R = Me, R1, R2 = CH2(C6H4), R3 = R4 = R5 = H (threo-) (88%)
Scheme 2.

68
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
(Me2N)2Ge
- 2 Me2NH
Me
Me
MeN(CH2CH2OH)2
[MeN(CH2CH2O)2Ge]2
Ph
Ph
N
N
Ph
Ph
3 (92%)
2 KC8
- 2 KBr
Scheme 3.
Br Ge
Br
Ge
O
O
O
O
2
14
8 (66%)
possible isomers which differ in the way in which they dimerize
(cis-(IIIa) or trans- (IIIb) diastereomers).
Scheme 5.
The analysis of structural data (X-ray data, more than 30
structures) of simple germylenes (where Y, Y0 ¼ O, N) shows that
“heavy carbenes” exist as dimers IIIa or IIIb. The introduction of the
ligands containing one group acting as additional donors leads to
an increase in a stability of the monomeric form. Two such donor
groups always stabilize the monomeric I form. It is important to
note that increasing the steric volume of a substituent near the Ge
center increases the stability of the monomeric form as well. The
structures of type II were not known for germylenes, where
germanium atom are bound to O or N.
structure for 8 but the type of the dimer is changed (IIIa) perhaps
due to packing effects. The germanium atom has the distorted
trigonal bipyramidal coordination where the base of the pyramid is
formed by one oxygen atom of the dialkanolaminate framework,
a bridging O atom from neighboring alcoholate and a lone pair in
one vertex. It is interesting to note that changing the dimer type (8
vs. 3) does not lead to significant changes in the geometric char-
acteristics of Ge center.
Increasing the coordination number of the germanium atom in 3
and 8 in comparison with 10 (see below) results to the elongation of
the GeeO and GeeN bonds in dimeric complexes 3, 8.
2.3.1. X-ray analysis
In the course of this work the structures of four germylenes 1, 3,
8, 10 were investigated by X-ray analysis (Tables 1, 2, Figs. 2e5).
The diffraction studies establish that the germylenes 1, 3 and 8
are dimeric and the germylene 10 is monomeric in the solid state.
The complex 1 (Fig. 2) is a centrosymmetric dimer (type IIIb).
The central Ge1eO20eGe1’eO2 ring is planar. The tetracoordinated
germanium atom has a distorted trigonal bipyramidal coordination.
Nitrogen and oxygen atom of another molecule are in the axial
positions, and diethanolamine oxygen atoms and a lone pair occupy
the equatorial positions of TBP. The GeeN bond distance
(2.584(2) Å) is significantly longer than that found in penta-
coordinated PhN(CH2CH2O)2GeCl2 (2.202(2) Å) but less than in
PhN(CH2CH2O)2GeMe2 (3.182(1) Å) [11]. These data correspond
well to the proposition that the electronic properties of substitu-
ents on the Ge atom affect the force of the transannular GeeN
interaction. The nitrogen atom in 1 is tetrahedral. Eight member-
ing cycles eGeeOeCeCeNeCeCeOe are in the “chair e bath”
conformation.
The complex 3 is also dimeric in the solid state (dimer of type IIIb)
with the coordination similar to 1 (TBP). The GeeN bond length
(2.315(1) Å) is sufficiently shorter than that in the complex 1. It should
be noted that the germanium atoms in 1 and 3 are hypercoordinated.
This fact significantly affects the bond distance GeeO in 1 and 3. The
interaction in the N/Ge)Oax fragment may be interpreted with the
theory of three center four-electron bond. The bond length in this
group is sensitive to the electronic and steric effects of the substitu-
ents. It is evident that the substitution of a Ph group for a Me group
leads to stronger GeeN interaction. The stronger N/Ge interaction
in 3 in comparison with that in 1 corresponds to a weaker Ge)Oax
bond (2.171(1) vs. 2.039(1) Å). The distances for the other two GeeO
bonds in 1 and 3 are shorter than Ge)Oax, where the shortest bondis
Ge-Ouncoordinate (1.838(1) vs. 1.856(1) Å). The same features are
observed in 8 in comparison with 1 and 3.
The germylene 10 contains substituents at different C atoms that
results in a monomeric structure. In the complex 10 germanium
atom has a distorted tetrahedral geometry where the electron lone
pair of Ge occupies one coordination place. The values of the
OeGeeO and NeGeeO angles exhibit the significant s-character of
this pair. For the germanium atom in 10 the “octet rule” is followed
so the GeeN bond is a classical donoreacceptor interaction. The
geometrical characteristics of 10 are close to those found earlier in
the related monomeric structure of [2,6-C5H3N(CH2CPh2O)2]Ge
(d(GeeO) 1.827(1), 1.881(1), d(GeeN) 2.110(1) Å) which contains
not penta- but hexamembered chelate cycles [9]. It should be noted
that the d(GeeO) in 10 are close to the distances found by X-ray
analysis in single monomeric dialkoxygermane (Ge[OC(t-Bu)3]2
(1.833(3), 1.855(3) vs. 1.83(1) Å)) where the coordination number of
Ge atom is equal to 2 [14]. As it may be expected enantiomerically
pure compound 10 crystallized in chiral space group (P21).
Previously we have studied the structure of various germylenes
by DFT calculations (as single molecules) [13], and the X-ray results
presented above are completely in agreement with the calculated
results regarding which structure type is preffered (monomeric or
dimeric). So we believe that the presence of one or two free OCH2
groups in the dialkanolaminate structure results in a dimeric
structure for germylenes. In other cases the germylenes of pre-
sented type are monomeric [9].
2.3.2. 1H and 13C NMR spectroscopy
The compounds obtained were investigated by 1H and 13C NMR
spectroscopy. The spectral data unambiguously confirm the
Y
Y
Y
Y
MII
MII
MII
A
A
A
The introduction of the substituents to one C atom of the dia-
lkanolamine framework near the Ge atom results in a dimeric
Y
Y
I
II
Ph
Y
Y
A
N
Y
PhN(CH2CH2O)2GeMe2 /toluene / 20oC
A
A
MII
MII
MII
MII
.
GeCl2
O
O
Y
Y
- 2 Me2GeCl2
- C4H8O2
O
Y
Y
Ge
O
A
2
Y
IIIa
IIIb
1 (60%)
Scheme 4.
Fig. 1. Possible structures for germylenes (M ¼ Ge).

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
69
Table 1
Selected bond lengths (Å) and angles (degrees) in 1 and 3.
1
Ge(1)eN(1)
Ge(1)eO(1)
Ge(1)eO(2)
Ge(1)eO(20)
N(1)eGe(1)eO(1)
N(1)eGe(1)eO(2)
3
2.584(2)
1.838(1)
1.982(2)
2.039(1)
74.2(2)
O(1)eGe(1)eO(2)
O(1)eGe(1)eO(20)
O(2)eGe(1)eO(20)
N(1)eGe(1)eO(20)
CeNeC
97.68(6)
87.85(5)
74.60(6)
142.5(2)
112.9(2)e117.0(2)
98.7(2)e107.3(2)
76.2(2)
CeNeGe
Ge(1)eO(1)
Ge(1)eO(2)
Ge(1)eO(2)#1
Ge(1)eN(1)
O(1)eGe(1)eO(2)
1.856(1)
1.933(1)
2.171(1)
2.315(1)
100.46(5)
O(1)eGe(1)eO(2)#1
O(2)eGe(1)eO(2)#1
O(1)eGe(1)eN(1)
O(2)eGe(1)eN(1)
O(2)#1eGe(1)eN(1)
85.66(4)
72.61(4)
80.12(4)
78.54(4)
144.80(4)
compositions of the complexes synthesized but do not clarify the
degree of oligomerization of the compounds in a solution. We can
state that the presence of voluminous groups in a germylene
molecule result in monomeric structures. The introduction of
substituents to C atoms results to magnetic nonequivalence of all
protons in the dialkanolamine framework and resonance signals
appear as a complex sets of multiplets.
Fig. 2. Molecular structure of complex 1. Hydrogen atoms are omitted for clarity.
It is known that metalloorganic derivatives of unsubstituted
dialkanolamines are divided into two groups in accordance with
external view of signals in 1H NMR spectra [15]. The first group
includes compounds for which NMR spectra give AA’XX0 system
(two triplets for NCH2CH2O). This situation is characteristic for
flexibility of dialkanolamine framework in a solution. The second
group includes germylenes in which the NCH2CH2O group forms
ABXY system (two multiplets for NCH2 and one multiplet for OCH2).
Such compounds exist as one “frozen” conformation in a solution at
room temperature. There are compounds of an intermediate type
which are characterized as an AA’XY system (triplet for OCH2 group
and one or two multiplets for NCH2).
The germylenes 1e3 belong to second group or may be char-
acterized as an AA’XY system (see Experimental part). So in these
compounds the conformational processes in penta- or eight
membering cycles are very slow. On the basis of external view of 1H
NMR spectra of unsubstituted germylenes one may estimate the
conformational processes in a solution but these data were not
sufficient for the investigation of transannular Ge)N interaction.
the monomeric derivatives under the studied reaction conditions
leads to the expected products with increasing metal oxidation
state. In contrast, the reactions of dimeric derivatives often results
to mixtures of unidentified compounds. This fact may be explained
by a primary reaction on one metal center but simultaneous pres-
ence of two metal atoms with different oxidation states results to
polymerization or decomposition.
2.4.1. Reactions with changing of germanium oxidation state
The reactions were studied for both monomeric and dimeric
germylenes by experiment and DFT calculations. We tested several
different model compounds prepared in the course of this work.
2.4.1.1. Oxidative insertion reactions
2.4.1.1.1. Halogenation by action of bromine, germanium tetra-
chloride and KICl2. In this work we investigated the insertion reac-
tion of dimeric germylene 8 with bromine (Scheme 6). The similar
monomeric germylene based on pyridine-contained dialcohols was
2.4. Reactivity of germylenes
The systematic investigation of the reactivity of monomeric and
dimeric germylenes obtained in this work and the determination of
the structural factors effecting on the reaction activity are the main
purposes of this work. We have investigated the reactivity of ger-
mylenes in the reactions which either involve changing the
oxidation state (insertion reactions, oxidation, cycloaddition) or do
not involve changes in the Ge oxidation state. It is established that
Table 2
Selected bond lengths (Å) and angles (degrees) in 8 and 10.
8
Ge(1)eO(1)
Ge(1)eO(2)
Ge(1)eO(2A)
Ge(1)eN(1)
O(1)eGe(1)eO(2)
10
1.8653(9)
1.9259(9)
2.1473(10)
2.3822(11)
98.68(4)
O(1)eGe(1)eO(2A)
O(2)eGe(1)eO(2A)
O(1)eGe(1)eN(1)
O(2)eGe(1)eN(1)
O(2A)eGe(1)eN(1)
88.12(4)
74.18(4)
78.36(4)
78.01(4)
146.75(4)
Ge(1)eO(2)
Ge(1)eO(1)
Ge(1)eN(1)
1.833(3)
1.855(3)
2.113(3)
O(2)eGe(1)eO(1)
O(2)eGe(1)eN(1)
O(1)eGe(1)eN(1)
98.8(1)
85.6(1)
84.0(1)
Fig. 3. Molecular structure of complex 3. Hydrogen atoms are omitted for clarity.

70
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
Me
Me
Ph
Ph
N
Ph
Ph
N
Br2
Ge
O
Br Ge
Br
O
O
O
2
8
14 (66%)
Scheme 6.
insertion into CeHal bond the complex is formed owing to gener-
ation of HaleGe contact. The insertion product is formed then from
a three-membered intermediate cycle. According to theoretical
works the insertion reaction is more energetically favored than
more electropositive substituents bound to Ge atom [17].
The mechanism of reaction of germylenes with bromine is
studied by DFT method in the case of dimeric ((3)2, trans-III, IIIb),
monomeric form of 3 and dicoordinated (t-BuO)2Ge 3a. The data
are present in Table 3 and Figs. 6e8.
Interaction of dimeric (3)2 results to a complex containing
simultaneously M(4þ) and M(2þ). This complex decomposes with
the formation of free dibromide and germylene. This situation is
true not only for bromination but also for following studied
reactions.
All investigated reactions are thermodynamically favored. It
should be noted that bromination of (t-BuO)2Ge is more energeti-
Fig. 4. Molecular structure of complex 8. Hydrogen atoms are omitted for clarity.
cally favored (
DH ¼ ꢀ58.5 kcal/mol), than bromination of mono-
meric 3. This fact may be explained by the stabilizing effect of
additional intramolecular interaction GeeN in 3. The activation
energies of these reactions are not very high and significantly
decrease with increasing of coordination number of Ge atoms [for
example Eact 3a (GeII) > Eact 3 (GeIII) > Eact (3)2 (GeIV), where GeII,
GeIII, GeIV are di-, tri- and tetracoordinated Ge atom]. The latter fact
is in accord with the presented mechanism and with the supposi-
tion that more electronic depletion on the metal atom may be
found with an increase of its coordination number.
There is interaction of the lone electron pairs of the Br atom and
suitable orbitals of the Ge atom in the transition state of bromi-
nation reaction. For example, in the reaction of monomeric 3 with
Br2 (Fig. 5) a three-centered four-electron bond with the partici-
pation of vacant 4pz orbital of Ge atom is formed in Br/Ge)N
fragment.
studied previously in this reaction [9], the formation of dibromide
was also found.
The reaction of “heavy” analogs of carbenes with bromine is
very useful reaction for the investigation of the reactivity of such
compounds [16]. At the moment it is common that the insertion of
germylenes in the XeY bond includes two steps (Scheme 7).
At the first stage the complex of “heavy carbene” with substrate
is formed due to donation of substrate electron density on vacant
orbital at Ge. In the case of Ge compounds with additional inter-
molecular interaction such a complex may be not formed. In the
case of insertion of the “heavy carbene” into OeH or NeH bonds the
bond forming in complex is short and strong enough because
oxygen and nitrogen atoms have lone electron pair which are
involved in the interaction with the vacant Ge orbital. In the case of
Fig. 5. Molecular structure of complex 10. Hydrogen atoms are omitted for clarity.

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
71
Y
Y
Y
Ge
B+
X
Ge
X
Ge
X
Ge
X
A
Y
A
B
A
A
B
B
Y
electrophilic
interaction
Y
X
Y
Y
X
Ge
nucleophilic
interaction
M
Scheme 7.
Halogenation of “heavy carbenes” may be occurred by action of
others reagents (for example BiCl3 [18]). For the first time we
investigate reaction of germylenes with GeCl4. It was found that in
this reaction dimeric 2 gives pentacoordinated 15. The driving force
for this reaction is formation of polymeric insoluble GeCl2 and
compound 15 with transannular interaction (Scheme 8).
Interaction of germylene 2 with KICl2 results in complex
reaction mixture from which we can isolate substituted dichlor-
ogermocane 15 with low yield. It is known that KICl2 is a source of
ICl [19]. Formation of 15 may be explained by the higher ther-
modynamic stability of the symmetric derivative which formes
under action of KCl on intermediate IClGe(OCH2CH2)2NMe
(Scheme 9).
Fig. 6. Reaction of monomeric 3 with bromine (structures of reagents, intermediates,
product) according to DFT.
We investigate the mechanism of the reaction of MeI with
germylenes by DFT. The results are presented in Table 4.
In our opinion in this reaction there are three possible direc-
tions: 1) insertion of germylene into CeI bond; 2) quaternization of
nitrogen atom; 3) cleavage of the GeeO bond while retaining the
oxidation state of the germanium atom (2þ). Formation of the ionic
complex [MeN(CH2CH2O)2GeMe]þIꢀ is unlikely due to the ligand
structure giving only one additional bond. The product of reaction
must contain short covalent a GeeI bond with a pentacoordinated
germanium atom so the first direction of reaction is the most
probable.
According to the data in Table 4 there are possible formation of
insertion product on CeI bond (thermodynamic control) and
formation of ate-complex of type Me2Nþ(CH2CH2O)2GeꢀI (kinetic
control). It should be noted that the difference between Eact of
formation of ate-complexes in case of (3)2 and 3 wider than the
difference between Eact of formation insertion products. This result
is correlated with experimental data about formation of unidenti-
fied product mixture in case of (3)2. The formation of the unstable
Me2Nþ(CH2CH2O)2GeꢀI compound is more preferred in the case of
(3)2. The main reason is the more basic nitrogen atom in (3)2 due to
the fact that the Ge atom forms a dimeric structure two additional
interaction, and the GeeN interaction is weaker than that in
monomeric germylenes.
2.4.1.1.2. Interaction with methyl iodide. The results obtained
earlier in the course of the investigation of the reactivity of dia-
lkoxy/diaryloxy- and diamidogermylenes and stannylenes indicate
that the structure of such “heavy carbenes” determines the
pathway of reaction. For example (ArO)2Ge [Ar
¼
2,4,6-
(Me2NCH2)3C6H2] with transannular interaction GeeN adds MeI
with forming mixture of insoluble compounds probably possessing
quaternized N [20]. The reaction of MeI with complex of dimesi-
tyloxygermylene with TMEDA at room temperature results in
a product of insertion on CeI bond [21]. At the same time inter-
action of (Me2NCH2CH2O)2Ge with methyl iodide results in
[(Me2NCH2CH2O)2GeMe]þIꢀ [22]. In this work we investigate the
reaction of synthesized monomeric (10) and dimeric (3) germy-
lenes with MeI (Scheme 10). Reaction of dimeric germylene 3 gives
mixture of unidentified compounds. On contrary, interaction of
monomeric enantiomerically pure complex 10 gives the expected
compound with pentacoordinated Ge atom.
In this reaction mixture of two possible diastereomers (16a and
16b, 2:1) is formed. We assume that these isomers are differed in
substituent disposition at the nitrogen atom.
The values of activation energy for insertion reactions are
significantly more than the energies found earlier in reaction with
bromine. This fact corresponds to higher bond energy for CeI in
comparing with the energy of the BreBr bond. Besides in the
interaction of “heavy carbene” with MeI (insertion reaction) the
activation energy with decreasing coordination number of the
central atom is decreased but in the case of bromination the inverse
relationship is found.
Table 3
DH and Eact (kcal/mol) in reaction of germylenes with Br2.
3ab
a
Reaction
3
(3)2
M(2þ)monomer þ Br2 / M(4þ)Br2
D
H
ꢀ55.5
e
e
ꢀ58.5
Eact 14.1c,d
16.2
2.4.1.1.3. Interaction with disulfides. The SeS bond in disulfides
is very reactive so insertion of “heavy” analogs of carbenes in
these compounds may be regarded as a way to synthesize of
disulfur germanium compounds. Interaction of Ge(OR)2 with
disulfides is very rare in the literature [20], so it is important to
investigate the behavior of the synthesized germylenes in this
reaction.
We have found that the disulfide structure has a critical influ-
ence on the reactivity in this reaction. The germylenes readily insert
into the SeS bond in diphenyldisulfide, but diethyldisulfide is inert
11.6
e
M(2þ)dimer þ Br2 / [M(4þ)Br2 M(2þ)monomer
]
D
Eact
H
ꢀ63.6
8.2
2.7
e
e
e
[M(4þ)Br2 M(2þ)monomer] /
M(4þ)Br2 þ M(2þ)monomer
DH
e
e
ꢀ8.6
e
e
Eact
0e
a
Dimeric trans-structure (IIIb).
(t-BuO)2Ge.
b
c
Two transition states differed in orientation of bromine atoms.
d
e
TS1.
Reaction has no barrier.

72
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
Fig. 7. Reaction of dimeric (3)2 with bromine (structures of reagents, intermediates, products) according to DFT.
in this reaction even under UV irradiation. This fact may be
explained by the stronger SeS bond in diethyldisulfide [1c]
(Scheme 11). The interaction of dimeric germylene 3 with diphe-
nyldisulfide results in a mixture of insertion product 19 and
disproportionation products 17e18 (Scheme 11).
The structure of Ge(SPh)4 (18) was confirmed by X-ray analysis
(Fig. 9). It should be noted that in this case the crystal packing is
chiral and crystal contains both enantiomers.
favorable due to the existence of four strong GeeO bonds and two
transannular interactions GeeN [23]. In contrast, in 19 the trans-
annularinteraction is lower duetothe presence of twothiolate groups
at Ge.
In 18 the germanium atom has a distorted tetrahedral coordi-
nation. The geometric characteristics of the Ge center in Ge(SPh)4
are close to those found previously for tetrahedral complexes [24].
It should be noted that we also found that closely related
monomeric germylene based on diethylenetriamine ligand
(RN(CH2CH2NR’ꢀ)2) behaves analogously to studied dimeric ger-
mylenes 3 and 8 [25].
In our opinion, during the first stage in this reaction ocane 19 is
formed exclusively. Then this compound is disproportionate into 17
and 18. Formation of [MeN(CH2CH2O)2]2Ge (17) is thermodynamically

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
73
Bn
N
Bn
N
KICl2
- KI
Ge
O
Cl Ge
Cl
O
O
O
2
15 (12%)
2
Scheme 9.
germylenes 3 and 8 in both reactions with benzyl and chalcone
[25]. So cycloaddition reactions of studied monomeric and dimeric
germylenes should result in desired products with high yield.
2.4.1.3. Oxidation. All attempt to oxidize dimeric germylene 3
with different oxidizing agents such as trimethylamine oxide,
diphenylphosphoryl azide and sulfur failed. In the cases of
Me3NO and DPPA the reactions led to unidentified product
mixtures, while germylene 3 with S8 didn’t react. It should be
noted that we also found that closely related monomeric ger-
Fig. 8. Reaction of (t-BuO)2Ge 3a with bromine (structures of reagents, intermediates,
products) according to DFT.
mylene
based
on
the
diethylenetriamine
ligand
(RN(CH2CH2NR’ꢀ)2) gave in these three reactions expected
products of Ge(4þ) [25].
2.4.1.2. Reaction of [1 þ 4]-cycloaddition. The reactions of [1 þ 4]-
cycloaddition with participation of “heavy” analogs of carbenes
have been known for a long time and include interaction with
various organic substrates with conjugated double bonds [26,1c]. In
this work we systematically investigate a number of such mole-
cules to find the dependence of the reaction pathways from
substrate structure. The polymeric or oligomeric materials are the
main side products in these reactions.
2.4.1.2.1. Interaction with benzil. Benzil is a typical reagent for
reaction of “heavy” carbene analogs in [1 þ 4]-cycloaddition reac-
tions [27]. In reaction of dimeric germylene 3 with benzyl the
expected complex 21 is formed (Scheme 12).
2.4.2. Reactions without changes of germanium oxidation state
The reactions of germylenes which do not change the oxidation
state of Ge are important because in such reactions germylenes may
be used as catalysts. In this work we investigated the reactivity of
the synthesized germylenes in reactions of nucleophilic substitu-
tion (Scheme 14).
It was found that the interaction of dimeric 3 with acetic
anhydride results in ester of dialkanolamine and Ge(OAc)2. It
should be noted that 25 is difficult to access.
The interaction of dimeric germylene 2 with water results in the
formation of free ligand BnN(CH2CH2OH)2 and solid which was
insoluble in common organic solvents. According to reaction
mechanism the last compound seems to be germanium hydroxide.
So in this reaction there is no formation of the germanol compound
(Scheme 15).
Reactions of germylenes were investigated by DFT calculations
(Table 5, Figs. 10e12).
It is established that the activation energies for the compounds
studied are low and are close to the energies found for bromination
reaction. The reaction occurs as single stage process with transition
states presented on Figs. 10e12, so the reaction proceeds as
a concerted process and metal atom simultaneously attached to
both O atoms.
It is evident that in this reaction the formation of insoluble
germanium hydroxide is thermodynamically favorable.
3. Conclusions
2.4.1.2.2. Interaction with trans-chalcone and its ferrocenic ana-
log. Germylenes 3 and 8 react with trans-chalcone and trans-
FcCH ¼ CHC(O)Ph forming products of a [1 þ 4]-cycloaddition
(Scheme 13).
The reaction of chalcone with germylene was investigated by
DFT calculations (Table 6). All studied reactions are thermody-
namically favorable.
It should be noted that we also found that closely related
monomeric germylene based on diethylenetriamine ligand
(RN(CH2CH2NR’ꢀ)2) behaves analogously to studied dimeric
In summary, a number of germylenes based on dialkanolamine
ligands was synthesized. Therefore, dialkanolamines may be
regarded as a good ligand for the stabilization of low valent
germanium derivatives. Compounds in which the dialkanolamine
ligand contains one or two unsubstituted OCH2 groups are dimeric.
In other cases the complexes are monomeric. Accordingly, germy-
lenes 1, 3 and 8 are dimeric and 10 is monomeric in the solid state.
The studied germylenes participate in reactions of insertion and
cycloaddition with the formation of the corresponding desired
products.
4. Experimental part
Bn
Bn
N
N
4.1. General methods and remarks
GeCl4
All manipulations were performed under a dry, oxygen-free argon
atmosphere using standard Schlenk techniques. trans-Stilbene oxide
[28], GeCl2*C4H8O2 [29], Ge[N(SiMe3)2]2 [14], (Me2N)2Ge [30],
PhN(CH2CH2O)2GeMe2 [11], BnN(CH2CH2OH)2 [31], MeN(CH2CH2
OH)2 [32], MeN(CH2CH2OH)(CH2CHMeOH) [33], MeN(CH2CH2
Ge
O
Cl Ge
Cl
O
- GeCl2
O
O
2
2
15 (95%)
Scheme 8.

74
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
Me
Me
N
N
MeI; 200C
Me
O
O
Ge
I
Ge
O
O
2
3
Me
Me
Me
Me
Me
Me
Ph
Ph
Ph
N
N
N
Ph
Ph
Ph
Ph
Ph
Ph
MeI; THF; -600C
Me Ge
I
O
+
Ge
I
O
O
Me
Ge
O
O
O
10
16a and 16b (65%)
Scheme 10.
OH)(CH2CHPhOH) (a)/MeN(CH2CH2OH)(CHPhCH2OH)(b) (a:b ¼ 9:1)
[34], erythroeMeN(CH2CH2OH)(CHPhCHPhOH) [35], threoeMeN
(CH2CH2OH)(CHPhCHPhOH) [35], MeN(CH2CH2OH)(CH2CPh2OH)
[35], threoeMeN(CH2CH2OH)[CH(CH2)4CHOH] [35], (1R,2S)eMeN
4.2. Synthesis of compounds
4.2.1. Synthesis of erythro,erythro-MeN(CHPhCHPhOH)2
4.2.1.1. Synthesis of erythro,erythro-HN[CH(Ph)CH(Ph)OH]2. The
solution of ammonia in methanol (5.5 ml of 2.0 M solution, 0.01 mol)
and trans-stilbene oxide (5.89 g, 0.03 mol) were mixed in the thick
walled bulb. The mixturewas stirred overnight, then it was heated at
60 ꢁC during 107 h. The precipitate was filtered off, washed with
hexane (3 ꢂ 10 ml) and vucuum dried. The HN[CH(Ph)CH(Ph)OH]2
was obtained as a white solid. Yield 3.43 g (83%). According to NMR
data, compound was obtained as a mixture of diastereomers in the
(CHMeCHPhOH)(CH2CPh2OH)
[36],
threoeMeN(CH2CH2OH)
[CH(CH2)3CHOH] [35], threoeMeN(CH2CH2OH)[CHCH2(C6H4)CHOH]
[35], (E)-FcC(O)CH¼CHPh [37] were synthesized according to the
literature procedures. GeCl4 (Aldrich), Et2S2 (Aldrich) were distilled
prior to use. PhN(CH2CH2OH)2 (Aldrich), Ph2S2 (Aldrich), (PhO)2P(O)N3
(Aldrich), PhC(O)C(O)Ph (Aldrich), trimethylamine oxide (Aldrich) and
sulfur (Aldrich) were used as supplied. 1H NMR (400 MHz) and 13C
NMR (100 MHz) spectra were recorded with a Bruker 400 spectrom-
eter (in CDCl3 or C6D6 at 295 K). Chemical shifts in the 1H and 13C NMR
spectra are given in ppm relative to internal Me4Si. Elemental analyses
were carried out by the Microanalytical Laboratory of the Chemistry
Department of the Moscow State University. Mass spectra (EI-MS,
70 eV) were recorded on a VARIAN CH-7a device (Philipps-University
Marburg, Germany); all assignments were made with reference to the
most abundant isotopes.
ratio 1:1. 1H NMR (400 MHz, CDCl3, ppm):
3.55, 3.77 (2d, 2H, NCH), 4.59, 4.84 (2d, 2H, OCH), 6.72e7.21 (20H,
aromatic hydrogens). Anal. Calc. for C28H27NO2 (409.520): C 82.12, H
6.65, N 3.42. Found: C 82.40, H 6.84, N 3.25.
d
¼ 2.54 (br s, 1H, NCH),
4.2.1.2. Synthesis of erythro,erythro-MeN[CH(Ph)CH(Ph)OH]2. A
solution of 30% solution of CH2O (0.30 ml, 3.00 mmol) was added to
erythro,erythro-HN[CH(Ph)CH(Ph)OH]2. Formic acid (0.14 g,
Table 4
DH and Eact (kcal/mol) in reaction of germylenes with MeI.
3ab
a
Reaction
3
(3)2
M(2þ)monomer þ MeI / M(4þ)(Me)I
D
H
ꢀ26.2c
ꢀ28.5
40.4c
41.1
57.3
ꢀ10.1
43.1
0.1
e
ꢀ33.0
Eact
e
38.1
M(2þ)monomer þ MeI / MeN(CH2CH2OMe)CH2CH2OeGeeI
M(2þ)monomer þ MeI / Me2Nþ(CH2CH2O)2GeꢀI
DH
e
ee
ee
ee
ee
e
Eact
e
DH
e
Eact
32.0
e
e
M(2þ)dimer þ MeI / [M(4þ)(Me)I M(2þ)monomer
]
DH
ꢀ18.2c
ꢀ16.8
37.9c
40.0
ꢀ1.6c
ꢀ0.3
ed
Eact
e
e
e
e
[M(4þ)(Me)I M(2þ)monomer] / M(4þ)(Me)I þ M(2þ)monomer
DH
Eact
e
e
e
e
e
e
e
e
M(2þ)dimerþ MeI / MeN(CH2CH2OMe)CH2CH2OeGeeI M(2þ)monomer
M(2þ)dimerþ MeI / Me2Nþ(CH2CH2O)2GeꢀI M(2þ)monomer
DH
6.2
Eact
50.8
5.3c
5.9
DH
Eact
e
26.8
e
a
Trans-dimer (IIIb).
(t-BuO)2Ge.
Structures with different orientation of methyl group and iodide.
Reaction without barrier.
b
c
d
e
Reactions were not studied.

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
75
Me
Me
N
N
Ph
Ph
Ph
Ph
Et2S2; THF
O
O
Ge
EtS
Ge
O
O
2
SEt
8
Me
Me
N
N
Ph2S2; THF; -400C
[MeN(CH2CH2O)2]2Ge
+
Ge[SPh]4
Ge
PhS
O
O
+
Ge
O
O
2
3
SPh
17
18
19
Scheme 11.
3.00 mmol) was added during 1 h, and then mixture was stirred at
75 ꢁC for 5 h. Volatiles were removed in vacuum, the residue was
extracted with Et2O. The water (50 ml) was added to organic extract
and the precipitate obtained was filtered off. erythro,erythro-MeN
[CH(Ph)CH(Ph)OH]2 was obtained as white solid. Yield 0.90 g (68%).
According to NMR data, compound was obtained as a mixture of
diastereomers in the ratio 5:4. 1H NMR (400 MHz, CDCl3, ppm):
room temperature. After 4 days the reaction mixture was concen-
trated under vacuum (approximately third part was removed), and
the solid formed was filtered off to give 1 as a white solid. Yield 0.12 g
(63%). 1H NMR (400 MHz, C6D6, ppm):
d
¼ 2.62e2.99 (m, 4H, NCH2),
3.94 (br s, 4H, OCH2), 6.82e6.87, 7.07e7.16 (2m, 5H, aromatic
hydrogens). 13C NMR (100 MHz, C6D6, ppm):
¼ 56.54 (NCH2), 61.82
(OCH2), 115.32, 118.95, 128.87, 129.27 (aromatic carbons).
Method B. solution of PhN(CH2CH2OH)2GeMe2 (0.12 g,
d
d
¼ 2.06, 2.58 (2s, 6H, NH3), 3.57, 3.95 (2d, 2H, NCH), 5.20, 5.44 (2d,
2H, OCH), 7.00e7.04, 7.11e7.25 (2m, 20H, aromatic hydrogens). 13C
NMR (100 MHz, CDCl3, ppm):
A
0.43 mmol) in toluene (20 ml) was added to a stirred solid of
GeCl2*C4H8O2 (0.10 g, 0.43 mmol). The reaction mixture was stirred
for 3 days at room temperature and all volatiles were removed
under reduced pressure. Then ether (10 ml) was added to the
residue, the precipitate was filtered off to give 1 as a white powder.
Yield 0.11 g (60%).
d
¼ 35.26, 35.90 (NCH3), 70.63, 71.40,
72.26, 72.43 (NCH, OCH), 126.30, 126.43, 127.33, 127.52, 127.55,
127.58, 127.62, 127.86, 127.96, 129.89, 129.95, 134.69, 135.42, 141.49,
141.57 (aromatic carbons). Signal of one carbon atom was not
found. Anal. Calc. for C29H29NO2 (423.546): C 82.24, H 6.90, N 3.31.
Found: C 82.01, H 7.07, N 3.08.
4.2.3. Synthesis of BnN(CH2CH2O)2Ge (2)
4.2.2. Synthesis of PhN(CH2CH2O)2Ge (1)
Analogously to 1 (Method A), complex 2 was prepared from
BnN(CH2CH2OH)2 (0.23 g, 1.20 mmol) and Ge[N(TMS)2]2 (0.47 g,
1.20 mmol) in toluene (20 ml). The mixture was stirred for 4 days at
room temperature and all volatiles were removed under reduced
pressure. Then ether (10 ml) was added to the residue, the
precipitate was filtered off to give 2 as a white solid. Yield 0.17 g
Method A. A solution of PhN(CH2CH2OH)2 (0.14 g, 0.76 mmol) in
toluene (10 ml) was added to a stirred solution of Ge[N(TMS)2]2
(0.30 g, 0.76 mmol) in toluene (10 ml), and the mixture was stirred at
(53%). 1H NMR (400 MHz, C6D6, ppm):
(2m, 4H, NCH2), 3.56 (s, 2H, CH2Ph), 3.56e3.60, 3.87e3.92 (2m,
4H, OCH2), 6.81e6.87, 7.03e7.06 (2m, 5H, aromatic hydrogens). 13
NMR (100 MHz, C6D6, ppm):
d
¼ 1.88e1.96, 2.50e2.56
C
d
¼ 50.38, 57.39, 58.06 (NCH2, OCH2),
128.23, 128.59, 131.50, 135.12 (aromatic carbons). Anal. Calc. for
C11H15GeNO2 (265.8523): C 49.70, H 5.69, N 5.27. Found: C 49.55, H
5.45, N 5.36.
4.2.4. Synthesis of MeN(CH2CH2O)2Ge (3)
Method A. Analogously to 2, complex 3 was prepared from
MeN(CH2CH2OH)2 (0.15 g, 1.25 mmol) and Ge[N(TMS)2]2 (0.49 g,
Me
Me
N
N
O
C
O
C
Ph
Ph
O
O
Ge
O
Ge
O
O
O
2
Ph
20 (64%)
3
Fig. 9. Molecular structure of complex Ge(SPh)4 (18). Hydrogen atoms are omitted for
clarity. Selected bond length (Å) and angles (ꢁ): Ge(1)eS(1) 2.2149(6), Ge(1)eS(2)
2.2191(5), S(1)eC(11) 1.7873(19), S(2)eC(21) 1.7927(19), S(1)eGe(1)eS(1A) 115.15(4),
S(1)eGe(1)eS(2) 105.461(19), S(1)eGe(1)eS(2) 107.848(19), C(11)eS(1)eGe(1)
99.67(6), C(21)eS(2) Ge(1) 98.13(6).
Ph
Scheme 12.

76
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
Table 5
DH and Eact (kcal/mol) in interaction of germylenes with benzil.
3ab
a
Reaction
3
(3)2
M(þ2)monomerþ PhC(O)-C(O)Ph /M(þ4)[(Ph)C(Oe) ¼ C(Oe)Ph]
D
Eact
H
ꢀ24.2
10.8c
8.5
e
e
ꢀ21.7
6.2
M(þ2)dimer þ PhC(O)-C(O)Ph/ [M(þ4)[(Ph)C(Oe) ¼ C(Oe)Ph]M(þ2)monomer
]
D
Eact
H
e
ꢀ14.9
4.0c
2.8
e
e
e
[M(þ4)[(Ph)C(Oe) ¼ C(Oe)Ph]M(þ2)monomer] / M(4þ)[(Ph)C(Oe) ¼ C(Oe)Ph] þ M(2þ)monomer
D
Eact
H
e
e
ꢀ9.3
e
e
0d
a
Trans-dimer IIIb.
(t-BuO)2Ge.
There are two transition states differed in orientation of O atoms.
Reaction without energetic barrier.
b
c
d
1.25 mmol) in toluene (20 ml). The product was isolated by filtration
to give 3 as a white solid. Yield 0.21 g (89%). 1H NMR (400 MHz, C6D6,
(0.17 g, 1.10 mmol). The reaction mixture was stirred for 4 days at
room temperature and all volatiles were removed under reduced
pressure. Then ether (10 ml) was added to the residue, the
precipitate was filtered off to give 3 as a white powder. Yield 0.16 g
(92%).
ppm):
4H, OCH2). 13C NMR (100 MHz, C6D6, ppm):
(NCH2), 66.27 (OCH2). 1H NMR (400 MHz, CDCl3, ppm):
3H, CH3N), 2.73e2.80 (m, 4H, NCH2), 3.96e4.18 (m, 4H, OCH2). 13
NMR (100 MHz, C6D6, ppm):
¼ 45.58 (CH3N), 60.50 (NCH2), 65.54
(OCH2). EI MS (rel. int.): [M]þ 192 (1); [MeCH2O]þ 161 (5).
d
¼ 1.87 (s, 3H, NCH3),1.89e2.01 (m, 4H, NCH2), 3.85e4.05 (m,
¼ 45.16 (CH3), 60.81
¼ 2.74 (s,
d
d
C
d
4.2.5. Synthesis of MeN(CH2CH2O)(CH2CHMeO)Ge (4)
Analogously to 2, complex 4 was prepared from MeN(CH2
-
Method B. A solution of MeN(CH2CH2OH)2 (0.13 g, 1.10 mmol) in
toluene (10 ml) was added to a stirred solution of (Me2N)2Ge
CH2OH)(CH2CHMeOH) (0.14 g, 1.04 mmol) and Ge[N(TMS)2]2
(0.41 g, 1.04 mmol) in toluene (20 ml). The product was isolated by
Fig. 10. Reaction of monomeric 3 with benzil (structures of reagents, intermediates, product) according to DFT.

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
77
Fig. 11. Reaction of dimeric (3)2 with benzil (structures of reagents, intermediates, product) according to DFT.
filtration to give 4 as a white solid. Yield 0.06 g (29%). 1H NMR
(400 MHz, C6D6, ppm):
¼ 1.12 (d, 3H, J ¼ 5.8 Hz, CH3CH), 1.93 (s,
3H, CH3N), 1.89e2.04 (m, 4H, NCH2), 3.94e4.13 (m, 2H, OCH2),
4.31e4.41 (m, 1H, OCH). 13C NMR (100 MHz, C6D6, ppm):
(CH3CH), 46.76 (CH3N), 61.82, 67.97 (NCH2), 68.95 (OCH2), 74.38
(OCH). Anal. Calc. for C6H13GeNO2 (203.783): C 35.36, H 6.43, N
6.87. Found: C 35.40, H 6.41, N 6.89.
4.2.7. Synthesis of erythro-MeN(CH2CH2O)(CHPhCHPhO)Ge (6)
Analogously to 2, complex was prepared from
erythroeMeN(CH2CH2OH)(CHPhCHPhOH) (0.38 g, 1.40 mmol) and
Ge[N(TMS)2]2 (0.55 g,1.40 mmol) in toluene (20 ml). The product was
isolated by filtration to give 6 as a white solid. Yield 0.41 g (86%). 1H
d
6
d
¼ 22.63
NMR (400 MHz, C6D6, ppm):
d
¼ 1.81 (s, 3H, CH3), 2.03e2.13,
2.58e2.69 (2m, 2H, NCH2), 3.46 (d, 1H, J ¼ 3.8 Hz, NCH), 3.86e3.97,
4.17e4.28 (2m, 2H, OCH2), 5.98 (d, 1H, J ¼ 3.8 Hz, OCH), 6.77e6.90,
6.99e7.07, 7.27e7.33 (3m, 10H, aromatic hydrogens). 13C NMR
4.2.6. Synthesis of MeN(CH2CH2O)(CH2CHPhO)Ge (5)
Analogously to 2, complex 5 was prepared from the insepa-
(100 MHz, C6D6, ppm):
d
¼ 42.42 (CH3), 62.08 (NCH2), 64.47 (OCH2),
rable mixture of MeN(CH2CH2OH)(CH2CHPhOH) (a)/MeN(CH2
80.02 (NCH), 80.95 (OCH), 126.38, 126.58, 127.88, 131.12, 134.97
(aromatic carbons). The signals of three carbon atoms were not found
due to overlap with the solvent signals. Anal. Calc. for C17H19GeNO2
(341.9483): C 59.71, H 5.60, N 4.10. Found: C 59.50, H 5.46, N 4.15.
-
CH2OH)(CHPhCH2OH) (b) (0.17 g, 0.87 mmol, a:b ¼ 9:1) and Ge
[N(TMS)2]2 (0.34 g, 0.87 mmol) in toluene (20 ml). The product
was isolated by filtration to give 5 as a white solid. Yield 0.17 g
(71%). 1H NMR (400 MHz, C6D6, ppm):
d
¼ 1.86 (s, 3H, CH3N),
1.89e2.14, 2.23e2.36 (2m, 4H, NCH2), 3.92e4.29 (m, 2H, CH2O),
5.35e5.45 (m, 1H, OCHPh), 7.20e7.30, 7.41e7.58 (2m, 5H,
4.2.8. Synthesis of threo-MeN(CH2CH2O)(CHPhCHPhO)Ge (7)
Analogously to 2, complex
7
was prepared from
aromatic hydrogens). 13C NMR (100 MHz, C6D6, ppm):
d
¼ 46.13
treoeMeN(CH2CH2OH)(CHPhCHPhOH) (0.18 g, 0.66 mmol) and Ge
[N(TMS)2]2 (0.26 g, 0.66 mmol) in toluene (20 ml). The product was
isolated by filtration to give 7 as a white solid. Yield 0.14 g (61%). 1H
NMR (400 MHz, C6D6, ppm):
2.82e2.99, 3.38e3.55, 3.95e4.11, 4.37e4.50, 5.70e5.89 (6m, 6H,
(CH3N), 61.21, 67.33 (NCH2), 68.93 (OCH2), 80.12 (OCH), 127.37,
128.41, 128.61, 144.29 (aromatic carbons). Anal. Calc. for
C11H15GeNO2 (265.8523): C 49.70, H 5.69, N 5.27. Found: C 49.67,
H 5.40, N 5.07.
d
¼ 1.87 (s, 3H, CH3N), 1.93e2.09,

78
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
Fig. 12. Reaction of (t-BuO)2Ge 3a with benzil (structures of reagents, intermediates, product) according to DFT.
NCH2, NCH, OCH2, OCH), 6.60e6.70, 6.81e6.98, 7.01e7.08,
7.31e7.40 (4m, 10H, aromatic hydrogens). 13C NMR spectra is not
recorded due to insolubility of 7. Anal. Calc. for C17H19GeNO2
(341.9483): C 59.71, H 5.60, N 4.10. Found: C 59.80, H 5.51, N 4.13.
CH2O), 7.17e7.23, 7.27e7.34, 7.53e7.62 (3m, 10H, Ph). Anal. Calc. for
C17H19GeNO2 (341.9483): C 59.71, H 5.60, N 4.10. Found: C 59.64, H
5.43, N 4.42.
Method B. KC8 (0.22 g, 1.60 mmol) was added to solution of
MeN(CH2CH2O)(CH2CPh2O)GeBr2 (14) (0.16 g, 0.32 mmol) in THF
(30 ml) at room temperature. Reaction mixture was stirred for 4
days. Volatiles were evaporated under reduced pressure, toluene
(20 ml) was added to mixture, slurry was filtered and solvent was
evaporated. The residue was recrystallized from toluene. The
product was isolated as white solid. Yield 0.07 (66%). NMR spectra
were identical to above mentioned.
4.2.9. Synthesis of MeN(CH2CH2O)(CH2CPh2O)Ge (8)
Method A. Analogously to 2, complex 8 was prepared from
MeN(CH2CH2OH)(CH2CPh2OH) (0.38 g, 1.42 mmol) and Ge
[N(TMS)2]2 (0.56 g, 1.42 mmol) in toluene (20 ml). The product was
isolated by filtration to give 8 as a white solid. Yield 0.47 g (96%). 1H
NMR (400 MHz, C6D6, ppm):
d
¼ 1.84 (s, 3H, CH3), 1.75e1.87 (m, 2H,
NCH2), 2.57, 3.14 (2d, 2H, J ¼ 13.0 Hz, AM system of NCH2CPh2 group
protons), 3.89e3.95, 3.99e4.10 (2m, 2H, OCH2), 6.93e7.04,
7.08e7.17, 7.60e7.74 (3m, 10H, aromatic hydrogens). 13C NMR
4.2.10. Synthesis of erythro,erythro-MeN(CHPhCHPhO)2Ge (9)
Analogously to 2, complex 9 was prepared from erythro,erythro-
MeN(CHPhCHPhOH)2 (0.45 g, 1.07 mmol) and Ge[N(TMS)2]2
(0.42 g, 1.07 mmol) in toluene (20 ml). The product was isolated by
filtration to give 9 as a yellow solid. Yield 0.22 g (42%). Compound 9
was obtained as a mixture of diastereomers in the ratio 2:1. 1H NMR
(100 MHz, C6D6, ppm):
d
¼ 45.45 (CH3), 63.69, 64.58, 66.48 (2NCH2,
OCH2), 84.20 (OCPh2), 125.74, 126.78, 126.93, 127.09, 128.31, 128.36,
147.95, 148.88 (aromatic carbons). 1H NMR (400 MHz, CDCl3, ppm):
d
¼ 2.40 (s, 3 H), 2.67e2.73, 2.84e2.92 (2m, 2H, NCH2CH2),
3.55e3.58 (m, 2H, NCH2CPh2), 3.79e3.89, 3.91e3.98 (2m, 2H,
(400 MHz, C6D6, ppm):
d
¼ 1.89, 2.25 (2s, 6H, CH3N), 3.86 (d, J ¼ 4.8
Hz), 4.03 (d, J ¼ 4.8 Hz), 4.52 (d, J ¼ 5.3 Hz), 5.50 (d, J ¼ 4.3 Hz), 6.49
(d, J ¼ 3.5 Hz), 6.49 (d, J ¼ 5.0 Hz) (8H, NCH, OCH), 6.61e6.74,
6.77e7.12, 7.39e7.47, 7.54e7.62 (4m, 40H, aromatic hydrogens).
Me
N
Me
13C NMR (100 MHz, C6D6, ppm):
d
¼ 45.70, 45.74 (CH3N), 71.94,
N
72.77, 78.09, 78.70, 81.35, 82.77 (NCH, OCH), 125.95, 126.09, 126.23,
126.35, 126.56, 127.09, 127.38, 127.68, 127.92, 128.14, 131.67, 131.72,
141.60, 141.99, 142.63, 142.96 (aromatic carbons). Anal. Calc. for
C29H27GeNO2 (494.1402): C 70.49, H 5.51, N 2.83. Found: C 69.99, H
5.13, N 3.10.
(E)-PhC(O)CH=CHPh
O
Ge
Ge
O
O
O
O
2
Ph
CH
Ph
21 (80%)
3
4.2.11. Synthesis of MeN((S)-CHMe-(R)-CHPhO)(CH2CPh2O)Ge (10)
Analogously to 2, complex 10 was prepared from (1R,2S)-
MeN(CHMeCHPhOH)(CH2CPh2OH) (0.87 g, 2.41 mmol) and Ge
[N(TMS)2]2 (0.95 g, 2.41 mmol) in toluene (20 ml). The product was
isolated by filtration to give 10 as a white solid. Yield 0.81 g (78%).
Me
N
Me
R2
R1
R2
R1
N
(E)-FcC(O)CH=CHPh
O
Ge
Ge
O
O
O
O
2
1H NMR (400 MHz, C6D6, ppm):
d
¼ 0.46 (d, 3H, J ¼ 6.8 Hz,
Fc
22. R1=R2= H (48%)
23. R1, R2 = Ph (45%)
CH
Ph
3, 8
NCHCH3), 1.88 (s, 3H, NCH3), 2.39e2.48 (m, 1H, NCHCH3), 3.22, 3.45
(2d, 2H, J ¼ 13.1 Hz, AM system of NCH2CPh2 group protons), 5.80
(d, 1H, J ¼ 2.0 Hz, OCHPh), 6.96e7.04, 7.06e7.23, 7.31e7.37,
Scheme 13.

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
79
Table 6
H and Eact (kcal/mol) in reaction of germylenes with chalcone.
D
3ab
a
Reaction
3
(3)2
M(þ2)monomer þ PhCH ¼ CH-C(O)Ph / M(þ4)[(Ph)C(Oe) ¼ CHCH(Ph)e]
D
H
ꢀ14.1c
ꢀ14.6
6.4c
3.6
e
e
ꢀ16.3
Eact
e
1.6c
4.1
e
M(þ2)dimerþ PhCH ¼ CHC(O)Ph / [M(þ4)[(Ph)C(Oe) ¼ CHCH(Ph)e]M(þ2)monomer
]
DH
ꢀ4.7c
ꢀ4.6
e4.9
ꢀ6.4
8.3c
9.2
Eact
e
e
e
e
e
e
9.2
4.7
[M(þ4)[(Ph)C(Oe) ¼ CHCH(Ph)e]M(þ2)monomer] / M(þ4)[(Ph)C(Oe) ¼ CHCH(Ph)e] þ M(2þ)monomer
DH
ꢀ2.1c
ꢀ2.0
e2.3
ꢀ3.8
0d
Eact
a
Trans-dimer (IIIb).
(t-BuO)2Ge.
b
c
It is found several structures which are differed in orientation of substituent.
Reaction without energetic barrier.
d
7.68e7.82 (4m, 15H, aromatic hydrogens). 13C NMR (100 MHz, C6D6,
ppm):
NCH2), 78.97 (OCHPh), 84.43 (OCPh2), 125.61, 126.58, 126.84,
126.88, 126.99, 127.13, 127.88, 128.45, 128.49, 142.93, 147.92, 149.15
(aromatic carbons). Anal. Calc. for C24H25GeNO2 (432.0708): C
66.72, H 5.83, N 3.24. Found: C 66.45, H 5.64, N 3.30.
4.2.14. Synthesis of threo-MeN(CH2CH2O)[CHCH2(C6H4)CHO]Ge
(13)
d
¼ 11.00 (NCHCH3), 41.00 (NCH3), 68.75, 70.33 (NCHCH3,
Analogously to 2, complex 13 was prepared from threo-
MeN(CH2CH2OH)[CHCH2(C6H4)CHOH] (0.19 g, 0.92 mmol) and Ge
[N(TMS)2]2 (0.36 g, 0.92 mmol) in toluene (20 ml). The product was
isolated by filtration to give 13 as a yellow solid. Yield 0.23 g (88%).
1H NMR (400 MHz, C6D6, ppm):
2.61e3.23, 3.52e3.95, 4.71e4.49 (4m, 8H, NCH2, NCH, OCH2, OCH,
CH2), 6.86e6.99 (m, 4H, aromatic hydrogens). 13C NMR spectrum is
not recorded due to insolubility of 13. 1H NMR (400 MHz, CDCl3,
d
¼ 2.38 (s, 3H, CH3N), 2.14e2.54,
4.2.12. Synthesis of threo-MeN(CH2CH2O)[CH(CH2)3CHO]Ge (11)
Analogously to 2, complex 11 was prepared from threo-
MeN(CH2CH2OH)[CH(CH2)3CHOH] (0.15 g, 0.97 mmol) and Ge
[N(TMS)2]2 (0.38 g, 0.97 mmol) in toluene (20 ml). The product was
isolated by filtration to give 11 as a white solid. Yield 0.14 g (64%). 1H
ppm):
d
¼ 2.91 (s, 3H, CH3N), 2.52e2.66, 2.70e2.97, 3.05e3.16,
3.80e3.93, 3.98e4.15, 4.55e4.69 (6m, 8H, NCH2, NCH, OCH2, OCH,
NMR (400 MHz, C6D6, ppm):
d
¼ 1.20e1.64 (m, 6H, C3H6), 1.99 (s,
CH2), 7.09e7.22 (m, 4H, aromatic hydrogens). 13C NMR (100 MHz,
3H, CH3N), 1.77e2.07, 2.27e2.56 (2m, 3H, NCH, NCH2), 3.72e3.90,
CDCl3, ppm):
d
¼ 35.09 (CH3N), 42.93, 50.91, 60.62, 76.32, 78.84
4.00e4.11, 4.30e4.47 (3m, 3H, OCH, OCH2). 13C NMR (100 MHz,
(NCH2, NCH, OCH2, OCH, CH2), 122.66, 126.26, 126.53, 127.52, 140.76
(aromatic carbons). Signal of one aromatic carbon was not found.
Anal. Calc. for C12H15GeNO2 (277.863): C 51.87, H 5.44, N 5.04.
Found: C 51.83, H 5.47, N 5.06.
C6D6, ppm):
d
¼ 19.52, 27.99, 30.16 (CH2), 41.47 (CH3N), 50.10
(NCH2), 61.42, 73.34 (NCH, OCH2), 77.09 (OCH). The satisfactory
results of elemental analysis were not obtained due to hygroscop-
icity of 11.
4.3. Reactions of germylenes with changing of germanium
oxidation state
4.2.13. Synthesis of threo-MeN(CH2CH2O)[CH(CH2)4CHO]Ge (12)
Analogously to 2, complex 12 was prepared from threo-
MeN(CH2CH2OH)[CH(CH2)4CHOH] (0.18 g, 1.04 mmol) and Ge
[N(TMS)2]2 (0.41 g, 1.04 mmol) in toluene (20 ml). The product was
isolated by filtration to give 12 as a yellow solid. Yield 0.15 g (60%).
4.3.1. Reaction of 8 with bromine. Synthesis of
MeN(CH2CH2O)(CH2CPh2O)GeBr2 (14)
A solution of bromine (0.05 g, 0.30 mmol) in toluene (10 ml) was
added to a stirred solution of 8 (0.11 g, 0.30 mmol) in toluene
(10 ml). The reaction mixture was stirred for 1 day at room
temperature and solvents were removed in vacuum. Then ether
(10 ml) was added to the residue, the precipitate was filtered off to
give 14 as a white solid. Yield 0.10 g (66%). The 1H and 13C NMR
spectra were in accord with the data of literature [13].
1H NMR (400 MHz, C6D6, ppm):
d
¼ 0.45e0.65, 0.67e1.01,
1.07e1.50, 1.56e1.67 (4m, 8H, C4H8), 1.89 (s, 3H, CH3N), 1.69e1.82,
2.20e2.35 (2m, 3H, NCH, NCH2), 3.73e3.85, 3.89e4.00, 4.03e4.14
(3m, 3H, OCH, OCH2). 13C NMR (100 MHz, C6D6, ppm):
d
¼ 22.44,
24.06, 25.29, 36.50 (CH2), 42.46 (CH3N), 52.79, 65.92, 73.05, 78.82
(NCH2, NCH, OCH2, OCH). The satisfactory results of elemental
analysis were not obtained due to hygroscopicity of 12.
4.3.2. Reaction of 2 with KICl2 or GeCl4. Synthesis of
BnN(CH2CH2O)2GeCl2 (15)
Method A. Reaction of 2 with KICl2. A solid KICl2 (0.12 g,
0.50 mmol) was added to a stirred solution of 2 (0.13 g, 0.50 mmol)
Me
N
Ac2O
Me(NCH2CH2OAc)2 + Ge(OAc)2
Ge
24
25
H2O
O
O
[BnN(CH2CH2O)2Ge]2
BnN(CH2CH2OH)2
2
- [Ge(OH)2]
2
3
Scheme 14.
Scheme 15.

80
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
in toluene (10 ml). The reaction mixture was refluxed for 15 h. The
precipitated solid was filtered. The filtrate was concentrated, and
the solid formed was filtered off to give 15 as a white solid. Yield
was obtained as a mixture of [MeN(CH2CH2O)2]2Ge (17), Ge(SPh)4
(18) and MeN(CH2CH2O)2Ge(SPh)2 (19) in the ratio 1:1:1. Complex
(17) (1H and 13C NMR data were in accordance with the data of
0.02 g (12%). 1H NMR (400 MHz, C6D6, ppm):
d
¼ 2.71e2.77,
literature [34]): 1H NMR (400 MHz, CDCl3, ppm):
d
¼ 2.46 (s, 6H,
CH3N), 2.58 (t, 8H, J ¼ 5.8 Hz, NCH2), 3.71 (t, 8H, J ¼ 5.8 Hz, OCH2).
13C NMR (100 MHz, CDCl3, ppm):
¼ 45.46 (NCH3), 57.26 (NCH2),
3.01e3.07 (2m, 4H, 2NCH2), 3.97e4.03, 4.08e4.14 (2m, 4H,
2OCH2), 4.00 (s, 2H, CH2Ph), 7.13e7.16, 7.21e7.23, 7.41e7.42 (3m,
d
5H, aromatic hydrogens). 13C NMR (100 MHz, C6D6, ppm):
(NCH2), 57.29 (NCH2Ph), 58.64 (OCH2), 129.14, 129.44, 131.01, 131.27
(aromatic carbons). Anal. Calc. for C11H15Cl2GeNO2 (336.7577): C
39.23, H 4.49, N 4.16. Found: C 39.35, H 4.50, N 4.28.
d
¼ 49.18
58.05 (OCH2). Complex (18): 1H NMR (400 MHz, CDCl3, ppm):
d
¼ 6.91e6.98, 7.45e7.50 (2m, 20H, aromatic hydrogens). 13C NMR
(100 MHz, CDCl3, ppm):
d
¼ 127.08, 128.12, 128.99, 129.47 (aromatic
carbons). Complex (19): 1H NMR (400 MHz, C6D6, ppm):
d
¼ 2.10 (t,
Method B. Reaction of 2 with GeCl4. A solution of GeCl4 (0.12 g,
0.56 mmol) in toluene (5 ml) was added to a stirred solution of 2
(0.15 g, 0.56 mmol) in toluene (10 ml). The reaction mixture was
stirred under reflux for 3 days. The solid formed (GeCl2) was filtered
off and all volatiles were removed in vacuum. Then ether (10 ml)
was added to the residue, the precipitate was filtered off, washed
with diethyl ether (2 ꢂ 2 ml) and dried under vacuum to give 15 as
a white solid. Yield 0.18 g (95%).
4H, J ¼ 5.6 Hz, NCH2), 2.11 (s, 3H, CH3N), 3.73 (t, 4H, J ¼ 5.6 Hz,
OCH2), 6.91e6.98, 7.45e7.50 (2m, 10H, aromatic hydrogens). 13C
NMR (100 MHz, C6D6, ppm):
d
¼ 47.07 (CH3N), 55.30 (2NCH2), 57.61
(2OCH2), 127.42, 128.82, 135.64, 136.92 (aromatic carbons).
Under recrystallization of reaction mixture from toluene a less
drop of complex 18 was isolated as colorless crystals.
4.3.6. Reaction of 8 with Et2S2
To a stirred solution of 8 (0.20 g, 0.58 mmol) in THF (10 ml) was
added dropwise solution of Et2S2 (0.07 g, 0.58 mmol) in THF (5 ml)
at ꢀ40 ꢁC. The reaction mixture was stirred for 20 min and allowed
to warm to room temperature. After 4 days the volatiles were
removed under reduce pressure to give a 0.22 g yellow solid.
According to NMR data, only starting materials were found in the
reaction mixture.
4.3.3. Reaction of 10 with MeI. synthesis of MeN((S)-CHMe-(R)-
CHPhO)(CH2CPh2O)GeMeI (16a and 16b)
To a stirred solution of 10 (0.35 g, 0.81 mmol) in THF (8 ml) was
added dropwise solution of MeI (0.23 g, 1.62 mmol) in THF (2 ml)
at ꢀ60 ꢁC. The reaction mixture was stirred for 20 min and allowed
to warm to room temperature. After 7 days the solid was filtered off
to give 16 as a white solid. Yield 0.30 g (65%). According to NMR data,
compound 10 was obtained as a mixture of diastereomers in the
ratio 2:1. Anal. Calc. for C25H28GeINO2 (574.0098): C 52.31, H 4.92, N
2.44. Found: C 52.38, H 4.90, N 2.42. Complex (16a): 1H NMR
4.3.7. Reaction of 3 with PhC(O)C(O)Ph. synthesis of
MeN(CH2CH2O)2Geecyclo-(OC(Ph)C(Ph)O) (20)
A solid PhC(O)C(O)Ph (0.13 g, 0.63 mmol) was added to a stirred
solution of 3 (0.12 g, 0.63 mmol) in toluene (10 ml). The reaction
mixture was stirred for 4 days at room temperature and volatiles
were removed in vacuum. Then ether (10 ml) was added to the
residue, the precipitate was filtered off to give 20 as a white solid.
(400 MHz, C6D6, ppm):
d
¼ 0.37 (d, 3H, J ¼ 6.6 Hz, NCHCH3), 1.38 (s,
3H, CH3Ge), 1.62 (s, 3H, NCH3), 2.62e2.64 (m, 1H, CHCH3), 3.33, 3.63
(2d, 2H, J ¼ 13.7 Hz, AM system of NCH2 group protons), 5.10e5.15
(m, 1H, OCHPh), 6.85e7.01, 7.05e7.10, 7.57e7.67, 7.74e7.84 (4m,
10H, aromatic hydrogens).13C NMR (100 MHz, C6D6, ppm):
d
¼ 10.45
Yield 0.16 g (64%). 1H NMR (400 MHz, CDCl3, ppm):
d
¼ 3.05 (s, 3H,
(NCHCH3), 23.95 (CH3Ge), 41.86 (NCH3), 60.58 (NCH2CPh), 65.97
(NCHCH3), 73.65 (OCHPh), 79.76 (OCPh2), 125.43, 125.99, 126.48,
126.86, 127.32, 127.56, 128.13, 128.36, 128.81, 140.90, 146.01, 147.67
(aromatic carbons). Complex (16b): 1H NMR (400 MHz, C6D6, ppm):
CH3N), 3.06e3.12, 3.21e3.24 (2m, 4H, NCH2), 4.16e4.18 (m, 4H,
OCH2), 7.32e7.40, 7.56e7.58, 7.65e7.67 (3m, 10H, aromatic hydro-
gens). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 44.08 (CH3N), 55.39
(NCH2), 57.15 (OCH2), 126.09, 126.61, 127.07, 127.51, 127.70, 127.90,
133.88, 135.26, 135.39, 138.10 (¼C and aromatic carbons). Anal. Calc.
for C19H21GeNO4 (399.9844): C 57.05, H 5.29, N 3.50. Found: C 57.26,
H 5.33, N 3.68.
d
¼ 0.72 (d, 3H, J ¼ 6.8 Hz, NCHCH3), 1.43 (s, 3H, CH3Ge), 1.58 (s, 3H,
NCH3), 2.62e2.65 (m,1H, CHCH3), 2.95e3.09 (m, 2H, NCH2), 4.96 (d,
1H, J ¼ 6.6 Hz, OCHPh), 6.85e7.01, 7.05e7.10, 7.57e7.67, 7.74e7.84
(4m, 10H, aromatic hydrogens). 13C NMR (100 MHz, C6D6, ppm):
d
¼ 10.71 (NCHCH3), 26.83 (CH3Ge), 45.40 (NCH3), 64.86 (NCH2CPh),
4.3.8. Reaction of 3 with (E)-PhC(O)CH ¼ CHPh. synthesis of
MeN(CH2CH2O)2Geecyclo-(OC(Ph)CHCH(Ph)) (21)
66.58 (NCHCH3), 73.65 (OCHPh), 77.62 (OCPh2), 125.12, 125.79,
126.35, 126.77, 127.21, 127.63, 127.90, 128.45, 128.79, 139.97, 146.57,
146.95 (aromatic carbons).
A solid (E)-PhC(O)CH ¼ CHPh (0.15 g, 0.74 mmol) was added to
a stirred solution of 3 (0.14 g, 0.74 mmol) in toluene (10 ml). The
reaction mixture was stirred for 4 days at room temperature and
volatiles were removed in vacuum. Then ether (10 ml) was added to
the residue, the precipitate was filtered off and recrystallized from
toluene to give 21 as a white solid. Yield 0.23 g (80%). 1H NMR
4.3.4. Reaction of 3 with MeI
To a stirred solution of MeN(CH2CH2O)2Ge (0.15 g, 0.80 mmol) in
toluene (5 ml) a solution of MeI (0.23 g, 1.60 mmol) in toluene
(5 ml) was added dropwise at room temperature. After 7 days all
volatiles were removed under reduced pressure. Then ether (10 ml)
was added to the residue, the precipitate was filtered to give
a white powder. According to NMR data, a mixture of unidentified
compounds was obtained.
(400 MHz, C6D6, ppm):
d
¼ 1.55 (s, 3H, CH3N), 1.94e2.20 (m, 4H,
2NCH2), 3.21e3.62 (m, 5H, CHPh and 2OCH2), 5.60e5.67 (m, 1H,
CH]C(O)Ph), 6.92e7.09, 7.34e7.42, 7.99e8.10 (3m, 10H, aromatic
hydrogens). 13C NMR (100 MHz, C6D6, ppm):
d
¼ 38.44 (CHPh),
42.61 (NCH3), 55.43, 55.69, 58.21, 58.26 (4OCH2), 98.39 (CH]C(O)
Ph), 125.64, 125.77, 125.93, 128.52, 129.28, 129.92 (aromatic
carbons), 145.38 (PhC(O) ¼ CH). The signals of two aromatic
carbons and one C(O) group were not found in spectrum. Anal. Calc.
for C20H23GeNO3 (398.012): C 60.35, H 5.82, N 3.52. Found: C 60.47,
H 5.78, N 3.45.
4.3.5. Reaction of 3 with Ph2S2. generation of [MeN(CH2CH2O)2]2Ge
(17), Ge(SPh)4 (18) and MeN(CH2CH2O)2Ge(SPh)2 (19)
To a stirred solution of 3 (0.06 g, 0.32 mmol) in THF (10 ml) was
added dropwise solution of Ph2S2 (0.07 g, 0.32 mmol) in THF (5 ml)
at ꢀ40 ꢁC. The reaction mixture was stirred for 20 min and allowed
to warm to room temperature. After 4 days the solvents were
removed under reduced pressure. Then THF (1 ml) was added to the
residue, the precipitate was filtered off to give 0.05 g of yellow
crystalline solid. According to NMR data, the yellow crystalline solid
4.3.9. Reaction of 3 with (E)-FcC(O)CH ¼ CHPh. synthesis of
MeN(CH2CH2O)2Ge-cyclo-(OC(Fc)CHCHPh) (22)
A solid (E)-FcC(O)CH ¼ CHPh (0.30 g, 0.95 mmol) was added to
a stirred solution of 3 (0.18 g, 0.95 mmol) in toluene (10 ml). The

M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
81
Table 7
Details of crystallographic experiments for 1, 3, 8, 10 and 18.
1
3
8
10
18
Formula
Fw
C20H26Ge2N2O4
503.65
C10H22Ge2N2O4
379.48
C34H38Ge2N2O4
683.84
C24H25GeNO2
432.04
C24H20GeS4
509.23
T, K
293(2)
150(2)
150(2)
150(2)
150(2)
Crystal system
Space group, Z
a (Å)
trigonal
Rꢀ3,9
monoclinic
P21/n, 2
monoclinic
C2/c, 4
monoclinic
P21, 2
orthorhombic
Pba2, 2
8.5827(9)
16.7199(17)
8.0734(9)
27.375(5)
27.375(5)
7.245(5)
6.3058(9)
12.6867(18)
8.9400(13)
98.023(2)
708.20(18)
1.780
16.9874(8)
18.1601(8)
11.8582(5)
122.365(1)
3089.9(2)
1.470
11.082(4)
6.249(2)
14.872(5)
91.123(5)
1029.6(6)
1.394
b (Å)
c (Å)
b
(o)
V (Å3)
4702(3)
1.601
2.905
1158.5(2)
1.460
1.691
dcalc (g cmꢀ3
)
Abs.coeff.(mmꢀ1
)
4.252
1.986
1.507
F(000)
q
2304
2.58e25.95
12,394
384
2.81e27.00
6571
1408
2.24e27.99
15,812
448
1.84e28.00
10,156
520
2.44e27.00
8663
Range (o)
Reflections collected
Unique reflections (Rint
)
2035 (0.0434)
2035/0/127
0.0210
1535 (0.0154)
1535/0/127
0.0151
3735 (0.0254)
3735/0/191
0.0214
4896 (0.0377)
4896/1/255
0.0472
2396 (0.0303)
2396/1/132
0.0194
Data/restraints/parameters
R1 [I > 2 (I)]
s
wR2 (all data)
0.0548
0.830
0.0404
1.079
0.0595
1.061
0.1291
1.072
0.0471
1.018
Goof on F2
Flack parameter
e
e
e
0.009(13)
1.046/ꢀ0.391
ꢀ0.003(9)
Largest difference peak/hole (e Åꢀ3
)
0.429/ꢀ0.185
0.316/ꢀ0.253
0.453/ꢀ0.240
0.373/-0.147
reaction mixture was stirred for 7 days at room temperature. The
volatiles were removed under reduced pressure. According to NMR
data, a mixture of initial compounds was obtained.
precipitate was filtered off to give 22 as an orange solid. Yield 0.23 g
(48%). 1H NMR (400 MHz, CDCl3, ppm):
d
¼ 2.43 (s, 3H, CH3N),
2.09e2.26, 2.65e2.78, 2.94e3.08 (3m, 4H, NCH2), 3.42e3.53 (m,1H,
CHPh), 3.68e4.23 (m, 6H, 2CH2O, C5H4), 4.26 (s, 5H, C5H5),
4.63e4.70 (m, 2H, C5H4), 5.13e5.18 (m, 1H, CH ¼ C(O)Fc), 7.31e7.51
(m, 5H, aromatic hydrogens). 13C NMR (100 MHz, CDCl3, ppm):
4.3.13. Reaction of 3 with (PhO)2P(O)N3
To
a stirred solution of MeN(CH2CH2O)2Ge (3) (0.10 g,
0.53 mmol) in toluene (15 ml) a solution of (PhO)2P(O)N3 (0.15 g,
0.53 mmol) in toluene (5 ml) was added at room temperature. After
d
¼ 37.33 (PhCH), 42.99 (CH3N), 55.49, 55.80 (2NCH2), 58.11, 58.20
4 days all volatiles were removed under reduced pressure.
According to NMR data, a mixture of unidentified compounds was
obtained.
(2OCH2), 66.49, 68.10, 81.28 (C5H4), 69.42 (C5H5), 96.07 (CHPh),
125.74, 128.46, 129.29, 142.15 (aromatic carbons),156.61 (CH ¼ C(O)
Fc). Anal. Calc. for C24H27FeGeNO3 (505.9311): C 56.98, H 5.38, N
2.77. Found: C 56.72, H 5.34, N 2.60.
4.4. Reactions without changes of germanium oxidation state
4.3.10. Reaction of 8 with (E)-FcC(O)CH ¼ CHPh. synthesis of
MeN(CH2CH2O)(CH2CPh2O)Ge-cyclo-(OC(Fc)CHCHPh) (23)
Analogously to 22, complex 23 was prepared from 8 (0.15 g,
0.44 mmol) and (E)-FcC(O)CH ¼ CHPh (0.14 g, 0.44 mmol) in
toluene (20 ml). The product was isolated by filtration to give 23 as
a yellow solid. Yield 0.13 g (45%). 1H NMR (400 MHz, C6D6, ppm):
4.4.1. Reaction of 8 with acetic anhydride. synthesis of MeN
[CH2CH2OC(O)CH3]2 (24) and Ge[OC(O)CH3]2 (25)
The solution of acetic anhydride (0.12 g, 1.20 mmol) in toluene
(10 ml) was added to solution of 3 (0.09 g, 0.50 mmol) in toluene
(10 ml). The reaction mixture was stirred for 7 days, then volatiles
were removed in vacuum and residue was washed with ether
(10 ml). According to NMR the mixture (1:1) of MeN[CH2CH2OC(O)
CH3]2 (24) j Ge[OC(O)CH3]2 (25) was obtained. Compound 24: 1H
d
¼ 1.61 (s, 3H, NCH3), 1.44e1.55 (m, 1H, NCH2CH2), 1.67e1.78 (m,
1H, NCH2CH2), 2.67, 2.86 (2d, 2H, J ¼ 13.5 Hz, AM system of
NCH2CPh2 group protons), 3.07e3.11 (m, 1H, PhCH), 3.32e3.41 (m,
2H, CH2O), 4.38 (s, 5H, C5H5), 4.02e4.14, 4.84e4.93 (2m, 4H, C5H4),
5.33e5.36 (m, 1H, CH ¼ C(O)Fc), 7.04e7.10, 7.20e7.38, 7.60e7.71
(3m, 15H, aromatic hydrogens). 13C NMR spectra is not recorded
due to insolubility of 23. Anal. Calc. for C36H35FeGeNO3 (658.123): C
65.70, H 5.36, N 2.13. Found: C 65.50, H 5.23, N 2.05.
NMR (400 MHz, C6D6, ppm):
d
¼ 1.67 (s, 6H, CH3CO), 2.12 (s, 3H,
NCH3), 2.50e2.60 (m, 4H, NCH2), 4.00 (t, 4H, J ¼ 5.7 Hz, OCH2). 13
C
NMR (100 MHz, C6D6, ppm):
d
¼ 20.39 (CH3CO), 41.31 (CH3N),
55.24, 58.79 (NCH2, OCH2), 170.00 (C]O). Compound 25: 1H NMR
(400 MHz, C6D6, ppm):
C6D6, ppm):
d
¼ 1.78 (s, 6H, CH3). 13C NMR (100 MHz,
d
¼ 21.42 (CH3), 166.30 (C]O).
4.3.11. Reaction of 3 with trimethylamine oxide
To
a
stirred solution of MeN(CH2CH2O)2Ge (3) (0.32 g,
4.4.2. Reaction of 2 with H2O. generation of BnN(CH2CH2OH)2
Water (0.02 g, 1.10 mmol) was added to solution of 2 (0.27 g,
1.00 mmol) in THF (5 ml). The reaction mixture was stirred for 5
days, volatiles were removed in vacuum. The residue was extrac-
ted with toluene (10 ml), filtered off, washed with toluene
(2 ꢂ 2 ml) and solvents were removed under reduced pressure to
1.70 mmol) in toluene (20 ml) trimethylamine oxide (0.13 g,
1.70 mmol) was added by small portions at room temperature.
After 4 days all volatiles were removed under reduced pressure.
Then ether (10 ml) was added to the residue, the precipitate was
filtered to give a white powder. According to NMR data, a mixture of
unidentified compounds was obtained.
give
a
yellow oil. According to NMR spectroscopy,
BnN(CH2CH2OH)2 was obtained [31]. 1H NMR (400 MHz, CDCl3,
ppm):
4.3.12. Reaction of 3 with S8
d
¼ 2.64 (t, 4H, J ¼ 5.1 Hz, CH2N), 3.55 (t, J ¼ 5.1 Hz, 4H,
To
a
stirred solution of MeN(CH2CH2O)2Ge (3) (0.15 g,
CH2O), 3.64 (s, 2H, PhCH2), 7.16e7.23 (m, 5H, aromatic hydrogens).
The solid formed during this reaction was insoluble in common
organic solvents.
0.80 mmol) in THF (15 ml) a sulfur in THF (10 ml) (0.03 g,
0.10 mmol) was added at room temperature. After 5 days all

82
M. Huang et al. / Journal of Organometallic Chemistry 706-707 (2012) 66e83
(k) A.V. Zabula, T. Pape, A. Hepp, F.E. Hahn, Organometallics 27 (2008) 2756;
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Experimental crystallographic data for 1, 3, 8, 10 and 18 are
given in Table 7. The data were collected on a Bruker SMART 1K (for
1) and on a Bruker SMART APEX II (for 3, 8, 10 and 18) diffrac-
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tometers using graphite monochromatized Mo-K
a radiation
ꢀ
(
l
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(2010) 11519;
and refined by full matrix least-squares on F2 [38]. In the structures
1, 8, 10 and 18 all hydrogen atoms were placed in calculated posi-
tions and refined using a riding model. As for 3, all hydrogen atoms
were found from difference Fourier synthesis and refined
isotropically.
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program using TZ2P basis [41,42]. Geometry optimization was
performed for all stable compounds and transition states. The
characters of the located stationary points (minimum or saddle
point) were determined by the calculation of Eigen values of the
matrix of the second derivatives of the energy with respect to the
coordinates of atomic nuclei. The correspondence between the
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Acknowledgment
Authors thank Russian foundation for basic research (Grants 09-
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Appendix A. Supplementary material
CCDC 836875e836879; contain the supplementary crystallo-
graphic data for 1, 3, 8, 10 and 18. These data can be obtained free of
charge from The Cambridge Crystallographic Data Center via www.
ccdc.cam.ac.uk/data_request/cif.
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