New stable germylenes, stannylenes, and related compounds. 1. Stable germanium(II) and tin(II) compounds M(OCH2CH2NMe2)2 (M = Ge, Sn) with intramolecular coordination metal-nitrogen bonds. Synthesis and structure

Article abstract of DOI:10.1021/om020719a

New stable monomeric germanium(II) and tin(II) compounds M(OCH₂CH₂NMe₂)₂ (M = Ge (1); M = Sn(2)), stabilized by two intramolecular coordination M←N bonds and containing no bulky groups on the metal atoms, were synthesized. The molecular and crystal structures of these compounds, and that of the previously synthesized compound (ArO)₂Sn (3; Ar = 2,4,6-(Me₂NCH₂)₃C₆H₂), were determined by X-ray diffraction analysis. The electronic structures of 1 and 2 were studied by the DFT method.

Full text of DOI:10.1021/om020719a

Organometallics 2003, 22, 1675-1681
1675
New Sta ble Ger m ylen es, Sta n n ylen es, a n d Rela ted
Com p ou n d s. 1. Sta ble Ger m a n iu m (II) a n d Tin (II)
Com p ou n d s M(OCH2CH2NMe2)2 (M ) Ge, Sn ) w ith
In tr a m olecu la r Coor d in a tion Meta l-Nitr ogen Bon d s.
Syn th esis a n d Str u ctu r e
Nikolay N. Zemlyansky,* Irina V. Borisova, and Marianna G. Kuznetsova
A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences (TIPS RAS),
29 Leninsky prosp., 119991-GSP-1, Moscow, Russian Federation
Victor N. Khrustalev
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation
Yuri A. Ustynyuk,* Mikhael S. Nechaev, and Valery V. Lunin
Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory,
11989 Moscow, Russian Federation
J acques Barrau* and Ghassoub Rima
Laboratoire d’He´te´rochimie Fondamentale et Applique´e, UPRES-A 5069 (CNRS),
Universite´ Paul-Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 4, France
Received September 5, 2002
New stable monomeric germanium(II) and tin(II) compounds M(OCH2CH2NMe2)2 (M )
Ge (1); M ) Sn (2)), stabilized by two intramolecular coordination MrN bonds and containing
no bulky groups on the metal atoms, were synthesized. The molecular and crystal structures
of these compounds, and that of the previously synthesized compound (ArO)2Sn (3; Ar )
2,4,6-(Me2NCH2)3C6H2), were determined by X-ray diffraction analysis. The electronic
structures of 1 and 2 were studied by the DFT method.
In tr od u ction
characterize the sterically stabilized, monomeric aryloxy
compounds (ArO)2M (M ) Ge, Sn; Ar ) C6H2Me-4-t-
Bu2-2,6).2a The diverse alkoxy derivatives (RO)2M
(M ) Ge, Sn) also have been described; depending on
the size of the RO groups, they are usually found to be
cyclodimeric (R ) t-Bu)3 or oligomeric (R ) Me, Et,
i-Pr),1b associated through intermolecular MrO coor-
dination, and, less frequently, monomeric (R ) t-Bu3C).2c
Furthermore, it is noteworthy that the series of divalent
compounds of group 14 elements R2M and (RX)2M have
been thermodynamically stabilized in monomeric form
by MrY (Y ) N, O) intramolecular coordination of
donor atom substituted sidearms of the bulky groups
R. In the chemistry of germanium(II) and tin(II) this is
documented by various stable aryl derivatives with one
In the past decade, considerable progress has been
made in the chemistry of stable organic derivatives of
divalent germanium and tin.1 Compounds of the type
R2M, containing hydrocarbon groups on the metal
atoms, are heavier congeners of carbenes (the true
germylenes and stannylenes). Their kinetic stability
afforded by bulky substituents R rests exclusively on
steric factors. Another and rather special group of
divalent species consists of the sterically hindered
compounds (RX)2M, in which the organic substituent R
is attached to the element through an electronegative
heteroatom (X ) O, S, N).1b,2 In all of these compounds
the frontier orbitals are strongly perturbed by interac-
tions with the orbitals of lone electron pairs of the
heteroatoms. Accordingly, their structures and reactivi-
ties are quite unique and different from those of
intrinsic singlet carbene analogues. Lappert and co-
workers were the first to prepare and structurally
(2) (a) C¸ etinkaya, B.; Gu¨mru¨kc¸u¨, I.; Lappert, M. F.; Atwood, J . L.;
Rogers, R. D.; Zaworotko, M. J . J . Am. Chem. Soc. 1980, 102, 2088.
(b) Hascall, T.; Rheingold, A. L.; Guzei, I.; Parkin, G. Chem. Commun.
1998, 101. (c) Fjeldberg, T.; Hitchcock, P. B.; Lappert, M. F.; Smith,
S. J .; Thorne, A. J . J . Chem. Soc., Chem. Commun. 1985, 939. (d)
Hitchcock, P. B.; Lappert, M. F.; Samways, B. J .; Weinberg, E. L. J .
Chem. Soc., Chem. Commun. 1983, 1492-1493. (e) Gyname, M. J . S.;
Harris, D. H.; Lappert, M. F.; Power, P. P.; Rivie´re, P.; Rivie´re-Baudet,
M. J . Chem. Soc., Dalton Trans. 1977, 2004. (f) Fjeldberg, T.; Hope,
H.; Lappert, M. F.; Power, P. P.; Thorne, A. J . J . Chem. Soc., Chem.
Commun. 1983, 639-641.
* To whom correspondence should be addressed. E-mail: N.N.Z.,
zemlyan@mail.cnt.ru; Y.A.U., yust@nmr.chem.msu.su; J .B., barrau@
chimie.ups-tlse.fr.
(1) Recent review: (a) Tokitoh, N.; Okazaki, R. Coord. Chem. Rev.
2000, 210, 251. (b) Barrau, J .; Rima, G. Coord. Chem. Rev. 1998, 178-
180, 593.
(3) Veith, M. Angew. Chem., Int. Ed. Engl. 1987, 26, 1-14.
10.1021/om020719a CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/18/2003

1676 Organometallics, Vol. 22, No. 8, 2003
Zemlyansky et al.
or two intramolecular coordination bonds4 and by some
examples of aryloxy compounds.5 It is doubtless of
interest to obtain more information on the relative
contributions of the different factors (thermodynamic
and kinetic) to the stabilization of germanium(II) and
tin(II) compounds. Herein we report the synthesis and
structures of stable, sterically nonhindered bis[2-(di-
methylamino)ethoxy]germanium and -tin M(OCH2CH2-
NMe2)2 (M ) Ge (1); M ) Sn (2)) compounds with
intramolecular coordination MrN bonds. The electronic
and molecular structures of these compounds is also
analyzed by density functional theory, and the MrN
binding energies are calculated. The X-ray study of the
previously synthesized bis{2,4,6-tris[(dimethylamino)-
methyl]phenoxy}tin (3)5c-f also is reported.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 1-3
1a
2b
3
M-O
MrN
1.868(1), 1.864(1);
1.861(1), 1.870(1)
2.329(2), 2.337(2);
2.324(2), 2.346(2)
2.056(2)
2.071(2), 2.073(2)
2.458(2)
2.427(3), 2.478(3)
O-M-O 98.79(6); 98.91(7)
96.52(11) 91.89(9)
NfMrN 156.38(6); 156.11(6) 145.78(9) 156.56(8)
O-MrN 80.48(6), 80.78(6),
83.89(6), 84.21(6);
76.71(6),
80.68(6)
80.75(8), 81.18(9),
81.55(9), 84.10(8)
80.22(6), 81.00(6),
83.85(6), 84.00(6)
a
b
For the two independent molecules. The molecule occupies
a special position on the 2-fold axis (C2).
A more convenient method for the synthesis of 1 and
2 is the alcoholysis of Lappert’s metal amides M[N-
(SiMe3)2]2 (M ) Ge, Sn)2e by (dimethylamino)ethanol,
which occurs rapidly and in almost quantitative yield
(eq 2). This method has been used previously for the
Resu lts a n d Discu ssion
Syn th esis of Bis[2-(d im eth yla m in o)eth oxy]ger -
m a n iu m (1) a n d -tin (2). Bis[2-(dimethylamino)eth-
oxy]germanium (1) and -tin (2) were prepared by two
methods. The redistribution of the functional groups
between the divalent species MCl2 and Et3MOCH2CH2-
NMe2 (M ) Ge, Sn) readily occurs at room temperature
in THF or diethyl ether (eq 1), giving moderate yields
of compounds 1 and 2 as white, crystalline solids, which
are soluble in standard organic solvents, stable under
anaerobic conditions, and easily sublimed in vacuo.
M¨ (NSiMe3)2 + 2HOCH2CH2NMe2 f
M¨ (OCH2CH2NMe2)2 + 2HN(SiMe3)2 (2)
1, 2
preparation of bis{2,4,6-tris[(dimethylamino)methyl]-
phenoxy}tin (3) and its germanium and lead analogues.5c
1
In the H NMR spectra of compounds 1 and 2, recorded
at room temperature in benzene-d6 or toluene-d8 solu-
tions, the OCH2CH2N signals appear as triplets and
those of the methyl groups on the nitrogen atoms as
singlets. The signals in the spectrum of 1 are noticeably
broadened, suggesting that a fairly rapid process occurs
in solution, during which the MrN coordination bonds
open and close (see below). The study of the dynamic
NMR spectra over a wide temperature interval is now
in progress.
Molecu la r a n d Cr ysta l Str u ctu r es of Bis[2-(d i-
m eth yla m in o)eth oxy]ger m a n iu m (1) a n d -tin (2).
The X-ray diffraction study showed that compounds 1
and 2 are monomers. These are the first structurally
characterized monomeric germanium(II) and tin(II)
compounds stabilized by only two intramolecular GerN
coordination bonds in the absence of steric shielding of
the metal atoms (Figures 1 and 2). The MIIrN bond
lengths are 2.329(2), 2.337(2) Å and 2.324(2), 2.346(2)
Å for two independent molecules of 1 and 2.458(2) Å
for 2 (Table 1). The GeII-N bond lengths for 1 are
considerably larger than the lengths of all the previously
known GeIIrN coordination bonds6 (except for the
diazogermylene ArGeC(N2)SiMe3 [Ar ) 2,6-(iPr2NCH2)2-
C6H3]).7 In contrast, the SnIIr N bond lengths in 2 are
much shorter than the previously reported lengths of
axial SnIIrN bonds (range of values 2.516(3)-2.660(3)
Å).4b,c,5a,8a,b The MII-O bond lengths (1.864(1), 1.868-
(1), and 1.861(1), 1.870(1) Å for two independent mol-
ecules of 1 and 2.056(2) Å for 2 (Table 1)) are typical
MCl2 + 2Et3M′OCH2CH2NMe2 f
M¨ (OCH2CH2NMe2)2 + 2Et3M′Cl (1)
1, 2
1: MCl2 ) GeCl2‚(dioxane), M′ ) Ge
2: M, M′ ) Sn
(4) Selected examples: (a) Drost, C.; Hitchcock, P. B.; Lappert, M.
F.; Pierssens, L. J .-M. Chem. Commun. 1997, 1141. (b) J astrzebski, J .
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Cardin, C. J .; Cardin, D. J .; Constantine, S. P.; Todd, A. K.; Teat, S.
J .; Coles, S. Organometallics 1998, 17, 2144. (j) Cardin, C. J .; Cardin,
D. J .; Constantine, S. P.; Drew, M. G. B.; Rashid, H.; Convery, M. A.;
Fenske, D. J . Chem. Soc., Dalton Trans. 1998, 2749. (k) Benet, S.;
Cardin, C. J .; Cardin, T. J .; Constantine, S. P.; Heath, P.; Rashid, H.;
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(l) J olly, B. S.; Lappert, M. F.; Engelhardt, L. M.; White, A. H. J . Chem.
Soc., Dalton Trans. 1993, 2653. (m) Al-J uaid, S. S.; Avent, A. G.;
Eaborn, C.; Hill, M. S.; Hitchcock, P. B.; Patel, D. J .; Smith, J . D.
Organometallics 2001, 20, 1223. (n) J utzi, P.; Keitemeyer, S.; Neu-
mann, B.; Stammler, A.; Stammler, H.-J . Organometallics 2001, 20,
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Group Met. Chem. 1999, 22, 703. (g) Kitamura, C.; Yoneda, A.; Sugiura,
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Chem.-Chem. Z. 2000, 342, 574.

New Stable Germylenes and Stannylenes
Organometallics, Vol. 22, No. 8, 2003 1677
F igu r e 1. Molecular structure of compound 1. The two crystallographically independent molecules presenting chiral
enantiomers are shown (ellipsoids are drawn at the 50% probability level).
metry C2, and the layers formed by them have sym-
metry pba2. However, the symmetry of the layers is
retained only in the case of 2, in the crystal of which
the layers are congruently imposed on each other (with
retention of the polar axis). In the crystal structure of
1, the layers are incongruently imposed on each other
with the turning at 180°; the polar axis is lost due to
that.
A wide set of pseudo-symmetric operations, which are
manifested as absences of the corresponding reflections
(see the Supporting Information), takes place in crystals
1 and 2 due to the characteristic shifts of the layers
relative to each other. The crystal structures of com-
pounds 1 and 2 represent one more striking example
for the layer-in-layer three-dimensional packing of
molecules described recently by Britton10 determining
the appearance of different pseudo-symmetric opera-
tions in crystals of compounds, which have, as a rule,
intrinsic symmetry elements.
F igu r e 2. Molecular structure of compound 2 (ellipsoids
are drawn at the 50% probability level).
The intramolecular SnrN coordination bonds, which
in compounds 1-3 result in the appearance of chirality
and favor crystallization of compounds 1 and 2 in
noncentrosymmetric space groups, could be used as an
important factor in the design of new materials with
some important physical properties (piezo- and segne-
toelectrics, nonlinear optical materials, etc.).
M-O distances for M(OR)2 compounds (range of values
for Ge-O bond lengths2b,4e,9a 1.765(6)-1.878(4) Å; range
of values for Sn-O bond lengths2b,5a,b,f-i,9a,b 1.956(7)-
2.202(6) Å). The O-M-O bond angles (98.79(6) and
98.91(7)° for two independent molecules of 1 and 96.52-
(11)° for 2 (Table 1)) are somewhat greater than that
observed for the sterically hindered compound 3 (see
below), indicating the absence of steric strain. The
central M(II) atom in 1 and 2 has a distorted-trigonal-
bipyramidal configuration (Table 1) with a lone electron
pair in the equatorial position. It occupies a spiro
position between two five-membered heterocycles in the
envelope conformation.
Both compounds 1 and 2 are chiral. The enantiomers
cocrystallize in noncentrosymmetric space groups P212121
(1) and Aba2 (2). The molecular packings in crystals of
1 and 2 are layered along the direction [001]. Note that,
due to the equality of the MIIrN bonds, molecules 1 and
2 (unlike molecule 3; see below), have intrinsic sym-
Molecu la r Str u ctu r e of Bis{2,4,6-tr is[(d im eth yl-
a m in o)m eth yl]p h en oxy}tin (3). The X-ray structural
study of 3 shows that the tin atom has a distorted-
trigonal-bipyramidal coordination, showing unambigu-
ously that the stabilizing effect of the aryloxy ligand in
the compound is due to the formation of two stable
intramolecular SnrN coordination bonds. The lone
electron pair and the oxygen atoms occupy the equato-
rial positions, and the nitrogen atoms are in the axial
positions. As for 2, the SnrN bond lengths (2.427(3) and
2.478(3) Å; Table 1 and Figure 3) are much shorter than
those reported for analogous bonds; however, in contrast
to that observed for 2 these two Sn-N bonds have
significantly different lengths, although from the formal
point of view these bonds should be chemically equiva-
(9) (a) Suh, S.; Hoffman, D. M. Inorg. Chem. 1996, 35, 6164. (b)
Barnhart, D. M.; Clark, D. L.; Watkin, J . G. Acta Crystallogr., Sect. C
1994, 50, 702.
(10) Britton, D. Acta Crystallogr., Sect. B 2000, 56, 828.

1678 Organometallics, Vol. 22, No. 8, 2003
Zemlyansky et al.
F igu r e 3. Molecular structure of compound 3 (ellipsoids are drawn at the 50% probability level).
F igu r e 4. DFT calculated structures of molecules 1, 2, 1a , 2a , 1b, and 2b.
lent. A search of the Cambridge Crystallographic Da-
tabase6 revealed that such nonequivalency is charac-
teristic of tin(II) compounds with Sn-N donor-acceptor
bonds; however, the bond lengths in them equalize if
the lone electron pair of the Sn(II) atom is involved in
Stu d y of th e Str u ctu r e of Bis[2-(d im eth yla m i-
n o)eth oxy]ger m a n iu m (1) a n d -tin (2) by th e DF T
Meth od . The structures of 1 and 2 were studied by the
density functional (PB E functional, ECP for innermost
electrons and TZ2p basis set for valence shell) using the
PRIRODA program.12 This approach and this program
have been used earlier by us successfully to study the
structure of organoelement betaines, compounds with
multiple bonds R2MdX and R2M: (M ) Si, Ge, Sn; X )
CR2, O, S, NR, Se).13a-d
The calculations satisfactorily reproduce the structure
and geometric parameters of molecules 1 and 2 (Table
2, Figure 4). On the potential energy surfaces of 1 and
2 we also found local minima for isomeric structures 1a ,
1b, 2a , and 2b, in which one (structures a ) and both
coordination bonds (structures b) are open. Opening of
the first coordination MrN bond (transitions 1 f 1a
and 2 f 2b) requires 7.6 and 10.2 kcal/mol for 1 and 2,
11a
coordination with acceptors such as BH3 or in binding
to transition metals.4b,c,11b,c The additional interactions
of both types have no substantial effect on the coordina-
tion SnrN bond lengths (range of values 2.456(2)-
2.608(4) Å, mean value 2.543 Å). The SnII-O bond
lengths (2.071(2) and 2.073(2) Å; Table 1) in 3 compare
well with the range found in the previously studied
alkoxy- and aryloxytin(II) compounds2b,5a,b,f-i,9a,b (range
of values 1.956(7)-2.202(6) Å). The O-Sn-O bond angle
91.89(9)° (Table 1) is close to 90° due to the presence of
two intramolecular coordination bonds and steric effects.
Compound 3 is chiral, as are 1 and 2. Both of its
enantiomers are cocrystallized in the centrosymmetric
space group P21/n. The packing of molecules 3 in a
crystal is stacked along the y axis. The molecules are
arranged at their van der Waals distances.
(12) Laikov, D. N. Ph.D. Dissertation, Moscow State University,
Moscow, 2000.
(13) (a) Nechaev, M. S.; Borisova, I. V.; Zemlyansky, N. N.; Laikov,
D. N.; Ustynyuk, Yu. A. Russ. Chem. Bull. (Engl. Transl.) 2000, 49,
1823. (b) Borisova, I. V.; Zemlyansky, N. N.; Khrustalev, V. N.;
Kuznetzova, M. G.; Ustynyuk, Yu. A.; Nechaev, M. S. Russ. Chem. Bull.
(Engl. Transl.) 2001, 50, 1679. (c) Ustynyuk, Yu. A.; Nechaev, M. S.;
Laikov, D. N.; Borisova, I. V.; Zemlyansky, N. N.; Khrustalev, V. N.
Russ. Chem. Bull. (Engl. Transl.) 2001, 50, 771. (d) Borisova, I. V.;
Nechaev, M. S.; Khrustalev, V. N.; Zemlyansky, N. N.; Ustynyuk, Yu.
A. Russ. Chem. Bull. (Engl. Transl.) 2002, 51, 721.
(11) (a) Drost, C.; Hitchcock, P. B.; Lappert, M. F. Organometallics
1998, 17, 3838. (b) Abicht, H.-P.; J urkschat, K.; Tzschach, A.; Peters,
K.; Peters, E.-M.; von Schnering, H. G. J . Organomet. Chem. 1987,
326, 357. (c) J astrzebski, J . T. B. H.; Sypkens, H. A. J .; des Tombe, F.
J . A.; van der Schaaf, P. A.; Boersma, J .; van Koten, G.; Spek, A. L.;
Duisenberg, A. J . M. J . Organomet. Chem. 1990, 396, 25.

New Stable Germylenes and Stannylenes
Organometallics, Vol. 22, No. 8, 2003 1679
Ta ble 2. Geom etr y P a r a m eter s of Molecu les 1, 1a ,
1b, 2, 2a , a n d 2b Accor d in g to DF T Ca lcu la tion sa
param
1
2
1a
2a
1b
2b
M-O1
1.896
1.896
2.428
2.428
98.4
2.082
2.082
2.556
2.556
96.3
1.844
1.861
2.280
5.097
99.0
2.035
2.048
2.435
5.420
97.8
1.799
1.799
5.081
5.081
94.3
1.989
1.989
5.222
5.222
91.9
M-O2
M-N1
M-N2
O1-M-O2
O1-M-N1
80.1
76.0
80.7
76.5
a
Internuclear distances in Å, and valence angles in deg.
F igu r e 6. LUMO in the molecules 1, 1a , and 1b (the
LUMO’s in 2, 2a , and 2b have similar shapes).
could be expected, the coordination bonds in isomers 1a
and 2a are stronger than those in isomers 1 and 2.
Analysis of the populations shows that the HOMO’s in
1 and 2 are localized on the metal atoms and occupied
by a lone electron pair, as shown for 1 (Figure 5). In
isomers a the HOMO’s are localized on the nitrogen
atoms of the NMe2 groups, which are not involved in
coordination, and in isomers b they are localized on the
oxygen and nitrogen atoms. The energies of the molec-
ular orbitals of the lone electron pair of the metal atoms
regularly decrease in the order 1 (2) > 1a (2a ) > 1b
(2b) (Table 3). The LUMO’s in all isomers of 1 and 2
are localized on the metal atoms (Figure 6). In b isomers
they represent pure 4pz and 5pz atomic orbitals of
germanium and tin in 1b and 2b, respectively. In
isomers 1 (2) and 1a (2a ) the LUMO’s contain additional
F igu r e 5. HOMO’s in the molecules 1, 1a , and 1b (the
HOMO’s in 2, 2a , and 2b have similar shapes).
respectively, and is accompanied by considerable short-
ening of the second bond (by 0.148 Å in 1a and 0,121 Å
in 2 a ). The lengths of both M-O bonds are simulta-
neously shortened, and the M-O bonds in the chelate
cycle remain shorter. The cleavage of the second chelate
cycle (transitions a f b) requires 11.6 kcal/mol in the
case of 1 and 16.4 kcal/mol in the case of 2. Thus, as

1680 Organometallics, Vol. 22, No. 8, 2003
Zemlyansky et al.
Ta ble 3. F r on tier Or bita l En er gies (eV) for 1, 1a ,
1b, 2, 2a , a n d 2b
[(Dim eth yla m in o)eth oxy]tr ieth ylger m a n iu m , Et 3Ge-
OCH2CH2NMe2. To a solution of ethoxytriethylgermanium
(8.95 g, 43.7 mmol) in 10 mL of benzene was added a solution
of (dimethylamino)ethanol (3.92 g, 44 mmol) in 5 mL of
benzene. The mixture was heated at reflux for 2 h. After
removal of the volatiles the colorless residue was distilled in
vacuo to give Et3GeOCH2CH2NMe2. Yield: 6.9 g, 64%. Bp: 73-
orbital
LUMO
HOMO
1
1a
1b
2
2a
2b
-0.11 -0.88 -2.36 -0.43 -1.46 -2.72
-4.36a -4.33 -4.64 -4.57a -4.76 -4.57
HOMO - 1 -5.00 -5.18a -4.70 -4.91 -5.25a -4.65
HOMO - 2 -5.52 -5.78 -6.03a -5.42 -5.41 -5.86a
20
1
74 °C/1 Torr. nD ) 1.4494. H NMR: δ 0.88 (q, 6H, GeCH2-
a
3
3
Lone electron pair (LEP) orbital localized on metal atom.
CH3, J HH ) 7.6 Hz), 1.00 (t, 9H, GeCH2CH3, J HH ) 7.6 Hz),
3
2.18(s, 6H, NMe2), 2.36 (t, 2H, NCH2, J HH ) 6.7 Hz), 3.61 (t,
2H, OCH2, J HH ) 6.7 Hz). Anal. Calcd for C10H25GeNO: C,
Ta ble 4. Hir tsch feld Atom ic Ch a r ges (a u ) in
Molecu les 1, 1a , 1b, 2, 2a , a n d 2b
3
48.45; H, 10.16; N, 5.65. Found: C, 48.33; H, 10.09; N, 5.51.
[(Dim eth yla m in o)eth oxy]tr ieth yltin , Et 3Sn OCH2CH2-
NMe2. In a similar way the reaction of methoxytriethylstan-
nane (13.44 g, 56.8 mmol) with (dimethylamino)ethanol (5.32
atom
1
1a
1b
2
2a
2b
M
+0.22
-0.26
-0.03
-0.26
-0.03
+0.25
-0.27
-0.02
-0.24
-0.09
+0.32
-0.22
-0.09
-0.22
-0.09
+0.29
-0.28
-0.04
-0.28
-0.04
+0.35
-0.29
-0.03
-0.27
-0.09
+0.42
-0.25
-0.09
-0.25
-0.09
O1
N1
O2
N2
g, 59.8 mmol) afforded Et3SnOCH2CH2NMe2 as a colorless
20
liquid. Yield: 11.68 g (70%). Bp: 88-89 °C/1 Torr. nD
)
1.4838. 1H NMR: δ 0.79-1.1 m, 6H, SnCH2CH3), 1.1-1.43
(m, 9H, SnCH2CH3), 2.14 (s, 6H, Me2N), 2.34 (t, 2H, CH2N,
3J HH ) 5.5 Hz), 3.85 (t, br, 2H, CH2O, J HH ) 5.5 Hz). 13C
3
contributions from the MO of nitrogen. The energies of
the LUMO’s also regularly decrease in the order 1 (2)
> 1a (2a ) > 1b (2b) (Table 3). It follows from the data
presented for the energies of frontier orbitals that the
reactivity of 1 and 2 in the series 1 (2) f 1a (2a ) f 1b
(2b) decreases with respect to electrophilic reactants but
increases with respect to nucleophiles. Charge distribu-
tion in isomers 1 (2), 1a (2a ), and 1b (2b) (Table 4)
shows that positive charges on the metal atoms increase
somewhat with opening of the coordination bonds in the
series 2 (3) > 2a (3a ) > 2b (3b), according to expecta-
tions. Changes in charges on the oxygen atoms are
insignificant. The negative charge on the nitrogen atom
increases when the coordination bond is cleaved.
1
119/117
NMR: δ 6.33 (SnCH2CH3,
J
) 381.5/364.5 Hz), 10.18
) 23.14), 46.30 (Me2N), 64.01 (CH2N),
Sn
2
119/117
(SnCH2CH3,
J
Sn
65.06 (CH2O). Anal. Calcd for C10H25NOSn: C, 40.85; H, 8.57;
N, 4.76. Found: C, 41.07; H, 8.52; N, 4.64.
Bis[(dim eth ylam in o)eth oxy]ger m an iu m , Ge(OCH2CH2-
NMe2)2 (1). (a) The mixture of Et3GeOCH2CH2NMe2 (6.46 g,
26.1 mmol) and GeCl2‚(dioxane) (3.02 g, 13.0 mmol) in 40 mL
of THF was kept at ambient temperature for 12 h. The solvent
was removed by distillation until the vapor temperature
reached 78 °C. Et3GeCl from the residual viscous oil was
distilled at 50-60 °C/1 Torr into a trap cooled by liquid
nitrogen. The residue in the distillation flask after recrystal-
lization from hexane at -12 °C gave 1 as white crystals.
Yield: 2.23 g (69%). Mp: 67-68 °C. The substance can be
purified additionally by sublimation at 70 °C/10-3 Torr. 1H
3
NMR: δ 2.22 (s, 12H, Me2N), 2.38 (t, br, 4H, CH2N, J HH
)
Con clu sion
5.2 Hz), 4.14 (t, 4H, CH2O, J HH ) 5.6 Hz). 13C NMR: δ 43.48
(Me2N), 60.41 (CH2N), 63.08 (br, CH2O). Because of the
extremely high sensitivity of compound 1 to moisture and
oxygen, a satisfactory elemental analysis was not obtained. A
second distillation of the liquid collected in the trap gave 3.88
g (76%) of Et3GeCl.
3
These results show that two powerful stabilizing
electronic effects such as the formation of the MIIrN
coordination bonds and the σ-acceptor ability of the
oxygen atoms in the alkoxy and aryloxy derivatives of
divalent tin and germanium are sufficient to allow the
existence of monomer species 1 and 2 at standard
temperature and under anaerobic conditions without
substantial steric shielding of the metal atoms. Other
compounds of this type will be described elsewhere.
(b) A 0.75 g (8.4 mmol) portion of (dimethylamino)ethanol
was added to 1.62 g (4.1 mmol) of bis[bis(trimethylsilyl)amino]-
germanium(II). The exothermic reaction was complete in
several minutes. After that hexamethyldisilazane was removed
in vacuo. The residue was recrystallized from hexane at -12
°C or sublimed at 70 °C/10-3 Torr. Yield: 1.01 g (98%). The
melting point and NMR parameters of this product were
identical with those described above.
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were carried out
under a purified argon atmosphere using standard Schlenk
and high-vacuum-line techniques. The commercially available
solvents were purified by conventional methods and distilled
immediately prior to use. Et3GeOEt,14 Et3SnOMe,15 Ge[N-
(SiMe3)2]2,5c Sn[N(SiMe3)2]2,5c and GeCl2‚(dioxane)16 were pre-
pared according to the procedures described in the literature.
Bis[(d im eth yla m in o)eth oxy]tin , Sn (OCH2CH2NMe2)2
(2). (a) A mixture of Et3SnOCH2CH2NMe2 (5.56 g, 18.9 mmol)
and SnCl2 (1.77 g, 9.3 mmol) in 50 mL of ether was kept at
ambient temperature for 12 h. After removal of the solvent
by distillation (until the vapor temperature rose to 78 °C) Et3-
SnCl from the residue was distilled at 50-60 °C/1 Torr and
condensed in the trap cooled by liquid nitrogen. The solid
residue in the distillation flask after recrystallization from
hexane at -12 °C gave 2 as white crystals. Yield: 1.3 g (47%).
Mp: 45-46 °C. 3 sublimes at 50-70 °C/10-3 Torr. Distillation
of the liquid collected in the trap gave 4.3 g (95%) of Et3SnCl.
1H NMR (C6D5CD3): δ 2.30 (s, 12H, Me2N), 2.53 (t, 4H, CH2N,
NMR spectra were recorded on
a Bruker AM-360 NMR
spectrometer at 360.134 MHz (1H), 90.555 MHz (13C), and
111.92 MHz (119Sn) for the samples in C6D6, except where
indicated. Chemical shifts are relative to SiMe4 for H and C
or indirectly referenced to TMS via the solvent signals and
relative to SnMe4 for 119Sn. The accuracy of the coupling
constant determination is (0.1 Hz, and the accuracy of
chemical shift measurements is (0.01 ppm (1H), (0.05 ppm
(13C), and (0.2 ppm (119Sn).
3
3J HH ) 5.5 Hz), 4.18 (t, 4H, CH2O, J HH ) 5.5 Hz). 13C NMR:
δ 44.51 (Me2N), 62.79 (CH2N), 63.14 (CH2O). 119Sn NMR (C6D5-
CD3): δ -309.9. Anal. Calcd for C8H20N2O2Sn: C, 32.58; H,
6.83; N, 9.50. Found: C, 32.24; H, 6.63; N, 9.40.
(b) (Dimethylamino)ethanol (1.39 g, 15.6 mmol) was added
to bis[bis(trimethylsilyl)amino]tin(II) (3.39 g, 7.7 mmol). After
the exothermic reaction was completed, hexamethyldisilazane
was removed in vacuo. The residue was recrystallized from
hexane at -12 °C or sublimed at 50-60 °C/10-3 Torr. Yield:
(14) Satge´, J . Bull. Soc. Chim. Fr. 1964, 630.
(15) Mehrotra, R. C.; Gupta, V. D. J . Organomet. Chem. 1965, 4,
237.
(16) Fjeldberg, T.; Haaland, A.; Schilling, B. E. R.; Lappert, M. F.;
Thorne, A. J . Chem. Soc., Dalton Trans. 1986, 1551.

New Stable Germylenes and Stannylenes
Organometallics, Vol. 22, No. 8, 2003 1681
Ta ble 5. Cr ysta llogr a p h ic Da ta for 1-3
1
2
3
empirical formula
fw
C8H20N2O2Ge
248.85
C8H20N2O2Sn
294.95
C30H52N6O2Sn
647.47
temp (K)
cryst size (mm)
cryst syst
space group
a, Å
110(2)
110(2)
148(2)
0.4 × 0.3 × 0.2
orthorhombic
P212121
10.1606(12)
11.2693(14)
20.387(2)
90
0.4 × 0.2 × 0.2
orthorhombic
Aba2
11.7705(18)
10.1142(18)
10.061(2)
90
0.3 × 0.3 × 0.2
monoclinic
P21/n
23.355(6)
6.260(2)
23.778(6)
90
106.18(2)
90
3338.6(16)
4
1.288
1360
0.799
2.16-27.06
-10 e h e 27
-8 e k e 7
-30 e l e 29
7074
b, Å
c, (Å)
R (deg)
â (deg)
90
90
90
90
γ (deg)
V (Å3)
2334.3(5)
8
1.416
1040
2.601
2.06-30.02
-14 e h e 14
-15 e k e15
-28 e l e 28
27535
6786
5412
0.0230; 0.0436
0.0330; 0.0449
6786/0/395
0.887
1197.8(4)
4
1.636
592
2.110
4.03-30.06
-16 e h e 16
-14 e k e 14
-14 e l e 14
6714
1709
1625
0.0190; 0.0464
0.0202; 0.0472
1709/1/100
1.060
Z
dc (Mg m-3
F(000)
)
µ (mm-1
)
θ range (deg)
index ranges
no. of rflns collected
no. of unique rflns
no. of rflns with I > 2σ(I)
R1; wR2 (I > 2σ(I))
R1; wR2 (all data)
no. of data/restraints/params
GOF on F2
6894
5482
0.0367; 0.0814
0.0563; 0.1052
6847/0/560
1.046
Flack param
0.003(7)
0.001
0.436/-0.354
0.862; 0.483
0.48(4)
0.001
0.865/-0.576
0.656; 0.425
none
0.001
1.151/-0.633
none
max shift/error
largest diff peak/hole (e Å-3
)
abs cor Tmax; Tmin
2.1 g (92%). The melting point and NMR parameters of this
product were identical with those described above. Using
method b for the preparation of 1 or 2, one has to give special
attention to the purification of M[N(SiMe3)2]2 (M ) Ge, Sn)
from highly volatile LiN(SiMe3)2. In the presence of the latter,
compounds 1 and 2 form the ate complexes LiM(OCH2CH2-
NR2)3, which will be described elsewhere. In the reaction of
M[N(SiMe3)2]2 (M ) Ge, Sn) with LiN(SiMe3)2 and (dimethyl-
amino)ethanol at an equimolar ratio of the reactants these
complexes are formed in quantitative yield.
Cr ysta llogr a p h y. Data were collected on a Bruker SMART
CCD 1000 diffractometer (compounds 1 and 2) and a Syntex
P21 four-circle automated diffractometer (compound 3); the
reflection intensities in the case of compounds 1 and 2 were
corrected for absorption.17 For details see Table 5. The
structures were solved by direct methods and by full-matrix
least-squares refinement with anisotropic thermal parameters
for non-hydrogen atoms. The absolute structure of the com-
pound 1 was objectively determined by the refinement of the
Flack parameter, which was 0.003(7). The value of the Flack
parameter for compound 2, 0.48(4), indicates that the absolute
structure in this case cannot be determined unambiguously
due to the specific centrosymmetric arrangement of heavy
atoms Sn(II). The hydrogen atoms were objectively localized
in the difference Fourier map and were refined isotropically.
All calculations were carried out by use of the SHELXTL (PC
version 5.10) program.18
Ack n ow led gm en t. This work was financially sup-
ported by the Russian Foundation for Basic Research
(Project Nos. 00-03-32807a, 00-15-97359, and 00-03-
32889a).
Su p p or tin g In for m a tion Ava ila ble: Tables of atom
coordinates, bond lengths and angles, and anisotropic dis-
placement parameters for 1-3 and tables of the space group
determinations for 1 and 2. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM020719A
(17) Sheldrick, G. M. SADABS (version 2.01): Bruker/Siemens Area
Detector Absorption Correction Program; Bruker AXS, Madison, WI,
1998.
(18) Sheldrick, G. M. SHELXTL (version 5.10); Bruker AXS, Madi-
son, WI, 1997.