Journal of Organometallic Chemistry 628 (2001) 11 – 24
www.elsevier.nl/locate/jorganchem
Stereoselective insertion of GeCl
2
into tungsten – chlorine bonds of
aminomethylene and aminocarbyne complexes
Alexander C. Filippou *, Peter Portius, Johannes G. Winter, Gabriele Kociok-Ko ¨hn
Institut fu ¨r Anorganische und Allgemeine Chemie der Humboldt -Uniersita ¨t zu Berlin, Hessische Straße 1 -2, D-10115 Berlin, Germany
Received 14 December 2000; accepted 16 January 2001
Dedicated to Professor Dr H. Brunner on the occasion of his 65th birthday on 4.10.2000
Abstract
Treatment of Cp*(CO)
2
WCNEt
2
(1) (Cp* =
5
-pentamethylcyclopentadienyl) with HCl affords the aminomethylene complex
cis -Cp*(Cl)(CO)
2
WC(H)NEt
2
(2). Complex 2 inserts stereoselectively GeCl
2
into the tungsten – chlorine bond to afford cis -
Cp*(GeCl
3
)(CO)
2
WC(H)NEt
2
(3). Complex 3 can also be obtained directly from 1 and GeCl
2
(diox) (diox =1,4-dioxane) in
CH
2
Cl
2
. Similarly, treatment of Cp**(CO)
2
WCNEt
2
(1a) (Cp** =
5
-ethyltetramethylcyclopentadienyl) with GeCl
2
(diox) in
toluene affords cis -Cp**(GeCl
3
)(CO)
2
WC(H)NEt
2
(3a). An isomerization equilibrium is established between 3 and trans -
Cp*(GeCl
3
)(CO)
2
WC(H)NEt
2
(4) in the melt (208°C), which favors the trans isomer (3:4 ratio =1:6). The aminocarbyne complex
cis -Cp*(Cl)
2
(CO)WCNEt
2
(5) reacts with GeCl
2
(diox) to yield stereoselectively spy -5-14-Cp*(Cl)(GeCl
3
)(CO)WCNEt
2
(6).
Complexes 2 – 6 were fully characterized and the crystal structures of the complexes 2, 3, 4 and 6 are presented. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: Germylenes; Insertion; Carbene complexes; Carbyne complexes; Tungsten
1. Introduction
Germylenes, the heavier Group 14 homologues of
carbenes, have been shown to insert into -bonds
providing an easy access to tetravalent germanium
compounds [1]. We have shown previously, that
GeCl
2
(diox) is a useful source of GeCl
2
reacting fast
and selectively with various chloro and hydrido com-
plexes of molybdenum and tungsten to afford respec-
tively trichlorogermyl and dichlorogermyl complexes of
the general formula (
5
-C
5
R
5
)M(CO)
3 -n
L
n
(GeCl
3 -m
-
H
m
) (R =H, Me; M =Mo, W; n =0–2; L =EtNC,
PMe
3
; m =0, 1) [1,2]. These complexes contain two
reactive sites for further functionalization, that are the
transition metal and the germanium center. This has
been demonstrated recently by the high-yield syntheses
of the dimetallagermanes [(
5
-C
5
R
5
)M(CO)
3
]
2
GeX
2
(R =H, Me; M =Mo, W; X =H, Cl) [3] and the
triazidogermyl complexes trans -(
5
-C
5
R
5
)W(CO)-
(PMe
3
)
2
Ge(N
3
)
3
(R =H, Me) [4].
Several features of the above mentioned GeCl
2
inser-
tion reactions are not consistent with pathways involv-
ing radicals or ionic intermediates. These are the lack of
evidence for the formation of escape products and the
increase in rate observed, when the reaction is carried
out in poorly coordinating solvents, when the metal
complex becomes more electron-rich, or when the lig-
and sphere becomes less crowded. These features sug-
gest instead the intermediate formation of an adduct, in
which the metal complex acts as a Lewis base and
GeCl
2
as a Lewis acid [5]. Additional support for the
latter pathway is given by the stereoselectivity of these
reactions. For example the chloro complexes (
5
-
C
5
R
5
)M(CO)
2
(PMe
3
)Cl (R =H, Me; M =Mo, W),
which exist exclusively as cis isomers in solution at
room temperature, afford with GeCl
2
(diox) stereoselec-
tively the cis trichlorogermyl complexes (
5
-
C
5
R
5
)M(CO)
2
(PMe
3
)GeCl
3
. These isomerize either in
solution or in the solid-state to the thermodynamically
more stable trans isomers [1,6]. In continuation of this
work, we report here on stereoselective insertions of
GeCl
2
into tungsten-chlorine bonds of aminomethylene
and aminocarbyne complexes.
* Corresponding author. Tel.: +49-30-20937385; fax: +49-30-
20936939.
E-mail address: filippou@chemie.hu-berlin.de (A.C. Filippou).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII:S0022-328X(01)00748-3