Erschien zuerst in: Journal of Organometallic Chemistry 641 (2002) 134–141
Alkynylcarbyne complexes containing various tri- and bidentate
ligands such as cyclopentadienide, tris(pyrazolyl)borate,
bis(pyrazolyl)acetate and tmeda: synthesis and spectroscopic
properties
Birgit Schwenzer, Joachim Schleu, Nicolai Burzlaff, Christoph Karl, Helmut Fischer *
Fachbereich Chemie, Uniersita ¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Received 4 July 2001; accepted 7 August 2001
Abstract
The (alkynylcarbyne)tungsten complexes [L
3
(CO)
2
WCCCR] (3a,b– 6a,b) [L
3
=hydro[tris(3,5-dimethylpyrazol-1-yl)]borato
(Tp, 3), hydro[tris(pyrazol-1-yl)]borato (Tp, 4), cyclopentadienyl (Cp, 5), bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza, 6);
R =SiMe
3
(a), Ph (b)] were prepared in a stepwise fashion from [W(CO)
6
] and Li[CCR], (CF
3
CO)
2
O and M[L
3
] (M=Na, K).
The formation of 6a,b was highly selective, only complexes with a trans arrangement of the carboxylate group of bdmpza and the
alkynylcarbyne ligand were detected. The reaction of [W(CO)
6
] with Li[CCR], C
2
O
2
Cl
2
and tmeda afforded trans -
[Cl(CO)
2
(tmeda)WCCCR] (7a,b). The electron-donating potential of the different tripodal ligands L
3
was studied by IR- and
13
C-NMR spectroscopy and compared to that of the ligand combination Cl/tmeda. The IR data suggest that in these complexes
bdmpza is a weaker electron donor than Tp and Tp but displays stronger electron-donating abilities than Cp. The structures of
6b and 7b were established by X-ray structural analyses. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Carbyne complexes; Tripodal ligands; Tungsten; Electron donating ability
1. Introduction
Organometallic compounds with extended -conju-
gated ligands have attracted considerable interest [1],
since bi- and polynuclear complexes containing -un-
saturated conjugated bridges are expected to exhibit
potentially useful physical and chemical properties. In
such bi- and polynuclear complexes the metal – ligand
fragment L
n
M can occupy an internal or/and a termi-
nating position in the chain. Various types of bridging
ligands have been proposed. In recent years attention
has focused on complexes with carbon-rich bridges,
[LnM(C)
m
ML
n
] [2]. Until now, complexes with an
even number of carbon atoms linking the metals (m up
to 20 [3]) are more readily accessible than those with an
odd number of carbon atoms. Usually, complexes with
an even number of carbon atoms are derived from
alkynes and alkynyl complexes via coupling reactions.
In contrast, precursors for the synthesis of complexes
with an odd number of bridging carbon atoms are
much less readily available.
Alkynylcarbyne complexes (alkynylidyne complexes),
L
n
MC(CC)
m
R, might be suitable starting com-
pounds for the synthesis of complexes with an odd
number of bridging carbon atoms. In addition, they
also might constitute interesting terminating groups.
However, until now there are only a few reports on
alkynylcarbyne complexes. The first complexes, trans -
X(CO)
4
WCCCPh (X =Cl, Br, I), were prepared by
Fischer et al. already in 1974 [4]. Since then, only a few
more alkynylcarbyne complexes containing bi- and tri-
dentate ligands, L
n
MCCC
n
Bu (M =Mo, W), have
been reported by Stone and coworkers [5].
We now report on the synthesis and the spectro-
scopic properties of a series of alkynylcarbyne com-
plexes of tungsten containing tripodal ligands,
* Corresponding author. Tel.: +49-7531-882783; fax: +49-7531-
883136.
E-mail address: helmut.fischer@uni-konstanz.de (H. Fischer).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII:S0022-328X(01)01310-9