Organometallics 2009, 28, 5285–5288 5285
DOI: 10.1021/om9005406
Simple Synthesis of (Triphenylphosphoniomethylidene)-
(pentamethylcyclopentadienyl)titanium(II) Dichloride and Its
Unexpected Reduction To Form a Trinuclear Titanium Cluster
Aichen Wang, Hongjian Sun, and Xiaoyan Li*
School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, 250100 Jinan,
People’s Republic of China
Received June 22, 2009
Summary: The novel titanium phosphoniomethylidene com-
Scheme 1
plex [Cp*TiCl2(-CHdPPh3)] (2; Cp*= η-C5Me5) was ob-
tained via a transylidation reaction of Cp*TiCl3 (1) with 2
equiv of the phosphorus ylide Ph3PdCH2. The trinuclear
titanium(III) cluster [Cp*Ti(μ-Cl)Cl]3 (3) was formed through
reduction of complex 2 with CO. Complexes 2 and 3 were
structurally characterized by X-ray diffraction.
phosphoniomethylidene complexes of tungsten and tanta-
The possibility of stabilizing highly reactive intermediates
lum with d0 electron configuration.6
as well as short-lived molecules is one of the great advantages
Usually, the insertion reaction of small molecules such as
of organometallic chemistry, located on the borderline be-
CO into multiple metal-carbon bonds is a decisive mechan-
tween organic and inorganic chemistry.1 The transition
istic step in the organometallic catalytic cycle. Therefore,
metal carbene and carbyne complexes in high oxidation
such reactions always arouse research interest. There are
states are important intermediates and play an important
some reports about this kind of research in the literature.7 In
role in chemical processes such as ring closing metathesis
(RCM), ring-opening metathesis (ROM), ring-opening meta-
thesis polymerization (ROMP), acetylene polymerization,
this paper we report a simple synthesis of an R-phosphonio-
methylidene complex of titanium, [Cp*TiCl2(-CHdPPh3)]
(2), from transylidation reactions of (pentamethylcyclo-
pentadienyl)titanium trichloride [Cp*TiCl3] (1) with 2 equiv
and Wittig-type or group-transfer reactions.2,3
There have been numerous examples of the successful use
of Ph3PdCH2. Unexpectedly, a trinuclear cluster, [Cp*Ti(μ-
Cl)Cl]3 (4), was formed through reduction of complex 2
of phosphorus ligands for late transition metals in metal-
catalyzed organic or polymer synthesis.4 However, very few
with CO.
examples of phosphoniomethylidene complexes with d0
electron configuration are known. Sundermeyer reported
Results and Discussion
R-phosphonio(methylidene) complexes of high-valent chro-
mium, molybdenum, tungsten, and rhenium, among them
Reaction of [Cp*TiCl3] with Ph3PdCH2. The reaction
the tetrahedral complexes [M(dNtBu)2(dCHPPh3)2] (M =
of [Cp*TiCl3] (1) with 2 equiv of Ph3PdCH2 led to an
Mo, W) (Scheme 1).5 Recently we also have successfully used
phosphorus ylides as a precursor for the formation of
R-phosphoniomethylidene complex of titanium, [Cp*TiCl2-
(-CHdPPh3)] (2) (eq 1).
*To whom correspondence should be addressed. E-mail: xli63@sdu.
edu.cn.
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r
2009 American Chemical Society
Published on Web 08/11/2009
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