Catalytic polymerization of alkynes with the quadruply bonded octachloroditungsten anion

Επιστημονική δημοσίευση - Άρθρο Περιοδικού uoadl:2928861 32 Αναγνώσεις

Μονάδα:
Τμήμα Χημείας
Τίτλος:
Catalytic polymerization of alkynes with the quadruply bonded octachloroditungsten anion
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
In this work are described the reactions of the quadruply bonded
ditungsten complexes Na-4[W2Cl8(THF)(x)] (1) and [W2Cl4(PMe3)(4)]
(2), which contain the W(2)4(+) core and have the sigma(2)pi(4)delta(2)
electronic configuration, as well as of the mononuclear [WCl4(THF)(2)]
(3) with alkynes (RC)-C-1 CH, (RC)-C-2 CR3 (R-1 =Ph (4), Bu-n, Bu-t,
Me3Si, (CH7)-H-10 (naphthyl), C12H9 (biphenyl); R-2=R-3=Me, R-2=Me,
R-3=Pr-n; R-2=R-3=Et; R-2=Ph, R-3=Me; R-2=Ph, R-3=Et; R-2=R-3=Ph;
R-2=R-3=ACO). Complex 1 acts as an efficient single-component initiator
for the homogeneous or heterogeneous high-yield polymerization of
monosubstituted alkynes. The reaction is very fast in CH2Cl2 or
heterogeneously and slow in THE The yield is not significantly affected
by the bulk of the alkyl substituents. The reaction is not so efficient
with internal alkynes, and is limited to those bearing the less
sterically demanding substituents. Polymerization of 4 in THF shows that
the reaction comprises three distinct steps. The first is very fast (t=
3 min), with consumption of nearly half of 4 (ca. 42%), producing
Poly(4). The polymer formed is degraded equally fast regenerating 4 (ca.
23%) and oligomeric species (M-n < 1000). Subsequent polymerization is
slower and complete within 8 h. Direct evidence for the metathetical
mechanism of the polymerization was obtained by the in situ examination
of the above reaction by H-1 NMR at various temperatures. In contrast,
complex 2 alone or activated with EtAlCl2 is unreactive towards 4,
whereas 3 produces Poly(4) in small yield (20%) and very broad
polydispersity. (C) 2008 Elsevier B.V. All rights reserved.
Έτος δημοσίευσης:
2008
Συγγραφείς:
Georgios Floros
Nikolaos Saragas
Patrina Paraskevopoulou
Ioannis Choinopoulos
Spyros Koinis
Nikolaos Psaroudakis
Marinos Pitsikalis
Konstantinos Mertis
Περιοδικό:
Journal of Molecular Catalysis A: Chemical
Εκδότης:
ELSEVIER BV
Τόμος:
289
Αριθμός / τεύχος:
1-2
Σελίδες:
76--81
Λέξεις-κλειδιά:
polymerization; metathesis; alkynes; ditungsten; quadruple bond
Κύρια θεματική κατηγορία:
Θετικές Επιστήμες
Επίσημο URL (Εκδότης):
DOI:
10.1016/j.molcata.2008.04.012
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