Summary:
The olefin metathesis reaction is induced by an abundance of mononuclear
catalytic systems, although there is a limited number of bimetallic complexes
inducing the above reaction. Within the latter, salts of the anions [W2Cl8]4-
[(W4W)4+, σ2π4δ2] and [W2Cl7(THF)2]- [(W3W)6+ , a’2e’4] have been proved to be
very effective initiators for the above reactions. In this context, scope of
this thesis has been the synthesis and study of the catalytic properties of
various salts of the analogous anions [M2Cl8]n- [(M4M)n+, σ2π4δ2; M=Mo, n=4,
(1), M=Re, n=6, (2)] and [Mo2X9]3- [(Mo3Mo)6+, a’2e’4 , X=Cl (3a), X=Br (3b),
X=I (3c)].
Complexes 1, 2, 3a have been prepared by literature methods. Attempts to
isolate the novel 3b,c produced mixtures from which the trinuclear
[nBu4N]2[Mo3Br11] (4) and tetranuclear [nBu4N]2[Mo4OI12] (5) clusters have been
isolated and characterized by spectroscopic methods (IR, UV-Vis, CV, ES-MS) and
X-Ray crystallography.
Compounds 1-4 fail to act as unicomponent initiators under a variety of
experimental conditions, but upon activation with cocatalysts induce the
polymerization and cyclotrimerization of PhCCH (PA) and the ROMP of selected
mono- and bicycloolefins [norbornene (NBE), norbornadiene (NBD),
dicyclopentadiene (DCPD), cyclopentene (CPE)], albeit in small yields. The
cyclotrimers and polymers have been characterised by IR, and NMR techniques.
Keywords:
Clusters, Alkyne polymerization, ROMP, Molybdenum, Rhenium