6974-97-6Relevant articles and documents
Preparation and Catalytic Application of a Novel Very Rigid Group 4 Ansa-Metallocene System
Erker, Gerhard,Psiorz, Christian,Froehlich, Roland,Grehl, Matthias,Krueger, Carl,et al.
, p. 4347 - 4358 (1995)
Treatment of 2,5-hexandione with cyclopentadiene in the presence of pyrrolidine yields the corresponding bisfulvene (5) that has been converted to the ligand system, isolated as the dilithio compound 8.Subsequent reaction with the group 4 metal halides MCl4 (M=Ti, Zr, Hf) gives the rigid ansametallocene dichlorides 9a-c.Their reaction with methyllithium yields the corresponding dimethyl-ansa-metallocenes 10a-c.Complexes 9a-c and 10a-c were characterized by X-ray diffraction.The zirconium and hafnium systems all exhibit very low D1-M-D2 angles (D1 and D2 denote the centroids of the Cp-ring systems) at around 116 deg.Consequently the homogeneous metallocene/methylalumoxane Ziegler-type catalyst systems derived from the zirconium complex 9b produce low molecular weight propene oligomers (in contrast to high molecular weight polypropylene formed at the titanium containing 9a/MAO catalyst system), which is probably due to an electronic control of the kpropagation/ktermination-ratio of the propene polymerization process.It is forseable that such ansa-metallocene derived catalyst systems favouring the formation of low molecular weight products instead of high molecular weight polyolefins will find increasing application in organic synthesis.
Dimerization method for high activity and selectivity propylene
-
Paragraph 0076; 0077; 0078, (2017/06/02)
The invention provides a dimerization method for high activity and selectivity propylene. The method includes the following steps that methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) is used as a catalyst promoter, and the propylene is subjected to a dimerization reaction under the catalytic action of an ethylidene bridged substituted diindene titanium group metal complex catalyst; and the ethylidene bridged substituted diindene titanium group metal complex catalyst is an internal compensation (meso-) ethylidene bridged substituted diindene titanium group metal complex catalyst or a racemization (rac-) ethylidene bridged substituted diindene titanium group metal complex catalyst. Compared with the prior art, the dimerization method provided by the invention is high in catalytic activity and high in dimerization selectivity, the rate can reach 99%, numerous follow-up operation steps in separation of products with the high degree of polymerization are omitted, the industrialization cost is reduced, and the industrial production needs can be met.
Bridged metallocene complex for the (co) polymerization of olefins
-
, (2008/06/13)
A “bridged” bis-cyclopentadienyl complex which can be advantageously used for the formation of a catalytic system active in the (co)polymerization of ethylene and other a-olefins is represented by means of the following formula (II): wherein: M represents a metal selected from titanium, zirconium or hafnium; A′ and A″ each independently represent an anion containing an η5-cyclopentadienyl ring coordinated to M; or R″ each independently represents a group of an anionic nature a-bound to the metal M; B represents an unsaturated bivalent organic residue having from 1 to 30 carbon atoms bound, respectively, to the ring of group and to the -CH2- methylene group by means unsaturated carbon atoms. This complex, combined with a suitable cocata forms a catalyst with a high activity in the poization of olefins, producing polymers with molecular weight, especially in the case of the merization of ethylene with a second α-olefir.
