Thesis (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Metalloxycarbene complexes [(CO)5M1=O(R)M2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L =
Cp, Cp*) were synthesized from the reaction between anionic Fischer-type carbene
complex salts [(CO)5M1=C(O)R][NEt4] and metallocene chlorides. The molecular and
crystal structures of [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] and
[(CO)5W=C(Ph)OHf(Cl)Cp2] determined by X-ray methods, show a short Ccarbene-O and
relatively long O-Zr and O-Hf separations. Metalloxycarbene complexes in the presence
of MAO are active catalysts for homo- and copolymerization of -olefins and produce
polymers with heterogeneous properties. 1-Pentene oligomers, homopolymers of ethylene
and ethylene/1-pentene copolymers were successfully synthesized using
metalloxycarbenes/MAO and the results obtained were critically compared with those
synthesized with metallocene/MAO catalysts. The GC and GPC show that 1-pentene
oligomers produced with both metalloxycarbenes and metallocenes catalysts range from
simple dimers to more complicated high molecular weight (2 600 g/mol) products. The
properties of polyethylene and ethylene/1-pentene copolymers were evaluated by, among
others, GPC, SEC-FTIR, preparative molecular weight fractionation and HPer DSC.
Generally the polymers obtained using metalloxycarbene/MAO catalysts have broad and
bimodal molecular weight distributions. The copolymers have higher concentration of 1-
pentene in the lower molecular weight fraction than those produced with metallocene/MAO as shown by SEC-FTIR. Consequently, HPer DSC shows a decrease
of melting and crystallization temperature towards the low molecular weight fractions. / AFRIKAANSE OPSOMMING: Metaaloksikarbeenkomplekse [(CO)5M1=C(R)OM2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L
= Cp, Cp*] is gesintetiseer in die reaksie tussen anioniese Fischer-tipe karbeenkomplekssoute,
[(CO)5M1=C(O)R][NEt4], en metalloseen dichloriedes. Die molekulêre- en
kristalstrukture van [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] en
[(CO)5W=C(Ph)OHf(Cl)Cp2] bepaal deur X-straalkristallografiese metodes, toon die
aanwesigheid van kort Ckarbeen-O- en relatief lang O-Zr- en O-Hf-bindings.
Metaaloksikarbeenkomplekse, in die aanwesigheid van MAO, is aktiewe katalisatore vir
die homo- en ko-polimerisering van α-olefiene en is verantwoordelik vir die vorming van
polimere met heterogene eienskappe. 1-Penteen oligomere, homopolimere van etileen en
etileen/1-penteen ko-polimere is suksesvol gesintetiseer met
metaaloksikarbeenkomplekse/MAO en die resultate sodoende verkry, is krities vergelyk
met produkte gesintetiseer vanuit metalloseen/MAO prekatalisatore.
Die GC en GPC resultate toon dat die 1-penteen oligomere, geproduseer met beide
metaaloksikarbeenkomplekse en metallosene, kan wissel van eenvoudige dimere tot meer
komplekse, hoë molekulêre massa (2 600g/mol) produkte. Die polietileen en etileen/1-
penteen ko-polimere is gekarakteriseer deur onder andere gevorderde, GPC, SEC-FTIR,
preparatiewe molekulêre massa fraksionering en HPer DSC. In die algemeen het die
polimere verkry met metaaloksikarbeen/MAO katalisatore, breë en bimodale molekulêre
massaverspreidings. Die ko-polimere bevat hoër konsentrasies van 1-penteen in die lae
molekulêre massa fraksie in vergelyking met dié gevorm vanuit metalloseen/MAO–gekataliseerde mengsels, soos aangedui deur SEC-FTIR-analise. HperDSC wys 'n
verlaging in smelt- en kristallisasietemperature in die laer molekulêre massa fraksies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21672 |
| Date | 03 1900 |
| Creators | Luruli, Nyambeni |
| Contributors | Raubenheimer, H.G., Pasch, H., Van Reenen, A.J., Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xxvi, 187 leaves : ill. |
| Rights | Stellenbosch University |
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