Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This project entailed the synthesis and characterization of mono- and multi-nuclear rhodium
and ruthenium iminopyridyl complexes and their application in the hydroformylation of 1-
octene. The multi-nuclear complexes were synthesized in order to investigate whether it
could produce catalysts with higher activity than their mononuclear analogues.
Four novel iminopyridyl ligands, ranging from mono- to tetra-functional compounds, were
synthesized. The synthesis was a two-step process initially involving a Schiff base
condensation reaction between 2-pyridinecarboxaldehyde and 4-aminophenol to produce a
hydroxy functionalized pyridine-imine. The latter was then subjected to a nucleophilic
substitution reaction with an appropriate benzyl bromide derivative to yield the target ligands.
All these ligands were isolated in moderate to good yields and characterized using a range of
analytical techniques. These ligands, together with the hydroxy functionalized pyridine imine, were then complexed
to both Rh(I) and Ru(II) metal precursors, yielding ten novel metal complexes. The
characterization of some of the complexes, especially the multi-nuclear complexes, were
slightly more difficult due to their low solubility. However, all these complexes could be
isolated in good to high yields as stable green-brown (in the case of Rh(I)) and yellow-orange
(in the case of Ru(II)) solids. Finally, these complexes were applied as catalyst precursors in the hydroformylation of 1-
octene. In the case of the Rh(I) complexes, relatively high activities were observed, with
conversions ranging between 50 – 90 % in all cases, when tested at 30 bar, 75 °C and a 0.05
mol% catalyst loading. The activity was found to increase when going from the mono- to the
bi-nuclear catalyst. However, solubility in the reaction medium was a major issue for the trinuclear
catalyst, as it contributed to the lower activity observed. High chemoselectivity
towards aldehydes was observed for all catalysts, which increased with reaction times.
During shorter reaction time, linear regioselectivity was also relatively high. This however,
decreased with increasing reaction time as the internal octenes formed initially, were
converted to branched aldehydes. When the Ru(II) complexes were tested under the same
conditions as the Rh(I) complexes, very low activity was observed. Under more stringent
conditions (45 bar, 120 °C, 0.5 mol%) the ruthenium catalysts performed relatively well,
compared to other complexes in the literature. The same trend in terms of the chemo- and regioselectivity for the Ru(II) complexes were observed. The Rh(I) complexes were far more
active than the Ru(II) complexes. / AFRIKAANSE OPSOMMING: Hierdie projek behels die sintese en karakterisering van mono- en multi-kernige rhodium en
ruthenium iminopiridiel komplekse en hul toepassing in the hidroformulering van 1-okteen.
Die multi-kernige komplekse is gesintetiseer met die doel om vas te stel of hulle katalisatore
wat meer aktief is as hul monokernige eweknieë, kan produseer.
Vier nuwe iminopiridiel ligande, wat strek vanaf mono- tot tetra-funksionele verbindings, is
gesintetiseer. Die sintese was ‘n twee-stap proses wat aanvanklik ‘n Schiff basis kondensasie
reaksie tussen 2-piridienaldehied en 4-aminofenol behels, om ‘n fenol gefunksioneerde
piridien-imien te vorm. Die laasgenoemde was gevolglik aan ‘n nukleofiliese substitusie
reaksie met ‘n gepaste bensiel bromied derivaat onderhewig. Al hierdie ligande is geisoleer in
matige tot goeie opbrengste en gekarakteriseer met ‘n reeks analitiese tegnieke. Hierdie ligande, tesame met die fenol gefunksioneerde piridien imien, is dan met Rh(I) en
Ru(II) metaal uitgangstowwe gekomplekseer, wat tien nuwe metaal komplekse tot gevolg
gehad het. Die karakterisering van sommige van die kompekse, spesifiek die multi-kernige
komplekse, was effens moeiliker as gevolg van hul swak oplosbaarheid. Al hierdie
komplekse kon egter in goeie tot hoë opbrengste as stabiele groen-bruin (in die geval van
Rh(I)) en geel-oranje (in die geval van Ru(II)) vastestowwe geisoleer word. Laastens is die komplekse as katalisator-voorlopers in die hidroformulering van 1-okteen
gebruik. In die geval van die Rh(I) komplekse is redelike hoë aktiwiteite waargeneem, met
omsettings tussen 50 – 90 % in alle gevalle, wanneer hulle by 30 bar, 75 °C en ‘n katalisator
lading van 0.05 mol% getoets is. Die aktiwiteit neem toe vanaf die mono- na die bi-kernige
katalisator. Oplosbaarheid in die reaksie medium was egter ‘n probleem vir die tri-kernige
katalisator, wat ‘n laer aktiwiteit tot gevolg gehad het. Hoë chemoselektiwiteit na aldehiede is
waargeneem vir al die katalisatore en dit neem toe met reaksietyd. Gedurende korter
reaksietye was die liniêre regioselektiwiteit ook redelik hoog, maar neem af met toenemende
reaksietyd soos die interne okteen wat aanvanklik vorm na vertakte aldehiede omgeskakel
word. Toe die Ru(II) komplekse onder dieselfde toestande as die Rh(I) komplekse getoets is,
was baie lae aktiwiteite waargeneem. Onder hoër temperatuur en druk (45 bar, 120 °C, 0.5
mol%) toon die ruthenium katalisatore redelik goeie aktiwiteite in vergelyking met ander
komplekse wat in die literatuur gerapporteer is. Dieselfde tendense in terme van die chemoen
regioselektiwiteit is vir die Ru(II) komplekse waargeneem. Die Rh(I) kompleks was baie
meer aktief as die Ru(II) komplekse.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97866 |
| Date | 25 November 2015 |
| Creators | October, Jacquin |
| Contributors | Mapolie, Selwyn Frank, Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xviii, 93 pages : illustrations (some colour) |
| Rights | Stellenbosch University |
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