Alkene hydrogenation catalysed by dinuclear rhodium complexes

Blagbrough, Tamzin C. (1990) Alkene hydrogenation catalysed by dinuclear rhodium complexes. (PhD thesis), Kingston Polytechnic, .


The work reported in this thesis is concerned with two separated but related studies. The first involved examination of hydrogenation reactions of alkenes, dienes and alkynes using (Rh[sub]2C1(CO)[sub]2(dppm)[sub]2JBPh[sub]4 as a catalyst. Kinetic studies have been performed on the reaction of hexene. The system only well-behaved in the presence of a base, R[sub]3N, where a rst order dependance on both catalyst and hydrogen concentations observed. The order with respect to alkene is of the Michaelis-Menton type. This behaviour suggests that the active catalyst is a neutral monohydride generated by deprotonation of a ionic dihydride. It is proposed that the active catalyst is a dinuclear species, since none of the likely mononuclear breakdown oducts shows any catalytic activity. A catalytic cycle for the reaction is proposed. The second study was an investigation into the use of fast atom bombardment (FAB) mass spectrometry as a means of anaylsis organometallic compounds which have proved difficult to identify using other ionisation modes. The technique was shown to informative spectra for a series of dinuclear rhodium-dppm mplexes and some dinuclear manganese carbonyl derivatives. FAB ionisation also proved effective for identification of phosphine and phosphite derivatives of [RCC0[sub]3(CO)[sub]9.] (R=CH[sub]3, C1). The technique was also combined with thin layer chromatography (TLC) in examining a reaction of [Mo(CO)[sub]6.] with Ph[sub]2P(CH[sub]2)[sub]2P(O)Ph[sub]2 (dppeO) which yields a mixture of seven products. It was found that good spectra of pure materials could be obtained TLC separation, followed by removal of the appropriate section silica support from the plate. This was subjected directly to FAB mass spectrometry without prior extraction of the product from silica. Using this technique, it proved possible to identify three new dppeO derivatives of [Mo(CO)[sub]4 (dppeO) derivatives of [Mo(CO)[sub]6. These are [Mo(CO)[sub]5 (dppeO)] cis-[Mo(CO)[sub]4 (dppeO)[sub]2] and [Mo[sub]2(CO)[sub] 4 (dppeO)[sub]2].

Actions (Repository Editors)

Item Control Page Item Control Page