Metathesis of cis-2-pentene has been studied with the catalytic system W(CO)5Pφ3, EtAlCl2. Oxygen has a drastic promoting effect on the catalytic system which exhibits, after O2 introduction, a very high efficiency for metathesis of internal as well as α-olefins. Whereas no significant interaction occurs between W(CO)5Pφ3 and EtAlCl2, O2 activation induces slow departure of two carbonyl groups. It is at the beginning of the release of CO that the system is the most active. Spectroscopic studies (uv, ir) indicate at this stage a complexing of a Lewis acid to the terminal oxygen of the trans-carbonyl group of W(CO)5Pφ3, with a net decrease of the elecronic density of W, so that the strength of the WCO bonds of the square plane is considerably lowered. It is therefore suggested that the main effect of O2 is to enhance the Lewis acidity of EtAlCl2, so as to favor an electrophilic attack of the Lewis acid to the tungsten through the carbonyl ligand.
ASJC Scopus subject areas
- Process Chemistry and Technology