Ring opening metathesis polymerization of norbornene by WCl6: Formation of WCl5 and WCl4 and their catalytic activity

Reaction between WCl6 and norbornene in benzene and cyclohexane, respectively, was investigated using UV/VIS, ESR and XPS spectroscopy in order to establish the main reaction products on the tungsten side and their relation to the initiation of ring opening metathesis polymerization (ROMP) of norbornene. The tungsten compounds: WCl5, insoluble WCl4 and soluble tungsten species having four chlorine atoms bound to tungsten, [WCl(4)L(n)] were found to be the main products. The catalytic activity of the respective compounds in ROMP of norbornene was found to decrease in the order: WCl5>WCl6 much greater than WCl4 approximate to[WCl(4)L(n)]. The polynorbornenes prepared with both WCl4 and [WCl(4)L(n)] possess higher content of cis double bonds in comparison with polymers prepared with WCl6 and WCl5 catalysts.