Pure WOCl4-x(OAr)x complexes (x = 1, 2,3 or 4; OAr = aryloxide, e.g., -OC6H3-2,6-Me2) were prepared in essentially quantitative yields by reacting tungsten oxytetrachloride (WOCl4) with the stoichiometric amount of the parent substituted phenol or lithium aryloxide. A structural study of WOCl2(OC6H3-2,6-Pr2i)2 and WO(OC6H3-2,6-Me2)4 procatalysts showed them to have pseudo-square-pyramidal geometry about the tungsten center (cf. WOCl4). A trans arrangement of 2,6-diisopropylphenoxide ligands was found for the WOCl2(OC6H3-2,6-Pr2i)2 procatalyst. The ring-opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) by WOCl3(OAr), WOCl2(OAr)2, and WOCl(OAr)3, in combination with trialkyltin hydrides (R3SnH) or triaryltin hydrides (Ar3SnH), was assessed. Pure tungsten-oxytetrachloride-based procatalysts, i.e., WOCl4-x(OAr)x, activated by a tin hydride, are capable of bulk-polymerizing dicyclopentadiene (DCPD) with very high polymer yields (greater-than-or-equal-to 99.5%). The polymerization ability of a particular procatalyst was correlated with the reduction potential (W(VI) --> W(V)) of the complex and the charge on the oxygen of the 2,6-disubstituted or 2,4,6-trisubstituted phenoxide ion. The effects of changing DCPD:W, Sn:W and rate moderator:W ratios on residual monomer levels were studied.
