Well-Defined Transition Metal Catalysts for Metathesis Polymerization - Late Transition Metal Polymerization Catalysis - page 157

Scheme 5.2 Synthesis of a ROMP-active cyclometallated aryl-
oxy(chloro)neopentylidene tungsten complex [60].

Finally, the synthesis of the aryloxy(chloro)tungsten alkylidene complex reported
by Basset et al. needs to be mentioned (Scheme 5.2) [60].
The synthesis may be accomplished via two independent routes. One entails
the reaction of W(C- t- Bu)Cl 3 ·DME (DME=1,2-dimethoxyethane) with 2 equiv. of
Ar =2,6-(C 6 H 5 ) 2 -C 6 H 3 ). The intermediary alkylidyne is believed to sponta-

neously isomerize to the desired alkylidene moiety. Alternatively, WCl 4 (OAr) 2 is
reacted with 2 equiv. of dineopentyl magnesium (Np 2 Mg). Elimination of neopen-
tane and HCl again results in the formation of desired catalyst. It has been re-
ported to be highly active and stereoselective in the ROMP of 1-methylnorbornene
to yield predominantly cis -polymers on a strong head to tail base [61].

OLi (Ar