Strategies for Catalytic Polymerization of Polar Monomers - Late Transition Metal Polymerization Catalysis - page 309

do not possess any strongly coordinating functionality, are also not polymerized
by any known transition metal-catalyzed systems. Recently, Jordan [11] and Wol-
czanski [12] have reported the reaction of vinyl halides rac- (EBI)ZrMe and
( t Bu 3 SiO) 3 TaH 2 , respectively. It was demonstrated that, following 1,2-insertion of
the alkene, -halide elimination occurs to generate a metal-halide bond. Since the

halophilicity of the transition metal ions tends to decrease on going from left to
right in the periodic table, we have examined the reactivity of vinyl halides to-
wards a late transition metal complex (palladium) [13].
The starting point of our investigation was the Brookhart-type cationic Pd(II)-
methyl species, 2 generated in our case by the addition of two equivalents of
AlCl 3 to the corresponding neutral Pd(II)-methylchloride, 1 (Scheme 9.1) [13]. Sev-
eral equivalents of vinyl bromide were added to a CD 2 Cl 2 solution of 2 at -90

C
and the reaction mixture was monitored by 1 H NMR spectroscopy as it was gradu-
ally warmed up (Scheme 9.1).
The coordination of vinyl bromide to the metal center in 2 was observed even at
-86 C, resulting in the formation of 3 . Warming the reaction mixture to -74 C

Scheme 9.1