Polymerization of σ-bonded organo-transition metal derivatives of styrene

Five new monomers of transition metal complexes containing a styryl group, trans-documentclass{article}pagestyle{empty}begin{document}$ {rm Pd}({rm PBu}_{rm 3})_2 rlap{--} ({rm C}_6 {rm H}_4 {rm CH} hbox{=hskip-2pt=} {rm CH}_2 ){rm X X hbox{=hskip-2pt=} Cl(Ia), X hbox{=hskip-2pt=} Br(Ib)}, {rm X hbox{=hskip-2pt=} CN(Ic), X hbox{=hskip-2pt=} Ph(Id)} $end{document} and trans-documentclass{article}pagestyle{empty}begin{document}${rm Pt(PBu}_{rm 3} {rm )}_{rm 2} rlap{--} ({rm C}_{rm 6} {rm H}_{rm 4} {rm CH} hbox{=hskip-2pt=} {rm CH}_2 ){rm Cl}({rm II})$end{document}, were synthesized. The monomers were readily homopolymerized in benzene with the use of AIBN or BBu₃–oxygen as the initiator. Copolymerization of Ia with styrene was carried out by using AIBN. From the Cl content of the copolymers by analysis, monomer reactivity ratios and Q–e values were obtained as follows: r₁ = 1.49, r₂ = 0.45; Q₂ = 0.41, e₂ = ?1.4 (M₁ = styrene, M₂ = Ia). Based on the above data, the σ-bonded palladium moiety at para position of styrene acts as a strongly electron-donating group to the phenyl ring. This is also supported by the olefinic β-carbon chemical shift of ¹³C NMR for Ia.