Addition-Isomerization Polymerization of Chiral Phosphaalkenes: Observation of Styrene–Phosphaalkene Linkages in a Random Copolymer

These studies provide
the first evidence for styrene–phosphaalkene
connectivities in a phosphaalkene copolymer. The synthesis and structural
characterization of new phosphaalkene–oxazolines, ArPC­(Ph)­(3-C6H4Ox) [1a,b, Ar = Mes
(1a), Mes* (1b), Ox = CNOCH­(iPr)­CH2], are reported. The radical-initiated
homo- and copolymerization of 1a with styrene affords P-functional poly­(methylene­phosphine) (4a: Mn = 5300 g mol–1, PDI = 1.2) and poly­(methylene­phosphine-co-styrene) (5a: Mn = 4000
g mol–1, PDI = 1.1). Multinuclear NMR spectroscopic
analyses of 4a and 5a provided evidence
for the predominance of an addition-isomerization mechanism for the
radical polymerization of 1a. In addition, signals could
be assigned to CHPh–P­(CHPhAr) (i.e., S–1a) and ArCH2–CH2 (i.e., 1a–S) linkages in copolymer 5a. With a monomer
feed ratio of 1a:S (1:2, 33 mol % 1a) the
inverse gated 13C­{1H} NMR spectrum suggested
an incorporation of 19 mol % 1a in copolymer 5a. Polymers 4a and 5a were further functionalized
to Au­(I)-containing macromolecules [4a·AuCl: Mn = 13 000, PDI = 1.2; 5a·AuCl: Mn = 7500, PDI = 1.1].