Living Polymerization of Bulky Aryl Isocyanide with Arylrhodium Complexes

Well-defined arylrhodium complexes Rh(Ar)(nbd)(PPh3) (Ar = Me2C6H3, 2,4,6-Pri3C6H2, 2-PhC6H4,
2-Me-1-naphthyl, 9-anthracenyl, C(Ph)CPh2; nbd = 2,5-norbornadiene) that were prepared from the
reaction of [Rh(nbd)Cl]2 with LiAr and PPh3 effectively initiated the living polymerization of aryl
isocyanides possessing bulky substituents at the ortho position in the presence of PPh3 to give poly(isocyanide)s with narrow polydispersity indexes in good yields. The bulky aryl groups on the Rh complex
were essential to achieving high initiator efficiency, whereas the bulky substituents on aryl isocyanides
were required for the formation of high molecular weight polymers. The living nature of the present
system was confirmed by kinetic studies as well as the formation of block copolymers. The polymerization
rate was dependent not on the concentration of monomers, but on the concentration of PPh3.