The organorhodium(I) complexes Rh(R)(nbd)(PPh3) (R = Me2C6H3, 2,4,6-Pri3C6H2, 2-PhC6H4; nbd = 2,5-norbornadiene), prepared from the reaction of [Rh(nbd)Cl]2 with PPh3 and LiR, effectively initiate the polymerization of aryl isocyanides possessing bulky substituents at an ortho position in the presence of PPh3 to provide polyisocyanides in good yields.