Transition metal mediated routes to poly(arylphosphine)s: investigation of novel phosphorus containing conjugated polymers

Poly(aryl-P-alkylphosphine)s were prepared via palladium and nickel mediated coupling and the spectral and electrochemical properties of the polymers were investigated. Palladium catalyzed carbonphosphorus bond formation was used for the preparation of poly(p-phenylene-P-alkylphoshpine)s (1a–b) via two routes. Low molecular weight polymers (1000–3000) were obtained by the condensation polymerization of 1,4-diiodobenzene with primary alkylphosphines. Higher molecular weight polymers (1000–14 000) were obtained via polymerization of p-bromophenylalkylphosphines (2a–b). Poly(4,4′-diphenyl-P-2,4,4-trimethylpentylphosphine (TMPPH2)) (4b) was also prepared via two routes, the palladium catalyzed cross-coupling of 4,4′-diiodobiphenyl with primary alkylphosphines and the nickel mediated homo-coupling of bis-p-bromophenylalkylphosphines. The molecular weight of 4b was low (1000–3000) via both routes due to poor solubility. The electronic properties of polymers 1a–b were investigated with UV–vis–NIR spectroscopy and cyclic voltammetry and suggest a degree of electronic delocalization along the polymer backbone through phosphorus.