Alkyne metathesis graft polymerization: Synthesis of poly(ferricinium)-based silica supports for anion-exchange chromatography of oligonucleotides

2-[3-(Ethynyl)phenyl]ethenyl]-1',2,2',3,3',4,4',5-octamethylferrocene (2) was prepared via Wittig- and chloro-Wittig-type reactions. 2 reacts with the well-defined Schrock-initiator Mo(N-2,6-Me2C6H3)(CHCMe2Ph)(OCMe(CF3)(2))(2) via alpha -addition. The resulting class VI polymerization system allows the living polymerization of 2 up to a degree of polymerization of 150. Mesoporous and nonporous silica (Nucleosil 300-5 and Micra, respectively) with different specific surface area (100 and 2 m(2)/g, respectively) were surface-derivatized with norborn-2-en-5-yltrichlorosilane, leading to an average surface functionalization of 230 and 50 mu mol norbornene/g, respectively. Monomer 2, ethynylferrocene (1), and 2- [4-(ethynyl)phenyl] ethenyl] -1',2,2',3,3',4,4',5-octamethylferrocene) (3) were surface-grafted onto these silica supports via alkyne metathesis polymerization using Mo(N-2,6-Me2C6H3)( CHCMe2Ph)(OCMe(CF3)(2))(2). Typical amounts of grafted monomer were in the range 50-5 mu mol/g. The resulting poly(ferrocene)-grafted supports were subsequently oxidized with iodine to tie corresponding poly(ferricinium)-grafted supports and successfully used for anion-exchange chromatography of oligonucleotides (dT)(12)-(dT)(18).