Ethylene polymerization catalysis by vanadium-based systems bearing sulfur-bridged calixarenes

Calixarenes bridged by thia (?S?), sulfinyl (?SO?), or sulfonyl (?SO 2-) linkers have been employed as ancillary ligands in vanadium-based ethylene polymerization and in the ring-opening polymerization of ε-caprolactone. For ethylene polymerization, all pro-catalysts [PPh 4][VOCl2(R-calix[4]areneH2)] (R = p-tert-butylthia (?S?) (1), sulfinyl (?SO?) (2), sulfonyl (?SO2?) (3)) were highly active, with the system bearing the sulfonyl (?SO 2?)-bridged calixarene displaying enhanced activity. The molecular structures of pro-catalysts 2 and 3 are reported. Pro-catalysts 1?3 were inactive for the ROP of ε-caprolactone. © 2011 American Chemical Society