Ethylene Polymerization Catalysis by Vanadium-Based Systems Bearing Sulfur-Bridged Calixarenes

Calixarenes bridged by thia (−S−), sulfinyl
(−SO−),
or sulfonyl (−SO2−) 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 [PPh4]­[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
(−SO2−)-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.