Synthesis, characterization, and reactivity of titanium(IV) complexes supported by proximally bridged p-tert-butylcalix[4]arene ligands

Abstract

Treatment of dilithium or dipotassium salt of p-tert-butylcalix[4]arene with t BuPCl 2 or PhPCl 2 produced 1,2-alternate phosphorus-bridged p-tert-butylcalix[4]arene derivatives ( t BuPC)H 2 (1) and (PhPC)H 2 ( 2), respectively. An X-ray diffraction study of 2 showed that it exists in 1,2-alternate conformation. Reaction of 2 with sulfur gave (PhSPC)H 2 ( 3), which exists in cone conformation. Treatment of TiCl 4 with 1– 3 produced the corresponding dichlorides L 2TiCl 2 [L 2= t BuPC ( 5); PhPC ( 6); and PhSPC ( 7)]. Reaction of R 2Mg·2THF (R=Me or CH 2Ph) with (DMSC)TiCl 2 ( 8) yielded (DMSC)TiMe 2 ( 9) and (DMSC)Ti(CH 2Ph) 2 ( 10), respectively. Cationic derivatives [(DMSC)Ti(NCCH 3)Me 2]BAr F 4 ( 11) and [(DMSC)Ti(NCCH 3)(CH 2Ph)]BAr F 4 ( 12) were prepared from the respective reactions of 9 and 10 with [Ph 3C]BAr F 4 [Ar F=(CF 3) 2C 6H 3] in the presence of CH 3CN. Similarly, 9 and 10 reacted with [Ph 3C]OTf (one equivalent) to yield [(DMSC)Ti(OTf)Me 2] ( 13) and [(DMSC)Ti(OTf)(CH 2Ph)] ( 14), respectively. NMR data showed that the more exposed exo-alkyl was abstracted. Complexes 5– 10 and 14 showed modest ethylene polymerization activities at 25°C with 500 molar equivalents of methylalumoxane (MAO) as cocatalyst.