Synthesis, characterization, and reactivity of titanium(IV) complexes supported by proximally bridged p-tert-butylcalix[4]arene ligands
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abstract
Treatment of dilithium or dipotassium salt of p-tert-butylcalix[4]arene with tBuPCl2 or PhPCl2 produced 1,2-alternate phosphorus-bridged p-tert-butylcalix[4]arene derivatives (tBuPC)H2 (1) and (PhPC)H2 (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)H2 (3), which exists in cone conformation. Treatment of TiCl4 with 1-3 produced the corresponding dichlorides L2TiCl2 [L2=tBuPC (5); PhPC (6); and PhSPC (7)]. Reaction of R2Mg2THF (R=Me or CH2Ph) with (DMSC)TiCl2 (8) yielded (DMSC)TiMe2 (9) and (DMSC)Ti(CH2Ph)2 (10), respectively. Cationic derivatives [(DMSC)Ti(NCCH3)Me2]BArF4 (11) and [(DMSC)Ti(NCCH3)(CH2Ph)]BArF4 (12) were prepared from the respective reactions of 9 and 10 with [Ph3C]BArF4 [ArF=(CF3)2C6H3] in the presence of CH3CN. Similarly, 9 and 10 reacted with [Ph3C]OTf (one equivalent) to yield [(DMSC)Ti(OTf)Me2] (13) and [(DMSC)Ti(OTf)(CH2Ph)] (14), respectively. NMR data showed that the more exposed exo-alkyl was abstracted. Complexes 5-10 and 14 showed modest ethylene polymerization activities at 25C with 500 molar equivalents of methylalumoxane (MAO) as cocatalyst. 1999 Elsevier Science S.A.
