Synthesis and Catalytic Behavior of Novel Divalent Lanthanide Complexes Bearing Silylene Bridged Bis-and Monocyclopentadienyl Ligands

摘要

A divalent silylene-bridged samarocene reacted with KOAr to give (aryloxy) samarate complexes (Me_2Si(C_5Me_4)(C_5Me_4K)Sm(OAr)(THF)_m)_n (2), which contained a neutral "C_5Me_4K" ligand. X-ray diffraction study showed that 2 possesses a polymeric structure. In constrast to unbridged complex ((C_5Me_5)(C_5Me_5K)Sm(ER)(THF)_m)_n (1) which was highly active for ethylene polymerization, complex 2 showed no activity toward ethylene. This result indicates that dissociation of the neutral Cp'K ligand from Sm(II) is an important step to produce an active species for the polymerization, and the active species is considered to he the unsaturated heteloleptic complex, (Cp'Sm(OAr)). Synthesis and structures of novel divalent lanthanide complexes having bidentate tetramethylcyclopentadienyl/ER (E = NR', PR') are also reported.