Synthesis of group 4 metal rac-(EBI)M(NR(2))(2) complexes by amine elimination. Scope and limitations

The synthesis of (EBI)M(NR(2))(2) (M = Ti, Zr, Hf; EBI = ethylene-1,2-bis(1-indenyl)) complexes by amine elimination reactions of (EBI)H-2(1,2-bis(3-indenyl)ethane) and M(NR(2))(4) complexes has been investigated. The reaction of (EBI)H-2 and Zr(NEt(2))(4) in toluene at 100 degrees C (15 h) yields the mono(indenyl) complex (eta(5)-C9H6CH2CH2C9H7)Zr(NEt(2))(3) via a single amine elimination. Under more forcing conditions (1,2-dichlorobenzene, 180 degrees C, 21 h) this reaction yields the metallocene dichloride derivative (EBI)ZrCl2 (80% NMR, rac/meso ratio = 1.7/1). The reaction of (EBI)H-2 with Zr(NMe(2))(2)((NPr2)-Pr-i)(2) in m-xylene at 140 degrees C (16 h) affords the sterically least hindered ansa-metallocene product, (EBI)Zr(NMe(2))(2) (70% NMR, rac/meso ratio = 2/1), via (NPr2H)-Pr-i elimination. The reaction of (EBI)H-2 with the pyrrolidide complex Zr(NC4H8)(4) in m-xylene at 140 degrees C (7 h) yields (EBI)Zr(NC4H8)(2) (95%, rac/meso ratio = 6/1) and pure rac-(EBI)Zr(NC4H8)(2) in 42% isolated yield. (EBI)H-2 reacts with the sterically open titanium azetidide complex Ti(NC3H6)(4) to yield the mono(indenyl) species (eta(5)-C9H6CH2CH2C9H7)Ti(NC3H6)(3) but does not react with Ti(NMe(2))(4) (toluene, 100 degrees C, 17 h), The reaction of (EBI)H-2 and Hf(NMe(2))(4) in m-xylene at 140 degrees C (21 h) provides (EBI)Hf(NMe(2))(2) in 85% NMR yield (rac/meso ratio = 6/1) and rac-(EBI)Hf(NMe(2))(2) in 47% isolated yield.