Synthesis, Structural Characterization, and Catalytic Property of Group 4 Metal Carborane Compounds with a iPr2NB-Bridged Constrained-Geometry Ligand

Interaction of i Pr 2 NB(C 9 H 7 )(C 2 B 10 H 11 ) with 1 equiv of Zr(NMe 2 ) 4 gave a constrained-geometry zirconium amide [η 5:σ- i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]Zr(NMe 2 ) 2 ( 2 ). Treatment of i Pr 2 NB(C 9 H 7 )(C 2 B 10 H 11 ) with 1 equiv of Ti(NMe 2 ) 4, however, led to the isolation of a deborated product (η 5 -C 2 B 9 H 11 )Ti(NMe 2 ) 2 (HNMe 2 ) ( 1 ). 2 reacted with excess Me 3 SiCl in toluene to give the chloro derivative [η 5:σ- i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]ZrCl 2 ( 4 ). Salt metathesis reaction between MCl 4 (THF) 2 and [ i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]Li 2 (Et 2 O) 2 afforded [η 5:σ- i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]MCl 2 (M = Ti ( 3 ), Zr ( 4 ), Hf ( 5 )). 3 was also prepared from the reaction of [ i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]Li 2 (Et 2 O) 2 with 1 equiv of TiCl 3 (THF) 3, followed by addition of 0.5 equiv of PbCl 2 in THF. Interaction of 2 with 4 equiv of Me 3 Al in toluene resulted in the isolation of [η 5:σ- i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]ZrMe 2 ( 6 ). 6 was also prepared via the reaction of 4 with 2 equiv of MeLi in THF. All of these compounds were fully characterized by various spectroscopic data and elemental analyses. The solid-state structures of compounds 1 and 2 were further confirmed by single-crystal X-ray analyses. Compounds 2 − 6 exhibited a moderate to very high (10 4 −10 6 g mol - 1 atm - 1 h - 1 ) ethylene polymerization activity upon activation with MAO. The activities depended upon both the central metal ion and co-ligand and followed the order 4 > 2, 6 > 3 > 5 .