Synthesis, structural characterization, and catalytic property of group 4 metal carborane compounds with a iPr2NB-bridged constrained-geometry ligand

Interaction of (Pr2NB)-Pr-i(C9H7)(C2B10H11) with 1 equiv of Zr(NMe2)(4) gave a constrained-geometry zirconium amide [eta(5):sigma-(Pr2NB)-Pr-i(C9H7)(C2B10H11)]Zr(NMe2)(2) (2). Treatment of (Pr2NB)-Pr-i(C9H7)(C2B10H11) with I equiv of Ti(NMe2)(4), however, led to the isolation of a deborated product (eta(5)-C2B9H11)Ti(NMe2)(2)(HNMe2) (1). 2 reacted with excess Me3SiCl in toluene to give the chloro derivative [eta(5):sigma-(Pr2NB)-Pr-i(C9H6)(C2B10H10)]ZrCl2 (4). Salt metathesis reaction between MCl4(THF)(2) and [(Pr2NB)-Pr-i(C9H6)(C2B10H10)]Li-2(Et2O)(2) afforded [eta(5):sigma(-i) Pr2NB(C9H6)(C2B10H10)]-MCl2 (M = Ti (3), Zr (4), Hf (5)). 3 was also prepared from the reaction of [(Pr2NB)-Pr-i(C9H6)-(C2B10H10)]Li-2(Et2O)(2) with 1 equiv of TiCl3(THF)(3), followed by addition of 0.5 equiv of PbCl2 in THF. Interaction of 2 with 4 equiv of Me3Al in toluene resulted in the isolation of [eta(5):sigma-(Pr2NB)-Pr-i(C9H6)(C2B10H10)]ZrMe2 (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.