Synthesis, Structural Characterization, and Catalytic Properties of Group 4 Metal Complexes Incorporating a Phosphorus-Bridged Indenyl-Carboranyl Constrained-Geometry Ligand

Abstract

Interaction of i Pr 2 NP(C 9 H 7 )(C 2 B 10 H 11 ) with 1 equiv of M(NR 2 ) 4 in toluene gave constrained-geometry group 4 metal amides [ η 5: σ - i Pr 2 NP(C 9 H 6 )(C 2 B 10 H 10 )]M(NMe 2 ) 2 (R = Me, M = Ti ( 1 ), Zr ( 2 ), Hf ( 3 ); R = Et, M = Hf ( 4 )) in good yields. Compound 2 reacted with 3 equiv of PhNCO to produce the tri-insertion product [η 5: σ - i Pr 2 NP(C 9 H 6 )(C 2 B 10 H 10 )]Zr[η 2 -OC(NMe 2 )NPh][η 2 -OC(NMe 2 )N(Ph)C (NPh)O] ( 5 ). No further insertion reaction occurred with another equivalent of PhNCO. Instead, the trimer (PhNCO) 3 was isolated. Compound 2 reacted with 2 equiv of n -BuLi in toluene to afford, after recrystallization from DME/toluene, the dilithium salt [Li(DME) 3 ][η 5: σ - i Pr 2 NP(C 9 H 6 )(C 2 B 10 H 10 )Li(DME)] ( 6 ). An equimolar reaction of 2 with acetylacetone resulted in the formation of Zr(acac) 4 . 2 exhibited an ethylene polymerization activity of 3.7 × 10 3 g PE mol - 1 atm - 1 h - 1 upon activation with MMAO. Furthermore, 2 was also able to efficiently initiate the polymerization of ε-caprolactone to give polymers of high molecular weights ( M n > 40 000) and low polydispersities ( M w / M n < 1.4) through the action of the nucleophilic amido-nitrogen atom, which represents the first example of the polymerization of ε-caprolactone catalyzed by group 4 metal amides.