(η³-Azaallyl)zirconium Chlorides: Synthesis, Characterization, and Ethylene (Co-)polymerization Activity

(2,6-Diisopropyl-N-(1-phenylvinyl)benzenamido)magnesium bromide (CH2(Ph)C(2,6-iPr2C6H3)NMgBr·2THF, 1b) reacted with 1 equiv of Me2NMe2SiCl to form the N-(2-((dimethylamino)dimethylsilyl)-1-phenylvinyl)-2,6-diisopropylbenzenamine (1c). The stoichiometric reaction of 1c with lithium diisopropylamide (LDA) formed lithium N-(2-((dimethylamino)dimethylsilyl)-1-phenylvinyl)-2,6-diisopropylbenzenamidate (Me2NMe2SiCH(Ph)C(2,6-iPr2C6H3)NLi·3THF, 1d) in high yields. The reaction of zirconium tetrachloride with 2 equiv of 1d produced the bisligated (η3-azaallyl)zirconium dichloride ((η3-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)2ZrCl2, 2), whereas the stoichiometric reaction of zirconium tetrachloride with 1d formed a monoligated zirconium trichloride complex ((η3:η1-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)ZrCl3, 3), in which the ligand acted as an η3-azaallyl species with N-donation via the dimethylamino group at the silyl bridge. All compounds were fully characterized by elemental and spectroscopic analyses and metal compounds by single-crystal X-ray diffraction. The azaallyl groups of the ligands act in a κ1-enamido fashion in compounds 1b,d, while the azaallyls appear as an η3-N,C,C mode in compound 2. The η3:η1 coordination of the azaallyl and dimethylsilyl groups provided a sterically constrained geometry around the zirconium in compound 3. The coordination geometries around each zirconium are pseudo-octahedral in both compounds 2 and 3. The modes of coordination affected their catalytic behaviors toward polymerization: high activity by 3 and good activity by 2.