Nickel(II) Complexes Bearing N,O-Chelate Ligands: Synthesis, Solid-Structure Characterization, and Reactivity toward the Polymerization of Polar Monomer

Two new moisture- and air-stable bis(β-ketoamino)nickel(II) complexes Ni[R1C(O)CHC(NAr)R2] 2 (Ar ≡ 2,6- i Pr 2 C 6 H 3; R1 = R2 = CH 3, 1; R1 = C 6 H 5, R2 = CH 3, 2 ), together with the moderately stable complex Ni 2 [CH 3 C(O)CHC(O)CH 3 ] 4 [H 2 N t Bu] 2 ( 3 ), which bears a monoanionic O,O-chelate bidentate β-diketone and an sp 3 -N atom of t BuNH 2 mixed ligands, were synthesized and characterized. The solid-state structures of the complexes have been determined by single-crystal X-ray diffractions. Additionally, these new complexes act as catalyst precursors for methyl methacrylate polymerization after activation with methylaluminoxane (MAO). The polymers obtained by 1 and 2 show broader polydispersity than that obtained by 3 . 13 C NMR analyses indicate that these catalytic systems initiate MMA polymerization to yield PMMA with rich syndiotacticity microstructure.