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

Abstract

Two new moisture- and air-stable bis(β-ketoamino)nickel(II) complexes Ni[R1C(O)CHC(NAr)R2]2 (Ar ≡ 2,6-iPr2C6H3; R1 = R2 = CH3, 1; R1 = C6H5, R2 = CH3, 2), together with the moderately stable complex Ni2[CH3C(O)CHC(O)CH3]4[H2NtBu]2 (3), which bears a monoanionic O,O-chelate bidentate β-diketone and an sp3-N atom of tBuNH2 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. 13C NMR analyses indicate that these catalytic systems initiate MMA polymerization to yield PMMA with rich syndiotacticity microstructure.