Polymerization of methyl methacrylate with nickel α-diimine catalysts: Effect of the methyl position in the ligand

Abstract

In the solution polymerizations of methyl methacrylate with (α-diimine)nickel(II)/methylaluminoxane (MAO), we observed effects of the position of two methyl substituents in the ligand on both the activities of the catalysts and the polymer microstructure. α-Diimine nickel(II) catalysts gave syndiotactic-rich poly(methyl methacrylate) with high molecular weight and narrow molecular weight distribution.

Polymerization of Methyl Methacrylate with Nickel(II) and Palladium(II) Iminopyridyl Mononuclear Bimetallic Complexes

“…It is interesting to note that the bimetallic Pd and Ni complexes exhibit higher activities than the corresponding monometallic complexes 5 and 6 (run no. 1 vs. 13 and 7 vs. 14), Ni(acac) 2 /MAO [31], Ni a-diimine/MAO and Fe/Co pyridyl bis(imine)/ MAO systems [11,12]. The similar results have been reported for MMA polymerization with a binuclear Ni and Cu acetylacetonato complexes/MAO systems [20].…”

“…However, only a limited number of catalysts based on late transition metals have been used for homo-and copolymerization of MMA. Ni(acac) 2 /methylaluminoxane (MAO) [7], Ni(II) complexes bearing N,O-chelate ligands activated with MAO [8][9][10], a-diimine Ni(II), and pyridyl bisimine Fe(II) and Co(II) complexes activated with MAO [11,12] yielded poly(methyl methacrylate) (PMMA) with syndiorich microstructure.…”

Polymerization of methyl methacrylate using bis(β‐ketoamino)nickel(II)–MAO catalytic systems

“…5, in the 0.8-3.8 ppm range, three groups of hydrogen protons appear, which are assigned to the hydrogen protons of α-methyl(H a ), methoxy(H d ) and methenes(H e ) in the MMA units, respectively. The 13 C NMR spectrum also shows the characteristic chemical-shift The triad tacticities were determined by using the area ratios of α-methyl(α -CH 3 ) carbon splitting peak in 13 C NMR spectra, and the resulting analyses of rr, mr, mm stereo-triad distributions obtained using the bis(β-ketoamino)nickel(II)(1-6)-MAO catalytic system at 50…”

“…The triad tacticities of the PMMA microstructure were determined by using the area ratios of α-methyl carbon splitting peaks in 13 C NMR spectra. FTIR spectra were recorded on a Nicolet 205 FTIR using conventional KBr pellets method.…”

“…Kim and co-workers reported that late transition metal complexes such as (α-diimine)nickel(II), (pyridyl bis-imine)iron(II) and (pyridyl bis-imine)cobalt(II), which are widely used for the polymerization of olefins, will also polymerize polar monomers such as MMA in combination with methylaluminoxane (MAO) to give syndiorich PMMA. 12,13 In our previous work, we briefly reported that nickel (II) complexes bearing β-ketiminato ligands [N, O] could polymerize MMA to give syndio-rich PMMA with relatively wide molecular weight distributions after activation with MAO.…”