Well-Defined and Highly Effective Nickel Catalysts Coordinated on Tridentate SNO Schiff-Base Derivatives for Alternating Copolymerization of Epoxides and Anhydrides.

A series of Ni complexes supported by SNO Schiff-base derivatives were synthesized in this study. Complex synthesis and characterization data are reported herein. Treatment of the pro-ligands [L-H = 2-(((2-(methylthio)ethyl)imino)methyl)phenol, L-H = 2,4-di--butyl-6-(((2-(methylthio)ethyl)imino)methyl)phenol, L-H = 2-(((2-(methylthio)ethyl)imino)methyl)-4,6-bis(2-phenylpropan-2-yl)phenol, L-H = 4-bromo-2-(((2-(methylthio)ethyl)imino)methyl)phenol, and L-H = 4-chloro-2-(((2-(methylthio)ethyl)imino)methyl)phenol] with Ni(OAc)·4HO in refluxing ethanol afforded six-coordinate mono-Ni(II) complexes [LNi] ( = 1-5). Noteworthy, a heptanuclear nickel(II) octacarboxylate species complex and dinuclear nickel complex resulted from treatment of L-H [4-fluoro-2-(((2-(methylthio)ethyl)imino)methyl)phenol] with different metal precursors [Ni(OAc)·4HO for 6; NiBr for ] giving a quantitative yield. The reaction of nickel acetate tetrahydrate and L-H to L-H [L-H = 2-methoxy-6-(((2-(methylthio)ethyl)imino)methyl)phenol, L-H = 5-methoxy-2-(((2-(methylthio)ethyl)imino)methyl)phenol, and L-H = 4-methoxy-2-(((2-(methylthio)ethyl)imino)methyl)phenol] produced the four-coordinate complexes [LNi] ( = 7-9). The highest performing catalyst was complex , which was highly efficient for the ring-opening copolymerization of phthalic anhydride (PA) and cyclohexene oxide (CHO) in the presence of a cocatalyst (4-dimethylaminopyridine). In addition, the same copolymerization conditions produced narrowly dispersed polyesters, with high selectivity and polymerization control. In addition to PA-CHO copolymerization, efficient diglycolic anhydride-PA and PA-propene oxide copolymerization was achieved under the same conditions. These catalysts are straightforward to produce and extend the scope of potential substrates.