Disclosed are nickel-containing complexation precursors having high complexation activity for bidentate phosphite ligands. Also disclosed are methods of making the complexation precursors. The disclosed method of generating the nickel-containing complexation precursor includes including contacting a nickel starting material with a reductant under conditions sufficient to generate a nickel-containing complexation precursor having at least about 1,500 ppmw sulfur in the form of sulfide.