Patent ID: 8652231

Claim:
A metal complex, represented by a following formula: [ligand 1] n -(metal) x -[ligand 2] m , wherein the metal is selected from the group consisting of iron, manganese, boron, zinc, molybdenum, nickel, cobalt, and copper, the ligand 1 is a lignosulfonate, and the ligand 2 is selected from the group consisting of citric acid, oxalic acid, malonic acid, succinic acid, malic acid, glutaric acid, phthalic acid, terephthalic acid, adipic acid, and salicylic acid, and n, x, and m are positive integers that satisfy requirements imposed by a number of bonds or of coordinations formed between the metal and the ligand 1 and between the metal and the ligand 2.