chelating agents (kēˈlātĭng) [key]. Certain organic compounds are capable of forming coordinate bonds (see chemical bond) with metals through two or more atoms of the organic compound; such organic compounds are called chelating agents. The compound formed by a chelating agent and a metal is called a chelate. A chelating agent that has two coordinating atoms is called bidentate; one that has three, tridentate; and so on. EDTA, or ethylenediaminetetraacetate, ( - O2CH2)2NCH2CH2N(CH2CO2 - )2, is a common hexadentate chelating agent. Chlorophyll is a chelate that consists of a magnesium ion joined with a complex chelating agent; heme, part of the hemoglobin in blood, is an iron chelate. Chelating agents are important in textile dyeing, water softening, and enzyme deactivation and as bacteriocides.