Chelating agents reduced catalyst

The antioxidant synergists enhance the effect of antioxidants. Chelating agents like ethylenediaminetetraacetic acid (EDTA) are commonly added to parenterals. They may reduce oxidative damage by forming complexes with oxidative metal ion catalysts. Chelating agents are further discussed in Section 14.2.6. 

In 1955, Warner-Jauregg et showed that copper (II) chelates were particularly efficient catalysts of the hydrolysis of DFP. For example, a CuS04-dipyridyl (1 1) complex (0.0228 M in pH 7.6 buffer) reduced the half-life to 4.5 min from an uncatalysed half-life of >2500 min. This work was extended by Courtney et who examined a series of chelating agents and various metal complexes as hydrolysis catalysts for DFP and sarin. Copper (II) catalysts as a group were shown to be the most effective. 

The catalyst systems may roughly be divided into two groups (1) Ziegler-Natta type catalysts composed of a Ni(II) salt or complex activated by a Lewis acid (frequently an organoaluminum compound) or a Bronsted acid and often modified by a P-donor [PR3 or P(0R)3] and (2) one-component systems, most of them composed of a Ni(II) chelate complex with a Ni—C bond that are active without a Lewis acid or reducing agent as cocatalyst. 

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