Bis-biguanide

The longest established silver(III) complexes are the red to brown bi-guanides, like the ethylene bis(biguanide) shown in Figure 4.14 persulphate oxidation of Ag+ in the presence of this ligand gives a silver(III) complex with essentially square planar coordination. 

A number of interesting studies have been carried out on the kinetics and mechanism of biquanide complexes, e.g. bis(biguanide) derivatives of Ni11 and Cu11.243 These kinetic studies have in some cases... 

Chlorhexidine Bis-biguanide Good antibacterial activity, low sensitizing potential and toxicity ... 

In view of the strong colours of many of the biguanide complexes, these have been used as colorimetric reagents, e.g. the use of phenylbiguanide for spectrophotometric determination of Fe and CN ions. A polarographic study" of a bis(biguanide)copper(II) complex gives a kinetically controlled wave prior to a two-electron transfer, followed by a diffusion controlled second wave due to the reduction of bis species in solution. 

The oxidant [Ag en(big)2 ] , where en(big)2 is ethylenediamine-bis(biguanide), reacts with alcohols and hydrazine in aqueous acidic media. In the former reactions, the rate law is first-order in both reactants and an inner-sphere mechanism involving rate-determining C-H bond cleavage is proposed. In the latter reaction, strong second-order catalysis by silver(I) is noted and apparently the Ag" couple is involved. 

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