Biguanide with metals

Complex compounds of biguanides and guanylureas with metallic elements. P. Ray, Chem. Rev., 1961,61,313-359(188). 

The numerous highly coloured metal complexes obtainable from biguanides and elements of the transition series have posed yet another interesting structural problem. The accumulated evidence suggests that the structures agreeing most satisfactorily with the observations are of type (I o M = divalent metal). This aspect of the subject has been discussed fully by Ray [532). 

Another variation of the synthesis of biguanides utilising the condensation of cyano-compoimds and amines is the reaction of dicyanimide and two moles of amine (457, 465, 581, 582). In practice (457) a dicyanimide metal salt is fused, or heated in water or in an organic solvent with an amine salt, preferably between 90 and 130°. Condensation may also be effected using free dicyanimide in aqueous acid media (581). 

The bivalent metals, as usual, combine with two molecules of biguanide to form 4-coordinated planar complexes, while the trivalent cobalt and chromium combine with three molecules of the ligand to produce a 6-coordinated octahedral configuration. The only exception is the trivalent silver which yields, however, a 4-coordinated planar complex. The preparation of the free tris(biguanidato) chromium, Cr(C2N5H6)s, in the anhydrous state,6 as well as of the corresponding anhydrous cobalt(III),8 copper(II), cobalt(II), palladium(II), and nickel(II) compounds, provides indisputable evidence for the structure proposed. Similar anhydrous metallic complexes with numerous substituted biguanides also have been included in the above-mentioned studies. 

These consist of a solution, dispersion or suspension of a biguanide polymer reacted with a crosslinking agent to form an adduct and an antimicrobial metal material. The resulting antimicrobial coating does not release biocidal levels of leachables into the surrounding solution. EUROPEAN COMMUNITY EUROPEAN UNION UK USA WESTERN EUROPE... 

In view of the presence of active functional groups at suitable sites in the above ligands and their substituted derivatives, these tend to form coordination compormds/chelates with a large number of metals. Excellent reviews have been published on the complex compounds of biguanides and guanylureas, and biuret. 

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