Nickel complexes biguanide

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. 

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