Complexes of 2,9-dimethyl-1,10-phenanthroline with palladium(II) and platinum(II) halides are described. The methyl groups of the ligand introduce strong steric hindrance in some of the normal geometries of these transition-metal complexes, and evidence is presented for five- coordination in the bis(dmp) compounds of these two metals.

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Solutions of copper(II) salts and excess 2,9-dimethyl-1,10-phenanthroline (dmp) in organic solvents yielded complexes of formula Cu(dmp),X,.H,O, where X=NO3, Cl, and Br. When excess of the copper(II) salt was present, mono complexes represented by CudmpX2, where X=NO3, Cl, Br ; 2X=SO4 were obtained. Copper(II) perchlorate-dmp mixtures yielded hydrated Cu(dmp),(ClO4)2. Aqueous solutions of the bis complexes changed colour when boiled and deposited red crystals of composition Cu(dmp)2X, with water of crystallization in some cases. Bis(dmp)copper(I) nitrate, perchlorate, and sulphate were also produced by reduction of the copper(II) complexes with hypophosphorus acid or hydroxylamine salts. The visible absorption curves for solutions of the complexes Cu(dmp)2X, corresponded with those reported in studies of the spectrophotometric estimation of copper using dmp. Mono complexes of formula CudmpX, where X=Cl, Br, and I, were prepared by reduction of the corresponding copper(II) complexes.

A direct synthesis of 2,9-dimethyl-1,10-phenanthroline has been developed. The method involves a Skraup type of reaction between o-phenylenediamine, crotonaldehyde, and either arsenic(V) oxide or sodium m-nitrobenzenesulphonate. Some derivatives of 2,9-dimethyl-1,10-phenanthroline have been characterized.

Four ions were studied at the dropping mercury electrode. They were [Pt(ophen)2]2+, [Pt(ophen)(en)]2+, [Pt(ophen)(py)2]2+, and [Pt(ophen)(py)Cl]+, where ophen= 1,10- phenanthroline, en=ethylenediamine, and py=pyridine. The shapes of the c-v curves of the ions in supporting electrolyte 0.1M KCl, were dependent on complex ion concentration. Adsorption phenomena occurred with some ions but the effects decreased as the complex ion concentration decreased. The reduction of [Pt(ophen)2]2+ produced evidence for compounds of platinum with valency less than two. Reduction of the other ions appeared to proceed directly to metallic platinum.