Copper complexes mercury ligands

Other metals for which complexes of ligand 79 have been isolated are iron(II)48, 5s, 56,58,59) ir0n(III) 47,52, s4, s6> 59), zinc(II) 57 59), cadmium(II) 59,60,78), mercury(II) 58,78), magnesium(II) S9 60), manganese(II)58>, nickel(II)79), and lead(II)80). The reduction of bis-amws 79 has been reported to afford ligand 81. In addition, the transition metal complexes of iron(III), cobalt(III), nickel(II), and copper(II) with ligand 81 have been prepared and characterized 53). 

Because the mercury chelate is more stable than the corresponding complexes of such cations as calcium, zinc, lead, or copper, complexation of these ions occurs only after the ligand has been freed by the electrode process. 

Soares, H.M.V.M., Vasconcelos, M.T.S.D., 1995. Application of potentiometric stripping analysis for speciation of copper complexes with adsorbable ligands on the mercury electrode. Anal. Chim. Acta 314, 241-249. 

The first metal-olefin complex was reported in 1827 by Zeise, but, until a few years ago, only palladium(II), platinum(Il), copper(I), silver(I), and mercury(II) were known to form such complexes (67, 188) and the nature of the bonding was not satisfactorily explained until 1951. However, recent work has shown that complexes of unsaturated hydrocarbons with metals of the vanadium, chromium, manganese, iron, and cobalt subgroups can be prepared when the metals are stabilized in a low-valent state by ligands such as carbon monoxide and the cyclopentadienyl anion. The wide variety of hydrocarbons which form complexes includes olefins, conjugated and nonconjugated polyolefins, cyclic polyolefins, and acetylenes. 

The Ni(II) complex of the hexaaza macrocyclic ligand 1 is reported to show a high activity for the electrocatalytic reduction of C02 to CO when a rotating copper disc electrode is used (85). In addition, water-soluble Niu-azacyclam complexes, 3a-3g, where R = carboxamide or sulfonamide, either aliphatic or aromatic, are found to be active in the electrocatalytic reduction of C02 at a mercury cathode. The efficiency is comparable to that of [Ni(cyclam)]2+ (14). 

The coordination of catenated nitrogen ligands to transition metals also dates back to the early work of Griess 89, 90), which included references to copper and silver derivatives of 1,3-diphenyltriazene. Around the turn of the century Meldola and Streatfeild 146-148), Meunier 150-152), Niemen-towski and Roszkowski 159), Cuisa and Pestalozza 55,56), and others reported extensively on triazene complexes of copper, silver, and mercury, and in the late 1930s and early 1940s Dwyer and colleagues 69-74) extended this work to include derivatives of nickel and palladium. However, most work on the coordination chemistry of triazenes and other catenated... 

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