The Fascinating Chemistry of Binary and Ternary Copper Oxides

1 The Fascinating Chemistry of Binary and Ternary Copper Oxides. 

TABLE 9 Reported Superconducting Transition Temperatures in the LiTi204 System. 

The Cupric, Cu2+ or Cu(II) State, 3d9 The most important and stable oxidation state for copper is divalent. There is a well-defined aqueous chemistry of the Cu2+ ion, which generates the familiar blue solution when complexed with water. A large number of copper coordination compounds exist and these have been studied extensively. A strong Jahn-Teller distortion is associated with the 3d9 electronic configuration of this ion. This implies that a regular tetrahedron or octahedron about the Cu2+ ion is never observed, except in the rare occurrence of a dynamic Jahn-Teller effect. The tetragonal distortion about an octahedron can lead to a square-planar coordination which is often observed in Cu(II) oxides. 

the mineral tenorite, and AgO are well known but their structures are quite different. More importantly the valence states in these two compounds are quite different. In CuO, the copper is formally in the divalent state, whereas in AgO, there exist two types of silver atoms, one in formal oxidation state 1+, the other in 3+. These two silver ions also possess strong covalent character. PdO and CuO, however, have similar crystal structures based on chains of opposite edged-shared, square-planar M04 groups. 

The best indicator of covalent-ionic character in the Cu-0 bond is the observed Cu-O bond length (see 3.2 below). 

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