Hydrothermal syntheses and structures of two mixed-valence copper(I,II) 2-pyrazinecarboxylate coordination polymers.

Replacement of linear ligand L in Cu(I)XL system (X = halide or pseudohalide; L = 4,4'-bipyridine or pyrazine) by neutral species Cu(pzc)2(H2O)x (pzc = 2-pyrazinecarboxylate) resulted in mixed-valence Cu(I,II) coordination polymers [Cu2(pzc)2Br(H2O)]n (1) and [Cu3(pzc)2(CN)2(H2O)2 x 2H2O]n (2). Complex 1 has two-dimensional (4,4) topological layer constructed by [CuBr]n chains and Cu(pzc)2(H2O) species, while 2 has a three-dimensional framework formed by linkage of two-dimensional (6,3) layers via ligand-unsupported Cu(I)-Cu(I) interactions. The two-dimensional (6,3) layer in 2 is constructed by zigzag [CuCN]n chains and Cu(pzc)2(H2O)2 species. Cyanides in 2 were produced by oxidative desulfation of SCN- anions.