Crystal structure of π-cyanido-1:2κ2N:C-dicyanido-1κC,2κC-bis(quinolin-8-amine-1κ2N,N')-2-silver(I)-1-silver(II): rare occurrence of a mixed-valence AgI,II compound

Abstract

The title dinuclear complex, [Ag2(CN)3(C9H8N2)2], may be considered as an AgII compound with the corresponding metal site coordinated by two bidentate quinolin-8-amine molecules, one cyanide group and one dicyanidoargentate(I) anion, [Ag(CN)2]-. Since this latter ligand contains an AgI atom, the complex should be a class 1 or class 2 mixed-valence compound, according to the Robin- Day classification. The AgII atom is six-coordinated in a highly distorted octahedral geometry, while the AgI atom displays the expected linear geometry. In the crystal, the amino groups of the quinolin-8-amine ligands form N-H⋯N hydrogen bonds with the N atoms of the non-bridging cyanide ligands, forming a two-dimensional network parallel to (102). The terminal cyanide ligands are not engaged in polymeric bonds and the title compound is an authentic molecular complex. The title molecule is thus a rare example of a stable AgI,II complex, and the first mixed-valence AgI,II molecular complex characterized by X-ray diffraction.