Plasticity of the coordination sphere of Ag²⁺

Abstract

The geometric distortions of the ligand environment around Ag2+ cations have been examined for over 20 structurally characterized fluorides of Ag2+. Divalent silver is subject to a strong Jahn–Teller effect and it is most frequently found in an elongated or a compressed octahedral site. Typical Ag–F bond lengths vary from 2.34 to 2.60 Å (axial, R ax) and from 2.01 to 2.11 Å (equatorial, R eq) for the elongated octahedral site. The corresponding values for the compressed octahedral coordination are 2.00–2.09 Å (R ax) and 2.20–2.42 Å (R eq). The ellipsoidal Ag2+ cation exhibits significant plasticity of its coordination sphere, similar to its lighter d9 congener, Cu2+: the dependence of R eq vs. R ax is inverse and monotonic. The Jahn–Teller distortion parameter D (=R ax/R eq) takes values from 0.83 to 1.29, with the forbidden range from 0.94 to 1.11 (close to ideal octahedron). Novel parametrization and subsequent analysis of the valence bond sums reveal that selected compounds of Ag2+ require careful structural re‐examination. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Polymorphism of Fluoroargentates(II): Facile Collapse of a Layered Network of α‐K2AgF4 Due to the Insufficient Size of the Potassium Cation

“…The α polymorph is two dimensional with puckered [AgF 2+4/2 ] 2-sheets and corner-sharing octahedra, whereas β-K 2 AgF 4 consists of chains of edge-sharing octahedra propagating along the crystallographic a axis (Figure 2). Large differences in bond lengths between the α and β polymorphs testify to the plasticity of the coordination sphere of Ag II , [13] similar to that found for analogous compounds of Cu II . [14] The coordination sphere of Ag 2+ in β-K 2 AgF 4 , consisting of two very long Ag-F bonds (2.710 Å) and four shorter contacts (2 ϫ 2.059 and 2 ϫ 2.103 Å), can be viewed as nearly planar, similar to that of Ag II [MF 4 ] 2 (M = Ag III , Au III ).…”

Pressure-induced transformations of AgIIF2—towards an ‘infinite layer’ d9material

“…(i) in this structure, Ag 2+ would attain the ligand environment of a nearly undistorted octahedron; this is very suspicious, provided that a 4d 9 system is subject to a very strong Jahn-Teller effect [19]; (ii) the claimed unit cell volume per formula unit is as small as 29.05Å…”

Silverland: the Realm of Compounds of Divalent Silver—and Why They are Interesting

“…The broken line is drawn for R ax = R eq ; the dotted line is a guide to the eye. Reproduced with permission from [69]; for an update, cf. [45] the 2(+4) case (compressed O h ) rather than the 4(+2) case (elongated O h ).…”