THE METASTABLE PARTIALLY POSITIVELY CHARGED Se6 MOLECULE: PREPARATION, CHARACTERISATION AND X-RAY CRYSTAL STRUCTURE OF [Ag2(Se6)(SO2)2][Sb(OTeF5)6]2, [Ag2Se6][AsF6]2 AND [AgSe6][Ag2(SbF6)3]

Reactions designed to give Se-6[Sb(OTeF5)(6)](2) by the reaction of Se2Br2, 4Se, and 2Ag[Sb(OTeF5)(6)] lead to products that include [Ag-2(Se-6)(SO2)(2)][Sb(OTeF5)(6)](2)(1). The distorted cubic (Ag2Se62+)(n) consists of a Se-6 molecule bicapped by two silver cations (local D-3d sym.). Reactions of AgMX6 (M = As, Sb) with selenium in liquid SO2 yielded crystals of [Ag2Se6][AsF6](2) (2) and [AgSe6][Ag-2(Sbr(6))(3)] (3). Both salts contain stacked arrays of [AgSe6](+) half-sandwich cationic units. [Ag2Se6][AsF6](2) in addition contains stronger linear Se-Ag-Se horizontal linkages between the vertically stacked cationic columns. [AgSe6][Ag-2(SbF6)(3)] features a remarkable three-dimensional {Ag-2(SbF6)(3)](-) anion held together by strong Sb-(FAg)-Ag-... contacts between component Ag+ and SbF6- ions. Hexagonal channels through this honeycomb-like anion are filled by the stacked [AgSe6+](x).