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 Se6[Sb(OTeF5)6]2 by the reaction of Se2Br2, 4Se, and 2Ag[Sb(OTeF5)6] lead to products that include [Ag2(Se6)(SO2)2][Sb(OTeF5)6]2 (1). The distorted cubic (Ag2Se6+2)n consists of a Se6 mol. bicapped by two silver cations (local D3d sym.). Reactions of AgMX6 (M = As, Sb) with selenium in liq. SO2 yielded crystals of [Ag2Se6][AsF6]2 (2) and [AgSe6][Ag2(SbF6)3] (3). Both salts contain stacked arrays of [AgSe6]+ half-sandwich cationic units. [Ag2Se6][AsF6]2 in addn. contains stronger, linear Se-Ag-Se horizontal linkages between the vertically stacked cationic columns. [AgSe6][Ag2(SbF6)3] features a remarkable three-dimensional [Ag2(SbF6)3]- anion held together by strong Sb-F...Ag contacts between component Ag+ and SbF6- ions. Hexagonal channels through this honeycomb-like anion are filled by the stacked [AgSe6+]x. [on SciFinder (R)]