Structures of M2(SO2)6B12F12 (M = Ag or K) and Ag2(H2O)4B12F12: Comparison of the Coordination of SO2 versus H2O and of B12F122- versus Other Weakly Coordinating Anions to Metal Ions in the Solid State

The structures of three solvated monovalent cation salts of the superweak anion B12F122- (Y2-), K-2(SO2)(6)Y, Ag-2(SO2)(6)Y, and Ag-2(H2O)Y are reported and discussed with respect to previously reported structures of Ag+ and K+ with other weakly coordinating anions. The structures of K-2(SO2)(6)Y and Ag-2(SO2)(6)Y are isomorphous and are based on expanded cubic close-packed arrays of Y2- anions with M(OSO)(6)(+) complexes centered in the trigonal holes of one expanded close packed layer of B-12 centroids (circle dot). The K+ and A(g)+ ions have virtually identical bicapped trigonal prism MO6F2 coordination spheres, with M-O distances of 2.735(1)-3.032(2) angstrom for the potassium salt and 2.526(5)-2.790(5) angstrom for the silver salt. Each M(OSO)(6)(+) complex is connected to three other cationic complexes through their six mu-SO2-kappa O-1,kappa O-2' ligands. The structure of Ag-2(H2O)(4)Y is unique [different from that of K-2(H2O)(4)Y]. Planes of close-packed arrays of anions are offset from neighboring planes along only one of the linear circle dot...circle dot...circle dot directions of the close-packed arrays, with [Ag(mu-H2O)(2)Ag(mu-H2O)(2))](infinity) infinite chains between the planes of anions. There are two nearly identical AgO4F2 coordination spheres, with Ag-O distances of 2.371(5)-2.524(5) angstrom and Ag-F distances of 2.734(4)-2.751(4) A. This is only the second structurally characterized compound with four H2O molecules coordinated to a Ag ion in the solid state. Comparisons with crystalline H2O and SO2 solvates of other Ag+ and K+ salts of weakly coordinating anions show that (i) N[(SO2)(2)(1,2-C6H4)](-), BF4, SbF6-, and Al(OC(CF3)(3))(4)(-) coordinate much more strongly to Ag+ than does Y2-, (ii) SnF62- coordinates somewhat more strongly to Kl" than does and (iii) (BCl122-)-Cl-12 coordinates to r about the same as, if not slightly weaker than, Y2-.