Structures of M(SO)BF (M = Ag or K) and Ag(HO)BF: Comparison of the Coordination of SO versus HO and of BF versus Other Weakly Coordinating Anions to Metal Ions in the Solid State.

The structures of three solvated monovalent cation salts of the superweak anion BF (Y), K(SO)Y, Ag(SO)Y, and Ag(HO)Y, are reported and discussed with respect to previously reported structures of Ag and K with other weakly coordinating anions. The structures of K(SO)Y and Ag(SO)Y are isomorphous and are based on expanded cubic close-packed arrays of Y anions with M(OSO) complexes centered in the trigonal holes of one expanded close-packed layer of B centroids (⊙). The K and Ag ions have virtually identical bicapped trigonal prism MOF coordination spheres, with M-O distances of 2.735(1)-3.032(2) Å for the potassium salt and 2.526(5)-2.790(5) Å for the silver salt. Each M(OSO) complex is connected to three other cationic complexes through their six μ-SO-κO,κO' ligands. The structure of Ag(HO)Y is unique [different from that of K(HO)Y]. Planes of close-packed arrays of anions are offset from neighboring planes along only one of the linear ⊙···⊙···⊙ directions of the close-packed arrays, with [Ag(μ-HO)Ag(μ-HO))] infinite chains between the planes of anions. There are two nearly identical AgOF coordination spheres, with Ag-O distances of 2.371(5)-2.524(5) Å and Ag-F distances of 2.734(4)-2.751(4) Å. This is only the second structurally characterized compound with four HO molecules coordinated to a Ag ion in the solid state. Comparisons with crystalline HO and SO solvates of other Ag and K salts of weakly coordinating anions show that (i) N[(SO)(1,2-CH)], BF, SbF, and Al(OC(CF)) coordinate much more strongly to Ag than does Y, (ii) SnF coordinates somewhat more strongly to K than does Y, and (iii) BCl coordinates to K about the same as, if not slightly weaker than, Y.