Approaching the gas-phase structures of [AgS8](+) and [AgS16](+) in the solid state

作者：Cameron TS; Decken A; Dionne I; Fang M; Krossing I^*; Passmore J

来源：Chemistry - A European Journal, 2002, 8(15): 3386-3401.

DOI：10.1002/1521-3765(20020802)8:15<3386::AID-CHEM3386>3.0.CO;2-9

• ab initio calculations
• cations
• density functional theory
• silver
• sulfur
• weakly coordinating anion

Upon treating elemental sulfur with [AgSbF6], [AgAl(hfip)(4)], [AgAl(pftb)(4)] (hfip=OCH(CF3)(2), pftb = OC(CF3)(3)) the compounds [Ag(S-8)(2)]-[SbF6] (1), [AgS8][Al(hfip)(4)] (2), and [Ag(S-8)(2)]+[[Al(pftb)(4)](-) (3) formed in SO2 (1), CS2 (2), or CH2Cl2 (3). Compounds 1-3 were characterized by single-crystal X-ray structure determinations: 1 by Raman spectroscopy, 2 and 3 by solution NMR spectroscopy and elemental analyses. Single crystals of [Ag(S-8)(2)](+)[Sb(OTeF5)(6)](-) 4 were obtained from a disproportionation reaction and only characterized by X-ray crystal structure analysis. The Ag+ ion in 1 coordinates two monodentate SbF6- anions and two bidentate S8 rings in the 1,3-position. Compound 2 contains an almost C-4v-symmetric {AgS8}(+) moiety; this is the first example of an eta(4)-coordinated S-8 ring (d(Ag-S) = 2.84-3.00 Angstrom). Compounds 3 and 4, with the least basic anions, contain undistorted, approximately centrosymmetric Ag(eta(4)-S-8)(2)(+) cations with less symmetric eta(4)-coordinated Ss rings (d(Ag-S)= 2.68-3.35 Angstrom). The thermochemical radius and volume of the undistorted Ag(S-8)(2)(+) cation was deduced as r(therm)(Ag(S-8)(2)(+)) = 3.378 + 0.076/ - 0.120 Angstrom and V-therm(Ag(S-8)(2)(+)) = 417+4/-6 Angstrom(3). AgS8+ and several isomers of the Ag(S-8)(2)(+) cation were optimized at the BP86, B3LYP, and MP2 levels by using the SVP and TZVPP basis sets. An analysis of the calculated geometries showed the MP2/TZVPP level to give geometries closest to the experimental data. Neither BP86 nor B3LYP reproduced the longer weak dispersive Ag-S interactions in Ag(eta(4)-S-8)2+ but led to Ag(eta(3)-S-8)(2)(+) geometries. With the most accurate MP2/TZVPP level, the enthalpies of formation of the gaseous [AgS8](+) and [Ag(S-8)(2)](+) cations were established as Delta(f)H(298)([Ag(S-8)(2)](+), g) = 856 kJ mol(-1) and Delta(f)H(298)([AgS8](+), g) = 902 kJ mol(-1). It is shown that the {AgSh}(+) moiety in 2 and the {AgS8}(2)(+) cations in 3 and 4 are the best approximation of these ions, which were earlier observed by MS methods.

• 出版日期2002-8-2