Silanethiolate salts of K(18-crown-6)+, N(CH3)4 +, Cs+, K+ were synthesized and characterized by vibrational and NMR spectroscopy. The [N(CH3)4][SSi(CH3)3] salt was used to prepare the new [N(CH3)4][WSF5] salt directly from WF6. Alternatively, [N(CH3)4][WSF5] was prepared by the reaction of WSF4 with [N(CH3)4][F]. Pure WSF4 was prepared via a facile new route and was fully characterized by Raman, infrared, and 19F NMR spectroscopy, and an improved crystal structure. The Lewis-acid properties of WSF4 were studied in reactions with pyridine, yielding the new WSF4·C5H5N adduct, which was studied by Raman and 19F NMR spectroscopy. A 2:1 stoichiometry of WSF4 and [N(CH3)4][F] yielded W2S2F9 - in solution. The novel W2SOF9 - anion was characterized in solution by 19F NMR spectroscopy. Molybdenum sulfide tetrafluoride was synthesized and unambiguously characterized by Raman, infrared, and 19F NMR spectroscopy and single-crystal X-ray diffraction. The experimental characterization of WSF4, MoSF4, WSF5 -, and SSi(CH3)3 - was supplemented by density functional theory calculations. / xv, 131 leaves : ill. ; 29 cm.