Electronic Properties of Thiolate Compounds of Oxomolybdenum(V) and Their Tungsten and Selenium Analogues. Effects of 17O, 98Mo, and 95Mo Isotope Substution upon ESR Spectra

Article abstract of DOI:10.1021/ja00398a013

The series of crystalline, mononuclear B^+- and triply bridged binuclear B^+- (M = Mo, W; X = S, Se; R = aryl; B = quaternary cation) salts have been isolated and the anions ^- (R = Et, CH2Ph) stabilized in solution at -60 deg C.The mononuclear anions are intensely colored due to a ligand-to-metal charge-transfer transition which is absent in the binuclear species.The magnetic susceptibilities of (Et4N) show a Curie dependence in the range 300-4.2 K with minor deviations in the tungsten compound.The behavior is essentially that of magnetically dilute 4d¹ and 5d¹ systems exhibiting a tetragonal ligand field and greatly reduced spin-orbit coupling on the metal.The presence of strong spin-spin coupling in the binuclear compounds leads to magnetic moments close to 0.ESR spectra (at X- and Q-band frequencies) of the mononuclear anions exhibit axial symmetry, and 98Mo and 95Mo isotope substitution and computer simulation permit accurate extraction of the g and hyperfine tensor anisotropies.Exceptionally narrow line widths permit observation of 17O-superhyperfine coupling in 17O-enriched <98MoO(SPh)4>^- (a = 22.2*10^-4 cm^-1).