Synthesis and nuclear magnetic resonance studies of molybdenum and tungsten thiolate complexes

Abstract

Reactions of [WCl₃(CO)₂(η⁵-C₅H₅)] with Tl[SC₆F₄H-4] and [WBr₃(CO)₂(η⁵-C₅H₅)] with Tl[SR](R = Ph or C₆H₄Me-4) in dichloromethane gave tungsten(IV) compounds [W(SPh)₃(CO)(η⁵-C₅H₅)]·0.25CH₂Cl₂1a, [W(SC₆H₄Me-4)₃(CO)(η⁵-C₅H₅)]1b and [W(SC₆F₄H-4)₃(CO)(η⁵-C₅H₅)]1c, respectively. Reaction of [MoCl(CO)₃(η⁵-C₅H₅)] with 2 molar equivalents of Tl[SC₆F₄H-4] in diethyl ether gave a mixture of [Mo(SC₆F₄H-4)(CO)₃(η⁵-C₅H₅)]2 and Tl[Mo(SC₆F₄H-4)₂(CO)₂(η⁵-C₅H₅)]3. The photochemical reaction of Tl[Mo(SC₆F₄H-4)₂(CO)₂(η⁵-C₅H₅)] and (SC₆F₄H-4)₂ in tetrahydrofuran (thf) afforded Tl[Mo(SC₆F₄H-4)₄(η⁵-C₅H₅)]4a whilst [WBr₃(CO)₂(η⁵-C₅H₅)] and 5 equivalents of Tl[SC₆F₄H-4] gave Tl[W(SC₆F₄H-4)₄(η⁵-C₅H₅)]4b. These were converted into [N(PPh₃)₂][M(SC₆F₄H-4)₄(η⁵-C₅H₅)](M = Mo or W) on reaction with [N(PPh₃)₂]Cl. Reactions of [W(SC₆F₄H-4)₃(CO)(η⁵-C₅H₅)] with alkali-metal derivatives M′[SC₆F₄H-4] in thf afforded M′[W(SC₆F₄H-4)₄(η⁵-C₅H₅)](M′= K 4c, Rb 4d or Cs 4e). With M′= Na the tetrathiolate complex was obtained as a thf solvate Na[W(SC₆F₄H-4)₄(η⁵-C₅H₅)]·thf 5. Fluorine-19 NMR spectroscopy revealed that 1c and 3–5 undergo several dynamic processes, viz. fluxional behaviour involving rotation/inversion of the SC₆F₄H-4 groups. The spectra of the thallium and caesium derivatives {and ¹³³Cs spectra in the case of Cs[M(SC₆F₄H)₄(η⁵-C₅H₅)]} in addition show coupling between the metal M′ and four of the o-fluorines of the SC₆F₄H-4 groups at low temperatures providing evidence for reversible co-ordination between the M′⁺ cation and the organometallic anion. This behaviour is solvent dependent, occurring more readily in more polar solvents.