Reversible co-ordination of alkali metals to sulfur-based organometallic ligands [M(SC6F5)4(cp)]–(M = Mo or W, cp =η5-C5H5)

Abstract

The photochemical reaction of Tl[Mo(SC₆F₅)₂(CO)₂(cp)](cp =η⁵-C₅H₅) with C₆F₅SSC₆F₅ in tetrahydrofuran (thf) solution affords the tetrathiolate Tl[Mo(SC₆F₅)₄(cp)]. Similarly the photochemical reaction of [W(SC₆F₅)(CO)₃(cp)] with 4 equivalents of Tl(SC₆F₅) gave Tl[W(SC₆F₅)₄(cp)] in low yield. Reactions of [MI₃(CO)₂(cp)](M = Mo or W) and [W(SC₆F₅)₃(CO)(cp)] with M′(SC₆F₅) in thf solution gave the ionic derivatives Cs[Mo(SC₆F₅)₄(cp)], M′[W(SC₆F₅)₄(cp)](M′= Cs, Rb or K) and the solvated derivatives [M′(thf)_n][W(SC₆F₅)₄(cp)](M′= Li, n= 4; M′= Na, n= 1). Fluorine-19 NMR studies reveal fluxional behaviour involving the C₆F₅ groups in all the derivatives. Dynamic ¹³³Cs and ¹⁹F NMR spectra of Cs[M(SC₆F₅)₄(cp)] in addition show coupling between caesium and four of the ortho-fluorines of the SC₆F₅ groups, J(Cs–F)≈ 58 Hz, at low temperatures providing evidence for reversible co-ordination between Cs⁺ and the organometallic anion.