Influence of H2S and Thiols on the Binding of Alkenes and Alkynes to ReS4-:  The Spectator Sulfido Effect

The three-component reaction of ReS4- (1), H2S, and unsaturated substrates (un = alkene, alkyne) affords the ReV derivatives Re(S)(S2un)(SH)2-. These adducts arise via the addition of H2S to intermediate dithiolates ReS2(S2C2R4)- and dithiolenes ReS2(S2C2R2)-. The species {ReS[S2C2(tms)2](SH)2}-, [ReS(S2C7H10)(SH)2]- (3), and [ReS(S2C2H4)(SH)2]- are prepared according to this route. Similarly, the selenolate−thiolate complex [ReS(S2C7H10)(SeH)(SH)]- (5) is produced by the reaction of [ReS2(S2C7H10)]- with H2Se. The corresponding reactions using benzenethiol in place of H2S afford the more thermally robust adducts {ReS[S2C2(tms)2](SH)(SPh)}-, [ReS(S2C7H10)(SH)(SPh)]- (7), and [ReS(S2C2H4)(SH)(SPh)]-. Norbornanedithiolato compounds 3, 5, and 7 are obtained as pairs of isomers that differ in terms of the relative orientation of the norbornane bridgehead relative to the ReS unit. The reaction of [ReS(S2C7H10)(SD)2]- (3-d2) with H2S to give 3 is proposed to proceed via elimination of D2S and subsequent addition of H2S. Variable-temperature 1H NMR measurements on the equilibrium of [ReS(S2C6H12)(SPh)(SH)]- with 1, 1-hexene, and PhSH gave the following results:  ΔH = −7 (±1) kJ·mol-1; ΔS = 23 (±4) J·mol-1·K-1. Solutions of ethanedithiol and 1 react with C2(tms)2 and C2H4 to give {ReS[S2C2(tms)2](S2C2H4)}- and [ReS(S2C2H4)2]-, respectively, concomitant with loss of H2S. The pathway for the ethanedithiol reaction is examined using 2-mercaptoethanol, affording {ReS[S2C2(tms)2](SC2H4OH)}-, which does not cyclize. Treatment of a solution of diphenylbutadiyne and 1 with PhSH gives two isomers of the dithiolene {ReS(SH)(SPh)[S2C2Ph(C2Ph)]}-. The corresponding reaction of ethanedithiol, diphenylbutadiyne, and 1 affords the 1,4-diphenylbutadiene-1,2,3,4-tetrathiolate complex {[ReS(S2C2H4)]2(S4C4Ph2)}2-.