VINYLIDENE, ACETYLIDE, AND CARBENE COMPLEXES FROM REACTIONS OF 2,5-DITHIAHEX-3-YNE (MESCCSME) WITH CP(PME3)2RU+

The alkyne MeSC = CSMe initially displaces Cl-in Cp(PMe3)2RuCl at room temperature in MeOH to form the sulfur-bound alkyne complex {Cp(PMe3)2Ru[S(Me)C = CSMe]}PF6 (1). When it is warmed, 1 rearranges to the vinylidene complex [Cp(PMe3)2Ru = C = C(SMe)2]PF6 (2). Complex 2 is reduced by Na[HBEt3] or Na/Hg to give the thioacetylide Cp(PMe3)2Ru - C = CSMe (5) and MeSSMe. The vinylidene complexes [Cp(PMe3)2Ru = C = C(R)(SMe)]+ (6, R = H; 7, R = Me) are formed by electrophilic addition to the beta-carbon of the thioacetylide 5. Addition of CuCl to 5 forms Cp(PMe3)2Ru(C = CSMe)(CuCl) (8), in which the copper is pi-bound through the C = C group. Reaction of 6 with methanol and ethanol yields the alkoxycarbene complexes [Cp(PMe3)2Ru = C(OR)(CH2SMe)]BF4 (11a, R = Me; 11b, R = Et). Deprotonation of 11a with NaOMe yields the vinyl complex Cp(PMe3)2Ru[C(OMe) = C(H)SMe] (12). Addition of [Me3O]BF4 to complexes 6 and 7 yields the first examples of sulfoniovinylidene dicationic complexes [Cp(PMe3)2Ru = C = C(R)(SMe2)](BF4)2 (9, R = H; 10, R = Me). An X-ray diffraction investigation shows that 9 crystallizes in space group P2(1)/n with a = 16.641 (2) angstrom, b = 8.861 (1) angstrom, c = 18.168 (2) angstrom, beta- = 114.80 (1)-degrees, and Z = 4. Complexes 7 and 10 undergo one-and two-electron reductions, respectively, to give the acetylide Cp(PMe3)2Ru-C = CMe (14) and MeSSMe (for 7) or SMe2 (for 10). Complexes 6 and 9 are readily deprotonated to give 5 and the sulfonioacetylide [Cp(PMe3)2Ru-C = CSMe2]BF4 (13), respectively. Mechanisms of the reactions and structural features of the vinylidenes are discussed.