Examples of Different Reactions of Benzylsulfanyl-Substituted Alkynes with Selected Complexes of TiII and CoI

Reactions of the group 4 metallocene alkyne complexes [Cp2M(L)(btmsa)] (Cp = (5)-cyclopentadienyl = (5)-C5H5, btmsa = (2)-Me3SiC2SiMe3; 1: M = Ti, L = none; 2: M = Zr, L = pyridine) and of the [(triphos)Co-I] moiety [triphos = 1,1,1-tris(diphenylphosphanylmethyl)ethane] with the benzylsulfanyl-substituted acetylenes PhCH2S-C-2-SCH2Ph (3) and PhCH2S-C-2-SFmoc (4) (Fmoc = fluorenylmethoxycarbonyl) have been investigated. Complex 1 reacted with 3 to give a mixture of a violet solid and [Cp2Ti(SCH2Ph)(2)] (5). Subsequently, the violet solid transformed in toluene at 70 degrees C into the dinuclear complex [(Cp2Ti)(2)(-(2)-(2)-BnSC4SBn)] (6) displaying two [Cp2Ti] moieties bridged by a 1,4-bis(benzylsulfanyl)-1,3-butadiyne in the trans configuration. Complex 6 was further degraded in toluene at 100 degrees C to the tetranuclear cluster [CpTiS](4) (7). Similar reactivity was deduced indirectly for the reaction partners 1/4 and 2/3. For Co-I, the side-on alkyne complexes [(triphos)Co(3)](PF6) (9-PF6) and [(triphos)Co(4)](PF6) (10-PF6) were obtained. Reductive removal of the benzyl groups in 9-PF6 and subsequent coordination of the [Cp(PPh3)Ru-II](+) moiety led to the dinuclear complex [(triphos)Co(-(2)-(2)-C2S2)RuCp(PPh3)] (13) displaying acetylene dithiolate (acdt(2-)) in a side-on carbon-sulfur chelate coordination mode. In contrast, the reaction of 10-PF6 with piperidine under very mild conditions resulted in the thio-alkyne complex [(triphos)Co(PhCH2SC2S)] (11) bearing a terminal sulfur substituent at the coordinated alkyne. However, a subsequent rearrangement reaction led to the Co-III dithiolene complex [(triphos)Co{S2C2(NC5H10)(CH2Ph)}](PF6) (14-PF6). The intricate rearrangement very likely involves a dinuclear Co species with a (2)-(2) coordination of the C2S2 moiety.