Electon-Deficient d- and f-Transition Metal Complexes with Sulfur Ligands

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(1)We have isolated variegated sulfide complexes from reactions of Li_2S_x(x=l, 2, 4)with Cp^*TaCl_4(Cp^*=eta^5-C_5Me_5). A common facet of these sulfide complexes is that they possess Li cations bound strongly to sulfur. By taking an advantage of having such lithiums, we found a new route to heteronuclear clusters comprising a common Cp^*TaS_3 unit. For example, [Cp^*TaS_3Li_2(thf)_2]_2 reacts with[RhCl(cod)]_2 to give the TaRh_2 trinuclear complex(Cp^*TaS_3)[Rh(cod)]_2. The structure was found not rigid in a solution, and the fluxional behavior was monitored by the ^1H-NMR signals arising from the olefinic protons in cod ligands. We postulate that the two Rh(cod)fragments migrate below the TaS^3 unit via a 3-coordinate intermediate, during which time each cod ligand switches its coordination site within the Rh(cod)unit,(2)The reaction of[Cp^*TaS_3Li_2(thf)_2]_2 with either(Ph_4P)_2(Fe_4S_4Cl_4), (Ph_4P)(Fe_3(SPh)_3), or(Ph_4P)_2(Fe_2S_2Cl_2)at 50ﾟC in THF gave rise to a formation of … More a Ta_<>2Fe cluster, (Cp^*TaS_3)Fe^<2->. This finding imply a possible dissociation of the iron-sulfur clusters in a solution.(3)In the reaction between Cp^*TaCl_4 and LiS^tBu we observed a stepwise replacement of chloride in with the thiolate. Thus, addition of a THF solution of 2 equiv LiS^tBu afforded Cp^*TaCl_2(S^tBu)_2 while Cp^*TaCl(S^tBu)_2 while Cp^*TaCl(S^tBu)_3 was prepared from the (1 : 3) Cp^*TaCl_4/LiS^tBu reaction system. When the amount of LiS^tBu was increased to 4 equiv, a facile C-S bond repture occurred to give rise to a sulfide complex, Cp^*TaS(S^tBu)_2. The main product of the reaction between Cp^*TaCl_4 and 6-8 equiv of LiS^tBu in THF is again the sulfide complex.(4)We have analyzed the fluydonal behavior of a homoleptic dithiolate complex of uranium[Li_4(dme)_4][U(SCH_2CH_2^S)_4] by ^<>H NMR to find that there are two dynamical processes ; one is a site exchange of sulfur atoms in the dodecahedral US8 coordination sphere, and the other is the conformation change of the USCCS ring. The activation parameters of these processes have been determined. Less