The reaction of the tantalocene trihydride complexes Cp' 2 TaH 3 1 (Cp'=η 5 -C 5 H 4 t Bu) or Cp C pTaH 3 1' (Cp = η 5 -C 5 H 2 -1,2-Me 2 -4- t Bu) with propylene sulfide was found to proceed via an unprecedented sulfur transfer and regioselective ring opening reaction at once to yield sulfido-thiolato tantalocene complexes Cp' 2 Ta( S)(S- i Pr) 2a whose structure has been determined by X-ray crystallography or Cp C pTa( S)(S- i Pr) 2'a. Complex 1 reacts with ethylene sulfide to give Cp' 2 Ta( S)(S-Et) 2b. The reactivity of 2a towards a variety of electrophilic moities has been investigated: protonation (with HBF 4 ) and alkylation (with MeI) reactions occur at the terminal sulfur ligand, leading to [Cp' 2 Ta(SH)(S- i Pr)]BF 4 4a, [Cp' 2 Ta(SMe)(S- i Pr)]I 5a; the reaction of 2b with EtI was found to yield [Cp' 2 Ta(S-Et) 2 ]I 6b. Complex 2a (or 2') binds the unsaturated organometallic fragments [W(CO) 5 ] and [W(CO) 4 ]; the new heterobimetallic complexes Cp' 2 Ta(S- i Pr)(μ-S)W(CO) 5 7a (or 7'a) and Cp'(μ-S,S- i Pr)]W(CO) 4 8a (or 8'a) were formed. Inversion of configuration at the bridging μ-S atoms has been observed at low temperature for 8a and has been studied by dynamic 1 H-NMR spectroscopy.