Sulfur-Coordinated Thiophene and Dibenzothiophene in Cp′(CO)₂Re(thiophene) Complexes

A series of stable S-bound thiophene complexes Cp′(CO)₂Re(Th), Cp′ = C₅H₅ or C₅Me₅, Th = thiophene (T), 2−MeT, 3−MeT, 2,5−Me₂T, Me₄T, and dibenzothiophene (DBT), are prepared by the reaction of Cp′(CO)₂Re(THF) with thiophenes. The first structural determination of a simple nonchelated S-coordinated thiophene complex Cp^*(CO)₂Re(T) is reported. Reactions of several of the Cp′(CO)₂Re(Th) complexes display-equation (Th = T, 2-MeT, and 3-MeT) with Fe₂(CO)₉ give thiophene-bridging dinuclear compounds Cp′(CO)₂Re-(μ₂−η⁴(S)-Th)Fe(CO)₃ in which thiophene is coordinated to the Re via the sulfur and to the Fe through the four carbons of the diene system. This reaction is the first to demonstrate that S coordination activates thiophene to undergo further reactions.