Multiple bonds between main group elements and transition metals-LXXXI. Condensation reactions of high-valent pentamethylcyclopentadienyl rhenium complexes with thiophenol and derivatives: Synthetic and structural aspects

The half-sandwich rhenium(VII) complex (η⁵-C₅Me₅)ReO₃ (1; Me = CH₃) undergoes reduction with thiophenol giving the rhenium(V) condensation product (η⁵-C₅Me₅)Re(O)(SC₆H₅)₂ (2a) in high yield. However, toluene-3,4-dithiol reacts only slowly with 1, with traces of the fully substituted rhenium(V) species (η⁵-C₅Me₅)Re(1,2-S₂C₆H₃-4-CH₃)₂ (3a) being formed. The related N,S-chelating ligand 2-aminothiophenol forms the amido derivative (η⁵-C₅Me₅)Re[1,2-S(HN)C₆H₄]₂ (3b) in good yield. Compounds 3a and 3b are also accessible by two alternative routes: (i) from (η⁵-C₅Me₅)Re(O)Cl₂ (4) and the corresponding thiols in the course of two-step substitution/condensation reactions via the intermediates (η⁵-C₅Me₅)Re(O)(1,2-S₂C₆H₃-4-CH₃) (2b) and (η⁵-C₅Me₅)Re(O)[1,2-S(HN)C₆H₄] (2c), respectively; (ii) from the tetrachloro complex (η⁵-C₅Me₅)ReCl₄ (5) and two equivalents of the respective ligands. Employing a 1 : 1 stoichiometry, reaction of (η⁵-C₅Me₄Et)ReCl₄ (5′; Et = C₂H₅) with 2-aminothiophenol yields the amidothiophenolato(N,S) complex of formula (η⁵-C₅Me₄Et)Re[1,2-S(HN)C₆H₄]Cl₂ (6′). The solid-state structure of the bis(dithiolato)rhenium(V) complex 3a was determined by means of X-ray diffraction techniques. The core geometry around the rhenium is almost perfectly square pyramidal, with the five-membered ring ligand occupying the apical position (centroid π-coordination), while the four sulphur atoms define the basal plane. The relatively short distances between the interligand sulphur atoms (297-301 pm) are compatible with possible bonding interactions, e.g. partial disulphide character.