[CpTi(mu(3)-S)(3){Rh(tfbb)}(3)]: An early-late heterometallic complex as molecular model for the deactivation of metal sulphide catalysts

The heterotetranuclear complex [CpTi(mu(3),-S)(3){Rh(tfbb)}(3)] (1) (tfbb = tetrafluorobenzobarrelene) has been prepared in moderate yield by reacting Cp(2)Ti(SH)(2) with [Rh(mu-MeO)(tfbb)](2) in toluene at room temperature, and its structure has been determined by an X-ray diffraction study. Crystals of 1 are monoclinic, space group P2(1)/a, with cell parameters a = 19.975(4), b = 27.352(6), c = 8.186(3) Angstrom, beta = 97.15(2)degrees and Z = 4. The complex displays an incomplete distorted cubane-type structure, involving the four metals and the three triple-bridging sulphur atoms. The metals exhibit usual pseudotetrahedral (Ti) and distorted square-planar (Rh) environments. This molecular structure could be considered as a molecular analogue for the understanding of poisoning of commercial metal sulphide catalysts. The direct bonding of titanium with sulphur atoms and the intermetallic Ti-Rh interactions, 2.912-2.940(3) Angstrom, could be involved in these undesirable processes. Replacement reactions of the diolefin ligands in 1 by CO and PPh(3) occur with retention of the structure and nuclearity giving [CpTi(mu(3)-S)(3){Rh(CO)(2)}(3)] (2) and [CpTi(mu(3)-S)(3){Rh(CO)(PPh(3))}(3)] (3), showing the remarkable stability of the incomplete cubane framework containing early and late transition metals bridged by sulphido ligands.