Nonheme binuclear transition metal complexes with hydrosulfide and polychalcogenides

Abstract

The intriguing chemistry of chalcogen (S, Se)-containing ligands and their capability to bridge multiple metal centres have resulted in a plethora of reports on transition metal complexes featuring hydrosulfide (HS⁻) and polychalcogenides (E_n²⁻, E = S, Se). While a large number of such molecules are strictly organometallic complexes, examples of non-organometallic complexes featuring HS⁻ and E_n²⁻ with N-/O-donor ligands are relatively rare. The general synthetic procedure for the transition metal–hydrosulfido complexes involves the reaction of the corresponding metal salts with HS⁻/H₂S and this is prone to generate sulfido bridged oligomers in the absence of sterically demanding ligands. On the other hand, the synthetic methods for the preparation of transition metal–polychalcogenido complexes include the reaction of the corresponding metal salts with E_n²⁻ or the two electron oxidation of low-valent metals with elemental chalcogen, often at an elevated temperature and/or for a long time. Recently, we have developed new synthetic methods for the preparation of two new classes of binuclear transition metal complexes featuring either HS⁻, or S_n²⁻ and Se_n²⁻ ligands. The new method for the synthesis of transition metal–hydrosulfido complexes involved transition metal-mediated hydrolysis of thiolates at room temperature (RT), while the method for the synthesis of transition metal–polychalcogenido complexes involved redox reaction of coordinated thiolates and exogenous elemental chalcogens at RT. An overview of the synthetic aspects, structural properties and intriguing reactivity of these two new classes of transition metal complexes is presented.