Reactions of Schiff Base‐Substituted Diselenides and ‐tellurides with Ni(II), Pd(II) and Pt(II) Phosphine Complexes

The salicylidene Schiff bases of bis(2‐aminophenyl)diselenide and ‐ditelluride react with [MIICl2(PPh3)2] (M = Ni, Pt) or [PdII(OAc)2(PPh3)2] with formation of square‐planar complexes with the general formulae [MII(LY)(PPh3)] (M = Ni, Pd, Pt, Y = Se, Te). The ligands coordinate to the metals as tridentate {O,N,Se/Te} chelates. The reduction of the dichalcogenides and the formation of the chalcogenolato ligands occurs in situ by released PPh3 ligands. A mechanism for such reactions has been derived from the experimental data with the aid of DFT calculations. It suggests a higher polarization of the dichalcogenide bond with partial charge separation upon coordination to a metal centre, which therefore facilitates the cleavage of the dichalcogenide bond with PPh3. In accordance with the proposed mechanism, best yields are obtained with a strict exclusion of oxygen, but in the presence of water. Stable nickel(II), palladium(II) and platinum(II) complexes with selenolato‐ or tellurolato‐substituted Schiff bases are obtained from reactions of the corresponding dichalcogenides with PPh3‐containing metal(II) starting materials. Released phosphine ligands act as selective reducing agents for metal‐coordinated dichalcogenides during such reactions.