Investigation on the reactivity of dithiophosphonato/dithiophosphato NiII complexes towards 2,4,6-tris-2-pyridyl-1,3,5-triazine: developments and new perspectives

Abstract

The reactions between tptz and differently substituted dithiophosphonato [Ni(ROpdt)₂] [ROpdt = (RO)(4-MeOC₆H₄)PS₂⁻; R = Et (2); Pr (3); i-Pr (4); Bu (5)] and dithiophosphato [Ni((EtO)₂PS₂)₂] (6) Ni^II complexes have been investigated, and the characterisation of the resulting neutral mixed complexes (2·tptz)-(6·tptz) is reported. In all these complexes, tptz forces one of the two dithiophosphonato/dithiophosphato ligands to behave as a monodentate ligand, a coordination mode rarely found in analogous Ni^II phosphorodithioato complexes. A comparison has been performed between the Ni–S bond distances of the new complexes and those of isologous dithiophosphonato, dithiophosphato and dithiophosphito Ni^II square-planar complexes, and of their penta- and hexa-coordinated adducts. The results, also supported by DFT calculations, are discussed and explained in terms of the structural trans-effect (STE). The reactivity of 2·tptz towards AgNO₃ and CuSO₄ to yield the complex [Ni(EtOpdt)(tptz)(H₂O)]NO₃ (7), and the dimer [(Ni(tptz)(μ-SO₄)(H₂O)]₂·6H₂O (8), respectively, is consistent with the proposed bonding models.