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

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) NiII 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 NiII 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 NiII 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)(m-SO4)(H2O)]2·6H2O (8), respectively, is consistent with the proposed bonding models.