A new convenient synthetic route to metal diselenophosphinates: Synthesis and characterization of [M2(Se2PPh2)4] (M = Zn, Cd and Hg) complexes

An efficient synthesis for group 12 metal diselenophosphinates has been elaborated based on original reaction between easily available ammonium diselenophosphinates, NH4[Se2PPh2] or Et2NH2[Se2PPh2] and corresponding metal(II) oxides (0–25 °C, acetone, 1–4 h). The Zn(II), Cd(II), and Hg(II) diselenophosphinates have been first fully characterized to reveal dimers [M2(Se2PPh2)4] in the solid state. These dinuclear species contain an eight-membered chair-like ring, (MSePSe)2, formed by two metal atoms connecting via Se–P–Se chains. The distorted tetrahedral environment of each metal center is defined by four Se atoms belonging to one chelating (η2) and two bridging (μ2, η2) diselenophosphinato ligands. A special feature for Cd(II) complex is the existence of a solvent- and temperature-dependent fluxional process (determined by VT 31P NMR spectroscopy) which was tentatively assigned for the exchange between bridging and chelating “dsepi” (diselenophosphinato) ligands. The free energy of activation for this equilibrium calculated from the coalescence temperature being ΔG≠(233K) = 41.9 kJ mol−1.