Cobalt(II) complexes of organophosphorus ligands with XPNSO skeleton (X = O, S). Solid state structure and solution behavior

Cobalt(II) complexes of type [Co{(XPR2)(O2SR′)N}2] [X = S; R = Ph; R′ = Me (1), Ph (2), C6H4CH3-4 (3); X = O; R = Ph, R′ = Ph (4), R = OEt, R′ = C6H4CH3-4 (5)] were prepared by salt metathesis reactions between CoCl2·6H2O and the potassium salt of the appropriate organophosphorus acid in a 1:2 M ratio. All compounds were characterized by UV–Vis spectroscopy in CH2Cl2 solutions, mass spectrometry, infrared spectroscopy and room temperature magnetic susceptibility. For compounds 1 and 5 electronic spectra were recorded in dimethylformamide (dmfa) as well. While the electronic spectra suggest a monomeric structure in CH2Cl2 solutions with a tetrahedral environment about cobalt(II), for compound 3 in solid state a dinuclear structure was determined by single-crystal X-ray diffraction, with two bridging S,O,O-bimetallic triconnective and two S,O-monometallic biconnective [(SPPh2)(O2SC6H4CH3-4)N]− ligand units. From a CH2Cl2 solution of 1 crystals of the oxidation product [Co(OH){(SPPh2)(O2SMe)N}2] (6) were isolated after standing for several weeks in open atmosphere. Compound 4 in dimethylformamide decomposed and formed the octahedral species [Co(O2PPh2)2(HO2PPh2)2(dmfa)2] (7) (dmfa = dimethylformamide). The redox behavior of 1 was investigated by cyclic voltammetry in CH2Cl2 solution.