Tetrahedral CoII complexes with CoI2O2 and CoO2S2 cores. Crystal structures of [Co{HN(OPPh2)(SPPh2)-O}2I2] and [Co{N(OPPh2)(SPPh2)-O,S}2]

The compound [CoII{HN(OPPh2)(SPPh2)-O}2I2] (1) was synthesised by the reaction of cobalt in powder with the iodine adduct of tetraphenylthiooxoimidodiphosphinic acid, HN(OPPh2)(SPPh2), in Et2O; treatment of compound 1 with NaOH resulted in deprotonation of the ligands bound to the metal ion and a separation of [CoII{N(OPPh2)(SPPh2)-O,S}2] (2). Molecular structures of complexes 1 and 2 were elucidated by X-ray diffraction analysis, which revealed a CoI2O2 tetrahedral core for compound 1 in which two neutral ligands bind through the oxygen atoms the CoII ion, and a tetrahedral CoO2S2 core for compound 2 with the oxygen and sulfur atoms of each anionic ligand chelating a CoII centre. Variable-temperature magnetic susceptibility measurements are consistent with tetrahedral high-spin (S = 3/2) CoII that possesses a 4A2 ground state with best fit parameters g = 2.25, |D| = 12.0 cm–1 and g = 2.37, |D| = 11.9 cm–1 for complexes 1 and 2, respectively. The compounds were further characterised by UV/Vis and IR spectroscopy. DFT calculations were performed on model complexes [CoII{N(OPH2)(SPH2)-O,S}2] (3) and [CoII{N(SPH2)2-S,S}2] (4) to compare the electronic properties of the CoO2S2 and CoS4 cores.