Five-coordinate low-spin cobalt(II) complexes with benzeneseleninato ions and ethylenediamine as ligands

Summary Five-coordinate bis(benzeneseleninato)tris(ethylenediamine) cobalt (II)complexes are obtained by reaction of Co(H₂O)₂ (XC₆ H4 SeO₂)2 complexes (X = H, p-Cl, m-CI, p-Br, ni-Br, p-Me,p-NO₂) with ethylenediamine. The diaquo complexes (one mole)react with ethylenediamine (three moles)to form O-seleninato derivatives. Spectral and magnetic properties show that the complexes are low-spin (s = 1/2) and,on the basis of the electronic spectra a distorted trigonal geometry,D_3h, is suggested. Assignments for the electronic spectra are proposed. Conductivity data indicate that these derivatives are nonelectrolytes. Both ethylenediamine and [RSeO₂ ]^– behave as monodentate ligands.