Preparation and characterization of Co(Et4dien)X2 (Et4dien = HN[CH2CH2N(C2H5)2]2; X = Cl, Br, I, N3, NCS) complexes are reported. Spectral and magnetic properties show that the complexes are high spin and five-coordinate in the solid state. Based on a ligand field model, an interpretation of the observed electronic spectra and magnetic moments is presented. © 1968, American Chemical Society. All rights reserved.