A new homoleptic Co(II) complex bearing two highly sterically congested 2-formiminopyrrolyl N,N'-chelating ligands is reported, displaying slow relaxation of the magnetisation at zero static (DC) field. This compound shows a large value for the zero-field splitting (ZFS) parameter D of -42.6(4) cm-1 leading to a spin-reversal energy barrier Ueff of 85 cm-1.