A qualitative molecular orbital study and a structural analysis of the bonding capabilities of the metal atoms in square planar ML(4) complexes of d(8) ions are presented. In addition to analyzing the donor-acceptor properties of the metal atom in such complexes, the following aspects are also studied: (a) the effect of axial groups (bases or acids) on the donor-acceptor properties of the metal atom; (b) the effect of the axial groups on the deviation of the ML(4) ensemble from planarity; (c) the effect of an axial group on the bond between the metal atom and another group in trans; and (d) the implications on chemical reactivity.