Taking in account the basic ideas in coordination chemistry governing the structure and reactivity of these compounds especially those of Palladium and Platinum complexes, a new set of Pd(II) and Pt(II) square planar complexes with varying structural isomerism have been prepared and studied. Their structure and spectral behavior have been discussed based on hard and soft acid base principles, back π-bonding, and redox behavior. Another MCl2(DMSO)2 [M=Pd (II) or Pt (II) complexes were prepared and used as starting materials to prepare the following types of complexes ;(1)- The reaction of both trans –Pd and cis- Pt complexes with Dithiooxamide (DTO) in ethanol gave cis MCl2 (DTO)-N, S). (2)- The reaction of cis –MCl2 (DTO) with a series of neutral N-and P-donor ligand s in ethanol gave new complexes with different geometries;* Triphenylphosphine (PPh3) and triphenylamine (NPh3) replace the Cl-trans to N of DTO giving N-trans-[MCl (L) (DTO-N, S)], (L=PPh3 or NPh3). * The reaction of linear Benzidine (Bnz) and 3,3-,5,5- tetremethylbenzidine (TMBnz) with MCl2 (DTO) in ethanol gave the tetra nuclear cage complexes [M4 (DTO)4L4] Cl4. [L=Bnz orTMBnz]*2,2- –dibyridyl (dipy) react with cis –PtCl2(DMSO)2 in ethanol to give PtCl2 (Dipy), the later gave the ionic mixed ligand complex [Pt(Dipy) (DTO-N,S)]Cl upon reaction with DTO in ethanol.All the prepared complexes were studied using FT-IR, UV-Vis spectroscopy, and magnetic susceptibility measurement. The metal content was determined using Atomic Absorption apparatus.The structural changes were discussed, and the tools of basic ideas of coordination with the aid of group's theoretical calculations for some complexes show to be very helpfull in understanding the structural change.The antibacterial activity against Escherichia Coli and Staphyl ococcus aureus, of all the prepared compounds, were pursued.