(II) complexes have played an important role in recent experimental and theoretical attempts to characterize the electronic structure of square planar complexes . Yet there is no full description of their infrared spectra and coordination behaviour.The compounds of PdCl2(PhCN)2, PdCI2 (DMSO)2 , PdCl2(DTO), NiC12(DTO) were chosen for the present experimental work and theoretical treatment.The reaction of PdCI2 with PhCN and DMSO gave two starting complexes PdCl2(PhCN)2 and PdCl2(DMSO)2 and then each of them reacting with DTO to give PdCl2(DTO). The reaction of NiCI2.6H20 with DTO gave NiCl2(DTO).All the prepared compounds were isolated and characterized by their melting points . vibrational and electronic spectra , and magnetic measurements.The ab-initio (3-21G) method at high level was used for calculating the relative energies of the conformers of the three prepared compounds PdCl2(PhCN)2, PdCI2 (DMSO)2, PdCl2(DTO), the ab-initio calculations help to predict the most stable structure among the other probable structures The Semi-emperical PM3 method was used for calculating the infrared spectra of all prepared compounds , heat of formation , and total relative energies for all conformers of Pd(II) and Ni(II) complexes.The semi-empirical PM3 and ab-initio (3-21G) methods were used for the calculation of total relative energies for Palladium complexes , and showed that PD1-trans isomer was the most stable for PdCl2(PhCN)2.For PdC12 (DMSO)2,the PDIO-DMSO-trans(O,O) was more stable than the other three isomers.The relative energy calculations for the six PdCl2(DTO) isomers, showed that , among the three amide isomers, the PD5-trans-A(N,S) was the most stable , and among the three imide isomers the PD6-cis-I-(N,N) was the most stable, among the total six amide and imide isomers , the PD5-trans-A(N,S) was more stable than PD6-cis-I(N,N).For Ni complexes, the results of relative energies which were calculated using semi-empirical (PM3) method showed that , among the three amide isomers the Ni3-cis-A(N,N) was the most stable , while among the three imide isomers the Ni6-cis-I(N,N) was the most stable.Among the total set of Nickel isomers the results of relative energy showed that the Ni6-cis-I(N,N) to be more stable than Ni3-cis-A(N,N).The results of vibrational calculations were in a good agreement with those obtained from energies calculations , except that of PD10-(DMSO)- trans(O,O) which did not , and experimental vibrational study came in accordance with the theoretical calculation..