A one-electron pseudopotential having an averaged d(9) open shell in the core has been obtained for the ground state of Pt atom. With this pseudopotential we have studied the electronic structure of PtH+, PtH, Pt-2, and Pt2H using large basis sets and an exact full configuration interaction wave function. In order to obtain reliable results, core-core repulsion, core-polarization and core-valence correlation effects have to be taken into account. These effects have been included through suitable core-core and core-polarization potentials. Comparison between existent and present calculations show that the one electron pseudopotential for Pt can be regarded as an average of the different real states arising from coupling of s valence shells with the open 5 d(9) levels of the d shell. Provided the extreme simplicity of the model, results obtained for small platinum containing systems are in fair agreement with previous highly sophisticated calculations and indicate that this one-electron pseudopotential for Pt can be effectively used to model surroundings of large surface cluster models or Pt complexes where d-d bonding is not dominant.