Multiple scattered wave study of the relativistic and nonrelativistic electronic structure and bonding for cis-diamminedichloroplatinum(II)

A detailed analysis of the valence molecular orbitals of cis-[Pt(NH₃)₂Cl₂] is presented. Ground-state results for the relativistic Dirac scattered wave (DSW) calculations and its nonrelativistic limit (DNR (c = ∞)) together with the nonrelativistic Schrödinger multiple scattered wave (MSW) results show the importance of relativistic effects in this molecule. The analysis yield interesting features; e.g., relativistic effects increase the relative splitting between levels containing significant 5d metal character. The Pauli decomposition for the orbitals showing large contributions from metal atoms suggests that spin contaminations are significant. Furthermore, the established MOs reveal that L → 5d(Pt) donation is low in comparison to L → 6p(Pt) donation so that metal p orbitals play a fundamental role in the bonding scheme for this molecule. Contour maps for the relativistic HOMO level show the existence of a Cl-Cl bonding region and suggest that an almost neutral ligand Cl₂ molecule exists in the complex, its free molecular electronegativity value is drastically reduced, and the Pt atom is responsible for this result.