Trans-Influence in Dinuclear Pt(III) Complexes: Electronic Structure, σ-Donation, and Pt–Pt Spin–Spin Coupling

This study investigates the trans influence in dinuclear platinum(III) complexes using a combined approach of ab initio molecular dynamics and natural localized molecular orbital (NLMO) analysis. Focusing on pivalamidate-bridged Pt^III complexes with axial ligands of varying σ-donation strength, it is quantified how ligand-metal interactions propagate through the Pt-Pt bond, and how they affect bond polarization, axial water coordination, and ¹<i>J</i>_PtPt spin-spin coupling constants. NLMO analysis reveals quantitatively that strong σ-donating ligands polarize the Pt-Pt bond, shifting the electron density toward the opposite platinum center. The polarization mechanism is identified as the primary reason for the observed reduction of ¹<i>J</i>_PtPt, because the bond polarization diminishes the transmission of the nuclear magnetic spin-induced electron spin density through the Pt-Pt bond. Additionally, the destabilization of axial water coordination at the opposite Pt site can be rationalized through a polarization-induced Pt^IV- Pt^II-like mixed-valence character.