Computational analysis of mesomerism in para-substituted mer-NCN pincer platinum(II) complexes, including its relationships with Hammett σp substituent parameters

Density Functional Theory studies of square‐planar Pt^II pincer structures, (4‐Z‐NCN)PtCl ([4‐Z‐NCN]⁻=[4‐Z‐2,6‐(Me₂NCH₂)₂C₆H₂‐N,C,N]⁻, Z=H, NO₂, CF₃, CO₂H, CHO, Cl, Br, I, F, SMe, SiMe₃, tBu, OH, NH₂, NMe₂), enable characterisation of mesomerism for the pincer‐Pt interaction. Relationships between Hammett σ_p substituent parameters of Z and DFT data obtained from NBO6 and AOMix computation are used to probe the interaction of the 5d_yz orbital of platinum with π‐orbitals of the arene ring. Analogous computation for 2,6‐(Me₂CH₂)₂C₆H₃Z (Z=H, CF₃, CHO, Cl, Br, I, F, SMe, SiMe₃, tBu, OH, NH₂) and (4‐H‐NCN)PtZ allows an estimation of the relative substituent effects of “(CH₂NMe₂)₂PtZ” on π‐delocalisation in the pincer system.