Computational Analysis of Mesomerism inpara-Substitutedmer-NCN Pincer Platinum(II) Complexes, Including its Relationships with Hammett σpSubstituent Parameters

Density Functional Theory studies of square-planar Pt(II)pincer structures, (4-Z-NCN)PtCl ([4-Z-NCN](-)=[4-Z-2,6-(Me2NCH2)(2)C6H2-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 sigma(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 pi-orbitals of the arene ring. Analogous computation for 2,6-(Me2CH2)(2)C(6)H(3)Z (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)(2)PtZ on pi-delocalisation in the pincer system.