Trifluoromethylthio-complexes of platinum(II): measurement of trans-influence by fluorine-19 nuclear magnetic resonance spectroscopy

Abstract

The synthesis and characterization of the following new complexes is reported: trans-[PtX(SCF₃)(PEt₃)₂](X = Ph, Me, H, CF₃, C₂F₃, CN, NO₂, SCF₃, N₃, I, NCS, NCO, Br, Cl, or NO₃), cis-[PtX(SCF₃)(PEt₃)₂](X = NO₂, SCF₃, N₃, NCS, NCO, Cl, or NO₃), cis-[Pt(SCF₃)₂L₂][L = PBuⁿ₃, P(OPh)₃, PPh₃, P(OMe)₃, PCIPh₂, or C₅H₅N], trans-[Pt(SCF₃)₂L₂](L = PBuⁿ₃, PPh₃, or C₅H₅N). trans-[Pt(SCF₃)(CH₃)(PPh₃)₂], and trans-[Ptl(CF₃)(PEt₃)₂]. Values of ³J(Pt–F) in trans-[PtX(SCF₃)(PEt₃)₂] and cis-[Pt(SCF₃)₂L₂] complexes are used to establish a scale of trans-influence for the X and L ligands and the results are discussed in terms of existing theories of the Fermi contact interaction. It is concluded that an equation similar to those used previously for directly bound and two-bond couplings is still approximately valid for the longer-range ³J(Pt–F) couplings. The question of nonzero intercepts in plots comparing trans-influence scales derived from couplings to different indicator ligands is discussed. A perturbation approach to the problem shows that non-zero intercepts arise when the indicator ligands have different sensitivities to the perturbation. One possible cause of differing sensitivities is the polarizability of the indicator ligand.