Hydrogen Bonding in Platinum Indolylphosphine Polyfluorido and Fluorido Complexes

The reaction of the Pt complexes cis-[Pt(CH₃ )(Ar){Ph₂ P(Ind)}₂ ] (Ind=2-(3-methyl)indolyl, Ar=4-tBuC₆ H₄ (1 a)_, 4-CH₃ C₆ H₄ (1 b), Ph (1 c), 4-FC₆ H₄ (1 d), 4-ClC₆ H₄ (1 e), 4-CF₃ C₆ H₄ (1 f)) with HF afforded the polyfluorido complexes trans-[Pt(F(HF)₂ )(Ar){Ph₂ P(Ind)}₂ ] 2 a-f, which can be converted into the fluoride derivatives trans-[Pt(F)(Ar){Ph₂ P(Ind)}₂ ] (3 a-f) by treatment with CsF. The compounds 2 a-f and 3 a-f were characterised thoroughly by multinuclear NMR spectroscopy. The data reveal hydrogen bonding of the fluorido ligand with HF molecules and the indolylphosphine ligand. Polyfluorido complexes 2 a-f show larger |¹ J(F,Pt)|, but lower ¹ J(H,F) coupling constants when compared to the fluorido complexes 3 a-f. Decreasing ¹ J(P,Pt) coupling constants in 2 a-f and 3 a-f suggest a cis influence of the aryl ligands in the following order: 4-tBuC₆ H₄ (a) ≈4-CH₃ C₆ H₄ (b)6 H₄ (d)<4-ClC₆ H₄ (e)<4-CF₃ C₆ H₄ (f). In addition, the larger cis influence of aryl ligands bearing electron-withdrawing groups in the para position correlates with decreasing magnitudes of |¹ J(F,Pt)| coupling constants. The interpretation of the experimental data was supported by quantum-chemical DFT calculations.