Metal-Involving Chalcogen Bond. The Case of Platinum(II) Interaction with Se/Te-Based σ-Hole Donors.

Platinum(II) complexes exhibiting an expressed -nucleophilicity of the positively charged metal centers, namely, [Pt(ppy)(acac)] (; acacH is acetylacetone; ppyH is 2-Ph-pyridine) and [Pt(ppy)(tmhd)] (; tmhdH is 2,2,6,6-tetramethylheptanedione-3,5), were cocrystallized with the chalcogen bond donors (4-NCF)Ch (Ch = Se, Te) to form two isostructural cocrystals ·/(4-NCF)Ch, and ·/(4-NCF)Se and ·(4-NCF)Te. The X-ray data for these cocrystals and appropriate theoretical DFT calculations (PBE0-D3BJ) allowed the recognition of the metal-involving chalcogen bond, namely, Ch···-Pt (its energy spans from -7 to -12 kcal/mol). In ·/(4-NCF)Ch, Ch···-Pt bonding is accompanied by the C···-Pt interaction, representing a three-center bifurcate, whereas in ·(4-NCF)Te the chalcogen bond Te···-Pt is purely two-centered and is stronger than that in ·/(4-NCF)Ch because of more efficient orbital overlap. The association of with (4-NCF)Te and the structure of the formed adduct in CDCl solutions was studied by using H, C, F, Pt, Te NMR, F-H HOESY, and diffusion NMR methods. The Pt and Te NMR titration and the isothermal titration calorimetry results revealed a 1:1 association of with (4-NCF)Te.