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

Platinum(II) complexes exhibiting an expressed d(z)(2)-nucleophilicity of the positively charged metal centers, namely, [Pt(ppy)(acac)] (1; acacH is acetylacetone; ppyH is 2-Ph-pyridine) and [Pt(ppy)(tmhd)] (2; tmhdH is 2,2,6,6-tetramethylheptanedione-3,S), were cocrystallized with the chalcogen bond donors (4-NC3F4)(2)Ch (Ch = Se, Te) to form two isostructural cocrystals 1.(1/2)(4-NCsF4)(2)Ch, and 2.2/3(4-NCsF4)(2)Se and 2.(4-NC5F4)(2)Te. The X-ray data for these cocrystals and appropriate theoretical DFT calculations (PBEO-D3BJ) allowed the recognition of the metal-involving chalcogen bond, namely, Ch center dot center dot center dot d(z)(2)-Pt-II (its energy spans from -7 to -12 kcal/mol). In 1.1/2(4-NC3F4)(2)Ch, Ch center dot center dot center dot d(z)(2)-(P)t(II) bonding is accompanied by the C center dot center dot center dot d(z)(2)-Pt-II interaction, representing a three-center bifurcate, whereas in 2.(4-NC3F4)(2)Te the chalcogen bond Te center dot center dot center dot d(z)(2)-Pt-II is purely two-centered and is stronger than that in 1.1/2(4-NC3F4)(2)Ch because of more efficient orbital overlap. The association of 2 with (4-NC5F4)(2)Te and the structure of the formed adduct in CDCl3 solutions was studied by using H-1, C-13, F-19, Pt-195, Te-125 NMR, F-19-H-1 HOESY, and diffusion NMR methods. The Pt-195 and Te-125 NMR titration and the isothermal titration calorimetry results revealed a 1:1 association of 2 with (4-NC5F4)(2)Te.

Automated summary

Platinum(II) complexes with expressed d(z)(2)-nucleophilicity of positively charged metal centers were cocrystallized with chalcogen bond donors to form two isostructural cocrystals. The interaction modes between chalcogen atoms (sulfur and tellurium) and the metal center were studied, revealing different bonding characteristics in the two cocrystals. The association of one of the cocrystals with a chalcogen bond donor was further investigated using NMR and calorimetry methods, confirming a 1:1 association between them.