Regulation of coin metal substituents and cooperativity on the strength and nature of tetrel bonds

Abstract

Ab initio calculations have been performed for the tetrel-bonded dyad MCN⋯TF₄ (M = Cu, Ag, and Au; T = C, Si, Ge, and Sn). A coin metal substituent greatly strengthens the tetrel bond, depending on the nature of the coin metal and tetrel atoms. The Ag substituent has the largest enhancing effect with the interaction energy approaching −16 kcal mol⁻¹. The strength of the tetrel bond in MCN⋯TF₄ can be further regulated by the cooperative effect with a π⋯metal interaction. It is strengthened in C₂H₄⋯MCN⋯TF₄ but is weakened in C₂(CN)₄⋯MCN⋯TF₄. The interaction energy of the tetrel bond amounts to about −16 kcal mol⁻¹ in C₂H₄⋯CuCN⋯SiF₄, becoming a strong interaction. The nature of the tetrel bond is changed due to the metal substituents and cooperativity.