Hans_Bauer96

Use of the dispersion energy donor (DED) ligand, C₆H₂−2,4,6-Cyp₃, affords an equilibrium mixture of the distannene {Sn(C₆H₂−2,4,6-Cyp₃)₂}₂, and cyclotristannane {Sn(C₆H₂−2,4,6-Cyp₃)₂}₃, which suppresses monomer dissociation. Multinuclear NMR and computational analyses indicated that DED interactions are the main arbiter of the dimer-trimer thermal interconversion.

Abstract

Reaction of {LiC₆H₂−2,4,6-Cyp₃⋅Et₂O}₂ (Cyp=cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl₂ afforded a mixture of the distannene {Sn(C₆H₂−2,4,6-Cyp₃)₂}₂ (2), and the cyclotristannane {Sn(C₆H₂−2,4,6-Cyp₃)₂}₃ (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH=33.36 kcal mol⁻¹ and ΔS=0.102 kcal mol⁻¹ K⁻¹, which gives a ΔG ^{300 K}=+2.86 kcal mol⁻¹, showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is −28.5 kcal mol⁻¹ per {Sn(C₆H₂−2,4,6-Cyp₃)₂ unit, which exceeds the DED energy in 2 of −16.3 kcal mol⁻¹ per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).