London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate

Reaction of {LiC6H2-2,4,6-Cyp(3).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-Cyp(3))(2)}(2) (2), and the cyclotristannane {Sn(C6H2-2,4,6-Cyp(3))(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 Delta H=33.36 kcal mol(-1) and Delta S=0.102 kcal mol(-1) K-1, which gives a Delta G(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-Cyp(3))(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).

Automated summary

The reaction between {LiC6H2-2,4,6-Cyp(3).Et2O}(2) and SnCl2 generates a mixture of {Sn(C6H2-2,4,6-Cyp(3))(2)}(2) and {Sn(C6H2-2,4,6-Cyp(3))(2)}(3). The equilibrium between 2 and 3 is influenced by temperature and the conversion of 3 to 2 is an endergonic process. Computational studies reveal that dispersion interactions play a crucial role in determining the stability of 3 and 2, with 3 being more stable due to higher DED stabilization energy.