Inorganic Chemistry, Vol.54, No.12, 6020-6027, 2015
Reversibility in Reactions of Linker-Bridged Distannenes with Terminal Alkynes at Ambient Temperature
The linker-bridged distannene [(2,6-Mes(2))-C6H3Sn](2)C12H8 (1) featuring an acenaphthene linker and the sterically demanding terphenyl substituent Ar-Me (= C6H3-2,6-Mes(2); Mes = C6H2-2,4,6-Me-3) was prepared and characterized by single-crystal analysis, NMR spectroscopy, as well as elemental analysis. Furthermore, the reactivity of distannene 1 and previously reported distannenes 2 and 3, bearing either a naphthalene or a 9,9-dimethylxanthene backbone and the terphenyl substituent Ar-Me, as well as bis(stannylene) 4, featuring a 9,9-dimethylxanthene backbone and the terphenyl substituent Ar-iPr (= C6H3-2,6-Trip(2); Trip = C6H2-2,4,6-i-Pr-3), toward terminal alkynes at ambient temperature was investigated, leading to the formal [2 + 2] cycloaddition products 5-9. The reactions of distannene 1 with trimethylsilylacetylene and phenylacetylene, the reaction of distannene 2 with trimethylsilyl-acetylene, as well as the reaction of bis(stannylene) 4 with phenylacetylene show reversibility, while distannenes 2 and 3 react irreversibly with phenylacetylene at room temperature. A van't Hoff analysis of variable-temperature H-1 NMR spectra of the cycloadduct of the reaction of distannene 1 with trimethylsilylacetylene afforded a dissociation enthalpy (Delta H-diss) of 71.6 kJ.mol(-1), which is in surprisingly good agreement with the results of accompanying DFT calculations (Delta H-diss = 70.9 kJ.mol(-1)).