Reactions of a Bis-silylene (LSi-SiL, L = PhC(NtBu)2) and a Heteroleptic Chloro Silylene (LSiCl) with Benzil: Formation of Bis(siladioxolene) and Monosiladioxolene Analogue with Five-Coordinate Silicon Atoms in Both Ring Systems

LSi-SiL (L = PhC(NtBu)(2)) (4) was reacted with benzil in toluene at room temperature to afford a compound that contains two siladioxolene rings connected by a Si Si bond. This is the first reactivity study of 4 where the central Si Si bond was not cleaved during the reaction. Furthermore, LSiCl (L = PhC(NtBu)(2)) (6) was treated with benzil at ambient temperature in toluene to yield 2,5-dioxal -silacyclopent-3-ene (7). Both 5 and 7 were characterized by single-crystal X-ray diffraction and additionally by NMR spectroscopy, El-MS spectrometry, and elemental analysis. Investigation of the molecular structure shows that the Si Si bond length in 5 is 2.36 angstrom, which is more than 2% shorter than the Si Si bond length in 4. The formal oxidation state of silicon in 5 is +3, which is in agreement with its structure. The existence of 5 and 7 as stable compounds indicates that siladioxolenes can be electronically stabilized by sigma-donor ligands.