Synthesis of a Stable Four-Membered Si₂O₂ Ring and a Dimer with Two Four-Membered Si₂O₂ Rings Bridged by Two Oxygen Atoms, with Five-Coordinate Silicon Atoms in Both Ring Systems

The base-stabilized bis-silylene (LSi−SiL, L = PhC(NtBu)2) was reacted with benzophenone in a 1:2 ratio in THF, which afforded a Si2O2 four-membered ring, stabilized by bulky amidinato ligands. The most striking phenomenon is the abstraction of oxygen from benzophenone and the simultaneous formation of a silicon carbon bond. The four-membered Si2O2 ring is planar, and both the silicon atoms are five-coordinate. The two silicon atoms are arranged opposite each other in the four-membered Si2O2 ring. Moreover LSi−SiL was treated with N2O to afford two four-membered Si2O2 rings connected with two oxygen atoms. In this structure also the silicon atoms are five-coordinate.