A Striking Mode of Activation of Carbon Disulfide with a Cooperative Bis(silylene)

The reactivity of the 1,4‐substituted bis(silylenyl)terphenylene 1, 1,4‐[ortho‐(LSi)C(6)H(4)](2)C(6)H(4), (L=RC(NtBu)(2), R=Ph, Mes) towards CS(2) is reported. It results in a dearomatization of the phenylene ring, affording the 1,3‐substituted cyclohexadiene derivative 2. According to DFT calculations, a transient silene containing a Si=C bond capable of π(C=C) addition at the aromatic phenylene ring is a key intermediate. In contrast, addition of CS(2) to the biphenyl‐substituted mono‐silylene ortho‐(LSi)C(6)H(4)‐C(6)H(5) 3 leaves the aromatic π‐system intact and forms, in a [1+2] cycloaddition reaction, the corresponding thiasilirane 4 with a three‐membered SiSC ring. Further experimental studies led to the isolation of the novel mesoionic five‐membered Si(2)S(2)C heterocycle 6, which reacts with CS(2) under C−C bond formation. All isolated new compounds were fully characterized and their molecular structures determined by single‐crystal X‐ray diffraction analyses.