Reactions of an Isolable Dialkylsilylene with Carbon Dioxide and Related Heterocumulenes

An isolable dicoordinate
dialkylsilylene, 2,2,5,5-tetrakis­(trimethylsilyl)­silacyclopentane-1,1-diyl
(6), was found to react with CO2 and ArNCX
(X = O, S) smoothly to give the corresponding bis­(silyl)­carbonate,
4-imino-1,3-dioxasiletane and 4-imino-1,3-dithiasiletane derivatives
in high yields, respectively. The molecular structures of these products
were determined by X-ray crystallography. All these reactions are
parallel to those of a hypercoordinate silylene with η5-pentamethylcyclopentadienyl ligands, decamethylsilicocene, reported
by Jutzi et al. and are suggested to involve similarly the formation
of the corresponding SiX doubly bonded compounds (X = O, S)
at the initial steps. Mechanistic details of the multistep reaction
of a model dialkylsilylene with CO2 were investigated using
DFT calculations.