Stabilization and One Electron Reduction of a Silicon Analogue of a Carboxylic Acid Anhydride

Reaction of the 1,2-disilylenes {(DipArAm)Si}2 (DipArAm = [(NDip)2CAr]-, Dip = 2,6-diisopropylphenyl, Ar = 4-C6H4But (Ar’) 1a or Ph 1b) and two abnormal N-heterocyclic silylenes, (DipArAm)SiOCSi{(NDip)2CAr} (Ar = Ar’ 3a or Ph 3b) with N2O led to formation of unprecedented examples of uncoordinated silicon analogues of carboxylic acid anhydrides, (DipArAm)(O=)SiOSi(=O)(DipArAm) (Ar = Ar’ 2a or Ph 2b). Both compounds have been fully characterized, and the mechanism of formation of one explored using DFT calculations. Reduction of sila-acid anhydride 2a with a dimagnesium(I) compound, [{(MesNacnac)Mg}2] (MesNacnac = [(MesNCMe)2CH]-, Mes = mesityl), led to the one-electron reduction of the anydride and formation of a magnesium complex of a sila-acid anhydride radical anion [(MesNacnac)Mg{(OSi(DipAr’Am)}2O]· 5. A combination of EPR spectroscopic studies and DFT calculations reveal the unpaired electron to largely reside on one of the amidinate ligands of the complex.