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

Reaction of the 1,2-disilylenes {( DipAr Am)Si} 2 ( DipAr Am=[(NDip) 2 CAr] - , Dip=2,6-diisopropylphenyl, Ar=4-C 6 H 4 Bu t (Ar') 1 a or Ph 1 b) and two abnormal N-heterocyclic silylenes, ( DipAr Am)SiOCSi{(NDip) 2 CAr} (Ar=Ar' 3 a or Ph 3 b) with N 2 O led to formation of unprecedented examples of uncoordinated silicon analogues of carboxylic acid anhydrides, ( DipAr Am)(O=)SiOSi(=O)( DipAr Am) (Ar=Ar' 2 a or Ph 2 b). Both compounds have been fully characterized, and the mechanism of formation of one explored using DFT calculations. Reduction of sila-acid anhydride 2 a with a dimagnesium(I) compound, [{( Mes Nacnac)Mg} 2 ] ( Mes Nacnac=[(MesNCMe) 2 CH] - , Mes=mesityl), led to the one-electron reduction of the anhydride and formation of a magnesium complex of a sila-acid anhydride radical anion [( Mes Nacnac)Mg{(OSi( DipAr' Am)} 2 O] 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.