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

ABSTRACT

Reaction of the 1,2-disilylenes {(DipAr Am)Si}2 (DipAr Am=[(NDip)2 CAr]- , Dip=2,6-diisopropylphenyl, Ar=4-C6 H4 But (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 N2 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.