“Wittig Reactions” of Unsaturated Silicon Compounds : Isolation and Structure of Possible Intermediates

Abstract

The metastable tBu2SiNSitBu3 reacts with benzaldehyde in pentane already at −125°C to give the oxaazasilacyclobutane 1a: with benzophenone, on the other hand, only the dark-red adduct 2 is formed at −78°C which does not react further to give 1b, even at room temperature and above. Characteristic of 2 are an unusually large SiO distance and a small CO distance (1.927(2) and 1.254(3) Å, resp.), i.e. the bonding between the reactants is loose.