Halogen-Exchange Reactions of Iminophosphonamido-Chlorosilylenes with Alkali Halides: Convenient Synthesis of Heavier Halosilylenes.

Halogen-substituted silylenes are an important building block for synthesizing silicon-based low-valent and multiple-bond species. However, the number of reports on heavier halosilylenes that contain bromine and iodine is still limited. Here, we present a convenient synthesis for bromo- and iodosilylenes supported by an iminophosphonamide ligand. The heavier halosilylenes [Ph 2 P( t BuN) 2 ]SiX ( 2 : X = Br, 3 : X = I) were successfully synthesized via the halogen-exchange reaction of chlorosilylene 1 with alkali halides in THF. As a demonstration of the reactivity of 2 and 3 , oxidative addition reactions of 2 and 3 with elemental selenium in C 6 D 6 afforded the corresponding bromo- ( 5 ) or iodosilylene-selone ( 6 ) as colorless crystals. The molecular structures of 2 , 3 , 5 , and 6 were fully characterized by spectroscopic means and single-crystal X-ray diffraction analysis. Furthermore, the effects of the halogen atom on the electronic state of halosilylenes 1 - 3 and halosilylene-selones 4 - 6 were investigated using density functional theory (DFT) calculations.