Synthesis, structure and reactivity of a donor-stabilised silylene with a bulky bidentate benzamidinato ligand

Abstract

The novel donor-stabilised silylene 5 was prepared in a four-step synthesis, starting from bis(2,6-diisopropylphenyl)carbodiimide (Dipp–NCN–Dipp), and its reactivity was studied in a series of oxidative addition reactions and a nucleophilic substitution reaction. The three-coordinate silicon(II) complex 5 contains the bulky bidentate amidinato ligand Dipp–NC(Ph)N–Dipp⁻ and a dimethylamido ligand. Treatment of 5 with N₂O afforded the dinuclear five-coordinate silicon(IV) complex 6 (SiO₂N₃ skeletons), and the reaction with S₈ yielded the dinuclear four-coordinate silicon(IV) complex 7 (SiS₂N₂ skeletons). Treatment of 5 with Se and Te afforded the respective four-coordinate silicon(IV) complexes 8 (SiSeN₃ skeleton) and 9 (SiTeN₃ skeleton), which contain an SiSe and SiTe double bond, respectively. The reaction of 5 with the silyl azide Me₃SiN₃ yielded the four-coordinate silicon(IV) complex 10 (SiN₄ skeleton) with an SiN double bond, whereas the reaction with the alkyl azide PhSCH₂N₃ gave the four-coordinate silicon(IV) complex 11 (SiSN₃ skeleton), the first silicon(IV) complex with an unsubstituted methyleneamido ligand. The reaction of 5 with [Fe(CO)₅] afforded the four-coordinate silicon(II) complex 12 (SiFeN₃ skeleton) with an Si–Fe bond. Compounds 5–12 (and the precursors 14 and 15 (five-coordinate silicon(IV) complexes with an SiCl₃N₂ and SiCl₂N₃ skeleton, respectively) in the synthesis of 5) were characterised by elemental analyses, crystal structure analyses and multinuclear NMR spectroscopic studies in the solid state and in solution.