Bis(amidinato)- and bis(guanidinato)silylenes and silylenes with one sterically demanding amidinato or guanidinato ligand: synthesis and reactivity

Abstract

This article deals with the synthesis and reactivity of the bis(amidinato)silylene [iPrNC(Ph)NiPr]₂Si (5), the bis(guanidinato)silylene [iPrNC(NiPr₂)NiPr]₂Si (6), the mono(amidinato)silylene [DippNC(Ph)NDipp]SiNMe₂ (Dipp = 2,6-diisopropylphenyl) (8) and the mono(guanidinato)silylene [DippNC(NMe₂)NDipp]SiN(SiMe₃)₂ (9). The reactions studied include (i) nucleophilic substitutions, (ii) Lewis acid/base reactions, (iii) Brønsted acid/base reactions, (iv) oxidative additions (bond activations, small-molecule activations), (v) cycloaddition reactions with unsaturated organic substrates, (vi) reductions and (vii) radical formation by muonium addition. Silylenes 5, 6, 8 and 9 have been demonstrated to display unique reactivity profiles and to be versatile precursors for the synthesis of novel four- or five-coordinate silicon(ii) and four-, five- or six-coordinate silicon(iv) complexes with unprecedented structural motifs. This article also deals with the structural characterisation of all the new silicon(ii) and silicon(iv) compounds synthesised. Crystal structure analyses and ²⁹Si NMR spectroscopic studies in the solid state and in solution were used to characterise the silicon coordination polyhedra of these compounds.