Neutral Pentacoordinate Silicon Fluorides Derived from Amidinate, Guanidinate, and Triazapentadienate Ligands and Base-Induced Disproportionation of Si2Cl6 to Stable Silylenes

Abstract

Pentacoordinate silicon fluorides (LSiF3)-Si-1 (2a), (LSiF3)-Si-2 (2b), and ((LSiF2)-Si-3)(2) (2c)(2) based on amidinate (L-1 = PhC((NBu)-Bu-t)(2)), guanidinate (L-2 = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate), and triazapentadienate = (L-3 = NC(NMe2)NC-(NMe2)NAr, Ar = 2,6-(Pr2C6H3)-Pr-i) ligands were prepared by fluorination of the corresponding chlorosilanes (LSiCl3)-Si-1 (1a), (LSiCl3)-Si-2 (1b), and (LSiCl2)-Si-3 (1c) with Me3SnF at ambient temperature. Compounds 1b. 1c, 2a, 2b, and (2c)(2) were characterized by H-1, C-13, F-19, and Si-29 NMR spectroscopic studies. Molecular structures of 1b, 1c, 2a, and (2c)(2) were determined by single crystal X-ray structural analysis. Invariom refinement involving non-spherical scattering factors of the Hansen-Coppens multipole model was performed for 1b. Compound (LSiF2)-Si-3 (2c) is dimeric both in the solid state and in solution, whereas its chloro-analogue lc is monomeric. The attempted synthesis of diamidinatotetrachlorodisilane by reaction of lithium amidinate with Si2Cl6 led to the formation of the silane (1a) and the silylene (LSiCl)-Si-1 (3). Reaction of Si2Cl6 with N-heterocyclic carbenes (NHC) afforded NHC adducts of dichlorosilylene and SiCl4. A one pot method for the preparation of base-stabilized silylenes from Si2Cl6 is discussed.