Neutral pentacoordinate silicon fluorides derived from amidinate, guanidinate, and triazapentadienate ligands and base-induced disproportionation of Si_2Cl_6 to stable silylenes

摘要

Pentacoordinate silicon fluorides L~1SiF_3 (2a), L ~2SiF_3 (2b), and (L~3SiF_2)_2 (2c)2 based on amidinate (L~1 = PhC(N~tBu) _2), guanidinate (L~2 = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1, 2-a]pyrimidinate), and triazapentadienate (L~3 = NC(NMe _2)NC(NMe_2)NAr; Ar = 2,6-~iPr_2C _6H_3) ligands were prepared by fluorination of the corresponding chlorosilanes L~1SiCl_3 (1a), L ~2SiCl_3 (1b), and L~3SiCl_2 (1c) with Me_3SnF at ambient temperature. Compounds 1b, 1c, 2a, 2b, and (2c)_2 were characterized by ~1H, ~(13)C, ~(19)F, and ~(29)Si 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 L~3SiF_2 (2c) is dimeric both in the solid state and in solution, whereas its chloro-analogue 1c is monomeric. The attempted synthesis of diamidinatotetrachlorodisilane by reaction of lithium amidinate with Si_2Cl_6 led to the formation of the silane (1a) and the silylene L~1SiCl (3). Reaction of Si_2Cl_6 with N-heterocyclic carbenes (NHC) afforded NHC adducts of dichlorosilylene and SiCl_4. A one pot method for the preparation of base-stabilized silylenes from Si_2Cl_6 is discussed.