Equilibrium between Tetra-, Penta-, and Hexacoordinate Imine and Enamine Chelates of Silicon: Crystal Structure and Variable-Temperature NMR

The Si-coordination sphere in the novel pentacoordinate silicon bischelate η2(N,O)-N-methyl-o-oxyacetophenoneiminato-N‘-methyl-N‘-1-(2-oxyphenyl)vinylaminatophenylsilicon, 2, which was analyzed by variable-temperature 29Si NMR spectroscopy and X-ray crystallography, was found to be temperature dependent. The
addition of a third equivalent of the chelating ligand
yields the hexacoordinate silicon complex bis-[η2(N,O)-(N-methyl-o-oxyacetophenoneiminato)]-η1(O)-(N-methyl-o-oxyacetophenoneiminato)phenylsilicon, 3, which undergoes Si−O bond cleavage as well as Si−N bond formation in solution.