Synthesis and Characterization of Neutral <i>cis</i>-Hexacoordinate Bis(β-diketonate) Silicon(IV) Complexes

Three new neutral cis-hexacoordinate bis(β-diketonato) silicon(IV) complexes, (thd)2SiX2, where X = Me (1), tBuO (2), and tAmO (3), and thd = 2,2,6,6-tetramethyl-3,5-heptanedionato, were synthesized in high yield. Single crystal X-ray crystallographic analysis revealed that 1 was monomeric with cis-hexacoordinate octahedral geometry on the silicon and oxygen atoms. Crystal data: empirical formula C24H46O4Si, crystal system monoclinic; space group P21/n; unit cell dimensions a = 10.4195(5) Å, b = 19.7297(10) Å, c = 13.6496(7) Å; β = 102.6590(10)°; Z = 4. Variable temperature NMR confirmed (thd)2SiX2 maintained cis-geometry in solution by observing two distinct methyl proton resonances (of thd) at room temperature or low temperatures. These compounds show potential for use as low temperature silicon oxide CVD precursors for transition metal silicate high κ gate dielectrics.