Novel neutral hexacoordinate silicon(iv) complexes with two bidentate monoanionic benzamidinato ligands

Abstract

The novel neutral hexacoordinate bis(benzamidinato)silicon(IV) complexes 1–10 (SiN₄X₂ skeletons; X = F, Cl, Br, C, N, S, Se) were synthesised and characterised by elemental analyses, single-crystal X-ray diffraction (except for 2) and NMR spectroscopy in the solid state and in solution. The dynamic behavior of 1 (SiN₄Cl₂ skeleton) and 3 (SiN₄F₂) was additionally studied by variable-temperature NMR experiments. Compounds 1 and 2 (SiN₄Br₂) were obtained by reaction of SiCl₄ and SiBr₄, respectively, with two molar equivalents of the corresponding lithium amidinate. Compound 1 served as the starting material in the syntheses of 3–10, in which the two chloro ligands of 1 were substituted by two (pseudo)halogeno or one bidentate dianionic S,S, S,Se or Se,Se ligand. Compound 4 contains an SiN₄C₂ skeleton and 5–7 contain an SiN₆ skeleton. With the preparation of 8 (SiN₄S₂ skeleton), 9 (SiN₄SSe) and 10 (SiN₄Se₂) it could be demonstrated that syntheses of hexacoordinate silicon(IV) complexes with soft chalcogeno ligand atoms are indeed feasible. Compounds 9 and 10 are the first hexacoordinate silicon(IV) complexes with Si–Se bonds.