Novel neutral hexacoordinate benzamidinatosilicon(iv) complexes with SiN3OF2, SiN3OCl2, SiN3OBr2, SiN5O and SiN3O3 skeletons

Abstract

The neutral pentacoordinate monoamidinatosilicon(IV) complex 1 (SiN₂Cl₃ skeleton) and the neutral hexacoordinate monoamidinatosilicon(IV) complexes 2–9 (SiN₃OF₂, SiN₃OCl₂, SiN₃OBr₂, SiN₅O and SiN₃O₃ skeletons) were synthesised and characterised by elemental analyses, single-crystal X-ray diffraction (except for 1) and NMR spectroscopy in the solid state and in solution. Compounds 2–9 contain one bidentate monoanionic N,N′-diisopropylbenzamidinato ligand, one bidentate monoanionic ligand derived from 8-hydroxyquinoline and (i) two identical monoanionic ligands (F, Cl, Br, N₃, NCO, NCS, OSO₂CF₃) or (ii) one bidentate dianionic benzene-1,2-diolato ligand. The dynamic behavior of 2–4 (SiN₃OX₂ skeleton; X = F, Cl, Br) and 9 (SiN₃O₃) in solution was studied by multinuclear variable-temperature NMR experiments. Compound 1 was synthesised by reaction of SiCl₄ with the corresponding lithium amidinate, and compound 2 was obtained by reaction of 1 with 8-hydroxyquinoline and triethylamine. Compound 2 served as the starting material in the syntheses of 3–9, in which the two chloro ligands of 2 were substituted by two identical (pseudo)halogeno ligands, two trifluoromethanesulfonato ligands or one benzene-1,2-diolato ligand. Compounds 3 and 4 contain the novel SiN₃OBr₂ and SiN₃OF₂ skeletons, while compounds 5–7 are the first neutral hexacoordinate silicon(IV) complexes with an SiN₅O skeleton.