A series of neutral pentacoordinate silicon(IV) complexes with an SiFO2NC, SiBrO2NC, SiO2NC2, SiO2N2C, SiFON2C, SiBrON2C, SiON2C2, or SiON3C skeleton was synthesized and structurally characterized by multinuclear NMR spectroscopy in the solid state and in solution and by single-crystal X-ray diffraction. The compounds studied contain a tridentate dianionic O,N,O or N,N,O ligand, a phenyl ligand, and a (pseudo)halogeno ligand (F, Br, CN, N3, NCS). The structures, NMR spectroscopic parameters, and chemical properties of these silicon(IV) complexes were compared with those of related compounds that contain an analogous tridentate dianionic S,N,O ligand instead of the O,N,O or N,N,O ligand (comparison of S/O/NMe analogues). In addition, two cationic pentacoordinate silicon(IV) complexes with an SiO2N2C and SiON3C skeleton, respectively, were synthesized (isolated as iodides) and structurally characterized. These compounds contain a tridentate O,N,O or N,N,O ligand, a phenyl ligand, and an acetonitrile ligand. The experimental investigations reported in this article were complemented by computational studies to better understand the different properties of some of the S/O/NMe analogues studied.