In this work, a novel organosilicon aldehyde was prepared for the first time. It could be used as an appropriate linker by condensation with ethanol amine producing a new bidentate Schiff base ligand. Its cobalt complex was prepared under ultrasonic agitation and characterized by FT-IR and NMR spectra. Attachment to magnetic nanoparticles (γ-Fe₂O₃, MNP) coated with starch (SMNP) under ultrasonic irradiation produced a magnetically separable Schiff base catalyst. TEM images revealed a uniform spherical shape with average size of 12–15 nm for as-prepared catalyst. The selective benzylic C–H oxidation of a variety of benzylic alcohols as well as alkyl benzenes to the related carbonyl compounds using molecular oxygen in combination with n-hydroxyphthalimide (NHPI) were efficiently enhanced under the catalytic influence of title magnetically separable catalyst. The reactions proceeded smoothly under heterogeneous conditions and catalyst could be recovered and reused efficiently by an external magnetic field. The strong attachment of catalyst to magnetic support was confirmed by FT-IR spectra.