Fe3O4 nanoparticles were coated with aminopropyltriethoxysilane and subsequently reacted with isatin to obtain imine‐bonded Fe3O4 nanoparticles. The addition of ZrOCl2⋅8H2O or CuCl2 led to the formation of complexes of Zr(IV)/isatin@Fe3O4 or Cu (II)/isatin@Fe3O4 as new magnetically separable catalysts. The synthesized catalysts were characterized using various techniques. These catalysts are shown to be efficient for chemo‐selective oxidation of sulfides to sulfoxides using hydrogen peroxide as oxidative agent. This system has many advantages, such as excellent level of reusability of magnetic catalysts, high yields, simplicity of separation of catalysts using an external magnet, environmental benignity and ease of handling. Copyright © 2016 John Wiley & Sons, Ltd.

The Zr‐based complex catalysts can be easily recovered ten times and the analogous Cu‐based complex seven times without noticeable deterioration in catalytic activity.