Placing Ni(II) Ions in Various Positions In/On Layered Double Hydroxides: Synthesis, Characterization and Testing in C–C Coupling Reactions

Ni(II)-containing layered double hydroxides (LDHs) were synthesized with various methods with the intention of placing the Ni(II) ions in different positions in/on the LDH. Ni(II) was introduced as a lattice-modifier into CaAl-, CaFe- and MgAl-LDHs or in the interlayer space in form of a complex anion or as the divalent component of NiAl-LDH or as surface dopant. The materials were structurally characterized by various instrumental methods; however, the final proof of lattice modification was proven by the Suzuki–Miyaura and the Heck coupling reactions. Each as-prepared catalyst was active and selective towards the coupling products with or without various additives. They could be recycled except the surface-doped material, in which intense leaching of the Ni(II) content was observed on reuse. Ni(II)-containing LDHs are active and recyclable catalysts in the Suzuki and Heck coupling reactions—this is the final proof that the Ni(II) ions are constituents of the lattice.