Synthesis of Silica-Supported Platinum(II) and Nickel(II) Complexes of Bis(Diphenylphosphinomethyl)Amino Ligand: Applications as Catalysts for the Synthesis of 2-Methyl-1,4-Naphthoquinone (Vitamin K3)

Pt(II) and Ni(II) complexes of N,N-bis(diphenylphosphinomethyl)aminopropyltriethoxysilane (CH₃CH₂O)₃Si(CH₂)₃N(CH₂PPh₂)₂] (DIPAPTES) and silica supported SiO₂–(DIPAPES)] ligands have been synthesized under nitrogen atmosphere using Schlenk method and characterized by using atomic absorption, FT-IR, NMR (¹H and ³¹P) and elemental analysis techniques. All the complexes were used as catalysts for the oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1,4-naphthoquinone (vitamin K₃, menadione, 2MNQ) using hydrogen peroxide as a clean and cheap oxidant. Pt–(DIPAPTES)Cl₂] and supported complex SiO₂–(DIPAPES)–PtCl₂] showed medium catalytic activity whereas Ni(II) complexes did not show any catalytic activity for the selective oxidation of 2-methyl naphthalene to 2-methyl-1,4-naphthoquinone.