Keggin type inorganic–organic hybrid material containing Mn(II) monosubstituted phosphotungstate and S-(+)-sec-butyl amine: Synthesis and characterization

Graphical abstract: A new organic–inorganic hybrid material containing Keggin type manganese substituted phosphotungstate and S-(+)-sec-butyl amine was synthesized and systematically characterized. Highlights: ► New hybrid material comprising Mn substituted phosphotungstate (PW11Mn) and S-(+)-sec-butyl amine (SBA) was synthesized. ► The spectral studies reveal the attachment of SBA to the PW11Mn without any distortion of structure. ► The synthesized material comprises chirality. ► The synthesized hybrid material can be used as a heterogeneous catalyst for carrying out asymmetric synthesis. -- Abstract: A new inorganic–organic POM-based hybrid material comprising Keggin type mono manganese substituted phosphotungstate and enantiopure S-(+)-sec-butyl amine was synthesized in an aqueous media by simple ligand substitution method. The synthesized hybrid material was systematically characterized in solid as well as solution by various physicochemical techniques such as elemental analysis, TGA, UV–vis, FT-IR, ESR and multinuclear solution NMR (31P, 1H, 13C). The presence of chirality in the synthesized material was confirmed by CD spectroscopy and polarimeter. The above study reveals the attachment of S-(+)-sec-butyl amine to Keggin type mono manganese substituted phosphotungstate through N → Mn bond. It also indicates the retainment of Keggin unit and presence of chirality in the synthesized material. An attempt was made to use the synthesized material as a heterogeneous catalyst for carrying out aerobic asymmetric oxidation of styrene using molecular oxygen. The catalyst shows the potential of being used as a stable recyclable catalytic material after simple regeneration without significant loss in conversion.