Synthesis, characterization and catalytic oxidation of cyclohexene with molecular oxygen over host (montmorillonite-K10)/guest (nickel(II) complexes of 12- and 13-membered diaza dioxa Schiff-base macrocyclic ligand) nanocatalyst (HGN)

Nickel(II) complexes of 12- and 13-membered diaza dioxa Schiff-base macrocyclic ligand, 1,4-diaza-7,10-dioxacyclododeca-1,3-diene, H2[12]1,3-dieneN2O2; 2,3-dimethyl-1,4-diaza-7,10-dioxacyclododeca-1,3-diene, (CH3)2[12]1,3-dieneN2O2; 2,3-diphenyl-1,4-diaza-7,10-dioxacyclododeca-1,3-diene, (C6H5)2[12]1,3-dieneN2O2; 2,4-dimethyl-1,5-diaza-8,11-dioxacyclotrideca-1,4-diene, (CH3)2[13]1,4-dieneN2O2; 2,4-diphenyl-1,5-diaza-8,11-dioxacyclotrideca-1,4-diene, (C6H5)2[13]1,4-dieneN2O2 were entrapped into an montmorillonite-K10 (denoted as K10) by simultaneous/pillaring encapsulation method. In this method the simultaneous encapsulation also occurred but the complex, also dissolved in methanol, was added to the clay dispersion. All materials were characterised by FT-IR, DRS, UV–vis and atomic absorption spectroscopy (AAS). In all cases the nickel(II) 12- and 13-membered diaza dioxa Schiff-base complex is mainly physically entrapped within the matrix, although some host–guest interactions with the matrix could be present. The host–guest nanocatalyst; HGN; ([Ni(R2[12]1,3-dieneN2O2)]2+@K10, [Ni(R2[13]1,4-dieneN2O2)]2+@K10; R = H, Me and Ph) is catalytically very efficient as compared to other neat complexes for oxidation of cyclohexene with molecular oxygen as oxidant in the absence of solvent at 70 °C, affording 2-cyclohexene-1-ol and 2-cyclohexene-1-one.

Nickel(II) complexes of 12- and 13-membered diaza dioxa Schiff-base macrocyclic ligand; (R2[12]1,3-dieneN2O2), (R2[13]1,4-dieneN2O2), R = H, Me and Ph; was entrapped into an montmorillonite-K10 (denoted as K10) by simultaneous/pillaring encapsulation method. In all cases the nickel(II) 12- and 13-membered diaza dioxa Schiff-base complex is mainly physically entrapped within the matrix, although some host–guest interactions with the matrix could be present. The host–guest nanocatalyst; HGN; ([Ni(R2[12]1,3-dieneN2O2)]2+@K10, [Ni(R2[13]1,4-dieneN2O2)]2+@K10); is catalytically very efficient as compared to other neat complexes for oxidation of cyclohexene with molecular oxygen as oxidant in the absence of solvent at 70 °C, affording 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Figure optionsDownload as PowerPoint slide