Synthesis, characterization and catalytic activity of novel monometallic and bimetallic Mn(II) complexes with thiocarboxamide and phenanthroline ligands

Novel manganese(II) complexes, 1–3, involving 1,10-phenanthroline and thiocarboxamide ligands, were prepared and characterized structurally using single-crystal X-ray diffraction that revealed monometallic and bimetallic nature of the octahedral complexes. The catalytic activities of 1–3 were investigated in the oxidation of selected primary and secondary alcohols. During the optimization of the oxidation reactions, 1, a bimetallic manganese(II) complex bearing phenanthroline and bridging anthranilate showed higher activity as catalyst precursor than monometallic 2 or 3 in the oxidation of primary alcohols. The catalytic reactions were carried out in the presence of various oxidants such as molecular oxygen, hydrogen peroxide and tert-butyl hydroperoxide (TBHP) and additives such as acetic acid and imidazole. In this study, the oxidant/additive combination of TBHP and imidazole was shown to be effective for the oxidation of substrates investigated and the degree of their impact on oxidation reaction is highly dependent on a balanced ratio between them. 1 and 2 were selected as the most effective catalyst precursor under optimized reaction conditions and revealed efficient for the oxidation of selected primary and secondary alcohols, respectively.