Preparation and characterization of cobalt(II) complexes derived from hexadentate 'tripod' ligand and their potentials as epoxidation catalysts

The ligand N,N,N',N'-tetrakis (1-hydroxymethyl-2-benzimidazolymethyl)-1,2- ethanediamine (HMEDTB) (L) has been prepared and characterized by elemental analyses and spectral data. Its reaction with cobalt(II) chloride hexahydrate, or cobalt(II) nitrate hexahydrate in the molar ratio of 1:2 in acetonitrile afforded the complexes [Co(L)](2+) 2NO(3)(-) (1), and [Co-2(L)Cl-2](2+) 2Cl(-) (2), respectively. Elemental analyses and spectral data on compound (1) show it to be a mononuclear cationic cobalt(Il) complex in an octahedral geometry, with two nitrate ions as counterions. Similar data on compound (2) reveal the presence of a cationic dicobalt complex with bridging hydroxide in possibly a trigonal bipyramidal geometry. Compounds(1) and (2) catalysed the epoxidation of styrene in 53.8 and 34.3% yields, respectively.