Synthesis and characterization of N3Py2 ligand-based cobalt(II), nickel(II) and copper(II) catalysts for efficient conversion of hydrocarbons to alcohols

Synthesis and characterization of cobalt(II), nickel(II) and copper(II) complexes supported by a pentadentate ligand N,N′-dimethyl-N-(2-(methyl(pyridin-2-ylmethyl)amino)ethyl)-N′-(pyridin-2-ylmethyl)ethane-1,2-diamine (N3Py2) have been reported. Catalytic activity and counter anion effect have been investigated in the C–H activation of cumene and adamantane. [Display omitted] •Co(II), Ni(II) & Cu(II) complexes of N3Py2 are synthesized and characterized.•Ligand N3Py2 has been reported for the first time.•Co(II) & Ni(II) complexes are characterized by X-ray crystallography.•All compounds showed good catalytic activity in the alkane oxidation.•Counter anion effect on product yields is investigated. Three new complexes [Co(N3Py2)(H2O)](ClO4)21, [Ni(N3Py2)(H2O)](ClO4)22 and [Cu(N3Py2)](ClO4)23 (N3Py2 is N,N′-dimethyl-N-(2-(methyl(pyridin-2-ylmethyl)amino)ethyl)-N′-(pyridin-2-ylmethyl)ethane-1,2-diamine) have been synthesized and characterized. Non-heme ligand N3Py2 have been prepared by Eschweiler-Clarke method and reported for the first time. Compounds 1 and 2 were characterized by single crystal X-ray structure analysis. The structure of 1 and 2 revealed that Co(II) cation in 1 and Ni(II) cation in 2 are bonded to the five nitrogen atoms of N3Py2 and a water molecule thus forming an octahedral motif [M(N3Py2)(H2O)]2+. For compound 3, a square pyramidal geometry has been proposed based on the spectroscopic, elemental analysis and ESI-MS data. Compounds 1–3 were tested as catalysts in the oxidation of cumene and adamantane using m-CPBA. Comparative effect of counter anions on the product yields was observed when the perchlorates anions of 1–3 were replaced with tetraphenylborates to give compounds 1a–3a. The turnover numbers of alcohol over ketone product increased in order of catalysts, 1(1a)>2(2a)>3(3a).