Cu(II) bipyridine and phenantroline complexes: Tailor-made catalysts for the selective oxidation of tetralin

Mononuclear Cu(II) complexes have been synthesized, and their structure thoroughly characterized by electrospray ionization mass spectrometry (ESI-MS). These 2,2'-bipyridine and 1,10-phenantroline mononuclear Cu(II) complexes have been tested as catalysts in the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene), using hydrogen peroxide as oxidant in acetonitrile/water as solvent. The complexes [Cu(bipy)(3)]Cl-2 center dot 6H(2)O (1), [Cu(bipy)(2)Cl]Cl center dot 5H(2)O (2), [Cu(bipy)Cl-2] (3), [Cu(Phen)(3)]Cl-2 center dot 6H(2)O(4), [Cu(phen)(2)Cl]Cl center dot 5H(2)O (5), [Cu(phen)Cl-2] (6) were able to oxidize tetralin at room temperature, at high degrees of conversion (62.1% with 2) into a-tetralol and alpha-tetralon at 91% selectivity (81% in 1-tetralon). Depending on nature and number of ligands (bipyridine or phenantroline) surrounding Cu2+ cation, one was able to tailor both the activity toward tetralin oxidation, and the selectivity toward 1-tetralol and 1-tetralone products, but also to raise the yield in valuable alpha-tetralone. (c) 2009 Elsevier B.V. All rights reserved.