Copper (II)-mediated oxidative dehydrogenation of amine ligands

The process of oxidative dehydrogenation of the pentadentate amine ligand 2,10-bis-(2'-pyridyl)-3,6,9-triazaundecane (L-am(1)) mediated by Cu(II) in the absence of an external oxidant led to the Cu(I) mono-imine complex, [(CuLim1)-L-1](BPh4). This complex was quite sensitive towards air oxidation, leading to the corresponding Cu(II) mono-imine complex. The complexes were characterized by C, H, N analysis, IR, NMR, and cyclic voltammetry. The structures of the Cu(II) mono-imine complexes, [(CuLLim1)-L-II (X)](BPh4)(2) (X = CH3 COCH3, CH3 SOCH3, or CH3 CN), and of the Cu(II) amine complex [(CuLam1)-L-II](BPh4 (NO3), were solved by X-ray crystallography. These complexes carried each a Cu(II)N-5 site, with five nitrogen atoms provided by either L-am(1) (2 sp(3) amino N, 1 sp(2) imino N, 2 sp(2) pyridine N), or L-am(1 )(3 sp(3) amino N, 2 sp(2) pyridine N). The Cu(II) promoted oxidative dehydrogenation of amine ligand L-am(1) did not require an external base in contrast to related Fe(III)/Fe(II) systems. (C) 2017 Elsevier B.V. All rights reserved.