Copper (II)-mediated oxidative dehydrogenation of amine ligands

• Published in: Inorganica Chimica Acta Vol. 481; pp. 189 - 196
• Main Authors: Sarmiento-Pavía, Pedro D., Flores-Álamo, Marcos, Solano-Peralta, Alejandro, Kroneck, Peter M.H., Sosa-Torres, Martha E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2018; Elsevier Science Ltd
• Subjects: Alcohol; Chemical compounds; Copper; Copper(I); Copper(II); Crystallography; Dehydrogenation; Infrared radiation; Ligands; Mono-imine; Nitrogen atoms; NMR; Nuclear magnetic resonance; Oxidation; Oxidative dehydrogenation; Pentadentate amine; Copper(I); Oxidative dehydrogenation; Pentadentate amine; Mono-imine; Copper(II)
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2017.10.019

[Display omitted] •O. D. of a polyamine Cu(II) compound led to imine and amine Cu(I) complexes.•Cu(II) carried out oxidative dehydrogenation (O.D.) with no external base nor oxidant.•Crystal structures of imine hexa and amine pentadentate Cu(II) complexes are presented.•Polyamine Cu(II) complex underwent a disproportionation reaction. The process of oxidative dehydrogenation of the pentadentate amine ligand 2,10-bis-(2′-pyridyl)-3,6,9-triazaundecane (L1am) mediated by Cu(II) in the absence of an external oxidant led to the Cu(I) mono-imine complex, [CuIL1im](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, [CuIIL1im(X)](BPh4)2 (X = CH3COCH3, CH3SOCH3, or CH3CN), and of the Cu(II) amine complex [CuIIL1am](BPh4)(NO3), were solved by X-ray crystallography. These complexes carried each a Cu(II)N5 site, with five nitrogen atoms provided by either L1im (2 sp3 amino N, 1 sp2 imino N, 2 sp2 pyridine N), or L1am (3 sp3 amino N, 2 sp2 pyridine N). The Cu(II) promoted oxidative dehydrogenation of amine ligand L1am did not require an external base in contrast to related Fe(III)/Fe(II) systems.