Beyond the Simple Copper(II) Coordination Chemistry with Quinaldinate and Secondary Amines

Copper(II) acetate has reacted in methanol with quinaldinic acid (quinoline-2-carboxylic acid) to form [Cu(quin)(2)(CH(3)OH)]∙CH(3)OH (1) (quin(−) = an anionic form of the acid) with quinaldinates bound in a bidentate chelating manner. In the air, complex 1 gives off methanol and binds water. The conversion was monitored by IR spectroscopy. The aqua complex has shown a facile substitution chemistry with alicyclic secondary amines, pyrrolidine (pyro), and morpholine (morph). trans-[Cu(quin)(2)(pyro)(2)] (2) and trans-[Cu(quin)(2)(morph)(2)] (4) were obtained in good yields. The morpholine system has produced a by-product, trans-[Cu(en)(2)(H(2)O)(2)](morphCOO)(2) (5) (morphCOO(−) = morphylcarbamate), a result of the copper(II) quinaldinate reaction with ethylenediamine (en), an inherent impurity in morpholine, and the amine reaction with carbon dioxide. (pyroH)[Cu(quin)(2)Cl] (3) forms on the recrystallization of [Cu(quin)(2)(pyro)(2)] from dichloromethane, confirming a reaction between amine and the solvent. Similarly, a homologous amine, piperidine (pipe), and dichloromethane produced (pipeH)[Cu(quin)(2)Cl] (11). The piperidine system has afforded both mono- and bis-amine complexes, [Cu(quin)(2)(pipe)] (6) and trans-[Cu(quin)(2)(pipe)(2)] (7). The latter also exists in solvated forms, [Cu(quin)(2)(pipe)(2)]∙CH(3)CN (8) and [Cu(quin)(2)(pipe)(2)]∙CH(3)CH(2)CN (9). Interestingly, only the piperidine system has experienced a reduction of copper(II). The involvement of amine in the reduction was undoubtedly confirmed by identification of a polycyclic piperidine compound 10, 6,13-di(piperidin-1-yl)dodecahydro-2H,6H-7,14-methanodipyrido[1,2-a:1′,2′-e][1,5]diazocine.