Abstract
Copper(II) acetate has reacted in methanol with quinaldinic acid (quinoline-2-carboxylic acid) to form [Cu(quin)2(CH3OH)]∙CH3OH (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(H2O)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)2Cl] (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)2Cl] (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]∙CH3CN (8) and [Cu(quin)2(pipe)2]∙CH3CH2CN (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.
Highlights
The coordination chemistry of copper is very rich because of its biological roles [1,2,3] and diverse practical applications, e.g., as catalysts, fungicides, and pesticides [4]
Its recrystallization from dichloromethane inadvertently resulted in[Cu(quin)2 Cl] (3), a product, which confirms that pyrrolidine, initially present as a ligand in the copper(II) complex, reacted with the solvent
It should be emphasized that our apyrrolidine or morpholine reaction mixtureswith didoxygen not show changes that would suggest reduction or of morpholine metal ions. reaction mixtures did not show color changes that would suggest a reduction of metal ions
Summary
The coordination chemistry of copper is very rich because of its biological roles [1,2,3] and diverse practical applications, e.g., as catalysts, fungicides, and pesticides [4]. The elongation of the axial bonds often results in a square-planar geometry ion The usually displays a distorted environment withare fourdue tightly bound donors in a plane described distortions of octahedral the coordination polyhedra to the operating. Complexes with quinaldinate and alicyclic secondary metal’s mode of action at the active sites in acid, enzymes amines as auxiliary ligands. Complexes with quinaldinate andinalicyclic secondary amines (shown in Scheme 1), is a biological molecule, mostly known for its role tryptophan metabolism as auxiliary ligands. − , readily forms complexes with many transition metal ions and has, form, abbreviated as quin characterized complexes with quinaldinate reveal a bidentate chelating manner through pyridine found useand in their quantitative gravimetric determination [10,11]. Quinaldinate pyrrolidine, morpholine, and piperidine (Scheme 1), was governed by their ability to bind uniformly compounds known prior toThe thisgroup reportshares [27].
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