The Effect of Zn super(II) Coordination on the Addition of 2-(Aminomethyl)benzimidazole to Acrylonitrile

The effects of N arrow right Zn coordination, solvent, and pH on the aza-addition reaction between 2-(aminomethyl)benzimidazole (HL) and acrylonitrile were studied. In the absence of Zn super(II) ion, the aza-addition reactions between HL and acrylonitrile (in aqueous media) depended on pH and were...

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Bibliographic Details
Published in:European journal of inorganic chemistry 2014-11, Vol.2014 (31), p.5415-5423
Main Authors: Falcon-Leon, Martha P, Tapia-Benavides, Antonio R, Tlahuext, Hugo, Galan-Vidal, Carlos, Suarez-Castillo, Oscar R, Tlahuextl, Margarita
Format: Article
Language:English
Subjects:
Acrylonitriles
Chelates
Coordination compounds
Mathematical models
Nitrogen atoms
Solvents
X ray diffraction
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Summary:The effects of N arrow right Zn coordination, solvent, and pH on the aza-addition reaction between 2-(aminomethyl)benzimidazole (HL) and acrylonitrile were studied. In the absence of Zn super(II) ion, the aza-addition reactions between HL and acrylonitrile (in aqueous media) depended on pH and were not selective. The mono-addition compound {3-[(1H-benzimidazol-2-ylmethyl)amino]propanenitri le} was always obtained in a greater proportion than the di-addition products [3,3'-[(1H-benzimidazol-2-ylmethyl)imino]di propanenitrile and 3-(2-{[(2-cyanoethyl)amino]methyl}-1H-benzimidazol -1-yl)propanenitrile]. Acrylonitrile selectively reacted at the amine group in the [ZnCl sub(3)(H sub(2)L)] and [ZnCl sub(2)(HL)] complexes in aqueous solutions. Moreover, [ZnCl(HL) sub(2)]Cl and [Zn(H sub(2)O) sub(2)(HL) sub(2)]Cl sub(2) complexes yielded mixtures of mono- and di-addition products. In contrast, Zn complexes formed with HL did not react with acrylonitrile in solution in DMSO. The synthesis of mono- and di-addition compounds was studied by super(1)H and super(13)C NMR spectroscopy and X-ray diffraction crystallography. Quantum theory of atoms in molecules (QTAIM) computations were used to demonstrate the probable presence of a mono-addition chelate complex. The aza additions of 2-(aminomethyl)benzimidazole (HL) to acrylonitrile depend on pH and are not selective. However, the N arrow right Zn coordination bonds in HL increase the selectivity of the aza addition to acrylonitrile because the Zn super(II) protects the imidazolic nitrogen atoms. Moreover, the aza addition of Zn super(II) complexes requires an aqueous medium.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.201402346