Metal chelates of N-benzothiazol-2-yl-, N-benzoxazol-2-yl- and N-(1H-benzimidazol-2-yl)-benzamide

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Abstract

The synthesis of the title ligands N-benzothiazol-2-yl-benzamide (1), N-benzoxazol-2-yl-benzamide (2) and N-(1H-benzimidazol-2-yl)-benzamide (3) is described. The molecular structure of 1 confirms the localization of a hydrogen atom at the nitrogen atom of the benzamide group. The ligands form 2:1 metal chelates under deprotonization with CuII, NiII, PdII and ZnII. 3 gives a cationic silver(I) complex. The complexes were characterized by XPS, NMR, and FAB mass spectroscopy. The molecular structure of two complexes was determined.

Introduction

Previous investigations of synthesis and characterization of metal complexes with guanidine and isourea structural elements [1], [2], [3] are followed now by studies of metal complexes from title ligands N-benzothiazol-2-yl-benzamide (1), N-benzoxazol-2-yl-benzamide (2), and N-(1H-benzimidazol-2-yl)-benzamide (3) (Scheme 1).

Metal complexes (mainly Zn(II)) with guanidinium structure and from benzimidazoles and related compounds are known as protease inhibitors [4] or are used in structure investigation of metallo proteins [5]. They are also of interest with respect to their connection to purin bases [6].

Section snippets

Experimental

All chemicals and solvents were dried and purified by the usual methods. Melting points are corrected and were measured using a Boetius melting-point apparatus. Mass spectra were recorded on a Masslab VG 12-250 device and for the ESI-spectrum of 3e on a LC-MS Platform 1 spectrometer, Fa. Micromass (1:1 H2O/acetonitrile). NMR spectra were recorded on a Unity 400 spectrometer, 1H: σ (ppm), 399.95 MHz, solvent DMSO-d6; 13C: σ (ppm), 100.58 MHz, solvent DMSO-d6. The XPS spectra were recorded on a

Synthesis and spectroscopic characterization of ligands and metal complexes

Synthesis of ligands 13 was performed easily by reaction of N-(ethoxyethylsulfanylmethylene)-benzamide [7] and ortho-substituted aniline derivatives XC6H4NH2 (X=SH; OH; NH2) in boiling ethanol (Scheme 3). Compounds 13 were obtained as crystals in very good yields (90%) and are pure after one recrystallization. Compound 1 furnished suitable single crystals for X-ray analysis.

Under the same conditions educts (3,4-diaminophenyl)phenylmethanone and 2-amino-4-methylphenol, respectively, gave

Supplementary material

Crystallographic data for the structures in this paper have been deposited with the Cambridge Crystallographic Data Center as supplementary publication Nos. CCDC-140164, -140165, and -140166 for 1, 1a, and 2b, respectively. Copies of the data can be obtained free of charge, on application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-336-033; e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk).

Acknowledgements

The authors (J.A-C., M.L-P.) wish to acknowledge the financial support given by DAAD Bonn.

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