The coordination chemistry of N-(2-aminophenyl)- and N-(3-aminophenyl)quinoline-2′-carboxamide; two potentially tridentate ligands containing secondary amide and N-donor groups

Abstract

New complexes of the general formulae Co( o-LH) 2X 2 (XCl, NCS), Co( o-LH) 2Br 2·EtOH (EtOHethanol), M( o-LH)(NO 3) 2 (MCo, Ni), Ni( o-LH) 2X 2 (XCl, Br, NCS), Cu( o-L)X (XCl, Br), Zn( o-LH)X 2 (XCl, Br), Pd( o-L)Cl, Pt( o-LH) 2Cl 2·H 2O, M( m-LH)Cl 2· nH 2O (MCo, Ni, Pd; n=0, 0.5, 1), Cu( m-LH)Cl 2·EtOH, M( m-LH) 2Cl 2· nH 2O (MCo, Zn, Pt; n=0, 1), M( m-LH)Br 2 (MCu, Zn), M( m-LH) 2Br 2 (MCo, Ni), Co( m-LH)(NCS) 2 and Co( m-LH) 2(NCS) 2, where o-LH= N-(2-aminophenyl)quinoline-2′-carboxamide and m-LH= N-(3-aminophenyl)quinoline-2′-carboxamide, have been prepared. The complexes were characterised by elemental analyses, conductivity measurements, X-ray powder patterns, thermogravimetric analyses, magnetic moments and spectral ( 1H NMR, IR, and electronic) studies. Copper(II) and palladium(II) promote amide deprotonation at nearly acidic pH on coordination with o-LH. A variety of stereochemistries is assigned for the complexes prepared. The deprotonated copper(II) and the nickel(II) and palladium(II) complexes of m-LH appear to be polymeric. The neutral amide group of the ligands is coordinated to the metal ions through oxygen, while N(amide)-coordination is observed for the deprotonated complexes. Coordination of the secondary amide group is not observed for Zn( m-LH) 2Cl 2, Pd( m-LH)Cl 2·0.5H 2O and platinum(II) complexes. The neutral ligand o-LH shows bidentate N(ring), O-behaviour, while the anion o-L − exhibits tridentate N,N,N-coordination. m-LH acts as a monodentate, bidentate and tridentate ligand depending on the metal ion, the anion and the preparative conditions.