Studies on the metal-amide bond. I. Metal complexes of the bis-amide tetradentate ligand N,N′-bis(2′-pyridinecarboxamide)-1,2-benzene

Complexes of general formula M(bpbH₂)Cl₂· nH₂O, where bpbH₂ = N,N′-bis(2′-pyridinecarboxamide)-1,2-benzene and M = Mn (n = 0), Co (n = 1), Co and Ni (n = 2) and Cu (n = 1.5) have been prepared. As well, the complexes Ag(bpbH₂)(NO₃) and Co(bpbH₂)(NCS)₂·2.5H₂O were isolated. The copper and nickel complexes exhibit clear evidence of neutral amide-N coordination. Several of the metal ions used promote amide deprotonation on coordination, and a series of complexes of formula M(bpb)·H₂O (M = Co, Ni, Cu, Zn and Pd) are reported. A planar M^IIN₄ system is proposed for these complexes. Stereochemistries for the complexes have been proposed utilising microanalyses, magnetic susceptibilities, thermogravimetric analyses and infrared and visible spectral data.