Cis-facial coordination of bis(pyrid-2-ylmethyl)amine (bpma). Synthesis, structure and spectral behaviour of [Ni(bpma)<SUB>2</SUB>]<SUP>2+</SUP>

Nickel(II) bis-complexes of bis(pyrid-2-ylmethyl)amine (bpma) and bis(benzimidazol-2-ylmethyl)amine (bbma) have been isolated. The complexes have been characterised using IR,UV-VIS and 1H NMR spectral techniques. The pink complex [Ni(bpma)2](ClO4)2 crystallises in the orthorhombic space group Fdd2, with a = 22.12(2), B = 28.087(2), C = 8.857(3) &#197;, &#945; = &#946; = GG = 90&#176; and Z = 8. The nickel(II) atom hasa slightly distorted octahedral structure in which the ligands are cis-facially coordinated. The M---Npy bond length in [M(bpma)2]2+ [M=Mn(II), Fe(II), Ni(II), Cu(II), Zn(II)] complexes decrease and then increase with increase in d-orbital population. The ligand field parameters of the new complexes are compared with those of other complexes with NiN6 chromophore