Structural flexibility in complexes bearing a tripodal nitrogen ligand

Complexes of the divalent metal ions of zinc, cobalt and nickel and a tripodal imidazol-based ligand were investigated for their solution chemistry in protic solvents of varying steric demand. Changes in the coordination number from 4 to 6 are observed depending on solvents, temperature and ions present in solution. With bio-relevant N,O ligands, e.g. amino acids as glycine and alanine, five-coordinate complexes are formed. The solid state structures of the five-coordinate complexes [LNi(H2O)Cl]Cl (3a′) and [LZn(pic)]NO3 (L = tris(2-isopropylimidazol-4(5)-yl)phosphane, pic = picolinato) were determined.