Structural diversity in the reactions of 4′-(pyridyl)-2,2′:6′,2″-terpyridine ligands and bis{4′-(4-pyridyl)-2,2′:6′,2″-terpyridine}iron(II) with copper(II) salts

We have demonstrated that treatment of [Fe(1)₂]²⁺ (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) with an excess of CuCl₂·2H₂O leads to competition between coordination of copper(II) by the pendant pyridine donors in [Fe(1)₂]²⁺, and transfer of ligand 1 from iron(II) to copper(II) to yield [{Cl₃Cu(µ-1)Fe(µ-1)}₂CuCl₂(OH₂)₂]Cl₂·4H₂O and [Cu(H1)Cl₂]Cl·4H₂O, respectively. Direct reaction of 1 with CuCl₂·2H₂O and variation in crystallization conditions results in the formation of either monomeric or polymeric complexes: [Cu(1)Cl₂]·4.75H₂O, [Cu(1)Cl₂]·H₂O·MeOH and [Cu(1)Cl₂·2H₂O]_n. The reaction of 1 with Cu(NO₃)₂·3H₂O gives the coordination polymer [Cu(1)(ONO₂)₂·H₂O]_n. Magnetic data for [Cu(1)Cl₂·2H₂O]_n and [Cu(1)(ONO₂)₂·H₂O]_n are consistent with antiferromagnetically-coupled chains. Reactions of CuCl₂·2H₂O with ligands 2 and 3 (2 = 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine, 3 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine) lead to monomeric complexes. With the exception of [Cu(3)Cl₂], the mononuclear complexes show a propensity for the incorporation of water into their crystal lattices; in the case of [Cu(H1)Cl₂]Cl·4H₂O and [Cu(H1)Cl₂]Cl·4.75H₂O, the small change in water content leads to the assembly of (5.8²)₂(5.6.8)₄(5².6)₂ or (4².6²)₃(4.6²)₆ water–chloride ion nets.