Site specificity of metal ions in heterodinuclear complexes derived from an "end-off" compartmental ligand

A phenol-based "end-off" compartmental ligand, 2-{N-[2-(dimethylamino)ethyl]iminomethyl}-6-[N,N-di(2-pyridylmethyl) -aminomethyl]-4-methylphenol (HL), having a bidentate arm and a tridentate arm attached to the 2 and 6 positions of the phenolic ring, has afforded the following heterodinuclear M_a^IIM_b^II complexes: [CuM(L)(AcO)₂]CIO₄ (M = Mn (1), Fe (2), Co (3), Ni (4), Zn (5)), [ZnM(L)(AcO)2]CIO₄ (M = Co (6), Ni (7)), and [CuNi(L)(AcO)(NCS)₂] (8). 1·MeOH (1′), 2·MeOH (2′), 3·MeOH (3′), 4·MeOH (4′), 5·MeOH (5′), and 7·MeOH (7′) are isostructural and have a heterodinuclear core bridged by the phenolic oxygen atom of L- and two acetate groups. In 1′-5′ the Cu^II is bound to the bidentate arm and has a square-pyramidal geometry with one acetate oxygen at the apical site. The M^II is bound to the tridentate arm and has a six-coordinate geometry together with two acetate oxygen atoms. In the case of 7′ the Zn is bound to the bidentate arm and the Ni is bound to the tridentate arm. 8·2-PrOH (8′) has a dinuclear core bridged by the phenolic oxygen atom of L- and one acetate group. The Cu bound to the bidentate arm has a square-pyramidal geometry with an isothiocyanate group at the apical site. The Ni bound to the tridentate arm has a six-coordinate geometry with further coordination of an isothiocyanate group. The site specificity of the metal ions is discussed together with the crystal structure of [Cu₄(L)₂(AcO)₃] (CIO₄)₃·H₂O (9) prepared in this work.