dlf Complexes with Uniform Coordination Geometry: Structural and Magnetic Properties of an LnNi2 Core Supported by a Heptadentate Amine Phenol Ligand

The synthesis and physical characterization of a series of lanthanide (Lnʹ") and nickel (Ni") mixed trimetallic complexes with the heptadentate (103) amine phenol ligand Hstm [tris(2ʹ-hydroxybenzylaminoethyl)amine] has been accomplished in order to extend our understanding of how amine phenol ligands can be used to coaggregate dand -block metal ions and to investigate further the magnetic interaction between these ions. The one-pot reaction in methanoi of stoichiometric amounts of Hstm with N-SIO (X = C104, NO3) followed by addition of the corresponding LnXsʹSHgO salt, and then base, produces complexes of the general formula [l-nNtnX-O. The complexes were characterized by a variety of analytical techniques. Crystals of five of the complexes were grown from methanoi solutions and their structures were determined by X-ray analysis: [PrNitrTCHsOHCCHsOH.H2O, [SmNi2(trn)2(CH30H)]N03-4CH30H-2H20, [TbNi2(trn)2(CH30H)]N03-4CH30H-3H20, [ErNi2(trn)2(CH30H)]N03-6CH30H, and [LuNi2(trn)2(CH30H)]N03-4.5CH30H-1.5H20. The [LnNi2(trn)2(CH30H) complex cation consists of two octahedral Mi" ions, each of which is encapsulated by the ligand trn in an N4O2 coordination sphere with one phenolate O atom not bound to Ni". Each [Ni(trn)]~ unit acts as a tridentate ligand toward the Lnʹ" ion via two bridging and one nonbridging phenolate donors. Remarkably, in all of the structurally characterized complexes, Lnʹ" is seven-coordinate and has a flattened pentagonal bipyramidal geometry. Such uniform coordination behavior along the whole lanthanide series is rare and can perhaps be attributed to a mismatch between the geometric requirements of the bridging and nonbridging phenolate donors. Magnetic studies indicate that ferromagnetic exchange occurs in the Ni"/Ln" complexes where Ln = Gd, Tb, Dy, Ho, or Er.