title: Immobilization, trapping, and anion exchange of perrhenate ion using copper-based tripodal complexes.
abstract: We describe a multidentate tripodal ligand in which three pendant arms carrying di(2-picolyl)amine units are linked to the ortho positions of a tris(o-xylyl) scaffold, providing N(CH(2)-o-C(6)H(4)CH(2)N(CH(2)py)(2))(3) (L). Reaction of L with CuCl(2) in the presence of hexafluorophosphate anion afforded blue cubes of [(CuCl)(3)L](PF(6))(3)·5H(2)O (1). Crystallographic studies of 1 revealed that the three symmetry-related arms each coordinate a {Cu(II)Cl} unit, and two molecules of 1 are connected to one another through a Cu(μ-Cl)(2)Cu bridge, extending the molecular structure to form a two-dimensional (2-D) layer. These 2-D layers pack in an ABCABC... fashion with PF(6)(-) anions located in between. Reaction of 1 with a stoichiometric amount of perrhenate ion afforded blue plates of [(CuCl)(3)L](PF(6))(ReO(4))(2)·3H(2)O (2). Compound 2 has the same lattice structure as 1, but the tricopper unit backbone now traps one ReO(4)(-) anion through Coulombic interactions. In addition, three molecules of 2 are bridged by a perrhenate ion, forming a Cu(3)(μ(3)-ReO(4)) cluster, to give a different 2-D structure displaying a rare tridentate bridging ReO(4)(-) mode. Thus, in addition to classic perrhenate trapping through weak Coulombic interactions, 2 represents an exceptional example in which the ReO(4)(-) anion is immobilized in an extended framework through tight covalent interactions. The interlamellar PF(6)(-) anions in 1 can be exchanged with other anions including perrhenate, perchlorate, or periodate. The structural similarity between perrhenate and pertechnetate makes these materials of potential interest for pertechnetate trapping.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Rui
authors.initials: R
authors.lastname: Cao
authors.forename: Brian D
authors.initials: BD
authors.lastname: McCarthy
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lippard
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010847:Picolines / Q000138:chemical synthesis / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry* / Q000302:isolation & purification; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D009942:Organometallic Compounds; D010847:Picolines; C015428:perrhenate; D012211:Rhenium; D003300:Copper