Synthesis and characterization of polyborates templated by cationic copper(II) complexes: Structural (XRD), spectroscopic, thermal (TGA/DSC) and magnetic properties

Abstract

Several polyborate containing species templated by cationic copper(II) coordination compounds have been synthesized. The ionic species [Cu(en)2][B5O6(OH)4]2·2H2O (en=1,2-diaminoethane) (1), [Cu(dmen)2(H2O)][B5O6(OH)4]2·3H2O (dmen=N,N-dimethyl-1,2-diaminoethane) (2), [Cu(pn)2{B5O6(OH)4}][B5O6(OH)4]·4H2O (pn=1,2-diaminopropane) (3), [Cu(dach)2(H2O)2][Cu(dach)2][B7O9(OH)5]2·4H2O (dach=1,2-diaminocyclohexane) (4), and the neutral species [Cu(dmen){B6O7(OH)6}]·4H2O (5) and [Cu(tmeda){B6O7(OH)6}]·6H2O (tmeda=N,N,N′,N′-tetramethyl-1,2-diaminoethane) (6) have been synthesized in aqueous solution and characterized by spectroscopic and thermal (TGA/DSC) methods. The previously prepared compound [Cu(en)2][B4O5(OH)4]2·2B(OH)3 (7) has also been prepared by an alternative route. Compounds 1–6 have been further characterized by single-crystal XRD studies. The new compounds show extensive H-bond interactions and display a range of structural features: 1–3 have isolated pentaborate(1-) anions whilst 4 possesses an isolated heptaborate(2-) anion. In addition, 3 has a pentaborate(1-) and 5 and 6 have hexaborate(2-) anions directly coordinated to their copper(II) centers, in mondentate and tridentate manners, respectively. The copper(II) centers show a variety of coordination numbers and geometries: square-planar (1, 7), octahedral (4) and square-based pyramidal (2, 3, 5, 6). Thermal studies (TGA/DSC) and magnetic susceptibility measurements have been undertaken on all compounds.