Oxidopolyborate chemistry: The self-assembled, templated, synthesis, and an XRD study of a 1-D coordination polymer, [Cu(en){B₆O₇(OH)₆}]^.3H₂O (en = 1,2-diaminoethane)

Abstract

[Cu(en){B₆O₇(OH)₆}]^.3H₂O (1) (en = 1,2-diaminoethane), obtained as a crystalline solid in low yield (31%) after prolonged standing of an aqueous solution initially containing [Cu(en)₂](OH)₂ and B(OH)₃ (1:7 ratio), was characterized by thermal analysis (TGA/DSC), ¹¹B NMR and IR spectroscopy, powder XRD, and single-crystal XRD studies, and magnetic susceptibility measurements. The single-crystal X-ray diffraction revealed that the oxidoborate complex is a 1D coordination polymer with the hexaborate(2-) ligand bridging two hexacoordinate Cu^(II) centers, in an alternating a fac-tridentate (κ³-O) and monodentate (κ¹-O) arrangement. Cu-O coordination bonds and extensive H-bonding networks promote and stabilize the self-assembly of [Cu(en){B₆O₇(OH)₆}]^.3H₂O from the Dynamic Combinatorial Libraries of available reactants. [Cu(en){B₆O₇(OH)₆}]^.3H₂O is thermally decomposed to CuB₆O₁₀ in air at 700 °C.

Graphical Abstract

Keywords:

• Copper(2+) complex
• 1D coordination polymer
• hexaborate(2)
• oxidoborate
• polyborate

Acknowledgments

We thank the EPSRC for the NCS X-ray crystallographic service (Southampton).

Supplemental materials

Crystallogaphic data for the structural analysis of compound 1 has been deposited at the Cambridge Crystallographic Data Center (CCDC number 1990215). Copies of the information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1 EZ, UK (Fax: + 44-1223-336033; email: [email protected] or www.ccdc.cam.ac.uk).

Disclosure statement

No potential conflict of interest was reported by the authors.

Figure 4. The unusual R₂²(6) interaction involving the amino hydrogen of the en ligand in a neighboring polymer chain.