Two New Octaborates Constructed of Two Different Sub-clusters and Supported by Metal Complexes

Abstract

Two inorganic–organic hybrid borates, [Zn(en)2{B8O11(OH)4}] (1, en = ethylenediamine) and [Cd(TREN){B8O11(OH)4}] (2, TREN = tris(2-aminoethyl)amine) have been made under hydro(solvo)thermal conditions and characterized by IR spectroscopy, elemental analysis, single crystal X-ray diffraction, diffuse-reflectance spectroscopy, thermogravimetric analyses, and powder X-ray diffraction. Crystal data for 1: triclinic, P−1, a = 8.7091(5) A, b = 8.8731(2) A, c = 12.7642(8) A, α = 87.042(4)°, β = 78.198(5)°, γ = 80.816(4)°, V = 952.96(9) A3. Crystal data for 2: monoclinic, P21/c, a = 11.5051(4) A, b = 8.7879(4) A, c = 19.9322(7) A, β = 91.433(3)°, V = 2014.63(14) A3. They both contain [B8O11(OH)4]2− cluster units, which linked each other to form 1-D chains. These 1-D chains are further joined together to produce 3-D supramolecular frameworks via H-bonding interactions. Interestingly, the [B8O11(OH)4]2− cluster in 1 is made of [B5O8(OH)2]3− and [B3O5(OH)2]2− sub-cluster units with two O atoms in common, while in 2 consists of [B5O7(OH)3]2− and [B3O6(OH)]4− sub-cluster units with two O atoms in common. The [B8O11(OH)4]2− ligands in 1 and 2 are coordinated to the supporting metal complexes in different ways. The anion in 1 is coordinated to the Zn(en)2 by a terminal OH group whereas the anion in 2 is coordinated by a bridging O atom. The in situ organic rearrangement reaction from triethylene tetramine (TETA) to tris(2-aminoethyl)amine (TREN) has been observed in the formation of 2.