Two New Borates Made of [B₅O₆(OH)₄]⁻ and [B₅O₁₀(OH)]⁶⁻ Clusters, Accompanying a Novel In Situ Organic Reaction

Two new pentaborate clusters, [MPD][B₅O₆(OH)₄] (1, MPD = 2-methyl-1,4,5,6-tetrahydropyrimidine-3-ium) and SrB₅O₈(OH) H₂O (2), have been hydro(solvo)thermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray structural analysis, respectively. Crystal data for 1: monoclinic, P2_1/c, a = 9.3384(3) Å, b = 17.3774(5) Å, c = 9.1886(3) Å, β = 93.172(3)°, Z = 4. Crystal data for 2: triclinic, P-1, a = 6.6406(6) Å, b = 6.6784(8) Å, c = 10.2162(15) Å, α = 98.905(11)°, β = 92.237(9)°, γ = 119.446(11)°, Z = 2. In compound 1, all the terminal O atoms of [B₅O₆(OH)₄]⁻ clusters are hydroxyl groups, which hinder the further connection of the [B₅O₆(OH)₄]⁻ clusters, only forming 3-D supramolecular frameworks via extensive hydrogen-bonding interactions. In compound 2, the [B₅O₁₀(OH)]⁶⁻ clusters link each other to form a 2-D layer, which are further extended to 3-D supramolecular frameworks via extensive hydrogen-bonding interactions. Interestingly, a novel in situ organic reaction between 1,3-diaminoprapane and CH₃COO⁻ group has been observed during the formation of compound 1.