Search Results (5)

The synthesis and characterization of six new substituted guanidium tetrahydroxidohexaoxidopentaborate(1-) salts are reported: [C(NH₂)₂(NHMe)][B₅O₆(OH)₄]·H₂O (1), [C(NH₂)₂(NH{NH₂})][B₅O₆(OH)₄] (2), [C(NH₂)₂(NMe₂)][B₅O₆(OH)₄] (3), [C(NH₂)(NMe₂)₂][B₅O₆(OH)₄] (4), [C(NHMe)(NMe₂)₂][B₅O₆(OH)₄]·B(OH)₃ (5), and [TBDH][B₅O₆(OH)₄] (6) (TBD = 1,5,7-triazabicyclo [4.4.0]dec-5-ene). Compounds 1–6 were prepared as crystalline salts from basic aqueous solution via self-assembly processes from B(OH)₃ and the appropriate substituted cation. Compounds 1–6 were characterized by spectroscopic (NMR and IR) and by single-crystal XRD studies. A thermal (TGA) analysis on compounds 1–3 and 6 demonstrated that they thermally decomposed via a multistage process to B₂O₃ at >650 °C. The low temperature stage (<250 °C) was endothermic and corresponded to a loss of H₂O. Reactant stoichiometry, solid-state packing, and H-bonding interactions are all important in assembling these structures. An analysis of H-bonding motifs in known unsubstituted guanidinium salts [C(NH₂)₃]₂[B₄O₅(OH)₄]·2H₂O, [C(NH₂)₃][B₅O₆(OH)₄]·H₂O, and [C(NH₂)₃]₃[B₉O₁₂(OH)₆] and in compounds 1–6 revealed that two important H-bonding R₂²(8) motifs competed to stabilize the observed structures. The guanidinium cation formed charge-assisted pincer cation–anion H-bonded rings as a major motif in [C(NH₂)₃]₂[B₄O₅(OH)₄]·2H₂O and [C(NH₂)₃]₃[B₉O₁₂(OH)₆], whereas the anion–anion ring motif was dominant in [C(NH₂)₃][B₅O₆(OH)₄]·H₂O and in compounds 1–6. This behaviour was consistent with the stoichiometry of the salt and packing effects also strongly influencing their solid-state structures. Full article

Several oxidoborates, self-assembled from B(OH)₃ and templated by cationic Ni^(II) coordination compounds, were synthesized by crystallization from aqueous solution. These include the ionic compounds trans-[Ni(NH₃)₄(H₂O)₂][B₄O₅(OH)₄]^.H₂O (1), s-[Ni(dien)₂][B₅O₆(OH)₄]₂ (dien = N-(2-aminoethyl)-1,2-ethanediamine (2), trans-[Ni(dmen)₂(H₂O)₂] [B₅O₆(OH)₄]₂^.2H₂O (dmen = N,N-dimethyl-1,2-diaminoethane) (3), [Ni(HEen)₂][B₅O₆(OH)₄]₂ (HEen = N-(2-hydroxyethyl)-1,2-diaminoethane) (4), [Ni(AEN)][B₅O₆(OH)₄]^.H₂O (AEN = 1-(3-azapropyl) -2,4-dimethyl-1,5,8-triazaocta-2,4-dienato(1-)) (5), trans-[Ni(dach)₂(H₂O)₂][Ni(dach)₂] [B₇O₉(OH)₅]₂^.4H₂O (dach = 1,2-diaminocyclohexane) (6), and the neutral species trans-[Ni(en)(H₂O)₂{B₆O₇(OH)₆}]^.H₂O (7) (en = 1,2-diaminoethane), and [Ni(dmen)(H₂O){B₆O₇(OH)₆}]^.5H₂O (8). Compounds 1–8 were characterized by single-crystal XRD studies and by IR spectroscopy and 2, 4–7 were also characterized by thermal (TGA/DSC) methods and powder XDR studies. The solid-state structures of all compounds show extensive stabilizing H-bond interactions, important for their formation, and also display a range of gross structural features: 1 has an insular tetraborate(2-) anion, 2–5 have insular pentaborate(1-) anions, 6 has an insular heptaborate(2-) anion (‘O⁺’ isomer), whilst 7 and 8 have hexaborate(2-) anions directly coordinated to their Ni^(II) centers, as bidentate or tridentate ligands, respectively. The Ni^(II) centers are either octahedral (1–4, 7, 8) or square-planar (5), and compound 6 has both octahedral and square-planar metal geometries present within the structure as a double salt. Magnetic susceptibility measurements were undertaken on all compounds. Full article

Crystalline materials containing hybrid inorganic–organic metal borates (complexes with oxidoborate ligands) display a variety of novel framework building blocks. The structural aspects of these hybrid metallaoxidoborates containing Cd^(II), Co^(II), Cu^(II), Ga^(III), In^(III), Mn^(II), Ni^(II) or Zn^(II) metal centers are discussed in this review. The review describes synthetic approaches to these hybrid materials, their physical properties, their spectroscopic properties and their potential applications. Full article

Two zinc(II) hexaborate(2−) complexes, [Zn{κ³O-B₆O₇(OH)₆}(κ³N-dien)]·0.5H₂O (dien = NH(CH₂CH₂NH₂)₂) (1) and (NH₄)₂[Zn{κ²O-B₆O₇(OH)₆}₂(H₂O)₂]·2H₂O (2), and a zinc(II) dodecaborate(6−) complex, (1,3-pnH₂)₃[(κ¹N-H₃N{CH₂}₃NH₂)Zn{κ³O-B₁₂O₁₈(OH)₆}]₂·14H₂O (1,3-pn = 1,3-diaminopropane) (3), have been synthesized and characterized by single-crystal XRD studies. The complexes crystallized through self-assembly processes, from aqueous solutions containing 10:1 ratios of B(OH)₃ and appropriate Zn(II) amine complex: [Zn(dien)₂](OH)₂, [Zn(NH₃)₄](OH)₂, and [Zn(pn)₃](OH)₂. The hexaborate(2−) anions in 1 and 2 are coordinated to octahedral Zn(II) centres as tridentate (1) or bidentate ligands (2) and the dodecaborate(6−) ligand in 3 is tridentate to a tetrahedral Zn(II) centre. Full article

The synthesis and characterization by single-crystal X-ray diffraction (XRD) studies of two new zinc(II) hexaborate(2−) complexes, [Zn(en){B₆O₇(OH)₆}]·2H₂O (en = 1,2-diaminoethane) (1) and [Zn(pn){B₆O₇(OH)₆}]·1.5H₂O (pn = 1,2-diaminopropane) (2), are reported. These complexes crystallize from aqueous solutions containing 10:1 ratios of B(OH)₃ and the appropriate Zn(II) amine complexes ([Zn(en)₃][OH]₂ or [Zn(pn)₃][OH]₂) through self-assembly processes. The hexaborate(2−) anions in 1 and 2 are coordinated to two Zn(II) centers and form one-dimensional (1-D) polymeric coordination chains. R₂²(8) and R₂²(6) inter-chain H-bond interactions play an important role in these self-assembly processes and are discussed. Full article