Oxidoborates Templated by Cationic Nickel(II) Complexes and Self-Assembled from B(OH)3

Mohammed A Altahan,Peter N Horton,Simon J Coles,Michael A Beckett

doi:10.3390/inorganics9090068

Mohammed A Altahan, Peter N Horton + Show 2 more

Open Access

https://doi.org/10.3390/inorganics9090068

Copy DOI

Journal: Inorganics	Publication Date: Aug 31, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Bangor University, University of Southampton

Abstract

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.

Highlights

IntroductionSynthetic borates (oxidoborates is the IUPAC recommended name for this class of compounds [1]) show great structural diversity and their structures complement the variety of structural motifs observed in borate minerals [2,3,4,5]
Synthetic borates show great structural diversity and their structures complement the variety of structural motifs observed in borate minerals [2,3,4,5]
Oxidoborate materials can be synthesized from aqueous solution or from solid-state or solvothermal methods and the latter non-aqueous methods often lead to the formation of the more highly condensed oxidoborate structures [5]

Summary

Introduction

Synthetic borates (oxidoborates is the IUPAC recommended name for this class of compounds [1]) show great structural diversity and their structures complement the variety of structural motifs observed in borate minerals [2,3,4,5]. Borates salts consist of metallic or non-metallic cationic centers and hydroxyoxidoborate units, with variable degrees of condensation, as either insular anions or as anionic 1-D chains, 2-D layers or 3-D networks [2,3,4,5]. Oxidoborate materials can be synthesized from aqueous solution or from solid-state or solvothermal methods and the latter non-aqueous methods often lead to the formation of the more highly condensed oxidoborate structures [5]. Oxidoborate speciation is pH and boron-concentration dependent [19,20], and a dynamic combinatorial library (DCL) [21] of oxidoborate anions co-exist in rapidly attained aqueous equilibria. Many oxidoborate anions have been successfully crystallized from aqueous solution using B(OH) and an appropriate templating cation, e.g., triborate(1-), tetraborate(2-), Inorganics 2021, 9, 68 pentaborate(1-), hexaborate(2-), heptaborate(2-) (two isomers), heptaborate(3-), octaborate(2-)

Methods

Results

Conclusion