Syntheses, properties, and structural characteristics of several new [tetrakis(1-pyrazolyl)borato]samarium(III) complexes: comparative study of the B(pyrazolyl)4 and BH(pyrazolyl)3 ligation

Bis[3-(anthracen-9-yl)pentane-2,4-dionato-κ2 O,O'](N,N-di-methyl-formamide-κO)[tris-(pyrazol-1-yl-κN 2)hydroborato]europium(III)

The title compound, [Eu(C9H10BN6)(C19H15O2)2(C3H7NO)] or [TpEu(Anthracac)2(DMF)], was synthesized by reaction of a tris-(pyrazol-yl)borate (Tp-) Eu3+ complex with 3-(anthracen-9-yl)pentane-2,4-dione (HAnthracac) in the presence of tri-ethyl-amine. In the title compound, Eu3+ is located in an octa-vertex square-pyramidal coordination environment. In the two Anthracac- ligands, the anthracene and nearly planar acetyl-acetonate fragments are almost orthogonal. Neighboring mol-ecules of TpEu(Anthracac)2(DMF) are connected in the crystal by inter-molecular van der Waals inter-actions, while π-stacking inter-actions are limited to the edges of two anthracene rings.

Side-on coordination mode of a pyrazolyl group in the structure of a divalent [Sm{B(3-Mepz)4}2] complex (3-Mepz is 3-methylpyrazol-1-yl)

The discovery of polypyrazolylborate ligands allowed the development of various chemical fields and these ligands are an alternative to cyclopentadienyl, because both ligands have the same charge and donate the same number of electrons, as well as adopting the same facial geometry. Easy control of the bulkiness of polypyrazolylborate ligands is possible by modification of the substituents in the 3- and 5-positions of the pyrazolyl rings. The title complex, bis[tetrakis(3-methyl-1H-pyrazol-1-yl)borato]samarium(II), [Sm(C₁₆H₂₀BN₈)₂], was synthesized from the reaction of SmI₂ with potassium tetrakis(3-methyl-1H-pyrazol-1-yl)borate, denoted K[B(3-Mepz)₄], in tetrahydrofuran. The X-ray structure analysis revealed an unusual side-on coordination mode of a 3-methylpyrazolyl group through an N=N group in the B(3-Mepz)₄ ligand. The distortion is defined by the B-N-N-Sm torsion angle [85.5 (4)°]. This is in contrast to the structure of the similar divalent samarium complex [Sm(Tp^Me2 is tris(3,5-dimethylpyrazol-1-yl)borate], which displays normal κ³-bonding modes of the Tp^Me2 ligands.

Selective lanthanide sorption and mechanism using novel hybrid Lewis base (N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide) ligand modified adsorbent

This study aims to develop a highly selective Lewis base adsorbent to investigate the selective sorption and recovery of Eu(III) and Sm(III) from wastewater. The oxygen and nitrogen donor atoms containing Lewis base N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) ligand was synthesized and subsequently an adsorbent was prepared by direct immobilization onto mesoporous silica. Determined maximum adsorption capacities were 125.63 and 124.38 mg/g for Eu(III) and Sm(III), respectively. Experiments with mixed-cations solutions showed that the sequence of preferential adsorption was Eu(III)>Sm(III). The lanthanide sorption by hybrid Lewis base adsorbent (HyLBA) was not adversely affected by the presence of sodium, potassium, calcium, magnesium, chloride, sulfate and nitrate ions due to strong affinity between hard Lewis acid lanthanide and hard Lewis base adsorbent. The crystallography for the Sm-MePhPTA complex suggested that MePhPTA was strongly coordinated to Sm(III) with oxygen and nitrogen by forming a stable complex with two 5-membered rings. The data clarified that bond lengths between Sm(III) and amide oxygen (2.475Å) were shorter than SmN (2.662Å) in phenanthroline moiety indicating strong oxygen driven HyLBA. The results suggested that HyLBA has a good prospect of promising applications for separation/sorption of lanthanide ions from effluents.