“…Accordingly, we report the synthesis and characterization of isostructural anionic complexes [Na(CH 3 CN) 3 (Et 2 O)][M(( S )-BINOLate) 3 ] [M = Nb ( 1-Nb ), Ta ( 1-Ta )] and describe a novel electrochemical method for separating these molecular compounds ( S Nb/Ta = 6 ± 2). Racemic tris(BINOLate) complexes, charge-balanced with ammonium counterions, were reported previously . However, that report lacked structural and NMR characterization data.…”
mentioning
confidence: 96%
“…Racemic tris(BINOLate) complexes, charge-balanced with ammonium counterions, were reported previously. 15 However, that report lacked structural and NMR characterization data. Herein, electrochemical studies on 1-M reveal differences in the M V/IV redox potentials, which are rationalized through computational studies in the context of ligand−metal π interactions.…”
mentioning
confidence: 99%
“…A difference in the energies of these states was predicted, with features corresponding to 1-Nb (2.872 and 1.904 eV) calculated to be red-shifted compared to those of 1-Ta (3.390 and 3.437 eV). Because of the use of the enantiopure (S)-BINOLate proligands and in contrast to the complexes reported by Andra, 15 1-M are enantiopure complexes, and circular dichroism spectroscopy was employed to characterize their chiroptical properties (see the SI for details).…”
The
critical metals niobium (Nb) and tantalum (Ta) coexist in mineral
sources, requiring a separation step to purify the elements from one
another. The industrial separation process by solvent extraction uses
stoichiometric hydrofluoric acid to manifest differences in the speciation
of these otherwise chemically similar elements. The identification
of alternative methods to separate Nb/Ta is desirable for fluoride
waste reduction. In pursuit of this goal, the novel complexes [Na(CH3CN)3(Et2O)][M((S)-BINOLate)3] [M = Nb (1-Nb), Ta (1-Ta)] were
synthesized and characterized. In electrochemical studies, a reduction
event at the potential −2.04 V versus ferrocene/ferrocenium
was observed for 1-Nb, whereas 1-Ta exhibited
no metal-based waves in the electrochemical window. In addition to
the inherent 4d/5d orbital energy differences between Nb/Ta, density
functional theory calculations suggest a larger degree of π
donation from the ligands to the metal cation in 1-Ta compared to 1-Nb, destabilizing the lowest unoccupied
molecular orbital. This phenomenon contributes to a calculated reduction
potential difference of ca. 0.75 V, allowing for the selective reduction
of 1-Nb and separation of the reduction product through
leaching with diethyl ether for a separation factor of 6 ± 2.
“…Accordingly, we report the synthesis and characterization of isostructural anionic complexes [Na(CH 3 CN) 3 (Et 2 O)][M(( S )-BINOLate) 3 ] [M = Nb ( 1-Nb ), Ta ( 1-Ta )] and describe a novel electrochemical method for separating these molecular compounds ( S Nb/Ta = 6 ± 2). Racemic tris(BINOLate) complexes, charge-balanced with ammonium counterions, were reported previously . However, that report lacked structural and NMR characterization data.…”
mentioning
confidence: 96%
“…Racemic tris(BINOLate) complexes, charge-balanced with ammonium counterions, were reported previously. 15 However, that report lacked structural and NMR characterization data. Herein, electrochemical studies on 1-M reveal differences in the M V/IV redox potentials, which are rationalized through computational studies in the context of ligand−metal π interactions.…”
mentioning
confidence: 99%
“…A difference in the energies of these states was predicted, with features corresponding to 1-Nb (2.872 and 1.904 eV) calculated to be red-shifted compared to those of 1-Ta (3.390 and 3.437 eV). Because of the use of the enantiopure (S)-BINOLate proligands and in contrast to the complexes reported by Andra, 15 1-M are enantiopure complexes, and circular dichroism spectroscopy was employed to characterize their chiroptical properties (see the SI for details).…”
The
critical metals niobium (Nb) and tantalum (Ta) coexist in mineral
sources, requiring a separation step to purify the elements from one
another. The industrial separation process by solvent extraction uses
stoichiometric hydrofluoric acid to manifest differences in the speciation
of these otherwise chemically similar elements. The identification
of alternative methods to separate Nb/Ta is desirable for fluoride
waste reduction. In pursuit of this goal, the novel complexes [Na(CH3CN)3(Et2O)][M((S)-BINOLate)3] [M = Nb (1-Nb), Ta (1-Ta)] were
synthesized and characterized. In electrochemical studies, a reduction
event at the potential −2.04 V versus ferrocene/ferrocenium
was observed for 1-Nb, whereas 1-Ta exhibited
no metal-based waves in the electrochemical window. In addition to
the inherent 4d/5d orbital energy differences between Nb/Ta, density
functional theory calculations suggest a larger degree of π
donation from the ligands to the metal cation in 1-Ta compared to 1-Nb, destabilizing the lowest unoccupied
molecular orbital. This phenomenon contributes to a calculated reduction
potential difference of ca. 0.75 V, allowing for the selective reduction
of 1-Nb and separation of the reduction product through
leaching with diethyl ether for a separation factor of 6 ± 2.
“…Complex ( R , R )- 1 is the only structurally characterized bis(binaphthoxide) complex of tantalum. A complex, H[Ta(O 2 C 20 H 12 ) 3 ], has been reported which was not structurally characterized 1 1 ORTEP diagram for the anion of [H 2 NEt 2 ][Ta(O 2 C 20 H 10 {SiMe 3 } 2 -3,3‘) 2 Cl 2 ], ( R , R )- 1 .…”
Reaction of dimeric [(Et2N)2Cl2Ta(μ-Cl)2TaCl2(NEt2)2] with (R)-[H2O2C20H10(R)2-3,3‘]
(R = SiMe3, SiMe2Ph, SiMePh2, or SiPh3) produces the 3,3‘-dialkyl-1,1‘-bi-2,2‘-naphthoxido
complexes (R,R)-[H2NEt2][Ta(O2C20H10{R}2-3,3‘)2Cl2] (R = SiMe3, (R,R)-1; SiMe2Ph, (R,R)-2; SiMePh2, (R,R)-3; SiPh3, (R,R)-4). Structural studies of the SiMe3 derivative (R,R)-1 show
a pseudo-octahedral anion with mutually cis chloride ligands. Although NMR studies indicate
that the anion of (R,R)-1 is stable in DMSO-d
6, an equilibrium mixture is observed in C6D6
solution with the neutral complex (R,R)-[Ta{O2C20H10(SiMe3)2-3,3‘}2Cl], (R,R)-1a, and
[H2NEt2]Cl. The temperature dependence of the equilibrium has been studied. Addition of
[nBu4N]Cl to a mixture of (R,R)-1/(R,R)-1a in C6D6 is shown (1H NMR) to shift the equilibrium
toward (R,R)-1. Alkylation of (R,R)-1 with Grignard reagents RMgCl results in formation of
the five-coordinate (R,R)-[Ta(O2C20H10{SiMe3}2-3,3‘}2R‘] (R‘ = CH2SiMe3, (R,R)-5; CH2Ph,
(R,R)-6; c-C5H9, (R,R)-7).
Aluminiumselenophenolat bzw. ‐1‐selenonaphtholat reagiert mit TiCl4, ZrCl4 und CrCl3 · 3THF zu Mn(SeR)n (M = Ti, Zr, Cr; R = C6H5, C10H7; n = 3, 4), während NbCl5, TaCl5 und WCl6 im Sinne einer Redoxreaktion Verbindungen des Typs M(SeR)3, (M = Nb, Ta; R = C6H5, C10H7) und W(SeC6H5)4 liefern. Durch Wechselwirkung der Nickel(II)‐, Kobalt(II)‐ und Kobalt(III)‐acetylacetonate mit Thiophenol, Selenophenol und 1‐Selenonaphthol werden polymere Verbindungen der Zusammensetzung Ni(XR)2, Co(XR)n (X = S, Se; R = C6H5, C10H7; n = 2 oder 3) und Co(SC6H5)2 · C6H5SH erhalten. Aus [(n‐C4H9)3P]2NiCl2 und Selenophenol ist bei Gegenwart von Triäthylamin das monomere (n‐C4H9)3P[2]Ni(SeC6H5)2 zugänglich.
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