Ion-pair complexes of oxidorhenate(v) with phenolate–oxazoline ligands: synthesis, solvatochromism and catalytic properties
- 1Institute of Chemistry, University of Graz Schubertstraße 1 8010 Graz Austria
- 2Innovation Center of the Faculty of Chemistry, Belgrade Studentski trg 12-16 11158 Belgrade Serbia
Abstract
Ion-pair complexes, in which an organic cation exists entirely in the second coordination sphere of an anionic metal complex, represent a structurally and electronically distinct compound class, whose solution behavior is influenced by solvent polarity and hydrogen-bonding interactions. Their capacity to undergo ion pair charge transfer (IPCT) transitions makes them attractive model complexes for ion-pairing equilibria and potential active species in catalytic cycles. Herein we report the synthesis, structural characterization, spectroscopic investigation and catalytic evaluation of the oxidorhenate(v) outer-sphere ion pair complexes (H2L1)[ReOCl3(L1)] (1) and (H2L2)[ReOCl3(L2)] (2). Both complexes crystallize as contact ion pairs stabilized by N–H⋯Cl and O–H⋯Cl hydrogen bonds. The hydrogen-bond-accepting Re–Cl bonds are significantly elongated as shown by single crystal X-ray diffraction analysis, indicating enhanced lability at these sites. Both complexes display a striking solvatochromism, assigned by UV/Vis spectroscopy to an IPCT transition operative exclusively in apolar media (λmax = 555 nm, ε = 2700 L mol−1 cm−1 for 1; λmax = 577 nm, ε = 920 L mol−1 cm−1 for 2, solvent: CHCl3). Additionally, DFT calculations across a series of solvents establish the thermodynamic basis for the observed solvent-dependent ion-pair equilibria. Cyclic voltammetry reveals quasi-reversible Re(v/vi) couples for 1 in both solvents and for 2 in MeCN (E1/2 = +0.431 V for 1; +0.258 V for 2 in MeCN vs. Fc+/Fc). Both complexes catalyze perchlorate reduction with dimethyl sulfide, achieving 92% conversion (TOF 0.37 h−1) for 1 and 55% (TOF 0.22 h−1) for 2. 1H NMR monitoring shows that 1 is not converted into the bis-chelate complex during catalysis.
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BibTeX
@article{doliner2026ionpair,
title = {{Ion-pair complexes of oxidorhenate(v) with phenolate–oxazoline ligands: synthesis, solvatochromism and catalytic properties}},
author = {Tobias A. Doliner and Anna M. Schlegl and Kristin Kogler and Milan Milovanović and A. D. Boese and Ferdinand Belaj and Antoine Dupé and Peter E. Hartmann and Jörg A. Schachner},
journal = {Dalton Transactions (Cambridge, England : 2003)},
year = {2026},
month = oct,
doi = {10.1039/d6dt02275h},
url = {https://doi.org/10.1039/d6dt02275h},
note = {CC BY 3.0},
}
RIS
TY - JOUR
TI - Ion-pair complexes of oxidorhenate(v) with phenolate–oxazoline ligands: synthesis, solvatochromism and catalytic properties
AU - Tobias A. Doliner
AU - Anna M. Schlegl
AU - Kristin Kogler
AU - Milan Milovanović
AU - A. D. Boese
AU - Ferdinand Belaj
AU - Antoine Dupé
AU - Peter E. Hartmann
AU - Jörg A. Schachner
PY - 2026
DA - 2026/10/27
JO - Dalton Transactions (Cambridge, England : 2003)
DO - 10.1039/d6dt02275h
UR - https://doi.org/10.1039/d6dt02275h
AB - Ion-pair complexes, in which an organic cation exists entirely in the second coordination sphere of an anionic metal complex, represent a structurally and electronically distinct compound class, whose solution behavior is influenced by solvent polarity and hydrogen-bonding interactions. Their capacity to undergo ion pair charge transfer (IPCT) transitions makes them attractive model complexes for ion-pairing equilibria and potential active species in catalytic cycles. Herein we report the synthesis, structural characterization, spectroscopic investigation and catalytic evaluation of the oxidorhenate(v) outer-sphere ion pair complexes (H2L1)[ReOCl3(L1)] (1) and (H2L2)[ReOCl3(L2)] (2). Both complexes crystallize as contact ion pairs stabilized by N–H⋯Cl and O–H⋯Cl hydrogen bonds. The hydrogen-bond-accepting Re–Cl bonds are significantly elongated as shown by single crystal X-ray diffraction analysis, indicating enhanced lability at these sites. Both complexes display a striking solvatochromism, assigned by UV/Vis spectroscopy to an IPCT transition operative exclusively in apolar media (λmax = 555 nm, ε = 2700 L mol−1 cm−1 for 1; λmax = 577 nm, ε = 920 L mol−1 cm−1 for 2, solvent: CHCl3). Additionally, DFT calculations across a series of solvents establish the thermodynamic basis for the observed solvent-dependent ion-pair equilibria. Cyclic voltammetry reveals quasi-reversible Re(v/vi) couples for 1 in both solvents and for 2 in MeCN (E1/2 = +0.431 V for 1; +0.258 V for 2 in MeCN vs. Fc+/Fc). Both complexes catalyze perchlorate reduction with dimethyl sulfide, achieving 92% conversion (TOF 0.37 h−1) for 1 and 55% (TOF 0.22 h−1) for 2. 1H NMR monitoring shows that 1 is not converted into the bis-chelate complex during catalysis.
SN - 1477-9226
SN - 1477-9234
ER -