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Updated: Jun 3, 2025

Author Spotlight: Functionalizing Metal-Organic Frameworks: Advancements, Challenges, and the Power of Post-Synthetic Ligand Exchange
Published on: June 23, 2023
Synthesis and characterization of heptacoordinated molybdenum(II) complexes supported with
Arno Estival1, Luis E Blancarte2, Loïc Pinto1
1LCC-CNRS, Université de Toulouse, CNRS, UPS, 205 route de Narbonne, BP44099 F-31077 Toulouse cedex 4, France. antoine.simonneau@lcc-toulouse.fr.
Abstract:
Functional pincer ligands that engage in metal-ligand cooperativity and/or are capable of redox non-innocence have found a great deal of success in catalysis. These two properties may be found in metal complexes of the 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligands. With this goal in mind, we have attempted the coordination of 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine (LCF3) and its Bu analogue 2,6-bis(5-tert-butylpyrazol-3-yl)pyridine (LtBu) to Mo(0) by reactions with mixed phosphine/carbonyl complexes [Mo(CO)2(MeCN)(PMe3-Ph)5-] 1-3 (1 ≤ n ≤ 3). These afforded mixtures of several Mo compounds among which low yields of heptacoordinated Mo(II) complexes [Mo(CO)2(bpp)(PMe3-Ph)2] 4a-c (LCF3-supported) and 5a-c (LtBu-supported) bearing a doubly deprotonated bpp ligand were systematically produced. More selective syntheses of 4a-c and 5a-c were achieved by repeating these experiments in the presence of an oxidant (AgOAc or Ag2O), with moderate to good yields. 4a-c and 5a-c were characterized by means of NMR, IR and UV-Vis spectroscopies, sc-XRD and cyclic and square-wave voltammetries for 4a, 4b and 5b. The deprotonated LtBu ligand in 5a-c is re-protonated with 2 equiv. of HOTf to afford the dicationic [Mo(CO)2(LtBu)(PMe3-Ph)2][OTf]2 complexes 6a-c. Acidic treatment of 4a-c led to the decomposition of the complexes.
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