Synthesis and characterization of heptacoordinated molybdenum( ii ) complexes supported with 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligands
Résumé
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 tBu 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)n−1(PMe3−nPhn)5−n] 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−nPhn)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−nPhn)2][OTf]2 complexes 6a–c. Acidic treatment of 4a–c led to the decomposition of the complexes.
Domaines
Chimie de coordination
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Estival, Synthesis and characterization of heptacoordinated molybdenum(ii), 2025.pdf (1)
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