Oxorhenium Complexes Bearing the Water-Soluble Tris(pyrazol-1-yl)methanesulfonate, 1,3,5-Triaza-7-phosphaadamantane, or Related Ligands, as Catalysts for Baeyer–Villiger Oxidation of Ketones

Abstract

(7) have been prepared from the Re(VII) oxide Re2O2 (1-6) or, in the case of 7, by ligand exchange from the benzoyldiazenido complex [ReCl2(N2C-(O)Ph}(Hpz)(PPh3)(2)], and characterized by IR and NMR spectroscopies, elemental analysis and electrochemical properties. Theoretical calculations at the density functional theory (DFT) level of theory indicated that the coordination of PTA to both Re(III) and Re(VII) centers by the P atom is preferable compared to the coordination by the N atom. This is interpreted in terms of the Re-PTA bond energy and hard-soft acid-base theory. The oxo-rhenium complexes 1-6 act as selective catalysts for the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g., 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone, and 3,3-dimethyl-2-butanone or pinacolone) to the corresponding lactones or esters, in the presence of aqueous H2O2. The effects of a variety of factors are studied toward the optimization of the process.

Water‐Soluble C‐Scorpionate Complexes – Catalytic and Biological Applications

“…The rapid development recently observed for the coordination chemistry of the water‐soluble cagelike aminophosphine 1,3,5‐triaza‐7‐phosphaadamantane (PTA), was extended by attempting to combine it or its related hexamethylenetetramine (HMT) with C‐scorpionate ligands at the same metal center. Thus, water‐soluble oxidorhenium(III) and (VII) complexes bearing PTA or the tetraamino HMT and the C‐scorpionate Tpm or Tpms have been synthesized readily from Re 2 O 7 as a convenient starting material in a methanolic solution at room temperature under a dinitrogen atmosphere (Scheme ): [ReO 3 (η 2 ‐Tpm)(PTA)][ReO 4 ] ( 17 ) and [ReO(Tpms)(HMT)] ( 18 ).…”

“…Compounds 17 and 18 are believed to be monomeric as pulsed field gradient spin‐echo NMR spectroscopy excluded the formation of polymeric species . By cyclic voltammetry at a platinum electrode, they undergo Re VII → Re VI ( 17 ) or Re III → Re II ( 18 ) reductions at potentials of ca.…”

First-Row-Transition Ion Metals(II)-EDTA Functionalized Magnetic Nanoparticles as Catalysts for Solvent-Free Microwave-Induced Oxidation of Alcohols

“…by tert-butylperoxyl and tert-butoxyl radicals [36,41,44] that can be produced upon oxidation or reduction of t-BuOOH with the MNPs (catalyst), as shown in Equations (1) and (2) [45,46]. Either tBuOO•or t-BuO can perform H-abstraction from the alcohol substrate.…”

Bis(alkynyl) PTA and DAPTA complexes of Pt(II) and Pd(II)

“…Transition-metal complexes containing either PTA or DAPTA ligands have been reported for metals of groups 6-12 [3]. Metal-catalyzed reactions involving complexes with the PTA and DAPTA ligands are known for a variety of processes including hydrogenation [4], hydroformylation [4b], hydroamination [5], Aza-Morita-Baylis-Hillman [6], Suzuki [7], and Sonogashira couplings [8], and Baeyer-Villiger oxidation [9] reactions using water as a solvent or an aqueous biphasic solvent system [10]. A significant number of studies on the use of water soluble transition-metal complexes containing the PTA and DAPTA ligands for their medicinal and therapeutic applications are known with numerous studies involving ruthenium systems [3,11].…”