Oxygen Atom Transfer Reactions with Molybdenum Cofactor Model Complexes That Contain a Tetradentate OSSO-Type Bis(phenolato) Ligand
2018; American Chemical Society; Volume: 37; Issue: 23 Linguagem: Inglês
10.1021/acs.organomet.8b00386
ISSN1520-6041
AutoresTobias Schindler, Andreas Sauer, Thomas P. Spaniol, Jun Okuda,
Tópico(s)Electrocatalysts for Energy Conversion
ResumoThe catalytic activity of molybdenum complexes in oxidation state +IV, +V, and +VI stabilized by a tetradentate dithiaalkanediyl-2,2′-bis(phenolato) (OSSO)-type ligand was tested in the oxygen atom transfer (OAT) reaction from DMSO to PPh3. The molybdenum(IV) complexes [(OSSO)MoCl2] (1a, b) were prepared from [MoCl4(NCMe)2] and the corresponding bis(phenol) (OSSO)H2. The molybdenum(V) complexes [(OSSO)MoOCl] (2a, b) were obtained by salt metathesis either from MoOCl4 or from MoOCl3 with the corresponding bis(phenolate) salts [(OSSO)M2] (M = Li, K). The reaction with MoOCl4 proceeds via the intermediate [(OSSO)MoOCl2] (A), which disproportionates into 2 and insoluble oligomers. Single crystal X-ray diffraction of 1a and 2b revealed octahedral cis-α-coordination of the metal center. EPR spectra of 2a and 2b show the characteristic signal of a molybdenum d1-spin system which is not coupled to the ligand. OAT reactions in the presence of 1–2 or of the bis(oxo) complex [(OSSO)MoO2] (3) revealed that the molybdenum(IV) complex 1b exerts the high catalytic activity with complete conversion of PPh3 to OPPh3 within 30 min at 60 °C. The high catalytic activity of 1 compared to that of 2–3 is explained by the formation of the unstable intermediate A, which decomposes to 2 in the absence of PPh3.
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