Oxido- versus imido-transfer reactions in oxido-imido molybdenum(VI) complexes: A combined experimental and theoretical study

Article abstract of DOI:10.1016/j.poly.2015.02.015

The reaction of the oxido-imido molybdenum(VI) compounds [Mo(O)(Nmes)(S₂CNR₂)₂] (mes = 2,4,6-C₆H₂Me₃, R₂ = ⁱPr₂, 1a; C₄H₄, 1b) with an excess of PMe₃ was investigated. [Mo(Nmes)(S₂CNR₂)₂(PMe₃)] (R₂ = ⁱPr₂, 2a; C₄H₄, 2b) complexes and the corresponding phosphane oxide OPMe₃ were exclusively detected as reaction products, according to an oxygen atom transfer (OAT) reaction. No evidence of the possible imido transfer reaction was observed. In order to explain the selective OAT reaction in this system, DFT calculations were carried out with the model compound [Mo(O)(N-2,6-Me₂C₆H₃)(S₂CNMe₂)₂], 1c, and PMe₃ as reactant. The two possible oxido transfer and imido transfer pathways were considered and the nucleophilic attack of the phosphane to the multiple bonded atom was the associative intermolecular processes modelled. The oxido transfer is thermodynamic and kinetically favoured with respect the imido one in agreement with the experimental results.