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

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.

Selective oxido transfer reaction to PMe3 from oxido–imido molybdenum(VI) compounds [Mo(O)(N-2,4,6-C6H2Me3)(S2CNR2)2] was observed without evidence of imido transfer. The oxido transfer was calculated to be thermodynamic and kinetically favoured with respect the imido one in agreement with the experimental results.Figure optionsDownload as PowerPoint slide