Synthesis, electrochemistry, geometric and electronic structure of oxo-molybdenum compounds involved in an oxygen atom transferring system

The oxygen atom transfer reactivity of Tp∗MoO2(SPh) (1) (where Tp∗ = hydrotris-(3,5-dimethylpyrazol-1-yl)borate) with trimethyl phosphine (PMe3) has been investigated. The reaction proceed through a diamagnetic phosphoryl intermediate complex, Tp∗MoO(SPh)(OPMe3) (2), which has been isolated and characterized by IR, NMR, UV–visible spectroscopy, and mass spectrometry. The molecular structure of 2 has been determined by X-ray crystallography. The complex crystallizes in monoclinic (P21/n) space group, a = 19.81 (1) Å, b = 11.1 (4) Å, c = 18.416 (5) Å, β = 121.2 (3)°, V = 3463.8 (25) Å3 with Z = 4. In acetonitrile, complex 2 exchanges its phosphoryl ligand with a solvent molecule resulting in Tp∗MoO(SPh)(MeCN) (3), which has been isolated and also characterized spectroscopically and by X-ray crystallography. Compound 3 crystallizes in triclinic (P1¯) space group, a = 10.159 (6) Å, b = 18.563 (5) Å, c = 7.986 (3) Å, α = 96.22 (3)°, β = 121.2 (3)°, γ = 84.64 (3)°, V = 1452.4 (11) Å3 with Z = 2. The electronic structures of the complexes have been investigated by density functional theory and the redox chemistry has been investigated by cyclic and differential pulse voltammetry. In acetonitrile, complex 2 spontaneously transforms to complex, 3 at a rate of 5.6 × 10−4 s−1.