Oxygen Atom Transfer Reactivity from a Dioxo-Mo(VI) Complex to Tertiary Phosphines: Synthesis, Characterization, and Structure of Phosphoryl Intermediate Complexes

The oxygen atom transfer (OAT) reactivity of Tp*MoO2Cl with PMe3, PEt3, and PPhMe2 (where Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) has been investigated. The OAT reactions proceed through a diamagnetic Mo(IV)
phosphoryl intermediate complex of general formula Tp*MoOCl(OPR3) (OPR3 = OPMe3, OPEt3, OPPhMe2), which
have been isolated and characterized by 1H and 31P NMR, UV−visible, and infrared spectroscopies and electrospray
ionization mass spectrometry. Solid-state crystal structures of Tp*MoOCl(OPMe3) and Tp*MoOCl(OPPhMe2) are
also reported, the oxygen-to-phosphorus distances agree with a double-bond formulation and a single bond between
the metal and the phosphoryl oxygen atom. The stability of the phosphoryl intermediate complexes depends on the
steric properties of the coordinated phosphine-oxides. These intermediate complexes have been converted to solvent-coordinated species, Tp*MoOCl(solv) (solv = acetonitrile or dmf), and the coordinated solvents exchange with the
bulk solvent.