Tetragonal-symmetry metal-oxo compounds with d-electron counts greater than two are typically unstable or highly reactive because the additional electrons populate the π*(M–O) orbital. We report that d3 metal-oxo complexes of the form M(O)L4Cl (M = Mo, W; L = neutral ligand) can be prepared via one-electron reduction of d2 [M(O)L4Cl]+ complexes. These reduced complexes can either be isolated or observed transiently depending on the nature of the equatorial L ligands. Electrochemical measurements of the M(IV)/M(III) redox couple and spectroscopic studies of the d3 complexes in solution reveal that their stability depends upon both the steric and electronic properties of the equatorial L groups. The molecular structure of d3 Mo(O)(dppe)2Cl (dppe = 1,2-bis(diphenylphosphino)ethane) has been established by X-ray crystallography, which provides an Mo–O bond length consistent with a formal bond order of 2.5. DFT calculations, electronic spectra, and magnetic measurements point to a (dxy)2(π*)1 electron configuration, consistent with the bond order. The reactions of the d3 complexes with oxidants, H+ sources, and select organic substrates will be described, and their potential utility in photoinitiated redox reactions will be discussed.

Synthesis, properties, and reactivity of d3 terminal–oxo molybdenum and tungsten complexes

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.