Reversible carbon-hydrogen bond oxidative addition across a W-W multiple bond

As previously reported, the reaction between W₂(NMe₂)₆ and 2,2′-methylenebis(6-tert-butyl-4-methyl-phenol), HO-CH₂-OH, in hydrocarbon solvents leads to W₂( μ-H)( μ-NMe₂)(η²-O-CH₂-O)(η³-O-CH-O)(HNMe₂)(NMe₂), 1, by oxidative cyclometallation to the ditungsten center. Upon heating 1 to greater than 60°C under dynamic vacuum W₂(NMe₂)₂(η²-O-CH₂-O)₂,2, is formed with elimination of HNMe₂. Compound 2 is proposed to have an ethane-like O₂NW≡WO₂N core based on NMR data. Addition of HNMe₂ to 2 at room temperature converts 2 to 1. The addition of other neutral ligands (pyridine, PMe₃) to hydrocarbon solutions of 2 promotes the C-H oxidative addition to the W₂ center and the pyridine adduct W₂( μ-H)( μ-NMe₂)(NMe₂)(py)(η²-O-CH₂-O)(η³-O-CH-O), 3, has been fully characterized by an X-ray study. Addition of PMe₃ to 2 at low temperatures reveals that Lewis base association occurs prior to C-H activation. There is no evidence for an agostic interaction for 2 by NMR or IR spectroscopy.