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

As previously reported, the reaction between W-2(NMe(2))(6) and 2,2'-methylenebis(6-tert-butyl-4-methyl- HO-CH2-OH, in hydrocarbon solvents leads to W-2(mu-H)(mu-NMe(2))(eta(2)-O-CH2-O)(eta(3)-O-CH-O)(HNMe(2)), 1, by oxidative cyclometallation to the ditungsten center. Upon heating 1 to greater than 60 degrees C under dynamic vacuum W-2(NMe(2))(2)(eta(2)-O-CH2-O)(2),2, is formed with elimination of HNMe(2). Compound 2 is proposed to have an ethane-like O2NW=WO2N core based on NMR data. Addition of HNMe(2) to 2 at room temperature converts 2 to 1. The addition of other neutral ligands (pyridine, PMe(3)) to hydrocarbon solutions of 2 promotes the C-H oxidative addition to the W-2 center and the pyridine adduct W-2(mu-H)(mu-NMe(2))(NMe(2))(py)(eta(2)-O-CH2-O)(eta(3)-O-CH-O), 3, has been fully characterized by an X-ray study. Addition of PMe(3) 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.