II ) bis ( amido ) Complex

General Considerations. Unless stated otherwise, all reactions and procedures were carried out in a VAC Atmosphere Nexus glovebox or using standard Schlenk techniques under a nitrogen atmosphere. Solvents were received from Sigma Aldrich, degassed and dried using a Vac Atmosphere Solvent Purifier system and stored over 3Å molecular sieves. Prior to drying, toluene, benzene and pentane were treated to remove thiophenes and olefins as appropriate, using standard techniques. Acetonitrile was dried by stirring over CaH2 and was then distilled under a nitrogen atmosphere. C6D6 was purchased from Cambridge Isotope Laboratories, dried over Na/K alloy, and then degassed by several freeze-pump-thaw cycles. All silanes were purchased from Gelest, stored under nitrogen and used as received. 2,6dimethylphenylisocyanide and 4-(N,N-dimethylamino)pyridine were purchased from Sigma Aldrich and used as received. Oxygen gas was purchased from Praxair and used without additional purification or drying. Lithium (trimethylsilyl)(2,6-diisopropylphenyl) amide was prepared according to a literature procedure. Molecular sieves were activated by evacuation overnight at approximately 200oC. GC-MS analysis was performed using an Agilent Technologies 6890N GC system equipped with an HP-5MS column and an Agilent Technologies 5973 Network Mass Selective detector. All NMR spectra were collected at ambient temperature (ca. 23°C) on Bruker AVB-400, AV-500, AV-600 or AVQ-400 NMR spectrometers equipped with a 5 mm BB probe, as appropriate and referenced to the residual proteo solvent signals. Solution magnetic susceptibilities were determined by H NMR spectroscopy using Evans’ method. X-ray analyses were carried out at UC Berkeley CHEXRAY crystallographic facility. Measurements of 1-5 were made on an APEX CCD area detector with graphite-monochromated Mo Kα radiation (λ = 0.71069 Å). IR spectra were collected on a Bruker Alpha-P FT-IR Spectrometer equipped with a “Platinum” Attenuated Total Reflection sample module. The abbreviation “IPr” refers to N,N'-1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene.