Leveraging Ligand Cooperativity to Accelerate C–H Activation of Alkynes Using a Tris(amido) Zirconium Complex

Early transition metal alkyl and hydride complexes have been widely explored for their propensity to faciltate C–H activation through a concerted σ-bond metathesis mechanism. Herein, we report the synthesis of a tris(amido) Zr(IV) alkyl complex 1 as a precursor of accessing a proposed transient Zr(IV)-hydride. Upon intramolecular C–H activation of a pendent methyl group, a strained cyclometalated complex 2 is obtained. Relief of ring strain and cooperative metal–ligand C–H activation provided access to Zr-acetylide complex 3, which is capable of undergoing insertion reactivity into carbonyl containing compounds, like aldehydes and ketones. Complexes 1–3 are characterized using multinuclear NMR spectroscopy, UV–vis spectroscopy, and X-ray crystallography. Newly reported electron-rich propargylic alcohols 6 and 7 are isolated and fully characterized using multinuclear NMR spectroscopy, ESI-MS, and FTIR.